HDL-associated estradiol stimulates endothelial NO synthase and vasodilation in an SR-BI–dependent manner
Ming Gong, … , Annette Uittenbogaard, Eric J. Smart
Ming Gong, … , Annette Uittenbogaard, Eric J. Smart
Published May 15, 2003
Citation Information: J Clin Invest. 2003;111(10):1579-1587. https://doi.org/10.1172/JCI16777.
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Article Cardiology

HDL-associated estradiol stimulates endothelial NO synthase and vasodilation in an SR-BI–dependent manner

Abstract

Cardiovascular diseases remain the leading cause of death in the United States. Two factors associated with a decreased risk of developing cardiovascular disease are elevated HDL levels and sex — specifically, a decreased risk is found in premenopausal women. HDL and estrogen stimulate eNOS and the production of nitric oxide, which has numerous protective effects in the vascular system including vasodilation, antiadhesion, and anti-inflammatory effects. We tested the hypothesis that HDL binds to its receptor, scavenger receptor class B type I (SR-BI), and delivers estrogen to eNOS, thereby stimulating the enzyme. HDL isolated from women stimulated eNOS, whereas HDL isolated from men had minimal activity. Studies with ovariectomized and ovariectomized/estrogen replacement mouse models demonstrated that HDL-associated estradiol stimulation of eNOS is SR-BI dependent. Furthermore, female HDL, but not male HDL, promoted the relaxation of muscle strips isolated from C57BL/6 mice but not SR-BI null mice. Finally, HDL isolated from premenopausal women or postmenopausal women receiving estradiol replacement therapy stimulated eNOS, whereas HDL isolated from postmenopausal women did not stimulate eNOS. We conclude that HDL-associated estrodial is capable of the stimulating eNOS. These studies establish a new paradigm for examining the cardiovascular effects of HDL and estrogen.

Authors

Ming Gong, Melinda Wilson, Thomas Kelly, Wen Su, James Dressman, Jeanie Kincer, Sergey V. Matveev, Ling Guo, Theresa Guerin, Xiang-An Li, Weifei Zhu, Annette Uittenbogaard, Eric J. Smart

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HDL-associated estradiol is responsible for eNOS stimulation. (a) HDL wa...
HDL-associated estradiol is responsible for eNOS stimulation. (a) HDL was isolated from female C57BL/6 mice that had intact ovaries (Intact), had the ovaries removed (OVX), or had the ovaries removed and a 17-β-estradiol pellet implanted (OVX + E2). HDL was also isolated from male age-matched C57BL/6 mice that had a 17-β-estradiol pellet implanted (Male + E2). In addition, HDL from control male mice was isolated and enriched with 17-β-estradiol in vitro (Male HDL + E2). LDL from female mice (LDL + E2) and BSA (BSA + E2) were also enriched with 17-β-estradiol in vitro. The in vitro–modified HDL, LDL, and BSA were reisolated, and the amount of estradiol associated was quantified before use (see Methods). Human microvascular endothelial cells were pretreated with 0.75 μCi/ml of [3H]arginine, followed by treatment with 10 μg/ml of each sample or 1 μg/ml of ionomycin for 15 minutes at 37°C. The cells were then processed to quantify the amount of citrulline generated. Each experiment included controls, using 1 mM L-NNA to demonstrate that over 99% of the generated citrulline was due to eNOS activity (data not shown). The data are from eight independent experiments, with triplicate measurements in each experiment (mean ± SE). (b) The same assay as described above was used, with the exception that 10 μM of ICI 182,780 was added to each of the reactions. The data are from four independent experiments, with triplicate measurements in each experiment (mean ± SE).