Deletion of MCP-1 Impedes Pathogenesis of Acid Ceramidase Deficiency

Combined treatment of Ketogenic diet and propagermanium reduces neuroinflammation in Tay-Sachs disease mouse model

Tay-Sachs disease is a rare lysosomal storage disorder caused by β-Hexosaminidase A enzyme deficiency causing abnormal GM2 ganglioside accumulation in the central nervous system. GM2 accumulation triggers chronic neuroinflammation due to neurodegeneration-based astrogliosis and macrophage activity with the increased expression level of Ccl2 in the cortex of a recently generated Tay-Sachs disease mouse model Hexa-/-Neu3-/-. Propagermanium blocks the neuroinflammatory response induced by Ccl2, which is highly expressed in astrocytes and microglia. The ketogenic diet has broad potential usage in neurological disorders, but the knowledge of the impact on Tay-Sach disease is limited. This study aimed to display the effect of combining the ketogenic diet and propagermanium treatment on chronic neuroinflammation in the Tay-Sachs disease mouse model. Hexa-/-Neu3-/- mice were placed into the following groups: (i) standard diet, (ii) ketogenic diet, (iii) standard diet with propagermanium, and (iv) ketogenic diet with propagermanium. RT-PCR and immunohistochemistry analyzed neuroinflammation markers. Behavioral analyses were also applied to assess phenotypic improvement. Notably, the expression levels of neuroinflammation-related genes were reduced in the cortex of 140-day-old Hexa-/-Neu3-/- mice compared to β-Hexosaminidase A deficient mice (Hexa-/-) after combined treatment. Immunohistochemical analysis displayed correlated results with the RT-PCR. Our data suggest the potential to implement combined treatment to reduce chronic inflammation in Tay-Sachs and other lysosomal storage diseases.

Endocannabinoid receptor 2 is a potential biomarker and therapeutic target for the lysosomal storage disorders

Herein, we studied the expression of endocannabinoid receptor 2 (CB2R), a known inflammation mediator, in several lysosomal storage disorder (LSD) animal models and evaluated it as a potential biomarker and therapeutic target for these diseases. CB2R was highly elevated in the plasma of Farber disease and mucopolysaccharidosis (MPS) type IIIA mice, followed by Fabry disease and MPS type I mice. Mice with acid sphingomyelinase-deficient Niemann-Pick disease (ASMD) and rats with MPS type VI exhibited little or no plasma CB2R elevation. High-level expression of CB2R was also observed in tissues of Farber and MPS IIIA mice. Treatment of MPS IIIIA patient cells with CB2R agonists led to a reduction of CB2R and monocyte chemoattractant protein-1 (MCP-1), a chemotactic factor that is elevated in this LSD. Treatment of MPS IIIA mice with one of these agonists (JWH133) led to a reduction of plasma and tissue CB2R and MCP-1, a reduction of glial fibrillary acidic protein (GFAP) in the brain, and an improvement in hanging test performance. JWH133 treatment of Farber disease mice also led to a reduction of MCP-1 in tissues and plasma, and treatment of these mice by enzyme replacement therapy (ERT) led to a reduction of plasma CB2R, indicating its potential to monitor treatment response. Overall, these findings suggest that CB2R should be further examined as a potential therapeutic target for the LSDs and may also be a useful biomarker to monitor the impact of therapies.

Spinal muscular atrophy-like phenotype in a mouse model of acid ceramidase deficiency

Mutations in ASAH1 have been linked to two allegedly distinct disorders: Farber disease (FD) and spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME). We have previously reported FD-like phenotypes in mice harboring a single amino acid substitution in acid ceramidase (ACDase), P361R, known to be pathogenic in humans (P361R-Farber). Here we describe a mouse model with an SMA-PME-like phenotype (P361R-SMA). P361R-SMA mice live 2-3-times longer than P361R-Farber mice and have different phenotypes including progressive ataxia and bladder dysfunction, which suggests neurological dysfunction. We found profound demyelination, loss of axons, and altered sphingolipid levels in P361R-SMA spinal cords; severe pathology was restricted to the white matter. Our model can serve as a tool to study the pathological effects of ACDase deficiency on the central nervous system and to evaluate potential therapies for SMA-PME.

