Abstracts
1997 Digestive Disease Week

Interleukin-10 receptor expression is downregulated with enterocyte differentiation.

LM Napolitano, MM Buzdon, H-J Shi, BL Bass. Department of Surgery, Baltimore VA Medical Center, University of Maryland School of Medicine, Baltimore MD.

IL 10 is a potent inhibitor of proinflammatory cytokine synthesis, and confers intestinal mucosal protection in animal models of colitis. IL 10 has also been shown to modulate intestinal function (ion secretion and permeability), although the possible effects of this cytokine on enterocyte growth and differentiation remain undefined. The objective of these studies was to determine if IL 10 modulates enterocyte proliferative response and to determine if IL 10-receptor expression varies with state of enterocyte differentation.

Methods: HT29 cells, derived from a human colon cancer cell line, reversibly differentiate in response to butyrate. HT29 cells were seeded at a density of 10,000 cells/well and allowed to attach for 24 h in serum-containing medium. Butyrate (5mM) was added at 24 h. IL 10 was then added in concentrations of 50, 100, 200 ug/ml. The cells were pulsed with [^{3}H]thymidine for 16 h prior to harvest. Cells were harvested at 24 and 48 h after the addition of IL-10 and thymidine uptake measured by scintillation counter. IL 10-receptor was measured by SDS/PAGE and Western blotting with anti-IL 10-receptor antibody after immunoprecipitation. IL 10 protein was measured by ELISA in culture supernatants; IL 10 mRNA measured by RT-PCR.

Results: Undifferentiated HT29 cells did not constitutively produce IL10 protein or mRNA, while IL-10 receptor was strongly expressed. Exposure of undifferentiated cells to IL10 resulted in a dose-response inhibition of cell growth with maximal inhibition of 40% relative to control. Butyrate-treated HT29 cells also failed to produce IL10 protein or mRNA. However, the differentiated phenotype was associated with loss of IL10 receptor expression, and no growth response to IL-10.

Conclusion: IL10 receptor expression varies with enterocyte phenotype and is lost in the differentiated enterocyte. Additionally, IL-10 diminishes the proliferative rate of undifferentiated enterocytes in response to serum in vitro. These data suggest that the mechanism by which IL10 modulates intestinal function is diverse and includes induction of important changes of enterocyte phenotype central to growth and differentiation. [Figures not available.]