title: C3 synthesis by A549 alveolar epithelial cells is increased by interferon-gamma and dexamethasone.
abstract: The third component of complement, C3, is produced in the lung by several cell types including alveolar epithelial cells. Since interferon-gamma (IFN-gamma) and dexamethasone regulate C3 gene expression in non-pulmonary cells, and because IFN-gamma and dexamethasone interact to regulate the functional activity of alveolar epithelial cells, we investigated the effects of IFN-gamma and dexamethasone on C3 production by A549 human alveolar epithelial cells. Treatment of A549 cells with IFN-gamma alone increased C3 production in a time-and dose-dependent manner. Maximal increase in C3 production occurred after stimulation of A549 cells with 500 IU/ml IFN-gamma for 3 days and was 3.4-fold greater than control. Dexamethasone (0.1 microM) stimulation of A549 cells increased C3 production 6.7-fold over controls on day 3. Treatment of A549 cells with IFN-gamma plus dexamethasone resulted in an 11-to 13-fold increase in C3 synthesis. C3 mRNA levels were increased in A549 cells treated with IFN-gamma and dexamethasone individually and in combination suggesting that IFN-gamma and dexamethasone increase C3 synthesis by a pre-translational mechanism. IFN-gamma and dexamethasone did not alter the two-chain structure of the C3 molecule produced by A549 cells, as assessed by Western blotting. We speculate that IFN-gamma and glucocorticoids may be important in the local regulation of C3 synthesis in the lung.
authors.affiliation: Department of Pediatrics, Creighton University, Omaha, Nebraska.
authors.forename: L D
authors.initials: LD
authors.lastname: Hill
authors.forename: L
authors.initials: L
authors.lastname: Sun
authors.forename: M P
authors.initials: MP
authors.lastname: Leuschen
authors.forename: T L
authors.initials: TL
authors.lastname: Zach
mesh_terms: D015152:Blotting, Northern; D015153:Blotting, Western; D002478:Cells, Cultured; D003176:Complement C3 / Q000096:biosynthesis* / Q000235:genetics; D003907:Dexamethasone / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D004848:Epithelium / Q000276:immunology; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology*; D007700:Kinetics; D011650:Pulmonary Alveoli / Q000276:immunology*; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins
chemical_list: D003176:Complement C3; D012333:RNA, Messenger; D011994:Recombinant Proteins; D003907:Dexamethasone; D007371:Interferon-gamma