Absolute Requirement of Aryl Hydrocarbon Receptor Nuclear Translocator Protein for Gene Activation by Hypoxia

doi:10.1006/abbi.1996.0469

Archives of Biochemistry and Biophysics

Volume 334, Issue 2, 15 October 1996, Pages 389-394

https://doi.org/10.1006/abbi.1996.0469 Get rights and content

Abstract

Hypoxia-inducible factor 1 (HIF-1) is a DNA-binding heterodimeric protein complex originally described in the transcriptional activation of the erythropoietin gene by hypoxia. This protein complex is composed of two subunits, HIF-1α and -1β (aryl hydrocarbon receptor nuclear translocator, ARNT). In this study, we used ARNT-deficient cells, derived from the mouse hepatoma cell line Hepa1c1c7, to further characterize HIF-1 complex formation and its relationship with gene activation by hypoxia and desferrioxamine (Df). Gel shift assays revealed that ARNT is absolutely required for the formation of the HIF-1 DNA-binding complex. Results from RNase protection assays and Northern blots showed that the lack of functional HIF-1 complex completely abrogated the response to hypoxia of vascular endothelial growth factor (VEGF) and the glycolytic enzymes aldolase A (ALDA) and phosphoglycerate kinase 1 (PGK-1), genes known to be upregulated by low oxygen tension. Desferrioxamine induction of VEGF and PGK-1 genes was reduced in the ARNT-deficient cells, but at difference with hypoxia, it was not completely suppressed. These results suggest that Df is able to activate gene transcription through HIF-1-independent mechanisms. Exposure to hypoxia or Df did not induce any changes in HIF-1α and -1β mRNA levels, suggesting that posttranscriptional mechanisms are involved in HIF-1 complex activation.

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Cited by (83)

