title: Loss of lipopolysaccharide-induced nitric oxide production and inducible nitric oxide synthase expression in scrapie-infected N2a cells.
abstract: In scrapie-infected cells, the conversion of the cellular prion protein to the pathogenic prion has been shown to occur in lipid rafts, which are suggested to function as signal transduction platforms. Neuronal cells may respond to bacterial lipopolysaccharide (LPS) treatment with a sustained and elevated nitric oxide (NO) release. Because prions and the major LPS receptor CD14 are colocalized in lipid rafts, the LPS-induced NO production in scrapie-infected neuroblastoma cells was studied. This study shows that LPS induces a dose- and time-dependent increase in NO release in the murine neuroblastoma cell line N2a, with a 50-fold increase in NO production at 1 microg/ml LPS after 96 hr, as measured by nitrite in the medium. This massive NO release was not caused by activation of the neuronal NO synthase (nNOS), but by increased expression of the inducible NOS (iNOS) mRNA and protein. However, in scrapie-infected N2a cells (ScN2a), the LPS-induced NO production was completely abolished. The absence of LPS-induced NO production in ScN2a was due not to abolished enzymatic activity of iNOS but to a complete inhibition of the LPS-induced iNOS gene expression as measured by Western blot and RT-PCR. These results indicate that scrapie infection inhibits the LPS-mediated signal transduction upstream of the transcriptional step in the signaling cascade and may reflect the important molecular and cellular changes induced by scrapie infection.
authors.affiliation: Department of Neurochemistry and Neurotoxicology, University of Stockholm, Stockholm, Sweden.
authors.forename: Heléne
authors.initials: H
authors.lastname: Lindegren
authors.forename: Pernilla
authors.initials: P
authors.lastname: Ostlund
authors.forename: Hanna
authors.initials: H
authors.lastname: Gyllberg
authors.forename: Katarina
authors.initials: K
authors.lastname: Bedecs
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D009252:NADPH Dehydrogenase / Q000187:drug effects / Q000378:metabolism; D009447:Neuroblastoma / Q000201:enzymology* / Q000473:pathology; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000187:drug effects / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000096:biosynthesis; D012608:Scrapie; D013997:Time Factors
chemical_list: D004791:Enzyme Inhibitors; D006146:Guanidines; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D009252:NADPH Dehydrogenase; C004479:pimagedine