Introduction
Drug-induced liver injury (DILI) is a major global health concern and a leading cause of acute liver failure. While intrinsic DILI, such as that caused by acetaminophen, is dose-dependent and predictable, idiosyncratic DILI (iDILI) occurs unpredictably at therapeutic doses. The incidence of iDILI is rising due to polypharmacy, aging populations, and increased use of herbal products. Although host factors such as age, immune response, and genetic variants (e.g., HLA alleles) influence susceptibility, they are not fully predictive. Emerging evidence points to acquired conditions—such as exposure to persistent organic pollutants (POPs) and preexisting hepatic steatosis—as contributors to iDILI by altering liver susceptibility and enhancing drug toxicity.

Methods
We used Upcyte human hepatocytes, which retain key metabolic and transport functions of primary liver cells. Hepatocytes were exposed to the POPs Bisphenol A (BPA) and Perfluorooctanoic acid (PFOA), with or without co-treatment with azathioprine, valproic acid (VPA), or amoxicillin/clavulanic acid. Cell viability was assessed using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. To model hepatic steatosis, cells were preincubated with 0.2 mM oleate/palmitate (2:1) for 44 hours. Triglyceride (TG) accumulation was measured using a fluorescence-based assay.

Results
A synergistic cytotoxic effect was observed in cells co-treated with azathioprine plus BPA, VPA plus BPA, and amoxicillin/clavulanic acid plus PFOA. Metabolic steatosis preconditioning enhanced TG accumulation when combined with azathioprine or VPA. Interestingly, BPA reduced the steatotic effect of VPA, possibly because BPA may operate as an antisteatotic polyphenol or due to modulation of estrogen receptor activity.

Conclusions
These preliminary findings suggest that environmental exposures and hepatic steatosis modulate drug toxicity and may increase susceptibility to iDILI. POPs like BPA and PFOA can exacerbate hepatotoxicity, highlighting the importance of including such factors in risk assessment and prevention strategies for drug-induced liver injury.