CD14 Counterregulates Lipopolysacharide-Induced Tumor Necrosis Factor-α Production in a Macrophage Subset

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Macrophages (MΦ) exhibit diverse inflammatory properties based on stimulation (GM-CSF vs. M-CSF).
• CD14 and Toll-like receptor 4 (TLR4) are crucial for lipopolysaccharide (LPS)-induced signaling.
• Differential expression of CD14 and TLR4 influences macrophage responses.

Purpose of the Study:

• To investigate the impact of anti-CD14 antibody blockade on LPS-induced cytokine production, signal transduction, and CD14/TLR4 expression in GM-MΦ and M-MΦ.
• To elucidate the role of CD14 in modulating LPS signaling pathways, including MyD88, TRIF, and MAPK.
• To understand how CD14 blockade affects the balance of pro- and anti-inflammatory cytokine responses.

Main Methods:

• Macrophage cultures (GM-MΦ and M-MΦ) were treated with LPS and anti-CD14 antibody.
• Cytokine production (IFN-β, IL-10, TNF-α) was measured.
• Expression levels of CD14 and TLR4 were assessed.
• Phosphorylation states of signaling molecules in MyD88, TRIF, and MAPK pathways were analyzed.

Main Results:

• M-MΦ expressed higher CD14/TLR4 and produced more IFN-β and IL-10, but less TNF-α, compared to GM-MΦ.
• CD14 blockade at high LPS concentrations increased pro-inflammatory cytokines and decreased IFN-β in M-MΦ, but not GM-MΦ.
• CD14 blockade decreased CD14 and TLR4 expression in M-MΦ, impairing TRIF signaling.
• TNF-α synthesis was upregulated upon CD14 blockade, suggesting TRIF's role in restricting its overproduction.

Conclusions:

• Surface CD14 plays a critical role in determining the biological response to LPS.
• CD14 blockade influences LPS-induced signaling pathways, particularly TRIF-mediated responses.
• The findings suggest a novel regulatory role for TRIF in limiting excessive TNF-α production during LPS stimulation.