IL6 receptor358Ala variant and trans-signaling are disease modifiers in amyotrophic lateral sclerosis

Inflammatory signature in amyotrophic lateral sclerosis predicting disease progression

Experimental studies identified a role of neuroinflammation in the pathogenesis of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). However, the role of inflammatory molecules as diagnostic and prognostic biomarkers in patients with ALS is unclear. In this cross-sectional study, the cerebrospinal fluid (CSF) levels of a set of inflammatory cytokines and chemokines were analyzed in 56 newly diagnosed ALS patients and in 47 age- and sex-matched control patients without inflammatory or degenerative neurological disorders. The molecules analyzed included: interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9, IL-10, IL-12, IL-13, IL-17, granulocyte colony stimulating factor (GCSF), macrophage inflammatory protein (MIP)-1a, MIP-1b, tumor necrosis factors (TNF), eotaxin. Principal component analysis (PCA) was used to explore possible associations between CSF molecules and ALS diagnosis. In addition, we analyzed the association between CSF cytokine profiles and clinical characteristics, including the disease progression rate score, and peripheral inflammation assessed using the Neutrophil-to-lymphocyte ratio (NLR). PCA identified six principal components (PCs) explaining 70.67% of the total variance in the CSF cytokine set. The principal component (PC1) explained 26.8% of variance and showed a positive load with CSF levels of IL-9, IL-4, GCSF, IL-7, IL-17, IL-13, IL-6, IL-1β, TNF, and IL-2. Logistic regression showed a significant association between PC1 and ALS diagnosis. In addition, in ALS patients, the same component was significantly associated with higher disease progression rate score and positively correlated with NLR. CSF inflammatory activation in present in ALS at the time of diagnosis and may characterize patients at higher risk for disease progression.

ATH-1105, a small-molecule positive modulator of the neurotrophic HGF system, is neuroprotective, preserves neuromotor function, and extends survival in preclinical models of ALS

Introduction

Amyotrophic lateral sclerosis (ALS), a progressive and fatal neurodegenerative disorder, primarily affects the motor neurons of the brain and spinal cord. Like other neurodegenerative conditions, ongoing pathological processes such as increased inflammation, excitotoxicity, and protein accumulation contribute to neuronal death. Hepatocyte growth factor (HGF) signaling through the MET receptor promotes pro-survival, anti-apoptotic, and anti-inflammatory effects in multiple cell types, including the neurons and support cells of the nervous system. This pleiotropic system is therefore a potential therapeutic target for treatment of neurodegenerative disorders such as ALS. Here, we test the effects of ATH-1105, a small-molecule positive modulator of the HGF signaling system, in preclinical models of ALS.

Methods

In vitro, the impact of ATH-1105 on HGF-mediated signaling was assessed via phosphorylation assays for MET, extracellular signal-regulated kinase (ERK), and protein kinase B (AKT). Neuroprotective effects of ATH-1105 were evaluated in rat primary neuron models including spinal motor neurons, motor neuron-astrocyte cocultures, and motor neuron-human muscle cocultures. The anti-inflammatory effects of ATH-1105 were evaluated in microglia- and macrophage-like cell systems exposed to lipopolysaccharide (LPS). In vivo, the impact of daily oral treatment with ATH-1105 was evaluated in Prp-TDP43A315T hemizygous transgenic ALS mice.

Results

In vitro, ATH-1105 augmented phosphorylation of MET, ERK, and AKT. ATH-1105 attenuated glutamate-mediated excitotoxicity in primary motor neurons and motor neuron- astrocyte cocultures, and had protective effects on motor neurons and neuromuscular junctions in motor neuron-muscle cocultures. ATH-1105 mitigated LPS-induced inflammation in microglia- and macrophage-like cell systems. In vivo, ATH-1105 treatment resulted in improved motor and nerve function, sciatic nerve axon and myelin integrity, and survival in ALS mice. Treatment with ATH-1105 also led to reductions in levels of plasma biomarkers of inflammation and neurodegeneration, along with decreased pathological protein accumulation (phospho-TDP-43) in the sciatic nerve. Additionally, both early intervention (treatment initiation at 1 month of age) and delayed intervention (treatment initiation at 2 months of age) with ATH-1105 produced benefits in this preclinical model of ALS.

