Interactions of butane, but-2-ene or xylene-like linked bispyridinium para-aldoximes with native and tabun-inhibited human cholinesterases.

Kinetic parameters were evaluated for inhibition of native and reactivation of tabun-inhibited human erythrocyte acetylcholinesterase (AChE, EC 3.1.1.

Oximes: Reactivators of phosphorylated acetylcholinesterase and antidotes in therapy against tabun poisoning.

One of the therapeutic approaches to organophosphate poisoning is to reactivate AChE with site-directed nucleophiles such as oximes. However, pyridinium oximes 2-PAM, HI-6, TMB-4 and obidoxime, found as the most effective reactivators, have limiting reactivating potency in tabun poisoning. We tested oximes varying in the type of ring (pyridinium and/or imidazolium), the length and type of the linker between rings, and in the position of the oxime group on the ring to find more effective oximes to reactivate tabun-inhibited human erythrocyte AChE.

Limitation of the Ellman method: cholinesterase activity measurement in the presence of oximes.

The Ellman method for assaying thiols is widely used for cholinesterase activity measurement. Cholinesterase activity is measured indirectly by quantifying the concentration of 5-thio-2-nitrobenzoic acid (TNB) ion formed in the reaction between the thiol reagent 5,5'-dithiobis-2-nitrobenzoic acid (DTNB) and thiocholine, a product of substrate (i.e.

Structure-activity approach in the reactivation of tabun-phosphorylated human acetylcholinesterase with bispyridinium para-aldoximes.

We investigated interactions of bispyridinium para-aldoximes N,N'-(propano)bis(4-hydroxyiminomethyl) pyridinium bromide (TMB-4), N,N'-(ethano)bis(4-hydroxyiminomethyl)pyridinium methanosulphonate (DMB-4), and N,N'-(methano)bis(4-hydroxyiminomethyl)pyridinium chloride (MMB-4) with human erythrocyte acetylcholinesterase phosphorylated by tabun. We analysed aldoxime conformations to determine the flexibility of aldoxime as an important feature for binding to the acetylcholinesterase active site. Tabun-inhibited human erythrocyte acetylcholinesterase was completely reactivated only by the most flexible bispyridinium aldoxime - TMB-4 with a propylene chain between two rings.

Interaction of pyridinium oximes with acetylcholinesterase and their effect on organophosphate-poisoned mice.

The progressive inhibition of acetylcholinesterase (AChE [EC 3.1.1.

Pretreatment with pyridinium oximes improves antidotal therapy against tabun poisoning.

Oximes K033 [1,4-bis(2-hydroxyiminomethylpyridinium) butane dibromide] and K048 [1-(4-hydroxyiminomethylpyridinium)-4-(4-carbamoylpyridinium) butane dibromide] were tested as pretreatment drugs in tabun-poisoned mice followed by treatment with atropine plus K033, K048, K027 [1-(4-hydroxyiminomethylpyridinium)-3-(4-carbamoylpyridinium) propane dibromide], TMB-4 [1,3-bis(4-hydroxyiminomethylpyridinium) propane dibromide] and HI-6 [(1-(2-hydroxyiminomethylpyridinium)-3-(4-carbamoylpyridinium)-2-oxapropane dichloride)]. Oxime doses of 25% or 5% of its LD(50) were used for pretreatment 15 min before tabun-poisoning and for treatment 1 min after tabun administration to mice. The best therapeutic effect was obtained when oxime K048 (25% of its LD(50)) was used in both pretreatment and treatment with atropine.

Evaluation of monoquaternary pyridinium oximes potency to reactivate tabun-inhibited human acetylcholinesterase.

Monoquaternary N-benzyl-4-hydroxyiminomethylpyridinium bromide (Py-4-H) and its analogous with diverse substituents introduced into the phenyl ring (Py-4-CH(3), Py-4-Br, Py-4-Cl and Py-4-NO(2)) were synthesized in order to examine their potency as reactivators of tabun-inhibited human erythrocyte acetylcholinesterase (AChE; EC 3.1.1.

para- and ortho-Pyridinium aldoximes in reaction with acetylthiocholine.

In the oximolysis reaction para-aldoximes K027 and TMB-4 react faster with ATCh than ortho-aldoximes HI-6 and K033. The reaction rate constants at 25 degrees C were 22 M(-1) min(-1) for HI-6 and K033, 230 M(-1) min(-1) for TMB-4 and 306 M(-1) min(-1) for K027. Semi-empirical calculations showed that differences in rates do not origin from different electron density on the oxygen of the oxime group, but can be explained by the steric hindrance of the oxime group within the molecule.

In vitro and in vivo evaluation of pyridinium oximes: mode of interaction with acetylcholinesterase, effect on tabun- and soman-poisoned mice and their cytotoxicity.

The increased concern about terrorist use of nerve agents prompted us to search for new more effective oximes against tabun and soman poisoning. We investigated the interactions of five bispyridinium oximes: K027 [1-(4-hydroxyiminomethylpyridinium)-3-(4-carbamoylpyridinium) propane dibromide], K048 [1-(4-hydroxyiminomethylpyridinium)-4-(4-carbamoylpyridinium) butane dibromide], K033 [1,4-bis(2-hydroxyiminomethylpyridinium) butane dibromide], TMB-4 [1,3-bis(4-hydroxyiminomethylpyridinium) propane dibromide] and HI-6 [(1-(2-hydroxyiminomethylpyridinium)-3-(4-carbamoylpyridinium)-2-oxapropane dichloride)] with human erythrocyte acetylcholinesterase (AChE; E.C.