E-N-(2-acetyl-phenyl)-3-phenyl-acrylamide targets abrin and ricin toxicity: Hitting two toxins with one stone

The efficacy of small molecule inhibitors (SMIs) against the enzymatic activity of Shiga toxin prompted the evaluation of their efficacy on related toxins viz. ricin and abrin. Ricin, like Shiga toxin, is listed as a category B bioweapon and belongs to the type II family of ribosome inactivating proteins (RIPs). Abrin though structurally and functionally similar to ricin, is considerably more toxic. In the present study, 35 compounds were evaluated in A549 cells in in vitro assays, of which 5 offered protection against abrin and 2 against ricin, with IC50 values ranging between 30.5-1379 μM and 300-341 μM, respectively. These findings are substantiated by fluorescence based thermal shift assay. Moreover, the binding of the promising compounds to the toxin components has been validated by Surface Plasmon Resonance assay and in vitro protein synthesis assay. In vivo studies reveal complete protection of mice with compound 4 E-N-(2-acetyl-phenyl)-3-phenyl-acrylamide against orally administered lethal doses of, both, abrin and ricin. The present study thus proposes the emergence of E-N-(2-acetyl-phenyl)-3-phenyl-acrylamide as a lead compound against RIPs.

Rational design, synthesis, and evaluation of uncharged, "smart" bis-oxime antidotes of organophosphate-inhibited human acetylcholinesterase

Organophosphate (OP) intoxications from nerve agent and OP pesticide exposures are managed with pyridinium aldoxime-based therapies whose success rates are currently limited. The pyridinium cation hampers uptake of OPs into the central nervous system (CNS). Furthermore, it frequently binds to aromatic residues of OP-inhibited acetylcholinesterase (AChE) in orientations that are nonproductive for AChE reactivation, and the structural diversity of OPs impedes efficient reactivation. Improvements of OP antidotes need to include much better access of AChE reactivators to the CNS and optimized orientation of the antidotes' nucleophile within the AChE active-center gorge. On the basis of X-ray structures of a CNS-penetrating reactivator, monoxime RS194B, reversibly bound to native and venomous agent X (VX)-inhibited human AChE, here we created seven uncharged acetamido bis-oximes as candidate antidotes. Both oxime groups in these bis-oximes were attached to the same central, saturated heterocyclic core. Diverse protonation of the heterocyclic amines and oxime groups of the bis-oximes resulted in equilibration among up to 16 distinct ionization forms, including uncharged forms capable of diffusing into the CNS and multiple zwitterionic forms optimal for reactivation reactions. Conformationally diverse zwitterions that could act as structural antidote variants significantly improved in vitro reactivation of diverse OP-human AChE conjugates. Oxime group reorientation of one of the bis-oximes, forcing it to point into the active center for reactivation, was confirmed by X-ray structural analysis. Our findings provide detailed structure-activity properties of several CNS-directed, uncharged aliphatic bis-oximes holding promise for use as protonation-dependent, conformationally adaptive, "smart" accelerated antidotes against OP toxicity.

Construction of a Bivalent Thrombin Binding Aptamer and Its Antidote with Improved Properties

Aptamers are short synthetic DNA or RNA oligonucleotides that adopt secondary and tertiary conformations based on Watson–Crick base-pairing interactions and can be used to target a range of different molecules. Two aptamers, HD1 and HD22, that bind to exosites I and II of the human thrombin molecule, respectively, have been extensively studied due to their anticoagulant potentials. However, a fundamental issue preventing the clinical translation of many aptamers is degradation by nucleases and reduced pharmacokinetic properties requiring higher dosing regimens more often. In this study, we have chemically modified the design of previously described thrombin binding aptamers targeting exosites I, HD1, and exosite II, HD22. The individual aptamers were first modified with an inverted deoxythymidine nucleotide, and then constructed bivalent aptamers by connecting the HD1 and HD22 aptamers either through a triethylene glycol (TEG) linkage or four consecutive deoxythymidines together with an inverted deoxythymidine nucleotide at the 3′-end. The anticoagulation potential, the reversal of coagulation with different antidote sequences, and the nuclease stability of the aptamers were then investigated. The results showed that a bivalent aptamer RNV220 containing an inverted deoxythymidine and a TEG linkage chemistry significantly enhanced the anticoagulation properties in blood plasma and nuclease stability compared to the existing aptamer designs. Furthermore, a bivalent antidote sequence RNV220AD efficiently reversed the anticoagulation effect of RNV220 in blood plasma. Based on our results, we believe that RNV220 could be developed as a potential anticoagulant therapeutic molecule.