Discussion

The consistent neuroprotective and anti-inflammatory effects demonstrated by ATH-1105 preclinically provide a compelling rationale for therapeutic interventions that leverage the positive modulation of the HGF pathway as a treatment for ALS.

Levels of Soluble Interleukin 6 Receptor and Asp358Ala Are Associated With Cognitive Performance and Alzheimer Disease Biomarkers

BACKGROUND AND OBJECTIVES

Alzheimer disease (AD) is a neurodegenerative disease process manifesting clinically with cognitive impairment and dementia. AD pathology is complex, and in addition to plaques and tangles, neuroinflammation is a consistent feature. Interleukin (IL) 6 is a multifaceted cytokine involved in a plethora of cellular mechanisms including both anti-inflammatory and inflammatory processes. IL6 can signal classically through the membrane-bound receptor or by IL6 trans-signaling forming a complex with the soluble IL6 receptor (sIL6R) and activating membrane-bound glycoprotein 130 on cells not expressing IL6R. IL6 trans-signaling has been demonstrated as the primary mechanism of IL6-mediated events in neurodegenerative processes. In this study, we performed a cross-sectional analysis to investigate whether inheritance of a genetic variation in the IL6R gene and associated elevated sIL6R levels in plasma and CSF were associated with cognitive performance.

METHODS

We genotyped the IL6R rs2228145 nonsynonymous variant (Asp³⁵⁸Ala) and assayed IL6 and sIL6R concentrations in paired samples of plasma and CSF obtained from 120 participants with normal cognition, mild cognitive impairment, or probable AD enrolled in the Wake Forest Alzheimer's Disease Research Center's Clinical Core. IL6 rs2228145 genotype and measures of plasma IL6 and sIL6R were assessed for relationships with cognitive status and clinical data, including the Montreal Cognitive Assessment (MoCA), modified Preclinical Alzheimer's Cognitive Composite (mPACC), cognitive domain scores obtained from the Uniform Data Set, and CSF concentrations of phosphoTau^T181 (pTau181), β-amyloid (Aβ) Aβ40 and Aβ42 concentrations.

RESULTS

We found that inheritance of the IL6R Ala³⁵⁸ variant and elevated sIL6R levels in plasma and CSF were correlated with lower mPACC, MoCA and memory domain scores, increases in CSF pTau181, and decreases in the CSF Aβ42/40 ratio in both unadjusted and covariate-adjusted statistical models.

DISCUSSION

These data suggest that IL6 trans-signaling and the inheritance of the IL6R Ala³⁵⁸ variant are related to reduced cognition and greater levels of biomarkers for AD disease pathology. Follow-up prospective studies are necessary, as patients who inherit IL6R Ala³⁵⁸ may be identified as ideally responsive to IL6 receptor-blocking therapies.

New developments and opportunities in drugs being trialed for amyotrophic lateral sclerosis from 2020 to 2022

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder that primarily affects motor neurons in the brain and spinal cord. In the recent past, there have been just two drugs approved for treatment, riluzole and edaravone, which only prolong survival by a few months. However, there are many novel experimental drugs in development. In this review, we summarize 53 new drugs that have been evaluated in clinical trials from 2020 to 2022, which we have classified into eight mechanistic groups (anti-apoptotic, anti-inflammatory, anti-excitotoxicity, regulated integrated stress response, neurotrophic factors and neuroprotection, anti-aggregation, gene therapy and other). Six were tested in phase 1 studies, 31 were in phase 2 studies, three failed in phase 3 studies and stopped further development, and the remaining 13 drugs were being tested in phase 3 studies, including methylcobalamin, masitinib, MN-166, verdiperstat, memantine, AMX0035, trazodone, CNM-Au8, pridopidine, SLS-005, IONN363, tofersen, and reldesemtiv. Among them, five drugs, including methylcobalamin, masitinib, AMX0035, CNM-Au8, and tofersen, have shown potent therapeutic effects in clinical trials. Recently, AMX0035 has been the third medicine approved by the FDA for the treatment of ALS after riluzole and edaravone.

