RESPONSE TO INJURY IN GAMMAGLUTAMYL CYCLE DEFICIENT MICE

丙谷氨酰循环缺陷小鼠对损伤的反应

基本信息

批准号：
6684176
负责人：
GEETHA M HABIB
金额：
$ 23.71万
依托单位：
BAYLOR COLLEGE OF MEDICINE
依托单位国家：
美国
项目类别：
财政年份：
1996
资助国家：
美国
起止时间：
1996-12-01 至 2006-11-30
项目状态：
已结题

项目摘要

The overall goal of this proposal is to define the function of glutathione (GSH) in mammals. Mice deficient in the heavy (catalytic) subunit of gamma-glutamyl cysteine synthetase (gamma-GCS-HSU), the rate limiting enzyme in GSH synthesis, diet at post coital day 7.5 and completely lack GSH; however, cell lines derived from gamma-GCS- HSU-deficient embryos survive if GSH is provided in the medium. These cells contain only 50-60 mum GSH (1-2% of wild type levels). Preliminary data indicate that removal of GSH from the medium produces a fall in GSH to undetectable levels, increased hydroxyl radical formation, activation of JNK/SAPK and cell death. These data suggest that very low GSH levels (,1% of wild type cells) whether "spontaneous" or induced by chemicals/radiation may be a key trigger that initiates the oxidative stress response and apoptosis. The gamma-GCS-HSU-deficient mice and cells we have developed and additional knock-out mice and cells we plan to construct provide a unique opportunity to test four hypotheses about GSH function: 1. Only low levels of GSH are required for survival of unstressed cells, but high levels are necessary to protect cells from chemical and radiation injury, and this protection is directly proportional to GSH level. 2. Very low/absent levels of cellular GSH activate a cellular stress response program that includes JNK/SAPK, p38 MAPK and NFkappaB, and activation of these pathways by chemicals radiation depends upon their ability to lower GSH levels. 3.Very low-absent levels of cellular GSH potentiate apoptotic cell death, and chemicals/radiation that induce apoptosis do so by lowering cellular GSH levels. The process involves suppression of anti-apoptotic factors and activation of pro-apoptotic factors. 4. Only low levels of GSH are needed for development and survival of unstressed mice. These low levels of GSH render mice hypersensitive to chemical injury.

该提案的总体目标是定义哺乳动物中谷胱甘肽（GSH）的功能。小鼠缺乏γ-谷氨酰基半胱氨酸合成酶（γ-GCS-HSU）的重（催化）亚基，速率限制GSH合成中的酶，饮食在第7.5天后饮食，完全缺乏GSH；然而，如果在培养基中提供GSH，则源自γ-GCS-HSU缺陷胚胎的细胞系可以生存。这些细胞仅包含50-60个MUM GSH（野生型水平的1-2％）。初步数据表明，从培养基中去除GSH会导致GSH下降至无法检测到的水平，羟基自由基形成增加，JNK/SAPK的激活和细胞死亡。这些数据表明，无论是“自发”还是由化学物质/辐射引起的，GSH水平（占野生型细胞的1％）可能是启动氧化应激反应和凋亡的关键触发因素。我们已经开发的伽玛 - GCS-HSU缺陷的小鼠和细胞，我们计划构建的其他敲除小鼠和细胞为测试四个关于GSH功能的四个假设提供了独特的机会：1。只有低水平的GSH对于无压力细胞的存活才需要高水平，但是高水平对于保护化学和辐射损伤是必不可少的，并且这种保护侵害了GSH级别的GSH水平。 2。非常低/不存在的细胞GSH激活包括JNK/SAPK，p38 MAPK和NFKAPPAB在内的细胞应力反应程序，化学品辐射对这些途径的激活取决于它们降低GSH水平的能力。 3.少量水平的细胞GSH降低了凋亡细胞死亡，而诱导凋亡的化学物质/辐射可以通过降低细胞GSH水平来做到这一点。该过程涉及抑制抗凋亡因子和促凋亡因素的激活。 4。对于无重理小鼠的发育和存活只需要低水平的GSH。这些低水平的GSH使小鼠对化学损伤过敏。