α1-Antitrypsin Pittsburgh (Met358 → Arg) Inhibits the Contact Pathway of Intrinsic Coagulation and Alters the Release of Human Neutrophil Elastase during Simulated Extracorporeal Circulation

Abstract

SummaryCardiopulmonary bypass prolongs bleeding time, increases postoperative blood loss, and triggers activation of plasma proteolytic enzyme systems and blood cells referred to as the “whole body inflammatory response”. Contact of blood with synthetic surfaces leads to qualitative and quantitative alterations in platelets, neutrophils, contact and complement systems. Contact and complement pathway proteins both induce neutrophil activation, a j-antitrypsin Pittsburgh (Met358 → Arg), a mutant of α1-antitrypsin, is a potent inhibitor of plasma kalli-krein and thrombin. We investigated whether this recombinant mutant protein inhibited platelet activation, as well as contact and/or complement-induced neutrophil activation during simulated extracorporeal circulation.Arg358 α1-antitrypsin did not prevent the 34% drop in platelet count at 5 min of recirculation, did not block the 50% decrease in ADP-induced platelet aggregation at 120 min of recirculation, nor inhibit the release of 6.06 α 1.07 µg/ml (3-thromboglobulin at 120 min of recirculation suggesting that the inhibitor had little effect on platelet activation. However, Arg358 α1 arantitrypsin totally blocked kallikrein-Cl-in-hibitor complex formation but not Cl-Cl-inhibitor complex formation. Most importantly, Arg358 α1-antitrypsin decreased the release of 1.11 α 0.16 µg/ml human neutrophil elastase by 43%. The attenuation of neutrophil activation in the absence of an effect on complement activation via the classical pathway, supports the concept that kallikrein is a major mediator of neutrophil degranulation during cardiopulmonary bypass.

NSP4 Is Stored in Azurophil Granules and Released by Activated Neutrophils as Active Endoprotease with Restricted Specificity

“…As a result, it causes episodic bleeding in heterozygous individuals. Given the sequence similarity between our a1PI variant and the Pittsburgh mutant, an enhanced inhibitory activity of the latter toward NSP4 is conceivable and may explain its attenuating effect on elastase release from activated neutrophils (30).…”

Potent and Selective Kunitz Domain Inhibitors of Plasma Kallikrein Designed by Phage Display

“…However, BPTI is a more potent inhibitor of plasmin. Aprotinin has been used in a wide variety of clinical states including acute pancreatitis, septic and hemorrhagic shock, adult respiratory distress syndrome and multiple trauma; recently it has shown promise both clinically and in models of cardiopulmonary bypass (11,12). As a broad spectrum Kunitz type serine protease inhibitor, aprotinin can prevent activation of the clotting cascade initiated by the contact activation pathway.…”

“…Aprotinin inhibits the contact, neutrophil, and platelet activation systems during simulated extracorporeal perfusion, as evidenced by a reduction in blood loss and kallikrein-C1-inhibitor and C1-C1-inhibitor complexes, as well as prevention of neutrophil degranulation, platelet activation and aggregation (11,12). It has been used during lipopolysaccharide-induced endotoxic shock in pigs and prevented arterial hypotension (36).…”

Overview of PES biocompatible/hemodialysis membranes: PES–blood interactions and modification techniques

“…On the other hand, the failure of thrombin and kallikrein inhibitors to decrease platelet activation recommends that platelet activation is at least in part mediated by other agonists. High complement reactions and leukocyte activation also cause the platelet adhesion [25][26][27].…”