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Stanley M. Parsons - One of the best experts on this subject based on the ideXlab platform.
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The impact of dopamine D2-like agonist/antagonist on [18F]VAT PET measurement of VAChT in the brain of nonhuman primates.
European Journal of Pharmaceutical Sciences, 2020Co-Authors: Hui Liu, Stanley M. Parsons, Zonghua Luo, Hubert P. Flores, Yun Zhou, Joel S. PerlmutterAbstract:Abstract Vesicular acetylcholine transporter (VAChT) is a promising target for a PET measure of cholinergic deficits which contribute to cognitive impairments. Dopamine D2-like agonists and antagonists are frequently used in the elderly and could alter cholinergic function and VAChT level. Therefore, pretreatment with dopamine D2-like drugs may interfere with PET measures using [18F]VAT, a specific VAChT radioligand. Herein, we investigated the impact of dopaminergic D2-like antagonist/agonist on VAChT level in the brain of macaques using [18F]VAT PET. PET imaging studies were carried out on macaques at baseline or pretreatment conditions. For pretreatment, animals were injected using a VAChT inhibitor (-)-Vesamicol, a D2-like antagonist (-)-eticlopride, and a D2-like agonist (-)-quinpirole, separately. (-)-Vesamicol was injected at escalating doses of 0.025, 0.05, 0.125, 0.25 and 0.35 mg/kg; (-)-eticlopride was injected at escalating doses of 0.01, 0.10 and 0.30 mg/kg; (-)-quinpirole was injected at escalating doses of 0.20, 0.30, and 0.50 mg/kg. PET data showed [18F]VAT uptake declined in a dose-dependent manner by (-)-Vesamicol pretreatment, demonstrating [18F]VAT uptake is sensitive to reflect the availability of VAChT binding sites. Furthermore, (-)-eticlopride increased [18F]VAT striatal uptake in a dose-dependent manner, while (-)-quinpirole decreased its uptake, suggesting striatal VAChT levels can be regulated by D2-like drug administration. Our findings confirmed [18F]VAT offers a reliable tool to in vivo assess the availability of VAChT binding sites. More importantly, PET with [18F]VAT successfully quantified the impact of dopaminergic D2-like drugs on striatal VAChT level, suggesting [18F]VAT has great potential for investigating the interaction between dopaminergic and cholinergic systems in vivo.
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Search for the acetylcholine and Vesamicol binding sites in vesicular acetylcholine transporter: the region around the lumenal end of the transport channel.
Journal of neurochemistry, 2010Co-Authors: Parul Khare, Anuprao Mulakaluri, Stanley M. ParsonsAbstract:J. Neurochem. (2010) 115, 984–993. Abstract Vesicular acetylcholine transporter (VAChT; TC 2.A.1.2.13) mediates storage of acetylcholine (ACh) by synaptic vesicles. A three-dimensional homology model of VAChT is available, but the binding sites for ACh and the allosteric inhibitor (−)-trans-2-(4-phenylpiperidino)cyclohexanol (Vesamicol) are unknown. In previous work, mutations of invariant W331 in the lumenal beginning of transmembrane helix VIII (TM VIII) of rat VAChT led to as much as ninefold loss in equilibrium affinity for ACh and no loss in affinity for Vesamicol. The current work investigates the effects of additional mutations in and around W331 and the nearby lumenal end of the substrate transport channel. Mutants of human VAChT were expressed in the PC12A123.7 cell line and characterized using radiolabeled ligands and filtration assays for binding and transport. Properties of a new and a repeat mutation in W331 are consistent with the original observations. Of 16 additional mutations in 13 other residues (Y60 in the beginning of lumenal Loop I/II, F231 in the lumenal end of TM V, W315, M316, K317, in the lumenal end of TM VII, M320, A321, W325, A330 in lumenal Loop VII/VIII, A334 in the lumenal beginning of TM VIII, and C388, C391, F392 in the lumenal beginning of TM X), only A334F impairs binding. This mutation decreases ACh and Vesamicol equilibrium binding affinities by 14- and 4-fold, respectively. The current results, combined with previous results, demonstrate existence of a spatial cluster of residues close to vesicular lumen that decreases affinity for ACh and/or Vesamicol when the cluster is mutated. The cluster is composed of invariant W331, highly conserved A334, and invariant F335 in TM VIII and invariant C391 in TM X. Different models for the locations of the ACh and Vesamicol binding sites relative to this cluster are discussed.
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Equilibrium binding and transport by vesicular acetylcholine transporter.
