Optimisation of the separation of four major neutral glycosphingolipids: application to a rapid and simple detection of urinary globotriaosylceramide in Fabry disease

Analytes’ Structure and Signal Response in Evaporating Light Scattering Detector (ELSD)

Background:

Working with an Evaporative Light Scattering Detector (ELSD), the target components are converted to a suspension of particles in a gas phase by a nebulizer and heated while the mobile phase is evaporated. Then, the incident light is directed at the remaining particles which are scattered and detected.

Methods:

The signal response of an ELS detector is studied through the correlation of the signal intensity of 65 compounds (at 30, 45 and 80°C) with their structural and physicochemical characteristics. Therefore, 67 physicochemical properties as well as structural features of the analytes were inserted as X variables and they were studied in correlation with their signal intensity (Y variable).

Results:

The collected data were statistically processed with the use of partial least squares method. The results proved that several properties were those that mainly affected the signal intensity either increasing or decreasing this response.

Conclusion:

The derived results proved that properties related to vapor pressure, size, density, melting and boiling point of the analytes were responsible for changes in the signal intensity. The light detected was also affected by properties relevant to the ability of a molecule to form hydrogen bonds (HBA and HBD) and its polarizability or refractivity, but at a lower extent.

Fabry's disease: an example of cardiorenal syndrome type 5

Cardiorenal syndrome type 5 (CRS-5) includes conditions where there is a simultaneous involvement of the heart and kidney from a systemic disorder. This is a bilateral organ cross talk. Fabry's disease (FD) is a devastating progressive inborn error of metabolism with lysosomal glycosphingolipid deposition in variety of cell types, capillary endothelial cells, renal, cardiac and nerve cells. Basic effect is absent or deficient activity of lysosomal exoglycohydrolase a-galactosidase A. Renal involvement consists of proteinuria, isosthenuria, altered tubular function, presenting in second or third decade leading to azotemia and end-stage renal disease in third to fifth decade mainly due to irreversible changes to glomerular, tubular and vascular structures, especially highlighted by podocytes foot process effacement. Cardiac involvement consists of left ventricular hypertrophy, right ventricular hypertrophy, arrhythmias (sinus node and conduction system impairment), diastolic dysfunction, myocardial ischemia, infarction, transmural replacement fibrosis, congestive heart failure and cardiac death. Management of FD is based on enzymatic replacement therapy and control of renal (with anti-proteinuric agents such as angiotensin-converting enzyme inhibitors-and/or angiotensin II receptor blockers), brain (coated aspirin, clopidogrel and statin to prevent strokes) and heart complications (calcium channel blockers for ischemic cardiomyopathy, warfarin and amiodarone or cardioverter device for arrhythmias).

Fourier Transform Mass Spectrometry and Nuclear Magnetic Resonance Analysis for the Rapid and Accurate Characterization of Hexacosanoylceramide

Ceramides are a central unit of all sphingolipids which have been identified as sites of biological recognition on cellular membranes mediating cell growth and differentiation. Several glycosphingolipids have been isolated, displaying immunomodulatory and anti-tumor activities. These molecules have generated considerable interest as potential vaccine adjuvants in humans. Accurate analyses of these and related sphingosine analogues are important for the characterization of structure, biological function, and metabolism. We report the complementary use of direct laser desorption ionization (DLDI), sheath flow electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) and high-field nuclear magnetic resonance (NMR) analysis for the rapid, accurate identification of hexacosanoylceramide and starting materials. DLDI does not require stringent sample preparation and yields representative ions. Sheath-flow ESI yields ions of the product and byproducts and was significantly better than monospray ESI due to improved compound solubility. Negative ion sheath flow ESI provided data of starting materials and products all in one acquisition as hexacosanoic acid does not ionize efficiently when ceramides are present. NMR provided characterization of these lipid molecules complementing the results obtained from MS analyses. NMR data was able to differentiate straight chain versus branched chain alkyl groups not easily obtained from mass spectrometry.

