Yasuhiro Ishihara

Hiroshima University, Hirosima, Hiroshima, Japan

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Publications (42)135.85 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Microglia are activated quickly in response to external pathogens or cell debris and clear these substances via the inflammatory response. However, excessive activation of microglia can be harmful to host cells due to the increased production of reactive oxygen species (ROS) and proinflammatory cytokines. Superoxide dismutase 2 (SOD2) is reportedly induced under various inflammatory conditions in the central nervous system. We herein demonstrated that activated microglia strongly express SOD2 and examined the role of SOD2, focusing on regulation of the microglial activity and their susceptibility to oxidative stress. When rat primary microglia were treated with LPS, poly (I:C), peptidoglycan or CpG oligodeoxynucleotide, respectively, the mRNA and protein levels of SOD2 largely increased. However, an increased expression of SOD2 was not detected in the primary neurons or astrocytes, indicating that SOD2 is specifically induced in microglia under inflammatory conditions. The activated microglia showed high tolerance to oxidative stress, while SOD2 knockdown conferred vulnerability to oxidative stress. Interestingly, the production of proinflammatory cytokines was increased in the activated microglia treated with SOD2 siRNA compared with that observed in the control siRNA-treated cells. Pretreatment with NADPH oxidase inhibitors, diphenylene iodonium and apocynin, decreased in not only ROS generation, but also the proinflammatory cytokine expression. Notably, SOD2 knockdown largely potentiated the nuclear factor kB (NF-kB) activity in the activated microglia. Taken together, increased SOD2 conferred tolerance to oxidative stress in the microglia and decreased proinflammatory cytokine production by attenuating the NF-kB activity. Therefore, SOD2 might regulate neuroinflammation by controlling the microglial activities. Copyright © 2015, The American Society for Biochemistry and Molecular Biology.
    Journal of Biological Chemistry 07/2015; DOI:10.1074/jbc.M115.659151 · 4.57 Impact Factor
  • Takuya Takemoto · Yasuhiro Ishihara · Atsuhiko Ishida · Takeshi Yamazaki
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    ABSTRACT: The protective roles of astrocytes in neurotoxicity induced by environmental chemicals, such as methylmercury (MeHg), are largely unknown. We found that conditioned medium of MeHg-treated astrocytes (MCM) attenuated neuronal cell death induced by MeHg, suggesting that astrocytes-released factors can protect neuronal cells. The increased expression of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) was observed in MeHg-treated astrocytes. NGF and BDNF were detected in culture media as homodimers, which are able to bind specific tyrosine kinase receptors, tropomyosin related kinase (Trk) A and TrkB, respectively. The TrkA antagonist and TrkB antagonist abolished the protective effects of MCM in neuronal cell death induced by MeHg. Taken together, astrocytes synthesize and release NGF and BDNF in response to MeHg to protect neurons from MeHg toxicity. This study is considered to show a novel defense mechanism against MeHg-induced neurotoxicity. Copyright © 2015 Elsevier B.V. All rights reserved.
    Environmental Toxicology and Pharmacology 06/2015; 40(1). DOI:10.1016/j.etap.2015.06.010 · 2.08 Impact Factor
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    ABSTRACT: The impact of nicorandil as adjunctive therapy for Percutaneous Coronary Intervention(PCI) in patients with ST-elevation myocardial infarction (STEMI) is controversial. We performed 15O-labeled water positron emission tomography (PET) to quantify regional myocardial perfusion in patients with STEMI who received nicorandil or no adjunctive therapy during PCI.
