Macrophage repolarization by epigallocatechin-3-gallate via NF-κB and CREB1/HO-1

Area of Science:

• Immunology
• Molecular Biology
• Pharmacology

Background:

• Epigallocatechin-3-gallate (EGCG), a potent catechin, exhibits significant physiological activity.
• The precise molecular mechanisms by which EGCG influences macrophage polarization and repolarization remain incompletely understood.
• Macrophage polarization plays a critical role in inflammatory responses and tissue homeostasis.

Purpose of the Study:

• To investigate whether EGCG can directly induce M2 macrophage polarization.
• To determine if EGCG can facilitate the repolarization of M1 macrophages to an M2 phenotype.
• To elucidate the involvement of nuclear factor-κB p65 (NF-κB p65) and cAMP response element binding protein 1 (CREB1)/heme oxygenase-1 (HO-1) pathways in EGCG-mediated macrophage modulation.

Main Methods:

• RAW264.7 cells were treated with EGCG to assess M1 and M2 marker expression at mRNA and protein levels.
• To evaluate M1-to-M2 repolarization, cells were pre-stimulated with lipopolysaccharide (LPS) and subsequently treated with EGCG.
• The molecular mechanisms were explored by analyzing the expression and phosphorylation of NF-κB p65, CREB1, and HO-1.

Main Results:

• EGCG treatment significantly upregulated M2 markers (CD206, CD163) and downregulated M1 markers (iNOS, MMP9).
• EGCG effectively shifted the macrophage phenotype from M1 towards M2.
• EGCG suppressed NF-κB p65 phosphorylation while promoting HO-1 expression and CREB1 phosphorylation.

Conclusions:

• EGCG demonstrates substantial potential in modulating macrophage-mediated immune responses.
• EGCG's action may lead to the mitigation of excessive tissue damage during inflammatory processes.
• The findings suggest EGCG can promote tissue repair through its influence on macrophage polarization.