Astrocytes and Microglia as Non-cell Autonomous Players in the Pathogenesis of ALS

Human VCP mutant ALS/FTD microglia display immune and lysosomal phenotypes independently of GPNMB

BACKGROUND

Microglia play crucial roles in maintaining neuronal homeostasis but have been implicated in contributing to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). However, the role of microglia in ALS/FTD remains incompletely understood.

METHODS

Here, we generated highly enriched cultures of VCP mutant microglia derived from human induced pluripotent stem cells (hiPSCs) to investigate their cell autonomous and non-cell autonomous roles in ALS pathogenesis. We used RNA-sequencing, proteomics and functional assays to study hiPSC derived VCP mutant microglia and their effects on hiPSC derived motor neurons and astrocytes.

RESULTS

Transcriptomic, proteomic and functional analyses revealed immune and lysosomal dysfunction in VCP mutant microglia. Stimulating healthy microglia with the inflammatory inducer lipopolysaccharide (LPS) showed partial overlap with VCP mutant microglia in their reactive transformation. LPS-stimulated VCP mutant microglia displayed differential activation of inflammatory pathways compared with LPS-stimulated healthy microglia. Conserved gene expression changes were identified between VCP mutant microglia, SOD1 mutant mice microglia, and postmortem ALS spinal cord microglial signatures, including increased expression of the transmembrane glycoprotein GPNMB. While knockdown of GPNMB affected inflammatory and phagocytosis processes in microglia, this was not sufficient to ameliorate cell autonomous phenotypes in VCP mutant microglia. Secreted factors from VCP mutant microglia were sufficient to activate the JAK-STAT pathway in hiPSC derived motor neurons and astrocytes.

CONCLUSIONS

VCP mutant microglia undergo cell autonomous reactive transformation involving immune and lysosomal dysfunction that partially recapitulate key phenotypes of microglia from other ALS models and post mortem tissue. These phenotypes occur independently of GPNMB. Additionally, VCP mutant microglia elicit non cell autonomous responses in motor neurons and astrocytes involving the JAK-STAT pathway.

Safety, tolerability, and efficacy of fasudil in amyotrophic lateral sclerosis (ROCK-ALS): a phase 2, randomised, double-blind, placebo-controlled trial

BACKGROUND

Fasudil is a small molecule inhibitor of Rho-associated kinase (ROCK) and is approved for the treatment of subarachnoid haemorrhage. In preclinical studies, fasudil has been shown to attenuate neurodegeneration, modulate neuroinflammation, and foster axonal regeneration. We aimed to investigate the safety, tolerability, and efficacy of fasudil in patients with amyotrophic lateral sclerosis.

METHODS

ROCK-ALS was a phase 2, randomised, double-blind, placebo-controlled trial conducted at 19 amyotrophic lateral sclerosis centres in Germany, France, and Switzerland. Individuals (aged 18-80 years) with at least probable amyotrophic lateral sclerosis (as per the revised El Escorial criteria), a disease duration of 6-24 months, and a slow vital capacity greater than 65% of predicted normal were eligible for inclusion. Patients were randomly assigned (1:1:1) to receive 30 mg (15 mg twice daily) or 60 mg (30 mg twice daily) fasudil or matched placebo intravenously for 20 days over a 4-week period. Follow-up assessments were performed at 45, 90, and 180 days after treatment initiation. The co-primary endpoints were safety until day 180 (defined as the proportion without drug-related serious adverse events) and tolerability during the treatment period (defined as the proportion who did not discontinue treatment due to suspected drug-related adverse events). The primary analyses were carried out in the intention-to-treat population, which included all participants who entered the treatment phase. This trial is registered at ClinicalTrials.gov (NCT03792490) and Eudra-CT (2017-003676-31) and is now completed.

FINDINGS

Between Feb 20, 2019, and April 20, 2022, 120 participants were enrolled and randomised; two individuals assigned fasudil 30 mg withdrew consent before the baseline visit. Thus, the intention-to-treat population comprised 35 in the fasudil 30 mg group, 39 in the fasudil 60 mg group, and 44 in the placebo group. The estimated proportion without a drug-related serious adverse event was 1·00 (95% CI 0·91 to 1·00) with placebo, 1·00 (0·89 to 1·00) with fasudil 30 mg, and 1·00 (0·90 to 1·00) with fasudil 60 mg; the difference in proportions was 0·00 (95% CI -0·11 to 0·10; p>0·99) for fasudil 30 mg versus placebo and 0·00 (-0·10 to 0·10; p>0·99) for fasudil 60 mg versus placebo. Treatment tolerability (the estimated proportion who did not discontinue) was 0·93 (95% CI 0·81 to 0·99) with placebo, 1·00 (0·90 to 1·00) with fasudil 30 mg, and 0·90 (0·76 to 0·97) with fasudil 60 mg; the difference in proportions was 0·07 (95% CI -0·05 to 0·20; p=0·25) for fasudil 30 mg versus placebo, and -0·03 (-0·18 to 0·10; p=0·70) for fasudil 60 mg versus placebo. Eight deaths occurred: two in the placebo group, four in the fasudil 30 mg group, and two in the fasudil 60 mg group. The most common serious adverse events were respiratory failure (seven events), gastrostomy (five events), pneumonia (four events), and dysphagia (four events). No serious adverse events or deaths were attributed to study treatment. Adverse events, which were mainly related to disease progression, occurred in 139 participants in the placebo group, 108 in the fasudil 30 mg group, and 105 in the fasudil 60 mg group.

INTERPRETATION

Fasudil was well tolerated and safe in people with amyotrophic lateral sclerosis. The effect of fasudil on efficacy outcomes should be explored in larger clinical trials with a longer treatment duration, oral administration, and potentially higher dose of the trial drug.

FUNDING

Framework of the E-Rare Joint Transnational Call 2016 "Clinical research for new therapeutic uses of already existing molecules (repurposing) in rare diseases".

BV2 Microglial Cell Activation/Polarization Is Influenced by Extracellular Vesicles Released from Mutated SOD1 NSC-34 Motoneuron-like Cells

Microglia-mediated neuroinflammation is a key player in the pathogenesis of amyotrophic lateral sclerosis (ALS) as it can contribute to the progressive degeneration of motor neurons (MNs). Here, we investigated the role of mSOD1 NSC-34 MN-like cell-derived extracellular vesicles (EVs) in inducing the activation of BV2 microglial cells. NSC-34-released EVs were isolated by culture medium differential ultracentrifugation to obtain two fractions, one containing small EVs (diameter < 200 nm) and the other containing large EVs (diameter > 200 nm). BV2 cells were incubated with the two EV fractions for 12, 24, and 48 h to evaluate 1) the state of microglial inflammation through RT-PCR of IL-1β, IL-6, IL-4, and IL-10 and 2) the expression of proteins involved in inflammasome activation (IL-β and caspase 1), cell death (caspase 3), and glial cell recruitment (CXCR1), and presence of the TGFβ cytokine receptor (TGFβ-R2). The obtained results suggest a mSOD1 type-dependent polarization of BV2 cells towards an early neurotoxic phenotype and a late neuroprotective status, with an appearance of mixed M1 and M2 microglia subpopulations. A significant role in driving microglial cell activation is played by the TGFβ/CX3CR1 axis. Therefore, targeting the dysregulated microglial response and modulating neuroinflammation could hold promise as a therapeutic strategy for ALS.

NADPH oxidase 4 (NOX4) as a biomarker and therapeutic target in neurodegenerative diseases

Diseases like Alzheimer's and Parkinson's diseases are defined by inflammation and the damage neurons undergo due to oxidative stress. A primary reactive oxygen species contributor in the central nervous system, NADPH oxidase 4, is viewed as a potential therapeutic touchstone and indicative marker for these ailments. This in-depth review brings to light distinct features of NADPH oxidase 4, responsible for generating superoxide and hydrogen peroxide, emphasizing its pivotal role in activating glial cells, inciting inflammation, and disturbing neuronal functions. Significantly, malfunctioning astrocytes, forming the majority in the central nervous system, play a part in advancing neurodegenerative diseases, due to their reactive oxygen species and inflammatory factor secretion. Our study reveals that aiming at NADPH oxidase 4 within astrocytes could be a viable treatment pathway to reduce oxidative damage and halt neurodegenerative processes. Adjusting NADPH oxidase 4 activity might influence the neuroinflammatory cytokine levels, including myeloperoxidase and osteopontin, offering better prospects for conditions like Alzheimer's disease and Parkinson's disease. This review sheds light on the role of NADPH oxidase 4 in neural degeneration, emphasizing its drug target potential, and paving the path for novel treatment approaches to combat these severe conditions.

