The modest impact of transcription factor Nrf2 on the course of disease in an ALS animal model

The SIRT-1/Nrf2/HO-1 axis: Guardians of neuronal health in neurological disorders

SIRT1 (Sirtuin 1) is a NAD+-dependent deacetylase that functions through nucleoplasmic transfer and is present in nearly all mammalian tissues. SIRT1 is believed to deacetylate its protein substrates, resulting in neuroprotective actions, including reduced oxidative stress and inflammation, increased autophagy, increased nerve growth factors, and preserved neuronal integrity in aging or neurological disease. Nrf2 is a transcription factor that regulates the genes responsible for oxidative stress response and substance detoxification. The activation of Nrf2 guards cells against oxidative damage, inflammation, and carcinogenic stimuli. Several neurological abnormalities and inflammatory disorders have been associated with variations in Nrf2 activation caused by either pharmacological or genetic factors. Recent evidence indicates that Nrf2 is at the center of a complex cellular regulatory network, establishing it as a transcription factor with genuine pleiotropy. HO-1 is most likely a component of a defense mechanism in cells under stress, as it provides negative feedback for cell activation and mediator synthesis. This mediator is upregulated by Nrf2, nitric oxide (NO), and other factors in various inflammatory states. HO-1 or its metabolites, such as CO, may mitigate inflammation by modulating signal transduction pathways. Neurological diseases may be effectively treated by modulating the activity of HO-1. Multiple studies have demonstrated that SIRT1 and Nrf2 share an important connection. SIRT1 enhances Nrf2, activates HO-1, protects against oxidative injury, and decreases neuronal death. This has been associated with numerous neurodegenerative and neuropsychiatric disorders. Therefore, activating the SIRT1/Nrf2/HO-1 pathway may help treat various neurological disorders. This review focuses on the current understanding of the SIRT1 and Nrf2/HO-1 neuroprotective processes and the potential therapeutic applications of their target activators in neurodegenerative and neuropsychiatric disorders.

NRF2 signaling cascade in amyotrophic lateral sclerosis: bridging the gap between promise and reality

Amyotrophic lateral sclerosis is a very disabling disease due to the degeneration of motor neurons. Symptoms include muscle weakness and atrophy, spasticity, and progressive paralysis. Currently, there is no treatment to reverse damage to motor neurons and cure amyotrophic lateral sclerosis. The only two treatments actually approved, riluzole and edaravone, have shown mitigated beneficial effects. The difficulty to find a cure lies in the complexity and multifaceted pattern of amyotrophic lateral sclerosis pathogenesis. Among mechanisms, abnormal RNA metabolism, nucleocytoplasmic transport defects, accumulation of unfolded protein, and mitochondrial dysfunction would in fine induce oxidative damage and vice versa. A potent therapeutic strategy will be to find molecules that break this vicious circle. Sharpening the nuclear factor erythroid-2 related factor 2 signaling may fulfill this objective since nuclear factor erythroid-2 related factor 2 has a multitarget profile controlling antioxidant defense, mitochondrial functioning, and inflammation. We here discuss the interest of developing nuclear factor erythroid-2 related factor 2-based therapy in regard to the pathophysiological mechanisms and we provide a general overview of the attempted clinical assays in amyotrophic lateral sclerosis.

Ferroptosis regulation through Nrf2 and implications for neurodegenerative diseases

This article provides an overview of the background knowledge of ferroptosis in the nervous system, as well as the key role of nuclear factor E2-related factor 2 (Nrf2) in regulating ferroptosis. The article takes Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS) as the starting point to explore the close association between Nrf2 and ferroptosis, which is of clear and significant importance for understanding the mechanism of neurodegenerative diseases (NDs) based on oxidative stress (OS). Accumulating evidence links ferroptosis to the pathogenesis of NDs. As the disease progresses, damage to the antioxidant system, excessive OS, and altered Nrf2 expression levels, especially the inhibition of ferroptosis by lipid peroxidation inhibitors and adaptive enhancement of Nrf2 signaling, demonstrate the potential clinical significance of Nrf2 in detecting and identifying ferroptosis, as well as targeted therapy for neuronal loss and mitochondrial dysfunction. These findings provide new insights and possibilities for the treatment and prevention of NDs.

Impact of NQO1 dysregulation in CNS disorders

NAD(P)H Quinone Dehydrogenase 1 (NQO1) plays a pivotal role in the regulation of neuronal function and synaptic plasticity, cellular adaptation to oxidative stress, neuroinflammatory and degenerative processes, and tumorigenesis in the central nervous system (CNS). Impairment of the NQO1 activity in the CNS can result in abnormal neurotransmitter release and clearance, increased oxidative stress, and aggravated cellular injury/death. Furthermore, it can cause disturbances in neural circuit function and synaptic neurotransmission. The abnormalities of NQO1 enzyme activity have been linked to the pathophysiological mechanisms of multiple neurological disorders, including Parkinson's disease, Alzheimer's disease, epilepsy, multiple sclerosis, cerebrovascular disease, traumatic brain injury, and brain malignancy. NQO1 contributes to various dimensions of tumorigenesis and treatment response in various brain tumors. The precise mechanisms through which abnormalities in NQO1 function contribute to these neurological disorders continue to be a subject of ongoing research. Building upon the existing knowledge, the present study reviews current investigations describing the role of NQO1 dysregulations in various neurological disorders. This study emphasizes the potential of NQO1 as a biomarker in diagnostic and prognostic approaches, as well as its suitability as a target for drug development strategies in neurological disorders.

