Downregulated FTO Promotes MicroRNA-155-mediated Inflammatory Response in Cerebral Ischemia/Reperfusion Injury

This study aimed to elucidate the mechanism for alteration of m⁶A RNA modification in cerebral ischemia/reperfusion(I/R) injury and identify novel therapeutic targets. A rat cerebral I/R injury model was established by middle cerebral artery occlusion (MCAO) followed by reperfusion. Changes in m⁶A RNA modification were evaluated by colorimetric quantification. The expression of the m⁶A methyltransferases METTL3, METTL14, and WTAP, and the demethylases FTO and ALKBH5 were determined using qPCR and western blot analyses. FTO was overexpressed in brain tissues via intracerebroventricular injection of adenoviruses encoding FTO. The protective effect of FTO on m⁶A RNA modification and cerebral I/R injury was assessed. MeRIP assays were used to detect the impact of FTO overexpression on m⁶A modification of pri-miR-155; qPCR analysis was used to identify its maturation. Finally, the role of miR-155 overexpression in the protective effects of FTO on cerebral I/R injury was examined. m⁶A levels of total RNA were increased, and m⁶A methyltransferase FTO expression was decreased in post-I/R injury cerebral tissues. FTO overexpression reversed the increase in m⁶A RNA modification and attenuated cerebral I/R injury. Furthermore, FTO overexpression increased the m⁶A modification of pri-miR-155 and enhanced its maturation to form miR-155. Notably, miR-155 overexpression blunted FTO's protective effect against cerebral I/R injury. We propose that downregulation of FTO expression contributes to increased m⁶A RNA modification in cerebral I/R injury. FTO overexpression reverses increased total m⁶A RNA modification and exerts a protective effect against cerebral I/R injury via downregulating m6A modification of pri-miR-155 to inhibit its maturation process.