HIF-1alpha and VEGF in Acetaminophen Toxicity and Repair

说明(申请人提供)：扑热息痛(APAP)是美国急性肝功能衰竭(ALF)的主要原因。解毒剂N-乙酰半胱氨酸(NAC)可增加肝脏GSH，减少共价结合，在毒性的早期阶段非常有效。然而，在出现毒性后，NAC的疗效有限，这些患者肝移植或死亡的发生率很高。这项建议将研究APAP引起的毒性的修复机制，因为APAP继发的ALF中固有修复机制的增强可能带来新的治疗方法。我们的初步研究揭示了肝细胞再生对APAP介导的ALF晚期恢复至关重要的机制。氧化应激、缺氧诱导因子1α(HIF-1？)而血管内皮生长因子(VEGF)似乎在肝脏对APAP毒性的反应中发挥核心作用。我们证明了HIF-1？APAP中毒小鼠肝脏中的血管内皮生长因子显著增加。此外，使用血管内皮生长因子抑制剂治疗可显著延缓肝细胞再生。在其他模型系统中，HIF-1？可以调节血管内皮生长因子的水平，但这在肝脏中还没有被研究过。血管内皮生长因子是器官修复中重要的血管生成因子。虽然低氧是HIF-1的一个重要机制。在许多模型中，我们最近的数据表明氧化应激诱导HIF-1？在APAP介导的ALF中处于中心地位。我们已经证明了HIF-1？在常氧条件下用APAP处理的新鲜分离的小鼠肝细胞被诱导，并被氧化应激抑制剂阻断。利用新鲜分离的肝细胞，我们最近报道了APAP诱导氧化应激和线粒体通透性转变导致细胞坏死。我们将检验以下三个假设：1)氧化应激导致HIF-1？APAP介导的小鼠肝毒性的诱导。核因子HIF-1？在小鼠APAP毒性中上调血管内皮生长因子的合成起关键作用。3)血管内皮生长因子及其受体的相互作用在APAP中毒小鼠肝细胞再生中起关键作用。本项目将研究扑热息痛中毒后小鼠肝脏修复的机制。更好地了解肝脏的恢复过程将有助于开发治疗急性肝功能衰竭的新疗法。

DESCRIPTION (provided by applicant): Acetaminophen (APAP) is the major cause of acute liver failure (ALF) in the U.S. The antidote, N- acetylcysteine (NAC), increases hepatic GSH, decreases covalent binding and is highly effective in the early stages of toxicity. However, after the onset of toxicity, NAC has limited efficacy and there is a high incidence of liver transplant or death in these patients. This proposal will investigate mechanisms of repair of APAP-induced toxicity because novel therapies are possible with augmentation of innate repair mechanisms in ALF secondary to APAP. Our preliminary studies reveal mechanisms of hepatocyte regeneration that are critical to recovery in the late stages of APAP mediated ALF. Oxidative stress, hypoxia inducible factor 1 alpha (HIF-1?) and vascular endothelial growth factor (VEGF) appear to play central roles in the liver's response to APAP toxicity. We show that HIF-1? and VEGF are dramatically increased in the livers of APAP intoxicated mice. Also, treatment with a VEGF inhibitor markedly delays hepatocyte regeneration. It is well established, in other model systems, that HIF-1? can regulate the levels of VEGF, however this has not been previously investigated in the liver. VEGF is an angiogenic factor important in organ repair. Although hypoxia is a well described mechanism of HIF-1? induction in many models, our recent data indicate that oxidative stress induces HIF-1? and is central to APAP mediated ALF. We have shown that HIF-1? is induced in freshly isolated mouse hepatocytes treated with APAP under normoxic conditions and blocked by inhibitors of oxidative stress. Using freshly isolated hepatocytes, we recently reported that APAP induced oxidative stress and mitochondrial permeability transition leading to cellular necrosis. We will test the three following hypotheses: 1) Oxidative stress leads to HIF-1? induction in APAP-mediated hepatotoxicity in mice. 2) Nuclear factor HIF-1? is critical for upregulation of VEGF synthesis in APAP toxicity in mice. 3) The interactions of VEGF and its receptors are critical to hepatocyte regeneration following APAP toxicity in mice. Lay description: This project will examine mechanisms of repair in the liver following acetaminophen toxicity in mice treated with acetaminophen. A better understanding of the recovery processes of the liver will lead to the development of new treatments for acute liver failure.