Role of β-naphthylalanine end-tags in the enhancement of antiendotoxin activities: Solution structure of the antimicrobial peptide S1-Nal-Nal in complex with lipopolysaccharide

Lipopolysaccharide (LPS, endotoxin) is the major component of Gram-negative bacterial outer surface membrane. LPS released from bacteria into bloodstream during infection may cause serious unwanted stimulation of host's immune system and lead to septic shock of the patient. Recently, we have developed a strategy to increase salt resistance and LPS neutralization of short antimicrobial peptides by adding β-naphthylalanine end-tags to their termini. Herein, correlations between membrane immersion depth, orientation, and antiendotoxin activities of the antimicrobial peptides S1 and S1-Nal-Nal have been investigated via solution structure, paramagnetic resonance enhancement, and saturation transfer difference NMR studies. Unlike the parent peptide S1, S1-Nal-Nal rotated its two terminal β-naphthylalanine residues into the hydrophobic lipid A motif of LPS micelles. The LPS-induced inflammation may then be prohibited by the blocked lipid A motif.

Polymeric nanoparticle-aptamer bioconjugates can diminish the toxicity of mercury in vivo

Targeted delivery drugs by nanoparticles and aptamers is a hot issue; however, the application to ameliorate toxicity of toxicants is unknown, and the information about nanoparticle-aptamer toxicology and pharmacology is limited. In this work, nanoparticle-aptamer was synthesized and then its toxicological and pharmacological information was studied. Mercury was selected as a model toxicant and the antidote was entrapped by nanoparticle-aptamer. The nanoparticle-aptamer with a suitable size of 120 nm avoided aptamer biodegradation and achieved an effective release of antidote. Rats were orally administered mercury-contaminated rice and then nanoparticle-aptamer was intravenously injected. The nanoparticle-aptamer markedly reduced the quantity of mercury in both the brain and kidney, and enhanced the excretion of urinary mercury. Water Maze and Open Field tests showed that nanoparticle-aptamer ameliorated the neurotoxicity and improved the learning and memory of rats. The pharmacology of nanoparticle-aptamer involved slow antidote release, antidote-toxicant antagonism, enhancement of crucial enzymes activity and decreased lipid peroxidation. Toxicology of nanoparticle-aptamer was also studied by hematologic tests (creatinine, urea, red and white blood cell), and exhibited little toxicity. Nanoparticle-aptamer can diminish the toxicity of mercury in vivo with few adverse effects, and is a potential tool in reducing the hazards of toxicants to human health.

Conformational and configurational analysis of an N,N carbonyl dipyrrinone-derived oximate and nitrone by NMR and quantum chemical calculations

The geometries and relative energies of new N,N carbonyl dipyrrinone-derived oxime molecules (E/Z-s-cis 4a and E/Z-s-cis 4b) have been investigated. The calculated energies, molecular geometries, and (1) H/(13) C NMR chemical shifts agree with experimental data, and the results are presented herein. The E-s-cis conformations of 4a and 4b and the Z-s-cis conformation of 5b were found to be the thermodynamically most stable isomers with the oxime hydrogen atom or the methyl functional group adopting an anti-orientation with respect to the dipyrrinone group. This conformation was unambiguously supported by a number of 2D NMR experiments.

A reversible aptamer improves outcome and safety in murine models of stroke and hemorrhage

Treatment of acute ischemic stroke with intravenous tissue-type plasminogen activator is underutilized partly due to the risk of life-threatening hemorrhage. In response to the clinical need for safer stroke therapy, we explored using an aptamer-based therapeutic strategy to promote cerebral reperfusion in a murine model of ischemic stroke. Aptamers are nucleic acid ligands that bind to their targets with high affinity and specificity, and can be rapidly reversed with an antidote. Here we show that a Factor IXa aptamer administered intravenously after 60 minutes of cerebral ischemia and reperfusion improved neurological function and was associated with reduced thrombin generation and decreased inflammation. Moreover, when the aptamer was administered in the setting of intracranial hemorrhage, treatment with its specific antidote reduced hematoma volume and improved survival. The ability to rapidly reverse a pharmacologic agent that improves neurological function after ischemic stroke should intracranial hemorrhage arise indicates that aptamer-antidote pairs may represent a novel, safer approach to treatment of stroke.