Exosomal GDNF from Bone Marrow Mesenchymal Stem Cells Moderates Neuropathic Pain in a Rat Model of Chronic Constriction Injury

Both of exosomes derived from mesenchymal stem cells (MSCs) and glial cell line-derived neurotrophic factor (GDNF) show potential for the treatment of neuropathic pain. Here, the analgesic effects of exosomes derived from bone marrow MSCs (BMSCs) were investigated. BMSCs-derived exosomes were isolated and characterized. Chronic constriction injury (CCI) was constructed to induce neuropathic pain in rats, which were then treated with exosomes. Pain behaviors were evaluated by measuring paw withdrawal thresholds and latency. The changes of key proteins, including cytokines, were explored using Western blot and ELISA. Administration of BMSCs-derived exosomes alleviated neuropathic pain, as demonstrated by the decrease of thermal hyperalgesia and mechanical allodynia, as well as the reduced secretion of pro-inflammatory cytokines in CCI rats. These effects were comparable to the treatment of GDNF alone. Mechanically, the exosomes suppressed the CCI-induced activation of TLR2/MyD88/NF-κB signaling pathway, while GDNF knockdown impaired their analgesic effects on CCI rat. BMSCs-derived exosomes may alleviate CCI-induced neuropathic pain and inflammation in rats by transporting GDNF.

Aberrant protein aggregation in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal disease. As its pathological mechanisms are not well understood, there are no efficient therapeutics for it at present. While it is highly heterogenous both etiologically and clinically, it has a common salient hallmark, i.e., aberrant protein aggregation (APA). The upstream pathogenesis and the downstream effects of APA in ALS are sophisticated and the investigation of this pathology would be of consequence for understanding ALS. In this paper, the pathomechanism of APA in ALS and the candidate treatment strategies for it are discussed.

Chemical composition and toxicity studies on Lantana camara L. flower essential oil and its in silico binding and pharmacokinetics to superoxide dismutase 1 for amyotrophic lateral sclerosis (ALS) therapy

Using the gas chromatography mass spectrometry method, the chemical components of essential oil from flowers of Lantana camara growing in Egypt are analyzed. Through this investigation, 22 chemicals from floral oil were identified. Most of the oil is made up of sesquiterpene caryophyllene (15.51%) and monoterpene sabinene (14.90%). When the oil's composition was compared to oils extracted from the same plant on several continents, we observed that the essential components were largely the same with some difference in proportions and some compounds due to geographical differences. A molecular docking study of essential oil components was conducted with human superoxide dismutase 1, a target involved in the pathophysiology of amyotrophic lateral sclerosis (ALS). Isospathulenol showed a comparable docking score to the reference ligand bound to the dismutase enzyme. Isospathulenol showed a reasonable drug score with some safety concerns. In addition, isospathulenol is predicted to have high GI absorption, good permeability through the blood-brain barrier and reasonable bioavailability score with ease access to synthetic modifications. In addition, the same compound is devoid from any violation to Lipinski rules or any PAINS alerts. This may establish the promising characteristics of such a compound to be optimized into potential drug candidates for treatment of ALS.

Superoxide dismutase and neurological disorders

Superoxide dismutase (SOD) is a common antioxidant enzyme found majorly in living cells. The main physiological role of SOD is detoxification and maintain the redox balance, acts as a first line of defence against Reactive nitrogen species (RNS), Reactive oxygen species (ROS), and other such potentially hazardous molecules. SOD catalyses the conversion of superoxide anion free radicals (O 2 -.) into molecular oxygen (O 2) and hydrogen peroxide (H 2O 2) in the cells. Superoxide dismutases (SODs) are expressed in neurons and glial cells throughout the CNS both intracellularly and extracellularly. Endogenous oxidative stress (OS) linked with enlarged production of reactive oxygen metabolites (ROMs), inflammation, deregulation of redox balance, mitochondrial dysfunction and bioenergetic crisis are found to be prerequisite for neuronal loss in neurological diseases. Clinical and genetic studies indicate a direct correlation between mutations in SOD gene and neurodegenerative diseases, like Amyotrophic Lateral Sclerosis (ALS), Huntington's disease (HD), Parkinson's Disease (PD) and Alzheimer's Disease (AD). Therefore, inhibitors of OS are considered as an optimistic approach to prevent neuronal loss. SOD mimetics like Metalloporphyrin Mn (II)-cyclic polyamines, Nitroxides and Mn (III)- Salen complexes are designed and used as therapeutic extensively in the treatment of neurological disorders. SODs and SOD mimetics are promising future therapeutics in the field of various diseases with OS-mediated pathology.

Novel insights into RAGE signaling pathways during the progression of amyotrophic lateral sclerosis in RAGE-deficient SOD1 G93A mice

Amyotrophic lateral sclerosis (ALS) is neurodegenerative disease characterized by a progressive loss of motor neurons resulting in paralysis and muscle atrophy. One of the most prospective hypothesis on the ALS pathogenesis suggests that excessive inflammation and advanced glycation end-products (AGEs) accumulation play a crucial role in the development of ALS in patients and SOD1 G93A mice. Hence, we may speculate that RAGE, receptor for advanced glycation end-products and its proinflammatory ligands such as: HMGB1, S100B and CML contribute to ALS pathogenesis. The aim of our studies was to decipher the role of RAGE as well as provide insight into RAGE signaling pathways during the progression of ALS in SOD1 G93A and RAGE-deficient SOD1 G93A mice. In our study, we observed alternations in molecular pattern of proinflammatory RAGE ligands during progression of disease in RAGE KO SOD1 G93A mice compared to SOD1 G93A mice. Moreover, we observed that the amount of beta actin (ACTB) as well as Glial fibrillary acidic protein (GFAP) was elevated in SOD1 G93A mice when compared to mice with deletion of RAGE. These data contributes to our understanding of implications of RAGE and its ligands in pathogenesis of ALS and highlight potential targeted therapeutic interventions at the early stage of this devastating disease. Moreover, inhibition of the molecular cross-talk between RAGE and its proinflammatory ligands may abolish neuroinflammation, gliosis and motor neuron damage in SOD1 G93A mice. Hence, we hypothesize that attenuated interaction of RAGE with its proinflammatory ligands may improve well-being and health status during ALS in SOD1 G93A mice. Therefore, we emphasize that the inhibition of RAGE signaling pathway may be a therapeutic target for neurodegenerative diseases.

Mitochondria Dysfunction and Neuroinflammation in Neurodegeneration: Who Comes First?

Neurodegenerative diseases (NDs) encompass an assorted array of disorders such as Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, each characterised by distinct clinical manifestations and underlying pathological mechanisms. While some cases have a genetic basis, many NDs occur sporadically. Despite their differences, these diseases commonly feature chronic neuroinflammation as a hallmark. Consensus has recently been reached on the possibility that mitochondria dysfunction and protein aggregation can mutually contribute to the activation of neuroinflammatory response and thus to the onset and progression of these disorders. In the present review, we discuss the contribution of mitochondria dysfunction and neuroinflammation to the aetiology and progression of NDs, highlighting the possibility that new potential therapeutic targets can be identified to tackle neurodegenerative processes and alleviate the progression of these pathologies.

The Diverse Roles of Reactive Astrocytes in the Pathogenesis of Amyotrophic Lateral Sclerosis

Astrocytes displaying reactive phenotypes are characterized by their ability to remodel morphologically, molecularly, and functionally in response to pathological stimuli. This process results in the loss of their typical astrocyte functions and the acquisition of neurotoxic or neuroprotective roles. A growing body of research indicates that these reactive astrocytes play a pivotal role in the pathogenesis of amyotrophic lateral sclerosis (ALS), involving calcium homeostasis imbalance, mitochondrial dysfunction, abnormal lipid and lactate metabolism, glutamate excitotoxicity, etc. This review summarizes the characteristics of reactive astrocytes, their role in the pathogenesis of ALS, and recent advancements in astrocyte-targeting strategies.

Astrocyte-Neuron Interactions Contributing to Amyotrophic Lateral Sclerosis Progression

Amyotrophic lateral sclerosis (ALS) is a complex disease impacting motor neurons of the brain, brainstem, and spinal cord. Disease etiology is quite heterogeneous with over 40 genes causing the disease and a vast ~90% of patients having no prior family history. Astrocytes are major contributors to ALS, particularly through involvement in accelerating disease progression. Through study of genetic forms of disease including SOD1, TDP43, FUS, C9orf72, VCP, TBK1, and more recently patient-derived cells from sporadic individuals, many biological mechanisms have been identified to cause intrinsic or glial-mediated neurotoxicity to motor neurons. Overall, many of the normally supportive and beneficial roles that astrocytes contribute to neuronal health and survival instead switch to become deleterious and neurotoxic. While the exact pathways may differ based on disease-origin, altered astrocyte-neuron communication is a common feature of ALS. Within this chapter, distinct genetic forms are examined in detail, along with what is known from sporadic patient-derived cells. Overall, this chapter highlights the interplay between astrocytes and neurons in this complex disease and describes the key features underlying: astrocyte-mediated motor neuron toxicity, excitotoxicity, oxidative/nitrosative stress, protein dyshomeostasis, metabolic imbalance, inflammation, trophic factor withdrawal, blood-brain/blood-spinal cord barrier involvement, disease spreading, and the extracellular matrix/cell adhesion/TGF-β signaling pathways.

