Mitochondrial dysfunction due to mutant copper/zinc superoxide dismutase associated with amyotrophic lateral sclerosis is reversed by N-acetylcysteine

Exploring antioxidant strategies in the pathogenesis of ALS

The central nervous system is essential for maintaining homeostasis and controlling the body's physiological functions. However, its biochemical characteristics make it highly vulnerable to oxidative damage, which is a common factor in neurodegenerative diseases like amyotrophic lateral sclerosis (ALS). ALS is a leading cause of motor neuron disease, characterized by a rapidly progressing and incurable condition. ALS often results in death from respiratory failure within 3-5 years from the onset of the first symptoms, underscoring the urgent need to address this medical challenge. The aim of this study is to present available data supporting the role of oxidative stress in the mechanisms underlying ALS and to discuss potential antioxidant therapies currently in development. These therapies aim to improve the quality of life and life expectancy for patients affected by this devastating disease.

Mitochondria: A Promising Convergent Target for the Treatment of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by the progressive loss of motor neurons, for which current treatment options are limited. Recent studies have shed light on the role of mitochondria in ALS pathogenesis, making them an attractive therapeutic intervention target. This review contains a very comprehensive critical description of the involvement of mitochondria and mitochondria-mediated mechanisms in ALS. The review covers several key areas related to mitochondria in ALS, including impaired mitochondrial function, mitochondrial bioenergetics, reactive oxygen species, metabolic processes and energy metabolism, mitochondrial dynamics, turnover, autophagy and mitophagy, impaired mitochondrial transport, and apoptosis. This review also highlights preclinical and clinical studies that have investigated various mitochondria-targeted therapies for ALS treatment. These include strategies to improve mitochondrial function, such as the use of dichloroacetate, ketogenic and high-fat diets, acetyl-carnitine, and mitochondria-targeted antioxidants. Additionally, antiapoptotic agents, like the mPTP-targeting agents minocycline and rasagiline, are discussed. The paper aims to contribute to the identification of effective mitochondria-targeted therapies for ALS treatment by synthesizing the current understanding of the role of mitochondria in ALS pathogenesis and reviewing potential convergent therapeutic interventions. The complex interplay between mitochondria and the pathogenic mechanisms of ALS holds promise for the development of novel treatment strategies to combat this devastating disease.

N-acetylcysteine Pharmacology and Applications in Rare Diseases-Repurposing an Old Antioxidant

N-acetylcysteine (NAC), a precursor of cysteine and, thereby, glutathione (GSH), acts as an antioxidant through a variety of mechanisms, including oxidant scavenging, GSH replenishment, antioxidant signaling, etc. Owing to the variety of proposed targets, NAC has a long history of use as a prescription product and in wide-ranging applications that are off-label as an over-the-counter (OTC) product. Despite its discovery in the early 1960s and its development for various indications, systematic clinical pharmacology explorations of NAC pharmacokinetics (PK), pharmacodynamic targets, drug interactions, and dose-ranging are sorely limited. Although there are anecdotal instances of NAC benefits in a variety of diseases, a comprehensive review of the use of NAC in rare diseases does not exist. In this review, we attempt to summarize the existing literature focused on NAC explorations in rare diseases targeting mitochondrial dysfunction along with the history of NAC usage, approved indications, mechanisms of action, safety, and PK characterization. Further, we introduce the research currently underway on other structural derivatives of NAC and acknowledge the continuum of efforts through pre-clinical and clinical research to facilitate further therapeutic development of NAC or its derivatives for rare diseases.

Oxidative Stress and Antioxidants in Neurodegenerative Disorders

Neurodegenerative disorders constitute a substantial proportion of neurological diseases with significant public health importance. The pathophysiology of neurodegenerative diseases is characterized by a complex interplay of various general and disease-specific factors that lead to the end point of neuronal degeneration and loss, and the eventual clinical manifestations. Oxidative stress is the result of an imbalance between pro-oxidant species and antioxidant systems, characterized by an elevation in the levels of reactive oxygen and reactive nitrogen species, and a reduction in the levels of endogenous antioxidants. Recent studies have increasingly highlighted oxidative stress and associated mitochondrial dysfunction to be important players in the pathophysiologic processes involved in neurodegenerative conditions. In this article, we review the current knowledge of the general effects of oxidative stress on the central nervous system, the different specific routes by which oxidative stress influences the pathophysiologic processes involved in Alzheimer's disease, Parkinson's disease, Amyotrophic Lateral Sclerosis and Huntington's disease, and how oxidative stress may be therapeutically reversed/mitigated in order to stall the pathological progression of these neurodegenerative disorders to bring about clinical benefits.

Analysis of SOD1 Variants in Chinese Patients with Familial Amyotrophic Lateral Sclerosis

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease, and genetic contributors exert a significant role in the complicated pathogenesis. Identification of the genetic causes in ALS families could be valuable for early diagnosis and management. The development of potential drugs for patients with genetic defects will shed new light on ALS therapy.

AIM

To identify causative variants in three Chinese families with familial ALS (FALS), reveal the pathogenic mechanism, and look for the targeted drug for ALS.

DESIGN AND METHODS

Whole-exome sequencing and bioinformatics were used to perform genetic analysis of the ALS families. Functional analysis was performed to study the variants' function and search for potential drug targets.

RESULTS

Three heterozygous missense variants of the SOD1 gene were identified in families with FALS. The clinical manifestations of these patients include spinal onset, predominant lower motor neurons presentation, and absence of cognitive involvement. Functional analysis showed that all three SOD1 variants led to increased reactive oxygen species (ROS) levels, reduced cell viability, and formation of cytoplasmic aggregates. Remarkably, the decreased cell viability induced by variants was rescued after treatment with the ROS inhibitor N-acetylcysteine.

CONCLUSIONS

This study identified three SOD1 variants in three families with FALS. The variant SOD1 toxicity was associated with oxidative damage and aggregation, and N-acetylcysteine could rescue the decreased cell viability induced by these variants. Our findings support a pathogenic role for ROS in SOD1 deficiencies, and provide a potential drug N-acetylcysteine for ALS therapy, especially in SOD1-patients with limb onset.

Intranasal Administration of N-acetyl-L-cysteine Combined with Cell-Penetrating Peptide-Modified Polymer Nanomicelles as a Potential Therapeutic Approach for Amyotrophic Lateral Sclerosis

Intranasal administration is a promising route for direct drug delivery to the brain; its combination with nanocarriers enhances delivery. We have previously shown that intranasal administration combined with PEG-PCL-Tat (a nanocarrier) efficiently delivers drugs to the brain and exhibits excellent therapeutic efficacy against brain diseases. We aimed to clarify whether intranasal administration combined with PEG-PCL-Tat represents a useful drug delivery system (DDS) for amyotrophic lateral sclerosis (ALS) pharmacotherapy. We used N-acetyl-L-cysteine (NAC) as a model drug with low transferability to the spinal cord and determined the physicochemical properties of NAC/PEG-PCL-Tat. After intranasal administration of NAC/PEG-PCL-Tat, we measured the survival duration of superoxide dismutase-1 G93A mutant transgenic mice (G93A mice), widely used in ALS studies, and quantitatively analyzed the tissue distribution of NAC/PEG-PCL-Tat in ddY mice. The mean particle size and zeta potential of NAC/PEG-PCL-Tat were 294 nm and + 9.29 mV, respectively. Treatment with repeated intranasal administration of NAC/PEG-PCL-Tat considerably prolonged the median survival of G93A mice by 11.5 days compared with that of untreated G93A mice. Moreover, the highest distribution after a single administration of NAC/PEG-PCL-Tat was measured in the spinal cord. These results suggest that intranasal administration combined with PEG-PCL-Tat might represent a useful DDS for ALS therapeutics.

Targeting the Mitochondrial Protein VDAC1 as a Potential Therapeutic Strategy in ALS

Impaired mitochondrial function has been proposed as a causative factor in neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), caused by motor neuron degeneration. Mutations in superoxide dismutase (SOD1) cause ALS and SOD1 mutants were shown to interact with the voltage-dependent anion channel 1 (VDAC1), affecting its normal function. VDAC1 is a multi-functional channel located at the outer mitochondrial membrane that serves as a mitochondrial gatekeeper controlling metabolic and energetic crosstalk between mitochondria and the rest of the cell and it is a key player in mitochondria-mediated apoptosis. Previously, we showed that VDAC1 interacts with SOD1 and that the VDAC1-N-terminal-derived peptide prevented mutant SOD1 cytotoxic effects. In this study, using a peptide array, we identified the SOD1 sequence that interacts with VDAC1. Synthetic peptides generated from the identified VDAC1-binding sequences in SOD1 directly interacted with purified VDAC1. We also show that VDAC1 oligomerization increased in spinal cord mitochondria isolated from mutant SOD1G93A mice and rats. Thus, we used the novel VDAC1-specific small molecules, VBIT-4 and VBIT-12, inhibiting VDAC1 oligomerization and subsequently apoptosis and associated processes such as ROS production, and increased cytosolic Ca2+. VBIT-12 was able to rescue cell death induced by mutant SOD1 in neuronal cultures. Finally, although survival was not affected, VBIT-12 administration significantly improved muscle endurance in mutant SOD1G93A mice. Therefore, VBIT-12 may represent an attractive therapy for maintaining muscle function during the progression of ALS.

N-Acetyl-Cysteine: Modulating the Cysteine Redox Proteome in Neurodegenerative Diseases

In the last twenty years, significant progress in understanding the pathophysiology of age-associated neurodegenerative diseases has been made. However, the prevention and treatment of these diseases remain without clinically significant therapeutic advancement. While we still hope for some potential genetic therapeutic approaches, the current reality is far from substantial progress. With this state of the issue, emphasis should be placed on early diagnosis and prompt intervention in patients with increased risk of neurodegenerative diseases to slow down their progression, poor prognosis, and decreasing quality of life. Accordingly, it is urgent to implement interventions addressing the psychosocial and biochemical disturbances we know are central in managing the evolution of these disorders. Genomic and proteomic studies have shown the high molecular intricacy in neurodegenerative diseases, involving a broad spectrum of cellular pathways underlying disease progression. Recent investigations indicate that the dysregulation of the sensitive-cysteine proteome may be a concurrent pathogenic mechanism contributing to the pathophysiology of major neurodegenerative diseases, opening new therapeutic opportunities. Considering the incidence and prevalence of these disorders and their already significant burden in Western societies, they will become a real pandemic in the following decades. Therefore, we propose large-scale investigations, in selected groups of people over 40 years of age with decreased blood glutathione levels, comorbidities, and/or mild cognitive impairment, to evaluate supplementation of the diet with low doses of N-acetyl-cysteine, a promising and well-tolerated therapeutic agent suitable for long-term use.

The panoramic view of amyotrophic lateral sclerosis: A fatal intricate neurological disorder

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurological disease affecting both upper and lower motor neurons. In the United States alone, there are 16,000-20,000 established cases of ALS. The early disease diagnosis is challenging due to many overlapping pathophysiologies with other neurological diseases. The etiology of ALS is unknown; however, it is divided into two categories: familial ALS (fALS) which occurs due to gene mutations & contributes to 5-10% of ALS, and sporadic ALS (sALS) which is due to environmental factors & contributes to 90-95% of ALS. There is still no curative treatment for ALS: palliative care and symptomatic treatment are therefore essential components in the management of these patients. In this review, we provide a panoramic view of ALS, which includes epidemiology, risk factors, pathophysiologies, biomarkers, diagnosis, therapeutics (natural, synthetic, gene-based, pharmacological, stem cell, extracellular vesicles, and physical therapy), controversies (in the clinical trials of ALS), the scope of nanomedicine in ALS, and future perspectives.

Intracellular Sources of ROS/H2O2 in Health and Neurodegeneration: Spotlight on Endoplasmic Reticulum

Reactive oxygen species (ROS) are produced continuously throughout the cell as products of various redox reactions. Yet these products function as important signal messengers, acting through oxidation of specific target factors. Whilst excess ROS production has the potential to induce oxidative stress, physiological roles of ROS are supported by a spatiotemporal equilibrium between ROS producers and scavengers such as antioxidative enzymes. In the endoplasmic reticulum (ER), hydrogen peroxide (H2O2), a non-radical ROS, is produced through the process of oxidative folding. Utilisation and dysregulation of H2O2, in particular that generated in the ER, affects not only cellular homeostasis but also the longevity of organisms. ROS dysregulation has been implicated in various pathologies including dementia and other neurodegenerative diseases, sanctioning a field of research that strives to better understand cell-intrinsic ROS production. Here we review the organelle-specific ROS-generating and consuming pathways, providing evidence that the ER is a major contributing source of potentially pathologic ROS.

Oxidative Stress in Amyotrophic Lateral Sclerosis: Pathophysiology and Opportunities for Pharmacological Intervention

Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease or Charcot disease, is a fatal neurodegenerative disease that affects motor neurons (MNs) and leads to death within 2–5 years of diagnosis, without any effective therapy available. Although the pathological mechanisms leading to ALS are still unknown, a wealth of evidence indicates that an excessive reactive oxygen species (ROS) production associated with an inefficient antioxidant defense represents an important pathological feature in ALS. Substantial evidence indicates that oxidative stress (OS) is implicated in the loss of MNs and in mitochondrial dysfunction, contributing decisively to neurodegeneration in ALS. Although the modulation of OS represents a promising approach to protect MNs from degeneration, the fact that several antioxidants with beneficial effects in animal models failed to show any therapeutic benefit in patients raises several questions that should be analyzed. Using specific queries for literature search on PubMed, we review here the role of OS-related mechanisms in ALS, including the involvement of altered mitochondrial function with repercussions in neurodegeneration. We also describe antioxidant compounds that have been mostly tested in preclinical and clinical trials of ALS, also describing their respective mechanisms of action. While the description of OS mechanism in the different mutations identified in ALS has as principal objective to clarify the contribution of OS in ALS, the description of positive and negative outcomes for each antioxidant is aimed at paving the way for novel opportunities for intervention. In conclusion, although antioxidant strategies represent a very promising approach to slow the progression of the disease, it is of utmost need to invest on the characterization of OS profiles representative of each subtype of patient, in order to develop personalized therapies, allowing to understand the characteristics of antioxidants that have beneficial effects on different subtypes of patients.

