Ultrastructure of blood-brain barrier and blood-spinal cord barrier in SOD1 mice modeling ALS

The role of glial cells in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) has traditionally been considered a neuron-centric disease. This view is now outdated, with increasing recognition of cell autonomous and non-cell autonomous contributions of central and peripheral nervous system glia to ALS pathomechanisms. With glial research rapidly accelerating, we comprehensively interrogate the roles of astrocytes, microglia, oligodendrocytes, ependymal cells, Schwann cells and satellite glia in nervous system physiology and ALS-associated pathology. Moreover, we highlight the inter-glial, glial-neuronal and inter-system polylogue which constitutes the healthy nervous system and destabilises in disease. We also propose classification based on function for complex glial reactive phenotypes and discuss the pre-requisite for integrative modelling to advance translation. Given the paucity of life-enhancing therapies currently available for ALS patients, we discuss the promising potential of harnessing glia in driving ALS therapeutic discovery.

C9ORF72 patient-derived endothelial cells drive blood-brain barrier disruption and contribute to neurotoxicity

The blood-brain barrier (BBB) serves as a highly intricate and dynamic interface connecting the brain and the bloodstream, playing a vital role in maintaining brain homeostasis. BBB dysfunction has been associated with multiple neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS); however, the role of the BBB in neurodegeneration is understudied. We developed an ALS patient-derived model of the BBB by using cells derived from 5 patient donors carrying C9ORF72 mutations. Brain microvascular endothelial-like cells (BMEC-like cells) derived from C9ORF72-ALS patients showed altered gene expression, compromised barrier integrity, and increased P-glycoprotein transporter activity. In addition, mitochondrial metabolic tests demonstrated that C9ORF72-ALS BMECs display a significant decrease in basal glycolysis accompanied by increased basal and ATP-linked respiration. Moreover, our study reveals that C9-ALS derived astrocytes can further affect BMECs function and affect the expression of the glucose transporter Glut-1. Finally, C9ORF72 patient-derived BMECs form leaky barriers through a cell-autonomous mechanism and have neurotoxic properties towards motor neurons.

Cellular and Noncellular Approaches for Repairing the Damaged Blood-CNS-Barrier in Amyotrophic Lateral Sclerosis

Numerous reports have demonstrated the breakdown of the blood-CNS barrier (B-CNS-B) in amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease. Re-establishing barrier integrity in the CNS is critical to prevent further motor neuron degeneration from harmful components in systemic circulation. Potential therapeutic strategies for repairing the B-CNS-B may be achieved by the replacement of damaged endothelial cells (ECs) via stem cell administration or enhancement of endogenous EC survival through the delivery of bioactive particles secreted by stem cells. These cellular and noncellular approaches are thoroughly discussed in the present review. Specific attention is given to certain stem cell types for EC replacement. Also, various nanoparticles secreted by stem cells as well as other biomolecules are elucidated as promising agents for endogenous EC repair. Although the noted in vitro and in vivo studies show the feasibility of the proposed therapeutic approaches to the repair of the B-CNS-B in ALS, further investigation is needed prior to clinical transition.

Brain-Gut-Microbiota Axis in Amyotrophic Lateral Sclerosis: A Historical Overview and Future Directions

Amyotrophic Lateral Sclerosis (ALS) is a devastating neurodegenerative disease which is strongly associated with age. The incidence of ALS increases from the age of 40 and peaks between the ages of 65 and 70. Most patients die of respiratory muscle paralysis or lung infections within three to five years of the appearance of symptoms, dealing a huge blow to patients and their families. With aging populations, improved diagnostic methods and changes in reporting criteria, the incidence of ALS is likely to show an upward trend in the coming decades. Despite extensive researches have been done, the cause and pathogenesis of ALS remains unclear. In recent decades, large quantities of studies focusing on gut microbiota have shown that gut microbiota and its metabolites seem to change the evolvement of ALS through the brain-gut-microbiota axis, and in turn, the progression of ALS will exacerbate the imbalance of gut microbiota, thereby forming a vicious cycle. This suggests that further exploration and identification of the function of gut microbiota in ALS may be crucial to break the bottleneck in the diagnosis and treatment of this disease. Hence, the current review summarizes and discusses the latest research advancement and future directions of ALS and brain-gut-microbiota axis, so as to help relevant researchers gain correlative information instantly.

The therapeutic potential of probucol and probucol analogues in neurodegenerative diseases

Neurodegenerative disorders present complex pathologies characterized by various interconnected factors, including the aggregation of misfolded proteins, oxidative stress, neuroinflammation and compromised blood-brain barrier (BBB) integrity. Addressing such multifaceted pathways necessitates the development of multi-target therapeutic strategies. Emerging research indicates that probucol, a historic lipid-lowering medication, offers substantial potential in the realm of neurodegenerative disease prevention and treatment. Preclinical investigations have unveiled multifaceted cellular effects of probucol, showcasing its remarkable antioxidative and anti-inflammatory properties, its ability to fortify the BBB and its direct influence on neural preservation and adaptability. These diverse effects collectively translate into enhancements in both motor and cognitive functions. This review provides a comprehensive overview of recent findings highlighting the efficacy of probucol and probucol-related compounds in the context of various neurodegenerative conditions, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and cognitive impairment associated with diabetes.

Urinary biomarkers for amyotrophic lateral sclerosis: candidates, opportunities and considerations

Amyotrophic lateral sclerosis is a relentless neurodegenerative disease that is mostly fatal within 3-5 years and is diagnosed on evidence of progressive upper and lower motor neuron degeneration. Around 15% of those with amyotrophic lateral sclerosis also have frontotemporal degeneration, and gene mutations account for ∼10%. Amyotrophic lateral sclerosis is a variable heterogeneous disease, and it is becoming increasingly clear that numerous different disease processes culminate in the final degeneration of motor neurons. There is a profound need to clearly articulate and measure pathological process that occurs. Such information is needed to tailor treatments to individuals with amyotrophic lateral sclerosis according to an individual's pathological fingerprint. For new candidate therapies, there is also a need for methods to select patients according to expected treatment outcomes and measure the success, or not, of treatments. Biomarkers are essential tools to fulfil these needs, and urine is a rich source for candidate biofluid biomarkers. This review will describe promising candidate urinary biomarkers of amyotrophic lateral sclerosis and other possible urinary candidates in future areas of investigation as well as the limitations of urinary biomarkers.

Effects of Acetyl-L-Carnitine on Oxidative Stress in Amyotrophic Lateral Sclerosis Patients: Evaluation on Plasma Markers and Members of the Neurovascular Unit

Oxidative stress, the alteration of mitochondrial function, and the neurovascular unit (NVU), play a role in Amyotrophic Lateral Sclerosis (ALS) pathogenesis. We aimed to demonstrate the changes in the plasma redox system and nitric oxide (NO) in 32 new ALS-diagnosed patients in treatment with Acetyl-L-Carnitine (ALCAR) compared to healthy controls. We also evaluated the effects of plasma on human umbilical cord-derived endothelial vascular cells (HUVEC) and astrocytes. The analyses were performed at the baseline (T0), after three months (T1), and after six months (T2). In ALS patients at T0/T1, the plasma markers of lipid peroxidation, thiobarbituric acid reactive substances (TBARS) and 4-hydroxy nonenal (4-HNE) were higher, whereas the antioxidants, glutathione (GSH) and the glutathione peroxidase (GPx) activity were lower than in healthy controls. At T2, plasma TBARS and 4-HNE decreased, whereas plasma GSH and the GPx activity increased in ALS patients. As regards NO, the plasma levels were firmly lower at T0-T2 than those of healthy controls. Cell viability, and mitochondrial membrane potential in HUVEC/astrocytes treated with the plasma of ALS patients at T0-T2 were reduced, while the oxidant release increased. Those results, which confirmed the fundamental role of oxidative stress, mitochondrial function, and of the NVU in ALS pathogenesis, can have a double meaning, acting as disease markers at baseline and potential markers of drug effects in clinical practice and during clinical trials.

