Hypoxia-inducible factor 2α regulates macrophage function in mouse models of acute and tumor inflammation
Hongxia Z. Imtiyaz, Emily P. Williams, Michele M. Hickey, Shetal A. Patel, Amy C. Durham, Li-Jun Yuan, Rachel Hammond, Phyllis A. Gimotty, Brian Keith, M. Celeste Simon
Hongxia Z. Imtiyaz, Emily P. Williams, Michele M. Hickey, Shetal A. Patel, Amy C. Durham, Li-Jun Yuan, Rachel Hammond, Phyllis A. Gimotty, Brian Keith, M. Celeste Simon
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Research Article Oncology

Hypoxia-inducible factor 2α regulates macrophage function in mouse models of acute and tumor inflammation

Abstract

Hypoxia-inducible factor 1α (HIF-1α) and HIF-2α display unique and sometimes opposing activities in regulating cellular energy homeostasis, cell fate decisions, and oncogenesis. Macrophages exposed to hypoxia accumulate both HIF-1α and HIF-2α, and overexpression of HIF-2α in tumor-associated macrophages (TAMs) is specifically correlated with high-grade human tumors and poor prognosis. However, the precise role of HIF-2α during macrophage-mediated inflammatory responses remains unclear. To fully characterize cellular hypoxic adaptations, distinct functions of HIF-1α versus HIF-2α must be elucidated. We demonstrate here that mice lacking HIF-2α in myeloid cells (Hif2aΔ/Δ mice) are resistant to lipopolysaccharide-induced endotoxemia and display a marked inability to mount inflammatory responses to cutaneous and peritoneal irritants. Furthermore, HIF-2α directly regulated proinflammatory cytokine/chemokine expression in macrophages activated in vitro. Hif2aΔ/Δ mice displayed reduced TAM infiltration in independent murine hepatocellular and colitis-associated colon carcinoma models, and this was associated with reduced tumor cell proliferation and progression. Notably, HIF-2α modulated macrophage migration by regulating the expression of the cytokine receptor M-CSFR and the chemokine receptor CXCR4, without altering intracellular ATP levels. Collectively, our data identify HIF-2α as an important regulator of innate immunity, suggesting it may be a useful therapeutic target for treating inflammatory disorders and cancer.

Authors

Hongxia Z. Imtiyaz, Emily P. Williams, Michele M. Hickey, Shetal A. Patel, Amy C. Durham, Li-Jun Yuan, Rachel Hammond, Phyllis A. Gimotty, Brian Keith, M. Celeste Simon

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Figure 9

Reduced migration and invasion, but normal ATP production in HIF-2α–deficient macrophages.

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Reduced migration and invasion, but normal ATP production in HIF-2α–defi...
(A) BMDMs were exposed to normoxia or hypoxia for 16 hours, and their in vitro migration capacity toward the chemoattractant M-CSF was determined by employing a barrier PET membrane (8 μm; BD Biosciences). Representative images are shown. Scale bars: 20 μm. (B) Quantification of migrated macrophages. Representative data are shown from n = 4 mice (*P < 0.05). (C) Invasion was tested as described above for migration, except that the barrier PET membrane was coated with Matrigel basement membrane matrix (BD Biosciences). Representative images are shown. Scale bars: 20 μm. (D) Quantification of macrophages that invaded through the Matrigel. Representative data from n = 3 mice are shown (*P < 0.05, **P < 0.01). (E) BMDMs were exposed to normoxia or hypoxia for 20 hours, and cellular ATP levels were determined using the ApoGlow Assay kit. Representative data from at least 3 independent experiments are shown. (F) Expression of M-CSFR under normoxia and hypoxia was determined by Western blotting. Representative data from 3 independent experiments are shown. Lanes were run on the same gel but were noncontiguous (white lines). (G) Cxcr4 and Fn1 expression in normoxic and hypoxic BMDMs was evaluated by QRT-PCR. Representative data from at least 3 independent experiments are shown (*P < 0.05, **P < 0.01). N, normoxia (21% O2); H, hypoxia (0.5% O2).