Pathogenesis and Treatment of Liver Disease in Transaldolase Deficiency

转醛醇酶缺乏性肝病的发病机制和治疗

• 批准号: 8078182
• 负责人: Andras Perl
• 金额: $ 32.77万
• 依托单位: UPSTATE MEDICAL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-01 至 2014-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8078182
• 关键词: 4 hydroxynonenal; Acetaminophen; Acetylcysteine; Acute; Acute Liver Failure; Age; Aldehyde Reductase; Aminophenols; Animal Model; Antioxidants; Apoptosis; Blood donor; Cancer Etiology; Case Study; Caucasians; Caucasoid Race; Cause of Death; Cell Death; Cells; Cessation of life; Child; Chronic; Cirrhosis; Code; Defect; Development; Disease; Dysplasia; Enzymes; Exhibits; Failure; Fatty Liver; Fibroblasts; Gene Mutation; Genes; Genetic; Genomics; Glucose; Glucose-6-Phosphate; Glutathione; Hepatocarcinogenesis; Hepatocyte; Human; Human Cloning; In Vitro; Inflammation; Inflammatory; JUN gene; Link; Lipid Peroxides; Lipids; Liver; Liver Cirrhosis; Liver Failure; Liver diseases; Malignant Neoplasms; Malondialdehyde; Mediating; Membrane Potentials; Metabolic; Metabolic Pathway; Mitochondria; Molecular; Mus; Mutation; NADP; Overdose; Oxidation-Reduction; Oxidative Stress; Oxidoreductase; Pathogenesis; Pathway interactions; Patients; Pentosephosphate Pathway; Phase; Phosphogluconate Dehydrogenase; Phosphorylation; Play; Predisposition; Prevalence; Primary carcinoma of the liver cells; Production; Protein Dephosphorylation; Proteins; Recycling; Relative (related person); Resistance; Role; Secondary to; Siblings; Supplementation; TNFRSF6 gene; Testing; Tissues; Toxic effect; Transaldolase; Tylenol; alpha-Fetoproteins; base; cell type; computerized data processing; hepatoma cell; in vivo; inhibitor/antagonist; liver cell proliferation; lymphoblast; mitochondrial dysfunction; mortality; multicatalytic endopeptidase complex; neoplastic cell; neuronal cell body; non-alcoholic fatty liver; nonalcoholic steatohepatitis; novel; polyol; prevent; public health relevance; receptor; research study; ribose-5-phosphate; sedoheptulose 7-phosphate; sugar; transcription factor; tumor; young adult

DESCRIPTION (provided by applicant): Although oxidative stress is implicated in both acute acetaminophen-induced liver failure and chronic liver diseases, cirrhosis and hepatocellular carcinoma (HCC), no common underlying metabolic pathways have been identified. The preliminary results indicate that deficiency of transaldolase (TAL, encoded by the TALDO1 genomic locus), an enzyme of the pentose phosphate pathway (PPP), is an important cause of oxidative stress in the liver that predisposes to acetaminophen-induced liver failure and hepatocarcinogenesis. Recent case reports suggested a link of homozygous mutations in the TAL gene with liver failure and cirrhosis in children. In fibroblasts and lymphoblasts of the first TAL-deficient patient, we found that deletion of S171 caused mis- folding, proteasome-mediated degradation and complete deficiency of enzymatic activity. TAL deficiency resulted in accumulation of sedoheptulose 7-phoshate (S7P) and depletion of glucose 6-phoshate (G6P), indicating a failure to recycle ribose 5-phosphate (R5P) into G6P through the non-oxidative branch of the PPP, thus reducing NADPH production by the oxidative branch. This patient's cells exhibited mitochondrial dysfunction, increased susceptibility to H2O 2 and resistance to Fas apoptosis. To create an animal model of TAL deficiency, we inactivated the TALDO1 genomic locus in the mouse. Cirrhosis and nodular dysplasia were highly prevalent in mice with partial deficiency (TAL+/-; 62/229, 27.0%) or complete deficiency of TAL (TAL-/-; 77/97, 79.4%), relative to wild-type littermates (TAL+/+; 1/102, 1.0%). Cirrhosis invariably followed the formation of microvesicular and macrovesicular lipid droplets indicating nonalcoholic fatty liver disease (NAFLD) and inflammatory changes resembling non-alcoholic steatohepatitis (NASH). HCC was the leading cause of death in both TAL+/- (39/229; 17%) and TAL-/- mice (45/97; 46%) as compared to