PPAR-alpha ligands inhibit H2O2-mediated activation of transforming growth factor-beta1 in human mesangial cells.
Transforming growth factor-beta1 (TGF-beta1) mediates the development of glomerulosclerosis by stimulating mesangial cell production of extracellular matrix (ECM) proteins. TGF-beta1 and several ECM genes are regulated by promoter O-tetradecanoylphorbol 13-acetate-responsive elements (TREs) that are transactivated by the activator protein-1 (AP-1) transcription factor complex. AP-1-TRE interactions are regulated by redox changes. Recently, peroxisome proliferator-activated receptors (PPARs) were shown to negatively regulate several transcription factor families. In these studies, we postulated that PPAR-alpha could antagonize TGF-beta1 expression by cultured human mesangial cells (HMC). A TGF-beta1 luciferase expression plasmid was transduced into HMC via recombinant deficient adenoviral vectors. The TGF-beta1 promoter activity increased twofold (209%) following 18-h treatments with H(2)O(2) (1,000 micro M). Using RT-PCR, we demonstrated that HMC possess PPAR-alpha RNA, and PPAR-alpha protein was identified by immunohistochemistry. Pretreatment of cells with the PPAR-alpha ligands WY14643 (100-500 micro M) or clofibrate (100-500 micro M) dose-dependently inhibited oxidant-mediated induction of TGF-beta1. This inhibition occurred without affecting the H(2)O(2)-mediated activation of the mitogen-activated protein kinase (MAPK) pathways extracellular regulated kinase, p38 MAPK, or Jun N-terminal kinase, which are responsible for the regulation of AP-1 phosphorylation. These studies are the first to identify PPAR-alpha expression by HMC. The results of these studies suggest that TGF-beta1 expression mediated by oxidant stress may be suppressible by PPAR-alpha activation.
Wilmer
William A
WA
Division of Nephrology, The Department of Internal Medicine, Dorothy M. Davis Heart-Lung Research Institute, The Ohio State University College of Medicine, Columbus, OH 43210, USA. wilmer.1@osu.edu
Dixon
Cynthia L
CL
Hebert
Courtney
C
Lu
Ling
L
Rovin
Brad H
BH
D002478:Cells, Cultured; D002994:Clofibrate / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005822:Genetic Vectors; D005920:Glomerular Mesangium / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D007150:Immunohistochemistry; D008024:Ligands; D008156:Luciferases / Q000235:genetics; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010957:Plasmids; D011401:Promoter Regions, Genetic / Q000502:physiology; D011743:Pyrimidines / Q000494:pharmacology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism* / Q000494:pharmacology; D014161:Transduction, Genetic; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D053773:Transforming Growth Factor beta1
D008024:Ligands; D011743:Pyrimidines; D018160:Receptors, Cytoplasmic and Nuclear; C508960:TGFB1 protein, human; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; C006253:pirinixic acid; D006861:Hydrogen Peroxide; D008156:Luciferases; D020928:Mitogen-Activated Protein Kinases; D002994:Clofibrate