Transplanted Human Bone Marrow Endothelial Progenitor Cells Prolong Functional Benefits and Extend Survival of ALS Mice Likely via Blood-Spinal Cord Barrier Repair

Amyotrophic lateral sclerosis (ALS) is a multifactorial disease with one of these factors being an impaired blood-spinal cord barrier (BSCB). In order to block harmful components in systemic circulation from accessing the CNS, barrier damage needs alleviation. Recently, we found that symptomatic ALS animals treated with intravenously delivered human bone marrow-derived CD34+ (hBM34+) cells or endothelial progenitor cells (hBMEPCs) showed delayed disease progression for 4 weeks post-transplant via BSCB repair. However, despite noted benefits from transplanted human bone marrow-derived stem cells, long-term effects of transplanted cells in ALS mice remain undetermined. This study aimed to determine prolonged effects of single equal doses of hBM34+ cells and hBMEPCs systemically transplanted into symptomatic G93A SOD1 mice on behavioral disease outcomes and mouse lifespan. Results showed that transplanted hBMEPCs better ameliorated disease behavioral outcomes than hBM34 + cells until near end-stage disease and significantly increased lifespan vs. media-treated mice. These results provide important evidence that transplanted hBMEPCs prolonged functional benefits and extended survival of ALS mice, potentially by repairing the damaged BSCB. However, due to modestly increased lifespan of hBMEPC-treated mice, repeated cell transplants into symptomatic ALS mice may more effectively delay motor function deficit and extend lifespan by continuous reparative processes via replacement of damaged endothelial cells during disease progression.

Blood-spinal cord barrier disruption in degenerative cervical myelopathy

Degenerative cervical myelopathy (DCM) is the most prevalent cause of spinal cord dysfunction in the aging population. Significant neurological deficits may result from a delayed diagnosis as well as inadequate neurological recovery following surgical decompression. Here, we review the pathophysiology of DCM with an emphasis on how blood-spinal cord barrier (BSCB) disruption is a critical yet neglected pathological feature affecting prognosis. In patients suffering from DCM, compromise of the BSCB is evidenced by elevated cerebrospinal fluid (CSF) to serum protein ratios and abnormal contrast-enhancement upon magnetic resonance imaging (MRI). In animal model correlates, there is histological evidence of increased extravasation of tissue dyes and serum contents, and pathological changes to the neurovascular unit. BSCB dysfunction is the likely culprit for ischemia-reperfusion injury following surgical decompression, which can result in devastating neurological sequelae. As there are currently no therapeutic approaches specifically targeting BSCB reconstitution, we conclude the review by discussing potential interventions harnessed for this purpose.

Implication of Central Nervous System Barrier Impairment in Amyotrophic Lateral Sclerosis: Gender-Related Difference in Patients

Central nervous system (CNS) barrier impairment has been reported in amyotrophic lateral sclerosis (ALS), highlighting its potential significance in the disease. In this context, we aim to shed light on its involvement in the disease, by determining albumin quotient (QAlb) at the time of diagnosis of ALS in a large cohort of patients. Patients from the university hospital of Tours (n = 307) were included in this monocentric, retrospective study. In total, 92 patients (30%) had elevated QAlb levels. This percentage was higher in males (43%) than in females (15%). Interestingly, QAlb was not associated with age of onset, age at sampling or diagnostic delay. However, we found an association with ALS functional rating scale-revised (ALSFRS-r) at diagnosis but this was significant only in males. The QAlb levels were not linked to the presence of a pathogenic mutation. Finally, we performed a multivariate survival analysis and found that QAlb was significantly associated with survival in male patients (HR = 2.3, 95% CI = 1.2-4.3, p = 0.009). A longitudinal evaluation of markers of barrier impairment, in combination with inflammatory biomarkers, could give insight into the involvement of CNS barrier impairment in the pathogenesis of the disease. The gender difference might guide the development of new drugs and help personalise the treatment of ALS.

Astrocytes: Dissecting Their Diverse Roles in Amyotrophic Lateral Sclerosis and Frontotemporal Dementia

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are fatal neurodegenerative disorders often co-occurring in the same patient, a feature that suggests a common origin of the two diseases. Consistently, pathological inclusions of the same proteins as well as mutations in the same genes can be identified in both ALS/FTD. Although many studies have described several disrupted pathways within neurons, glial cells are also regarded as crucial pathogenetic contributors in ALS/FTD. Here, we focus our attention on astrocytes, a heterogenous population of glial cells that perform several functions for optimal central nervous system homeostasis. Firstly, we discuss how post-mortem material from ALS/FTD patients supports astrocyte dysfunction around three pillars: neuroinflammation, abnormal protein aggregation, and atrophy/degeneration. Furthermore, we summarize current attempts at monitoring astrocyte functions in living patients using either novel imaging strategies or soluble biomarkers. We then address how astrocyte pathology is recapitulated in animal and cellular models of ALS/FTD and how we used these models both to understand the molecular mechanisms driving glial dysfunction and as platforms for pre-clinical testing of therapeutics. Finally, we present the current clinical trials for ALS/FTD, restricting our discussion to treatments that modulate astrocyte functions, directly or indirectly.

Promoting regeneration while blocking cell death preserves motor neuron function in a model of ALS

Amyotrophic lateral sclerosis (ALS) is a devastating and fatal neurodegenerative disease of motor neurons with very few treatment options. We had previously found that motor neuron degeneration in a mouse model of ALS can be delayed by deleting the axon damage sensor MAP3K12 or dual leucine zipper kinase (DLK). However, DLK is also involved in axon regeneration, prompting us to ask whether combining DLK deletion with a way to promote axon regeneration would result in greater motor neuron protection. To achieve this, we used a mouse line that constitutively expresses ATF3, a master regulator of regeneration in neurons. Although there is precedence for each individual strategy in the SOD1G93A mouse model of ALS, these have not previously been combined. By several lines of evidence including motor neuron electrophysiology, histology and behaviour, we observed a powerful synergy when combining DLK deletion with ATF3 expression. The combinatorial strategy resulted in significant protection of motor neurons with fewer undergoing cell death, reduced axon degeneration and preservation of motor function and connectivity to muscle. This study provides a demonstration of the power of combinatorial therapy to treat neurodegenerative disease.

Extracellular matrix proteins in construction and function of in vitro blood-brain barrier models

The blood-brain barrier (BBB) is a highly impermeable barrier separating circulating blood and brain tissue. A functional BBB is critical for brain health, and BBB dysfunction has been linked to the pathophysiology of diseases such as stroke and Alzheimer’s disease. A variety of models have been developed to study the formation and maintenance of the BBB, ranging from in vivo animal models to in vitro models consisting of primary cells or cells differentiated from human pluripotent stem cells (hPSCs). These models must consider the composition and source of the cellular components of the neurovascular unit (NVU), including brain microvascular endothelial cells (BMECs), brain pericytes, astrocytes, and neurons, and how these cell types interact. In addition, the non-cellular components of the BBB microenvironment, such as the brain vascular basement membrane (BM) that is in direct contact with the NVU, also play key roles in BBB function. Here, we review how extracellular matrix (ECM) proteins in the brain vascular BM affect the BBB, with a particular focus on studies using hPSC-derived in vitro BBB models, and discuss how future studies are needed to advance our understanding of how the ECM affects BBB models to improve model performance and expand our knowledge on the formation and maintenance of the BBB.

