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Thromboxane synthase inhibitors inhibit the final enzyme (thromboxane synthase) in the synthesis of thromboxane. Ifetroban is a potent and selective thromboxane receptor antagonist. [10] Dipyridamole antagonizes this receptor too, but has various other mechanisms of antiplatelet activity as well.
The human thromboxane A (TXA) synthase is a 60 kDa cytochrome P450 protein with 533 amino acids and a heme prosthetic group. This enzyme, anchored to the endoplasmic reticulum, is found in platelets, monocytes, and several other cell types. The NH2 terminus contains two hydrophobic segments whose secondary structure is believed to be helical.
The endothelium (pl.: endothelia) is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. [1] The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel wall.
Activation of TP receptors stimulates vascular endothelial cell pro-inflammatory responses such as increased expression of cell surface adhesion proteins (i.e. ICAM-1, VCAM-1, and E-selectin); stimulates apoptosis (i.e. cell death) of CD4+ and CD8+ lymphocytes; causes the chemokinesis (i.e. cell movement) of native T cells; and impairs the ...
Cyclooxygenase 1 (COX-1), also known as prostaglandin-endoperoxide synthase 1 (HUGO PTGS1), is an enzyme that in humans is encoded by the PTGS1 gene. [ 5 ] [ 6 ] In humans it is one of three cyclooxygenases .
Thromboxane A 2 (TXA 2) is generated from prostaglandin H 2 by thromboxane-A synthase in a metabolic reaction which generates approximately equal amounts of 12-hydroxyheptadecatrienoic acid (12-HHT). Aspirin irreversibly inhibits platelet cyclooxygenase 1 preventing the formation of prostaglandin H 2, and therefore TXA 2.
Endothelial activation is a proinflammatory and procoagulant state of the endothelial cells lining the lumen of blood vessels. [1] It is most characterized by an increase in interactions with white blood cells (leukocytes), and it is associated with the early states of atherosclerosis and sepsis , among others. [ 2 ]
The underlying mechanism for the deleterious effect proposes that endothelial cells lining the microvasculature in the body express COX-2, whose selective inhibition results in levels of prostaglandin I2 (PGI2, prostacyclin) down-regulated relative to thromboxane (since COX-1 in platelets is unaffected).