Ceramide Is Involved in Temozolomide Resistance in Human Glioblastoma U87MG Overexpressing EGFR.

Glioblastoma multiforme (GBM) is the most frequent and deadly brain tumor. Many sphingolipids are crucial players in the regulation of glioma cell growth as well as in the response to different chemotherapeutic drugs. In particular, ceramide (Cer) is a tumor suppressor lipid, able to induce antiproliferative and apoptotic responses in different types of tumors including GBM, most of which overexpress the epidermal growth factor receptor variant III (EGFRvIII). In this paper, we investigated whether Cer metabolism is altered in the U87MG human glioma cell line overexpressing EGFRvIII (EGFR+ cells) to elucidate their possible interplay in the mechanisms regulating GBM survival properties and the response to the alkylating agent temozolomide (TMZ). Notably, we demonstrated that a low dose of TMZ significantly increases Cer levels in U87MG cells but slightly in EGFR+ cells (sensitive and resistant to TMZ, respectively). Moreover, the inhibition of the synthesis of complex sphingolipids made EGFR+ cells sensitive to TMZ, thus involving Cer accumulation/removal in TMZ resistance of GBM cells. This suggests that the enhanced resistance of EGFR+ cells to TMZ is dependent on Cer metabolism. Altogether, our results indicate that EGFRvIII expression confers a TMZ-resistance phenotype to U87MG glioma cells by counteracting Cer increase.

Glyconanoparticles as tools to prevent antimicrobial resistance.

The increased phenomenon of antimicrobial resistance and the slow pace of development of new antibiotics are at the base of a global health concern regarding microbial infections. Antibiotic resistance kills an estimated 700,000 people each year worldwide, and this number is expected to increase dramatically if efforts are not made to develop new drugs or alternative containment strategies. Increased vaccination coverage, improved sanitation or sustained implementation of infection control measures are among the possible areas of action. Indeed, vaccination is one of the most effective tools of preventing infections. Starting from 1970s polysaccharide-based vaccines against Meningococcus, Pneumococcus and Haemophilus influenzae type b have been licensed, and provided effective protection for population. However, the development of safe and effective vaccines for infectious diseases with broad coverage remains a major challenge in global public health. In this scenario, nanosystems are receiving attention as alternative delivery systems to improve vaccine efficacy and immunogenicity. In this report, we provide an overview of current applications of glyconanomaterials as alternative platforms in the development of new vaccine candidates. In particular, we will focus on nanoparticle platforms, used to induce the activation of the immune system through the multivalent-displacement of saccharide antigens.

Exploring calixarene-based clusters for efficient functional presentation of Streptococcus pneumoniae saccharides.

Calixarenes are promising scaffolds for an efficient clustered exposition of multiple saccharide antigenic units. Herein we report the synthesis and biological evaluation of a calix[6]arene functionalized with six copies of the trisaccharide repeating unit of Streptococcus pneumoniae (SP) serotype 19F. This system has demonstrated its ability to efficiently inhibit the binding between the native 19F capsular polysaccharide and anti-19F antibodies, despite a low number of exposed saccharide antigens, well mimicking the epitope presentations in the polysaccharide. The calix[6]arene mobile scaffold has been selected for functionalization with SP 19F repeating unit after a preliminary screening of four model glycocalixarenes, functionalized with N-acetyl mannosamine, and differing in the valency and/or conformational properties. This work is a step forward towards the development of new fully synthetic calixarenes comprising small carbohydrate antigens as potential carbohydrate-based vaccine scaffolds.

Synthesis and biological evaluation of a trisaccharide repeating unit derivative of Streptococcus pneumoniae 19A capsular polysaccharide.

Streptococcus pneumoniae (SP) is a common human pathogen associated with a broad spectrum of diseases and it is still a leading cause of mortality and morbidity worldwide, especially in children. Moreover, SP is increasingly associated with drug resistance. Vaccination against the pathogen may thus represent an important strategy to overcome its threats to human health. In this context, revealing the molecular determinants of SP immunoreactivity may be relevant for the development of novel molecules with therapeutic perspectives as vaccine components. Serogroup 19 comprises the immune-cross reactive types 19F, 19A, 19B and 19C and it accounts for a high percentage of invasive pneumococcal diseases, mainly caused by serotypes 19F and 19A. Herein, we report the synthesis and biological evaluation of an aminopropyl derivative of the trisaccharide repeating unit of SP 19A. We compare two different synthetic strategies, based on different disconnections between the three monosaccharides which make up the final trisaccharide, to define the best approach for the preparation of the trisaccharide. Synthetic accessibility to the trisaccharide repeating unit lays the basis for the development of more complex biopolymer as well as saccharide conjugates. We also evaluate the binding affinity of the trisaccharide for anti-19A and anti-19F sera and discuss the relationship between the chemical properties of the trisaccharide unit and biological activity.

Glyco-gold nanoparticles: synthesis and applications.