Effect of Various Pathological Conditions on Nitric Oxide Level and L-Citrulline Uptake in Motor Neuron-Like (NSC-34) Cell Lines

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disorder that causes progressive paralysis. L-Citrulline is a non-essential neutral amino acid produced by L-arginine via nitric oxide synthase (NOS). According to previous studies, the pathogenesis of ALS entails glutamate toxicity, oxidative stress, protein misfolding, and neurofilament disruption. In addition, L-citrulline prevents neuronal cell death in brain ischemia; therefore, we investigated the change in the transport of L-citrulline under various pathological conditions in a cell line model of ALS. We examined the uptake of [14C]L-citrulline in wild-type (hSOD1wt/WT) and mutant NSC-34/ SOD1G93A (MT) cell lines. The cell viability was determined via MTT assay. A transport study was performed to determine the uptake of [14C]L-citrulline. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis was performed to determine the expression levels of rat large neutral amino acid transported 1 (rLAT1) in ALS cell lines. Nitric oxide (NO) assay was performed using Griess reagent. L-Citrulline had a restorative effect on glutamate induced cell death, and increased [14C]L-citrulline uptake and mRNA levels of the large neutral amino acid transporter (LAT1) in the glutamate-treated ALS disease model (MT). NO levels increased significantly when MT cells were pretreated with glutamate for 24 h and restored by co-treatment with L-citrulline. Co-treatment of MT cells with L-arginine, an NO donor, increased NO levels. NSC-34 cells exposed to high glucose conditions showed a significant increase in [14C]L-citrulline uptake and LAT1 mRNA expression levels, which were restored to normal levels upon co-treatment with unlabeled L-citrulline. In contrast, exposure of the MT cell line to tumor necrosis factor alpha, lipopolysaccharides, and hypertonic condition decreased the uptake significantly which was restored to the normal level by co-treating with unlabeled L-citrulline. L-Citrulline can restore NO levels and cellular uptake in ALS-affected cells with glutamate cytotoxicity, pro-inflammatory cytokines, or other pathological states, suggesting that L-citrulline supplementation in ALS may play a key role in providing neuroprotection.

Role of Senataxin in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive, uncurable neurodegenerative disorder characterized by the degradation of motor neurons leading to muscle impairment, failure, and death. Senataxin, encoded by the SETX gene, is a human helicase protein whose mutations have been linked with ALS onset, particularly in its juvenile ALS4 form. Using senataxin's yeast homolog Sen1 as a model for study, it is suggested that senataxin's N-terminus interacts with RNA polymerase II, whilst its C-terminus engages in helicase activity. Senataxin is heavily involved in transcription regulation, termination, and R-loop resolution, enabled by recruitment and interactions with enzymes such as ubiquitin protein ligase SAN1 and ribonuclease H (RNase H). Senataxin also engages in DNA damage response (DDR), primarily interacting with the exosome subunit Rrp45. The Sen1 mutation E1597K, alongside the L389S and R2136H gain-of-function mutations to senataxin, is shown to cause negative structural and thus functional effects to the protein, thus contributing to a disruption in WT functions, motor neuron (MN) degeneration, and the manifestation of ALS clinical symptoms. This review corroborates and summarizes published papers concerning the structure and function of senataxin as well as the effects of their mutations in ALS pathology in order to compile current knowledge and provide a reference for future research. The findings compiled in this review are indicative of the experimental and therapeutic potential of senataxin and its mutations as a target in future ALS treatment/cure discovery, with some potential therapeutic routes also being discussed in the review.

The microRNAs (miRs) overexpressing mesenchymal stem cells (MSCs) therapy in neurological disorders; hope or hype

Altered expression of multiple miRNAs was found to be extensively involved in the pathogenesis of different neurological disorders including Alzheimer's disease, Parkinson's disease, stroke, epilepsy, multiple sclerosis, amyotrophic lateral sclerosis, and Huntington's disease. One of the biggest concerns within gene-based therapy is the delivery of the therapeutic microRNAs to the intended place, which is obligated to surpass the biological barriers without undergoing degradation in the bloodstream or renal excretion. Hence, the delivery of modified and unmodified miRNA molecules using excellent vehicles is required. In this light, mesenchymal stem cells (MSCs) have attracted increasing attention. The MSCs can be genetically modified to express or overexpress a particular microRNA aimed with promote neurogenesis and neuroprotection. The current review has focused on the therapeutic capabilities of microRNAs-overexpressing MSCs to ameliorate functional deficits in neurological conditions.

The Key Role of Astrocytes in Amyotrophic Lateral Sclerosis and Their Commitment to Glutamate Excitotoxicity

In the last two decades, there has been increasing evidence supporting non-neuronal cells as active contributors to neurodegenerative disorders. Among glial cells, astrocytes play a pivotal role in driving amyotrophic lateral sclerosis (ALS) progression, leading the scientific community to focus on the "astrocytic signature" in ALS. Here, we summarized the main pathological mechanisms characterizing astrocyte contribution to MN damage and ALS progression, such as neuroinflammation, mitochondrial dysfunction, oxidative stress, energy metabolism impairment, miRNAs and extracellular vesicles contribution, autophagy dysfunction, protein misfolding, and altered neurotrophic factor release. Since glutamate excitotoxicity is one of the most relevant ALS features, we focused on the specific contribution of ALS astrocytes in this aspect, highlighting the known or potential molecular mechanisms by which astrocytes participate in increasing the extracellular glutamate level in ALS and, conversely, undergo the toxic effect of the excessive glutamate. In this scenario, astrocytes can behave as "producers" and "targets" of the high extracellular glutamate levels, going through changes that can affect themselves and, in turn, the neuronal and non-neuronal surrounding cells, thus actively impacting the ALS course. Moreover, this review aims to point out knowledge gaps that deserve further investigation.

Anti-Inflammatory Effects of Miyako Bidens pilosa in a Mouse Model of Amyotrophic Lateral Sclerosis and Lipopolysaccharide-Stimulated BV-2 Microglia

Neuroinflammation is a fundamental feature in the pathogenesis of amyotrophic lateral sclerosis (ALS) and arises from the activation of astrocytes and microglial cells. Previously, we reported that Miyako Bidens pilosa extract (MBP) inhibited microglial activation and prolonged the life span in a human ALS-linked mutant superoxide dismutase-1 (SOD1G93A) transgenic mouse model of ALS (G93A mice). Herein, we evaluated the effect of MBP on microglial activation in the spinal cord of G93A mice and lipopolysaccharide-stimulated BV-2 microglial cells. The administration of MBP inhibited the upregulation of the M1-microglia/macrophage marker (interferon-γ receptor (IFN-γR)) and pro-inflammatory cytokines (tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6) in G93A mice. However, MBP did not affect the increase in the M2-microglia/macrophage marker (IL-13R) and anti-inflammatory cytokines (transforming growth factor (TGF)-β and IL-10) in G93A mice. BV-2 cell exposure to MBP resulted in a decrease in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium (MTT) reduction activity and bromodeoxyuridine incorporation, without an increase in the number of ethidium homodimer-1-stained dead cells. Moreover, MBP suppressed the production of lipopolysaccharide-induced pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in BV-2 cells. These results suggest that the selective suppression of M1-related pro-inflammatory cytokines is involved in the therapeutic potential of MBP in ALS model mice.

Recent Advances in Extracellular Vesicles in Amyotrophic Lateral Sclerosis and Emergent Perspectives

Amyotrophic lateral sclerosis (ALS) is a severe and incurable neurodegenerative disease characterized by the progressive death of motor neurons, leading to paralysis and death. It is a rare disease characterized by high patient-to-patient heterogeneity, which makes its study arduous and complex. Extracellular vesicles (EVs) have emerged as important players in the development of ALS. Thus, ALS phenotype-expressing cells can spread their abnormal bioactive cargo through the secretion of EVs, even in distant tissues. Importantly, owing to their nature and composition, EVs' formation and cargo can be exploited for better comprehension of this elusive disease and identification of novel biomarkers, as well as for potential therapeutic applications, such as those based on stem cell-derived exosomes. This review highlights recent advances in the identification of the role of EVs in ALS etiopathology and how EVs can be promising new therapeutic strategies.

Seeding the aggregation of TDP-43 requires post-fibrillization proteolytic cleavage

Despite the strong evidence linking the transactive response DNA-binding protein 43 (TDP-43) aggregation to the pathogenesis of frontotemporal lobar degeneration with TDP-43, amyotrophic lateral sclerosis and several neurodegenerative diseases, our knowledge of the sequence and structural determinants of its aggregation and neurotoxicity remains incomplete. Herein, we present a new method for producing recombinant full-length TDP-43 filaments that exhibit sequence and morphological features similar to those of brain-derived TDP-43 filaments. We show that TDP-43 filaments contain a β-sheet-rich helical amyloid core that is fully buried by the flanking structured domains of the protein. We demonstrate that the proteolytic cleavage of TDP-43 filaments and exposure of this amyloid core are necessary for propagating TDP-43 pathology and enhancing the seeding of brain-derived TDP-43 aggregates. Only TDP-43 filaments with exposed amyloid core efficiently seeded the aggregation of endogenous TDP-43 in cells. These findings suggest that inhibiting the enzymes mediating cleavage of TDP-43 aggregates represents a viable disease-modifying strategy to slow the progression of amyotrophic lateral sclerosis and other TDP-43 proteinopathies.

