In Vitro Evaluation of Acetylcholinesterase Reactivators as Potential Antidotes Against Tabun Nerve Agent Poisonings

Searching for new potent acetylcholinesterase (AChE; E.C. 3.1.1.7) reactivators (oximes) is a very time-consuming process. At our department, we are able to synthesize more than 50 new AChE reactivators per year. Owing to this fact, we have to select promising reactivators using our in vitro method (potentiometric titration, pH 8 and temperature 25°C; source of cholinesterases, rat brain homogenate; time of inhibition by nerve agents, 30 min; time of reactivation, 10 min) prior to in vivo experiments. For this purpose, we are using two-phase in vitro evaluation of reactivator potency. In the first phase, reactivation potency of all newly synthesized AChE reactivators is tested at two concentrations: 10^?3 M and 10^?5 M. Afterwards, all reactivators achieving reactivation potency over 15% (especially at the concentration 10^?5 M) are tested. The second phase consists of the measurement of the relationship between concentration of the oxime and its reactivation ability. In most cases, the reactivation bell-shaped curve is obtained. The most potent AChE reactivators are selected and provided for further experiments during our development process.     

Pretreatment with pyridinium oximes improves antidotal therapy against tabun poisoning

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 LD(50) were used for pretreatment 15 min before tabun-poisoning and for treatment 1 min after tabun administration to mice. The best therapeutic effect was obtained when oxime K048 (25% of its LD(50)) was used in both pretreatment and treatment with atropine. This regiment insured survival of all tested animals after the application of 10 LD(50) 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.     

Reactivating potency of obidoxime, pralidoxime, HI 6 and HLö 7 in human erythrocyte acetylcholinesterase inhibited by highly toxic organophosphorus compounds

The treatment of poisoning by highly toxic organophosphorus compounds (nerve agents) is unsatisfactory. Until now, the efficacy of new potential antidotes has primarily been evaluated in animals. However, the extrapolation of these results to humans is hampered by species differences. Since oximes are believed to act primarily through reactivation of inhibited acetylcholinesterase (AChE) and erythrocyte AChE is regarded to be a good marker for the synaptic enzyme, the reactivating potency can be investigated with human erythro‐cyte AChE in vitro. The present study was undertaken to evaluate the ability of various oximes at concentrations therapeutically relevant in humans to reactivate human erythrocyte AChE inhibited by different nerve agents. Isolated human erythrocyte AChE was inhibited with soman, sarin, cyclosarin, tabun or VX for 30?min and reactivated in the absence of inhibitory activity over 5–60?min by obidoxime, pralidoxime, HI 6 or HLö 7 (10 and 30?μM). The AChE activity was determined photometrically. The reactivation of human AChE by oximes was dependent on the organophosphate used. After soman, sarin, cyclosarin, or VX the reactivating potency decreased in the order HLö 7 > HI 6 > obidoxime > pralidoxime. Obidoxime and pralidoxime were weak reactivators of cyclosarin-inhibited AChE. Only obidoxime and HLö 7 reactivated tabun-inhibited AChE partially (20%), while pralidoxime and HI 6 were almost ineffective (5%). Therefore, HLö 7 may serve as a broad-spectrum reactivator in nerve agent poisoning at doses therapeutically relevant in humans.     

Reactivation of organophosphate-inhibited human, Cynomolgus monkey, swine and guinea pig acetylcholinesterase by MMB-4: a modified kinetic approach

Treatment of poisoning by highly toxic organophosphorus compounds (OP, nerve agents) is a continuous challenge. Standard treatment with atropine and a clinically used oxime, obidoxime or pralidoxime is inadequate against various nerve agents. For ethical reasons testing of oxime efficacy has to be performed in animals. Now, it was tempting to investigate the reactivation kinetics of MMB-4, a candidate oxime to replace pralidoxime, with nerve agent-inhibited acetylcholinesterase (AChE) from human and animal origin in order to provide a kinetic basis for the proper assessment of in vivo data. By applying a modified kinetic approach, allowing the use of necessary high MMB-4 concentrations, it was possible to determine the reactivation constants with sarin-, cyclosarin-, VX-, VR- and tabun-inhibited AChE. MMB-4 exhibited a high reactivity and low affinity towards OP-inhibited AChE, except of tabun-inhibited enzyme where MMB-4 had an extremely low reactivity. Species differences between human and animal AChE were low (Cynomolgus) to moderate (swine, guinea pig). Due to the high reactivity of MMB-4 a rapid reactivation of inhibited AChE can be anticipated at adequate oxime concentrations which are substantially higher compared to HI-6. Additional studies are necessary to determine the in vivo toxicity, tolerability and pharmacokinetics of MMB-4 in humans in order to enable a proper assessment of the value of this oxime as an antidote against nerve agent poisoning.     

