Immune response in leukodystrophies

Exploration of potential immune mechanisms in cervical dystonia

BACKGROUND

Although there are many possible causes for cervical dystonia (CD), a specific etiology cannot be identified in most cases. Prior studies have suggested a relationship between autoimmune disease and some cases of CD, pointing to possible immunological mechanisms.

OBJECTIVE

The goal was to explore the potential role of multiple different immunological mechanisms in CD.

METHODS

First, a broad screening test compared neuronal antibodies in controls and CD. Second, unbiased blood plasma proteomics provided a broad screen for potential biologic differences between controls and CD. Third, a multiplex immunoassay compared 37 markers associated with immunological processes in controls and CD. Fourth, relative immune cell frequencies were investigated in blood samples of controls and CD. Finally, sequencing studies investigated the association of HLA DQB1 and DRB1 alleles in controls versus CD.

RESULTS

Screens for anti-neuronal antibodies did not reveal any obvious abnormalities. Plasma proteomics pointed towards certain abnormalities of immune mechanisms, and the multiplex assay pointed more specifically towards abnormalities in T lymphocytes. Abnormal immune cell frequencies were identified for some CD cases, and these cases clustered together as a potential subgroup. Studies of HLA alleles indicated a possible association between CD and DRB1*15:03, which is reported to mediate the penetrance of autoimmune disorders.

CONCLUSIONS

Altogether, the association of CD with multiple different blood-based immune measures point to abnormalities in cell-mediated immunity that may play a pathogenic role for a subgroup of individuals with CD.

Immune response of BV-2 microglial cells is impacted by peroxisomal beta-oxidation

Microglia are crucial for brain homeostasis, and dysfunction of these cells is a key driver in most neurodegenerative diseases, including peroxisomal leukodystrophies. In X-linked adrenoleukodystrophy (X-ALD), a neuroinflammatory disorder, very long-chain fatty acid (VLCFA) accumulation due to impaired degradation within peroxisomes results in microglial defects, but the underlying mechanisms remain unclear. Using CRISPR/Cas9 gene editing of key genes in peroxisomal VLCFA breakdown (Abcd1, Abcd2, and Acox1), we recently established easily accessible microglial BV-2 cell models to study the impact of dysfunctional peroxisomal β-oxidation and revealed a disease-associated microglial-like signature in these cell lines. Transcriptomic analysis suggested consequences on the immune response. To clarify how impaired lipid degradation impacts the immune function of microglia, we here used RNA-sequencing and functional assays related to the immune response to compare wild-type and mutant BV-2 cell lines under basal conditions and upon pro-inflammatory lipopolysaccharide (LPS) activation. A majority of genes encoding proinflammatory cytokines, as well as genes involved in phagocytosis, antigen presentation, and co-stimulation of T lymphocytes, were found differentially overexpressed. The transcriptomic alterations were reflected by altered phagocytic capacity, inflammasome activation, increased release of inflammatory cytokines, including TNF, and upregulated response of T lymphocytes primed by mutant BV-2 cells presenting peptides. Together, the present study shows that peroxisomal β-oxidation defects resulting in lipid alterations, including VLCFA accumulation, directly reprogram the main cellular functions of microglia. The elucidation of this link between lipid metabolism and the immune response of microglia will help to better understand the pathogenesis of peroxisomal leukodystrophies.

Elucidating the Therapeutic Utility of Olaparib in Sulfatide-Induced Human Astrocyte Toxicity and Neuroinflammation

