Objective: Stressful exercise reduces the plasma pro-inflammatory cytokine concentration in response to lipopolysaccharide (LPS). The aim of this study was to clarify the mechanism of exhaustive exercise-induced suppression of the plasma tumor necrosis factor (TNF)-alpha concentration in response to LPS. Methods: Male C3H/HeN mice (n = 66) were randomized to treadmill running to exhaustion (Ex) or a sedentary (Non-Ex) condition. Monocytes and splenic macrophages were collected from some animals, and other animals were injected with LPS (1 mg/kg) immediately after the exercise. The liver, lung and spleen tissues in the mice were removed 30 min after the LPS injection for determination of TNF-alpha mRNA expression. Blood and tissue samples were collected for determination of TNF-alpha and TNF receptors (TNFR) 1 h after the LPS injection. Results: Although there was a significant suppression in LPS-induced plasma TNF-alpha in the Ex mice when compared to the Non-Ex mice (p < 0.01), soluble TNFR in plasma was not affected by the exercise. There was no change in cell-surface expression of Toll-like receptor 4 (TLR4) and in LPS-induced TNF-alpha mRNA expression and TNFR content in tissues between the Ex and Non-Ex groups. Interestingly, TNF-alpha contents in the liver, lung and spleen of the Ex mice were significantly lower than those of the Non-Ex group (p < 0.01, p < 0.01 and p < 0.05, respectively). Conclusion: These data suggest that exhaustive exercise-induced suppression of the plasma TNF-alpha concentration despite LPS stimulation might depend on translation of TNF-alpha in tissues. Copyright (C) 2010 S. Karger AG, Basel