Sraer J, Bens M, Ardaillou R
INSERM 64, Hôpital Tenon, Paris, France.
Biochem Pharmacol. 1989 Jun 15;38(12):1947-54. doi: 10.1016/0006-2952(89)90493-0.
Because the oxygenated metabolites of arachidonate synthesized by macrophages, particularly prostaglandins (PG)I2 and E2, thromboxane (TX)A2 and 12-hydroxyeicosatetraenoic acid (12-HETE) have been shown to modulate the immune response of T-cells, we tested the effect of cyclosporine A (CsA), a potent immunosuppressor agent, on arachidonate (AA) metabolism in cultured peritoneal rat macrophages. Endogenous AA release and 12-HETE synthesis were estimated by radiometric HPLC after prelabelling of macrophages with [3H]AA whereas PG were determined either by radiometric HPLC or by direct radioimmunoassay in the culture mediums. Exposure of prelabelled cells for 16 hr to CsA led to a large increase in the release of AA itself and of its oxygenated metabolites, PG and 12-HETE, indicating stimulation of phospholipase activity. This effect was time- and dose-dependent at concentrations of CsA between 2 and 50 microM. There was also a marked increase in the ratio PGI2/TX, suggesting, in addition to activation of phospholipase, a partial blockade of TX synthase. When macrophages were triggered by A 23187 calcium ionophore (2 microM) or opsonized zymosan (1 mg/ml), the only detectable effect of CsA was a strong and specific inhibition (50%) of TX synthesis. Addition of an excess of exogenous AA (5 micrograms/ml) to cells treated by CsA confirmed the fact that CsA acted by specifically blocking the transformation of AA into TX without affecting PGI2 or 12-HETE synthesis. These results demonstrate that CsA acts at two different levels: it promotes phospholipase activation on resting cells but simultaneously induces a partial blockade of TX-synthase. This latter effect predominates when cells are stimulated. The resulting change in the ratio PGI2/TX promotes immunosuppression to the expense of immunostimulation. This may represent one of the factors underlying the potent immunosuppressive role of CsA.
由于巨噬细胞合成的花生四烯酸的氧化代谢产物，特别是前列腺素（PG）I2和E2、血栓素（TX）A2和12-羟基二十碳四烯酸（12-HETE）已被证明可调节T细胞的免疫反应，我们测试了强效免疫抑制剂环孢素A（CsA）对培养的大鼠腹膜巨噬细胞中花生四烯酸（AA）代谢的影响。在用[3H]AA预标记巨噬细胞后，通过放射性HPLC估计内源性AA释放和12-HETE合成，而PG则通过放射性HPLC或在培养基中通过直接放射免疫测定法测定。将预标记的细胞暴露于CsA 16小时导致AA本身及其氧化代谢产物PG和12-HETE的释放大幅增加，表明磷脂酶活性受到刺激。在2至50 microM的CsA浓度下，这种效应具有时间和剂量依赖性。PGI2/TX比值也显著增加，这表明除了磷脂酶激活外，TX合酶也受到部分阻断。当巨噬细胞由A 23187钙离子载体（2 microM）或调理酵母聚糖（1 mg/ml）触发时，CsA唯一可检测到的作用是对TX合成的强烈且特异性抑制（50%）。向经CsA处理的细胞中添加过量的外源性AA（5微克/毫升）证实了CsA通过特异性阻断AA向TX的转化而发挥作用，而不影响PGI2或12-HETE的合成。这些结果表明CsA在两个不同水平上起作用：它促进静息细胞上的磷脂酶激活，但同时诱导TX合酶的部分阻断。当细胞受到刺激时，后一种效应占主导。PGI2/TX比值的由此变化以免疫刺激为代价促进免疫抑制。这可能代表了CsA强效免疫抑制作用的潜在因素之一。
