Activators of the peroxisome proliferator-activated receptor γ (PPARγ), originally found to be implicated in lipid metabolism and glucose homeostasis, have been shown to modulate inflammatory responses through interference with cytokine and chemokine production. Given the central role of mesangial cell-derived chemokines in glomerular leukocyte recruitment in human and experimental glomerulonephritis, we studied the influence of natural and synthetic PPARγ activators on INF-γ-induced expression of the T cell-attracting chemokines IP-10/CXCL10, Mig/CXCL9 and I-TAC/CXCL11 in mouse mesangial cells.Methods
INF-γ-treated mesangial cells were cultured in the presence or absence of either the naturally occurring PPARγ ligand 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) or synthetic PPARγ activators of the glitazone group. Chemokine mRNA and protein expression and activation of the JAK/STAT signalling pathway were analysed.Results
The 15d-PGJ2, but not synthetic PPARγ ligands, dose-dependently inhibited INF-γ-induced chemokine gene (mRNA and protein) expression. Combined results from EMSA and western blot analysis revealed the inhibitory ability of 15d-PGJ2, but not of synthetic PPARγ ligands, on IFN-γ-induced tyrosine phosphorylation of JAK1, JAK2, STAT1 and nuclear STAT1 translocation and DNA binding.Conclusions
Our results demonstrate that 15d-PGJ2 inhibits INF-γ-induced chemokine expression in mesangial cells by targeting the JAK/STAT signalling pathway. This effect is independent of an interference with PPARγ.