联合应用QSM及MRS技术在体研究铁螯合剂对多发性硬化脑内铁超载及氧化应激状态的干预机制

The high cost of immunomodulatory therapy has hampered its wide use for multiple sclerosis (MS) in clinic. Iron overload is a hot topic currently in the pathogenesis of MS. Iron chelation therapy targeting to decease iron overload and block iron-relative pathological events is a potential novel strategy for MS patients. Preliminary clinical studies have confirmed the therapeutic effect of iron chelation on MS. However, the therapeutic mechanism and the reasons of various clinical responses to iron chelation therapy remain unknown due to the limited investigation technology. Our preliminary study found that the overload level of iron varied significantly among individual MS patient and also depended on the disease duration. The new MRI technologies, such as quantitative susceptibility mapping (QSM) and MR spectroscopy (MRS), enable us to quantify and monitor the levels of cerebral iron and glutathione, an endogenous biomarker for cerebral oxidative stress in vivo. Thus, in this project, we plan to apply iron chelation therapy on experimental autoimmune encephalomyelitis (EAE) mice under different therapeutic courses. We will monitor the dynamic changes of cerebral iron and glutathione levels pre- and post-therapy by using MRI (QSM and MRS) and histological techniques (mass spectrometry test, oxygen free radicals and mitochondrial function tests), and then compare the results between MRI and histological techniques. This project aims to study the impact of systemic administration of iron chelation on the local cerebral iron overload and iron-related oxidative stress in EAE mouse model, so as to assess the differences of clinical efficacy caused by iron chelation therapy administrated in different disease courses. We believe this study will elucidate the therapeutic mechanism of iron chelation, provide the scientific evidence for the development and optimization of the therapeutic strategy, as well as to establish a non-invasive tool for dynamic monitoring and assessing its clinical efficacy.

多发性硬化(MS) 免疫调节治疗的昂贵价格限制了其临床应用。铁超载是目前MS发病机制的研究热点，以其为靶点的驱铁治疗是MS新的潜在治疗手段。初期临床研究已证实MS驱铁治疗的有效性，但限于技术条件未能阐明其治疗机制及临床疗效存在显著差异的原因。本项目前期研究发现①MS患者脑铁超载具有显著个体差异性和病程依赖性；②MRI新技术QSM和MRS可以在体定量检测脑铁及谷胱甘肽(脑氧化应激状态的内源性生物标记)的含量。据此，本项目拟在不同病程EAE模型上采用铁螯合剂进行驱铁治疗，采用QSM及MRS技术动态监测治疗前后脑内铁和谷胱甘肽的含量，并与铁质谱分析、氧自由基及线粒体功能等检测结果进行原位对照，研究全身用药的驱铁治疗对脑内局部铁负荷及脑内氧化应激状态的影响，量化评估不同病程MS驱铁治疗的疗效差异，为阐明驱铁治疗的治疗机制，制定并优化临床应用策略，建立无创性疗效评估手段提供可靠的理论依据。

多发性硬化(MS) 是中枢神经系统最常见的慢性炎症性脱髓鞘疾病，主要累及中青年，且复发迁延、致残率高。免疫调节治疗为其主要的治疗方法，但昂贵的价格限制了其临床应用。铁超载是目前MS发病机制的研究热点，以其为靶点的驱铁治疗极有可能是MS新的潜在治疗手段。本项目前期研究也发现MS病灶内确实存在铁超载现象，据此提出假说：“铁超载是MS重要的致病机制之一，且通过病灶局部氧自由基ROS增加介导组织损伤”。本项目通过一系列临床及动物实验不仅验证了上述假说，而且在脑铁含量和氧自由基含量的在体无创性检测的MRI方法学上有重大突破。本项目的主要研究结果如下：①MS病灶内确实存在铁超载现象，MS病灶内的铁超载程度与病灶的年龄密切相关，变化最快的是新发的强化MS病灶。②铁超载不仅发生于MS病灶内，也对MS患者看似正常脑区的铁含量产生影响。③MS病灶局部氧自由基ROS增加确实是MS病灶铁超载的组织损伤途径之一。④驱铁治疗后MS病灶内ROS含量下降，进一步证实ROS增加参与了铁超载所致的组织损伤，也提示MS驱铁治疗极有可能成为新的潜在得MS治疗手段。⑤研发了ROS－CEST成像技术，首次开创了在体无创性检测氧自由基ROS的MRI成像方法。⑥建立了在体无创性检测铁含量的MRI成像方法QSM，验证了QSM测量磁性物质的准确性。本项目参与建立的ROS－CEST和QSM成像为所有涉及脑内铁含量和氧自由基含量变化的疾病的机制研究提供了方法学上的突破。本项目验证了MS铁超载的致病机制假说，并初步尝试了MS驱铁治疗的可行性，为以铁超载作为潜在治疗靶点的 MS 驱铁治疗提供可靠的理论依据和坚实的实验基础。