Kyushu University Academic Staff Educational and Research Activities Database
List of Presentations
Yusaku Nakabeppu Last modified date:2021.12.09

Professor / Division of Neurofunctional Genoimics / Department of Immunobiology and Neuroscience / Medical Institute of Bioregulation


Presentations
1. Guianfranco Mazzei, Nona Abolhassani, Ryohei Ikegami, Naoki Haruyama, Kunihiko Sakumi, Takashi Saito, Takaomi C. Saido, Yusaku Nakabeppu, High-fat diet aggravates the hippocampal Alzheimer disease pathology in the AppNL-F/NL-F mouse model, SfN Global Connectome, 2021.01, Insulin resistance, a major symptom of type-2 diabetes mellitus (T2DM), is a known risk factor for Alzheimer’s disease (AD). Emerging evidence has shown that both diseases share similar pathophysiology which includes amyloidogenesis and cognitive decline. In the present study, we aimed to understand how T2DM or related conditions contribute to AD pathogenesis. We used the AppNL-F/NL-F knock-in mouse model of AD, which contains a humanized Aβ region along with two pathogenic mutations, the Swedish “NL” and the Iberian “F” to express APP at wild-type levels while producing elevated pathogenic Aβ. AppNL-F/NL-F mice recapitulate several AD-associated pathologies, including amyloid plaques in the cortex and hippocampus, and show signs of very mild cognitive impairment at 18 months of age, but avoid potential artifacts introduced by APP transgene. For this study, 6-month-old AppNL-F/NL-F and wild-type male mice were fed with a regular diet (RD) or high-fat diet (HFD) for 12 consecutive months. We then compared the effects of the diet on the AD..
2. Pathology caused by chemical modifications of nucleic acids by reactive molecules and the defense mechanisms.
3. Nona Abolhassani, Masaaki Hokama, Daisuke Saitou, Masahiro Shijo, Takashi Saito, Takaomi C. Saido, Mikita Suyama, Toru Iwaki, Yutaka Kiyohara, Yusaku Nakabeppu, Disturbed glutamate signaling in AD hippocampus revealed by an integrated analysis of altered expression profiles of genes in both human and mouse brains with Alzheimer's disease pathology, The 42nd Annual Meeting of the Molecular Biology Society of Japan, 2019.12.
4. Naoki Haruyama, Nona Abolhassani, Guianfranco Mazzei, Julio Leon, Zijing Sheng, Sugako Oka, Mizuki Ohno, Kunihiko Sakumi, Daisuke Tsuchimoto, Yusaku Nakabeppu, Defense mechanisms against the dysfunction resulting from damage to the genome by reactive oxygen species during aging, The 11th International Association of Gerontology and Geriatrics Asia/Oceania Regional Congress 2019, 2019.10.
5. Yusaku Nakabeppu, Naoki Haruyama, Kunihiko Sakumi, Atsuhisa Katogi, Daisuke Tsuchimoto, Gabriele De Luca, Margherita Bignami, 8-Oxoguanine accumulation in aged female brain impairs neurogenesis in dentate gyrus and major island of Calleja, and thus causing sexually dimorphic phenotypes, The 42nd Annual Meeting of The Japan Neuroscience Society, 2019.07, Neurons need to survive and function throughout the life of the individual. However, postmitotic neurons are known to be lost owing to dysfunction associated with aging, particularly via oxidative stress. Consequently, several defense mechanisms function to retain neural networks, including the supply of newborn neurons from neural progenitors in the adult brain. Despite the many defense mechanisms evolved by eukaryotic cells, various oxidized lipids, proteins, carbohydrates and nucleic acids have been found to accumulate in the brains of animals including humans during aging, and under pathological conditions.
Among all nucleobases, guanine is the most susceptible to oxidation, and is modified to 8-oxo-7,8-dihydro-guanine (8-oxoG), which is one of the major oxidized bases in the nucleotide pool or DNA, and is known to be highly accumulated in patient’s brains with aging-related neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease and Huntington’s disease. In mammals, including humans, MTH1 with 8-oxo-dGTPase and OGG1 with 8-oxoG DNA glycosylase minimize 8-oxoG accumulation in genomic DNA.
In the present study, we investigated age-related alterations in behavior, 8-oxoG levels, and neurogenesis in the brains of Mth1/Ogg1-double knockout (TO-DKO), Ogg1-knockout, and human MTH1-transgenic (hMTH1-Tg) mice. Spontaneous locomotor activity in the home cage was significantly decreased in wild-type mice with age, and females consistently exhibited higher locomotor activity than males. This decrease was significantly suppressed in female but not male TO-DKO mice and markedly enhanced in female hMTH1-Tg mice. Long-term memory retrieval was impaired in middle-aged female TO-DKO mice. 8-OxoG accumulation significantly increased in nuclear DNA, particularly in the dentate gyrus (DG), subventricular zone (SVZ) and major island of Calleja (ICjM) in middle-aged female TO-DKO mice. In middle-aged female TO-DKO mice, neurogenesis was severely impaired in SVZ and DG, accompanied by ICjM and DG atrophy. Conversely, expression of hMTH1 efficiently suppressed 8-oxoG accumulation in both SVZ and DG with hypertrophy of ICjM. These findings indicate that increased accumulation of 8-oxoG in nuclear DNA of neural progenitors in females is caused by 8-oxo-dGTP incorporation into the nuclear genome during proliferation, causing depletion of neural progenitors, altered behavior, and cognitive function changes with age, as sexually dimorphic phenotypes..
6. Guianfranco Mazzei, Nona Abolhassani, Ryohei Ikegami, Naoki Haruyama, Takashi Saito, Takaomi C. Saido, Yusaku Nakabeppu, High-fat diet exacerbates neuropathology in AppNL-F/NL-F mouse model of Alzheimer’s disease., The 42nd Annual Meeting of The Japan Neuroscience Society, 2019.07.
7. Nona Abolhassani, Yuri Mizuno, Guianfranco Mazzei, Takashi Saito, Takaomi C. Saido, Yusaku Nakabeppu, Altered gene expression profiles in Alzheimer’s disease model mice caused by deficiency in three genes counteracting the buildup of 8-oxoguanine in DNA., The 42nd Annual Meeting of The Japan Neuroscience Society, 2019.07.
8. Yusaku Nakabeppu, Alzheimer's disease brain exhibits feature of brain diabetes with impaired insulin signaling, mitochondrial dysfunction and oxidative stress, Korean Society for Biochemistry and Molecular Biology International Conference 2019, 2019.06, Accumulating clinical data indicate that insulin resistance and diabetes mellitus (DM) are major risk factors for Alzheimer’s disease (AD); however, the exact mechanisms on how insulin resistance and DM act as risk factors for AD remain unclear. We examined gene expression profiles in postmortem human brains donated for the Hisayama study, and revealed that brain insulin production and insulin signaling are significantly impaired, indicating that AD brain exhibits a feature of brain diabetes with depletion of brain insulin. Moreover, the gene expression profiles indicate mitochondrial dysfunction with increased oxidative stress in AD brain. Such diabetic condition in early stage of AD brain can be exacerbated by peripheral DM, namely, through hyperglycemia, hyperinsulinemia or impaired insulin response. Using mouse model of AD and AD model neurons derived from human induced pluripotent stem cells, we demonstrated that suppression of mitochondrial dysfunction decreases production of reactive oxygen species in AD brain, and further attenuates amyloid beta accumulation with alteration of gene expression profiles, thus improving cognitive function. These results provide new insights into potential novel therapeutic targets..
9. Daisuke Tsuchimoto, Yuichiro Koga, Yoshinori Hayashi, Nona Abolhassani, Yasuto Yoneshima, Hiroshi Nakanishi, Yusaku Nakabeppu, Neural stem cell-specific Itpa knockout mouse as a model of human ITPA deficiency, The 13th International Symposium of the Institute Network for Biomedical Sciences joint with the 3rd Symposium of the Inter-University Research Network for Trans-Omics Medicine & the 28th Hot Spring Harbor Symposium, 2018.10.
10. Yusaku Nakabeppu, Sugako Oka, Julio Leon, Nona Abolhassani, Tomomi Ide, Dongchon Kang, Molecular pathophysiology of insulin depletion, mitochondrial dysfunction, and oxidative stress in Alzheimer's disease brain, The 30th International Conference of the Korean Society for Molecular and Cellular Biology, 2018.09, [URL], In normal brain, some neurons in the cortex and hippocampus produce insulin, which modulates glucose metabolism and cognitive functions. Recent progress in Alzheimer’s disease (AD) research revealed that insulin production and signaling are severely impaired in AD brain, thereby resulting in mitochondrial dysfunction and increased oxidative stress. Here, we examined the effects of transgenic expression of human mitochondrial transcriptional factor A (hTFAM) on the pathology of a mouse model of AD (3xTg-AD), because TFAM is known to protect mitochondria from oxidative stress through maintenance of mitochondrial DNA. Expression of hTFAM significantly improved cognitive function, reducing accumulation of both 8-oxoguanine, an oxidized form of guanine, in mitochondrial DNA and intracellular A in 3xTg-AD mice and increasing expression of transthyretin, known to inhibit A aggregation. Next, we found that AD model neurons derived from human induced pluripotent stem cells carrying a mutant PSEN1P117L gene, exhibited mitochondrial dysfunction, accumulation of 8-oxoguanine and single-strand breaks in mitochondrial DNA, and impaired neuritogenesis with a decreased expression of transthyretin. Extracellular treatment with recombinant hTFAM effectively suppressed these deleterious outcomes. Moreover, the treatment increased expression of transthyretin, accompanied by reduction of intracellular A. These results provide new insights into potential novel therapeutic targets..
11. Naoki Haruyama, Kunihiko Sakumi, Atsuhisa Katogi, Daisuke Tsuchimoto, Yusaku Nakabeppu, Accumulation of 8-oxoguanine in nuclear genome of neural progenitors in aged mouse brain causes atrophy of major island of Calleja resulting in locomotor hyperactivity, The 41st Annual Meeting of The Japan Neuroscience Society, 2018.07.
12. Daisuke Tsuchimoto, Yuichiro Koga, Yoshinori Hayashi, Nona Abolhassani, Yasuto Yoneshima, Hiroshi Nakanishi, Yusaku Nakabeppu, Neural stem cell-specific Itpa knockout mouse as a model of human ITPA deficiency, The 41st Annual Meeting of The Japan Neuroscience Society, 2018.07.
13. Nona Abolhassani, Ryohei Ikegami, Naoki Haruyama, Guianfranco Mazzei, Takashi Saito, Takaomi C Saido, Yusaku Nakabeppu, Long-term exposure to high-fat diet significantly exacerbated cognitive deficit in aged AppNL-F/NL-F knock-in mouse model of Alzheimer´s disease along with persistent impaired glucose tolerance, The 41st Annual Meeting of The Japan Neuroscience Society, 2018.07.
14. Yusaku Nakabeppu, Nona Abolhassani, Eiko Ohta, Zijing Sheng, Mizuki Ohno, Daisuke Tsuchimoto, Kunihiko Sakumi, Oxidative DNA damage and Repair in Cancer and Aging, The 14th Japan - Korea Joint Symposium on Cancer and Ageing Research, 2018.06.
15. Yusaku Nakabeppu, Sugako Oka, Julio Leon, Nona Abolhassani, Tomomi Ide, Dongchon Kang, Protection of mitochondrial DNA from oxidative damage effectively blocks the mitochondria-mediated vicious cycle of Alzheimer's disease, Consortium of Biological Sciences 2017, 2017.12.
16. Guianfranco Mazzei, Kunihiko Sakumi, Yusaku Nakabeppu, Impaired hippocampal neurogenesis in APP mouse model of Alzheimer disease., Third International meeting in Bioscience, Young Peruvian Scientist Network, 2017.12.
17. Yusaku Nakabeppu, Naoki Haruyama, Guianfranco Mazzei, Ryouhei Ikegami, Nona Abolhassani, Molecular Pathophysiology of Impaired Glucose Metabolism, Mitochondrial Dysfunction, and Oxidative DNA Damage in Alzheimer's Disease Brain, The 5th Annual World Congress of Geriatrics and Gerontology 2017, 2017.12.
18. Naoki Haruyama, Kunihiko Sakumi, Atsuhisa Katogi, Daisuke Tsuchimoto, Yusaku Nakabeppu, Accumulation of 8-oxoguanine in the nuclei of newly-generated GABAergic neurons in the nucleus accumbens and islands of Calleja contributes to locomotor hyperactivity in aged mice., The 27th Hot Spring Harbor International Symposium, 2017.10, Mammals including humans possess 8-oxo-2’-deoxyguanosine triphosphatase (8-oxo-dGTPase) encoded by MTH1 gene and 8-oxoguanine DNA glycosylase encoded by OGG1 gene, thus minimizing accumulation of 8-oxoguanine in genomic DNA. We investigated correlation between levels of 8-oxoguanine in mouse brains and their locomotor activities during aging from 10 weeks (young), 36 weeks (middle-aged) to 81 weeks (old ) of age, using Mth1/Ogg1-double knockout (TO-DKO) and human MTH1-transgenic (hMTH1-Tg) mice.
First, we found strong nuclear 8-oxoguanine immunoreactivity in hippocampal dentate gyrus and subventricular zone (SVZ), where adult neurogenesis occurs, and in the shell of the nucleus accumbens (NAccSh), especially in middle-aged TO-DKO brains. Among them, the major islands of Calleja (ICj) located in NAccSh, into which a separate mass of cells, referred to as the "ventral migratory mass" migrates from the SVZ to supply newborn GABAergic neurons postnatally, exhibited prominent 8-oxoguanine immunoreactivity. Four weeks after bromodeoxyuridine (BrdU) injection (i. p.), there were significant reduction in number of BrdU-labeled newborn cells in NAccSh + ICj of TO-DKO brains in comparison with wild-type controls. In addition, the number of neurons and volume of ICj were significantly decreased in middle-aged TO-DKO, compared with wild-type mice.
In behavior analyses, we found middle-aged and old TO-DKO, but not young mice were hyperactive in a familiar environment in comparison with wild-type controls. Conversely, middle-aged and old hMTH1-Tg mice were hypoactive. Moreover, the locomotor activities of mice were significantly correlated with both levels of nuclear 8-oxoguanine in NAccSh + ICj and numbers of neurons in ICj.
We concluded that accumulation of nuclear 8-oxoguanine in post-mitotic NAccSh and ICj neurons in the aged mice is a consequence of 8-oxo-dGTP incorporation into the nuclear genomes of neuronal progenitors during their proliferation, thus resulting in their depletion during aging, probably because nuclear 8-oxoguanine is known to induce apoptosis through the process of base excision repair..
19. Naoki Haruyama, Atsuhisa Katogi, Kunihiko Sakumi, Daisuke Tsuchimoto, Yusaku Nakabeppu, Nuclear accumulation of 8-oxoguanine in nucleus accumbens neurons contributes to age-related locomotor hyperactivity in Mth1/Ogg1-double knockout mice.
, 九州大学教育改革シンポジウム2017, 2017.07, Mammals possess 8-oxo-dGTPase encoded by MTH1 gene and 8-oxoguanine DNA glycosylase encoded by OGG1 gene, thus minimizing accumulation of 8-oxoguanine in genomic DNA. Middle-aged and old Mth1/Ogg1-double knockout (TO-DKO) mice were hyperactive in a familiar environment. These abnormal behaviors were correlated with nuclear accumulation of 8-oxoguanine in neurons of the nucleus accumbens shell (NAccSh) and the islands of Calleja (ICj). In the aged TO-DKO brain, the nuclear 8-oxoguanine was detected predominantly in immature neurons present in NAccSh, ICj, and subventricular zone. Number of ΔFOSB-positive neurons is significantly increased in the nucleus accumbens core, suggesting hyperdopaminergic state in NAccCo. .
20. Yusaku Nakabeppu, Oxidative DNA damage and repair in Alzheimer’s disease brain, 6th US-Japan DNA Repair Meeting, 2017.05.
21. Yusaku Nakabeppu, Oxidative DNA damage and repair in carcinogenesis and neurodegeneration, International Symposium on Immune Diversity and Cancer Therapy Kobe 2017, 2017.01, 8-oxoguanine, the most common oxidized base, has been characterized as a natural cause of mutagenesis. Levels of 8-oxoguanine in genomes are maintained very low by coordinated actions of MTH1 hydrolyzing 8-oxo-dGTP formed in nucleotide pool, OGG1 excising 8-oxoguanine opposite cytosine in DNA, and MUTYH excising adenine inserted opposite 8-oxoguanine in template DNA. Studies with mutant mice lacking MTH1, OGG1 and MUTYH, revealed that accumulation of 8-oxoguanine in nuclear genome causes increased occurrence of spontaneous somatic or germline mutations, mainly G to T transversions. The somatic mutations result in carcinogenesis or accelerated aging, and the germline mutations cause genetic alterations of phenotypes and are transmitted to the offspring. Among the three genes, MUTYH exhibits the strongest tumor suppression, probably through induction of p53-dependent cell death. While, we have shown that 8-oxoguanine accumulation in nuclear or mitochondrial DNA in brains under oxidative conditions is highly associated with neurodegeneration, and that MTH1 and OGG1 protect brains by preventing the 8-oxoguanine accumulation, while MUTYH accelerates neurodegeneration. Isolated neurons from wild-type and MTH1/OGG1-deficient mice exhibited efficient neuritogenesis in the presence of antioxidants, however, in the absence of antioxidants MTH1/OGG1-deficient neurons increased 8-oxoguanine accumulation in their mitochondrial DNA, and exhibited significantly poor neuritogenesis, indicating that MUTYH induces neuronal dysfunction when 8-oxogianine accumulated in mitochondrial DNA in neurons. Oxidative stress markedly activated microglia isolated from wild-type but not MUTYH-deficient brains, and only the former significantly induced neuronal death in co-culture experiments. These results indicate that MUTYH induces neuronal dysfunction and microglial activation, independently, and thus accelerates neurodegeneration. These results indicate that MUTYH plays pivotal roles in neuro-inflammatory responses in brain.

