Glycodendrimers as Chondroitin Sulfate Mimetics: Synthesis and Binding to Growth Factor Midkine

Sulfation of Heparan and Chondroitin Sulfate Ligands Enables Cell-Specific Homing of Nanoprobes

Demystifying the sulfation code of glycosaminoglycans (GAGs) to induce precise homing of nanoparticles in tumor cells or neurons influences the development of a potential drug- or gene-delivery system. However, GAGs, particularly heparan sulfate (HS) and chondroitin sulfate (CS), are structurally highly heterogeneous, and synthesizing well-defined HS/CS composed nanoparticles is challenging. Here, we decipher how specific sulfation patterns on HS and CS regulate receptor-mediated homing of nanoprobes in primary and secondary cells. We discovered that aggressive cancer cells such as MDA-MB-231 displayed a strong uptake of GAG-nanoprobes compared to mild or moderately aggressive cancer cells. However, there was no selectivity towards the GAG sequences, thus indicating the presence of more than one form of receptor-mediated uptake. However, U87 cells, olfactory bulb, and hippocampal primary neurons showed selective or preferential uptake of CS-E-coated nanoprobes compared to other GAG-nanoprobes. Furthermore, mechanistic studies revealed that the 4,6-O-disulfated-CS nanoprobe used the CD44 and caveolin-dependent endocytosis pathway for uptake. These results could lead to new opportunities to use GAG nanoprobes in nanomedicine.

Multivalent glycosystems for human lectins

Human lectins are involved in a wide variety of biological processes, both physiological and pathological, which have attracted the interest of the scientific community working in the glycoscience field. Multivalent glycosystems have been employed as useful tools to understand carbohydrate-lectin binding processes as well as for biomedical applications. The review shows the different scaffolds designed for a multivalent presentation of sugars and their corresponding binding studies to lectins and in some cases, their biological activities. We summarise this research by organizing based on lectin types to highlight the progression in this active field. The paper provides an overall picture of how these contributions have furnished relevant information on this topic to help in understanding and participate in these carbohydrate-lectin interactions.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2017-2018

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2018. Also included are papers that describe methods appropriate to glycan and glycoprotein analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, new methods, matrices, derivatization, MALDI imaging, fragmentation and the use of arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Most of the applications are presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and highlights the impact that MALDI imaging is having across a range of diciplines. MALDI is still an ideal technique for carbohydrate analysis and advancements in the technique and the range of applications continue steady progress.

Chondroitin sulfate proteoglycan is a potential target of memantine to improve cognitive function via the promotion of adult neurogenesis

BACKGROUND AND PURPOSE

Chondroitin sulfate proteoglycan (CSPG) constitutes the neurogenic niche in the hippocampus. The reduction of hippocampal neurogenesis is involved in aging-related cognitive decline and dementia. The purpose of this study is to find candidates that improve cognitive function by analyzing the effects of memantine (MEM), a therapeutic agent for Alzheimer's disease, on CSPG and adult hippocampal neurogenesis.

EXPERIMENTAL APPROACH

The effects of MEM on neurogenesis-related cells and CSPG content were assessed in the hippocampus of middle-aged mice. The MEM-induced alterations in gene expressions of neurotrophins and enzymes associated with biosynthesis and degradation of CSPG in the hippocampus were also measured. The effects of MEM on cognitive function were estimated using a behavioral test battery. The same set of behavioral tests was applied to evaluate the effects of pharmacological depletion of CSPG in the hippocampus.

KEY RESULTS

The densities of newborn granule cells and content of CSPG in the hippocampus were increased by MEM. The expression levels of the enzyme responsible for the biosynthesis CSPG were increased by MEM. The neurotrophin-related molecules were activated by MEM. Short- and long-term memory performance was improved by MEM. Pharmacological depletion of CSPG impairs the effects of MEM on cognitive improvement in middle-aged mice.

