The abnormalities of lysosomal enzymes in mucopolysacc- haridoses

The ameliorating effect of Rutin on hepatotoxicity and inflammation induced by the daily administration of vortioxetine in rats

BACKGROUND

Vortioxetine (VORTX) is a potent and selective type of selective serotonin reuptake inhibitor (SSRI) that is mainly prescribed for treating major depression along with mood disorders as the first drug of choice. Limited previous findings have indicated evidence of liver injury and hepatotoxicity associated with daily VORTX treatment. Rutin (RUT), which is known for its antioxidant properties, has demonstrated several beneficial health actions, including hepatoprotection. Therefore the current study aimed to evaluate and assess the ameliorative effect of RUT against the hepatotoxic actions of daily low and high-dose VORTX administration.

METHODS

The experimental design included six groups of rats, each divided equally. Control, rats exposed to RUT (25 mg/kg), rats exposed to VORTX (28 mg/kg), rats exposed to VORTX (28 mg/kg) + RUT (25 mg/kg), rats exposed to VORTX (80 mg/kg), and rats exposed to VORTX (80 mg/kg) + RUT (25 mg/kg). After 30 days from the daily exposure period, assessments were conducted for serum liver enzyme activities, hepatotoxicity biomarkers, liver antioxidant endogenous enzymes, DNA fragmentation, and histopathological studies of liver tissue.

RESULTS

Interestingly, the risk of liver damage and hepatotoxicity related to VORTX was attenuated by the daily co-administration of RUT. Significant improvements were observed among all detected liver functions, oxidative stress, and inflammatory biomarkers including aspartate aminotransferase (AST), alanine transaminase (ALT), lactate dehydrogenase (LDH), albumin, malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH), glutathione S-transferase (GST), total protein, acid phosphatase, N-Acetyl-/β-glucosaminidase (β-NAG), β-Galactosidase (β-Gal), alpha-fetoprotein (AFP), caspase 3, and cytochrom-C along with histopathological studies, compared to the control and sole RUT group.

CONCLUSION

Thus, RUT can be considered a potential and effective complementary therapy in preventing hepatotoxicity and liver injury induced by the daily or prolonged administration of VORTX.

β-Galactosidase deficiency in the GLB1 spectrum of lysosomal storage disease can present with severe muscle weakness and atrophy

Deficiency of the enzyme β-galactosidase due to variants in the GLB1-gene is associated with metabolic disorders: Morquio B and GM1-gangliosidosis. Here, we report a case compound heterozygous for variants in the GLB1-gene and a severe muscular phenotype. Full body T1-w MRI was conducted for muscular involvement. Biopsy was stained with hematoxylin and eosin for histopathological evaluation. EDTA blood-sample was subjected to whole exome sequencing. Metabolic analysis included residual enzyme activity and evaluation urinary substrate secretion. Additionally, electroneurography, echocardiography, forced volume capacity and biochemistry were evaluated. Examination showed severe proximal weakness (MRC: hip flexion 2, hip extension 2, and shoulder rotation 2), Gower's sign, no extrapyramidal symptoms and normal creatine kinase levels. MRI showed severe muscle wasting of the thigh and shoulder girdle. Muscle biopsy showed mild myopathic changes. β-galactosidase activity was reduced to 28%-34%. Urinary glycosaminoglycan was elevated by 5.9-8.6 mg/mmol (ref.:0-5.1 mg/mmol). Electrophoresis indicated excess keratan sulfate. Exome sequencing revealed two missense variants in the GLB1 gene. Clinical features, genetic testing and laboratory findings indicate a case of β-galactosidase-deficiency with a muscular phenotype.

Effectual Endeavors of Silk Protein Sericin against Isoproterenol Induced Cardiac Toxicity and Hypertrophy in Wistar Rats

The silkworm cocoon has been used in the treatment of various ailments in different Asian countries. This research was designed to evaluate the effect of sericin on myocardial necrosis and hypertrophy in isoproterenol-challenged rats. The rats were administered with sericin (500 and 1000 mg/kg, p.o.) for 28 days, followed by administration of isoprenaline (85 mg/kg, s.c.) on the 29th and 30th days. The cardioprotective activity was assessed by various physical, enzymatic, and histopathological parameters along with apoptotic marker expression. The cardioprotective effect showed that pre-treatment of rats with sericin significantly increased the non-enzymatic antioxidants marker in serum and heart tissue (glutathione, vitamin E, and vitamin C). The results were the same in enzymatic antioxidant marker, mitochondrial enzymes, and protein. The grading of heart, heart/body weight ratio, gross morphology, cardiac markers, oxidative stress markers in serum and heart tissue, glucose, serum lipid profiling and Lysosomal hydrolases, heart apoptotic markers such as MHC expression by western blot, apoptosis by flow cytometry, total myocardial collagen content, fibrosis estimation, myocyte size were significantly decreased when compared with isoproterenol (ISG) group however histopathological studies showed normal architecture of heart in both control and treated rats. The pharmacological study reflects that sericin on both doses i.e., 500 mg/kg and 1000 mg/kg have potent cardioprotective action against the experimental model which was confirmed by various physical, biochemical, and histopathological parameters evaluated further research is required to examine the molecular mechanism of cardioprotective effect of sericin.

Emerging Approaches for Fluorescence-Based Newborn Screening of Mucopolysaccharidoses

Interest in newborn screening for mucopolysaccharidoses (MPS) is growing, due in part to ongoing efforts to develop new therapies for these disorders and new screening assays to identify increased risk for the individual MPSs on the basis of deficiency in the cognate enzyme. Existing tests for MPSs utilize either fluorescence or mass spectrometry detection methods to measure biomarkers of disease (e.g., enzyme function or glycosaminoglycans) using either urine or dried blood spot (DBS) samples. There are currently two approaches to fluorescence-based enzyme function assays from DBS: (1) manual reaction mixing, incubation, and termination followed by detection on a microtiter plate reader; and (2) miniaturized automation of these same assay steps using digital microfluidics technology. This article describes the origins of laboratory assays for enzyme activity measurement, the maturation and clinical application of fluorescent enzyme assays for MPS newborn screening, and considerations for future expansion of the technology.

