Shacter E, Lopez R L, Pati S
Laboratory of Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Biochem Pharmacol. 1991;41(6-7):975-84. doi: 10.1016/0006-2952(91)90204-i.
The results presented herein demonstrate that the non-steroidal anti-inflammatory drug (NSAID) indomethacin is a strong inhibitor of the formation of HOCl by murine neutrophils (50% inhibition at 15 microM). Addition of 40 microM indomethacin to activated neutrophils caused 80% inhibition of HOCl formation throughout a 60-min time course while slightly increasing the levels of O2- and H2O2 produced. Comparable degrees of inhibition were achieved when the cells were stimulated with phorbol myristate acetate and with opsonized zymosan. Control experiments indicated that the drug did not act by scavenging HOCl. Direct inhibition of the chlorinating activity of myeloperoxidase (MPO) was confirmed using highly purified human enzyme in vitro. Kinetic analysis of the mechanism of inhibition showed that the drug was competitive with respect to Cl- and uncompetitive with respect to H2O2, showing a Ki of 37 microM. In contrast to its inhibition of the oxidation of Cl- by MPO, indomethacin had no effect on the peroxidative activity of the enzyme (oxidation of 4-aminoantipyrene), nor did it inhibit the activity of several other enzymes involved in H2O2 metabolism, including horseradish peroxidase, catalase, xanthine oxidase, and superoxide dismutase. Finally, it was found that inhibition of HOCl formation was a shared but non-uniform property of many NSAIDs; piroxicam, salicylate, sulindac, ibuprofen, and aspirin were all inhibitory but at widely different concentrations [Ki(app) values of 0.05, 0.18, 0.18, greater than 1, and 3 mM respectively] that correlated only partially with their therapeutic dose range. The results encourage further studies into the possibility that inhibition of HOCl formation may constitute an additional mechanism whereby NSAIDs reduce tissue destruction in chronically inflamed tissues.
本文呈现的结果表明，非甾体抗炎药（NSAID）吲哚美辛是小鼠中性粒细胞形成次氯酸（HOCl）的强效抑制剂（在15微摩尔时抑制率达50%）。向活化的中性粒细胞中添加40微摩尔吲哚美辛，在整个60分钟的时间进程中，次氯酸形成的抑制率达80%，同时略微增加了超氧阴离子（O2-）和过氧化氢（H2O2）的生成水平。当用佛波酯肉豆蔻酸酯和调理酵母聚糖刺激细胞时，也能达到相当程度的抑制。对照实验表明，该药物并非通过清除次氯酸起作用。使用高度纯化的人髓过氧化物酶（MPO）在体外证实了其对MPO氯化活性的直接抑制作用。抑制机制的动力学分析表明，该药物对氯离子（Cl-）具有竞争性，对过氧化氢（H2O2）具有非竞争性，其抑制常数（Ki）为37微摩尔。与它对MPO氧化Cl-的抑制作用相反，吲哚美辛对该酶的过氧化活性（4-氨基安替比林的氧化）没有影响，也不抑制参与H2O2代谢的其他几种酶的活性，包括辣根过氧化物酶、过氧化氢酶、黄嘌呤氧化酶和超氧化物歧化酶。最后发现，抑制次氯酸形成是许多NSAIDs共有的但并非一致的特性；吡罗昔康、水杨酸盐、舒林酸、布洛芬和阿司匹林都具有抑制作用，但浓度差异很大[表观抑制常数（Ki(app)）值分别为0.05、0.18、0.18、大于1和3毫摩尔]，且仅部分与其治疗剂量范围相关。这些结果促使人们进一步研究抑制次氯酸形成是否可能构成NSAIDs减少慢性炎症组织中组织破坏的另一种机制。
