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)

The vasoconstrictor actions of prostaglandin (PG) endoperoxide, PGH2, were examined in isolated rabbit aortic rings suspended for measurement of isometric tension. In aortic rings with an intact endothelium, PGH2 caused concentration-dependent contractions which were blocked by SQ 29548 (a PGH2-thromboxane A2 receptor blocker) or superoxide dismutase (a superoxide anion scavenger) but not by carbethoxyhexyl imidazole (a thromboxane A2 synthase inhibitor) or catalase (a hydrogen peroxide scavenger). In contrast U 46619, a thromboxane A2 mimic, caused contractions, which were blocked by SQ 29548 but not by superoxide dismutase. PGH2 caused significantly greater contractions in aortic rings without endothelium or in those with intact endothelium treated with NG-nitro-L-arginine, a nitric oxide inhibitor; these contractions were inhibited by SQ 29548 but not by superoxide dismutase. In aortic rings with endothelium contracted with phenylephrine, a subthreshold concentration of PGH2, but not U 46619, impaired relaxations to acetylcholine; the inhibition was prevented by treatment with SQ 29548 or superoxide dismutase, indicating that the abnormality of endothelial cell function was specific for PGH2. These observations indicate that PGH2 causes contractions and inhibits endothelium-dependent relaxation by a mechanism involving formation of superoxide anion, which interacts with endothelium-derived nitric oxide.
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PMID:Role of superoxide anion and endothelium in vasoconstrictor action of prostaglandin endoperoxide. 132 Mar 40

Renal prostaglandins (PGs) help maintain renal blood flow and glomerular filtration rate when the kidney is exposed to a vasoconstrictor stress. In addition, they aid pressure natriuresis and blunt the antidiuretic effect of vasopressin. Angiotensin-converting enzyme (ACE) inhibitors could decrease renal PG synthesis by reducing angiotensin II (Ang II) formation or increase it by preventing kinin inactivation. Additionally, they could affect PG synthesis or catabolism directly. The effects of ACE inhibitors on blood pressure and renal hemodynamics appear to be largely independent of changes in renal PG synthesis. Similarly, there is no evidence that pressure natriuresis is modified by ACE inhibitors. A kinin induced increase in collecting duct PG synthesis may account for the water diuresis seen clinically with ACE inhibitors. A possible beneficial interaction between thromboxane synthesis inhibitors and ACE inhibitors may exist. Thromboxane synthetase inhibitors can reduce renal vascular resistance by redirecting PG endoperoxide synthesis toward prostacyclin. This effect may be offset by a prostaglandin-induced increase in renin release and Ang II formation. ACE inhibitors, by preventing Ang II synthesis, may increase the vasodilation due to thromboxane synthesis inhibition.
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PMID:Renal prostaglandin synthesis and angiotensin-converting enzyme inhibition. 138 64

A 2-year-old spayed female Whippet with membranoproliferative glomerulonephritis and nephrotic syndrome was treated with a specific thromboxane synthetase inhibitor (3-methyl-2[3-pyridyl]-1-indoleoctanoic acid), resulting in decreased proteinuria and resolution of ascites and edema. Glomerular histology, however, appeared unaffected by treatment. Discontinuation of treatment for 10 weeks resulted in increased proteinuria and decreased serum albumin concentrations that were again attenuated when treatment was reinitiated. Thromboxane synthetase inhibitors have been used successfully to treat experimentally induced glomerulonephritis in several species and this treatment appears to hold promise for naturally occurring glomerulonephritis in dogs.
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PMID:Treatment of membranoproliferative glomerulonephritis and nephrotic syndrome in a dog with a thromboxane synthetase inhibitor. 158 45

Polymerase chain reaction techniques have been used to isolate a cDNA clone containing the entire protein coding region of thromboxane A2 synthase (EC 5.3.99.5) from a human lung cDNA library. The cDNA clone hybridizes with a single 2.1-kilobase mRNA species in phorbol ester-induced human erythroleukemia and monocytic leukemia cell lines. A second cDNA, differing only by an insert of 163 base pairs near the 3'-end of the translated region, was also found to be present in the same library. The proteins predicted from both nucleic acid sequences include the three polypeptide sequences determined from amino acid sequencing of the purified human platelet enzyme, five potential sites for N-glycosylation, and a hydrophobic region that may serve to anchor the synthase in the endoplasmic reticulum membrane. The longer predicted protein, designated thromboxane synthase-I, contains 534 amino acids, with a Mr of 60,684, whereas the shorter protein, designated thromboxane synthase-II, contains 460 amino acids and has a Mr of 52,408. Although thromboxane synthase-II lacks the conserved cysteine that serves as the proximal heme ligand in the other cytochromes, significant sequence similarities exist among thromboxane synthase-I and -II and several P450s, particularly those in family 3. The overall amino acid identity is considerably less than 40%, making it likely that thromboxane synthase represents a previously undefined family of cytochrome P450.
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PMID:Primary structure of human thromboxane synthase determined from the cDNA sequence. 173 Jun 69

