Sporn P H, Peters-Golden M
Department of Internal Medicine, University of Michigan, Ann Arbor.
J Biol Chem. 1988 Oct 15;263(29):14776-83.
We have previously shown that the biologically important reactive oxygen metabolite hydrogen peroxide (H2O2) stimulates arachidonic acid (AA) release and thromboxane A2 synthesis in the rat alveolar macrophage. We have now investigated the effects of H2O2 on alveolar macrophage 5-lipoxygenase metabolism. H2O2 failed to stimulate detectable synthesis of leukotriene B4, leukotriene C4, or 5-hydroxyeicosatetraenoic acid (5-HETE) as determined by reverse-phase high performance liquid chromatography (RP-HPLC) and sensitive radioimmunoassays (RIAs). This was not explained by oxidative degradation of leukotrienes by H2O2 at the concentrations used. Moreover, RIA and RP-HPLC analyses demonstrated that H2O2 dose-dependently inhibited synthesis of leukotriene B4, leukotriene C4, and 5-HETE induced by the agonists A23187 (10 microM) and zymosan (100 micrograms/ml), over the same concentration range at which it augmented synthesis of the cyclooxygenase products thromboxane A2 and 12-hydroxy-5,8,10-heptadecatrienoic acid. Four lines of evidence suggested that H2O2 inhibited alveolar macrophage leukotriene and 5-HETE synthesis by depleting cellular ATP, a cofactor for 5-lipoxygenase. 1) H2O2 depleted ATP in A23187- and zymosan-stimulated alveolar macrophages with a dose dependence very similar to that for inhibition of agonist-induced leukotriene synthesis. 2) The time courses of ATP depletion and inhibition of leukotriene B4 synthesis by H2O2 were compatible with a rate-limiting effect of ATP on leukotriene synthesis in H2O2-exposed cultures. 3) Treatment of alveolar macrophages with the electron transport inhibitor antimycin A prior to A23187 stimulation depleted ATP and inhibited leukotriene B4 and C4 synthesis to equivalent degrees, while thromboxane A2 production was spared. 4) Incubation with the ATP precursors inosine plus phosphate attenuated both ATP depletion and inhibition of leukotriene B4 and C4 synthesis in alveolar macrophages stimulated with A23187 in the presence of H2O2. Our results show that H2O2 has the capacity to act both as an agonist for macrophage AA metabolism, and as a selective inhibitor of the 5-lipoxygenase pathway, probably as a result of its ability to deplete ATP. Depletion of cellular energy stores by oxidants generated during inflammation in vivo may be a means by which the inflammatory response is self-limited.
我们之前已经表明，具有生物学重要性的活性氧代谢产物过氧化氢（H₂O₂）可刺激大鼠肺泡巨噬细胞释放花生四烯酸（AA）并合成血栓素A₂。我们现在研究了H₂O₂对肺泡巨噬细胞5-脂氧合酶代谢的影响。通过反相高效液相色谱（RP-HPLC）和灵敏的放射免疫分析（RIA）测定，H₂O₂未能刺激检测到白三烯B₄、白三烯C₄或5-羟基二十碳四烯酸（5-HETE）的合成。在所使用的浓度下，H₂O₂对白三烯的氧化降解并不能解释这一现象。此外，RIA和RP-HPLC分析表明，在与增强环氧化酶产物血栓素A₂和12-羟基-5,8,10-十七碳三烯酸合成相同的浓度范围内，H₂O₂剂量依赖性地抑制激动剂A23187（10 microM）和酵母聚糖（100微克/毫升）诱导的白三烯B₄、白三烯C₄和5-HETE的合成。四条证据表明，H₂O₂通过消耗细胞内ATP（5-脂氧合酶的一种辅助因子）来抑制肺泡巨噬细胞白三烯和5-HETE的合成。1）H₂O₂在A23187和酵母聚糖刺激的肺泡巨噬细胞中消耗ATP，其剂量依赖性与抑制激动剂诱导的白三烯合成非常相似。2）H₂O₂消耗ATP和抑制白三烯B₄合成的时间进程与ATP对暴露于H₂O₂的培养物中白三烯合成的限速作用相符。3）在A23187刺激之前，用电子传递抑制剂抗霉素A处理肺泡巨噬细胞会消耗ATP并同等程度地抑制白三烯B₄和C₄的合成，而血栓素A₂的产生则不受影响。4）在H₂O₂存在的情况下，用ATP前体肌苷加磷酸盐孵育可减轻A23187刺激的肺泡巨噬细胞中ATP的消耗以及对白三烯B₄和C₄合成的抑制。我们的结果表明，H₂O₂既有能力作为巨噬细胞AA代谢的激动剂，又有能力作为5-脂氧合酶途径的选择性抑制剂，这可能是由于其消耗ATP的能力所致。体内炎症过程中产生的氧化剂消耗细胞能量储备可能是炎症反应自我限制的一种方式。
