Enhanced VDUP-1 gene expression by PPARγ agonist induces apoptosis in human mlacrophage

The fate and phenotype of lesion macrophages is regulated by cellular oxidative stress. Thioredoxin-1 (Trx-1) plays a major role in the regulation of cellular redox balance, with resultant effects on gene expression and cellular responses including cell growth and death. Trx-1 activity is inhibited by interaction with vitamin D-upregulated protein-1 (VDUP-1). Peroxisome proliferator-activated receptor gamma (PPAR gamma) is expressed by human monocyte-derived macrophages (HMDM) and PPAR gamma agonism has been reported to decrease expression of inflammatory genes and to promote apoptosis of these cells. To determine whether VDUP-1 may be involved in regulating the effects of PPAR gamma agonists in macrophages, we investigated the effect of a synthetic PPAR gamma agonist (GW929) on the expression of VDUP-1 in HMDM. GW929 concentration-dependently increased HMDM expression of VDUP-1 (mRNA and protein). Transfection of different fragments of the VDUP-1 promoter as well as gel shift analysis revealed the presence of functional PPAR gamma response elements (PPRE) in the promoter. Under conditions in which PPAR agonism altered levels of VDUP-1, caspase-3 activity, and macrophage apoptosis were also elevated. The results suggest that PPAR gamma activation stimulates apoptosis in human macrophages by altering the cellular redox balance via regulation of VDUP-1.