Association of the IL-6R gene polymorphic variant rs2228145(C>A) with IL-6 gene polymorphisms in a healthy cohort of Turkish population

The main aim of this study was to investigate the relationship of the carriership of rs2228145 allelic variations of IL-6R with two other allelic variations in IL-6 gene at rs1800795 and rs1800796 loci and with the laboratory data of a healthy cohort of the Turkish population. The data of 121 healthy Turkish subjects (aged 12–84 years) including the past diseases, comorbidities were collected. The laboratory parameters were compared by the frequency of alleles of rs2228145 (C>A). The possible association of polymorphism at rs2228145 locus with the age, gender, and body mass index (BMI) and the frequencies of alleles of rs1800795 and rs1800796 polymorphisms were evaluated. The majority of the subjects had allele A at rs2228145 locus and allele G at rs1800796 locus. The number of white blood cells, platelets, neutrophils and monocytes were significantly higher in the subjects with allele C than those with allele A at rs2228145 locus (P < 0.05). The concentrations of total and direct bilirubin, iron, Sex Hormone Binding Globulin (SHBG) and folic acid of the subjects with allele C were significantly lower than those with allele A (P < 0.05). The uric acid and fasting insulin levels were higher in the subjects with allele C compared with those allele A (P = 0.04). The diversities of the hematological parameters, laboratory findings of liver function tests and renal panel and hormone levels may be explained by the variants of rs2228145 locus at IL-6R gene among healthy Turkish individuals.

Neuroimmune Crosstalk Between the Peripheral and the Central Immune System in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal disease characterized by the degeneration and death of motor neurons. Systemic neuroinflammation contributes to the pathogenesis of ALS. The proinflammatory milieu depends on the continuous crosstalk between the peripheral immune system (PIS) and central immune system (CIS). Central nervous system (CNS) resident immune cells interact with the peripheral immune cells via immune substances. Dysfunctional CNS barriers, including the blood–brain barrier, and blood–spinal cord barrier, accelerate the inflammatory process, leading to a systemic self-destructive cycle. This review focuses on the crosstalk between PIS and CIS in ALS. Firstly, we briefly introduce the cellular compartments of CIS and PIS, respectively, and update some new understanding of changes specifically occurring in ALS. Then, we will review previous studies on the alterations of the CNS barriers, and discuss their crucial role in the crosstalk in ALS. Finally, we will review the moveable compartments of the crosstalk, including cytokines, chemokines, and peripheral immune cells which were found to infiltrate the CNS, highlighting the interaction between PIS and CIS. This review aims to provide new insights into pathogenic mechanisms and innovative therapeutic approaches for ALS.

Cerebrospinal fluid biomarkers of disease activity and progression in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a relentlessly progressive neurodegenerative disease, and only modest disease-modifying strategies have been established to date. Numerous clinical trials have been conducted in the past years, but have been severely hampered by the wide-ranging heterogeneity of both the biological origins and clinical characteristics of the disease. Thus, reliable biomarkers of disease activity are urgently needed to stratify patients into homogenous groups with aligned disease trajectories to allow a more effective design of clinical trial. In this review, the most promising candidate biomarkers in the cerebrospinal fluid (CSF) of patients with ALS will be summarised. Correlations between biomarker levels and clinical outcome parameters are discussed, while highlighting potential pitfalls and intercorrelations of these clinical parameters. Several CSF molecules have shown potential as biomarkers of progression and prognosis, but large, international, multicentric and longitudinal studies are crucial for validation. A more standardised choice of clinical endpoints in these studies, as well as the application of individualised models of clinical progression, would allow the quantification of disease trajectories, thereby allowing a more accurate analysis of the clinical implications of candidate biomarkers. Additionally, a comparative analysis of several biomarkers and ideally the application of a multivariate analysis including comprehensive genotypic, phenotypic and clinical characteristics collectively contributing to biomarker levels in the CSF, could promote their verification. Thus, reliable prognostic markers and markers of disease activity may improve clinical trial design and patient management in the direction of precision medicine.

