Leukotriene inhibitors attenuate rat lung injury induced by hydrogen peroxide

It is known that reactive oxygen species cause lung injury in association with activation of arachidonate metabolism. Because metabolites of the cyclooxygenase pathway do not appear to mediate the injury, we considered that the 5-lipoxygenase pathway might be activated and that inhibition of the pathway could interfere with the development of the injury. Thus, we sought to induce an oxidant lung injury and to prevent such injury by inhibiting lipoxygenase pathway or by blocking leukotriene action. In isolated rat lungs, glucose oxidase added to a glucose-containing, cell-free perfusate was used to produce the injurious oxygen species. Lung edema occurred and increased with increasing oxygen tension in the inspired air. Light microscopy of the lung showed perivascular fluid cuffs, and electron microscopy showed endothelial cell damage. Measurements in the lung effluent showed that concentrations of 5-hydroxyeicosatetraenoic acid (5-HETE) and of cyclooxygenase metabolites increased after glucose oxidase administration; BW 755C, U60,257, and FPL 55712 inhibited the glucose-oxidase-induced lung edema. And U60,257 also inhibited the glucose-oxidase-induced increase in 5-HETE without concomitant inhibition of cyclooxygenase metabolites. Thus, glucose oxidase via generation of active oxygen species stimulated the lung 5-lipoxygenase pathway, and inhibitors of 5-lipoxygenase protected against the oxidant lung injury. Further, in these experiments, the injury occurred in the absence of circulating blood cells and was augmented by increasing the inspired oxygen concentration.