Induction of citrulline-nitric oxide (NO) cycle enzymes and NO production in immunostimulated rat RPE-J cells.
Nitric oxide (NO) has been implicated in many physiological and pathological conditions in the eyes. The induction of inducible NO synthase (iNOS) and NO production have been noted in immunostimulated retinal pigment epithelial (RPE) cells. Cellular NO production depends on the availability of arginine, a substrate for NOS. Arginine can be regenerated from citrulline, another product of the NOS reaction, by argininosuccinate synthetase and argininosuccinate lyase, forming the citrulline-NO cycle. When rat RPE-J cells were treated with interferon-gamma (IFNgamma), tumor necrosis factor-alpha (TNFalpha) and lipopolysaccharide (LPS), and expression of the citrulline-NO cycle enzymes and related enzymes was analyzed, iNOS and argininosuccinate synthetase were highly induced at both mRNA and protein levels. On the other hand, argininosuccinate lyase was not induced. Among other related enzymes and transporters, mRNA for cationic amino acid transporter (CAT)-1 was weakly induced, whereas those for CAT-2, arginase I and II, ornithine aminotransferase and ornithine decarboxylase remained little changed. NO was produced by cells after stimulation with TNFalpha, IFNgamma and LPS. The induction of iNOS mRNA and the production of NO by these immunostimulated cells was further enhanced by cAMP. NO was produced from citrulline as well as from arginine. Our findings indicate that in activated RPE-J cells citrulline-arginine recycling is important for NO production.
Koga
Takahisa
T
Department of Molecular Genetics, Kumamoto University School of Medicine, Honjo 2-2-1, Kumamoto, Japan.
Zhang
Wen Yi
WY
Gotoh
Tomomi
T
Oyadomari
Seiichi
S
Tanihara
Hidenobu
H
Mori
Masataka
M
D000818:Animals; D001120:Arginine / Q000378:metabolism*; D001123:Argininosuccinate Lyase / Q000096:biosynthesis; D001124:Argininosuccinate Synthase / Q000096:biosynthesis; D018929:Cell Culture Techniques / Q000379:methods; D002460:Cell Line; D002956:Citrulline / Q000378:metabolism*; D000242:Cyclic AMP / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D004790:Enzyme Induction; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005938:Glucocorticoids / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000235:genetics; D019001:Nitric Oxide Synthase / Q000096:biosynthesis; D010857:Pigment Epithelium of Eye / Q000201:enzymology / Q000276:immunology / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D005938:Glucocorticoids; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D002956:Citrulline; D009569:Nitric Oxide; D003907:Dexamethasone; D007371:Interferon-gamma; D001120:Arginine; D000242:Cyclic AMP; D019001:Nitric Oxide Synthase; D001123:Argininosuccinate Lyase; D001124:Argininosuccinate Synthase