Cristina Nativi

Inhibition and Dispersion of Pseudomonas aeruginosa Biofilms by Glycopeptide Dendrimers Targeting the Fucose-Specific Lectin LecB

The human pathogenic bacterium Pseudomonas aeruginosa produces a fucose-specific lectin, LecB, implicated in tissue attachment and the formation of biofilms. To investigate if LecB inhibition disrupts these processes, high-affinity ligands were obtained by screening two 15,536-member combinatorial libraries of multivalent fucosyl-peptide dendrimers. The most potent LecB-ligands identified were dendrimers FD2 (C-Fuc-LysProLeu)(4)(LysPheLysIle)(2)LysHisIleNH(2) (IC(50) = 0.14 microM by ELLA) and PA8 (OFuc-LysAlaAsp)(4)(LysSerGlyAla)(2)LysHisIleNH(2) (IC(50) = 0.11 microM by ELLA). Dendrimer FD2 led to complete inhibition of P. aeruginosa biofilm formation (IC(50) approximately 10 microM) and induced complete dispersion of established biofilms in the wild-type strain and in several clinical P. aeruginosa isolates. These experiments suggest that LecB inhibition by high-affinity multivalent ligands could represent a therapeutic approach against P. aeruginosa infections by inhibition of biofilm formation and dispersion of established biofilms.

A Glycopeptide Dendrimer Inhibitor of the Galactose-Specific Lectin Leca and of Pseudomonas Aeruginosa Biofilms.

Biofilm inhibition is achieved with a phenylgalactosyl peptide dendrimer (see picture) that binds to the galactose-specific lectin LecA of P. aeruginosa. The multivalency of the ligands is critical for biofilm inhibition, although the nature of the linker between the peptide dendrimer and the galactose can provide additional contacts to the lectin and also has an effect on the interaction.

Carbonic anhydrase IX from cancer-associated fibroblasts drives epithelial-mesenchymal transition in prostate carcinoma cells

Extracellular acidification, a mandatory feature of several malignancies, has been mainly correlated with metabolic reprogramming of tumor cells toward Warburg metabolism, as well as to the expression of carbonic anydrases or proton pumps by malignant tumor cells. We report herein that for aggressive prostate carcinoma, acknowledged to be reprogrammed toward an anabolic phenotype and to upload lactate to drive proliferation, extracellular acidification is mainly mediated by stromal cells engaged in a molecular cross-talk circuitry with cancer cells. Indeed, cancer-associated fibroblasts, upon their activation by cancer delivered soluble factors, rapidly express carbonic anhydrase IX (CA IX). While expression of CAIX in cancer cells has already been correlated with poor prognosis in various human tumors, the novelty of our findings is the upregulation of CAIX in stromal cells upon activation. The de novo expression of CA IX, which is not addicted to hypoxic conditions, is driven by redox-based stabilization of hypoxia-inducible factor-1. Extracellular acidification due to carbonic anhydrase IX is mandatory to elicit activation of stromal fibroblasts delivered metalloprotease-2 and -9, driving in cancer cells the epithelial-mesenchymal transition epigenetic program, a key event associated with increased motility, survival and stemness. Both genetic silencing and pharmacological inhibition of CA IX (with sulfonamide/sulfamides potent inhibitors) or metalloprotease-9 are sufficient to impede epithelial-mesenchymal transition and invasiveness of prostate cancer cells induced by contact with cancer-associated fibroblasts. We also confirmed in vivo the upstream hierarchical role of stromal CA IX to drive successful metastatic spread of prostate carcinoma cells. These data include stromal cells, as cancer-associated fibroblasts as ideal targets for carbonic anhydrase IX-directed anticancer therapies.

Phthalimidosulfenyl chloride. Part 5. Reaction with enolizable carbonyl compounds and synthesis of functionalized thiones.

Abstract β-Ketothio derivatives 4, prepared by reaction of phthalimidosulphenyl chloride with enolizable carbonyl compounds, afford, in presence of pyridine, unstable functionalized thiones which can be trapped with 1,3-dienes to give the corresponding cycloaddition products 8 and 9.

Chiral Diaminopyrrolic Receptors for Selective Recognition of Mannosides, Part 1: Design, Synthesis, and Affinities of Second‐Generation Tripodal Receptors

A new generation of chiral tripodal receptors for recognition of carbohydrates, featuring trans-1,2-diaminocyclohexane as a key structural element, and their recognition properties toward a set of glycosides of biologically relevant monosaccharides is described. The introduction of a chelating diamino unit into the pyrrolic tripodal architecture markedly enhanced their binding abilities compared with the parent aminopyrrolic receptors previously reported by our group. In addition, the chirality of the structure had a clear impact on affinities, as well as on selectivities, displaying high enantiodiscrimination levels. These second-generation diaminopyrrolic tripodal receptors are highly selective for mannose among other monosaccharides, with two members of the family being selective for the α and the β anomers respectively. The measured affinities in acetonitrile, 83 μM of (S)-7 for the β mannoside and 127 μM of (R)-5 for the α mannoside, make them the most effective synthetic receptors for mannosides reported to date. The affinity assessment required a further evolution of the BC(0)(50) parameter, a previously developed binding descriptor, which in its ultimate formulation has now been extended to include, with no restrictions, complexes of any stoichiometry, and can thus be generally employed to rank affinity data from heterogeneous systems on a common scale.

