Age alters cerebrovascular inflammation and effects of estrogen

Menopause causes metabolic and cognitive impairments in a chronic cerebral hypoperfusion model of vascular contributions to cognitive impairment and dementia

BACKGROUND

The vast majority of women with dementia are post-menopausal. Despite clinical relevance, menopause is underrepresented in rodent models of dementia. Before menopause, women are less likely than men to experience strokes, obesity, and diabetes-known risk factors for vascular contributions to cognitive impairment and dementia (VCID). During menopause, ovarian estrogen production stops and the risk of developing these dementia risk factors spikes. Here, we aimed to determine if menopause worsens cognitive impairment in VCID. We hypothesized that menopause would cause metabolic dysfunction and increase cognitive impairment in a mouse model of VCID.

METHODS

We performed a unilateral common carotid artery occlusion surgery to produce chronic cerebral hypoperfusion and model VCID in mice. We used 4-vinylcyclohexene diepoxide to induce accelerated ovarian failure and model menopause. We evaluated cognitive impairment using behavioral tests including novel object recognition, Barnes maze, and nest building. To assess metabolic changes, we measured weight, adiposity, and glucose tolerance. We explored multiple aspects of brain pathology including cerebral hypoperfusion and white matter changes (commonly observed in VCID) as well as changes to estrogen receptor expression (which may mediate altered sensitivity to VCID pathology post-menopause).

RESULTS

Menopause increased weight gain, glucose intolerance, and visceral adiposity. VCID caused deficits in spatial memory regardless of menopausal status. Post-menopausal VCID specifically led to additional deficits in episodic-like memory and activities of daily living. Menopause did not alter resting cerebral blood flow on the cortical surface (assessed by laser speckle contrast imaging). In the white matter, menopause decreased myelin basic protein gene expression in the corpus callosum but did not lead to overt white matter damage (assessed by Luxol fast blue). Menopause did not significantly alter estrogen receptor expression (ERα, ERβ, or GPER1) in the cortex or hippocampus.

CONCLUSIONS

Overall, we have found that the accelerated ovarian failure model of menopause caused metabolic impairment and cognitive deficits in a mouse model of VCID. Further studies are needed to identify the underlying mechanism. Importantly, the post-menopausal brain still expressed estrogen receptors at normal (pre-menopausal) levels. This is encouraging for any future studies attempting to reverse the effects of estrogen loss by activating brain estrogen receptors.

Improvement of Cardiovascular Function in Aging Females by the Prolonged Activation of G Protein-Coupled Estrogen Receptor

Ample evidence suggests that estrogen replacement therapy is associated with beneficial effects with regard to cardiovascular diseases when the therapy is initiated temporally close to menopause but not when it is initiated later. Little is known about the complex interactions between hormone receptors after menopause. Coronary artery function and cardiac function were measured in rats that had either received no treatment or had been pretreated with an androgen receptor (AR) antagonist and/or a GPER agonist G-1. ICI 182,780 was used to block the classical estrogen receptors (ERs) to investigate their complex interactions with GPER. The beneficial effects of GPER were only observed by blocking ARs and classical ERs in aged female rats. The results demonstrate that GPER activation is a potential therapeutic target for the inhibition of age-dependent coronary artery dysfunction and cardiac dysfunction under the condition of blocking ARs and classical ERs after menopause. CLINICAL RELEVANCE: The risk of cardiovascular disease in postmenopausal women significantly increased. The role of sex hormones and their receptors during this process is still complicated. Our present study demonstrated that the imbalance of androgen and estrogen may contribute to the impairment of vascular reactivity and subsequent cardiac function. Treatment with GPER agonist G1 combined with the inhibition of ERα and ERβ could improve vascular function and reduce the myocardial ischemia reperfusion injury. These findings may provide the novel and effective strategy for the treatment of cardiovascular diseases in postmenopausal women.

