Temporal control of macrophage pro-inflammatory phenotype by a biphasic HIF-1α regulatory program

Area of Science:

• Immunology
• Cellular Metabolism
• Molecular Biology

Background:

• Hypoxia-inducible factor 1α (HIF-1α) is a key regulator of cellular metabolism, particularly in inflammatory macrophages.
• The precise timing and mechanisms by which HIF-1α influences early inflammatory responses and metabolic reprogramming after pattern recognition receptor activation are not fully understood.

Purpose of the Study:

• To investigate the early functional activation of HIF-1α in macrophages following inflammatory stimulation.
• To elucidate the role of the Rubicon (RUBCN)-NADPH oxidase (NOX2) reactive oxygen species (ROS) circuit in early HIF-1α stabilization and subsequent inflammatory signaling.
• To determine how early HIF-1α activity impacts metabolic adaptation and antimicrobial functions in macrophages.

Main Methods:

• Macrophage cell culture and stimulation with inflammatory stimuli.
• Assessment of HIF-1α activity, ROS production, and glycolysis.
• Measurement of cytokine production, nitric oxide (NO) generation, and bacterial killing.
• Analysis of mitochondrial function and electron transport chain activity.

Main Results:

• HIF-1α becomes functionally active shortly after macrophage stimulation via a RUBCN-NOX2 ROS circuit.
• Early HIF-1α activation drives glycolysis, cytokine production, and bacterial killing preceding significant protein accumulation.
• Primed HIF-1α promotes inducible nitric oxide synthase (iNOS) and NO production, leading to mitochondrial dysfunction independently of the initial RUBCN-NOX2 pathway.

Conclusions:

• A temporally coordinated HIF-1α pathway integrates RUBCN-NOX2 redox signaling to control early macrophage inflammatory responses.
• This pathway is critical for metabolic adaptation, including enhanced glycolysis and NO production.
• The findings reveal a novel mechanism linking early redox signaling to metabolic reprogramming and antimicrobial defense in macrophages.