Neuropharmacology: Oxime antidotes for organophosphate pesticide and nerve agent poisoning

Organophosphate (OP) toxic compounds remain a great threat for humans because they are used as pesticides or misused as chemical warfare nerve agents. Their mechanism of toxicity involves the irreversible inhibition of the acetylcholinesterase (AChE) enzyme important in the control of cholinergic neurotransmission at the periphery and in the brain. An available pharmacological treatment are reactivators of OP-inhibited AChE that are not equally effective for every possible OP and they cross the blood-brain barrier (BBB) poorly. Novel oximes are being designed and synthesized at a high rate and scale and their pharmacological efficiency is being addressed mostly with the in vitro reactivation assay. Nevertheless, none of the newly synthesized oximes have shown better pharmacological properties than the ones developed more than 65 years ago since their potential to act as efficient antidotes in vivo depends on their pharmacokinetic and neuropharmacokinetics profiles. This paper provides an overview of all the important aspects that should be accounted for in the search for a centrally active oxime. Furthermore, it lists the most important BBB oxime delivery strategies employed until now, and the available pharmacokinetic data on old and new oximes. It should, therefore, serve as a guideline for the future development and evaluation of novel antidotes for OP poisoning.</p

Učinci imidazolijevih i kloriranih bispiridinijevih oksima povezani s njihovom toksičnosti na stanicama SH-SY5Y

Current research has shown that several imidazolium and chlorinated bispyridinium oximes are cytotoxic and activate different mechanisms or types of cell death. To investigate this further, we analysed interactions between these oximes and acetylcholine receptors (AChRs) and how they affect several signalling pathways to find a relation between the observed toxicities and their effects on these specific targets. Chlorinated bispyridinium oximes caused time-dependent cytotoxicity by inhibiting the phosphorylation of STAT3 and AMPK without decreasing ATP and activated ERK1/2 and p38 MAPK signal cascades. Imidazolium oximes induced a time-independent and significant decrease in ATP and inhibition of the ERK1/2 signalling pathway along with phosphorylation of p38 MAPK, AMPK, and ACC. These pathways are usually triggered by a change in cellular energy status or by external signals, which suggests that oximes interact with some membrane receptors. Interestingly, in silico analysis also indicated that the highest probability of interaction for all of our oximes is with the family of G-coupled membrane receptors (GPCR). Furthermore, our experimental results showed that the tested oximes acted as acetylcholine antagonists for membrane AChRs. Even though oxime interactions with membrane receptors need further research and clarification, our findings suggest that these oximes make promising candidates for the development of specific therapies not only in the field of cholinesterase research but in other fields too, such as anticancer therapy via altering the Ca2+ flux involved in cancer progression.Praćenjem učinka odabranih imidazolijevih i kloriranih bispiridinijevih oksima utvrđeno je da uzrokuju citotoksičnost i aktiviraju različite mehanizme ili tipove stanične smrti. Kako bismo to detaljnije istražili, analizirali smo aktivaciju nekoliko signalnih putova, kao i interakcije acetilkolinskih receptora (AChR) s navedenim oksimima te procijenili može li se opaženi toksični učinak objasniti njihovim utjecajem na ove specifične mete. Rezultati su pokazali da su klorirani bispiridinijevi oksimi prouzročili vremenski-ovisnu citotoksičnost, bez smanjenja razine ATP-a uz aktivaciju ERK1/2 i p38 MAPK-vezanih signalnih kaskada i inhibiciju fosforilacije STAT3 i AMPK proteina. Imidazolijevi oksimi djelovali su vremenski neovisno, uz značajno smanjenje razine ATP-a i inhibiciju ERK1/2 signalnog puta te fosforilaciju p38 MAPK, AMPK i ACC proteina. Navedeni signalni putovi obično se aktiviraju ili promjenom unutarnjega staničnog statusa, osobito energetskoga, ili vanjskim signalima, što upućuje na moguće interakcije oksima s nekim membranskim receptorima. Zanimljivo, in silico analizom procijenjeno je da je najvjerojatnija interakcija testiranih oksima s porodicom G-protein-spregnutih membranskih receptora (GPCR). K tomu, eksperimentalno je potvrđeno da testirani oksimi djeluju kao mogući antagonisti acetilkolina za vezanje na membranske AChR, potvrđujući tako i računalnu in silico procjenu. Iako interakcije ispitanih oksima s membranskim receptorima treba dodatno potvrditi, takve bi ih interakcije učinile kandidatima za razvoj specifičnih terapija u drugim područjima istraživanja, osim u istraživanjima povezanima s kolinesterazama, npr. kao moguće protutumorske lijekove, putem utjecaja na fluks iona Ca2+ uključenoga u progresiju tumora

