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OBJECTIVE: Blunt chest trauma is accompanied by an early increase in plasma cytokine concentrations. However, the local sources of these mediators are poorly defined. We investigated the impact of blunt chest trauma on the inflammatory mediator milieu in different compartments (lung tissue, bronchoalveolar lavage, liver tissue, Kupffer cells, plasma) along with the time course of trauma-induced pulmonary endothelial barrier dysfunction to elucidate potential relationships. In addition, the correlation between intratracheally instilled interleukin-6 and its systemic release were studied. DESIGN: Prospective, randomized, controlled animal study. SETTING: Basic science laboratory of a university affiliated level 1 trauma center. SUBJECTS: Male C3H/HeN mice, 8-9 wks old, n = 141. INTERVENTIONS: Blunt chest trauma induced by a focused blast wave, intravenous injection of Evans blue, and intratracheal instillation of recombinant human interleukin-6. MEASUREMENTS AND MAIN RESULTS: Two hours after blunt chest trauma, plasma interleukin-6 was markedly increased. Simultaneously, interleukin-6, tumor necrosis factor-alpha, macrophage inflammatory protein-2, monocyte chemotactic polypeptide-1 and neutrophil/monocyte accumulation in bronchoalveolar lavage and interleukin-6, monocyte chemotactic polypeptide-1, and myeloperoxidase activity in lung tissue were significantly increased. This was accompanied by a coinciding elevation in the Evans blue lung-plasma ratio. Recombinant human interleukin-6, instilled intratracheally before blunt chest trauma, was detected in a dose-dependent manner in the plasma of the mice. Additionally, Kupffer cell interleukin-6, tumor necrosis factor-alpha, and interleukin-10 production was significantly augmented as early as 30 mins after the insult. CONCLUSIONS: These results indicate that early increased cytokine concentrations in the lung, particularly interleukin-6, are important mediator sources as their local peak coincides with the systemic inflammatory response and is accompanied by a simultaneous impaired function of the pulmonary endothelial barrier. A direct relationship between their local and systemic concentrations can be established. Furthermore, this is the first study to show that Kupffer cells are activated early after blunt chest trauma. [ABSTRACT FROM AUTHOR]