    06/2015; 31. DOI:10.1016/j.ijcha.2015.05.011
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    ABSTRACT: A rare sugar, D-allulose (also called D-psicose), has recently been applied as a food supplement in view of controlling diabetes and obesity in Japan. D-allulose has been proven to have unique effects against hyperglycemia and hyperlipidemia in a number of studies using several species of rats and mice. However, the antiobesity effects of D-allulose have not yet been assessed in Lep(ob) /Lep(ob) (ob/ob) mice. Therefore, this study explored the dietary supplemental effects of this sugar in leptin-deficient ob/ob mice. Consequently, the subchronic ingestion of D-allulose in ob/ob mice for 15 wk significantly decreased the body and liver weights, and the loss of body weight was involved in the reduction of the total fat mass, including abdominal visceral fat, and not fat-free body mass, including muscle. Furthermore, D-allulose improved hepatic steatosis, as evaluated using hepatic histological studies and MRI. In the normal mice, none of these parameters were influenced by the single or long-term ingestion of D-allulose. These results indicate that dietary supplementation of D-allulose especially influences postprandial hyperglycemia and obesity-related hepatic steatosis, without exercise therapy or dietary restriction. Therefore, D-allulose may be useful as a supplement for preventing and improving obesity and obesity-related disorders. © 2015 Institute of Food Technologists®
    Journal of Food Science 05/2015; DOI:10.1111/1750-3841.12908 · 1.79 Impact Factor
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    ABSTRACT: The management of status epilepticus (SE) is important to prevent mortality and the development of post-SE symptomatic epilepsy. Acquired epilepsy after an initial brain insult by SE can be experimentally reproduced in the murine model of SE induced by pilocarpine. In the present study, we evaluated the possibility of treatment with a high-dose of levetiracetam in this model. Repeated treatment with high-dose levetiracetam after termination of SE by diazepam significantly prevented the incidence of spontaneous recurrent seizures and mortality for at least 28 days. To determine the brain alterations after SE, magnetic resonance imaging was performed. Both T2-weighted imaging and diffusion-weighted imaging showed changes in the limbic regions. These changes in the limbic regions demonstrated the development of cytotoxic edema three hours after SE, followed by the development of vasogenic edema two days after SE. In the pilocarpine-SE model, the incidence of spontaneous recurrent seizures after SE was strongly associated with neuronal damage within a few hours to days after SE by the development of vasogenic edema via the breakdown of the blood-brain barrier in the limbic regions. High-dose levetiracetam significantly suppressed the parameters in the limbic areas. These data indicate that repeated treatment with high-dose levetiracetam for at least two days after SE termination by diazepam is important for controlling the neuronal damage by preventing brain edema. Therefore, these findings suggest that early treatment with high-dose levetiracetam after SE termination by diazepam may protect against adverse sequelae via the inhibition of neurotoxicity induced by brain edema events. Copyright © 2015 Elsevier B.V. All rights reserved.
    Brain Research 03/2015; 1608. DOI:10.1016/j.brainres.2015.03.005 · 2.83 Impact Factor
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    ABSTRACT: Vascular endothelial growth factor-A (VEGF-A) released from adipocytes promotes angiogenesis; and thereby ameliorates the local hypoxia-induced adipose inflammation and insulin resistance. Here, we newly found that eicosapentaenoic acid (EPA) upregulated both mRNA expression and release of VEGF-A in mature 3T3-L1 adipocytes. Silencing mRNA of G-protein coupled receptor 120 (GPR120) and specific inhibition of peroxisome proliferator-activated receptor γ (PPARγ) by GW9662 respectively attenuated the EPA-induced augmentation of VEGF-A release by adipocytes. Furthermore, transfection of GPR120 gene alone and PPARγ gene alone to HEK293 cells respectively increased the promoter activity of VEGF-A as assessed by luciferase reporter assay, which was further augmented when both genes were co-transfected. Promoter deletion analysis and chromatin immunoprecipitation assay revealed that co-transfection of GPR120 enhanced EPA-induced PPARγ binding to PPAR-response element in VEGF-A promoter region. Thus, by the synchronized activation of a membrane receptor GRP120 and a nuclear receptor PPARγ, EPA enhances VEGF-A production in adipocytes. Copyright © 2015. Published by Elsevier Ireland Ltd.
