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Inhibitory Potency (inhibitory + potency)
Selected AbstractsSearch for Histamine H3 Receptor Antagonists with Combined Inhibitory Potency at N, -Methyltransferase: Ether Derivatives.CHEMINFORM, Issue 22 2005J. Apelt Abstract For Abstract see ChemInform Abstract in Full Text. [source] Co-administration of proton pump inhibitors delays elimination of plasma methotrexate in high-dose methotrexate therapyBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 1 2009Kunihiro Suzuki WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT , Co-administration of proton pump inhibitors (PPIs) increases plasma methotrexate (MTX) concentration in cancer patients receiving high-dose MTX (HDMTX) therapy. , There is controversy as to whether or not co-administration of PPIs affects plasma MTX elimination in HDMTX therapy. , Inhibitory activity of PPIs on breast cancer resistance protein (BCRP) is a possible mechanism for the drug interaction between MTX and PPIs. WHAT THIS STUDY ADDS , Co-administration of a PPI (omeprazole, lansoprazole, or rabeprazole) was more frequently observed in the delayed MTX elimination group than in the normal MTX elimination group. , Multiple logistic regression analysis with adjustment for significant covariates revealed that PPI co-administration was a significant risk factor for delayed plasma MTX elimination. , The half-maximal inhibitory concentration of each PPI in inhibiting BCRP function was much higher than the therapeutic unbound concentration in the plasma. AIM To assess whether or not co-administration of proton pump inhibitors (PPIs) is a risk factor for delayed elimination of plasma methotrexate (MTX) in high-dose MTX (HDMTX) therapy for malignant diseases. METHODS To assess the effects of PPI co-administration on elimination of plasma MTX, we examined plasma MTX concentration data on 171 cycles of HDMTX therapy performed in 74 patients. We performed multiple logistic regression analysis to evaluate PPI co-administration as a risk factor. Inhibitory potencies of omeprazole, lansoprazole, rabeprazole and pantoprazole on MTX transport via breast cancer resistance protein (BCRP, ABCG2) were also investigated in an in vitro study using membrane vesicles expressing human BCRP. RESULTS We identified co-administration of PPIs as a risk factor for delayed elimination (odds ratio 2.65, 95% confidence interval 1.03, 6.82) as well as renal and liver dysfunction. All four PPIs inhibited BCRP-mediated transport of MTX, with half-maximal inhibitory concentrations of 5.5,17.6 µM , considerably higher than the unbound plasma concentrations of the PPIs. CONCLUSIONS Our results support previous findings suggesting that PPI co-administration is associated with delayed elimination of plasma MTX in patients with HDMTX therapy. This drug interaction, however, cannot be explained solely by the inhibitory effects of PPIs on BCRP-mediated MTX transport. [source] Arginine-based structures are specific inhibitors of cathepsin CFEBS JOURNAL, Issue 11 2000Application of peptide combinatorial libraries Novel synthetic peptide inhibitors of lysosomal cysteine proteinase cathepsin C have been designed through the use of soluble peptide combinatorial libraries. The uncovered structural inhibitory module consists of the N-terminal cluster of l -arginine residues. Its modification with d -amino acids or arginine derivatives did not increase the inhibition strength. Inhibitory potency of oligoarginines improves with the elongation of peptide chain reaching a maximum for octa- l -arginine. The oligoarginines specifically interact with the cathepsin C active site as shown by competitive-type inhibition kinetics (Ki , 10,5 m) and intrinsic fluorescence measurements. The inhibitory interaction of oligoarginines is established through the specific spatial contact of a net of guanidino groups in the arginine side-chains, as indicated by comparison with inhibitory action of low molecular mass guanidine derivatives (Ki , 10,3 m). Nonarginine polyionic compounds cannot mimic the inhibitory effect of oligoarginines. The arginine-based peptide inhibitors were selective towards cathepsin C among other cysteine proteinases tested. [source] Lectin-Based Drug Design: Combined Strategy to Identify Lead Compounds using STD NMR Spectroscopy, Solid-Phase Assays and Cell Binding for a Plant Toxin ModelCHEMMEDCHEM, Issue 3 2010Abstract The growing awareness of the sugar code,i.e. the biological functionality of glycans,is leading to increased interest in lectins as drug targets. The aim of this study was to establish a strategic combination of screening procedures with increased biorelevance. As a model, we used a potent plant toxin (viscumin) and lactosides synthetically modified at the C6/C6, positions and the reducing end aglycan. Changes in the saturation transfer difference (STD) in NMR spectroscopy, applied in inhibition assays, yielded evidence for ligand activity and affinity differences. Inhibitory potency was confirmed by the blocking of lectin binding to a glycoprotein-bearing matrix. In cell-based assays, iodo/azido-substituted lactose derivatives were comparatively active. Interestingly, cell-type dependence was observed, indicating the potential of synthetic carbohydrate derivative to interact with lectins in a cell-type (glycan profile)-specific manner. These results are relevent to research into human lectins, glycosciences, and beyond. [source] Benzene-di- N -substituted carbamates as conformationally constrained analogs of Pseudomonas lipase substratesEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 11 2007Ming-Cheng Lin Abstract Benzene-1,2-, -1,3-, and -1,4-di- N -substituted carbamates (1,15) are synthesized as the constrained analogs of gauche, eclipsed, and anti conformations of diesters of ethylene glycol, respectively. Carbamates 1,15 are characterized as the pseudo-substrate inhibitors of Pseudomonas species lipase. Long-chain carbamates are more potent inhibitors than short-chain ones. Different geometries of benzene-di-substituted carbamates, such as benzene-1,2-di- N -octylcarbamate (3) (ortho compound), benzene-1,3-di- N -octylcarbamate (8) (meta