Cathepsin L Activity Is Increased in Alveolar Macrophages and Bronchoalveolar Lavage Fluid of Smokers

Abstract

Elastinolytic enzymes derived from alveolar macrophages (AM) are considered to play an important role in the development of emphysema associated with cigarette smoking. In this study, the enzyme activity and mRNA expression of cathepsin L were quantitated in AM and bronchoalveolar lavage (BAL) fluid obtained from current smokers and compared with those from nonsmokers. Activity was measured with the synthetic substrate Z-Phe-Arg-MCA combined with a novel cathepsin B inhibitor, CA-074. We found that the specific activity of cathepsin L was significantly elevated in BAL cells from smokers (7.1 +/- 0.7 mumol/mg protein/h, mean +/- SEM) compared with cells from nonsmokers (2.9 +/- 0.3) (p < 0.01). The expression of cathepsin L mRNA in BAL cells as determined by dot-blot analysis was also higher in BAL cells from smokers, which was comparable to the increase in the enzyme activity. About 5 to 6% of the specific activity of cathepsin L in BAL cell lysates was detected in unconcentrated BAL fluid; specific activity was also significantly higher in samples from smokers (0.38 +/- 0.04 mumol/mg protein/h) than from nonsmokers (0.14 +/- 0.02). In addition, procathepsin L (42 kD) and the mature form of cathepsin L (33 kD) were demonstrated in BAL fluid by immunoblot analyses. These data suggest that cigarette smoking induces mRNA expression and the synthesis of cathepsin L in AM and the release of procathepsin from AM into extracellular milieu. Furthermore, increased activity levels of cathepsin L in extracellular compartments may contribute to the proteolysis of elastin in the process of lung destruction associated with cigarette smoking.

Cysteine proteinase cathepsin H in tumours and sera of lung cancer patients: relation to prognosis and cigarette smoking

“…This is the first evidence indicating association of Cath H expression or regulation with cigarette smoking in human lung cancer and is consistent with previous studies revealing an increase of Cath B and L activity in lung tissue of smokers (Knoch et al, 1994;Werle et al, 1995), in their alveolar macrophages and alveolar lavage fluid (Chang et al, 1986;Takahashi et al, 1993) as well as in alveolar macrophages and bronchoalveolar lavage fluid of rats exposed to cigarette smoke Lesser et al, 1989;Chapman et al, 1997). Furthermore, Yukio Ishii (1991aIshii ( , 1991b clearly demonstrated that Cath H is secreted mainly with surfactant from Type II alveolar epithelial cells and alveolar macrophages of rat lung.…”

Inactivation of Human β-Defensins 2 and 3 by Elastolytic Cathepsins

“…Cathepsins are cysteine proteases produced predominantly by macrophages and are involved in matrix remodeling and Ag processing (24). Elevated levels of active cathepsin L have been shown in the bronchoalveolar lavage (BAL) of smokers and individuals with emphysema due to the increased numbers of macrophages present, and they are thought to play an important role in the lung destruction observed in the emphysematous lung (23,25). The observation of SLPI proteolysis by cathepsins B, L, and S has raised the question of whether members of the defensin family are also susceptible to proteolytic cleavage by the cathepsins.…”

Pathogenic Mechanisms in Emphysema: From Protease Anti-Protease Imbalance to Apoptosis

“…Smokers have increased expression of cathepsin L in AM compared to non-smokers (Takahashi et al,1993), and also increased activity of cathepsin S in AM lysates (Reilly et al, 1991). Pro-inflammatory mediators induce expression of MMPs, such as the marked increase in mRNA for MMP12 in cultured AM by lipopolysaccharide (LPS) .…”