Prebiotic oligosaccharides directly modulate proinflammatory cytokine production in monocytes via activation of TLR4

Area of Science:

• Immunology
• Microbiology
• Nutrition Science

Background:

• Prebiotic oligosaccharides are recognized for their influence on gut microbiota composition and function.
• Their direct effects on immune cells, independent of microbial interactions, remain less understood.

Purpose of the Study:

• To investigate the direct, microbiota-independent effects of prebiotics on monocytes and T lymphocytes in vitro.
• To elucidate the signaling pathways involved in prebiotic-induced immune cell modulation.

Main Methods:

• In vitro culture of mouse splenocytes, rat monocytes, and human peripheral blood monocytes.
• Stimulation with prebiotics (fructooligosaccharides and inulin) and lipopolysaccharide (LPS).
• Measurement of cytokine secretion (TNF-α, IL-6, IL-10, IFN-γ, IL-17, IL-1β, IL-8) and analysis of signaling pathways (TLR4, NF-κB, MAPK, PI3K).

Main Results:

• Prebiotics induced cytokine secretion (TNF-α, IL-6, IL-10) in mouse splenocytes and human monocytes.
• Prebiotics inhibited LPS-induced IFN-γ and IL-17 release in mouse splenocytes, an effect preserved in TLR4(-/-) mice.
• Fructooligosaccharides and inulin upregulated TNF-α, growth-regulated oncogene α, and IL-10 in rat monocytes via NF-κB, MAPK, and PI3K pathways.
• Minimal effects were observed on T lymphocytes.

Conclusions:

• Prebiotics can directly modulate monocyte cytokine production, independent of their effects on gut microbiota.
• Prebiotics may act as Toll-like receptor 4 (TLR4) ligands or modulators, upregulating cytokine secretion in monocytes.
• These findings highlight a direct immunomodulatory role for prebiotics on innate immune cells.