Dithiol-based compounds maintain expression of antioxidant protein peroxiredoxin 1 that counteracts toxicity of mutant huntingtin

Peroxiredoxin 1 inhibits streptozotocin-induced Alzheimer's disease-like pathology in hippocampal neuronal cells via the blocking of Ca2+/Calpain/Cdk5-mediated mitochondrial fragmentation

Oxidative stress plays an essential role in the progression of Alzheimer's disease (AD), the most common age-related neurodegenerative disorder. Streptozotocin (STZ)-induced abnormal brain insulin signaling and oxidative stress play crucial roles in the progression of Alzheimer's disease (AD)-like pathology. Peroxiredoxins (Prxs) are associated with protection from neuronal death induced by oxidative stress. However, the molecular mechanisms underlying Prxs on STZ-induced progression of AD in the hippocampal neurons are not yet fully understood. Here, we evaluated whether Peroxiredoxin 1 (Prx1) affects STZ-induced AD-like pathology and cellular toxicity. Prx1 expression was increased by STZ treatment in the hippocampus cell line, HT-22 cells. We evaluated whether Prx1 affects STZ-induced HT-22 cells using overexpression. Prx1 successfully protected the forms of STZ-induced AD-like pathology, such as neuronal apoptosis, synaptic loss, and tau phosphorylation. Moreover, Prx1 suppressed the STZ-induced increase of mitochondrial dysfunction and fragmentation by down-regulating Drp1 phosphorylation and mitochondrial location. Prx1 plays a role in an upstream signal pathway of Drp1 phosphorylation, cyclin-dependent kinase 5 (Cdk5) by inhibiting the STZ-induced conversion of p35 to p25. We found that STZ-induced of intracellular Ca2+ accumulation was an important modulator of AD-like pathology progression by regulating Ca2+-mediated Calpain activation, and Prx1 down-regulated STZ-induced intracellular Ca2+ accumulation and Ca2+-mediated Calpain activation. Finally, we identified that Prx1 antioxidant capacity affected Ca2+/Calpain/Cdk5-mediated AD-like pathology progress. Therefore, these findings demonstrated that Prx1 is a key factor in STZ-induced hippocampal neuronal death through inhibition of Ca2+/Calpain/Cdk5-mediated mitochondrial dysfunction by protecting against oxidative stress.

The Role of the Thioredoxin System in Brain Diseases

The thioredoxin system, consisting of thioredoxin (Trx), thioredoxin reductase (TrxR), and NADPH, plays a fundamental role in the control of antioxidant defenses, cell proliferation, redox states, and apoptosis. Aberrations in the Trx system may lead to increased oxidative stress toxicity and neurodegenerative processes. This study reviews the role of the Trx system in the pathophysiology and treatment of Alzheimer's, Parkinson's and Huntington's diseases, brain stroke, and multiple sclerosis. Trx system plays an important role in the pathophysiology of those disorders via multiple interactions through oxidative stress, apoptotic, neuro-immune, and pro-survival pathways. Multiple aberrations in Trx and TrxR systems related to other redox systems and their multiple reciprocal relationships with the neurodegenerative, neuro-inflammatory, and neuro-oxidative pathways are here analyzed. Genetic and environmental factors (nutrition, metals, and toxins) may impact the function of the Trx system, thereby contributing to neuropsychiatric disease. Aberrations in the Trx and TrxR systems could be a promising drug target to prevent and treat neurodegenerative, neuro-inflammatory, neuro-oxidative stress processes, and related brain disorders.

