Role of AQP4 in ameliorating heat stress-induced cellular injury in a cell line model through active heat acclimation.

Introduction: Heat stress (HS) can progress to heat stroke, a life-threatening condition. Aquaporin-4 (AQP4) has been implicated in HS-induced brain injury, but its role in heat acclimation (HA)-mediated protection remains unclear. This study investigated whether HA ameliorates HS-induced brain damage through AQP4. Methods: 9L/lacZ cells were randomly assigned to four groups: Control (37 °C, 5% CO₂), HA (39 °C, 5% CO₂, 2 h/day for 6 days), HS (43 °C, 5% CO₂, 2 h), and HA+HS (HA pretreatment followed by HS). In addition, cells in the Control and HS groups were treated with the selective AQP4 inhibitor TGN-020 (0.1 μmol/mL, 2 h before HS). The expression of HSP70, HSP90, and AQP4 was measured by western blotting; AQP4 mRNA levels were assessed by RT-PCR. Cell proliferation viability was evaluated by CCK-8 assay, and apoptosis was detected by flow cytometry. Results: Notably, AQP4 expression (RT-PCR and Western blot) was lower in the HA+HS group than in the HS group. Flow cytometry revealed that both HA+HS and TGN-020 treatment reduced apoptosis compared with HS alone. Discussion: These findings indicate that HA attenuates HS-induced injury by downregulating AQP4 expression, and that AQP4 inhibition mimics this protective effect. AQP4 represents a potential therapeutic target for heat stroke.