Methods in molecular biology (Clifton N.J.), 2010Co-Authors: Parul Khare, Aubrey R. White, Anuprao Mulakaluri, Stanley M. ParsonsAbstract:The method describes production and the selection of neurosecretory PC12A123.7 cells stably transfected with human vesicular acetylcholine transporter (hVAChT). Transfected cells provide postnuclear supernatant used to characterize equilibrium binding of the neurotransmitter acetylcholine (ACh), the pH dependence for transport of ACh, and the rate behavior for dissociation of the allosteric, high-affinity inhibitor Vesamicol. Retention of radiolabeled ACh or Vesamicol, mediated by hVAChT in synaptic-like microvesicles of postnuclear supernatant, is measured using filter assays. The procedure for regression analysis of data also is described.
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Multiple protonation states of vesicular acetylcholine transporter detected by binding of [3H]Vesamicol.
Biochemistry, 2009Co-Authors: Parul Khare, Aubrey R. White, Stanley M. ParsonsAbstract:Vesicular acetylcholine transporter (VAChT) is inhibited by (-)-Vesamicol [(-)-trans-2-(4-phenylpiperidino)cyclohexanol], which binds tightly to an allosteric site. The tertiary alkylamine center in (-)-Vesamicol is protonated and positively charged at acidic and neutral pH and unprotonated and uncharged at alkaline pH. Deprotonation of the amine has been taken to explain loss of (-)-Vesamicol binding at alkaline pH. However, binding data deviate from a stereotypical bell shape, and more binding occurs than expected at alkaline pH. The current study characterizes the binding of (-)-Vesamicol from pH 5 to pH 10 using filter assays, (-)-[3H]Vesamicol (hereafter called [3H]Vesamicol), and human VAChT expressed in PC12(A123.7) cells. At acidic pH, protons and [3H]Vesamicol compete for binding to VAChT. Preexposure or long-term exposure of VAChT to high pH does not affect binding, thus eliminating potential denaturation of VAChT and failure of the filter assay. The dissociation constant for the complex between protonated [3H]Vesamicol and VAChT decreases from 12 nM at neutral pH to 2.1 nM at pH 10. The simplest model of VAChT that explains the behavior requires a proton at site 1 to dissociate with pK1 = 6.5 +/- 0.1, a proton at site A to dissociate with pKA = 7.6 +/- 0.2, and a proton at site B to dissociate with pKB = 10.0 +/- 0.1. Deprotonation of the site 1 proton is obligatory for [3H]Vesamicol binding. Deprotonation of site A decreases affinity (2.2 +/- 0.5)-fold, and deprotonation of site B increases affinity (18 +/- 4)-fold. Time-dependent dissociation of bound [3H]Vesamicol is biphasic, but equilibrium saturation curves are not. The contrasting phasicity suggests that the pathway to and from the [3H]Vesamicol binding site exists in open and at least partially closed states. The potential significance of the findings to development of PET and SPECT ligands based on (-)-Vesamicol for human diagnostics also is discussed.
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Specificity of the rat vesicular acetylcholine transporter.
Neurochemical Research, 2003Co-Authors: Myung Hee Kim, Gary A. Rogers, Stanley M. Parsons, Louis B. HershAbstract:The protein kinase A–deficient PC12 cell line PC12A123.7 lacks both choline acetyltransferase and the vesicular acetylcholine transporter. This cell line has been used to establish a stably transfected cell line expressing recombinant rat vesicular acetylcholine transporter that is appropriately trafficked to small synaptic vesicles. Acetylcholine is transported by the rat vesicular acetylcholine transporter at a maximal rate of 1.45 nmol acetylcholine/min/mg protein and exhibits a Km for transport of 2.5 mM. The transporter binds Vesamicol with a Kd of 7.5 nM. The ability of structural analogs of acetylcholine to inhibit both acetylcholine uptake and Vesamicol binding was measured. The results demonstrate that like Torpedo vesicular acetylcholine transporter, the mammalian transporter can bind a diverse group of acetylcholine analogs.
Simon M. N. Efange - One of the best experts on this subject based on the ideXlab platform.
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Hydroxylated decahydroquinolines as ligands for the vesicular acetylcholine transporter: synthesis and biological evaluation.
Journal of medicinal chemistry, 1999Co-Authors: Simon M. N. Efange, A.b Khare, Robert H. Mach, Stanley M. ParsonsAbstract:Analogues of the potent anticholinergic 2-(4-phenylpiperidino)cyclohexanol (Vesamicol, 1) in which the cyclohexyl fragment was replaced with an N-acyl or N-alkyl trans-decahydroquinolyl moiety were synthesized and evaluated as potential ligands for the vesicular acetylcholine transporter (VAChT). The binding of compounds, such as 18, 20, and 21, was both stereospecific and of comparable magnitude to that of the closely related Vesamicol analogue 2,3-trans-4a,8a-trans-3-hydroxy-2-(4-phenylpiperidino)-1,2,3,4,5,6,7,8-decahydronaphthalene (6) which displays subnanomolar affinity for this transporter. However, these compounds also demonstrated high affinities for σ1 and σ2 receptors and thus failed to show significantly improved selectivity over previously reported Vesamicol analogues.
