Lactosylceramide in lysosomal storage disorders: a comparative immunohistochemical and biochemical study

Immunohistochemical studies of the presence of lactosylceramide (LacCer) in lysosomal storage disorders (LSDs) were done using anti-LacCer monoclonal antibody of the CDw 17 type (clone MG-2). No sign of an association between LacCer and the lysosomal system in normal cells was observed, except for histiocytes active in phagocytosis. A comparative study of a group of LSDs showed a general tendency for LacCer to increase in storage cells in Niemann-Pick disease type C (NPC), and types A and B, GM1 gangliosidosis, acid lipase deficiency, glycogen storage disease type II and mucopolysaccharidoses. LacCer accumulated in storage cells despite normal activity of relevant lysosomal degrading enzymes. The accumulation of LacCer displayed variability within storage cell populations, and was mostly expressed in neurons in NPC. An absence of the increase in LacCer in storage cells above control levels was seen in neuronal ceroid lipofuscinoses (neurons and cardiocytes) and in Fabry disease. Gaucher and Krabbe cells showed significantly lower levels, or even the absence, of LacCer compared with control macrophages. Results of immunohistochemistry were corroborated by semiquantitative lipid thin-layer chromatography (TLC). It is suggested that different associations of LacCer with the lysosomal storage process may reflect differences in glycosphingolipid turnover induced by the storage-compromised lysosomal/endosomal system.

A variant form of neuronal ceroid lipofuscinosis in American bulldogs

Neuronal ceroid lipofuscinoses (NCLs) are inherited neurodegenerative diseases characterized by accumulations of autofluorescent lipopigments within cells of the nervous system. Nine related American Bulldogs demonstrated dysmetria in all limbs and paraparesis. Nonambulatory tetraparesis was observed only in the later stages of the disease. The clinical signs developed between 1 and 3 years of age and were slowly progressive over several years, which is inconsistent with most reports in other breeds. Results from blood tests for 8 different lysosomal storage diseases on 4 affected and 6 related but unaffected dogs were negative. Four affected dogs were euthanized and histopathologic examinations showed diffuse accumulations of periodic acid-Schiff-positive inclusions in neurons and axonal spheroids along the entire neuraxis and retinae. The most severe lesions were in the brainstem proprioceptive nuclei and spinal cord, consistent with clinical signs. The storage material was autofluorescent and immunohistochemically positive for products of lipid peroxidation. Ultrastructural analysis was consistent with NCL. Pedigree analysis supports an autosomal-recessive mode of inheritance. NCL has not been previously reported in the American Bulldog and these findings suggest a variant form of the canine disease.

Histiocytic proliferations in childhood

Histiocytic disorders occur with increased frequency in children and young adults. The wide spectrum of neoplastic and nonneoplastic diseases characterized by histiocytic proliferation was reflected in the cases submitted to the 2003 Society for Hematopathology and the European Association for Haematopathology Workshop. This review focuses on the entities represented at the workshop. It includes an overview of the classification and immunophenotype of the histiocytic disorders. The clinical and pathologic features of each entity are illustrated with representative cases submitted to the workshop, with an emphasis on recent biologic and genetic insights. In addition, a brief review of the pathologic features of the lysosomal storage disorders is included, with an emphasis on findings relevant to the practicing hematopathologist, exemplified with cases presented at the workshop.

Hippocampal pathology in the human neuronal ceroid-lipofuscinoses: distinct patterns of storage deposition, neurodegeneration and glial activation

The neuronal ceroid-lipofuscinoses (NCLs) are recessively inherited lysosomal storage diseases, currently classified into 8 forms (CLN1-CLN8). Collectively, the NCLs constitute the most common group of progressive encephalopathies of childhood, and present with visual impairment, psychomotor deterioration and severe seizures. Despite recent identification of the underlying disease genes, the mechanisms leading to neurodegeneration and epilepsy in the NCLs remain poorly understood. To investigate these events, we examined the patterns of storage deposition, neurodegeneration, and glial activation in the hippocampus of patients with CLN1, CLN2, CLN3, CLN5 and CLN8 using histochemistry and immunohistochemistry. These different forms of NCL shared distinct patterns of neuronal degeneration in the hippocampus, with heavy involvement of sectors CA2-CA4 but relative sparing of CA1. This selective pattern of degeneration was also observed in immunohistochemically identified interneurons, which exhibited a graded severity of loss according to phenotype, with calretinin-positive interneurons relatively spared. Furthermore, glial activation was also regionally specific, with microglial activation most pronounced in areas of greatest neuronal loss, and astrocyte activation prominent in areas where neuronal loss was less evident. In conclusion, the NCLs share a common pattern of selective hippocampal pathology, distinct from that seen in the majority of temporal lobe epilepsies.