Preclinical investigation in FAAH inhibition as a neuroprotective therapy for frontotemporal dementia using TDP-43 transgenic male mice

BACKGROUND

Frontotemporal dementia (FTD) is a heterogeneous group of early onset and progressive neurodegenerative disorders, characterized by degeneration in the frontal and temporal lobes, which causes deterioration in cognition, personality, social behavior and language. Around 45% of the cases are characterized by the presence of aggregates of the RNA-binding protein TDP-43.

METHODS

In this study, we have used a murine model of FTD that overexpresses this protein exclusively in the forebrain (under the control of the CaMKIIα promoter) for several biochemical, histological and pharmacological studies focused on the endocannabinoid system.

RESULTS

These mice exhibited at postnatal day 90 (PND90) important cognitive deficits, signs of emotional impairment and disinhibited social behaviour, which were, in most of cases, maintained during the first year of life of these animals. Motor activity was apparently normal, but FTD mice exhibited higher mortality. Their MRI imaging analysis and their ex-vivo histopathological evaluation proved changes compatible with atrophy (loss of specific groups of pyramidal neurons: Ctip2- and NeuN-positive cells) and inflammatory events (astroglial and microglial reactivities) in both cortical (medial prefrontal cortex) and subcortical (hippocampus) structures at PND90 and also at PND365. The analysis of the endocannabinoid system in these mice proved a decrease in the hydrolysing enzyme FAAH in the prefrontal cortex and the hippocampus, with an increase in the synthesizing enzyme NAPE-PLD only in the hippocampus, responses that were accompanied by modest elevations in anandamide and related N-acylethanolamines. The potentiation of these elevated levels of anandamide after the pharmacological inactivation of FAAH with URB597 resulted in a general improvement in behaviour, in particular in cognitive deterioration, associated with the preservation of pyramidal neurons of the medial prefrontal cortex and the CA1 layer of the hippocampus, and with the reduction of gliosis in both structures.

CONCLUSIONS

Our data confirmed the potential of elevating the endocannabinoid tone as a therapy against TDP-43-induced neuropathology in FTD, limiting glial reactivity, preserving neuronal integrity and improving cognitive, emotional and social deficits.

Masitinib: The promising actor in the next season of the Amyotrophic Lateral Sclerosis treatment series

Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease with high mortality and morbidity rate affecting both upper and lower motor neurons (MN). Muscle force reduction, behavioral change, pseudobulbar affect, and cognitive impairments are the most common clinical manifestations of ALS. The main physiopathology of ALS is still unclear, though several studies have identified that oxidative stress, proteinopathies, glutamate-related excitotoxicity, microglial activation, and neuroinflammation may be involved in the pathogenesis of ALS. From 1995 until October 2022, only Riluzole, Dextromethorphan Hydrobromide (DH) with Quinidine sulfate (Q), Edaravone, and Sodium phenylbutyrate with Taurursodiol (PB/TUDCO) have achieved FDA approval for ALS treatment. Despite the use of these four approved agents, the survival rate and quality of life of ALS patients are still low. Thus, finding novel treatments for ALS patients is an urgent requirement. Masitinib, a tyrosine kinase inhibitor, emphasizes the neuro-inflammatory activity of ALS by targeting macrophages, mast cells, and microglia cells. Masitinib downregulates the proinflammatory cytokines, indirectly reduces inflammation, and induces neuroprotection. Also, it was effective in phase 2/3 and 3 clinical trials (CTs) by increasing overall survival and delaying motor, bulbar, and respiratory function deterioration. This review describes the pathophysiology of ALS, focusing on Masitinib's mechanism of action and explaining why Masitinib could be a promising actor in the treatment of ALS patients. In addition, Masitinib CTs and other competitor drugs in phase 3 CTs have been discussed.

Microglial heterogeneity in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is an intractable neurodegenerative disease of the central nervous system that is pathologically characterized by motor neuron loss. Although the cause of the disease is still unknown, its pathophysiology is considered heterogeneous. In recent years, there have been a series of reports on the existence of disease-associated microglia (DAM) in the lesions of various neurodegenerative diseases. DAM have also been reported in SOD1-deficient mice, a disease model of ALS. However, the role of DAM in sporadic ALS remains unclear. This study revealed that spinal cord lesions in ALS can be pathologically distinguished into 2 subgroups (TMEM119+ and TMEM119- microglia) according to the type of microglia. Expression of the microglial activation marker CD68 and endothelial activation were also observed in the TMEM119+ microglia group, suggesting the presence of inflammatory processes in ALS lesions. Since DAM suppress the expression of TMEM119, the TMEM119+ microglia group may indicate DAM-independent inflammatory neurodegeneration. These results may explain why, in some clinical trials of anti-inflammatory drugs for ALS, only some cases showed suppression of disease progression.

Connexin 30 Deficiency Ameliorates Disease Progression at the Early Phase in a Mouse Model of Amyotrophic Lateral Sclerosis by Suppressing Glial Inflammation

Connexin 30 (Cx30), which forms gap junctions between astrocytes, regulates cell adhesion and migration, and modulates glutamate transport. Cx30 is upregulated on activated astroglia in central nervous system inflammatory lesions, including spinal cord lesions in mutant superoxide dismutase 1 (mSOD1) transgenic amyotrophic lateral sclerosis (ALS) model mice. Here, we investigated the role of Cx30 in mSOD1 mice. Cx30 was highly expressed in the pre-onset stage in mSOD1 mice. mSOD1 mice with knockout (KO) of the Cx30 gene (Cx30KO-mSOD1 mice) showed delayed disease onset and tended to have an extended survival period (log-rank, p = 0.09). At the progressive and end stages of the disease, anterior horn cells were significantly preserved in Cx30KO-mSOD1 mice. In lesions of these mice, glial fibrillary acidic protein/C3-positive inflammatory astroglia were decreased. Additionally, the activation of astrocytes in Cx30KO-mSOD1 mice was reduced compared with mSOD1 mice by gene expression microarray. Furthermore, expression of connexin 43 at the pre-onset stage was downregulated in Cx30KO-mSOD1 mice. These findings suggest that reduced expression of astroglial Cx30 at the early disease stage in ALS model mice protects neurons by attenuating astroglial inflammation.

Finding Common Ground on the Site of Onset of Amyotrophic Lateral Sclerosis

The fundamental origin of amyotrophic lateral sclerosis (ALS) has remained an enigma since its earliest description as a relentlessly progressive degeneration with prominent neuromuscular manifestations that are associated with upper and lower motor neuron dysfunction. Although this remains the hallmark of ALS, a significant proportion of patients will also demonstrate one or more features of frontotemporal dysfunction, including a frontotemporal dementia (FTD). Understanding whether these 2 seemingly disparate syndromes are simply reflective of the co-occurrence of 2 distinct pathologic processes or the clinical manifestations of a common pathophysiologic derangement involving the brain more widely has gripped contemporary ALS researchers. Supporting a commonality of causation, both ALS and FTD show an alteration in the metabolism of TAR DNA-binding protein 43, marked by a shift in nucleocytoplasmic localization alongside a broad range of neuronal cytoplasmic inclusions consisting of pathologic aggregates of RNA-binding proteins. Similarly, several disease-associated or disease-modifying genetic variants that are shared between the 2 disorders suggest shared underlying mechanisms. In both, a prominent glial response has been postulated to contribute to non-cell-autonomous spread. A more contemporary hypothesis, however, suggests that syndromes of cortical and subcortical dysfunction are driven by impairments in discrete neural networks. This postulates that such networks, including networks subserving motor or cognitive function, possess unique and selective vulnerabilities to either single molecular toxicities or combinations thereof. The co-occurrence of one or more network dysfunctions in ALS and FTD is thus a reflection not of unique neuroanatomic correlates but rather of shared molecular vulnerabilities. The basis of such shared vulnerabilities becomes the fulcrum around which the next advances in our understanding of ALS and its possible therapy will develop.

