SIRT1/mTOR pathway-mediated autophagy dysregulation promotes Pb-induced hepatic lipid accumulation in HepG2 cells

Lead (Pb) is a common and toxic metal pollutant in the ecological environment and has drawn significant attention due to its presence in various channels, including the use of lead-based paint, mineral extraction and smelting, exhaust gas from gasoline combustion. Autophagy is an essential catabolic pathway and blocked autophagy may result in abnormal lipid metabolism in liver. A body of evidence demonstrates that Pb exposure causes abnormal lipid droplet (LDs) accumulation in the liver, but the mechanism remains unknown. Here, we investigated whether Pb induced lipid accumulation by regulating autophagy in HepG2 cells. In this study, we found that Pb (50 μM) blocked the autophagy flux mainly by transcription factor EB (TFEB)-mediated impairment of lysosome formation and activity. Then we demonstrated that the dense lipid accumulation was observed upon Pb exposure, and induction of autophagy by the autophagy activator rapamycin (Rap) alleviated Pb-induced lipid accumulation, while suppression of autophagy by chloroquine (CQ) exacerbated Pb-induced lipid accumulation, suggested that Pb-induced autophagy blockage might be responsible for lipid accumulation. Moreover, we demonstrated that the SIRT1/mTOR pathway participated in Pb-induced autophagy dysregulation, leading to Pb-induced hepatic lipid accumulation. In summary, these results revealed a new insight into the relationship between Pb-caused autophagy dysregulation and lipid accumulation for the first time and highlight autophagy as a novel therapeutic target against Pb-induced hepatic lipid accumulation which supplying the theoretical basis and potential strategies for the intervention and treatment of Pb-related disease.