To elucidate the differentiation-associated expression of enzymes catalyzing arachidonic acid metabolism, we measured arachidonate metabolites by reverse-phase high pressure liquid chromatography in monocytoid leukemia (ML-1, THP-1, and U937) and myeloid leukemia (KG-1) cell lines. Undifferentiated ML-1 or THP-1 cells produced trace amounts of eicosanoids via the cyclooxygenase (COX) and lipoxygenase (LOX) pathways. Upon differentiation induced by phorbol ester (phorbol 12-myristate 13-acetate [PMA]), metabolites via the COX pathway were increased by 100-fold in ML-1 and THP-1 cells, while the LOX products remained barely detectable. All the COX metabolites were elevated, but thromboxane A2 (TXA2) formation was threefold higher in ML-1 cells than in THP-1 cells. Similar time-related increases in COX metabolites were observed in THP-1 cells induced to differentiate with retinoic acid. Undifferentiated U937 cells were capable of generating a much higher quantity of COX products than ML-1 or THP-1 cells, but, upon PMA-induced differentiation, COX products were increased by only two-fold to threefold over the undifferentiated cells and the total COX products in differentiated U937 cells were only one-seventh of those produced by differentiated ML-1 or THP-1 cells. KG-1 cells had an entirely different metabolic profile. They produced a large quantity of a metabolite coeluted with prostaglandin D2, and PMA had no effect on inducing changes in arachidonic acid (AA) metabolism. Increased COX metabolite formation in differentiated THP-1 and ML-1 cells was due to an enhanced level of prostaglandin H synthase enzyme mass, as measured by Western blot analysis. The TXA synthase activity was also increased by approximately 100-fold in PMA-induced ML-1 cells and 10-fold in THP-1 cells. These findings indicate that increased expression of prostaglandin H and TXA synthase enzymes is a feature of differentiated monocytoid leukemia cell lines.
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PMID:Differentiation-associated expression of prostaglandin H and thromboxane A synthases in monocytoid leukemia cell lines. 174 85

Platelet deposition upon endarterectomy sites is a likely cause for early postoperative thrombosis, embolism and restenosis. Platelets aggregate by the thromboxane-prostacycline mechanism. Thromboxane synthetase inhibitors which have been safely administered to humans should reduce platelet deposition after surgical therapy and therefore reduce peri-operative mortality and the prevalence of stroke. A randomized prospective controlled trial was designed to determine vessel patency and platelet deposition associated with the use of 3 mg/kg and 30 mg/kg of Furegrelate (Upjohn U63557A) daily in dogs, who were to have carotid endarterectomy. The 46 treated and 46 control dogs had total carotid patency of 96% and 76% respectively (P less than 0.01). Fourteen dogs treated with 30 mg/kg Furegrelate had no occlusions, compared with a 19% prevalence in 13 controls (P less than 0.02). Furegrelate 10 mg/kg significantly lowered platelet aggregation. Platelet deposition was not significantly changed, however. The reason for this disparity was a probable persistence of vessel wall factors which promoted platelet deposition. This approach might therefore lower rates of peri-operative thrombosis but it would be very unlikely to alter the incidence of restenosis or embolism. Further research could be directed towards modifying the stimuli for platelet deposition upon the endarterectomy site.
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PMID:Effects of Furegrelate (Upjohn 63557A) on patency and platelet deposition after canine carotid endarterectomy. 186 16

2,3,5-Trimethyl-6-(3-pyridylmethyl)-1,4-benzoquinone (CV-6504) has inhibitory activities on both thromboxane A2 synthase and 5-lipoxygenase as well as scavenging activity against active oxygen species. The latter two activities are closely related to the quinone moiety, which is reduced to a hydroquinone in the living body. Comparison of these two activities for both the quinone and hydroquinone showed that the hydroquinone form had superior activities. Concerning the reduction mechanism by PB-3c cells we can see that superoxide dismutase (SOD) has no influence on the rate of reduction, but dicumarol almost completely inhibits the reduction at a concentration greater than 1 x 10(-6) M. Therefore, it can be concluded that CV-6504 is reduced mainly by two electron donating enzymes without the intermediary of a semiquinone radical and that the resulting hydroquinone inhibits lipid peroxidation as well as 5-lipoxygenase activity.
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PMID:Reduction of 2,3,5-trimethyl-6-(3-pyridylmethyl)-1,4-benzoquinone by PB-3c cells and biological activity of its hydroquinone. 189 98

Kawasaki disease, a mucocutaneous lymph node syndrome predominantly prevalent in children, presents with coronary artery aneurysms and thrombocytosis, and investigators have suggested use of anticoagulants in addition to platelet inhibiting drugs. In Kawasaki disease, hypersensitivity reactions due to antigen/antibody complexes (Arthus type III) may damage the vessel wall and induce arteritis, and antigens may be of microbial or viral origin. Since thromboxane has been implicated in the pathogenesis of Kawasaki disease, I suggest use of ginger and carbon dioxide, novel thromboxane synthetase inhibitors. Thromboxane synthetase inhibitors may act as anticoagulants, platelet inhibitors, anti-inflammatory agents, and agents with both antimicrobial and antiviral activity.
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PMID:Implication of thromboxane in the pathogenesis of Kawasaki disease and a suggestion for using novel thromboxane synthetase inhibitors in its treatment. 190 78

