Galectin-3-Binding Glycomimetics that Strongly Reduce Bleomycin-Induced Lung Fibrosis and Modulate Intracellular Glycan Recognition.

Discovery of glycan-competitive galectin-3-binding compounds that attenuate lung fibrosis in a murine model and that block intracellular galectin-3 accumulation at damaged vesicles, hence revealing galectin-3-glycan interactions involved in fibrosis progression and in intracellular galectin-3 activities, is reported. 3,3'-Bis-(4-aryltriazol-1-yl)thiodigalactosides were synthesized and evaluated as antagonists of galectin-1, -2, -3, and -4 N-terminal, -4 C-terminal, -7 and -8 N-terminal, -9 N-terminal, and -9 C-terminal domains. Compounds displaying low-nanomolar affinities for galectins-1 and -3 were identified in a competitive fluorescence anisotropy assay. X-ray structural analysis of selected compounds in complex with galectin-3, together with galectin-3 mutant binding experiments, revealed that both the aryltriazolyl moieties and fluoro substituents on the compounds are involved in key interactions responsible for exceptional affinities towards galectin-3. The most potent galectin-3 antagonist was demonstrated to act in an assay monitoring galectin-3 accumulation upon amitriptyline-induced vesicle damage, visualizing a biochemically/medically relevant intracellular lectin-carbohydrate binding event and that it can be blocked by a small molecule. The same antagonist administered intratracheally attenuated bleomycin-induced pulmonary fibrosis in a mouse model with a dose/response profile comparing favorably with that of oral administration of the marketed antifibrotic compound pirfenidone.

Epoxyalcohols: bioactivation and conjugation required for skin sensitization.

Allylic alcohols, such as geraniol 1, are easily oxidized by varying mechanisms, including the formation of both 2,3-epoxides and/or aldehydes. These epoxides, aldehydes, and epoxy-aldehydes can be interconverted to each other, and the reactivity of them all must be considered when considering the sensitization potential of the parent allylic alcohol. An in-depth study of the possible metabolites and autoxidation products of allylic alcohols is described, covering the formation, interconversion, reactivity, and sensitizing potential thereof, using a combination of in vivo, in vitro, in chemico, and in silico methods. This multimodal study, using the integration of diverse techniques to investigate the sensitization potential of a molecule, allows the identification of potential candidate(s) for the true culprit(s) in allergic responses to allylic alcohols. Overall, the sensitization potential of the investigated epoxyalcohols and unsaturated alcohols was found to derive from metabolic oxidation to the more potent aldehyde where possible. Where this is less likely, the compound remains weakly or nonsensitizing. Metabolic activation of a double bond to form a nonconjugated, nonterminal epoxide moiety is not enough to turn a nonsensitizing alcohol into a sensitizer, as such epoxides have low reactivity and low sensitizing potency. In addition, even an allylic 2,3-epoxide moiety is not necessarily a potent sensitizer, as shown for 2, where formation of the epoxide weakens the sensitization potential.

Epoxy resin monomers with reduced skin sensitizing potency.

Epoxy resin monomers (ERMs), especially diglycidyl ethers of bisphenol A and F (DGEBA and DGEBF), are extensively used as building blocks for thermosetting polymers. However, they are known to commonly cause skin allergy. This research describes a number of alternative ERMs, designed with the aim of reducing the skin sensitizing potency while maintaining the ability to form thermosetting polymers. The compounds were designed, synthesized, and assessed for sensitizing potency using the in vivo murine local lymph node assay (LLNA). All six epoxy resin monomers had decreased sensitizing potencies compared to those of DGEBA and DGEBF. With respect to the LLNA EC3 value, the best of the alternative monomers had a value approximately 2.5 times higher than those of DGEBA and DGEBF. The diepoxides were reacted with triethylenetetramine, and the polymers formed were tested for technical applicability using thermogravimetric analysis and differential scanning calorimetry. Four out of the six alternative ERMs gave polymers with a thermal stability comparable to that obtained with DGEBA and DGEBF. The use of improved epoxy resin monomers with less skin sensitizing effects is a direct way to tackle the problem of contact allergy to epoxy resin systems, particularly in occupational settings, resulting in a reduction in the incidence of allergic contact dermatitis.

