Influence of sex steroid hormones on cerebrovascular function

Estrogen-receptor-mediated protection of cerebral endothelial cell viability and mitochondrial function after ischemic insult in vitro

Protective effects of estrogen against experimental stroke and neuronal ischemic insult are well-documented, but it is not known whether estrogen prevents ischemic injury to brain endothelium, a key component of the neurovascular unit. Increasing evidence indicates that estrogen exerts protective effects through mitochondrial mechanisms. We previously found 17beta-estradiol (E2) to improve mitochondrial efficiency and reduce mitochondrial superoxide in brain blood vessels and endothelial cells. Thus we hypothesized E2 will preserve mitochondrial function and protect brain endothelial cells against ischemic damage. To test this, an in vitro ischemic model, oxygen-glucose deprivation (OGD)/reperfusion, was applied to immortalized mouse brain endothelial cells (bEnd.3). OGD/reperfusion-induced cell death was prevented by long-term (24, 48 h), but not short-term (0.5, 12 h), pretreatment with 10 nmol/L E2. Protective effects of E2 on endothelial cell viability were mimicked by an estrogen-receptor (ER) agonist selective for ERalpha (PPT), but not by one selective for ERbeta (DPN). In addition, E2 significantly decreased mitochondrial superoxide and preserved mitochondrial membrane potential and ATP levels in early stages of OGD/reperfusion. All of the E2 effects were blocked by the ER antagonist, ICI-182,780. These findings indicate that E2 can preserve endothelial mitochondrial function and provide protection against ischemic injury through ER-mediated mechanisms.

The effect of ovariectomy and estrogen on penetrating brain arterioles and blood-brain barrier permeability

OBJECTIVE

We investigated the effect of estrogen replacement on the structure and function of penetrating brain arterioles (PA) and blood-brain barrier (BBB) permeability.

MATERIALS AND METHODS

Female ovariectomized Sprague-Dawley rats were replaced with estradiol (E(2)) and estriol (E(3)) (OVX + E; N=13) and compared to ovariectomized animals without replacement (OVX; N=14) and intact controls (CTL, proestrous; N=13). Passive and active diameters, percent tone, and passive distensibility of pressurized PA were compared. In addition, BBB permeability to Lucifer Yellow, a marker of transcellular transport, was compared in cerebral arteries.

RESULTS

Ovariectomy increased myogenic tone in PA, compared to CTL, that was not ameliorated by estrogen treatment. Percent tone at 75 mmHg for CTL vs. OVX and OVX + E was 44+/-3% vs. 51+/-1% and 54+/-3% (P<0.01 vs. CTL for both). No differences were found in passive diameters or distensibility between the groups. BBB permeability increased 500% in OVX vs. CTL animals; however, estrogen replacement restored barrier properties: flux of Lucifer Yellow for CTL, OVX, and OVX + E was (ng/mL): 3.4+/-1.2, 20.2+/-5.3 (P<0.01 vs. CTL), and 6.15+/-1.2 (n.s.).

CONCLUSIONS

These results suggest that estrogen replacement may not be beneficial for small-vessel disease in the brain, but may limit BBB disruption and edema under conditions that cause it.

Intima-media thickness and regional cerebral blood flow in older adults

BACKGROUND AND PURPOSE

The relationship between the thickness of the carotid intima (IMT) and brain function remains unclear in those without clinical manifestations of cerebrovascular disease. Understanding the neural correlates of this vascular measure is important in view of emerging evidence linking poorer cognitive performance with increased IMT in individuals without clinical cerebrovascular disease.

METHODS

Seventy-three participants in the Baltimore Longitudinal Study of Aging (70.9 years; SD, 7.3) were evaluated with carotid artery ultrasound and resting [(15)O]H(2)O positron emission tomography.

RESULTS

After adjusting for age, gender, and gray and white matter volumes in the regions where IMT is related to regional cerebral blood flow (rCBF), we found that higher IMT was associated with lower rCBF in lingual, inferior occipital, and superior temporal regions. Higher IMT was also associated with higher rCBF in medial frontal gyrus, putamen, and hippocampal-uncal regions (P=0.001). Whereas women had lower IMT (P=0.01) and mean arterial pressure (P=0.05) than men, they showed more robust associations between IMT and rCBF. The relationship between IMT and rCBF was only minimally affected by additional adjustment for mean arterial pressure.

CONCLUSIONS

IMT is related to patterns of resting rCBF in older adults without clinical manifestations of cerebrovascular disease, suggesting that there are regional differences in CBF that are associated with subclinical vascular disease.

Combination therapy of 17beta-estradiol and recombinant tissue plasminogen activator for experimental ischemic stroke

Thrombolysis with recombinant tissue plasminogen activator (rtPA) in ischemic stroke is limited by the increased risk of hemorrhage transformation due to blood-brain barrier breakdown. We determined the interaction of 17beta-estradiol (E2) and rtPA on activation of plasminogen system and matrix metalloproteinases (MMPs) in a transient middle cerebral artery occlusion (MCAO) model. Ovariectomized female rats were subjected to 1-h transient focal cerebral ischemia using a suture MCAO model. Ischemic lesion volume was significantly reduced with acute treatment of E2 despite of exogenous administration of rtPA. The expression and activation of urokinase (uPA), MMP2, and MMP9 were significantly increased in ischemic hemisphere after transient cerebral ischemia. Exogenous rtPA administration further enhanced expression and activation of uPA, MMP2, and MMP9, which was blocked by E2 treatment. We further determined the effect of combination therapy of E2 and rtPA in an embolic MCAO model. Although no protection was indicated upon acute treatment of E2 alone, combination treatment of E2 and rtPA provided protective action at 3 h after embolism. Collectively, the present study suggests that estrogen could be a candidate for combination therapy with rtPA to attenuate its side effect and hence expand its short therapeutic window for treatment of ischemic stroke.

Family cohesion moderates the relation between free testosterone and delinquent behaviors in adolescent boys and girls

PURPOSE

This study examined the associations of free testosterone and family environment with delinquent and aggressive behaviors among adolescent boys and girls with elevated low-density lipoprotein (LDL)-cholesterol levels.

