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The misuse of novichok agents in assassination attempts has been reported in the international media since 2018. These relatively new class of neurotoxic agents is claimed to be more toxic than the agents of the G and V series and so far, there is no report yet in literature about potential antidotes against them. To shed some light into this issue, we report here the design and synthesis of NTMGMP, a surrogate of A-242 and also the first surrogate of a novichok agent useful for experimental evaluation of antidotes. Furthermore, the efficiency of the current commercial oximes to reactivate NTMGMP-inhibited acetylcholinesterase (AChE) was evaluated. The Ellman test was used to confirm the complete inhibition of AChE, and to compare the subsequent rates of reactivation in vitro as well as to evaluate aging. In parallel, molecular docking, molecular dynamics and MM-PBSA studies were performed on a computational model of the human AChE (HssAChE)/NTMGMP complex to assess the reactivation performances of the commercial oximes in silico. Experimental and theoretical studies matched the exact hierarchy of efficiency and pointed to trimedoxime as the most promising commercial oxime for reactivation of AChE inhibited by A-242. [ABSTRACT FROM AUTHOR]

Organophosphorus poisoning caused by some pesticides and nerve agents is a life-threating condition that must be swiftly addressed to avoid casualties. Despite the availability of medical countermeasures, the clinically available compounds lack a broad spectrum, are not effective towards all organophosphorus toxins, and have poor pharmacokinetics properties to allow them crossing the blood-brain barrier, hampering cholinesterase reactivation at the central nervous system. In this work, we designed and synthesised novel isatin derivatives, linked to a pyridinium 4-oxime moiety by an alkyl chain with improved calculated properties, and tested their reactivation potency against paraoxon- and NEMP-inhibited acetylcholinesterase in comparison to the standard antidote pralidoxime. Our results showed that these compounds displayed comparable in vitro reactivation also pointed by the in silico studies, suggesting that they are promising compounds to tackle organophosphorus poisoning. [ABSTRACT FROM AUTHOR]

Benchmark dose (BMD) approach, as an advanced statistical methodology for dose-effect analysis in toxicological research (1) was used to quantitatively characterize in vivo efficacy of two experimental bispyridinium oximes K203 and K027, following promising findings on their low acute toxicity and potential to reactivate acetylcholinesterase (AChE) inhibited by organophosphorus (OP) pesticides and nerve agents in vitro and in vivo (2). Immediately after DDVP challenge (75% LD50, s.c.), male Wistar rats were treated with oxime (0/1.25/2.5/5/25/50% LD50, i.m.). Erythrocyte and diaphragm AChE activity was determined by Ellman's method 60 min after the treatment. Benchmark analysis was done in PROAST software ver. 65.5 (RIVM, The Netherlands). Derived BMDer were K203 = 194 (153, 243) and K027 = 100 (81, 125) μmol/kg bw, BMDdiaph were K203 = 117 (56, 209) and K027 = 21 (10, 37) μmol/kg bw, indicating that oxime K027 induces the same effect size with 2 and 5.5-times lower dose compared to oxime K203 in erythrocites and diaphragm, respectively. Quantification of equieffective doses of oxime reactivators would enable more reliable definition of their therapeutic widths, which further contributes to better determination of therapeutic dosage regimens and, finally, increases the relevance of results obtained in animal models for the human population. [ABSTRACT FROM AUTHOR]

The chromatographic behavior was studied of a series of potential acetylcholinesterase reactivators, pyridinium oximes, bearing linear aliphatic chains of the length of the aliphatic bridge from 1 to 12 carbon atoms, on a pentafluorophenyl-modified stationary phase. The retention mechanisms and the dependence of the capacity factor on mobile phase composition, aliphatic chain bridge length and calculated log P were evaluated and discussed in detail. The separation of the studied oximes was found to be driven by hydrophobic interactions when a lower content of organic modifier was used in mobile phase; however, the ion-exchange mechanism was the leading one when a large portion of organic modifier was used. In addition, the lipophilicity was found to be a driving mechanism of the separation of oximes bearing a connecting chain of the length of 6–12 carbon atoms, whereas the retention of oximes with shorter connecting chains was significantly influenced by other separation mechanisms such as aromatic or π–π interaction. These results can be useful for the development of new, efficient acetylcholinesterase reactivators. [ABSTRACT FROM AUTHOR]

