Basics of Coagulation Pathways

Isolation of a Novel Metalloproteinase from Agkistrodon Venom and Its Antithrombotic Activity Analysis

Snake venom contains large amounts of active proteins and peptides. In this study, a novel snake protein, metalloproteinase SP, was successfully isolated from the venom of Agkistrodon acutus by multi-gel chromatography. The isolated protein exhibits anti-platelet aggregation activity. Animal experiments showed that it exhibited defibration, anticoagulation, and antithrombotic effects and contributes to improved blood rheology and antiplatelet aggregation. In vivo experiments demonstrated that it prolonged clotting time, partial thromboplastin time, prothrombin time, thrombin time, fibrinogen time and reduced fibrinogen content of mice. Also, metalloproteinase SP inhibited carrageenan-induced tail thrombosis, ADP-induced acute pulmonary embolism, and ADP, Arachidonic acid (AA), or collagen-induced platelet aggregation. In vitro experiments showed that the protein cleaved the α, β, and γ chains of fibrinogen. Metabolomic analysis upon metalloproteinase SP treatment revealed that 14 metabolites, which are mainly involved in phenylalanine, tyrosine, and tryptophan biosynthesis, responded to metalloproteinase SP treatment. In summary, the isolated snake venom protein inhibits formation of acute pulmonary embolism probably through regulating and restoring perturbed energy, lipid, and amino acid metabolism.

Osteosarcoma cell-calcium signaling through tissue factor-factor VIIa complex and factor Xa

The cells responsible for bone formation express protease-activated receptors. Although serine protease thrombin has been shown to elicit functional responses in bone cells that impact on cell survival and alkaline phosphatase activity, nothing is known about tissue factor, factor VIIa, and factor Xa, the serine proteases that act upstream of thrombin in the coagulation cascade. This paper demonstrates that tissue factor is expressed in the osteoblast-like cell line SaOS-2 and, that tissue factor in a factor VIIa-bound complex induces a transient intracellular Ca(2+) increase through protease-activated receptor-2. In SaOS-2 cells, factor Xa induced a sustained intracellular Ca(2+) response, as does SLIGRL, a PAR2-activating peptide, and PAR-1-dependent cell viability.

The kallikrein-kinin system: current and future pharmacological targets

The kallikrein-kinin system is an endogenous metabolic cascade, triggering of which results in the release of vasoactive kinins (bradykinin-related peptides). This complex system includes the precursors of kinins known as kininogens and mainly tissue and plasma kallikreins. The pharmacologically active kinins, which are often considered as either proinflammatory or cardioprotective, are implicated in many physiological and pathological processes. The interest of the various components of this multi-protein system is explained in part by the multiplicity of its pharmacological activities, mediated not only by kinins and their receptors, but also by their precursors and their activators and the metallopeptidases and the antiproteases that limit their activities. The regulation of this system by serpins and the wide distribution of the different constituents add to the complexity of this system, as well as its multiple relationships with other important metabolic pathways such as the renin-angiotensin, coagulation, or complement pathways. The purpose of this review is to summarize the main properties of this kallikrein-kinin system and to address the multiple pharmacological interventions that modulate the functions of this system, restraining its proinflammatory effects or potentiating its cardiovascular properties.

[rFVIIa administration in patient with a left ventricular assistance patient]

We report the case of a left ventricular mechanical assistance (Incor Berlinheart) in a woman that experienced a postoperative non-surgical haemorrhagic complication following a reconstructive pedicled omentoplasty for implanted materials infection. After massive substitutive therapy failure at reducing blood loss and because of an hypovolaemic shock, high dosage (70 microg/kg twice) of recombinant activated factor VII (r-VIIa) was administrated resulting in spectacular cessation of bleeding and haemodynamic restoration. Continuous repeated clinical evaluation, cardiac echography and electronic monitoring of the axial pump device characteristic did not reveal any thromboembolic accident. This observation brings some indirect arguments for safe rFVIIa treatment in this type of pathology with a high thromboembolic risk.