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Genotoxicity of tri- and hexavalent chromium compounds in vivo and their modes of action on DNA damage in vitro.

Fang Z, Zhao M, Zhen H, Chen L, Shi P, Huang Z - PLoS ONE (2014)

Bottom Line: Hexavalent chromium [Cr(VI)] compounds are extensively used in diverse industries, and trivalent chromium [Cr(III)] salts are used as micronutrients and dietary supplements.Cr(VI) intercalates DNA and Cr(III) interferes base pair stacking.Based on our results, we conclude that Cr(III) can directly cause genotoxicity in vivo.

View Article: PubMed Central - PubMed

Affiliation: College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, China.

ABSTRACT
Chromium occurs mostly in tri- and hexavalent states in the environment. Hexavalent chromium [Cr(VI)] compounds are extensively used in diverse industries, and trivalent chromium [Cr(III)] salts are used as micronutrients and dietary supplements. In the present work, we report that they both induce genetic mutations in yeast cells. They both also cause DNA damage in both yeast and Jurkat cells and the effect of Cr(III) is greater than that of Cr(VI). We further show that Cr(III) and Cr(VI) cause DNA damage through different mechanisms. Cr(VI) intercalates DNA and Cr(III) interferes base pair stacking. Based on our results, we conclude that Cr(III) can directly cause genotoxicity in vivo.

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The effects of pH (A–C), temperature (D) and DTT (E) on chromium-induced plasmid DNA damadge.(A) Plasmid DNA samples were treated with increasing concentrations of CrO3 (0 µM, 20 µM, 40 µM, 80 µM, and 120 µM) in Tris-HCl buffers of pH 5, pH 7, and pH 10.58 and analyzed with agarose gel electrophoresis. (B) Plasmid DNA samples were treated with increasing concentrations of CrCl3 (0 µM, 20 µM, 40 µM, 80 µM, and 120 µM) in Tris-HCl buffers of pH 5, pH 7, and pH 10.58 and analyzed with agarose gel electrophoresis. (C) Plasmid DNA samples were treated with or without CrO3 (80 µM) or CrCl3 (80 µM) in PBS buffers of pH 4, pH 5, pH 7, and pH 10. (D) Plasmid DNA samples were treated with or without CrO3 (80 µM) or CrCl3 (80 µM) at 0°C, 20°C, 30°C, and 37°C. (E) Plasmid DNA samples were treated with or without CrO3 (80 µM) or CrCl3 (80 µM) in the presence or absence of increasing concentrations of DTT (0.1 mM, 0.5 mM, 1.5 mM, 5.0 mM and 10 mM). DTT concentration used in the absence of a chromium compound was 10 mM.
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pone-0103194-g004: The effects of pH (A–C), temperature (D) and DTT (E) on chromium-induced plasmid DNA damadge.(A) Plasmid DNA samples were treated with increasing concentrations of CrO3 (0 µM, 20 µM, 40 µM, 80 µM, and 120 µM) in Tris-HCl buffers of pH 5, pH 7, and pH 10.58 and analyzed with agarose gel electrophoresis. (B) Plasmid DNA samples were treated with increasing concentrations of CrCl3 (0 µM, 20 µM, 40 µM, 80 µM, and 120 µM) in Tris-HCl buffers of pH 5, pH 7, and pH 10.58 and analyzed with agarose gel electrophoresis. (C) Plasmid DNA samples were treated with or without CrO3 (80 µM) or CrCl3 (80 µM) in PBS buffers of pH 4, pH 5, pH 7, and pH 10. (D) Plasmid DNA samples were treated with or without CrO3 (80 µM) or CrCl3 (80 µM) at 0°C, 20°C, 30°C, and 37°C. (E) Plasmid DNA samples were treated with or without CrO3 (80 µM) or CrCl3 (80 µM) in the presence or absence of increasing concentrations of DTT (0.1 mM, 0.5 mM, 1.5 mM, 5.0 mM and 10 mM). DTT concentration used in the absence of a chromium compound was 10 mM.

Mentions: The normal pH values of the CrO3 and CrCl3 solutions are 4.18 and 4.12, respectively.We next investigated whether the effects of Cr(VI) and Cr(III) on DNA degradation might be related to the low pH of these solutions. We found that Tris buffers at pH 5, pH 7, and pH 10.58 all prevented DNA degradation by both Cr(VI) and Cr(III) (Fig. 4A and 4B, compared to Fig. 3A and 3B). From these results, it was hard to conclude whether the preventive effects are caused by Tris or by the higher pH. To investigate this further, we next tested the effects of PBS buffers at pH 4, pH 5, pH 7, and pH 10 on DNA degradation by Cr(VI) and Cr(III). Under the conditions used, PBS at all four pH values blocked or reduced DNA degradation by CrCl3 (at 80 uM) (Fig. 4C). However, the protective effect offered by the solution at pH 10 was smaller than that by those solutions at lower pH values. These results suggest that Cr(III)-induced DNA degradation is not caused by the low pH of the solutions.


