Molecular species analysis of monosialogangliosides from sea urchin Strongylocentrotus nudus by RPLC-ESI-MS/MS

Characterization of Gangliosides in Three Sea Urchin Species by HILIC-ESI-MS/MS

Sea urchin gangliosides (SU-GLSs) are well acknowledged for their nerve regeneration activity and neuroprotective property. The present study sought to characterize and semi-quantitate different SU-GLS subclasses in three sea urchin species, including Strongylocentrotus nudus, Hemicentrotus pulcherrimus, and Glyptocidaris crenularis. A total of 14 SU-GLS subclasses were identified by a hydrophilic interaction liquid chromatography-Q-Exactive tandem mass spectrometry method. Three sialic acid (Sia) structures, including Neu5Ac, Neu5Gc, and KDN, were identified in SU-GLSs, of which Neu5Ac and Neu5Gc had their corresponding sulfated forms. The linkage among Sias was determined to be 2-8. Additionally, KDN2-6Glc1-1Cer, KDN2-8Neu5Gc2-6Glc1-1Cer, and KDN2-8Neu5Gc2-8Neu5Gc2-6Glc-1Cer were speculated to be novel SU-GLS structures. Furthermore, the total SU-GLS content was 2.0-7.3 mg/g in the three sea urchin species. These results will provide useful data for developing a SU-GLS database of aquatic products. Besides, this study will provide a theoretical basis to explore the nutritional values of seafood products further.

Maternal diet with sea urchin gangliosides promotes neurodevelopment of young offspring via enhancing NGF and BDNF expression

Neurodevelopment of fetal and infant brains is an essential process not just during infancy but throughout the whole life. Previous studies have verified the neurotrophic effects of GM1 and milk gangliosides (GLSs) on brain development. However, it remains unclear whether the maternal GLS diet during the perinatal period can program the brain development of young offspring. Sea urchin, as a popular sea food, is a good resource of marine-derived GLSs. This study evaluated the effects of maternal diet with sea urchin gangliosides (SU-GLSs) on the utero and neonatal neurodevelopment and compared their efficacy with common GM1 and sialic acid (SA). Herein, SU-GLSs, as well as GM1 and SA, were orally administered to pregnant mice from pregnancy to lactation. The morphological and functional development of the brain was evaluated in postnatal 15-day (P15) mice. SU-GLSs were superior to GM1 and SA in enhancing neuritogenesis, spinous dendrite growth and synapse function in the hippocampus and cortex of P15 mice. Mechanistic studies found that SU-GLSs upregulated the expressions of NGF and BDNF more effectively than GM1 and SA. Furthermore, different glycosylated SU-GLSs promoted the neural differentiation of Neuro2a cells in a structure-selective manner. Sulfate-type and disialo-type GLSs were more effective than GM1. These findings suggested that maternal SU-GLS diet could promote the neurodevelopment of young offspring and would be a potential nutrition enriching substance for the early developing brain.

Sea urchin gangliosides exhibit neuritogenic effects in neuronal PC12 cells via TrkA- and TrkB-related pathways

Gangliosides (GLSs) are ubiquitously distributed in all tissues but highly enriched in nervous system. Currently, it is unclear how exogenous GLSs regulate neuritogenesis, although neural functions of endogenous GLSs are widely studied. Herein, we evaluated the neuritogenic activities and mechanism of sea urchin gangliosides (SU-GLSs) in vitro. These different glycosylated SU-GLSs, including GM4(1S), GD4(1S), GD4(2A), and GD4(2G), promoted differentiation of NGF-induced PC12 cells in a dose-dependent and structure-selective manner. Sulfate-type and disialo-type GLSs exhibited stronger neuritogenic effects than monosialoganglioside GM1. Furthermore, SU-GLSs might act as neurotrophic factors possessing neuritogenic effects, via targeting tyrosine-kinase receptors (TrkA and TrkB) and activating MEK1/2-ERK1/2-CREB and PI3K-Akt-CREB pathways. This activation resulted in increased expression and secretion of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF). These pathways were verified by specific inhibitors. Our results confirmed the neuritogenic functions of SU-GLS in vitro and indicated their potential roles as natural nutrition for neuritogenesis.

Characterizing gangliosides in six sea cucumber species by HILIC-ESI-MS/MS

An HILIC-ESI-MS/MS method was established to analyze ganglioside (GLS) in sea cucumbers. In total, 17 GLS subclasses were detected in six sea cucumber species. The basic sea cucumber GLSs (SC-GLSs) were elucidated as NeuGc2-6Glc1-1Cer (SC-GM₄). The polymerization degree of the sialic acid (Sia) of SC-GLSs can be up to 4, and the linkage among Sias was mostly determined to be 2-8 or 2-11. Neu5Gc, sulfated and fucosylated NeuGc prevalently existed in SC-GLSs. Moreover, a new SC-GLSs structure with phosphoinositidyled Sia was first observed in Bohadschia marmorata. For the first time, we demonstrated that the content of SC-GD₄, which is the dominant GLS in sea cucumbers, was 27-67%. Minor GLSs characterized as SC-GT₂(Neu5GcMe) and SC-GQ₂(Neu5GcMe) were also discovered. Additionally, SC-GD₄ and SC-GD₄(1S) could significantly promote the differentiation of PC12 cells with structure-selectivity (p < 0.05). Our results provide insights into SC-GLSs to elucidate their Sia substituent and core saccharide chain linkage.

