Evidence for increased mitochondrial superoxide production in Down syndrome

Triplication of HSA21 on alterations in structure and function of mitochondria

Triplication of genes encoded in human chromosome 21 (HSA21) is responsible for the phenotypes of Down syndrome (DS). The dosage-imbalance of the nuclear genes and the extra-nuclear mitochondrial DNA (mtDNA) jointly contributes to patho-mechanisms in DS. The mitochondrial organelles are the power house of cells for generation of ATP and maintaining cellular calcium and redox homeostasis, and cellular energy-metabolism processes. Each cell contains hundreds to thousands of mitochondria depending on their energy consumption. The dynamic structure of mitochondria is maintained with continuous fission and fusion events, and thus, content of mtDNA and its genetic composition are widely variable among cells. Cells of brain and heart tissues of DS patients and DS-mouse models have demonstrated elevated number but reduced amount of mtDNA due to higher fission process. This mechanism perturbs the oxidative phosphorylation (OXPHOS) and generates more free radicals such as reactive oxygen species (ROS), suggesting contribution of mtDNA in proliferation and protection of cells from endogenous toxic environment and external stressors. Gene-dosage in DS population collectively contributes to mitochondrial dysfunction by lowering energy production and respiratory capacity via the impaired OXPHOS, and damaged redox homeostasis and mitochondrial dynamics in all types of cells in DS. The context is highly complex and affects the functioning of all organs. The effect in brain and heart tissues promotes myriads of neurodegenerative diseases and cardiac complexities in individuals with DS. Crosstalk between trisomic nuclear and mitochondrial genome has been crucial for identification of potential therapeutic targets.

Future Perspectives in Oxidative Stress in Trisomy 13 and 18 Evaluation

Autosomal aneuploidies are the most frequently occurring congenital abnormalities and are related to many metabolic disorders, hormonal dysfunctions, neurotransmitter abnormalities, and intellectual disabilities. Trisomies are generated by an error of chromosomal segregation during cell division. Accumulating evidence has shown that deregulated gene expression resulting from the triplication of chromosomes 13 and 18 is associated with many disturbed cellular processes. Moreover, a disturbed oxidative stress status may be implicated in the occurrence of fetal malformations. Therefore, a literature review was undertaken to provide novel insights into the evaluation of trisomy 13 (T13) and 18 (T18) pathogeneses, with a particular concern on the oxidative stress. Corresponding to the limited literature data focused on factors leading to T13 and T18 phenotype occurrence, the importance of oxidative stress evaluation in T13 and T18 could enable the determination of subsequent disturbed metabolic pathways, highlighting the related role of mitochondrial dysfunction or epigenetics. This review illustrates up-to-date T13 and T18 research and discusses the strengths, limitations, and possible directions for future studies. The progressive unification of trisomy-related research protocols might provide potential medical targets in the future along with the implementation of the foundation of modern prenatal medicine.

Impaired Brain Mitochondrial Bioenergetics in the Ts65Dn Mouse Model of Down Syndrome Is Restored by Neonatal Treatment with the Polyphenol 7,8-Dihydroxyflavone

Down syndrome (DS), a major genetic cause of intellectual disability, is characterized by numerous neurodevelopmental defects. Previous in vitro studies highlighted a relationship between bioenergetic dysfunction and reduced neurogenesis in progenitor cells from the Ts65Dn mouse model of DS, suggesting a critical role of mitochondrial dysfunction in neurodevelopmental alterations in DS. Recent in vivo studies in Ts65Dn mice showed that neonatal supplementation (Days P3–P15) with the polyphenol 7,8-dihydroxyflavone (7,8-DHF) fully restored hippocampal neurogenesis. The current study was aimed to establish whether brain mitochondrial bioenergetic defects are already present in Ts65Dn pups and whether early treatment with 7,8-DHF positively impacts on mitochondrial function. In the brain and cerebellum of P3 and P15 Ts65Dn pups we found a strong impairment in the oxidative phosphorylation apparatus, resulting in a deficit in mitochondrial ATP production and ATP content. Administration of 7,8-DHF (dose: 5 mg/kg/day) during Days P3–P15 fully restored bioenergetic dysfunction in Ts65Dn mice, reduced the levels of oxygen radicals and reinstated the hippocampal levels of PGC-1α. No pharmacotherapy is available for DS. From current findings, 7,8-DHF emerges as a treatment with a good translational potential for improving mitochondrial bioenergetics and, thus, mitochondria-linked neurodevelopmental alterations in DS.

