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Interferon-gamma downregulates ion transport in murine small intestine cultured in vitro
1Division of Digestive and Liver Diseases, Department of Medicine College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
Insights
Interferon-gamma (IFN-gamma) impairs small intestinal function by reducing ion transport and Na(+)-K(+)-ATPase activity. These effects on villus height and nutrient absorption are significant in murine models.
Area of Science:
- Gastroenterology
- Immunology
- Physiology
Background:
- Mammalian small intestinal ion transport is crucial for nutrient and fluid homeostasis.
- Interferon-gamma (IFN-gamma) is a cytokine with known immunomodulatory functions.
- Understanding IFN-gamma's impact on intestinal physiology is vital for inflammatory bowel disease research.
Purpose of the Study:
- To investigate the effects of IFN-gamma on murine small intestinal ion transport and cellular function in vitro.
- To elucidate the mechanisms underlying IFN-gamma-induced changes in intestinal physiology.
- To assess the role of lymphocytes in IFN-gamma-mediated villus atrophy.
Main Methods:
- Utilized Ussing chambers to study ion transport in isolated murine small intestinal sheets.
- Maintained tissue viability in vitro for up to 48 hours.
- Assessed short-circuit current (I(sc)), tissue resistance, mucosal ion content, and ATPase activity.
- Compared responses between normal and SCID (severe combined immunodeficiency) mice.
Main Results:
- IFN-gamma significantly inhibited basal and stimulated short-circuit current (I(sc)), indicating impaired ion transport.
- IFN-gamma exposure led to a dose-dependent decrease in I(sc) responses to glucose and theophylline.
- Villus height diminished significantly after 36 hours, with less atrophy observed in SCID mouse intestine.
- IFN-gamma inhibited Na(+)-K(+)-ATPase activity, but effects were not mediated by nitric oxide (NO).
Conclusions:
- Murine small intestinal sheets are viable in vitro for studying cytokine effects.
- Prolonged IFN-gamma exposure downregulates active ion transport, Na(+)-coupled glucose absorption, and Na(+)-K(+)-ATPase activity.
- Lymphocytes may contribute to IFN-gamma-induced villus atrophy in the small intestine.
Abstract:
Effects of IFN-gamma on mammalian small intestinal ion transport were studied in vitro using incubated sheets of murine small intestine in Ussing chambers. In oxygenated standard culture medium containing hydrocortisone and antibiotics, they maintained their short-circuit current (I(sc)) responses to glucose and theophylline for 48 h. Histological examination revealed a 50% diminution of villus height over 36 h but no change in crypts. Height was better maintained during a 36-h incubation of small intestine from SCID mice, suggesting a role for B or T lymphocytes in villus atrophy. Exposure of small intestine to 100 U/ml IFN-gamma for 36 h decreased basal I(sc) by 40% and I(sc) responses to glucose and theophylline by approximately 70%; at 1,000 U/ml for 36 h, IFN-gamma inhibited these I(sc) responses by 90%. An inhibitor of inducible NO synthase did not reverse these effects, suggesting that they are not mediated by NO. Tissue resistance, mucosal K(+) content, and epithelial morphology were not affected. Ouabain-sensitive ATPase activity in homogenates was inhibited 60% by IFN-gamma (100 U/ml for 36 h). IFN-gamma inhibition of I(sc) responses to glucose and theophylline also occurred in SCID mouse small intestine. Thus murine small intestinal sheets can be maintained viable in vitro for at least 48 h, although villus blunting develops (but less so in SCID mouse small intestine). Also, prolonged exposure to IFN-gamma downregulates Na(+)-coupled glucose absorption, active Cl(-) secretion, and Na(+)-K(+)-ATPase activity, effects unlikely to be mediated by enhanced NO.
