Potentiation of cytotoxicity by two metabolites of 3‐(3,5‐dichlorophenyl)‐2,4‐thiazolidinedione (DCPT) in HepG2 cells

Abstract

Previously, we showed that 3‐(3,5‐dichlorophenyl)‐2,4‐thiazolidinedione (DCPT) is cytotoxic in human hepatoma HepG2 cell line. DCPT is converted into [[(3,5‐dichlorophenyl)amino]carbonyl]thioglycolic acid (DCTA), which can potentially degrade into 3,5‐dichlorophenyl isocyanate (DPI) and mercaptoacetic acid (MAA). The goal of these studies was to determine which metabolite of DCPT is the proximal agent for toxicity. HepG2 cells were therefore incubated with 200 μM DCPT, DCTA, DPI, MAA or a combination of DPI plus MAA. Cell viability and proliferation were assessed over a 24 hr period. DCTA and the combination treatment (DPI plus MAA) were significantly more cytotoxic at 24 hr (~65% cell loss) than DCPT, DPI or MAA alone. To further study the cytotoxicity of the combination treatment (DPI plus MAA), HepG2 cells were pretreated (4 hr) with either 200 μM DPI or MAA, and then challenged with the alternative compound. The DPI pretreatment followed by MAA caused a loss in cell viability beginning at 2 hr. On the other hand, pretreatment with MAA followed by DPI caused a loss in viability at 24 hr. Our results suggest that the presence of both hydrolytic products of DCTA may contribute to DCPT cytotoxicity in HepG2 cells. Furthermore, there appears to be an additive/synergistic cytotoxic effect between DPI and MAA. Supported by PHS grant ES012499 and the USciences Department of Pharmaceutical Sciences.