A chemogenomic approach is required for effective treatment of amyotrophic lateral sclerosis

ALS is a fatal untreatable disease involving degeneration of motor neurons. Μultiple causative genes encoding proteins with versatile functions have been identified indicating that diverse biological pathways lead to ALS. Chemical entities still represent a promising choice to delay ALS progression, attenuate symptoms and/or increase life expectancy, but also gene-based and stem cell-based therapies are in the process of development, and some are tested in clinical trials. Various compounds proved effective in transgenic models overexpressing distinct ALS causative genes unfortunately though, they showed no efficacy in clinical trials. Notably, while animal models provide a uniform genetic background for preclinical testing, ALS patients are not stratified, and the distinct genetic forms of ALS are treated as one group, which could explain the observed discrepancies between treating genetically homogeneous mice and quite heterogeneous patient cohorts. We suggest that chemical entity-genotype correlation should be exploited to guide patient stratification for pharmacotherapy, that is administered drugs should be selected based on the ALS genetic background.

Dissecting the IL-6 pathway in cardiometabolic disease: a Mendelian randomization study on both IL6 and IL6R

BACKGROUND

Chronic inflammation is a risk factor for cardiovascular disease. IL-6 signaling perturbation through IL-6 or IL-6R blockade may have potential benefit on cardiovascular risk. It is unknown whether targeting either IL-6 or IL-6 receptor may result in similar effects on CVD and adverse events. We compared the anticipated effects of targeting IL-6 and IL-6 receptor on cardiometabolic risk and potential side effects.

METHODS

We constructed four instruments: two main instruments with genetic variants in the IL6 and IL6R loci weighted for their association with CRP, and two after firstly filtering variants for their association with IL-6 or IL-6R expression. Analyses were performed for coronary artery disease (CAD), ischemic stroke, atrial fibrillation (AF), heart failure, type 2 diabetes (T2D), rheumatoid arthritis (RA), infection endpoints, and quantitative hematological, metabolic, and anthropometric parameters.

RESULTS

A 1 mg/L lower CRP by the IL6 instrument was associated with lower CAD (OR 0.86, 95% CI 0.77;0.96), AF, and T2D risk. A 1mg/L lower CRP by the IL6R instrument was associated with lower CAD (OR 0.90, 95% CI 0.86;0.95), any stroke and ischemic stroke, AF, RA risk and higher pneumonia risk. The eQTL filtered results were in concordance with the main results, but with wider confidence intervals.

CONCLUSIONS

IL-6 signalling perturbation by either IL6 or IL6R genetic instruments is associated with a similar risk reduction for multiple cardiometabolic diseases, suggesting that both IL-6 and IL-6R are potential therapeutic targets to lower CVD. Moreover, IL-6 rather than IL-6R inhibition might have a more favorable pneumonia risk.

An Intercellular Flow of Glutathione Regulated by Interleukin 6 Links Astrocytes and the Liver in the Pathophysiology of Amyotrophic Lateral Sclerosis

Oxidative stress has been proposed as a major mechanism of damage to motor neurons associated with the progression of amyotrophic lateral sclerosis (ALS). Astrocytes are the most numerous glial cells in the central nervous system and, under physiological conditions, protect neurons from oxidative damage. However, it is uncertain how their reactive phenotype may affect motor neurons during ALS progression. In two different ALS mouse models (SOD1^G93A and FUS-R521C), we found that increased levels of proinflammatory interleukin 6 facilitate glutathione (GSH) release from the liver to blood circulation, which can reach the astrocytes and be channeled towards motor neurons as a mechanism of antioxidant protection. Nevertheless, although ALS progression is associated with an increase in GSH efflux from astrocytes, generation of reactive oxygen species also increases, suggesting that as the disease progresses, astrocyte-derived oxidative stress could be key to motor-neuron damage.

