Search results for "Thromboxane A2"
showing 10 items of 26 documents
Decreased bioavailability of nitric oxide in aorta from ovariectomized senescent mice. Role of cyclooxygenase.
2015
This study investigates the effects of aging and/or ovariectomy on vascular reactivity to thromboxane A2 (TXA2) receptor stimulation with U46619, and the modulation by nitric oxide (NO) and cyclooxygenase (COX) in aorta from female senescence-accelerated mice (SAMP8) and from senescence resistant mice (SAMR1). Five-month-old female SAMR1 and SAMP8 were divided into three groups: sham-operated, ovariectomized and ovariectomized plus estradiol. Twenty-eight days after surgery, thoracic aortic rings were mounted for isometric recording of tension and concentration-response curves for U46619 (10(-10)-3 × 10(-7) M) were performed in the absence and in the presence of the NO synthase inhibitor N(…
Extracellular histones disarrange vasoactive mediators reléase through COX-NOS interaction in human endothelial cells
2017
Abstract Extracellular histones are mediators of inflammation, tissue injury and organ dysfunction. Interactions between circulating histones and vascular endothelial cells are key events in histone‐mediated pathologies. Our aim was to investigate the implication of extracellular histones in the production of the major vasoactive compounds released by human endothelial cells (HUVECs), prostanoids and nitric oxide (NO). HUVEC exposed to increasing concentrations of histones (0.001 to 100 μg/ml) for 4 hrs induced prostacyclin (PGI2) production in a dose‐dependent manner and decreased thromboxane A2 (TXA2) release at 100 μg/ml. Extracellular histones raised cyclooxygenase‐2 (COX‐2) and prostac…
Endogenous peroxynitrite modulates PGHS-1–dependent thromboxane A2 formation and aggregation in human platelets
2008
Aggregation of activated platelets is considerably mediated by the autocrine action of thromboxane A2 (TxA2) which is formed in a prostaglandin endoperoxide H2 synthase-1 (PGHS-1 or COX-1)-dependent manner. The activity of PGHS-1 can be stimulated by peroxides, an effect termed "peroxide tone", that renders PGHS-1 the key regulatory enzyme in the formation of TxA2. Activated platelets release nitric oxide (*NO) and superoxide (O*2) but their interactions with the prostanoid pathway have been controversially discussed in platelet physiology and pathophysiology. The current study demonstrates that endogenously formed peroxynitrite at nanomolar concentrations, originating from the interaction …
Increased thromboxane biosynthesis in type IIa hypercholesterolemia.
1992
BACKGROUND Increased platelet thromboxane (TX)A2 production has been described in type IIa hypercholesterolemia. To verify the relevance of these capacity-related measurements to the actual rate of TXA2 biosynthesis in vivo, we studied the urinary excretion of its major enzymatic metabolites in 46 patients with type IIa hypercholesterolemia and 20 age-matched controls. METHODS AND RESULTS Urinary 11-dehydro-TXB2 and 2,3-dinor-TXB2 were measured by previously validated radioimmunoassays. The excretion rate of 11-dehydro-TXB2 was significantly (p less than 0.001) higher in patients (68.7 +/- 35.1 ng/hr, mean +/- SD) than in controls (22.4 +/- 9.4 ng/hr), with metabolite excretion greater tha…
Inhibition of thromboxane biosynthesis and platelet function by simvastatin in type IIa hypercholesterolemia
1995
Abstract Thromboxane A 2 (TXA 2 ) biosynthesis is enhanced in the majority of patients with type IIa hypercholesterolemia. Because simvastatin (a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor) was previously shown to reduce platelet aggregation and TXB 2 production ex vivo, we investigated TXA 2 biosynthesis and platelet function in 24 patients with type IIa hypercholesterolemia randomized to receive in a double-blind fashion simvastatin (20 mg/d) or placebo for 3 months. The urinary excretion of 11-dehydro-TXB 2 , largely a reflection of platelet TXA 2 production in vivo, was measured by a previously validated radioimmunoassay technique. Blood lipid levels and urinary 11-dehyd…
Picotamide, a combined inhibitor of thromboxane A2 synthase and receptor, reduces 2-year mortality in diabetics with peripheral arterial disease: the…
2004
Aims Patients with diabetes are at excessive risk of mortality and cardiovascular morbidity. Previous studies suggest that aspirin may be less effective in diabetic patients. In this multi-centre, randomized, double blind trial picotamide, a dual inhibitor of thromboxane A2 synthase and receptor, was compared with aspirin for the prevention of mortality and major cardiovascular events in diabetics with peripheral arterial disease (PAD). Methods and results A total of 1209 adults aged 40–75 years with type 2 diabetes and PAD were randomized to receive picotamide (600 mg bid) or aspirin (320 mg od) for 24 months. The cumulative incidence of the 2 years overall mortality was significantly lowe…
Inhibition of thromboxane biosynthesis by triflusal in type 2 diabetes mellitus.
