The role of hepatocyte cAMP/PDE4 in alcohol-induced liver steatosis and injury

肝细胞cAMP/PDE4在酒精性肝脂肪变性和损伤中的作用

• 批准号: 8638593
• 负责人: Leila Gobejishvili
• 金额: $ 21.56万
• 依托单位: UNIVERSITY OF LOUISVILLE
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-02-05 至 2016-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8638593
• 关键词: ADD-1 protein; Acute; Adenylate Cyclase; Affect; Alcoholic Liver Diseases; Alcohols; Anabolism; Animal Feed; Apoptosis; Apoptotic; Cause of Death; Cell physiology; Cessation of life; Chronic; Cirrhosis; Clinical Treatment; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Cyclic AMP-Responsive DNA-Binding Protein; Data; Development; Endotoxins; Enzymes; Ethanol; FDA approved; Family; Fatty Acids; Fatty Liver; Fibrosis; Future; Genes; Glucocorticoids; Goals; Hepatic; Hepatocyte; Hepatorenal Syndrome; Hepatotoxicity; Homeostasis; Hydrolysis; In Vitro; Individual; Inflammatory; Injury; Injury to Liver; Intervention; Knock-out; Kupffer Cells; Label; Liver; Liver diseases; Metabolism; Mus; Patients; Pentoxifylline; Peroxisome Proliferator-Activated Receptors; Pharmacotherapy; Phosphodiesterase Inhibitors; Phosphorylation; Play; Predisposition; Prevention; Regulation; Role; Rolipram; Second Messenger Systems; Severities; Staging; Steroid Resistance; Steroid therapy; Stimulus; System; TNF gene; Therapeutic; Toxic effect; United States; Up-Regulation; Work; alcohol effect; alcohol exposure; alcohol response; base; chronic alcohol ingestion; cytokine; fatty acid oxidation; feeding; in vivo; inhibitor/antagonist; intervention effect; lipid biosynthesis; lipid metabolism; liver injury; macrophage; monocyte; mortality; oxidation; phosphoric diester hydrolase; problem drinker; public health relevance; receptor; response; second messenger; translational study

DESCRIPTION (provided by applicant): Alcoholic liver disease (ALD) remains a leading cause of death from liver disease in the United States. Steatosis is the initial, most frequent hepatic manifestation that occurs in response to acute as well as chronic ethanol consumption. Although steatosis is reversible, it is now established that the severity of steatosis predicts the progression of liver disease to more advanced stages including fibrosis and cirrhosis. Alcohol causes hepatic steatosis by enhancing de novo lipogenesis and impairing fatty acid beta-oxidation system with subsequent susceptibility to injury by inflammatory cytokines, particularly TNF. However, gaps remain in our understanding of alcohol-responsive mechanisms that contribute to dysregulation of genes involved in hepatic steatosis and subsequent cytokine hepatotoxicity. Cyclic AMP (cAMP), through activation of protein kinase A (PKA), has been shown to modulate genes involved in lipid metabolism and apoptosis.!cAMP levels are tightly regulated through biosynthesis by adenyl cylases (ACs) and hydrolysis by phosphodiesterases (PDEs). Our earlier work shows that expression of cAMP-specific PDE4 is significantly increased in response to alcohol exposure in monocytes/macrophages including hepatic Kupffer cells. Notably, our recent preliminary data suggest that ethanol exposure of primary mouse hepatocytes leads to a significant up-regulation of the PDE4 sub-family of enzymes, PDEA, B and D. Based on these findings we postulate that chronic ethanol feeding decreases cAMP levels in hepatocytes in a PDE4-dependent manner. There is no FDA-approved therapy for any stage of alcoholic liver disease (ALD). The most widely-used (off-label) drug therapies are glucocorticoids and pentoxifylline (PTX). Unfortunately, an important subset of AH patients treated with glucocorticoids have "steroid resistance", and some patients have contraindications to steroid therapy. PTX is a broad spectrum PDE inhibitor with only a weak PDE4 inhibitor activity, and the data available from the limited studies suggest a positive intervention effect. Hence, a more directed intervention aimed at inhibiting PDE4 may be significantly more effective. In this regard our recent preliminary data show that treatment with PDE4 specific inhibitor, rolipram, markedly inhibits hepatic steatosis in ethanol-fed animals. Our central hypothesis is that alcohol exposure increases cAMP degrading PDE4 expression in hepatocytes lowering cAMP levels with a resultant increase in lipogenesis and a decrease in fatty acid beta oxidation, leading to the development of steatosis and sensitization to TNF-induced toxicity. Importantly, as a corollary, lowering PDE4 activity may provide a significant therapeutic approach. The specific objectives of these mechanistic as well as translational studies are 1) to examine the effect of alcohol exposure on hepatocyte PDE4 expression, cAMP metabolism and development of hepatic steatosis and injury and 2) to determine the role of PDE4 subclasses and effect of PDE4 inhibition on the development of alcohol induced hepatic steatosis and injury. Our future goal is to provide a conceptual basis for targeting PDE4 activity as a clinical treatment for alcoholic patients. !

