Role of Microglia in Ataxias

Value of Quantitative Susceptibility Mapping in Clinical Neuroradiology

Quantitative susceptibility mapping (QSM) is a unique technique for providing quantitative information on tissue magnetic susceptibility using phase image data. QSM can provide valuable information regarding physiological and pathological processes such as iron deposition, hemorrhage, calcification, and myelin. QSM has been considered for use as an imaging biomarker to investigate physiological status and pathological changes. Although various studies have investigated the clinical applications of QSM, particularly regarding the use of QSM in clinical practice, have not been examined well. This review provides on an overview of the basics of QSM and its clinical applications in neuroradiology. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 2.

Aloe-emodin from Sanhua Decoction inhibits neuroinflammation by regulating microglia polarization after subarachnoid hemorrhage

ETHNOPHARMACOLOGICAL RELEVANCE

Subarachnoid hemorrhage (SAH) triggers a cascade of events that lead to early brain injury (EBI), which contributes to poor outcomes and appears within 3 days after SAH initiation. EBI involves multiple process including neuronal death, blood-brain barrier (BBB) injury and inflammation response. Microglia are cluster of immune cells originating in the brain which respond to SAH by changing their states and releasing inflammatory molecules through various signaling pathways. M0, M1, M2 are three states of microglia represent resting state, promoting inflammation state, and anti-inflammation state respectively, which can be modulated by pharmacological strategies.

AIM OF THE STUDY

After identified potential active ingredients and targets of Sanhua Decoction (SHD) for SAH, we selected aloe-emodin (AE) as a potential ingredient modulating microglia activation states.

MATERIALS AND METHODS

Molecular mechanisms, targets and pathways of SHD were reveal by network pharmacology technique. The effects of AE on SAH were evaluated in vivo by assessing neurological deficits, neuronal apoptosis and BBB integrity in a mouse SAH model. Furthermore, BV-2 cells were used to examine the effects of AE on microglial polarization. The influence of AE on microglia transformation was measured by Iba-1, TNF-α, CD68, Arg-1 and CD206 staining. The signal pathways of neuronal apoptosis and microglia polarization was measured by Western blot.

RESULTS

Network pharmacology identified potential active ingredients and targets of SHD for SAH. And AE is one of the active ingredients. We also confirmed that AE via NF-κB and PKA/CREB pathway inhibited the microglia activation and promoted transformation from M1 phenotype to M2 at EBI stage after SAH.

CONCLUSIONS

AE, as one ingredient of SHD, can alleviate the inflammatory response and protecting neurons from SAH-induced injury. AE has potential value for treating SAH-induced nerve injury and is expected to be applied in clinical practice.

The Neuroimmune System and the Cerebellum

The recognition that there is an innate immune system of the brain, referred to as the neuroimmune system, that preforms many functions comparable to that of the peripheral immune system is a relatively new concept and much is yet to be learned. The main cellular components of the neuroimmune system are the glial cells of the brain, primarily microglia and astrocytes. These cell types preform many functions through secretion of signaling factors initially known as immune factors but referred to as neuroimmune factors when produced by cells of the brain. The immune functions of glial cells play critical roles in the healthy brain to maintain homeostasis that is essential for normal brain function, to establish cytoarchitecture of the brain during development, and, in pathological conditions, to minimize the detrimental effects of disease and injury and promote repair of brain structure and function. However, dysregulation of this system can occur resulting in actions that exacerbate or perpetuate the detrimental effects of disease or injury. The neuroimmune system extends throughout all brain regions, but attention to the cerebellar system has lagged that of other brain regions and information is limited on this topic. This article is meant to provide a brief introduction to the cellular and molecular components of the brain immune system, its functions, and what is known about its role in the cerebellum. The majority of this information comes from studies of animal models and pathological conditions, where upregulation of the system facilitates investigation of its actions.