Blood-CNS barrier dysfunction in amyotrophic lateral sclerosis: Proposed mechanisms and clinical implications

There is strong evidence for blood-brain and blood-spinal cord barrier dysfunction at the early stages of many neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). Since impairment of the blood-central nervous system barrier (BCNSB) occurs during the pre-symptomatic stages of ALS, the mechanisms underlying this pathology are likely also involved in the ALS disease process. In this review, we explore how drivers of ALS disease, particularly mitochondrial dysfunction, astrocyte pathology and neuroinflammation, may contribute to BCNSB impairment. Mitochondria are highly abundant in BCNSB tissue and mitochondrial dysfunction in ALS contributes to motor neuron death. Likewise, astrocytes adopt key physical, transport and metabolic functions at the barrier, many of which are impaired in ALS. Astrocytes also show raised expression of inflammatory markers in ALS and ablating ALS-causing transgenes in astrocytes slows disease progression. In addition, key drivers of neuroinflammation, including TAR DNA-binding protein 43 (TDP-43) pathology, matrix metalloproteinase activation and systemic inflammation, affect BCNSB integrity in ALS. Finally, we discuss the translational implications of BCNSB dysfunction in ALS, including the development of biomarkers for disease onset and progression, approaches aimed at restoring BCNSB integrity and in vitro modelling of the neurogliovascular system.

Patching Up the Permeability: The Role of Stem Cells in Lessening Neurovascular Damage in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a debilitating disease with poor prognosis. The pathophysiology of ALS is commonly debated, with theories involving inflammation, glutamate excitotoxity, oxidative stress, mitochondria malfunction, neurofilament accumulation, inadequate nutrients or growth factors, and changes in glial support predominating. These underlying pathological mechanisms, however, act together to weaken the blood brain barrier and blood spinal cord barrier, collectively considered as the blood central nervous system barrier (BCNSB). Altering the impermeability of the BCNSB impairs the neurovascular unit, or interdependent relationship between the brain and advances the concept that ALS is has a significant neurovascular component contributing to its degenerative presentation. This unique categorization of ALS opens a variety of treatment options targeting the reestablishment of BCNSB integrity. This review will critically assess the evidence implicating the significant neurovascular components of ALS pathophysiology, while also offering an in-depth discussion regarding the use of stem cells to repair these pathological changes within the neurovascular unit.

The Role of Extracellular Matrix in Human Neurodegenerative Diseases

The dense neuropil of the central nervous system leaves only limited space for extracellular substances free. The advent of immunohistochemistry, soon followed by advanced diagnostic tools, enabled us to explore the biochemical heterogeneity and compartmentalization of the brain extracellular matrix in exploratory and clinical research alike. The composition of the extracellular matrix is critical to shape neuronal function; changes in its assembly trigger or reflect brain/spinal cord malfunction. In this study, we focus on extracellular matrix changes in neurodegenerative disorders. We summarize its phenotypic appearance and biochemical characteristics, as well as the major enzymes which regulate and remodel matrix establishment in disease. The specifically built basement membrane of the central nervous system, perineuronal nets and perisynaptic axonal coats can protect neurons from toxic agents, and biochemical analysis revealed how the individual glycosaminoglycan and proteoglycan components interact with these molecules. Depending on the site, type and progress of the disease, select matrix components can either proactively trigger the formation of disease-specific harmful products, or reactively accumulate, likely to reduce tissue breakdown and neuronal loss. We review the diagnostic use and the increasing importance of medical screening of extracellular matrix components, especially enzymes, which informs us about disease status and, better yet, allows us to forecast illness.

Sarm1 knockout modifies biomarkers of neurodegeneration and spinal cord circuitry but not disease progression in the mSOD1G93A mouse model of ALS

The mechanisms underlying the loss of motor neuron axon integrity in amyotrophic lateral sclerosis (ALS) are unclear. SARM1 has been identified as a genetic risk variant in sporadic ALS, and the SARM1 protein is a key mediator of axon degeneration. To investigate the role of SARM1 in ALS-associated axon degeneration, we knocked out Sarm1 (Sarm1^KO) in mSOD1^G93ATg (mSOD1) mice. Animals were monitored for ALS disease onset and severity, with motor function assessed at pre-symptomatic and late-stage disease and lumbar spinal cord and sciatic nerve harvested for immunohistochemistry at endpoint (20 weeks). Serum was collected monthly to assess protein concentrations of biomarkers linked to axon degeneration (neurofilament light (NFL) and tau), and astrogliosis (glial fibrillary acidic protein (GFAP)), using single molecule array (Simoa®) technology. Overall, loss of Sarm1 in mSOD1 mice did not slow or delay symptom onset, failed to improve functional declines, and failed to protect motor neurons. Serum NFL levels in mSOD1 mice increased between 8 -12 and 16-20 weeks of age, with the later increase significantly reduced by loss of SARM1. Similarly, loss of SARM1 significantly reduced an increase in serum GFAP between 16 and 20 weeks of age in mSOD1 mice, indicating protection of both global axon degeneration and astrogliosis. In the spinal cord, Sarm1 deletion protected against loss of excitatory VGluT2-positive puncta and attenuated astrogliosis in mSOD1 mice. In the sciatic nerve, absence of SARM1 in mSOD1 mice restored the average area of phosphorylated neurofilament reactivity towards WT levels. Together these data suggest that Sarm1^KO in mSOD1 mice is not sufficient to ameliorate functional decline or motor neuron loss but does alter serum biomarker levels and provide protection to axons and glutamatergic synapses. This indicates that treatments targeting SARM1 could warrant further investigation in ALS, potentially as part of a combination therapy.

Taking Advantages of Blood–Brain or Spinal Cord Barrier Alterations or Restoring Them to Optimize Therapy in ALS?

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder that still lacks an efficient therapy. The barriers between the central nervous system (CNS) and the blood represent a major limiting factor to the development of drugs for CNS diseases, including ALS. Alterations of the blood–brain barrier (BBB) or blood–spinal cord barrier (BSCB) have been reported in this disease but still require further investigations. Interestingly, these alterations might be involved in the complex etiology and pathogenesis of ALS. Moreover, they can have potential consequences on the diffusion of candidate drugs across the brain. The development of techniques to bypass these barriers is continuously evolving and might open the door for personalized medical approaches. Therefore, identifying robust and non-invasive markers of BBB and BSCB alterations can help distinguish different subgroups of patients, such as those in whom barrier disruption can negatively affect the delivery of drugs to their CNS targets. The restoration of CNS barriers using innovative therapies could consequently present the advantage of both alleviating the disease progression and optimizing the safety and efficiency of ALS-specific therapies.

A Historical Review of Brain Drug Delivery

The history of brain drug delivery is reviewed beginning with the first demonstration, in 1914, that a drug for syphilis, salvarsan, did not enter the brain, due to the presence of a blood-brain barrier (BBB). Owing to restricted transport across the BBB, FDA-approved drugs for the CNS have been generally limited to lipid-soluble small molecules. Drugs that do not cross the BBB can be re-engineered for transport on endogenous BBB carrier-mediated transport and receptor-mediated transport systems, which were identified during the 1970s-1980s. By the 1990s, a multitude of brain drug delivery technologies emerged, including trans-cranial delivery, CSF delivery, BBB disruption, lipid carriers, prodrugs, stem cells, exosomes, nanoparticles, gene therapy, and biologics. The advantages and limitations of each of these brain drug delivery technologies are critically reviewed.

Breached Barriers: A Scoping Review of Blood-Central Nervous System Barrier Pathology in Amyotrophic Lateral Sclerosis

Introduction

Recent studies have implicated changes in the blood-central nervous system barriers (BCNSB) in amyotrophic lateral sclerosis (ALS). The objective of this scoping review is to synthesize the current evidence for BCNSB structure and functional abnormalities in ALS studies and propose how BCNSB pathology may impact therapeutic development.

