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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In addition to its effects on sexual differentiation and reproduction, estrogen has important impact on the immune system and on bone. It has also been evident that the effects of estrogen on bone to a large extent are mediated via its action on immune cells. Estrogen has a dichotomous impact on the immune system by downregulation of inflammatory immune responses but simultaneous upregulation of immunoglobulin production. Consequently, immune-mediated diseases in humans and in animal models are modulated by estrogen. Estrogen deficiency after ovariectomy in mice and after menopause in women is associated with significant bone loss. In rheumatic diseases such as rheumatoid arthritis (RA), osteoporosis is frequent, and in patients with postmenopausal RA, the degree of bone loss is dramatically increased. Hormone replacement therapy (HRT) in murine and human arthritis has beneficial effects on bone loss, as expected, but it also ameliorates inflammation and inflammation-triggered joint destruction. Long-term use of HRT has been associated with increased risk of breast cancer, thrombosis, and possibly also stroke. Accordingly, there is great need for new activators of estrogen receptors (ERs) selectively reproducing only the beneficial effects of estrogen. To achieve this aim, better knowledge of the mechanisms of how activation of ER-alpha and ER-beta modulates the immune system and bone at the cellular and molecular levels is necessary.
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PMID:Immune responses and bone loss: the estrogen connection. 1631 50

Estrogen therapy has been well established as an effective treatment for relief of vasomotor symptoms. In light of recent evidence from large randomized trials showing serious risks associated with use of estrogen treatment, current recommendations for hormone therapy emphasize using the lowest effective dose for the shortest possible time. The purpose of this review is to examine what has been learned from the Women's Health Initiative (WHI) Hormone Trials and other studies about the short-term risks and benefits of estrogen use. A second purpose is to examine whether short-term risks differ for women most likely to use hormone treatment, including individuals with vasomotor symptoms; women in their 50s; and women, with and without intact ovaries, who have had a hysterectomy. During the first 1 to 2 years of use of conjugated equine estrogens alone (E-alone) or combined with medroxyprogesterone acetate (E + P), women experience an elevated risk of coronary heart disease, stroke, and deep vein thrombosis or pulmonary embolism. The magnitude of risk is greater for E + P than for E-alone. Fracture risk is not reduced with 1 to 2 years of use, but a fracture benefit is seen within 5 years of use. Increased risk of breast cancer does not appear until after 4 to 5 years of E + P use and was not increased with E-alone use after < or =7 years of treatment. This pattern of risks and benefits is generally similar for women with vasomotor symptoms, women in their 50s, and women, with and without > or =1 intact ovary, who have had a hysterectomy.
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PMID:Estrogen with and without progestin: benefits and risks of short-term use. 1641 31

Estrogen has been shown to protect against stroke-induced brain damage, yet the mechanism is unknown. During the early hours of stroke, cerebral edema forms as increased transport of Na and Cl from blood into brain occurs across an intact blood-brain barrier (BBB). We showed previously that a luminal BBB Na-K-Cl cotransporter is stimulated by hypoxia and arginine vasopressin (AVP), factors present during cerebral ischemia, and that inhibition of the cotransporter by intravenous bumetanide greatly reduces edema in rats subjected to permanent middle cerebral artery occlusion (MCAO). The present study was conducted to determine whether estrogen protects in stroke at least in part by reducing activity of the BBB cotransporter, thereby decreasing edema formation. Ovariectomized rats were subjected to 210 mins of permanent MCAO after 7-day or 30-min pretreatment with 17beta-estradiol and then brain swelling and 2,3,5-triphenyltetrazolium chloride staining were assessed as measures of brain edema and lesion volume, respectively. Diffusion-weighed imaging was used to monitor permanent MCAO-induced decreases in apparent diffusion coefficient (ADC) values, an index of changes in brain water distribution and mobility. Na-K-Cl cotransporter activity of cerebral microvascular endothelial cells (CMECs) was assessed as bumetanide-sensitive K influx and cotransporter abundance by Western blot analysis after estradiol treatment. Estradiol significantly decreased brain swelling and lesion volume and attenuated the decrease in ADC values during permanent MCAO. Estradiol also abolished CMEC cotransporter stimulation by chemical hypoxia or AVP and decreased cotransporter abundance. These findings support the hypothesis that estrogen attenuates stimulation of BBB Na-K-Cl cotransporter activity, reducing edema formation during stroke.
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PMID:Estradiol reduces activity of the blood-brain barrier Na-K-Cl cotransporter and decreases edema formation in permanent middle cerebral artery occlusion. 1642 6

