Inflammation in neurodegenerative diseases – an update

A Long Shot? Could neurodegenerative disease be caused by a cyanobacterial toxin?

Amyotrophic lateral sclerosis (ALS) and Huntington disease (HD) are lethal neurodegenerative diseases affecting motor function. Though their etiology and pathology are distinct, recent evidence suggests commonalities between TAR DNA-binding protein (TDP-43), which is associated with 97% of ALS cases, and huntingtin (HTT), the causative protein of HD. ALS is a heterogeneous, lethal neurodegenerative disease characterized by the progressive loss of upper and lower motor neurons, as well as brainstem and spinal cord degeneration. The causes of ALS are complex, variable, and, in some cases, unknown, but most cases involve mislocalization of the protein TDP-43. In contrast, HD is a monogenic, autosomal dominant, lethal neurodegenerative disease caused by polyglutamine expansion in HTT protein and characterized by the progressive loss of neurons in the brain, particularly in the striatum, which results in motor, cognitive, and behavioral changes. Although HD is not typically associated with motor neuron loss, recent evidence suggests a link between HTT and TDP-43 within the context of both ALS and HD, as well as links to related neurodegenerative diseases, such as frontotemporal dementia (FTD) and spinocerebellar ataxia type 2 (SCA2). Herein, we discuss confirmed cases of concurrent ALS and HD and the overlap of underlying disease mechanisms that potentially contribute to the onset and progression of these two devastating neurodegenerative diseases, with a focus on commonalities between TDP-43 and HTT. We propose that elucidating these commonalities will aid in the identification of broad-spectrum disease risk factors and potential overlapping treatment targets.

EDITORIAL article Front. Neurosci., 06 January 2016Sec. Neurodegeneration Volume 9 - 2015 | https://doi.org/10.3389/fnins.2015.00489

Neurodegenerative diseases, including Alzheimer's, Parkinson's, and Huntington's diseases, are characterized by progressive neuronal dysfunction and loss. Recent evidence highlights the importance of the nuclear factor erythroid 2-related factor 2 (NRF2) pathway, a key regulator of cellular defense mechanisms, in maintaining neuronal health and function. A narrative literature search was conducted using PubMed, Scopus, Web of Science, and Google Scholar to identify relevant experimental, clinical, and review studies on NRF2 signaling, physical exercise, oxidative stress, muscle-brain crosstalk, and neurodegenerative diseases. Keywords included "NRF2", "Nrf2/Keap1/ARE", "physical exercise", "exercise-induced oxidative stress", "myokines", "exerkines", "Alzheimer's disease", "Parkinson's disease", "Huntington's disease", and "amyotrophic lateral sclerosis". NRF2 modulates the expression of a variety of antioxidant and cytoprotective genes, contributing to the protection of neurons against oxidative stress, inflammation, and protein aggregation, processes central to the pathogenesis of neurodegenerative diseases. Additionally, physical activity has been identified as a powerful modulator of NRF2 activation, with exercise offering neuroprotective effects through the induction of NRF2-mediated pathways. This review explores the interplay between NRF2 activation and physical exercise in the context of neurodegenerative diseases, detailing the molecular mechanisms by which exercise influences NRF2 activity to combat cellular damage and enhance neuroprotection. We discuss the therapeutic potential of combining exercise regimens with NRF2-targeted therapies, highlighting the promise of this dual approach in slowing disease progression, improving cognitive function, and enhancing quality of life in affected individuals. Furthermore, we examine the challenges and future directions for clinical implementation, including optimal exercise protocols and the development of NRF2-based pharmacological interventions. This review underscores the importance of NRF2 as a central mediator of neuroprotection and the therapeutic promise of physical activity in the management of neurodegenerative diseases.

