hepcidin调控脑铁水平的分子、细胞机制

Brain iron homeostasis is very important for nervous system development and normal function maintenance. The endothelial cells forming the blood-brain barrier have a pivotal role in brain iron transportation. Our previous studies have revealed that the brain could express hepcidin. In vitro, Hepcidin increases the iron content in bENd3.1 cells by regulating the level of FPN1. Our preliminary experiments have also discovered that brain iron level is significantly elevated after knocking out the hepcidin. However, the cellular and molecular mechanisms involved in the regulation of brain iron level by hepcidin in vivo are still not fully elucidated. Based on our preceding discovery that hepcidin is highly expressed in astrocytes, we will utilize different animal models, including hepcidin knockout mice, the mice in which hepcidin is knockdown or over-expressed specifically in astrocytes or conditional knockout FPN1 in endothelial cells, and combine biotechnologies containing double immunofluorescence, cell co-culture, etc, aiming to explore the concrete molecular and cellular mechanisms that hepcidin generated from astrocytes can regulate the expression and distribution of FPN1 in the membrane of the endothelial cells in blood-brain barrier after its release from the footplate of astrocytes, and therefore controlling the circulated iron into the brain. Our research will have momentous meaning in perfecting of brain iron metabolism theories and finding new methods for prevention and treatment of brain iron imbalance-related diseases.

脑铁稳态是神经系统发育和功能正常维持的重要保证。血脑屏障内皮细胞是铁进入脑内的关键部位，我们前期的研究结果证实脑内能够表达hepcidin，hepcidin能够调节体外培养bEnd3.1细胞FPN1的表达而影响细胞的铁含量。预实验结果也发现hepcidin基因敲除明显增加脑铁水平。然而，在体情况下，hepcidin调节脑铁水平的细胞和分子机制仍未被阐明。本研究在发现星形胶质细胞高表达hepcidin的基础上，运用hepcidin基因敲除、星形胶质细胞特异性敲低和过表达hepcidin小鼠、内皮细胞特异敲除FPN1小鼠，免疫双标、细胞共培养等技术，探索星形胶质细胞生成的hepcidin通过其终足释放到血脑屏障微血管内皮细胞，调节其膜上FPN1的表达分布，进而控制循环铁入脑，维持脑铁稳态的分子、细胞机制。对于完善脑铁代谢理论，发现预防和治疗脑铁代谢失衡相关疾病的新方法具有重要意义。

由于有血脑屏障的存在，脑铁代谢的控制具有其独特的规律。进入脑内的铁主要途径是通过血脑屏障，因此调节该途径对脑铁稳态至关重要。人们普遍认为，膜铁转运蛋白1（FPN1）是唯一已知的细胞铁输出蛋白，是铁从脑微血管内皮细胞（BMVEC）进入大脑的关键通道。但是，目前还没有直接的证据来阐明这一过程及其调控机制。之前的研究结果证实脑内能够表达hepcidin，hepcidin可以调节体外培养的BMVEC的FPN1而影响细胞的铁含量，hepcidin基因敲除可以明显增加脑铁水平。但是在体情况下，hepcidin调节脑铁水平的细胞和分子机制仍未被阐明。本研究运用hepcidin基因敲除、星形胶质细胞特异性敲低和过表达hepcidin小鼠、内皮细胞特异敲除FPN1小鼠，免疫双标、细胞共培养等技术，在发现星形胶质细胞高表达hepcidin的基础上，研究结果显示在BMVEC条件性敲除FPN1的小鼠中，FPN1确实是铁跨越血脑屏障从血液输送到脑中的主要途径。我们还发现，星形胶质细胞分泌的铁调素通过星形胶质细胞终足和BMVEC相接触的位置调节BMVEC中FPN1的表达。了解铁进入大脑的途径和如何被调节为开发神经退行性疾病或脑铁水平失衡疾病，如神经炎症，帕金森病和阿尔茨海默病的治疗方法提供了重要的理论基础。