Estrogen receptor agonists induce anti‑edema effects by altering α and β estrogen receptor gene expression

The present study aimed to examine whether the attenuation of estrogen receptor expression is prevented by propyl pyrazole triol (PPT), an agonist for estrogen receptor α (ERα) or and diarypropiolnitrile (DPN), an agonist for estrogen receptor β (ERβ) after traumatic brain injury (TBI). The tests performed on ovariectomized female Wistar rats included sham group, vehicle group, and treated groups: PPT, DPN, and PPT+DPN 30 minutes after TBI. Blood‑brain barrier (BBB) disruption and brain water content were estimated. RT‑PCR and\r\nwestern blotting were utilized to evaluate ESR1 and ESR2 gene and protein expression. The data indicated that PPT, DPN, and PPT+DPN attenuated TBI‑induced brain edema. Also, BBB disruption after TBI was prevented in PPT, DPN, and PPT+DPN‑treated TBI animals. Estrogen agonist‑treated animals showed a significant elevation in Esr1 mRNA and protein expression levels in the brain tissue of TBI rats. In addition, the data indicated a significant elevation of Esr2 mRNA and protein expression levels in the brain tissue of estrogen agonist‑treated TBI rats. The data shows that both ESR1 and ESR2 agonists can enhance ER mRNA and protein levels in TBI animals' brain. It appears that this effect contributes to the neuroprotective function of ER agonists.

Endocrine Therapy With or Without CDK4/6 Inhibitors in Women With Hormone-receptor Positive Breast Cancer: What do we Know About the Effects on Cognition?

Adjuvant endocrine therapy (ET) is the cornerstone of treatment for hormone-receptor positive breast cancer. Recently, ET is increasingly combined with "cyclin-dependent kinases 4 and 6'' (CDK4/6) inhibitors. Given the importance of estrogens in neural processes and the role of cyclin D in hippocampal cell proliferation, it is plausible that these therapies affect cognition, but studies on these potential cognitive effects are sparse. In this review, we summarize existing knowledge on the cognitive effects of ET and CDK4/6 inhibitors in pre-, peri- and postmenopausal patients with breast cancer. We show that several clinical studies support adverse cognitive effects, especially on verbal memory, after ET-induced decrease of estrogen-levels or inactivation of estrogen-receptors. Clinical studies on the cognitive effects of CDK4/6 inhibitors are virtually non-existent and no conclusions can yet be drawn. Longitudinal studies on the cognitive effects of the combined ET-CDK4/6 inhibitors are highly needed to properly inform patients about potential short-term and long-term cognitive side effects. These studies should preferably include cognitive assessments (including a measurement prior to ET), and be designed in such a way that they can account for variables such as type and duration of ET, CDK4/6 inhibition, menopausal status, and other disease- and treatment-related symptoms that can impact cognition, such as fatigue and distress.

Reduced plasma Fetuin-A is a promising biomarker of depression in the elderly

Depression affects 7% of the elderly population, and it often remains misdiagnosed or untreated. Peripheral biomarkers might aid clinicians by allowing more accurate and well-timed recognition of the disease. We sought to determine if plasma protein levels predict the severity of depressive symptomatology or distinguish patients from healthy individuals. The severity of depressive symptoms and global cognitive functioning were assessed by the Geriatric Depression Scale (GDS) and Mini-Mental State Examination (MMSE) in 152 elderly subjects, 76 of which with major depressive disorder (MDD). Plasma levels of 24 proteins were measured by multiplexing and analyzed as continuous predictors or dichotomized using the median value. The association between individual plasma proteins and MDD risk or depressive symptoms severity was investigated using multiple logistic and linear regressions including relevant covariates. Sensitivity analyses were performed excluding cognitively impaired individuals or non-acute patients with MDD. After adjusting for possible confounders and false discovery rate (FDR) correction, we found lower Fetuin-A levels in MDD patients vs. controls (p_FDR = 1.95 × 10^-6). This result was confirmed by the sensitivity and dichotomized analyses. Lower prolactin (PRL) levels predicted more severe depressive symptoms in acute MDD patients (p_FDR = 0.024). Fetuin-A is a promising biomarker of MDD in the elderly as this protein was negatively associated with the disorder in our sample, regardless of the global cognitive functioning. Lower PRL levels may be a peripheral signature of impaired neuroprotective processes and serotoninergic neurotransmission in more severely depressed patients.

