Regulation of Phospholipase A2 in Human Amnion

描述（由申请人提供）：羊膜是分娩过程中产生PGE2的主要部位，是产生PG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，总体上是羊膜上皮细胞的5倍。在羊膜成纤维细胞中，我们已经发现糖皮质激素通过上调cPLA2和PGHS-2酶来增加PGE2的合成。我们描述了胎膜中存在细胞质和微粒体PGE合成酶异构体（cPGES和mPGES），但它们的表达不随胎龄或分娩而改变，也不会在分离的上皮细胞或成纤维细胞中被糖皮质激素诱导。花生四烯酸级联中的酶现在已知在离散的细胞位置上功能偶联以产生特定的PG。我们不知道分娩时羊膜细胞中的cPLA2和PGHS-2是否与cPGES或mPGES偶联以产生PGE2。在足月患者获得的胎膜中，我们观察到cPGES和mPGES免疫染色的间断模式，与苏丹黑B（一种脂质染色）相同。因此，这些酶可能定位于脂质体（脂滴），这些脂质体是炎症细胞中产生类二十烷的焦点，其中cPLA2， PGHS-2， p38 MAP激酶和ERK1, 2信号转导分子与它们相关。脂质体可能在组织或细胞固定过程中丢失，这可能是先前在胎膜中缺乏识别的原因。在各种细胞类型中，发现亲脂素和脂周蛋白与脂滴有关，可能在结构和功能上起作用。亲脂素和periilipin的表达均可通过转录因子ppar - γ的配体上调。我们已经证明，在整个妊娠期间，人胎膜中的亲脂素表达增加，显然与脂质体有关。最近研究表明，低氧可诱导亲脂素的表达，在无血管胎膜中，低氧可能调节亲脂素的表达。

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.