Analyses of interactions between organophosphorus compounds and esterases and other targets for therapy in poisoning (OPEsterOX)

Croatian Science Foundation: Research project IP-2022-10-6885

Team members: Goran Šinko, Tena Čadež, Dora Kolić, Višnja Stepanić, Vesna Gabelica Marković, Zoran Radić

Duration: 48 months, 2023-2027

Abstract

Exposure to organophosphates (OP) from both pesticides and nerve agents leads to the covalent inhibition of the pivotal enzyme acetylcholinesterase (AChE) that leads to accumulation of neurotransmitter acetylcholine, which induces cholinergic crisis, that is, overstimulation of muscarinic and nicotinic membrane receptors in the central and peripheral nervous system. In severe cases, subsequent desensitisation of the receptors results in hypoxia, vasodepression, and respiratory arrest, followed by death. Standard therapy of OP poisoning that generally involves administration of anticholinergic atropine and an oxime reactivator of phosphylated AChE has limitations especially in the case of phosphoroamidates due to the structural-related mechanism of reactivation. An alternative therapy is the related enzyme butyrylcholinesterase (BChE) which binds OP compounds and as such acts as stoichiometric bioscavenger of OP. Therefore, this project utilizes known (e.g. tabun, methamidophos and fenamiphos), and new compounds (A-agents) to gain a better understanding of the mechanistic basis of cholinesterase family interactions and their limitations to find new effective leads for treatment. The biochemical mechanism of enzyme interactions will be comprehensively studied on a molecular level with in silico, in vitro, and ex vivo methods to define binding affinities, kinetic constants of inhibition and efficiency of reactivation of both enzymes. The possible mechanisms of toxicity of selected OPs will be studied at cell-culture level, and on mice exposed to OP. The neuroinflammatory effect of OP as w ell as the neuroprotective effectiveness of oxime therapy will be examined on the mouse brain by monitoring specific markers of astrogliosis, microgliosis and neuron viability. These comprehensive analyses will undoubtedly contribute to the knowledge of phosphoroamidate interactions and improved therapeutics in OP poisoning.

Publications

1. Kolić, Dora ; Kovarik, Zrinka. NMDA receptors: structure, function and role in organophosphorus compound poisoning // Biofactors, in press (2024), doi: 10.1002/biof.2048