paraoxon
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Organofosforové pesticidy (OFP) patří do skupiny vysoce toxických ireverzibilních inhibitorů acetylcholinesterasy (AChE). Kauzálními léčivy při intoxikacích OFP jsou oximové reaktivátory AChE. Reaktivační účinnost pěti nově připravených bispyridiniových reaktivátorů acetylcholinesterasy byla otestována na modelu paraoxonem inhibovaného enzymu. Reaktivační účinnost byla testována za pomoci standardního in vitro testu, kde byl jako zdroj acetylcholinesterasy použit homogenát mozku laboratorního potkana. Výsledky byly porovnány s pěti komerčně dostupnými reaktivátory AChE.
Organophosphorus pesticides (OPs) are ranked among the group of highly toxic irreversible inhibitors of acetylcholinesterase (AChE). The causal drugs in OPs intoxications are oxime reactivators of AChE. The reactivating efficacy of five newly prepared bispyridinium reactivators of acetylcholinesterase was tested on a model of a paraoxon-inhibited enzyme. The reactivating efficacy was tested by means of the standard in vitro test, the laboratory rat brain homogenate being used as the source of acetylcholinesterase. The result were compared with five commercially available AChE reactivators.
Four novel bisquaternary aldoxime cholinesterase reactivators differing in their chemical structure were prepared. Afterwards, their biological activity was evaluated for their ability to reactivate acetylcholinesterase (AChE; EC 3.1.1.7) and butyrylcholinesterase (BuChE; EC 3.1.1.8) inhibited by paraoxon. Their reactivation activity was compared with standard reactivators--pralidoxime, obidoxime and HI-6--which are clinically used at present. As it resulted, none of the prepared compounds surpassed obidoxime, which is considered to be the most potent compound if used for reactivation of AChE inhibited by paraoxon. In case of BuChE reactivation, two compounds (K053 and K068) achieved similar results as obidoxime.
- MeSH
- acetylcholinesterasa účinky léků metabolismus MeSH
- butyrylcholinesterasa účinky léků metabolismus MeSH
- enzymové reaktivátory farmakologie MeSH
- magnetická rezonanční spektroskopie MeSH
- oximy chemie MeSH
- paraoxon farmakologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Photometric microplate assay was performed for testing of paraoxon-inhibited acetylcholinesterase (AChE) using three reactivators for reactivation purposes: obidoxime, pralidoxime, and HI-6. 3-D graphs (percent of reactivation vs. concentration of reactivator and vs. time of reactivator effecting) were constructed for each reactivator to compare their efficacy. The best results were obtained using obidoxime where reactivation was near to 80%. Suitability of photometric microplates for following of reactivation procedures is discussed.
Organophosphates, useful agents as pesticides, also represent a serious danger due to their high acute toxicity. There is indication that oximes, when administered before organophosphate exposure, can protect from these toxic effects. We have tested at equitoxic dosage (25% of LD01 ) the prophylactic efficacy of five experimental (K-48, K-53, K-74, K-75, K-203) and two established oximes (pralidoxime and obidoxime) to protect from mortality induced by the organophosphate paraoxon. Mortalities were quantified by Cox analysis and compared with those observed after pretreatment with a strong acetylcholinesterase inhibitor (10-methylacridine) and after the FDA-approved pretreatment compound pyridostigmine. All nine tested substances statistically significantly reduced paraoxon-induced mortality. Best protection was conferred by the experimental oxime K-48, reducing the relative risk of death (RR) to 0.10, which was statistically significantly superior to pyridostigmine (RR = 0.31). The other oximes reduced the RR to 0.13 (obidoxime), 0.20 (K-203), 0.21 (K-74), 0.24 (K-75) and 0.26 (pralidoxime), which were significantly more efficacious than 10-methylacridine (RR = 0.65). These data support the hypothesis that protective efficacy is not primarily due to cholinesterase inhibition and indicate that the tested experimental oximes may be considered promising alternatives to the established pretreatment compound pyridostigmine.