Methods

A literature search was conducted using Ovid Medline, EMBASE, and Web of Science, from inception to November 2021 and limited to entries in English language. Simplified search strategy included the terms ALS/motor neuron disease and [BCNSB or blood-brain barrier (BBB) or blood-spinal cord barrier (BSCB)]. Henceforth, BCNSB is used as a term that is inclusive of the BBB and BSCB. Four independent reviewers conducted a title and abstract screening, hand-searched the reference lists of review papers, and performed a full text review of eligible studies. Included studies were original peer-reviewed full text publications, evaluating the structure and function of the BCNSB in preclinical models of ALS, clinical ALS, or postmortem human ALS tissue. There was no restriction on study design. The four reviewers independently extracted the data.

Results

The search retrieved 2,221 non-duplicated articles and 48 original studies were included in the synthesis. There was evidence that the integrity of the BCNSB is disrupted throughout the course of the disease in rodent models, beginning prior to symptom onset and detectable neurodegeneration. Increased permeability, pharmacoresistance with upregulated efflux transporters, and morphological changes in the supporting cells of the BCNSB, including pericytes, astrocytes, and endothelial cells were observed in animal models. BCNSB abnormalities were also demonstrated in postmortem studies of ALS patients. Therapeutic interventions targeting BCNSB dysfunction were associated with improved motor neuron survival in animal models of ALS.

Conclusion

BCNSB structural and functional abnormalities are likely implicated in ALS pathophysiology and may occur upstream to neurodegeneration. Promising therapeutic strategies targeting BCNSB dysfunction have been tested in animals and can be translated into ALS clinical trials.

The Potential Role of Peripheral Oxidative Stress on the Neurovascular Unit in Amyotrophic Lateral Sclerosis Pathogenesis: A Preliminary Report from Human and In Vitro Evaluations

Oxidative stress, the alteration of mitochondrial function, and changes in the neurovascular unit (NVU) could play a role in Amyotrophic Lateral Sclerosis (ALS) pathogenesis. Our aim was to analyze the plasma redox system and nitric oxide (NO) in 25 ALS new-diagnosed patients and five healthy controls and the effects of plasma on the peroxidation/mitochondrial function in human umbilical cord-derived endothelial vascular cells (HUVEC) and astrocytes. In plasma, thiobarbituric acid reactive substances (TBARS), glutathione (GSH), and nitric oxide (NO) were analyzed by using specific assays. In HUVEC/astrocytes, the effects of plasma on the release of mitochondrial reactive oxygen species (mitoROS) and NO, viability, and mitochondrial membrane potential were investigated. In the plasma of ALS patients, an increase in TBARS and a reduction in GSH and NO were found. In HUVEC/astrocytes treated with a plasma of ALS patients, mitoROS increased, whereas cell viability and mitochondrial membrane potential decreased. Our results show that oxidative stress and NVU play a central role in ALS and suggest that unknown plasma factors could be involved in the disease pathogenesis. Quantifiable changes in ALS plasma related to redox state alterations can possibly be used for early diagnosis.

Comprehensive Research on Past and Future Therapeutic Strategies Devoted to Treatment of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a rapidly debilitating fatal neurodegenerative disorder, causing muscle atrophy and weakness, which leads to paralysis and eventual death. ALS has a multifaceted nature affected by many pathological mechanisms, including oxidative stress (also via protein aggregation), mitochondrial dysfunction, glutamate-induced excitotoxicity, apoptosis, neuroinflammation, axonal degeneration, skeletal muscle deterioration and viruses. This complexity is a major obstacle in defeating ALS. At present, riluzole and edaravone are the only drugs that have passed clinical trials for the treatment of ALS, notwithstanding that they showed modest benefits in a limited population of ALS. A dextromethorphan hydrobromide and quinidine sulfate combination was also approved to treat pseudobulbar affect (PBA) in the course of ALS. Globally, there is a struggle to prevent or alleviate the symptoms of this neurodegenerative disease, including implementation of antisense oligonucleotides (ASOs), induced pluripotent stem cells (iPSCs), CRISPR-9/Cas technique, non-invasive brain stimulation (NIBS) or ALS-on-a-chip technology. Additionally, researchers have synthesized and screened new compounds to be effective in ALS beyond the drug repurposing strategy. Despite all these efforts, ALS treatment is largely limited to palliative care, and there is a strong need for new therapeutics to be developed. This review focuses on and discusses which therapeutic strategies have been followed so far and what can be done in the future for the treatment of ALS.

Altered Blood-Brain Barrier and Blood-Spinal Cord Barrier Dynamics in Amyotrophic Lateral Sclerosis: Impact on Medication Efficacy and Safety

The access of drugs into the central nervous system (CNS) is regulated by the blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB). A large body of evidence supports perturbation of these barriers in neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. Modifications to the BBB and BSCB are also reported in amyotrophic lateral sclerosis (ALS), albeit these modifications have received less attention relative to those in other neurodegenerative diseases. Such alterations to the BBB and BSCB have the potential to impact on CNS exposure of drugs in ALS, modulating the effectiveness of drugs intended to reach the brain and the toxicity of drugs that are not intended to reach the brain. Given the clinical importance of these phenomena, this review will summarise reported modifications to the BBB and BSCB in ALS, discuss their impact on CNS drug exposure and suggest further research directions so as to optimise medicine use in people with ALS.

The blood-brain barrier in aging and neurodegeneration

The blood-brain barrier (BBB) is vital for maintaining brain homeostasis by enabling an exquisite control of exchange of compounds between the blood and the brain parenchyma. Moreover, the BBB prevents unwanted toxins and pathogens from entering the brain. This barrier, however, breaks down with age and further disruption is a hallmark of many age-related disorders. Several drugs have been explored, thus far, to protect or restore BBB function. With the recent connection between the BBB and gut microbiota, microbial-derived metabolites have been explored for their capabilities to protect and restore BBB physiology. This review, will focus on the vital components that make up the BBB, dissect levels of disruption of the barrier, and discuss current drugs and therapeutics that maintain barrier integrity and the recent discoveries of effects microbial-derived metabolites have on BBB physiology.

Blood-Spinal Cord Barrier: Its Role in Spinal Disorders and Emerging Therapeutic Strategies

The blood-spinal cord barrier (BSCB) has been long thought of as a functional equivalent to the blood-brain barrier (BBB), restricting blood flow into the spinal cord. The spinal cord is supported by various disc tissues that provide agility and has different local immune responses compared to the brain. Though physiologically, structural components of the BSCB and BBB share many similarities, the clinical landscape significantly differs. Thus, it is crucial to understand the composition of BSCB and also to establish the cause–effect relationship with aberrations and spinal cord dysfunctions. Here, we provide a descriptive analysis of the anatomy, current techniques to assess the impairment of BSCB, associated risk factors and impact of spinal disorders such as spinal cord injury (SCI), amyotrophic lateral sclerosis (ALS), peripheral nerve injury (PNI), ischemia reperfusion injury (IRI), degenerative cervical myelopathy (DCM), multiple sclerosis (MS), spinal cavernous malformations (SCM) and cancer on BSCB dysfunction. Along with diagnostic and mechanistic analyses, we also provide an up-to-date account of available therapeutic options for BSCB repair. We emphasize the need to address BSCB as an individual entity and direct future research towards it.

Basal lamina changes in neurodegenerative disorders

BACKGROUND

Neurodegenerative disorders are a group of age-associated diseases characterized by progressive degeneration of the structure and function of the CNS. Two key pathological features of these disorders are blood-brain barrier (BBB) breakdown and protein aggregation.