Metachromatic leukodystrophy (MLD) is a severe demyelinating, autosomal recessive genetic leukodystrophy, with no curative treatment. The disease is underpinned by mutations in the arylsulfatase A gene (ARSA), resulting in deficient activity of this lysosomal enzyme, and consequential accumulation of galactosylceramide-3-O-sulfate (sulfatide) in the brain. Most of the effects in the brain have been attributed to the accumulation of sulfatides in oligodendrocytes and their cell damage. In contrast, less is known regarding sulfatide toxicity in astrocytes. Poly (ADP-ribose) polymerase (PARP) inhibitors are anti-cancer therapeutics that have proven efficacy in preclinical models of many neurodegenerative and inflammatory diseases, but have never been tested for MLD. Here, we examined the toxic effect of sulfatides on human astrocytes and restoration of this cell damage by the marketed PARP-1 inhibitor, Olaparib. Cultured human astrocytes were treated with increasing concentrations of sulfatides (5-100 μM) with or without Olaparib (100 nM). Cell viability assays were used to ascertain whether sulfatide-induced toxicity was rescued by Olaparib. Immunofluorescence, calcium (Ca2+) imaging, ROS, and mitochondrial damage assays were also used to explore the effects of sulfatides and Olaparib. ELISAs were performed and chemotaxis of peripheral blood immune cells was measured to examine the effects of Olaparib on sulfatide-induced inflammation in human astrocytes. Here, we established a concentration-dependent (EC50∼20 μM at 24 h) model of sulfatide-induced astrocyte toxicity. Our data demonstrate that sulfatide-induced astrocyte toxicity involves (i) PARP-1 activation, (ii) pro-inflammatory cytokine release, and (iii) enhanced chemoattraction of peripheral blood immune cells. Moreover, these sulfatide-induced effects were attenuated by Olaparib (IC50∼100 nM). In addition, sulfatide caused impairments of ROS production, mitochondrial stress, and Ca2+ signaling in human astrocytes, that were indicative of metabolic alterations and that were also alleviated by Olaparib (100 nM) treatment. Our data support the hypothesis that sulfatides can drive astrocyte cell death and demonstrate that Olaparib can dampen many facets of sulfatide-induced toxicity, including, mitochondrial stress, inflammatory responses, and communication between human astrocytes and peripheral blood immune cells. These data are suggestive of potential therapeutic utility of PARP inhibitors in the sphere of rare demyelinating diseases, and in particular MLD. Graphical abstract. Proposed mechanism of action of Olaparib in sulfatide-treated astrocytes. Human astrocytes treated for 24 h with sulfatides increase PARP-1 expression and die. PARP-1 overexpression is modulated by Ca2+ release from the endoplasmic reticulum, thus enhancing intracellular Ca2+ concentration. PARP-1 inhibition with Olaparib reduces Ca2+ influx and cell death. Olaparib also decreases IL-6, IL-8, IL-17, and CX3CL1 release from sulfatide-stimulated astrocytes, suggesting that PARP-1 plays a role in dampening neuroinflammation in MLD. This is confirmed by the reduction of immune cell migration such as lymphocytes, NK cells, and T cells towards sulfatide-treated astrocytes. Moreover, mitochondrial stress and ROS production induced by sulfatides are rescued by PARP-1 inhibition. Future studies will focus on the signaling cascades triggered by PARP-1-mediated currents in reactive astrocytes and Olaparib as a potential therapeutic target for MLD.

Myelin oligodendrocyte glycoprotein antibodies in genetic leukodystrophies

Accumulation of intermediate metabolites due to enzyme deficiencies and demyelination can provoke inflammation in genetic leukodystrophies. Thirty patients with genetic leukodystrophy and 48 healthy control sera were tested for anti-myelin oligodendrocyte glycoprotein (MOG) antibodies by fixed and/or live cell-based assays. MOG-IgG was detected in two late infantile metachromatic leukodystrophy (MLD) cases, both of which were also weakly positive for IgG1, and one with IgG3 as the dominant anti-MOG IgG subclass. MOG-IgG was borderline positive in a vanishing white matter (VWM) disease patient. These results suggest that inherited metabolic or degenerative processes can have an autoimmune component, possibly as an epiphenomenon.

Existing Evidence for the Repurposing of PARP-1 Inhibitors in Rare Demyelinating Diseases

Simple Summary

Poly (ADP-ribose) polymerase-1 (PARP-1) inhibitors are successful cancer therapeutics that impair DNA repair machinery, leading to an accumulation of DNA damage and consequently cell death. The shared underlying mechanisms driving malignancy and demyelinating disease, together with the success of anticancer drugs as repurposed therapeutics, makes the repurposing of PARP-1 inhibitors for demyelinating diseases a worthy concept to consider. In addition, PARP-1 inhibitors demonstrate notable neuroprotective effects in demyelinating disorders, including multiple sclerosis which is considered the archetypical demyelinating disease.

