Chemoprotective effect of thymol against genotoxicity induced by bleomycin in human lymphocytes

Bleomycin (BLM) as an anti-cancer agent causes tissue toxicities through DNA damaging and cell deaths. The aim of this study was to investigate the effects of thymol against genotoxicity and anti-proliferation induced by BLM in normal human lymphocytes and ovarian cancer cells. Peripheral blood samples were collected from human volunteers and were incubated with thymol at different concentrations at 50, 100, and 150 μM. After 2 h incubation, the whole blood was treated with BLM. Then the lymphocytes were cultured with mitogenic stimulation to determine the micronuclei in cytokinesis blocked binucleated lymphocyte. Human ovarian cancer cells (SKOV-3) were treated with thymol at various concentrations and/or BLM with their combinations and then cell viability were evaluated. Incubation of whole blood with thymol exhibited a significant decrease in the incidence of micronuclei in lymphocytes caused by BLM, as compared with similarly BLM-treated lymphocytes without thymol. Neither enhanced cell death nor cell protective effect was observed using thymol pre-treatment of SKOV-3 cells. This study showed that thymol selectively protects human lymphocytes against DNA damage induced by BLM without any protection on cancer cell. This result is promising for using this natural product in treatment of ovarian cancer with BLM.