METHODS

Participants were 164 boys and 180 girls 11-14 years of age. The female parent provided ratings of family cohesion and of child aggressive and delinquent behaviors. Tanner ratings of pubertal development were obtained during physical examination, and a blood sample was drawn for assessment of serum levels of free testosterone.

RESULTS

Hierarchical regression analyses revealed significant two-way interactions of free testosterone and family cohesion on delinquent behaviors among adolescent boys and girls. Specifically, under conditions of low family cohesion, free testosterone was positively associated with delinquent behaviors among boys, whereas in families with high cohesion no association between free testosterone and delinquent behavior was observed. In contrast, free testosterone was negatively associated with delinquent behaviors among adolescent girls in low-cohesion families. For girls, family cohesion was negatively associated with aggressive behaviors; for boys, LDL-C was positively associated with aggressive behaviors.

CONCLUSIONS

Child gender and family environment factors appear to modify the associations between free testosterone and delinquent behaviors in adolescent boys and girls.

Reversible Cerebral Vasoconstriction Syndrome with Posterior Leucoencephalopathy after Oral Contraceptive Pills

Reversible cerebral vasoconstriction syndrome (RCVS) is characterized by sudden-onset recurrent ‘thunderclap’ headaches with reversible multifocal narrowing of the cerebral arteries, often associated with focal neurological deficits from ischaemic or haemorrhagic stroke. It has been associated with exposure to vasoconstrictive drugs, pregnancy, migraine, and a variety of other conditions. Whereas the pathophysiology of RCVS remains unclear, changes in the levels of female hormones are considered important because RCVS predominantly affects women and is frequently associated with pregnancy. We report a patient with angiographically confirmed RCVS whose MRI showed reversible brain oedema, suggesting an overlap between RCVS and the reversible posterior leucoencephalopathy syndrome. The only identified risk factor was oral contraceptive pills started 1 month prior to onset, supporting a role for female reproductive hormones in precipitating this overlap syndrome.

Effects of estrogen on postischemic pial artery reactivity to ADP

OBJECTIVE

The aims of this work were to determine if 1) ischemia alters pial artery responsiveness to the partially nitric oxide (NO)-dependent dilator, ADP, 2) the alteration depends on 17beta-estradial (E2), and 3) NO contributes to E2 protective effects.

MATERIALS AND METHODS

Response to ADP and the non-NO-dependent dilator, PGE(2), were examined through closed cranial windows. Ovariectomized (OVX) and E2-replaced (E25, 0.025 mg; or E50, 0.05 mg) rats were subjected to 15-minute forebrain ischemia and one-hour reperfusion. Endothelial NO synthase (eNOS) expression was determined in pre- and postischemic isolated cortical microvessels.

RESULTS

In OVX rats, ischemia depressed pial responses to ADP, but not to PGE(2). Both doses of E2 maintained responses to ADP and had no effect on the response to PGE(2). eNOS inhibition decreased the ADP response by 60% in the E25 rats and 50% in the E50 rats, but had no effect in the OVX rats. Compared to the OVX group, microvessel expression of eNOS was increased by E2, but postischemic eNOS was unchanged in both groups.

CONCLUSIONS

The nearly complete loss of postischemic dilation to ADP suggests that normal non-NO-mediated dilatory mechanisms may be acutely impaired after ischemic injury. Estrogen's protective action on ADP dilation may involve both NO- and non-NO-mediated mechanisms.

Sex differences in stroke epidemiology: a systematic review

BACKGROUND AND PURPOSE

Epidemiological studies, mainly based on Western European surveys, have shown that stroke is more common in men than in women. In recent years, sex-specific data on stroke incidence, prevalence, subtypes, severity and case-fatality have become available from other parts of the world. The purpose of this article is to give a worldwide review on sex differences in stroke epidemiology.

METHODS

We searched PubMed, tables-of-contents, review articles, and reference lists for community-based studies including information on sex differences. In some areas, such as secular trends, ischemic subtypes and stroke severity, noncommunity-based studies were also reviewed. Male/female ratios were calculated.

RESULTS

We found 98 articles that contained relevant sex-specific information, including 59 incidence studies from 19 countries and 5 continents. The mean age at first-ever stroke was 68.6 years among men, and 72.9 years among women. Male stroke incidence rate was 33% higher and stroke prevalence was 41% higher than the female, with large variations between age bands and between populations. The incidence rates of brain infarction and intracerebral hemorrhage were higher among men, whereas the rate of subarachnoidal hemorrhage was higher among women, although this difference was not statistically significant. Stroke tended to be more severe in women, with a 1-month case fatality of 24.7% compared with 19.7% for men.

CONCLUSIONS

Worldwide, stroke is more common among men, but women are more severely ill. The mismatch between the sexes is larger than previously described.

Dihydrotestosterone stimulates cerebrovascular inflammation through NFkappaB, modulating contractile function

Our previous studies show that long-term testosterone treatment augments vascular tone under physiological conditions and exacerbates endotoxin-induced inflammation in the cerebral circulation. However, testosterone can be metabolized by aromatase to estrogen, evoking a balance between androgenic and estrogenic effects. Therefore, we investigated the effect of the nonaromatizable androgen receptor agonist, dihydrotestosterone (DHT), on the inflammatory nuclear factor-kappaB (NFkappaB) pathway in cerebral blood vessels. Cerebral arteries were isolated from orchiectomized male rats treated chronically with DHT in vivo. Alternatively, pial arteries were isolated from orchiectomized males and were exposed ex vivo to DHT or vehicle in culture medium. DHT treatment, in vivo or ex vivo, increased nuclear NFkappaB activation in cerebral arteries and increased levels of the proinflammatory products of NFkappaB activation, cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS). Effects of DHT on COX-2 and iNOS were attenuated by flutamide. In isolated pressurized middle cerebral arteries from DHT-treated rats, constrictions to the selective COX-2 inhibitor NS398 or the selective iNOS inhibitor L-nil, [L-N6-(Iminoethyl)lysine], were increased, confirming a functional consequence of DHT exposure. In conclusion, activation of the NFkappaB-mediated COX-2/iNOS pathway by the selective androgen receptor agonist, DHT, results in a state of vascular inflammation. This effect may contribute to sex-related differences in cerebrovascular pathophysiology.

