Spangelo B L, Jarvis W D, Judd A M, MacLeod R M
Department of Medicine, University of Virginia Health Sciences Center, Charlottesville 22908.
Endocrinology. 1991 Dec;129(6):2886-94. doi: 10.1210/endo-129-6-2886.
We have reported previously that a subpopulation(s) of anterior pituitary cells released IL-6 and that this release was stimulated by interleukin-1 (IL-1) through a non-cAMP-dependent mechanism. We now report that IL-1 induces IL-6 release from anterior pituitary cells in an eicosanoid-dependent manner. Dispersed rat anterior pituitary cells were briefly prelabeled (2-3 h) with [3H]arachidonic acid (AA) to esterify the fatty acid within the lipid pool. Incubation of these prelabeled cells with 25 ng/ml IL-1 beta caused an increase only within 1-2 min in the amount of free [3H]AA detected in the extracts of the cells. During 15- to 30-min incubations, IL-1 beta (25 ng/ml) caused an increased accumulation of [3H]AA in the incubation medium which reached levels similar to those induced by 100 nM TRH. Perifused anterior pituitary cells responded to IL-1 beta (25 ng/ml) with a rapid (less than 2 min), biphasic, and reversible efflux of [3H]AA. The [3H]AA appears to have been derived from choline phospholipids, as formation of [3H]glycerophosphorylcholine was substantially increased by exposure of [3H]choline-prelabeled cells to either IL-1 alpha (171%) or IL-1 beta (236%); in addition, the complete deacylation of phosphatidylcholine suggests that other fatty acid species are liberated as a consequence of IL-1 receptor activation and, thus, may also contribute to the actions of IL-1 alpha and IL-1 beta. However, the levels of [3H]phosphorylcholine and [3H]choline were unchanged as well as those of catabolites of other lipid species. These data suggested an involvement of phospholipase-A2 (PLA2) in mediating the IL-1 induction of IL-6 release. Subsequently, we used inhibitors of the PLA2, cyclooxygenase, and lipoxygenase enzymes to investigate a possible role for the generation of AA and its subsequent enzymatic conversion in the signal transduction pathway activated by IL-1. The PLA2 inhibitor aristolochic acid (10 microM) blocked IL-1 beta-induced IL-6 release and the release of IL-6 caused by Pyrularia pubera thionin (5 micrograms/ml), a stimulator of PLA2 activity. The cyclooxygenase inhibitor indomethacin (10 microM) did not inhibit IL-1 beta-induced IL-6 release. In contrast, the general lipoxygenase inhibitor nordihydroguaiaretic acid (10 microM) and the more specific 5-lipoxygenase inhibitors AA861 and RHC5901 (both 10 microM) reduced basal and blocked IL-1 beta-induced IL-6-release.(ABSTRACT TRUNCATED AT 400 WORDS)
我们之前报道过，垂体前叶细胞的一个亚群可释放白细胞介素-6（IL-6），且白细胞介素-1（IL-1）通过非环磷酸腺苷（cAMP）依赖机制刺激这种释放。我们现在报道，IL-1以类花生酸依赖的方式诱导垂体前叶细胞释放IL-6。将分散的大鼠垂体前叶细胞用[3H]花生四烯酸（AA）短暂预标记（2 - 3小时），以使脂肪酸酯化到脂质池中。用25 ng/ml IL-1β孵育这些预标记细胞，仅在1 - 2分钟内细胞提取物中检测到的游离[3H]AA量就增加了。在15至30分钟的孵育过程中，IL-1β（25 ng/ml）使孵育培养基中[3H]AA的积累增加，达到与100 nM促甲状腺激素释放激素（TRH）诱导的水平相似。灌注的垂体前叶细胞对IL-1β（25 ng/ml）的反应是[3H]AA快速（不到2分钟）、双相且可逆的流出。[3H]AA似乎来源于胆碱磷脂，因为将[3H]胆碱预标记的细胞暴露于IL-1α（171%）或IL-1β（236%）时，[3H]甘油磷酸胆碱的形成显著增加；此外，磷脂酰胆碱的完全脱酰基表明，由于IL-1受体激活，其他脂肪酸种类也被释放出来，因此也可能有助于IL-1α和IL-1β的作用。然而，[3H]磷酸胆碱和[3H]胆碱的水平以及其他脂质种类的代谢产物水平均未改变。这些数据表明磷脂酶A2（PLA2）参与介导IL-1诱导的IL-6释放。随后，我们使用PLA2、环氧化酶和脂氧合酶的抑制剂来研究AA的生成及其随后的酶促转化在IL-1激活的信号转导途径中的可能作用。PLA2抑制剂马兜铃酸（10 μM）阻断了IL-1β诱导的IL-6释放以及由PLA2活性刺激物野樱素（5 μg/ml）引起的IL-6释放。环氧化酶抑制剂吲哚美辛（10 μM）不抑制IL-1β诱导的IL-6释放。相反，通用脂氧合酶抑制剂去甲二氢愈创木酸（10 μM）以及更特异的5-脂氧合酶抑制剂AA861和RHC5901（均为10 μM）降低了基础水平并阻断了IL-1β诱导的IL-6释放。（摘要截断于400字）
