Gangliosidome of human anencephaly: A high resolution multistage mass spectrometry study

Advanced profiling and structural analysis of anencephaly gangliosides by ion mobility tandem mass spectrometry

Anencephaly, the most severe type of neural tube defects (NTDs) in humans, occurs between the third and fourth gestational weeks (GW), involves the cranial part of the NT and results in the absence of the forebrain and skull. Exposed to amniotic fluid toxicity, neural tissue is degraded and prevented from development. Currently, little is known about the molecular bases of the disease and the possible involvement of glycans. In this context, considering the role played by gangliosides (GGs) in fetal brain development and the previous achievements of ion mobility separation (IMS) mass spectrometry (MS) in biomarker discovery, we report here on the introduction of this advanced analytical technique in NTD research, and its optimization for a comprehensive determination of anencephaly gangliosidome. Three native GG extracts from residual brains of anencephalic fetuses in 28, 35 and 37 GW were comparatively profiled by IMS MS, structurally analyzed by IMS MS/MS, and finally assessed against a native GG mixture from normal fetal brain. IMS MS provided data on 343 anencephaly gangliosides vs. only 157 known before and revealed for the first time the incidence of the entire penta-to octasialylated series. The comparative assay disclosed variations in GG expression with fetal age and a correlation of the pattern with the developmental stage. In contrast to the normal fetal brain, the neural tissue in anencephaly was found to contain an elevated number of polysialogangliosides and a lower expression of O-Ac- and GalNAc-modified glycoforms. These species worth further detailed investigation as new potential anencephaly markers.

Advances in Mass Spectrometry of Gangliosides Expressed in Brain Cancers

Gangliosides are highly abundant in the human brain where they are involved in major biological events. In brain cancers, alterations of ganglioside pattern occur, some of which being correlated with neoplastic transformation, while others with tumor proliferation. Of all techniques, mass spectrometry (MS) has proven to be one of the most effective in gangliosidomics, due to its ability to characterize heterogeneous mixtures and discover species with biomarker value. This review highlights the most significant achievements of MS in the analysis of gangliosides in human brain cancers. The first part presents the latest state of MS development in the discovery of ganglioside markers in primary brain tumors, with a particular emphasis on the ion mobility separation (IMS) MS and its contribution to the elucidation of the gangliosidome associated with aggressive tumors. The second part is focused on MS of gangliosides in brain metastases, highlighting the ability of matrix-assisted laser desorption/ionization (MALDI)-MS, microfluidics-MS and tandem MS to decipher and structurally characterize species involved in the metastatic process. In the end, several conclusions and perspectives are presented, among which the need for development of reliable software and a user-friendly structural database as a search platform in brain tumor diagnostics.

Gangliosidome of a Human Hippocampus in Temporal Lobe Epilepsy Resolved by High-Resolution Tandem Mass Spectrometry

In this study, we developed a high-resolution tandem mass spectrometry (HR MS) approach to assess presumed changes in gangliosidome of a human hippocampus affected by temporal lobe epilepsy (TLE) in comparison with a normal hippocampus. Gangliosides, membrane glycolipids, are particularly diverse and abundant in the human brain, and participate in ion transport and modulation of neuronal excitability. Changes in structural ganglioside pattern potentially linked to TLE molecular pathogenesis have not been explored in detail. Aiming to characterize TLE-specific gangliosidome, we analyzed the native gangliosides purified from a human hippocampal tissue sample affected by TLE and a control hippocampus using HR MS. Marked differences of ganglioside expression were shown in TLE vs. control, particularly with respect to the sialylation degree of components, discovered as a characteristic feature of TLE. Another major finding is the occurrence of tetrasialofucogangliosides in TLE and species modified by either O-acetylation or CH3COO−. Structural analysis by higher-energy collisional dissociation (HCD) MS/MS gave rise to fragmentation patterns implying that the GQ1b (d18:1/18:0) isomer is specifically associated with TLE. Further investigation in a larger sample is needed in order to confirm the discovery of ganglioside structures specifically expressed in human TLE and to provide information on the probable role of gangliosides in the molecular events underlying seizures.

