Nrf2 Signaling: An Adaptive Response Pathway for Neurodegenerative Disorders

Oxidative damage contributes to pathogenesis in many neurodegenerative diseases. As the indicator and regulator of oxidative stress, the nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway has been shown to have dynamic changes and examined for its neuroprotective role in many cases. Nrf2 is emerging as a regulatory protein in neuronal death, since it helps neuronal cells to meet with oxidative insults. In this chapter, we summarize the role of Nrf2 as a master regulator of oxidative stress. Furthermore, we treat some natural and chemical substances able to modulate the Nrf2 pathway and, therefore, their possible use in the neurodegenerative diseases therapeutic treatment

Gly482Ser PGC-1α gene polymorphism and exercise-related oxidative stress in amyotrophic lateral sclerosis patients

The role of exercise in Amyotrophic lateral sclerosis (ALS) pathogenesis is controversial and unclear. Exercise induces a pleiotropic adaptive response in skeletal muscle, largely through the peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), a transcriptional coactivator that regulates mitochondrial biogenesis and antioxidant defense mechanisms. It has been suggested that a Gly482Ser substitution in PGC-1α has functional relevance in human disorders and in athletic performance. To test this hypothesis, we examined the genotype distribution of PGC-1α Gly482Ser (1444 G > A) in ALS patients to evaluate whether or not the minor serine-encoding allele 482Ser is involved in oxidative stress responses during physical exercise. We genotyped 197 sporadic ALS patients and 197 healthy controls in order to detect differences in allelic frequencies and genotype distribution between the two groups. A total of 74 ALS patients and 65 controls were then comparatively assessed for plasmatic levels of the oxidative stress biomarkers, advanced oxidation protein products, ferric reducing ability and thiol groups. In addition a subgroup of 35 ALS patients were also assessed for total SOD and catalase plasmatic activity. Finally in 28 ALS patients we evaluated the plasmatic curve of the oxidative stress biomarkers and lactate during an incremental exercise test. No significant differences were observed in the genotype distribution and allelic frequency in ALS patients compared to the controls. We found significant increased advanced oxidation protein products (p A SNP, ALS patients with Gly482Ser allelic variant show increased exercise-related oxidative stress. This thus highlights the possible role of this antioxidant defense transcriptional coactivator in ALS

α-Synuclein Heterocomplexes with β-Amyloid Are Increased in Red Blood Cells of Parkinson's Disease Patients and Correlate with Disease Severity

Neurodegenerative disorders (NDs) are characterized by abnormal accumulation/misfolding of specific proteins, primarily α-synuclein (α-syn), β-amyloid1-42(Aβ1-42) and tau, in both brain and peripheral tissues. In addition to oligomers, the role of the interactions of α-syn with Aβ or tau has gradually emerged. Nevertheless, despite intensive research, NDs have no accepted peripheral markers for biochemical diagnosis. In this respect, Red Blood Cells (RBCs) are emerging as a valid peripheral model for the study of aging-related pathologies. Herein, a small cohort (N= 28) of patients affected by Parkinson's disease (PD) and age-matched controls were enrolled to detect the content of α-syn (total and oligomeric), Aβ1-42and tau (total and phosphorylated) in RBCs. Moreover, the presence of α-syn association with tau and Aβ1-42was explored by co-immunoprecipitation/western blotting in the same cells, and quantitatively confirmed by immunoenzymatic assays. For the first time, PD patients were demonstrated to exhibit α-syn heterocomplexes with Aβ1-42and tau in peripheral tissues; interestingly, α-syn-Aβ1-42concentrations were increased in PD subjects with respect to healthy controls (HC), and directly correlated with disease severity and motor deficits. Moreover, total-α-syn levels were decreased in PD subjects and inversely related to their motor deficits. Finally, an increase of oligomeric-α-syn and phosphorylated-tau was observed in RBCs of the enrolled patients. The combination of three parameters (total-α-syn, phosphorylated-tau and α-syn-Aβ1-42concentrations) provided the best fitting predictive index for discriminating PD patients from controls. Nevertheless further investigations should be required, overall, these data suggest α-syn hetero-aggregates in RBCs as a putative tool for the diagnosis of PD

α-Synuclein Aggregates with β-Amyloid or Tau in Human Red Blood Cells: Correlation with Antioxidant Capability and Physical Exercise in Human Healthy Subjects

