Glial degeneration with oxidative damage drives neuronal demise in MPSII disease

Glycosaminoglycan-induced proinflammatory cytokine levels as disease marker in mucopolysaccharidosis

Recently, it has been shown disturbances in oxidant/antioxidant system and increases in some inflammatory markers in animal studies and in some Mucopolysaccharidoses (MPSs) patients. In this study, we aimed to determine the oxidative stress/antioxidant parameters and pro-inflammatory cytokine levels in the serum of MPS patients, in order to evaluate the possible role of inflammation in these patient groups regarding to accumulated metabolites. MPS I (n = 3), MPS II (n = 8), MPS III (n = 4), MPS IVA (n = 3), MPS VI (n = 3), and VII (n = 1) patients and 20 age-matched healthy subjects were included into the study. There was no statistically significant change in activities of SOD, Catalase, GSH-Px and lipid peroxidation levels in erythrocytes between the MPS patients and healthy controls. While IL-1alpha (p = 0.054), IL-6 (p = 0.008) levels, and chitotriosidase activity (p = 0.003) elevated in MPS3 patients, IL1α (p = 0.006), IL-1β (p = 0.006), IL-6 (p = 0.006), IFNγ (p = 0.006), and NFκB (p = 0.006) levels increased in MPS-6 patients. Elevated levels of IL-6, IL1α and chitotriosidase activity demonstrated macrophage activation in MPSIII untreated with enzyme replacement. Our study showed for the first time that high levels of IL1α, IL-6, IL1β and NFκB were present in MPSVI patients, demonstrating the induction of inflammation by dermatan sulphate. The low level of paraoxonase in MPSVI patients may be a good marker for cardiac involvement. Overall, this study provides important insights into the relationship between lysosomal storage of glycosaminoglycan and inflammation in MPS patients. It highlights possible pathways for the increased release of inflammatory molecules and suggests new targets for the development of treatments.

Lysosomal storage diseases

Lysosomal storage disorders (LSDs) are a group of inherited metabolic diseases caused by dysfunction of the lysosomal system, with subsequent progressive accumulation of macromolecules, activation of inflammatory response, and cell death. Neurologic damage is almost always present, and it is usually degenerative. White matter (WM) involvement may be primary or secondary. Diseases with primary WM involvement are leukodystrophies, demyelinating (Krabbe disease and metachromatic leukodystrophy), and hypomyelinating leukodystrophies (free sialic acid storage disease, fucosidosis, and mucolipidosis type IV). LSDs with secondary WM involvement are classified as leukoencephalopathies and include gangliosidosis, mucopolysaccharidosis (MPS), ceroid neuronal lipofuscinosis, multiple sulfatase deficiency, alpha-mannosidosis, Pompe disease, and Fabry disease. Neurologic manifestations may overlap among LSDs and include developmental delays, motor, cognitive and speech impairments, seizures, visual failure, ataxia, and extrapyramidal signs. Most of LSDs are typically present in early or late infancy, but juvenile and adult forms also exist and are associated with predominantly neuropsychiatric and behavioral symptoms. The outcome of these disorders is generally poor and specific treatments (enzyme replacement therapy, hematopoietic stem cell transplantation, or gene therapy) are only available in a small number of them.

Enzyme replacement with transferrin receptor-targeted α-L-iduronidase rescues brain pathology in mucopolysaccharidosis I mice

Mucopolysaccharidosis I (MPS I), a lysosomal storage disease caused by dysfunction of α-L-iduronidase (IDUA), is characterized by the deposition of dermatan sulfate (DS) and heparan sulfate (HS) throughout the body, which causes several somatic and central nervous symptoms. Although enzyme-replacement therapy (ERT) is currently available to treat MPS I, it does not alleviate central nervous disorders, as it cannot penetrate the blood-brain barrier. Here we evaluate the brain delivery, efficacy, and safety of JR-171, a fusion protein comprising humanized anti-human transferrin receptor antibody Fab and IDUA, using monkeys and MPS I mice. Intravenously administered JR-171 was distributed in major organs, including the brain, and reduced DS and HS concentrations in the central nervous system and peripheral tissues. JR-171 exerted similar effects on peripheral disorders similar to conventional ERT and further reversed brain pathology in MPS I mice. We found that JR-171 improved spatial learning ability, which was seen to deteriorate in the vehicle-treated mice. Further, no safety concerns were noted in repeat-dose toxicity studies in monkeys. This study provides nonclinical evidence that JR-171 might potentially prevent and even improve disease conditions in patients with neuronopathic MPS I without serious safety concerns.

