Neuraminidase activity in the mucolipidoses (types I, II and III) and the cherry-red spot myoclonus syndrome

Identification and Evaluation of Flavone-glucosides Isolated from Barley Sprouts and their Inhibitory Activity against Bacterial Neuraminidase

Neuraminidase (NA) is one of the key enzymes responsible for bacterial infection and pathogenesis. This study aimed to gain deeper insights into the inhibitory effects of flavone-glucosides (1–9) isolated from barley sprouts (BS) on neuraminidase activity. The isolated compounds were identified as, lutonarin (1), saponarin (2), isoorientin (3), orientin (4), isovitexin (5), isoscoparin-7- O-[6-sinapoyl]-glucoside (6), isoscoparin-7- O-[6-feruloyl]-glucoside (7), isovitexin-7- O-[6-sinapoyl]-glucoside (8), and isovitexin-7- O-[6-feruloyl]-glucoside (9). Among them, compounds 1–5 exhibited neuraminidase-inhibitory activities in a dose-dependent manner, with IC50 values ranging from 20.1 to 32.7 μM, in a non-competitive inhibition mode according to kinetic studies. Moreover, the individual flavone-glucoside levels differed notably, in particular, lutonarin (1) and saponarin (2) were shown to be present in the greatest amounts, according to UPLC analysis. Consequently, our results suggest that BS may be utilized as an effective NA inhibitor in human health food, additives, and feed.

Virus load kinetics and resistance development during oseltamivir treatment in infants and children infected with Influenza A(H1N1) 2009 and Influenza B viruses

BACKGROUND

Infants and small children are the most effective transmitters of influenza, while bearing a high risk of hospitalization and adverse disease outcomes. This study aims to investigate virus load kinetics and resistance development during oseltamivir therapy in infants and children infected with influenza A(H1N1) 2009 and influenza B viruses.

METHODS

Virus load in nasopharyngeal samples and phenotypic/genotypic neuraminidase inhibitor resistance were determined at baseline, at day 5 and in additional follow-up samples, if available. Patient-specific viral clearance indices CLν(i) were determined along with estimates of the time required to achieve nondetectable virus load.

RESULTS

No evidence of baseline oseltamivir resistance was detected in 36 patients infected with influenza A(H1N1) 2009 (n = 27) or influenza B (Victoria, Yamagata; n = 9) before oseltamivir therapy. On average, viral loads were lower for influenza type B (median = 5.9·10/mL) than for drug-resistant (median = 2.6·10/mL) and sensitive A(H1N1) 2009 (median = 4.8·10/mL), P = 0.04 and P = 0.09, respectively. Time required to achieve nondetectable virus load was significantly longer in drug-resistant A(H1N1) 2009 (median 15.4 days) compared with drug-sensitive A(H1N1) 2009 (P = 0.003; median 7.7 days) and drug-sensitive influenza B (P = 0.001; median 5 days). No evidence of viral rebound was observed once viral clearance was achieved.

CONCLUSIONS

Our data indicate that influenza subtyping in combination with baseline viral load measurements might help to optimize the duration of antiviral therapy in the individual child. Lower than expected virologic response rates in patients without malabsorption or compliance issues may suggest resistance development.

A longitudinal study of Taiwanese sialidosis type 1: an insight into the concept of cherry-red spot myoclonus syndrome

BACKGROUND AND PURPOSE

Sialidosis type 1 (ST-1) is a neurodegenerative disorder with limited long-term follow-up report. This study is to document the chronological profile of ST-1.

METHODS

We perform serial analysis of 17 Taiwanese patients with ST-1 focusing on evolution of clinical features, electrophysiological findings, genetic studies, and neuroimage examinations.

