NF-κB-Jmjd3调控通路参与高尿酸血症认知功能障碍的表观遗传机制研究

Hyperuricemia is a risk factor for cognitive dysfunction. Recent studies have reported that hyperuricemia induces cognitive dysfunction by activating the NF-κB pathway in the hippocampus and inducing the expression and release of inflammatory mediators through gene modification. Therefore, it is of an important significance that further studying the specific molecular signal transduction mechanism of NF-κB was able to block the inflammation and treat the cognitive dysfunction. Some studies have shown that histone H3K27 demethylase Jmjd3 play a key role in regulating the expression and release of NF-κB downstream inflammatory mediators, but the epigenetic mechanism is not clear so far. Our previous researches showed that NF-κB, Jmjd3 and inflammatory cytokines expression were significantly increased in the hippocampus of hyperuricaemia rats. We hypothesized that the activation of NF-κB-Jmjd3 regulatory pathway may be involved in the regulation of hyperuricemia-induced cognitive dysfunction. Based on the previous research results, we established hyperuricemia rat model to study the role of NF-κB-Jmjd3 regulatory pathway in hippocampal inflammation, and also analyzed the relationship between methylation level and gene expression of NF-κB/p65, Jmjd3 and H3K27me3 along transcription start binding sites of inflammatory cytokines. Therefore, our study helps to provide new theoretical basis and therapeutic targets for the prevention and treatment of hyperuricaemia-induced cognitive dysfunction.

高尿酸血症是认知功能障碍的危险因素。近年报道高尿酸通过激活海马中NF-κB通路，诱导基因修饰调控炎症介质的表达和释放，导致认知功能障碍。故探索NF-κB通路具体分子信号转导机制对炎症的阻断和认知功能障碍的防治具有重要意义。研究表明组蛋白H3K27去甲基化酶Jmjd3在NF-κB调控下游炎症介质的表达释放中发挥关键作用，但目前其表观遗传调控机制尚不明确。我们前期研究发现高尿酸血症大鼠海马NF-κB、Jmjd3和多种炎症介质表达显著升高，推测NF-κB-Jmjd3调控通路活化可能参与高尿酸血症认知功能障碍的形成。本课题在前期成果基础上，构建高尿酸血症大鼠模型，研究高尿酸诱导NF-κB-Jmjd3通路在海马炎症中的作用，分析下游炎症介质转录起始位点区NF-κB/p65、Jmjd3以及H3K27me3甲基化水平与基因表达的关系，从而为高尿酸血症认知功能障碍的防治提供理论依据和治疗靶点。

尿酸持续性升高或长期嘌呤代谢紊乱对于多种神经退行性疾病的发生发展起到关键作用，是认知功能障碍的危险因素。近期研究表明高尿酸通过激活海马中NF-κB信号通路，诱导基因修饰调控炎症介质的表达和释放，导致认知功能障碍。表观遗传研究发现，基因表观事件的发生与神经炎症导致的认知功能障碍有着密切的关系，其中组蛋白甲基化修饰起关键作用。Jmjd3可催化H3K27me3去甲基化调控转录，涉及NF-κB信号通路转导，可视为终末调控环节，在调控炎症介质释放发挥重要作用。研究内容基于构建高尿酸血症大鼠模型，验证高尿酸诱导NF-κB-Jmjd3通路在海马炎症中的作用，分析下游炎症介质转录起始位点区NF-κB/p65、Jmjd3以及H3K27me3甲基化水平与基因表达的关系。研究结果：利用RT-PCR、Western blot和免疫荧光技术对高尿酸血症大鼠海马组织进行筛查，发现Jmjd3表达显著升高。通过海马定位插管术，将高浓度尿酸注入小鼠脑内，再利用分子生物技术检测海马组织中Jmjd3表达水平，同样显示出较高的表达水平。基于构建药理抑制模型，采用海马定位注射Jmjd3抑制剂（GSK-J4），再利用RT-PCR、Western blot、免疫荧光技术以及Morris水迷宫检测海马组织中炎症介质表达水平和小鼠的认知功能，结果显示NF-κB、IL-6、IL-1β和TNF-α等炎症介质表达水平显著降低，小鼠的认知功能也得到改善。海马组织中炎症介质的转录起始结合位点区域NF-κB/p65、Jmjd3、H3K27me3募集关系利用染色质免疫共沉淀试剂盒建立目标DNA文库，ChIP-qPCR分析在目标基因IL-6、IL-1β等炎症介质转录起始结合位点区域NF-κB/p65、Jmjd3、H3K27me3有募集关系。综上研究证实，明确组蛋白H3K27去甲基化酶Jmjd3介导高尿酸诱发的NF-κB信号通路下游炎症介质的表达与释放；揭示NF-κB-Jmjd3调控通路参与高尿酸血症海马炎症和认知功能障碍的发生发展及其表观遗传机制，从而为高尿酸血症认知功能障碍的防治提供理论依据和治疗靶点。