GVS-111 prevents oxidative damage and apoptosis in normal and Down's syndrome human cortical neurons

Repurposing cancer drugs identifies kenpaullone which ameliorates pathologic pain in preclinical models via normalization of inhibitory neurotransmission

Inhibitory GABA-ergic neurotransmission is fundamental for the adult vertebrate central nervous system and requires low chloride concentration in neurons, maintained by KCC2, a neuroprotective ion transporter that extrudes intracellular neuronal chloride. To identify Kcc2 gene expression‑enhancing compounds, we screened 1057 cell growth-regulating compounds in cultured primary cortical neurons. We identified kenpaullone (KP), which enhanced Kcc2/KCC2 expression and function in cultured rodent and human neurons by inhibiting GSK3ß. KP effectively reduced pathologic pain-like behavior in mouse models of nerve injury and bone cancer. In a nerve-injury pain model, KP restored Kcc2 expression and GABA-evoked chloride reversal potential in the spinal cord dorsal horn. Delta-catenin, a phosphorylation-target of GSK3ß in neurons, activated the Kcc2 promoter via KAISO transcription factor. Transient spinal over-expression of delta-catenin mimicked KP analgesia. Our findings of a newly repurposed compound and a novel, genetically-encoded mechanism that each enhance Kcc2 gene expression enable us to re-normalize disrupted inhibitory neurotransmission through genetic re-programming.

Noopept Attenuates Diabetes-Mediated Neuropathic Pain and Oxidative Hippocampal Neurotoxicity via Inhibition of TRPV1 Channel in Rats

Neuropathic pain and oxidative neurotoxicity are two adverse main actions of diabetes mellitus (DM). The expression levels of calcium ion (Ca²⁺) permeable TRPV1 channels are high in the dorsal root ganglion (DRGs) and hippocampus (HIPPO). TRPV1 is activated by capsaicin and reactive free oxygen radicals (fROS) to mediate peripheral neuropathy and neurotoxicity. Noopept (NP) acted several protective antioxidant actions against oxidative neurotoxicity. As DM is known to increase the levels of fROS, the protective roles of antioxidant NP were evaluated on the DM-mediated neurotoxicity and neuropathic pain via the modulation of TRPV1 in rats. Thirty-six rats were equally divided into control, NP, DM (streptozotocin, STZ), and STZ + NP groups. A decrease on the STZ-mediated increase of neuropathic pain (via the analyses of Von Frey and hot plate) and blood glucose level was observed by the treatment of NP. A protective role of NP via downregulation of TRPV1 activity on the STZ-induced increase of apoptosis, mitochondrial fROS, lipid peroxidation, caspase -3 (CASP-3), caspase -9 (CASP-9), TRPV1 current density, glutathione (GSH), cytosolic free Zn²⁺, and Ca²⁺ concentrations in the DRGs and HIPPO was also observed. The STZ-mediated decrease of glutathione peroxidase, GSH, vitamin E, and β-carotene concentrations in the brain cortex, erythrocyte, liver, kidney, and plasma was also attenuated by the treatment of NP. The STZ-mediated increase of TRPV1, CASP-3, and CASP-9 expressions was decreased in the DRGs and HIPPO by the treatment of NP. In conclusion, the treatment of NP induced protective effects against STZ-induced adverse peripheral pain and HIPPO oxidative neurotoxicity. These effects might attribute to the potent antioxidant property of NP.

Noopept; a nootropic dipeptide, modulates persistent inflammation by effecting spinal microglia dependent Brain Derived Neurotropic Factor (BDNF) and pro-BDNF expression throughout apoptotic process

There are largely unknown associations between changes in pain behavior responses during persistent peripheral inflammation and spinal cell alteration such as apoptosis. Some evidence suggests that microglia and microglia related mediators play notable roles in induction and maintenance of central nervous system pathologies and inflammatory pain. By considering those relationships and microglia related nootrophic factors, such as the Brain Derived Neurotrophic Factor (BDNF) in CNS, we attempted to assess the relationship between microglia dependent BDNF and its precursor with pain behavior through spinal cell apoptosis as well as the effect of Noopept on this relationship. Persistent peripheral inflammation was induced by a single subcutaneous injection of Complete Freund's Adjuvant (CFA) on day 0. Thermal hyperalgesia, paw edema, microglial activity, microglia dependent BDNF, pro-BDNF expression, and apoptosis were assessed in different experimental groups by confirmed behavioral and molecular methods on days 0, 7, and 21 of the study. Our findings revealed hyperalgesia and spinal cell apoptosis significantly increased during the acute phase of CFA-induced inflammation but was then followed by a decrement in the chronic phase of the study. Aligned with these variations in spinal microglial activity, microglia dependent BDNF significantly increased during the acute phase of CFA-induced inflammation. Our results also indicated that daily administration of Noopept (during 21 days of the study) not only caused a significant decrease in hyperalgesia and microglia dependent BDNF expression but also changed the apoptosis process in relation to microglia activity alteration. It appears that the administration of Noopept can decrease spinal cell apoptosis and hyperalgesia during CFA-induced inflammation due to its direct effects on microglial activity and microglia dependent BDNF and pro-BDNF expression.

Antioxidants in Down Syndrome: From Preclinical Studies to Clinical Trials

There is currently no effective pharmacological therapy to improve the cognitive dysfunction of individuals with Down syndrome (DS). Due to the overexpression of several chromosome 21 genes, cellular and systemic oxidative stress (OS) is one of the most important neuropathological processes that contributes to the cognitive deficits and multiple neuronal alterations in DS. In this condition, OS is an early event that negatively affects brain development, which is also aggravated in later life stages, contributing to neurodegeneration, accelerated aging, and the development of Alzheimer's disease neuropathology. Thus, therapeutic interventions that reduce OS have been proposed as a promising strategy to avoid neurodegeneration and to improve cognition in DS patients. Several antioxidant molecules have been proven to be effective in preclinical studies; however, clinical trials have failed to show evidence of the efficacy of different antioxidants to improve cognitive deficits in individuals with DS. In this review we summarize preclinical studies of cell cultures and mouse models, as well as clinical studies in which the effect of therapies which reduce oxidative stress and mitochondrial alterations on the cognitive dysfunction associated with DS have been assessed.