Skin sensitization of epoxyaldehydes: importance of conjugation.

Structure-activity relationship (SAR) models are important tools for predicting the skin sensitization potential of new compounds without animal testing. In compounds possessing a structural alert (aldehyde) and an activation alert (double bond), it is important to consider bioactivation/autoxidation (e.g., epoxidation). In the present study, we have explored a series of aldehydes with regard to contact allergy. The chemical reactivity of these 6 aldehydes toward a model hexapeptide was investigated, and their skin sensitization potencies were evaluated using the local lymph node assay (LLNA). Overall, we observed a similar trend for the in vitro reactivity and the in vivo sensitization potency for the structural analogues in this study. The highly reactive conjugated aldehydes (α,ß-unsaturated aldehydes and 2,3-epoxyaldehydes) are sensitizing moieties, while nonconjugated aldehydes and nonterminal aliphatic epoxides show low reactivity and low sensitization potency. Our data show the importance of not only double bond conjugation to aldehyde but also epoxide-aldehyde conjugation. The observations indicate that the formation of nonconjugated epoxides by bioactivation or autoxidation is not sufficient to significantly increase the sensitization potency of weakly sensitizing parent compounds.

Regulation of transforming growth factor-ß1-driven lung fibrosis by galectin-3.

RATIONALE: Idiopathic pulmonary fibrosis (IPF) is a chronic dysregulated response to alveolar epithelial injury with differentiation of epithelial cells and fibroblasts into matrix-secreting myofibroblasts resulting in lung scaring. The prognosis is poor and there are no effective therapies or reliable biomarkers. Galectin-3 is a ß-galactoside binding lectin that is highly expressed in fibrotic tissue of diverse etiologies. OBJECTIVES: To examine the role of galectin-3 in pulmonary fibrosis. METHODS: We used genetic deletion and pharmacologic inhibition in well-characterized murine models of lung fibrosis. Further mechanistic studies were performed in vitro and on samples from patients with IPF. MEASUREMENTS AND MAIN RESULTS: Transforming growth factor (TGF)-ß and bleomycin-induced lung fibrosis was dramatically reduced in mice deficient in galectin-3, manifest by reduced TGF-ß1-induced EMT and myofibroblast activation and collagen production. Galectin-3 reduced phosphorylation and nuclear translocation of ß-catenin but had no effect on Smad2/3 phosphorylation. A novel inhibitor of galectin-3, TD139, blocked TGF-ß-induced ß-catenin activation in vitro and in vivo and attenuated the late-stage progression of lung fibrosis after bleomycin. There was increased expression of galectin-3 in the bronchoalveolar lavage fluid and serum from patients with stable IPF compared with nonspecific interstitial pneumonitis and controls, which rose sharply during an acute exacerbation suggesting that galectin-3 may be a marker of active fibrosis in IPF and that strategies that block galectin-3 may be effective in treating acute fibrotic exacerbations of IPF. CONCLUSIONS: This study identifies galectin-3 as an important regulator of lung fibrosis and provides a proof of principle for galectin-3 inhibition as a potential novel therapeutic strategy for IPF.

Cinnamyl alcohol oxidizes rapidly upon air exposure.

