DHEA:PPAR-Dependent and Independent Mechanisms of Action

DHEA：PPAR 依赖性和独立作用机制

• 批准号: 6572974
• 负责人: RUSSELL Allen PROUGH
• 金额: $ 27.73万
• 依托单位: UNIVERSITY OF LOUISVILLE
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-03-15 至 2006-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6572974
• 关键词: cell proliferation; cytochrome P450; dehydroepiandrosterone; enzyme induction /repression; gas chromatography mass spectrometry; gene induction /repression; gene targeting; genetic techniques; hamsters; hormone regulation /control mechanism; human tissue; laboratory mouse; laboratory rat; liver cells; microsomes; peroxisome; steroid hormone metabolism; steroid hormone receptor; tissue /cell culture; unspecific monooxygenase

DESCRIPTION (provided by applicant): We hypothesize that the protective action of DHEA, in part, involves the modulation of the expression of cytochrome P450 monooxygenase(s) and/or other detoxification enzymes required for the bioactivation and disposition of chemicals through both Peroxisome Proliferator Activated Receptor Alpha dependent and independent pathways. Several studies have demonstrated that DHEA ameliorates environmental diseases at dosages lower than those required for DHEA-dependent peroxisome proliferation. The goal of Specific Aim 1 is to establish whether metabolites of DHEA serve as proximal activators of PPAR or other nuclear receptors using cell-based reporter assays. We will test the ability of DHEA metabolites to activate PPAR-alpha, PXR, CAR, LXR, and FXR/BAR using reporter assays. The goal of Specific Aim 2 is to test the hypothesis that 7a-hydroxy-DHEA and 7-oxo-DHEA are formed from DHEA in the hippocampus of rats and to characterize the gene regulation of these enzymes. The effect of DHEA treatment on levels of 7a-hydroxy- and 7-oxo-DHEA in the dentate gyrus region of hippocampus in rats will be determined. The goal of Specific Aim 3 is to test the hypothesis that DHEA treatment activates PPAR by altering PPAR phosphorylation. Therefore, we will test the hypothesis that DHEA activates PPAR by affecting its phosphorylation status in rat hepatocytes and increases its action in transcription. The goal of Specific Aim 4 is to test the hypothesis that the induction of Cyp3all in mouse liver by DHEA treatment is a PXR-dependent process. We will use PPAR-alpha and PXR-null mice to test the hypothesis that induction of Cyp3a11 and other target genes by DHEA is PXR-dependent. The goal of Specific Aim 5 is to test the hypothesis that DHEA induces gene expression through processes other than those mediated by PPAR-alpha and PXR. We will test changes in gene expression after DHEA treatment of wild-type, PPAR -null, and PXR-null mice using a mouse gene array to assess common pathways of regulation of these genes through PPAR, PXR, or unknown signaling pathways.

描述（由申请人提供）：我们假设 DHEA 的保护作用部分涉及通过过氧化物酶体增殖物激活受体 α 依赖性和独立途径调节细胞色素 P450 单加氧酶和/或化学物质生物活化和处置所需的其他解毒酶的表达。多项研究表明，DHEA 可以在低于 DHEA 依赖性过氧化物酶体增殖所需剂量的剂量下改善环境疾病。具体目标 1 的目标是使用基于细胞的报告基因检测确定 DHEA 代谢物是否充当 PPAR 或其他核受体的近端激活剂。我们将使用报告基因检测测试 DHEA 代谢物激活 PPAR-α、PXR、CAR、LXR 和 FXR/BAR 的能力。具体目标 2 的目标是检验大鼠海马中 DHEA 形成 7a-羟基-DHEA 和 7-氧代-DHEA 的假设，并表征这些酶的基因调控。将确定 DHEA 治疗对大鼠海马齿状回区域 7a-羟基-和 7-氧代-DHEA 水平的影响。具体目标 3 的目标是检验 DHEA 治疗通过改变 PPAR 磷酸化来激活 PPAR 的假设。因此，我们将检验以下假设：DHEA 通过影响大鼠肝细胞中 PPAR 的磷酸化状态来激活 PPAR，并增加其转录作用。具体目标 4 的目标是检验以下假设：DHEA 治疗在小鼠肝脏中诱导 Cyp3all 是一个 PXR 依赖性过程。我们将使用 PPAR-alpha 和 PXR-null 小鼠来检验 DHEA 对 Cyp3a11 和其他靶基因的诱导是 PXR 依赖性的假设。具体目标 5 的目标是检验 DHEA 通过 PPAR-α 和 PXR 介导以外的过程诱导基因表达的假设。我们将使用小鼠基因阵列测试 DHEA 处理野生型、PPAR 缺失和 PXR 缺失小鼠后基因表达的变化，以评估通过 PPAR、PXR 或未知信号通路调节这些基因的常见途径。