Neural Stem Cells as a Therapeutic Approach for Amyotrophic Lateral Sclerosis

Rationale: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the progressive loss of motor neurons in the central nervous system (CNS). Non-neuronal cells, particularly astrocytes, have been recognized as pivotal contributors to ALS onset and progression. However, the underlying mechanisms of interactions between astrocytes and motor neurons during ALS remain unclear. Recent studies have identified the neuronal Hippo kinase mammalian sterile 20-like kinase 1 (MST1) as a key regulator of neurodegeneration in ALS. Yes-associated protein (YAP), a major downstream effector of the Hippo pathway, is predominantly expressed in astrocytes. However, the role of astrocytic YAP in ALS and its underlying mechanisms remain unexplored.Methods: To evaluate the function of YAP in ALS, we established a C9orf72-poly-GA mouse model (ALS mice) via intracerebroventricular injection of AAV viruses. Furthermore, mice with conditional knockout (CKO) of YAP in astrocytes (YAPGFAP-CKO mice) were generated and then YAPGFAP-CKO ALS mice and their littermate controls (YAPf/f ALS mice) were used as experimental subjects. Behavioral tests, immunostaining, Nissl staining, quantitative real-time PCR (qPCR), and Western blotting were used to assess the effects of astrocytic YAP deletion in ALS progression. In addition, we investigated the role and mechanism of astrocytic YAP in the pathogenesis of ALS by integrating RNA sequencing (RNA-seq) from primary cultured astrocytes with single-nucleus transcriptomic (snRNA-seq) from C9orf72-ALS/FTD patients. Then, in vitro experiments including primary cultured astrocytes and neurons were used to further elucidate the potential molecular mechanism of astrocytic YAP in ALS. Finally, we evaluated the therapeutic effects of the excitatory amino acid transporter-2 (EAAT2) activator LDN-212320 and the Hippo kinase MST1/2 inhibitor XMU-MP-1 as candidate treatments for ALS.Results: We found that YAP was upregulated and activated specifically in astrocytes, but not in neurons or microglia, within the motor cortex of ALS mice. Conditional knockout of YAP in astrocytes exacerbated motor deficits, neuronal loss, pathological translocation of TDP-43, inflammatory infiltration, and reduced astrocytic proliferation in ALS mice. Mechanistically, Wnts secreted by degenerating neurons and astrocytes activated YAP/β-catenin signaling and further promoted the expression of EAAT2 in astrocytes, which prevented neuronal glutamate excitotoxicity, neuronal loss, and motor dysfunction in ALS mice. Interestingly, treatment with LDN-212320 promoted EAAT2 expression and partially restored motor deficits and neuronal loss in YAPGFAP-CKO ALS mice. Finally, activation of YAP by XMU-MP-1 upregulated β-catenin and EAAT2 expression, and partially alleviated motor deficits and neurodegeneration in ALS mice.Conclusions: These results identify an unrecognized mechanism of self-protection in degenerating neurons mediated by astrocytic YAP through Wnts/β-catenin/EAAT2 signaling to prevent glutamate excitotoxicity of neurons in ALS mice, and provide a novel drug target for ALS.

The devastating age-dependent neurodegenerative disorders, including prevalent Alzheimer's (AD) and Parkinson's diseases (PD), as well as rare such as Huntington's chorea (HD) and Amyotrophic Lateral Sclerosis (ALS), affect millions of people worldwide.Their prevalence is projected to increase due to ageing of the population, with a corresponding increase in the associated socioeconomic impact.Currently, there is no disease-modifying therapy for any neurodegenerative disease.Symptomatic treatments are available for some conditions such as PD and HD, but the therapeutic benefits are transient and limited.Although the causative factors and clinical manifestations are distinct for each neurodegenerative disease, their molecular pathogeneses share common underlying factors, such as excessive levels of reactive oxygen species (ROS), largely due to mitochondrial impairment, neuroinflammation, and disturbances in protein homeostasis (proteostasis).This raises the exciting possibility for developing a universal treatment, targeting these common drivers of neurodegeneration.The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) orchestrates a major endogenous defense mechanism against oxidative and xenobiotic stress, and inflammation, and plays a role in the maintenance of mitochondrial function and cellular proteostasis, suggesting potential benefits of therapeutic targeting of Nrf2 to counteract neurodegeneration.Under stress condition(s), Nrf2 activates the transcriptional upregulation of a large network of cytoprotective genes, allowing adaptation and survival [1].The levels (and activity) of Nrf2 are tightly regulated through ubiquitination and proteasomal degradation mediated by several ubiquitin ligase systems, including Kelch-like ECHassociated protein 1 (Keap1)-Cullin3 (Cul3)/Rbx1, β-transducin repeats-containing protein (β-TrCP)-Cul1, and synoviolin (Hrd1) [2].Of these, Keap1 is the best-understood key negative regulator of Nrf2.Keap1 serves as a sensor for electrophiles and oxidants, which chemically modify specific cysteines in Keap1, resulting in conformational changes that protect Nrf2 from Keap1-directed degradation.As a

Macrophage-mediated inflammation and glial response in the skeletal muscle of a rat model of familial amyotrophic lateral sclerosis (ALS)

