C/EBP AND ALVEOLAR TYPE II CELL DIFFERENTIATION

肺泡上皮的II型细胞参与了 脂蛋白复合体--肺表面活性物质的合成 从而降低表面张力，防止肺泡塌陷。精神障碍 表面活性物质被认为会导致呼吸窘迫综合征 早产儿、新生儿先天性肺泡蛋白沉积症和 成人呼吸窘迫综合征。这背后的假设是 建议是C/EBP转录因子家族，已知 在表现出特殊脂肪代谢的细胞中起着重要作用， 参与维持II型细胞的分化状态。 C/EBPs可以刺激多种上皮细胞的基因表达。 C/EBPs最初是从肝脏中提纯出来的；然而，它们在肺中被发现 也是。初步数据表明，C/EBPSα、β和增量 都存在于成年大鼠的II型细胞中。我们已经证明，当 第二类细胞被从肺中取出并纯化，其水平 C/EBPalpha迅速下降。我们已经证明了C/EBPalpha的水平 在胎鼠发育后期，mRNA和蛋白质水平增加，而 人胎肺外植体中C/EBPDelta随肺成熟而增加 发生。C/EBPalpha在NC-H441中可通过免疫印迹检测到，a 表达SP-A和SP-B的肺源性细胞株 反义C/EBPalpha对NC-H441细胞SP-A和SP-B的抑制作用 基因表达。C/EBPalpha表达载体导入A549细胞的研究 细胞，被认为是从II型细胞衍生而来，但不再是 表达表面活性蛋白基因诱导表面活性蛋白基因 在这些细胞中表达。我们假设C/EBPs在 表面活性剂体系的维护将通过以下几个方面进行测试：1)堵塞 反义RNA或反义腺病毒载体表达c/EBP基因 产生表面活性蛋白A和B的细胞系以及 2)用腺病毒载体诱导C/EBPs合成 转化为不再表达表面活性物质的II型来源的细胞系 蛋白质，以恢复它们的分化特性，还 筛选稳定表达C/EBPs和3)的亚系 检查C/EBPS直接竞标大鼠SP-A中的站点的能力 基因导入并激活SP-A基因。

The type II cells of the alveolar epithelium are involved in the synthesis of pulmonary surfactant, a complex of lipids and proteins which lowers surface tension preventing alveolar collapse. Disorders of surfactant are postulated to cause respiratory distress syndrome in premature infants, congenital alveolar proteinosis in newborns and respiratory distress syndrome in adults. The hypothesis underlying this proposal is that the C/EBP family of transcription factors, known to play an important role in cells exhibiting specialized lipid metabolism, is involved in maintaining the differentiated state of the type II cell. C/EBPs can stimulate gene expression in a variety of epithelial cells. C/EBPs were first purified from liver; however, they are found in lungs as well. Preliminary data indicates that C/EBPs alpha, beta and delta are all present in adult rat type II cells. We have shown that when the type II cells are removed from the lung and purified, the level of C/EBPalpha rapidly declines. We have shown that levels of C/EBPalpha mRNA and protein increase late in fetal rat development while levels of C/EBPdelta increase in human fetal lung explants as lung maturation occurs. C/EBPalpha is detectable by immunoslot blotting in NC-H441, a lung-derived cell line which expresses SP-A and SP-B, while transfection of NC-H441 cells with antisense against C/EBPalpha reduces SP-A and SP-B gene expression. Introduction of C/EBPalpha expression vector into A549 cells, which are thought to be derived from type II cells but no longer express surfactant protein genes induces surfactant protein gene expression in these cells. Our hypothesis that C/EBPs play a role in the maintenance of the surfactant system will be tested by: 1) blocking c/EBP expression with antisense RNA or antisense adenoviral vectors in a cell line which produces surfactant proteins A and B as well as in rate type II cells; 2) using adenoviral vectors to induce synthesis of C/EBPs into type II-derived cell lines which no longer express surfactant proteins in order to restore their differentiated properties and also selecting stably transfected sublines which express C/EBPs and 3) examining the ability of C/EBPs to directly bid to sites in the rat SP-A gene and activate SP-A in transfection experiments.