Cytosolic Phospholipase A2 Activity in Neutrophilic Oxidative Stress of Platelet-activating Factor-induced Acute Lung Injury

Abstract

Background: The present investigation was performed in rats and isolated human neutrophils in order to confirm the presumptive role of the positive feedback loop of cytosolic phospholipase () activation by plateletactivating factor (PAF). Methods: The possible formation of the positive feedback loop of the activation and neutrophilic respiratory burst was investigated in vivo and in vitro by measurement of the parameters denoting acute lung injury. In addition, morphological examinations and electron microscopic cytochemistry were performed for the detection of free radicals in the lung. Results: Five hours after intratracheal instillation of PAF (), the lung leak index, lung myeloperoxidase (MPO) activity, the number of neutrophils and the concentration of cytokine-induced neutrophil chemoattractant (CINC) in bronchoalveolar lavage fluid were increased by PAF as compared with those of control rats. The NBT assay and cytochrome-c reduction assay revealed an increased neutrophilic respiratory burst in isolated human neutrophils following exposure to PAF. Lung and neutrophilic activity were increased following PAF exposure and exposure to hydrogen peroxide increased activity in the lung. Histologically, inflammatory findings of the lung were observed after PAF treatment. Remarkably, as determined by cytochemical electron microscopy, increased production of hydrogen peroxide was identified in the lung after PAF treatment. Conclusion: PAF mediates acute oxidative lung injury by the activation of , which may provoke the generation of free radicals in neutrophils.