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myc-immortalized microglial cells express a functional platelet-activating factor receptor
M Righi1, O Letari, P Sacerdote
1CNR-Center of Cytopharmacology, University of Milan, Italy.
Abstract:
The autacoid platelet-activating factor (PAF) takes part in a complex network of interactions regarding the cellular components of nervous tissues. Efforts aimed at characterizing the effects of PAF in the brain have been recently focalized on neurons because PAF exerts pleiotropic effects on these cells. Less attention has instead been paid to the glial component of the brain. We have used microglial cell lines immortalized from 13-day-old mouse embryo brains by a myc-transducing retrovirus. When exposed to physiological doses of PAF, immortalized microglial cells showed increases in intracellular free calcium concentrations due to release of calcium from internal stores, as well as to extracellular calcium influxes. These profiles of reactivity were independent from the immortalizing process, being observable in primary microglial cultures and in immortalized clones showing different proliferative rates. PAF was also able to induce transient expression of the c-fos protooncogene in serum-starved cultures and induced a strong chemotactic response in microglial cells. In contrast with control macrophage cultures, PAF did not promote prostaglandin or leukotriene synthesis in immortalized cells. This was most likely due to the low amount of total arachidonic acid found in immortal microglia, with respect to that observed in freshly isolated cells. Our data suggest that several of the effects observed after PAF stimulation might be independent from PAF-induced arachidonic acid metabolism. The availability of an in vitro microglial model might now help in studying the proinflammatory effects of PAF, both direct or microglia mediated, in the neural environment.
Insights
Platelet-activating factor (PAF) activates microglia in the brain, increasing intracellular calcium and c-fos expression. This study introduces a microglial cell model for investigating PAF
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Platelet-activating factor (PAF) plays a role in nervous tissue interactions.
- Research on PAF's brain effects has focused on neurons, neglecting glial cells.
- Microglia are key immune cells in the central nervous system.
Purpose of the Study:
- To investigate the effects of PAF on microglial cells.
- To establish and characterize an in vitro microglial model for studying PAF.
- To explore PAF-induced signaling pathways and responses in microglia.
Main Methods:
- Utilized immortalized microglial cell lines derived from mouse embryos.
- Exposed cells to physiological doses of PAF.
- Measured intracellular calcium concentrations, c-fos protooncogene expression, and chemotaxis.
- Compared responses with primary microglial cultures and macrophage cultures.
Main Results:
- PAF stimulation increased intracellular calcium via internal stores and extracellular influx in immortalized microglia.
- These calcium responses were consistent across different microglial cultures and proliferative rates.
- PAF induced transient c-fos expression and chemotaxis in microglial cells.
- PAF did not stimulate prostaglandin or leukotriene synthesis in immortalized microglia, potentially due to lower arachidonic acid levels.
Conclusions:
- PAF exerts significant effects on microglia, including calcium signaling, gene expression, and migration.
- The observed effects suggest PAF-mediated responses can be independent of arachidonic acid metabolism.
- The developed in vitro microglial model is valuable for studying PAF's role in neuroinflammation.