Fig. 1

Effects of antibiotic treatment with or without MV on neutrophil infiltration in the lungs and PA phagocytic activity as well as activity of AMs. WT mice received intramuscular injection of combined antibiotic for 6 days and mechanical ventilation for 3 h and lung tissues were harvested and assayed. a MV decreased the PA phagocytic activity of AMs and antibiotic treatment for 6 days further decreased the PA phagocytic activity of AMs. AMs were collected and resuspended in HBSS as 10⁶ cells/ml. After 5 min of preincubation, the cell suspension was incubated with P. aeruginosa (10⁸/ml). The cells were removed and P. aeruginosa number in the supernatant was counted. Data are presented as mean ± SEM. b Antibiotic treatment for 6 days also significantly decreased activity of AMs. Antibiotic treatment before MV further decreased activity of AMs. AMs were harvested from adult mice by bronchoalveolar lavage (BAL). Cells were then cultured in 96-well microtiter plates to remove nonadherent cells. Adherent monolayer cells were stimulated with 0.5 or 5 µg/ml of LPS (from Escherichia coli O26:B6 Sigma-Aldrich). Supernatants were assayed for TNF-α. Data are presented as mean ± SEM. c Mechanical ventilation increased lung MPO activity. Antibiotic treatment did not change the MPO activity in sham or MV group. Data are presented as mean ± SEM; PA, P. aeruginosa; MPO: myeloperoxidase. *P < 0.05, **P < 0.01, ***P < 0.001