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N-hydroxyalkyl derivatives of 3β-phenyltropane and 1-methylspiro[1H-indoline-3,4'-piperidine] : Vesamicol analogues with affinity for monoamine transporters
Journal of medicinal chemistry, 1997Co-Authors: Simon M. N. Efange, A.b Khare, Robert H. Mach, Ashok P. Kamath, Mei-ping Kung, Stanley M. ParsonsAbstract:As part of our ongoing structure−activity studies of the vesicular acetylcholine transporter ligand 2-(4-phenylpiperidino)cyclohexanol (Vesamicol, 1), 22 N-hydroxy(phenyl)alkyl derivatives of 3β-phenyltropane, 6, and 1-methylspiro[1H-indoline-3,4‘-piperidine], 7, were synthesized and tested for binding in vitro. Although a few compounds displayed moderately high affinity for the vesicular acetylcholine transporter, no compound was more potent than the prototypical vesicular acetylcholine transporter ligand Vesamicol. However, a few derivatives of 6 displayed higher affinity for the dopamine transporter than cocaine. We conclude that modification of the piperidyl fragment of 1 will not lead to more potent vesicular acetylcholine transporter ligands.
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Pharmacological characterization of the Vesamicol analogue (+)-[125I]MIBT in primate brain
European journal of pharmacology, 1997Co-Authors: Julie K. Staley, Stanley M. Parsons, A.b Khare, Deborah C. Mash, Simon M. N. EfangeAbstract:Abstract The Vesamicol analogue, meta-[ 125 I ]iodobenzyltrozamicol [(+)-[ 125 I ]MIBT] was evaluated as a probe for the in vitro labeling of the vesicular acetylcholine transporter in primate brain. In the striatum, (+)-[ 125 I ]MIBT bound a single high-affinity site with a Kd value of 4.4±0.7 nM. Competition for (+)-[ 125 I ]MIBT binding to the striatum by a group of Vesamicol analogues displayed a pharmacological profile similar to the rank order of potency previously observed for the vesicular acetylcholine transporter on Torpedo synaptic vesicles. High-affinity binding of (+)-[ 125 I ]MIBT in the occipital cortex was characterized by a Kd value of 4.6±1.1 nM. However, the rank order of potency for inhibition of (+)-[ 125 I ]MIBT binding to the occipital cortex by the same test compounds differed from that observed in the striatum. The results suggest that (+)-[ 125 I ]MIBT is a reliable probe of the vesicular acetylcholine transporter in primate striatum, but its binding in primate occipital cortex is more complex.
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pharmacological characterization of the Vesamicol analogue 125i mibt in primate brain
European Journal of Pharmacology, 1997Co-Authors: Julie K. Staley, Stanley M. Parsons, A.b Khare, Deborah C. Mash, Simon M. N. EfangeAbstract:Abstract The Vesamicol analogue, meta-[ 125 I ]iodobenzyltrozamicol [(+)-[ 125 I ]MIBT] was evaluated as a probe for the in vitro labeling of the vesicular acetylcholine transporter in primate brain. In the striatum, (+)-[ 125 I ]MIBT bound a single high-affinity site with a Kd value of 4.4±0.7 nM. Competition for (+)-[ 125 I ]MIBT binding to the striatum by a group of Vesamicol analogues displayed a pharmacological profile similar to the rank order of potency previously observed for the vesicular acetylcholine transporter on Torpedo synaptic vesicles. High-affinity binding of (+)-[ 125 I ]MIBT in the occipital cortex was characterized by a Kd value of 4.6±1.1 nM. However, the rank order of potency for inhibition of (+)-[ 125 I ]MIBT binding to the occipital cortex by the same test compounds differed from that observed in the striatum. The results suggest that (+)-[ 125 I ]MIBT is a reliable probe of the vesicular acetylcholine transporter in primate striatum, but its binding in primate occipital cortex is more complex.
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Vesamicol analogues as sigma ligands. Molecular determinants of selectivity at the Vesamicol receptor.
