Mouse primary microglia respond differently to LPS and poly(I:C) in vitro

Area of Science:

• Neuroimmunology
• Innate Immunity

Background:

• Microglia are key innate immune cells in the central nervous system (CNS).
• Toll-like receptors (TLRs) 3 and 4 recognize viral dsRNA (poly(I:C)) and bacterial endotoxin (LPS), respectively, activating microglia.
• Limited comparative studies exist on LPS- vs. poly(I:C)-induced microglial activation phenotypes and mechanisms.

Purpose of the Study:

• To comprehensively compare the functional phenotypes and downstream molecular mechanisms of primary mouse microglia stimulated by LPS and poly(I:C).
• To elucidate the distinct signaling pathways and gene expression profiles triggered by these two TLR agonists.
• To assess the impact of LPS- and poly(I:C)-activated microglia on neurotoxicity.

Main Methods:

• Primary mouse microglia were stimulated with LPS and poly(I:C).
• Phenotypic analyses included morphology, proliferation, secretion, chemotaxis, and phagocytosis.
• Genome-wide gene expression analysis and exploration of downstream signaling cascades (e.g., NF-κB, type I interferon pathways) were performed.
• Neurotoxicity was evaluated in a co-culture system.

Main Results:

• LPS induced an ameboid microglial morphology and proliferation, while poly(I:C) induced a bushy morphology without significant proliferation.
• Differential modulation of microglial chemotaxis and phagocytosis was observed between LPS and poly(I:C) treatments.
• Genome-wide analysis revealed distinct gene expression patterns, linked to NF-κB and type I interferon pathways.
• Both LPS- and poly(I:C)-activated microglia exhibited neurotoxic effects in co-culture.

Conclusions:

• LPS and poly(I:C) elicit distinct microglial activation patterns and downstream molecular responses.
• These findings highlight the importance of selecting appropriate inflammatory microglial models for research.
• The study provides insights into potential therapeutic targets for neuroinflammatory conditions.