MAIN BODY

The BBB is composed of various cell types and a non-cellular component---the basal lamina (BL). Although how different cells affect the BBB is well studied, the roles of the BL in BBB maintenance and function remain largely unknown. In addition, located in the perivascular space, the BL is also speculated to regulate protein clearance via the meningeal lymphatic/glymphatic system. Recent studies from our laboratory and others have shown that the BL actively regulates BBB integrity and meningeal lymphatic/glymphatic function in both physiological and pathological conditions, suggesting that it may play an important role in the pathogenesis and/or progression of neurodegenerative disorders. In this review, we focus on changes of the BL and its major components during aging and in neurodegenerative disorders, including Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). First, we introduce the vascular and lymphatic systems in the CNS. Next, we discuss the BL and its major components under homeostatic conditions, and summarize their changes during aging and in AD, PD, and ALS in both rodents and humans. The functional significance of these alterations and potential therapeutic targets are also reviewed. Finally, key challenges in the field and future directions are discussed.

CONCLUSIONS

Understanding BL changes and the functional significance of these changes in neurodegenerative disorders will fill the gap of knowledge in the field. Our goal is to provide a clear and concise review of the complex relationship between the BL and neurodegenerative disorders to stimulate new hypotheses and further research in this field.

MG53 Preserves Neuromuscular Junction Integrity and Alleviates ALS Disease Progression

Respiratory failure from progressive respiratory muscle weakness is the most common cause of death in amyotrophic lateral sclerosis (ALS). Defects in neuromuscular junctions (NMJs) and progressive NMJ loss occur at early stages, thus stabilizing and preserving NMJs represents a potential therapeutic strategy to slow ALS disease progression. Here we demonstrate that NMJ damage is repaired by MG53, an intrinsic muscle protein involved in plasma membrane repair. Compromised diaphragm muscle membrane repair and NMJ integrity are early pathological events in ALS. Diaphragm muscles from ALS mouse models show increased susceptibility to injury and intracellular MG53 aggregation, which is also a hallmark of human muscle samples from ALS patients. We show that systemic administration of recombinant human MG53 protein in ALS mice protects against injury to diaphragm muscle, preserves NMJ integrity, and slows ALS disease progression. As MG53 is present in circulation in rodents and humans under physiological conditions, our findings provide proof-of-concept data supporting MG53 as a potentially safe and effective therapy to mitigate ALS progression.

Beneficial Effects of Transplanted Human Bone Marrow Endothelial Progenitors on Functional and Cellular Components of Blood-Spinal Cord Barrier in ALS Mice

Convincing evidence of blood-spinal cord barrier (BSCB) alterations has been demonstrated in amyotrophic lateral sclerosis (ALS) and barrier repair is imperative to prevent motor neuron dysfunction. We showed benefits of human bone marrow-derived CD34+ cells (hBM34+) and endothelial progenitor cells (hBM-EPCs) intravenous transplantation into symptomatic G93A SOD1 mutant mice on barrier reparative processes. These gains likely occurred by replacement of damaged endothelial cells, prolonging motor neuron survival. However, additional investigations are needed to confirm the effects of administered cells on integrity of the microvascular endothelium. The aim of this study was to determine tight junction protein levels, capillary pericyte coverage, microvascular basement membrane, and endothelial filamentous actin (F-actin) status in spinal cord capillaries of G93A SOD1 mutant mice treated with human bone marrow-derived stem cells. Tight junction proteins were detected in the spinal cords of cell-treated versus non-treated mice via Western blotting at four weeks after transplant. Capillary pericyte, basement membrane laminin, and endothelial F-actin magnitudes were determined in cervical/lumbar spinal cord tissues in ALS mice, including controls, by immunohistochemistry and fluorescent staining. Results showed that cell-treated versus media-treated ALS mice substantially increased tight junction protein levels, capillary pericyte coverage, basement membrane laminin immunoexpressions, and endothelial cytoskeletal F-actin fluorescent expressions. The greatest benefits were detected in mice receiving hBM-EPCs versus hBM34+ cells. These study results support treatment with a specific cell type derived from human bone marrow toward BSCB repair in ALS. Thus, hBM-EPCs may be advanced for clinical applications as a cell-specific approach for ALS therapy through restored barrier integrity.

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.

Blood-Brain Barrier and Neurodegenerative Diseases-Modeling with iPSC-Derived Brain Cells

The blood-brain barrier (BBB) regulates the delivery of oxygen and important nutrients to the brain through active and passive transport and prevents neurotoxins from entering the brain. It also has a clearance function and removes carbon dioxide and toxic metabolites from the central nervous system (CNS). Several drugs are unable to cross the BBB and enter the CNS, adding complexity to drug screens targeting brain disorders. A well-functioning BBB is essential for maintaining healthy brain tissue, and a malfunction of the BBB, linked to its permeability, results in toxins and immune cells entering the CNS. This impairment is associated with a variety of neurological diseases, including Alzheimer's disease and Parkinson's disease. Here, we summarize current knowledge about the BBB in neurodegenerative diseases. Furthermore, we focus on recent progress of using human-induced pluripotent stem cell (iPSC)-derived models to study the BBB. We review the potential of novel stem cell-based platforms in modeling the BBB and address advances and key challenges of using stem cell technology in modeling the human BBB. Finally, we highlight future directions in this area.

TDP-43 and Phosphorylated TDP-43 Levels in Paired Plasma and CSF Samples in Amyotrophic Lateral Sclerosis

Objective: The aim of this study was to measure both plasma and cerebrospinal fluid (CSF) TAR DNA-binding protein 43 (TDP-43) and phosphorylated TDP-43 (pTDP-43) levels in sporadic amyotrophic lateral sclerosis (sALS) patients, and to compare them with that of healthy controls. The correlation between plasma or CSF TDP-43/pTDP-43 and clinical indicators of ALS patients was assessed. Methods: Paired plasma and CSF TDP-43/pTDP-43 levels in 69 ALS patients and 59 healthy controls were measured by sandwich ELISA. Time to generalization (TTG), an indicator suggested that the time of symptoms spreading from spinal or bulbar localization to both, was evaluated in all patients screened for mutations in genes associated with ALS. Results: Both of the plasma TDP-43 and pTDP-43 levels were significantly higher in ALS patients than HCs (P < 0.001). The pTDP-43/TDP-43 ratios in plasma were significantly higher in HCs than ALS patients (P < 0.001). The area under the curve (AUC) value was 0.924 for plasma TDP-43 level, with a 91.3% sensitivity and 91.5% specificity. Moreover, the correlation between plasma and CSF TDP-43 was observed in each ALS patient (r = 0.195, P = 0.027). A correlation between CSF pTDP-43 levels and the ALSFRS-R (r = -0.245; P = 0.042) was established. A correlation was observed between plasma TDP-43 levels and TTG in ALS patients, which indicated that high levels of plasma TDP-43 correlated with prolonged TTG (r = 0.415; P = 0.004). Conclusion: The plasma TDP-43 and pTDP-43 levels might play an important role in diagnosis in the future study of ALS. The plasma TDP-43 might differentiate ALS and HC groups based on high sensitivity and specificity, and as an indicator of progression of disease.