Biochemical pharmacology, 1995Co-Authors: Simon M. N. Efange, A.b Khare, Robert H. Mach, Cynthia R. Smith, Catherine Foulon, Surya K. Akella, Steven R. Childers, Stanley M. ParsonsAbstract:Abstract The present study compares the affinities of 2-(4-phenylpiperidino)cyclohexanol (Vesamicol, 1) and selected analogues of the latter at the Vesamicol receptor (VR) with the corresponding affinities at σ1 and σ2 binding sites. For this study, the parent structure 1 was divided into three fragments: A (cyclohexyl), B (piperidyl) and C (phenyl). Vesamicol analogues were then selected to reflect structural modifications in these fragments. Consistent with earlier reports, Vesamicol was found to exhibit nanomolar affinities at the VR and σ1 and σ2 sites, resulting in poor selectivity for the VR over the sigma sites. Vesamicol analogues characterized by an acyclic A-fragment showed moderate to low affinities at the VR and moderate to high affinities at σ1 and σ2 sites. As a result, many of these analogues showed poor selectivity for the VR. Replacement of the C4 carbon of 1 with a halobenzyl amine resulted in higher affinities at the VR coupled with moderate to low affinities at σ1 and σ2 sites. The introduction of a benzofused substituent at the C4 and C5 positions of 1 (compound 2) resulted in a 200-fold increase in affinity at the VR accompanied by a 5- to 6-fold decrease in affinity at σ1 and σ2 sites relative to the parent structure. Consequently, compound 2 showed 12,000-fold higher affinity at the VR than at sigma sites. Restricting the rotation of fragment C relative to B (by means of alkyl and alkenyl bridges) generally yielded analogues with subnanomolar affinities at the VR. The corresponding affinities of these spirofused conformationally restricted analogues were moderate to poor at σ1 and σ2 sites when fragment A was preserved. In contrast, the affinities at σ1 and σ2 sites were decreased 3- to 11-fold when fragment A was modified at position C4 and decreased up to 100-fold with benzofusion at the C4 and C5 positions of fragment A. Consequently, the spirofused analogues 15–19 were among the most selective VR ligands examined. Thus, the effect of conformational restriction in fragments A and B-C is to increase affinity at the VR while decreasing affinity at σ1 and σ2 sites, and thereby increasing selectivity for the VR over the sigma sites.
A.b Khare - One of the best experts on this subject based on the ideXlab platform.
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Hydroxylated decahydroquinolines as ligands for the vesicular acetylcholine transporter: synthesis and biological evaluation.
Journal of medicinal chemistry, 1999Co-Authors: Simon M. N. Efange, A.b Khare, Robert H. Mach, Stanley M. ParsonsAbstract:Analogues of the potent anticholinergic 2-(4-phenylpiperidino)cyclohexanol (Vesamicol, 1) in which the cyclohexyl fragment was replaced with an N-acyl or N-alkyl trans-decahydroquinolyl moiety were synthesized and evaluated as potential ligands for the vesicular acetylcholine transporter (VAChT). The binding of compounds, such as 18, 20, and 21, was both stereospecific and of comparable magnitude to that of the closely related Vesamicol analogue 2,3-trans-4a,8a-trans-3-hydroxy-2-(4-phenylpiperidino)-1,2,3,4,5,6,7,8-decahydronaphthalene (6) which displays subnanomolar affinity for this transporter. However, these compounds also demonstrated high affinities for σ1 and σ2 receptors and thus failed to show significantly improved selectivity over previously reported Vesamicol analogues.
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N-hydroxyalkyl derivatives of 3β-phenyltropane and 1-methylspiro[1H-indoline-3,4'-piperidine] : Vesamicol analogues with affinity for monoamine transporters
Journal of medicinal chemistry, 1997Co-Authors: Simon M. N. Efange, A.b Khare, Robert H. Mach, Ashok P. Kamath, Mei-ping Kung, Stanley M. ParsonsAbstract:As part of our ongoing structure−activity studies of the vesicular acetylcholine transporter ligand 2-(4-phenylpiperidino)cyclohexanol (Vesamicol, 1), 22 N-hydroxy(phenyl)alkyl derivatives of 3β-phenyltropane, 6, and 1-methylspiro[1H-indoline-3,4‘-piperidine], 7, were synthesized and tested for binding in vitro. Although a few compounds displayed moderately high affinity for the vesicular acetylcholine transporter, no compound was more potent than the prototypical vesicular acetylcholine transporter ligand Vesamicol. However, a few derivatives of 6 displayed higher affinity for the dopamine transporter than cocaine. We conclude that modification of the piperidyl fragment of 1 will not lead to more potent vesicular acetylcholine transporter ligands.
