Sirt3: A Key Player Against PCB-Induced Mitochondrial Injury

描述（由申请人提供）：长期暴露于多氯联苯（PCBs）已与广泛的毒性作用相关，包括肝毒性、致癌性、激素紊乱和神经毒性。多氯联苯在环境中的持久性及其“生物蓄积性”使多氯联苯在高污染地区成为一个重大的健康危害，尽管美国在1977年禁止生产。最近的研究表明，多氯联苯和多氯联苯代谢物可以通过增加线粒体超氧化物和过氧化氢来增加线粒体功能障碍并引起氧化损伤，这表明线粒体是一个主要的目标。Sirtuin 3 （Sirt3）是哺乳动物线粒体中主要的去乙酰化酶，与线粒体乙酰化酶的调节和几种代谢酶（如MnSOD）的激活有关，以应对环境胁迫。此外，这种线粒体保真度蛋白的功能丧失似乎通过在体外和体内导致异常氧化代谢和基因组不稳定，增强了应激诱导的损伤过程。因此，当前应用的目标是确定Sirt3活性是否可以防止多氯联苯诱导的线粒体功能障碍、氧化应激和组织损伤。为了实现这一目标，我们将通过以下具体目的严格验证Sirt3功能调节线粒体乙酰酶改变以维持氧化稳态的假设，以应对pcb诱导的线粒体损伤。在Aim 1中，我们将确定Sirt3功能的丧失是否会在pcb诱导的线粒体功能障碍和氧化应激中破坏线粒体乙酰酶的维持。因此，该目的将确定Sirt3功能的丧失是否会增强多氯联苯诱导的线粒体功能障碍（aim 1a）和氧化应激（aim 1b），以及暴露于多氯联苯是否会改变负责保护线粒体乙酰体氧化稳态的Sirt3乙酰化靶标（aim 1c）。在Aim 2中，我们将确定Sirt3是否通过翻译后修饰关键乙酰赖氨酸来指导MnSOD活性（Aim 2a），从而防止pcb诱导的线粒体损伤，以及MnSOD中关键赖氨酸乙酰化状态的变化是否调节pcb诱导的线粒体功能障碍（Aim 2b）。在Aim 3中，我们将确定PCB暴露后线粒体功能的变化是否会导致Sirt3+/+和Sirt3-/-小鼠肝脏中线粒体相关基因的差异表达。成功完成这些特定目标将有助于对线粒体保真蛋白Sirt3在组织损伤和线粒体功能障碍中的作用的机制理解，并有可能确定由多氯联苯暴露引起的健康问题的药理学操作的新靶点。从拟议的研究中获得的信息也将推进NIEHS的使命，即减少由环境原因引起的人类疾病和功能障碍的负担。此外，该申请将为本科生和研究生提供符合区域计划目标的生物医学研究经验。

DESCRIPTION (provided by applicant): Chronic exposure to polychlorinated biphenyls (PCBs) has been associated with a wide range of toxic effects, including hepatotoxicity, carcinogenicity, hormonal disruption, and neurotoxicity. The persistence of PCBs in the environment combined with their "bioaccumulative" nature make PCBs a significant health hazard in highly contaminated areas, even though U.S. production was banned in 1977. Recent research has demonstrated that PCBs and PCB metabolites can increase mitochondrial dysfunction and cause oxidative injury via increases in mitochondrial superoxide and hydrogen peroxide, suggesting that mitochondria are a major target. Sirtuin 3 (Sirt3), which is the major deacetylase in mammalian mitochondria, has been linked to the regulation of the mitochondrial acetylome and activation of several metabolic enzymes (e.g., MnSOD) in response to environmental stresses. Furthermore, loss of function of this mitochondrial fidelity protein appears to enhance the injury processes induced by stress by contributing to aberrant oxidative metabolism and genomic instability in vitro and in vivo. Therefore, the goal of the current application is to determine whether Sirt3 activity can protect against PCB-induced mitochondrial dysfunction, oxidative stress, and tissue injury. In pursuit of this goal, we will rigorously test he hypothesis that Sirt3 function regulates the alterations in the mitochondrial acetylome to maintain oxidative homeostasis in response to PCB-induced mitochondrial injury through the following specific aims. In Aim 1, we will determine if loss of Sirt3 function disrupts the maintenance of the mitochondrial acetylome in response to PCB-induced mitochondrial dysfunction and oxidative stress. Thus, this aim will determine whether loss of Sirt3 function enhances PCB-induced mitochondrial dysfunction (Aim 1a) and oxidative stress (Aim 1b) and whether exposure to PCBs alters the Sirt3 acetylation targets responsible for protecting oxidative homeostasis in the mitochondrial acetylome (Aim 1c). In Aim 2, we will determine if Sirt3 protects against PCB-induced mitochondrial injury by directing MnSOD activity via post-translational modification of critical acetyl lysines (Aim 2a) and whether the changes in acetylation status of critical lysines in MnSOD modulate PCB-induced mitochondrial dysfunction (Aim 2b). In Aim 3, we will determine if the changes in mitochondrial function following PCB exposure result in differential expression of mitochondria-related genes in the livers of Sirt3+/+ and Sirt3-/- mice. Successful completion of these specific aims will contribute to the mechanistic understanding of the role of a mitochondrial fidelity protein, Sirt3, in tissue injury and mitochondrial dysfunction with potential identification of novel targets for pharmacologic manipulation for the health problems arising from PCB exposure. The information to be gained from the proposed studies will also advance the mission of the NIEHS to reduce the burden of human illness and dysfunction from environmental causes. Furthermore, this application will provide biomedical research experience for undergraduate and graduate students in line with the AREA program objectives.