Mitochondrial dysfunction has been implicated as a cause of age-related disorders, and the mitochondrial theory of aging links aging, exercise, and diet. Endothelial dysfunction is a key paradigm for vascular disease and aging, and there is considerable evidence that exercise and dietary restriction protect against cardiovascular disease. Recent studies demonstrate that estrogen receptors are present in mitochondria and that estrogen promotes mitochondrial efficiency and decreases oxidative stress in the cerebral vasculature. Chronic estrogen treatment increases mitochondrial capacity for oxidative phosphorylation while decreasing production of reactive oxygen species. The effectiveness of estrogen against age-related cardiovascular disorders, including stroke, may thus arise in part from hormonal effects on mitochondrial function. Estrogen-mediated mitochondrial efficiency may also be a contributing factor to the longer lifespan of women.
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PMID:Estrogen and mitochondria: a new paradigm for vascular protection? 1650 48

Post-menopausal osteoporosis represents a major public health problem. Osteoporotic fractures in older women constitute a major cause of disability, mortality and economic burden. Cardiovascular disease (CVD) is the primary cause of death in women in westernized countries, with more than one in two women dying from CVD. In literature it is well established that an early menopause increases the risk of CVD and that a later menopause is associated with longer overall survival. Until a few years ago, in the management guidelines, a combination of lifestyle and use of hormonal replacement therapy (HRT) was suggested to reduce the CVD risk in post-menopausal women. However, recent studies such as the Women's Health Initiative (WHI) trial and the Heart and Estrogen/Progestin Replacement Study (HERS) I and II has forced practitioners to reconsider their options for prevention of CVD in post-menopausal women. The increased risk of CVD and stroke which were not counterbalanced by the smaller reduction in numbers of hip fractures in the WHI and in the HERS I-II suggest new characteristics of women in which HRT could possibly exert a favourable risk/benefit ratio. The use of HRT in post-menopausal women might be considered in symptomatic women and it might be individualized for each patients. Therefore, for cardiovascular and osteoporosis risk, regular prevention programmes should serve the needs of middle-aged women.
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PMID:Osteoporosis and cardiovascular disease: benefit-risk of hormone replacement therapy. 1655 Jul 29

Estrogen is neuroprotective against ischemia in both in vivo and in vitro injury models. Because of the promising preclinical data on neuroprotection, the Women's Estrogen for Stroke Trial was initiated. The outcomes from this trial were, however, unsuccessful and questions emerged about the safety of chronic estrogen treatment in women. In contrast to the chronic estrogen treatment strategy, the present study aims to investigate: (1) the neuroprotective efficacy of single estrogen pretreatment/preconditioning; and (2) the existence of a similarity between estrogen- and ischemic preconditioning-induced neuroprotection against cerebral ischemia. The efficacy of estrogen was tested in an in vitro model of cerebral ischemia using hippocampal organotypic slice culture system. The hippocampal organotypic slice cultures were generated from female neonatal (9-11 days old) Sprague-Dawley rats. The slices were exposed to estradiol-17beta (0.5, 1, 5 nM) for various durations (1, 2 or 4 h) 48 h prior to ischemia (40 min of oxygen-glucose deprivation). For ischemic preconditioning, slices were exposed to sublethal oxygen-glucose deprivation (15 min), 48 h prior to lethal oxygen-glucose deprivation. Quantification of cell death in hippocampal CA1 region was conducted by using propidium iodide fluorescence staining technique. Results demonstrated that estrogen preconditioning significantly protects the hippocampal CA1 region against ischemia (P<0.001) and mimicked ischemic preconditioning-induced neuroprotection. The propidium iodide fluorescence values of estrogen preconditioning, ischemic preconditioning and ischemia groups were 21+/-2 (mean+/-S.E.M.) (1 nM; 2 h; n=15), 18+/-2 (5 nM; 4 h; n=12), 32+/-3 (n=8), 65+/-3 (n=27), respectively. Further, estrogen preconditioning initiated a calcium-mediated signaling pathway leading to protection of CA1 neurons against ischemia. Future investigations in estrogen preconditioning may suggest new estrogen regimens that avoid potential side effects of chronic estrogen treatment for stroke patients.
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PMID:Estrogen preconditioning protects the hippocampal CA1 against ischemia. 1677 51

