The barrier function of intestinal epithelial cells is mediated largely by tight junctions between adjacent cells. Tight junctional permeability is regulated by a number of disparate factors including several inflammatory mediators, by processes which involve changes in the cellular cytoskeleton. There is accumulating evidence that increased junctional permeability could play an important role in the etiology, progression and maintenance of chronic diarrheal and inflammatory bowel diseases. In particular, an inherited disorder in junctional permeability may predispose individuals to Crohn's disease. In order to understand the molecular basis for increased junctional permeability, a better basic understanding is needed of the physical nature of this paracellular pathway and the mechanisms and factors which regulate its permeability. This application will identify the role and mechanism of insulin and insulin-like growth factors (IGFs) in regulation of junctional permeability. Using monolayer cultures of the differentiated human colonic epithelial cell line, T84, we have shown that insulin and IGFs cause a specific, reversible and dose dependent increase in junctional permeability. Using monolayer cultures of the differentiated human colonic epithelial cell line, T84, we have shown that insulin and IGFs cause a specific, reversible and dose dependent increase in junctional permeability. Using this model system, we will investigate how these peptide hormones regulate permeability by 1) identifying the receptors which mediate the effect; 2) identifying intracellular mechanisms involved in transducing the response; and 3) identifying changes in the cellular cytoskeleton which accompany changes in permeability. We will then determine whether autocrine production of IGF-like peptides accounts for the inability of T84 cells to retain high transepithelial resistance when grown in defined, serum-free media. Completion of this aim will result in defined, serum-free media conditions useful in examining the production and response of cultured epithelial cells to other growth factors and cytokines. Finally, we will extend our observations to non-tumorigenic cell lines in culture and to tissues from rabbits with experimentally induced colitis to determine whether insulin-like growth factors are likely to mediate increased mucosal permeability in vivo. These experiments are likely to elucidate the factors and mechanisms involved in regulating junctional permeability. This could lead to a more rational approach in understanding the etiology and in improving treatment for inflammatory bowel disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK042874-02
Application #
3244054
Study Section
General Medicine A Subcommittee 2 (GMA)
Project Start
1991-08-01
Project End
1994-07-31
Budget Start
1992-08-01
Budget End
1993-07-31
Support Year
2
Fiscal Year
1992
Total Cost
Indirect Cost
City
Torrance
State
CA
Country
United States
Zip Code
90502
Zeeh, J M; Mohapatra, N; Lund, P K et al. (1998) Differential expression and localization of IGF-I and IGF binding proteins in inflamed rat colon. J Recept Signal Transduct Res 18:265-80
Zeeh, J M; Ennes, H S; Hoffmann, P et al. (1997) Expression of insulin-like growth factor I receptors and binding proteins by colonic smooth muscle cells. Am J Physiol 272:G481-7
Zeeh, J M; Hoffmann, P; Sottili, M et al. (1995) Up-regulation of insulinlike growth factor I binding sites in experimental colitis in rats. Gastroenterology 108:644-52
LeDuc, L E; McRoberts, J A; Vidrich, A (1994) Eicosanoid production by a differentiated canine colonic epithelial cell line, VNCC. Gastroenterology 106:297-305
McRoberts, J A; Riley, N E (1994) Role of insulin and insulin-like growth factor receptors in regulation of T84 cell monolayer permeability. Am J Physiol 267:G883-91
Yuan, Q X; McRoberts, J A; Lakshmanan, J et al. (1993) Newborn rabbit gastric smooth muscle cell culture: EGF and TGF-alpha are potent mitogens. J Pediatr Gastroenterol Nutr 17:153-60
McRoberts, J A; Riley, N E (1992) Regulation of T84 cell monolayer permeability by insulin-like growth factors. Am J Physiol 262:C207-13