Oxime K203 is a new compound designed to be used as an acetylcholinesterase reactivator for the treatment of intoxication following exposure to tabun and certain pesticides. After intramuscular administration of a therapeutic (23 mg/kg) dose, the time-course of plasma concentrations of K203 in rats was determined by HPLC. Maximum concentrations were reached between 4.0 and 60 rain (16.5±2.1 µg/ml in 40 min and 16.6±2.0 in 60 min, respectively) with the concentration being relatively constant during this period. There was no significant effect on the plasma concentration of thiobarbituric acid reactive substances (TBARS) during the administration of K203, indicating an absence of oxidative stress. Indeed, administration of K203 led to a significant increase in low molecular weight antioxidants which could tentatively be interpreted as representing a beneficial effect. [ABSTRACT FROM AUTHOR]

Illegal poisoning of wildlife and domestic animals is a worldwide issue. The carbamates primarily used as pesticides are often misused for such a purpose. In this study, 181 birds, mammals and baits were analysed over the period 2004-09 for possible intoxication by carbamates. Intoxication by carbamate carbofuran was diagnosed in 89 cases, and in another 19 cases (nine Wild Boars and 10 Bisons) intoxication with another carbamate -- methomyl -- was proven. Incidental ingestion of the marten bait was the main cause of intoxication. Although the distribution of carbofuran was prohibited in 2007, no decline in the number of intoxicated animals in the following two years was detected. New cases of intoxication by carbofuran are anticipated in the future until all remaining stock is expended. [ABSTRACT FROM AUTHOR]

The pyridinium oxime therapy for treatment of organophosphate poisoning is a well established, but not sufficient method. Recent trends also focus on prophylaxis as a way of preventing even the entrance of organophosphates into the nervous system. One of the possible prophylactic methods is increasing the concentration of butyrylcholinesterase in the blood with the simultaneous administration of butyrylcholinesterase reactivators, when the enzyme is continuously reactivated by oxime. This article summarizes and sets forth the structural differences between butyrylcholinesterase and acetylcholinesterase, essential for the future design of butyrylcholinesterase reactivators. Butyrylcholinesterase lacks the reactivator aromatic binding pocket found in acetylcholinesterase, which is itself a part of the acetylcholinesterase peripheral anionic site. This difference finally renders the current acetylcholinesterase reactivators, when used in butyrylcholinesterase, non-functional. [ABSTRACT FROM AUTHOR]

Trimedoxime is a bisquaternary oxime that is widely used in the treatment of organophosphorous poisoning caused by tabun and paraoxon. We tested its affinity to acetylcholinesterase (AChE), its mechanism of interaction and effect on the cholinergic system of the rat bladder. The half maximal inhibitory concentration (IC50) of trimedoxime to recombinant AChE was found to be 82.0 mM ± 30.1 mM. This represents a weak inhibition. Its interaction with AChE seems to be very similar to obidoxime - one aromatic nucleus interacts with the peripheral anionic site and the other with the residues TYR337 and TYR341 inside the cavity. Also the oxime moiety is moving towards the catalytic triade ready for the reactivation of the inhibited AChE. In the organ bath experiment no significant effect of trimedoxime was observed on the contraction of the detrusor caused by the muscarinic agonist metacholine. [ABSTRACT FROM AUTHOR]

In this in vitro study, using the HPLC method, we determined the ability of acetylcholinesterase (AChE) reactivators, used clinically, to penetrate the blood-brain barrier (BBB). We evaluated pralidoxime, HI-6, obidoxime, trimedoxime and methoxime - reactivators varying in the position of the oxime group on the pyridinium ring and linker connecting the pyridinium rings. Our results indicated that pralidoxime, a monoquaternary AChE reactivator, was the oxime with the most penetration. Molecular weight seems to be the most important factor for passive transport through the BBB. From the structural perspective, the connecting linker also plays a key role in the ability of the reactivators to penetrate the CNS. In this case, the simple and short linker is favorable for permeation of these compounds. The location of the oxime group on the pyridine ring may also influence passive transport into the brain; the best position of the oxime group seems to be position four. [ABSTRACT FROM AUTHOR]

Some compounds, although not primarily designed as supportive drugs in chemotherapy, are promising candidates for clinical use. The ability of HI-6 oxime to relieve the side effects of irinotecan was recently determined in vitro. In this animal study, we investigated the efficacy of HI-6 in vivo, when given as a pre-treatment and concomitantly with irinotecan. We evaluated the cholinesterase (ChE)/acetylcholinesterase (AChE) activity, the levels of oxidative stress markers, DNA damage and the radical scavenging capacity of HI-6. Both HI-6 and irinotecan inhibited ChE/AChE activity but showed different levels of ChE inhibition in plasma and AChE inhibition in the liver and brain tissue. We also observed a weak antioxidant capacity of HI-6, undiscovered until now, and found an acceptable genotoxicity profile in three types of somatic cells in rats. The in vivo erythrocyte micronucleus assay showed that HI-6 did not significantly change either the frequency of micronuclei or the ratio of polychromatic and normorchromatic erythrocytes. Taken together, our results provide a good argument in favour of HI-6 as a promising molecule for further studies and eventual use in humans. [ABSTRACT FROM AUTHOR]