TAL+/+ littermates (1/102; 1%). Oxidative stress in TAL-deficient livers was characterized by the accumulation of S7P, failure to recycle R5P for the oxidative PPP, depleted NADPH and glutathione levels, and increased production of lipid hydroperoxides (LPO). Reduced 2-catenin phosphorylation and enhanced c-jun expression in TAL-/- livers reflected adaptation to oxidative stress. TAL-/- hepatocytes were resistant to CD95/Fas-mediated apoptosis in vitro and in vivo. Remarkably, lifelong administration of N-acetylcysteine (NAC) blocked acetaminophen susceptibility, restored Fas-dependent apoptosis, phosphorylation of 2-catenin, activation of c-jun and prevented the development of NASH, cirrhosis, and hepatocarcinogenesis in TAL-deficient mice. We also found an increased prevalence of TAL haploinsufficiency in human livers with cirrhosis and HCC. Thus, the preliminary studies identify TAL deficiency as a novel cause of liver cirrhosis and HCC which are preventable by lifelong supplementation of the potent antioxidant NAC. The proposed studies will test the hypothesis that TAL deficiency leads to oxidative stress, through diminished production of NADPH leading to secondary depletion of GSH that underlies the susceptibility of acetaminophen-induced liver failure and chronic liver disease, progressing from NAFLD to NASH, cirrhosis, and HCC. Under Specific Aim 1, we will determine the molecular mechanisms that cause NADPH depletion in TAL-deficient hepatocytes. Under Specific Aim 2, we will test the hypothesis that hepatocarcinogenesis of TAL-deficient mice is triggered by NADPH depletion- induced oxidative stress, mediated by the over-expression of aldose reductase (AR) and the activation of 2- catenin and c-jun, and prevented by post-natal treatment with N-acetylcysteine or AR blockade. Under Specific Aim 3, we will determine the prevalence and molecular basis of TAL deficiency in patients with acetaminophen-induced liver failure, NAFLD, NASH, cirrhosis and HCC. These studies will generate fundamental new information on the pathogenesis and treatment of liver disease. PUBLIC HEALTH RELEVANCE: Hepatocellular carcinoma (HCC) is the fifth most common cancer and the third leading cause of cancer- related death worldwide. Acetaminophen (also known as Tylenol) overdose is the leading cause of acute liver failure in the US. Although oxidative stress has been implicated in HCC and acetaminophen toxicity, the genetic causes that predispose patients to these diseases are unknown. Recently, deficiency of transaldolase (TAL) was discovered in children with liver failure and cirrhosis. TAL is an enzyme that helps the utilization of the sugar glucose in certain cells of the body, such as liver cells, to produce and sustain normal levels of the compounds NADPH and glutathione which protect the integrity of the cells against oxidative stress. We created an animal model of TAL deficiency by a targeted genetic mutation in the mouse. Although mice partially (TAL+/-) or completely deficient of TAL (TAL-/-) develop normally, they are 27-fold and 79-fold more likely to develop cirrhosis and HCC than their siblings having normal TAL gene and activity. TAL-deficient (TAL-/-) mice are also more susceptible to acetaminophen-induced liver failure and death than their siblings carrying the normal TAL gene. Thus, the preliminary studies identify TAL deficiency as a novel cause of liver cirrhosis and HCC as well as acetaminophen-induced liver failure. We hypothesize that NADPH plays critical roles in the survival and multiplication of tumor cells in the liver. The proposed experiments will determine the mechanism of NADPH depletion, whether a correctable defect is responsible for the tumor-causing proliferation of liver cells, and examine the involvement of TAL deficiency in patients with acetaminophen- induced liver failure, fatty liver inflammation, cirrhosis and HCC. These studies should generate fundamental new information on the cause and treatment of potentially fatal diseases of the liver.

