Shogo Tokuyama

Kobe Gakuin University, Kōbe, Hyōgo, Japan

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Publications (87)157 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We recently demonstrated that exposure to early life stress exacerbates nerve injury-induced thermal and mechanical hypersensitivity in adult male and female mice. Accumulating evidence suggests that chronic pain causes emotional dysfunction, such as anxiety and depression. In the present study, we investigated the impact of early life stress on depression-like behavior after nerve injury in mice. In addition, we examined the expression of brain-derived neurotrophic factor (BDNF), which is known to be involved in the pathogenesis of depression. Early life stress was induced by maternal separation between 2 and 3 weeks of age combined with social isolation after weaning (MSSI). At 9 weeks of age, the sciatic nerve was partially ligated to elicit neuropathic pain. Depression-like behavior was evaluated using the forced swim test at 12 weeks of age. Tissue samples from different regions of the brain were collected at the end of maternal separation (3 weeks of age) or after the forced swim test (12 weeks of age). At 12 weeks of age, immobility time in the forced swim test was increased only in MSSI-stressed female mice with nerve injury. BDNF expression was increased in male, but not female, MSSI-stressed mice at 3 weeks of age. However, MSSI stress did not impact BDNF expression in male or female mice at 12 weeks of age. Our findings suggest that exposure to early life stress exacerbates emotional dysfunction induced by neuropathic pain in a sex-dependent manner. Changes in BDNF expression after early life stress may be associated with neuropathic pain-induced depression-like behavior in adulthood. Furthermore, sex differences in BDNF expression after exposure to early life stress may contribute to sex-specific susceptibility to neuropathic pain-induced emotional dysfunction. Copyright © 2015. Published by Elsevier Ireland Ltd.
    Neuroscience Letters 02/2015; 592. DOI:10.1016/j.neulet.2015.02.053 · 2.06 Impact Factor
  • YAKUGAKU ZASSHI 01/2015; 135(5):687-95. DOI:10.1248/yakushi.14-00234-1 · 0.31 Impact Factor
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    ABSTRACT: Early life stress contributes to the pathogenesis of psychiatric disorders and chronic pain in adult patients. However, information about the effect of early life stress on chronic pain in mice is limited. In the present study, we evaluated the effect of early life stress on baseline pain sensitivity and thermal or mechanical hypersensitivity induced by nerve injury in male and female mice. Early life stress was induced by maternal separation and social isolation (MSSI). Mice were separated from dam and littermates for 6 h/day during postnatal days 15-21 and then were housed individually until the end of the study. At 9 weeks of age, the sciatic nerve was partially ligated to elicit neuropathic pain. Thermal and mechanical sensitivity were measured by plantar and von Frey tests. At 7 weeks of age, MSSI induced depression-like behaviors in both male and female mice, but induced anxiety-like behaviors only in female mice. MSSI had no effect on thermal and mechanical sensitivity before nerve injury. However, MSSI enhanced nerve-injury-induced thermal and mechanical hypersensitivity in both male and female mice. MSSI exacerbated neuropathic pain in adult male and female mice. Overall, this model may be useful for understanding the molecular mechanisms underlying the reciprocal relationship between early life stress and chronic pain. Copyright © 2014. Published by Elsevier Inc.
