Yasuhiro Ishihara

Hiroshima University, Hirosima, Hiroshima, Japan

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Publications (27)76.37 Total impact

  • [Show abstract] [Hide abstract]
    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;
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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; · 2.56 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 01/2014; 5:3634. · 10.74 Impact Factor
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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; · 2.46 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; · 3.28 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. · 3.53 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.
    BioMed research international. 01/2013; 2013:134813.
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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; · 3.98 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; · 2.06 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. · 3.37 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. · 2.15 Impact Factor
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    ABSTRACT: Tributyltin (TBT) has been used as a heat stabilizer, agricultural pesticide and antifouling agents on ships, boats and fish-farming nets; however, the neurotoxicity of TBT has recently become a concern. TBT is suggested to stimulate the generation of reactive oxygen species (ROS) inside cells. The aim of this study was to determine the mechanism of neuronal oxidative injury induced by TBT using rat organotypic hippocampal slice cultures. The treatment of rat hippocampal slices with TBT induced ROS production, lipid peroxidation and cell death. Pretreatment with antioxidants such as superoxide dismutase, catalase or trolox, suppressed the above phenomena induced by TBT, indicating that TBT elicits oxidative stress in hippocampal slices, which causes neuronal cell death. TBT dose-dependently inhibited glutathione S-transferase (GST), but not glutathione peroxidase or glutathione reductase in the cytosol of rat hippocampus. The treatment of hippocampal slices with TBT decreased the GST activity. Pretreatment with reduced glutathione attenuated the reduction of GST activity and cell death induced by TBT, indicating that the decrease in GST activity by TBT is involved in hippocampal cell death. When hippocampal slices were treated with sulforaphane, the expression and activity of GST were increased. Notably, TBT-induced oxidative stress and cell death were significantly suppressed by pretreatment with sulforaphane. These results indicate that GST inhibition could contribute, at least in part, to the neuronal cell death induced by TBT in hippocampal slices. This study is the first report to show the link between neuronal oxidative injury and the GST inhibition elicited by TBT.
    Neurochemistry International 03/2012; 60(8):782-90. · 2.66 Impact Factor
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    ABSTRACT: Treatment of intracerebral hemorrhage is often pointless, although considerable effort has been devoted to developing treatments for ischemic stroke. The purpose of this study was to determine the influence of drugs in improving neurological outcomes with pharmaceutical therapy after intracerebral hemorrhage. The free-radical hypothesis for intracerebral hemorrhage is based on the cytotoxicity triggered by blood components and its degradation products, such as heme and iron as a potent pro-oxidant atom. Sulfaphenazole (SPZ) has a different mechanism such as reactive oxygen species scavenging, in addition to the inhibition of superoxide production by cytochrome P450. The present study investigated the properties of SPZ in collagenase-induced intracerebral hemorrhage rat brain damage. The results show that systemic SPZ treatment after intracerebral hemorrhage reduces striatal dysfunction, the elevation of lipid peroxidation, and brain edema in the rat. These results suggest that SPZ is a potentially effective therapeutic approach for intracerebral hemorrhage as the effect of SPZ was initiated for either 1 h or 3 d post-intracerebral hemorrhage.
    Biological & Pharmaceutical Bulletin 01/2012; 35(10):1849-53. · 1.85 Impact Factor
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    ABSTRACT: Two mechanisms have been proposed to explain quinone cytotoxicity: oxidative stress via the redox cycle, and the arylation of intracellular nucleophiles. The redox cycle is catalyzed by intracellular reductases, and therefore the toxicity of redox cycling quinone is considered to be closely associated with the reductase activity. This study examined the relationship between quinone toxicity and the intracellular reductase activity using 3 kinds of hepatic cells; rat primary hepatocytes, HepG2 and H4IIE. The intracellular reductase activity was; primary hepatocyte >HepG2>H4IIE. The three kinds of cells showed almost the same vulnerability to an arylating quinone, 1,4-naphthoquinone (NQ). However, the susceptibility to a redox cycling quinone, 2,3-dimethoxy-1,4-naphthoquinone (DMNQ) was; primary hepatocyte>HepG2>H4IIE. In addition, the cytotoxicity elicited by DMNQ was significantly attenuated in HepG2 cells and almost completely suppressed in primary hepatocytes by diphenyleneiodonium chloride, a reductase inhibitor. These data suggest that cells with a high reductase activity are susceptible to redox cycling quinones. This study provides essential evidence to assess the toxicity of quinone-based drugs during their developmental processes.
