Selective loss of glucocerebrosidase activity in sporadic Parkinson's disease and dementia with Lewy bodies.

BACKGROUND: Lysosomal dysfunction is thought to be a prominent feature in the pathogenetic events leading to Parkinson's disease (PD). This view is supported by the evidence that mutations in GBA gene, coding the lysosomal hydrolase ß-glucocerebrosidase (GCase), are a common genetic risk factor for PD. Recently, GCase activity has been shown to be decreased in substantia nigra and in cerebrospinal fluid of patients diagnosed with PD or dementia with Lewy Bodies (DLB). Here we measured the activity of GCase and other endo-lysosomal enzymes in different brain regions (frontal cortex, caudate, hippocampus, substantia nigra, cerebellum) from PD (n = 26), DLB (n = 16) and age-matched control (n = 13) subjects, screened for GBA mutations. The relative changes in GCase gene expression in substantia nigra were also quantified by real-time PCR. The role of potential confounders (age, sex and post-mortem delay) was also determined. FINDINGS: Substantia nigra showed a high activity level for almost all the lysosomal enzymes assessed. GCase activity was significantly decreased in the caudate (-23%) and substantia nigra (-12%) of the PD group; the same trend was observed in DLB. In both groups, a decrease in GCase mRNA was documented in substantia nigra. No other lysosomal hydrolase defects were determined. CONCLUSION: The high level of lysosomal enzymes activity observed in substantia nigra, together with the selective reduction of GCase in PD and DLB patients, further support the link between lysosomal dysfunction and PD pathogenesis, favoring the possible role of GCase as biomarker of synucleinopathy. Mapping the lysosomal enzyme activities across different brain areas can further contribute to the understanding of the role of lysosomal derangement in PD and other synucleinopathies.

Antioxidative capacity of Lactobacillus fermentum LF31 evaluated in vitro by oxygen radical absorbance capacity assay.

OBJECTIVE: The aim of this study was to evaluate the performance of the overall antioxidant of Lactobacillus fermentum LF31 bacterium with prebiotic supplement in human colon cultured cells. METHODS: The antioxidant capability of L. fermentum LF31 has been assayed in vitro on human colon adenocarcinoma HT-29 cell line using the oxygen radical absorbance capacity method. RESULTS: The analysis revealed that the interaction of probiotic strain cells supplemented with a prebiotic exerts a remarkable antioxidant capacity. CONCLUSION: The L. fermentum used in the present study exhibited significant in vitro antioxidant capacity, increasing the total antioxidant potential.

Factors influencing the measurement of lysosomal enzymes activity in human cerebrospinal fluid.

Measurements of the activities of lysosomal enzymes in cerebrospinal fluid have recently been proposed as putative biomarkers for Parkinson's disease and other synucleinopathies. To define the operating procedures useful for ensuring the reliability of these measurements, we analyzed several pre-analytical factors that may influence the activity of ß-glucocerebrosidase, α-mannosidase, ß-mannosidase, ß-galactosidase, α-fucosidase, ß-hexosaminidase, cathepsin D and cathepsin E in cerebrospinal fluid. Lysosomal enzyme activities were measured by well-established fluorimetric assays in a consecutive series of patients (n = 28) with different neurological conditions, including Parkinson's disease. The precision, pre-storage and storage conditions, and freeze/thaw cycles were evaluated. All of the assays showed within- and between-run variabilities below 10%. At -20°C, only cathepsin D was stable up to 40 weeks. At -80°C, the cathepsin D, cathepsin E, and ß-mannosidase activities did not change significantly up to 40 weeks, while ß-glucocerebrosidase activity was stable up to 32 weeks. The ß-galactosidase and α-fucosidase activities significantly increased (+54.9±38.08% after 4 weeks and +88.94±36.19% after 16 weeks, respectively). Up to four freeze/thaw cycles did not significantly affect the activities of cathepsins D and E. The ß-glucocerebrosidase activity showed a slight decrease (-14.6%) after two freeze/thaw cycles. The measurement of lysosomal enzyme activities in cerebrospinal fluid is reliable and reproducible if pre-analytical factors are accurately taken into consideration. Therefore, the analytical recommendations that ensue from this study may contribute to the establishment of actual values for the activities of cerebrospinal fluid lysosomal enzymes as putative biomarkers for Parkinson's disease and other neurodegenerative disorders.

