Pfeilschifter J, Schalkwijk C, Briner V A, van den Bosch H
Department of Pharmacology, University of Basel, Switzerland.
J Clin Invest. 1993 Nov;92(5):2516-23. doi: 10.1172/JCI116860.
Potent pro-inflammatory cytokines, such as interleukin 1 (IL-1) or tumor necrosis factor (TNF) alpha have been found to increase group II phospholipase A2 (PLA2) synthesis and secretion by mesangial cells. In all cases 85-90% of the enzyme is secreted from the cells and a parallel increase in prostaglandin (PG)E2 synthesis is observed. We report here that co-incubation with a monoclonal antibody that specifically binds and neutralizes rat group II PLA2 attenuates IL-1 beta and TNF alpha-stimulated PGE2 production by 45% and 52%, respectively. CGP43182, a specific inhibitor of group II PLA2, potently blocks mesangial cell group II PLA2 in vitro with a half-maximal inhibitory concentration (IC50) of 1.5 microM, while only slightly affecting mesangial cell high molecular weight PLA2. CGP 43182 markedly attenuates IL-1 beta- and TNF alpha-stimulated PGE2 synthesis in intact mesangial cells with IC50's of 1.3 and 1.0 microM, respectively. PLA2 secreted from cytokine-stimulated mesangial cells was purified to homogeneity. Addition of the purified enzyme to unstimulated mesangial cells causes a marked release of arachidonic acid and a subsequent increased synthesis of PGE2. Moreover, addition of purified PLA2 to a cloned rat glomerular epithelial cell line and cultured bovine glomerular endothelial cells augmented both arachidonic acid release and PGE2 synthesis, with the endothelial cells being especially sensitive. Thus, cytokine-triggered synthesis and secretion of group II PLA2 by mesangial cells contributes, at least in part, to the observed synthesis of PGE2 that occurs in parallel to the enzyme secretion. Furthermore, extracellular PLA2 secreted by mesangial cells is able to stimulate arachidonic acid release and PGE2 synthesis by the adjacent endothelial and epithelial cells. These data suggest that expression and secretion of group II PLA2 triggered by pro-inflammatory cytokines may crucially participate in the pathogenesis of inflammatory processes within the glomerulus.
已发现强效促炎细胞因子，如白细胞介素1（IL-1）或肿瘤坏死因子（TNF）α，可增加系膜细胞中II型磷脂酶A2（PLA2）的合成与分泌。在所有情况下，85%-90%的该酶从细胞中分泌出来，同时观察到前列腺素（PG）E2合成呈平行增加。我们在此报告，与特异性结合并中和大鼠II型PLA2的单克隆抗体共同孵育，可分别使IL-1β和TNFα刺激的PGE2产生减少45%和52%。CGP43182是II型PLA2的特异性抑制剂，在体外能有效阻断系膜细胞的II型PLA2，其半数最大抑制浓度（IC50）为1.5微摩尔，而对系膜细胞高分子量PLA2的影响较小。CGP 43182可显著减弱完整系膜细胞中IL-1β和TNFα刺激的PGE2合成，其IC50分别为1.3和1.0微摩尔。从细胞因子刺激的系膜细胞分泌的PLA2被纯化至同质。将纯化的该酶添加到未刺激的系膜细胞中会导致花生四烯酸的显著释放以及随后PGE2合成的增加。此外，将纯化的PLA2添加到克隆的大鼠肾小球上皮细胞系和培养的牛肾小球内皮细胞中，可增强花生四烯酸的释放和PGE2的合成，其中内皮细胞尤为敏感。因此，系膜细胞由细胞因子触发的II型PLA2的合成与分泌至少部分促成了与该酶分泌平行发生的PGE2合成。此外，系膜细胞分泌的细胞外PLA2能够刺激相邻内皮细胞和上皮细胞释放花生四烯酸并合成PGE2。这些数据表明，促炎细胞因子触发的II型PLA2的表达与分泌可能在肾小球内炎症过程的发病机制中起关键作用。
