title: TGF-β1 induces the dissolution of tight junctions in human renal proximal tubular cells: role of the RhoA/ROCK signaling pathway.
abstract: The RhoA/ROCK signaling pathway plays a significant role in transforming growth factor (TGF)-β1-mediated epithelial-mesenchymal transition (EMT). It remains unclear, however, whether the RhoA/ROCK signaling pathway mediates TGF-β1-induced EMT by promoting the dissolution of tight junctions (TJs) in renal proximal tubular epithelial cells. In this study, we aimed to investigate the association between TGF-β1-mediated Rho/ROCK signaling and TJs in a cell line derived from human renal proximal tubular cells (HK-2 cells). HK-2 cells were treated with 5 ng/ml TGF-β1 for 0, 12, 24 and 48 h. Zona occludens protein 1 (also known as tight junction protein 1; ZO-1) and occludin mRNA and protein levels were determined by real-time PCR and western blot analysis, respectively. The HK-2 cells were then divided into three groups: a control group (serum-free culture medium for 24 h); a TGF-β1 group (treated with 5 ng/ml TGF-β1 for 24 h); and a TGF-β1 + Y-27632 (a specific ROCK inhibitor) group (pre-treated with 10 µM Y-27632 for 2 h and subsequently treated with 5 ng/ml TGF-β1 for 24 h). The levels of ZO-1 and occludin were detected by real-time PCR, western blot analysis and immunofluorescence. As shown by our results, the mRNA and protein levels of ZO-1 and occludin were decreased in the HK-2 cells following treatment with TGF-β1 in a time-dependent manner; in addition, ZO-1 and occludin levels in the TGF-β1 + Y-27632 group were significantly increased compared with those of the TGF-β1 group (P<0.05), with no significant changes compared with the control group. Our results indicate that the Rho/ROCK signaling pathway mediated by TGF-β1 plays a role in the dissolution of TJs during EMT.
authors.affiliation: Department of Nephrology, The Third Xiangya Hospital, Central South University, Changsha, Hunan 410013, P.R. China.
authors.forename: Ke
authors.initials: K
authors.lastname: Zhang
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Hui
authors.initials: H
authors.lastname: Xiang
authors.forename: Jishi
authors.initials: J
authors.lastname: Liu
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.forename: Xianming
authors.initials: X
authors.lastname: Zhang
authors.forename: Jianwen
authors.initials: J
authors.lastname: Wang
authors.forename: Youzhou
authors.initials: Y
authors.lastname: Tang
mesh_terms: D000577:Amides / Q000494:pharmacology; D002460:Cell Line; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000166:cytology*; D062793:Occludin / Q000235:genetics / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D019108:Tight Junctions / Q000187:drug effects* / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*; D062826:Zonula Occludens-1 Protein / Q000235:genetics / Q000378:metabolism; D054460:rho-Associated Kinases / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
chemical_list: D000577:Amides; D062793:Occludin; D011725:Pyridines; D053773:Transforming Growth Factor beta1; D062826:Zonula Occludens-1 Protein; C108830:Y 27632; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein