N-Stearoylethanolamine Inhibits Integrin-Mediated Activation, Aggregation, and Adhesion of Human Platelets.

N-stearoylethanolamine (NSE), a lipid mediator that belongs to the N-acylethanolamine (NAE) family, has anti-inflammatory, antioxidant, and membranoprotective actions. In contrast to other NAEs, NSE does not interact with cannabinoid receptors. The exact mechanism of its action remains unclear. The aim of this study is to evaluate the action of NSE on activation, aggregation, and adhesion of platelets that were chosen as a model of cellular response. Aggregation of platelets was measured to analyze the action of NSE (10-6-10-10 M) on platelet reactivity. Changes in granularity and shape of resting platelets and platelets stimulated with ADP in the presence of NSE were monitored by flow cytometry, and platelet deganulation was monitored by spectrofluorimetry. In vivo studies were performed using obese insulin-resistant rats. Binding of fibrinogen to the GPIIb/IIIa receptor was estimated using indirect ELISA and a scanning electron microscopy (SEM). It was found that NSE inhibits the activation and aggregation of human platelets. Our results suggest that NSE may decrease the activation and subsequent aggregation of platelets induced by ristocetin, epinephrine, and low doses of ADP. NSE also reduced the binding of fibrinogen to GPIIb/IIIa on activated platelets. These effects could be explained by the inhibition of platelet activation mediated by integrin receptors: the GPIb-IX-V complex for ristocetin-induced activation and GPIIb/IIIa when epinephrine and low doses of ADP were applied. The anti-platelet effect of NSE complements its anti-inflammatory effect and allows us to prioritize studies of NSE as a potent anti-thrombotic agent. SIGNIFICANCE STATEMENT: N-stearoylethanolamine (NSE) was shown to possess inhibitory action on platelet activation, adhesion, and aggregation. The mechanism of inhibition possibly involves integrin receptors. This finding complements the known anti-inflammatory effects of NSE.

The Rise of Factor X Level in Blood Plasma of Patients at Severe Burn Injuries.

This work is dedicated to the detection of imbalance between the pro- and anticoagulant branches of hemostasis at severe burn injuries by evaluating the content or activity of individual clotting factors. To select the targets for accurate diagnostics we measured the concentrations of soluble fibrin monomeric complexes and fibrinogen, levels of total prothrombin, factor X, protein C, and antithrombin III, and recorded the time of clotting in activated partial thromboplastin time and prothrombin time (PT) tests. Factor X level was increased in 26% of patients on the 1st day after the burn and it rose further in 62% patients on the 14th day of recovery. Increasing factor X level is assumed to be a risk factor of thrombotic complications. We propose to use it as a marker of predisposition to thrombosis at severe burn injury.

Non-enzymatic activation of prothrombin induced by interaction with fibrin ß26-42 region.

We have discovered that addition of monomeric desAB fibrin to prothrombin leads to appearance of the thrombin-like activity of prothrombin towards S2238 chromogenic substrate. DesA and desABß(15-42)2 fibrin forms did not cause any activation of prothrombin. From this observation we could suggested that amino acid residues of the 15-42 fragment of BßN-domain presented in desAB fibrin, cleaved in desABß(15-42)2 fibrin and protected in desA fibrin, play a crucial role in the non-enzymatic activation of prothrombin. To identify the Bß amino acid residues involved in the fibrin-prothrombin binding we used monoclonal antibodies 1-5G and 2d2a with epitopes in Bß26-42 and Bß12-26 fibrin fragments respectively. The thrombin-like activity in the mixture of prothrombin and desAB fibrin was monitored in the presence of each of these monoclonal antibodies. It was found that anti-Bß12-26 antibody does not exhibit any inhibitory effect on the thombin-like activity of the mixture. In contrast, adding of Bß26-42 antibody into the mixture of desAB fibrin with prothrombin diminished the thrombin-like activity by 70%. Recombinant dimeric peptides Bß(15-44)2 and Bß(15-66)2 that mimic amino acid residues in fibrin were also tested for their ability to activate prothrombin. It was found that both peptides were able to induce non-enzymatic activation of prothrombin. The activation was more evident in the case of Bß(15-44)2 peptide. From the data obtained we can conclude that desAB fibrin binds to prothrombin through the Bß26-42 amino acid residues and the formation of such a complex caused a non-enzymatic activation of prothrombin.