We hypothesized that endotoxin injection in rats would stimulate in vivo nuclear factor-kappa B (NF-kappa B) activation in lung tissue and that antioxidant treatment before endotoxin injection would attenuate endotoxin-induced NF-kappa B activation, chemokine gene expression, and neutrophilic lung inflammation. We studied NF-kappa B activation in rat lung tissue following a single i.p. injection of endotoxin (6 mg/kg). After in vivo endotoxin treatment, lung NF-kappa B activation peaked at 2 h and temporally correlated with the expression of cytokine-induced neutrophil chemoattractant mRNA in lung tissue. Treatment with the antioxidant N-acetylcysteine (NAC) 1 h before endotoxin resulted in decreased lung NF-kappa B activation in a dose-dependent manner (from 200-1000 mg/kg) and diminished cytokine-induced neutrophil chemoattractant mRNA expression in lung tissue. Treatment with NAC significantly suppressed endotoxin-induced neutrophilic alveolitis. The average total lung lavage neutrophil count was 5.5 x 10(6) with endotoxin treatment vs 0.9 x 10(6) with NAC treatment before endotoxin. The NF-kappa B pathway represents an attractive therapeutic target for strategies to control neutrophilic inflammation and lung injury.