BACKGROUND: Cinnamyl alcohol and cinnamal are frequent fragrance contact allergens. Both are included in the European baseline fragrance mix I, which is used for screening of contact allergy in dermatitis patients. OBJECTIVES: The aim of this study was to investigate the autoxidation of cinnamyl alcohol and to identify the oxidation products formed on air exposure. We also wanted to evaluate the effect of autoxidation on the sensitization potency of cinnamyl alcohol. METHODS: Samples of commercially available cinnamyl alcohol with and without purification were exposed to air, and the autoxidation was followed by chemical analysis. The analysis was performed with mass spectrometry (LC/MS/MS). Sensitization potencies of compounds were determined with the murine local lymph node assay (LLNA) in mice. RESULTS: Chemical analysis showed that the concentration of cinnamyl alcohol in the air-exposed samples decreased rapidly over time, and that autoxidation products were formed. Cinnamal, epoxy cinnamyl alcohol and cinnamic acid were identified as oxidation products. According to our study, cinnamal and epoxy cinnamyl alcohol were the first autoxidation products formed. The epoxy cinnamyl alcohol was shown to be the oxidation product with the highest sensitization potency. The analysis of our samples of commercially available cinnamyl alcohol showed that there was already a content of 1.5% cinnamal at the start of the autoxidation experiments. CONCLUSION: Cinnamyl alcohol readily autoxidizes upon air exposure, and forms strong sensitizers as determined by the LLNA. Cinnamal was formed in the largest amounts, showing that cinnamal is not only formed via bioactivation, as has previously been shown. A highly sensitizing epoxide was also identified and quantified in the oxidation mixture.

Analogues of the epoxy resin monomer diglycidyl ether of bisphenol F: effects on contact allergenic potency and cytotoxicity.

Diglycidyl ethers of bisphenol A (DGEBA) and bisphenol F (DGEBF) are widely used as components in epoxy resin thermosetting products. They are known to cause occupational and nonoccupational allergic contact dermatitis. The aim of this study is to investigate analogues of DGEBF with regard to contact allergy and cytotoxicity. A comprehensive knowledge of the structural features that contribute to the allergenic and cytotoxic effects of DGEBF will guide the development of future novel epoxy resin systems with reduced health hazards for those coming into contact with them. It was found that the allergenic effects of DGEBF were dependent on its terminal epoxide groups. In contrast, it was found that the cytotoxicity in monolayer cell culture was dependent not only on the presence of epoxide groups but also on other structural features.

Impact of a heteroatom in a structure-activity relationship study on analogues of phenyl glycidyl ether (PGE) from epoxy resin systems.

Epoxy resins are among the most common causes of occupational contact dermatitis. They are normally used in so-called epoxy resin systems (ERS). These commercial products are combinations of epoxy resins, curing agents, modifiers, and reactive diluents. The most frequently used resins are diglycidyl ethers based on bisphenol A (DGEBA) and bisphenol F (DGEBF). In this study, we have investigated the contact allergenic properties of a series of analogues to the reactive diluent phenyl glycidyl ether (PGE), all with similar basic structures but with varying heteroatoms or with no heteroatom present. The chemical reactivity of the compounds in the test series toward the hexapeptide H-Pro-His-Cys-Lys-Arg-Met-OH was investigated. All epoxides were shown to bind covalently to both cysteine and proline residues. The percent depletion of nonreacted peptide was also studied resulting in ca. 60% depletion when using either PGE, phenyl 2,3-epoxypropyl sulfide (2), or N-(2,3-epoxypropyl)aniline (3), and only 15% when using 1,2-epoxy-4-phenylbutane (4) at the same time point. The skin sensitization potencies of the epoxides using the murine local lymph node assay (LLNA) were evaluated in relation to the observed physicochemical and reactivity properties. To enable determination of statistical significance between structurally closely related compounds, a nonpooled LLNA was performed. It was found that all investigated compounds containing a heteroatom in the α-position to the epoxide were strong sensitizers, congruent with the reactivity data, indicating that the impact of a heteroatom is crucial for the sensitizing capacity for this type of epoxides.

Structure--activity relationship between the in vivo skin sensitizing potency of analogues of phenyl glycidyl ether and the induction of Nrf2-dependent luciferase activity in the KeratinoSens in vitro assay.

