Immunofluorescence detection of globotriaosylceramide deposits in conjunctival biopsies of Fabry disease patients

Exploring Pro-Inflammatory Immunological Mediators: Unraveling the Mechanisms of Neuroinflammation in Lysosomal Storage Diseases

Lysosomal storage diseases are a group of rare and ultra-rare genetic disorders caused by defects in specific genes that result in the accumulation of toxic substances in the lysosome. This excess accumulation of such cellular materials stimulates the activation of immune and neurological cells, leading to neuroinflammation and neurodegeneration in the central and peripheral nervous systems. Examples of lysosomal storage diseases include Gaucher, Fabry, Tay–Sachs, Sandhoff, and Wolman diseases. These diseases are characterized by the accumulation of various substrates, such as glucosylceramide, globotriaosylceramide, ganglioside GM2, sphingomyelin, ceramide, and triglycerides, in the affected cells. The resulting pro-inflammatory environment leads to the generation of pro-inflammatory cytokines, chemokines, growth factors, and several components of complement cascades, which contribute to the progressive neurodegeneration seen in these diseases. In this study, we provide an overview of the genetic defects associated with lysosomal storage diseases and their impact on the induction of neuro-immune inflammation. By understanding the underlying mechanisms behind these diseases, we aim to provide new insights into potential biomarkers and therapeutic targets for monitoring and managing the severity of these diseases. In conclusion, lysosomal storage diseases present a complex challenge for patients and clinicians, but this study offers a comprehensive overview of the impact of these diseases on the central and peripheral nervous systems and provides a foundation for further research into potential treatments.

Frequency Doubling Technology Visual Field Loss in Fabry Subjects Related to Retinal Ganglion Cell Function as Explored by ERG and OSOME

Purpose

This study aims to evaluate potential causes of FDT visual field loss in a selected group of Fabry subjects.

Patients and Methods

This is a pilot observational study. Subjects were assessed during 2 visits. The following tests were performed: visual acuity, tonometry, optical coherence tomography (OCT) optic nerve scan, frequency doubling time (FDT) and threshold (SAP) VF, ERG, and Online Spectro-reflectometry Oxygenation Measurement in the Eye (OSOME). Results are compared across visits and, when indicated, interpreted against those collected on non-Fabry population matched for age and sex.

Results

The study population was composed of 3 males (34.3 ± 8.9 y.o.) and 5 females (46.4 ± 6.5 y.o). For all subjects, BCVA remained 6/6 OU throughout the study and OCT optic nerve scans were normal. FDT showed a defect in at least 1 quadrant for all participants, in contrast with SAP. FDT PSD value was found different vs SAP. For ERG, the i-wave (52.1 + 2.7 ms) and B-waves (31.6 ± 2.1 ms) peak times were significantly longer compared to a non-Fabry population (p < 0.05). Overall blood oxygenation varied from 61.3% ± 4% to 68.1% ± 4% at the second visit, suggesting a loss of capillary perfusion. Blood volume varied based on location (superior/inferior), eye tested (OD/OS) and time (visit 1/2). The range of values exceeds normal subjects findings (p < 0.05). Blood volume was correlated to FDT PSD value for the superior area of the optic nerve.

Conclusion

The results suggest that Fabry subjects present FDT deficits and abnormal ERG patterns that may be explained by a retinal dysfunction affecting retinal ganglion cells (RGCs), second to vascular alterations.

[Morphological characteristics of renal changes in Fabry disease]

Fabry disease is an X-linked progressive lysosomal disease caused by a mutation in the gene that encodes the enzyme alpha-galactosidase A and leads to the intracellular accumulation of globotriazylceramide (GL-3). Kidney damage manifested itself as microproteinuria and microalbuminuria, followed by renal failure, is fatal to a patient.

MATERIAL AND METHODS

Fabry disease was diagnosed in 5 out of 600 cases of various kidney diseases, by using the 2014-2018 material. Light-optical, immunohistochemical, and electron microscopy methods were used to examine kidney biopsy specimens in Fabry disease.

RESULTS

The glomeruli clearly exhibited intralysosomal inclusions, myelin bodies, and fatty vacuoles in the cytoplasm of podocytes, the small processes of which were predominantly reduced. The mesangial space was expanded; the mesangiocytes were in the proliferation state; there were fatty vacuoles in the cytoplasm; the deposits of immune complexes located intramembranously and paramesangially were also found in all cases. An immunohistochemical study revealed that each case was detected to have fixations of IgG, kappa and lambda immunoglobulin chains on the glomerular basement membrane of focal granular pattern. There was fixation of fibrinogen in 3 cases, that of IgM in 2 cases, and that of IgA and complement component 3 in one case. Thus, it can be supposed that although Fabry disease is a lysosomal disease with deposits in the podocytes and mesangiocytes of myelin bodies and fatty vacuoles; however, immunohistochemical and electron microscopic studies cannot exclude the involvement of immune processes in the development of glomerular injury.

