| Co-Investigator(Kenkyū-buntansha) |
IWABUCHI Yushiharu 東北大学, 大学院・薬学研究科, 教授 (20211766)
MORIOKA Motohiro 熊本大学, 医学部付属病院, 准教授 (20295140)
KASAHARA Jiro 徳島大学, 大学院・ヘルスバイオサイエンス研究部, 准教授 (10295131)
MORIGUCHI Shigeki 東北大学, 大学院・薬学研究科, 講師 (70374949)
SHIODA Norifumi 東北大学, 大学院・薬学研究科, 助手 (00374950)
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| Research Abstract |
We have introduced novel neuroprotective drugs including calmodulin antagonist DY-9760e and protein kinase B (Akt) activator VO (OPT) in the ischemic neurodegeneration. However, the mechanisms underlying neurovascular unit protection by these compounds remain unclear. We found that DY-9760e and its active metabolite, DY-9836 are potent inhibitors of calcium/calmodulin dependent nitric oxide synthase (NOS) in vivo. We here defined pathophysiological role and mechanism of superoxide generation through uncoupled eNOS in phenylephrine (PE)-induced hypertrophic cardiomyocytes. In PE-induced hypertrophic cardiomyocytes, the superoxide generation was associated with increased uncoupling state of eNOS. Thus, uncoupling of eNOS accounts for superoxide generation by prolonged PE exposure, thereby inducing apoptotic cell death. Furthermore, cardioprotective effects of DY-9836 well correlated with inhibition of aberrant superoxide generation by suppression of eNOS activity. DY-9836 treatment also
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protected cardiomyocytes from breakdown of caveolin-3/dystrophin, which are major components to scaffold eNOS in cardiomyocyte caveolae. Similarly, DY-9836 treatment also attenuated superoxide generation following brain ischemia by uncoupled eNOS in vascular endothelial cells. Thus the inhibition of superoxide production by DY-9760e/DY9836 is critical for protection of neurovascular units in ischemia-induced neurodegenaration.
Neurogenesis is well documented in the subgranular zone (SGZ) of hippocampus. Especially, in the hippocampal neurogenesis, fundamental role of neurogenesis in learning and memory formation has been addressed. We here assessed whether VO (OPT), a stimulator of phosphatidylinositol 3-kinase (PI3K)/Akt and extracellular signal regulated kinase (ERK) pathways promotes neurogenesis following brain ischemia using a mouse transient middle cerebral artery occlusion (MCAO) model. Intraperitoneal administrations of VO (OPT), which is a potent inhibitor for protein tyrosine phosphatases (PTPs), stimulated neurogenesis in the adult dentate gyrus (DG) following brain ischemia. VO (OPT) led to activation of PI3K/Akt and ERK pathways, which are inhibited by treatment with specific inhibitor, wortmannin or U-0126, respectively. Each treatment of them significantly inhibited the neurogenesis, suggesting that both pathways need to elicit VO (OPT)-induced neurogenesis following brain ischemia. In some behavioral studies, we showed that VO (OPT)-induced neurogenesis accounts for improvement of memory deficits following brain ischemia. These results suggest that intraperitoneal administrations of VO (OPT) stimulate neurogenesis following brain ischemia through PI3K/Akt and ERK activation. Moreover, Akt- and ERK-induced neurogenesis is critical for improvement of memory deficits following brain ischemia. Less
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