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Activation of the Human Ah Receptor by Aza-Polycyclic Aromatic Hydrocarbons and Their Halogenated Derivatives.

2003; Pharmaceutical Society of Japan; Volume: 26; Issue: 4 Linguagem: Inglês

10.1248/bpb.26.448

1347-5215

Ken‐ichi Saeki, Tomonari Matsuda, Takaaki Kato, Katsuya Yamada, Takaharu Mizutani, Saburo Matsui, Kiyoshi Fukuhara, Naoki Miyata,

Effects and risks of endocrine disrupting chemicals

Aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor through which dioxins and carcinogenic polycyclic aromatic hydrocarbons cause altered gene expression and toxicity. Ten aza-polycyclic aromatic hydrocarbons (aza-PAHs), consisting of nitrogen substituted naphthalenes, phenanthrenes, chrysenes, and benzo[a]pyrenes (BaPs), were subjected to analysis of their structure-activity relationships as an AhR ligand by using a yeast AhR signaling assay, in which AhR ligand activity was evaluated as lacZ units. Most of the aza-PAHs showed similar or more potent AhR ligand activities than the corresponding parent PAHs. About a 100-fold increased in ligand activity was observed in 10-azaBaP compared with BaP. Halogen-substitution effects on AhR ligand activity in aza-polycyclic aromatics were also investigated with quinoline, benzo[f]quinoline (BfQ), benzo[h]quinoline (BhQ) and 1,7-phenanthroline (1,7-Phe). Position-specific induction of AhR ligand activity was observed in aza-tricyclic aromatic compounds, BfQ, BhQ, and 1,7-Phe, and the ratio of the ligand activities (lacZ units/microM) of monochlorinated and monobrominated aza-tricyclic aromatic compounds to those of the corresponding parent non-halogenated compounds ranged from 2.2- to 254-fold. Greatest enhancement of ligand activity was observed in 2-brominated BfQ (2-Br-BfQ), and its ligand activity was higher than that of BaP. These results suggest that even monohalogenation markedly enhances AhR ligand activity in aza-PAHs.