低剂量亚硝酸钠诱导CHL细胞DNA损伤的适应性反应

The adaptive response of low dose sodium nitrite pretreatment on cultured CHL cells to DNA damage caused by high dose sodium nitrite

目的:研究低剂量亚硝酸钠(NaNO2)诱导CHL细胞DNA损伤的适应性反应及其形成机制。方法:采用单细胞凝胶电泳试验检测DNA的损伤程度。分别以浓度为0.01mg/L、0.1mg/L和1mg/L的NaNO2预处理CHL细胞6h后,观察细胞对随后的1g/L冲击剂量NaNO2的适应性反应;用3-氨基苯甲酰胺(3-AB)分别在低剂量预处理前和预处理6h后抑制聚ADP核糖聚合酶(PARP-1)的活性,观察其对适应性反应的阻断情况。结果:未经低剂量预处理的细胞,接触1g/L的NaNO218h后,DNA损伤较严重,其细胞拖尾率为7.87%,明显高于正常对照组(P<0.01);浓度为0.01mg/L和0.1mg/L的NaNO2预处理CHL细胞后,可明显缓解1g/L冲击剂量的NaNO2对CHL细胞DNA的损伤作用,其细胞拖尾率分别为3.55%和1.06%,明显低于未经低剂量NaNO2预处理组细胞的拖尾率(P<0.05;P<0.01);而经1mg/L的NaNO2预处理的细胞,接触1g/L的NaNO218h后,DNA损伤较严重,其细胞拖尾率为6.09%,与未经低剂量NaNO2预处理组细胞的拖尾率相比,差异无显著(P>0.05)。距离指标及复合指标也有相同趋势。在低剂量NaNO2预处理细胞前采用3AB抑制PARP-1活性可阻断适应性反应的产生;而在低剂量NaNO2预处理细胞6h后再用3AB抑制PARP-1活性,则不会阻断适应性反应的产生。结论:浓度等于或低于0.1mg/L的NaNO2可通过激活PARP-1诱导CHL细胞DNA损伤的适应性反应,而且,能诱导适应性反应的剂量很可能对机体DNA不造成损伤。

AIM： To study if low dose NaNO2 can induce the adaptive response of cultured Chinese hamster lung cells（ CHL cells）to DNA damage. METHODS： Single cell gel electrophoresis technique was used to detect the DNA damage in CHL cells exposed to NaNO2 at different concentrations. CHL cells were pretreated with NaNO2 of concentrations of 0. 01 mg/L, 0. 1 mg/L and 1 mg/L respectively. And the adaptive response to the toxicity of 1g/L NaNO2 was observed. The activity of polyADP - ribose polymerase （ PARP - 1 ） of CHL cells was inhibited with 3 - aminobenzamide（3AB） before or after pretreated with low dose of NaNO2. And the changes of the adaptive response were observed. RESULTS ： The rate of tailing cells was 7.87% when the cells were exposed to 1 g/L NaNO2 without pretreatment with low dose NaNO2. An extremely remarkable statistics significance （ P 〈 0. 01 ） was observed when compared the difference to control group. NaNO2 of 0. 01 mg/L and 0. 1 mg/L could induce the adaptive response of cultured CHL cells to DNA damage caused by 1 g/L NaNO2. The rate of tailing cells was 3.55% and 1.06% respectively, which was much lower than that of no - pretreatment group（P 〈0.05 ; P 〈 0. 01 ）. But the rate of tailing cells was 6. 09% when the cells were exposed to 1 g/L NaNO2 with pretreatment of 1 mg/L NaNO2, which had no significant difference compared with the rate of tailing cells in control group （P 〉0.05）. The adaptive response could be blocked when the activity of PARP - 1 was inhibited with 3AB before the low dose pretreatment, but could not be blocked when the activity of PARP - 1 was inhibited after low dose NaNO2 pretreatment 6 h. CONCLUSION： NaNO2 of concentration that equals to or lowers than 0. 1 mg/L can induce the adaptive response of cultured CHL cells to DNA damage caused by high dose NaNO2 through PARP - 1 activation. And the dose of NaNO. that can induce adaptive response migtht not cause the DNA damage.