Compounds that extend longevity are protective in neurodegenerative diseases and provide a novel treatment strategy for these devastating disorders

While aging is the greatest risk factor for the development of neurodegenerative disease, the role of aging in these diseases is poorly understood. In the inherited forms of these diseases, the disease-causing mutation is present from birth but symptoms appear decades later. This indicates that these mutations are well tolerated in younger individuals but not in older adults. Based on this observation, we hypothesized that changes taking place during normal aging make the cells in the brain (and elsewhere) susceptible to the disease-causing mutations. If so, then delaying some of these age-related changes may be beneficial in the treatment of neurodegenerative disease. In this review, we examine the effects of five compounds that have been shown to extend longevity (metformin, rapamycin, resveratrol, N-acetyl-l-cysteine, curcumin) in four of the most common neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis). While not all investigations observe a beneficial effect of these compounds, there are multiple studies that show a protective effect of each of these lifespan-extending compounds in animal models of neurodegenerative disease. Combined with genetic studies, this suggests the possibility that targeting the aging process may be an effective strategy to treat neurodegenerative disease.

Role of DRAM1 in mitophagy contributes to preeclampsia regulation in mice

Preeclampsia (PE) is a complication during pregnancy that is diagnosed by a new onset of hypertension and proteinuria. Although the pathogenesis of PE is not fully understood, a growing body of evidence indicates that oxidative stress and mitochondrial dysfunction might contribute to the progression of PE. Therefore, the aim of the present study was to determine the role of mitophagy in mitochondrial dysfunction and oxidative stress in PE, and to evaluate the role of DNA damage‑regulated autophagy modulator 1 (DRAM1) in the development of PE. First, a mouse model of PE induced by hypoxia‑inducible factor 1α was established, and high levels of oxidative stress, apoptosis and mitochondrial dysfunction were found in the placentas of PE mice. Additionally, the placentas of PE mice exhibited decreased mitophagy and significantly decreased DRAM1 expression. To further explore the role of DRAM1 in mitophagy, DRAM1 was overexpressed in the placental tissues of PE mice, and this overexpression effectively improved the symptoms of PE mice and significantly reduced blood lipid and urine protein levels. DRAM1 overexpression also improved mitochondrial function and reduced oxidative stress in the placentas of PE mice. In addition, the overexpression of DRAM1 improved mitochondrial fusion and fission, and enhanced mitophagy. Altogether, these results indicated a key role for DRAM1 in mitophagy that contributed to the regulation of PE. To the best of the authors' knowledge, the present study provided the first evidence of a role for DRAM1 in PE, and offered novel insight into the pathophysiological mechanisms of PE.

Oil and extract of safflower seed improve fructose induced metabolic syndrome through modulating the homeostasis of trace elements, TNF-α and fatty acids metabolism

ETHNOPHARMACOLOGICAL RELEVANCE

Safflower (Carthamus tinctorius) has many applications in folk medicine. Its oil is used traditionally to treat obesity and other metabolic disorders. The anti-hypercholesterolemic and antioxidant effects of this plant have been well documented, but the anti-inflammatory effects and its role on fatty acid oxidation and homeostasis of trace elements are not fully understood.

OBJECTIVE

The aim of this study was to evaluate the protective effects of different doses of oil and extract of safflower seed against fructose induced metabolic syndrome by investigating the homeostasis of trace elements, TNF-α, and fatty acids metabolism.

METHODS

Eighty adult male Sprague-Dawley rats were randomly divided into ten groups and treated daily for 16 weeks. At the end of the study, plasma levels of liver enzymes, lipid profiles, blood glucose, insulin and TNF-α were measured. The levels of antioxidant enzymes and lipid peroxidation were also measured along with the expression of CD36, fatty acyl-CoA synthetase (FAS), and Carnitine palmitoyl transferase I (CPT-1) beta genes in the liver.

RESULTS

The antioxidant enzymes activity significantly decreased and lipid peroxidation, lipid profiles, liver enzymes, and TNF-α significantly increased in fructose-induced metabolic syndrome compared to the control groups, as well as the level of some trace elements significantly changed (p < 0.05). Treatment with oil and safflower seed extract in a dose dependent manner could improve biochemical parameters in groups of metabolic syndrome treated with oil and extract compared to metabolic syndrome (p < 0.05). The results also showed that the expression of above mentioned genes significantly increased in groups of metabolic syndrome treated with oil and extract compared to control and metabolic syndrome groups (p < 0.05).

CONCLUSION

It can be concluded that safflower seed extract and its oil can improve fructose-induced metabolic syndrome through antioxidant and anti-inflammatory effects, adjustment of homeostasis of trace elements, and enhancing the beta-oxidation capacity of the liver by increasing the expression of CD36, FAS, and CPT-1beta genes.

Riluzole Selective Antioxidant Effects in Cell Models Expressing Amyotrophic Lateral Sclerosis Endophenotypes

Objective

Until recently, riluzole was the only drug licensed for amyotrophic lateral sclerosis (ALS). In spite of its efficacy, the mechanism of action remains elusive, and both blocking of glutamate release and antioxidant properties have been postulated. Here we characterized human SH-SY5Y neuroblastoma cell lines, taking advantage of their insensitivity to excitotoxic insults, in order to selectively assess the presence of a direct antioxidant effect of riluzole.

Methods

SH-SY5Y cells, either parental or overexpressing the G93A SOD1 mutation, were exposed for 24 hours to the selected stimuli.

Results

Riluzole (1–10 μM) was able to counteract the effects of H₂O₂ exposure (200 μM/24 hr), limiting both cell death and whole-cell reactive oxygen species (ROS) increase. The same experiments were repeated using SH-SY5Y cells carrying the familial ALS-related G93A-SOD1 mutation and constitutively expressing two-fold increased whole-cell ROS levels with respect to wild-type cells: riluzole was ineffective in this paradigm. Analogously, riluzole was ineffective in preventing cell death induced by exposing SH-SY5Y cells to 3-morpholino-sydnonimine (SIN-1, 1.5 mM/24 hr), a reactive nitrogen species (RNS) donor.

Conclusion

Our data support a direct antioxidant action of riluzole. Furthermore, the lack of efficacy of riluzole observed in the SOD1 cell model mirrors the lack of efficacy already demonstrated in cognate mouse models of ALS, plausibly reflecting differences in the underlying pathogenic mechanisms. Finally, riluzole inefficacy against nitrosative stress might support the idea that a combined therapeutic intervention may result more effective in ALS patients, as in the case of co-administration of edaravone, a drug known to reduce RNS.