[Oxidative activity of electrochemically synthesized sodium persulfate solutions against some psychotropic agents]

By using some psychotropic agents as an example, investigations of the oxidative activity of electrochemically synthesized sodium persulfate solutions were continued. The derivatives of phenothiazines, xanthene, and dibenzazepines were shown to be oxidized by synthesized sodium persulfate solution to low-toxic products. Oxidation products were ascertained to coincide with the known products of their biotransformation in the body.

Monooxime reactivators of acetylcholinesterase with (E)-but-2-ene linker—Preparation and reactivation of tabun- and paraoxon-inhibited acetylcholinesterase

Acetylcholinesterase reactivators are crucial antidotes for the treatment of organophosphate intoxication. Fifteen new monooxime reactivators of acetylcholinesterase with a (E)-but-2-ene linker were developed in an effort to extend the properties of K-oxime (E)-1-(4-carbamoylpyridinium)-4-(4-hydroxyiminomethylpyridinium)-but-2-ene dibromide (K203). The known reactivators (pralidoxime, HI-6, obidoxime, K075, K203) and the new compounds were tested in vitro on a model of tabun- and paraoxon-inhibited AChE. Monooxime reactivators were not able to exceed the best known compounds for tabun poisoning, but some of them did show reactivation comparable with known compounds for paraoxon poisoning. However, extensive differences were found by a SAR study for various substitutions on the non-oxime part of the reactivator molecule.

Application of Recombinant DNA Methods for Production of Cholinesterases as Organophosphate Antidotes and Detectors

To develop new avenues for synthesizing novel antidotes for organophosphate poisoning and for detection of the organophosphates, we have turned to recombinant DNA methods to synthesize cholinesterases with unusual properties. For antidotal therapy we describe mutations of the native mouse and human enzymes that allow for enhanced rates of oxime reactivation. Such enzymes, when localized in the circulation, would enable the circulating cholinesterase to become a catalytic rather than simply a stoichiometric scavenger. Hence, "oxime-assisted catalysis" provides a means for scavenging the organophosphates in the circulation thereby minimizing their tissue penetration and toxicity. Accordingly, the oxime antidote or prophylactic agent has a dual action within the circulation and at the tissue level. Second, through a novel chemistry, termed freeze-frame, click chemistry, we have used organophosphate conjugates of acetylcholinesterase as templates for the synthesis of novel nucleophilic reactivating agents. Finally, acetylcholinesterase can be modified through cysteine substitution mutagenesis and attachment of fluorophores at the substitution positions. When linked at certain locations in the molecule, the attached fluorophore is sensitive to organophosphate conjugation with acetylcholinesterase, and thus the very target of insecticide or nerve agent action becomes a detection molecule for organophosphate exposure.

Novel S-Substituted Aminoalkylamino Ethanethiols as Potential Antidotes against Sulfur Mustard Toxicity

Sulfur mustard (SM) is a highly toxic chemical warfare agent. A satisfactory treatment regimen is not yet available for this toxicant. In a search for an effective antidote against SM, a series of novel S-2(omega-aminoalkylamino)ethyl alkyl/aryl thioethers [H(2)N(CH(2))(n)()NHCH(2)CH(2)SR], where R = alky, alicyclic, aryl, and heterocyclic substituents, have been designed and synthesized as candidate antidotes against SM toxicity. These compounds were screened for their protective efficacy through the oral route against dermally applied sulfur mustard in female mice measured on the basis of percent survival following percutaneous administration of SM. A number of compounds demonstrated significant protection.

