Ricin is a potent cytotoxin with no available antidote. Its catalytic subunit, RTA, damages the ribosomal RNA (rRNA) of eukaryotic cells, preventing protein synthesis and eventually leading to cell death. The combination between easiness of obtention and high toxicity turns ricin into a potential weapon for terrorist attacks, urging the need of discovering effective antidotes. On this context, we used computational techniques, in order to identify potential ricin inhibitors among approved drugs. Two libraries were screened by two different docking algorithms, followed by molecular dynamics simulations and MM-PBSA calculations in order to corroborate the docking results. Three drugs were identified as potential ricin inhibitors: deferoxamine, leucovorin and plazomicin. Our calculations showed that these compounds were able to, simultaneously, form hydrogen bonds with residues of the catalytic site and the secondary binding site of RTA, qualifying as potential antidotes against intoxication by ricin.Communicated by Ramaswamy H. Sarma.

• Klíčová slova
• Ricin inhibitors, biological warfare agents, drug repurposing, ricin, virtual screening,
• MeSH
• antidota MeSH
• přehodnocení terapeutických indikací léčivého přípravku MeSH
• ricin * chemie   metabolismus   farmakologie   MeSH
• simulace molekulární dynamiky MeSH
• simulace molekulového dockingu MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• antidota MeSH
• ricin * MeSH

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

• Klíčová slova
• Isatin, antidotes, cholinesterase reactivators, nerve agents, organophosphorus poisoning, pyridine oximes,
• MeSH
• acetylcholinesterasa účinky léků   MeSH
• isatin farmakologie   MeSH
• počítačová simulace MeSH
• pyridiny farmakologie   MeSH
• reaktivátory cholinesterázy farmakologie   MeSH
• techniky in vitro MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• acetylcholinesterasa MeSH
• isatin MeSH
• pyridine MeSH Prohlížeč
• pyridiny MeSH
• reaktivátory cholinesterázy MeSH

Ricin is a toxin found in the castor seeds and listed as a chemical weapon by the Chemical Weapons Convention (CWC) due to its high toxicity combined with the easiness of obtention and lack of available antidotes. The relatively frequent episodes of usage or attempting to use ricin in terrorist attacks reinforce the urge to develop an antidote for this toxin. In this sense, we selected in this work the current RTA (ricin catalytic subunit) inhibitor with the best experimental performance, as a reference molecule for virtual screening in the PubChem database. The selected molecules were then evaluated through docking studies, followed by drug-likeness investigation, molecular dynamics simulations and Molecular Mechanics Poisson-Boltzmann Surface Area (MM-PBSA) calculations. In every step, the selection of molecules was mainly based on their ability to occupy both the active and secondary sites of RTA, which are located right next to each other, but are not simultaneously occupied by the current RTA inhibitors. Results show that the three PubChem compounds 18309602, 18498053, and 136023163 presented better overall results than the reference molecule itself, showing up as new hits for the RTA inhibition, and encouraging further experimental evaluation.

• Klíčová slova
• chemical/biological warfare agents, ligand-based virtual screening, molecular dynamics, ricin, ricin inhibitors,
• MeSH
• algoritmy MeSH
• chemické bojové látky chemie   MeSH
• ligandy MeSH
• molekulární konformace MeSH
• molekulární struktura MeSH
• objevování léků MeSH
• ricin antagonisté a inhibitory   chemie   MeSH
• simulace molekulární dynamiky MeSH
• simulace molekulového dockingu MeSH
• vazebná místa MeSH
• vodíková vazba MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chemické bojové látky MeSH
• ligandy MeSH
• ricin 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.

• Klíčová slova
• bioremediation, molecular modeling, organophosphorus compounds, phosphotriesterase,
• 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
• Názvy látek
• ethylparaoxon MeSH Prohlížeč
• insekticidy MeSH
• N-ethylmercapto-3-4-dihydroxy-2-hydroxymethylpyrrolidine MeSH Prohlížeč
• organofosforové sloučeniny MeSH
• paraoxon MeSH
• pesticidy MeSH
• půda MeSH
• pyrrolidiny 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.

