Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P24557 (thromboxane A2 synthase)
 124 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Picotamide is an antiplatelet drug with a peculiar dual mechanism of action: it inhibits thromboxane A2 synthase and antagonizes the pharmacological responses mediated by thromboxane A2 receptor. We investigated the in vitro effect of picotamide on smooth muscle cell migration and proliferation. Picotamide (1-500 microM) decreased human and rat smooth muscle cell proliferation, evaluated as cell number, in a concentration-dependent and reversible manner. Picotamide inhibited DNA synthesis induced by fetal calf serum (10%), platelet-derived growth factor (PDGF-BB (20 ng/ml)), epidermal growth factor (EGF (1 nM)) and (15S)-hydroxy-11,9-(epoxymethano)prosta-5Z,13E-dienoic acid (U46619 (10 microM, thromboxane A2 receptor agonist)). Co-incubation of U46619 together with EGF or PDGF-BB resulted in a marked amplification of [3H]thymidine incorporation that was completely reversed by picotamide. The drug also inhibited smooth muscle cell migration induced by fibrinogen (600 microg/ml) or PDGF-BB (20 ng/ml) in a concentration-dependent manner. The ability of picotamide to interfere with myocyte migration and proliferation confers, at least in vitro, a pharmacological interest on the compound in atherogenesis.
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PMID:Picotamide, an antithromboxane agent, inhibits the migration and proliferation of arterial myocytes. 975 41

A new series of omega-disubstituted alkenoic acid derivatives derived from samixogrel 5 were designed and synthesized as combined thromboxane A2 receptor antagonists/thromboxane A2 synthase inhibitors with improved solubility and reduced protein binding compared to 5. Hexenoic acid derivatives with a 3-pyridyl group and 3-(2-cyano-3-alkyl-guanidino)phenyl substituent were found to be optimal with regard to this dual mode of action. The most potent compound, E-6-(3-(2-cyano-3-tert-butyl-guanidino)phenyl)-6-(3-pyridyl)hex-5-eno ic acid, "terbogrel" 32 inhibits the thromboxane A2 synthase in human gel-filtered platelets with an IC50 value of 4.0 +/- 0.5 nM (n = 4). Radioligand binding studies with 3H-SQ 29,548 revealed that 32 blocks the thromboxane A2/endoperoxide receptor on washed human platelets with an IC50 of 11 +/- 6 nM (n = 2) and with an IC50 of 38 +/- 1 nM (n = 15) in platelet-rich plasma. Terbogrel inhibits the collagen-induced platelet aggregation in human platelet-rich plasma and whole blood with an IC50 of 310 +/- 18 nM (n = 8) and 52 +/- 20 nM (n = 6), respectively. This was shown to translate into a potent antithrombotic effect in vivo as demonstrated in studies using a model of arterial thrombosis in rabbits (ED50 = 0.19 +/- 0.07 mg/kg; n = 20). Thus, terbogrel is the first compound with a guanidino moiety demonstrating both a potent TXA2 synthase inhibition and a potent TXA2 receptor antagonism and has been selected for further clinical development.
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PMID:Guanidine derivatives as combined thromboxane A2 receptor antagonists and synthase inhibitors. 1019 67

The effect of inhibitors of the thromboxane A2 pathway on spontaneous contractions of intestinal smooth muscle preparations was studied. The thromboxane A2 antagonists Bay u3405, SK and F 88046 and KW-3635 concentration-dependently inhibited both the amplitude and the frequency of spontaneous contractions of the longitudinal muscle from the rat proximal colon. A concentration-dependent inhibition of the myogenic contractions was also observed with the thromboxane A2 synthase inhibitor U-51605, and with the combined cyclooxygenase/lipoxygenase inhibitor nordihydroguaiaretic acid, whereas indomethacin, a pure cyclooxygenase inhibitor, was ineffective. None of these inhibitors affected the contractile response evoked by the cholinergic agonist carbachol, excluding non-specific actions on intestinal motility. A similar response was observed for the rabbit jejunum, which, in contrast to the rat colon, exhibits more regular, high-frequency spontaneous contractions, which were inhibited by Bay u3405, SK and F 88046 and KW-3635 in a concentration-dependent manner, whereas the response to carbachol remained unaffected. These results suggest a role for thromboxane A2 in the generation and/or facilitation of spontaneous smooth muscle contractions in the gut.
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PMID:Inhibition of spontaneous smooth muscle contractions in rat and rabbit intestine by blockers of the thromboxane A2 pathway. 1021 49