Mitochondrial Dysfunction: A Common Denominator in Neurodevelopmental Disorders?

Mitochondria, the organelles classically seen as the powerhouse of the cell, are increasingly associated with a wide variety of neurodevelopmental disorders. Although individually rare, a myriad of pediatric neurogenetic disorders have been identified in the last few years, thanks to advances in clinical genetic sequencing and data analysis. As this exponential growth continues, mitochondrial dysfunction is increasingly implicated in childhood neurodevelopmental disorders, with clinical presentations ranging from syndromic autism, intellectual disability, and epileptic encephalopathies to childhood onset neurodegeneration. Here we review recent evidence demonstrating mitochondrial involvement in neurodevelopmental disorders, identify emerging mechanistic trends, and reconsider the long-standing question of the role of mitochondria in light of new evidence: causation versus mere association.

Peripheral Oxidation Markers in Down Syndrome Patients: The Better and the Worse

Oxidative stress plays an important role in Down syndrome (DS) pathology since the gene dose effect leads to abnormal levels of certain enzymes and metabolites. In this review, we focused on relatively easy-to-obtain, peripheral markers of oxidative stress and inflammation, in order to compare the levels of these markers in DS patients and chromosomally healthy persons. Studies taking into account age- and sex-matched control groups were of particular interest in this context. We analyzed the factors that influence the levels of said markers in both groups (i.e., the usefulness of the markers), including the age of DS patients, occurrence of regular trisomy 21 or mosaicism, physical activity of patients, and the onset of Alzheimer's disease in DS. This paper was conceived as a handbook-to help for selecting suitable, easy-to-obtain markers for monitoring of the health status of DS patients (e.g., in nutritional studies and during dietary supplementation).

Down syndrome and Alzheimer's disease: common molecular traits beyond the amyloid precursor protein

Alzheimer’s disease (AD) is the most prevalent type of dementia. Down syndrome (DS) is the leading genetic risk factor for Early-Onset AD, prematurely presenting the classic pathological features of the brain with AD. Augmented gene dosage, including the APP gene, could partially cause this predisposition. Recent works have revealed that alterations in chromosome location due to the extra Chromosome 21, as well as epigenetic modifications, could promote changes in gene expression other than those from Chromosome 21. As a result, similar pathological features and cellular dysfunctions in DS and AD, including impaired autophagy, lysosomal activity, and mitochondrial dysfunction, could be controlled beyond APP overexpression. In this review, we highlight some recent data regarding the origin of the shared features between DS and AD and explore the mechanisms concerning cognitive deficiencies in DS associated with dementia, which could shed some light into the search for new therapeutic targets for AD treatment.

Metabolic and Growth Rate Alterations in Lymphoblastic Cell Lines Discriminate Between Down Syndrome and Alzheimer's Disease

BACKGROUND

Deficits in mitochondrial function and oxidative stress play pivotal roles in Down syndrome (DS) and Alzheimer's disease (AD) and these alterations in mitochondria occur systemically in both conditions.

OBJECTIVE

We hypothesized that peripheral cells of elder subjects with DS exhibit disease-specific and dementia-specific metabolic features. To test this, we performed a comprehensive analysis of energy metabolism in lymphoblastic-cell-lines (LCLs) derived from subjects belonging to four groups: DS-with-dementia (DSAD), DS-without-dementia (DS), sporadic AD, and age-matched controls.

METHODS

LCLs were studied under regular or minimal feeding regimes with galactose or glucose as primary carbohydrate sources. We assessed metabolism under glycolysis or oxidative phosphorylation by quantifying cell viability, oxidative stress, ATP levels, mitochondrial membrane potential (MMP), mitochondrial calcium uptake, and autophagy.

