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Department of Pharmacology and Toxicology, Medical College of Georgia, 1120 15th St., Augusta, GA 30912-2300, USA.
AJP Heart and Circulatory Physiology (Impact Factor: 3.84). 11/2005; 289(4):H1468-75. DOI: 10.1152/ajpheart.01173.2004
Source: PubMed


Although previous studies demonstrated beneficial effects of estrogen on cardiovascular function, the Women's Health Initiative has reported an increased incidence of coronary heart disease and stroke in postmenopausal women taking hormone replacement therapy. The objective of the present study was to identify a molecular mechanism whereby estrogen, a vasodilatory hormone, could possibly increase the risk of cardiovascular disease. Isometric contractile force recordings were performed on endothelium-denuded porcine coronary arteries, whereas molecular and fluorescence studies identified estrogen signaling molecules in coronary smooth muscle. Estrogen (1-1,000 nM) relaxed arteries in an endothelium-independent fashion; however, when arteries were pretreated with agents to uncouple nitric oxide (NO) production from NO synthase (NOS), estrogen contracted coronary arteries with an EC(50) of 7.3 +/- 4 nM. Estrogen-induced contraction was attenuated by reducing superoxide (O(2)(-)). Estrogen-stimulated O(2)(-) production was detected in NOS-uncoupled coronary myocytes. Interestingly, only the type 1 neuronal NOS isoform (nNOS) was detected in myocytes, making this protein a likely target mediating both estrogen-induced relaxation and contraction of endothelium-denuded coronary arteries. Estrogen-induced contraction was completely inhibited by 1 muM nifedipine or 10 muM indomethacin, indicating involvement of dihydropyridine-sensitive calcium channels and contractile prostaglandins. We propose that a single molecular mechanism can mediate the dual and opposite effect of estrogen on coronary arteries: by stimulating type 1 nNOS in coronary arteries, estrogen produces either vasodilation via NO or vasoconstriction via O(2)(-).

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    • "Furthermore, we observed that inhibiting the binding of L-arginine to NOS with L-NMMA could convert the expected vasodilatory response of E2 into a vasoconstrictor effect. We observed a similar phenomenon in porcine coronary arteries, and attributed this unusual response to E2-stimulated superoxide production due to uncoupled NOS activity [22]. The present findings have now documented E2-induced vasoconstriction in the microvasculature as well. "
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    ABSTRACT: Few studies have examined the potential effects of childbirth on the responses of the female vasculature--especially the resistance microvasculature of non-reproductive tissues. In the present study we have investigated the response of mesenteric microvascular resistance vessels to estrogen (E2), an important vasoactive hormone. Vessels were obtained from either nulliparous or postpartum female Sprague-Dawley rats, and isometric tension studies were performed. We found that E2 induced a concentration-dependent, endothelium-independent relaxation of microvessels precontracted with 10(-5) M phenylephrine; however, E2-induced relaxation was reduced by nearly half in vessels from postpartum animals compared to nulliparous controls. Inhibiting nitric oxide synthase activity with 10(-4) M L-NMMA or L-NPA (which exhibits selectivity for type 1 or nNOS) attenuated the relaxation effect of E2 on arteries from nulliparous animals. In contrast, L-NPA had little effect on arteries from postpartum animals, suggesting a reduced influence of nNOS after parturition. Moreover, expression of nNOS protein in microvessels was decreased 39% in the postpartum state compared to arteries from nulliparous animals. We propose that the impaired E2-induced relaxation response of microvessels from postpartum animals reflects a downregulation of NO production due to lower nNOS expressed in vascular smooth muscle cells. We measured a 73% decrease in serum E2 levels in the postpartum state compared to nulliparous animals. Because E2 has been shown to increase nNOS protein expression, we propose that lower E2 levels after parturition decrease expression of nNOS, leading to a reduced vasodilatory capacity of resistance microvessels.
