Beers M F, Solarin K O, Guttentag S H, Rosenbloom J, Kormilli A, Gonzales L W, Ballard P L
Pulmonary and Critical Care Division, Department of Medicine, University of Pennsylvania School of Medicine, Department of Pediatrics, Allegheny University School of Medicine, Philadelphia, Pennsylvania 19134, USA.
Am J Physiol. 1998 Nov;275(5):L950-60. doi: 10.1152/ajplung.1998.275.5.L950.
Transforming growth factor-beta1 (TGF-beta1) is a multifunctional cytokine shown to play a critical role in organ morphogenesis, development, growth regulation, cellular differentiation, gene expression, and tissue remodeling after injury. We examined the effect of exogenously administered TGF-beta1 on the expression of surfactant proteins (SPs) and lipids, fatty acid synthetase, and ultrastructural morphology in human fetal lung cultured for 5 days with and without dexamethasone (10 nM). Expression of the type II cell-specific marker surfactant proprotein C (proSP-C), studied by [35S]Met incorporation and immunoprecipitation, increased sevenfold with dexamethasone treatment. TGF-beta1 (0.1-100 ng/ml) in the presence of dexamethasone inhibited 21-kDa proSP-C expression in a dose-dependent manner (maximal inhibition 31% of control level at 100 ng/ml). There was no change in [35S]Met incorporation into total protein in any of the treatment groups vs. the control group. In immunoblotting experiments, TGF-beta1 blocked culture-induced accumulation of SP-A and SP-B. Under the same conditions, TGF-beta1 reduced mRNA content for SP-A, SP-B, and SP-C to 20, 38, and 41%, respectively, of matched control groups but did not affect levels of beta-actin mRNA. SP transcription rates after 24 h of exposure to TGF-beta1 were reduced to a similar extent (20-50% of control level). In both control and dexamethasone-treated explants, TGF-beta1 (10 ng/ml) also decreased fatty acid synthetase mRNA, protein, and enzyme activity and the rate of [3H]choline incorporation into phosphatidylcholine. By electron microscopy, well-differentiated type II cells lining potential air spaces were present in explants cultured with dexamethasone, whereas exposure to TGF-beta1 with or without dexamethasone resulted in epithelial cells lacking lamellar bodies. We conclude that exogenous TGF-beta1 disrupts culture-induced maturation of fetal lung epithelial cells and inhibits expression of surfactant components through effects on gene transcription.
转化生长因子-β1（TGF-β1）是一种多功能细胞因子，已证实在器官形态发生、发育、生长调节、细胞分化、基因表达以及损伤后的组织重塑中起关键作用。我们研究了在添加和不添加地塞米松（10 nM）的情况下，外源性给予TGF-β1对培养5天的人胎肺表面活性物质蛋白（SPs）和脂质、脂肪酸合成酶以及超微结构形态的影响。通过[35S]甲硫氨酸掺入和免疫沉淀研究的II型细胞特异性标志物表面活性物质前体蛋白C（proSP-C）的表达，在地塞米松处理后增加了7倍。在地塞米松存在的情况下，TGF-β1（0.1 - 100 ng/ml）以剂量依赖性方式抑制21-kDa proSP-C的表达（在100 ng/ml时最大抑制率为对照水平的31%）。与对照组相比，任何处理组中[35S]甲硫氨酸掺入总蛋白均无变化。在免疫印迹实验中，TGF-β1阻断了培养诱导的SP-A和SP-B的积累。在相同条件下，TGF-β1将SP-A、SP-B和SP-C的mRNA含量分别降至匹配对照组的20%、38%和41%，但不影响β-肌动蛋白mRNA水平。暴露于TGF-β1 24小时后的SP转录率也降低到类似程度（为对照水平的20 - 50%）。在对照和地塞米松处理的外植体中，TGF-β1（10 ng/ml）还降低了脂肪酸合成酶的mRNA、蛋白质和酶活性以及[3H]胆碱掺入磷脂酰胆碱的速率。通过电子显微镜观察，在用糖皮质激素培养的外植体中，潜在气腔内衬有分化良好的II型细胞，而无论有无地塞米松，暴露于TGF-β1都会导致上皮细胞缺乏板层小体。我们得出结论，外源性TGF-β1通过影响基因转录破坏培养诱导的胎肺上皮细胞成熟并抑制表面活性物质成分的表达。
