CARCINOGEN METABOLIZING P450S - REGULATION BY CYTOKINES

致癌物质代谢 P450S - 细胞因子的调节

• 批准号: 3199703
• 负责人: DAVID S PASCO
• 金额: $ 16.34万
• 依托单位: MAHARISHI UNIVERSITY OF MANAGEMENT
• 依托单位国家: 美国
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-08-15 至 1995-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3199703
• 关键词: DNA binding protein; DNA footprinting; chemical carcinogen; cytochrome P450; cytokine; enzyme activity; enzyme induction /repression; genetic regulatory element; genetic transcription; interleukin 1; laboratory rat; liver cells; liver metabolism; toxin metabolism; transfection /expression vector

Cytokines may be one of the most comprehensive physiological modulators of P450 levels, influencing members of many P450 subfamilies. Many of these, including the polycyclic aromatic hydrocarbon-inducible P450s, P4501A1 and P4501A2, metabolize carcinogens, contributing to their detoxification and/or activation. We have found that interleukin-1 inhibits the transcriptional activation of P4501A1 and P4501A2 by polycyclic compounds. Furthermore, this inhibition can be blocked by raising cellular glutathione levels. By modulating P450 levels, cytokines could substantially influence carcinogen metabolism. Furthermore, cytokine levels can vary dramatically within different tissues and organs and also systemically between individuals, due to particular physiological states (acute or chronic inflammation or infection, cigarette smoking, diet, cytokine set point, immunoreactivity, etc.). There may also be genetic differences in some of these variables, such as cytokine set point and immunoreactivity. Our long term working hypothesis is that differences in cytokine levels or differences in the responsiveness of P450 genes to cytokines could differentially affect the expression of carcinogen-metabolizing P450s and, therefore, could be an important factor contributing to genetically and/or environmentally determined differences among individuals in their susceptibility to carcinogens. It is also possible that the suppression of P450 expression by cytokines represents an important adaptive response, that of reducing P450-mediating carcinogen metabolism at times of increased free radical generation. The specific hypotheses tested by this research are that cytokine-dependent suppression of P4501A1 and P4501A2 transcription is mediated by the interaction of specific proteins with cis-acting regulatory sequences and that cellular redox potential modulates responsiveness to cytokines. Specific objectives are as follows: 1. Determine the cis-acting sequences responsible for mediating cytokine suppression of P4501A1 and P4501A2 transcriptional activation. We will use DNA-mediated gene transfer of expression vectors into isolated rat hepatocytes to characterize these cis-acting regulatory sequences and the mobility shift DNA binding assay and DNA footprinting techniques to identify DNA binding proteins. 2. Determine the relationship between reactive oxygen intermediates/cellular redox potential and the cytokine-dependent suppression of P450 expression. Inducer-dependent P4501A1 and P4501A2 transcription and mRNA expression will be determined in hepatocytes treated with cytokines and/or reagents that modify levels of reactive oxygen intermediates or cellular redox potential. 3. Accomplishing the above research objectives will provide information crucial for the identification of physiological factors which participate in and/or modify this adaptive response. This is necessary for determining the nature and importance of this response and how it might contribute to inter-individual differences in susceptibility to chemically-induced cancer.

细胞因子可能是最全面的生理调节剂之一， P450水平，影响许多P450亚家族的成员。 其中许多， 包括多环芳烃诱导型P450、P4501A1和 P4501A2，代谢致癌物质，有助于其解毒 和/或激活。 我们已经发现白细胞介素-1抑制了 P4501A1和P4501A2通过多环化合物的转录激活。 此外，这种抑制作用可以通过提高细胞谷胱甘肽水平来阻断。 程度. 通过调节P450水平，细胞因子可以显著影响 致癌物质代谢 此外，细胞因子水平可以显著变化， 在不同的组织和器官中， 个体，由于特定的生理状态（急性或慢性 炎症或感染，吸烟，饮食，细胞因子设定点， 免疫反应性等）。 也可能有一些遗传差异， 这些变量，如细胞因子设定点和免疫反应性。 我们的长期工作假设是细胞因子水平的差异或 P450基因对细胞因子反应性的差异可能 差异影响致癌物代谢P450的表达， 因此，可能是一个重要因素，有助于遗传和/或 环境决定的个体差异， 对致癌物的敏感性。 也有可能是抑制 细胞因子引起的P450表达是一种重要的适应性反应， 减少P450介导的致癌物质代谢的时间增加， 自由基生成。 本研究检验的具体假设是， P4501A1和P4501A2转录的抑制是由 特定蛋白质与顺式作用调节序列的相互作用， 细胞氧化还原电位调节细胞因子的反应性。 具体目标如下： 1. 确定负责介导细胞因子的顺式作用序列 抑制P4501A1和P4501A2转录激活。 我们将使用 DNA介导的表达载体向离体大鼠的基因转移 肝细胞来表征这些顺式作用调控序列， 迁移率改变DNA结合分析和DNA足迹技术， 鉴定DNA结合蛋白。 2. 确定活性氧之间的关系 中间体/细胞氧化还原电位和烟碱依赖性 抑制P450表达。 诱导剂依赖性P4501A1和P4501A2 将在处理的肝细胞中测定转录和mRNA表达 用细胞因子和/或改变活性氧水平的试剂 中间体或细胞氧化还原电位。 3. 实现上述研究目标将提供信息 对于鉴定参与的生理因素至关重要， 和/或改变这种适应性反应。 这对于确定 这种反应的性质和重要性，以及它如何有助于 个体间对化学诱导的 癌