Age effects on liver inflammation and injury

年龄对肝脏炎症和损伤的影响

• 批准号: 8293122
• 负责人: Alex B. Lentsch
• 金额: $ 29.89万
• 依托单位: UNIVERSITY OF CINCINNATI
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-01 至 2015-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8293122
• 关键词: 26S proteasome; Acute; Adult; Age; Age-Months; Binding; Biochemical; Cell Death; Cells; Childhood; Clinical; Clinical Research; Complication; Data; Defect; Event; Excision; Funding; Gene Expression; Hepatic; Hepatocyte; Incidence; Individual; Inflammation; Inflammatory Response; Injury; Ischemia; Kupffer Cells; Lead; Liver; Liver Dysfunction; Liver Failure; Modeling; Molecular Chaperones; Morbidity - disease rate; Multiple Organ Failure; Mus; NF-kappa B; Nature; Organ Transplantation; Organ failure; Pathogenesis; Patients; Phosphorylation; Population; Process; Protein Subunits; Proteins; Reperfusion Injury; Reperfusion Therapy; Resistance; Role; Stress; Testing; Tissues; Transfection; Transplantation; Trauma; Vascular Diseases; Work; age effect; age related; base; cell type; cytokine; graft function; in vivo; inhibitor/antagonist; mortality; multicatalytic endopeptidase complex; particle; public health relevance; response to injury; restoration; therapeutic development; therapeutic target; valosin-containing protein

DESCRIPTION (provided by applicant): Hepatic ischemia/reperfusion (I/R) injury is a primary cause of liver dysfunction in both pediatric and adult patients. During the previous funding period, using an established model of murine hepatic I/R, we found that old mice (12-13 months of age) have significantly greater liver injury after I/R than do young mice (4-6 weeks of age). These findings are consistent with clinical studies of trauma patients which suggest that pediatric patients have a far lower incidence of multiple organ dysfunction syndrome than do adult patients. We discovered that the increased injury was associated with decreased activation of the transcription factor, NF- kB, in hepatocytes of old mice. Our previous work suggests that NF-kB has divergent functions that are dependent upon the cell type involved. For example, activation of NF-kB in Kupffer cells appears to drive the inflammatory response, while NF-kB activation in hepatocytes appears to function in a cell-protective mechanism. Our more recent studies have begun to explore the mechanism by which NF-kB activation is different in young and old mice. We have found a major defect in the processing of the cytoplasmic inhibitor of NF-kB, IkBa, in old mice. First, we have shown that gene expression of specific subunits of the 19S regulatory particle of the 26S proteasome are significantly reduced in old mice. These protein subunits are involved in recruitment of ubiquitinylated substrates to the proteasome for degradation. Our studies suggest that decreased expression of these subunits reduce the degradation of IkBa and therefore decrease NF-kB activation in the livers of old mice. Secondly, we have preliminary data suggesting that a mode of recruitment of ubiquitinlylated IkBa to the proteasome is altered in old mice. The cytoplasmic chaperone, valosin- containing protein (VCP), is known to bind to ubiquitinylated proteins, including IkBa, and facilitate their recruitment to the proteasome. Phosphorylation of VCP by Akt regulates VCP's association with ubiquitinylated proteins. Our preliminary data demonstrate a defect in Akt activation in the livers of old mice. As such, the global hypothesis of this project is that age-dependent alterations to components of the proteasome and to substrate recruitment mechanisms in hepatocytes of old mice results in decreased activation of NF-kB which renders them more susceptible to ischemic stress than hepatocytes from young mice, resulting in increased oxidative tissue injury and cell death. We will test this hypothesis with three specific aims. Aim 1 will determine the mechanism by which age alters the chaperone function of VCP. Aim 2 will determine the specific roles of individual subunits of the 19S regulatory particle on substrate recruitment and degradation by the 26S proteasome. Finally, Aim 3 will determine whether in vivo protein transfection of 19S subunits and/or constitutively active Akt restores normal activation of NF-kB and reduces liver injury induced by I/R in old mice. These studies may identify therapeutic targets that could help lead to new treatments for acute liver injury resulting from a number of different clinical events including trauma, surgery, transplantation, vascular disease, etc. PUBLIC HEALTH RELEVANCE: This proposal will identify biochemical changes in liver cells that occur with age. A better understanding of these changes may lead to the development of therapeutic treatments that could be applied to patients undergoing liver resection and transplantation that would enhance organ and graft function and reduce morbidity and mortality.

描述（由申请人提供）：肝缺血/再灌注（I/R）损伤是儿科和成人患者肝功能障碍的主要原因。在上一个资金期间，使用既定的鼠肝I/R模型，我们发现老鼠（12-13个月大）在I/R后的肝损伤明显高于年轻小鼠（4-6周龄）。这些发现与创伤患者的临床研究一致，这表明小儿患者的发病率要比成年患者低得多。我们发现增加的损伤与老鼠肝细胞中转录因子NF-KB的激活降低有关。我们以前的工作表明，NF-KB具有不同的功能，取决于所涉及的细胞类型。例如，Kupffer细胞中NF-KB的激活似乎可以驱动炎症反应，而肝细胞中的NF-KB激活似乎在细胞保护机制中起作用。我们最近的研究开始探索年轻小鼠NF-KB激活不同的机制。我们在老鼠中发现了NF-KB，IKBA的细胞质抑制剂的加工中的主要缺陷。首先，我们已经表明，在旧小鼠中，26S蛋白酶体的19S调节粒子的特定亚基的基因表达显着降低。这些蛋白质亚基参与了将泛素化底物募集到蛋白酶体降解的。我们的研究表明，这些亚基的表达降低减少了IKBA的降解，因此减少了旧小鼠肝脏中NF-KB的激活。其次，我们有初步数据表明，在旧小鼠中募集了泛素化的ikba为蛋白酶体的募集方式。已知细胞质伴侣，含瓣膜蛋白（VCP），与泛素化蛋白（包括IKBA）结合，并促进它们募集到蛋白酶体中。 AKT对VCP的磷酸化调节VCP与泛素化蛋白的关联。我们的初步数据证明了旧小鼠肝脏中Akt激活的缺陷。因此，该项目的全球假设是，蛋白酶体的成分的年龄依赖性改变以及旧小鼠肝细胞中的底物募集机制导致NF-KB的激活降低，这使得它们对缺血性压力更敏感，而不是年轻小鼠的肝细胞，从而增加了氧化损伤，从而增加了氧化损伤，从而增加了氧化损伤。我们将以三个特定的目标检验这一假设。 AIM 1将确定年龄改变VCP的伴侣功能的机制。 AIM 2将确定19S调节粒子各个亚基在26S蛋白酶体降解和降解中的特定作用。最后，AIM 3将确定19S亚基的体内蛋白转染和/或组成型活性AKT是否会恢复NF-KB的正常激活，并减少旧小鼠I/R引起的肝损伤。这些研究可能会确定可以帮助导致许多不同临床事件引起的急性肝损伤治疗的治疗靶标，包括创伤，手术，移植，血管疾病等。 公共卫生相关性：该提案将确定随着年龄的增长而发生的肝细胞的生化变化。对这些变化的更好理解可能会导致治疗性治疗的发展，这些治疗方法可用于接受肝切除和移植的患者，从而增强器官和移植功能并降低发病率和死亡率。