Troglitazone, a PPAR-gamma activator prevents endothelial cell adhesion molecule expression and lymphocyte adhesion mediated by TNF-alpha

Abstract

Background: Cytokine mediated induction of the mucosal addressin cell adhesion molecule-1(MAdCAM-1) expression is associated with the onset and progression of inflammatory bowel disease (IBD).

Results: Using western blotting and cell-based ELISA, we show in this study that troglitazone, an activator of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma), widely used in the treatment of diabetes, has as well recently been highlighted as protective in models of inflammation and cancer. We found that troglitazone (10-40 microM), significantly reduced the TNF-alpha (1 ng/ml) mediated induction of endothelial MAdCAM-1 in a dose-dependent manner, achieving a 34.7% to 98.4% reduction in induced MAdCAM-1. Trogliazone (20 microM) reduced TNF-alpha induced VCAM-1, ICAM-1 and E-selectin expression. Moreover, troglitazone significantly reduced alpha4beta7-integrin dependent lymphocyte adhesion to TNF-alpha cultured endothelial cells.

Conclusions: These results suggest that PPAR-gamma agonists like troglitazone may be useful in the clinical treatment of IBD.

Figure 1

PPAR-γ expression in SVEC endothelial cell. Western blotting for PPAR-γ in SVEC cells reveals a 55 kD band after reacting with anti-PPAR-γ peptide antibody, indicating that PPAR-γ is in fact present within the cells used in this study.

Figure 2

TNF-α induced MAdCAM-1 protein expression is reduced by troglitazone, a PPAR-γ ligand. TNF-α (1 ng/ml, 24 h) induced MAdCAM-1 expression was dose dependently blocked by the PPAR-γ ligand, troglitazone at concentrations between 10 to 40 μM (Fig. 2).

Figure 3

TNF-α induced VCAM-1 protein expression is reduced by troglitazone, a PPAR-γ ligand. TNF-α (1 ng/ml, 24 h) induced VCAM-1 expression was also blocked by the PPAR-γ ligand, troglitazone at 20 μM (Fig. 3). Alone, this compound had no effect on the expression of VCAM-1 (Fig. 3).

Figure 4

TNF-α induced ICAM-1 protein expression is reduced by troglitazone, a PPAR-γ ligand. TNF-α (1 ng/ml, 24 h) induced ICAM-1 expression was dose dependently blocked by the PPAR-γ ligand, troglitazone at 20 μM (Fig. 4). Alone, this compound had no effect on the expression of ICAM-1 (Fig. 4).

Figure 5

TNF-α induced E-selectin protein expression is reduced by troglitazone, a PPAR-γ ligand. TNF-α (1 ng/ml, 24 h) induced E-selectin expression was blocked by the PPAR-γ ligand, troglitazone at 20 μM (Fig. 5). Alone, this compound had no effect on the expression of E-selectin (Fig. 5).

Figure 6

Adhesion of α4β7 expressing lymphocytes (TK-1) to TNF-α stimulated endothelium. TNF-α stimulation (24 h) significantly increased adhesion of TK-1 lymphocytes to monolayers of SVEC cells. Troglitazone (20 μM) significantly reduced TK-1 adhesion in response to TNF-α stimulation at 24 h (Fig. 6).

Figure 7

TNF-α induced phosphorylation of NF-kB p65 is prevented by troglitazone, a PPAR-γ ligand. TNF-α (1 ng/ml, 1 h) induced phosphorylation of NF-kB p65 was significantly attenuated by the PPAR-γ ligand, troglitazone (20 μM). Alone, troglitazone also attenuated phosphorylation of NF-kB p65.