TDP-43胞浆聚集导致SAH后轴突损伤及干预机制的实验研究

Axonal damage after Subarachnoid hemorrhage(SAH) is the major cause of neurological disorders such as cognitive deficits. Different from early brain injury in disease course, the mechanism of axonal damage after SAH remains to be studied. A nucleoprotein, TDP-43, plays a key role in processes such as transportation of mRNA. Pathologically, TDP-43 aggregates and forms inclusion bodies in neuron cytoplasm, which consequently induces damage of neurons and axons. Our previous studies suggest existence of TDP-43 aggregates in neuron cytoplasm after SAH. We hypothesize that TDP-43 cytoplasmic aggregation contributes to axonal damage after SAH. Furthermore, oxidative stress mediated acetylation of TDP-43 were proved to govern its cytoplasmic aggregation, we hypothesize that deacetylation of TDP-43 by activation of HSF1-HSP70/HSJ1a will prevent TDP-43 aggregation and axonal damage after SAH. More clinically suitable, we will explore the possibility of clearance of TDP-43 inclusion bodies by stem cell derived miR-17-92 cluster enriched exosomes, which activate Akt/GSK3β cascade to promote endocytosis therefore reduce TDP-43 aggregation and axonal damage.

蛛网膜下腔出血（Subarachnoid hemorrhage，SAH）患者的轴突损伤，是导致认知等神经功能障碍的主要原因，其病程可能不同于早期脑损伤，需探索其机制。TDP-43(transactive response DNA-binding protein of 43ku)是一种核蛋白，执行mRNA转运等功能；病变后在胞浆聚集形成包涵体，损伤神经元及轴突。前期研究发现SAH模型的神经元存在TDP-43胞浆聚集，推测其可导致轴突损伤，拟进行验证。氧化应激诱导的乙酰化，被认为是控制TDP-43胞浆聚集的关键因素，既往研究表明HSF1-HSP70具有抗氧化作用，拟探讨其抑制TDP-43胞浆聚集，减轻轴突损伤。清除晚期病变的TDP-43包涵体，更符合临床实际。我们将探索干细胞来源的miR-17-92外泌体，激活Akt/GSK3β后，通过促进细胞内吞、加快TDP-43包涵体清除，减轻轴突损伤。

蛛网膜下腔出血（Subarachnoid hemorrhage，SAH）常因颅内动脉瘤破裂、导致的急性脑血管病。近年死亡率逐步下降，同时幸存者认知功能障碍的危害性也逐渐凸显，脑白质（轴突及髓鞘）是主要的损伤靶标。TDP-43(transactive response DNA-binding protein of 43ku)是一种核蛋白，转运RNA至胞浆，维持神经系统的生理功能。在神经运动性疾病及长期脑外伤患者的神经元胞浆中，存在聚集的病理学包涵体，其导致核内生理性TDP-43 消耗，从而引起神经功能障碍。既往研究认为TDP-43的乙酰化、磷酸化修饰，促进其在胞浆中病理性凝集。近年研究表明，乙酰化修饰的TDP-43只是启始、乙酰化TDP-43为液液相分离状态；线粒体恢复后在ATP的支持下，转化为生理性TDP-43；如无足够ATP的支持，中间态的TDP-43去乙酰化、磷酸化，形成病理性聚集。我们研究表明，SAH诱导HDAC1与HSP70结合，促进TDP-43在细胞质中凝集；SAHA通过抑制HDAC1增强HSP70乙酰化来促进TDP-43的降解，促进神经轴突的生长，并减轻了SAH模型的轴突损伤，改善了SAH大鼠的行为学评分；另外，干细胞来源的miR-140-5p外泌体，通过 IGFBP5介导的PI3K/AKT途径，减少TDP-43聚集诱发的神经元损伤。TDP-43在神经系统的发育及正常功能的维持中起重要作用，胞浆内聚集的病理过程也特别复杂，涉及乙酰化、磷酸化、泛素化等多种修饰，以及复杂的相变过程。HSP70等伴侣蛋白，有助于乙酰化TDP-43维持在浓缩相（相分离状态）；线粒体、溶酶体功能的恢复，有利于TDP-43转换为稀释相（生理状态）；持续的损伤，导致TDP-43去乙酰化、磷酸化，TDP-43转换为聚集相（病理状态）。课题组还在继续检测相分离状态，同时还发现TDP-43聚集对髓鞘也存在影响。总之，TDP-43的生理、病理作用机制尚未阐明，我们只做了部分工作，还需深入研究。