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Microglia endotoxin tolerance is retained after enforced repopulation
Tiago Medeiros-Furquim1, Anneke Miedema1, Edwin Schilder1
1Department of Biomedical Sciences, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands.
Brain, Behavior, and Immunity
|April 24, 2025
Summary
Microglia develop innate immune memory, a state called endotoxin tolerance, which persists even after depletion and repopulation. This finding impacts the clinical use of microglia-depleting strategies for brain diseases.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglia, the brain's immune cells, are vital for central nervous system (CNS) homeostasis.
- Systemic inflammation can influence microglia, potentially contributing to neurodegeneration.
- Microglia, like other innate immune cells, can develop innate immune memory (IIM), altering responses to subsequent inflammatory stimuli.
Purpose of the Study:
- To investigate if microglia depletion-repopulation can reverse lipopolysaccharide (LPS)-induced endotoxin tolerance in mice.
- To understand the functional and molecular state of repopulated microglia.
Main Methods:
- Utilized BLZ945, a colony-stimulating factor 1 receptor inhibitor, to deplete microglia in mice.
- Induced endotoxin tolerance using LPS preconditioning.
- Analyzed gene expression profiles of repopulated microglia, focusing on homeostasis, metabolism, and immune response genes.
Main Results:
- Repopulated microglia showed altered gene expression, with reduced homeostatic and mitochondrial respiration genes but increased immune activation genes.
- Despite repopulation, the blunted inflammatory response characteristic of LPS-induced endotoxin tolerance persisted.
- This suggests that endotoxin tolerance in microglia is resistant to reversal by depletion-repopulation strategies.
Conclusions:
- Microglia endotoxin tolerance demonstrates remarkable persistence following a depletion-repopulation cycle.
- Strategies involving microglia depletion may have limited effectiveness in restoring normal microglial function in conditions involving prior inflammatory challenges.
- Further research is needed to understand the mechanisms maintaining this persistent tolerance and its implications for neurodegenerative diseases.