RESULTS

DS and DSAD LCLs showed slower growth rates under minimal feeding. DS LCLs mainly dependent on mitochondrial respiration exhibited significantly slower growth and higher levels of oxidative stress compared to other groups. While ATP levels (under mitochondrial inhibitors) and mitochondrial calcium uptake were significantly reduced in DSAD and AD cells, MMP was decreased in DS, DSAD, and AD LCLs. Finally, DS LCLs showed markedly reduced levels of the autophagy marker LC3-II, underscoring the close association between metabolic dysfunction and impaired autophagy in DS.

CONCLUSION

There are significant mitochondrial functional changes in LCLs derived from DS, DSAD, and AD patients. Several parameters analyzed were consistently different between DS, DSAD, and AD lines suggesting that metabolic indicators between LCL groups may be utilized as biomarkers of disease progression and/or treatment outcomes.

Mitochondria as pharmacological targets in Down syndrome

Mitochondria play a pivotal role in cellular energy-generating processes and are considered master regulators of cell life and death fate. Mitochondrial function integrates signalling networks in several metabolic pathways controlling neurogenesis and neuroplasticity. Indeed, dysfunctional mitochondria and mitochondrial-dependent activation of intracellular stress cascades are critical initiating events in many human neurodegenerative or neurodevelopmental diseases including Down syndrome (DS). It is well established that trisomy of human chromosome 21 can cause DS. DS is associated with neurodevelopmental delay, intellectual disability and early neurodegeneration. Recently, molecular mechanisms responsible for mitochondrial damage and energy deficits have been identified and characterized in several DS-derived human cells and animal models of DS. Therefore, therapeutic strategies targeting mitochondria could have great potential for new treatment regimens in DS. The purpose of this review is to highlight recent studies concerning mitochondrial impairment in DS, focusing on alterations of the molecular pathways controlling mitochondrial function. We will also discuss the effects and molecular mechanisms of naturally occurring and chemically synthetized drugs that exert neuroprotective effects through modulation of mitochondrial function and attenuation of oxidative stress. These compounds might represent novel therapeutic tools for the modulation of energy deficits in DS.

Plasma antioxidant enzymes and lipoperoxidation status in children with Down syndrome

OBJECTIVES

Oxidative stress (OS) may play a critical role in cell aging and neurologic disorders that are often seen in Down syndrome (DS) patients. The aim of this study was to determine the antioxidant enzyme level and lipoperoxidation status in blood from DS children.

DESIGN AND METHODS

In a cross-sectional study, we recruited a total of 36 DS children and 40 healthy controls (HCs). All subjects were free of infection according to the C reactive protein (CRP) value and routine peripheral blood profile. The activities of total superoxide dismutases (SODs), extracellular glutathione peroxidase (GPx3),malondialdehyde (MDA) and nitric oxide synthase (NOS) concentrations in peripheral blood were measured by spectrophotometric methods. The relationship of SOD and GPx3 was analyzed in the two groups.

RESULTS

The two groups were similar with respect to age, gender and peripheral blood profiles. The total SOD activity was significantly increased, while the GPx3 activity was significantly reduced in the DS group compared to the HCs (p=0.000, p=0.033 respectively). The MDA level was higher in DS children (p=0.013). There was no significant difference in NOS between DS and HCs (p=0.708). A significant negative correlation between GPx3 and SOD activity was identified in DS (r=-0.14, p=0.018) but not in the HC group.

CONCLUSIONS

Abnormal redox metabolism takes place in DS individuals. Reducing GPx3 may be a compensatory mechanism of protection against intracellular OS. Moreover, monitoring of decreases in GPx3 activity may be a useful biomarker for evaluating OS in DS patients.