The broad-spectrum reactivator is a valuable oxime able to reactivate acetylcholinesterase (AChE) inhibited by nerve agents and pesticides. At present there are many AChE reactivators (oximes) which are suitable candidates as broad-spectrum reactivators and among them is the oxime HI-6, highly enough thought of to have been recommended by many armies for use as a universal antidote. In this study, we wanted to establish whether the designation "broad-spectrum" is a an accurate description or if there are some lacks in reactivation of nerve agents or pesticides. For this purpose, the general in vitro test for the evaluation ofAChE reactivators was used. Tabun, sarin, cyclosarin, soman, VX agent, Russian VX were used as nerve agents for testing, and chiorpyrifos, paraoxon, methyl-chiorpyrifos and dichlorvos (DDVP) were used as typical examples of organophoshorus pesticides. The results obtained showed that oxime HI-6 did .not reactivate tabun- and DDVP-inhibited AChE, and, in the case of the other pesticides, only a high dose of oxime HI-6 was able to reactivate pesticide-inhibited AChE. [ABSTRACT FROM AUTHOR]

We studied the influence of four methods of euthanasia (decapitation, exsanguination via cardiocentesis following ether anaesthesia, Nembutal anaesthesia, or immersion in a CO2 atmosphere) on the activity of acetylcholinesterase (AChE) and butyryicholinesterase (BChE) in the brain and in the blood of mature female rats. A significant decrease was observed in the activity of AChE in the whole blood in the group treated with Nembutal. There were no significant changes in the activity of BChE with any method of euthanasia. Euthanasia in a CO2 atmosphere was the best technique with respect to the results indicating lack of affect on the activity of AChE and BChE in the periphery and the brain, as well as from the point of view of the welfare of the animals. [ABSTRACT FROM AUTHOR]

This article is focused on an optimization of acetylcholinesterase immobilization on screen printed platinum electrodes. An acetylcholinesterase layer cross linked by glutaraldehyde and another non cross linked were compared according to several parameters including background current, current before and current after inhibition by paraoxon. The percentage of inhibition was also calculated. The results obtained confirmed the importance of glutaraldehyde cross linking in the design of the acetylcholinesterase based biosensor. [ABSTRACT FROM AUTHOR]

Acetylcholinesterase (AChE) is a widely spread enzyme playing a very important role in nerve signal transmission. As AChE controls key processes, its inhibition leads to the very fast death of an organism, including humans. However, when this feature is to be used for killing of unwanted organisms (i.e. mosquitoes), one is faced with the question - how much do AChEs differ between species and what are the differences? Here, a theoretical point of view was utilized to identify the structural basis for such differences. The various primary and tertiary alignments show that AChEs are very evolutionary conserved enzymes and this fact could lead to difficulties, for example, in the search for inhibitors specific for a particular species. [ABSTRACT FROM AUTHOR]

The article presents a study which examined how equine butyrylchlolinesterase (Eq BuChE) protects rats against inhalation exposure to sublethal sarin concentrations. Cholinesterase and brain acetylcholinesterase (AChE) activities were determined. Results showed decreases in plasma Eq BuChE activity and red blood cells and brain AChE activities in rats after sarin inhalation exposure.

The article presents an in vitro study of three potential acetylcholinesterase (AChE) reactivators taken from a monoquaternary reactivator pralidoxime. The compounds used in the study include pyridinium-2-aldoxime-4- carbamoyl-N-methyl iodide, pyridinium-2-aldoxime-4-ethoxycarbonyl-N-methyl iodide, and pyridinium-2-aldoxime-5-ethoxycarbonyl-N-methyl iodide. Results showed that none of the tested oximes was able to reactivate cyclosarin-inhibited AChE.

