Sweet Drugs for Bad Bugs: A Glycomimetic Strategy against the DC-SIGN-Mediated Dissemination of SARS-CoV-2.

The C-type lectin receptor DC-SIGN is a pattern recognition receptor expressed on macrophages and dendritic cells. It has been identified as a promiscuous entry receptor for many pathogens, including epidemic and pandemic viruses such as SARS-CoV-2, Ebola virus, and HIV-1. In the context of the recent SARS-CoV-2 pandemic, DC-SIGN-mediated virus dissemination and stimulation of innate immune responses has been implicated as a potential factor in the development of severe COVID-19.

Enhancing the enthalpic contribution of hydrogen bonds by solvent shielding.

In biological systems, polar interactions are heavily burdened by high desolvation penalties resulting from strong solute-solvent interactions. As a consequence thereof, enthalpic contributions of hydrogen bonds to the free energy of binding are severely diminished. However, this effect is strongly attenuated for interactions within solvent-shielded areas of proteins.

Selective inhibition of anti-MAG IgM autoantibody binding to myelin by an antigen-specific glycopolymer.

Anti-myelin-associated glycoprotein (MAG) neuropathy is a disabling autoimmune peripheral neuropathy that is caused by circulating monoclonal IgM autoantibodies directed against the human natural killer-1 (HNK-1) epitope. This carbohydrate epitope is highly expressed on adhesion molecules such as MAG, a glycoprotein present in myelinated nerves. We previously showed the therapeutic potential of the glycopolymer poly(phenyl disodium 3-O-sulfo-β-d-glucopyranuronate)-(1→3)-β-d-galactopyranoside (PPSGG) in selectively neutralizing anti-MAG IgM antibodies in an immunological mouse model and ex vivo with sera from anti-MAG neuropathy patients.

Dynamic Combinatorial Chemistry: A New Methodology Comes of Age.

Dynamic combinatorial chemistry (DCC) has repeatedly proven to be an effective approach to generate directed ligand libraries for macromolecular targets. In the absence of an external stimulus, a dynamic library forms from reversibly reacting building blocks and reaches a stable thermodynamic equilibrium. However, upon addition of a macromolecular host which can bind and stabilize certain components of the library, the equilibrium composition changes and induces an evolution-like selection and enrichment of high-affinity ligands.

KinITC-One Method Supports both Thermodynamic and Kinetic SARs as Exemplified on FimH Antagonists.

Affinity data, such as dissociation constants (K ) or inhibitory concentrations (IC ), are widely used in drug discovery. However, these parameters describe an equilibrium state, which is often not established in vivo due to pharmacokinetic effects and they are therefore not necessarily sufficient for evaluating drug efficacy. More accurate indicators for pharmacological activity are the kinetics of binding processes, as they shed light on the rate of formation of protein-ligand complexes and their half-life.

The price of flexibility - a case study on septanoses as pyranose mimetics.

Seven-membered ring mimetics of mannose were studied as ligands for the mannose-specific bacterial lectin FimH, which plays an essential role in the first step of urinary tract infections (UTI). A competitive binding assay and isothermal titration calorimetry (ITC) experiments indicated an approximately ten-fold lower affinity for the seven-membered ring mannose mimetic 2--heptyl-1,6-anhydro-d--d-galactitol () compared to -heptyl α-d-mannopyranoside (), resulting exclusively from a loss of conformational entropy. Investigations by solution NMR, X-ray crystallography, and molecular modeling revealed that establishes a superimposable H-bond network compared to mannoside , but at the price of a high entropic penalty due to the loss of its pronounced conformational flexibility.

Epitope mapping of histo blood group antigens bound to norovirus VLPs using STD NMR experiments reveals fine details of molecular recognition.

Attachment of human noroviruses to histo blood group antigens (HBGAs) is thought to be critical for the infection process. Therefore, we have determined binding epitopes of synthetic type 1 to 6 blood group A- and B-tetrasaccharides binding to GII.4 human Norovirus virus like particles (VLPs) using STD NMR experiments.

Target-directed Dynamic Combinatorial Chemistry: A Study on Potentials and Pitfalls as Exemplified on a Bacterial Target.

Target-directed dynamic combinatorial chemistry (DCC) is an emerging technique for the efficient identification of inhibitors of pharmacologically relevant targets. In this contribution, we present an application for a bacterial target, the lectin FimH, a crucial virulence factor of uropathogenic E. coli being the main cause of urinary tract infections.

