Synthesis of β-d-galactopyranoside-Presenting Glycoclusters, Investigation of Their Interactions with Pseudomonas aeruginosa Lectin A (PA-IL) and Evaluation of Their Anti-Adhesion Potential

Abstract

Pseudomonas aeruginosa is an opportunistic human pathogen associated with cystic fibrosis. This bacterium produces, among other virulence factors, a soluble d-galactose-specific lectin PA-IL (LecA). PA-IL plays an important role in the adhesion to the host cells and is also cytotoxic. Therefore, this protein is an interesting therapeutic target, suitable for inhibition by carbohydrate-based compounds. In the current study, β-d-galactopyranoside-containing tri- and tetravalent glycoclusters were synthesized. Methyl gallate and pentaerythritol equipped with propargyl groups were chosen as multivalent scaffolds and the galactoclusters were built from the above-mentioned cores by coupling ethylene or tetraethylene glycol-bridges and peracetylated propargyl β-d-galactosides using 1,3-dipolar azide-alkyne cycloaddition. The interaction between galactoside derivatives and PA-IL was investigated by several biophysical methods, including hemagglutination inhibition assay, isothermal titration calorimetry, analytical ultracentrifugation, and surface plasmon resonance. Their ability to inhibit the adhesion of P. aeruginosa to bronchial cells was determined by ex vivo assay. The newly synthesized multivalent galactoclusters proved to be significantly better ligands than simple d-galactose for lectin PA-IL and as a result, two representatives of the dendrimers were able to decrease adhesion of P. aeruginosa to bronchial cells to approximately 32% and 42%, respectively. The results may provide an opportunity to develop anti-adhesion therapy for the treatment of P. aeruginosa infection.

Modified Galacto‐ or Fuco‐Clusters Exploiting the Siderophore Pathway to Inhibit the LecA‐ or LecB‐Associated Virulence of Pseudomonas aeruginosa

“…Such a 70 % inhibition of PA ability to colonise pulmonary cell ex‐vivo using β‐D‐galactopyranoside‐presenting glycoclusters was also observed by Malinovská and co‐workers using higher concentrations of inhibitor (up to 2 mM) [10c] . The galactoclusters developed herein seem, up to date, being more efficient to reduce PA infection on pulmonary cells and should be good candidates to further in vivo protection assay in an animal model.…”

Synthesis of Tetravalent Thio- and Selenogalactoside-Presenting Galactoclusters and Their Interactions with Bacterial Lectin PA-IL from Pseudomonas aeruginosa

“…Digalactosyl diselenide 4a and digalactosyl disulfide 4b [ 19 ] are known from the literature and were also suitable and available for binding studies as divalent galactoside ligands. The tetravalent glycoconjugates were built up by copper (I)-mediated azide-alkyne click reaction of alkyne 2a or 2b with azido-scaffold 5 [ 12 ] . The acetylated thiogalactocluster 6a and selenogalactocluster 6b were isolated with a yield of 81% and 88%, respectively.…”

“…In summary, tetravalent S - and Se -galactoclusters synthesized by click-chemistry were found to be suitable ligands of the lectin PA-IL in vitro, with significant, about 64 times better inhibitory activity than simple d -galactose. We can also conclude that enzymatically stable S - [ 32 ] and Se -interglycosidic linkages [ 17 , 18 ] do not influence the potency of ligands compared with the appropriate O -glycosides [ 12 ]. We could prove using STD-NMR techniques that the multivalent ligands compete with the natural ligand for the binding sites of the protein.…”

“…Our previous works presented several potential inhibitors of various lectins of bacterial and fungal origin [ 11 ]. Recently, a tetravalent lead compound I for anti-adhesion therapy of Pseudomonas aeruginosa infections was developed ( Figure 1 ) [ 12 ].…”

“…P. aerugin produces a tetrameric D-galactose-specific lectin named PA-IL (LecA) which is conside to be involved in adhesion, biofilm formation, cellular invasion and cytotoxicity [6][7][8][9][10] Our previous works presented several potential inhibitors of various lectins of b terial and fungal origin [11]. Recently, a tetravalent lead compound I for anti-adhes therapy of Pseudomonas aeruginosa infections was developed (Figure 1) [12]. Our current aim is to synthesize the thio-and selenoglycoside analogues of the te valent lead-structure as well as their intermediate compounds to investigate their bind properties towards lectin PA-IL and the effect of sulfur and selenium on lectin bindi Several selenium-containing carbohydrates are known from the literature.…”