Rational design and molecular diversity for the construction of anti-alpha-bungarotoxin antidotes with high affinity and in vivo efficiency

The structure of peptide p6.7, a mimotope of the nicotinic receptor ligand site that binds alpha-bungarotoxin and neutralizes its toxicity, was compared to that of the acetylcholine binding protein. The central loop of p6.7, when complexed with alpha-bungarotoxin, fits the structure of the acetylcholine binding protein (AChBP) ligand site, whereas peptide terminal residues seem to be less involved in toxin binding. The minimal binding sequence of p6.7 was confirmed experimentally by synthesis of progressively deleted peptides. Affinity maturation was then achieved by random addition of residues flanking the minimal binding sequence and by selection of new alpha-bungarotoxin binding peptides on the basis of their dissociation kinetic rate. The tetra-branched forms of the resulting high-affinity peptides were effective as antidotes in vivo at a significantly lower dose than the tetra-branched lead peptide.

A branched peptide mimotope of the nicotinic receptor binding site is a potent synthetic antidote against the snake neurotoxin alpha-bungarotoxin

We previously produced synthetic peptides mimicking the snake neurotoxin binding site of the nicotinic receptor. These peptide mimotopes bind the snake neurotoxin alpha-bungarotoxin with higher affinity than peptides reproducing native receptor sequences and inhibit toxin binding to nicotinic receptors in vitro; yet their efficiency in vivo is low. Here we synthesized one of the peptide mimotopes in a tetrabranched MAP form. The MAP peptide binds alpha-bungarotoxin in solution and inhibits its binding to the receptor with a K(A) and an IC(50) similar to the monomeric peptide. Nonetheless, it is at least 100 times more active in vivo. The MAP completely neutralizes toxin lethality when injected in mice at a dose compatible with its use as a synthetic antidote in humans. The in vivo efficacy of the tetrameric peptide cannot be ascribed to a kinetic and thermodynamic effect and is probably related to different pharmacokinetic behavior of the tetrameric molecule, with respect to the monomer. Our findings bring new perspectives to the therapeutic use of multimeric peptides.

Antidotal efficacy of pyridinium oximes and cholineacetyltransferase inhibitors against organophosphorus intoxication in rodents

In an attempt to develop effective antidote against organophosphorus intoxication, some new imidazole-pyridinium mono-oximes, long chain pyridinium mono-oximes and cholineacetyltransferase inhibitors were synthesised. These compounds were evaluated for their in vivo therapeutic protection and neuromuscular function studies in rodents. The results indicate that SPK-series oximes may be useful against sarin poisoning without any beneficial effect against VX (O-Ethyl S-2-NN-diisopropylaminoethyl methylphosphonofluoridate) intoxication. The cholineacetyltransferase (ChAT) inhibitors may not be of any help against any of the OP compounds studied in this study.

Improvements in scavenger protection against organophosphorus agents by modification of cholinesterases

The ability of stoichiometric scavengers, such as ChEs, to protect against a variety of OP agents has been demonstrated in several in vivo models. To improve the detoxification of OP agents by ChEs, several approaches have been recently used to increase the stoichiometry, stability, and in vivo effectiveness of ChEs as OP scavengers. For example, the in vitro stoichiometric neutralization of sarin by AChE was increased from 1:1 to 3200:1 by the addition of the oxime HI-6, while the in vivo stoichiometry was increased to 57:1 in mice by HI-6. The aging rate of soman-inhibited mouse AChE was reduced 12-fold in a mutant AChE (E202Q) which resulted in a two-fold increase in oxime-assisted detoxification of soman. To improve the duration of scavenger protection provided by ChEs, the mean residence times of five tissue-derived and two recombinant ChEs injected i.v. in mice were compared with their oligosaccharide profiles. The mean residence times of these ChEs were found to increase with molecular weight and with the levels of oligosaccharide sialylation. The stability of AChE in non-physiological environments was improved by immobilizing it in a polyurethane foam matrix that allowed AChE to retain enzymatic activity at high temperature (75 degrees C) where soluble enzyme denatured. These developments in scavenger technology have improved the in vivo protection provided by OP scavengers and extended their applicability to provide external decontamination of chemical agents and pesticides.

