Yasuhiro Ishihara

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Two mechanisms have been proposed to explain quinone cytotoxicity: oxidative stress via the redox cycle and the arylation of intracellular nucleophiles. As the redox cycle is catalyzed by NADPH cytochrome P450 reductase, cytochrome P450 systems are expected to be related to the cytotoxicity induced by redox-cycling quinones. Thus, we investigated the(More)
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(More)
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).(More)
BACKGROUND The presence of chronic kidney disease is a significant independent risk factor for poor prognosis in patients with chronic heart failure. However, the mechanisms and mediators underlying this interaction are poorly understood. In this study, we tested our hypothesis that chronic cardiac volume overload leads to de novo renal dysfunction by(More)
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(More)
BACKGROUND 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.(More)
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(More)
AIMS 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. MAIN METHODS Organotypic hippocampal slices were prepared from neonatal rats and then(More)
Although CYP2C9 and CYP2C19 display 91% sequence identity at the amino acid level, the two enzymes have distinct substrate specificities for compounds such as diclofenac, progesterone and (S)-mephenytoin. Amino acid substitutions in CYP2C9 were made based on an alignment of CYP2C9, CYP2C19 and monkey CYP2C43 sequences. Mutants of CYP2C9 were expressed in(More)
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(More)