Abstract

Over the past decade, Poly (ADP-ribose) polymerase-1 (PARP-1) inhibitors have arisen as a novel and promising targeted therapy for breast cancer gene (BRCA)-mutated ovarian and breast cancer patients. Therapies targeting the enzyme, PARP-1, have since established their place as maintenance drugs for cancer. Here, we present existing evidence that implicates PARP-1 as a player in the development and progression of both malignancy and demyelinating disease. These findings, together with the proven clinical efficacy and marketed success of PARP-1 inhibitors in cancer, present the repurposing of these drugs for demyelinating diseases as a desirable therapeutic concept. Indeed, PARP-1 inhibitors are noted to demonstrate neuroprotective effects in demyelinating disorders such as multiple sclerosis and Parkinson’s disease, further supporting the use of these drugs in demyelinating, neuroinflammatory, and neurodegenerative diseases. In this review, we discuss the potential for repurposing PARP-1 inhibitors, with a focus on rare demyelinating diseases. In particular, we address the possible use of PARP-1 inhibitors in examples of rare leukodystrophies, for which there are a paucity of treatment options and an urgent need for novel therapeutic approaches.

Sphingolipids as Regulators of Neuro-Inflammation and NADPH Oxidase 2

Neuro-inflammation accompanies numerous neurological disorders and conditions where it can be associated with a progressive neurodegenerative pathology. In a similar manner, alterations in sphingolipid metabolism often accompany or are causative features in degenerative neurological conditions. These include dementias, motor disorders, autoimmune conditions, inherited metabolic disorders, viral infection, traumatic brain and spinal cord injury, psychiatric conditions, and more. Sphingolipids are major regulators of cellular fate and function in addition to being important structural components of membranes. Their metabolism and signaling pathways can also be regulated by inflammatory mediators. Therefore, as certain sphingolipids exert distinct and opposing cellular roles, alterations in their metabolism can have major consequences. Recently, regulation of bioactive sphingolipids by neuro-inflammatory mediators has been shown to activate a neuronal NADPH oxidase 2 (NOX2) that can provoke damaging oxidation. Therefore, the sphingolipid-regulated neuronal NOX2 serves as a mechanistic link between neuro-inflammation and neurodegeneration. Moreover, therapeutics directed at sphingolipid metabolism or the sphingolipid-regulated NOX2 have the potential to alleviate neurodegeneration arising out of neuro-inflammation.

Genetic defects in the sphingolipid degradation pathway and their effects on microglia in neurodegenerative disease

Sphingolipids, which function as plasma membrane lipids and signaling molecules, are highly enriched in neuronal and myelin membranes in the nervous system. They are degraded in lysosomes by a defined sequence of enzymatic steps. In the related group of disorders, the sphingolipidoses, mutations in the genes that encode the individual degradative enzymes cause lysosomal accumulation of sphingolipids and often result in severe neurodegenerative disease. Here we review the information indicating that microglia, which actively clear sphingolipid-rich membranes in the brain during development and homeostasis, are directly affected by these mutations and promote neurodegeneration in the sphingolipidoses. We also identify parallels between the sphingolipidoses and more common forms of neurodegeneration, which both exhibit evidence of defective sphingolipid clearance in the nervous system.

Failure of intrathecal allogeneic mesenchymal stem cells to halt progressive demyelination in two boys with cerebral adrenoleukodystrophy

Cerebral adrenoleukodystrophy is an inflammatory demyelinating condition that is the result of a mutation in the X‐linked ABCD1 gene, a peroxisomal very long chain fatty acid transporter. Although mutations in this gene result in adrenal insufficiency in the majority of affected individuals, 40% of those affected develop the demyelinating cerebral form, cerebral adrenoleukodystrophy (CALD). CALD is characterized by imaging findings of demyelination and contrast enhancement on magnetic resonance imaging (MRI). Although allogeneic hematopoietic cell transplantation can arrest progression of CALD early in its course, there is no accepted therapy for patients with advanced CALD. Mesenchymal stem cells (MSCs) have been used in a variety of clinical trials to capitalize on their anti‐inflammatory properties as well as promote tissue repair. We delivered MSCs via intrathecal (IT) route to two boys with rapidly advancing CALD. The first boy received three doses 1 week apart, whereas the second boy received a single dose of IT MSCs. We note delivery of IT MSCs was feasible and without complication. Follow‐up MRI scans after IT MSC delivery showed progressive demyelination in the first patient and no change in demyelination or contrast enhancement in the second patient. Although the infusion of IT MSCs was safe, it did not halt CALD progression in this setting, and future studies should focus on patient selection and dose optimization.