Mucopolysaccharidosis: What Pediatric Rheumatologists and Orthopedics Need to Know

Mucopolysaccharidosis (MPS) is a group of disorders caused by the reduced or absent activity of enzymes involved in the glycosaminoglycans (GAGs) degradation; the consequence is the progressive accumulation of the substrate (dermatan, heparan, keratan or chondroitin sulfate) in the lysosomes of cells belonging to several tissues. The rarity, the broad spectrum of manifestations, the lack of strict genotype-phenotype association, and the progressive nature of MPS make diagnosing this group of conditions challenging. Musculoskeletal involvement represents a common and prominent feature of MPS. Joint and bone abnormalities might be the main clue for diagnosing MPS, especially in attenuated phenotypes; therefore, it is essential to increase the awareness of these conditions among the pediatric rheumatology and orthopedic communities since early diagnosis and treatment are crucial to reduce the disease burden of these patients. Nowadays, enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT) are available for some MPS types. We describe the musculoskeletal characteristics of MPS patients through a literature review of MPS cases misdiagnosed as having rheumatologic or orthopedic conditions.

Rag2-/- accelerates lipofuscin accumulation in the brain: Implications for human stem cell brain transplantation studies

Immunodeficient mice are widely used in human stem cell transplantation research. Recombination activating gene 1 (Rag1) deletion results in immunodeficiency and leads to accelerated aging in zebrafish with increased cytosolic accumulation of lipofuscin (LF). Unlike zebrafish, mammals have two homologs, Rag1 and Rag2, that regulate adaptive immunity. Currently, little is known if and how Rag1-/- and Rag2-/- may impact aging and LF accumulation in immunodeficient mouse brains and how this may confound results in human neural cell transplantation studies. Here, we demonstrate that in Rag2-/- mouse brains, LF appears early, spreads broadly, emits strong autofluorescence, and accumulates with age. LF is found in various types of glial cells, including xenografted human microglia. Surprisingly, in Rag1-/- mouse brains, LF autofluorescence is seen at much older ages compared with Rag2-/- brains. This study provides direct evidence that Rag2-/- expedites LF occurrence and sets a context for studies using aged immunodeficient mice.

Azithromycin Protects Retinal Glia Against Oxidative Stress-Induced Morphological Changes, Inflammation, and Cell Death

The reactivity of retinal glia in response to oxidative stress has a significant effect on retinal pathobiology. The reactive glia change their morphology and secret cytokines and neurotoxic factors in response to oxidative stress associated with retinal neurovascular degeneration. Therefore, pharmacological intervention to protect glial health against oxidative stress is crucial for maintaining homeostasis and the normal function of the retina. In this study, we explored the effect of azithromycin, a macrolide antibiotic with antioxidant, immunomodulatory, anti-inflammatory, and neuroprotective properties against oxidative stress-induced morphological changes, inflammation, and cell death in retinal microglia and Müller glia. Oxidative stress was induced by H₂O₂, and the intracellular oxidative stress was measured by DCFDA and DHE staining. The change in morphological characteristics such as the surface area, perimeter, and circularity was calculated using ImageJ software. Inflammation was measured by enzyme-linked immunosorbent assays for TNF-α, IL-1β, and IL-6. Reactive gliosis was characterized by anti-GFAP immunostaining. Cell death was measured by MTT assay, acridine orange/propidium iodide, and trypan blue staining. Pretreatment of azithromycin inhibits H₂O₂-induced oxidative stress in microglial (BV-2) and Müller glial (MIO-M1) cells. We observed that azithromycin inhibits oxidative stress-induced morphological changes, including the cell surface area, circularity, and perimeter in BV-2 and MIO-M1 cells. It also inhibits inflammation and cell death in both the glial cells. Azithromycin could be used as a pharmacological intervention on maintaining retinal glial health during oxidative stress.

