Circulating and intracellular HSP72 responds acutely to cumulative exercise stress, heat stress, dehydration, and rehydration and may be mediated by collective effects of multiple stress‐specific transcription factors

We have previously shown that protective protein HSP72 responds acutely and chronically during 11d of daily exercise‐heat stress. In this study (n=6, men), we aimed to characterize acute HSP72 and transcription factor responses to 2d of sequential stress and rest periods. In each of 4 repeat visits, participants: 1) passively dehydrated overnight, 2) exercised for 2h with no fluid in a hot and humid environmental chamber, 3) rested and rehydrated for 1h, 4) maximally exercised for 0.5h, and 5) returned after 24h of at‐home recovery and rehydration. We tracked rectal temperature, hydration status, circulating HSP72, and intracellular (flow cytometry) expression of HSP72 and cellular stress‐specific transcription factor NFAT5. We found that circulating and intracellular HSP72 significantly correlated (p<0.05) with physiological manifestations of heat, exercise, and dehydration stresses and recovery/rehydration periods. NFAT5 expression correlated (p<0.05) with measures of hydration status suggesting for the first time that this cellular osmotic stress‐induced transcription factor may reflect whole body hydration status, and contribute to general protective responses during aggregate stress.