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Updated: Aug 8, 2026
Primary Microglia Isolation from Mixed Glial Cell Cultures of Neonatal Rat Brain Tissue
Published on: August 15, 2012
Activation of microglia reveals a non-proteolytic cytokine function for tissue plasminogen activator in the central
1Program in Pharmacology, MSTP Program, Department of Psychiatry, University Medical Center at Stony Brook, Stony Brook, NY 11794-8101, USA.
Abstract:
Tissue plasminogen activator mediates excitotoxin-induced neurodegeneration and microglial activation in the mouse hippocampus. Here we show that tissue plasminogen activator (tPA) acts in a protease-independent manner to modulate the activation of microglia, the cells of the central nervous system with macrophage properties. Cultured microglia from tPA-deficient mice can phagocytose as efficiently as wild-type microglia. However, tPA-deficient microglia in mixed cortical cultures exhibit attenuated activation in response to lipopolysaccharide, as judged by morphological changes, increased expression of the activation marker F4/80 and the release of the pro-inflammatory cytokine tumor necrosis factor-(&agr;). When tPA is added to tPA deficient cortical cultures prior to endotoxin stimulation, microglial activation is restored to levels comparable to that observed in wild-type cells. Proteolytically-inactive tPA can also restore activation of tPA-deficient microglia in culture and in vivo. However, this inactive enzyme does not restore susceptibility of tPA-deficient hippocampal neurons to excitotoxin-mediated cell death. These results dissociate two different functions of tPA: inactive enzyme can mediate microglial activation, whereas proteolytically-competent protein also promotes neuronal degeneration. Thus tPA is identified as a new cytokine in the central nervous system.
Insights
Tissue plasminogen activator (tPA) modulates microglial activation independently of its enzymatic activity. This finding reveals tPA
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglia are the primary immune cells in the central nervous system.
- Tissue plasminogen activator (tPA) is known to play roles in the nervous system.
- The precise mechanisms of tPA's influence on microglial function are not fully understood.
Purpose of the Study:
- To investigate the role of tissue plasminogen activator (tPA) in excitotoxin-induced neurodegeneration and microglial activation.
- To determine whether tPA's protease activity is required for its effects on microglia and neurons.
Main Methods:
- Utilized tPA-deficient mice and wild-type mice.
- Cultured microglia and mixed cortical cultures were used.
- Stimulation with lipopolysaccharide (endotoxin) was performed.
- Proteolytically-inactive tPA was employed to assess functional roles.
Main Results:
- tPA-deficient microglia showed reduced activation in response to lipopolysaccharide.
- Addition of tPA, even proteolytically inactive forms, restored microglial activation.
- Proteolytically inactive tPA did not protect neurons from excitotoxin-induced death.
- Proteolytically active tPA was linked to neuronal degeneration.
Conclusions:
- tPA modulates microglial activation through a protease-independent mechanism.
- tPA has distinct functions: mediating microglial activation (protease-independent) and promoting neuronal degeneration (protease-dependent).
- tPA is identified as a novel cytokine within the central nervous system.
