Inducible nitric oxide synthase mediates prostaglandin h2 synthase nitration and suppresses eicosanoid production.
Nitric oxide (NO) modulates the biological levels of arachidonate-derived cell signaling molecules by either enhancing or suppressing the activity of prostaglandin H(2) isoforms (PGHS-1 and PGHS-2). Whether NO activates or suppresses PGHS activity is determined by alternative protein modifications mediated by NO and NO-derived species. Here, we show that inducible NO synthase (iNOS) and PGHS-1 co-localize in atherosclerotic lesions of ApoE(-/-) mouse aortae. Immunoblotting and immunohistochemistry revealed Tyr nitration in PGHS-1 in aortic lesions but markedly less in adjacent nonlesion tissue. PGHS-2 was also found in lesions, but 3-nitrotyrosine incorporation was not detected. 3-Nitrotyrosine formation in proteins is considered a hallmark reaction of peroxynitrite, which can form via NO-superoxide reactions in an inflammatory setting. That iNOS-derived NO is essential for 3-nitrotyrosine modification of PGHS-1 was confirmed by the absence of 3-nitrotyrosine in lesions from ApoE(-/-)iNOS(-/-) mice. Mass spectrometric studies specifically identified the active site residue Tyr385 as a 3-nitrotyrosine modification site in purified PGHS-1 exposed to peroxynitrite. PGHS-mediated eicosanoid (PGE(2)) synthesis was more than fivefold accelerated in cultured iNOS(-/-) versus iNOS-expressing mouse aortic smooth muscle cells, suggesting that iNOS-derived NO markedly suppresses PGHS activity in vascular cells. These results further suggest a regulatory role of iNOS in eicosanoid biosynthesis in human atherosclerotic lesions.
Deeb
Ruba S
RS
Department of Pathology and Laboratory Medicine, Center of Vascular Biology, Weill Medical College of Cornell University, 1300 York Ave., New York, NY 10021, USA.
Shen
Hao
H
Gamss
Caryn
C
Gavrilova
Tatyana
T
Summers
Barbara D
BD
Kraemer
Rosemary
R
Hao
Gang
G
Gross
Steven S
SS
Lainé
Muriel
M
Maeda
Nobuyo
N
Hajjar
David P
DP
Upmacis
Rita K
RK
D000818:Animals; D001011:Aorta / Q000378:metabolism / Q000473:pathology; D001057:Apolipoproteins E / Q000172:deficiency / Q000235:genetics; D015152:Blotting, Northern; D015153:Blotting, Western; D002478:Cells, Cultured; D003324:Coronary Artery Disease / Q000378:metabolism* / Q000473:pathology; D015777:Eicosanoids / Q000096:biosynthesis*; D005260:Female; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D001057:Apolipoproteins E; D015777:Eicosanoids; C002744:3-nitrotyrosine; D014443:Tyrosine; D052247:Nitric Oxide Synthase Type II; D011451:Prostaglandin-Endoperoxide Synthases