The effect of ferulic acid against lead-induced oxidative stress and DNA damage in kidney and testes of rats

Oxidative stress is an imbalance between free radicals and antioxidants which leads to reactive oxygen species (ROS) production in cells. Reactive oxygen species contains oxygen radicals that easily react with other molecules in the biological system. For decades, lead acetate (Pb(C₂H₃O2)₂) is used as an additive for many widely used chemical products such as insecticides, hair dyes, and cosmetics; however, contact with lead acetate may irritate skin, eyes, and mucous membranes.In the present study, the antioxidant and anti-inflammatory effect of using ferulic acid to inhibit lead acetate-induced toxicity in rats is investigated. Lead acetate was orally given at a dose of 20 mg/kg body weight for 10 days, either alone or with ferulic acid at dose 25 mg/kg. Serum luteinizing hormone (LH), total testosterone, and follicle-stimulating hormone (FSH) levels were measured. Also, reactive oxygen species (ROS), lipid peroxidation (LPO), total antioxidant capacity (TAC), and catalase (CAT) activities were determined. In addition, histopathological changes of testes and kidney were examined. Results showed that administration of lead acetate induced oxidative stress through attenuation of luteinizing hormone, total testosterone, and follicle-stimulating hormone levels in serum. Moreover, the kidney and testes of lead acetate-treated animals exhibited elevation of ROS level, lipid peroxide levels, as well as lysosomal enzyme activity such acid phosphatase and N-acetyl-β-glucosminidase. DNA fragmentation and histological changes were also observed in lead acetate-treated group. In contrast, ferulic acid treatment reduced the deleterious effects induced by lead acetate in both testes and kidney tissues. These results illustrated that ferulic acid has a protective action against toxicity caused by lead acetate in rats. In conclusions, ferulic acid may have future therapeutic relevance in the prevention of lead acetate-induced testicular and renal toxicity in rats.

Ursolic acid modulates MMPs, collagen-I, α-SMA, and TGF-β expression in isoproterenol-induced myocardial infarction in rats

In the present study, the modulatory effect of ursolic acid (UA) on cardiac fibrosis and mitochondrial and lysosomal enzymes activity in isoproterenol-induced myocardial infarction (MI) in rats were examined. Isoproterenol hydrochloride (ISO; 85 mg/kg body weight) was administered subcutaneously for first two consecutive days. ISO-induced MI in rats significantly decreased the activities of mitochondrial tricarboxylic acid cycle enzymes and respiratory chain enzymes while increased the activities of lysosomal glycohydrolases and cathepsins. The expression of matrix metalloproteinase 2 (MMP-2), MMP-9, collagen type I, α-smooth muscle actin (α-SMA), and transforming growth factor-β (TGF-β) were upregulated in ISO-induced MI in rats. UA administration to rats showed increased activities of mitochondrial tricarboxylic acid cycle enzymes and respiratory chain enzymes and decreased activities of lysosomal glycohydrolases and cathepsins in ISO-induced rats. Furthermore, expression of MMP-2, MMP-9, collagen type I, α-SMA, and TGF-β downregulated in UA-administered rats. Thus, our results demonstrate that UA has an anti-fibrotic effect and attenuates the mitochondrial and lysosomal dysfunction in ISO-induced MI in rats.

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.

A homozygous founder missense variant in arylsulfatase G abolishes its enzymatic activity causing atypical Usher syndrome in humans

PURPOSE

We aimed to identify the cause of disease in patients suffering from a distinctive, atypical form of Usher syndrome.

METHODS

Whole-exome and genome sequencing were performed in five patients from three families of Yemenite Jewish origin, suffering from distinctive retinal degeneration phenotype and sensorineural hearing loss. Functional analysis of the wild-type and mutant proteins was performed in human fibrosarcoma cells.

RESULTS

We identified a homozygous founder missense variant, c.133G>T (p.D45Y) in arylsulfatase G (ARSG). All patients shared a distinctive retinal phenotype with ring-shaped atrophy along the arcades engirdling the fovea, resulting in ring scotoma. In addition, patients developed moderate to severe sensorineural hearing loss. Both vision and hearing loss appeared around the age of 40 years. The identified variant affected a fully conserved amino acid that is part of the catalytic site of the enzyme. Functional analysis of the wild-type and mutant proteins showed no basal activity of p.D45Y.

CONCLUSION

Homozygosity for ARSG-p.D45Y in humans leads to protein dysfunction, causing an atypical combination of late-onset Usher syndrome. Although there is no evidence for generalized clinical manifestations of lysosomal storage diseases in this set of patients, we cannot rule out the possibility that mild and late-onset symptoms may appear.

Anti-arthritic activity of 11-O-(4′-O-methyl galloyl)-bergenin and Crassula capitella extract in rats

Objectives

Isolation and identification of phytochemicals of Crassula capitella (Thunberg), evaluation of the anti-arthritic potential of the extract and the major isolated compound; 11-O-(4′-O-methyl galloyl)-bergenin and underlying their mechanism on rat model of rheumatoid arthritis (RA).

Methods

Different fractions were subjected to column chromatography giving fourteen compound identified by mass and NMR spectroscopic techniques. RA was induced by intraplantar injection of complete Freund's adjuvant into the right hind paw of rats. Influence of tested samples in comparable to methotrexate on paw oedema, body weight gain, serum diagnostic markers, cartilage and bone degeneration enzymes, pro-inflammatory mediators and oxidative stress biomarkers in arthritic rats.

Key findings

Fourteen phenolic compounds were isolated and identified for the first time from C. capitella. The major compound identified as 11-O-(4′-O-methyl galloyl)-bergenin. Treatment of arthritic rats with extract or 11-O-(4′-O-methyl galloyl)-bergenin with the tested doses can reduce the progression and severity of RA.

