POTENCY OF ANTILEUKOPROTEASE AND ALPHA-1-ANTITRYPSIN TO INHIBIT DEGRADATION OF FIBRINOGEN BY ADHERENT POLYMORPHONUCLEAR LEUKOCYTES FROM NORMAL SUBJECTS AND PATIENTS WITH CHRONIC GRANULOMATOUS-DISEASE

We have studied the relative efficacy of antileukoprotease (ALP) and alpha-1-antitrypsin (alpha-1AT) to inhibit the degradation of substrate by polymorphonuclear leukocytes (PMN) attached onto a fibrinogen matrix. PMN elastase activity was assayed by radioimmunoassay of a specific 21-residue cleavage product from the amino terminus of the A-alpha-chain, A-alpha(1-21), of fibrinogen. The adherence of PMN (1.0 x 10(6)) to a fibrinogen matrix was facilitated by incubation with recombinant tumor necrosis factor-alpha (1 nM). Subsequently, the cells were exposed to inhibitors before stimulation with cytochalasin B and formylmethionylleucylphenylalanine. Under these conditions, ALP inhibited A-alpha(1-21) formation with an IC50 of 85 +/- 30 nM and alpha-1AT gave an IC50 of 220 +/- 98 nM (mean +/- SD). The effect of oxidant production on A-alpha(1-21) formation was evaluated by comparing the effect of PMN from normal subjects with PMN from subjects with X-linked NADPH oxidase deficiency. Stimulation of PMN from the latter subjects in a similar fashion as described above resulted in the formation of 40 +/- 4 pmol/ml A-alpha(1-21), or approximately twice the amount seen with cells from normal subjects. Preincubation with ALP or alpha-1AT in a concentration range between 10 to 900 nM resulted in an IC50 of 50 +/- 13 nM for ALP compared with 150 +/- 21 nM for alpha-1AT. Both inhibitors are more effective to prevent fibrinogen degradation caused by chronic granulomatous disease (CGD) PMN than by normal PMN despite the fact that CGD PMN generated more A-alpha(1-21) than did normal PMN. However, myeloperoxidase activity released by the two groups of cells was comparable. ALP was more potent than alpha-1AT to inhibit fibrinogen degradation by both CGD and normal PMN in this system. Possible reasons for the increased potency of ALP over alpha-1AT include its greater accessibility to the interface between PMN and the fibrinogen matrix because of its relative low molecular mass (12 kD) and/or its high isoelectric point (pI > 9).