Advancing Stem Cell Therapy for Repair of Damaged Lung Microvasculature in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal disease of motor neuron degeneration in the brain and spinal cord. Progressive paralysis of the diaphragm and other respiratory muscles leading to respiratory dysfunction and failure is the most common cause of death in ALS patients. Respiratory impairment has also been shown in animal models of ALS. Vascular pathology is another recently recognized hallmark of ALS pathogenesis. Central nervous system (CNS) capillary damage is a shared disease element in ALS rodent models and ALS patients. Microvascular impairment outside of the CNS, such as in the lungs, may occur in ALS, triggering lung damage and affecting breathing function. Stem cell therapy is a promising treatment for ALS. However, this therapeutic strategy has primarily targeted rescue of degenerated motor neurons. We showed functional benefits from intravenous delivery of human bone marrow (hBM) stem cells on restoration of capillary integrity in the CNS of an superoxide dismutase 1 (SOD1) mouse model of ALS. Due to the widespread distribution of transplanted cells via this route, administered cells may enter the lungs and effectively restore microvasculature in this respiratory organ. Here, we provided preliminary evidence of the potential role of microvasculature dysfunction in prompting lung damage and treatment approaches for repair of respiratory function in ALS. Our initial studies showed proof-of-principle that microvascular damage in ALS mice results in lung petechiae at the late stage of disease and that systemic transplantation of mainly hBM-derived endothelial progenitor cells shows potential to promote lung restoration via re-established vascular integrity. Our new understanding of previously underexplored lung competence in this disease may facilitate therapy targeting restoration of respiratory function in ALS.

Repeated infusion of mesenchymal stem cells maintain the condition to inhibit deteriorated motor function, leading to an extended lifespan in the SOD1G93A rat model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative fatal disorder in which motor neurons within the brain and spinal cord degenerate. A single infusion of mesenchymal stem cells (MSCs) delays disease progression by protecting motor neurons and restoring the blood-spinal cord barrier in the SOD1G93A transgenic ALS rat model. However, the therapeutic effect of a single infusion of MSCs is transient and does not block disease progression. In this study, we demonstrated that repeated administration of MSCs (weekly, four times) increased the survival period, protected motor functions, and reduced deterioration of locomotor activity compared to a single infusion and vehicle infusion, after which rats displayed progressive deterioration of hind limb function. We also compared the days until gait ability was lost in rats and found that the repeated-infused group maintained gait ability compared to the single-infusion and vehicle-infusion groups. These results suggest that repeated administration of MSCs may prevent the deterioration of motor function and extend the lifespan in ALS.

Intravenous infusion of mesenchymal stem cells delays disease progression in the SOD1G93A transgenic amyotrophic lateral sclerosis rat model

ALS is a devastating neurodegenerative disease with few curative strategies. Both sporadic and familial ALS display common clinical features that show progressive paralysis. The pathogenesis remains unclear, but disruption of the blood-spinal cord barrier (BSCB) may contribute to the degeneration of motor neurons. Thus, restoration of the disrupted BSCB and neuroprotection for degenerating motor neurons could be therapeutic targets. We tested the hypothesis that an intravenous infusion of MSCs would delay disease progression through the preservation of BSCB function and increased expression of a neurotrophic factor, neurturin, in SOD1G93A ALS rats. When the open-field locomotor function was under 16 on the Basso, Beattie, and Bresnahan (BBB) scoring scale, the rats were randomized into two groups; one received an intravenous infusion of MSCs, while the other received vehicle alone. Locomotor function was recorded using BBB scoring and rotarod testing. Histological analyses, quantitative reverse transcription-polymerase chain reaction (qRT-PCR), were performed. The MSC group exhibited reduced deterioration of locomotor activity compared to the vehicle group, which displayed progressive deterioration of hind limb function. We observed the protection of motor neuron loss and preservation of microvasculature using Evans blue leakage and immunohistochemical analyses in the MSC group. Confocal microscopy revealed infused green fluorescent protein+ (GFP+) MSCs in the spinal cord, and the GFP gene was detected by nested PCR. Neurturin expression levels were significantly higher in the MSC group. Thus, restoration of the BSCB and the protection of motor neurons might be contributing mechanisms to delay disease progression in SOD1G93A ALS rats.

Decreased blood CD4+ T lymphocyte helps predict cognitive impairment in patients with amyotrophic lateral sclerosis

Background

ALS patients have changed peripheral immunity. It is unknown whether peripheral immunity is related to cognitive dysfunction in ALS patients.

Objective

To explore the relationship between the peripheral blood lymphocyte subsets and the cognitive status in ALS patients.

Methods

Among 81 ALS patients, we compared the demographic, clinical, and peripheral levels of total T lymphocyte, CD4+ T lymphocyte, CD8+ T lymphocyte, B lymphocyte, and NK cell between those with cognitive impairment (ALS-ci) and those without (ALS-nci). The cognitive status was evaluated via the Chinese version of the Edinburgh cognitive and behavioral screen (ECAS). Significant predictors of cognitive impairment in univariate logistic regression analysis were further examined using multivariate logistic regression analysis.

Results

39.5% of all ALS patients had cognitive impairment. The ALS-ci group had shorter education time, older age at both symptom onset and testing, longer disease duration, and lower levels of peripheral total, CD4+, and CD8+ T lymphocyte and B lymphocyte than the ALS-nci group. Frequency of behavioral impairment did not differ between the two groups. While parameters with significant differences identified by group comparison were also significant predictors of cognitive impairment in univariate logistic regression analysis except the level of B lymphocyte, only older age at testing, education time less than 9 years, and lower level of CD4+ T lymphocyte remained significant in multivariate logistic regression analysis. The predictive model combining these three parameters had an area under the receiver operating characteristic curve value of 0.842 with a sensitivity of 90.6% and a specificity of 67.3%.

Conclusion

In Chinese ALS patients, blood CD4+ T lymphocyte might help evaluate cognitive impairment along with age and education level.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02185-w.

Disease-Induced Modulation of Drug Transporters at the Blood-Brain Barrier Level

The blood–brain barrier (BBB) is a highly selective and restrictive semipermeable network of cells and blood vessel constituents. All components of the neurovascular unit give to the BBB its crucial and protective function, i.e., to regulate homeostasis in the central nervous system (CNS) by removing substances from the endothelial compartment and supplying the brain with nutrients and other endogenous compounds. Many transporters have been identified that play a role in maintaining BBB integrity and homeostasis. As such, the restrictive nature of the BBB provides an obstacle for drug delivery to the CNS. Nevertheless, according to their physicochemical or pharmacological properties, drugs may reach the CNS by passive diffusion or be subjected to putative influx and/or efflux through BBB membrane transporters, allowing or limiting their distribution to the CNS. Drug transporters functionally expressed on various compartments of the BBB involve numerous proteins from either the ATP-binding cassette (ABC) or the solute carrier (SLC) superfamilies. Pathophysiological stressors, age, and age-associated disorders may alter the expression level and functionality of transporter protein elements that modulate drug distribution and accumulation into the brain, namely, drug efficacy and toxicity. This review focuses and sheds light on the influence of inflammatory conditions and diseases such as Alzheimer’s disease, epilepsy, and stroke on the expression and functionality of the BBB drug transporters, the consequential modulation of drug distribution to the brain, and their impact on drug efficacy and toxicity.

A Novel Anti-Inflammatory d-Peptide Inhibits Disease Phenotype Progression in an ALS Mouse Model

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterised by selective neuronal death in the brain stem and spinal cord. The cause is unknown, but an increasing amount of evidence has firmly certified that neuroinflammation plays a key role in ALS pathogenesis. Neuroinflammation is a pathological hallmark of several neurodegenerative disorders and has been implicated as driver of disease progression. Here, we describe a treatment study demonstrating the therapeutic potential of a tandem version of the well-known all-d-peptide RD2 (RD2RD2) in a transgenic mouse model of ALS (SOD1*G93A). Mice were treated intraperitoneally for four weeks with RD2RD2 vs. placebo. SOD1*G93A mice were tested longitudinally during treatment in various behavioural and motor coordination tests. Brain and spinal cord samples were investigated immunohistochemically for gliosis and neurodegeneration. RD2RD2 treatment in SOD1*G93A mice resulted not only in a reduction of activated astrocytes and microglia in both the brain stem and lumbar spinal cord, but also in a rescue of neurons in the motor cortex. RD2RD2 treatment was able to slow progression of the disease phenotype, especially the motor deficits, to an extent that during the four weeks treatment duration, no significant progression was observed in any of the motor experiments. Based on the presented results, we conclude that RD2RD2 is a potential therapeutic candidate against ALS.

