Synergystic induction of HIF-1alpha transcriptional activity by hypoxia and lipopolysaccharide in macrophages
| Autor: | Mark Creighton-Gutteridge, Luigi Varesio, Annamaria Rapisarda, Alan D. Brooks, Zenghui Mi, Giovanni Melillo, Lynn S. Taylor |
|---|---|
| Rok vydání: | 2008 |
| Předmět: |
Lipopolysaccharides
Transcriptional Activation Lipopolysaccharide Nitric Oxide Synthase Type II Biology Response Elements Cell Line chemistry.chemical_compound Mice Gene expression medicine Animals Binding site Molecular Biology Messenger RNA Macrophages NF-kappa B Cell Biology Hypoxia (medical) Hypoxia-Inducible Factor 1 alpha Subunit Molecular biology Cell Hypoxia Nitric oxide synthase chemistry Cell culture biology.protein Signal transduction medicine.symptom Developmental Biology |
| Zdroj: | Cell cycle (Georgetown, Tex.). 7(2) |
| ISSN: | 1551-4005 |
| Popis: | Hypoxia Inducible Factor-1 (HIF-1) is activated by a variety of stimuli, including inflammatory mediators. In this report we investigated the role that bacterial lipopolysaccharide (LPS) and hypoxia play in the regulation of HIF-1-dependent gene expression in macrophages. We report that murine macrophages stimulated with low concentrations of LPS (1-10 ng/ml) expressed significantly higher levels of inducible nitric oxide synthase (iNOS) mRNA when cultured under hypoxic compared to normoxic conditions. Functional studies of the iNOS promoter demonstrated that the synergistic interaction between LPS and hypoxia was mediated, at least in part, by the NFkappaB and the HIF-1 binding sites. In addition, transient transfection experiments using a Hypoxia Response Element (HRE)-containing plasmid showed that LPS and hypoxia synergistically induced HIF-1-dependent transcriptional activity. Interestingly, LPS did not significantly affect HIF-1alpha protein levels or HIF-1 DNA binding activity relative to hypoxic induction. HIF-1alpha, but not HIF-2alpha, was critical for the synergistic induction of HRE-dependent transcriptional activity in macrophages, as indicated by experiments using siRNA targeting HIF-1alpha or HIF-2alpha. Addition of ROS-scavengers completely abrogated the synergistic induction of HIF-1 transcriptional activity by LPS and hypoxia, but neither inhibited HIF-1 transcriptional activity induced by hypoxia alone nor affected HIF-1alpha protein levels or HIF-1 DNA binding induced by hypoxia alone or hypoxia plus LPS. Taken together, our results demonstrate that LPS and hypoxia act synergistically to induce HIF-1alpha-transcriptional activity and they emphasize the existence of a cross talk between hypoxic and non-hypoxic signaling pathways in the regulation of macrophages gene expression. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|