Direct assay of A alpha(1-21), a PMN elastase-specific cleavage product of fibrinogen, in the chimpanzee

D-dimers are degraded by human neutrophil elastase

To see if D-dimers were degraded by human neutrophil elastase (HNE), cross-linked fibrin was obtained by adding thrombin to purified fibrinogen in the presence of calcium ions and factor XIII, and the fibrin clot subsequently degraded by plasmin. Thereafter, the supernatant containing fibrin degradation products was removed and incubated with HNE. D-dimer levels were measured by two rapid semiquantitative tests, a latex agglutination test and the Nycocard immunofiltration test, and a quantitative ELISA-method. With increasing incubation time, D-dimer levels as measured by the latex and Nycocard tests rapidly decreased and subsequently became undetectable, while the ELISA D-dimer values remained essentially unchanged. By using SDS-electrophoresis and immunoblotting, the degradation of plasmic derivatives of cross-linked fibrin by fiNE was visualised. We conclude that in a purified system, D-dimers formed during plasmin mediated lysis of cross linked fibrin are further degraded by HNE. Such HNE degradation reduces the D-dimer concentration as measured by rapid semiquantitive tests, and may be partly responsible for discrepant results when using different D-dimer assays.

Formation of polymorphonuclear leukocyte elastase: alpha 1 proteinase inhibitor complex and A alpha (1-21) fibrinopeptide in human blood stimulated with the calcium ionophore A23187. A model to characterize inhibitors of polymorphonuclear leukocyte elastase

Incubation of human blood with the secretagogue A23187 resulted in the formation of increased plasma concentrations of polymorphonuclear leukocyte (PMN) elastase: alpha 1 proteinase inhibitor (PMNE:alpha 1 PI) complex as well as A alpha(1-21) fibrinopeptide [A alpha(1-21)]. The formation of these species was both time and A23187 concentration dependent. Using a sandwich ELISA and a radioimmunoassay, we determined the comparative potencies of several compounds to inhibit the formation of PMNE: alpha 1 PI complexes and A alpha(1-21), respectively. L-658,758, a substituted cephalosporin, essentially irreversible elastase inhibitor, inhibited the formation of PMNE: alpha 1 PI and A alpha(1-21) with IC50 values of 38 and 15 microM, respectively. L-683,845, a monocyclic beta-lactam, was much more potent against isolated PMNE than L-658,758. However in this system it was approximately equivalent to L-658,758 with an IC50 of 15 microM against both species. ICI-200,880, a competitive slow-binding elastase inhibitor, was significantly less potent to inhibit A alpha(1-21), having an IC50 of 75 microM, while Declaben, a reversible noncompetitive inhibitor, was inactive at concentrations as great as 200 microM. We propose that evaluating inhibitors in the complex milieu of blood will provide a useful method to predict their therapeutic potential in vivo.

Degradation of the alpha-chain of fibrin by human neutrophil elastase reduces the stimulating effect of fibrin on plasminogen activation

The degradation of fibrin by human neutrophil elastase (HNE) and the interference of such degradation on the stimulating effect of fibrin on plasminogen activation by tissue plasminogen activator (t-PA) was studied. By using SDS electrophoresis and Western blotting with subsequent immunostaining with monoclonal antibodies, degradation of the fibrin molecule was monitored. This degradation was related to the stimulating effect on plasminogen activation. Degradation of the alpha-chain was seen to occur before degradation of the beta- and gamma-chains. On the alpha-chain it was found that C-terminal degradation occurred prior to visible degradation of the N-terminal end. This C-terminal degradation was associated with a fall in the stimulation of plasminogen activation, coinciding with a corresponding reduction in the polymerization of fibrin. With further degradation, including N-terminal proteolysis of the alpha-chain, the stimulating effect of fibrin was reduced to that of fibrinogen.

CONCLUSIONS

Our results indicate that HNE degradation of the alpha-chain of fibrin occurs initially from the C-terminal end, affecting the polymerization of fibrin. This impaired polymerization may be important for the observed reduction in the t-PA mediated plasminogen activation.

Impaired coagulation of fibrinogen due to digestion of the C-terminal end of the A alpha-chain by human neutrophil elastase

Human neutrophil elastase (HNE) possesses fibrinogenolytic capacity, with a high susceptibility towards degradation of the A alpha-chain. To study the influence of HNE digestion of the A alpha-chain on the coagulation of fibrinogen by thrombin, fibrinogen was incubated with human neutrophil elastase (HNE). At intervals, thrombin clotting time (TCT) and clottability were determined and compared with the patterns obtained with SDS electrophoresis and Western blotting with subsequent immunostaining, using monoclonal antibodies against the N-terminal end and C-terminal half of the A alpha-chain. Apparently, initial HNE digestion of the fibrinogen molecule occurred from the C-terminal end of the A alpha-chain, and was associated with prolongation of the TCT. With further C-terminal degradation TCT became indefinite and the degradation products were no longer clottable. Finally, N-terminal degradation of the A alpha-chain was observed. The present observations suggest that initial HNE-digestion of fibrinogen occurs from the C-terminal end of the A alpha-chain, and that the C-terminal end is crucial for the coagulation of fibrinogen.

