Manganese (II) chloride leads to dopaminergic neurotoxicity by promoting mitophagy through BNIP3-mediated oxidative stress in SH-SY5Y cells

BACKGROUND: Manganese overexposure can induce neurotoxicity, lead to manganism and result in clinical manifestations similar to those of parkinsonism. However, the underlying molecular mechanism is still unclear. This study demonstrated that MnCl(2) induces mitophagy and leads to neurotoxicity by promoting BNIP3-mediated reactive oxygen species (ROS) generation. METHODS: Human neuroblastoma SH-SY5Y cells were used throughout our experiments. Cell viability was detected by cell proliferation/toxicity test kits. Mitochondrial membrane potential was measured by flow cytometry. ROS generation was detected using a microplate reader. Protein levels were evaluated by Western blot. Transmission electron microscopy was used to evaluate mitochondrial morphology. Co-immunoprecipitation was used to verify the interaction between BNIP3 and LC3. RESULTS: MnCl(2) led to loss of mitochondrial membrane potential and apoptosis of SH-SY5Y cells by enhancing expression of BNIP3 and conversion of LC3-I to LC3-II. Moreover, MnCl(2) reduced expression of the mitochondrial marker protein TOMM20 and promoted interaction between BNIP3 and LC3. The results also indicated that a decrease in BNIP3 expression reduced the mitochondrial membrane potential loss, attenuated apoptosis and reduced mitochondrial autophagosome formation in SH-SY5Y cells after MnCl(2) treatment. Finally, we found that manganese-induced ROS generation could be reversed by the antioxidant N-acetyl cysteine (NAC) or silencing BNIP3 expression. CONCLUSIONS: BNIP3 mediates MnCl(2)-induced mitophagy and neurotoxicity in dopaminergic SH-SY5Y cells through ROS. Thus, BNIP3 contributes to manganese-induced neurotoxicity by functioning as a mitophagy receptor protein.