The neuroprotective effects of fisetin, a natural flavonoid in neurodegenerative diseases: Focus on the role of oxidative stress

Oxidative stress (OS) disrupts the chemical integrity of macromolecules and increases the risk of neurodegenerative diseases. Fisetin is a flavonoid that exhibits potent antioxidant properties and protects the cells against OS. We have viewed the NCBI database, PubMed, Science Direct (Elsevier), Springer-Nature, ResearchGate, and Google Scholar databases to search and collect relevant articles during the preparation of this review. The search keywords are OS, neurodegenerative diseases, fisetin, etc. High level of ROS in the brain tissue decreases ATP levels, and mitochondrial membrane potential and induces lipid peroxidation, chronic inflammation, DNA damage, and apoptosis. The subsequent results are various neuronal diseases. Fisetin is a polyphenolic compound, commonly present in dietary ingredients. The antioxidant properties of this flavonoid diminish oxidative stress, ROS production, neurotoxicity, neuro-inflammation, and neurological disorders. Moreover, it maintains the redox profiles, and mitochondrial functions and inhibits NO production. At the molecular level, fisetin regulates the activity of PI3K/Akt, Nrf2, NF-κB, protein kinase C, and MAPK pathways to prevent OS, inflammatory response, and cytotoxicity. The antioxidant properties of fisetin protect the neural cells from inflammation and apoptotic degeneration. Thus, it can be used in the prevention of neurodegenerative disorders.

Reactive Species in Progeroid Syndromes and Aging-Related Processes

Significance: Reactive species have been classically considered causative of age-related degenerative processes, but the scenario appears considerably more complex and to some extent counterintuitive than originally anticipated. The impact of reactive species in precocious aging syndromes is revealing new clues to understand and perhaps challenge the resulting degenerative processes. Recent Advances: Our understanding of reactive species has considerably evolved, including their hormetic effect (beneficial at a certain level, harmful beyond this level), the occurrence of diverse hormetic peaks in different cell types and organisms, and the extended type of reactive species that are relevant in biological processes. Our understanding of the impact of reactive species has also expanded from the dichotomic damaging/signaling role to modulation of gene expression. Critical Issues: These new concepts are affecting the study of aging and diseases where aging is greatly accelerated. We discuss how notions arising from the study of the underlying mechanisms of a progeroid disease, Cockayne syndrome, represent a paradigm shift that may shed a new light in understanding the role of reactive species in age-related degenerative processes. Future Issues: Future investigations urge to explore established and emerging notions to elucidate the multiple contributions of reactive species in degenerative processes linked to pathophysiological aging and their possible amelioration. Antioxid. Redox Signal. 37, 208-228.

Human Huntington's disease pluripotent stem cell-derived microglia develop normally but are abnormally hyper-reactive and release elevated levels of reactive oxygen species

Background

Neuroinflammation may contribute to the pathogenesis of Huntington’s disease, given evidence of activated microglia and elevated levels of inflammatory molecules in disease gene carriers, even those many years from symptom onset. We have shown previously that monocytes from Huntington’s disease patients are hyper-reactive to stimulation in a manner dependent on their autonomous expression of the disease-causing mutant HTT protein. To date, however, whether human microglia are similarly hyper-responsive in a cell-autonomous manner has not been determined.

Methods

Microglial-like cells were derived from human pluripotent stem cells (PSCs) expressing mutant HTT containing varying polyglutamine lengths. These included lines that are otherwise isogenic, such that any observed differences can be attributed with certainty to the disease mutation itself. Analyses by quantitative PCR and immunofluorescence microscopy respectively of key genes and protein markers were undertaken to determine whether Huntington’s disease PSCs differentiated normally to a microglial fate. The resultant cultures and their supernatants were then assessed by various biochemical assays and multiplex ELISAs for viability and responses to stimulation, including the release of pro-inflammatory cytokines and reactive oxygen species. Conditioned media were applied to PSC-derived striatal neurons, and vice versa, to determine the effects that the secretomes of each cell type might have on the other.

Results

Human PSCs generated microglia successfully irrespective of the expression of mutant HTT. These cells, however, were hyper-reactive to stimulation in the production of pro-inflammatory cytokines such as IL-6 and TNFα. They also released elevated levels of reactive oxygen species that have neurotoxic potential. Accompanying such phenotypes, human Huntington’s disease PSC-derived microglia showed increased levels of apoptosis and were more susceptible to exogenous stress. Such stress appeared to be induced by supernatants from human PSC-derived striatal neurons expressing mutant HTT with a long polyglutamine tract.

