Persistent neutrophil activation despite count normalization suggests immune dysregulation in exertional heat stroke.

BACKGROUND

The role of neutrophils in exertional heat stroke (EHS), a life-threatening condition characterized by systemic inflammation, remains poorly defined. This study aimed to characterize the longitudinal profiles of neutrophil recruitment and activation in EHS patients.

METHODS

In this retrospective study with a small sample size, we analyzed clinical data and biobanked serum samples from 18 EHS patients and 18 matched healthy controls. Serum levels of interleukin-6 (IL-6), IL-8, IL-17, granulocyte colony-stimulating factor (G-CSF), CXCL1, CXCL2, C-reactive protein (CRP), serum amyloid A (SAA), myeloperoxidase (MPO), and neutrophil elastase (NE) were quantified by ELISA at onset and on days 3, 5, and 7 post-treatment.

RESULTS

At onset, EHS patients exhibited significant neutrophilia and elevated levels of IL-8, CXCL1, CXCL2, and IL-17 (all P < 0.05). While neutrophil counts normalized within days post-treatment, MPO and NE levels remained persistently and significantly elevated throughout the 7-day follow-up compared to controls (all P < 0.0001). Furthermore, strong positive correlations were observed between the levels of CXCL1/CXCL2 and MPO/NE at disease onset.

CONCLUSION

In this exploratory study, our findings reveal a dissociation between neutrophil recruitment and activation in EHS. The persistent elevation of MPO and NE long after count normalization suggests a prolonged state of neutrophil dysregulation that could contribute to both acute tissue injury and long-term immune complications in EHS survivors.