Detoxification of paraquat poisoning: effects of alkylsulfates and alkylsulfonates on paraquat poisoning in mice and rats

The study revealed that high molecular polyvinyl sulfate (PVP) or sulfonate (PVS), and low molecular alkyldisulfonates (NaO3S(CH2)nSO3Na, n = 2--5: EDS, TDS, BDS and PDS) can alleviate acute toxicity of the herbicide, paraquat dichloride (PQ) in mice. Their activity as antidotes and the mode of the action varied depending on molecular size. The survival rate for mice receiving PQ at 200 mg/kg alone was increasingly improved when the dose of antidotes was increased from 8 to 10 times the dose of PQ; all the test compounds, except EDS (70% survival), achieved a survival rate of 100%. When test compounds were orally dosed to mice in a mixture with PQ, they improved LD50 of PQ alone. With the low molecular compounds EDS, TDS, BDS and PDS, the value increased to about 2 to 3 times (300-458 mg/kg) over that of PQ alone (140 mg/kg). With high molecular PVS and PVP, the combination reached about a 7 fold (900-1000 mg/kg) increase in LD50 value. The formation of lipid peroxide in lungs of rats due to PQ tended to be suppressed by concomitant administration of carbohydrate sulfate (DS and GS). PVP, BDS and TDS were more effective in depressing synthesis of lipid peroxide than DS or GS in the lungs, although BDS and TDS were less effective in suppressing PQ absorption from the rat small intestine than DS, GS or PVP.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbamate derivatives of 2-arylimidazo[1,2-a]pyridinium salts as acetylcholinesterase inhibitors and protective agents against organophosphorus compounds

A series of 2-arylimidazo[1,2-a]pyridinium salts with (N,N-dimethylcarbamoyl)oxy or (N-methylcarbamoyl)oxy groups at the 3'- or 4'-position on the phenyl substituent and various substituents on the imidazo[1,2-a]pyridine ring have been synthesized. The compounds show in vitro inhibitory activity against electric eel acetylcholinesterase (AChE), type III, and several of the compounds show protective effects toward the organophosphorus AChE inhibitor soman in mice. The possible structural relationship of these compounds to physostigmine and pyridostigmine is considered.

Carbamates of (hydroxyphenoxy)methyl heteroaromatic salts as acetylcholinesterase inhibitors and protective agents against organophosphorus compounds

A series of N,N-dimethylcarbamates of 2-[(2'-, 3'-, and 4'-hydroxyphenoxy)methyl] heteroaromatic salts has been prepared. Pyridine, imidazole, quinoline, benzimidazole, and imidazo-[1,2-alpha]pyridine derivatives were included. Most of the compounds are inhibitors of electric eel acetylcholinesterase and also show prophylactic activity toward a 2LD50 dose of soman in mice.

Quaternary salts of 3,3'-bis-pyridinium monooximes: synthesis and biological activity

Two new series of asymetrically substituted 3,3'-bis-pyridinium monooximes bridged by oxopropane and propane groups were synthesized and characterized by spectral data and acid dissociation constants (pKas). Both the in vitro reactivation potency, in experiments with lyophilized electric eel acetylcholinesterase (AChE) inhibited by diisopropylfluorophosphate, and in vivo protection efficacy against diisopropylfluorophosphate intoxication in mice of these compounds were evaluated and compared with those of trimedoxime and 2-pyridine-aldoxime methiodide. The compounds were also evaluated for in vitro inhibition of AChE. The compounds with the oxopropane link were stronger inhibitors and weaker reactivators than the corresponding propane derivatives. No significant correlation was observed among pKa, oxime inhibition of AChE, reactivation of inhibited AChE, and protection index. Changing substituents in pyridine rings or altering linking groups between pyridine rings did not improve antidotal efficacy compared with trimedoxime and 2-pyridine-aldoxime methiodide.

The 3,3'-bis-pyridinium mono-oximes as antidotes against organophosphorous intoxication

In an attempt to develop effective antidotes against organophosphorous intoxication, three new structurally related bispyridinium mono-oximes with a 2-oxopropane bridge were synthesized. The compounds were evaluated for in-vivo therapeutic protection and cholinesterase reactivation in blood and various brain regions. In neuromuscular function studies against diisopropyl-fluorophosphate and isopropyl methylphosphonofluoridate poisoning, the oximes produced significant protection. The compounds produced marked peripheral reactivation and beneficial effects on neuromuscular transmission. The reactivation of cholinesterase in cerebral cortex by the oximes, in spite of their being quaternary salts is a notable feature.

