title: Human resting extracellular heat shock protein 72 concentration decreases during the initial adaptation to exercise in a hot, humid environment.
abstract: Heat shock protein (Hsp) 72 is a cytosolic protein that also is present in the circulation. Extracellular Hsp72 (eHsp72) is inducible by exercise and is suggested to act as a danger signal to the immune system. The adaptive response of eHsp72 to repeated exercise-heat exposures in humans remains to be determined. An intracellular animal study found a reduced Hsp72 response, with no change in resting levels, during heat stress after a single day of passive heat acclimation. The current study therefore tested whether adaptations in human eHsp72 levels would similarly occur 24 hours after a single exercise-heat exposure. Seven males completed cycle exercise (42.5% V(O2peak) for 2 hours) in a hot, humid environment (38 degrees C, 60% relative humidity) on each of 2 consecutive days. Blood samples were obtained from an antecubital vein before exercise and 0 hours and 22 hours postexercise for the analysis of eHsp72. Exercise-heat stress resulted in enhanced eHsp72, with a similar absolute increase found on both days (day 1: 1.26 ng/mL [0.80 ng/mL]; day 2: 1.29 ng/mL [1.60 ng/mL]). Resting eHsp72 decreased from rest on day 1 to day 2's 22-hour postexercise sample (P < 0.05). It is suggested that the reduction in resting eHsp72 after 2 consecutive exercise-heat exposures is possibly due to an enhanced removal from the circulation, for either immunoregulatory functions, or for improved cellular stress tolerance in this initial, most stressful period of acclimation.
authors.affiliation: Department of Applied Physiology, Faculty of Science, University of Strathclyde, Glasgow, G4 0QU, UK.
authors.forename: Helen C
authors.initials: HC
authors.lastname: Marshall
authors.forename: Richard A
authors.initials: RA
authors.lastname: Ferguson
authors.forename: Myra A
authors.initials: MA
authors.lastname: Nimmo
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D001833:Body Temperature Regulation / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D050884:HSP72 Heat-Shock Proteins / Q000378:metabolism* / Q000502:physiology; D006358:Hot Temperature; D006801:Humans; D006813:Humidity; D008297:Male; D013997:Time Factors
chemical_list: D050884:HSP72 Heat-Shock Proteins