Antiproteinase deficiency, emphysema and replacement therapy

Role of elastases in the pathogenesis of chronic obstructive pulmonary disease: implications for treatment

Neutrophil elastase, metalloproteinases, and their inhibitors play an important role in the development of chronic obstructive pulmonary disease (COPD), resulting in extensive tissue damage and malfunctioning of the airways. Nearly fifty years after the protease-antiprotease imbalance hypothesis has been suggested for the cause of emphysema, it is still appealing, but it does not explain the considerable variation in the clinical expressions of emphysema. However, there are many recent research findings to support the imbalance hypothesis as will be shown in this review. Although limited, there might be openings for the treatment of the disease.

Secretory leukocyte proteinase inhibitor, alpha-1-antitrypsin deficiency and emphysema: Preliminary study, speculation and an hypothesis

OBJECTIVES

This study investigated (i) whether adequate concentrations of secretory leukocyte proteinase inhibitor (SLPI) in the lungs of alpha-1-antitrypsin (A1AT) deficient patients can explain the variability in the development of emphysema in these individuals, and (ii) whether cigarette smoking jeopardises the protective screen provided by functional SLPI.

METHODOLOGY

Four subjects [two normal proteinase inhibitor M (PiM), two abnormal PiZ] were selected from patients presenting for diagnostic bronchoscopy and lung function testing (spirometry, DLco). Each subject underwent BAL and had blood taken for A1AT and SLPI estimation.

RESULTS

As expected serum and BAL A1AT concentrations were within the normal range in the normal PiM subjects. In normal subjects, SLPI concentrations in serum and BAL were within the normal range. A1AT-deficient subjects had reduced serum and BAL levels of A1AT reflecting their genetic disorder but showed increased concentrations of SLPI in BAL and serum. Percentage neutrophil elastase (NE) inhibitory capacity of BAL fluid was low in both A1AT-deficient subjects and a cigarette-smoking normal subject. In contrast, the NE inhibitory capacity for the normal subject who had never smoked was normal.

CONCLUSIONS

These findings suggest that in A1AT deficiency there may be a compensatory increase in SLPI. This may protect the lung against the development of emphysema in A1AT-deficient individuals. Cigarette smokers may have a lower SLPI concentration than non-smokers. This provides an explanation for at least some of the observed variation in the development of emphysema in A1AT deficient subjects.

Inhibition of human neutrophil elastase-induced acute lung injury in hamsters by recombinant human pre-elafin (trappin-2)

STUDY OBJECTIVES

Pre-elafin, also known as trappin-2, is an elastase-specific inhibitor that could be an ideal candidate for the treatment of neutrophil elastase-driven lung diseases. The inhibitory activity of pre-elafin resides in the COOH-terminal region that can be released as mature elafin. The NH(2)-terminal moiety of pre-elafin is characterized by the presence of a specific repeating sequence, termed cementoin, believed to immobilize the inhibitor to lung protein components and restrict its diffusion from the desired sites of action. This property should confer an advantage to pre-elafin compared to elafin in the treatment of neutrophil elastase-driven lung diseases.

MEASUREMENTS

The inhibitory effect of recombinant human pre-elafin was assessed in a human neutrophil elastase-induced acute lung injury model in Golden Syrian hamsters. BAL fluid hemoglobin content was used as a marker of lung injury.

RESULTS

Recombinant human pre-elafin administered intratracheally 1 h prior to neutrophil elastase dose-dependently inhibited the lung hemorrhage with a calculated half-effective dose of 8.1 microg/kg (0.7 nmol/kg). Pre-elafin was equally efficient when administered 3 h before neutrophil elastase. In contrast to pre-elafin, commercial synthetic elafin was ineffective in inhibiting neutrophil elastase-induced lung hemorrhage even at a dose of 4.45 nmol/kg.

CONCLUSIONS

Our results suggest that pre-elafin may be eventually used in the treatment of neutrophil elastase-driven lung diseases.