title: Inhibition of inducible nitric oxide synthase expression by interferons alpha and beta in bovine retinal pigmented epithelial cells.
abstract: Bovine retinal pigmented epithelial (RPE) cells express an inducible nitric oxide synthase (NOS-2) after activation with interferon (IFN)-gamma and lipopolysaccharide (LPS). Experiments were performed to investigate the effects of IFN-alpha and IFN-beta on NOS-2 activity. These types of interferons did not aid LPS in the production of nitrite, but markedly inhibited in a concentration-dependent manner the nitrite release due to LPS/IFN-gamma. Analysis by Western and Northern blots showed that RPE cells co-stimulated with IFN-alpha or IFN-beta with LPS/IFN-gamma accumulated lower levels of NOS-2 protein and mRNA than in the presence of LPS/IFN-gamma alone. The presence of IFN-alpha or IFN-beta did not accelerate mRNA degradation, implying that these interferons did not affect NOS-2 mRNA stability, but more probably NOS-2 gene expression. Furthermore, IFN-gamma binding studies demonstrated that the inhibitory effect of IFN-alpha and IFN-beta is not caused by a blocking of IFN-gamma receptors. Analysis of NF-kappaB activation by electrophoretic mobility shift assay demonstrated that LPS/IFN-gamma-induced NF-kappaB binding was not changed by the presence of IFN-alpha. However, similar experiments revealed that the activation of interferon regulatory factor-1 (IRF-1) by LPS/IFN-gamma was decreased by IFN-alpha. This phenomenon could be due to the decline of IRF-1 mRNA and the up-regulation of IRF-2 mRNA, an IRF-1 repressor, by IFN-alpha. These results suggest that the inhibitory effect of IFN-alpha and -beta on NOS-2 induction could be partially explained by their effect on the induction of the IRFs, which were involved in NOS-2 gene transcription.
authors.affiliation: Développement, Vieillissement et Pathologie de la Rétine, U450 Institut National de la Santé et de la Recherche Médicale, Association Claude Bernard, 75016 Paris, France.
authors.forename: V
authors.initials: V
authors.lastname: Faure
authors.forename: Y
authors.initials: Y
authors.lastname: Courtois
authors.forename: O
authors.initials: O
authors.lastname: Goureau
mesh_terms: D000818:Animals; D002417:Cattle; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D015971:Gene Expression Regulation, Enzymologic; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D016898:Interferon-alpha / Q000494:pharmacology*; D016899:Interferon-beta / Q000494:pharmacology*; D016328:NF-kappa B / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000235:genetics*; D010750:Phosphoproteins / Q000096:biosynthesis; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000201:enzymology*; D012333:RNA, Messenger / Q000235:genetics; D012097:Repressor Proteins; D014157:Transcription Factors / Q000096:biosynthesis
chemical_list: D004268:DNA-Binding Proteins; D050856:Interferon Regulatory Factor-1; D050836:Interferon Regulatory Factor-2; D016898:Interferon-alpha; D016328:NF-kappa B; D010750:Phosphoproteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D014157:Transcription Factors; D016899:Interferon-beta; D019001:Nitric Oxide Synthase