Microglia play an important role in PRV infection-induced immune responses of the central nervous system

Pseudorabies virus (PRV) can infect multiple hosts and lead to fatal encephalitis. There is a significant increase in the number of microglia in the brain of animals infected with PRV. However, whether and how microglia contribute to central nervous system damage in PRV infection remain unknown. In the present study, we elucidated that PRV infection can cause more severe inflammatory cell infiltration, thicker and more numerous vessel sleeve walls, and more severe inflammatory responses in the brains of natural hosts (pigs) than in those of nonnatural hosts (mice). In a mice infection model, activated microglia restricted viral replication in the early stage of infection. Acute neuroinflammation caused by microglia hyperactivation at late-stage of infection. Furthermore, in vitro experiments revealed that microglia restricted viral replication and decreased viral infectivity. This may be associated with the phagocytic ability of microglia because we observed a significant increase in the expression of the membrane receptor TREM2 in microglia, which is closely related to phagocytosis, we observed that depletion of microglia exacerbated neurological symptoms, blood-brain barrier breakdown, and peripheral lymphocyte infiltration. Taken together, we revealed the dual role of microglia in protecting the host and neurons from PRV infection.

Reactive Bergmann glia play a central role in spinocerebellar ataxia inflammation via the JNK pathway

The spinocerebellar ataxias (SCAs) are devastating neurological diseases characterized by progressive cerebellar incoordination. While neurons bear the brunt of the pathology, a growing body of evidence suggests that glial cells are also affected. It has, however, been difficult to understand the role of glia, given the diversity of subtypes, each with their individual contributions to neuronal health. Using human SCA autopsy samples we have discovered that Bergmann glia-the radial glia of the cerebellum, which form intimate functional connections with cerebellar Purkinje neurons-display inflammatory JNK-dependent c-Jun phosphorylation. This phosphorylation defines a signaling pathway not observed in other activated glial populations, providing an opportunity to isolate the role of Bergmann glia in SCA inflammation. Turning to an SCA1 mouse model as a paradigmatic SCA, we demonstrate that inhibiting the JNK pathway reduces Bergmann glia inflammation accompanied by improvements in the SCA1 phenotype both behaviorally and pathologically. These findings demonstrate the causal role for Bergmann glia inflammation in SCA1 and point to a novel therapeutic strategy that could span several ataxic syndromes where Bergmann glia inflammation is a major feature.

Alteration in mitochondrial dynamics promotes the proinflammatory response of microglia and is involved in cerebellar dysfunction of young and aged mice following LPS exposure

Cerebellar dysfunction is implicated in impaired motor coordination and balance, thus disturbing the dynamics of sensorimotor integration. Neuroinflammation and aging could be prominent contributors to cerebellar aberration. Additionally, changes in mitochondrial dynamics may precede microglia activation in several chronic neurodegenerative diseases; however, the underlying mechanism remains largely unknown.Here using LPS (1 mg/kg i.p. for four consecutive days) stimulation in both young (3 months old) and aged (12 months old) mice, followed by molecular analysis on the 21st day, we have explored the correlation between aging and mitochondrial dynamic alteration in the backdrop of chronic neuroinflammation. Following LPS stimulation, we observed microglia activation and subsequent elevation in proinflammatory cytokines (M1; TNF-α, IFN-γ) with NLRP3 activationand a concomitant reduction in the expression of anti-inflammatory markers (M2; YM1, TGF-β1) in the cerebellar tissue of aged mice compared with the young LPS and aged controls. Remarkably, senescence (p21, p27, p53) and epigenetic (HDAC2) markers were found upregulated in the cerebellum tissue of the aged LPS group, suggesting their crucial role in LPS-induced cerebellar deficit. Further, we demonstrated alteration in the antagonistic forces of mitochondrial fusion and fission with increased expression of the mitochondrial fission-related gene [FIS1] and decreased fusion-related genes [MFN1 and MFN2]. We noted increased mtDNA copy number, microglia activation, and inflammatory response of IL1β and IFN-γ post-chronic neuroinflammation in aged LPS group. Our results suggest that the crosstalk between mitochondrial dynamics and altered microglial activation paradigm in chronic neuroinflammatory conditions may be the key to understanding the cerebellar molecular mechanism.