Accumulation of free oligosaccharides and tissue damage in cytosolic α-mannosidase (Man2c1)-deficient mice.

Free Man(7-9)GlcNAc2 is released during the biosynthesis pathway of N-linked glycans or from misfolded glycoproteins during the endoplasmic reticulum-associated degradation process and are reduced to Man5GlcNAc in the cytosol. In this form, free oligosaccharides can be transferred into the lysosomes to be degraded completely. α-Mannosidase (MAN2C1) is the enzyme responsible for the partial demannosylation occurring in the cytosol. It has been demonstrated that the inhibition of MAN2C1 expression induces accumulation of Man(8-9)GlcNAc oligosaccharides and apoptosis in vitro. We investigated the consequences caused by the lack of cytosolic α-mannosidase activity in vivo by the generation of Man2c1-deficient mice. Increased amounts of Man(8-9)GlcNAc oligosaccharides were recognized in all analyzed KO tissues. Histological analysis of the CNS revealed neuronal and glial degeneration with formation of multiple vacuoles in deep neocortical layers and major telencephalic white matter tracts. Enterocytes of the small intestine accumulate mannose-containing saccharides and glycogen particles in their apical cytoplasm as well as large clear vacuoles in retronuclear position. Liver tissue is characterized by groups of hepatocytes with increased content of mannosyl compounds and glycogen, some of them undergoing degeneration by hydropic swelling. In addition, lectin screening showed the presence of mannose-containing saccharides in the epithelium of proximal kidney tubules, whereas scattered glomeruli appeared collapsed or featured signs of fibrosis along Bowman's capsule. Except for a moderate enrichment of mannosyl compounds and glycogen, heterozygous mice were normal, arguing against possible toxic effects of truncated Man2c1. These findings confirm the key role played by Man2c1 in the catabolism of free oligosaccharides.

NGF induces the expression of group IIA secretory phospholipase A2 in PC12 cells: the newly synthesized enzyme is addressed to growing neurites.

We proposed that group IIA secretory phospholipase A(2) (GIIA) participates in neuritogenesis based on our observations that the enzyme migrates to growth cones and neurite tips when PC12 cells are induced to differentiate by nerve growth factor (NGF) (Ferrini et al., Neurochem Res 35:2168-2174, 2010). The involvement of other secretory PLA(2) isoforms in neuronal development has been suggested by others but through different mechanisms. In the present study, we compared the subcellular distribution of GIIA and group X sPLA(2) (GX) after stimulation of PC12 cells with NGF. We found that GIIA, but not GX, localized at the neuritic tips after treatment with NGF, as demonstrated by immunofluorescence analysis. We also found that NGF stimulated the expression and the activity of GIIA. In addition, NGF induced the expressed myc-tagged GIIA protein to migrate to neurite tips in its active form. We propose that GIIA expression, activity, and subcellular localization is regulated by NGF and that the enzyme may participate in neuritogenesis through intracellular mechanisms, most likely by facilitating the remodelling of glycerophospholipid molecular species by deacylation-reacylation reactions necessary for the incorporation of polyunsaturated fatty acids.

Cerebrospinal fluid lysosomal enzymes and alpha-synuclein in Parkinson's disease.