    Molecular and Cellular Endocrinology 02/2015; 406. DOI:10.1016/j.mce.2015.02.012 · 4.24 Impact Factor
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    Yasuhiro Ishihara · Takuya Takemoto · Atsuhiko Ishida · Takeshi Yamazaki
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    ABSTRACT: Steroid hormones synthesized in and secreted from peripheral endocrine glands pass through the blood-brain barrier and play a role in the central nervous system. In addition, the brain possesses an inherent endocrine system and synthesizes steroid hormones known as neurosteroids. Increasing evidence shows that neuroactive steroids protect the central nervous system from various harmful stimuli. Reports show that the neuroprotective actions of steroid hormones attenuate oxidative stress. In this review, we summarize the antioxidative effects of neuroactive steroids, especially 17β-estradiol and progesterone, on neuronal injury in the central nervous system under various pathological conditions, and then describe our recent findings concerning the neuroprotective actions of 17β-estradiol and progesterone on oxidative neuronal injury induced by organometallic compounds, tributyltin, and methylmercury.
    Oxidative medicine and cellular longevity 01/2015; 2015:1-16. DOI:10.1155/2015/343706 · 3.36 Impact Factor
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    Yasuhiro Ishihara · Kouichi Itoh · Atsuhiko Ishida · Takeshi Yamazaki
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    ABSTRACT: Growing evidence shows that steroid hormones, especially 17β-estradiol (E2), protect neuronal cells by attenuating excess activation of microglia. However, the use of E2 in the clinic is controversial because of its peripheral actions in reproductive organs and its potential to increase risk for endometrial cancer and breast cancer. Selective estrogen-receptor modulators (SERMs) bind to estrogen receptors (ERs), but their effects as ER agonists or antagonists are dependent on the target tissue. SERMs pose very little cancer risk as a result of their anti-estrogen action in reproductive organs, but their action in the brain is not well understood. In this study, we investigated the effects of SERMs tamoxifen (Tam) and raloxifene (Rlx) on microglial activation and subsequent neuronal injury. Tam and Rlx suppressed the increases in proinflammatory cytokines and chemokine expression that were induced by lipopolysaccharide (LPS) in rat primary microglia cultures. The microglial-conditioned media pretreated with Tam or Rlx significantly attenuated cellular injury in SH-SY5Y cells elicited by microglial-conditioned media treated with LPS alone. Rat primary microglia expressed ERα and ERβ primarily in the nucleus, and thus we examined the involvement of ERs in the suppressive action of Tam and Rlx on microglial activation using a pure ER antagonist, ICI182,780. Pretreatment with ICI182,780 abolished the suppressive effects of SERMs on microglial activation, as well as their protective action on SH-SY5Y cells. A luciferase assay using a vector with 3 estrogen response elements (EREs) revealed that Tam and Rlx activated ERE-mediated transcription in rat primary microglia. Taken together, these results suggest that Tam and Rlx suppress microglial activation and subsequent neuronal cell death via an ER-mediated transcription pathway. SERMs could represent a novel therapeutic strategy for disorders of the central nervous system based on their ability to suppress neuroinflammation.
