Estrogens as neuroprotectants against ischemic stroke

Sex-specific blood biomarkers linked to memory changes in middle-aged adults: The Framingham Heart Study

The relationship between sex-specific blood biomarkers and memory changes in middle-aged adults remains unclear. We aimed to investigate this relationship using the data from the Framingham Heart Study (FHS). We conducted association analysis, partial correlation analysis, and causal dose-response curves using blood biomarkers and other data from 793 middle-aged participants (≤ 60 years) from the FHS Offspring Cohort. The results revealed associations of adiponectin and fasting blood glucose with midlife memory change, along with a U-shaped relationship of high-density lipoprotein cholesterol with memory change. No significant associations were found for the other blood biomarkers (e.g., amyloid beta protein 42) with memory change. To our knowledge, this is the first sex-specific network analysis of blood biomarkers related to midlife memory change in a prospective cohort study. Our findings highlight the importance of targeting cardiometabolic risks and the need to validate midlife-specific biomarkers that can accelerate the development of primary preventive strategies.

Sexual dimorphism in immune cell responses following stroke

Recent bodies of work in regard to stroke have revealed significant sex differences in terms of risk and outcome. While differences in sex hormones have been the focus of earlier research, the reasons for these differences are much more complex and require further identification. This review covers differences in sex related immune responses with a focus on differences in immune cell composition and function. While females are more susceptible to immune related diseases, they seem to have better outcomes from stroke at the experimental level with reduced pro-inflammatory responses. However, at the clinical level, the picture is much more complex with worse neurological outcomes from stroke. While the use of exogenous sex steroids can replicate some of these findings, it is apparent that many other factors are involved in the modulation of immune responses. As a result, more research is needed to better understand these differences and identify appropriate interventions and risk modification.

Effects of low-dose contraceptive pills on the risk factors of cardiovascular diseases among 15-35-year-old women: A retrospective cohort

Background

Cardiovascular diseases could be preventable; as a result, understanding the risk factors was regarded as the major priority for healthcare providers.

Objective

The main objective of this research was to achieve a deeper insight into the effect of long-term use of low-dose oral contraceptive pills (OCP) on the risk factors of cardiovascular diseases.

Materials and Methods

This research was a retrospective cohort conducted (historical and prospectively) conducted on 100 women with normal menstrual cycles aged 15 to 35 yr, who were referred to the healthcare centers in Yazd, Iran. The participants were categorized into two groups: The OCP group was consuming the pills for 0-3, 4-23, and 24-36 months, and the non-OCP group. Participants were followed up for a minimum of 3 months and a maximum of six months.

Results

The highest level of low-density lipoprotein (LDL), homocysteine, cholesterol, triglyceride levels, and systolic blood pressure was observed in the OCP group in the duration of 24 to 36 months. The Tukey's test demonstrated that there were comprehensible differences in the LDL (p = 0.01), cholesterol (p = 0.01), triglyceride (p < 0.001), and homocysteine levels (p < 0.001), also systolic blood pressure (p = 0.04).

Conclusion

It was realized that the long-term consumption of low-dose OCP can augment the incidence of some risk factors (systolic blood pressure, homocysteine levels, cholesterol, LDL-c, and triglyceride) and lead to developing cardiovascular diseases amongst the healthy women.

Effect of Achillea millefolium aqueous extract on memory deficit and anxiety caused by stroke in ovariectomized rats

