Astragalus polysaccharide treatment relieves cerebral ischemia‒reperfusion injury by promoting M2 polarization of microglia by enhancing O-GlcNAcylation.

Cerebral ischemia‒reperfusion (I/R) injury seriously threatens the lives of patients. Astragalus polysaccharide (APS) is the main active ingredient of Astragalus membranaceus and has a wide range of pharmacological activities. Here, we aimed to explore the impacts of APS on cerebral I/R injury and its specific mechanisms. We established a cerebral I/R injury model using middle cerebral artery occlusion (MCAO)-treated rats and oxygen glucose deprivation/reoxygenation (OGD/R)-treated BV2 cells. The interleukin 1β (IL-1β), interleukin 6 (IL-6) and interleukin (IL-10) levels were determined using corresponding ELISA kits and RT‒qPCR. The levels of M1 microglial markers (INOS and CD16) and M2 microglial markers (Arg-1 and CD206) were measured by RT‒qPCR. The O-linked N-acetylglucosamine modification (O-GlcNAcylation), O-GlcNAc transfer (OGT) and O-GlcNAc glycosidase (OGA) protein levels were measured by Western blot. Our results showed that APS treatment decreased IL-1β (179.72 ± 9.08 vs. 81.33 ± 6.30) and IL-6 (445.56 ± 33.09 vs. 234.75 ± 27.62) levels and increased IL-10 (41.95 ± 4.18 vs. 86.40 ± 7.16) levels in OGD/R-treated BV2 cells (p < 0.001). In addition, APS promoted the M2 polarization of OGD/R-treated BV2 cells, manifested by an increase in Arg-1 (0.43 ± 0.04 vs. 0.76 ± 0.03) and CD206 (0.36 ± 0.03 vs. 0.65 ± 0.06) and a decrease in INOS (2.84 ± 0.39 vs. 1.56 ± 0.19) and CD16 (4.04 ± 0.36 vs. 1.88 ± 0.09) in OGD/R-treated BV2 cells (p < 0.001). Additionally, APS treatment increased the O-GlcNAcylation and OGT levels in OGD/R-treated BV2 cells, while OGT knockdown reversed the effect of APS in OGD/R-treated BV2 cells and MCAO-treated rats (p < 0.05). Our study demonstrated that APS alleviated cerebral I/R injury by promoting the M2 polarization of microglia by enhancing OGT-mediated O-GlcNAcylation. [ABSTRACT FROM AUTHOR]