Effects of progesterone and norethisterone on cephalexin transport and peptide transporter PEPT1 expression in human intestinal cell line Caco-2.

We investigated the effects of progesterone and norethisterone on the apical-to-basolateral and basolateral-to-apical transports of cephalexin, a typical peptide transporter PEPT1 substrate, and the PEPT1 mRNA and protein expression levels, using the human intestinal cell line, Caco-2. Caco-2 cell monolayers (passages 50 to 60) were cultured on permeable membrane, plastic culture dish and culture tube. The Caco-2 cell monolayers were pretreated with progesterone and norethisterone (3, 10, 30 microM) for 24 h. After the pretreatment, the apical-to-basolateral and basolateral-to-apical transports of cephalexin were measured, and the densities of PEPT1 mRNA and protein expression levels were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot, respectively. The apical-to-basolateral transport of cephalexin was significantly decreased by the progesterone and norethisterone (30 microM each) pretreatments. By contrast, the basolateral-to-apical transport of cephalexin was not altered by the same pretreatments. The densities of PEPT1 mRNA and protein expressions were significantly decreased by progesterone and norethisterone (each at 3 and 10 microM) pretreatments compared with those of the non-treated Caco-2 cells. The results suggest that the transcription of the PEPT1 gene is downregulated by the progesterone and norethisterone pretreatments. Further studies are needed to clarify whether the inhibition of the PEPT1 gene transcription by progesterone pretreatment proceeds via sigma1-receptor or progesterone receptor.