title: Hypoxia-inducible factor prolyl-hydroxylase-2 mediates transforming growth factor beta 1-induced epithelial-mesenchymal transition in renal tubular cells.
abstract: Transforming growth factor beta 1 (TGF-β1)-induced epithelial-mesenchymal transition (EMT) in kidney epithelial cells plays a key role in renal tubulointerstitial fibrosis in chronic kidney diseases. As hypoxia-inducible factor (HIF)-1α is found to mediate TGF-β1-induced signaling pathway, we tested the hypothesis that HIF-1α and its upstream regulator prolyl hydroxylase domain-containing proteins (PHDs) are involved in TGF-β1-induced EMT using cultured renal tubular cells. Our results showed that TGF-β1 stimulated EMT in renal tubular cells as indicated by the significant decrease in epithelial marker P-cadherin, and the increase in mesenchymal markers α-smooth muscle actin (α-SMA) and fibroblast-specific protein 1 (FSP-1). Meanwhile, we found that TGF-β1 time-dependently increased HIF-1α and that HIF-1α siRNA significantly inhibited TGF-β1-induced EMT, suggesting that HIF-1α mediated TGF-β1 induced-EMT. Real-time PCR showed that PHD1 and PHD2, rather than PHD3, could be detected, with PHD2 as the predominant form of PHDs (PHD1:PHD2=0.21:1.0). Importantly, PHD2 mRNA and protein, but not PHD1, were decreased by TGF-β1. Furthermore, over-expression of PHD2 transgene almost fully prevented TGF-β1-induced HIF-1α accumulation and EMT marker changes, indicating that PHD2 is involved in TGF-β1-induced EMT. Finally, Smad2/3 inhibitor SB431542 prevented TGF-β1-induced PHD2 decrease, suggesting that Smad2/3 may mediate TGF-β1-induced EMT through PHD2/HIF-1α pathway. It is concluded that TGF-β1 decreased PHD2 expression via an Smad-dependent signaling pathway, thereby leading to HIF-1α accumulation and then EMT in renal tubular cells. The present study suggests that PHD2/HIF-1α is a novel signaling pathway mediating the fibrogenic effect of TGF-β1, and may be a new therapeutic target in chronic kidney diseases.
authors: Department of Pharmacology & Toxicology, Virginia Commonwealth University, Richmond, VA, USA.
authors: Wei-Qing
authors: WQ
authors: Han
authors: Qing
authors: Q
authors: Zhu
authors: Junping
authors: J
authors: Hu
authors: Pin-Lan
authors: PL
authors: Li
authors: Fan
authors: F
authors: Zhang
authors: Ningjun
authors: N
authors: Li
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D058750:Epithelial-Mesenchymal Transition; D005455:Fluorescent Antibody Technique; D000860:Hypoxia / Q000378:metabolism* / Q000473:pathology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases; D007684:Kidney Tubules / Q000166:cytology / Q000378:metabolism*; D011393:Procollagen-Proline Dioxygenase / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism*
chemical_list: C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D053773:Transforming Growth Factor beta1; D011393:Procollagen-Proline Dioxygenase; C580731:Egln1 protein, rat; D064799:Hypoxia-Inducible Factor-Proline Dioxygenases