Interleukin-6 as a marker of Huntington's disease progression: Systematic review and meta-analysis

Huntington's disease (HD) is a rare, inherited disorder with a broad spectrum of manifestations that vary with disease severity and progression. Although genetic testing can readily confirm the initial diagnosis of HD, markers sensitive to HD progression are needed to aid the development of individual treatment plans. The current analysis aims to identify plasma Interleukin-6 (IL-6) as a marker of disease progression in HD patients. A systematic search of PubMed and Medline from conception through October 2021 was conducted. Studies reporting plasma IL-6 levels of mutation-positive HD patients and healthy controls that met inclusion criteria were selected. The search strategy collected 303 studies, 9 of which met analysis inclusion criteria. From included studies, plasma IL-6 levels of 469 individuals with the HD mutation and 206 healthy controls were collected. Plasma IL-6 levels were meta-analytically compared between healthy controls and individuals with the confirmed HD mutation at all stages of disease and correlated to performance on standardized measures of total cognitive and motor function. Plasma IL-6 was significantly increased in HD groups compared to controls (g = 0.73, 95% CI = 0.31,1.16, P < 0.01) and increased significantly throughout most stages of disease progression, notably between pre-manifest and manifest (g = 0.31, 95% CI = 0.04,0.59, P < 0.05) and early and moderate HD stages (g = 0.52, 95% CI = 0.18,0.86, P < 0.01). Significant correlations between plasma IL-6 levels and HD symptomatic progression were identified, with increased cytokine levels associated with more severe motor impairments (r = 0.179, 95% CI = 0.0479,0.304, P = 0.008) and more extreme disabilities in activities of daily living and/or work tasks (r = -0.229, 95% CI = -0.334, -0.119, P < 0.001). Conclusively, plasma IL-6 levels correlate with disease and motor symptom progression and may act as a viable marker for clinical use. Analysis is limited by small study numbers and highlights the need for future work to identify definitive ranges or rates of change of plasma IL-6 levels that correlate to progressive HD disease states.

Identification of biomarkers differentiating Alzheimer's disease from other neurodegenerative diseases by integrated bioinformatic analysis and machine-learning strategies

Background

Alzheimer's disease (AD) is the most common neurodegenerative disease, imposing huge mental and economic burdens on patients and society. The specific molecular pathway(s) and biomarker(s) that distinguish AD from other neurodegenerative diseases and reflect the disease progression are still not well studied.

Methods

Four frontal cortical datasets of AD were integrated to conduct differentially expressed genes (DEGs) and functional gene enrichment analyses. The transcriptional changes after the integrated frontal cortical datasets subtracting the cerebellar dataset of AD were further compared with frontal cortical datasets of frontotemporal dementia and Huntingdon's disease to identify AD-frontal-associated gene expression. Integrated bioinformatic analysis and machine-learning strategies were applied for screening and determining diagnostic biomarkers, which were further validated in another two frontal cortical datasets of AD by receiver operating characteristic (ROC) curves.

Results

Six hundred and twenty-six DEGs were identified as AD frontal associated, including 580 downregulated genes and 46 upregulated genes. The functional enrichment analysis revealed that immune response and oxidative stress were enriched in AD patients. Decorin (DCN) and regulator of G protein signaling 1 (RGS1) were screened as diagnostic biomarkers in distinguishing AD from frontotemporal dementia and Huntingdon's disease of AD. The diagnostic effects of DCN and RGS1 for AD were further validated in another two datasets of AD: the areas under the curve (AUCs) reached 0.8148 and 0.8262 in GSE33000, and 0.8595 and 0.8675 in GSE44770. There was a better value for AD diagnosis when combining performances of DCN and RGS1 with the AUCs of 0.863 and 0.869. Further, DCN mRNA level was correlated to CDR (Clinical Dementia Rating scale) score (r = 0.5066, p = 0.0058) and Braak staging (r = 0.3348, p = 0.0549).

Conclusion

DCN and RGS1 associated with the immune response may be useful biomarkers for diagnosing AD and distinguishing the disease from frontotemporal dementia and Huntingdon's disease. DCN mRNA level reflects the development of the disease.

The CB2 cannabinoid receptor as a therapeutic target in the central nervous system

INTRODUCTION

Targeting CB2 cannabinoid receptor (CB2r) represents a promising approach for the treatment of central nervous system disorders. These receptors were identified in peripheral tissues, but also in neurons in the central nervous system. New findings have highlighted the interest to target these central receptors to obtain therapeutic effects devoid of the classical cannabinoid side-effects.