Conclusion

Crassula capitella is a new natural and abundant source for 11-O-(4′-O-methyl galloyl)-bergenin for resolving chronic inflammatory diseases as RA through antioxidant, anti-inflammatory and membrane stabilizing mechanism.

From rare to common and back again: 60years of lysosomal dysfunction

Sixty years after its discovery, the lysosome is no longer considered as cell's waste bin but as an organelle playing a central role in cell metabolism. Besides its well known association with lysosomal storage disorders (mostly rare and life-threatening diseases), recent data have shown that the lysosome is also a player in some of the most common conditions of our time; and, perhaps even most important, it is not only a target for orphan drugs (rare disease therapeutic approaches) but also a putative target to treat patients suffering from common complex diseases worldwide. Here we review the striking associations linking rare lysosomal storage disorders such as the well-known Gaucher disease, or even the recently discovered, extremely rare Neuronal Ceroid Lipofuscinosis-11 and some of the most frequent, multifaceted and complex disorders of modern society such as cancer, Parkinson's disease and frontotemporal lobar degeneration.

Diagnostic value of alpha-L-fucosidase for hepatocellular carcinoma: a meta-analysis

Alpha-fetoprotein (AFP) is the primary marker for detecting hepatocellular carcinoma (HCC) and has been used widely in the clinic, but AFP is a biomarker characterized by poor sensitivity and specificity. Alpha-L-fucosidase (AFU) has been proposed as a tumor marker for diagnosis of HCC in many studies. However, conclusions of its diagnostic value are inconsistent. The current review aimed to evaluate the diagnostic value of AFU for HCC. After systematic review of 12 related studies, sensitivity, specificity, and diagnostic odds ratio (DOR) were pooled using random-effect models. Summary receiver operating characteristic (sROC) curve analysis was used to summarize the overall test performance. The pooled sensitivity for AFU was 0.72 (95% confidence interval (CI) 0.69-0.76), while the pooled specificity was 0.78 (95% CI 0.74-0.81). DOR was 10.26 (95% CI 5.99-17.59), and the area under the curve (AUC) was 0.8125. AFU had great value for the diagnosis of HCC as a serum marker.

A profile of bioactive compounds of Rumex vesicarius L

The present study was designed to investigate the bioactive compounds in extracts of Rumex vesicarius L. (Polygonaceae), a wild edible herb growing in Egypt. Ethyl acetate and n-butanol fractions of leaves of R. vesicarius were conducted by HPLC-PDA-MS/MS-ESI in the negative mode to analyze phenolics content. Results revealed the identification of 13 phenolic compounds: 8-C-glucosyl-apigenin, 8-C-glucosyl-luteolin, 6-C-hexosyl-quercetin, 3-O-rutinosyl-quercetin, 7-O-rhamno-hexosyl-diosmetin, 7-O-rhamno-acetylhexosyl-diosmetin, catechin, epicatechin, ferulohexoside, 6-C-glucosyl-naringenin, epicatechin gallate, 6-C-glucosyl-catechin, and epigallocatechin gallate. Quantification of the identified compounds revealed that 6-C-glucosyl-naringenin was the major compound. Also, qualitative and quantitative analysis of the hydro-ethanolic extract of leaves was carried out for ascorbic acid, α-tocopherol, β-carotene. The essential oil as well as lipids analysis of saponifiable and unsaponifiable matters. The biochemical studies were conducted to evaluate the antioxidant and hepatoprotective potential of roots (REE), leaves (LEE), and fruits (FEE) ethanolic extracts of R. vesicarius (100 mg/kg b.wt., p.o., each) against hepatotoxicity induced by CCl(4) (0.5 mL/kg b.wt., p.o., 3 times a week) compared with silymarin (50 mg/kg b.wt., p.o.) as standard drug. The results confirmed that coadministration of the tested extracts or silymarin with CCl(4) for 4 wk exhibited a marked hepatoprotective activity, attributed to their antioxidant potential, membrane stabilizing effect, and antifibrogenic activities. Practical Application:  Investigation of the effect of hommad as a safe hepatoprotective diet that prospectively directs the attention to a valuable therapeutic natural herb rich in bioactive constituents.

Modeling neuronal defects associated with a lysosomal disorder using patient-derived induced pluripotent stem cells

By providing access to affected neurons, human induced pluripotent stem cells (iPSc) offer a unique opportunity to model human neurodegenerative diseases. We generated human iPSc from the skin fibroblasts of children with mucopolysaccharidosis type IIIB. In this fatal lysosomal storage disease, defective α-N-acetylglucosaminidase interrupts the degradation of heparan sulfate (HS) proteoglycans and induces cell disorders predominating in the central nervous system, causing relentless progression toward severe mental retardation. Partially digested proteoglycans, which affect fibroblast growth factor signaling, accumulated in patient cells. They impaired isolation of emerging iPSc unless exogenous supply of the missing enzyme cleared storage and restored cell proliferation. After several passages, patient iPSc starved of an exogenous enzyme continued to proliferate in the presence of fibroblast growth factor despite HS accumulation. Survival and neural differentiation of patient iPSc were comparable with unaffected controls. Whereas cell pathology was modest in floating neurosphere cultures, undifferentiated patient iPSc and their neuronal progeny expressed cell disorders consisting of storage vesicles and severe disorganization of Golgi ribbons associated with modified expression of the Golgi matrix protein GM130. Gene expression profiling in neural stem cells pointed to alterations of extracellular matrix constituents and cell-matrix interactions, whereas genes associated with lysosome or Golgi apparatus functions were downregulated. Taken together, these results suggest defective responses of patient undifferentiated stem cells and neurons to environmental cues, which possibly affect Golgi organization, cell migration and neuritogenesis. This could have potential consequences on post-natal neurological development, once HS proteoglycan accumulation becomes prominent in the affected child brain.