Because of regulatory constraints and ethical considerations, research on alternatives to animal testing to predict the skin sensitization potential of novel chemicals has become a high priority. Ideally, these alternatives should not only predict the hazard of novel chemicals but also rate the potency of skin sensitizers. Currently, no alternative method gives reliable potency estimations for a wide range of chemicals in differing structural classes. Performing potency estimations within specific structural classes has thus been proposed. Detailed structure-activity studies for the in vivo sensitization capacity of a series of analogues of phenyl glycidyl ether (PGE) were recently published. These studies are part of an investigation regarding the allergenic activity of epoxy-resin monomers. Here we report data on the same chemicals in the KeratinoSens in vitro assay, which is based on a stable transgenic keratinocyte cell line with a luciferase gene under the control of an antioxidant response element. A strong correlation between the EC3 values in the local lymph node assay (LLNA) and both the luciferase-inducing concentrations and the cytotoxicity in the cell-based assay was established for six analogues of PGE. This correlation allowed the potency in the LLNA of two novel structurally closely related derivatives to be predicted by read-across with errors of 1.4- and 2.6-fold. However, the LLNA EC3 values of two structurally different bifunctional monomers were overpredicted on the basis of this data set, indicating that accurate potency estimation by read-across based on in vitro data might be restricted to a relatively narrow applicability domain.

Protein flexibility and conformational entropy in ligand design targeting the carbohydrate recognition domain of galectin-3.

Rational drug design is predicated on knowledge of the three-dimensional structure of the protein-ligand complex and the thermodynamics of ligand binding. Despite the fundamental importance of both enthalpy and entropy in driving ligand binding, the role of conformational entropy is rarely addressed in drug design. In this work, we have probed the conformational entropy and its relative contribution to the free energy of ligand binding to the carbohydrate recognition domain of galectin-3. Using a combination of NMR spectroscopy, isothermal titration calorimetry, and X-ray crystallography, we characterized the binding of three ligands with dissociation constants ranging over 2 orders of magnitude. (15)N and (2)H spin relaxation measurements showed that the protein backbone and side chains respond to ligand binding by increased conformational fluctuations, on average, that differ among the three ligand-bound states. Variability in the response to ligand binding is prominent in the hydrophobic core, where a distal cluster of methyl groups becomes more rigid, whereas methyl groups closer to the binding site become more flexible. The results reveal an intricate interplay between structure and conformational fluctuations in the different complexes that fine-tunes the affinity. The estimated change in conformational entropy is comparable in magnitude to the binding enthalpy, demonstrating that it contributes favorably and significantly to ligand binding. We speculate that the relatively weak inherent protein-carbohydrate interactions and limited hydrophobic effect associated with oligosaccharide binding might have exerted evolutionary pressure on carbohydrate-binding proteins to increase the affinity by means of conformational entropy.

Metal swap between Zn7-metallothionein-3 and amyloid-beta-Cu protects against amyloid-beta toxicity.

Aberrant interactions of copper and zinc ions with the amyloid-beta peptide (Abeta) potentiate Alzheimer's disease (AD) by participating in the aggregation process of Abeta and in the generation of reactive oxygen species (ROS). The ROS production and the neurotoxicity of Abeta are associated with copper binding. Metallothionein-3 (Zn(7)MT-3), an intra- and extracellularly occurring metalloprotein, is highly expressed in the brain and downregulated in AD. This protein protects, by an unknown mechanism, cultured neurons from the toxicity of Abeta. Here, we show that a metal swap between Zn(7)MT-3 and soluble and aggregated Abeta(1-40)-Cu(II) abolishes the ROS production and the related cellular toxicity. In this process, copper is reduced by the protein thiolates forming Cu(I)(4)Zn(4)MT-3, in which an air-stable Cu(I)(4)-thiolate cluster and two disulfide bonds are present. The discovered protective effect of Zn(7)MT-3 from the copper-mediated Abeta(1-40) toxicity may lead to new therapeutic strategies for treating AD.

Preliminary investigations of the effect of lipophilic analogues of the active metabolite of isoniazid toward bacterial and plasmodial strains.

