15-hydroperoxy-5-8-11-13-eicosatetraenoic-acid and Thrombosis

Atherosclerotic cardiovascular diseases are the leading causes of morbidity and mortality worldwide. We have previously shown that arachidonate 15-lipoxygenase B (ALOX15B) is highly expressed in atherosclerotic carotid plaques, and elucidation of mechanisms downstream of activated lipoxygenases may be relevant to our understanding of the genesis of atherosclerotic diseases. We examined 120 carotid plaques from patients with symptomatic carotid artery stenosis and showed that the extent of ALOX15B staining was significantly increased in carotid plaques with thrombosis. Impedance aggregometry analyses showed that the ALOX15B enzyme products 15-HETE and 15-HPETE increased platelet aggregation. By using a calibrated automatic thrombin assay, we showed that the ALOX15B products also increased both peak levels of thrombin and the total endogenous thrombin potential. Moreover, platelet aggregation was increased by addition of cell lysates from ischemic human macrophages, whereas platelet aggregation was reduced after knockdown of ALOX15B in human macrophages. Our data show that ALOX15B expression in human carotid plaques is associated with thrombus formation and that enzyme products of ALOX15B increase platelet aggregation and thrombin generation. We therefore propose that activated ALOX15B in macrophages may play a role in the induction of atherothrombotic events by increasing platelet aggregation and thrombin generation.

Topics: Aged; Arachidonate 15-Lipoxygenase; Calibration; Carotid Arteries; Carotid Stenosis; Female; Gene Silencing; Humans; Hydroxyeicosatetraenoic Acids; Immunohistochemistry; Leukotrienes; Lipid Peroxides; Macrophages; Male; Middle Aged; Phenotype; Platelet Aggregation; RNA, Small Interfering; Thrombin; Thrombosis

A segment of fresh rabbit thoracic aorta (RbA) was turned inside out and superfused (1.5 ml/min) with citrated (3.8%) or heparinized (10 U/ml) blood of rabbit and the superfusate was discarded. RbA gained in weight due to deposition of thrombi on its endothelial surface. These thrombi were mainly composed of platelets. The interaction between platelets and endothelium was augmented in RbAs from animals with atherosclerosis and in RbAs pretreated with aspirin (110 microM) or 15-HPETE (150 microM) or by the enzymatic system generating oxygen free radicals (xanthine:xanthine oxidase - 100 microM: 0.1 U/ml). On the other hand, this interaction was impaired by superoxide dismutase (20 U/ml) or catalase (0.2 U/ml). Finally, the dissipation of thrombi by thromboxane A2-synthetase inhibitor--dazoxiben was found to be related to an increase in endothelial generation of prostacyclin.

Topics: Animals; Aorta, Thoracic; Arteriosclerosis; Aspirin; Blood Platelets; Endothelium, Vascular; Epoprostenol; Imidazoles; Indomethacin; Leukotrienes; Lipid Peroxides; Platelet Adhesiveness; Rabbits; Superoxide Dismutase; Thrombosis; Xanthine; Xanthine Oxidase; Xanthines

Prostaglandins play an important role in platelet-vessel wall interaction. The inhibition of PGI2 synthetase by 15-hydroxyarachidonic acid (15-HPAA) results in an enhancement of local thrombus formation.

Topics: Animals; Arachidonic Acids; Arteries; Blood Platelets; Cyclooxygenase Inhibitors; Epoprostenol; In Vitro Techniques; Leukotrienes; Lipid Peroxides; Male; Peroxides; Platelet Aggregation; Prostaglandins; Rats; Thrombosis

Topics: Adenosine Diphosphate; Arachidonic Acids; Arteries; Blood Platelets; Cyclooxygenase Inhibitors; Humans; In Vitro Techniques; Leukotrienes; Lipid Peroxides; Peroxidases; Thrombosis