Inhibitory effects of PPARγ ligands on TGF-β1-induced CTGF expression in cat corneal fibroblasts. (September 2015)

• Record Type: Journal Article
• Authors: Jeon, Kye-Im; Phipps, Richard P.; Sime, Patricia J.; Huxlin, Krystel R.
• Is Part Of: Experimental eye research. Volume 138(2015:Sep.)
• Page Start: 52
• Page End: 58
• Publication Date: 2015-09
• Subjects: Rosiglitazone -- Troglitazone -- 15d-PGJ2 -- JNK -- p38 MAPK -- ERK -- AKT; CTGF connective tissue growth factor -- CCN cyr61, ctgf, neuroblastoma over-expressed gene -- Nov neuroblastoma over-expressed gene -- ECM extracellular matrix -- PRK photorefractive keratectomy -- PPARγ peroxisome proliferator activated receptor gamma -- 15d-PGJ2 15-deoxy-delta 12, 14-prostaglandin J2 -- UCAR University of Rochester Committee on Animal Research -- TGF-β transforming growth factor-beta -- αSMA alpha smooth muscle actin -- MAPK mitogen-activated protein kinase -- JNK c-jun N-terminal kinase -- AKT protein kinase B -- ERK extracellular signal-regulated kinase -- FGF fibroblast growth factor -- LPR1 low-density lipoprotein receptor-related protein-1 -- M6P/IGF-2-R mannose 6-phosphate/insulin-like growth factor 2 receptor -- epidermal growth factor (EGF) insulin-like growth factor (IGF)-2 -- mouse embryonic fibroblasts (MEFs) focal adhesion kinase (FAK); Ophthalmology -- Periodicals; Eye -- Periodicals; Œil -- Périodiques; Ophthalmology; Periodicals; Electronic journals; 612.8405
• DOI: 10.1016/j.exer.2015.06.028
• Languages: English
• ISSNs: 0014-4835

Abstract

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. Highlights: TGFβ increases the expression of CTGF and αSMA in cultured cat corneal fibroblasts. CTGF siRNA blocks TGFβ-induced myofibroblast differentiation in corneal fibroblasts. PPARγ ligands block TGFβ-induced up-regulation of CTGF, independently of p38 MAPK.