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Microglial activation and dopaminergic cell injury: an in vitro model relevant to Parkinson's disease
1Department of Neurology, Baylor College of Medicine, Houston, Texas 77030, USA.
Abstract:
Microglial activation and oxidative stress are significant components of the pathology of Parkinson's disease (PD), but their exact contributions to disease pathogenesis are unclear. We have developed an in vitro model of nigral injury, in which lipopolysaccharide-induced microglial activation leads to injury of a dopaminergic cell line (MES 23.5 cells) and dopaminergic neurons in primary mesencephalic cell cultures. The microglia are also activated by PD IgGs in the presence of low-dose dopa-quinone- or H(2)O(2)-modified dopaminergic cell membranes but not cholinergic cell membranes. The activation requires the microglial FCgammaR receptor as demonstrated by the lack of activation with PD IgG Fab fragments or microglia from FCgammaR-/- mice. Although microglial activation results in the release of several cytokines and reactive oxygen species, only nitric oxide and H(2)O(2) appear to mediate the microglia-induced dopaminergic cell injury. These studies suggest a significant role for microglia in dopaminergic cell injury and provide a mechanism whereby immune/inflammatory reactions in PD could target oxidative injury relatively specifically to dopaminergic cells.
Insights
Microglia activation contributes to Parkinson's disease (PD) pathology. This study shows activated microglia, via oxidative stress, specifically injure dopaminergic cells, suggesting a key role in PD pathogenesis.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglial activation and oxidative stress are implicated in Parkinson's disease (PD) pathogenesis.
- The precise mechanisms linking these factors to dopaminergic neuron loss remain incompletely understood.
Purpose of the Study:
- To investigate the role of microglial activation in dopaminergic cell injury using an in vitro model.
- To elucidate the specific mediators and receptors involved in microglia-induced neurotoxicity relevant to PD.
Main Methods:
- Developed an in vitro model of nigral injury using lipopolysaccharide (LPS) to induce microglial activation.
- Utilized dopaminergic cell lines (MES 23.5) and primary mesencephalic cultures exposed to activated microglia.
- Investigated microglial activation by Parkinson's disease immunoglobulin G (PD IgGs) in the presence of modified cell membranes and assessed the role of the FCgammaR receptor.
Main Results:
- LPS-induced microglial activation led to injury of dopaminergic cells and neurons.
- Microglia were activated by PD IgGs when combined with modified dopaminergic, but not cholinergic, cell membranes.
- FCgammaR receptor engagement was essential for microglial activation by PD IgGs.
- Nitric oxide and hydrogen peroxide (H2O2) were identified as key mediators of microglia-induced dopaminergic cell injury.
Conclusions:
- Microglia play a significant role in causing dopaminergic cell injury.
- Immune and inflammatory responses in PD may specifically target dopaminergic cells through oxidative stress mechanisms involving nitric oxide and H2O2.
- The FCgammaR pathway is critical for mediating microglial responses to PD-associated triggers.