L-Arginine/NO in Liver Transplant Preservation Injury

L-精氨酸/NO 在肝移植保存损伤中的作用

• 批准号: 7233304
• 负责人: DAVID A GELLER
• 金额: $ 26.36万
• 依托单位: UNIVERSITY OF PITTSBURGH AT PITTSBURGH
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-06-01 至 2009-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7233304
• 关键词: Arginine; NO; Liver; Transplant; Preservation

DESCRIPTION (provided by applicant): Liver transplant preservation injury represents a "cold" ischemia/reperfusion (I/R) injury. Patients receiving livers with severe preservation injury exhibit significant increases in the length of ICU stay, infection, renal failure, biliary strictures, and allograft rejection. A profound arginine-deficient state occurs post-transplant due to arginase release from the injured liver graft. We believe arginine is critical for early hepatic protection, mediated in part by NO synthesis, and that arginine deficiency further contributes to ongoing liver graft injury. L-arginine supplementation does not result in increased circulating arginine levels and achieves only modest improvement in liver injury. Therefore, we hypothesize that inhibition of arginase will be required to enhance arginine availability and minimize damage resulting from liver preservation injury. This is a completely novel approach to combat organ injury; essentially nothing is known about the effects of arginase blockade in vivo. Preliminary data with injection of the arginase inhibitor, Nu-hydroxy-nor-L-arginine (nor-NOHA), showed that serum arginase activity was inhibited and circulating arginine levels were restored. This resulted in a significant decrease in liver enzyirie release and improvement in liver histology. In this proposal, we will pursue two aims to characterize arginine metabolism post-transplant and determine the effects of arginase blockade on liver cold I/R injury: AIM I: TO DETERMINE WHETHER ENHANCING ARGININE AVAILABILITY THROUGH ARGINASE BLOCKADE PREVENTS LIVER TRANSPLANT ISCHEMIA/REPERFUSION INJURY. We will characterize arginine metabolism post-transplant and determine if arginine transport is modified during liver I/R injury. The effects of arginase blockade on serum and tissue arginine levels will be determined. The conditions that optimize arginine availability to maximize organ protection will be established. The potential adverse consequences of arginase inhibition on polyamine/proline synthesis, urea excretion, blood pressure, and alloimmurie response will be investigated. AIM II: TO IDENTIFY THE MECHANISMS OF PROTECTION MEDIATED BY IMPROVING ARGININE AVAILABILITY ON LIVER GRAFT INJURY. We will determine if the beneficial effects of enhanced arginine availability are mediated by NO synthesis. The secondary mechanisms of tissue protection will be identified including the effects of enhanced arginine concentration on neutrophil infiltration, cytokine release, apoptosis, ultrastructural damage, hepatic blood flow, and HO-1 expression. The information gained will increase our understanding of the molecular pathophysiology of liver graft injury, and will provide completely new information regarding the in vivo effects of arginase blockade. We expect these findings to have broad implications far beyond transplant preservation injury that may be applicable to any form of liver injury resulting in hepatocellular arginase release and arginine depletion.

描述（由申请人提供）： 肝移植保存损伤代表“冷”缺血/再灌注（I/R）损伤。接受严重保存损伤肝脏的患者在ICU住院时间、感染、肾衰竭、胆管狭窄和同种异体移植排斥反应方面表现出显著增加。由于从受损的肝移植物中释放出辅酶A酶，移植后发生严重的辅酶A缺乏状态。我们认为精氨酸对早期肝脏保护至关重要，部分通过NO合成介导，并且精氨酸缺乏进一步导致持续的肝移植损伤。补充L-精氨酸不会导致循环精氨酸水平增加，仅能适度改善肝损伤。因此，我们假设，抑制精氨酸酶将需要提高精氨酸的可用性，并尽量减少肝脏保存损伤造成的损害。这是一种对抗器官损伤的全新方法;基本上，对体内抑制酶的效果一无所知。注射精氨酸酶抑制剂Nu-hydroxy-nor-L-arginine（nor-NOHA）的初步数据显示，血清精氨酸酶活性受到抑制，循环精氨酸水平得到恢复。这导致肝酶释放的显著减少和肝组织学的改善。在这个提议中，我们将追求两个目标来表征移植后精氨酸代谢，并确定精氨酸酶阻断对肝脏冷I/R损伤的影响：目的I：确定通过精氨酸酶阻断增强精氨酸可用性是否预防肝移植缺血/再灌注损伤。我们将描述移植后精氨酸代谢的特点，并确定精氨酸转运在肝I/R损伤期间是否发生改变。将确定精氨酸酶阻断对血清和组织精氨酸水平的影响。将建立优化精氨酸可用性以最大化器官保护的条件。将研究精氨酸酶抑制对多胺/脯氨酸合成、尿素排泄、血压和异免疫反应的潜在不良后果。目的II：确定通过提高精氨酸利用度介导的对肝移植物损伤的保护机制。我们将确定增强精氨酸可用性的有益作用是否由NO合成介导。将确定组织保护的次要机制，包括增强精氨酸浓度对中性粒细胞浸润、细胞因子释放、细胞凋亡、超微结构损伤、肝血流量和HO-1表达的影响。所获得的信息将增加我们对肝移植损伤的分子病理生理学的理解，并将提供关于阻断腺苷三磷酸酶的体内效应的全新信息。我们希望这些发现具有广泛的意义，远远超出移植保存损伤，可能适用于任何形式的肝损伤，导致肝细胞凋亡酶释放和精氨酸耗尽。