Microglia-derived exosomal miR-302a-3p suppresses ferroptosis to alleviate cerebral ischemia/reperfusion injury by inhibiting neuronal ferritinophagy via regulating the Keap1/Nrf2 axis Running title: The effect of BV2-Exo on cerebral I/R injury

Abstract Recently, the protective effect of exosomes on ischemia/reperfusion (I/R) injury has become a research hotspot. The purpose of this study was to explore the therapeutic potential of microglia-derived exosomes on cerebral I/R injury. BV2 cell-derived exosomes (BV2-Exo) were extracted and characterized. The cerebral I/R model was constructed in vivo and intervened by using exosomes loaded with miR-302a-3p. The oxygen and glucose deprivation (OGD) model was constructed in vitro to simulate cerebral I/R injury. The binding sites of miR-302a-3p to Keap1 were analyzed by bioinformatics prediction and confirmed by dual-luciferase reporter assay. A study of whether exosomal miR-302a-3p affected cerebral I/R injury via the Keap1/Nrf2 axis was carried out by overexpression of keap1 (oe-keap1). Experimental results in vivo showed exosomal miR-302a-3p significantly repaired the cognitive impairment and suppressed the cell death of hippocampal neurons induced by cerebral I/R injury. Besides, exosomal miR-302a-3p inhibited the expression of ferroptosis-related proteins NCOA4, PTGS2, and p53 in cerebral I/R-treated mice. Bioinformatics prediction and double-luciferase reporter assay showed that Keap1 was the direct downstream target of miR-302a-3p. Experiment results in vitro showed that oe-Keap1 reversed the therapeutic effect of exosomal miR-302a-3p on cerebral I/R injury via the Keap1/Nrf2 axis, promoting the high expression of NCOA4, PTGS2, and p53 and the increase of Fe2+, MDA and ROS levels. These results demonstrated that microglia-exosomal miR-302a-3p suppressed ferroptosis to alleviate cerebral I/R injury by inhibiting neuronal ferritinophagy via regulating the Keap1/Nrf2 axis.