Inducible nitric oxide synthase inhibition attenuates lung injury and decreases NADPH oxidase expression and activation during ischemia‐reperfusion in the ventilated rabbit lung

Abstract

Lung ischemia‐reperfusion (IR) causes arteriolar constriction and platelet adhesion in correlation with inducible nitric oxide synthase (iNOS) expression/activity and reactive nitrogen species (RNS). While iNOS was elevated during reperfusion, RNS were only elevated in lungs that underwent ischemia. To determine oxidative stress, and if attenuation of vascular dysfunction by iNOS inhibition could be due to decreased NADPH oxidase stimulation, we assessed p47 phox translocation and vascular leakage. In anesthetized rabbits with open chest, we ventilated the lungs with an oxygen mixture and examined subpleural microvessels and alveoli in the right lung during brief periods when the lungs were statically inflated (10 cm H2O), IR was induced by occluding the right pulmonary artery for 2 h. Fluorescently labeled albumin was injected via the right atrium to assess vascular leakage. Oxidative stress was assessed by translocation of the cytosolic NADPH oxidase subunit, p47 phox, to the membrane fraction by immunoblotting. Vascular leakage and translocation of p47 phox were greater in reperfused ventilated lungs than in contralateral or control lungs, and were attenuated by pretreatment with an iNOS activity inhibitor (1400W). Our data suggest that stimulation of NADPH oxidase is an important component in acute lung injury in conjunction with iNOS overexpression. Supported by ALA of KY and NIH grant # HL080394.