Activity and therapeutic antagonism of the TP receptor in cardiomyopathy of muscular dystrophy

项目摘要 杜氏肌营养不良症（DMD）的特征是膜不稳定，钙内流和坏死， 肌细胞在心脏中，心肌细胞的进行性破坏导致纤维化和一种潜在的扩张性心肌炎。 心肌病心力衰竭是DMD患者死亡的主要原因，其发生在 第三个十年，尽管传统的心脏支持疗法。我们的初步研究表明， 血栓素-前列腺素样受体（TPr）是导致心肌细胞死亡的驱动力 和纤维化，防止这种活动可以保护肌营养不良症患者的心脏功能。我们 研究小组发现，用拮抗剂伊非曲班阻断TPr活性可改善存活率、心脏功能和 在两种严重DMD小鼠模型和一种肢带型肌营养不良模型中的心脏纤维化。基于 在这些研究中，伊非曲班在DMD患者中的2期临床研究目前正在招募。然而，关键 存在知识差距。我们知道，TPr激活导致纤维化与增强的肿瘤生长因子（TGF）- β活性，但不是它如何激活TGFβ。在这里，我们将测试TPr激活介导TGF-β的假设， 从大的潜在复合物中释放，导致心脏纤维化。我们将在TPr的上下文中对此进行测试 使用mdx/utrn（+/-）小鼠或含有潜伏性TGF-β结合蛋白-4（LTBP 4）的mdx小鼠， 多态性，并与分离的成纤维细胞确认。我们的早期数据还表明， TPr调节心肌细胞膜稳定性、心律失常和心脏功能可能与此不同。 我们假设这是通过调节钙内流和钙激活信号传导发生的， 拮抗作用以与标准护理疗法相加的方式改善了mdx/utrn（+/-）小鼠中的这种情况。的DMD 含有心肌细胞特异性TPr缺失的小鼠模型将心肌细胞起始的 成纤维细胞效应最后，我们正在进行的试验提供了一个评估分子结果的独特机会 在人类患者中纵向地进行，并鉴定生物标志物以反映对TPr拮抗作用的心脏反应。为 为此，我们将对DMD患者参与者的外周血单核细胞进行表达谱分析， 伊非曲班临床试验，与治疗反应比较。解决这些问题将阐明 TPr在DMD心肌病中的作用，预测TPr拮抗DMD心肌病的人体反应和机制， DMD患者，并可以提供有价值的替代终点的药物反应。

PROJECT SUMMARY Duchenne muscular dystrophy (DMD) is characterized by membrane instability, calcium influx, and necrosis of myocytes. In the heart, progressive breakdown of cardiomyocytes causes fibrosis and an insidious dilated cardiomyopathy. Heart failure is the primary cause of death in patients with DMD, which occurs around the third decade despite traditional cardiosupportive therapeutics. Our preliminary research suggests that signaling from the thromboxane-prostanoid receptor (TPr) in the heart is a driving force leading to cardiomyocyte death and fibrosis, and preventing this activity may preserve cardiac function in muscular dystrophy patients. Our group has found that blocking TPr activity with the antagonist ifetroban improves survival, cardiac function, and cardiac fibrosis in two mouse models of severe DMD and a model of limb-girdle muscular dystrophy. Based on these studies, a Phase 2 clinical study of ifetroban in DMD patients is currently recruiting. However, key knowledge gaps exist. We know that TPr activation leads to fibrosis with enhanced tumor growth factor (TGF)- β activity, but not how it activates TGFβ. Here we will test the hypothesis that TPr activation mediates TGF-β release from the large latent complex, leading to cardiac fibrosis. We will test this in the context of TPr blockade or deletion, using mdx/utrn(+/-) mice or mdx mice containing latent TGF-β binding protein-4 (LTBP4) polymorphism, and confirm with isolated fibroblasts. Our early data also suggests that the mechanism by which TPr regulates cardiomyocyte membrane stability, arrhythmia, and cardiac function may be distinct from this. We hypothesize this occurs via regulation of calcium influx and calcium-activated signaling, and that antagonism improves this in mdx/utrn(+/-) mice in a manner additive with standard-of-care therapies. A DMD mouse model containing a cardiomyocyte-specific deletion of TPr will separate cardiomyocyte-initiated from fibroblast effects. Finally, our ongoing trial presents a unique opportunity to assess molecular outcomes longitudinally in human patients, and identify biomarkers to reflect the cardiac response to TPr antagonism. For this aim, we will do expression profiling of peripheral blood mononuclear cells from DMD patient participants in the ifetroban clinical trial, compared with response to treatment. Resolving these questions will illuminate the role of the TPr in DMD cardiomyopathy, anticipate human response and mechanism of TPr antagonism in DMD patients, and could provide valuable surrogate endpoints for drug response.