Soy phytoestrogens are neuroprotective against stroke-like injury in vitro

Diets high in soy are neuroprotective in experimental stroke. This protective effect is hypothesized to be mediated by phytoestrogens contained in soy, because some of these compounds have neuroprotective effects in in vitro models of cell death. We tested the ability of the soy phytoestrogens genistein, daidzein, and the daidzein metabolite equol to protect embryonic rat primary cortical neurons from ischemic-like injury in vitro at doses typical of circulating concentrations in human populations (0.1-1 microM). All three phytoestrogens inhibited lactate dehydrogenase (LDH) release from cells exposed to glutamate toxicity or the calcium-ATPase inhibitor, thapsigargin. In cells exposed to hypoxia or oxygen-glucose deprivation (OGD), pretreatment with the phytoestrogens inhibited cell death in an estrogen receptor (ER) dependent manner. Although OGD results in multiple modes of cell death, examination of alpha-spectrin cleavage and caspase-3 activation revealed that the phytoestrogens were able to inhibit apoptotic cell death in this model. In addition, blockade of phosphoinositide 3-kinase prevented the protective effects of genistein and daidzein, and blockade of mitogen-activated protein kinase prevented genistein-dependent neuroprotection. These results suggest that pretreatment with dietary levels of soy phytoestrogens can mimic neuroprotective effects observed with estrogen and appear to use the same ER-kinase pathways to inhibit apoptotic cell death.

Gender and sex hormones in multiple sclerosis pathology and therapy

Several lines of evidence indicate that gender affects the susceptibility and course of multiple sclerosis (MS) with a higher disease prevalence and overall better prognosis in women than men. This sex dimorphism may be explained by sex chromosome effects and effects of sex steroid hormones on the immune system, blood brain barrier or parenchymal central nervous system (CNS) cells. The well known improvement in disease during late pregnancy has also been linked to hormonal changes and has stimulated recent clinical studies to determine the efficacy of and tolerance to sex steroid therapeutic approaches. Both clinical and experimental studies indicate that sex steroid supplementation may be beneficial for MS. This could be related to anti-inflammatory actions on the immune system or CNS and to direct neuroprotective properties. Here, clinical and experimental data are reviewed with respect to the effects of sex hormones or gender in the pathology or therapy of MS or its rodent disease models. The different cellular targets as well as some molecular mechanisms likely involved are discussed.

Migraine and stroke: current perspectives

OBJECTIVE

The purpose of this article is to review the latest concepts regarding migraine and ischemic stroke. In addition, focal neurological deficits and MRI changes in migraine patients will be reviewed.

METHODS

A PubMed search of neurological literature pertaining to this study was conducted using specific keyword search terms pertaining to migraine and ischemic stroke.

RESULTS

Migraine, especially with aura, is a relative risk factor for stroke. Neuroimaging demonstrates the posterior circulation as being most vulnerable, although the reason for this distribution is unclear. Factors that may contribute to stroke in migraine include changes during cortical spreading depression with hyper- or hypoperfusion of neural tissue, vasospasm and endothelial dysfunction. Estrogen affects migraine expression as well as cerebral circulation, yet most women with migraine without aura are not at increased risk. Co-morbidity with patent foramen ovale can be mechanism of both disorders via presumed lack of filtration of microemboli or toxic substances; however, closure with reversal of right to left shunt seems to be more beneficial for cryptogenic stroke than migraine. Migraine and stroke are found in specific genetic disorders such as CADASIL, HERNS and MELAS giving clues to genetic factors. Stroke associated with migraine treatments such as ergots or triptans is rare, and usually associated with special circumstances such as overuse or concomitant thrombogenic conditions.

CONCLUSION

Although true migrainous infarction is rare, our understanding of the subtle associations between migraine and cerebrovascular behavior is expanding.

Sex differences in stroke

Increasing evidence suggests that sex differences exist in the etiology, presentation, treatment, and outcome from stroke. The reasons for these sex disparities are becoming increasingly explored, but large gaps still exist in our knowledge. Experimental studies over the past several years have demonstrated intrinsic sex differences both in vivo and in animal models which may have relevance to our understanding of stroke in clinical populations. A greater understanding of the differences and similarities between males and females with respect to the risk factors, pathophysiology, and response to stroke will facilitate the design of future clinical trials and enhance the development of treatment strategies to improve stroke care in both sexes. This article reviews the current literature on sex differences in stroke with an emphasis on the clinical data, incorporating an analysis of bench research as it pertains to the bedside.

Latent state-trait structure of cerebral blood flow in a resting state

Cerebral blood flow (CBF) is an important parameter for the study of brain function. The present paper examines to what extent CBF in a resting state reflects a stable latent trait and to what extent it reflects phasic situational effects. In 38 healthy subjects resting CBF was measured with continuous arterial spin labeling. Data analyses were performed within the methodological framework of latent state-trait theory, which allows the decomposition of the measured variables into temporally stable differences, occasion-specific fluctuations, and measurement errors. For most of the regions of interest, about 70% of the observed variance in resting CBF was determined by individual differences on a latent physiological trait whereas about 20% of the variance was due to occasion-specific influences. Thus, an aggregation across measurement occasions is not necessary in order to yield a stable physiological trait.

