Biomedical subjects

Thierry Langer

Publications and source records attributed to Thierry Langer.

At least 19 recordsLinked to original sources

PubMed2006

Further studies on imidazo[4,5-b]pyridine AT1 angiotensin II receptor antagonists. Effects of the transformation of the 4-phenylquinoline backbone into 4-phenylisoquinolinone or 1-phenylindene scaffolds.

The 4-phenylquinoline fragment of novel AT(1) receptor antagonists 4 based on imidazo[4,5-b]pyridine moiety was replaced by 4-phenylisoquinolinone (compounds 5) or 1-phenylindene (compounds 6) scaffolds to investigate the structure-activity relationships. Binding studies showed that most of the synthesized compounds display high affinity for the AT(1) receptor. Because of the in vitro high potency of carboxylic acids 5b,f, they were evaluated in permeability (in Caco-2 cells) and in pharmacokinetic studies in comparison with quinoline derivatives 4b,i,j,k. The studies showed that these compounds are characterized by rapid excretion, low membrane permeability, and low oral bioavailability. The structure optimization of the indene derivatives led to compounds 6e,f possessing interesting AT(1) receptor affinities. Optimization produced polymerizing AT(1) receptor ligand 6c, which forms a thermoreversible polymer (poly-6c) and is released from the latter by a temperature-dependent kinetics. The results suggest the possibility of developing novel polymeric prodrugs based on a new release mechanism. Finally, a set of 34 AT(1) receptor antagonists was used as a new test for the evaluation of the predictive capability of the previously published qualitative and quantitative pharmacophore models.

Angiotensin II Type 1 Receptor Blockers↗

PubMed2006

Design, synthesis, and SAR analysis of novel selective sigma1 ligands.

A new series of arylalkyl- and alkenylamines was designed, synthesized, and evaluated for binding to sigma(1) and sigma(2) receptors. Many compounds exhibited nanomolar affinity for sigma(1) subtype receptor with good selectivity over sigma(2). A molecular modeling study was conducted in order to rationalize the experimental data, and the structure-receptor affinities are discussed.

Animals↗

PubMed2006

Efficient overlay of small organic molecules using 3D pharmacophores.

Aligning and overlaying two or more bio-active molecules is one of the key tasks in computational drug discovery and bio-activity prediction. Especially chemical-functional molecule characteristics from the view point of a macromolecular target represented as a 3D pharmacophore are the most interesting similarity measure when describing and analyzing macromolecule-ligand interaction. In this study, a novel approach for aligning rigid three-dimensional molecules according to their chemical-functional pharmacophoric features is presented and compared to the overlay of experimentally determined poses in a comparable macromolecule coordinate frame. The presented approach identifies optimal chemical feature pairs using distance and density characteristics obtained by correlating pharmacophoric geometries and thus proves to be faster than existing combinatorial alignment methods and creates more reasonable alignments than pure atom-based methods. Examples will be provided to demonstrate the feasibility, speed and intuitiveness of this method.

Algorithms↗

PubMed2006

High-throughput structure-based pharmacophore modelling as a basis for successful parallel virtual screening.

In order to assess bioactivity profiles for small organic molecules we propose to use parallel pharmacophore-based virtual screening. Our aim is to provide a fast, reliable and scalable system that allows for rapid in silico activity profile prediction of virtual molecules. In this proof of principle study, carried out with the new structure-based pharmacophore modelling tool LigandScout and the high-performance database mining platform Catalyst, we present a model work for the application of parallel pharmacophore-based virtual screening on a set of 50 structure-based pharmacophore models built for various viral targets and 100 antiviral compounds. The latter were screened against all pharmacophore models in order to determine if their known biological targets could be correctly predicted via an enrichment of corresponding pharmaco-phores matching these ligands. The results demonstrate that the desired enrichment, i.e. a successful activity profiling, was achieved for approximately 90% of all input molecules. Additionally, we discuss descriptors for output validation, as well as various aspects influencing the analysis of the obtained activity profiles, and the effect of the searching mode utilized for screening. The results of the study presented here clearly indicate that pharmacophore-based parallel screening comprises a reliable in silico method to predict the potential biological activities of a compound or a compound library by screening it against a series of pharmacophore queries.

