Exposure to responsible components of PM2.5 induces hepatic steatosis: An in silico, in vitro, and in vivo study based on adverse outcome pathway

Mounting evidence suggests that exposure to PM_2.5 is closely associated with hepatic steatosis. However, due to the complex composition of PM_2.5, evidence regarding the effects of its specific chemical components on hepatic steatosis remains insufficient. This study aims to expand our previous research by investigating whether direct exposure to PM_2.5-bound responsible components induces hepatic steatosis. Additionally, we seek to elucidate the molecular mechanisms based on an adverse outcome pathway (AOP) strategy. Initially, molecular dynamics simulations and dual-luciferase assays identified several responsible components of PM_2.5 that activate PPARγ, ERα, and LXRα, or antagonize PPARα-molecular initiation events (MIEs) that are critical for inducing hepatic steatosis. Subsequently, these components were systematically evaluated for their capacity to induce lipid metabolism abnormalities (key events, KEs) and hepatic steatosis (adverse outcome, AO) in HepG2 cells. The results indicate that all studied components induced lipid accumulation, with tris-2-ethylhexyl phosphate (TEHP) prioritized as the highest-risk compound. Finally, in vivo validation indicated that TEHP chronic exposure resulted in hepatic steatosis and composition alterations in mice. This study underscores the effectiveness of AOP-based strategies in prioritizing chemicals and is anticipated to establish a paradigm for mechanism-oriented screening of hazardous components in complex environmental samples.