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Biphasic Dose-Response of Mn-Induced Mitochondrial Damage, PINK1/Parkin Expression, and Mitophagy in SK-N-SH Cells
Yue Zhang1,2, Hong-Tao Hu2, Yu-Min Cao3
1Department of Pediatrics, Hospital of Chongqing Medical University/Chongqing Health Center for Women and Children, Chongqing, China.
Abstract:
Excessive manganese (Mn) exposure produces neurotoxicity with mitochondrial damage. Mitophagy is a protective mechanism to eliminate damaged mitochondria to protect cells. The aim of this study was to determine the dose-response of Mn-induced mitochondria damage, the expression of mitophagy-mediated protein PINK1/Parkin and mitophagy in dopamine-producing SK-N-SH cells. Cells were exposed to 0, 300, 900, and 1500 μM Mn2+ for 24 h, and ROS production, mitochondrial damage and mitophagy were examined. The levels of dopamine were detected by ELISA and neurotoxicity and mitophagy-related proteins (α-synuclein, PINK1, Parkin, Optineurin, and LC3II/I) were detected by western blot. Mn increased intracellular ROS and apoptosis and decreased mitochondrial membrane potential in a concentration-dependent manner. However, at the low dose of 300 μM Mn, autophagosome was increased 11-fold, but at the high dose of 1500 μM, autophagosome was attenuated to 4-fold, together with decreased mitophagy-mediated protein PINK1/Parkin and LC3II/I ratio and increased Optineurin expression, resulting in increased α-synuclein accumulation and decreased dopamine production. Thus, Mn-induced mitophagy exhibited a novel biphasic regulation: at the low dose, mitophagy is activated to eliminate damaged mitochondria, however, at the high dose, cells gradually loss the adaptive machinery, the PINK1/Parkin-mediated mitophagy weakened, resulting in neurotoxicity.
Insights
Manganese (Mn) exposure causes neurotoxicity by damaging mitochondria. While low Mn doses activate mitophagy to protect cells, high doses impair this process, leading to dopamine loss and neurodegeneration.
Area of Science:
- Neuroscience
- Toxicology
- Cell Biology
Background:
- Excessive manganese (Mn) exposure is linked to neurotoxicity, often involving mitochondrial dysfunction.
- Mitophagy, the selective removal of damaged mitochondria, is a crucial cellular defense mechanism.
Purpose of the Study:
- To investigate the dose-dependent effects of Mn on mitochondrial damage, mitophagy proteins (PINK1/Parkin), and mitophagy in dopamine-producing SK-N-SH cells.
- To elucidate the biphasic regulation of mitophagy by Mn exposure.
Main Methods:
- SK-N-SH cells were exposed to varying Mn concentrations (0, 300, 900, 1500 μM).
- Assessed were reactive oxygen species (ROS) production, mitochondrial damage, apoptosis, dopamine levels, and mitophagy-related proteins (α-synuclein, PINK1, Parkin, Optineurin, LC3II/I) via ELISA and Western blot.
Main Results:
- Mn exposure increased ROS, apoptosis, and decreased mitochondrial membrane potential in a dose-dependent manner.
- Low Mn (300 μM) enhanced mitophagy (11-fold increase in autophagosomes).
- High Mn (1500 μM) attenuated mitophagy (4-fold increase), decreased PINK1/Parkin and LC3II/I, increased Optineurin, leading to α-synuclein accumulation and reduced dopamine.
Conclusions:
- Mn-induced mitophagy exhibits biphasic regulation: activation at low doses and impairment at high doses.
- High Mn exposure overwhelms cellular adaptive mechanisms, weakening PINK1/Parkin-mediated mitophagy and causing neurotoxicity.
- This impaired mitophagy contributes to α-synuclein accumulation and dopamine depletion.
