The aryl hydrocarbon receptor interacts with nuclear factor erythroid 2-related factor 2 to mediate induction of NAD(P)H:quinoneoxidoreductase 1 by 2,3,7,8-tetrachlorodibenzo-p-dioxin

• Published in: Archives of biochemistry and biophysics 2013-09, Vol.537 (1), p.31-38
• Main Authors: Wang, Liping, He, Xiaoqing, Szklarz, Grazyna D., Bi, Yongyi, Rojanasakul, Yon, Ma, Qiang
• Format: Article
• Language: English
• Subjects: agonists; Ah receptor; Animals; ARE; benzo(a)pyrene; Cell Line; chromatin; Cross-interaction; enzymes; genes; Hepatocytes - drug effects; Hepatocytes - metabolism; knockout mutants; liver; Liver - drug effects; Liver - metabolism; Mice; Mice, Inbred C57BL; Mice, Knockout; NAD (coenzyme); NAD(P)H Dehydrogenase (Quinone) - metabolism; NF-E2-Related Factor 2 - genetics; NF-E2-Related Factor 2 - metabolism; NQO1; Nrf2; Polychlorinated Dibenzodioxins - toxicity; precipitin tests; Receptors, Aryl Hydrocarbon - metabolism; Signal Transduction - drug effects; Signal Transduction - physiology; TCDD; tetrachlorodibenzo-p-dioxin
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/j.abb.2013.06.001

•Induction of Nqo1 by TCDD involved cross-talks between the AhR and the Nrf2 pathways.•TCDD induced stabilization, nuclear accumulation, and promoter binding of Nrf2.•Activation of Nrf2 by TCDD showed delayed kinetics compared with activation of AhR.•TCDD induced physical interactions between AhR and Nrf2 to activate Nrf2.•The mechanism explains a role of Nrf2 in the induction of AhR genes by environmental chemicals. NAD(P)H:quinoneoxidoreductase 1 (NQO1) belongs to a group of the aryl hydrocarbon receptor (AhR) battery of drug-metabolizing enzymes that are characteristically induced by both AhR agonists and nuclear factor erythroid 2-related factor 2 (Nrf2) activators. We have previously reported that induction of Nqo1 by the AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in hepa1c1c7 cells involves Nrf2 (Ma et al., Biochem J 377, 205–213, 2004). Here we analyzed the molecular mechanism of induction. Induction required AhR and its DNA-binding partner Arnt because induction was not observed in AhR or Arnt-defective cells, but induction was restored upon reconstitution of the variant cells with functional AhR or Arnt. Induction also required Nrf2, as induction by benzo[a]pyrene was lost in the liver of Nrf2 knockout mice similarly to induction by butyl hydroxyanisol, demonstrating a cross-interaction between the AhR and Nrf2 pathways for induction in vivo. TCDD increased the protein level and induced the nuclear accumulation of Nrf2 with a delayed kinetics compared with activation of AhR. Chromatin immunoprecipitation revealed that TCDD recruited both AhR and Nrf2 to the Nqo1 promoter enhancer region containing a DRE and an ARE in time-dependent manners. Co-immunoprecipitation experiments revealed that, in addition to AhR-Arnt binding, TCDD induced an interaction between AhR and Nrf2 as well as Keap1. The findings reveal that TCDD induces multi protein complexes to mediate cross-interaction between the AhR and Nrf2 pathways, uncovering a novel mechanistic aspect of gene regulation by environmental chemicals through AhR and Nrf2.