Butyrylcholinesterase (BChE) inhibitors were identified from a collection containing cinchonine, cinchonidine and synthetic derivatives, and further characterized using cytotoxicity and molecular docking studies. The most active ones were: (10 triple bond)-10,11-dibromo-10,11-dihydrocinchonidine (11), a competitive inhibitor with Ki = 3.45 +/- 0.39 microM, and IC50 BChE = 9.83 +/- 0.30 microM/human (h)BChE = 34.47 +/- 4.63 and O-(trimethylsilyl)cinchonine (15), a mixed inhibitor with Kiuc = 1.73 +/- 0.46 microM and Kic = 0.85 +/- 0.26 microM, and IC50 BChE = 0.56 +/- 0.14 microM/hBChE = 0.24 +/- 0.04. In cytotoxicity experiments, > or = 80% of the cells remained viable when exposed to concentrations of up to 80 microM of both inhibitors in four different cell lines, including neurons. Due to the bulkier trimethylsilyl side group of 15, it covered the active site of hBChE better than 11 with an OH-group while not being able to fit into the active site gorge of hAChE, thus explaining the selectivity of 15 towards hBChE.
Given the fundamentally multifactorial character of Alzheimer's disease (AD), addressing more than one target for disease modification or therapy is expected to be highly advantageous. Here, following the cholinergic hypothesis, we aimed to inhibit both acetyl- and butyrylcholinesterase (AChE and BCHE) in order to increase the concentration of acetylcholine in the synaptic cleft. In addition, the formation of the amyloid beta fibrils should be inhibited and already preformed fibrils should be destroyed. Based on a recently identified AChE inhibitor with a 1,4-substituted 4-(1H)-pyridylene-hydrazone skeleton, a substance library has been generated and tested for inhibition of AChE, BCHE, and fibril formation. Blood-brain barrier mobility was ensured by a transwell assay. Whereas the p-nitrosubstituted compound 18C shows an anti-AChE activity in the nanomolar range of concentration (IC50=90nM), the bisnaphthyl substituted compound 20L was found to be the best overall inhibitor of AChE/BCHE and enhances the fibril destruction.
The presented project started by screening a library consisting of natural and natural based compounds for their acetylcholinesterase AChE and butyrylcholinesterase BChE inhibitory activity Active compounds were chemically clustered into groups and further tested on the human cholinesterases isoforms The aim of the presented study was to identify compounds that could be used as leads to target two key mechanisms associated with the AD's pathogenesis simultaneously cholinergic depletion and beta amyloid Abeta aggregation Berberin palmatine and chelerythrine chemically clustered in the so-called isoquinoline group showed promising cholinesterase inhibitory activity and were therefore further investigated Moreover the compounds demonstrated moderate to good inhibition of Abeta aggregation as well as the ability to disaggregate already preformed Abeta aggregates in an experimental set-up using HFIP as promotor of Abeta aggregates Analysis of the kinetic mechanism of the AChE inhibition revealed chelerythrine as a mixed inhibitor Using molecular docking studies it was further proven that chelerythrine binds on both the catalytic site and the peripheral anionic site PAS of the AChE In view of this we went on to investigate its effect on inhibiting Abeta aggregation stimulated by AChE Chelerythrine showed inhibition of fibril formation in the same range as propidium iodide This approach enabled for the first time to identify a cholinesterase inhibitor of natural origin-chelerythrine-acting on AChE and BChE with a dual ability to inhibit Abeta aggregation as well as to disaggregate preformed Abeta aggregates This compound could be an excellent starting point paving the way to develop more successful anti-AD drugs.
In this contribution, a chemical collection of aromatic compounds was screened for inhibition on butyrylcholinesterase (BChE)'s hydrolase activity using Ellman's reaction. A set of diarylimidazoles was identified as highly selective inhibitors of BChE hydrolase activity and amyloid beta (Abeta) fibril formation. New derivatives were synthesized resulting in several additional hits, from which the most active was 6c, 4-(3-ethylthiophenyl)-2-(3-thienyl)-1H-imidazole, an uncompetitive inhibitor of BChE hydrolase activity (IC(5)(0) BChE=0.10 muM; K(i)=0.073 +/- 0.011 muM) acting also on Abeta fibril formation (IC(5)(0)=5.8 muM). With the aid of structure-activity relationship (SAR) studies, chemical motifs influencing the BChE inhibitory activity of these imidazoles were proposed. These bifunctional inhibitors represent good tools in basic studies of BChE and/or promising lead molecules for AD therapy.
The role of butyrylcholinesterase (BChE) in the progression of Alzheimer's disease (AD) has recently become more crucial. In the AD brain, selective BChE inhibitors have been demonstrated to have a beneficial effect in vivo, probably by recovering cholinergic activity and/or by restoring AChE:BChE activity ratios to the levels observed in the healthy brain. Thienothiazines are compounds sharing some structural features with phenothiazines, which are known to be potent BChE inhibitors. Thus, in this contribution 45 thienothiazines were investigated for their BChE inhibitory activity. Six of them were proven to be potent and selective inhibitors of equine BChE's hydrolase activity. Structure-activity relationships were laid out, and a tentative pharmacophore model for BChE inhibitors of the thienothiazine type was proposed. The most active compound, 3f, displayed a mixed type of inhibition and was also active against the human BChE (huBChE) with an IC(50) huBChE of 0.51 +/- 0.07 muM. Computational studies suggested that 3f likely binds to the catalytic site and nearby to the peripheral site of the huBChE in an extended form. In addition, the chemical space occupied by the active thienothiazines, as opposed to phenothiazines and other representative chemical classes of BChE inhibitors, was explored with the aid of ChemGPS-NP, and the relevant chemical space regions were identified. This study shows for the first time that thienothiazines represent a new group of BChE inhibitors that can be used as molecular probes for studying the role of BChE in the brain or for developing newer drug leads for AD therapy.
Title: Discovery of dual binding site acetylcholinesterase inhibitors identified by pharmacophore modeling and sequential virtual screening techniques Gupta S, Fallarero A, Jarvinen P, Karlsson D, Johnson MS, Vuorela PM, Mohan CG Ref: Bioorganic & Medicinal Chemistry Lett, 21:1105, 2011 : PubMed
Dual binding site acetylcholinesterase (AChE) inhibitors are promising for the treatment of Alzheimer's disease (AD). They alleviate the cognitive deficits and AD-modifying agents, by inhibiting the beta-amyloid (Abeta) peptide aggregation, through binding to both the catalytic and peripheral anionic sites, the so called dual binding site of the AChE enzyme. In this Letter, chemical features based 3D-pharmacophore models were developed based on the eight potent and structurally diverse AChE inhibitors (I-VIII) obtained from high-throughput in vitro screening technique. The best 3D-pharmacophore model, Hypo1, consists of two hydrogen-bond acceptor lipid, one hydrophobe, and two hydrophobic aliphatic features obtained by Catalyst/HIPHOP algorithm adopted in Discovery studio program. Hypo1 was used as a 3D query in sequential virtual screening study to filter three small compound databases. Further, a total of nine compounds were selected and followed on in vitro analysis. Finally, we identified two leads--Specs1 (IC(50)=3.279 muM) and Spec2 (IC(50)=5.986 muM) dual binding site compounds from Specs database, having good AChE enzyme inhibitory activity.