References
[1] Ohno, M., Sakumi, K., Fukumura, R., Furuichi, M., Iwasaki, Y., Hokama, M., Ikemura, T., Tsuzuki, T., Gondo, Y., Nakabeppu, Y., 8-oxoguanine causes spontaneous de novo germline mutations in mice, Sci Rep 4 (2014) 4689.
[2] Sheng, Z., Oka, S., Tsuchimoto, D., Abolhassani, N., Nomaru, H., Sakumi, K., Yamada, H., Nakabeppu, Y., 8-Oxoguanine causes neurodegeneration during MUTYH-mediated DNA base excision repair, J Clin Invest 122 (2012) 4344-4361.
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22. Ohno Mizuki, Kunihiko Sakumi, Yusaku Nakabeppu, Regulation of base substitution mutagenesis and chromosome recombination induced by 8-oxoguanine accumulated in the genome, The 39th Annual Meeting of the Molecular Biology Society of Japan, 2016.12.
23. Guianfranco Mazzei, Erika Castillo, Kunihiko Sakumi, Takashi Saito, Takaomi Saido, Yusaku Nakabeppu, Impaired hippocampal neurogenesis in App-knock-in model mice of Alzheimer’s disease, The 39th Annual Meeting of the Molecular Biology Society of Japan, 2016.12.
24. Erika Castillo, Julio Leon, Nona Abolhassani, Guianfranco Mazzei, Kunihiko Sakumi, Takashi Saito, Takaomi Saido, Yusaku Nakabeppu, Comparative gene expression profiling of triple-transgenic 3xTg-AD and APP-knock-in model mice of Alzheimer’s disease, The 46th Annual Meeting of Society for Neuroscience, 2016.11, Alzheimer’s disease (AD) is the major type of senile dementia, but there is no successful treatment until now due to its complexity. To better understand the molecular mechanisms underlying AD pathology, several mouse models have been developed to mimic the main neuropathological hallmarks. In the present study, we performed a comparative gene expression profiling of two different AD model mice: the classical triple-transgenic model mice 3xTg-AD which carry two mutated human transgenes, APP (KM670/671NL) and MAPT (P301L) driven by exogenous Thy1.2 promoter with a knock-in mutation of Psen1 (M146V) that promotes formation of plaques and tangles; and the recently established AD model mice APP NL-G-F with three pathogenic App knock-in mutations (Swedish KM670/671NL, Arctic E693G and Iberian I716F) that promote aggressive amyloidosis under the control of endogenous App promoter. We prepared total RNA from cortex of 12-month-old male mice of each AD model and control, obtained their gene expression profiles using microarray technology and performed a comparative analysis. In both AD models, we observed no significant reduction in expression levels of neuronal markers, but genes involved in neuroprotection (Fos, Nr4a1, Nr4a2, Nr4a3, Egr2) were commonly downregulated. Among 306 significantly altered genes in the 3xTg-AD cortex (fold change < -1.2 or > 1.2, ANOVA p < 0.05), we found genes related to neurological diseases (21), metabolic disorders (21) and immune response (17). In contrast, among 257 altered genes in the APP NL-G-F cortex, the most significantly upregulated genes encode proteins involved in the inflammatory (18) and immune (18) responses (top 5: Cst7, Clec7a, Ccl3l3, Lilrb4), accompanied by a significant upregulation of astrocyte markers (Aqp4, Gfap, S100b) and genes encoding complement components (C1qa, C1qb, C1qc, Tyrobp), as well as alterations in genes related to neurological disease (18) and lipid metabolism (13). The results observed in APP NL-G-F mice suggest that amyloidosis induced by endogenous expression of pathogenic APP protein may cause strong inflammatory/immune responses that would play important roles in AD pathogenesis. Recent reports highlight the contribution of astrocytic activation to neuroinflamation in AD, however the mechanism involved is still unclear. To delineate the astrocytic activation by endogenous β-amyloid, we are now examining the gene expression profiles, biochemical and physiological properties of cultured astrocytes isolated from adult APP NL-G-F..
25. Shunji Nakatake, Yusuke Murakami, Yasuhiso Ikeda, Kota Fujiwara, Takashi Tachibana, Toshio Hisatomi, Shigeo Yoshida, Tatsuro Ishibashi, Yusaku Nakabeppu, Koh -hei Sonoda, Oxidative DNA Damage in Microglia Exacerbates Retinal Inflammation and Degeneration through MUTYH-mediated Base Excision Repair in a Mouse Model of Retinitis Pigmentosa, ARVO 2016 Annual Meeting, 2016.05.
26. Sugako Oka, Nona Abolhassani, Julio Leon, Masaaki Hokama, Masahiro Shijo, Hideomi Hamasaki, Toru Iwaki, Yutaka Kiyohara, Tomomi Ide, Dongchon Kang, Yusaku Nakabeppu, Molecular pathophysiology of insulin depletion, mitochondrial dysfunction and oxidative stress in Alzheimer's disease brain, The 11th International Symposium on Geriatrics and Gerontology, 2016.02, Comparative analyses of gene expression profiles in brains of sporadic Alzheimer’s disease (SAD) patients donated for Hisayama study and a mouse model of AD (3xTg-AD) revealed that genes involved in noninsulin-dependent diabetes mellitus (DM) and obesity were significantly altered in AD brains, as were genes related to psychiatric disorders and AD. Neuronal expression of MET, receptor for HGF known to cooperatively regulate hepatic insulin-signaling and glucose metabolism, and PCSK1, essential for proinsulin processing, was significantly decreased in SAD hippocampi. Expression of AEBP1, known to bind IB and activate NF-B, was highly increased in SAD hippocampal neurons. The alterations in the expression profiles of DM-related genes in SAD were independent of peripheral DM-related abnormalities. These results indicate that altered expression of genes related to DM in SAD brains is a result of AD pathology, which may thereby be exacerbated by peripheral insulin resistance or DM.
The expression profiles also revealed mitochondrial dysfunction and increased oxidative stress in AD brain. Transgenic expression of human TFAM (hTFAM), mitochondrial transcription factor A in 3xTg-AD mice significantly ameliorated mitochondrial dysfunction and oxidative stress resulting in improved cognitive dysfunction and AD pathology. hTFAM expression significantly reduced mitochondrial accumulation of 8-oxoguanine (8-oxoG) in 3xTg-AD brains. In order to evaluate whether 8-oxoG contributes to neurodegeneration in AD, we introduced MTH1 and OGG1 deficiencies, the former hydrolyzes 8-oxo-dGTP and the latter excise 8-oxoG in DNA, thus minimizing 8-oxoG accumulation in DNA, into the 3xTg-AD mice. The 3xTg-AD mice with MTH1/OGG1 deficiencies exhibited severe cognitive dysfunction and neurodegeneration with increased mitochondrial accumulation of 8-oxoG. In contrast, human MTH1 expression in 3xTg-AD mice improved cognitive dysfunction and AD pathology. We previously reported that expression of MTH1 and OGG1 proteins is significantly decreased in SAD brains, thus suggesting that increased 8-oxoG accumulation in mitochondrial DNA exacerbates neurodegeneration in SAD brains..
27. Nona Abolhassani, Masaaki Hokama, Daisuke Saitou, Mikita Suyama, Toru Iwaki, Yutaka Kiyohara, Yusaku Nakabeppu, Characterization of transcript variants expressed in Alzheimer’s disease brain with human transcriptome array and deep RNA sequencing analyses: The Hisayama Study, 2nd Zing Neurodegeneration Conference, 2015.12.
28. Julio Leon, Kunihiko Sakumi, Sugako Oka, Erika Castillo, Yusaku Nakabeppu, 8-Oxoguanine accumulated in mitochondrial DNA disturbs neuritic regeneration of cultured adult mouse cortical neurons under conditions of oxidative stress, 45th Annual Meeting of Society for Neuroscience, 2015.10.
29. Shunji Nakatake, Yusuke Murakami, Yasuhiro Ikeda, Noriko Yoshida, Takashi Tachibana, Toshio Hisatomi, Yusaku Nakabeppu, Tatsuro Ishibashi, MUTYH, a Base Excision Repair Enzyme against Oxidative DNA Damage, Induces Single-strand Break Formation and Mediates Photoreceptor Cell Death in a Mouse Model of Retinitis Pigmentosa, The 8th Joint Meeting of Japan-China-Korea Ophthalmologists, 2015.10.
30. Mizuki Ohno, Noriko Takano, Kunihiko Sakumi, Ryutaro Fukumura, Yuki Iwasaki, Toshimichi Ikemura, Yoichi Gondo, Yusaku Nakabeppu, Yoshimichi Nakatsu, Teruhisa Tsuzuki, The role of MUTYH in the oxidative stress-induced mutagenesis and tumorigenesis in the mouse intestine, The Zing conference on “Genomic Integrity", 2015.08, Germline mutation (GM) generates genetic diversity, and is regarded as a driving force of molecular evolution. Besides, spontaneously occurring somatic mutations (SMs) increase the cancer risk.
To clarify the common cause of spontaneous SMs and GMs in mammals, we focused on the role of oxidative DNA damage and its repair system. 8-Oxoguanine (8-oxoG), a major oxidized form of guanine, is a potent pre-mutagenic lesion that causes G:C to T:A transversions. MUTYH, OGG1, and MTH1 are key enzymes that prevent this mutagenesis. Previously, we showed that oxidative stress dramatically increases SMs and tumor incidence in the intestines of Mutyh-deficient mice.
To assess the influence of 8-oxoG on spontaneous GMs, Mth1, Ogg, and Mutyh triple-knockout (TOY-KO) mice were generated and maintained by intragenerational crosses. In this mouse line, we observed an increased tumor incidence, shortened life span, and reduced litter size. Notably, congenital phenotypic abnormalities were frequently observed in the offspring. This was an expected consequence of the high GM rate. Based on a whole-exome sequencing analysis, we detected an 18-fold increase in the GM rate relative to that of wild-type mice. Most of the GMs detected in TOY-KO mice were G:C to T:A transversions. These data indicate that the 8-oxoG content and the repair system influence the rate of G to T transversions not only in somatic cells but also in germline cells.
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31. Nona Abolhassani, Masaaki Hokama, Daisuke Saitou, Mikita Suyama, Toru Iwaki, Yutaka Kiyohara, Yusaku Nakabeppu, Characterization of transcript variants expressed in Alzheimer´s disease brains with human transcriptome array and deep RNA sequencing analyses: The Hisayama Study, The 38th Annual Meeting of the Japan Neuroscience Society, 2015.07, To identify molecular pathological alterations in Alzheimer´s disease (AD) brains, we had previously performed comparative gene expression profiling with GeneChip Human Gene Array using RNAs prepared from postmortem human brains donated for the Hisayama study. The hippocampi of AD brains showed the most significant alteration in gene expression profile. Genes involved in noninsulin–dependent diabetes mellitus and obesity were significantly altered in both AD brains and the AD mouse model, as were genes related to psychiatric disorders and AD (Hokama M. et al., Cerebral Cortex, 2014). Recently it has been shown that transcript variants of some genes are associated with AD. In the present study, in order to obtain a comprehensive view of the transcriptome in AD, we applied a high throughput GeneChip Human Transcriptome Array (HTA) to the hippocampal RNAs. HTA enables us to identify expression changes at the exon and sub-exon levels, taking into account the diversity of transcript isoforms generated by alternative transcription initiation and splicing. We thus discovered significant altered expression profiles of transcript variants in various genes such as RGS4, PRKCB, MET, PCSK1 and GABRA1, in addition to confirming the significantly altered expression profile found in the previous study. But in particular microarray probes cover small regions and not a full transcript structure. To determine the full structure of transcripts whose change is associated with AD, we also performed deep RNA sequencing using same samples. We will present the altered expression profiles in AD brains revealed by these analyses..
32. Julio Jesus Leon Incio, Kunihiko Sakumi, Sugako Oka, Erika Castillo, Yusaku Nakabeppu, Cortical neurons isolated from adult Mth1/Ogg1-double-knockout mouse exhibit impaired neurite regeneration under conditions of oxidative stress, The 38th Annual Meeting of the Japan Neuroscience Society, 2015.07, Oxidative damage and mitochondrial dysfunction are known to play pivotal roles in aging and neurodegenerative diseases, such as Alzheimer´s disease (AD). AD brains accumulate increased level oxidized base lesions such as 8-oxoguanine (8-oxoG) in both nuclear and mitochondrial DNAs as well as in RNA. MTH1 with an 8-oxo-dGTPase activity hydrolyzes 8-oxo-dGTP to 8-oxodGMP and pyrophosphate in nucleotide pools, while OGG1 with an 8-oxoG DNA glycosylase activity excises 8-oxoG paired with cytosine in DNA, thereby maintaining low levels of 8-oxoG in the cellular DNAs. Our group has reported that Mth1/Ogg1-double knockout (Mth1/Ogg1-DKO) mice are highly vulnerable to 3-nitropropionic acid-induced striatal degeneration with increased accumulation of 8-oxoG in mitochondrial DNA of striatal neurons in comparison to wild-type mice. In the present study, we compared the efficiency of neurite regeneration of adult cortical neurons isolated from adult wild-type and Mth1/Ogg1-DKO brains. We cultured cortical neurons isolated from 15-19 week-old mice and maintained them in medium supplemented with B27 with or without antioxidants for 48h. Regenerating neurites were identified by MAP2-immunofluorescence with confocal imaging. Neuronal populations were classified according to the following criteria: stage 1 neurons lacking neurites, stage 2 with one or more minor neurites, and stage 3 with one neurite at least twice as long as any other. We found similar distributions of cortical neurons isolated from both Mth1/Ogg1-DKO and wild-type mice maintained in medium supplemented with B27 containing antioxidants; about 10% in stage 1, 15 to 20% in stage 2, and 60% in stage 3. However, we found that when the neurons were maintained in medium supplemented with B27 lacking antioxidant, neurons isolated from Mth1/Ogg1-DKO brains exhibited significantly less population in stage 3 (20%), compared to those isolated from wild-type brain (60% in stage 3). Moreover, Mth1/Ogg1-DKO neurons were approximately 50% in stage 2 and 25% in stage 1, while wild-type neurons were about 25% in stage 2 and less than 10% in stage 1. We are now analyzing whether the impaired neurite regeneration in Mth1/Ogg1-DKO neurons is due to mitochondrial dysfunction associated with the accumulation of 8-oxoG in mitochondrial DNA..
33. Atsuhisa Katogi, Hiroko Nomaru, Yoshinori N. Ohnishi, Kunihiko Sakumi, Yusaku Nakabeppu, Characterization of Fosb gene products expressed in various Fosb mutant mice, The 38th Annual Meeting of the Japan Neuroscience Society, 2015.07, Fosb gene products compose AP-1 transcription factors and regulate expression of various genes related to neuronal function. Fosb gene produces two forms of mature transcripts, Fosb and ΔFosb mRNAs because it has an intron-like sequence in exon 4, which allows alternative splicing. Fosb mRNA encodes full-length FOSB and vFOSB, while ΔFosb mRNA encodes ΔFOSB and Δ2ΔFOSB. Δ2ΔFOSB is a product of alternative initiation of translation from Met79 codon in the ΔFosb mRNA. vFOSB is also likely to be a product of an alternative initiation of translation of Fosb mRNA. We have established Fosb-null mice and Fosbd/d mutant mice, the latter expressing only ΔFOSB and Δ2ΔFOSB. Recently, we also established FosbF/F mutant mice expressing only Fosb mRNA. In the present study, we characterized the Fosb gene products expressed in each Fosb mutant mice by 2-D electrophoresis followed by western blotting. We found multiple spots representing FOSB, vFOSB, ΔFOSB and Δ2ΔFOSB, respectively, and we thus considered possible post-translational modifications of each Fosb gene product. Although some of the spots were disappeared after phosphatase treatment, there were still multiple spots remained, suggesting that each Fosb gene product is post-translationally modified in various manners including phosphorylation. We thus analyzed Fosb gene products by mass spectrometry in order to identify post-translational modifications of each Fosb gene product..
34. Kosuke Kajitani, Yusaku Nakabeppu, Yoshihiko Kadoya, Hidenori Horie, Characterization of galectin-1-positive cells in the mouse hippocampus: the relevance of galectin-1 to interneurons, The 38th Annual Meeting of the Japan Neuroscience Society, 2015.07, Galectin-1 (gal-1) is one of several well-studied proteins from the galectin family. It is a 14.5 kDa glycoprotein with a single carbohydrate-binding domain. To examine the distribution and properties of gal-1 in the mouse hippocampus, we performed immunohistochemistry using an anti-gal-1 antibody. We found that most gal-1-positive cells showed both NeuN and β-tubulin III (Tuj-1) immunoreactivity (NeuN: 93%, β-tubulin III: 88%). Furthermore, we determined that 77% of gal-1-positive cells in the mouse hippocampus expressed somatostatin. Additionally, 79% expressed GAD67, 34% expressed parvalbumin, 5% expressed calretinin, 2% expressed calbindin, and 31% expressed neuropeptide Y.
