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Cell response to N-alkyl quaternary quinuclidine oxime treatment

Quinuclidine derivatives are recognized as compounds with diverse biological and pharmacological activities. Their oxime analogues have been evaluated as antidotes for organophosphorus compounds (OPCs) poisoning. Although globally used as pesticides or misused as chemical weapons, there is still no efficient treatment for OPCs. According to our previous studies, it is advisable to perform cell-based assays for antidote candidates prior to other studies of their efficiency, especially in vivo, since many of them are excluded from advanced testing due to possible adverse effects. With that in mind, in a present study, we tested seven newly synthesized 3-hydroxyimino quinuclidinium bromides with different alkyl chain lengths (CnQNOH ; n = 8 – 16). Human hepatocyte (HepG2) cell line was used to determine their influence on cell viability and homeostasis, membrane integrity and oxidative status. We used standard methods for evaluating specific targets: activity of mitochondrial succinate dehydrogenase by the tetrazolium salt MTS, lactate dehydrogenase (LDH) leakage by fluorescent resazurin, mitochondrial membrane potential assay through TMRM signal and induction of reactive oxygen species (ROS) by fluorescent dye DCFDA, respectively. Our results showed that quinuclidinium oximes with a long side alkyl chain (C12, C14 and C16) were the most toxic to cells with IC50 values in micromolar range. Furthermore, compound with C12 alkyl chain displayed a notable time-dependent toxicity. More detailed analysis revealed that all three cytotoxic compounds triggered significant LDH release and decrease in membrane mitochondrial potential, indicating a necrotic-like impact. In concentrations corresponding to IC50 values, tested oximes also significantly induced ROS generation. Such results indicate that these oximes induced negative effects and could not be considered for further evaluation as antidotes. However, their observed influence on cells opens up a new perspective to investigate them as drugs for specific conditions and diseases.

antidotes, quinuclidine oximes, cytotoxicity, necrosis, ROS

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