Evangelia Dimitriou

The expanding spectrum of disorders with elevated plasma chitotriosidase activity : An update

Summary: A striking elevation of plasma chitotriosidase activity, greater than 150 times the normal median value, was found in two galactosialidosis patients. Furthermore, increased plasma chitotriosidase activity, 10–53 times the normal median value, was also observed in fucosidosis, glycogen storage disease type IV, Alagille syndrome and hydrops fetalis due to congenital herpes virus infection.

Loss of β-glucocerebrosidase activity does not affect alpha-synuclein levels or lysosomal function in neuronal cells.

To date, a plethora of studies have provided evidence favoring an association between Gaucher disease (GD) and Parkinson’s disease (PD). GD, the most common lysosomal storage disorder, results from the diminished activity of the lysosomal enzyme β-glucocerebrosidase (GCase), caused by mutations in the β-glucocerebrosidase gene (GBA). Alpha-synuclein (ASYN), a presynaptic protein, has been strongly implicated in PD pathogenesis. ASYN may in part be degraded by the lysosomes and may itself aberrantly impact lysosomal function. Therefore, a putative link between deficient GCase and ASYN, involving lysosomal dysfunction, has been proposed to be responsible for the risk for PD conferred by GBA mutations. In this current work, we aimed to investigate the effects of pharmacological inhibition of GCase on ASYN accumulation/aggregation, as well as on lysosomal function, in differentiated SH-SY5Y cells and in primary neuronal cultures. Following profound inhibition of the enzyme activity, we did not find significant alterations in ASYN levels, or any changes in the clearance or formation of its oligomeric species. We further observed no significant impairment of the lysosomal degradation machinery. These findings suggest that additional interaction pathways together with aberrant GCase and ASYN must govern this complex relation between GD and PD.

Characterization of glucocerebrosidase in Greek Gaucher disease patients : mutation analysis and biochemical studies

SummaryGaucher disease is the most frequent lysosomal storage disease in Greece, accounting for 24% of all lysosomal disorders diagnosed during the last 13 years at the Institute of Child Health in Athens. The nature of the defects in glucocerebrosidase in Greek Gaucher patients with non-neuronopathic (type 1) and neuronopathic (types 2 and 3) phenotypes was investigated at the level of the glucocerebrosidase gene and enzyme activity. Mutation analysis performed in 10/23 Gaucher patients with different types of the disorder led to the identification of four mutations, N370S, L444P, R463C and D409H, comprising 75% of the investigated alleles. N370S was only found in association with type 1 disease. The genotype D409H/R463C was identified for the first time and was associated with the severe type 2 disorder. There was no correlation between residualin vitro enzyme activity and either phenotype or genotype. However, in cultured fibroblasts of the neuronopathic cases, glucocerebrosidase protein concentration was reduced and the capacity to degrade exogenous C6NBD-glucosylceramide was more severely impaired.

Serial chitotriosidase activity estimations in neonatal systemic candidiasis

Sir, Human chitotriosidase is a recently identified enzyme that belongs to the chitinase family. In contrast to the other mammalian chitinases, it is a functional chitinolytic enzyme (1). In the present study we had the opportunity to assay for chitotriosidase activity (1) in serial plasma and urine samples taken from a neonate with systemic fungal infection. All the studies at the Institute of Child Health are approved by the Institute’s Ethical Committee. The index case was admitted to the neonatal intensive care unit because of poor feeding, pyrexia and irritability. Chitotriosidase activity in plasma was assayed for the first time on the 15th day of hospitalization (I) when Candida albicans-positive venous blood and urine cultures were obtained. Assays were also performed in consecutive plasma and urine samples (I–V) taken at approximately 1 week intervals for the following 5 weeks. At that point neither hyphae nor growth on culture had been observed in three consecutive samples of urine. Increased plasma (I:88, II:105, III:80, IV:57, V:53; controls of similar age group 39, 39, 25, 14 nmol/ml/h) and urine (I:not determined, II:440, III:67, IV:4, V:0; controls of similar age: 3, 7, 5, 0 nmol/mg creatinine/h) chitotriosidase activity, as compared to controls, was found in the initial samples obtained from our patient, that decreased over the period studied. In fact by the end of the 5-week period, when no microbes could be cultured, the chitotriosidase activity had reached a completely normal level in urine and showed a very modest elevation in plasma compared to controls. The reduction of chitotriosidase levels ran in parallel to the improvement of the clinical condition of the patient as well as that of other laboratory parameters, in particular WBC counts and erythrocyte sedimentation rate. The observed reduction was not due to the inhibition of chitotriosidase by the administered anti-fungal drugs, since the activity in samples prepared by mixing plasma from the index case and patients with high chitotriosidase activity, ranged from 95 to 100% of the expected sum of the individual activities. Using a neutralizing anti-human chito riosidase antiserum (1), it was noted that chitotriosidase activity in plasma and urine samples from the patient was always inactivated by.95%, indicating that it originated predominantly from phagocytes of the patient. The role of the human chitinase is still an open question. In chitin-containing organisms, chitinases are believed to participate in morphogenesis, host–parasite interactions and their defence against fungal infection (3). The observation that in humans the enzyme is expressed in cells involved in defence mechanisms and increased synthesis occurs in stressed macrophages, suggests a similar to the latter role in humans (1, 2). Our observations support such a role. Furthermore they indicate that serial estimations of the enzymic activity could be exploited to monitor the r sponse to the applied therapy in fungal infections. Further studies involving not only chitotriosidase measurements in more patients, but also the investigation of other parameters such as mRNA synthesis and expression in cells of the immune system during fungal infections, will be very important in elucidating the role of the human enzyme in the defence against chitin-containing microbes.

