Exercise increases serum Hsp72 in humans

Recent evidence suggests that heat shock proteins (Hsps) may have an import ant systemic role as a signal to activate the immune system. Since acute ex ercise is known to induce Hsp72 (the inducible form of the 70-kDa family of Hsp) in a variety of tissues including contracting skeletal muscle, we hyp othesized that such exercise would result in the release of Hsp72 from stre ssed cells into the blood. Six humans (5 males, 1 female) ran on a treadmil l for 60 minutes at a workload corresponding to 70% of their peak oxygen co nsumption. Blood was sampled from a forearm vein at rest (R), 30 minutes du ring exercise, immediately postexercise (60 minutes), and 2, 8, and 24 hour s after exercise. These samples were analyzed for serum Hsp72 protein. In a ddition, plasma creatine kinase (CK) was measured at these time points as a crude marker of muscle damage. With the exception of the sample collected at 30 minutes, muscle biopsies (n = 5 males) were also obtained from the va stus lateralis at the time of blood sampling and analyzed for Hsp72 gene an d protein expression. Serum Hsp72 protein increased from rest, both during and after exercise (0.13 0.10 vs 0.87 +/- 0.24 and 1.02 +/- 0.41 ng/mL at r est, 30 and 60 minutes, respectively, P < 0.05, mean SE). In addition, plas ma CK was elevated (P < 0.05) 8 hours postexercise. Skeletal muscle Hsp72 m RNA expression increased 6.5-fold (P < 0.05) from rest 2 hours postexercise , and although there was a tendency for Hsp72 protein expression to be elev ated 2 and 8 hours following exercise compared with rest, results were not statistically significant. The increase in serum Hsp72 preceded any increas e in Hsp72 gene or protein expression in contracting muscle, suggesting tha t Hsp72 was released from other tissues or organs. This study is the first to demonstrate that acute exercise can increase Hsp72 in the peripheral cir culation, suggesting that during stress these proteins may indeed have a sy stemic role.