CONCLUSIONS AND IMPLICATIONS

MEM regulates the biosynthesis and degradation of CSPG, which may underlie the improvement of cognitive function via the promotion of adult hippocampal neurogenesis. These results imply that CSPG-related enzymes may be potentially attractive candidates for the treatment of aging-related cognitive decline.

Multigram scale preparation of a semi-synthetic N-trifluoroacetyl protected chondroitin disaccharide building block: Towards the stereoselective synthesis of chondroitin sulfates disaccharides

The chemoselective N-trifluoroacetylation of a chondroitin disaccharide obtained from controlled acid hydrolysis of a commercially available polymeric chondroitin sulfate is reported for the first time. We also described the multi-gram scale synthesis of a donor block having a benzylidene moiety further used for the expeditious and stereocontrolled synthesis of glycosides fitted with various aglycons. Stereocontrolled β-glycosylation, sulfation and efficient N-TFA deprotection steps afforded the desired disaccharides in good yields.

Multivalent glycans for biological and biomedical applications

Recognition of glycans by proteins plays a crucial role in a variety of physiological processes in cells and living organisms. In addition, interactions of glycans with proteins are involved in the development of diverse diseases, such as pathogen infection, inflammation and tumor metastasis. It is well-known that multivalent glycans bind to proteins much more strongly than do their monomeric counterparts. Owing to this property, numerous multivalent glycans have been utilized to elucidate glycan-mediated biological processes and to discover glycan-based biomedical agents. In this review, we discuss recent advances (2014-2020) made in the development and biological and biomedical applications of synthetic multivalent glycans, including neoglycopeptides, neoglycoproteins, glycodendrimers, glycopolymers, glyconanoparticles and glycoliposomes. We hope this review assists researchers in the design and development of novel multivalent glycans with predictable activities.

Synthesis, self-assembly and Langerin recognition studies of a resorcinarene-based glycocluster exposing a hyaluronic acid thiodisaccharide mimetic

Herein, we report the synthesis of an octavalent glycocluster exposing a thiodisaccharide mimetic of the repetitive unit of hyaluronic acid, βSGlcA(1 → 3)βSGlcNAc, constructed on a calix[4]resorcinarene scaffold by CuAAC reaction of suitable precursors. This glycocluster showed a strong tendency toward self-aggregation. DOSY-NMR and DLS experiments demonstrated the formation of spherical micelles of d ≅ 6.2 nm, in good agreement. TEM micrographs showed the presence of particles of different sizes, depending on the pH of the starting solution, thus evidencing that the negative charge on the micelle surface due to ionization of the GlcA residues plays an important role in the aggregation process. STD-NMR and DLS experiments provided evidence of the interaction between the synthetic glycocluster and Langerin, a relevant C-type lectin. This interaction was not observed in the STD-NMR experiments performed with the basic disaccharide, providing evidence of a multivalent effect.

GAG Multivalent Systems to interact with Langerin

Langerin is a C-type Lectin expressed at the surface of Langerhans cells, which play a pivotal role in protecting organisms against pathogen infections. To address this aim, Langerin presents at least two recognition sites, one Ca2+-dependent and another one independent, capable of recognizing a variety of carbohydrate ligands. In contrast to other lectins, Langerin recognizes sulfated glycosaminoglycans (GAGs), a family of complex and heterogeneous polysaccharides present in the cell membrane and the extracellular matrix at the interphase generated in the trimeric form of Langerin but absent in the monomeric form. The complexity of these oligosaccharides has impeded the development of well-defined monodisperse structures to study these interaction processes. However, in the last few decades, an improvement of synthetic developments to achieve the preparation of carbohydrate multivalent systems mimicking the GAGs has been described. Despite all these contributions, very few examples are reported where the GAG multivalent structures are used to evaluate the interaction with Langerin. These molecules should pave the way to explore these GAG-Langerin interactions.