New approach to the analysis of oximes designed to protect central nervous system in organophosphorus poisoning

Toksični organofosforni spojevi inhibiraju acetilkolinesterazu (AChE; EC 3.1.1.7) u sinapsama perifernog i središnjeg živčanog sustava (SŽS) te uzrokuju smrt ili dugotrajne neurološke poremećaje. Današnja terapija jesu oksimski reaktivatori inhibirane AChE, ali oni ne postižu dovoljne koncentracije u SŽS-u. Učinkovitost novosintetiziranih hidroksipiridinskih i klorpiridinijevih oksima dizajniranih s ciljem prolaska u SŽS ispitana je detaljnim kinetičkim istraživanjima reaktivacije AChE i butirilkolinestereraze (EC 3.1.1.8) inhibirane sarinom, ciklosarinom, VX-om, tabunom i paraoksonom. Analize njihovih fizikalno-kemijskih svojstava bitnih za prolazak u SŽS, in vitro toksičnosti, metaboličke stabilnosti i farmakokinetičkog profila na modelu miša, poslužile su za racionalan odabir vodećeg oksima za daljnja istraživanja, oksima 2-[(hidroksiimino)metil]-6-[4-(morfolin-4-il)butil]piridin-3-ola, koji ima potencijal reaktivirati AChE u perifernim tkivima i mozgu. Ovaj pristup analizi omogućio je bolji probir vodećih reaktivatora od uobičajene analize bazirane na reaktivacijskoj učinkovitosti oksima. Stoga se preporuča da ovakva evaluacija reaktivatora prethodi in vivo antidotskim testiranjima u smislu uvažavanja općeprihvaćenih pravila za zaštitu životinja.Toxic organophosphorus compounds inhibit acetylcholinesterase (AChE; EC 3.1.1.7) in the synapses of the peripheral and central nervous system (CNS) and cause death or long-term neurological impairments. Therapy includes oxime reactivators of the inhibited AChE, but they do not achieve sufficient concentrations in the CNS. The efficiency of newly-synthesized hydroxyl-pyridine and chloro-pyridinium oximes, designed with an aim to cross into the CNS, was evaluated here with a detailed kinetic investigation of the reactivation of AChE and butyrylcholinesterase (EC 3.1.1.8) inhibited by sarin, cyclosarin, VX, tabun and paraoxon. Analyses of physicochemical properties important for crossing into the CNS, in vitro toxicity, metabolic stability and pharmacokinetic profile in mouse model, were used for the rational determination of the lead oxime for further tests, 2-((hydroxyimino)methyl)-6-(4-(morpholin-4-yl)butyl)pyridin-3-ol oxime, that has potency to reactivate AChE in peripheral tissues and the brain. This approach enabled better screening for lead compounds in comparison to the standard analysis based on the reactivation efficiency of the oximes. Therefore, this kind of reactivatior evaluation is recommended before in vivo antidotal testing, as it would singificantly improve adherence to rules for animal welfare

New approach to the analysis of oximes designed to protect central nervous system in organophosphorus poisoning

