Ryu J S, Majeska R J, Ma Y, LaChapelle L, Guller S
Department of Obstetrics, New York University School of Medicine, New York 10016, USA.
Endocrinology. 1999 Sep;140(9):3904-8. doi: 10.1210/endo.140.9.6999.
Maintenance of uterine-placental attachment during human pregnancy may depend at least partly on adhesive interactions between cytotrophoblasts and their extracellular matrix (ECM). Such interactions are often mediated by integrins, signal-transducing heterodimeric transmembrane glycoproteins. We previously showed that glucocorticoid (GC) suppressed the expression of collagen and laminin in human placenta; here we show that GC also modulates the expression by human cytotrophoblasts of the integrin subunits alpha2 and beta1, components of a known receptor for these ECM ligands. Cytotrophoblasts were isolated from human term placentas, cultured up to 4 days in the presence of 0-1000 nM dexamethasone (DEX), and assayed for 1) integrin messenger RNA (mRNA) levels by Northern hybridization, 2) integrin subunit synthesis after [35S]methionine labeling, or 3) cell surface integrin levels after 125I labeling by lactoperoxidase. In four independent experiments, 100 nM DEX reduced mRNA levels for integrin alpha2 to 6+/-1% of the control value. This effect was similar between 1-4 days of treatment and was dose dependent between 1-1000 nM DEX. Cortisol treatment (100 nM) inhibited levels of integrin alpha2 mRNA, but 100 nM testosterone, estradiol, and progesterone were less effective, suggesting that this response was specific to GC. In immunoprecipitation studies, treatment of cytotrophoblasts with 100 nM DEX for 2 days reduced the rates of synthesis of the alpha2 integrin subunit as well as its expression on the cell surface to 1-10% of control levels. DEX effects on the beta1 integrin subunit were less dramatic. DEX reduced beta1 mRNA levels to only 69+/-8% of control levels, a smaller reduction compared with effects on alpha2 integrin mRNA. DEX inhibited beta1 protein synthesis and cell surface expression to 60-70% of control levels. In all experiments, DEX had no effect on total protein synthesis. Thus, our results demonstrate that GC treatment specifically and markedly down-regulates expression of alpha2 integrin subunit by human cytotrophoblasts. This finding is consistent with the concept that uterine-placental adherence across gestation may be regulated by coordinate effects on ECM ligands and cellular adhesion receptors.
人类妊娠期间子宫 - 胎盘附着的维持可能至少部分取决于细胞滋养层细胞与其细胞外基质（ECM）之间的黏附相互作用。这种相互作用通常由整合素介导，整合素是信号转导异二聚体跨膜糖蛋白。我们之前表明糖皮质激素（GC）会抑制人胎盘中胶原蛋白和层粘连蛋白的表达；在此我们表明GC还会调节人细胞滋养层细胞中整合素亚基α2和β1的表达，这两种亚基是这些ECM配体已知受体的组成部分。从足月人胎盘中分离出细胞滋养层细胞，在0 - 1000 nM地塞米松（DEX）存在的情况下培养4天，然后进行以下检测：1）通过Northern杂交检测整合素信使核糖核酸（mRNA）水平；2）用[35S]甲硫氨酸标记后检测整合素亚基的合成；3）用乳过氧化物酶进行125I标记后检测细胞表面整合素水平。在四项独立实验中，100 nM DEX将整合素α2的mRNA水平降至对照值的6±1%。在治疗的第1 - 4天，这种效果相似，并且在1 - 1000 nM DEX之间呈剂量依赖性。皮质醇处理（100 nM）会抑制整合素α2 mRNA的水平，但100 nM睾酮、雌二醇和孕酮的效果较差，这表明这种反应对GC具有特异性。在免疫沉淀研究中，用100 nM DEX处理细胞滋养层细胞2天，会将α2整合素亚基的合成速率及其在细胞表面的表达降至对照水平的1 - 10%。DEX对β1整合素亚基的影响较小。DEX仅将β1 mRNA水平降至对照水平的69±8%，与对α2整合素mRNA的影响相比，降低幅度较小。DEX会抑制β1蛋白的合成以及细胞表面表达至对照水平的60 - 70%。在所有实验中，DEX对总蛋白合成没有影响。因此，我们的结果表明GC处理会特异性且显著地下调人细胞滋养层细胞中α2整合素亚基的表达。这一发现与整个妊娠期子宫 - 胎盘黏附可能受对ECM配体和细胞黏附受体的协同作用调节这一概念相一致。
