九州大学 研究者情報
論文一覧
山下 智大(やました ともひろ) データ更新日:2019.04.22

助教 /  薬学研究院 臨床薬学部門


原著論文
1. Tatsuhiro Igawa, Shuhei Kishikawa, Yoshito Abe, Tomohiro Yamashita, Saki Nagai, Mitsunori Shiroishi, Chinatsu Shinozaki, Hiroyuki Tanaka, Hidetoshi Saitoh, Tsuda Makoto, Kazuhide Inoue, Tadashi Ueda, Evidence for detection of rat P2X4 receptor expressed on cells by generating monoclonal antibodies recognizing the native structure, Purinergic Signalling, 10.1007/s11302-019-09646-5, 2019.01, [URL], P2X purinergic receptors are ATP-driven ionic channels expressed as trimers and showing various functions. A subtype, the P2X4 receptor present on microglial cells is highly involved in neuropathic pain. In this study, in order to prepare antibodies recognizing the native structure of rat P2X4 (rP2X4) receptor, we immunized mice with rP2X4’s head domain (rHD, Gln111–Val167), which possesses an intact structure stabilized by S-S bond formation (Igawa and Abe et al. FEBS Lett. 2015), as an antigen. We generated five monoclonal antibodies with the ability to recognize the native structure of its head domain, stabilized by S-S bond formation. Site-directed mutagenesis revealed that Asn127 and Asp131 of the rHD, in which combination of these amino acid residues is only conserved in P2X4 receptor among P2X family, were closely involved in the interaction between rHD and these antibodies. We also demonstrated the antibodies obtained here could detect rP2X4 receptor expressed in 1321N1 human astrocytoma cells..
2. Shota Yamamoto, Tomohiro Yamashita, Mayu Ito, Jose Manuel Martinez Caaveiro, Nobuaki Egashira, Hidetoshi Saitoh, Tsuda Makoto, New pharmacological effect of fulvestrant to prevent oxaliplatin-induced neurodegeneration and mechanical allodynia in rats, International Journal of Cancer, 10.1002/ijc.32043, 2018.12, [URL], Oxaliplatin, which is widely used as chemotherapy for certain solid cancers, frequently causes peripheral neuropathy. Commonly described neuropathic symptoms include aberrant sensations such as mechanical allodynia (hypersensitivity to normally innocuous stimuli). Although oxaliplatin neuropathy is a dose-limiting toxicity, there are no established preventive strategies available at present. By screening several sets of small-molecule chemical libraries (more than 3,000 compounds in total) using a newly established in vitro high-throughput phenotypic assay, we identified fulvestrant, a clinically approved drug for the treatment of breast cancer in postmenopausal women, as having a protective effect on oxaliplatin-induced neuronal damage. Furthermore, histological and behavioural analyses using a rat model of oxaliplatin neuropathy demonstrated the in vivo efficacy of fulvestrant to prevent oxaliplatin-induced axonal degeneration of the sciatic nerve and mechanical allodynia. Furthermore, fulvestrant did not interfere with oxaliplatin-induced cytotoxicity against cancer cells. Thus, our findings reveal a previously unrecognised pharmacological effect of fulvestrant to prevent oxaliplatin-induced painful peripheral neuropathy without impairing its cytotoxicity against cancer cells and may represent a novel prophylactic option for patients receiving oxaliplatin chemotherapy..
3. Tomohiro Yamashita, Tsuda Makoto, Hidetoshi Saitoh, Kazuhide Inoue, Green Pharma
A New Strategy for Drug Discovery in Academia by Targeting Glial Cells and ATP Receptors, Yakugaku Zasshi, 10.1248/yakushi.17-00211-1, 138, 8, 1027-1031, 2018.01, [URL],  Neuropathic pain associated with cancer, diabetic neuropathy, and postherpetic neuralgia is a type of intractable chronic pain characterized by mechanical allodynia and abnormal pain hypersensitivity evoked by innocuous stimuli. However, this disorder has no specific treatment. We previously showed that the purinergic receptor P2X4 (P2X4R), a subtype of ATP-gated nonselective cation channels, is highly upregulated in spinal microglia after peripheral nerve injury, and blocking the function of P2X4R reverses mechanical allodynia. In the present study, we screened a chemical library of 1979 clinically approved compounds (a gift from the Drug Discovery Initiative at the University of Tokyo) aimed at achieving "Eco-Pharma," which refers to seeking new effects of existing drugs. We demonstrated that duloxetine, a serotonin and noradrenaline reuptake inhibitor, has an inhibitory effect on rat and human P2X4R. In rat primary cultured microglial cells, duloxetine also inhibited P2X4R-mediated responses. Moreover, intrathecal administration of duloxetine in a model of neuropathic pain reversed nerve injury-induced mechanical allodynia. Based on those results, we suggest that the inhibition of P2X4R expressed in microglial cells may be involved in the antiallodynic effect of duloxetine in neuropathic pain. Furthermore, in this review, we discuss a new strategy for drug discovery called "Green Pharma" (a merger of "Eco-Pharma" and "Green chemistry" and referring to the development of eco-friendly pharmaceuticals)..