Introduction: Some studies indicated that the decrease of estrogen level in menopausal woman results in increasing the risk of stroke. Although estrogen is a neuroprotective factor, high consumption of this compound may develop breast cancer and endometriosis. The present study investigated the effect of Achilles millefolium extract, containing estrogenlike compounds, on memory impairment and anxiogenic-like behaviors caused by cerebral ischemia in ovariectomized rats. Methods: Permanent middle cerebral artery ligation was performed, as a model for studying postmenopausal condition, in 48 female Wistar rats weighing 200-250 g. The aqueous extract of A. millefolium was prepared and gavaged for 4 weeks after inducing cerebral ischemia. Memory and anxiety-like behavior assessments were evaluated by step-through and elevated plus maze apparatus, respectively. Result: According to the results, cerebral ischemia in ovariectomized rats induced amnesia and anxiogenic-like behaviors which were restored by 7 mg/kg of A. millefolium aqueous extract. Furthermore, inactivation of estrogen receptors (ERs) by tamoxifen (100 µg/kg, intraperitoneally) blocked the restoration effect of A. millefolium on behaviors induced by cerebral ischemia. Conclusion: It could be concluded that, oral administration of A. millefolium extract is able to restore memory impairment and anxiogenic-like behaviors induced by ischemia via ERs in ovariectomized rat.

Effect of Estradiol on Neurotrophin Receptors in Basal Forebrain Cholinergic Neurons: Relevance for Alzheimer's Disease

The basal forebrain is home to the largest population of cholinergic neurons in the brain. These neurons are involved in a number of cognitive functions including attention, learning and memory. Basal forebrain cholinergic neurons (BFCNs) are particularly vulnerable in a number of neurological diseases with the most notable being Alzheimer's disease, with evidence for a link between decreasing cholinergic markers and the degree of cognitive impairment. The neurotrophin growth factor system is present on these BFCNs and has been shown to promote survival and differentiation on these neurons. Clinical and animal model studies have demonstrated the neuroprotective effects of 17β-estradiol (E2) on neurodegeneration in BFCNs. It is believed that E2 interacts with neurotrophin signaling on cholinergic neurons to mediate these beneficial effects. Evidence presented in our recent study confirms that altering the levels of circulating E2 levels via ovariectomy and E2 replacement significantly affects the expression of the neurotrophin receptors on BFCN. However, we also showed that E2 differentially regulates neurotrophin receptor expression on BFCNs with effects depending on neurotrophin receptor type and neuroanatomical location. In this review, we aim to survey the current literature to understand the influence of E2 on the neurotrophin system, and the receptors and signaling pathways it mediates on BFCN. In addition, we summarize the physiological and pathophysiological significance of E2 actions on the neurotrophin system in BFCN, especially focusing on changes related to Alzheimer's disease.

Non-Selective Cannabinoid Receptor Antagonists, Hinokiresinols Reduce Infiltration of Microglia/Macrophages into Ischemic Brain Lesions in Rat via Modulating 2-Arachidonolyglycerol-Induced Migration and Mitochondrial Activity

Growing evidence suggests that therapeutic strategies to modulate the post-ischemic inflammatory responses are promising approaches to improve stroke outcome. Although the endocannabinoid system has been emerged as an endogenous therapeutic target to regulate inflammation after stroke insult, the downstream mechanisms and their potentials for therapeutic intervention remain controversial. Here we identified trans- and cis-hinokiresinols as novel non-selective antagonists for two G-protein-coupled cannabinoid receptors, cannabinoid receptor type 1 and type 2. The Electric Cell-substrate Impedance Sensing and Boyden chamber migration assays using primary microglial cultures revealed that both hinokiresinols significantly inhibited an endocannabinoid, 2-arachidonoylglycerol-induced migration. Hinokiresinols modulated 2-arachidonoylglycerol-induced mitochondrial bioenergetics in microglia as evidenced by inhibition of ATP turnover and reduction in respiratory capacity, thereby resulting in impaired migration activity. In rats subjected to transient middle cerebral artery occlusion (1.5-h) followed by 24-h reperfusion, post-ischemic treatment with hinokiresinols (2 and 7-h after the onset of ischemia, 10 mg/kg) significantly reduced cerebral infarct and infiltration of ED1-positive microglial/macrophage cells into cerebral ischemic lesions in vivo. Co-administration of exogenous 2-AG (1 mg/kg, i.v., single dose at 2 h after starting MCAO) abolished the protective effect of trans-hinokiresionol. These results suggest that hinokiresinols may serve as stroke treatment by targeting the endocannabinoid system. Alteration of mitochondrial bioenergetics and consequent inhibition of inflammatory cells migration may be a novel mechanism underlying anti-ischemic effects conferred by cannabinoid receptor antagonists.

