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Distinct P2Y Receptors Mediate Extension and Retraction of Microglial Processes in Epileptic and Peritumoral Human
Giampaolo Milior1,2, Mélanie Morin-Brureau3, Farah Chali3
1Cortex and Epilepsie, Institut National de la Santé et de la Recherche Médicale U1127, Centre National de la Recherche Scientifique Unité Mixte de Recherche 7225, Université Pierre et Marie Curie, Université Paris 6, Institut du Cerveau et de la Moelle épinière, Paris 75013, France, giampaolo.milior@college-de-france.fr.
Abstract:
Microglia exhibit multiple, phenotype-dependent motility patterns often triggered by purinergic stimuli. However, little data exist on motility of human microglia in pathological situations. Here we examine motility of microglia stained with a fluorescent lectin in tissue slices from female and male epileptic patients diagnosed with mesial temporal lobe epilepsy or cortical glioma (peritumoral cortex). Microglial shape varied from ramified to amoeboid cells predominantly in regions of high neuronal loss or closer to a tumor. Live imaging revealed unstimulated or purine-induced microglial motilities, including surveillance movements, membrane ruffling, and process extension or retraction. At different concentrations, ADP triggered opposing motilities. Low doses triggered process extension. It was suppressed by P2Y12 receptor antagonists, which also reduced process length and surveillance movements. Higher purine doses caused process retraction and membrane ruffling, which were blocked by joint application of P2Y1 and P2Y13 receptor antagonists. Purinergic effects on motility were similar for all microglia tested. Both amoeboid and ramified cells from mesial temporal lobe epilepsy or peritumoral cortex tissue expressed P2Y12 receptors. A minority of microglia expressed the adenosine A2A receptor, which has been linked with process withdrawal of rodent cells. Laser-mediated tissue damage let us test the functional significance of these effects. Moderate damage induced microglial process extension, which was blocked by P2Y12 receptor antagonists. Overall, the purine-induced motility of human microglia in epileptic tissue is similar to that of rodent microglia in that the P2Y12 receptor initiates process extension. It differs in that retraction is triggered by joint activation of P2Y1/P2Y13 receptors.SIGNIFICANCE STATEMENT Microglial cells are brain-resident immune cells with multiple functions in healthy or diseased brains. These diverse functions are associated with distinct phenotypes, including different microglial shapes. In the rodent, purinergic signaling is associated with changes in cell shape, such as process extension toward tissue damage. However, there are little data on living human microglia, especially in diseased states. We developed a reliable technique to stain microglia from epileptic and glioma patients to examine responses to purines. Low-intensity purinergic stimuli induced process extension, as in rodents. In contrast, high-intensity stimuli triggered a process withdrawal mediated by both P2Y1 and P2Y13 receptors. P2Y1/P2Y13 receptor activation has not previously been linked to microglial morphological changes.
Insights
Human microglia exhibit distinct motility patterns in response to purinergic signals, with low doses promoting process extension via P2Y12 receptors and high doses causing retraction through P2Y1/P2Y13 receptors.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglia, the brain's resident immune cells, display diverse motility patterns influenced by purinergic stimuli.
- Limited data exist on human microglial motility in pathological conditions like epilepsy and glioma.
Purpose of the Study:
- To investigate the motility patterns of human microglia in epileptic and peritumoral brain tissue.
- To elucidate the role of purinergic signaling in modulating microglial shape and movement in disease states.
Main Methods:
- Utilized fluorescent lectin staining to visualize microglia in human brain slices from epilepsy and glioma patients.
- Performed live imaging to observe unstimulated and purine-induced microglial motilities.
- Tested the effects of various purinergic concentrations and receptor antagonists (P2Y12, P2Y1, P2Y13) on microglial behavior.
- Assessed microglial responses to laser-mediated tissue damage.
Main Results:
- Microglial shape varied from ramified to amoeboid, correlating with neuronal loss or tumor proximity.
- Low ADP concentrations induced microglial process extension, mediated by P2Y12 receptors.
- Higher purine concentrations triggered process retraction and membrane ruffling, blocked by P2Y1 and P2Y13 receptor antagonists.
- Both ramified and amoeboid microglia expressed P2Y12 receptors; a minority expressed adenosine A2A receptors.
- Laser-induced damage prompted microglial process extension, inhibited by P2Y12 antagonists.
Conclusions:
- Human microglial motility in epileptic tissue shares similarities with rodent models, with P2Y12 initiating process extension.
- Distinctly, human microglia exhibit process retraction upon joint P2Y1/P2Y13 receptor activation, a novel finding.
- Purinergic signaling differentially regulates human microglial morphology and motility in pathological brain environments.