Defective DNA repair and increased chromatin binding of DNA repair factors in Down syndrome fibroblasts

Down syndrome (DS) is characterized by genetic instability, neurodegeneration, and premature aging. However, the molecular mechanisms leading to this phenotype are not yet well understood. Here, we report that DS fibroblasts from both fetal and adult donors show the presence of oxidative DNA base damage, such as dihydro-8-oxoguanine (8-oxodG), and activation of a DNA damage response (DDR), already during unperturbed growth conditions. DDR with checkpoint activation was indicated by histone H2AX and Chk2 protein phosphorylation, and by increased p53 protein levels. In addition, both fetal and adult DS fibroblasts were more sensitive to oxidative DNA damage induced by potassium bromate, and were defective in the removal of 8-oxodG, as compared with age-matched cells from control healthy donors. The analysis of core proteins participating in base excision repair (BER), such as XRCC1 and DNA polymerase β, showed that higher amounts of these factors were bound to chromatin in DS than in control cells, even in the absence of DNA damage. These findings occurred in concomitance with increased levels of phosphorylated XRCC1 detected in DS cells. These results indicate that DS cells exhibit a BER deficiency, which is associated with prolonged chromatin association of core BER factors.

RCAN1 regulates mitochondrial function and increases susceptibility to oxidative stress in mammalian cells

Mitochondria are the primary site of cellular energy generation and reactive oxygen species (ROS) accumulation. Elevated ROS levels are detrimental to normal cell function and have been linked to the pathogenesis of neurodegenerative disorders such as Down's syndrome (DS) and Alzheimer's disease (AD). RCAN1 is abundantly expressed in the brain and overexpressed in brain of DS and AD patients. Data from nonmammalian species indicates that increased RCAN1 expression results in altered mitochondrial function and that RCAN1 may itself regulate neuronal ROS production. In this study, we have utilized mice overexpressing RCAN1 (RCAN1^ox) and demonstrate an increased susceptibility of neurons from these mice to oxidative stress. Mitochondria from these mice are more numerous and smaller, indicative of mitochondrial dysfunction, and mitochondrial membrane potential is altered under conditions of oxidative stress. We also generated a PC12 cell line overexpressing RCAN1 (PC12^RCAN1). Similar to RCAN1^ox neurons, PC12^RCAN1 cells have an increased susceptibility to oxidative stress and produce more mitochondrial ROS. This study demonstrates that increasing RCAN1 expression alters mitochondrial function and increases the susceptibility of neurons to oxidative stress in mammalian cells. These findings further contribute to our understanding of RCAN1 and its potential role in the pathogenesis of neurodegenerative disorders such as AD and DS.

Chronic melatonin treatment rescues electrophysiological and neuromorphological deficits in a mouse model of Down syndrome

The Ts65Dn mouse (TS), the most commonly used model of Down syndrome (DS), exhibits several key phenotypic characteristics of this condition. In particular, these animals present hypocellularity in different areas of their CNS due to impaired neurogenesis and have alterations in synaptic plasticity that compromise their cognitive performance. In addition, increases in oxidative stress during adulthood contribute to the age-related progression of cognitive and neuronal deterioration. We have previously demonstrated that chronic melatonin treatment improves learning and memory and reduces cholinergic neurodegeneration in TS mice. However, the molecular and physiological mechanisms that mediate these beneficial cognitive effects are not yet fully understood. In this study, we analyzed the effects of chronic melatonin treatment on different mechanisms that have been proposed to underlie the cognitive impairments observed in TS mice: reduced neurogenesis, altered synaptic plasticity, enhanced synaptic inhibition and oxidative damage. Chronic melatonin treatment rescued both impaired adult neurogenesis and the decreased density of hippocampal granule cells in trisomic mice. In addition, melatonin administration reduced synaptic inhibition in TS mice by increasing the density and/or activity of glutamatergic synapses in the hippocampus. These effects were accompanied by a full recovery of hippocampal LTP in trisomic animals. Finally, melatonin treatment decreased the levels of lipid peroxidation in the hippocampus of TS mice. These results indicate that the cognitive-enhancing effects of melatonin in adult TS mice could be mediated by the normalization of their electrophysiological and neuromorphological abnormalities and suggest that melatonin represents an effective treatment in retarding the progression of DS neuropathology.

Redox processes in neurodegenerative disease involving reactive oxygen species

Much attention has been devoted to neurodegenerative diseases involving redox processes. This review comprises an update involving redox processes reported in the considerable literature in recent years. The mechanism involves reactive oxygen species and oxidative stress, usually in the brain. There are many examples including Parkinson’s, Huntington’s, Alzheimer’s, prions, Down’s syndrome, ataxia, multiple sclerosis, Creutzfeldt-Jacob disease, amyotrophic lateral sclerosis, schizophrenia, and Tardive Dyskinesia. Evidence indicates a protective role for antioxidants, which may have clinical implications. A multifaceted approach to mode of action appears reasonable.