    The Journal of Steroid Biochemistry and Molecular Biology 10/2014; 145. DOI:10.1016/j.jsbmb.2014.10.002 · 4.05 Impact Factor
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    ABSTRACT: Regulatory T cells (Tregs) play a crucial role in the negative regulation of immune responses. Recent studies suggest that Tregs are involved in the pathogenesis of atherosclerosis and myocarditis. Here, we investigated the involvement of Tregs on worsening heart failure (HF) in patients with reduced ejection fraction (HF-REF). The study population consisted of 32 HF-REF patients who were hospitalized for worsening HF, and 18 control subjects. Cardiac function was evaluated by echocardiography. A single venous blood sample was collected before discharge. Circulating T cells were evaluated by flow cytometry. Tregs were defined as CD4(+)CD25(+)Foxp3(+)T cells, and the correlations between the frequency of Tregs and CRP, IL-6 and several echoparameters were analysed. Furthermore, all HF-REF patients were followed up to 12 months from discharge to examine the predictors of recurrent hospitalization.In HF-REF patients, Tregs were significantly decreased (5.9 ± 1.4 versus 8.0 ± 2.2%, P < 0.01), while CD4(+)HLADR(+)T cells were increased (10.1 ± 5.4 versus 7.3 ± 3.1%, P < 0.05), compared with controls. Tregs were negatively correlated with left ventricular end-diastolic dimension, and levels of CRP and IL-6. Eleven of 32 HF-REF patients were rehospitalized for worsening HF within 12 months. Multivariate Cox regression analysis showed that CD4/CD8 and frequency of Tregs were independent predictors for recurrent hospitalization. Furthermore, HF-REF patients expressing under 6% Treg/CD4(+)T cells showed a significantly higher incidence of recurrent hospitalization for worsening HF within 12 months.Our data suggest that Tregs might be involved in the pathogenesis of decompensated HF, and may be a novel predictor of poor prognosis in HF-REF patients.
    International Heart Journal 05/2014; DOI:10.1536/ihj.13-343 · 1.13 Impact Factor
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    ABSTRACT: Genetic deficiencies in transcription factors can lead to the loss of certain types of cells and tissue. The steroidogenic tissue-specific nuclear receptor Ad4BP/SF-1 (NR5A1) is one such gene, because mice in which this gene is disrupted fail to develop the adrenal gland and gonads. However, the specific role of Ad4BP/SF-1 in these biological events remains unclear. Here we use chromatin immunoprecipitation sequencing to show that nearly all genes in the glycolytic pathway are regulated by Ad4BP/SF-1. Suppression of Ad4BP/SF-1 by small interfering RNA reduces production of the energy carriers ATP and nicotinamide adenine dinucleotide phosphate, as well as lowers expression of genes involved in glucose metabolism. Together, these observations may explain tissue dysgenesis as a result of Ad4BP/SF-1 gene disruption in vivo. Considering the function of estrogen-related receptor α, the present study raises the possibility that certain types of nuclear receptors regulate sets of genes involved in metabolic pathways to generate energy carriers.
    Nature Communications 04/2014; 5:3634. DOI:10.1038/ncomms4634 · 10.74 Impact Factor
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    ABSTRACT: Angiotensin (Ang) II receptor blockers (ARBs) alleviate obesity-related insulin resistance, which suggests an important role for the Ang II type 1 receptor (AT1R) in the regulation of adipocytokines. Therefore, we treated mature 3T3-L1 adipocytes with 50 μmol l(-1) of valsartan, a selective AT1R blocker without direct agonism to peroxisome proliferator-activated receptor (PPAR)-γ. In the absence of effective concentrations of Ang II, unstimulated mature adipocytes expressed and secreted high levels of interleukin (IL)-6. This constitutive proinflammatory activity was attenuated by the suppression of extracellular signal-regulated kinase phosphorylation by valsartan but was unaffected by the Ang II type 2 receptor blocker PD123319. COS7 cells co-transfected with AT1R and IL-6, which expressed NF-κB but lacked PPAR-γ, showed no constitutive but substantial ligand-dependent IL-6 reporter activity, which was counteracted by valsartan. Valsartan preserved cytosolic IκB-α and subsequently reduced nuclear NF-κB1 protein expression in mature adipocytes. Interestingly, valsartan did not increase PPAR-γ messenger RNA expression per se but enhanced the transcriptional activity of PPAR-γ in mature adipocytes; this enhancement was accompanied by upregulation of the PPAR coactivator (PGC)-1α. Moreover, T0090907, a PPAR-γ inhibitor, increased IL-6 expression, and this increase was attenuated by valsartan. Indeed, addition of valsartan without direct PPAR-γ agonism increased adiponectin production in mature adipocytes. Together, the findings indicate that valsartan blocks the constitutive AT1R activity involving the NF-κB pathway that limits PPAR-γ activity in mature adipocytes. Thus, inverse agonism of AT1R attenuates the spontaneous proinflammatory response and enhances the constitutive insulin-sensitizing activities of mature adipocytes, which may underlie the beneficial metabolic impacts of ARBs.Hypertension Research advance online publication, 6 March 2014; doi:10.1038/hr.2014.51.
