围生期甲状腺功能低下大鼠海马神经元凋亡机制研究

目的:探讨甲状腺功能低下(简称甲低)发育期大鼠海马神经元凋亡途径.方法:孕15 d SD大鼠丙基硫氧嘧啶(50 mg/d)灌胃造成仔鼠甲低动物模型.采用化学发光法测定1、5、10、15日龄仔鼠血清FT3及FT 4水平.应用透射电镜观察10日龄仔鼠海马神经元线粒体超微结构.Western Blottin g检测各日龄海马神经元胞浆及线粒体中Bax、细胞色素C与AIF基因以及胞浆中caspase-3活性片段P20蛋白表达的变化.结果:模型仔鼠各日龄血清FT4水平始终接近于药盒检测限(2.8 pmol/L),明显低于对照仔鼠(1、5日龄均P<0.01;10、15日龄均P<0.001);血清FT3较同日龄对照仔鼠降低(1日龄P<0.05;其它日龄均P<0.01).模型仔鼠形态改变的线粒体与对照相比明显增多(分别为57%和19%) . 与同日龄正常仔鼠比较,甲低仔鼠胞浆中Bax表达增加(均P<0.05),线粒体中Bax表达增加非常显著(均P<0.001);甲低仔鼠胞浆中细胞色素C表达增加(1、10、15日龄均 P<0.05,5日龄 P<0.001),线粒体中表达下降(均P<0.05);甲低仔鼠胞浆中AIF表达增加(均P<0.001),线粒体中表达下降(1、5日龄均P<0.001,10、15 日龄均P<0.01);甲低仔鼠caspase-3 P20表达明显增加(1、15日龄均P<0.01; 5、10日龄均P<0.001).结论:甲低发育期大鼠海马神经元凋亡可能通过线粒体凋亡途径介导.

Mechanism for apoptosis of hippocampus neuron induced by hypothyroi dism in perinatal rats

Objective: To investigate the mechanism for the apoptosis of hippocampus neuron induced by hypothyroidism in perinatal rats. Methods: Hypothyroidism was induced by administration of propylthiouracil (PTU,50 mg/d) solution to the dams from gestational day 15 by gavage.Pups from both hypothyroid and control groups were harvested at 1,5,10 and 15 d,respectively.Blood samples were collected at the time of death for the determination of thyroid hormone.Serum free triiodothyronine (FT_(3)) and free thyroxine (FT_(4)) were measured by chemoluminescence.Hippocampus specimens were collected from the control and hypothyroid pups.Mitochondia was examined under transmission electron microscopy.Translocation of apoptogenic molecules (Bax,cytochrome C and AIF) and activation of caspase-3 were analyzed by Western Blotting. Results: Significantly low circulating FT_(3) and FT_(4) levels confirmed the hypothyroid status of the experimental pups.Electron microscopy showed that altered morphology of mitochondria significantly increased under hypothyroid conditions.The expression of Bax in the cytosol of hypothyroid pups was higher than that of control pups at all stages of development (P<0.05),and significantly higher in mitochondria (P<0.001).The expression of cytochrome c in the cytosol of hypothyroid pups was significantly higher than that of control pups at all stages of development (1,10 and 15 d:P<0.05,5 d:P<0.001),and lower in mitochondria (P<0.05).The expression of AIF in the cytosol of hypothyroid pups was higher than that of control pups at all stages of development(P<0.001),and significantly lower in mitochondria (1,5 d:P<0.001,10,15 d:P<0.01).The expression of caspase-3 P20 in the cytosol of hypothyroid pups was significantly higher as compared with that of the age-matched controls (1,15 d:P<0.01,5,10 d:P<0.001). Conclusion: The intrinsic death pathway in mitochondria may be one of the mechanisms with which hypothyroid induces apoptosis of hippocampus neuron in developing rats.