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Glucose Levels in Culture Medium Determine Cell Death Mode in MPP(+)-treated Dopaminergic Neuronal Cells
1Department of Systems Biology, Yonsei University College of Life Science and Biotechnology, Seoul 03722, Korea.
Abstract:
We previously demonstrated that 1-methyl-4-phenylpyridinium (MPP(+)) causes caspase-independent, non-apoptotic death of dopaminergic (DA) neuronal cells. Here, we specifically examined whether change of glucose concentration in culture medium may play a role for determining cell death modes of DA neurons following MPP(+) treatment. By incubating MN9D cells in medium containing varying concentrations of glucose (5~35 mM), we found that cells underwent a distinct cell death as determined by morphological and biochemical criteria. At 5~10 mM glucose concentration (low glucose levels), MPP(+) induced typical of the apoptotic dell death accompanied with caspase activation and DNA fragmentation as well as cell shrinkage. In contrast, MN9D cells cultivated in medium containing more than 17.5 mM (high glucose levels) did not demonstrate any of these changes. Subsequently, we observed that MPP(+) at low glucose levels but not high glucose levels led to ROS generation and subsequent JNK activation. Therefore, MPP(+)-induced cell death only at low glucose levels was significantly ameliorated following co-treatment with ROS scavenger, caspase inhibitor or JNK inhibitor. We basically confirmed the quite similar pattern of cell death in primary cultures of DA neurons. Taken together, our results suggest that a biochemically distinct cell death mode is recruited by MPP(+) depending on extracellular glucose levels.
Insights
Extracellular glucose levels determine how 1-methyl-4-phenylpyridinium (MPP(+)) induces cell death in dopaminergic (DA) neurons. Low glucose promotes apoptosis, while high glucose prevents it by altering reactive oxygen species (ROS) and JNK activation.
Area of Science:
- Neuroscience
- Cell Biology
- Toxicology
Background:
- 1-methyl-4-phenylpyridinium (MPP(+)) is known to induce non-apoptotic death in dopaminergic (DA) neurons.
- The influence of glucose concentration on MPP(+)-induced DA neuronal cell death modes remains unclear.
Purpose of the Study:
- To investigate the role of extracellular glucose concentration in modulating MPP(+)-induced cell death pathways in DA neurons.
- To determine if glucose levels affect the mode of cell death (apoptotic vs. non-apoptotic) triggered by MPP(+).
Main Methods:
- MN9D cells and primary DA neuronal cultures were treated with MPP(+) in media with varying glucose concentrations (5-35 mM).
- Morphological and biochemical criteria were used to assess cell death modes, including caspase activation and DNA fragmentation.
- Reactive oxygen species (ROS) generation and JNK activation were measured.
- The effects of ROS scavengers, caspase inhibitors, and JNK inhibitors were evaluated.
Main Results:
- Low glucose levels (5-10 mM) induced apoptotic cell death with caspase activation and DNA fragmentation in MPP(+)-treated cells.
- High glucose levels (>17.5 mM) prevented these apoptotic markers.
- MPP(+) induced ROS generation and JNK activation specifically under low glucose conditions.
- Cell death at low glucose was attenuated by ROS scavengers, caspase inhibitors, and JNK inhibitors.
- Similar glucose-dependent cell death patterns were observed in primary DA neuron cultures.
Conclusions:
- Extracellular glucose concentration significantly influences the mode of MPP(+)-induced DA neuronal cell death.
- Low glucose facilitates an apoptotic pathway involving ROS and JNK activation, whereas high glucose inhibits it.
- These findings highlight glucose availability as a critical factor in neuroprotection against MPP(+) toxicity.