4. Tsuda Makoto, Satoshi Ishii, Takahiro Masuda, Shigeo Hasegawa, Koji Nakamura, Kenichiro Nagata, Tomohiro Yamashita, Hidemasa Furue, Hidetoshi Saitoh, Megumu Yoshimura, Schuichi Koizumi, Takao Shimizu, Kazuhide Inoue, Reduced pain behaviors and extracellular signal-related protein kinase activation in primary sensory neurons by peripheral tissue injury in mice lacking platelet-activating factor receptor, Journal of Neurochemistry, 10.1111/j.1471-4159.2007.04796.x, 102, 5, 1658-1668, 2007.09, [URL], Peripheral tissue injury causes the release of various mediators from damaged and inflammatory cells, which in turn activates and sensitizes primary sensory neurons and thereby produces persistent pain. The present study investigated the role of platelet-activating factor (PAF), a phospholipid mediator, in pain signaling using mice lacking PAF receptor (pafr-/- mice). Here we show that pafr-/- mice displayed almost normal responses to thermal and mechanical stimuli but exhibit attenuated persistent pain behaviors resulting from tissue injury by locally injecting formalin at the periphery as well as capsaicin pain and visceral inflammatory pain without any alteration in cytoarchitectural or neurochemical properties in dorsal root ganglion (DRG) neurons and a defect in motor function. However, pafr-/- mice showed no alterations in spinal pain behaviors caused by intrathecally administering agonists for N-methyl-d-aspartate (NMDA) and neurokinin1 receptors. A PAFR agonist evoked an intracellular Ca2+ response predominantly in capsaicin-sensitive DRG neurons, an effect was not observed in pafr-/- mice. By contrast, the PAFR agonist did not affect C- or Aδ-evoked excitatory post-synaptic currents in substantia gelatinosa neurons in the dorsal horn. Interestingly, mice lacking PAFR showed reduced phosphorylation of extracellular signal-related protein kinase (ERK), an important kinase for the sensitization of primary sensory neurons, in their DRG neurons after formalin injection. Furthermore, U0126, a specific inhibitor of the ERK pathway suppressed the persistent pain by formalin. Thus, PAFR may play an important role in both persistent pain and the sensitization of primary sensory neurons after tissue injury..
5. Kenichiro Nagata, Toshiyasu Imai, Tomohiro Yamashita, Tsuda Makoto, Hidetoshi Saitoh, Kazuhide Inoue, Antidepressants inhibit P2X4 receptor function
A possible involvement in neuropathic pain relief, Molecular Pain, 10.1186/1744-8069-5-20, 5, 2009.04, [URL], Background: Neuropathic pain is characterized by pain hypersensitivity to innocuous stimuli (tactile allodynia) that is nearly always resistant to known treatments such as non-steroidal anti-inflammatory drugs or even opioids. It has been reported that some antidepressants are effective for treating neuropathic pain. However, the underlying molecular mechanisms are not well understood. We have recently demonstrated that blocking P2X4 receptors in the spinal cord reverses tactile allodynia after peripheral nerve injury in rats, implying that P2X4 receptors are a key molecule in neuropathic pain. We investigated a possible role of antidepressants as inhibitors of P2X4 receptors and analysed their analgesic mechanism using an animal model of neuropathic pain. Results: Antidepressants strongly inhibited ATP-mediated Ca2+ responses in P2X4 receptor-expressing 1321N1 cells, which are known to have no endogenous ATP receptors. Paroxetine exhibited the most powerful inhibition of calcium influx via rat and human P2X4 receptors, with IC50 values of 2.45 μM and 1.87 μM, respectively. Intrathecal administration of paroxetine produced a striking antiallodynic effect in an animal model of neuropathic pain. Co-administration of WAY100635, ketanserin or ondansetron with paroxetine induced no significant change in the antiallodynic effect of paroxetine. Furthermore, the antiallodynic effect of paroxetine was observed even in rats that had received intrathecal pretreatment with 5,7-dihydroxytryptamine, which dramatically depletes spinal 5-hydroxytryptamine. Conclusion: These results suggest that paroxetine acts as a potent analgesic in the spinal cord via a mechanism independent of its inhibitory effect on serotonin transporters. Powerful inhibition on P2X4 receptors may underlie the analgesic effect of paroxetine, and it is possible that some antidepressants clinically used in patients with neuropathic pain show antiallodynic effects, at least in part via their inhibitory effects on P2X4 receptors..
