BRCA1调控mtDNA氧化损伤在铝暴露损害认知功能中的作用及机制

Aluminum, which is widely used and can impair cognitive function, is an important environmental pathogenic factor of neurodegenerative disorders. The oxidative damage to mitochondrial DNA of neurons is causally associated with cognitive impairment. Breast cancer susceptibility gene 1 (BRCA1) might play an important role against mitochondrial DNA oxidative damage. However, the mechanism of BRCA1 regulation system is not clear till now. Based on the findings of our previous work that aluminum could induce oxidative stress and interfere PKA/CREB as well as Nrf2/ARE pathway, meanwhile, quercetin could improve learning and memory ability impaired by aluminum, we further put forward the hypothesis here that aluminum could induce excessive ROS, cause oxidative damage to mtDNA, through interfering with the activity-dependent BRCA1 expression mediated by CREB and BDNF, then influencing the transcriptional activation of BRCA1-mediated BER enzymes and Nrf2/ARE-dependent genes against mitochondria oxidative damage, thus induce the accumulation of mtDNA damage and mitochondrial dysfunction, therefore, ultimately injury cognitive function. We plan to conduct in vitro and in vivo experiments by the techniques in neuroethology, electrophysiology, biochemistry and molecular biology to validate the hypothesis mentioned above from the aspects of signaling pathway, the interaction between proteins along with transcription regulation. This grant will provide new evidence and clue for further clarifying the mechanism underlying cognitive impairment caused by aluminum and searching the potential therapeutic molecular targets for early effective intervention against aluminum-related neurodegenerative disorders.

铝应用广泛，影响认知功能，是神经退行性疾病一个重要的环境致病因子。神经元mtDNA氧化损伤，与认知障碍有因果关联，BRCA1可能在其中发挥重要的调控作用，但机制尚未阐明。在我们前期研究发现铝致氧化应激，引起PKA/CREB、Nrf2/ARE通路改变，而橡黄素干预改善学习记忆的基础上，本研究进一步提出假说：铝可产生过多ROS，引起mtDNA氧化损伤，通过干扰活动依赖性CREB、BDNF调控BRCA1的表达，进而影响BRCA1调控BER途径关键酶及Nrf2/ARE通路抗氧化酶的转录，造成mtDNA损伤累积和线粒体功能障碍，最终损害认知功能。本研究拟采用体内、体外试验相结合的方法，应用神经行为学、电生理学、分子生物学等技术手段，从信号通路、蛋白间相互作用、转录调控等不同层面来验证上述假说。本项目将为深入阐明铝损害认知功能的机制，并为寻找早期干预铝相关神经退行性疾病的分子靶点提供新的线索和依据。

铝应用广泛，影响认知功能，是神经退行性疾病一个重要的环境致病因子。神经元mtDNA氧化损伤，与认知障碍有因果关联，BRCA1可能在其中发挥重要的调控作用，但机制尚未阐明。本项目通过不同发育阶段饮水染铝12w或36w制作亚慢性和慢性铝暴露大鼠模型，并结合体外原代神经元和SH-SY5Y细胞培养发现，铝暴露可降低海马系数和海马/脑比值，损伤动物学习记忆能力；整体动物电生理学HFS诱导LTP的PS幅值增强率减少，从突触水平证实铝对海马学习记忆功能的损害；铝引起海马细胞氧化应激，线粒体呼吸链复合物ComplexI、ComplexIV下降，mtDNA拷贝数下降，mtDNA氧化损伤，nDNA完整性下降，线粒体功能降低；BRCA1转录及蛋白水平降低，采用cAMP信号激动剂Forskolin、PKA抑制剂H89干预证实BRCA1表达受PKA/CREB通路的调控；铝暴露减少BRCA1与Nrf2蛋白间相互作用，使得Nrf2泛素化水平升高，稳定性降低，引起Nrf2及其通路相关蛋白表达下降；铝暴露引起脑组织线粒体OGG1、APE1水平的改变，且OGG1与BRCA1存在共定位；采用抗氧化剂槲皮素、白藜芦醇干预，损伤有所减轻，而促氧化剂BSO作用则加重损伤。尤其特别的是，BER关键酶OGG1、APE1随染毒时间延长出现先升高后下降的现象，推测可能是亚慢性铝暴露引发机体对抗mtDNA氧化损伤的BER修复途径偿性激活，而慢性暴露导致失代偿反应的具体表现。超微结构观察发现铝暴露组神经元核异染色质增多，线粒体空泡样变，嵴数量减少；神经突触活性带变短，后致密物减少，间隙模糊，突触小泡减少，可能是铝致认知障碍的形态学基础。本研究从神经行为学、电生理学、分子生物学等技术手段，从信号通路、蛋白间相互作用、蛋白降解等不同层面证实了铝暴露通过损伤BRCA1调控Nrf2/ARE和BER通路引起mtDNA氧化损伤累积，线粒体功能下降最终导致认知障碍的假说。本项目结果为深入阐明铝损害认知功能的机制，从氧化损伤角度寻找早期干预铝相关神经退行性疾病的分子靶点提供了新的线索和依据。