Redox Mechanisms in Neurodegeneration: From Disease Outcomes to Therapeutic Opportunities

SIGNIFICANCE

Once considered to be mere by-products of metabolism, reactive oxygen, nitrogen and sulfur species are now recognized to play important roles in diverse cellular processes such as response to pathogens and regulation of cellular differentiation. It is becoming increasingly evident that redox imbalance can impact several signaling pathways. For instance, disturbances of redox regulation in the brain mediate neurodegeneration and alter normal cytoprotective responses to stress. Very often small disturbances in redox signaling processes, which are reversible, precede damage in neurodegeneration. Recent Advances: The identification of redox-regulated processes, such as regulation of biochemical pathways involved in the maintenance of redox homeostasis in the brain has provided deeper insights into mechanisms of neuroprotection and neurodegeneration. Recent studies have also identified several post-translational modifications involving reactive cysteine residues, such as nitrosylation and sulfhydration, which fine-tune redox regulation. Thus, the study of mechanisms via which cell death occurs in several neurodegenerative disorders, reveal several similarities and dissimilarities. Here, we review redox regulated events that are disrupted in neurodegenerative disorders and whose modulation affords therapeutic opportunities.

CRITICAL ISSUES

Although accumulating evidence suggests that redox imbalance plays a significant role in progression of several neurodegenerative diseases, precise understanding of redox regulated events is lacking. Probes and methodologies that can precisely detect and quantify in vivo levels of reactive oxygen, nitrogen and sulfur species are not available.

FUTURE DIRECTIONS

Due to the importance of redox control in physiologic processes, organisms have evolved multiple pathways to counteract redox imbalance and maintain homeostasis. Cells and tissues address stress by harnessing an array of both endogenous and exogenous redox active substances. Targeting these pathways can help mitigate symptoms associated with neurodegeneration and may provide avenues for novel therapeutics. Antioxid. Redox Signal. 30, 1450-1499.

Cerebrospinal Fluid from Patients with Sporadic Amyotrophic Lateral Sclerosis Induces Degeneration of Motor Neurons Derived from Human Embryonic Stem Cells

Disease modeling has become challenging in the context of amyotrophic lateral sclerosis (ALS), as obtaining viable spinal motor neurons from postmortem patient tissue is an unlikely possibility. Limitations in the animal models due to their phylogenetic distance from human species hamper the success of translating possible findings into therapeutic options. Accordingly, there is a need for developing humanized models as a lead towards identifying successful therapeutic possibilities. In this study, human embryonic stem cells-BJNHem20-were differentiated into motor neurons expressing HB9, Islet1, and choline acetyl transferase using retinoic acid and purmorphamine. These motor neurons discharged spontaneous action potentials with two different frequencies (< 5 and > 5 Hz), and majority of them were principal neurons firing with < 5 Hz. Exposure to cerebrospinal fluid from ALS patients for 48 h induced several degenerative changes in the motor neurons as follows: cytoplasmic changes such as beading of neurites and vacuolation; morphological alterations, viz., dilation and vacuolation of mitochondria, curled and closed Golgi architecture, dilated endoplasmic reticulum, and chromatin condensation in the nucleus; lowered activity of different mitochondrial complex enzymes; reduced expression of brain-derived neurotrophic factor; up-regulated neurofilament phosphorylation and hyperexcitability represented by increased number of spikes. All these changes along with the enhanced expression of pro-apoptotic proteins-Bax and caspase 9-culminated in the death of motor neurons.

An investigation into closed-loop treatment of neurological disorders based on sensing mitochondrial dysfunction

Dynamic feedback based closed-loop medical devices offer a number of advantages for treatment of heterogeneous neurological conditions. Closed-loop devices integrate a level of neurobiological feedback, which allows for real-time adjustments to be made with the overarching aim of improving treatment efficacy and minimizing risks for adverse events. One target which has not been extensively explored as a potential feedback component in closed-loop therapies is mitochondrial function. Several neurodegenerative and psychiatric disorders including Parkinson's disease, Major Depressive disorder and Bipolar disorder have been linked to perturbations in the mitochondrial respiratory chain. This paper investigates the potential to monitor this mitochondrial function as a method of feedback for closed-loop neuromodulation treatments. A generic model of the closed-loop treatment is developed to describe the high-level functions of any system designed to control neural function based on mitochondrial response to stimulation, simplifying comparison and future meta-analysis. This model has four key functional components including: a sensor, signal manipulator, controller and effector. Each of these components are described and several potential technologies for each are investigated. While some of these candidate technologies are quite mature, there are still technological gaps remaining. The field of closed-loop medical devices is rapidly evolving, and whilst there is a lot of interest in this area, widespread adoption has not yet been achieved due to several remaining technological hurdles. However, the significant therapeutic benefits offered by this technology mean that this will be an active area for research for years to come.

Misfolded SOD1 Accumulation and Mitochondrial Association Contribute to the Selective Vulnerability of Motor Neurons in Familial ALS: Correlation to Human Disease

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder, with a 10% genetic linkage, of which 20% of these cases may be attributed to mutations in superoxide dismutase (SOD1). Specific mutations in SOD1 have been associated with disease duration, which can be highly variable ranging from a life expectancy of 3 to beyond 10 years. SOD1 neurotoxicity has been attributed to aberrant accumulation of misfolded SOD1, which in its soluble form binds to intracellular organelles disrupting their function or forms insoluble toxic aggregates. To understand whether these biophysical properties of the mutant protein may influence disease onset and duration, we generated 19 point mutations in the SOD1 gene, based on available clinical data of disease onset and progression from patients. By overexpressing these mutants in motor-neuron-like NSC-34 cells, we demonstrate a variability in misfolding capacity between the different mutants with a correlation between the degree of protein misfolding and mutation severity. We also show a clear variation of the different SOD1 mutants to associate with mitochondrial-enriched fractions with a correlation between mutation severity and this association. In summary, these findings reveal a correlation between the accumulation of misfolded SOD1 species and their mitochondrial association with disease duration but not with disease onset, and they have implications for the potential therapeutic role of suppressing the accumulation of misfolded SOD1.

Energy Homeostasis and Abnormal RNA Metabolism in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease that is clinically characterized by progressive muscle weakness and impaired voluntary movement due to the loss of motor neurons in the brain, brain stem and spinal cord. To date, no effective treatment is available. Ample evidence suggests that impaired RNA homeostasis and abnormal energy status are two major pathogenesis pathways in ALS. In the present review article, we focus on recent studies that report molecular insights of both pathways, and discuss the possibility that energy dysfunction might negatively regulate RNA homeostasis via the impairment of cytoplasmic-nuclear shuttling in motor neurons and subsequently contribute to the development of ALS.