    Life Sciences 12/2014; 121. DOI:10.1016/j.lfs.2014.11.012 · 2.30 Impact Factor
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    ABSTRACT: Background and purposeOmega-3 polyunsaturated fatty acids have antinociceptive effects against inflammatory and neuropathic pain; however, the underlying mechanisms remain unclear. We have demonstrated that docosahexaenoic acid-induced antinociception may be mediated by the G protein-coupled receptor 40/free fatty acid receptor 1 (GPR40/FFAR1). Here, we examined the involvement of supraspinal GPR40/FFAR1 signaling in the regulation of inhibitory pain control systems consisting of serotonergic and noradrenergic neurons.Experimental approachFormalin-induced pain behaviors were measured in mice. GPR40/FFAR1 agonist-induced antinociception was examined by intrathecal injections of a catecholaminergic toxin and noradrenaline or serotonin antagonists/agonists. The expression of GPR40/FFAR1 protein and c-Fos was estimated by immunohistochemistry, and the levels of noradrenaline and serotonin in the spinal cord were measured by LC-MS/MS.Key resultsGPR40/FFAR1 was colocalized with NeuN (a neuron marker) in the medulla oblongata and with tryptophan hydroxylase (TPH; a serotonergic neuron marker) and dopamine beta-hydroxylase (DBH; a noradrenergic neuron marker). A single intracerebroventricular injection of GW9508, a GPR40/FFAR1 agonist, significantly increased the number of c-Fos-positive cells and the number of neurons double-labeled for c-Fos and TPH and/or DBH. It significantly decreased formalin-induced pain behavior. This effect was inhibited by pretreatment with 6-hydroxydopamine, DL-p-chlorophenylalanine, yohimbine, or WAY100635. Furthermore, GW9508 facilitated the release of noradrenaline and serotonin in the spinal cord. In addition, GW1100, a GPR40/FFAR1 antagonist, significantly increased formalin-induced pain-related behavior.Conclusion and ImplicationsOur findings suggest that the activation of the GPR40/FFAR1 signaling pathway may play an important role in the regulation of the descending pain control system.
    British Journal of Pharmacology 11/2014; 172(5). DOI:10.1111/bph.13003 · 4.99 Impact Factor
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    ABSTRACT: Central post-stroke pain (CPSP), one of the complications of cerebral ischemia and neuropathic pain syndrome, is associated with specific somatosensory abnormalities. Although CPSP is a serious problem, detailed underlying mechanisms and standard treatments for CPSP are not well established. In this study, we assessed the role of GPR40, a long-chain fatty acid receptor, showing anti-nociceptive effects, in CPSP. We also examined the role of astrocytes in CPSP due to their effects in mediating the release of polyunsaturated fatty acids, which act as potential GPR40 ligands. The aim of this study was to determine the interactions between CPSP and astrocyte/GPR40 signaling. Male ddY mice were subjected to 30min of bilateral carotid artery occlusion (BCAO). The development of hind paw mechanical hyperalgesia was measured after BCAO using the von Frey test. Neuronal damage was estimated by histological analysis on day 3 after BCAO. The thresholds for hind paw mechanical hyperalgesia were significantly decreased on days 1-28 after BCAO when compared with pre-BCAO assessments. BCAO-induced mechanical hyperalgesia was significantly decreased by intracerebroventricular injection of docosahexaenoic acid or GW9508, a GPR40 agonist; furthermore, these effects were reversed by GW1100, a GPR40 antagonist. The expression levels of glial fibrillary acidic protein, an astrocytic marker, and some free fatty acids were significantly decreased 5h after BCAO, although no effects of BCAO were noted on hypothalamic GPR40 protein expression. Our data show that BCAO-induced mechanical hyperalgesia is possible to be regulated by astrocyte activation and stimulation of GPR40 signaling.
    European Journal of Pharmacology 09/2014; 744. DOI:10.1016/j.ejphar.2014.09.036 · 2.68 Impact Factor
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    ABSTRACT: Altered expression of P-glycoprotein (P-gp), a drug efflux transporter expressed by brain capillary endothelial cells (BCECs), may contribute to the development of opioid analgesic tolerance, as demonstrated by cumulative evidence from research. However, the detailed mechanism by which chronic morphine treatment increases P-gp expression remains unexplained. Ezrin/radixin/moesin (ERM) are scaffold proteins that are known to regulate the plasma membrane localization of some drug transporters such as P-gp in peripheral tissues, although a few reports suggest its role in the central nervous system as well. In this study, we investigated the involvement of ERM in the development of morphine analgesic tolerance through altered P-gp expression in BCECs. Repeated treatment with morphine (10 mg/kg/day, s.c. for 5 days) decreased its analgesic effect in the tail-flick test and increased P-gp protein expression in BCECs, as determined by Western blotting. Furthermore, moesin protein expression increased in the same fraction whereas that of ezrin decreased; no change was observed in the radixin expression. Furthermore, immunoprecipitation and immunofluorescence assays revealed interaction between moesin and P-gp molecules, along with co-localization, in BCECs. In conclusion, an increase in moesin expression may contribute to the increased expression of P-gp in BCECs, leading to the development of morphine analgesic tolerance.
