Butanolysis Derivatization: Improved Sensitivity in LC-MS/MS Quantitation of Heparan Sulfate in Urine from Mucopolysaccharidosis Patients

Application of tandem mass spectrometry in the screening and diagnosis of mucopolysaccharidoses

Mucopolysaccharidoses (MPSs) are caused by a deficiency in the enzymes needed to degrade glycosaminoglycans (GAGs) in the lysosome. The storage of GAGs leads to the involvement of several systems and even to the death of the patient. In recent years, an increasing number of therapies have increased the treatment options available to patients. Early treatment is beneficial in improving the prognosis, but children with MPSs are often delayed in their diagnosis. Therefore, there is an urgent need to develop a method for early screening and diagnosis of the disease. Tandem mass spectrometry (MS/MS) is an analytical method that can detect multiple substrates or enzymes simultaneously. GAGs are reliable markers of MPSs. MS/MS can be used to screen children at an early stage of the disease, to improve prognosis by treating them before symptoms appear, to evaluate the effectiveness of treatment, and for metabolomic analysis or to find suitable biomarkers. In the future, MS/MS could be used to further identify suitable biomarkers for MPSs for early diagnosis and to detect efficacy.

Discovery of small-molecule protein stabilizers toward exogenous alpha-l-iduronidase to reduce the accumulated heparan sulfate in mucopolysaccharidosis type I cells

Synthesis of a series of l-iduronic acid (IdoA)- and imino-IdoA-typed C-glycosides for modulating α-l-iduronidase (IDUA) activity is described. In an enzyme inhibition study, IdoA-typed C-glycosides were more potent than imino-IdoA analogs, with the most potent IdoA-typed C-glycoside 27c showing an IC₅₀ value of 1 μM. On the other hand, co-treatment of 12 with rh-α-IDUA in mucopolysaccharidosis type I (MPS I) fibroblasts exhibited a nearly 3-fold increase of the IDUA activity, resulting in a clear reduction of the accumulated heparan sulfate (HS) compared to the exogenous enzyme treatment alone. This is the first report of small molecules facilitating IDUA stabilization, enhancing enzyme activity, and reducing accumulated HS in MPS I cell-based assays, which reveals that small molecules as rh-α-IDUA stabilizers to improve enzyme replacement therapy (ERT) efficacy toward MPS I is feasible and promising.

Detection of Glycosaminoglycans in Biological Specimens

Proteoglycans (PGs) are macromolecules formed by a protein backbone to which one or more glycosaminoglycan (GAG) side chains are covalently attached. Most PGs are present in connective tissues, cell surfaces, and intracellular compartments. The major biological function of PGs derives from the GAG component of the molecule, which is involved in cell growth and proliferation, embryogenesis, maintenance of tissue hydration, and interactions of the cells via receptors. PGs are categorized into four groups based on their cellular and subcellular localization, including cell surfaces and extracellular, intracellular, and pericellular locations. GAGs are a crucial component of PGs involved in various physiological and pathological processes. GAGs also serve as biomarkers of metabolic diseases such as mucopolysaccharidoses and mucolipidoses. Detection of specific GAGs in various biological fluids helps manage various genetic metabolic disorders before it causes irreversible damage to the patient (Amendum et al., Diagnostics (Basel) 11(9):1563, 2021). There are several methods for detecting GAGs; this chapter focuses on measuring GAGs using enzyme-linked immunosorbent assay, liquid chromatographic tandem mass spectrometry, and automated high-throughput mass spectrometry.

Blood-brain barrier delivery for lysosomal storage disorders with IgG-lysosomal enzyme fusion proteins

The majority of lysosomal storage diseases affect the brain. Treatment of the brain with intravenous enzyme replacement therapy is not successful, because the recombinant lysosomal enzymes do not cross the blood-brain barrier (BBB). Biologic drugs, including lysosomal enzymes, can be re-engineered for BBB delivery as IgG-enzyme fusion proteins. The IgG domain of the fusion protein is a monoclonal antibody directed against an endogenous receptor-mediated transporter at the BBB, such as the insulin receptor or the transferrin receptor. This receptor transports the IgG across the BBB, in parallel with the endogenous receptor ligand, and the IgG acts as a molecular Trojan horse to ferry into brain the lysosomal enzyme genetically fused to the IgG. The IgG-enzyme fusion protein is bi-functional and retains both high affinity binding for the BBB receptor, and high lysosomal enzyme activity. IgG-lysosomal enzymes are presently in clinical trials for treatment of the brain in Mucopolysaccharidosis.

