Senkyunolide I attenuates oxygen-glucose deprivation/reoxygenation-induced inflammation in microglial cells

• Senkyunolide I suppressed the expression and release of inflammatory mediators in BV-2 cells induced by OGD/R.
• The anti-inflammatory effect of Senkyunolide I was mediated by inhibiting TLR4/NF-κB pathway, but not MAPK pathway.
• The anti-inflammatory effect of Senkyunolide I was partly dependent on activating HSF-1 and inducing Hsp70.
• Senkyunolide I inhibited TLR4/NF-κB pathway via upregulating Hsp70 in primary microglial cells stimulated by OGD/R.

Over-activated microglia during stroke has been documented to aggravate brain damage. Our previous studies showed that senkyunolide I (SEI) exerted anti-inflammatory effects against endotoxin insult in vitro and ameliorative effects on cerebral ischemia/reperfusion (I/R) injury in vivo. Using oxygen-glucose deprivation/reoxygenation (OGD/R) to mimic stroke, we here investigated the anti-inflammatory effect of SEI on microglial cells and explored the underlying mechanisms. OGD for 3 h followed by reoxygenation for 12 h significantly enhanced the release of pro-inflammatory cytokines and expressions of inflammation-related enzymes in BV-2 cells, which was inhibited by pretreatment with SEI. To elucidate the mechanisms, we studied its effect on upstream signaling pathways. It was found that SEI suppressed the activation of NF-κB pathway induced by OGD/R and the MAPK pathway was shown not to be involved. Furthermore, SEI significantly down-regulated TLR4/MyD88 pathway with specifically improving inducible Hsp70 level through increasing HSF-1/DNA binding activity, and these regulations responsive to SEI were attenuated by transfecting Hsp70 siRNA and HSF-1 decoy ODNs. Additionally, SEI exerted similar influence on Hsp70/TLR4/NF-κB pathway in rat primary microglial cells. The results suggested that SEI had a potent effect against stroke-induced neuroinflammation through suppressing the TLR4/NF-κB pathway by up-regulating Hsp70 dependent on HSF-1.