AhR-activating pesticides increase the bovine ABCG2 efflux activity in MDCKII-bABCG2 cells

PLoS One. 2020 Aug 7;15(8):e0237163. doi: 10.1371/journal.pone.0237163. eCollection 2020.

Abstract

In bovine mammary glands, the ABCG2 transporter actively secretes xenobiotics into dairy milk. This can have significant implications when cattle are exposed to pesticide residues in feed. Recent studies indicate that the fungicide prochloraz activates the aryl hydrocarbon receptor (AhR) pathway, increasing bovine ABCG2 (bABCG2) gene expression and efflux activity. This could enhance the accumulation of bABCG2 substrates in dairy milk, impacting pesticide risk assessment. We therefore investigated whether 13 commonly used pesticides in Europe are inducers of AhR and bABCG2 activity. MDCKII cells expressing mammary bABCG2 were incubated with pesticides for up to 72 h. To reflect an in vivo situation, applied pesticide concentrations corresponded to the maximum residue levels (MRLs) permitted in bovine fat or muscle. AhR activation was ascertained through CYP1A mRNA expression and enzyme activity, measured by qPCR and 7-ethoxyresorufin-Ο-deethylase (EROD) assay, respectively. Pesticide-mediated increase of bABCG2 efflux activity was assessed using the Hoechst 33342 accumulation assay. For all assays, the known AhR-activating pesticide prochloraz served as a positive control, while the non-activating tolclofos-methyl provided the negative control. At 10-fold MRL concentrations, chlorpyrifos-methyl, diflufenican, ioxynil, rimsulfuron, and tebuconazole significantly increased CYP1A1 mRNA levels, CYP1A activity, and bABCG2 efflux activity compared to the vehicle control. In contrast, dimethoate, dimethomorph, glyphosate, iprodione, methiocarb and thiacloprid had no impact on AhR-mediated CYP1A1 mRNA levels, CYP1A activity or bABCG2 efflux. In conclusion, the MDCKII-bABCG2 cell model proved an appropriate tool for identifying AhR- and bABCG2-inducing pesticides. This provides an in vitro approach that could reduce the number of animals required in pesticide approval studies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily G, Member 2 / agonists
  • ATP Binding Cassette Transporter, Subfamily G, Member 2 / metabolism*
  • Animal Testing Alternatives / methods*
  • Animals
  • Cattle
  • Dogs
  • Fungicides, Industrial / toxicity*
  • Germany
  • Lactation / drug effects
  • Madin Darby Canine Kidney Cells
  • Receptors, Aryl Hydrocarbon / agonists*
  • Receptors, Aryl Hydrocarbon / metabolism
  • Recombinant Proteins / metabolism
  • Toxicity Tests, Chronic / methods*

Substances

  • ATP Binding Cassette Transporter, Subfamily G, Member 2
  • Fungicides, Industrial
  • Receptors, Aryl Hydrocarbon
  • Recombinant Proteins

Grants and funding

MSD Animal Health Innovation GmbH provided support in the form of salary for author SH, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of the author are given in the ‘author contributions’ section.