ADAR1 Promotes NUPR1 A-to-I RNA Editing to Exacerbate Ischemic Brain Injury by Microglia Mediated Neuroinflammation.

Abstract

Microglial cells occupy a crucial position as potential therapeutic targets in the context of ischemic stroke (IS). Nonetheless, the intrinsic mechanisms that govern microglial activation in the aftermath of IS remain incompletely elucidated. ADAR1 p150 plays a significant role in immune regulation and stress responses; however, the specific pathways through which it modulates microglial activation and the subsequent mechanisms that unfold following IS have yet to be clearly delineated. The distal middle cerebral artery occlusion (dMCAO) mouse model was utilized to induce IS. The evaluation of infarct volume was conducted through TTC staining, while neurological function was assessed using the modified Neurological Severity Score (mNSS). To evaluate the expression of ADAR1 and apoptosis-related proteins, immunofluorescence and Western blot techniques were employed. BV2 cells were subjected to oxygen-glucose deprivation followed by reperfusion (OGD/R). Additionally, a co-culture system of BV2 cells and neurons was established, and subsequent assessments of neuronal viability and apoptosis were performed using CCK-8 assays and LDH release assays. ADAR1 p150 expression was significantly upregulated in the brains of ischemic mice, particularly within microglial cells. The overexpression of ADAR1 p150 was found to promote microglial activation and enhance pro-inflammatory responses, whereas the knockdown of ADAR1 p150 yielded the opposite effect. Additionally, the knockdown of ADAR1 p150 in microglia resulted in a marked reduction in neuronal apoptosis within the co-culture system. Rescue experiments indicated that the knockdown of NUPR1 partially reinstated the inflammatory response previously induced by ADAR1 p150 knockdown. Notably, ADAR1 p150 knockdown also inhibited A-to-I RNA editing while simultaneously upregulating NUPR1. Furthermore, the reduction of ADAR1 expression was associated with decreased infarct volume, improved neurological outcomes, and a significant attenuation of neuroinflammation in dMCAO mice. ADAR1 p150 enhances the microglial inflammatory response and neuronal apoptosis in IS by facilitating A to I RNA editing of NUPR1.