Neuroprotective Dipeptide Noopept Prevents DNA Damage in Mice with Modeled Prediabetes

In experiments on BALB/c mice, prediabetes was modeled by administration of streptozotocin in a dose of 130 mg/kg. DNA damage was assessed by the method of DNA comets. Noopept (0.5 mg/kg intraperitoneally) was administered for 14 days before and for 6, 13, or 14 days after streptozotocin administration. Despite moderate hyperglycemia and increased malondialdehyde level, the intensity of DNA damage in cells of the pancreas, liver, and kidneys significantly surpassed the control values. Noopept normalized these parameters due to its pronounced antigenotoxic effect. For both the damaging effect of streptozotocin and the normalizing effect of Noopept, DNA changes manifested mainly in terms of atypical DNA comets. Our findings confirm the role of DNA damage in the pathogenesis of diabetes. They indicate the possibility of pharmacological protection of pancreatic β cells with the neuroprotective drug and provide an important argument in favor of the hypothesis about the similarity of the mechanisms of formation of the resistance of neurons and β cells to the cytotoxic influences.

Translational validity and implications of pharmacotherapies in preclinical models of Down syndrome

Neurodevelopmental disorders are challenging to study in the laboratory, and despite a large investment, few novel treatments have been developed in the last decade. While animal models have been valuable in elucidating disease mechanisms and in providing insights into the function of specific genes, the predictive validity of preclinical models to test potential therapies has been questioned. In the last two decades, diverse new murine models of Down syndrome (DS) have been developed and numerous studies have demonstrated neurobiological alterations that could be responsible for the cognitive and behavioral phenotypes found in this syndrome. In many cases, similar alterations were found in murine models and in individuals with DS, although several phenotypes shown in animals have yet not been confirmed in the human condition. Some of the neurobiological alterations observed in mice have been proposed to account for their changes in cognition and behavior, and have received special attention because of being putative therapeutic targets. Those include increased oxidative stress, altered neurogenesis, overexpression of the Dyrk1A gene, GABA-mediated overinhibition and Alzheimer's disease-related neurodegeneration. Subsequently, different laboratories have tested the efficacy of pharmacotherapies targeting these alterations. Unfortunately, animal models are limited in their ability to mimic the extremely complex process of human neurodevelopment and neuropathology. Therefore, the safety and efficacy identified in animal studies are not always translated to humans, and most of the drugs tested have not demonstrated any positive effect or very limited efficacy in clinical trials. Despite their limitations, though, animal trials give us extremely valuable information for developing and testing drugs for human use that cannot be obtained from molecular or cellular experiments alone. This chapter reviews some of these therapeutic approaches and discusses some reasons that could account for the discrepancy between the findings in mouse models of DS and in humans, including: (i) the incomplete resemble of the genetic alterations of available mouse models of DS and human trisomy 21, (ii) the lack of evidence that some of the phenotypic alterations found in mice (e.g., GABA-mediated overinhibition, and alterations in adult neurogenesis) are also present in DS individuals, and (iii) the inaccuracy and/or inadequacy of the methods used in clinical trials to detect changes in the cognitive and behavioral functions of people with DS. Despite the shortcomings of animal models, animal experimentation remains an invaluable tool in developing drugs. Thus, we will also discuss how to increase predictive validity of mouse models.

Drug with Neuroprotective Properties Noopept Does Not Stimulate Cell Proliferation

Effects of Noopept (N-phenylacetyl-L-prolylglycine ethyl ester) on the relative level of proliferation marker Ki-67 and cell cycle parameters were studied in HEK293 and SH-SY5Y cell lines. The previously established multifactorial mechanism of action of the drug includes enhancement of neurotrophin NGF and BDNF expression and increase in HIF-1 activity. The possible mitogenic action of Noopept was estimated by its effect on cell proliferation. Noopept did not affect cell distribution over G1, S, G2 cell cycle phases and the relative level of proliferation marker Ki-67 in the cell lines under study. These data suggest that Noopept does not stimulate cell growth.

Novel Technologies for Dipeptide Drugs Design and their Implantation

The article is an overview of author's data obtained in the framework of the project "The Creation of dipeptide preparations" at the V.V. Zakusov Institute of Pharmacology, Moscow, Russia. Advantages of dipeptides over longer peptides consist in that they are orally active owing to higher stability and ability to penetrate biological barriers due to the presence of specific ATP-dependent transporters in enterocytes and blood-brain barrier. Two original approaches for dipeptide drugs design have been developed. Both of them are based on the idea of a leading role of central dipeptide fragment of the peptide chain beta-turn in the peptide-receptor interaction. The first approach, named "peptide drug-based design" represents the transformation of known nonpeptide drug into its dipeptide topological analog. The latter usually corresponds to a beta-turn of some regulatory peptide. The second approach represents the design of tripeptoide mimetic of the beta-turn of regulatory peptide or protein. The results of the studies, which led to the discovery of endogenous prototypes of the known non-peptide drugs piracetam and sulpiride, are presented herein. The paper discusses the process, based on the abovementioned principles, that was used in designing of nontoxic, orally available, highly effective dipeptide drugs: nootropic noopept, dipeptide analog of piracetam; antipsychotic dilept, neurotensin tripeptoid analog; selective anxiolytic GB-115, tripeptoid analog of CCK-4, and potential neuroprotector GK-2, homodimeric dipeptide analog of NGF.

