Myelin alters the inflammatory phenotype of macrophages by activating PPARs

Area of Science:

• Neuroimmunology
• Cellular Biology
• Biochemistry

Background:

• Foamy macrophages containing myelin debris are prevalent in active multiple sclerosis (MS) lesions.
• Myelin internalization alters macrophage phenotype, but mechanisms and impact on lesion progression are unclear.

Purpose of the Study:

• To investigate how myelin affects macrophage phenotype.
• To elucidate the role of myelin-derived lipids in modulating macrophage function.
• To explore the therapeutic potential of targeting myelin-mediated macrophage activation in MS.

Main Methods:

• Macrophages were treated with myelin and phosphatidylserine (PS).
• Nitric oxide (NO) production and inflammatory mediator release were measured.
• Peroxisome proliferator-activated receptor beta/delta (PPARβ/δ) activation was assessed.
• Experimental autoimmune encephalomyelitis (EAE) model was used to evaluate the therapeutic effect of PS-containing liposomes (PSLs).

Main Results:

• Myelin and PS reduced macrophage nitric oxide production via PPARβ/δ activation.
• Intravenous injection of PSLs suppressed inflammatory mediators and ameliorated EAE.
• PSL treatment reduced immune cell infiltration into the central nervous system and splenic T-cell proliferation.
• PPARβ/δ was activated in foamy macrophages within active MS lesions.

Conclusions:

• Myelin modulates macrophage phenotype through PPAR activation, potentially dampening MS lesion progression.
• Myelin-derived PS activates PPARβ/δ in macrophages following myelin uptake.
• Naturally occurring myelin lipids, particularly PS, show promise as immunomodulatory agents for MS therapeutics.