Antiviral Agents↗

PubMed2006

The discovery of new 11beta-hydroxysteroid dehydrogenase type 1 inhibitors by common feature pharmacophore modeling and virtual screening.

11beta-Hydroxysteroid dehydrogenase (11beta-HSD) enzymes catalyze the conversion of biologically inactive 11-ketosteroids into their active 11beta-hydroxy derivatives and vice versa. Inhibition of 11beta-HSD1 has considerable therapeutic potential for glucocorticoid-associated diseases including obesity, diabetes, wound healing, and muscle atrophy. Because inhibition of related enzymes such as 11beta-HSD2 and 17beta-HSDs causes sodium retention and hypertension or interferes with sex steroid hormone metabolism, respectively, highly selective 11beta-HSD1 inhibitors are required for successful therapy. Here, we employed the software package Catalyst to develop ligand-based multifeature pharmacophore models for 11beta-HSD1 inhibitors. Virtual screening experiments and subsequent in vitro evaluation of promising hits revealed several selective inhibitors. Efficient inhibition of recombinant human 11beta-HSD1 in intact transfected cells as well as endogenous enzyme in mouse 3T3-L1 adipocytes and C2C12 myotubes was demonstrated for compound 27, which was able to block subsequent cortisol-dependent activation of glucocorticoid receptors with only minor direct effects on the receptor itself. Our results suggest that inhibitor-based pharmacophore models for 11beta-HSD1 in combination with suitable cell-based activity assays, including such for related enzymes, can be used for the identification of selective and potent inhibitors.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗

PubMed2006

GBPM: GRID-based pharmacophore model: concept and application studies to protein-protein recognition.

MOTIVATION: Automatic procedures to obtain pharmacophore models from experimentally determined macromolecular complexes can help in the drug discovery process, especially when protein-protein recognition plays an important biological role. RESULTS: The GRID-based pharmacophore model (GBPM) is a fully objective method for defining most relevant interaction areas in complexes deriving pharmacophore models from three-dimensional (3D) molecular structure information. It is based on logical and clustering operations with 3D maps computed by the GRID program on structurally known molecular complexes. In this manuscript we describe the concept and discuss application examples regarding protein-protein recognition. In particular two complexes selected in the Protein Data Bank have been tested to evaluate the GBPM capability to identify interaction areas. The results obtained show the capabilities of this new bioinformatic method.

Algorithms↗

PubMed2006

Why is 11beta-hydroxysteroid dehydrogenase type 1 facing the endoplasmic reticulum lumen? Physiological relevance of the membrane topology of 11beta-HSD1.

11Beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) is essential for the local activation of glucocorticoid receptors (GR). Unlike unliganded cytoplasmic GR, 11beta-HSD1 is an endoplasmic reticulum (ER)-membrane protein with lumenal orientation. Cortisone might gain direct access to 11beta-HSD1 by free diffusion across membranes, indirectly via intracellular binding proteins or, alternatively, by insertion into membranes. Membranous cortisol, formed by 11beta-HSD1 at the ER-lumenal side, might then activate cytoplasmic GR or bind to ER-lumenal secretory proteins. Compartmentalization of 11beta-HSD1 is important for its regulation by hexose-6-phosphate dehydrogenase (H6PDH), which regenerates cofactor NADPH in the ER lumen and stimulates oxoreductase activity. ER-lumenal orientation of 11beta-HSD1 is also essential for the metabolism of the alternative substrate 7-ketocholesterol (7KC), a major cholesterol oxidation product found in atherosclerotic plaques and taken up from processed cholesterol-rich food. An 11beta-HSD1 mutant adopting cytoplasmic orientation efficiently catalyzed the oxoreduction of cortisone but not 7KC, indicating access to cortisone from both sides of the ER-membrane but to 7KC only from the lumenal side. These aspects may be relevant for understanding the physiological role of 11beta-HSD1 and for developing therapeutic interventions to control glucocorticoid reactivation.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗

PubMed2006

Taspine: bioactivity-guided isolation and molecular ligand-target insight of a potent acetylcholinesterase inhibitor from Magnolia x soulangiana.