Simultaneous quantification of selected glycosaminoglycans by butanolysis-based derivatization and LC-SRM/MS analysis for assessing glycocalyx disruption in vitro and in vivo

Glycosaminoglycans (GAGs) constitute the main building blocks of the endothelial glycocalyx (GLX), and disruption of GLX initiates and promotes endothelial dysfunction. Here, we aimed to develop a novel, specific and accurate LC-SRM/MS-based method for glycosaminoglycans (GAGs) profiling. The method involved butanolysis derivatization to facilitate GAG-specific disaccharide generation and its subsequent retention in LC-reversed-phase mode followed by mass spectrometric detection performed in positive ion-selected reaction monitoring (SRM) mode. GAG contents were measured in media of endothelial cells (EA.hy926) subjected to various GAG-degrading enzymes, as well as in murine plasma and urine in apolipoprotein E/low-density lipoprotein receptor-deficient (ApoE/LDLR -/-) mice and age-matched wild-type C57BL/6 mice. Alternatively, GLX disruption was verified by atomic force microscopy (AFM)-based analysis of GLX thickness. The proposed assay to quantify GAG-specific disaccharides presented high sensitivity for each of the analytes (LLOQ: 0.05-0.1 μg/mL) as well as accuracy and precision (86.8-114.9% and 2.0-14.3%, respectively). In medium of EA.hy926 cells subjected to GAG-degrading enzymes various GAG-specific disaccharides indicating the degradation of keratan sulphate (KS), heparan sulphate (HS), chondroitin sulphate (CHS) or hyaluronan (HA) were detected as predicted based on the characteristics of individual enzyme activity. In turn, AFM-based assessment of GLX thickness was reduced to a similar extent by all single enzyme treatments, whereas the most prominent reduction of GLX thickness was detected following the enzyme mixture. Plasma measurements of GAGs revealed age- and hypercholesterolemia-dependent decrease in GAGs concentration. In summary, a novel LC-SRM/MS-based method for GAG profiling was proposed that may inform on GLX status in cell culture for both in vitro and in vivo conditions.

Newborn screening of mucopolysaccharidosis type I

Mucopolysaccharidosis type I (MPS I), a lysosomal storage disease caused by a deficiency of α-L-iduronidase, leads to storage of the glycosaminoglycans, dermatan sulfate and heparan sulfate. Available therapies include enzyme replacement and hematopoietic stem cell transplantation. In the last two decades, newborn screening (NBS) has focused on early identification of the disorder, allowing early intervention and avoiding irreversible manifestations. Techniques developed and optimized for MPS I NBS include tandem mass-spectrometry, digital microfluidics, and glycosaminoglycan quantification. Several pilot studies have been conducted and screening programs have been implemented worldwide. NBS for MPS I has been established in Taiwan, the United States, Brazil, Mexico, and several European countries. All these programs measure α-L-iduronidase enzyme activity in dried blood spots, although there are differences in the analytical strategies employed. Screening algorithms based on published studies are discussed. However, some limitations remain: one is the high rate of false-positive results due to frequent pseudodeficiency alleles, which has been partially solved using post-analytical tools and second-tier tests; another involves the management of infants with late-onset forms or variants of uncertain significance. Nonetheless, the risk-benefit ratio is favorable. Furthermore, long-term follow-up of patients detected by neonatal screening will improve our knowledge of the natural history of the disease and inform better management.

From Cancer to COVID-19: A Perspective on Targeting Heparan Sulfate-Protein Interactions

Heparan sulfate (HS) is a complex, polyanionic polysaccharide ubiquitously expressed on cell surfaces and in the extracellular matrix. HS interacts with numerous proteins to mediate a vast array of biological and pathological processes. Inhibition of HS-protein interactions is thus an attractive approach for new therapeutic development for cancer and infectious diseases, including COVID-19; however, synthesis of well-defined native HS oligosaccharides remains challenging. This has aroused significant interest in the development of HS mimetics which are more synthetically tractable and have fewer side effects, such as undesired anticoagulant activity. This account provides a perspective on the design and synthesis of different classes of HS mimetics with useful properties, and the development of various assays and molecular modelling tools to progress our understanding of their interactions with HS-binding proteins.

