Elastase and lysozyme activities in human alveolar macrophages. Effects of cigarette smoking.

We compared the elastase and lysozyme activities of cells obtained by bronchoalveolar lavage from normal smokers and nonsmokers. After total and differential cell counts were obtained for the initial lavage cell population, we determined the enzyme activities of the total lavage cell population, the culture vessel's adherent alveolar macrophage cell fraction, and the cell culture supernatant medium. Our data indicated that macrophages, particularly from smokers, synthesized a calcium-dependent activity against a synthetic elastase substrate, succinyl-trialanine-p-nitroanilide. This activity was enhanced in smokers and was distinct from the polymorphonuclear leukocyte elastase as measured with this synthetic substrate. Measurements using insoluble elastin labeled with 3H demonstrated that smokers' macrophages also contained a serine-proteinase activity whose inhibitor profile resembled that of polymorphonuclear leukocyte elastase. Finally, macrophages from smokers secreted 5 times more lysozyme and contained more lactate dehydrogenase activity than did nonsmokers' macrophages. We suggest that pulmonary macrophages take up the polymorphonuclear leukocyte elastase and contain a synthetic substrate, "elastase". The biologic significance of this elastase activity is unclear. The enhanced lysozyme secretion by smokers' alveolar macrophages indicated increased biosynthetic activity by these cells.