Acid Ceramidase Deficiency: Bridging Gaps between Clinical Presentation, Mouse Models, and Future Therapeutic Interventions

Farber disease (FD) and spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME) are ultra-rare, autosomal-recessive, acid ceramidase (ACDase) deficiency disorders caused by ASAH1 gene mutations. Currently, 73 different mutations in the ASAH1 gene have been described in humans. These mutations lead to reduced ACDase activity and ceramide (Cer) accumulation in many tissues. Presenting as divergent clinical phenotypes, the symptoms of FD vary depending on central nervous system (CNS) involvement and severity. Classic signs of FD include, but are not limited to, a hoarse voice, distended joints, and lipogranulomas found subcutaneously and in other tissues. Patients with SMA-PME lack the most prominent clinical signs seen in FD. Instead, they demonstrate muscle weakness, tremors, and myoclonic epilepsy. Several ACDase-deficient mouse models have been developed to help elucidate the complex consequences of Cer accumulation. In this review, we compare clinical reports on FD patients and experimental descriptions of ACDase-deficient mouse models. We also discuss clinical presentations, potential therapeutic strategies, and future directions for the study of FD and SMA-PME.

The role of brain innate immune response in lysosomal storage disorders: fundamental process or evolutionary side effect?

Sphingolipidoses are diseases caused by mutations in genes responsible for sphingolipid degradation and thereby lead to sphingolipid accumulation. Most sphingolipidoses have a neurodegenerative manifestation characterized by innate immune activation in the brain. However, the role of the immune response in disease progression is ill-understood. In contrast to infectious diseases, immune activation is unable to eliminate the offending agent in sphingolipidoses resulting in ineffective, chronic inflammation. This paradox begs two fundamental questions: Why has this immune response evolved in sphingolipidoses? What role does it play in disease progression? Here, starting from the observation that sphingolipids (SLs) are elevated also in infectious diseases, I discuss the possibility that the activation of the brain immune response by SLs has evolved as a part of the immune response against pathogens and plays no major role in sphingolipidoses.

Elusive Roles of the Different Ceramidases in Human Health, Pathophysiology, and Tissue Regeneration

Ceramide and sphingosine are important interconvertible sphingolipid metabolites which govern various signaling pathways related to different aspects of cell survival and senescence. The conversion of ceramide into sphingosine is mediated by ceramidases. Altogether, five human ceramidases—named acid ceramidase, neutral ceramidase, alkaline ceramidase 1, alkaline ceramidase 2, and alkaline ceramidase 3—have been identified as having maximal activities in acidic, neutral, and alkaline environments, respectively. All five ceramidases have received increased attention for their implications in various diseases, including cancer, Alzheimer’s disease, and Farber disease. Furthermore, the potential anti-inflammatory and anti-apoptotic effects of ceramidases in host cells exposed to pathogenic bacteria and viruses have also been demonstrated. While ceramidases have been a subject of study in recent decades, our knowledge of their pathophysiology remains limited. Thus, this review provides a critical evaluation and interpretive analysis of existing literature on the role of acid, neutral, and alkaline ceramidases in relation to human health and various diseases, including cancer, neurodegenerative diseases, and infectious diseases. In addition, the essential impact of ceramidases on tissue regeneration, as well as their usefulness in enzyme replacement therapy, is also discussed.

DPP-4 inhibitor reduces striatal microglial deramification after sensorimotor cortex injury induced by external force impact

Dipeptidyl peptidase-4 inhibitors (or gliptins), a class of antidiabetic drugs, have recently been shown to have protective actions in the central nervous system. Their cellular and molecular mechanisms responsible for these effects are largely unknown. In the present study, two structurally different gliptins, sitagliptin and vildagliptin, were examined for their therapeutic actions in a controlled cortical impact (CCI) model of moderate traumatic brain injury (TBI) in mice. Early post-CCI treatment with sitagliptin, but not vildagliptin, significantly reduced body asymmetry, locomotor hyperactivity, and brain lesion volume. Sitagliptin attenuated post-CCI microglial deramification in the ipsilateral dorsolateral (DL) striatum, while vildagliptin had no effect. Sitagliptin also reduced striatal expression of galectin-3 and monocyte chemoattractant protein 1(MCP-1), and increased the cortical and striatal levels of the anti-inflammatory cytokine IL-10 on the ipsilateral side. These data support a differential protective effect of sitagliptin against TBI, possibly mediated by an anti-inflammatory effect in striatum to preserve connective network. Both sitagliptin and vildagliptin produced similar increases of active glucagon-like peptide-1 (GLP-1) in blood and brain. Increasing active GLP-1 may not be the sole molecular mechanisms for the neurotherapeutic effect of sitagliptin in TBI.

