Saeki KI, Matsuda T, Kato TA, Yamada K, Mizutani T, Matsui S, Fukuhara K, Miyata N. Activation of the human Ah receptor by aza-polycyclic aromatic hydrocarbons and their halogenated derivatives.
Biol Pharm Bull 2003;
26:448-52. [PMID:
12673023 DOI:
10.1248/bpb.26.448]
[Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
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.
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