Glyco-gold nanoparticles combine in a single entity the peculiar properties of gold nanoparticles with the biological activity of carbohydrates. The result is an exciting nanosystem, able to mimic the natural multivalent presentation of saccharide moieties and to exploit the peculiar optical properties of the metallic core. In this review, we present recent advances on glyco-gold nanoparticle applications in different biological fields, highlighting the key parameters which inspire the glyco nanoparticle design.

Molecular Architecture and Symmetry Properties of 1,3-Alternate Calix[4]arenes with Orientable Groups at the Para Position of the Phenolic Rings.

Two glycoclusters constituted by four fully acetylated ß-acetylmannosamine residues linked through trimethylenethioureido spacers to a calix[4]arene core and differing for the presence of methoxy or propoxy groups at the lower rim were synthesized. One of the two compounds is fixed in the 1,3-alternate geometry by the presence of the propoxy groups, while the other is potentially free to assume one of the different geometries allowed in calix[4]arene. Their similar NMR spectra in chloroform clearly suggest the same 1,3-alternate geometry. Both compounds were submitted to a conformational investigation with the DFT approach at the standard B3LYP/6-31G(d) level. The two glycocalixarenes showed a large conformational preference for the same geometry that put the mannosamine moiety of one substituent close to the thioureido group of the opposite substituent. This allows the formation of intramolecular hydrogen bonds and originates a series of through-space close contacts. A comparison with the NOESY maps evidence an excellent correspondence between experimental and theoretical data, thus giving an experimental validation of the highly symmetrical conformation that the two glycocalixarenes assume in apolar solvents.

Direct interaction, instrumental for signaling processes, between LacCer and Lyn in the lipid rafts of neutrophil-like cells.

Lactosylceramide [LacCer; ß-Gal-(1-4)-ß-Glc-(1-1)-Cer] has been shown to contain very long fatty acids that specifically modulate neutrophil properties. The interactions between LacCer and proteins and their role in cell signaling processes were assessed by synthesizing two molecular species of azide-photoactivable tritium-labeled LacCer having acyl chains of different lengths. The lengths of the two acyl chains corresponded to those of a short/medium and very long fatty acid, comparable to the lengths of stearic and lignoceric acids, respectively. These derivatives, designated C18-[(3)H]LacCer-(N3) and C24-[(3)H]LacCer-(N3), were incorporated into the lipid rafts of plasma membranes of neutrophilic differentiated HL-60 (D-HL-60) cells. C24-[(3)H]LacCer-(N3), but not C18-[(3)H]LacCer-(N3), induced the phosphorylation of Lyn and promoted phagocytosis. Incorporation of C24-[(3)H]LacCer-(N3) into plasma membranes, followed by illumination, resulted in the formation of several tritium-labeled LacCer-protein complexes, including the LacCer-Lyn complex, into plasma membrane lipid rafts. Administration of C18-[(3)H]LacCer-(N3) to cells, however, did not result in the formation of the LacCer-Lyn complex. These results suggest that LacCer derivatives mimic the biological properties of natural LacCer species and can be utilized as tools to study LacCer-protein interactions, and confirm a specific direct interaction between LacCer species containing very long fatty acids, and Lyn protein, associated with the cytoplasmic layer via myristic/palmitic chains.

Cone Calix[4]arenes with Orientable Glycosylthioureido Groups at the Upper Rim: An In-Depth Analysis of Their Symmetry Properties.

The two glycoclusters α- and ß-d-mannosylthioureidocalix[4]arenes 1 and 2 in the cone geometry have been submitted to a conformational investigation with the DFT approach at the standard B3LYP/6-31G(d) level and using a water continuum solvent model. After a reasoned choice of the level of calculation and the evaluation of the properties of the monomeric components of 1 and 2, the intrinsic conformational properties of cone calix[4]arenes with orientable groups at the upper rim were thoroughly analyzed. From the possible combinations of the directions that the groups may assume, 10 different geometries derive, all chiral. These geometries are interchangeable through two different processes, named breathing equilibrium and arrow rotation, that allow a dense network connection among them. When the modeling of whole macrocycles 1 and 2 was performed, a huge difference in their conformational behavior that heavily influences the presentation mode of their saccharidic moieties was found.

Anionic glycolipids related to glucuronosyldiacylglycerol inhibit protein kinase Akt.

New glucuronosyldiacylglycerol (GlcADG) analogues based on a 2-O-ß-D-glucopyranosyl-sn-glycerol scaffold and carrying one or two acyl chains of different lengths have been synthesized as phosphatidylinositol 3-phosphate (PI3P) mimics targeting the protein kinase Akt. The Akt inhibitory effect of the prepared compounds was assayed using an in vitro kinase assay. The antiproliferative activity of the compounds was tested in the human ovarian carcinoma IGROV-1 cell line in which we found that two of them could inhibit proliferation, in keeping with the target inhibitory effect.