circHIPK3 regulates apoptosis and mitochondrial dysfunction induced by ischemic stroke in mice by sponging miR-148b-3p via CDK5R1/SIRT1

Circular RNAs (circRNAs) are aberrantly expressed in the brain and play a role in a variety of central nervous system diseases. However, the essential role and therapeutic potential of circRNAs in ischemic stroke (IS) are poorly understood. Here, using circRNA sequencing, we showed that circRNA homeodomain-interacting protein kinase 3 (circHIPK3) was abundantly expressed in ischemic brain tissues in transient middle cerebral artery occlusion (tMCAO)-evoked stroke model mice. Knockdown of circHIPK3 markedly reduced the infarct volume, brain water content, neurological deficit scores, and blood-brain permeability and ameliorated brain microvascular endothelial cell (BMEC) apoptosis and mitochondrial dysfunction in tMCAO mice. Gain- and loss-offunction experiments were performed to verify the effects of miR-148b-3p on oxygen-glucose deprivation (OGD)-induced BMEC apoptosis and mitochondrial dysfunction. Mechanistically, circHIPK3 functions as an endogenous sponge of miR-148b-3p to decrease its activity, resulting in upregulation of CDK5R1 and CDK5 expression, downregulation of SIRT1 expression and subsequent BMEC apoptosis and mitochondrial dysfunction. Collectively, our findings suggest that circHIPK3 and its coupling mechanism are implicated in IS, providing translational evidence that circHIPK3 could be a key therapeutic target for IS.