6. Emika Toyomitsu, Tsuda Makoto, Tomohiro Yamashita, Hidetoshi Saitoh, Yoshitaka Tanaka, Kazuhide Inoue, CCL2 promotes P2X4 receptor trafficking to the cell surface of microglia, Purinergic Signalling, 10.1007/s11302-011-9288-x, 8, 2, 301-310, 2012.06, [URL], P2X4 receptors (P2X4Rs), a subtype of the purinergic P2X family, play important roles in regulating neuronal and glial functions in the nervous system. We have previously shown that the expression of P2X4Rs is upregulated in activated microglia after peripheral nerve injury and that activation of the receptors by extracellular ATP is crucial for maintaining nerve injury-induced pain hypersensitivity. However, the regulation of P2X4R expression on the cell surface of microglia is poorly understood. Here, we identify the CC chemokine receptor CCR2 as a regulator of P2X4R trafficking to the cell surface of microglia. In a quantitative cell surface biotinylation assay, we found that applying CCL2 or CCL12, endogenous ligands for CCR2, to primary cultured microglial cells, increased the levels of P2X4R protein on the cell surface without changing total cellular expression. This effect of CCL2 was prevented by an antagonist of CCR2. Time-lapse imaging of green fluorescent protein (GFP)-tagged P2X4R in living microglial cells showed that CCL2 stimulation increased the movement of P2X4R-GFP particles. The subcellular localization of P2X4R immunofluorescence was restricted to lysosomes around the perinuclear region. Notably, CCL2 changed the distribution of lysosomes with P2X4R immunofluorescence within microglial cells and induced release of the lysosomal enzyme β-hexosaminidase, indicating lysosomal exocytosis. Moreover, CCL2-stimulated microglia enhanced Akt phosphorylation by ATP applied extracellularly, a P2X4R-mediated response. These results indicate that CCL2 promotes expression of P2X4R protein on the cell surface of microglia through exocytosis of P2X4R-containing lysosomes, which may be a possible mechanism for pain hypersensitivity after nerve injury..
7. Tatsuhiro Igawa, Sadayuki Higashi, Yoshito Abe, Takatoshi Ohkuri, Hiroyuki Tanaka, Satoshi Morimoto, Tomohiro Yamashita, Tsuda Makoto, Kazuhide Inoue, Tadashi Ueda, Preparation and characterization of a monoclonal antibody against the refolded and functional extracellular domain of rat P2X4 receptor, Journal of Biochemistry, 10.1093/jb/mvs143, 153, 3, 275-282, 2013.03, [URL], The P2X4 purinergic receptor is a key molecule in neuropathic pain, particularly in the allodynia after peripheral nerve injury. We therefore sought to establish an anti-P2X4 receptor monoclonal antibody that would be useful for detection and characterization of the P2X4 receptor. We first prepared the refolded extracellular domain of the rat P2X4 receptor expressed in Escherichia coli. Then, we established a B-cell hybridoma producing the monoclonal antibody for the head domain of the rat P2X4 receptor with strict recognition, including S-S bond formation. In addition, we succeeded in the detection and immune precipitation of rat P2X4 receptor molecules on cultured cells. As the antibody specifically binds to the rat P2X4 receptor molecule, it is expected that the established monoclonal antibody will be applicable as a tool for detecting increasing expression levels of the P2X4 receptor molecule accompanied with increasing intensity of neuropathic pain..
