RELATIVE ROLE OF CHLORAMINES, HYPOCHLOROUS ACID, AND PROTEASES IN THEACTIVATION OF HUMAN POLYMORPHONUCLEAR LEUKOCYTE COLLAGENASE

The activation of collagenase released by polymorphonuclear leukocytes (PMNs) has been extensively studied in vitro, but the activation of t he enzyme in vivo is not fully understood, For further evaluation of t he relative role of oxidative and proteolytic mechanisms in the activa tion of collagenase, PMNs were stimulated by serum-opsonized zymosan u nder both aerobic and anaerobic conditions, The results showed that si milar amounts of collagenase were released by the PMNs under aerobic a nd anaerobic conditions, but the activity of the released collagenase was twice as high under aerobic conditions as under anaerobic conditio ns, Under aerobic conditions the enzyme was rapidly activated by hypoc hlorous acid and chloramines, which are products of the myeloperoxidas e-H2O2-chloride system of the PMNs. There was also a slow proteolytic activation of the enzyme, which could be ascribed to cathepsin G and p ossibly to some other serine proteases of PMNs. When extrapolating the se findings to in vivo conditions, it seems probable that the oxidativ e activation of collagenase will proceed mainly by chloramines, which are more long-lived in the tissue than hypochlorous acid, In poorly ox ygenated tissues, collagenase may be mainly activated by proteolytic m echanisms.