17β-estradiol inhibits MMP-9 and SUR1/TrpM4 expression and activation and thereby attenuates BSCB disruption/hemorrhage after spinal cord injury in male rats

Blood-spinal cord barrier (BSCB) disruption and progressive hemorrhage after spinal cord injury (SCI) lead to secondary injury and the subsequent apoptosis and/or necrosis of neuron and glia, causing permanent neurological deficits. In this study, we examined the effect of 17β-estradiol (E2) on BSCB breakdown and hemorrhage as well as subsequent inflammation after SCI. After a moderate contusion injury at the 9th thoracic segment of spinal cord, E2 (300 μg/kg) was administered by iv injection immediately after SCI, and the same dose of E2 was then administered 6 and 24 hours after injury. Our data show that E2 attenuated BSCB permeability and hemorrhage and reduced the infiltration of neutrophils and macorphages after SCI. Consistent with this finding, the expression of inflammatory mediators was significantly reduced by E2. Furthermore, E2 treatment significantly inhibited the expression of sulfonylurea receptor 1 and transient receptor potential melastatin 4 after injury, which are known to mediate hemorrhage at an early stage after SCI. Moreover, the expression and activation of matrix metalloprotease-9 after injury, which is known to disrupt BSCB, and the degradation of tight junction proteins, such as zona occludens-1 and occludin, were significantly inhibited by E2 treatment. Furthermore, the protective effects of E2 on BSCB disruption and functional improvement were abolished by an estrogen receptor antagonist, ICI 182780 (3 mg/kg). Thus, our study provides evidence that the neuroprotective effect of E2 after SCI is, in part, mediated by inhibiting BSCB disruption and hemorrhage through the down-regulation of sulfonylurea receptor 1/transient receptor potential melastatin 4 and matrix metalloprotease-9, which is dependent on estrogen receptor.

17β-estradiol increases expression of the oxidative stress response and DNA repair protein apurinic endonuclease (Ape1) in the cerebral cortex of female mice following hypoxia

While it is well established that 17β-estradiol (E2) protects the rodent brain from ischemia-induced damage, it has been unclear how this neuroprotective effect is mediated. Interestingly, convincing evidence has also demonstrated that maintaining or increasing the expression of the oxidative stress response and DNA repair protein apurinic endonuclease 1 (Ape1) is instrumental in reducing ischemia-induced damage in the brain. Since E2 increases expression of the oxidative stress response proteins Cu/Zn superoxide dismutase and thioredoxin in the brain, we hypothesized that E2 may also increase Ape1 expression and that this E2-induced expression of Ape1 may help to mediate the neuroprotective effects of E2 in the brain. To test this hypothesis, we utilized three model systems including primary cortical neurons, brain slice cultures, and whole animals. Although estrogen receptor α and Ape1 were expressed in primary cortical neurons, E2 did not alter Ape1 expression in these cells. However, immunofluorescent staining and quantitative Western blot analysis demonstrated that estrogen receptor α and Ape1 were expressed in the nuclei of cortical neurons in brain slice cultures and that E2 increased Ape1 expression in the cerebral cortex of these cultures. Furthermore, Ape1 expression was increased and oxidative DNA damage was decreased in the cerebral cortices of ovariectomized female C57Bl/6J mice that had been treated with E2 and exposed to hypoxia. Taken together, our studies demonstrate that the neuronal microenvironment may be required for increased Ape1 expression and that E2 enhances expression of Ape1 and reduces oxidative DNA damage, which may in turn help to reduce ischemia-induced damage in the cerebral cortex and mediate the neuroprotective effects of E2.