Naringin provides neuroprotection in CCL2-induced cognition impairment by attenuating neuronal apoptosis in the hippocampus

Background

Chemokine C–C motif ligand 2 (CCL2) is one of the most widely recognised proinflammatory chemokines in cognitive disorders. Currently, CCL2-targeting drugs are extremely limited. Thus, this study aimed to explore the neuroprotection afforded by naringin in CCL2-induced cognitive impairment in rats.

Methods

Before the CCL2 intra-hippocampal injection, rats were treated with naringin for 3 consecutive days via intraperitoneal injection. Two days post-surgery, the Morris water maze (MWM) and novel object recognition (NORT) tests were performed to detect spatial learning and memory and object cognition, respectively. Nissl staining and dUTP nick-end labelling (TUNEL) staining were performed to assess histopathological changes in the hippocampus. Commercial kits were used to measure the activity of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) and the content of malondialdehyde (MDA). Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to examine the relative mRNA expression of interleukin 1β, (IL-1β), interleukin 6 (IL-6), glutamate/aspartate transporter (GLAST), glutamate transporter-1 (GLT-1), phosphate-activated glutaminase (PAG), cysteine aspartic acid-specific protease 8 (caspase-8), cysteine aspartic acid-specific protease 3 (caspase-3), cell lymphoma/leukaemia-2 (Bcl-2), and Bcl-2 associated X protein (Bax).

Results

In the MWM, the average escape latency and average swimming distance were significantly reduced and the crossing times were increased in the naringin-treated groups, compared with the CCL2 group. The NORT results revealed that, compared with the CCL2 rats, the discrimination index in the naringin-treated rats increased significantly. Nissl and TUNEL staining revealed that naringin protected the structure and survival of the neurons in the CA1 zone of the hippocampus. In the naringin-treated groups, the SOD and GSH-Px activities were increased, whereas the MDA levels were decreased. Furthermore, in the naringin-treated groups, the relative mRNA expression of IL-1β and IL-6 was significantly decreased; GLAST and GLT-1 mRNA expression levels were increased, whereas PAG was decreased. In the naringin-treated groups, the relative mRNA expression levels of caspase-8, caspase-3, and Bax were decreased, whereas that of Bcl-2 was increased.

Conclusion

Collectively, these data indicated that naringin alleviated the CCL2-induced cognitive impairment. The underlying mechanisms could be associated with the inhibition of neuroinflammation, oxidative stress, apoptosis, and the regulation of glutamate metabolism.

Acid Sphingomyelinase Deficiency Ameliorates Farber Disease

Farber disease is a rare lysosomal storage disorder resulting from acid ceramidase deficiency and subsequent ceramide accumulation. No treatments for Farber disease are clinically available, and affected patients have a severely shortened lifespan. We have recently reported a novel acid ceramidase deficiency model that mirrors the human disease closely. Acid sphingomyelinase is the enzyme that generates ceramide upstream of acid ceramidase in the lysosomes. Using our acid ceramidase deficiency model, we tested if acid sphingomyelinase could be a potential novel therapeutic target for the treatment of Farber disease. A number of functional acid sphingomyelinase inhibitors are clinically available and have been used for decades to treat major depression. Using these as a therapeutic for Farber disease, thus, has the potential to improve central nervous symptoms of the disease as well, something all other treatment options for Farber disease can’t achieve so far. As a proof-of-concept study, we first cross-bred acid ceramidase deficient mice with acid sphingomyelinase deficient mice in order to prevent ceramide accumulation. Double-deficient mice had reduced ceramide accumulation, fewer disease manifestations, and prolonged survival. We next targeted acid sphingomyelinase pharmacologically, to test if these findings would translate to a setting with clinical applicability. Surprisingly, the treatment of acid ceramidase deficient mice with the acid sphingomyelinase inhibitor amitriptyline was toxic to acid ceramidase deficient mice and killed them within a few days of treatment. In conclusion, our study provides the first proof-of-concept that acid sphingomyelinase could be a potential new therapeutic target for Farber disease to reduce disease manifestations and prolong survival. However, we also identified previously unknown toxicity of the functional acid sphingomyelinase inhibitor amitriptyline in the context of Farber disease, strongly cautioning against the use of this substance class for Farber disease patients.