compound), and benzene-1,4-di- N -octylcarbamate (13) (para compound), show similar inhibitory potencies for the enzyme. In other words, kinetic data suggest that the enzyme does not discriminate ortho, meta, and para geometries of these constrained analogs. [source] Differential mechanisms for the inhibition of human cytochrome P450 1A2 by apigenin and genisteinJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 4 2010Hideaki Shimada Abstract The inhibitory effects of flavonoids on the human cytochrome P450 1A2 (CYP1A2) were examined. Among flavonoids tested, galangin, kaempferol, chrysin, and apigenin were potent inhibitors. Although apigenin belonging to flavones and genistein belonging to isoflavones are similar in the chemical structures, the inhibitory potencies for CYP1A2 were distinguished markedly between these two flavonoids. In computer-docking simulation, apigenin interacted with the same mode of cocrystallized ,-naphthoflavone in the active site of CYP1A2, and then the B ring of apigenin was placed close to the heme iron of the enzyme with a single orientation. In contrast, the docked genistein conformation showed two different binding modes, and the A ring of genistein was oriented to the heme iron of CYP1A2. Furthermore, the binding free energy of apigenin was lower than that of genistein. These results demonstrate a possible mechanism that causes the differential inhibitory potencies of apigenin and genistein for CYP1A2. © 2010 Wiley Periodicals, Inc. J Biochem Mol Toxicol 24:230,234, 2010; View this article online at wileyonlinelibrary.com. DOI 10.1002/jbt.20328 [source] Benzene-1,2-, 1,3-, and 1,4-di- N -substituted carbamates as conformationally constrained inhibitors of acetylcholinesteraseJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 6 2007Ming-Cheng Lin Abstract Benzene-1,2-, 1,3-, and 1,4-di- N -substituted carbamates (1,15) are synthesized as the conformationally constrained inhibitors of acetylcholinesterase and mimic gauche, eclipsed, and anti -conformations of acetylcholine, respectively. All carbamates 1,15 are characterized as the pseudo substrate inhibitors of acetylcholinesterase. For a series of geometric isomers, the inhibitory potencies are as follows: benzene-1,4-di- N -substituted carbamate (para compound) > benzene-1,3-di- N -substituted carbamate (meta compound) > benzene-1,2-di- N -substituted carbamate (ortho compound). Therefore, benzene-1,4-di- N -substituted carbamates (para compounds), with the angle of 180° between two C(benzene),O bonds, mimic the preferable anti C,O/C,N conformers of acetylcholine for the choline ethylene backbone in the acetylcholinesterase catalysis. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:348,353, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20202 [source] Hypersensitivity reactions to penicillins: studies in a group of patients with negative benzylpenicillin G skin testJOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 3 2009H.-L. Qiao MD PhD Summary Background:, Although skin tests are usually employed to evaluate current penicillin allergy status, a negative result does not exclude hypersensitivity. There is a need for accurate in vitro tests to exclude hypersensitivity. A radioallergosorbent test (RAST) is a potentially good supplementary approach, but there is little information on the suitability of this method to diagnose penicillin hypersensitivity in subjects with a negative skin test to benzylpenicillin. Methods:, A total of 133 patients with a negative skin test to benzylpenicillin G (PG) and all of whom developed allergic reactions to PG were studied. RAST was used to detect eight kinds of specific IgE antibodies to penicillins in serum, which included four kinds of major and minor antigenic determinants to four penicillin drugs. The combination sites for the specific IgE antibodies were studied by RAST inhibition test. Results:, The rate of positive reactions for the specific IgE antibodies was 59·40% (79/133). Of the eight kinds of antigenic determinants, the positive rates for specific IgE against the major and minor determinants were 39·10% (52) and 42·86% (57) respectively. Of the four drugs, positive cases only to PG were 10 (7·5%), were significantly fewer than the cross-reacting positive cases (36) to PG (P < 0·01). In the RAST inhibition studies all drugs exhibited good inhibitory potencies, and in some instances the side-chain of the penicillins could induce specific responses with a variable degree of cross-reactivity among the different penicillins. Conclusion:, Radioallergosorbent test is a good complementary test in persons who are skin-test negative with PG, and the sensitivity of RAST increaes with increasing specificity of IgE antibodies to be detected. 6-APA and the groups, making part of the different side-chains on penicillins, all contributed to the cross-reactivity. [source] Human brain aminopeptidase A: biochemical properties and distribution in brain nucleiJOURNAL OF NEUROCHEMISTRY, Issue 1 2008Nadia De Mota Abstract Aminopeptidase A (APA) generated brain angiotensin III, one of the main effector peptides of the brain renin angiotensin system, exerting a tonic stimulatory effect on the control of blood pressure in hypertensive rats. The distribution of APA in human brain has not been yet studied. We first biochemically characterized human brain APA (apparent molecular mass of 165 and 130 kDa) and we showed that the human enzyme exhibited similar enzymatic characteristics to recombinant mouse APA. Both enzymes had similar sensitivity to Ca2+. Kinetic studies showed that the Km (190 ,mol/L) of the human enzyme for the synthetic substrate- l -glutamyl-,-naphthylamide was close from that of the mouse enzyme (256 ,mol/L). Moreover, various classes of inhibitors including the specific and selective APA inhibitor, (S)-3-amino-4-mercapto-butyl sulfonic acid, had similar inhibitory potencies toward both enzymes. Using (S)-3-amino-4-mercapto-butyl sulfonic acid, we then specifically measured the activity of APA in 40 microdissected areas of the adult human brain. Significant heterogeneity was found in the activity of APA in the various analyzed regions. The highest activity was