To assess the discriminating power of multiple cerebrospinal fluid (CSF) biomarkers for Parkinson's disease (PD), we measured several proteins playing an important role in the disease pathogenesis. The activities of ß-glucocerebrosidase and other lysosomal enzymes, together with total and oligomeric α-synuclein, and total and phosphorylated tau, were thus assessed in CSF of 71 PD patients and compared to 45 neurological controls. Activities of ß-glucocerebrosidase, ß-mannosidase, ß-hexosaminidase, and ß-galactosidase were measured with established enzymatic assays, while α-synuclein and tau biomarkers were evaluated with immunoassays. A subset of PD patients (n = 44) was also screened for mutations in the ß-glucocerebrosidase-encoding gene (GBA1). In the PD group, ß-glucocerebrosidase activity was reduced (P < 0.05) and patients at earlier stages showed lower enzymatic activity (P < 0.05); conversely, ß-hexosaminidase activity was significantly increased (P < 0.05). Eight PD patients (18%) presented GBA1 sequence variations; 3 of them were heterozygous for the N370S mutation. Levels of total α-synuclein were significantly reduced (P < 0.05) in PD, in contrast to increased levels of α-synuclein oligomers, with a higher oligomeric/total α-synuclein ratio in PD patients when compared with controls (P < 0.001). A combination of ß-glucocerebrosidase activity, oligomeric/total α-synuclein ratio, and age gave the best performance in discriminating PD from neurological controls (sensitivity 82%; specificity 71%, area under the receiver operating characteristic curve = 0.87). These results demonstrate the possibility of detecting lysosomal dysfunction in CSF and further support the need to combine different biomarkers for improving the diagnostic accuracy of PD.

Changes in endolysosomal enzyme activities in cerebrospinal fluid of patients with Parkinson's disease.

Parkinson's disease (PD) is characterized neuropathologically by the cytoplasmic accumulation of misfolded α-synuclein in specific brain regions. The endolysosomal pathway appears to be involved in α-synuclein degradation and, thus, may be relevant to PD pathogenesis. This assumption is further strengthened by the association between PD and mutations in the gene encoding for the lysosomal hydrolase glucocerebrosidase. The objective of the present study was to determine whether endolysosomal enzyme activities in cerebrospinal fluid (CSF) differ between PD patients and healthy controls. Activity levels of 6 lysosomal enzymes (ß-hexosaminidase, α-fucosidase, ß-mannosidase, ß-galactosidase, ß-glucocerebrosidase, and cathepsin D) and 1 endosomal enzyme (cathepsin E) were measured in CSF from 58 patients with PD (Hoehn and Yahr stages 1-3) and 52 age-matched healthy controls. Enzyme activity levels were normalized against total protein levels. Normalized cathepsin E and ß-galactosidase activity levels were significantly higher in PD patients compared with controls, whereas normalized α-fucosidase activity was reduced. Other endolysosomal enzyme activity levels, including ß-glucocerebrosidase activity, did not differ significantly between PD patients and controls. A combination of normalized α-fucosidase and ß-galactosidase discriminated best between PD patients and controls with sensitivity and specificity values of 63%. In conclusion, the activity of a number of endolysosomal enzymes is changed in CSF from PD patients compared with healthy controls, supporting the alleged role of the endolysosomal pathway in PD pathogenesis. The usefulness of CSF endolysosomal enzyme activity levels as PD biomarkers, either alone or in combination with other markers, remains to be established in future studies.

Cerebrospinal fluid biomarkers in Parkinson disease.

Clinical diagnosis of Parkinson disease (PD) is difficult in early stages of disease, with high risk of misdiagnosis. The long preclinical phase of PD provides the possibility for early therapeutic intervention once disease-modifying therapies have been developed, but lack of biomarkers for early diagnosis and monitoring of disease progression represents a major obstacle to achievement of this goal. Accordingly, research efforts aimed at identification of novel biomarkers have been increasing in the past 5 years. Cerebrospinal fluid (CSF) is an accessible source of brain-derived proteins, which mirror molecular changes that take place in the CNS. In this Review, we discuss evidence from numerous studies that have focused on identification of candidate CSF biomarkers for PD. Notably, molecular pathways related to α-synuclein, tau and ß-amyloid peptides have received considerable attention. CSF levels of the protein DJ-1 are also of interest, although further investigation of this candidate marker is required. These studies support the usefulness of a combination of various CSF biomarkers of PD to increase diagnostic accuracy during early phases of the disease, and to differentiate PD from other neurodegenerative disorders.