Toksični organofosforni spojevi inhibiraju acetilkolinesterazu (AChE; EC 3.1.1.7) u sinapsama perifernog i središnjeg živčanog sustava (SŽS) te uzrokuju smrt ili dugotrajne neurološke poremećaje. Današnja terapija jesu oksimski reaktivatori inhibirane AChE, ali oni ne postižu dovoljne koncentracije u SŽS-u. Učinkovitost novosintetiziranih hidroksipiridinskih i klorpiridinijevih oksima dizajniranih s ciljem prolaska u SŽS ispitana je detaljnim kinetičkim istraživanjima reaktivacije AChE i butirilkolinestereraze (EC 3.1.1.8) inhibirane sarinom, ciklosarinom, VX-om, tabunom i paraoksonom. Analize njihovih fizikalno-kemijskih svojstava bitnih za prolazak u SŽS, in vitro toksičnosti, metaboličke stabilnosti i farmakokinetičkog profila na modelu miša, poslužile su za racionalan odabir vodećeg oksima za daljnja istraživanja, oksima 2-[(hidroksiimino)metil]-6-[4-(morfolin-4-il)butil]piridin-3-ola, koji ima potencijal reaktivirati AChE u perifernim tkivima i mozgu. Ovaj pristup analizi omogućio je bolji probir vodećih reaktivatora od uobičajene analize bazirane na reaktivacijskoj učinkovitosti oksima. Stoga se preporuča da ovakva evaluacija reaktivatora prethodi in vivo antidotskim testiranjima u smislu uvažavanja općeprihvaćenih pravila za zaštitu životinja.Toxic organophosphorus compounds inhibit acetylcholinesterase (AChE; EC 3.1.1.7) in the synapses of the peripheral and central nervous system (CNS) and cause death or long-term neurological impairments. Therapy includes oxime reactivators of the inhibited AChE, but they do not achieve sufficient concentrations in the CNS. The efficiency of newly-synthesized hydroxyl-pyridine and chloro-pyridinium oximes, designed with an aim to cross into the CNS, was evaluated here with a detailed kinetic investigation of the reactivation of AChE and butyrylcholinesterase (EC 3.1.1.8) inhibited by sarin, cyclosarin, VX, tabun and paraoxon. Analyses of physicochemical properties important for crossing into the CNS, in vitro toxicity, metabolic stability and pharmacokinetic profile in mouse model, were used for the rational determination of the lead oxime for further tests, 2-((hydroxyimino)methyl)-6-(4-(morpholin-4-yl)butyl)pyridin-3-ol oxime, that has potency to reactivate AChE in peripheral tissues and the brain. This approach enabled better screening for lead compounds in comparison to the standard analysis based on the reactivation efficiency of the oximes. Therefore, this kind of reactivatior evaluation is recommended before in vivo antidotal testing, as it would singificantly improve adherence to rules for animal welfare

New approach to the analysis of oximes designed to protect central nervous system in organophosphorus poisoning

Toksični organofosforni spojevi inhibiraju acetilkolinesterazu (AChE; EC 3.1.1.7) u sinapsama perifernog i središnjeg živčanog sustava (SŽS) te uzrokuju smrt ili dugotrajne neurološke poremećaje. Današnja terapija jesu oksimski reaktivatori inhibirane AChE, ali oni ne postižu dovoljne koncentracije u SŽS-u. Učinkovitost novosintetiziranih hidroksipiridinskih i klorpiridinijevih oksima dizajniranih s ciljem prolaska u SŽS ispitana je detaljnim kinetičkim istraživanjima reaktivacije AChE i butirilkolinestereraze (EC 3.1.1.8) inhibirane sarinom, ciklosarinom, VX-om, tabunom i paraoksonom. Analize njihovih fizikalno-kemijskih svojstava bitnih za prolazak u SŽS, in vitro toksičnosti, metaboličke stabilnosti i farmakokinetičkog profila na modelu miša, poslužile su za racionalan odabir vodećeg oksima za daljnja istraživanja, oksima 2-[(hidroksiimino)metil]-6-[4-(morfolin-4-il)butil]piridin-3-ola, koji ima potencijal reaktivirati AChE u perifernim tkivima i mozgu. Ovaj pristup analizi omogućio je bolji probir vodećih reaktivatora od uobičajene analize bazirane na reaktivacijskoj učinkovitosti oksima. Stoga se preporuča da ovakva evaluacija reaktivatora prethodi in vivo antidotskim testiranjima u smislu uvažavanja općeprihvaćenih pravila za zaštitu životinja.Toxic organophosphorus compounds inhibit acetylcholinesterase (AChE; EC 3.1.1.7) in the synapses of the peripheral and central nervous system (CNS) and cause death or long-term neurological impairments. Therapy includes oxime reactivators of the inhibited AChE, but they do not achieve sufficient concentrations in the CNS. The efficiency of newly-synthesized hydroxyl-pyridine and chloro-pyridinium oximes, designed with an aim to cross into the CNS, was evaluated here with a detailed kinetic investigation of the reactivation of AChE and butyrylcholinesterase (EC 3.1.1.8) inhibited by sarin, cyclosarin, VX, tabun and paraoxon. Analyses of physicochemical properties important for crossing into the CNS, in vitro toxicity, metabolic stability and pharmacokinetic profile in mouse model, were used for the rational determination of the lead oxime for further tests, 2-((hydroxyimino)methyl)-6-(4-(morpholin-4-yl)butyl)pyridin-3-ol oxime, that has potency to reactivate AChE in peripheral tissues and the brain. This approach enabled better screening for lead compounds in comparison to the standard analysis based on the reactivation efficiency of the oximes. Therefore, this kind of reactivatior evaluation is recommended before in vivo antidotal testing, as it would singificantly improve adherence to rules for animal welfare

