Organophosphorus compounds induce irreversible inhibition of acetylcholinesterase, which then produces clinically manifested muscarinic, nicotinic and central effects. The aim of the study was to analyse the clinical signs of acute paraoxon poisoning in rats and to determine the relationship between the intensity of signs of poisoning and the dose of paraoxon and/or the outcome of poisoning in rats. Animals were treated with either saline or atropine (10 mg/kg intramuscularly). The median subcutaneous lethal dose (LD50) of paraoxon was 0.33 mg/kg and protective ratio of atropine was 2.73. The presence and intensity of signs of poisoning in rats (dyspnoea, lacrimation, exophthalmos, fasciculations, tremor, ataxia, seizures, piloerection, stereotypic movements) were observed and recorded for 4 h after the injection of paraoxon. Intensity of these toxic phenomena was evaluated as: 0 - absent, 1 - mild/moderate, 2 - severe. Fasciculations, seizures and tremor were more intense at higher doses of paraoxon and in non-survivors. In unprotected rats piloerection occurred more often and was more intense at higher doses of paraoxon as well as in non-survivors. In atropine-protected rats, piloerection did not correlate with paraoxon dose or outcome of poisoning. The intensity of fasciculations and seizures were very strong prognostic parameters of the poisoning severity.
- MeSH
- acetylcholinesterasa * MeSH
- atropin farmakologie MeSH
- fascikulace MeSH
- krysa rodu rattus MeSH
- paraoxon * toxicita MeSH
- tremor MeSH
- záchvaty chemicky indukované MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Antidotes against organophosphates often possess physicochemical properties that mitigate their passage across the blood-brain barrier. Cucurbit[7]urils may be successfully used as a drug delivery system for bisquaternary oximes and improve central nervous system targeting. The main aim of these studies was to elucidate the relationship between cucurbit[7]uril, oxime K027, atropine, and paraoxon to define potential risks or advantages of this delivery system in a complex in vivo system. For this reason, in silico (molecular docking combined with umbrella sampling simulation) and in vivo (UHPLC-pharmacokinetics, toxicokinetics; acetylcholinesterase reactivation and functional observatory battery) methods were used. Based on our results, cucurbit[7]urils affect multiple factors in organophosphates poisoning and its therapy by (i) scavenging paraoxon and preventing free fraction of this toxin from entering the brain, (ii) enhancing the availability of atropine in the central nervous system and by (iii) increasing oxime passage into the brain. In conclusion, using cucurbit[7]urils with oximes might positively impact the overall treatment effectiveness and the benefits can outweigh the potential risks.
- MeSH
- atropin chemie MeSH
- hematoencefalická bariéra MeSH
- imidazoly chemie MeSH
- myši MeSH
- oximy chemie MeSH
- paraoxon chemie toxicita MeSH
- počítačová simulace MeSH
- přemostěné cyklické sloučeniny chemie MeSH
- pyridinové sloučeniny chemie MeSH
- reaktivátory cholinesterázy chemie toxicita MeSH
- simulace molekulového dockingu MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
BACKGROUND: Oximes are used in addition to atropine to treat organophosphate poisoning. However, the efficiency of oximes is still a matter of debate. In vitro experiments suggested than new oximes are more potent than the commercial oximes. However, the antidotal activity of new oximes has not been assessed in vivo. METHODS: The aim of this work was to assess the safety and efficiency of new oximes compared to pralidoxime in a rat model of diethyl paraoxon-induced non-lethal respiratory toxicity. RESULTS: Safety study of oximes showed no adverse effects on ventilation in rats. KO-33, KO-48, KO-74 oximes did not exhibit significant antidotal effect in vivo. In contrast, KO-27 and BI-6 showed evidence of antidotal activity by normalization of respiratory frequency and respiratory times. KO-27 became inefficient only during the last 30 min of the study. In contrast, pralidoxime demonstrated to be inefficient at 30 min post injection. Inversely, the antidotal activity of BI-6 occurred lately, within the last 90 min post injection. CONCLUSION: This study showed respiratory safety of new oximes. Regarding, the efficiency, KO-27 revealed to be a rapid acting antidote toward diethylparaoxon-induced respiratory toxicity, meanwhile BI-6 was a late-acting antidote. Simultaneous administration of these two oximes might result in a complete and prolonged antidotal efficiency.