    Hypertension Research 03/2014; DOI:10.1038/hr.2014.51 · 2.94 Impact Factor
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    ABSTRACT: Neuroactive steroids are reported to protect neurons from various harmful compounds; however, the protective mechanisms remain largely unclear. In this study, we examined the suppressive effects of 17β-estradiol (E2) on tributyltin (TBT)-induced neurotoxicity. Organotypic hippocampal slices were prepared from neonatal rats and then cultured. Cell death was assayed by propidium iodide uptake. Levels of reactive oxygen species (ROS) were determined by dihydroethidium staining. Protein phosphorylation was evaluated by immunoblotting. Pretreatment of the slices with E2 dose-dependently attenuated the neuronal injury induced by TBT. An estrogen receptor antagonist, ICI182,780 abrogated these neuroprotective effects. The de novo protein synthesis inhibitors actinomycin D and cycloheximide showed no effects on the neuroprotective mechanism, indicating that a nongenomic pathway acting via the estrogen receptor may be involved in the neuroprotection conferred by E2. E2 suppressed the ROS production and lipid peroxidation induced by TBT, and these effects were almost completely canceled by ICI182,780. TBT decreased Akt phosphorylation, and this reduction was suppressed by E2. An Akt inhibitor, triciribine, attenuated the decreases in both the ROS production and neuronal injury mediated by E2. E2 enhances the phosphorylation of Akt, thereby attenuating the oxidative stress and subsequent neuronal injury induced by TBT.
    Life sciences 01/2014; 99(1). DOI:10.1016/j.lfs.2014.01.061 · 2.30 Impact Factor
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    ABSTRACT: Ca(2+)/calmodulin-dependent protein kinase phosphatase (CaMKP/PPM1F) and its nuclear homolog CaMKP-N (PPM1E) are Ser/Thr protein phosphatases that belong to the PPM family. CaMKP-N is expressed in the brain and undergoes proteolytic processing to yield a C-terminally truncated form. The physiological significance of this processing, however, is not fully understood. Using a wheat-embryo cell-free protein expression system, we prepared human CaMKP-N (hCaMKP-N(WT)) and the truncated form, hCaMKP-N(1-559), to compare their enzymatic properties using a phosphopeptide substrate. The hCaMKP-N(1-559) exhibited a much higher V max value than the hCaMKP-N(WT) did, suggesting that the processing may be a regulatory mechanism to generate a more active species. The active form, hCaMKP-N(1-559), showed Mn(2+) or Mg(2+)-dependent phosphatase activity with a strong preference for phospho-Thr residues and was severely inhibited by NaF, but not by okadaic acid, calyculin A, or 1-amino-8-naphthol-2,4-disulfonic acid, a specific inhibitor of CaMKP. It could bind to postsynaptic density and dephosphorylate the autophosphorylated Ca(2+)/calmodulin-dependent protein kinase II. Furthermore, it was inactivated by H2O2 treatment, and the inactivation was completely reversed by treatment with DTT, implying that this process is reversibly regulated by oxidation/reduction. The truncated CaMKP-N may play an important physiological role in neuronal cells.
