Regulation of Phospholipase A2 in Human Amnion

描述(申请人提供)：羊膜是PGE2在分娩过程中产生的主要部位，是PG生产的前体花生四烯酸的丰富来源。在胎膜中，羊膜成纤维细胞每个细胞产生的PGE2大约是羊膜上皮细胞的50倍，总体而言是羊膜上皮细胞的5倍。在羊膜成纤维细胞中，我们发现糖皮质激素通过上调cPLA2和PGHS-2酶来增加PGE2的合成。我们描述了细胞质和微粒体PGE合成酶亚型(cPGES和mPGES)在胎膜中的存在，但它们的表达不随胎龄或分娩而改变，也不是在分离的上皮细胞或成纤维细胞中被糖皮质激素诱导的。花生四烯酸级联中的酶现在已知在不同的细胞位置上功能偶联，以产生特定的PG。我们不知道cPLA2和PGHS-2是否在分娩时与羊膜细胞中的cPGES或mPGES偶联来产生PGE2。在足月患者的胎膜中，我们观察到cPGES和mPGES免疫染色的点状模式，与苏丹黑B相同，苏丹黑B是一种脂质染色。因此，这些酶可能定位于脂体(脂滴)，在炎症细胞中，cPLA2、PGHS-2、p38 MAP激酶和ERK1、2信号转导分子与其相关，是产生二十烷基类化合物的焦点。脂肪小体可能会在组织或细胞固定过程中丢失，这可能是以前胎膜没有识别的原因。阿迪波菲林和Perilipin被发现与脂滴有关，可能在各种类型的细胞中发挥结构和功能作用。脂联素和Perilipin的表达都被转录因子PPAR-Gamma的配体上调。我们已经证明，在整个妊娠过程中，人类胎膜中脂联素的表达增加，这显然与脂体有关。最近发现低氧可诱导脂联素的表达，在无血管的胎膜中，低氧可能调节脂联素的表达。 有待检验的假设是，cPGES或mPGES在功能上与cPLA2和PGHS-2偶联，在分娩时产生PGE2，这可能发生在脂滴中，这是参与二十多糖合成的酶的积累部位，包括cPLA2，PGHS-2，cPGES，mPGES，p38MAP Kinase和ERK1，2，PPAR-Gamma和低氧调节蛋白ADIPPHIN和PERPIN在脂滴的组装和功能中发挥关键作用。

DESCRIPTION (provided by applicant): The amnion is a major site of PGE2 production during labor and is a rich source of arachidonic acid, the precursor of PG production. In the fetal membranes, the amnion fibroblast cells produce approx 50-fold greater PGE2 per cell and overall account for a 5-fold greater production than the amnion epithelium. In the amnion fibroblasts, we have shown glucocorticoids increase PGE2 synthesis by up-regulation of cPLA2 and PGHS-2 enzymes. We described the presence of both the cytosolic and microsomal PGE synthase isoforms (cPGES and mPGES) in fetal membranes but that their expression did not change with gestational age or labor, nor were they induced by glucocorticoid treatment in isolated epithelial or fibroblast cells. The enzymes in the arachidonic acid cascade are now know to be functionally coupled at discrete cellular locations to produce specific PG's. We do not know if cPLA2 and PGHS-2 are coupled to either cPGES or mPGES in amnion cells at labor to produce PGE2. In fetal membranes obtained from patients at term, we observed a punctuate pattern of immunostaining for cPGES and mPGES, identical to that with Sudan Black B, a stain for lipid. Thus these enzymes may localize to lipid bodies (lipid droplets) which are foci for production of eicosanoids in inflammatory cells where cPLA2, PGHS-2, p38 MAP kinase and ERK1, 2 signal transduction molecules are associated with them. Lipid bodies can be lost during tissue or cell fixation possibly accounting for the previous absence of recognition in fetal membranes. Adipophilin and perilipin are found in association with lipid droplets perhaps serving structural and functional roles in various cell types. Both adipophilin and perilipin expression are upregulated by ligands to the transcription factor PPAR-gamma. We have demonstrated increasing adipophilin expression in the human fetal membranes throughout gestation, apparently in association with lipid bodies. Adipophilin was recently shown to be inducible by hypoxia and it is possible that in the avascular fetal membranes hypoxia may regulate adipophilin expression. The hypotheses to be tested are that either cPGES or mPGES are functionally coupled to cPLA2, and PGHS-2 to produce PGE2 at labor, that this may occur in lipid droplets, which are sites of accumulation of enzymes involved in eicosanoid synthesis including, cPLA2, PGHS-2, cPGES, mPGES, p38MAP Kinase and ERK1, 2, and that the PPAR-gamma and hypoxia-regulated proteins adipophilin and peripin play key roles in assembly and function of lipid droplets.