The role of estrogen receptor α and β in regulating vascular smooth muscle cell proliferation is based on sex.
ABSTRACT We previously demonstrated that vascular smooth muscle cells (VSMC) proliferation and development of neointimal hyperplasia as well as the ability of nitric oxide (NO) to inhibit these processes is dependent on sex and hormone status. The aim of this study was to evaluate the role of estrogen receptor (ER) in mediating proliferation in male and female VSMC.
Proliferation was assessed in primary rat aortic male and female VSMC using (3)H-thymidine incorporation in the presence or absence of ER alpha (α) inhibitor methyl-piperidino-pyrazole, the ER beta (β) inhibitor (R,R)-5,11-Diethyl-5,6,11,12-tetrahydro-2,8-chrysenediol, the combined ERαβ inhibitor ICI 182,780, and/or the NO donor DETA/NO. Proliferation was also assessed in primary aortic mouse VSMC harvested from wildtype (WT), ERα knockout (ERα KO), and ERβ knockout (ERβ KO) mice in the presence or absence of DETA/NO and the ERα, ERβ, and ERαβ inhibitors. Protein levels were assessed using Western blot analysis.
Protein expression of ERα and ERβ was present and equal in male and female VSMC, and did not change after exposure to NO. Inhibition of either ERα or ERβ had no effect on VSMC proliferation in the presence or absence of NO in either sex. However, inhibition of ERαβ in rat VSMC mitigated NO-mediated inhibition in female but not male VSMC (P < 0.05). Evaluation of proliferation in the knockout mice revealed distinct patterns. Male ERαKO and ERβKO VSMC proliferated faster than male WT VSMC (P < 0.05). Female ERβKO proliferated faster than female WT VSMC (P < 0.05), but female ERαKO VSMC proliferated slower than female WT VSMC (P < 0.05). Last, we evaluated the effect of combined inhibition of ERα and ERβ in these knockout strains. Combined ERαβ inhibition abrogated NO-mediated inhibition of VSMC proliferation in female WT and knockout VSMC (P < 0.05), but not in male VSMC.
These data clearly demonstrate a role for the ER in mediating VSMC proliferation in both sexes. However, these data suggest that the antiproliferative effects of NO may be regulated by the ER in females but not males.
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ABSTRACT: Among sex steroids, especially estrogen metabolism has been considered to play a role in the function and pathology of human veins. We investigated the expression and activity of the estrogen-producing enzyme aromatase and estrogen receptor (ER) in human vena cava to assess possible in situ biosynthesis of estrogens and their modes of action. We first examined aromatase expression by immunohistochemistry in human inferior vena cava obtained from 29 autopsy cases (11 males, 18 females, 63.6 +/- 3.0 years old). We then semiquantitated the level of aromatase mRNA by reverse transcriptase-polymerase chain reaction in 24 cases and aromatase activity by 3H-water assay in 15 cases to examine whether or not and in which cell types aromatase was expressed. We also studied alternative use of multiple exon 1s of its gene and immunolocalization of 17beta-hydroxysteroid dehydrogenase type I (17beta-HSD I), which converts estrone produced by aromatase to estradiol, a biologically active estrogen and ER. Aromatase and 17beta-HSD I immunoreactivity were both detected in smooth muscle cells (SMC) of the media in all the cases and in endothelial cells (EC) in 20 and 22 cases, respectively. ER immunoreactivity was detected in SMC of vena cava in 21 cases. The amount of aromatase mRNA was significantly greater in the cases utilizing 1c (I.3) or 1d (P.II) of exon 1 (9 cases, 191.1 +/- 26.3 attomol/ng total RNA) than those utilizing 1b (I.4) as the promoter (14 cases, 50.6 +/- 13.0 attomol/ng total RNA) (p < 0.01). Significant correlation (p < 0.05) was observed between the amount of aromatase mRNA and aromatase activity in 15 cases examined. No significant correlation was detected between the amount of aromatase mRNA or aromatase labeling index and the ER status. These results suggest that estrone and estradiol are produced in the human vena cava and that their production is mediated by aromatase and 17beta-HSD I, respectively but not all of these locally synthesized estrogens may not work directly in situ.Endocrine Journal 04/1999; 46(2):233-42. · 2.03 Impact Factor