    Steroids 03/2011; 76(10-11):991-7. DOI:10.1016/j.steroids.2011.03.011 · 2.64 Impact Factor
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    • "Taken together, these pharmacological studies strongly suggest an essential role for Hsp90 in mediating estrogen-induced relaxation of coronary arteries. We have shown previously that estrogen stimulates nNOS activity in CASM to enhance BK Ca channel activity via a rapid, nongenomic mechanism of action (White et al., 2002, 2005; Han et al., 2007). In support of this conclusion are recent studies indicating that nNOS mediates estrogen action in urethral smooth muscle as well (Hayashi et al., 2007). "
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    ABSTRACT: Under normal physiological conditions, estrogen is a coronary vasodilator, and this response involves production of NO from endothelial cells. In addition, estrogen also stimulates NO production in coronary artery smooth muscle (CASM); however, the molecular basis for this nongenomic effect of estrogen is unclear. The purpose of this study was to investigate a potential role for the 90-kDa heat shock protein (Hsp90) in estrogen-stimulated neuronal nitric-oxide synthase (nNOS) activity in coronary artery smooth muscle. 17Beta-estradiol produced a concentration-dependent relaxation of endothelium-denuded porcine coronary arteries in vitro, and this response was attenuated by inhibiting Hsp90 function with 1 microM geldanamycin (GA) or 100 microg/ml radicicol (RAD). These inhibitors also prevented estrogen-stimulated NO production in human CASM cells and reversed the stimulatory effect of estrogen on calcium-activated potassium (BK(Ca)) channels. These functional studies indicated a role for Hsp90 in coupling estrogen receptor activation to NOS stimulation in CASM. Furthermore, coimmunoprecipitation studies demonstrated that estrogen stimulates bimolecular interaction of immunoprecipitated nNOS with Hsp90 and that either GA or RAD could inhibit this association. Blocking estrogen receptors with ICI182780 (fulvestrant) also prevented this association. These findings indicate an essential role for Hsp90 in nongenomic estrogen signaling in CASM and further suggest that Hsp90 might represent a prospective therapeutic target to enhance estrogen-stimulated cardiovascular protection.
    Journal of Pharmacology and Experimental Therapeutics 04/2009; 329(3):850-5. DOI:10.1124/jpet.108.149112 · 3.97 Impact Factor
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    • "However, if eNOS becomes " uncoupled " in the absence of the NOS cofactor tetrahydrobiopterin (BH 4 ), then NOS produces superoxide anion (O 2 @BULLET− ) rather than NO [10]. Since estrogen exposure has been demonstrated to increase O 2 @BULLET− production rather than the beneficial NO in NOS uncoupled cells [11], it is biologically plausible that NOS activity becomes increasingly uncoupled as women age thereby increasing their predisposition to oxidative stress when exposed to estrogen. "
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    ABSTRACT: In this study, we investigated a mechanism by which estrogen-induced oxidants control endothelial cell differentiation into tubelike structures via redox sensitive signaling molecule Id3. Using a matrigel cell culture, we determined whether superoxide or hydrogen peroxide signaled estrogen-induced tube formation. Overexpression of the superoxide scavenger MnSOD and the hydrogen peroxide scavenger catalase inhibited tube formation in estrogen treated endothelial cells. Since tube formation on matrigel is not specific for endothelial cells, we verified our results in a co-culture model that better represents tube formation in vivo. Antioxidants ebselen and N-acetylcysteine as well as overexpression of MnSOD and catalase inhibited tube formation in estrogen exposed endothelial cells co-cultured with fibroblasts. We previously showed that estrogen-induced mitochondrial oxidants depended on the cytoskeleton so we tested tube formation dependence on the cytoskeleton. Estrogen-induced tube formation was inhibited by the actin cytoskeleton disruptor cytochalasin D and the microtubule destabilizer colchicine. Estrogen increased Id3 phosphorylation which was reduced by catalase and N-acetylcysteine treatments. We determined the functional role of Id3 in tube formation by RNA intereference and showed Id3 siRNA to inhibit tube formation in estrogen exposed cells. The major novel findings presented here are that: (i) estrogen-induced tube formation requires the presence of Id3, a member of the helix-loop-helix family of transcriptional factors and (ii) estrogen increases Id3 phosphorylation via a redox-dependent process. Furthermore, these studies demonstrate Id3 to be an important signaling molecule in estrogen stimulated vascularization and may serve as a therapeutic target in the prevention and treatment of vasculoproliferative disorders.
    Atherosclerosis 06/2008; 198(1):12-21. DOI:10.1016/j.atherosclerosis.2007.12.048 · 3.99 Impact Factor
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