Potential Involvement of Peroxisome in Multiple Sclerosis and Alzheimer's Disease : Peroxisome and Neurodegeneration

Peroxisomopathies are rare diseases due to dysfunctions of the peroxisome in which this organelle is either absent or with impaired activities. These diseases, at the exception of type I hyperoxaluria and acatalasaemia, affect the central and peripheral nervous system. Due to the significant impact of peroxisomal abnormalities on the functioning of nerve cells, this has led to an interest in peroxisome in common neurodegenerative diseases, such as Alzheimer's disease and multiple sclerosis. In these diseases, a role of the peroxisome is suspected on the basis of the fatty acid and phospholipid profile in the biological fluids and the brains of patients. It is also speculated that peroxisomal dysfunctions could contribute to oxidative stress and mitochondrial alterations which are recognized as major players in the development of neurodegenerative diseases. Based on clinical and in vitro studies, the data obtained support a potential role of peroxisome in Alzheimer's disease and multiple sclerosis.

Neuroimmunology - the past, present and future

Neuroimmunology as a separate discipline has its roots in the fields of neurology, neuroscience and immunology. Early studies of the brain by Golgi and Cajal, the detailed clinical and neuropathology studies of Charcot and Thompson's seminal paper on graft acceptance in the central nervous system, kindled a now rapidly expanding research area, with the aim of understanding pathological mechanisms of inflammatory components of neurological disorders. While neuroimmunologists originally focused on classical neuroinflammatory disorders, such as multiple sclerosis and infections, there is strong evidence to suggest that the immune response contributes to genetic white matter disorders, epilepsy, neurodegenerative diseases, neuropsychiatric disorders, peripheral nervous system and neuro-oncological conditions, as well as ageing. Technological advances have greatly aided our knowledge of how the immune system influences the nervous system during development and ageing, and how such responses contribute to disease as well as regeneration and repair. Here, we highlight historical aspects and milestones in the field of neuroimmunology and discuss the paradigm shifts that have helped provide novel insights into disease mechanisms. We propose future perspectives including molecular biological studies and experimental models that may have the potential to push many areas of neuroimmunology. Such an understanding of neuroimmunology will open up new avenues for therapeutic approaches to manipulate neuroinflammation.

SIRT1 activation alleviates brain microvascular endothelial dysfunction in peroxisomal disorders

Peroxisomal disorders are genetically heterogeneous metabolic disorders associated with a deficit of very long chain fatty acid β-oxidation that commonly manifest as early-onset neurodegeneration. Brain microvascular endothelial dysfunction with increased permeability to monocytes has been described in X-linked adrenoleukodystrophy, one of the most common peroxisomal disorders caused by mutations of the ATP binding cassette subfamily D member 1 (ABCD1) gene. The present study demonstrated that dysregulation of sirtuin 1 (SIRT1) in human brain microvascular endothelial cells (HBMECs) mediates changes in adhesion molecules and tight-junction protein expression, as well as increased adhesion to monocytes associated with peroxisomal dysfunction due to ABCD1 or hydroxysteroid 17-β dehydrogenase 4 silencing. Furthermore, enhancement of the function of SIRT1 by resve-ratrol attenuated this molecular and functional dysregulation of HBMECs via modulation of the nuclear factor-κB and Krüppel-like factor 4 signaling pathways.

Cerebral adrenoleukodystrophy is associated with loss of tolerance to profilin

Childhood cerebral adrenoleukodystrophy (cALD) is a devastating manifestation of ALD accompanied by demyelination, inflammation, and blood brain barrier (BBB) disruption with shared characteristics of an auto-immune disease. We utilized plasma samples pre- and postdevelopment of cALD to determine the presence of specific auto-antibodies. Mass spectrometry of protein specifically bound with post-cALD plasma antibody identified Profilin1 (PFN1) as the target. In a screen of 94 boys with cALD 48 (51%) had anti-PFN1 antibodies, whereas only 2/29 boys with ALD but without cerebral disease, and 0/30 healthy controls showed anti-PFN1 immunoreactivity. Cerebral spinal fluid from those with cALD showed higher levels of PFN1 protein compared with non-cALD samples (324 ± 634 versus 42 ± 23 pg/mL, p = 0.04). Boys that were anti-PFN positive had a significant increase in the amount of gadolinium signal observed on MRI when compared to boys that were anti-PFN1 negative (p = 0.04) possibly indicating increased BBB disruption. Anti-PFN1 positivity was also associated with elevated levels of very long chain fatty acids (C26 of 1.12 ± 0.41 versus 0.97 ± 0.30 mg/dL, p = 0.03) and increased plasma BAFF (973 ± 277 versus 733 ± 269 pg/mL, p = 0.03). In conclusion, anti-PFN may be a novel biomarker associated with the development of cALD in boys with ALD.

