High perfluorooctanoic acid exposure induces autophagy blockage and disturbs intracellular vesicle fusion in the liver

Arch Toxicol. 2017 Jan;91(1):247-258. doi: 10.1007/s00204-016-1675-1. Epub 2016 Feb 15.

Abstract

Perfluorooctanoic acid (PFOA) has been shown to cause hepatotoxicity and other toxicological effects. Though PPARα activation by PFOA in the liver has been well accepted as an important mechanism of PFOA-induced hepatotoxicity, several pieces of evidence have shown that the hepatotoxic effects of PFOA may not be fully explained by PPARα activation. In this study, we observed autophagosome accumulation in mouse livers as well as HepG2 cells after PFOA exposure. Further in vitro study revealed that the accumulation of autophagosomes was not caused by autophagic flux stimulation. In addition, we observed that PFOA exposure affected the proteolytic activity of HepG2 cells while significant dysfunction of lysosomes was not detected. Quantitative proteomic analysis of crude lysosomal fractions from HepG2 cells treated with PFOA revealed that 54 differentially expressed proteins were related to autophagy or vesicular trafficking and fusion. The proteomic results were further validated in the cells in vitro and livers in vivo after PFOA exposure, which implied potential dysfunction at the late stage of autophagy. However, in HepG2 cells, it seemed that further inhibition of autophagy did not significantly alter the effects of PFOA on cell viability. Although these findings demonstrate that PFOA blocked autophagy and disturbed intracellular vesicle fusion in the liver, the changes in autophagy were observed only at high cytotoxic concentrations of PFOA, suggesting that autophagy may not be a primary target or mode of toxicity. Furthermore, since altered liver autophagy was not observed at concentrations of PFOA associated with human exposures, the relevance of these findings must be questioned.

Keywords: Autophagy; Perfluorooctanoic acid; Proteome; Vesicle fusion.

MeSH terms

  • Animals
  • Autophagosomes / drug effects*
  • Autophagosomes / metabolism
  • Autophagosomes / pathology
  • Autophagy / drug effects*
  • Autophagy-Related Proteins / antagonists & inhibitors
  • Autophagy-Related Proteins / genetics
  • Autophagy-Related Proteins / metabolism
  • Caprylates / administration & dosage
  • Caprylates / toxicity*
  • Cell Survival / drug effects
  • Chemical and Drug Induced Liver Injury / metabolism
  • Chemical and Drug Induced Liver Injury / pathology*
  • Cytoskeletal Proteins / antagonists & inhibitors
  • Cytoskeletal Proteins / genetics
  • Cytoskeletal Proteins / metabolism
  • Dose-Response Relationship, Drug
  • Environmental Pollutants / administration & dosage
  • Environmental Pollutants / toxicity*
  • Fluorocarbons / administration & dosage
  • Fluorocarbons / toxicity*
  • Gene Expression Profiling
  • Gene Expression Regulation / drug effects
  • Hep G2 Cells
  • Humans
  • Liver / drug effects*
  • Liver / metabolism
  • Liver / pathology
  • Lysosomes / drug effects
  • Lysosomes / metabolism
  • Lysosomes / pathology
  • Male
  • Membrane Fusion Proteins / antagonists & inhibitors
  • Membrane Fusion Proteins / genetics
  • Membrane Fusion Proteins / metabolism
  • Mice, Inbred BALB C
  • Proteolysis / drug effects
  • RNA Interference
  • Random Allocation

Substances

  • Autophagy-Related Proteins
  • Caprylates
  • Cytoskeletal Proteins
  • Environmental Pollutants
  • Fluorocarbons
  • Membrane Fusion Proteins
  • perfluorooctanoic acid