Occurrence of Melibiose-Containing Glycosphingolipids in a Sample of a Sponge-Coral Association (Desmapsamma anchorata/Carijoa riisei).

In our research on biologically active compounds from Vietnamese marine invertebrates, rare melibiose-containing glycosphingolipids were found in a sample of a sponge-coral association (Desmapsamma anchorata/Carijoa riisei). Melibiosylceramides were analyzed as constituents of some multi-component RP-HPLC fractions, and the structures of 14 new (1b, 3b, 4a-4c, 6a-6c, 8b, 9a, 9b, 10b, 11a, 11b) and five known (2b, 5a-5c, 7b) natural compounds were elucidated using NMR, mass spectrometry, optical rotation, and chemical transformations. These α-d-Galp-(1→6)-ß-d-Glcp-(1 ↔ 1)-ceramides (presumably sponge-derived compounds) were shown to contain phytosphingosine-type n-t17:0 (1), (6E)-n-t17:1 (2), i-t17:0 (3), n-t18:0 (4), (6E)-n-t18:1 (5), i-t18:0 (6), (6E)-i-t18:1 (7), i-t19:0 (8), (6E)-i-t19:1 (9), ai-t19:0 (10), and (6E)-ai-t19:1 (11) backbones N-acylated with saturated straight-chain (2R)-2-hydroxy C21 (a), C22 (b), and C23 (c) acids. Characteristic trends in the fragmentations of the terminal parts of tetraacetylated normal-chain and iso- and anteiso-branched sphingoid bases were observed using GC/MS. The total sum of melibiosylceramides and compound 5b caused a reduction in colony formation of human melanoma cells.

Novel Lactulose and Melibiose Targeting Autophagy to Reduce PolyQ Aggregation in Cell Models of Spinocerebellar Ataxia 3.

Trehalose, a chemical chaperone and mTOR-independent autophagy enhancer, has shown promise in models of Huntington's disease, Parkinson's disease and tauopathies. In this study, two trehalase analogs, lactulose and melibiose, were examined for their potentials in spinocerebellar ataxia treatment. Using a SCA3 ATXN3/Q75-GFP cell model, we found that the ATXN3/Q75 aggregation was significantly prohibited by lactulose and melibiose because of their abilities to up-regulate autophagy. Meanwhile, lactulose and melibiose reduced reactive oxygen species production in ATXN3/Q75 cells. Both of them further inhibited the ATXN3/Q75 aggregation in neuronally differentiated SH-SY5Y cells. These findings suggest the therapeutic applications of novel trehalose analogs in polyglutamine aggregation-associated neurodegenerative diseases.

The potential of lactulose and melibiose, two novel trehalase-indigestible and autophagy-inducing disaccharides, for polyQ-mediated neurodegenerative disease treatment.

The unique property of trehalose encourages its pharmaceutical application in aggregation-mediated neurodegenerative disorders, including Alzheimer's, Parkinson's, and many polyglutamine (polyQ)-mediated diseases. However, trehalose is digested into glucose by trehalase and which reduced its efficacy in the disease target tissues. Therefore, searching trehalase-indigestible analogs of trehalose is a potential strategy to enhance therapeutic effect. In this study, two trehalase-indigestible trehalose analogs, lactulose and melibiose, were selected through compound topology and functional group analyses. Hydrogen-bonding network analyses suggest that the elimination of the hydrogen bond between the linker ether and aspartate 321 (D321) of human trehalase is the key for lactulose and melibiose to avoid the hydrolyzation. Using polyQ-mediated spinocerebellar ataxia type 17 (SCA17) cell and slice cultures, we found the aggregation was significantly prohibited by trehalose, lactulose, and melibiose, which may through up-regulating of autophagy. These findings suggest the therapeutic applications of trehalase-indigestible trehalose analogs in aggregation-associated neurodegenerative diseases.

Comparison of the binding properties of the mushroom Marasmius oreades lectin and Griffonia simplicifolia I-B isolectin to alphagalactosyl carbohydrate antigens in the surface phase.

