Objective: Endogenous and exogenous nitric oxide (NO) may have important antibacterial effects in patients with pneumonia. NO administration has been limited to the continuous inhalation of gas-phase NO (ie, inhaled NO [iNO]). Intermittent nebulization of NONOates, novel NO donors, may permit the continuous intrapulmonary delivery of NO. Thus, we assessed the effects of nebulized diethylenetetraamine-NONOate (DETA-NO) in a model of acute Pseudomonas aeruginosa pneumonia.
Design: Randomized, controlled study.
Subjects: Male C57Bl/6 mice.
Interventions: Pneumonia was induced by intratracheal instillation of P aeruginosa (3 × 107 CFU in 50 μL). Pneumonia and sham mice were randomized to receive no treatment, nebulized DETA-NO (12.5 or 125 μmol) at 4 h and 12 h, or continuous iNO for 24 h (10 or 40 ppm) until they were killed at 24 h.
Main results: The nebulization of DETA-NO was associated with a marked increase in mean (± SEM) exhaled NO levels (after nebulization, 484 ± 34 parts per billion [ppb]; baseline, 13.4 ± 0.4 ppb; p < 0.01) and plasma levels of nitrites/nitrates (after nebulization, 73 ± 28 μM; at baseline, 14 ± 3 μM; p < 0.05). Nebulized DETA-NO decreased the pulmonary bacterial load in mice with pneumonia by 65 ± 19% (p < 0.05 vs untreated mice) but had no effect on pulmonary leukocyte infiltration. Although the growth of P aeruginosa colonies in vitro was impaired on exposure to DETA-NO, growth was similarly impaired by exposure to DETA nucleophile/backbone alone.
Conclusions: The nebulization of DETA-NO provides a method for the prolonged intrapulmonary delivery of NO. The antibacterial effect of DETA-NO in vivo and in vitro is due, in large part, to the DETA nucleophile moiety and is independent of NO, suggesting a limited therapeutic role for exogenous NO in pneumonia.