Sirt3 inhibits cerebral ischemia-reperfusion injury through normalizing Wnt/β-catenin pathway and blocking mitochondrial fission

Cerebral ischemia-reperfusion injury (IRI) potentiates existing brain damage and increases mortality and morbidity via poorly understood mechanisms. The aim of our study is to investigate the role of Sirtuin 3 (Sirt3) in the development and progression of cerebral ischemia-reperfusion injury with a focus on mitochondrial fission and the Wnt/β-catenin pathway. Our data indicated that Sirt3 was downregulated in response to cerebral IRI. However, the overexpression of Sirt3 reduced the brain infarction area and repressed IRI-mediated neuron apoptosis. Functional assays demonstrated that IRI augmented mitochondrial fission, which induced ROS overproduction, redox imbalance, mitochondrial pro-apoptotic protein leakage, and caspase-9-dependent cell death pathway activation. However, the overexpression of Sirt3 blocked mitochondrial fission and induced pro-survival signals in neurons subjected to IRI. At the molecular level, our data further illustrated that the Wnt/β-catenin pathway is required for the neuroprotection exerted by Sirt3 overexpression. Wnt/β-catenin pathway activation via inhibiting β-catenin phosphorylation attenuates mitochondrial fission and mitochondrial apoptosis. Collectively, our data show that cerebral IRI is associated with Sirt3 downregulation, Wnt/β-catenin pathway phosphorylated inactivation, and mitochondrial fission initiation, causing neurons to undergo caspase-9-dependent cell death. Based on this, strategies for enhancing Sirt3 activity and activating the Wnt/β-catenin pathway could be therapeutic targets for treating cerebral ischemia-reperfusion injury.