The role of mitochondria in amyotrophic lateral sclerosis

ALSUntangled #79: alpha-lipoic acid

Alpha-lipoic acid (ALA) is a naturally occurring fatty acid. It serves as an essential cofactor for enzymatic reactions in mitochondrial energy production, is a potent antioxidant and has anti-inflammatory effects, which are plausible mechanisms in slowing ALS progression. In ALS preclinical studies, ALA slowed motor function decline and improved survival. There were self-reported cases of improved muscle strength in ALS patients when ALA was taken with numerous additional supplements, making it difficult to discern its efficacy. One small, 6-month open-label study showed improved quality of life, fatigue, and mood after participants took it with B vitamins and amino acids for the first 3 months. So far, no clinical trials have been published in people living with amyotrophic lateral sclerosis (PALS). Given the insufficient clinical data, we cannot endorse ALA and will support more research on its efficacy in slowing ALS progression.

Single-cell RNA-sequencing reveals early mitochondrial dysfunction unique to motor neurons shared across FUS- and TARDBP-ALS

Mutations in FUS and TARDBP cause amyotrophic lateral sclerosis (ALS), but the precise mechanisms of selective motor neuron degeneration remain unresolved. To address if pathomechanisms are shared across mutations and related to either gain- or loss-of-function, we performed single-cell RNA sequencing across isogenic induced pluripotent stem cell-derived neuron types, harbouring FUS P525L, FUS R495X, TARDBP M337V mutations or FUS knockout. Transcriptional changes were far more pronounced in motor neurons than interneurons. About 20% of uniquely dysregulated motor neuron transcripts were shared across FUS mutations, half from gain-of-function. Most indicated mitochondrial impairments, with attenuated pathways shared with mutant TARDBP M337V as well as C9orf72-ALS patient motor neurons. Mitochondrial motility was impaired in ALS motor axons, even with nuclear localized FUS mutants, demonstrating shared toxic gain-of-function mechanisms across FUS- and TARDBP-ALS, uncoupled from protein mislocalization. These early mitochondrial dysfunctions unique to motor neurons may affect survival and represent therapeutic targets in ALS.

Unveiling ten novel SETX mutations: implications for ALS pathogenesis and clinical diversity

OBJECTIVE

To investigate the relationship between newly identified senataxin (SETX) gene mutations and the clinical manifestation of Amyotrophic Lateral Sclerosis (ALS), enhancing understanding of the genetic underpinnings associated with this disorder.

METHODS

A cohort study was conducted at Nanfang Hospital, involving comprehensive genetic sequencing of ALS patients to identify novel SETX mutations. Homology modelling and structural analysis were employed to predict the functional impacts of these mutations on the senataxin protein. Clinical assessments, including symptom evaluation, age of onset, and progression rate, were integrated with electrophysiological studies to establish correlations between genetic variants and clinical outcomes.

RESULTS

Ten novel SETX mutations were identified, expanding the genetic landscape of ALS. These mutations exhibited diverse impacts on clinical presentations, with patients showing variability in onset age, symptom severity, and progression rates. Computational modelling suggested that certain mutations cause significant structural changes in senataxin, potentially affecting its RNA/DNA helicase function. Electrophysiological findings consistently revealed nerve conduction abnormalities, indicating that these mutations may influence neuronal excitability and contribute to ALS pathogenesis.

CONCLUSION

The discovery of novel SETX mutations provides valuable insights into the genetic and clinical complexity of ALS. This study underscores the importance of genetic screening for SETX mutations and suggests potential personalised therapeutic approaches targeting senataxin dysfunction. By elucidating genotype-phenotype correlations, these findings contribute to the broader understanding of ALS and offer pathways for developing targeted interventions to address the challenges posed by this disabling disease.

Mitochondria-Associated Membranes: A Key Point of Neurodegenerative Diseases

BACKGROUND

Neurodegenerative diseases pose significant health challenges in the 21st century, with increasing morbidity and mortality, particularly among the elderly population. One of the key factors contributing to the pathogenesis of these diseases is the disrupted crosstalk between mitochondria and the endoplasmic reticulum. Mitochondria-associated membranes (MAMs), which are regions where the ER interfaces with mitochondria, serve as crucial platforms facilitating communication between these organelles.

OBJECTIVES

This review focuses on the structural composition and functions of MAMs and highlights their roles. Additionally, in this review, we summarize the relationship between MAM dysfunction and various neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and others. The involvement of key proteins such as Sig-1R, IP3R, and VAPB in maintaining ER-mitochondrial communication and their dysfunction in neurodegenerative diseases is emphasized.

CONCLUSION

Through analyzing the effects of MAM on neurodegenerative diseases, we provide the newest insights and potential therapeutic targets for the treatment of these debilitating conditions.

Autophagy induction by piplartine ameliorates axonal degeneration caused by mutant HSPB1 and HSPB8 in Charcot-Marie-Tooth type 2 neuropathies

HSPB1 [heat shock protein family B (small) member 1] and HSPB8 are essential molecular chaperones for neuronal proteostasis, as they prevent protein aggregation. Mutant HSPB1 and HSPB8 primarily harm peripheral neurons, resulting in axonal Charcot-Marie-Tooth neuropathies (CMT2). Macroautophagy/autophagy is a shared mechanism by which HSPB1 and HSPB8 mutations cause neuronal dysfunction. Autophagosome formation is reduced in mutant HSPB1-induced pluripotent stem-cell-derived motor neurons from CMT type 2F patients. Likewise, the HSPB8K141N knockin mouse model, mimicking CMT type 2 L, exhibits axonal degeneration and muscle atrophy, with SQSTM1/p62-positive deposits. We show here that mouse embryonic fibroblasts isolated from a HSPB8K141N/green fluorescent protein (GFP)-LC3 model have diminished autophagosome production under conditions of MTOR inhibition. To correct the autophagic deficits in the HSPB1 and HSPB8 models, we screened by high-throughput autophagosome quantification the repurposing Spectrum Collection library for molecules that could boost the autophagic activity above the canonical MTOR inhibition. Hit compounds were validated on motor neurons obtained by differentiation of HSPB1P182L and HSPB8K141N patient-derived induced pluripotent stem cells, focusing on autophagy induction as well as neurite network density, axonal degeneration, and mitochondrial morphology. We identified molecules that specifically stimulate autophagosome formation in the HSPB8K141N cells, without affecting autophagy flux. Two top lead compounds induced autophagy and reduced axonal degeneration, thus promoting neuronal network maturation in the CMT2 patient-derived motor neurons. Based on these findings, the phenotypical screen revealed that piplartine rescued autophagy deficiencies in both the HSPB1 and HSPB8 models, demonstrating autophagy induction as an effective therapeutic strategy for CMT neuropathies and other chaperonopathies.

Discovering Novel Biomarkers and Potential Therapeutic Targets of Amyotrophic Lateral Sclerosis Through Integrated Machine Learning and Gene Expression Profiling

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder that has multiple factors that make its molecular pathogenesis difficult to understand and its diagnosis and treatment during the early stages difficult to determine. Discovering novel biomarkers in ALS for diagnostic and therapeutic potential has become important. Consequently, bioinformatics and machine learning algorithms are useful for identifying differentially expressed genes (DEGs) and potential biomarkers, as well as understanding the molecular mechanisms and intricacies of diseases such as ALS. To achieve the aim of the present study, six datasets obtained from the Gene Expression Omnibus (GEO) were utilized and analyzed using an integrative bioinformatics and machine learning approach. Log transformation was done during data preprocessing, RMA normalization was performed, and the batch effect was corrected. Differential expression analysis identified 206 DEGs that were significantly associated with different biological processes, including muscle function, energy metabolism, and mitochondrial membrane activity. Functional enrichment analysis highlighted pathways, including those related to prion disease, Parkinson's disease, and ATP synthesis via chemiosmotic coupling. We employed a multi-step machine learning framework incorporating random forest, LASSO regression, and SVM-RFE to identify robust biomarkers. This approach identified three key genes, CHRNA1, DLG5, and PLA2G4C, which could be explored as promising biomarkers for ALS after further validation. The internal validation, including principal component analysis (PCA) and ROC-AUC analysis, demonstrated strong diagnostic potential of these hub genes, achieving an AUC of 0.96. This work highlights the utility of bioinformatics and machine learning in identifying key genes as biomarkers for diagnostic and therapeutic potential in ALS.