The untapped potential of targeting NRF2 in neurodegenerative disease

Since its initial discovery almost three decades ago, the transcription factor nuclear factor erythroid 2-related factor 2 (NRF2) has been shown to regulate a host of downstream transcriptional responses and play a critical role in preventing or promoting disease progression depending on the context. Critically, while the importance of proper nuclear factor erythroid 2-related factor 2 function has been demonstrated across a variety of pathological settings, the ability to progress NRF2-targeted therapeutics to clinic has remained frustratingly elusive. This is particularly true in the case of age-related pathologies, where nuclear factor erythroid 2-related factor 2 is a well-established mitigator of many of the observed pathogenic effects, yet options to target this pathway remain limited. Along these lines, loss of nuclear factor erythroid 2-related factor 2 function has clearly been shown to enhance neuropathological outcomes, with enhancing nuclear factor erythroid 2-related factor 2 pathway activation to prevent neurodegenerative/neurological disease progression continuing to be an active area of interest. One critical obstacle in generating successful therapeutics for brain-related pathologies is the ability of the compound to cross the blood brain barrier (BBB), which has also hampered the implementation of several promising nuclear factor erythroid 2-related factor 2 inducers. Another limitation is that many nuclear factor erythroid 2-related factor 2 activators have undesirable off-target effects due to their electrophilic nature. Despite these constraints, the field has continued to evolve, and several viable means of targeting nuclear factor erythroid 2-related factor 2 in a neuropathological context have emerged. In this perspective, we will briefly discuss the key findings and promising therapeutic options that have been discovered to date, as well as highlight emerging areas of NRF2-neurodegeneration research that provide hope for successfully targeting this pathway in the future.

The Impact of Mitochondrial Dysfunction in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive and highly fatal neurodegenerative disease. Although the pathogenesis of ALS remains unclear, increasing evidence suggests that a key contributing factor is mitochondrial dysfunction. Mitochondria are organelles in eukaryotic cells responsible for bioenergy production, cellular metabolism, signal transduction, calcium homeostasis, and immune responses and the stability of their function plays a crucial role in neurons. A single disorder or defect in mitochondrial function can lead to pathological changes in cells, such as an impaired calcium buffer period, excessive generation of free radicals, increased mitochondrial membrane permeability, and oxidative stress (OS). Recent research has also shown that these mitochondrial dysfunctions are also associated with pathological changes in ALS and are believed to be commonly involved in the pathogenesis of the disease. This article reviews the latest research on mitochondrial dysfunction and its impact on the progression of ALS, with specific attention to the potential of novel therapeutic strategies targeting mitochondrial dysfunction.

Activation of the Nrf2 Pathway as a Therapeutic Strategy for ALS Treatment

Amyotrophic lateral sclerosis is a progressive and fatal disease that causes motoneurons degeneration and functional impairment of voluntary muscles, with limited and poorly efficient therapies. Alterations in the Nrf2-ARE pathway are associated with ALS pathology and result in aberrant oxidative stress, making the stimulation of the Nrf2-mediated antioxidant response a promising therapeutic strategy in ALS to reduce oxidative stress. In this review, we first introduce the involvement of the Nrf2 pathway in the pathogenesis of ALS and the role played by astrocytes in modulating such a protective pathway. We then describe the currently developed activators of Nrf2, used in both preclinical animal models and clinical studies, taking into consideration their potentialities as well as the possible limitations associated with their use.

Impaired antioxidant KEAP1-NRF2 system in amyotrophic lateral sclerosis: NRF2 activation as a potential therapeutic strategy

BACKGROUND

Oxidative stress (OS) is an imbalance between oxidant and antioxidant species and, together with other numerous pathological mechanisms, leads to the degeneration and death of motor neurons (MNs) in amyotrophic lateral sclerosis (ALS).

MAIN BODY

Two of the main players in the molecular and cellular response to OS are NRF2, the transcription nuclear factor erythroid 2-related factor 2, and its principal negative regulator, KEAP1, Kelch-like ECH (erythroid cell-derived protein with CNC homology)-associated protein 1. Here we first provide an overview of the structural organization, regulation, and critical role of the KEAP1-NRF2 system in counteracting OS, with a focus on its alteration in ALS. We then examine several compounds capable of promoting NRF2 activity thereby inducing cytoprotective effects, and which are currently in different stages of clinical development for many pathologies, including neurodegenerative diseases.

CONCLUSIONS

Although challenges associated with some of these compounds remain, important advances have been made in the development of safer and more effective drugs that could actually represent a breakthrough for fatal degenerative diseases such as ALS.