To better understand metabolites of arachidonic acid generated from human mast cells, the present study assessed the capacity of human mast cells to synthesize thromboxane B2 (TXB2). Anti-IgE challenge of human sinus mast cells resulted in the generation of TXB2 in a dose-dependent manner with a maximal generation of 8.2+/-4.4 ng/10(6) cells (n = 12), which is about 10-fold lower than the maximal generation of prostaglandin D2 (PGD2). Pretreatment of the cells with OKY-046, an inhibitor of TXA synthase, prevented formation of TXB2 in a dose-dependent manner without affecting the generation of PGD2 or leukotriene C4. Experiments using indomethacin or MK-591, a potent FLAP inhibitor, showed that shunting of arachidonic acid did not occur in a single-cell suspension of mast cells. Analysis by RT-PCR revealed that two species of TXA synthase, the full-length TXA synthase mRNA (TXAS-1, 570 BP) and a small quantity of the alternate-spliced form (400 BP), were present in mast cells. When cellular levels of TXAS-1 mRNA were normalized to those of G3PDH mRNA, the relative concentration of TXAS-1 was 2.06+/-0.60 (n = 7) in highly purified sinus mast cells (92.3+/-3.0% pure) and 3.66+/-0.98 (n = 5) in eosinophils.
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PMID:Generation of thromboxane A2 from highly purified human sinus mast cells after immunological stimulation. 1035 19

We applied a microdialysis technique for the measurement of hypothalamic thromboxane B2, a stable metabolite of thromboxane A2, in urethane-anesthetized rats. Perfusion with N-methyl-D-aspartate (1.5 and 2.5mM) of the paraventricular nucleus by microdialysis probe concentration-dependently elevated the levels of thromboxane B2 in this region and plasma levels of catecholamines. The elevation of adrenaline was much more marked than that of noradrenaline. Pretreatment with dizocilpine maleate (0.1 mM), a non-competitive antagonist of N-methyl-D-aspartate receptors, of the paraventricular nucleus by microdialysis probe attenuated the N-methyl-D-aspartate (1.5 mM)-induced elevations of both thromboxane B2 and plasma catecholamines. Intracerebroventricular administration of furegrelate (250 microg/animal), a thromboxane A2 synthase inhibitor, also abolished the responses evoked by N-methyl-D-aspartate. These results indicate that N-methyl-D-aspartate applied into the paraventricular nucleus produces thromboxane A2 in this region and elevates plasma levels of catecholamines, especially adrenaline. Thromboxane A2 produced in this hypothalamic nucleus is probably involved in the N-methyl-D-aspartate-induced central adrenomedullary outflow.
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PMID:Perfusion of the hypothalamic paraventricular nucleus with N-methyl-D-aspartate produces thromboxane A2 and centrally activates adrenomedullary outflow in rats. 1071 38

