PGC-1α acts as an mediator of Sirtuin2 to protect annulus fibrosus from apoptosis induced by oxidative stress through restraining mitophagy

Apoptosis of annulus fibrosus (AF) is observed widely in intervertebral disc degeneration (IVDD) which causes weaken of tension in the annulus of intervertebral disc. Previous studies reported that apoptosis of AF is induced mainly by oxidative stress. SIRT2 is a major regulator of mitochondria to mediate ROS production. However, the mechanism of SIRT2 in IVDD remains unclear. Here, the expression of SIRT2 was detected in AF cells exposed to tert-Butyl hydroperoxide (TBHP) by western blotting. Autophagic flux and apoptosis were assessed by western blotting, flow cytometry and immunofluorescence respectively. Safranin 0 staining, HE, and immunohistochemical were used to assess the IVDD after 3, 6 and 9 months of surgical procedure in vivo. The expression of SIRT2 was decreased in AF cells treated with TBHP. Repression of mitophagy alleviated the apoptosis of AF cells caused by TBHP. Overexpression of PGC-1 alpha prevented AF cells from apoptosis and mitophagy after applying Lenti-PGC-1 alpha to transfect AF cells. These protections of PGC-1 alpha were reduced by FCCP. Furthermore, the expression of PGC-1 alpha was reduced and the level of mitophagy was increased in IVDD models. In conclusion, this study indicates that the regulation of PGC-1 alpha expression provide a new theoretical basis for the mechanism of IVDD. (C) 2019 The Authors. Published by Elsevier B.V.