title: Mechanisms of human complement factor B induction in sepsis and inhibition by activated protein C.
abstract: To investigate the potential role of the local expression of alternative complement factor B (hBf) in human sepsis, we examined the induction of Bf gene expression in human peripheral blood monocytes (PBMCs) from patients with septic shock and the mechanisms of hBf gene regulation by tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, and lipopolysaccharide (LPS) in human monocytes. PBMCs from septic shock patients showed increased hBf mRNA expression when compared with control patients. Costimulation with TNF-alpha and IFN-gamma or stimulation with LPS demonstrated a time- and dose-dependent induction of hBf mRNA expression in human PBMCs. A region of the hBf promoter between -735 and +128 bp was found to mediate IFN-gamma, TNF-alpha, and LPS responsiveness as well as the synergistic effect of IFN-gamma/TNF-alpha on hBf promoter activity. Site-directed mutagenesis of a IFN-gamma-activation site (GAS) cis element (-90 to -82 bp) abrogated IFN-gamma responsiveness. Mutagenesis of a nuclear factor (NF)-kappaB cis element at -466 to -456 bp abrogated TNF-alpha and LPS responsiveness of the Bf promoter. Thus hBf gene expression is induced in PBMCs from septic shock patients, and the induction of hBf by IFN-gamma, TNF-alpha, and LPS is through GAS and NF-kappaB cis-binding sites on the hBf promoter. Furthermore, activated protein C (APC) inhibited LPS-stimulated hBf promoter activity and protein expression in human monocytes suggesting that the beneficial effect of APC therapy in sepsis may in part be due to inhibition of complement induction and/or activation via the alternative pathway.
authors.affiliation: Department of Critical Care Medicine, Univesity of Calgary, Calgary, Alberta, Canada T2N 4N1.
authors.forename: Kim
authors.initials: K
authors.lastname: Goring
authors.forename: Yong
authors.initials: Y
authors.lastname: Huang
authors.forename: Connie
authors.initials: C
authors.lastname: Mowat
authors.forename: Caroline
authors.initials: C
authors.lastname: Léger
authors.forename: Teik-How
authors.initials: TH
authors.lastname: Lim
authors.forename: Raza
authors.initials: R
authors.lastname: Zaheer
authors.forename: Dereck
authors.initials: D
authors.lastname: Mok
authors.forename: Lee Anne
authors.initials: LA
authors.lastname: Tibbles
authors.forename: David
authors.initials: D
authors.lastname: Zygun
authors.forename: Brent W
authors.initials: BW
authors.lastname: Winston
mesh_terms: D001483:Base Sequence; D011415:Complement Factor B / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D003170:Complement Pathway, Alternative / Q000276:immunology; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D008969:Molecular Sequence Data; D009000:Monocytes / Q000276:immunology* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics / Q000276:immunology; D011486:Protein C / Q000276:immunology / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D018805:Sepsis / Q000276:immunology* / Q000378:metabolism / Q000503:physiopathology*; D015533:Transcriptional Activation / Q000187:drug effects / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D011486:Protein C; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma; D011415:Complement Factor B