Annexin A1 alleviates heatstroke by inhibiting RIPK3/MLKL-mediated necroptosis through an FPR2-dependent pathway in male mice

Heatstroke is a life-threatening condition characterised by severe inflammation and often linked to necroptosis, a form of programmed cell death mediated by receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like pseudokinase (MLKL). Annexin A1 (AnxA1) is known to play a role in resolving inflammation, but its effects on heatstroke remain unclear. This study investigates the role of AnxA1 in heatstroke and its potential mechanisms.

The levels of AnxA1 were measured in patients with heatstroke and in a mouse model of heatstroke. The severity of heatstroke symptoms was compared between wild-type (WT) male C57BL/6 mice and those lacking AnxA1 or its receptor FPR2 on a C57BL/6 background. Additionally, recombinant AnxA1 was administered in vivo and in vitro to assess its therapeutic potential and to investigate underlying mechanisms.

The expression of AnxA1 increased significantly in response to heat stress in both heatstroke patients and mice. The absence of AnxA1 or FPR2 exacerbated heatstroke severity, while administering AnxA1 alleviated the symptoms in heat-stressed mice and cell models. These protective effects were mediated through the FPR2 receptor. Further analysis of the mechanism revealed that AnxA1 treatment inhibited the phosphorylation of key necroptosis proteins, RIPK3 and MLKL.

This study highlights the activation of the endogenous AnxA1-FPR2 signalling pathway following heat exposure and demonstrates that AnxA1 can mitigate heatstroke by inhibiting RIPK3/MLKL-mediated necroptosis. These findings suggest that enhancing endogenous AnxA1 levels or administering recombinant AnxA1 may be promising therapeutic strategies for managing heatstroke.