IL-6 activates HSP72 gene expression in human skeletal muscle

To determine whether the cytokine interleukin (IL)-6 induces heat shock protein (HSP) 72 gene expression in skeletal muscle, 18 healthy, young men had either a high dose of IL-6 (HiIL-6; n = 6), low dose IL-6 (LoIL-6; n = 6), or saline (CON; n = 6) infused into one femoral artery for 3 h. Muscle biopsies were obtained from the vastus lateralis of the infusion limb and samples were analyzed for HSP72 mRNA. In addition, blood samples were collected from the femoral vein of the infusion limb and analyzed for plasma IL-6. In CON, femoral vein IL-6 concentration remained at basal levels throughout the experiment but in both HiIL-6 and LoIL-6, femoral vein IL-6 concentrations were markedly elevated (P < 0.05). HSP72 gene expression did not increase above resting levels in CON. In contrast, in both HiIL-6 and LoIL-6, HSP72 mRNA increased (P < 0.05) 2.5- and 2.3-fold, respectively after 30 min of infusion and remained elevated (P < 0.05) for 24 h following infusion. These data demonstrate that IL-6 can rapidly induce HSP72 gene expression in human skeletal muscle.