Loss of intracellular ATP affects axoplasmic viscosity and pathological protein aggregation in mammalian neurons

Neurodegenerative diseases display synaptic deficits, mitochondrial defects, and protein aggregation. We show that intracellular adenosine triphosphate (ATP) regulates axoplasmic viscosity and protein aggregation in mammalian neurons. Decreased intracellular ATP upon mitochondrial inhibition leads to axoterminal cytosol, synaptic vesicles, and active zone component condensation, modulating the functional organization of mouse glutamatergic synapses. Proteins involved in the pathogenesis of Parkinson's disease (PD), Alzheimer's disease (AD), and amyotrophic lateral sclerosis (ALS) condensed and underwent ATP-dependent liquid phase separation in vitro. Human inducible pluripotent stem cell-derived neurons from patients with PD and ALS displayed reduced axoplasmic fluidity and decreased intracellular ATP. Last, nicotinamide mononucleotide treatment successfully rescued intracellular ATP levels and axoplasmic viscosity in neurons from patients with PD and ALS and reduced TAR DNA-binding protein 43 (TDP-43) aggregation in human motor neurons derived from a patient with ALS. Thus, our data suggest that the hydrotropic activity of ATP contributes to the regulation of neuronal homeostasis under both physiological and pathological conditions.

Mitochondrial and energy metabolism dysfunctions are hallmarks of TDP-43G376D fibroblasts from members of an Amyotrophic Lateral Sclerosis family

Amyotrophic Lateral Sclerosis (ALS) is an incurable neurodegenerative disease, causing degeneration of motor neurons, paralysis, and death. About 5-10% of cases are associated with gene mutations inherited from a family member (fALS). Among them, mutations in the transactive-response (TAR)-DNA-binding protein (TARDBP), which encodes for the TAR DNA binding protein 43 (TDP-43) are responsible for 4-5% of fALS but the molecular mechanisms that initiate and sustain the neurodegenerative process are largely unknown. Metabolic impairments might be involved in the pathogenesis of ALS and are currently under investigation. In order to correlate biochemical and metabolic alterations with disease progression, here, we established the metabolic fingerprint of dermal fibroblasts derived from symptomatic and asymptomatic members of a family with fALS cases carrying to the p.G376D mutation in TDP-43. We found that increased proliferation, unbalanced oxidative homeostasis and higher ATP production rate coupled with enhanced metabolic activity are underlying traits of this family. Fibroblasts from carrier individuals deploy several mechanisms to increase mitochondrial respiration to meet increasing energy demands. This is accompanied by an upregulation of glycolysis corresponding to a metabolic reprograming towards a glycolytic phenotype for ATP production during ALS progression, particularly in late disease stages. In summary, we uncover alterations in energy metabolism in TDP43G376D patient-derived primary fibroblasts that may be used as risk biomarkers and/or to monitor ALS progression.

A role for mitochondria-ER crosstalk in amyotrophic lateral sclerosis 8 pathogenesis

Protein aggregates in motoneurons, a pathological hallmark of amyotrophic lateral sclerosis, have been suggested to play a key pathogenetic role. ALS8, characterized by ER-associated inclusions, is caused by a heterozygous mutation in VAPB, which acts at multiple membrane contact sites between the ER and almost all other organelles. The link between protein aggregation and cellular dysfunction is unclear. A yeast model, expressing human mutant and WT-VAPB under the control of the orthologous yeast promoter in haploid and diploid cells, was developed to mimic the disease situation. Inclusion formation was found to be a developmentally regulated process linked to mitochondrial damage that could be attenuated by reducing ER-mitochondrial contacts. The co-expression of the WT protein retarded P56S-VAPB inclusion formation. Importantly, we validated these results in mammalian motoneuron cells. Our findings indicate that (age-related) damage to mitochondria influences the propensity of the mutant VAPB to form aggregates via ER-mitochondrial contacts, initiating a series of events leading to disease progression.

Mitochondrial respiratory complex IV deficiency recapitulates amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is categorized into ~10% familial and ~90% sporadic cases. While familial ALS is caused by mutations in many genes of diverse functions, the underlying pathogenic mechanisms of ALS, especially in sporadic ALS (sALS), are largely unknown. Notably, about half of the cases with sALS showed defects in mitochondrial respiratory complex IV (CIV). To determine the causal role of this defect in ALS, we used transcription activator-like effector-based mitochondrial genome editing to introduce mutations in CIV subunits in rat neurons. Our results demonstrate that neuronal CIV deficiency is sufficient to cause a number of ALS-like phenotypes, including cytosolic TAR DNA-binding protein 43 redistribution, selective motor neuron loss and paralysis. These results highlight CIV deficiency as a potential cause of sALS and shed light on the specific vulnerability of motor neurons, marking an important advance in understanding and therapeutic development of sALS.

Evodiamine rescues lipopolysaccharide-induced cognitive impairment via C/EBP-β-COX2 axis-regulated neuroinflammation

Neuroinflammation is a key driver of neurological disorders. Evodiamine (EVO), an alkaloid from the traditional Chinese herb Evodia rutaecarpa, possesses potent biological activities, notably anticancer and anti-inflammatory effects. This study investigates EVO's potential to attenuate LPS-induced neuroinflammation, focusing on identifying its therapeutic targets and mechanisms of action. EVO treatment significantly improved mitochondrial function and reduced oxidative stress in LPS-stimulated BV2 cells, while also lowering levels of pro-inflammatory factors (IL-6, NO, IL-1β) in brain organoids. In mice, EVO treatment alleviated behavioral abnormalities, especially in cognition and memory, and lowered hippocampal inflammation marker levels. To elucidate the critical mechanisms by which EVO exerts its anti-inflammatory effects, we analyzed LPS-induced inflammatory injury in BV2 cells and used transcriptomics to investigate whether EVO modulates the C/EBP-β signaling pathway. Further validation using si-C/EBP-β confirmed EVO's regulatory effect on the C/EBP-β-COX2 axis, showing that knockdown significantly reduced pro-inflammatory factor expression, thereby providing neuroprotection. Moreover, molecular docking and dynamics simulations confirmed a stable interaction between EVO and C/EBP-β, supporting its role in attenuating LPS-induced neuroinflammation. In summary, these findings suggest that EVO regulates inflammation-related pathways by targeting the C/EBP-β-COX2 axis, offering neuroprotective benefits and mitigating neuroinflammatory responses.

Dysfunctional Mitochondria Characterize Amyotrophic Lateral Sclerosis Patients' Cells Carrying the p.G376D TARDBP Pathogenetic Substitution

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease caused by the degeneration of upper and lower motor neurons in the brain, brainstem and spinal cord. About 10% of familial ALS cases are linked to pathogenetic substitution in TARDBP, the gene encoding the TDP-43 protein. A novel rare causative variant in TARDBP (p.G376D) was recently reported in ALS patients. It leads to TDP-43 cytoplasmic mislocalization, increased oxidative stress and reduced cell viability. However, functional studies on the effects of this molecular defect have not yet been carried out. Mitochondria are highly dynamic organelles, and their deregulation has emerged as a key factor in many diseases, among which is ALS. Therefore, this study aimed at determining the impact of this causative variant on mitochondria. In cellular models expressing TDP-43G376D and in fibroblasts derived from patients carrying this molecular defect, we observed alterations of mitochondrial functionality. We demonstrated increased localization of the mutated protein to mitochondria and a reduced abundance of subunits of complex I and complex II of the mitochondrial respiratory chain, associated with a decrease in mitochondrial membrane potential, in cellular respiration and in cytochrome C oxidase (COX) activity. Moreover, ALS cells showed increased mitochondrial fragmentation and reduced abundance of antioxidant enzymes causing increased oxidative stress. These results expand our knowledge about the molecular mechanisms underlying ALS pathogenesis associated with TDP-43 p.G376D and could help to identify new therapeutic strategies to counteract this disease.

