Induction of autophagy contributes to the neuroprotection of nicotinamide phosphoribosyltransferase in cerebral ischemia

作者：Pei Wang, Yun‐Feng Guan, Hui Du, Qiwei Zhai, Ding‐Feng Su, Chao‐Yu Miao · 发表于：Autophagy · 年份：2012 · DOI：10.4161/auto.8.1.18274 · 被引用次数：320 · 研究领域：Autophagy in Disease and Therapy、Sirtuins and Resveratrol in Medicine、Calcium signaling and nucleotide metabolism

Recent reports indicate that autophagy serves as a stress response and may participate in pathophysiology of cerebral ischemia. Nicotinamide phosphoribosyltransferase (Nampt, also known as visfatin), the rate-limiting enzyme in mammalian NAD (+) biosynthesis, protects against ischemic stroke through inhibiting neuronal apoptosis and necrosis. This study was taken to determine the involvement of autophagy in neuroprotection of Nampt in cerebral ischemia. Middle cerebral artery occlusion (MCAO) in rats and oxygen-glucose deprivation (OGD) in cultured cortical neurons were performed. Nampt was overexpressed or knocked-down using lentivirus-mediated gene transfer in vivo and in vitro. Immunochemistry (LC3-II), electron microscope and immunoblotting assays (LC3-II, beclin-1, mammalian target of rapamycin [mTOR], S6K1 and tuberous sclerosis complex-2 [TSC2]) were performed to assess autophagy. We found that overexpression of Nampt increased autophagy (LC3 puncta immunochemistry staining, LC3-II/beclin-1 expression and autophagosomes number) both in vivo and in vitro at 2 hours after MCAO. At the early stage of OGD, autophagy inducer rapamycin protected against neuronal injury induced by Nampt knockdown, whereas autophagy inhibitor 3-methyladenine abolished the neuroprotective effect of Nampt partly. Overexpression or knockdown of Nampt regulated the phosphorylation of mTOR and S6K1 signaling pathway upon OGD stress through enhancing phosphorylation of TSC2 at Ser1387 but not Thr146...