The mucopolysaccharidoses: a success of molecular medicine

The mucopolysaccharidoses represent a devastating group of lysosomal storage diseases affecting approximately 1 in 25 000 individuals. Advances in biochemistry and genetics over the past 25 years have resulted in the identification of the key hydrolases underlying the mucopolysaccharidoses, with subsequent isolation and characterisation of the genes involved. Ultimately these advances have led to the recent development of specific treatment regimens for some of the mucopolysaccharidoses, in the form of direct enzyme replacement. Direct replacement of the defective gene product has been attempted for very few genetic disorders, and thus the experience gained in the lysosomal storage diseases by the development, evaluation and integration of treatment regimens into healthcare is instructive for other rare genetic disorders. This review focuses on the pathophysiology of the mucopolysaccharidoses and highlights the complex biochemical and physiological perturbations that underlie the disease phenotype.

Improved behavior and neuropathology in the mouse model of Sanfilippo type IIIB disease after adeno-associated virus-mediated gene transfer in the striatum

Sanfilippo syndrome is a mucopolysaccharidosis (MPS) caused by a lysosomal enzyme defect interrupting the degradation pathway of heparan sulfates. Affected children develop hyperactivity, aggressiveness, delayed development, and severe neuropathology. We observed relevant behaviors in the mouse model of Sanfilippo syndrome type B (MPSIIIB), in which the gene coding for alpha-N-acetylglucosaminidase (NaGlu) is invalidated. We addressed the feasibility of gene therapy in these animals. Vectors derived from adeno-associated virus serotype 2 (AAV2) or 5 (AAV5) coding for NaGlu were injected at a single site in the putamen of 45 6-week-old MPSIIIB mice. Normal behavior was observed in treated mice. High NaGlu activity, far above physiological levels, was measured in the brain and persisted at 38 weeks of age. NaGlu immunoreactivity was detected in neuron intracellular organelles, including lysosomes. Enzyme activity spread beyond vector diffusion areas. Delivery to the entire brain was reproducibly obtained with both vector types. NaGlu activity was higher and distribution was broader with AAV5-NaGlu than with AAV2-NaGlu vectors. The compensatory increase in the activity of various lysosomal enzymes was improved. The accumulation of gangliosides GM2 and GM3 present before treatment and possibly participating in neuropathology was reversed. Characteristic vacuolations in microglia, perivascular cells, and neurons, which were prominent before the age of treatment, disappeared in areas in which NaGlu was present. However, improvement was only partial in some animals, in contrast to high NaGlu activity. These results indicate that NaGlu delivery from intracerebral sources has the capacity to alleviate most disease manifestations in the MPSIIIB mouse model.

A model of mucopolysaccharidosis IIIB (Sanfilippo syndrome type IIIB): N-acetyl-alpha-D-glucosaminidase deficiency in Schipperke dogs

Mucopolysaccharidosis III (MPS III) is characterized by lysosomal accumulation of the glycosaminoglycan (GAG) heparan sulphate (HS). In humans, the disease manifests in early childhood, and is characterized by a progressive central neuropathy leading to death in the second decade. This disease has also been described in mice (MPS IIIA and IIIB), dogs (MPS IIIA), emus (MPS IIIB) and goats (MPS IIID). We now report on dogs with naturally occurring MPS IIIB, detailing the clinical signs, diagnosis, histopathology, tissue enzymology and substrate levels. Two 3-year-old Schipperke dogs were evaluated for tremors and episodes of stumbling. Examination of the animals found signs consistent with cerebellar disease including dysmetria, hind limb ataxia and a wide-based stance with truncal swaying. There were mildly dystrophic corneas and small peripheral foci of retinal degeneration. Magnetic resonance imaging of the brain and skeletal radiographs were normal. Intracytoplasmic granules were found in the white cells of peripheral blood and cerebral spinal fluid, and in myeloid lineages in bone marrow. Electrophoresis of urinary GAGs indicated the presence of HS, while assays of cultured fibroblasts found N-acetyl-alpha-D-glucosaminidase (Naglu) activity of between 4.3% and 9.2% of normal. Owing to neurological deterioration, both dogs were euthanized, and post-mortem examinations were performed. Biochemical studies of liver and kidney from both animals demonstrated profound deficiency of Naglu activity and abnormally high GAG levels. Pathology of the brain included severe cerebellar atrophy, Purkinje cell loss, and cytoplasmic vacuolation in neurons and perithelial cells throughout the central nervous system. Pedigree analyses and Naglu levels of family members supported an autosomal recessive mode of inheritance. Using an obligate heterozygote, a breeding colony has been established to aid in understanding the pathogenesis of MPS IIIB and testing of potential therapies.

Translocation of phosphatidylthreonine and -serine to mitochondria diminishes exponentially with increasing molecular hydrophobicity

Some cultured cells contain significant amounts of a rarely recognized phospholipid, phosphatidylthreonine. Since phosphatidylthreonine is a structural analog of phosphatidylserine, the question rises whether it is transported to mitochondria and decarboxylated to phosphatidylisopropanolamine therein. We studied this issue with hamster kidney cell-line using a novel approach, i.e. electrospray mass-spectrometry and stable isotope-labeled precursors. Scanning for a neutral loss of 155, which is characteristic for phosphatidylisopropanolamine, indicated that this lipid is indeed present. The identity of phosphatidylisopropanolamine was supported by the following: (i) it co-chromatographed with phosphatidylethanolamine; (ii) its molecular species profile was similar to that of phosphatidylethanolamine; (iii) its head group was labeled from 13C-threonine; and (iv) its concentration increased in parallel with phosphatidylthreonine. Tests with solubilized decarboxylase and subcellular fractionation studies indicated that the low cellular content of phosphatidylisopropanolamine is due to inefficient decarboxylation, rather than poor translocation of phosphatidylthreonine to mitochondria. Importantly, the average hydrophobicity of phosphatidylisopropanolamine molecular species was significantly less than that of phosphatidylthreonine species, indicating that hydrophilic phosphatidylthreonine species translocate to mitochondria far more rapidly than hydrophobic ones. Parallel results were obtained for phosphatidylserine. These findings imply that efflux from the ER membrane could be the rate-limiting step in the phosphatidylthreonine and -serine translocation to mitochondria.