Compared with their two normotensive (LN and LL) controls, genetically hypertensive rats of the Lyon strain (LH) exhibit increased renal vascular resistance and a blunted pressure natriuresis function as well as an increased urinary excretion of vasoconstrictor prostanoids. The aim of this study was to assess in the kidneys of these animals the synthesis of vasoconstrictor or sodium-retaining prostanoids. The relative abundance of the mRNAs of cyclooxygenases (COX) 1 and 2 and of thromboxane A2 synthase (TXS), was measured by reverse-transcription polymerase chain reaction (RT-PCR) in renal cortex and medulla dissected in groups of male LH, LN, and LL rats either in baseline conditions or after 1 week of salt loading (1.5% NaCl in the drinking water). In basal conditions, at 3 and 11 weeks of age COX1 was expressed in the kidneys of all rats more markedly in medulla than in cortex. COX2 was poorly expressed in the whole kidney. TXS expression was usually too low to be quantified. No difference could be observed among LH, LN, and LL rats. After salt loading, the expression of COX1 was enhanced in the medulla and that of COX2 reduced in the cortex. LH rats differed from controls by a significantly more marked increase in medullary COX1 expression. The present work excludes any primary generalized increase in the renal expression of the genes that control the synthesis of vasoconstrictor prostanoids in LH rats, but suggests that medullary COX1 is upregulated by salt in these animals.
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PMID:Cyclooxygenases 1 and 2 and thromboxane synthase in kidneys of Lyon hypertensive rats. 1082 43

GPIIb/IIIa antagonists are expected to have a beneficial effect on acute cerebral infarction, however, the occurrence of intracranial hemorrhage has not been as widely investigated. A rabbit focal thrombotic occlusion model of the middle cerebral artery was established by creating a photochemical reaction between green light and Rose Bengal. Hemorrhagic transformation was common in the area of cerebral infarction. Using this model, the effect of a GPIIb/IIIa antagonist, ME3277 (low dose, (L); 0.15 mg/kg + 0.125 mg/kg x h, middle dose, (M); 0.3 mg/kg + 0.25 mg/kg x h and high dose, (H); 0.6 mg/kg + 0.5 mg/kg x h), aspirin (20 mg/kg) and sodium ozagrel (thromboxane A2 synthase inhibitor, 1 mg/kg + 2 mg/ kg x h) were evaluated. Drugs were intravenously administrated 30 minutes after the photochemical reaction for 24 hours. Aspirin inhibited the ex vivo platelet aggregation induced by arachidonic acid and collagen but not by adenosine diphosphate (ADP), while sodium ozagrel only inhibited the arachidonic acid-induced aggregation. ME3277 dose-dependently inhibited the platelet aggregation induced by all the inducers (approximately 60% in L, 80% in M, and 90% in H). At 24 hours of middle cerebral artery (MCA) occlusion, infarct volume was significantly reduced by aspirin and each dose of ME3277. These agents improved neurologic deficits, with ME3277 being more potent than aspirin. Sodium ozagrel did not alter the infarct volume nor neurologic deficits. No drug was found to worsen hemorrhage volume despite increasing bleeding time (2-3 fold) in the skin. In this model, the occluded artery was spontaneously recanalized and re-thrombosed frequently. One mechanism by which antiplatelet agents reduced infarct volume was inhibition of rethrombosis of the MCA. These results suggest that treatment with a GPIIb/IIIa antagonist is a useful intervention for acute cerebral infarction prolonging dose bleeding time to 3 times the basal value.
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PMID:ME3277, a GPIIb/IIIa antagonist reduces cerebral infarction without enhancing intracranial hemorrhage in photothrombotic occlusion of rabbit middle cerebral artery. 1089 82

Beta-adrenoreceptor antagonists, such as propranolol, can provoke severe bronchoconstriction in asthmatic subjects. Recently we developed an animal model of propranolol-induced bronchoconstriction and investigated the involvement of chemical mediators in this reaction. The purpose of this study was to elucidate the role of thromboxane A2 in the development of propranolol-induced bronchoconstriction after allergic bronchoconstriction. Passively sensitized guinea pigs were anesthetized and treated with diphenhydramine hydrochloride and were then artificially ventilated. Propranolol at a concentration of 10 mg/ml was inhaled 20 min after an aerosolized antigen challenge. A potent and selective thromboxane A2 synthase inhibitor, CS-518, in doses of 0.01, 0.1 and 1 mg/kg and vehicle were administered intravenously 15 min after the antigen challenge. Another study was performed in naive guinea pigs; ascending doses of methacholine (12.5, 25, 50, 100 and 200 microg/ml) were inhaled for 20 sec at 5-min intervals, 10 min after intravenous administration of CS-518. Propranolol inhaled 20 min after the antigen challenge caused bronchoconstriction in sensitized guinea pigs. CS-518 administered 15 min after the antigen challenge significantly inhibited propranolol-induced bronchoconstriction in a dose-dependent manner, while CS-518 did not influence the dose-dependent response to inhaled methacholine in naive guinea pigs. We conclude that thromboxane A2 contributes to the development of propranolol-induced bronchoconstriction following allergic reaction in our guinea pig model.
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PMID:Effect of thromboxane synthase inhibitor, CS-518, on propranolol-induced bronchoconstriction in guinea pigs. 1089 53