Conclusions

These studies show, for the first time, that human Huntington’s disease PSC-derived microglia are hyper-reactive due to their autonomous expression of mutant HTT. This provides a cellular basis for the contribution that neuroinflammation might make to Huntington’s disease pathogenesis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02147-6.

Mitochondrial and Redox-Based Therapeutic Strategies in Huntington's Disease

Significance: The molecular processes that determine Huntington's disease (HD) pathogenesis are not yet fully understood, and until now no effective neuroprotective therapeutic strategies have been developed. Mitochondria are one of most important organelles required for neuronal homeostasis, by providing metabolic pathways relevant for energy production, regulating calcium homeostasis, or controlling free radical generation and cell death. Because augmented reactive oxygen species (ROS) accompanied by mitochondrial dysfunction are relevant early HD mechanisms, targeting these cellular mechanisms may constitute relevant therapeutic approaches. Recent Advances: Previous findings point toward a close relationship between mitochondrial dysfunction and redox changes in HD. Mutant huntingtin (mHTT) can directly interact with mitochondrial proteins, as translocase of the inner membrane 23 (TIM23), disrupting mitochondrial proteostasis and favoring ROS production and HD progression. Furthermore, abnormal brain and muscle redox signaling contributes to altered proteostasis and motor impairment in HD, which can be improved with the mitochondria-targeted antioxidant mitoquinone or resveratrol, an SIRT1 activator that ameliorates mitochondrial biogenesis and function. Critical Issues: Various antioxidants and metabolic enhancers have been studied in HD; however, the real outcome of these molecules is still debatable. New compounds have proven to ameliorate mitochondrial and redox-based signaling pathways in early stages of HD, potentially precluding selective neurodegeneration. Future Directions: Unraveling the molecular etiology of deregulated mitochondrial function and dynamics, and oxidative stress opens new prospects for HD therapeutics. In this review, we explore the role of redox unbalance and mitochondrial dysfunction in HD progression, and further describe advances on clinical trials in HD based on mitochondrial and redox-based therapeutic strategies.

Social modulation of ageing: mechanisms, ecology, evolution

Human life expectancy increases, but the disease-free part of lifespan (healthspan) and the quality of life in old people may not show the same development. The situation poses considerable challenges to healthcare systems and economies, and calls for new strategies to increase healthspan and for sustainable future approaches to elder care. This call has motivated innovative research on the role of social relationships during ageing. Correlative data from clinical surveys indicate that social contact promotes healthy ageing, and it is time to reveal the causal mechanisms through experimental research. The fruit fly Drosophila melanogaster is a prolific model animal, but insects with more developed social behaviour can be equally instrumental for this research. Here, we discuss the role of social contact in ageing, and identify lines of study where diverse insect models can help uncover the mechanisms that are involved. This article is part of the theme issue 'Ageing and sociality: why, when and how does sociality change ageing patterns?'

Peroxiredoxins in Neurodegenerative Diseases

Substantial evidence indicates that oxidative/nitrosative stress contributes to the neurodegenerative diseases. Peroxiredoxins (PRDXs) are one of the enzymatic antioxidant mechanisms neutralizing reactive oxygen/nitrogen species. Since mammalian PRDXs were identified 30 years ago, their significance was long overshadowed by the other well-studied ROS/RNS defense systems. An increasing number of studies suggests that these enzymes may be involved in the neurodegenerative process. This article reviews the current knowledge on the expression and putative roles of PRDXs in neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and dementia with Lewy bodies, multiple sclerosis, amyotrophic lateral sclerosis and Huntington's disease.

