Inhibition of proprotein convertase subtilisin/kexin type 9 attenuates neuronal apoptosis following focal cerebral ischemia via apolipoprotein E receptor 2 downregulation in hyperlipidemic mice

The inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9) protects a variety of cell types against neuronal apoptosis by binding to apolipoprotein E receptor 2 (ApoER2). The present study aimed to determine the association between PCSK9/ApoER2 signaling and neuronal apoptosis following middle cerebral artery occlusion (MCAO) injury in hyperlipidemic mice. For this purpose, C57BL/6 mice fed with a high-fat diet (HFD) for 6 weeks were exposed to NICAO. Subsequently, PCSK9 was inhibited by a lentiviral vector harboring short-hairpin RNA (shRNA) targeting PCSK9, which was stereotaxically injected into the cerebral cortex of mice. At 48 h post-ischemia, hematoxylin-eosin staining and a terminal deoxynucleotidyl transferase dUTP nick end labeling assay were performed to determine cerebral tissue injury and apoptosis. PCSK9 and ApoER2 expression levels were assessed by reverse transcription-quantitative polymerase chain reaction, immunohistochemistry and western blotting. The results indicated that hyperlipidemia and increased PCSK9 expression were evident in RFD mice. Cerebral histological injury and neuronal apoptosis, as well as PCSK9 and ApoER2 levels, which were increased upon ischemia in hyperlipidemic mice, were attenuated by PCSK9 shRNA treatment. These protective effects of PCSK9 shRNA interference were associated with decreased neuronal apoptosis and a reduced level of ApoER2 expression in the hippocampus and cortex. The data of the present study demonstrated that the PCSK9 shRNA-mediated anti-apoptotic effect induced by MCAO in hyperlipidemic mice is associated with ApoER2 downregulation, which may be a potential new therapy for stroke treatment in patients with hyperlipidemia.