Potential mechanism, of emphysem recovered from lungs of cigarette s methionineand has decreased elas

The elastase inhibitory capacity per mg of a,- proteinase inhibitor (a1PI) was measured in the bronchoalveolar lavage (BAL) fluid from 26 healthy smokers and 24 nonsmokers. Activity was decreased by 40% in smokers' BAL fluid compared to nonsmokers. This effect was demonstrable by using human neu- trophil elastase as well as porcine pancreatic elastase as test en- zyme (elastase, EC 3.4.21.11) and was reproducible when selected individuals in each group underwent lavage on repeated occasions. In contrast, the functional activity of ai-antichymotrypsin was not decreased in smokers' BAL fluid. Crossed antigen-antibody elec- trophoresis confirmed that inactivation of' aPI was responsible for the decrease in the elastase inhibitory capacity of smokers' BAL fluid. a1PI purified from smokers' BAL fluids contained me- thionine sulfoxide (4 mol/mol of inactive alPI), whereas a5PI, from nonsmokers' BAL fluid did not. Smokers' alPI was indistin- guishable from nonsmokers' a1PI on the basis of electrophoretic mobility, molecular weight, and immunoreactivity. Thus, oxida- tion of methionine residues in lung axPI is associated with cigarette smoking. Because chemical oxidation of alPI in vitro causes loss of its elastase inhibitory activity, the present observations suggest that methionine oxidation may also be the cause of decreased func- tional activity of lung a1PI in smokers. Oxidative inactivation of a1PI in the lungs of cigarette smokers may play a role in the de- velopment of pulmonary emphysema in this group.