Quistad Gary B, Casida John E
Environmental Chemistry and Toxicology Laboratory, Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720-3112, USA.
Toxicol Appl Pharmacol. 2004 May 1;196(3):319-26. doi: 10.1016/j.taap.2004.01.005.
Lysophospholipases (LysoPLAs) are a large family of enzymes for removing lysophospholipids from cell membranes. Potent inhibitors are needed to define the importance of LysoPLAs as targets for toxicants and potential therapeutics. This study considers organophosphorus (OP) inhibitors with emphasis on mouse brain total LysoPLA activity relative to the mipafox-sensitive neuropathy target esterase (NTE)-LysoPLA recently established as 17% of the total activity and important in the action of OP delayed toxicants. The most potent inhibitors of total LysoPLA in mouse brain are isopropyl dodecylphosphonofluoridate (also for LysoPLA of Vibrio bacteria), ethyl octylphosphonofluoridate (EOPF), and two alkyl-benzodioxaphosphorin 2-oxides (BDPOs)[(S)-octyl and dodecyl] (IC50 2-8 nM). OP inhibitors acting in vitro and in vivo differentiate a more sensitive portion but not a distinct NTE-LysoPLA compared with total LysoPLA activity. For 10 active inhibitors, NTE-LysoPLA is 17-fold more sensitive than total LysoPLA, but structure-activity comparisons give a good correlation (r(2) = 0.94) of IC50 values, suggesting active site structural similarity or identity. In mice 4 h after intraperitoneal treatment with discriminating doses, EOPF, tribufos (a plant defoliant), and dodecanesulfonyl fluoride inhibit 41-57% of the total brain LysoPLA and 85-99% of the NTE-LysoPLA activity. Total LysoPLA as well as NTE-LysoPLA is decreased in activity in Nte(+/-)-haploinsufficient mice compared to their Nte(+/+) littermates. The lysolecithin level of spinal cord but not brain is elevated significantly following EOPF treatment (3 mg/kg), thereby focusing attention on localized rather than general alterations in lysophospholipid metabolism in OP-induced hyperactivity and toxicity.
溶血磷脂酶（LysoPLAs）是一类能从细胞膜上去除溶血磷脂的酶大家族。需要强效抑制剂来确定溶血磷脂酶作为毒物靶点和潜在治疗靶点的重要性。本研究关注有机磷（OP）抑制剂，重点是小鼠脑总溶血磷脂酶活性与最近确定为总活性17%且在OP延迟毒物作用中起重要作用的米帕明敏感神经病变靶酯酶（NTE）-溶血磷脂酶的关系。小鼠脑中总溶血磷脂酶最有效的抑制剂是异丙基十二烷基磷酰氟（也用于抑制弧菌的溶血磷脂酶）、乙基辛基磷酰氟（EOPF）和两种烷基苯并二氧磷杂环己二烯2-氧化物（BDPOs）[（S）-辛基和十二烷基]（IC50为2-8 nM）。与总溶血磷脂酶活性相比，在体外和体内起作用的OP抑制剂能区分出更敏感的部分，但不是一种独特的NTE-溶血磷脂酶。对于10种活性抑制剂，NTE-溶血磷脂酶比总溶血磷脂酶敏感17倍，但结构-活性比较显示IC50值具有良好的相关性（r(2)=0.94），表明活性位点结构相似或相同。在用区分剂量腹腔注射处理小鼠4小时后，EOPF、三丁基锡（一种植物脱叶剂）和十二烷基磺酰氟抑制了41-57%的脑总溶血磷脂酶活性和85-99%的NTE-溶血磷脂酶活性。与它们的Nte(+/+)同窝小鼠相比，Nte(+/-)单倍体不足小鼠的总溶血磷脂酶以及NTE-溶血磷脂酶活性均降低。EOPF处理（3 mg/kg）后，脊髓而非脑的溶血卵磷脂水平显著升高，从而将注意力集中在OP诱导的多动和毒性中溶血磷脂局部而非整体的变化上。
