CATALASE EFFECT ON ADRIAMYCIN CARDIOTOXICITY

癌症化疗应用的主要障碍是 阿霉素是其心脏毒性。研究表明，生产 活性氧在其细胞内代谢过程中， 负责阿霉素的细胞毒性作用。过氧化氢酶是一种主要的 过氧化氢（H2 O2）解毒酶， 哺乳动物细胞 以往的研究表明，过氧化氢酶活性， 与其他器官相比，心脏组织的g含量非常低，仅 约为小鼠肝脏的2%。 最重要的H202 解毒酶谷胱甘肽过氧化物酶也表现出较低的 在大多数品系的小鼠中，心脏的活性比肝脏的活性高。 这 心脏处理反应性物质的能力相对不足 氧物种可能是负责不寻常的敏感性， 心脏阿霉素毒性。我们最近开发了15个健康的 过氧化氢酶活性组成型的转基因小鼠系 特别是在心脏组织中过度表达。每条线都有一个 稳定升高的过氧化氢酶活性，范围从2- 500倍高 较常年该模型是研究过氧化氢酶在 预防阿霉素引起的心脏损伤。 所以我们 我建议用这些转基因小鼠来检验这一假设， 过氧化氢酶活性升高可提供针对阿霉素的保护 心脏毒性 我们的长期目标是提供一种分子和 了解不寻常的易感性的生化基础 心脏注射阿霉素。 具体目的和实验步骤， 本研究的主要内容如下：（1）确定 过氧化氢酶活性升高导致心脏对阿霉素的抵抗 毒性，我们将选择5个转基因品系， 提高过氧化氢酶活性从2到200倍，并比较急性和 阿霉素的慢性毒性与过氧化氢酶富集 转基因炉膛和对照。我们将确定不同的影响 过氧化氢酶活性对阿霉素诱导的细胞形态和功能的影响 改变和药物的致命性。(2)探讨 过氧化氢酶活性升高可能提供 对阿霉素心脏毒性的保护，我们将确定 不同过氧化氢酶活性对阿霉素诱导的脂质的影响 心脏的过氧化反应此外，为了确定 过氧化氢酶通过解毒作用提供心脏保护， 我们将使用从过氧化氢酶中分离的肌细胞的原代培养物 富集的转基因心脏和对照比较 过氧化氢酶活性变化对阿霉素诱导的细胞损伤的影响， H202。 (3)为了估计过氧化氢酶对 细胞防御阿霉素心脏毒性，我们将确定 过氧化氢酶是否可以取代谷胱甘肽的保护作用 过氧化物酶/谷胱甘肽系统在转基因心脏耗尽 谷胱甘肽（由丁硫基亚砜亚胺）。我们还将确定 过氧化氢酶表达的细胞类型的重要性和 酶的亚细胞定位在心肌保护中的作用 这些 这些研究应能为今后的研究提供坚实的信息基础。 临床研究，可能导致改善使用 阿霉素在癌症化疗中的应用。

A major impediment in the cancer chemotherapeutic application of Adriamycin is its cardiotoxicity. Studies have shown that production of reactive oxygen species during its intracellular metabolism is responsible for the cytotoxic effect of Adriamycin. Catalase is a major enzyme involved in detoxification of hydrogen peroxide (H2O2) in mammalian cells. Previous studies have shown that catalase activity per g heart tissue is very low in comparison to other organs, being only about 2% that of liver in the mouse. The other important H202 detoxification enzyme glutathione peroxidase also exhibits lower activity in the heart than in the liver in most strains of mice. This relative deficit in the heart in its ability to dispose of reactive oxygen species may be responsible for the unusual sensitivity of the heart to Adriamycin toxicity. We have recently developed 15 healthy transgenic mouse lines in which catalase activity is constitutively overexpressed specifically in the heart tissue. Each line exhibits a stably elevated catalase activity, ranging from 2- to 500-fold higher than normal. The model is ideal to study the role of catalase in protection against Adriamycin-induced heart damage. Therefore, we propose to use these transgenic mice to test the hypothesis that elevated catalase activity provides protection against Adriamycin cardiotoxicity. Our long term goal is to provide a molecular and biochemical basis for understanding the unusual susceptibility of the heart to Adriamycin. The specific aims and experimental procedures to be carried out in this study are as follows: (1) To determine whether elevated catalase activity confers cardiac resistance to Adriamycin toxicity, we will select 5 transgenic lines spanning the range of elevated catalase activity from 2 to 200-fold and compare the acute and chronic toxicities of Adriamycin between the catalase-enriched transgenic hearth and controls. We will determine the effects of varying catalase activities on Adriamycin induced morphological and functional alterations and on the lethality of the drug. (2) To investigate possible mechanisms by which elevated catalase activity provides protection against Adriamycin cardiotoxicity, we will determine the effects of varying catalase activities on Adriamycin induced lipid peroxidation in the heart. Furthermore, to determine whether the catalase provides cardioprotection against Adriamycin by detoxifying H2O2 we will use primary cultures of myocytes isolated from catalase enriched transgenic hearts and controls to compare she effects of varying catalase activities on cell injuries induced by Adriamycin and by H202. (3) To estimate the importance of the catalase contribution to cellular defense against Adriamycin cardiotoxicity, we will determine whether catalase can replace the protective role of the glutathione peroxidase/glutathione system in transgenic hearts depleted of glutathione(by buthionine sulfoximine). We will also determine the importance of cell type to which the catalase is expressed and the enzyme~s subcellular localizations in the cardioprotection. These studies should provide a substantial base of information for future clinical investigations, potentially leading to improved use of Adriamycin in cancer chemotherapy.