Neurogenesis impairment: An early developmental defect in Down syndrome

Down syndrome (DS) is characterized by brain hypotrophy and intellectual disability starting from early life stages. Accumulating evidence shows that the phenotypic features of the DS brain can be traced back to the fetal period since the DS brain exhibits proliferation potency reduction starting from the critical time window of fetal neurogenesis. This defect is worsened by the fact that neural progenitor cells exhibit reduced acquisition of a neuronal phenotype and an increase in the acquisition of an astrocytic phenotype. Consequently, the DS brain has fewer neurons in comparison with the typical brain. Although apoptotic cell death may be increased in DS, this does not seem to be the major cause of brain hypocellularity. Evidence obtained in brains of individuals with DS, DS-derived induced pluripotent stem cells (iPSCs), and DS mouse models has provided some insight into the mechanisms underlying the developmental defects due to the trisomic condition. Although many triplicated genes may be involved, in the light of the studies reviewed here, DYRK1A, APP, RCAN1 and OLIG1/2 appear to be particularly important determinants of many neurodevelopmental alterations that characterize DS because their triplication affects both the proliferation and fate of neural precursor cells as well as apoptotic cell death. Based on the evidence reviewed here, pathways downstream to these genes may represent strategic targets, for the design of possible interventions.

Chronic Melatonin Administration Reduced Oxidative Damage and Cellular Senescence in the Hippocampus of a Mouse Model of Down Syndrome

Previous studies have demonstrated that melatonin administration improves spatial learning and memory and hippocampal long-term potentiation in the adult Ts65Dn (TS) mouse, a model of Down syndrome (DS). This functional benefit of melatonin was accompanied by protection from cholinergic neurodegeneration and the attenuation of several hippocampal neuromorphological alterations in TS mice. Because oxidative stress contributes to the progression of cognitive deficits and neurodegeneration in DS, this study evaluates the antioxidant effects of melatonin in the brains of TS mice. Melatonin was administered to TS and control mice from 6 to 12 months of age and its effects on the oxidative state and levels of cellular senescence were evaluated. Melatonin treatment induced antioxidant and antiaging effects in the hippocampus of adult TS mice. Although melatonin administration did not regulate the activities of the main antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathione S-transferase) in the cortex or hippocampus, melatonin decreased protein and lipid oxidative damage by reducing the thiobarbituric acid reactive substances (TBARS) and protein carbonyls (PC) levels in the TS hippocampus due to its ability to act as a free radical scavenger. Consistent with this reduction in oxidative stress, melatonin also decreased hippocampal senescence in TS animals by normalizing the density of senescence-associated β-galactosidase positive cells in the hippocampus. These results showed that this treatment attenuated the oxidative damage and cellular senescence in the brain of TS mice and support the use of melatonin as a potential therapeutic agent for age-related cognitive deficits and neurodegeneration in adults with DS.

Dipeptide Piracetam Analogue Noopept Improves Viability of Hippocampal HT-22 Neurons in the Glutamate Toxicity Model

Effect of noopept (N-phenylacetyl-prolylglycine ethyl ester) on viability of neurons exposed to neurotoxic action of glutamic acid (5 mM) was studied in vitro in immortalized mouse hippocampal HT-22 neurons. Noopept added to the medium before or after glutamic acid improved neuronal survival in a concentration range of 10-11-10-5 M. Comparison of the effective noopept concentrations determined in previous studies on cultured cortical and cerebellar neurons showed that hippocampal neurons are more sensitive to the protective effect of noopept.

Pharmacological approaches to improving cognitive function in Down syndrome: current status and considerations

Down syndrome (DS), also known as trisomy 21, is the most common genetic cause of intellectual disability (ID). Although ID can be mild, the average intelligence quotient is in the range of 40-50. All individuals with DS will also develop the neuropathology of Alzheimer's disease (AD) by the age of 30-40 years, and approximately half will display an AD-like dementia by the age of 60 years. DS is caused by an extra copy of the long arm of human chromosome 21 (Hsa21) and the consequent elevated levels of expression, due to dosage, of trisomic genes. Despite a worldwide incidence of one in 700-1,000 live births, there are currently no pharmacological treatments available for ID or AD in DS. However, over the last several years, very promising results have been obtained with a mouse model of DS, the Ts65Dn. A diverse array of drugs has been shown to rescue, or partially rescue, DS-relevant deficits in learning and memory and abnormalities in cellular and electrophysiological features seen in the Ts65Dn. These results suggest that some level of amelioration or prevention of cognitive deficits in people with DS may be possible. Here, we review information from the preclinical evaluations in the Ts65Dn, how drugs were selected, how efficacy was judged, and how outcomes differ, or not, among studies. We also summarize the current state of human clinical trials for ID and AD in DS. Lastly, we describe the genetic limitations of the Ts65Dn as a model of DS, and in the preclinical testing of pharmacotherapeutics, and suggest additional targets to be considered for potential pharmacotherapies.

Neuroprotective effect of novel cognitive enhancer noopept on AD-related cellular model involves the attenuation of apoptosis and tau hyperphosphorylation

Background

Noopept (N-phenyl-acetyl-L-prolylglycine ethyl ester) was constructed as a dipeptide analog of the standard cognition enhancer, piracetam. Our previous experiments have demonstrated the cognition restoring effect of noopept in several animal models of Alzheimer disease (AD). Noopept was also shown to prevent ionic disbalance, excitotoxicity, free radicals and pro-inflammatory cytokines accumulation, and neurotrophine deficit typical for different kinds of brain damages, including AD. In this study, we investigated the neuroprotective action of noopept on cellular model of AD, Aβ_25–35-induced toxicity in PC12 cells and revealed the underlying mechanisms.

Results

The neuroprotective effect of noopept (added to the medium at 10 μM concentration, 72 hours before Аβ_25–35) was studied on Аβ_25–35-induced injury (5 μM for 24 h) in PC12 cells. The ability of drug to protect the impairments of cell viability, calcium homeostasis, ROS level, mitochondrial function, tau phosphorylation and neurite outgrowth caused by Аβ_25–35 were evaluated.

Following the exposure of PC12 cells to Аβ_25–35 an increase of the level of ROS, intracellular calcium, and tau phosphorylation at Ser396 were observed; these changes were accompanied by a decrease in cell viability and an increase of apoptosis. Noopept treatment before the amyloid-beta exposure improved PC12 cells viability, reduced the number of early and late apoptotic cells, the levels of intracellular reactive oxygen species and calcium and enhanced the mitochondrial membrane potential. In addition, pretreatment of PC12 cell with noopept significantly attenuated tau hyperphosphorylation at Ser396 and ameliorated the alterations of neurite outgrowth evoked by Аβ_25–35.

