Effect of Neutral Proteases from Blood Leukocytes on Human Platelets

Abstract

SummaryTwo highly purified neutral proteases from human leukocytes i.e. elastase-like protease (ELP) and chymotrypsin-like protease (CLP) do not destroy human platelets since no difference was found in 51Cr liberation from control and enzyme-treated platelets. As with pancreatic chymotrypsin (α-CT) ELP does not induce the release of 3H-serotonin while CLP provokes 3H- serotonin secretion, in an enzyme concentration and time dependent fashion. The rate and degree of 3H-serotonin release by CLP is similar to that produced by thrombin. Incubation of platelets at 37° C for 30 min with α-CT or ELP renders them resistant to thrombin-releasing activity. Thrombin did not liberate any additional label from platelets which lost over 60% of serotonin during the preceding incubation with CLP. α-CT and ELP do not aggregate platelets either in the presence or absence of apyrase. CLP does aggregate platelets suspended in Tyrode buffer without apyrase but not in the presence of apyrase (100 mg/1). The action of α-CT, ELP and CLP on washed platelets induces a progressive prolongation of lag phase and a decrease in changes of light transmission during aggregation by thrombin. Similarly to α-CT-treated platelets, those subjected to CLP action aggregate in the presence of human fibrinogen.It is concluded that: (1) neutral proteases possibly contribute to development of defects in platelet function in pathological states associated with liberation of leukocyte content into the circulation, (2) CLP similarly to a-CT, exposes fibrinogen receptors but in contrast to α-CT, CLP aggregates platelets and stimulates serotonin secretion.

Structure and function of platelet membrane glycoproteins Ib and V

“…In agreement with previous findings [36], platelets treated with leukocyte elastase did not react spontaneously with fibrinogen as is the case with chymotrypsin-treated platelets [37,381 or platelets treated with porcine pancreatic elastase [39]. After prolonged treatment with elastase, the shapechange response to thrombin was very slow and the platelets did not release or aggregate.…”

“…10) though in the case of the calcium-activated protease the difference was not large. Calcium-activated protease [19,49], chymotrypsin [44,45] and elastase [36] d o not activate platelets while thrombin and trypsin [52] do. All these proteases cleave GPV.…”

Human Neutrophil Elastase Proteolytically Activates the Platelet Integrin αIIbβ3 through Cleavage of the Carboxyl Terminus of the αIIb Subunit Heavy Chain

“…1, panel A) and exocytosis of internal granules was barely detectable (0.8 Ϯ 0.3% release of 5-[ 14 C]HT, n ϭ 5), in agreement with previous reports (17)(18)(19). By contrast, addition of 400 nM NE 10 s before stimulation of platelets with threshold of cathepsin G resulted in an extensive aggregation, similar to that induced by the optimal concentration of cathepsin G (Fig.…”

“…Another important serine proteinase released from the azurophilic granules concomitantly with cathepsin G is neutrophil elastase (NE). While NE fails to trigger platelet aggregation and exocytosis (17)(18)(19), it has been demonstrated that when cathepsin G and NE are added together at concentrations comparable to those released by fMLP-activated neutrophils, NE potentiates the capacity of platelets to aggregate in response to cathepsin G (18,19). However, the molecular mechanism underlying this synergism remains unknown.…”

Immunomodulatory derivatives induce PU.1 down-regulation, myeloid maturation arrest, and neutropenia

“…[29][30][31] Like thrombin, CG potently stimulates platelet aggregation through structurally related proteaseactivated receptors. 32,33 Although NE2 does not activate platelets by itself, [34][35][36][37] it significantly enhances the platelet aggregating property of CG, especially at lower concentrations. 30 CG and NE2 can proteolytically cleave the integrin ␣ IIb ␤ 3 , the mediator of platelet aggregation.…”