Lipid accumulation in multi-walled carbon nanotube-exposed HepG2 cells: Possible role of lipophagy pathway

Nanoparticle (NP) exposure might promote hepatic steatosis , but relatively few studies investigated the influence of multi-walled carbon nanotubes (MWCNTs) on lipid accumulation in hepatocytes in vitro . This study investigated lipid accumulation and the possible role of lipophagy (autophagic degradation of lipid droplets) in MWCNT-exposed HepG2 cells. Pristine (XFM19) and carboxylated MWCNTs (XFM21) were internalized, accompanying cytotoxicity, lysosomal destabilization , and intracellular reactive oxygen species (ROS) production. Compared with XFM21, XFM19 promoted lipid accumulation in HepG2 cells more effectively, which was further enhanced by pre-incubation with autophagy inhibitor NH 4 Cl. In addition, MWCNTs increased the expression of lipophagy genes PLIN2 and BECN1 but decreased that of ATG7 . The expression of endoplasmic reticulum (ER) stress regulators, namely DDIT3 , HSPA5 , and XBP- 1s, was also altered in MWCNT exposed HepG2 cells. Combined, these results suggested that MWCNT exposure might promote lipid accumulation in hepatocytes probably through the modulation of lipophagy pathway.