In this work in vitro evaluation of the reactivation potency of the newly synthesized reactivators for acetylcholinesterase (AChE; EC 3.1.1.7) is described. Using this method, reactivation potency of 21 potential reactivators of AChE inhibited by the nerve agent sarin has been evaluated. We have confirmed the fact that currently the most promising AChE reactivator, HI-6, is the most effective reactivator of sarin-inhibited AChE. There are only three AChE reactivators—HI-6, TO033 and TO047—able to satisfactorily reactivate sarin-inhibited AChE at the concentration 10 -5 M, which is nontoxic for human use. On the other hand, there are 14 AChE reactivators, that are able to reactivate sarin-inhibited AChE at the concentration 10 -3 M. However, this concentration of reactivator is probably toxic for human use. [ABSTRACT FROM AUTHOR]

Abstract: It was shown that intoxications with GF-agent are rather resistant to convential oxime therapy; therefore, the development of new oximes in an effort to improve this unsatisfactory situation continues. Upon screening in vitro reactivation test for oximes, that were either newly synthesized at our department, or those that have never been tested for reactivation of GF-inhibited acetylcholinesterase (AChE), three oximes {(1,4-bis(4-hydroxyiminomethylpyridinium)butane dibromide) (K033); (1-(2-hydroxyiminomethylpyridinium)-3-(3-carbamoylpyridinium)-2-oxa-propane dichloride) (HS-6); and (1-(2-hydroxyiminomethylpyridinium)-4-(4-carbamoylpyridinium)-but-2-ene dibromide) (BI-6)} with the highest reactivation potency were chosen for in vivo testing in our study. 1,3-Bis(4-hydroxyiminomethylpyridinium)-2-oxa-propane dibromide) (obidoxime); (1-(2-hydroxyiminomethylpyridinium)-3-(4-carbamoylpyridinium)-2-oxa-propane dichloride) (HI-6); and (1,1-bis(4-hydroxyiminomethylpyridinium)-methane dibromide) (methoxime) were chosen for comparison as a standard antidotal treatment. All the oximes were applied at the same proportion of their LD50 value (5%), and because of the different acute toxicity of the oximes, the molar concentrations of their solutions for intramuscular (i.m.) administration were considerably different. The highest therapeutic ratio was achieved for therapeutic regimen consisting of HI-6 and atropine. The significantly (P < 0.05) lowest effectivity in treatment of supralethal GF-agent poisoning in comparison with all the other therapeutic regimens, was surprisingly observed for methoxime. HS-6, K033 and BI-6 as well as obidoxime were comparably effective antidotes against GF-agent intoxication and their therapeutic ratios were similar. [Copyright &y& Elsevier]

A comparison of one mono- and seven bisquaternary acetylcholinesterase (AChE) reactivators of acetylcholinesterase inhibited by VX agent was performed. As a source of the acetylcholinesterase, a rat brain homogenate was taken. There were significant differences in reactivation potency of all tested oximes. The oxime TO205 seems to be the most efficacious followed by TO046, HI-6, HS-6, K027, obidoxime, MMC and 2-PAM. In addition, the results of this study showed that the reactivation potency of the tested reactivators depends on many factors - such as the number of pyridinium rings, the number of oxime groups and their position, as well as the length and the shape of linkage bridge between two pyridinium rings. [ABSTRACT FROM AUTHOR]

This article describes acetylcholinesterase (AChE), an enzyme involved in parasympathetic neurotransmission, its activity, and how its inhibition can be pharmacologically useful for treating dementia, caused by Alzheimer's disease, or as a warfare method due to the action of nerve agents. The chemical concepts related to the irreversible inhibition of AChE, its reactivation, and aging are discussed, along with a relationship to the current international legislation on chemical weapons. [ABSTRACT FROM AUTHOR]

Certain AChE reactivators, asoxime, obidoxime, K027, K048, and K075, when taken in overdoses and sometimes even when introduced within therapeutic ranges, may injure the different organs. As a continuation of previously published data, in this study, Wistar rats have sacrificed 24 hrs and 7 days after single im application of 0.1LD50, 0.5LD50 and 1.0LD50 of each reactivator, and examinated tissue samples were obtained for pathohistological and semiquantitative analysis. A severity of tissue alteration, expressed as different tissue damage scores were evaluated. Morphological structure of examinated tissues treated with of 0.1LD50 of all reactivators was comparable with the control group of rats. Moderate injuries were seen in visceral tissues treated with 0.5LD50 of asoxime, obidoxime and K027. Acute damages were enlarged after treatment with 0.5LD50 and 1.0LD50 of all reactivators during the next 7 days. The most prominent changes were seen in rats treated with 1.0LD50 of K048 and K075 (P < 0.001 vs. control and asoxime-treated group). All reactivators given by a single, high, unitary dose regimen, have an adverse effect not only on the main visceral tissue, but on the whole rat as well, but the exact mechanism of cellular injury remains to be confirmed in further investigation. [ABSTRACT FROM AUTHOR]

