Application of delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry for analysis of sphingolipids in cultured skin fibroblasts from sphingolipidosis patients

Glycosphingolipids with Very Long-Chain Fatty Acids Accumulate in Fibroblasts from Adrenoleukodystrophy Patients

Adrenoleukodystrophy (X-ALD) is an X-linked genetic disorder caused by mutation of the ATP-binding cassette subfamily D member 1 gene, which encodes the peroxisomal membrane protein, adrenoleukodystrophy protein (ALDP). ALDP is associated with the transport of very-long-chain fatty acids (VLCFAs; carbon chain length ≥ 24) into peroxisomes. Defective ALDP leads to the accumulation of saturated VLCFAs in plasma and tissues, which results in damage to myelin and the adrenal glands. Here, we profiled the glycosphingolipid (GSL) species in fibroblasts from X-ALD patients. Quantitative analysis was performed using liquid chromatography–electrospray ionization–tandem mass spectrometry with a chiral column in multiple reaction monitoring (MRM) mode. MRM transitions were designed to scan for precursor ions of long-chain bases to detect GSLs, neutral loss of hexose to detect hexosylceramide (HexCer), and precursor ions of phosphorylcholine to detect sphingomyelin (SM). Our results reveal that levels of C25 and C26-containing HexCer, Hex2Cer, NeuAc-Hex2Cer, NeuAc-HexNAc-Hex2Cer, Hex3Cer, HexNAc-Hex3Cer, and SM were elevated in fibroblasts from X-ALD patients. In conclusion, we precisely quantified SM and various GSLs in fibroblasts from X-ALD patients and determined structural information of the elevated VLCFA-containing GSLs.

Identification of neutral and acidic glycosphingolipids in the human dermal fibroblasts

Skin fibroblasts are recognized as a valuable model of primary human cells able of mirroring the chronological and biological aging. Here, a lipidomic study of glycosphingolipids (GSL) occurring in the easily accessible human dermal fibroblasts (HDF) is presented. Reversed-phase liquid chromatography with negative electrospray ionization (RPLC-ESI) coupled to either orbitrap or linear ion-trap multiple-stage mass spectrometry was applied to characterize GSL in commercially adult and neonatal primary human fibroblast cells and in skin samples taken from an adult volunteer. Collision-induced dissociation in negative ion mode allowed us to get information on the monosaccharide number and ceramide composition, whereas tandem mass spectra on the ceramide anion was useful to identify the sphingoid base. Nearly sixty endogenous GSL species were successfully recognized, namely 33 hexosyl-ceramides (i.e., HexCer, Hex₂Cer and Hex₃Cer) and 24 gangliosides as monosialic acid GM1, GM2 and GM3, along with 5 globosides Gb4. An average content of GSLs was attained and the most representative GSL in skin fibroblasts were Hex₃Cer, also known as Gb3Cer, followed by Gb4, HexCer and Hex₂Cer , while gangliosides were barely quantifiable. The most abundant GSLs in the examined cell lines share the same ceramide base (i.e. d18:1) and the relative content was d18:1/24:1 > d18:1/24:0 > d18:1/16:0 > d18:1/22:0.

MALDI-MSI of Lipids in Human Skin

Matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) is now a well-established technique for imaging analysis of sectioned biological tissues. One of the growing areas of interest is in the analysis of skin. MALDI-MSI can provide a wealth of information from within sections of skin. This includes information on the distribution of pharmaceuticals following topical treatments, through to the examination of the composition of different skin layers and studies of proteomic, lipidomic, and metabolomic responses to disease, wounds, and external stimuli. Here, we describe the handling procedures, preparatory treatment, and mass spectrometry setup required for the MALDI MSI analysis of lipids within human skin samples.