Conclusions

Taken together, these data provide evidence that novel cognitive enhancer noopept protects PC12 cell against deleterious actions of Aβ through inhibiting the oxidative damage and calcium overload as well as suppressing the mitochondrial apoptotic pathway. Moreover, neuroprotective properties of noopept likely include its ability to decrease tau phosphorylation and to restore the altered morphology of PC12 cells. Therefore, this nootropic dipeptide is able to positively affect not only common pathogenic pathways but also disease-specific mechanisms underlying Aβ-related pathology.

Nerve growth factor metabolic dysfunction in Down's syndrome brains

Basal forebrain cholinergic neurons play a key role in cognition. This neuronal system is highly dependent on NGF for its synaptic integrity and the phenotypic maintenance of its cell bodies. Basal forebrain cholinergic neurons progressively degenerate in Alzheimer's disease and Down's syndrome, and their atrophy contributes to the manifestation of dementia. Paradoxically, in Alzheimer's disease brains, the synthesis of NGF is not affected and there is abundance of the NGF precursor, proNGF. We have shown that this phenomenon is the result of a deficit in NGF's extracellular metabolism that compromises proNGF maturation and exacerbates its subsequent degradation. We hypothesized that a similar imbalance should be present in Down's syndrome. Using a combination of quantitative reverse transcription-polymerase chain reaction, enzyme-linked immunosorbent assay, western blotting and zymography, we investigated signs of NGF metabolic dysfunction in post-mortem brains from the temporal (n = 14), frontal (n = 34) and parietal (n = 20) cortex obtained from subjects with Down's syndrome and age-matched controls (age range 31-68 years). We further examined primary cultures of human foetal Down's syndrome cortex (17-21 gestational age weeks) and brains from Ts65Dn mice (12-22 months), a widely used animal model of Down's syndrome. We report a significant increase in proNGF levels in human and mouse Down's syndrome brains, with a concomitant reduction in the levels of plasminogen and tissue plasminogen activator messenger RNA as well as an increment in neuroserpin expression; enzymes that partake in proNGF maturation. Human Down's syndrome brains also exhibited elevated zymogenic activity of MMP9, the major NGF-degrading protease. Our results indicate a failure in NGF precursor maturation in Down's syndrome brains and a likely enhanced proteolytic degradation of NGF, changes which can compromise the trophic support of basal forebrain cholinergic neurons. The alterations in proNGF and MMP9 were also present in cultures of Down's syndrome foetal cortex; suggesting that this trophic compromise may be amenable to rescue, before frank dementia onset. Our study thus provides a novel paradigm for cholinergic neuroprotection in Alzheimer's disease and Down's syndrome.

Comparative activity of proline-containing dipeptide noopept and inhibitor of dipeptidyl peptidase-4 sitagliptin in a rat model of developing diabetes

Developing diabetes was modeled on adult male Wistar rats by repeated intraperitoneal injections of streptozotocin in a subdiabetogenic dose of 30 mg/kg for 3 days. Proline-containing dipeptide drug Noopept or a standard diabetic drug dipeptidyl peptidase-4 inhibitor sitagliptin was administered per os in a dose of 5 mg/kg before each injection of the toxin and then for 16 days after streptozotocin course. In active control group, spontaneously increase glucose level and reduced tolerance to glucose load (1000 mg/kg intraperitoneally) were observed on the next day after the third administration of toxin. Basal glucose level decreased by day 16, but glucose tolerance remained impaired. Noopept normalized the basal blood glucose level and tolerance to glucose load on the next day after administration of streptozotocin. The effect of Noopept persisted to the end of the experiment. At early terms of the experiment, sitagliptin was somewhat superior to Noopept by the effect on baseline glucose level, but was inferior by the influence on glucose tolerance.. By the end of the experiment, Noopept significantly (by 2 times) surpassed sitagliptin by its effect on glucose tolerance.

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.

Bisphenol A delays the perinatal chloride shift in cortical neurons by epigenetic effects on the Kcc2 promoter

Bisphenol A (BPA) is a ubiquitous compound that is emerging as a possible toxicant during embryonic development. BPA has been shown to epigenetically affect the developing nervous system, but the molecular mechanisms are not clear. Here we demonstrate that BPA exposure in culture led to delay in the perinatal chloride shift caused by significant decrease in potassium chloride cotransporter 2 (Kcc2) mRNA expression in developing rat, mouse, and human cortical neurons. Neuronal chloride increased correspondingly. Treatment with epigenetic compounds decitabine and trichostatin A rescued the BPA effects as did knockdown of histone deacetylase 1 and combined knockdown histone deacetylase 1 and 2. Furthermore, BPA evoked increase in tangential interneuron migration and increased chloride in migrating neurons. Interestingly, BPA exerted its effect in a sexually dimorphic manner, with a more accentuated effect in females than males. By chromatin immunoprecipitation, we found a significant increase in binding of methyl-CpG binding protein 2 to the "cytosine-phosphate-guanine shores" of the Kcc2 promoter, and decrease in binding of acetylated histone H3K9 surrounding the transcriptional start site. Methyl-CpG binding protein 2-expressing neurons were more abundant resulting from BPA exposure. The sexually dimorphic effect of BPA on Kcc2 expression was also demonstrated in cortical neurons cultured from the offspring of BPA-fed mouse dams. In these neurons and in cortical slices, decitabine was found to rescue the effect of BPA on Kcc2 expression. Overall, our results indicate that BPA can disrupt Kcc2 gene expression through epigenetic mechanisms. Beyond increase in basic understanding, our findings have relevance for identifying unique neurodevelopmental toxicity mechanisms of BPA, which could possibly play a role in pathogenesis of human neurodevelopmental disorders.

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.

