Article

Endothelial HIF-2α regulates murine pathological angiogenesis and revascularization processes.

Howard Hughes Medical Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6160, USA.
The Journal of clinical investigation (Impact Factor: 13.77). 03/2012; 122(4):1427-43. DOI: 10.1172/JCI57322
Source: PubMed

ABSTRACT Localized tissue hypoxia is a consequence of vascular compromise or rapid cellular proliferation and is a potent inducer of compensatory angiogenesis. The oxygen-responsive transcriptional regulator hypoxia-inducible factor 2α (HIF-2α) is highly expressed in vascular ECs and, along with HIF-1α, activates expression of target genes whose products modulate vascular functions and angiogenesis. However, the mechanisms by which HIF-2α regulates EC function and tissue perfusion under physiological and pathological conditions are poorly understood. Using mice in which Hif2a was specifically deleted in ECs, we demonstrate here that HIF-2α expression is required for angiogenic responses during hindlimb ischemia and for the growth of autochthonous skin tumors. EC-specific Hif2a deletion resulted in increased vessel formation in both models; however, these vessels failed to undergo proper arteriogenesis, resulting in poor perfusion. Analysis of cultured HIF-2α-deficient ECs revealed cell-autonomous increases in migration, invasion, and morphogenetic activity, which correlated with HIF-2α-dependent expression of specific angiogenic factors, including delta-like ligand 4 (Dll4), a Notch ligand, and angiopoietin 2. By stimulating Dll4 signaling in cultured ECs or restoring Dll4 expression in ischemic muscle tissue, we rescued most of the HIF-2α-dependent EC phenotypes in vitro and in vivo, emphasizing the critical role of Dll4/Notch signaling as a downstream target of HIF-2α in ECs. These results indicate that HIF-1α and HIF-2α fulfill complementary, but largely nonoverlapping, essential functions in pathophysiological angiogenesis.

0 Followers
 · 
143 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Seventy years from the formalization of the Krebs cycle as the central metabolic turntable sustaining the cell respiratory process, key functions of several of its intermediates, especially succinate, and fumarate, have been recently uncovered. The presumably immutable organization of the cycle has been challenged by a number of observations, and the variable subcellular location of a number of its constitutive protein components is now well recognized, although yet unexplained. Nonetheless, the most striking observations have been made in the recent period while investigating human diseases, especially a set of specific cancers, revealing the crucial role of Krebs cycle intermediates as factors affecting genes methylation and thus cell remodeling. We review here the recent advances and persisting incognita about the role of Krebs cycle acids in diverse aspects of cellular life and human pathology.
    Biochimica et Biophysica Acta 03/2014; 1837(8). DOI:10.1016/j.bbabio.2014.03.013 · 4.66 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Lymphangiogenesis, the formation of new lymphatic vessels, is thought to constitute a route for the tumor cells to metastasize. We previously demonstrated that endothelin-1 (ET-1) induces the expression of lymphangiogenic factors through hypoxia-inducible factor (HIF)-1α and HIF-2α. The stability of these transcriptional factors is essential for lymph/angiogenesis and tumor progression. Here we analyse the molecular mechanism through which ET-1 regulates HIF-1α and HIF-2α protein levels and how these transcriptional factors are implicated in controlling lymphatic endothelial cell (LEC) behaviour. Using Western blotting assay and a reporter gene containing the HIF-1α oxygen-dependent degradation domain we monitored the capacity of ET-1 to increase HIF-1α and HIF-2α stability and nuclear accumulation. In addition, using siRNA against HIF-1α or HIF-2α, we investigated the implication of these transcriptional factors in ET-1-mediated tube-like structure formation. As HIF-1α proteosomal degradation is controlled by site-specific hydroxylation carried out by HIF-prolyl hydroxylase domain (PHD) enzymes, we analysed the expression of PHD-2 isoform. We show that ET-1 through its receptor, ETBR, controls HIF-α stability and nuclear accumulation by inhibiting prolyl hydroxylation and reduces PHD2 mRNA and protein levels. Transfection with HIF-1α or HIF-2α siRNA abrogated the capacity of ET-1 to induce tube-like structure formation. These results reveal a PHD2-mediated mechanism through which ET-1 stabilizes HIF-1α and HIF-2α pathway thereby regulating LEC behaviour and lymphangiogenesis.
    Life sciences 03/2014; 118(2). DOI:10.1016/j.lfs.2014.02.030 · 2.30 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Arteriogenesis requires growth of pre-existing arteriolar collateral networks and determines clinical outcome in arterial occlusive diseases. Factors responsible for the development of arteriolar collateral networks are poorly understood. The Notch ligand Delta-like 4 (Dll4) promotes arterial differentiation and restricts vessel branching. We hypothesized that Dll4 may act as a genetic determinant of collateral arterial networks and functional recovery in stroke and hind limb ischemia models in mice. Genetic loss- and gain-of-function approaches in mice showed that Dll4-Notch signaling restricts pial collateral artery formation by modulating arterial branching morphogenesis during embryogenesis. Adult Dll4(+/-) mice showed increased pial collateral numbers, but stroke volume upon middle cerebral artery occlusion was not reduced compared with wild-type littermates. Likewise, Dll4(+/-) mice showed reduced blood flow conductance after femoral artery occlusion, and, despite markedly increased angiogenesis, tissue ischemia was more severe. In peripheral arteries, loss of Dll4 adversely affected excitation-contraction coupling in arterial smooth muscle in response to vasopressor agents and arterial vessel wall adaption in response to increases in blood flow, collectively contributing to reduced flow reserve. We conclude that Dll4-Notch signaling modulates native collateral formation by acting on vascular branching morphogenesis during embryogenesis. Dll4 furthermore affects tissue perfusion by acting on arterial function and structure. Loss of Dll4 stimulates collateral formation and angiogenesis, but in the context of ischemic diseases such beneficial effects are overruled by adverse functional changes, demonstrating that ischemic recovery is not solely determined by collateral number but rather by vessel functionality.
    Development 04/2013; 140(8):1720-9. DOI:10.1242/dev.092304 · 6.27 Impact Factor