ABSTRACT
Investigation into Heliobacter pylori binding to Lewis b (Leb) antigens through the blood group antigen binding adhesion protein (BabA) requires structurally well-defined tools. A Leb hexasaccharide thioglycoside donor was chemically prepared through a linear approach starting from D-lactose. This donor can be used to attach reducing end linkers providing a range of options for conjugation techniques or to further extend the oligosaccharide structure. To evaluate its efficiency as a donor, it was coupled to a 6-OH GalNAc acceptor, producing an extended Leb-containing Tn mucin core structure in 84% yield, and to L-serine in 72% yield. The latter compound was subsequently functionalized with a photolabile diazirine linker and biotin, creating a Leb hexasaccharide structure-function tool suitable for lectin tagging interaction studies. This donor opens a wide range of possibilities for conjugation of Leb structures to produce a variety of chemical biology tools to assist in the study of these interactions.
Subject(s)
Mucins , Thioglycosides , Lewis Blood Group Antigens , Mucins/chemistry , Mucins/metabolism , Oligosaccharides/chemistry , SerineABSTRACT
Airway mucus in cystic fibrosis (CF) is highly elastic, but the mechanism behind this pathology is unclear. We hypothesized that the biophysical properties of CF mucus are altered because of neutrophilic oxidative stress. Using confocal imaging, rheology, and biochemical measures of inflammation and oxidation, we found that CF airway mucus gels have a molecular architecture characterized by a core of mucin covered by a web of DNA and a rheological profile characterized by high elasticity that can be normalized by chemical reduction. We also found that high levels of reactive oxygen species in CF mucus correlated positively and significantly with high concentrations of the oxidized products of cysteine (disulfide cross-links). To directly determine whether oxidation can cross-link mucins to increase mucus elasticity, we exposed induced sputum from healthy subjects to oxidizing stimuli and found a marked and thiol-dependent increase in sputum elasticity. Targeting mucin disulfide cross-links using current thiol-amino structures such as N-acetylcysteine (NAC) requires high drug concentrations to have mucolytic effects. We therefore synthesized a thiol-carbohydrate structure (methyl 6-thio-6-deoxy-α-D-galactopyranoside) and found that it had stronger reducing activity than NAC and more potent and fast-acting mucolytic activity in CF sputum. Thus, oxidation arising from airway inflammation or environmental exposure contributes to pathologic mucus gel formation in the lung, which suggests that it can be targeted by thiol-modified carbohydrates.
Subject(s)
Cross-Linking Reagents/metabolism , Gels/metabolism , Lung/physiology , Mucins/metabolism , Mucus/metabolism , Polymers/metabolism , Acetylcysteine/pharmacology , Animals , Biomechanical Phenomena/drug effects , Cystic Fibrosis/pathology , Cystic Fibrosis/physiopathology , DNA/metabolism , Disulfides/metabolism , Elasticity/drug effects , Expectorants/pharmacology , Galactose/chemistry , Galactose/pharmacology , Humans , Lung/drug effects , Mice, Inbred C57BL , Oxidation-Reduction/drug effects , Oxidative Stress/drug effects , Reducing Agents/pharmacology , Sputum/drug effects , Sulfhydryl Compounds/chemistry , Sulfhydryl Compounds/pharmacologyABSTRACT
For the investigation of glycosidases, and for the construction of glycan arrays the p-nitrophenyl- and p-aminophenyl glycosides of mucin O-glycan core structures 1-7 and the 2,6-ST-antigen have been chemically synthesized using d-galactose as a precursor for GalNAc residues. GlcNAc residues have partly been introduced using a 4,6-di-O-benzoyl-2,3-N,O-oxazolidinone-protected donor, which allowed deprotection of the formed di- and tri-saccharides in one step using sodium methoxide.