Interaction of pentylsarin analogues with human acetylcholinesterase: A kinetic study

Previous kinetic studies investigating the interactions between human acetylcholinesterase (AChE), structurally different organophosphorus compounds (OP) and oximes did not reveal a conclusive structure–activity relationship of the different reactions. The only exception was for a homologous series of methylphosphonofluoridates bearing C1–C4 O-n- or O-i-alkyl residues. Hence, it was tempting to investigate the kinetic interactions between different pentylsarin analogues, human AChE and two oximes, obidoxime and HI 6, in order to increase the understanding of structure–activity relationship between highly toxic OP and human AChE.     

Changes of Cholinesterase Activities in the Rat Blood and Brain After Sarin Intoxication Pretreated with Butyrylcholinesterase

After sarin inhalation exposure of rats pretreated with equine serum butyrylcholinesterase (EqBuChE), cholinesterase activities of the whole blood, acetylcholinesterase (AChE) in erythrocytes, pontomedullar area, frontal cortex, and striatum of the brain, and plasma butyrylcholinesterase (BuChE) were determined. Using different doses of EqBuChE as a pretreatment (intraperitoneal injection), dose-dependent increases in plasma BuChE activity and no changes in the erythrocyte and brain AChE activities were demonstrated. Decreases in plasma BuChE activity and red blood cells (RBC) and brain AChE activities were observed in control rats after sarin inhalation exposure without EqBuChE pretreatment. In rats pretreated with EqBuChE, this inhibition was lower compared with control animals not only in the blood but also in the brain structures studied. These results demonstrate protective effects of EqBuChE pretreatment in rats intoxicated with sublethal concentrations of sarin by inhalation.     

Detoxification of nerve agents by a substituted β-cyclodextrin: Application of a modified biological assay

Chemical warfare agents (nerve agents) are still available and present a real threat to the population. Numerous in vitro and in vivo studies showed that various nerve agents, e.g. tabun and cyclosarin, are resistant towards standard therapy with atropine and oxime. Based on these facts we applied a modified biological assay for the easy, semi-quantitative testing of the detoxifying properties of the β-cyclodextrin derivative CD-IBA. Cyclosarin, sarin, tabun and VX were incubated with CD-IBA for 1–50 min at 37 °C, then an aliquot was added to erythrocyte acetylcholinesterase (AChE) and the percentage of AChE inhibition was determined. The validity of the assay was confirmed by concomitant quantification of tabun by GC–MS.     

Inhibition of N-methyl-D-aspartate receptors increases paraoxon-induced apoptosis in cultured neurons

Organophosphorus (OP) compounds, used as insecticides and chemical warfare agents, are potent neurotoxins. We examined the neurotoxic effect of paraoxon (O,O-diethyl O-p-nitrophenyl phosphate), an organophosphate compound, and the role of NMDA receptors as a mechanism of action in cultured cerebellar granule cells. Paraoxon is neurotoxic to cultured rat cerebellar granule cells in a time- and concentration-dependent manner. Cerebellar granule cells are less sensitive to the neurotoxic effects of paraoxon on day in vitro (DIV) 4 than neurons treated on DIV 8. Surprisingly, the N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801, enhances paraoxon-mediated neurotoxicity suggesting that NMDA receptors may play a protective role. Pretreatment with a subtoxic concentration of N-methyl-D-aspartate (NMDA) [100 microM] protects about 40% of the vulnerable neurons that would otherwise die from paraoxon-induced neurotoxicity. Moreover, addition of a neuroprotective concentration of NMDA 3 h after treatment with paraoxon provides the same level of protection. Because paraoxon-mediated neuronal cell death is time-dependent, we hypothesized that apoptosis may be involved. Paraoxon increases apoptosis about 10-fold compared to basal levels. The broad-spectrum caspase inhibitor (Boc-D-FMK) and the caspase-9-specific inhibitor (Z-LEHD-FMK) protect against paraoxon-mediated apoptosis, paraoxon-stimulated caspase-3 activity and neuronal cell death. MK-801 increases, whereas NMDA blocks paraoxon-induced apoptosis and paraoxon-stimulated caspase-3 activity. These results suggest that activation of NMDA receptors protect neurons against paraoxon-induced neurotoxicity by blocking apoptosis initiated by paraoxon.     

