Analysis and Effect of Persistent Ah Receptor Activation

我们研究的总体目标是了解卤代芳烃（HAHs）、多环芳烃（PAHs）及其相关化学物质与Ah受体（AhR）相互作用改变细胞和动物对这些诱导剂的基因表达和反应的分子机制。AhR是一种依赖配体的转录因子，介导了环芳烃和多环芳烃的大部分生物学和毒理学作用。据报道，暴露于多环芳烃和环芳烃后观察到的毒性和生物反应谱以及产生这些反应所需的化学物质浓度存在显著的物种、组织和配体特异性差异，其中环芳烃明显比多环芳烃更有效。虽然靶细胞对环芳烃和多环芳烃的不同反应可能是由多种生化和生理特性引起的，但人们普遍认为，环芳烃更强的毒理学和生物学效力是由于其明显更高的AhR结合亲和力和代谢抗性。最近的证据表明，与ahr依赖性基因表达直接相关的激活因子不同，环芳烃和多环芳烃作为ahr依赖性基因表达激活因子的效力和功效存在差异。我们假设PAHs和HAHs产生的效力和生物学反应的一些差异与AhR蛋白和/或AhR蛋白复合物结构的配体特异性差异直接相关，这种差异改变了AhR的功能及其对DNA/染色质的相对亲和力/特异性。因此，我们建议进行详细的比较研究，以表征体外和培养细胞中选定的HAHs和PAHs占据的小鼠AhR在配体激活和持久性以及DNA/染色质结合方面的异同，并鉴定和表征AhR结构的配体依赖性变化。的DREnucleotide

The overall goal of our research is to understand the molecular mechanism by which halogenated aromatic hydrocarbons (HAHs), polycyclic aromatic hydrocarbons (PAHs) and related chemicals interact with the Ah receptor (AhR) to alter gene expression and responses of cells and animals to these inducers. The AhR is a ligand-dependent transcription factor that mediates the majority of the biological and toxicological actions of HAHs and PAHs. Significant species, tissue- and ligand-specific differences have been reported in the spectrum of toxic and biological responses observed following exposure to HAHs and PAHs but also in the concentration of chemicals needed to produce these responses, with HAHs being significantly more potent than PAHs. Although differential responsiveness to HAHs and PAHs can result from a variety of biochemical and physiological characteristics in target cells, it is generally accepted that the greater toxicological and biological potency of HAHs results from their significantly higher AhR binding affinity and resistance to metabolism. Recent evidence has demonstrated that differences exist in the potency and efficacy of HAHs and PAHs as activators of AhR-dependent gene expression that are separate from those directly related to their persistence and metabolic stability in the cell. We hypothesize that some of the differences in the potency and biological responses produced by PAHs and HAHs are directly related to ligand-specific differences in the structure of the AhR protein and/or AhR protein complex that alters the functionality of the AhR and its relative affinity/specificity for DNA/chromatin. Accordingly, here we propose to conduct detailed comparative studies to characterize the similarities and differences in the activation and persistence of ligand and DNA/chromatin binding of mouse AhR occupied by selected HAHs and PAHs in vitro and in cells in culture and to identify and characterize ligand-dependent changes in AhR structure. The DREnucleotide specificity for transcriptional activation of gene expression by AhR complexes bound by HAHs and PAHs and similarities and differences in HAH- and PAH-induction of gene expression assessed in cells culture and CYP null mice using microarrays. Finally, transgenic animals expressing a consitutively active (e.g., ligand-independent) AhR complex will be generated to examine contributions of the AhR and the ligand to the adverse effects associated with this persistent AhR activation. Overall, these studies will provide insights into the species- and ligand-specific differences in the ability of HAHs and PAHs to activate the AhR, the mechanisms responsible for the persistence of this activation and the role that it plays in the toxic and biological effects of HAHs and PAHs.