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Pathological study of mitochondrial DNA deletion in circulatory diseases

循环系统疾病中线粒体DNA缺失的病理学研究

基本信息

批准号：
13670234
负责人：
JIMI Shiro
金额：
$ 1.22万
依托单位：
Fukuoka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

项目摘要

To explore the mechanism of the formation of mitochondrial DNA (mtDNA) deletion in vivo, we examined age-related 4834bp mtDNA deletion using different disease models in rats. This deletion in the brain, heart and kidney cortex started to accumulate in accordance with increase of age, however its level was grater in the brain and heart than the kidney cortex, which supports the idea that mtDNA deletion accumulate in postmitotic tissues, and proliferative tissue -could eliminate its accumulation. Based on the findings, we focused on the mtDNA deletion in the kidney cortex. Young and old rat were 5/6-nephrecomized, and maintained for 3 months. Both of the rats with 5/6 nephrectomy revealed glomerular compensatory expansion and sclerosis, and tubular expansion with epithelial cell atrophy in remaining tissue. The activity of cytochrome oxidase (COX) in tubular epithelial cells decreased drastically in nephrectomized rats, while no different was however found between the young and old rats. … More MtDNA deletion was not accumulated by nephrectomy in either young or old rats, and the levels were almost equivalent to that of untreated control rats. We next used a rat model of human type 2, insulin-independent, diabetic mellitus, namely Otuska Long Evance Tokushima Fatty (OLETF) rats, which reveals obesity, hyperglycemia, and hyperlipidemia along with development of diabetic kidney diseases. During aging process, kidney disease was advanced, and 4834bp mtDNA deletion was also accumulated in the cortex. Moreover, senescent-associated beta-galactosidase (SA-β-gal), a marker of cell senescence beyond proliferative capacity, was expressed in some tubular epithelial cells. Finally, to specify the relationship between tubular senescence and mtDNA deletion, cadmium (Cd) intoxication was examined in vitro and in vivo. Cd in vitro initially perturbed mitochondrial membrane potential of tubular epithelial cells, and strongly induced apoptosis. When cells survived from Cd toxicity were cultured for more than 100 days, mtDNA deletion could not be induced. This may be due to the selective elimination mechanisms with high proliferation capacity in cultured cells. On the other hand, rats exposed for long time by low dose Cd induced kidney dysfunction and tubular epithelial damages along with decreased mitochondrial number, accumulation of oxidation products and expression of SA-B-gal. Moreover, 4834bp mtDNA deletion in kidney cortex was enormously accumulated over the occurrence of age-related mtDNA deletion. These studies indicated that when toxic stimuli are chronically loaded on tissues during senescence, mtDNA deletion even in proliferative tissue accumulates, results in functional deterioration. This phenomenon may be important in the pathogenesis, of the development of senescence-related diseases. Less

为探讨线粒体DNA（mtDNA）缺失在体内形成的机制，我们采用不同的疾病模型检测了大鼠mtDNA 4834 bp的缺失。这种缺失在大脑、心脏和肾脏皮质中随着年龄的增长而开始积累，但其在大脑和心脏中的水平高于肾脏皮质，这支持了mtDNA缺失在有丝分裂后组织中积累的观点，而增殖组织可以消除其积累。在此基础上，我们对肾皮质线粒体DNA缺失进行了研究。青年和老年大鼠5/6肾切除，并维持3个月。2只5/6肾切除的大鼠均显示肾小球代偿性扩张和硬化，肾小管扩张伴剩余组织中的上皮细胞萎缩。肾切除后肾小管上皮细胞的细胞色素氧化酶（考克斯）活性明显降低，而青年组与老年组无明显差异。 ...更多信息无论是年轻还是年老的大鼠，肾切除后线粒体DNA缺失均未累积，其水平几乎与未处理的对照组大鼠相当。我们接下来使用了人2型胰岛素非依赖性糖尿病大鼠模型，即Otuska Long Evance德岛脂肪（OLETF）大鼠，其揭示了肥胖、高血糖和高脂血症沿着糖尿病肾病的发展。在衰老过程中，肾脏疾病进展，4834 bp的mtDNA缺失也在大脑皮层积累。此外，衰老相关β-半乳糖苷酶（SA-β-gal），细胞衰老超过增殖能力的标志物，在一些肾小管上皮细胞中表达。最后，具体说明肾小管衰老和线粒体DNA缺失之间的关系，镉（Cd）中毒进行了检查，在体外和体内。镉在体外首先干扰肾小管上皮细胞线粒体膜电位，并强烈诱导细胞凋亡。当镉毒性存活的细胞培养超过100天时，不能诱导mtDNA缺失。这可能是由于在培养的细胞中具有高增殖能力的选择性消除机制。长期低剂量镉暴露可导致大鼠肾功能损害，肾小管上皮细胞沿着损伤，线粒体数量减少，氧化产物积累减少，SA-B-gal表达减少。此外，肾皮质4834 bp mtDNA缺失的发生与年龄相关的mtDNA缺失的发生有很大的关系。这些研究表明，当毒性刺激在衰老过程中长期加载在组织上时，即使在增殖组织中也会积累mtDNA缺失，导致功能退化。这种现象可能是重要的发病机制，衰老相关疾病的发展。少