title: Inhibition of serotonin transporter expression by C/EBPβ in LPS-activated macrophage cells (HD11).
abstract: Serotonin (5-hydroxytryptamine; 5-HT) transporter (5-HTT) is involved in inflammation and the stress response. In this study, we examined the regulation of 5-HTT expression in macrophage HD11 cells in response to bacterial LPS. Long-term exposure of cells to LPS (6-18 h) produced a decrease in 5-HTT mRNA expression. Accordingly, reduced 5-HTT activity measured by 5-HT uptake was also observed in LPS-treated HD11 cells. Moreover, LPS treatment, as well as co-transfection with an expression vector encoding the chicken CCAAT/enhancer binding protein beta (C/EBPβ), resulted in inhibition of 5-HTT promoter activity. Indeed, sequence analysis revealed several C/EBPβ binding motifs in the upstream region of the 5-HTT gene, which specifically interacted with C/EBPβ both in an in vitro band shift assay and in living HD11 cells. The C/EBPβ binding was activated in cells treated with LPS. The role of C/EBPβ in LPS inhibition of 5-HTT expression was further confirmed by small interfering RNA interference, which demonstrated that knockdown of endogenous C/EBPβ attenuated the inhibition of 5-HTT expression in LPS-treated cells. Taken together, the results suggest that C/EBPβ plays a critical role in regulating the 5-HTT gene in macrophages in response to pro-inflammatory stimuli.
authors.affiliation: Friedrich-Loeffler-Institut, Institute of Animal Welfare and Animal Husbandry, Celle, Germany.
authors.forename: Katrin
authors.initials: K
authors.lastname: Zimmermann
authors.affiliation: Institute of Radiology, Klinikum rechts der Isar, Technische Universität München, München, Germany.
authors.forename: Valerie D
authors.initials: VD
authors.lastname: van Phi
authors.affiliation: Friedrich-Loeffler-Institut, Institute of Animal Welfare and Animal Husbandry, Celle, Germany.
authors.forename: Angela
authors.initials: A
authors.lastname: Brase
authors.affiliation: Friedrich-Loeffler-Institut, Institute of Animal Welfare and Animal Husbandry, Celle, Germany loc.phivan@fli.bund.de.
authors.forename: Loc
authors.initials: L
authors.lastname: Phi-van
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000235:genetics; D023081:CCAAT-Binding Factor / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002645:Chickens; D015536:Down-Regulation / Q000235:genetics; D008070:Lipopolysaccharides / Q000276:immunology; D008264:Macrophages / Q000276:immunology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D050486:Serotonin Plasma Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D023081:CCAAT-Binding Factor; D008070:Lipopolysaccharides; D034741:RNA, Small Interfering; D050486:Serotonin Plasma Membrane Transport Proteins
keywords: 5-HT; C/EBPß; HD11 cells; LPS; serotonin transporter