Proinflammatory activation of microglia in the cerebellum hyperexcites Purkinje cells to trigger ataxia

Specific medications to combat cerebellar ataxias, a group of debilitating movement disorders characterized by difficulty with walking, balance and coordination, are still lacking. Notably, cerebellar microglial activation appears to be a common feature in different types of ataxic patients and rodent models. However, direct evidence that cerebellar microglial activation in vivo is sufficient to induce ataxia is still lacking. Here, by employing chemogenetic approaches to manipulate cerebellar microglia selectively and directly, we found that specific chemogenetic activation of microglia in the cerebellar vermis directly leads to ataxia symptoms in wild-type mice and aggravated ataxic motor deficits in 3-acetylpyridine (3-AP) mice, a classic mouse model of cerebellar ataxia. Mechanistically, cerebellar microglial proinflammatory activation induced by either chemogenetic M3D(Gq) stimulation or 3-AP modeling hyperexcites Purkinje cells (PCs), which consequently triggers ataxia. Blockade of microglia-derived TNF-α, one of the most important proinflammatory cytokines, attenuates the hyperactivity of PCs driven by microglia. Moreover, chemogenetic inhibition of cerebellar microglial activation or suppression of cerebellar microglial activation by PLX3397 and minocycline reduces the production of proinflammatory cytokines, including TNF-α, to effectively restore the overactivation of PCs and alleviate motor deficits in 3-AP mice. These results suggest that cerebellar microglial activation may aggravate the neuroinflammatory response and subsequently induce dysfunction of PCs, which in turn triggers ataxic motor deficits. Our findings thus reveal a causal relationship between proinflammatory activation of cerebellar microglia and ataxic motor symptoms, which may offer novel evidence for therapeutic intervention for cerebellar ataxias by targeting microglia and microglia-derived inflammatory mediators.

Cerebellar presence of immune cells in patients with neuro-coeliac disease

Although various neurodegenerative disorders have been associated with coeliac disease (CD), the underlying neuropathological link between these brain and gut diseases remains unclear. We postulated that the neuronal damage sporadically observed in CD patients is immune-mediated. Our aim was to determine if the loss of neurons, especially Purkinje cells, coincides with microglia activation and T- and B-cell infiltration in the cerebellum of patients with CD and a concomitant idiopathic neurological disease affecting the cerebellum (NeuroCD). Post-mortem cerebellar tissue was collected of validated NeuroCD cases. Gender- and age-matched genetic spinocerebellar ataxia (SCA) controls and non-neurological controls (NNC) were selected based on clinical reports and pathological findings. Cerebellar tissue of seventeen patients was included (6 NeuroCD, 5 SCA, 6 NNC). In SCA cases we found that the Purkinje cell layer was 58.6% reduced in comparison with NNC. In NeuroCD cases this reduction was even more prominent with a median reduction of 81.3% compared to NNC. Marked increased numbers of both CD3+ and CD8+ cells were observed in the NeuroCD but not in SCA patients. This coincided with significantly more microglial reactivity in NeuroCD patients. These findings demonstrate that the massive loss of Purkinje cells in the cerebellum of neuro CD patients is accompanied by local innate and T-cell mediated immune responses.

