Identification of novel pregnane X receptor activators from traditional Chinese medicines

https://doi.org/10.1016/j.jep.2011.04.022Get rights and content

Abstract

Aim of the study

To investigate the ability of traditional Chinese medicines (TCMs) and their bioactive compounds to activate pregnane X receptor (PXR) signalling pathway.

Materials and methods

We screened ethanol extracts of 28 commonly used TCMs for their capability to induce cytochrome P450 3A4 (CYP3A4) via PXR signalling pathway using a cell-based reporter gene assay combined with RT-PCR analysis. In addition, 34 bioactive components from these TCMs were examined for their potential to activate PXR.

Results

Our observations showed that 22 ethanol extracts and 8 compounds could activate human PXR and induce CYP3A4 reporter construct in HepG2 cells. Among them, Ginkgo biloba, Ligusticum chuanxiong, Chinese angelica, prepared Rehmannia root, Epimedium brevicornum, Atractylodes macrocephala, Schisandra chinensis, Paeonia lactiflora, Ophiopogon japonicus, Polygonum multiflorum, Coptis chinensis, Artemisia scoparia, Trichosanthes kirilowii, Silybum marianum, Gardenia fruit and Lycium chinense could strongly trans-activate PXR. Moreover, ligustilide, schisantherin A, berberine hydrochloride and trans-resveratrol were identified for the first time as efficacious PXR agonists.

Conclusions

Twenty-two TCM ethanol extracts and eight bioactive compounds could activate PXR signalling pathway and induce CYP3A4 reporter gene. Therefore, caution should be taken when these PXR activators are used in combination with prescribed drugs metabolized by CYP3A4.

Introduction

Herbal remedies including traditional Chinese medicines (TCMs), Japanese and Indian medicines are gaining more and more popularity in the world, which gives an alternate choice to treat all kinds of diseases. Herbal medicines are believed to be natural and therefore safe by many patients. However, frequent and indiscriminate use of herbal products has been associated with adverse effects including interactions with therapeutic drugs (Fugh-Berman, 2000, Izzo and Ernst, 2009). For example, a number of clinical reports indicate pharmacokinetic interactions between St. John's wort and prescribed medications such as immunosuppressants (Bauer et al., 2003), contraceptives (Pfrunder et al., 2003) and antiretroviral drugs (Piscitelli et al., 2000). Some of these interactions were found to be attributed to the inducing effect of St. John's wort on hepatic and intestinal CYP3A4 (Dürr et al., 2000, Moore et al., 2000).

Many herbal medicines are known to up-regulate the expression of CYP3A4, however, the molecular mechanisms by which these herbs induce CYP3A4 have remained largely unclear. The discovery of pregnane X receptor (PXR) gives insight into the signalling mechanism of CYP3A4 induction (Bertilsson et al., 1998, Lehmann et al., 1998). It is a ligand-activated transcription factor that plays a key role in the regulation of CYP3A4 (Kliewer et al., 2002). Upon binding to a ligand, the activated PXR forms a heterodimer with retinoid X receptor, recruits cofactors, and binds to the promoter region of CYP3A4 gene, resulting in increased CYP3A4 transcription (Willson and Kliewer, 2002). Therefore, caution should be taken when PXR activators were administered with prescribed medications metabolized by CYP3A4 at the same time.

Human PXR activators include a variety of structurally diverse compounds such as prescribed drugs (Drocourt et al., 2001), herbal constituents (Watkins et al., 2003), endogenous hormones (Kliewer et al., 1998) and environmental pollutants (Coumoul et al., 2002). Herbal medicines demonstrated to trans-activate PXR include licorice (Mu et al., 2006), gugulipid (Brobst et al., 2004), Schisandra chinensis (Mu et al., 2006), Ginkgo biloba (Yeung et al., 2008) and St. John's wort (Moore et al., 2000). Furthermore some herbal ingredients have been identified as PXR activators such as hyperforin (Wentworth et al., 2000), taxol (Harmsen et al., 2009), artemisinin (Burk et al., 2005), guggulsterone (Brobst et al., 2004), schisandrol B, schisandrins A and B (Mu et al., 2006).

In our previous work, Danshen ethanol extract was found to activate PXR and its active components tanshinone IIA and cryptotanshinone were characterized as PXR activators (Yu et al., 2009). The aim of the present study was to investigate whether other commonly used TCMs and their bioactive compounds could activate PXR signalling pathway and thus have the potential to induce the expression of CYP3A4.

Section snippets

Materials

Moloney murine leukemia virus (M-MuLV) reverse transcriptase was obtained from MBI Fermentas (Hanover, MD). Dual-luciferase reporter assay system and pRL-TK vector were provided by Promega (Madison, WI). Plasmid miniprep kit was purchased from Qiagen (Hilden, Germany). Dulbecco's modified Eagle's medium (DMEM), fetal bovine serum, minimal essential medium (MEM) non-essential amino acids and lipofectamine 2000 were ordered from Invitrogen (Carlsbad, CA).

Ginkgo biloba and Isatis indigotica were

Activation of human PXR by ethanol extracts of TCMs

The tested 28 TCMs are most frequently used in China and likely to be taken with prescribed drugs. Reporter gene assays were performed to evaluate the trans-activation profile of human PXR by the ethanol extracts of these TCMs. As presented in Table 1, Ginkgo biloba, Ligusticum chuanxiong, Chinese angelica, prepared Rehmannia root, Epimedium brevicornum, Atractylodes macrocephala, Schisandra chinensis, Paeonia lactiflora, Ophiopogon japonicus, Polygonum multiflorum, Coptis chinensis, Artemisia

Discussion

A number of studies have been conducted to investigate the effect of individual compounds especially synthetic drugs on PXR activity, however, much less is known as to which herbal remedy is able to trans-activate this receptor. In the present study, twenty-eight commonly used TCMs were examined for their capability to activate PXR signalling pathway using an in vitro cell-based reporter gene assay. Our data showed that twenty-two of them could activate PXR and induce the CYP3A4 reporter gene,

Conclusion

In summary, we employed a reporter gene assay to evaluate the role of 28 TCMs and 34 bioactive components from these TCMs on trans-activation of human PXR. Our findings showed that 22 of these TCMs and 8 of their bioactive compounds could activate PXR signalling pathway and induce the CYP3A4 reporter gene. Therefore, these TCMs and constituents should be used with caution by patients to avoid unwanted herb–drug interactions. Nevertheless, there are several limitations in the present study. For

Acknowledgements

This work was supported by National Major Special Project for Science and Technology Development of Ministry of Science and Technology of China (2009ZX09304-003) (S. Zeng) and National Natural Science Foundation of China (81001475) (C.N. Yu).

References (28)

  • D.E. Brobst et al.

    Guggulsterone activates multiple nuclear receptors and induces CYP3A gene expression through the pregnane X receptor

    Journal of Pharmacology and Experimental Therapeutics

    (2004)
  • O. Burk et al.

    Antimalarial artemisinin drugs induce cytochrome P450 and MDR1 expression by activation of xenosensors pregnane X receptor and constitutive androstane receptor

    Molecular Pharmacology

    (2005)
  • L. Drocourt et al.

    Calcium channel modulators of the dihydropyridine family are human pregnane X receptor activators and inducers of CYP3A, CYP2B, and CYP2 C in human hepatocytes

    Drug Metabolism and Disposition

    (2001)
  • D. Dürr et al.

    St John's Wort induces intestinal P-glycoprotein/MDR1 and intestinal and hepatic CYP3A4

    Clinical Pharmacology & Therapeutics

    (2000)
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