title: Dioscorea alata attenuates renal interstitial cellular fibrosis by regulating Smad- and epithelial-mesenchymal transition signaling pathways.
abstract: Renal interstitial fibrosis is characterized by increased extracellular matrix (ECM) synthesis. Epithelial-mesenchymal transition (EMT) in kidneys is driven by regulated expression of fibrogenic cytokines such as transforming growth factor-beta (TGF-β). Yam, or Dioscorea alata (DA) is an important herb in Chinese medicine widely used for the treatment of clinical diabetes mellitus. However, the fibrosis regulatory effect of DA is unclear. Thus, we examined TGF-β signaling mechanisms against EMT in rat fibroblast cells (NRK-49F). The characterization of DA water-extracts used various methods; after inducing cellular fibrosis in NRK-49F cells by treatment with β-hydroxybutyrate (β-HB) (10 mM), we used Western blotting to examine the protein expression in the TGF-β-related signal protein type I and type II TGF-β receptors, Smads2 and Smad3 (Smad2/3), pSmad2 and Smad3 (pSmad2/3), Smads4, Smads7, and EMT markers. These markers included E-cadherin, alpha-smooth muscle actin (α-SMA), and matrix metalloproteinase-2 (MMP-2). Bioactive TGF-β and fibronectin levels in the culture media were determined using ELISA. Expressions of fibronectin and Snail transcription factor, an EMT-regulatory transcription factor, were assessed by immunofluorescence staining. DA extract dose-dependently (50-200 µg/mL) suppressed β-HB-induced expression of fibronectin in NRK-49F cells concomitantly with the inhibition of Smad2/3, pSmad2/3, and Smad4. By contrast, Smad7 expression was significantly increased. DA extract caused a decrease in α-SMA (α-smooth muscle actin) and MMP-2 levels, and an increase in E-cadherin expression. We propose that DA extract might act as a novel fibrosis antagonist, which acts partly by down regulating the TGF-β/smad signaling pathway and modulating EMT expression.
authors.affiliation: Department of Internal Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Shu-Fen
authors.initials: SF
authors.lastname: Liu
authors.forename: Shan-Yu
authors.initials: SY
authors.lastname: Chang
authors.forename: Tao-Chen
authors.initials: TC
authors.lastname: Lee
authors.forename: Lea-Yea
authors.initials: LY
authors.lastname: Chuang
authors.forename: Jinn-Yuh
authors.initials: JY
authors.lastname: Guh
authors.forename: Chien-Ya
authors.initials: CY
authors.lastname: Hung
authors.forename: Tsung-Jen
authors.initials: TJ
authors.lastname: Hung
authors.forename: Yu-Ju
authors.initials: YJ
authors.lastname: Hung
authors.forename: Po-Yi
authors.initials: PY
authors.lastname: Chen
authors.forename: Pei-fang
authors.initials: PF
authors.lastname: Hsieh
authors.forename: Yu-Lin
authors.initials: YL
authors.lastname: Yang
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000378:metabolism; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004365:Drugs, Chinese Herbal / Q000627:therapeutic use*; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects*; D005353:Fibronectins / Q000378:metabolism; D005355:Fibrosis / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D007674:Kidney Diseases / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology*; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D051896:Smad Proteins, Receptor-Regulated / Q000378:metabolism*; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism
chemical_list: D015820:Cadherins; D004365:Drugs, Chinese Herbal; D005353:Fibronectins; D051896:Smad Proteins, Receptor-Regulated; C000604450:Snai2 protein, rat; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D020155:3-Hydroxybutyric Acid