Inhibition of Na+,K+-ATPase by interferon γ down-regulates intestinal epithelial transport and barrier function☆☆☆

Abstract Background & Aims: To determine how interferon (IFN)-γ inhibits epithelial barrier and ion transport functions, intestinal T84 cells were studied. Methods: Acute and chronic effects of IFN-γ on T84 barrier function, Na + ,K + –adenosine triphosphatase (ATPase) activity, and certain ion transport and tight junctional proteins were determined. To assess the role of Na + ,K + -ATPase and intracellular Na + , similar studies with the Na + ,K + -ATPase inhibitor ouabain and Na + ionophore monensin were performed. To determine the role of nitric oxide (NO), the NO donor SPER-NO was used. Results: IFN-γ acutely ( + ,K + -ATPase activity, followed later (>24 hours) by decreases in expression of Na/K/2Cl, the α subunit of Na + ,K + -ATPase, occludin, and ZO-1. In contrast, cystic fibrosis transmembrane conductance regulator or the Na + pump β subunit were unchanged. Ouabain and monensin caused nearly identical changes to IFN-γ. Incubation in low Na + media significantly blunted the chronic effects of IFN-γ. Hypotonic-induced cell swelling, in contrast, had effects similar to IFN-γ but did not alter the expression of the Na + pump α subunit. The NO donor SPER-NO rapidly inhibited Na + ,K + -ATPase and also down-regulated transport and barrier proteins. Conclusions: IFN-γ inhibition of Na + ,K + -ATPase activity acutely causes increases in intracellular Na i concentration and cell volume, which are distinct signaling events that ultimately result in a leaky and dysfunctional epithelium associated with chronic inflammation. GASTROENTEROLOGY 2001;120:1393-1403