Di(2-ethylhexyl) Phthalate Induces Apoptosis Through Peroxisome Proliferators-Activated Receptor-Gamma and ERK 1/2 Activation in Testis of Sprague-Dawley Rats

Abstract

Di(2-ethylhexyl) phthalate (DEHP) is a well-known hepatic and reproductive toxicant whose toxicity may be mediated by peroxisome proliferators-activated receptor (PPAR). This study examined the effects of DEHP on the expression of PPAR-regulated genes involved in testicular cells apoptosis. Sprague-Dawley male rats were treated orally with 250, 500, or 750 mg/kg/d DEHP for 28 d, while control rats were given corn oil. The levels of cell cycle regulators (pRb, cyclins, CDKs, and p21) and apoptosis-related proteins were analyzed by Western blot analysis. The role of PPAR-gamma (PPAR-γ), class B scavenger receptor type 1 (SR-B1), and ERK1/2 was further studied to examine the signaling pathway for DEHP-induced apoptosis. Results showed that the levels of pRB, cyclin D, CDK2, cyclin E, and CDK4 were significantly lower in rats given 500 and 750 mg/kg/d DEHP, while levels of p21 were significantly higher in rat testes. Dose-dependent increases in PPAR-γ and RXRα proteins were observed in testes after DEHP exposure, while there was a significant decrease in RXRγ protein levels. In addition to PPAR-γ, DEHP also significantly increased SR-B1 mRNA and phosphorylated ERK1/2 protein levels. Furthermore, DEHP treatment induced pro-caspase-3 and cleavage of its substrate protein, poly(ADP-ribose) polymerase (PARP), in a dose-dependent manner. Data suggest that DEHP exposure may induce the expression of apoptosis-related genes in testes through induction of PPAR-γ and activation of the ERK1/2 pathway.

This work was supported in part by the Korea Research Foundation (KRF-2004-041-E00392) through a grant funded by the Korean Government. J. J. Ryu was supported by grants from the Brain Korea 21 project.