CaMK: Central Regulators of the response to Surgical Sepsis

 描述(申请人提供)：在美国，每年有超过75万人患上严重的脓毒症，超过三分之一的人死亡，主要是由于多器官功能障碍(MOD)。尽管在过去的十年里，在识别MOD的细胞和分子机制方面取得了巨大的进展，但我们的知识仍然存在重大差距。最近的研究表明，最初的“器官功能障碍”是由于一种受调控的低代谢状态的诱导，其目的是保护细胞。然而，需要一个微妙的平衡。诱导不充分的，如 在衰老过程中观察到，可能会导致不可恢复的细胞损伤和器官功能障碍。另一方面，在长时间或过度严重的侮辱下，这种细胞保护机制实际上可能会导致器官损伤。滴定这种反应的能力可能为逆转MOD提供了一个机会。我们的实验室试图描述脓毒症时器官功能障碍的生物学决定因素。我们重点研究了钙离子的调节和信号转导，表明钙离子/钙调蛋白依赖的蛋白激酶(CaMK)家族调节自噬，这是一种保守的细胞保护反应，使细胞能够循环利用细胞质成分来适应应激时期。然而，Ca~(2+)信号对细胞的能量状态非常敏感，线粒体是有氧能量的主要来源，既调节又受Ca~(2+)的调节。我们现在假设，脓毒症诱导CaMK信号，该信号调节线粒体功能的适应性变化，以限制细胞损伤。这些机制在衰老过程中会发生变化，这可能会增加不可逆转的器官衰竭和死亡的风险。我们认为，在脓毒症早期，CaMK控制线粒体功能的适应性变化，并诱导低代谢的冬眠状态，其目的是保护细胞。严重的脓毒症扰乱了线粒体的功能，导致线粒体去极化，这一刺激事件激活了CaMK。这些CaMK标记了线粒体对CaMK依赖的有丝分裂的破坏(即线粒体的受控细胞降解)。同时，CaMK启动线粒体生物发生，恢复健康的线粒体群体、有氧代谢和器官功能。这些机制的表达在衰老过程中发生变化，这是器官功能障碍风险增加的基础。根据我们的假设，我们提出了以下具体目标：1.确定细胞内和线粒体钙信号激活CaMK家族，调节脓毒症时线粒体呼吸和功能的适应性降低。具体目的2.研究脓毒症时线粒体钙信号选择性靶向CaMK依赖的有丝分裂吞噬功能障碍的线粒体，并诱导CaMK依赖的线粒体生物发生。这些机制减轻了细胞损伤，促进了器官恢复。具体目的3.为了确定在衰老过程中，CaMK信号的进行性丧失是败血症期间吞丝分裂和线粒体生物合成减弱以及器官功能障碍风险增加的基础。这些调查具有很高的创新性，并以强有力的初步数据为基础。了解器官功能障碍的可逆原因的机制将使我们能够识别高危人群(即老年人)，并开发即使在已确定的器官功能障碍的背景下也能促进康复的治疗方法。

 DESCRIPTION (provided by applicant): Severe sepsis annually affects over 750,000 people in the US, and more than a third die, primarily due to multiple organ dysfunction (MOD). Though the last decade has seen immense progress in identifying the cellular and molecular mechanisms of MOD, major gaps in our knowledge still remain. Recent studies propose that the initial `organ dysfunction' is due to a regulated induction of a hypometabolic state, the purpose of which is cellular protection. However a delicate balance is required. Insufficient induction, as is observed in aging, may lead to irrecoverable cellular injury and organ dysfunction. On the other hand, with prolonged or overly severe insult, this mechanism of cytoprotection may actually contribute to organ injury. The ability to titrate this response may provide an opportunit to reverse MOD. Our lab seeks to delineate the biological determinants of organ dysfunction during sepsis. We have focused upon calcium (Ca2+) regulation and signaling to show that a family of Ca2+/calmodulin-dependent protein kinases (CaMK) regulate autophagy, a conserved cytoprotective response that enables a cell to recycle cytoplasmic components to adapt to periods of stress. However, Ca2+ signaling is inherently sensitive to the energy status of the cell, and mitochondria, the primary source of aerobic energy, both regulate and are regulated by Ca2+. We now hypothesize that sepsis induces CaMK signaling, which regulates adaptive changes in mitochondrial function to limit cellular injury. These mechanisms are altered during the aging process, which may underlie an increased risk of irreversible organ failure and death. We propose that early during sepsis the CaMK control adaptive changes in mitochondrial function and induce a hypometabolic, hibernating state, the purpose of which is to protect the cell. Severe sepsis perturbs mitochondrial function, leading to mitochondrial depolarization, the inciting event activating the CaMK. These CaMK mark damaged mitochondria for CaMK-dependent mitophagy (i.e. controlled cellular degradation of mitochondria). Concomitantly, the CaMK initiate mitochondrial biogenesis that restores a healthy mitochondrial population, aerobic metabolism, and organ function. Altered expression of these mechanisms occurs during the aging process, which underlies an increased risk of organ dysfunction. In accordance with our hypothesis we propose the following specific aims: Specific Aim 1. To determine that intracellular and mitochondrial Ca2+ signaling activate the family of CaMK to regulate adaptive reductions in mitochondrial respiration and function during sepsis. Specific Aim 2. To determine that mitochondrial Ca2+ signaling selectively targets dysfunctional mitochondria for CaMK-dependent mitophagy and induces CaMK-dependent mitochondrial biogenesis during sepsis. These mechanisms mitigate cellular injury and foster organ recovery. Specific Aim 3. To determine that during aging, a progressive loss in CaMK signaling underlies an attenuation in mitophagy and mitochondrial biogenesis and an increased risk of organ dysfunction during sepsis. These investigations are highly innovative and based upon strong preliminary data. Understanding the mechanisms of a reversible cause of organ dysfunction will enable us to identify high-risk populations (i.e. elderly) and develop therapies to foster recovery even in the setting of established organ dysfunction.