title: Hypoxia stimulates low-density lipoprotein receptor-related protein-1 expression through hypoxia-inducible factor-1α in human vascular smooth muscle cells.
abstract: OBJECTIVE
  Hypoxia is considered a key factor in the progression of atherosclerotic lesions. Low-density lipoprotein receptor-related protein (LRP1) plays a pivotal role in the vasculature. The aim of this study was to investigate the effect of hypoxia on LRP1 expression and function in vascular smooth muscle cells (VSMC) and the role of hypoxia-inducible factor-α (HIF-1α).
  
  
  RESULTS
  Real-time polymerase chain reaction and Western blot analysis demonstrated that hypoxia (1% O(2)) time-dependently induced LRP1 mRNA (maximum levels at 1 to 2 hours) and protein expression (maximum levels at 12 to 24 hours). The delayed hypoxic upregulation of LRP1 protein versus mRNA may be explained by the long half-life of LRP1 protein. Luciferase assays demonstrated that hypoxia and HIF-1α overaccumulation induced LRP1 promoter activity and that 2 consensus hypoxia response element sites located at -1072/-1069 and -695/-692 participate in the induction. Chromatin immunoprecipitation showed the in vivo binding of HIF-1α to LRP1 promoter in hypoxic VSMC. Hypoxia effects on LRP1 protein expression were functionally translated into an increased cholesteryl ester (CE) accumulation from aggregated low-density lipoprotein (agLDL) uptake. The blockade of HIF-1α expression inhibited the upregulatory effect of hypoxia on LRP1 expression and agLDL-derived intracellular CE overaccumulation, suggesting that both LRP1 overexpression and CE overaccumulation in hypoxic vascular cells are dependent on HIF-1α. Immunohistochemical analysis showed the colocalization of LRP1 and HIF-1α in vascular cells of human advanced atherosclerotic plaques.
  
  
  CONCLUSIONS
  Hypoxia upregulates LRP1 expression and agLDL-derived intracellular CE accumulation in human VSMC through HIF-1α induction.
authors: Cardiovascular Research Center of Barcelona, Consejo Superior de Investigaciones Científicas-Institut Català Ciències Cardiovasculars, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain.
authors: Jose
authors: J
authors: Castellano
authors: Rosa
authors: R
authors: Aledo
authors: Judith
authors: J
authors: Sendra
authors: Paula
authors: P
authors: Costales
authors: Oriol
authors: O
authors: Juan-Babot
authors: Lina
authors: L
authors: Badimon
authors: Vicenta
authors: V
authors: Llorente-Cortés
mesh_terms: D015703:Antigens, CD / Q000235:genetics*; D050197:Atherosclerosis / Q000378:metabolism; D015687:Cell Hypoxia; D002478:Cells, Cultured; D002788:Cholesterol Esters / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000502:physiology*; D008077:Lipoproteins, LDL / Q000378:metabolism; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000235:genetics*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D051780:Sterol Regulatory Element Binding Protein 1 / Q000032:analysis; D051782:Sterol Regulatory Element Binding Protein 2 / Q000032:analysis
chemical_list: D015703:Antigens, CD; D002788:Cholesterol Esters; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C475476:LRP1 protein, human; D008077:Lipoproteins, LDL; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D012333:RNA, Messenger; C497387:SREBF1 protein, human; C497390:SREBF2 protein, human; D051780:Sterol Regulatory Element Binding Protein 1; D051782:Sterol Regulatory Element Binding Protein 2