New Cinchona Oximes Evaluated as Reactivators of Acetylcholinesterase and Butyrylcholinesterase Inhibited by Organophosphorus Compounds

For the last six decades, researchers have been focused on finding efficient reactivators of organophosphorus compound (OP)-inhibited acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). In this study, we have focused our research on a new oxime scaffold based on the Cinchona structure since it was proven to fit the cholinesterases active site and reversibly inhibit their activity. Three Cinchona oximes (C1, C2, and C3), derivatives of the 9-oxocinchonidine, were synthesized and investigated in reactivation of various OP-inhibited AChE and BChE. As the results showed, the tested oximes were more efficient in the reactivation of BChE and they reactivated enzyme activity to up to 70% with reactivation rates similar to known pyridinium oximes used as antidotes in medical practice today. Furthermore, the oximes showed selectivity towards binding to the BChE active site and the determined enzyme-oxime dissociation constants supported work on the future development of inhibitors in other targeted studies (e.g., in treatment of neurodegenerative disease). Also, we monitored the cytotoxic effect of Cinchona oximes on two cell lines Hep G2 and SH-SY5Y to determine the possible limits for in vivo application. The cytotoxicity results support future studies of these compounds as long as their biological activity is targeted in the lower micromolar range

Stoichiometry of the Heteromeric Nicotinic Receptors of the Renshaw Cell

International audienceHeteromeric nicotinic receptors assemble alpha and beta subunits in pentameric structures, which can adopt two stoichiometries: 3:2or 2alpha:3beta. Both stoichiometric variants are present in the CNS, but they have never been located and characterized functionally atthe level of an identified synapse. Our data indicate that 3alpha:2beta receptors are present at the spinal cord synapses between motoneuronsand Renshaw cells, where their dual mode of activation (by high concentrations of ACh for synaptic receptors, by lowconcentrations of ACh for extrasynaptic receptors) likely accounts for the biphasic character of the synaptic current. Moregenerally, 3alpha:2beta nicotinic receptors appear unique by their capacity to operate both in the cleft of classical synapses and atextrasynaptic locations

Sex-specific declines in cholinergic-targeting tRNA fragments in the nucleus accumbens in Alzheimer\u27s disease

INTRODUCTION: Females with Alzheimer\u27s disease (AD) suffer accelerated dementia and loss of cholinergic neurons compared to males, but the underlying mechanisms are unknown. Seeking causal contributors to both these phenomena, we pursued changes in transfer RNS (tRNA) fragments (tRFs) targeting cholinergic transcripts (CholinotRFs). METHODS: We analyzed small RNA-sequencing (RNA-Seq) data from the nucleus accumbens (NAc) brain region which is enriched in cholinergic neurons, compared to hypothalamic or cortical tissues from AD brains; and explored small RNA expression in neuronal cell lines undergoing cholinergic differentiation. RESULTS: NAc CholinotRFs of mitochondrial genome origin showed reduced levels that correlated with elevations in their predicted cholinergic-associated mRNA targets. Single-cell RNA seq from AD temporal cortices showed altered sex-specific levels of cholinergic transcripts in diverse cell types; inversely, human-originated neuroblastoma cells under cholinergic differentiation presented sex-specific CholinotRF elevations. DISCUSSION: Our findings support CholinotRFs contributions to cholinergic regulation, predicting their involvement in AD sex-specific cholinergic loss and dementia

New Uncharged reactivators for cholinesterases inhibited by organophosphorus nerve agents

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