    Drug Metabolism and Pharmacokinetics 07/2014; 29(6). DOI:10.2133/dmpk.DMPK-14-RG-042 · 2.86 Impact Factor
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    ABSTRACT: In clinical pharmacotherapy, therapeutic benefits and adverse effects of medicines differ substantially between individuals and are often determined by their blood levels. Critical regulators influencing the pharmacokinetics and pharmacodynamics of drugs include drug transporters and drug-metabolizing enzymes. Among these, we have focused on P-glycoprotein (P-gp), a drug efflux transporter. A growing body of evidence indicates that the expression and functional activity of P-gp are altered under several pathological conditions, by exposure to substrate drugs of P-gp, and by ingestion of certain foods. In this critical review, we discuss the mechanisms by which anticancer drugs, most of which are P-gp substrates, alter the expression and functional activity of P-gp in tumors and normal tissues after chronic treatment. Accumulating evidence shows that various transcription factors, in addition to epigenetic and post-translational factors, modulate P-gp expression, which alters the pharmacokinetics and pharmacological effects of drugs. Therefore, it is important to consider individual patients with regard to drug-taking history, as well as levels of P-gp expression and function, when providing clinical pharmacotherapy.
    Journal of Pharmacological Sciences 07/2014; 125(3). DOI:10.1254/jphs.14R01CR · 2.11 Impact Factor
  • Y. Yamazaki, S. Harada, S. Tokuyama
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    ABSTRACT: Cerebral ischemia can be exacerbated by post-ischemic hyperglycemia, which may involve the cerebral sodium-glucose transporter (SGLT). However, the contribution of each SGLT isoform in cerebral ischemia is still unclear. SGLT-1, -3, -4, and -6 have been reported to be expressed in various brain regions. Among these isoforms, only SGLT-3 does not transport glucose, but depolarizes the plasma membrane when glucose is bound, suggesting that SGLT-3 is a glucose sensor. Therefore, in this study, we investigated the involvement of cerebral SGLT-3 in the development of ischemia. The mouse model of focal ischemia was generated by middle cerebral artery occlusion (MCAO). Neuronal damage was assessed by histological and behavioral analyses. Fasting blood glucose levels on day 1 after MCAO were not affected in SGLT-3 siRNA-mediated knockdown of SGLT-3. The development of infarct volume and behavioral abnormalities on day 1 after MCAO were exacerbated in SGLT-3 knockdown mice (control group: n = 7, 94.2 ± 21.8 mm3, 2 (1.6–2.4), SGLT-3 knockdown group: n = 6, 1414.8 ± 492.4 mm3, 6 (5.8–6.3), P < 0.05). Moreover, SGLT-3 expression levels were significantly decreased in the striatum (65.0 ± 8.1%, P < 0.05) on day 1, and in the hippocampus (67.6 ± 7.2%, P < 0.05) and hypothalamus (47.5 ± 5.1%, P < 0.01) on day 3 after MCAO (n = 12–13). These effects were significantly inhibited by donepezil (DPZ) treatment (SGLT-3 knockdown group: n = 6, 1419.0 ± 181.5 mm3, 3.6 (3.4–3.7), SGLT-3 knockdown and 3 mg/kg DPZ-treated group: n = 5, 611.3 ± 205.3 mm3, 1.5 (1.4–1.8), P < 0.05). Immunofluorescence revealed that SGLT-3 and choline acetyltransferase were co-localized in the cortex. Our results indicated that cerebral SGLT-3 suppressed neuronal damage by the activation of cholinergic neurons, which are neuroprotective. In contrast, other cerebral SGLT isoforms may be involved in the development of ischemia.