8. Ryoichi Tashima, Satsuki Mikuriya, Daisuke Tomiyama, Miho Shiratori, Tomohiro Yamashita, Yuta Koro, Hidetoshi Saitoh, Kazuhide Inoue, Tsuda Makoto, Bone marrow-derived cells in the population of spinal microglia after peripheral nerve injury, Scientific Reports, 10.1038/srep23701, 6, 2016.03, [URL], Accumulating evidence indicates that peripheral nerve injury (PNI) activates spinal microglia that are necessary for neuropathic pain. Recent studies using bone marrow (BM) chimeric mice have reported that after PNI, circulating BM-derived cells infiltrate into the spinal cord and differentiate into microglia-like cells. This raises the possibility that the population of spinal microglia after PNI may be heterogeneous. However, the infiltration of BM cells in the spinal cord remains controversial because of experimental adverse effects of strong irradiation used for generating BM chimeric mice. In this study, we evaluated the PNI-induced spinal infiltration of BM-derived cells not only by irradiation-induced myeloablation with various conditioning regimens, but also by parabiosis and mice with genetically labelled microglia, models without irradiation and BM transplantation. Results obtained from these independent approaches provide compelling evidence indicating little contribution of circulating BM-derived cells to the population of spinal microglia after PNI..
9. Yuta Matsumura, Tomohiro Yamashita, Atsushi Sasaki, Eriko Nakata, Keita Kohno, Takahiro Masuda, Hidetoshi Saitoh, Toshiyasu Imai, Yasushi Kuraishi, Tsuda Makoto, Kazuhide Inoue, A novel P2X4 receptor-selective antagonist produces anti-allodynic effect in a mouse model of herpetic pain, Scientific Reports, 10.1038/srep32461, 6, 2016.08, [URL], Accumulating evidence indicates that purinergic P2X4 receptors (P2X4R: cation channels activated by extracellular ATP) expressed in spinal microglia are crucial for pathological chronic pain caused by nerve damage, suggesting a potential target for drug discovery. We identified NP-1815-PX (5-[3-(5-thioxo-4H-[1,2,4]oxadiazol-3-yl)phenyl]-1H-naphtho[1, 2-b][1,4]diazepine-2,4(3H,5H)-dione) as a novel antagonist selective for P2X4R with high potency and selectivity compared with other P2XR subtypes. In in vivo assay for acute and chronic pain, intrathecal administration of NP-1815-PX produced an anti-allodynic effect in mice with traumatic nerve damage without affecting acute nociceptive pain and motor function (although its oral administration did not produce the effect). Furthermore, in a mouse model of herpetic pain, P2X4R upregulation in the spinal cord exclusively occurred in microglia, and intrathecal NP-1815-PX suppressed induction of mechanical allodynia. This model also showed K+/Cl- cotransporter 2 (KCC2) downregulation, which is implicated in dorsal horn neuron hyperexcitability; this downregulation was restored by intrathecal treatment with NP-1815-PX or by interfering with brain-derived neurotrophic factor (BDNF) signaling, a P2X4R-activated microglial factor implicated in KCC2 downregulation. Taken together, the newly developed P2X4R antagonist NP-1815-PX produces anti-allodynic effects in chronic pain models without altering acute pain sensitivity, suggesting that microglial P2X4R could be an attractive target for treating chronic pain..
10. Tomohiro Yamashita, Shota Yamamoto, Jiaming Zhang, Miho Kometani, Daisuke Tomiyama, Keita Kohno, Hidetoshi Saitoh, Kazuhide Inoue, Tsuda Makoto, Duloxetine inhibits microglial P2X4 receptor function and alleviates neuropathic pain after peripheral nerve injury, PLoS One, 10.1371/journal.pone.0165189, 11, 10, 2016.10, [URL], P2X4 receptors (P2X4R) are a family of ATP-gated non-selective cation channels. We previously demonstrated that activation of P2X4R in spinal microglia is crucial for neuropathic pain, a highly debilitating chronic pain condition, suggesting that P2X4R is a potential therapeutic target for treating neuropathic pain. Thus, the identification of a compound that has a potent inhibitory effect on P2X4R is an important clinical challenge. In the present study, we screened a chemical library of clinically approved drugs and show for the first time that duloxetine, a serotonin and noradrenaline reuptake inhibitor, has an inhibitory effect on rodent and human P2X4R. In primary cultured microglial cells, duloxetine also inhibited P2X4R-, but not P2X7R-, mediated responses. Moreover, intrathecal administration of duloxetine in a model of neuropathic pain produced a reversal of nerve injury-induced mechanical allodynia, a cardinal symptom of neuropathic pain. In rats that were pretreated with a serotonin-depleting agent and a noradrenaline neurotoxin, the antiallodynic effect of duloxetine was reduced, but still remained. Based on these results, we suggest that, in addition to duloxetine's primary inhibitory action on serotonin and noradrenaline transporters, an inhibitory effect on P2X4R may be involved at least in part in an antiallodynic effect of intrathecal duloxetine in a model of neuropathic pain..