RESULTS

All patients had a mutation at 554A-->G in exon 3 of the NEU1 gene causing Ser182Gly substitution. Fifteen patients were homozygous. Two patients were heterozygous with novel mutations, 956C-->T causing Ala319Val in one and 163C-->T causing Gln55stop codon in the other. The neuraminidase activity was markedly decreased in all 11 available patients. Only three patients (17.6%) manifested the macular cherry-red spot. The majority of patients (82.3%) developed full-blown manifestation of myoclonus, ataxia, and seizures within 5 years. Abnormal somatosensory evoked potentials with giant cortical waves were found in all patients. Prolonged P100 peak latency of the visual evoked potentials (VEPs) were found in 16 patients (94.1%) in the early stage even without visual symptoms.

CONCLUSION

ST-1 in Taiwanese population illustrates distinct characteristics of phenotype with infrequent cherry-red spot. We suggest to screen the NEU1 mutations in patients presenting action myoclonus with abnormal VEPs, even without macular cherry-red spots.

Amniotic fluid for screening of lysosomal storage diseases presenting in utero (mainly as non-immune hydrops fetalis)

Seventy amniotic fluids (AF) were sampled because of abnormal ultrasound findings (mainly non-immune hydrops fetalis (54 cases) or of the presence of vacuolated lymphocytes in fetal blood (3 cases)). They were analysed by a procedure involving AF supernatant analysis (glycosaminoglycans, oligosaccharides, free sialic acid and acid hydrolase activities) and biochemical study of cultured AF cells. Ten cases of lysosomal storage diseases (LSD) were diagnosed. The reported procedure allows an orientating screening within 3 days by analysis of 15 ml of third trimester AF supernatant (except for Gaucher and Niemann-Pick diseases). In some cases, the results allow an LSD diagnosis and a medical abortion without waiting for the formal diagnosis (in cultured AF cells that needs 3 more weeks), considering the poor prognosis of these LSD presenting in utero. Furthermore, the formal assessment of the diagnosis in the cultured fetal cells allows accurate genetic counselling for the couple.

Removal of sialic acid from a glycoprotein in CHO cell culture supernatant by action of an extracellular CHO cell sialidase

We have directly tested the hypothesis that Chinese hamster ovary (CHO) cell-produced glycoproteins are subject to extracellular degradation by a sialidase endogenous to the CHO cell line. Factors important to understanding the potential for extracellular degradation are addressed including the glycoprotein specificity, subcellular source, mechanism of release, and stability of the sialidase activity. The extracellular CHO cell sialidase apparently originates from the cytosol of the cells, and is released to the cell culture supernatant as a result of damage to the cellular membrane. The extracellular sialidase is active toward a variety of CHO cell-produced glycoproteins, and can hydrolyze sialic acid from the recombinant glycoprotein gp120 in the culture supernatant. While measuring the actual degradation of a glycoprotein by extracellular CHO cell sialidase can be difficult, data presented here suggest that the level of degradation can be estimated indirectly by using a more convenient fluorescent substrate, 4-methylumbelliferyl-alpha-D-N-acetylneuraminic acid, to quantify sialidase activity. Degradation by sialidase is minimized through addition of the sialidase inhibitor 2,3-dehydro-2-deoxy-N-acetylneuraminic acid to the culture supernatant. The results in this study suggest additional potential approaches for minimizing degradation by sialidase, including isolation of a sialidase-deficient CHO cell line.

Involvement of thiol proteases in galactosialidosis

The activities of Z-Phe-Arg-NMec(ZPA) hydrolase, cathepsin B and cathepsin H and the concentration of endogenous thiol protease inhibitor in fibroblasts from patients with galactosialidosis were found not to be significantly different from those in control fibroblasts. Culture for 5 days with thiol protease inhibitors such as leupeptin, E-64 or Z-Phe-Phe-CHN2 partially restored the beta-galactosidase activity of fibroblasts from patients, but did not affect the beta-galactosidase activity of fibroblasts from control subjects. However, culture with leupeptin, but not other protease inhibitors, increased the ZPA hydrolase and cathepsin B activities of fibroblasts from both patients and controls 2- to 4-fold. Sephadex G-75 chromatography showed that the activity of high molecular weight ZPA hydrolase, which was initially predominant in fibroblasts, decreased markedly during their culture with leupeptin, while the activities of lower molecular weight ZPA hydrolase and cathepsin B increased about 5-fold. These results suggest that high molecular weight ZPA hydrolase, which is presumably cathepsin J, degrades beta-galactosidase, and that the defect in galactosialidosis is impaired protection of beta-galactosidase from degradation.

