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Endothelial cell activation by endotoxin involves superoxide/NO‐mediated nitration of prostacyclin synthase and thromboxane receptor stimulation
Author(s) -
Bachschmid Markus,
Thurau Svenja,
Zou Ming-Hui,
Ullrich Volker
Publication year - 2003
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.02-0530fje
Subject(s) - peroxynitrite , prostacyclin , chemistry , thromboxane a2 , superoxide , nitric oxide synthase , thromboxane a synthase , angiotensin ii , medicine , biochemistry , receptor , endocrinology , biology , enzyme
In bovine coronary artery segments, peroxynitrite inhibits prostacyclin (PGI 2 ) 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 A 2 (TxA 2 ) receptor blocker. In parallel, PGI 2 synthesis decreases in favor of prostaglandin E 2 formation. Immunoprecipitation and costaining with an anti‐nitrotyrosine antibody identified PGI 2 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 N ω ‐monomethyl‐ 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 PGI 2 synthase. The remaining 15‐hydroxy‐prostaglandin 9,11‐endoperoxide (PGH 2 ) first activates the TxA 2 /PGH 2 receptor and then is converted to prostaglandin E 2 (PGE 2 ) by smooth muscle cells. PGE 2 together with a lack of NO and PGI 2 is known to promote the adhesion of white blood cells and their immigration to the inflammatory locus.