EIF4A3-Induced circ_0029941 Promotes Astrocyte Activation Through Enhancing Autophagy via miR-224-5p/NFAT5 Axis

The abnormal expression of circular RNA (circRNA) has been implicated in the development of many human diseases, including acute ischemic stroke (AIS). However, the role and mechanism of circ_0029941 in AIS progression remain unclear. Transient middle cerebral artery occlusion (tMCAO) was constructed to mimic AIS mice model, and oxygen-glucose deprivation/reoxygenation (OGD/R)-induced astrocytes were used to mimic AIS cell model. The expression of circ_0029941, eukaryotic translation initiation factor 4A-III (EIF4A3), microRNA (miR)-224-5p and nuclear factor activated T cell 5 (NFAT5) were determined by quantitative real-time PCR. Triphenyl tetrazolium chloride staining was used to evaluate infarct size in mice, and immunostaining was performed to confirm GFAP, MAP1LC3B, and NFAT5 levels. Protein expression was tested by western blot analysis, and FISH was used for co-location. The interaction between circ_0029941 and miR-224-5p was verified by RIP and RNA pull-down assays. And the interaction between miR-224-5p and NFAT5 was confirmed by RIP and dual-luciferase reporter assays. Circ_0029941 had elevated expression in AIS patients, tMCAO models and OGD/R-induced astrocytes. Knockdown of circ_0029941 alleviated brain infarction in tMCAO mice. Also, circ_0029941 knockdown inhibited astrocyte activation and ATG5-mediated autophagy. In addition, EIF4A3 promoted circ_0029941 level, and circ_0029941 sponged miR-224-5p to regulate NFAT5. Besides, miR-224-5p inhibitor or NFAT5 overexpression reversed the inhibition effect of circ_0029941 knockdown on astrocyte activation and autophagy. In addition, antagomiR-224-5p also abolished the relieving effect of circ_0029941 knockdown on brain infarction of tMCAO mice. EIF4A3-induced circ_0029941 promoted astrocyte activation and autophagy through regulating the miR-224-5p/NFAT5 axis.