Thrombin‐stimulated platelet aggregation is inhibited by kallikrein in a time‐ and concentration‐dependent manner

The Kallikrein Inhibitor from Bauhinia bauhinioides (BbKI) shows antithrombotic properties in venous and arterial thrombosis models

The Bauhinia bauhinioides Kallikrein Inhibitor (BbKI) is a Kunitz-type serine peptidase inhibitor of plant origin that has been shown to impair the viability of some tumor cells and to feature a potent inhibitory activity against human and rat plasma kallikrein (Kiapp 2.4 nmol/L and 5.2 nmol/L, respectively). This inhibitory activity is possibly responsible for an effect on hemostasis by prolonging activated partial thromboplastin time (aPTT). Because the association between cancer and thrombosis is well established, we evaluated the possible antithrombotic activity of this protein in venous and arterial thrombosis models. Vein thrombosis was studied in the vena cava ligature model in Wistar rats, and arterial thrombosis in the photochemical induced endothelium lesion model in the carotid artery of C57 black 6 mice. BbKI at a concentration of 2.0 mg/kg reduced the venous thrombus weight by 65% in treated rats in comparison to rats in the control group. The inhibitor prolonged the time for total artery occlusion in the carotid artery model mice indicating that this potent plasma kallikrein inhibitor prevented thrombosis.

Kinetic study of neuropeptide Y (NPY) proteolysis in blood and identification of NPY3-35: a new peptide generated by plasma kallikrein

There is little information on how neuropeptide Y (NPY) proteolysis by peptidases occurs in serum, in part because reliable techniques are lacking to distinguish different NPY immunoreactive forms and also because the factors affecting the expression of these enzymes have been poorly studied. In the present study, LC-MS/MS was used to identify and quantify NPY fragments resulting from peptidolytic cleavage of NPY(1-36) upon incubation with human serum. Kinetic studies indicated that NPY(1-36) is rapidly cleaved in serum into 3 main fragments with the following order of efficacy: NPY(3-36) >> NPY(3-35) > NPY(2-36). Trace amounts of additional NPY forms were identified by accurate mass spectrometry. Specific inhibitors of dipeptidyl peptidase IV, kallikrein, and aminopeptidase P prevented the production of NPY(3-36), NPY(3-35), and NPY(2-36), respectively. Plasma kallikrein at physiological concentrations converted NPY(3-36) into NPY(3-35). Receptor binding assays revealed that NPY(3-35) is unable to bind to NPY Y1, Y2, and Y5 receptors; thus NPY(3-35) may represent the major metabolic clearance product of the Y2/Y5 agonist, NPY(3-36).

Acidic peptides enhanced genistein-dependent inhibition of human platelet aggregation: potential protective effect of digestible peptides plus genistein against atherosclerosis

The leading cause of death in the United States and European countries is coronary heart disease. We hypothesized that the ingestion of soy compounds may not only have beneficial effects on atherosclerotic risk by lowering lipid compounds, but also by reducing platelet aggregability. Therefore, we analyzed in vitro the influence of defined and digestible peptides, frequently found in glycinin and beta-conglycinin as important proteins of soy bean, on platelet aggregation of 180 healthy volunteers with or without the isoflavone genistein by aggregometry and flow cytometry. (i) The predominating share of amino acids and acidic, neutral, and basic di- and tripeptides of up to 2 mmol/L did not modify platelet aggregation induced by collagen, adenosine diphosphate, epinephrine, or arachidonic acid. (ii) Genistein inhibited agonist-induced platelet aggregation dose dependently. (iii) In the presence of the acidic peptides glutamate-glutamate and aspartate-aspartate-aspartate (1 mmol/L each), genistein reduced collagen- and ADP-dependent platelet activation stronger than 250 micromol/L of this isoflavone alone. Other peptides were less effective (eg, glutamate-glutamate-glutamate) or ineffective (eg, asparagine-asparagine). (iv) Glutamate-glutamate-glutamate (1 nmol/L), glutamate-glutamate (1 micromol/L), and aspartate-aspartate-aspartate (1 micromol/L) enhanced the inhibition of genistein on platelet aggregation induced by arachidonic acid. Thus, the results of the present in vitro investigation allow the assumption that nutrition with specific compounds of soy--acidic peptides together with genistein--might protect against coronary atherosclerosis by attenuating platelet activity. In vivo studies are warranted to check this assumption.

Varying the ratio of dietary n−6/n−3 polyunsaturated fatty acid alters the tendency to thrombosis and progress of atherosclerosis in apoE−/− LDLR−/− double knockout mouse

We have investigated the influence of dietary n-6/n-3 (ù-6/ù-3) polyunsaturated fatty acid-balance on the tendency to arterial thrombosis and the progress of atherosclerosis in apoE-/- LDLR-/- double knockout mouse. Homozygous apoE-/- LDLR-/- double knockout mouse (DKO mice, 129XC57BL/6J background) and male C57BL/6 mice aged 6 weeks were divided into four groups. Each group was fed a diet containing a different n-6/n-3 ratio (Group l: 0.29; Group 2: 1.43; Group 3: 5.00; Group 4: 8), prepared with high linolenic (LNA) flaxseed oil (n-3 rich) and high linoleic (LA) safflower oil (n-6 rich). There were no statistical differences in the gain in body weight between the four groups. After 16 weeks, plasma triglyceride and LDL levels in Group 1 were significantly lower than in the other groups. Conversely, HDL was the highest. After 8 and 16 weeks, the tendency to arterial thrombosis was assessed using a He-Ne laser-induced thrombosis model. The degree of atherosclerosis was measured using the entire aorta method employing image analysis software. The n-6/n-3 ratio had a dose-dependent antithrombotic effect (thrombus volume decreased 23%, Group 1 vs. Group 4), In addition, the extent of atherosclerosis was less in the animals fed a low n-6/n-3 ratio compared with the high n-6/n-3 ratio group (atherosclerotic area decreased 40%, Group 1 vs. Group 4). The lowest n-6/n-3 ratio tested (0.29) was the most effective in suppressing the thrombotic and atherosclerotic parameters in these DKO mice.