The roles of oxidative stress and Beclin-1 in the autophagosome clearance impairment triggered by cardiac arrest.

During cardiac arrest and return of spontaneous circulation (CA-ROSC), autophagosome clearance in the cortex is progressively impaired, but the role of reactive oxygen species (ROS) in this process and the mechanism underlying the autophagy impairment remain unknown. In this study, we investigated the impacts of ROS on the autophagy-lysosome pathway after CA-ROSC in rats. Cortices from CA-ROSC rats revealed accumulation of LC3, p62 and ubiquitin, indicating impaired autophagic flux. Furthermore, impairment of autophagic flux was related to lysosomal lesion, as indicated by decreased cathepsin D and lysosomal-associated membrane protein 2 (LAMP2) levels after CA-ROSC. In vitro, the resulting ROS generation blocked autophagosome processing and caused accumulation of LC3-II, ubiquitin, and p62, leading to mitochondrial dysfunction and cell death; this outcome was alleviated by cyclosporine A (CsA) pretreatment. Interestingly, ischemia/reperfusion injury was connected with ROS-mediated Beclin-1 upregulation and a reduction in LAMP2, which is a pivotal protein in the autophagy-lysosome pathway. Recovery of the LAMP2 levels and partial Beclin-1 silencing restored the autophagic flux and reduced cell death after CA-ROSC. Taken together, our data indicate that CA-ROSC injury impairs autophagosome clearance partially through a ROS-induced decline in LAMP2 and increase in Beclin-1, leading to increased neuronal cell death.