Lysosomal storage disorders

Although the first description of a lysosomal storage disorder was that of Tay-Sachs disease in 1881, the lysosome was not discovered until 1955, by Christian De Duve. The first demonstration by Hers in 1963 of a link between an enzyme deficiency and a storage disorder (Pompe's disease) paved the way for a series of seminal discoveries about the intracellular biology of these enzymes and their substrates, culminating in the successful treatment of Gaucher's disease with beta-glucosidase in the early 1990s. It is now recognized that these disorders are not simply a consequence of pure storage, but result from perturbation of complex cell signalling mechanisms. These in turn give rise to secondary structural and biochemical changes, which have important implications for therapy. Significant challenges remain, particularly the treatment of central nervous system disease. It is hoped that recent advances in our understanding of lysosomal biology will enable successful therapies to be developed.

Secondary accumulation of gangliosides in lysosomal storage disorders

Glycosphingolipids (GSLs) known as gangliosides have been documented to accumulate in a wide range of lysosomal storage disorders, including those with and without primary defects in ganglioside degradation. The same two gangliosides, GM2 and GM3, are often found elevated in diseased neurons whereas in normal mature neurons both are essentially undetectable. Altered expression of these two gangliosides does not appear to result solely from cellularity changes or gliosis since immunocytochemical studies show that both GM2 and GM3 reside in vesicular structures within affected neurons. Elevated expression of one of these gangliosides (GM2) has also been found to closely correlate with the growth of ectopic dendrites on susceptible neurons, a phenomenon that uniquely characterizes many lysosomal diseases. Understanding the precise role of the endosomal-lysosomal system in the overall homeostatic control of GSL expression in neurons can be expected to provide key insight into both the function of gangliosides and the pathogenic mechanisms underlying lysosomal disease.

Dysmorphic facial features in aspartylglucosaminuria patients and carriers

The facial photos of 76 aspartylglucosaminuria (AGU) patients, 29 obligate carriers and 78 unrelated controls were evaluated for dysmorphic features to see whether this autosomal recessive lysosomal storage disease includes a dysmorphic facial gestalt in addition to the well-known age-related coarsening of the facies and whether the carrier status of AGU might have an effect on the facial features. A consistent dysmorphic gestalt with hypertelorism, a short and broad nose with round nares, simple often small ears with small or missing lobule and modest folding of helices, thick lips and a square shape of face, was found to be present long before the coarsening begins. Recognition of this pattern of facial features might help in the early diagnosis of AGU. Statistically, puffy eyelids were found to be significantly more frequent in AGU carriers than in controls. These findings support an earlier implication that AGU carrier status might have a slight influence on the phenotype.

Lysosomal Storage Diseases: Is Impaired Apoptosis a Pathogenic Mechanism?

Lysosomal storage disorders are inborn diseases resulting from the lack or activity of lysosomal hydrolases, transporters, or integral membrane proteins. Although most of the genes encoding these proteins have been characterized and many gene defects identified, the molecular bases underlying the pathophysiology of these genetic diseases still remain obscure. In this mini-review, the potential role of apoptotic cell death in the development of the cellular and tissue lesions seen in lysosomal storage disorders, and particularly in neurological diseases, is discussed. A list of observations documenting either a decrease or an exacerbation in apoptosis induction are presented. The putative, yet controversial contribution of certain sphingolipids and cathepsins in the regulation of these phenomena is emphasized.