measured in the choroids plexus and the pineal gland. High activity was also detected in the dorsomedial medulla oblongata, in the septum, the prefrontal cortex, the olfactory bulb, the nucleus accumbens, and the hypothalamus, especially in the paraventricular and supraoptic nuclei. Immunostaining of human brain sections at the level of the medulla oblongata strengthened these data, showing for the first time a high density of immunoreactive neuronal cell bodies and fibers in the motor hypoglossal nucleus, the dorsal motor nucleus of the vagus, the nucleus of the solitary tract, the Roller nucleus, the ambiguus nucleus, the inferior olivary complex, and in the external cuneate nucleus. APA immunoreactivity was also visualized in vessels and capillaries in the dorsal motor nucleus of the vagus and the inferior olivary complex. The presence of APA in several human brain nuclei sensitive to angiotensins and involved in blood pressure regulation suggests that APA in humans is an integral component of the brain renin angiotensin system and strengthens the idea that APA inhibitors could be clinically tested as an additional therapy for the treatment of certain forms of hypertension. [source] Methyl esters of N -(dicyclohexyl)acetyl-piperidine-4-(benzylidene-4-carboxylic acids) as drugs and prodrugs: A new strategy for dual inhibition of 5,-reductase type 1 and type 2JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2005Martina Streiber Abstract Steroid 5,-reductase (5,R) inhibitory potency of three N -(dicyclohexyl)acetyl-piperidine-4-(benzylidene-4-carboxylic acids) and their corresponding methyl esters was monitored for type 2 isoenzyme in a benign prostatic hyperplasia cell free preparation and for type 1 isoenzyme in DU145 cells and in a cell free assay. The hydrolytic stability of the esters and their bioconversion to the corresponding acids was assessed in aqueous buffered solution (pH 7.4) and in selected biological media having measurable esterase activities. The carboxylic acids 1, 2, and 3 with high type 2 inhibitory potencies displayed only little type 1 inhibition. The esters 1a, 2a, and 3a, originally designed as prodrugs to enhance cell permeation, proved to be potent type 1 inhibitors and are therefore acting as drugs themselves. They are stable in buffered salt solution (pH 7.4), Caco-2 cells, and human plasma, whereas all esters are cleaved into the corresponding acids in benign prostatic hyperplasia tissue homogenate. Methyl esters, applied as hydrolytically stable precursor drugs to facilitate cell permeation, will yield the corresponding carboxylic acids as type 2 inhibitors after hydrolysis in the target organ. The esters themselves,stable in human plasma and Caco-2 cells,are acting as potent drugs toward 5,R type 1. Thus, dual inhibition of 5,R type 1 and type 2 can be achieved by applying a single parent compound. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:473,480, 2005 [source] Association of the antagonism of von Willebrand factor but not fibrinogen by platelet ,IIb,3 antagonists with prolongation of bleeding timeJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 10 2005T. AOKI Summary.,Background:,The ,IIb,3 antagonists inhibit platelet aggregation and are used as antithrombotic agents for cardiothrombotic disease. The present study investigates the correlation of inhibition of fibrinogen and von Willebrand factor (VWF) binding by ,IIb,3 antagonists with the inhibition of platelet aggregation and prolongation of bleeding time (BT). Methods:,Inhibition of fibrinogen and VWF binding were assessed in a purified ,IIb,3 -binding assay. As an in vitro cell-based assay, platelet aggregation and VWF-mediated adhesion studies were performed using human platelets. In vivo effects on BT were measured using a template device in dogs at the same time as an ex vivo aggregation study was performed. Results:,In vitro studies demonstrated that the antiaggregatory effects of ,IIb,3 antagonists correlate with their inhibition of fibrinogen binding, but not VWF. Interestingly, the effects of ,IIb,3 antagonists on BT could be differentiated from the inhibition of platelet aggregation. Furthermore, this differentiation was strongly correlated with the different inhibitory potencies between fibrinogen and VWF binding, as well as that between VWF-mediated adhesion and aggregation. Conclusions:,Our study provides novel evidence showing that the inhibitory effect of ,IIb,3 antagonists on VWF, but not fibrinogen binding, correlates with their ability to prolong BT. [source] Manipulation of Electrostatic and Saccharide Linker Interactions in the Design of Efficient Glycopolypeptide-Based Cholera Toxin InhibitorsMACROMOLECULAR BIOSCIENCE, Issue 1 2010Ronak Maheshwari Abstract Multivalent, glycopolymer inhibitors designed for the treatment of disease and pathogen infection have shown improvements in binding correlated with general changes in glycopolymer architecture and composition. We have previously demonstrated that control of glycopolypeptide backbone extension and ligand spacing significantly impacts the inhibition of the cholera toxin B subunit pentamer (CT B5) by these polymers. In the studies reported here, we elucidate the role of backbone charge and linker length in modulating the inhibition event. Peptides of the sequence AXPXG (where X is a positive, neutral or negative amino acid), equipped with the alkyne functionality of propargyl glycine, were designed and synthesized via solid-phase peptide synthetic methods and glycosylated via Cu(I)-catalyzed alkyne-azide cycloaddition reactions. The capacity of the glycopeptides to inhibit the binding of the B5 subunit of cholera toxin was evaluated. These studies indicated that glycopeptides with a negatively charged backbone show improved inhibition of the binding event relative to the other glycopeptides. In addition, variations in the length of the linker between the peptide and the saccharide ligand also affected the inhibition of CT by the glycopeptides. Our findings suggest that, apart from appropriate saccharide spacing and polypeptide chain extension, saccharide linker conformation and the systematic placement of charges on the polypeptide