Regulation of scavenger receptor class BI gene expression by angiotensin II in vascular endothelial cells

Hypertension. 2007 Jun;49(6):1378-84. doi: 10.1161/HYPERTENSIONAHA.106.082479. Epub 2007 Apr 2.

Abstract

High-density lipoprotein mediates a normal physiological process called reverse cholesterol transport. In this process, a scavenger receptor of the B class (SR-BI)/human homologue of SR-BI, CD36, and LIMPII analogous-1 (hSR-BI/CLA-1) facilitates the cellular uptake of cholesterol from high-density lipoprotein. In endothelial cells, high-density lipoprotein activates endothelial NO synthase via hSR-BI/CLA-1. Angiotensin II (Ang II) is a powerful accelerator of atherosclerosis and modulates the expression of endothelial NO synthase. In the present study, we have examined the role of Ang II on hSR-BI/CLA-1 expression in human umbilical vein endothelial cells. Our results showed that endogenous expression of hSR-BI/CLA-1 was suppressed by exposure to Ang II in human umbilical vein endothelial cells. Administration of the Ang II type-1 receptor blocker olmesartan inhibited Ang II-induced hSR-BI/CLA-1 protein repression. In Ang II-treated cells, high-density lipoprotein had no effect on endothelial NO synthase activation. Ang II decreased transcriptional activity of the hSR-BI/CLA-1 promoter. The inhibitory effect of Ang II on hSR-BI/CLA-1 promoter activity was abrogated by wortmannin and LY294002, specific inhibitors of phosphatidylinositol 3-kinase. Exposure of human umbilical vein endothelial cells to Ang II elicited a rapid phosphorylation of Akt and FoxO1, a known target of Akt signaling. Constitutively active Akt inhibits the activity of the hSR-BI/CLA-1 promoter, and a dominant-negative mutant of Akt or mutagenesis of a FoxO1 response element in the hSR-BI/CLA-1 abolished the ability of Ang II to suppress promoter activity. Together, these results indicate that the phosphatidylinositol 3-kinase/Akt/FoxO1 pathway participates in Ang II suppression of hSR-BI/CLA-1 expression and suggests that the endothelial receptor for hSR-BI/CLA-1 is downregulated by the renin-angiotensin system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Androstadienes / pharmacology
  • Angiotensin II / genetics
  • Angiotensin II / physiology*
  • Cells, Cultured
  • Chromones / pharmacology
  • Down-Regulation
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / metabolism*
  • Forkhead Box Protein O1
  • Forkhead Transcription Factors / genetics
  • Forkhead Transcription Factors / physiology
  • Gene Expression Regulation / physiology*
  • Humans
  • Imidazoles / pharmacology
  • Morpholines / pharmacology
  • Nitric Oxide Synthase / metabolism
  • Oncogene Protein v-akt / genetics
  • Oncogene Protein v-akt / physiology
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / physiology
  • Phosphoinositide-3 Kinase Inhibitors
  • Phosphorylation / drug effects
  • Promoter Regions, Genetic / genetics
  • Promoter Regions, Genetic / physiology
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Receptor, Angiotensin, Type 1 / physiology
  • Renin-Angiotensin System / physiology
  • Scavenger Receptors, Class B / genetics
  • Scavenger Receptors, Class B / metabolism*
  • Tetrazoles / pharmacology
  • Wortmannin

Substances

  • Androstadienes
  • Chromones
  • FOXO1 protein, human
  • Forkhead Box Protein O1
  • Forkhead Transcription Factors
  • Imidazoles
  • Morpholines
  • Phosphoinositide-3 Kinase Inhibitors
  • RNA, Messenger
  • Receptor, Angiotensin, Type 1
  • SCARB1 protein, human
  • Scavenger Receptors, Class B
  • Tetrazoles
  • Angiotensin II
  • 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
  • olmesartan
  • Nitric Oxide Synthase
  • Oncogene Protein v-akt
  • Wortmannin