A Secondary Structural Element in a Wide Range of Fucosylated Glycoepitopes.

The increasing understanding of the essential role of carbohydrates in development, and in a wide range of diseases fuels a rapidly growing interest in the basic principles governing carbohydrate-protein interactions. A still heavily debated issue regarding the recognition process is the degree of flexibility or rigidity of oligosaccharides. Combining NMR structure determination based on extensive experimental data with DFT and database searches, we have identified a set of trisaccharide motifs with a similar conformation that is characterized by a non-conventional C-H⋅⋅⋅O hydrogen bond.

Urinary Tract Infection: Which Conformation of the Bacterial Lectin FimH Is Therapeutically Relevant?

Frequent antibiotic treatment of urinary tract infections has resulted in the emergence of antimicrobial resistance, necessitating alternative treatment options. One such approach centers around FimH antagonists that block the bacterial adhesin FimH, which would otherwise mediate binding of uropathogenic Escherichia coli to the host urothelium to trigger the infection. Although the FimH lectin can adopt three distinct conformations, the evaluation of FimH antagonists has mainly been performed with a truncated construct of FimH locked in one particular conformation.

Selective in vivo removal of pathogenic anti-MAG autoantibodies, an antigen-specific treatment option for anti-MAG neuropathy.

Anti-MAG (myelin-associated glycoprotein) neuropathy is a disabling autoimmune peripheral neuropathy caused by monoclonal IgM autoantibodies that recognize the carbohydrate epitope HNK-1 (human natural killer-1). This glycoepitope is highly expressed on adhesion molecules, such as MAG, present in myelinated nerve fibers. Because the pathogenicity and demyelinating properties of anti-MAG autoantibodies are well established, current treatments are aimed at reducing autoantibody levels.

Mutation of Tyr137 of the universal fimbrial adhesin FimH relaxes the tyrosine gate prior to mannose binding.

The most prevalent diseases manifested by are acute and recurrent bladder infections and chronic inflammatory bowel diseases such as Crohn's disease. clinical isolates express the FimH adhesin, which consists of a mannose-specific lectin domain connected a pilin domain to the tip of type 1 pili. Although the isolated FimH lectin domain has affinities in the nanomolar range for all high-mannosidic glycans, differentiation between these glycans is based on their capacity to form predominantly hydrophobic interactions within the tyrosine gate at the entrance to the binding pocket.

Carbohydrate-Lectin Interactions: An Unexpected Contribution to Affinity.

Uropathogenic E. coli exploit PapG-II adhesin for infecting host cells of the kidney; the expression of PapG-II at the tip of bacterial pili correlates with the onset of pyelonephritis in humans, a potentially life-threatening condition. It was envisaged that blocking PapG-II (and thus bacterial adhesion) would provide a viable therapeutic alternative to conventional antibiotic treatment.

Carbohydrate-based amphiphilic nano delivery systems for cancer therapy.

Nanoparticles (NPs) are novel drug delivery systems that have been attracting more and more attention in recent years, and have been used for the treatment of cancer, infection, inflammation and other diseases. Among the numerous classes of materials employed for constructing NPs, organic polymers are outstanding due to the flexibility of design and synthesis and the ease of modification and functionalization. In particular, NP based amphiphilic polymers make a great contribution to the delivery of poorly-water soluble drugs.

Structural basis for sulfation-dependent self-glycan recognition by the human immune-inhibitory receptor Siglec-8.

Siglec-8 is a human immune-inhibitory receptor that, when engaged by specific self-glycans, triggers eosinophil apoptosis and inhibits mast cell degranulation, providing an endogenous mechanism to down-regulate immune responses of these central inflammatory effector cells. Here we used solution NMR spectroscopy to dissect the fine specificity of Siglec-8 toward different sialylated and sulfated carbohydrate ligands and determined the structure of the Siglec-8 lectin domain in complex with its prime glycan target 6'-sulfo sialyl Lewis(x) A canonical motif for sialic acid recognition, extended by a secondary motif formed by unique loop regions, recognizing 6-O-sulfated galactose dictates tight specificity distinct from other Siglec family members and any other endogenous glycan recognition receptors. Structure-guided mutagenesis revealed key contacts of both interfaces to be equally essential for binding.

The Conformational Variability of FimH: Which Conformation Represents the Therapeutic Target?

