Oxidant injury of the extracellular matrix: Potential role in the pathogenesis of pulmonary emphysema

This paper reviews evidence supporting a role for oxidants in the pathogenesis of pulmonary emphysema. Recent studies have shown that connective tissue components are directly degraded by oxidantsin vitro. Exposure of animals to oxidant gases causes degradation of lung connective tissue and results in an emphysematous lesion in the lung several weeks after recovery. Oxidant injury is also associated with an influx of inflammatory cells which release proteolytic enzymes. It is proposed that the emphsematous lesion found after exposure to an oxidant gas is the result of two mechanisms causing degradation of lung connective tissue: direct cleavage by free radicals and enzymatic proteolysis. It is possible that oxidant injury to the extracellular matrix is involved in the pathogenesis of emphysema in humans since cigarette smoke contains an exceedingly high concentration of oxidants.