The binding of two alpha-galactophilic lectins, Marasmius oreades agglutinin (MOA), and Griffonia simplicifolia I isolectin B(4) (GS I-B(4)) to neoglycoproteins and natural glycoproteins were compared in a surface phase assay. Neoglycoproteins carrying various alpha-galactosylated glycans and laminin from basement membrane of mouse sarcoma that contains the xenogenic Galalpha1-3Gal1-4GlcNAc epitope were immobilized in microtiter plate wells and lectin binding determined with an enzyme-linked assay. After 24 h of incubation, MOA had higher affinity for the xenogenic pentasaccharide (Galalpha1-3Gal1-4GlcNAcbeta1-3Galbeta1-4Glc) than for the Galalpha-monosaccharide. The binding properties of MOA and GS I-B(4) to the xenogenic disaccharide (Galalpha1-3Galbeta1) were comparable while the binding of MOA to the xenogenic pentasaccharide was much stronger than the binding of GS I-B(4) to the same epitope. Non-xenogenic disaccharide-coupled neoglycoproteins having galactose end groups linked alpha1-2 or alpha1-4 to Gal or linked alpha1-3 to GalNAc bound very weakly to MOA, whereas GS I-B(4) recognized all of these disaccharides with similarly high affinity. MOA also showed high affinity for laminin. The results indicate that the Marasmius oreades lectin has nearly the same affinities as does GS I-B(4) for the simple xenogenic carbohydrate antigens, but MOA has greater affinity for the pentasaccharide and is far more specific in its binding preferences than the Griffonia lectin.

Galectin-3 modulates carbohydrate-dependent thymocyte interactions with the thymic microenvironment.

The process of thymocyte differentiation occurs within the context of the thymic microenvironment, in which T cell precursors interact with thymic microenvironmental cells and extracellular matrix. Here we studied the expression of galectin-3, a beta-galactoside binding lectin, in the thymus of young adult mice. Galectin-3 was found mainly in the medulla and to a lesser extent in the cortex. We further showed that distinct microenvironmental elements, such as thymic epithelial cells, the epithelial component of thymic nurse complexes and phagocytic cells of the thymic reticulum produce, secrete and accumulate galectin-3 on the cell surface. Functionally, galectin-3-enriched medium inhibited in vitro thymocyte interactions with thymic microenvironmental cells, accelerated the release of thymocytes from thymic nurse cells and inhibited the reconstitution of these lymphoepithelial complexes. These effects were blocked by exogenous lactose (Galbeta1-4Glc), but not melibiose (Galalpha1-6Glc), and by a monospecific anti-galectin-3 antibody. Recombinant galectin-3 also inhibited thymocyte/thymic epithelial cell interactions. Our data indicate that intrathymically produced galectin-3 disrupts thymocyte/microenvironmental cell interactions, thus acting as a de-adhesion molecule.

Characterization of a mutant alpha-galactosidase gene product for the late-onset cardiac form of Fabry disease.

The expression product of a mutant alpha-galactosidase gene, Q279E (279Gln-->Glu), found in an atypical variant (cardiac form) of Fabry disease, was purified and characterized. It had kinetic properties similar to those of normal alpha-galactosidase, but was markedly thermolabile at neutral pH. Galactose and melibiose at high concentrations stabilized the mutant enzyme in vitro. Its catalytic activity was 15% of that for the normal enzyme, when it was expressed in COS-1 cells at 37 degrees C. The activity increased at 30 degrees C or in the presence of galactose at 37 degrees C. An increase was also observed in lymphoblasts from a patient with this mutation in the presence of galactose or melibiose. We conclude that this mutant protein is posttranslationally inactivated under the neutral conditions in the cells. The possibility of a new therapeutic approach is suggested.

Interaction of Artocarpus lectins with human IgA does not involve asparagine-linked oligosaccharide of the immunoglobulin.

In view of the controversy with respect to the interaction of jacalin with human IgA2, a study was undertaken to assess the reactivity of the Artocarpus heterophyllus lectin, as well as the lectin from Artocarpus integer (lectin C), with subclasses of human immunoglobulin A by ELISA. Our data is consistent with the view that Artocarpus lectins have no affinity for the IgA2 immunoglobulins. In further support of the findings, we have established that N-linked oligosaccharide moieties of IgA have no significant bearing in the lectin-immunoglobulin binding. Interaction was also not affected in the presence of 1% (w/v) BSA.