Sphingolipidomics: methods for the comprehensive analysis of sphingolipids

Sphingolipids comprise a highly diverse and complex class of molecules that serve as both structural components of cellular membranes and signaling molecules capable of eliciting apoptosis, differentiation, chemotaxis, and other responses in mammalian cells. Comprehensive or "sphingolipidomic" analyses (structure specific, quantitative analyses of all sphingolipids, or at least all members of a critical subset) are required in order to elucidate the role(s) of sphingolipids in a given biological context because so many of the sphingolipids in a biological system are inter-converted structurally and metabolically. Despite the experimental challenges posed by the diversity of sphingolipid-regulated cellular responses, the detection and quantitation of multiple sphingolipids in a single sample has been made possible by combining classical analytical separation techniques such as high-performance liquid chromatography (HPLC) with state-of-the-art tandem mass spectrometry (MS/MS) techniques. As part of the Lipid MAPS consortium an internal standard cocktail was developed that comprises the signaling metabolites (i.e. sphingoid bases, sphingoid base-1-phosphates, ceramides, and ceramide-1-phosphates) as well as more complex species such as mono- and di-hexosylceramides and sphingomyelin. Additionally, the number of species that can be analyzed is growing rapidly with the addition of fatty acyl Co-As, sulfatides, and other complex sphingolipids as more internal standards are becoming available. The resulting LC-MS/MS analyses are one of the most analytically rigorous technologies that can provide the necessary sensitivity, structural specificity, and quantitative precision with high-throughput for "sphingolipidomic" analyses in small sample quantities. This review summarizes historical and state-of-the-art analytical techniques used for the identification, structure determination, and quantitation of sphingolipids from free sphingoid bases through more complex sphingolipids such as sphingomyelins, lactosylceramides, and sulfatides including those intermediates currently considered sphingolipid "second messengers". Also discussed are some emerging techniques and other issues remaining to be resolved for the analysis of the full sphingolipidome.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update covering the period 2001-2002

This review is the second update of the original review on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates that was published in 1999. It covers fundamental aspects of the technique as applied to carbohydrates, fragmentation of carbohydrates, studies of specific carbohydrate types such as those from plant cell walls and those attached to proteins and lipids, studies of glycosyl-transferases and glycosidases, and studies where MALDI has been used to monitor products of chemical synthesis. Use of the technique shows a steady annual increase at the expense of older techniques such as FAB. There is an increasing emphasis on its use for examination of biological systems rather than on studies of fundamental aspects and method development and this is reflected by much of the work on applications appearing in tabular form.

Quantitative evaluation of sphingolipids using delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry with sphingosylphosphorylcholine as an internal standard

Fabry disease is a glycolipid storage disorder caused by a defect of alpha-galactosidase A, and characterized by the systemic deposition of glycosphingolipids with terminal alpha-galactosyl moieties, mainly globotriaosylceramide, in tissues. Using delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry (DE MALDI-TOF-MS), we analyzed the sphingolipids in the cardiac valves from a 49-year-old male patient with Fabry disease who suffered from congestive cardiac failure. Crude lipids were extracted from the cardiac valves with chloroform and methanol. After mild alkaline treatment of the crude lipids, a sphingolipid fraction was prepared and analyzed by DE MALDI-TOF-MS. The results were as follows: (a) ion peaks with m/z values corresponding to different ceramide trihexoside (CTH) species were detected; (b) with sphingosylphosphorylcholine (SPC) as the internal standard for semi-quantification of CTH, the relative peak height of CTH was calculated and plotted versus its amount loaded on the sample plate for MALDI-TOF-MS. The relative peak height of CTH with fatty acid C16:0 showed linearity between 0 and 50 ng CTH (regression coefficient, r>0.95); (c) semi-quantitative analysis revealed striking accumulation of CTH in the cardiac valves from the patient with Fabry disease. It was indicated that the accumulation of CTH in cardiac valves from Fabry disease patients can be detected with the DE MALDI-TOF-MS method. SPC is commercially available, and this semi-quantitative method involving MALDI-TOF-MS was found to be convenient, reliable and useful for CTH. It is expected to be applied to the quantification of CTH in small amounts of body fluids or other tissues and to clinical examination. It is also expected to be applicable to the quantification of other glycosphingolipids.