    08/2013; 2013(6):134813. DOI:10.1155/2013/134813
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    Sonoko Danjo · Yasuhiro Ishihara · Masatomo Watanabe · Yu Nakamura · Kouichi Itoh
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    ABSTRACT: Dysfunction of the blood-brain barrier (BBB) is one of the major pathophysiological consequences of epilepsy. The increase in the permeability caused by BBB failure is thought to contribute to the development of epileptic outcomes. We developed a method by which the BBB permeability can be demonstrated by gadolinium-enhanced T1 weighted imaging (GdET1WI). The present study examined the changes in the BBB permeability in mice with generalized convulsive seizures (GCS) induced by acute pentylentetrazole (PTZ) injection. At fifteen minutes after PTZ-induced GCS, the BBB temporarily leaks BBB-impermeable contrast agent into the parenchyma of the diencephalon, hippocampus and cerebral cortex in mice, and the loss of BBB integrity was gradually recovered by 24 hours. The temporary BBB failure is a critical link to the glutamatergic activities that occur following the injection of PTZ. PTZ activates the glutamatergic pathway via the NMDA receptor, then nitric oxide (NO) is generated by NMDA receptor-coupled neuronal NO synthase (nNOS). To examine the influence of nNOS-derived NO induced by PTZ on the increases of the BBB permeability, GdET1WI was performed using conventional nNOS gene-deficient mice with or without PTZ injection. The failure of the BBB induced by PTZ was completely protected by nNOS deficiency in the brain. These results suggest that nNOS-derived excess NO in the glutamatergic pathway plays a key role in the failure of the BBB during PTZ-induced GCS. The levels of NO synthetized by nNOS in the brain may represent an important target for the future development of drugs to protect the BBB.
    Brain research 07/2013; 1530. DOI:10.1016/j.brainres.2013.06.043 · 2.83 Impact Factor
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    ABSTRACT: Abstract Oxidative stress is considered to be related to the onset and/or progression of Alzheimer's disease (AD), but there is insufficient evidence of its role(s). In this study, we evaluated the relationships between the brain redox state and cognitive function using a triple transgenic mouse model of AD (3xTg-AD mouse). One group of 3xTg-AD mice started to receive an α-tocopherol-supplemented diet at two months of age, and another group of 3xTg-AD mice was fed a normal diet. The levels of α-tocopherol, reduced glutathione, oxidized glutathione and lipid peroxidation were decreased in the cerebral cortex and hippocampus at four months of age in the 3xTg-AD mice fed a normal diet. These reductions were abrogated by the supplementation of α-tocopherol in the diet. During Morris water maze testing, the 3xTg-AD mice did not exhibit cognitive impairment at four months of age, but started to show cognitive dysfunction at six months of age, and α-tocopherol supplementation suppressed this dysfunction. Magnetic resonance imaging (MRI) using 3-hydroxymethyl-proxyl as a probe showed decreases in the signal intensity in the brains of 3xTg-AD mice at four months of age, and this reduction was clearly attenuated by α-tocopherol supplementation. Taken together, these findings suggest that oxidative stress can be associated with the cognitive impairment in 3xTg-AD mice. Furthermore, MRI might be a powerful tool to noninvasively evaluate the increases in reactive radicals, especially those occurring during the early stages of AD.
    Free Radical Research 06/2013; 47(9). DOI:10.3109/10715762.2013.818218 · 2.99 Impact Factor
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    ABSTRACT: Estrogen, a class of female sex steroids, is neuroprotective. Estrogen is synthesized in specific areas of the brain. There is a possibility that the de novo synthesized estrogen exerts protective effect in brain, although direct evidence for the neuroprotective function of brain-synthesized estrogen has not been clearly demonstrated. Methylmercury (MeHg) is a neurotoxin that induces neuronal degeneration in the central nervous system. The neurotoxicity of MeHg is region-specific, and the molecular mechanisms for the selective neurotoxicity are not well defined. In this study, the protective effect of de novo synthesized 17β-estradiol on MeHg-induced neurotoxicity in rat hippocampus was examined. Neurotoxic effect of MeHg on hippocampal organotypic slice culture was quantified by propidium iodide fluorescence imaging. Twenty-four-hour treatment of the slices with MeHg caused cell death in a dose-dependent manner. The toxicity of MeHg was attenuated by pre-treatment with exogenously added estradiol. The slices de novo synthesized estradiol. The estradiol synthesis was not affected by treatment with 1 µM MeHg. The toxicity of MeHg was enhanced by inhibition of de novo estradiol synthesis, and the enhancement of toxicity was recovered by the addition of exogenous estradiol. The neuroprotective effect of estradiol was inhibited by an estrogen receptor (ER) antagonist, and mimicked by pre-treatment of the slices with agonists for ERα and ERβ, indicating the neuroprotective effect was mediated by ERs. Hippocampus de novo synthesized estradiol protected hippocampal cells from MeHg-induced neurotoxicity via ERα- and ERβ-mediated pathways. The self-protective function of de novo synthesized estradiol might be one of the possible mechanisms for the selective sensitivity of the brain to MeHg toxicity.
