Inhibition of Na+,K+-ATPase by interferon gamma down-regulates intestinal epithelial transport and barrier function.
OBJECTIVE
To determine how interferon (IFN)-gamma inhibits epithelial barrier and ion transport functions, intestinal T84 cells were studied.


METHODS
Acute and chronic effects of IFN-gamma 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-gamma acutely (<6 hour) decreased cellular Na+,K+-ATPase activity, followed later (>24 hours) by decreases in expression of Na/K/2Cl, the alpha 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 low Na+ media significantly blunted the chronic effects of IFN-gamma. Hypotonic-induced cell swelling, in contrast, had effects similar to IFN-gamma but did not alter the expression of the Na+ pump alpha subunit. The NO donor SPER-NO rapidly inhibited Na+,K+-ATPase and also down-regulated transport and barrier proteins.


CONCLUSIONS
IFN-gamma 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.
Sugi
K
K
Martin Boyer Laboratories of the Inflammatory Bowel Disease Research Center, Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA.
Musch
M W
MW
Field
M
M
Chang
E B
EB
D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D048429:Cell Size; D002470:Cell Survival / Q000187:drug effects; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D007413:Intestinal Mucosa / Q000187:drug effects* / Q000378:metabolism; D009589:Nitrogen Oxides; D010042:Ouabain / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*; D013096:Spermine / Q000031:analogs & derivatives / Q000494:pharmacology
D004791:Enzyme Inhibitors; D009589:Nitrogen Oxides; C091861:spermine nitric oxide complex; D013096:Spermine; D010042:Ouabain; D007371:Interferon-gamma; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase