CARCINOGEN METABOLIZING P450S - REGULATION BY CYTOKINES

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。其中的许多， 包括多环芳香烃诱导的P450、P4501A1和 P4501A2，代谢致癌物，有助于其解毒 和/或激活。我们已经发现，白介素1抑制了 多环化合物对P4501A1和P4501A2的转录激活作用 此外，这种抑制可以通过提高细胞内的谷胱甘肽来阻断。 级别。 通过调节P450水平，细胞因子可以显著影响 致癌物新陈代谢。此外，细胞因子水平可能会有很大的差异。 在不同的组织和器官内，也系统地 个人，由于特定的生理状态(急性或慢性 炎症或感染，吸烟，饮食，细胞因子设定值， 免疫反应性等)。在一些基因上也可能存在差异 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或 P450基因对细胞因子的反应性差异可能 差异地影响致癌物代谢的P450的表达， 因此，可能是导致遗传和/或 环境决定的个体之间的差异 对致癌物的易感性。也有可能的是，对 细胞因子表达P450代表一种重要的适应性反应， 在P450增加的时候降低P450-中介致癌物的代谢 自由基生成。 这项研究检验的具体假设是细胞因子依赖 抑制P4501A1和P4501A2转录是通过 特定蛋白质与顺式作用调控序列的相互作用 细胞氧化还原电位调节对细胞因子的反应。 具体目标如下： 1.确定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介导的表达载体对隔离大鼠的基因转移 肝细胞来鉴定这些顺式作用的调控序列和 移动性转移DNA结合分析和DNA足迹技术 鉴定DNA结合蛋白。 2.确定活性氧间的关系 中间体/细胞氧化还原电位与细胞因子依赖性 抑制P450的表达。依赖诱导物的P4501A1和P4501A2 经处理的肝细胞的转录和mRNA表达将被测定。 用细胞因子和/或试剂改变活性氧的水平 中间体或细胞氧化还原潜力。 3.完成上述研究目标将提供信息 对识别参与的生理因素至关重要 和/或修改该自适应响应。这对于确定 这一反应的性质和重要性，以及它可能如何有助于 化学诱导性的个体间差异 癌症。

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.