    Biological & Pharmaceutical Bulletin 01/2012; 35(4):634-8. · 1.85 Impact Factor
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    ABSTRACT: The anti-oxidative activity of the rare sugar D-allose has recently been reported, but the mechanism is largely unclear. In this study, we evaluated the reactive oxygen species (ROS) scavenging activities of D-allose and then examined the effects of D-allose on ROS production in mitochondria to clarify the antioxidant properties of D-allose. While D-allose did not scavenge hydrogen peroxide and superoxide anions, it eliminated hydroxyl radicals to the same extent as D-glucose. Rotenone, an uncoupler of mitochondrial respiratory complex I, induces ROS production in mouse neuroblastoma Neuro2A cells in the presence of D-glucose. However, in the presence of D-allose, there was no change in the ROS levels in Neuro2A cells following rotenone treatment. Furthermore, treatment with D-allose attenuated the D-glucose-dependent ROS generation induced by rotenone. Whereas treatment with D-glucose enhanced ATP synthesis in Neuro2A cells, D-allose was less effective in producing intracellular ATP than D-glucose. Treatment with D-allose inhibited the ATP synthesis stimulated by D-glucose. These results suggest that D-allose suppresses ROS production in the mitochondria due to competition with D-glucose at the cellular level.
    Journal of Bioscience and Bioengineering 08/2011; 112(6):638-42. · 1.74 Impact Factor
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    ABSTRACT: Reactive oxygen species (ROS) have a fundamental role in intracellular signaling transduction. We show here that time-dependent extracellular signal-regulated kinase (ERK) activation due to inactivation of protein tyrosine phosphatases was closely linked to hepatocyte apoptosis under sustained exposure to ROS, which is produced through inhibition of ROS-scavenging enzymes. We found, for the first time, that active ERK transcriptionally increased BimEL expression among seven proteins of the Bcl-2 family. Transfection of Bim siRNA inhibited BimEL expression and hepatocyte apoptosis. Although ERK activation also elicited BimEL phosphorylation and subsequent ubiquitination, exposure to ROS for 9 h decreased proteasome activity. Collectively, the amount of BimEL was elevated by its increased expression and decreased degradation, leading to apoptosis. Exposure to ROS for 6 h caused neither reduction of proteasome activity nor hepatocyte apoptosis. These results indicate that the duration of exposure to ROS determines the fate of cells, that is, survival or death, in addition to the species, amounts, and generation sites of ROS.
    Journal of Cellular Physiology 04/2011; 226(4):1007-16. · 4.22 Impact Factor
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    Yasuhiro Ishihara, Fumiaki Ito, Norio Shimamoto
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    ABSTRACT: We previously reported that the inhibition of catalase and glutathione peroxidase activities by treatment with 3-amino-1,2,4-triazole (ATZ) and mercaptosuccinic acid evoked sustained increases in the levels of reactive oxygen species and apoptosis in rat primary hepatocytes. Apoptosis was accompanied by increased expression of BimEL, following activation of extracellular signal-regulated kinase. The aim of this study was to characterize the mechanism underlying hepatocyte apoptosis by identifying the transcription factor that induces BimEL expression. The bim promoter region was cloned into a promoterless-luc vector, and promoter activity was monitored by a luciferase assay. The luciferase activity increased in the presence of ATZ + mercaptosuccinic acid. Pretreatment with a MEK inhibitor, U0126, or an antioxidant, vitamin C, suppressed the promoter activity. Furthermore, ATZ + mercaptosuccinic acid-induced luciferase activity was attenuated by mutation of the activator protein-1 binding site in the bim promoter region. The amounts of total and phosphorylated c-Fos increased over time in the presence of ATZ + mercaptosuccinic acid, whereas the amounts of total and phosphorylated c-Jun remained unchanged. Chromatin immunoprecipitation revealed that both c-Fos and c-Jun localized to the activator protein-1-binding site in the bim promoter region. BimEL expression and hepatocyte apoptosis were suppressed by knockdown of c-Fos and c-Jun, respectively. These results indicate that increases in c-Fos following extracellular signal-regulated kinase activation are critical for BimEL upregulation and apoptosis.
    FEBS Journal 03/2011; 278(11):1873-81. · 4.25 Impact Factor
