Future perspectives for glycolipid research in medicine

Accurate quantification of sphingosine-1-phosphate in normal and Fabry disease plasma, cells and tissues by LC-MS/MS with (13)C-encoded natural S1P as internal standard

We developed a mass spectrometric procedure to quantify sphingosine-1-phosphate (S1P) in biological materials. The use of newly synthesized (13)C5 C18-S1P and commercial C17-S1P as internal standards rendered very similar results with respect to linearity, limit of detection and limit of quantitation. Caution is warranted with determination of plasma S1P levels. Earlier it was reported that S1P is elevated in plasma of Fabry disease patients. We investigated this with the improved quantification. No clear conclusion could be drawn for patient plasma samples given the lack of uniformity of blood collection and plasma preparation. To still obtain insight, plasma and tissues were identically collected from α-galactosidase A deficient Fabry mice and matched control animals. No significant difference was observed in plasma S1P levels. A significant 2.3 fold increase was observed in kidney of Fabry mice, but not in liver and heart. Comparative analysis of S1P in cultured fibroblasts from normal subjects and classically affected Fabry disease males revealed no significant difference. In conclusion, accurate quantification of S1P in biological materials is feasible by mass spectrometry using the internal standards (13)C5 C18-S1P or C17-S1P. Significant local increases of S1P in the kidney might occur in Fabry disease as suggested by the mouse model.

Characterization of Gaucher disease bone marrow mesenchymal stromal cells reveals an altered inflammatory secretome

Gaucher disease causes pathologic skeletal changes that are not fully explained. Considering the important role of mesenchymal stromal cells (MSCs) in bone structural development and maintenance, we analyzed the cellular biochemistry of MSCs from an adult patient with Gaucher disease type 1 (N370S/L444P mutations). Gaucher MSCs possessed a low glucocerebrosidase activity and consequently had a 3-fold increase in cellular glucosylceramide. Gaucher MSCs have a typical MSC marker phenotype, normal osteocytic and adipocytic differentiation, growth, exogenous lactosylceramide trafficking, cholesterol content, lysosomal morphology, and total lysosomal content, and a marked increase in COX-2, prostaglandin E2, interleukin-8, and CCL2 production compared with normal controls. Transcriptome analysis on normal MSCs treated with the glucocerebrosidase inhibitor conduritol B epoxide showed an up-regulation of an array of inflammatory mediators, including CCL2, and other differentially regulated pathways. These cells also showed a decrease in sphingosine-1-phosphate. In conclusion, Gaucher disease MSCs display an altered secretome that could contribute to skeletal disease and immune disease manifestations in a manner distinct and additive to Gaucher macrophages themselves.

Minimum structure requirement of immunomodulatory glycolipids for predominant Th2 cytokine induction and the discovery of non-linear phytosphingosine analogs

Analogs of immunomodulatory glycolipid OCH (2) were prepared and minimum structure requirement to exhibit equivalent profiles was disclosed. Analogs bearing non-linear hydrocarbon chain in the phytosphingosine moiety (18, 19) were shown for the first time to possess comparable cytokine inducing profile to 2. Molecular modeling of 2/hCD1d complex based on the crystal structure of alpha-GalCer (1)/hCD1d complex is also described.

CCL18: a urinary marker of Gaucher cell burden in Gaucher patients

Glucosylceramide-laden tissue macrophages in Gaucher patients secrete large quantities of chitotriosidase and CC chemokine ligand 18 (CCL18), resulting in markedly increased plasma levels. We have comparatively investigated the occurrence of both parameters in plasma and urine samples of Gaucher patients. Chitotriosidase was high in urine samples of some symptomatic patients, but elevations did not correlate with increased plasma concentrations. Urinary chitotriosidase was particularly high in a patient with severe kidney involvement and local storage cell infiltration. Urinary levels of CCL18 were also highly elevated in samples from Gaucher patients as compared to controls. The median value of the CCL18/creatinine ratio in urine samples of 31 Gaucher patients was 143.3 pg/micromol (range 32-551) and in those of 12 normal subjects was 4.1 pg/micromol (range 1.3-6.8). In sharp contrast to chitotriosidase, increases in the low-molecular-mass chemokine CCL18 in urine and plasma specimens of Gaucher patients correlated well. A correlation was also observed for reductions in urinary and plasma CCL18 following therapy. It is concluded that assessment of urinary CCL18 of Gaucher patients gives insight into the total body burden on Gaucher cells, whereas that of chitotriosidase does not. Urinary chitotriosidase appears rather to be a reflection of renal pathology.

Recent advances in the biochemistry and genetics of sphingolipidoses

Sphingolipidoses are a subgroup of lysosomal storage diseases. They are defined as disorders caused by a genetic defect in catabolism of sphingosine-containing lipids. Catabolism of these lipids involves enzymes and activator proteins. After the discovery of lysosomes by de Duve and the demonstration of the first defective lysosomal enzyme by Hers in 1963, the first enzyme deficiency for sphingolipidoses was characterized in 1965 and all the defective enzymes were demonstrated in the last three decades. In 1984, the first activator protein was found and it expanded the concept of sphingolipidoses. In the following years, many researches have been undertaken to understand the molecular basis of these diseases, the mechanism of pathogenesis, the mechanism of lysosomal digestion of glycosphingolipids (GSLs) and the functional domains of lysosomal enzymes. New hypotheses and theories have been put forward for the mechanism of lysosomal digestion and pathogenesis. However, although much has been done, the pathogenesis of sphingolipidoses has not been fully elucidated. Mouse models of these diseases have facilitated the elucidation of pathogenesis and the development of therapeutic strategies for these diseases, which are not treatable at present except for Fabry and type 1 Gaucher disease. The purpose of this review is to collect information on the recent researches related to sphingolipidoses. The review includes the hydrolysis of GSLs in lysosome, mechanism of hydrolysis, pathogenesis and genetics of sphingolipidoses, a brief mouse model and therapeutic strategies of these diseases.