Nano-LC and HPLC-chip-ESI-MS: an emerging technique for glycobioanalysis

In less than 5 years, an impressive number of methods based on nano-LC and HPLC-chip coupled online to MS were developed and implemented to comprehensively address structural heterogeneity of glycoconjugates and glycans in biological matrices. C18, graphitized carbon and amide-based stationary phases were adapted to nanoflow level and on chip format, leading to improved sensitivity of structural analysis and superior level of information on highly complex glycan and glycoconjugate mixtures. This review offers a summary of the recent progress in the application of nano-LC and HPLC-chip-MS in glycoanalytics of glycopeptides, glycoprotein glycans, glycosaminoglycans, oligosaccharides and glycosphingolipids.

Fabry disease

Fabry disease (FD) is a progressive, X-linked inherited disorder of glycosphingolipid metabolism due to deficient or absent lysosomal α-galactosidase A activity. FD is pan-ethnic and the reported annual incidence of 1 in 100,000 may underestimate the true prevalence of the disease. Classically affected hemizygous males, with no residual α-galactosidase A activity may display all the characteristic neurological (pain), cutaneous (angiokeratoma), renal (proteinuria, kidney failure), cardiovascular (cardiomyopathy, arrhythmia), cochleo-vestibular and cerebrovascular (transient ischemic attacks, strokes) signs of the disease while heterozygous females have symptoms ranging from very mild to severe. Deficient activity of lysosomal α-galactosidase A results in progressive accumulation of globotriaosylceramide within lysosomes, believed to trigger a cascade of cellular events. Demonstration of marked α-galactosidase A deficiency is the definitive method for the diagnosis of hemizygous males. Enzyme analysis may occasionnally help to detect heterozygotes but is often inconclusive due to random X-chromosomal inactivation so that molecular testing (genotyping) of females is mandatory. In childhood, other possible causes of pain such as rheumatoid arthritis and 'growing pains' must be ruled out. In adulthood, multiple sclerosis is sometimes considered. Prenatal diagnosis, available by determination of enzyme activity or DNA testing in chorionic villi or cultured amniotic cells is, for ethical reasons, only considered in male fetuses. Pre-implantation diagnosis is possible. The existence of atypical variants and the availability of a specific therapy singularly complicate genetic counseling. A disease-specific therapeutic option - enzyme replacement therapy using recombinant human α-galactosidase A - has been recently introduced and its long term outcome is currently still being investigated. Conventional management consists of pain relief with analgesic drugs, nephroprotection (angiotensin converting enzyme inhibitors and angiotensin receptors blockers) and antiarrhythmic agents, whereas dialysis or renal transplantation are available for patients experiencing end-stage renal failure. With age, progressive damage to vital organ systems develops and at some point, organs may start to fail in functioning. End-stage renal disease and life-threatening cardiovascular or cerebrovascular complications limit life-expectancy of untreated males and females with reductions of 20 and 10 years, respectively, as compared to the general population. While there is increasing evidence that long-term enzyme therapy can halt disease progression, the importance of adjunctive therapies should be emphasized and the possibility of developing an oral therapy drives research forward into active site specific chaperones.

Determination of globotriaosylceramide in plasma and urine by mass spectrometry

BACKGROUND

Fabry disease is an X-chromosomally inherited lysosomal storage disorder leading to accumulation of glycosphingolipids, mainly globotriaosylceramide (ceramide-trihexoside, Gb3). Concentrations of Gb3 in plasma and urine have been used to diagnose Fabry disease and to monitor enzyme replacement therapy with recombinant alpha-galactosidase.

METHODS

Gb3 was purified from plasma or urine by combined liquid extraction/protein precipitation and solid-phase extraction, and was detected by flow-injection analysis electrospray mass spectrometry (MS) using multi-reaction-monitoring. Calibration was performed via standard addition using C17-Gb3 as internal standard. The most abundant isoforms were monitored for calculation of total Gb3.

