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      Development of small bisquaternary cholinesterase inhibitors as drugs for pre-treatment of nerve agent poisonings

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          Abstract

          Background

          Intoxication by nerve agents could be prevented by using small acetylcholinesterase inhibitors (eg, pyridostigmine) for potentially exposed personnel. However, the serious side effects of currently used drugs led to research of novel potent molecules for prophylaxis of organophosphorus intoxication.

          Methods

          The molecular design, molecular docking, chemical synthesis, in vitro methods (enzyme inhibition, cytotoxicity, and nicotinic receptors modulation), and in vivo methods (acute toxicity and prophylactic effect) were used to study bispyridinium, bisquinolinium, bisisoquinolinium, and pyridinium-quinolinium/isoquinolinium molecules presented in this study.

          Results

          The studied molecules showed non-competitive inhibitory ability towards human acetylcholinesterase in vitro that was further confirmed by molecular modelling studies. Several compounds were selected for further studies. First, their cytotoxicity, nicotinic receptors modulation, and acute toxicity (lethal dose for 50% of laboratory animals [LD 50]; mice and rats) were tested to evaluate their safety with promising results. Furthermore, their blood levels were measured to select the appropriate time for prophylactic administration. Finally, the protective ratio of selected compounds against soman-induced toxicity was determined when selected compounds were found similarly potent or only slightly better to standard pyridostigmine.

          Conclusion

          The presented small bisquaternary molecules did not show overall benefit in prophylaxis of soman-induced in vivo toxicity.

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          Most cited references 29

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          Cholinesterase reactivators and bioscavengers for pre- and post-exposure treatments of organophosphorus poisoning.

          Organophosphorus agents (OPs) irreversibly inhibit acetylcholinesterase (AChE) causing a major cholinergic syndrome. The medical counter-measures of OP poisoning have not evolved for the last 30 years with carbamates for pretreatment, pyridinium oximes-based AChE reactivators, antimuscarinic drugs and neuroprotective benzodiazepines for post-exposure treatment. These drugs ensure protection of peripheral nervous system and mitigate acute effects of OP lethal doses. However, they have significant limitations. Pyridostigmine and oximes do not protect/reactivate central AChE. Oximes poorly reactivate AChE inhibited by phosphoramidates. In addition, current neuroprotectants do not protect the central nervous system shortly after the onset of seizures when brain damage becomes irreversible. New therapeutic approaches for pre- and post-exposure treatments involve detoxification of OP molecules before they reach their molecular targets by administrating catalytic bioscavengers, among them phosphotriesterases are the most promising. Novel generation of broad spectrum reactivators are designed for crossing the blood-brain barrier and reactivate central AChE. This is an article for the special issue XVth International Symposium on Cholinergic Mechanisms.
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            Design of a potent reactivator of tabun-inhibited acetylcholinesterase--synthesis and evaluation of (E)-1-(4-carbamoylpyridinium)-4-(4-hydroxyiminomethylpyridinium)-but-2-ene dibromide (K203).

            Acetylcholinesterase reactivators are crucial antidotes for the treatment of organophosphate intoxication. Among the organophosphates, with the exception of soman, tabun (GA) intoxications are the least responsive to treatment with commercially available therapeutics. A rational design was used to increase reactivation ability and decrease the toxicity of the novel reactivator. (E)-1-(4-carbamoylpyridinium)-4-(4-hydroxyiminomethylpyridinium)-but-2-ene dibromide (K203) has better properties than previously tested compounds in vitro and, therefore, is a potential candidate for the treatment of GA intoxication in vivo.
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              Preparation and in vitro screening of symmetrical bis-isoquinolinium cholinesterase inhibitors bearing various connecting linkage--implications for early Myasthenia gravis treatment.

              Inhibitors of acetylcholinesterase are compounds widely used in the treatment of various diseases, such as Alzheimer's disease, glaucoma and Myasthenia gravis (MG). Compounds used in the therapy of MG posses a positive charge in the molecule to ensure peripheral effect of action and minimal blood-brain barrier penetration. The most prescribed carbamate inhibitors are however known for many severe side effects related to the carbamylation of AChE. This paper describes preparation and in vitro evaluation of 20 newly prepared bis-isoquinolinium inhibitors of potential concern for MG. The newly prepared compounds were evaluated in vitro on human recombinant AChE and human plasmatic butyrylcholinesterase (BChE). Their inhibitory ability was expressed as IC50 and compared to chosen standards ambenonium dichloride, edrophonium chloride, BW284c51 and ethopropazine hydrochloride. Three novel compounds presented promising inhibition (in nM range) of both enzymes in vitro better or similar to edrophonium and BW284c51, but worse to ambenonium. The novel inhibitors did not present higher selectivity toward AChE or BChE. The kinetic assay confirmed non-competitive inhibition of hAChE by two selected promising novel compounds. Two newly prepared compounds were also chosen for docking studies that confirmed apparent π-π or π-cationic interactions aside the cholinesterases catalytic sites. The SAR findings were discussed. Copyright © 2010 Elsevier Masson SAS. All rights reserved.
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                Author and article information

                Journal
                Drug Des Devel Ther
                Drug Des Devel Ther
                Drug Design, Development and Therapy
                Drug Design, Development and Therapy
                Dove Medical Press
                1177-8881
                2018
                09 March 2018
                : 12
                : 505-512
                Affiliations
                [1 ]Department of Chemistry, Faculty of Science, University of Hradec Kralove
                [2 ]Biomedical Research Center, University Hospital Hradec Kralove
                [3 ]Department of Toxicology and Military Pharmacy, Faculty of Military Health Sciences, University of Defence
                [4 ]Department of Neurology, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
                Author notes
                Correspondence: Kamil Kuca, Biomedical Research Center, University Hospital Hradec Kralove, Sokolska 581, 500 05 Hradec Kralove, Czech Republic, Tel +420 603 289 166, Email kamil.kuca@ 123456fnhk.cz
                Article
                dddt-12-505
                10.2147/DDDT.S133038
                5849933
                © 2018 Kuca et al. This work is published and licensed by Dove Medical Press Limited

                The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

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                Original Research

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