Macrophage migration inhibitory factor as a component of selective vulnerability of motor neurons in ALS

Amyotrophic lateral sclerosis (ALS) is a progressive adult-onset neurodegenerative disorder characterized by the selective loss of upper and lower motor neurons. Mutations in superoxide dismutase (SOD1) cause about 20 percent of familial ALS which is accompanied by accumulation of misfolded SOD1 onto intracellular organelles. Recently, we identified the 12 kDa macrophage migration inhibitory factor (MIF) as a chaperone for mutant SOD1 which is abundant in non-neuronal tissues. Purified recombinant MIF was shown to directly inhibit mutant SOD1 misfolding and association with mitochondria and ER. Elevating MIF in neuronal cells inhibited the accumulation of misfolded SOD1 and its association with mitochondria and ER, and extended survival of mutant SOD1-expressing motor neurons. Our results revealed that the levels of MIF protein are very low in motor neurons, implicating low chaperone activity as a component of selective vulnerability of motor neurons to mutant SOD1 misfolding and toxicity.

Mitochondrial diseases of the brain

Neurodegenerative disorders are debilitating diseases of the brain, characterized by behavioral, motor and cognitive impairments. Ample evidence underpins mitochondrial dysfunction as a central causal factor in the pathogenesis of neurodegenerative disorders including Parkinson's disease, Huntington's disease, Alzheimer's disease, Amyotrophic lateral sclerosis, Friedreich's ataxia and Charcot-Marie-Tooth disease. In this review, we discuss the role of mitochondrial dysfunction such as bioenergetics defects, mitochondrial DNA mutations, gene mutations, altered mitochondrial dynamics (mitochondrial fusion/fission, morphology, size, transport/trafficking, and movement), impaired transcription and the association of mutated proteins with mitochondria in these diseases. We highlight the therapeutic role of mitochondrial bioenergetic agents in toxin and in cellular and genetic animal models of neurodegenerative disorders. We also discuss clinical trials of bioenergetics agents in neurodegenerative disorders. Lastly, we shed light on PGC-1α, TORC-1, AMP kinase, Nrf2-ARE, and Sirtuins as novel therapeutic targets for neurodegenerative disorders.

Regulation of system x(c)- in the SOD1-G93A mouse model of ALS

The cystine/glutamate antiporter (system xc-) is critical for the generation of the antioxidant glutathione by transporting cystine into the cell. At the same time, system xc- also releases glutamate, which can potentially lead to excitotoxicity. The dual actions of system xc- make it of great interest in any disease, like amyotrophic lateral sclerosis (ALS), in which there is evidence of the involvement of both oxidative stress and excitotoxicity. The present study investigated the regulation of system xc- in the spinal cord of the SOD1-G93A transgenic mouse model of ALS. In acute spinal cord slices of 70day old SOD1-G93A transgenic mice cystine uptake by system xc- was significantly increased compared to age matched non-transgenic mice; but it was not significantly different at 55, 100, or 130days. The 70day old SOD1-G93A transgenic mice also showed significantly increased glutamate release in the presence of cystine. d-Aspartate uptake through excitatory amino acid transporters (EAATs), the main mechanism by which glutamate is cleared from the extracellular space, was also examined. In spinal cord slices of 70day old SOD1-G93A mice no change in d-aspartate uptake was found. Together, these findings suggest that at 70days of age, SOD1-G93A transgenic mice have increased system xc- activity, but no change in EAAT function. These results raise the possibility that excitotoxicity in the SOD1-G93A transgenic mouse, at least at early time points, may be due to increased system xc- activity and not decreased EAAT function.

Pro-oxidant copper-binding mode of the Apo form of ALS-linked SOD1 mutant H43R denatured at physiological temperature

The mutation of Cu,Zn-superoxide dismutase (SOD1), a major antioxidant enzyme, is associated with amyotrophic lateral sclerosis (ALS). In a previous study, we showed that the metal-depleted apo form of an ALS-linked mutant, H43R, undergoes denaturation at physiological temperature (37 °C) in 90 min and acquires pro-oxidant activity in the presence of Cu(2+) and H2O2. In this study, we have examined the Cu(2+)-binding mode of denatured apo-H43R by circular dichroism (CD), fluorescent oxidation, UV Raman spectroscopy, and photooxidation. CD spectroscopy indicates that denatured apo-H43R loses native β-barrel structure and the binding of Cu(2+) to the denatured apo form induces local refolding. Fluorescent-oxidation assays in the absence and presence of Cu(2+) chelators show that denatured apo-H43R contains two Cu(2+)-binding sites with higher and lower Cu(2+) affinities and with pro-oxidant activities in the reverse order. UV Raman spectroscopy gives evidence that His residues are bound to Cu(2+) mainly through the imidazole Nτ atom at the higher-affinity site and through the Nπ atom at the lower-affinity site, sharing one His residue with each other. The Cu(2+)-binding mode of denatured apo-H43R is analogous to but different from the Cu,Zn-binding mode of the native holo form. Photooxidation experiments confirm the involvement of His residues in the pro-oxidant activity. Taken together, it is suggested that the binding of Cu(2+) induces the local refolding of denatured apo-H43R to create toxic catalytic centers that convert the enzyme from antioxidant to pro-oxidant, leading to the pathogenesis of ALS. His residues are essential for both Cu(2+)-binding and pro-oxidant activities.

Dysregulation of iron protein expression in the G93A model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by selective loss of motor neurons which leads to progressive paralysis and death by respiratory failure. Although the cause of sporadic ALS is still unknown, oxidative stress is suggested to play a major role in the pathogenesis of this disease and of the rare familial form, which often exhibits mutations of the superoxide dismutase 1 (SOD1) gene. Since enhanced iron levels are discussed to participate in oxidative stress and neuronal death, we analyzed the expression levels of Fe-related mRNAs in a cell culture ALS model with the G93A mutation of SOD1. We observed an increased total iron content in G93A-SOD1 SH-SY5Y neuroblastoma cells compared to wild-type (WT)-SOD1 cells. mRNA expression for transferrin receptor 1 (TfR1) and divalent metal transporter 1 was increased in G93A-SOD1 cells, which was in accordance with higher iron uptake. Experiments with the iron chelator deferoxamine revealed a normal reaction of WT and mutant cells to cytoplasmic iron depletion, i.e. TfR1 upregulation, suggesting a basically conserved function of the iron-responsive element/iron regulatory protein (IRE/IRP) pathway, designed to adapt gene expression to iron levels. Expression levels of mitoferrin 1 and 2, frataxin, and iron-sulfur cluster scaffold protein were also significantly increased in G93A-SOD1 cells, suggesting higher mitochondrial iron import and utilization in biosynthetic pathways within the mitochondria. Moreover, expression of these transcripts was further enhanced, if G93A-SOD1 cells were differentiated by retinoic acid (RA). Since RA treatment increased cytoplasmic reactive oxygen species (ROS) levels in these cells, an IRE/IRP independent, ROS-mediated mechanism may account for dysregulation of iron-related genes.