MUCOPOLYSACCHARIDOSIS II (MPS II) IN A FREE-LIVING KAKA (NESTOR MERIDIONALIS) IN NEW ZEALAND

A lysosomal storage disease, identified as a mucopolysaccharidosis (MPS), was diagnosed in a free-living Kaka (Nestor meridionalis), an endemic New Zealand parrot, which exhibited weakness, incoordination, and seizures. Histopathology showed typical colloid-like cytoplasmic inclusions in Purkinje cells and many other neurons throughout the brain. Electron microscopy revealed that storage bodies contained a variety of linear, curved, or circular membranous profiles and electron-dense bodies. Because the bird came from a small isolated population of Kaka in the northern South Island, a genetic cause was deemed likely. Tandem mass spectrometry revealed increased levels of heparan sulfate-derived disaccharides in the brain and liver compared with tissues from controls. Enzymatic assays documented low levels of iduronate-2-sulfatase activity, which causes a lysosomal storage disorder called MPS type II or Hunter syndrome. A captive breeding program is currently in progress, and the possibility of detecting carriers of this disorder warrants further investigation.

Characterization of disease-specific chondroitin sulfate nonreducing end accumulation in mucopolysaccharidosis IVA

Morquio syndrome type A, also known as MPS IVA, is a rare autosomal recessive disorder caused by deficiency of N-acetylgalactosamine-6-sulfatase, a lysosomal hydrolase critical in the degradation of keratan sulfate (KS) and chondroitin sulfate (CS). The CS that accumulates in MPS IVA patients has a disease-specific nonreducing end (NRE) terminating with N-acetyl-D-galactosamine 6-sulfate, which can be specifically quantified after enzymatic depolymerization of CS polysaccharide chains. The abundance of N-acetyl-D-galactosamine 6-sulfate over other possible NRE structures is diagnostic for MPS IVA. Here, we describe an assay for the liberation and measurement of N-acetyl-D-galactosamine 6-sulfate and explore its application to MPS IVA patient samples in pilot studies examining disease detection, effects of age and treatment with enzyme-replacement therapy. This assay complements the existing urinary KS assay by quantifying CS-derived substrates, which represent a distinct biochemical aspect of MPS IVA. A more complete understanding of the disease could help to more definitively detect disease across age ranges and more completely measure the pharmacodynamic efficacy of therapies. Larger studies will be needed to clarify the potential value of this CS-derived substrate to manage disease in MPS IVA patients.

Diagnosis of Mucopolysaccharidoses and Mucolipidosis by Assaying Multiplex Enzymes and Glycosaminoglycans

Mucopolysaccharidoses (MPS) and mucolipidosis (ML II/III) are a group of lysosomal storage disorders (LSDs) that occur due to a dysfunction of the lysosomal hydrolases responsible for the catabolism of glycosaminoglycans (GAGs). However, ML is caused by a deficiency of the enzyme uridine-diphosphate N-acetylglucosamine:lysosomal-enzyme-N-acetylglucosamine-1-phosphotransferase (GlcNAc-1-phosphotransferase, EC2.7.8.17), which tags lysosomal enzymes with a mannose 6-phosphate (M6P) marker for transport to the lysosome. A timely diagnosis of MPS and ML can lead to appropriate therapeutic options for patients. To improve the accuracy of diagnosis for MPS and ML in a high-risk population, we propose a combination method based on known biomarkers, enzyme activities, and specific GAGs. We measured five lysosomal enzymes (α-L-iduronidase (MPS I), iduronate-2-sulfatase (MPS II), α-N-acetylglucosaminidase (MPS IIIB), N-acetylglucosamine-6-sulfatase (MPS IVA), and N-acetylglucosamine-4-sulfatase (MPS VI)) and five GAGs (two kinds of heparan sulfate (HS), dermatan sulfate (DS), and two kinds of keratan sulfate (KS)) in dried blood samples (DBS) to diagnose suspected MPS patients by five-plex enzyme and simultaneous five GAGs assays. We used liquid chromatography-tandem mass spectrometry (LC-MS/MS) for both assays. These combined assays were tested for 43 patients with suspected MPS and 103 normal control subjects. We diagnosed two MPS I, thirteen MPS II, one MPS IIIB, three MPS IVA, two MPS VI, and six ML patients with this combined method, where enzymes, GAGs, and clinical manifestations were compatible. The remaining 16 patients were not diagnosed with MPS or ML. The five-plex enzyme assay successfully identified MPS patients from controls. Patients with MPS I, MPS II, and MPS IIIB had significantly elevated HS and DS levels in DBS. Compared to age-matched controls, patients with ML and MPS had significantly elevated mono-sulfated KS and di-sulfated KS levels. The results indicated that the combination method could distinguish these affected patients with MPS or ML from healthy controls. Overall, this study has shown that this combined method is effective and can be implemented in larger populations, including newborn screening.