RESULTS

A MS-based assay for quantification of Gb3 in plasma and urine was established and validated. Intra- and inter-assay coefficient of variation (CV) of the method were <or=12%. However, at low concentrations the CV was 16%. The linear range covers roughly two orders of magnitude, down to 0.54 mg/L in plasma and 0.07 mg/L in urine. Careful adjustment of tuning parameters was necessary to obtain identical isoform intensities and quantitative results on different mass spectrometers. Gb3 concentrations in healthy controls were <4 mg/L in EDTA-plasma and <10 microg/mmol creatinine in urine. Significantly increased Gb3 concentrations were found in plasma and urine from male and female patients with Fabry disease.

CONCLUSIONS

An improved MS protocol for Gb3 quantification has been developed, validated, and shown to be suitable for diagnosis and monitoring of Fabry patients.

Retention behaviour of polyunsaturated fatty acid methyl esters on porous graphitic carbon

Retention with porous graphitic carbon was investigated with 25 structures of fatty acid methyl esters (FAMEs) with two different mobile phases: CH(3)CN:CHCl(3) 60:40 (v/v) and CH(3)OH:CHCl(3) 60:40 (v/v) with both 0.1% triethylamine (TEA) and an equimolar amount of HCOOH. Preliminary results showed that the use of TEA/HCOOH led to the response increase of saturated FAMEs with evaporative light scattering detection. No increase was observed for unsaturated one. These modifiers may slightly reduce the retention of FAMEs but did not significantly modify the separation factor with porous graphitic carbon. Thermodynamic parameters were calculated for each structure using Van't Hoff plot measured over the temperature range from 10 to 50 degrees C, with the both mobile phase conditions. All the studied compounds were found linked by the same retention mechanism on porous graphitic carbon. Quantitative in silico analysis of the retention using a molecular mechanics calculation demonstrated a good correlation between the retention factors and the molecular interaction energy values (r>0.93). Especially the Van der Waals energy was predominant, and the contribution of electrostatic energy was negligible for the quantitative analysis of the retention. The results indicate that Van der Waals force, hydrophobic interaction, is predominant for the retention of FAMEs on this packing material. The relative retention for highly unsaturated homologues can be changed by the selection of the weak solvent CH(3)CN or CH(3)OH. Then isomers differing only in the position of the carbon double bond on the alkyl chain can be separated and their behaviour is summarised as the closer the carbon double bonds to the FAME polar head, the more the retention decreases. Finally, the more important the number of carbon double bonds in the alkyl chain is, the smaller the retention is.

[Neurological aspects of Fabry's disease]

Fabry disease is a rare X-linked disorder caused by deficient activity of the lysosomal enzyme alpha-galactosidase A. Progressive accumulation in lysosomes of the undegraded glycosphingolipids leads to a multi-system disease with dermatological, ocular, renal, cardiac, and neurological manifestations. Peripheral nerve involvement, neuropathic pain and chronic acroparesthesiae, are frequent and early-onset signs revealing the disease. They are due to the involvement of small nerve fiber, thus explaining the normality of electroneuromyography. Cochleo-vestibular and autonomic nervous system involvement is frequent. Besides rare aseptic meningitis, central nervous system involvement is essentially represented by cerebrovascular events (stroke, transient ischemic attack). Affecting essentially the posterior circulation, their etiologies have to be clarified: progressive stenosis of small vessels with globotriasocylceramide deposits, arterial remodeling, endothelial dysfunction, pro-thrombotic state, cerebral hypoperfusion consecutive to dysautonaumy, cardiac embolism. MRI shows numerous silent lesions, increasing with age, mainly in small perforant arteries (periventricular white matter, brainstem, cerebellum, basal ganglia). Pulvinar calcifications, due to an increase in cerebral hyperperfusion, could be specific of Fabry disease. Positon tomography analysis shows a reduced cerebral flow velocity and impaired cerebral autoregulation, secondary to the glycosphingolipid storage in vascular endothelial cells. Enzyme replacement therapy has to be carefully monitored.