    Neuroscience 06/2014; 269:134–142. DOI:10.1016/j.neuroscience.2014.03.046 · 3.33 Impact Factor
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    ABSTRACT: Expressions of vascular endothelial growth factor (VEGF) receptors in astrocytes are increased in damaged brains. To clarify the regulatory mechanisms of VEGF receptors, the effects of endothelin-1 (ET-1) were examined in rat cultured astrocytes. Expressions of VEGF-R1 and -R2 receptor mRNA were at similar levels, while the mRNA expressions of VEGF-R3 and Tie-2, a receptor for angiopoietins, were lower. Placenta growth factor (PLGF), a selective agonist of the VEGF-R1 receptor, induced phosphorylation of focal adhesion kinase (FAK) and extracellular signal regulated kinase 1/2 (ERK1/2). Phosphorylations of FAK and ERK 1/2 were also stimulated by VEGF-E, a selective VEGF-R2 agonist. Increased phosphorylations of FAK and ERK1/2 by VEGF165 were reduced by selective antagonists for VEGF-R1 and -R2. Treatment with ET-1 increased VEGF-R1 mRNA and protein levels. The effects of ET-1 on VEGF-R1 mRNA were mimicked by Ala(1,3,11,15) -ET-1, a selective agonist for ETB receptors, and inhibited by BQ788, an ETB antagonist. ET-1 did not affect the mRNA levels of VEGF-R2, -R3 and Tie-2. Pre-treatment with ET-1 potentiated the effects of PLGF on phosphorylations of FAK and ERK1/2. These findings suggest that ET-1 induces up-regulation of VEGF-R1 receptors in astrocytes, and potentiates VEGF signals in damaged nerve tissues. This article is protected by copyright. All rights reserved.
    Journal of Neurochemistry 05/2014; 130(6). DOI:10.1111/jnc.12770 · 4.24 Impact Factor
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    ABSTRACT: The functional role of brain G protein-coupled receptor 40 (GPR40) remains unclear. We investigated GPR40 signaling in depression-related behavior in mice via the forced swim test. A repeated but not a single intracerebroventricular administration of the GPR40 agonist, GW9508, reduced the duration of immobility behavior. Moreover, the levels of hippocampal nonesterified docosahexaenoic acid and arachidonic acid were decreased immediately after the forced swimming. These results suggested that brain GPR40 signaling may regulate depression-related behavior.
    Journal of Pharmacological Sciences 04/2014; 125(1). DOI:10.1254/jphs.14001SC · 2.11 Impact Factor
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    ABSTRACT: Orexin-A (a neuropeptide in the hypothalamus) plays an important role in many physiological functions, including the regulation of glucose metabolism. We have previously found that the development of post-ischemic glucose intolerance is one of the triggers of ischemic neuronal damage, which is suppressed by hypothalamic orexin-A. Other reports have shown that the communication system between brain and peripheral tissues through the autonomic nervous system (sympathetic, parasympathetic and vagus nerve) is important for maintaining glucose and energy metabolism. The aim of this study was to determine the involvement of the hepatic vagus nerve on hypothalamic orexin-A-mediated suppression of post-ischemic glucose intolerance development and ischemic neuronal damage. Male ddY mice were subjected to middle cerebral artery occlusion (MCAO) for 2 h. Intrahypothalamic orexin-A (5 pmol/mouse) administration significantly suppressed the development of post-ischemic glucose intolerance and neuronal damage on day 1 and 3, respectively after MCAO. MCAO-induced decrease of hepatic insulin receptors and increase of hepatic gluconeogenic enzymes on day 1 after was reversed to control levels by orexin-A. This effect was reversed by intramedullary administration of the orexin-1 receptor antagonist, SB334867, or hepatic vagotomy. In the medulla oblongata, orexin-A induced the co-localization of cholin acetyltransferase (cholinergic neuronal marker used for the vagus nerve) with orexin-1 receptor and c-Fos (activated neural cells marker). These results suggest that the hepatic branch vagus nerve projecting from the medulla oblongata plays an important role in the recovery of post-ischemic glucose intolerance and mediates a neuroprotective effect by hypothalamic orexin-A.
    PLoS ONE 04/2014; 9(4):e95433. DOI:10.1371/journal.pone.0095433 · 3.53 Impact Factor
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    ABSTRACT: Oxaliplatin, a platinum-based chemotherapeutic agent, causes an acute peripheral neuropathy triggered by cold in almost all patients during or within hours after its infusion. We recently reported that a single administration of oxaliplatin induced cold hypersensitivity 2 h after the administration in mice. In this study, we examined whether standard analgesics relieve the oxaliplatin-induced acute cold hypersensitivity. Gabapentin, tramadol, mexiletine, and calcium gluconate significantly inhibited and morphine and milnacipran decreased the acute cold hypersensitivity, while diclofenac and amitriptyline had no effects. These results suggest that gabapentin, tramadol, mexiletine, and calcium gluconate are effective against oxaliplatin-induced acute peripheral neuropathy.