Pharmacokinetics, distribution, and excretion of sodium oligomannate, a recently approved anti-Alzheimer's disease drug in China

The National Medical Products Administration has authorized sodium oligomannate for treating mild-to-moderate Alzheimer's disease. In this study, an LC-MS/MS method was developed and validated to quantitate sodium oligomannate in different biomatrices. The plasma pharmacokinetics, tissue distribution, and excretion of sodium oligomannate in Sprague-Dawley rats and beagle dogs were systematically investigated. Despite its complicated structural composition, the absorption, distribution, metabolism, and excretion profiles of the oligosaccharides in sodium oligomannate of different sizes and terminal derivatives were indiscriminate. Sodium oligomannate mainly crossed the gastrointestinal epithelium through paracellular transport following oral administration, with very low oral bioavailability in rats (0.6%–1.6%) and dogs (4.5%–9.3%). Absorbed sodium oligomannate mainly resided in circulating body fluids in free form with minimal distribution into erythrocytes and major tissues. Sodium oligomannate could penetrate the blood-cerebrospinal fluid (CSF) barrier of rats, showing a constant area under the concentration-time curve ratio (CSF/plasma) of approximately 5%. The cumulative urinary excretion of sodium oligomannate was commensurate with its oral bioavailability, supporting that excretion was predominantly renal, whereas no obvious biliary secretion was observed following a single oral dose to bile duct-cannulated rats. Moreover, only 33.7% (male) and 26.3% (female) of the oral dose were recovered in the rat excreta within 96 h following a single oral administration, suggesting that the intestinal flora may have ingested a portion of unabsorbed sodium oligomannate as a nutrient.

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ADME profiles of sodium oligomannate oligosaccharides were indiscriminate.

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An LC-MS/MS method was developed and validated for the ADME study of sodium oligomannate.

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Sodium oligomannate was absorbed through paracellular transport with very low BA.

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Approximately 5% of sodium oligomannate penetrated the blood–CSF barrier of rats.

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The absorbed drug was excreted through the kidney; unabsorbed drug was excreted in feces.

Is SGSH heterozygosity a risk factor for early-onset neurodegenerative disease?

Lysosomal dysfunction may be an important factor in the pathogenesis of neurodegenerative disorders such as Parkinson's disease (PD). Heterozygous mutations in the gene encoding the lysosomal enzyme glucocerebrosidase (GBA1) have been found in PD patients, and some but not all mutations in other lysosomal enzyme genes, for example, NPC1 and MCOLN1 have been associated with PD. We have examined the behaviour and brain structure of mice carrying a D31N mutation in the sulphamidase (Sgsh) gene which encodes a lysosomal sulphatase. Female heterozygotes and wildtype mice aged 12-, 15-, 18- and 21-months of age underwent motor phenotyping and the brain was comprehensively evaluated for disease-associated lesions. Heterozygous mice exhibited impaired performance in the negative geotaxis test when compared with wildtype mice. Whilst the brain of Sgsh heterozygotes aged up to 21-months did not exhibit any of the gross features of PD, Alzheimer's disease or the neurodegenerative lysosomal storage disorders, for example, loss of striatal dopamine, reduced GBA activity, α-synuclein-positive inclusions, perturbation of lipid synthesis, or cerebellar Purkinje cell drop-out, we noted discrete structural aberrations in the dendritic tree of cortical pyramidal neurons in 21-month old animals. The overt disease lesions and resultant phenotypic changes previously described in individuals with heterozygous mutations in lysosomal enzyme genes such as glucocerebrosidase may be enzyme dependent. By better understanding why deficiency in, or mutant forms of some but not all lysosomal proteins leads to heightened risk or earlier onset of classical neurodegenerative disorders, novel disease-causing mechanisms may be identified.