Immunology and microbiome: Implications for motor systems

Immune-inflammatory mechanisms seem to play a relevant role in neurodegenerative disorders affecting motor systems, particularly Parkinson's disease, where activity changes in inflammatory cells and evidence of neuroinflammation in experimental models and patients is available. Amyotrophic lateral sclerosis is also characterized by neuroinflammatory changes that involve primarily glial cells, both microglia and astrocytes, as well as systemic immune dysregulation associated with more rapid progression. Similarly, the exploration of gut dysbiosis in these two prototypical neurodegenerative motor disorders is advancing rapidly. Altered composition of gut microbial constituents and related metabolic and putative functional pathways is supporting a pathophysiological link that is currently explored in preclinical, germ-free animal models. Less compelling, but still intriguing, evidence suggests that motor neurodevelopmental disorders, e.g., Tourette syndrome, are associated with abnormal trajectories of maturation that include also immune system development. Microglia has a key role also in these disorders, and new therapeutic avenues aiming at its modulation are exciting prospects. Preclinical and clinical research on the role of gut dysbiosis in Tourette syndrome and related behavioral disorders is still in its infancy, but early findings support the rationale to delve deeper into its contribution to neural and immune maturation abnormalities in its spectrum.

Contribution of Glial Cells to Polyglutamine Diseases: Observations from Patients and Mouse Models

Neurodegenerative diseases are broadly characterized neuropathologically by the degeneration of vulnerable neuronal cell types in a specific brain region. The degeneration of specific cell types has informed on the various phenotypes/clinical presentations in someone suffering from these diseases. Prominent neurodegeneration of specific neurons is seen in polyglutamine expansion diseases including Huntington's disease (HD) and spinocerebellar ataxias (SCA). The clinical manifestations observed in these diseases could be as varied as the abnormalities in motor function observed in those who have Huntington's disease (HD) as demonstrated by a chorea with substantial degeneration of striatal medium spiny neurons (MSNs) or those with various forms of spinocerebellar ataxia (SCA) with an ataxic motor presentation primarily due to degeneration of cerebellar Purkinje cells. Due to the very significant nature of the degeneration of MSNs in HD and Purkinje cells in SCAs, much of the research has centered around understanding the cell autonomous mechanisms dysregulated in these neuronal cell types. However, an increasing number of studies have revealed that dysfunction in non-neuronal glial cell types contributes to the pathogenesis of these diseases. Here we explore these non-neuronal glial cell types with a focus on how each may contribute to the pathogenesis of HD and SCA and the tools used to evaluate glial cells in the context of these diseases. Understanding the regulation of supportive and harmful phenotypes of glia in disease could lead to development of novel glia-focused neurotherapeutics.

Development of microglia-targeting adeno-associated viral vectors as tools to study microglial behavior in vivo

Here we describe the microglia-targeting adeno-associated viral (AAV) vectors containing a 1.7-kb putative promoter region of microglia/macrophage-specific ionized calcium-binding adaptor molecule 1 (Iba1), along with repeated miRNA target sites for microRNA (miR)-9 and miR-129-2-3p. The 1.7-kb genomic sequence upstream of the start codon in exon 1 of the Iba1 (Aif1) gene, functions as microglia preferential promoter in the striatum and cerebellum. Furthermore, ectopic transgene expression in non-microglial cells is markedly suppressed upon adding two sets of 4-repeated miRNA target sites for miR-9 and miR-129-2-3p, which are expressed exclusively in non-microglial cells and sponged AAV-derived mRNAs. Our vectors transduced ramified microglia in healthy tissues and reactive microglia in lipopolysaccharide-treated mice and a mouse model of neurodegenerative disease. Moreover, live fluorescent imaging allowed the monitoring of microglial motility and intracellular Ca2+ mobilization. Thus, microglia-targeting AAV vectors are valuable for studying microglial pathophysiology and therapies, particularly in the striatum and cerebellum.