    Journal of Pharmacological Sciences 03/2014; 124(4). DOI:10.1254/jphs.13249SC · 2.11 Impact Factor
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    ABSTRACT: Previously, we reported that repeated oral administration of etoposide (ETP) activates the ezrin/radixin/moesin (ERM) scaffold proteins for P-glycoprotein (P-gp) via Ras homolog gene family member A (RhoA)/Rho-associated coiled-coil containing protein kinase (ROCK) signaling, leading to increased ileal P-gp expression. Recent studies indicate that phosphatidyl inositol 4,5-bisphosphate [PtdIns(4,5)P2] regulates the plasma-membrane localization of certain proteins, and its synthase, the type I phosphatidyl inositol 4-phosphate 5-kinase (PI4P5K), is largely controlled by RhoA/ROCK. Here, we examined whether PtdIns(4,5)P2 and PI4P5K are involved in the increased expression of ileal P-gp following the ERM activation by ETP treatment. Male ddY mice (4-week-old) were treated with ETP (10 mg/kg/day, per os, p.o.) for 5 days. Protein-expression levels were measured by either western blot or dot blot analysis and molecular interactions were assessed using immunoprecipitation assays. ETP treatment significantly increased PI4P5K, ERM, and P-gp expression in the ileal membrane. This effect was suppressed following the coadministration of ETP with rosuvastatin (a RhoA inhibitor) or fasudil (a ROCK inhibitor). Notably, the PtdIns(4,5)P2 expression in the ileal membrane, as well as both P-gp and ERM levels coimmunoprecipitated with anti-PtdIns(4,5)P2 antibody, were increased by ETP treatment. PtdIns(4,5)P2 and PI4P5K may contribute to the increase in ileal P-gp expression observed following the ETP treatment, possibly through ERM activation via the RhoA/ROCK pathway. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
    Journal of Pharmaceutical Sciences 02/2014; 103(2). DOI:10.1002/jps.23811 · 3.01 Impact Factor
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    ABSTRACT: In pharmaceutical therapy, the onset of pharmacological and adverse effects of drugs varies widely among individuals. Since these effects are mostly dependent on the blood level of each drug, it is particularly important to monitor and regulate those levels after drug administration. Factors influencing the pharmacokinetics and pharmacodynamics of drugs include drug transporters, drug metabolizing enzymes and the plasma protein-binding ratio. Among these factors, we focused on P-glycoprotein (P-gp), a drug efflux transporter. The expression and function of P-gp are reported to alter under several pathological conditions and by administrating some foods or substrate drugs for P-gp.In this mini-review, we introduce alterations in the expression and functional activity of P-gp by anti-cancer drugs, most of which are P-gp substrates, in addition to their mechanism of action. In tumorous or healthy tissues, the expression and function of P-gp were increased by chronic exposure to anti-cancer drugs. A large number of previous studies have proposed that not only various transcriptional factors for P-gp but also post-translational factors such as ezrin/radixin/moesin are involved in changes in P-gp. The expression and function of P-gp seem to be altered during anti-cancer treatment possibly through the above pathways, which may in turn affect the pharmacokinetics and pharmacodynamics of drugs. Therefore, the response should take into account the kinds of drugs each patient uses and their status of P-gp expression and function in clinical pharmacotherapy.