Plasmalogen levels in Gaucher disease

Plasmalogens represent a unique type of phospholipids characterized by the presence of a vinyl-ether bond at the sn-1 position of the glycerol backbone. Peroxisomes are essential in their biosynthesis. Their suggested functions include protection against oxidative stress, participation in signal transduction, membrane fusion events, cholesterol transport and membrane trafficking, processes known to be disturbed in sphingolipidoses. We here report on red blood cell membrane plasmalogen levels in Gaucher disease patients. Plasmalogen levels were measured as their dimethylacetal derivatives (DMA) by gas chromatography in lipid extracts of erythrocytes from 15 patients. Their relative amount was estimated as the ratio between C18:0 DMA and methylstearate (C18:0), as well as C16:0 DMA and methylpalmitate (C16:0). Statistically significant lower levels of both plasmalogen species were observed in Gaucher disease patients compared to normal individuals. Furthermore, a negative correlation between plasmalogen levels and chitotriosidase was observed in the patients, which was statistically significant for the C18:0 species. Upon therapy, a significant rise of plasmalogen levels and fall in chitotriosidase activity was observed. However, C18:0 DMA/C18:0 was still significantly lower in Gaucher disease patients compared to controls and the negative correlation to chitotriosidase persisted. At both time points there was no indication of an overt peroxisomal dysfunction, very long chain fatty acid, phytanate and pristanate levels being normal. In conclusion, reduced plasmalogen levels that show a significant rise following treatment and a negative correlation to total disease burden, as expressed by chitotriosidase activity, are observed in Gaucher disease.

Sanfilippo B syndrome: molecular defects in Greek patients

Sanfilippo syndrome type B [mucopolysaccharidosis IIIB (MPS IIIB] is the most prevalent type of MPS III in Greece, accounting for 81% of all MPS III cases diagnosed at the Institute of Child Health (Athens) over the last 20 years. The majority of the patients originated from East Central/Central Greece, Thessaly, and Macedonia. We present the results of mutation analysis in 21 Greek patients from 18 different families, all of whom had the severe form of the disorder. Patients were initially screened for five previously known mutations by restriction enzyme digestion of polymerase chain reaction products. Unknown mutations were identified by single‐strand conformation polymorphism analysis and DNA sequencing and were confirmed by restriction enzyme analysis. Seven previously described mutations (Y140C, R626X, 503‐512del, H414R, G292R, 334del25, and E452K) and four novel mutations (P516L, L242P, E446K, and R482Q) were identified. Expression of the latter and H414R showed that they were all null activity mutations. Considerable genetic heterogeneity has been described in MPS IIIB patients of different origins. In our population, Y140C, H414R, and R626X account for approximately 70% of the studied alleles. Our findings, especially in combination with the origin of individual patients, can improve carrier detection and genetic counseling in affected families.