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Pharmacological characterization of the Vesamicol analogue (+)-[125I]MIBT in primate brain
European journal of pharmacology, 1997Co-Authors: Julie K. Staley, Stanley M. Parsons, A.b Khare, Deborah C. Mash, Simon M. N. EfangeAbstract:Abstract The Vesamicol analogue, meta-[ 125 I ]iodobenzyltrozamicol [(+)-[ 125 I ]MIBT] was evaluated as a probe for the in vitro labeling of the vesicular acetylcholine transporter in primate brain. In the striatum, (+)-[ 125 I ]MIBT bound a single high-affinity site with a Kd value of 4.4±0.7 nM. Competition for (+)-[ 125 I ]MIBT binding to the striatum by a group of Vesamicol analogues displayed a pharmacological profile similar to the rank order of potency previously observed for the vesicular acetylcholine transporter on Torpedo synaptic vesicles. High-affinity binding of (+)-[ 125 I ]MIBT in the occipital cortex was characterized by a Kd value of 4.6±1.1 nM. However, the rank order of potency for inhibition of (+)-[ 125 I ]MIBT binding to the occipital cortex by the same test compounds differed from that observed in the striatum. The results suggest that (+)-[ 125 I ]MIBT is a reliable probe of the vesicular acetylcholine transporter in primate striatum, but its binding in primate occipital cortex is more complex.
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pharmacological characterization of the Vesamicol analogue 125i mibt in primate brain
European Journal of Pharmacology, 1997Co-Authors: Julie K. Staley, Stanley M. Parsons, A.b Khare, Deborah C. Mash, Simon M. N. EfangeAbstract:Abstract The Vesamicol analogue, meta-[ 125 I ]iodobenzyltrozamicol [(+)-[ 125 I ]MIBT] was evaluated as a probe for the in vitro labeling of the vesicular acetylcholine transporter in primate brain. In the striatum, (+)-[ 125 I ]MIBT bound a single high-affinity site with a Kd value of 4.4±0.7 nM. Competition for (+)-[ 125 I ]MIBT binding to the striatum by a group of Vesamicol analogues displayed a pharmacological profile similar to the rank order of potency previously observed for the vesicular acetylcholine transporter on Torpedo synaptic vesicles. High-affinity binding of (+)-[ 125 I ]MIBT in the occipital cortex was characterized by a Kd value of 4.6±1.1 nM. However, the rank order of potency for inhibition of (+)-[ 125 I ]MIBT binding to the occipital cortex by the same test compounds differed from that observed in the striatum. The results suggest that (+)-[ 125 I ]MIBT is a reliable probe of the vesicular acetylcholine transporter in primate striatum, but its binding in primate occipital cortex is more complex.
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Vesamicol analogues as sigma ligands. Molecular determinants of selectivity at the Vesamicol receptor.
Biochemical pharmacology, 1995Co-Authors: Simon M. N. Efange, A.b Khare, Robert H. Mach, Cynthia R. Smith, Catherine Foulon, Surya K. Akella, Steven R. Childers, Stanley M. ParsonsAbstract:Abstract The present study compares the affinities of 2-(4-phenylpiperidino)cyclohexanol (Vesamicol, 1) and selected analogues of the latter at the Vesamicol receptor (VR) with the corresponding affinities at σ1 and σ2 binding sites. For this study, the parent structure 1 was divided into three fragments: A (cyclohexyl), B (piperidyl) and C (phenyl). Vesamicol analogues were then selected to reflect structural modifications in these fragments. Consistent with earlier reports, Vesamicol was found to exhibit nanomolar affinities at the VR and σ1 and σ2 sites, resulting in poor selectivity for the VR over the sigma sites. Vesamicol analogues characterized by an acyclic A-fragment showed moderate to low affinities at the VR and moderate to high affinities at σ1 and σ2 sites. As a result, many of these analogues showed poor selectivity for the VR. Replacement of the C4 carbon of 1 with a halobenzyl amine resulted in higher affinities at the VR coupled with moderate to low affinities at σ1 and σ2 sites. The introduction of a benzofused substituent at the C4 and C5 positions of 1 (compound 2) resulted in a 200-fold increase in affinity at the VR accompanied by a 5- to 6-fold decrease in affinity at σ1 and σ2 sites relative to the parent structure. Consequently, compound 2 showed 12,000-fold higher affinity at the VR than at sigma sites. Restricting the rotation of fragment C relative to B (by means of alkyl and alkenyl bridges) generally yielded analogues with subnanomolar affinities at the VR. The corresponding affinities of these spirofused conformationally restricted analogues were moderate to poor at σ1 and σ2 sites when fragment A was preserved. In contrast, the affinities at σ1 and σ2 sites were decreased 3- to 11-fold when fragment A was modified at position C4 and decreased up to 100-fold with benzofusion at the C4 and C5 positions of fragment A. Consequently, the spirofused analogues 15–19 were among the most selective VR ligands examined. Thus, the effect of conformational restriction in fragments A and B-C is to increase affinity at the VR while decreasing affinity at σ1 and σ2 sites, and thereby increasing selectivity for the VR over the sigma sites.
Barbara Wenzel - One of the best experts on this subject based on the ideXlab platform.
