mTORC1 Signaling Regulates Proinflammatory Macrophage Function and Metabolism

Area of Science:

• Immunology
• Cellular Metabolism
• Molecular Biology

Background:

• Metabolic programming critically influences immune cell function, particularly macrophage differentiation.
• Proinflammatory M1 macrophages utilize glycolysis for energy and antimicrobial compounds.
• Alternatively activated M2 macrophages rely on oxidative phosphorylation for wound healing.
• Mammalian target of rapamycin (mTOR) signaling regulates immune cell metabolism and function.
• mTORC2 is essential for M2 macrophage generation, while mTORC1's role in M1 glycolysis is debated.

Purpose of the Study:

• To investigate the role of mTORC1 signaling in M1 macrophage metabolism and function.
• To explore the mechanistic basis for observed changes in M1 macrophage activity upon mTORC1 deletion.

Main Methods:

• Genetic deletion of mTORC1 signaling in C57BL/6 mouse macrophages.
• In vitro and in vivo assessment of M1 macrophage function.
• Analysis of macrophage glycolytic metabolism.
• Investigation of the role of sirtuins and histone acetylation.

Main Results:

• Genetic deletion of mTORC1 signaling enhanced M1 macrophage function both in vitro and in vivo.
• This enhancement occurred despite a significant defect in M1 macrophage glycolytic metabolism.
• Mechanistically, enhanced M1 function was attributed to the inhibition of sirtuins, leading to increased histone acetylation.

Conclusions:

• Enhanced M1 macrophage function can occur independently of increased cellular metabolism.
• Inhibition of sirtuins and subsequent histone acetylation are key mechanisms driving enhanced M1 function.
• These findings challenge the established paradigm linking cellular metabolism to immune cell function.
• The study identifies sirtuins as a potential pharmacologic target for modulating inflammatory responses.