Mouse models of Down syndrome as a tool to unravel the causes of mental disabilities

Down syndrome (DS) is the most common genetic cause of mental disability. Based on the homology of Hsa21 and the murine chromosomes Mmu16, Mmu17 and Mmu10, several mouse models of DS have been developed. The most commonly used model, the Ts65Dn mouse, has been widely used to investigate the neural mechanisms underlying the mental disabilities seen in DS individuals. A wide array of neuromorphological alterations appears to compromise cognitive performance in trisomic mice. Enhanced inhibition due to alterations in GABA(A)-mediated transmission and disturbances in the glutamatergic, noradrenergic and cholinergic systems, among others, has also been demonstrated. DS cognitive dysfunction caused by neurodevelopmental alterations is worsened in later life stages by neurodegenerative processes. A number of pharmacological therapies have been shown to partially restore morphological anomalies concomitantly with cognition in these mice. In conclusion, the use of mouse models is enormously effective in the study of the neurobiological substrates of mental disabilities in DS and in the testing of therapies that rescue these alterations. These studies provide the basis for developing clinical trials in DS individuals and sustain the hope that some of these drugs will be useful in rescuing mental disabilities in DS individuals.

Mitochondrial dysfunction and Down's syndrome: is there a role for coenzyme Q(10) ?

Structural changes and abnormal function of mitochondria have been documented in Down's syndrome (DS) cells, patients, and animal models. DS cells in culture exhibit a wide array of functional mitochondrial abnormalities including reduced mitochondrial membrane potential, reduced ATP production, and decreased oxido-reductase activity. New research has also brought to central stage the prominent role of oxidative stress in this condition. This review focuses on recent advances in the field with a particular emphasis on novel translational approaches involving the utilization of coenzyme Q(10) (CoQ(10) ) to treat a variety of clinical phenotypes associated with DS that are linked to increased oxidative stress and energy deficits. CoQ(10) has already provided promising results in several different conditions associated with altered energy metabolism and oxidative stress in the CNS. Two studies conducted in Ancona investigated the effect of CoQ(10) treatment on DNA damage in DS patients. Although the effect of CoQ(10) was evidenced only at single cell level, the treatment affected the distribution of cells according to their content in oxidized bases. In fact, it produced a strong negative correlation linking cellular CoQ(10) content and the amount of oxidized purines. Results suggest that the effect of CoQ(10) treatment in DS not only reflects antioxidant efficacy, but likely modulates DNA repair mechanisms.

Mitochondrial dysfunction in some oxidative stress-related genetic diseases: Ataxia-Telangiectasia, Down Syndrome, Fanconi Anaemia and Werner Syndrome

Oxidative stress is a phenotypic hallmark in several genetic disorders characterized by cancer predisposition and/or propensity to premature ageing. Here we review the published evidence for the involvement of oxidative stress in the phenotypes of Ataxia-Telangiectasia (A-T), Down Syndrome (DS), Fanconi Anaemia (FA), and Werner Syndrome (WS), from the viewpoint of mitochondrial dysfunction. Mitochondria are recognized as both the cell compartment where energetic metabolism occurs and as the first and most susceptible target of reactive oxygen species (ROS) formation. Thus, a critical evaluation of the basic mechanisms leading to an in vivo pro-oxidant state relies on elucidating the features of mitochondrial impairment in each disorder. The evidence for different mitochondrial dysfunctions reported in A-T, DS, and FA is reviewed. In the case of WS, clear-cut evidence linking human WS phenotype to mitochondrial abnormalities is lacking so far in the literature. Nevertheless, evidence relating mitochondrial dysfunctions to normal ageing suggests that WS, as a progeroid syndrome, is likely to feature mitochondrial abnormalities. Hence, ad hoc research focused on elucidating the nature of mitochondrial dysfunction in WS pathogenesis is required. Based on the recognized, or reasonably suspected, role of mitochondrial abnormalities in the pathogenesis of these disorders, studies of chemoprevention with mitochondria-targeted supplements are warranted.