Diagnosis and management of kidney involvement in Fabry disease

Interest in the diagnosis and treatment of Fabry disease has been greatly stimulated by the availability of Food and Drug Administration-approved, effective enzyme replacement therapy. This review will update the progress in this area since enzyme replacement therapy has become available. Fabry disease is often associated with proteinuric chronic kidney disease (CKD), and it appears that the treatment paradigms that have proven to be so effective in diabetes mellitus and other forms of proteinuric kidney disease are also effective in conjunction with enzyme replacement therapy for treating the kidney manifestations of Fabry disease. As such, Fabry disease represents an interesting example of progressive proteinuric kidney disease in which the usual blood pressure is lower than in other forms of CKD. This makes the use of effective antiproteinuric therapy challenging, especially considering the autonomic dysfunction that appears to be part of the disease. Comprehensive therapy for Fabry disease includes enzyme replacement therapy and all of the adjunctive therapies that are currently used to treat all forms of proteinuric CKD. It is anticipated that this approach will preserve kidney function and also benefit the cardiac and cerebrovascular systems in patients with Fabry disease.

Simultaneous quantification of different cyclodextrins and Gantrez by HPLC with evaporative light scattering detection

A rapid and simple HPLC method with evaporative scattering detection (ELSD) has been developed for the separation and quantitation of beta-cyclodextrin (beta-CD), 2-hydroxypropyl-beta-cyclodextrin (2-HP-beta-CD) and poly(methyl vinyl ether-co-maleic anhydride) (Gantrez). Separation was carried out on a Zorbax Eclipse XDB-Phenyl narrow bore column, with water-acetonitrile in gradient elution as mobile phase at a flow-rate of 0.25 ml/min. Polyethylenglycol 6000 was used as internal standard. The limit of quantification was of about 0.2 mg/ml for cyclodextrins and 0.05 mg/ml for Gantrez. The precision did not exceed 7%. This method was successfully applied to the rapid analysis of CD-Gantrez nanoparticle conjugates without interference from other components of the formulation.

Atmospheric pressure photoionization coupled to porous graphitic carbon liquid chromatography for the analysis of globotriaosylceramides. Application to Fabry disease

Globotriaosylceramides (Gb(3)) are biological compounds implicated in Fabry disease, a lysosomal storage disease due to the deficient activity of alpha-D-galactosidase A, which results in an accumulation of Gb(3) in many organs. The naturally occurring samples are composed of mixtures of several molecular species differing by the structure of the alkyl chains and the nature of the sphingoid base. Atmospheric pressure photoionization mass spectrometry (APPI-MS) proved to be an efficient method for the analysis of globotriaosylceramide molecular species, both in direct injection and by coupling with liquid chromatography (LC). In the positive ion mode, in-source fragmentations yield very precious information that can be used to determine the structure of the alkyl chains. In the negative ion mode, the chloroform solvent participates to the analyte ionization by forming an adduct with chloride ions generated in situ. Combination of LC on a Porous Graphitic Carbon stationary phase and APPI-MS allowed the detection of a great number of species from biological samples isolated from Fabry patients. This method could be an interesting analytical tool for the biochemical investigation of (sphingo) lipid metabolism.