There is an autocrine relationship between eicosanoid and cytokine synthesis, with the ratio of prostaglandin E2 (PGE2)/thromboxane A2 (TXA2) being one of the determinants of the level of cytokine synthesis. In monocytes, cyclooxygenase type 1 (COX-1) activity appears to favor TXA2 production and COX-2 activity appears to favor PGE2 production. This has led to speculation regarding possible linkage of COX isozymes with PGE and TXA synthase. We have studied the kinetics of PGE2 and TXA2 synthesis under conditions that rely on COX-1 or -2 activity. With small amounts of endogenously generated prostaglandin H2 (PGH2), TXA2 synthesis was greater than PGE2. With greater amounts of endogenously generated PGH2, PGE2 synthesis was greater than TXA2. Also, TXA synthase was saturated at lower substrate concentrations than PGE synthase. This pattern was observed irrespective of whether PGH2 was produced by COX-1 or COX-2 or whether it was added directly. Furthermore, the inhibition of eicosanoid production by the action of nonsteroidal anti-inflammatory drugs or by the prevention of COX-2 induction with the p38 mitogen-activated protein kinase inhibitor SKF86002 was greater for PGE2 than for TXA2. It is proposed that different kinetics of PGE synthase and TXA synthase account for the patterns of production of these eicosanoids in monocytes under a variety of experimental conditions. These properties provide an alternative explanation to notional linkage or compartmentalization of COX-1 or -2 with the respective terminal synthases and that therapeutically induced changes in eicosanoid ratios toward predominance of TXA2 may have unwanted effects in long-term anti-inflammatory and anti-arthritic therapy.
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PMID:Differential regulation of prostaglandin E2 and thromboxane A2 production in human monocytes: implications for the use of cyclooxygenase inhibitors. 1090 70

Since serotonin (5-HT) is implicated in exacerbating acute coronary syndromes, we studied the reactivity of atrial coronary arterioles (70-140 microm) of atherosclerotic patients undergoing cardiac surgery to 5-HT, substance P (Sub P), and sodium nitroprusside by video-microscopy. Before ischemia, 5-HT-induced relaxation was not affected by NS398 (cyclooxygenase inhibitor), H2O2 or U63557A (thromboxane A2 synthase inhibitor), but was reduced by L-NNA. 5-HT elicited a potent contractile response after ischemia that was inhibited by NS398, Indo, and U63557A. While Sub P relaxation was decreased after ischemia, SNP relaxation was unchanged. The mRNA steady-state levels of NOS-3, NOS-2, prostacyclin synthase, and COX- 1 were not altered by ischemia. COX-2 mRNA and protein levels (Westernblotting), however, were increased (mean +/- SEM) 2.4 +/- 0.4 and 3.2 +/- 0.7 fold, respectively, in ischemic atrium corroborating with the immunohistochemistry of atrial tissue. It is concluded that myocardial ischemia enhanced contractile response of coronary arterioles to 5-HT maybe due to the stimulated prostaglandin release (likely thromboxane A2) secondary to induction of COX-2 expression. These findings may have implications regarding the cause of coronary spasm during acute myocardial ischemia.
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PMID:Serotonin-induced human coronary microvascular contraction during acute myocardial ischemia is blocked by COX-2 inhibition. 1121 33


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