Di-N-octylphthalate acts as a proliferative agent in murine cell hepatocytes by regulating the levels of TGF-β and pro-apoptotic proteins.

Di-n-octylphthalate (DNOP) is a phthalate used in the manufacturing of a wide variety of polyvinyl chloride-containing medical and consumer products. A study on chronic exposure to DNOP in rodents showed the development of pre-neoplastic hepatic lesions following exposure to a tumor initiator. The objective of this study was to identify the mechanisms by which DNOP leads to pre-neoplastic hepatic lesions. Mouse hepatocyte AML-12 and FL83B cells were treated with DNOP. The rate of cell proliferation was increased in treated cells in a concentration-dependent manner. DNOP increased the expression of transforming growth factor-β (tgf-β) in both cell lines, and primary culture mouse hepatocytes. The TGF-β receptor inhibitor LY2109761 impaired the effect of DNOP. The presence of pro-apoptotic proteins decreased in the presence of DNOP. Our observation indicates that DNOP, through an increase in the expression of tgf-β and a decrease in the levels of pro-apoptotic proteins, acts as a proliferative agent in normal mouse hepatocytes. We also studied the morphological and functional changes of the mouse liver upon a short-term treatment of DNOP. Mice exposed to DNOP displayed an epithelial-to-mesenchymal transition and cholestasis, which was reflected in an increase in hepatic bile acids and glutathione levels.