Neurodegenerative disorders (NDs) are characterized by abnormal accumulation/misfolding of specific proteins, primarily α-synuclein (α-syn), β-amyloid1–42 (Aβ), and tau, in both brain and peripheral tissue. In addition to homo-oligomers, the role of α-syn interactions with Aβ or tau has gradually emerged. The altered protein accumulation has been related to both oxidative stress and physical activity; nevertheless, no correlation among the presence of peripheral α-syn hetero-aggregates, antioxidant capacity, and physical exercise has been discovered as of yet. Herein, the content of α-syn, Aβ, tau, and of their heterocomplexes was determined in red blood cells (RBCs) of healthy subjects (sedentary and athletes). Such parameters were related to the extent of the antioxidant capability (AOC), a key marker of oxidative stress in aging-related pathologies, and to physical exercise, which is known to play an important preventive role in NDs and to modulate oxidative stress. Tau content and plasma AOC toward hydroxyl radicals were both reduced in older or sedentary subjects; in contrast, α-syn and Aβ accumulated in elderly subjects and showed an inverse correlation with both hydroxyl AOC and the level of physical activity. For the first time, α-syn heterocomplexes with Aβ or tau were quantified and demonstrated to be inversely related to hydroxyl AOC. Furthermore, α-syn/Aβ aggregates were significantly reduced in athletes and inversely correlated with physical activity level, independent of age. The positive correlation between antioxidant capability/physical activity and reduced protein accumulation was confirmed by these data and suggested that peripheral α-syn heterocomplexes may represent new indicators of ND-related protein misfolding

Common and rare variant association analyses in amyotrophic lateral sclerosis identify 15 risk loci with distinct genetic architectures and neuron-specific biology

A cross-ancestry genome-wide association meta-analysis of amyotrophic lateral sclerosis (ALS) including 29,612 patients with ALS and 122,656 controls identifies 15 risk loci with distinct genetic architectures and neuron-specific biology. Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with a lifetime risk of one in 350 people and an unmet need for disease-modifying therapies. We conducted a cross-ancestry genome-wide association study (GWAS) including 29,612 patients with ALS and 122,656 controls, which identified 15 risk loci. When combined with 8,953 individuals with whole-genome sequencing (6,538 patients, 2,415 controls) and a large cortex-derived expression quantitative trait locus (eQTL) dataset (MetaBrain), analyses revealed locus-specific genetic architectures in which we prioritized genes either through rare variants, short tandem repeats or regulatory effects. ALS-associated risk loci were shared with multiple traits within the neurodegenerative spectrum but with distinct enrichment patterns across brain regions and cell types. Of the environmental and lifestyle risk factors obtained from the literature, Mendelian randomization analyses indicated a causal role for high cholesterol levels. The combination of all ALS-associated signals reveals a role for perturbations in vesicle-mediated transport and autophagy and provides evidence for cell-autonomous disease initiation in glutamatergic neurons

Evaluation of nuclear factor erythroid 2-related factor 2 gene as a genic modulator of response to oxidative stress in neurodegenerative diseases.

