Equilin in conjugated equine estrogen increases monocyte-endothelial adhesion via NF-κB signaling.

Fumitake Ito,Jo Kitawaki,Yukiko Tanaka,Hisashi Kataoka,Akemi Koshiba,Taisuke Mori,Yosuke Tarumi,Hiroyuki Okimura

doi:10.1371/journal.pone.0211462

Abstract

The adhesion of monocytes to endothelial cells, which is mediated by adhesion molecules, plays a crucial role in the onset of atherosclerosis. Conjugated equine estrogen, which is widely used for estrogen-replacement therapy, contains both estrone sulfate and various nonhuman estrogens, including equilin. To investigate the association between various estrogen types and atherosclerosis risk, we examined their effect on adhesion-molecule expression in human umbilical vein endothelial cells (HUVECs). In estrogen-treated HUVECs, the mRNA and protein expression levels of adhesion molecules were quantified by real-time polymerase chain reaction and enzyme immunoassay. Additionally, a flow-chamber system was used to assess the effects of estrogens on the adherence of U937 monocytoid cells to HUVECs. Equilin, but not 17β-estradiol (E2) or other types of estrogen, significantly increased the mRNA (P < 0.01) and protein (P < 0.05) expression of the adhesion molecules E-selectin and intercellular adhesion molecule-1 as compared with levels in controls. Equilin treatment increased the adherence of U937 monocytoid cells to HUVECs relative to the that in the control (P < 0.05), decreased estrogen receptor (ER)β expression, and increased the expression of proteins involved in nuclear factor kappa-B (NF-κB) activation relative to levels in controls. Furthermore, the accumulation of NF-κB subunit p65 in HUVEC nuclei was promoted by equilin treatment. By contrast, E2 treatment neither increased the number of adhered monocytoid cells to HUVECs nor altered the expression of ERβ or NF-κB-activating proteins. Our findings suggest that in terms of the adhesion of monocytes at the onset of atherosclerosis, E2 may be preferable for estrogen-replacement therapy. Further studies comparing equilin treatment with that of E2 are needed to investigate their differential impacts on atherosclerosis.

Highlights

We previously reported the adverse effects of medroxyprogesterone acetate, which is coadministered in most Hormone-replacement therapy (HRT) regimens, on endothelial cells and its association with the risk of atherosclerosis development [5]; few studies have compared the effects of different estrogen types on cardiovascular events associated with estrogen-replacement therapy (ERT) [6,7]
The results revealed that the mRNA levels of adhesion molecules in human umbilical vein endothelial cells (HUVECs) treated with Eq were ~2.6-fold higher than the levels observed in the control (P < 0.05; Fig 1A–1D)
There were no significant differences in the expression of cell-adhesion molecules between HUVECs treated with other estrogens and the control

Summary

Introduction

Hormone-replacement therapy (HRT) is commonly prescribed for postmenopausal women to treat climacteric disorders caused by estrogen deficiency and to reduce the risk of osteoporosis. We previously reported the adverse effects of medroxyprogesterone acetate, which is coadministered in most HRT regimens, on endothelial cells and its association with the risk of atherosclerosis development [5]; few studies have compared the effects of different estrogen types on cardiovascular events associated with estrogen-replacement therapy (ERT) [6,7]. Few basic studies have investigated the cardiovascular benefits associated with various types of estrogen [8]. To investigate whether various types of estrogen are associated with atherosclerosis risk, we examined the effects of various estrogens on the expression of cell-adhesion molecules and the actual adherence of monocytoid cells to HUVECs under flow conditions. We explored the mechanisms underlying changes in adhesion-molecule expression during estrogen treatment

Materials and methods

Results

Discussion