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.

Tocilizumab is safe and tolerable and reduces C-reactive protein concentrations in the plasma and cerebrospinal fluid of ALS patients

INTRODUCTION/AIMS

We tested safety, tolerability, and target engagement of tocilizumab in amyotrophic lateral sclerosis (ALS) patients.

METHODS

Twenty-two participants, whose peripheral blood mononuclear cell (PBMC) gene expression profile reflected high messenger ribonucleic acid (mRNA) expression of inflammatory markers, were randomized 2:1 to three tocilizumab or placebo treatments (weeks 0, 4, and 8; 8 mg/kg intravenous). Participants were followed every 4 wk in a double-blind fashion for 16 wk and assessed for safety, tolerability, plasma inflammatory markers, and clinical measures. Cerebrospinal fluid (CSF) was collected at baseline and after the third treatment. Participants were genotyped for Asp³⁵⁸ Ala polymorphism of the interleukin 6 receptor (IL-6R) gene.

RESULTS

Baseline characteristics, safety, and tolerability were similar between treatment groups. One serious adverse event was reported in the placebo group; no deaths occurred. Mean plasma C-reactive protein (CRP) level decreased by 88% in the tocilizumab group and increased by 4% in the placebo group (-3.0-fold relative change, P < .001). CSF CRP reduction (-1.8-fold relative change, P = .01) was associated with IL-6R C allele count. No differences in PBMC gene expression or clinical measures were observed between groups.

DISCUSSION

Tocilizumab treatment was safe and well tolerated. PBMC gene expression profile was inadequate as a predictive or pharmacodynamic biomarker. Treatment reduced CRP levels in plasma and CSF, with CSF effects potentially dependent on IL-6R Asp³⁵⁸ Ala genotype. IL-6 trans-signaling may mediate a distinct central nervous system response in individuals inheriting the IL-6R C allele. These results warrant further study in ALS patients where IL-6R genotype and CRP levels may be useful enrichment biomarkers.

Biomarkers in amyotrophic lateral sclerosis: a review of new developments

PURPOSE OF REVIEW

This review draws together the most recent findings in ALS biomarker research from biochemical, imaging and neurophysiology techniques.

RECENT FINDINGS

The potential of circulating RNA is highlighted, including new retrieval techniques. With ongoing genetic clinical trials, the need for pharmacodynamic biomarkers is essential. There is a strong case for neurofilament proteins being validated in ALS; their biomarker profile is discussed. Oxidative stress and neuroinflammation studies offer insight into disease mechanisms and offer good biomarker potential. Recent metabolic studies include investigation of lipid profiles, creatinine and ferritin. The potential of chitinase proteins as pharmacodynamic and prognostic biomarkers is highlighted. The role of tau and amyloidβ is debated, as evidenced by the articles presented here. Proteomic approaches provide unbiased discoveries of novel biomarkers, together with confirmation of previous findings. The use of imaging techniques is outlined to demonstrate selective atrophy, volume loss, muscle and tract involvement. In-vivo imaging is discussed with reference to histone deacetylase, oxidative stress, neuroinflammation and metabolic changes. New applications of electrophysiology demonstrate objective muscle biomarkers and brain network perturbations.

SUMMARY

The biomarker research field continues to provide insight into the disease. Multicentre collaborations are needed to validate these promising recent findings.