α‐O‐Linked Glycopeptide Mimetics: Synthesis, Conformation Analysis, and Interactions with Viscumin, a Galactoside‐Binding Model Lectin

Efficient cycloaddition of a silylidene-protected galactal with a suitable heterodiene yielded the basis for a facile diastereoselective route to a glycopeptide-mimetic scaffold. Its carbohydrate part was further extended by beta1-3-linked galactosylation. The pyranose rings retain their (4)C(1) chair conformation, as shown by molecular modeling and NMR spectroscopy, and the typical exo-anomeric geometry was observed for the disaccharide. The expected bioactivity was ascertained by saturation-transfer-difference NMR spectroscopy by using the galactoside-specific plant toxin viscumin as a model lectin. The experimental part was complemented by molecular docking. The described synthetic route and the strategic combination of computational and experimental techniques to reveal conformational properties and bioactivity establish the prepared alpha-O-linked glycopeptide mimetics as promising candidates for further exploitation of this scaffold to give O-glycans for lectin blocking and vaccination.

A TRPA1 antagonist reverts oxaliplatin-induced neuropathic pain

Neuropathic pain (NeP) is generally considered an intractable problem, which becomes compelling in clinical practice when caused by highly effective chemotherapeutics, such as in the treatment of cancer with oxaliplatin (OXA) and related drugs. In the present work we describe a structurally new compound, ADM_09, which proved to effectively revert OXA-induced NeP in vivo in rats without eliciting the commonly observed negative side-effects. ADM_09 does not modify normal behavior in rats, does not show any toxicity toward astrocyte cell cultures, nor any significant cardiotoxicity. Patch-clamp recordings demonstrated that ADM_09 is an effective antagonist of the nociceptive sensor channel TRPA1, which persistently blocks mouse as well as human variants of TRPA1. A dual-binding mode of action has been proposed for ADM_09, in which a synergic combination of calcium-mediated binding of the carnosine residue and disulphide-bridge-forming of the lipoic acid residue accounts for the observed persistent blocking activity toward the TRPA1 channel.

ortho‐Thioquinones, New Acceptors for the Stereoselective Synthesis of Aryl 2‐Deoxy‐O‐Glycosides

Unconventionalglycosylation: Under mild conditions, aryl 2-deoxy-α or -β-O-glycosides can be selectively obtained by capitalizing on ortho-thioquinones as new acceptors (scheme).

Chiral Diaminopyrrolic Receptors for Selective Recognition of Mannosides, Part 2: A 3D View of the Recognition Modes by X‐ray, NMR Spectroscopy, and Molecular Modeling

The structural features of a representative set of five complexes of octyl α- and β-mannosides with some members of a new generation of chiral tripodal diaminopyrrolic receptors, namely, (R)-5 and (S)- and (R)-7, have been investigated in solution and in the solid state by a combined X-ray, NMR spectroscopy, and molecular modeling approach. In the solid state, the binding arms of the free receptors 7 delimit a cleft in which two solvent molecules are hydrogen bonded to the pyrrolic groups and to the benzenic scaffold. In a polar solvent (CD(3)CN), chemical shift and intermolecular NOE data, assisted by molecular modeling calculations, ascertained the binding modes of the interaction between the receptor and the glycoside for these complexes. Although a single binding mode was found to adequately describe the complex of the acyclic receptor 5 with the α-mannoside, for the complexes of the cyclic receptors 7 two different binding modes were required to simultaneously fit all the experimental data. In all cases, extensive binding through hydrogen bonding and CH-π interactions is responsible for the affinities measured in the same solvent. Furthermore, the binding modes closely account for the recognition preferences observed toward the anomeric glycosides and for the peculiar enantiodiscrimination properties exhibited by the chiral receptors.

A Cancer Therapeutic Vaccine based on Clustered Tn‐Antigen Mimetics Induces Strong Antibody‐Mediated Protective Immunity

Tumor-associated carbohydrate antigens (TACAs) are key components of cancer vaccines. A variety of vaccines based on native TACAs such as α-Tn have shown immunogenicity and protection in preclinical animal studies, however, their weak immunogenicity, low in vivo instability, and poor bioavailability, have discouraged their further evaluations in clinical studies. A new improved vaccine prototype is reported. It is composed of four clustered Tn-antigen mimetics and a immunogenic peptide epitope that are conjugated to a cyclopeptide carrier. The immunization of mice with this vaccine 1) was safe, 2) induced a strong and long-lasting Tn-specific response with IgM/IgG antibodies able to recognize native carbohydrate antigens; 3) produced high titers of IgG1, IgG2a, and IgG3 antibodies; and 4) produced a significant antibody-dependent regression of tumors and conferred protection. Altogether, these findings pave the way for the clinical development of safe and effective therapeutic vaccines against Tn-expressing cancers.