Chemical, biochemical, pharmacokinetic, and biological properties of L-680,833: a potent, orally active monocyclic beta-lactam inhibitor of human polymorphonuclear leukocyte elastase

A series of potent and highly selective time-dependent monocyclic beta-lactam inhibitors of human polymorphonuclear leukocyte elastase (PMNE, EC 3.4.21.37) is described. The intrinsic potency of these compounds, as exemplified by L-680,833 (k(inactivation)/K(i) of 622,000 M-1.s-1), is reflected at the cellular level where it inhibits generation of the specific N-terminal cleavage product A alpha-(1-21) from the A alpha chain of fibrinogen by enzyme released from isolated polymorphonuclear leukocytes stimulated with fMet-Leu-Phe with an IC50 of 0.06 microM. The inhibitory activity of L-680,833 is also apparent in whole blood stimulated with A23187, where it inhibits formation of A alpha-(1-21) and PMNE-alpha 1-proteinase inhibitor complex formation with IC50 values of 9 microM. Pharmacokinetic studies indicate that after oral dosing L-680,833 is bioavailable in rats and rhesus monkeys. This oral bioavailability is reflected by the inhibition (i) of tissue damage elicited in hamster lungs by intratracheal instillation of human PMNE and (ii) enzyme released from human PMN stimulated after their transfer into the pleural cavity of mice. The properties of L-680,833 allow it to effectively supplement the activity of natural inhibitors of PMNE in vivo, suggesting that this type of low-molecular-weight synthetic inhibitor could have therapeutic value in diseases where PMNE damages tissue.

Induction of emphysema and bronchial mucus cell hyperplasia by intratracheal instillation of lipopolysaccharide in the hamster

The aim of this study was to determine whether lipopolysaccharide-induced elastase release from recruited neutrophils in the hamster lung would induce emphysema, measured by mean linear intercept (Lm) and bronchial mucus cell hyperplasia (BMCH), scored in tissue sections stained with periodic acid-Schiff. Lipopolysaccharide (LPS) was instilled transorally twice a week for up to 5 weeks in hamsters. At 4 weeks after seven LPS instillations, Lm amounted to 87.6 +/- 1.2 microns, while it was 68.3 +/- 1.5 microns after seven saline instillations (P less than 0.01). At 6 months after the sixth LPS instillation, the Lm of these lungs was 83.3 +/- 1.6 microns, indicating irreversible tissue destruction. LPS-treated hamsters showed marked to severe BMCH, which was most evident in large intrapulmonary airways. Instillations of highly selective inhibitor of hamster PMN elastase resulted in 50 per cent inhibition of LPS-induced emphysema. The development of BMCH was inhibited by approximately 35 per cent by this agent. To study the response in time of cellular infiltration after a single LPS instillation, the lungs of groups of four hamsters were lavaged at different time points. PMN recruitment showed peak values at 4 and 48 h after LPS instillation and returned to baseline values at 96 h. Simultaneous intratracheal instillation of LPS and anti-TNF alpha antiserum resulted in a considerable reduction of neutrophil influx into bronchoalveolar spaces in the first 6 h after instillation.

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 formylmethionyl-leucylphenylalanine. 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.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in neutrophil deformability following in vitro smoke exposure: mechanism and protection

We have previously demonstrated a reduction in the deformability of neutrophils, exposed to whole particulate cigarette smoke in vitro, by measuring their ability to filter through a micropore membrane with pore dimensions similar to those of the average pulmonary capillary segment. In this study, we exposed neutrophils to the vapor phase of cigarette smoke and investigated the mechanism of the reduction in neutrophil filterability. Although both stimulated neutrophils and smoke-exposed neutrophils demonstrated an increase in filtration pressures, and thus a reduction in cell deformability, compared with control untreated cells, the spontaneous release of the reactive oxygen intermediates hydrogen peroxide and the superoxide anion was depressed following in vitro smoke exposure and there was no shape change to suggest that smoke-exposed cells were activated. The presence of erythrocytes, plasma, or the antioxidants albumin and glutathione prevented the reduction in cell filterability following smoke exposure, suggesting that in vitro smoke exposure, in our system, was mediated by oxidants. Indeed, the increase in filtration pressures, produced by smoke, could be mimicked by the addition of the oxidant hypochlorous acid. The cytoskeletal inhibitors cytochalasin B and D improved the filterability of smoke-exposed cells, suggesting that smoke may change neutrophil deformability through an effect on the actin component of the cytoskeleton. By contrast, colchicine, a specific inhibitor of the microtubules, had no effect. Preincubation with a monoclonal antibody to the CD18 antigen, to block this major neutrophil adhesive glycoprotein, did not alter the filtration pressure developed by stimulated or smoke-exposed neutrophils, suggesting that increased adhesivity was not the mechanism of the increase in filtration pressures observed following smoke exposure.(ABSTRACT TRUNCATED AT 250 WORDS)