Hepatic pathology and altered gene transcription in a murine model of acid ceramidase deficiency

Farber disease (FD) is a rare lysosomal storage disorder (LSD) characterized by systemic ceramide accumulation caused by a deficiency in acid ceramidase (ACDase). In its classic form, FD manifests with painful lipogranulomatous nodules in extremities and joints, respiratory complications, and neurological involvement. Hepatosplenomegaly is commonly reported, and severe cases of FD cite liver failure as a cause of early death. Mice homozygous for an orthologous patient mutation in the ACDase gene (Asah1^P361R/P361R) recapitulate the classical form of human FD. In this study, we demonstrate impaired liver function and elevation of various liver injury markers in Asah1^P361R/P361R mice as early as 5 weeks of age. Histopathology analyses demonstrated significant formation and recruitment of foamy macrophages, invasion of neutrophils, progressive tissue fibrosis, increased cell proliferation and death, and significant storage pathology within various liver cell types. Lipidomic analyses revealed alterations to various lipid concentrations in both serum and liver tissue. A significant accumulation of ceramide and other sphingolipids in both liver and hepatocytes was noted. Sphingolipid acyl chains were also altered, with an increase in long acyl chain sphingolipids coinciding with a decrease in ultra-long acyl chains. Hepatocyte transcriptome analyses revealed significantly altered gene transcription. Molecular pathways related to inflammation were found activated, and molecular pathways involved in lipid metabolism were found deactivated. Altered gene transcription within the sphingolipid pathway itself was also observed. The data presented herein demonstrates that deficiency in ACDase results in liver pathology as well as sphingolipid and gene transcription profile changes that lead to impaired liver function.

Hematopoietic stem cell transplant does not prevent neurological deterioration in infants with Farber disease: Case report and literature review

Farber disease (FD) is an inherited autosomal recessive disorder of lipid metabolism. The hallmark of the disease is systemic accumulation of ceramide due to lysosomal acid ceramidase deficiency. The involvement of the central nervous system is critical in this disorder leading to rapid deterioration and death within a few years after birth. Efforts to treat patients by hematopoietic stem cell transplant (HSCT) have resulted in favorable results in the absence of neurological manifestations. We report the outcomes of HSCT in two patients with FD who received early HSCT and had neurological deterioration posttransplant. We also present a new understanding of the limitations of HSCT in FD management based on our observations of the clinical course of the two patients after therapy.

Acid Ceramidase Deficiency in Mice Leads to Severe Ocular Pathology and Visual Impairment

Farber disease (FD) is a debilitating lysosomal storage disorder characterized by severe inflammation and neurodegeneration. FD is caused by mutations in the ASAH1 gene, resulting in deficient acid ceramidase (ACDase) activity. Patients with ACDase deficiency exhibit a broad clinical spectrum. In classic cases, patients develop hepatosplenomegaly, nervous system involvement, and childhood mortality. Ocular manifestations include decreased vision, a grayish appearance to the retina with a cherry red spot, and nystagmus. That said, the full effect of ACDase deficiency on the visual system has not been studied in detail. We previously developed a mouse model that is orthologous for a known patient mutation in Asah1 that recapitulates human FD. Herein, we report evidence of a severe ocular pathology in Asah1^P361R/P361R mice. Asah1^P361R/P361R mice exhibit progressive retinal and optic nerve pathology. Through noninvasive ocular imaging and histopathological analyses of these Asah1^P361R/P361R animals, we revealed progressive inflammation, the presence of retinal dysplasia, and significant storage pathology in various cell types in both the retina and optic nerves. Lipidomic analyses of retinal tissues revealed an abnormal accumulation of ceramides and other sphingolipids. Electroretinograms and behavioral tests showed decreased retinal and visual responses. Taken together, these data suggest that ACDase deficiency leads to sphingolipid imbalance, inflammation, dysmorphic retinal and optic nerve pathology, and severe visual impairment.