High-Resolution Tandem Mass Spectrometry Identifies a Particular Ganglioside Pattern in Early Diabetic Kidney Disease of Type 2 Diabetes Mellitus Patients

Considering the valuable information provided by glycosphingolipids as molecular markers and the limited data available for their detection and characterization in patients suffering from Type 2 diabetic kidney disease (DKD), we developed and implemented a superior method based on high-resolution (HR) mass spectrometry (MS) and tandem MS (MS/MS) for the determination of gangliosides in the urine of DKD patients. This study was focused on: (i) testing of the HR MS and MS/MS feasibility and performances in mapping and sequencing of renal gangliosides in Type 2 DM patients; (ii) determination of the changes in the urine gangliosidome of DKD patients in different stages of the disease-normo-, micro-, and macroalbuminuria-in a comparative assay with healthy controls. Due to the high resolution and mass accuracy, the comparative MS screening revealed that the sialylation status of the ganglioside components; their modification by O-acetyl, CH3COO-, O-fucosyl, and O-GalNAc; as well as the composition of the ceramide represent possible markers for early DKD detection, the assessment of disease progression, and follow-up treatment. Moreover, structural investigation by MS/MS demonstrated that GQ1d(d18:1/18:0), GT1α(d18:1/18:0) and GT1b(d18:1/18:0) isomers are associated with macroalbuminuria, meriting further investigation in relation to their role in DKD.

Gangliosides as Biomarkers of Human Brain Diseases: Trends in Discovery and Characterization by High-Performance Mass Spectrometry

Gangliosides are effective biochemical markers of brain pathologies, being also in the focus of research as potential therapeutic targets. Accurate brain ganglioside mapping is an essential requirement for correlating the specificity of their composition with a certain pathological state and establishing a well-defined set of biomarkers. Among all bioanalytical methods conceived for this purpose, mass spectrometry (MS) has developed into one of the most valuable, due to the wealth and consistency of structural information provided. In this context, the present article reviews the achievements of MS in discovery and structural analysis of gangliosides associated with severe brain pathologies. The first part is dedicated to the contributions of MS in the assessment of ganglioside composition and role in the specific neurodegenerative disorders: Alzheimer’s and Parkinson’s diseases. A large subsequent section is devoted to cephalic disorders (CD), with an emphasis on the MS of gangliosides in anencephaly, the most common and severe disease in the CD spectrum. The last part is focused on the major accomplishments of MS-based methods in the discovery of ganglioside species, which are associated with primary and secondary brain tumors and may either facilitate an early diagnosis or represent target molecules for immunotherapy oriented against brain cancers.

High-resolution mass spectrometry reveals a complex ganglioside pattern and novel polysialylated structures associated with the human motor cortex

We have developed here a superior methodology based on high-resolution mass spectrometry for screening and fragmentation analysis of gangliosides extracted and purified from the human motor cortex . The experiments, conducted on a nanoelectrospray Orbitrap mass spectroscope in the negative ion mode, allowed the discrimination in the native mixture extracted from human motor cortex of no less than 83 different gangliosides, which represents the highest number of structures identified so far in this brain region. The spectral data, acquired in high-resolution mass spectrometry mode with a remarkable sensitivity and an average mass accuracy of 4.48 ppm, also show that the gangliosidome of motor cortex is generally characterized by species exhibiting a much higher degree of sialylation than previously known. Motor cortex was found dominated by complex structures with a sialylation degree ≥3, exhibiting long saccharide chains, in the G1 class. Fucogangliosides and species with the glycan chain elongated by either O-acetylation and/or acetate anion attachments were also detected; the later modification was for the first time discovered in this brain region. Of major significance is the identification of hepta and octasialylated species of GS1 and GO1 type, which are among the structures with the longest oligosaccharide chain discovered so far in the human brain. In the last stage of research, tandem mass spectrometry performed by higher energy collision dissociation provided structural data documenting the occurrence of GT1b (d18:1/20:0) isomer in the human motor cortex.