CONCLUSION

Fabry disease is a rare lysosomal disease accompanied by globotriazylceramide deposits in the podocytes and mesangiocytes. However, at the same time, the fact that immune mechanisms are involved in the development of this disease cannot be denied.

An antibody binding-based fluorescent assay for the rapid quantification of globotriaosylceramide levels in human Fabry cells

Fabry disease is caused by reduced α-GAL A activity and accumulation of globotriaosylceramide (Gb₃). Here, we describe a microplate Gb₃ assay using fluorophore-tagged antibody and crude cellular lipid extracts. The assay is able to detect higher Gb₃ concentrations in human Fabry cells compared to non-diseased cells. This result was verified by immunofluorescence staining that revealed large amounts of Gb₃ deposits in Fabry cell lines, demonstrating the accuracy of this method. This assay may provide the basis for detecting Fabry disease by quantifying Gb₃ deposits from human biological samples, for example, from urine and blood.

Skin Globotriaosylceramide 3 Load Is Increased in Men with Advanced Fabry Disease

BACKGROUND

The X-chromosomally linked life-limiting Fabry disease (FD) is associated with deposits of the sphingolipid globotriaosylceramide 3 (Gb3) in various tissues. Skin is easily accessible and may be used as an additional diagnostic and follow-up medium. Our aims were to visualize skin Gb3 deposits in FD patients applying immunofluorescence and to determine if cutaneous Gb3 load correlates with disease severity.

METHODS

At our Fabry Center for Interdisciplinary Therapy we enrolled 84 patients with FD and 27 healthy controls. All subjects underwent 5-mm skin punch biopsy at the lateral lower leg and the back. Skin samples were processed for immunohistochemistry using antibodies against CD77 (i.e. Gb3). Cutaneous Gb3 deposition was quantified in a blinded manner and correlated to clinical data.

RESULTS

We found that Gb3 load was higher in distal skin of male FD patients compared to healthy controls (p<0.05). Men (p<0.01) and women (p<0.05) with a classic FD phenotype had higher distal skin Gb3 load than healthy controls. Men with advanced disease as reflected by impaired renal function, and men and women with small fiber neuropathy had more Gb3 deposits in distal skin samples than males with normal renal function (p<0.05) and without small fiber neuropathy. Gb3 deposits were not different between patients with and without enzyme replacement therapy.

CONCLUSIONS

Immunofluorescence on minimally invasive skin punch biopsies may be useful as a tool for assessment and follow-up in FD patients.

Beyond the cherry-red spot: Ocular manifestations of sphingolipid-mediated neurodegenerative and inflammatory disorders

Sphingolipids are a ubiquitous membrane lipid present in every cell and found most abundantly in neural tissues. Disorders such as Tay-Sachs or Niemann-Pick disease are the most familiar examples of dysfunction in sphingolipid metabolism and are typically associated with neurodegeneration and ocular findings such as blindness. More recently, the role of bioactive sphingolipids has been established in a multitude of cellular events, including cell survival, growth, senescence and apoptosis, inflammation, and neovascularization. We discuss our current knowledge and understanding of sphingolipid metabolism and signaling in the pathogenesis of ocular diseases.

Leukocyte perturbation associated with Fabry disease

Fabry disease is an X-linked lysosomal storage disorder of glycosphingolipid catabolism due to the deficient activity of the enzyme alpha-galactosidase A. The non-degraded substrate, mainly globotriaosylceramide (Galα1-4Galβ1-4Glcβ1-1Cer; Gb(3)) accumulates progressively in the lysosome of various cells. The aim of this work was to analyse changes in leukocyte subpopulations and surface markers and to determine whether Gb(3) is increased in leukocytes of patients with untreated and treated Fabry disease. Blood samples obtained from 22 male Fabry patients (11 untreated and 11 on enzyme replacement therapy) and 22 normal controls were subjected to flow cytometric analysis of Gb(3) intracellular content, leukocyte subpopulations and cell markers. Based on the fluorescence intensity of bound monoclonal antibody, and relative to normal control leukocytes, Gb(3) appeared significantly increased in lymphocytes (but not in monocytes or granulocytes) from patients with Fabry disease. A significantly higher percentage of lymphocytes and CD19(+) cells and a reduced proportion of monocytes, CD8(+) cells and myeloid dendritic cells were detected in samples from Fabry patients compared with normal controls. CD1d expression was significantly lower and MHC class II surface expression was significantly higher in monocytes from Fabry patients than in normal controls. As previously observed for other adhesion molecules, the expression of CD31 (PECAM) was higher in leukocytes from Fabry patients. In conclusion, the differences recorded in this study reveal a leukocyte perturbation associated with the disease state in Fabry patients, whereas some abnormalities are less marked in treated patients.

