Di-n-butyl phthalate modifies PMA-induced macrophage differentiation of THP-1 monocytes via PPARγ

The present study examined the effects of di-n-butyl phthalate (DBP) on phorbol myristate acetate (PMA)-induced macrophage differentiation of THP-1 monocytes, determined by morphological classification and flow cytometry. Focusing on the expression of the surface marker CD36, the potential role of peroxisome proliferator-activated receptor gamma (PPAR gamma) was examined using various PPAR gamma agonists and antagonists. As the PPAR gamma ligand-binding domain contains multiple ligand-binding sites (LBS), agonist and antagonists targeting the different sites were used. DBP accelerated PMA-induced morphological changes and increased expression of CD36, although to a lesser degree than the PPAR gamma agonists rosiglitazone and 15-deoxy-Delta 12,14-prostaglandin J(2) (15d-PGJ(2)). A proteomics screening revealed that DBP enhanced the expression of PPAR gamma-regulated proteins. During combined exposures, DBP partly attenuated the effect of rosiglitazone, an agonist binding reversibly to PPAR gamma's canonical LBS. In contrast, DBP increased expression of CD36 in combination with 15d-PGJ(2) which binds irreversibly to the canonical LBS. Thus, DBP appears to interact with both the canonical and alternative LBS. Accordingly, the antagonist GW9662, which binds to the canonical LBS, only partly reduced the DBP-induced CD36 expression, while the dual-site antagonist SR16832 completely blocked the effects of DBP. Overall, the results show that DBP modifies PMA-induced differentiation of THP-1 cells through interaction with PPAR gamma.