Related Experiment Videos
Intestinal inflammation reduces expression of DRA, a transporter responsible for congenital chloride diarrhea
1Department of Internal Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
Abstract:
The pathogenesis of diarrhea in intestinal inflammatory states is a multifactorial process involving the effects of inflammatory mediators on epithelial transport function. The effect of colonic inflammation on the gene expression of DRA (downregulated in adenoma), a chloride-sulfate anion transporter that is mutated in patients with congenital chloridorrhea, was examined in vivo as well as in an intestinal epithelial cell line. DRA mRNA expression was diminished five- to sevenfold in the HLA-B27/beta2m transgenic rat compared with control. In situ hybridization showed that DRA, which is normally expressed in the upper crypt and surface epithelium of the colon, was dramatically reduced in the surface epithelium of the HLA-B27/beta2m transgenic rat, the interleukin-10 (IL-10) knockout mouse with spontaneous colitis, and in patients with ulcerative colitis. Immunohistochemistry demonstrated that mRNA expression of DRA reflected that of protein expression in vivo. IL-1beta reduced DRA mRNA expression in vitro by inhibiting gene transcription. The loss of transport function in the surface epithelium of the colon by attenuation of transporter gene expression, perhaps inhibited at the level of gene transcription by proinflammatory cytokines, may play a role in the pathogenesis of diarrhea in colitis.
Insights
Inflammation reduces DRA transporter gene expression in the colon, potentially causing diarrhea in inflammatory bowel diseases like ulcerative colitis. This impacts epithelial transport function.
Area of Science:
- Gastroenterology
- Molecular Biology
- Immunology
Background:
- Diarrhea in inflammatory conditions results from inflammatory mediators affecting epithelial transport.
- The downregulated in adenoma (DRA) transporter is crucial for chloride-sulfate transport and is implicated in congenital chloridorrhea.
Purpose of the Study:
- To investigate the impact of colonic inflammation on DRA gene expression in vivo and in vitro.
- To explore the role of DRA transporter dysfunction in the pathogenesis of diarrhea associated with colitis.
Main Methods:
- Examined DRA mRNA and protein expression in HLA-B27/beta2m transgenic rats, IL-10 knockout mice with colitis, and human ulcerative colitis patients.
- Utilized in situ hybridization and immunohistochemistry to localize DRA expression.
- Investigated the effect of IL-1beta on DRA mRNA expression in an intestinal epithelial cell line using in vitro transcription assays.
Main Results:
- DRA mRNA expression was significantly reduced (five- to sevenfold) in inflamed colons of transgenic rats compared to controls.
- DRA expression was dramatically decreased in the surface epithelium of inflamed colons across all models studied (transgenic rat, IL-10 knockout mouse, ulcerative colitis patients).
- Interleukin-1beta was found to inhibit DRA gene transcription, reducing DRA mRNA expression in vitro.
Conclusions:
- Colonic inflammation leads to a significant reduction in DRA transporter expression, particularly in the surface epithelium.
- The downregulation of DRA, potentially mediated by proinflammatory cytokines inhibiting gene transcription, may contribute to impaired epithelial transport and diarrhea in colitis.
- Loss of DRA transport function is a potential mechanism in the pathogenesis of diarrhea in inflammatory bowel diseases.