Retrospective detection of exposure to nerve agents: analysis of phosphofluoridates originating from fluoride-induced reactivation of phosphylated BuChE

The utility was explored of a new approach to detect retrospectively exposure to nerve agents by means of conversion of the inhibitor moiety bound to the active site of the enzyme BuChE in plasma with fluoride ions into a phosphofluoridate which is subsequently analyzed by means of gas chromatography (GC). This quantifies >or=0.01% inhibition of BuChE and identifies the structure of the inhibitor except for the original leaving group. A three-tiered approach was followed involving the five classical nerve agents GA, GB, GF, GD, and VX, as well as the active metabolite of parathion, i.e., paraoxon: in vivo experiments in rhesus monkeys after iv administration of a sign-free dose of agent and concomitant in vitro experiments in plasma of rhesus monkeys and humans should allow an assessment of in vivo retrospectivity in humans. A systematic investigation was performed in order to find a single set of reaction conditions which yields a maximum amount of phosphofluoridate for all nerve agents. Fluoride-induced reactivation at 25 degrees C at a final concentration of 250 mM KF during 15 min in a pH-range between 4 and 6 appears to be effective. The in vitro decrease with time in reactivatibility of inhibited BuChE in plasma from humans and rhesus monkeys was largely due to aging of the phosphyl moiety, except for VX where spontaneous reactivation was a major cause. The decrease followed first-order except for a biphasic course in the case of GF in human and rhesus monkey plasma as well as of GD in rhesus plasma. In vitro half-lifes in human plasma ranged between ca. 14 h for GB and ca. 63 h for GA. A comparison of the in vivo data from rhesus monkeys and the in vitro data is complicated by the observation that the in vivo decrease with time of fluoride-reactivated phosphofluoridate is biphasic for all nerve agents. The terminal in vivo phase pertains to a small fraction of the amount of initially regenerated phosphofluoridate but is responsible for a considerable degree of retrospectivity, ranging between 14 and 56 days for GF and GB, respectively. The new procedure can be used in a variety of practical applications, e.g., (i) biomonitoring in health surveillance at exposure levels that are several orders of magnitude lower than presently possible; (ii) diagnosis in case of alleged exposure to nerve agents in time of war or after terrorist attacks; (iii) in forensic cases against suspected terrorists that have handled organophosphate anticholinesterases; and (iv) in research applications such as investigations on lowest observable effect levels of exposure to nerve agents.     

黄芪甲苷对帕金森病体外、体内模型的神经保护作用研究

目的:研究黄芪甲苷对帕金森病(PD)体外、体内模型的神经保护作用。方法:MPP+诱导PC12细胞损伤复制体外PD模型,1-甲基-4-苯基-1,2,3,6-四氢吡啶(MPTP)复制PD小鼠模型。采用MTT法测定黄芪甲苷对MPP+诱导的PC12细胞的存活率及培养液中乳酸脱氢酶(LDH)和丙二醛(MDA)的影响,以及对模型小鼠自发活动及纹状体多巴胺(DA)及其高香草酸(HVA)含量的影响。结果:25、50、100μmol·L-1黄芪甲苷可呈浓度依赖性抑制MPP+诱导的PC12细胞存活率降低,并显著降低培养上清液中LDH和MDA的含量;10、20、40mg·kg-1黄芪甲苷可显著增加模型小鼠自发活动计数值,并显著降低纹状体DA及HVA的含量。结论:黄芪甲苷对PD体外、体内模型均有显著的神经保护作用。     

Tissue-Specific Effects of Chlorpyrifos on Carboxylesterase and Cholinesterase Activity in Adult Rats: An in Vitro and in Vivo Comparison