Application of Dendrimers for Treating Parasitic Diseases

Despite advances in medical knowledge, parasitic diseases remain a significant global health burden and their pharmacological treatment is often hampered by drug toxicity. Therefore, drug delivery systems may provide useful advantages when used in combination with conventional therapeutic compounds. Dendrimers are three-dimensional polymeric structures, characterized by a central core, branches and terminal functional groups. These nanostructures are known for their defined structure, great water solubility, biocompatibility and high encapsulation ability against a wide range of molecules. Furthermore, the high ratio between terminal groups and molecular volume render them a hopeful vector for drug delivery. These nanostructures offer several advantages compared to conventional drugs for the treatment of parasitic infection. Dendrimers deliver drugs to target sites with reduced dosage, solving side effects that occur with accepted marketed drugs. In recent years, extensive progress has been made towards the use of dendrimers for therapeutic, prophylactic and diagnostic purposes for the management of parasitic infections. The present review highlights the potential of several dendrimers in the management of parasitic diseases.

Synthesis of structurally defined chondroitin sulfate: Paving the way to the structure-activity relationship studies

Chondroitin sulfate (CS) is one of the major and widespread glycosaminoglycans, a family of structurally complex, linear, anionic hetero-co-polysaccharides. CS plays a vital role in various normal physiological and pathological processes, thus, showing varieties of biological activities, such as anti-oxidation, anti-atherosclerosis, anti-thrombosis, and insignificant immunogenicity. However, the heterogeneity of the naturally occurring CS potentially leads to function unspecific and limits further structure-activity relationship studies. Therefore, the synthesis of CS with well-defined and uniform chain lengths is of major interest for the development of reliable drugs. In this review, we examine the remarkable progress that has been made in the chemical, enzymatic and chemoenzymatic synthesis of CS and its derivatives, providing a broad spectrum of options to access CS of well controlled chain lengths.

The synthesis and biological evaluation of chondroitin sulfate E glycodendrimers

Aim: Chondroitin sulfate (CS) is a class of highly sulfated polysaccharides that possess many important biological functions. The heterogeneity of CS limits pharmacological research and leads to ambiguous mechanisms. Thus, glycomimetics are demanded as replacement of natural polysaccharides to explore important biological processes. Results & methodology: Here the preparation of CS glycodendrimers is reported as well as their use as CS mimetics to regulate the NF-κB pathway. Multivalent presentation of sugar epitopes on appropriate dendrimer scaffolds increased the suppression of the NF-κB pathway. The interaction between CS-E molecules and TNF-α was examined by nuclear magnetic resonance technology. Conclusion: Overall, the glycodendrimer reported here may be potentially employed as molecular tool to investigate the biological functions of CS.

Synthesis of a Fluorous-Tagged Hexasaccharide and Interaction with Growth Factors Using Sugar-Coated Microplates

Here, we report the synthesis of a sulfated, fully protected hexasaccharide as a glycosaminoglycan mimetic and the study of its interactions with different growth factors: midkine, basic fibroblast growth factor (FGF-2) and nerve growth factor (NGF). Following a fluorous-assisted approach, monosaccharide building blocks were successfully assembled and the target oligosaccharide was prepared in excellent yield. The use of more acid stable 4,6-O-silylidene protected glucosamine units was crucial for the efficiency of this strategy because harsh reaction conditions were needed in the glycosylations to avoid the formation of orthoester side products. Fluorescence polarization experiments demonstrated the strong interactions between the synthesized hexamer, and midkine and FGF-2. In addition, we have developed an alternative assay to analyse these molecular recognition events. The prepared oligosaccharide was non-covalently attached to a fluorous-functionalized microplate and the direct binding of the protein to the sugar-immobilized surface was measured, affording the corresponding K_D,surf value.