Ca2+ homeostasis in brain microvascular endothelial cells

Blood brain barrier (BBB) is formed by the brain microvascular endothelial cells (BMVECs) lining the wall of brain capillaries. Its integrity is regulated by multiple mechanisms, including up/downregulation of tight junction proteins or adhesion molecules, altered Ca²⁺ homeostasis, remodeling of cytoskeleton, that are confined at the level of BMVECs. Beside the contribution of BMVECs to BBB permeability changes, other cells, such as pericytes, astrocytes, microglia, leukocytes or neurons, etc. are also exerting direct or indirect modulatory effects on BBB. Alterations in BBB integrity play a key role in multiple brain pathologies, including neurological (e.g. epilepsy) and neurodegenerative disorders (e.g. Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis etc.). In this review, the principal Ca²⁺ signaling pathways in brain microvascular endothelial cells are discussed and their contribution to BBB integrity is emphasized. Improving the knowledge of Ca²⁺ homeostasis alterations in BMVECa is fundamental to identify new possible drug targets that diminish/prevent BBB permeabilization in neurological and neurodegenerative disorders.

ALS-causing SOD1 mutants regulate occludin phosphorylation/ubiquitination and endocytic trafficking via the ITCH/Eps15/Rab5 axis

It is increasingly recognized that blood-spinal cord barrier (BSCB) breakdown is a hallmark of amyotrophic lateral sclerosis (ALS). BSCB integrity is disrupted prior to disease onset. Occludin, as the functional component of the endothelial barrier, is downregulated in mouse models expressing ALS-linked superoxide dismutase-1 (SOD1) mutants. However, the molecular mechanisms underlying the regulation of occludin expression remain elusive. Here, using SOD1^G93A transgenic mice and endothelial cells expressing SOD1 mutants of different biochemical characteristics, we found that the SOD1 mutation disrupted endothelial barrier integrity and that the occludin expression level was downregulated with disease progression. Our mechanistic studies revealed that abnormal reactive oxygen species (ROS) in mutant SOD1-expressing cells induced occludin phosphorylation, which facilitated the subsequent occludin ubiquitination mediated by the E3 ligase ITCH. Moreover, ubiquitinated occludin interacted with Eps15 to initiate its internalization, then trafficked to Rab5-positive vesicles and be degraded by proteasomes, resulting in a reduction in cell surface localization and total abundance. Notably, either ITCH or Eps15 knockdown was sufficient to rescue occludin degradation and ameliorate endothelial barrier disruption. In conclusion, our study reveals a novel mechanism of occludin degradation mediated by ALS-causing SOD1 mutants and demonstrates a role for occludin in regulating BSCB integrity.

Detection of endothelial cell-associated human DNA reveals transplanted human bone marrow stem cell engraftment into CNS capillaries of ALS mice

Repairing the altered blood-CNS-barrier in amyotrophic lateral sclerosis (ALS) is imperative to prevent entry of detrimental blood-borne substances into the CNS. Cell transplantation with the goal of replacing damaged endothelial cells (ECs) may be a new therapeutic approach for barrier restoration. We showed positive effects of human bone marrow-derived CD34+ cells (hBM34+) and endothelial progenitor cells (hBM-EPCs) intravenous transplantation into symptomatic G93A SOD1 mutant mice on barrier reparative processes. These benefits mainly occurred by administered cells engraftment into vascular walls in ALS mice; however, additional studies are needed to confirm cell engraftment within capillaries. The aim of this investigation was to determine the presence of human DNA within microvascular ECs isolated from the CNS tissues of G93A SOD1 mutant mice treated with human bone marrow-derived stem cells. The CNS tissues were obtained from previously cell-treated and media-treated G93A mice at 17 weeks of age. Real-time PCR (RT-PCR) assay for detection of human DNA was performed in ECs isolated from mouse CNS tissue. Viability of these ECs was determined using the LIVE/DEAD viability/cytotoxicity assay. Results showed appropriate EC isolation as verified by immunoexpression of endothelial cell marker. Human DNA was detected in isolated ECs from cell-treated mice with greater concentrations in mice receiving hBM-EPCs vs. hBM34⁺ cells. Also, higher numbers of live ECs were determined in mice treated with hBM-EPCs vs. hBM34⁺ cells or media-injection. Results revealed that transplanted human cells engrafted into mouse capillary walls and efficaciously maintained endothelium function. These study results support our previous findings showing that intravenous administration of hBM-EPCs into symptomatic ALS mice was more beneficial than hBM34⁺ cell treatment in repair of barrier integrity, likely due to replacement of damaged ECs in mouse CNS vessels. Based on this evidence, hBM-EPCs may be advanced as a cell-specific approach for ALS therapy through restored CNS barrier integrity.

Effects of Exercise in Patients With Amyotrophic Lateral Sclerosis: A Systematic Review and Meta-Analysis

OBJECTIVE

The aim of this study was to systematically review the efficacy and safety of exercise in patients with amyotrophic lateral sclerosis (ALS).

DESIGN

Randomized controlled trials of exercises for ALS were searched in PubMed, EMBASE, Web of Science, Cochrane Library, China Biology Medicine database, China National Knowledge Internet, VIP database, and Wanfang database. The primary outcomes were functional ability, pulmonary function, and quality of life. The secondary outcomes were muscle strength, fatigue and adverse events. Meta-analysis was performed using the RevMan Version 5.3 software.

RESULTS

Seven randomized controlled trials including 322 patients with ALS met the inclusion criteria. Meta-analysis showed that the functional scores at long-term (standardized means difference, 0.47; 95% confidence interval, 0.08-0.86; P = 0.02) and forced vital capacity percentage predicted (mean difference, 1.71; 95% confidence interval, 0.10-3.31; P = 0.04) of patients with ALS in the exercise group were significantly higher than those in the group of no exercise or usual care. No significant difference was observed in muscle strength and quality of life. Endurance or aerobic exercise improved the functional scores of patients with ALS (standardized means difference, 0.36; 95% confidence interval, 0.04-0.68; P = 0.03). Exercise did not aggravate fatigue or result in adverse event.

CONCLUSION

Exercise can significantly improve the functional ability and pulmonary function of patients with ALS safely.

Multiplexed chemogenetics in astrocytes and motoneurons restore blood-spinal cord barrier in ALS

Chemogenetic motoneuron excitation and astrocyte GPCR-Gi signaling restore blood–spinal cord barrier, disrupted in four ALS mouse models, revealing its role in disease progression but not initiation.

Blood–spinal cord barrier (BSCB) disruption is thought to contribute to motoneuron (MN) loss in amyotrophic lateral sclerosis (ALS). It is currently unclear whether impairment of the BSCB is the cause or consequence of MN dysfunction and whether its restoration may be directly beneficial. We revealed that SOD1^G93A, FUS^ΔNLS, TDP43^G298S, and Tbk1^+/− ALS mouse models commonly shared alterations in the BSCB, unrelated to motoneuron loss. We exploit PSAM/PSEM chemogenetics in SOD1^G93A mice to demonstrate that the BSCB is rescued by increased MN firing, whereas inactivation worsens it. Moreover, we use DREADD chemogenetics, alone or in multiplexed form, to show that activation of Gi signaling in astrocytes restores BSCB integrity, independently of MN firing, with no effect on MN disease markers and dissociating them from BSCB disruption. We show that astrocytic levels of the BSCB stabilizers Wnt7a and Wnt5a are decreased in SOD1^G93A mice and strongly enhanced by Gi signaling, although further decreased by MN inactivation. Thus, we demonstrate that BSCB impairment follows MN dysfunction in ALS pathogenesis but can be reversed by Gi-induced expression of astrocytic Wnt5a/7a.

