Sex Differences in Heat Shock Protein 72 Expression in Peripheral Blood Mononuclear Cells to Acute Exercise in the Heat

Abstract

Background: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 sexes in Hsp72 expression in response to exercise, however, human data is lacking.Objectives:To determine sex differences in intracellular heat shock protein 72 (Hsp72) following exercise in the heat.Patients and Methods:Nine non-heat acclimated women with normal menstrual cycles (VO2pk 58 ± 5 mL.kgFFM-1.min-1) and nine non-heat acclimated men (VO2pk 60 ± 7 ml.kgFFM-1.min-1) completed 2 treadmill bouts at 60% VO2pk for 60 min in a 42°C, 20% RH environment. Women were tested in follicular (fol) and luteal (lut) phases. The duplicate trials were separated by 12 days for men and women. Blood samples were drawn pre, immediately post, 1, and 4 hrs post-exercise.Results:Men and women differed in their Hsp72 response after exercise (time X sex X trial interaction; P < 0.05). Men increased Hsp72 after exercise more than women. Both men and women produced less Hsp72 during trial 2 compared to trial 1. Estrogen (r = 0.24; P > 0.05) and progesterone (r = 0.27, P > 0.05) concentrations were not correlated with Hsp72.Conclusion:Our findings suggest that men and women differ in their cellular stress response. Men up-regulated Hsp72 after a single bout of exercise in the heat, which persists for 12 days, suggesting an accumulation of Hsp72 which may lead to acquired cellular thermotolerance.

Leukocyte Hsp72 mRNA transcription does not differ between males and females during heat acclimation

“…In contrast to our hypothesis, this experiment demonstrates that the Hsp72 mRNA response is similar between males and females on D1, D5, and D10 of a controlled hyperthermia HA. This suggests that sex differences in HSP following acute 20 and Table 3. Physiological and performance measures on D1, D5, and D10 of controlled hyperthermia heat acclimation.…”

“…Height was measured using a fixed stadiometer recorded to 1 cm (Detecto Physicians Scales; Cranlea & Co., Birmingham, UK), and nude body mass (BM) recorded to 0.01 kg from digital scales (ADAM GFK 150, USA). A graded exercise test was performed in temperate laboratory conditions [20 C, 40% relative humidity (RH)] to determine V̇O 2 peak using a cycle ergometer (Monark e724, Vansbro, Sweden). The cycling intensity was set to 80 W and resistance was applied to the flywheel to elicit a 16 to 24 W.min ¡1 increase (selected depending on the BM of the participant).…”

“…19 Gillum et al (2013) reported higher intracellular HSP72 concentrations following a single bout of exercise in the heat in males compared with females (in both the follicular and luteal phase of the menstrual cycle), despite similar baseline values and identical endogenous stimuli for Hsp72 mRNA transcription. 20 Differential sex responses were also suggested to be a result of estrogen providing cellular protection and thus, decreasing the necessity for translation of HSP72 in females. Although, stress-mediated sex specific differences in the HSP72 have been seen, 16,20 they have not been examined at an mRNA level across the course of controlled hyperthermia HA.…”

“…20 Differential sex responses were also suggested to be a result of estrogen providing cellular protection and thus, decreasing the necessity for translation of HSP72 in females. Although, stress-mediated sex specific differences in the HSP72 have been seen, 16,20 they have not been examined at an mRNA level across the course of controlled hyperthermia HA.…”

“…16,20 Absence of data in female populations could be problematic for practitioners who may adopt HA protocols that are informed by mechanistic cellular adaptations from male only cohorts. 7,21 This may reduce the magnitude to which females are protected against heat injury.…”