Chromogen-based double immunohistochemical detection of mitochondrial respiratory chain deficiencies in human brain tissue

Studies of the mitochondrial respiratory chain (MRC) have given important insights into the pathology of mitochondrial and neurodegenerative disorders. Immunohistochemical methods for staining MRC complexes are particularly valuable for assessing quantitative changes in situ, especially in complex tissues with cellular heterogeneity, such as the brain. However, traditional approaches have notable limitations. Chromogen-based staining, while preserving tissue morphology, has been restricted to a single antigen per section, preventing co-assessment of MRC complexes and mitochondrial mass on the same section. Immunofluorescence, which allows multiplex staining of multiple targets, partially addresses this limitation but compromises tissue morphology and can be highly variable in postmortem brain samples. To address these challenges, we have established a dual-antigen, chromogen-based immunohistochemical method that allows simultaneous assessment of each MRC complex and the mitochondrial marker voltage-dependent anion channel 1 (VDAC1) on the same section. As proof of concept, we apply this method on brain tissue from patients with neurological disease caused by mutations in the mitochondrial DNA polymerase gamma (POLG). Our findings demonstrate that this approach is both reliable and robust. Moreover, this method enables more precise identification of MRC deficiencies in neurons and significantly reduces the amount of tissue required for analysis, a critical advantage when working with scarce human brain samples.

Comparative Study of Structural and Functional Rearrangements in Skeletal Muscle Mitochondria of SOD1-G93A Transgenic Mice at Pre-, Early-, and Late-Symptomatic Stages of ALS Progression

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a progressive multisystem disease characterized by limb and trunk muscle weakness that is attributed, in part, to abnormalities in mitochondrial ultrastructure and impaired mitochondrial functions. This study investigated the time course of structural and functional rearrangements in skeletal muscle mitochondria in combination with motor impairments in Tg (copper-zinc superoxide dismutase enzyme (SOD1) G93A) dl1/GurJ (referred to as SOD1-G93A/low) male mice, a familial ALS model, as compared with non-transgenic littermates.

METHODS

The neurological status and motor functions were assessed weekly using the paw grip endurance method and the grid suspension test with two-limb and four-limb suspension tasks. Transmission electron microscopy followed by quantitative analysis was performed to study ultrastructural alterations in the quadriceps femoris. Functional analysis of skeletal muscle mitochondria was performed using high-resolution Oxygraph-2k (O2K) respirometry and methods for assessing the calcium retention capacity index and the content of lipid peroxidation products in freshly isolated preparations.

RESULTS

Based on the behavioral phenotyping data, specific age groups were identified: postnatal day 56 (P56) (n = 10-11), 84 (P84) (n = 10-11), and 156 (P154) (n = 10-12), representing the pre-symptomatic, early-symptomatic and late-symptomatic stages of ALS progression in SOD1-G93A/low mice, respectively. Electron microscopy showed mosaic destructive changes in subsarcolemmal mitochondria in fibers of the quadriceps femoris from 84-day-old SOD1-G93A/low mice. Morphometric analysis revealed an elevation in the mean size of the mitochondria in SOD1-G93A mice at P84 and P154. In addition, the P154 transgenic group demonstrated a decrease in sarcomere width and the number of mitochondria per unit area. At the symptomatic stage, SOD1-G93A mice exhibited a decreased respiratory control ratio, ADP-stimulated, and uncoupled respiration rates of mitochondria isolated from the quadriceps femoris muscle, as measured by high-resolution respirometry. In parallel, the mitochondria showed lower calcium retention capacity and increased levels of lipid peroxidation products compared with the control.

CONCLUSIONS

Taken together, these results indicate stage-dependent changes in skeletal muscle mitochondrial ultrastructure and functions associated with defective oxidative phosphorylation, impaired calcium homeostasis, and oxidative damage in the SOD1-G93A/low mouse model, which appears to be a promising direction for the development of combination therapies for ALS.

Emerging Ferroptosis Involvement in Amyotrophic Lateral Sclerosis Pathogenesis: Neuroprotective Activity of Polyphenols

Neurodegenerative diseases are a group of diseases that share common features, such as the generation of misfolded protein deposits and increased oxidative stress. Among them, amyotrophic lateral sclerosis (ALS), whose pathogenesis is still not entirely clear, is a complex neurodegenerative disease linked both to gene mutations affecting different proteins, such as superoxide dismutase 1, Tar DNA binding protein 43, Chromosome 9 open frame 72, and Fused in Sarcoma, and to altered iron homeostasis, mitochondrial dysfunction, oxidative stress, and impaired glutamate metabolism. The purpose of this review is to highlight the molecular targets common to ALS and ferroptosis. Indeed, many pathways implicated in the disease are hallmarks of ferroptosis, a recently discovered type of iron-dependent programmed cell death characterized by increased reactive oxygen species (ROS) and lipid peroxidation. Iron accumulation results in mitochondrial dysfunction and increased levels of ROS, lipid peroxidation, and ferroptosis triggers; in addition, the inhibition of the Xc- system results in reduced cystine levels and glutamate accumulation, leading to excitotoxicity and the inhibition of GPx4 synthesis. These results highlight the potential involvement of ferroptosis in ALS, providing new molecular and biochemical targets that could be exploited in the treatment of the disease using polyphenols.

Mitochondria and astrocyte reactivity: Key mechanism behind neuronal injury

In this special issue to celebrate the 30th anniversary of the Uruguayan Society for Neuroscience (SNU), we find it pertinent to highlight that research on glial cells in Uruguay began almost alongside the history of SNU and contributed to the understanding of neuron-glia interactions within the international scientific community. Glial cells, particularly astrocytes, traditionally regarded as supportive components in the central nervous system (CNS), undergo notable morphological and functional alterations in response to neuronal damage, a phenomenon referred to as glial reactivity. Among the myriad functions of astrocytes, metabolic support holds significant relevance for neuronal function, given the high energy demand of the nervous system. Although astrocytes are typically considered to exhibit low mitochondrial respiratory chain activity, they possess a noteworthy mitochondrial network. Interestingly, both the morphology and activity of these organelles change following glial reactivity. Despite receiving less attention compared to studies on neuronal mitochondria, recent studies indicate that mitochondria play a crucial role in driving the transition of astrocytes from a quiescent to a reactive state in various neurological disorders. Notably, stimulating mitochondria in astrocytes has been shown to reduce damage associated with the neurodegenerative disease amyotrophic lateral sclerosis. Here, we focus on studies supporting the emerging paradigm that metabolic reprogramming occurs in astrocytes following damage, which is associated with their phenotypic shift to a new functional state that significantly influences the progression of pathology. Thus, exploring mitochondrial activity and metabolic reprogramming within glial cells may provide valuable insights for developing innovative therapeutic approaches to mitigate neuronal damage. In this review, we focus on studies supporting the emerging paradigm that metabolic reprogramming occurs in astrocytes following damage, which is associated with their phenotypic shift to a new functional state that significantly influences the progression of pathology. Thus, exploring mitochondrial activity and metabolic reprogramming within glial cells may provide valuable insights for developing innovative therapeutic approaches to mitigate neuronal damage.