Is the eye a window to the brain in Sanfilippo syndrome?

Sanfilippo syndrome is an untreatable form of childhood-onset dementia. Whilst several therapeutic strategies are being evaluated in human clinical trials including i.v. delivery of AAV9-based gene therapy, an urgent unmet need is the availability of non-invasive, quantitative measures of neurodegeneration. We hypothesise that as part of the central nervous system, the retina may provide a window through which to 'visualise' degenerative lesions in brain and amelioration of them following treatment. This is reliant on the age of onset and the rate of disease progression being equivalent in retina and brain. For the first time we have assessed in parallel, the nature, age of onset and rate of retinal and brain degeneration in a mouse model of Sanfilippo syndrome. Significant accumulation of heparan sulphate and expansion of the endo/lysosomal system was observed in both retina and brain pre-symptomatically (by 3 weeks of age). Robust and early activation of micro- and macroglia was also observed in both tissues. There was substantial thinning of retina and loss of rod and cone photoreceptors by ~ 12 weeks of age, a time at which cognitive symptoms are noted. Intravenous delivery of a clinically relevant AAV9-human sulphamidase vector to neonatal mice prevented disease lesion appearance in retina and most areas of brain when assessed 6 weeks later. Collectively, the findings highlight the previously unrecognised early and significant involvement of retina in the Sanfilippo disease process, lesions that are preventable by neonatal treatment with AAV9-sulphamidase. Critically, our data demonstrate for the first time that the advancement of retinal disease parallels that occurring in brain in Sanfilippo syndrome, thus retina may provide an easily accessible neural tissue via which brain disease development and its amelioration with treatment can be monitored.

High-Throughput Liquid Chromatography-Tandem Mass Spectrometry Quantification of Glycosaminoglycans as Biomarkers of Mucopolysaccharidosis II

We recently developed a blood-brain barrier (BBB)-penetrating enzyme transport vehicle (ETV) fused to the lysosomal enzyme iduronate 2-sulfatase (ETV:IDS) and demonstrated its ability to reduce glycosaminoglycan (GAG) accumulation in the brains of a mouse model of mucopolysaccharidosis (MPS) II. To accurately quantify GAGs, we developed a plate-based high-throughput enzymatic digestion assay coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) to simultaneously measure heparan sulfate and dermatan sulfate derived disaccharides in tissue, cerebrospinal fluid (CSF) and individual cell populations isolated from mouse brain. The method offers ultra-high sensitivity enabling quantitation of specific GAG species in as low as 100,000 isolated neurons and a low volume of CSF. With an LOD at 3 ng/mL and LLOQs at 5-10 ng/mL, this method is at least five times more sensitive than previously reported approaches. Our analysis demonstrated that the accumulation of CSF and brain GAGs are in good correlation, supporting the potential use of CSF GAGs as a surrogate biomarker for brain GAGs. The bioanalytical method was qualified through the generation of standard curves in matrix for preclinical studies of CSF, demonstrating the feasibility of this assay for evaluating therapeutic effects of ETV:IDS in future studies and applications in a wide variety of MPS disorders.

Advances in glycosaminoglycan detection

BACKGROUND

Glycosaminoglycans (GAGs) are negatively charged long linear (highly sulfated) polysaccharides consisting of repeating disaccharide units that are expressed on the surfaces of all nucleated cells. The expression of GAGs is required for embryogenesis, regulation of cell growth and proliferation, maintenance of tissue hydration, and interactions of the cells via receptors. Mucopolysaccharidoses (MPS) are caused by deficiency of specific lysosomal enzymes that result in the accumulation of GAGs in multiple tissues leading to organ dysfunction. Therefore, GAGs are important biomarkers for MPS. Without any treatment, patients with severe forms of MPS die within the first two decades of life.