- MeSH
- antidota farmakologie MeSH
- bezpečnost MeSH
- cholinesterasové inhibitory toxicita MeSH
- dýchání účinky léků MeSH
- krysa rodu rattus MeSH
- otrava organofosfáty farmakoterapie etiologie MeSH
- oximy farmakologie MeSH
- paraoxon toxicita MeSH
- potkani Sprague-Dawley MeSH
- větrání metody MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
AIMS: Organophosphates (OPCs), useful agents as pesticides, also represent a serious health hazard. Standard therapy with atropine and established oxime-type enzyme reactivators is unsatisfactory. Experimental data indicate that superior therapeutic results can be obtained when reversible cholinesterase inhibitors are administered before OPC exposure. Comparing the protective efficacy of five such cholinesterase inhibitors (physostigmine, pyridostigmine, ranitidine, tacrine, or K-27), we observed best protection for the experimental oxime K-27. The present study was undertaken in order to determine if additional administration of K-27 immediately after OPC (paraoxon) exposure can improve the outcome. METHODS: Therapeutic efficacy was assessed in rats by determining the relative risk of death (RR) by Cox survival analysis over a period of 48 h. Animals that received only pretreatment and paraoxon were compared with those that had received pretreatment and paraoxon followed by K-27 immediately after paraoxon exposure. RESULTS: Best protection from paraoxon-induced mortality was observed after pretreatment with physostigmine (RR = 0.30) and K-27 (RR = 0.34). Both substances were significantly more efficacious than tacrine (RR = 0.67), ranitidine (RR = 0.72), and pyridostigmine (RR = 0.76), which were less efficacious but still significantly reduced the RR compared to the no-treatment group (paraoxon only). Additional administration of K-27 immediately after paraoxon exposure (posttreatment) did not further reduce mortality. Statistical analysis between pretreatment before paraoxon exposure alone and pretreatment plus K-27 posttreatment did not show any significant difference for any of the pretreatment regimens. CONCLUSIONS: Best outcome is achieved if physostigmine or K-27 are administered prophylactically before exposure to sublethal paraoxon dosages. Therapeutic outcome is not further improved by additional oxime therapy immediately thereafter.
- MeSH
- analýza přežití MeSH
- cholinesterasové inhibitory aplikace a dávkování toxicita MeSH
- fysostigmin aplikace a dávkování chemie MeSH
- krysa rodu rattus MeSH
- organofosfáty toxicita MeSH
- oximy aplikace a dávkování chemie MeSH
- paraoxon chemie toxicita MeSH
- postexpoziční profylaxe MeSH
- potkani Wistar MeSH
- preexpoziční profylaxe MeSH
- proporcionální rizikové modely MeSH
- pyridostigmin-bromid aplikace a dávkování chemie MeSH
- ranitidin chemie farmakologie MeSH
- reaktivátory cholinesterázy farmakologie MeSH
- takrin aplikace a dávkování chemie MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Organophosphorus compounds (OP) are chemicals widely used as pesticides in different applications such as agriculture and public health (vector control), and some of the highly toxic forms have been used as chemical weapons. After application of OPs in an environment, they persist for a period, suffering a degradation process where the biotic factors are considered the most relevant forms. However, to date, the biodegradation of OP compounds is not well understood. There are a plenty of structure-based biodegradation estimation methods, but none of them consider enzymatic interaction in predicting and better comprehending the differences in the fate of OPs in the environment. It is well known that enzymatic processes are the most relevant processes in biodegradation, and that hydrolysis is the main pathway in the natural elimination of OPs in soil samples. Due to this, we carried out theoretical studies in order to investigate the interactions of these OPs with a chosen enzyme-the phosphotriesterase. This one is characteristic of some soils' microorganisms, and has been identified as a key player in many biodegradation processes, thanks to its capability for fast hydrolyzing of different OPs. In parallel, we conducted an experiment using native soil in two conditions, sterilized and not sterilized, spiked with specific amounts of two OPs with similar structure-paraoxon-ethyl (PXN) and O-(4-nitrophenyl) O-ethyl methylphosphonate (NEMP). The amount of OP present in the samples and the appearance of characteristic hydrolysis products were periodically monitored for 40 days using analytical techniques. Moreover, the number of microorganisms present was obtained with plate cell count. Our theoretical results were similar to what was achieved in experimental analysis. Parameters calculated by enzymatic hydrolysis were better for PXN than for NEMP. In soil, PXN suffered a faster hydrolysis than NEMP, and the cell count for PXN was higher than for NEMP, highlighting the higher microbiological toxicity of the latter. All these results pointed out that theoretical study can offer a better comprehension of the possible mechanisms involved in real biodegradation processes, showing potential in exploring how biodegradation of OPs relates with enzymatic interactions.
- MeSH
- biodegradace * MeSH
- chemická válka MeSH
- hydrolýza MeSH
- insekticidy chemie metabolismus MeSH
- lidé MeSH
- organofosforové sloučeniny chemie metabolismus MeSH
- paraoxon analogy a deriváty chemie MeSH
- pesticidy chemie toxicita MeSH
- půda chemie MeSH
- pyrrolidiny chemie MeSH
- veřejné zdravotnictví MeSH
- zemědělství MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
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.