To maintain redox homeostasis is imperative for normal function of the brain. This process is regulated by antioxidants, detoxifying proteins and other molecules. With age, genetic and environmental risk factors, the oxidative-redox system becomes imbalanced and oxidative stress (OS) ensues through increased levels of reactive oxygen species (ROS) and reactive nitrogen species (RNS). The rate of ROS/RNS production eventually overwhelms our endogenous antioxidant defenses leading to the accumulation of oxidative damage such as post-translational modifications of lipids, proteins and DNA/RNA, a common feature of many neurodegenerative diseases. The oxidative modifications affect the physiological functions of these cell components and cause abnormal deposits in neurons and/or glia in diseases such as Alzheimer's disease (AD), Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS). Although it remains hard to understand whether or no OS is the cause or effect of the disease, also because of the multifactorial nature of neuronal death and additive effects of pathogenic mechanisms on neuronal vitality along disease course, the association between oxidative damage and the disease makes therapeutic targeting of the antioxidant systems an attractive option. The nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway is a primary sensor and a master regulator of OS via its ability to modulate the expression of hundreds of antioxidant and detoxifying genes. Activation of the Nrf2-ARE pathway has shown benefits in animal models of many neurodegenerative disorders supporting the concept of developing pharmaceuticals to activate the Nrf2-ARE pathway in the brain. Nrf2 belongs to the Cap’n’collar (Cnc) transcription factor family and is considered the “master regulator” of the antioxidant response since it modulates the expression and the coordinated induction of an array of defensive genes encoding phase II detoxifying enzymes and antioxidant proteins, such as NAD(P)H: quinine oxidoreductases (NQOs), heme oxygenase- 1 (HO-1), the glutathione S-transferase (GST) family, multidrug resistance-associated proteins (Mrps). TheNrf2 is a very unstable protein, typically present in association with its negative regulator Kelch-like ECH-associated protein 1 (Keap1), which acts as a molecular sensor of cellular redox homeostasis disturbance. Under basal condition, Keap1 retains Nrf2 in the cytoplasm, linking this transcriptional factor to the actin cytoskeleton and driving its degradation. Specifically, Keap1 acts as a linker protein between Nrf2 and the Cul3-based E3-ubiquitin ligase complex, promoting Nrf2 ubiquitination and consequent degradation by the 26S proteasome. This quenching interaction between the two proteins is a dynamic process controlled by specific intracellular cascades that allow for a fine-tuned regulation of inducible expression of Nrf2 target genes under OS or after exposure to toxic electrophiles. In fact, activation of Nrf2 requires its cytosolic stabilization via oxidative modification of distinct Keap1 cysteine residues and/or Keap1 ubiquitination and proteasomal degradation. It has been largely demonstrated that also Nrf2 phosphorylation facilitates its dissociation from Keap1. Therefore, several signaling pathways, such as the activation of mitogen-activated protein kinase (MAPK) cascade, phosphatidylinositol 3-kinase (PI3K), and protein kinaseC (PKC), favour Nrf2 detachment from its repressors and the consequent translocation to the nucleus. In the nuclear compartment Nrf2 forms a heterodimer with its partner small Maf and binds specific cis-acting antioxidant response element (ARE) sequences, ultimately transactivating a battery of highly inducible cytoprotective genes thus allowing cell to efficiently cope with endogenous stress and exogenous toxicants. Nrf2 has also been shown to modulate the transcription of genes promoting mitochondrial biogenesis, such as mitochondrial transcription factors (TFAM), and consequently to be directly involved in mitochondrial maintenance. Considering the pivotal defensive role exerted by the Nrf2/ARE pathway, it is evident that the dysregulation of Nrf2-regulated genes offers a logical explanation for the direct and indirect association between OS and several neurodegenerative conditions, such as PD, AD and ALS. AD is probably the most common neurodegenerative disease, accounting for 60% to 70% of cases of dementia with nearly 44 million affected people worldwide, and although its etiology is still unclear, it is characterized by the presence of brain amyloid plaques and neurofibrillary tangles whose accumulation ultimately leads to extensive neuronal loss and progressive decline of cognitive function. They are deposits of proteins distributed throughout