SCOPE OF REVIEW

Accurate measurement of GAGs is important to understand the diagnosis and pathogenesis of MPS and to monitor therapeutic efficacy before, during, and after treatment of the disease. This review covers various qualitative and quantitative methods for measurement of GAGs, including dye specific, thin layer chromatography (TLC), capillary electrophoresis, high-performance liquid chromatography (HPLC), liquid chromatography-tandem mass spectrometry (LC-MS/MS), gas chromatography, ELISA, and automated high-throughput mass spectrometry. Major conclusion: There are several methods for GAG detection however, specific GAG detection in the various biological systems requires rapid, sensitive, specific, and cost-effective methods such as LC-MS/MS.

GENERAL SIGNIFICANCE

This review will describe different methods for GAG detection and analysis, including their advantages and limitation.

Technologies to improve the sensitivity of existing chromatographic methods used for bioanalytical studies

Chromatographic method has long been recognized as the most widely used separation method in bioanalytical research. However, the relatively low sensitivity of existing chromatographic methods remains a significant challenge, as the requirements for experimental procedures become more demanding. This review discusses the main causes for the low sensitivity of chromatographic methods and aims to introduce different technologies for enhancing their sensitivity in the following aspects: (i) different pretreatment methods for improving clean-up efficiency and recovery; (ii) derivatization step for altering the chromatographic behavior of analytes and enhancing MS ionization efficiency; (iii) optimal LC-MS conditions and appropriate separation mechanism; and (iv) applications of other chromatographic methods, including miniaturized LC, 2D-LC, 2D-GC, and supercritical fluid chromatography. Altogether, this review is devoted to summarizing the recent technologies reported in the literature and providing new strategies for the detection of bioanalytes.

Mucopolysaccharidosis type II (Hunter syndrome): Clinical and biochemical aspects of the disease and approaches to its diagnosis and treatment

Mucopolysaccharidosis type II (MPS II, Hunter syndrome) is a rare X-linked lysosomal storage disease caused by mutations of the gene encoding the lysosomal enzyme iduronate-2-sulfatase (IDS), the role of which is to hydrolytically remove O-linked sulfates from the two glycosaminoglycans (GAGs) heparan sulfate (HS) and dermatan sulfate (DS). HS and DS are linear, heterogeneous polysaccharides composed of repeating disaccharide subunits of l-iduronic acid (IdoA) or d-glucuronic acid, (1→4)-linked to d-glucosamine (for HS), or (1→3)-linked to 2-acetamido-2-deoxy-d-galactose (N-acetyl-d-galactosamine) (for DS). In healthy cells, IDS cleaves the sulfo group found at the C-2 position of terminal non-reducing end IdoA residues in HS and DS. The loss of IDS enzyme activity leads to progressive lysosomal storage of HS and DS in tissues and organs such as the brain, liver, spleen, heart, bone, joints and airways. Consequently, this leads to the phenotypic features characteristic of the disease. This review provides an overview of the disease profile and clinical manifestation, with a particular focus on the biochemical basis of the disease and chemical approaches to the development of new diagnostics, as well as discussing current treatment options and emerging new therapies.

Synthetic Disaccharide Standards Enable Quantitative Analysis of Stored Heparan Sulfate in MPS IIIA Murine Brain Regions

Heparan sulfate (HS) is a complex polysaccharide from the glycosaminoglycan (GAG) family that accumulates in tissues in several neurological lysosomal storage diseases known as mucopolysaccharidosis (MPS) disorders. The quantitation of HS in biological samples is important for studying MPS disorders but is very challenging because of its high molecular weight and heterogeneity. Recently, acid-catalyzed butanolysis followed by LC-MS/MS analysis has emerged as a promising method for the determination of HS. Butanolysis of HS produces fully desulfated disaccharide cleavage products which are detected by LC-MS/MS. Herein we describe the synthesis of butylated HS disaccharide standards and their use for determining the identity of major product peaks in LC-MS chromatograms from butanolysis of HS as well as the related GAGs heparin and heparosan. Furthermore, synthesis of a d₉-labeled disaccharide internal standard enabled the development of a quantitative LC-MS/MS assay for HS. The assay was utilized for the analysis of MPS IIIA mouse brain tissues, revealing significant differences in abundance and in the regional accumulation of the various HS disaccharides in affected mice.