Targeting macrophages with baculovirus-produced lysosomal enzymes: implications for enzyme replacement therapy of the glycoprotein storage disorder galactosialidosis

Lysosomal storage diseases (LSDs) are monogenic disorders of metabolism caused by deficiency of hydrolytic enzymes. In several LSDs, cells of the reticuloendothelial (RE) system are the primary targets of the disease. Exogenous administration of recombinant enzymes overproduced in mammalian cells has proved effective for treating the systemic phenotype in nonneuropathic patients with LSDs. However, for the treatment of diseases with primary involvement of the RE system, the production of the therapeutic enzyme in insect cells could be an alternative and advantageous method because glycoproteins expressed in insect cells carry carbohydrates of the pauci-mannose or core-type. These recombinant enzymes are in principle already poised to be internalized by cells that express mannose receptors, including macrophages. Here, we demonstrate that three baculovirus-expressed enzymes, protective protein/cathepsin A (PPCA), neuraminidase (Neu1), and beta-glucosidase, were readily taken up and restored lysosomal function in enzyme-deficient mouse macrophages. The capacity of recombinant PPCA and Neu1 to clear the lysosomal storage in target cells was assessed in PPCA-/- mice, a model of galactosialidosis. Intravenously injected PPCA-/- mice efficiently internalized the corrective enzymes in resident macrophages of many organs. In addition, treated mice showed overall clearance of lysosomal storage in the most affected systemic organs, kidney, liver, and spleen. Our results suggest that ERT with baculovirus-expressed enzymes might be an effective treatment for nonneuropathic patients with galactosialidosis and possibly for others with LSDs that primarily involve the RE system.

Autosomal dominant adult neuronal ceroid lipofuscinosis: a novel form of NCL with granular osmiophilic deposits without palmitoyl protein thioesterase 1 deficiency

We describe the neuropathological and biochemical autopsy findings in 3 patients with autosomal dominant adult neuronal ceroid lipofuscinosis (ANCL, Parry type; MIM 162350), from a family with 6 affected individuals in 3 generations. Throughout the brain of these patients, there was abundant intraneuronal lysosomal storage of autofluorescent lipopigment granules. Striking loss of neurons in the substantia nigra was found. In contrast, little neuronal cell loss occurred in other cerebral areas, despite massive neuronal inclusions. Visceral storage was present in gut, liver, cardiomyocytes, skeletal muscle, and in the skin eccrine glands. The storage material showed highly variable immunoreactivity with antiserum against subunit c of mitochondrial ATP synthase, but uniform strong immunoreactivity for saposin D (sphingolipid activating protein D). Protein electrophoresis of isolated storage material revealed a major protein band of about 14 kDa, recognized in Western blotting by saposin D antiserum (but not subunit c of mitochondrial ATPase (SCMAS) antiserum). Electron microscopy showed ample intraneuronal granular osmiophilic deposits (GRODs), as occurs in CLN1 and congenital ovine NCL. These forms of NCL are caused by the deficiencies of palmitoyl protein thioesterase 1 and cathepsin D, respectively. However, activities of these enzymes were within normal range in our patients. Thus we propose that a gene distinct from the cathepsin D and CLN1-CLN8 genes is responsible for this autosomal dominant form of ANCL.

Pseudo-lysosomal storage disease caused by EMLA cream

Prilocaine-lidocaine emulsion (EMLA cream) is a topical anaesthetic commonly used prior to diagnostic and therapeutic procedures. While undergoing clinical investigation for the suspicion of a metabolic disorder, a series of children underwent skin biopsy with EMLA cream pretreatment. In each case, the pathologist identified ultrastructural features consistent with a lysosomal storage disorder, yet the clinical features were not consistent with the pathological findings. Ultrastructural artefact was suspected, resulting from the use of the EMLA cream. All patients underwent repeat skin biopsy without EMLA cream. Biopsies were reviewed by two pathologists blinded to the previous biopsy findings. Electron microscopy repeated without the use of EMLA cream was normal. It is concluded that the use of EMLA cream causes ultrastructural artefact and should be avoided prior to skin biopsy for electron microscopy.

Sequelae of storage in Fabry disease--pathology and comparison with other lysosomal storage diseases

AIM

To evaluate the sequelae of the lysosomal storage of globotriaosylceramide (Gb3) in a series of patients with Fabry disease.