The Neonatal Microbiome: Implications for Amyotrophic Lateral Sclerosis and Other Neurodegenerations

Most brain development occurs in the "first 1000 days", a critical period from conception to a child's second birthday. Critical brain processes that occur during this time include synaptogenesis, myelination, neural pruning, and the formation of functioning neuronal circuits. Perturbations during the first 1000 days likely contribute to later-life neurodegenerative disease, including sporadic amyotrophic lateral sclerosis (ALS). Neurodevelopment is determined by many events, including the maturation and colonization of the infant microbiome and its metabolites, specifically neurotransmitters, immune modulators, vitamins, and short-chain fatty acids. Successful microbiome maturation and gut-brain axis function depend on maternal factors (stress and exposure to toxins during pregnancy), mode of delivery, quality of the postnatal environment, diet after weaning from breast milk, and nutritional deficiencies. While the neonatal microbiome is highly plastic, it remains prone to dysbiosis which, once established, may persist into adulthood, thereby inducing the development of chronic inflammation and abnormal excitatory/inhibitory balance, resulting in neural excitation. Both are recognized as key pathophysiological processes in the development of ALS.

Mitochondrial Dysfunction in Neurodegenerative Diseases

Mitochondrial dysfunction represents a pivotal characteristic of numerous neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. These conditions, distinguished by unique clinical and pathological features, exhibit shared pathways leading to neuronal damage, all of which are closely associated with mitochondrial dysfunction. The high metabolic requirements of neurons make even minor mitochondrial deficiencies highly impactful, driving oxidative stress, energy deficits, and aberrant protein processing. Growing evidence from genetic, biochemical, and cellular investigations associates impaired electron transport chain activity and disrupted quality-control mechanisms, such as mitophagy, with the initial phases of disease progression. Furthermore, the overproduction of reactive oxygen species and persistent neuroinflammation can establish feedforward cycles that exacerbate neuronal deterioration. Recent clinical research has increasingly focused on interventions aimed at enhancing mitochondrial resilience-through antioxidants, small molecules that modulate the balance of mitochondrial fusion and fission, or gene-based therapeutic strategies. Concurrently, initiatives to identify dependable mitochondrial biomarkers seek to detect pathological changes prior to the manifestation of overt symptoms. By integrating the current body of knowledge, this review emphasizes the critical role of preserving mitochondrial homeostasis as a viable therapeutic approach. It also addresses the complexities of translating these findings into clinical practice and underscores the potential of innovative strategies designed to delay or potentially halt neurodegenerative processes.

Calcium-mediated regulation of mitophagy: implications in neurodegenerative diseases

Calcium signaling plays a pivotal role in diverse cellular processes through precise spatiotemporal regulation and interaction with effector proteins across distinct subcellular compartments. Mitochondria, in particular, act as central hubs for calcium buffering, orchestrating energy production, redox balance and apoptotic signaling, among others. While controlled mitochondrial calcium uptake supports ATP synthesis and metabolic regulation, excessive accumulation can trigger oxidative stress, mitochondrial membrane permeabilization, and cell death. Emerging findings underscore the intricate interplay between calcium homeostasis and mitophagy, a selective type of autophagy for mitochondria elimination. Although the literature is still emerging, this review delves into the bidirectional relationship between calcium signaling and mitophagy pathways, providing compelling mechanistic insights. Furthermore, we discuss how disruptions in calcium homeostasis impair mitophagy, contributing to mitochondrial dysfunction and the pathogenesis of common neurodegenerative diseases.

Kaempferol enhances ER-mitochondria coupling and protects motor neurons from mitochondrial dysfunction and ER stress in C9ORF72-ALS

Repeat expansions in the C9ORF72 gene are a frequent cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. Considerable progress has been made in identifying C9ORF72-mediated disease and resolving its underlying etiopathogenesis. The contributions of intrinsic mitochondrial deficits as well as chronic endoplasmic reticulum stress to the development of the C9ORF72-linked pathology are well established. Nevertheless, to date, no cure or effective therapy is available, and thus attempts to find a potential drug target, have received increasing attention. Here, we investigated the mode of action and therapeutic effect of a naturally occurring dietary flavanol, kaempferol in preclinical rodent and human models of C9ORF72-ALS. Notably, kaempferol treatment of C9ORF72-ALS human patient-derived motor neurons/neurons, resolved mitochondrial deficits, promoted resiliency against severe ER stress, and conferred neuroprotection. Treatment of symptomatic C9ORF72 mice with kaempferol, normalized mitochondrial calcium uptake, restored mitochondria function, and diminished ER stress. Importantly, in vivo, chronic kaempferol administration ameliorated pathological motor dysfunction and inhibited motor neuron degeneration, highlighting the translational potential of kaempferol. Lastly, in silico modelling identified a novel kaempferol target and mechanistically the neuroprotective mechanism of kaempferol is through the iP3R-VDAC1 pathway via the modulation of GRP75 expression. Thus, kaempferol holds great promise for treating neurodegenerative diseases where both mitochondrial and ER dysfunction are causally linked to the pathophysiology.

Mitochondrial Dysfunction in Neurodegenerative Diseases: Mechanisms and Corresponding Therapeutic Strategies

Neurodegenerative disease (ND) refers to the progressive loss and morphological abnormalities of neurons in the central nervous system (CNS) or peripheral nervous system (PNS). Examples of neurodegenerative diseases include Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). Recent studies have shown that mitochondria play a broad role in cell signaling, immune response, and metabolic regulation. For example, mitochondrial dysfunction is closely associated with the onset and progression of a variety of diseases, including ND, cardiovascular diseases, diabetes, and cancer. The dysfunction of energy metabolism, imbalance of mitochondrial dynamics, or abnormal mitophagy can lead to the imbalance of mitochondrial homeostasis, which can induce pathological reactions such as oxidative stress, apoptosis, and inflammation, damage the nervous system, and participate in the occurrence and development of degenerative nervous system diseases such as AD, PD, and ALS. In this paper, the latest research progress of this subject is detailed. The mechanisms of oxidative stress, mitochondrial homeostasis, and mitophagy-mediated ND are reviewed from the perspectives of β-amyloid (Aβ) accumulation, dopamine neuron damage, and superoxide dismutase 1 (SOD1) mutation. Based on the mechanism research, new ideas and methods for the treatment and prevention of ND are proposed.

Nanotechnology in Parkinson's Disease: overcoming drug delivery challenges and enhancing therapeutic outcomes

The global prevalence of Parkinson's Disease (PD) is on the rise, driven by an ageing population and ongoing environmental conditions. To gain a better understanding of PD pathogenesis, it is essential to consider its relationship with the ageing process, as ageing stands out as the most significant risk factor for this neurodegenerative condition. PD risk factors encompass genetic predisposition, exposure to environmental toxins, and lifestyle influences, collectively increasing the chance of PD development. Moreover, early and precise PD diagnosis remains elusive, relying on clinical assessments, neuroimaging techniques, and emerging biomarkers. Conventional management of PD involves dopaminergic medications and surgical interventions, but these treatments often become less effective over time and do not address disease treatment. Challenges persist due to the blood-brain barrier's (BBB) impermeability, hindering drug delivery. Recent advancements in nanotechnology offer promising novel approaches for PD management. Various drug delivery systems (DDS), including nanosized polymers, lipid-based carriers, and nanoparticles (such as metal/metal oxide, protein, and carbonaceous particles), aim to enhance drug and gene delivery. These modifications seek to improve BBB permeability, ultimately benefiting PD patients. This review underscores the critical role of ageing in PD development and explores how age-related neuronal decline contributes to substantia nigra loss and PD manifestation in susceptible individuals. The review also highlights the advancements and ongoing challenges in nanotechnology-based therapies for PD.

