ToxSci Advance Access published online on March 10, 2008
Toxicological Sciences, doi:10.1093/toxsci/kfn048
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Heme-oxygenase 1 gene expression is a marker for hexavalent chromium-induced stress and toxicity in human dermal fibroblasts
* Molecular Carcinogenesis Laboratory, Toxicology and Molecular Biology Branch, National Institute for Occupational Safety and Health (NIOSH), Morgantown, WV
1 Address correspondences to: Pius Joseph, MS 3014, Molecular Carcinogenesis Laboratory, Toxicology and Molecular Biology Branch, National Institute for Occupational Safety and Health, 1095 Willowdale Road, Morgantown, WV 26505 Tel: (304)285-6240; Fax: (304)285-5708; e-mail: pjoseph1{at}cdc.gov
Received November 19, 2007; revision received January 14, 2008; accepted February 27, 2008
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Abstract |
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Several adverse health effects, including irritant and allergic contact dermatitis, have been reported among workers who are occupationally exposed to chromium-containing compounds. Human dermal fibroblasts were used as an in vitro experimental model to study the potential mechanisms underlying hexavalent chromium [Cr(VI)]-induced dermal toxicity. Exposure of the fibroblasts to 5 µM Cr(VI) (LC50 for a 24-hour exposure period) followed by microarray analysis of the gene expression profile revealed overexpression of several genes including those involved in cell stress response. The cellular level of glutathione, the major antioxidant molecule present in the cells, was significantly lower in the Cr(VI)-treated cells compared to the corresponding control cells. The Cr(VI)-induced overexpression of hemeoxygenase 1 mRNA (HO-1) in the fibroblasts was significantly blocked by actinomycin D and by inhibitors of MAP kinase pathways. The Cr(VI)-induced cytotoxicity and the overexpression of the HO-1 gene were dependent on the glutathione level of the fibroblasts. Buthionine sulfoximine-mediated GSH depletion resulted in enhanced Cr(VI) cytotoxicity and further overexpression of the HO-1 gene. On the other hand, elevated cellular levels of GSH resulting from pre-treating the cells with GSH significantly protected the cells against the Cr(VI)-induced cytotoxicity and blocked the HO-1 gene's overexpression. Pre-treating the fibroblasts with N-acetyl cysteine also significantly reduced the Cr(VI)-induced cytotoxicity and overexpression of the HO-1 gene. In conclusion, depletion of GSH leading to cellular stress is a major mechanism responsible for Cr(VI)-induced cytotoxicity. Furthermore, the expression level of HO-1 gene is a marker for Cr(VI)-induced cell stress leading to cytotoxicity.
Key Words: Hexavalent chromium; Cell stress; Glutathione; Cytotoxicity; Heme oxygenase 1 gene.
+ Present address: CyDex, Inc., 10513 W. 84th Terrace, Lenexa, KS 66214