Underlying mechanisms of metabolic dysfunction-associated steatotic liver disease induced by 2-ethylhexyl diphenyl phosphate and its hydroxylated metabolite in zebrafish (Danio rerio).

2-Ethylhexyl diphenyl phosphate (EHDPHP) is ubiquitous in various environmental media and organisms. Due to its susceptibility to biotransformation, its primary product 2-ethyl-5-hydroxyhexyl diphenyl phosphate (5-OH-EHDPHP) is almost at equal level in organisms. However, their hepatotoxicity remains unclear. In this study, adult zebrafish were exposed to 5, 35, or 245 µg/L of EHDPHP for 28 days. Distinct metabolic dysfunction-associated steatotic liver disease (MASLD) was observed in treated zebrafish, indicated by increased hepatic lipid levels (total cholesterol, triglycerides, nonesterified fatty acids, and fat droplets), steatosis (hepatic ballooning), and inflammation (tnf-α and il-6). Combined the in vitro hepatic cell test, molecular docking and molecular dynamics simulation, it was revealed that peroxisome proliferator-activated receptor gamma (pparγ) was upregulated upon EHDPHP exposure, thereby facilitating lipid synthesis and hepatic lipid accumulation. Notably, its main metabolite 5-OH-EHDPHP induced stronger hepatocyte toxicity and PPARγ transcription. Additionally, serious liver function damage was observed, with aspartate aminotransferase, alanine transaminase, albumin, and γ-glutamyl transferase levels markedly disrupted. This increases the risk of development of cardiovascular disease, hepatic cirrhosis or other chronic conditions. Collectively, the results demonstrate that EHDPHP may cause strong hepatic toxicities, which may be pounded by its hydroxylated metabolites.