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

Background & Aims: To determine how interferon (IFN)-gamma inhibits epithel ial barrier and ion transport functions, intestinal T84 cells were studied. Methods: Acute and chronic effects of IFN-gamma on T84 barrier function, N a+,H+-adenosine triphosphatase (ATPase) activity, and certain ion transport and tight junctional proteins were determined. To assess the role of Na+,H +-ATPase and intracellular Na+, similar studies with the Na+,K+-ATPase inhi bitor ouabain and Na+ ionophore monensin were performed. To determine the r ole of nitric oxide (NO), the NO donor SPER-NO was used, Results: IFN-gamma acutely (<6 hour) decreased cellular Na+,H+-ATPase activity, followed late r (> 24 hours) by decreases in expression of Na/H/2Cl, the ow subunit of Na +,K+-ATPase, occludin, and ZO-1, In contrast, cystic fibrosis transmembrane conductance regulator or the Na+ pump beta subunit were unchanged, Ouabain and monensin caused nearly identical changes to IFN-gamma, Incubation in l ow Na+ media significantly blunted the chronic effects of IFN-gamma. Hypoto nic-induced cell swelling, in contrast, had effects similar to IFN-gamma bu t did not alter the expression of the Na+ pump oi subunit, The NO donor SPE R-NO rapidly inhibited Na+,H+-ATPase and also down-regulated transport and barrier proteins. Conclusions: IFN-gamma Inhibition of Na+,K+-ATPase activi ty acutely causes increases in intracellular Na-i concentration and cell vo lume, which are distinct signaling events that ultimately result in a leaky and dysfunctional epithelium associated with chronic inflammation.