The Influence of Apoptosis on Intestinal Barrier Integrity in Rats

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Abstract
Background: Apoptosis is a critical step responsible for maintaining the cellular balance between proliferation and death and for controlling tumorigenesis. Although an increase in intestinal apoptotic cells has been considered to be associated with the pathogenesis of gastrointestinal injury, little is understood concerning the role of apoptosis in the development of intestinal barrier dysfunction. Methods: Apoptosis induced by intraperitoneal injection of doxorubicin in rats was evaluated by transmission electron microscopy and the TUNEL histochemistry method. Treatment with deoxy-D-glucose (a glycolytic pathway inhibitor) or cycloheximide (a protein synthesis inhibitor) was performed after doxorubicin challenge. Passage of human serum albumin from blood to the intestinal interstitium and the intestinal lumen or from the intestine to the intestinal interstitium and blood was evaluated by means of albumin clearance. Results: A significant increase in gut water content, albumin flux, and bidirectional clearance of albumin accompanied by apoptotic epithelial cell increase was noted in doxorubicin-challenged rats treated with saline. The increase in endothelial and epithelial permeability and the increase of apoptosis could partly be prevented by treatment with deoxy-D-glucose or cycloheximide. Conclusion: Doxorubicin-increased epithelial apoptosis within the intestine occurs simultaneously with increased bidirectional permeability of the intestinal barrier, probably associated with both glycolytic and protein synthesis pathways. Apoptosis may thus play a role in the pathogenesis of intestinal barrier dysfunction.