FimH is a bacterial lectin found at the tips of type 1 pili of uropathogenic Escherichia coli (UPEC). It mediates shear-enhanced adhesion to mannosylated surfaces. Binding of UPEC to urothelial cells initiates the infection cycle leading to urinary tract infections (UTIs).

FimH Antagonists: Phosphate Prodrugs Improve Oral Bioavailability.

The widespread occurrence of urinary tract infections has resulted in frequent antibiotic treatment, contributing to the emergence of antimicrobial resistance. Alternative approaches are therefore required. In the initial step of colonization, FimH, a lectin located at the tip of bacterial type 1 pili, interacts with mannosylated glycoproteins on the urothelial mucosa.

Catch-bond mechanism of the bacterial adhesin FimH.

Ligand-receptor interactions that are reinforced by mechanical stress, so-called catch-bonds, play a major role in cell-cell adhesion. They critically contribute to widespread urinary tract infections by pathogenic Escherichia coli strains. These pathogens attach to host epithelia via the adhesin FimH, a two-domain protein at the tip of type I pili recognizing terminal mannoses on epithelial glycoproteins.

Quantitative profiling of prostaglandins as oxidative stress biomarkers in vitro and in vivo by negative ion online solid phase extraction - Liquid chromatography-tandem mass spectrometry.

Free radical-mediated oxidation of arachidonic acid to prostanoids has been implicated in a variety of pathophysiological conditions such as oxidative stress. Here, we report on the development of a liquid chromatography-mass spectrometry method to measure several classes of prostaglandin derivatives based on regioisomer-specific mass transitions down to levels of 20 pg/ml applied to the measurement of prostaglandin biomarkers in primary hepatocytes. The quantitative profiling of prostaglandin derivatives in rat and human hepatocytes revealed the increase of several isomers on stress response.

Application of lipid peroxidation products as biomarkers for flutamide-induced oxidative stress in vitro.

The early identification of hepatotoxicity is a fundamental goal of preclinical safety studies in drug discovery and early development. Sensitive biomarkers warrant the determination of potential underlying mechanisms that help characterizing a disruption of physiological conditions prior to cell death. This study shows the potential of different lipid peroxidation products, namely isoprostanes and hydroxynonenal (HNE) derivatives, to serve as early safety biomarkers of hepatotoxicity caused by oxidative stress as underlying mechanism.

E-selectin ligand complexes adopt an extended high-affinity conformation.

E-selectin is a cell-adhesion molecule of the vascular endothelium that promotes essential leukocyte rolling in the early inflammatory response by binding to glycoproteins containing the tetrasaccharide sialyl Lewis(x) (sLe(x)). Efficient leukocyte recruitment under vascular flow conditions depends on an increased lifetime of E-selectin/ligand complexes under tensile force in a so-called catch-bond binding mode. Co-crystal structures of a representative fragment of the extracellular E-selectin region with sLe(x) and a glycomimetic antagonist thereof reveal an extended E-selectin conformation, which is identified as a high-affinity binding state of E-selectin by molecular dynamics simulations.

The tyrosine gate of the bacterial lectin FimH: a conformational analysis by NMR spectroscopy and X-ray crystallography.

Urinary tract infections caused by uropathogenic E. coli are among the most prevalent infectious diseases. The mannose-specific lectin FimH mediates the adhesion of the bacteria to the urothelium, thus enabling host cell invasion and recurrent infections.

Enantiomeric cyclic peptides with different Caco-2 permeability suggest carrier-mediated transport.

Recently, oral absorption of cyclic hexapeptides was improved by N-methylation of their backbone amides. However, the number and position of N-methylations or of solvent exposed NHs did not correlate to intestinal permeability, measured in a Caco-2 model. In this study, we investigate enantiomeric pairs of three polar and two lipophilic peptides to demonstrate the participation of carrier-mediated transporters.

FimH antagonists: bioisosteres to improve the in vitro and in vivo PK/PD profile.

Urinary tract infections (UTIs), predominantly caused by uropathogenic Escherichia coli (UPEC), belong to the most prevalent infectious diseases worldwide. The attachment of UPEC to host cells is mediated by FimH, a mannose-binding adhesin at the tip of bacterial type 1 pili. To date, UTIs are mainly treated with antibiotics, leading to the ubiquitous problem of increasing resistance against most of the currently available antimicrobials.