描述(由申请人提供)：酒精性肝病(ALD)仍然是美国肝病死亡的主要原因。脂肪变性是急性和慢性酒精摄入后最常见的肝脏表现。尽管脂肪变性是可逆的，但现在已经确定，脂肪变性的严重程度可以预测 肝病进展到更严重的阶段，包括纤维化和肝硬变。酒精通过促进新生脂肪生成和损害脂肪酸β-氧化系统而导致肝脏脂肪变性，继而容易受到炎性细胞因子，特别是肿瘤坏死因子的损害。然而，我们对酒精反应机制的理解仍然存在空白，酒精反应机制导致涉及肝脏脂肪变性和随后的细胞因子肝毒性的基因调节失调。环磷酸腺苷(CAMP)通过蛋白激酶A(PKA)的激活，调节与脂质代谢和细胞凋亡相关的基因。cAMP水平通过腺苷环酶(ACS)的生物合成和磷酸二酯酶(PDE)的水解而受到严格的调控。我们早期的工作表明，在酒精暴露下，包括肝脏枯否细胞在内的单核/巨噬细胞中cAMP特异性PDE4的表达显著增加。值得注意的是，我们最近的初步数据表明，乙醇暴露于原代小鼠肝细胞导致PDE4亚家族酶PDEA、B和D的显著上调。基于这些发现，我们假设长期酒精喂养以PDE4依赖的方式降低肝细胞中的cAMP水平。目前还没有FDA批准的任何阶段的酒精性肝病(ALD)治疗方法。最广泛使用的(标签外)药物疗法是糖皮质激素和己酮可可碱(PTX)。不幸的是，接受糖皮质激素治疗的AH患者中有一个重要的亚群存在“类固醇抵抗”，一些患者对类固醇治疗有禁忌症。PTX是一种广谱的PDE抑制剂，只有微弱的PDE4抑制剂活性，有限的研究数据表明，PTX具有积极的干预效果。因此，旨在抑制PDE4的更有针对性的干预可能会明显更有效。在这方面，我们最近的初步数据显示，PDE4特异性抑制剂Rolipram的治疗显著抑制了乙醇喂养动物的肝脏脂肪变性。我们的中心假设是，酒精暴露增加了肝细胞中cAMP降解PDE4的表达，降低了cAMP水平，结果是脂肪生成增加，脂肪酸β氧化减少，导致脂肪变性的发生和对肿瘤坏死因子诱导的毒性的敏化。重要的是，作为推论，降低PDE4活性可能提供一种重要的治疗方法。这些机制研究和翻译研究的具体目的是：1)研究酒精暴露对肝细胞PDE4表达、cAMP代谢的影响以及肝脂肪变性和肝损伤的发生；2)确定PDE4亚类在酒精性肝脂肪变性和损伤中的作用及抑制PDE4对肝脂肪变性和损伤的影响。我们未来的目标是为将PDE4活性作为酒精患者的临床治疗提供一个概念性的基础。好了！