Five lipophilic analogues 1-5 of the active metabolite of the antitubercular drug isoniazid (INH), selected as inhibitors of Mycobacterium smegmatis and Mycobacterium tuberculosis growth, were evaluated for their activity against Corynebacterium glutamicum (lacking in InhA activity), Escherichia coli (to test mycobacteria selectivity), and Plasmodium falciparum (as possible parasite target). Compound 3 was the only one that did not inhibit C. glutamicum growth. The poor InhA inhibitors 1 and 2 were able to inhibit C. glutamicum and their anti(myco)bacterial mechanisms of action involve targets other than InhA. For the effective InhA inhibitors 4 and 5, also active against C. glutamicum and M. tuberculosis strains, more than one pathway should be envisaged to explain their actions. Pyridine-base ring analogues (1, 2, and 3) have no ability to inhibit the growth of E. coli even at a high concentration. Compound 3 thus exhibited a selective inhibitory action toward M. tuberculosis, while it was inactive on C. glutamicum and on E. coli growth. It presented an activity profile similar to that of INH suggesting InhA inhibition as one of the possible mechanisms of action. Finally, although a homologue of the reductase InhA exists in the FAS-II system of P. falciparum, 3 was unable to display antiplasmodial activity.

Development of isoniazid-NAD truncated adducts embedding a lipophilic fragment as potential bi-substrate InhA inhibitors and antimycobacterial agents.

Isoniazid-NAD truncated adducts embedding a lipophilic fragment were designed, synthesized and evaluated as inhibitors of the enoyl-acyl carrier protein (ACP) reductase (InhA) of Mycobacterium tuberculosis and as antimycobacterial agents. These compounds, planned as bi-substrate inhibitors and inspired from the active metabolite of isoniazid, combine both the nicotinamide moiety of the cofactor NAD and a lipophilic hydrocarbon chain mimic of the InhA substrate. The lipophilic fragment was introduced using either Suzuki-Miyaura cross-coupling or a classical nucleophilic substitution reaction. Several compounds developed in this work were indeed able to inhibit the InhA activity and showed promising antimycobacterial activities. However a direct correlation between the expressed activity and the bi-substrate mode of action could not yet be unambiguously demonstrated.

Synthesis and antitumor evaluation of analogues of the marine pyrroloiminoquinone tsitsikammamines.

Two series of analogues of the marine pyrroloiminoquinone alkaloids tsitsikammamine have been synthesized on the basis of a Michael addition between 2'-amino-1-(4-methoxyphenyl)-ethanol and two indolediones. All the compounds were evaluated in vitro for antiproliferative activity against distinct cancer cell lines.

Synthesis of 3-azido-3-deoxy-beta-D-galactopyranosides.

Three efficient routes to 3-azido-3-deoxy-beta-D-galactopyranosides were developed relying on a double inversion protocol at C3. Two of the routes were demonstrated to work with both O- and S-glycosides. In all three routes, the 2-O-acetyl-3-azido-4,6-O-benzylidene-3-deoxy-beta-D-galactopyranosides were obtained by an azide inversion of the key intermediates 2-O-acetyl-4,6-O-benzylidene-3-O-trifluoromethanesulfonyl-beta-D-gulopyranosides. The intermediate gulopyranosides were in turn obtained from 2-O-acetyl-4,6-O-benzylidene-3-O-trifluoromethanesulfonyl-beta-D-galactopyranosides, installed in one pot from the 4,6-O-benzylidene-beta-D-galactopyranosides, by inversion with nitrite or acetate. For O-glycosides, the gulopyranoside configuration could alternatively be obtained from the 4,6-O-benzylidene-beta-D-galactopyranoside by elimination to give the 2,3-dianhydro derivative followed by a highly stereoselective cis-dihydroxylation.

Galectin-3 targeted therapy with a small molecule inhibitor activates apoptosis and enhances both chemosensitivity and radiosensitivity in papillary thyroid cancer.

