The Elastase Inhibitory Capacity and the α₁-Proteinase Inhibitor and Bronchial Inhibitor Content of Bronchoalveolar Lavage Fluids from Healthy Subjects

Abstract

Pulmonary emphysema is currently thought to be due to an elastase-antielastase imbalance with resultant destruction of alveolar structures. The present study was aimed at testing whether α^-proteinase inhibitor (c^PI) is the major component of the antielastase screen of the lower respiratory tract of healthy subjects. Bronchoalveolar lavage was performed in 8 nonsmokers (27.8 ± 3.8 years) and 9 smokers (25 ± 0.96 years). The lavage fluids were tested for leukocyte and pancreatic elastase inhibitory capacity (LEIC and PEIC) and immunoreactive o^PI and bronchial inhibitor (brl) content. The mean ± s.e.m. levels of LEIC, PEIC, o^PI and brl were 0.16 ± 0.039, 0.042 ± 0.006, 0.09 ± 0.007 and 0.013 ± 0.002 mol/mol albumin, respectively. Thus, on the average, the molar concentration of brl was about 14% that of ajPI. The difference between LEIC and c^PI did not reach statistical significance (P = 0.0503). The PEIC was however significantly lower than the c^PI levels (P < 0.05), indicating that the lavage fluids contained both active and inactive o^PI. Nonsmokers and smokers did not differ in their LEIC, PEIC, c^PI and brl levels. When the data were examined on an individual basis, the subjects could be divided into 2 groups: group I (n = 9; 3 nonsmokers, 6 smokers) whose LEIC/ajPI molar ratios were higher than unity and group II (n = 8; 5 nonsmokers, 3 smokers) whose LEIC/ajPI molar ratios were equal or lower than unity. Group I subjects had significantly higher LEIC values (0.26 ± 0.05 mol elastase inhibited/mol albumin) than group II individuals (0.055 ± 0.006;P < 0.001) but the two groups had similar levels of immunoreactive c^PI (0.09 and 0.08 mol α^ΡΙ/mol albumin for group I and II, respectively), functionally active c^PI (percentage of active cXjPI: 53% and 37% for group I and II, respectively) and immunoreactive brl (0.016 and 0.010 mol brl/mol albumin for group I and II, respectively). These results suggested that the lavage fluids from group I contained significant amounts of undefined leukocyte elastase inhibitor(s). Gel filtration of a lavage fluid from group I showed that the undefined elastase inhibitor(s) co-eluted with brl. Most of the lavage fluids were still able to inhibit leukocyte elastase following removal of a x PI by perchloric acid precipitation. The mean LEIC of the acid-treated fluids (15.4 ± 2.7 χ 10~~8M), was significantly higher than their mean brl concentration (2.3 ± 0.6 χ 10~8M); (P < 0.01), confirming the occurence of undefined elastase inhibitors. The LEIC/brI molar ratios were greater than 1 in 13/17 acid-treated fluids. The highest ratios were found in group I subjects, confirming that the antielastase screen of these subjects is mainly composed of elastase inhibitors different from c^PI and brl. Removal of brl from some acid-treated fluids by immunoadsorption did not abolish the LEIC of these fluids. Enzymes:Porcine pancreatic elastase (EC 3.4.21.11); Human leukocyte elastase (EC 3.4.21.11). Abbreviations: QijPI: aj-proteinase inhibitor (α^-antitrypsin); brl: bronchial inhibitor (ant...

Anti-neutrophil elastase defense of the normal human respiratory epithelial surface provided by the secretory leukoprotease inhibitor.

“…In quantitative terms, rSLPI was 96±1% active against NE and 0% active against PPE, while a lAT was 98±1% active against NE and 100±2% active against PPE. This differential inhibitory activity by SLPI and a lAT was used to characterize the antiprotease activity in lavage fluid of normal individuals, a valid approach since SLPI and a 1 AT are the two major antiproteases in respiratory ELF, and because a lAT in normal individuals is > 95% active (10,(27)(28)(29)(30). The average anti-NE capacity oflavage fluid was 27.9±3.1 nM, while the average anti-PPE capacity was 25.3±3.2 nM, i.e., the average anti-PPE capacity is very close to the anti-NE capacity (Fig.…”

“…It has been recognized for some time that secretory leukoprotease inhibitor is present in cells lining the tracheobronchial tree (7)(8)(9) and in the epithelial lining fluid lining the respiratory tract (10)(11)(12)(13) Finally, in the context that 95% ofa I AT in respiratory ELF is functional, but only one-third ofthe SLPI is functional, even though the molar ratio of SLPI to a IAT present in lavage fluid recovered from the respiratory surface is 0.56, the estimated molar ratio of functional SLPI to functional a 1 AT is only 0. 16.…”

“…Since SLPI is susceptible to oxidation, it is conceivable that SLPI on the epithelial surface is oxidized in vivo by oxidants, for instance, from inflammatory cells present on the epithelial surface or inhaled oxidants in ambient air. If this is the case, it would have to be put in the context that a lAT in normal respiratory epithelial fluid is not oxidized (10,(27)(28)(29)(30) …”

“…Although SLPI is clearly present on the respiratory epithelial surface (10)(11)(12)(13), its form and function in lung epithelial lining fluid (ELF) is not well understood, nor is it clear whether it plays a role in the anti-NE protective screen of the pulmonary epithelium of normal individuals. The purpose of this study was to evaluate the amount and function of SLPI in lung ELF of healthy nonsmokers.…”

Targeting neutrophil elastase in cystic fibrosis

“…Another candidate as an anti-NE molecule for CF is recombinant SLPI, a 12-kDa-nonglycosylated single-chain polypeptide identical to the naturally occurring SLPI [80][81][82][83]. Advantages of SLPI as a potential therapeutic option are that it is acid stable which may allow it to retain function in the acidic pH of the metabolically active neutrophils [84,85], its isoelectric point of 9 is close to that of NE which may allow it to track and bind to tissue sites favoured by NE [86,87], its relative imperviousness to degradation by NE and its possible enhanced antioxidant function by increasing glutathione levels in the local milieu [88].…”