Myeloperoxidase, imaging biomarker and treatment target for multiple sclerosis

描述（由申请人提供）：多发性硬化症（MS）是影响年轻人的最常见的非创伤性神经系统疾病。然而，由于MS的症状和常规MR成像结果都是非特异性的，并且并不总是相互对应，因此疾病活动性的及时诊断和治疗随访提出了重大挑战。此外，目前治疗多发性硬化症的方法只是部分有效，患者往往有突破性的疾病活动。髓过氧化物酶（Myeloperoxidase， MPO）是一种高度氧化的酶，由活跃的巨噬细胞/小胶质细胞和炎症中的某些单核细胞大量分泌，在活跃的炎性MS病变中发现。我们最近在体外和体内实验中表明，MR显像剂bis-5HT-DTPA-Gd （MPO- gd）对MPO活性具有高度特异性和敏感性。我们发现MPO-Gd无毒，具有高Gd稳定性，即使在高剂量下也能被动物耐受。我们发现在小鼠实验性自身免疫性脑脊髓炎（EAE）模型中，MPO-Gd成像可以检测和确认临床前疾病，并且与常规MR对比成像相比，可以识别出40%以上和40%以下的病变。我们和其他研究人员还发现，在多发性硬化症和多发性硬化症动物模型中，髓过氧化物酶活性与小胶质细胞/巨噬细胞浸润和脱髓鞘区域高度相关。初步研究表明，在EAE诱导的小鼠中给予mpo特异性抑制剂可减少炎症细胞募集并改善症状。因此，我们推测MPO不仅是跟踪MS疾病活动的理想生物标志物，而且可能在脱髓鞘的发病机制中发挥重要作用。由于目前针对MS的免疫调节疗法主要针对淋巴细胞，通过改变巨噬细胞/小胶质细胞功能的最终产物（即MPO活性）来靶向巨噬细胞/小胶质细胞炎症，可能是治疗MS的一个新领域。此外，该策略可能与针对淋巴细胞的治疗相结合，潜在地实现协同有益效果，从而允许使用更低剂量的每种治疗来降低药物毒性。因此，本研究旨在利用EAE小鼠模型，1)通过跟踪和调节MPO在疾病恶化和缓解过程中的活性，将成像、生化和组织病理学变化与炎症和抗炎标志物以及免疫细胞群的变化联系起来，建立MPO作为炎症脱髓鞘的生物标志物，2)建立MPO- gd成像作为跟踪治疗效果的优越方法。并设计新的协同治疗方案，治疗淋巴细胞和巨噬细胞/小胶质细胞炎症。我们期望这项研究结果将验证MPO作为一种成像生物标志物和治疗靶点，改变目前专注于淋巴细胞和使用非特异性常规成像验证的药物开发策略，并为MPO- gd成像和MPO治疗未来转化为人类MS奠定基础。

DESCRIPTION (provided by applicant): Multiple sclerosis (MS) is the most common non-traumatic neurological disorder affecting young adults. Yet because both symptoms and conventional MR imaging findings of MS are nonspecific and do not always correspond to each other, prompt diagnosis of disease activity and treatment follow-up present significant challenges. Furthermore, current therapies for MS are only partially effective and patients often have breakthrough disease activity. Myeloperoxidase (MPO) is a highly oxidizing enzyme abundantly secreted by active macrophages/microglial cells and certain monocytes in inflammation, and is found in active inflammatory MS lesions. We have recently shown that the MR imaging agent, bis-5HT-DTPA-Gd (MPO-Gd) is highly specific and sensitive to MPO activity in in vitro and in vivo experiments. We have found that MPO-Gd to be nontoxic, possesses high Gd stability, and is well tolerated by animals even at high doses. We found that MPO-Gd imaging can detect and confirm preclinical disease, and can identify 40% more and 40% smaller lesions compared to conventional MR contrast imaging in the mouse experimental autoimmune encephalomyelitis (EAE) model. We and others have also found that myeloperoxidase activity is highly associated with areas of microglia/macrophage infiltration and demyelination both in MS and animal models of MS. Preliminary studies administering an MPO-specific inhibitor in mice induced with EAE reduced inflammatory cell recruitment and ameliorated symptoms. Therefore, we hypothesize that MPO is not only an ideal biomarker to track MS disease activity, but may also play an important role in the pathogenesis of demyelination. As current immunomodulatory therapies for MS target predominately lymphocytes, targeting macrophage/microglial inflammation by modifying the end product of macrophage/microglia function (i.e., MPO activity), may represent a new area for treating MS. In addition, this strategy may be combined with therapies targeting lymphocytes to potentially achieve synergistic beneficial effects, thus allowing lower doses of each therapy to be used to decrease drug toxicity. Therefore, using the EAE mouse model, this proposal aims to 1) establish MPO as a biomarker for inflammatory demyelination by tracking and modulating MPO activity as the disease exacerbates and remits, correlating imaging, biochemical, and histopathological changes to inflammatory and anti-inflammatory markers and immune cell populations shifts, and 2) establish MPO-Gd imaging as a superior method for tracking treatment effects, and design novel synergistic therapeutic regimen to treat both lymphocytic and macrophage/microglial inflammation. We expect the results of this proposal will validate MPO as an imaging biomarker and treatment target, change drug development strategies that are currently focused on lymphocytes and validated using nonspecific conventional imaging, and set the stage for future translation of MPO-Gd imaging and MPO treatment to human MS.