Differential anti-ischemic efficacy and therapeutic time window of trans- and cis-hinokiresinols: stereo-specific antioxidant and anti-inflammatory activities

During cerebral ischemia, neurons are injured by various mechanisms including excitotoxicity, oxidative stress, and inflammatory responses. Thus, pharmacological manipulation of multiple cytotoxic pathways has been pursued for the treatment of ischemic injury. Cis-hinokiresinol, a naturally occurring phenylpropanoid, was previously reported to possess anti-oxidant, anti-inflammatory and estrogen-like activities. In the present study, we investigated anti-ischemic effects of trans- and cis-hinokiresinols using in vitro as well as in vivo experimental models. The ORAC and DPPH assays showed that two isomers had similar free radical scavenging activities. However, only trans-hinokiresinol significantly decreased neuronal injury in cultured cortical neurons exposed to oxygen-glucose deprivation (75 min) followed by re-oxygenation (9 h). The differential neuroprotective effect could be due to the stereo-specific augmentation of Cu/Zn-SOD activity by trans-hinokiresinol, when compared with cis-hinokiresinol. Similarly, in rats subjected to transient middle cerebral artery occlusion (1.5 h) followed by 24-h reperfusion, pre-ischemic treatment with trans-hinokiresinol, but not with cis-isomer, reduced cerebral infarct volume. Interestingly, however, post-ischemic treatment with both hinokiresinols (2 and 7 h after onset of ischemia) significantly reduced cerebral infarct. When administered after onset of ischemia, trans-hinokiresinol, but not its cis-isomer reduced nitrotyrosine immunoreactivity in ischemic regions. In contrast, both hinokiresinols suppressed neutrophil infiltration and IL-1β release to a similar extent. The observed differential anti-oxidant, but comparable anti-inflammatory, activities may explain the stereo-specific anti-ischemic activities and different therapeutic time windows of the hinokiresinols examined. More detailed delineation of the anti-ischemic mechanism(s) of hinokiresinols may provide a better strategy for development of efficacious regimens for cerebral ischemic stroke.

Novel effects of hormonal contraceptive use on the plasma proteome

Background

Hormonal contraceptive (HC) use may increase cardiometabolic risk; however, the effect of HC on emerging cardiometabolic and other disease risk factors is not clear.

Objectives

To determine the association between HC use and plasma proteins involved in established and emerging disease risk pathways.

Method

Concentrations of 54 high-abundance plasma proteins were measured simultaneously by LC-MRM/MS in 783 women from the Toronto Nutrigenomics and Health Study. C-reactive protein (CRP) was measured separately. ANCOVA was used to test differences in protein concentrations between users and non-users, and among HC users depending on total hormone dose. Linear regression was used to test the association between duration (years) of HC use and plasma protein concentrations. Principal components analysis (PCA) was used to identify plasma proteomic profiles in users and non-users.

Results

After Bonferroni correction, 19 proteins involved in inflammation, innate immunity, coagulation and blood pressure regulation were significantly different between users and non-users (P<0.0009). These differences were replicated across three distinct ethnocultural groups. Traditional markers of glucose and lipid metabolism were also significantly higher among HC users. Neither hormone dose nor duration of use affected protein concentrations. PCA identified 4 distinct proteomic profiles in users and 3 in non-users.

Conclusion

HC use was associated with different concentrations of plasma proteins along various disease-related pathways, and these differences were present across different ethnicities. Aside from the known effect of HC on traditional biomarkers of cardiometabolic risk, HC use also affects numerous proteins that may be biomarkers of dysregulation in inflammation, coagulation and blood pressure.

Estrogen prevents β-amyloid inhibition of sympathetic α7-nAChR-mediated nitrergic neurogenic dilation in porcine basilar arteries

AIM

β-amyloid peptides (Aβs) have been shown to block cerebral nitrergic neurogenic vasodilation by blocking sympathetic α7-nAChRs, and that oestrogen prevents Aβ-induced neurotoxicity. We examined whether Aβ-inhibition of α7-nAChR-mediated cerebral nitrergic vasodilation was prevented by oestrogen.

METHODS

Effects of Aβ and 17β-oestradiol on neurogenic nitrergic vasodilation in isolated porcine basilar arteries were examined using wire-myography. Drug effects on nicotine- and choline-induced calcium influx and inward currents in porcine cultured superior cervical ganglion (SCG) were investigated using confocal microscopy and patch-clamp techniques respectively.