NRF2 as a therapeutic opportunity to impact in the molecular roadmap of ALS

Amyotrophic Lateral Sclerosis (ALS) is a devastating heterogeneous disease with still no convincing therapy. To identify the most strategically significant hallmarks for therapeutic intervention, we have performed a comprehensive transcriptomics analysis of dysregulated pathways, comparing datasets from ALS patients and healthy donors. We have identified crucial alterations in RNA metabolism, intracellular transport, vascular system, redox homeostasis, proteostasis and inflammatory responses. Interestingly, the transcription factor NRF2 (nuclear factor (erythroid-derived 2)-like 2) has significant effects in modulating these pathways. NRF2 has been classically considered as the master regulator of the antioxidant cellular response, although it is currently considered as a key component of the transduction machinery to maintain coordinated control of protein quality, inflammation, and redox homeostasis. Herein, we will summarize the data from NRF2 activators in ALS pre-clinical models as well as those that are being studied in clinical trials. As we will discuss, NRF2 is a promising target to build a coordinated transcriptional response to motor neuron injury, highlighting its therapeutic potential to combat ALS.

Oxidative Stress as a Therapeutic Target in Amyotrophic Lateral Sclerosis: Opportunities and Limitations

Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND) and Lou Gehrig’s disease, is characterized by a loss of the lower motor neurons in the spinal cord and the upper motor neurons in the cerebral cortex. Due to the complex and multifactorial nature of the various risk factors and mechanisms that are related to motor neuronal degeneration, the pathological mechanisms of ALS are not fully understood. Oxidative stress is one of the known causes of ALS pathogenesis. This has been observed in patients as well as in cellular and animal models, and is known to induce mitochondrial dysfunction and the loss of motor neurons. Numerous therapeutic agents have been developed to inhibit oxidative stress and neuroinflammation. In this review, we describe the role of oxidative stress in ALS pathogenesis, and discuss several anti-inflammatory and anti-oxidative agents as potential therapeutics for ALS. Although oxidative stress and antioxidant fields are meaningful approaches to delay disease progression and prolong the survival in ALS, it is necessary to investigate various animal models or humans with different subtypes of sporadic and familial ALS.

Role of Oxidative Stress in the Pathogenesis of Amyotrophic Lateral Sclerosis: Antioxidant Metalloenzymes and Therapeutic Strategies

Amyotrophic lateral sclerosis (ALS) affects motor neurons in the cerebral cortex, brainstem and spinal cord and leads to death due to respiratory failure within three to five years. Although the clinical symptoms of this disease were first described in 1869 and it is the most common motor neuron disease and the most common neurodegenerative disease in middle-aged individuals, the exact etiopathogenesis of ALS remains unclear and it remains incurable. However, free oxygen radicals (i.e., molecules containing one or more free electrons) are known to contribute to the pathogenesis of this disease as they very readily bind intracellular structures, leading to functional impairment. Antioxidant enzymes, which are often metalloenzymes, inactivate free oxygen radicals by converting them into a less harmful substance. One of the most important antioxidant enzymes is Cu²⁺Zn²⁺ superoxide dismutase (SOD1), which is mutated in 20% of cases of the familial form of ALS (fALS) and up to 7% of sporadic ALS (sALS) cases. In addition, the proper functioning of catalase and glutathione peroxidase (GPx) is essential for antioxidant protection. In this review article, we focus on the mechanisms through which these enzymes are involved in the antioxidant response to oxidative stress and thus the pathogenesis of ALS and their potential as therapeutic targets.

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.

Dysregulation of metabolic pathways by carnitine palmitoyl-transferase 1 plays a key role in central nervous system disorders: experimental evidence based on animal models

The etiology of CNS diseases including multiple sclerosis, Parkinson’s disease and amyotrophic lateral sclerosis remains elusive despite decades of research resulting in treatments with only symptomatic effects. In this study, we provide evidence that a metabolic shift from glucose to lipid is a key mechanism in neurodegeneration. We show that, by downregulating the metabolism of lipids through the key molecule carnitine palmitoyl transferase 1 (CPT1), it is possible to reverse or slowdown disease progression in experimental models of autoimmune encephalomyelitis-, SOD1^G93A and rotenone models, mimicking these CNS diseases in humans. The effect was seen both when applying a CPT1 blocker or by using a Cpt1a P479L mutant mouse strain. Furthermore, we show that diet, epigenetics, and microbiota are key elements in this metabolic shift. Finally, we present a systemic model for understanding the complex etiology of neurodegeneration and how different regulatory systems are interconnected through a central metabolic pathway that becomes deregulated under specific conditions.

