Heat Acclimation and HSP-72 Expression in Exercising Humans

Abstract

The purpose of this research was to determine the effect of a 7-day heat acclimation protocol on HSP-72 expression in human skeletal muscle, and to examine the relationships between molecular and physiological markers of heat acclimation. Ten recreationally active male subjects (age = 23.3 +/- 2.81 yrs, VO(2peak) = 3.85 +/- 0.11 L . min (-1)) completed a 7-day heat acclimation protocol consisting of cycling at 75 % of VO(2peak) in a hot environment (39.5 degrees C, 27 % RH). Muscle biopsies were obtained on days 1 (HTT1) and 7 (HTT2) prior to, 6 h post, and 24 h postexercise to measure HSP-72 protein via SDS-PAGE and silver staining. Core rectal temperatures (T(C)), intramuscular temperatures (T(IM)), skin temperatures (T(SK)), heart rate (HR), oxygen uptake (VO(2)), sweat rate (SR), and plasma cortisol were measured. TC, HR, and plasma cortisol were significantly lower in HTT2 than HTT1 (p < or = 0.05). No significant differences were seen for VO(2), TIM, TSK, or SR when comparing HTT2 with HTT1 (p < or = 0.05). No significant time or day x time interactions were detected for HSP-72 expression (24.48 +/- 2.55 vs. 25.04 +/- 1.43 ng/microg protein for HTT1 and HTT2, respectively, p < or = 0.05). Evidence of heat acclimation was seen at the physiological level; however, no evidence of enhanced thermotolerance at the cellular level was indicated by HSP-72 expression.

Eleven days of moderate exercise and heat exposure induces acclimation without significant HSP70 and apoptosis responses of lymphocytes in college-aged males

“…Among the five or so studies that have examined intracellular HSP70 during acclimation, two show evidence to the contrary in intracellular studies of HSP70 during acclimation (Marshall et al 2007;Watkins et al 2008). Our results apparently contribute to the evidence that basal intracellular HSP70 does not reflect whole-body acclimation.…”

“…Relatedly, lower core temperatures and heart rate maximums were seen in the acclimation study of Marshall et al (2007), which found no change in intracellular HSP70 during early acclimation. Although Watkins et al (2008) also saw no change in intracellular HSP70 with observations of heart rates that reached between 165 and 185 bpm, their observed maximum core temperature was approximately 38.8°C and they measured HSP70 of muscle tissue lysates. If we attribute to possible differences in cell type or tissue response of HSP70, as has been shown (reviewed in Yamada et al 2008), it is possible that in order to perceive HSP70 responses in circulating cells, acclimating subjects must experience extreme hyperthermia and cardiovascular strain during daily exercise-heat exposures.…”

“…Thus, it might be more meaningful to measure IC HSP70 levels when exploring cellular adaptations that occur with heat acclimation. To our knowledge, only a few studies have examined IC HSP70 levels during heat acclimation (Marshall et al 2007;Yamada et al 2007;McClung et al 2008;Watkins et al 2008;Magalhaes Fde et al 2010).…”

Heat shock response and autophagy—cooperation and control

“…143,167,168 Elevation of HSP70 in response to high-intensity and long-term training is also found after an 11-d training program, but not in response to short or moderate intensity exercise. 146,[169][170][171][172] Besides exercise intensity, training status and the type of exercise seem to exert considerable effect on HSP70 expression. In untrained subjects, 5-8 wk of triceps brachii training produce a significant increase in HSP70, 173 whereas 12 wk of concentric contraction of biceps brachii decrease HSP70 protein expression in trained athletes.…”

Effects of whole-body heat acclimation on cell injury and cytokine responses in peripheral blood mononuclear cells

“…Although heat acclimation is recommended to athletes, to persons in certain occupations, and to military personnel at risk of heat illness, it is surprising that only recently have investigators begun to investigate the cellular adaptations (Yamada et al 2007;McClung et al 2008;Watkins et al 2008;Magalhães et al 2010). The present study was the first to test the hypothesis that changes in protein expression with whole-body acclimation in humans HA could modify the cellular response to stressors normally experienced by heat stroke patients.…”