HIF-1α coordinates lymphangiogenesis during wound healing and in response to inflammation.
ABSTRACT This study aimed to investigate the mechanisms that coordinate lymphangiogenesis. Using mouse models of lymphatic regeneration and inflammatory lymphangiogenesis, we explored the hypothesis that hypoxia inducible factor-α (HIF-1α) is a central regulator of lymphangiogenesis. We show that HIF-1α inhibition by small molecule inhibitors (YC-1 and 2-methyoxyestradiol) results in delayed lymphatic repair, decreased local vascular endothelial growth factor-C (VEGF-C) expression, reduced numbers of VEGF-C(+) cells, and reductions in inflammatory lymphangiogenesis. Using transgenic HIF-1α/luciferase mice to image HIF-1α expression in real time in addition to Western blot analysis and pimonidazole staining for cellular hypoxia, we demonstrate that hypoxia stabilizes HIF-1α during initial stages of wound repair (1-2 wk); whereas inflammation secondary to gradients of lymphatic fluid stasis stabilizes HIF-1α thereafter (3-6 wk). In addition, we show that CD4(+) cell-mediated inflammation is necessary for this response and regulates HIF-1α expression by macrophages, as CD4-deficient or CD4-depleted mice demonstrate 2-fold reductions in HIF-1α expression as compared to wild-types. In summary, we show that HIF-1α is a critical coordinator of lymphangiogenesis by regulating the expression of lymphangiogenic cytokines as part of an early response mechanism to hypoxia, inflammation, and lymphatic fluid stasis.
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ABSTRACT: Hypoxia inducible factor-1 (HIF-1) is as a key transcriptional mediator of the hypoxic response in eukaryotic cells, regulating the expression of a myriad of genes involved in oxygen transport, glucose uptake and glycolysis and angiogenesis. Deregulation of HIF-1 activity occurs in many human cancers, usually at the level of the HIF-1alpha subunit. HIF-1 is regulated by a variety of mechanisms including transcription, translation post-translational modification, protein-protein interaction and degradation. Our understanding of the key signalling pathways that regulate HIF-1 has significantly progressed in recent years and has highlighted the potential for targeting the HIF-1 pathway as a basis for the development of new cancer therapies.Biochimica et Biophysica Acta 08/2005; 1755(2):107-20. · 4.66 Impact Factor
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ABSTRACT: Hypoxia-inducible factor-1alpha (HIF-1alpha) is believed to promote tumor growth, and thus, is viewed as one of the most compelling cancer therapy targets. YC-1 is widely used as a potent inhibitor of HIF-1alpha both in vitro and in vivo, and is also being developed as a novel anticancer drug. However, little is known about the effects of YC-1 on tumor invasion or metastasis. In the present study, we found that the Hep3B cell migration-stimulatory effect of hypoxia was abolished by HIF-1alpha siRNA or YC-1. YC-1 also significantly inhibited the migrations of other cancer cells. Furthermore, YC-1 effectively inhibited cell invasion through Matrigel. In nude mice, GFP-expressing stable cell-lines of Hep3B or H1299 were inoculated into spleens to induce liver metastasis or into the pleural cavity to induce lung invasion. In untreated mice, many tumor lesions emitting strong fluorescence were found in livers or lungs, and fluorescence intensities and tumor lesion numbers were markedly reduced in YC-1-treated mice. These results suggest that YC-1 effectively inhibits tumor invasion and metastasis, and imply that YC-1 is worth while to further develop as a multipurpose anticancer drug.Cancer Letters 10/2007; 255(1):107-16. · 4.24 Impact Factor
Article: Overexpression of VEGF-C causes transient lymphatic hyperplasia but not increased lymphangiogenesis in regenerating skin.[show abstract] [hide abstract]
ABSTRACT: Vascular endothelial growth factor (VEGF)-C is necessary for lymphangiogenesis and holds potential for lymphangiogenic therapy in diseases lacking adequate lymphatic drainage. However, the ability of VEGF-C to enhance sustainable, functional lymphatic growth in adult tissues remains unclear. To address this, we evaluated VEGF-C overexpression in adult lymphangiogenesis in regenerating skin. We used a model of mouse tail skin regeneration incorporating a suspension of either VEGF-C overexpressing tumor cells, which provide a continuous supplement of excess VEGF-C to the natural regenerating environment for more than 25 days, or otherwise identical control-transfected tumor cells. We found that excess VEGF-C did not enhance the rate of lymphatic endothelial cell (LEC) migration, the density of lymphatic vessels, or the rate of functionality -- even though lymphatic hyperplasia was present early on. Furthermore, the hyperplasia disappeared when VEGF-C levels diminished, which occurred after 25 days, rendering the lymphatics indistinguishable from those in control groups. In vitro, we showed that whereas cell-derived VEGF-C could induce chemoattraction of LECs across a membrane (which involves amoeboid-like transmigration), it did not increase LEC chemoinvasion within a 3-dimensional fibrin matrix (which requires proteolytic migration). These results suggest that whereas excess VEGF-C may enhance early LEC proliferation and cause lymphatic vessel hyperplasia, it does not augment the physiological rate of migration or functionality, and by itself cannot sustain any lasting effects on lymphatic size, density, or organization in regenerating adult skin.Circulation Research 07/2005; 96(11):1193-9. · 9.49 Impact Factor