RESULTS

Precontracted endothelium-denuded basilar arteries relaxed exclusively upon transmural nerve stimulation (TNS, 8 Hz), and applications of nicotine (100 μm) or choline (1 mm), which was sensitive to nitro-L-arginine (L-NNA, 30 μm) and tetrodotoxin (0.3 μm). The relaxation induced by nicotine and choline but not that by TNS was blocked reversibly by Aβ(1-40) in a concentration-dependent manner. Aβ(1-40) also reversibly blocked nicotine- and choline-induced increase of calcium influx and inward currents in the SCG neurons. Aβ inhibition of nicotine- and choline-induced α7-nAChR-mediated nitrergic vasodilation and inward currents was prevented by 17β-oestradiol (10 μm), but not by α-oestradiol (10 μm) or testosterone (10 μm).

CONCLUSION

These results provide further evidence supporting that Aβ is an antagonist for the α7-nAChR found on post-ganglionic sympathetic adrenergic nerve terminals originating in the SCG. Aβ can cause constriction of cerebral arteries with possible decreased regional cerebral blood flow by blocking sympathetic nerve-mediated release of nitric oxide from the perivascular nitrergic nerves. This effect of Aβ can be prevented by endogenous oestrogen but not testosterone.

Neuroprotective actions of estradiol and novel estrogen analogs in ischemia: translational implications

This review highlights our investigations into the neuroprotective efficacy of estradiol and other estrogenic agents in a clinically relevant animal model of transient global ischemia, which causes selective, delayed death of hippocampal CA1 neurons and associated cognitive deficits. We find that estradiol rescues a significant number of CA1 pyramidal neurons that would otherwise die in response to global ischemia, and this is true when hormone is provided as a long-term pretreatment at physiological doses or as an acute treatment at the time of reperfusion. In addition to enhancing neuronal survival, both forms of estradiol treatment induce measurable cognitive benefit in young animals. Moreover, estradiol and estrogen analogs that do not bind classical nuclear estrogen receptors retain their neuroprotective efficacy in middle-aged females deprived of ovarian hormones for a prolonged duration (8weeks). Thus, non-feminizing estrogens may represent a new therapeutic approach for treating the neuronal damage associated with global ischemia.

Young women have poorer outcomes than men after stroke

BACKGROUND AND PURPOSE

Gender differences in stroke outcome have not been fully assessed in young patients.

METHODS

We conducted an observational study of consecutive young ischemic stroke patients (≤ 50 years of age) admitted to a stroke unit (January 1999 to December 2009). Basal data, subtype of ischemic stroke, stroke severity [Canadian Neurological Scale (CNS)], length of hospital stay, inhospital complications, mortality and functional outcome at discharge [modified Rankin Scale (mRS) score] were analyzed. For stroke severity and outcome analyses, 2 age groups were established: 15-30 (very young group) and 31-50 years old (middle-aged young group).

RESULTS

A total of 310 patients were enrolled; 128 females and 182 males. The mean age was similar in women and men (41.07 ± 8.6 vs. 42.12 ± 8.2, NS). Migraine was more frequent in women, whereas arterial hypertension, hyperlipidemia, alcohol abuse, current smoking and atherothrombotic infarction were more frequent in men (p < 0.05). Females presented greater stroke severity than men [median CNS (IQR) = 8 (3.5) vs. 9 (2.5), p = 0.014] except in the very young group [median CNS (IQR) = 9 (1.8) vs. 8 (5), p = 0.022]. Female sex was a predictor of unfavorable outcomes (mRS >2) at discharge in the total sample (OR = 3.33; 95% CI = 1.41-7.84) and in the middle-aged young group (OR = 2.62; 95% CI = 1.05-6.53), adjusted by baseline data, stroke subtype, inhospital complications, length of stay and stroke severity.

CONCLUSIONS

Female gender is associated with worse outcomes in adult ischemic stroke patients up to 50 years old. However, this effect is not observed in younger patients (15-30 years).

