IκBα modulated severity of acute pneumonia-induced ALI. Overexpression of IκBα attenuated the decrement in arterial oxygenation (A), and in static lung compliance (B), and decreased BAL protein concentrations (C), after Escherichia coli-induced ALI. Beneficial effects were greatest with the intermediate IκBα (1 × 1010 particles) dose but were abolished by the higher IκBα (5 × 1010 particles) dose. No effect of IκBα was noted on BAL neutrophil infiltration (D). The gray bars represent sham (that is, uninfected) animals. Vehicle, animals that received intratracheal vehicle alone; IκBα 5 × 109, animals that received 5 × 109 AAV6 particles encoding IκBα; IκBα 1 × 1010, animals that received 1 × 1010 AAV6 particles encoding IκBα; IκBα 5 × 1010, animals that received 5 × 1010 AAV6 particles encoding IκBα. Significantly different from vehicle group (P < 0.05, ANOVA).