H2O2 oxidative damage in cultured oral epithelial cells: The effect of short-term vitamin C exposure

Smoking is the main etiology of oral cancer and generates oxygen free radic als in the oral cavity. Free radicals have been implicated in apoptosis and in DNA damage inducing alteration of the cell cycle. The antioxidant vitam in C (VC) is reported to inhibit damage induced by free radicals. We expose d cultures of normal human oral epithelial cells to hydrogen peroxide (H2O2 ) in the presence and absence of VC. Generation of hydroxyl radicals was me asured by electron paramagnetic resonance (EPR), cell cycle alterations by flow cytometry, cell death by SYTO 11 and morphology by organotypic culture . Human primary cell culture was given four treatments - control, VC alone, H2O2 alone and VC followed by H2O2. Cell cycle analysis indicated cultures treated with H2O2 had fewer cells in GI phase (26%) and higher number of c ells in S phase (44%) compared to the control (GI 70% & S 14%). Cell cycle of 48 hour VC treatment followed by H2O2 was similar to H2O2 alone. SYTO 11 showed 22% cell death when treated with H2O2 alone compared to 9% of norma l control. By organotypic culture H2O2 alone induced a two-fold cell prolif eration, loss of maturation, nuclear hyperchromatism and nuclear crowding. Our results suggest that H2O2 is capable of altering the cell cycle and mor phology of cultured normal human oral epithelial cells. Forty-eight hour ex posure to Vitamin C does not prevent the cell cycle changes caused by hydro xyl radicals.