Early disease course is unaltered in mucopolysaccharidosis type IIIA (MPS IIIA) mice lacking α-synuclein

BACKGROUND

Sanfilippo syndrome (mucopolysaccharidosis type IIIA; MPS IIIA) is an inherited paediatric-onset neurodegenerative disorder caused by the lysosomal deficiency of sulphamidase with subsequent accumulation of heparan sulphate. The pathological mechanisms responsible for clinical disease are unknown; however, intraneuronal accumulation of aggregation-prone proteins such as α-synuclein, phosphorylated tau and amyloid precursor protein suggests inefficient intracellular trafficking and lysosomal degradation.

AIM

To investigate the contribution the accumulating α-synuclein plays in early symptom emergence that is, impaired cognition, reduced anxiety and motor deficits, first detectable between 3-5 months of age.

METHODS

We have crossed congenic MPS IIIA mice with α-synuclein-deficient (Snca^tm1Rosl /J) mice and evaluated phenotype and brain disease lesions.

RESULTS

In a battery of behavioural tests performed on mice aged 12-22 weeks, we were unable to differentiate α-synuclein-deficient MPS IIIA mice from those with one or both copies of the α-synuclein gene; all three affected genotypes were significantly impaired in test performance when compared to wild-type littermates. Histological studies revealed that the rate, location and nature of deposition of other proteinaceous lesions, the disruption to endolysosomal protein expression and the inflammatory response seen in the brain of α-synuclein-deficient MPS IIIA mice reflected that seen in MPS IIIA mice homo- or heterozygous for α-synuclein.

CONCLUSION

Deletion and/or deficiency of α-synuclein does not influence clinical and neuropathological disease progression in murine MPS IIIA, demonstrating that in and of itself, this protein does not initiate the cognitive and motor symptoms that occur in the first 5 months of life in MPS IIIA mice.

Development of a Post-Column Liquid Chromatographic Chiral Addition Method for the Separation and Resolution of Common Mammalian Monosaccharides

The first solely MS-based methodology for the identification and resolution of the ten common mammalian monosaccharides is presented. Based on Cooks' fixed ligand kinetic method, this technique is effective on multiple classes of monosaccharides and includes the first example of two fixed ligand combinations used in a single multiplexed experiment. Subsequently, a post-HPLC chiral addition method is used in conjunction with this newly developed MS methodology for the separation and identification of mixtures of common neutral mammalian monosaccharides. This proposed technique is able to overcome a limitation of present carbohydrate analysis methods, namely the simultaneous isomeric resolution of multiple monosaccharides in a mixture. Graphical Abstract.

Data in support for the measurement of heparan sulfate and dermatan sulfate by LC-MS/MS analysis

This article provides supplementary data for the paper “LC–MS/MS method for simultaneous quantification of heparan sulfate and dermatan sulfate in urine by butanolysis derivatization” (Forni et al., 2018). Several parameters were tested to optimize sample preparation by butanolysis in order to carry out simultaneous quantifications of HS and DS by tandem mass spectrometry.

Here we describe step-by-step instructions to perform HS and DS analysis in urine samples using external calibration curves of standards of known concentration. Sample are quantified by interpolation from the calibration curve and reported in µg/mL. Then, HS and DS are normalized to creatinine concentration and reported as mg/g uCr.

Synthesis and mass spectrometric analysis of disaccharides from methanolysis of heparan sulfate

Heparan sulfate (HS) disaccharides were synthesized to identify HS methanolysis products by LC-MS/MS with applications for mucopolysaccharidosis disorders.

A novel conditional Sgsh knockout mouse model recapitulates phenotypic and neuropathic deficits of Sanfilippo syndrome