Different methods for administering 17beta-estradiol to ovariectomized rats result in opposite effects on ischemic brain damage

Background

Numerous stroke studies have controversially shown estrogens to be either neuroprotective or neurodamaging. The discordant results observed in rat brain ischemia models may be a consequence of discrepancies in estrogen administration modes resulting in plasma concentration profiles far from those intended. To test this hypothesis we reproduced in detail and extended an earlier study from our lab using a different mode of 17β-estradiol administration; home-made silastic capsules instead of commercial slow-release 17β-estradiol pellets. Four groups of female rats (n = 12) were ovariectomized and administered 17β-estradiol or placebo via silastic capsules. All animals underwent MCAo fourteen days after ovariectomy and were sacrificed three days later.

Results

In contrast to our earlier results using the commercial pellets, the group receiving 17β-estradiol during the entire experiment had significantly smaller lesions than the group receiving placebo (mean ± SEM: 3.85 ± 0.70% versus 7.15 ± 0.27% of total slice area, respectively; p = 0.015). No significant neuroprotection was found when the 17β-estradiol was administered only during the two weeks before or the three days immediately after MCAo.

Conclusions

The results indicate that different estrogen treatment regimens result in diametrically different effects on cerebral ischemia. Thus the effects of estrogens on ischemic damage seem to be concentration-related, with a biphasic, or even more complex, dose-response relation. These findings have implications for the design of animal experiments and also have a bearing on the estrogen doses used for peri-menopausal hormone replacement therapy.

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.

Relationship between estradiol and antioxidant enzymes activity of ischemic stroke

Some evidence suggests the neuroprotection of estrogen provided by the antioxidant activity of this compound. The main objective of this study was to determine the level of estradiol and its correlation with the activity of antioxidant enzymes, total antioxidant status and ferritin from ischemic stroke subjects. The study population consisted of 30 patients with acute ischemic stroke and 30 controls. There was no significant difference between estradiol in stroke and control group. The activity of superoxide dismutase and level of ferritin was higher in stroke compared with control group (P < .05, P < .001, resp.). There was no significant correlation between estradiol and glutathione peroxidase, glutathione reductase, catalase, total antioxidant status, and ferritin in stroke and control groups. We observed inverse correlation between estradiol with superoxide dismutase in males of stroke patients (r = -0.54, P = .029). Our results supported that endogenous estradiol of elderly men and women of stroke or control group has no antioxidant activity.

Dose-related neuroprotective versus neurodamaging effects of estrogens in rat cerebral ischemia: a systematic analysis

Numerous studies of the effects of estrogens for stroke prevention have yielded conflicting results in human and animal studies alike. We present a systematical analysis of study design and methodological differences between 66 studies where estrogens' impact on ischemic brain damage in rat models has been investigated, providing evidence that the differences in results may be explained by high estrogen doses produced by slow-release pellets. These pellets have been used in all studies showing increased neurologic damage because of estrogens. Our data indicate that the increased neurologic damage is related to the pellets' plasma concentration profile with an early, prolonged, supraphysiological peak. Neither the method of inducing the ischemic brain lesions, the choice of variables for measuring outcome, the measured plasma concentrations of estrogens at the time of ischemia nor rat population attributes (sex, strain, age, and diseases) are factors contributing to the discrepancies in results. This suggests that the effects of estrogens for stroke prevention are concentration related with a complex dose-response curve, and underscores the importance of carefully validating the experimental methods used. Future studies of hormone-replacement therapy in women may have to take dosage and administration regimens into account.

Long-term oral contraceptive treatment, metabolic syndrome and measures of cardiovascular risk in pre-menopausal women: National Health and Nutrition Examination Survey 1999-2004

AIM

Differences in subclinical cardiometabolic measures were examined as a function of oral contraceptive pills (OCP) treatment duration to compare never-treated women with four OCP-treatment groups (<1, 1-5, 5-10 and >10 years).

