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-␣ (HIF-1␣). Methods and 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-1␣ overaccumulation induced LRP1 promoter activity and that 2 consensus hypoxia response element sites located at Ϫ1072/Ϫ1069 and Ϫ695/Ϫ692 participate in the induction. Chromatin immunoprecipitation showed the in vivo binding of HIF-1␣ 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-1␣ 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-1␣. Immunohistochemical analysis showed the colocalization of LRP1 and HIF-1␣ in vascular cells of human advanced atherosclerotic plaques. H ypoxia plays a pivotal role in the pathophysiology of cancer, myocardial infarction, and atherosclerosis. Arterial wall thickness associated with atherosclerotic plaque progression reduces the oxygen supply in certain areas of the vascular intima. 1,2 Hypoxia is present in human advanced atherosclerotic lesions and correlates with the presence of angiogenesis and thrombus. 3,4 Most of the cells in hypoxic areas of atherosclerotic plaques respond by altering the expression of genes involved in vasculogenesis, angiogenesis, inflammation, and lipid deposition. [5][6][7][8][9][10][11] These genes are activated through hypoxia-inducible factor-1 complex (HIF-1). The HIF-1␣ subunit is subjected to quick oxygendependent proteasomal degradation through hydroxylation of proline residues by hydroxylases. [12][13][14] Under low oxygen tensions, HIF-1␣ accumulates and heterodimerizes with the constitutively expressed beta subunit, allowing the HIF-1 complex to bind to hypoxia response element (HRE) sequences in target promoters. 15 It has been reported that HIF-1␣ accumulation in macrophages promotes foam cell formation and atherosclerosis. 16 In experimental models of hypercholesterolemia and hypertension, HIF-1␣ is also associated with vascular smooth muscle cells (VSMC). 17 30 -32 It is unknown whether hypoxia may modulate LRP1 expression in human atherosclerotic plaques and, if so, which transcription ...

These results demonstrate that TF induction by agLDL depends on LRP1 expression and requires Rho A translocation to the cellular membrane.