In vitro studies of the biochemical toxicity of perfluorooctane sulfonic acid and its possible interaction with 2,3,7,8-tetrachlorodibenzo- P-dioxin

In the current study, three aspects of the biochemical toxicity of perfluorooctane sulfonic acid (PFOS) were investigated using in vitro cell culture systems. The effects of PFOS on aryl hydrocarbon receptor (AhR) mediated cytochrome P4501A1 (CYP1A1) activity were tested using in vitro cell bioassays. The results showed that PFOS had neither adverse effect on cell viability nor direct effect on CYP1A1 activity within the dose range tested. However when cells were dosed with PFOS and TCDD in combination, interactive effects on both CYP1A1 induction and AhR activation were observed at environmentally relevant concentrations, in which PFOS increased the effects of TCDD by 30--40%. It was further tested with time course experiment and transcription inhibition experiment that this interactive effect possibly occurred at transcriptional level. In addition, the effects of PFOS on gap junctional intercellular communication (GJIC) were tested. PFOS inhibited GJIC in a dose-dependent manner, and the inhibitory effect occurred in a very short time period. It was proven that this inhibitory effect was neither species-specific nor tissue-specific. Finally aromatase assay was conducted, results from which indicated that PFOS at a concentration of 50 mg/L could induce aromatase activity in vitro by 1.5 fold for 24 hrs exposure, and by 1.7 fold for 48 hrs exposure for PFOS concentration at 10 mg/L and 50 mg/L.