The Effects of PP2A on TNF Signaling and Smoke-Induced Lung Injury

描述(申请人提供)：到目前为止，还没有有效的治疗方法可以抵消暴露在肺部的香烟烟雾的有害影响。事实上，在过去的30年里，慢性阻塞性肺疾病(COPD)的年龄调整死亡率上升了71%。为了改善这一趋势，需要制定更有效的治疗潜在疾病机制的战略。信号通路的异常激活在本病发生的病理生理反应中起着中心作用。这些蛋白的活性受到细胞内磷酸酶的严格调控；然而，我们对这些蛋白在慢性阻塞性肺疾病发病机制中的作用的了解极其有限。PP2A是存在于所有真核细胞中的主要丝氨酸苏氨酸蛋白磷酸酶。在其众多功能中，它对JNK和c-Jun都有去磷酸化和失活作用，因此，它是肺内肿瘤坏死因子信号通路的主要调节因子。我们最近发表了超氧化物歧化酶-1(SOD1)，一种肺部抗氧化剂，可以防止香烟烟雾引起的炎症和小鼠肺气肿的形成。我们实验室的进一步研究表明，SOD1和谷胱甘肽过氧化物酶-1(GPX1)增加了这些转基因小鼠肺中PP2A的活性，降低了AP-1的活性。这表明，抗氧化剂通过对PP2A的影响，可以改变这一关键信号通路在本病中的激活状态。我们假设，抗氧化剂通过增强PP2A活性从而减少肺内AP-1信号来保护肺免受吸烟所致的肺损伤。这一假说基于我们实验室以前的研究中的三个重要发现：1)SOD1/GPX1在不改变表达或蛋白水平的情况下增加肺中PP2A的活性；2)小鼠肺中PP2A活性的增加与肺中AP-1核结合的减少有关；3)JNK抑制减少了香烟烟雾诱导的小鼠肺部炎症。这项提案将解决抗氧化剂如何改变PP2A活性(目标1)。此外，它还将确定在这种疾病中，增加的PP2A活性是否能对抗肿瘤坏死因子信号和吸烟诱导的肺损伤(目标2)。最后，它将解决PP2A活动或分布是否改变肺气肿患者肺部的肿瘤坏死因子信号(目标3)。我们相信，从这些研究中获得的见解将为治疗这种疾病提供更有针对性的战略，并具有在未来为公共卫生做出重大贡献的强大潜力。此外，我们的发现不仅对COPD，而且对肿瘤坏死因子信号和炎症发挥核心作用的其他疾病也有重要意义。 公共卫生相关性：虽然大量研究已经阐明了蛋白激酶在慢性阻塞性肺疾病中的作用，但对蛋白磷酸酶的影响知之甚少。这项提议将通过确定PP2A，一种主要的真核丝氨酸/苏氨酸磷酸酶，如何改变肺部对香烟烟雾暴露的伤害反应，来促进公众健康。

DESCRIPTION (provided by applicant): To date, there are no effective therapies that can counteract the damaging effects of cigarette smoke exposure in the lung. In fact, the age-adjusted mortality for chronic obstructive pulmonary disease (COPD) has risen 71% over the past thirty years. To improve this trend more effective strategies of treating the underlying disease mechanisms need to be developed. Aberrant activation of signaling kinases exerts a central role on the pathophysiologic responses that occur in this disease. The activity of these kinases is tightly regulated by intracellular phosphatases; however, our knowledge of the role of these proteins in the pathogenesis of COPD is extremely limited. PP2A is the major serine threonine protein phosphatase present in all eukaryotic cells. Among its many functions, it dephosphorylates and inactivates both JNK and c-Jun; thus, it is a major regulator of the TNF signaling pathway in the lung. We have recently published that superoxide dismutase-1 (SOD1), a lung antioxidant, prevents cigarette smoke-induced inflammation and emphysema formation in mice. Further studies in our laboratory demonstrated that SOD1 and glutathione peroxidase-1 (GPX1) increase PP2A activity and decrease AP-1 activation in the lungs of these transgenic mice. This indicates that antioxidants, via their effects on PP2A, can alter the activation state of this pivotal signaling pathway in this disease. We hypothesize that antioxidants protect against smoke-induced lung injury by enhancing PP2A activity thereby decreasing AP-1 signaling in the lung. This hypothesis is based on three important findings from prior studies in our laboratory: 1) SOD1/GPX1 increases PP2A activity in the lung without altering expression or protein levels, 2) Increases in PP2A activity in the lungs of mice is associated with reduced AP-1 nuclear binding in the lung and 3) JNK inhibition decreases cigarette smoke-induced lung inflammation in mice. This proposal will address how antioxidants alter PP2A activity (Aim 1). In addition, it will determine whether increasing PP2A activity counters TNF signaling and smoke-induced lung injury in this disease (Aim 2). Finally, it will address if PP2A activity or distribution alters TNF signaling in the lungs of emphysema patients (Aim 3). We believe that the insights gained from these studies will provide more targeted strategies of treating this disease and have the strong potential to make a significant contribution to public health in the future. Moreover, our findings will have important implications not only for COPD but also for other diseases where TNF signaling and inflammation play a central role. PUBLIC HEALTH RELEVANCE: While a significant body of research has elucidated the role that protein kinases exert in COPD, much less is know about the effects of protein phosphatases. This proposal will advance public health by determining how PP2A, the primary eukaryotic serine/threonine phosphatase, alters the injurious responses to cigarette smoke exposure in the lung.