Amyotrophic lateral sclerosis: new insights into underlying molecular mechanisms and opportunities for therapeutic intervention

Recent years have witnessed a renewed interest in the pathogenic mechanisms of amyotrophic lateral sclerosis (ALS), a late-onset progressive degeneration of motor neurons. The discovery of new genes associated with the familial form of the disease, along with a deeper insight into pathways already described for this disease, has led scientists to reconsider previous postulates. While protein misfolding, mitochondrial dysfunction, oxidative damage, defective axonal transport, and excitotoxicity have not been dismissed, they need to be re-examined as contributors to the onset or progression of ALS in the light of the current knowledge that the mutations of proteins involved in RNA processing, apparently unrelated to the previous "old partners," are causative of the same phenotype. Thus, newly envisaged models and tools may offer unforeseen clues on the etiology of this disease and hopefully provide the key to treatment.

Thinking outside the cleft to understand synaptic activity: contribution of the cystine-glutamate antiporter (System xc-) to normal and pathological glutamatergic signaling

System x(c)(-) represents an intriguing target in attempts to understand the pathological states of the central nervous system. Also called a cystine-glutamate antiporter, system x(c)(-) typically functions by exchanging one molecule of extracellular cystine for one molecule of intracellular glutamate. Nonvesicular glutamate released during cystine-glutamate exchange activates extrasynaptic glutamate receptors in a manner that shapes synaptic activity and plasticity. These findings contribute to the intriguing possibility that extracellular glutamate is regulated by a complex network of release and reuptake mechanisms, many of which are unique to glutamate and rarely depicted in models of excitatory signaling. Because system x(c)(-) is often expressed on non-neuronal cells, the study of cystine-glutamate exchange may advance the emerging viewpoint that glia are active contributors to information processing in the brain. It is noteworthy that system x(c)(-) is at the interface between excitatory signaling and oxidative stress, because the uptake of cystine that results from cystine-glutamate exchange is critical in maintaining the levels of glutathione, a critical antioxidant. As a result of these dual functions, system x(c)(-) has been implicated in a wide array of central nervous system diseases ranging from addiction to neurodegenerative disorders to schizophrenia. In the current review, we briefly discuss the major cellular components that regulate glutamate homeostasis, including glutamate release by system x(c)(-). This is followed by an in-depth discussion of system x(c)(-) as it relates to glutamate release, cystine transport, and glutathione synthesis. Finally, the role of system x(c)(-) is surveyed across a number of psychiatric and neurodegenerative disorders.

Protective efficacy of coenzyme Q10 against DDVP-induced cognitive impairments and neurodegeneration in rats

The present study was carried out to elucidate the effects of coenzyme Q(10) (CoQ(10)) against cognitive impairments induced by dichlorvos (DDVP). We have previously shown organophosphate, DDVP-induced impairments in neurobehavioral indices viz. rota rod, passive avoidance, and water maze tests. In addition to this, we have also reported that chronic DDVP exposure leads to decreased mitochondrial electron transfer activities of cytochrome oxidase along with altered mitochondrial complexes I-III activity. Administration of CoQ(10) (4.5 mg/kg, i.p. for 12 weeks prior to DDVP administration daily) to DDVP-treated rats improved cognitive performance in passive avoidance task and Morris water maze test. Furthermore, CoQ(10) treatment also reduced oxidative stress (as evident by reduced malondialdehyde, decreased ROS and increased Mn-SOD activity) in DDVP-treated rats' hippocampus region, along with enhanced activity of complexes I-III and complex IV. Electron microscope studies of rat hippocampus mitochondria revealed that CoQ(10) administration leads to near normal physiology of mitochondria with well-defined cristae compared with DDVP-treated animals where enlarged mitochondria with distorted cristae are observed. CoQ(10) administration also attenuated neuronal damage in hippocampus as evident from histopathological studies. These results demonstrate the beneficial effects of CoQ(10) against organophosphate-induced cognitive impairments and hippocampal neuronal degeneration.

Mitochondrial dysfunction in ALS

In the present article, we review the many facets of mitochondrial dysfunction in amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease due to loss of upper motor neurons in cerebral cortex and lower motor neurons in brainstem and spinal cord. Accumulating evidence from recent studies suggests that the many, interconnected facets of mitochondrial dysfunction may play a more significant role in the etiopathogenesis of this disorder than previously thought. This notion stems from our expanding knowledge of the complex physiology of mitochondria and of alteration of their properties that might confer an intrinsic susceptibility to long-lived, post-mitotic motor neurons to energy deficit, calcium mishandling and oxidative stress. The wealth of evidence implicating mitochondrial dysfunction as a major event in the pathology of ALS has prompted new studies aimed to the development of new mitochondria-targeted therapies. However, it is now clear that drugs targeting more than one aspect of mitochondrial dysfunction are needed to fight this devastating disease.

Nigrostriatal neuronal death following chronic dichlorvos exposure: crosstalk between mitochondrial impairments, α synuclein aggregation, oxidative damage and behavioral changes

BACKGROUND

In recent years, several lines of evidence have shown an increase in Parkinson's disease prevalence in rural environments where pesticides are heavily used. Although, the underlying mechanism for neuronal degeneration in sporadic PD remains unknown, mitochondrial dysfunction, oxidative stress and proteasomal dysfunction are proposed as contributing factors. In this study rats were chronically and continuously exposed to the pesticide, dichlorvos to identify the molecular mechanism of nigrostaital neuronal degeneration.

RESULT

Chronic dichlorvos exposure (2.50 mg/kg b.wt.s.c/daily for 12 weeks) caused nigrostriatal dopaminergic degeneration. The degenerative changes were accompanied by a loss of 60-80% of the nigral dopamine neurons and 60-70% reduction in striatal dopamine and tyrosine hydroxylase levels. Dichlorvos exposed animals also showed α -synuclein and ubiquitin positive inclusions along with swollen, dystrophic neurites and mitochondrial abnormalities like decreased complex I&IV activities, increased mitochondrial size, axonal degeneration and presence of electron dense perinuclear cytoplasmic inclusions in the substantia nigra of rats. These animals also showed evidence of oxidative stress, including increased mitochondrial ROS levels, decreased MnSOD activity and increased lipid peroxidation. Measurable impairments in neurobehavioral indices were also observed. Notable exacerbations in motor impairments, open field and catalepsy were also evident in dichlorvos exposed animals.

CONCLUSION

All these findings taken together indicate that chronic dichlorvos exposure may cause nigrostaital neurodegenaration and significant behavioral impairments.

