Synergistic effects of interferon γ and tumour necrosis factor α on T84 cell function

Abstract

BACKGROUND: Inflammatory bowel disease (IBD) is characterised by chronic intestinal inflammation and increased epithelial permeability. Both tumour necrosis factor α (TNF-α) and interferon γ (IFN-γ) have been implicated in IBD. AIMS: To understand better the effects of these cytokines on epithelial cell function. METHODS: T84 cells were cultured with IFN-γ and TNF-α and changes in transepithelial resistance (TER), fluorescein isothiocyanate (FITC) dextran flux, short circuit current ( I sc ), cystic fibrosis transmembrane conductance regulator (CFTR) protein levels, cell morphology, TNF receptor gene expression, and apoptosis were assayed. RESULTS: Relative to controls, significant changes (p<0.05) occurred in cells incubated with IFN-γ for two days: TER was decreased to 20 (6.2)%, FITC–dextran flux was increased by 109 (19)-fold, cAMP and Ca dependent I sc were decreased to 51 (6.4)% and 24 (2.2)%, respectively, and CFTR levels were decreased to 47 (11)%. Cell morphology was altered but cell death was not induced. TNF receptor mRNA levels were increased. When added with IFN-γ, TNF-α accelerated IFN-γ dependent changes. Relative to controls, significant changes occurred after one day of culture with IFN-γ plus TNF-α: TER was decreased to 27 (3.5)%, FITC–dextran flux was increased by 185 (45)-fold, and cAMP and Ca dependent I sc were decreased to 66 (12)% and 35 (6.8)%, respectively. TNF-α also enhanced IFN-γ dependent changes in cell morphology but did not induce cell death. CONCLUSION: IFN-γ alters T84 cell epithelial properties and TNF-α can enhance these effects, perhaps due to IFN-γ dependent increases in TNF receptor gene expression. Overall, these studies suggest that in IBD, TNF-α may have synergistic effects on IFN-γ mediated alterations of epithelial cell function.