Myeloperoxidase, imaging biomarker and treatment target for multiple sclerosis

描述(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疾病。然而，由于MS的症状和常规MRI表现都是非特异性的，并不总是相互对应的，因此及时诊断疾病活动和治疗随访面临着巨大的挑战。此外，目前治疗多发性硬化症的方法只有部分有效，患者往往有突破性的疾病活动。髓过氧化物酶(MPO)是一种高度氧化的酶，在炎症中由活跃的巨噬细胞/小胶质细胞和某些单核细胞大量分泌，在活动期炎症性MS病变中发现。我们最近的研究表明，磁共振显像剂双-5-羟色胺-DTPA-Gd(MPO-Gd)在体外和体内实验中对MPO活性具有高度的特异性和敏感性。我们发现MPO-Gd无毒，具有很高的Gd稳定性，即使在高剂量下也能很好地被动物耐受。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，并可以识别出比常规MR对比成像多40%和小40%的病变。我们和其他人还发现，在MS和MS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诱导的小鼠中应用MPO特异性抑制剂可以减少炎性细胞募集并改善症状。因此，我们推测MPO不仅是追踪MS疾病活动性的理想生物标志物，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的免疫调节治疗主要针对淋巴细胞，通过改变巨噬细胞/小胶质细胞功能的最终产物(即MPO活性)来针对巨噬细胞/小胶质细胞炎症，这可能是治疗MS的一个新领域。此外，这一策略可能与针对淋巴细胞的治疗相结合，以潜在地达到协同有益的效果，从而允许使用较低剂量的每种治疗方法来降低药物毒性。因此，利用EAE小鼠模型，该建议的目的是1)通过跟踪和调节MPO的活性来建立炎症脱髓鞘的生物标志物，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相关联；2)建立MPO-Gd成像作为追踪治疗效果的更好方法，并设计新的协同治疗方案来治疗淋巴细胞和巨噬细胞/小胶质细胞炎症。我们期待这项提案的结果将验证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并使用非特异性常规成像验证的药物开发策略，并为未来MPO-Gd成像和MPO治疗向人类多发性硬化症的转化奠定基础。 公共卫生相关性：这项建议旨在验证对髓过氧化物酶(MPO)活性高度敏感和特异的MR显像剂MPO-Gd，以非侵入性跟踪多发性硬化症小鼠模型中的炎性疾病活动，并更好地了解MPO在活动性脱髓鞘发病机制中所起的作用。这项建议将进一步确定优化的治疗方案，以改善目前的治疗方法。由于人类MPO的活性是老鼠MPO的数倍，MPO-Gd成像具有潜在的平移性。这项研究的结果可以改善对治疗变化的跟踪，使更及时和准确地诊断MS患者的亚临床活动性炎症，并通过靶向巨噬细胞/小胶质细胞功能开辟新的治疗领域，这些功能可以单独使用，也可以与当前的治疗方案协同使用，以减少剂量和毒性，最终为患者带来更好的结果。

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. PUBLIC HEALTH RELEVANCE: This proposal seeks to validate the MR imaging agent MPO-Gd that is highly sensitive and specific to myeloperoxidase (MPO) activity, to noninvasively track inflammatory disease activity in a mouse model of multiple sclerosis and to better understand the roles MPO plays in the pathogenesis of active demyelination. This proposal will further identify optimized therapeutic regimens to improve current therapy. As human MPO is many times more active than mouse MPO, MPO-Gd imaging is potentially translational. The results of this study could improve tracking of treatment changes, allow more timely and accurate diagnosis of subclinical active inflammation in MS patients, and open up a new area for therapy by targeting macrophage/microglial function that may be used either alone or in synergy with current therapy to reduce dose and toxicity, and ultimately lead to better outcome for patients.