Tissue expression and plasma concentrations of TNFα, IL-1β, and IL-6 following treadmill exercise in mice

Exercise can increase plasma inflammatory cytokine concentrations in humans, but tissue responses are not well studied. We examined plasma concentrations and tissue expression of TNF alpha IL-1 beta, and IL-6 following treadmill running in mice. C57B1/6 mice were randomly assigned to: non-exercise control (CON), sacrifice at 0 or 1.5 h after 60 min running (MODO, MOD 1.5), sacrifice at 0, 1.5, or 3 h after fatiguing running (similar to3 h) (EXO, EX1.5, EX3), or lipopolysaccharide (25 mug) with no exercise (LPS). Lung, liver, muscle, and brain mRNA expression was analyzed (n=4-6/group) using reverse transcriptase-rapid polymerase chain reaction (RT-RPCR), Plasma cytokine concentrations were determined (n = 4-10/group) by ELISA. Plasma IL-6 was higher in EX1.5, and lung TNF alpha mRNA was higher in EX1.5 and EX3 compared to CON (P < 0.05). No significant increases in plasma cytokine concentrations or tissue cytokine expression were found in other EX groups. LPS significantly increased these cytokine measures in tissues and plasma, with the exception of plasma IL-beta which was undetectable. The source of the plasma IL-6 following exercise does not appear to be lung, liver, muscle, or brain tissue, and remains to be determined. These data also suggest that tissue level cytokine expression may not necessarily lead to increased plasma cytokine concentrations.