A bioactivity-guided approach was taken to identify the acetylcholinesterase (AChE, EC 3.1.1.7) inhibitory agent in a Magnolia x soulangiana extract using a microplate enzyme assay with Ellman's reagent. This permitted the isolation of the alkaloids taspine (1) and (-)-asimilobine (2), which were detected for the first time in this species. Compound 1 showed a significantly higher effect on AChE than the positive control galanthamine and selectively inhibited the enzyme in a long-lasting and concentration-dependent fashion with an IC(50) value of 0.33 +/- 0.07 muM. Extensive molecular docking studies were performed with human and Torpedo californica-AChE employing Gold software to rationalize the binding interaction. The results suggested ligand 1 to bind in an alternative binding orientation when compared to galanthamine. While this is located in close vicinity to the catalytic amino acid triad, the 1-AChE complex was found to be stabilized by (i) sandwich-like pi-stacking interactions between the planar aromatic ligand (1) and the Trp84 and Phe330 of the enzyme, (ii) an esteratic site anchoring with the amino side chain, and (iii) a hydrogen-bonding network.

Alkaloids↗

PubMed2006

Synthesis, biological evaluation and 3D-QSAR of 1,3,5-trisubstituted-4,5-dihydro-(1H)-pyrazole derivatives as potent and highly selective monoamine oxidase A inhibitors.

The present report provides a extended study of the chemistry, the inhibitory activity against monoamino oxidases (MAO), and molecular modeling including the 3D-QSAR hypothesis of 1,3,5-trisubstituted-4,5-dihydro-(1H)-pyrazole derivatives. Four series of about eighty novel pyrazoline derivatives were prepared and investigated for their ability to inhibit the activity of the A and B isoforms of MAO selectively. Most of the new synthesized compounds proved more reversible, potent, and selective inhibitors of MAO-A than of MAO-B, and could be taken into account to develop the search further in this field, knowing that reversible and selective MAO-A inhibitors are used as antidepressant and antianxiety drug. The 30 most active compounds show inhibitory activity on MAO-A in the 8.6 x 10(-8) - 9.0 x 10(-9)M range. Moreover, it should be pointed out that for most of them a high IC(50) > or = 10(-9)M value is associated with a high A-selectivity (Selectivity Index MAO-B/MAO-A in the 10,000-16,250 range). Furthermore, due to the presence of a chiral centre at the C5 position of the pyrazole moiety, we performed the semi-preparative chromatographic enantioseparation of the most potent, selective, and chiral compounds. The separated enantiomers were then submitted to in vitro biological evaluation, and from the results of these experiments it has been possible to point out a difference in inhibiting the two isoforms selectively between the racemic mixture and the single enantiomers. The molecular modeling work was carried out combining the Glide docking approach with CoMFA with the aim to rationalize the structure-activity relationships of each pyrazoline inhibitor toward MAO-A and MAO-B isoforms and to derive a suitable selectivity model.

Animals↗

PubMed2006

Predicting drug metabolism induction in silico.

The inducibility of drug-metabolizing enzymes and transporters by numerous xenobiotics has become a vital issue to be considered in the drug development process. Activation of so-called orphan nuclear receptors has been identified to result in increased expression of these detoxifying systems and consequently altered drug levels in the human body. In order to anticipate such mechanisms already in early stages of drug design and to avoid dangerous drug-drug interactions, reliable in silico simulation tools are highly desirable. This review aims to give an introduction into induction of drug metabolism and transport and focuses on computer-assisted molecular modeling prediction techniques, on their applicability and limitations, on recent case studies, and on success stories.

Animals↗

PubMed2006

Development and validation of an in silico P450 profiler based on pharmacophore models.

In today's drug discovery process, the very early consideration of ADME properties is aimed at a reduction of drug candidate drop out rate in later development stages. Apart from in vitro testing, in silico methods are evaluated as complementary screening tools for compounds with unfavorable ADME attributes. Especially members of the cytochrome P450 (P450) enzyme superfamily-- e.g. P450 1A2, P450 2C9, P450 2C19, P450 2D6, and P450 3A4-- contribute to xenobiotic metabolism, and compound interaction with one of these enzymes is therefore critically evaluated. Pharmacophore models are widely used to identify common features amongst ligands for any target. In this study, both structure-based and ligand-based models for prominent drug-metabolizing members of the P450 family were generated employing the software packages LigandScout and Catalyst. Essential chemical ligand features for substrate and inhibitor activity for all five P450 enzymes investigated were determined and analyzed. Finally, a collection of 11 pharmacophores for substrates and inhibitors was evaluated as an in silico P450 profiling tool that could be used for early ADME estimation of new chemical entities.