Infantile type 2 sialidosis in a Pakistani family--a clinical and biochemical study

Two siblings of consanguineous parents presented in infancy with failure to thrive, mild coarsening of facies, visceromegaly and corneal opacities. One showed reduced hepatic beta-galactosidase activity suggesting a GM1-gangliosidosis variant. Both patients developed progressive coarsening of facies, slow neurological deterioration, macular cherry-red spots and punctate cataracts over the first decade. Urine screening with thin layer chromatography revealed abnormal excretion of two slow-moving oligosaccharide bands and leukocyte and fibroblast neuraminidase activity was grossly reduced. The mother, phenotypically normal, showed levels of neuraminidase compatible with heterozygosity. These patients have primary neuraminidase deficiency. The clinical and biochemical variables are reviewed.

Lysosomal sialidase deficiency in sialidosis with partial beta-galactosidase deficiency

We analyzed the subcellular localization of sialidases in human lymphocytes from a patient with adult type sialidosis with partial beta-galactosidase deficiency and normal controls. Sialidase activities were measured with alpha,2 leads to 3 NeuAc-lactitol, 4-methylumbelliferyl-NeuAc and GM3 ganglioside as substrates. Sialidases in the lysosomes were sonication-labile and hydrolyzed mainly hydrophilic substrates such as NeuAc-lactitol and 4-methylumbelliferyl-NeuAc, but hydrolyzed subsidiarily GM3 ganglioside. On the other hand, sialidases in the plasma membrane were sonication-stable and hydrolyzed both hydrophilic substrates and GM3 ganglioside. In sialidosis with partial beta-galactosidase deficiency, the sialidases of the lysosomes showed 3-5% activity toward hydrophilic substrates and 25% activity toward GM3 ganglioside as compared with sialidase activities of the controls. However, there are no differences in the activities of the sialidases in the plasma membrane. These results demonstrate that the essential defect in this disease is the deficiency of a lysosomal sialidase.

Characterization of human placental neuraminidases. Stability, substrate specificity and molecular weight

1. At least two components of neuraminidase can be distinguished on the basis of thermolability and sedimentability by using the artificial fluorogenic substrate 4-methylumbelliferyl N-acetyl-alpha-D-neuraminate. 2. In crude homogenates, thermodenaturation at 25 degrees C showed a biphasic curve corresponding to component A (half-life, 21 min) and B (half-life, 85 min). The two components were partially resolved by centrifugation. A being soluble and B sedimentable. Both had similar pH-activity curves (pH optimum, 4.4), Km values (A, 0.10 mM; B, 0.06 mM) and molecular weight as determined by radiation inactivation (A, 67000; B, 63000). 3. The soluble A form was still aggregated or bound to membranous debris since almost all neuraminidase activity was eluted near or at the void volume of a Sephacryl S-300 column. 4. Both soluble and sedimentable fractions of placenta hydrolysed the GD1A ganglioside and N-acetyl-neuraminyl-D-lactose linearly for 12 h but no fetuin hydrolysis was detected. 5. The neuraminidase activity with the artificial fluorogenic substrate was inhibited by N-acetylneuraminyl-D-lactose but not by the GD1A ganglioside. These preliminary results suggest that there exist two closely related enzymes hydrolysing both the artificial substrate and N-acetylneuraminyl-D-lactose and a third one hydrolysing the GD1A ganglioside exclusively.

