Delayed Radioprotection by Thiols

硫醇的延迟辐射防护

• 批准号: 6765096
• 负责人: DAVID J. GRDINA
• 金额: $ 30.54万
• 依托单位: UNIVERSITY OF CHICAGO
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-07-01 至 2007-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6765096
• 关键词: antioxidants; catalase; cell proliferation; enzyme activity; flow cytometry; gene expression; glutathione peroxidase; hydrogen peroxide; immunoprecipitation; laboratory mouse; neoplasm /cancer radiation therapy; neoplastic growth; nuclear factor kappa beta; peroxynitrites; radiation dosage; radiation sensitivity; radioprotective agents; superoxide dismutase; thiols; tissue /cell culture; western blottings

DESCRIPTION (provided by applicant): The goal of this investigation is the characterization of the delayed radioprotective effect induced following exposure of cells to non-protein thiols (NPT). The underlying hypothesis is that NPT exposure of cells results in activation of the redox sensitive nuclear transcription factor kappaB (NFkappaB) and enhancement in manganese superoxide dismutase (MnSOD) gene expression followed by elevated intracellular levels of active MnSOD protein. MnSOD is an anti-oxidant protein that can confer protection against oxidative radical species induced by ionizing radiation. The ability of NPT to induce at a later time elevated MnSOD levels results in a delayed radioprotective effect that will have implications in radioprotection in general, and tumor protection in particular. This study focuses on four clinically approved NPT, amifostine, mesna, Nacetylcysteine (NAC), and captopril. These NPT are currently in clinical use, and the potential for their induction of a delayed radioprotective effect in tumors of patients undergoing cancer treatment is a here-tofore unrecognized problem. Four specific aims are proposed. Aim 1 seeks to test the hypothesis that NPT over a range of doses will enhance MnSOD gene expression, leading to elevated intracellular levels of active MnSOD protein accompanied by increased catalase and glutathione peroxidase (GPx) activities in cultured tumor and non-tumor cells. Aim 2 will test the hypothesis that elevated MnSOD activity will result in enhanced radioprotection, especially at 2 Gy. Aim 3 is focused on testing the hypothesis that either single or multiple exposures of animals to NPT will result in elevated MnSOD gene expression and protein activity in both normal and tumor tissues, the latter grown as pulmonary tumor nodules or solid tumors in the hind legs of animals. Aim 4 will test the hypothesis that elevated MnSOD activity will result in delayed radioprotection to selected normal and tumor tissues as determined by quantitative survival assays, i.e., spleen colony assay, intestinal microcolony assay, lung colony assay, and the TCD50 assay. Two alternative hypotheses will also be tested. One elevated MnSOD activity can result in anti-oxidant imbalance relating to catalase and GPx activities, resulting in hydrogen peroxide buildup and radiation sensitization. Two, elevation in MnSOD level without a concomitant increase in enzymatic activity can result from nitration of MnSOD by peroxynitrite (ONOO-).

描述（由申请人提供）：本研究的目的是表征细胞暴露于非蛋白硫醇（NPT）后诱导的延迟辐射防护效应。潜在的假设是，细胞暴露于 NPT 会导致氧化还原敏感核转录因子 kappaB (NFkappaB) 的激活和锰超氧化物歧化酶 (MnSOD) 基因表达的增强，随后活性 MnSOD 蛋白的细胞内水平升高。 MnSOD 是一种抗氧化蛋白，可以针对电离辐射诱导的氧化自由基物种提供保护。 NPT 在稍后诱导 MnSOD 水平升高的能力导致延迟的辐射防护作用，这将对一般辐射防护，特别是肿瘤防护产生影响。本研究重点关注四种临床批准的 NPT：氨磷汀、美司钠、N乙酰半胱氨酸 (NAC) 和卡托普利。这些 NPT 目前正在临床使用，它们对接受癌症治疗的患者的肿瘤诱导延迟辐射防护作用的潜力是迄今为止尚未认识到的问题。提出了四个具体目标。目标 1 旨在检验以下假设：一定剂量的 NPT 将增强 MnSOD 基因表达，导致细胞内活性 MnSOD 蛋白水平升高，同时培养的肿瘤和非肿瘤细胞中过氧化氢酶和谷胱甘肽过氧化物酶 (GPx) 活性增加。目标 2 将检验以下假设：MnSOD 活性升高将导致辐射防护增强，尤其是在 2 Gy 下。目标 3 重点测试以下假设：动物单次或多次暴露于 NPT 会导致正常组织和肿瘤组织中 MnSOD 基因表达和蛋白质活性升高，后者在动物后腿中生长为肺肿瘤结节或实体瘤。动物。目标 4 将检验以下假设：MnSOD 活性升高将导致对选定的正常组织和肿瘤组织的放射防护延迟，这是通过定量生存测定（即脾集落测定、肠微集落测定、肺集落测定和 TCD50 测定）确定的。还将测试两个替代假设。 MnSOD 活性升高会导致与过氧化氢酶和 GPx 活性相关的抗氧化失衡，从而导致过氧化氢积聚和辐射过敏。第二，过氧亚硝酸盐 (ONOO-) 硝化 MnSOD 可能导致 MnSOD 水平升高，但酶活性并未随之增加。