Cytochrome P-450 Enzyme Inhibitors↗

PubMed2005

Synthesis and pharmacological evaluation of 1H-imidazoles as ligands for the estrogen receptor and cytotoxic inhibitors of the cyclooxygenase.

The 1H-imidazoles 7a-e were synthesized and tested for biological activity in vitro. The results pointed to a clear structure-activity relationship. The introduction of an ethyl chain at C5 of the 1,2,4-tris(4-hydroxyphenyl)-1H-imidazole 7a caused hormonal activity in estrogen receptor positive MCF-7-2a cells. An o-chlorine substituent in the phenolic rings at C2 and C4 as realized in 7b and 7c increased the antiproliferative effects against human breast cancer cell lines MCF-7 and MDA-MB 231. Additionally, both compounds showed strong inhibitory effects on cyclooxygenase enzymes. Therefore, a mode of action including the interference in the arachidonic acid cascade might be possible.

Antineoplastic Agents↗

PubMed2005

Pharmacophore modeling, docking, and principal component analysis based clustering: combined computer-assisted approaches to identify new inhibitors of the human rhinovirus coat protein.

The development and application of a sophisticated virtual screening and selection protocol to identify potential, novel inhibitors of the human rhinovirus coat protein employing various computer-assisted strategies are described. A large commercially available database of compounds was screened using a highly selective, structure-based pharmacophore model generated with the program Catalyst. A docking study and a principal component analysis were carried out within the software package Cerius and served to validate and further refine the obtained results. These combined efforts led to the selection of six candidate structures, for which in vitro anti-rhinoviral activity could be shown in a biological assay.

Antiviral Agents↗

PubMed2005

Discovery of high-affinity ligands of sigma1 receptor, ERG2, and emopamil binding protein by pharmacophore modeling and virtual screening.

ERG2, emopamil binding protein (EBP), and sigma-1 receptor (sigma(1)) are enzymes of sterol metabolism and an enzyme-related protein, respectively, that share high affinity for various structurally diverse compounds. To discover novel high-affinity ligands, pharmacophore models were built with Catalyst based upon a series of 23 structurally diverse chemicals exhibiting K(i) values from 10 pM to 100 microM for all three proteins. In virtual screening experiments, we retrieved drugs that were previously reported to bind to one or several of these proteins and also tested 11 new hits experimentally, of which three, among them raloxifene, had affinities for sigma(1) or EBP of <60 nM. When used to search a database of 3525 biochemicals of intermediary metabolism, a slightly modified ERG2 pharmacophore model successfully retrieved 10 substrate candidates among the top 28 hits. Our results indicate that inhibitor-based pharmacophore models for sigma(1), ERG2, and EBP can be used to screen drug and metabolite databases for chemically diverse compounds and putative endogenous ligands.

Animals↗

PubMed2005

Structure-activity relationships and molecular modelling of 5-arylidene-2,4-thiazolidinediones active as aldose reductase inhibitors.

The structure-activity relationships (SARs) of 5-arylidene-2,4-thiazolidinediones active as aldose reductase inhibitors (ARIs) were extended by varying the substitution pattern on the 5-arylidene moiety and on N-3. In particular, the introduction of an additional aromatic ring or an H-bond donor group on the 5-benzylidene ring enhanced ALR2 inhibitory potency. Moreover, the presence of a carboxylic anionic chain on N-3 was shown to be an important, although not essential, structural requisite to produce high levels of ALR2 inhibition. The length of this carboxylic chain was critical and acetic acids 4 were the most effective inhibitors among the tested derivatives. Molecular docking simulations into the ALR2 active site accorded with the in vitro inhibition data. They allowed the rationalization of the observed SARs and provided a pharmacophoric model for this class of ARIs.

Aldehyde Reductase↗

PubMed2005

Discovering COX-inhibiting constituents of Morus root bark: activity-guided versus computer-aided methods.