Organophosphate (OP) pesticides can bind to carboxylesterase(CaE), which may lower the concentration of OPs at the targetsite enzyme, acetylcholinesterase (ChE). It is unclear fromthe literature whether it is the CaE's affinity for the OP and/orthe number of CaE molecules which is the dominant factor indetermining the protective potential of CaE. We undertook adetailed, in vitro and in vivo survey of both CaE and ChE toascertain if in vitro sensitivity of CaE and ChE predicted thepattern of inhibition seen after in vivo dosing with chlorpyrifos(CPF; 80 mg/ kg, p.o.) in male or female adult Long-Evans rats.For the brain, the in vitro sensitivity to CPF-oxon did predictthe in vivo patterns of inhibition: In vitro, brain ChE wasapproximately 25 times more sensitive to the active metabolite,CPF-oxon, than brain CaE, and in vivo brain ChE was more inhibitedthan brain CaE. In contrast, the in vitro sensitivity of plasmaChE and CaE did not correlate well with the in vivo patternof inhibition: In vitro, plasma ChE was approximately 6.5 timesless sensitive to CPF-oxon than plasma CaE, but in vivo, plasmaChE was more inhibited than CaE. In order to understand therole of CaE in protecting the brain ChE from inhibition by CPF-oxonin vitro, adult rat striatal tissue was incubated in the presenceand absence of adult rat liver tissue and IC₅₀S of CPF-oxonwere determined. The increase in the striatal CPF-oxon IC₅₀value noted for ChE in the presence of liver suggested thatCaE was binding the CPF-oxon and limiting its access to ChE.Male liver CaE, which has the same affinity for binding CPF-oxonas female liver CaE but has twice as many binding sites, causeda greater increase in the striatal CPF-oxon IC₅₀ than femaleliver, suggesting that the number of binding sites does playa role in the detoxification potential of a tissue. In summary,we found that (1) there are tissue and gender-related differencesfor basal ChE and CaE activity; (2) the in vitro sensitivityof CaE or ChE to CPF-oxon is highly tissue-specific; (3) thepattern of ChE and CaE inhibition after in vivo dosing withCPF is not necessarily predictable from the in vitro IC₅₀ forthese same enzymes, and (4) the number of CaE molecules mayplay a role in modifying the toxicity of CPF.     

酪酸梭菌活菌片对常用抗菌药物的体外敏感性检测

目的 检测酪酸梭菌活菌片中活性酪酸梭菌对常见抗菌药物的体外敏感性.方法 选取15种常见抗菌药物,通过纸片法进行体外抗菌药物敏感性试验.结果 酪酸梭菌种对头孢噻肟、头孢唑林、氨基苷类、磺胺类抗菌药物表现为耐药;对青霉素、大环内酯类、喹诺酮类药物敏感.结论 酪酸梭菌可与头孢菌素、氨基苷类、磺胺类等抗菌药物联用,应避免与青霉素类、大环内酯类、喹诺酮类药物联用.     

注射用盐酸头孢唑兰与3种常用抗菌药物体外抗菌活性比较

目的：本研究旨在评价头孢唑兰对临床分离菌株的体外抗菌作用,为头孢唑兰的临床使用提供参考依据。方法：采用琼脂双倍稀释法测定头孢唑兰对14类127株呼吸系统和泌尿系统感染分离出的病原菌株的体外抗菌活性,并与已经上市的3种常用抗菌药物进行了体外抗菌活性比较,试验平行3次,观察结果。结果：头孢唑兰对7种临床分离G＋菌株包括金黄色葡萄球菌、化脓性链球菌、肺炎链球菌、无乳链球菌、甲氧西林敏感表皮葡萄球菌（MSSE）、甲氧西林敏感金黄色葡萄球菌（MSSA）的MIC50均在0.125-1μg·ml^-1之间,MIC90在0.5-8μg·ml^-1之间;对肺炎克雷伯菌、大肠埃希菌、奇异变形杆菌、流感嗜血杆菌、产气肠杆菌、铜绿假单胞菌、阴沟肠杆菌的MIC均值分别为0.23,0.21,0.42,4.74,6.31,8.75,16.35μg·ml^-1。结论：头孢唑兰对14类127株呼吸系统和泌尿系统感染菌株的体外抗菌活性明显,具有显著的体外抗菌活性。     