Central nervous system diseases associated with blood brain barrier breakdown - A Comprehensive update of existing literatures

Blood vessels that supply and feed the central nervous system (CNS) possess unique and exclusive properties, named as blood–brain barrier (BBB). It is responsible for tight regulation of the movement of ions, molecules, and cells between the blood and the brain thereby maintaining controlled chemical composition of the neuronal milieu required for appropriate functioning. It also protects the neural tissue from toxic plasma components, blood cells and pathogens from entering the brain. In this review the importance of BBB and its disruption causing brain pathology and progression to different neurological diseases like Alzheimer’s disease (AD), Parkinson’s disease (PD), Amyotrophic lateral sclerosis (ALS), Huntington’s disease (HD) etc. will be discussed.

A validated quantitative method for the assessment of neuroprotective barrier impairment in neurodegenerative disease models

The blood-brain barrier (BBB) and blood-spinal cord barrier (BSCB) are highly specialized structures that limit molecule entry from the blood and maintain homeostasis within the central nervous system (CNS). BBB and BSCB breakdown are associated with multiple neurodegenerative diseases. Given the key role of neuroprotective barrier impairment in neurodegeneration, it is important to identify an effective quantitative method to assess barrier integrity in animal models. In this study, we developed and validated a quantitative method for assessing BBB and BSCB integrity using sodium fluorescein, a compound that outperformed other fluorescent dyes. We demonstrated using this method that multiple CNS regions progressively increase in permeability in models of Huntington's disease and amyotrophic lateral sclerosis, whereas biphasic disruption occurred in a mouse model of Alzheimer's disease with disease progression. Collectively, we report a quantitative fluorometric marker with validated reproducible experimental methods that allows the effective assessment of BBB and BSCB integrity in animal models. This method could be useful to further the understanding of the contribution of these neuroprotective barriers to neurodegeneration processes.

Peripheral and Central Nervous System Immune Response Crosstalk in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by muscle weakness due to the degeneration of the upper and lower motor neurons. Neuroinflammation is known as a prominent pathological feature of ALS. Although neuroinflammation cannot trigger ALS, activated central nervous system (CNS) microglia and astrocytes, proinflammatory periphery monocytes/macrophages and T lymphocytes, and infiltrated monocytes/macrophages and T lymphocytes, as well as the immunoreactive molecules they release, are closely related to disease progression. The crosstalk between the peripheral and CNS immune components mentioned above significantly correlates with survival in patients with ALS. This review provides an update on the role of this crosstalk between the CNS and peripheral immune responses in ALS. Additionally, we discuss changes in the composition of gut microbiota because these can directly or indirectly influence this crosstalk. These recent advances may well provide innovative ways for targeting the molecules associated with this crosstalk and breaking the current treatment impasse in ALS.

Dysfunction of ABC transporters at the blood-brain barrier: Role in neurological disorders

ABC (ATP-binding cassette) transporters represent one of the largest and most diverse superfamily of proteins in living species, playing an important role in many biological processes such as cell homeostasis, cell signaling, drug metabolism and nutrient uptake. Moreover, using the energy generated from ATP hydrolysis, they mediate the efflux of endogenous and exogenous substrates from inside the cells, thereby reducing their intracellular accumulation. At present, 48 ABC transporters have been identified in humans, which were classified into 7 different subfamilies (A to G) according to their phylogenetic analysis. Nevertheless, the most studied members with importance in drug therapeutic efficacy and toxicity include P-glycoprotein (P-gp), a member of the ABCB subfamily, the multidrug-associated proteins (MPRs), members of the ABCC subfamily, and breast cancer resistance protein (BCRP), a member of the ABCG subfamily. They exhibit ubiquitous expression throughout the human body, with a special relevance in barrier tissues like the blood-brain barrier (BBB). At this level, they play a physiological function in tissue protection by reducing or limiting the brain accumulation of neurotoxins. Furthermore, dysfunction of ABC transporters, at expression and/or activity level, has been associated with many neurological diseases, including epilepsy, multiple sclerosis, Alzheimer's disease, and amyotrophic lateral sclerosis. Additionally, these transporters are strikingly associated with the pharmacoresistance to central nervous system (CNS) acting drugs, because they contribute to the decrease in drug bioavailability. This article reviews the signaling pathways that regulate the expression and activity of P-gp, BCRP and MRPs subfamilies of transporters, with particular attention at the BBB level, and their mis-regulation in neurological disorders.

6-Deoxyjacareubin, a natural compound preventing hypoxia-induced cell death, ameliorates neurodegeneration in a mouse model of familial amyotrophic lateral sclerosis

The central nervous system (CNS) uses a significant amount of oxygen for energy production. Decreased oxygen supply due to impaired blood supply critically damages the CNS. As chronic hypoxic conditions have diverse effects via the excessive production of reactive oxygen species, protection from hypoxic damage is important for cell survival. Recent studies have revealed that various markers of hypoxia are altered in age-related neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS), indicating the involvement of hypoxia. However, therapeutic strategies targeting hypoxia-induced pathways in ALS have not been developed yet. We previously screened small-molecule compounds that inhibit hypoxia-induced cell death and identified 6-deoxyjacareubin. We hypothesized that the modulation of hypoxia signaling by 6-deoxyjacareubin might protect motor neurons in ALS. Here, we show that 6-deoxyjacareubin indeed ameliorates neurodegeneration in a mouse model of familial ALS. Administration of 6-deoxyjacareubin to this familial ALS model significantly attenuated disease progression and improved locomotor dysfunction. We also found that 6-deoxyjacareubin reduced motor neuron loss and glial activation. Our results indicate that 6-deoxyjacareubin might serve as a potential therapeutic tool for ALS. Moreover, these results suggest that modulation of hypoxia signaling pathways provides a promising strategy to develop therapies for other types of neurodegenerative diseases also characterized by hypoxia.

The influence of metallothionein treatment and treadmill running exercise on disease onset and survival in SOD1G93A amyotrophic lateral sclerosis mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease, characterised by the degeneration of motor neurons innervating skeletal muscle. The mechanisms underlying neurodegeneration in ALS are not yet fully elucidated, and with current therapeutics only able to extend lifespan by a matter of months there is a clear need for novel therapies to increase lifespan and patient quality of life. Here, we evaluated whether moderate-intensity treadmill exercise and/or treatment with metallothionein-2 (MT2), a neuroprotective protein, could improve survival, behavioural or neuropathological outcomes in SOD1^G93A familial ALS mice. Six-week-old female SOD1^G93A mice were allocated to one of four treatment groups: MT2 injection, i.m.; moderate treadmill exercise; neither MT2 nor exercise; or both MT2 and exercise. MT2-treated mice survived around 3% longer than vehicle-treated mice, with this mild effect reaching statistical significance in Cox proportional hazards analysis once adjusted for potential confounders. Mixed model body weight trajectories over time indicated that MT2-treated mice, with or without exercise, reached maximum body weight at a later age, suggesting a delay in disease onset of around 4% compared to saline-treated mice. Exercise alone did not significantly increase survival or delay disease onset, and neither exercise nor MT2 substantially ameliorated gait abnormalities or muscle strength loss. We conclude that neither exercise nor MT2 treatment was detrimental in female SOD1^G93A mice, and further study could determine whether the mild effect of peripheral MT2 administration on disease onset and survival could be improved via direct administration of MT2 to the central nervous system.