Myelin basic protein charge isomers change macrophage polarization

Area of Science:

• Neuroimmunology
• Cellular Biology

Background:

• Neuronal injury triggers immune cell infiltration and myelin breakdown.
• Myelin basic protein (MBP) acts as a ligand for immune cells, with post-translational modifications creating various isomers.
• The distinct effects of MBP isomers on macrophage activity remain largely unknown.

Purpose of the Study:

• To investigate the differential effects of MBP charge isomers on macrophage polarization.
• To determine how specific MBP isomers influence macrophage phenotypes (M1 vs. M2).

Main Methods:

• Purified MBP isomers were used to treat RAW 264.7 macrophages.
• Macrophage polarization markers (iNOS for M1, Arginase-1 for M2) were quantified via ELISA.
• Rac activity was assessed using a G-LISA assay.
• Receptor for advanced glycation end-products (RAGE) and high mobility group box 1 (HMGB1) expression were analyzed by Western blot.

Main Results:

• The C1 isomer of MBP increased arginase-1 (M2 marker) and Rac activity, while decreasing iNOS (M1 marker) and not affecting HMGB1.
• The C1 isomer significantly elevated surface RAGE expression.
• The deiminated C8 isomer of MBP increased HMGB1 secretion but did not alter arginase-1 or RAGE levels.

Conclusions:

• MBP isomers exhibit distinct immunomodulatory functions.
• The C1 isomer promotes M2 macrophage polarization, potentially via RAGE and Rac signaling.
• The C8 isomer appears to induce an M1-like phenotype, evidenced by HMGB1 secretion.