EGLIN-C, A POLYPEPTIDE DERIVED FROM THE MEDICINAL LEECH, PREVENTS HUMAN NEUTROPHIL ELASTASE-INDUCED EMPHYSEMA AND BRONCHIAL SECRETORY-CELL METAPLASIA IN THE HAMSTER

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Abstract
Eglin-c (Eg-c), a polypeptide with a molecular mass of 8,100 daltons, was purified from the medicinal leech Hirudo medicinalis. The Eg-c was tritiated by reductive methylation for in vitro studies. Incubation of 2.1 .times. 10-10 moles of human neutrophil elastase (HNE) with 3H-elastin in the presence of 8.2 .times. 10-10 moles of 3H-Eg-c inhibited 98.7% of the elastolytic activity of the enzyme. Using Sephadex G 100 chromatography and 1.7 moles of 3H-Eg-c per mole of HNE, a 34,000-dalton complex (3H-Eg-c-HNE) was observed. The stability of the complex formed between 3H-Eg-c and HNE that had been inactivated with succinyl-ala2-pro-val CH2Cl was much less than that of the 3H-Eg-c-HNE complex. In vivo studies were carried out in weight-matched groups of anesthetized golden Syrian hamsters given 100, 300, 500, or 2,000 .mu.g of Eg-c in 0.5 ml saline intratracheally 1 h before 300 .mu.g HNE was administered intratracheally. Control animals received saline followed by HNE or 2 doses of saline 1 h apart. Eight weeks later, lung statics and dynamics were measured in anesthetized animals, followed by histologic study of lung parenchyma and the mucosa of the large intrapulmonary airways. There were no deaths, and final mean body weights were similar in all groups. Protection from the induction of emphysema by 300 .mu.g HNE was complete after treatment with 2,000 .mu.g of Eg-c, as judged by lung volumes, quasi-static compliance, microscopy, and the mean linear intercept; the emphysema was ameliorated by treatment with 300 or 500 .mu.g of Eg-c but development of emphysema was not influenced by treatment with 100 .mu.g of Eg-c. Bronchial secretory cell metaplasia induced by HNE was ameliorated by the larger doses of Eg-c. The 2 highest doses of Eg-c appeared to induce a mild degree of secretory cell metaplasia and a decrease in mean linear intercept. We conclude that Eg-c is a potent inhibitor of HNE that forms a tight complex with HNE; the isolated complex exhibits minimal activity against insoluble tritiated elastin. Eglin-c administered to hamsters 1 h before intratracheal HNE is capable of preventing or ameliorating the induction of emphysema and bronchial secretory cell metaplasia.