    01/2014; 40(4):193-207. DOI:10.5649/jjphcs.40.193
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    ABSTRACT: Previously, we reported that repeated oral administration of etoposide (ETP) increases P-glycoprotein (P-gp) expression in association with activation of ezrin/radixin/moesin (ERM) via Ras homolog gene family member A (RhoA)/Rho-associated coiled-coil containing protein kinase (ROCK) signaling in the small intestine. However, the detailed mechanisms of this pathway have yet to be fully elucidated. Recently, phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2], one of the most abundant phosphoinositides in the plasma membrane, has attracted attention regarding its involvement in the plasma membrane localization of various membrane proteins. PtdIns(4,5)P2 is an essential factor in the dissociation and subsequent membrane translocation (activation) of ERM, and its synthetic pathway is known to be highly regulated by RhoA/ROCK signaling. Here, we examined the involvement of PtdIns(4,5)P2 in the mechanism by which ETP treatment increases small intestinal P-gp levels, and we determined which protein within ERM contributes to this phenomenon. Repeated oral treatment with ETP (10 mg/kg/d) over 5 d significantly increased PtdIns(4,5)P2 expression in the ileal membrane as measured by dot blot. Furthermore, this increase was suppressed by co-administration of a RhoA inhibitor, rosuvastatin (5 mg/kg/d, per os (p.o.)), or a ROCK inhibitor, fasudil (5 mg/kg/d, p.o.). In immunoprecipitation assays, radixin (but not ezrin or moesin) binding to PtdIns(4,5)P2 was observed to increase in association with the up-regulation of P-gp in the same fraction, and immunofluorescence studies indicated that radixin co-localized with PtdIns(4,5)P2 in the ileal tissue. In conclusion, ETP treatment appears to up-regulate PtdIns(4,5)P2 expression via RhoA/ROCK signaling, leading to the activation of ERM, presumably through the physical interaction of radixin with PtdIns(4,5)P2. This in turn increases the expression of ileal P-gp.
    Biological & Pharmaceutical Bulletin 01/2014; 37(7):1124-31. DOI:10.1248/bpb.b13-00953 · 1.78 Impact Factor
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    ABSTRACT: Fatty acids, one class of essential nutrients for humans, are an important source of energy and an essential component of cell membranes. They also function as signal transduction molecules in a variety of biological phenomena. The important functional role of fatty acids in both onset and suppression of pain has become increasingly apparent in recent years. Recently, we have also demonstrated that the release of an endogenous opioid peptide, β-endorphin, plays an important role in the induction of docosahexaenoic acid (DHA)-induced antinociception. It is well known that fatty acids affect intracellular and intercellular signaling as well as the membrane fluidity of neurons. In addition to intracellular actions, unbound free fatty acids (FFAs) can also carry out extracellular signaling by stimulating the G protein-coupled receptor (GPCR). Among these receptors, G protein-coupled receptor 40 (GPR40) has been reported to be activated by long-chain fatty acids such as DHA, eicosapentaenoic acid (EPA) and arachidonic acid. In the peripheral area, GPR40 is preferentially expressed in pancreatic β-cells and is known to relate to the secretion of hormone and peptides. On the other hand, even though this receptor is widely distributed in the central nervous system, reports studying the role and functions of GPR40 in the brain have not been found. In this review, we summarize the findings of our recent study about the long-chain fatty acid receptor GPR40 as a novel pain regulatory system.
    YAKUGAKU ZASSHI 01/2014; 134(3):397-403. DOI:10.1248/yakushi.13-00236-4 · 0.31 Impact Factor
  • Yakugaku zasshi journal of the Pharmaceutical Society of Japan 01/2014; 134(6):689-99. DOI:10.1248/yakushi.13-00255-1 · 0.31 Impact Factor
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    ABSTRACT: GPR40 has been reported to be activated by long-chain fatty acids, such as docosahexaenoic acid (DHA). However, reports studying functional role of GPR40 in the brain are lacking. The present study focused on the relationship between pain regulation and GPR40, investigating the functional roles of hypothalamic GPR40 during chronic pain caused using a complete Freund's adjuvant (CFA)-induced inflammatory chronic pain mouse model. GPR40 protein expression in the hypothalamus was transiently increased at day 7, but not at days 1, 3 and 14, after CFA injection. GPR40 was co-localized with NeuN, a neuron marker, but not with glial fibrillary acidic protein (GFAP), an astrocyte marker. At day 1 after CFA injection, GFAP protein expression was markedly increased in the hypothalamus. These increases were significantly inhibited by the intracerebroventricular