Determination of K869, a Novel Oxime Reactivator of Acetylcholinesterase,in Rat Body Fluids and Tissues by Liquid-Chromatography Methods: Pharmacokinetic Study

Oxime reactivators of acetylcholinesterase (AChE) represent an integral part of standard antidote treatment of organophosphate poisoning. Oxime K869 is a novel bisquaternary non-symmetric pyridinium aldoxime with two pyridinium rings connected by a tetramethylene bridge where two chlorines modify the pyridinium ring bearing the oxime moiety. Based on in vitro assays, K869 is a potent AChE and butyrylcholinesterase (BChE) reactivator. For the investigation of the basic pharmacokinetic properties of K869 after its intramuscular application, new HPLC-UV and LC-MS/MS methods were developed and validated for its determination in rat body fluids and tissues. In this study, the SPE procedure for sample pretreatment was optimized as an alternative to routine protein precipitation widely used in oxime pharmacokinetics studies.K869 oxime is quickly absorbed into the central compartment reaching its maximum in plasma (39 ± 4 μg/mL) between 15 and 20 min. The majority of K869 was eliminated by kidneys via urine when compared with biliary excretion. However, only a limited amount of K869 (65 ± 4 ng/g of brain tissue) was found in the brain 30 min after oxime administration. Regarding the brain/plasma ratio calculated (less than 1%), the penetration of K869 into the brain did not exceed conventionally used oximes.     

Comparison of several oximes on reactivation of soman-inhibited blood,brain and tissue cholinesterase activity in rats

The ability of three oximes, HI-6, MMB-4 and ICD-467, to reactivate cholinesterase (ChE) inhibited by the organophosphorus compound soman was compared in blood (plasma and erythrocytes), brain regions (including spinal cord) and peripheral tissues of rats. Animals were intoxicated with soman (100 g/kg, SC; equivalent to 0.9 × LD₅₀ dose) and treated 1 min later with one of these oximes (100 or 200 mol/kg, IM). Toxic sign scores and total tissue ChE activities were determined 30 min later. Soman markedly inhibited ChE activity in blood (93–96%), brain regions (ranging from 78% to 95%), and all peripheral tissues (ranging from 48.9% to 99.8%) except liver (11.9%). In blood, treatment with HI-6 or ICD-467 resulted in significant reactivation of soman-inhibited ChE. In contrast, MMB-4 was completely ineffective. HI-6 and ICD-467 were equally effective at the high dose. At the low dose ICD-467 treatment resulted in significantly higher plasma ChE than HI-6 treatment, whereas HI-6 treatment resulted in higher erythrocyte ChE than ICD-467 treatment. However, none of these three oximes reactivated or protected soman-inhibited ChE in the brain. In all peripheral tissues (except liver) studied, MMB-4 was not effective. HI-6 reactivated soman-inhibited ChE in all tissues except lung, heart, and skeletal muscle. ICD-467 was highly effective in reactivating ChE in all tissues and afforded a complete recovery of ChE to control levels in intercostal muscle and salivary gland. Oxime treatments did not modify the toxic scores produced by soman. However, treatment with the high dose (200 mol/kg) of ICD-467 depressed respiration and two of the six rats died in 10 min. These observations indicate that MMB-4 is completely ineffective in protecting and/or reactivating soman-inhibited ChE, HI-6 is an effective ChE reactivator as reported earlier in rats and other species, and the imidazolium oxime ICD-467 is a powerful reactivator of somaninhibited ChE; however, its toxic interactions with soman may not be related to tissue ChE levels.The experiments reported here were conducted according to the Guide for the Care and Use of Laboratory Animals (1985), as prepared by the Committee on Care and Use of Laboratory Animals, National Research Council, NIH Publication No. 85-23. The opinions or assertions contained herein are the private views of the author and are not to be construed as official or as reflecting the views of the Department of the Army or the Department of Defense     