[Synthesis of gallic acid derivatives with L-thiazolidin-4-carboxylic acid and study on their antiradical and antitoxic activity]

The authors report the synthesis of three new derivatives of gallic acid with L-thiazolidine-4-carboxylic acid. The new compounds were tested for radical scavenger activity against doxorubicin toxicity in mice and for antitoxic activity against acetaldehyde and formaldehyde toxicities in rats. Unlike the utilized standards, the new compounds show no activity.

Quaternary salts of 2-[(hydroxyimino)methyl]imidazole. 3. Synthesis and evaluation of (alkenyloxy)-, (alkynyloxy)-, and (aralkyloxy)methyl quaternarized 2-[(hydroxyimino)methyl]-1-alkylimidazolium halides as reactivators and therapy for soman intoxication

A series of structurally related monosubstituted 1-[(alkenyloxy)methyl]-, 1-[(alkynyloxy)methyl]-, and 1-[(aralkyloxy)methyl]-2-[(hydroxyimino)methyl]-3-methyli midazolium halides were prepared and evaluated. All new compounds were characterized with respect to (hydroxyimino)methyl acid dissociation constant, nucleophilicity, and octanol-buffer partition coefficient. The alkynyloxy-substituted compounds were also evaluated in vitro with respect to reversible inhibition of human erythrocyte (RBC) acetylcholinesterase (AChE) and kinetics of reactivation of human AChE inhibited by ethyl p-nitrophenyl methylphosphonate (EPMP). In vivo evaluation in mice revealed that coadministration of alkynyloxy-substituted imidazolium compounds with atropine sulfate provided significant protection against a 2 x LD50 challenge of GD. For the alkynyloxy-substituted imidazolium drugs there is a direct relationship between in vitro and in vivo activity: the most potent in vivo compounds against GD proved to be potent in vitro reactivators against EPMP-inhibited human AChE. These results differ from the observations made on the sterically hindered imidazolium compounds (see previous article) and suggest that several antidotal mechanisms of protective action may be applicable for the imidazolium aldoxime family of therapeutics. The ability of the alkynyloxy substituents to provide life-saving protection against GD intoxication was not transferable to the pyridinium or triazolium heteroaromatic ring systems.

Synthesis of some 5-azo(4'-substituted benzene-sulphamoyl)-8-hydroxyquinolines with antidotal and antibacterial activities

5-Azo(4'-substituted benzenesulphamoyl)-8-hydroxyquinolines(III) have been prepared by coupling of the appropriate p-substituted benzenesulphamoyldiazonium acetates with 8-hydroxyquinoline. The corresponding copper chelates(IV) and iron chelates(V) were also prepared in a 1:2 metal to ligand ratio. Structures of III, IV and V were confirmed by some representative UV, IR, and NMR spectrometry in addition to microanalysis. Antidotal activity of four ligands (IIIa, IIId, IIIf, and IIIi) has been evaluated in mice against the toxicity of lead acetate and copper sulphate. Study revealed that compound IIIf elicited significant antidotal activity against lead and copper poisoning, while IIIi was potent only against lead poisoning. Antibacterial activity of compounds III, IV, and V was also determined in comparison to sulphanilamide against Staph. aureus, Bacill. cereus, and Esch. coli. The test compounds showed variable bacteriostatic activities, and some of them (IIIc, IIId, IIIf, Ve, IIIg, and Vi) are more effective than the reference drug, especially against Bacill. cereus.

