Ashani Y, Leader H, Rothschild N, Dosoretz C
Israel Institute for Biological Research, Ness-Ziona, Israel.
Biochem Pharmacol. 1998 Jan 15;55(2):159-68. doi: 10.1016/s0006-2952(97)00430-9.
Reactivation of inhibited acetylcholinesterase (AChE) is essential for rapid recovery after organophosphate (OP) poisoning. However, following administration of an oxime reactivator, such as pralidoxime mesylate (P2S), in patients poisoned with certain diethylphosphorothioate pesticides, no reactivation is observed, presumably due to reinhibition by circulating anti-cholinesterase OPs. Pretreatment alone with organophosphorus hydrolases (OPH) that are capable of rapidly hydrolyzing OPs was demonstrated, in animals, to confer significant protection against OP toxicity. One strategy to augment the potentially therapeutic scope of OPHs is a combined post-exposure treatment consisting of a drug(s) commonly used against OP toxicity and a suitable hydrolase. In this study, we examined the in vitro ability of OPH from Pseudomonas sp. (OPHps) to prevent reinhibition of P2S-reactivated AChE by excess OPs. The kinetic parameters of the reactivation of a series of diethylphosphoryl-AChE (DEP--AChE) conjugates, obtained by the use of various diethylphosphates, were determined and compared with the rates of reactivation in the presence of OPHps, with and without the OP inhibitors in the reactivation medium. Extrapolation of the in vitro results to in vivo conditions suggests that an OPHps concentration as low as 1 microgram/mL blood would result in a 100-fold decrease in the concentration of circulating anti-AChE pesticides within less than one blood-circulation time, thereby minimizing reinhibition of the reactivated enzyme. Thus, for DEP-based pesticides, the combination of P2S-OPH treatment can significantly improve clinical recovery after OP intoxication. In addition, it is shown here for the first time that an OPH can effectively hydrolyze quaternary ammonium-containing OPs. This indicates that hydrolysis of phosphorylated oximes, toxic side products of oxime treatment, may also be accelerated by OPHs.
抑制性乙酰胆碱酯酶（AChE）的重新激活对于有机磷（OP）中毒后的快速恢复至关重要。然而，在使用肟类复活剂（如甲磺磷定，P2S）治疗某些二乙硫代磷酸酯类农药中毒患者时，未观察到重新激活现象，推测这是由于循环中的抗胆碱酯酶有机磷导致的再抑制作用。在动物实验中，已证明单独使用能够快速水解有机磷的有机磷水解酶（OPH）进行预处理，可对有机磷毒性提供显著保护。扩大有机磷水解酶潜在治疗范围的一种策略是采用联合暴露后治疗，即使用一种或多种常用于对抗有机磷毒性的药物与一种合适的水解酶。在本研究中，我们检测了来自假单胞菌属的有机磷水解酶（OPHps）在体外防止过量有机磷对P2S重新激活的AChE产生再抑制作用的能力。通过使用各种二乙磷酸酯获得了一系列二乙磷酰基 - AChE（DEP - AChE）缀合物的重新激活动力学参数，并将其与在有和没有OPHps存在的情况下、且重新激活介质中有无OP抑制剂时的重新激活速率进行了比较。将体外实验结果外推至体内情况表明，血液中低至1微克/毫升的OPHps浓度可在不到一个血液循环时间内使循环中的抗AChE农药浓度降低100倍，从而将对重新激活酶的再抑制作用降至最低。因此，对于基于DEP的农药，P2S - OPH联合治疗可显著改善有机磷中毒后的临床恢复情况。此外，本文首次表明一种OPH能够有效水解含季铵的有机磷。这表明OPH也可能加速肟治疗的有毒副产物——磷酸化肟的水解。
