Dioscin ameliorates cerebral ischemia/reperfusion injury through the downregulation of TLR4 signaling via HMGB-1 inhibition

Abstract

We previously reported the promising effect of dioscin against hepatic ischemia/reperfusion (I/R) injury, but its effect on cerebral I/R injury remains unknown. In this work, an in vitro oxygen-glucose deprivation and reoxygenation (OGD/R) model and an in vivo middle cerebral artery occlusion (MCAO) model were used. The results indicated that dioscin clearly protected PC12 cells and primary cortical neurons against OGD/R insult and significantly prevented cerebral I/R injury. Further research demonstrated that dioscin-induced neuroprotection was accompanied by a significant inhibition in the expression and the nuclear to cytosolic translocation of HMGB-1, reflected by decreased TLR4 expression. Blockade of the TLR4/MyD88/TRAF6 signaling pathway by dioscin inhibited NF-κB and AP-1 transcriptional activities, MAPK and STAT3 phosphorylation, and pro-inflammatory cytokine responses, and upregulated the levels of anti-inflammatory factors. In addition, small interfering RNA (siRNA) and overexpressed genes of HMGB-1 and TLR4 were applied in in vitro experiments, respectively, and the results further confirmed that dioscin showed an efficient neuroprotection because of its inhibiting effects on HMGB-1/TLR4 signaling and subsequent suppressing inflammation. These findings provide new insights that will aid in elucidating the effect of dioscin against cerebral I/R injury and support the development of dioscin as a potential treatment for ischemic stroke.

Keywords: Cerebral ischemia/reperfusion; Dioscin; HMGB-1; Inflammation; TLR4 signaling pathway.