Synthetic Multimeric Heptyl Mannosides as Potent Antiadhesives of UropathogenicEscherichia coli

Clusters of ligands on dendrimer surfaces

The development of methodology that is designed to allow a significant increase in the patterning and in the functionalization of the dendrimer is the ultimate goal of the research described here. Glycoside clusters based on TRIS were formed using click chemistry and were attached to PAMAM dendrimers. A series of dendrimers bearing tris-mannoside and an ethoxyethanol group was synthesized, and the binding interactions of these dendrimers with Concanavalin A were evaluated using inhibition ELISAs. The results of the inhibition ELISAs suggest that tris-mannoside clusters can replace individual sugars on the dendrimer without loss of function. Since tris-mannoside clustering allows for a redistribution of the dendrimers' surface functionalities, from this chemistry one can envision patterned dendrimers that incorporate multiple groups to increase the function and utility of the dendrimer.

Lactuca indica extract interferes with uroepithelial infection by Escherichia coli

ETHNOPHARMACOLOGICAL RELEVANCE

Uropathogenic Escherichia coli is the major cause for urinary tract infections (UTI). Due to emerging antimicrobial resistances treatment of UTI is becoming increasingly difficult. Therefore, alternative treatment strategies are required. We sought to investigate the molecular mechanisms of a traditionally used decoction from Vietnamese dandelion (Lactuca indica L.) mediating local protection of the bladder epithelium.

MATERIALS AND METHODS

To study the influence of herbal preparations on the interaction between bladder epithelial cells and uropthogenic Escherichia coli, a cell culture model of UTI was applied. In addition, the direct effect of the herbal extract on Escherichia coli was analyzed.

RESULTS

Although no direct antibacterial activity was determined, Lactuca indica decreased bacterial colonization of bladder epithelial cells remarkably. Reduced bacterial adherence was accompanied by lowered activation of focal adhesion kinase (FAK) in Lactuca indica exposed cells. Treatment with a chemical FAK inhibitor supported this mechanism of action.

CONCLUSIONS

These findings indicate that, in addition to its diuretic action, Lactuca indica exhibits secondary effects directly on epithelial cells which may protect against Escherichia coli infection. These properties might be useful for the development of alternative strategies in the treatment of UTI.

Novel concentrated cranberry liquid blend, UTI-STAT with Proantinox, might help prevent recurrent urinary tract infections in women

OBJECTIVES

To determine the safety, tolerability, maximal tolerated dose, and efficacy of a concentrated cranberry liquid blend, UTI-STAT with Proantinox, in female patients with a history of recurrent urinary tract infections (rUTIs).

METHODS

The study agent was administered orally at 15, 30, 45, 60, and 75 mL daily for 12 weeks to women with a history of 2.78 ± 0.73 rUTIs <6 months. Blood and urine samples were collected at baseline and weeks 4 and 12. The women took daily doses of the agent. The primary endpoints were the safety, tolerability, and maximal tolerated dose. The secondary endpoints were the efficacy with regard to rUTI and quality-of-life (QOL) symptoms.

RESULTS

A total of 28 subjects were included in the study. Of these 28 women, the data from 23 were analyzable. The average age was 46.5 ± 12.8 years. The maximal tolerated dose of UTI-STAT was 75 mL/d, and the recommended dose was set at 60 mL/d. The secondary endpoints demonstrated that only 2 (9.1%) of 23 reported a rUTI, a markedly better rate than the historical data. At 12 weeks, the reduction in worry about rUTIs and increased QOL with regard to the physical functioning domain and role limitations from physical health domain, as measured by the Medical Outcomes Study short-form 36-item questionnaire, were significant (P = .0097). A lower American Urological Association Symptom Index indicating greater QOL was also significant (P = .045).

CONCLUSIONS

The novel concentrated cranberry liquid blend showed a good safety profile and tolerability in both pre- and postmenopausal women with history of rUTIs. The secondary endpoints demonstrated its effectiveness in reducing the incidence of rUTI and increasing QOL. Given this evidence, supplementation might be beneficial in the prevention of rUTIs in this population.

Structure-based drug design and optimization of mannoside bacterial FimH antagonists

FimH-mediated cellular adhesion to mannosylated proteins is critical in the ability of uropathogenic E. coli (UPEC) to colonize and invade the bladder epithelium during urinary tract infection. We describe the discovery and optimization of potent small-molecule FimH bacterial adhesion antagonists based on alpha-d-mannose 1-position anomeric glycosides using X-ray structure-guided drug design. Optimized biarylmannosides display low nanomolar binding affinity for FimH in a fluorescence polarization assay and submicromolar cellular activity in a hemagglutination (HA) functional cell assay of bacterial adhesion. X-ray crystallography demonstrates that the biphenyl moiety makes several key interactions with the outer surface of FimH including pi-pi interactions with Tyr-48 and an H-bonding electrostatic interaction with the Arg-98/Glu-50 salt bridge. Dimeric analogues linked through the biaryl ring show an impressive 8-fold increase in potency relative to monomeric matched pairs and represent the most potent FimH antagonists identified to date. The FimH antagonists described herein hold great potential for development as novel therapeutics for the effective treatment of urinary tract infections.

