Background: Myoclonus, Epilepsy and Ragged-Red-Fibers (MERRF) is a mitochondrial encephalomyopathy due to heteroplasmic mutations in mitochondrial DNA (mtDNA) most frequently affecting the tRNALys gene at position m.8344A > G. Defective tRNALys severely impairs mitochondrial protein synthesis and respiratory chain when a high percentage of mutant heteroplasmy crosses the threshold for full-blown clinical phenotype. Therapy is currently lim- ited to symptomatic management of myoclonic epilepsy, and supportive measures to counteract muscle weakness with co-factors/supplements. Methods: We tested two therapeutic strategies to rescue mitochondrial function in cybrids and fibroblasts carry- ing different loads of the m.8344A > G mutation. The first strategy was aimed at inducing mitochondrial biogenesis directly, over-expressing the master regulator PGC-1α, or indirectly, through the treatment with nicotinic acid, a NAD+ precursor. The second was aimed at stimulating the removal of damaged mitochondria through prolonged rapamy- cin treatment. Results: The first approach slightly increased mitochondrial protein expression and respiration in the wild type and intermediate-mutation load cells, but was ineffective in high-mutation load cell lines. This suggests that induction of mitochondrial biogenesis may not be sufficient to rescue mitochondrial dysfunction in MERRF cells with high-muta- tion load. The second approach, when administered chronically (4 weeks), induced a slight increase of mitochondrial respiration in fibroblasts with high-mutation load, and a significant improvement in fibroblasts with intermediate- mutation load, rescuing completely the bioenergetics defect. This effect was mediated by increased mitochondrial biogenesis, possibly related to the rapamycin-induced inhibition of the Mechanistic Target of Rapamycin Complex 1 (mTORC1) and the consequent activation of the Transcription Factor EB (TFEB). Conclusions: Overall, our results point to rapamycin-based therapy as a promising therapeutic option for MERRF.

Rapamycin rescues mitochondrial dysfunction in cells carrying the m.8344A > G mutation in the mitochondrial tRNALys / Mariantonietta Capristo , Valentina Del Dotto , Concetta Valentina Tropeano , Claudio Fiorini , Leonardo Caporali , Chiara La Morgia , Maria Lucia Valentino , Monica Montopoli , Valerio Carelli , Alessandra Maresca. - In: MOLECULAR MEDICINE. - ISSN 1528-3658. - ELETTRONICO. - 28:1(2022), pp. 90.1-90.18. [10.1186/s10020-022-00519-z]

Rapamycin rescues mitochondrial dysfunction in cells carrying the m.8344A > G mutation in the mitochondrial tRNALys

Mariantonietta Capristo
Primo
;
Valentina Del Dotto;Concetta Valentina Tropeano;Claudio Fiorini;Leonardo Caporali;Chiara La Morgia;Maria Lucia Valentino;Valerio Carelli
;
Alessandra Maresca
Ultimo
2022

Abstract

Background: Myoclonus, Epilepsy and Ragged-Red-Fibers (MERRF) is a mitochondrial encephalomyopathy due to heteroplasmic mutations in mitochondrial DNA (mtDNA) most frequently affecting the tRNALys gene at position m.8344A > G. Defective tRNALys severely impairs mitochondrial protein synthesis and respiratory chain when a high percentage of mutant heteroplasmy crosses the threshold for full-blown clinical phenotype. Therapy is currently lim- ited to symptomatic management of myoclonic epilepsy, and supportive measures to counteract muscle weakness with co-factors/supplements. Methods: We tested two therapeutic strategies to rescue mitochondrial function in cybrids and fibroblasts carry- ing different loads of the m.8344A > G mutation. The first strategy was aimed at inducing mitochondrial biogenesis directly, over-expressing the master regulator PGC-1α, or indirectly, through the treatment with nicotinic acid, a NAD+ precursor. The second was aimed at stimulating the removal of damaged mitochondria through prolonged rapamy- cin treatment. Results: The first approach slightly increased mitochondrial protein expression and respiration in the wild type and intermediate-mutation load cells, but was ineffective in high-mutation load cell lines. This suggests that induction of mitochondrial biogenesis may not be sufficient to rescue mitochondrial dysfunction in MERRF cells with high-muta- tion load. The second approach, when administered chronically (4 weeks), induced a slight increase of mitochondrial respiration in fibroblasts with high-mutation load, and a significant improvement in fibroblasts with intermediate- mutation load, rescuing completely the bioenergetics defect. This effect was mediated by increased mitochondrial biogenesis, possibly related to the rapamycin-induced inhibition of the Mechanistic Target of Rapamycin Complex 1 (mTORC1) and the consequent activation of the Transcription Factor EB (TFEB). Conclusions: Overall, our results point to rapamycin-based therapy as a promising therapeutic option for MERRF.
2022
Rapamycin rescues mitochondrial dysfunction in cells carrying the m.8344A > G mutation in the mitochondrial tRNALys / Mariantonietta Capristo , Valentina Del Dotto , Concetta Valentina Tropeano , Claudio Fiorini , Leonardo Caporali , Chiara La Morgia , Maria Lucia Valentino , Monica Montopoli , Valerio Carelli , Alessandra Maresca. - In: MOLECULAR MEDICINE. - ISSN 1528-3658. - ELETTRONICO. - 28:1(2022), pp. 90.1-90.18. [10.1186/s10020-022-00519-z]
Mariantonietta Capristo , Valentina Del Dotto , Concetta Valentina Tropeano , Claudio Fiorini , Leonardo Caporali , Chiara La Morgia , Maria Lucia Valentino , Monica Montopoli , Valerio Carelli , Alessandra Maresca
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/898986
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