Imaging and Treating Inflammation in Stroke by Targeting Myeloperoxidase

描述（由申请人提供）：中风的治疗仅限于少数已批准的治疗方案，如溶栓治疗，这些治疗方案必须在严格的短时间内进行，导致许多患者被排除在外。超过这个时限，有效的治疗方案就更少了。因此，扩展目前的治疗方法并开发新的治疗方案将是非常可取的。已知炎症可延长缺血性脑损伤并对预后产生不利影响。虽然抗炎疗法在实验模型中是有效的，但到目前为止，人体试验还没有显示出明显的益处。虽然这种差异可能是多因素的，但其中一个因素可能与使用广泛的抗炎剂而不是针对特定分子途径和酶的更集中的治疗有关，这些治疗被证明是有害的，同时保持炎症反应的有益效果。评估和实施新型抗炎治疗中风的一个主要障碍是缺乏一种无创手段来跟踪中风期间炎症的演变，以观察靶向治疗在体内动物模型和人类中的影响。髓过氧化物酶（MPO）是一种高度氧化性和破坏性的酶，由许多活化的炎症细胞分泌，在中风病变中大量发现。我们已经证明MR显像剂bis-5HT- DTPA-Gd （MPO- gd）对检测MPO活性具有高度敏感性和特异性。我们发现MPO- gd成像可以报告和连续跟踪MPO活动，以获得以前只能从离体研究中获得的信息。MPO- gd成像结果与梗死面积和梗死后21天检测到的MPO活性密切相关。在初步研究中，用MPO抑制剂治疗的野生型小鼠和MPO缺陷小鼠在第21天的梗死体积显著减少。因此，我们假设分泌的MPO是炎症和梗死扩展的关键生物标志物，降低MPO活性将改善卒中预后。本研究的总体目标是研究MPO与炎症在卒中演变中的关系，并通过调节MPO活性/表达并结合溶栓治疗来制定治疗方案，以限制炎症损伤。具体目的是1)建立MPO作为脑卒中炎症的成像生物标志物，2)评估MPO作为脑卒中治疗靶点，3)确定MPO抑制与溶栓治疗之间的协同治疗方案。这些研究将为MPO分子成像在未来研究中风炎症的基本病理生物学和旨在改变炎症的新型治疗干预措施的影响提供一个平台。最终，该提案的结果将为转化项目奠定基础，通过提供一种无创方法来评估中风期间的炎症状态，改进动物和人类新型抗炎疗法的评估，并为中风提供新的治疗靶点。

DESCRIPTION (provided by applicant): Treatment of stroke is limited to a few approved therapeutic options, such as thrombolytic therapy, that have to be administered within rigid short timeframes resulting in the exclusion of many patients. Beyond the this timeframe even fewer effective treatment options exist. Therefore, extending current therapies and developing new treatment options would be highly desirable. Inflammation has been known to extend ischemic brain injury and adversely affect outcome. Although anti-inflammatory therapies can be effective in experimental models, thus far human trials have not shown a clear benefit. While the discrepancy is likely multifactorial, one contributing factor may be related to the use of broad anti-inflammatory agents rather than more focused therapies that target specific molecular pathways and enzymes demonstrated to be deleterious while maintaining the beneficial effects of the inflammatory response. A central obstacle in evaluating and implementing novel anti-inflammatory therapies for stroke is the lack of a noninvasive means to track the evolution of inflammation during stroke to observe the impact of targeted therapies in in vivo animal models and humans. Myeloperoxidase (MPO), a highly oxidizing and damaging enzyme secreted by many activated inflammatory cells, is found abundantly in stroke lesions. We have shown that the MR imaging agent, bis-5HT- DTPA-Gd (MPO-Gd) is highly sensitive and specific for detecting MPO activity. We found that MPO-Gd imaging can report and serially track MPO activity to obtain information that was previously only available from ex vivo studies. MPO-Gd imaging results correlated well with infarct volume and detected MPO activity in the infarct even 21 days post occlusion. In preliminary studies, wild-type mice treated with an MPO inhibitor as well as MPO deficient mice demonstrated substantial decrease in day 21 infarct volume. Therefore, we hypothesize that secreted MPO is a key biomarker for inflammation and infarct propagation, and that reducing MPO activity would improve stroke outcome. The overall goals of this proposal are to study the relationship between MPO and inflammation in stroke evolution and to develop treatment regimens to limit the inflammatory damage by modulating MPO activity/expression and in combination with thrombolytic therapy. The specific aims are 1) to establish MPO as an imaging biomarker for inflammation in stroke, 2) to assess MPO as a treatment target for stroke, and 3) to determine synergistic treatment regimens between MPO inhibition and thrombolytic therapy. The proposed investigations will provide a platform for the use of MPO molecular imaging in future investigations of basic pathobiology of inflammation in stroke and the impact of novel therapeutic interventions aimed at altering inflammation. Ultimately, the results of this proposal will set the stage for translational projects to benefit stroke patients by providing a noninvasive method to assess the inflammatory status during stroke, improving assessment of novel anti-inflammatory therapies in animals and in humans, and offering a new treatment target for stroke. PUBLIC HEALTH RELEVANCE: Because MPO-Gd is highly stable, nontoxic, and can be used to image MPO activity in a a wide range of clinically important inflammatory diseases, these investigations may provide the basis for application of MPO imaging for diagnostic evaluation of inflammation in humans and MPO inhibition for novel therapeutic interventions to improve outcome in stroke and other diseases.