Modulation of Mitochondria-Endoplasmic Reticulum Contacts (MERCs) by Small Molecules as a New Strategy for Restoring Lipid Metabolism in an Amyotrophic Lateral Sclerosis Model

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease without effective treatment. The progressive motoneuron death in ALS is associated with alterations in lipid metabolism. As its regulation occurs in mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs), modulation of mitochondria-ER contacts (MERCs) is emerging as a crucial factor in MAM formation and lipid metabolism control. Using the MERLIN biosensor in a high-throughput screening within the EU-OPENSCREEN ERIC, we discovered small molecules that increase MERCs in HCT116 cells, enhancing their ability to uptake cholesterol. We demonstrated that cholesterol trafficking is decreased in an ALS patient-derived cell model, and this trafficking is restored after treatment with the discovered MERC modulator 24. Electron microscopy revealed that treatment with compound 24 increases MERCs, promotes lipid droplet formation, and restores mitochondrial cristae. Overall, the brain-permeable MERC modulator, compound 24, may serve as a valuable pharmacological tool for studying MAM function and holds potential for in vivo studies in ALS and other MAM dysfunction diseases.

Mechanisms by which microbiome-derived metabolites exert their impacts on neurodegeneration

Recent developments in microbiome research suggest that the gut microbiome may remotely modulate central and peripheral neuronal processes, ranging from early brain development to age-related changes. Dysbiotic microbiome configurations have been increasingly associated with neurological disorders, such as neurodegeneration, but causal understanding of these associations remains limited. Most mechanisms explaining how the microbiome may induce such remote neuronal effects involve microbially modulated metabolites that influx into the 'sterile' host. Some metabolites are able to cross the blood-brain barrier (BBB) to reach the central nervous system, where they can impact a variety of cells and processes. Alternatively, metabolites may directly signal to peripheral nerves to act as neurotransmitters or exert modulatory functions, or impact immune responses, which, in turn, modulate neuronal function and associated disease propensity. Herein, we review the current knowledge highlighting microbiome-modulated metabolite impacts on neuronal disease, while discussing unknowns, controversies and prospects impacting this rapidly evolving research field.

Therapeutic targeting of the oxidative stress generated by pathological molecular pathways in the neurodegenerative diseases, ALS and Huntington's

Neurodegenerative disorders are characterized by a progressive decline of specific neuronal populations in the brain and spinal cord, typically containing aggregates of one or more proteins. They can result in behavioral alterations, memory loss and a decline in cognitive and motor abilities. Various pathways and mechanisms have been outlined for the potential treatment of these diseases, where redox regulation is considered as one of the most common druggable targets. For example, in amyotrophic lateral sclerosis (ALS) with superoxide dismutase-1 (SOD1) pathology, there is a downregulation of the antioxidant response nuclear factor erythroid 2-related factor 2 (Nrf2) pathway. TDP-43 proteinopathy in ALS is associated with elevated levels of reactive oxygen species and mitochondrial dyshomeostasis. In ALS with mutant FUS, poly ADP ribose polymerase-dependent X ray repair cross complementing 1/DNA-ligase recruitment to the sites of oxidative DNA damage is affected, thereby causing defects in DNA damage repair. Oxidative stress in Huntington's disease (HD) with mutant huntingtin accumulation manifests as protein oxidation, metabolic energetics dysfunction, metal ion dyshomeostasis, DNA damage and mitochondrial dysfunction. The impact of oxidative stress in the progression of these diseases further warrants studies into the role of antioxidants in their treatment. While an antioxidant, edaravone, has been approved for therapeutics of ALS, numerous antioxidant molecules failed to pass the clinical trials despite promising initial studies. In this review, we summarize the oxidative stress pathways and redox modulators that are investigated in ALS and HD using various models.

Altered mitochondria-associated ER membrane (MAM) function shifts mitochondrial metabolism in amyotrophic lateral sclerosis (ALS)

Mitochondrial function is modulated by its interaction with the endoplasmic reticulum (ER). Recent research indicates that these contacts are disrupted in familial models of amyotrophic lateral sclerosis (ALS). We report here that this impairment in the crosstalk between mitochondria and the ER impedes the use of glucose-derived pyruvate as mitochondrial fuel, causing a shift to fatty acids to sustain energy production. Over time, this deficiency alters mitochondrial electron flow and the active/dormant status of complex I in spinal cord tissues, but not in the brain. These findings suggest mitochondria-associated ER membranes (MAM domains) play a crucial role in regulating cellular glucose metabolism and that MAM dysfunction may underlie the bioenergetic deficits observed in ALS.

Oxidative stress and inflammation in the pathogenesis of neurological disorders: Mechanisms and implications

Neuroprotection is a proactive approach to safeguarding the nervous system, including the brain, spinal cord, and peripheral nerves, by preventing or limiting damage to nerve cells and other components. It primarily defends the central nervous system against injury from acute and progressive neurodegenerative disorders. Oxidative stress, an imbalance between the body's natural defense mechanisms and the generation of reactive oxygen species, is crucial in developing neurological disorders. Due to its high metabolic rate and oxygen consumption, the brain is particularly vulnerable to oxidative stress. Excessive ROS damages the essential biomolecules, leading to cellular malfunction and neurodegeneration. Several neurological disorders, including Alzheimer's, Parkinson's, Amyotrophic lateral sclerosis, multiple sclerosis, and ischemic stroke, are associated with oxidative stress. Understanding the impact of oxidative stress in these conditions is crucial for developing new treatment methods. Researchers are exploring using antioxidants and other molecules to mitigate oxidative stress, aiming to prevent or slow down the progression of brain diseases. By understanding the intricate interplay between oxidative stress and neurological disorders, scientists hope to pave the way for innovative therapeutic and preventive approaches, ultimately improving individuals' living standards.

Single-nucleus transcriptome atlas of orbitofrontal cortex in amyotrophic lateral sclerosis with a deep learning-based decoding of alternative polyadenylation mechanisms

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are two age-related and fatal neurodegenerative disorders that lie on a shared disease spectrum. While both disorders involve complex interactions between neuronal and glial cells, the specific cell-type alterations and their contributions to disease pathophysiology remain incompletely understood. Here, we applied single-nucleus RNA sequencing of the orbitofrontal cortex, a region affected in ALS-FTLD, to map cell-type specific transcriptional signatures in C9orf72-related ALS (with and without FTLD) and sporadic ALS cases. Our findings reveal disease- and cell-type-specific transcriptional changes, with neurons exhibiting the most pronounced alterations, primarily affecting mitochondrial function, protein homeostasis, and chromatin remodeling. A comparison with independent datasets from different cortical regions of C9orf72 and sporadic ALS cases showed concordance in several pathways, with neuronal STMN2 and NEFL showing consistent up-regulation between brain regions and disease subtypes. We also interrogated alternative polyadenylation (APA) as an additional layer of transcriptional regulation, demonstrating that APA events are not correlated with identified gene expression changes. To interpret these events, we developed APA-Net, a deep learning model that integrates transcript sequences with RNA-binding protein expression profiles, revealing cell type-specific patterns of APA regulation. Our atlas illuminates cell type-specific pathomechanisms of ALS/FTLD, providing a valuable resource for further investigation.

CHCHD10P80L knock-in zebrafish display a mild ALS-like phenotype

Mutations in the nuclear-encoded mitochondrial gene CHCHD10 have been observed in patients with a spectrum of diseases that include amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). To investigate the pathogenic nature of disease-associated variants of CHCHD10 we generated a zebrafish knock-in (KI) model expressing the orthologous ALS-associated CHCHD10P80L variant (zebrafish: Chchd10P83L). Larval chchd10P83L/P83L fish displayed reduced Chchd10 protein expression levels, motor impairment, reduced survival and abnormal neuromuscular junctions (NMJ). These deficits were not accompanied by changes in transcripts involved in the integrated stress response (ISR), phenocopying previous findings in our knockout (chchd10-/-). Adult, 11-month old chchd10P83L/P83L zebrafish, displayed smaller slow- and fast-twitch muscle cell cross-sectional areas compared to wild type zebrafish muscle cells. Motoneurons in the spinal cord of chchd10P83L/P83L zebrafish displayed similar cross-sectional areas to that of wild type motor neurons and significantly fewer motor neurons were observed when compared to chchd2-/- adult spinal cords. Bulk RNA sequencing using whole spinal cords of 7-month old fish revealed transcriptional changes associated with neuroinflammation, apoptosis, amino acid metabolism and mt-DNA inflammatory response in our chchd10P83L/P83L model. The findings presented here, suggest that the CHCHD10P80L variant confers an ALS-like phenotype when expressed in zebrafish.

