OBJECTIVE: To study the effects of N-acetyl cysteine (NAC) on the oxidative DNA damage and cell survival rate of malignant BERP35T-1 cells exposed upon α-particles.METHODS:Western blot was applied for the detection of the protein expression of vH2AX in the human bronchial epithelial cell line BEP2D, RH22, and BERP35T-1 cells, and BERP35T-1 treated with 0~2 mmol/L NAC for 48 h.Immunocytochemistry was used to compare the different expression levels of 8-OH-dG in BERP35T-1 treated with 1 mmol/L NAC for 0~48 h.Using DCHF-DA, the generation of active oxygen radicals (ROS) in BERP35T-1 treated with 1mmol/L NAC for 48h was monitored by flow cytometry.MTT assay was used to examine the cell survival rate of BERP35T-1 cells treated by 1mmol/L NAC for 48h or/and 2 Gy y-ray.RESULTS:Compared to BEP2D cells, increased level of γH2AX was detected in RH22 and BERP35T-1 cells (P<0.01).The protein expression of γH2AX in BERP35T-1 was higher than in RH22 cells (P<0.01).After treated with 1 ~2 mmol/L NAC for 48h, the expression level of vH2AX in BERP35T-1 significantly decreased (P<0.01).Decreased expression level of 8-OH-dG was seen in BERP35T-1 treated with 1mmol/L NAC for 24~48 h (P<0.05 or P<0.01).After treated by 1 mmol/L NAC for 48 h, the basal level of ROS in BERP35T-1 decreased (P<0.05).In addition, the cell survival rate of BERP35T-1 treated with NAC decreased (P<0.01).Meanwhile, compared to BERP35T-1 treated with γ-ray, increased cell survival rate was detected in BERP35T-1 treated by γ-ray combined with NAC (P<0.05).CONCLUSION: NAC,as an antioxidant, may up-regulate the antioxidant defense ability of BERP35T-1, which results in decreased ROS level and oxidative DNA damage and increased genomic stability to reverse the malignant phenotype.of BERP35T-1 partially.