Alzheimer's disease in Down syndrome: neurobiology and risk

Down syndrome (DS) is characterized by increased mortality rates, both during early and later stages of life, and age-specific mortality risk remains higher in adults with DS compared with the overall population of people with mental retardation and with typically developing populations. Causes of increased mortality rates early in life are primarily due to the increased incidence of congenital heart disease and leukemia, while causes of higher mortality rates later in life may be due to a number of factors, two of which are an increased risk for Alzheimer's disease (AD) and an apparent tendency toward premature aging. In this article, we describe the increase in lifespan for people with DS that has occurred over the past 100 years, as well as advances in the understanding of the occurrence of AD in adults with DS. Aspects of the neurobiology of AD, including the role of amyloid, oxidative stress, Cu/ZN dismutase (SOD-1), as well as advances in neuroimaging are presented. The function of risk factors in the observed heterogeneity in the expression of AD dementia in adults with DS, as well as the need for sensitive and specific biomarkers of the clinical and pathological progressing of AD in adults with DS is considered.

Effects of chronic administration of SGS-111 during adulthood and during the pre- and post-natal periods on the cognitive deficits of Ts65Dn mice, a model of Down syndrome

The Ts65Dn mouse is the most commonly used model of Down syndrome. This mouse shows many phenotypic characteristics present in people with Down syndrome, including behavioral and cognitive deficits. SGS-111 is a novel analogue of the nootropic piracetam, which prevents oxidative damage and apoptosis in both normal and Down syndrome human cortical neurons. In this work we tested the ability of chronic administration of SGS-111 to adult Ts65Dn mice to reverse the cognitive deficit found in these mice. Moreover, since oxidative stress has been reported as early as the fetal stage, SGS-111 was also administered to pregnant Ts65Dn females from the day of conception throughout the pregnancy and to Ts65Dn pups during their entire life (5 months), from birth to the end of the behavioral testing period. A characterization of the effects of SGS-111 treatment on Ts65Dn and control mice sensorimotor abilities, motor coordination, spontaneous activity, activity in the open field, exploration, anxiety and spatial and non-spatial short- and long-term learning and memory was performed. The behavioral characterization showed that chronic administration of the antioxidant SGS-111 reduced the hyperactivity shown by Ts65Dn mice in their home cage, in the open field and in the hole board test. SGS-111 administration during adulthood improved performance in the first session in the Morris water maze in control mice, and when administered during the pre- and post-natal periods, improved spatial learning in the control mice but not in Ts65Dn mice. Chronic SGS-111 administration failed to affect behavior and cognition in Ts65Dn mice.

Coenzyme Q10 absorption and tolerance in children with Down syndrome: a dose-ranging trial

Controlled studies of coenzyme Q(10) dosing and tolerance have been reported in adults, but not in pediatric patients. This study compares low- and high-dose coenzyme Q(10) (LiQ-NOL syrup) absorption and tolerance in children with Down syndrome. After a 1-month low-dose (1.0 mg/kg/day) run-in period, all participants received high-dose coenzyme Q(10) (10.0 mg/kg/day) for two additional months (in randomized sequence as one daily dose or split into two daily doses). Chemistry profiles and complete blood counts were determined just before and at the study completion. Plasma coenzyme Q(10) concentrations were determined initially and at each study visit. Parents reported adverse events and study drug evaluations using standardized forms. Most of the 16 children who completed this study tolerated high-dose coenzyme Q(10) well. Uncooperative behavior resulted in premature withdrawal of two participants, and may have been treatment-related. Pre- and posttreatment laboratory test changes were considered to be clinically nonsignificant. Study results indicate that high-dose coenzyme Q(10) (10 mg/kg/day) is well-absorbed and well-tolerated by most children with Down syndrome, and appears to provide plasma concentrations which are comparable to previous adult studies administering much higher coenzyme Q(10) dosages.

Oxidative stress and hematologic and biochemical parameters in individuals with Down syndrome

OBJECTIVE

To evaluate the levels of thiobarbituric acid reactive substances (TBARS), uric acid, and seric superoxide dismutase and catalase activities, as well as total serum iron, total iron-binding capacity (TIBC), erythrocyte osmotic fragility, and hemograms in people with Down syndrome.

