Burelle Yan, Bemeur Chantal, Rivard Marie-Eve, Thompson Legault Julie, Boucher Gabrielle, Morin Charles, Coderre Lise, Des Rosiers Christine
Faculty of Pharmacy, Université de Montréal, Montréal, Canada.
Montreal Heart Institute, Montreal, Canada; Department of Nutrition, Faculty of Medicine, Université de Montréal, Montreal, Canada.
PLoS One. 2015 Apr 2;10(3):e0120767. doi: 10.1371/journal.pone.0120767. eCollection 2015.
Mutations in LRPPRC are responsible for the French Canadian variant of Leigh Syndrome (LSFC), a severe disorder characterized biochemically by a tissue-specific deficiency of cytochrome c oxidase (COX) and clinically by the occurrence of severe and deadly acidotic crises. Factors that precipitate these crises remain unclear. To better understand the physiopathology and identify potential treatments, we performed a comprehensive analysis of mitochondrial function in LSFC and control fibroblasts. Furthermore, we have used this cell-based model to screen for conditions that promote premature cell death in LSFC cells and test the protective effect of ten interventions targeting well-defined aspects of mitochondrial function. We show that, despite maintaining normal ATP levels, LSFC fibroblasts present several mitochondrial functional abnormalities under normal baseline conditions, which likely impair their capacity to respond to stress. This includes mitochondrial network fragmentation, impaired oxidative phosphorylation capacity, lower membrane potential, increased sensitivity to Ca2+-induced permeability transition, but no changes in reactive oxygen species production. We also show that LSFC fibroblasts display enhanced susceptibility to cell death when exposed to palmitate, an effect that is potentiated by high lactate, while high glucose or acidosis alone or in combination were neutral. Furthermore, we demonstrate that compounds that are known to promote flux through the electron transport chain independent of phosphorylation (methylene blue, dinitrophenol), or modulate fatty acid (L-carnitine) or Krebs cycle metabolism (propionate) are protective, while antioxidants (idebenone, N-acetyl cysteine, resveratrol) exacerbate palmitate plus lactate-induced cell death. Collectively, beyond highlighting multiple alterations in mitochondrial function and increased susceptibility to nutrient-induced cytotoxicity in LSFC fibroblasts, these results raise questions about the nature of the diets, particularly excess fat intake, as well as on the use of antioxidants in patients with LSFC and, possibly, other COX defects.
LRPPRC基因突变是导致法裔加拿大人型Leigh综合征（LSFC）的原因，这是一种严重疾病，其生化特征为细胞色素c氧化酶（COX）组织特异性缺乏，临床特征为发生严重致命的酸中毒危机。引发这些危机的因素尚不清楚。为了更好地理解其生理病理学并确定潜在治疗方法，我们对LSFC和成纤维细胞对照的线粒体功能进行了全面分析。此外，我们利用这个基于细胞的模型筛选促进LSFC细胞过早死亡的条件，并测试针对线粒体功能明确方面的十种干预措施的保护作用。我们发现，尽管LSFC成纤维细胞维持正常的ATP水平，但在正常基线条件下仍存在多种线粒体功能异常，这可能损害其应对压力的能力。这包括线粒体网络碎片化、氧化磷酸化能力受损、膜电位降低、对Ca2+诱导的通透性转换敏感性增加，但活性氧生成没有变化。我们还发现，当暴露于棕榈酸时，LSFC成纤维细胞对细胞死亡的易感性增强，高乳酸会增强这种效应，而单独或联合使用高葡萄糖或酸中毒则无影响。此外，我们证明，已知能促进电子传递链通量而不依赖磷酸化的化合物（亚甲蓝、二硝基苯酚），或调节脂肪酸（L-肉碱）或三羧酸循环代谢的化合物（丙酸盐）具有保护作用，而抗氧化剂（艾地苯醌、N-乙酰半胱氨酸、白藜芦醇）会加剧棕榈酸加乳酸诱导的细胞死亡。总的来说，这些结果不仅突出了LSFC成纤维细胞线粒体功能的多种改变以及对营养物质诱导的细胞毒性易感性增加，还引发了关于饮食性质的问题，特别是过量脂肪摄入，以及LSFC患者和可能其他COX缺陷患者使用抗氧化剂的问题。
