Role of mast cell activation in inducing microglial cells to release neurotrophin

Area of Science:

• Neuroscience
• Immunology
• Pain Research

Background:

• Brain-derived neurotrophic factor (BDNF) is crucial for pain hypersensitivity.
• Microglia express P2X4 receptors (P2X4R), which bind BDNF, but the regulation of P2X4R is unclear.
• Mast cell activation is linked to pain hypersensitivity, yet the mechanism remains unknown.

Purpose of the Study:

• To investigate the mechanism by which mast cell activation influences P2X4R expression in microglia.
• To elucidate the role of mast cells in regulating BDNF and P2X4R in the context of pain hypersensitivity.

Main Methods:

• Utilized mast cell activation models and microglial cell cultures.
• Employed techniques including antibody blocking, gene-deficient cell lines (tryptase-deficient HMC-1, PAR2-deficient microglia), and Western blotting for kinase phosphorylation.
• Measured P2X4R and BDNF expression and release.

Main Results:

• Mast cell activation significantly increased P2X4R and BDNF expression in microglia.
• This activation enhanced BDNF release from microglia upon ATP stimulation.
• Mast cell-derived tryptase activated PAR2, upregulating P2X4R expression and BDNF release.
• Inhibition of tryptase or PAR2, or use of deficient cells, abolished these effects.
• Increased mitogen-activated protein kinase (MAPK) phosphorylation was observed.

Conclusions:

• Mast cell activation promotes P2X4R and BDNF expression and release in microglia.
• The tryptase-PAR2 pathway is central to mast cell-induced P2X4R upregulation in microglia.
• This pathway contributes to the link between mast cells and pain hypersensitivity.