Hypericum perforatum: which constituents may induce intestinal MDR1 and CYP3A4 mRNA expression?

In vitro and in vivo studies suggest that extracts of St John's wort (Hypericum perforatum, L .; SJWE) interact with various drugs, by enhancing their elimination, due to induction of intestinal and hepatic cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp), the gene product of multidrug resistance gene 1 (MDR1/ABCB1). The aim of our study was to identify the major constituents responsible for this induction and their relative importance. Therefore, plant extracts were investigated that vary in these constituents with respect to their effect on mRNA expression of MDR1/CYP3A4. First, different pure constituents of Hypericum perforatum L . were investigated. Secondly, diverse SJWE with different concentrations of hyperforin, quercitrin and hypericin were investigated. The concentrations of hyperforin, hypericin, and quercitrin in the plant extracts were determined by HPLC, and an "artificial extract" containing the same mixture of these constituents was investigated. Different plant extracts, pure constituents or "artificial extracts" were applied to the human colon carcinoma-derived cell line (LS180) and the induction of MDR1 and CYP3A4 expression was analyzed by quantitative RT-PCR. MDR1 and CYP3A4 mRNA expression were both induced by single constituents of SJW such as hypericin and hyperforin in a concentration of 10 microM. Additionally, CYP3A4 mRNA expression was induced by quercitrin. SJW extracts containing hyperforin induced significantly MDR1 mRNA expression, whereas no CYP3A4 induction was observed after treatment with any of the investigated SJWE. These effects could be mimicked by "artificial extracts" containing the same compositions of hyperforin, hypericin and quercitrin as the plant extracts.

Interaction of St John's wort with low-dose oral contraceptive therapy: a randomized controlled trial.

AIMS: Breakthrough bleeding or even unwanted pregnancies have been reported in women during concomitant therapy with oral contraceptives and St John's wort extract. The aim of the present study was to investigate the effects of St John's wort extract on oral contraceptive therapy with respect to ovarian activity, breakthrough bleeding episodes and the pharmacokinetics of ethinyloestradiol and 3-ketodesogestrel. METHODS: Eighteen healthy females were treated with a low-dose oral contraceptive (0.02 mg ethinyloestradiol, 0.150 mg desogestrel) alone (control cycle) or combined with 300 mg St John's wort extract given twice daily (cycle A) or three times daily (cycle B). Ovarian activity was assessed by measuring follicle maturation and serum oestradiol and progesterone concentrations. The number of breakthrough bleeding episodes and the pharmacokinetics of ethinyloestradiol and 3-ketodesogestrel were assessed under steady-state conditions. RESULTS: During concomitant administration of low-dose oral contraceptive and St John's wort, there was no significant change in follicle maturation, serum oestradiol or progesterone concentrations when compared with oral contraceptive treatment alone. However, significantly more subjects reported intracyclic bleeding during cycles A (13/17 (77%), P < 0.015) and cycle B (15/17 (88%), P < 0.001) than with oral contraceptives alone (6/17 (35%)). The AUC(0,24 h) and Cmax of ethinyloestradiol remained unchanged during all study cycles, whereas the AUC(0,24 h) and Cmax of 3-ketodesogestrel decreased significantly from 31.2 ng ml-1 h to 17.7 ng x ml-1 h (43.9%; 95% confidence interval (CI) -49.3, -38.5, P = 0.001) and from 3.6 ng x ml -1 to 3.0 ng x ml -1(17.8%; CI -29.9, -5.7, P = 0.005), respectively, during cycle A and by 41.7% (CI -47.9, -35.6; P = 0.001) and by 22.8% (CI -31.2, -13.3; P < 0.001) during cycle B respectively, compared with the control cycle. CONCLUSIONS: There was no evidence of ovulation during low-dose oral contraceptive and St John's wort extract combination therapy, but intracyclic bleeding episodes increased. Bleeding irregularities may adversely effect compliance to oral contraceptives and together with St John's wort-induced decreases in serum 3-ketodesogestrel concentrations, enhance the risk of unintended pregnancies.

Gene expression of CYP3A4, ABC-transporters (MDR1 and MRP1-MRP5) and hPXR in three different human colon carcinoma cell lines.

Colon carcinoma cell lines are used widely as screening models for intestinal absorption of drugs. However, the expression of important transport systems and of metabolic enzymes is not completely characterized yet. The expression and inducibility of multidrug resistance gene 1 (MDR1) and cytochrome P450 isoform 3A4 (CYP3A4) was investigated in Caco-2 parental, Caco-2 TC-7 (TC-7) and LS180 cell lines. In the same three cell lines, we investigated the expression of isoforms of the multidrug resistance associated protein family (MRP1-MRP5) and the human pregnane X receptor (hPXR), which may be important for MDR1 and CYP3A4 induction. Cells were treated with rifampicin or 1alpha,25-dihydroxycholecalciferol (1,25(OH)(2)D(3)) for 72 h and the total RNA was extracted. Afterwards reverse transcription real-time polymerase chain reaction (TaqMan) assay was performed to determine the mRNA expression level. We have shown that in LS180 cells, MDR1 and CYP3A4 were inducible with both inducers. In Caco-2 parental and TC-7 cells, CYP3A4 was only inducible with 1,25(OH)(2)D(3). Furthermore, differences were shown in gene expression of several transport proteins (MDR1 and MRP1-MRP5) and CYP3A4 in different human colon carcinoma derived cell lines. hPXR mRNA was expressed in all three cell lines but the amount of mRNA detected was significantly higher in LS180 cells than in Caco-2 and TC-7 cells. We concluded that LS180 cells were a suitable model to study MDR1 and CYP3A4 induction, but for drug transport studies Caco-2 parental and TC-7 cells would be preferred as the more physiological model.