Neuronal Cells Rearrangement During Aging and Neurodegenerative Disease: Metabolism, Oxidative Stress and Organelles Dynamic

Brain cells normally respond adaptively to oxidative stress or bioenergetic challenges, resulting from ongoing activity in neuronal circuits. During aging and in neurodegenerative disorders, these mechanisms are compromised. In fact, neurons show unique age-related changes in functions and metabolism, resulting in greater susceptibility to insults and disease. Aging affects the nervous system as well as other organs. More precisely, as the nervous system ages, neuron metabolism may change, inducing glucose hypometabolism, impaired transport of critical substrates underlying metabolism, alterations in calcium signaling, and mitochondrial dysfunction. Moreover, in neuronal aging, an accumulation of impaired and aggregated proteins in the cytoplasm and in mitochondria is observed, as the result of oxidative stress: reduced antioxidant defenses and/or increase of reactive oxygen species (ROS). These changes lead to greater vulnerability of neurons in various regions of the brain and increased susceptibility to several diseases. Specifically, the first part of the review article will focus on the major neuronal cells’ rearrangements during aging in response to changes in metabolism and oxidative stress, while the second part will cover the neurodegenerative disease areas in detail.

The Role of Mitochondria in Reactive Oxygen Species Generation and Its Implications for Neurodegenerative Diseases

Mitochondria are dynamic cellular organelles that consistently migrate, fuse, and divide to modulate their number, size, and shape. In addition, they produce ATP, reactive oxygen species, and also have a biological role in antioxidant activities and Ca²⁺ buffering. Mitochondria are thought to play a crucial biological role in most neurodegenerative disorders. Neurons, being high-energy-demanding cells, are closely related to the maintenance, dynamics, and functions of mitochondria. Thus, impairment of mitochondrial activities is associated with neurodegenerative diseases, pointing to the significance of mitochondrial functions in normal cell physiology. In recent years, considerable progress has been made in our knowledge of mitochondrial functions, which has raised interest in defining the involvement of mitochondrial dysfunction in neurodegenerative diseases. Here, we summarize the existing knowledge of the mitochondrial function in reactive oxygen species generation and its involvement in the development of neurodegenerative diseases.

Mild Exercise Differently Affects Proteostasis and Oxidative Stress on Motor Areas During Neurodegeneration: A Comparative Study of Three Treadmill Running Protocols

Proteostasis and oxidative stress were evaluated in motor cortex and spinal cord of aged Lewis rats exposed to 1 mg/kg/day of rotenone during 4 or 8 weeks, prior or after practicing three protocols of mild treadmill running. Results demonstrated that exercise done after the beginning of neurodegeneration reverted the increased oxidative stress (measured by H₂O₂ levels and SOD activity), increased neuron strength, and improved proteostasis in motor cortex. Spinal cord was not affected. Treadmill running practiced before neurodegeneration protected cortical motor neurons of the rotenone-exposed rats; but in this case, oxidative stress was not altered, whereas proteasome activity was increased and autophagy decreased. Spinal cord was not protected when exercise was practiced before neurodegeneration. Prolonged treadmill running (10 weeks) increased oxidative stress, autophagy, and proteasome activity, whereas neuron viability was decreased in motor cortex. In spinal cord, this protocol decreased oxidative stress and increased proteasome activity. Major conclusions were that treadmill running practiced before or after the beginning of neurodegeneration may protect motor cortex neurons, whereas prolonged mild running seems to be beneficial for spinal cord.

A Mitochondria-Associated Oxidative Stress Perspective on Huntington's Disease

Huntington's disease (HD) is genetically caused by mutation of the Huntingtin (HTT) gene. At present, the mechanisms underlying the defect of HTT and the development of HD remain largely unclear. However, increasing evidence shows the presence of enhanced oxidative stress in HD patients. In this review article, we focus on the role of oxidative stress in the pathogenesis of HD and discuss mediators and potential mechanisms involved in mutant HTT-mediated oxidative stress generation and progression. Furthermore, we emphasize the role of the unicellular organism Saccharomyces cerevisiae in investigating mutant HTT-induced oxidative stress. Overall, this review article provides an overview of the latest findings regarding oxidative stress in HD and potential therapeutic targets for HD.

