title: Attenuation of EMT in RPE cells and subretinal fibrosis by an RAR-γ agonist.
abstract: Subretinal fibrosis contributes to the loss of vision associated with age-related macular degeneration (AMD). Retinal pigment epithelial (RPE) cells play a key role in the pathogenesis of AMD including the fibrotic reaction. We examined the role of retinoic acid receptor-γ (RAR-γ) in the epithelial-mesenchymal transition (EMT) and other fibrosis-related processes in mouse RPE cells cultured in a type I collagen gel. Transforming growth factor-β2 (TGF-β2)-induced collagen gel contraction mediated by the RPE cells was inhibited by the RAR-γ agonist R667 in a concentration- and time-dependent manner. Expression of the mesenchymal markers α-smooth muscle actin and fibronectin, the release of interleukin-6, and the phosphorylation of paxillin, mitogen-activated protein kinases (ERK, p38, and JNK), Smad2, and AKT induced by TGF-β2 were also suppressed by the RAR-γ agonist. Furthermore, gelatin zymography and immunoblot analysis revealed that the TGF-β2-induced release of matrix metalloproteinase (MMP)-2, MMP-3, MMP-8, and MMP-9 from RPE cells was inhibited by R667, and the MMP inhibitor GM6001 attenuated TGF-β2-induced RPE cell contraction. Finally, immunohistofluorescence analysis with antibodies to glial fibrillary acidic protein showed that R667 inhibited the development of subretinal fibrosis in a mouse model in vivo. Our results thus suggest that RAR-γ agonists may prove effective for the treatment of subretinal fibrosis associated with AMD.
  
  
  CONCLUSIONS
  RAR-γ agonist R667 suppressed collagen gel contraction mediated by RPE cells. Epithelial-mesenchymal transition (EMT) in RPE cells was inhibited by RAR-γ agonist R667. RAR-γ agonist R667 inhibited fibrosis-related processes in RPE cells. RAR-γ agonists may attenuate AMD-associated fibrosis.
authors.affiliation: Department of Ophthalmology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube City, Yamaguchi, 755-8505, Japan, k.kimura@yamaguchi-u.ac.jp.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kimura
authors.forename: Tomoko
authors.initials: T
authors.lastname: Orita
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.forename: Yang
authors.initials: Y
authors.lastname: Yang
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Tokuda
authors.forename: Taishi
authors.initials: T
authors.lastname: Kurakazu
authors.forename: Takeshi
authors.initials: T
authors.lastname: Noda
authors.forename: Ryoji
authors.initials: R
authors.lastname: Yanai
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Morishige
authors.forename: Atsunobu
authors.initials: A
authors.lastname: Takeda
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Ishibashi
authors.forename: Koh-Hei
authors.initials: KH
authors.lastname: Sonoda
mesh_terms: D000199:Actins / Q000096:biosynthesis; D000818:Animals; D002460:Cell Line; D003094:Collagen / Q000378:metabolism; D004151:Dipeptides / Q000494:pharmacology; D058750:Epithelial-Mesenchymal Transition; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005353:Fibronectins / Q000096:biosynthesis; D005355:Fibrosis / Q000188:drug therapy* / Q000473:pathology; D005904:Glial Fibrillary Acidic Protein / Q000276:immunology; D015850:Interleukin-6 / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008268:Macular Degeneration / Q000473:pathology; D020782:Matrix Metalloproteinases / Q000378:metabolism; D051379:Mice; D051419:Paxillin / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology*; D018168:Receptors, Retinoic Acid / Q000819:agonists*; D012160:Retina / Q000473:pathology; D055213:Retinal Pigment Epithelium / Q000166:cytology*; D051899:Smad2 Protein / Q000378:metabolism; D053781:Transforming Growth Factor beta2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D000097768:Retinoic Acid Receptor gamma
chemical_list: D000199:Actins; D003094:Collagen; D004151:Dipeptides; D048049:Extracellular Signal-Regulated MAP Kinases; D005353:Fibronectins; D005904:Glial Fibrillary Acidic Protein; D015850:Interleukin-6; D048031:JNK Mitogen-Activated Protein Kinases; D020782:Matrix Metalloproteinases; D051419:Paxillin; D051057:Proto-Oncogene Proteins c-akt; D011720:Pyrazoles; D018168:Receptors, Retinoic Acid; D051899:Smad2 Protein; D053781:Transforming Growth Factor beta2; D048051:p38 Mitogen-Activated Protein Kinases; D000097768:Retinoic Acid Receptor gamma; C078131:N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide; C511499:R667 compound; C497783:Smad2 protein, mouse; C544013:alpha-smooth muscle actin, mouse