Distribution of Fibrinolytic and Proteolytic Enzymes in Subcellular Fractions of Human Granulocytes

Abstract

SummaryThe Cohn and Hirsch method was applied for preparation of human granulocyte subfractions. It was found that specific granules contained about 50-60% of the total activity of acid phosphatase, alkaline and acid protease. The activities of fibrinolytic enzymes (plasminogen, activator of plasminogen and spontaneous fibrinolytic activity) were rather equally distributed in all subfractions.A significant rise of a total fibrinolytic activity was found during fractionation. The results suggest the existence of a fibrinolytic inhibitor in the granulocytes. This suggestion was substantiated by analysing dilution curves of the plasminogen activity in the granulocyte subfractions.The inhibitor showed both “antiurokinase”, “antistreptokinase” and antiplasmin activity.On the basis of experimental data it has been suggested that plasma plasminogen may be derived from the granulocytes.

An alternative pathway for fibrinolysis. I. The cleavage of fibrinogen by leukocyte proteases at physiologic pH.

“…This observation is consistent with the results of other studies (11)(12)(13) in which plasmin activity and the antigenic determinants of plasmin were not demonstrable in leukocytes. In contrast, Prokopowicz not only found evidence for the presence of the plasminogen system in leukocytes but also isolated plasminogen from leukocytes (14,17). Our observations do not resolve these apparent inconsistencies; but in preliminary observations, utilizing sensitive radioimmunochemical approaches (25,29), we have detected very low levels of plasmin-related antigens within several leukocyte preparations (nanogram levels per 10' cells).…”

“…Within the confines of the vascular compartment, leukocytes frequently accumulate in complex thrombi consisting of fibrin and platelets (1)(2)(3)(4)(5); whereas in extravascular sites, the migration of leukocytes to sites of injury where fibrin has accumulated is a central feature of the inflammatory response (5)(6)(7)(8)(9). In both circumstances, the interaction of these cells with fibrin may be active rather than passive, based on the morphologic identification of fibrin within leukocytes (5)(6)(7)(8)(9), the accumulation of leukocytes in thrombi relative to their concentration in blood (4), and the demonstration that fibrinolytic activity of leukocytes is not confined to low pH, at which many cathepsins are active, but also is observed at neutral pH (10)(11)(12)(13)(14)(15)(16).…”

“…plasminogen and its proactivator, may be constituents of leukocytes (14,17), a number of studies have demonstrated within the cells a fibrinolytic system distinct from plasmin. This conclusion is based on the differential sensitivity of the systems to inhibitors, as well as comparisons of the molecular characteristics of the enzymes (11)(12)(13)(14).…”

“…This conclusion is based on the differential sensitivity of the systems to inhibitors, as well as comparisons of the molecular characteristics of the enzymes (11)(12)(13)(14). The purpose of the present study is to examine the alternative fibrinolytic system of leukocytes with respect to: (a) the relative contribution of the plasminogen and the plasminogen-independent system to the total fibrinolytic activity of the leukocytes; (b) the molecular characteristics of cleavage of fibrinogen by leukocyte proteases; (c) the biologic properties of the fibrinogen cleavage fragments generated by leukocyte protease; and (d) the release of protease from leukocytes when subjected to appropriate stimulus.…”

Degradation products of fibrinogen by elastase-like neutral protease from human granulocytes. Characterization and effects on blood coagulation in vitro.

“…Further studies indicated that both fibrinogen and fibrin are susceptible to the action of leukocyte enzymes (3)(4)(5) and that the intrinsic enzymatic system of the leukocytes is distinct from plasmin (6)(7)(8)(9)(10). Apparently, intracellular plasminogen does not account for fibrinolysis, as only very low plasminogen levels have been detected in polymorphonuclear leukocytes (8,11,12).…”