Six novel brominated bis-pyridinium oximes were designed and synthesized to increase their nucleophilicity and reactivation ability of phosphorylated acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Their pKa was valuably found lower to parent non-halogenated oximes. Stability tests showed that novel brominated oximes were stable in water, but the stability of di-brominated oximes was decreased in buffer solution and their degradation products were prepared and characterized. The reactivation screening of brominated oximes was tested on AChE and BChE inhibited by organophosphorus surrogates. Two mono-brominated oximes reactivated AChE comparably to non-halogenated analogues, which was further confirmed by reactivation kinetics. The acute toxicity of two selected brominated oximes was similar to commercially available oxime reactivators and the most promising brominated oxime was tested in vivo on sarin- and VX-poisoned rats. This brominated oxime showed interesting CNS distribution and significant reactivation effectiveness in blood. The same oxime resulted with the best protective index for VX-poisoned rats.

• Keywords
• Cholinesterase, Nerve agent, Nucleophile, Organophosphate, Oxime, Reactivation,
• MeSH
• Acetylcholinesterase * metabolism   drug effects   MeSH
• Butyrylcholinesterase * metabolism   MeSH
• Chemical Warfare Agents toxicity   MeSH
• Cholinesterase Inhibitors * toxicity   pharmacology   MeSH
• Halogenation MeSH
• Rats MeSH
• Nerve Agents * toxicity   MeSH
• Organothiophosphorus Compounds * toxicity   MeSH
• Oximes * pharmacology   chemistry   MeSH
• Rats, Wistar MeSH
• Pyridinium Compounds pharmacology   MeSH
• Cholinesterase Reactivators * pharmacology   chemistry   MeSH
• Sarin * toxicity   MeSH
• Drug Stability MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Acetylcholinesterase * MeSH
• Butyrylcholinesterase * MeSH
• Chemical Warfare Agents MeSH
• Cholinesterase Inhibitors * MeSH
• Nerve Agents * MeSH
• Organothiophosphorus Compounds * MeSH
• Oximes * MeSH
• Pyridinium Compounds MeSH
• Cholinesterase Reactivators * MeSH
• Sarin * MeSH
• VX MeSH Browser

Oxime reactivators of acetylcholinesterase are commonly used to treat highly toxic organophosphate poisoning. They are effective nucleophiles that can restore the catalytic activity of acetylcholinesterase; however, their main limitation is the difficulty in crossing the blood-brain barrier (BBB) because of their strongly hydrophilic nature. Various approaches to overcome this limitation and enhance the bioavailability of oxime reactivators in the CNS have been evaluated; these include structural modifications, conjugation with molecules that have transporters in the BBB, bypassing the BBB through intranasal delivery, and inhibition of BBB efflux transporters. A promising approach is the use of nanoparticles (NPs) as the delivery systems. Studies using mesoporous silica nanomaterials, poly (L-lysine)-graft-poly(ethylene oxide) NPs, metallic organic frameworks, poly(lactic-co-glycolic acid) NPs, human serum albumin NPs, liposomes, solid lipid NPs, and cucurbiturils, have shown promising results. Some NPs are considered as nanoreactors for organophosphate detoxification; these combine bioscavengers with encapsulated oximes. This study provides an overview and critical discussion of the strategies used to enhance the bioavailability of oxime reactivators in the central nervous system.

• Keywords
• Acetylcholinesterase, Blood–brain barrier, Delivery system, Nanoparticle, Oxime, Reactivator,
• MeSH
• Acetylcholinesterase * MeSH
• Biological Availability MeSH
• Biological Transport MeSH
• Central Nervous System * MeSH
• Blood-Brain Barrier MeSH
• Humans MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Acetylcholinesterase * MeSH

The blood-brain barrier plays a vital role in the protection of the central nervous system. It is composed of endothelial cells with tight-junctions to limit the penetration of many endogenous and exogenous compounds, particularly hydrophilic xenobiotics. Nerve agents and pesticides are groups of compounds with high penetration potential into the central nervous system. However, oxime type antidotes are known to penetrate blood-brain barrier only in low concentration. The aim of presented study is to describe the pharmacokinetic profile of oxime K027 a novel antidote candidate. The main focus is on penetration of tested substance into the selected brain regions following time-dependent manner. The maximum concentration of the oxime K027 was attaining 15 and 30 min after i.m. application in plasma and brain tissue, respectively. The perfused brain tissue concentration was relatively high (10(-7) M order of magnitude) and depending on the brain region it was constant 15-60 min after application. The highest concentration was found in the frontal cortex 15 min after application while the lowest measured concentration was determined in the basal ganglia. This study showed that oxime K027 is able to achieve high concentration level in perfused brain tissue relatively quickly, but also demonstrated rapid clearance from the central nervous system. These results are probably due to low overall uptake of oxime K027 into the brain.

• MeSH
• Time Factors MeSH
• Central Nervous System drug effects   metabolism   MeSH
• Blood-Brain Barrier drug effects   metabolism   MeSH
• Rats MeSH
• Brain drug effects   metabolism   MeSH
• Oximes metabolism   pharmacokinetics   MeSH
• Rats, Wistar MeSH
• Pyridinium Compounds metabolism   pharmacokinetics   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• 1-(4-hydroxyiminomethylpyridinium)-3-(carbamoylpyridinium) propane dibromide MeSH Browser
• Oximes MeSH
• Pyridinium Compounds MeSH