Phagocytic release of human leukocyte neutral proteases: Analysis of cartilage degradation products

Abstract

Human polymorphonuclear leukocyte neutral proteases (HLNP) released during the process of phagocytosis of aggregated human gamma globulin were tested for their ability to degrade intact rabbit ear cartilage. Using 35S-labeled cartilage as substrate, HLNP derived from 45 × 10 7 cells released about 45% of the total incorporated 35S. DE-52 chromatography of incubation supernatants revealed a single 35S peak associated with minimal quantities of peptide or protein material as estimated by absorbance at OD 230 + 280 nm. Analytical ultracentrifugation gave a molecular weight of 51,800. Incubation of cartilage with excess α-chymotrypsin released 35S-containing protein and peptide elements ( M r 79,400). Therefore, degradation, of the proteoglycans of intact cartilage by HLNP is more extensive than that noted with bovine pancreas α-chymotrypsin. The products of HLNP and α-chymotrypsin digestion of cartilage contained chondroitin sulfates A and/or C since both materials (after column chromatography) were sensitive to chrondroitinase ABC and AC digestion. Collagenolytic activity of HLNP is minimal compared to proteolytic activity as evidenced by the lack of hydroxyproline containing peptides released from cartilage during enzyme incubation. It is suggested that HNLP incubated with intact cartilage may serve as a relevant model in the search for new agents which could combat enzyme-mediated cartilage destruction.