Increased SOD1 association with chromatin, DNA damage, p53 activation, and apoptosis in a cellular model of SOD1-linked ALS

Mutations in the gene encoding cytosolic Cu,Zn-superoxide dismutase (SOD1) have been linked to familial amyotrophic lateral sclerosis (FALS). However the molecular mechanisms of motor neuron death are multi-factorial and remain unclear. Here we examined DNA damage, p53 activity and apoptosis in SH-SY5Y human neuroblastoma cells transfected to achieve low-level expression of either wild-type or mutant Gly(93)-->Ala (G93A) SOD1, typical of FALS. DNA damage was investigated by evaluating the levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) and DNA strand breaks. Significantly higher levels of DNA damage, increased p53 activity, and a greater percentage of apoptotic cells were observed in SH-SY5Y cells transfected with G93A SOD1 when compared to cells overexpressing wild-type SOD1 and untransfected cells. Western blot, FACS, and confocal microscopy analysis demonstrated that G93A SOD1 is present in the nucleus in association with DNA. Nuclear G93A SOD1 has identical superoxide dismutase activity but displays increased peroxidase activity when compared to wild-type SOD1. These results indicate that the G93A mutant SOD1 association with DNA might induce DNA damage and trigger the apoptotic response by activating p53. This toxic activity of mutant SOD1 in the nucleus may play an important role in the complex mechanisms associated with motor neuron death observed in ALS pathogenesis.

A novel decoy that interrupts G93A-superoxide dismutase gain of interaction with malate dehydrogenase improves survival in an amyotrophic lateral sclerosis cell model

Human G93A-superoxide dismutase-1 (G93AhSOD1) mutation causes amyotrophic lateral sclerosis (ALS) in rodents and humans. Recent observations indicate gain of interaction of G93AhSOD1 with cytosolic malate dehydrogenase (MDH1) and subsequent impairment in the malate aspartate shuttle which is vital to neurons. Using fluorescence resonance energy transfer (FRET), we screened an MDH1 derived peptide library for a decoy that would interrupt the G93AhSOD1-MDH1 interaction. A specific 23 amino acid blocker of this interaction was thus discovered, and interruption of interaction was confirmed by pull-down immunoprecipitation studies. A cell permeable 5-carboxytetramethylrhodamine derivative of the decoy peptide improved ATP content of motor neuron derived NSC-34 cells expressing G93AhSOD1 and enhanced cell survival under rotenone and low glucose challenges. Decoy agents capable of interrupting the gain of toxic interaction of G93AhSOD1 with MDH1 provide further evidence for the role of malate aspartate shuttle inhibition in G93AhSOD1 toxicity and a promising new route in ALS drug research.

LACTATE STRESS TESTING IN SPORADIC AMYOTROPHIC LATERAL SCLEROSIS

Mitochondrial dysfunction is frequently observed in ALS. Mitochondrial dysfunction may result in increased serum lactate at rest or low levels of exercise, being used for diagnostic purposes. The study investigated if resting-lactate-determination is superior to lactate-stress-testing (LST) in demonstrating mitochondrial dysfunction in ALS. Included were 15 ALS patients, 4 women, 11 men, aged 37-72. Severity of the disease was assessed by the Norris-score. The control group comprised 66 healthy subjects, 40 women, 26 men, aged 36-76. Serum lactate was determined before, three times during, and once after a constant workload with 30 W on a bicycle ergometer. According to the EIEscorial criteria 8 patients had definite, 4 probable, 3 possible ALS. Resting lactate was increased in 2 patients, 1 with definite and 1 with possible ALS. The LST was abnormal in 5 patients with definite, 1 with probable and 1 with possible ALS. The mean Norris-score was 67.8 in patients with abnormal LST and 74.6 in patients with normal LST. In conclusion, the LST is more suitable than resting-lactate-determination in demonstrating mitochondrial dysfunction in ALS. The LST suggests mitochondrial dysfunction in half of the ALS patients. Mitochondrial dysfunction in ALS is related to the clinical severity of the disease.

Mitochondrial approaches for neuroprotection

A large body of evidence from postmortem brain tissue and genetic analysis in humans and biochemical and pathological studies in animal models (transgenic and toxin) of neurodegeneration suggest that mitochondrial dysfunction is a common pathological mechanism. Mitochondrial dysfunction from oxidative stress, mitochondrial DNA deletions, pathological mutations, altered mitochondrial morphology, and interaction of pathogenic proteins with mitochondria leads to neuronal demise. Therefore, therapeutic approaches targeting mitochondrial dysfunction and oxidative damage hold great promise in neurodegenerative diseases. This review discusses the potential therapeutic efficacy of creatine, coenzyme Q10, idebenone, synthetic triterpenoids, and mitochondrial targeted antioxidants (MitoQ) and peptides (SS-31) in in vitro studies and in animal models of Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and Alzheimer's disease. We have also reviewed the current status of clinical trials of creatine, coenzyme Q10, idebenone, and MitoQ in neurodegenerative disorders. Further, we discuss newly identified therapeutic targets, including peroxisome proliferator-activated receptor-gamma-coactivator and sirtuins, which provide promise for future therapeutic developments in neurodegenerative disorders.

Amyotrophic lateral sclerosis: from current developments in the laboratory to clinical implications

Amyotrophic lateral sclerosis (ALS) is a late-onset progressive degeneration of motor neurons occurring both as a sporadic and a familial disease. The etiology of ALS remains unknown, but one fifth of instances are due to specific gene defects, the best characterized of which is point mutations in the gene coding for Cu/Zn superoxide dismutase (SOD1). Because sporadic and familial ALS affect the same neurons with similar pathology, it is hoped that understanding these gene defects will help in devising therapies effective in both forms. A wealth of evidence has been collected in rodents made transgenic for mutant SOD1, which represent the best available models for familial ALS. Mutant SOD1 likely induces selective vulnerability of motor neurons through a combination of several mechanisms, including protein misfolding, mitochondrial dysfunction, oxidative damage, cytoskeletal abnormalities and defective axonal transport, excitotoxicity, inadequate growth factor signaling, and inflammation. Damage within motor neurons is enhanced by noxious signals originating from nonneuronal neighboring cells, where mutant SOD1 induces an inflammatory response that accelerates disease progression. The clinical implication of these findings is that promising therapeutic approaches can be derived from multidrug treatments aimed at the simultaneous interception of damage in both motor neurons and nonmotor neuronal cells.

Expression of a Cu,Zn superoxide dismutase typical for familial amyotrophic lateral sclerosis increases the vulnerability of neuroblastoma cells to infectious injury

Background

Infections can aggravate the course of neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). Mutations in the anti-oxidant enzyme Cu,Zn superoxide dismutase (EC 1.15.1.1, SOD1) are associated with familial ALS. Streptococcus pneumoniae, the most frequent respiratory pathogen, causes damage by the action of the cholesterol-binding virulence factor pneumolysin and by stimulation of the innate immune system, particularly via Toll-like-receptor 2.

Methods

SH-SY5Y neuroblastoma cells transfected with the G93A mutant of SOD1 typical for familial ALS (G93A-SOD1) and SH-SY5Y neuroblastoma cells transfected with wildtype SOD1 were both exposed to pneumolysin and in co-cultures with cultured human macrophages treated with the Toll like receptor 2 agonist N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2RS)-propyl]-[R]-cysteinyl-[S]-seryl-[S]-lysyl-[S]-lysyl-[S]-lysyl-[S]-lysyl-[S]-lysine × 3 HCl (Pam₃CSK₄). Cell viability and apoptotic cell death were compared morphologically and by in-situ tailing. With the help of the WST-1 test, cell viability was quantified, and by measurement of neuron-specific enolase in the culture supernatant neuronal damage in co-cultures was investigated. Intracellular calcium levels were measured by fluorescence analysis using fura-2 AM.

