Letters in Drug Design & Discovery, 2005, 2, 23-25 23 In-Vitro Searching for a New Potent Reactivator of Acetylcholinesterase Inhibited by Nerve Agent VX K. Kuca *,1 , J. Cabal 1 , J. Bajgar 1 and D. Jun 1,2 1 Purkyne Military Medical Academy, Department of Toxicology, Hradec Kralove, Czech Republic 2 Department of Pharmaceutical Botany and Ecology, Charles University in Prague, Faculty of Pharmacy in Hradec Kralove, Hradec Kralove, Czech Republic Received June 10, 2004: Accepted July 28, 2004 Abstract: Organophosphorus compounds, especially nerve agents, inhibit enzyme acetylcholinesterase (AChE; EC 3.1.1.7) in an irreversible manner. Atropine plus an oxime reactivator are used as an effective treatment of organophosphate poisoning. In this work, we have evaluated reactivation potency of twenty reactivators of different chemical structures in reactivation of VX-inhibited AChE. Rat brain AChE homogenate was used as the appropriate source of the enzyme. According to our results, trimedoxime seems to be the most potent reactivator of VX-inhibited AChE at the concentration 10 -3 M. Keywords: Nerve agent, reactivation, inhibition, acetylcholinesterase, trimedoxime, oxime, VX agent. INTRODUCTION organophosphate poisoning. Oxime reactivators break the bond between enzyme and organophosphate and restore the functional enzyme (Scheme 1 – Reactivation). However, none from the currently used AChE reactivators is able to satisfactorily reactivate AChE inhibited by all kinds of OPs [2a]. Organophosphorus compounds (OPs) have been widely used as pesticides in many parts of the world and have been also misused as chemical warfare agents [ 1]. From this group, nerve agents are the most known [ 2]. In the past, they were also used in terroristic attack in Tokyo subway [ 3]. Therefore, the threat of the intoxication with OPs is relatively high. The most potent nerve agents are represented Many laboratories over the world are interested in the synthesis of the so-called “broad spectrum” reactivator that AC hE O - AChE O P O H 3 C OCH 2 CH 3 P O H 3 CH 2 CO CH 3 S - CH 2 CH 2 N CH CH CH 3 CH 3 CH 3 CH 3 + N O - N AC hE O - AC hE O P O H 3 C OC H 2 CH 3 + N ON P CH 3 H 3 CH 2 CO O - S CH 2 CH 2 N CH CH CH 3 CH 3 CH 3 CH 3 Intact enzyme VX - agent Inhibition Phosphorylated enzyme Leaving Phosphorylated enzyme Reactivator of AChE Reactivation Liberated enzyme Phosphorylated oxime Scheme 1. VX-inhibition and oxime-induced reactivation of acetylcholinesterase. by sarin, soman and VX. VX is lipophilic liquid with extremely high toxicity. Thanks to its very high lipophilicity it can easily penetrate through the intact skin [ 4]. VX agent as well as all other OPs inhibit irreversibly enzyme acetylcholinesterase (AChE; EC 3.1.1.7). This action is described as the phosphorylation of the active site of the enzyme (Scheme 1 - Inhibition) and is considered to be the main cause of nerve agents toxicity [5]. would be able to restore the activity of AChE inhibited by broader spectrum of nerve agents [6]. The purpose of this study was to examine the reactivation potency of twenty structurally different AChE reactivators using a standard in vitro reactivation test and to choose the most potent promising reactivator of OPs- inhibited AChE for further investigation. MATERIAL AND METHODS Atropine plus an oxime reactivators such as 2-PAM, obidoxime or HI-6 are used as an effective treatment of Oxime HS-6 was obtained from Dr. Stojiljkovic (National Poison Control Centre; Military Medical Academy; Serbia and Montenegro). Pralidoxime and trimedoxime were purchased from Lé c ˆ iva (Czech Republic) and obidoxime from Merck (Germany). All other tested *Address correspondence to this author at the Purkyne Military Medical Academy, Department of Toxicology, Trebesska 1575, Hradec Kralove, 500 01, Czech Republic; Tel: + 420 973 251 523; Fax: + 420 495 518 094; E-mail: kucakam@pmfhk.cz 1570-1808/05 $50.00+.00 © 2005 Bentham Science Publishers Ltd.