Contributions of sex to cerebrovascular function and pathology

Sex differences exist in how cerebral blood vessels function under both physiological and pathological conditions, contributing to observed sex differences in risk and outcomes of cerebrovascular diseases (CBVDs), such as vascular contributions to cognitive impairment and dementia (VCID) and stroke. Throughout most of the lifespan, women are protected from CBVDs; however, risk increases following menopause, suggesting sex hormones may play a significant role in this protection. The cerebrovasculature is a target for sex hormones, including estrogens, progestins, and androgens, where they can influence numerous vascular functions and pathologies. While there is a plethora of information on estrogen, the effects of progestins and androgens on the cerebrovasculature are less well-defined. Estrogen decreases cerebral tone and increases cerebral blood flow, while androgens increase tone. Both estrogens and androgens enhance angiogenesis/cerebrovascular remodeling. While both estrogens and androgens attenuate cerebrovascular inflammation, pro-inflammatory effects of androgens under physiological conditions have also been demonstrated. Sex hormones exert additional neuroprotective effects by attenuating oxidative stress and maintaining integrity and function of the blood brain barrier. Most animal studies utilize young, healthy, gonadectomized animals, which do not mimic the clinical conditions of aging individuals likely to get CBVDs. This is also concerning, as sex hormones appear to mediate cerebrovascular function differently based on age and disease state (e.g. metabolic syndrome). Through this review, we hope to inspire others to consider sex as a key biological variable in cerebrovascular research, as greater understanding of sex differences in cerebrovascular function will assist in developing personalized approaches to prevent and treat CBVDs.

Sex differences in risk factors for vascular contributions to cognitive impairment & dementia

Vascular contributions to cognitive impairment and dementia (VCID) is the second most common cause of dementia. While males overall appear to be at a slightly higher risk for VCID throughout most of the lifespan (up to age 85), some risk factors for VCID more adversely affect women. These include female-specific risk factors associated with pregnancy related disorders (e.g. preeclampsia), menopause, and poorly timed hormone replacement. Further, presence of certain co-morbid risk factors, such as diabetes, obesity and hypertension, also may more adversely affect women than men. In contrast, some risk factors more greatly affect men, such as hyperlipidemia, myocardial infarction, and heart disease. Further, stroke, one of the leading risk factors for VCID, has a higher incidence in men than in women throughout much of the lifespan, though this trend is reversed at advanced ages. This review will highlight the need to take biological sex and common co-morbidities for VCID into account in both preclinical and clinical research. Given that there are currently no treatments available for VCID, it is critical that we understand how to mitigate risk factors for this devastating disease in both sexes.

The metabolic and neuroinflammatory changes induced by consuming a cafeteria diet are age-dependent

OBJECTIVES

To compare the effects of a palatable cafeteria diet on serum parameters and neuroinflammatory markers of young and aged female Wistar rats.

METHODS

Three-month-old (young) and 18-month-old (aged) female Wistar rats had access to a cafeteria diet (Caf-Young, Caf-Aged) or a standard chow diet (Std-Young, Std-Aged).

RESULTS

The Caf-Young group showed a higher food consumption, weight gain, visceral fat depot, serum insulin and leptin levels, and the insulin resistance index (HOMA-IR) than the Std-Young group. The Caf-Aged group exhibited an increase in interleukin-1 levels in the cerebral cortex and hippocampus. The number of GFAP-positive cells did not differ between the groups, but there was a diet effect in the cerebral cortex and an age effect in the hippocampus. Phospho-tau expression did not differ between the groups.

DISCUSSION

The 3- and 18-month-old rats responded differently to a cafeteria diet. Insulin and leptin levels are elevated in young animals fed a cafeteria diet, whereas aged animals are prone to neuroinflammation (indicated by an increase in interleukin-1β levels). A combination of hypercaloric diet and senescence have detrimental effects on the inflammatory response in the brain, which may predispose to neurological diseases.