Decreased Mitochondrial Function, Biogenesis, and Degradation in Peripheral Blood Mononuclear Cells from Amyotrophic Lateral Sclerosis Patients as a Potential Tool for Biomarker Research

Amyotrophic lateral sclerosis (ALS) is a multifactorial and progressive neurodegenerative disease of unknown etiology. Due to ALS’s unpredictable onset and progression rate, the search for biomarkers that allow the detection and tracking of its development and therapeutic efficacy would be of significant medical value. Considering that alterations of energy supply are one of ALS’s main hallmarks and that a correlation has been established between gene expression in human brain tissue and peripheral blood mononuclear cells (PBMCs), the present work investigates whether changes in mitochondrial function could be used to monitor ALS. To achieve this goal, PBMCs from ALS patients and control subjects were used; blood sampling is a quite non-invasive method and is cost-effective. Different parameters were evaluated, namely cytosolic calcium levels, mitochondrial membrane potential, oxidative stress, and metabolic compounds levels, as well as mitochondrial dynamics and degradation. Altogether, we observed lower mitochondrial calcium uptake/retention, mitochondria depolarization, and redox homeostasis deregulation, in addition to a decrease in critical metabolic genes, a diminishment in mitochondrial biogenesis, and an augmentation in mitochondrial fission and autophagy-related gene expression. All of these changes can contribute to the decreased ATP and pyruvate levels observed in ALS PBMCs. Our data indicate that PBMCs from ALS patients show a significant mitochondrial dysfunction, resembling several findings from ALS’ neural cells/models, which could be exploited as a powerful tool in ALS research. Our findings can also guide future studies on new pharmacological interventions for ALS since assessments of brain samples are challenging and represent a relevant limited strategy.

ALS-associated TBK1 variant p.G175S is defective in phosphorylation of p62 and impacts TBK1-mediated signalling and TDP-43 autophagic degradation

Mutations affecting SQSTM1 coding for p62 and TANK-Binding Kinase 1 (TBK1) have been implicated in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). TBK1 is a serine-threonine kinase that regulates p62's activity as an autophagy receptor via phosphorylation and also has roles in neuroinflammatory signalling pathways. The mechanisms underlying ALS and FTLD pathogenesis as a result of TBK1 mutations are incompletely understood, however, loss of TBK1 function can lead to dysregulated autophagy and mitophagy. Here, we report that an ALS-associated TBK1 variant affecting the kinase domain, p.G175S, is defective in phosphorylation of p62 at Ser-403, a modification critical for regulating its ubiquitin-binding function, as well as downstream phosphorylation at Ser-349. Consistent with these findings, expression of p.G175S TBK1 was associated with decreased induction of autophagy compared to wild type and reduced degradation of the ALS-linked protein TDP-43. Expression of wild type TBK1 increased NF-κB signalling ~300 fold in comparison to empty vector cells, whereas p.G175S TBK1 was unable to promote NF-κB signalling above levels observed in empty vector transfected cells. We also noted a hitherto unknown role for TBK1 as a suppressor of oxidative stress (Nrf2) signalling and show that p.G175S TBK1 expressing cells lose this inhibitory function. Our data suggest that TBK1 ALS mutations may broadly impair p62-mediated cell signalling, which ultimately may reduce neuronal survival, in addition TDP-43 was not efficiently degraded, together these effects may contribute to TBK1 mutation associated ALS and FTLD pathogenesis.

Exercise-Related Oxidative Stress as Mechanism to Fight Physical Dysfunction in Neuromuscular Disorders

Neuromuscular diseases (NMDs) are a group of often severely disabling disorders characterized by dysfunction in one of the main constituents of the motor unit, the cardinal anatomic-functional structure behind force and movement production. Irrespective of the different pathogenic mechanisms specifically underlying these disease conditions genetically determined or acquired, and the related molecular pathways involved in doing that, oxidative stress has often been shown to play a relevant role within the chain of events that induce or at least modulate the clinical manifestations of these disorders. Due to such a putative relevance of the imbalance of redox status occurring in contractile machinery and/or its neural drive in NMDs, physical exercise appears as one of the most important conditions able to positively interfere along an ideal axis, going from a deranged metabolic cell homeostasis in motor unit components to the reduced motor performance profile exhibited by the patient in everyday life. If so, it comes out that it would be important to identify a proper training program, suitable for load and type of exercise that is able to improve motor performance in adaptation and response to such a homeostatic imbalance. This review therefore analyzes the role of different exercise trainings on oxidative stress mechanisms, both in healthy and in NMDs, also including preclinical studies, to elucidate at which extent these can be useful to counteract muscle impairment associated to the disease, with the final aim of improving physical functions and quality of life of NMD patients.

The role of sequestosome 1/p62 protein in amyotrophic lateral sclerosis and frontotemporal dementia pathogenesis

Amyotrophic lateral sclerosis and frontotemporal lobar degeneration are multifaceted diseases with genotypic, pathological and clinical overlap. One such overlap is the presence of SQSTM1/p62 mutations. While traditionally mutations manifesting in the ubiquitin-associated domain of p62 were associated with Paget’s disease of bone, mutations affecting all functional domains of p62 have now been identified in amyotrophic lateral sclerosis and frontotemporal lobar degeneration patients. p62 is a multifunctional protein that facilitates protein degradation through autophagy and the ubiquitin-proteasome system, and also regulates cell survival via the Nrf2 antioxidant response pathway, the nuclear factor-kappa B signaling pathway and apoptosis. Dysfunction in these signaling and protein degradation pathways have been observed in amyotrophic lateral sclerosis and frontotemporal lobar degeneration, and mutations that affect the role of p62 in these pathways may contribute to disease pathogenesis. In this review we discuss the role of p62 in these pathways, the effects of p62 mutations and the effect of mutations in the p62 modulator TANK-binding kinase 1, in relation to amyotrophic lateral sclerosis-frontotemporal lobar degeneration pathogenesis.

