Calycosin attenuates the inflammatory damage of microglia induced by oxygen and glucose deprivation through the HMGB1/TLR4/NF-κB signaling pathway: Calycosin attenuates OGD/R damage in microglia

Stroke seriously threatens human life and health worldwide, but only very few effective stroke medicines are currently available. Our previous studies have indicated that the phytoestrogen calycosin exerts neuroprotective effects in cerebral ischemia and reperfusion injury rats. Therefore, the objective of this study is to further explore the protective effect of calycosin on inflammatory injury in microglia after oxygen-glucose deprivation/reoxygenation (OGD/R) and to clarify whether its protective effect is related to the HMGB1/TLR4/NF-κB signaling pathway. Here, the OGD/R model of rodent microglia is established in vitro to simulate cerebral ischemia-reperfusion injury. Through the CCK-8 test, ELISA, qRT-PCR, and western blot analysis, we find that the activity of microglia is decreased, the expressions of HMGB1 and TLR4 and the phosphorylation of NF-κB (p-NF-κB) are increased, and the releases of the inflammatory factors IL-6, IL-1β, and TNF-α are increased after OGD/R. Pretreatment with calycosin could ameliorate these states, increase cell viability, reduce HMGB1, TLR4 and p-NF-κB expression, and reduce inflammatory cytokine production. In addition, the effect of calycosin is similar to that of TAK-242 (an inhibitor of TLR4), and the effect of the combined treatment is better than that of the single treatment. The results indicate that calycosin protects microglia from OGD/R injury and reduces the inflammatory response. Calycosin might alleviate cerebral ischemia-reperfusion injury by inhibiting the HMGB1/TLR4/NF-κB pathway.