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AuthorAnwar-Mohamed, Anwar
AuthorElshenawy, Osama H.
AuthorSoshilov, Anatoly A.
AuthorDenison, Michael S.
AuthorLe, X. Chris
AuthorKlotz, Lars-Oliver
AuthorEl-Kadi, Ayman O.S.
Available date2016-04-26T14:13:24Z
Publication Date2014-02
Publication NameFree Radical Biology and Medicine
CitationAnwar-Mohamed, A., Elshenawy, O.H., Soshilov, A.A., Denison, M.S., Chris Le, X., Klotz, L.-O., El-Kadi, A.O.S. "Methylated pentavalent arsenic metabolites are bifunctional inducers, as they induce cytochrome P450 1A1 and NAD(P)H:quinone oxidoreductase through AhR- and Nrf2-dependent mechanisms" (2014) Free Radical Biology and Medicine, 67, pp. 171-187.
AbstractActivation of the aryl hydrocarbon receptor (AhR) ultimately leads to the induction of the carcinogen-activating enzyme cytochrome P450 1A1 (CYP1A1), and activation of the nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) in addition to the AhR pathway induces the expression of the NADP(H):quinone oxidoreductase (NQO1). Therefore, the aim of this study was to examine the effect of As(III) pentavalent metabolites, MMA(V), DMA(V), and TMA(V), on AhR and Nrf2 activation and on the expression of their prototypical downstream targets CYP1A1 and NQO1, respectively. Our results showed that treatment of HepG2 cells with MMA(V), DMA(V), or TMA(V) in the absence and presence of 2,3,7,8-tetrachlorodibenzo-p-dioxin or sulforaphane significantly induced both CYP1A1 and NQO1 at the mRNA, protein, and catalytic activity levels. Furthermore, these metabolites increased the AhR-dependent XRE-driven and the Nrf2-dependent ARE-driven luciferase reporter activities, which coincided with increased nuclear accumulation of both transcription factors. However, none of these metabolites were shown to be AhR ligands. The induction of CYP1A1 by these metabolites seems to be ligand-independent, possibly through a decrease in HSP90 protein expression levels. The metabolites also increased ROS production, which was significantly higher than that produced by As(III). Upon knockdown of AhR and Nrf2 the MMA(V)-, DMA(V)-, and TMA(V)-mediated induction of both CYP1A1 and NQO1 proteins was significantly decreased. In conclusion, this study demonstrates for the first time that methylated pentavalent arsenic metabolites are bifunctional inducers, as they increase CYP1A1 by activating the AhR/XRE signaling pathway and they increase NQO1 by activating the Nrf2/ARE signaling pathway in addition to the AhR/XRE pathway.
SponsorNatural Sciences and Engineering Research Council of Canada Discovery Grant RGPIN 250139
PublisherElsevier Inc.
SubjectAntioxidant Response Elements
SubjectCytochrome P-450 CYP1A1
SubjectGene Expression Regulation
SubjectGenes, Reporter
SubjectHep G2 Cells
SubjectHSP90 Heat-Shock Proteins
SubjectNAD(P)H Dehydrogenase (Quinone)
SubjectNF-E2-Related Factor 2
SubjectReceptors, Aryl Hydrocarbon
SubjectSignal Transduction
TitleMethylated pentavalent arsenic metabolites are bifunctional inducers, as they induce cytochrome P450 1A1 and NAD(P)H:quinone oxidoreductase through AhR- and Nrf2-dependent mechanisms
Volume Number67

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