中文摘要：

目的检测纳米SiO2（nano-SiO2）暴露的体外培养的人皮肤表皮细胞（HaCaT）基因组DNA总体甲基化水平及DNA甲基转移酶DNMT1的表达改变。方法应用5-甲基胞嘧啶免疫荧光法和流式细胞定量分析法检测nano-SiO2（0、2.5、5和10μg/ml）和10μg/ml微米级二氧化硅（micro-SiO2）以及DAC组（10μg/ml nano-SiO2＋3μm DAC）暴露后细胞基因组DNA整体甲基化变化趋势,以Real-time Q-PCR和Western blot方法检测DNMT1的mRNA和蛋白的表达变化。结果与对照细胞组相比,5-甲基胞嘧啶免疫荧光强度逐渐降低,在nano-SiO2致HaCaT细胞损伤的过程中,DNA的总体甲基化程度有随nano-SiO2浓度升高而降低的趋势,同剂量的纳米暴露组与溶剂对照组及微米级对照组相比具有更低的基因组DNA甲基化水平。流式细胞定量分析实验结果显示,溶剂对照组的平均荧光荧光强度为153.43,不同浓度的nano-SiO2处理细胞24 h（2.5,5和10μg/ml）后,其平均荧光强度分别为76.32,53.26和55.16,溶剂对照组和微米对照组（Micro-SiO2）的甲基化程度差异没有统计学意义。DNMT1的mRNA和蛋白表达水平一致,在细胞暴露于nano-SiO2过程中,DNMT1表达呈下降趋势。结论本试验条件下,基因组DNA甲基化水平的降低可能与DNMT1水平降低有关。

英文摘要：

Objective Changes of genome DNA methylation and the expression of DNMT1 were observed in HaCaT cells induced by SiO2 nanoparticles.Methods Nano-SiO2（0,2.5,5,10 μg/ml） groups,Micro-SiO2group and DAC group were set up.The genome DNA methylation levels were detected by 5-methylcytosine immunofluorescence assay and flow cytometry assay.The mRNA and protein expression for DNMT1 were measured by Real-time quantitative PCR and Western Blot assay.Results The mean density of fluorescence of 5-methylcytosine decreased gradually in HaCaT cells exposed to SiO2 nanoparticles compared to solvent control group.The flow cytometry assay supported the result.When HaCaT cells induced by 10 μg/ml nano-SiO2 particle,the mean density of fluorescence was reduced to 55.16,while 153.43,76.32,53.26 for control,2.5 and 5 μg/ml groups,respectively.There was no statistically significant difference between control and micro-SiO2 groups.The alterations at protein level were similar to those at the mRNA level for DNMT1.DNMT1 decreased gradually with increased concentration of SiO2 nanoparticles.Conclusion The genome methylation level decreased gradually in HaCaT cells exposed to SiO2nanoparticles,which was associated with the reduction in the expression of DNMT1.