11. Matsunaga Naoya, Eriko Ikeda, Keisuke Kakimoto, Miyako Watanabe, Naoya Shindo, Akito Tsuruta, Hisako Ikeyama, Kengo Hamamura, Kazuhiro Higashi, Tomohiro Yamashita, Hideaki Kondo, Yuya Yoshida, Masaki Matsuda, Takashi Ogino, Kazutaka Tokushige, Kazufumi Itcho, Yoko Furuichi, Takaharu Nakao, Kaori Yasuda, Atsushi Doi, Toshiaki Amamoto, Hironori Aramaki, Tsuda Makoto, Kazuhide Inoue, Akio Ojida, Koyanagi Satoru, Shigehiro Ohdo, Inhibition of G0/G1 Switch 2 Ameliorates Renal Inflammation in Chronic Kidney Disease, EBioMedicine, 10.1016/j.ebiom.2016.10.008, 13, 262-273, 2016.11, [URL], Chronic kidney disease (CKD) is a global health problem, and novel therapies to treat CKD are urgently needed. Here, we show that inhibition of G0/G1 switch 2 (G0s2) ameliorates renal inflammation in a mouse model of CKD. Renal expression of chemokine (C-C motif) ligand 2 (Ccl2) was increased in response to p65 activation in the kidneys of wild-type 5/6 nephrectomy (5/6Nx) mice. Moreover, 5/6Nx Clk/Clk mice, which carry homozygous mutations in the gene encoding circadian locomotor output cycles kaput (CLOCK), did not exhibit aggravation of apoptosis or induction of F4/80-positive cells. The renal expression of G0s2 in wild-type 5/6Nx mice was important for the transactivation of Ccl2 by p65. These pathologies were ameliorated by G0s2 knockdown. Furthermore, a novel small-molecule inhibitor of G0s2 expression was identified by high-throughput chemical screening, and the inhibitor suppressed renal inflammation in 5/6Nx mice. These findings indicated that G0s2 inhibitors may have applications in the treatment of CKD..
12. Hidetoshi Saitoh, Hiroyuki Miyata, Tomohiro Yamashita, Katsuyuki Matsushita, Tsuda Makoto, Kazuhide Inoue, P2Y12 receptors in primary microglia activate nuclear factor of activated T-cell signaling to induce C–C chemokine 3 expression, Journal of Neurochemistry, 10.1111/jnc.13968, 141, 1, 100-110, 2017.04, [URL], Microglia are widely accepted as surveillants in the central nervous system that are continually searching the local environment for signs of injury. Following an inflammatory situation, microglia alter their morphology, extend ramified processes, and undergo cell body hypertrophy. Extracellular nucleotides are recognized as a danger signal by microglia. ADP acting on P2Y12 receptors induce process extension of microglia thereby attracting microglia to the site of adenosine tri-phosphate/ADP leaking or release. However, the question whether ADP/P2Y12 receptor signaling directly stimulates the production or release of inducible factors such as cytokines remains unclear. In this study, we found that CC chemokine ligand 3 (CCL3) is induced by ADP-treated primary microglia. Pharmacological characterization using pertussis toxin, a P2Y12 receptor inhibitor, and a calcium chelator revealed that CCL3 induction was caused by P2Y12 receptor-mediated intracellular calcium elevation. Next, nuclear factor of activated T-cell dephosphorylation and nuclear translocalization were observed. Calcineurin, an inhibitor for nuclear factor of activated T cell, suppressed CCL3 induction. These data indicate that microglial P2Y12 receptors are utilized to trigger an acute inflammatory response in microglia via rapid CCL3 induction after ADP stimulation. (Figure presented.)..

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