AREAS COVERED

In this review, we searched PubMed (January 1991-May 2021), ClinicalTrials.gov and Cochrane Library databases for articles, reviews and clinical trials. We first introduce the relevance of CB2r as a key component of the endocannabinoid system. We discuss CB2r interest as a possible novel target in the treatment of pain. This receptor has raised interest as a potential target for neurodegenerative disorders treatment, as we then discussed. Finally, we underline studies revealing a novel potential CB2r interest in mental disorders treatment.

EXPERT OPINION

In spite of the interest of targeting CB2r for pain, clinical trials evaluating CB2r agonist analgesic efficacy have currently failed. The preferential involvement of CB2r in preventing the development of chronic pain could influence the failure of clinical trials designed for the treatment of already established pain syndromes. Specific trials should be designed to target the prevention of chronic pain development.

Dapagliflozin improves behavioral dysfunction of Huntington's disease in rats via inhibiting apoptosis-related glycolysis

AIMS

Huntington's disease is a rare neurodegenerative disorder which is associated with defected glucose metabolism with consequent behavioral disturbance including memory and locomotion. 3-nitropropionic acid (3-NP) can cause, in high single dose, an acute striatal injury/Huntington's disease. Dapagliflozin, which is one of the longest duration of action of SGLTIs family, may be able to diminish that injury and its resultant behavioral disturbances.

MATERIAL AND METHODS

Forty rats were divided into four groups (n = 10 in each group): normal control group (CTRL), dapagliflozin (CTRL + DAPA) group, 3-nitropropionic acid (3-NP) group, and dapagliflozin plus 3-nitropropionic acid (DAPA + 3-NP) group. Behavioral tests (beam walking test, hanging wire test, limb withdrawal test, Y-maze spontaneous alteration, elevated plus maze) were performed with evaluating neurological scoring. In striatum, neurotransmitters (glutamate, aspartate, GABA, ACh and AChE activity) were measured. In addition, apoptosis and glycolysis markers (NF-κB, Cyt-c, lactate, HK-II activity, P53, calpain, PEA15 and TIGAR) were determined. Inflammation (IL-1β, IL-6, IL-8 and TNF-α) and autophagy (beclin-1, LC3 and DRAM) indicators were measured. Additionally, histopathological screening was conducted.

KEY FINDINGS

3-Nitropropionic acid had the ability to perturb the neurotransmission which was reflected in impaired behavioral outcome. All of glycolysis, apoptosis and inflammation markers were elevated after 3-NP acute intoxication but autophagy parameters, except DRAM, were reduced. However, DAPA markedly reversed the abovementioned parameters.

SIGNIFICANCE

Dapagliflozin demonstrated anti-glycolytic, anti-apoptotic, anti-inflammatory and autophagic effects on 3-NP-damaged striatal cells and promoted the behavioral outcome.

How Do Post-Translational Modifications Influence the Pathomechanistic Landscape of Huntington's Disease? A Comprehensive Review

Huntington’s disease (HD) is an autosomal dominant inherited neurodegenerative disorder characterized by the loss of motor control and cognitive ability, which eventually leads to death. The mutant huntingtin protein (HTT) exhibits an expansion of a polyglutamine repeat. The mechanism of pathogenesis is still not fully characterized; however, evidence suggests that post-translational modifications (PTMs) of HTT and upstream and downstream proteins of neuronal signaling pathways are involved. The determination and characterization of PTMs are essential to understand the mechanisms at work in HD, to define possible therapeutic targets better, and to challenge the scientific community to develop new approaches and methods. The discovery and characterization of a panoply of PTMs in HTT aggregation and cellular events in HD will bring us closer to understanding how the expression of mutant polyglutamine-containing HTT affects cellular homeostasis that leads to the perturbation of cell functions, neurotoxicity, and finally, cell death. Hence, here we review the current knowledge on recently identified PTMs of HD-related proteins and their pathophysiological relevance in the formation of abnormal protein aggregates, proteolytic dysfunction, and alterations of mitochondrial and metabolic pathways, neuroinflammatory regulation, excitotoxicity, and abnormal regulation of gene expression.

Quantification of huntingtin protein species in Huntington's disease patient leukocytes using optimised electrochemiluminescence immunoassays

BACKGROUND

Huntington's disease (HD) is an autosomal dominant neurodegenerative condition caused by an expanded CAG repeat in the gene encoding huntingtin (HTT). Optimizing peripheral quantification of huntingtin throughout the course of HD is valuable not only to illuminate the natural history and pathogenesis of disease, but also to detect peripheral effects of drugs in clinical trial.

RATIONALE

We previously demonstrated that mutant HTT (mHTT) was significantly elevated in purified HD patient leukocytes compared with controls and that these levels track disease progression. Our present study investigates whether the same result can be achieved with a simpler and more scalable collection technique that is more suitable for clinical trials.