Gangliosides of Human Glioblastoma Multiforme: A Comprehensive Mapping and Structural Analysis by Ion Mobility Tandem Mass Spectrometry

Glioblastoma multiforme (GBM), a malignant, highly aggressive, grade IV brain tumor, which rapidly infiltrates into the nearby tissue, has drawn a significant amount of attention because of its poor prognosis and the limited treatment options available. In GBM, nearly all tumor cells exhibit aberrant cell-surface glycosylation patterns due to the alteration of their biosynthesis or postsynthesis modification process. Since gangliosides (GGs) are acknowledged as tumor-associated antigens, we have carried out here a comprehensive profiling of native ganglioside mixtures extracted and purified from GBM specimens. For this purpose, high performance ion mobility separation mass spectrometry (IMS MS) was thoroughly optimized to allow the discovery of GBM-specific structures and the assessment of their roles as tumor markers or possible associated antigens. GG separation by IMS according to the charge state, carbohydrate chain length, degree of sialylation, and ceramide composition led to the identification of no less than 160 distinct components, which represents 3-fold the number of structures identified before. The detected GGs and asialo-GGs were found characterized by a high heterogeneity in their ceramide and glycan compositions, encompassing up five Neu5Ac residues. The tumor was found dominated in equal and high proportions by GD3 and GT1 forms, with a particular incidence of C24:1 fatty acids in the ceramide. By the occurrence of only one mobility feature and the diagnostic fragment ions, the IMS tandem MS conducted using collision-induced dissociation (CID) disclosed for the first time the presence of GT1c(d18:1/24:1) newly proposed here as a potential GBM marker.

High resolution mass spectrometry provides novel insights into the ganglioside pattern of brain cavernous hemangioma

In this study we have optimized nanoelectrospray ionization (nanoESI) high resolution mass spectrometry (HR MS) performed on Orbitrap instrument in the negative ion mode for the determination of the composition and structure of gangliosides extracted from human brain cavernous hemangioma. The optimized HR MS platform, allowed the discrimination of 62 ions, corresponding to 52 different ganglioside species, which represents roughly twice the number of species existing in the current inventory of human brain hemangioma-associated gangliosides. The experiments revealed a ganglioside pattern dominated by GD-type of structures as well as an elevated incidence of species characterized by a low degree of sialylation and short glycan chains, including asialo GA1 (d18:1/18:0), which offer a new perspective upon the ganglioside composition in this benign tumor. Many of the structures are characteristic for this type of tumor only and are to be considered in further investigations for their potential use in early brain hemangioma diagnosis based on molecular markers. The detailed fragmentation analysis performed by collision-induced dissociation (CID) tandem MS provided information of structural elements related to the glycan core and ceramide moiety, which confirmed the molecular configuration of GD3 (d18:1/24:1) and GD3 (d18:1/24:2) species with potential biomarker role.

Orbitrap mass spectrometry for monitoring the ganglioside pattern in human cerebellum development and aging

We have developed here a superior approach based on high-resolution (HR) mass spectrometry (MS) for monitoring the changes occurring with development and aging in the composition and structure of cerebellar gangliosidome. The experiments were focused on the comparative screening and structural analysis of gangliosides expressed in fetal and aged cerebellum by Orbitrap MS with nanoelectrospray ionization (nanoESI) in the negative ion mode. The employed ultrahigh-resolution MS platform allowed the discrimination, without the need of previous separation, of 159 ions corresponding to 120 distinct species in the native ganglioside mixtures from fetal and aged cerebellar biopsies, many more than detected before, when MS platforms of lower resolution were employed. A number of gangliosides, in particular polysialylated belonging to GT, GQ, GP, and GS classes, modified by O-fucosylation, O-acetylation, or CH₃ COO^- were discovered here, for the first time in human cerebellum. These components, found differently expressed in fetal and aged tissues, indicated that the ganglioside profile in cerebellum is development stage- and age-specific. Following the fragmentation analysis by high-energy collision-induced dissociation (HCD) tandem MS (MS/MS), we have also observed that the intimate structure of certain compounds has not changed during the development and aging of the brain, an aspect which could open new directions in the investigation of ganglioside biomarkers in cerebellar tissue.