METHODS

Biopsy and post-mortem samples from 12 patients with Fabry disease were examined microscopically, including, in some cases, immunohistochemistry and electron microscopy. Where possible, comparisons were made with other lysosomal storage disorders.

RESULTS

Storage of Gb3 in cardiocytes leads commonly to progressive hypertrophy, which is a non-specific phenomenon also observed in other lysosomal storage disorders. Capillary endothelial storage was associated with a tendency for capillary basement membrane multiplication. In the single angiokeratoma studied, the basement membrane was rudimentary. Sinusoids in the adrenal cortex and liver displayed either a slight degree of storage or were unaffected. The glomeruli of the kidney exhibited focal hyalinization starting in the mesangial region. Proximal tubular cells were essentially free of lysosomal accumulation, including protein absorption droplets, despite the presence of proteinuria. In only one case, an autopsied Fabry heterozygote, were the proximal tubular cells loaded with protein absorption droplets. The arterial wall in large muscular arteries (coronary, renal and intrarenal) displayed arteriopathy with pronounced involvement of the smooth muscle cells in the media. Arteriopathy started with storage, followed by cell degeneration and breakdown, extracellular matrix deposition and, often, calcification (confined to the muscular layer). Smooth muscle cells occasionally exhibited shrinkage-type necrosis, with dispersion of the stored lipid into the dense cytoplasmic mass. Intimal and mitral valve fibroblasts exhibited variable storage, which was associated with cell loss and necrosis. Intensive storage was found in Leydig cells and in the epididymal epithelium.

CONCLUSION

These long-term sequelae of Gb3 storage are mostly irreversible. Some may interfere with enzyme replacement therapy. It is important, therefore, to consider starting enzyme replacement therapy as early as possible.

Deficiency of mannose 6-phosphate receptors and lysosomal storage: a morphometric analysis of hepatocytes of neonatal mice

Transport of lysosomal enzymes is mediated by two mannose 6-phosphate receptors: a cation dependent (CD-MPR) and a cation independent receptor (CI-MPR). In the present study the effect of MPR-deficiency on the lysosomal system of neonatal mouse hepatocytes was studied by ultrastructural morphometric analyses. The volume density of the lysosomal system in hepatocytes of mice that lack both receptors was significantly increased in comparison with controls and with mice deficient for CI-MPR only. This higher volume density was due to a nine-fold increase of residual bodies. In CI-MPR-deficient mice the volume density of the lysosomal system was not different from controls and no increase of residual bodies was observed. It is concluded that in hepatocytes of MPR-deficient neonatal mice lysosomal storage occurs when both MPRs are lacking, whereas deficiency of CI-MPR only has no effect on the ultrastructure of the lysosomal system.

Metabolic disorders causing childhood ataxia

Ataxia is a common neurologic finding in many disease processes of the nervous system, and has classically been associated with numerous metabolic disorders. An error of metabolism should be considered when the ataxia is either intermittent or progressive. Acute exacerbation or worsening after high protein ingestion, concurrent febrile illness, or other physical stress is also suggestive. A positive family history can be an important diagnostic clue. Progressive molecular and biochemical techniques are revolutionizing this area of medicine, and there has been rapid advancement in understanding of the disease processes.

A case of galactosialidosis

Galactosialidosis is a lysosomal storage disease associated with a combined deficiency of beta-galactosidase and neuraminidase, caused by a defect of another lysosomal protein, the protective protein. Three subtypes are recognized: the early infantile form, the late infantile form and the juvenile/adult form. We saw a patient with galactosialidosis of the juvenile/adult form, a 51-year-old Japanese man with angiokeratomas on both elbows and knees, myoclonus, ataxia, mental retardation and macular cherry-red spots. An electron-microscopic study of a skin biopsy showed membrane-limited vacuoles in the cytoplasm of the endothelial cells, pericytes and fibroblasts. Assays of enzymatic activity in cultured fibroblasts showed a marked decrease in both beta-galactosidase and neuraminidase (sialidase). The substance contained in the cytoplasmic vacuoles appears to be glycoproteins with sialic acid, which is a terminal glycosyl residue, because the cytoplasm of the endothelial cells of the vessels and pericytes are stained by the Limax flavus agglutinin, a lectin that binds specifically with sialic acid. This technology may be useful for easy investigation of the distribution of the accumulation of such substances in the central nervous system.