Pathogenic Roles of Heparan Sulfate and Its Use as a Biomarker in Mucopolysaccharidoses

Heparan sulfate (HS) is an essential glycosaminoglycan (GAG) as a component of proteoglycans, which are present on the cell surface and in the extracellular matrix. HS-containing proteoglycans not only function as structural constituents of the basal lamina but also play versatile roles in various physiological processes, including cell signaling and organ development. Thus, inherited mutations of genes associated with the biosynthesis or degradation of HS can cause various diseases, particularly those involving the bones and central nervous system (CNS). Mucopolysaccharidoses (MPSs) are a group of lysosomal storage disorders involving GAG accumulation throughout the body caused by a deficiency of GAG-degrading enzymes. GAGs are stored differently in different types of MPSs. Particularly, HS deposition is observed in patients with MPS types I, II, III, and VII, all which involve progressive neuropathy with multiple CNS system symptoms. While therapies are available for certain symptoms in some types of MPSs, significant unmet medical needs remain, such as neurocognitive impairment. This review presents recent knowledge on the pathophysiological roles of HS focusing on the pathogenesis of MPSs. We also discuss the possible use and significance of HS as a biomarker for disease severity and therapeutic response in MPSs.

Lysosomal positioning diseases: beyond substrate storage

Lysosomal storage diseases (LSDs) comprise a group of inherited monogenic disorders characterized by lysosomal dysfunctions due to undegraded substrate accumulation. They are caused by a deficiency in specific lysosomal hydrolases involved in cellular catabolism, or non-enzymatic proteins essential for normal lysosomal functions. In LSDs, the lack of degradation of the accumulated substrate and its lysosomal storage impairs lysosome functions resulting in the perturbation of cellular homeostasis and, in turn, the damage of multiple organ systems. A substantial number of studies on the pathogenesis of LSDs has highlighted how the accumulation of lysosomal substrates is only the first event of a cascade of processes including the accumulation of secondary metabolites and the impairment of cellular trafficking, cell signalling, autophagic flux, mitochondria functionality and calcium homeostasis, that significantly contribute to the onset and progression of these diseases. Emerging studies on lysosomal biology have described the fundamental roles of these organelles in a variety of physiological functions and pathological conditions beyond their canonical activity in cellular waste clearance. Here, we discuss recent advances in the knowledge of cellular and molecular mechanisms linking lysosomal positioning and trafficking to LSDs.

Secondary Mitochondrial Dysfunction as a Cause of Neurodegenerative Dysfunction in Lysosomal Storage Diseases and an Overview of Potential Therapies

Mitochondrial dysfunction has been recognised a major contributory factor to the pathophysiology of a number of lysosomal storage disorders (LSDs). The cause of mitochondrial dysfunction in LSDs is as yet uncertain, but appears to be triggered by a number of different factors, although oxidative stress and impaired mitophagy appear to be common inhibitory mechanisms shared amongst this group of disorders, including Gaucher’s disease, Niemann–Pick disease, type C, and mucopolysaccharidosis. Many LSDs resulting from defects in lysosomal hydrolase activity show neurodegeneration, which remains challenging to treat. Currently available curative therapies are not sufficient to meet patients’ needs. In view of the documented evidence of mitochondrial dysfunction in the neurodegeneration of LSDs, along with the reciprocal interaction between the mitochondrion and the lysosome, novel therapeutic strategies that target the impairment in both of these organelles could be considered in the clinical management of the long-term neurodegenerative complications of these diseases. The purpose of this review is to outline the putative mechanisms that may be responsible for the reported mitochondrial dysfunction in LSDs and to discuss the new potential therapeutic developments.

Dose-dependent effects of a brain-penetrating iduronate-2-sulfatase on neurobehavioral impairments in mucopolysaccharidosis II mice