Elevated serum circulating cell-free mitochondrial DNA in amyotrophic lateral sclerosis

BACKGROUND AND PURPOSE

The substantial role of inflammation in amyotrophic lateral sclerosis (ALS) is gaining support from recent research. Studies indicate that circulating cell-free mitochondrial DNA (ccf-mtDNA) can activate the immune system and is associated with neurodegenerative diseases. This research was designed to quantify ccf-mtDNA levels in the serum of ALS patients.

METHODS

The medical records of ALS patients were reviewed. Serum ccf-mtDNA levels of patients with ALS (n = 62) and age-matched healthy controls (n = 46) were measured and compared. Additionally, serum interleukin-6 (IL-6) levels were measured using an enzyme-linked immunosorbent assay in 26 ALS patients. Correlations between variables were analyzed.

RESULTS

Serum ccf-mtDNA was notably higher in the patients with ALS. When stratified by genotype, the superoxide dismutase 1 (SOD1) mutation group showed the greatest increase in ccf-mtDNA levels relative to other ALS patients. Among all 108 individuals, a cut-off set at 1.1 × 105 mtDNA copies on a receiver-operating characteristic curve identified patients with ALS with 80.7% sensitivity and 50.0% specificity; the area under the curve was 0.69 (p < 0.001). Furthermore, serum ccf-mtDNA levels correlated negatively with the progression rate of ALS (ΔFS; rs = -0.26, p = 0.044), but not the ALSFRS-R score (rs = 0.06, p = 0.625). Importantly, the correlation between ccf-mtDNA and ΔFS was more pronounced in the SOD1 mutation group (rs = -0.62, p = 0.018). Lastly, a significant positive association was observed between serum ccf-mtDNA levels and IL-6 levels in ALS (r s= 0.41, p = 0.038).

CONCLUSION

Our study found increased serum ccf-mtDNA in ALS patients, suggesting a link to inflammatory processes and disease mechanism. Moreover, ccf-mtDNA could be an indicator for ALS progression, especially in those with the SOD1 mutation.

The Neuroprotective Effect of the X Protein of Orthobornavirus Bornaense Type 1 in Amyotrophic Lateral Sclerosis

In amyotrophic lateral sclerosis (ALS), early mitochondrial dysfunction may contribute to progressive motor neuron loss. Remarkably, the ectopic expression of the Orthobornavirus bornaense type 1 (BoDV-1) X protein in mitochondria blocks apoptosis and protects neurons from degeneration. Therefore, this study examines the neuroprotective effects of X protein in an ALS mouse model. We first tested in vitro the effect of the X-derived peptide (PX3) on motoneurons primary cultures of SOD1G93A mice. The total intracellular adenosine triphosphate (ATP) content was measured after incubation of the peptide. We next tested in vivo the intramuscular injection of X protein using a canine viral vector (CAV2-X) and PX3 intranasal administrations in SOD1G93A mice. Disease onset and progression were assessed through rotarod performance, functional motor unit analysis via electrophysiology, and motor neuron survival by immunohistochemistry. The results showed that in vitro PX3 restored the ATP level in SOD1G93A motor neurons. In vivo, treated mice demonstrated better motor performance, preserved motor units, and higher motor neuron survival. Although life expectancy was not extended in this severe mouse model of motor neuron degeneration, the present findings clearly demonstrate the neuroprotective potential of X protein in a model of ALS. We are convinced that further studies may improve the therapeutic impact of X protein with optimized administration methods.

Polygonatum sibiricum polysaccharides: A promising strategy in the treatment of neurodegenerative disease

Neurodegenerative diseases (NDDs), as a neurological disorder characterised by neuronal degeneration and death, are a serious threat to human health and have long attracted attention due to their complex pathogenesis and the ineffectiveness of therapeutic drugs. Existing studies have shown that Polygonatum Sibiricum polysaccharides (PSP) have immunoregulatory, antioxidant, anti-inflammatory and other pharmacological effects, and their neuroprotective effects have been demonstrated in several scientific studies. This paper reviews the main pharmacological effects and mechanisms of PSP in the protection and treatment of NDDs, to provide a reference for the clinical application and basic research of PSP in NDDs.

Mitochondrial complex I inhibition enhances astrocyte responsiveness to pro-inflammatory stimuli

Inhibition of the mitochondrial oxidative phosphorylation (OXPHOS) system can lead to metabolic disorders and neurodegenerative diseases. In primary mitochondrial disorders, reactive astrocytes often accompany neuronal degeneration and may contribute to neurotoxic inflammatory cascades that elicit brain lesions. The influence of mitochondria to astrocyte reactivity as well as the underlying molecular mechanisms remain elusive. Here we report that mitochondrial Complex I dysfunction promotes neural progenitor cell differentiation into astrocytes that are more responsive to neuroinflammatory stimuli. We show that the SWItch/Sucrose Non-Fermentable (SWI/SNF/BAF) chromatin remodeling complex takes part in the epigenetic regulation of astrocyte responsiveness, since its pharmacological inhibition abrogates the expression of inflammatory genes. Furthermore, we demonstrate that Complex I deficient human iPSC-derived astrocytes negatively influence neuronal physiology upon cytokine stimulation. Together, our data describe the SWI/SNF/BAF complex as a sensor of altered mitochondrial OXPHOS and a downstream epigenetic regulator of astrocyte-mediated neuroinflammation.

The Scientific and Therapeutic Rationale for Off-Label Treatments in Amyotrophic Lateral Sclerosis

There are no dramatically effective pharmacological treatments for most patients with amyotrophic lateral sclerosis, a complex disease with multiple underlying mechanisms, such as neuroinflammation, oxidative stress, mitochondrial dysfunction, microbiome alteration, and antiretroviral activity. We sifted through 15 years of reviews by a group called ALSUntangled to identify 8 alternative and off-label treatments that target ≥1 of these mechanisms, and have ≥1 human trial suggesting meaningful benefits. Given the overlapping pathological mechanisms of the highlighted products, we suggest that combinations of these treatments targeting diverse mechanisms might be worthwhile for future amyotrophic lateral sclerosis therapy development. ANN NEUROL 2024.

ALSUntangled #74: Withania Somnifera (Ashwagandha)

ALSUntangled reviews alternative and off-label treatments on behalf of people with ALS (PALS) who ask about them. Here, we review withania somnifera (WS) commonly known as ashwagandha or winter cherry. WS has plausible mechanisms for slowing ALS progression because of its effects on inflammation, oxidative stress, autophagy, mitochondrial function, and apoptosis. Preclinical trials demonstrate that WS slows disease progression in multiple different animal models of ALS. Of the five individuals we found who described using WS for their ALS, two individuals reported moderate benefit while none reported experiencing any significant side effects. There is currently one clinical trial using WS to treat PALS; the results are not yet published. There are no serious side effects associated with WS and the associated cost of this treatment is low. Based on the above information, WS appears to us to be a good candidate for future ALS trials.

Signaling Pathways Concerning Mitochondrial Dysfunction: Implications in Neurodegeneration and Possible Molecular Targets

Mitochondrion is an important organelle present in our cells responsible for meeting energy requirements. All higher organisms rely on efficient mitochondrial bioenergetic machinery to sustain life. No other respiratory process can produce as much power as generated by mitochondria in the form of ATPs. This review is written in order to get an insight into the magnificent working of mitochondrion and its implications in cellular homeostasis, bioenergetics, redox, calcium signaling, and cell death. However, if this machinery gets faulty, it may lead to several disease states. Mitochondrial dysfunctioning is of growing concern today as it is seen in the pathogenesis of several diseases which includes neurodegenerative disorders, cardiovascular disorders, diabetes mellitus, skeletal muscle defects, liver diseases, and so on. To cover all these aspects is beyond the scope of this article; hence, our study is restricted to neurodegenerative disorders only. Moreover, faulty functioning of this organelle can be one of the causes of early ageing in individuals. This review emphasizes mutations in the mitochondrial DNA, defects in oxidative phosphorylation, generation of ROS, and apoptosis. Researchers have looked into new approaches that might be able to control mitochondrial failure and show a lot of promise as treatments.