Casualties caused by organophosphorus pesticides are a burden for health systems in developing and poor countries. Such compounds are potent acetylcholinesterase irreversible inhibitors, and share the toxic profile with nerve agents. Pyridinium oximes are the only clinically available antidotes against poisoning by these substances, but their poor penetration into the blood-brain barrier hampers the efficient enzyme reactivation at the central nervous system. In searching for structural factors that may be explored in future SAR studies, we evaluated neutral aryloximes as reactivators for paraoxon-inhibited Electrophorus eel acetylcholinesterase. Our findings may result into lead compounds, useful for development of more active compounds for emergencies and supportive care. [ABSTRACT FROM AUTHOR]

Synthesis of a new asymmetric bisquaternary reactivator of tabun-inhibited acetylcholinesterase-1-(4-hydroxyiminomethylpyridinium)-4-(4-carbamoylpyridinium) butane dibromide is described. Reactivation potency of this oxime is compared to the currently used reactivators—pralidoxime, obidoxime and H-oxime HI-6. [Copyright &y& Elsevier]

Two methods for the synthesis of a new unsymmetric bispyridinium oxime-1-(4-hydroxyiminomethylpyridinium)-3-(carbamoylpyridinium)propane dibromide are described. In vitro efficacy of this new oxime to reactivate sarin-inhibited acetylcholinesterase has been evaluated. [Copyright &y& Elsevier]

The novel 7-methoxytacrine-4-pyridinealdoxime agent, named hybrid 5C, is a hybrid compound comprised of a linkage between 7-methoxytacrine (7-MEOTA-4-PA) and reactivator 4-pyridinealdoxime (4-PA) moieties through a 5-carbon length-spacer. This compound was formerly designed as a prophylactic agent for intoxication by organophosphates (OP), able to form a complex with acetylcholinesterase (AChE) and reactivate this enzyme in case of OP inhibition. In order to check if the 5 carbons spacer is the ideal to maximize the interactions of this compound inside AChE, we performed in this work docking, molecular dynamics and mmpbsa studies on a series of analogues of hybrid 5C, varying the spacer-length from 1 to 10 carbons long. Our results helped to elucidate the interactions of these compounds with the different binding sites inside human AChE (HssAChE) and pointed to the 4 and 5 carbons long as the best spacers for optimizing these interactions. [ABSTRACT FROM AUTHOR]

Progress in the development of biodegradable ionic liquids (ILs) [1] allowed finding sustainable fragments to assist the synthesis of sustainable molecules by means of "benign by design" approach. Based on our recent experience in creating micellar catalytic systems for decomposition of organophosphates [2, 3] we have elaborated the following oxime-functionalized low-toxic biodegradable ILs as potential AcChE reactivators: amide/ester linked (amino acid free) IL (I) as well as L-alanine (II) and L-phenylalanine (III) containing compounds with pyridinium aldoxime moiety in cationic part. Variation of amino acid variation (e.g. Me for I and phenyl for II) can help us to analyze a role of hydrophobicity of IL's cation in AcChE reactivation. The reactivation capacity of novel ILs were evaluated towards AcChE inhibited by typical toxic organophosphate agents. The regularities of antidotal activity of studied compounds are to use in the further improvement of their structures. [ABSTRACT FROM AUTHOR]

Nerve agents (NA) pose as a great risk in the modern world. NA from the V-series, such as VX, are currently recognized as the most toxic among those compounds. However, the emergence of new classes of toxicants recently included in the Chemical Weapons Convention (CWC), such as the A-series NA, a class of organophosphorus compounds related to phosphoramidates, pose a new source of concern due to the lack of information. In order advance in the investigation on the toxicity of such toxic chemicals, we performed in vitro studies to compare representatives of the V- and A-series using affordable surrogates. Results suggest a similar inhibition potency between both agents. • Nerve agents are a great concern in the modern world. • V-series nerve agents are the most toxic organophosphorus compounds known. • There are insufficient data on A-series nerve agents. • Preliminary in vitro study comparing of V- an A-series' surrogates were performed. • Toxicity of V- an A-series' surrogates were comparable under assays' conditions. [ABSTRACT FROM AUTHOR]

An abstract of a paper on acetylcholinesterase reactivating drugs, discussed at the 17th Scientific Symposium of the Austrian Pharmacological Society's (APHAR) meeting with the Hungarian Society of Experimental and Clinical Pharmacology (MFT) in Innsbruck, Austria, is presented.

