DHEA:PPAR-Dependent and Independent Mechanisms of Action

描述（由申请人提供）：我们假设DHEA的保护作用部分涉及细胞色素P450单加氧酶和/或其他解毒酶的表达调节，这些解毒酶是通过过氧化物酶体增殖物激活受体α依赖和独立途径进行生物激活和处置所需的。几项研究表明，脱氢表雄酮改善环境疾病的剂量低于脱氢表雄酮依赖性过氧化物酶体增殖所需的剂量。Specific Aim 1的目的是通过基于细胞的报告基因测定来确定脱氢表雄酮的代谢物是否作为PPAR或其他核受体的近端激活剂。我们将测试DHEA代谢物激活ppar - α、PXR、CAR、LXR和FXR/BAR的能力。特异性目的2的目的是验证大鼠海马中脱氢表雄酮形成7a-羟基脱氢表雄酮和7-氧-脱氢表雄酮的假设，并表征这些酶的基因调控。测定脱氢表雄酮处理对大鼠海马齿状回7- a-羟基和7-氧-脱氢表雄酮水平的影响。特异性目的3的目的是验证DHEA治疗通过改变PPAR磷酸化激活PPAR的假设。因此，我们将验证DHEA通过影响PPAR在大鼠肝细胞中的磷酸化状态并增加其转录作用来激活PPAR的假设。Specific Aim 4的目的是验证DHEA治疗诱导小鼠肝脏Cyp3all是pxr依赖过程的假设。我们将使用PPAR-alpha和PXR-null小鼠来验证DHEA诱导Cyp3a11和其他靶基因依赖于pxr的假设。Specific Aim 5的目的是验证脱氢表雄酮通过ppar - α和PXR介导的其他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 -null和PXR-null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共同途径。

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.