In order to examine whether gal-1 influences the number of interneurons in the mouse hippocampus, we next compared the number of interneuron marker-expressing cells between gal-1 knockout (KO) and wild-type (WT) mice by using stereological counting techniques. We counted the number of somatostatin-, parvalbumin-, and GAD67-positive cells in the hippocampi of both gal-1 KO and WT mice. However, no significant differences were found.
These results indicate that gal-1 is expressed in interneurons that express β-tubulin III, and that it may be a novel marker for interneuron subpopulations in the hippocampus; however, gal-1 does not affect the number of interneurons in the adult mouse hippocampus..
35. Zijing Sheng, Yusaku Nakabeppu, Cranial irradiation causes hippocampal degeneration through accumulation of 8-oxoguanine in mitochondrial DNA in neurons, The 38th Annual Meeting of the Japan Neuroscience Society, 2015.07, 8-Oxoguanine (8-oxoG) is one of the major oxidative base lesions in DNA, and is highly mutagenic because it can pair with adenine as well as cytosine. To counteract oxidative damage to nucleic acids, MTH1 hydrolyzes oxidized purine nucleoside triphosphates, thus sanitizing nucleotide pools. OGG1, an 8-oxoguanine DNA glycosylase, prevents buildup of 8-oxoguanine in both nuclear and mitochondrial genomes.
It has been shown that cranial irradiation during the treatment of malignancies induces cognitive impairments, and oxidative DNA damage has been inferred to be involved in this process. However, the underlying mechanisms responsible for radiation-induced cognitive deficits are largely unknown.
In the present study, we first found that cranial irradiation of Ogg1/Mth1-double knockout (DKO) mice decreased their locomotor activities in open field test, and cognitive impairments were observed in passive avoidance test. We then demonstrated that cranial irradiation caused severe degeneration of hippocampal axons and loss of synapses in the Ogg1/Mth1-DKO mice in comparison to wild-type mice. Furthermore, we confirmed that 8-oxoG accumulated in mitochondrial DNA was significantly increased in both neuronal soma and axons in the Ogg1/Mth1-DKO mice.
Our results indicate that MTH1 and OGG1 play pivotal roles for neuroprotection under cranial irradiation, especially by maintaining mitochondrial DNA integrity in hippocampal neurons, thus providing new mechanistic insights into the cognitive impairments induced by cranial irradiation..
36. Yusuke Yoshii, Taikai Inoue, Takahiro Satou, Masayasu Kojima, Yusaku Nakabeppu, Mami Noda, Neuroprotective effect of hydrogen-water induced ghrelin in Parkinson's disease model animal, The 38th Annual Meeting of the Japan Neuroscience Society, 2015.07, The therapeutic potential of molecular hydrogen (H2) is emerging in a number of human diseases and in their animal models, including in particular Parkinson's disease (PD). We have previously showed that molecular hydrogen (H2) in drinking water reduced dopaminergic neuronal loss in MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-induced PD model mice. We found that (H2) supplementation increased gastric expression mRNA encoding ghrelin, a growth hormone secretagogue, and ghrelin secretion, and that the neuroprotective effect was abolished by either administration of the ghrelin receptor -antagonist, D-Lys3 GHRP-6, or β1-adrenoceptor blocker, atenolol. It had been reported that ghrelin protects dopaminergic neurons via up-regulation of mitochondrial uncoupling protein 2 (UCP2) in substantia nigra, however, we did not observe up-regulation of UCP2 in our PD model mice treated with H2 water. Thus, the neuroprotective effect of ghrelin, whose expression and secretion are enhanced by H2 water in the PD model mice, might be mediated by different mechanism. Neuroprotective potential of ghrelin via parasympathetic nerve and neuroprotective effect of H2 water in ghrelin-knock out mice are currently tested.

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37. Sugako Oka, Julio Leon, Nona Abolhassani, Masaaki Hokama, Toru Iwaki, Yutaka Kiyohara, Dongchon Kang, Yusaku Nakabeppu, Interspecies comparative gene expression profiling revealed impaired insulin production and insulin signaling in Alzheimer's disease brains: The Hisayama Study , The 2015 Alzheimer's Disease Congress, 2015.06, To identify molecular pathological alterations in Alzheimer’s disease (AD) brains, we performed interspecies comparative microarray analyses using RNA prepared from postmortem human brain tissues donated for the Hisayama study, and hippocampal RNAs from the triple-transgenic mouse model of AD (3xTg-AD). We found altered expression of genes involved in insulin production, insulin signaling and mitochondrial function in AD brains. Mitochondrial dysfunction is considered to have a pivotal role for developing AD, we further examined effects of human mitochondrial transcriptional factor A (hTFAM) transgene, which plays important roles to maintain mitochondrial homeostasis, on the pathology of 3xTg-AD mice..
38. Yusaku Nakabeppu, Oxidation of nucleic acids and control mechanisms of spontaneous mutagenesis and tumorigenesis in mammals, The CRUK/MRC Oxford Institute for Radiation Oncology 2015 Seminar Series , 2015.06, For living organisms, the most fundamental biological function is maintaining the integrity of their genomic DNAs harboring the genetic information and transmitting them precisely from cell to cell, as well as from parents to their offspring. The genomic DNA and its precursor nucleotides are always in danger of oxidation by reactive oxygen species (ROS) which are generated both as byproducts of oxidative metabolism and as a consequence of exposure to pathogens, ionizing radiation, chemicals and other environmental factors. Increased accumulation of oxidized bases in genomic DNAs of somatic cells may cause mutations resulting in cancer, while non-lethal mutations in germ lineage cells may cause genetic disorders or result in genetic polymorphisms in populations of sexually reproductive organisms and are thus regarded as a driving force of evolution. Among the four nucleobases, guanine is the most susceptible to oxidation, and its simple oxidized form, 8-oxoguanine (8-oxoG), is one of the major oxidation products in DNA or nucleotides. It is well known that 8-oxoG is a pre-mutagenic lesion because it can pair with adenine as well as cytosine during DNA replication, and causes G to T or A to C base substitutions. To counteract mutagenic potential of 8-oxoG, human and rodents are equipped with three distinct enzymes, MTH1, OGG1 and MUTYH. MTH1 hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP and pyrophosphate, thus avoiding incorporation of 8-oxoG into DNA. OGG1 and MUTYH are DNA glycosylases excising 8-oxoG opposite cytosine and adenine opposite 8-oxoG in DNA, respectively. To evaluate the influence of 8-oxoG on genetic diversity in mammals, we established mutant mice lacking these three genes, and examined levels of 8-oxoG accumulation in their genomes and spontaneous occurrence of heritable mutations. In comparison to wild-type mice, Mth1/Ogg1/Mutyh triple knockout (TOY-TKO) mice accumulated 2 to 4-fold increased levels of 8-oxoG in the nuclear DNA of gonadal cells. Using exome analyses covering 40.9 Mb of mouse transcribed regions, we found increased frequencies of G to T mutations in offspring of TOY-TKO mice at a rate of 2 × 10-7 mutations/base/generation, which is about 200-fold higher incidence found in normal human population. By tracing each mutated allele in the pedigree, we reproduced the appearance, transmission, fixation and disappearance of the spontaneously generated mutations in TOY-TKO mice. Moreover, we found that accumulation of 8-oxoG in the genome of gonadal cells increase meiotic chromosome recombination, thus further enhancing the genomic diversity. Finally, we demonstrated that MUTYH, adenine DNA glycosylase, whose expression is dependent on p53, induces cell death when 8-oxoG highly accumulated in the genomes, thus mediating p53 tumor suppression.

References:
1. Oka, S., Leon, J., Tsuchimoto, D., Sakumi, K. and Nakabeppu, Y. (2014) MUTYH, an adenine DNA glycosylase, mediates p53 tumor suppression via PARP-dependent cell death. Oncogenesis, 3, e121.
2. Ohno, M., Sakumi, K., Fukumura, R., Furuichi, M., Iwasaki, Y., Hokama, M., Ikemura, T., Tsuzuki, T., Gondo, Y. & Nakabeppu, Y. (2014) 8-oxoguanine causes spontaneous de novo germline mutations in mice. Sci Rep 4: 4689.
3. Sheng, Z., Oka, S., Tsuchimoto, D., Abolhassani, N., Nomaru, H., Sakumi, K., Yamada, H. & Nakabeppu, Y. (2012) 8-Oxoguanine causes neurodegeneration during MUTYH-mediated DNA base excision repair. J Clin Invest 122, 4344-4361.
4. Oka, S., Ohno, M., Tsuchimoto, D., Sakumi, K., Furuichi, M. and Nakabeppu, Y. (2008) Two distinct pathways of cell death triggered by oxidative damage to nuclear and mitochondrial DNAs. EMBO J, 27, 421-432.
5. Ohno, M., Miura, T., Furuichi, M., Tominaga, Y., Tsuchimoto, D., Sakumi, K. and Nakabeppu, Y. (2006) A genome-wide distribution of 8-oxoguanine correlates with the preferred regions for recombination and single nucleotide polymorphism in the human genome. Genome Res, 16, 567-575.
5. Sakumi, K., Tominaga, Y., Furuichi, M., Xu, P., Tsuzuki, T., Sekiguchi, M. and Nakabeppu, Y. (2003) Ogg1 knockout-associated lung tumorigenesis and its suppression by Mth1 gene disruption. Cancer Res, 63, 902-905.
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39. Yusaku Nakabeppu, Sugako Oka, Zijing Sheng, Kunihiko Sakumi, MUTYH-dependent programmed cell death triggered by 8-oxoguanine and its implication in tumor suppression and neurodegeneration, 15th International Congress of Radition Research: ICRR2015, 2015.05.
40. Sugako Oka, Ohno Mizuki, Daisuke Tsuchimoto, Kunihiko Sakumi, Yusaku Nakabeppu, Two distinct pathways of cell death triggered by oxidative damage to nuclear and mitochondrial DNAs, BIT’8th, Annual World Cancer Congress-2015, 2015.05.
41. Shunji Nakatake, Yusuke Murakami, Yasuhiro Ikeda, Noriko Yoshida, Takashi Tachibana, Toshio Hisatomi, Yusaku Nakabeppu, Tatsuro Ishibashi, MUTYH, a Base Excision Repair Enzyme against Oxidative DNA Damage, Induces Single-strand Break Formation and Mediates Photoreceptor Cell Death in a Mouse Model of Retinitis Pigmentosa, The Annual Meeting of the Association for Research in Vision and Ophthalmology (ARVO) 2015, 2015.05.
42. Sugako Oka, Julio Leon, Nona Abolhassani, Masaaki Hokama, Toru Iwaki, Yutaka Kiyohara, Dongchon Kang, Yusaku Nakabeppu, Interspecies comparative gene expression profiling revealed impaired insulin production and insulin signaling accompanied by mitochondrial dysfunction in Alzheimer's disease brains: The Hisayama Study, 第88回薬理学会年会, 2015.03.
43. Sugako Oka, Julio Leon, Masaaki Hokama, Toru Iwaki, Yutaka Kiyohara, Dongchon Kang, Yusaku Nakabeppu, Impaired insulin production/signaling accompanied by mitochondrial dysfunction and oxidative stress in Alzheimer's disease brains, Progress 100: Kyushu-U and Stanford-U Joint Research and Education Program:First Symposium: From Genes to Human Diseases, 2015.03.
44. Yusaku Nakabeppu, Sugako Oka, Julio Leon, Nona Abolhassani, Masaaki Hokama, Toru Iwaki, Yutaka Kiyohara, Dongchon Kang, Impaired insulin production and insulin signaling accompanied by mitochondrial dysfunction in Alzheimer's disease brains: The Hisayama Study, 包括型脳科学研究推進支援ネットワーク 冬のシンポジウム, 2014.12, To identify molecular pathological alterations in Alzheimer’s disease (AD) brains, we performed interspecies comparative microarray analyses using RNA prepared from postmortem human brain tissues donated for the Hisayama study, and hippocampal RNAs from the triple-transgenic mouse model of AD (3xTg-AD). The hippocampi of AD brains showed the most significant alteration in gene expression profile. Genes involved in noninsulin-dependent diabetes mellitus (DM) and obesity were significantly altered in both AD brains and the AD mouse model, as were genes related to psychiatric disorders and AD. The altered expression profiles in AD brains were independent of peripheral DM-related abnormalities. Moreover, the altered gene expression profiles in AD brains indicate mitochondrial dysfunction and increased ROS production supporting that mitochondrial dysfunction is considered to have a pivotal role for developing AD.
We thus further examined effects of human mitochondrial transcriptional factor A (hTFAM) transgene on the pathology of 3xTg-AD mice. TFAM is now known to contribute not only in transcription of mitochondrial DNA but also maintenance of mitochondrial DNA, and thus protecting mitochondria from oxidative stress. In the Morris Water Maze test, 13-month-old 3xTg-AD hemizygous mice carrying hemizygous hTFAM transgene exhibited significant improvement of learning and memory deficit compared to 3xTg-AD hemizygous mice. Accumulation of Aβ was markedly decreased in cerebral cortices and hippocampi of the 3xTg-AD/hTFAM mice. Moreover, 3xTg-AD/hTFAM mice exhibited much less accumulation of 8-oxo-dG, an oxidative stress marker, in cerebral cortices and hippocampi in comparison to 3xTg-AD mice which accumulated higher level of 8-oxo-dG. To clarify the mechanism of improvement of AD phenotype by hTFAM, we are currently performing gene expression profiling using hippocampal RNA prepared from these animals. These results will provide the new insight to understand the molecular mechanisms of AD pathology and possible new strategies for the therapy of AD..
45. Teruhisa Tsuzuki, Mizuki Ohno, Noriko Takano, Kenichi Taguchi, Yusaku Nakabeppu, Yasunobu Aoki, Takehiko Nohmi, Yoshimichi Nakatsu, Oxidative stress-induced intestinal tumors in Mutyh-deficient mice treated with low doses of potassium bromate, 4th Asian Conference of Environmental Mutagens, 2014.12, Reactive oxygen species (ROS) are generated in vivo by the exposure of chemicals and ionizing radiation. ROS induce oxidative DNA damages that cause mutagenesis and tumorigenesis in mammals. The antimutagenic activity against oxidative DNA damage appears to be a factor that determines the susceptibility for tumorigenesis among individuals. MUTYH is an enzyme, adenine DNA glycosylase that can remove adenine incorporated opposite to 8-oxo-guanine during DNA replication, and is suppressing the spontaneous mutation. Previously we have established an experimental system for oxidative DNA damage-induced tumorigenesis in the gastrointestinal tract in Mutyh-deficient mice.
To assess the dose-dependent relation between the level of oxidative stress and tumor incidence we performed oxidative stress-induced intestinal tumorigenesis experiments using Mutyh-deficient mice as well as the wild-type mice as a control. Mice were divided into five groups and were received the different doses of potassium bromate; 0, 0.05, 0.1, 0.15, 0.2%, in drinking water for sixteen weeks. No tumor was developed in Mutyh-deficient mice untreated or treated at the dose of 0.05%, whereas a number of tumors were observed in small intestine of all the mice treated at the dose of 0.1% or higher. The average number of tumor per mouse was 8.8, 41.6, 61.8 at the dose of 0.1%, 0.15%, 0.2%, respectively. In contrast, the average number of tumor per mouse was only 0.9 when 0.2% solution, the highest dose applied, was given to wild-type mice. These results suggest that the intestinal tumorigenesis correlates to the level of oxidative stress in Mutyh-deficient mice.
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46. Nona Abolhassani, Massaki Hokama, Toru Iwaki, Yutaka Kiyohara, Yusaku Nakabeppu, Characterization of transcript variants expressed in Alzheimer’s disease brains with human transcriptome array and deep RNA sequencing analyses: The Hisayama Study, 第37回日本分子生物学会年会, 2014.11.
47. Yusaku Nakabeppu, Mizuki Ohno, Sugako Oka, Zijing Sheng, Kunihiko Sakumi, Control mechanisms of genetic diversity and programed cell death induced by 8-oxoguanine in mammals, 9th 3R (Replication, Repair, recombination) symposium, 2014.11, Among the four nucleobases, guanine is the most susceptible to oxidation, and its simple oxidized form, 8-oxoguanine (8-oxoG), is one of the major oxidation products in DNA or nucleotides. It is well known that 8-oxoG is a pre-mutagenic lesion because it can pair with adenine as well as cytosine during DNA replication, and causes G to T or A to C base substitutions. To counteract mutagenic potential of 8-oxoG, human and rodents are equipped with three distinct enzymes, MTH1, OGG1 and MUTYH. MTH1 hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP and pyrophosphate, thus avoiding incorporation of 8-oxoG into DNA. OGG1 and MUTYH are DNA glycosylases excising 8-oxoG opposite cytosine and adenine opposite 8-oxoG in DNA, respectively.
To evaluate the influence of 8-oxoG on genetic diversity in mammals, we established mutant mice lacking these three genes, and examined levels of 8-oxoG accumulation in their genomes and spontaneous occurrence of heritable mutations. In comparison to wild-type mice, Mth1/Ogg1/Mutyh triple knockout (TOY-TKO) mice accumulated 2 to 4-fold increased levels of 8-oxoG in the nuclear DNA of gonadal cells. Using exome analyses covering 40.9 Mb of mouse transcribed regions, we found increased frequencies of G to T mutations in offspring of TOY-TKO mice at a rate of 2 × 10-7 mutations/base/generation, which is about 200-fold higher incidence found in normal human population. By tracing each mutated allele in the pedigree, we reproduced the appearance, transmission, fixation and disappearance of the spontaneously generated mutations in TOY-TKO mice. Moreover, accumulation of 8-oxoG in the genome of gonadal cells increase meiotic chromosome recombination, thus further enhancing the genomic diversity.
