Direct effects of Bisphenol A on lipid homeostasis in rat hepatoma cells

Abstract

Bisphenol A (BPA), used in the manufacture of polycarbonate plastic and epoxy resin, is one of the most abundant endocrine disruptors in the environment, considered as a xenoestrogen. BPA has recently become of additional public health concern because of increasing evidence of deleterious effects on metabolism. Dietary intake seems the most important route for BPA exposure, followed by rapid biotransformation in the gut and liver and elimination in the urine. Although hepatocytes can represent a significant target for this compound, little is known on the direct effects and mechanisms of action of BPA on lipid homeostasis at the cellular level. In this work, the effects of BPA (0.3-3-30-300 ng mL(-1), 24 h) were investigated in rat FaO hepatoma, a well differentiated liver cell line. At both 30 and 300 ng mL(-1), BPA significantly increased intracellular triglyceride (TAG) content and lipid accumulation in lipid droplets (LDs), without affecting cell viability. The effects of BPA were associated with decreased mRNA levels of the transcription factors Peroxisome Proliferator-Activated Receptor (PPAR) isoforms α and βδ, as well as of their downstream genes acyl-CoA oxidase (AOX) and carnitine palmitoyl transferase (CPT1) involved in lipid oxidation. No increase in transcription of lipogenic genes was observed. BPA also decreased mRNA levels of ApolipoproteinB (apoB) and the extracellular TAG content, indicating alterations in lipid secretion. FaO cells did not express Estrogen Receptor α (ERα and showed a very low expression of ERβ compared to rat liver. All the effects of BPA were prevented by cell pretreatment with Wortmannin, indicating the involvement of phosphatidyl inositol-3 kinase activation. The results demonstrate a direct action of BPA on lipid homeostasis in FaO cells through interference with lipid oxidation and secretion, and add further information on the cellular pathways that can be perturbed by this compound.