The effect of the rate of heat storage on serum heat shock protein 72 in humans

Abstract

Hsp72 concentration has been shown to be higher in the serum (eHsp72) of runners with symptoms of heat illness than in non-ill runners. Recently, it has been suggested that the rate of heat storage during exercise in the heat may be an important factor in the development of heat stroke. Therefore, we compared the effect of two rates of heat storage on eHsp72 concentration during exercise in which subjects reached the same final core temperature. We hypothesized that with a lower rate of heat storage the increase in eHsp72 would be attenuated compared to a higher rate of heat storage. Nine heat acclimated subjects performed two exercise trials in a counterbalanced order in the heat (42 degrees C, 30% relative humidity). The trials consisted of walking on a treadmill (approximately 50% VO (2) peak) dressed in military summer fatigues until rectal temperature reached 38.5 degrees C. A high rate of heat storage (HS, 1.04 +/- 0.10 W m(-2) min(-1), mean +/- SE) occurred when subjects walked without cooling. To produce a lower rate of heat storage (LS, 0.54 +/- 0.09 W m(-2) min(-1)) subjects walked while wearing a water-perfused cooling vest underneath clothing. eHsp72 increased pre- to post-exercise (P < 0.05) but there was no difference (P > 0.05) in eHSP between the two rates of heat storage (LS 1.25 +/- 0.73 to 2.23 +/- 0.70 ng ml(-1), HS 1.04 +/- 0.57 to 2.02 +/- 0.60 ng ml(-1)). This result suggests that eHsp72 is a function of the core temperature attained rather than the rate of heat storage.

Extracellular Hsp72 concentration relates to a minimum endogenous criteria during acute exercise-heat exposure

“…Data from present study supports this "minimum endogenous criteria" notion (Table 2) from VHOT which elicited a greater internal temperature, rate of internal temperature rise and a greater duration at critical T rec than TEMP and HOT. Our data is supportive of the existence of minimum endogenous criteria for the induction of eHsp72 into the circulation during exercise-heat stress as suggested by Amorim et al (2008). Supporting the absence of eHsp72 increases in TEMP and HOT (T rec of 37.90±0.29°C and 38.35±0.52°C, respectively) in the present study, parallel exercise induced changes in T rec data (mean maximum T rec 38.48°C) resulting in no change in basal eHsp72 have been reported by Hom et al (2012) during treadmill walking.…”

“…Increased systemic eHsp72 has been shown to be exercise intensity and duration dependent in temperate conditions (Fehrenbach et al 2005), with the addition of thermal stress (evidenced by increase T rec ) further increasing the magnitude of response (Marshall et al 2006). Consequently, a heat storage independent threshold of 38.5°C (T rec ) has been postulated (Amorim et al 2008) and demonstrated central to the magnifying influence of thermal stress on eHsp72 concentrations (Amorim et al 2008), compared to moderate intensity matched exercise. Data from present study supports this "minimum endogenous criteria" notion (Table 2) from VHOT which elicited a greater internal temperature, rate of internal temperature rise and a greater duration at critical T rec than TEMP and HOT.…”

“…) and the delta change in T rec (VHOT 2.22±0.65°C), it may be more appropriate to implement an isothermic (controlled hyperthermia) model of exercise-heat exposure (Garrett et al 2009(Garrett et al , 2011(Garrett et al , 2012 where the rate of heat production can be accelerated (Amorim et al 2008) and proposed minimum endogenous temperatures targeted (Amorim et al 2011). This model requires greater exercise intensity during the early stages of the exposure, thus ensuring a more rapid increase in T rec and consequently greater change in T rec , followed by a reduction in workload once a desired temperature has been achieved.…”

Plasma Hsp72 (HSPA1A) and Hsp27 (HSPB1) expression under heat stress: influence of exercise intensity

“…Concomitantly, the development of metabolic and cardiovascular strain varied between exercise at 60% and 75% V Á o 2 max. Previous research has suggested that the expression of eHsp72 is a function of the core temperature attained following an acute bout of exercise, rather than the rate at which hyperthermia develops (i.e., the rate of heat storage) (Ruell et al 2006;Amorim et al 2008). Accordingly, a significant correlation has been noted between eHsp72 concentration and core temperature in athletes completing a race in cool environmental conditions (21°C, 33% RH and 28 km h −1 wind velocity) (Ruell et al 2006).…”

Cancer Therapy Combining Modalities of Hyperthermia and Chemotherapy: in vitro Cellular Response after Rapid Heat Accumulation in the Cancer Cell

“…The HSPs are a family of highly conserved stress proteins present in the cells of all living organisms [113]. It could be found to be expressed at very low levels in healthy cells to help newly synthesized proteins to fold to an appropriate special conformation.…”