Abstract: Kinetic parameters were evaluated for inhibition of native and reactivation of tabun-inhibited human erythrocyte acetylcholinesterase (AChE, EC 3.1.1.7) and human plasma butyrylcholinesterase (BChE, EC 3.1.1.8) by three bispyridinium para-aldoximes with butane (K074), but-2-ene (K075) or xylene-like linker (K114). Tested aldoximes reversibly inhibited both cholinesterases with the preference for binding to the native AChE. Both cholinesterases showed the highest affinity for K114 (K i was 0.01mM for AChE and 0.06mM for BChE). The reactivation of tabun-inhibited AChE was efficient by K074 and K075. Their overall reactivation rate constants were around 2000min−1 M−1, which is seven times higher than for the classical bispyridinium para-aldoxime TMB-4. The reactivation of tabun-inhibited AChE assisted by K114 was slow and reached 90% after 20h. Since the aldoxime binding affinity of tabun-inhibited AChE was similar for all tested aldoximes (and corresponded to their K i ), the rate of the nucleophilic displacement of the phosphoryl-moiety from the active site serine was the limiting factor for AChE reactivation. On the other hand, none of the aldoximes displayed a significant reactivation of tabun-inhibited BChE. Even after 20h, the reactivation maximum was 60% for 1mM K074 and K075, and only 20% for 1mM K114. However, lower BChE affinities for K074 and K075 compared to AChE suggest that the fast tabun-inhibited AChE reactivation by these compounds would not be obstructed by their interactions with BChE in vivo. [Copyright &y& Elsevier]

We report a green chemistry approach for preparation of oxime-functionalized ILs as AChE reactivators: amide/ester linked IL, l -alanine, and l -phenylalanine derived salts bearing pyridinium aldoxime moiety. The reactivation capacities of the novel oximes were evaluated towards AChE inhibited by typical toxic organophosphates, sarin (GB), VX, and paraoxon (PON). The studied compounds are mostly non-toxic up to the highest concentrations screened (2 mM) towards Gram-negative and Gram-positive bacteria cell lines and both filamentous fungi and yeasts in the in vitro screening experiments as well as towards the eukaryotic cell (CHO–K1 cell line). Introduction of the oxime moiety in initially biodegradable structure decreases its ability to biodegradation. The compound 3d was shown to reveal remarkable activity against the AChE inhibited by VX, exceeding conventional reactivators 2-PAM and obidoxime. The regularities on antidotal activity, cell viability, plasma stability, biodegradability as well as molecular docking study of the newly synthesized oximes will be used for further improvement of their structures. [Display omitted] • Series of AChE reactivators were synthesized using sustainable IL-based molecular platforms. • Physico-chemical properties and toxicity of novel reactivators were evaluated. • Reactivation capacity were evaluated towards AChE inhibited by typical toxic organophosphates. • Selected oximes demonstrate activity, exceeding conventional reactivators. [ABSTRACT FROM AUTHOR]

Multi-target drug discovery is one of the most followed approaches in the active central nervous system (CNS) therapeutic area, especially in the search for new drugs against Alzheimer's disease (AD). This is because innovative multi-target-directed ligands (MTDLs) could more adequately address the complexity of this pathological condition. In a continuation of our efforts aimed at a new series of anti-AD MTDLs, we combined the structural features of the cholinesterase inhibitor drug tacrine with that of resveratrol, which is known for its purported antioxidant and anti-neuroinflammatory activities. The most interesting hybrid compounds ( 5 , 8 , 9 and 12 ) inhibited human acetylcholinesterase at micromolar concentrations and effectively modulated Aβ self-aggregation in vitro. In addition, 12 showed intriguing anti-inflammatory and immuno-modulatory properties in neuronal and glial AD cell models. Importantly, the MTDL profile is accompanied by high-predicted blood-brain barrier permeability, and low cytotoxicity on primary neurons. [ABSTRACT FROM AUTHOR]