Deposition of heparan sulfate (HS) in the brain of patients with mucopolysaccharidosis II (MPS II) is believed to be the leading cause of neurodegeneration, resulting in several neurological signs and symptoms, including neurocognitive impairment. We recently showed that pabinafusp alfa, a blood-brain-barrier-penetrating fusion protein consisting of iduronate-2-sulfatase and anti-human transferrin receptor antibody, stabilized learning ability by preventing the deposition of HS in the CNS of MPS II mice. We further examined the dose-dependent effect of pabinafusp alfa on neurological function in relation to its HS-reducing efficacy in a mouse model of MPS II. Long-term intravenous treatment with low (0.1 mg/kg), middle (0.5 mg/kg), and high (2.0 mg/kg) doses of the drug dose-dependently decreased HS concentration in the brain and cerebrospinal fluid (CSF). A comparable dose-dependent effect in the prevention of neuronal damage in the CNS, and dose-dependent improvements in neurobehavioral performance tests, such as gait analysis, pole test, Y maze, and Morris water maze, were also observed. Notably, the water maze test performance was inversely correlated with the HS levels in the brain and CSF. This study provides nonclinical evidence substantiating a quantitative dose-dependent relationship between HS reduction in the CNS and neurological improvements in MPS II.

Innate Immunity in Mucopolysaccharide Diseases

Mucopolysaccharidoses are rare paediatric lysosomal storage disorders, characterised by accumulation of glycosaminoglycans within lysosomes. This is caused by deficiencies in lysosomal enzymes involved in degradation of these molecules. Dependent on disease, progressive build-up of sugars may lead to musculoskeletal abnormalities and multi-organ failure, and in others, to cognitive decline, which is still a challenge for current therapies. The worsening of neuropathology, observed in patients following recovery from flu-like infections, suggests that inflammation is highly implicated in disease progression. This review provides an overview of the pathological features associated with the mucopolysaccharidoses and summarises current knowledge regarding the inflammatory responses observed in the central nervous system and periphery. We propose a model whereby progressive accumulation of glycosaminoglycans elicits an innate immune response, initiated by the Toll-like receptor 4 pathway, but also precipitated by secondary storage components. Its activation induces cells of the immune system to release pro-inflammatory cytokines, such as TNF-α and IL-1, which induce progression through chronic neuroinflammation. While TNF-α is mostly associated with bone and joint disease in mucopolysaccharidoses, increasing evidence implicates IL-1 as a main effector of innate immunity in the central nervous system. The (NOD)-like receptor protein 3 inflammasome is therefore implicated in chronic neuroinflammation and should be investigated further to identify novel anti-inflammatory treatments.

Enzyme Replacement Therapy with Pabinafusp Alfa for Neuronopathic Mucopolysaccharidosis II: An Integrated Analysis of Preclinical and Clinical Data

Enzyme replacement therapy (ERT) improves somatic manifestations in mucopolysaccharidoses (MPS). However, because intravenously administered enzymes cannot cross the blood-brain barrier (BBB), ERT is ineffective against the progressive neurodegeneration and resultant severe central nervous system (CNS) symptoms observed in patients with neuronopathic MPS. Attempts to surmount this problem have been made with intrathecal and intracerebroventricular ERT in order to achieve CNS effects, but the burdens on patients are inimical to long-term administrations. However, since pabinafusp alfa, a human iduronate-2-sulfatase fused with a BBB-crossing anti-transferrin receptor antibody, showed both central and peripheral efficacy in a mouse model, subsequent clinical trials in a total of 62 patients with MPS-II (Hunter syndrome) in Japan and Brazil substantiated this dual efficacy and provided an acceptable safety profile. To date, pabinafusp alfa is the only approved intravenous ERT that is effective against both the somatic and CNS symptoms of patients with MPS-II. This article summarizes the previously obtained preclinical and clinical evidence related to the use of this drug, presents latest data, and discusses the preclinical, translational, and clinical challenges of evaluating, ameliorating, and preventing neurodegeneration in patients with MPS-II.

Oxidative Stress in Mucopolysaccharidoses: Pharmacological Implications

Although mucopolysaccharidoses (MPS) are caused by mutations in genes coding for enzymes responsible for degradation of glycosaminoglycans, storage of these compounds is crucial but is not the only pathomechanism of these severe, inherited metabolic diseases. Among various factors and processes influencing the course of MPS, oxidative stress appears to be a major one. Oxidative imbalance, occurring in MPS and resulting in increased levels of reactive oxidative species, causes damage of various biomolecules, leading to worsening of symptoms, especially in the central nervous system (but not restricted to this system). A few therapeutic options are available for some types of MPS, including enzyme replacement therapy and hematopoietic stem cell transplantation, however, none of them are fully effective in reducing all symptoms. A possibility that molecules with antioxidative activities might be useful accompanying drugs, administered together with other therapies, is discussed in light of the potential efficacy of MPS treatment.