Modeling and rescue of defective blood-brain barrier function of induced brain microvascular endothelial cells from childhood cerebral adrenoleukodystrophy patients

Background

X-linked adrenoleukodystrophy (X-ALD) is caused by mutations in the ABCD1 gene. 40% of X-ALD patients will convert to the deadly childhood cerebral form (ccALD) characterized by increased permeability of the brain endothelium that constitutes the blood–brain barrier (BBB). Mutation information and molecular markers investigated to date are not predictive of conversion. Prior reports have focused on toxic metabolic byproducts and reactive oxygen species as instigators of cerebral inflammation and subsequent immune cell invasion leading to BBB breakdown. This study focuses on the BBB itself and evaluates differences in brain endothelium integrity using cells from ccALD patients and wild-type (WT) controls.

Methods

The blood–brain barrier of ccALD patients and WT controls was modeled using directed differentiation of induced pluripotent stem cells (iPSCs) into induced brain microvascular endothelial cells (iBMECs). Immunocytochemistry and PCR confirmed characteristic expression of brain microvascular endothelial cell (BMEC) markers. Barrier properties of iBMECs were measured via trans-endothelial electrical resistance (TEER), sodium fluorescein permeability, and frayed junction analysis. Electron microscopy and RNA-seq were used to further characterize disease-specific differences. Oil-Red-O staining was used to quantify differences in lipid accumulation. To evaluate whether treatment with block copolymers of poly(ethylene oxide) and poly(propylene oxide) (PEO–PPO) could mitigate defective properties, ccALD-iBMECs were treated with PEO–PPO block copolymers and their barrier properties and lipid accumulation levels were quantified.

Results

iBMECs from patients with ccALD had significantly decreased TEER (2592 ± 110 Ω cm²) compared to WT controls (5001 ± 172 Ω cm²). They also accumulated lipid droplets to a greater extent than WT-iBMECs. Upon treatment with a PEO–PPO diblock copolymer during the differentiation process, an increase in TEER and a reduction in lipid accumulation were observed for the polymer treated ccALD-iBMECs compared to untreated controls.

Conclusions

The finding that BBB integrity is decreased in ccALD and can be rescued with block copolymers opens the door for the discovery of BBB-specific molecular markers that can indicate the onset of ccALD and has therapeutic implications for preventing the conversion to ccALD.

Electronic supplementary material

The online version of this article (10.1186/s12987-018-0094-5) contains supplementary material, which is available to authorized users.

An unusual neuroimaging finding and response to immunotherapy in a child with genetically confirmed vanishing white matter disease

BACKGROUND

We present an unusual neuroimaging finding in a young girl with genetically confirmed vanishing white matter disease and a possible response to immunotherapy.

METHODS AND RESULTS

2.5 yr old girl, presented with acute onset unsteadiness and encephalopathy following a viral illness. MRI showed global symmetric white matter abnormality, with symmetric enhancement of cranial nerves (III and V) and of cervical and lumbar roots. She received immunotherapy for her encephalopathic illness with white matter changes. Follow up neuroimaging showed resolution of white matter edema and resolution of the change in the brainstem. Genetic testing confirmed a diagnosis of vanishing white matter disease (VWMD).

CONCLUSION

Craniospinal nerve enhancement and possible response to immunotherapy has not been described in vanishing white matter disease.

Bone marrow-derived macrophages and the CNS: An update on the use of experimental chimeric mouse models and bone marrow transplantation in neurological disorders

The central nervous system (CNS) is a very unique system with multiple features that differentiate it from systemic tissues. One of the most captivating aspects of its distinctive nature is the presence of the blood brain barrier (BBB), which seals it from the periphery. Therefore, to preserve tissue homeostasis, the CNS has to rely heavily on resident cells such as microglia. These pivotal cells of the mononuclear lineage have important and dichotomous roles according to various neurological disorders. However, certain insults can overwhelm microglia as well as compromising the integrity of the BBB, thus allowing the infiltration of bone marrow-derived macrophages (BMDMs). The use of myeloablation and bone marrow transplantation allowed the generation of chimeric mice to study resident microglia and infiltrated BMDM separately. This breakthrough completely revolutionized the way we captured these 2 types of mononuclear phagocytic cells. We now realize that microglia and BMDM exhibit distinct features and appear to perform different tasks. Since these cells are central in several pathologies, it is crucial to use chimeric mice to analyze their functions and mechanisms to possibly harness them for therapeutic purpose. This review will shed light on the advent of this methodology and how it allowed deciphering the ontology of microglia and its maintenance during adulthood. We will also compare the different strategies used to perform myeloablation. Finally, we will discuss the landmark studies that used chimeric mice to characterize the roles of microglia and BMDM in several neurological disorders. This article is part of a Special Issue entitled: Neuro Inflammation edited by Helga E. de Vries and Markus Schwaninger.