Astrocytes in Motor Neuron Diseases

Motor neuron disorders are highly debilitating and mostly fatal conditions for which only limited therapeutic options are available. To overcome this limitation and develop more effective therapeutic strategies, it is critical to discover the pathogenic mechanisms that trigger and sustain motor neuron degeneration with the greatest accuracy and detail. In the case of Amyotrophic Lateral Sclerosis (ALS), several genes have been associated with familial forms of the disease, whilst the vast majority of cases develop sporadically and no defined cause can be held responsible. On the contrary, the huge majority of Spinal Muscular Atrophy (SMA) occurrences are caused by loss-of-function mutations in a single gene, SMN1. Although the typical hallmark of both diseases is the loss of motor neurons, there is increasing awareness that pathological lesions are also present in the neighbouring glia, whose dysfunction clearly contributes to generating a toxic environment in the central nervous system. Here, ALS and SMA are sequentially presented, each disease section having a brief introduction, followed by a focussed discussion on the role of the astrocytes in the disease pathogenesis. Such a dissertation is substantiated by the findings that built awareness on the glial involvement and how the glial-neuronal interplay is perturbed, along with the appraisal of this new cellular site for possible therapeutic intervention.

LanCL1 promotes motor neuron survival and extends the lifespan of amyotrophic lateral sclerosis mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of motor neurons. Improving neuronal survival in ALS remains a significant challenge. Previously, we identified Lanthionine synthetase C-like protein 1 (LanCL1) as a neuronal antioxidant defense gene, the genetic deletion of which causes apoptotic neurodegeneration in the brain. Here, we report in vivo data using the transgenic SOD1^G93A mouse model of ALS indicating that CNS-specific expression of LanCL1 transgene extends lifespan, delays disease onset, decelerates symptomatic progression, and improves motor performance of SOD1^G93A mice. Conversely, CNS-specific deletion of LanCL1 leads to neurodegenerative phenotypes, including motor neuron loss, neuroinflammation, and oxidative damage. Analysis reveals that LanCL1 is a positive regulator of AKT activity, and LanCL1 overexpression restores the impaired AKT activity in ALS model mice. These findings indicate that LanCL1 regulates neuronal survival through an alternative mechanism, and suggest a new therapeutic target in ALS.

Angiogenin activates the astrocytic Nrf2/antioxidant-response element pathway and thereby protects murine neurons from oxidative stress

The angiogenin (ANG) gene is mutated frequently in individuals with amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease characterized by the progressive loss of motor neurons. Delivering human ANG to mice that display ALS-like symptoms extends their lifespan and improves motor function. ANG is a secretory vertebrate RNase that enters neuronal cells and cleaves a subset of tRNAs, leading to the inhibition of translation initiation and the assembly of stress granules. Here, using murine neuronal and astrocytic cell lines, we find that ANG triggers the activation of the Nrf2 (nuclear factor erythroid 2-related factor 2) pathway, which provides a critical cellular defense against oxidative stress. This activation, which occurred in astrocytes but not in neurons, promoted the survival of proximal neurons that had oxidative injury. These findings extend the role of ANG as a neuroprotective agent and underscore its potential utility in ALS management.

Semantic Analysis of Posttranslational Modification of Proteins Accumulated in Thyroid Cancer Cells Exposed to Simulated Microgravity

When monolayers of tissue cancer cells of various origins are exposed to real or simulated microgravity, many cells leave the monolayer and assemble to three-dimensional (3D) aggregates (spheroids). In order to define the cellular machinery leading to this change in growth behavior of FTC-133 human thyroid cancer cells and MCF-7 breast cancer cells, we recently performed proteome analyses on these cell lines and determined the proteins’ accumulation in monolayer cells grown under 1g-conditions as well as in the cells of spheroids assembled under simulated microgravity during three and 14 days, respectively. At that time, an influence of the increment or decrement of some of the more than 5000 proteins detected in each cell line was investigated. In this study, we focused on posttranslational modifications (PTMs) of proteins. For this purpose, we selected candidates from the list of the proteins detected in the two preceding proteome analyses, which showed significant accumulation in spheroid cells as compared to 1g monolayer cells. Then we searched for those PTMs of the selected proteins, which according to the literature have already been determined experimentally. Using the Semantic Protocol and RDF Query Language (SPARQL), various databases were examined. Most efficient was the search in the latest version of the dbPTM database. In total, we found 72 different classes of PTMs comprising mainly phosphorylation, glycosylation, ubiquitination and acetylation. Most interestingly, in 35 of the 69 proteins, N6 residues of lysine are modifiable.