Neuroprotective and nootropic drug noopept rescues α-synuclein amyloid cytotoxicity

Parkinson's disease is a common neurodegenerative disorder characterized by α-synuclein (α-Syn)-containing Lewy body formation and selective loss of dopaminergic neurons in the substantia nigra. We have demonstrated the modulating effect of noopept, a novel proline-containing dipeptide drug with nootropic and neuroprotective properties, on α-Syn oligomerization and fibrillation by using thioflavin T fluorescence, far-UV CD, and atomic force microscopy techniques. Noopept does not bind to a sterically specific site in the α-Syn molecule as revealed by heteronuclear two-dimensional NMR analysis, but due to hydrophobic interactions with toxic amyloid oligomers, it prompts their rapid sequestration into larger fibrillar amyloid aggregates. Consequently, this process rescues the cytotoxic effect of amyloid oligomers on neuroblastoma SH-SY5Y cells as demonstrated by using cell viability assays and fluorescent staining of apoptotic and necrotic cells and by assessing the level of intracellular oxidative stress. The mitigating effect of noopept against amyloid oligomeric cytotoxicity may offer additional benefits to the already well-established therapeutic functions of this new pharmaceutical.

Reversal of diabetic nephropathy by a ketogenic diet

Intensive insulin therapy and protein restriction delay the development of nephropathy in a variety of conditions, but few interventions are known to reverse nephropathy. Having recently observed that the ketone 3-beta-hydroxybutyric acid (3-OHB) reduces molecular responses to glucose, we hypothesized that a ketogenic diet, which produces prolonged elevation of 3-OHB, may reverse pathological processes caused by diabetes. To address this hypothesis, we assessed if prolonged maintenance on a ketogenic diet would reverse nephropathy produced by diabetes. In mouse models for both Type 1 (Akita) and Type 2 (db/db) diabetes, diabetic nephropathy (as indicated by albuminuria) was allowed to develop, then half the mice were switched to a ketogenic diet. After 8 weeks on the diet, mice were sacrificed to assess gene expression and histology. Diabetic nephropathy, as indicated by albumin/creatinine ratios as well as expression of stress-induced genes, was completely reversed by 2 months maintenance on a ketogenic diet. However, histological evidence of nephropathy was only partly reversed. These studies demonstrate that diabetic nephropathy can be reversed by a relatively simple dietary intervention. Whether reduced glucose metabolism mediates the protective effects of the ketogenic diet remains to be determined.

A role for thrombospondin-1 deficits in astrocyte-mediated spine and synaptic pathology in Down's syndrome

BACKGROUND

Down's syndrome (DS) is the most common genetic cause of mental retardation. Reduced number and aberrant architecture of dendritic spines are common features of DS neuropathology. However, the mechanisms involved in DS spine alterations are not known. In addition to a relevant role in synapse formation and maintenance, astrocytes can regulate spine dynamics by releasing soluble factors or by physical contact with neurons. We have previously shown impaired mitochondrial function in DS astrocytes leading to metabolic alterations in protein processing and secretion. In this study, we investigated whether deficits in astrocyte function contribute to DS spine pathology.

METHODOLOGY/PRINCIPAL FINDINGS

Using a human astrocyte/rat hippocampal neuron coculture, we found that DS astrocytes are directly involved in the development of spine malformations and reduced synaptic density. We also show that thrombospondin 1 (TSP-1), an astrocyte-secreted protein, possesses a potent modulatory effect on spine number and morphology, and that both DS brains and DS astrocytes exhibit marked deficits in TSP-1 protein expression. Depletion of TSP-1 from normal astrocytes resulted in dramatic changes in spine morphology, while restoration of TSP-1 levels prevented DS astrocyte-mediated spine and synaptic alterations. Astrocyte cultures derived from TSP-1 KO mice exhibited similar deficits to support spine formation and structure than DS astrocytes.

CONCLUSIONS/SIGNIFICANCE

These results indicate that human astrocytes promote spine and synapse formation, identify astrocyte dysfunction as a significant factor of spine and synaptic pathology in the DS brain, and provide a mechanistic rationale for the exploration of TSP-1-based therapies to treat spine and synaptic pathology in DS and other neurological conditions.

Effects of voluntary physical exercise on adult hippocampal neurogenesis and behavior of Ts65Dn mice, a model of Down syndrome

The Ts65Dn (TS) mouse is the most widely used model of Down syndrome (DS). This mouse shares many phenotypic characteristics with the human condition including cognitive and neuromorphological alterations. In this study the effects of physical exercise on hippocampal neurogenesis and behavior in TS mice were assessed. 10-12 month-old male TS and control (CO) mice were submitted to voluntary physical exercise for 7 weeks and the effects of this protocol on hippocampal morphology, neurogenesis and apoptosis were evaluated. Physical exercise improved performance in the acquisition sessions of the Morris water maze in TS but not in CO mice. Conversely, it did not have any effect on anxiety or depressive behavior in TS mice but it did reduce the cognitive components of anxiety in CO mice. TS mice presented a reduced dentate gyrus (DG) volume, subgranular zone area and number of granule neurons. Hippocampal neurogenesis was reduced in TS mice as shown by the reduced number of 5-bromo-2-deoxyuridine (BrdU) positive cells. Voluntary physical exercise did not rescue these alterations in TS mice but it did increase the number of doublecortin (DCX)-and phospho histone 3 (PH3)-positive neurons in CO mice. It is concluded that physical exercise produced a modest anxiolytic effect in CO mice and that this was accompanied by an increased number of immature cells in the hippocampal DG. On the other hand, voluntary physical exercise exerted a positive effect on TS mice learning of the platform position in the Morris water maze that seems to be mediated by a neurogenesis-independent mechanism.

The relationship of ceruloplasmin and neural tube defects

OBJECTIVE

To compare the levels of ceruloplasmin (cp) in the amniotic fluids and maternal bloods of second trimester fetuses with and without neural tube defects (NTD).

