Pigment epithelium-derived factor induces interleukin-10 expression in human macrophages by induction of PPAR gamma

In search for the anti-inflammation mechanism of PEDF, we investigate whether pigment epithelium-derived factor (PEDF) induces the gene expression of interleukin (IL)-10 in human macrophages and determine the molecular basis of this induction. Human macrophages derived from a monocytic cell line, THP-1, and peripheral monocytes were treated with PEDF. IL-10 expression was assessed by quantitative real-time PCR, enzyme-linked immunosorbent assay, semi-quantitative reverse transcriptase (RT)-PCR, and promoter–reporter assay. Activity of extracellular signal-regulated kinase 2 (ERK2) and p38 mitogen-activated protein kinase (MAPK) was assessed by immunoblotting using antibodies targeting phosphorylated kinases forms. Elk-1 and ATF-2 phosphorylation was determined as well. Pharmacological inhibitors were used to examine the involvement of ERK, p38 MAPK, and peroxisome proliferator-activated receptor gamma (PPARγ) on the IL-10 expression induced by PEDF. PEDF increased the levels of IL-10 mRNA and protein in THP-1 cells and human macrophages derived from peripheral monocytes. Blockade of activity of ERK or p38 MAPK attenuated PEDF effects on induction of PPARγ and IL-10. PEDF increased the transcriptional activity of IL-10 promoter. The effect was synergistically augmented by PPARγ agonist, but attenuated by inhibitors of PPARγ, ERK or p38 MAPK. These results showed that PEDF promotes IL-10 expression at transcriptional level, and that this is achieved through the ERK2/p38MAPK-dependent PPARγ expression. The anti-inflammatory property of PEDF may in part through the induction of IL-10 in macrophages. Our study supports the therapeutic potential of PEDF and PPARγ agonists in inflammatory diseases.