Mutual antagonism between aryl hydrocarbon receptor and hypoxia-inducible factor-1α (AhR/HIF-1α) signaling: Impact on the aging process
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Citation Excerpt :
However, the activation of AhR did not reduce the expression of HIF-1α-dependent target genes, e.g., EPO and aldolase A (ALDA), in HepG2 cells. Salceda et al. [78] demonstrated that ARNT factor was crucially required for the formation of the HRE-binding complexes and transcription of hypoxia-responsible genes. The expression of HIF-1α factor increased the level of ARNT protein through its stabilization in several cultured cell types [79].
The ambient oxygen level, many environmental toxins, and the rays of ultraviolet light (UV) provide a significant risk for the maintenance of organismal homeostasis. The aryl hydrocarbon receptors (AhR) represent a complex sensor system not only for environmental toxins and UV radiation but also for many endogenous ligands, e.g., L-tryptophan metabolites. The AhR signaling system is evolutionarily conserved and AhR homologs existed as many as 600 million years ago. The ancient atmosphere demanded the evolution of an oxygen-sensing system, i.e., hypoxia-inducible transcription factors (HIF) and their prolyl hydroxylase regulators (PHD). Given that both signaling systems have important roles in embryogenesis, it seems that they have been involved in the evolution of multicellular organisms. The evolutionary origin of the aging process is unknown although it is most likely associated with the evolution of multicellularity. Intriguingly, there is compelling evidence that while HIF-1α signaling extends the lifespan, that of AhR promotes many age-related degenerative processes, e.g., it increases oxidative stress, inhibits autophagy, promotes cellular senescence, and aggravates extracellular matrix degeneration. In contrast, HIF-1α signaling stimulates autophagy, inhibits cellular senescence, and enhances cell proliferation. Interestingly, there is a clear antagonism between the AhR and HIF-1α signaling pathways. For instance, (i) AhR and HIF-1α factors heterodimerize with the same factor, ARNT/HIF-1β, leading to their competition for DNA-binding, (ii) AhR and HIF-1α signaling exert antagonistic effects on autophagy, and (iii) co-chaperone p23 exhibits specific functions in the signaling of AhR and HIF-1α factors. One might speculate that it is the competition between the AhR and HIF-1α signaling pathways that is a driving force in the aging process.
Hypoxia signaling and oxygen metabolism in cardio-oncology
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Cardio-oncology is a rapidly growing field in cardiology that focuses on the management of cardiovascular toxicities associated with cancer-directed therapies. Tumor hypoxia is a central driver of pathologic tumor growth, metastasis, and chemo-resistance. In addition, conditions that mimic hypoxia (pseudo-hypoxia) play a causal role in the pathogenesis of numerous types of cancer, including renal cell carcinoma. Therefore, therapies targeted at hypoxia signaling pathways have emerged over the past several years. Though efficacious, these therapies are associated with significant cardiovascular toxicities, ranging from hypertension to cardiomyopathy. This review focuses on oxygen metabolism in tumorigenesis, the role of targeting hypoxia signaling in cancer therapy, and the relevance of oxygen metabolism in cardio-oncology. This review will specifically focus on hypoxia signaling mediated by hypoxia-inducible factors and the prolyl hydroxylase oxygen-sensing enzymes, the cardiovascular effects of specific cancer targeted therapies mediated on VEGF and HIF signaling, hypoxic signaling in cardiovascular disease, and the role of oxygen in anthracycline cardiotoxicity. The implications of these therapies on myocardial biology and cardiac function are discussed, underlining the fine balance of hypoxia signaling in cardiac homeostasis. Understanding these cardiovascular toxicities will be important to optimize treatment for cancer patients while mitigating potentially severe cardiovascular side effects.
Monocyte-derived macrophages matured under prolonged hypoxia transcriptionally up-regulate HIF-1α mrna
2011, Immunobiology
Citation Excerpt :
HIF-1 is the main hypoxia-inducible transcription factor, and is responsible for controlling the expression of at least 70 genes (Ebert et al. 1995; Forsythe et al. 1996; Salceda et al. 1996; Wenger et al. 2005).
This study tested the hypothesis that prolonged severe hypoxia during monocyte to macrophage differentiation results in macrophages with a pattern of gene expression and phenotype distinct from those maturing in normal oxygen levels. Macrophages accumulate in hypoxic and anoxic areas within pathological sites such as tumours, wounds, and arthritic joints, and have been proposed as vehicles for gene therapy delivery to such tissues. Several non-pathological tissues are also hypoxic. We therefore argue that differentiation from monocyte to macrophage in hypoxic conditions is a common occurrence. However, the effect of long term severe hypoxia on monocyte to macrophage differentiation has not been studied. Here, using primary human peripheral blood monocytes, we show that maturation for 5 days in 0.2% oxygen results in decreased phagocytosis, and decreased CD40 and CD206 expression. Chronic hypoxia induced much higher mRNA levels of the pro-angiogenic cytokine, VEGF, in adherence-purified macrophages (27-fold), CD14-magnetic bead purified monocytes (90-fold), and PBMC (104-fold) compared to acute (24 h) hypoxia (11, 17 and 9-fold, respectively). This suggests that macrophages may play an even greater role in angiogenesis than previously appreciated. Furthermore, chronic hypoxia resulted in up-regulation of HIF-1α mRNA, in all monocyte-derived macrophage types studied. Actinomycin D experiments indicate that the increases in HIF-1α mRNA were not due to increased mRNA stability. To our knowledge this is the first study demonstrating up-regulation of HIF-1α mRNA by hypoxia in macrophages. Taken together, the data support the hypothesis that hypoxia affects monocyte to macrophage maturation, resulting in a distinct gene expression pattern and phenotype.
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2008, American Journal of Pathology
Endometriosis, the presence of ectopic endometrial tissue outside the uterine cavity, is a common disease affecting women during their reproductive years. Current therapeutic success is often unsatisfactory because of limited insight into disease mechanisms. Nevertheless, angiogenesis plays an essential role in the pathogenesis of the disease, making it a potential novel target for therapy. In the current study, we demonstrate in an established mouse model of endometriosis that transient hypoxia in transplanted endometriosis-like lesions results in the up-regulation of hypoxia-inducible factor-1α (HIF-1α), leading to the expression of vascular endothelial growth factor (VEGF), a key player in endometriosis-associated angiogenesis. Systemic treatment with the angiogenesis inhibitor 2-methoxyestradiol suppressed HIF-1α expression in vivo, resulting in a decreased downstream expression of HIF-1α target genes, such as for VEGF, phosphoglycerate kinase, and glucose transporter-1. 2-Methoxyestradiol also suppressed VEGF-induced vascular permeability, as demonstrated in a modified Miles assay. Finally, systemic treatment with 2-methoxyestradiol significantly inhibited the growth of endometriosis-like lesions in a dose-dependent manner. In conclusion, hypoxia appears to play an important role in the pathogenesis of endometriosis and endometriosis-associated angiogenesis, and the angiogenesis inhibitor 2-methoxyestradiol may be a potential candidate for systemic treatment in the future.
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¹: To whom correspondence should be addressed at Cardeza Foundation for Hematologic Research, Department of Medicine, Jefferson Medical College of Thomas Jefferson University, 1015 Walnut Street, Philadelphia, PA 19107. Fax: 215-923-3836.

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Regular ArticleAbsolute Requirement of Aryl Hydrocarbon Receptor Nuclear Translocator Protein for Gene Activation by Hypoxia

Abstract

Regular Article
Absolute Requirement of Aryl Hydrocarbon Receptor Nuclear Translocator Protein for Gene Activation by Hypoxia