Persistent binding of ligands to the aryl hydrocarbon receptor

Jessica E. Bohonowych, Michael S. Denison

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that mediates many of the biological and toxic effects of halogenated aromatic hydrocarbons (HAHs), polycyclic aromatic hydrocarbons (PAHs), and other structurally diverse ligands. While HAHs are several orders of magnitude more potent in producing AhR-dependent biochemical effects than PAHs or other AhR agonists, only the HAHs have been observed to produce AhR-dependent toxicity in vivo. Here we have characterized the dissociation of a prototypical HAH ligand ([3H] 2,3,7,8-tetrachlorodibenzo-p-dioxin [TCDD]) and PAH-like ligand ([3H] β-naphthoflavone [βNF]) from the guinea pig, hamster, mouse, and rat hepatic cytosolic AhR in order to elucidate the relationship between the apparent ligand-binding affinities and the divergent potency of these chemicals. Both compounds dissociated very slowly from the AhR with the amount of specific binding remaining at 96 h ranging from 53% to 70% for [3H]TCDD and 26% to 85% for [3H] βNF, depending upon the species examined. The rate of ligand dissociation was unaffected by protein concentration or incubation temperature. Preincubation of cytosol with 2,3,7,8-tetrachlorodibenzofuran, carbaryl, or primaquine, prior to the addition of [3H]TCDD, shifted the apparent IC50 of these compounds as competitive AhR ligands by ∼10- to 50-fold. Our results support the need for reassessment of previous AhR ligand-binding affinity calculations and competitive binding analysis since these measurements are not carried out at equilibrium binding conditions. Our studies suggest that AhR binding affinity/occupancy has little effect on the observed differences in the persistence of gene expression by HAHs and PAHs.

Original languageEnglish (US)
Pages (from-to)99-109
Number of pages11
JournalToxicological Sciences
Volume98
Issue number1
DOIs
StatePublished - Jul 2007

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Aryl Hydrocarbon Receptors
Halogenated Hydrocarbons
Aromatic Hydrocarbons
Ligands
Polycyclic Aromatic Hydrocarbons
Aromatic hydrocarbons
Primaquine
Carbaryl
Competitive Binding
Poisons
Gene expression
Cricetinae
Cytosol
Inhibitory Concentration 50
Toxicity
Rats
Guinea Pigs
Transcription Factors
Gene Expression
Temperature

Keywords

  • 2,3,7,8-tetrachlorodibenzo-p-dioxin
  • Ah receptor
  • b-naphthoflavone
  • TCDD

ASJC Scopus subject areas

  • Toxicology

Cite this

Persistent binding of ligands to the aryl hydrocarbon receptor. / Bohonowych, Jessica E.; Denison, Michael S.

In: Toxicological Sciences, Vol. 98, No. 1, 07.2007, p. 99-109.

Research output: Contribution to journalArticle

Bohonowych, Jessica E. ; Denison, Michael S. / Persistent binding of ligands to the aryl hydrocarbon receptor. In: Toxicological Sciences. 2007 ; Vol. 98, No. 1. pp. 99-109.
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