3种齐墩果酸纳米粒对小鼠HCa-F细胞体外抑制作用比较

目的:比较齐墩果酸(OA)/乳酸羟基乙酸共聚物纳米粒(OPN)、OA/乳酸羟基乙酸共聚物-水溶性维生素E纳米粒(OPTN)和OA/聚己内酯-聚乳酸-水溶性维生素E纳米粒(OPPTN)对小鼠腹水型肝癌高淋巴道转移细胞(HCa-F)的体外抑制作用。方法:采用水溶性四氮唑(WST-1)法比较低、中、高浓度(2.5、10、20μg·mL-1)的OPN、OPTN、OPPTN、OA溶液剂(OS)组和阳性对照(氟尿嘧啶注射液)组对HCa-F细胞培养24、48、72h后的细胞生长抑制率(IR)和3种纳米粒的半数抑制浓度(IC50),另设立空白纳米粒(NPs)组、空白组(不加任何物质)、阴性对照组(加入培养液)。结果:浓度分别为2.5、10、20μg·mL-1的OPN组在72h时的IR分别为(42.9±0.9)%、(63.6±1.1)%、(75.4±1.3)%,OPTN组分别为(54.3±1.2)%、(79.2±1.4)%、(92.6±1.5)%,OPPTN组分别为(50.8±0.8)%、(71.7±1.3)%、(83.9±1.2)%,阳性对照组分别为(31.5±0.9)%、(50.3±0.8)%、(60.6±0.9)%。与阳性对照组相同浓度比较,72h时OPN、OPTN、OPPTN组的中、高浓度的IR均明显升高(P均<0.01)。3种纳米粒对HCa-F细胞的IC50均随时间延长逐渐减小,其中OPTN组(8.64、1.39、0.38μg·mL-1)明显小于OPPTN组(11.86、5.52、3.46μg·mL-1)和OPN组(30.27、8.21、5.00μg·mL-1)(P<0.05或P<0.01)。结论:OPTN对HCa-F细胞的IR最高,表明OPTN体外具有良好的细胞相容性和显著的抗肿瘤活性。     

Influence of Intoxication by Anticholinesterase Agents on Core Temperature in Rats: Relationships between Hypothermia and Acetylcholinesterase Inhibition in Different Brain Areas

Abstract: The early and late effects of three anticholinesterase agents (physostigmine, paraoxon and soman) on core temperature and brain acetylcholinesterase (AcChE) inhibition are compared. The study was performed in adult male rats using sublethal doses of all drugs. AcChE activity was determined in hypothalamus, striatum, hippocampus, medulla oblongata-pons and rest of the brain. The co-existence of intoxication symptoms, hypothermia and AcChE inhibition was clearly shown by the early effects. However, no relationship was found between the degree of hypothermia and that of inhibition whatever brain area. In contrast, late AcChE inhibition was not accompanied by symptoms and lowering of core temperature. Several hypotheses have been suggested to explain this phenomenon: de novo synthesis of enzyme, decreased sensitivity of neurotransmitter or return to normal of brain acetylcholine level through a negative feed back at the presynaptic level. The present data suggest that this latter assumption is the most likely.     

A Comparison of the Therapeutic and Reactivating Efficacy of Newly Developed Oximes (K117, K127) and Currently Available Oximes (Obidoxime,Trimedoxime, HI-6) in Tabun-Poisoned Rats and Mice

The potency of newly developed bispyridinium compounds (K117, K127) to reactivate tabun-inhibited acetylcholinesterase and reduce tabun-induced lethal toxic effects was compared with currently available oximes (obidoxime, trimedoxime, oxime HI-6) by using in vivo methods. A study that determined the percentage of reactivation of tabun-inhibited blood and tissue acetylcholinesterase in poisoned rats showed that the reactivating efficacy of newly developed oxime K127 is comparable with obidoxime and trimedoxime in blood but lower than the reactivating potency of trimedoxime and obidoxime in the diaphragm and brain. The potency of another newly developed K117 to reactivate tabun-inhibited acetylcholinesterase is comparable with obidoxime or trimedoxime in the diaphragm, but it is significantly lower than the reactivating potency of trimedoxime and obidoxime in the blood and brain. The oxime, K127, was also found to be relatively effective in reducing lethal toxic effects in tabun-poisoned mice. Its therapeutic efficacy is consistent with the therapeutic potency of obidoxime. On the other hand, the potency of the oxime, K117, to reduce acute toxicity of tabun is significantly lower compared to trimedoxime and obidoxime. The therapeutic efficacy of K117 and K127 corresponds to their potency to reactivate tabun-inhibited acetylcholinesterase, especially in the diaphragm and brain. Contrary to obidoxime and trimedoxime, the oxime, HI-6, is not an effective oxime in the reactivation of tabun-inhibited acetycholinesterase and in reducing the lethal effects of tabun. The reactivating and therapeutic potency of both newly developed oximes does not prevail over the effectiveness of currently available obidoxime and trimedoxime and, therefore, they are not suitable for their replacement of commonly used oximes for the treatment of acute tabun poisoning.     