First pilot newborn screening for four lysosomal storage diseases in an Italian region: identification and analysis of a putative causative mutation in the GBA gene.

We report the first newborn screening pilot study in an Italian region for four lysosomal disorders including Pompe disease, Gaucher disease, Fabry disease and mucopolysaccharidosis type 1. The screening has been performed using enzymatic assay on Dry Blood Spot on filter paper. A total of 3403 newborns were screened. One newborn showed a reduction of ß-glucosidase activity in leucocytes. Molecular analysis revealed a status of compound heterozygous for the panethnic mutation N370S and for the sequence variation E388K, not yet correlated to Gaucher disease onset. The functional consequences of the E388K replacement on ß-glucosidase activity were evaluated by in vitro expression, showing that the mutant protein retained 48% of wild type activity. Structural modeling predicted that the E388K replacement, localized to a surface of the enzyme, would change the local charges distribution which, in the native protein, displays an overwhelming presence of negative charges. However, the newborn, and a 4 year old sister showing the same genomic alterations, are currently asymptomatic. This pilot newborn screening for lysosomal diseases appears to be feasible and affordable to be extended to large populations. Moreover other lysosomal diseases for which a therapy is available or will be available, could be included in the screening.

Lysosomal di-N-acetylchitobiase-deficient mouse tissues accumulate Man2GlcNAc2 and Man3GlcNAc2.

Most lysosomal storage diseases are caused by defects in genes encoding for acidic hydrolases. Deficiency of an enzyme involved in the catabolic pathway of N-linked glycans leads to the accumulation of the respective substrate and consequently to the onset of a specific storage disorder. Di-N-acetylchitobiase and core specific α1-6mannosidase represent the only exception. In fact, to date no lysosomal disease has been correlated to the deficiency of these enzymes. We generated di-N-acetylchitobiase-deficient mice by gene targeting of the Ctbs gene in murine embryonic stem cells. Accumulation of Man2GlcNAc2 and Man3GlcNAc2 was evaluated in all analyzed tissues and the tetrasaccharide was detected in urines. Multilamellar inclusion bodies reminiscent of polar lipids were present in epithelia of a scattered subset of proximal tubules in the kidney. Less constantly, enlarged Kupffer cells were observed in liver, filled with phagocytic material resembling partly digested red blood cells. These findings confirm an important role for lysosomal di-N-acetylchitobiase in glycans degradation and suggest that its deficiency could be the cause of a not yet described lysosomal storage disease.

Human α-mannosidase produced in transgenic tobacco plants is processed in human α-mannosidosis cell lines.

Deficiency in human lysosomal α-mannosidase (MAN2B1) results in α-mannosidosis, a lysosomal storage disorder; patients present a wide range of neurological, immunological, and skeletal symptoms caused by a multisystemic accumulation of mannose-containing oligosaccharides. Here, we describe the expression of recombinant MAN2B1 both transiently in Nicotiana benthamiana leaves and in the leaves and seeds of stably transformed N. tabacum plants. After purification from tobacco leaves, the recombinant enzyme was found to be N-glycosylated and localized in vacuolar compartments. In the fresh leaves of tobacco transformants, MAN2B1 was measured at 10,200 units/kg, and the purified enzyme from these leaves had a specific activity of 32-45 U/mg. Furthermore, tobacco-produced MAN2B1 was biochemically similar to the enzyme purified from human tissues, and it was internalized and processed by α-mannosidosis fibroblast cells. These results strongly indicate that plants can be considered a promising expression system for the production of recombinant MAN2B1 for use in enzyme replacement therapy.

Identification and molecular characterization of six novel mutations in the UDP-N-acetylglucosamine-1-phosphotransferase gamma subunit (GNPTG) gene in patients with mucolipidosis III gamma.

