Elevated neuronal α-synuclein promotes microglia activation after spinal cord ischemic/reperfused injury

Area of Science:

• Neuroscience
• Immunology
• Cell Biology

Background:

• Ischemia/reperfusion (I/R) injury is a significant cause of neuronal damage.
• Microglia activation plays a critical role in neuroinflammation following I/R injury.
• The precise mechanisms linking neuronal injury to microglia activation require further elucidation.

Purpose of the Study:

• To investigate the role of alpha-synuclein (α-synuclein) in mediating microglia activation following ischemia/reperfusion (I/R) injury.
• To identify the specific receptors and signaling pathways involved in α-synuclein-induced microglia activation.

Main Methods:

• Primary spinal neuron cultures subjected to in vitro I/R conditions.
• Analysis of α-synuclein protein levels using Western blot, immunofluorescence, and ELISA.
• Co-culture experiments with injured neurons and microglia.
• Assessment of microglia activation markers (nitric oxide, H2O2, TNF-α).
• Inhibition studies using α-synuclein antibodies and pathway inhibitors (p38 MAPK, NF-κB).
• Evaluation of toll-like receptor (TLR) involvement (TLR2, TLR3, TLR4).

Main Results:

• I/R exposure significantly increased α-synuclein expression and release from injured neurons.
• Supernatants from injured neurons induced microglia activation, characterized by increased nitric oxide generation, H2O2 production, and TNF-α expression.
• Pretreatment with α-synuclein antibody attenuated I/R-induced microglia activation.
• Microglia activation was mediated by toll-like receptor 2 (TLR2), not TLR3 or TLR4.
• α-synuclein-induced microglia activation involved p38 MAPK and NF-κB signaling pathways.
• Inhibition of these pathways reduced NADPH oxidase 2 (Nox2) expression in microglia.

Conclusions:

• Ischemia/reperfusion-injured neurons release elevated levels of α-synuclein.
• Released α-synuclein activates microglia through toll-like receptor 2 (TLR2).
• This activation process is dependent on p38 MAPK and NF-κB signaling, leading to increased Nox2 expression.
• The findings elucidate a novel mechanism of neuroinflammation in I/R injury involving α-synuclein and TLR2.