Can serial cerebral MRIs predict the neuronopathic phenotype of MPS II?

OBJECTIVE

To advance the prediction of the neurocognitive development in MPS II patients by jointly analyzing MRI and neurocognitive data in mucopolysaccharidosis (MPS) II patients.

METHODS

Cognitive ability scores (CAS) were obtained by neuropsychological testing. Cerebral MRIs were quantified using a disease-specific protocol. MRI sumscores were calculated for atrophy, white-matter abnormalities (WMA) and Virchow-Robin spaces (VRS). To distinguish between atrophy and hydrocephalus the Evans' index and the callosal angle (CA) were measured. A random effects repeated measurement model was used to correlate CAS with the three MRI sumscores.

RESULTS

MRI (n = 47) and CAS scores (n = 78) of 19 male patients were analyzed. Ten patients were classified as neuronopathic and nine as non-neuronopathic. Neuronopathic patients had normal cognitive development until age 3 years. Mental age plateaued between ages 3 and 6, and subsequently declined with loss of skills at a maximum developmental age of 4 years. MRIs of neuronopathic patients showed abnormal atrophy sumscores before CAS dropped below the threshold for intellectual disability (<70). White-matter abnormalities (WMA) and brain atrophy progressed. The calculated sumscores were inversely correlated with CAS (r = -.90 for atrophy and -.69 for WMA). This was not biased by the influence of hydrocephalus as shown by measurement of the Evans' and callosal angle. Changes over time in the Virchow-Robin spaces (VRS) on MRI were minimal.

CONCLUSION

In our cohort, brain atrophy showed a stronger correlation to a decline in CAS when compared to WMA. Atrophy-scores were higher in young neuronopathic patients than in non-neuronopathic patients and atrophy was an important early sign for the development of the neuronopathic phenotype, especially when observed jointly with white-matter abnormalities.

Acute Arterial Ischemic Stroke in a Treated Child with Hunter's Syndrome: A Case Report and Review of the Literature

Enzyme replacement therapy (ERT) has limited therapeutic effects on neurologic, skeletal, and cardiovascular pathophysiology. We report an acute right-sided flaccid hemiparesis in an 11-year-old boy with the severe neuronopathic phenotype of Hunter's syndrome who was receiving weekly idursulfase ERT. Due to his psychomotor regression and epilepsy, his presentation to the hospital was delayed. Computed tomography scan of brain showed no acute changes or hemorrhage. Stroke code was not called as patient was already outside of the time window for tissue plasminogen activator (tPA) therapy. Brain magnetic resonance imaging (MRI) showed diffuse cortical and deep atrophy consistent with his baseline neurological status and restricted diffusion in the territory of the left-middle cerebral artery (MCA) consistent with recent infarction. T1-weighted MRI revealed low signal intensity of the left insular cortex, as well as volume loss, consistent with previous undiagnosed stroke in the same vascular territory. In addition, MR angiogram (MRA) demonstrated left terminal M1 segment MCA occlusion. Echocardiogram showed aortic root dilation and moderate aortic valve insufficiency. Patient was also noted to have bacteremia related to port infection. ERT is limited by blood–brain barrier and the underlying glycosaminoglycans (GAGs) extracellular tissue accumulation which produces a proinflammatory state. GAG and bacterial lipopolysaccharide (LPS) are known to activate toll-like receptor 4 (TLR-4). GAGs released in the extracellular space of intracranial vessels induce inflammation by activating the TLR-4 pathway which is exacerbated by bacterial LPS contributing to focal arteritis. Our case suggests the importance of GAGs in the activation of the TLR-4 pathway as a cause of stroke in Hunter's syndrome.