Micro-RNAs Shuttled by Extracellular Vesicles Secreted from Mesenchymal Stem Cells Dampen Astrocyte Pathological Activation and Support Neuroprotection in In-Vitro Models of ALS

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with no effective cure. Astrocytes display a toxic phenotype in ALS and contribute to motoneuron (MN) degeneration. Modulating astrocytes' neurotoxicity can reduce MN death. Our previous studies showed the beneficial effect of mesenchymal stem cell (MSC) administration in SOD1^G93A ALS mice, but the mechanisms are still unclear. We postulated that the effects could be mediated by extracellular vesicles (EVs) secreted by MSCs. We investigated, by immunohistochemical, molecular, and in vitro functional analyses, the activity of MSC-derived EVs on the pathological phenotype and neurotoxicity of astrocytes isolated from the spinal cord of symptomatic SOD1^G93A mice and human astrocytes (iAstrocytes) differentiated from inducible neural progenitor cells (iNPCs) of ALS patients. In vitro EV exposure rescued mouse and human ALS astrocytes' neurotoxicity towards MNs. EVs significantly dampened the pathological phenotype and neuroinflammation in SOD1^G93A astrocytes. In iAstrocytes, exposure to EVs increased the antioxidant factor Nrf2 and reduced reactive oxygen species. We previously found nine miRNAs upregulated in MSC-derived EVs. Here, the transfection of SOD1^G93A astrocytes with single miRNA mimics reduced astrocytes' activation and the expression of neuroinflammatory factors. Moreover, miR-466q and miR-467f mimics downregulate Mapk11, while miR-466m-5p and miR-466i-3p mimics promote the nuclear translocation of Nrf2. In iAstrocytes, transfection with miR-29b-3p mimic upregulated NQO1 antioxidant activity and reduced neurotoxicity towards MNs. MSC-derived EVs modulate astrocytes' reactive phenotype and neurotoxicity through anti-inflammatory and antioxidant-shuttled miRNAs, thus representing a therapeutic strategy in ALS.

Catching a killer: Mechanisms of programmed cell death and immune activation in Amyotrophic Lateral Sclerosis

In the central nervous system (CNS), execution of programmed cell death (PCD) is crucial for proper neurodevelopment. However, aberrant activation of these pathways in adult CNS leads to neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). How a cell dies is critical, as it can drive local immune activation and tissue damage. Classical apoptosis engages several mechanisms to evoke "immunologically silent" responses, whereas other forms of programmed death such as pyroptosis, necroptosis, and ferroptosis release molecules that can potentiate immune responses and inflammation. In ALS, a fatal neuromuscular disorder marked by progressive death of lower and upper motor neurons, several cell types in the CNS express machinery for multiple PCD pathways. The specific cell types engaging PCD, and ultimate mechanisms by which neuronal death occurs in ALS are not well defined. Here, we provide an overview of different PCD pathways implicated in ALS. We also examine immune activation in ALS and differentiate apoptosis from necrotic mechanisms based on downstream immunological consequences. Lastly, we highlight therapeutic strategies that target cell death pathways in the treatment of neurodegeneration and inflammation in ALS.

Status of ALS Treatment, Insights into Therapeutic Challenges and Dilemmas

Amyotrophic lateral sclerosis (ALS) is an extremely heterogeneous disease of motor neurons that eventually leads to death. Despite impressive advances in understanding the genetic, molecular, and pathological mechanisms of the disease, the only drug approved to date by both the FDA and EMA is riluzole, with a modest effect on survival. In this opinion view paper, we will discuss how to address some challenges for drug development in ALS at the conceptual, technological, and methodological levels. In addition, socioeconomic and ethical issues related to the legitimate need of patients to benefit quickly from new treatments will also be addressed. In conclusion, this brief review takes a more optimistic view, given the recent approval of two new drugs in some countries and the development of targeted gene therapies.

The Role of Metals in the Neuroregenerative Action of BDNF, GDNF, NGF and Other Neurotrophic Factors

Mature neurotrophic factors and their propeptides play key roles ranging from the regulation of neuronal growth and differentiation to prominent participation in neuronal survival and recovery after injury. Their signaling pathways sculpture neuronal circuits during brain development and regulate adaptive neuroplasticity. In addition, neurotrophic factors provide trophic support for damaged neurons, giving them a greater capacity to survive and maintain their potential to regenerate their axons. Therefore, the modulation of these factors can be a valuable target for treating or preventing neurologic disorders and age-dependent cognitive decline. Neuroregenerative medicine can take great advantage by the deepening of our knowledge on the molecular mechanisms underlying the properties of neurotrophic factors. It is indeed an intriguing topic that a significant interplay between neurotrophic factors and various metals can modulate the outcome of neuronal recovery. This review is particularly focused on the roles of GDNF, BDNF and NGF in motoneuron survival and recovery from injuries and evaluates the therapeutic potential of various neurotrophic factors in neuronal regeneration. The key role of metal homeostasis/dyshomeostasis and metal interaction with neurotrophic factors on neuronal pathophysiology is also highlighted as a novel mechanism and potential target for neuronal recovery. The progress in mechanistic studies in the field of neurotrophic factor-mediated neuroprotection and neural regeneration, aiming at a complete understanding of integrated pathways, offers possibilities for the development of novel neuroregenerative therapeutic approaches.

Eye Movement Abnormalities in Amyotrophic Lateral Sclerosis in a Tunisian Cohort

Few studies have reported abnormal ocular movements in cases of amyotrophic lateral sclerosis (ALS) and their link with other disease features. Our study aimed to describe and analyse eye movement abnormalities in ALS patients. Specifically, we set out to investigate the correlation between non-motor signs and oculomotor impairment in order to understand the pathogenesis of the disease. All ALS patients seen from 2018 to 2020 in the department of Neurology of Razi hospital underwent the recording of saccadic eye movements. Results were compared with healthy controls. Sixty-two patients were included. Altered saccadic eye movements (72.6%) correlated with tongue atrophy and bladder dysfunction. The most common finding was altered smooth pursuit (56.5%), which showed correlation with bladder dysfunction and altered frontal assessment battery (FAB) scores. Prolonged latencies of horizontal saccades (34%) correlated with sensory and extrapyramidal signs. Our study is the first to examine the characteristics of eye movements in a large African cohort of ALS patients and to show correlations with extra-motor clinical signs. Our findings showed extra-motor cortex dysfunction in ALS with greater frequency of eye movement abnormalities in comparison with previous studies. Altered horizontal pursuit, the core abnormality, confirmed the extension of the neurodegenerative process to the frontal and prefrontal cortices. Prolonged horizontal saccade latencies reflect mainly the involvement of the parietal eye field. Anti-saccadic abnormalities were the least common finding and showed, paradoxically, no link with executive dysfunction.

Increased pyroptosis activation in white matter microglia is associated with neuronal loss in ALS motor cortex

Amyotrophic lateral sclerosis (ALS) is characterized by the degeneration of motor neurons in the motor cortex, brainstem, and spinal cord. Although ALS is considered a motor neuron disorder, neuroinflammation also plays an important role. Recent evidence in ALS disease models indicates activation of the inflammasome and subsequent initiation of pyroptosis, an inflammatory type of cell death. In this study, we determined the expression and distribution of the inflammasome and pyroptosis effector proteins in post-mortem brain and spinal cord from ALS patients (n = 25) and controls (n = 19), as well as in symptomatic and asymptomatic TDP-43^A315T transgenic and wild-type mice. Furthermore, we evaluated its correlation with the presence of TDP-43 pathological proteins and neuronal loss. Expression of the NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome, pyroptosis effector protein cleaved Gasdermin D (GSDMD), and IL-18 was detected in microglia in human ALS motor cortex and spinal cord, indicative of canonical inflammasome-triggered pyroptosis activation. The number of cleaved GSDMD-positive precentral white matter microglia was increased compared to controls and correlated with a decreased neuronal density in human ALS motor cortex. Neither of this was observed in the spinal cord. Similar results were obtained in TDP-43^A315T mice, where microglial pyroptosis activation was significantly increased in the motor cortex upon symptom onset, and correlated with neuronal loss. There was no significant correlation with the presence of TDP-43 pathological proteins both in human and mouse tissue. Our findings emphasize the importance of microglial NLRP3 inflammasome-mediated pyroptosis activation for neuronal degeneration in ALS and pave the way for new therapeutic strategies counteracting motor neuron degeneration in ALS by inhibiting microglial inflammasome/pyroptosis activation.

Insights into Human-Induced Pluripotent Stem Cell-Derived Astrocytes in Neurodegenerative Disorders

Most neurodegenerative disorders have complex and still unresolved pathology characterized by progressive neuronal damage and death. Astrocytes, the most-abundant non-neuronal cell population in the central nervous system, play a vital role in these processes. They are involved in various functions in the brain, such as the regulation of synapse formation, neuroinflammation, and lactate and glutamate levels. The development of human-induced pluripotent stem cells (iPSCs) reformed the research in neurodegenerative disorders allowing for the generation of disease-relevant neuronal and non-neuronal cell types that can help in disease modeling, drug screening, and, possibly, cell transplantation strategies. In the last 14 years, the differentiation of human iPSCs into astrocytes allowed for the opportunity to explore the contribution of astrocytes to neurodegenerative diseases. This review discusses the development protocols and applications of human iPSC-derived astrocytes in the most common neurodegenerative conditions.