MATERIALS AND METHODS

66 pregnant women were included in the study. Amniocentesis was performed in 32 women in a patient group diagnosed as NTD or anencephaly and 34 pregnants in a control group with positive Down Syndrome screening test. Maternal bloods were also taken. Cp was measured with Erel's ceruloplasmin measurement method.

RESULTS

The cp levels of the amniotic fluid of patients and controls were not statistically different (p>0.05). The cp levels of the maternal bloods were not different in two groups (p>0.05).

CONCLUSION

As an antioxidant, no relation was found between cp and NTD.

Molecular basis of pharmacotherapies for cognition in Down syndrome

Intellectual disability in Down syndrome (DS) ranges from low normal to severely impaired and has a significant impact on the quality-of-life of the individuals affected and their families. Because the incidence of DS remains at approximately 1 in 700 live births and the lifespan is now >50 years, development of pharmacotherapies for cognitive deficits is an important goal. DS is due to an extra copy of human chromosome 21 and has often been considered too complex a genetic abnormality to be amenable to intervention. However, recent successes in rescuing learning/memory impairments in a mouse model of DS suggest that this negative outlook may not be justified. In this contribution, we first review the DS phenotype, chromosome 21 gene content and mouse models. We then discuss recent successes and the remaining challenges in the identification of targets for and preclinical evaluation of potential therapeutics.

Proliferation deficits and gene expression dysregulation in Down's syndrome (Ts1Cje) neural progenitor cells cultured from neurospheres

Down's syndrome neurophenotypes are characterized by mental retardation and a decreased brain volume. To identify whether deficits in proliferation could be responsible for this phenotype, neural progenitor cells were isolated from the developing E14 neocortex of Down's syndrome partial trisomy Ts1Cje mice and euploid (WT) littermates and grown as neurospheres. Ts1Cje neural progenitors proliferated at a slower rate, because of a longer cell cycle, and a greater number of cells were positive for glial fibrillary acidic protein. An increase in cell death was also noted. Gene expression profiles of neural progenitor cells from Ts1Cje and WT showed that 54% of triploid genes had expression ratios (Ts1Cje/WT) significantly greater than the expected diploid gene ratio of 1.0. Some diploid genes associated with proliferation, differentiation, and glial function were dysregulated. Interestingly, proliferation and gene expression dysregulation detected in the Ts1Cje mice did not require overexpression of the chromosome 21 genes amyloid precursor protein (App) and soluble superoxide dismutase 1 (Sod1).

A role for synaptic zinc in activity-dependent Abeta oligomer formation and accumulation at excitatory synapses

Soluble amyloid beta oligomers (AbetaOs) interfere with synaptic function and bind with high affinity to synapses, but the mechanism underlying AbetaO synaptic targeting is not known. Here, we show that the accumulation of synthetic or native Alzheimer's disease (AD)-brain oligomers at synapses is regulated by synaptic activity. Electrical or chemical stimulation increased AbetaO synaptic localization and enhanced oligomer formation at synaptic terminals, whereas inhibition with TTX blocked AbetaO synaptic localization and reduced AbetaO synaptic load. The zinc-binding 8-OH-quinoline clioquinol markedly reduced AbetaO synaptic targeting, which was also reduced in brain sections of animals deficient in the synaptic vesicle zinc transporter ZnT3, indicating that vesicular zinc released during neurotransmission is critical for AbetaO synaptic targeting. Oligomers were not internalized in recycled vesicles but remained at the cell surface, where they colocalized with NR2B NMDA receptor subunits. Furthermore, NMDA antagonists blocked AbetaO synaptic targeting, implicating excitatory receptor activity in oligomer formation and accumulation at synapses. In AD brains, oligomers of different size colocalized with synaptic markers in hippocampus and cortex, where oligomer synaptic accumulation correlated with synaptic loss.

The induction of apoptosis by daunorubicin and idarubicin in human trisomic and diabetic fibroblasts

In this study, we investigated apoptosis induced in human trisomic and diabetic fibroblasts by daunorubicin (DNR) and its derivative, idarubicin (IDA). The cells were incubated with DNR or IDA for 2 h and then cultured in a drug-free medium for a further 2–48 h. The apoptosis in the cultured cell lines was assessed by biochemical analysis. We found that both drugs induced a timedependent loss of mitochondrial membrane potential, and a significant increase in intracellular calcium and caspase-3 activity. Mitochondrial polarization and changes in the level of intracellular calcium were observed during the first 2–6 h after drug treatment. Caspase-3 activation occurred in the late stages of the apoptotic pathway. Our findings also demonstrated that idarubicin was more cytotoxic and more effective than daunorubicin in inducing apoptosis in trisomic and diabetic fibroblasts.

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.

Involvement of reactive oxygen species in aclarubicin-induced death of human trisomic and diabetic fibroblasts

We investigated the mode of cell death induced by aclarubicin in human trisomic and diabetic fibroblasts. The cells were incubated with aclarubicin for 2 h and then were cultured in drug-free medium for up to 96 h. Aclarubicin in trisomic and diabetic fibroblasts, compared with normal cells, induced lesser changes in the level of reactive oxygen species (ROS) and the content of intracellular calcium. The drug induced ROS-mediated apoptotic and necrotic pathways in all cell lines. The extent of apoptosis and necrosis was strongly dependent on the cell line, sensitivity to drug and post-treatment time. These results indicate that most resistant diabetic cells died prevalently by apoptosis. In the case of trisomic fibroblasts, the number of apoptotic cells decreased with post-incubation time. The role of reactive oxygen species in aclarubicin-induced cell death was confirmed by the diminution effects of antioxidants (N-acetylcysteine and pyrrolidine-dithiocarbamate) on drug-induced ROS formation, increase of intracellular calcium and the extent of apoptosis and necrosis in fibroblast cell lines.