- MeSH
- analýza přežití MeSH
- LD50 MeSH
- obidoxim chlorid aplikace a dávkování farmakologie MeSH
- ochranné látky aplikace a dávkování farmakologie MeSH
- paraoxon chemie toxicita MeSH
- potkani Wistar MeSH
- pralidoximové sloučeniny aplikace a dávkování farmakologie MeSH
- proporcionální rizikové modely MeSH
- reaktivátory cholinesterasy aplikace a dávkování farmakologie MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The aim of this study was to determine optimal conditions for in vitro skin decontamination using water and detergents as decontamination agents and to test the cleansing efficiency of selected detergents. Experiments were performed using a peristaltic pump for showering of pig skin in modified static diffusion cells. Several conditions were tested including different flow rates (from 5 to 33 ml s-1), quantity of rinsing fluid (from 40 to 400 ml) and concentration of detergents (2; 5; 10%). Further, several types of detergents/commercial decontamination agents were evaluated under the selected conditions to find the most effective means of decontamination. The amount of paraoxon removed from the skin surface following wet-type decontamination was detected in the rinsing fluid spectrophotometrically after hydrolysis of paraoxon - a model contaminant. The efficacy of rinsing by water/Spolapon AES 253 increased with flow rate up to 25 ml s-1 and a rinsing volume of 200 ml. Lutensol AT 25 achieved maximum efficacy at the lowest tested concentration (2%). A flow rate of 16 ml s-1, rinsing volume of 100 ml (values from the middle part of the sigmoid curve) and 5% concentration of decontaminant solution were used for further evaluation of detergents as cleansing agents under the selected conditions. Cetylpyridinium bromide (cationic surfactant), carbethopendecinii bromidum (cationic surfactant) and polyoxyethylene-10-tridecyl ether (non-ionic surfactant), SDS (anionic surfactant), althosan MB (cationic surfactant), sodium dodecylbenzene sulphonate (anionic surfactant), neodekont (mixture), tergitol NPX (non-ionic surfactant), Korynt P (non-ionic surfactant) were found to be the most effective. These decontaminants were able to wash away more than 92% of paraoxon from the contaminated skin.
A dipstick for fast assay of nerve agents and organophosphate pesticides was developed. Indicator pH papers were used as detectors. The principle of the assay is based on enzymatic hydrolysis of acetylcholine into acetic acid and choline by acetylcholinesterase. Acidification of the reaction medium due to accumulation of acetic acid was visible. The colour changed from dark red to yellow as the pH indicator recognized pH shift. Presence of an organophosphate pesticide or a nerve agent results in irreversible inhibition of acetylcholinesterase intercepted on the dipstick. The inhibition stops the enzymatic reaction. The inhibition appears as no change of the medium pH. Three compounds were assayed: paraoxon-ethyl as representative organophosphate pesticides and nerve agents sarin and VX. The achieved limit of detection was 5 x 10(-8)M for paraoxon-ethyl and 5 x 10(-9)M for sarin and VX. Dipsticks were found stable for at least one month. Suitability of these dipsticks for routine assay is discussed.
Organophosphorus pesticides (e.g. chlorpyrifos, malathion, and parathion) and nerve agents (sarin, tabun, and VX) are highly toxic organophosphorus compounds with strong inhibition potency against two key enzymes in the human body-acetylcholinesterase (AChE; EC 3.1.1.7) and butyrylcholinesterase (BuChE; EC 3.1.1.8). Subsequent accumulation of acetylcholine at synaptic clefts can result in cholinergic crisis and possible death of intoxicated organism. For the recovery of inhibited AChE, derivatives from the group of pyridinium or bispyridinium aldoximes (called oximes) are used. Their efficacy depends on their chemical structure and also type of organophosphorus inhibitor. In this study, we have tested potency of selected cholinesterase reactivators (pralidoxime, obidoxime, trimedoxime, methoxime and H-oxime HI-6) to reactivate human erythrocyte AChE and human plasma BuChE inhibited by pesticide paraoxon. For this purpose, modified Ellman's method was used and two different concentrations of oximes (10 and 100 microM), attainable in the plasma within antidotal treatment of pesticide intoxication were tested. Results demonstrated that obidoxime (96.8%) and trimedoxime (86%) only reached sufficient reactivation efficacy in case of paraoxon-inhibited AChE. Other oximes evaluated did not surpassed more than 25% of reactivation. In the case of BuChE reactivation, none of tested oximes surpassed 12.5% of reactivation. The highest reactivation efficacy was achieved for trimedoxime (12.4%) at the concentration 100 microM. From the data obtained, it is clear that only two from currently available oximes (obidoxime and trimedoxime) are good reactivators of paraoxon-inhibited AChE. In the case of BuChE, none of these reactivators could be used for its reactivation.
