Macrophage activation by exopolysaccharides from Streptococcus thermophilus fermented milk through TLRs-mediated...

Area of Science:

• Immunology and Microbiology
• Biochemistry and Molecular Biology

Background:

• Lactic acid bacteria exopolysaccharides (EPS) are recognized for their immunomodulatory properties.
• A novel exopolysaccharide, EPS-3A, was previously isolated from Streptococcus thermophilus (ZJUIDS-2-01) and structurally characterized.

Purpose of the Study:

• To investigate the effects of EPS-3A on macrophage activation.
• To elucidate the underlying molecular mechanisms of EPS-3A-induced macrophage activation.

Main Methods:

• Macrophage activation assays measuring TNF-α secretion and phagocytic activity.
• RNA sequencing (RNA-seq) to identify differentially expressed genes (DEGs).
• Bioinformatic analyses including Gene Ontology (GO), Protein-Protein Interaction (PPI) networks, and KEGG pathway analysis.
• Western blot and functional assays to validate key signaling pathways (MAPK, NF-κB) and receptors (TLR2, TLR4).

Main Results:

• EPS-3A significantly promoted TNF-α secretion and enhanced phagocytic uptake in macrophages.
• RNA-seq identified 949 DEGs, predominantly enriched in immune-related metabolic pathways.
• MAPK and NF-κB signaling pathways were identified as key regulators of TNF-α expression.
• Toll-like receptors 2 (TLR2) and 4 (TLR4) were implicated in the recognition of EPS-3A.

Conclusions:

• EPS-3A effectively activates macrophages, enhancing their immune functions.
• Macrophage activation by EPS-3A is mediated through the MAPK and NF-κB signaling pathways.
• The recognition of EPS-3A by macrophages involves TLR2 and TLR4, highlighting their role in mediating the immune response.