X-linked adrenoleukodystrophy (X-ALD) is a fatal neurodegenerative disorder, characterized by progressive cerebral demyelination cerebral childhood adrenoleukodystrophy (CCALD) or spinal cord neurodegeneration (adrenomyeloneuropathy, AMN), adrenal insufficiency and accumulation of very long-chain fatty acids (VLCFA) in tissues. The disease is caused by mutations in the ABCD1 gene, which encodes a peroxisomal transporter that plays a role in the import of VLCFA or VLCFA-CoA into peroxisomes. The Abcd1 knockout mice develop a spinal cord disease that mimics AMN in adult patients, with late onset at 20 months of age. The mechanisms underlying cerebral demyelination or axonal degeneration in spinal cord are unknown. Here, we present evidence by gas chromatography/mass spectrometry that malonaldehyde-lysine, a consequence of lipoxidative damage to proteins, accumulates in the spinal cord of Abcd1 knockout mice as early as 3.5 months of age. At 12 months, Abcd1- mice accumulate additional proteins modified by oxidative damage arising from metal-catalyzed oxidation and glycoxidation/lipoxidation. While we show that VLCFA excess activates enzymatic antioxidant defenses at the protein expression levels, both in neural tissue, in ex vivo organotypic spinal cord slices from Abcd1- mice, and in human ALD fibroblasts, we also demonstrate that the loss of Abcd1 gene function hampers oxidative stress homeostasis. We find that the alpha-tocopherol analog Trolox is able to reverse oxidative lesions in vitro, thus providing therapeutic hope. These results pave the way for the identification of therapeutic targets that could reverse the deregulated response to oxidative stress in X-ALD.

Mutations in mitochondrial oxidative phosphorylation complex I are associated with multiple pathologies, and complex I has been proposed as a crucial regulator of animal longevity. In yeast, the single-subunit NADH dehydrogenase Ndi1 serves as a non-proton-translocating alternative enzyme that replaces complex I, bringing about the reoxidation of intramitochondrial NADH. We have created transgenic strains of Drosophila that express yeast NDI1 ubiquitously. Mitochondrial extracts from NDI1-expressing flies displayed a rotenone-insensitive NADH dehydrogenase activity, and functionality of the enzyme in vivo was confirmed by the rescue of lethality resulting from RNAi knockdown of complex I. NDI1 expression increased median, mean, and maximum lifespan independently of dietary restriction, and with no change in sirtuin activity. NDI1 expression mitigated the aging associated decline in respiratory capacity and the accompanying increase in mitochondrial reactive oxygen species production, and resulted in decreased accumulation of markers of oxidative damage in aged flies. Our results support a central role of mitochondrial oxidative phosphorylation complex I in influencing longevity via oxidative stress, independently of pathways connected to nutrition and growth signaling.aging | mitochondria | respiratory chain | free radicals M itochondria are key metabolic organelles whose oxidative phosphorylation (OXPHOS) system is considered to be one of the most efficient producers of bioenergy. When OX-PHOS function is compromized (e.g., by mutations or toxins), bioenergy supply and cellular homeostasis are seriously disrupted, which can be lethal.OXPHOS complex I plays a central role in the regulation of ATP production, intermediary metabolism, and apoptosis (1, 2), and mutations affecting it cause many human pathologies (3). It has also been proposed as a pacemaker of the aging process (4). Treatments inferred to decrease the production of reactive oxygen species (ROS) at the level of complex I can prolong lifespan in Drosophila (5). All these characteristics make it essential to understand better the role of complex I in vivo and its involvement in aging.Many organisms possess alternative enzymes that can bypass or replace the proton-translocating complexes of the mitochondrial respiratory chain. These include the alternative oxidases (AOX) and the NADH dehydrogenases of the Ndi and Nde families. Together these enzymes provide an alternative respiratory chain that potentially allows the maintenance of redox homeostasis and intermediary metabolism under conditions where flux through the "standard" respiratory chain is limited by high ATP levels, the action of toxins or other physiological restraints (6, 7). AOX acts as a bypass of complexes III and IV, whereas Nde or Ndi can bypass complex I.In previous studies these bypass enzymes were shown to be active when introduced into the mitochondria of higher metazoans such as mammals (8-12), arthropods (13), or nematodes (14), all of which lack endogenous alternative enzymes. Fu...

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ObjectiveAxonal degeneration is a main contributor to disability in progressive neurodegenerative diseases in which oxidative stress is often identified as a pathogenic factor. We aim to demonstrate that antioxidants are able to improve axonal degeneration and locomotor deficits in a mouse model of X-adrenoleukodystrophy (X-ALD).MethodsX-ALD is a lethal disease caused by loss of function of the ABCD1 peroxisomal transporter of very long chain fatty acids (VLCFA). The mouse model for X-ALD exhibits a late onset neurological phenotype with locomotor disability and axonal degeneration in spinal cord resembling the most common phenotype of the disease, adrenomyeloneuropathy (X-AMN). Recently, we identified oxidative damage as an early event in life, and the excess of VLCFA as a generator of radical oxygen species (ROS) and oxidative damage to proteins in X-ALD.ResultsHere, we prove the capability of the antioxidants N-acetyl-cysteine, α-lipoic acid, and α-tocopherol to scavenge VLCFA-dependent ROS generation in vitro. Furthermore, in a preclinical setting, the cocktail of the 3 compounds reversed: (1) oxidative stress and lesions to proteins, (2) immunohistological signs of axonal degeneration, and (3) locomotor impairment in bar cross and treadmill tests.InterpretationWe have established a direct link between oxidative stress and axonal damage in a mouse model of neurodegenerative disease. This conceptual proof of oxidative stress as a major disease-driving factor in X-AMN warrants translation into clinical trials for X-AMN, and invites assessment of antioxidant strategies in axonopathies in which oxidative damage might be a contributing factor. Ann Neurol 2011;