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Do spiroindolines have the potential to replace Vesamicol as lead compound for the development of radioligands targeting the vesicular acetylcholine transporter
Bioorganic & medicinal chemistry, 2017Co-Authors: Marcel Lindemann, Peter Brust, Winnie Deuther-conrad, Rp Moldovan, Kondapalli Venkata Gowri Chandra Sekhar, Barbara WenzelAbstract:The vesicular acetylcholine transporter (VAChT) is an important target for in vivo imaging of neurodegenerative processes using positron emission tomography (PET). So far the development of VAChT PET radioligands is based on the single known lead compound Vesamicol. In this study we investigated a recently published spiroindoline based compound class (Sluder et al., 2012), which was suggested to have potential in the development of VAChT ligands. Therefore, we synthesized a small series of N,N-substituted spiro[indoline-3,4'-piperidine] derivatives and determined their in vitro binding affinities toward the VAChT. In order to investigate the selectivity, the off-target binding toward σ1 and σ2 receptors was determined. The compounds possessed VAChT affinities with Ki values in the range of 39-376nM. Binding affinities toward the σ1 and σ2 receptors are in a similar range indicating that the strong structural difference between the spiroindolines and Vesamicol did not improve the selectivity. The observed potential to additionally bind to σ receptors let us assume that the herein investigated spiroindolines are not suitable to replace Vesamicol as lead compound for the development of VAChT ligands.
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Enantioseparation of Vesamicol and novel Vesamicol analogs by high-performance liquid chromatography on different chiral stationary phases.
Journal of chromatography. A, 2010Co-Authors: Barbara Wenzel, Steffen Fischer, Peter Brust, Jörg SteinbachAbstract:High-performance liquid chromatography enantioseparation of Vesamicol and six novel azaspiroVesamicols (amino alcohols) was accomplished on different chiral stationary phases (CSPs) by using an optical rotation based chiral detector for identification of the resolved enantiomers. The Pirkle-type column Reprosil Chiral-NR was found to be most suitable for chiral resolution in normal phase (NP) mode; all compounds could be enantioseparated successfully. Also the cellulose-based column Reprosil Chiral-OM showed appropriate separation properties by using NP conditions. The amylose-type column Reprosil Chiral-AM-RP was most suitable for enantioseparation in reversed phase (RP) mode; five out of seven compounds were resolved. This CSP showed a considerably higher capability for chiral recognition of Vesamicol derivatives in RP mode than the corresponding cellulose-based column Reprosil Chiral-OM-RP. Enantioseparation with the teicoplanin aglycone-based column Reprosil Chiral-AA was successful under polar ionic mobile phase conditions.
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First CoMFA Characterization of Vesamicol Analogs as Ligands for the Vesicular Acetylcholine Transporter
Journal of medicinal chemistry, 2008Co-Authors: Andrzej Szymoszek, Barbara Wenzel, Matthias Scheunemann, Jörg Steinbach, Gerrit SchüürmannAbstract:Vesamicol derivatives are promising candidates as ligands for the vesicular acetylcholine transporter (VAChT) to enable in vivo imaging of cholinergic deficiencies if applied as positron emission t...
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A new 18F-labeled fluoroacetylmorpholino derivative of Vesamicol for neuroimaging of the vesicular acetylcholine transporter
Nuclear medicine and biology, 2008Co-Authors: Dietlind Sorger, Barbara Wenzel, Matthias Scheunemann, Reinhard Schliebs, Udo Großmann, Steffen Fischer, Johnny Vercouille, Achim Hiller, Ali Roghani, Peter BrustAbstract:Abstract With the aim of producing selective radiotracers for in vivo imaging of the vesicular acetylcholine transporter (VAChT) using positron mission tomography (PET), here, we report synthesis and analysis of a new class of conformationally constrained Vesamicol analogues with moderate lipophilicity. The sequential ring opening on trans -1,4-cyclohexadiene dioxide enabled an approach to synthesize 6-arylpiperidino-octahydrobenzo[1,4]oxazine-7-ols [morpholino Vesamicols]. The radiosynthesis of the [ 18 F]fluoroacetyl-substituted derivative ([ 18 F]FAMV) was achieved starting from a corresponding bromo precursor [2-Bromo-1-[7-hydroxy-6-(4-phenyl-piperidin-1-yl)-octahydro-benzo[1,4]oxazin-4-yl]-ethanone] and using a modified commercial computer-controlled module system with a radiochemical yield of 27±4%, a high radiochemical purity (99%) and a specific activity of 35 GBq/μmol. In competitive binding assays using a PC12 cell line overexpressing VAChT and [ 3 H]-(−) Vesamicol, 2-fluoro-1-[7-hydroxy-6-(4-phenyl-piperidin-1-yl)-octahydro-benzo[1,4]oxazin-4-yl]-ethanone (FAMV) demonstrated a high selectivity for binding to VAChT ( K i : 39.9±5.9 nM) when compared to its binding to sigma 1/2 receptors ( K i >1500 nM). The compound showed a moderate lipophilicity (logD (pH 7) =1.9) and a plasma protein binding of 49%. The brain uptake of [ 18 F]FAMV was about 0.1% injected dose per gram at 5 min after injection and decreased continuously with time. Notably, an increasing accumulation of radioactivity in the lateral brain ventricles was observed. After 1 h, the accumulation of [ 18 F]FAMV, expressed as ratio to the cerebellum, was 4.5 for the striatum, 2.0 for the cortical and 1.5 for the hippocampal regions, measured on brain slices using ex vivo autoradiography. At the present time, 75% of [ 18 F]FAMV in the plasma was shown to be metabolized to various hydrophilic compounds, as detected by high-performance liquid chromatography. The degradation of [ 18 F]FAMV was also detected in brain extracts as early as 15 min post injection (p.i.) and increased to 50% at 1 h postinjection. In conclusion, although the chemical properties of [ 18 F]FAMV and the selectivity of binding to VAChT appear to be promising indicators of a useful PET tracer for imaging VAChT, a low brain extraction, in combination with only moderate specific accumulation in cholinergic brain regions and an insufficient in vivo stability prevents the application of this compound for neuroimaging in humans.
