Role of the endothelin system in vascular dysfunction in women
Date
2021
Authors
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Journal ISSN
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Publisher
University of Delaware
Abstract
Postmenopausal women have increased rates of cardiovascular disease compared to age-matched men and premenopausal women. Vascular dysfunction precedes the development of cardiovascular disease and is characterized by a pro-constrictor state of the blood vessel. Changes in vascular function can be due to phenotypic changes in the vascular endothelium and smooth muscle. Endothelin-1 (ET-1) is a potent vasoconstrictor that contributes to the development of vascular dysfunction. ET-1 is primarily produced by vascular endothelial cells and acts on endothelin A (ETAR) and endothelin B receptors (ETBR) on the vascular smooth muscle cells to cause vasoconstriction. However, ETBR are also located on endothelial cells and mediate vasodilation. Overexpression of ET-1, loss of endothelial ETBR and increased expression of ETBR and ETAR on vascular smooth muscle cells all play a role in mediating vascular dysfunction. There are age- and hormone-related changes in the endothelin system which can impact the phenotypic and functional properties of the system. However, data regarding the phenotypic changes in the endothelin system and changes in sensitivity to ET-1 are unknown in women. Additionally, data are lacking on the impact of estradiol (E2) on vascular endothelin receptors, leaving a gap in our understanding of the hormonal modulation of the endothelin system. Accordingly, the central hypothesis was that overactivity of the endothelin system contributes to vascular dysfunction in postmenopausal women and E2 differentially modulates endothelin receptor expression on endothelial compared to vascular smooth muscle cells. Methods: Multiple research techniques were used to test our central hypothesis. Venous endothelial cells were collected from premenopausal (YW) and postmenopausal (PMW) women and protein expression for ET-1 and ETBR was determined using immunocytochemistry. Intradermal microdialysis in combination with laser doppler flowmetry was used to determine the dose-response relation of ET-1 and skin blood flow in the cutaneous microcirculation of YW and PMW. Human umbilical vein endothelial and smooth muscle cells were treated with a range of E2 concentrations (0-100ng/mL) for 24 hours, harvested, and evaluated for endothelin protein receptor expression using western blotting. Vascular smooth muscle cells were pre-treated with glucose for 24hr to upregulate ETAR and ETBR prior to the addition of E2. Results: Venous endothelial cell expression of ET-1 was lower in PMW compared to YW (PMW; 0.58 ℗ł 0.21 vs. YW; 0.85 ℗ł 0.28 a.u, p=0.003). The vasoconstrictor response to exogenous ET-1 was similar in YW and PMW (p=0.51, d=1.08) and there was no difference between groups for the maximal constriction response to ET-1 (p=0.46). Venous endothelial cell ETBR expression was lower in PMW (0.46 ℗ł 0.11 AU) compared to YW (0.58 ℗ł 0.14 AU; P=0.02). In human umbilical vein endothelial cells treated with E2, ETBR expression was significantly increased (p=0.01) at the highest concentration of E2 (100ng/mL) compared to 0, 0.1, and 10ng/mL (all p<0.03). There was a 49% increase of ETBR expression from baseline to the highest concentration of E2 tested. In human umbilical vein vascular smooth muscle cells, ETAR expression was not altered from E2 treatment; however, there was a significant increase in ETBR expression (p=0.01) with differences being observed at the highest concentration of estradiol (100ng/mL) from the two lowest concentrations (0ng/mL; p=0.04 and 0.1ng/mL; p=0.01). There was a 21% increase in ETBR from baseline to the highest concentration of E2 tested. Conclusion: These data demonstrate age and hormonal influence on the endothelin system. In PMW there was attenuated endothelial cell ET-1 and ETBR expression compared to YW. However, there was no significant difference in the constrictor responses to exogenous ET-1. In cell culture studies there was no impact of E2 on ETAR expression in vascular smooth muscle cells. Interestingly ETBR expression was increased in both endothelial and vascular smooth muscle cells following E2 treatment. These findings demonstrate the complexity of the endothelin system and further contribute to the understanding of endothelin-mediated vascular dysfunction in postmenopausal women. Future studies are needed to explore mechanisms underlying these changes associated with aging and hormone loss as well at the impact of hormonal therapy in postmenopausal women.
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Keywords
Premenopausal women, Cardiovascular disease, Vascular function