    PLoS ONE 04/2013; 8(2):e55559. DOI:10.1371/journal.pone.0055559 · 3.23 Impact Factor
  • Yasuhiro Ishihara · Tomohito Kawami · Atsuhiko Ishida · Takeshi Yamazaki
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    ABSTRACT: Increasing evidence shows that progesterone, a neuroactive steroid, has protective actions in central nervous system, but there is little evidence to show the protective mechanism of progesterone on neurotoxicity induced by environmental chemicals. In this study, we examined the effects of progesterone on neuronal injury induced by tributyltin (TBT) in rat hippocampal slices. Treatment with progesterone dose-dependently suppressed hippocampal neuronal injury induced by TBT. The neuroprotective action of progesterone was completely cancelled with pretreatment by finasteride, a 5α-reductase inhibitor, but it was not affected by mifepristone, a progesterone receptor antagonist, or by SU-10603, a cytochrome P450 17α inhibitor. The content of allopregnanolone in the slices was significantly increased by treatment with progesterone, and this increment was greatly suppressed with a pretreatment of finasteride. Treatment with allopregnanolone attenuated neuronal injury induced by TBT in a dose-dependent manner. The neuroprotective effects not only of progesterone but also of allopregnanolone were cancelled by bicuculline, a potent gamma-aminobutyric acid A (GABA(A)) receptor antagonist. Pretreatment with muscimol, a GABA(A) receptor agonist, attenuated hippocampal neuronal injury elicited by TBT. Taken together, allopregnanolone converted from progesterone in hippocampal slices could protect neurons from TBT-induced neurotoxicity due to a GABA(A) receptor-dependent mechanism. One of the physiological roles of neuroactive steroids might be neuroprotection from environmental chemicals.
    The Journal of steroid biochemistry and molecular biology 12/2012; 135(1). DOI:10.1016/j.jsbmb.2012.12.013 · 4.05 Impact Factor
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    ABSTRACT: Increased reactive oxygen species (ROS) contribute to numerous brain disorders, and ROS generation has been examined in diverse experimental models of lipopolysaccharide (LPS)-induced inflammation. The in vivo electron paramagnetic resonance (EPR)/nitroxide spin probe method has been used to analyze the redox status in animal models modulated by ROS generation. In this study, a blood-brain barrier (BBB)-permeable nitroxide spin probe, 3-hydroxymethyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (HMP), was used as a redox-sensitive nitroxide probe. Magnetic resonance images of mouse head after the injection of HMP showed that HMP was distributed throughout all regions of the mouse head including the brain, suggesting that HMP can reveal redox information in all regions of the mouse head. After the injection of HMP through the mouse tail vein 6 h after the injection of LPS, three-dimensional (3D) EPR images were obtained each minute under a field scanning of 0.3 s and with 81 projections. The reduction reaction of HMP in septic mouse heads was remarkably accelerated compared to that in control mice, and this accelerated reaction was inhibited by aminoguanidine and allopurinol, which inhibit enzymatic activities of induced nitric oxide synthase and xanthine oxidase, respectively. Based on the pharmacokinetics of HMP in mouse heads, the half-life mapping of HMP was performed in LPS-treated mouse head. Half-life maps clearly show a difference in the redox status induced by ROS generation in the presence or absence of inhibitors of ROS-generating enzymes. The present results suggest that a 3D in vivo EPR imaging system combined with BBB-permeable HMP is a useful noninvasive tool for assessing changes in the redox status in rodent models of brain disease under oxidative stress.
