Production and degradation of oxygen metabolites during inflammatory states in the human lung.

Lung represents a tissue that encounters a high oxidant burden but is also endowed with efficient protection against oxygen and reactive oxygen species (ROS). The oxidant stress experienced by the lung is enhanced by exogenous oxidant producing toxins most importantly pollutants and cigarette smoke, as well as by increased oxidant production during lung inflammation. The major oxidant generating enzymes present in human lung include NADPH oxidase, myeloperoxidase, eosinophil peroxidase and nitric oxide synthases, all of which are induced during inflammatory states. The antioxidant machinery of human lung against ROS is more versatile than often assumed. In addition to metal binding proteins, mucus components and small molecular weight antioxidants and vitamins, lung tissue possesses a highly cell specific and compartmentalized defense system containing several antioxidant enzymes with variable locations, inducibilities and kinetics. Inflammatory states like asthma, chronic obstructive lung disease (COPD) and parenchymal lung disorders have been shown to lead to serious disturbances in the oxidant/antioxidant balance of the lung with consequent oxidant mediated cell injury. Novel synthetic antioxidant mimetics may have the potential to slow or terminate the progression of lung diseases associated with free radicals.