Differential activities of peroxisomes along the mouse intestinal epithelium

The presence of peroxisomes in mammalian intestine has been revealed formerly by catalase staining combined with electron microscopy. Despite the central role of intestine in lipid uptake and the established importance of peroxisomes in different lipid-related pathways, few data are available on the physiological role of peroxisomes in intestinal metabolism, more specifically, α-, β-oxidation, and etherlipid synthesis. Hence, the peroxisomal compartment was analyzed in more detail in mouse intestine. On the basis of immunohistochemistry, the organelles are mainly confined to the epithelial cells. The expression of the classical peroxisome marker catalase was highest in the proximal part of jejunum and decreased along the tract. PEX14 showed a similar profile, but was still substantial expressed in large intestinal epithelium. Immunoblotting of epithelial cells, isolated from the different segments, showed also such gradient for some enzymes, ie, catalase, ACOX1, and D-specific multifunctional protein 2, and for the ABCD1 transporter, being high in small and low or absent in large intestine. Other peroxisomal enzymes (PHYH, HACL1, and ACAA1), the ABCD2 and ABCD3 transporters, and peroxins PEX13 and PEX14, however, did not follow this pattern, displaying rather constant signals throughout the intestinal epithelium. The small intestine displayed the highest peroxisomal β-oxidation activity and is particularly active on dicarboxylic acids. Etherlipid synthesis was high in the large intestine, and colonic cells had the highest content of plasmalogens. Overall, these data suggest that peroxisomes exert different functions according to the intestinal segment.