Sex differences in stroke: epidemiology, clinical presentation, medical care, and outcomes

Stroke has a greater effect on women than men because women have more events and are less likely to recover. Age-specific stroke rates are higher in men, but, because of their longer life expectancy and much higher incidence at older ages, women have more stroke events than men. With the exception of subarachnoid haemorrhage, there is little evidence of sex differences in stroke subtype or severity. Although several reports found that women are less likely to receive some in-hospital interventions, most differences disappear after age and comorbidities are accounted for. However, sex disparities persist in the use of thrombolytic treatment (with alteplase) and lipid testing. Functional outcomes and quality of life after stroke are consistently poorer in women, despite adjustment for baseline differences in age, prestroke function, and comorbidities. Here, we comprehensively review the epidemiology, clinical presentation, medical care, and outcomes of stroke in women.

Does hormone therapy affect attention and memory in sleep-deprived women?

OBJECTIVES

To evaluate whether hormone therapy (HT) modifies cognitive performance during sleep deprivation in postmenopausal women. Comparison was made with a group of young women.

METHODS

Participants included 26 postmenopausal women (age 58-72 years, 16 HT users, 10 non-users), 11 young women (age 20-26 years). They spent four consecutive nights in the sleep laboratory. Cognitive tests of attention, working memory, and verbal episodic memory were carried out after the baseline night, 25-h sleep deprivation, and recovery night.

RESULTS

Sleep deprivation impaired performance in all groups. It was manifested either as delayed practice effect or deteriorated performance (p < 0.05). In simple reaction time and 10-choice reaction time, non-users and young maintained their performance, whereas HT users suffered a minor impairment (p < 0.01). In other measurements, there was no interaction of group and condition. In 10-choice reaction time and vigilance, postmenopausal women made fewer errors and omissions than the young (p < 0.05). For most tasks, all groups showed improvement after one recovery night.

CONCLUSIONS

HT had a minor adverse effect on cognitive performance during sleep deprivation. Attention and memory deteriorated similarly in postmenopausal and young women, despite the lower initial performance level of postmenopausal women. One night of sleep ensured recovery in most tasks.

Effects of estrogen and progestin on the CO2 sensitivity of hemispheric cerebral blood volume

OBJECTIVE

High CO2 sensitivity is one of the major characteristics of the cerebrovascular bed. It has been shown to be influenced by many differrent factors (eg, sex hormones).

DESIGN

The effect of ovariectomy and subsequent female sexual hormone treatment on the steady-state hemispheric cerebral blood volume and CO2 responsiveness of the hemispheric blood vessels was studied on anesthetized, ventilated, normotensive, normoxic rats. Cerebral blood volume was measured with Tomita's photoelectric method with Sandor's modification.

RESULTS

Steady-state cerebral blood volume values in ovariectomized rats did not differ from those found in control animals. The CO2 responsiveness of hemispheric blood vessels was higher in ovariectomized and progestin-treated, but not estrogen-treated, animals compared with controls.

CONCLUSIONS

Our results demonstrate that the CO2 sensitivity of the hemispheric vessels is sex hormone dependent. Estrogen and progestin treatment have opposite effects on this cerebral circulatory parameter.

The injured nervous system: a Darwinian perspective

Much of the permanent damage that occurs in response to nervous system damage (trauma, infection, ischemia, etc.) is mediated by endogenous secondary processes that can contribute to cell death and tissue damage (excitotoxicity, oxidative damage and inflammation). For humans to evolve mechanisms to minimize secondary pathophysiological events following CNS injuries, selection must occur for individuals who survive such insults. Two major factors limit the selection for beneficial responses to CNS insults: for many CNS disease states the principal risk factor is advanced, post-reproductive age and virtually all severe CNS traumas are fatal in the absence of modern medical intervention. An alternative hypothesis for the persistence of apparently maladaptive responses to CNS damage is that the secondary exacerbation of damage is the result of unavoidable evolutionary constraints. That is, the nervous system could not function under normal conditions if the mechanisms that caused secondary damage (e.g., excitotoxicity) in response to injury were decreased or eliminated. However, some vertebrate species normally inhabit environments (e.g., hypoxia in underground burrows) that could potentially damage their nervous systems. Yet, neuroprotective mechanisms have evolved in these animals indicating that natural selection can occur for traits that protect animals from nervous system damage. Many of the secondary processes and regeneration-inhibitory factors that exacerbate injuries likely persist because they have been adaptive over evolutionary time in the healthy nervous system. Therefore, it remains important that researchers consider the role of the processes in the healthy or developing nervous system to understand how they become dysregulated following injury.

Flutamide protects against trauma-hemorrhage-induced liver injury via attenuation of the inflammatory response, oxidative stress, and apopotosis

Although studies have shown that administration of testosterone receptor antagonist, flutamide, following trauma-hemorrhage, improves hepatic, cardiovascular, and immune functions, the precise cellular/molecular mechanisms responsible for producing these salutary effects remain largely unknown. To study this, male C3H/HeN mice were subjected to a midline laparotomy and hemorrhagic shock (35+/-5 mmHg for approximately 90 min), followed by resuscitation with Ringer lactate. Flutamide (25 mg/kg) or vehicle was administered subcutaneously at the onset of resuscitation, and animals were killed 2 h thereafter. Hepatic injury was assessed by plasma alpha-glutathione S-transferase concentration, liver myeloperoxidase activity, and nitrotyrosine formation. Hepatic malondialdehyde and 4-hydroxyalkenals (lipid peroxidation indicators), cellular DNA fragmentation, and the expression of inducible nitric oxide synthase and hypoxia-inducible factor-1alpha were also evaluated. Cytokines (TNF-alpha, IL-6) and chemokines (keratinocyte-derived chemokine and monocyte chemoattractant protein-1) levels were determined by cytometric bead array. The results indicate that flutamide administration after trauma-hemorrhage reduced liver injury, which was associated with decreased levels of alpha-glutathione S-transferase, myeloperoxidase activity, nitrotyrosine formation, lipid peroxidation, and cytokines/chemokines (systemic, liver tissue, and intracellular cytokines/chemokines). Cellular apoptosis, hepatocyte hypoxia-inducible factor-1alpha, and inducible nitric oxide synthase expression were also decreased under such conditions. Thus administration of flutamide following trauma-hemorrhage protects against liver injury via reduced inflammation, cellular oxidative stress, and apoptosis.

