Protective role of adenosine 2A receptor in NAFLD

腺苷2A受体在NAFLD中的保护作用

• 批准号: 8504439
• 负责人: Chaodong Wu
• 金额: $ 32.9万
• 依托单位: TEXAS A&M AGRILIFE RESEARCH
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-04-15 至 2018-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8504439
• 关键词: Adenosine; Agonist; Anti-Inflammatory Agents; Anti-inflammatory; Binding; Binding Proteins; Bone Marrow Transplantation; Carbohydrates; Cells; Coculture Techniques; Conditioned Culture Media; Development; Diet; Elements; Enzymes; Event; Exhibits; Family; Fatty Liver; Fatty acid glycerol esters; Functional disorder; G-Protein-Coupled Receptors; Gene Expression; Genes; Goals; Hepatic; Hepatocyte; Immune; In Vitro; Inflammation; Inflammatory; Inflammatory Response; Interleukin-6; Knowledge; Kupffer Cells; Leukocytes; Liver; Liver Cirrhosis; Liver diseases; Metabolic; Metformin; Methionine; Mus; Myeloid Cells; Nutrient; Palmitates; Pathogenesis; Phosphorylation; Play; Prevention; Primary carcinoma of the liver cells; Property; Purinergic P1 Receptors; Receptor Activation; Receptor Inhibition; Regulatory Element; Research; Role; Sterols; TNF gene; Testing; Wild Type Mouse; base; cell type; choline deficient diet; cytokine; effective therapy; evidence base; expectation; feeding; in vivo; knock-down; lipid biosynthesis; liver inflammation; macrophage; member; non-alcoholic fatty liver; nonalcoholic steatohepatitis; novel; novel strategies; prevent; promoter; public health relevance; receptor; receptor function; research study

DESCRIPTION (provided by applicant): Nonalcoholic fatty liver disease (NAFLD) is one of the most common causes of terminal liver diseases including liver cirrhosis and hepatocellular carcinoma. Growing evidence demonstrates the critical importance of inflammation in the pathogenesis of NAFLD. For instance, nutrient overload triggers inflammation, which can act through stimulating lipogenesis to increase hepatic steatosis. The latter, in turn, can exacerbate liver inflammation and progress to non-alcoholic steatohepatitis (NASH). However, the precise mechanisms underlying the interaction between hepatic steatosis and liver inflammation remain to be elucidated. Thus, the long-term goal of the proposed research is to dissect the metabolic and inflammatory mechanisms underlying NAFLD in order that novel evidence-based approaches can be developed for preventing and/or treating NASH. As a G-protein-coupled receptor, adenosine 2A receptor (A2AR) is abundantly expressed in immune cells and exhibits powerful anti-inflammatory properties. A2AR is also highly expressed in hepatocytes, in which A2AR functions are largely unknown. For this project, the central hypothesis is that the A2AR in hepatocytes and macrophages protects against the development of different aspects of NAFLD in a cell-type-dependent manner. This hypothesis is based on the following novel findings: 1) A2AR deficiency in hepatocytes plays a more important role than A2AR deficiency in myeloid cells (macrophages) in exacerbating high-fat diet (HFD)- induced hepatic steatosis, which is associated with increased hepatic expression of lipogenic enzymes; 2) A2AR deficiency exacerbates HFD-induced liver inflammation, which is likely attributed to increased macrophage/Kupffer cell proinflammatory activation; and 3) A2AR activation by a specific agonist protects mice from HFD-induced NAFLD. Thus, the goal of this project is to define a novel protective role for A2AR in NAFLD. For this purpose, mice that lack A2AR in hepatocytes and/or myeloid cells are generated. For Specific Aim 1, in vivo experiments will be performed to examine the extent to which the A2AR in hepatocytes acts through inhibiting lipogenesis to protect against NAFLD. Moreover, cellular experiments will be performed to elucidate the involvement of SREBP1c and ChREBP in A2AR inhibition of lipogenic gene expression. For Specific Aim 2, in vivo experiments will be performed to examine the extent to which the A2AR in macrophages or hepatocytes protects against NAFLD by suppressing liver inflammatory response. For Specific Aim 3, in vivo experiments will be performed to define A2AR coordination of hepatocyte-macrophage crosstalk in NAFLD. Moreover, in vitro co-culture experiments will be performed to examine the extent to which factors generated by A2AR-deficient macrophages, i.e., TNF? and IL-6, stimulate hepatocyte lipogenesis, and the extent to which factors generated by A2AR-deficient hepatocytes, i.e., palmitate, stimulate macrophage proinflammatory activation. Together, the proposed research will illustrate a new paradigm on NAFLD, and provide the experimental basis for prevention and/or treatment of NASH by means of A2AR activation.

描述（由申请人提供）：非酒精性脂肪性肝病（NAFLD）是包括肝硬化和肝细胞癌在内的晚期肝病的最常见原因之一。越来越多的证据表明炎症在 NAFLD 发病机制中至关重要。例如，营养过剩会引发炎症，炎症可以通过刺激脂肪生成来增加肝脏脂肪变性。后者反过来会加剧肝脏炎症并发展为非酒精性脂肪性肝炎（NASH）。然而，肝脂肪变性和肝脏炎症之间相互作用的确切机制仍有待阐明。因此，本研究的长期目标是剖析 NAFLD 的代谢和炎症机制，以便开发新的循证方法来预防和/或治疗 NASH。作为一种 G 蛋白偶联受体，腺苷 2A 受体 (A2AR) 在免疫细胞中大量表达，并表现出强大的抗炎特性。 A2AR 在肝细胞中也高度表达，但 A2AR 的功能很大程度上未知。对于该项目，中心假设是肝细胞和巨噬细胞中的 A2AR 以细胞类型依赖性方式防止 NAFLD 不同方面的发展。这一假说基于以下新发现：1) 肝细胞中的 A2AR 缺乏比骨髓细胞（巨噬细胞）中的 A2AR 缺乏在加剧高脂饮食 (HFD) 诱导的肝脂肪变性方面发挥着更重要的作用，这与肝脏脂肪生成酶表达增加有关； 2) A2AR 缺乏会加剧 HFD 诱导的肝脏炎症，这可能是由于巨噬细胞/库普弗细胞促炎激活增加所致； 3) 特定激动剂激活 A2AR 可保护小鼠免受 HFD 诱导的 NAFLD。因此，该项目的目标是确定 A2AR 在 NAFLD 中的新型保护作用。为此，产生了肝细胞和/或骨髓细胞中缺乏 A2AR 的小鼠。对于具体目标 1，将进行体内实验来检查肝细胞中 A2AR 通过抑制脂肪生成来预防 NAFLD 的作用程度。此外，将进行细胞实验以阐明 SREBP1c 和 ChREBP 在 A2AR 脂肪生成基因表达抑制中的作用。对于具体目标 2，将进行体内实验，以检查巨噬细胞或肝细胞中的 A2AR 通过抑制肝脏炎症反应来预防 NAFLD 的程度。对于具体目标 3，将进行体内实验以确定 NAFLD 中肝细胞-巨噬细胞串扰的 A2AR 协调。此外，将进行体外共培养实验，以检查 A2AR 缺陷型巨噬细胞产生因子（即 TNF？）的程度。和 IL-6，刺激肝细胞脂肪生成，以及 A2AR 缺陷肝细胞产生的因子（即棕榈酸酯）刺激巨噬细胞促炎激活的程度。总之，拟议的研究将阐明 NAFLD 的新范式，并为通过 A2AR 激活预防和/或治疗 NASH 提供实验基础。