Expression of extracellular glutathione peroxidase in human and mouse gastrointestinal tract

Extracellular glutathione peroxidase (EGPx) is a glycosylated selenoprotein capable of reducing hydrogen peroxide, organic hydroperoxides, free fatty acid hydroperoxides, and phosphatidylcholine hydroperoxides. We found that human large intestinal explant cultures synthesize EGPx and cellular glutat hione peroxidase (CGPx) and secrete EGPx. The level of EGPx mRNA expression relative to a-tubulin was similar throughout the mouse gastrointestinal tr act. EGPx mRNA transcripts have been localized to mature absorptive epithel ial cells in human and mouse large intestine. Western blot analysis of mous e intestinal protein has demonstrated the presence of EGPx protein in the s mall intestine, cecum, and large intestine, with the highest protein levels found in the cecum. Immunohistochemistry studies of human large intestine and mouse small and large intestine sections demonstrated the presence of E GPx protein within mature absorptive epithelial cells. In human large intes tine and mouse small intestine, EGPx protein is also present in the extrace llular milieu. These results suggest a role for EGPx in protection of the i ntestinal tract from peroxidative damage and/or in intercellular metabolism of peroxides.