Metabolism of Glycosphingolipids and Their Role in the Pathophysiology of Lysosomal Storage Disorders

Glycosphingolipids (GSLs) are a specialized class of membrane lipids composed of a ceramide backbone and a carbohydrate-rich head group. GSLs populate lipid rafts of the cell membrane of eukaryotic cells, and serve important cellular functions including control of cell-cell signaling, signal transduction and cell recognition. Of the hundreds of unique GSL structures, anionic gangliosides are the most heavily implicated in the pathogenesis of lysosomal storage diseases (LSDs) such as Tay-Sachs and Sandhoff disease. Each LSD is characterized by the accumulation of GSLs in the lysosomes of neurons, which negatively interact with other intracellular molecules to culminate in cell death. In this review, we summarize the biosynthesis and degradation pathways of GSLs, discuss how aberrant GSL metabolism contributes to key features of LSD pathophysiology, draw parallels between LSDs and neurodegenerative proteinopathies such as Alzheimer's and Parkinson's disease and lastly, discuss possible therapies for patients.

Sphingolipids in food and their critical roles in human health

Sphingolipids (SLs) are ubiquitous structural components of cell membranes and are essential for cell functions under physiological conditions or during disease progression. Abundant evidence supports that SLs and their metabolites, including ceramide (Cer), ceramide-1-phosphate (C1P), sphingosine (So), sphingosine-1-phosphate (S1P), are signaling molecules that regulate a diverse range of cellular processes and human health. However, there are limited reviews on the emerging roles of exogenous dietary SLs in human health. In this review, we discuss the ubiquitous presence of dietary SLs, highlighting their structures and contents in foodstuffs, particularly in sea foods. The digestion and metabolism of dietary SLs is also discussed. Focus is given to the roles of SLs in both the etiology and prevention of diseases, including bacterial infection, cancers, neurogenesis and neurodegenerative diseases, skin integrity, and metabolic syndrome (MetS). We propose that dietary SLs represent a "functional" constituent as emerging strategies for improving human health. Gaps in research that could be of future interest are also discussed.

Mass spectrometry for protein sialoglycosylation

Sialic acids are a family of structurally unique and negatively charged nine-carbon sugars, normally found at the terminal positions of glycan chains on glycoproteins and glycolipids. The glycosylation of proteins is a universal post-translational modification in eukaryotic species and regulates essential biological functions, in which the most common sialic acid is N-acetyl-neuraminic acid (2-keto-5-acetamido-3,5-dideoxy-D-glycero-D-galactononulopyranos-1-onic acid) (Neu5NAc). Because of the properties of sialic acids under general mass spectrometry (MS) conditions, such as instability, ionization discrimination, and mixed adducts, the use of MS in the analysis of protein sialoglycosylation is still challenging. The present review is focused on the application of MS related methodologies to the study of both N- and O-linked sialoglycans. We reviewed MS-based strategies for characterizing sialylation by analyzing intact glycoproteins, proteolytic digested glycopeptides, and released glycans. The review concludes with future perspectives in the field.

The role of fatty acids and triglycerides in the gonads of Paracentrotus lividus from Sardinia: Growth, reproduction and cold acclimatization

A detailed characterization of lipid extracts from gonads of P. lividus over a year has been performed combining GC and NMR measurements. For this purpose, sea urchins from two different Sardinian coastal areas were collected monthly. The results underlined a correlation between gonad fatty acids profiles and both water temperature and reproduction process. In particular, EPA and ARA appear to be the most altered fatty acids following seasonal changes. It is suggested that EPA could represent a biomarker of reproduction, reaching a content around 14% during gametogenesis, mainly due to an increase of the sn-1,3 position in TAGs. On the contrary, ARA seems to play a more important role in response to cold acclimatization, which is reflected in a modulation of ARA content in the sn-1,3 position in TAGs.

Gangliosides: Structures, Biosynthesis, Analysis, and Roles in Cancer

Gangliosides are acidic glycosphingolipids containing one or more sialic acid residues. They are essential compounds at the outer leaflet of the plasma membrane, where they interact with phospholipids, cholesterol, and transmembrane proteins, forming lipid rafts. They are involved in cell adhesion, proliferation, and recognition processes, as well as in the modulation of signal transduction pathways. These functions are mainly governed by the glycan moiety, and changes in the structures of gangliosides occur under pathological conditions, particularly in neuro-ectoderm-derived cancers. With the progress in mass spectrometry analysis of gangliosides, their role in cancer progression can be now investigated in more detail. In this review we summarize the current knowledge on the biosynthesis of gangliosides and their role in cancers, together with the recent development of cancer immunotherapy targeting gangliosides.