We also found that excessive accumulation of 8-oxoG in nuclear or mitochondrial genomes induces cell death, which is involved in cancer suppression or neurodegeneration, and that the cell death is mediated by MUTYH-initiated base excision repair of adenine inserted opposite 8-oxoG during replication.

References:
Ohno, M., Sakumi, K., Fukumura, R., Furuichi, M., Iwasaki, Y., Hokama, M., Ikemura, T., Tsuzuki, T., Gondo, Y. & Nakabeppu, Y. (2014) 8-oxoguanine causes spontaneous de novo germline mutations in mice. Sci Rep 4, 4689.
Nakabeppu, Y. (2014) Cellular Levels of 8-Oxoguanine in either DNA or the Nucleotide Pool Play Pivotal Roles in Carcinogenesis and Survival of Cancer Cells. Int J Mol Sci 15, 12543-12557.
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48. Michel J. Massaad, Daisuke Tsuchimoto, Janet Chou, Toshiro Ohsumi, Jia Zhou, Haifa Jabara, Jennifer Kane, Klaus Schmitz, Markianos Kyriacos, Kumiko Torisu, Yusaku Nakabeppu, Peter Kang, Eliane Choueiry, Andre Megarbane, Masayuki Mizui, George Tsokos, Waleed El-Herz, Luigi Notarangelo, Susan Wallace, Raif S. Geha, THE HUMAN NEI ENDONUCLEASE VIII-LIKE 3 (NEIL3) IS A NOVEL GENE ASSOCIATED WITH THE DEVELOPMENT OF AUTO-ANTIBODIES , 16th Biennial Meeting of the European Society for Immunodeficiency, 2014.10, We identified the genetic cause of a combined immunodeficiency in a consanguineous family with history of severe recurrent infections, autoimmunity, chronic diarrhea, and death.
The patients had normal numbers of T/B cells and normal T cell function. However, B cell proliferation and immunoglobulin production were decreased. Furthermore, the patients had high levels of serum auto-antibodies. Whole genome sequencing (WGS) identified a mutation in a highly conserved residue in the base excision repair enzyme NEIL3. The mutation does not affect protein expression but abolishes enzymatic activity. To determine the effect of loss of NEIL3 function, we studied Neil3-/- mice. Neil3-/- mice had no overt immune defect, however, they had high levels of serum auto-antibodies, and developed autoimmune kidney damage following treatment with the TLR3 ligand polyI:C. We later identified an unrelated asymptomatic individual with the same mutation in NEIL3, and found that she had high levels of serum auto-antibodies. LRBA lies in the same region of homozygosity as NEIL3. Further analysis of the WGS data identified a homozygous duplication of exons 49-53 of LRBA. We confirmed this duplication at the level of mRNA/cDNA, and showed that it resulted in loss of LRBA expression.
We identified NEIL3 as a novel gene associated with the development of auto-antibodies. While the mutations in both NEIL3 and LRBA contribute to the patient’s autoimmunity, the infections and colitis are likely due to the mutation in LRBA. This mutation would have been missed by whole exome sequencing, underlining the importance of WGS for the detection of disease-causing structural variations.
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49. Teruhisa Tsuzuki, Mizuki Ohno, Noriko Takano, Kenichi Taguchi, Yusaku Nakabeppu, Yasunobu Aoki, Takehiko Nohmi, Yoshimichi Nakatsu, Oxidative stress-induced intestinal tumors in Mutyh-deficient mice treated with low doses of potassium bromate, 5th US-Japan DNA Repair Meeting, 2014.10, Reactive oxygen species (ROS) are generated in vivo by the exposure of chemicals and ionizing radiation. ROS induce oxidative DNA damages that cause mutagenesis and tumorigenesis in mammals. The antimutagenic activity against oxidative DNA damage appears to be a factor that determines the susceptibility for tumorigenesis among individuals. MUTYH is an enzyme, adenine DNA glycosylase that can remove adenine incorporated opposite to 8-oxo-guanine during DNA replication, and is suppressing the spontaneous mutation. Previously we have established an experimental system for oxidative DNA damage-induced tumorigenesis in the gastrointestinal tract in Mutyh-deficient mice.
To assess the dose-dependent relation between the level of oxidative stress and tumor incidence we performed oxidative stress-induced intestinal tumorigenesis experiments using Mutyh-deficient mice as well as the wild-type mice as a control. Mice were divided into five groups and were received the different doses of potassium bromate; 0, 0.05, 0.1, 0.15, 0.2%, in drinking water for sixteen weeks. No tumor was developed in Mutyh-deficient mice untreated or treated at the dose of 0.05%, whereas a number of tumors were observed in small intestine of all the mice treated at the dose of 0.1% or higher. The average number of tumor per mouse was 8.8, 41.6, 61.8 at the dose of 0.1%, 0.15%, 0.2%, respectively. In contrast, the average number of tumor per mouse was only 0.9 when 0.2% solution, the highest dose applied, was given to wild-type mice. These results suggest that the intestinal tumorigenesis correlates to the level of oxidative stress in Mutyh-deficient mice.
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50. Yusaku Nakabeppu, Sugako Oka, Zijing Sheng, Kunihiko Sakumi, MUTYH-dependent programed cell death induced by 8-oxoguanine accumulated in cellular DNAs and its implication in tumorigenesis and neruodegeneration, 5th US-Japan DNA Repair Meeting, 2014.10, 8-Oxoguanine, a major oxidized base lesion formed by reactive oxygen species, can pair with adenine as well as cytosine in DNA, thus resulting in G to T transversion mutation or cell death in mammals, if it accumulates in DNA. 8-Oxoguanine can originate as 8-oxo-dGTP, formed in the nucleotide pool, or by direct oxidation of the DNA guanine base. MTH1 with 8-oxo-dGTP hydrolyzing activity, 8-oxoguanine DNA glycosylase (OGG1) an 8-oxoG DNA glycosylase, and MutY homolog (MUTYH) with adenine DNA glycosylase activity, minimize the accumulation of 8-oxoG in DNA: deficiencies in these enzymes increase susceptibility to spontaneous and induced tumorigenesis. As expected, the triple-knockout mice of all three genes exhibit extremely increased incidences of spontaneous tumors in various tissues with significantly shortened life span. Interestingly, Mth1/Ogg1-double knockout mice are rather resistant to such spontaneous tumorigenesis. We found that 8-oxoguanine accumulated in cellular DNAs induces programed cell death dependent on MUTYH-initiated base excision repair. Moreover, we demonstrated that excessive accumulation of 8-oxoG in nuclear or mitochondrial DNAs in brain tissue induces neurodegeneration in which MUTYH plays an essential role..
51. Taikai Inoue, Akio Matsumoto, Megumi Yamafuji, Tomoko Tachibana, Yusaku Nakabeppu, Haruaki Nakaya, Mami Noda, Stomach-brain interaction induced by molecular hydrogen in Parkinson’s disease model animal , 第37回日本神経科学大会, 2014.09.
52. Yusaku Nakabeppu, Control mechanisms of genetic diversity and cell death caused by 8-oxoguanine in mammal, Invited Seminar at University of Maryland, School of Medicine, 2014.09,  .
53. Hiroko Nomaru, Kunihiko Sakumi, Atsuhisa Katogi, Daisuke Tsuchimoto, Yusaku Nakabeppu, Fosb gene products contribute to excitotoxic microglial activation by regulating the expression of complement C5a receptors in microglia, 第37回日本神経科学大会, 2014.09, The Fosb gene encodes subunits of the activator protein-1 transcription factor complex. Two mature mRNAs, Fosb and ΔFosb,encoding full-length FOSB and ΔFOSB proteins respectively, are formed by alternative splicing of FosbmRNA. Fosb products are expressed in several brain regions. Moreover, Fosb-null mice exhibit depressive-like behaviors and adult-onset spontaneous epilepsy, demonstrating important roles in neurological and psychiatric disorders. Study ofFosb products has focused almost exclusively on neurons; their function in glial cells remains to be explored. In this study, we found that microglia express equivalent levels of Fosb and ΔFosb mRNAs to hippocampal neurons and, using microarray analysis, we identified six microglial genes whose expression is dependent on Fosb products. Of these genes, we focused on C5ar1 and C5ar2, which encode receptors for complement C5a. In isolated Fosb-null microglia, chemotactic responsiveness toward the truncated form of C5a was significantly lower than that in wild-type cells. Fosb-null mice were significantly resistant to kainate-induced seizures compared with wild-type mice. C5ar1 mRNA levels and C5aR1 immunoreactivity were increased in wild-type hippocampus 24 hours after kainate administration; however, such induction was significantly reduced in Fosb-null hippocampus. Furthermore, microglial activation after kainate administration was significantly diminished in Fosb-null hippocampus, as shown by significant reductions in CD68 immunoreactivity, morphological change and reduced levels of Il6 and Tnf mRNAs, although no change in the number of Iba-1-positive cells was observed. These findings demonstrate that, under excitotoxicity, Fosb products contribute to a neuroinflammatory response in the hippocampus through regulation of microglial C5ar1 and C5ar2 expression. .
54. Yusaku Nakabeppu, Sugako Oka, Donchong Kang, Expression of human mitochondrial transcriptional factor A (hTFAM) improves cognitive function in Alzheimer’s disease model mice, The 3rd International Conference and Exhibition on Neurology & Therapeutics (Neurology-2014), 2014.09, Mitochondrial dysfunction is considered to have a pivotal role for developing Alzheimer's disease (AD). Accumulation of Amyloid β (Aβ) in neurons induces mitochondrial dysfunction and reactive oxygen species (ROS) production. It has been reported that 8-oxoguanine (8-oxoG), one of the major oxidation products in DNA/RNA and nucleotides, accumulates in AD brain. Oxidative DNA damage especially in mitochondria can lead to synaptic dysfunction and neuronal loss, and thereby causing neurodegenation. In the present study, we examined effects of human mitochondrial transcriptional factor A (hTFAM) transgene on the pathology of a mouse model of AD (3xTg-AD) harboring PS1M146V, APP(Swe), and MAPT(P301L) transgenes. TFAM is now known to contribute not only in transcription of mitochondrial DNA but also its maintenance, and thus protecting mitochondria from oxidative stress. In the Morris Water Maze test, 13-month-old 3xTg-AD hemizygous mice carrying hemizygoushTFAM transgene exhibited significant improvement of learning and memory deficit compared to 3xTg-AD hemizygous mice. Accumulation of Aβ was markedly decreased in cerebral cortices and hippocampi of the 3xTg-AD/hTFAM mice. Moreover, 3xTg-AD/hTFAM mice exhibited much less 8-oxo-dG immunoreactivity in cerebral cortices and hippocampi in comparison to 3xTg-AD mice which accumulated higher level of 8-oxo-dG. To clarify the mechanism of improvement of AD phenotype by hTFAM, we are currently performing gene expression profiling using hippocampal RNA prepared from these animals. These results will provide the new insight to understand the molecular mechanisms of AD pathology and possible new strategies for the therapy of AD..
55. Mami Noda, Akio Matsumoto, Megumi Yamafuji, Taikai Inoue, Tomoko Tachibana, Haruyuki Nakaya, Yusaku Nakabeppu, PROTECTIVE EFFECT OF NEW MEDICAL GAS AGAINST PARKINSON’S DISEASE , International Congress on Neurosciences in Krasnoyarsk, 2014.06, [Aim] Therapeutic applications of molecular hydrogen (H2) , one of medical gases, have been reported in a variety of human diseases and their animal models. Although the mechanism of action of H2 has not been clearly demonstrated, it is assumed that its anti-oxidative properties are likely to underlie therapeutic efficacy. We have previously showed that H2 in drinking water reduced dopaminergic neuronal loss in Parkinson's disease (PD) model mice. However, inhalation of H2 did not remain in brain tissue for several minutes and drinking water with saturated H2 (H2 water) did not increase H2 concentration in striatum. These results may imply that the effect of H2 is an indirect effect. The aim of this study was to investigate the mechanism of action of H2 water.
[Methods] MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-induced PD model mice (C57BL/6J) were used. Saturated H2 water was generated by bubbling H2 gas. Ghrelin expression was tested by quantitative RT-PCR and ELISA. Nigral dopaminergic neurons were counted by stereological and immunological analyses.
[Results] H2 supplementation increases gastric expression of mRNA encoding ghrelin, a growth hormone secretagogue, and ghrelin secretion, which are antagonized by the β1-adrenoceptor blocker, atenolol. Strikingly, the neuroprotective effect of H2 water was abolished by either administration of the ghrelin receptor-antagonist, D-Lys3 GHRP-6, or atenolol.
[Conclusion] The neuroprotective effect of H2 water in PD is mediated by enhanced production of ghrelin. Our findings point to potential, novel strategies for ameliorating pathophysiology in which a protective effect of H2 supplementation has been demonstrated.
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56. Sugako Oka, Julio Leon, Atsuhisa Katogi, Kunihiko Sakumi, Tomomi Ide, Dongchon Kang, Yusaku Nakabeppu, Expression of human mitochondrial transcriptional factor A (hTFAM) improves cognitive function in Alzheimer’s disease model mice, International Meeting on Mitochondrial Pathology (Euromit 2014), 2014.06, Mitochondrial dysfunction is considered to have a pivotal role for developing Alzheimer's disease (AD). Accumulation of amyloid β (Aβ) in cytoplasm induces mitochondrial dysfunction and ROS production. It has been reported that 8-oxoguanine (8-oxoG), one of the major oxidation products in DNA/RNA and nucleotides, accumulates in AD brain. Oxidative DNA damage especially in mitochondria can lead to synaptic dysfunction and neuronal loss, and thereby causing neurodegenation. In the present study, we examined effects of human mitochondrial transcriptional factor A (hTFAM) transgene on the pathology of a mouse model of AD (3xTg-AD) harboring PS1M146V, APP(Swe), and tauP301L transgenes. TFAM is now known to contribute not only in transcription of mitochondrial DNA but also maintenance of mitochondrial DNA, and thus protecting mitochondria from oxidative stress. In the Morris Water Maze test, 13-month-old 3xTg-AD hemizygous mice carrying hemizygous hTFAM transgene exhibited significant improvement of learning and memory deficit compared to 3xTg-AD hemizygous mice. Accumulation of Aβ was markedly decreased in cerebral cortices and hippocampi of the 3xTg-AD/hTFAM mice. 3xTg-AD/hTFAM mice exhibited much less 8-oxo-dG immunoreactivity in cerebral cortices and hippocampi in comparison to 3xTg-AD mice which accumulated higher level of 8-oxo-dG. Moreover, we found that Alzheimer’s disease model human neurons, which were derived from iPS cells with a mutant (P117L) copy of preseninlin-1 introduced, show mitochondrial dysfunction and treatment by recombinant hTFAM significantly improves their function. These results provide the new insights to understand the molecular mechanisms of AD pathology and possible new strategies for the therapy of AD..
57. Mami Noda, Akio Matsumoto, Megumi Yamafuji, Tomoko Tachibana, Yusaku Nakabeppu, Haruyuki Nakaya, Stomach-brain interaction induced by oral ‘hydrogen water’ in Parkinson’s disease model animal., The 2nd Asian Clinical Congress (ACC2), 2014.04, Therapeutic applications of molecular hydrogen (H2) have been reported in a variety of human diseases and their animal models. Although the mechanism of action of H2 has not been clearly demonstrated, it is assumed that its anti-oxidative properties are likely to underlie therapeutic efficacy. Unlike other medical-gas therapy, H2 can be applied in air for inhalation or in solution for drinking, intravenous injection or dialysis. Whereas intravenous injection or dialysis delivers H2 directly into the blood stream, oral H2-supplemented water (H2-water) must be absorbed into the circulation resulting in limited H2 concentrations in the blood and in target organs.
Parkinson's disease (PD) has been a major focus in the field of oxidative stress and disease, because it is thought that degeneration of dopaminergic neurons can be triggered and aggravated by the accumulation of oxidative damage. We have previously showed that H2 in drinking water reduced dopaminergic neuronal loss in MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-induced PD model mice. However, inhalation of H2 did not remain in brain tissue for several minutes and drinking water with saturated H2 (hydrogen water) did not increase H2 concentration in striatum. These results may imply that the effect of H2 is an indirect effect. Here we show that H2 supplementation increases gastric expression of mRNA encoding ghrelin, a growth hormone secretagogue, and ghrelin secretion, which are antagonized by the β1-adrenoceptor blocker, atenolol. Strikingly, the neuroprotective effect of H2 water was abolished by either administration of the ghrelin receptor-antagonist, D-Lys3 GHRP-6, or atenolol. Thus, the neuroprotective effect of H2 water in PD is mediated by enhanced production of ghrelin. Our findings point to potential, novel strategies for ameliorating pathophysiology in which a protective effect of H2 supplementation has been demonstrated..