Activated immune response in an inherited leukodystrophy disease caused by the loss of oligodendrocyte gap junctions

Oligodendrocyte:oligodendrocyte (O:O) gap junction (GJ) coupling is a widespread and essential feature of the CNS, and is mediated by connexin47 (Cx47) and Cx32. Loss of function mutations affecting Cx47 results in a severe leukodystrophy, Pelizeus-Merzbacher-like disease (also known as Hypomyelinating Leukodystrophy 2), which can be reproduced in mice lacking both Cx47 and Cx32. Here we report the gene expression profile of the cerebellum--an affected brain region--in mice lacking both Cx47 and Cx32. Of the 43,174 mRNA probes examined, we find decreased expression of 23 probes (corresponding to 23 genes) and increased expression of 545 probes (corresponding to 348 genes). Many of the genes with reduced expression map to oligodendrocytes, and two of them (Fa2h and Ugt8a) are involved in the synthesis of myelin lipids. Many of the genes with increased expression map to lymphocytes and microglia, and involved in leukotrienes/prostaglandins synthesis and chemokines/cytokines interactions and signaling pathways. In accord, immunostaining showed T- and B-cells in the cerebella of mutant mice as well as activated microglia and astrocytes. Thus, in addition to the loss of GJ coupling, there is a prominent immune response in mice lacking both Cx47 and Cx32.

Diverse intracellular pathogens activate type III interferon expression from peroxisomes

Type I interferon responses are considered the primary means by which viral infections are controlled in mammals. Despite this view, several pathogens activate antiviral responses in the absence of type I interferons. The mechanisms controlling type I interferon-independent responses are undefined. We found that RIG-I like receptors (RLRs) induce type III interferon expression in a variety of human cell types, and identified factors that differentially regulate expression of type I and type III interferons. We identified peroxisomes as a primary site of initiation of type III interferon expression, and revealed that the process of intestinal epithelial cell differentiation upregulates peroxisome biogenesis and promotes robust type III interferon responses in human cells. These findings highlight the importance of different intracellular organelles in specific innate immune responses.

Multiple endocrine disorders associated with adrenomyeloneuropathy and a novel mutation of the ABCD1 gene

INTRODUCTION

X-linked adrenomyeloneuropathy (X-AMN) is a genetic disorder that primarily affects the adrenal cortex and the nervous system. The disease shows a wide range of phenotypic expression, age of onset, and rate of progression.

PATIENT DESCRIPTION

We present a thalassemic 23-year-old man with X-AMN and multiple endocrine disorders. At age 2 years, he was diagnosed with thalassaemia intermedia, and he was receiving occasional blood transfusions and maintaining an adequate hemoglobin level without signs of extramedullar hematopoiesis or hemosiderosis. During adolescence, he was diagnosed with growth hormone deficiency, primary hypothyroidism, and primary adrenal insufficiency. In his early 20s he demonstrated progressive tetraparesis, and the diagnosis of X-AMN was confirmed by DNA analysis of the ABCD1 gene.

CONCLUSION

This patient expands the phenotype X-AMN by adding growth hormone deficiency and hypothyroidism.

Hypoperfusion predicts lesion progression in cerebral X-linked adrenoleukodystrophy