Transcriptional profiling of macrophages in situ in metastatic melanoma reveals localization-dependent phenotypes and function

Modulation of immune function at the tumor site could improve patient outcomes. Here, we analyze patient samples of metastatic melanoma, a tumor responsive to T cell-based therapies, and find that tumor-infiltrating T cells are primarily juxtaposed to CD14+ monocytes/macrophages rather than melanoma cells. Using immunofluorescence-guided laser capture microdissection, we analyze transcriptomes of CD3+ T cells, CD14 + monocytes/macrophages, and melanoma cells in non-dissociated tissue. Stromal CD14+ cells display a specific transcriptional signature distinct from CD14+ cells within tumor nests. This signature contains LY75, a gene linked with antigen capture and regulation of tolerance and immunity in dendritic cells (DCs). When applied to TCGA cohorts, this gene set can distinguish patients with significantly prolonged survival in metastatic cutaneous melanoma and other cancers. Thus, the stromal CD14+ cell signature represents a candidate biomarker and suggests that reprogramming of stromal macrophages to acquire DC function may offer a therapeutic opportunity for metastatic cancers.

Acute Cerebellar Inflammation and Related Ataxia: Mechanisms and Pathophysiology

The cerebellum governs motor coordination and motor learning. Infection with external microorganisms, such as viruses, bacteria, and fungi, induces the release and production of inflammatory mediators, which drive acute cerebellar inflammation. The clinical observation of acute cerebellitis is associated with the emergence of cerebellar ataxia. In our animal model of the acute inflammation of the cerebellar cortex, animals did not show any ataxia but hyperexcitability in the cerebellar cortex and depression-like behaviors. In contrast, animal models with neurodegeneration of the cerebellar Purkinje cells and hypoexcitability of the neurons show cerebellar ataxia. The suppression of the Ca²⁺-activated K⁺ channels in vivo is associated with a type of ataxia. Therefore, there is a gap in our interpretation between the very early phase of cerebellar inflammation and the emergence of cerebellar ataxia. In this review, we discuss the hypothesized scenario concerning the emergence of cerebellar ataxia. First, compared with genetically induced cerebellar ataxias, we introduce infection and inflammation in the cerebellum via aberrant immunity and glial responses. Especially, we focus on infections with cytomegalovirus, influenza virus, dengue virus, and SARS-CoV-2, potential relevance to mitochondrial DNA, and autoimmunity in infection. Second, we review neurophysiological modulation (intrinsic excitability, excitatory, and inhibitory synaptic transmission) by inflammatory mediators and aberrant immunity. Next, we discuss the cerebellar circuit dysfunction (presumably, via maintaining the homeostatic property). Lastly, we propose the mechanism of the cerebellar ataxia and possible treatments for the ataxia in the cerebellar inflammation.

A Breakdown of Immune Tolerance in the Cerebellum

Cerebellar dysfunction can be associated with ataxia, dysarthria, dysmetria, nystagmus and cognitive deficits. While cerebellar dysfunction can be caused by vascular, traumatic, metabolic, genetic, inflammatory, infectious, and neoplastic events, the cerebellum is also a frequent target of autoimmune attacks. The underlying cause for this vulnerability is unclear, but it may be a result of region-specific differences in blood–brain barrier permeability, the high concentration of neurons in the cerebellum and the presence of autoantigens on Purkinje cells. An autoimmune response targeting the cerebellum—or any structure in the CNS—is typically accompanied by an influx of peripheral immune cells to the brain. Under healthy conditions, the brain is protected from the periphery by the blood–brain barrier, blood–CSF barrier, and blood–leptomeningeal barrier. Entry of immune cells to the brain for immune surveillance occurs only at the blood-CSF barrier and is strictly controlled. A breakdown in the barrier permeability allows peripheral immune cells uncontrolled access to the CNS. Often—particularly in infectious diseases—the autoimmune response develops because of molecular mimicry between the trigger and a host protein. In this review, we discuss the immune surveillance of the CNS in health and disease and also discuss specific examples of autoimmunity affecting the cerebellum.