Characterization of Lung Injury following Abrin Pulmonary Intoxication in Mice: Comparison to Ricin Poisoning

Abrin is a highly toxic protein obtained from the seeds of the rosary pea plant Abrus precatorius, and it is closely related to ricin in terms of its structure and chemical properties. Both toxins inhibit ribosomal function, halt protein synthesis and lead to cellular death. The major clinical manifestations following pulmonary exposure to these toxins consist of severe lung inflammation and consequent respiratory insufficiency. Despite the high similarity between abrin and ricin in terms of disease progression, the ability to protect mice against these toxins by postexposure antibody-mediated treatment differs significantly, with a markedly higher level of protection achieved against abrin intoxication. In this study, we conducted an in-depth comparison between the kinetics of in vivo abrin and ricin intoxication in a murine model. The data demonstrated differential binding of abrin and ricin to the parenchymal cells of the lungs. Accordingly, toxin-mediated injury to the nonhematopoietic compartment was shown to be markedly lower in the case of abrin intoxication. Thus, profiling of alveolar epithelial cells demonstrated that although toxin-induced damage was restricted to alveolar epithelial type II cells following abrin intoxication, as previously reported for ricin, it was less pronounced. Furthermore, unlike following ricin intoxication, no direct damage was detected in the lung endothelial cell population following abrin exposure. Reduced impairment of intercellular junction molecules following abrin intoxication was detected as well. In contrast, similar damage to the endothelial surface glycocalyx layer was observed for the two toxins. We assume that the reduced damage to the lung stroma, which maintains a higher level of tissue integrity following pulmonary exposure to abrin compared to ricin, contributes to the high efficiency of the anti-abrin antibody treatment at late time points after exposure.     

Comparison of the AMPA Antagonist Action of New 2,3-Benzodiazepines in Vitro and Their Neuroprotective Effects in Vivo

PURPOSE: AMPA receptor-mediated excitotoxicity is thought to be a critical process in diseases accompanied by neuronal cell loss following a hypoxic/anoxic state of the central nervous system. It has been suggested that blockade of AMPA receptors might result in significant protection of neurons against cellular damage. For testing the hypothesis, in vitro efficacy and in vivo neuroprotective action of new 2,3-benzodiazepine (2,3BDZ) AMPA antagonists have been compared. METHODS: 2.3BDZs were tested on kainate-evoked whole-cell currents in cultured neurons as well as on population spikes (PS) in rat hippocampal slices. Data were correlated with those obtained from the spreading depression (SD) experiments in chicken retina. Compounds were also examined in the gerbil bilateral carotid occlusion model (BCO), where percentage decrease of ischemia-related hypermotility (HM), impaired spatial memory (SA), and hypoxia-induced hippocampal CA1 neuronal cell death (CA1) were evaluated. RESULTS: Certain structural modifications of classical 2,3BDZs resulted in increased in vitro activity and improved in vivo efficacy. In particular, the halogen-substituted compounds EGIS-9879 and EGIS-9883 showed the highest neuroprotective efficacy (84% and 47% protection in CA1, 71% and 82% decrease in HM, respectively; 4 x 5 mg/kg i.p.) in BCO. PS and SD were correlated to the decrease of neuronal loss in the CA1 area. Lack of significant correlation was found between PS and CA1 (r = 0.437, p = 0.079) or SD and CA1 (r = 0.380, p = 0.146). CONCLUSIONS: Several new 2.3BDZ AMPA receptor antagonists have been synthesized at EGIS Pharmaceuticals characterized by remarkable in vitro and corresponding in vivo neuroprotective properties.