Rutin pretreatment promotes microglial M1 to M2 phenotype polarization

Microglial cells are important resident innate immune components in the central nervous system that are often activated during neuroinflammation. Activated microglia can display one of two phenotypes, M1 or M2, which each play distinct roles in neuroinflammation. Rutin, a dietary flavonoid, exhibits protective effects against neuroinflammation. However, whether rutin is able to influence the M1/M2 polarization of microglia remains unclear. In this study, in vitro BV-2 cell models of neuroinflammation were established using 100 ng/mL lipopolysaccharide to investigate the effects of 1-hour rutin pretreatment on microglial polarization. The results revealed that rutin pretreatment reduced the expression of the proinflammatory cytokines tumor necrosis factor-α, interleukin-1β, and interleukin-6 and increased the secretion of interleukin-10. Rutin pretreatment also downregulated the expression of the M1 microglial markers CD86 and inducible nitric oxide synthase and upregulated the expression of the M2 microglial markers arginase 1 and CD206. Rutin pretreatment inhibited the expression of Toll-like receptor 4 and myeloid differentiation factor 88 and blocked the phosphorylation of I kappa B kinase and nuclear factor-kappa B. These results showed that rutin pretreatment may promote the phenotypic switch of microglia M1 to M2 by inhibiting the Toll-like receptor 4/nuclear factor-kappa B signaling pathway to alleviate lipopolysaccharide-induced neuroinflammation.