The Involvement of RAGE and Its Ligands during Progression of ALS in SOD1 G93A Transgenic Mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by a progressive degeneration of upper and lower motor neurons that causes paralysis and muscle atrophy. The pathogenesis of the disease is still not elucidated. Receptor for Advanced Glycation End Product (RAGE) is a major component of the innate immune system and has implications in ALS pathogenesis. Multiple studies suggest the role of RAGE and its ligands in ALS. RAGE and its ligands are overexpressed in human and murine ALS motor neurons, astrocytes, and microglia. Here, we demonstrated the expression of RAGE and its ligands during the progression of the disease in the transgenic SOD1 G93A mouse lumbar spinal cord. We observed the highest expression of HMGB1 and S100b proteins at ALS onset. Our results highlight the potential role of RAGE and its ligands in ALS pathogenesis and suggest that some of the RAGE ligands might be used as biomarkers in early ALS diagnosis and potentially be useful in targeted therapeutic interventions at the early stage of this devastating disease.

MPO/HOCl Facilitates Apoptosis and Ferroptosis in the SOD1G93A Motor Neuron of Amyotrophic Lateral Sclerosis

Background. Oxidative stress and reactive oxygen species (ROS) are important in the pathogenesis of amyotrophic lateral sclerosis (ALS). Hypochlorous acid (HOCl) is a powerful oxidant of the reactive oxygen species (ROS) family. HOCl’s role in the progress of ALS remains unclear due to the lack of an effective HOCl detection method. Cumulative evidence supports oxidative damage incurred by mutant hSOD1 contributing to motor neuron death; however, whether HOCl as well as its catalytic enzyme myeloperoxidase (MPO) function in the cell death of SOD1G93A ALS remains elusive. Methods. The hSOD1WT and hSOD1G93A NSC-34 cell and SOD1G93A ALS mouse models were employed. With a novel fluorescent HOCl probe, HKOCl-3, we detected the expressions of HOCl and its catalytic enzyme, MPO, in the above models in vitro and in vivo. The regulation of MPO/HOCl by hSOD1G93A mutation and cell deaths by MPO/HOCl were also assayed, including apoptosis, ferroptosis, and autophagy. Results. Our results showed that hSOD1G93A mutation promoted the activation of the MPO/HOCl pathway in SOD1G93A ALS cell models. The activation of MPO/HOCl pathways facilitated apoptosis and ferroptosis through increasing the Bax/Bcl-2 ratio and expression of caspase-3 or inhibiting the expressions of GPX4 and NQO1 and thus leading to irreversible lipid peroxidation. Overexpressed FSP1, a glutathione-independent suppressor, could ameliorate ferroptosis. In vivo, we demonstrated that the activation of the MPO/HOCl pathway occurred differently in motor neurons of the motor cortices, brain stems, and spinal cords in male and female SOD1G93A transgenic mice. In addition, inhibiting MPO improved the motor performance of SOD1G93A transgenic mice, as demonstrated by the rotarod test. Conclusions. We concluded that aggregation of mutant hSOD1 proteins contributed to activation of the MPO/HOCl pathway, triggering apoptosis and ferroptosis in motor neuronal deaths and exerting impaired motor performance.

Phosphorylated TDP-43 aggregates in peripheral motor nerves of patients with amyotrophic lateral sclerosis

Phosphorylated TDP-43 (pTDP-43) aggregates in the cytoplasm of motor neurons and neuroglia in the brain are one of the pathological hallmarks of amyotrophic lateral sclerosis. Although the axons exceed the total volume of motor neuron soma by several orders of magnitude, systematic studies investigating the presence and distribution of pTDP-43 aggregates within motor nerves are still lacking. The aim of this study is to define the TDP-43/pTDP-43 pathology in diagnostic motor nerve biopsies performed on a large cohort of patients presenting with a lower motor neuron syndrome and to assess whether this might be a discriminating tissue biomarker for amyotrophic lateral sclerosis and non-amyotrophic lateral sclerosis cases.

We retrospectively evaluated 102 lower motor neuron syndrome patients referred to our centre for a diagnostic motor nerve biopsy. Histopathological criteria of motor neuron disease and motor neuropathy were applied by two independent evaluators, who were blind to clinical data. TDP-43 and pTDP-43 were evaluated by immunohistochemistry, and results compared to final clinical diagnosis.

We detected significant differences between amyotrophic lateral sclerosis and non-amyotrophic lateral sclerosis cases in pTDP-43 expression in myelinated fibres: axonal accumulation was detected in 98.2% of patients with amyotrophic lateral sclerosis versus 30.4% of non-amyotrophic lateral sclerosis samples (P < 0.0001), while concomitant positive staining in Schwan cell cytoplasm was found in 70.2% of patients with amyotrophic lateral sclerosis versus 17.4% of patients who did not have amyotrophic lateral sclerosis (P < 0.001). Importantly, we were also able to detect pTDP-43 aggregates in amyotrophic lateral sclerosis cases displaying normal features at standard histopathological analysis.

Our findings demonstrated that a specific pTDP-43 signature is present in the peripheral nervous system of patients with amyotrophic lateral sclerosis, and could be exploited as a specific, accessible tissue biomarker. The detection of pTDP-43 aggregates within motor nerves of living patients with amyotrophic lateral sclerosis, occurring before axonal degeneration, suggests that this is an early event that may contribute to amyotrophic lateral sclerosis pathogenesis.

Differences of Transport Activity of Arginine and Regulation on Neuronal Nitric Oxide Synthase and Oxidative Stress in Amyotrophic Lateral Sclerosis Model Cell Lines

L-Arginine, a semi-essential amino acid, was shown to delay dysfunction of motor neurons and to prolong the lifespan, upon analysis of transgenic mouse models of amyotrophic lateral sclerosis (ALS). We investigated the transport function of arginine and neuronal nitric oxide synthase (nNOS) expression after pretreatment with L-arginine in NSC-34 hSOD1^WT (wild-type, WT) and hSOD1^G93A (mutant-type, MT) cell lines. [³H]L-Arginine uptake was concentration-dependent, voltage-sensitive, and sodium-independent in both cell lines. Among the cationic amino acid transporters family, including system y+, b^0,+, B^0,+, and y⁺L, system y⁺ is mainly involved in [³H]L-arginine transport in ALS cell lines. System b^0,+ accounted for 23% of the transport in both cell lines. System B^0,+ was found only in MT, and whereas, system y⁺L was found only in WT. Lysine competitively inhibited [³H]L-arginine uptake in both cell lines. The nNOS mRNA expression was significantly lower in MT than in WT. Pretreatment with arginine elevated nNOS mRNA levels in MT. Oxidizing stressor, H₂O₂, significantly decreased their uptake; however, pretreatment with arginine restored the transport activity in both cell lines. In conclusion, arginine transport is associated with system y⁺, and neuroprotection by L-arginine may provide an edge as a possible therapeutic target in the treatment of ALS.

Non-Cell Autonomous and Epigenetic Mechanisms of Huntington's Disease

Huntington's disease (HD) is a rare neurodegenerative disorder caused by an expansion of CAG trinucleotide repeat located in the exon 1 of Huntingtin (HTT) gene in human chromosome 4. The HTT protein is ubiquitously expressed in the brain. Specifically, mutant HTT (mHTT) protein-mediated toxicity leads to a dramatic degeneration of the striatum among many regions of the brain. HD symptoms exhibit a major involuntary movement followed by cognitive and psychiatric dysfunctions. In this review, we address the conventional role of wild type HTT (wtHTT) and how mHTT protein disrupts the function of medium spiny neurons (MSNs). We also discuss how mHTT modulates epigenetic modifications and transcriptional pathways in MSNs. In addition, we define how non-cell autonomous pathways lead to damage and death of MSNs under HD pathological conditions. Lastly, we overview therapeutic approaches for HD. Together, understanding of precise neuropathological mechanisms of HD may improve therapeutic approaches to treat the onset and progression of HD.

Dysfunction of RNA/RNA-Binding Proteins in ALS Astrocytes and Microglia

Amyotrophic Lateral Sclerosis is a neurological disease that primarily affects motor neurons in the cortex, brainstem, and spinal cord. The process that leads to motor neuron degeneration is strongly influenced by non-motor neuronal events that occur in a variety of cell types. Among these, neuroinflammatory processes mediated by activated astrocytes and microglia play a relevant role. In recent years, it has become clear that dysregulation of essential steps of RNA metabolism, as a consequence of alterations in RNA-binding proteins (RBPs), is a central event in the degeneration of motor neurons. Yet, a causal link between dysfunctional RNA metabolism and the neuroinflammatory processes mediated by astrocytes and microglia in ALS has been poorly defined. In this review, we will discuss the available evidence showing that RBPs and associated RNA processing are affected in ALS astrocytes and microglia, and the possible mechanisms involved in these events.