METHODS

The NHANES (1999-2004) database was used to evaluate 2089 healthy, pre-menopausal women, aged 18-55 years, with or without OCP history, no other hormonal treatment or history of systemic conditions. Outcome measures included body mass, central obesity, blood pressure, glycemia, insulinemia, lipid profile and inflammation. Analyses evaluated differences in prevalence of Metabolic Syndrome (MetS), constituent MetS and other clinical risk criteria, as well as outcome magnitudes. Analyses controlled for demographic and health-related variables, and study-eligible conditions.

RESULTS

Relative to other groups, women with >10 years OCP-use, and to some extent those with 5-10 years treatment, displayed no differences in prevalence of MetS and most risk criteria. Further analysis showed that, relative to women treated for <5 years, those with more prolonged OCP treatment displayed lower body mass and fasting glycemia with higher HDL-c levels, but more elevated LDL-c and total cholesterol.

CONCLUSIONS

The findings of both beneficial and detrimental subclinical cardiometabolic differences with more long-term OCP-treatment reinforces the need to monitor changes in these factors within the context of the treated patient's risk-benefit profile. However, because the magnitude of these differences was small, relative to normative ranges, it may be concluded that OCPs, as used in recent decades, are unlikely to markedly affect cardiometabolic risk.

Changes in experimental stroke outcome across the life span

Acute ischemic stroke is a leading cause of mortality and disability in the elderly. Age is the most important nonmodifiable risk factor for stroke, yet many preclinical models continue to examine only young male animals. It remains unclear how experimental stroke outcomes change with aging and with biologic sex. If sex differences are present, it is not known whether these reflect an intrinsic differing sensitivity to stroke or are secondary to the loss of estrogen with aging. We subjected both young and aging mice of both sexes to middle cerebral artery occlusion (MCAO). Young female mice had smaller strokes compared with age-matched males, an effect that was reversed by ovariectomy. Stroke damage increased with aging in female mice, whereas male mice had decreased damage after MCAO. Blood-brain barrier (BBB) permeability changes are correlated with infarct size. However, aging mice had significantly less edema formation, an effect that was independent of sex and histologic damage. Differences in the cellular response to stroke occur across the life span in both male and female mice. These differences need to be considered when developing relevant therapies for stroke patients, the majority of whom are elderly.

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.

Pathways to ischemic neuronal cell death: are sex differences relevant?

We have known for some time that the epidemiology of human stroke is sexually dimorphic until late in life, well beyond the years of reproductive senescence and menopause. Now, a new concept is emerging: the mechanisms and outcome of cerebral ischemic injury are influenced strongly by biological sex as well as the availability of sex steroids to the brain. The principal mammalian estrogen (17 β estradiol or E2) is neuroprotective in many types of brain injury and has been the major focus of investigation over the past several decades. However, it is becoming increasingly clear that although hormones are a major contributor to sex-specific outcomes, they do not fully account for sex-specific responses to cerebral ischemia. The purpose of this review is to highlight recent studies in cell culture and animal models that suggest that genetic sex determines experimental stroke outcome and that divergent cell death pathways are activated after an ischemic insult. These sex differences need to be identified if we are to develop efficacious neuroprotective agents for use in stroke patients.

17Alpha-estradiol arrests cell cycle progression at G2/M and induces apoptotic cell death in human acute leukemia Jurkat T cells

