Cysteine proteinases and cystatin C in bronchoalveolar lavage fluid from subjects with subclinical emphysema

This study examined the role of cysteine proteinases and their inhibitor in the development of emphysema in comparison with neutrophil elastase (NE) c omplexed with alpha(1)-protease inhibitor (NE-alpha(1)-PI), which was previ ously demonstrated to be increased in bronchoalveolar lavage (BAL) fluid fr om subjects with subclinical emphysema. Eight nonsmokers and 31 current smokers with (n=17) and without (n=14) emph ysema, as evidenced by lung computed tomographic scans, were studied. The concentrations of immunologically detected cathepsin L and cystatin C, but not cathepsin B, were significantly increased in BAL fluid from the smo kers with emphysema compared with those without emphysema, although the act ivity of cathepsin L, measured using a synthetic substrate and cathepsin L released from cultured alveolar macrophages at 24 h, did not show any signi ficant difference between the two groups. When comparison was made only for the subjects aged <60 yrs, the difference between the two groups disappear ed for cathepsin L, but remained for NE-alpha(1)-PI There was no significan t correlation between the level of cathepsin L and that of NE-alpha(1)-PI i n BAL fluid from the subjects with emphysema. In conclusion, increased levels of cathepsin L and cystatin C were demonstr ated in bronchoalveolar lavage fluid from subjects with subclinical emphyse ma. However, the roles of cathepsin L and neutrophil elastase in the develo pment of emphysema may vary between subjects and between the young and the old.