The nootropic and neuroprotective proline-containing dipeptide noopept restores spatial memory and increases immunoreactivity to amyloid in an Alzheimer's disease model

The effects of the novel proline-containing nootropic and neuroprotective dipeptide, noopept (GVS-111, N-phenylacetyl-L-prolylglycine ethyl ester) were investigated in NMRI mice following olfactory bulbectomy. We have shown previously that these animals developed Alzheimer's disease (AD)-like behaviour, morphology and biochemistry including impairment of spatial memory, regional neuronal degeneration and elevated Abeta peptide brain levels. In the current investigation, spatial memory was assessed using the Morris water maze and serum antibodies to in vitro morphologically characterized amyloid structures of both Abeta((25-35)) peptide and equine lysozyme, as well as to neurotrophic glial factor S100b, were analyzed by enzyme-linked immunosorbent assay (ELISA). Noopept (administered at a dose of 0.01 mg/kg for a period of 21 days and during a further 5 days training) restored spatial memory and increased serum antibody levels to oligomers of Abeta((25-35)) peptide but not to equine lysozyme amyloid or S100b protein in bulbectomized animals. The positive immunotropic effect of noopept to Abeta((25-35)) peptide prefibrillar aggregates was more marked in sham-operated compared to the bulbectomized subjects which were characterized by an overall suppression of immunoreactivity. Enhancement of the immune response to Abeta((25-35)) peptide prefibrils caused by noopept may attenuate the neurotoxic consequences of amyloid fibrillization and also be associated with an improvement in spatial memory in bulbectomized mice. These actions of noopept, combined with its previously reported neuroprotective and cholinomimetic properties, suggests that this dipeptide may well be useful for improving cognitive deficits induced by neurodegenerative diseases.

Oxidative stress: A bridge between Down's syndrome and Alzheimer's disease

Besides the genetic, biochemical and neuropathological analogies between Down's syndrome (DS) and Alzheimer's disease (AD), there is ample evidence of the involvement of oxidative stress (OS) in the pathogenesis of both disorders. The present paper reviews the publications on DS and AD in the past 10 years in light of the "gene dosage" and "two-hit" hypotheses, with regard to the alterations caused by OS in both the central nervous system and the periphery, and the main pipeline of antioxidant therapeutic strategies. OS occurs decades prior to the signature pathology and manifests as lipid, protein and DNA oxidation, and mitochondrial abnormalities. In clinical settings, the assessment of OS has traditionally been hampered by the use of assays that suffer from inherent problems related to specificity and/or sensitivity, which explains some of the conflicting results presented in this work. For DS, no scientifically proven diet or drug is yet available, and AD trials have not provided a satisfactory approach for the prevention of and therapy against OS, although most of them still need evidence-based confirmation. In the future, a balanced up-regulation of endogenous antioxidants, together with multiple exogenous antioxidant supplementation, may be expected to be one of the most promising treatment methods.

Piracetam improves mitochondrial dysfunction following oxidative stress

1.--Mitochondrial dysfunction including decrease of mitochondrial membrane potential and reduced ATP production represents a common final pathway of many conditions associated with oxidative stress, for example, hypoxia, hypoglycemia, and aging. 2.--Since the cognition-improving effects of the standard nootropic piracetam are usually more pronounced under such pathological conditions and young healthy animals usually benefit little by piracetam, the effect of piracetam on mitochondrial dysfunction following oxidative stress was investigated using PC12 cells and dissociated brain cells of animals treated with piracetam. 3.--Piracetam treatment at concentrations between 100 and 1000 microM improved mitochondrial membrane potential and ATP production of PC12 cells following oxidative stress induced by sodium nitroprusside (SNP) and serum deprivation. Under conditions of mild serum deprivation, piracetam (500 microM) induced a nearly complete recovery of mitochondrial membrane potential and ATP levels. Piracetam also reduced caspase 9 activity after SNP treatment. 4.--Piracetam treatment (100-500 mg kg(-1) daily) of mice was also associated with improved mitochondrial function in dissociated brain cells. Significant improvement was mainly seen in aged animals and only less in young animals. Moreover, the same treatment reduced antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase, and glutathione reductase) in aged mouse brain only, which are elevated as an adaptive response to the increased oxidative stress with aging. 5.--In conclusion, therapeutically relevant in vitro and in vivo concentrations of piracetam are able to improve mitochondrial dysfunction associated with oxidative stress and/or aging. Mitochondrial stabilization and protection might be an important mechanism to explain many of piracetam's beneficial effects in elderly patients.

Taurine rescues hippocampal long-term potentiation from ammonia-induced impairment

Hyperammonemia, a major pathophysiological factor in hepatic encephalopathy, impairs long-term potentiation (LTP) of synaptic transmission, a cellular model of learning and memory, in the hippocampus. We have now studied the protective action of taurine on this paradigm by analyzing LTP characteristics in mouse hippocampal slices treated with ammonium chloride (1 mM) in the presence of taurine (1 mM), an ubiquitous osmolyte, antioxidant, and neuromodulator, as well as other substances with such properties. Ammonia-treated slices displayed a significant impairment of LTP maintenance. Taurine and the mitochondrial enhancer l-carnitine, but not the antioxidants (ascorbate, carnosine, and the novel compound GVS-111) or the osmolyte betaine prevented this impairment. The protective effect of taurine was preserved under the blockade of inhibitory GABA(A) and glycine receptors. It is suggested that taurine may rescue the mechanisms of hippocampal synaptic plasticity by improving mitochondrial function under hyperammonemic conditions.