58. Yusaku Nakabeppu, Mizuki Ohno, Ryutaro Fukumura, Yuki Iwasaki, Toshimichi Ikemura, Yoichi Gondo, Kunihiko Sakumi, Oxidation of nucleic acids and control mechanisms of genetic diversity in mammals, International Symposium on Germline Mutagenesis and Biodiversification, 2014.03, For living organisms, the most fundamental biological function is maintaining the integrity of their genomic DNAs harboring the genetic information and transmitting them precisely from cell to cell, as well as from parents to their offspring. The genomic DNA and its precursor nucleotides are always in danger of oxidation by reactive oxygen species (ROS) which are generated both as byproducts of oxidative metabolism and as a consequence of exposure to pathogens, ionizing radiation, chemicals and other environmental factors. Increased accumulation of oxidized bases in genomic DNAs of somatic cells may cause mutations resulting in cancer, while non-lethal mutations in germ lineage cells may cause genetic disorders or result in genetic polymorphisms in populations of sexually reproductive organisms and are thus regarded as a driving force of evolution. Among the four nucleobases, guanine is the most susceptible to oxidation, and its simple oxidized form, 8-oxoguanine (8-oxoG), is one of the major oxidation products in DNA or nucleotides. It is well known that 8-oxoG is a pre-mutagenic lesion because it can pair with adenine as well as cytosine during DNA replication, and causes G to T or A to C base substitutions. To counteract mutagenic potential of 8-oxoG, human and rodents are equipped with three distinct enzymes, MTH1, OGG1 and MUTYH. MTH1 hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP and pyrophosphate, thus avoiding incorporation of 8-oxoG into DNA. OGG1 and MUTYH are DNA glycosylases excising 8-oxoG opposite cytosine and adenine opposite 8-oxoG in DNA, respectively. To evaluate the influence of 8-oxoG on genetic diversity in mammals, we established mutant mice lacking these three genes, and examined levels of 8-oxoG accumulation in their genomes and spontaneous occurrence of heritable mutations. In comparison to wild-type mice, Mth1/Ogg1/Mutyh triple knockout (TOY-TKO) mice accumulated 2 to 4-fold increased levels of 8-oxoG in the nuclear DNA of gonadal cells. Using exome analyses covering 40.9 Mb of mouse transcribed regions, we found increased frequencies of G to T mutations in offspring of TOY-TKO mice at a rate of 2 × 10-7 mutations/base/generation, which is about 200-fold higher incidence found in normal human population. By tracing each mutated allele in the pedigree, we reproduced the appearance, transmission, fixation and disappearance of the spontaneously generated mutations in TOY-TKO mice. Moreover, we found that accumulation of 8-oxoG in the genome of gonadal cells increase meiotic chromosome recombination, thus further enhancing the genomic diversity.
References:
1. Ohno, M., Miura, T., Furuichi, M., Tominaga, Y., Tsuchimoto, D., Sakumi, K., and Nakabeppu, Y. (2006). A genome-wide distribution of 8-oxoguanine correlates with the preferred regions for recombination and single nucleotide polymorphism in the human genome. Genome Res 16: 567-575.
2. Nakabeppu, Y., Sakumi, K., Sakamoto, K., Tsuchimoto, D., Tsuzuki, T., and Nakatsu, Y. (2006). Mutagenesis and carcinogenesis caused by the oxidation of nucleic acids. Biological Chemistry 387: 373-379..
59. Megumi Yamafuji, Akio Matsumoto, Tomoko Tachibana, Nakabeppu Yusaku, Mami Noda, Haruyuki Nakaya, Drinking ‘hydrogen water’ induces ghrelin secretion and protects dopaminergic neurons in MPTP-induced Parkinson’s disease model mice., 第87回 日本薬理学会年会, 2014.03, The therapeutic potential of molecular hydrogen (H2) is emerging in a number of human diseases and in their animal models, including in particular Parkinson’s disease (PD). We have previously showed that H2 in drinking water reduced dopaminergic neuronal loss in MPTP-induced Parkinson’s disease model mice. However, inhalation of H2 did not remain in brain tissue for several minutes and drinking water with saturated H2 (hydrogen water) did not increase H2 concentration in striatum. These results may imply that the effect of H2 is an indirect effect. Here we show that H2 supplementation increases gastric expression of mRNA encoding ghrelin, a growth hormone secretagogue, and ghrelin secretion, which are antagonized by the β1-adrenoceptor blocker, atenolol. Strikingly, the neuroprotective effect of H2 water was abolished by either administration of the ghrelin receptor-antagonist, D-Lys3 GHRP-6, or atenolol. Thus, the neuroprotective effect of H2 water in PD is mediated by enhanced production of ghrelin. Our findings point to potential, novel strategies for ameliorating pathophysiology in which a protective effect of H2 supplementation has been demonstrated..
60. Zijing Sheng, Sugako Oka, Yasuhiro Ikeda, Margherita Bignami, Yusaku nakabeppu, 8-oxo-dGTP generated in nucleotide pools is a major cause of neurodegeneration under oxidative stress, International symposium "New Frontier of Molecular Neuropathology 2014", 2014.03, Mitochondrial dysfunction and microglial activation are involved in neurodegeneration, and are related to oxidative stress. Activation of calpain, PARP and AIF is known to be involved in various neurodegenerative diseases such as Alzheimer’s disease in which 8-oxoguanine, a major oxidized lesion in DNA, is accumulated in cellular DNA. We demonstrated that accumulation of 8-oxoguanine in mitochondrial DNA of neurons causes calpain-dependent neuronal loss, while its accumulation in nuclear DNA of microglia causes PARP-dependent activation of AIF, resulting in microgliosis. Moreover, we demonstrated that 8-oxoguanine in cellular DNA is primarily derived from 8-oxo-dGTP generated in nucleotide pools under oxidative stress..
61. 大野 みずき, 作見 邦彦, 福村 龍太郎, 岩崎 裕貴, 池村 淑道, 續 輝久, 権藤 洋一, 中別府 雄作, 8-Oxoguanine causes spontaneous de novo germline mutations : a study from the mutator mouse line, SMBE Satellite Meeting / NIG International Symposium: The Causes of Genome Evolution, 2014.03, Spontaneous germline mutation (GM) generates genetic variation and is regarded as a driving force of molecular evolution. Elucidation of the causes and mechanisms of spontaneous GM may bring us closer to a better understanding of genome evolution in mammal.
We focus on the oxidative DNA lesions as an endogenous cause of spontaneous GM in mammals. Among the four bases, guanine is the most susceptible to oxidation, and 8-oxoguanine (8-oxoG) is a major form of oxidized guanine, which is spontaneously and constantly generated by reactive oxygen species in vivo. 8-OxoG is known as a potent pre-mutagenic lesion, because it can pair with adenine as well as cytosine during DNA replication and cause a G:C to T:A transversion mutation. In E. coli, inactivation of any of the genes; MutM, MutT, and MutY, in the system for preventing 8-oxoG-induced mutation leads to a mutator phenotype.
To assess the contribution of 8-oxoG in de novo spontaneous GM in mouse, we generated Mth1/Ogg1/ Mutyh triple knockout (TOY-KO) mouse deficient in 8-oxoG-induced mutation avoidance system. To expect the accumulation of GMs in the progeny, TOY-KO mice were maintained by the intragenerational cross until generation eighth. In this mouse line, we found higher tumor incidence and shorter life span than the control. Moreover, as generation proceeded, we observed the decreased litter size and increased frequency of congenital phenotypic abnormality. By whole exome sequencing analysis, we successfully detected accumulated GMs in the offspring’s genome, which occurred in the mice in ancestral generations.
It's notable that most of mutations were G to T transversion, which were caused by 8-oxoG. The mutation rate per generation was increased approximately 18-fold in this mutator mouse line. These results suggest that 8-oxoG potentially induces de novo spontaneous GMs, and its repair system is effectively suppressing those mutations in wild-type animals to maintain their genome and phenotype stable.
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62. Hiroko Nomaru, Kunihiko Sakumi, Atsuhisa Katogi, Yoshinori N Ohnishisi, Daisuke Tsuchimoto, Yusaku Nakabeppu, Microglial activation by Fosb Gene, International Symposium between Kyushu University Post-Global Centers of Excellence Program and School of Biomedical Sciences, Monash University, Melbourne, Australia, 2014.02, The Fosb gene encodes subunits of the activator protein-1 transcription factor complex. Two types of mature mRNA, Fosb and ∆Fosb encoding full-length FOSB and ∆FOSB proteins, respectively, are formed by alternative splicing of the Fosb gene. Fosb products are expressed in several brain regions. Moreover, Fosb-null mice exhibit depressive-like behaviors and altered seizure activity, demonstrating their important roles in neurological and psychiatric disorders. Study of Fosb products has focused almost on neurons; their function in glial cells remains to be explored. In this study, we found that microglia express equivalent levels of Fosb and ∆Fosb mRNAs as hippocampal neurons, and identified six microglial genes whose expression is dependent on Fosb products using microarray analysis. Of these genes, we focused on C5ar1 and C5ar2, which encode receptors for complement C5a. In isolated Fosb-null microglia, chemotactic responsiveness toward the truncated form of C5a and levels of C5ar1 and C5ar2 mRNAs were significantly lower than those in wild-type. Fosb-null mice were significantly resistant to kainate-induced seizures compared with wild-type. Twenty-four hours after kainate administration, C5ar1 mRNA levels were increased more than eightfold, with increased C5aR1 immunoreactivity, in wild-type hippocampus; however, such induction was significantly diminished in Fosb-null hippocampus. Furthermore, microglial activation after kainate administration was significantly diminished in Fosb-null hippocampus. These findings demonstrate that Fosb products are required for inducing a neuroinflammatory response in hippocampus through the regulation of C5ar1 and C5ar2 expression in microglia..
63. Yasuto Yoneshima, Daisuke Tsuchimoto, Nona Abolhassani, Teruaki Iyama, Kunihiko SakumiI, Naoko Shiomi, Masahiko Mori, Tadahiro Shiomi, Yusaku Nakabeppu, Accumulation of deoxyinosine triphosphate induces mismatch repair-dependent cell growth arrest and instability of genomic DNA, International Symposium between Kyushu University Post-Global Centers of Excellence Program and School of Biomedical Sciences, Monash University, Melbourne, Australia, 2014.02, DNA damage is known to cause genome instability or cellular dysfunction, thus resulting in various disorders. We have demonstrated that damaged nucleotides generated in nucleotide pools, which are incorporated into DNA through DNA replication, are major sources of DNA damage. To minimize incorporation of damaged nucleotides into DNA, organisms are equipped with specific enzymes hydrolyzing such deleterious nucleotides. Deoxyinosine triphosphate (dITP) is a damaged nucleotide generated by oxidative deamination of dATP. We previously reported that inosine triphosphatase (ITPA) and nudix (nucleoside diphosphate linked moiety X)-type motif 16 (NUDT16) hydrolyze dITP or dIDP to dIMP in mammalian cells, and their deficiency causes cell growth arrest (1, 2). In the present study, we analyzed roles of repair systems for DNA containing deoxyinosine (dI) in the cell growth arrest caused by deficiency in ITPA or NUDT16. We found that knock-down of MLH1, an essential gene for DNA mismatch repair (MMR) system, efficiently suppressed the cell growth arrest and the accumulation of single-strand breaks caused by knock-down of NUDT16 in HeLa MR cells. Although MLH1-deficient HCT116 cells did not show any abnormal growth after knock-down of ITPA, H414 cells, which were established by knock-in of wild-type MLH1 allele into the HCT116 cells, again exhibited cell growth arrest after knock-down of ITPA, accompanied by increased single-stranded DNA breaks. We then performed electrophoresis gel mobility shift assay using double-stranded oligo-DNA containing dI and nuclear extract of HeLa MR or H414 cells. Only oligo-DNA containing dI:deoxyguanosine (dG) pair showed a shifted band, which was specifically disappeared in the presence of anti-MSH6 antibody. In summary, these results suggest that MMR complex may recognize dI:dG pairs in DNA, which are generated by replication-dependent incorporation of dITP accumulated in the nucleotide pool, and subsequently incise DNA during the repair process, thus inducing cell growth arrest.

(References)
(1) N. Abolhassani, Nucleic Acids Res. (2010) 38, p2891-2903
(2) T. Iyama, Nucleic Acids Res. (2010) 38, p4834-4843.
64. 中別府 雄作, 大野 みずき, 作見 邦彦, Oxidation of nucleic acids by reactive oxygen species and control mechanisms of genetic diversity in mammals, International Symposium between Kyushu University Post-Global Centers of Excellence Program and School of Biomedical Sciences, Monash University, 2014.02, For living organisms, the most fundamental biological function is maintaining the integrity of their genomic DNAs harboring the genetic information and transmitting them precisely from cell to cell, as well as from parents to their offspring. The genomic DNA and its precursor nucleotides are always in danger of oxidation by reactive oxygen species (ROS) which are generated both as byproducts of oxidative metabolism and as a consequence of exposure to pathogens, ionizing radiation, chemicals and other environmental factors. Increased accumulation of oxidized bases in genomic DNAs of somatic cells may cause mutations resulting in cancer, while non-lethal mutations in germ lineage cells may cause genetic disorders or result in genetic polymorphisms in populations of sexually reproductive organisms and are thus regarded as a driving force of evolution.
Among the four nucleobases, guanine is the most susceptible to oxidation, and its simple oxidized form, 8-oxoguanine (8-oxoG), is one of the major oxidation products in DNA or nucleotides. It is well known that 8-oxoG is a pre-mutagenic lesion because it can pair with adenine as well as cytosine during DNA replication, and causes G to T or A to C base substitutions. To counteract mutagenic potential of 8-oxoG, human and rodents are equipped with three distinct enzymes, MTH1, OGG1 and MUTYH. MTH1 hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP and pyrophosphate, thus avoiding incorporation of 8-oxoG into DNA. OGG1 and MUTYH are DNA glycosylases excising 8-oxoG opposite cytosine and adenine opposite 8-oxoG in DNA, respectively.
To evaluate the influence of 8-oxoG on genetic diversity in mammals, we established mutant mice lacking these three genes, and examined levels of 8-oxoG accumulation in their genomes and spontaneous occurrence of heritable mutations. In comparison to wild-type mice, Mth1/Ogg1/Mutyh triple knockout (TOY-TKO) mice accumulated 2 to 4-fold increased levels of 8-oxoG in the nuclear DNA of gonadal cells. Using exome analyses covering 40.9 Mb of mouse transcribed regions, we found increased frequencies of G to T mutations in offspring of TOY-TKO mice at a rate of 2 × 10-7 mutations/base/generation, which is about 200-fold higher incidence found in normal human population. By tracing each mutated allele in the pedigree, we reproduced the appearance, transmission, fixation and disappearance of the spontaneously generated mutations in TOY-TKO mice. Moreover, we found that accumulation of 8-oxoG in the genome of gonadal cells increase meiotic chromosome recombination, thus further enhancing the genomic diversity.

(References)
(1) Ohno, M., Miura, T., Furuichi, M., Tominaga, Y., Tsuchimoto, D., Sakumi, K., and Nakabeppu, Y. (2006). A genome-wide distribution of 8-oxoguanine correlates with the preferred regions for recombination and single nucleotide polymorphism in the human genome. Genome Res 16: 567-575.
(2) Nakabeppu, Y., Sakumi, K., Sakamoto, K., Tsuchimoto, D., Tsuzuki, T., and Nakatsu, Y. (2006). Mutagenesis and carcinogenesis caused by the oxidation of nucleic acids. Biological chemistry 387: 373-379..
65. Erika Castillo, Julio Leon, 秋本 頼子, 作見 邦彦, 岡 素雅子, 土本 大介, 中別府 雄作, Cytotoxic effects of X-ray irradiation on proliferating and differentiated human neuroblastoma cell line SH-SY5Y, and their modulation by BDNF and inhibitors for CDK5 and calpains, 第36回日本分子生物学会, 2013.12.
66. Hiroko Nomaru, Kunihiko Sakumi, Daisuke Tsuchimoto, Yusaku Nakabeppu, Fosb gene products regulate expression of C5ar1 and C5l2 genes and microglial activation, The 43rd annual meeting of the Society for Neuroscience, 2013.11.
67. Yuko Kobayakawa, Kunihiko Sakumi, Yusaku Nakabeppu, Dual effects of Galectin-1 in amyotrophic lateral screlosis, The 43rd annual meeting of the Society for Neuroscience, 2013.11.
68. Sugako Oka, Julio Leon, Masaaki Hokama, Atsuhisa Katogi, Kunihiko Sakumi, Dongchon Kang, Yusaku Nakabeppu, Expression of human mitochondrial transcriptional factor A (hTFAM) improves cognitive function in Alzheimer’s disease model mice, International Symposium on Mitochondria 2013(第13回日本ミトコンドリア学会), 2013.11.
69. Zijing Sheng, Sugako Oka, Yusaku Nakabeppu, MUTYH-dependent neurodegeneration initiated by mitochondrial accumulation of 8-oxoguanine in neurons is efficiently suppressed by MTH1 and OGG1., 10th Conference of the Asian Society of Mitochondrial Research and Medicine (ASMRM) , 2013.11, Oxidative stress is considered to be important in the etiology of several neurodegenerative disorders, and it has been shown that levels of 8-oxoguanine (8-oxoG), one of the major oxidation products in DNA and nucleotides which can pair with adenine as well as cytosine, are significantly increased in mitochondrial DNA as well as nuclear DNA in the brains of patients with Parkinson’s disease (PD), Alzheimer’s disease (AD) and Huntington’s disease (HD) in comparison to control brains. Mammalian cells are equipped with elaborate means of minimizing accumulation of 8-oxoG in DNA. 8-Oxo-2’-deoxyguanosine triphosphatase (8-oxo-dGTPase) encoded by MTH1 hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP and pyrophosphate in nucleotide pools, thereby avoiding incorporation of 8-oxo-dGMP into DNA. 8-OxoG DNA glycosylase encoded by OGG1 excises 8-oxoG paired with cytosine in DNA, while adenine DNA glycosylase encoded by MUTYH removes the adenine inserted opposite 8-oxoG in template DNA during DNA replication, thus preventing mutagenesis. Expression levels of MTH1, OGG1 and MUTYH are also significantly altered in the brains of such patients, suggesting that their altered expression along with accumulation of 8-oxoG in brain cause neurodegeneration; however, how 8-oxoG and these enzymes are associated with the neurodegenerative process is poorly understood.
