雌二醇和睾酮对小鼠肝脏牛磺酸及其合成酶的调控研究

发布时间：2018-04-14 11:25

本文选题：牛磺酸 + 雌二醇　；参考：《中国农业大学》2015年博士论文

【摘要】：半胱亚磺酸脱羧酶(CSAD)和半胱氨酸双加氧酶(CDO)是牛磺酸合成的限速酶,它们在肝脏生理和病理过程中发挥诸多作用,并且其表达水平与体内的性激素含量有一定关联。然而牛磺酸合成酶与性激素在小鼠肝脏中的具体调控关系尚不明确。本研究的目的是在小鼠肝脏和肝实质细胞中探索雌二醇和睾酮如何调控牛磺酸的含量及其合成酶的表达。我们初步观察到：相对于发情间期,雌性小鼠在发情期CSAD、CDO和牛磺酸的水平较低。随后用不同剂量雌二醇来处理摘除卵巢后的小鼠,肝实质细胞和HepG2细胞系,并分析CSAD和CDO的表达以及牛磺酸的含量。结果显示雌二醇可以降低血清中和肝脏中牛磺酸的含量,并且这种作用主要是通过抑制CSAD和CDO的表达水平来实现的。之后我们进一步确定了介导雌二醇发挥该作用的受体类型。实验结果显示在肝脏和肝实质细胞中雌激素受体α (ERα)的表达要高于雌激素受体β (ERβ)。在雌激素受体抑制剂ICI182,780提前处理肝脏和肝实质细胞中,雌二醇对二者CSAD、CDO和牛磺酸水平的抑制程度有所解除。在雌激素受体敲除小鼠实验中发现,外源和内源的雌二醇都不能在ERa敲除小鼠中抑制牛磺酸合成酶的表达水平和降低血清中与肝脏中牛磺酸的含量。在雄鼠中,肝内牛磺酸及其合成酶CSAD与CDO的表达水平会被睾丸摘除显著地降低,然而外源雄激素注射后会明显地回补其到正常水平。在肝实质细胞和HepG2细胞系中也有观察到睾酮对胞内CSAD表达水平的促进。随后我们发现,氟他胺的提前处理可以部分地解除睾酮对牛磺酸含量及其牛磺酸合成酶表达的促进作用。荧光素酶实验也证明了睾酮发挥对CSAD的促进作用依赖于雄激素受体。此外我们还发现了睾酮对CDO的调控主要体现在对CDO蛋白质水平的调控而非在mRNA表达层面。此外,我们的实验结果还发现了CSAD以及CDO的表达与HepG2细胞系和293FT细胞系中活性氧含量间存在正相关,然而这种相关性与胞内谷胱甘肽的含量没有直接关联。具体的机制还有待进一步深入的研究。综上所述,我们的实验结果表明,性激素可以在小鼠肝内和肝细胞内调控牛磺酸的含量以及牛磺酸合成酶的表达,并且这种作用有核受体依赖性。此外牛磺酸合成酶的表达水平也与胞内的活性氧水平有关。
[Abstract]:Cysteinesulfonic acid decarboxylase (CSAD) and cysteine dioxygenase (CDO) are rate-limiting enzymes for taurine synthesis. They play many roles in the physiological and pathological processes of the liver, and their expression level is related to the content of sex hormones in vivo.However, the specific regulatory relationship between taurine synthase and sex hormone in mouse liver is unclear.The aim of this study was to explore how estradiol and testosterone regulate taurine content and the expression of synthase in liver and parenchyma cells of mice.We preliminarily observed that the levels of CSAD CDO and taurine were lower in female mice than in estrus.After ovariectomized mice liver parenchyma cells and HepG2 cell lines were treated with different doses of estradiol. The expression of CSAD and CDO and the content of taurine were analyzed.The results showed that estradiol could decrease the content of taurine in serum and liver, and this effect was mainly achieved by inhibiting the expression of CSAD and CDO.We then further identified the type of receptor that mediates the role of estradiol.The results showed that the expression of estrogen receptor 伪 (ER 伪) in liver and hepatic parenchyma cells was higher than that in estrogen receptor 尾 (ER 尾).The inhibition of estradiol on CDO and taurine levels in liver and hepatic parenchyma cells was relieved by estrogen receptor inhibitor ICI182780.In estrogen receptor knockout mice, it was found that both exogenous and endogenous estradiol could not inhibit the expression of taurine synthase in ERa knockout mice and decrease the content of taurine in serum and liver.In male rats, the expression of taurine and its synthase CSAD and CDO in the liver was significantly decreased by testicular excision, but it was significantly restored to normal level after injection of exogenous androgen.The effect of testosterone on intracellular CSAD expression was also observed in hepatic parenchymal cells and HepG2 cell lines.After that, we found that the advance treatment of flutamide could partially remove the effect of testosterone on taurine content and taurine synthase expression.Luciferase assay also demonstrated that testosterone plays a role in promoting CSAD dependent on androgen receptors.In addition, we also found that the regulation of testosterone on CDO is mainly reflected in the regulation of CDO protein level rather than in the level of mRNA expression.In addition, we also found that there was a positive correlation between the expression of CSAD and CDO and the content of reactive oxygen species in HepG2 and 293FT cell lines, but there was no direct correlation between the expression of CSAD and CDO and the content of intracellular glutathione.The specific mechanism remains to be further studied.In conclusion, our results suggest that sex hormones can regulate taurine content and taurine synthase expression in the liver and hepatocytes of mice, and this effect is nuclear receptor-dependent.In addition, the expression level of taurine synthase is also related to the level of reactive oxygen species.
【学位授予单位】：中国农业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：S865.13

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