New mutations in two Dutch patients with early infantile galactosialidosis

Galactosialidosis is an autosomal recessive lysosomal storage disease caused by a combined deficiency of lysosomal beta-galactosidase and neuraminidase as a result of a primary defect in the protective protein/cathepsin A (PPCA). We report the first 2 Dutch cases of early infantile galactosialidosis, both presenting with neonatal ascites. The defect was identified in urine, leukocytes, and fibroblasts. Residual activity was determined with a modified assay for cathepsin A and was <5% in leukocytes and <1% in fibroblasts. Histological examination of the placenta in case 1 showed extensive vacuolization in all cell types. Northern blot analysis of RNA isolated from the patients' cultured fibroblasts showed substantially decreased levels of the PPCA transcript, which nevertheless had the correct size of 2 kb. Mutation analysis of both mRNA and genomic DNA from the patients identified two novel mutations in the PPCA locus. Case 1 was a compound heterozygote, with a single missense mutation in one allele, which resulted in Gly57Ser amino acid substitution, and a single C insertion at nucleotide position 899 in the second allele, which gave rise to a frame shift and premature termination codon. Case 2 was homozygous for the same C899 insertion found in case 1.

Glycosphingolipid lysosomal storage diseases: therapy and pathogenesis

Paediatric neurodegenerative diseases are frequently caused by inborn errors in glycosphingolipid (GSL) catabolism and are collectively termed the glycosphingolipidoses. GSL catabolism occurs in the lysosome and a defect in an enzyme involved in GSL degradation leads to the lysosomal storage of its substrate(s). GSLs are abundantly expressed in the central nervous system (CNS) and the disorders frequently have a progressive neurodegenerative course. Our understanding of pathogenesis in these diseases is incomplete and currently few options exist for therapy. In this review we discuss how mouse models of these disorders are providing insights into pathogenesis and also leading to progress in evaluating experimental therapies.

Clinicopathological features of genetically confirmed Danon disease

BACKGROUND

Danon disease is due to primary deficiency of lysosome-associated membrane protein-2.

OBJECTIVE

To define the clinicopathologic features of Danon disease.

METHODS

The features of 20 affected men and 18 affected women in 13 families with genetically confirmed Danon disease were reviewed.

RESULTS

All patients had cardiomyopathy, 18 of 20 male patients (90%) and 6 of 18 female patients (33%) had skeletal myopathy, and 14 of 20 male patients (70%) and one of 18 female patients (6%) had mental retardation. Men were affected before age 20 years whereas most affected women developed cardiomyopathy in adulthood. Muscle histology revealed basophilic vacuoles that contain acid phosphatase-positive material within membranes that lack lysosome-associated membrane protein-2. Heart transplantation is the most effective treatment for the otherwise lethal cardiomyopathy.

CONCLUSIONS

Danon disease is an X-linked dominant multisystem disorder affecting predominantly cardiac and skeletal muscles.

Biosynthesis of lysosomal proteinases in health and disease

Proteolytic maturation of lysosomal proteinases is initiated after receptor-mediated targeting to prelysosomal compartments, while terminal processing occurs upon delivery to lysosomes. These late processing events are impaired in patients suffering from inherited lysosomal disorders, such as sialic acid storage disease and mucolipidosis II (I-cell disease). Lysosomes in the affected cells display marked changes in their physiological and morphological properties, with features reminiscent of prelysosomal compartments. This indicates that the absence of mature lysosomes interferes with the final processing steps during the biosynthesis of lysosomal proteinases. Thus, impaired proteinase maturation reflects an incompetent lysosomal apparatus and as such can be seen as a hallmark of lysosomal storage diseases.

