Study objective: Neutrophils are involved in acute lung injury during ARDS via several mechanisms. This study focuses on neutrophil-derived oxidative stress. Hypochlorite is a major neutrophil-derived oxidant. This study characterizes hypochlorite-induced acute changes in pulmonary circulation and the involvement of tissue lipid peroxidation (LPO) and reduced glutathione (rGSH) depletion.
Methods: Hypochlorite (500, 1,000, and 2,000 nmol/min) or buffer (control) were infused into isolated rabbit lungs. Pulmonary artery pressure (PAP), capillary filtration coefficient (Kf,c) [10(4)/mL/s/cm H(2)O/g], and lung weight were measured. Experiments were terminated after 105 min or when fluid retention was > 50 g. Lung tissue was frozen immediately after termination of the experiments and analyzed for LPO products and rGSH (nanomoles per milligram of protein).
Results: Baseline PAP and Kf,c values averaged from 6.1 to 6.5 mm Hg and from 0.97 to 1.23, respectively, in all groups. Hypochlorite infusion of 500, 1,000, and 2,000 nmol/min (n = 5 to 7 per group) evoked an increase (mean +/- SEM) in maximum PAP (PAPmax) [12.9 +/- 2.1, 14.3 +/- 1.7, and 13.3 +/- 2.2 mm Hg], in maximum Kf,c (Kf,cmax) [1.9 +/- 1.2, 6.34 +/- 1.2, and >10.0], and in tissue LPO products (1.7 +/- 0.06, 2.1 +/- 0.06, and 2.3 +/- 0.11 vs 1.4 +/- 0.04 in controls), and a decrease in tissue rGSH (73.4 +/- 8.7, 43.0 +/- 9.6, and 50.4 +/- 7.2 vs 139 +/- 12.6 in controls). Parameters of lung injury (PAPmax and Kf,cmax) of each single experiment were closely correlated with tissue rGSH but did not correlate with tissue LPO products. All changes are significant (p < 0.05) vs control.
Conclusion: The neutrophil-specific oxidant hypochlorite induces acute lung injury, rGSH depletion, and LPO in isolated rabbit lungs. The lung injury correlates with rGSH depletion, suggesting an important mechanistic role in hypochlorite-induced acute lung injury.