Quantitative susceptibility mapping reveals alterations of dentate nuclei in common types of degenerative cerebellar ataxias

The cerebellar nuclei are a brain region with high iron content. Surprisingly, little is known about iron content in the cerebellar nuclei and its possible contribution to pathology in cerebellar ataxias, with the only exception of Friedreich’s ataxia. In the present exploratory cross-sectional study, quantitative susceptibility mapping was used to investigate volume, iron concentration and total iron content of the dentate nuclei in common types of hereditary and non-hereditary degenerative ataxias. Seventy-nine patients with spinocerebellar ataxias of types 1, 2, 3 and 6; 15 patients with Friedreich’s ataxia; 18 patients with multiple system atrophy, cerebellar type and 111 healthy controls were also included. All underwent 3 T MRI and clinical assessments. For each specific ataxia subtype, voxel-based and volumes-of-interest-based group analyses were performed in comparison with a corresponding age- and sex-matched control group, both for volume, magnetic susceptiblity (indicating iron concentration) and susceptibility mass (indicating total iron content) of the dentate nuclei. Spinocerebellar ataxia of type 1 and multiple system atrophy, cerebellar type patients showed higher susceptibilities in large parts of the dentate nucleus but unaltered susceptibility masses compared with controls. Friedreich’s ataxia patients and, only on a trend level, spinocerebellar ataxia of type 2 patients showed higher susceptibilities in more circumscribed parts of the dentate. In contrast, spinocerebellar ataxia of type 6 patients revealed lower susceptibilities and susceptibility masses compared with controls throughout the dentate nucleus. Spinocerebellar ataxia of type 3 patients showed no significant changes in susceptibility and susceptibility mass. Lower volume of the dentate nuclei was found to varying degrees in all ataxia types. It was most pronounced in spinocerebellar ataxia of type 6 patients and least prominent in spinocerebellar ataxia of type 3 patients. The findings show that alterations in susceptibility revealed by quantitative susceptibility mapping are common in the dentate nuclei in different types of cerebellar ataxias. The most striking changes in susceptibility were found in spinocerebellar ataxia of type 1, multiple system atrophy, cerebellar type and spinocerebellar ataxia of type 6. Because iron content is known to be high in glial cells but not in neurons of the cerebellar nuclei, the higher susceptibility in spinocerebellar ataxia of type 1 and multiple system atrophy, cerebellar type may be explained by a reduction of neurons (increase in iron concentration) and/or an increase in iron-rich glial cells, e.g. microgliosis. Hypomyelination also leads to higher susceptibility and could also contribute. The lower susceptibility in SCA6 suggests a loss of iron-rich glial cells. Quantitative susceptibility maps warrant future studies of iron content and iron-rich cells in ataxias to gain a more comprehensive understanding of the pathogenesis of these diseases.

Cerebellar and hepatic alterations in ACBD5-deficient mice are associated with unexpected, distinct alterations in cellular lipid homeostasis

ACBD5 deficiency is a novel peroxisome disorder with a largely uncharacterized pathology. ACBD5 was recently identified in a tethering complex mediating membrane contacts between peroxisomes and the endoplasmic reticulum (ER). An ACBD5-deficient mouse was analyzed to correlate ACBD5 tethering functions with the disease phenotype. ACBD5-deficient mice exhibit elevated very long-chain fatty acid levels and a progressive cerebellar pathology. Liver did not exhibit pathologic changes but increased peroxisome abundance and drastically reduced peroxisome-ER contacts. Lipidomics of liver and cerebellum revealed tissue-specific alterations in distinct lipid classes and subspecies. In line with the neurological pathology, unusual ultra-long chain fatty acids (C > 32) were elevated in phosphocholines from cerebelli but not liver indicating an organ-specific imbalance in fatty acid degradation and elongation pathways. By contrast, ether lipid formation was perturbed in liver towards an accumulation of alkyldiacylglycerols. The alterations in several lipid classes suggest that ACBD5, in addition to its acyl-CoA binding function, might maintain peroxisome-ER contacts in order to contribute to the regulation of anabolic and catabolic cellular lipid pathways.

