Response of human oral epithelial cells to oxidative damage and the effect of vitamin E

Abstract 

Smoking and periodontal inflammation are various conditions with the potential to induce oxidative stress and thus DNA damage in the oral cavity. In cellular defense systems, vitamin E is considered the most powerful lipid-soluble antioxidant. To investigate whether oxygen-free radicals alter normal progression of the cell cycle and whether vitamin E prevents this damage, we exposed cultured normal human oral epithelial cells to hydrogen peroxide (H₂O₂) in the presence or absence of vitamin E. Two primary cell lines were analyzed for the presence of hydroxyl radical, cell cycle distribution and morphology. Each cell line received five treatments: control, ethanol only, vitamin E only, H₂O₂ only or vitamin E followed by H₂O₂. Degradation of hydroxyl radicals was detected by electron paramagnetic resonance analysis, cell cycle by flow cytometry and morphology by organotypic technique. Hydroxyl radicals were generated in H₂O₂-treated cells at an initial concentration, which decreased over a period of time. Cell cycle analysis showed that H₂O₂-treated cells differed from normal cells in that the percentage of cells in the G₁ phase decreased markedly (34.3 vs. 61.2% in control) and the S phase increased (35.5 vs. 15.6% in control). Organotypic cultures treated with H₂O₂ demonstrated nuclear hyperchromatism, loss of maturation and prominent nucleoli, features consistent with premalignant epithelial transformation. In conclusion, our data suggest that H₂O₂ produced hydroxyl radicals and altered the cell cycle. Also, vitamin E may have the potential to reduce oxidative damage caused by hydroxyl radicals.

Keywords:  Oxidative damage, Vitamin E, Response, Oral, Epithelial cells