A direct continuous spectrophotometric assay for glycosidases with 3-nitro-2-pyridyl glycosides by tautomerization of 2-hydroxy-3-nitropyridine

Two kinds of 3-nitro-2-pyridyl glycosides were synthesized and evaluated as substrates for continuous spectrophotometric assay for glycosidases. The liberated aglycon, 2-hydroxy-3-nitropyridine, immediately tautomerized to 3-nitro-2(1H)-pyridone, causing an absorption shift of ca. 60 nm even under acidic conditions (pH 3-6). Consequently, the enzymatic hydrolysis of these glycosides was monitored continuously in the acidic to neutral pH range (pH 4-7), the optimum pH for most glycosidases. The absorbance of liberated aglycon increased linearly at 390 nm until 10% consumption of the substrate to enable the initial rate to be determined at once without terminating the reaction. The kinetic parameters for the hydrolysis of 3-nitro-2-pyridyl glycosides were obtained from the slopes of the progress curves and were compared with those obtained from the conventional discontinuous assay using p- and o-nitrophenyl glycosides as substrates. The kinetic parameters indicated that 3-nitro-2-pyridyl glycosides were more activated and specific substrates, but with less affinity to the enzymes than the corresponding nitrophenyl glycosides. Moreover, the absorbance shift by tautomerization should promise further applications to continuous spectrophotometric assays for other enzymes acting under acidic conditions, such as acid proteases and acid phosphatases.

Mouse model of Sanfilippo syndrome type B produced by targeted disruption of the gene encoding alpha-N-acetylglucosaminidase

The Sanfilippo syndrome type B is an autosomal recessive disorder caused by mutation in the gene (NAGLU) encoding alpha-N-acetylglucosaminidase, a lysosomal enzyme required for the stepwise degradation of heparan sulfate. The most serious manifestations are profound mental retardation, intractable behavior problems, and death in the second decade. To generate a model for studies of pathophysiology and of potential therapy, we disrupted exon 6 of Naglu, the homologous mouse gene. Naglu-/- mice were healthy and fertile while young and could survive for 8-12 mo. They were totally deficient in alpha-N-acetylglucosaminidase and had massive accumulation of heparan sulfate in liver and kidney as well as secondary changes in activity of several other lysosomal enzymes in liver and brain and elevation of gangliosides G(M2) and G(M3) in brain. Vacuolation was seen in many cells, including macrophages, epithelial cells, and neurons, and became more prominent with age. Although most vacuoles contained finely granular material characteristic of glycosaminoglycan accumulation, large pleiomorphic inclusions were seen in some neurons and pericytes in the brain. Abnormal hypoactive behavior was manifested by 4.5-mo-old Naglu-/- mice in an open field test; the hyperactivity that is characteristic of affected children was not observed even in younger mice. In a Pavlovian fear conditioning test, the 4.5-mo-old mutant mice showed normal response to context, indicating intact hippocampal-dependent learning, but reduced response to a conditioning tone, perhaps attributable to hearing impairment. The phenotype of the alpha-N-acetylglucosaminidase-deficient mice is sufficiently similar to that of patients with the Sanfilippo syndrome type B to make these mice a good model for study of pathophysiology and for development of therapy.

Alterations in certain lysosomal glycohydrolases and cathepsins in rats on dexamethasone administration

Glucocorticoids have been used in the treatment of a number of diseases where immunological intolerance plays a predominant role. Since immunological intolerance points to the involvement of lysosomal enzymes and glucocorticoids are known to affect their activities, we have attempted to study the effect of these steroids on cardiac and renal enzymes. Dexamethasone, a glucocorticoid, is administered subcutaneously to male Wistar rats at a dosage of 2.5 mg/kg/week on alternate days for two weeks. After withdrawing the steroid, the animals are monitored for one week to oversee the recovery process. Total and free activities of glycohydrolases and cathepsins in serum, heart and kidney are assayed on the days 4, 8, 12, 16 of dexamethasone administration and also on days 4 and 8 following discontinuation of the steroid. During dexamethasone administration, a significant decrease in both the free and total activities of beta-glucuronidase, beta-N-acetyl glucosaminidase, beta-galactosidase, alpha-galactosidase, alpha-mannosidase, cathepsin B and cathepsin D are observed in heart and kidney, but the enzyme levels are shown to increase in serum. On withdrawal of the steroid, the activities of beta-glucuronidase, beta-N-acetyl glucosaminidase, beta-galactosidase are found to be increased in heart and kidney, whereas, the activity of alpha-mannosidase remains within normal values. Thus, it could be seen that dexamethasone alters the pattern of glycohydrolases and cathepsins, which are involved in protein degradation.

Tay-Sachs disease with atypical chronic course and limited brain storage: alpha-locus hexosaminidase genetic compound

A 19-year-old Irish-Jewish male had a slow neurologic regression starting at age 4 1/2 years with stuttering. The chronic course resembled that of Spielmeyer-Vogt (juvenile ceroid-lipofuscinosis) disease. The brain was atrophic with neuronal losses and huge compound inclusions in the remaining neurons. Lipid NANA was within normal limits in gray and white matter and GM2 gangliosides were moderately elevated at 11.5% lipid NANA. Beta-hexosaminidase A activity was reduced, secondary to a compound mutation at the alpha-locus. Lysosomal hydrolase activities and lipid composition showed nonspecific abnormalities. Exhaustive tissue extraction ruled out the possibility of tightly bound gangliosides to account for the relatively low GM2 ganglioside concentration. The extract contained unidentified chromogenic substances interfering with the resorcinol reaction. The similarly affected patient's sister lived to age 26 years and her brain was even more atrophic. No biochemical abnormality to account for progressive neuronal losses and relative lack of GM2 ganglioside storage was found.

Effect of radiation on serum glycoproteins and glycosidases in patients with cervical carcinoma

OBJECTIVE

The serum glycan moieties of glycoproteins and the activities of glycosidases were analyzed in order to elucidate the metabolism of glycoprotein in uterine cervical cancer.

