The total synthesis of a ganglioside Hp-s1 analogue possessing neuritogenic activity by chemoselective activation glycosylation

Hp-s1 Ganglioside Suppresses Proinflammatory Responses by Inhibiting MyD88-Dependent NF-κB and JNK/p38 MAPK Pathways in Lipopolysaccharide-Stimulated Microglial Cells

Hp-s1 ganglioside is isolated from the sperm of sea urchin (Hemicentrotus pulcherrimus). In addition to neuritogenic activity, the biological function of Hp-s1 in neuroinflammation is unknown. In this study, we investigated the anti-neuroinflammatory effect of Hp-s1 on lipopolysaccharide (LPS)-stimulated microglial cells. MG6 microglial cells were stimulated with LPS in the presence or absence of different Hp-s1 concentrations. The anti-inflammatory effect and underlying mechanism of Hp-s1 in LPS-activated microglia cells were assessed through a Cell Counting kit-8 assay, Western blot analysis, and immunofluorescence. We found that Hp-s1 suppressed not only the expression of inducible nitric oxide synthase and cyclooxygenase-2 but also the expression of proinflammatory cytokines, such as TNF-α, IL-1β, and IL-6. Hp-s1 inhibited the LPS-induced NF-κB signaling pathway by attenuating the phosphorylation and translocation of NF-κB p65 and by disrupting the degradation and phosphorylation of inhibitor κB-α (IκBα). Moreover, Hp-s1 inhibited the LPS-induced phosphorylation of p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK). Hp-s1 also reduced the expression of myeloid differentiation factor 88 (MyD88) and TNF receptor-associated factors 6 (TRAF6), which are prerequisites for NF-κB and MAPKs activation. These findings indicated that Hp-s1 alleviated LPS-induced proinflammatory responses in microglial cells by downregulating MyD88-mediated NF-κB and JNK/p38 MAPK signaling pathways, suggesting further evaluation as a new anti-neuroinflammatory drug.

(2-Ketulosonyl)onate 2,3-O-thionocarbonate donors for the synthesis of KO and KDO α-glycosides and a one-pot glycosylation method for 2-keto acid donors

Bifunctional (2-ketulosonyl)onate thionocarbonates are effective donors for the synthesis of KO and KDO α-glycosides with perfect control in stereoselectivity.

Ganglioside Hp-s1 Analogue Inhibits Amyloidogenic Toxicity in Alzheimer's Disease Model Cells

Alzheimer's disease (AD) is characterized by extracellular deposition of amyloid plaques, which are predominantly composed of amyloid-β (Aβ) peptide derived from amyloid precursor protein (APP) cleavage. APP interacts with tropomyosin receptor kinase A, a neurotrophic receptor associated with gangliosides and mediating neuronal survival and differentiation through the extracellular signal-regulated protein kinase (ERK) pathway. The ganglioside Hp-s1's analogue Hp-s1A exerts neuritogenic activity; however, its effect on AD pathology remains unknown. To test the hypothesis that Hp-s1A is a potential candidate to treat AD, we established the AD-modeled cell line by expressing human Swedish and Indiana APP gene (APP-Swe/Ind) in N2a mouse neuroblastoma cells. The cells were treated with Hp-s1A or monosialoganglioside GM1 for comparison. The AD model cells expressing APP-Swe/Ind exhibited a significant reduction in viability, as well as neurite outgrowth rate, in comparison to the control cells expressing APP-695. APP C-terminal fragment-β (CTFβ) and Aβ42 were increased in the AD cell lysates and the culture media, respectively. With the treatment of either Hp-s1A or GM1 at 1 μM, the AD model cells showed a significant increase in viability; however, only Hp-s1A reduced CTFβ levels in these cells. Further analysis of the culture media revealed that Hp-s1A also reduced Aβ42 production from AD model cells. The phosphorylation of ERK was elevated and the neurite outgrowth rate was restored with Hp-s1A treatment. In conclusion, the ganglioside analogue Hp-s1A inhibited amyloidogenic processing of APP and promoted neurotrophic activity and survival of AD model cells. Hp-s1A has great potential in AD therapeutic development.