Development of an aggregation assay to screen FimH antagonists

Alpha-D-mannopyranosides are potent FimH antagonists, which inhibit the adhesion of Escherichia coli to highly mannosylated uroplakin Ia on the urothelium and therefore offer an efficient therapeutic opportunity for the treatment and prevention of urinary tract infection. For the evaluation of the therapeutic potential of FimH antagonists, their effect on the disaggregation of E. coli from Candida albicans and guinea pig erythrocytes (GPE) was studied. The mannose-specific binding of E. coli to yeast cells and erythrocytes is mediated by type 1 pili and can be monitored by aggregometry. Maximal aggregation of C. albicans or GPE to E. coli is reached after 600 s. Then the FimH antagonist was added and disaggregation determined by light transmission over a period of 1400 s. A FimH-deleted mutant of E. coli, which does not induce any aggregation, was used in a control experiment. The activities of FimH antagonists are expressed as IC(50)s, the half maximal inhibitory concentration of the disaggregation potential. n-Heptyl alpha-D-mannopyranoside (1) was used as a reference compound and exhibits an IC(50) of 77.14 microM , whereas methyl alpha-D-mannopyranoside (2) does not lead to any disaggregation at concentrations up to 800 microM. o-Chloro-p-[N-(2-ethoxy-3,4-dioxocyclobut-1-enyl)amino]phenyl alpha-D-mannopyranoside (3) shows a 90-fold and 2-chloro-4-nitrophenyl alpha-D-mannopyranoside (4) a 6-fold increased affinity compared to 1. Finally, 4-nitrophenyl alpha-D-mannopyranoside (5) exhibits an activity similar to 1. As negative control, D-galactose (6) was used. The standardized aggregation assay generates concentration-dependent, reproducible data allowing the evaluation of FimH antagonists according to their potency to inhibit E. coli adherence and can therefore be employed to select candidates for experimental and clinical studies for treatment and prevention of urinary tract infections.

Efficient synthesis of fluorescent squaraine rotaxane dendrimers

A squaraine rotaxane scaffold with four alkyne groups is readily converted into a range of dendritic architectures using high-yielding copper-catalyzed alkyne azide cycloaddition (CuAAC) chemistry. A convergent synthesis approach is more efficient than a divergent pathway. Dendritic squaraine rotaxanes with peripheral amine groups can be further functionalized to produce multivalent deep-red fluorescent derivatives that exhibit high brightness and outstanding chemical stability in biological solution. The surface groups on these functionalized fluorescent dendrimers include guanidinium, mannose, and phosphatidylcholine.

Design and creativity in synthesis of multivalent neoglycoconjugates

From the authors' opinion, this chapter constitutes a modest extension of the seminal and inspiring contribution of Stowell and Lee on neoglycoconjugates published in this series [C. P. Stowell and Y. C. Lee, Adv. Carbohydr. Chem. Biochem., 37 (1980) 225-281]. The outstanding progresses achieved since then in the field of the "glycoside cluster effect" has witnessed considerable creativity in the design and synthetic strategies toward a vast array of novel carbohydrate structures and reflects the dynamic activity in the field even since the recent chapter by the Nicotra group in this series [F. Nicotra, L. Cipolla, F. Peri, B. La Ferla, and C. Radaelli, Adv. Carbohydr. Chem. Biochem., 61 (2007) 353-398]. Beyond the more classical neoglycoproteins and glycopolymers (not covered in this work) a wide range of unprecedented and often artistically beautiful multivalent and monodisperse nanostructures, termed glycodendrimers for the first time in 1993, has been created. This chapter briefly surveys the concept of multivalency involved in carbohydrate-protein interactions. The topic is also discussed in regard to recent steps undertaken in glycobiology toward identification of lead candidates using microarrays and modern analytical tools. A systematic description of glycocluster and glycodendrimer synthesis follows, starting from the simplest architectures and ending in the most complex ones. Presentation of multivalent glycostructures of intermediate size and comprising, calix[n]arene, porphyrin, cyclodextrin, peptide, and carbohydrate scaffolds, has also been intercalated to better appreciate the growing synthetic complexity involved. A subsection describing novel all-carbon-based glycoconjugates such as fullerenes and carbon nanotubes is inserted, followed by a promising strategy involving dendrons self-assembling around metal chelates. The chapter then ends with those glycodendrimers that have been prepared using commercially available dendrimers possessing varied functionalities, or systematically synthesized using either divergent or convergent strategies.