Approaches to protection against nerve agent poisoning. (Naphthylvinyl)pyridine derivatives as potential antidotes

Analogues of the potent inhibitor of choline acetyltransferase (CAT) (E)-4-(1-naphthylvinyl)pyridine methiodide were synthesized and evaluated for their ability to inhibit CAT and protect against nerve agent intoxication. Several compounds, notably (E)-1-(2-hydroxyethyl)-(1-naphthylvinyl)pyridinium bromide (3), (E)-1-methyl-4-(1-naphthylvinyl)-1,2,3,6-tetrahydropyridine hydrochloride (22), and (E)-1-methyl-4-(1-naphthylvinyl)piperidine hydrochloride (23), were found to afford significant protection against sarin in the mouse and against soman in the guinea pig. However, protection was apparently not related to CAT inhibition. Compound 23, our most effective compound in protecting against nerve agent, was without CAT inhibitory activity. Compound 22, which proved to be a potent CAT inhibitor, most likely owed this activity to being dehydrogenated back to the pyridinium quaternary salt by oxidative enzymes. Several of the (naphthylvinyl)pyridine quaternary salts, but not their tertiary amine analogues, were found to be effective in slowing the rate of aging of soman-inhibited acetylcholinesterase. Ability to slow the rate of aging was enhanced by introduction of methoxy substituents on the aryl moiety whereas the aging rate was actually accelerated by chloro substituents. To date, our most effective compound in slowing the rate of aging, (E)-4-[(4-methoxy-1-naphthyl)vinyl]pyridine methochloride (6), did not provide significant protection against soman in the mouse.

Sugar conjugates of pyridinium aldoximes as antidotes against organophosphate poisoning

A series of pyridinium aldoximes having a sugar conjugated to the pyridine ring has been prepared as potential antidotes against organophosphate poisoning. The sugar residue was attached either directly through C-1 or C-6 of the pyranose ring or through a C3 bridge between the glycosyl group and the nitrogen atom of the pyridine moiety. Attachment of a sugar group to the oxime derivative seems to increase the bioavailability of the antidote. The clearance rate of the sugar conjugates was significantly lower than that of their non-sugar analogs and thus they were retained longer in the blood circulation. The sugar derivatives were more potent in decreasing paraoxon-induced hypothermia (which is regulated within the central nervous system) than N-methyl-2-pyridiniumaldoxime methanesulfonate, one of the most commonly used mono-oximes. The sugar analogs were also less toxic than the non-sugar analogs; some also displayed higher efficacy. The mechanism underlying the improved features of the sugar oximes, and the structural requirements in relation to the sugar attachment to the oxime function, are discussed.

A toxicology program for evaluating the safety of a chemical warfare decontaminant

An ideal topical decontaminant for chemical warfare agents should be highly efficacious, easy to use, and have low toxicity. For toxicity assessment, a stepwise approach linking type of toxicity study to stage of decontaminant development is both efficient and economical. In the initial exploratory phase, range-finding acute toxicity studies using a few animals will suffice to screen out highly toxic decontaminants . More definitive acute toxicity studies and a short term mutagenic test are sufficient during the live agent efficacy testing phase. When an efficacious decontaminant is found and is ready to be formulated into a product, a more extensive toxicologic program including a 2-week dermal toxicity study, a skin sensitization study, and an inhalation study (for aerosol or powder formulations) should be implemented before clinical trials.

Chelation therapy for methylmercury(II) poisoning. Synthesis and determination of solubility properties of MeHg(II) complexes of thiol and dithiol antidotes

Methylmercury(II) complexes of the most widely studied antidotes for mercury poisoning have been prepared, and both the water solubility and 1-octanol/water partition coefficients determined for these complexes and the L-cysteine complex. New complexes of N-acetyl-D,L-penicillamine, 2-mercaptosuccinic acid, meso-dimercaptosuccinic acid, and Unithiol have been synthesized and characterized, and are found to have the formulations MeHgSCMe2CH(NHCOMe)CO2H, MeHgSCH(CO2H)CH2CO2H, MeHgSCH(CO2H)CH(CO2H)SHgMe, and Na[MeHgSCH2CH-(SHgMe)CH2SO3], respectively. Trends in octanol/water partition coefficients are consistent with reported studies of the effectiveness of antidotes for MeHg(II) poisoning and redistribution of MeHg(II) on administration of antidotes, particularly for British anti-Lewisite, Unithiol, and meso-dimercaptosuccinic acid.

Sugar-oximes, new potential antidotes against organophosphorus poisoning

In attempt to improve distribution and transport qualities of antidotes against organophosphorus poisoning, a new series of pyridine aldoximes linked to glucose moiety were synthesized and studied both in vivo and in vitro. Preliminary results describing the biological activity of the new compounds are presented and discussed in this report.