A Mitochondria-Associated Oxidative Stress Perspective on Huntington's Disease

Huntington's disease (HD) is genetically caused by mutation of the Huntingtin (HTT) gene. At present, the mechanisms underlying the defect of HTT and the development of HD remain largely unclear. However, increasing evidence shows the presence of enhanced oxidative stress in HD patients. In this review article, we focus on the role of oxidative stress in the pathogenesis of HD and discuss mediators and potential mechanisms involved in mutant HTT-mediated oxidative stress generation and progression. Furthermore, we emphasize the role of the unicellular organism Saccharomyces cerevisiae in investigating mutant HTT-induced oxidative stress. Overall, this review article provides an overview of the latest findings regarding oxidative stress in HD and potential therapeutic targets for HD.

The Association of VDAC with Cell Viability of PC12 Model of Huntington's Disease

It is becoming increasingly apparent that mitochondria dysfunction plays an important role in the pathogenesis of Huntington’s disease (HD), but the underlying mechanism is still elusive. Thus, there is a still need for further studies concerning the upstream events in the mitochondria dysfunction that could contribute to cell death observed in HD. Taking into account the fundamental role of the voltage-dependent anion-selective channel (VDAC) in mitochondria functioning, it is reasonable to consider the channel as a crucial element in HD etiology. Therefore, we applied inducible PC12 cell model of HD to determine the relationship between the effect of expression of wild type and mutant huntingtin (Htt and mHtt, respectively) on cell survival and mitochondria functioning in intact cells under conditions of undergoing cell divisions. Because after 48 h of Htt and mHtt expression differences in mitochondria functioning co-occurred with differences in the cell viability, we decided to estimate the effect of Htt and mHtt expression lasted for 48 h on VDAC functioning. Therefore, we isolated VDAC from the cells and tested the preparations by black lipid membrane system. We observed that the expression of mHtt, but not Htt, resulted in changes of the open state conductance and voltage-dependence when compared to control cells cultured in the absence of the expression. Importantly, for all the VDAC preparations, we observed a dominant quantitative content of VDAC1, and the quantitative relationships between VDAC isoforms were not changed by Htt and mHtt expression. Thus, Htt and mHtt-mediated functional changes of VDAC, being predominantly VDAC1, which occur shortly after these protein appearances in cells, may result in differences concerning mitochondria functioning and viability of cells expressing Htt and mHtt. The assumption is important for better understanding of cytotoxicity as well as cytoprotection mechanisms of potential clinical application.

Oxidative Stress and the Central Nervous System

Biochemical integrity of the brain is vital for normal functioning of the central nervous system (CNS). One of the factors contributing to cerebral biochemical impairment is a chemical process called oxidative stress. Oxidative stress occurs upon excessive free radical production resulting from an insufficiency of the counteracting antioxidant response system. The brain, with its high oxygen consumption and lipid-rich content, is highly susceptible to oxidative stress. Therefore, oxidative stress-induced damage to the brain has a strong potential to negatively impact normal CNS functions. Although oxidative stress has historically been considered to be involved mainly in neurodegenerative disorders such as Alzheimer disease, Huntington disease, and Parkinson disease, its involvement in neuropsychiatric disorders, including anxiety disorders and depression, is beginning to be recognized. This review is a discussion of the relevance of cerebral oxidative stress to impairment of emotional and mental well-being.

Oxidative Stress and Huntington's Disease: The Good, The Bad, and The Ugly

Redox homeostasis is crucial for proper cellular functions, including receptor tyrosine kinase signaling, protein folding, and xenobiotic detoxification. Under basal conditions, there is a balance between oxidants and antioxidants. This balance facilitates the ability of oxidants, such as reactive oxygen species, to play critical regulatory functions through a direct modification of a small number of amino acids (e.g. cysteine) on signaling proteins. These signaling functions leverage tight spatial, amplitude, and temporal control of oxidant concentrations. However, when oxidants overwhelm the antioxidant capacity, they lead to a harmful condition of oxidative stress. Oxidative stress has long been held to be one of the key players in disease progression for Huntington's disease (HD). In this review, we will critically review this evidence, drawing some intermediate conclusions, and ultimately provide a framework for thinking about the role of oxidative stress in the pathophysiology of HD.