Haplotype analysis suggests a single Balkan origin for the Gaucher disease [D409H;H255Q] double mutant allele

Gaucher disease is an autosomal recessive lysosomal storage disease that is mainly due to mutations in the GBA gene. Most of the mutant alleles described so far bear a single mutation. However, there are a few alleles bearing two or more DNA changes. It has been reported that patients homozygous for the [D409H;H255Q] double mutant allele (HGVS‐approved nomenclature, p.[D448H;H294Q]) present a more severe phenotype than patients homozygous for the relatively common D409H mutation. In this study, we confirmed the detrimental cumulative effect of these two mutations at the enzymatic activity level by the heterologous expression of the single and double mutant alleles. Additionally, we found a high frequency of the [D409H;H255Q] allele in patients from the Balkans and the Adriatic area of Italy. This prompted us to perform a haplotype analysis, using five microsatellite polymorphisms close to the GBA gene, to determine the origin of this allele. The results of the 37 chromosomes analysed showed that most of them share a common haplotype and are consistent with a single origin in the Balkans and the Adriatic area of Italy for the [D409H;H255Q] allele.

Iron overload and kidney lysosomes.

Iron overload has been associated with damage of the liver and other organs of patients with primary or secondary increased iron load. In order to study the effect of iron overload on the pathophysiology of kidney lysosomes, experimentally induced iron overload models were employed. Iron overload was achieved through intraperitoneal injections of Fe-dextran (Imferon) in male rats, at different final iron concentrations (825 and 1650 mg/kg, single and double dose groups respectively). Controls were injected with dextran following a similar protocol. The animals were killed at different time points after the last injection. Subcellular fractionation studies of kidney homogenates were carried out by differential centrifugation and density gradient centrifugation. The kidney iron load was increased with both doses. Iron appeared to accumulate mainly in the lysosomes, bringing about distinct changes in the behaviour of the organelles as judged by subcellular fractionation studies. Lysosomes became more fragile and showed increased density. The extent of the above changes seemed to correlate with the extent and duration of iron accumulation and could be reversed when the iron load was reduced.

Niemann–Pick type C disease: a novel NPC1 mutation segregating in a Greek island

Niemann–Pick type C (NPC) disease is a rare autosomal recessive lysosomal storage disease, exhibiting an extremely heterogeneous clinical phenotype. It is a cellular lipid trafficking disorder characterized by the accumulation in the lysosomal/late endosomal system of a variety of lipids, especially unesterified cholesterol. So far two genes, NPC1 or NPC2, have been linked to the disorder. It is a panethnic disease for which two isolates have been described. We present a novel NPC1 mutation (p.A1132P; c.3394G>C) identified in homozygosity in two patients originating from the same small town of an Aegean Sea island and the results of the broad screening of their extended families. Overall 153 individuals have so far been investigated and a total of 64 carriers were identified. Moreover a common descent of the individuals tested was revealed and all carriers could be traced back to a common surname, apparently originating from a common ancestor couple six generations back. The mutation was found associated with an uncommon haplotype in the island that is also present in other populations.

Gaucher disease: Plasmalogen levels in relation to primary lipid abnormalities and oxidative stress

Plasmalogens represent a unique class of phospholipids. Reduced red blood cell plasmalogen levels in Gaucher disease patients were reported, correlating to total disease burden. The relation between plasmalogen abnormalities in Gaucher disease patients and primary glycosphingolipid abnormalities, malonyldialdehyde levels, an indicator of lipid peroxidation, and the total antioxidant status was further investigated. Significant reduction of C16:0 and C18:0 plasmalogens in red blood cells of Gaucher disease patients was confirmed. In parallel, a significant increase in the glucosylceramide/ceramide ratio in red blood cell membranes, as well as an average 200-fold increase in plasma glucosylsphingosine levels was observed. Red blood cell malonyldialdehyde levels were significantly increased in patients, whereas their total antioxidant status was significantly reduced. A negative correlation between plasmalogen species and glucosylceramide, ceramide, glucosylceramide/ceramide ratio, glucosylsphingosine and malonyldialdehyde, significant for the C16:0 species and all the above parameters with the exception of malonyldialdehyde levels, was found along with a positive non-significant correlation with the total antioxidant status. Our results indicate that increased lipid peroxidation and reduced total antioxidant status exist in Gaucher disease patients. They demonstrate a clear link between plasmalogen levels and the primary glycolipid abnormalities characterizing the disorder and an association with the increased oxidative stress observed in Gaucher disease patients.