Inhibition of Peroxiredoxin 6 PLA2 Activity Decreases Oxidative Stress and the Severity of Acute Lung Injury in the Mouse Cecal Ligation and Puncture Model

Abstract

IntroductionALI is associated with bacterial infection (sepsis), either as an initiating factor or as a secondary complication. Activation of polymorphonuclear leucocytes (PMN) recruited into the lungs causes the release of free radicals and reactive oxygen species (ROS) that are responsible for many of the clinical manifestations of ALI. Since NADPH oxidase (NOX2) is the major source of ROS (i.e., superoxide anion) in PMN, NOX2 blockade has been proposed for the treatment of Acute Lung Injury (ALI). We reasoned that NOX2 blockers would be counter‐productive in ALI associated with bacterial infection by interfering with the bactericidal activity of PMN.HypothesisPhospholipase A2 inhibitory peptide (PIP‐2) that inhibits NOX2 activation (by preventing activation of Rac, a necessary NOX2 co‐factor) would inhibit the bactericidal activity of PMN and thereby limit clearance of bacteria from the lung; we posited that this effect of PIP‐2 could be overcome by the administration of appropriate antibiotics.MethodsUsing the cecal ligation and puncture (CLP) model of ALI associated with sepsis, we investigated the effect of inhibiting NOX2derived ROS production by administration of PIP‐2.ResultsThe number of colony‐forming bacteria in lungs and peritoneal fluid of mice with CLP approximately doubled at 18 h after intravenous treatment with 2 µg PIP‐2 /gram body weight (wt). Treatment with 10 µg PIP‐2/g body wt resulted in 100% mortality within 18 hr. Antibiotic treatment abolished both the increase in lung bacteria with low dose PIP‐2 and the increased mortality with high dose PIP‐2. Treatment with PIP‐2 in the presence of antibiotics resulted in significantly improved lung histology, decreased PMN infiltration, decreased lung fluid accumulation, and decreased oxidative lung injury compared to antibiotics alone.ConclusionAdministration of PIP‐2 provides partial protection against lung injury in a model of ALI due to bacterial infection while concurrent antibiotic treatment abolishes the deleterious effects of PIP‐2 on lung bacterial clearance. These results suggest that addition of PIP‐2 to the antibiotic regimen would be beneficial for treatment of ALI associated with bacterial infection.