Ryan D. Himes
Scholarship of Discovery
Hexavalent chromium, or Cr(VI), is a potent oxidizer and known carcinogen, that is found at varying levels in the water sources of more than 200 million Americans. However, the exact mechanism of carcinogenicity remains unknown, and though the government currently regulates total chromium levels, they have yet to determine a permissible exposure limit for Cr(VI). Moreover, there is currently no preventative treatment for Cr(VI). Because of Cr(VI)’s strong oxidative power, we hypothesized that it causes DNA mutation and cell death via oxidation and that antioxidants could prevent this from occurring. To test this, we first assessed the viability of human cell culture exposed to Cr(VI) with or without either of the antioxidants vitamin C or epigallocatechin gallate (EGCG). Further, an Ames test was performed to determine the mutagenicity of Cr(VI) with and without either antioxidant.
We found that Cr(VI) is significantly toxic to cell culture at concentrations of 200 ppb (parts per billion) or more. Both vitamin C and EGCG blocked this effect at 10 ppm (parts per million) and 15 ppm, respectively, while neither antioxidant was observed to be cytotoxic when treated alone. Cr(VI) was also found to be significantly mutagenic at 20 ppb and greater. This mutagenicity was significantly reduced by cotreatment with 20 ppm vitamin C at 200 and 2000 ppb Cr(VI), while vitamin C was not found to be mutagenic when tested individually. With these combined data, we conclude that Cr(VI) is both cytotoxic and mutagenic via an oxidative mechanism and these effects can be abrogated by antioxidants. Though continued study is merited, this information further validates the protective potential of antioxidants against toxicants like Cr(VI).
Mayotte, Timothy P., "Hexavalent Chromium-Induced Cytotoxicity and Mutagenicity: A Study of Protection by Ascorbic Acid and Epigallocatechin Gallate" (2019). Honors Program Projects. 96.
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