backbone are also significant variables that can be tuned to improve the inhibitory potencies of glycopolypeptide-based multivalent inhibitors. [source] Multivalent Drug Design and Inhibition of Cholera Toxin by Specific and Transient Protein,Ligand InteractionsCHEMICAL BIOLOGY & DRUG DESIGN, Issue 5 2008Jiyun Liu Multivalent inhibitors of the cholera toxin B pentamer are potential therapeutic drugs for treating cholera and serve as models for demonstrating multivalent ligand effects through a structure-based approach. A crucial yet often overlooked aspect of multivalent drug design is the length, rigidity and chemical composition of the linker used to connect multiple binding moieties. To specifically study the role of chemical linkers in multivalent ligand design, we have synthesized a series of compounds with one and two binding motifs connected by several different linkers. These compounds have affinity for and potency against the cholera toxin B pentamer despite the fact that none can simultaneously bind two toxin receptor sites. Results from saturation transfer difference NMR reveal transient, non-specific interactions between the cholera toxin and linker groups contribute significantly to overall binding affinity of monovalent compounds. However, the same random protein,ligand interactions do not appear to affect binding of bivalent molecules. Moreover, the binding affinities and potencies of these ,non-spanning' bivalent ligands appear to be wholly independent of linker length. Our detailed analysis identifies multiple effects that account for the improved inhibitory potencies of bivalent ligands and suggest approaches to further improve the activity of this class of compounds. [source] Interaction between Anticonvulsants and Human Placental Carnitine TransporterEPILEPSIA, Issue 3 2004Shu-Pei Wu Summary: Purpose: To examine the inhibitory effect of anticonvulsants (AEDs) on carnitine transport by the human placental carnitine transporter. Methods: Uptake of radiolabeled carnitine by human placental brush-border membrane vesicles was measured in the absence and presence of tiagabine (TGB), vigabatrin (VGB), gabapentin (GBP), lamotrigine (LTG), topiramate (TPM), valproic acid (VPA), and phenytoin (PHT). The mechanism of the inhibitory action of TGB was determined. Results: Most of the AEDs inhibited placental carnitine transport. Kinetic analyses showed that TGB had the greatest inhibitory effect [50% inhibitory concentration (IC50, 190 ,M)], and the order of inhibitory potency was TGB > PHT > GBP > VPA > VGB, TPM > LTG. Further studies showed that TGB competitively inhibited carnitine uptake by the human placental carnitine transporter, suggesting that it may be a substrate for this carrier. Conclusions: Although the involvement of carnitine deficiency in fetal anticonvulsant syndrome requires further evaluation, potential interference with placental carnitine transport by several AEDs was demonstrated. Despite the higher inhibitory potency of TGB, given the therapeutic unbound concentrations, the results for VPA and PHT are probably more clinically significant. [source] Design syntheses and mitochondrial complex I inhibitory activity of novel acetogenin mimicsFEBS JOURNAL, Issue 9 2000Kaoru Kuwabara Some natural acetogenins are the most potent inhibitors of mitochondrial complex I. These compounds are characterized by two functional units [i.e. hydroxylated tetrahydrofuran (THF) and ,,,-unsaturated ,-lactone ring moieties] separated by a long alkyl spacer. To elucidate which structural factors of acetogenins, including their active conformation, are crucial for the potent inhibitory activity we synthesized a novel bis-acetogenin and its analogues possessing two ,-lactone rings connected to bis-THF rings by flexible alkyl spacers. The inhibitory potency of the bis-acetogenin with bovine heart mitochondrial complex I was identical to that of bullatacin, one of the most potent natural acetogenins. This result indicated that one molecule of the bis-acetogenin does not work as two reactive inhibitors, suggesting that a ,-lactone and the THF ring moieties act in a cooperative manner on the enzyme. In support of this, either of the two ring moieties synthesized individually showed no or very weak inhibitory effects. Moreover, combined use of the two ring moieties at various molar ratios exhibited no synergistic enhancement of the inhibitory potency. These observations indicate that both functional units work efficiently only when they are directly linked by a flexible alkyl spacer. Therefore, some specific conformation of the spacer must be important for optimal positioning of the two units in the enzyme. Furthermore, the ,,,-unsaturated ,-lactone, the 4-OH group in the spacer region, the long alkyl tail attached to the THF unit and the stereochemistry surrounding the hydroxylated bis-THF rings were not crucial for the activity, although these are the most common structural features of natural acetogenins. The present study provided useful guiding principles not only for simplification of complicated acetogenin structure, but also for further wide structural modifications of these molecules. [source] Inhibitory activity of brown algal phlorotannins against hyaluronidaseINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2002Toshiyuki Shibata The inhibitory effect of brown algal phlorotannins on hyaluronidase was evaluated by an in vitro assay. Crude phlorotannins from the brown algae Eisenia bicyclis and Ecklonia kurome had a stronger inhibitory effect than well-known inhibitors such as catechins and sodium cromoglycate. IC50 values of the following six phlorotannins: phloroglucinol, an unknown tetramer, eckol (a trimer), phlorofucofuroeckol A (a pentamer), dieckol and 8,8,-bieckol (hexamers), were 280, 650, >800, 140, 120 and 40 ,M, respectively. The IC50 of catechin, epigallocatechin gallate and sodium cromoglycate was 620, 190 and 270 ,M, respectively. 