Although most patients with papillary thyroid cancer (PTC) have favorable outcomes, some have advanced PTC that is refractory to external beam radiation and systemic chemotherapy. Galectin-3 (Gal-3) is a beta-galactoside-binding protein with antiapoptotic activity that is consistently overexpressed in PTC. The purpose of this study is to determine if Gal-3 inhibition promotes apoptosis, chemosensitivity, and radiosensitivity in PTC. PTC cell lines (8505-C and TPC-1) and human ex vivo PTC were treated with a highly specific small molecule inhibitor of Gal-3 (Td131_1). Apoptotic activity was determined by flow cytometric analysis as well as caspase-3 and PARP cleavage. The minimum inhibitory concentrations of Td131_1 and doxorubicin were determined, and their combined effects were measured to test for synergistic activity. The effects of Td131_1 on radiosensitivity were determined by a clonogenic assay. Td131_1 promoted apoptosis, improved radiosensitivity, and synergistically enhanced chemosensitivity to doxorubicin in PTC cell lines. In PTC ex vivo, Td131_1 treatment alone induced the cleavage of caspase-3 and PARP. Td131_1 and doxorubicin together activated apoptosis in PTC ex vivo to a greater degree than their combined individual effects. Td131_1 activated apoptosis and had synergistic activity with doxorubicin in PTC. We conclude that Gal-3 targeted therapy is a promising therapeutic strategy for advanced PTC that is refractory to surgery and radioactive iodine therapy.

Galectin-inhibitory thiodigalactoside ester derivatives have antimigratory effects in cultured lung and prostate cancer cells.

Aromatic 3,3'-diesters of thiodigalactoside were synthesized in a rapid three-step sequence from commercially available thiodigalactoside and evaluated as inhibitors of cancer- and immunity-related galectins. For each of galectins-1, -3, -7, and -9N-terminal domain, aromatic 3,3'-diesters of thiodigalactoside were found to have affinities in the low micromolar range, which represents a 7-70 fold enhancement over thiodigalactoside itself. No significant improvement was found for galectin-8 N-terminal domain. Two of the compounds were selected for testing in cell culture and were shown to have potent antimigratory effects on human PC-3 prostate and human A549 nonsmall-cell lung cancer cells.

Binding of the tautomeric forms of isoniazid-NAD adducts to the active site of the Mycobacterium tuberculosis enoyl-ACP reductase (InhA): a theoretical approach.

The front-line antituberculosis drug isoniazid (INH) inhibits InhA, the NADH-dependent fatty acid biosynthesis enoyl ACP-reductase from Mycobacterium tuberculosis, via formation of covalent adducts with NAD (INH-NAD adducts). While ring tautomers were found the main species formed in solution, only the 4S chain INH-NAD tautomer was evidenced in the crystallized InhA:INH-NAD complex. In this study we attempted to explore the modes of interaction and energy binding of the different isomers placed in the active site of InhA with the help of various molecular modelling techniques. Ligand and enzyme models were generated with the help of the Vega ZZ program package. Resulting ligands were then docked into the InhA active site individually using computational automated docking package AUTODOCK 3.0.5. The more relevant docked conformations were then used to compute the interaction energy between the ligands and the InhA cavity. The AM1 Hamiltonian and the QM/MM ONIOM methodologies were used and the results compared. The various tautomers were found docked in almost the same place where INH-NAD was present as predicted by earlier X-ray crystallographic studies. However, some changes of ligand conformation and of the interactions ligand-protein were evidenced. The lower binding energy was observed for the 4S chain adduct that probably represents the effective active form of the INH-NAD adducts, as compared to the 4R epimer. The two 4S,7R and 4R,7S ring tautomers show intermediate and similar binding energies contrasting with their different experimental inhibitory potency on InhA. As a possible explanation based on calculated conformations, we formulated the hypothesis of an initial binding of the two ring tautomers to InhA followed by opening of only the ring hemiamidal 4S,7R tautomer (possibly catalyzed by Tyr158 phenolate basic group) to give the 4S chain INH-NAD tight-binding inhibitor. The predictions of ligand-protein interactions at the molecular level can be of primary importance in elucidating the mechanisms of action of isoniazid and InhA-related resistances, in identifying the effective mycobactericidal entities and, in further step, in the design of a new generation of antitubercular drugs.

Synthesis of the isonicotinoylnicotinamide scaffolds of the naturally occurring isoniazid-NAD(P) adducts.

The first syntheses of the 1-hydroxy-1-(pyridin-4-yl)-1,2-dihydro-3H-pyrrolo[3,4-c]pyridin-3-one heterocycle and the 3-aminocarbonyl-4-isonicotinoyl-1,4-dihydropyridine framework present in the isoniazid-NAD(P) adducts are described.