Results

SH-SY5Y neuroblastoma cells transfected with the G93A mutant of SOD1 typical for familial ALS (G93A-SOD1) were more vulnerable to the neurotoxic action of pneumolysin and to the attack of monocytes stimulated by Pam₃CSK₄ than SH-SY5Y cells transfected with wild-type human SOD1. The enhanced pneumolysin toxicity in G93A-SOD1 neuronal cells depended on the inability of these cells to cope with an increased calcium influx caused by pores formed by pneumolysin. This inability was caused by an impaired capacity of the mitochondria to remove cytoplasmic calcium. Treatment of G93A-SOD1 SH-SY5Y neuroblastoma cells with the antioxidant N-acetylcysteine reduced the toxicity of pneumolysin.

Conclusion

The particular vulnerability of G93A-SOD1 neuronal cells to hemolysins and inflammation may be partly responsible for the clinical deterioration of ALS patients during infections. These findings link infection and motor neuron disease and suggest early treatment of respiratory infections in ALS patients.

Mutant SOD1-induced neuronal toxicity is mediated by increased mitochondrial superoxide levels

Amyotrophic lateral sclerosis (ALS), the most common motor neuron disease in adults, is characterized by the selective degeneration and death of motor neurons leading to progressive paralysis and eventually death. Approximately 20% of familial ALS cases are associated with mutations in SOD1, the gene encoding Cu/Zn-superoxide dismutase (CuZnSOD). Previously, we reported that overexpression of the mitochondrial antioxidant manganese superoxide dismutase (MnSOD or SOD2) attenuates cytotoxicity induced by expression of the G37R-SOD1 mutant in a human neuroblastoma cell culture model of ALS. In the present study, we extended these earlier findings using several different SOD1 mutants (G93C, G85R, and I113T). Additionally, we tested the hypothesis that mutant SOD1 increases mitochondrial-produced superoxide (O(2) (*)) levels and that SOD2 overexpression protects neurons from mutant SOD1-induced toxicity by reducing O(2) (*) levels in mitochondria. In the present study, we demonstrate that SOD2 overexpression markedly attenuates the neuronal toxicity induced by adenovirus-mediated expression of all four SOD1 mutants (G37R, G93C, G85R, or I113T) tested. Utilizing the mitochondrial-targeted O(2) (*)-sensitive fluorogenic probe MitoSOX Red, we observed a significant increase in mitochondrial O(2) (*) levels in neural cells expressing mutant SOD1. These elevated O(2) (*) levels in mitochondria were significantly diminished by the overexpression of SOD2. These data suggest that mitochondrial-produced O(2) (*) radicals play a critical role in mutant SOD1-mediated neuronal toxicity and implicate mitochondrial-produced free radicals as potential therapeutic targets in ALS.

Reactive oxygen and nitrogen species: Implications for cardiovascular device engineering

The development of medical devices for cardiovascular applications has suffered due to lack of understanding of why vascular wall cells act nonphysiologically when exposed to biomaterials. One possible reason might be the chemical environment associated with cardiovascular disease. An improved understanding of cellular and subcellular mechanisms may assist in future device design to account for the disease environment. Reactive oxygen and nitrogen species (ROS/RNS) are produced through normal cellular metabolism and are rendered harmless by enzymatic systems. However, during a disease process, these systems may act aberrantly, and either fail to convert ROS and RNS to harmless substances or by producing more oxidants. There is indirect evidence that the implantation of biomedical materials may also be responsible for the triggering of these aberrant pathways that may lead to the eventual failure of the device. The understanding of how the vascular environment may be changed at the subcellular level by the presence of a biomaterial is critical. In the following pages, we hope to review the current thinking within vascular biology regarding ROS and RNS, how they are measured, and how they may impact vascular cells.

Mitochondria in amyotrophic lateral sclerosis: a trigger and a target

Strong evidence shows that mitochondrial dysfunction is involved in amyotrophic lateral sclerosis (ALS), but despite the fact that mitochondria play a central role in excitotoxicity, oxidative stress and apoptosis, the intimate underlying mechanism linking mitochondrial defects to motor neuron degeneration in ALS still remains elusive. Morphological and functional abnormalities occur in mitochondria in ALS patients and related animal models, although their exact nature and extent are controversial. Recent studies postulate that the mislocalization in mitochondria of mutant forms of copper-zinc superoxide dismutase (SOD1), the only well-documented cause of familial ALS, may account for the toxic gain of function of the enzyme, and hence induce motor neuron death. On the other hand, mitochondrial dysfunction in ALS does not seem to be restricted only to motor neurons as it is also present in other tissues, particularly the skeletal muscle. The presence of this 'systemic' defect in energy metabolism associated with the disease is supported in skeletal muscle tissue by impaired mitochondrial respiration and overexpression of uncoupling protein 3. In addition, the lifespan of transgenic mutant SOD1 mice is increased by a highly energetic diet compensating both the metabolic defect and the motorneuronal function. In this review, we will focus on the mitochondrial dysfunction linked to ALS and the cause-and-effect relationships between mitochondria and the pathological mechanisms thought to be involved in the disease.

The role of ubiquitin-protein ligases in neurodegenerative disease

Alzheimer's disease and Parkinson's disease are the most common neurodegenerative conditions associated with the ageing process. The pathology of these and other neurodegenerative disorders, including polyglutamine diseases, is characterised by the presence of inclusion bodies in brain tissue of affected patients. In general, these inclusion bodies consist of insoluble, unfolded proteins that are commonly tagged with the small protein, ubiquitin. Covalent tagging of proteins with chains of ubiquitin generally targets them for degradation. Indeed, the ubiquitin/proteasome system (UPS) is the major route through which intracellular proteolysis is regulated. This strongly implicates the UPS in these disease-associated inclusions, either due to malfunction (of specific UPS components) or overload of the system (due to aggregation of unfolded/mutant proteins), resulting in subsequent cellular toxicity. Protein targeting for degradation is a highly regulated process. It relies on transfer of ubiquitin molecules to the target protein via an enzyme cascade and specific recognition of a substrate protein by ubiquitin-protein ligases (E3s). Recent advances in our knowledge gained from the Human Genome Mapping Project have revealed the presence of potentially hundreds of E3s within the human genome. The discovery that parkin, mutations in which are found in at least 50% of patients with autosomal recessive juvenile parkinsonism, is an E3 further highlights the importance of the UPS in neurological disease. To date, parkin is the only E3 confirmed to have a direct causal role in neurodegenerative disorders. However, a number of other (putative) E3s have now been identified that may cause disease directly or interact with neurological disease-associated proteins. Many of these are either lost or mutated in a given disease or fail to process disease-associated mutant proteins correctly. In this review, we will discuss the role(s) of E3s in neurodegenerative disorders.