Peixoto E B M I, Collares-Buzato C B
Department of Histology and Embryology, Institute of Biology, State University of Campinas, UNICAMP, Campinas, CP 6109, R. Charles Darwin s/n, 13083-970 Campinas, SP, Brazil.
Cell Biol Int. 2006 Feb;30(2):101-13. doi: 10.1016/j.cellbi.2005.08.004. Epub 2006 Feb 7.
Glucocorticoids and prolactin (PRL) have a direct effect on the formation and maintenance of tight junctions (TJs) in cultured endothelial and mammary gland epithelial cells. In this work, we investigated the effect of a synthetic glucocorticoid dexamethasone (DEX) and PRL on the paracellular barrier function in MDCK renal epithelial cells. DEX (4 microM)+PRL (2 microg/ml) and DEX alone increased significantly the transepithelial electrical resistance after chronic treatment (4 days) of confluent MDCK monolayers or after 24 h treatment of subconfluent monolayers. Immunoblotting and immunocytochemistry revealed no changes in the expression and distribution of TJ-associated proteins occludin, ZO-1 and claudin-1 in confluent monolayers after hormone addition. However, a marked increase in junctional content for occludin and ZO-1 with no changes in their total expression was observed in subconfluent MDCK monolayers 24 h exposed to DEX or DEX+PRL. No change in cell proliferation/growth was detected at subconfluent conditions following hormone treatment. An increase in the total number of viable cells was observed only in confluent MDCK monolayers after exposure to DEX+PRL suggesting that the main effect of these hormones on already established barrier may be associated with the inhibition of cell death. In conclusion, our data suggest that these hormones (specially dexamethasone) have an effect on TJ structure and function only during the formation of MDCK epithelial barrier by probably modulating the localization, stability or assembly of TJ proteins to membrane sites of intercellular contact.
糖皮质激素和催乳素（PRL）对培养的内皮细胞和乳腺上皮细胞紧密连接（TJ）的形成和维持有直接影响。在本研究中，我们调查了合成糖皮质激素地塞米松（DEX）和PRL对MDCK肾上皮细胞旁细胞屏障功能的影响。在汇合的MDCK单层细胞经慢性处理（4天）或亚汇合单层细胞经24小时处理后，DEX（4 microM）+PRL（2微克/毫升）和单独的DEX显著增加了跨上皮电阻。免疫印迹和免疫细胞化学显示，添加激素后，汇合单层细胞中TJ相关蛋白闭合蛋白、ZO-1和claudin-1的表达和分布没有变化。然而，在暴露于DEX或DEX+PRL 24小时的亚汇合MDCK单层细胞中，观察到闭合蛋白和ZO-1的连接含量显著增加，而它们的总表达没有变化。在亚汇合条件下，激素处理后未检测到细胞增殖/生长的变化。仅在暴露于DEX+PRL后的汇合MDCK单层细胞中观察到活细胞总数增加，这表明这些激素对已建立的屏障的主要作用可能与抑制细胞死亡有关。总之，我们的数据表明，这些激素（特别是地塞米松）仅在MDCK上皮屏障形成过程中对TJ结构和功能有影响，可能是通过调节TJ蛋白在细胞间接触膜位点的定位、稳定性或组装来实现的。
