LPS induces limited activation of hypoxia-inducible factor-1α in macrophages

Hypoxia-inducible factor-1α (HIF-1α) plays a crucial role in cellular and tissue adaptation to low oxygen conditions. Although inflammatory stimuli such as lipopolysaccharide (LPS) also increase HIF-1α levels under normoxia, its transcriptional activity and regulatory mechanisms in this context remain unclear. To address this, we performed chromatin immunoprecipitation sequencing and transcriptome analyses in murine macrophages stimulated with either LPS or hypoxia. Both stimuli stabilized HIF-1α protein but via distinct mechanisms: hypoxia acted post-translationally, whereas LPS increased Hif-1α mRNA expression. Genome-wide HIF-1α binding was observed under both conditions; however, only hypoxia induced broad transcriptional activation of target genes, whereas LPS upregulated a restricted set, mostly glycolytic genes. Motif enrichment analysis revealed that hypoxia, but not LPS, promoted cooperative transcription factor engagement, including HIF-1β, ETS, and bZIP family members. Hypoxia also increased H3K27 acetylation at HIF-1α target loci, consistent with a transcriptionally permissive chromatin state. In contrast, LPS led to reduced H3K27ac at noninduced loci, suggesting epigenetic repression. Mechanistically, HIF-1α exhibited a phosphorylation-dependent band shift under hypoxia but not LPS. Although both conditions showed comparable overall phosphorylation levels by Phos-tag analysis, only hypoxia triggered a conformational change, suggesting site-specific phosphorylation linked to transcriptional competence. These findings demonstrate that HIF-1α binding alone is insufficient for gene activation and that phosphorylation and chromatin context determine its transcriptional output in a stimulus-dependent manner.

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Journal
Journal of Biological Chemistry
Published
2025-11-13
DOI
https://doi.org/10.1016/j.jbc.2025.110932
Primary Topic
Cancer, Hypoxia, and Metabolism
Type
article
Field-Weighted Citation Impact
0.00

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article

LPS induces limited activation of hypoxia-inducible factor-1α in macrophages

Daigo Sawaki, Shun Minatsuki, Kazutoshi Ono, Masamichi Ito et al.
Journal of Biological Chemistry
Cancer, Hypoxia, and Metabolism
article

LPS induces limited activation of hypoxia-inducible factor-1α in macrophages

Daigo Sawaki, Shun Minatsuki, Kazutoshi Ono, Masamichi Ito, Takahiro Kuchimaru, Toshinaru Kawakami, Christian Stockmann, Ichiro Manabe, Thuc Toan Pham, Norihiko Takeda, Hiroki Sugimoto, M. Morioka, Yasutomi Higashikuni, Takahide Kohro, Masataka Asagiri, Takayuki Isagawa, Hidemasa U. Bono, Ryohei Tanaka, Tatsuyuki Sato, Hiroshi Harada, Shigeru Sato, Hiroaki Semba, Masaki Wake, Chuluun-Erdene Ariunbold
article en

Abstract

Hypoxia-inducible factor-1α (HIF-1α) plays a crucial role in cellular and tissue adaptation to low oxygen conditions. Although inflammatory stimuli such as lipopolysaccharide (LPS) also increase HIF-1α levels under normoxia, its transcriptional activity and regulatory mechanisms in this context remain unclear. To address this, we performed chromatin immunoprecipitation sequencing and transcriptome analyses in murine macrophages stimulated with either LPS or hypoxia. Both stimuli stabilized HIF-1α protein but via distinct mechanisms: hypoxia acted post-translationally, whereas LPS increased Hif-1α mRNA expression. Genome-wide HIF-1α binding was observed under both conditions; however, only hypoxia induced broad transcriptional activation of target genes, whereas LPS upregulated a restricted set, mostly glycolytic genes. Motif enrichment analysis revealed that hypoxia, but not LPS, promoted cooperative transcription factor engagement, including HIF-1β, ETS, and bZIP family members. Hypoxia also increased H3K27 acetylation at HIF-1α target loci, consistent with a transcriptionally permissive chromatin state. In contrast, LPS led to reduced H3K27ac at noninduced loci, suggesting epigenetic repression. Mechanistically, HIF-1α exhibited a phosphorylation-dependent band shift under hypoxia but not LPS. Although both conditions showed comparable overall phosphorylation levels by Phos-tag analysis, only hypoxia triggered a conformational change, suggesting site-specific phosphorylation linked to transcriptional competence. These findings demonstrate that HIF-1α binding alone is insufficient for gene activation and that phosphorylation and chromatin context determine its transcriptional output in a stimulus-dependent manner.

Journal of Biological ChemistryVol. 301(12)
Hiroshima University (JP), Jichi Medical University (JP), Chiba University (JP), Yamaguchi University (JP), University of Zurich (CH), Japan Society for the Promotion of Science (JP), Kyoto University (JP), RIKEN Center for Integrative Medical Sciences (JP), The University of Tokyo (JP)
Cell Science Research Foundation, Nakatomi Foundation, Fukuda Foundation for Medical Technology, Jichi Medical University, Tsuchiya Foundation, Japan Society for the Promotion of Science
Openalex Percentile: Top 58%
Cancer, Hypoxia, and Metabolism
DOIOpen Access PDFOpenAlex
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