Proteins that mediate protein aggregation and cytotoxicity distinguish Alzheimer's hippocampus from normal controls

Neurodegenerative diseases are distinguished by characteristic protein aggregates initiated by disease‐specific ‘seed’ proteins; however, roles of other co‐aggregated proteins remain largely unexplored. Compact hippocampal aggregates were purified from Alzheimer's and control‐subject pools using magnetic‐bead immunoaffinity pulldowns. Their components were fractionated by electrophoretic mobility and analyzed by high‐resolution proteomics. Although total detergent‐insoluble aggregates from Alzheimer's and controls had similar protein content, within the fractions isolated by tau or Aβ_1–42 pulldown, the protein constituents of Alzheimer‐derived aggregates were more abundant, diverse, and post‐translationally modified than those from controls. Tau‐ and Aβ‐containing aggregates were distinguished by multiple components, and yet shared >90% of their protein constituents, implying similar accretion mechanisms. Alzheimer‐specific protein enrichment in tau‐containing aggregates was corroborated for individuals by three analyses. Five proteins inferred to co‐aggregate with tau were confirmed by precise in situ methods, including proximity ligation amplification that requires co‐localization within 40 nm. Nematode orthologs of 21 proteins, which showed Alzheimer‐specific enrichment in tau‐containing aggregates, were assessed for aggregation‐promoting roles in C. elegans by RNA‐interference ‘knockdown’. Fifteen knockdowns (71%) rescued paralysis of worms expressing muscle Aβ, and 12 (57%) rescued chemotaxis disrupted by neuronal Aβ expression. Proteins identified in compact human aggregates, bound by antibody to total tau, were thus shown to play causal roles in aggregation based on nematode models triggered by Aβ_1–42. These observations imply shared mechanisms driving both types of aggregation, and/or aggregate‐mediated cross‐talk between tau and Aβ. Knowledge of protein components that promote protein accrual in diverse aggregate types implicates common mechanisms and identifies novel targets for drug intervention.

Time-Course Analysis of Protein and Lipid Oxidation in the Brains of Yac128 Huntington's Disease Transgenic Mice

Huntington's disease (HD) is caused by an expansion of cytosine-adenine-guanine (CAG) repeats within the coding region of the HD gene, which expresses the protein huntingtin and is characterized by selective degeneration of specific neuronal populations, mainly in the striatum and the cortex. The mechanisms that account for this selective neuronal death are multifaceted, but oxidative stress might play an important role in this process. To determine whether changes in the intracellular redox state will result in oxidative damage to cellular macromolecules with disease progression, we analyzed levels of lipid peroxidation (with the thiobarbituric acid reactive substances [TBARS] assay) and protein carbonyl formation (using the 2,4-dinitrophenylhydrazine reaction) in the cerebellum, cerebral cortex, prefrontal cortex, striatum, and hippocampus of the YAC128 HD mouse model at 3, 6, and 12 months of age. With the exception of a transient increase in protein carbonyl levels in the YAC128 prefrontal cortex at 6 months of age, levels of lipid peroxidation and protein oxidation were not significantly different between YAC128 mice and their age-matched wild-type counterparts in any of the brain regions analyzed up to 12 months of age. However, age-related increases in oxidative stress were observed in various brain regions. These results suggest that lipid and protein oxidative damage is not a major contributor to neurodegeneration in the YAC128 brain up to 12 months of age.

Thiol-disulfide Oxidoreductases TRX1 and TMX3 Decrease Neuronal Atrophy in a Lentiviral Mouse Model of Huntington's Disease

