同: thromboxane A2

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/11/19 20:24:58」(JST)

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Thromboxane A2 (TXA2) is a thromboxane. It is produced by activated platelets and has prothrombotic properties: it stimulates activation of new platelets as well as increases platelet aggregation. This is achieved by mediating expression of the glycoprotein complex GP IIb/IIIa in the cell membrane of platelets. Circulating fibrinogen binds these receptors on adjacent platelets, further strengthening the clot. Thromboxane A2 is also a known vasoconstrictor and is especially important during tissue injury and inflammation. It is also regarded responsible for Prinzmetal's angina.

Receptors that mediate TXA2 actions are thromboxane A2 receptors. The human TXA2 receptor (TP) is a typical G protein-coupled receptor (GPCR) with seven transmembrane segments. In humans, two TP receptor splice variants - TPα and TPβ - have so far been cloned.

Synthesis and breakdown

TXA2 is generated from prostaglandin H2 by thromboxane-A synthase. Aspirin irreversibly inhibits platelet cyclooxygenase 1 preventing the formation of prostaglandin H2, and therefore thromboxane A2.

TXA2 is very unstable in aqueous solution, since it is hydrolyzed within about 30 seconds to the biologically inactive thromboxane B2. Due to its very short half life, TXA2 primarily functions as an autocrine or paracrine mediator in the nearby tissues surrounding its site of production. Most work in the field of TXA2 is done instead with synthetic analogs such as U46619 and I-BOP.^[1] In human studies, 11-dehydrothromboxane B2 levels are used to indirectly measure TXA2 production.^[2]^[3]

Eicosanoid synthesis.

References

^ Michael P. Walsh, et all. "Thromboxane A2-induced contraction of rat caudal arterial smooth muscle involves activation of Ca2+ entry and Ca2+sensitization: Rho-associated kinase-mediated phosphorylation of MYPT1 at Thr-855 but not Thr-697".
^ Catella F, Healy D, Lawson JA, FitzGerald GA (1986). "11-Dehydrothromboxane B2: a quantitative index of thromboxane A2 formation in the human circulation". PNAS 83 (16): 5861–5865. doi:10.1073/pnas.83.16.5861. PMC 386396. PMID 3461463.
^ Lordkipanidzé M, Pharand C, Schampaert E, Turgeon J, Palisaitis DA, Diodati JG (2007). "A comparison of six major platelet function tests to determine the prevalence of aspirin resistance in patients with stable coronary artery disease". Eur Heart J 28 (14): 1702–1708. doi:10.1093/eurheartj/ehm226. PMID 17569678.

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2. 血小板生物学 platelet biology
3. COX-2選択的阻害剤：有害な心血管系への影響 cox 2 selective inhibitors adverse cardiovascular effects
4. アスピリン：リウマチ性疾患における作用機序、主な毒性、および使用 aspirin mechanism of action major toxicities and use in rheumatic diseases
5. COX-2選択的阻害剤の概要 overview of selective cox 2 inhibitors

English Journal

Toll-like receptor 4 contributes to blood pressure regulation and vascular contraction in spontaneously hypertensive rats.

Bomfim GF, Dos Santos RA, Oliveira MA, Giachini FR, Akamine EH, Tostes RC, Fortes ZB, Webb RC, Carvalho MH.Source*Department of Pharmacology, University of Sao Paulo, Sao Paulo, SP, Brazil.
Clinical science (London, England : 1979).Clin Sci (Lond).2012 Jun 1;122(11):535-43.
Activation of TLRs (Toll-like receptors) induces gene expression of proteins involved in the immune system response. TLR4 has been implicated in the development and progression of CVDs (cardio-vascular diseases). Innate and adaptive immunity contribute to hypertension-associated end-organ damage, al
PMID 22233532

Substrate specificity of acetoxy derivatives of coumarins and quinolones towards Calreticulin mediated transacetylation: Investigations on antiplatelet function.

Kathuria A, Priya N, Chand K, Singh P, Gupta A, Jalal S, Gupta S, Raj HG, Sharma SK.SourceBioorganic Laboratory, Department of Chemistry, University of Delhi, Delhi 110 007, India.
Bioorganic & medicinal chemistry.Bioorg Med Chem.2012 Feb 15;20(4):1624-38. Epub 2011 Nov 16.
Calreticulin transacetylase (CRTAase) is known to catalyze the transfer of acetyl group from polyphenolic acetates (PA) to certain receptor proteins (RP), thus modulating their activity. Herein, we studied for the first time the substrate specificity of CRTAase towards N-acetylamino derivatives of c
PMID 22264757

Japanese Journal

Thromboxane A2 Generation, in the Absence of Platelet COX-1 Activity, in Patients With and Without Atherothrombotic Myocardial Infarction

DeFilippis Andrew P.,Oloyede Oluwasegun S.,Andrikopoulou Efstathia,Saenger Amy K.,Palachuvattil Joel M.,Fasoro Yetunde A.,Guallar Eliseo,Blumenthal Roger S.,Kickler Thomas S.,Jaffe Allan S.,Gerstenblith Gary,Schulman Steven P.,Rade Jeffrey J.
Circulation Journal, 2013
… Background: Aspirin's therapeutic action is via inhibition of platelet cyclooxygenase 1 (COX-1) thromboxane A2 (TxA2) production. … The aim of this study was to evaluate TxA2 production, in the absence of platelet COX-1 activity, in coronary atherosclerotic heart disease patients with and without atherothrombotic myocardial infarction (MI). …
NAID 130003361848

Thromboxane A2 Mediates Iron-Overload Cardiomyopathy in Mice Through Calcineurin-Nuclear Factor of Activated T Cells Signaling Pathway

Lin Heng,Li Hsiao-Fen,Lian Wei-Shiung,Chen Hsi-Hsien,Lan Yi-Fan,Lai Pei-Fang,Cheng Ching-Feng
Circulation Journal, 2013
… Because thromboxane A2 (TXA2) and prostacyclin are the 2 major prostanoids in the cardiovascular system, and TXA2 plays a major role in vascular atherosclerosis and has pro-inflammatory characteristics, we intended to elucidate the role of TXA2 in iron-overload cardiomyopathy. …
NAID 130003361810

くも膜下出血後の脳血管平滑筋収縮性亢進の分子機構

吉川雄一郎,佐々木富男,平野真弓 [他],平野勝也,Kikkawa Yuichiro,Sasaki Tomio,Hirano Mayumi,Hirano Katsuya,キッカワユウイチロウ,ササキトミオ,ヒラノマユミ,ヒラノカツヤ
福岡医学雑誌 102(12), 325-332, 2011-12-25
… 思われる．脳血管攣縮の発症メカニズムは，攣縮誘発因子の産生と血管反応性の増大という二つの側面からとらえることができる．トロンビン，オキシヘモグロビン，エンドセリン（ET-1)，トロンボキサンA2（TXA2)，血小板由来増殖因子（PDGF)，スフィンゴシン-1 リン酸（S1P)など，動物モデルなどで血管収縮作用が認められる様々な血液および血小板由来物質が髄液中に増加し，脳動脈に対する直接的な収縮刺激として作 …
NAID 40019177334

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Thromboxane A2
Identifiers
CAS number	57576-52-0
PubChem	5280497
MeSH	Thromboxane+A2
Properties
Molecular formula	C20H32O5
Molar mass	352.465 g/mol
	Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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	Infobox references