Mucolipidosis type III (MLIII) is an autosomal recessive disorder affecting lysosomal hydrolase trafficking. In a study of 10 patients from seven families with a clinical phenotype and enzymatic diagnosis of MLIII, six novel GNPTG gene mutations were identified. These included missense (p.T286M) and nonsense (p.W111X) mutations and a transition in the obligate AG-dinucleotide of the intron 8 acceptor splice site (c.610-2A>G). Three microdeletions were also identified, two of which (c.611delG and c.640_667del28) were located within the coding region whereas one (c.609+28_610-16del) was located entirely within intron 8. RT-PCR analysis of the c.610-2A>G transition demonstrated that the change altered splicing, leading to the production of two distinct aberrantly spliced forms, viz. the skipping of exon 9 (p.G204_K247del) or the retention of introns 8 and 9 (p.G204VfsX28). RT-PCR analysis, performed on a patient homozygous for the intronic deletion (c.609+28_610-16del), failed to detect any GNPTG RNA transcripts. To determine whether c.609+28_610-16del allele-derived transcripts were subject to nonsense-mediated mRNA decay (NMD), patient fibroblasts were incubated with the protein synthesis inhibitor anisomycin. An RT-PCR fragment retaining 43 bp of intron 8 was consistently detected suggesting that the 33-bp genomic deletion had elicited NMD. Quantitative real-time PCR and GNPTG western blot analysis confirmed that the homozygous microdeletion p.G204VfsX17 had elicited NMD resulting in failure to synthesize GNPTG protein. Analysis of the sequences surrounding the microdeletion breakpoints revealed either intrinsic repetitivity of the deleted region or short direct repeats adjacent to the breakpoint junctions. This is consistent with these repeats having mediated the microdeletions via replication slippage and supports the view that the mutational spectrum of the GNPTG gene is strongly influenced by the properties of the local DNA sequence environment.

Identification of two novel beta-mannosidosis-associated sequence variants: biochemical analysis of beta-mannosidase (MANBA) missense mutations.

Beta-mannosidosis (OMIM # 248510) is an autosomal-recessive lysosomal storage disorder caused by deficiency of the lysosomal enzyme beta-mannosidase (MANBA, E.C. 3.2.1.25). The disorder has been reported in goat, cattle and man. The human disorder is rare and only 20 cases in 16 families have been reported. We have sequenced the exons and exon-intron borders in a European patient with infantile onset of beta-mannosidosis. The patient was compound heterozygous for a silent mutation (c.375A>G) in exon 3 causing alternative splicing, and a missense mutation (c.1513T>C, p.Ser505Pro) in exon 12. The alternative splicing event deleted four nucleotides from the transcript and was predicted to result in premature termination of translation. In order to evaluate the consequence of the missense mutation, we inserted the human beta-mannosidase gene into an expression vector, performed site-directed mutagenesis and expressed the normal and mutant enzyme in COS-7 cells. We also included the previously reported beta-mannosidosis-associated missense mutations c.544C>T (p.Arg182Trp) and c.1175G>A (p.Gly392Glu), which were found in patients presenting a milder phenotype. Cells transfected with the wild-type construct showed a 33-fold increase in beta-mannosidase activity compared to mock-transfected cells, whereas cells transfected with the mutant constructs showed no detectable increase in activity. We propose that the milder phenotype described in some beta-mannosidosis patients with missense mutations in the MANBA gene is not due to residual beta-mannosidase activity, but rather caused by epigenetic and/or environmental factors.

Molecular cloning and structural organization of the gene encoding the mouse lysosomal di-N-acetylchitobiase (ctbs).