METHODS

Serum was collected from patients at different stages of cervical cancer before and after treatment. The results were analyzed using Student's t-test.

RESULTS

The glycan moieties such as sialic acid and fucose were significantly elevated even in the early stages of carcinoma, whereas a significant elevation in hexose and hexosamine levels was observed only in the advanced stages. Among the investigated lysosomal glycohydrolases, beta-D-galactosidase, N-acetyl-beta-D-glucosaminidase and alpha-L-fucosidase activities were elevated significantly at all stages except for stage I. The altered levels of glycoproteins and glycosidases were reduced to near-normal levels after radiotherapy.

CONCLUSION

The levels of glycan moieties and the activities of glycosidases can be used as diagnostic markers to assess the stage of cancer and can be used as prognostic markers during therapy.

In vivo inhibition of beta-glucosidase and beta-mannosidase activity in rats by 2-deoxy-2-fluoro-beta-glycosyl fluorides and recovery of activity in vivo and in vitro

2-Deoxy-2-fluoro-beta-glucosyl and -beta-mannosyl fluorides administered to rats in a single dose (10 mg/kg) inhibited beta-glucosidase and beta-mannosidase activity respectively after 1 h in brain, spleen, liver and kidney tissues. This inhibition, presumably caused by accumulation of 2-deoxy-2-fluoroglycosyl-enzyme intermediates, indicates that intact 2-deoxy-2-fluoroglycosyl fluorides are distributed to these organs and, in the case of brain, that they cross the blood/brain barrier. beta-Glucosidase activity recovered completely or partially in brain, spleen, liver and kidney by 20-48 h. beta-Mannosidase activity partially recovered in all tissues by 48 h. beta-Galactosidase activity in brain and kidney was not significantly affected by administration of either the gluco or manno compounds at this dosage, indicating that these inhibitors are directed towards specific glycosidases. Observation of similar relatively rapid rates of beta-glycosidase re-activation in vivo and in tissue homogenates in vitro at 37 degrees C suggests that hydrolysis or transglycosylation of 2-deoxy-2-fluoroglycosyl-enzymes, not protein synthesis, are the primary mechanisms involved in the recovery of glycosidase activity inhibited by this class of compounds in vivo.

Regulation of expression of the gene encoding human acid beta-glucosidase in different cell types

Acid beta-glucosidase (beta Glc) activity and mRNA levels were measured in several human cell lines, and found to vary over 50-fold. A comparison between relative levels of beta Glc enzyme and mRNA levels revealed three patterns. The first group, including epithelial, lymphoblast, histiocyte, glioblastoma and astrocytoma cell lines, showed a direct relationship between relative levels of mRNA and enzyme activity, indicating that mRNA levels play an important role in determining enzyme activity. The second group, including fibroblast, promyelocyte and neuroglioma cell lines, also showed a direct relationship between beta Glc enzyme and mRNA levels within this group, but had enzyme activities that were approximately sixfold higher than expected, when compared with enzymes within the first group. The third pattern was exhibited by a single monocyte cell line, which showed high levels of beta Glc mRNA, but only intermediate levels of enzyme activity. These results suggest that although beta Glc mRNA levels play a major role in regulating beta Glc activity, other mechanisms also influence enzyme levels in certain cell lines. These results also demonstrate the importance of examining several different cell types when considering mechanisms of housekeeping gene regulation. Additionally, culturing cells in the presence of the beta Glc-specific inhibitor, conduritol-B-epoxide, did not affect beta Glc mRNA levels, and cells derived from normals had levels of beta Glc mRNA comparable to those from Gaucher disease patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Fucosyltransferases: differential plasma and tissue alterations in hepatocellular carcinoma and cirrhosis

To determine whether abnormal metabolism of L-fucose in hepatocellular carcinoma is accompanied by alterations in the activities of fucosyltransferases, the latter were determined in plasma and liver tissue of patients with this disease and in cirrhotic and normal subjects. Activities of alpha-2/alpha-3 and alpha-6-L-fucosyltransferases were all significantly greater in plasma from patients with hepatocellular carcinoma than in plasma from cirrhotic patients or normal subjects (p less than 0.025). The activity of each enzyme was dependent, to a similar extent, on Mn2+, Mg2+ and triton X-10, irrespective of the source, and all displayed pH optimums in the range of 7.5 to 8.0. In contrast, activities of alpha-2/alpha-3 fucosyltransferases were significantly lower (p less than 0.025) in homogenates prepared from tumorous liver tissue than in that prepared from nontumorous tissue from hepatocellular carcinoma and cirrhotic patients, whereas for the alpha-6 enzyme the situation was reversed (typically, tumor tissue levels were 5 pmol/hr/mg; in nontumor tissue they were 2 pmol/hr/mg). Activities of galactosyl and mannosyltransferase in tumor tissue were greater in all cases than in nontumor cirrhotic tissue. Plasma fucosyltransferases are specifically elevated in hepatocellular carcinoma but different mechanisms appear to underlie the changes seen for alpha-2/alpha-3 and alpha-6-L-fucosyltransferases.

Influence of isoproterenol-induced myocardial infarction on certain glycohydrolases and cathepsins in rats

The changes in the activities of certain lysosomal hydrolases, viz., beta-glucuronidase, beta-N-acetylglucosaminidase, beta-galactosidase, beta-glucosidase, alpha-glucosidase, alpha-galactosidase, alpha-mannosidase, cathepsin B, cathepsin D, and collagenolytic cathepsin, in serum and heart of rats subject to myocardial infarction with isoproterenol, were studied during the periods of peak infarction and recovery. The activities of all the enzymes assayed exhibited a significant increase both in serum and in heart at peak infarction stage and these levels returned to normal during the stage of recovery and repair. The infiltration of inflammatory cells at the infarct regions and the altered lysosomal fragility are probably responsible for the increased activity of the enzymes studied. This may also bring about the catabolism of connective tissue constituents as reported in literature.

