Integrin Signaling Laboratory, Department of Vascular Biology and Inflammation, Centro Nacional de Investigaciones Cardiovasculares (CNIC), Melchor Fernández Almagro 3, 28029 Madrid, Spain.
J Cell Sci. 2010 Dec 15;123(Pt 24):4321-31. doi: 10.1242/jcs.071647. Epub 2010 Nov 23.
Epithelial-to-mesenchymal transition (EMT) of peritoneal mesothelial cells is a pathological process that occurs during peritoneal dialysis. EMT leads to peritoneal fibrosis, ultrafiltration failure and eventually to the discontinuation of therapy. Signaling pathways involved in mesothelial EMT are thus of great interest, but are mostly unknown. We used primary mesothelial cells from human omentum to analyze the role of the p38 MAPK signaling pathway in the induction of EMT. The use of specific inhibitors, a dominant-negative p38 mutant and lentiviral silencing of p38α demonstrated that p38 promotes E-cadherin expression both in untreated cells and in cells co-stimulated with the EMT-inducing stimuli transforming growth factor (TGF)-β1 and interleukin (IL)-1β. p38 inhibition also led to disorganization and downregulation of cytokeratin filaments and zonula occludens (ZO)-1, whereas expression of vimentin was increased. Analysis of transcription factors that repress E-cadherin expression showed that p38 blockade inhibited expression of Snail1 while increasing expression of Twist. Nuclear translocation and transcriptional activity of p65 NF-κB, an important inducer of EMT, was increased by p38 inhibition. Moreover, p38 inhibition increased the phosphorylation of TGF-β-activated kinase 1 (TAK1), NF-κB and IκBα. The effect of p38 inhibition on E-cadherin expression was rescued by modulating the TAK1-NF-κB pathway. Our results demonstrate that p38 maintains E-cadherin expression by suppressing TAK1-NF-κB signaling, thus impeding the induction of EMT in human primary mesothelial cells. This represents a novel role of p38 as a brake or 'gatekeeper' of EMT induction by maintaining E-cadherin levels.
上皮-间充质转化（EMT）是腹膜间皮细胞在腹膜透析过程中发生的一种病理过程。EMT 导致腹膜纤维化、超滤衰竭，最终导致治疗中断。因此，参与间皮 EMT 的信号通路非常重要，但大多未知。我们使用人网膜原代间皮细胞分析 p38 MAPK 信号通路在 EMT 诱导中的作用。使用特异性抑制剂、p38 显性失活突变体和慢病毒沉默 p38α 表明，p38 在未经处理的细胞以及与 EMT 诱导刺激转化生长因子 (TGF)-β1 和白细胞介素 (IL)-1β 共同刺激的细胞中均促进 E-钙粘蛋白的表达。p38 抑制也导致细胞角蛋白丝和紧密连接蛋白 (ZO)-1 的紊乱和下调，而波形蛋白的表达增加。分析抑制 E-钙粘蛋白表达的转录因子表明，p38 阻断抑制了 Snail1 的表达，同时增加了 Twist 的表达。核转位和转录活性 p65 NF-κB，EMT 的重要诱导剂，被 p38 抑制所增强。此外，p38 抑制增加了 TGF-β 激活激酶 1 (TAK1)、NF-κB 和 IκBα 的磷酸化。通过调节 TAK1-NF-κB 途径，p38 抑制对 E-钙粘蛋白表达的影响得到挽救。我们的结果表明，p38 通过抑制 TAK1-NF-κB 信号来维持 E-钙粘蛋白的表达，从而阻碍人原代间皮细胞 EMT 的诱导。这代表了 p38 作为 EMT 诱导的“制动器”或“守门员”通过维持 E-钙粘蛋白水平的新作用。