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Structural changes of benzylether derivatives of Vesamicol and their influence on the binding selectivity to the vesicular acetylcholine transporter.
European journal of medicinal chemistry, 2005Co-Authors: Barbara Wenzel, Dietlind Sorger, Katrin Heinitz, Matthias Scheunemann, Reinhard Schliebs, Jörg Steinbach, Osama SabriAbstract:Abstract 18 F labelled Vesamicol analogues, which bind to the vesicular acetylcholine transporter (VAChT) in central cholinergic nerve terminals, are expected to be potential radioligands for the visualisation of cholinergic transmission deficits via positron emission tomography (PET). In this report the regioselective synthesis of five novel Vesamicol analogues as well as their in vitro binding properties to the VAChT are described. Beside having the 4-fluorobenzylether-substitution at the cyclohexyl ring as an unique structural feature, the new compounds are additionally modified at the phenyl and piperidine moiety of the Vesamicol skeleton. The affinity and selectivity to the VAChT were analysed by competitive binding studies using tritium labelled radioligands. The VAChT affinities (K i -values) of the novel compounds were estimated ranging between 7.8 ± 3.5 nM and 161.6 ± 17.3 nM, thus some of them are binding with higher affinity to the transporter than Vesamicol. However, the compounds tested demonstrated also affinities to the sigma receptors σ 1 and σ 2 ranging between 4.1 ± 1.5 nM and 327.5 ± 75.9 nM. Nevertheless, these data provide the basis for future structure-binding-studies and further underline the potential and usefulness of Vesamicol analogues for imaging of the VAChT.
Jörg Steinbach - One of the best experts on this subject based on the ideXlab platform.
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New systematically modified Vesamicol analogs and their affinity and selectivity for the vesicular acetylcholine transporter - A critical examination of the lead structure.
European journal of medicinal chemistry, 2015Co-Authors: Claudia Barthel, Dietlind Sorger, Matthias Scheunemann, Jörg Steinbach, Ali Roghani, Winnie Deuther-conrad, Stephanie Schweiger, Petra Jäckel, Gerrit Schüürmann, Osama SabriAbstract:To verify Vesamicol as lead structure in the development of radioligands for imaging of VAChT in the brain by PET, we systematically modified this molecule and investigated four different groups of derivatives. Structural changes were conducted in all three ring systems A, B, and C resulting in a library of different Vesamicol analogs. Based on their in vitro binding affinity toward VAChT as well as σ1 and σ2 receptors, we performed a structure-affinity relationship (SAR) study regarding both affinity and selectivity. The compounds possessed VAChT affinities in the range of 1.32 nM (benzoVesamicol) to >10 μM and selectivity factors from 0.1 to 73 regarding σ1 and σ2 receptors, respectively. We could confirm the exceptional position of benzoVesamicols as most affine VAChT ligands. However, we also observed that most of the compounds with high VAChT affinity demonstrated considerable affinity in particular to the σ1 receptor. Finally, none of the various Vesamicol analogs in all four groups showed an in vitro binding profile suitable for specific VAChT imaging in the brain.
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Enantioseparation of Vesamicol and novel Vesamicol analogs by high-performance liquid chromatography on different chiral stationary phases.
