To explore the roles of mesenteric lymph on lung injury in heatstroke (HS), HS rat model was prepared in a prewarmed incubator. Vascular endothelium injury biomarkers (circulating endothelial cell [CEC] as well as von Willebrand factor [vWF] and thrombomodulin [TM]), proinflammatory factors (tumor necrosis factor-α [TNF-α], interleukin-1β [IL-1β], IL-6, and high mobility group box 1), and coagulant markers (activated partial thromboplastin time, prothrombin time, D-Dimer, and platelet count) were tested in HS and HS with mesenteric lymph duct ligation (LDL) rats. In addition, lung histopathology; arterial blood gas; Evans Blue dye (EBD) and protein lung permeability; intralung inflammatory parameters including bronchoalveolar lavage fluid (BALF) TNF-α, IL-1β, and IL-6 levels; myeloperoxidase (MPO) activity; and vWF immune staining were analyzed. LDL prolonged HS onset time but not HS survival time. LDL significantly attenuated endothelial cell injury for decreased CEC counts as well as plasma vWF and TM concentrations; downregulated systemic inflammation for decreased plasma TNF-α, IL-1β, IL-6, and high mobility group box 1 levels; and ameliorated coagulant disorders for decreased activated partial thromboplastin time, prothrombin time, and D-Dimer levels as well as increased platelet counts. LDL also significantly reduced acute lung pathological injury; improved lung function indexes including arterial blood PaO2, pH, PaCO2, and lactic acid; decreased BALF TNF-α, IL-1β, and IL-6 levels and lung MPO activity; improved EBD and protein lung permeability; and inhibited lung vascular endothelium vWF expression. However, all of these parameters were not recovered to the normal states. In summary, LDL developed protection roles systemically and alleviated lung injury in HS rats which indicated that modulating mesenteric lymph flow may have some potential benefits in HS.

Background Thrombocytopenia, an early common complication in heatstroke (HS), has been widely considered as a mortality predictor of HS. The mechanism underlying thrombocytopenia in HS remains unknown. It is not known whether NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is activated in HS platelet, which, in turn, induces platelet activation and thrombocytopenia. This study tried to clarify the activation of the NOD-like receptor signaling pathway under HS conditions and investigate its roles in mediating HS-induced thrombocytopenia. Methods Rat HS models were established in a certain ambient temperature and humidity. Platelets, isolated from blood, were counted and CD62P, an index of platelet activation, was measured by flow cytometry in all rats. The colocalization of NLRP3 inflammasome in platelet was detected by confocal fluorescence microscopy. Mitochondrial-derived reactive oxygen species (ROS) was detected using the molecular probes. Plasma HMGB1 and IL-1β levels were measured by ELISA. Results Platelet activation, showed by upregulated CD62P, and thrombocytopenia were observed in HS rats. HS activated the NLRP3 inflammasome, which was induced by elevated levels of ROS, while the upregulated CD62P and thrombocytopenia triggered by NLRP3 inflammasome were attributed to the high mobility group box protein 1 (HMGB1) inplasma. Moreover, inhibition of the NOD-like receptor signaling pathway 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 The NOD-like receptor signaling pathway induces platelet activation and thrombocytopenia in HS rats. These findings suggested that the NLRP3 inflammasome might be the potential target for HS treatment.