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The Toll-like receptor agonist imiquimod is metabolized by aryl hydrocarbon receptor-regulated cytochrome P450 enzymes in human keratinocytes and mouse liver

Archives of Toxicology volume 93, pages 1917–1926 (2019)Cite this article

Abstract

The Toll-like receptor 7 agonist imiquimod (IMQ) is an approved drug for the topical treatment of various skin diseases that, in addition, is currently tested in multiple clinical trials for the immunotherapy of various types of cancers. As all of these trials include application of IMQ to the skin and evidence exists that exposure to environmental pollutants, i.e., tobacco smoke, affects its therapeutic efficacy, the current study aims to elucidate the cutaneous metabolism of the drug. Treatment of human keratinocytes with 2.5 µM benzo[a]pyrene (BaP), a tobacco smoke constituent and aryl hydrocarbon receptor (AHR) agonist, for 24 h induced cytochrome P450 (CYP) 1A enzyme activity. The addition of IMQ 30 min prior measurement resulted in a dose-dependent inhibition of CYP1A activity, indicating that IMQ is either a substrate or inhibitor of CYP1A isoforms. Incubation of 21 recombinant human CYP enzymes with 0.5 µM IMQ and subsequent LC–MS analyses, in fact, identified CYP1A1 and CYP1A2 as being predominantly responsible for IMQ metabolism. Accordingly, treatment of keratinocytes with BaP accelerated IMQ clearance and the associated formation of monohydroxylated IMQ metabolites. A co-incubation with 5 µM 7-hydroxyflavone, a potent inhibitor of human CYP1A isoforms, abolished basal as well as BaP-induced IMQ metabolism. Further studies with hepatic microsomes from CD-1 as well as solvent- and β-naphthoflavone-treated CYP1A1/CYP1A2 double knock-out and respective control mice confirmed the critical contribution of CYP1A isoforms to IMQ metabolism. Hence, an exposure to life style-related, dietary, and environmental AHR ligands may affect the pharmacokinetics and, thus, treatment efficacy of IMQ.

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Acknowledgements

We thank Daniel W. Nebert for generously providing CYP1A1/CYP1A2 double KO mice, and Franziska Weigner, Melanie Scheinpflug, Ragnhild Wirth, and Diane Schmiegelt for technical support. Research in the THS lab is supported by DFG grant HA 7346/2–1 and the Juergen Manchot Foundation. The CAB lab thanks NIEHS grant ES028377.

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Affiliations

  1. IUF - Leibniz Research Institute for Environmental Medicine, 40225, Düsseldorf, Germany

    Melina Mescher, Julia Tigges, Katharina M. Rolfes, Christian Vogeley, Jean Krutmann & Thomas Haarmann-Stemmann

  2. The McArdle Laboratory for Cancer Research, Department of Oncology, School of Medicine and Public Health, University of Wisconsin, Madison, WI, USA

    Anna L. Shen, Jeremiah S. Yee & Christopher A. Bradfield

  3. Medical Faculty, Heinrich-Heine-University, Düsseldorf, Germany

    Jean Krutmann

  4. Bayer AG, Pharmaceuticals, DMPK Drug Metabolism, 42096, Wuppertal, Germany

    Dieter Lang

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  1. Melina Mescher
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Correspondence to Thomas Haarmann-Stemmann.

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Mescher, M., Tigges, J., Rolfes, K.M. et al. The Toll-like receptor agonist imiquimod is metabolized by aryl hydrocarbon receptor-regulated cytochrome P450 enzymes in human keratinocytes and mouse liver. Arch Toxicol 93, 1917–1926 (2019). https://doi.org/10.1007/s00204-019-02488-5

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Keywords

  • Aryl hydrocarbon receptor
  • Cytochrome P450
  • Imiquimod
  • Immunotherapy
  • Psoriasis