Mn²⁺ enhances phagocytosis of macrophages against Staphylococcus aureus by regulating autophagy

Area of Science:

• Immunology
• Cell Biology
• Trace Element Metabolism

Background:

• Macrophages are crucial for combating Staphylococcus aureus (S. aureus) infections.
• The role of manganese (Mn²⁺) in regulating macrophage phagocytosis against S. aureus via autophagy remains unclear.
• Autophagy plays a complex role in cellular defense mechanisms.

Purpose of the Study:

• To investigate whether Mn²⁺ regulates macrophage phagocytosis of S. aureus through autophagy.
• To elucidate the molecular mechanisms underlying Mn²⁺'s effect on macrophage-mediated bacterial clearance.
• To explore the impact of Mn²⁺ on autophagy-related protein expression and signaling pathways.

Main Methods:

• RAW264.7 macrophage cells were transfected with p3×Flag-CMV10-ube2c plasmids.
• Cells were treated with Mn²⁺ followed by infection with S. aureus.
• Analysis included protein expression (LC3-II, p62, RhoB), autophagosome formation, protein phosphorylation (mTOR, p38, JNK, ERK), cytokine production (IL-6, IL-2, IFN-β, IFN-γ), and nitric oxide (NO) levels.
• Phagocytosis assays were performed to quantify bacterial clearance.

Main Results:

• Mn²⁺ treatment significantly increased LC3-II and p62 protein levels, indicating enhanced autophagy.
• Autophagosome formation and RhoB expression were elevated, suggesting improved phagocytic capacity.
• Mn²⁺ modulated key signaling pathways, decreasing mTOR, p38, and JNK phosphorylation while enhancing ERK phosphorylation.
• Production of pro-inflammatory cytokines (IL-6, IL-2, IFN-β, IFN-γ) and NO was significantly increased.
• Macrophage phagocytosis against S. aureus was markedly enhanced.

Conclusions:

• Mn²⁺ promotes early autophagy activation and inhibits late-stage autophagosome degradation in S. aureus-infected macrophages via Ube2C.
• This modulation of autophagy by Mn²⁺ leads to enhanced phagocytosis of S. aureus by macrophages.
• The findings provide a molecular basis for understanding how Mn²⁺ bolsters macrophage defense against bacterial pathogens.