Abu-Raya S, Bloch-Shilderman E, Shohami E, Trembovler V, Shai Y, Weidenfeld J, Yedgar S, Gutman Y, Lazarovici P
Department of Pharmacology and Experimental Therapeutics, School of Pharmacy, Faculty of Medicine, The Hebrew University, Jerusalem, Israel.
J Pharmacol Exp Ther. 1998 Dec;287(3):889-96.
The effect of Pardaxin, a neurotoxin that induces neurotransmitter release from neurons, on the arachidonic acid (AA) cascade was studied in PC12 cells. Both native and the synthetic Pardaxin selectively stimulated phospholipase A2 (PLA2) activity (measured by [3H]AA release) in the presence as well as in the absence of extracellular calcium. Pardaxin-stimulated PLA2 activity was also evident in the increased formation of lysophosphatidylcholine. Pardaxin analogs, lacking the alpha-helical structure that is essential for insertion into the plasma membrane, were ineffective in stimulating the AA cascade in PC12 cells. Pardaxin stimulation of PLA2 was markedly inhibited by the nonselective PLA2 inhibitors bromophenacyl bromide and mepacrine, by methyl arachidonyl fluorophosphonate, a dual inhibitor of calcium-dependent cytosolic PLA2 and the calcium-independent PLA2 and by bromoenol lactone[(E)-6-(bromoethylene)tetrahydro-3-(1-naphthalenyl-2H-pyran -2- one], a highly specific inhibitor of calcium-independent PLA2. After Pardaxin treatment, there was increased release of AA metabolites produced by the cyclooxygenase pathway as expressed in an 8-fold increase of PGE2 release. The release of other eicosanoids, such as 6-keto-PGF1alpha and thromboxane B2, was also augmented. Pardaxin-induced PGE2 release was observed in calcium-free medium and in the absence of any increase in cytosolic calcium. Dexamethasone partially inhibited Pardaxin-induced PGE2 release. This effect was reversed by the type II corticosteroid receptor antagonist RU-38486. Our results indicate that Pardaxin stimulates release of AA and eicosanoids, independently of calcium, and suggest that calcium-independent PLA2 plays an important role in Pardaxin stimulation of the AA cascade.
在PC12细胞中研究了 Pardaxin（一种可诱导神经元释放神经递质的神经毒素）对花生四烯酸（AA）级联反应的影响。无论是天然的还是合成的 Pardaxin，在存在和不存在细胞外钙的情况下，均能选择性地刺激磷脂酶A2（PLA2）活性（通过[3H]AA释放来测定）。Pardaxin刺激的PLA2活性在溶血磷脂酰胆碱形成增加中也很明显。缺乏插入质膜所必需的α-螺旋结构的Pardaxin类似物，在刺激PC12细胞中的AA级联反应方面无效。非选择性PLA2抑制剂溴苯酰溴和米帕林、钙依赖性胞质PLA2和非钙依赖性PLA2的双重抑制剂甲基花生四烯酰氟磷酸酯以及非钙依赖性PLA2的高度特异性抑制剂溴烯醇内酯[（E）-6-（溴乙烯基）四氢-3-（1-萘基-2H-吡喃-2-酮]，均能显著抑制Pardaxin对PLA2的刺激。Pardaxin处理后，环氧化酶途径产生的AA代谢产物的释放增加，表现为PGE2释放增加了8倍。其他类二十烷酸，如6-酮-PGF1α和血栓素B2的释放也增加。在无钙培养基中且胞质钙没有任何增加的情况下，观察到了Pardaxin诱导的PGE2释放。地塞米松部分抑制了Pardaxin诱导的PGE2释放。II型糖皮质激素受体拮抗剂RU-38486可逆转这种作用。我们的结果表明，Pardaxin可独立于钙刺激AA和类二十烷酸的释放，并提示非钙依赖性PLA2在Pardaxin刺激的AA级联反应中起重要作用。
