Inhibition of Transforming Growth Factor-Activated Kinase 1 (TAK1) Blocks and Reverses Epithelial to Mesenchymal Transition of Mesothelial Cells

Abstract

Peritoneal fibrosis is a frequent complication of peritoneal dialysis following repeated low grade inflammatory and pro-fibrotic insults. This pathological process may lead to ultrafiltration failure and eventually to the discontinuing of the therapy. Fibrosis is linked to epithelial to mesenchymal transition (EMT) of the peritoneal mesothelial cells, which acquire invasive and fibrogenic abilities. Here, we analyzed the role of the transforming growth factor-activated kinase-1 (TAK1) in the EMT of primary mesothelial cells from human peritoneum. The inhibition of TAK1 in mesenchymal-like mesothelial cells from the effluents of patients undergoing peritoneal dialysis led to the reacquisition of the apical to basolateral polarity, to increased expression of epithelial and to down-regulation of mesenchymal markers. TAK1 inhibition also resulted in decreased migratory/invasive abilities of effluent-derived mesothelial cells. Simultaneous inhibition of ERK1/2 and TAK1 pathways did not lead to an additive effect in the reacquisition of the epithelial phenotype. Inhibition of TAK1 also blocked EMT in vitro and reduced the levels of PAI-1, which is involved in fibrosis and invasion. Analysis of signalling pathways downstream of TAK1 involved in EMT induction, showed that TAK1 inhibition reduced the transcriptional activity of NF-κB and Smad3, as well as the phosphorylation of c-jun, while enhancing Smad1–5–8 activity. These results demonstrate that TAK1 is a cross-point in a network including different pro-EMT transcription factors, such as NF-κB, Snail, AP-1 and Smads. The identification of TAK1 as a main biochemical mediator of EMT and fibrosis in mesothelial cells from human peritoneum and the study of signalling pathways induced by its activity may be relevant in the design of new therapies aimed to counteract peritoneal fibrosis.

Carcinoma‐associated fibroblasts derive from mesothelial cells via mesothelial‐to‐mesenchymal transition in peritoneal metastasis

“…The enhanced invasion triggered by tumour cells could be a consequence of the acquisition of a mesenchymal phenotype by MCs. In fact, we have previously demonstrated that during the MMT process, MCs increase their migration/invasion capacity . MCs that have invaded the matrix could, in turn, further promote the invasion of carcinoma cells.…”

“…To induce MMT with conditioned media, omentum MCs were treated with 75% of carcinoma cell supernatants for 72 h or 6 days, as described in Supplementary materials and methods. As a control of MMT in vitro, MCs were treated with 0.5 ng/ml transforming growth factor-β1 (TGFβ1) plus 2.5 ng/ml interleukin-1β (IL-1β; R&D Systems) for 72 h or 6 days, which has been shown to be a suitable MMT model [7,8,23]. To interfere with the MMT process, omentum MCs were treated for 72 h with SKOV-3-conditioned medium or with TGFβ1 (1 ng/ml) in the presence or absence of a selective inhibitor of the TGFβ type I receptor Carcinoma-associated fibroblasts and mesothelial cells 519 material, Table S1) or western blot in mesothelial and SKOV-3 cells, as described in Supplementary materials and methods.…”

Mesothelial-to-mesenchymal transition in the pathogenesis of post-surgical peritoneal adhesions

“…Numerous experimental models of peritoneal fibrosis have demonstrated that treatments directed against MMT, or against the MMT-promoting stimuli, reduce the accumulation of myofibroblasts and ameliorate submesothelial fibrosis and angiogenesis, improving peritoneal structure and function [17,44,[55][56][57][58][59][60][61]. Thus, it is tempting to speculate that MMT may also be a therapeutic target to diminish the formation of PAs.…”

Stabilization of ATF5 by TAK1–Nemo-Like Kinase Critically Regulates the Interleukin-1β-Stimulated C/EBP Signaling Pathway

“…Because several studies showed that TAK1 is an upstream regulator of NLK (2,3,5,37,42,43) and a downstream effector of IL-1␤-triggered signaling (22,23,(44)(45)(46), we examined the roles of TAK1 in ATF5 stabilization and C/EBP activation. In accordance with the results of the NLK experiments, overexpression of TAK1 activated C/EBP in cooperation with ATF5 in HEK293T cells (Fig.…”