Mechanistic insights into bisphenol A – Induced liver fibrosis: Evidence of PPARγ downregulation and AKT1/FN1 signaling from multi-level analysis

Non-alcoholic fatty liver disease (NAFLD) has rapidly ascended to become the foremost chronic liver disorder globally, yet the precise molecular mechanisms by which pervasive environmental endocrine-disrupting chemicals (EDCs) contribute to its pathogenesis remain largely unelucidated. This study presents a robust, multi-scale analytical framework, integrating human population genetics with cell-type-resolved molecular pathology, to definitively establish bisphenol A (BPA) as a causal accelerant of NAFLD progression. Utilizing two-sample Mendelian randomization （MR） with publicly available GWAS summary statistics from over 300,000 participants, we support a compelling causal association between genetically proxied BPA exposure and elevated NAFLD susceptibility (β = 0.68, P < 5 × 10⁻¹⁰). Subsequent single-nucleus RNA sequencing (snRNA-seq) of 42 human liver samples delineated BPA-responsive transcriptional programs, predominantly localized within activated hepatic stellate cells (HSCs). Through the synergistic integration of weighted gene co-expression network analysis （WGCNA） and toxicogenomic profiling, we pinpointed a pivotal six-gene nexus-comprising PPARG, AKT1, FN1, HSP90AA1, CAV1, and ESR1-that orchestrates aberrant lipid metabolism, oxidative stress, and extracellular matrix remodeling, all critical hallmarks of NAFLD. Structure-based molecular docking simulations further revealed sub-micromolar affinities of BPA for key proteins within this nexus, including PPARγ, estrogen receptor-α （ESR1）, and HSP90AA1, implicating receptor interference and chaperone modulation as primary initiating molecular events. In vitro validation using LX-2 HSCs exposed to environmentally relevant BPA concentrations (10 nM-1 µM) faithfully recapitulated these in silico predictions: manifesting as PPARγ functional repression, AKT1 hyper-phosphorylation, reactive oxygen species accumulation, mitochondrial depolarization, heightened cytokine secretion, increased apoptosis, and augmented collagen-I deposition. The multi-faceted evidence reclassifies BPA from a merely correlational environmental pollutant to a mechanistically validated metabolo-fibrogenic agent in NAFLD.