Targeting crosstalk between Nuclear factor (erythroid-derived 2)-like 2 and Nuclear factor kappa beta pathway by Nrf2 activator dimethyl fumarate in epileptogenesis

Purpose/Aim: Epilepsy is a complex, chronic neurological disorder characterized by increased and abnormal synchronization of neuronal electrical activity, which is manifested as seizures. It is associated with many comorbid conditions such as depression, anxiety, sleep disorder, psychiatric disorder etc., which consequently causes higher mortality rate. The understanding of its cellular and molecular mechanism is partial, because of which it remains an ongoing health problem, despite the increasing availability of newer antiepileptic drugs. Although recurrent seizures are the clinical indication of epilepsy, the disease process (epileptogenesis) begins before the onset of the first seizure. This dormant phase before the onset of first seizure provides an opportune time window for modifying the epileptogenic process by intervening in its progression with an appropriate treatment.

MATERIAL AND METHODS

Studies have shown that in epilepsy, there is a chronic state of oxidative stress and inflammation, which plays a key role in epileptic pathogenesis. Various antioxidant mechanisms maintain the redox balance in the body by either scavenging or regulating the generation of free radicals. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathway is a well-established antioxidant pathway in various diseases such as diabetes, renal disease, various neurodegenerative disorders such as Parkinson's disease, Alzheimer's disease, Huntington's disease, amyotrophic lateral sclerosis, traumatic brain injury, etc. Results: It has been observed that single-target therapies are inefficient in providing anticonvulsant and disease-modifying effects in epilepsy.

CONCLUSIONS

So, preventing the progression of epilepsy by targeting Nrf2-activated antioxidant pathway along with the other established antiepileptic pathways can prove beneficial in epilepsy treatment.

IGF1 affects macrophage invasion and activation and TNF-α production in the sciatic nerves of female SOD1G93A mice

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease leading to paralysis and death within 3-5 years of its diagnosis. The SOD1G93A mouse is used extensively as an ALS animal model. Increasing evidence shows that non-neuronal cellscontribute to the pathogenesis and progression of ALS. Among them, many studies focus on microgliosis in the spinal cord (SC); while few on macrophage activation in the sciatic nerves. Substantial evidence shows that insulin-like growth factor 1 (IGF1) delays disease progression and increases the lifespan of SOD1G93A mice, and some studies indicate that IGF1 reduces inflammation in the SC of ALS mice. However, no studies have focused on the effect of IGF on sciatic nerve inflammation. Here, we find that ALS progression is characterized by increasing macrophage invasion and activation accompanied by significant TNF-α production in the sciatic nerve. Furthermore, IGF1 treatment and knockdown alleviate and aggravate these responses, respectively. Collectively, our findings show the first time that IGF1 has an anti-inflammatory effect in the sciatic nerves of SOD1G93A mice.

Diminished stress resistance and defective adaptive homeostasis in age-related diseases

Adaptive homeostasis is defined as the transient expansion or contraction of the homeostatic range following exposure to subtoxic, non-damaging, signaling molecules or events, or the removal or cessation of such molecules or events (Mol. Aspects Med. (2016) 49, 1-7). Adaptive homeostasis allows us to transiently adapt (and then de-adapt) to fluctuating levels of internal and external stressors. The ability to cope with transient changes in internal and external environmental stress, however, diminishes with age. Declining adaptive homeostasis may make older people more susceptible to many diseases. Chronic oxidative stress and defective protein homeostasis (proteostasis) are two major factors associated with the etiology of age-related disorders. In the present paper, we review the contribution of impaired responses to oxidative stress and defective adaptive homeostasis in the development of age-associated diseases.

Are Astrocytes the Predominant Cell Type for Activation of Nrf2 in Aging and Neurodegeneration?

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that regulates hundreds of antioxidant genes, and is activated in response to oxidative stress. Given that many neurodegenerative diseases including Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, Huntington’s disease and multiple sclerosis are characterised by oxidative stress, Nrf2 is commonly activated in these diseases. Evidence demonstrates that Nrf2 activity is repressed in neurons in vitro, and only cultured astrocytes respond strongly to Nrf2 inducers, leading to the interpretation that Nrf2 signalling is largely restricted to astrocytes. However, Nrf2 activity can be observed in neurons in post-mortem brain tissue and animal models of disease. Thus this interpretation may be false, and a detailed analysis of the cell type expression of Nrf2 in neurodegenerative diseases is required. This review describes the evidence for Nrf2 activation in each cell type in prominent neurodegenerative diseases and normal aging in human brain and animal models of neurodegeneration, the response to pharmacological and genetic modulation of Nrf2, and clinical trials involving Nrf2-modifying drugs.