Matrix Metalloproteinases in Normal Pregnancy and Preeclampsia

Normal pregnancy is associated with marked hemodynamic and uterine changes that allow adequate uteroplacental blood flow and uterine expansion for the growing fetus. These pregnancy-associated changes involve significant uteroplacental and vascular remodeling. Matrix metalloproteinases (MMPs) are important regulators of vascular and uterine remodeling. Increases in MMP-2 and MMP-9 have been implicated in vasodilation, placentation, and uterine expansion during normal pregnancy. The increases in MMPs could be induced by the increased production of estrogen and progesterone during pregnancy. MMP expression/activity may be altered during complications of pregnancy. Decreased vascular MMP-2 and MMP-9 may lead to decreased vasodilation, increased vasoconstriction, hypertensive pregnancy, and preeclampsia. Abnormal expression of uteroplacental integrins, cytokines, and MMPs may lead to decreased maternal tolerance, apoptosis of invasive trophoblast cells, inadequate remodeling of spiral arteries, and reduced uterine perfusion pressure (RUPP). RUPP may cause imbalance between the antiangiogenic factors soluble fms-like tyrosine kinase-1 and soluble endoglin and the proangiogenic vascular endothelial growth factor and placental growth factor, or stimulate the release of inflammatory cytokines, hypoxia-inducible factor, reactive oxygen species, and angiotensin AT1 receptor agonistic autoantibodies. These circulating factors could target MMPs in the extracellular matrix as well as endothelial and vascular smooth muscle cells, causing generalized vascular dysfunction, increased vasoconstriction and hypertension in pregnancy. MMP activity can also be altered by endogenous tissue inhibitors of metalloproteinases (TIMPs) and changes in the MMP/TIMP ratio. In addition to their vascular effects, decreases in expression/activity of MMP-2 and MMP-9 in the uterus could impede uterine growth and expansion and lead to premature labor. Understanding the role of MMPs in uteroplacental and vascular remodeling and function could help design new approaches for prediction and management of preeclampsia and premature labor.

The Post-Ovariectomy Interval Affects the Antidepressant-Like Action of Citalopram Combined with Ethynyl-Estradiol in the Forced Swim Test in Middle Aged Rats

The use of a combined therapy with low doses of estrogens plus antidepressants to treat depression associated to perimenopause could be advantageous. However the use of these combinations is controversial due to several factors, including the time of intervention in relation to menopause onset. This paper analyzes whether time post-OVX influences the antidepressant-like action of a combination of ethynyl-estradiol (EE₂) and citalopram (CIT) in the forced swim test (FST). Middle-aged (15 months old) female Wistar rats were ovariectomized and after one or three weeks treated with EE₂ (1.25, 2.5 or 5.0 µg/rat, s.c.; −48 h) or CIT (1.25, 2.5, 5.0 or 10 mg/kg, i.p./3 injections in 24 h) and tested in the FST. In a second experiment, after one or three weeks of OVX, rats received a combination of an ineffective dose of EE₂ (1.25 µg/rat, s.c., −48 h) plus CIT (2.5 mg/kg, i.p./3 injections in 24 h) and subjected to the FST. Finally, the uteri were removed and weighted to obtain an index of the peripheral effects of EE₂ administration. EE₂ (2.5 or 5.0 µg/rat) reduced immobility after one but not three weeks of OVX. In contrast, no CIT dose reduced immobility at one or three weeks after OVX. When EE₂ (1.25 µg/rat) was combined with CIT (2.5 mg/kg) an antidepressant-like effect was observed at one but not three weeks post-OVX. The weight of the uteri augmented when EE₂ was administrated three weeks after OVX. The data suggest that the time post-OVX is a crucial factor that contributes to observe the antidepressant-like effect of EE₂ alone or in combination with CIT.

Effects of estrogen on cerebrovascular function: age-dependent shifts from beneficial to detrimental in small cerebral arteries of the rat

In the present study, interactions of age and estrogen in the modulation of cerebrovascular function were examined in small arteries <150 μM. The hypothesis tested was that age enhances deleterious effects of exogenous estrogen by augmenting constrictor prostanoid (CP)-potentiated reactivity of the female (F) cerebrovasculature. F Sprague-Dawley rats approximating key stages of "hormonal aging" in humans were studied: perimenopausal (mature multi-gravid, MA, cyclic, 5-6 mo of age) and postmenopausal (reproductively senescent, RS, acyclic 10-12 mo of age). Rats underwent bilateral ovariectomy and were given estrogen replacement therapy (E) or placebo (O) for 14-21 days. Vasopressin reactivity (VP, 10(-12)-10(-7) M) was measured in pressurized middle cerebral artery segments, alone or in the presence of COX-1- (SC560, 1 μM) or COX-2- (NS398, 10 μM) selective inhibitors. VP-stimulated release of prostacyclin (PGI2) and thromboxane (TXA2) were assessed by radioimmunoassay of 6-keto-PGF1α and TXB2 (stable metabolites). VP-induced vasoconstriction was attenuated in ovariectomized + estrogen-replaced, multigravid adult rats (5-6 mo; MAE) but potentiated in older ovariectomized + estrogen-replaced, reproductively senescent rats (12-14 mo; RSE). SC560 and NS398 reduced reactivity similarly in ovariectomized multigravid adult rats (5-6 mo; MAO) and ovariectomized reproductively senescent rat (12-14 mo; RSO). In MAE, reactivity to VP was reduced to a greater extent by SC560 than by NS398; however, in RSE, this effect was reversed. VP-stimulated PGI2 was increased by estrogen, yet reduced by age. VP-stimulated TXA2 was increased by estrogen and age in RSE but did not differ in MAO and RSO. Taken together, these data reveal that the vascular effects of estrogen are distinctly age-dependent in F rats. In younger MA, beneficial and protective effects of estrogen are evident (decreased vasoconstriction, increased dilator prostanoid function). Conversely, in older RS, detrimental effects of estrogen begin to be manifested (enhanced vasoconstriction and CP function). These findings may lead to age-specific estrogen replacement therapies that maximize beneficial and minimize detrimental effects of this hormone on small cerebral arteries that regulate blood flow.