2004
Abstract Triflusal is an antiplatelet drug related to aspirin, with different pharmacological properties and a lower haemorrhagic risk. We aimed at comparing their effects on platelet and endothelial activation in type 2 diabetes mellitus (T2DM). In a randomized, double-blind, parallel group study, we compared the effects of three daily regimens (300, 600, and 900mg) of triflusal, and aspirin (100mg/day) on urinary 11-dehydro-thromboxane (TX)B 2 , index of in vivo platelet activation, ex vivo platelet function using the analyzer PFA-100, plasma von Willebrand factor (vWF), P-selectin, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and serum nitrite a…
Role of NO-synthases and cyclooxygenases in the hyperreactivity of male rabbit carotid artery to testosterone under experimental diabetes.
2009
Abstract Cardiovascular disease is the major cause of morbidity and mortality in diabetic patients, which in turn is also associated with low levels of serum testosterone. The working hypothesis was that diabetes might modify the mechanisms involved in the vascular actions of testosterone in isolated rabbit carotid arteries. Testosterone (10 −8 –3 × 10 −4 M) induced a concentration-dependent relaxation of precontracted carotid arteries, which was higher in diabetic than in control rabbits. In control rabbits neither endothelium removal nor the nitric oxide synthase (NOS) inhibitor N G -nitro- l -arginine ( l -NOArg, 10 −5 M) modified the relaxant action of testosterone, and the cyclooxyge…
Mechanisms involved in the relaxant action of testosterone in the renal artery from male normoglycemic and diabetic rabbits.
2009
Kidney disease is a frequent complication in diabetes, and significant differences have been reported between male and female patients. Our working hypothesis was that diabetes might modify the vascular actions of testosterone in isolated rabbit renal arteries and the mechanisms involved in these actions. Testosterone (10(-8) to 10(-4)M) induced relaxation of precontracted arteries, without significant differences between control and diabetic rabbits. Both in control and diabetic rabbits endothelium removal inhibited testosterone relaxant action. In arteries with endothelium, incubation with indomethacin (10(-5)M), N(G)-nitro-l-arginine (10(-5)M) or tetraethylammonium (10(-5)M) did not modi…
Involvement of prostacyclin and potassium channels in the diabetes-induced hyporeactivity of the rabbit carotid artery to B-type natriuretic peptide
2012
The relation between diabetes and stroke is bidirectional: diabetes is an important risk factor for ischemic stroke, and acute stroke frequently induces hyperglycemia. On the other hand, plasma B-type natriuretic peptide (BNP) levels are raised in diabetes and stroke. The purpose was to study how alloxan-induced diabetes might modify the effects of BNP in rabbit carotid arteries and the mechanisms involved in such actions. To do this, isometric tension in isolated rabbit carotid artery was recorded and prostanoids release and plasma NT-proBNP were measured by enzyme immunoassay. BNP induced a relaxation of phenylephrine-precontracted carotid arteries, and this relaxation was lower in diabet…