Potestio F A, Olson D M
Department of Pediatrics, Lawson Research Institute, St. Joseph's Health Centre of London, University of Western Ontario, Canada.
J Clin Endocrinol Metab. 1990 Mar;70(3):647-54. doi: 10.1210/jcem-70-3-647.
Glucocorticoids inhibit prostaglandin (PG) synthesis in several cell types, presumably by inhibiting arachidonic acid (AA) deacylation from phospholipids. We studied the effects of glucocorticoids on cultured term human amnion cell AA release. Confluent monolayer cultures of amnion cells were adapted to serum-free medium, and phospholipids were labeled for 18 h with [14C]AA. The calcium ionophore A23187 (0.2-5.0 mumol/L) stimulated [14C]AA release (up to 2.2-fold) in a dose- and time-dependent manner. The apparent sources of the liberated [14C]AA were phosphatidylcholine and phosphatidylethanolamine. Pretreatment for 24 h with the synthetic glucocorticoid dexamethasone (0.1-1000 nmol/L) significantly inhibited (P less than 0.01) basal (unstimulated) [14C]AA release by 69% in subsequent 1-h experiments. The sole apparent source of free [14C]AA during this inhibitory state was phosphatidylethanolamine. Dexamethasone pretreatment slightly inhibited (13%; P less than 0.05) calcium ionophore-stimulated [14C]AA release; however, it was still 3.8-fold greater than basal release, suggesting that the glucocorticoid effect on stimulated AA release was not biologically relevant. Further characterization of the glucocorticoid effect revealed that preincubation of the cultures with dexamethasone for as little as 20 min inhibited basal [14C]AA release. Furthermore, studies involving actinomycin-D and cycloheximide demonstrated that inhibition of RNA and protein synthesis failed to block the glucocorticoid inhibition of basal AA liberation. The glucocorticoid receptor antagonist RU 38486, alone or in the presence of dexamethasone, also inhibited unstimulated [14C]AA release. Cortisol, dehydroisoandrosterone sulfate, 17 beta-estradiol, and progesterone all inhibited basal [14C]AA liberation. We conclude that glucocorticoids inhibit unstimulated AA release from cultured amnion cells, but do not prevent calcium ionophore from stimulating a large increase in AA release.(ABSTRACT TRUNCATED AT 250 WORDS)
糖皮质激素可抑制多种细胞类型中前列腺素（PG）的合成，推测是通过抑制磷脂中花生四烯酸（AA）的脱酰作用来实现的。我们研究了糖皮质激素对培养的足月人羊膜细胞AA释放的影响。将羊膜细胞的汇合单层培养物适应无血清培养基，并用[14C]AA标记磷脂18小时。钙离子载体A23187（0.2 - 5.0 μmol/L）以剂量和时间依赖性方式刺激[14C]AA释放（高达2.2倍）。释放的[14C]AA的明显来源是磷脂酰胆碱和磷脂酰乙醇胺。在随后1小时的实验中，用合成糖皮质激素地塞米松（0.1 - 1000 nmol/L）预处理24小时可显著抑制（P < 0.01）基础（未刺激）[14C]AA释放达69%。在此抑制状态下，游离[14C]AA的唯一明显来源是磷脂酰乙醇胺。地塞米松预处理轻微抑制（13%；P < 0.05）钙离子载体刺激的[14C]AA释放；然而，它仍比基础释放高3.8倍，这表明糖皮质激素对刺激的AA释放的影响在生物学上不相关。对糖皮质激素作用的进一步表征表明，用地塞米松预孵育培养物仅20分钟就可抑制基础[14C]AA释放。此外，涉及放线菌素-D和环己酰亚胺的研究表明，抑制RNA和蛋白质合成未能阻断糖皮质激素对基础AA释放的抑制作用。糖皮质激素受体拮抗剂RU 38486单独或与地塞米松一起存在时，也可抑制未刺激的[14C]AA释放。皮质醇、硫酸脱氢表雄酮、17β - 雌二醇和孕酮均抑制基础[14C]AA释放。我们得出结论，糖皮质激素可抑制培养的羊膜细胞中未刺激的AA释放，但不能阻止钙离子载体刺激AA释放大幅增加。（摘要截短于250字）
