Mechanisms of cytotoxicity of eugenol in human osteoblastic cells in vitro

Aim: To evaluate the mechanisms of cytotoxicity of eugenol in human osteoblastic cells in vitro. Methodology: Cytotoxicity and cell proliferation assays were performed to elucidate the toxic effects of eugenol on the human osteoblastic cell line U2OS. Furthermore, the effects of antioxidants catalase (scavenger of H2O2), superoxide dismutase (SOD, an extracellular superoxide free radical scavenger) and N-acetyl-L-cysteine (NAC, a cell-permeable glutathione precursor) were added to discover the possible mechanisms of eugenol-induced cytotoxicity. Paired Student's t-test was applied for the statistical analysis of the results. Results: Eugenol demonstrated a cytotoxic effect to U2OS cells in a dose-dependent manner (P < 0.05). The 50% inhibition concentration of eugenol was approximately 0.75 mmol L-1. Eugenol also inhibited cell proliferation during a 4-day culture period (P < 0.05). Addition of NAC extracellularly protected the cells from eugenol-induced cytotoxicity (P < 0.05). Neither, SOD nor catalase provided any protective effects on eugenol-induced cytotoxicity (P > 0.05). Conclusions: The levels of eugenol tested inhibited growth and proliferation of U2OS cells. Eugenol has significant potential for periapical toxicity. These inhibitory effects were associated with glutathione levels.