The 40th Anniversary of the HDBMB

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Neuropharmacology: Oxime antidotes for organophosphate pesticide and nerve agent poisoning

Organophosphate (OP) toxic compounds remain a great threat for humans because they are used as pesticides or misused as chemical warfare nerve agents. Their mechanism of toxicity involves the irreversible inhibition of the acetylcholinesterase (AChE) enzyme important in the control of cholinergic neurotransmission at the periphery and in the brain. An available pharmacological treatment are reactivators of OP-inhibited AChE that are not equally effective for every possible OP and they cross the blood-brain barrier (BBB) poorly. Novel oximes are being designed and synthesized at a high rate and scale and their pharmacological efficiency is being addressed mostly with the in vitro reactivation assay. Nevertheless, none of the newly synthesized oximes have shown better pharmacological properties than the ones developed more than 65 years ago since their potential to act as efficient antidotes in vivo depends on their pharmacokinetic and neuropharmacokinetics profiles. This paper provides an overview of all the important aspects that should be accounted for in the search for a centrally active oxime. Furthermore, it lists the most important BBB oxime delivery strategies employed until now, and the available pharmacokinetic data on old and new oximes. It should, therefore, serve as a guideline for the future development and evaluation of novel antidotes for OP poisoning.</p

Advancements in recombinant technology for production of butyrylcholinesterase, a bioscavenger of nerve agents

Butyrylcholinesterase (BChE) is a serine hydrolase present in plasma and other mammalian tissues. As a target of organophosphorous pesticides and warfare nerve agents, BChE acts as their stoichiometric bioscavenger. However, so far it has been a significant challenge to produce BChE at large scales and low cost. For decades, numerous research efforts have been directed first at isolation from human volunteers and later at production of BChE in eukaryotic and prokaryotic expression systems. In this review we focused on recent studies on recombinant BChE discussing reasons why the efficient, economically sensible expression system for recombinant butyrylcholinesterase is hard to develop. We also bring the most recent advancements in the use of expression of human BChE in vivo as an effective prophylactic against organophosphate poisoning.</p

Poboljšanje razlučivanja fenotipova butirilkolinesteraze s fluorid-rezistentnom inačicom

Correct recognition of butyrylcholinesterase (BChE; EC 3.1.1.8) variants in human serum is essential if patients susceptible to a prolonged reaction following treatment with short acting muscle relaxants, like suxamethonium, are to be reliably identified. The dimethylcarbamate Ro 02-0683 is used in standard procedures for identification of BChE variant by measuring residual activity after two hours of inhibition. Such a long inhibition time distinguishes well between the usual (U) and atypical (A), but less successfully the fluoride-resistant (F) variant. In this paper, inhibition rate constants were determined from the initial time course of inhibition of homozygous (FF) and heterozygous (UF and AF) BChE phenotypes by Ro 02-0683; 1.6x106, 2.7x106 and 6.2x106 dm3 mol-1 min-1 for AF, FF and UF, respectively. After only 30 min of inhibition the resolution between the phenotypes was even better than after two hours. Hence, determination of the residual activity after 30 min inhibition is recommended for the segregation of the suxamethonium sensitive fluoride-resistant variants.Ispravno prepoznavanje inačica (varijanti) butirilkolinesteraze (BChE; EC 3.1.1.8) u ljudskom serumu nužno je kako bi se identificirali pacijenti osjetljivi na produljeno djelovanje kratkodjelujućih mišićnih relaksansa poput suksametonija (sukcinildikolina). Atipična (A) i fluorid-rezistentna (F) inačica normalne, obične (U) BChE veoma sporo razgrađuju suksametonij, pa njegova primjena kod pacijenta može izazvati produženu paralizu mišića. Da bi se odredile inačice BChE, odnosno fenotip, u serumu se određuje inhibicija aktivnosti BChE sa specifičnim inhibitorima. U standardnom postupku fenotipiziranja rabi se dvosatna inhibicija BChE dimetilnim karbamatom Ro 02-0683. Tako duga inhibicija omogućuje dobro razlikovanje normalne i atipične inačice BChE, ali ne i fluorid-rezistentne inačice. U ovom radu određene su konstante brzine inhibicije iz početnog dijela vremenskog toka inhibicije homozigota (FF) i heterozigota (UF i AF) BChE s Ro 02-0683: 1.6x106, 2.7x106 i 6.2x106 dm3 mol-1min-1 za AF, FF i UF. Prema vrijednosti ovih konstanti fenotipovi se mogu dobro razlikovati. Nakon samo 30 minuta inhibicije razlučivanje između ovih fenotipova bolje je nego nakon dva sata. Stoga je preporuka da se u rutinskom postupku određivanja fenotipova BChE vrijeme inhibicije skrati s dva sata na 30 minuta

