| With the widely application of nanomaterials in cosmitics,toothpaste,and food supplements,the potential of dangerous to health of exposing to nanomaterials is getting concerned.In the study,we used mouse as model system to investigate the effect of nano titanium dioxide on female mouse reproductive function after exposure orally to nano-titanium dioxide.Firstly,we investigated the effects of nano-titanium dioxide on ovary functions.60 of 5-6 weeks old ICR female mice were random assigned into four groups with 15 mice in each grou.These four groups were adminstrated orally with nano-titanium dioxide in the dose of 0 mg/kg/d(0,as the control),100 mg/kg/d(100),300 mg/kg/d(300)and 500 mg/kg/d(500)for 10 days,respectively.On the secondy of last adminstration,10 mice were random selected from each group,and paired individually with male for 90 days.The numbers of litters and litter size were recorded.The rest of the mice were weighed and sacrificed.Their blood were collected for estrogen and progesterone assays;their ovaries were removed,weighted,and preserved for histological analysis.The average concentrations of estrogen and progestern in serums of the mice were 22.32 ± 6.48 pg/m L(0),20.94 ± 0.97 pg/m L(100),16.61±10.89 pg/m L(300),and 15.27±4.10 pg/m L(500)and 13.13±2.27 ng/m L(0),13.04±2.50 ng/m L(100),12.47±3.32 ng/m L(300),and 7.07±3.87 ng/m L(500),respectively.These results showed that the high doses of nano titanium dioxide have significantly affected the ovary secreting both estrogen(0=100>300 &500,P<0.05)and progesterone(0,100,and 300>500,P<0.05).The average numbers of follicles(total follicles excluding atretic follicles)and atretic follicles in each ovary for each group were 185.67±6.13 and 38.67±6.94(100),116.33±29.33 and 28.67±10.34(300),and 94.67±29.85,52±15.25(500),and 273.33±6.18 and 14.33 ± 3.39(0),which demonstrated that the numbers of follicles reduced significantly and the atretic follicles increased remarkably with increasing of administration of nano titanium dioxide doses.In parallel,the fertility of the mice dropped down significantly.Next we study the potential for the ovary function recovering after the mice exposed to nano-titanium dioxide.The same methods and treatments as above were used in this section study.Except the data were collected 30 days and 60 days after the last admistration of nano-titanium dioxide.The average concentration of progesterone of each mouse was8.09±1.40 ng/m L(100),6.07±1.46 ng/m L(300),1.35±1.07 ng/m L(500),and 17.51±0.74 ng/m L(0)and 10.29±1.09 ng/m L(100),8.77±1.08 ng/m L(300),1.69±1.07 ng/m L(500),and 22.82±2.51 ng/m L(0)for 30 d and 60 d recovering period,respectively;the average concentration of estrogen of each mouse was 11.19 ± 1.84 pg/m L(100),7.17 ± 1.60 pg/m L(300),2.1 ± 1.58 pg/m L(500),and 28.47±6.11 pg/m L(0)and 16.86±2.98 pg/m L(100),12.74±2.19 pg/m L(300),2.64±1.72 pg/m L(500),41.61±4.24 pg/m L(0)for recovering 30 d and 60 d,repectively.Regardless of the recovering for 30 d or 60 d,the mice serum estrogen and progesterone concentrations were reduced significantly with increasing in administration of nano-titanium dioxide doses,and were remarkably lower than that of controls(0>100>300>500).The average numbers of follicles(total follicles but excluding atretic follicles)and atretic follicles per ovary were 76.33±4.92 and 43.33±2.49(100),65±6.16 and 50.67±15.17(300),56±6.98 and 62.67±2.05(500),and 183.67±15.28 and 21.67±6.60(0)of the mice recovering for 30d;and are 73±16.06 and 33.33±9.88(100),53.67±9.03 and 51.57±5.79(300),34.67±4.03 and 77.33±10.62(500),and 148.33±11.32 and 26.33±10.21(0)of the mice recovering for 60 d.The results of numbers of follicles in the ovaries of 30 d and 60 d have shown the similar pattern,the number of follicles in ovary descreased(0>100>300>500)and the atretic follicles increased with increasing in the administration doses of nano titanium dioxide(0<100<300<500).The levels of gene expression in ovarian tissue also decreased significantly with increasing in administration doses of nano titanium dioxide.These results showed that the exposure to nano-titanium dioxide will cause permanent damage to ovary functions.Finally,we extended our investigation to the mechanism of causing ovary function damage by nano titanium dioxide.By doing so,we cultured the granulose cells for 24 h in vitro with supplement of different concentration of nano titanium dioxide.As we expected,the nano-titanium dioxide indeed could cause granulosa cells apoptosis in a dose-dependent manner with support of detection of apoptoic proteins with western blot.Additionally,nano titanium dioxide could change the mitochondrial membrane potential and significantly increase the content of reactive oxygen species in mitochondria.Therefore,we speculate that the remarkable descreasing follicle numbers and increasing follicular atresia in the ovaries of the mice exposed to nano-titanium dioxide may be caused by inducing granulosa cell apoptosis.Taken all together,we conclude that mice orally exposed to nano-titanium dioxide can lead permantent ovary damage with significamtly descreasing the numbers of follicles,increasing the numbers of atresia follicles,and reducing the amount of Steroid hormone secreting.The consequence is reduing fertility of the mice.This study indicates there is a greater risky of exposoing to nano-titanium dioxide for human. |
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