the brain of AD patients, particularly in the entorhinal cortex, hippocampus, and temporal, frontal, and inferior parietal lobes. Some of the major risk factors for AD are unhealthy aging in sporadic AD cases, the presence of ApoE-4 alleles in both sporadic and familial AD and genetic factors, such as mutation in amyloid precursor protein (APP) and presenilin-1 (PS1) in familial AD among others. AD brain is characterized by mitochondrial dysfunction, reactive gliosis and oxidative damage to lipids and proteins. Growing evidence demonstrates that the AD brain is under tremendous OS. A significantly increased HO-1 expression was reported in post-mortem AD temporal cortex and hippocampus compared to aged-matched control. Additionally, an increased Nqo1 activity and expression was found in astrocytes and neurons of AD brain and Nrf2 was predominantly localized in cytoplasm in AD hippocampal neurons. Furthermore, there is increased protein oxidation and lipid peroxidation in AD brain when compared to aged matched controls. Recent studies in aged APP/PS1 AD mouse models showed reduced Nrf2, Nqo1, GCL catalytic subunit (GCLC) and GCL modifier subunit (GCLM) mRNA and Nrf2 protein levels. PD affects more than 1% of the population over 60 years of age and is the second most common neurodegenerative disorder after AD. The majority of cases (90%) are sporadic, while about 10% show monogenic inheritance. PD is caused by the degeneration of dopaminergic neurons within the substantia nigra pars compacta (SNc) and although there is still no clear explanation for the intrinsic vulnerability of these neurons, it is known that they are more prone and susceptible to OS. Data indicate that OS plays an important role in αSyn proteostasis. As the master regulator of the cellular antioxidant defense system, the Nrf2-ARE pathway is a logical target to examine for neuroprotection against misfolded proteins induced pathology. Activation of theNrf2-ARE pathway has been shown to be protective against the toxic forms of αSyn in several studies. In SK-N-SH neuroblastoma cells, ferrous iron promotes αSyn aggregation through inhibiting Nrf2 pathway. αSyn aggregation exacerbates ferrous iron-induced oxidative damage, mitochondrial impairment and apoptosis. Recently studies have identified the importance of astrocytic Nrf2 regulating αSyn proteostasis. Astrocytic over expression of Nrf2 (GFAP-Nrf2) can reduce αSyn aggregates in the central nervous system of a PD mouse model with neuronal over expression of human αSyn mutant A53T. These observations are not due to Nrf2-mediated down regulation of the hαSynA53T transgene levels in the mice. ALS is a rare adult-onset neurodegenerative disease characterized by the selective degeneration of motor neurons in the motor cortex, brainstem, and spinal cord. Most of the cases (90%) are sporadic (SALS), while the remainder presents a family history (FALS). Although the exact cause of ALS is still unknown, a major step forward in the understanding of the pathogenetic events involved in ALS was provided in 1993 by the observation that mutations in the gene coding for the antioxidant enzyme Cu/Zn superoxide dismutase (SOD1) are carried by the 15– 20% of FALS patients. ALS is a complex and multifactorial disease characterized by the involvement of several interconnected pathogenic events, such as OS, mitochondrial dysfunction, inflammation, glutamate excitotoxicity, protein misfolding and aggregation, aberrant RNA metabolism, and altered gene expression. In particular, OS is one of the most detrimental contributors of disease onset and progression. In fact, several distinctive oxidation markers have been observed in both nervous and peripheral tissues in SALS and FALS patients. Elevated protein carbonyl and 3- nitrotyrosine levels have been detected in spinal cord and motor cortex from SALS and FALS patients, particularly in large ventral motor neurons. Lipid oxidation has also been identified in motor neurons, astrocytes, and microglia of SALS patients compared to control individuals. Elevated levels of HNE have been detected also in CSF and in sera from ALS patients. Additionally, mitochondrial defects have been reported as a major hallmark in motor neuron degeneration in ALS. These dysfunctions are tightly interrelated with OS cascades, activating overlapping molecular pathways in a vicious cycle of harmful events. Notably, impairment in defensive mechanisms has also been revealed in ALS, including downregulation of members of glutathione S-transferase family, peroxiredoxins, and, in particular, the transcriptional factor Nrf2. The aim of this research project has been to evaluate a possible association between -653 A> G, - 651 G> A and -617 C> functional polymorphisms in the NRF2 promoter