Changes of expression and functions of dipeptide transporter after anoxia/reoxygenation in Caco-2 cells

AIM: To determine the changes of biological functions and expression of dipeptide transporter in Caco-2 cells with anoxia/reoxygenation(A/R) injury. METHOD: The human adenocarcinoma cell line Caco-2 cells were as the in vitro model of human small intestine and cephalexin as the model substrate for dipeptide transporter (PepT1). Caco-2 cells grown on multiple well dishes (24 pore) were cultured with or without A/R injury and then uptake of cephalexin was measured. Apoptosis of Caco-2 cells was examined by Flow-cytometry, and PepT1 mRNA were also determined by Northern blotting. RESULT: The uptake of cephelaxin across apical membranes of Caco-2 cells after the injury of A/R was significantly decreased compared with that of controls (P < 0.05). Examination of Flow-cytometry indicated that the apoptosis index of injuried Caco-2 cells remarkably increased. Northern blotting analysis showed that the level of PepT1 mRNA of injuried Caco-2 cells was greatly decreased compared to controls. CONCLUSION: The present results indicated that the functions of dipeptide transporter in Caco-2 cells were greatly downregulated after A/R injury. The alteration in the gene expression may be a mechanism of regulation of PepT1. In addition, Caco-2 cells take up cephalexin by a Proton-dependent dipeptide transporters that closely resemble the transporters present in the intestine. Caco-2 cells represent an ideal cellular model for future studies of the dipeptide transporter.