The Effects of Estrogen Receptors' Antagonist on Brain Edema, Intracranial Pressure and Neurological Outcomes after Traumatic Brain Injury in Rat

Background:

In previous studies, the neuroprotective effect of 17β-estradiol in diffuse traumatic brain injury has been shown. This study used ICI 182,780, a non-selective estrogen receptor antagonist, to test the hypothesis that the neuroprotective effect of 17β-estradiol in traumatic brain injury is mediated by the estrogen receptors.

Methods:

The ovariectomized rats were divided into eight groups. Brain injury was induced by Marmarou’s method. Estrogen was injected 30 minutes after traumatic brain injury, and ICI 182,780 was injected before traumatic brain injury and also before estrogen treatment. In one group only ICI 182,780 was injected. The brain water content and Evans blue dye content were measured 24 and 5 hours after traumatic brain injury, respectively. The neurologic outcomes and intracranial pressure were assessed before, 4, and 24 hours after traumatic brain injury.

Results:

Brain water content and Evans blue content were less in estrogen-treated group comparison to vehicle group. ICI 182,780 eliminated the effects of estrogen on brain edema and brain blood barrier permeability. Intracranial pressure was increased significantly after trauma, and estrogen decreased intracranial pressure at 4 and 24 hours after traumatic brain injury in comparison to vehicle. This inhibitory effect was also eliminated by treatment with ICI182,780. ICI 182,780 also inhibited the estrogen induced increase in neurologic outcomes following traumatic brain injury. However, the use of ICI 182,780 alone had no neuroprotective effect after traumatic brain injury.

Conclusion:

The results suggest that classical estrogen receptors have probably a role in the neuroprotective function of estrogen following traumatic brain injury.

E3 ubiquitin ligase NKLAM positively regulates macrophage inducible nitric oxide synthase expression

Stimulated macrophages generate potent anti-microbial reactive oxygen and nitrogen species within their phagosomes. Previous studies have shown that the E3 ubiquitin ligase natural killer lytic-associated molecule (NKLAM) is a macrophage phagosomal protein that plays a role in macrophage anti-bacterial activity. In vivo, NKLAM-knockout (KO) mice produce less nitric oxide (NO) upon exposure to lipopolysaccharide (LPS) than wild type (WT) mice. In vitro, we found that NO production and inducible nitric oxide synthase (iNOS) protein were diminished in LPS-stimulated NKLAM-KO bone marrow-derived and splenic macrophages. Additionally, LPS-stimulated NKLAM-KO macrophages displayed defects in STAT1 tyrosine phosphorylation and production of interferon beta (IFNβ). The JAK/STAT pathway is critical for the production of IFNβ, which augments iNOS protein expression in mice. iNOS protein expression is also regulated by the transcription factor NFκB, thus we investigated whether NKLAM influences NFκB function. LPS-stimulated NKLAM-KO macrophages showed evidence of delayed nuclear translocation of the NFκB subunit p65. This was associated with a reduction in p65/DNA colocalization. The defect in p65 translocation was independent of IKBα degradation. NKLAM-KO macrophages also expressed less p65 and showed evidence of defective p65 phosphorylation at serine 536. Importantly, LPS-stimulated NKLAM-KO macrophages have diminished NFκB transcriptional activity as assessed by transfection of a luciferase reporter plasmid. Collectively, our data implicate NKLAM as a novel modulator of macrophage iNOS expression.

Effects of hormone therapy on cognition and mood

OBJECTIVE

Results of the Women's Health Initiative (WHI) and Women's Health Initiative Memory Study (WHIMS) suggested that hormone therapy (HT) may be detrimental to cognitive health. This article reviews clinical studies that address issues relevant to those results.