gene, and the respective risk of ALS, PD and AD disease and their possible implication in molecular mechanisms of cellular response to oxidative damage. In particular, the following evaluations were assessed: • the distribution of allelic and genotypic frequencies of the three functional single nucleotide polymorphisms (SNPs) -653 A> G, -651 G> A and -617 C> A in 154 ALS patients, 172 PD patients, 240 AD patients and 186 healthy controls; genotyping was carried out by DNA direct sequencing. • the plasma levels of some oxidative stress biomarkers in 73 ALS patients, 47 PD patients, 139 AD patients and 68 healthy controls ; in particular, as oxidative damage markers, we evaluated the protein oxidation products (AOPP) and, as non-enzymatic antioxidant markers we evaluated the Antioxidant Iron Reduction Capacity (FRAP) and total plasma thiol groups. The biomarkers levels were carried out by spectrophotometric methods • the mRNA expression level by Real Time PCR in 13 ALS patients, 15 PD patients and 14 AD patients • the possible association of the functional polymorphisms in the NRF2 gene promoter with the clinical features of the patients. • the possible association of the functional polymorphisms in the NRF2 gene promoter with the NRF2 transcript levels and oxidative stress biomarkers The analysis of AD population shows that the allelic variant -653G is associated with increased risk of disease (OR 1.27 IC95% 1.01-1.59); relative to the polymorphisms -651 G> A and -617 C> A, any significant differences in the genotypic distribution and allelic frequencies of patients with AD compared to the controls has been found. The evaluation of peripheral oxidative stress biomarkers shows a significant decrease in FRAP (p<0.01) and thiol groups levels (p<0.001). We not found any imbalance in the AOPP level of AD patients compared to controls. mRNA expression in individuals carrying one (AG) or two (GG) mutated alleles of the -653 A>G SNP promoter was significantly decreased (p<0.01) compared to wild-type (AA) carriers at this position, this both for AG and GG carriers. Analysis of PD population data shows that the allelic variant -653G is associated with increased risk of disease (OR 1.34 IC95% 1.08-1.67); with respect to the polymorphisms -651 G>A and -617 C> A, any significant differences has been found in the genotypic distribution and in allelic frequencies of PD patients compared to the controls. The evaluation of peripheral oxidative stress biomarkers shows a significant decrease in FRAP (p< 0.0001) and thiol groups levels (p<0.001). Any imbalance in the AOPP level of PD patients compared to controls has been found. mRNA expression in individuals carrying one (AG) or two (GG) mutated alleles of the -653 A>G promoter SNP was significantly decreased (p<0.01) compared to wild-type (AA) carriers at this position. Also in this case the difference was significant difference or both AG and GG carriers. Finally, also in PD patients, a correlation between -653G variant, mRNA expression level and oxidative stress biomarkers has been found. Analysis of ALS population data shows that the allelic -653G variant is associated with increased risk of disease (OR 1.71 IC95% 1.18-2.48); in relation to the polymorphisms -651 G> A and -617 C> A, no significant differences has been found in the genotypic distribution and in the allelic frequencies of patients with ALS compared to the controls. The evaluation of peripheral oxidative stress biomarkers shows a significant increase in AOPP levels (p< 0.001) and a significant decrease in thiol groups levels (p<0.01) in ALS patients; we did not found any imbalance in the FRAP level of ALS patients compared to controls. mRNA expression in individuals carrying one (AG) or two (GG) mutated alleles of the -653 A>G SNP promoter was significantly decreased (p>0.05) compared to wild-type (AA) carriers at this position; this observed between the G non carriers and G carriers, although at of genotypic levels, AG and GG. Finally, the data obtained showed a correlation between -653G variant, mRNA expression level and oxidative stress biomarkers. The data obteined suggest that the -653G variant in NRF2 promoter gene is a common risk factor for AD or PD and ALS. This variant is always associated to decreased level of NRF2 mRNA as evaluated in peripheral lymphocytes. All together these underlines that Nrf2-ARE pathway can be one of the molecular mechanisms commonly involved in neurodegeneration, although the different profile of alteration of redox balance indicates that the effects are different in each one of the neurodegenerative disorders. In any case, conclusive remarks can be assumed in terms of relevance of oxidative stress events as integral part of the pathogenic complex of these diseases

