Estrogen-induced contraction of coronary arteries is mediated by superoxide generated in vascular smooth muscle

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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    • "cNOS is expressed in ECs (eNOS; Liu et al. 1997) and its activation is calcium and calmodulin dependent (Förstermann 2010), whereas iNOS is located in vascular smooth muscle cells (VSMCs) and its expression is regulated by cytokines and endotoxins (Kanno et al. 1994). Type 1 nNOS has been recently identified as a predominant isoform expressed in porcine and human coronary artery smooth muscle (White et al. 2005), and it has been proposed that E 2 relaxes coronary artery not only by targeting eNOS but also by increasing NO production in smooth muscle cells via nNOS activation (Han et al. 2007). The androgen receptor (AR) has been identified in vascular cells (Liu et al. 2003), and recent reports show that this receptor mediates a variety of actions of androgens in ECs and VSMCs (Li & Al-Azzawi 2009). "
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    ABSTRACT: The aim of the present study was to investigate the effect of testosterone on the modulation of cellular events associated with vascular homeostasis. In rat aortic strips, 5-20 min treatment with physiological concentrations of testosterone significantly increased nitric oxide (NO) production. The rapid action of the steroid was suppressed by the presence of an androgen receptor antagonist (flutamide). We obtained evidence that the enhancement in NO synthesis was dependent on the influx of calcium from extracellular medium, because in the presence of a calcium channel blocker (verapamil) the effect of testosterone was reduced. Using endothelial cell (EC) cultures, we demonstrated that androgen directly acts at the endothelial level. Chelerythrine or PD98059 compound completely suppressed the increase in NO production, suggesting that the mechanism of action of the steroid involves protein kinase C and mitogen-activated protein kinase pathways. It is known that endothelial NO released into the vascular lumen serves as an inhibitor of platelet activation and aggregation. We showed that testosterone inhibited platelet aggregation and this effect was dependent on endothelial NO synthesis. Indeed, the enhancement of NO production elicited by androgen was associated with EC growth. The steroid significantly increased DNA synthesis after 24 h of treatment, and this mitogenic action was blunted in the presence of NO synthase inhibitor N-nitro-l-arginine methyl ester. In summary, testosterone modulates vascular EC growth and platelet aggregation through its direct action on endothelial NO production.
    Preview · Article · Jan 2012 · Journal of Endocrinology
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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.
    Preview · Article · Mar 2011 · Steroids
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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.
    Preview · Article · Apr 2009 · Journal of Pharmacology and Experimental Therapeutics
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