Magnetic resonance imaging sequences such as diffusion and spectroscopy have been well studied in X-linked adrenoleukodystrophy, but no data exist on magnetic resonance perfusion imaging. Since inflammation is known to modulate the microcirculation, we investigated the hypothesis that changes in the local perfusion might be one of the earliest signs of lesion development. Twenty patients with different phenotypes of adrenoleukodystrophy and seven age-matched controls were evaluated between 2006 and 2011. Fluid attenuated inversion recovery, post-contrast T(1)-weighted and normalized dynamic susceptibility contrast magnetic resonance perfusion cerebral blood volume maps were co-registered, segmented when cerebral lesion was present, and normalized cerebral blood volume values were analysed using a Food and Drug Association approved magnetic resonance perfusion software (NordicICE). Clinical and imaging data were reviewed to determine phenotype and status of progression. All eight patients with cerebral adrenoleukodystrophy had an average 80% decrease in normalized cerebral blood volume at the core of the lesion (P < 0.0001). Beyond the leading edge of contrast enhancement cerebral perfusion varied, patients with progressive lesions showed an average 60% decrease in normalized cerebral blood volume (adults P < 0.05; children P < 0.001), while one child with arrested progression normalized cerebral blood volume in this region. In six of seven patients with cerebral adrenoleukodystrophy lesions and follow-up imaging (2-24 month interval period), we found progression of contrast enhancement into the formerly hypoperfused perilesional zone. Asymptomatic, adrenomyeloneuropathy and female heterozygote patients had no significant changes in cerebral perfusion. Our data indicate that decreased brain magnetic resonance perfusion precedes leakage of the blood-brain barrier as demonstrated by contrast enhancement in cerebral adrenoleukodystrophy and is an early sign of lesion progression.

Treating inflammation in childhood neurodegenerative disorders

Inflammation of the central nervous system is a prominent feature in many childhood neurodegenerative conditions, with various studies demonstrating the upregulation of the innate and adaptive immune system. Recent evidence also suggests that this inflammatory process can contribute to further neurodegeneration. Furthermore, immunosuppression in mouse models of a few lysosomal storage disorders has demonstrated that attenuation of this immune response can influence the clinical and neuropathological progression. However, there are significant challenges before this finding translates to patient care. Treating inflammation in neurodegenerative conditions requires the identification of the time point when inflammation becomes pathogenic, after which the safest therapeutic strategies are required to target the various components and confounders of inflammation. Nevertheless, as the progress made towards effective gene-, cellular-, and enzyme-based therapy in most of these disorders has been disappointing, treating pathogenic inflammation may offer the clinician another therapeutic strategy in managing these devastating disorders.

Evaluation of neuroinflammation in X-linked adrenoleukodystrophy

We present findings of (11)C-[R]-PK11195 positron emission tomography in a child with X-linked adrenoleukodystrophy. (11)C-[R]-PK11195 is a radioligand with a high and specific affinity for peripheral benzodiazepine receptors, expressed by activated microglia in cases of neuroinflammation, and therefore it is applicable to the in vivo detection of neuroinflammation with positron emission tomography. (11)C-[R]-PK11195 positron emission tomography demonstrated increased tracer binding in the occipital, parietal, and posterior temporal white matter, in the genu of the corpus callosum, the bilateral posterior thalami, most of the posterior limb of the internal capsule, the bilateral cerebral peduncles, and the brainstem, indicating underlying neuroinflammation. The rest of the brain, including the cerebral cortices and cerebellum, exhibited minimal (11)C-[R]-PK11195 binding. Our findings indicate significant neuroinflammation associated with white matter destruction in X-linked adrenoleukodystrophy, which can be visualized in vivo with an (11)C-[R]-PK11195 positron emission tomography scan. (11)C-[R]-PK11195 positron emission tomography may also help evaluate the inflammatory burden and follow-up of the disease evolution. This technique may be particularly useful for evaluating treatment response, which is not easy with other imaging modalities, after white matter is significantly and extensively damaged.

Pharmacokinetics of clofarabine in patients with high-risk inherited metabolic disorders undergoing brain-sparing hematopoietic cell transplantation

Clofarabine, a newer purine analog with reduced central nervous system toxicity, may prove advantageous in hematopoietic cell transplantation in patients for whom neurotoxicity is a natural part of disease progression. This study evaluated clofarabine pharmacokinetics in adult and pediatric patients undergoing hematopoietic cell transplantation for the treatment of high-risk, inherited metabolic disorders. Clofarabine (40 mg/m(2)/d) was administered intravenously on days -7 to -3. Kinetic sampling occurred with doses 1 and 5, along with a single level collected on day of transplant (day(0)). Sixteen patients were studied with a median (range) age and body surface area (BSA) of 7.5 years (0.5-43) and 0.94 m(2) (0.31-2.3), respectively. Clofarabine area under the concentration-time curve from time 0 to infinity was 931 ng·h/mL (685-1876), maximum concentration was 226 ng/mL (162-600), and minimum concentration was 3.2 ng/mL (1.7-5.6). Clofarabine clearance was 1.6 L/h/kg (0.7-2.4) and weakly correlated with weight (r(2) = 0.33) and BSA (r(2) = 0.26). No difference in plasma concentrations was found between dose 1 and dose 5 (all P > .05). All concentrations were below the limit of quantification (1 ng/mL) on day(0) in patients with normal renal function. Variability in clofarabine clearance was approximately 3-fold and was not adequately explained by covariates describing renal function and body size. In patients with adequate renal function, no drug accumulation occurs with consecutive daily dosing.

