Related Experiment Videos
Microglial tissue plasminogen activator (tPA) triggers neuronal apoptosis in vitro
1Department of Pediatrics, Queen's University, Kingston, Ontario, Canada. mf6@post.queensu.ca
Abstract:
Several CNS disorders feature microglial activation. Microglia are known to have both restorative and cytotoxic capabilities. Neuronal apoptosis has been noted after an acute insult such as ischemia. Microglia may participate in this event. We previously showed that conditioned medium (CM) harvested from peritoneal macrophages or from activated microglia triggered apoptosis in rat hippocampal neurons in culture. We wished to characterize the factor responsible for triggering neuronal death. Quiescent microglia produced CM that did not disrupt hippocampal neurons. Lipopolysaccharide-activated microglia produced CM which resulted in neuronal death. This effect was blocked by plasminogen activator inhibitor-1, by tPA STOP, and by co-incubation with tPA antibody. Recombinant human tPA exaggerated the neurotoxic effects of microglial CM, while tPA alone was toxic only at very high concentrations. This in vitro system, which probably excludes any significant impact of microglial free radicals, suggests that microglial tPA may contribute significantly to hippocampal neuronal death.
Insights
Microglia activation can harm brain cells. This study found that tissue plasminogen activator (tPA) released by activated microglia contributes to neuronal death in the hippocampus, a key brain region for memory.
Area of Science:
- Neuroscience
- Cell Biology
- Pathology
Background:
- Microglial activation is observed in central nervous system (CNS) disorders.
- Microglia possess both beneficial and harmful functions.
- Neuronal apoptosis, or cell death, occurs after acute injuries like ischemia.
Purpose of the Study:
- To identify the specific factor released by activated microglia that induces neuronal apoptosis.
- To investigate the role of tissue plasminogen activator (tPA) in microglial-induced neurotoxicity.
Main Methods:
- Cultured rat hippocampal neurons were exposed to conditioned medium (CM) from quiescent and lipopolysaccharide (LPS)-activated microglia.
- The neurotoxic effects of CM were assessed with and without inhibitors of tPA (plasminogen activator inhibitor-1, tPA STOP, tPA antibody).
- The impact of recombinant human tPA on neuronal survival was evaluated.
Main Results:
- CM from LPS-activated microglia, but not quiescent microglia, induced significant neuronal death.
- The neurotoxicity of microglial CM was significantly reduced by tPA inhibitors.
- Recombinant tPA potentiated the neurotoxic effects of microglial CM, while tPA alone was toxic only at high concentrations.
Conclusions:
- Microglial-derived tPA plays a significant role in inducing hippocampal neuronal apoptosis in vitro.
- This mechanism may contribute to neuronal damage in CNS disorders involving microglial activation, independent of free radicals.