The aim of this study was to compare the efficiency of two well known approaches for the discovery of the bioactive principle/s in medicinal plants, namely the activity-guided isolation versus the computer-aided drug discovery by means of virtual screening (VS) techniques. Morus root bark of Morus sp. L. (Moraceae) was selected as application example for the discovery of compounds with anti-inflammatory activity. The two cyclooxygenase isoenzymes COX-1 and COX-2 were chosen as targets and the corresponding pharmacophore models were generated by our research. The activity-guided fractionation of the methanol extract of the root bark resulted in the isolation of nine compounds. Their structures were elucidated by mass spectrometry, 1- and 2-dimensional NMR experiments and identified as moracins B, M, the regioisomers O/P as a mixture, and sanggenons B, C, D, E and O. The COX-1 and COX-2 inhibiting activities of these compounds were established in an enzyme assay and compared with the predicted hits obtained from the VS. Sanggenons C, E, and O, that were tested the first time for an inhibitory effect on COX-1 and -2, showed IC50 values of 10-14 microM, and 40-50 microM, respectively. The results show that the COX activities obtained for the sanggenons are correctly predicted by the in silico filtering experiment. In the case of the isolated moracins, however, it failed because the COX inhibiting activities of moracins M and P/O were not retrieved by the VS. Structure-activity relationships of the isolated compounds are discussed as well as potential pitfalls and advantages of the applied strategies.

Cyclooxygenase 1↗

PubMed2005

Comparative enzymology of 11beta-hydroxysteroid dehydrogenase type 1 from six species.

11beta-Hydroxysteroid dehydrogenase type 1 (11beta-HSD1), catalyzing the intracellular activation of cortisone to cortisol, is currently considered a promising target to treat patients with metabolic syndrome; hence, there is considerable interest in the development of selective inhibitors. For preclinical tests of such inhibitors, the characteristics of 11beta-HSD1 from the commonly used species have to be known. Therefore, we determined differences in substrate affinity and inhibitor effects for 11beta-HSD1 from six species. The differences in catalytic activities with cortisone and 11-dehydrocorticosterone were rather modest. Human, hamster and guinea-pig 11beta-HSD1 displayed the highest catalytic efficiency in the oxoreduction of cortisone, while mouse and rat showed intermediate and dog the lowest activity. Murine 11beta-HSD1 most efficiently reduced 11-dehydrocorticosterone, while the enzyme from dog showed lower activity than those from the other species. 7-ketocholesterol (7KC) was stereospecifically converted to 7beta-hydroxycholesterol by recombinant 11beta-HSD1 from all species analyzed except hamster, which showed a slight preference for the formation of 7alpha-hydroxycholesterol. Importantly, guinea-pig and canine 11beta-HSD1 displayed very low 7-oxoreductase activities. Furthermore, we demonstrate significant species-specific variability in the potency of various 11beta-HSD1 inhibitors, including endogenous compounds, natural chemicals and pharmaceutical compounds. The results suggest significant differences in the three-dimensional organization of the hydrophobic substrate-binding pocket of 11beta-HSD1, and they emphasize that species-specific variability must be considered in the interpretation of results obtained from different animal experiments. The assessment of such differences, by cell-based test systems, may help to choose the appropriate animal for safety and efficacy studies of novel potential drug candidates.

11-beta-Hydroxysteroid Dehydrogenase Type 1↗

PubMed2004

Acetylcholinesterase inhibitory activity of scopolin and scopoletin discovered by virtual screening of natural products.

For the targeting selection of acetylcholinesterase (AChE) inhibitors from natural sources we generated a structure-based pharmacophore model utilizing an in silico filtering experiment for the discovery of promising candidates out of a 3D multiconformational database consisting of more than 110,000 natural products. In our study, scopoletin (1) and its glucoside scopolin (2) emerged as potential AChE inhibitors by the virtual screening procedure. They were isolated by different chromatographic methods from the medicinal plant Scopolia carniolica Jaqc. and tested in an enzyme assay using Ellman's reagent. They showed moderate, but significant, dose-dependent and long-lasting inhibitory activities. In the in vivo experiments (icv application of 2 micromol) 1 and 2 increased the extracellular acetylcholine (ACh) concentration in rat brain to about 170% and 300% compared to basal release, respectively. At the same concentration, the positive control galanthamine increased the ACh concentration to about the same level as 1. These are the first in vivo results indicating an effect of coumarins on brain ACh.

Acetylcholine↗