The role of platelets in lung injury has not been well defined. In the present study of isolated perfused rat lungs, phorbol myristate acetate (PMA; 0.15 microgram/ml) or platelets (6.7 X 10(4)/ml) alone did not discernibly change the pulmonary arterial pressure (PAP) or lung weight (LW). However, the combination of platelets and PMA drastically increased the PAP and LW (delta PAP 26.2 +/- 1.0 mmHg, delta LW 2.7 +/- 0.4 g). delta PAP was positively correlated with the increase in thromboxane B2 produced by infusion of platelets and PMA (thromboxane B2 = 35.6 + 0.97 delta PAP, r = 0.67, P less than 0.01). The hypertension and edema formation induced by PMA and platelets were strongly attenuated by indomethacin, an inhibitor of platelet cyclooxygenase (delta PAP 5.6 +/- 2.0 mmHg, P less than 0.001; delta LW 0.0 +/- 0.1 g, P less than 0.001), and by imidazole, an inhibitor of thromboxane A2 synthase (PAP 8.0 +/- 2.5 mmHg, P less than 0.001; LW 0.0 +/- 0.3 g, P less than 0.01). Inactivation of platelet lipoxygenase with nordihydroguaiaretic acid mildly depressed pulmonary pressure but did not affect delta LW (delta PAP 18.9 +/- 1.6 mmHg, P less than 0.05; delta LW 3.1 +/- 0.3 g, P greater than 0.05). In vitro experiments showed that the capacity of platelets to release oxygen radicals was only 2.6% of that found for granulocytes. These results suggest that platelets may be activated by PMA to increase PAP and vascular permeability.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cyclooxygenase pathway mediates lung injury induced by phorbol and platelets. 190 12

We have validated an established animal model of acute inflammatory bowel disease in indomethacin-treated rats. Studies in both in vitro and in vivo 51chromium-labelled ethylenediamine tetra-acetate (51Cr-EDTA) permeability and tissue myeloperoxidase activity, a marker of inflammatory cell invasion, showed increased permeability and enzyme levels, respectively, in treated animals compared to controls (in vitro 51Cr-EDTA permeability: (mean (SE] control 0.10 (0.02) microliter/mg per tissue, experimental 0.17 (0.02) (p < 0.01, 2 way analysis of variance); in vivo 51Cr-EDTA permeability: control 3.9 (1.3) (% dose recovered), experimental 12.1 (1.5) (p < 0.01); tissue myeloperoxidase: control 10.8 (0.4) mU/mg, experimental 17.2 (0.5) p less than 0.01). Pretreatment or simultaneous treatment of indomethacin-treated animals with glucocorticoids, sulphasalazine, or tetracycline reduced the permeability changes and the tissue inflammatory response (in vitro 51Cr-EDTA permeability: (mean (SE] sulphasalazine + indomethacin 0.11 (0.2) microliter/mg tissue (p < 0.01), prednisolone +/- indomethacin 0.12 (0.02) (p < 0.01), tetracycline + indomethacin 0.12 (0.02) (p < 0.01]. Glucocorticoids and sulphasalazine, but not tetracycline, administered after the indomethacin also partially corrected the permeability and inflammatory changes induced by indomethacin (in vitro 51Cr-EDTA permeability: sulphasalazine 0.15 (0.02) microliter/mg, p < 0.02; prednisolone 0.12 (0.02) microliter/mg, p < 0.01). This approach was used to investigate the effects of two different thromboxane synthetase inhibitors in indomethacin-treated animals. Simultaneous treatment with thromboxane synthetase inhibitors and indomethacin prevented the 51Cr-EDTA permeability and tissue myeloperoxidase increases induced by indomethacin alone (in vitro 51Cr-EDTA permeability: thromboxane synthetase inhibitors + indomethacin 0.11 (0.01) microliter/mg (p0.01); tissue myeloperoxidase: 11 (0.4) mU/mg, (p < 0.01). Thromboxane synthetase inhibitors administered after the indomethacin also partially corrected the permeability and inflammatory changes induced by indomethacin (in vitro 51Cr-EDTA permeability: thromboxane synthetase inhibitors 0.12 (0.02) mU/mg (p < 0.01); tissue myeloperoxidase 13.8 (0.5) (p < 0.01). These studies indicate that thromboxane synthetase inhibitors partially correct the intestinal lesion non-steroidal anti-inflammatory drug enteropathy and may therefore be of use in inflammatory bowel diseases in humans.
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PMID:Experimental non-steroidal anti-inflammatory drug-induced enteropathy in the rat: similarities to inflammatory bowel disease and effect of thromboxane synthetase inhibitors. 1128 36


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