Lysosomal-storage disorder induced by elmiron following 90-days gavage administration in rats and mice

Elmiron, a highly sulfated, semisynthetic pentose polysaccharide with properties similar to heparin, is used for the treatment of interstitial cystitis. Thirteen-week gavage studies were conducted by administering the drug in deionized water to F344/N rats and B6C3F1 mice once daily, 5 days per week for up to 13 consecutive weeks, at doses of 0, 63, 125, 250, 500, and 1,000 mg/kg body weight. No significant drug-related effects were observed in body weight, survival, clinical, and necropsy results. Significant organ weight increases were seen in the liver, lungs, and spleen of both species and the kidneys of rats, mainly in groups treated with 250 mg/kg/day and above. Hematological analysis indicated increases for both species in the white blood cell and lymphocyte counts. Sites of toxicity identified histopathologically were the rectum, liver, mesenteric and mandibular lymph nodes (both sexes), spleen (mice only), and lungs and kidneys (rats only). Lesions consisted mainly of infiltration into multiple tissues of vacuolated histiocytes, which, by histochemical investigation, indicated the presence of neutral and acidic mucins and lipidic material within the vacuoles. Transmission electron microscopy identified these vacuoles as lysosomal structures that exhibited a variety of contents. On the basis of our findings, we propose that Elmiron was absorbed through the focally disrupted rectal mucosa, was deposited in the lamina propria, accumulated within macrophages, and then was distributed by these cells or as a free chemical via the lymphatics and blood, to the various organ sites manifesting histiocytic infiltration. The cytoplasmic membrane-bound structures within macrophages were lysosomes containing membranous material of cellular origin and, perhaps, remnants of the deposited test material, Elmiron.

Overlapping functions of lysosomal acid phosphatase (LAP) and tartrate-resistant acid phosphatase (Acp5) revealed by doubly deficient mice

To date, two lysosomal acid phosphatases are known to be expressed in cells of the monocyte/phagocyte lineage: the ubiquitously expressed lysosomal acid phosphatase (LAP) and the tartrate-resistant acid phosphatase-type 5 (Acp5). Deficiency of either acid phosphatase results in relatively mild phenotypes, suggesting that these enzymes may be capable of mutual complementation. This prompted us to generate LAP/Acp5 doubly deficient mice. LAP/Acp5 doubly deficient mice are viable and fertile but display marked alterations in soft and mineralised tissues. They are characterised by a progressive hepatosplenomegaly, gait disturbances and exaggerated foreshortening of long bones. Histologically, these animals are distinguished by an excessive lysosomal storage in macrophages of the liver, spleen, bone marrow, kidney and by altered growth plates. Microscopic analyses showed an accumulation of osteopontin adjacent to actively resorbing osteoclasts of Acp5- and LAP/Acp5-deficient mice. In osteoclasts of phosphatase-deficient mice, vacuoles were frequently found which contained fine filamentous material. The vacuoles in Acp5- and LAP/Acp5 doubly-deficient osteoclasts also contained crystallite-like features, as well as osteopontin, suggesting that Acp5 is important for processing of this protein. This is further supported by biochemical analyses that demonstrate strongly reduced dephosphorylation of osteopontin incubated with LAP/Acp5-deficient bone extracts. Fibroblasts derived from LAP/Acp5 deficient embryos were still able to dephosphorylate mannose 6-phosphate residues of endocytosed arylsulfatase A. We conclude that for several substrates LAP and Acp5 can substitute for each other and that these acid phosphatases are essential for processing of non-collagenous proteins, including osteopontin, by osteoclasts.

The role of ceramide in receptor- and stress-induced apoptosis studied in acidic ceramidase-deficient Farber disease cells

The activation of sphingomyelinases leading to the generation of ceramide has been implicated in various apoptotic pathways. However, the role of ceramide as an essential death mediator remains highly controversial. In the present study, we investigated the functional relevance of ceramide in a genetic model by using primary cells from a Farber disease patient. These cells accumulate ceramide as the result of an inherited deficiency of acidic ceramidase. We demonstrate that Farber disease lymphocytes and fibroblasts underwent apoptosis induced by various stress stimuli, including staurosporine, anticancer drugs and gamma-irradiation, equally as normal control cells. In addition, caspase activation by these proapoptotic agents occurred rather similarly in Farber disease and control fibroblasts. Interestingly, Farber disease lymphoid cells underwent apoptosis induced by the CD95 death receptor more rapidly than control cells. Our data therefore suggest that ceramide does not play an essential role as a second messenger in stress-induced apoptosis. However, in accordance with a role in lipid-rich microdomains, ceramide by altering membrane composition may function as an amplifier in CD95-mediated apoptosis.