Legionella-Infected Macrophages Engage the Alveolar Epithelium to Metabolically Reprogram Myeloid Cells and Promote...

Area of Science:

• Immunology
• Cell Biology
• Microbiology

Background:

• Alveolar macrophages are key early responders to inhaled pathogens.
• Pathogens like Legionella pneumophila can evade macrophage defenses by inhibiting host translation.
• Despite impaired responses in infected macrophages, a controlled inflammatory response is mounted via interleukin-1 (IL-1).

Purpose of the Study:

• To elucidate the mechanism by which IL-1 directs inflammatory cytokine production in recruited cells.
• To investigate the role of alveolar epithelial cells in coordinating antimicrobial responses.
• To understand how monocytes are metabolically reprogrammed for antibacterial inflammation.

Main Methods:

• Investigated the interaction between alveolar macrophages, alveolar epithelium, and recruited monocytes during Legionella infection.
• Analyzed the production of cytokines, specifically IL-1 and granulocyte-macrophage colony-stimulating factor (GM-CSF).
• Examined the metabolic reprogramming of monocytes, focusing on Toll-like receptor (TLR)-induced glycolysis.

Main Results:

• IL-1 signaling induces alveolar epithelial cells to produce GM-CSF.
• GM-CSF amplifies inflammatory cytokine production in recruited monocytes.
• This amplification is mediated by enhanced TLR-induced glycolysis in monocytes.
• Alveolar macrophages initiate this communication pathway.

Conclusions:

• Alveolar epithelial cells are critical partners in controlling Legionella infection.
• The alveolar epithelium, stimulated by IL-1, produces GM-CSF that reprograms monocytes.
• Monocyte reprogramming involves metabolic shifts enhancing their inflammatory capacity.
• This study reveals a novel mechanism of inter-cellular communication for metabolic reprogramming of immune cells during infection.