To evaluate an in vitro model suitable for investigating intestinal first-pass drug metabolism, CYP3A4 and MDR1 mRNA induction by 1alpha,25-dihydroxyvitamin D(3) (VD3) was examined in two human intestinal cell lines, Caco-2 and LS180, under various culture conditions. CYP3A4 mRNA expression was induced by 100 nM VD3 at levels between 234-549 times above normal in Caco-2 cells for 2 weeks and by 74-200 times above normal in LS180 cells for 2 days. The CYP3A4 induction effect of 250 nM VD3 was similar to or slightly higher than that of 100 nM VD3 in both Caco-2 and LS180 cells. Also, CYP3A4 was induced in Caco-2 and LS180 cells when they were cultured on a polystyrene plate slightly less than when they were cultured on a porous membrane. The increase in fetal bovine serum (FBS) content in the culture medium resulted in little or only slight increase of CYP3A4 induction in both Caco-2 and LS180 cells. MDR1 mRNA expression was marginally increased by VD3 in LS180 cells, but not in Caco-2 cells, and neither increased FBS content nor use of a porous membrane significantly affected MDR1 induction in LS180 cells. The transepithelial electrical resistance of LS180 cells was almost zero, whereas that of Caco-2 cells was high and was marginally decreased by VD3. These findings indicate that Caco-2 cells cultured on a porous membrane with 100 nM VD3 for 2 weeks may be used as a model to investigate the intestinal absorption and first-pass metabolism of drugs, while LS180 cells may be utilized to elucidate the mechanisms which regulate intestinal CYP3A4 mRNA expression.

The aim of this study was to evaluate the usefulness of human intestinal LS180 cells for studying the induction of CYP3A4 mRNA expression via vitamin D receptor (VDR). CYP3A4 mRNA expression in LS180 cells treated with 100 nM 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)) for 6 and 24 h was approximately 80- and 500-fold higher than the control, respectively. A protein kinase (PK) inhibitor (staurosporine), c-jun N-terminal kinase (JNK) pathway inhibitor (curcumin), and JNK inhibitor (SP600125) attenuated 1alpha,25(OH)(2)D(3)-induced CYP3A4 mRNA expression, suggesting that the PK-JNK pathway contributed to the rapid and drastic induction of CYP3A4 expression via VDR in LS180 cells. The ability of CYP3A4 mRNA induction in LS180 cells was highly dependent on the site and number of vitamin D(3) and D(2) hydroxylation. In addition, short-time (6 h) treatment of LS180 cells with cytotoxic secondary bile acids, lithocholic acid (LCA) and 3-keto-LCA also significantly induced the mRNA expression of CYP3A4. LS180 cells may be useful to quickly investigate the CYP3A4-inducing effect of drugs, xenobiotics, and/or endogenous substrates in the intestinal epithelia.

Efficacy of vancomycin was associated with AUTL, a novel pharmacokinetic parameter. Determining the target AUTL or trough concentration may enhance the efficacy of vancomycin therapy in elderly patients with MRSA pneumonia. Given that nephrotoxicity may increase with a Ctrough in excess of 15 μg/mL, this level should ideally not be exceeded.

Clock genes encoding transcription factors that regulate circadian rhythms may inform chronomodulated chemotherapy, where time-dependent dose alterations might affect drug efficacy and reduce side effects. For example, inhibiting the essential cystine transporter xCT with sulfasalazine induces growth arrest in cancer cells. Although the anticancer effects of sulfasalazine have been studied extensively, its effects on transcriptional control of xCT expression have not been studied. Here, we show that sulfasalazine administration during the period of increased xCT expression improves its anticancer effects and that the gene itself induces xCT expression and regulates its circadian rhythm. Our findings highlight the clinical potential of chronomodulated chemotherapy and the importance of xCT-mediated transcriptional regulation in the utility of such strategies..

The aim of this study was to investigate the involvement of the peptide transporter for absorption of levofloxacin in Caco-2 cells. To evaluate the activity of apical and basolateral peptide transport, we first performed pharmacokinetic analysis of transcellular transport of glycylsarcosine (Gly-Sar) in cell monolayers grown on porous membrane filters. Transcellular transport of Gly-Sar at the medium pH 6 was greater in the apical-to-basolateral direction than in the opposite direction. Influx clearance of Gly-Sar at the apical membrane was much greater than basolateral influx and efflux clearance, indicating that the apical peptide transporter plays an important role in directional transcellular transport of the dipeptide across Caco-2 cell monolayers. We then evaluated the effect of various compounds on the uptake of Gly-Sar and levofloxacin at the apical membrane of Caco-2 cells. The apical uptake of [3H]Gly-Sar was significantly inhibited by Ala-Ala, Gly-Sar, and also levofloxacin, whereas that of [14C]levofloxacin was not inhibited by Ala-Ala and Gly-Sar. On the other hand, the apical uptake of [14C]levofloxacin was inhibited by nicotine, enalapril, fexofenadine, and L-carnitine. These findings indicated that the apical uptake transporter of levofloxacin is distinct from the peptide transporter in Caco-2 cells.