Title: Peroxisome proliferator-activated receptor gamma is required for the inhibitory effect of ciglitazone but not 15-deoxy-Delta 12,14-prostaglandin J2 on the NFkappaB pathway in human endothelial cells.
Authors: Kaplan, Jennifer; Cook, James A; O'Connor, Michael; Zingarelli, Basilia
Published In Shock, (2007 Dec)
Abstract: Peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-activated nuclear receptor with effects on inflammation, atherosclerosis, and apoptosis. The endogenous PPARgamma ligand, 15-deoxy-Delta12,14-PGJ2 (15d-PGJ2), and the synthetic ligand, ciglitazone, have anti-inflammatory properties in endothelial cells. In addition to PPARgamma-dependent effects on the anti-inflammatory process, it has been proposed that PPARgamma ligands may also inhibit the nuclear transcription factor kappaB (NFkappaB) pathway in a PPARgamma-independent manner. The purpose of this study was to compare the effects of 15d-PGJ2 and ciglitazone on the cytokine-induced activation of the NFkappaB pathway. Human umbilical vein endothelial cells (HUVECs) were transiently transfected with NFkappaB-luciferase or PPARgamma elements-luciferase reporter constructs for 48 h. The HUVECs were pretreated with 15d-PGJ2 or ciglitazone (30 microM) for 1 h, followed by a 4-h stimulation with tumor necrosis factor alpha (100 U/mL). Luciferase assay was performed to determine reporter activity. Additionally, HUVECs were transiently transfected with a dominant-negative mutant, which retains ligand and DNA binding but exhibits markedly reduced transactivation. Stimulation of HUVEC with tumor necrosis factor alpha increased NFkappaB activation while decreasing PPARgamma activity. Overexpression of a dominant-negative PPARgamma mutant prevented the inhibitory effect of ciglitazone on cytokine-induced NFkappaB activation in transfected human endothelial cells. Conversely, 15d-PGJ2 inhibited the cytokine-induced NFkappaB activation even in the absence of PPARgamma. Our data suggest that 15d-PGJ2 exerts direct inhibitory effects on the NFkappaB pathway through a PPARgamma-independent mechanism. On the contrary, the inhibitory effect of ciglitazone on the NFkappaB pathway seems to require PPARgamma activation.
PubMed ID: 17621259
MeSH Terms: Cells, Cultured; Cyclooxygenase 2/metabolism; Dose-Response Relationship, Drug; E-Selectin/metabolism; Endothelial Cells/cytology; Endothelial Cells/drug effects*; Endothelial Cells/metabolism; Enzyme-Linked Immunosorbent Assay; Humans; Intercellular Adhesion Molecule-1/metabolism; Luciferases/genetics; Luciferases/metabolism; Mutation; NF-kappa B/genetics; NF-kappa B/metabolism*; PPAR gamma/genetics; PPAR gamma/metabolism*; Prostaglandin D2/analogs & derivatives*; Prostaglandin D2/pharmacology; Recombinant Fusion Proteins/genetics; Recombinant Fusion Proteins/metabolism; Signal Transduction/drug effects; Thiazolidinediones/pharmacology*; Transfection; Tumor Necrosis Factor-alpha/pharmacology; Vascular Cell Adhesion Molecule-1/metabolism