PPARgamma and PPARgamma agonists in septic shock

描述（由申请方提供）：脓毒症是对感染的全身性反应，其特征为血流动力学和代谢紊乱，导致休克、多器官系统衰竭和死亡。老年患者的发病率和死亡率不成比例地增加，其治疗是一个主要的临床挑战。因此，研究年龄依赖性脓毒症易感性的分子机制至关重要。科学证据表明，线粒体功能和生物能量学的深刻变化在疾病过程中发挥作用。功能障碍的线粒体的积累可能进一步增加氧化应激和细胞死亡。在过去的资助周期中，我们已经证明，年龄依赖性的易感性败血症与核激素受体，过氧化物酶体增殖物激活受体-？(PPAR?), PPAR？，和肝脏X受体-？(LXR?),众所周知的代谢和抗炎细胞反应的调节剂。在新的初步研究中，我们已经观察到，在败血症期间，与年轻动物（2-3个月大）相比，老年小鼠（11-12个月大）的肝脏线粒体复合物I功能受损。老年小鼠的这一事件与LC 3 II的表达减少有关，LC 3 II是自噬的标志物，自噬是使细胞能够处理有缺陷的线粒体的重要过程。我们还发现，老年小鼠的肝脏表现出减少核表达的过氧化物酶体增殖物激活受体？辅激活因子1-？（PGC-1？），线粒体生物发生的主调节器，并减少AMP激活的蛋白激酶（AMPK），一个重要的能量状态传感器，这是已知的激活PGC-1？并负调节自噬控制器，雷帕霉素复合物1（mTORC 1）的哺乳动物目标。有趣的是，用AMPK激活剂治疗能够改善脓毒症老年小鼠的肝功能并提高早期存活率。因此，这些初步数据提出了一个新的假设，即年龄相关的AMPK失调可能导致自噬和线粒体生物合成受损的恶性循环，从而增强对脓毒症的易感性并损害器官恢复。提出了三个具体目标来验证这一新概念。目的1：研究多菌性脓毒症小鼠自噬和线粒体生物合成的变化及其与AMPK活化的相关性。通过药理学功能获得和遗传学功能丧失的研究，在目标2中，我们将建立AMPK通过下游mTORC 1和PGC-1在调节自噬和线粒体生物合成中的确切作用？途径。药理学研究还将确定AMPK激活剂是否减轻脓毒症诱导的全身炎症反应、多器官衰竭和死亡。通过对年轻或老年小鼠原代肝细胞和肌细胞的体外研究，我们将在目标3中检验AMPK也影响PPAR？核功能的假设，PPAR？而LXR呢其随后有助于自噬和线粒体生物发生的机制。这些研究可能对开发新的治疗方法以降低脓毒症发病率和死亡率产生影响。

DESCRIPTION (provided by applicant): Sepsis is a systemic response to infection characterized by hemodynamic and metabolic derangements that result in shock, multiple organ system failure and death. The incidence and mortality is disproportionately increased in elderly patients, whose treatment represents a major clinical challenge. Thus, the investigation of the molecular mechanisms underlying the age-dependent susceptibility to sepsis is of utmost importance. Scientific evidence suggests that profound changes in mitochondrial function and bioenergetics play a role in the disease process. Accumulation of dysfunctional mitochondria may further increase oxidative stress and cell death. During the past funding cycle, we have demonstrated that the age-dependent susceptibility to sepsis is associated with a marked dysfunction of the nuclear hormone receptors, peroxisome proliferator-activated receptor-? (PPAR?), PPAR?, and liver X receptor-? (LXR?), well-known regulators of metabolic and anti- inflammatory cellular responses. In new preliminary studies, we have observed that mitochondrial complex I function is impaired in liver of old mice (11-12 months of age) when compared to young animals (2-3 months of age) during sepsis. This event in old mice is associated with reduced expression of LC3 II, a marker of autophagy, an important process that enables the cells to dispose defective mitochondria. We also have found that liver of old mice exhibits reduced nuclear expression of the PPAR? coactivator 1-? (PGC-1?), the master regulator of mitochondrial biogenesis, and reduced activation of AMP-activated protein kinase (AMPK), a crucial energy status sensor, which is known to activate PGC-1? and negatively regulate the autophagy controller, the mammalian target of rapamycin complex 1 (mTORC1). Interestingly, treatment with an AMPK activator was able to ameliorate liver function and improve early survival rate in septic old mice. Thus, these preliminary data raise the novel hypothesis that an age-related dysregulation of AMPK may lead to a vicious cycle of impaired autophagy and mitochondrial biogenesis, thus enhancing susceptibility to sepsis and impairing organ recovery. Three specific aims are proposed to validate this novel concept. In aim 1 we will investigate the changes of autophagy and mitochondrial biogenesis and their correlation with AMPK activation from infancy through senescence in polymicrobial sepsis in mice. With pharmacological gain-of-function and genetic loss-of-function studies, in aim 2 we will establish the precise role of AMPK in modulating autophagy and mitochondrial biogenesis through the downstream mTORC1 and PGC-1? pathways. Pharmacological studies will also establish whether AMPK activators mitigate sepsis-induced systemic inflammatory response, multiple organ failure and death. With in vitro studies in primary hepatocytes and myocytes from young or old mice, in aim 3 we will test the hypothesis that AMPK also affects the nuclear function of PPAR?, PPAR? and LXR?, which then contribute to the mechanisms of autophagy and mitochondrial biogenesis. These studies may have an impact in developing novel therapies to decrease sepsis morbidity and mortality.