Here, we show that the mitochondrial inhibitor 3-nitropropionic acid(3-NP)-treated mutant mice lacking MTH1 and/or OGG1 exhibit severe striatal neurodegeneration, while mutant mice lacking both OGG1 and MUTYH are resistant to the neurodegeneration. 8-OxoG accumulated in mitochondrial DNA of neurons caused calpain-dependent neuronal loss, while delayed nuclear 8-oxoG accumulation in microglia caused poly (ADP-ribose) polymerase-dependent activation of apoptosis-inducing factor, thus exacerbating microgliosis. These separate signaling pathways were initiated by accumulation of single-strand breaks (SSBs) in each type of DNA caused by MUTYH. These results demonstrate that 8-oxoG accumulated in nuclear and mitochondrial DNA is differentially involved in neurodegeneration.
Overexpression of human MTH1 in mouse striatum efficiently abrogates 3-NP-induced striatal degeneration accompanied by effective suppression of 8-oxoG accumulation in the striatum. Mth1/Ogg1-DKO mice exhibited the highest susceptibility to the 3-NP-induced striatal degeneration with the highest levels of 8-oxoG in striatal DNAs. These findings indicate that the major source of 8-oxoG accumulated in DNA are 8-oxo-dGTP generated in nucleotide pool; the former is repaired by OGG1 and the latter is hydrolyzed by MTH1. DNA replication is essential for accumulation of 8-oxoG in the respective DNA, and moreover, insertion of adenine opposite 8-oxoG also depends on replication. Neurons are postmitotic and only mitochondrial DNA but not nuclear DNA is always replicated in neurons in order to support energy essential for maintenance of neuronal functions. 8-OxoG is therefore dominantly accumulated in mitochondrial DNA of neurons under oxidative stress, resulting in SSBs accumulation in mitochondrial DNA during MUTYH-initiated base excision repair (BER) of adenine inserted opposite 8-oxoG. While microglia is mitotic, thus 8-oxoG and SSBs accumulated in nuclear DNA dependent on its replication and MUTYH-initiated BER. Thus, replication of the respective DNAs in neurons and microglia determines which of the two separate signaling pathways must be activated upon accumulation of 8-oxoG under oxidative stress.
We now propose that MUTYH-initiated BER may represent a common mechanism shared among various neurodegenerative diseases. Suppression of MUTYH together with inhibition of calpain and PARP in brain may thus be an efficient strategy for protecting brain under conditions of oxidative stress.

Keywords: oxidative damage, nucleotide pool, base excision repair, Huntington’s disease model

Acknowledgements: This work was supported by grants from JSPS KAKENHI Grant numbers 18300124, 19390114, 22221004, and 22501014.
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70. Sugako Oka, Dongchon Kang, Yusaku Nakabeppu, Expression of human mitochondrial transcriptional factor A (hTFAM) improves cognitive function in Alzheimer’s disease model mice, 2013 Alzheimer's Association International Conference, 2013.07, Mitochondrial dysfunction are is considered to have a pivotal role for developing Alzheimer's disease (AD). It has been reported that amyloid β (Aβ) accumulated in cytoplasm induce mitochondrial dysfunction and ROS production by interacting with amyloid Aβ-binding alcohol dehydrogenase, mitochondrial matrix components. We It previously has been reported that 8-oxoguanine (8-oxoG), one of the major oxidation products in DNA/RNA and nucleotides, accumulates in mitochondrial DNA of AD brain neurons. Oxidative DNA damage especially in mitochondrial DNA can lead to synaptic dysfunction and neuronal cell deathloss, and synaptic dysfunction, and thereby may causecausing neurodegenation. In the present study, we examined the effects of human mitochondrial transcriptional factor A (hTFAM) overexpressiontransgene on the pathology of AD a mouse model of AD mice (3xTg-AD) harboring PS1M146V, APP(Swe), and tauP301L transgenes. TFAM is now known to contribute not only in the replication transcription of mitochondrial DNA but also its maintenance of mitochondrial DNA, and thus protecting DNA mitochondria from oxidative stress. In the Morris Water Maze test, 13-month-old 3xTg-AD hemizygous mice carrying hemizygous hTFAM transgeneTg mice exhibited significantly improvement of learning and memory deficit compared to 3xTgAD hemizygous mice without the hTFAM transgene. Accumulation of Aβ was markedly decreased in cerebral cortices and hippocampi of the 3xTg-AD/hTFAM hemizygous mice. The expression of hTFAM suppressed the increase of the signal against anti-8-oxoG observed in cerebral cortex, hippocampi of 3xTgAD mice. Moreover, 3xTg-AD/hTFAM hemizygous mice exhibited much less 8-oxo-dG immunoreactivity in cerebral cortices and hippocampi in comparison to 3xTgAD hemizygous mice which accumulated higher level of 8-oxo-dG in axonal mitochondria. To clarify the mechanism of improvement of AD phenotype by hTFAM, we are currently performing gene expression profiling using hippocampal RNA prepared from these animals. These results will provide the new insight to understand the molecular mechanisms of AD pathology and possible new strategies for the therapy of AD..
71. Yoriko Akimoto, Sugako Oka, Julio Leon, Yusaku Nakabeppu, Quantitative detection of oxidative DNA damage in brains of the triple transgenic Alzheimer’s disease mouse model, 2013 Alzheimer's Association International Conference, 2013.07, Modified nucleotides are known to cause various biological effects (e.g. cancer, neurodegenerative diseases). 8-oxo-guanine and 8-oxo-adenine are major oxidized products of guanine and adenine, respectively. These modified nucleobases can lead to mutations, altered protein synthesis, or cell death. 8-oxo-guanine is known to pair with adenine and cytosine, thus causing GC to TA or AT to CG transversion mutations. 8-oxo-adenine can form a base pair with cytosine or guanine, thereby it may cause AT to GC transition and AT to CG transversion mutation, respectively. It has been reported that these major oxidized lesions are highly accumulated in the postmortem brain tissues of Alzheimer’s disease patients. In the present study, we focused on the accumulation of 8-oxo-deoxyadenosine and 8-oxo-deoxyguanosine in brains of the triple-transgenic Alzheimer’s disease mouse model (3xTg-AD). Prior to the quantification, we prepared and purified 13C, 15N-labeled 8-oxo-deoxyadenosine as an internal control. We previously found that 8-oxo-deoxyadenosine was effectively generated by X-ray irradiation. 13C, 15N-labeled deoxyadenosine was exposed to X-rays and then 13C, 15N-labeled 8-oxo-deoxyadenosine was separated and purified by HPLC. DNA samples were prepared from hippocampi, cerebral cortices, cerebelli, brain stems and striata of over 100-weeks old non-transgenic control mice and 3xTg-AD homozygous (3xTg-AD-H) mice harboring PS1M146V, APP(Swe), and tauP301L transgenes. The absolute levels of 8-oxo-deoxyadenosine and 8-oxo-deoxyguanosine in each brain region were determined by LC-MS/MS analysis using the stable isotope-labeled internal standards. These results will provide the new insight to understand the mechanisms in the pathogenesis of the Alzheimer’s disease with a mouse model. .
72. Pathophysiology caused by oxidative modification of nucleic acids and protective mechanisms

For living organisms, the most fundamental biological function is maintaining the integrity of their genomic DNAs harboring the genetic information and transmitting them precisely from cell to cell, as well as from parents to their offspring. The genomic DNA and its precursor nucleotides, are always in danger of chemical modification by reactive molecules such as reactive oxygen (ROS) or nitrogen species (RNS), which are produced as byproducts during the oxygen respiration and other normal metabolisms or as true products for host defense or signal transduction. In DNA or nucleotide pools, various chemical modifications of bases and nucleotides such as oxidation, deamination and nitration are induced by the reactive molecules, and such modified nucleic acids may cause mutations or cell death if they are not repaired or eliminated. Mutations may induce cancers, and cell death may be related to various degenerative diseases. In mammals including human, mitochondrion also maintains its genomic DNA as does nucleus in which vast majority of genetic information is maintained as nuclear genome. Mitochondria produce energy essential for maintenance of life by oxygen respiration, however, superoxide anions are always generated through reduction of oxygens by electrons leaked from the electron transport chain. Because highly reactive molecules such as hydrogen peroxides, hydroxyl radicals or peroxynitrites are easily formed from superoxide anions, mitochondria are always exposed to oxidative stress.
While exploring cellular damage caused by chemical modification of nucleotides or DNA as well as protective mechanisms against such damage, we found that 8-oxoguanine (8-oxoG), a common DNA lesion caused by ROS, is associated with not only mutagenesis but also cell death, the former resulting in carcinogenesis, and the latter in tissue degeneration. 8-OxoG accumulated in either nuclear or mitochondrial DNA is recognized by a common sensor molecule, MUTYH once adenine is inserted opposite 8-oxoG during replication, and thus triggering two distinct programs of cell death through activation of various effector molecules, respectively. We recently demonstrated that the two distinct programs of cell death play crucial roles during striatal degeneration induced by 3-nitropropionic acid or retinitis pigmentosa in Pde6b mutant mice. In this symposium, I will present our recent studies on the pathophysiology caused by 8-oxoG accumulated in cellular genomes and protective mechanisms against the damage..
73. Hiroko Nomaru, Kunihiko Sakumi, Noriko Yutsudo, Daisuke Tsuchimoto, Yusaku Nakabeppu, Comprehensive analysis of gene expression regulated by Fosb gene in brain-derived cells, Neuro2013 Joint Conference of: The 36th annual Meeting of the Japan Neuroscience Society The 56th Annual Meeting of the Japanese Society for Neurochemistry The 23rd Annual Meeting of Japanese Neural Network Society, 2013.06, Fosb gene produces two mature transcripts, Fosb and ΔFosb mRNAs by alternative splicing, thus encoding multiple subunits of AP-1 (activator protein-1) transcription factors. ΔFOSB and Δ2ΔFOSB proteins encoded by ΔFosb mRNA lack the C-terminal 101 amino acids of FOSB protein encoded by the Fosb mRNA. It is likely that the Fosb gene products, FOSB, ΔFOSB and Δ2ΔFOSB may differentially modulate the expression of various AP-1 targets. The expression of Fosb is weakly detected in throughout normal brain, especially cerebral cortex and hippocampus, and is highly inducible in response to various brain stimuli. We recently found that Fosb-null mice exhibit depressive behavior and adult-onset epilepsy, while Fosbd/d mutant mice expressing only ΔFOSB and Δ2ΔFOSB exhibit increased locomotor activity.In the present study, we isolated neurons, astrocytes and microglia from cortex and hippocampus and compared the expression levels of Fosb and ΔFosb mRNAs. We found that expression levels of Fosb and ΔFosb mRNAs vary according to types of cells. We then compared gene expression profiles in microglia and astrocytes isolated from wild-type, Fosb-null and Fosbd/d mutant mice by microarray analyses. Among the three mouse lines, 8 genes exhibit significantly different expression levels with fold changes greater than 1.5 in microglia, while expression levels of 24 genes are significantly different in astrocytes. It is noteworthy that only Ercc2 exhibits significantly decreased expression in both microglia and astrocytes derived from Fosb-null and Fosbd/d mutant mice in comparison to wild-type mice. Expression levels of 4 genes including C5ar and Gpr77, C5a receptor genes, were significantly decreased in Fosb-null and Fosbd/d microglia but not in Fosb-null and Fosbd/d astrocyte. In summary, Fosb gene products differentially modulate the expression of their targets in different cell types. .
74. Yuko Kobayakawa, Kunihiko Sakumi, Yusaku Nakabeppu, Dual effects of Galectin-1 in amyotrophic lateral sclerosis, Neuro2013 Joint Conference of: The 36th annual Meeting of the Japan Neuroscience Society The 56th Annual Meeting of the Japanese Society for Neurochemistry The 23rd Annual Meeting of Japanese Neural Network Society, 2013.06, Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease which shows progressive muscle weakness associated with degeneration of motor neurons. Its molecular mechanism is still largely unclear. Galectin-1, a member of the β-galactoside-binding lectin family, expresses in various tissues and has multiple functions such as cell proliferation, cell adhesion, tumor metastasis and apoptosis of activated T cell. It has been shown that reduced form of Galectin-1 exists as a homodimer while its oxidized form exists as a monomer, and each form exerts different effects on cells. The oxidized Galectin-1 is known to promote the axonal regeneration after axotomy of peripheral nerve.
It has been reported that Galectin-1 is accumulated in axonal spheroids of spinal cord, in both sporadic and SOD1 mutant familial ALS patients. Additionally, the oxidized Galectin-1 has been shown to be neuroprotective in a mutant SOD1-Tg mouse model of ALS. We thus examined roles of Galectin-1 in the pathogenesis of ALS by cross-breeding the ALS model mice (SOD1G93A) with Galectin-1 null mice (Lgals1-/-).
First, we elucidated the expression pattern of Galectin-1 in SOD1G93A mice. Galectin-1 is accumulated in axonal spheroids long before disease onset. While after the onset, astrocytes around axons of motor neurons express high level of Galectin-1. We then evaluated effects of Galectin-1 knockout in the SOD1G93A mice. SOD1G93A/Lgals1-/- mice exhibit significantly delayed onset of motor dysfunction in comparison to SOD1G93A/Lgals1+/+ mice. However, disease progression was accelerated in SOD1G93A/Lgals1-/- mice after the onset of motor dysfunction, and there was no difference in survival curve between SOD1G93A/Lgals1-/- mice and SOD1G93A/Lgals1+/+ mice.We thus suggest that Galectin-1 accumulated in the axons of motor neurons promotes neuronal degeneration, however, Galectin-1 expressed in astrocytes at the symptomatic stage is neuroprotective. .
75. Zijing Sheng, Yusaku Nakabeppu, Expression of the defense enzymes MTH1, OGG1 and MUTYH against oxidative damage in nucleic acids in the mouse brain, Neuro2013 Joint Conference of: The 36th annual Meeting of the Japan Neuroscience Society The 56th Annual Meeting of the Japanese Society for Neurochemistry The 23rd Annual Meeting of Japanese Neural Network Society, 2013.06, Oxidative DNA damage has been inferred to be involved in the neurodegenerative diseases as well as brain aging. To counteract oxidative damage to nucleic acids, human and rodents are equipped with three defense enzymes, MTH1, OGG1 and MUTYH. MTH1 hydrolyzes oxidized purine nucleoside triphosphates to the monophosphates, thus sanitizing nucleotide pools. OGG1, an 8-oxoguanine DNA glycosylase, prevents buildup of 8-oxoguanine in both nuclear and mitochondrial genomes. MUTYH, an adenine DNA glycosylase, excises adenine opposite 8-oxoguanine and 2-hydroxyadenine opposite guanine. Using knockout mice of each gene, we have shown that MTH1, OGG1, or MUTYH play different roles in various brain regions such as hippocampus, striatum or substantia nigra under increased oxidative stress (Sheng et al., J Clin Invest, 2012; Yamaguchi et al., Cell Death Differ, 2006). However, their expression and distribution in the mouse brain have yet to be inestigated in detail. In the present study, the expression of MTH1, OGG1 and MUTYH proteins in the mouse brain was examined immunohistochemically with light microscopy (LM), laser scanning confocal microscopy (LSCM) and electron microscopy (EM) . First, we observed that expression of MTH1, OGG1 or MUTYH is abundantly detected in various brain regions, including the striatum, hippocampus, and substantia nigra. LSCM confirmed that various neuronal marker-positive cells express MTH1, OGG1 or MUTYH, respectively. Furthermore, EM revealed that immunogold particles for MTH1, OGG1 or MUTYH, are detected in nuclei, cytoplasm, and mitochondria of neurons, respectively. These results strongly suggest that these defense enzymes contribute to the maintenance of nuclear and mitochondrial genomic integrities in neurons, thus may play important roles in protection of brains from oxidative stress. Our results provide important morphological bases for further understanding of functions of these enzymes in the mouse brain..
76. Yoriko Akimoto, Sugako Oka, Yusaku Nakabeppu, Quantitative detection of oxidative DNA damage in brains of the triple transgenic Alzheimer's disease mouse model, Neuro2013 Joint Conference of: The 36th annual Meeting of the Japan Neuroscience Society The 56th Annual Meeting of the Japanese Society for Neurochemistry The 23rd Annual Meeting of Japanese Neural Network Society, 2013.06, Modified nucleotides are known to cause various biological effects (e.g. cancer, neurodegenerative diseases). 8-oxo-guanine and 8-oxo-adenine are major oxidization products of guanine and adenine, respectively. These modified nucleobases can lead to mutations, altered protein synthesis, or cell death. 8-oxo-guanine is known to pair with adenine and cytosine, thus causing GC to TA or AT to CG transversion mutations. 8-oxo-adenine can form a base pair with cytosine or guanine, thereby it may cause AT to GC transition and AT to CG transversion mutation, respectively. It has been reported that these major oxidized lesions are highly accumulated in the postmortem brain tissues of Alzheimer's disease patients. In the present study, we focused on the accumulation of 8-oxo-deoxyadenosine and 8-oxo-deoxyguanosine in brains of the triple-transgenic Alzheimer's disease mouse model (3xTg-AD). Prior to the quantification, we prepared and purified 13C, 15N-labeled 8-oxo-deoxyadenosine as an internal control. We previously found that 8-oxo-deoxyadenosine was effectively generated by X-ray irradiation. 13C, 15N-labeled deoxyadenosine was exposed to X-rays and then 13C, 15N-labeled 8-oxo-deoxyadenosine was separated and purified by HPLC. DNA samples were prepared from hippocampi, cerebral cortices, cerebelli, brain stems and striata of non-transgenic control mice and 3xTg-AD homozygous (3xTg-AD-H) mice harboring PS1M146V, APP(Swe), and tauP301L transgenes,.The absolute levels of 8-oxo-deoxyadenosine and 8-oxo-deoxyguanosine in each brain region were determined by LC-MS/MS analysis using the stable isotope-labeled internal standards..
