title: Inhibitory effects of PPARγ ligands on TGF-β1-induced CTGF expression in cat corneal fibroblasts.
abstract: Ligands of Peroxisome Proliferator Activated Receptor gamma (PPARγ) possess strong anti-fibrotic properties in the cornea and several other body tissues. In the cornea, we recently showed this class of molecules to prevent stromal myofibroblast differentiation partially by blocking the actions of p38 mitogen-activated protein kinase (MAPK). However, given the important role assigned to connective tissue growth factor (CTGF) in mediating corneal fibrosis, here we asked whether PPARγ ligands also act by affecting transforming growth factor-β (TGF-β) 1-induced expression of CTGF in cultured corneal fibroblasts. Corneal keratocytes were isolated from young, adult cats and early passage cells were exposed to TGF-β1 with or without the PPARγ ligands Rosiglitazone, Troglitazone and 15d-PGJ2. Western blots were used to assay levels of CTGF and alpha smooth muscle actin (αSMA), a marker of myofibroblast differentiation. CTGF siRNA demonstrated a critical role for CTGF in TGF-β1-mediated myofibroblast differentiation, while exogenously applied CTGF potentiated the pro-fibrogenic effects of TGF-β1. TGF-β1-mediated increases in CTGF and αSMA expression were strongly inhibited by all three PPARγ ligands tested, and by a c-jun N-terminal kinase (JNK) inhibitor. However, while extracellular signal-regulated kinase (ERK) 1/2, protein kinase B (AKT) and p38 MAPK inhibitors also blocked TGF-β1-induced αSMA induction, they did not dampen TGF-β1-induced increases in levels of CTGF. Thus, we conclude that PPARγ ligands block TGF-β1-induced increases in CTGF levels in cat corneal fibroblasts. They appear to do this in addition to their anti-fibrotic effect on p38 MAPK, providing a second intracellular pathway by which PPARγ ligands block αSMA induction.
authors.affiliation: Flaum Eye Institute, University of Rochester, Rochester, NY, USA.
authors.forename: Kye-Im
authors.initials: KI
authors.lastname: Jeon
authors.affiliation: Flaum Eye Institute, University of Rochester, Rochester, NY, USA; Department of Environmental Medicine, University of Rochester, Rochester, NY, USA; Department of Medicine, University of Rochester, Rochester, NY, USA.
authors.forename: Richard P
authors.initials: RP
authors.lastname: Phipps
authors.affiliation: Department of Environmental Medicine, University of Rochester, Rochester, NY, USA; Department of Medicine, University of Rochester, Rochester, NY, USA.
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Sime
authors.affiliation: Flaum Eye Institute, University of Rochester, Rochester, NY, USA; Center for Visual Science, University of Rochester, Rochester, NY, USA. Electronic address: huxlin@cvs.rochester.edu.
authors.forename: Krystel R
authors.initials: KR
authors.lastname: Huxlin
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002415:Cats; D002478:Cells, Cultured; D002839:Chromans / Q000494:pharmacology; D024042:Collagen Type I / Q000378:metabolism; D055513:Connective Tissue Growth Factor / Q000235:genetics / Q000378:metabolism*; D060527:Corneal Keratocytes / Q000187:drug effects* / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008024:Ligands; D047495:PPAR gamma / Q000378:metabolism*; D015230:Prostaglandin D2 / Q000031:analogs & derivatives / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D000077154:Rosiglitazone; D045162:Thiazolidinediones / Q000494:pharmacology; D053773:Transforming Growth Factor beta1 / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D000077288:Troglitazone; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: C477819:15-deoxyprostaglandin J2; D000199:Actins; D002839:Chromans; D024042:Collagen Type I; D005353:Fibronectins; D007004:Hypoglycemic Agents; D008024:Ligands; D047495:PPAR gamma; D034741:RNA, Small Interfering; D045162:Thiazolidinediones; D053773:Transforming Growth Factor beta1; D000077154:Rosiglitazone; D055513:Connective Tissue Growth Factor; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D000077288:Troglitazone; D015230:Prostaglandin D2
keywords: 15d-PGJ2; AKT; ERK; JNK; Rosiglitazone; Troglitazone; p38 MAPK