Investigation of Genetic Variations of IL6 and IL6R as Potential Prognostic and Pharmacogenetics Biomarkers: Implications for COVID-19 and Neuroinflammatory Disorders

In the present study, we investigated the distribution of genetic variations in IL6 and IL6R genes, which may be employed as prognostic and pharmacogenetic biomarkers for COVID-19 and neurodegenerative diseases. The study was performed on 271 samples representative of the Italian general population and identified seven variants (rs140764737, rs142164099, rs2069849, rs142759801, rs190436077, rs148171375, rs13306435) in IL6 and five variants (rs2228144, rs2229237, rs2228145, rs28730735, rs143810642) within IL6R, respectively. These variants have been predicted to affect the expression and binding ability of IL6 and IL6R. Ingenuity Pathway Analysis (IPA) showed that IL6 and IL6R appeared to be implicated in several pathogenetic mechanisms associated with COVID-19 severity and mortality as well as with neurodegenerative diseases mediated by neuroinflammation. Thus, the availability of IL6-IL6R-related biomarkers for COVID-19 may be helpful to counteract harmful complications and prevent multiorgan failure. At the same time, IL6-IL6R-related biomarkers could also be useful for assessing the susceptibility and progression of neuroinflammatory disorders and undertake the most suitable treatment strategies to improve patients' prognosis and quality of life. In conclusion, this study showed how IL6 pleiotropic activity could be exploited to meet different clinical needs and realize personalized medicine protocols for chronic, age-related and modern public health emergencies.

Patients with obstructive sleep apnea have suppressed levels of soluble cytokine receptors involved in neurodegenerative disease, but normal levels with airways therapy

Purpose

Obstructive sleep apnea (OSA) results in systemic intermittent hypoxia. By one model, hypoxic stress signaling in OSA patients alters the levels of inflammatory soluble cytokines TNF and IL6, damages the blood brain barrier, and activates microglial targeting of neuronal cell death to increase the risk of neurodegenerative disorders and other diseases. However, it is not yet clear if OSA significantly alters the levels of the soluble isoforms of TNF receptors TNFR1 and TNFR2 and IL6 receptor (IL6R) and co-receptor gp130, which have the potential to modulate TNF and IL6 signaling.

Methods

Picogram per milliliter levels of the soluble isoforms of these four cytokine receptors were estimated in OSA patients, in OSA patients receiving airways therapy, and in healthy control subjects. Triplicate samples were examined using Bio-Plex fluorescent bead microfluidic technology. The statistical significance of cytokine data was estimated using the nonparametric Wilcoxon rank-sum test. The clustering of these high-dimensional data was visualized using t-distributed stochastic neighbor embedding (t-SNE).

Results

OSA patients had significant twofold to sevenfold reductions in the soluble serum isoforms of all four cytokine receptors, gp130, IL6R, TNFR1, and TNFR2, as compared with control individuals (p = 1.8 × 10⁻¹³ to 4 × 10⁻⁸). Relative to untreated OSA patients, airways therapy of OSA patients had significantly higher levels of gp130 (p = 2.8 × 10⁻¹³), IL6R (p = 1.1 × 10⁻⁹), TNFR1 (p = 2.5 × 10⁻¹⁰), and TNFR2 (p = 5.7 × 10⁻⁹), levels indistinguishable from controls (p = 0.29 to 0.95). The data for most airway-treated patients clustered with healthy controls, but the data for a few airway-treated patients clustered with apneic patients.

Conclusions

Patients with OSA have aberrantly low levels of four soluble cytokine receptors associated with neurodegenerative disease, gp130, IL6R, TNFR1, and TNFR2. Most OSA patients receiving airways therapy have receptor levels indistinguishable from healthy controls, suggesting a chronic intermittent hypoxia may be one of the factors contributing to low receptor levels in untreated OSA patients.

Electronic supplementary material

The online version of this article (10.1007/s11325-020-02205-y) contains supplementary material, which is available to authorized users.

