Mechanism of resveratrol in alleviating neuroinflammation after cerebral ischemia reperfusion by inhibiting Toll like receptor 4 signaling pathway

Abstract

Objective To explore the mechanism of resveratrol in alleviating neuroinflammation after cerebral ischemia-reperfusion injury by inhibiting Toll like receptor 4 (TLR4) signaling pathway. Methods Sixty adult male SD rats were randomly divided into sham-operated group, cerebral ischemia-reperfusion injury group, and resveratrol treatment group (n=20). Rat models of transient middle cerebral artery occlusion (MCAO) in the latter two groups were prepared by modified thread embolization method; reperfusion was performed after 2 h of occlusion, and 20 mg/kg normal saline or resveratrol via tail vein injection was given 15 min before model preparation and one min before reperfusion, respectively. At 72 h after MACO, neurological severity scale (NSS) was applied to evaluate the neurological functions of rats. Enzyme linked immunosorbent assay was performed to detect the expressions of pro-inflammatory cytokines interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and anti-inflammatory cytokines IL-4, IL-10, and transforming growth factor (TGF)-β. Reverse transcription-polymerase chain reaction was performed to detect the mRNA expressions of M1 signature markers IL-1β and CD32 and M2 signature markers CD206 and Arginase-1. Western blotting was used to detect the expressions of TLR4 signaling molecules TLR4, myeloid differentiation protein 88 (MyD88), tumor necrosis factor receptor-associated factor 6 (TRAF6), IL-1 receptor associated kinase 1 (IRAK1) and nuclear factor (NF)-κB. Results As compared with those in the sham-operated group, rats in the cerebral ischemia-reperfusion injury group had significantly decreased NSS scores, significantly elevated levels of IL-1β, IL-6, TNF-α, IL-4, IL-10, and TGF-β in the damaged brain tissues, significantly elevated mRNA expression levels of IL-1β, CD32, CD206, and Arginase-1, and significantly elevated protein expression levels of TLR4, MyD88, TRAF6, IRAK1 and NF-κB (P<0.05). As compared with rats in the cerebral ischemia-reperfusion injury group, rats in the resveratrol treatment group had significantly decreased NSS scores, significantly decreased levels of IL-1β, IL-6, and TNF-α, significantly elevated levels of IL-4, IL-10, and TGF-β in the damaged brain tissues, significantly deceased mRNA expression levels of IL-1β and CD32, significantly elevated mRNA expression levels of CD206 and Arginase-1, and significantly decreased protein expression levels of TLR4, MyD88, TRAF6, IRAK1 and NF-κB (P<0.05). Conclusion Resveratrol inhibits microglia M1-type polarization and promotes M2-type polarization after cerebral ischemia reperfusion by inhibiting TLR4 signaling pathway, which further reduces neuroinflammation and neurological deficits. Key words: Resveratrol; Cerebral ischemia reperfusion; Toll like receptor 4; Microglia; Neuroinflammation