The problem of the efficient treatment of acute organophosphorus (OP) poisoning needs more efforts in the development of a versatile antidote, applicable for treatment of the injuries of both peripheral and central nervous systems. A series of N –H, N -methyl, N- butyl, and N -phenyl derivatives of benzhydroxamic (1a-1d), 3-methoxybenzhydroxamic (2a-2d), 4-methoxybenzhydroxamic (3a-3d) acids, and corresponding salycilhydroxamates (4a-4d) was prepared. Their predicted hydrophobicity (log P) was evaluated as regards to ВВВ score by the open access cheminformatics tools; prediction of the passive transport across the BBB was found by means on the parallel artificial membrane permeability assay (PAMPA). The data on reactivation capacity of human acetylcholinesterase (Hss AChE) inhibited by GB, VX, and paraoxon was supported by molecular docking study on binding to the active site of the AChE, viability study against mammalian cells (Chinese hamster ovary CHO–K1), and biodegradability (Closed Bottle test OECD 301D). Among the studied compounds, N -butyl derivatives have better balanced combination of properties; among them, N -butylsalicylhydroxamic acid is most promising. The studied compounds demonstrate modest reactivation capacity; change of N –H by N– Me ensures the reactivation capacity in studied concentrations on all studied OP substrates; among N- butyl derivatives, the N -butylsalicylhydroxamic acid demonstrates most promising results within the series. The found regularities may lead to selection of perspective structures to complement current formulations for medical countermeasures against poisoning by organophosphorus toxicants. [Display omitted] • Introduction of N -substituents leads to optimization of hydroxamic acids properties. • Molecular docking parameters fit requirements for reactivators of OP-inhibited AChE. • Selected compounds have high predicted BBB permeation with modest reactivation capacity. • N -Butylsalicylhydroxamic acid reveals most promising properties in the series. • The found regularities may lead to further improvement of prospective antidotes. [ABSTRACT FROM AUTHOR]

Abstract: Administration of acetylcholinesterase (AChE) reactivators (oximes) is usually used in order to counteract the poisoning effects of nerve agents. The possibility was suggested that oximes may show some therapeutic and/or adverse effects through their action in central nervous system. There are no sufficient data about interaction of oximes with monoaminergic neurotransmitter''s systems in the brain. Oxime-type AChE reactivators pralidoxime, obidoxime, trimedoxime, methoxime and HI-6 were tested for their potential to affect the activity of monoamine oxidase of type A (MAO-A) and type B (MAO-B) in crude mitochondrial fraction of pig brains. The compounds were found to inhibit fully MAO-A with half maximal inhibitory concentration (IC 50) of 0.375mmol/l (pralidoxime), 1.53mmol/l (HI-6), 2.31mmol/l (methoxime), 2.42mmol/l (obidoxime) and 4.98mmol/l (trimedoxime). Activity of MAO-B was fully inhibited by HI-6 and pralidoxime only with IC 50 4.81mmol/l and 11.01mmol/l, respectively. Methoxime, obidoxime and trimedoxime displayed non-monotonic concentration dependent effect on MAO-B activity. Because oximes concentrations effective for MAO inhibition could not be achieved in vivo at the cerebral level, we suppose that oximes investigated do not interfere with brain MAO at therapeutically relevant concentrations. [Copyright &y& Elsevier]

Abstract: In this work a theoretical methodology for evaluation of the association and kinetic reactivation constants of oximes using the Molegro® and Spartan® softwares was proposed and validated facing in vitro data previously reported in the literature. Results showed a very good agreement between the theoretical binding free energies of the reactivators and experimental data, suggesting that the proposed methodology could work well in the prediction of kinetic and thermodynamics parameters for oximes that might be helpful for the design and selection of new and more effective oximes. [ABSTRACT FROM AUTHOR]

Abstract: Improving the efficacy of antidotal treatment of poisonings with nerve agents is still a challenge for the scientific community. This study investigated the interactions of four bispyridinium oximes with human erythrocyte acetylcholinesterase (AChE) and their effects on soman- and tabun-poisoned mice. Oximes HI-6 and TMB-4 were used for comparison. These oximes inhibited AchE with inhibitory potency (IC50) ranging from 0.02 to 1.0mM. The best reactivating potency (%R) was obtained with K074, when AChE was inhibited by tabun. The protective potency (P50) of all oximes in human erythrocyte AChE inhibited by soman and tabun could not be determined. In tabun-poisoned mice very good antidotal efficacy was obtained with K027, K048, and K074, which makes them interesting for future investigation. The combination of HI-6 and atropine is the therapy of choice for soman poisoning. [Copyright &y& Elsevier]