Protective effects of estradiol in the brain of rats with genetic or mineralocorticoid-induced hypertension

Abnormalities of hippocampus and hypothalamus are commonly observed in rats with genetic (SHR) or mineralocorticoid/salt-induced hypertension. In the hippocampus, changes include decreased cell proliferation in the dentate gyrus (DG), astrogliosis and decreased neuronal density in the hilus, whereas in the hypothalamus expression of arginine vasopressin (AVP) is markedly elevated. Here, we report that estradiol treatment overturns these abnormalities. We used 16-week-old male SHR with blood pressure (BP) approximately 190 mmHg and their normotensive Wistar-Kyoto (WKY) controls, and male Sprague-Dawley rats made hypertensive by administration of 10mg deoxycorticosterone acetate (DOCA) every other day plus 1% NaCl as drinking fluid for 4 weeks (BP approximately 160 mmHg). Controls received oil vehicle plus 1% NaCl only. Half of the animals in each group were implanted s.c. with a single estradiol benzoate pellet weighing 14 mg for 2 weeks. Estradiol-treated SHR and DOCA-salt rats showed, in comparison to their respective steroid-free groups: (a) enhanced proliferation in the DG measured by bromodeoxyuridine incorporation; (b) decreased number of glial fibrillary acidic protein (GFAP) immunopositive astrocytes; (c) increased density of neurons in the hilus of the DG, and (d) decreased hypothalamic AVP mRNA expression. These results indicate that neuronal and glial alterations of hypertensive models are plastic events reversible by steroid treatment. The estradiol protective effects may be of pharmacological interest to attenuate the consequences of hypertensive encephalopathy.

Mitochondrial effects of estrogen are mediated by estrogen receptor alpha in brain endothelial cells

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.

Stroke and the female brain

Stroke is a major public health problem. The female population carries a higher stroke burden than the male population, both because females have a longer life expectancy and because most stroke deaths occur in women. Differences between the sexes in relation to stroke are increasingly being recognized; for example, among stroke survivors, women tend to have worse outcomes than men, as indicated by more-severe disability and an increased likelihood of institutionalization in women. Women and men with stroke also differ in their risk factor profiles, and they respond differently to primary-prevention and acute stroke treatment. Women experience variations in endogenous estrogens throughout their life cycle and might also be exposed to exogenous estrogens, both of which markedly affect the brain. An understanding of the effects of endogenous and exogenous estrogens on cerebral hemodynamics could guide research into explaining how hormone therapy increases the risk of stroke in postmenopausal women. This Review summarizes the sex differences related to stroke, and the effect of endogenous and exogenous hormones on the cerebrovasculature of the female brain. It also proposes potential research approaches, the results of which could fill in gaps in our knowledge regarding the mechanism of action of estrogen in the brain.

Brain microglia express steroid-converting enzymes in the mouse

In the CNS, steroid hormones play a major role in the maintenance of brain homeostasis and it's response to injury. Since activated microglia are the pivotal immune cell involved in neurodegeneration, we investigated the possibility that microglia provide a discrete source for the metabolism of active steroid hormones. Using RT-PCR, our results showed that mouse microglia expressed mRNA for 17beta-hydroxysteroid dehydrogenase type 1 and steroid 5alpha-reductase type 1, which are involved in the metabolism of androgens and estrogens. Microglia also expressed the peripheral benzodiazepine receptor and steroid acute regulatory protein; however, the enzymes required for de novo formation of progesterone and DHEA from cholesterol were not expressed. To test the function of these enzymes, primary microglia cultures were incubated with steroid precursors, DHEA and AD. Microglia preferentially produced delta-5 androgens (Adiol) from DHEA and 5alpha-reduced androgens from AD. Adiol behaved as an effective estrogen receptor agonist in neuronal cells. Activation of microglia with pro-inflammatory factors, LPS and INFgamma did not affect the enzymatic properties of these proteins. However, PBR ligands reduced TNFalpha production signifying an immunomodulatory role for PBR. Collectively, our results suggest that microglia utilize steroid-converting enzymes and related proteins to influence inflammation and neurodegeneration within microenvironments of the brain.

Menopause and stroke and the effects of hormonal therapy

The incidence of stroke increases substantially after menopause, and in the United States it is the third leading cause of death. Data exist suggesting that women have worse outcomes for stroke than do men. Trials of aspirin use further suggest that there is a gender difference regarding stroke. While men may have a coronary benefit from aspirin, postmenopausal women do not; yet ischemic stroke may be decreased in women but not in men. Among the traditional risk factors for stroke (such as smoking, hypertension, diabetes, obesity), hormonal therapy (HT) has been suggested to be a risk as well, although the data are not consistent. The previous Position Statement of the IMS published in 2004 was relatively silent on the issue of stroke. The annual rate of stroke in women increases rapidly with aging in postmenopausal women. While the rate is approximately 0.6-0.8/1000/year at age 50-59, it is over 2/1000 after age 60. In white women in the USA, it is 4.2/1000 at 65-74 years of age, and 11.3/1000 between ages 75 and 84 years. Thus, in trials such as the Women's Health Initiative (WHI), most of the strokes occurred in older women. Both the conjugated equine estrogen/medroxyprogesterone acetate (CEE/MPA) and CEE-alone trials in the WHI reported an increased risk of stroke in the entire population using nominal statistics: 1.41 (95% confidence interval (CI) 1.07-1.85) and 1.39 (95% CI 1.10-1.77), respectively. The increased risk was related to ischemic stroke and not hemorrhagic stroke. The absolute risk for the entire population was 0.8/1000 and 1.2/1000 woman-years (<1/1000 signifies a 'rare' event using the CIOMS classification). However, the risk was not increased in the 50-59-year-old age group, although the numbers are small. Here, the background prevalence of stroke is much lower as noted above. The results of the observational trial of the WHI were not consistent with the randomized clinical trial data and were more in keeping with older observational data showing no increased risk of stroke. The authors reconcile these differences by suggesting differences in the timing of initiation of hormones, which was at an earlier age in the observational cohort. Several recent observational studies, which will be presented, show no increased risk of ischemic stroke in younger cohorts, but possibly an increase in the risk of transient ischemic attack. These recent studies suggested the risk to be less with lower doses of estradiol < or =1 mg and to be consistent with older studies showing no risk with doses < 0.625 mg CEE. In addition, the risk was possibly lower with non-oral therapy, and was reduced if started prior to menopause. The existence of hypertension was shown to substantially increase the risk. However, data on progestogen use versus unopposed estrogen have not been consistent. At the same time, a recent body of evidence from basic science studies has reaffirmed the neuronal and stroke protective effects of estrogen. Thus, the discrepancy between these data and clinical data showing no benefit or increased risk of stroke remains to be explained. Recent trials in older women with osteoporosis have suggested an increased risk of stroke with tibolone and of stroke mortality with raloxifene. In conclusion, the current data suggest no increased risk of stroke with hormone therapy in younger (50-59 years) normotensive postmenopausal women, particularly when lower doses are prescribed soon after menopause.

