Endothelial cell activation by endotoxin involves superoxide/NO-mediated nitration of prostacyclin synthase and thromboxane receptor stimulation.
In bovine coronary artery segments, peroxynitrite inhibits prostacyclin (PGI2) synthase by tyrosine nitration. Using this pharmacological model, we show that a 1 h exposure of bovine coronary artery segments to endotoxin (lipopolysaccharide [LPS]) inhibits the relaxation phase following angiotensin II (Ang II) stimulation and causes a vasospasm that can be suppressed by a thromboxane A2 (TxA2) receptor blocker. In parallel, PGI2 synthesis decreases in favor of prostaglandin E2 formation. Immunoprecipitation and costaining with an anti-nitrotyrosine antibody identified PGI2 synthase as the main nitrated protein in the endothelium. All effects of LPS could be prevented in the presence of the nitric oxide (NO) synthase inhibitor Nomega-mono-methyl-L-arginine and polyethylene-glycolated Cu/Zn- superoxide dismutase. Thus, the early phase of endothelial cell activation in bovine coronary arteries by inflammatory agents proceeds by a protein synthesis-independent priming process for a source of superoxide that we tentatively attribute to xanthine oxidase. Upon receptor activation, Ang II stimulates NO and superoxide production, resulting in a peroxynitrite-mediated nitration and inhibition of PGI2 synthase. The remaining 15-hydroxy-prostaglandin 9,11-endoperoxide (PGH2) first activates the TxA2/PGH2 receptor and then is converted to prostaglandin E2 (PGE2) by smooth muscle cells. PGE2 together with a lack of NO and PGI2 is known to promote the adhesion of white blood cells and their immigration to the inflammatory locus.
Bachschmid
Markus
M
Faculty of Biology, University of Konstanz, 78457 Konstanz, Germany.
Thurau
Svenja
S
Zou
Ming-Hui
MH
Ullrich
Volker
V
D015121:6-Ketoprostaglandin F1 alpha / Q000378:metabolism; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D003329:Coronary Vasospasm / Q000139:chemically induced / Q000378:metabolism; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D019746:Intramolecular Oxidoreductases / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D030421:Peroxynitrous Acid / Q000378:metabolism; D011092:Polyethylene Glycols / Q000494:pharmacology; D011449:Prostaglandin Endoperoxides / Q000378:metabolism; D017482:Receptors, Thromboxane / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*; D014661:Vasoconstriction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects; D014969:Xanthine Oxidase / Q000378:metabolism; D019323:omega-N-Methylarginine / Q000494:pharmacology
D008070:Lipopolysaccharides; D009566:Nitrates; D011449:Prostaglandin Endoperoxides; D017482:Receptors, Thromboxane; D013481:Superoxides; D000804:Angiotensin II; D030421:Peroxynitrous Acid; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D011092:Polyethylene Glycols; D015121:6-Ketoprostaglandin F1 alpha; D003577:Cytochrome P-450 Enzyme System; D019001:Nitric Oxide Synthase; D013482:Superoxide Dismutase; C063471:polyethylene glycol-superoxide dismutase; D014969:Xanthine Oxidase; D019746:Intramolecular Oxidoreductases; C022461:prostacyclin synthetase