EDITORIAL article Front. Cell. Neurosci., 31 October 2013Sec. Cellular Neuropathology Volume 7 - 2013 | https://doi.org/10.3389/fncel.2013.00199

Control of neuroinflammation as a therapeutic strategy for amyotrophic lateral sclerosis and other neurodegenerative disorders

The role of astrocytes and microglia in neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) remains incompletely understood. In this issue of The EMBO Journal , Alami et al (2018) employ a sophisticated genetic system that allows precise temporal control of NF‐κB activation in astrocytes to demonstrate that the timing of astrocyte activation is a key determinant of disease progression. Their results suggest that astrocyte activation drives microglia proliferation and that this can amplify not only the protective microglial effects in the presymptomatic phase of ALS, but also the detrimental microglial effects in the symptomatic phase.

Amyotrophic lateral sclerosis (ALS) is a severe neuromuscular disease characterised by a progressive loss of motor neurons that usually results in paralysis and death within 2 to 5 years after disease onset. The pathophysiological mechanisms involved in ALS remain largely unknown and to date there is no effective treatment for this disease. Here, we review clinical and experimental evidence suggesting that dysregulation of copper homeostasis in the central nervous system is a crucial underlying event in motor neuron degeneration and ALS pathophysiology. We also review and discuss novel approaches seeking to target copper delivery to treat ALS. These novel approaches may be clinically relevant not only for ALS but also for other neurological disorders with abnormal copper homeostasis, such as Parkinson's, Huntington's and Prion diseases.

Neuronal loss is one of the striking causes of various central nervous system (CNS) disorders, including major neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and Amyotrophic lateral sclerosis (ALS). Although these diseases have different features and clinical manifestations, they share some common mechanisms of disease pathology. Progressive regional loss of neurons in patients is responsible for motor, memory, and cognitive dysfunctions, leading to disabilities and death. Neuronal cell death in neurodegenerative diseases is linked to various pathways and conditions. Protein misfolding and aggregation, mitochondrial dysfunction, generation of reactive oxygen species (ROS), and activation of the innate immune response are the most critical hallmarks of most common neurodegenerative diseases. Thus, endoplasmic reticulum (ER) stress, oxidative stress, and neuroinflammation are the major pathological factors of neuronal cell death. Even though the exact mechanisms are not fully discovered, the notable role of mentioned factors in neuronal loss is well known. On this basis, researchers have been prompted to investigate the neuroprotective effects of targeting underlying pathways to determine a promising therapeutic approach to disease treatment. This review provides an overview of the role of ER stress, oxidative stress, and neuroinflammation in neuronal cell death, mainly discussing the neuroprotective effects of targeting pathways or molecules involved in these pathological factors.

Objective:To estimate risks of neurodegenerative and psychiatric diseases among patients with amyotrophic lateral sclerosis (ALS) and their families.Methods:We conducted a register-based nested case-control study during 1990–2013 in Sweden to assess whether patients with ALS had higher risks of other neurodegenerative and psychiatric diseases before diagnosis. We included 3,648 patients with ALS and 36,480 age-, sex-, and county of birth–matched population controls. We further conducted a follow-up study of the cases and controls to assess the risks of other neurodegenerative and psychiatric diseases after ALS diagnosis. To assess the potential contribution of familial factors, we conducted similar studies for the relatives of patients with ALS and their controls.Results:Individuals with previous neurodegenerative or psychiatric diseases had a 49% increased risk of ALS (odds ratio 1.49, 95% confidence interval 1.35–1.66) compared to individuals without these diseases. After diagnosis, patients with ALS had increased risks of other neurodegenerative or psychiatric diseases (hazard ratio 2.90, 95% confidence interval 2.46–3.43) compared to individuals without ALS. The strongest associations were noted for frontotemporal dementia, Parkinson disease, other dementia, Alzheimer disease, neurotic disorders, depression, stress-related disorders, and drug abuse/dependence. First-degree relatives of patients with ALS had higher risk of neurodegenerative diseases, whereas only children of patients with ALS had higher risk of psychiatric disorders, compared to relatives of the controls.Conclusions:Familial aggregation of ALS and other neurodegenerative diseases implies a shared etiopathogenesis among all neurodegenerative diseases. The increased risk of psychiatric disorders among patients with ALS and their children might be attributable to nonmotor symptoms of ALS and severe stress response toward the diagnosis.

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