Department of Animal Science and Aquaculture, Agricultural University of Athens, 75 Iera Odos, 11855 Athens, Greece.
J Dairy Res. 2011 Aug;78(3):365-72. doi: 10.1017/S002202991100046X.
There is conflicting evidence in the literature as to whether up-regulation of urokinase plasminogen activator (u-PA) expression is related to bovine mammary epithelial cell growth. The role of u-PA receptor (u-PAR) and that of the plasminogen activator inhibitors type 1 and type 2 (PAI-1 and PAI-2) in bovine mammary epithelial cell proliferation is not known. The effect of growth factors and various hormones known to affect mammary function on expression of u-PA, u-PAR, PAI-1, PAI-2 and cell proliferation using the BME-UV1 bovine mammary epithelial cell line was examined. Cell proliferation was measured using the MTT assay and direct cell enumeration. Results showed that both IGF-1 and EGF increased cell proliferation but EGF was a more potent mitogen than IGF-1. Furthermore, IGF-1 increased by 2-fold expression of both u-PA and u-PAR while EGF increased by 3·8-fold the expression of only u-PAR. Both growth factors had no effect on expression of PAI-1 and PAI-2. In a manner consistent with changes in gene expression, EGF and to a lesser extent IGF-1 up-regulated total cell associated, membrane-bound and secreted u-PA activity. Thus, a strong correlation exists between u-PAR gene expression along with the activity of u-PA present on cell membranes and cell proliferation. Dexamethasone, prolactin and surprisingly insulin had no effect on cell proliferation. Dexamethasone alone and when combined with insulin or prolactin up-regulated gene expression of both PAI- and PAI-2 but not that of u-PA and u-PAR. Decreased total cell-associated, membrane-bound and secreted u-PA activity was detected in cells cultured in the presence of dexamethasone when combined with insulin or prolactin. However no such effect was observed in the presence of dexamethasone alone. Thus, dexamethasone acting synergistically with prolactin or insulin inhibits the activation of the plasmin-plasminogen system but this inhibition is not correlated with any changes in cell proliferation.
文献中关于尿激酶纤溶酶原激活物(u-PA)表达上调是否与牛乳腺上皮细胞生长有关存在矛盾的证据。u-PA 受体(u-PAR)以及纤溶酶原激活物抑制剂 1 型和 2 型(PAI-1 和 PAI-2)在牛乳腺上皮细胞增殖中的作用尚不清楚。本研究采用 BME-UV1 牛乳腺上皮细胞系，研究了已知影响乳腺功能的生长因子和各种激素对 u-PA、u-PAR、PAI-1、PAI-2 表达和细胞增殖的影响。采用 MTT 法和直接细胞计数法测定细胞增殖。结果表明，IGF-1 和 EGF 均可促进细胞增殖，但 EGF 是一种比 IGF-1 更有效的有丝分裂原。此外，IGF-1 使 u-PA 和 u-PAR 的表达增加 2 倍，而 EGF 仅使 u-PAR 的表达增加 3.8 倍。两种生长因子对 PAI-1 和 PAI-2 的表达均无影响。与基因表达变化一致，EGF 并在较小程度上 IGF-1 增加了总细胞相关、膜结合和分泌的 u-PA 活性。因此，u-PAR 基因表达以及细胞膜上存在的 u-PA 活性与细胞增殖之间存在很强的相关性。地塞米松、催乳素和令人惊讶的胰岛素对细胞增殖没有影响。地塞米松单独以及与胰岛素或催乳素联合使用均可上调 PAI-和 PAI-2 的基因表达，但不能上调 u-PA 和 u-PAR 的基因表达。与胰岛素或催乳素联合培养时，细胞中检测到总细胞相关、膜结合和分泌的 u-PA 活性降低，但单独使用地塞米松时未观察到这种作用。因此，地塞米松与催乳素或胰岛素协同作用抑制纤溶酶原系统的激活，但这种抑制与细胞增殖的任何变化无关。