Fucosidosis revisited: a review of 77 patients

Fucosidosis is a rare, autosomal recessive, lysosomal storage disorder caused by a severe deficiency of alpha-L-fucosidase in all tissues. We have conducted a review of fucosidosis, compiling data from published reports and an international questionnaire survey. Seventy-seven patients affected with fucosidosis of which 19 had not been reported before have been identified. A major aim of the present study was to define the natural history of fucosidosis. The clinical picture of fucosidosis consists of progressive mental (95%) and motor (87%) deterioration, coarse facies (79%), growth retardation (78%), recurrent infections (78%), dysostosis multiplex (58%), angiokeratoma corporis diffusum (52%), visceromegaly (44%), and seizures (38%). Whereas the original fucosidosis patients described by Durand et al. (J. Pediatr 75:665-674, 1969) were decerebrate and died before age 5 years, most fucosidosis patients have a slower course of degeneration. Mortality before age 5 years was observed in only 7 patients (9%), whereas 36 patients (64%) reached the second decade. We did not find evidence for the existence of clinical heterogeneity with a rapidly progressive type I and a slowly progressive type II fucosidosis as suggested in the literature. Instead, there seems to exist a wide continuous clinical spectrum. At the biochemical level no heterogeneity in residual fucosidase enzyme activity or cross-reacting immunoreactive fucosidase protein was observed. At the DNA level at least 4 different mutations must be responsible for fucosidosis. These genotypic differences however do not explain the observed phenotypic differences.

Characterization of liver lysosomal enzyme activity in hepatocytes, Kupffer and endothelial cells during aging: effect of dietary restriction

The specific activity of 4 lysosomal enzymes was studied in homogenate, hepatocytes, Kupffer and endothelial cells isolated from the livers of female Sprague-Dawley rats aged 3.5, 12 and 24 months. Cells were obtained by enzymatic digestion and centrifugal elutriation. Cell viability was not affected by age or diet. In hepatocytes, the activities of all enzymes (acid phosphatase, beta-galactosidase, arylsulfatase B and cathepsin D) increased with age in rats fed ad libitum (A) but were not altered significantly by dietary restriction. The activities of all enzymes except acid phosphatase were systematically higher at 3.5 months of age in Kupffer and endothelial cells than in hepatocytes. Acid phosphatase, arylsulfatase B and cathepsin D activities increased with age in both Kupffer and endothelial cells. Beta galactosidase was decreased significantly with age in Kupffer cells but was elevated in endothelial cells. Rats exposed to dietary restriction (R) showed higher activities of beta-galactosidase, arylsulfatase B and cathepsin D when compared to corresponding A animals with the exception of the younger age group. No clear cut pattern was observed in acid phosphatase activity. Thus, the activities of liver lysosomal enzymes increase with age but the pattern of change differs with respect to enzyme and cell populations. The heightened enzyme activity in Kupffer and endothelial cells from R rats may reflect a more efficient phagocytic capacity in these animals.

Abnormal glycosphingolipid metabolism in the nervous system of galactosialidosis

In an autopsy case of galactosialidosis, GM3, GM2, GM1, and GD1a were accumulated in sympathetic and spinal ganglia and grey matter of the spinal cord. Especially, the accumulations of GM3 and GM2 amounted to 41- and 86-fold increases in sympathetic ganglia, respectively, as compared to normal controls. In addition LacCer, GA2 and GA1 were accumulated in sympathetic and spinal ganglia. The accumulations of GM3 and GD1a are considered to be the result of defective lysosomal sialidase activity and the accumulation of GM1, LacCer and GA1 is also considered to be due to decreased beta-galactosidase activity in this disorder. To better understand the possible mechanism of GM2 accumulation, we determined the activity of GM2 synthesizing enzyme (GM3:UDP-GalNAc transferase), as well as hexosaminidase activity, in sympathetic ganglia, but they did not change. Abnormal ganglioside and neutral glycosphingolipid metabolism, as well as sialyloligosaccharide and sialylglycoprotein metabolism, may be involved in the pathogenesis of this disorder.

Fluorometric assay of peroxisomal oxidases

The present paper deals with the adaptation of the fluorometric measurement of H2O2 originally described by Guilbault et al. (1967, Anal. Chem. 39, 271) for the assay of the peroxisomal oxidation of D-amino acids, L-alpha-hydroxyacids, uric acid, and acyl-CoA esters. The present work essentially covers three facets: (i) the general kinetics of the assay of peroxisomal oxidases and the influence of each component of the assay medium on these kinetics; (ii) the measurement of peroxisomal oxidase activities in subcellular fractions and tissues from human and untreated and clofibrate-treated rodents; and (iii) the comparison between the oxidase activities measured by the fluorometric and spectrophotometric methods.

Purification of alpha-L-fucosidase by C-glycosylic affinity chromatography, and the enzymic synthesis of alpha-L-fucosyl disaccharides

An alpha-L-fucosidase from porcine liver was purified using the new C-glycosylic affinity adsorbent, Sepharose-epsilon-aminocaproyl-3-(alpha-L-fucopyranosyl)propylamine. The C-fucosylic linkage was synthesized by a radical reaction of 2,3,4-tri-O-acetyl-alpha-L-fucopyranosyl bromide with acrylonitrile. In transglycosylation reactions with p-nitrophenyl alpha-L-fucopyranoside or alpha-L-fucopyranosyl fluoride as donor and methyl beta-D-galactopyranoside as acceptor, the enzyme mediated the formation of (1----2)- and (1----6)-linked alpha-L-fucosyl derivatives (6.5 and 10.0%, respectively).