A lipidomic study of the effects of N-methyl-N'-nitro-N-nitrosoguanidine on sphingomyelin metabolism

Systems biology is a new and rapidly developing research area in which, by quantitatively describing the interaction among all the individual components of a cell, a systems-level understanding of a biological response can be achieved. Therefore, it requires high-throughput measurement technologies for biological molecules, such as genomic and proteomic approaches for DNA/RNA and protein, respectively. Recently, a new concept, lipidomics, which utilizes the mass spectrometry (MS) method for lipid analysis, has been proposed. Using this lipidomic approach, the effects of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) on sphingomyelin metabolism, a major class of sphingolipids, were evaluated. Sphingomyelin molecules were extracted from cells and analyzed by matrix-assisted laser desorption ionization-time of flight MS. It was found that MNNG induced profound changes in sphingomyelin metabolism, including the appearance of some new sphingomyelin species and the disappearance of some others, and the concentrations of several sphingomyelin species also changed. This was accompanied by the redistribution of acid sphingomyelinase (ASM), a key player in sphingomyelin metabolism. On the other hand, imipramine, an inhibitor of ASM, caused the accumulation of sphingomyelin. It also prevented some of the effects of MNNG, as well as the redistribution of ASM. Taken together, these data suggested that the lipidomic approach is highly effective for the systematic analysis of cellular lipids metabolism.

Sphingolipids are involved in N-methyl-N'-nitro-N-nitrosoguanidine-induced epidermal growth factor receptor clustering

Previously we have found that N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), an alkylating agent, can induce the clustering of cellular surface receptors including tumor necrosis factor receptor (TNFR) and epidermal growth factor receptor (EGFR). Since sphingolipids, especially ceramide, have been suggested as major players in ligand-induced receptor clustering, their involvement in this ligand-independent, chemical-induced receptor clustering was evaluated. It was shown that MNNG-induced EGFR clustering occurred primarily at lipid rafts, as nystatin, which can disrupt lipid raft structure, significantly decreasing MNNG-induced EGFR clustering. Lipidomic studies revealed that MNNG treatment induced profound changes in sphingolipids metabolism, which were not the same as those induced by EGF treatment. Acid sphingomyelinase (ASM) is responsible for hydrolyzing sphingomyelin to generate ceramide, and it was demonstrated that MNNG treatment caused ASM distribution changing from diffused state to concentrated area of cells, which colocalized with lipid rafts. Nystatin treatment also abolished the redistribution of ASM. In addition, blockage of ceramide production by ASM inhibitor imipramine interrupted MNNG-induced receptor clustering. Taken together, these data suggested that sphingolipids are involved in MNNG-induced receptor clustering; however, the specific species involved may be different from those involved in EGF-mediated receptor clustering.

Evaluation of sphingolipids in vitreous bodies from a patient with Gaucher disease, using delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry

Gaucher disease is a glycolipid storage disorder characterized by the accumulation of glucosylceramide in tissues. Using delayed extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry (DE MALDI-TOF-MS), we analyzed sphingolipids in vitreous bodies from a patient with Gaucher disease who suffered from vitreous opacities. Crude lipids were extracted from the freeze-dried vitreous bodies with chloroform and methanol. After mild alkaline treatment of the crude lipids, a sphingolipid fraction was prepared and analyzed by DE MALDI-TOF-MS. The results were as follows: (a). the m/z values of the ions found in the mass spectra for both the control and the Gaucher disease patient corresponded to different sphingomyelin species. (b). The mass spectrum of the Gaucher disease patient showed additional ions with m/z values corresponding to different ceramide monohexoside (CMH) species. It was indicated that the accumulation of CMH in vitreous bodies from Gaucher disease patients could be easily detected with the DE MALDI-TOF-MS method.