Emphysema induced in vitro and in vivo in dogs by a purified elastase from homologous leukocytes.
The protease hypothesis of emphysema development evolved from systems using intratracheal instillation or aerosols of heterologous enzymes, such as papain or porcine pancreatic elastase, which bear no relation to the animal species treated. Although these enzymes did produce experimental emphysema, their exogenous origin and superphysiological dosages limit their use in definitive model systems. The observation that dog leukocyte homogenates could induce canine emphysema led us to purify the causative agent from canine neutrophils. This report establishes that a single elastolytic enzyme from dog neutrophils is responsible for inducing experimental emphysema in the dog. Two purification methods were employed. The first used solvents of increasing ionic strength in a sequential extraction of acetone powders of purified dog neutrophils. The ability to initiate emphysema-like lesions was tested in every fraction of the purification and was localized in the extract with the highest true elastolytic activity. The second purification involved neutrophil intracytoplasmic organelle fractionation and established that only extracts of the lysosomal granules were capable of emphysema induction. Finally, the enzyme was purified to homogeneity from the granules using affinity chromatography and was shown to be a true elastase. Emphysema development was quantitated using mean linear intercept and was shown to be dependent on elastase concentration. There does not appear to be any other single enzyme in the canine neutrophil capable of inducing experimental emphysema.