Darwisch, von Spangenberg et al. show that ACBD5‐deficient mice exhibit elevated levels of very long‐chain fatty acids and a progressive cerebellar pathology. A complex metabolic phenotype suggests that ACBD5 with its acyl‐CoA binding and peroxisome‐ER tethering functions might contribute to the regulation of anabolic and catabolic cellular lipid pathways.

Polyglutamine spinocerebellar ataxias: emerging therapeutic targets

INTRODUCTION

Six of the most frequent dominantly inherited spinocerebellar ataxias (SCAs) worldwide - SCA1, SCA2, SCA3, SCA6, SCA7, and SCA17 - are caused by an expansion of a polyglutamine (polyQ) tract in the corresponding proteins. While the identification of the causative mutation has advanced knowledge on the pathogenesis of polyQ SCAs, effective therapeutics able to mitigate the severe clinical manifestation of these highly incapacitating disorders are not yet available.

AREAS COVERED

This review provides a comprehensive and critical perspective on well-established and emerging therapeutic targets for polyQ SCAs; it aims to inspire prospective drug discovery efforts.

EXPERT OPINION

The landscape of polyQ SCAs therapeutic targets and strategies includes (1) the mutant genes and proteins themselves, (2) enhancement of endogenous protein quality control responses, (3) abnormal protein-protein interactions of the mutant proteins, (4) disturbed neuronal function, (5) mitochondrial function, energy availability and oxidative stress, and (6) glial dysfunction, growth factor or hormone imbalances. Challenges include gaining a clearer definition of therapeutic targets for the drugs in clinical development, the discovery of novel drug-like molecules for challenging key targets, and the attainment of a stronger translation of preclinical findings to the clinic.

Pathogenic mechanisms underlying spinocerebellar ataxia type 1

The family of hereditary cerebellar ataxias is a large group of disorders with heterogenous clinical manifestations and genetic etiologies. Among these, over 30 autosomal dominantly inherited subtypes have been identified, collectively referred to as the spinocerebellar ataxias (SCAs). Generally, the SCAs are characterized by a progressive gait impairment with classical cerebellar features, and in a subset of SCAs, accompanied by extra-cerebellar features. Beyond the common gait impairment and cerebellar atrophy, the wide range of additional clinical features observed across the SCAs is likely explained by the diverse set of mutated genes that encode proteins with seemingly disparate functional roles in nervous system biology. By synthesizing knowledge obtained from studies of the various SCAs over the past several decades, convergence onto a few key cellular changes, namely ion channel dysfunction and transcriptional dysregulation, has become apparent and may represent central mechanisms of cerebellar disease pathogenesis. This review will detail our current understanding of the molecular pathogenesis of the SCAs, focusing primarily on the first described autosomal dominant spinocerebellar ataxia, SCA1, as well as the emerging common core mechanisms across the various SCAs.

Suppression of microglial activation and monocyte infiltration ameliorates cerebellar hemorrhage induced-brain injury and ataxia

Ataxia, characterized by uncoordinated movement, is often found in patients with cerebellar hemorrhage (CH), leading to long-term disability without effective management. Microglia are among the first responders to CNS insult. Yet the role and mechanism of microglia in cerebellar injury and ataxia after CH are still unknown. Using Ki20227, an inhibitor for colony-stimulating factor 1 receptor which mediates the signaling responsible for the survival of microglia, we determined the impact of microglial depletion on cerebellar injury and ataxia in a murine model of CH. Microglial depletion reduced cerebellar lesion volume and alleviated gait abnormality, motor incoordination, and locomotor dysfunction after CH. Suppression of CH-initiated microglial activation with minocycline ameliorated cerebellum infiltration of monocytes/macrophages, as well as production of proinflammatory cytokines and chemokine C-C motif ligand-2 (CCL-2) that recruits monocytes/macrophages. Furthermore, both minocycline and bindarit, a CCL-2 inhibitor, prevented apoptosis and electrophysiological dysfunction of Purkinje cells, the principal neurons and sole outputs of the cerebellar cortex, and consequently improved ataxia-like motor abnormalities. Our findings suggest a detrimental role of microglia in neuroinflammation and ataxic motor symptoms after CH, and pave a new path to understand the neuroimmune mechanism underlying CH-induced cerebellar ataxia.