METHODS

We collected whole blood at 133 patient visits in two sample sets and generated peripheral blood mononuclear cells (PBMCs). Levels of mHTT, as well as N-, and C-terminal and mid-region huntingtin were measured in the PBMCs using ELISA-based Meso Scale Discovery (MSD) electrochemiluminescence immunoassay platforms, and we evaluated the relationship between different HTT species, disease stage, and brain atrophy on magnetic resonance imaging.

CONCLUSIONS

The assays were sensitive and accurate. We confirm our previous findings that mHTT increases with advancing disease stage in patient PBMCs, this time using a simple collection protocol and scalable assay.

Neural and mesenchymal stem cells in animal models of Huntington's disease: past experiences and future challenges

Huntington's disease (HD) is an inherited disease that causes progressive nerve cell degeneration. It is triggered by a mutation in the HTT gene that strongly influences functional abilities and usually results in movement, cognitive and psychiatric disorders. HD is incurable, although treatments are available to help manage symptoms and to delay the physical, mental and behavioral declines associated with the condition. Stem cells are the essential building blocks of life, and play a crucial role in the genesis and development of all higher organisms. Ablative surgical procedures and fetal tissue cell transplantation, which are still experimental, demonstrate low rates of recovery in HD patients. Due to neuronal cell death caused by accumulation of the mutated huntingtin (mHTT) protein, it is unlikely that such brain damage can be treated solely by drug-based therapies. Stem cell-based therapies are important in order to reconstruct damaged brain areas in HD patients. These therapies have a dual role: stem cell paracrine action, stimulating local cell survival, and brain tissue regeneration through the production of new neurons from the intrinsic and likely from donor stem cells. This review summarizes current knowledge on neural stem/progenitor cell and mesenchymal stem cell transplantation, which has been carried out in several animal models of HD, discussing cell distribution, survival and differentiation after transplantation, as well as functional recovery and anatomic improvements associated with these approaches. We also discuss the usefulness of this information for future preclinical and clinical studies in HD.

Huntington disease

Huntington disease is devastating to patients and their families - with autosomal dominant inheritance, onset typically in the prime of adult life, progressive course, and a combination of motor, cognitive and behavioural features. The disease is caused by an expanded CAG trinucleotide repeat (of variable length) in HTT, the gene that encodes the protein huntingtin. In mutation carriers, huntingtin is produced with abnormally long polyglutamine sequences that confer toxic gains of function and predispose the protein to fragmentation, resulting in neuronal dysfunction and death. In this Primer, we review the epidemiology of Huntington disease, noting that prevalence is higher than previously thought, geographically variable and increasing. We describe the relationship between CAG repeat length and clinical phenotype, as well as the concept of genetic modifiers of the disease. We discuss normal huntingtin protein function, evidence for differential toxicity of mutant huntingtin variants, theories of huntingtin aggregation and the many different mechanisms of Huntington disease pathogenesis. We describe the genetic and clinical diagnosis of the condition, its clinical assessment and the multidisciplinary management of symptoms, given the absence of effective disease-modifying therapies. We review past and present clinical trials and therapeutic strategies under investigation, including impending trials of targeted huntingtin-lowering drugs and the progress in development of biomarkers that will support the next generation of trials. For an illustrated summary of this Primer, visit: http://go.nature.com/hPMENh.

Huntington disease: natural history, biomarkers and prospects for therapeutics

Huntington disease (HD) can be seen as a model neurodegenerative disorder, in that it is caused by a single genetic mutation and is amenable to predictive genetic testing, with estimation of years to predicted onset, enabling the entire range of disease natural history to be studied. Structural neuroimaging biomarkers show that progressive regional brain atrophy begins many years before the emergence of diagnosable signs and symptoms of HD, and continues steadily during the symptomatic or 'manifest' period. The continued development of functional, neurochemical and other biomarkers raises hopes that these biomarkers might be useful for future trials of disease-modifying therapeutics to delay the onset and slow the progression of HD. Such advances could herald a new era of personalized preventive therapeutics. We describe the natural history of HD, including the timing of emergence of motor, cognitive and emotional impairments, and the techniques that are used to assess these features. Building on this information, we review recent progress in the development of biomarkers for HD, and potential future roles of these biomarkers in clinical trials.

Oxidative stress and inflammation biomarkers in the blood of patients with Huntington's disease

OBJECTIVES

Huntington's disease (HD) is a neurodegenerative disorder for which there is no effective treatment. Oxidative stress and inflammation are known to be involved in HD, but the precise relationship between the two remains unclear. The aim of this study was to analyze oxidative stress and inflammation biomarkers in blood of patients with HD with a view to identifying potential links between them.

