PGC-1α调节Hepcidin表达及铁动态平衡的分子机制研究

发布时间：2018-01-02 04:01

本文关键词：PGC-1α调节Hepcidin表达及铁动态平衡的分子机制研究　出处：《南京师范大学》2011年硕士论文　论文类型：学位论文

更多相关文章： PGC-1α Hepcidin 铁代谢 炎症

【摘要】：在成年人体内,铁离子的水平处在一个非常精细的动态平衡调节之中。如果这个平衡被打破,会导致铁离子的缺失或者过载,从而引发一系列的疾病。在铁离子的动态平衡调节机制中,Hepcidin起着至关重要的作用。Hepcidin能结合到细胞表面的铁离子的关键输出通道Ferroportinl (FPN1)上,导致FPN1的泛素化并在溶酶体内降解,从而破坏铁离子的动态平衡。Hepcidin的表达是高度活泼可控的,受到细胞内外多种刺激因素如缺氧、内质网压力和炎症的调节。特别需要指出的是,在慢性炎症病人体内Hepcidin的表达比健康人群高,从而发生炎性贫血(anemia of inflammation,AI)。目前仅知道炎性因子IL-6能通过STAT-3 (signal transduction and activator of transcription-3)信号通路上调Hepcidin的表达,但对炎症刺激与铁动态平衡之间的媒介分子仍不是很清楚。转录共激活因子PGC-1α(peroxisome proliferator activated receptorγcoactivator1α)是重要的能量代谢调节因子,它能够选择性地和核转录因子(包括HNF4α(hepatic nuclear factor 4α))发生相互作用,激活下游纷繁众多的代谢通路。现已有研究表明,Hepcidin启动子含有HNF4α的保守结合位点,并且在HNF4α肝脏特异性敲除的小鼠中,Hepcidin的mRNA表达水平显著升高。综合以上前人的研究结果,我们不难发现,炎性信号、PGC-1α、HNF4α以及Hepcidin之间似乎存在着千丝万缕的联系,但是,这其中具体的信号转导机制到底如何呈现? 为了回答这个问题,本论文分别在细胞和整体动物水平上进行研究。在体外细胞实验中,我们采用PGC-1α过表达腺病毒感染HepG2和HuH7人肝癌细胞株,发现无论是在转录还是翻译水平,PGC-1α都能以浓度依赖性的方式下调Hepcidin的本底表达水平,并拮抗LPS和IL-6对Hepcidin的诱导作用。荧光素酶报告基因分析实验显示,PGC-1α和HNF4α能协同抑制Hepcidin启动子片段(-775～+100)的转录活性。染色体免疫共沉淀实验表明,PGC-1α锚定在Hepcidin启动子的DR-2区域,并降低该区域的组蛋白3的乙酰化水平,从而对抗LPS或IL-6对Hepcidin启动子的活化效应。在体内动物实验中,我们通过腹腔注射LPS建立了小鼠急性炎症模型,并配合尾静脉注射PGC-1α过表达腺病毒的干预手段,使其肝脏特异性高表达PGC-1α。基因和血清学检测结果显示,LPS显著抑制PGC-1α和HNF4α的mRNA表达,但刺激hepcidin的表达,小鼠出现明显的血清铁缺乏症状；而在PGC-1α肝脏特异性过表达的小鼠中,LPS对hepcidin表达的诱导效应被削弱,缺铁状况明显缓解。综上所述,PGC-1α是调控Hepcidin表达和铁动态平衡的关键性分子,它能和HNF4α协同抑制Hepcidin的表达。而在发生炎症时,PGC-1α和HNF4α的作用减弱,此时对Hepcidin的抑制解除,Hepcidin的表达和活性升高：最终导致炎性贫血。我们的结论丰富了现有对炎性贫血发生机制的理解,并为未来治疗铁异常疾病的药物开发提供了新的靶标分子。
[Abstract]:In adults, the iron level in a very fine dynamic balance. If the balance is broken, can lead to iron deficiency or overload, causing a series of diseases. In the dynamic balance of iron ion regulatory mechanisms, Hepcidin plays a crucial role in the.Hepcidin can bind to the key output channel iron ion cell surface Ferroportinl (FPN1), leading to the ubiquitination of FPN1 and lysosomal degradation, thus undermining the expression of dynamic balance of iron ions in.Hepcidin is highly active controllable, fine by many extracellular stimuli such as hypoxia, regulation of endoplasmic reticulum stress and inflammation. It is especially pointed out that the expression of Hepcidin in patients with chronic inflammation than healthy people, resulting in anemia of inflammation (anemia of, inflammation, AI). The only known inflammatory factor IL-6 by STAT-3 ( Signal transduction and activator of transcription-3 signal pathway upregulates Hepcidin expression, but it is still not clear about the mediator between inflammatory stimulation and iron homeostasis.
Transcriptional co activator PGC-1 alpha (peroxisome proliferator activated receptor y coactivator1 alpha) is a regulator of energy metabolism is important, it can selectively and nuclear transcription factors (including HNF4 (hepatic nuclear factor alpha 4 alpha)) interact to activate metabolic pathways downstream. Numerous studies now show that conserved binding sites of Hepcidin the promoter contains HNF4 alpha, alpha and HNF4 in liver specific knockout mice, the expression level of Hepcidin mRNA increased significantly. According to the results of previous research, we find that the inflammatory signal, PGC-1 alpha, alpha HNF4 and Hepcidin between there seems to be inextricably linked, but the signal how specific transduction mechanism?
In order to answer this question, this paper makes research on cell and whole animal level. In vitro experiment, we used PGC-1 alpha overexpression adenovirus infection of HepG2 and HuH7 in human hepatocellular carcinoma cell line, was found both in the transcription or translation level of PGC-1 alpha can with concentration dependent manner and down-regulation of Hepcidin the expression level of LPS and IL-6, and antagonized the induction of Hepcidin. Luciferase reporter gene analysis showed that, PGC-1 alpha and HNF4 alpha inhibition of Hepcidin promoter fragment (-775 ~ +100). The results show that the transcriptional activity of chromatin immunoprecipitation, PGC-1 alpha anchored in the DR-2 region of the Hepcidin promoter, and to reduce the area of histone acetylation level of 3, and against LPS or IL-6 on the activation of the Hepcidin promoter. In in vivo animal experiments, we established acute inflammation in mice by intraperitoneal injection of LPS The model, combined with intravenous injection of PGC-1 alpha overexpression adenovirus intervention, the liver specific expression of PGC-1 alpha gene and serological test results. The expression of LPS showed significant inhibition of PGC-1 alpha and HNF4 alpha mRNA, but stimulated hepcidin expression in mice, significantly serum iron deficiency symptoms; and over expression of PGC-1 in mice liver specific, LPS on the expression of hepcidin induced by iron deficiency condition is weakened, relieved.
In summary, PGC-1 alpha is a key molecule regulating the expression of Hepcidin and iron homeostasis, which can express HNF4 alpha and Hepcidin. The synergistic inhibition of inflammation, decrease of PGC-1 alpha and HNF4 alpha, the inhibition of Hepcidin release, increased Hepcidin expression and activity which leads to anemia of inflammation. We the conclusion enriches the existing on the inflammatory mechanism of anemia in understanding, and provides a new molecular target for future drug development for iron disorders.

【学位授予单位】：南京师范大学
【学位级别】：硕士
【学位授予年份】：2011
【分类号】：R363

【共引文献】