Ventilation-induced neutrophil infiltration and apoptosis depend on apoptosis signal-regulated kinase 1 pathway*

Objective:Positive pressure ventilation with large tidal volumes has been shown to cause release of cytokines, including macrophage inflammatory protein (MIP)-2, a functional equivalent of human interleukin-8, neutrophil infiltration, and apoptosis. The mechanisms regulating ventilation-induced cytokine production and lung cell death are unclear. Based on our previous in vitro and in vivo models of lung cell stretch, we hypothesized that high tidal volume ventilation-induced MIP-2 production, neutrophil infiltration, and apoptosis are dependent on the activation of apoptosis signal-regulated kinase 1 (ASK1), the upstream activator of c-Jun N-terminal kinase (JNK). Design:Prospective, controlled animal experiment. Setting:University research laboratory. Subjects:Male C57BL/6 mice, weighting 20–25 g. Interventions:C57BL/6 mice were exposed to high tidal volume (30 mL/kg) or low tidal volume (6 mL/kg) mechanical ventilation for 15 mins to 5 hrs. Measurements and Main Results:High tidal volume ventilation induced MIP-2 messenger RNA expression, MIP-2 protein production, neutrophil migration into the lung, airway epithelial cell apoptosis, and activation of ASK1, JNK, and activator protein (AP)-1 DNA binding in a dose-dependent and time-dependent manner. ASK1 inhibition with thioredoxin attenuated high tidal volume ventilation-induced MIP-2 messenger RNA expression, MIP-2 protein production, neutrophil migration into the lung, airway epithelial cell apoptosis, activation of JNK, and AP-1 DNA binding. Conclusions:Our data showed that high tidal volume ventilation-induced MIP-2 production, neutrophil sequestration, and apoptotic cell death were dependent, in part, on activation of the ASK1/JNK/AP-1 pathway.