Catalytically defective ganglioside neuraminidase in mucolipidosis IV

Cultured skin fibroblasts from patients with mucolipidosis IV were found to be deficient in neuraminidase activity toward GD1a and GD1b gangliosides radiolabelled in C8 and C7 analogs of their sialic acid residues. Neuraminidase activities toward 4-methylumbelliferyl-N-acetyl-neuraminic acid, neuraminlactose, and radiolabelled neuraminlactitol, fetuin and alpha 1-acid glycoprotein were within the range of normal controls. Fibroblasts from parents of patients with mucolipidosis IV demonstrated intermediate levels of ganglioside neuraminidase activity and normal levels of glycoprotein neuraminidase activity. The residual acidic neuraminidase activity toward GD1a ganglioside in the patients' fibroblasts did not differ from that of controls in its pH optimum and thermostability, but had an abnormal apparent Km which was about 18 times higher than that of the normal enzyme. These findings suggest that mucolipidosis IV is a ganglioside sialidosis due to a catalytically defective ganglioside neuraminidase.

Neuraminidase activities in sialidosis and mucolipidosis

Defects of neuraminidase activities towards sialyloligosaccharides in fibroblasts and leucocytes and enhanced excretion of sialyloligosaccharides in urine were shown in patients with adult type sialidosis with partial deficiency of beta-galactosidase and cherry red spot-myoclonus syndrome. No differences in their neuraminidase residual levels and urinary excretion patterns on thin-layer chromatography were found between these two disorders. In mucolipidosis II and III patients, the neuraminidase activities towards sialyloligosaccharides were almost normal in leucocytes, although decreased in fibroblasts. The discrepancy of neuraminidase activities towards 2 leads to 3 and 2 leads to 6 sialyloligosaccharide isomers was not noticed in all cases.

beta-Galactosidase-neuraminidase deficiency in adults: deficiency of a freeze-labile neuraminidase in leukocytes and fibroblasts

4-methylumbelliferyl neuraminidase activity was studied in fibroblasts, leukocytes, and frozen tissues from adult patients with beta-galactosidase-neuraminidase deficiency and specific clinical manifestations. This enzyme was almost completely deficient in fibroblasts, but the residual activity was relatively high (20% of the control mean) in the leukocytes from the patients. The frozen liver from one patient showed the enzyme activity as high as controls. This enzyme consisted of two components, freeze-labile and freeze-stable, and it was demonstrated that only the labile enzyme was deficient in fibroblasts and leukocytes. The apparently normal activity of neuraminidase in frozen autopsy tissues of a patient may be explained by the loss of the labile component in control tissues after a long-term freezing. The neuraminidase activity was variable in parents and no definite conclusion was drawn on the hereditary nature of the disease.

Mucolipidosis I: studies of sialidase activity and a prenatal diagnosis

The characteristics of the sialidase (N-acetyl-alpha-neuraminidase) of human leukocytes, fibroblasts and amniotic fluid cell cultures were determined with a radioactive assay method utilizing neuramin-[3H]lactitol as the enzyme substrate. Fibroblast cultures from patients with the inherited sialidase deficiency diseases including mucolipidosis I, sialidosis I and sialidosis II, juvenile type have less than 10% of normal sialidase activity using either this substrate, 2-(3'-methoxyphenyl)-N-acetyl-alpha-neuraminic acid, or 2'-(4-methylumbelliferyl)-N-acetyl-alpha-neuraminic acid. The total sialic acid content of fibroblasts and leukocytes from mucolipidosis I and sialidosis I patients is greatly elevated; this parameter is useful in establishing a diagnosis of sialidase deficiency. The sialic acid content of sialidosis II, juvenile type, with coexistent sialidase and beta-galactosidase deficiencies, is only slightly elevated above normal levels. A patient with mucolipidosis I has 16% of normal neuramin-[3H]lactitol sialidase activity in his peripheral leukocytes. His parents were clearly distinguished from the normal range using leukocyte enzyme levels and a maternal aunt was identified as a possible carrier. The presence of this enzyme in amniotic fluid cell cultures, both fibroblastic and mixed cell type, makes possible the prenatal detection of these diseases. A pregnancy from a family at risk for having a child with mucolipidosis I was monitored by amniocentesis and subsequent sialidase measurement of the amniotic fluid cell cultures.