A pharmacological dose (2.5-10 microM) of 17alpha-estradiol (17alpha-E(2)) exerted a cytotoxic effect on human leukemias Jurkat T and U937 cells, which was not suppressed by the estrogen receptor (ER) antagonist ICI 182,780. Along with cytotoxicity in Jurkat T cells, several apoptotic events including mitochondrial cytochrome c release, activation of caspase-9, -3, and -8, PARP degradation, and DNA fragmentation were induced. The cytotoxicity of 17alpha-E(2) was not blocked by the anti-Fas neutralizing antibody ZB-4. While undergoing apoptosis, there was a remarkable accumulation of G(2)/M cells with the upregulatoin of cdc2 kinase activity, which was reflected in the Thr56 phosphorylation of Bcl-2. Dephosphorylation at Tyr15 and phosphorylation at Thr161 of cdc2, and significant increase in the cyclin B1 level were underlying factors for the cdc2 kinase activation. Whereas the 17alpha-E(2)-induced apoptosis was completely abrogated by overexpression of Bcl-2 or by pretreatment with the pan-caspase inhibitor z-VAD-fmk, the accumulation of G(2)/M cells significantly increased. The caspase-8 inhibitor z-IETD-fmk failed to influence 17alpha-E(2)-mediated caspase-9 activation, but it markedly reduced caspase-3 activation and PARP degradation with the suppression of apoptosis, indicating the contribution of caspase-8; not as an upstream event of the mitochondrial cytochrome c release, but to caspase-3 activation. In the presence of hydroxyurea, which blocked the cell cycle progression at the G(1)/S boundary, 17alpha-E(2) failed to induce the G(2)/M arrest as well as apoptosis. These results demonstrate that the cytotoxicity of 17alpha-E(2) toward Jurkat T cells is attributable to apoptosis mainly induced in G(2)/M-arrested cells, in an ER-independent manner, via a mitochondria-dependent caspase pathway regulated by Bcl-2.

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.

A high soy diet reduces programmed cell death and enhances bcl-xL expression in experimental stroke

Soy phytoestrogens have been proposed as an alternative to estrogen replacement therapy and have demonstrated potential neuroprotective effects in the brain. We have shown that a high soy diet significantly reduces infarct size following permanent middle cerebral artery occlusion (MCAO). Here, we tested the hypothesis that a high soy diet would attenuate programmed cell death after stroke. Adult female Sprague-Dawley rats were ovariectomized and fed either an isoflavone-reduced diet (IFP) or a high soy diet (SP) for 2 weeks before undergoing 90 min of transient middle cerebral artery occlusion (tMCAO) followed by 22.5 h reperfusion. Infarct size, as assessed by triphenyltetrazolium chloride staining, was significantly reduced by a high soy diet (P<0.05). Apoptosis in the ischemic cortex, measured by TUNEL staining, was significantly reduced by the high soy diet. The number of active caspase-3 positive cells and caspase-mediated alpha-spectrin cleavage were also significantly decreased in the ischemic cortex of SP rats. Furthermore, nuclear translocation of apoptosis-inducing factor (AIF) was significantly reduced in the ischemic cortex of SP rats. Soy significantly increased bcl-x(L) mRNA and protein expression in the ischemic cortex compared with IFP rats. Immunohistochemistry revealed increased neuronal expression of bcl-2 and bcl-x(L) in the ischemic cortex of both IFP and SP rats following tMCAO. These results suggest that a high soy diet decreases both caspase-dependent and caspase-independent programmed cell death following tMCAO. Further, a high soy diet enhances expression of the cell survival factor bcl-x(L) following tMCAO, contributing to the neuroprotective effects of soy in the ischemic cortex.

Molecular and cellular immune mediators of neuroprotection

Our view of the immune privileged status of the brain has dramatically changed during the past two decades. Even though systemic immune stimuli have the ability to activate different populations of neurons, cells of monocytic lineage also have access to the neuronal tissue and populate it as microglia. Although such a phenomenon is limited in intact brains, it is greatly increased during neurodegenerative processes associated with innate immunity and the release of pro-inflammatory molecules by either resident microglia or those derived from the bone marrow stem cells. The role of these events is currently a matter of great debate and controversy, especially as it relates to brain protection, repair, or further injury. In recent years, accumulating data have supported the notion that when immune molecules are timely released by microglia, they limit neuronal injury in the presence of pathogens and toxic agents, help clear debris from degenerated cells, and restore the cerebral environment for repair. It has been shown that alteration of the natural innate immune response by microglia has direct consequences in exacerbating the damages following acute injury to neurons. This article presents and discusses these data, supporting a powerful neuroprotective role for microglia and their innate immune reactions in response to pathogens and central nervous system insults.