Article

Mitochondrial Effects of Estrogen Are Mediated by Estrogen Receptor α in Brain Endothelial Cells

Department of Pharmacology, School of Medicine, University of California, Irvine, CA 92697-4625, USA.
Journal of Pharmacology and Experimental Therapeutics (Impact Factor: 3.86). 07/2008; 325(3):782-90. DOI: 10.1124/jpet.107.134072
Source: PubMed

ABSTRACT Mitochondrial reactive oxygen species (ROS) and endothelial dysfunction are key contributors to cerebrovascular pathophysiology. We previously found that 17beta-estradiol profoundly affects mitochondrial function in cerebral blood vessels, enhancing efficiency of energy production and suppressing mitochondrial oxidative stress. To determine whether estrogen specifically affects endothelial mitochondria through receptor mechanisms, we used cultured human brain microvascular endothelial cells (HBMECs). 17beta-Estradiol treatment for 24 h increased mitochondrial cytochrome c protein and mRNA; use of silencing RNA for estrogen receptors (ERs) showed that this effect involved ERalpha, but not ERbeta. Mitochondrial ROS were determined by measuring the activity of aconitase, an enzyme with an iron-sulfur center inactivated by mitochondrial superoxide. 17beta-Estradiol increased mitochondrial aconitase activity in HBMECs, indicating a reduction in ROS. Direct measurement of mitochondrial superoxide with MitoSOX Red showed that 17beta-estradiol, but not 17alpha-estradiol, significantly decreased mitochondrial superoxide production, an effect blocked by the ER antagonist, ICI-182,780 (fulvestrant). Selective ER agonists demonstrated that the decrease in mitochondrial superoxide was mediated by ERalpha, not ERbeta. The selective estrogen receptor modulators, raloxifene and 4-hydroxy-tamoxifen, differentially affected mitochondrial superoxide production, with raloxifene acting as an agonist but 4-hydroxy-tamoxifen acting as an estrogen antagonist. Changes in superoxide by 17beta-estradiol could not be explained by changes in manganese superoxide dismutase. Instead, ERalpha-mediated decreases in mitochondrial ROS may depend on the concomitant increase in mitochondrial cytochrome c, previously shown to act as an antioxidant. Mitochondrial protective effects of estrogen in cerebral endothelium may contribute to sex differences in the occurrence of stroke and other age-related neurodegenerative diseases.

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    • "This is in line with other results showing that neuroprotection involves attenuation of NADPH oxidase activation and superoxide production via an ERα-mediated nongenomic signaling cascade (Zhang et al., 2009). In human brain microvascular endothelial cells physiological levels of 17β-Estradiol but not its enantiomer 17α-Estradiol suppressed mitochondrial superoxide production mediated through ERα receptor (Razmara et al., 2008). The failure of 17α-Estradiol, which does not activate ER but shares antioxidant properties, underlines the irrelevance of estradiol's direct antioxidant activity at physiological levels. "
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    Brain Research 11/2014; 1589. DOI:10.1016/j.brainres.2014.08.029 · 2.83 Impact Factor
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    • "The role of endothelial cells is important in mediating the effects of circulating as well as locally-synthesized steroids during fetal brain development. The cerebral blood vessels are affected by sex steroids in different ways (Krause et al., 2011), and the hormones may alter endothelial functions via specific vascular receptors (Razmara et al., 2008). Since steroids play an important role in neuroprotection qualitative PCR and immunocytochemical analysis for ER-a and b investigation were performed. "
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    ABSTRACT: Immortalized cell lines from fetal brain are an experimental model for studying the in vitro molecular pathways regulating neural cell differentiation and the development of neural networks. The procedures are described to obtain an established cell line from the 90-day old fetal sheep hypothalamus. Viral oncogene LT-SV40 transformation was used to isolate a stable cell line (ENOS-01) that was characterized immunocytochemically. Immortalized cells can be classified as an endothelial cell line of hypothalamic microvasculature. Furthermore, mRNA expression and immunocytochemical of estrogen receptors α and β were also evaluated. Since it is known that cerebral vessels are directly targeted by sex steroids, our established cell line represents an alternative system to study estradiol/receptor interactions during brain development. Our in vitro model can provide a tool to investigate the complex relationships among the cell types forming the blood-brain barrier, which is known to be involved in the pathogenesis of sheep transmissible neurological diseases.
    Research in Veterinary Science 11/2012; 94(3). DOI:10.1016/j.rvsc.2012.10.022 · 1.51 Impact Factor
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    • "A recent study (Krause et al. 2011) has established that cerebral blood vessels are affected by sex steroids in various ways. Estrogens and androgens can alter vascular tone, endothelial functions, oxidative stress and inflammatory responses via specific vascular receptors (Razmara et al. 2008). Moreover, endothelial cells in cerebral arteries also express enzymes involved in the metabolism of sex steroids (Gonzales et al. 2007). "
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