Fatal stagger poisoning by consumption of Festuca argentina (Speg.) Parodi in goats from Argentine Patagonia

The present study describes the spontaneous and experimental poisoning of goats by Festuca argentina in Argentine Patagonia. In April 2017, eight seven-month-old Creole male goats were accidentally introduced into a paddock that contained F. argentina. After four days, two of the goats were found dead and four out of the six remaining goats were clinically affected. Two of the latter had to be later euthanized in extremis. The main clinical signs were progressive nervous signs, starting with moderate muscle tremors, wide-based stance and ataxia. Postmortem examination was performed on the two euthanized goats. Epidermal fragments of F. argentina were found in the rumen samples from the necropsied goats and the fecal samples from the four affected goats. For the experimental poisoning, fresh sheaths of F. argentina collected from the paddock were offered to two goats at 10 g/kg body weight for 3 days. After 24-36 h, both animals exhibited severe muscle tremors, reluctance to move, tetanic convulsions, and opisthotonus. In both the spontaneously and experimentally poisoned goats, gross lesions were similar and consisted of dehydration, petechial hemorrhages in the epicardium and congestion. The main microscopic findings consisted of degeneration and loss of Purkinje cells and torpedoes in the granular layer of the cerebellum. The F. argentina sheaths collected from the pasture were found to contain tremorgenic indole-diterpene alkaloids. Taken together, the results of the present study suggest that the tremorgenic syndrome observed in the spontaneously poisoned goats was due to poisoning by F. argentina.

Cerebellar Astrocytes: Much More Than Passive Bystanders In Ataxia Pathophysiology

Ataxia is a neurodegenerative syndrome, which can emerge as a major element of a disease or represent a symptom of more complex multisystemic disorders. It comprises several forms with a highly variegated etiology, mainly united by motor, balance, and speech impairments and, at the tissue level, by cerebellar atrophy and Purkinje cells degeneration. For this reason, the contribution of astrocytes to this disease has been largely overlooked in the past. Nevertheless, in the last few decades, growing evidences are pointing to cerebellar astrocytes as crucial players not only in the progression but also in the onset of distinct forms of ataxia. Although the current knowledge on this topic is very fragmentary and ataxia type-specific, the present review will attempt to provide a comprehensive view of astrocytes’ involvement across the distinct forms of this pathology. Here, it will be highlighted how, through consecutive stage-specific mechanisms, astrocytes can lead to non-cell autonomous neurodegeneration and, consequently, to the behavioral impairments typical of this disease. In light of that, treating astrocytes to heal neurons will be discussed as a potential complementary therapeutic approach for ataxic patients, a crucial point provided the absence of conclusive treatments for this disease.

Molecular Mechanisms and Therapeutics for Spinocerebellar Ataxia Type 2

The effective therapeutic treatment and the disease-modifying therapy for spinocerebellar ataxia type 2 (SCA2) (a progressive hereditary disease caused by an expansion of polyglutamine in the ataxin-2 protein) is not available yet. At present, only symptomatic treatment and methods of palliative care are prescribed to the patients. Many attempts were made to study the physiological, molecular, and biochemical changes in SCA2 patients and in a variety of the model systems to find new therapeutic targets for SCA2 treatment. A better understanding of the uncovered molecular mechanisms of the disease allowed the scientific community to develop strategies of potential therapy and helped to create some promising therapeutic approaches for SCA2 treatment. Recent progress in this field will be discussed in this review article.