Clearance of heparan sulfate in the brain prevents neurodegeneration and neurocognitive impairment in MPS II mice

Mucopolysaccharidosis II (MPS II), a lysosomal storage disease caused by mutations in iduronate-2-sulfatase (IDS), is characterized by a wide variety of somatic and neurologic symptoms. The currently approved intravenous enzyme replacement therapy with recombinant IDS (idursulfase) is ineffective for CNS manifestations due to its inability to cross the blood-brain barrier (BBB). Here, we demonstrate that the clearance of heparan sulfate (HS) deposited in the brain by a BBB-penetrable antibody-enzyme fusion protein prevents neurodegeneration and neurocognitive dysfunctions in MPS II mice. The fusion protein pabinafusp alfa was chronically administered intravenously to MPS II mice. The drug reduced HS and attenuated histopathological changes in the brain, as well as in peripheral tissues. The loss of spatial learning abilities was completely suppressed by pabinafusp alfa, but not by idursulfase, indicating an association between HS deposition in the brain, neurodegeneration, and CNS manifestations in these mice. Furthermore, HS concentrations in the brain and reduction thereof by pabinafusp alpha correlated with those in the cerebrospinal fluid (CSF). Thus, repeated intravenous administration of pabinafusp alfa to MPS II mice decreased HS deposition in the brain, leading to prevention of neurodegeneration and maintenance of neurocognitive function, which may be predicted from HS concentrations in CSF.

The rapidly evolving view of lysosomal storage diseases

Lysosomal storage diseases are a group of metabolic disorders caused by deficiencies of several components of lysosomal function. Most commonly affected are lysosomal hydrolases, which are involved in the breakdown and recycling of a variety of complex molecules and cellular structures. The understanding of lysosomal biology has progressively improved over time. Lysosomes are no longer viewed as organelles exclusively involved in catabolic pathways, but rather as highly dynamic elements of the autophagic-lysosomal pathway, involved in multiple cellular functions, including signaling, and able to adapt to environmental stimuli. This refined vision of lysosomes has substantially impacted on our understanding of the pathophysiology of lysosomal disorders. It is now clear that substrate accumulation triggers complex pathogenetic cascades that are responsible for disease pathology, such as aberrant vesicle trafficking, impairment of autophagy, dysregulation of signaling pathways, abnormalities of calcium homeostasis, and mitochondrial dysfunction. Novel technologies, in most cases based on high-throughput approaches, have significantly contributed to the characterization of lysosomal biology or lysosomal dysfunction and have the potential to facilitate diagnostic processes, and to enable the identification of new therapeutic targets.

Detrimental effects of fructose on mitochondria in mouse motor neurons and on C. elegans healthspan

BACKGROUND

Fructose-common sweetener, consumed in large quantities, is now known to be associated with various metabolic diseases. Recent reports suggest fructose's involvement in neurodegeneration, neurotoxicity, and neuroinflammation. But, its impact at cellular and subcellular level and on energy metabolism, especially, mitochondrial bioenergetics, in neurons is not known.

OBJECTIVES

To study the adverse effects of high fructose in general, and on the mitochondria in a spinal cord motor neuron cell line, NSC-34, in vitro, and Caenorhabditis elegans in vivo.

METHODS

NSC-34 was treated with 0.5%-5% of fructose for different time periods. Fructose's effect on cell viability (MTT assay), metabolic activity (XF24 Seahorse assays) and C. elegans, chronically fed with 5% fructose and alteration in healthspan/mitochondria was monitored.

RESULTS

In NSC-34: Fructose at 4-5% elicits 60% cell death. Unlike 1%, 5% fructose (F5%) decreased mitochondrial membrane potential by 29%. Shockingly, 6hours F5% treatment almost abolished mitochondrial respiration - basal-respiration (∨123%), maximal-respiration (∨ 95%) and spare-respiratory-capacity (∨ 83%) and ATP production (∨98%) as revealed by XF 24- Seahorse assays. But non - mitochondrial respiration was spared. F5% treatment for 48hrs resulted in the total shutdown of respiratory machinery including glycolysis. Chronic feeding of wildtype C.elegans to F5% throughout, shortened lifespan by ~3 days (∨ 17%), progressively reduced movement (day-2 -∨10.25%, day-5 -∨25% and day-10 -∨56%) and food intake with age (day-5-∨9% and day-10 -∨48%) and instigated mitochondrial swelling and disarray in their arrangement in adult worms body-wall muscle cells.

CONCLUSION

Chronic exposure to high fructose negatively impacts cell viability, mitochondrial function, basal glycolysis, and healthspan.