• Klíčová slova
• acetylcholinesterase, antidotes, drug design, neutral oximes, pesticides,
• 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
• Názvy látek
• acetylcholinesterasa MeSH
• enzymové reaktivátory MeSH
• oximy MeSH
• paraoxon MeSH
• rybí proteiny MeSH

Casualties caused by nerve agents, potent acetylcholinesterase inhibitors, have attracted attention from media recently. Poisoning with these chemicals may be fatal if not correctly addressed. Therefore, research on novel antidotes is clearly warranted. Pyridinium oximes are the only clinically available compounds, but poor penetration into the blood-brain barrier hampers efficient enzyme reactivation at the central nervous system. In searching for structural factors that may be explored in SAR studies, we synthesized and evaluated neutral aryloximes as reactivators for acetylcholinesterase inhibited by NEMP, a VX surrogate. Although few tested compounds reached comparable reactivation results with clinical standards, they may be considered as leads for further optimization.

• Klíčová slova
• Acetylcholinesterase reactivators, Chemical defence, Drug screening, Nerve agents' surrogates, Neutral oximes,
• MeSH
• acetylcholinesterasa chemie   metabolismus   MeSH
• Anguilliformes MeSH
• antidota chemická syntéza   metabolismus   MeSH
• cholinesterasové inhibitory chemie   metabolismus   MeSH
• organothiofosforové sloučeniny chemie   metabolismus   MeSH
• oximy chemie   metabolismus   MeSH
• pyrrolidiny chemie   metabolismus   MeSH
• reaktivátory cholinesterázy chemická syntéza   metabolismus   MeSH
• vztahy mezi strukturou a aktivitou MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• acetylcholinesterasa MeSH
• antidota MeSH
• cholinesterasové inhibitory MeSH
• N-ethylmercapto-3-4-dihydroxy-2-hydroxymethylpyrrolidine MeSH Prohlížeč
• organothiofosforové sloučeniny MeSH
• oximy MeSH
• pyrrolidiny MeSH
• reaktivátory cholinesterázy MeSH
• VX MeSH Prohlížeč

Aflatoxin M1 (AFM1) is a mycotoxin produced by Aspergillus fungi and found in contaminated milk, breastfeed and dairy products, being highly toxic and carcinogenic to humans and other mammalian species. It is also produced in the human body as a metabolite of aflatoxin B1 (AFB1), one of the most toxic natural products known. Previous studies have shown that AFM1 is a potential inhibitor of the enzyme acetylcholinesterase (AChE), and therefore, a potential neurotoxic agent. In this work, surface screening (SS) and molecular dynamics (MD) simulation on human acetylcholinesterase AChE (HssAChE) were performed to corroborate literature data regarding preferential binding sites and type of inhibition. Also, an inedited theoretical study on the interactions of AFM1 with human butyrylcholinesterase (HssBChE) was performed. In vitro inhibition tests on both enzymes were done to support theoretical results. MD simulations suggested the catalytic anionic site of HssAChE as the preferential binding site for AFM1 and also that this metabolite is not a good inhibitor of HssBChE, corroborating previous studies. In vitro assays also corroborated molecular modeling studies by showing that AFM1 did not inhibit BChE and was able to inhibit AChE, although not as much as AFB1.

