Environmental stimuli shape microglial plasticity in glioma

Area of Science:

• Neuroscience
• Immunology
• Oncology

Background:

• Glioma creates an immunosuppressed microenvironment by promoting cytokine and chemokine production in microglia and macrophages.
• This pro-tumorigenic environment hinders anti-tumor immune responses.

Purpose of the Study:

• To investigate how environmental enrichment (EE) impacts the phenotype of myeloid cells in glioma-bearing mice.
• To elucidate the mechanisms by which EE modulates the brain's immune microenvironment.

Main Methods:

• Glioma-bearing mice were housed in an enriched environment (EE).
• Analysis of myeloid cell gene expression, activity (branching, patrolling, phagocytosis), and immune cell populations (NK cells).
• Investigated the roles of interferon-gamma (IFN-γ), interleukin-15 (IL-15), and brain-derived neurotrophic factor (BDNF).

Main Results:

• EE reverted the immunosuppressive phenotype of infiltrating myeloid cells by modulating inflammatory gene expression.
• EE increased myeloid cell activity, including branching, patrolling, and phagocytosis.
• The EE-induced modulation was dependent on natural killer (NK) cells and interferon-gamma (IFN-γ), and mimicked by interleukin-15 (IL-15).
• Brain-derived neurotrophic factor (BDNF) produced in EE mediated IL-15 expression in CD11b+ cells.

Conclusions:

• Environmental enrichment can reprogram the brain's immune microenvironment to be anti-tumorigenic.
• Novel mechanisms link environmental cues to immune modulation in glioma, involving NK cells, IFN-γ, IL-15, and BDNF.