Exercise increases serum Hsp72 in humans

Abstract

Recent evidence suggests that heat shock proteins (Hsps) may have an important systemic role as a signal to activate the immune system. Since acute exercise 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 hypothesized that such exercise would result in the release of Hsp72 from stressed cells into the blood. Six humans (5 males, 1 female) ran on a treadmill for 60 minutes at a workload corresponding to 70% of their peak oxygen consumption. Blood was sampled from a forearm vein at rest (R), 30 minutes during exercise, immediately postexercise (60 minutes), and 2, 8, and 24 hours after exercise. These samples were analyzed for serum Hsp72 protein. In addition, 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 vastus lateralis at the time of blood sampling and analyzed for Hsp72 gene and 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 rest, 30 and 60 minutes, respectively, P < 0.05, mean SE). In addition, plasma CK was elevated (P < 0.05) 8 hours postexercise. Skeletal muscle Hsp72 mRNA 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 elevated 2 and 8 hours following exercise compared with rest, results were not statistically significant. The increase in serum Hsp72 preceded any increase in Hsp72 gene or protein expression in contracting muscle, suggesting that Hsp72 was released from other tissues or organs. This study is the first to demonstrate that acute exercise can increase Hsp72 in the peripheral circulation, suggesting that during stress these proteins may indeed have a systemic role.

Fig 1.

Typical standard curve for the Hsp72 protein enzyme-linked immunosorbent assay. Hsp72 concentration (ng/mL) vs corrected absorbance at 450 nm. Hsp72 standard concentrations: 0, 0.78, 1.56, 3.13, 6.25, 12.50, 25.00, and 50.00 ng/mL. Log-log axis, linear fit, r² = 0.999

Fig 2.

Serum Hsp72 before (rest), at 30 and 60 minutes of treadmill running at 70% of maximal oxygen uptake and 2, 8, and 24 hours postexercise. * denotes difference (P < 0.05) compared with rest. Data expressed as means ± SE (n = 6)

Fig 3.

Hsp72 gene expression in vastus lateralis before (rest), after 60 minutes of treadmill running at 70% of maximal oxygen uptake, and 2, 8, and 24 hours postexercise. * denotes difference (P < 0.05) compared with rest. Data (mean ± SE) expressed relative to the resting sample for each subject (n = 5)

Fig 4.

Hsp72 protein expression in vastus lateralis before (rest), after 60 minutes of treadmill running at 70% of maximal oxygen uptake, and 2, 8, and 24 hours postexercise. Data expressed for each individual and as mean ± SE. Data expressed relative to the resting sample for each subject (n = 5)

Fig 5.

Plasma creatine kinase before (rest), at 30 and 60 minutes of treadmill running at 70% of maximal oxygen uptake, and 2, 8, and 24 hours postexercise. * denotes difference (P < 0.05) compared with rest. Data expressed as means ± SE (n = 6)