Different conformations of amyloid beta induce neurotoxicity by distinct mechanisms in human cortical neurons

Characterization of soluble oligomeric amyloid beta (Abeta) species in the brains of Alzheimer's disease (AD) patients and transgenic models has raised the possibility that different conformations of Abeta may contribute to AD pathology via different mechanisms. To characterize the toxic effect of different Abeta conformations, we tested side by side the effect of well characterized Abeta oligomers (AbetaOs), Abeta-derived diffusible ligands (ADDLs), and fibrillar Abeta (Abetaf) preparations in human cortical neurons (HCNs). Both AbetaOs and ADDLs bind rapidly and with high affinity to synaptic contacts and cellular membranes. AbetaOs (5 microm) induced rapid and massive neuronal death. Calcium influx accelerated, but was not required for, AbetaO toxicity. AbetaOs elicited a stereotyped succession of cellular changes consistent with the activation of a mitochondrial death apoptotic pathway. At low concentrations AbetaOs caused chronic and subtler mitochondrial alterations but minimal cell death. ADDLs induced similar toxic changes as AbetaOs but on a fivefold longer time scale. Higher concentrations of Abetaf and longer incubation times were required to produce widespread neuritic dystrophy but modest HCN cell death. Thus various Abeta species may play relevant roles in AD, causing neurotoxicity by distinct non-overlapping mechanisms affecting neuronal function and viability over multiple time courses.

ets-2 promotes the activation of a mitochondrial death pathway in Down's syndrome neurons

Down's syndrome (DS) is characterized by mental retardation and development of Alzheimer's disease (AD). Oxidative stress and mitochondrial dysfunction are both related to neurodegeneration in DS. Several genes in chromosome 21 have been linked to neuronal death, including the transcription factor ets-2. Cortical cultures derived from normal and DS fetal brains were used to study the role of ets-2 in DS neuronal degeneration. ets-2 was expressed in normal human cortical neurons (HCNs) and was markedly upregulated by oxidative stress. When overexpressed in normal HCNs, ets-2 induced a stereotyped sequence of apoptotic changes leading to neuronal death. DS HCNs exhibit intracellular oxidative stress and increased apoptosis after the first week in culture (Busciglio and Yankner, 1995). ets-2 levels were increased in DS HCNs, and, between 7 and 14 d in vitro, DS HCNs showed increased bax, cytoplasmic translocation of cytochrome c and apoptosis inducing factor, and active caspases 3 and 7, consistent with activation of an apoptotic mitochondrial death pathway. Degeneration of DS neurons was reduced by dominant-negative ets-2, suggesting that increased ets-2 expression promotes DS neuronal apoptosis. In the human brain, ets-2 expression was found in neurons and astrocytes. Strong ets-2 immunoreactivity was observed in DS/AD and sporadic AD brains associated with degenerative markers such as bax, intracellular Abeta, and hyperphosphorylated tau. Thus, in DS/AD and sporadic AD brains, converging pathological mechanisms leading to chronic oxidative stress and ets-2 upregulation in susceptible neurons may result in increased vulnerability by promoting the activation of a mitochondrial-dependent proapoptotic pathway of cell death.

Proteomic analysis of Down's syndrome patients with gout

BACKGROUND

In this study, the expression of hypoxanthine-guanine phosphoribosyl transferase (HPRT) in Down's syndrome patients with gout (DS/G) was determined, and possible underlying mechanisms of gout were characterized using proteomic tools.

METHODS

Serum was obtained from DS/G, healthy controls and gout patients (without DS), recruited from the rheumatology clinic. Baseline enzyme assays were recorded and RT-PCR used to identify HPRT gene expression. 2-D electrophoresis and mass spectrometry were utilized to determine a plausible explanation concerning the mechanisms leading to increased uric acid levels in DS patients.

RESULTS

Two DS patients were diagnosed with gouty arthritis. Their HPRT enzyme activity was slightly lower than that of normal controls. HPRT expression was also slightly decreased in DS/G patients compared with controls. Serum protein profiles of these two DS/G patients revealed that haptoglobin alpha chain and apolipoprotein A1 (ApoA1) were both significantly down-regulated. Protein expression was validated by immunoblot.

CONCLUSION

Our results revealed that low levels of haptoglobin in the two DS/G patients were related to renal dysfunction may have affected uric acid excretion and caused gout. However, decreased ApoA1 revealed a positive correlation between defective lipid metabolism and gouty arthritis in DS/G patients.

Complementary and alternative therapies for Down syndrome

In their role as committed advocates, parents of children with Down syndrome have always sought alternative therapies, mainly to enhance cognitive function but also to improve their appearance. Nutritional supplements have been the most frequent type of complementary and alternative therapy used. Cell therapy, plastic surgery, hormonal therapy, and a host of other therapies such as massage therapy have been used. There is a lack of well-designed scientific studies on the use of alternative therapies in individuals with Down syndrome. Antioxidants hold theoretical promise for treatment of the cognitive, immune, malignancy, and premature aging problems associated with Down syndrome. Medications for treatment of Alzheimer's disease may also result in benefit for the population of individuals with Down syndrome.

Down's syndrome astrocytes have greater antioxidant capacity than euploid astrocytes

Down's syndrome (trisomy 21) brain tissue is considered to be susceptible to oxidative injury, mainly because its increased Cu/Zn-superoxide dismutase (SOD1) activity is not followed by an adaptive rise in hydrogen peroxide metabolizing enzymes. In vitro, trisomic neurons suffer oxidative stress and degenerate. We studied the response of trisomy 21 neuron and astrocyte cultures to hydrogen peroxide injury and found that they were, respectively, more and less vulnerable than their euploid counterparts. Differences were detected 24 h after exposures in the region of 50 microm and 500 microm hydrogen peroxide for neuron and astrocyte cultures, respectively. Cytotoxicity results were paralleled by a decrease in cellular glutathione. In addition, trisomic astrocytes showed a lower basal content of superoxide ion and a higher clearance of hydrogen peroxide from the culture medium. In the presence of hydrogen peroxide, trisomic astrocytes maintained their concentration of intracellular superoxide and hydroperoxides at a lower level than euploid astrocytes. Consistent with these results, trisomic astrocytes in neuron coculture were more neuroprotective than euploid astrocytes against hydrogen peroxide injury. We suggest that SOD1 overexpression has beneficial effects on astrocytes, as it does in other systems with similarly high disposal of hydroperoxides. In addition to a higher enzymatic activity of SOD1, cultures of trisomic astrocytes showed slightly higher glutathione reductase activity than euploid cultures. Thus, trisomy 21 astrocytes showed a greater antioxidant capacity against hydrogen peroxide than euploid astrocytes, and they partially counteracted the oxidative vulnerability of trisomic neurons in culture.