8,8,-Bieckol, the strongest HAase inhibitor in this study, acted as a competitive inhibitor with an inhibition constant (Ki) of 35 ,M. Acetylation of the phlorotannins markedly decreased their inhibitory potency. [source] Discovery and design of novel inhibitors of botulinus neurotoxin A: targeted ,hinge' peptide librariesJOURNAL OF APPLIED TOXICOLOGY, Issue 1 2003J. Hayden Abstract Intoxication by the zinc protease botulinus neurotoxin A (BoNT-A) results from cleavage of a single Q,R bond in the neuronal protein SNAP-25, which disables the docking mechanism required for neurotransmitter release. In the present study, potential inhibitors of BoNT-A were assessed from their effects on the BoNT-A cleavage of a synthetic 17-mer peptide (SNAP-25, residues 187,203) spanning the Q,R cleavage site. Compounds that inhibited BoNT-A included thiols (zinc chelators) such as dithiothreitol, dimercaptopropanesulfonic acid, mercaptosuccinic acid and captopril. In addition, compounds containing multiple acidic functions, such as the SNARE motif V2 (ELDDRADALQ), the tripeptide Glu-Glu-Glu and the steroid glycoside glycyrrhizic acid, were effective inhibitors. ,Hinge' peptide mini-libraries (PMLs) having the structure acetyl-X1 -X2 -linker-X3 -X4 -NH2 or X1 -X2 -linker-X3, where X1,X4 were mixtures of selected amino acids and the flexible linker was 4-aminobutyric acid, also provided effective inhibition. Targeted PMLs containing the acidic amino acids Asp and Glu, the scissile-bond amino acids Gln and Arg and the zinc chelators His and Cys produced pronounced inhibition of BoNT-A. Deconvolution of these libraries will provide novel ligands with improved inhibitory potency as leads in the design of peptide mimetics to treat BoNT poisoning. Copyright ? 2003 Crown in the right of Canada. Published by John Wiley and Sons, Ltd. [source] Methyl esters of N -(dicyclohexyl)acetyl-piperidine-4-(benzylidene-4-carboxylic acids) as drugs and prodrugs: A new strategy for dual inhibition of 5,-reductase type 1 and type 2JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2005Martina Streiber Abstract Steroid 5,-reductase (5,R) inhibitory potency of three N -(dicyclohexyl)acetyl-piperidine-4-(benzylidene-4-carboxylic acids) and their corresponding methyl esters was monitored for type 2 isoenzyme in a benign prostatic hyperplasia cell free preparation and for type 1 isoenzyme in DU145 cells and in a cell free assay. The hydrolytic stability of the esters and their bioconversion to the corresponding acids was assessed in aqueous buffered solution (pH 7.4) and in selected biological media having measurable esterase activities. The carboxylic acids 1, 2, and 3 with high type 2 inhibitory potencies displayed only little type 1 inhibition. The esters 1a, 2a, and 3a, originally designed as prodrugs to enhance cell permeation, proved to be potent type 1 inhibitors and are therefore acting as drugs themselves. They are stable in buffered salt solution (pH 7.4), Caco-2 cells, and human plasma, whereas all esters are cleaved into the corresponding acids in benign prostatic hyperplasia tissue homogenate. Methyl esters, applied as hydrolytically stable precursor drugs to facilitate cell permeation, will yield the corresponding carboxylic acids as type 2 inhibitors after hydrolysis in the target organ. The esters themselves,stable in human plasma and Caco-2 cells,are acting as potent drugs toward 5,R type 1. Thus, dual inhibition of 5,R type 1 and type 2 can be achieved by applying a single parent compound. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:473,480, 2005 [source] Characterisation of the effects of potassium channel modulating agents on mouse intestinal smooth muscleJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 3 2002Chi-Kong Yeung The actions of agents which modulate ATP-sensitive potassium (KATP) channels in excitable cells were investigated in an in-vitro preparation of mouse ileum from which the mucosa was removed. A range of potassium channel openers of diverse structure, cromakalim (0.1,100 ,M), pinacidil (0.1,200 ,M) and its analogue P1060 (0.1,200 ,M), SDZ PCO400 ((-)-(3S,4R)-3,4-dihydro-3-hydroxy-2,2-dimethyl-4-(3-oxo-cyclopent-1-enyloxy)-2H -1-benzopyran-6-carbonitrile) (0.3,60 ,M), caused concentration-related reduction in twitch height of electrical field stimulated ileum. P1060 and SDZ PCO400 were the most potent agents; diazoxide (0.1,100 ,M) was without effect. The order of inhibitory potency, based on EC50 values (concentration of a relaxant producing 50% of the maximum inhibition of twitch) was: P1060 = SDZ PCO400 > cromakalim > pinacidil. The relaxant effect of the potassium channel openers was antagonised by the sulfonylureas glibenclamide (0.1-1.0 ,M) and glipizide (3,30 ,M) but the nature of the antagonism differed. Antagonism of P1060 and SDZ PCO400 by glibenclamide appeared to be competitive whereas the antagonism of relaxation induced by cromakalim and pinacidil was apparently not competitive. Both phentolamine (1,10 ,M) and tolbutamide (100,300 ,M) showed competitive antagonism of the actions of pinacidil while yohimbine (1,20 ,M) did not antagonise relaxation and appeared to have actions at sites other than the KATP channel in this preparation. The relative effectiveness of the antagonists on pinacidil-induced relaxation was found to be: glibenclamide >phentolamine >tolbutamide >yohimbine, which is in agreement with studies in other tissues. The results show that many structurally diverse potassium channel openers are potent relaxants of mouse ileum. These observations are consistent with the existence of ATP-dependent K+ channels in murine intestinal muscle which, however, differ somewhat in properties from those reported for vascular muscle and pancreatic ,-cells. [source] Influence of Extracellular K+ Concentrations on Quinidine-induced K+ Current Inhibition in Rat Ventricular MyocytesJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 1 2000MICHIKO HIROTA Hypokalaemia is one of the important risk factors for development of torsades de pointes. We recently reported that hypokalaemia increased the electrocardiographic QT interval in rats treated with quinidine, but did not alter the arrhythmogenic potency of quinidine. In this study, we have investigated the influence of extracellular potassium concentration ([K+]o) on the inhibition of several types of cardiac potassium currents by quinidine. Such types of currents include the delayed rectifier potassium current (IK), the transient outward current (Ito), and the inward rectifier potassium current (IK1), as measured in isolated rat ventricular cells using patch-clamp techniques. Concentration-dependent effects of quinidine on IK, Ito, and IK1 were evaluated under both normal ([K+]o = 5.4 mM) and hypokalaemic ([K+]o = 3.5 mM) conditions. In contrast to both IK and Ito, which were barely influenced by changes in [K+]o, IK1 was significantly inhibited by hypokalaemia. Furthermore, while quinidine suppressed both IK and Ito in a concentration-dependent manner, the inhibitory potency of quinidine on these currents was not influenced by changes in [K+]o. The respective normal and hypokalaemic IC50 values for quinidine were 11.4 and 10.0 ,M (IK), and 17.6 and 17.3 ,M (Ito). Although higher concentrations of quinidine were required to inhibit IK1, the inhibitory potency of quinidine was also found to be insensitive to changes in [K+]o. Thus, in rats, the inhibitory potency of quinidine for the K+ current-types IK, Ito and IK1 is barely influenced by changes in [K+]o. These findings are consistent with our previous report showing that the QT-prolonging potency of quinidine was not altered under hypokalaemic conditions. However, whilst hypokalaemia does not affect IK or Ito, it can inhibit IK1 and can result in QT prolongation in-vivo. [source] Synthesis of Novel Uracil Non-Nucleoside Derivatives as Potential Reverse Transcriptase Inhibitors of HIV-1ARCHIV DER PHARMAZIE, Issue 11 2009Nasser R. El-Brollosy Abstract Novel emivirine and TNK-651 analogues 5a,d were synthesized by reaction of chloromethyl ethyl ether and / or benzyl chloromethyl ether, respectively, with uracils having 5-ethyl and 6-(4-methylbenzyl) or 6-(3,4-dimethoxybenzyl) substituents. A series of new uracil non-nucleosides substituted at N-1 with cyclopropylmethyloxymethyl 9a,d, 2-phenylethyloxymethyl 9e,h, and 3-phenylprop-1-yloxymethyl 9i,l were prepared on treatment of the corresponding uracils with the appropriate acetals 8a,c. Some of the tested compounds showed good activity against HIV-1 wild type. Among them, 1-cyclopropylmethyloxymethyl-5-ethyl-6-(3,5-dimethylbenzyl)uracil 9c and 5-ethyl-6-(3,5-dimethylbenzyl)-1-(2-phenylethyloxymethyl)uracil 9g showed inhibitory potency equally to emivirine against HIV-1 wild type. Furthermore, compounds 9c and 9g showed marginal better activity against NNRTI resistant mutants than emivirine. [source] Nitric Oxide Synthase Inhibition by Pentacycloundecane Conjugates of Aminoguanidine and TryptamineARCHIV DER PHARMAZIE, Issue 2 2009Dennis K. Wilkes Abstract This paper describes the synthesis and in-vitro activity of pentacycloundecane-conjugated aminoguanidine and tryptamine analogues on nitric oxide synthase (NOS) using rat brain homogenate. Both aminoguanidine and tryptamine-derived NOS inhibitors show selectivity towards the inducible and neuronal isoforms of the NOS enzyme, but are weak inhibitors and complete inhibition of the enzyme occurs only at high millimolar concentrations. In view of the increased NOS inactivation observed with alkyl substitution of these structures, the present study aimed to evaluate the effect of the pentacycloundecane cage moiety as an alkyl substituent on the in vitro NOS inhibition of aminoguanidine and tryptamine compounds. Comparison of the IC50 values of aminoguanidine (IC50 = 2.306×10,3 M) and 8-imino- N -guanidino-pentacyclo-undecane 2 (IC50 = 8.803×10,5 M) revealed a more than 26-fold increase in potency. The ability of tryptamine to inhibit NOS activity was also markedly improved by the various pentacycloundecane substituents. The compounds, 3-hydroxy-4-[3-(2-aminoethyl)indole]-azahexacyclo[5.4.1.02,6.03,10.05,9.08,11]dodecane 4 and 8-[3-(2-aminoethyl) indole]-pentacyclo[5.4.02,6.03,10.05,9]undecane 7 showed the best activity of the tryptamine analogues with a more than 3-fold increase in nitric oxide synthase inhibition. The results confirmed that the pentacycloundecane structure substantially enhanced the NOS inhibitory potency as observed for the six new NOS inhibitors. [source] Structure of aminopeptidase N from Escherichia coli complexed with the transition-state analogue aminophosphinic inhibitor PL250ACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2009Marie-Claude Fournié-Zaluski Aminopeptidase N (APN; EC 3.4.11.2) purified from Escherichia coli has been crystallized with the optically pure aminophosphinic inhibitor PL250, H3N+ -CH(CH3)-P(O)(OH)-CH2 -CH(CH2Ph)-CONH-CH(CH2Ph)CO2,, which mimics the transition state of the hydrolysis reaction. PL250 inhibits APN with a Ki of 1.5,2.2,nM and its three-dimensional structure in complex with E. coli APN showed its interaction with the S1, S,1 and S,2 subsites of the catalytic site. In this structure, the Zn ion was shown to be pentacoordinated by His297, His301 and Glu320 of APN and the two O atoms of the phosphinic moiety of PL250. One of these O atoms is also involved in a hydrogen bond to Tyr381, supporting the proposed role of this amino acid in the stabilization of the transition state of the enzymatic process. The strength of the phosphinic zinc binding and the occupancy of the S,2 subsite account for the 100-fold increase in affinity of PL250 compared with the dipeptide-derived inhibitor bestatin (Ki = 4.1 × 10,6,M). Accordingly, the removal of the C-terminal phenylalanine of PL250 resulted in a large decrease in affinity (Ki = 2.17 × 10,7,M). Furthermore, it was observed that the C-terminal carboxyl group of the inhibitor makes no direct interactions with the amino acids of the APN active site. Interestingly, PL250 exhibits the same inhibitory potency for E. coli APN and for mammalian enzymes, suggesting that the structure of the complex could be used as a template for the rational design of various human APN inhibitors needed to study the role of this aminopeptidase in various pathologies. [source] Preclinical pharmacokinetics and metabolism of 6-(4-(2,5-difluorophenyl)oxazol-5-yl)-3-isopropyl-[1,2,4]-triazolo[4,3- a]pyridine, a novel and selective p38, inhibitor: identification of an active metabolite in preclinical species and human liver microsomesBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 8 2006Amit S. Kalgutkar Abstract The disposition of 6-(4-(2,5-difluorophenyl)oxazol-5-yl)-3-isopropyl-[1,2,4]-triazolo[4,3- a]pyridine (1), a potent and selective inhibitor of mitogen activated protein (MAP) kinase p38,, was characterized in several animal species in support of its selection for preclinical safety studies and potential clinical development. 1 demonstrated generally favorable pharmacokinetic properties in all species examined. Following intravenous (i.v.) administration, 1 exhibited low volumes of distribution at steady state (Vdss) ranging from 0.4,1.3 l/kg (2.4,26 l/m2) in the rat, dog and monkey. Systemic plasma clearance was low in cynomolgus monkeys (6.00 ml/min/kg, 72.0 ml/min/m2) and Sprague-Dawley rats (7.65±1.08 ml/min/kg, 45.9±6.48 ml/min/m2 in male rats and 3.15±0.27 ml/min/kg, 18.9±1.62 ml/min/m2 in female rats) and moderate in beagle dogs (12.3±5.1 ml/min/kg, 246±102 ml/min/m2) resulting in plasma half-lives ranging from 1 to 5 h in preclinical species. Moderate to high bioavailability of 1 was observed in rats (30,65%), dogs (87%) and monkeys (40%) after oral (p.o.) dosing consistent with the in vitro absorption profile of 1 in the Caco-2 permeability assay. In rats, the oral pharmacokinetics were dose dependent over the dose range studied (5, 50 and 100 mg/kg). The principal route of clearance of 1 in rat, dog, monkey and human liver microsomes and in vivo in preclinical species involved oxidative metabolism mediated by cytochrome P450 enzymes. The major metabolic fate of 1 in preclinical species and humans involved hydroxylation on the isopropyl group to yield the tertiary alcohol metabolite 2. In human liver microsomes, this transformation was catalysed by CYP3A4 as judged from reaction phenotyping analysis using isozyme-specific inhibitors and recombinant CYP enzymes. Metabolite 2 was also shown to possess inhibitory potency against p38, in a variety of in vitro assays. 1 as well as the active metabolite 2 were moderately to highly bound to plasma proteins (fu,0.1,0.33) in rat, mouse, dog, monkey and human. 1 as well as the active metabolite 2 did not exhibit competitive inhibition of the five major cytochrome P450 enzymes namely CYP1A2, 2C9, 2C19, 2D6 and 3A4 (IC50>50 µM). Overall, these results indicate that the absorption, distribution, metabolism and excretion (ADME) profile of 1 is relatively consistent across preclinical species and predict potentially favorable pharmacokinetic properties in humans, supporting its selection for toxicity/safety assessment studies and possible investigations in humans as an anti-inflammatory agent. Copyright © 2006 John Wiley & Sons, Ltd. [source] Rofecoxib is a potent inhibitor of cytochrome P450 1A2: studies with tizanidine and caffeine in healthy subjectsBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 3 2006Janne T. Backman Aims Case reports suggest an interaction between rofecoxib and the CYP1A2 substrate tizanidine. Our objectives were to explore the extent and mechanism of this possible interaction and to determine the CYP1A2 inhibitory potency of rofecoxib. Methods In a randomized, double-blind, two-phase cross-over study, nine healthy subjects took 25 mg rofecoxib or placebo daily for 4 days and, on day 4, each ingested 4 mg tizanidine. Plasma concentrations and the urinary excretion of tizanidine, its metabolites (M) and rofecoxib, and pharmacodynamic variables were measured up to 24 h. On day 3, a caffeine test was performed to estimate CYP1A2 activity. Results Rofecoxib increased the area under the plasma concentration,time curve (AUC0,,) of tizanidine by 13.6-fold [95% confidence interval (CI) 8.0, 15.6; P < 0.001), peak plasma concentration (Cmax) by 6.1-fold (4.8, 7.3; P < 0.001) and elimination half-life (t1/2) from 1.6 to 3.0 h (P < 0.001). Consequently, rofecoxib markedly increased the blood pressure-lowering and sedative effects of tizanidine (P < 0.05). Rofecoxib increased several fold the tizanidine/M-3 and tizanidine/M-4 ratios in plasma and urine and the tizanidine/M-5, tizanidine/M-9 and tizanidine/M-10 ratios in urine (P < 0.05). In addition, it increased the plasma caffeine/paraxanthine ratio by 2.4-fold (95% CI 1.4, 3.4; P = 0.008) and this ratio correlated with the tizanidine/metabolite ratios. Finally, the AUC0,25 of rofecoxib correlated with the placebo phase caffeine/paraxanthine ratio (r = 0.80, P = 0.01). Conclusions Rofecoxib is a potent inhibitor of CYP1A2 and it greatly increases the plasma concentrations and adverse effects of tizanidine. The findings suggest that rofecoxib itself is also metabolized by CYP1A2, raising concerns about interactions between rofecoxib and other CYP1A2 substrate and inhibitor drugs. [source] Role of multidrug resistance protein 2 (MRP2) in glutathione-bimane efflux from Caco-2 and rat renal proximal tubule cellsBRITISH JOURNAL OF PHARMACOLOGY, Issue 5 2001Sylvie A Terlouw The multidrug resistance protein 2 (MRP2) has been shown to play an important role in the transport of glutathione conjugates in the liver. Its importance in renal excretion, however, is still uncertain and other organic anion transporters may be involved. The objective of the present study was to characterize glutathione conjugate efflux from rat kidney proximal tubule cells (PTC), and to determine the contribution of Mrp2. We used isolated PTC in suspension, as well as grown to monolayer density. For comparison, transport characteristics were also determined in the human intestinal epithelial cell line Caco-2, an established model to study MRP2-mediated transport. The cells were loaded with monochlorobimane (MCB) at 10°C. MCB enters the cells by simple diffusion and is conjugated with glutathione to form the fluorescent glutathione-bimane (GS-B). In primary cultures of rat PTC, no indications for a transporter-mediated mechanism were found. The efflux of GS-B from Caco-2 cells and freshly isolated PTC was time- and temperature-dependent. Furthermore, GS-B transport in both models was inhibited by chlorodinitrobenzene (CDNB), with an inhibitory constant of 46.8±0.9 ,M in freshly isolated PTC. In Caco-2 cells, the inhibitory potency of CDNB was approximately 20 fold higher. Finally, efflux of GS-B from freshly isolated PTC from Mrp2-deficient (TR,) rats was studied. As compared to normal rat PTC, transport characteristics were not different. We conclude that in freshly isolated rat PTC glutathione conjugate excretion is mediated by other organic anion transporters rather than by Mrp2. British Journal of Pharmacology (2001) 134, 931,938; doi:10.1038/sj.bjp.0704284 [source] Ketamine and its preservative, benzethonium chloride, both inhibit human recombinant ,7 and ,4,2 neuronal nicotinic acetylcholine receptors in Xenopus oocytesBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2001Kristen M Coates Ketamine is a dissociative anaesthetic that is formulated as Ketalar, which contains the preservative benzethonium chloride (BCl). We have studied the effects of pure racemic ketamine, the preservative BCl and the Ketalar mixture on human neuronal nicotinic acetylcholine receptors (nAChRs) composed of the ,7 subunit or ,4 and ,2 subunits expressed in Xenopus laevis oocytes. Ketamine inhibited responses to 1 mM acetylcholine (ACh) in both the human ,7 and ,4,2 nAChRs, with IC50 values of 20 and 50 ,M respectively. Inhibition of the ,7 nAChRs occurred within a clinically relevant concentration range, while inhibition of the ,4,2 nAChR was observed only at higher concentrations. The Ketalar formulation inhibited nAChR function more effectively than was expected given its ketamine concentration. The surprising increased inhibitory potency of Ketalar compared with pure ketamine appeared to be due to the activity of BCl, which inhibited both ,7 (IC50 value of 122 nM) and ,4,2 (IC50 value of 49 nM) nAChRs at concentrations present in the clinical formulation of Ketalar. Ketamine is a noncompetitive inhibitor at both the ,7 and ,4,2 nAChR. In contrast, BCl causes a parallel shift in the ACh dose-response curve at the ,7 nAChR suggesting competitive inhibition. Ketamine causes both voltage-dependent and use-dependent inhibition, only in the ,4,2 nAChR. Since ,7 nAChRs are likely to be inhibited during clinical use of Ketalar, the actions of ketamine and BCl on this receptor subtype may play a role in the profound analgesia, amnesia, immobility and/or autonomic modulation produced by this anaesthetic. British Journal of Pharmacology (2001) 134, 871,879; doi:10.1038/sj.bjp.0704315 [source] Selection and optimization of MCF-7 cell line for screening selective inhibitors of 11,-hydroxysteroid dehydrogenase 2CELL BIOCHEMISTRY AND FUNCTION, Issue 6 2010Chi Hyun Kim Abstract An 11,-hydroxysteroid dehydrogenase type 1 (11,-HSD1) produces glucocorticoid (GC) from 11-keto metabolite, and its modulation has been suggested as a novel approach to treat metabolic diseases. In contrast, type 2 isozyme 11,-HSD2 is involved in the inactivation of glucocorticoids (GCs), protecting the non-selective mineralocorticoid receptor (MR) from GCs in kidney. Therefore, when 11,-HSD1 inhibitors are pursued to treat the metabolic syndrome, preferential selectivity of inhibitors for type 1 over type 2 isozyme is rather important than inhibitory potency. Primarily, to search for cell lines with 11,-HSD2 activity, we investigated the expression profiles of enzymes or receptors relevant to GC metabolism in breast, colon, and bone-derived cell lines. We demonstrated that MCF-7 cells had high expression for 11,-HSD2, but not for 11,-HSD1 with its cognate receptor. Next, for the determination of enzyme activity indirectly, we adopted homogeneous time resolved fluorescence (HTRF) cortisol assay. Obviously, the feasibility of HTRF to cellular 11,-HSD2 was corroborated by constructing inhibitory response to an 11b-HSD2 inhibitor glycyrrhetinic acid (GA). Taken together, MCF-7 that overexpresses type 2 but not type 1 enzyme is chosen for cellular 11,-HSD2 assay, and our results show that a nonradioactive HTRF assay is applicable for type 2 as well as type 1 isozyme. Copyright © 2010 John Wiley & Sons, Ltd. [source] Photoactivation of an Inhibitor of the 12/15-Lipoxygenase PathwayCHEMBIOCHEM, Issue 7 2006Stephan Herre Abstract Lipoxygenases are lipid-peroxidizing enzymes that have been implicated in the pathogenesis of inflammatory diseases and lipoxygenase inhibitors may be developed as anti-inflammatory drugs. Structure comparison with known lipoxygenase inhibitors has suggested that (2Z)-2-(3-benzylidene)-3-oxo-2,3-dihydrobenzo[b]thiophene-7-carboxylic acid methyl ester might inhibit the lipoxygenase pathway but we found that it exhibited only a low inhibitory potency for the pure 12/15-lipoxygenase (IC50=0.7 mM). However, photoactivation, which induces a Z -to- E isomerization of the double bond, strongly augmented the inhibitory potency and an IC50 value of 0.021 mM was determined for the pure E isomer. Similar isomer-specific differences were observed with the recombinant enzyme and its 12-lipoxygenating Ile418Ala mutant, as well as in intracellular lipoxygenase activity. Structure modeling of the enzyme/inhibitor complex suggested the molecular reasons for this isomer specificity. Since light-induced isomerization may proceed in the skin, such photoreactive compounds might be developed as potential drugs for inflammatory skin diseases. [source] Synthesis and Biological Evaluation of Bicyclic Nucleosides as Inhibitors of M.,tuberculosis Thymidylate KinaseCHEMMEDCHEM, Issue 10 2006Daele, Ineke Van Abstract Herein we describe the synthesis and conformational analysis of a series of bicyclic thymidine derivatives and their evaluation as inhibitors of thymidine monophosphate kinase from Mycobacterium tuberculosis (TMPKmt), based on previously discovered bicyclic sugar nucleosides. With a Ki value of 2.3,,m, 1-[3-aminomethyl-3,5-dideoxy-2- O,6- N -(thiocarbonyl)-,- D -ribofuranosyl]thymine emerged as the most potent TMPK inhibitor of this series. Moreover, this promising compound displays inhibitory potency against Mycobacteria cultures with an IC99 value of 100,,g,mL,1, thus promoting TMPKmt for the first time as a validated target for further inhibitory design. Attempts to rationalise the observed structure,activity relationship (SAR) involving molecular modelling and conformational analysis are described. [source] | ||||||||||||||||