Abstract: Oximes K033 [1,4-bis(2-hydroxyiminomethylpyridinium) butane dibromide] and K048 [1-(4-hydroxyiminomethylpyridinium)-4-(4-carbamoylpyridinium) butane dibromide] were tested as pretreatment drugs in tabun-poisoned mice followed by treatment with atropine plus K033, K048, K027 [1-(4-hydroxyiminomethylpyridinium)-3-(4-carbamoylpyridinium) propane dibromide], TMB-4 [1,3-bis(4-hydroxyiminomethylpyridinium) propane dibromide] and HI-6 [(1-(2-hydroxyiminomethylpyridinium)-3-(4-carbamoylpyridinium)-2-oxapropane dichloride)]. Oxime doses of 25% or 5% of its LD50 were used for pretreatment 15min before tabun-poisoning and for treatment 1min after tabun administration to mice. The best therapeutic effect was obtained when oxime K048 (25% of its LD50) was used in both pretreatment and treatment with atropine. This regiment insured survival of all tested animals after the application of 10 LD50 of tabun. In addition, since butyrylcholinesterase (BChE; EC 3.1.1.8) is considered an endogenous bioscavenger of anticholinesterase compounds and its interactions with oximes could be masked by AChE interactions, we evaluated kinetic parameters for interactions of tested oximes with native and tabun-inhibited human plasma BChE and compared them with results obtained previously for human erythrocyte acetylcholinesterase (AChE; EC 3.1.1.7). Progressive inhibition of BChE by tabun was slightly faster than that of AChE. The reactivation of tabun-inhibited BChE by oximes was very slow, and BChE binding affinity for oximes was lower than AChE''s. Therefore, BChE could scavenge tabun prior to AChE inhibition, but fast oxime-assisted reactivation of tabun-inhibited AChE or protection of AChE by oxime against inhibition with tabun would not be obstructed by interaction between BChE and oximes. [Copyright &y& Elsevier]

Abstract: The increased concern about terrorist use of nerve agents prompted us to search for new more effective oximes against tabun and soman poisoning. We investigated the interactions of five bispyridinium oximes: K027 [1-(4-hydroxyiminomethylpyridinium)-3-(4-carbamoylpyridinium) propane dibromide], K048 [1-(4-hydroxyiminomethylpyridinium)-4-(4-carbamoylpyridinium) butane dibromide], K033 [1,4-bis(2-hydroxyiminomethylpyridinium) butane dibromide], TMB-4 [1,3-bis(4-hydroxyiminomethylpyridinium) propane dibromide] and HI-6 [(1-(2-hydroxyiminomethylpyridinium)-3-(4-carbamoylpyridinium)-2-oxapropane dichloride)] with human erythrocyte acetylcholinesterase (AChE; E.C. 3.1.1.7) and their effects on tabun- and soman-poisoned mice. All the oximes reversibly inhibited AChE, and the enzyme-oxime dissociation constants were between 17 and 180μM. Tabun-inhibited AChE was completely reactivated by TMB-4, K027 and K048, with the overall reactivation rate constants of 306, 376 and 673min−1 M−1, respectively. The reactivation of tabun-inhibited AChE by K033 reached 50% after 24h, while HI-6 failed to reactivate any AChE at all. Soman-inhibited AChE was resistant to reactivation by 1mM oximes. All studied oximes protected AChE from phosphorylation with both soman and tabun. In vivo experiments showed that the studied oximes were relatively toxic to mice; K033 was the most toxic (LD50 =33.4mg/kg), while K027 was the least toxic (LD50 =672.8mg/kg). The best antidotal efficacy was obtained with K048, K027 and TMB-4 for tabun poisoning, and HI-6 for soman poisoning. Moreover, all tested oximes showed no cytotoxic effect on several cell lines in concentrations up to 0.8mM. The potency of the oximes K048 and K027 to protect mice from five-fold LD50 of tabun and their low toxicity make these compounds leading in the therapy of tabun poisoning. The combination of HI-6 and atropine is the therapy of choice for soman poisoning. [Copyright &y& Elsevier]

Casualties caused by nerve agents, potent acetylcholinesterase inhibitors, have attracted attention from media recently. Poisoning with these chemicals may be fatal if not correctly addressed. Therefore, research on novel antidotes is clearly warranted. Pyridinium oximes are the only clinically available compounds, but poor penetration into the blood-brain barrier hampers efficient enzyme reactivation at the central nervous system. In searching for structural factors that may be explored in SAR studies, we synthesized and evaluated neutral aryloximes as reactivators for acetylcholinesterase inhibited by NEMP, a VX surrogate. Although few tested compounds reached comparable reactivation results with clinical standards, they may be considered as leads for further optimization. • A practical method for synthesis of neutral aryloximes is presented. • A VX surrogate was used as inhibitor for Electrophorus eel Acetylcholinesterase. • Neutral aryloximes retrieved promising predicted properties for use as reactivators. • Seven compounds were identified as potential leads for further optimization. [ABSTRACT FROM AUTHOR]