Prevention of anthracycline-induced cardiotoxicity by Nur77 activation

项目摘要 多柔比星（Dox）是一种蒽环类化疗药物，是一种公认的高效化疗药物 这种药物通常用于治疗多种癌症类型，但其使用受到心脏毒性的限制。Dox患者 治疗通常发展为不存在有效疗法的迟发性心肌病。分子 这种药物毒性的机制仍然知之甚少，可能是多因素的。DNA损伤， 线粒体功能障碍、p53激活和过度的心肌细胞凋亡是心肌细胞凋亡的主要原因。 Dox诱导的心脏毒性的发病机制，但药理学策略是否可以同时起作用 在接受Dox治疗的患者中逆转所有这些事件的方法尚未发现。我们的实验室 在研究核受体4A（NR4A）生物学在心血管疾病中的作用方面有着悠久的历史， 稳态和疾病。在最近的工作中，我们已经产生了大量的证据来支持 一个新的概念，减少心脏表达的Nur77，一个家庭成员的NR4A受体，发挥因果关系， 在Dox心肌病发病机制中的作用。我们发现：1）Nur77在心脏的表达是 在Dox处理的心肌细胞和心脏中显著降低，和2）心脏特异性过表达 Nur77有效地预防Dox诱导的心功能不全、心肌细胞凋亡和纤维化。此外，本发明还提供了一种方法， 我们已经确定DNA拓扑异构酶II β结合蛋白1（TopBP1）是Nur77的关键下游效应子 在心脏中，并且已经发现其表达在Dox处理的心脏中显著降低。更重要的是， 我们的初步数据表明Nur77通过诱导TopBP 1-拓扑异构酶II β来预防心脏毒性 (Top2β）相互作用，这反过来又有效地保护Top2 β/基因组DNA免受Dox诱导的损伤。 心这些数据使我们假设Nur77是一种重要的心脏保护剂， Nur 77的靶向激活可以有效预防Dox诱导的心肌病，同时具有极低或无 影响其抗癌行为。我们将在以下三个目标中检验这一假设。目标1将执行 通过使用Nur77心脏特异性敲除小鼠（cNur77-KO）进行功能丧失研究，以确定是否 Nur77的心脏特异性缺失通过增强细胞凋亡，纤维化， 以及心脏的炎症目的2将确定Nur77表现出其 对Dox诱导的心脏损伤的心脏保护作用。心脏特异性TopBP 1转基因和敲除 将使用小鼠来评估TopBP 1对小鼠中Nur77引发的心脏保护的贡献 Dox心脏毒性模型。目的3研究Nur77的药理学激活是否具有这种能力， 在不损害药物抗癌活性的情况下阻断Dox心肌病。成功完成 这些目标将指导我们开发新的治疗剂，以防止抗癌药物的选择性毒性， 心脏这种靶向在人类中的预测效用和可行性有利于翻译潜力， 拟议研究的最终影响。

Project summary Doxorubicin (Dox), an anthracycline chemotherapeutic, is a well-established and highly effective chemotherapy drug commonly used to treat multiple cancer types, but its use is limited by cardiotoxicity. Patients with Dox therapy often develop delayed cardiomyopathy for which no effective therapies exist. The molecular mechanisms of this drug toxicity remain poorly understood and are likely to be multifactorial. DNA damage, mitochondrial dysfunction, p53 activation, and excessive cardiomyocyte apoptosis are major contributors to the pathogenesis of Dox-induced cardiac toxicity, but whether a pharmacological strategy can simultaneously work to reverse all of these events in patients that receive Dox treatment has yet to be uncovered. Our laboratories have a long track record in studying the role of nuclear receptor 4A (NR4A) biology in cardiovascular homeostasis and disease. In recent work, we have generated a significant body of evidence to support the novel concept that reduced cardiac expression of Nur77, a family member of NR4A receptors, plays a causal role in the pathogenesis of Dox cardiomyopathy. We have found that 1) Cardiac expression of Nur77 is significantly reduced in Dox treated cardiomyocytes and hearts and that 2) Cardiac specific overexpression of Nur77 effectively prevents Dox induced cardiac dysfunction, cardiomyocyte apoptosis, and fibrosis. In addition, we have identified DNA topoisomerase IIβ-binding protein 1 (TopBP1) as a key downstream effector of Nur77 in the heart, and have found that its expression is substantially reduced in Dox-treated hearts. More importantly, our preliminary data indicate that Nur77 prevents cardiac toxicity by inducing TopBP1-topoisomerase IIβ (Top2β) interactions, which in turn effectively shields Top2β/genomic DNA from Dox-induced damage in the heart. These data led us to hypothesize that Nur77 serves as an important cardioprotective agent and that targeted activation of Nur77 can effectively prevent Dox-induced cardiomyopathy while having minimal to no effects on its anti-cancer behaviors. We will test this hypothesis in the following three aims. Aim 1 will perform loss-of-function studies by employing Nur77 cardiac specific knockout mice (cNur77-KO) to determine whether cardiac specific deletion of Nur77 exacerbates Dox-induced cardiotoxicity through enhanced apoptosis, fibrosis, and inflammation in the heart. Aim 2 will determine the underlying mechanisms by which Nur77 exhibits its cardioprotective effects against Dox-induced cardiac injury. Cardiac specific TopBP1 transgenic and knockout mice will be used to assess the contribution of TopBP1 to the Nur77-initiated cardiac protection in mouse models of Dox cardiotoxicity. Aim 3 will study whether pharmacological activation of Nur77 holds the capacity to block Dox cardiomyopathy without compromising anti-cancer activity of the drug. Successful completion of these aims will guide us to develop new therapeutic agents to prevent selective toxicity of anticancer drugs to the heart. The predicted utility and feasibility of such targeting in humans favors the translational potential and ultimate impact of the proposed studies.