DESIGN

Literature review.

INTERVENTION(S)

A search of Pubmed and Web of Science was conducted using the search terms HT and cognition, HT and mood. Clinical and observational studies were selected if they were published after the year 2000. Theories of HT mechanisms of action, pharmacology, biology, and observational and clinical trials are discussed.

RESULT(S)

Although observational and clinical trials show conflicting findings, methodologic considerations must be acknowledged. HT formulation and dose, route of administration, timing of initiation, length of treatment, and health of participants all contribute to inconsistencies in results. Transdermal estradiol and micronized progesterone administered at time of menopause are generally associated with cognitive and affective benefit.

CONCLUSION(S)

At the present time, results from existing studies are equivocal regarding the benefits of HT on cognition and affect. Future studies, such as the Kronos Early Estrogen Prevention Study (KEEPS), should address methodologic inconsistencies to provide clearer answers to this important question.

Estrogen and cerebrovascular regulation in menopause

Estrogen (E2), classically viewed as a reproductive steroid hormone, has non-reproductive functions throughout the body including in the brain and vasculature. Studies report diminished neuroprotection with declining E2 levels, corresponding with higher incidence of cerebrovascular and neurological disease. However, the effects of menopausal hormone therapy (MHT) on the cerebral vasculature and brain function remain controversial. This review will focus on evidence of 17β-estradiol actions in the cerebral vasculature, with a particular emphasis on the vasoactive, anti-inflammatory, anti-oxidant, metabolic and molecular properties. Controversies surrounding MHT in relation to cerebrovascular disease and stroke risk will be discussed, particularly the emerging evidence from clinical trials supporting the critical period hypothesis of estrogen protection.

Aging, estrogen loss and epoxyeicosatrienoic acids (EETs)

Inflammation is a key element in many cardiovascular diseases. Both estrogen loss, caused by menopause, and aging have inflammatory consequences. Epoxyeicosatrienoic acids (EETs) are anti-inflammatory molecules synthesized by various cytochrome P450 (Cyp) enzymes from arachidonic acid. EETs are in the third (Cytochrome P450) pathway of arachindonic acid metabolism, others being cyclooxygenases and lipoxygenases. We hypothesized that aging and estrogen loss would reduce levels of anti-inflammatory EETs. Adult (6 mo) and aged (22 mo) ovariectomized rats with (OP) and without (Ovx) 17-∃-estradiol replacement were used in this study. Mass spectrometry was used to measure levels of EETs and their metabolites, dihydroxyeicosatrienoic acids (DHETs). Levels of Cyp2C2, Cyp2C6, and Cyp2J2, the principal Cyps responsible for EETs synthesis, as well as soluble epoxide hydrolase (sEH), which metabolizes EETS to DHETs, were determined via western blot. Overall Cyp levels decreased with age, though Cyp2C6 increased in the liver. sEH was increased in the kidney with estrogen replacement. Despite protein changes, no differences were measured in plasma or aortic tissue levels of EETs. However, plasma 14,15 DHET was increased in aged Ovx, and 5,6 DHET in adult OP. In conclusion neither aging nor estrogen loss decreased the anti-inflammatory EETs in the cardiovascular system.

Synergy of homocysteine, microRNA, and epigenetics: a novel therapeutic approach for stroke

Homocysteine (Hcy) is a thiol-containing amino acid formed during methionine metabolism. Elevated level of Hcy is known as hyperhomocysteinemia (HHcy). HHcy is an independent risk factor for cerebrovascular diseases such as stroke, dementia, Alzheimer's disease, etc. Stroke, which is caused by interruption of blood supply to the brain, is one of the leading causes of death and disability in a number of people worldwide. The HHcy causes an increased carotid artery plaque that may lead to ischemic stroke but the mechanism is currently not well understood. Though mutations or polymorphisms in the key genes of Hcy metabolism pathway have been well elucidated in stroke, emerging evidences suggested epigenetic mechanisms equally play an important role in stroke development such as DNA methylation, chromatin remodeling, RNA editing, noncoding RNAs (ncRNAs), and microRNAs (miRNAs). However, there is no review available yet that describes the role of genetics and epigenetics during HHcy in stroke. The current review highlights the role of genetics and epigenetics in stroke during HHcy and the role of epigenetics in its therapeutics. The review also highlights possible epigenetic mechanisms, potential therapeutic molecules, putative challenges, and approaches to deal with stroke during HHcy.

