HIF1α-dependent hypoxia response in myeloid cells requires IRE1α

Area of Science:

• Immunology
• Cellular Biology
• Molecular Biology

Background:

• Cellular adaptation to hypoxia and metabolic stress is vital for immune cell function in injured tissues.
• Hypoxia-Inducible Factor (HIF)-1α is essential for myeloid cell inflammatory responses, regulating glycolysis.
• The precise triggers for HIF1α activation during inflammation remain largely unknown.

Purpose of the Study:

• To investigate the role of the inositol-requiring enzyme 1α (IRE1α/XBP1) axis in initiating HIF1α-dependent inflammatory responses.
• To elucidate the mechanisms by which innate immune cells adapt to low oxygen tension and metabolic stress.
• To determine the impact of IRE1α and HIF1α on pathological angiogenesis in sterile inflammation.

Main Methods:

• Utilizing knockout models of HIF1α and IRE1α in myeloid cells.
• Analyzing cytokine production (IL1β, IL6, VEGF-A) under hypoxic conditions.
• Evaluating vascular phenotypes in a model of sterile inflammatory retinal angiogenesis.

Main Results:

• The IRE1α/XBP1 axis is required for HIF1α-dependent production of key inflammatory cytokines.
• Knockout of HIF1α or IRE1α in myeloid cells significantly reduces vascular abnormalities in pathological angiogenesis.
• ER stress pathways, in conjunction with HIF1α, appear to co-regulate immune adaptation to hypoxia.

Conclusions:

• The IRE1α/XBP1 pathway is a critical upstream regulator of HIF1α activation in innate immune cells.
• Targeting the IRE1α/HIF1α axis may offer therapeutic strategies for inflammatory diseases characterized by hypoxia and angiogenesis.
• Immune cell adaptation to low oxygen involves a coordinated interplay between ER stress and HIF1α signaling.