PARTICIPANTS AND METHODS

The study sampled (July to December 2003) 50 people with Down syndrome and 50 individuals without Down syndrome (control group) matched by age and sex. The levels of TBARS were measured by the TBARS method. Serum superoxide dismutase and catalase activities and uric acid levels were determined spectrophotometrically. Erythrocyte osmotic fragility was assessed by the percentage of hemolysis. Hemograms, total serum iron level, and TIBC were determined with automated systems.

RESULTS

The results showed that levels of TBARS, uric acid, and seric superoxide dismutase and catalase activities were higher in the Down syndrome group compared with the control group. We also observed a slight increase in erythrocyte osmotic fragility in the Down syndrome group, but the total serum iron levels, TIBC, and hemograms for both groups were within the age-related reference values.

CONCLUSION

This was the first time, to our knowledge, that increases in seric superoxide dismutase and catalase activities were observed in people with Down syndrome. Although other studies are necessary, our results add to the understanding of the mechanisms responsible for the increased oxidative stress observed in individuals with Down syndrome and may be useful in supporting future antioxidant therapies that will improve the lives of people with Down syndrome.

Drosophila melanogaster homolog of Down syndrome critical region 1 is critical for mitochondrial function

Mitochondrial dysfunction has emerged as a common theme that underlies numerous neurological disorders, including Down syndrome. Down syndrome cultures and tissues show mitochondrial damage such as impaired mitochondrial enzyme activities, defective mitochondrial DNA repairs and accumulation of toxic free radicals, but the cause of mitochondrial dysfunction remains elusive. Here we demonstrate that the Drosophila melanogaster homolog of human Down syndrome critical region gene 1 (DSCR1), nebula (also known as sarah, sra), has a crucial role in the maintenance of mitochondrial function and integrity. We report that nebula protein is located in the mitochondria. An alteration in the abundance of nebula affects mitochondrial enzyme activities, mitochondrial DNA content, and the number and size of mitochondria. Furthermore, nebula interacts with the ADP/ATP translocator and influences its activity. These results identify nebula/DSCR1 as a regulator of mitochondrial function and integrity and further suggest that an increased level of DSCR1 may contribute to the mitochondrial dysfunction seen in Down syndrome.

Antioxidant enzymes and lipid peroxides in children with cerebral palsy

Impaired antioxidant mechanisms are unable to inactivate free radicals that may induce a number of pathophysiological processes and result in cell injury. Thus, any abnormality in antioxidant defense systems could affect neurodevelopmental processes and could have an important role in the etiology of cerebral palsy (CP). The plasma levels of lipid peroxidation as plasma levels of malondialdehyde (MDA), activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR) in plasma and erythrocytes were investigated in 34 CP children and compared with 61 normal controls. SOD, GPx and GR activities were spectrophotometrically assayed. Activities of SOD, GPx and GR in plasma did not differ significantly between CP children and the control group. Activities of erythrocyte GR in the CP patients were significantly lower compared with controls. MDA concentration did not differ statistically between the CP children and healthy subjects. In conclusion our results suggest that increased activities of erythrocyte GPx and decreased erythrocyte GR activities might be due to lesser physical activity of children with CP.

Down's syndrome

The sequencing of chromosome 21 and the use of models of Down's syndrome in mice have allowed us to relate genes and sets of genes to the neuropathogenesis of this syndrome, and to better understand its phenotype. Research in prenatal screening and diagnosis aims to find methods to identify fetuses with Down's syndrome, and reduce or eliminate the need for amniocentesis. Other areas of active research and clinical interest include the association of Down's syndrome with coeliac disease and Alzheimer's disease, and improved median age of death. Medical management of the syndrome requires an organised approach of assessment, monitoring, prevention, and vigilance. Improvements in quality of life of individuals with Down's syndrome have resulted from improvements in medical care, identification and treatment of psychiatric disorders (such as depression, disruptive behaviour disorders, and autism), and early educational interventions with support in typical educational settings. Approaches and outcomes differ throughout the world.