    Magnetic Resonance Imaging 08/2012; 31(1). DOI:10.1016/j.mri.2012.06.021 · 2.02 Impact Factor
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    ABSTRACT: Increasing evidence shows that cytochrome P450 (CYP) contributes to cardiac reperfusion injury. However, there have been few reports about the roles of CYPs in cardiac ischemia. The aim of the present study was to investigate the CYP expression and activity during ischemia using an in vivo rat model of myocardial infarction. Cardiac ischemia was evoked by ligation of the left anterior descending coronary artery for 1h. The protein levels of CYP 2C6, 2E1 and 2J3 increased in the ischemic region of the rat hearts, while the mRNA levels of CYPs were unchanged. CYP 2C6 activity was significantly elevated in the ischemic region, and the activities of 2E1 and 2J3 tended to increase during ischemia. The proteasome activity decreased and the expression of ubiquitinated proteins increased in the ischemic region. Remarkably, ubiquitinated CYP 2C6, 2E1 and 2J3 were detected in the ischemic area, suggesting that CYP proteins accumulate in the ischemic region as a result of the suppression of their degradation due to the reduction of proteasome activity. The amounts of reactive oxygen species and protein carbonyls increased, and proteasome subunits, Rpt3 and Rpt5, were carbonylated in the ischemic region of the hearts, indicating that the proteasome is oxidized during ischemia. Taken together, our findings indicate that CYPs, especially CYP 2C6, were accumulated by oxidative impairment of the proteasome in the ischemic region of rat hearts. Accumulated CYPs might be involved in myocardial infarction and dysfunction during reperfusion.
    Archives of Biochemistry and Biophysics 08/2012; 527(1):16-22. DOI:10.1016/j.abb.2012.07.015 · 3.04 Impact Factor
  • Yasuhiro Ishihara · Norio Shimamoto
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    ABSTRACT: We previously reported the administration of a potent cytochrome P450 inhibitor, sulfaphenazole (SPZ), to suppress oxidative stress and the extension of myocardial infarct size in a rat model of cardiac ischemia-reperfusion (I/R). The aim of this study was to investigate the effects of SPZ on the myocardial cell apoptosis induced by I/R in rats. I/R injury was evoked by ligation of the left anterior descending coronary artery for 1 h, followed by reperfusion for 3 h. TUNEL-positive nuclei were detected and nucleosomal DNA fragmentation was observed 3 h after reperfusion. The administration of SPZ largely suppressed the cardiac DNA fragmentation induced by I/R. A pan-caspase inhibitor, z-VAD-fmk, had no effect on DNA fragmentation. Caspase-3/7 was not activated 3 h after reperfusion. Decreases in the mitochondrial membrane potential and cytochrome c release from the mitochondria to cytosol were detected 3 h after reperfusion. The expression levels of BimEL and Noxa were elevated 3 h after reperfusion. These phenomena were suppressed by the administration of SPZ. Taken together, treatment with SPZ could attenuate the myocardial cell apoptosis accompanied with I/R by inhibiting the mitochondrial dysfunction due to decreases in the expression of BimEL and Noxa.
    Journal of Pharmacological Sciences 06/2012; 119(3):251-9. DOI:10.1254/jphs.12079FP · 2.11 Impact Factor

Publication Stats

324 Citations
135.85 Total Impact Points

Institutions

  • 2012–2015
    • Hiroshima University
      • Graduate School of Integrated Arts and Sciences
      Hirosima, Hiroshima, Japan
  • 2009–2015
    • Kagawa University
      • Department of Cardiorenal and Cerebrovascular Medicine
      Takamatu, Kagawa, Japan
  • 2007–2013
    • Tokushima Bunri University
      • Faculty of Pharmaceutical Sciences
      Tokusima, Tokushima, Japan
  • 2005–2006
    • Osaka University
      • Graduate School of Science
      Suika, Ōsaka, Japan