SCLEROSI LATERALE AMIOTROFICA E STRESS OSSIDATIVO: UNO STUDIO ALL'ESORDIO DI MALATTIA

La Sclerosi Laterale Amiotrofica (SLA) o malattia di Lou-Gehrig è una patologia neurodegenerativa che comporta la progressiva perdita dei motoneuroni a livello della corteccia motoria, del bulbo e del midollo spinale. Tra le ipotesi formulate riguardo le modalità di insorgenza della SLA, le più accreditate, oltre quella eccitotossica, chiamano in causa lo stress ossidativo e le alterazioni a carico del mitocondrio. Lo stress ossidativo descrive una condizione in cui si manifesta un’alterazione dell’equilibrio fra la produzione delle specie chimiche reattive ossidanti e la loro degradazione da parte dei sistemi di difesa antiossidante. Tra le specie chimiche reattive, l’aumento intracellulare delle specie reattive dell’ossigeno (ROS) provoca alterazione della struttura e della funzione delle membrane biologiche, danno al DNA, alle proteine e ai lipidi. Lo stress ossidativo sembra svolgere un ruolo patogenetico rilevante sia nel processo d’invecchiamento precoce che in alcune gravi patologie a sfondo infiammatorio e/o degenerativo. Infatti, il sistema nervoso centrale è altamente vulnerabile al danno ossidativo, a causa di un basso livello di enzimi antiossidanti, un elevato contenuto di substrati ossidabili e una gran quantità di ROS prodotte durante le reazioni neurochimiche. In questo lavoro di tesi sono stati analizzati biomarcatori plamatici di stress ossidativo in 32 pazienti affetti da SLA sporadica (13/19 M / F, età media 63,3 ± 10,8 anni) al momento della diagnosi della malattia e in 54 soggetti sani (25/29 M/F, età media 69,3 ± 9,2 anni). La valutazione della risposta cellulare all’insulto ossidativo è stata effettuata tramite la determinazione di marcatori periferici di danno alle proteine (AOPP), la determinazione della capacità ferro riducente del plasma (FRAP) e la determinazione dei tioli plasmatici (-SH) tramite l’utilizzo di tecniche spettrofotometriche. I risultati ottenuti dall’analisi di marcatori di danno ossidativo sembrano confermare una consistente alterazione del profilo redox nei pazienti rispetto ai controlli; che si riflette in un aumento dei livelli medi di AOPP ed una diminuzione dei livelli medi della FRAP e dei tioli plasmatici nei pazienti affetti da SLA. Non è stata osservata alcuna correlazione tra AOPP, FRAP e –SH e fenotipo di malattia. I risultati ottenuti rinforzano il ruolo dello stress ossidativo nella SLA, anche in una fase molto precoce della malattia. I marcatori analizzati possono rappresentare marcatori utili per rilevare lo squilibrio redox nella SLA, fornendo così un valido strumento non invasivo per monitorare lo stato ossido riduttivo e la risposta alle terapie antiossidanti

.Clinical features and pathogenesis of Alzheimer's disease: involvement of mitochondria and mitochondrial DNA.

Alzheimer's disease (AD) is a neurodegenerative disorder which results in the irreversible loss of cortical neurons, particularly in the associative neocortex and hippocampus. AD is the most common form of dementia in the elderly people. Apart from the neuronal loss, the pathological hallmarks are extracellular senile plaques containing the peptide beta-amyloid (AP) and neurofibrillary tangles. The Af cascade hypothesis remains the main pathogenetic model, as suggested by familiar AD, mainly associated to mutation in amyloid precursor protein and presenilin genes. The remaining 95% of AD patients are mostly sporadic late-onset cases, with a complex aetiology due to interactions between environmental conditions and genetic features of the individual. Mitochondria play a central role in the bioenergetics of the cell and apoptotic cell death. Morphological, biochemical and genetic abnormalities of the mitochondria in several AD tissues have been reported. Impaired mitochondrial respiration, particularly COX deficiency, has been observed in brain, platelets and fibroblasts of AD patients. Somatic mutations in mitochondrial DNA (mtDNA) could cause energy failure and increased oxidative stress. No causative mutations in the mtDNA have been detected and studies on mtDNA polymorphisms are controversial, but the "mitochondrial cascade hypothesis" here revised, could explain many of the biochemical, genetic and pathological features of sporadic AD

Effects of aerobic training on exercise-related oxidative stress in mitochondrial myopathies.

In mitochondrial myopathies with respiratory chain deficiency impairment of energy cell production may lead to in excess reactive oxygen species generation with consequent oxidative stress and cell damage. Aerobic training has been showed to increase muscle performance in patients with mitochondrial myopathies. Aim of this study has been to evaluate, in 7 patients (6 F e 1M, mean age 44.9 ± 12.1 years) affected by mitochondrial disease, concomitantly to lactate exercise curve, the occurrence of oxidative stress, as indicated by circulating levels of lipoperoxides, in rest condition and as effect of exercise, and also, to verify if an aerobic training program is able to modify, in these patients, ox-redox balance efficiency. At rest and before training blood level of lipoperoxides was 382.4 ± 37.8 AU, compared to controls (318.7 ± 63.8; P<0.05), this corresponding to a moderate oxidative stress degree according to the adopted scale. During incremental exercise blood level of lipoperoxides did not increase, but maintained significantly higher compared to controls. After an aerobic training of 10 weeks the blood level of lipoperoxides decreased by 13.7% at rest (P<0.01) and 10.4%, 8.6% and 8.5% respectively at the corresponding times during the exercise test (P=0.06). These data indicate that, in mitochondrial patients, oxidative stress occurs and that an aerobic training is useful in partially reverting this condition