Fluorescence probe assisted post-column detection for lipid analysis in microbore-LC

A general approach, still few exploited so far and never associated with microbore-LC, consisting of detection of various lipid classes (i.e. phospholipids, triglycerides, ceramides and glycosphingolipids) by non-covalent association with 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence probe is developed. This mode of detection was coupled with non-aqueous reversed-phase microbore-LC (C18) by using classical post-column fluorescence detection. The classical LC system was first adapted to microbore-chromatography (internal diameter 1 mm) without apparatus miniaturization of the solvent delivery system and the detection cell. For this purpose, the detection parameters (probe concentration, post-column flow rate, post-column reactor length and post-column system temperature) were optimized by a central composite design (CCD) using a mixture of phosphatidylcholine (PC) species as a lipid model and DPH (lambda(ex) = 350 nm, lambda(em) = 430 nm) as a fluorescence probe. The optimal conditions of detection for the various molecular species of PC were determined for a DPH concentration of 3.35 micromol/L, a post-column flow rate of 0.5 mL/min, a reactor length of 1.4 m and a temperature of 35 degrees C. The fluorescence response was linear over a wide range of PC species from 5 microg/mL to 100 microg/mL and the lower limit of detection (signal/noise = 3) was about 1 microg/mL, that is equivalent to evaporative light scattering detection (ELSD). Others molecular species of various classes of lipids, i.e. triglycerides, ceramides and glycosphingolipids were also easily detected. Thus, this study demonstrated the versatility of the proposed system of detection which was shown to be sensitive, easy to perform, non-destructive and allowed, in contrast to ELSD, for a linear response with various polarity lipid classes.

Fast fingerprinting by MALDI-TOF mass spectrometry of urinary sediment glycosphingolipids in Fabry disease

Fabry disease (FD) is an X-linked inborn error of glycosphingolipid (GSL) metabolism, caused by a deficiency of the lysosomal alpha-galactosidase A, which results in high levels in lysosomes and biological fluids of globotriaosylceramide (Gb3) and digalactosylceramide (Ga2), also known as galabiosylceramide. We report here a detailed study of the molecular species of GSLs in urinary samples obtained from hemizygous and heterozygous patients by use of matrix-assisted laser desorption ionisation and tandem mass spectrometry (MALDI-MS-MS). Twenty-two and fifteen molecular species were identified in the globotriaosylceramide and digalabiosylceramide series, respectively. The major sphingoid base was sphingosine (d18:1), and dihydrosphingosine (C18:0) and sphingadienine (d18:2) were also present. The molecular profiles obtained by MALDI-TOF-MS enabled us to show significant differences between GSLs composition for young, adult or atypic hemizygote and heterozygote patients. Thus, MALDI-TOF-MS and MS-MS proved a powerful tool for screening a population of patients with clinical signs suggestive of FD by direct and rapid GSL fingerprinting and identification, and for study of the biological processes occurring in glycosphingolipid accumulation.

Fabry disease: diagnosis and management, with emphasis on the renal manifestations

PURPOSE OF REVIEW

Interest in the diagnosis and treatment of Fabry disease has been greatly stimulated by the availability of Food and Drug Administration-approved, effective enzyme-replacement therapy. This review will update the progress in this area over the last 18 months that effective enzyme-replacement therapy has become available.

RECENT FINDINGS

Fabry disease is often associated with proteinuric chronic kidney disease, and it appears that the treatment paradigms that have proven to be so effective in diabetes mellitus and other forms of proteinuric renal disease are also effective, in conjunction with enzyme-replacement therapy for treating the renal manifestations of Fabry disease. As such, Fabry disease represents an interesting example of progressive proteinuric renal disease in which the usual blood pressure is lower than in other renal diseases. This makes the use of effective anti-proteinuric therapy challenging, especially considering the autonomic dysfunction that appears to be part of the disease. Recent advances are considered in this review, with emphasis on the role of kidney biopsy, effective dosing and maximal comprehensive therapy of Fabry disease.

SUMMARY

Maximal, comprehensive therapy for Fabry disease includes effective enzyme-replacement therapy and all of the adjunctive therapies that are currently used to treat all forms of proteinuric chronic kidney disease. It is anticipated that this approach will preserve kidney function and also benefit the cardiac and cerebrovascular systems in patients with Fabry disease.