Intermittent hypoxia reduces cerebrovascular sensitivity to isocapnic hypoxia in humans

The purpose of this study was to determine the changes in human cerebrovascular function associated with intermittent poikilocapnic hypoxia (IH). Healthy men (n=8; 24+/-1 years) were exposed to IH for 10 days (12% O(2) for 5min followed by 5min of normoxia for 1h). During the hypoxic exposures, oxyhemoglobin saturation (SaO(2)) was 85% and the end-tidal partial pressure of CO(2) was permitted to fall as a result of hypoxic hyperventilation. Pre- and post-IH intervention subjects underwent a progressive isocapnic hypoxic test where ventilation, blood pressure, heart rate, and cerebral blood flow velocity (middle cerebral artery, transcranial Doppler) were measured to determine the ventilatory, cardiovascular and cerebrovascular sensitivities to isocapnic hypoxia. When compared to the pre-IH trial, cerebrovascular sensitivity to hypoxia significantly decreased (pre-IH=0.28+/-0.15; post-IH=0.16+/-0.14cms(-1)%SaO(2)(-1); P<0.05). No changes in ventilatory, blood pressure or heart rate sensitivity were observed (P>0.05). We have previously shown that the ability to oxygenate cerebral tissue measured using spatially resolved near infrared spectroscopy is significantly reduced following IH in healthy humans. Our collective findings indicate that intermittent hypoxia can blunt cerebrovascular regulation. Thus, it appears that intermittent hypoxia has direct cerebrovascular effects that can occur in the absence of changes to the ventilatory and neurovascular control systems.

Androgenic/estrogenic balance in the male rat cerebral circulation: metabolic enzymes and sex steroid receptors

Tissues from males can be regulated by a balance of androgenic and estrogenic effects because of local metabolism of testosterone and expression of relevant steroid hormone receptors. As a critical first step to understanding sex hormone influences in the cerebral circulation of males, we investigated the presence of enzymes that metabolize testosterone to active products and their respective receptors. We found that cerebral blood vessels from male rats express 5alpha-reductase type 2 and aromatase, enzymes responsible for conversion of testosterone into dihydrotestosterone (DHT) and 17beta-estradiol, respectively. Protein levels of these enzymes, however, were not modulated by long-term in vivo hormone treatment. We also showed the presence of receptors for both androgens (AR) and estrogens (ER) from male cerebral vessels. Western blot analysis showed bands corresponding to the full-length AR (110 kDa) and ERalpha (66 kDa). Long-term in vivo treatment of orchiectomized rats with testosterone or DHT, but not estrogen, increased AR levels in cerebral vessels. In contrast, ERalpha protein levels were increased after in vivo treatment with estrogen but not testosterone. Fluorescent immunostaining revealed ERalpha, AR, and 5alpha-reductase type 2 in both the endothelial and smooth muscle layers of cerebral arteries, whereas aromatase staining was solely localized to the endothelium. Thus, cerebral vessels from males are target tissues for both androgens and estrogen. Furthermore, local metabolism of testosterone might balance opposing androgenic and estrogenic influences on cerebrovascular as well as brain function in males.

Cerebral blood flow is increased during controlled ovarian stimulation

Estrogen appears to enhance cerebral blood flow (CBF). An association between CBF and physiologically altered hormonal levels due to menstrual cycle, menopause, or exogenous manipulations such as ovariectomy or hormone replacement therapy has been demonstrated. The purpose of this study was to determine the association between ovarian stimulation and CBF in vivo by measuring blood flow in the internal carotid artery (ICA) after pituitary suppression and during controlled ovarian stimulation in women undergoing in vitro fertilization treatment cycles. ICA volume flows were measured by angle-independent dual-beam ultrasound Doppler in 12 women undergoing controlled ovarian stimulation. Measurements were performed after pituitary/ovarian suppression, in the late follicular phase, and at midluteal phase. Blood flow in the ICA increased by 22.2% and 32% in the late follicular and midluteal phases compared with the respective values obtained during ovarian suppression (P < 0.0005 and P < 0.0001, respectively). There was a significant correlation between increments in estrogen levels and increments in CBF when the late follicular phase was compared with the ovarian suppression period (r = 0.8, P < 0.001). Mean blood flow velocity significantly increased (by 15.7% and 16.9%, respectively) and cerebral vascular resistance significantly decreased (by 17.6% and 26.5%) during the late follicular and midluteal phases compared with respective measures during ovarian suppression. There was a significant correlation between an increase in estrogen levels and a decrease in cerebral vascular resistance when the late follicular phase was compared with the ovarian suppression period (r = -0.6, P < 0.05). These changes imply sex hormone-associated intracranial vasodilation leading to increased CBF during controlled ovarian stimulation.