77. Kazunori Sango, Shizuka Takaku, Hiroko Yanagisawa, Kazuhiko Watabe, Kunihiko Sakumi, Yusaku Nakabeppu, Francoise Poirier, Hidenori Horie, Toshihiko Kadoya, Involvement of galectin-1 and galectin-3 in GDNF-induced neurite outgrowth from adult rat DRG neurons, Neuro2013 Joint Conference of: The 36th annual Meeting of the Japan Neuroscience Society The 56th Annual Meeting of the Japanese Society for Neurochemistry The 23rd Annual Meeting of Japanese Neural Network Society, 2013.06, Galectin-1 (GAL-1), a member of a family of β-galactoside binding animal lectins, is predominantly expressed in isolectin B4 (IB4)-binding small non-peptidergic (glial cell line-derived neurotrophic factor (GDNF)-responsive) sensory neurons in the sections of adult rat dorsal root ganglia (DRG). We observed that recombinant GDNF (50 ng/ml) significantly enhanced neurite outgrowth and protein expression of GAL-1 in cultured adult rat DRG neurons. These GDNF effects were attenuated by anti-GDNF family receptor (RET) antibody and phosphatidyl inositol-3'-phosphate-kinase (PI3K) inhibitor LY294002, suggesting that the neurite-outgrowth promoting activity of GDNF is attributable, at least partially, to the upregulation of GAL-1 through RET-PI3K pathway. On the contrary, no significant differences were observed between GAL-1 knockout and wild-type mice in DRG neurite outgrowth in the presence or absence of GDNF. Considerable immunohistochemical colocalization of GAL-3 with GAL-1 in DRG sections and GDNF-induced upregulation of GAL-3 in cultured DRG neurons imply the functional redundancy between these galectins..
78. Noriko Yutsudo, Takashi Kamada, Kosuke Kajitani, Hiroko Nomaru, Atsuhisa Katogi, Yoko H. Ohnishi, Yoshinori N. Ohnishi, Kei-ichiro Takase, SAKUMI Kunihiko, Hiroshi Shigeto, Yusaku Nakabeppu, fosB-null mice display impaired adult hippocampal neurogenesis and spontaneous epilepsy with depressive behavior, Neuro2013 Joint Conference of: The 36th annual Meeting of the Japan Neuroscience Society The 56th Annual Meeting of the Japanese Society for Neurochemistry The 23rd Annual Meeting of Japanese Neural Network Society, 2013.06, Patients with epilepsy are at high risk for major depression relative to the general population, and both disorders are associated with changes in adult hippocampal neurogenesis, although the mechanisms underlying disease onset remain unknown. The expression of ΔFosB protein, an alternative splice product of the immediate early gene fosB is known to be induced in neural progenitor cells within the subventricular zone of the lateral ventricles and subgranular zone of the hippocampus following transient forebrain ischemia in the rat brain, and adenovirus-mediated ΔFosB expression can promote neural stem cell proliferation. We recently found that fosB-null mice show increased depressive-like behaviors, thus suggesting impaired neurogenesis in fosB-null mice. We analyzed neurogenesis in the hippocampal dentate gyrus of fosB-null and fosBd/d mice expressing ΔFosB but not FosB, the other alternative splice product of the fosB gene, in comparison with wild-type mice using stereological counting methods, as well as neuropathology, behaviors and gene expression profiles. fosB-null mice but not fosBd/d mice displayed impaired neurogenesis in the adult hippocampus and spontaneous epilepsy. Microarray analysis revealed that genes related to neurogenesis, depression and epilepsy are altered in the hippocampus of fosB-null mice. We therefore concluded that the fosB-null mouse is the first animal model providing a genetic and molecular basis for the comorbidity between depression and epilepsy with abnormal neurogenesis, all of which are caused by loss of a single gene, fosB..
79. Sugako Oka, Dongchon Kang, Yusaku Nakabeppu, Expression of human mitochondrial transcriptional factor A (hTFAM) improves cognitive function in Alzheimer's disease model mice, Neuro2013 Joint Conference of: The 36th annual Meeting of the Japan Neuroscience Society The 56th Annual Meeting of the Japanese Society for Neurochemistry The 23rd Annual Meeting of Japanese Neural Network Society, 2013.06, Mitochondrial dysfunction is considered to have a pivotal role for developing Alzheimer's disease (AD). It has been reported that amyloid β (Aβ) accumulated in cytoplasm induce mitochondrial dysfunction and ROS production by interacting with Aβ-binding alcohol dehydrogenase, mitochondrial matrix components. It has been reported that 8-oxoguanine (8-oxoG), one of the major oxidation products in DNA/RNA and nucleotides, accumulates in AD brain. Oxidative DNA damage especially in mitochondrial DNA can lead to synaptic dysfunction and neuronal loss, and thereby causing neurodegenation. In the present study, we examined effects of human mitochondrial transcriptional factor A (hTFAM) transgene on the pathology of a mouse model of AD (3xTg-AD) harboring PS1M146V, APP(Swe), and tauP301L transgenes. TFAM is now known to contribute not only in transcription of mitochondrial DNA but also maintenance of mitochondrial DNA, and thus protecting mitochondria from oxidative stress. In the Morris Water Maze test, 13-month-old 3xTg-AD hemizygous mice carrying hemizygous hTFAM transgene exhibited significant improvement of learning and memory deficit compared to 3xTgAD hemizygous mice without the hTFAM transgene. Accumulation of Aβ was markedly decreased in cerebral cortices and hippocampi of the 3xTg-AD/hTFAM hemizygous mice. Moreover, 3xTg-AD/hTFAM hemizygous mice exhibited much less 8-oxo-dG immunoreactivity in cerebral cortices and hippocampi in comparison to 3xTgAD hemizygous mice which accumulated higher level of 8-oxo-dG in axonal mitochondria. To clarify the mechanism of improvement of AD phenotype by hTFAM, we are currently performing gene expression profiling using hippocampal RNA prepared from these animals. These results will provide the new insight to understand the molecular mechanisms of AD pathology and possible new strategies for the therapy of AD..
80. Megumi Yamafugi, Kyota Fujita, Margaret Hamner, Nozomi Akimoto, Mizuho A Kido, Yoshinori Tanaka, Yusaku Nakabeppu, Bruce Ransom, Mami Noda, Molecular hydrogen protects against ischemic injury in optic nerves, Neuro2013 Joint Conference of: The 36th annual Meeting of the Japan Neuroscience Society The 56th Annual Meeting of the Japanese Society for Neurochemistry The 23rd Annual Meeting of Japanese Neural Network Society, 2013.06, Background: Molecular hydrogen selectively reduces hydroxyl radicals, the most cytotoxic of reactive oxygen species (ROS). Hydrogen (H2) in drinking water reduced dopaminergic neuronal loss by buffering ROS in MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-treated mice (Fujita et al., 2009). Central nervous system (CNS) white matter (WM) ischemia is an important clinical problem and may produce injury, in part, by ROS-induced mitochondrial dysfunction. Using the mouse optic nerve (MON) WM model, we tested whether hydrogen in drinking water reduced functional WM ischemic injury. Results: A 60 min period of oxygen and glucose deprivation (OGD) caused prompt loss of the compound action potential (CAP) followed by an average 20% recovery. After mice received H2-containing drinking water for 7-10 days, the CAP area did not disappear during ischemia and recovered to a significantly great extent during reperfusion with oxygen and glucose. Immunostaining of axonal neurofilament by SMI-31 labeling also showed significant protection by previous drinking of H2-water. Accumulation of nuclear 8-oxoguanine, a marker of oxidative DNA damage, was observed mainly in oligodendrocytes after OGD. The level of 8-oxoguanine after OGD were significantly reduced in optic nerves from H2-water drinking mice.Conclusions: Our results show that several days of H2 exposure reduced the extent of CNS WM irreversible injury associated with OGD. The importance of these observations is that ischemic protection of myelinated CNS WM took several days to develop, lasted several days and provided partial protection in a novel manner from what has been previously described. These observations raise intriguing therapeutic options..
81. Mami Noda, Kyota Fujita, Margaret Hamner, Chieri Higashi, Megumi Yamafuji, Nozami Akimoto, Mizuho A Kido, Yoshinori Tanaka, Yusaku Nakabeppu, Bruce Ransom, Neuroprotection and slow aging induced by oxidative stress-resistant signaling driven by medical gas, Neuro2013 Joint Conference of: The 36th annual Meeting of the Japan Neuroscience Society The 56th Annual Meeting of the Japanese Society for Neurochemistry The 23rd Annual Meeting of Japanese Neural Network Society, 2013.06, Molecular hydrogen selectively reduces hydroxyl radicals, the most cytotoxic of reactive oxygen species (ROS). Hydrogen (H2) in drinking water reduced dopaminergic neuronal loss in substantia nigra by buffering ROS in Parkinson's Disease model animals. In the brain, oxidative damage in not only gray matter but also white matter (WM) is important clinical problem. Among them, WM ischemia may produce injury, in part, by ROS-induced mitochondrial dysfunction. Using the mouse optic nerve (MON) WM model, H2 in drinking water (H2 water) reduced functional WM ischemic injury, even though the intake of H2 was before starting in vitro experiments. Oxygen and glucose deprivation (OGD) in the perfusing solution as an ischemic condition caused prompt loss of the compound action potential (CAP). After 60 min, MON was reperfused with oxygen and glucose for 3 hours, which produced CAP area recovery only 20% in average. After mice received H2 water for 7-10 days, the CAP area did not disappear during OGD and recovered to a significantly great extent during reperfusion with oxygen and glucose. Immunostaining of axonal neurofilaments also showed significant protection by previous drinking of H2 water. These results show that several days of H2 intake reduced the extent of irreversible injury in MON neurofilaments associated with oxidative stress. The importance of these observations is that neuroprotection against oxidative stress by H2 took several days to develop, lasted several days and provided partial protection in a novel manner from what has been previously described. These observations raise intriguing therapeutic options..
82. Yusaku Nakabeppu, Quality Control of Nucleotide Pools is Essential for Cellular Homeostasis, Invited seminar at Institute of Molecular Cancer Research University of Zurich, Switzerland, 2013.04.
83. Zijing Sheng, Sugako Oka, Daisuke Tsuchimoto, Kunihiko Sakumi, Yusaku Nakabeppu, 8-Oxoguanine in brain causes complex neurodegeneration through DNA repair, Gordon research conference on Oxidative Stress & Disease, 2013.04, 8-Oxoguanine (8-oxoG), a common DNA lesion caused by reactive oxygen species, is associated with carcinogenesis and neurodegeneration. Although the mechanism by which 8-oxoG causes carcinogenesis is well understood, the mechanism by which it causes neurodegeneration is unknown. Here, we report that neurodegeneration is triggered by an adenine-DNA glycosylase (MUTYH)-mediated excision repair of 8-oxoG-paired adenine. Mutant mice lacking 8-oxo-2’-deoxyguanosine triphosphatase (MTH1) and/or 8-oxoguanine DNA glycosylase (OGG1) exhibited severe striatal neurodegeneration, whereas mutant mice lacking MUTYH or OGG1/MUTYH were resistant to neurodegeneration under conditions of oxidative stress. These results indicate that OGG1 and MTH1 are protective, while MUTYH promotes neurodegeneration. We observed that 8-oxoG accumulated in the mitochondrial DNA of neurons and caused calpain-dependent neuronal loss, while delayed nuclear accumulation of 8-oxoG in microglia resulted in poly (ADP-ribose) polymerase (PARP)-dependent activation of apoptosis-inducing factor (AIF) and exacerbated microgliosis. These results revealed that neurodegeneration is a complex process caused by 8-oxoG accumulation in the genomes of neurons and microglia. Different signaling pathways were triggered by the accumulation of single-strand breaks in each type of DNA generated during base excision repair initiated by MUTYH, suggesting that suppression of MUTYH may protect the brain under conditions of oxidative stress..
84. Yusaku Nakabeppu, Zijing Sheng, Sugako Oka, Oxidative damage in brain genomes and neuroprotective mechanisms, 第90回日本生理学会大会, 2013.03, 8-Oxoguanine (8-OxoG), a major oxidized base lesion produced by reactive oxygen species, is associated with various pathological conditions including carcinogenesis and neurodegenerative disorders such as Parkinson’s disease and Alzheimer’s disease. Although the mechanism by which 8-oxoG causes carcinogenesis is well understood, the mechanism by which it causes neurodegeneration is unknown. We recently demonstrated that excision repair of adenine inserted opposite 8-oxoG by adenine DNA glycosylase encoded by Mutyh triggers complex neurodegeneration under oxidative stress. Mutant mice lacking 8-oxo-dGTPase encoded by Mth1 and/or 8-oxoG DNA glycosylase encoded by Ogg1 exhibited severe neurodegeneration, whereas mutant mice lacking Mutyh or Ogg1/Mutyh were resistant to neurodegeneration when mitochondrial neurotoxin, 3-nitropropionic acid was administered. These results indicate that OGG1 and MTH1 protect brain while MUTYH promotes neurodegeneration under oxidative stress. 8-OxoG accumulated in mitochondrial DNA of neurons and caused calpain-dependent neuronal loss, while delayed nuclear accumulation of 8-oxoG in microglia resulted in PARP-dependent activation of apoptosis-inducing factor and exacerbated microgliosis. These results reveal that neurodegeneration under oxidative stress is a complex process caused by 8-oxoG accumulation in the genomes of neurons and microglia in the brain. Different signaling pathways were triggered by the accumulation of single-strand breaks in each type of DNA generated during base excision repair initiated by MUTYH..
85. Yusaku Nakabeppu, Quality Control of Nucleotide Pools is Essential for Cellular Homeostasis, Invited seminar at Istituto Superiore di Sanitá, Roma, Italy, 2013.03.
86. Genome DNA is constantly exposed to reactive oxygen species which are generated by extrinsic factors such as ionizing radiation or chemicals, and intrinsic factors such as cellular respiration. 8-Oxoguanine (8-oxoG) is known to be a major cause of spontaneous mutation because it can pair with not only cytosine but also adenine. Many organisms possess effective system to reduce 8-oxoG-induced mutation. In mouse, Mth1 hydrolyzes 8-oxo-dGTP to mono-phosphate form to prevent the incorporation of 8-oxo-dGTP during DNA replication. Ogg1, 8-oxoG DNA glycosylase, remove 8-oxoG in the genome to prevent accumulation of 8-oxoG. Mutyh remove adenine which incorporates opposite to 8-oxoG in template strand to prevent mispairing.
To elucidate the effect of 8-oxoG in the genome of somatic cell and germ cell, we established a triple knockout mouse line which lacks three genes, Ogg1, Mth1, Mutyh. The mutant mice exhibited a short life-span and early-onset carcinogenesis in multiple organs. We observed apparent increases in neonatal death with occasional congenital abnormalities such as spina bifida. We found hydrocephalus, microphthalmia, white spot and other abnormal phenotypes. The hydrocephalus and white spot were consistent with autosomal dominant transmission. These results suggest that the lacking three genes increase mutation rates not only in somatic cells but also germ cells. We will also present sequence data obtained from genomes of the mutant mouse line..
87. Eiko Ohta, Kunihiko Sakumi, Daisuke Tsuchimoto, Yuka Takiguchi, Yusaku Nakabeppu, 2-OH-ATP as a signal molecule for the oxidative stress in mammalian cells, The 8th 3R Symposium (International Symposium on DNA Replication, Recombination and Repair), 2012.11, 2-Hydroxyl-adenosine triphosphate (2-OH-ATP) is one of oxidized forms of ATP generated under oxidative conditions. MTH1 protein, which is encoded by the Mth1 (Nudt1) gene in mouse and possesses an oxidized purine nucleoside triphosphatase activity, most efficiently hydrolyses 2-OH-ATP among known substrates. We have reported that 2-OH-ATP causes a growth arrest of the Mth1-deficient cells. We hypothesize that 2-OH-ATP acts as a signal molecule under the oxidative stress in mammalian cells. In this scenario, ATP, a most abundant nucleotide in cell, functions as a sensor molecule. Using affymetrix GeneChip® Mouse Gene 1.0 ST Array, we demonstrated that 2-OH-adenosine (2-OH-Ado, a precursor of 2-OH-ATP) alters gene expression profile in the Mth1–deficient cells, and the expression of human MTH1 protein suppresses these alterations caused by 2-OH-Ado. Among the genes affected by 2-OH-Ado, we focus on the Ccne genes (genes for cyclin E). By quantitative PCR analysis, we observed that the level of Ccne2 mRNA started to decrease 1.5 hr after 2-OH-Ado administration, and reached about 10% level of the control after 6 hr. The decrease occurred in a p38 MAPK-dependent manner, because it was suppressed by SB203580, an inhibitor of p38 MAPK. The signaling pathway from 2-OH-ATP to the decreased expression of of Ccne mRNA and cell growth arrest is still under investigation. Because ATP is the most abundant nucleotide in cell, and is required for many kinds of biological processes, a contamination of the modified ATP molecule, such as 2-OH-ATP, may result in an alteration of normal cellular processes. 2-OH-ATP is a good candidate for the signal molecule transmitting the intracellular oxidative stress to the p38-MAPK pathway, and thus causing the cell cycle arrest at G1-S boundary, which guarantees a better condition for DNA replication. .
