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）：该研究的目的是在细胞暴露于非蛋白硫醇（NPT）后引起的延迟放射保护作用的表征。潜在的假设是，细胞的NPT暴露会导致氧化还原敏感的核转录因子Kappab（NFKappab）激活锰超氧化物歧化酶（MNSOD）基因表达的增强，随后是活性MNSOD蛋白的细胞内水平升高。 MNSOD是一种抗氧化蛋白，可以赋予因电离辐射引起的氧化自由基物种的保护。 NPT在以后诱导的MNSOD水平升高的能力会导致延迟的放射保护作用，这将对辐射保护具有一般影响，尤其是肿瘤保护。这项研究侧重于四个经过临床批准的NPT，amifostine，mesna，nacetylcyene（NAC）和卡托普利（Captopril）。这些NPT目前正在临床上使用，并且它们在接受癌症治疗的患者肿瘤中诱导延迟辐射保护作用的潜力是在这里无法识别的问题。提出了四个具体目标。 AIM 1试图检验以下假设：NPT在一系列剂量上将增强MNSOD基因的表达，从而导致细胞内的活性MNSOD蛋白伴随着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）活性的增加。 AIM 2将检验以下假设：升高的MNSOD活性将导致辐射保护增强，尤其是在2 Gy时。 AIM 3的重点是检验以下假设：动物对NPT的单一或多个暴露将导致正常和肿瘤组织中的MNSOD基因表达和蛋白质活性升高，后者作为肺部肿瘤结节或动物后腿的实体瘤而生长。 AIM 4将检验以下假设：升高的MNSOD活性将导致对选定的正常和肿瘤组织的延迟辐射保护，这是由定量生存测定法确定的，即脾菌落分析，肠道微菌落测定，肺菌落分析和TCD50分析。还将测试两个替代假设。一种升高的MNSOD活性会导致与过氧化氢酶和GPX活性有关的抗氧化失衡，从而导致过氧化氢的积累和辐射敏化。第二，MNSOD水平的升高而没有酶活性而没有同时增加的酶促升高，这可能是由于过氧亚硝酸盐（Onoo-）硝化的。