Amyotrophic Lateral Sclerosis: Insights and New Prospects in Disease Pathophysiology, Biomarkers and Therapies

Amyotrophic Lateral Sclerosis (ALS) is a severe neurodegenerative disorder marked by the gradual loss of motor neurons, leading to significant disability and eventual death. Despite ongoing research, there are still limited treatment options, underscoring the need for a deeper understanding of the disease's complex mechanisms and the identification of new therapeutic targets. This review provides a thorough examination of ALS, covering its epidemiology, pathology, and clinical features. It investigates the key molecular mechanisms, such as protein aggregation, neuroinflammation, oxidative stress, and excitotoxicity that contribute to motor neuron degeneration. The role of biomarkers is highlighted for their importance in early diagnosis and disease monitoring. Additionally, the review explores emerging therapeutic approaches, including inhibitors of protein aggregation, neuroinflammation modulators, antioxidant therapies, gene therapy, and stem cell-based treatments. The advantages and challenges of these strategies are discussed, with an emphasis on the potential for precision medicine to tailor treatments to individual patient needs. Overall, this review aims to provide a comprehensive overview of the current state of ALS research and suggest future directions for developing effective therapies.

A pathogenic mutation in the ALS/FTD gene VCP induces mitochondrial hypermetabolism by modulating the permeability transition pore

Valosin-containing protein (VCP) is a ubiquitously expressed type II AAA+ ATPase protein, implicated in both amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). This study aimed to explore the impact of the disease-causing VCPR191Q/wt mutation on mitochondrial function using a CRISPR/Cas9-engineered neuroblastoma cell line. Mitochondria in these cells are enlarged, with a depolarized mitochondrial membrane potential associated with increased respiration and electron transport chain activity. Our results indicate that mitochondrial hypermetabolism could be caused, at least partially, by increased calcium-induced opening of the permeability transition pore (mPTP), leading to mild mitochondrial uncoupling. In conclusion, our findings reveal a central role of the ALS/FTD gene VCP in maintaining mitochondrial homeostasis and suggest a model of pathogenesis based on progressive alterations in mPTP physiology and mitochondrial energetics.

Metabolic Syndrome and Risk of Amyotrophic Lateral Sclerosis: Insights from a Large-Scale Prospective Study

OBJECTIVE

Although metabolic abnormalities are implicated in the etiology of neurodegenerative diseases, their role in the development of amyotrophic lateral sclerosis (ALS) remains a subject of controversy. We aimed to identify the association between metabolic syndrome (MetS) and the risk of ALS.

METHODS

This study included 395,987 participants from the UK Biobank to investigate the relationship between MetS and ALS. Cox regression model was used to estimate hazard ratios (HR). Stratified analyses were performed based on gender, body mass index (BMI), smoking status, and education level. Mediation analysis was conducted to explore potential mechanisms.

RESULTS

In this study, a total of 539 cases of ALS were recorded after a median follow-up of 13.7 years. Patients with MetS (defined harmonized) had a higher risk of developing ALS after adjusting for confounding factors (HR: 1.50, 95% CI: 1.19-1.89). Specifically, hypertension and high triglycerides were linked to a higher risk of ALS (HR: 1.53, 95% CI: 1.19-1.95; HR: 1.31, 95% CI: 1.06-1.61, respectively). Moreover, the quantity of metabolic abnormalities showed significant results. Stratified analysis revealed that these associations are particularly significant in individuals with a BMI <25. These findings remained stable after sensitivity analysis. Notably, mediation analysis identified potential metabolites and metabolomic mediators, including alkaline phosphatase, cystatin C, γ-glutamyl transferase, saturated fatty acids to total fatty acids percentage, and omega-6 fatty acids to omega-3 fatty acids ratio.

INTERPRETATION

MetS exhibits a robust association with an increased susceptibility to ALS, particularly in individuals with a lower BMI. Furthermore, metabolites and metabolomics, as potential mediators, provide invaluable insights into the intricate biological mechanisms. ANN NEUROL 2024;96:788-801.

Poly-GP accumulation due to C9orf72 loss of function induces motor neuron apoptosis through autophagy and mitophagy defects

The GGGGCC hexanucleotide repeat expansion (HRE) of the C9orf72 gene is the most frequent cause of amyotrophic lateral sclerosis (ALS), a devastative neurodegenerative disease characterized by motor neuron degeneration. C9orf72 HRE is associated with lowered levels of C9orf72 expression and its translation results in the production of dipeptide-repeats (DPRs). To recapitulate C9orf72-related ALS disease in vivo, we developed a zebrafish model where we expressed glycine-proline (GP) DPR in a c9orf72 knockdown context. We report that C9orf72 gain- and loss-of-function properties act synergistically to induce motor neuron degeneration and paralysis with poly(GP) accumulating preferentially within motor neurons along with Sqstm1/p62 aggregation indicating macroautophagy/autophagy deficits. Poly(GP) levels were shown to accumulate upon c9orf72 downregulation and were comparable to levels assessed in autopsy samples of patients carrying C9orf72 HRE. Chemical boosting of autophagy using rapamycin or apilimod, is able to rescue motor deficits. Proteomics analysis of zebrafish-purified motor neurons unravels mitochondria dysfunction confirmed through a comparative analysis of previously published C9orf72 iPSC-derived motor neurons. Consistently, 3D-reconstructions of motor neuron demonstrate that poly(GP) aggregates colocalize to mitochondria, thus inducing their elongation and swelling and the failure of their processing by mitophagy, with mitophagy activation through urolithin A preventing locomotor deficits. Finally, we report apoptotic-related increased amounts of cleaved Casp3 (caspase 3, apoptosis-related cysteine peptidase) and rescue of motor neuron degeneration by constitutive inhibition of Casp9 or treatment with decylubiquinone. Here we provide evidence of key pathogenic steps in C9ALS-FTD that can be targeted through pharmacological avenues, thus raising new therapeutic perspectives for ALS patients.

Gut microbiota immune cross-talk in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by the loss of motor neurons. While there has been significant progress in defining the genetic contributions to ALS, greater than 90 ​% of cases are sporadic, which suggests an environmental component. The gut microbiota is altered in ALS and is an ecological factor that contributes to disease by modulating immunologic, metabolic, and neuronal signaling. Depleting the microbiome worsens disease in the SOD1 ALS animal model, while it ameliorates disease in the C9orf72 model of ALS, indicating critical subtype-specific interactions. Furthermore, administering beneficial microbiota or microbial metabolites can slow disease progression in animal models. This review discusses the current state of microbiome research in ALS, including interactions with different ALS subtypes, evidence in animal models and human studies, key immunologic and metabolomic mediators, and a path toward microbiome-based therapies for ALS.

Advancements in Pharmacological Interventions and Novel Therapeutic Approaches for Amyotrophic Lateral Sclerosis

(1) Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease in which the patient suffers from an affection of both upper and lower motor neurons at the spinal and brainstem level, causing a progressive paralysis that leads to the patient's demise. Gender is also considered a predisposing risk factor for developing the disease. A brief review of the pathophysiological mechanisms of the disease is also described in this work. Despite the fact that a cure for ALS is currently unknown, there exists a variety of pharmacological and non-pharmacological therapies that can help reduce the progression of the disease over a certain period of time and alleviate symptoms. (2) We aim to analyze these pharmacological and non-pharmacological therapies through a systematic review. A comprehensive, multidisciplinary approach to treatment is necessary. (3) Drugs such as riluzole, edaravone, and sodium phenylbutyrate, among others, have been investigated. Additionally, it is important to stay updated on research on new drugs, such as masitinib, from which very good results have been obtained. (4) Therapies aimed at psychological support, speech and language, and physical therapy for the patient are also available, which increase the quality of life of the patients.