Evidence for the presence of a very high concentration of arylsulfatase A in the pig thyroid: identification of arylsulfatase A subunits as the two major glycoproteins in purified thyroid lysosomes

In addition to their general function in cellular homeostasis, thyroid lysosomes play an essential role in the biosynthesis of thyroid hormones by cleaving the macromolecular prohormone, thyroglobulin. In the present work, we have attempted to determine whether the enzyme composition of thyroid lysosomes differs from that of lysosomes from other tissues. Lysosomal enzymes, cathepsin D, beta-D-galactosidase, beta-D-glucosidase, alpha-D-mannosidase, alpha-L-fucosidase, hexosaminidase, and arylsulfatase A and B, were assayed in crude fractions from various pig tissues, heart, brain, liver, kidney, thyroid, adrenals, ovary, and spleen. It appeared that the specific activity of arylsulfatase A was at least 20 times higher in the thyroid than in most other tissues. Thyroid lysosomes purified by isopycnic centrifugation on Percoll gradients contained two major polypeptides with apparent molecular weights of 58,000 and 54,000 representing about 30% of the total protein. These polypeptides were glycosylated and were exclusively found in the intralysosomal soluble fraction obtained by osmotic pressure-dependent lysis. By fractionating intralysosomal soluble proteins by velocity sedimentation on sucrose gradients or gel permeation chromatography we identified a thyroid arylsulfatase A holoenzyme which corresponds to a 120,000 Mr species. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses of the gradient or column fractions showed that the 120-kDa protein peak with arylsulfatase A activity essentially contained the 58- and 54-kDa polypeptides in equivalent amounts. In conclusion, arylsulfatase A, a heterodimer of 120 kDa composed of two nonidentical subunits, is the major protein component of thyroid lysosomes. The superabundance of this protein in purified thyroid lysosomes is related to the very high specific activity of the enzyme in the thyroid as compared to other tissues.

Colorimetric assay for free and bound L-fucose

A novel, rapid, and reliable colorimetric method for measuring L-fucose has been developed. This method utilizes NADH formed from the interaction of L-fucose with fucose dehydrogenase and NAD to generate color in a reaction involving CuSO4 and neocuproine. NADH reduces Cu2+ to Cu1+ and the latter interacts with neocuproine to yield a complex with a maximal absorption at 455 nm. The reaction of NADH with copper-neocuproine is immediate and under the conditions of the assay the color formed remains stable for at least 2 h. When the assay is used to determine levels of L-fucose, the absorbance is found to be linearly proportional to exogenously added fucose concentrations from 16 to 179 nmol with resulting molar extinction coefficient of 13,660. Using this procedure, L-fucose released by acid hydrolysis from porcine submaxillary mucin, and by alpha-L-fucosidase from p-nitrophenyl-alpha-L-fucopyranoside, was quantitated.

Non-identity of human plasma lysozyme and 4-methylumbelliferyl-tetra-N-acetyl-beta-D-chitotetraoside hydrolase

1. Using 4-methylumbelliferyl-tetra-N-acetyl-beta-D-chitotetraoside (MU-TACT) as substrate, it is possible to measure the activity of purified lysozyme and to demonstrate lysozyme activity in the urine of patients with acute monocytic leukemia, characterized by massive lysozymuria. 2. Notwithstanding this observation, we present evidence that in normal human plasma another acid endoglucosaminidase is hydrolyzing the substrate. 3. The following data support the hypothesis of the existence of a separate hydrolase: (a) Thermoinactivation is different for MU-TACT hydrolase and lysozyme. (b) In plasma and many other biological samples, the concentration of lysozyme is too low to be measured with the artificial substrate and there is no correlation between MU-TACT hydrolase and lysozyme. (c) Serum of lysozyme deficient rabbits has normal MU-TACT hydrolase activity. (d) On Sephadex G-200 and DEAE cellulose chromatography, lysozyme and MU-TACT hydrolase are eluted separately. (e) Immunoremoval of lysozyme from human plasma does not affect the activity towards MU-TACT. (f) The effect of N-acetylglucosamine and N-acetylmuramic acid on the activity of lysozyme and MU-TACT hydrolase is different.

Purification and characterization of plasma membranes obtained from rat neurons prepared by bulk-isolation

The properties of neuronal plasma membranes are highly specialized, since they include the receptors by which many hormones, neurotransmitters, drugs, and toxins initiate their actions, as well as the components necessary for receiving synaptic input from a variety of sources and for generating the appropriate pattern of action potentials. To be able to study plasma membranes of neurons, it is necessary to separate sufficient quantities of neurons from the other cell types, processes, and myelin found in brain. The methodology for obtaining neurons by bulk-isolation from 10-day-old rat brain has been established, and techniques for purifying the plasma membranes are presented here. The procedure involves swelling the cells in a buffered solution, homogenizing the cells vigorously, and separating the membrane fragments on discontinuous sucrose gradients. The plasma membrane fraction is enriched in plasma membrane marker enzymes and has low activity for contaminating enzymes for subcellular organelles. Electron micrographs show that the fraction consists of membrane vesicles and profiles of various sizes. The protein composition reveals over 60 proteins with molecular weights as high as 100,000 to a low of 14,000. This plasma membrane fraction now can be the focus for studying receptors, glycoproteins, and cell-specific markers of neurons in health and disease.

Fucosidosis in an English springer spaniel presenting as a malabsorption syndrome

A case of alpha-fucosidosis in a 2-year-old male English Springer Spaniel presented as a malabsorption syndrome without any clinical neurological abnormalities. The dog had a history of chronic weight loss, diarrhoea, mild anaemia, hypoproteinemia and reduced jejunal absorption of D-xylose. A diagnosis of fucosidosis with intestinal malabsorption was based on these findings, markedly reduced plasma fucosidase levels and the diffuse infiltration of the lamina propria and submucosa of the stomach, small intestine, Peyer's patches and mesenteric lymph nodes by macrophages with finely vacuolated cytoplasm. Cytoplasmic vacuolation was also a feature of cells of the pancreas, thryroid, parathyroid and adenohypophysis and the epithelia lining respiratory airways and the urogenital tract. Neurons of the autonomic plexuses of the gastrointestinal tract and the urinary bladder as well as those of the brain, spinal cord, spinal ganglia and retina were also vacuolated. The profound decrease in sigma-fucosidase activity in the brain, liver and kidney was accompanied by a marked increase in 6 other lysosomal enzymes, especially beta-n-acetyl glucosaminidase.