Modeling Mucopolysaccharidosis Type II in the Fruit Fly by Using the RNA Interference Approach

Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disorder that occurs due to the deficit of the lysosomal enzyme iduronate 2-sulfatase (IDS) that leads to the storage of the glycosaminoglycan heparan- and dermatan-sulfate in all organs and tissues. It is characterized by important clinical features and the severe form presents with a heavy neurological involvement. However, almost nothing is known about the neuropathogenesis of MPS II. To address this issue, we developed a ubiquitous, neuronal, and glial-specific knockdown model in Drosophila melanogaster by using the RNA interference (RNAi) approach. Knockdown of the Ids/CG12014 gene resulted in a significant reduction of the Ids gene expression and enzymatic activity. However, glycosaminoglycan storage, survival, molecular markers (Atg8a, Lamp1, Rab11), and locomotion behavior were not affected. Even strongly reduced, IDS-activity was enough to prevent a pathological phenotype in a MPS II RNAi fruit fly. Thus, a Drosophila MPS II model requires complete abolishment of the enzymatic activity.

Reactive Oxygen Species and Oxidative Stress in the Pathogenesis and Progression of Genetic Diseases of the Connective Tissue

Connective tissue is known to provide structural and functional “glue” properties to other tissues. It contains cellular and molecular components that are arranged in several dynamic organizations. Connective tissue is the focus of numerous genetic and nongenetic diseases. Genetic diseases of the connective tissue are minority or rare, but no less important than the nongenetic diseases. Here we review the impact of reactive oxygen species (ROS) and oxidative stress on the onset and/or progression of diseases that directly affect connective tissue and have a genetic origin. It is important to consider that ROS and oxidative stress are not synonymous, although they are often closely linked. In a normal range, ROS have a relevant physiological role, whose levels result from a fine balance between ROS producers and ROS scavenge enzymatic systems. However, pathology arises or worsens when such balance is lost, like when ROS production is abnormally and constantly high and/or when ROS scavenge (enzymatic) systems are impaired. These concepts apply to numerous diseases, and connective tissue is no exception. We have organized this review around the two basic structural molecular components of connective tissue: The ground substance and fibers (collagen and elastic fibers).

Evidence for inflammasome activation in the brain of mucopolysaccharidosis type II mice

Hunter syndrome or mucopolysaccharidosis type II (MPS II) is an X-linked recessive disease caused by the deficiency of iduronate 2-sulfatase (IDS), leading to storage of undegraded heparan and dermatan sulfate. Patients with the severe form present neurological abnormalities, but the mechanisms of such alterations are unknown. Here, we hypothesized that the undegraded substances found in this disease could be recognized as damage-associated molecular patterns (DAMPS), leading to activation of the inflammasome. Brains from 2 and 5 months normal and MPS II mice were studied. We observed an increase in cathepsin B activity in the brain tissue and leakage of this enzyme from the lysosome to the cytoplasm in a MPS II neuronal cell line, which is a known activator of the inflammasome. Furthermore, Caspase-1 activity and IL-1-beta levels were elevated at 5 months, confirming that this pathway is indeed altered. Our results suggest that undegraded GAG activate the inflammasome pathway in MPS II and future studies could focus on blocking such pathway to better understand the role of this process to the pathogenesis of MPS II.

Mucopolysaccharidosis Type II: One Hundred Years of Research, Diagnosis, and Treatment

Mucopolysaccharidosis type II (MPS II, Hunter syndrome) was first described by Dr. Charles Hunter in 1917. Since then, about one hundred years have passed and Hunter syndrome, although at first neglected for a few decades and afterwards mistaken for a long time for the similar disorder Hurler syndrome, has been clearly distinguished as a specific disease since 1978, when the distinct genetic causes of the two disorders were finally identified. MPS II is a rare genetic disorder, recently described as presenting an incidence rate ranging from 0.38 to 1.09 per 100,000 live male births, and it is the only X-linked-inherited mucopolysaccharidosis. The complex disease is due to a deficit of the lysosomal hydrolase iduronate 2-sulphatase, which is a crucial enzyme in the stepwise degradation of heparan and dermatan sulphate. This contributes to a heavy clinical phenotype involving most organ-systems, including the brain, in at least two-thirds of cases. In this review, we will summarize the history of the disease during this century through clinical and laboratory evaluations that allowed its definition, its correct diagnosis, a partial comprehension of its pathogenesis, and the proposition of therapeutic protocols. We will also highlight the main open issues related to the possible inclusion of MPS II in newborn screenings, the comprehension of brain pathogenesis, and treatment of the neurological compartment.

