Suppression of the neutral protease activity of macrophages treated with asbestos in vitro.

Macrophages are often conspicuous in asbestos-induced inflammatory lesions. Chrysotile type B elicits macrophages into the peritoneal cavity of mice which produce high levels of the neutral protease, plasminogen activator; in vitro addition of these same fibers to mouse peritoneal macrophages stimulates enzyme production. It is reported here that, for endotoxin-elicited mouse peritoneal macrophages fed chrysotile type B in vitro, the increased plasminogen activator activity is suppressed by low concentrations of anti-inflammatory steroids. Other active drugs include colchicine and vinblastine. These studies are considered important, as they suggest an approach to controlling the levels of a potentially deleterious enzyme system (PA-plasmin) from macrophages treated with asbestos fibers.