Wednesday, December 1, 2010

Mitochondrial Fe-S cluster biogenesis, frataxin and the modulation of susceptibility to drug-induced cardiomyopathy

Aging (Albany NY). 2010 Nov 27.
Michael N. Sack
NHLBI Center for Molecular Medicine, National Institutes of Health, Bethesda, MD 20892, USA
Commentary on: Schulz et al. Activation of mitochondrial energy metabolism protects against cardiac failure. Aging 2010; 2: this issue

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An intriguing new finding, by Shultz et al is published in AGING regarding the induction of frataxin. Mutations in frataxin result in the development of Friedreich's Ataxia, an inherited neurodegenerative disease associated with the development of severe cardiomyopathy. Frataxin, itself is involved in mitochondrial iron-sulphur cluster biogenesis which functions, in part, to incorporate appropriate amounts of iron into mitochondrial proteins including aconitase and succinate dehydrogenase [13]. Whether frataxin functions as an iron-chaperone protein or plays a regulatory role in controlling iron and sulphur flux within mitochondria is not yet completely characterized. Nevertheless, the study by Shultz and colleagues [14] shows that increased cardiac frataxin enhances tricarboxylic acid cycle function resulting in increased cardiac ATP, NADH, NADPH and reduced glutathione levels. This array of features is consistent with an enhanced bioenergetic capacity and increased antioxidant defenses. The authors go on to demonstrate that overexpression of frataxin is cardioprotective against doxorubicin-induced cardiomyopathy. This intriguing study shows that the modulation of the mitochondria at the fundamental level of integrating cofactors required for protein functional integrity have beneficial effects in disease processes that are exacerbated by mitochondrial dysfunction. This study further highlights the complexity of mitochondrial function and adds a new level of regulation operational in the pathophysiology of heart failure that may be amenable to therapeutic modulation.

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