Effect of heat acclimation on heat shock protein 72 and interleukin-10 in humans

Abstract

Heat acclimation (HA) results in whole body adaptations that increase heat tolerance, and in addition, HA may also result in protective cellular adaptations. We hypothesized that, after HA, basal intracellular heat shock protein (HSP) 72 and extracellular IL-10 levels would increase, while extracellular HSP72 levels decrease. Ten male and two female subjects completed a 10-day exercise/HA protocol (100-min exercise bout at 56% of maximum O(2) uptake in a 42.5 degrees C DB, 27.9% RH environment); subjects exhibited classic adaptations that accompany HA. Peripheral blood mononuclear cells (PBMCs) were isolated before and after each acclimation session on days 1, 6, and 10; plasma and serum were collected before and after exercise on the 1st and 10th day of HA. SDS-PAGE was used to determine PBMC HSP72 levels during HA, and ELISA was used to measure plasma IL-10 and serum HSP72 concentrations. The increase in PBMC HSP72 from pre- to postexercise on the 1st day of HA was not significant (mean +/- SD, 1.0 +/- 0 vs. 1.6 +/- 0.6 density units). Preexercise HSP72 levels on day 1 were significantly lower compared with the pre- and postexercise samples on days 6 and 10 (mean +/- SD, day 6: 2.1 +/- 1.0 and 2.2 +/- 1.0, day 10: 2.0 +/- 1.3 and 2.2 +/- 1.0 density units, respectively, P < 0.05). There were no differences in plasma IL-10 and serum HSP72 postexercise or after 10 days of HA. The sustained elevation of HSP72 from days 6 to 10 may be evidence of a cellular adaptation to HA that contributes to improved heat tolerance and reduced heat illness risk.

Exercise-heat acclimation in humans alters baseline levels and ex vivo heat inducibility of HSP72 and HSP90 in peripheral blood mononuclear cells

“…An exercise-HA protocol was employed that was similar to that employed by occupational and military workers exposed to heat. Only two recent studies have previously examined human HSP responses to heat acclimation (22,38), and the present study expanded upon those findings. The following new observations were made: 1) exercise-HA resulted in increased baseline expression of HSP72 and HSP90, 2) ex vivo inducibility to heat shock of HSP72 was blunted after HA, and 3) volunteers demonstrating the greatest physiological HA tended to exhibit the greatest blunting of ex vivo HSP induction in response to heat shock.…”

“…Heat acclimation and ATT are complementary with the former reducing physiological strain and the latter providing cellular protection against serious heat injury for any degree of physiological strain. Few studies have examined the coincident induction of HA and ATT in humans and the relationship between HA and expression of cytoprotective heat shock proteins (HSPs) (22,38).…”

“…However, it should be noted that full heat acclimatization generally requires 5-10 days (28,30). Yamada et al (38) examined PBMC HSP72 expression during a 10-day HA program and found elevated baseline levels from day 6 through day 10. The present study expands upon those two recent studies by including HSP90 and determining the response of HSP72 and 90 to ex vivo exposure to heat shock during HA in humans.…”

Heat shock response and autophagy—cooperation and control

“…144 Similarly, a 10-d acclimation program involving treadmill walking or running in a hot environment augments HSP70 content in peripheral blood mononuclear cells. 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.…”

“…Ryan et al showed that treadmill exercise results in no apparent increase in HSP70 protein expression in human leukocytes. 142 Similarly, 2 50-min bouts of moderate intensity aerobic exercise 143,144 do not affect HSP70 levels in peripheral blood mononuclear cells (PBMCs). In our recent studies, strenuous treadmill running (rectal temperature of 40 C) produces a timedependent increase in HSP70 protein expression in peripheral leukocytes, but the difference did not reach statistical significance.…”