Exposure to monomethylarsonous acid (MMA(III)) leads to altered selenoprotein synthesis in a primary human lung cell model

    Authors

    S. R. Meno; R. Nelson; K. J. Hintze;W. T. Self

    Comments

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    Abbreviated Journal Title

    Toxicol. Appl. Pharmacol.

    Keywords

    Monomethylarsonous acid; Thioredoxin reductase; Antioxidant response; element; Arsenic; Selenium; Carcinogenesis; ANTIOXIDANT RESPONSE ELEMENT; HUMAN UROTHELIAL CELLS; HUMAN BLADDER; CELLS; THIOREDOXIN REDUCTASE; TRIVALENT ARSENICALS; RAT HEPATOCYTES; MESSENGER-RNAS; SELENIUM; METHYLATION; INDUCTION; Pharmacology & Pharmacy; Toxicology

    Abstract

    Monomethylarsonous acid (MMA(III)), a trivalent metabolite of arsenic, is highly cytotoxic and recent cell culture studies suggest that it might act as a carcinogen. The general consensus of studies indicates that the cytotoxicity of MMA(III) is a result of increased levels of reactive oxygen species (ROS). A longstanding relationship between arsenic and selenium metabolism has led to the use of selenium as a supplement in arsenic exposed populations, however the impact of organic arsenicals (methylated metabolites) on selenium metabolism is still poorly understood. In this study we determined the impact of exposure to MMA(III) on the regulation of expression of TrxR1 and its activity using a primary lung fibroblast line, WI-38. The promoter region of the gene encoding the selenoprotein thioredoxin reductase 1 (TrxR1) contains an antioxidant responsive element (ARE) that has been shown to be activated in the presence of electrophilic compounds. Results from radiolabeled selenoproteins indicate that exposure to low concentrations of MMA(III) resulted in increased synthesis of TrxR1 in WI-38 cells, and lower incorporation of selenium into other selenoproteins. MMA(III) treatment led to increased mRNA encoding TrxR1 in WI-38 cells, while lower levels of mRNA coding for cellular glutathione peroxidase (cGpx) were detected in exposed cells. Luciferase activity of TrxR1 promoter fusions increased with addition of MMA(III), as did expression of a rat quinone reductase (QR) promoter fusion construct. However, MMA(III) induction of the TRX1 promoter fusion was abrogated when the ARE was mutated, suggesting that this regulation is mediated via the ARE. These results indicate that MMA(III) alters the expression of selenoproteins based on a selective induction of TrxR1, and this response to exposure to organic arsenicals that requires the ARE element. (C) 2008 Elsevier Inc. All rights reserved.

    Journal Title

    Toxicology and Applied Pharmacology

    Volume

    239

    Issue/Number

    2

    Publication Date

    1-1-2009

    Document Type

    Article

    Language

    English

    First Page

    130

    Last Page

    136

    WOS Identifier

    WOS:000269585800002

    ISSN

    0041-008X

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