Crossroads in Life Sciences

This is editorial, no abstract</p

Exploring the Active Sites of Cholinesterases by Inhibition with Bambuterol and Haloxon

The paper describes the inhibition of mouse acetylcholinesterase (AChE; EC 3.1.1.7) and mouse, human, and horse butyrylcholinesterase (BChE; EC 3.1.1.8) by 5-[2-(tert-butylamino)-1-hydroxyethyl]-m-phenylene-bis(dimethylcarbamate) hydrochloride (bambuterol) and by O,O-bis-(2-chloroethyl)-O-(3-chloro-4-methylcoumarin-7-yl) phosphate (haloxon). The haloxon inhibition rate constant (ki) for mouse BChE was 3.7 &times; 107 min–1 mol–1 dm3, which was 40-fold higher than the rate constant for mouse AChE. Bambuterol inhibition of horse BChE (ki = 2.1 &times; 105 min–1 mol–1 dm3) was about 25-fold slower than that of human or mouse BChE, whereas the respective haloxon inhibition of horse BChE (ki = 1.2 &times; 107 min–1 mol–1 dm3) was about 2-3-fold slower. Sequence alignments and the computational model of the three-dimensional structure of horse BChE suggest that residues inside the active site at positions 69, 277 and 285 are important for the differences in the inhibition of these three BChE species

Exploring the Active Sites of Cholinesterases by Inhibition with Bambuterol and Haloxon

The paper describes the inhibition of mouse acetylcholinesterase (AChE; EC 3.1.1.7) and mouse, human, and horse butyrylcholinesterase (BChE; EC 3.1.1.8) by 5-[2-(tert-butylamino)-1-hydroxyethyl]-m-phenylene-bis(dimethylcarbamate) hydrochloride (bambuterol) and by O,O-bis-(2-chloroethyl)-O-(3-chloro-4-methylcoumarin-7-yl) phosphate (haloxon). The haloxon inhibition rate constant (ki) for mouse BChE was 3.7 &times; 107 min–1 mol–1 dm3, which was 40-fold higher than the rate constant for mouse AChE. Bambuterol inhibition of horse BChE (ki = 2.1 &times; 105 min–1 mol–1 dm3) was about 25-fold slower than that of human or mouse BChE, whereas the respective haloxon inhibition of horse BChE (ki = 1.2 &times; 107 min–1 mol–1 dm3) was about 2-3-fold slower. Sequence alignments and the computational model of the three-dimensional structure of horse BChE suggest that residues inside the active site at positions 69, 277 and 285 are important for the differences in the inhibition of these three BChE species

Detoksikacija živčanih bojnih otrova

Phosphylation of the pivotal enzyme acetylcholinesterase (AChE) by nerve agents (NAs) leads to irreversible inhibition of the enzyme and 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. Prompt action is therefore critical to improve the chances of victim’s survival and recovery. Standard therapy of NA poisoning generally involves administration of anticholinergic atropine and an oxime reactivator of phosphylated AChE. Anticholinesterase compounds or NA bioscavengers can also be applied to preserve native AChE from inhibition. With this review of 70 years of research we aim to present current and potential approaches to counteracting NA poisoning.Fosfilacijom esencijalnog enzima acetilkolinesteraze (AChE) živčanim bojnim otrovom, enzim postaje ireverzibilno inhibiran, što dovodi do nakupljanja neurotransmitera acetilkolina i kolinergičke krize zbog prekomjerne stimulacije muskarinskih i nikotinskih membranskih receptora u središnjem i perifernom živčanom sustavu. U teškim slučajevima desenzibilizacija receptora rezultira hipoksijom, nesvjesticom i zastojem disanja, nakon čega slijedi smrt. Stoga je brzo djelovanje presudno za preživljavanje osobe izložene živčanom bojnom otrovu. Standardna terapija u slučaju otrovanja uključuje antikolinergik atropin i oksimski reaktivator fosfilirane AChE. Kako bi se očuvala aktivnost nativne AChE u slučaju izloženosti živčanom bojnom otrovu, istražuju se i drugačiji pristupi terapiji, kao što su spojevi koji kratkotrajno i reverzibilno inhibiraju AChE te egzogeni enzimi koji djeluju kao biološka čistila živčanih bojnih otrova. U ovom preglednom radu cilj nam je predstaviti trenutačne i potencijalne pristupe u terapiji i detoksikaciji živčanih bojnih otrova