Recovery of MERRF Fibroblasts and Cybrids Pathophysiology by Coenzyme Q10

Abstract

Mitochondrial DNA mutations are an important cause of human disease for which there is no effective treatment. Myoclonic epilepsy with ragged-red fibers (MERRF) is a mitochondrial disease usually caused by point mutations in transfer RNA genes encoded by mitochondrial DNA. The most common mutation associated with MERRF syndrome, m.8344A>G in the gene MT-TK, which encodes transfer RNA Lysine , affects the translation of all mitochondrial DNA encoded proteins. This impairs the assembly of the electron transport chain complexes leading to decreased mitochondrial respiratory function. Here we report on how this mutation affects mitochondrial function in primary fibroblast cultures established from patients harboring the A8344G mutation. Coenzyme Q 10 (CoQ) levels, as well as mitochondrial respiratory chain activity, and mitochondrial protein expression levels were significantly decreased in MERRF fibroblasts. Mitotracker staining and imaging analysis of individual mitochondria indicated the presence of small, rounded, depolarized mitochondria in MERRF fibroblasts. Mitochondrial dysfunction was associated with increased oxidative stress and increased degradation of impaired mitochondria by mitophagy. Transmitochondrial cybrids harboring the A8344G mutation also showed CoQ deficiency, mitochondrial dysfunction, and increased mitophagy activity. All these abnormalities in patient-derived fibroblasts and cybrids were partially restored by CoQ supplementation, indicating that these cell culture models may be suitable for screening and validation of novel drug candidates for MERRF disease.

Coenzyme Q supplementation or over-expression of the yeast Coq8 putative kinase stabilizes multi-subunit Coq polypeptide complexes in yeast coq null mutants

“…It is also possible that exogenous Q restored mitochondrial protein levels by increasing the content of mitochondria in coq null mutants. Q deficiencies may result from mitochondrial mutations affecting other processes; this is consistent with the observed effects of Q deficiency on mitophagy, and the inhibition of mitophagy by Q supplementation [93, 94]. The findings presented here suggest that Q supplementation may correct defects in mitochondrial function through its beneficial effects in stabilizing the CoQ-synthome and de novo biosynthesis of Q, as well as contributing to enhanced respiratory electron transport and mitochondrial metabolism.…”

“…Dietary supplementation with Q 10 can be an effective treatment for patients with partial defects in Q biosynthesis [87, 88], and also shows benefit in mouse and C. elegans models of Q deficiency [89–92], and in cell culture models of mitochondrial diseases [93, 94]. In this study we found that inclusion of exogenous Q 6 in the growth medium increased steady-state levels of mitochondrial polypeptides involved in respiratory electron transport and the citric acid cycle, including Rip1 (a subunit of complex III), Atp2 (a subunit of F 1 of complex V), and Mdh1, malate dehydrogenase.…”

Macroautophagy and Cell Responses Related to Mitochondrial Dysfunction, Lipid Metabolism and Unconventional Secretion of Proteins

“…Dysregulation of mitophagy has also been associated with the pathogenesis of neurodegenerative diseases such as Parkinson disease [66,67,68], Alzheimer disease [69] and several syndromes associated with mtDNA defects. Indeed, in primary fibroblast cultures of patients harbouring the A8344G MERRF (Myoclonic Epilepsy with Ragged-Red Fibres) mutation, mitochondrial dysfunction and oxidative stress were associated with increased mitophagy of impaired organelles [70]. The same laboratory also reported similar results for another mitochondrial myopathy, MELAS (Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes), associated with the A3243G mutation within mtDNA [71].…”

Coenzyme Q₁₀ Therapy

“…Overall, it appears that larger CoQ 10 dosages are indicated for mitochondrial disorders. Recently, our group has demonstrated the benefits of CoQ 10 supplementation in several cellular models of mitochondrial diseases [Rodríguez-Hernández et al, 2009;Cotán et al, 2011;De la Mata et al, 2012;. However, the clinical evidence supporting a benefit of CoQ 10 treatment in primary mitochondrial disease is limited.…”