Gender Difference in Heat Shock Protein Expression and Inflammation in Response to Acute Exercise in the Heat.

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Heat shock protein 72 (Hsp72) is responsible for maintaining critical cellular function during heat stress. Hsp72 confers thermotolerance and may play a role in heat acclimation. Animal research suggests a difference between genders in Hsp72 expression in response to exercise. However, there have been no human studies examining this response. PURPOSE: To compare the effect of gender on intracellular Hsp72 and pro- and anti-inflammatory cytokine expression in response to an acute bout of exercise in the heat. METHODS: 4 women and 3 men ran on a treadmill at 60% VO2max for 60 min in a 42°C room. Women were regularly menstruating and not taking hormonal contraceptives. Women were tested in the Luteal phase. Blood was drawn pre, post, 1 hr, and 4 hrs post exercise. Flow cytometry was used to analyze cells for Hsp72, IL-1ra, IL-6, and TNF-a.TABLERESULTS: Final rectal temperature was 39.28°C for men (age 25 ± 5, 11.0± 5.5 % BF, 54.4 ± 7.3 ml/kg/min) and 38.72°C for women (age 21.5 ± 2.5, 21.3 ± 3.6 % BF, 44.5 ± 4.5 ml/kg/min). 2 of the 4 women tested were unable to complete the full 60 min of exercise because of heat illness symptoms. An overall group effect was evident with men expressing higher Hsp72 (p=.01), IL-1ra (p=. 02), IL-6 (p=. 01), and TNF-a (p=. 01) MFI levels than women. CONCLUSION: This preliminary data suggests that men and women differ in the amount of Hsp72 expressed in blood mononuclear cells in response to exercise. Women increased the amount of Hsp72 with exercise, but not to the same extent as men. In addition, there appears to be gender differences in IL-1ra, IL-6, and TNF-a production in response to exercise in the heat. We speculate that estrogen may be acting as an anti-oxidant and cell membrane stabilizer to confer cellular protection to exercise in the heat.