The lysosomal enzyme di-N-acetylchitobiase hydrolyzes N-acetylglucosamine from the reducing-end of the N,N' diacetylchitobiose core of N-linked-oligosaccharides. The presence of chitobiase in the tissues of different species is probably responsible for differences in the structure of oligosaccharides accumulated in the lysosomal storage disease beta-mannosidosis. The disease has so far been described in humans, cats, cattle and goats. Low chitobiase activity has been observed in the tissues of ruminants and it has been hypothesized that in cattle this low level of expression is due to evolutionary changes in the promoter region. A cDNA encoding the mouse chitobiase has been isolated, sequenced and its identity confirmed by expression in COS-7 cells. Comparison of the mouse genomic sequence with the cDNA sequence revealed the presence of seven exons within the chitobiase gene. The gene spans about 15 kb and a single transcription initiation site was determined by 5'RACE. Chitobiase is differentially and ubiquitously expressed in mouse tissues as demonstrated by qRT-PCR analysis. Chitobiase is differentially expressed at lower levels in bovine tissues. In two bovine tissues (heart and muscle) mRNA was not detectable. Mouse and bovine promoters have been isolated and sequenced and their activities compared. The activity of the bovine promoter is very low and might explain the low activity of chitobiase observed in cattle.

Effects of vitamin C on fibroblasts from sporadic Alzheimer's disease patients.

Several therapies for Alzheimer's Disease (AD) are currently under investigation. Some studies have reported that concentration of vitamins in biological fluids are lower in AD patients compared to control subjects and clinical evidence has shown the therapeutic potential of vitamin C and E in delaying AD progression. However, the molecular mechanism(s) that are engaged upon their administration in the APP metabolism in vitro or in vivo still need clarifying. Here, we investigate the effects of vitamin C supplementation, at physiological concentration, in skin fibroblasts obtained from SAD and FAD patients. This study shows that SAD patients' fibroblasts exhibited the exclusive appearance of C-terminal fragments, derived from APP processing, without giving rise to the beta-amyloid peptide, other than corresponding decreased levels of lysosomal enzymes, such as beta-hexosaminidase, alpha-mannosidase and cathepsins B, L, and D.

Cathepsin D expression is decreased in Alzheimer's disease fibroblasts.

Cathepsin D (CTSD), a protease detectable in different cell types whose primary function is to degrade proteins by bulk proteolysis in lysosomes, has been suggested to be involved in Alzheimer's disease (AD). In fact, there is increasing evidence that disturbance of the normal balance and localization of cathepsins may contribute to neurodegeneration in AD [Nakanishi H. Neuronal and microglial cathepsins in aging and age-related diseases. Aging Res Rev 2003; 2(4):367-81]. Here, we provide evidence of an altered balance of CTSD in skin fibroblasts from patients affected either by sporadic or familial forms of AD. In particular, we demonstrate that CTSD is down regulated at both transcriptional and translational level and its processing is altered in AD fibroblasts. The oncogene Ras is involved in the regulation of CTSD, as high expression level of the constitutively active form of Ras in normal or AD fibroblasts induces CTSD down-regulation. p38 MAPK signalling pathway also appears to down-modulate CTSD level. Overall results reinforce the hypothesis that a lysosomal impairment may be involved in AD pathogenesis and can be detected not only in the CNS but also at a peripheral level.

Lysosomal hydrolases in cerebrospinal fluid from subjects with Parkinson's disease.

Recent studies have shown a genetic association between glucocerebrosidase deficiencies and Parkinson's disease (PD). To further explore this issue the activity of beta-glucocerebrosidase and the activities of other lysosomal enzymes, alpha-mannosidase, beta-mannosidase, beta-hexosaminidase, and beta-galactosidase have been evaluated in the cerebrospinal fluid (CSF) of PD patients. The activities of alpha-mannosidase, beta-mannosidase, beta-glucocerebrosidase, and beta-hexosaminidase were substantially decreased in the CSF of PD patients, while levels of beta-galactosidase were essentially identical to controls. This study indicates that in PD several lysosomal hydrolases have decreased activities, further supporting a possible link between pathophysiological mechanisms underlying PD and lysosomal hydrolases.