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Mechanism of neurodegeneration of neurons with mitochondrial DNA mutations

Lookup NU author(s): Dr Tora Smulders-Srinivasan, Dr Denise Kirby, Professor Robert Lightowlers, Emeritus Professor Doug Turnbull

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Abstract

Mutations of mitochondrial DNA are associated with a wide spectrum of disorders, primarily affecting the central nervous system and muscle function. The specific consequences of mitochondrial DNA mutations for neuronal pathophysiology are not understood. In order to explore the impact of mitochondrial mutations on neuronal biochemistry and physiology, we have used fluorescence imaging techniques to examine changes in mitochondrial function in neurons differentiated from mouse embryonic stem-cell cybrids containing mitochondrial DNA polymorphic variants or mutations. Surprisingly, in neurons carrying a severe mutation in respiratory complex I (< 10% residual complex I activity) the mitochondrial membrane potential was significantly increased, but collapsed in response to oligomycin, suggesting that the mitochondrial membrane potential was maintained by the F1Fo ATPase operating in 'reverse' mode. In cells with a mutation in complex IV causing similar to 40% residual complex IV activity, the mitochondrial membrane potential was not significantly different from controls. The rate of generation of mitochondrial reactive oxygen species, measured using hydroethidium and signals from the mitochondrially targeted hydroethidine, was increased in neurons with both the complex I and complex IV mutations. Glutathione was depleted, suggesting significant oxidative stress in neurons with a complex I deficiency, but not in those with a complex IV defect. In the neurons with complex I deficiency but not the complex IV defect, neuronal death was increased and was attenuated by reactive oxygen species scavengers. Thus, in neurons with a severe mutation of complex I, the maintenance of a high potential by F1Fo ATPase activity combined with an impaired respiratory chain causes oxidative stress which promotes cell death.

Publication metadata

Author(s): Abramov AY, Smulders-Srinivasan TK, Kirby DM, Acin-Perez R, Enriquez JA, Lightowlers RN, Duchen MR, Turnbull DM

Publication type: Article

Publication status: Published

Journal: Brain

Year: 2010

Volume: 133

Issue: 3

Pages: 797-807

Print publication date: 01/03/2010

ISSN (print): 0006-8950

ISSN (electronic): 1460-2156

Publisher: Oxford University Press

URL: http://dx.doi.org/10.1093/brain/awq015

DOI: 10.1093/brain/awq015

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