- MeSH
- acetylcholinesterasa MeSH
- butyrylcholinesterasa metabolismus MeSH
- cholinesterasové inhibitory toxicita MeSH
- enzymové reaktivátory farmakologie MeSH
- financování organizované MeSH
- lidé MeSH
- organofosforové sloučeniny toxicita MeSH
- oximy farmakologie MeSH
- paraoxon toxicita MeSH
- techniky in vitro MeSH
- Check Tag
- lidé MeSH
INTRODUCTION: Organophosphorus pesticides and nerve agents are highly toxic to humans and other living organisms, primarily because of their interaction with enzyme acetylcholinesterase. The aim of our study was to find suitable reactivators of acetylcholinesterase and butyrylcholinesterase and to recommend the most efficacious compounds for the next evaluation as antidotes for intoxication by pesticides. METHODS: Eighteen structurally different oxime reactivators were tested for their in vitro ability to reactivate paraoxon-inhibited human erythrocyte acetylcholinesterase and human plasma butyrylcholinesterase to find out structure-activity relationship within this set of compounds. Their reactivation ability was compared with commercially available acetylcholinesterase reactivators (pralidoxime, methoxime, trimedoxime, obidoxime, and HI-6). RESULTS AND DISCUSSION: The best reactivation ability was achieved with obidoxime, trimedoxime, compounds K027, K075, K203, and K048. We have also tested reactivation of butyrylcholinesterase with the aim to recommend an efficient reactivator, able to perform a "pseudo catalytic" bioscavenger with butyrylcholinesterase, which is developed as new antidote of organophosphate poisonings. Such combination could allow an enhancement of prophylactic and therapeutic efficiency of administered enzyme. Compounds K117, K269, K075, and trimedoxime were found to be the most potent reactivators of inhibited butyrylcholinesterase. CONCLUSIONS: In this work, we have evaluated only reactivation of paraoxon-inhibited cholinesterases. To get better understanding of this problem, a larger number of organophosphorus inhibitors should be used.
- MeSH
- acetylcholinesterasa metabolismus MeSH
- antidota farmakologie chemie MeSH
- cholinesterasové inhibitory toxicita MeSH
- erytrocyty enzymologie účinky léků MeSH
- kultivované buňky MeSH
- kvantitativní vztahy mezi strukturou a aktivitou MeSH
- lidé MeSH
- molekulární struktura MeSH
- paraoxon toxicita MeSH
- reaktivátory cholinesterasy farmakologie chemie MeSH
- Check Tag
- lidé MeSH
Three asymmetrical AChE reactivators with cyano-moiety and propane linker were synthesized using modification of currently known synthetic pathways. Their potency to reactivate AChE inhibited by nerve agent tabun and insecticide paraoxon was tested in vitro and compared to pralidoxime, HI-6, obidoxime, K027, and K048. According to the results, three compounds seem to be promising against paraoxon-inhibited AChE. Better results were obtained for bisquaternary substances at least with one oxime group in position four. None of tested substances was able to satisfactorily reactivate tabun-inhibited AChE at concentration applicable for in vivo experiments.
OBJECTIVES: Organophosphorus compounds represent nerve agents, pesticides and several industrial compounds. Treatment after exposure to organophosphates involves the use of parasympatolytics, acetylcholinesterase (AChE) reactivators/modulators and anticonvulsive drugs. Wider clinical use of several AChE reactivators/modulators might be limited because of possible side effects, including gastrointestinal toxicity. In this study we evaluated the effect of paraoxon and an AChE reactivator (HI-6) on the gastric myoelectric activity in experimental pigs. METHODS: Six female experimental pigs (mean weight 33 kg) entered the study. Intramuscular paraoxon (1.5 g) was administrated after the baseline gastric electrogastrography (EGG) recording, followed by HI-6 dimethansulphonate (1.5 g i.m.) 10 min. later. A further ten 15-minute-interval EGG recordings were performed. Running spectral analysis was used for the elemental evaluation of the EGG. The results were expressed as dominant frequency of slow waves at all intervals of EGG recordings. EGG power analysis was performed in all animals. RESULTS: Paraoxon induced a non-significant decrease of dominant frequency (2.8±0.6 vs. 2.6±0.5 cycles per min.; p=0.092). Subsequent administration of HI-6 normalised dominant frequency to basal values and increased it significantly within the subsequent 30 minutes (3.0±0.4; p<0.001). Paraoxon administration did not influence the power (within a 10-minute exposure). However, the amplitudes increased significantly 90 minutes after administration of HI-6 (819±109 vs. 5054±732 μV2; p<0.001). CONCLUSIONS: AChE reactivator HI-6 blocked the gastric effect of paraoxon significantly. Subsequent myoelectric changes in the dominant frequency and power were executed by HI-6. The effect of paraoxon was non-significant.
- MeSH
- elektromyografie MeSH
- injekce intramuskulární MeSH
- modely u zvířat MeSH
- oximy aplikace a dávkování MeSH
- paraoxon aplikace a dávkování MeSH
- prasata MeSH
- pyridinové sloučeniny aplikace a dávkování MeSH
- reaktivátory cholinesterasy aplikace a dávkování MeSH
- srdeční frekvence účinky léků fyziologie MeSH
- žaludek účinky léků fyziologie MeSH
- zvířata MeSH
- Check Tag
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
