Apoptosis in mitochondrial myopathies is linked to mitochondrial proliferation
Apoptosis in mitochondrial myopathies is linked to mitochondrial proliferation
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DOI：
10.1093/brain/awl061
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发表时间：
2006-05-01
期刊：
影响因子：
14.5
通讯作者：
Lombès, A
中科院分区：
文献类型：
--
作者：
Auré, K;Fayet, G;Lombès, A
在线粒体缺陷的许多模型中已经显示出对凋亡的易感性增加，但它与人类疾病的相关性仍在讨论中。我们解决了线粒体DNA(MtDNA)紊乱患者肌肉中存在细胞凋亡的问题。利用与异质线粒体DNA改变相关的肌肉形态异常的镶嵌模式，我们使用了一种原位方法来研究细胞凋亡与呼吸缺陷、线粒体增殖和突变负荷之间的关系。对线粒体DNA大量缺失(16例)或MELAS突变(4例)的肌肉进行分析，可发现不同的线粒体形态改变。患者活检时的年龄从0.4岁到66岁不等，肌肉突变的mtDNA比例从32%到82%。通过caspase3激活、细胞核DNA断裂[末端脱氧核苷酸转移酶介导的dUTP缺口末端标记法]或促凋亡因子Bax的过度表达三种不同的检测方法，在20例活检组织中的16例的肌纤维中观察到少量的肌纤维凋亡。对34000多根肌纤维的细胞色素c氧化酶(COX)和琥珀酸脱氢酶(琥珀酸脱氢酶)活性与细胞色素C氧化酶(COX)和琥珀酸脱氢酶(琥珀酸脱氢酶)活性的平行分析表明，细胞凋亡只发生在有线粒体增殖的肌纤维(RRF)中，而与COX活性无关。对单个肌肉纤维的分子分析证明，正如预期的那样，COX缺陷的存在与突变mtDNA的比例较高和正常mtDNA的数量较少有关。在COX缺陷纤维中，线粒体增殖的存在与mtDNA含量的增加有关，但正常和突变mtDNA分子的比例没有变化，这表明线粒体增殖伴随着正常和突变mtDNA分子的相似扩增。在RRF中，细胞凋亡与较高的突变比例有关，这表明它是由严重的呼吸缺陷和线粒体质量增加同时引起的。综上所述，细胞凋亡很可能是线粒体病理的一部分。它与线粒体增殖和高突变负荷密切相关。当考虑训练疗法时，人们必须考虑到诱导线粒体增殖的同时诱导细胞凋亡的可能性。
Increased susceptibility to apoptosis has been shown in many models of mitochondrial defects but its relevance to human diseases is still discussed. We addressed the presence of apoptosis in muscle from patients with mitochondrial DNA (mtDNA) disorders. Taking advantage of the mosaic pattern of muscle morphological anomalies associated with heteroplasmic mtDNA alterations, we have used an in situ approach to address the relationship between apoptosis and respiratory defect, mitochondrial proliferation and mutation load. Different patterns of mitochondrial morphological alterations were provided by the analysis of muscles with large mtDNA deletion (16 cases) or with the MELAS mutation (4 cases). The patient's age at biopsy ranged from 0.4 to 66 years and the muscle mutant mtDNA proportion from 32 to 82%. Apoptotic muscle fibres were observed in a small proportion of muscle fibres of 16 out of the 20 biopsies by three different detection methods for different steps of apoptosis: caspase 3 activation, fragmentation of nuclear DNA [terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assay] or overexpression of the pro-apoptotic factor Bax. Analysis of apoptotic features in parallel to cytochrome c oxidase (COX) and succinate dehydrogenase activity of more than 34 000 individual muscle fibres showed that apoptosis occurred only in muscle fibres with mitochondrial proliferation (ragged red fibres, RRF) irrespective of their COX activity. Molecular analyses of single muscle fibres evidenced that, as expected, the presence of COX defect was associated with higher proportion of mutant mtDNA and lower amount of normal mtDNA. Within COX-defective fibres, the presence of mitochondrial proliferation was associated with increase of the mtDNA content but without change in the ratio between normal and mutant mtDNA molecules, thus showing that mitochondrial proliferation was accompanied by similar amplification of normal and mutant mtDNA molecules. Within RRF, apoptosis was associated with higher mutation proportion, suggesting that it was provoked by severe respiratory defect in the same time as increased mitochondrial mass. In conclusion, apoptosis most probably contributes to mitochondrial pathology. It is tightly linked to mitochondrial proliferation and high mutation load. When considering training therapeutics, one will have to take into account the possibility to induce apoptosis in parallel to mitochondrial proliferation.