Effect of gender and sex hormones on vascular oxidative stress

1. It is well documented that the incidence and severity of several vascular diseases, such as hypertension, atherosclerosis and stroke, are lower in premenopausal women than men of similar age and post-menopausal women. The mechanisms responsible for gender differences in the incidence and severity of vascular disease are not well understood. However, emerging evidence suggests that sex hormone-dependent differences in vascular oxidative stress may play an important role. The aim of the present brief review is to provide an insight into the effect of gender and sex hormones on vascular oxidative stress. 2. When production of reactive oxygen species (ROS) is enhanced and/or their metabolism by anti-oxidant enzymes is impaired, a condition known as 'oxidative stress' can develop. Oxidative stress is believed to play an important role in both the initiation and progression of a variety of vascular diseases, including hypertension and atherosclerosis. NADPH oxidases are believed to be the major source of vascular ROS. Moreover, excessive production of ROS by NADPH oxidases has been linked to the development of vascular oxidative stress. 3. Increasing evidence suggests that levels of vascular ROS may be lower in women than men during health and disease. Indeed, the activity and expression of vascular NADPH oxidase is lower in female versus male animals under healthy, hypertensive and atherosclerotic conditions. 4. Gonadal sex hormones may play an important role in the regulation of vascular oxidative stress. For example, oestrogens, which are present in highest levels in premenopausal women, have been reported to lower vascular oxidative stress by modulating the expression and function of NADPH oxidases, as well as anti-oxidant enzymes. 5. Further studies are needed to clarify whether lower vascular oxidative stress in women in fact protects against the initiation and development of vascular disease and to further define the roles of gonadal sex hormones in such an effect. Knowledge gained from these studies may potentially lead to advances in the clinical diagnosis and treatment of vascular disease in both genders.

A pharmacogenomic evaluation of migraine therapy

Migraine is a common idiopathic primary headache disorder with significant mental, physical and social health implications. Accompanying an intense unilateral pulsating head pain other characteristic migraine symptoms include nausea, emesis, phonophobia, photophobia and in approximately 20-30% of migraine cases, neurologic disturbances associated with the aura phase. Although selective serotonin (5-HT) receptor agonists (i.e., 5-HT(1B/1D)) are successful in alleviating migrainous symptoms in < or = 70% of known sufferers, for the remaining 30%, additional migraine abortive medications remain unsuccessful, not tested or yet to be identified. Genetic characterization of the migrainous disorder is making steady progress with an increasing number of genomic susceptibility loci now identified on chromosomes 1q, 4q, 5q, 6p, 11q, 14q, 15q, 17p, 18q, 19p and Xq. The 4q, 5q, 17p and 18q loci involve endophenotypic susceptibility regions for various migrainous symptoms. In an effort to develop individualized pharmacotherapeutics, the identification of these migraine endophenotypic loci may well be the catalyst needed to aid in this goal. In this review the authors discuss the present treatment of migraine, known genomic susceptibility regions and results from migraine (genetic) association studies. The authors also discuss pharmacogenomic considerations for more individualized migraine prophylactic treatments.

Medroxyprogesterone acetate prevents the cardioprotective and anti-inflammatory effects of 17β-estradiol in an in vivo model of myocardial ischemia and reperfusion

Previous studies demonstrated the protective effects of estrogen administration in models of cardiovascular disease. However, there is a discrepancy between these data and those from the recent clinical trials with hormone replacement therapy in menopausal women. One possible explanation for the divergent results is the addition of progestin to the hormone regimen in the Women's Health Initiative and the Heart and Estrogen/Progestin Replacement Study trials. The aim of the present study was to examine the effects of a combination of 17β-estradiol (E2, 20 μg) and medroxyprogesterone acetate (MPA, 80 μg) on infarct size in New Zealand White rabbits. Infarct size as a percentage of the area at risk was significantly reduced by administration of E2 30 min before induction of myocardial ischemia compared with vehicle (19.5 ± 3.1 vs. 55.7 ± 2.6%, P < 0.001). However, E2 + MPA failed to elicit a reduction in infarct size (52.5 ± 4.6%), and MPA had no effect (50.8 ± 2.6%). E2 also reduced serum levels of cardiac troponin I, immune complex deposition in myocardial tissue, activation of the complement system, and lipid peroxidation. All these effects were reversed by MPA. The results suggest that MPA antagonizes the infarct-sparing effects of E2, possibly through modulation of the immune response after ischemia and reperfusion.

Regional variations and the effects of age and gender on glutamate concentrations in the human brain

Proton magnetic resonance spectroscopy was performed at 3 T using the echo time-averaged point-resolved spectroscopy method to determine the effects of age, gender and brain region on glutamate (Glu) concentrations in the healthy human brain. Thirty healthy men and 20 healthy women aged between 21 and 71 years were studied. Significant regional variations of Glu concentrations were observed. Glu concentration in the gray matter (GM) was approximately 25% higher than that in the white matter. Significant age-dependent decreases in Glu concentrations were observed in the basal ganglia (r=-0.75, P<.001) and parietal GM (r=-0.66, P<.001) of men but not those of women. Our findings demonstrate regional variations of Glu concentrations and suggest that the male brain may be more vulnerable to aging than the female brain. Our results also highlight the importance of brain region, age and gender matching in clinical studies.

Acute effects of neurosteroids in a rodent model of primary paroxysmal dystonia

The pathophysiology of various types of dyskinesias, including dystonias, is poorly understood. Clinical and epidemiological studies in humans revealed that the severity of dyskinesias and the frequency of paroxysmal forms of the disease are altered by factors such as the onset of puberty, pregnancy, cyclical changes and stress, indicating an underlying hormonal component. The dystonic phenotype in the dt(sz) hamster, a genetic animal model of paroxysmal dystonia, has been suggested to be based on a deficit of striatal gamma-aminobutyric acid (GABA)ergic interneurons and changes in the GABA(A) receptor complex. In this animal model, hormonal influences seem to be also involved in the pathophysiology, but an influence of peripheral sex hormones has already been excluded. Possibly, neurosteroids as endogenous regulators of the GABA(A) receptor may be critically involved in the pathophysiology of dystonia in this animal model. Therefore, in the present study, the effects of the neurosteroids allopregnanolone acetate and allotetrahydrodeoxycorticosterone (THDOC), representing positive modulators of the GABA(A) receptor, as well as of the negative GABA(A) receptor modulators pregnenolone sulfate and dehydroepiandrosterone (DHEA), on severity of dystonia were examined in dt(sz) hamsters after acute intraperitoneal injections. Allopregnanolone acetate and THDOC exerted a moderate reduction of dystonia, whereas pregnenolone sulfate and DHEA had no significant effects. Although the effects of allopregnanolone acetate and THDOC were moderate and short-lasting, the present results suggest that changes in neurosteroid levels might be involved in the initiation of dystonic episodes. Future studies have to include measurements of brain neurosteroid levels as well as of chronic neurosteroid administrations to clarify the pathophysiological role and therapeutic potential of neurosteroids in dystonia.