Stem cells in genetic myelin disorders

The genetic myelin disorders are a range of diseases that manifest with severe neurological problems, often from infancy. It has been postulated for some time that stem cells might be an effective treatment for these disorders, primarily as agents to restore dysfunctional or lost myelin. Stem cells, however, may offer a wider range of therapeutic potential, for instance as vehicles to replace abnormal enzymes or genes, or to provide trophic support for residual CNS tissue. This article will review several of the more common genetic myelin disorders and currently available therapies, including bone marrow transplantation for adrenoleukodystrophy. Specific stem cell subtypes and their relevance to potential therapeutic use will be discussed and stem cell transplantation in animal model studies will also be reviewed.

Common and uncommon pathogenic cascades in lysosomal storage diseases

Lysosomal storage diseases (LSDs), of which about 50 are known, are caused by the defective activity of lysosomal proteins, resulting in accumulation of unmetabolized substrates. As a result, a variety of pathogenic cascades are activated such as altered calcium homeostasis, oxidative stress, inflammation, altered lipid trafficking, autophagy, endoplasmic reticulum stress, and autoimmune responses. Some of these pathways are common to many LSDs, whereas others are only altered in a subset of LSDs. We now review how these cascades impact upon LSD pathology and suggest how intervention in the pathways may lead to novel therapeutic approaches.

Transplant outcomes in leukodystrophies

Hematopoietic stem cell transplantation (HSCT) has been used for three decades as therapy for lysosomal storage diseases. Stable engraftment following transplantation has the potential to provide a source of an enzyme for the life of a patient. Recombinant enzyme is available for disorders that do not have a primary neurologic component. However, for diseases affecting the central nervous system (CNS), intravenous enzyme is ineffective due to its inability to cross the blood-brain barrier. For selected lysosomal disorders, including metachromatic leukodystrophy and globoid cell leukodystrophy, disease phenotype and the extent of disease at the time of transplantation are of fundamental importance in determining outcomes. Adrenoleukodystrophy is an X-linked, peroxisomal disorder, and in approximately 40% of cases a progressive, inflammatory condition develops in the CNS. Early in the course of the disease, allogeneic transplantation can arrest the disease process in cerebral adrenoleukodystrophy, while more advanced patients do poorly. In many of these cases, the utilization of cord blood grafts allows expedient transplantation, which can be critical in achieving optimal outcomes.

Cerebrospinal fluid neopterin in paediatric neurology: a marker of active central nervous system inflammation

AIM

Cerebrospinal fluid (CSF) neopterin production is increased by interferon-gamma stimulation and appears to act as a marker of intrathecal immune activation. We aimed to test the usefulness of elevated CSF neopterin as a biological marker of central nervous system (CNS) inflammation.

METHOD

We retrospectively reviewed CSF neopterin in 158 children (89 males, 69 females, mean age 4y 1mo, SD 3y 11mo, range 1mo-15y).

RESULTS

CSF neopterin levels in children with chronic static CNS disorders (n=105) were predominantly low, suggesting that inflammation is rare in these patients. We created an upper value of normal (chronic static group 95th centile 27.4 nmol/l). CSF neopterin was elevated in all 10 patients with acute encephalitis and in 10 of 12 patients with other acute inflammatory CNS disorders (demyelination, post-infectious ataxia, myelitis). CSF neopterin was also significantly elevated in patients with chronic progressive disorders of inflammatory origin. Interestingly, CSF neopterin was elevated in four of six patients with chronic static disorders who were tested during a febrile exacerbation of seizures or dystonia, suggesting that intrathecal immune activation may be important in this setting.

INTERPRETATION

Neopterin has a short half-life and was useful for monitoring inflammation activity in a patient with relapsing-remitting encephalitis. CSF neopterin is a useful marker of inflammation in a broad range of acute and chronic CNS disorders, and is a significantly more sensitive marker of inflammation than CSF pleocytosis.