HMGB1-induced NLRP3 Inflammasome Participating in Platelet Activation and Thrombocytopenia in Heatstroke

Abstract Background: Previous studies have suggested that NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome plays an important role in heat stroke (HS). As a common complication in HS, thrombocytopenia has been widely considered as a good predictor of HS-related mortality. However, little is known about the relationship between inflammasome and thrombocytopenia as well as platelet activation in HS. Methods: We established a rat HS model to investigate the roles of NLRP3 inflammasome in both platelet activation and thrombocytopenia, platelet activation was reflected with Flow cytometry while thrombocytopenia was measured by platelet count. The colocalization of NLRP3 inflammasome was detected by confocal fluorescence microscopy. Mitochondrial-derived reactive oxygen species (ROS) were detected using the molecular probes. Plasma HMGB1 levels were measured by ELISA.Results: Activation of the inflammasome was detected in platelet of rats in HS. Elevated ROS activated NLRP3 inflammasome in HS group could significantly induce platelet activation and thrombocytopenia. The upregulated P-selectin (CD62P ) and decreased platelet count triggered by NLRP3 inflammasome were attributed to the high mobility group box protein 1 (HMGB1) in plasma. Moreover, inhibition of HMGB1, caspase-1, NLRP3, or ROS in rats with HS suppressed platelet activation and the decline of platelet count. Similar results were obtained when the receptor toll-like receptor 4 (TLR4) / advanced glycation end product (RAGE) was blocked. Conclusions: This study indicated that platelets were activated by NLRP3 inflammasome through TLR4/RAGE/HMGB1 signaling pathway. The NLRP3 inflammasome might be the potential target for HS treatment.