injection of flavopiridol (15 nmol), a cyclin-dependent kinase inhibitor, depending on the decreases in both the increment of GPR40 protein expression and the induction of mechanical allodynia and thermal hyperalgesia at day 7 after CFA injection. Furthermore, the level of DHA in the hypothalamus tissue was significantly increased in a flavopiridol reversible manner at day 1, but not at day 7, after CFA injection. The intracerebroventricular injection of DHA (50 mu g) and GW9508 (1.0 mu g), a GPR40-selective agonist, significantly reduced mechanical allodynia and thermal hyperalgesia at day 7, but not at day 1, after CFA injection. These effects were inhibited by intracerebroventricular pretreatment with GW1100 (10 mg), a GPR40 antagonist. The protein expression of GPR40 was colocalized with that of beta-endorphin and proopiomelanocortin, and a single intracerebroventricular injection of GW9508 (1.0 mg) significantly increased the number of neurons double-stained for c-Fos and proopiomelanocortin in the arcuate nucleus of the hypothalamus. Our findings suggest that
    PLoS ONE 12/2013; 8(12):e81563. DOI:10.1371/journal.pone.0081563 · 3.53 Impact Factor
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    ABSTRACT: Diabetes mellitus and impaired glucose metabolism are the most important risk factors for stroke. We recently demonstrated that cerebral ischemic stress causes hyperglycemia (i.e., post-ischemic hyperglycemia) and may worsen ischemic neuronal damage in a mouse model of focal ischemia. However, the detailed mechanisms are still unknown. The sodium-glucose transporter (SGLT) generates inward currents in the process of transporting glucose into cells, resulting in depolarization and increased excitability, which is well known to be caused by cerebral ischemia. Hence, we focused on the role of SGLT on the development of neuronal damage using a global ischemic model. Male ddY mice were subjected to 30min of bilateral carotid artery occlusion (BCAO). The neuronal damage was estimated by histological analysis using HE staining on day 3 after BCAO. Intraperitoneal (i.p.) administration of phlorizin (a specific and competitive inhibitor of SGLT, 200mg/kg immediately after reperfusion) suppressed the development of post-ischemic hyperglycemia on day 1 after BCAO. In contrast, intracerebroventricular (i.c.v.) administration of phlorizin (40μg/mouse immediately and 6h after reperfusion) had no effect on day 1 after BCAO. Interestingly, the development of ischemic neuronal damage was significantly suppressed by i.p. and i.c.v. administration of phlorizin on day 3 after BCAO. In addition, BCAO-induced spasticity was significantly suppressed by PHZ (40μg/mouse, i.c.v.) from using gait analysis. Our results indicated that cerebral SGLT was involved in the development of ischemic neuronal damage in global ischemia.
    Brain research 10/2013; DOI:10.1016/j.brainres.2013.09.041 · 2.83 Impact Factor
  • Shinichi Harada, Kazuo Nakamoto, Shogo Tokuyama
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    ABSTRACT: Aims Systemic administration of opiate analgesics such as morphine remains the most effective treatment for alleviating severe pain across a range of conditions including acute pain. However, chronic or repeated administration of opiate analgesics results in the development of analgesic tolerance. Glial cells such as microglia and astrocytes are known to release various inflammatory cytokines and neurotrophic factors leading to regulation of neuronal function. Recently, glial cells were reported to play important roles in the development of analgesic tolerance to morphine. Here, we focused on the involvement of midbrain glial cells, particularly astrocytes, in the development of analgesic tolerance to morphine. Main methods Mice were treated with morphine (10mg/kg, s.c.) or vehicle once a day for 5days. Pentoxifilline (an inhibitor of glial activation; 20mg/kg, i.p. or 50 and 100μg/mouse, i.c.v.) was administered 30min before morphine treatment. Flavopiridol (a cyclin-dependent kinase inhibitor; 5nmol/mouse, i.c.v.) was administered 10min before and 10hr after morphine treatment. The analgesic effect of morphine was measured using the tail flick method. Key findings The development of analgesic tolerance to morphine was gradually observed during daily treatment of morphine for 5days in mice. On day 1 and 3 after repeated morphine treatment, astrocyte marker glial fibrillary acidic protein expression levels were significantly increased, as determined by western blot analyses. These phenomena were significantly inhibited following pre-treatment with pentoxifilline or flavopiridol. Significance We demonstrated that midbrain astrocytes play an important role in the development of analgesic tolerance to morphine.
    Life sciences 08/2013; 93(16). DOI:10.1016/j.lfs.2013.08.009 · 2.30 Impact Factor