Huntington’s disease (HD) is caused by a trinucleotide CAG repeat in the huntingtin gene (HTT) that results in expression of a polyglutamine-expanded mutant huntingtin protein (mHTT). N-terminal fragments of mHTT accumulate in brain neurons and glia as soluble monomeric and oligomeric species as well as insoluble protein aggregates and drive the disease process. Decreasing mHTT levels in brain provides protection and reversal of disease signs in HD mice making mHTT a prime target for disease modification. There is evidence for aberrant thiol oxidation within mHTT and other proteins in HD models. Based on this, we hypothesized that a specific thiol-disulfide oxidoreductase exists that decreases mHTT levels in cells and provides protection in HD mice. We undertook an in-vitro genetic screen of key thiol-disulfide oxidoreductases then completed secondary screens to identify those with mHTT decreasing properties. Our in-vitro experiments identified thioredoxin 1 and thioredoxin-related transmembrane protein 3 as proteins that decrease soluble mHTT levels in cultured cells. Using a lentiviral mouse model of HD we tested the effect of these proteins in striatum. Both proteins decreased mHTT-induced striatal neuronal atrophy. Findings provide evidence for a role of dysregulated protein-thiol homeostasis in the pathogenesis of HD.

A unique four-hub protein cluster associates to glioblastoma progression

Gliomas are the most frequent brain tumors. Among them, glioblastomas are malignant and largely resistant to available treatments. Histopathology is the gold standard for classification and grading of brain tumors. However, brain tumor heterogeneity is remarkable and histopathology procedures for glioma classification remain unsatisfactory for predicting disease course as well as response to treatment. Proteins that tightly associate with cancer differentiation and progression, can bear important prognostic information. Here, we describe the identification of protein clusters differentially expressed in high-grade versus low-grade gliomas. Tissue samples from 25 high-grade tumors, 10 low-grade tumors and 5 normal brain cortices were analyzed by 2D-PAGE and proteomic profiling by mass spectrometry. This led to identify 48 differentially expressed protein markers between tumors and normal samples. Protein clustering by multivariate analyses (PCA and PLS-DA) provided discrimination between pathological samples to an unprecedented extent, and revealed a unique network of deranged proteins. We discovered a novel glioblastoma control module centered on four major network hubs: Huntingtin, HNF4α, c-Myc and 14-3-3ζ. Immunohistochemistry, western blotting and unbiased proteome-wide meta-analysis revealed altered expression of this glioblastoma control module in human glioma samples as compared with normal controls. Moreover, the four-hub network was found to cross-talk with both p53 and EGFR pathways. In summary, the findings of this study indicate the existence of a unifying signaling module controlling glioblastoma pathogenesis and malignant progression, and suggest novel targets for development of diagnostic and therapeutic procedures.

Nitrosative stress induces peroxiredoxin 1 ubiquitination during ischemic insult via E6AP activation in endothelial cells both in vitro and in vivo

AIMS

Although there is accumulating evidence that increased formation of reactive nitrogen species in cerebral vasculature contributes to the progression of ischemic damage, but the underlying molecular mechanisms remain elusive. Peroxiredoxin 1 (Prx1) can initiate the antioxidant response by scavenging free radicals. Therefore, we tested the hypothesis that Prx1 regulates the susceptibility to nitrosative stress damage during cerebral ischemia in vitro and in vivo.

RESULTS

Proteomic analysis in endothelial cells revealed that Prx1 was upregulated after stress-related oxygen-glucose deprivation (OGD). Although peroxynitrite upregulated Prx1 rapidly, this was followed by its polyubiquitination within 6 h after OGD mediated by the E3 ubiquitin ligase E6-associated protein (E6AP). OGD colocalized E6AP with nitrotyrosine in endothelial cells. To assess translational relevance in vivo, mice were studied after middle cerebral artery occlusion (MCAO). This was accompanied by Prx1 ubiquitination and degradation by the activation of E6AP. Furthermore, brain delivery of a lentiviral vector encoding Prx1 in mice inhibited blood-brain barrier leakage and neuronal damage significantly following MCAO.

INNOVATION AND CONCLUSIONS

Nitrosative stress during ischemic insult activates E6AP E3 ubiquitin ligase that ubiquitinates Prx1 and subsequently worsens cerebral damage. Thus, targeting the Prx1 antioxidant defense pathway may represent a novel treatment strategy for neurovascular protection in stroke.