Immunity in amyotrophic lateral sclerosis: blurred lines between excessive inflammation and inefficient immune responses

Despite wide genetic, environmental and clinical heterogeneity in amyotrophic lateral sclerosis, a rapidly fatal neurodegenerative disease targeting motoneurons, neuroinflammation is a common finding. It is marked by local glial activation, T cell infiltration and systemic immune system activation. The immune system has a prominent role in the pathogenesis of various chronic diseases, hence some of them, including some types of cancer, are successfully targeted by immunotherapeutic approaches. However, various anti-inflammatory or immunosuppressive therapies in amyotrophic lateral sclerosis have failed. This prompted increased scrutiny over the immune-mediated processes underlying amyotrophic lateral sclerosis. Perhaps the biggest conundrum is that amyotrophic lateral sclerosis pathogenesis exhibits features of three otherwise distinct immune dysfunctions-excessive inflammation, autoimmunity and inefficient immune responses. Epidemiological and genome-wide association studies show only minimal overlap between amyotrophic lateral sclerosis and autoimmune diseases, so excessive inflammation is usually thought to be secondary to protein aggregation, mitochondrial damage or other stresses. In contrast, several recently characterized amyotrophic lateral sclerosis-linked mutations, including those in TBK1, OPTN, CYLD and C9orf72, could lead to inefficient immune responses and/or damage pile-up, suggesting that an innate immunodeficiency may also be a trigger and/or modifier of this disease. In such cases, non-selective immunosuppression would further restrict neuroprotective immune responses. Here we discuss multiple layers of immune-mediated neuroprotection and neurotoxicity in amyotrophic lateral sclerosis. Particular focus is placed on individual patient mutations that directly or indirectly affect the immune system, and the mechanisms by which these mutations influence disease progression. The topic of immunity in amyotrophic lateral sclerosis is timely and relevant, because it is one of the few common and potentially malleable denominators in this heterogenous disease. Importantly, amyotrophic lateral sclerosis progression has recently been intricately linked to patient T cell and monocyte profiles, as well as polymorphisms in cytokine and chemokine receptors. For this reason, precise patient stratification based on immunophenotyping will be crucial for efficient therapies.

What do we know about the variability in survival of patients with amyotrophic lateral sclerosis?

INTRODUCTION

ALS is a fatal neurodegenerative disease. However, patients show variability in the length of survival after symptom onset. Understanding the mechanisms of long survival could lead to possible avenues for therapy.

AREAS COVERED

This review surveys the reported length of survival in ALS, the clinical features that predict survival in individual patients, and possible factors, particularly genetic factors, that could cause short or long survival. The authors also speculate on possible mechanisms.

EXPERT OPINION

a small number of known factors can explain some variability in ALS survival. However, other disease-modifying factors likely exist. Factors that alter motor neurone vulnerability and immune, metabolic, and muscle function could affect survival by modulating the disease process. Knowing these factors could lead to interventions to change the course of the disease. The authors suggest a broad approach is needed to quantify the proportion of variation survival attributable to genetic and non-genetic factors and to identify and estimate the effect size of specific factors. Studies of this nature could not only identify novel avenues for therapeutic research but also play an important role in clinical trial design and personalized medicine.

The Peripheral Immune System and Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disease that is defined by loss of upper and lower motor neurons, associated with accumulation of protein aggregates in cells. There is also pathology in extra-motor areas of the brain, Possible causes of cell death include failure to deal with the aggregated proteins, glutamate toxicity and mitochondrial failure. ALS also involves abnormalities of metabolism and the immune system, including neuroinflammation in the brain and spinal cord. Strikingly, there are also abnormalities of the peripheral immune system, with alterations of T lymphocytes, monocytes, complement and cytokines in the peripheral blood of patients with ALS. The precise contribution of the peripheral immune system in ALS pathogenesis is an active area of research. Although some trials of immunomodulatory agents have been negative, there is strong preclinical evidence of benefit from immune modulation and further trials are currently underway. Here, we review the emerging evidence implicating peripheral immune alterations contributing to ALS, and their potential as future therapeutic targets for clinical intervention.