Journal of chromatography. A, 2010Co-Authors: Barbara Wenzel, Steffen Fischer, Peter Brust, Jörg SteinbachAbstract:High-performance liquid chromatography enantioseparation of Vesamicol and six novel azaspiroVesamicols (amino alcohols) was accomplished on different chiral stationary phases (CSPs) by using an optical rotation based chiral detector for identification of the resolved enantiomers. The Pirkle-type column Reprosil Chiral-NR was found to be most suitable for chiral resolution in normal phase (NP) mode; all compounds could be enantioseparated successfully. Also the cellulose-based column Reprosil Chiral-OM showed appropriate separation properties by using NP conditions. The amylose-type column Reprosil Chiral-AM-RP was most suitable for enantioseparation in reversed phase (RP) mode; five out of seven compounds were resolved. This CSP showed a considerably higher capability for chiral recognition of Vesamicol derivatives in RP mode than the corresponding cellulose-based column Reprosil Chiral-OM-RP. Enantioseparation with the teicoplanin aglycone-based column Reprosil Chiral-AA was successful under polar ionic mobile phase conditions.
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First CoMFA Characterization of Vesamicol Analogs as Ligands for the Vesicular Acetylcholine Transporter
Journal of medicinal chemistry, 2008Co-Authors: Andrzej Szymoszek, Barbara Wenzel, Matthias Scheunemann, Jörg Steinbach, Gerrit SchüürmannAbstract:Vesamicol derivatives are promising candidates as ligands for the vesicular acetylcholine transporter (VAChT) to enable in vivo imaging of cholinergic deficiencies if applied as positron emission t...
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Structural changes of benzylether derivatives of Vesamicol and their influence on the binding selectivity to the vesicular acetylcholine transporter.
European journal of medicinal chemistry, 2005Co-Authors: Barbara Wenzel, Dietlind Sorger, Katrin Heinitz, Matthias Scheunemann, Reinhard Schliebs, Jörg Steinbach, Osama SabriAbstract:Abstract 18 F labelled Vesamicol analogues, which bind to the vesicular acetylcholine transporter (VAChT) in central cholinergic nerve terminals, are expected to be potential radioligands for the visualisation of cholinergic transmission deficits via positron emission tomography (PET). In this report the regioselective synthesis of five novel Vesamicol analogues as well as their in vitro binding properties to the VAChT are described. Beside having the 4-fluorobenzylether-substitution at the cyclohexyl ring as an unique structural feature, the new compounds are additionally modified at the phenyl and piperidine moiety of the Vesamicol skeleton. The affinity and selectivity to the VAChT were analysed by competitive binding studies using tritium labelled radioligands. The VAChT affinities (K i -values) of the novel compounds were estimated ranging between 7.8 ± 3.5 nM and 161.6 ± 17.3 nM, thus some of them are binding with higher affinity to the transporter than Vesamicol. However, the compounds tested demonstrated also affinities to the sigma receptors σ 1 and σ 2 ranging between 4.1 ± 1.5 nM and 327.5 ± 75.9 nM. Nevertheless, these data provide the basis for future structure-binding-studies and further underline the potential and usefulness of Vesamicol analogues for imaging of the VAChT.
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Synthesis of novel 4- and 5-substituted benzyl ether derivatives of Vesamicol and in vitro evaluation of their binding properties to the vesicular acetylcholine transporter site
Bioorganic & medicinal chemistry, 2004Co-Authors: Matthias Scheunemann, Barbara Wenzel, Dietlind Sorger, Katrin Heinitz, Reinhard Schliebs, Osama Sabri, Margrit Klingner, Jörg SteinbachAbstract:Detection of the central cholinergic deficits, a consistent feature of Alzheimer's disease, is essential to allow preventive measures and/or symptomatic treatment already at a very early stage of the disease. The vesicular acetylcholine transporter (VAChT) represents an appropriate target to establish PET radiotracer that are adequate for brain imaging the loss of cholinergic terminals. Here we describe the synthesis and binding characteristics of novel derivatives of Vesamicol, known to represent a specific antagonist of VAChT sites. Novel benzyl ether derivatives of Vesamicol either 4- or 5-substituted at the cyclohexylring have been synthesized by different regioselective ring opening reactions of a same epoxide precursor. The affinity and selectivity of the novel compounds to VAChT sites were analyzed by competitive radioligand binding studies in rat brain and liver membrane preparations using tritium labeled radioligands. The 4-substituted fluorobenzylether of Vesamicol 10b was shown to exhibit a high affinity to VAChT sites (Ki-value10b=10.7±1.7 nM), but demonstrated also binding capacities to sigma receptors (Ki-value10b=18.5±6.9 nM, [3H]DTG; Ki-value10b=30.6±9.6 nM, [3H]haloperidol). The data suggest the potential of Vesamicol derivatives to design appropriate radiotracer for PET imaging of central cholinergic deficits.