Mucopolysaccharidosis (MPS) type IIIA, or Sanfilippo syndrome, is a neurodegenerative lysosomal storage disorder caused by a deficiency of the lysosomal enzyme N-sulfoglucosamine sulfohydrolase (SGSH), involved in the catabolism of heparan sulfate. The clinical spectrum is broad and the age of symptom onset and the degree of preservation of cognitive and motor functions appears greatly influenced by genotype. To explore this further, we generated a conditional knockout (Sgsh ^KO ) mouse model with ubiquitous Sgsh deletion, and compared the clinical and pathological phenotype with that of the spontaneous Sgsh ^D31N MPS-IIIA mouse model. Phenotypic deficits were noted in Sgsh ^KO mice prior to Sgsh ^D31N mice, however these outcomes did not correlate with any shift in the time of appearance nor rate of accumulation of primary (heparan sulfate) or secondary substrates (GM2/GM3 gangliosides). Other disease lesions (elevations in lysosomal integral membrane protein-II expression, reactive astrocytosis and appearance of ubiquitin-positive inclusions) were also comparable between affected mouse strains. This suggests that gross substrate storage and these neuropathological markers are neither primary determinants, nor good biomarkers/indicators of symptom generation, confirming similar observations made recently in MPS-IIIA patients. The Sgsh ^KO mouse will be a useful tool for elucidation of the neurological basis of disease and assessment of the clinical efficacy of new treatments for Sanfilippo syndrome.

Recent Liquid Chromatographic Approaches and Developments for the Separation and Purification of Carbohydrates

Carbohydate purification remains a bottleneck in securing analytical standards from natural sources or by chemical or enzymatic synthesis. This review highlights the scope and remaining limitations of recent approaches and methods development in liquid chromatography for robust and higher-throughput carbohydrate separation and isolation.

Abnormally High Content of Free Glucosamine Residues Identified in a Preparation of Commercially Available Porcine Intestinal Heparan Sulfate

Heparan sulfate (HS) polysaccharides are ubiquitous in animal tissues as components of proteoglycans, and they participate in many important biological processes. HS carbohydrate chains are complex and can contain rare structural components such as N-unsubstituted glucosamine (GlcN). Commercially available HS preparations have been invaluable in many types of research activities. In the course of preparing microarrays to include probes derived from HS oligosaccharides, we found an unusually high content of GlcN residue in a recently purchased batch of porcine intestinal mucosal HS. Composition and sequence analysis by mass spectrometry of the oligosaccharides obtained after heparin lyase III digestion of the polysaccharide indicated two and three GlcN in the tetrasaccharide and hexasaccharide fractions, respectively. ¹H NMR of the intact polysaccharide showed that this unusual batch differed strikingly from other HS preparations obtained from bovine kidney and porcine intestine. The very high content of GlcN (30%) and low content of GlcNAc (4.2%) determined by disaccharide composition analysis indicated that N-deacetylation and/or N-desulfation may have taken place. HS is widely used by the scientific community to investigate HS structures and activities. Great care has to be taken in drawing conclusions from investigations of structural features of HS and specificities of HS interaction with proteins when commercial HS is used without further analysis. Pending the availability of a validated commercial HS reference preparation, our data may be useful to members of the scientific community who have used the present preparation in their studies.

The levels of urinary glycosaminoglycans of patients with attenuated and severe type of mucopolysaccharidosis II determined by liquid chromatography-tandem mass spectrometry

Glycosaminoglycans (GAGs) play important roles on the regulation of extracellular signaling, neuronal development, and cartilage maintenance. The extracellular concentration of total GAGs has been used as an established measure for the diagnosis of mucopolysaccharidoses (MPSs). Heparan sulfate (HS), Dermatan sulfate (DS) and chondroitin sulfate are known to be elevated in the GAGs under pathological conditions associated with MPS. Furthermore, the selective accumulation of disease-specific one of, or a combination of, them has also been used for the estimation of subtypes of MPS. A previously developed method [Auray-Blais C et al. Molecular Genetics and Metabolism 102 (2011) 49–56.] measures the concentration of GAGs using liquid chromatography with tandem mass spectrometry (LC-MS/MS) with higher precision. To ask whether the selective accumulation of HS and DS in the urine of MPS II patients discriminate the attenuated and severe type of MPS II, we examined the concentrations of HS and DS by this methodology. Compared to the healthy controls, we found a marked elevation of HS and DS in all of the MPS II-affected patients. Among patients who received ERT with confirmed elevation of antibody titer, the concentrations of HS in the urine of patients with attenuated type were lower than those with severe type of MPS II. In these patients, the concentrations of DS by LC-MS/MS and of total GAG by DMB failed to depend on the accumulation of antibody. These results suggest that the LC-MS/MS method employed in this study might discriminate the subtypes of MPS II in different clinical background.