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    ABSTRACT: Quinone toxicity is induced by two principal mechanisms: arylation/alkylation and a redox cycle. We have previously shown that increases in intracellular levels of superoxide anion and cell death induced by 2,3-dimethoxy-1,4-naphthoquinone (DMNQ), a redox cycling quinone, are enhanced by pretreatment of rat primary hepatocytes with cytochrome P450 inhibitors. This indicates a novel interaction of quinones with cytochrome P450, and is thus worthy of further investigation using an in vivo model. The aim of this study was to examine the effects of cytochrome P450 inhibitors on DMNQ-induced hepatotoxicity in rats. When DMNQ was administered intraperitoneally, the activities of serum alanine aminotransferase and aspartate aminotransferase were found to increase in a dose-dependent manner, indicating that hepatotoxicity was induced by treatment with DMNQ. Pretreatment with the cytochrome P450 inhibitors SKF-525A (SKF), cimetidine and ketoconazole potentiated the DMNQ-induced hepatotoxicity. The blood concentration of DMNQ was not affected by administration of SKF. Pretreatment with the antioxidant α-tocopherol almost completely attenuated the hepatotoxicity induced by DMNQ and by the combination of DMNQ with SKF. Levels of reduced glutathione in the liver were decreased and levels of oxidized glutathione were increased by treatment with DMNQ. These effects were potentiated by pretreatment with SKF. DMNQ-induced lipid peroxidation in the liver was also enhanced by pretreatment with SKF. Taken together, these results indicate that DMNQ-induced hepatotoxicity is augmented by inhibition of cytochrome P450 and that this augmentation is due to the enhancement of oxidative stress.
    Journal of Applied Toxicology 03/2011; 31(2):173-8. · 2.60 Impact Factor
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    ABSTRACT: Cardiac ischemia-reperfusion injury is evoked by reactive oxygen species (ROS). We previously reported that sulfaphenazole (SPZ) attenuated cardiac ROS levels and ischemia-reperfusion injury in rats. SPZ has distinct two actions: a) elimination of ROS and b) inhibition of cytochrome P450 (CYP) that is responsible for ROS production. The aim of this study is to determine which action contributes to the attenuation of cardiac ischemia-reperfusion injury using SPZ and its derivatives [acetyl-SPZ (Ac-SPZ) and dichloro-SPZ (2Cl-SPZ)]. Administration of 2Cl-SPZ or SPZ prior to ischemia significantly reduced myocardial infarct size, myocardial lipid peroxides, and ROS levels. In addition, they inhibited rat cardiac CYP activity. However, Ac-SPZ neither reduced infarct size nor inhibited cardiac CYP activity. The three compounds had similar effects on ROS scavenging activity in that they scarcely scavenged hydrogen peroxide and superoxide anions but reduced hydroxyl radicals with the same efficacy. The serum concentration of each compound was almost the same until 24 h after reperfusion. Collectively, our findings indicate that the suppressive effects of SPZ and 2Cl-SPZ on ischemia-reperfusion injury are associated with the reduction of ROS levels, which is primarily due to a decrease in ROS production via inhibition of cardiac CYP, not via ROS scavenging activity.
    Journal of Pharmacological Sciences 01/2010; 113(4):335-42. · 2.15 Impact Factor
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    ABSTRACT: The effects of inhibitors of cytochrome P450 on myocardial regional ischemia-reperfusion injury were examined in rats. Ischemia-reperfusion injury was evoked by ligation of the left anterior descending coronary artery for 1 h, followed by reperfusion for 24 h. Injuries were evident in causing infarction, decreases in left ventricular systolic pressure and left ventricle (dP/dt max)/P and an increase in left ventricular end-diastolic pressure. Increases in lipid peroxidation and reactive oxygen species levels in the ischemic region were observed. Intravenous injection of the potent cytochrome P450 inhibitor sulfaphenazole at 10 and 30 mg/kg at the time of reperfusion reduced infarct size by 41.7 and 73.2%, respectively; and improved cardiac function accompanied by the decrease in content of lipid peroxide and reactive oxygen species in the area at risk. Cardiac testosterone metabolism was inhibited by sulfaphenazole administration, indicating its inhibitory effects on cardiac cytochrome P450 activity. Another cytochrome P450 inhibitor, cimetidine, given intravenously, had similar effects to sulfaphenazole on reperfusion injury. Taken together, these results indicate that reactive oxygen species derived from cytochrome P450 play an important part in myocardial regional ischemia-reperfusion injury in vivo, and strongly support the hypothesis that cytochrome P450 inhibitors are promising therapeutic agents for cardiac ischemia-reperfusion injury.
    European journal of pharmacology 05/2009; 611(1-3):64-71. · 2.59 Impact Factor

Publication Stats

168 Citations
76.37 Total Impact Points

Institutions

  • 2011–2014
    • Hiroshima University
      • Graduate School of Integrated Arts and Sciences
      Hirosima, Hiroshima, Japan
  • 2007–2013
    • Tokushima Bunri University
      Tōkyō, Japan
  • 2005–2006
    • Osaka University
      • Department of Biological Sciences
      Ōsaka-shi, Osaka-fu, Japan