PARKIN modifies peripheral immune response and increases neuroinflammation in active experimental autoimmune encephalomyelitis (EAE)

Neuroinflammation plays an important role in the pathogenesis of several neurodegenerative disorders. To elucidate the effects of the mitophagy-related gene Parkin on neuroinflammation, we used a mouse model of experimental autoimmune encephalomyelitis (EAE). Female Parkin^-/- and female wild type control mice were immunized with myelin oligodendrocyte glycoprotein to develop active EAE. Compared to the wild type controls, the Parkin^-/- mice showed an earlier onset and greater severity of EAE with a greatly increased number of CD8αβ⁺TCRαβ⁺ T cells in the spleen and brain as well as a stronger T-cell proliferative response and an altered cytokine secretion in splenocytes. Furthermore, the Parkin^-/- mice showed massive recruitment of monocytes/macrophages and activated microglia in the spinal cord during the acute phase of the disease. They also showed accumulation of microglia co-expressing M1 and M2 markers in the brain and a strong over-expression of A1 reactive astrocytes in the spinal cord. Furthermore, the Parkin^-/- mice that developed persistent disease exhibited reduced glial cell numbers and abnormalities in mitochondrial morphology. Our study sheds light on the role of PARKIN protein in modulating peripheral immune cells-mediated immunity during EAE, highlighting its importance in neuroinflammation, and thus elucidating its potential in the development of novel neuroprotective therapies.

The neuroprotective potential of carotenoids in vitro and in vivo

BACKGROUND

Despite advances in research on neurodegenerative diseases, the pathogenesis and treatment response of neurodegenerative diseases remain unclear. Recent studies revealed a significant role of carotenoids to treat neurodegenerative diseases. The aim of this study was to systematically review the neuroprotective potential of carotenoids in vivo and in vitro and the molecular mechanisms and pathological factors contributing to major neurodegenerative diseases (Alzheimer's disease, Huntington's disease, Parkinson's disease, amyotrophic lateral sclerosis, and stroke).

HYPOTHESIS

Carotenoids as therapeutic molecules to target neurodegenerative diseases.

RESULTS

Aggregation of toxic proteins, mitochondrial dysfunction, oxidative stress, the excitotoxic pathway, and neuroinflammation were the major pathological factors contributing to the progression of neurodegenerative diseases. Furthermore, in vitro and in vivo studies supported the beneficiary role of carotenoids, namely lycopene, β-carotene, crocin, crocetin, lutein, fucoxanthin and astaxanthin in alleviating disease progression. These carotenoids provide neuroprotection by inhibition of neuro-inflammation, microglial activation, excitotoxic pathway, modulation of autophagy, attenuation of oxidative damage and activation of defensive antioxidant enzymes. Additionally, studies conducted on humans also demonstrated that dietary intake of carotenoids lowers the risk of neurodegenerative diseases.

CONCLUSION

Carotenoids may be used as drugs to prevent and treat neurodegenerative diseases. Although, the in vitro and in vivo results are encouraging, further well conducted clinical studies on humans are required to conclude about the full potential of neurodegenerative diseases.

Dysfunction of oligodendrocyte inwardly rectifying potassium channel in a rat model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease caused by the death of motor neurons in the spinal cord and the brain. Although this disease is characterized by motoneuron degeneration, non-neuronal cells such as oligodendrocytes play an important role in the disease onset and progression. The aim of our study was to examine functional properties of oligodendrocytes in the SOD1^G93A rat model of ALS with a particular focus on the inwardly rectifying potassium channel Kir4.1 that is abundantly expressed in these glial cells and plays a role in the regulation of extracellular K⁺ . First, we demonstrate that the expression of Kir4.1 is diminished in the spinal cord oligodendrocytes of the SOD1^G93A rat. Moreover, our data show an elevated number of dysmorphic oligodendrocytes in the ALS spinal cord that is indicative of a degenerative phenotype. In order to assess physiological properties of oligodendrocytes, we prepared cell cultures from the rat spinal cord. Oligodendrocytes isolated from the SOD1^G93A spinal cord display similar ramification of the processes as the control but express a lower level of Kir4.1. We further demonstrate an impairment of oligodendrocyte functional properties in ALS. Remarkably, whole-cell patch-clamp recordings revealed compromised membrane biophysical properties and diminished inward currents in the SOD1^G93A oligodendrocytes. In addition, the Ba²⁺ -sensitive Kir currents were decreased in ALS oligodendrocytes. Altogether, our findings provide the evidence of impaired Kir4.1 expression and function in oligodendrocytes of the SOD1^G93A spinal cord, suggesting oligodendrocyte Kir4.1 channel as a potential contributor to the ALS pathophysiology.

κ-Carrageenan Oligosaccharides Inhibit the Inflammation of Lipopolysaccharide-Activated Microglia Via TLR4/NF-κB and p38/JNK MAPKs Pathways

Microglial inflammation plays an essential role in neurodegenerative disease. Our previous studies had shown that κ-carrageenan oligosaccharides (KOS) could inhibit the excessive activation of microglia that induced by LPS, while the interrelated mechanisms were still indistinct. Therefore, we detected the inflammatory signaling pathway on LPS-activated microglia that pretreat by different content of KOS to reveal the mechanism on KOS's inhibition of microglia inflammatory response. ELISA was used to detect the effects of KOS on the secretion of interleukin-1 (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and prostaglandin E2 (PG-2) by LPS-activated microglia, respectively. The production of reactive oxygen species (ROS) and nitric oxide (NO) in microglia cells was detected by flow cytometry, and the protein expression of immunoinflammation-related signaling pathways were detected by Western Blot. The results showed that KOS could significantly protected the microglia from the over-activated inflammatory by inhibiting the release of inflammatory cytokines and the oxidative stress response. And KOS could reduce the expression of the protein that related to the TLR4/NF-κB and p38/JNK MAPKs pathways activated by LPS in microglia. However, there may be no specific target of KOS in cells. Therefore, KOS, a natural algal source oligosaccharide, has immunomodulatory effects and can be used as a potential intervention therapy for inflammatory related neurodegenerative diseases.

Change in Cationic Amino Acid Transport System and Effect of Lysine Pretreatment on Inflammatory State in Amyotrophic Lateral Sclerosis Cell Model

Amyotrophic lateral sclerosis (ALS) is a lethal neurological disorder characterized by the deterioration of motor neurons. The aim of this study was to investigate alteration of cationic amino acid transporter (CAT-1) activity in the transport of lysine and the pretreatment effect of lysine on pro-inflammatory states in an amyotrophic lateral sclerosis cell line. The mRNA expression of cationic amino acid transporter 1 was lower in NSC-34/hSOD1^G93A (MT) than the control cell line (WT), lysine transport is mediated by CAT-1 in NSC-34 cell lines. The uptake of [³H]L-lysine was Na⁺-independent, voltage-sensitive, and strongly inhibited by inhibitors and substrates of cationic amino acid transporter 1 (system y⁺). The transport process involved two saturable processes in both cell lines. In the MT cell line, at a high-affinity site, the affinity was 9.4-fold higher and capacity 24-fold lower than that in the WT; at a low-affinity site, the capacity was 2.3-fold lower than that in the WT cell line. Donepezil and verapamil competitively inhibited [³H]L-lysine uptake in the NSC-34 cell lines. Pretreatment with pro-inflammatory cytokines decreased the uptake of [³H]L-lysine and mRNA expression levels in both cell lines; however, the addition of L-lysine restored the transport activity in the MT cell lines. L-Lysine exhibited neuroprotective effects against pro-inflammatory states in the ALS disease model cell lines. In conclusion, studying the alteration in the expression of transporters and characteristics of lysine transport in ALS can lead to the development of new therapies for neurodegenerative diseases.

Interplay between immunity and amyotrophic lateral sclerosis: Clinical impact

Amyotrophic lateral sclerosis (ALS) is a debilitating and rapidly fatal neurodegenerative disease. Despite decades of research and many new insights into disease biology over the 150 years since the disease was first described, causative pathogenic mechanisms in ALS remain poorly understood, especially in sporadic cases. Our understanding of the role of the immune system in ALS pathophysiology, however, is rapidly expanding. The aim of this manuscript is to summarize the recent advances regarding the immune system involvement in ALS, with particular attention to clinical translation. We focus on the potential pathophysiologic mechanism of the immune system in ALS, discussing local and systemic factors (blood, cerebrospinal fluid, and microbiota) that influence ALS onset and progression in animal models and people. We also explore the potential of Positron Emission Tomography to detect neuroinflammation in vivo, and discuss ongoing clinical trials of therapies targeting the immune system. With validation in human patients, new evidence in this emerging field will serve to identify novel therapeutic targets and provide realistic hope for personalized treatment strategies.

Interleukin-17 and Th17 Lymphocytes Directly Impair Motoneuron Survival of Wildtype and FUS-ALS Mutant Human iPSCs

Amyotrophic lateral sclerosis (ALS) is a progressive disease leading to the degeneration of motor neurons (MNs). Neuroinflammation is involved in the pathogenesis of ALS; however, interactions of specific immune cell types and MNs are not well studied. We recently found a shift toward T helper (Th)1/Th17 cell-mediated, pro-inflammatory immune responses in the peripheral immune system of ALS patients, which positively correlated with disease severity and progression. Whether Th17 cells or their central mediator, Interleukin-17 (IL-17), directly affects human motor neuron survival is currently unknown. Here, we evaluated the contribution of Th17 cells and IL-17 on MN degeneration using the co-culture of iPSC-derived MNs of fused in sarcoma (FUS)-ALS patients and isogenic controls with Th17 lymphocytes derived from ALS patients, healthy controls, and multiple sclerosis (MS) patients (positive control). Only Th17 cells from MS patients induced severe MN degeneration in FUS-ALS as well as in wildtype MNs. Their main effector, IL-17A, yielded in a dose-dependent decline of the viability and neurite length of MNs. Surprisingly, IL-17F did not influence MNs. Importantly, neutralizing IL-17A and anti-IL-17 receptor A treatment reverted all effects of IL-17A. Our results offer compelling evidence that Th17 cells and IL-17A do directly contribute to MN degeneration.

