Cotton dust contains proteolytic and elastolytic enzymes not inhibited by alpha-1-proteinase inhibitor

Others have found proteolytic activity in cotton dust and correlated this with the prevalence of acute byssinosis. The present study characterized the proteases in aqueous extracts of cotton dust after controlling for potential artifact from microbial contamination. We tested cotton dust, generated in a model card room operated by the U.S. Department of Agriculture (USDA), for total proteolytic activity (hydrolysis of azocasein) and elastolytic activity (degradation of insoluble 3H-elastin). Both coarse dust and a respirable fraction (aerodynamic diameter less than or equal to 1.7 microgram) yielded proteolytic activity. Proteolysis was inhibited by EDTA (39%), diisopropylfluorophosphate (DFP) (33%) and alpha-1-proteinase inhibitor (alpha 1 PI) (30%), but not by iodoacetic acid or pepstatin. Elastolytic activity was also present, and was inhibited by DFP (80%) and alpha 1 PI (70%), but not by EDTA. We conclude that cotton dust contains preformed metallo- and serine proteases, and serine elastolytic protease(s) which are incompletely inhibited by alpha 1 PI. These findings may be relevant to the development of chronic lung disease in people exposed to cotton dust.