Loureirin C ameliorates ischemia and reperfusion injury in rats by inhibiting the activation of the TLR4/NF‐κB pathway and promoting TLR4 degradation

Abstract Ischemic stroke is a leading cause of death and disability worldwide. Post‐ischemia, microglia respond immediately to the alternations in neuronal activity and mediate inflammation. Toll‐like receptor 4 (TLR4) plays a key role in this phenomenon. To explore the effect of loureirin C, an effective compound from Chinese Dragon's blood, on ischemic stroke, Sprague–Dawley rats were subjected to middle cerebral artery occlusion/reperfusion (MCAO/R) with/without intragastric administration of loureirin C (7, 14, and 28 mg/kg). Loureirin C alleviated MCAO/R‐induced brain impairment evaluated by neurological scores ( p < 0.001), brain water content ( p < 0.001), and cerebral infarct volume ( p = 0.001). The neuroprotective ( p < 0.001) and inhibitory effects on microglial activation ( p < 0.001) of loureirin C were revealed by immunofluorescence. Rescue studies with TLR4 overexpression in BV‐2 microglia showed that the antiinflammatory effect of loureirin C was attributable to the inhibition of TLR4 protein expression. Moreover, co‐immunoprecipitation assays showed that the binding of Triad3A, an E3 ubiquitin ligase of TLR4, was increased by loureirin C ( p = 0.003). Our study demonstrates that loureirin C could be a promising therapeutic agent for the management of ischemic stroke by inhibiting microglial activation, potentially by Triad3A‐mediated promotion of TLR4 ubiquitination and degradation.