METHODS

Blood samples were collected from 13 patients with HD and from 10 age- and sex-matched controls, and the following were measured: C-reactive proteins, myeloperoxidase (MPO)/white blood cell (WBC) ratio, interleukin-6 (IL-6), thioredoxin reductase-1 (TrRd-1), thioredoxin-1 (Trx-1), total nitrites (NOx), nitric oxide synthase (NOS) and nitrotyrosine.

RESULTS

Results showed that HD is associated to a reduction of TrRd-1 and Trx-1 levels in plasma and erythrocytes, and with an increase in the MPO/WBC ratio. A positive correlation was observed between global oxidative stress (GOS) and MPO/WBC. No changes were found in NOS and Nox levels with respect to controls.

CONCLUSION

Oxidative damage may be linked to the inflammatory response in HD, via a peripheral immune response.

Current understanding of the glial response to disorders of the aging CNS

In this special issue of Frontiers in Pharmacology, we have asked leading experts to comment and review the evidence that inflammatory cells play a leading role in the pathological processes underlying neurodegenerative disorders. We now seek to draw these various observations together into a conclusion, with the hope that this will inform further work in this area and result in the identification of new therapeutic targets that will have a disease modifying effect.

Development of biomarkers for Huntington's disease

Huntington's disease is an autosomal dominant, progressive neurodegenerative disorder, for which there is no disease-modifying treatment. By use of predictive genetic testing, it is possible to identify individuals who carry the gene defect before the onset of symptoms, providing a window of opportunity for intervention aimed at preventing or delaying disease onset. However, without robust and practical measures of disease progression (ie, biomarkers), the efficacy of therapeutic interventions in this premanifest Huntington's disease population cannot be readily assessed. Current progress in the development of biomarkers might enable evaluation of disease progression in individuals at the premanifest stage of the disease; these biomarkers could be useful in defining endpoints in clinical trials in this population. Clinical, cognitive, neuroimaging, and biochemical biomarkers are being investigated for their potential in clinical use and their value in the development of future treatments for patients with Huntington's disease.

MicroRNAs as biomarkers of disease onset

MicroRNAs (miRNAs) are small, noncoding RNA molecules with the ability to posttranscriptionally regulate gene expression via targeting the 3' untranslated region of messenger RNAs. miRNAs are critical for normal cellular functions such as the regulation of the cell cycle, differentiation, and apoptosis, and they target genes during embryonal and postnatal development, whereas their expression is unbalanced in various pathological states. Importantly, miRNAs are abundantly present in body fluids (e.g., blood), which are routinely examined in patients. These molecules circulate in free and exosome encapsulated forms, and can be efficiently detected and amplified by means of molecular biology tools such as real-time PCR. Together with relative stability, specificity, and reproducibility, they are seen as good candidates for early recognition of the onset of disease. Thus, miRNAs might be considered as biomarkers for many pathological states.

LIF in the regulation of T-cell fate and as a potential therapeutic

At the heart of lineage commitment within the adaptive immune response is the intrinsic genetic plasticity of the naive peripheral T lymphocyte (T cell). Primary activation by presentation of cognate antigen is coupled to rapid T-cell cycling and progressive epigenetic changes that guide the cell down distinct T-cell lineages, either effector (Th1, Th2, Th17) or tolerogenic (Treg). Fate choice is influenced both by strength of the priming activation signal and by cues from the micro-environment that are integrated with lineage-specific gene expression profiles, eventually becoming hard-wired in the fully differentiated cell. The micro-environmental cues include cytokines, and the discovery that leukaemia inhibitory factor (LIF) and interleukin (IL)-6 counter-regulate development of the Treg and Th17 lineages places LIF within the core regulatory circuitry of T cells. I first summarise current understanding of LIF and the LIF receptor in the context of T cells. Next, the central relevance of the LIF/IL-6 axis in immune-mediated disease is set in the context of (i) a new nano-therapeutic approach for targeted delivery of LIF and (ii) MARCH-7, a novel E3-ligase discovered to have a central mechanistic role in LIF-mediated T-cell biology, functioning as a rheostat-type regulator of endogenous LIF-signalling.

The clinical and genetic features of Huntington disease

Huntington disease (HD) is a dominantly inherited neurodegenerative disorder that usually presents in adulthood with characteristic motor and cognitive features and with variable and diverse psychiatric disturbances. Following the discovery of the causative defect in the HTT gene in 1993, great advances in understanding the pathogenesis of HD have been made, yet no effective disease-modifying therapy has been identified. In this new era of HD research, we have seen the emergence of a number of large clinical trials, the systematic search for novel biomarkers and the recent initiation of the first pre-manifest HD clinical studies. In this review, we seek to provide an overview of the clinical and genetic features of HD together with a summary of clinical research at this time.