In vivo experimental approach to treatment against tabun poisoning

Hrvat

Katalinić

et al. 2015

Chem. Res. Toxicol.

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Exposure to the nerve agent soman is difficult to treat due to the rapid dealkylation of soman-acetylcholinesterase (AChE) conjugate known as aging. Oxime antidotes commonly used to reactivate organophosphate inhibited AChE are ineffective against soman, while the efficacy of the recommended nerve agent bioscavenger butyrylcholinesterase is limited by strictly stoichiometric scavenging. To overcome this limitation, we tested ex vivo, in human blood, and in vivo, in soman exposed mice, the capacity of aging-resistant human AChE mutant Y337A/F338A in combination with oxime HI-6 to act as a catalytic bioscavenger of soman. HI-6 was previously shown in vitro to efficiently reactivate this mutant upon soman, as well as VX, cyclosarin, sarin and paraoxon inhibition. We here demonstrate that ex vivo, in whole human blood, 1 μM soman was detoxified within 30 minutes when supplemented with 0.5 μM Y337A/F338A AChE and 100 μM HI-6. This combination was further tested in vivo. Catalytic scavenging of soman in mice improved the therapeutic outcome and resulted in the delayed onset of toxicity symptoms. Furthermore, in a preliminary in vitro screen we identified an even more efficacious oxime than HI-6, in a series of forty-two pyridinium aldoximes, and five imidazole 2-aldoxime N-propyl pyridinium derivatives. One of the later imidazole aldoximes, RS-170B, was a 2–3 –fold more effective reactivator of Y337A/F338A AChE than HI-6 due to the smaller imidazole ring, as indicated by computational molecular models, that affords a more productive angle of nucleophilic attack.

Section: Methodsmentioning

confidence: 99%

Catalytic Soman Scavenging by the Y337A/F338A Acetylcholinesterase Mutant Assisted with Novel Site-Directed Aldoximes

Hrvat

Katalinić

et al. 2015

Chem. Res. Toxicol.

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“…with TAB2OH (10 or 25 mg/kg) together with atropine sulfate (10 mg/kg), one minute after subcutaneous (s.c.) OP exposure [19, 20]. Nerve agent stock solutions were prepared in isopropyl alcohol or in propylene glycol.…”

Section: Methodsmentioning

confidence: 99%

Catalytic detoxification of nerve agent and pesticide organophosphates by butyrylcholinesterase assisted with non-pyridinium oximes

Radić

Dale

et al. 2013

Biochemical Journal

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SYNOPSIS We present here a comprehensive in vitro, ex vivo and in vivo study on hydrolytic detoxification of nerve agent and pesticide organophosphates (OPs) catalyzed by purified human butyrylcholinesterase (hBChE) in combination with novel non-pyridinium oxime reactivators. We identified 2-trimethylammonio-6-hydroxybenzaldehyde oxime (TAB2OH) as an efficient reactivator of OP-hBChE conjugates formed by the nerve agents, VX and cyclosarin, and the pesticide, paraoxon. It was also functional in reactivation of sarin and tabun inhibited hBChE. A three to five-fold enhancement of in vitro reactivation of VX, cyclosarin and paraoxon inhibited hBChE was observed, when compared to the commonly used N-methylpyridinium aldoxime reactivator, 2PAM. Kinetic analysis showed the enhancement resulted from improved molecular recognition of corresponding OP-hBChE conjugates by TAB2OH. The unique features of TAB2OH stem from an exocyclic quaternary nitrogen and a hydroxyl, both ortho to an oxime group on a benzene ring. pH dependences reveal participation of the hydroxyl (pKa=7.6) forming an additional ionizing nucleophile to potentiate the oxime (pKa=10) at physiological pH. The TAB2OH protective indices in therapy of sarin and paraoxon exposed mice were enhanced by 30% – 60% when they were treated with a combination of TAB2OH and sub-stoichiometric hBChE. These results establish that oxime-assisted catalysis is feasible for OP bioscavenging.

“…(at the specified dose) together with atropine sulfate (10 mg/kg) 1 min after subcutaneous OP administration (24,25). Stock solutions of nerve agents were prepared in isopropyl alcohol or in propylene glycol.…”

Section: Methodsmentioning

confidence: 99%

Refinement of Structural Leads for Centrally Acting Oxime Reactivators of Phosphylated Cholinesterases

Radić

Sit

Journal of Biological Chemistry

et al. 2012

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106

140

Background: Contemporary oxime antidotes to organophosphate poisoning cannot penetrate CNS to reactivate inhibited acetylcholinesterase. Results: Structural, in vitro optimization of ionizable hydroxyiminoacetamido amine acetylcholinesterase reactivators produced superior antidotal responses for VX-, sarin-, paraoxon-, and tabun-exposed mice. Conclusion: Ionizable hydroxyiminoacetamido amines are promising centrally active acetylcholinesterase reactivators. Significance: A mechanism-based iterative refinement of acetylcholinesterase reactivation kinetics coupled with pharmacokinetic analyses yields efficient CNS penetrating antidotes.