*3.2. Protection against H2O2- and Ro-Induced DNA Damage*

Using the comet assay we investigated the possible protective effect of vitamin C against DNA damage caused by H2O2 or Ro plus light after pre-incubating HeLa cells with vitamin C (5–200 μM) for 30 min or 6 h. In HeLa cells the yield of damage, net H2O2-induced breaks or net Ro-induced FPG-sensitive sites, was unchanged by the vitamin C incubation (Figures 2A,B and 3A,B).

**Figure 2.** Effect of pre-incubation of HeLa cells with different concentrations of vitamin C for 30 min (**A**) or 6 h (**B**) on damage induced by H2O2. Net H2O2-induced damage was calculated by subtracting comet score without H2O2 (as in Figure 1) from the total comet score with H2O2. Bars: SD calculated from the results of 3 independent experiments. No significant effects were seen.

**Figure 3.** Effect of pre-incubation of HeLa cells with different concentrations of vitamin C for 30 min (**A**) or 6 h (**B**) on FPG-sensitive sites induced by Ro plus light. Net Ro-induced damage was calculated by subtracting the FPG-sensitive sites without Ro plus light (as in Figure 1) from the FPG-sensitive sites with Ro plus light. Bars: SD calculated from the results of 3 independent experiments. No significant effects were seen.