88. Yoriko Akimoto, Yusaku Nakabeppu, Identification and quantification of radiation-induced modified purine nucleosides, The 8th 3R Symposium (International Symposium on DNA Replication, Recombination and Repair), 2012.11, The radiotherapy is widely used as the effective treatment for malignant tumors. For effective radiotherapy, it is an important principle to induce selective death of neoplastic cells, however, it is also essential to consider effects of radiation on normal cells. It has been considered that DNA double-strand breaks are the most important damage resulting in severe radiation injury during the radiotherapy. On the other hand, effects of radiation on nucleotide pools, which supply precursor nucleotides during DNA and RNA synthesis, have not been considered yet, even though radiation can cause various chemical modifications on the nucleotides by radicals produced during radiolysis of water molecules. Modified nucleotides are known to cause various biological effects (e.g. cancer, neurodegenerative diseases), however, it is largely unknown whether those are involved in exerting the radiation-induced biological effects. In the present study, we focused on the effects of X-ray irradiation on purine nucleosides. We identified and quantified radiation-induced modified purine nucleosides using HPLC-PDA (photodiode array detector) and LC-MS/MS methods, and examined dependencies on both X-ray doses and nucleoside concentrations. In addition to known oxidized purine nucleosides, we found many unknown modified nucleosides after X-ray irradiation. We also irradiated DNA solution, which was extracted from mouse liver, and quantified modified nucleosides. We found that free nucleosides were more susceptible to X-ray induced oxidation than were nucleosides in DNA. These results indicate that nucleotide pools are significantly susceptible to X-ray-induced modification, and may be more important targets of radiation than DNA itself..
89. Yusaku Nakabeppu, Quality control in the nucleotide pools is essential for cellular homeostasis, Invited seminar at Laboratory of Molecular Gerontology, National Institute on Aging, NIH, 2012.04.
90. Yusaku Nakabeppu, Quality control in the nucleotide pools is essential for cellular homeostasis, Invited seminar at National Institute of Environmental Health Science, NIH, 2012.04.
91. Yusaku Nakabeppu, 8-Oxoguanine, a spontaneously oxidized guanine base, promotes somatic and meiotic recombination, thus contributing to carcinogenesis and genomic diversity, Invited seminar at Laboratory of Molecular Biology, National Heart, Lung, and Blood Institute, NIH, 2012.04.
92. MUTYH is a potential mediator of p53 tumor suppression.
93. NUDT16 is a (deoxy)inosine diphosphatase, and its deficiency induces accumulation of single-strand breaks in nuclear DNA and growth arrest.
94. The mechanism of cell death by an oxidized nucleotide, 2-OH-ATP.
95. 8-oxoguanine increases the frequency of meiotic homologous recombination via DNA strand breaks.
96. Genome damage caused by the disruption of nucleotide pool homeostasis under environmental stress and its prevention.
97. Molecular pathologies associated with the disruption of nucleotide pool homeostasis under environmental stress.
98. The mitochondrial toxin, 3-nitropropionic acid induces MUTYH-dependent striatal neurodegeneration with accumulation of 8-oxoguanine which is effectively suppressed by OGG1 and MTH1.
99. Biological effects of 2-OH-ATP on mammalian cells.
100. Ogg1/Mth1/Mutyh triple knockout mice have a mutator phenotype exhibiting frequent hereditary congenital abnormalities.
101. Identification and functional analysis of a novel damaged nucleotide cleaning enzyme, ITPBP2.
102. Hereditary hydrocephalus occurred as a result of mutator phenotype in Ogg1, Mth1, Mutyh triple knockout mice.
103. A programmed cell death triggered by simultaneous accumulation of 8-oxoguanine in both nuclear and mitochondrial DNAs .
104. Oxidative stress-induced tumorigenesis in the small intestine of the mice with defects in DNA repair-related genes..
105. MUTYH triggers two distinct cell death pathways by monitoring 8-oxoguanine in nuclear and mitochondrial DNAs .
106. Introduction of 8-oxo-dGTP provokes A:T to C:G transversion in mammalian cells.
107. Oxidative stress-induced intestinal tumorigenesis in Msh2-deficient mice.
108. 8-Oxoguanine enhances chromosomal recombination and thus contributes genomic diversity.
109. Ogg1/Mth1/Mutyh triple knockout mice have a mutator phenotype exhibiting frequent hereditary congenital abnormalities.
110. Oxidative stress-induced tumorigenesis in the small intestine of Mutator Mutant Mice.
111. Yohei Tominaga, Yasuhiro Ushijima, Daisuke Tsuchimoto, Masaki Mishima, Masahiro Shirakawa, Seiki Hirano, Kunihiko Sakumi, Yusaku Nakabeppu (2004,3/7-12): A germ-line mutation of hMUTYH gene found in patients with autosomal recessive colorectal adenomatous polyposis impairs the protective function of MUTYH preventing APEX1 and OGG1 from inappropriately processing its product, Gordon Research Conference on Mutagenesis and Carcinogenesis (Ventura, CA, USA).
112. Kunihiko Sakumi, Yohei Tominaga, Masato Furuichi, Ping Xu, Teruhisa Tsuzuki, Mutsuo Sekiguchi and Yusaku Nakabeppu (2004, 2/17-22):Ogg1 Knockout-associated Lung Tumorigenesis and Its Suppression by Mth1 Gene Disruption, Keystone symposium on Mouse Models of Human Cancer (Keystone, Colorado, USA).
113. Yusaku Nakabeppu, Daisuke Tsuchimoto, Akimasa Ichinoe, Mizuki Ohno, Hiroo Yamaguchi, Yasuhito Ide, Seiki Hirano, Daisuke Yoshimura, Yohei Tominaga, Masato Furuichi and Kunihiko Sakumi (2003, 11/7): Biological Significance of the Defense Mechanisms against Oxidative Damage in Nucleic Acids Caused by Reactive Oxygen Species: Implication for Carcinogenesis and Neurodegeneration, Biennial Meeting of the Society for Free Radical Research, Asia "Free Radicals in Health and Disease" (Seoul).
114. Daisuke Tsuchimoto, Yasuhito Ide, Manabu Nakashima, Takeshi Watanabe and Yusaku Nakabeppu (2003, 11/12):Establishment and characterization of APEX2 null mice, The 4th International 3R Symposium (Awaji-Yumebutai, Hyogo).
115. Y. Nakatsu, K. Yamauchi, K. Sakamoto, Y. Tominaga, K. Yoshiyama, A. Egashira, S. Kura, K. Sakumi, H. Maki, Y. Nakabeppu & T. Tsuzuki (2003, 11/12):Spontaneous tumorigenesis and mutagenesis in mice with a targeted disruption of the Mutyh gene, The 4th International 3R Symposium (Awaji-Yumebutai, Hyogo).
116. Yusaku Nakabeppu, Daisuke Tsuchimoto, Akimasa Ichinoe, Mizuki Ohno, Hiroo Yamaguchi, Yasuhito Ide, Seiki Hirano, Daisuke Yoshimura, Yohei Tominaga, Masato Furuichi and Kunihiko Sakumi (2003, 11/12) : Biological Significance of the Defense Mechanisms against Oxidative Damage in Nucleic Acids: Implication for Carcinogenesis and Neurodegeneration, The 4th International 3R Symposium (Awaji-Yumebutai, Hyogo).
117. Tsuchimoto, D., Ushijima, Y., Tominaga, Y., Hirano, S., Ichinoe, A., Sakumi, K. and Nakabeppu, Y. (2003, 10/18): Repair mechanism of misincorporated adenine opposite 8-oxoG by mammalian MutY homolog, MUTYH: its relevance to mutagenesis and carcinogenesis, The 76th annual meeting of the Japanese Biochemcal Society (Yokohama, Japan).
118. Hirano, S., Tominaga, T., Ichinoe, A., Ushijima, Y., Tsuchimoto, D., Honda-Ohnishi, Y., Ohtsubo, T., Sakumi, K. and Nakabeppu, Y. (2003, 9/24): A germ-line mutation MUTYH(G382D) found in patients with autosomal recessive colorectal adenomatous polyposis and mutator phenotype, The 75th Annual meeting of the Genetics Soceity of Japan (Sendai, Japan).
119. Yusaku Nakabeppu, Daisuke Tsuchimoto, Yohei Tominaga, Masato Furuichi and Kunihiko Sakumi (2003, 8/21): Oxidation of Nucleic Acids and Carcinogenesis, The Second International Symposium on Redox Life Science (Niseko).
120. Kenji Tamura, Katsuhisa Yamazaki, Kazunori Sugahara, Keikichi Miyata, Yulan Jin, Limei Guo, Hideaki Enzan, Saburo Onishi, Yusaku Nakabeppu, Shigetaka Kitajima, Taro Shuin, and Teijiro Aso (2003, 8/27-8/31):Functional characterization of transcription elongation factor elongin a and identification of a novel exonuclease family member as its interacting partner, Cold Spring Harbor Laboratory Meeting (New York, USA).
121. Yusaku Nakabeppu, Daisuke Tsuchimoto, Akimasa Ichinoe, Mizuki Ohno, Hiroo Yamaguchi, Yasuhito Ide, Seiki Hirano, Daisuke Yoshimura, Yohei Tominaga, Masato Furuichi and Kunihiko Sakumi (2003, 5/27):Biological Significance of the Defense Mechanisms against Oxidative Damage in Nucleic Acids Caused by Reactive Oxygen Species: Implication for Carcinogenesis and Neurodegeneration,The 20th International Kumamoto Medical BioScience Symposium「Redox Biosignaling and Stress Responses」(Kumamoto).
122. Yoshimura T., Oka S., Ohno M., Yamaguchi H., Tsuchimoto D., Ide Y., Tominaga Y., Furuichi M, Sakumi K., Nakabeppu Y. (2003, 2/5):Mechanisms Protecting Genomic Integrity from Damage Caused by Reactive Oxygen Species: Implications for Carcinogenesis and Neurodegeneration, The Asian Society for Mitochondrial Research and Medicine (Seoul).
123. Kazuhiko Tsuruya, Masatomo Taniguchi, Kohsuke Masutani, Makoto Hirakawa, Masanori Tokumoto, Kyoichi Fukuda, Hidetoshi Kanai, Hideki Hirakata, Hidenori Horie, Toshihiko Kadoya, Mitsuo Iida, Yusaku Nakabeppu (2002, 11/1): Possible involvement of galectin-1 (Gal-1) in renal tubular regeneration of cisplatin-induced acute renal failure (ARF), 35th Annual Meeting & Scientific Exposition, The American Society of Nephrology (Philadelphia, PA, USA).
124. Y. Ohnishi, K. Sakumi, T. Miura, K. Yamazaki, Y. Ohnishi, Y. Tominaga, H. Horie, T. Kadoya, Y. Nakabeppu (2002, 11/2): Expression of A Multi-Functional Lectin, Galectin-1 Is Dependent on FosB, 32nd Anual meeting, Society for Neuroscience (Orlando, Florida, USA).
125. Yasunari Sakai, Masato Furuichi, Masayuki Takahashi, Masaki Mishima, Shigenori Iwai, Masahiro Shirakawa, and Yusaku Nakabeppu (2001,11/6):A Molecular Basis for the Selective Recognition of 2-Hydroxy-dATP and 8-Oxo-dGTP by MTH1 Which Is Known to Suppress Spontaneous Carcinogenesis,The 3rd International 3R Symposium(Miki).
126. Masayuki Takahashi, Yasunari Sakai, Hiroyuki Yakushiji, Mutsuo Sekiguchi, Shigenori Iwai, and Yusaku Nakabeppu (2001,11/6):Role of tryptophan residues in the recognition of mutagenic oxidized nucleotides by human antimutator MTH1 protein,The 3rd International 3R Symposium(Miki).
127. Masaki Mishima, Noriyuki Itoh, Yasunari Sakai, Hiroyuki Kamiya, Yusaku Nakabeppu, Masahiro Shiorakawa. (2001,11/6):Structural studies of the human MTH1,The 3rd International 3R Symposium(Miki)..
128. Yusaku Nakabeppu (2001, 10/28):Oxidative damage in nucleic acids caused by reactive oxygen species, and protective mechanisms against the damage,The 8th International Conference on Environmental Mutagens, Satellite meeting (Nara).
129. Hiroyuki Kamiya, Hiroyuki Yakushiji, Yusaku Nakabeppu and Hideyoshi Harashima (2001, 10/27):The human MTH1 protein does not act on damaged dGTPs formed by nitric oxide,The 8th International Conference on Environmental Mutagens, Satellite meeting (Nara).
130. Masaki MISHIMA, Noriyuki ITO, Takahisa IKEGAMI, Yuriko YAMAGATA, Mutsuo SEKIGUCHI, Yusaku NAKABEPPU and Masahiro SHIRAKAWA (2001, 8/20):Tertiary structure of human MTH1 and its interaction with oxidative-damaged DNA precursors, XIX International Conference on Magnetic Resonance in Biological Systems (Florence,Italy).
131. Teijiro Aso, Katsuhisa Yamazaki, Kazunori Sugahara, Deshun Ma, Yusaku Nakabeppu and Shigetaka Kitajima (2001, 8/30):Functional Characterization Of Transcription Elongation Factor Elongin And The Vhl Tumor Suppressor Protein, Cold Spring Harbor Laboratory Meeting (NewYork,USA).
132. Tsuchimoto, D., Sakai, Y., Sakumi, K., Nishioka, K., Sasaki, M., Fujiwara, T. and Nakabeppu, Y. (2001/1/21-1/26): Human APE2 protein is mostly localized in the nuclei and to some extent in the mitochondria, while nuclear APE2 is partly associated with proliferating cell nuclear antigen. Gordon Research Conference on Mammalian DNA Repair (Ventura, California, USA).
133. Y. Nakabeppu, T. Nishioka and K. Sakumi. (2000, 3/3-3/5): FosB and DFosB encoded by alternatively spliced fosB mRNAs initiate cell differentiation. 10th Annual Winternational Symposium on GENES AND DEVELOPMENT (Canadian Society of Biochemistry and Molecular & Cellular Biology) (Banff, Alberta, CANADA).
134. Yusaku Nakabeppu. (2000, 3/10-13): Regulation of Intracellular Localization of Human MTH1, OGG1 and MYH Proteins for Repair of Oxidative DNA Damages. DNA Base Excision Repair Workshop, 2000, Galveston, TX, USA..
135. Yusaku Nakabeppu . (2000, 2/27-3/2): Structural Analysis of Human MTH1 revealed that Biological Significance of an Oxidized Form of Adenine, 2-Hydroxyadenine. Gordon Research Conference on Mutagenesis and Carcinogenesis (Ventura, California, USA).
136. Toshio Ohtsubo, Kenichi Nishioka, Yasuyuki Imaiso, Shigenori Iwai, Hisanobu Oda, Toshiyuki Fujiwara, and Yusaku Nakabeppu. (1999, 11/17): Human MYH protein possesses a novel repair activity for 2-hydroxyadenine in DNA. The 2nd 3R (Replication, Recombination, Repair) Symposium (Miki).
137. Yusaku Nakabeppu . (1999, 9/22): Molecular Genetics and Structural Biology of Human MutT Homolog, MTH1. The First Fujihara International Seminar, (Tokyo, Japan).
138. Nakabeppu, Y. (1999, 2/20-2/21): Molecular mechanisms protecting genomic integrity from dameges caused by reactive oxygen species.The 8th Hot Spring Harbor Symposium (Fukuoka, Japan).
139. Nishioka, K., Ohtsubo, T., Oda, H., Fujiwara, T., Kang, D., Sugimachi, K., and Nakabeppu, Y.(1999, 2/7-2/12): Regulation of expression and intracellular localization of the 8-oxoguanine DNA glycosylases (OGG1 proteins) in human cells.Gordon Research Conference on Mammalian DNA repair (Ventura, California, USA).
140. Nishioka, K., Ohtsubo, T., Oda, H., Fujiwara, T., Kang, D., Sugimachi, K., and Nakabeppu, Y.(1999, 2/22-2/25): Regulation of expression and intracellular localization of the 8-oxoguanine DNA glycosylases (OGG1 proteins) in human cells. The 14th Workshop on "DNA Repair, Recombination and Mutagenesis '99" (Osaka, Japan).
141. Tominaga, Y., Ohtsubo, T., Nishioka, K., Sakumi, K., Tsuzuki, T., Tsukiyama , T., andNakabeppu, Y. (1998, 10/26-10/28): Biological Significance of the Error Avoiding Mechanisms for 8-Oxoguanine in Mammals. The 14th Workshop on DNA Replication (Fukuoka, Japan).
142. Nishioka, K., Ohtsubo, T., Oda, H., Fujiwara, T., Kang, D., Sugimachi, K., and Nakabeppu.Y. (1998, 10/26-10/28): Regulation of expression and intracellular localization of the 8-oxoguanine DNA glycosylases (OGG1 proteins) in human cells. The 14th Workshop on DNA Replication (Fukuoka, Japan).
143. Oda, H., Furuichi, M., Kang, D., Fujiwara, T., and Nakabeppu, Y. (1998, 8/9-8/14): Alternative Splicing and Alternative Translational Initiation of the Human MTH1 transcripts Encoding 8-Oxo-dGTPase. Gordon Research Conference on DNA alteration in transformed cells (New London, New Hampshire, USA).