Neural Stem Cells from Shank3-ko Mouse Model Autism Spectrum Disorders

Autism spectrum disorders (ASD) comprise a complex of neurodevelopmental disorders caused by a variety of genetic defects and characterized by alterations in social communication and repetitive behavior. Since the mechanisms leading to early neuronal degeneration remain elusive, we chose to examine the properties of NSCs isolated from an animal model of ASD in order to evaluate whether their neurogenic potential may recapitulate the early phases of neurogenesis in the brain of ASD patients. Mutations of the gene coding for the Shank3 protein play a key role in the impairment of brain development and synaptogenesis in ASD patients. Experiments here reported show that NSCs derived from the subventricular zone (SVZ) of adult Shank3Δ11-/- (Shank3-ko) mice retain self-renewal capacity in vitro, but differentiate earlier than wild-type (wt) cells, displaying an evident endosomal/lysosomal and ubiquitin aggregation in astroglial cells together with mitochondrial impairment and inflammasome activation, suggesting that glial degeneration likely contributes to neuronal damage in ASD. These in vitro observations obtained in our disease model are consistent with data in vivo obtained in ASD patients and suggest that Shank3 deficit could affect the late phases of neurogenesis and/or the survival of mature cells rather than NSC self-renewal. This evidence supports Shank3-ko NSCs as a reliable in vitro disease model and suggests the rescue of glial cells as a therapeutic strategy to prevent neuronal degeneration in ASD.

Toll-like receptor 4 modulation influences human neural stem cell proliferation and differentiation

Toll-like receptor 4 (TLR4) activation is pivotal to innate immunity and has been shown to regulate proliferation and differentiation of human neural stem cells (hNSCs) in vivo. Here we study the role of TLR4 in regulating hNSC derived from the human telencephalic-diencephalic area of the fetal brain and cultured in vitro as neurospheres in compliance with Good Manifacture Procedures (GMP) guidelines. Similar batches have been used in recent clinical trials in ALS patients. We found that TLR2 and 4 are expressed in hNSCs as well as CD14 and MD-2 co-receptors, and TLR4 expression is downregulated upon differentiation. Activation of TLR4 signaling by lipopolysaccharide (LPS) has a positive effect on proliferation and/or survival while the inverse is observed with TLR4 inhibition by a synthetic antagonist. TLR4 activation promotes neuronal and oligodendrocyte differentiation and/or survival while TLR4 inhibition leads to increased apoptosis. Consistently, endogenous expression of TLR4 is retained by hNSC surviving after transplantation in ALS rats or immunocompromised mice, thus irrespectively of the neuroinflammatory environment. The characterization of downstream signaling of TLR4 in hNSCs has suggested some activation of the inflammasome pathway. This study suggests TLR4 signaling as essential for hNSC self-renewal and as a novel target for the study of neurogenetic mechanisms.

Brain RNA-Seq Profiling of the Mucopolysaccharidosis Type II Mouse Model

Lysosomal storage disorders (LSDs) are a group of about 50 genetic metabolic disorders, mainly affecting children, sharing the inability to degrade specific endolysosomal substrates. This results in failure of cellular functions in many organs, including brain that in most patients may go through progressive neurodegeneration. In this study, we analyzed the brain of the mouse model for Hunter syndrome, a LSD mostly presenting with neurological involvement. Whole transcriptome analysis of the cerebral cortex and midbrain/diencephalon/hippocampus areas was performed through RNA-seq. Genes known to be involved in several neurological functions showed a significant differential expression in the animal model for the disease compared to wild type. Among the pathways altered in both areas, axon guidance, calcium homeostasis, synapse and neuroactive ligand-receptor interaction, circadian rhythm, neuroinflammation and Wnt signaling were the most significant. Application of RNA sequencing to dissect pathogenic alterations of complex syndromes allows to photograph perturbations, both determining and determined by these disorders, which could simultaneously occur in several metabolic and biochemical pathways. Results also emphasize the common, altered pathways between neurodegenerative disorders affecting elderly and those associated with pediatric diseases of genetic origin, perhaps pointing out a general common course for neurodegeneration, independent from the primary triggering cause.