EMMPRIN-mediated induction of uterine and vascular matrix metalloproteinases during pregnancy and in response to estrogen and progesterone

Pregnancy is associated with uteroplacental and vascular remodeling in order to adapt for the growing fetus and the hemodynamic changes in the maternal circulation. We have previously shown upregulation of uterine matrix metalloproteinases (MMPs) during pregnancy. Whether pregnancy-associated changes in MMPs are localized to the uterus or are generalized in feto-placental and maternal circulation is unclear. Also, the mechanisms causing the changes in uteroplacental and vascular MMPs during pregnancy are unclear. MMPs expression, activity and tissue distribution were measured in uterus, placenta and aorta of virgin, mid-pregnant (mid-Preg) and late pregnant (late-Preg) rats. Western blots and gelatin zymography revealed increases in MMP-2 and -9 in uterus and aorta of late-Preg compared with virgin and mid-Preg rats. In contrast, MMP-2 and -9 were decreased in placenta of late-Preg versus mid-Preg rats. Extracellular MMP inducer (EMMPRIN) was increased in uterus and aorta of pregnant rats, but was less in placenta of late-Preg than mid-Preg rats. Prolonged treatment of uterus or aorta of virgin rats with 17β-estradiol and progesterone increased the amount of EMMPRIN, MMP-2 and -9, and the sex hormone-induced increases in MMPs were prevented by EMMPRIN neutralizing antibody. Immunohistochemistry revealed that MMP-2 and -9 and EMMPRIN increased in uterus and aorta of pregnant rats, but decreased in placenta of late-Preg versus mid-Preg rats. Thus pregnancy-associated upregulation of uterine MMPs is paralleled by increased vascular MMPs, and both are mediated by EMMPRIN and induced by estrogen and progesterone, suggesting similar role of MMPs in uterine and vascular tissue remodeling and function during pregnancy. The decreased MMPs and EMMPRIN in placenta of late-Preg rats suggests reduced role of MMPs in feto-placental circulation during late pregnancy.

Ovarian hormones promote recovery from sleep deprivation by increasing sleep intensity in middle-aged ovariectomized rats

Sleep disturbances are commonly associated with menopause. Hormone replacement therapy is often used to treat various menopausal symptoms, but its efficacy for improving sleep is a matter of debate. We addressed this question by using a rodent model of ovarian hormone loss and replacement in midlife. Middle-aged female rats were ovariectomized and implanted with capsules containing estradiol with or without progesterone, or oil. After two weeks, sleep/wake states were recorded polygraphically during a 24-h baseline period, followed by 6h of sleep deprivation in the second half of the light phase, and a 24-h recovery period. During the baseline dark phase, hormone treatments increased wakefulness, and decreased non-rapid eye movement sleep (NREMS) by shortening NREMS episodes; however, NREMS EEG delta power or energy (cumulative power) was unaffected by combined hormones. Following sleep deprivation, all the groups showed NREMS and rapid eye movement sleep (REMS) rebounds, with similar relative increases from respective baseline levels. The increases in NREMS EEG delta power/energy during recovery were enhanced by combined hormones. These results from middle-aged ovariectomized rats indicate that replacement with estrogen with or without progesterone reduces baseline NREMS without affecting sleep intensity, particularly during the dark (active) phase, whereas following sleep deprivation the same hormone treatments do not affect the ability to increase NREMS or REMS, but treatment with both hormones, in particular, enhances the intensity of recovery sleep. These results support the usefulness of ovariectomized middle-aged rats as a model system to study the biological effects of hormone replacement on sleep regulation.

Stroke: understanding the differences between males and females

Stroke is a significant cause of death and long-term disability in the USA. The incidence, mortality, and outcomes of stroke are significantly different between men and women. As with many diseases that affect men and women differently, an understanding on the reasons underlying those differences is critical to effective diagnosis and treatment. This review will examine the sex differences in stroke in both humans and animal models of stroke and review what is known about potential mechanisms underlying these differences. It is clear that there is a complex interaction between hormonal, genetic, and unknown factors at play in generating the sex differences in stroke.

