Characterization of the Pathways Linking Ah Receptor

连接 Ah 受体途径的表征

• 批准号: 7064096
• 负责人: Norbert E Kaminski
• 金额: $ 29.75万
• 依托单位: MICHIGAN STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-04-01 至 2011-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7064096
• 关键词: B lymphocyte; DNA methylation; aromatic hydrocarbon receptor; benzofurans; binding proteins; biological signal transduction; carbopolycyclic compound; cell differentiation; cell growth regulation; computational biology; cytokine receptors; dioxins; environmental contamination; gene expression; halobiphenyl /halotriphenyl compound; humoral immunity; immune response; immunofluorescence technique; immunomagnetic separation; immunosuppression; interferon gamma; laboratory mouse; microarray technology; model design /development; molecular biology; polymerase chain reaction; transcription factor; western blottings

The overall goal of this 5 year research plan is two-fold: (a) to characterize the molecular mechanism for impairment of B cell differentiation by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and dioxin-like compounds; and (b) to develop a computational model describing the biochemical pathways that regulate B cell differentiation and the interaction of this pathway with the aryl hydrocarbon reception (AhR). Previous studies have established the B cell as a sensitive cellular target for TCDD as evidenced by suppression of immunoglobulin (lg)M through a direct effect on B cells involving the AhR. Moreover, suppression of the IgM response by TCDD is mediated at the level of transcription and, in part, occurs through AhR binding to dioxin response elements (ORE) in regulatory domains within the Ig heavy chain (IgH) 3'a enhancer. Importantly, in addition to IgH suppression, the Ig kappa light chain (Igk), IgM joining chain (J chain) and X-box protein-1 (XBP-1), which are essential for IgM assembly and secretion, are also markedly suppressed by TCDD suggesting the involvement of additional targets other than just the IgH 3'a enhancer. Moreover, TCDD alters the levels of B lymphocyte.-induced maturation protein-1 (Blimp-1), a master regulatory of B cell differentiation and its downstream target, Pax5, a transcriptional represser of B cell differentiation, which represses IgH, Igk, J chain and XBP-1. We also show that TCDD treatment of B cells: (a) altered the magnitude of DNA methylation and MRNA levels of DNA methylating enzymes, Dnmt3b, which putatively influences the expression of genes crucial to B cell differentiation, including Pax5; (b) is functionally antagonized by IFNg; and (c) rapidly induces the suppressor of cytokine signaling-2 (SOCS-2), a protein that negatively regulates signaling through cytokine receptors coupled to the JAK/STAT pathway, such as the IFNg receptor (IFNgR). The project objective is to test the hypothesis: Suppression of the primary humoral immune response by AhR agonists is mediated through changes in the B cell differentiation program via a mechanism that is blocked by IFNg. A computational description of the biochemical pathway of B cell differentiation and the direct interactions of AhR agonists on this pathway, will provide a mechanistic approach for predicting the effects of AhR agonists, alone and in combination as complex mixtures, on the pathway and on humoral immune responses.

这个 5 年研究计划的总体目标有两个：(a) 表征 2,3,7,8-四氯二苯并-对二恶英 (TCDD) 和二恶英样物质损害 B 细胞分化 化合物； (b) 开发一个计算模型来描述调节 B 的生化途径 细胞分化以及该途径与芳烃接收（AhR）的相互作用。以前的 研究已将 B 细胞确定为 TCDD 的敏感细胞靶点，这一点通过抑制 免疫球蛋白 (lg)M 通过直接作用于涉及 AhR 的 B 细胞。此外，抑制IgM TCDD 的反应是在转录水平介导的，部分是通过 AhR 与二恶英的结合而发生的 Ig 重链 (IgH) 3'a 增强子内调节域中的反应元件 (ORE)。重要的是， 除了 IgH 抑制外，Ig kappa 轻链 (Igk)、IgM 连接链 (J 链) 和 X-box Protein-1 (XBP-1) 对于 IgM 组装和分泌至关重要，也被 TCDD 显着抑制 表明除了 IgH 3'a 增强子之外还涉及其他靶标。此外，TCDD 改变 B 淋巴细胞的水平。诱导成熟蛋白 1 (Blimp-1)，B 细胞的主要调节因子 分化及其下游靶标 Pax5，B 细胞分化的转录抑制因子， 抑制 IgH、Igk、J 链和 XBP-1。我们还表明，TCDD 对 B 细胞的治疗：(a) 改变了 DNA 甲基化程度和 DNA 甲基化酶 Dnmt3b 的 mRNA 水平，推测 影响对 B 细胞分化至关重要的基因的表达，包括 Pax5； (b) 功能上 被IFNg拮抗； (c) 快速诱导细胞因子信号传导抑制因子 2 (SOCS-2)，这是一种蛋白质 通过与 JAK/STAT 途径偶联的细胞因子受体对信号传导进行负调节，例如 干扰素g受体（IFNgR）。该项目的目标是检验假设：抑制原发性 AhR 激动剂的体液免疫反应是通过 B 细胞分化的变化介导的 通过 IFNg 阻断的机制进行程序。生化途径的计算描述 B 细胞分化的过程以及 AhR 激动剂在此途径上的直接相互作用，将提供一种机制 预测 AhR 激动剂（单独或组合为复杂混合物）对 途径和体液免疫反应。