The Skeletal Muscle Emerges as a New Disease Target in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder that leads to progressive degeneration of motor neurons (MNs) and severe muscle atrophy without effective treatment. Most research on ALS has been focused on the study of MNs and supporting cells of the central nervous system. Strikingly, the recent observations of pathological changes in muscle occurring before disease onset and independent from MN degeneration have bolstered the interest for the study of muscle tissue as a potential target for delivery of therapies for ALS. Skeletal muscle has just been described as a tissue with an important secretory function that is toxic to MNs in the context of ALS. Moreover, a fine-tuning balance between biosynthetic and atrophic pathways is necessary to induce myogenesis for muscle tissue repair. Compromising this response due to primary metabolic abnormalities in the muscle could trigger defective muscle regeneration and neuromuscular junction restoration, with deleterious consequences for MNs and thereby hastening the development of ALS. However, it remains puzzling how backward signaling from the muscle could impinge on MN death. This review provides a comprehensive analysis on the current state-of-the-art of the role of the skeletal muscle in ALS, highlighting its contribution to the neurodegeneration in ALS through backward-signaling processes as a newly uncovered mechanism for a peripheral etiopathogenesis of the disease.

Variability of the Expression Patterns of Neuroinflammatory Genes in Mononuclear Cells of Peripheral Blood in Amyotrophic Lateral Sclerosis

Abstract—Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease with steadily progressing death of motor neurons in the brain and spinal cord. The disease is incurable and results in the patient’s death within 3–5 years on average. The mechanisms of initiation, progression, and spread of the pathological process remain unclear. It seems that inflammatory reactions may be important for disease progression but this is not certain. We performed multiplex analysis of the expression of neuroinflammatory genes in mononuclear cells of peripheral blood from patients with different rates of ALS progression (n = 22) and compared these data with those observed in healthy volunteers. We found that the expression of 14 genes, specifically BAX, CLN3, PLEKHM1, AKT1, LAMP1, RAC2, VAV1, MPG, TFG, BRD2, CSK, MSN, GBA, and VIM, differed between the groups of patients and healthy volunteers (p < 0.05; q < 0.05). Genes associated with autophagia, apoptosis, adaptive immunity, and growth factor cascades prevail among these genes. We did not find any substantial differences in gene expression between patients with rapid and slow ALS progression. We revealed a subgroup of patients who exhibited significantly different expression of 208 or 262 genes compared to other ALS patients or healthy volunteers, respectively (p < 0.05; q < 0.05). Our data show the importance of not only central but also peripheral inflammatory reactions in the development of the pathological process associated with ALS.

Perturbations of the Proteome and of Secreted Metabolites in Primary Astrocytes from the hSOD1(G93A) ALS Mouse Model

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease whose pathophysiology is largely unknown. Despite the fact that motor neuron (MN) death is recognized as the key event in ALS, astrocytes dysfunctionalities and neuroinflammation were demonstrated to accompany and probably even drive MN loss. Nevertheless, the mechanisms priming astrocyte failure and hyperactivation are still obscure. In this work, altered pathways and molecules in ALS astrocytes were unveiled by investigating the proteomic profile and the secreted metabolome of primary spinal cord astrocytes derived from transgenic ALS mouse model overexpressing the human (h)SOD1(G93A) protein in comparison with the transgenic counterpart expressing hSOD1(WT) protein. Here we show that ALS primary astrocytes are depleted of proteins-and of secreted metabolites-involved in glutathione metabolism and signaling. The observed increased activation of Nf-kB, Ebf1, and Plag1 transcription factors may account for the augmented expression of proteins involved in the proteolytic routes mediated by proteasome or endosome-lysosome systems. Moreover, hSOD1(G93A) primary astrocytes also display altered lipid metabolism. Our results provide novel insights into the altered molecular pathways that may underlie astrocyte dysfunctionalities and altered astrocyte-MN crosstalk in ALS, representing potential therapeutic targets to abrogate or slow down MN demise in disease pathogenesis.

Novel Applications of NSAIDs: Insight and Future Perspectives in Cardiovascular, Neurodegenerative, Diabetes and Cancer Disease Therapy

Once it became clear that inflammation takes place in the modulation of different degenerative disease including neurodegenerative, cardiovascular, diabetes and cancer the researchers has started intensive programs evaluating potential role of non-steroidal anti-inflammatory drugs (NSAIDs) in the prevention or therapy of these diseases. This review discusses the novel mechanism of action of NSAIDs and its potential use in the pharmacotherapy of neurodegenerative, cardiovascular, diabetes and cancer diseases. Many different molecular and cellular factors which are not yet fully understood play an important role in the pathogenesis of inflammation, axonal damage, demyelination, atherosclerosis, carcinogenesis thus further NSAID studies for a new potential indications based on precise pharmacotherapy model are warranted since NSAIDs are a heterogeneous group of medicines with relative different pharmacokinetics and pharmacodynamics profiles. Hopefully the new data from studies will fill in the gap between experimental and clinical results and translate our knowledge into successful disease therapy.

GLT1 gene delivery based on bone marrow-derived cells ameliorates motor function and survival in a mouse model of ALS

Amyotrophic lateral sclerosis (ALS) is an intractable neurodegenerative disease. CD68-positive bone marrow (BM)-derived cells (BMDCs) accumulate in the pathological lesion in the SOD1(G93A) ALS mouse model after BM transplantation (BMT). Therefore, we investigated whether BMDCs can be applied as gene carriers for cell-based gene therapy by employing the accumulation of BMDCs. In ALS mice, YFP reporter signals were observed in 12-14% of white blood cells (WBCs) and in the spinal cord via transplantation of BM after lentiviral vector (LV) infection. After confirmation of gene transduction by LV with the CD68 promoter in 4-7% of WBCs and in the spinal cord of ALS mice, BM cells were infected with LVs expressing glutamate transporter (GLT) 1 that protects neurons from glutamate toxicity, driven by the CD68 promoter, which were transplanted into ALS mice. The treated mice showed improvement of motor behaviors and prolonged survival. Additionally, interleukin (IL)-1β was significantly suppressed, and IL-4, arginase 1, and FIZZ were significantly increased in the mice. These results suggested that GLT1 expression by BMDCs improved the spinal cord environment. Therefore, our gene therapy strategy may be applied to treat neurodegenerative diseases such as ALS in which BMDCs accumulate in the pathological lesion by BMT.

Inactivation of the CB2 receptor accelerated the neuropathological deterioration in TDP-43 transgenic mice, a model of amyotrophic lateral sclerosis

The activation of the cannabinoid receptor type‐2 (CB₂) afforded neuroprotection in amyotrophic lateral sclerosis (ALS) models. The objective of this study was to further investigate the relevance of the CB₂ receptor through investigating the consequences of its inactivation. TDP‐43(A315T) transgenic mice were crossed with CB₂ receptor knock‐out mice to generate double mutants. Temporal and qualitative aspects of the pathological phenotype of the double mutants were compared to TDP‐43 transgenic mice expressing the CB₂ receptor. The double mutants exhibited significantly accelerated neurological decline, such that deteriorated rotarod performance was visible at 7 weeks, whereas rotarod performance was normal up to 11 weeks in transgenic mice with intact expression of the CB₂ receptor. A morphological analysis of spinal cords confirmed an earlier death (visible at 65 days) of motor neurons labelled with Nissl staining and ChAT immunofluorescence in double mutants compared to TDP‐43 transgenic mice expressing the CB₂ receptor. Evidence of glial reactivity, measured using GFAP and Iba‐1 immunostaining, was seen in double mutants at 65 days, but not in TDP‐43 transgenic mice expressing the CB₂ receptor. However, at 90 days, both genotypes exhibited similar changes for all these markers, although surviving motor neurons of transgenic mice presented some morphological abnormalities in absence of the CB₂ receptor that were not as evident in the presence of this receptor. This faster deterioration seen in double mutants led to premature mortality compared with TDP‐43 transgenic mice expressing the CB₂ receptor. We also investigated the consequences of a pharmacological inactivation of the CB₂ receptor using the selective antagonist AM630 in TDP‐43 transgenic mice, but results showed only subtle trends towards a greater deterioration. In summary, our results confirmed the potential of the CB₂ receptor agonists as a neuroprotective therapy in ALS and strongly support the need to progress towards an evaluation of this potential in patients.