Inhibition of tumor-necrosis-factor-α induced endothelial cell activation by a new class of PPAR-γ agonists -: An in vitro study showing receptor-independent effects

Proinflammatory cytokines and adhesion molecules expressed by endothelial cells (ECs) play a critical role in initiating and promoting atherosclerosis. Agents that oppose these inflammatory effects in vascular cells include peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligands, including 15-deoxy-delta(12,14) -prostaglandin J2 (15d-PGJ2) and synthetic thiazolidinediones. Recently, a new structural class of potent PPAR-gamma agonists, 1,1-bis(3'-indolyl)1-( p-substituted phenyl) methanes, has been characterized. The purpose of this study was to evaluate the anti-inflammatory effects of two PPAR-gamma-active members of this class, 1,1- bis(3'-indolyl)-1-(p-t-butylphenyl)methane (DIM-C-pPhtBu) and 1,1-bis(3'- indolyl)-1-(pbiphenyl) methane (DIM-C-pPhC(6)H(5)), in ECs in vitro. Pretreatment of ECs with DIM-C-pPhC(6)H(5), DIM-C-pPhtBu, or 15d-PGJ2 decreased tumor necrosis factor-alpha (TNF-alpha)-induced intercellular adhesion molecule (ICAM)-1 expression in a concentration-dependent manner. At a concentration of 10 mu M, DIM-C-pPhtBu and DIM-C-pPhC(6)H(5) decreased ICAM-1expression by 77.5 and 71.3%, respectively, and comparable inhibition (84.4%) was observed for 10 mu M 15d-PGJ2 ( p < 0.05). In contrast, 10 mu M ciglitazone and DIM-C-pPhCH(3), which exhibits low PPAR-gamma agonist activity, were inactive. The two new PPAR-gamma agonists and 15d-PGJ2 also inhibited TNF-alpha-induced interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) production in supernatants of TNF-alpha-stimulated ECs, whereas ciglitazone and DIM-C-pPhCH 3 did not decrease TNF-alpha-induced expression of these two proteins. This new structural class of PPAR-gamma agonists inhibited the expression of ICAM-1 and the production of IL-6 and MCP-1 in TNF-alpha-activated ECs at lower concentrations than other synthetic PPAR-gamma agonists, suggesting the potential clinical utility of 1,1-bis(3'-indolyl)1-( p-substituted phenyl) methanes for decreasing endothelial inflammation. Copyright (C) 2005 S. Karger AG, Basel.