ALS-FTLD associated mutations of SQSTM1 impact on Keap1-Nrf2 signalling

The transcription factor Nrf2 and its repressor protein Keap1 play key roles in the regulation of antioxidant stress responses and both Keap1-Nrf2 signalling and oxidative stress have been implicated in the pathogenesis of the ALS-FTLD spectrum of neurodegenerative disorders. The Keap1-binding partner and autophagy receptor SQSTM1/p62 has also recently been linked genetically to ALS-FTLD, with some missense mutations identified in patients mapping within or close to its Keap1-interacting region (KIR, residues 347–352). Here we report the effects on protein function of four different disease associated mutations of SQSTM1/p62 which affect the KIR region. Only mutations mapping precisely to the KIR (P348L and G351A) were associated with a loss of Keap1 binding in co-immunoprecipitations comparable to wild-type SQSTM1/p62. These selective effects on Keap1 recognition were entirely rational based on protein structural models. Consistent with impaired Keap1 binding, the P348L and G351A KIR mutants showed reduced ability to activate Nrf2 signalling compared to wild-type SQSTM1/p62 in antioxidant response element (ARE)-luciferase reporter assays. The results suggest that SQSTM1 mutations within the KIR of SQSTM1/p62 contribute to aetiology of some cases of ALS-FTLD through a mechanism involving aberrant expression or regulation of oxidative response genes.

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ALS-FTLD associated KIR mutations of SQSTM1/p62 disrupt Keap1 binding.

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KIR mutants of SQSTM1/p62 are unable to activate Nrf2 signalling in reporter assays.

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Some SQSTM1 mutations may contribute to ALS-FTLD through an aberrant antioxidant stress response.

Functional links between SQSTM1 and ALS2 in the pathogenesis of ALS: cumulative impact on the protection against mutant SOD1-mediated motor dysfunction in mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by a selective loss of motor neurons in the brain and spinal cord. Multiple toxicity pathways, such as oxidative stress, misfolded protein accumulation, and dysfunctional autophagy, are implicated in the pathogenesis of ALS. However, the molecular basis of the interplay between such multiple factors in vivo remains unclear. Here, we report that two independent ALS-linked autophagy-associated gene products; SQSTM1/p62 and ALS2/alsin, but not antioxidant-related factor; NFE2L2/Nrf2, are implicated in the pathogenesis in mutant SOD1 transgenic ALS models. We generated SOD1^H46R mice either on a Nfe2l2-null, Sqstm1-null, or Sqstm1/Als2-double null background. Loss of SQSTM1 but not NFE2L2 exacerbated disease symptoms. A simultaneous inactivation of SQSTM1 and ALS2 further accelerated the onset of disease. Biochemical analyses revealed that loss of SQSTM1 increased the level of insoluble SOD1 at the intermediate stage of the disease, whereas no further elevation occurred at the end-stage. Notably, absence of SQSTM1 rather suppressed the mutant SOD1-dependent accumulation of insoluble polyubiquitinated proteins, while ALS2 loss enhanced it. Histopathological examinations demonstrated that loss of SQSTM1 accelerated motor neuron degeneration with accompanying the preferential accumulation of ubiquitin-positive aggregates in spinal neurons. Since SQSTM1 loss is more detrimental to SOD1^H46R mice than lack of ALS2, the selective accumulation of such aggregates in neurons might be more insulting than the biochemically-detectable insoluble proteins. Collectively, two ALS-linked factors, SQSTM1 and ALS2, have distinct but additive protective roles against mutant SOD1-mediated toxicity by modulating neuronal proteostasis possibly through the autophagy-endolysosomal system.

Nrf2--a therapeutic target for the treatment of neurodegenerative diseases

The brain is very sensitive to changes in redox status; thus maintaining redox homeostasis in the brain is critical for the prevention of accumulating oxidative damage. Aging is the primary risk factor for developing neurodegenerative diseases. In addition to age, genetic and environmental risk factors have also been associated with disease development. The primary reactive insults associated with the aging process are a result of oxidative stress (OS) and nitrosative stress (NS). Markers of increased oxidative stress, protein and DNA modification, inflammation, and dysfunctional proteostasis have all been implicated in contributing to the progression of neurodegeneration. The ability of the cell to combat OS/NS and maintain a clearance mechanism for misfolded aggregating proteins determines whether or not it will survive. A critical pathway in this regard is the Nrf2 (nuclear factor erythroid 2-related factor 2)- antioxidant response element (ARE) pathway. Nrf2 activation has been shown to mitigate a number of pathologic mechanisms associated with Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease, and multiple sclerosis. This review will focus on the role of Nrf2 in these diseases and the potential for Nrf2 activation to attenuate disease progression.

RBM45 Modulates the Antioxidant Response in Amyotrophic Lateral Sclerosis through Interactions with KEAP1

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the selective loss of motor neurons. Various factors contribute to the disease, including RNA binding protein dysregulation and oxidative stress, but their exact role in pathogenic mechanisms remains unclear. We have recently linked another RNA binding protein, RBM45, to ALS via increased levels of protein in the cerebrospinal fluid of ALS patients and its localization to cytoplasmic inclusions in ALS motor neurons. Here we show RBM45 nuclear exit in ALS spinal cord motor neurons compared to controls, a phenotype recapitulated in vitro in motor neurons treated with oxidative stressors. We find that RBM45 binds and stabilizes KEAP1, the inhibitor of the antioxidant response transcription factor NRF2. ALS lumbar spinal cord lysates similarly show increased cytoplasmic binding of KEAP1 and RBM45. Binding of RBM45 to KEAP1 impedes the protective antioxidant response, thus contributing to oxidative stress-induced cellular toxicity. Our findings thus describe a novel link between a mislocalized RNA binding protein implicated in ALS (RBM45) and dysregulation of the neuroprotective antioxidant response seen in the disease.