Replacement of alpha-galactosidase A in Fabry disease: effect on fibroblast cultures compared with biopsied tissues of treated patients

The function and intracellular delivery of enzyme therapeutics for Fabry disease were studied in cultured fibroblasts and in the biopsied tissues of two male patients to show diversity of affected cells in response to treatment. In the mutant fibroblasts cultures, the final cellular level of endocytosed recombinant alpha-galactosidases A (agalsidases, Fabrazyme, and Replagal) exceeded, by several fold, the amount in control fibroblasts and led to efficient direct intra-lysosomal hydrolysis of ((3)H)Gb3Cer. In contrast, in the samples from the heart and some other tissues biopsied after several months of enzyme replacement therapy (ERT) with Fabrazyme, only the endothelial cells were free of storage. Persistent Gb3Cer storage was found in cardiocytes (accompanied by increase of lipopigment), smooth muscle cells, fibroblasts, sweat glands, and skeletal muscle. Immunohistochemistry of cardiocytes demonstrated, for the first time, the presence of a considerable amount of the active enzyme in intimate contact with the storage compartment. Factors responsible for the limited ERT effectiveness are discussed, namely post-mitotic status of storage cells preventing their replacement by enzyme supplied precursors, modification of the lysosomal system by longstanding storage, and possible relative lack of Sap B. These observations support the strategy of early treatment for prevention of lysosomal storage.

Misleading terms in Anderson-Fabry disease

BACKGROUND

Signs and symptoms of classic Fabry disease manifest itself on the skin (angiokeratoma), the nervous system (acroparaesthesia), the heart (restrictive cardiomyopathy) and a variety of other organs.

MATERIALS AND METHODS

Diagnosis of Fabry disease was confirmed by genetic tests in a cohort of 100 patients and a standardized examination programme was performed in all patients. We were puzzled when applying well-established and textbook-anchored signs and symptoms to our patients.

RESULTS

Among the 47 male and 53 female patients (mean age 41 +/- 16 years) with genetically proven disease, the Fabry-type vascular skin lesions were without hyperkeratotic aspect and keratomas were virtually absent. The peripheral neuropathic pain found in all male patients was not compatible with the wording 'acro' and 'paraesthesia', suggesting a different pathophysiological mechanism. Upon echocardiographic examination, patients mainly revealed diastolic relaxation abnormalities of the heart and only one patient had a restrictive cardiac pattern.

CONCLUSIONS

Our findings suggest that some terms used to describe signs and symptoms of Fabry disease are historically derived and do not comply with state-of-the-art examination. We propose to replace the term 'angiokeratoma' with 'angioma', the term 'acroparaesthesia' with 'neuropathic pain' and the term 'restrictive cardiomyopathy' with 'cardiac hypertrophic storage disease'. As most of the physicians are not familiar with Fabry disease, terms used in the past might prevent the correct diagnosis of a potentially treatable disease.

Cellular and tissue localization of globotriaosylceramide in Fabry disease

The pathogenesis of Fabry disease is poorly understood. We used a variety of immunohistological techniques to localize globotriaosylceramide, the main glycolipid that accumulates in Fabry disease. Globotriaosylceramide immunoreactivity in a heterogenous pattern was present in all organs examined of a patient on long-term enzyme replacement therapy. In the brain, immmunopositivity was found only in the parahippocampal region. Globotriaosylceramide immunostaining was present in the cell membrane and cytoplasm of endothelial cells, even in the absence of lysosomal inclusions. In kidney tissue, globotriaosylceramide colocalized with lysosomal, endoplasmic reticulum, and nuclear markers. Pre- and postembedding immunogold electron microscopy of skin biopsies and untreated patient cultured skin fibroblasts confirmed the presence of globotriaosylceramide in the cell membrane, in various cytoplasmic structures, and in the nucleus. Control organ tissues and cultured fibroblasts from five unaffected subjects were uniformly negative for globotriaosylceramide by immunohistochemistry and immunogold electron microscopy. We conclude that a substantial amount of lysosomal and extralysosomal globotriaosylceramide immunoreactivity remains in cells and tissues even after years of enzyme replacement therapy in Fabry disease. These findings are crucial for the understanding of the disease mechanism and suggest the usefulness of immunostaining for globotriaosylceramide as a means to assess response to novel, specific therapies.

Aspects pédiatriques de la maladie de Fabry

Fabry's disease is a rare X-linked inborn error of glycosphingolipid metabolism characterised by an abnormal lipid storage due to a defect of lysozomal alphagalactosidase. The consequence is a storage of glycosphingolipides in all tissues. This storage in vessels's endothelial cells is responsible, in males, for severe ischemic lesions leading to progressive kidney failure, cardiac and cerebral dysfunctions. Similarly, it involves ocular tissues, mainly the cornea, the conjunctiva and the lens. The corneal storage, known as cornea verticillata, is a clinical marker easy to recognize by slit lamp examination of the affected males and carrier females. The enzymatic activity of alphagalactosidase is reduced in tears. Characteristic lamellar bodies can be observed by electron microscopy study of a conjunctival biopsy. Until recently, treatment was limited to symptomatic management of pain, and end-stage complications of renal failure, cardiac or brain disease. Recent studies have demonstrated that enzyme replacement therapy by genetic engineering is now shown to be promising for affected patients.