Unexpected loss of stereoselectivity in glycosylation reactions during the synthesis of chondroitin sulfate oligosaccharides

Here, we present an exploratory study on the fluorous-assisted synthesis of chondroitin sulfate (CS) oligosaccharides. Following this approach, a CS tetrasaccharide was prepared. However, in contrast to our previous results, a significant loss of β-selectivity was observed in [2 + 2] glycosylations involving N-trifluoroacetyl-protected D-galactosamine donors and D-glucuronic acid (GlcA) acceptors. These results, together with those obtained from experiments employing model monosaccharide building blocks, highlight the impact of the glycosyl acceptor structure on the stereoselectivity of glycosylation reactions. Our study provides useful data about the substitution pattern of GlcA units for the efficient synthesis of CS oligomers.

Facile saccharide-free mimetics that recapitulate key features of glycosaminoglycan sulfation patterns

We report a new class of saccharide-free glycosaminoglycan (GAG) mimetics where polyproline imparts facilely-made sulfation patterns with GAG-like structure, function and tunability.

Controlling glycosaminoglycan (GAG) activity to exploit its immense potential in biology ultimately requires facile manipulation of sulfation patterns associated with GAGs. However, satisfying this requirement in full remains challenging, given that synthesis of GAGs is technically arduous while convenient GAG mimetics often produce sulfation patterns that are uncharacteristic of GAGs. To overcome this, we develop saccharide-free polyproline-based GAG mimetics (PGMs) that can be facilely assembled via amide coupling chemistry. Molecular dynamics simulations show that PGMs recapitulate key GAG structural features (i.e. ∼9 Å-sized repeating units, periodicity and helicity) and as with GAGs, can be tuned to introduce systematic variations in sulfate clustering and spacing. Functionally, a variety of PGMs control various GAG activities (concerning P-selectin, neurotrophic factors and heparinase) and exhibit GAG-like characteristics such as progressive modulation, comparable effectiveness with heparins, need for different sequences to suit different activities and the presence of a “minimal bioactive length”. Furthermore, PGMs produce consistent effects in vivo and successfully provide therapeutic benefits over cancer metastasis. Taken together with their high level of biosafety, PGMs answer the long-standing need for an effective and practicable strategy to manipulate GAG-appropriate sulfation patterns and exploit GAG activity in medicine and biotechnology.

An Approach to Synthesize Chondroitin Sulfate-E (CS-E) Oligosaccharide Precursors

An approach was developed to synthesize chondroitin sulfate-E (CS-E) oligosaccharides by adopting a postglycosylation-transformation strategy: different from all of the traditional approaches, the characteristic groups of CS-E were introduced following the assembly of the oligosaccharides. The adjusted strategy rendered an easy chain elongation strategy. All of the elongation steps generated high yields with excellent glycosylation outcomes. An orthogonally protected disaccharide was used as the building block to provide flexibility for the group transformation and derivatization at the N-2 position of the GalNAc residue and the O-1,5 positions of the GlcA residue, thereby providing ready access for the further examination of the structure-activity relationship (SAR) of CS-E molecules.

Synthetic Oligosaccharide Libraries and Microarray Technology: A Powerful Combination for the Success of Current Glycosaminoglycan Interactomics

Glycosaminoglycans (GAGs) are extracellular matrix and/or cell-surface sulfated glycans crucial to the regulation of various signaling proteins, the functions of which are essential in many pathophysiological systems. Because structural heterogeneity is high in GAG chains and purification is difficult, the use of structurally defined GAG oligosaccharides from natural sources as molecular models in both biophysical and pharmacological assays is limited. To overcome this obstacle, GAG-like oligosaccharides of well-defined structures are currently being synthesized by chemical and/or enzymatic means in many research groups around the world. These synthetic GAG oligosaccharides serve as useful molecular tools in studies of GAG-protein interactions. In this review, besides discussing the commonest routes used for the synthesis of GAG oligosaccharides, we also survey some libraries of these synthetic models currently available for research and discuss their activities in interaction studies with functional proteins, especially through the microarray approach.