• Klíčová slova
• Acetylcholinesterase, Aflatoxin M1, Butyrylcholinesterase, Molecular modeling, Surface screening,
• MeSH
• acetylcholinesterasa chemie   metabolismus   MeSH
• aflatoxin B1 chemie   metabolismus   MeSH
• aflatoxin M1 chemie   metabolismus   MeSH
• Aspergillus metabolismus   MeSH
• butyrylcholinesterasa chemie   metabolismus   MeSH
• katalytická doména MeSH
• lidé MeSH
• povrchové vlastnosti MeSH
• simulace molekulární dynamiky MeSH
• termodynamika MeSH
• vazebná místa MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• acetylcholinesterasa MeSH
• aflatoxin B1 MeSH
• aflatoxin M1 MeSH
• butyrylcholinesterasa MeSH

Aflatoxins are secondary metabolites of the fungi Aspergillus flavus and A. parasiticus. Among them, aflatoxin B1 (AFB1) is the most frequent type in nature and the most carcinogenic for mammals. It can contaminate many kinds of food like seeds, oil, olives, milk, dairy products, corn and meat, causing acute and chronic damages to the organism, especially in the liver, being, for this reason, considered highly hepatotoxic. AFB1 is also a mixed inhibitor of the enzyme acetylcholinesterase (AChE). This fact, together with its high toxicity and carcinogenicity, turns AFB1 into a potential chemical and biological warfare agent, as well as its metabolites. In order to investigate this, we performed inedited molecular modeling studies on the interactions of AFB1 and its metabolites inside the peripheral anionic site of human AChE (HssAChE), to verify their stability, suggest the preferential ways of inhibition, and compare their behavior to each other. Our results suggest that all metabolites can be better inhibitors of HssAChE than AFB1 and that AFBO and AFM1, the most toxic and carcinogenic metabolites of AFB1, are also the most effective HssAChE inhibitors among the AFB1 metabolites. Communicated by Ramaswamy H. Sarma.

• Klíčová slova
• acetylcholinesterase, aflatoxin B1, biological warfare agents, chemical warfare agents, metabolites,
• MeSH
• acetylcholinesterasa chemie   metabolismus   MeSH
• aflatoxin B1 chemie   metabolismus   MeSH
• anionty MeSH
• lidé MeSH
• ligandy MeSH
• metabolom * MeSH
• molekulární modely * MeSH
• simulace molekulární dynamiky MeSH
• simulace molekulového dockingu MeSH
• termodynamika MeSH
• vodíková vazba MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• acetylcholinesterasa MeSH
• aflatoxin B1 MeSH
• anionty MeSH
• ligandy 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.

• Klíčová slova
• Ellman’s method, TOPSIS-AHP, acetylcholinesterase, molecular modeling, multicriteria decision making, neutral oxime,
• 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
• Názvy látek
• cholinesterasové inhibitory MeSH
• oximy MeSH
• paraoxon MeSH
• reaktivátory cholinesterázy MeSH

The most common type of aflatoxin (AFT) found in nature is aflatoxin B1 (AFB1). This micotoxin is extremely hepatotoxic and carcinogenic to mammals, with acute and chronic effects. It is believed that this could be related to the capacity of AFB1 and its metabolites in inhibiting the enzyme acetylcholinesterase (AChE). In a previous work, we performed an inedited theoretical investigation on the binding modes of these molecules on the peripheral anionic site (PAS) of human AChE (HssAChE), revealing that the metabolites can also bind in the PAS in the same way as AFB1. Here, we investigated the binding modes of these compounds on the catalytic anionic site (CAS) of HssAChE to compare the affinity of the metabolites for both binding sites as well as verify which is the preferential one. Our results corroborated with experimental studies pointing to AFB1 and its metabolites as mixed-type inhibitors, and pointed to the residues relevant for the stabilization of these compounds on the CAS of HssAChE.

• Klíčová slova
• acetylcholinesterase, aflatoxin B1, catalytic anionic site, metabolites,
• MeSH
• acetylcholinesterasa chemie   metabolismus   MeSH
• aflatoxin B1 chemie   metabolismus   MeSH
• cholinesterasové inhibitory chemie   metabolismus   MeSH
• hydrofobní a hydrofilní interakce MeSH
• katalytická doména MeSH
• lidé MeSH
• molekulární modely * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• acetylcholinesterasa MeSH
• aflatoxin B1 MeSH
• cholinesterasové inhibitory MeSH