DHEA:PPAR-Dependent and Independent Mechanisms of Action

描述(由申请人提供)：我们假设脱氢表雄酮的保护作用部分涉及通过依赖和独立的途径调节细胞色素P450单加氧酶(S)和/或其他解毒酶的表达，这些酶是生物激活和处置化学物质所必需的。几项研究已经证明，DHEA在低于依赖DHEA的过氧化体增殖所需的剂量时，可以改善环境疾病。具体目标1的目标是利用基于细胞的报告分析确定DHEA的代谢物是否作为PPAR或其他核受体的近端激活剂。我们将使用报告分析来测试DHEA代谢产物激活PPAR-α、PXR、CAR、LXR和FXR/BAR的能力。特异性目标2的目的是验证7a-羟基-DHEA和7-oxo-DHEA在大鼠海马区由DHEA形成的假说，并表征这些酶的基因调控。DHEA处理对大鼠海马齿状回7a-羟基和7-氧-DHEA水平的影响将被确定。具体目标3的目的是验证DHEA治疗通过改变PPAR磷酸化来激活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而激活PPAR，并增强其在转录中的作用的假设。具体目标4的目的是验证这样的假设，即DHEA在小鼠肝脏中诱导Cyp3all是一个依赖于PXR的过程。我们将使用PPAR-α和PXR缺失的小鼠来验证DHEA诱导Cyp3a11和其他靶基因是PXR依赖的假设。具体目标5的目的是检验DHEA通过PPAR-α和PXR介导的过程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治疗野生型、PPAR缺失和PXR缺失小鼠后基因表达的变化，以评估通过PPAR、PXR或未知信号途径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.