engleski

Ex vivo experiments support Y337A/F338A human AChE as a potential pseudo-catalytic bioscavenger in the event of soman poisoning

Acetylcholinesterase (AChE) inhibition by organophosphorus compounds (OP) results in the accumulation of neurotransmitter acetylcholine (ACh) and causes several adverse effects, which can eventually even lead to death. All OP poisonings call for immediate therapeutic treatment, which usually consists of a combined administration of anticholinergic drugs and an oxime as the reactivator of AChE. However, AChE inhibited by nerve agent soman is less susceptible to reactivation due to the rapid dealkylation (˝ageing˝) of the soman-AChE conjugate. Earlier studies have shown that certain single- and double-site amino acid substitutions in the AChE active center could slow-down ageing and enable oximes to reactivate the soman-AChE conjugate prior to its ageing. Our earlier in vitro studies have uncovered a unique potential of the human AChE mutant, the hY337A/F338A, that combines the increase in the active center accessibility to oximes of the Y337A mutant with the ageing resistance of the F338A mutation. We have proposed that this AChE mutant could be administered to exposed individuals in the form of a pre-treatment to act as pseudo catalytic bioscavenger. Catalytic OP turnover should provide protection by degrading the OP before it reacts with the target AChE. In this study we evaluated in vitro reactivation capacities of several oximes for the soman-inhibited hY337A/F338A. Among the tested oximes, only ICD-585 [1-(3-(4-carbamoylpyridinium-1-yl)propyl)-2-((hydroxyimino)methyl)pyridinium chloride] showed a notable reactivation capability, albeit still smaller than the oxime HI-6, which is currently used in therapy. We furthermore performed an ex vivo study on whole human blood, the source of natural total cholinesterases, combining it with the mutant and either HI-6 or ICD-585 oxime in order to test the mutant’s bioscavenging potential. Indeed, 0.5 µM concentration of soman was decomposed within 25 minutes when human whole blood was supplemented with 500 nM hY337A/F338A and 1 mM HI-6. These ex vivo findings confirm our earlier in vitro data that hY337A/F338A possesses a true bioscavenging potential when combined with HI-6. The ICD-585 oxime was in turn proven to be promising reactivator of the soman-hY337A/F338A conjugate. Acknowledgments: We wish to thank Dr Irwin Koplovitz (USAMRICD, USA) for supplying us with ICD-585 oxime. Supported by the NIH (Grant No. U01 NS058046) and by the Croatian Ministry of Science, Education and Sports (Grant No.022-0222148-2889).

human AChE ; soman ; mutant Y337A/F338A ; aging ; pre-treatment ; catalytic bioscavenger

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