HIF-1alpha and VEGF in Acetaminophen Toxicity and Repair

描述（由申请人提供）：对乙酰氨基酚（APAP）是美国急性肝衰竭（ALF）的主要原因。解毒剂N-乙酰半胱氨酸（NAC）可增加肝脏GSH，降低共价结合，在毒性早期非常有效。然而，在毒性发作后，NAC的疗效有限，这些患者的肝移植或死亡发生率很高。该提案将研究APAP诱导的毒性的修复机制，因为新的治疗方法可能会增强继发于APAP的ALF中的先天修复机制。我们的初步研究揭示了肝细胞再生的机制，这是至关重要的APAP介导的ALF的后期阶段的恢复。氧化应激，缺氧诱导因子1 α（HIF-1？）和血管内皮生长因子（VEGF）似乎在肝脏对APAP毒性的反应中起着重要作用。我们发现HIF-1？和VEGF在APAP中毒小鼠的肝脏中显著增加。此外，用VEGF抑制剂治疗显著延迟肝细胞再生。它是公认的，在其他模型系统，HIF-1？可以调节VEGF的水平，然而这在以前没有在肝脏中研究过。VEGF是器官修复中重要的血管生成因子。虽然缺氧是一个很好的描述HIF-1的机制？诱导在许多模型中，我们最近的数据表明，氧化应激诱导HIF-1？并且是APAP介导的ALF的中心。我们已经证明，HIF-1？在常氧条件下用APAP处理的新鲜分离的小鼠肝细胞中诱导，并被氧化应激抑制剂阻断。我们最近报道，使用新鲜分离的肝细胞，APAP诱导氧化应激和线粒体通透性转换，导致细胞坏死。我们将测试以下三个假设：1）氧化应激导致HIF-1？诱导小鼠APAP介导的肝毒性。2)核因子HIF-1？在小鼠中APAP毒性中对VEGF合成的上调至关重要。3)VEGF及其受体的相互作用对小鼠APAP毒性后的肝细胞再生至关重要。说明：本项目将研究对乙酰氨基酚治疗小鼠对乙酰氨基酚中毒后肝脏的修复机制。更好地了解肝脏的恢复过程将导致开发急性肝衰竭的新治疗方法。

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.