NLRP3 ablation enhances tolerance in heat stroke pathology by inhibiting IL-1β-mediated neuroinflammation

BackgroundPatients with prior illness are more vulnerable to heat stroke-induced injury, but the underlying mechanism is unknown. Recent studies suggested that NLRP3 inflammasome played an important role in the pathophysiology of heat stroke.MethodsIn this study, we used a classic animal heat stroke model. Prior infection was mimicked by using lipopolysaccharide (LPS) or lipoteichoic acid (LTA) injection before heat stroke (LPS/LTA 1mg/kg). Mice survival analysis curve and core temperature (T-C) elevation curve were produced. NLRP3 inflammasome activation was measured by using real-time PCR and Western blot. Mice hypothalamus was dissected and neuroinflammation level was measured. To further demonstrate the role of NLRP3 inflammasome, Nlrp3 knockout mice were used. In addition, IL-1 beta neutralizing antibody was injected to test potential therapeutic effect on heat stroke.ResultsPrior infection simulated by LPS/LTA injection resulted in latent inflammation status presented by high levels of cytokines in peripheral serum. However, LPS/LTA failed to cause any change in animal survival rate or body temperature. In the absence of LPS/LTA, heat treatment induced heat stroke and animal death without significant systemic or neuroinflammation. Despite a decreased level of IL-1 beta in hypothalamus, Nlrp3 knockout mice demonstrated no survival advantage under mere heat exposure. In animals with prior infection, their heat tolerance was severely impaired and NLRP3 inflammasome induced neuroinflammation was detected. The use of Nlrp3 knockout mice enhanced heat tolerance and alleviated heat stroke-induced death by reducing mice hypothalamus IL-1 beta production with prior infection condition. Furthermore, IL-1 beta neutralizing antibody injection significantly extended endotoxemic mice survival under heat stroke.ConclusionsBased on the above results, NLRP3/IL-1 beta induced neuroinflammation might be an important mechanistic factor in heat stroke pathology, especially with prior infection. IL-1 beta may serve as a biomarker for heat stroke severity and potential therapeutic method.

Automated summary

Prior infection simulated by LPS/LTA injection resulted in latent inflammation with high cytokine levels, but did not affect animal survival or body temperature. Heat treatment induced heat stroke and death in animals without prior infection, showing no significant systemic or neuroinflammation. NLRP3 inflammasome-induced neuroinflammation was detected in animals with prior infection, and Nlrp3 knockout mice showed enhanced heat tolerance and reduced hypothalamus IL-1 beta production. IL-1 beta neutralizing antibody injection extended endotoxemic mice survival under heat stroke.