描述（由申请人提供）：虽然氧化应激与急性对乙酰氨基酚诱导的肝衰竭和慢性肝病、肝硬化和肝细胞癌（HCC）有关，但尚未确定共同的潜在代谢途径。初步结果表明，转醛醇酶（TAL，由 TALDO1 基因组位点编码）（戊糖磷酸途径 (PPP) 的一种酶）的缺乏是肝脏氧化应激的重要原因，易导致对乙酰氨基酚诱导的肝衰竭和肝癌发生。最近的病例报告表明，TAL 基因的纯合突变与儿童肝衰竭和肝硬化有关。在第一位 TAL 缺陷患者的成纤维细胞和淋巴母细胞中，我们发现 S171 的缺失导致错误折叠、蛋白酶体介导的降解和酶活性完全缺乏。 TAL 缺乏导致景天庚酮糖 7-磷酸 (S7P) 积累和葡萄糖 6-磷酸 (G6P) 消耗，表明无法通过 PPP 的非氧化分支将核糖 5-磷酸 (R5P) 再循环为 G6P，从而减少NADPH 由氧化分支产生。该患者的细胞表现出线粒体功能障碍、对 H2O 2 的敏感性增加以及对 Fas 细胞凋亡的抵抗。为了创建 TAL 缺陷的动物模型，我们灭活了小鼠的 TALDO1 基因组位点。相对于野生型同窝小鼠，肝硬化和结节性发育不良在 TAL 部分缺乏 (TAL+/-; 62/229, 27.0%) 或完全缺乏 (TAL-/-; 77/97,​​ 79.4%) 的小鼠中非常普遍。总和+/+；1/102，1.0%）。肝硬化总是伴随着微泡和大泡脂滴的形成，这表明非酒精性脂肪性肝病（NAFLD）和类似于非酒精性脂肪性肝炎（NASH）的炎症变化。与 TAL+/+ 同窝小鼠（1/102；1%）相比，HCC 是 TAL+/- 小鼠（39/229；17%）和 TAL-/- 小鼠（45/97；46%）的主要原因。 TAL 缺陷肝脏中氧化应激的特点是 S7P 积累、无法将 R5P 回收用于氧化 PPP、NADPH 和谷胱甘肽水平耗尽以及脂质氢过氧化物 (LPO) 的产生增加。 TAL-/- 肝脏中 2-catenin 磷酸化的减少和 c-jun 表达的增强反映了对氧化应激的适应。 TAL-/- 肝细胞在体外和体内均能抵抗 CD95/Fas 介导的细胞凋亡。值得注意的是，终身施用 N-乙酰半胱氨酸 (NAC) 可阻断对乙酰氨基酚的敏感性，恢复 Fas 依赖性细胞凋亡、2-连环蛋白磷酸化、c-jun 激活，并防止 TAL 缺陷小鼠发生 NASH、肝硬化和肝癌。我们还发现患有肝硬化和肝癌的人类肝脏中 TAL 单倍体不足的患病率有所增加。因此，初步研究确定 TAL 缺乏是肝硬化和肝癌的新原因，而肝硬化和肝癌可以通过终身补充强效抗氧化剂 NAC 来预防。拟议的研究将检验这样的假设：TAL 缺乏会导致氧化应激，通过 NADPH 产生减少导致 GSH 继发性消耗，从而导致对乙酰氨基酚诱导的肝衰竭和慢性肝病（从 NAFLD 发展为 NASH、肝硬化和慢性肝病）的易感性。肝癌。在具体目标 1 下，我们将确定导致 TAL 缺陷肝细胞中 NADPH 消耗的分子机制。在具体目标 2 下，我们将检验以下假设：TAL 缺陷小鼠的肝癌发生是由 NADPH 耗竭诱导的氧化应激触发的，而氧化应激是由醛糖还原酶 (AR) 的过度表达以及 2-catenin 和 c-jun 的激活介导的，并可通过产后 N-乙酰半胱氨酸或 AR 阻断治疗来预防。在具体目标 3 下，我们将确定对乙酰氨基酚诱导的肝衰竭、NAFLD、NASH、肝硬化和 HCC 患者中 TAL 缺乏的患病率和分子基础。这些研究将产生有关肝病发病机制和治疗的基本新信息。 公共卫生相关性：肝细胞癌 (HCC) 是全球第五大常见癌症，也是全球癌症相关死亡的第三大原因。对乙酰氨基酚（也称为泰诺）过量是美国急性肝衰竭的主要原因。尽管氧化应激与肝癌和对乙酰氨基酚毒性有关，但导致患者易患这些疾病的遗传原因尚不清楚。最近，在患有肝衰竭和肝硬化的儿童中发现转醛醇酶（TAL）缺乏。 TAL 是一种酶，有助于体内某些细胞（例如肝细胞）利用葡萄糖来产生和维持 NADPH 和谷胱甘肽化合物的正常水平，从而保护细胞的完整性免受氧化应激。我们通过对小鼠进行靶向基因突变，创建了 TAL 缺乏症的动物模型。尽管部分 (TAL+/-) 或完全缺乏 TAL (TAL-/-) 的小鼠发育正常，但它们患肝硬化和肝癌的可能性比具有正常 TAL 基因和活性的小鼠兄弟姐妹高 27 倍和 79 倍。与携带正常 TAL 基因的小鼠相比，TAL 缺陷（TAL-/-）小鼠也更容易受到对乙酰氨基酚诱导的肝衰竭和死亡的影响。因此，初步研究确定 TAL 缺乏是肝硬化和 HCC 以及对乙酰氨基酚诱发的肝衰竭的新原因。我们假设 NADPH 在肝脏肿瘤细胞的存活和增殖中发挥着关键作用。拟议的实验将确定 NADPH 消耗的机制，可纠正的缺陷是否会导致肝细胞的肿瘤增殖，并检查 TAL 缺乏与对乙酰氨基酚诱导的肝衰竭、脂肪肝炎症、肝硬化和 HCC 患者的关系。这些研究应该产生关于潜在致命肝脏疾病的原因和治疗的基本新信息。