The mucolipidoses: identification by abnormal electrophoretic patterns of lysosomal hydrolases

The human mucolipidoses (ML) are characterized by abnormal activities and abnormal electrophoretic patterns of fibroblast lysosomal hydrolases. These altered mobility patterns can be used to confirm the clinical diagnosis of the four mucolipidoses. The mobility patterns of one nonlysosomal and seven lysosomal enzymes were tested in fibroblasts from two ML I (sialidosis type 2, infantile), fifteen ML II (I-cell disease), eight ML III (pseudohurler polydystrophy), and one ML IV patients. A single sialidosis type 2, juvenile, line was also examined. Characteristic mobility patterns were found which identify each of the four mucolipidoses. Both the ML I and sialidosis type 2 juvenile lines displayed anodal mobility patterns, but distinct differences between the two disorders were observed. Lysosomal hydrolases from ML II lines demonstrated reduced activities or had altered mobilities. Differing electrophoretic patterns demonstrated the presence of at least two groups within the clinical phenotype diagnosed as ML II, indicating heterogeneity. The ML III lines showed normal electrophoretic patterns for most lysosomal hydrolases. The ML IV line expressed normal mobilities for every enzyme studied, with a single exception. The electrophoretic patterns of only beta-hexosaminidase, acid phosphatase-2, alpha-galactosidase, and esterase A4 were sufficient to identify and distinguish the different mucolipidosis types. Electrophoretic variation was also seen in liver but not kidney extracts from three ML II patients. beta-Hexosaminidase and alpha-mannosidase B secreted into the medium by ML II and ML III fibroblasts had mobility patterns different from normal and from their intracellular patterns. These data suggest that the mucolipidoses are genetically distinct with heterogeneity within them.

Studies on the sialidoses: properties of human leucocyte neuraminidases

At least two components of neuraminidase (acylneuraminyl hydrolase, EC 3.2.1.18) can be distinguished in human leucocytes on the basis of pH optimum, thermolability at 30 degrees C and the effect of the detergent octyl-beta-D-glucoside. With 4-methylumbelliferyl-alpha-D-N-acetylneuraminate as substrate, the A component has a pH optimum of 5.0, is labile at 30 degrees C and is unaffected by 0.2 M octyl-beta-glucoside. The B component has a pH optimum of 4.0-4.2, is stable at 30 degrees C but loses most of its activity in the presence of 0.2 M octyl-beta-glucoside. Both A and B components are membrane-bound but only the A component is solubilized by octyl-beta-glucoside in an active form. Molecular weights of neuraminidases by gamma-ray radiation inactivation (a method that does not require solubilization of the enzyme) were found to be 240 000 +/- 19 000 for the B component, 203 000 +/- 17 000 for the A component and 238 000 +/- 8000 for the octyl-beta-glucoside-solubilized A component. Gel filtration of soluble A component on Sephacryl S-300, in the presence of octyl-beta-glucoside, showed a single peak of activity eluted at or near the void volume suggesting that the enzyme is still in an aggregated form. Profound deficiency of neuraminidase activity was found for both A and B components in leucocytes of patients affected with sialidoses type 1 and 2 (less than 15% normal) and intermediate activity in obligate heterozygotes. These results suggest that the A and B components of leucocyte neuraminidase are closely related from the genetic point of view and that rapid diagnosis of sialidoses can be done by fluorimetric assay of neuraminidase in leucocytes.