From Brain to Muscle: The Role of Muscle Tissue in Neurodegenerative Disorders

Neurodegenerative diseases (NDs), like amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), and Parkinson's disease (PD), primarily affect the central nervous system, leading to progressive neuronal loss and motor and cognitive dysfunction. However, recent studies have revealed that muscle tissue also plays a significant role in these diseases. ALS is characterized by severe muscle wasting as a result of motor neuron degeneration, as well as alterations in gene expression, protein aggregation, and oxidative stress. Muscle atrophy and mitochondrial dysfunction are also observed in AD, which may exacerbate cognitive decline due to systemic metabolic dysregulation. PD patients exhibit muscle fiber atrophy, altered muscle composition, and α-synuclein aggregation within muscle cells, contributing to motor symptoms and disease progression. Systemic inflammation and impaired protein degradation pathways are common among these disorders, highlighting muscle tissue as a key player in disease progression. Understanding these muscle-related changes offers potential therapeutic avenues, such as targeting mitochondrial function, reducing inflammation, and promoting muscle regeneration with exercise and pharmacological interventions. This review emphasizes the importance of considering an integrative approach to neurodegenerative disease research, considering both central and peripheral pathological mechanisms, in order to develop more effective treatments and improve patient outcomes.

Neurodegenerative disorders, metabolic icebergs, and mitohormesis

Neurodegenerative disorders are typically "split" based on their hallmark clinical, anatomical, and pathological features, but they can also be "lumped" by a shared feature of impaired mitochondrial biology. This leads us to present a scientific framework that conceptualizes Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD) as "metabolic icebergs" comprised of a tip, a bulk, and a base. The visible tip conveys the hallmark neurological symptoms, neurodegenerative regions, and neuronal protein aggregates for each disorder. The hidden bulk depicts impaired mitochondrial biology throughout the body, which is multifaceted and may be subdivided into impaired cellular metabolism, cell-specific mitotypes, and mitochondrial behaviours, functions, activities, and features. The underlying base encompasses environmental factors, especially modern industrial toxins, dietary lifestyles, and cognitive, physical, and psychosocial behaviours, but also accommodates genetic factors specific to familial forms of AD, PD, and ALS, as well as HD. Over years or decades, chronic exposure to a particular suite of environmental and genetic factors at the base elicits a trajectory of impaired mitochondrial biology that maximally impacts particular subsets of mitotypes in the bulk, which eventually surfaces as the hallmark features of a particular neurodegenerative disorder at the tip. We propose that impaired mitochondrial biology can be repaired and recalibrated by activating "mitohormesis", which is optimally achieved using strategies that facilitate a balanced oscillation between mitochondrial stressor and recovery phases. Sustainably harnessing mitohormesis may constitute a potent preventative and therapeutic measure for people at risk of, or suffering with, neurodegenerative disorders.

Activation of the Keap1/Nrf2 pathway suppresses mitochondrial dysfunction, oxidative stress, and motor phenotypes in C9orf72 ALS/FTD models

Mitochondrial dysfunction is a common feature of C9orf72 amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD); however, it remains unclear whether this is a cause or consequence of the pathogenic process. Analysing multiple aspects of mitochondrial biology across several Drosophila models of C9orf72-ALS/FTD, we found morphology, oxidative stress, and mitophagy are commonly affected, which correlated with progressive loss of locomotor performance. Notably, only genetic manipulations that reversed the oxidative stress levels were also able to rescue C9orf72 locomotor deficits, supporting a causative link between mitochondrial dysfunction, oxidative stress, and behavioural phenotypes. Targeting the key antioxidant Keap1/Nrf2 pathway, we found that genetic reduction of Keap1 or pharmacological inhibition by dimethyl fumarate significantly rescued the C9orf72-related oxidative stress and motor deficits. Finally, mitochondrial ROS levels were also elevated in C9orf72 patient-derived iNeurons and were effectively suppressed by dimethyl fumarate treatment. These results indicate that mitochondrial oxidative stress is an important mechanistic contributor to C9orf72 pathogenesis, affecting multiple aspects of mitochondrial function and turnover. Targeting the Keap1/Nrf2 signalling pathway to combat oxidative stress represents a therapeutic strategy for C9orf72-related ALS/FTD.

Skeletal muscle dysfunction in amyotrophic lateral sclerosis: a mitochondrial perspective and therapeutic approaches

Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neuromuscular disease that results in the loss of motor neurons and severe skeletal muscle atrophy. The etiology of ALS is linked to skeletal muscle, which can activate a retrograde signaling cascade that destroys motor neurons. This is why satellite cells and mitochondria play a crucial role in the health and performance of skeletal muscles. This review presents current knowledge on the involvement of mitochondrial dysfunction, skeletal muscle atrophy, muscle satellite cells, and neuromuscular junction (NMJ) in ALS. It also discusses current therapeutic strategies, including exercise, drugs, stem cells, gene therapy, and the prospective use of mitochondrial transplantation as a viable therapeutic strategy.

Stroke studies in large animals: Prospects of mitochondrial transplantation and enhancing efficiency using hydrogels and nanoparticle-assisted delivery

One of the most frequent reasons for mortality and disability today is acute ischemic stroke, which occurs by an abrupt disruption of cerebral circulation. The intricate damage mechanism involves several factors, such as inflammatory response, disturbance of ion balance, loss of energy production, excessive reactive oxygen species and glutamate release, and finally, neuronal death. Stroke research is now carried out using several experimental models and potential therapeutics. Furthermore, studies are being conducted to address the shortcomings of clinical care. A great deal of research is being done on novel pharmacological drugs, mitochondria targeting compounds, and different approaches including brain cooling and new technologies. Still, there are many unanswered questions about disease modeling and treatment strategies. Before these new approaches may be used in therapeutic settings, they must first be tested on large animals, as most of them have been done on rodents. However, there are several limitations to large animal stroke models used for research. In this review, the damage mechanisms in acute ischemic stroke and experimental acute ischemic stroke models are addressed. The current treatment approaches and promising experimental methods such as mitochondrial transplantation, hydrogel-based interventions, and strategies like mitochondria encapsulation and chemical modification, are also examined in this work.

Epigenetic Orchestration of Neurodegenerative Disorders: A Possible Target for Curcumin as a Therapeutic

Epigenetic modulations play a major role in gene expression and thus are responsible for various physiological changes including age-associated neurological disorders. Neurodegenerative diseases such as Alzheimer's (AD), Parkinson's (PD), Huntington's disease (HD), although symptomatically different, may share common underlying mechanisms. Most neurodegenerative diseases are associated with increased oxidative stress, aggregation of certain proteins, mitochondrial dysfunction, inactivation/dysregulation of protein degradation machinery, DNA damage and cell excitotoxicity. Epigenetic modulations has been reported to play a significant role in onset and progression of neurodegenerative diseases by regulating these processes. Previous studies have highlighted the marked antioxidant and neuroprotective abilities of polyphenols such as curcumin, by increased activity of detoxification systems like superoxide dismutase (SOD), catalase or glutathione peroxidase. The role of curcumin as an epigenetic modulator in neurological disorders and neuroinflammation apart from other chronic diseases have also been reported by a few groups. Nonetheless, the evidences for the role of curcumin mediated epigenetic modulation in its neuroprotective ability are still limited. This review summarizes the current knowledge of the role of mitochondrial dysfunction, epigenetic modulations and mitoepigenetics in age-associated neurological disorders such as PD, AD, HD, Amyotrophic Lateral Sclerosis (ALS), and Multiple Sclerosis (MS), and describes the neuroprotective effects of curcumin in the treatment and/or prevention of these neurodegenerative diseases by regulation of the epigenetic machinery.