Ovarian hormones can protect against brain injury, neurodegeneration, and cognitive decline. Most attention has focused on estrogens and accumulating data demonstrate that estrogen seems to specifically protect cortical and hippocampal neurons from ischemic injury and from damage due to severe seizures. Although multiple studies demonstrate protection by estrogen, in only a few instances is the issue of how the steroid confers protection known. Here, we first review data evaluating the neuroprotective effects of estrogens, a selective estrogen receptor modulator (SERM), and estrogen receptor alpha- and beta-selective ligands in animal models of focal and global ischemia. Using focal ischemia in ovariectomized ERalphaKO, ERbetaKO, and wild-type mice, we clearly established that the ERalpha subtype is the critical ER mediating neuroprotection in mouse focal ischemia. In rats and mice, the middle cerebral artery occlusion (MCAO) model was used to represent cerebrovascular stroke, while in gerbils the two-vessel occlusion model, representing global ischemia, was used. The gerbil global ischemia model was used to evaluate the neuroprotective effects of estrogen, SERMs, and ERalpha- and ERbeta-selective compounds in the hippocampus. Analysis of neurogranin mRNA, a marker of viability of hippocampal neurons, with in situ hybridization, revealed that estrogen treatment protected the dorsal CA1 regions not only when administered before, but also when given 1 h after occlusion. Estrogen rarely is secreted alone and studies of neuroprotection have been less extensive for a second key ovarian hormone progesterone. In the second half of this review, we present data on neuroprotection by estrogen and progesterone in animal model of epilepsy followed by exploration into ovarian steroid effects on neuronal damage in models of multiple sclerosis and traumatic brain injury.
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PMID:Neuroprotection by ovarian hormones in animal models of neurological disease. 1678 98

The cerebral vasculature is a target tissue for sex steroid hormones. Estrogens, androgens, and progestins all influence the function and pathophysiology of the cerebral circulation. Estrogen decreases cerebral vascular tone and increases cerebral blood flow by enhancing endothelial-derived nitric oxide and prostacyclin pathways. Testosterone has opposite effects, increasing cerebral artery tone. Cerebrovascular inflammation is suppressed by estrogen but increased by testosterone and progesterone. Evidence suggests that sex steroids also modulate blood-brain barrier permeability. Estrogen has important protective effects on cerebral endothelial cells by increasing mitochondrial efficiency, decreasing free radical production, promoting cell survival, and stimulating angiogenesis. Although much has been learned regarding hormonal effects on brain blood vessels, most studies involve young, healthy animals. It is becoming apparent that hormonal effects may be modified by aging or disease states such as diabetes. Furthermore, effects of testosterone are complicated because this steroid is also converted to estrogen, systemically and possibly within the vessels themselves. Elucidating the impact of sex steroids on the cerebral vasculature is important for understanding male-female differences in stroke and conditions such as menstrual migraine and preeclampsia-related cerebral edema in pregnancy. Cerebrovascular effects of sex steroids also need to be considered in untangling current controversies regarding consequences of hormone replacement therapies and steroid abuse.
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PMID:Influence of sex steroid hormones on cerebrovascular function. 1679 20

Oral contraceptive pills (OCs) are widely used method of contraception for its effectiveness and easier compliance. However, adverse effects associated with OCs use notably the increased risk of cardiovascular diseases (CVD), manifesting as ischaemic and haemorrhagic stroke, myocardial infarction (MI) and venous thromboembolic diseases were reported soon after their introduction to the market in the early 1960s. Various modifications were made in an attempt to lower these risks including a reduction in the estrogen dose and changes in the progestogen compound. Currently used OCs containing the new progestin (Levonorgestrel, Desogestrel, gestodene or norgestimate) classified as low dose because all contain less than 35 microg of ethinyl estradiol. Despite their low steroid content, all have proved to be highly effective. The rationale of this reviewed study based upon cardiovascular risks in relation to these monophasic low-dose oral contraceptives. To review all relevant articles it is concluded that the risk for cardiovascular disease is lower with current preparations of oral contraceptives. Cardiovascular diseases occur mainly among oral contraceptive users who smoke or have predisposing factors--such as age more than 35 years, overweight, diabetes & hypertension.
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PMID:Risk of cardiovascular diseases with oral contraceptives. 1687 10

Estrogen reduces brain injury after experimental cerebral ischemia in part through a genomic mechanism of action. Using DNA microarrays, we analyzed the genomic response of the brain to estradiol, and we identified a transcript, cocaine- and amphetamine-regulated transcript (CART), that is highly induced in the cerebral cortex by estradiol under ischemic conditions. Using in vitro and in vivo models of neural injury, we confirmed and characterized CART mRNA and protein up-regulation by estradiol in surviving neurons, and we demonstrated that i.v. administration of a rat CART peptide is protective against ischemic brain injury in vivo. We further demonstrated binding of cAMP response element (CRE)-binding protein to a CART promoter CRE site in ischemic brain and rapid activation by CART of ERK in primary cultured cortical neurons. The findings suggest that CART is an important player in estrogen-mediated neuroprotection and a potential therapeutic agent for stroke and other neurodegenerative diseases.
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PMID:Role of cocaine- and amphetamine-regulated transcript in estradiol-mediated neuroprotection. 1697 88


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