Protective effect of vitamin C towards N-nitrosamine-induced DNA damage in the single-cell gel electrophoresis (SCGE)/HepG2 assay

Toxicol In Vitro. 2007 Oct;21(7):1311-7. doi: 10.1016/j.tiv.2007.03.015. Epub 2007 Apr 14.


The aim of this study was to investigate the protective effect of vitamin C towards N-nitrosamine-induced DNA damage in the single-cell gel electrophoresis (SCGE)/HepG2 assay. None of the vitamin C concentrations tested (1-10 microM) in presence or absence of formamidopyrimidine-DNA glycosylase (Fpg enzyme) caused DNA damage per se. HepG2 cells simultaneously treated with vitamin C and N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR), N-nitrosodibutylamine (NDBA) or N-nitrosopiperidine (NPIP) reduced the genotoxic effects of the N-nitrosamines in a dose-dependent manner. At concentrations of 1-5 microM vitamin C, the protective effect was higher towards NPYR-induced oxidative DNA damage (78-79%) than against NDMA (39-55%), NDBA (12-14%) and NPIP (3-55%), in presence of Fpg enzyme. However, a concentration of 10 microM vitamin C led to a maximum reduction in NDBA (94%), NPYR (81%), NPIP (80%) and NDMA (61%)-induced oxidative DNA damage, in presence of Fpg enzyme. The greatest protective effect of vitamin C (10 microM) was higher towards NDBA-induced oxidative DNA damage. One feasible mechanism by which vitamin C exerted its protective effect is that may interact with the enzyme systems catalyzing the metabolic activation of the N-nitrosamines, blocking the production of genotoxic intermediates. Vitamin C (10 microM) strongly reduced the coumarin hydroxylase (82%) activity. However, the p-nitrophenol hydroxylase and the ethoxyresorufine O-deethylation activities were slightly and weakly reduced (32-19%), respectively.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antioxidants / administration & dosage
  • Antioxidants / pharmacology*
  • Aryl Hydrocarbon Hydroxylases / drug effects
  • Aryl Hydrocarbon Hydroxylases / metabolism
  • Ascorbic Acid / administration & dosage
  • Ascorbic Acid / pharmacology*
  • Carcinoma, Hepatocellular
  • Cell Line, Tumor
  • Comet Assay
  • Cytochrome P-450 CYP1A1 / drug effects
  • Cytochrome P-450 CYP1A1 / metabolism
  • Cytochrome P-450 CYP2A6
  • Cytochrome P-450 CYP2E1 / drug effects
  • Cytochrome P-450 CYP2E1 / metabolism
  • DNA Damage / drug effects*
  • DNA-Formamidopyrimidine Glycosylase / drug effects
  • DNA-Formamidopyrimidine Glycosylase / metabolism
  • Dimethylnitrosamine / toxicity
  • Dose-Response Relationship, Drug
  • Humans
  • Mixed Function Oxygenases / drug effects
  • Mixed Function Oxygenases / metabolism
  • N-Nitrosopyrrolidine / toxicity
  • Nitrosamines / toxicity*
  • Oxidative Stress / drug effects


  • Antioxidants
  • Nitrosamines
  • N-nitrosopiperidine
  • dibutylnitrosamine
  • Mixed Function Oxygenases
  • Cytochrome P-450 CYP2E1
  • Aryl Hydrocarbon Hydroxylases
  • Cytochrome P-450 CYP1A1
  • Cytochrome P-450 CYP2A6
  • DNA-Formamidopyrimidine Glycosylase
  • Dimethylnitrosamine
  • Ascorbic Acid
  • N-Nitrosopyrrolidine