The ER mitochondria calcium cycle and ER stress response as therapeutic targets in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive loss of upper and lower motor neurons. Although the etiology remains unclear, disturbances in calcium homoeostasis and protein folding are essential features of neurodegeneration in this disorder. Here, we review recent research findings on the interaction between endoplasmic reticulum (ER) and mitochondria, and its effect on calcium signaling and oxidative stress. We further provide insights into studies, providing evidence that structures of the ER mitochondria calcium cycle serve as a promising targets for therapeutic approaches for treatment of ALS.

Lack of association between nuclear factor erythroid-derived 2-like 2 promoter gene polymorphisms and oxidative stress biomarkers in amyotrophic lateral sclerosis patients

Oxidative stress involvement has been strongly hypothesized among the possible pathogenic mechanisms of motor neuron degeneration in amyotrophic lateral sclerosis (ALS). The intracellular redox balance is finely modulated by numerous complex mechanisms critical for cellular functions, among which the nuclear factor erythroid-derived 2-like 2 (NFE2L2/Nrf2) pathways. We genotyped, in a cohort of ALS patients (n = 145) and healthy controls (n = 168), three SNPs in Nrf2 gene promoter: −653 A/G, −651 G/A, and −617 C/A and evaluated, in a subset (n = 73) of patients, advanced oxidation protein products (AOPP), iron-reducing ability of plasma (FRAP), and plasma thiols (-SH) as oxidative damage peripheral biomarkers. Nrf2 polymorphisms were not different among patients and controls. Increased levels of AOPP (P < 0.05) and decreased levels of FRAP (P < 0.001) have been observed in ALS patients compared with controls, but no difference in -SH values was found. Furthermore, no association was found between biochemical markers of redox balance and Nrf2 polymorphisms. These data confirm an altered redox balance in ALS and indicate that, while being abnormally modified compared to controls, the oxidative stress biomarkers assessed in this study are independent from the −653 A/G, −651 G/A, and −617 C/A Nrf2 SNPs in ALS patients.

Oxidative stress and autophagic alteration in brainstem of SOD1-G93A mouse model of ALS

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease involving both upper and lower motor neurons. The mechanism of motor neuron degeneration is still unknown. Although many studies have been performed on spinal motor neurons, few have been reported on brainstem and its motor nuclei. The aim of this study was to investigate oxidative stress and autophagic changes in the brainstem and representative motor nuclei of superoxide dismutase 1 (SOD1)-G93A mouse model of ALS. The expression levels of cluster of differentiation molecule 11b (CD11b), glial fibrillary acidic protein, glutamate-cysteine ligase catalytic subunit, heme oxygenase-1, NAD(P)H: quinone oxidoreductase 1, voltage-dependent anion-selective channel protein 1, Sequestosome 1/p62 (p62), microtubule-associated protein 1 light chain 3B (LC3), and SOD1 proteins in brainstem were examined by Western blot analysis. Immunohistochemistry and immunofluorescence were performed to identify the cellular localization of SOD1, p62, and LC3B, respectively. The results showed that there were progressive asctrocytic proliferation and microglial activation, induction of antioxidant proteins, and increased p62 and LC3II expression in brainstem of SOD1-G93A mice. Additionally, SOD1 and p62 accumulated in hypoglossal, facial, and red nuclei, but not in oculomotor nucleus. Furthermore, electron microscope showed increased autophagic vacuoles in affected brainstem motor nuclei. Our results indicate that brainstem share similar gliosis, oxidative stress, and autophagic changes as the spinal cord in SOD1-G93A mice. Thus, SOD1 accumulation in astrocytes and neurons, oxidative stress, and altered autophagy are involved in motor neuron degeneration in the brainstem, similar to the motor neurons in spinal cord. Therefore, therapeutic trials in the SOD1G93A mice need to target the brainstem in addition to the spinal cord.

SOD1 and DJ-1 converge at Nrf2 pathway: a clue for antioxidant therapeutic potential in neurodegeneration

Neurodegenerative diseases share diverse pathological features and among these oxidative stress (OS) plays a leading role. Impaired activity and reduced expression of antioxidant proteins have been reported as common events in several aging-associated disorders. In this review paper, we first provide an overview of the involvement of reactive oxygen species- (ROS-) induced oxidative damage in Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS). Subsequently, we focus on DJ-1 and SOD1 proteins, which are involved in PD and ALS and also exert a prominent role in the interaction between redox homeostasis and neurodegeneration. Interestingly, recent studies demonstrated that DJ-1 and SOD1 are both tightly connected with Nrf2 protein, a transcriptional factor and master regulator of the expression of many antioxidant/detoxification genes. Nrf2 is emerging as a key neuroprotective protein in neurodegenerative diseases, since it helps neuronal cells to cope with toxic insults and OS. We herein summarize the recent literature providing a detailed picture of the promising therapeutic efficacy of Nrf2 natural and synthetic inducers as disease-modifying molecules for the treatment of neurodegenerative diseases.