title: Fibulin-5 is up-regulated by hypoxia in endothelial cells through a hypoxia-inducible factor-1 (HIF-1α)-dependent mechanism.
abstract: Hypoxia modulates gene expression and affects multiple aspects of endothelial cell biology. Fibulin-5 (FBLN5) is an extracellular matrix protein essential for elastic fiber assembly and vasculogenesis that participates in vascular remodeling and controls endothelial cell adhesion, motility, and proliferation. In this context, we aimed to analyze FBLN5 regulation by hypoxia in endothelial cells. Hypoxia (1% O(2)) increased FBLN5 mRNA levels in endothelial cells in a time-dependent manner. Maximal induction (∼2.5-fold) was achieved after 24 h of hypoxia. This effect paralleled an increase in both intracellular and extracellular FBLN5 protein levels. The increase in FBLN5 mRNA levels observed in hypoxic cells was blocked by inhibitors of the PI3K/Akt/mTOR pathway (LY294002 and rapamycin) and mimicked by dimethyl oxal glycine, which prevents proline hydroxylase-mediated degradation of HIF-1α. Silencing of HIF-1α completely prevented hypoxia-induced FBLN5 up-regulation. Accordingly, both hypoxia and HIF-1α overexpression increased FBLN5 transcriptional activity. Serial promoter deletion and mutagenesis studies revealed the involvement of a putative hypoxia response element (HRE) located at -78 bp. In fact, EMSA and ChIP assays demonstrated increased HIF-1 binding to this site in hypoxic cells. Interestingly, the rate of endothelial cells undergoing apoptosis in cultures exposed to hypoxia increased in FBLN5 knockdown cells, suggesting that hypoxia-induced FBLN5 expression contributes to preserve cell survival. These results provide evidence that HIF-1 signaling underlies the increase of FBLN5 expression elicited by hypoxia in endothelial cells and suggest that FBLN5 induction could be involved in the adaptive survival response of endothelial cells to hypoxia.
authors.affiliation: Centro de Investigación Cardiovascular, Consejo Superior de Investigaciones Científicas-Institut Català de Ciències Cardiovasculars, Sant Pau, Hospital de la Santa Creu i Sant Pau, Sant Antoni Maria Claret 167, 08025 Barcelona, Spain.
authors.forename: Anna
authors.initials: A
authors.lastname: Guadall
authors.forename: Mar
authors.initials: M
authors.lastname: Orriols
authors.forename: Ricardo
authors.initials: R
authors.lastname: Rodríguez-Calvo
authors.forename: Olivier
authors.initials: O
authors.lastname: Calvayrac
authors.forename: Javier
authors.initials: J
authors.lastname: Crespo
authors.forename: Rosa
authors.initials: R
authors.lastname: Aledo
authors.forename: José
authors.initials: J
authors.lastname: Martínez-González
authors.forename: Cristina
authors.initials: C
authors.lastname: Rodríguez
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology; D017209:Apoptosis / Q000502:physiology; D002417:Cattle; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology / Q000502:physiology*; D005109:Extracellular Matrix / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014471:Umbilical Veins / Q000166:cytology; D015854:Up-Regulation / Q000502:physiology
chemical_list: D016326:Extracellular Matrix Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D034741:RNA, Small Interfering; D058570:TOR Serine-Threonine Kinases; C492373:FBLN5 protein, human; C497442:HIF1A protein, human; C546842:MTOR protein, human