Article: Effects of estrogen on the vascular injury response in estrogen receptor alpha, beta (double) knockout mice.[show abstract] [hide abstract]
ABSTRACT: The two known estrogen receptors, ERalpha and ERbeta, mediate the effects of estrogen in all target tissues, including blood vessels. We have shown previously that estrogen inhibits vascular injury response to the same extent in female wild-type (WT), ERalpha knockout (ERalphaKO(CH)), and ERbeta knockout (ERbetaKO(CH)) mice. We generated mice harboring disruptions of both ERalpha and ERbeta genes (ERalpha,betaKO(CH)) by breeding and studied the effect of 17beta-estradiol (E2) on vascular injury responses in ovariectomized female ERalpha,betaKO(CH) mice and WT littermates. E2 inhibited increases in vascular medial area following injury in the WT mice but not in the ERalpha,betaKO(CH) mice, demonstrating for the first time that the two known estrogen receptors are necessary and sufficient to mediate estrogen inhibition of a component of the vascular injury response. Surprisingly, as in WT littermates, E2 still significantly increased uterine weight and inhibited vascular smooth muscle cell (VSMC) proliferation following injury in the ERalpha,betaKO(CH) mice. These data support that the role of estrogen receptors differs for specific components of the vascular injury response in the ERalpha,betaKO(CH) mice. The results leave unresolved whether E2 inhibition of VSMC proliferation in ERalpha,betaKO(CH) mice is caused by a receptor-independent mechanism, an unidentified receptor responsive to estrogen, or residual activity of the ERalpha splice variant reported previously in the parental ERalphaKO(CH) mice. These possibilities may be resolved by studies of mice in which ERalpha has been fully disrupted (ERalphaKO(St)), which are in progress.Circulation Research 10/2001; 89(6):534-9. · 9.49 Impact Factor
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ABSTRACT: Hyperlipidemia contributes to the development of intimal hyperplasia and subsequent accelerated atherosclerosis in vein bypass grafts. This study examines the effect of dietary supplementation with L-arginine on the development of intimal hyperplasia and the vasomotor function of vein grafts in hypercholesterolemic animals. Thirty male New Zealand White rabbits had a right carotid vein bypass graft and were sacrificed at 28 days postoperatively. Twenty animals received a 1% cholesterol diet for 4 weeks prior to surgery and this diet was continued until harvest. Of these, 10 also received L-arginine (2.25%, 2 g/kg, p.o.) 7 days preoperatively and thereafter until harvest. The last 10 animals were controls. Vein grafts were harvested either for morphology or for in vitro isometric tension studies. Cumulative dose-response curves to norepinephrine, serotonin, and bradykinin were recorded, and following norepinephrine precontraction, relaxation to acetylcholine and sodium nitroprusside were determined. After in situ pressure fixation, intimal thicknesses of the vein grafts were measured by videomorphometry. The addition of L-arginine doubled the serum arginine concentrations. Intimal hyperplasia of both groups of hypercholesterolemic vein grafts contained foam cells and lipid-laden endothelial and smooth muscle cells. There was a 24% reduction in the intimal thickness of vein graft intimal hyperplasia in the L-arginine group compared to that in the hypercholesterolemia group (P < 0.05). All hypercholesterolemic vein grafts were two-fold thicker than in the control group. L-arginine supplementation resulted in the preservation of acetylcholine-mediated relaxation but did not change hypercholesterolemia-induced contractile agonist supersensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)Journal of Surgical Research 08/1995; 59(1):35-42. · 2.25 Impact Factor