Genotoxicity of tri- and hexavalent chromium compounds in vivo and their modes of action on DNA damage in vitro.

Fang Z, Zhao M, Zhen H, Chen L, Shi P, Huang Z - PLoS ONE (2014)

The effects of pH (A–C), temperature (D) and DTT (E) on chromium-induced plasmid DNA damadge.(A) Plasmid DNA samples were treated with increasing concentrations of CrO3 (0 µM, 20 µM, 40 µM, 80 µM, and 120 µM) in Tris-HCl buffers of pH 5, pH 7, and pH 10.58 and analyzed with agarose gel electrophoresis. (B) Plasmid DNA samples were treated with increasing concentrations of CrCl3 (0 µM, 20 µM, 40 µM, 80 µM, and 120 µM) in Tris-HCl buffers of pH 5, pH 7, and pH 10.58 and analyzed with agarose gel electrophoresis. (C) Plasmid DNA samples were treated with or without CrO3 (80 µM) or CrCl3 (80 µM) in PBS buffers of pH 4, pH 5, pH 7, and pH 10. (D) Plasmid DNA samples were treated with or without CrO3 (80 µM) or CrCl3 (80 µM) at 0°C, 20°C, 30°C, and 37°C. (E) Plasmid DNA samples were treated with or without CrO3 (80 µM) or CrCl3 (80 µM) in the presence or absence of increasing concentrations of DTT (0.1 mM, 0.5 mM, 1.5 mM, 5.0 mM and 10 mM). DTT concentration used in the absence of a chromium compound was 10 mM.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4128586&req=5

pone-0103194-g004: The effects of pH (A–C), temperature (D) and DTT (E) on chromium-induced plasmid DNA damadge.(A) Plasmid DNA samples were treated with increasing concentrations of CrO3 (0 µM, 20 µM, 40 µM, 80 µM, and 120 µM) in Tris-HCl buffers of pH 5, pH 7, and pH 10.58 and analyzed with agarose gel electrophoresis. (B) Plasmid DNA samples were treated with increasing concentrations of CrCl3 (0 µM, 20 µM, 40 µM, 80 µM, and 120 µM) in Tris-HCl buffers of pH 5, pH 7, and pH 10.58 and analyzed with agarose gel electrophoresis. (C) Plasmid DNA samples were treated with or without CrO3 (80 µM) or CrCl3 (80 µM) in PBS buffers of pH 4, pH 5, pH 7, and pH 10. (D) Plasmid DNA samples were treated with or without CrO3 (80 µM) or CrCl3 (80 µM) at 0°C, 20°C, 30°C, and 37°C. (E) Plasmid DNA samples were treated with or without CrO3 (80 µM) or CrCl3 (80 µM) in the presence or absence of increasing concentrations of DTT (0.1 mM, 0.5 mM, 1.5 mM, 5.0 mM and 10 mM). DTT concentration used in the absence of a chromium compound was 10 mM.
Mentions: The normal pH values of the CrO3 and CrCl3 solutions are 4.18 and 4.12, respectively.We next investigated whether the effects of Cr(VI) and Cr(III) on DNA degradation might be related to the low pH of these solutions. We found that Tris buffers at pH 5, pH 7, and pH 10.58 all prevented DNA degradation by both Cr(VI) and Cr(III) (Fig. 4A and 4B, compared to Fig. 3A and 3B). From these results, it was hard to conclude whether the preventive effects are caused by Tris or by the higher pH. To investigate this further, we next tested the effects of PBS buffers at pH 4, pH 5, pH 7, and pH 10 on DNA degradation by Cr(VI) and Cr(III). Under the conditions used, PBS at all four pH values blocked or reduced DNA degradation by CrCl3 (at 80 uM) (Fig. 4C). However, the protective effect offered by the solution at pH 10 was smaller than that by those solutions at lower pH values. These results suggest that Cr(III)-induced DNA degradation is not caused by the low pH of the solutions.

Bottom Line: Hexavalent chromium [Cr(VI)] compounds are extensively used in diverse industries, and trivalent chromium [Cr(III)] salts are used as micronutrients and dietary supplements.Cr(VI) intercalates DNA and Cr(III) interferes base pair stacking.Based on our results, we conclude that Cr(III) can directly cause genotoxicity in vivo.

View Article: PubMed Central - PubMed

Affiliation: College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, China.

ABSTRACT
Chromium occurs mostly in tri- and hexavalent states in the environment. Hexavalent chromium [Cr(VI)] compounds are extensively used in diverse industries, and trivalent chromium [Cr(III)] salts are used as micronutrients and dietary supplements. In the present work, we report that they both induce genetic mutations in yeast cells. They both also cause DNA damage in both yeast and Jurkat cells and the effect of Cr(III) is greater than that of Cr(VI). We further show that Cr(III) and Cr(VI) cause DNA damage through different mechanisms. Cr(VI) intercalates DNA and Cr(III) interferes base pair stacking. Based on our results, we conclude that Cr(III) can directly cause genotoxicity in vivo.

Show MeSH
Related in: MedlinePlus