Absence of infiltrating peripheral myeloid cells in the brains of mouse models of lysosomal storage disorders

Approximately 70 lysosomal storage diseases are currently known, resulting from mutations in genes encoding lysosomal enzymes and membrane proteins. Defects in lysosomal enzymes that hydrolyze sphingolipids have been relatively well studied. Gaucher disease is caused by the loss of activity of glucocerebrosidase, leading to accumulation of glucosylceramide. Gaucher disease exhibits a number of subtypes, with types 2 and 3 showing significant neuropathology. Sandhoff disease results from the defective activity of β-hexosaminidase, leading to accumulation of ganglioside GM2. Niemann-Pick type C disease is primarily caused by the loss of activity of the lysosomal membrane protein, NPC1, leading to storage of cholesterol and sphingosine. All three disorders display significant neuropathology, accompanied by neuroinflammation. It is commonly assumed that neuroinflammation is the result of infiltration of monocyte-derived macrophages into the brain; for instance, cells resembling lipid-engorged macrophages ('Gaucher cells') have been observed in the brain of Gaucher disease patients. We now review the evidence that inflammatory macrophages are recruited into the brain in these diseases and then go on to provide some experimental data that, at least in the three mouse models tested, monocyte-derived macrophages do not appear to infiltrate the brain. Resident microglia, which are phenotypically distinct from infiltrating macrophages, are the only myeloid population present in significant numbers within the brain parenchyma in these authentic mouse models, even during the late symptomatic stages of disease when there is substantial neuroinflammation. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/. This article is part of the Special Issue "Lysosomal Storage Disorders".

Acid ceramidase deficiency: Farber disease and SMA-PME

Acid ceramidase (ACDase) deficiency is a spectrum of disorders that includes a rare lysosomal storage disorder called Farber disease (FD) and a rare epileptic disorder called spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME). Both disorders are caused by mutations in the ASAH1 gene that encodes the lysosomal hydrolase that breaks down the bioactive lipid ceramide. To date, there have been fewer than 200 reported cases of FD and SMA-PME in the literature. Typical textbook manifestations of classical FD include the formation of subcutaneous nodules, accumulation of joint contractures, and development of a hoarse voice. In reality, however, the clinical presentation is much broader. Patients may develop severe pathologies leading to death in infancy or may develop attenuated forms of the disorder wherein they are often misdiagnosed or not diagnosed until adulthood. A clinical variability also exists for SMA-PME, in which patients develop progressive muscle weakness and seizures. Currently, there is no known cure for FD or for SMA-PME. The main treatment is symptom management. In rare cases, treatment may include surgery or hematopoietic stem cell transplantation. Research using disease models has provided insights into the pathology as well as the role of ACDase in the development of these conditions. Recent studies have highlighted possible biomarkers for an effective diagnosis of ACDase deficiency. Ongoing work is being conducted to evaluate the use of recombinant human ACDase (rhACDase) for the treatment of FD. Finally, gene therapy strategies for the treatment of ACDase deficiency are actively being pursued. This review highlights the broad clinical definition and outlines key studies that have improved our understanding of inherited ACDase deficiency-related conditions.

Non-alcoholic fatty liver disease: Insights from sphingolipidomics

Non-alcoholic fatty liver disease (NAFLD) is a major clinical concern and its treatment consumes abundant resources. While accumulation of lipids in hepatocytes initiates the disease, this in itself is not necessarily harmful; rather, initiation of inflammation and subsequent fibrosis and cirrhosis are critical steps in NAFLD pathology. Mechanisms linking lipid overload to downstream disease progression are not fully understood; however, bioactive lipid metabolism may underlie instigation of proinflammatory signaling. With the advent of high-throughput, sensitive, and quantitative mass spectrometry-based methods for assessing lipid profiles in NAFLD, several trends have emerged, including that increases in specific sphingolipids correlate with the transition from the relatively benign condition of simple fatty liver to the much more concerning inflamed state. Continued studies that implement sphingolipid profiling will enable the extrapolations of candidate enzymes and pathways involved in NAFLD, either in biopsies or plasma from human samples, and also in animal models, from which data are much more abundant. While most data thus far are derived from targeted lipidomics approaches, unbiased, semi-quantitative approaches hold additional promise for furthering our understanding of sphingolipids as markers of and players in NAFLD.