Idiopathic hemoptysis in pregnant women: a distinct entity?

In pregnant women, the reported cases of hemoptysis were most often mild and had an identified cause. Between November 2003 and January 2006, three pregnant women at 16-20 weeks gestation were admitted to our respiratory intensive care unit for massive hemoptysis. One of the women had experienced mild hemoptysis, considered as idiopathic, during her first pregnancy, with no recurrence until her second pregnancy. In all three cases, hemoptysis was massive. CT scan after iodine injection did not reveal any cause. Opacification of the bronchial artery showed hyperemia from abnormally dilated and tortuous bronchial arteries. Bronchial artery embolization (BAE) was performed in all three patients, successfully in two. Intravenous vasopressin was used as second-line treatment for recurrent bleeding after BAE in one patient. The women carried the pregnancy to term with delivery of healthy infants. Further complete investigation after the births did not identify any possible local (pulmonary) or general cause of bleeding in these three patients. Although these cases could be considered idiopathic, the close association with duration of pregnancy suggests the hemoptysis may be related to hormonal changes.

Neurotrophic and neuroprotective actions of estrogen: basic mechanisms and clinical implications

Estrogen is an important hormone signal that regulates multiple tissues and functions in the body. This review focuses on the neurotrophic and neuroprotective actions of estrogen in the brain, with particular emphasis on estrogen actions in the hippocampus, cerebral cortex and striatum. Sex differences in the risk, onset and severity of neurodegenerative disease such as Alzheimer's disease, Parkinson's disease and stroke are well known, and the potential role of estrogen as a neuroprotective factor is discussed in this context. The review assimilates a complex literature that spans research in humans, non-human primates and rodent animal models and attempts to contrast and compare the findings across species where possible. Current controversies regarding the Women's Health Initiative (WHI) study, its ramifications, concerns and the new studies needed to address these concerns are also addressed. Signaling mechanisms underlying estrogen-induced neuroprotection and synaptic plasticity are reviewed, including the important concepts of genomic versus nongenomic mechanisms, types of estrogen receptor involved and their subcellular targeting, and implicated downstream signaling pathways and mediators. Finally, a multicellular mode of estrogen action in the regulation of neuronal survival and neurotrophism is discussed, as are potential future directions for the field.

Estradiol augments peri-infarct cerebral vascular density in experimental stroke

Peri-infarct increase of vascular density has been observed in animals and in humans with ischemic stroke. Increased peri-infarct vascular density correlates with improved functional outcome after stroke. We hypothesized that pre-treatment with estradiol will increase post-ischemic peri-infarct capillary density in a rat model of transient ischemic stroke. Estradiol, compared to placebo, augmented post-ischemic peri-infarct vascular density by 22% 10 days after stroke. Recovery of forelimb function was not improved with estradiol treatment on day three and nine post-stroke. Loss of estradiol may limit repair in the peri-infarct region by limiting angiogenesis, but functional significance in stroke recovery requires further investigation.

Age alters cerebrovascular inflammation and effects of estrogen

In young adult females, estrogen treatment suppresses the cerebrovascular inflammatory response; this is mediated in part via NF-kappaB, a key regulator of inflammatory genes. To examine whether age modifies effects of estrogen on vascular inflammation in the brain, female rats, 3 and 12 mo of age, were ovariectomized; half were treated with estrogen for 4 wk. Cerebral blood vessels were isolated from the animals at 4 and 13 mo of age. Inflammation was induced by LPS, either injected in vivo or incubated with isolated vessels ex vivo. Basal levels of cytoplasmic NF-kappaB were significantly higher in cerebral vessels of young rats, but the ratio of nuclear to cytoplasmic levels was greater in middle-aged animals. LPS exposure increased nuclear NF-kappaB DNA binding activity, protein levels of inducible nitric oxide synthase and cyclooxygenase-2, and production of nitric oxide and PGE(2) in cerebral vessels. All effects of LPS were markedly greater in vessels from the older animals. Estrogen significantly inhibited the LPS-induced increase in NF-kappaB DNA binding activity in cerebral vessels from animals at both ages. In 4-mo-old rats, estrogen also significantly suppressed LPS induction of inducible nitric oxide synthase and cyclooxygenase-2 proteins, as well as production of nitric oxide and PGE(2). In contrast, in 13-mo-old females, estrogen did not significantly affect these indexes of cerebrovascular inflammation. Thus the protective, anti-inflammatory effect of estrogen on cerebral blood vessels that is observed in young adults may be attenuated in aged animals, which exhibit a greater overall cerebrovascular response to inflammatory stimuli.

Guarding the blood-brain barrier: a role for estrogen in the etiology of neurodegenerative disease

Although the effect of estrogen replacement therapy on the incidence of the neurodegenerative disease such as Alzheimer's disease is controversial, experimental studies indicate that estrogen replacement to young adult animals is neuroprotective and that perimenopausal estrogen replacement is associated with a decreased incidence of Alzheimer's disease. Estrogen affects a wide variety of cellular processes that can protect neuronal health. This article considers the disruption of the blood-brain barrier in Alzheimer's disease and forwards the hypothesis that estrogen may preserve neural health by maintaining the integrity of the blood-brain barrier.