Adaptive Response And Its Mechanism In Mec-1 Cell Induced By Low-dose X-ray Radiation

Objective: The aims of this study were to investigate possibility of the adaptive response in vitro of Mec-1 cells(mucoepidermoid carcinoma,MEC-1 cell)induced by X-rays low-dose radiation and to study on its potential mechanism.Methods:Mec-1 cells were cultured in vitro and divided to 4 groups:control group(D0 group),low-dose radiation group(D1 group: 30 m Gy,50 m Gy,75 m Gy,100 m Gy),high-dose radiation group(D2 group,2Gy),low-dose plus high-dose radiation group(D1+D2group,30 m Gy+2 Gy,50 m Gy+2Gy,75 m Gy+2Gy,100 m Gy+2Gy,the interval of low and high-radiation being 4 hours).Each group was exposed to radiation and cultured 37? with 5% CO2 incubator,the proliferation rate was examined respectively after 12 h,24h,48 h and 7d to screen the most sensitive dose by CCK8 method;at the most sensitive dose point(75m Gy),to detected the intracellular reactive oxygen species(ROS)?apoptosis?proportion of cell cycle and the expression of p53?bcl-2 and mdm2 in m RNA were tested.Results: In comparison with D0 group,cell proliferation rate was most significant when cells were cultured to 48 h after the exposure of 75 m Gy radiation in D1 group.There were no changes in ROS after 48 h,and cell apoptosis was remarkably correlated linearly with the radiation dose.Obvious cell cycle block was observed in G2/M phase after 48 h with the treatment of radiation.The expression level of p53 was improved while the mdm2 was decreased,changes in bcl-2 varied.Conclusions: Low dose radiation dose not induce adaptive response in Mec-1 cells and its potential mechanism result from the increase in the expression of mdm2 and decrease the level of p53,subsequently regulate the cell apoptosis.