Role of PPARG the PPARG Target Gene RBP7 in the Endothelium

PPARG 的作用 PPARG 靶基因 RBP7 在内皮细胞中的作用

• 批准号: 9249635
• 负责人: Curt Daniel Sigmund
• 金额: $ 61.64万
• 依托单位: UNIVERSITY OF IOWA
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-01 至 2020-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9249635
• 关键词: Adipose tissue; All-Trans-Retinol; Anti-Inflammatory Agents; Anti-inflammatory; Antioxidants; Aorta; Binding; Biological Assay; Biology; Blood Vessels; CRISPR/Cas technology; Cardiovascular Diseases; Cardiovascular system; Carotid Arteries; Cell Nucleus; Cells; Cellular biology; Cerebrovascular Circulation; Complement; Data; Development; Dominant-Negative Mutation; Endothelial Cells; Endothelium; Exhibits; Family; Functional disorder; Gene Expression; Gene Expression Profiling; Gene Targeting; Genes; Genetic; Genetic Transcription; High Fat Diet; Human; Hypertension; Impairment; Knock-in Mouse; Knock-out; Laboratories; LacZ Genes; Ligand Binding; Ligands; Lipids; Mediating; Molecular; Monitor; Mus; Mutation; Nitric Oxide; Nuclear Translocation; Oxidation-Reduction; Oxidative Stress; PPAR alpha; PPAR delta; PPAR gamma; PPARG gene; Pathway interactions; Phenotype; Physiology; Play; RNA Interference; RXR; Reactive Oxygen Species; Regulation; Reporting; Research Personnel; Retinol Binding Proteins; Risk Factors; Role; Signal Transduction; Stress; Superoxides; Techniques; Testing; Transcriptional Regulation; Transgenic Mice; Vasomotor; adiponectin; basilar artery; cardiovascular risk factor; early onset; efficacy testing; endothelial dysfunction; fatty acid-binding proteins; genome editing; innovation; insulin sensitivity; lipid transport; mutant; novel; overexpression; public health relevance; response; rosiglitazone; selective expression; transcription factor; transcriptome sequencing; vasoconstriction

 DESCRIPTION (provided by applicant): PPARγ is a ligand activated transcription factor best known for its role in regulating insulin sensitivity and adipose tissue development and expansion. There is now convincing evidence to support an important beneficial role for endothelial PPARγ in the regulation of endothelial function. However, little is known about the transcriptional targets for PPARγ, how PPARγ selectively activates some targets over others, and their mechanisms of action in the endothelium. Selective expression of a dominant negative mutant of PPARγ in the endothelium (E-V290M) has no effect on endothelial function in aorta, carotid or basilar arteries in young transgenic mice at baseline, but induces severe dysfunction if the mice are challenged by a high fat diet, Ang-II, or are old. The cerebral circulation is particularly sensitive to oxidative stress in response to the interference with PPARγ signaling. Conversely, increased expression of wildtype PPARγ specifically in the endothelium (E- PPARγ-WT) reduced vasoconstriction to Ang-II. These data strongly suggest that PPARγ plays a protective role in the endothelium under stressed conditions, and the dysfunction resulting from PPARγ impairment is caused by oxidative stress. We identified retinol-binding protein 7 (RBP7) as a PPARγ target gene in the endothelium. RBP7 is an intracellular retinol binding protein belonging to the family of intracellular lipid and fatty acid-binding proteins. Expression of RBP7 is endothelial cell-specific. RBP7-deficient mice exhibit the same high fat diet-induced and Ang-II-induced phenotype as E-V290M mice which selectively express a dominant negative mutant of PPARγ in the endothelium. This led us to consider the innovative concept that the beneficial effects of PPARγ in the endothelium may be mediated by RBP7. Intracellular lipid and fatty acid binding proteins have been reported to bind ligands which activate other ligand activated transcription factors. Thus conceptually, we hypothesize that PPARγ and RBP7 may form a transcriptional regulatory loop (or hub) in endothelial cells, which is required to support an anti oxidant state and when impaired induces a pro-oxidant state. We will examine this concept in two Specific Aims. Specific Aim 1 will test the hypotheses that a) the beneficial effects of wildtype PPARγ over-expression in the endothelium require RBP7, b) that the effects of RBP7 are mediated by its retinol-binding and lipid transport activity, and c) RBP7 is required for the PPARγ- mediated anti-oxidant response, including the expression and function of endothelial adiponectin. Specific Aim 2 will evaluate the molecular mechanisms by which RBP7 regulates PPARγ transcriptional activity by testing the hypothesis that RBP7 with its intrinsic retinol binding and nuclear translocation activity is required for transcriptional activity of PPARγ.

 描述（由申请方提供）：PPARγ是一种配体激活的转录因子，其在调节胰岛素敏感性和脂肪组织发育和扩张中的作用最为知名。现在有令人信服的证据支持内皮细胞PPARγ在调节内皮功能中的重要有益作用。然而，对PPARγ的转录靶点、PPARγ如何选择性激活某些靶点以及它们在内皮中的作用机制知之甚少。在内皮细胞中选择性表达一种显性失活突变的PPARγ（E-V290 M）对年轻转基因小鼠主动脉、颈动脉或基底动脉的内皮功能没有影响，但如果 小鼠受到高脂肪饮食、Ang-II的攻击，或者是年老的。脑循环对氧化应激特别敏感，这是对干扰PPARγ信号的反应。相反，内皮中特异性野生型PPARγ表达增加（E-PPAR γ-WT）可降低血管对Ang-II的收缩。这些数据有力地表明，在应激条件下，过氧化物酶体增殖物激活物受体γ在内皮中起保护作用，并且过氧化物酶体增殖物激活物受体γ损伤导致的功能障碍是由氧化应激引起的。我们鉴定了视黄醇结合蛋白7（RBP 7）作为内皮中的PPARγ靶基因。RBP 7是属于细胞内脂质和脂肪酸结合蛋白家族的细胞内视黄醇结合蛋白。RBP 7的表达是内皮细胞特异性的。RBP 7缺陷小鼠表现出与E-V290 M小鼠相同的高脂饮食诱导和Ang-II诱导表型，E-V290 M小鼠在内皮中选择性表达PPARγ的显性负突变体。这使我们考虑了一个创新的概念，即PPARγ在内皮中的有益作用可能是由RBP 7介导的。已经报道细胞内脂质和脂肪酸结合蛋白结合激活其它配体激活的转录因子的配体。因此，从概念上讲，我们假设PPARγ和RBP 7可能在内皮细胞中形成一个转录调节环（或枢纽），这是支持抗 氧化剂状态，并且当受损时诱导促氧化剂状态。我们将在两个具体目标中考察这一概念。具体目标1将检验以下假设：a）内皮中野生型PPARγ过表达的有益作用需要RBP 7，B）RBP 7的作用由其视黄醇结合和脂质转运活性介导，以及c）RBP 7是PPARγ介导的抗氧化反应（包括内皮脂联素的表达和功能）所必需的。具体目标2将通过检验具有内在视黄醇结合和核转位活性的RBP 7是PPARγ转录活性所需的假设，评价RBP 7调节PPARγ转录活性的分子机制。