- MeSH
- acetylcholinesterasa metabolismus MeSH
- Electrophorus metabolismus MeSH
- enzymové reaktivátory chemie farmakologie MeSH
- molekulární struktura MeSH
- oximy chemie farmakologie MeSH
- paraoxon toxicita MeSH
- rybí proteiny metabolismus MeSH
- techniky in vitro MeSH
- vztahy mezi strukturou a aktivitou MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Organophosphates (OPs) irreversibly inhibit acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. The reactivation of these inhibited enzymes is paramount for their normal function. Present study evaluates reactivation potency of two newly developed oximes, K456 and K733, against paraoxon (POX)-inhibited human-RBC-AChE and human-plasma-BChE in comparison to reported reactivator, pralidoxime (2-PAM). In vitro studies showed higher intrinsic toxicities of both oximes than 2-PAM for AChE. No substantial reactivation of hBChE was noted by tested concentration. Contrary to 2-PAM, the in silico study predicted lower binding free energies for both oximes. However, the detailed interaction study revealed inability of oximes to interact with catalytic anionic site of AChE and hBChE in contrast to 2-PAM. Both in vitro and in silico studies conclude that K456 and K733 are unlikely to be used as reactivators of paraoxon-inhibited AChE or BChE.
- MeSH
- acetylcholinesterasa chemie MeSH
- butyrylcholinesterasa chemie MeSH
- cholinesterasové inhibitory farmakologie MeSH
- erytrocyty enzymologie MeSH
- lidé MeSH
- oximy farmakologie MeSH
- paraoxon antagonisté a inhibitory farmakologie MeSH
- pyridinové sloučeniny farmakologie MeSH
- reaktivátory cholinesterázy farmakologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
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 cholinesterázy aplikace a dávkování farmakologie MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The present work aimed to compare the small, neutral and monoaromatic oxime, isatin-3-oxime (isatin-O), to the commercial ones, pralidoxime (2-PAM) and obidoxime, in a search for a new potential reactivator for acetylcholinesterase (AChE) inhibited by the pesticide paraoxon (AChE/POX) as well as a novel potential scaffold for further synthetic modifications. The multicriteria decision methods (MCDM) allowed the identification of the best docking poses of those molecules inside AChE/POX for further molecular dynamic (MD) studies, while Ellman's modified method enabled in vitro inhibition and reactivation assays. In corroboration with the theoretical studies, our experimental results showed that isatin-O have a reactivation potential capable of overcoming 2-PAM at the initial moments of the assay. Despite not achieving better results than obidoxime, this molecule is promising for being an active neutral oxime with capacity of crossing the blood⁻brain barrier (BBB), to reactivate AChE/POX inside the central and peripheral nervous systems. Moreover, the fact that isatin-O can also act as anticonvulsant makes this molecule a possible multipotent reactivator. Besides, the MCDM method showed to be an accurate method for the selection of the best docking poses generated in the docking studies.
- MeSH
- cholinesterasové inhibitory farmakologie MeSH
- erytrocyty účinky léků enzymologie MeSH
- molekulární modely * MeSH
- molekulární struktura MeSH
- oximy chemie farmakologie MeSH
- paraoxon chemie farmakologie MeSH
- reaktivátory cholinesterázy chemie farmakologie MeSH
- simulace molekulární dynamiky MeSH
- simulace molekulového dockingu MeSH
- Publikační typ
- časopisecké články MeSH
BACKGROUND: In the last decade, the concept of uncharged reactivators potentially able to penetrate the CNS has been introduced as an alternative to the classic charged oxime reactivators. However, this concept brings with it several associated drawbacks such as higher lipophilicity, difficulty in administration, lower affinity to cholinesterases, and higher toxicity risk. OBJECTIVE: In this study, we compare data obtained for a set of five classic charged reactivators and a set of three recently published uncharged oximes supplemented by two novel ones. METHODS: This time, we used only in silico prediction and in vitro approaches. RESULTS: Our data showed that tested uncharged oximes have low affinity for cholinesterases, do not possess high reactivation potency, and certainly represent a greater toxicity risk due to higher lipophilicity. We assume that balanced physicochemical properties will be required for the successful treatment of OP poisoning. Nevertheless, the compound meeting such criteria and pinpointed in silico (K1280) failed in this particular case. CONCLUSION: From the presented data, it seems that the concept of uncharged reactivators will have to be modified, at least to improve the bioavailability and to satisfy requirements for in vivo administration.
- MeSH
- antidota chemická syntéza farmakologie toxicita MeSH
- butyrylcholinesterasa metabolismus MeSH
- cholinesterasové inhibitory chemická syntéza farmakologie toxicita MeSH
- hematoencefalická bariéra účinky léků MeSH
- krysa rodu rattus MeSH
- myši MeSH
- organofosfáty toxicita MeSH
- otrava organofosfáty farmakoterapie MeSH
- oximy chemická syntéza farmakologie toxicita MeSH
- paraoxon toxicita MeSH
- počítačová simulace MeSH
- reaktivátory cholinesterázy chemická syntéza farmakologie toxicita MeSH
- sarin toxicita MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