Oxidative stress and neurodegenerative disorders

Living cells continually generate reactive oxygen species (ROS) through the respiratory chain during energetic metabolism. ROS at low or moderate concentration can play important physiological roles. However, an excessive amount of ROS under oxidative stress would be extremely deleterious. The central nervous system (CNS) is particularly vulnerable to oxidative stress due to its high oxygen consumption, weakly antioxidative systems and the terminal-differentiation characteristic of neurons. Thus, oxidative stress elicits various neurodegenerative diseases. In addition, chemotherapy could result in severe side effects on the CNS and peripheral nervous system (PNS) of cancer patients, and a growing body of evidence demonstrates the involvement of ROS in drug-induced neurotoxicities as well. Therefore, development of antioxidants as neuroprotective drugs is a potentially beneficial strategy for clinical therapy. In this review, we summarize the source, balance maintenance and physiologic functions of ROS, oxidative stress and its toxic mechanisms underlying a number of neurodegenerative diseases, and the possible involvement of ROS in chemotherapy-induced toxicity to the CNS and PNS. We ultimately assess the value for antioxidants as neuroprotective drugs and provide our comments on the unmet needs.

Role of oxidative DNA damage in mitochondrial dysfunction and Huntington's disease pathogenesis

Huntington's disease (HD) is a neurodegenerative disorder with an autosomal dominant expression pattern and typically a late-onset appearance. HD is a movement disorder with a heterogeneous phenotype characterized by involuntary dance-like gait, bioenergetic deficits, motor impairment, and cognitive and psychiatric deficits. Compelling evidence suggests that increased oxidative stress and mitochondrial dysfunction may underlie HD pathogenesis. However, the exact mechanisms underlying mutant huntingtin-induced neurological toxicity remain unclear. The objective of this paper is to review recent literature regarding the role of oxidative DNA damage in mitochondrial dysfunction and HD pathogenesis.

Association between Machado-Joseph disease and oxidative stress biomarkers

Spinocerebellar ataxia type 3, also called Machado-Joseph disease (MJD), is an hereditary autosomal dominant neurodegenerative disease that affects the cerebellum and its afferent and efferent connections. Since the mechanism by which mutant ataxin-3 eventually leads to neuronal death is poorly understood, additional investigations to clarify the biological alterations related to Machado-Joseph disease are necessary. Recent investigations suggest that oxidative stress may contribute significantly to Machado-Joseph disease. We compared markers of oxidative stress between Machado-Joseph disease and healthy control subjects. The results showed that Machado-Joseph patients have higher catalase levels and lower thiol protein levels compared to control subjects. The peripheral blood lymphocyes of MJD patients also showed higher levels of DNA damage by the comet assay than control subjects. Our results corroborate the hypothesis that the oxidative stress is associated with MJD patients. However, whether strategies to increase cellular antioxidative capacity may be effective therapies for the treatment of Machado-Joseph disease is an open question.

Neuroprotective effects of PrxI over-expression in an in vitro human Alzheimer's disease model

Peroxiredoxins are ubiquitous proteins that recently attracted major interests in view of the strict correlation observed in several cell lines and/or tissues between different levels of their expression and the increased capacity of cells to survive in different pathophysiological conditions. They are recently considered as the most important enzymes regulating the concentration of hydroperoxides inside the cells. Most of neurodisorders such as Parkinson, Huntington, Alzheimer's diseases, and ischemic injury are characterized by conditions of oxidative stress inside cells. In these pathophysiological conditions, a strict correlation between cell survival and Prx expression has been found. In CNS all the Prx isoforms are present though with different expression pattern depending on cell phenotype. Interestingly, neurons treated with amyloid beta peptide (Aβ), showed an overexpression of PrxI. In this study, the neuroprotective effect of PrxI after Aβ exposure and the underlying mechanisms by which PrxI expression counteracts cell death was investigated in a well established human AD in vitro model. Taking advantage on cells transfected by a construct where human PrxI is fused with a Green fluorescent protein (GFP) at the C-terminus, we report some events at the basis of cell survival after Aβ injury, suggesting possible new signal cascades dealing with the antiapoptotic effect of PrxI. The results obtained indicated a protective role for PrxI in counteracting Aβ injury by increasing cell viability, preserving neurites, and decreasing cell death.