Nitric oxide inhibits inducible nitric oxide synthase mRNA expression in RAW 264.7 macrophages.
Using cultured murine RAW 264.7 macrophages, the present study investigates the influence of nitric oxide (NO) on the expression of the inducible NO synthase (iNOS) enzyme at the transcriptional level. Incubation of cells with lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) led to a marked increase in iNOS mRNA levels. Inhibition of LPS/IFN-gamma-induced NO synthesis with the L-arginine analogue N(G)-monomethyl-L-arginine (L-NMMA) was accompanied by a significant up-regulation of iNOS mRNA that was reversed in the presence of the NO donor sodium nitroprusside (SNP). Treatment of cells with SNP alone decreased LPS/IFN-gamma-induced iNOS mRNA levels in a concentration-dependent manner. The inhibitory effect of SNP on iNOS mRNA expression was not prevented by 1H-[1,2, 4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ), a selective inhibitor of the soluble guanylyl cyclase. In agreement with this finding, incubation of cells with the membrane-permeable cyclic GMP analogue 8-bromo cyclic GMP left LPS/IFN-gamma-induced iNOS mRNA expression virtually unaltered. Together, our results demonstrate that both iNOS-derived and exogenous NO exert an inhibitory effect on the expression of iNOS by a mechanism independent of the soluble guanylyl cyclase/cyclic GMP pathway. In conclusion, NO may control the extent of iNOS mRNA expression by a negative autoregulatory feedback.
Hinz
B
B
Department of Experimental and Clinical Pharmacology and Toxicology, Friedrich Alexander University Erlangen-Nürnberg, Fahrstrasse 17, Erlangen, D-91054, Germany. hinz@pharmakologie.uni-erlangen.de
Brune
K
K
Pahl
A
A
D000818:Animals; D002460:Cell Line; D002470:Cell Survival; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007202:Indicators and Reagents / Q000494:pharmacology; D007371:Interferon-gamma / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism; D008264:Macrophages / Q000201:enzymology*; D051379:Mice; D009569:Nitric Oxide / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D009599:Nitroprusside / Q000494:pharmacology; D010069:Oxadiazoles / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D004791:Enzyme Inhibitors; D007202:Indicators and Reagents; D008070:Lipopolysaccharides; D009573:Nitrites; D010069:Oxadiazoles; D011810:Quinoxalines; D012333:RNA, Messenger; D009599:Nitroprusside; D009569:Nitric Oxide; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse