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Different Inhibitors (different + inhibitor)
Selected AbstractsOvercoming surfactant inhibition with polymersACTA PAEDIATRICA, Issue 12 2000PA Dargaville Inhibition of the function of pulmonary surfactant in the alveolar space is an important element of the pathophysiology of many lung diseases, including meconium aspiration syndrome, pneumonia and acute respiratory distress syndrome. The known mechanisms by which surfactant dysfunction occurs are (a) competitive inhibition of phospholipid entry into the surface monolayer (e.g. by plasma proteins), and (b) infiltration and destabilization of the surface film by extraneous lipids (e.g. meconium-derived free fatty acids). Recent data suggest that addition of non-ionic polymers such as dextrano and polyethylene glycol to surfactant mixtures may significantly improve resistance to inhibition. Polymers have been found to neutralize the effects of several different inhibitors, and can produce near-complete restoration of surfactant function. The anti-inhibitory properties of polymers, and their possible role as an adjunct to surfactant therapy, deserve further exploration. [source] Capillary electrophoresis versus differential scanning calorimetry for the analysis of free enzyme versus enzyme-ligand complexes: In the search of the ligand-free status of cholinesterasesELECTROPHORESIS, Issue 2 2006Daniel Rochu Dr. Abstract Cholinesterases (ChEs) are highly efficient biocatalysts whose active site is buried in a deep, narrow gorge. The talent of CE to discover inhibitors in the gorge of highly purified preparations has fairly altered the meaning of a ChE ligand-free status. To attempt at a description of this one, we investigated the stability of Bungarus fasciatus acetylcholinesterase (AChE), alone or complexed with different inhibitors. Determination of midtransition temperature for thermal denaturation, using differential scanning calorimetry (DSC) and CE, provided conflicting results. Discrepancies strongly question the reality of a ligand-free AChE state. DSC allowed estimation of the stability of AChE-ligands complexes, and to rank the stabilizing effect of different inhibitors. CE acted as a detector of hidden ligands, provided that they were charged, reversibly bound, and thus dissociable upon action of electric fields. Then, CE allowed quantification of the stability of ligand-free AChE. CE and DSC providing each fractional and nonredundant information, cautious attention must be paid for actual estimation of the conformational stability of ChEs. Because inhibitors used in purification of ChEs by affinity chromatography are charged, CE remains a leading method to estimate enzyme stability and detect the presence of bound hidden ligands. [source] High-throughput screening of kinase inhibitors by multiplex capillary electrophoresis with UV absorption detectionELECTROPHORESIS, Issue 1-2 2003Yan He Abstract Protein kinases play a major role in the transformation of cells and are often used as molecular targets for the new generation of anticancer drugs. We present a novel technique for high-throughput screening of inhibitors of protein kinases. The technique involves the use of multiplexed capillary electrophoresis (CE) for the rapid separation of the peptides, phosphopeptides, and various inhibitors. By means of UV detection, diversified peptides with native amino acid sequences and their phosphorylated counterparts can be directly analyzed without the need for radioactive or fluorescence labeling. The effects of different inhibitors and their IC50 value were determined using three different situations involving the use of a single purified kinase, two purified kinases, and crude cell extracts, respectively. The results suggest that multiplexed CE/UV may prove to be a straightforward and general approach for high-throughput screening of compound libraries to find potent and selective inhibitors of the various protein kinases. [source] Structural and thermodynamic insights into the binding mode of five novel inhibitors of lumazine synthase from Mycobacterium tuberculosisFEBS JOURNAL, Issue 20 2006Ekaterina Morgunova Recently published genomic investigations of the human pathogen Mycobacterium tuberculosis have revealed that genes coding the proteins involved in riboflavin biosynthesis are essential for the growth of the organism. Because the enzymes involved in cofactor biosynthesis pathways are not present in humans, they appear to be promising candidates for the development of therapeutic drugs. The substituted purinetrione compounds have demonstrated high affinity and specificity to lumazine synthase, which catalyzes the penultimate step of riboflavin biosynthesis in bacteria and plants. The structure of M. tuberculosis lumazine synthase in complex with five different inhibitor compounds is presented, together with studies of the binding reactions by isothermal titration calorimetry. The inhibitors showed the association constants in the micromolar range. The analysis of the structures demonstrated the specific features of the binding of different inhibitors. The comparison of the structures and binding modes of five different inhibitors allows us to propose the ribitylpurinetrione compounds with C4,C5 alkylphosphate chains as most promising leads for further development of therapeutic drugs against M. tuberculosis. [source] Thermodynamic analysis of binding of p -substituted benzamidines to trypsinFEBS JOURNAL, Issue 6 2001Reinskje Talhout Understanding the structural basis of inhibitor,enzyme interactions, important for the design of new drugs, requires a complete thermodynamic characterization of the binding process as well as a description of the structure of the complex. In this paper, the binding of p -substituted benzamidinium derivatives to the structurally well-characterized serine proteinase bovine pancreatic trypsin has been studied using isothermal titration calorimetry. These experiments have permitted a complete characterization of the temperature dependence of the inhibitor-binding thermodynamics. At 25 °C, both the enthalpy and entropy of binding are favourable for all studied derivatives, but this is only true for a relatively narrow temperature range. As binding is characterized by a negative change in heat capacity, the process is characterized by enthalpy,entropy compensation, resulting in a change of the net thermodynamic driving force for association from entropic to enthalpic with increasing temperature. These phenomena are not unusual when hydrophobic forces play an important role. The trend in the relative binding potencies can, to a significant extent, be attributed to the electron-donating/withdrawing character of the substituent at the para position, as shown by the Hammett plot for the different inhibitors; the more polar the p -substituted benzamidine, the less potent it will be as a trypsin inhibitor. This behaviour might result from a bulk solvation effect, meaning that the more polar, lower potency inhibitors will be more stabilized in water than the less polar, higher potency inhibitors. [source] Inhibitors of the Large Ribosomal Subunit from Haloarcula marismortuiISRAEL JOURNAL OF CHEMISTRY, Issue 1 2010Peter Abstract The crystal structures that have been obtained for 23 different inhibitors bound to the large ribosomal subunit from Haloarcula marismortui are reviewed here. These structures provide important insights into how anti-ribosomal antibiotics inhibit protein synthesis, how species specificity arises, and the relationship between ribosomal mutations and antibiotic resistance. These structural studies also provide compelling evidence that the conformation of the peptidyl transferase center of the large ribosomal subunit is intrinsically variable, and that conformational equilibria play a role in determining its functional properties. [source] Can MM-PBSA calculations predict the specificities of protein kinase inhibitors?JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 16 2006Christopher S. Page Abstract An application of the Molecular mechanics Poisson,Boltzmann surface area (MM-PBSA) protocol to the prediction of protein kinase inhibitor selectivity is presented. Six different inhibitors are placed in equivalent orientations in each of six different receptors. Fully solvated molecular dynamics is then run for 1 ns on each of the 36 complexes, and the resulting trajectories scored, using the implicit solvent model. The results show some correlation with experimentally-determined specificities; anomalies may be attributed to a variety of causes, including difficulties in quantifying induced fit penalties and variabilities in normal modes calculations. Decomposing interaction energies on a per-residue basis yields more useful insights into the natures of the binding modes and suggests that the real value of such calculations lies in understanding interactions rather than outright prediction. © 2006 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] Molecular Modeling Of The Aldose Reductase-Inhibitor Complex Based On The X-Ray Crystal Structure And Studies With Single-Site- Directed MutantsJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 2 2000S.B. Singh Aldose reductase (AR) has been implicated in the etiology of the secondary complications of diabetes. This enzyme catalyzes the reduction of glucose to sorbitol using nicotinamide adenine dinucleotide phosphate as an essential cofactor. AR has been localized at the sites of tissue damage, and inhibitors of this enzyme prevent the development of neuropathy, nephropathy, retinopathy, and cataract formation in animal models of diabetes. The crystal structure of AR complexed with zopolrestat, a potent inhibitor of AR, has been described. (1) We have generated a model of the AR-inhibitor complex based on the reported C alpha coordinates of the protein and results of a structure-activity relationship study using four structurally distinct classes of inhibitors, recombinant human AR, and four single-site-directed mutants of this enzyme. The effects of the site-directed mutations on residues within the active site of the enzyme were evaluated by average interaction energy calculations and by calculations of carbon atom surface area changes. These values correlated well with the IC50 values for zopolrestat with the wildtype and mutant enzymes, validating the model. On the basis of the zopolrestat-binding model, we have proposed binding models for 10 other AR inhibitors. Our models have enabled us to gain a qualitative understanding of the binding domains of the enzyme and how different inhibitors impact the size and shape of the binding site. [source] Relevance of caspase activity during apoptosis in pubertal rat spermatogenesisMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 5 2008Veronica A. Codelia Abstract Caspases are a family of cysteine-proteases, activated upon several different stimuli, which execute apoptosis in many cell death models. Previous work of our group has shown rats have the highest rate of apoptosis during the first wave of spermatogenesis (between 20 and 25 days after birth), as evaluated by TUNEL and caspase activity. However, the hierarchical order of caspase activation and the relevance of each caspase during germ cell apoptosis are not clear. Thus, the goal of this work is to take a pharmacological approach to dissect the apoptosis pathway of caspase activation. Results showed that intratesticular injection of a caspase-8 inhibitor (z-IETD-fmk), or a pan-caspase inhibitor (z-VAD- fmk), significantly decreased the cleavage of p115 and PARP, two endogenous substrates of caspases, in 22-day-old rats. Additionally, these inhibitors promoted a significant reduction in the number of apoptotic germ cells. On the other hand, intratesticular injection of two different inhibitors of the intrinsic pathway (z-LEHD-fmk and minocycline) did not have any effect upon caspase substrates cleavage (p115 and PARP) or the number of apoptotic germ cells. Therefore, we conclude that the extrinsic pathway of apoptosis plays an important role in physiological germ cell apoptosis during the first round of spermatogenesis in the rat. Mol. Reprod. Dev. 75: 881,889, 2008. © 2007 Wiley-Liss, Inc. [source] Cannabinoid receptor 1 signalling dampens activity and mitochondrial transport in networks of enteric neuronesNEUROGASTROENTEROLOGY & MOTILITY, Issue 9 2009W. Boesmans Abstract, Cannabinoid (CB) receptors are expressed in the enteric nervous system (ENS) and CB1 receptor activity slows down motility and delays gastric emptying. This receptor system has become an important target for GI-related drug development such as in obesity treatment. The aim of the study was to investigate how CB1 ligands and antagonists affect ongoing activity in enteric neurone networks, modulate synaptic vesicle cycling and influence mitochondrial transport in nerve processes. Primary cultures of guinea-pig myenteric neurones were loaded with different fluorescent markers: Fluo-4 to measure network activity, FM1-43 to image synaptic vesicles and Mitotracker green to label mitochondria. Synaptic vesicle cluster density was assessed by immunohistochemistry and expression of CB1 receptors was confirmed by RT-PCR. Spontaneous network activity, displayed by both excitatory and inhibitory neurones, was significantly increased by CB1 receptor antagonists (AM-251 and SR141716), abolished by CB1 activation (methanandamide, mAEA) and reduced by two different inhibitors (arachidonylamide serotonin, AA-5HT and URB597) of fatty acid amide hydrolase. Antagonists reduced the number of synaptic vesicles that were recycled during an electrical stimulus. CB1 agonists (mAEA and WIN55,212) reduced and antagonists enhanced the fraction of transported mitochondria in enteric nerve fibres. We found immunohistochemical evidence for an enhancement of synaptophysin-positive release sites with SR141716, while WIN55,212 caused a reduction. The opposite effects of agonists and antagonists suggest that enteric nerve signalling is under the permanent control of CB1 receptor activity. Using inhibitors of the endocannabinoid degrading enzyme, we were able to show there is endogenous production of a CB ligand in the ENS. [source] Octopamine and 5-hydroxytryptamine mediate hemocytic phagocytosis and nodule formation via eicosanoids in the beet armyworm, Spodoptera exiguaARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 3 2009Geun Seob Kim Abstract Octopamine and 5-hydroxytryptamine (5-HT) have been known to mediate cellular immune responses, such as hemocytic phagocytosis and nodule formation, during bacterial invasion in some insects. In addition, eicosanoids also mediate these cellular immune reactions in various insects, resulting in clearing the bacteria circulating in the hemolymph. This study investigated a hypothesis on signal cross-talk between both types of immune mediators in the beet armyworm, Spodoptera exigua, which had been observed in the effect of eicosanoids on mediating the cellular immune responses. In response to bacterial infection, octopamine or 5-HT markedly enhanced both hemocytic phagocytosis and nodule formation in S. exigua larvae. Their specific antagonists, phentolamine (an octopamine antagonist) or ketanserin (a 5-HT antagonist) suppressed both cellular immune responses of S. exigua. These effects of biogenic monoamines on the immune mediation were expressed through eicosanoids because the inhibitory effects of both antagonists were rescued by the addition of arachidonic acid (a precursor of eicosanoid biosynthesis). Furthermore, the stimulatory effects of both monoamines on the cellular immune responses were significantly suppressed by different inhibitors acting at their specific levels of eicosanoid biosynthesis. Taken together, this study suggests that octopamine and 5-HT can mediate hemocytic phagocytosis and nodule formation through a downstream signal pathway relayed by eicosanoids in S. exigua. © 2009 Wiley Periodicals, Inc. [source] Neuronal nitric oxide synthase activity in rat urinary bladder detrusor: participation in M3 and M4 muscarinic receptor functionAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 3 2005B. Orman Summary 1,The aim of this paper was to determine the different signalling cascades involved in contraction of the rat urinary bladder detrusor muscle mediated via muscarinic acetylcholine receptors (muscarinic AChR). Contractile responses, phosphoinositides (IPs) accumulation, nitric oxide synthase (NOS) activity and cyclic GMP (cGMP) production were measured to determine the reactions associated with the effect of cholinergic agonist carbachol. The specific muscarinic AChR subtype antagonists and different inhibitors of the enzymatic pathways involved in muscarinic receptor-dependent activation of NOS and cGMP were tested. 2,Carbachol stimulation of M3 and M4 muscarinic AChR increased contractility, IPs accumulation, NOS activity and cGMP production. All of these effects were selectively blunted by 4-DAMP and tropicamide, M3 and M4 antagonists respectively. 3,The inhibitors of phospholipase C (PLC), calcium/calmodulin (CaM), neuronal NOS (nNOS) and soluble guanylate cyclase, but not of protein kinase C and endothelial NOS (eNOS), inhibited the carbachol action on detrusor contractility. These inhibitors also attenuated the muscarinic receptor-dependent increase in cGMP and activation of NOS. 4,In addition, sodium nitroprusside and 8-bromo-cGMP, induced negative relaxant effect. 5,The results obtained suggest that carbachol activation of M3 and M4 muscarinic AChRs, exerts a contractile effect on rat detrusor that is accompanied by an increased production of cGMP and nNOS activity. The mechanism appears to occur secondarily to stimulation of IPs turnover via PLC activation. This in turn, triggers cascade reactions involving CaM, leading to activation of nNOS and soluble guanylate cyclase. They, in turn, exert a modulator inhibitory cGMP-mediated mechanism limiting the effect of muscarinic AChR stimulation of the bladder. [source] The vascular effects of different arginase inhibitors in rat isolated aorta and mesenteric arteriesBRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2009NN Huynh Background and purpose:, Arginase and nitric oxide (NO) synthase share the common substrate L-arginine, and arginase inhibition is proposed to increase NO production by increasing intracellular levels of L-arginine. Many different inhibitors are used, and here we have examined the effects of these inhibitors on vascular tissue. Experimental approach:, Each arginase inhibitor was assessed by its effects on isolated rings of aorta and mesenteric arteries from rats by: (i) their ability to preserve the tolerance to repeated applications of the endothelium-dependent agonist acetylcholine (ACh); and (ii) their direct vasorelaxant effect. Key results:, In both vessel types, tolerance (defined as a reduced response upon second application) to ACh was reversed with addition of L-arginine, (S)-(2-boronethyl)-L-cysteine HCl (BEC) or NG -Hydroxy-L-arginine (L-NOHA). On the other hand, N, -hydroxy-nor-L-arginine (nor-NOHA) significantly augmented the response to ACh, an effect that was partially reversed with L-arginine. No effect on tolerance to ACh was observed with L-valine, nor-valine or D,L, ,-difluoromethylornithine (DFMO). BEC, L-NOHA and nor-NOHA elicited endothelium-independent vasorelaxation in both endothelium intact and denuded aorta while L-valine, DFMO and nor-valine did not. Conclusions and implications:, BEC and L-NOHA, but not nor-NOHA, L-valine, DFMO or nor-valine, significantly reversed tolerance to ACh possibly conserving L-arginine levels and therefore increasing NO bioavailability. However, both BEC and L-NOHA caused endothelium-independent vasorelaxation in rat aorta, suggesting that these inhibitors have a role beyond arginase inhibition alone. Our data thus questions the interpretation of many studies using these antagonists as specific arginase inhibitors in the vasculature, without verification with other methods. [source] | ||||||||||||||||