Chemistry and Biology of Bioactive Glycolipids of Marine Origin

Glycolipids represent a broad class of natural products structurally featured by a glycosidic fragment linked to a lipidic molecule. Despite the large structural variety of these glycoconjugates, they can be classified into three main groups, i.e., glycosphingolipids, glycoglycerolipids, and atypical glycolipids. In the particular case of glycolipids derived from marine sources, an impressive variety in their structural features and biological properties is observed, thus making them prime targets for chemical synthesis. In the present review, we explore the chemistry and biology of this class of compounds.

Synthesis and Bioassay of Neurogenically Potent Gangliosides DSG-A, Hp-s1 and Their Analogues

In the search of a potent candidate for neurotherapy, we designed and synthesized various analogues of ganglioside Hp-s1. The modification includes the change in hydrophobicity by varying the carbon chain length, altering the number of hydrogen bonds, and replacing the anomeric atom. The chemical synthesis was carried out by using various methods and discussed in details. The neuritogenic activities of these analogues are confirmed in a human neuroblastoma cell line SH-SY5Y. A higher activity of ganglioside Hp-s1 analogue on IL-17A transcript upregulation than ganglioside Hp-s1 was found.

Synthesis and Evaluation of GM2-Monophosphoryl Lipid A Conjugate as a Fully Synthetic Self-Adjuvant Cancer Vaccine

An efficient method was developed for the synthesis of a GM2 derivative suitable for the conjugation with various biomolecules. This GM2 derivative was covalently linked to keyhole limpet hemocyanin (KLH) and monophosphoryl lipid A (MPLA) to form novel therapeutic cancer vaccines. Immunological evaluations of the resultant conjugates in mice revealed that they elicited robust GM2-specific overall and IgG antibody responses. Moreover, the GM2-MPLA conjugate was disclosed to elicit strong immune responses without the use of an adjuvant, proving its self-adjuvant property. The antisera of both conjugates showed strong binding and mediated similarly effective complement-dependent cytotoxicity to GM2-expressing cancer cell line MCF-7. Based on these results, it was concluded that both GM2-MPLA and GM2-KLH are promising candidates as therapeutic cancer vaccines, whereas fully synthetic GM2-MPLA, which has homogeneous and well-defined structure and self-adjuvant property, deserves more attention and studies.

Assistance of the C-7,8-Picoloyl Moiety for Directing the Glycosyl Acceptors into the α-Orientation for the Glycosylation of Sialyl Donors

An efficient α-sialylation method for many primary hydroxyl acceptors that include 6-OH glycosides has been developed. 7,8-Di-O-picoloyl sialyl glycoside was used as the glycosyl donor, and α-glycoconjugation was controlled by using the 7,8-di-O-picoloyl moiety in CH₂Cl₂. The methodology was successfully applied to the total synthesis of ganglioside Hp-s1 possessing neuritogenic activity.

Design, Synthesis, and Biological Evaluation of Ganglioside Hp-s1 Analogues Varying at Glucosyl Moiety

Ganglioside Hp-s1 is isolated from the ovary of sea urchin Diadema setosum. It exhibited better neuritogenic activity than GM1 in pheochromocytoma 12 cells. To explore the roles of glucosyl moiety of Hp-s1 in contributing to the neurogenic activity, we developed feasible procedures for synthesis of Hp-s1 analogues (2a-2f). The glucosyl moiety of Hp-s1 was replaced with α-glucose, α-galactose, β-galactose, α-mannose, and β-mannose, and their biological activities on SH-SY5Y cells and natural killer T (NKT) cells were evaluated. We found that the orientation of C-2 hydroxyl group at glucosyl moiety of Hp-s1 plays an important role to induce neurite outgrowth of SH-SY5Y cells. Surprisingly, compound 2d could activate NKT cells to produce interleukin 2, although it did not show great activity on neurite outgrowth of SH-SY5Y cells. In general, the Hp-s1 might be considered as a lead compound for the development of novel drugs aimed at modulating the activity of neuronal cells.

First total synthesis of ganglioside DSG-A possessing neuritogenic activity

The first total synthesis of ganglioside DSG-A (1) is achievedviachemoselective glycosylation and a [1 + 1 + 2] synthetic strategy.

Synthesis of ganglioside Hp-s1

The complete synthesis of the ganglioside Hp-s1 (1) is described in 10 steps.