纳米二氧化钛对小鼠心肌细胞DNA的损伤及叔丁基对苯二酚的拮抗作用

 目的  探讨纳米二氧化钛(nano-titanium dioxide,Nano-TiO2)对小鼠心肌细胞DNA的损伤作用,并进一步研究核因子NF-E2相关因子（nuclear factor erythroid 2 related factor 2,Nrf2）诱导剂叔丁基对苯二酚(tert-butylhydroquinone,tBHQ)是否可降低此种损伤。方法  30只ICR小鼠随机分为6组:对照组,Nano-TiO2 低(0.5 g/kg)、中(1 g/kg)、高(2 g/kg)剂量组,tBHQ组,tBHQ+ Nano-TiO2组。Nano-TiO2灌胃给予,tBHQ腹腔注射,均1次/天,连续7天。末次染毒后24 h处死小鼠,取新鲜心脏组织,胰酶消化法制备心肌细胞悬液,采用单细胞凝胶电泳技术检测心肌细胞DNA损伤程度。 结果  (1)对照组心肌细胞核呈圆形荧光团,强度均匀,大小较一致,无明显拖尾。不同剂量Nano-TiO2染毒后,各组均存在不同数量的DNA受损心肌细胞,出现彗星拖尾现象,且其尾部的拖尾程度及荧光强度随Nano-TiO2剂量的增加而增强。经CASP软件分析,低、中、高剂量Nano-TiO2组尾部DNA含量(tail DNA percent,TD)分别为28.45±1.70、35.08±0.81、39.94±4.46，明显高于对照组(23.96±2.59),差异有统计学意义(P<0.01),并有良好的剂量 效应关系(r=0.9947)。低、中、高剂量Nano-TiO2组彗星尾矩(olive tail moment,OTM)较对照组均有明显增加且差异有统计学意义(P<0.05),并有良好的剂量-效应关系(r=0.9886)。(2) tBHQ组心肌细胞细胞核呈圆形,无拖尾;Nano-TiO2中剂量(1 g/kg)组细胞拖尾明显,但给予tBHQ可明显降低Nano-TiO2所致的细胞核拖尾程度;与Nano-TiO2组相比,tBHQ +Nano-TiO2组两项指标TD及OTM均明显降低,且差异有统计学意义(P<0.05)。结论  Nano-TiO2可剂量依赖性地引起心肌细胞DNA损伤,而Nrf2诱导剂tBHQ可拮抗Nano-TiO2所致心肌细胞DNA损伤。

Nanoparticulate titanium dioxide induce DNA damage of cardiac myocytes in mice and the antagonistic effects of tert-butylhydroquinone

Objective  To investigate the DNA damage induced by Nano-TiO2 on cardiac myocytes in mice,and to further evaluate whether a Nrf2 inducer,tertiary butylhydroquinone (tBHQ) could alleviate the DNA damage.Methods  Thirty ICR mice were randomly divided into six groups:control group,0.5 g/kg,1 g/kg and 2 g/kg Nano-TiO2 groups,tBHQ group,and tBHQ+1g/kg Nano-TiO2 group.Nano-TiO2 was given through gastric gavage and tBHQ was given through intraperitoneal injection,once a day for seven consecutive days.Animals were scarificed 24 hours after the last exposure.Cardiac myocytes suspension was prepared from the heart using trypsin digestion method.DNA damage of cardiac myocytes was detected through single cell gel electrophoresis,and data was analyzed by CASP analysis software.Results  (1) In control group,the cardiac myocytes nucleus were circular fluorophore with uniform strength and size,no obvious tailing.After exposed to different doses of Nano TiO2,various number of DNA damaged cardiac myocytes were detected with comet tail.The tailing degree and fluorescence intensity were elevated with the increase of the dose of Nano-TiO2.Analyzed by CASP software,the tail DNA percentage (TD) for low,medium and high dose groups (28.45±1.70,35.08±0.81,39.94±4.46,respectively) were significantly elevated with the increase of the dose of Nano TiO2,compared with the control group (23.96±2.59) (P<0.05,r=0.994 7).In addition,the olive tail moment(OTM) of Nano-TiO2 treatment groups were significantly higher than that of the control group with a good dose-effect relationship (P<0.05,r=0.988 6).(2) The cardiac myocytes nuclei of the tBHQ group were round with no tails.Morevoer,Treatment with tBHQ significantly alleviate the degree of comet tail induced by Nano-TiO2 (1g/kg).Compared with the Nano-TiO2 group,the two indicators were significantly decreased in the (tBHQ + Nano-TiO2) group (P<0.05).Conclusions  Nano-TiO2 could induce the DNA damage of cardiac myocytes dose-dependently,and tBHQ,the inducer of Nrf2,may be has an antagonistic effect against the DNA damage of cardiac myocytes caused by Nano-TiO2.