Oral contraceptives and nicotine synergistically exacerbate cerebral ischemic injury in the female brain

Oral contraceptives (OC) and smoking-derived nicotine (N) are known to synergistically increase the risk and severity of cerebral ischemia in women. Although it has been known for some time that long-term use of OC and nicotine will have an increased risk of peripheral thrombus formation, little is known about how the combination of OC and nicotine increases severity of brain ischemia. Recent laboratory studies simulating the conditions of nicotine exposure produced by cigarette smoking and OC regimen of women in female rats confirms that the severity of ischemic hippocampal damage is far greater in female rats simultaneously exposed to OC than to nicotine alone. These studies also demonstrated that the concurrent exposure of OC and nicotine reduces endogenous 17β-estradiol levels and inhibits estrogen signaling in the brain of female rats. The endogenous 17β-estradiol plays a key role in cerebrovascular protection in women during their pre-menopausal life and loss of circulating estrogen at reproductive senescence increases both the incidence and severity of cerebrovascular diseases. Therefore, OC and nicotine induced severe post-ischemic damage might be a consequence of lack of estrogen signaling in the brain. In the present review we highlight possible mechanisms by which OC and nicotine inhibits estrogen signaling that could be responsible for severe ischemic damage in females.

Sex, stroke, and inflammation: the potential for estrogen-mediated immunoprotection in stroke

Stroke is the third leading cause of death and the primary cause of disability in the developed world. Experimental and clinical data indicate that stroke is a sexually dimorphic disease, with males demonstrating an enhanced intrinsic sensitivity to ischemic damage throughout most of their lifespan. The neuroprotective role of estrogen in the female brain is well established, however, estrogen exposure can also be deleterious, especially in older women. The mechanisms for this remain unclear. Our current understanding is based on studies examining estrogen as it relates to neuronal injury, yet cerebral ischemia also induces a robust sterile inflammatory response involving local and systemic immune cells. Despite the potent anti-inflammatory effects of estrogen, few studies have investigated the contribution of estrogen to sex differences in the inflammatory response to stroke. This review examines the potential role for estrogen-mediated immunoprotection in ischemic injury.

Interactions between age, sex, and hormones in experimental ischemic stroke

Age, sex, and gonadal hormones have profound effects on ischemic stroke outcomes, although how these factors impact basic stroke pathophysiology remains unclear. There is a plethora of inconsistent data reported throughout the literature, primarily due to differences in the species examined, the timing and methods used to evaluate injury, the models used, and confusion regarding differences in stroke incidence as seen in clinical populations vs. effects on acute neuroprotection or neurorepair in experimental stroke models. Sex and gonadal hormone exposure have considerable independent impact on stroke outcome, but these factors also interact with each other, and the contribution of each differs throughout the lifespan. The contribution of sex and hormones to experimental stroke will be the focus of this review. Recent advances and our current understanding of age, sex, and hormone interactions in ischemic stroke with a focus on inflammation will be discussed.

Increased MMPs expression and decreased contraction in the rat myometrium during pregnancy and in response to prolonged stretch and sex hormones

Normal pregnancy is associated with uterine relaxation to accommodate the stretch imposed by the growing fetus; however, the mechanisms underlying the relationship between pregnancy-associated uterine stretch and uterine relaxation are unclear. We hypothesized that increased uterine stretch during pregnancy is associated with upregulation of matrix metalloproteinases (MMPs), which in turn cause inhibition of myometrium contraction and promote uterine relaxation. Uteri from virgin, midpregnant (day 12), and late-pregnant rats (day 19) were isolated, and myometrium strips were prepared for measurement of isometric contraction and MMP expression and activity using RT-PCR, Western blot analysis, and gelatin zymography. Oxytocin caused concentration-dependent contraction of myometrium strips that was reduced in mid- and late-pregnant rats compared with virgin rats. Pretreatment with the MMP inhibitors SB-3CT (MMP-2/MMP-9 Inhibitor IV), BB-94 (batimastat), or Ro-28-2653 (cipemastat) enhanced contraction in myometrium of pregnant rats. RT-PCR, Western blot analysis, and gelatin zymography demonstrated increased mRNA expression, protein amount, and activity of MMP-2 and MMP-9 in myometrium of late-pregnant>midpregnant>virgin rats. Prolonged stretch of myometrium strips of virgin rats under 8 g basal tension for 18 h was associated with reduced contraction and enhanced expression and activity of MMP-2 and MMP-9, which were reversed by MMP inhibitors. Concomitant treatment of stretched myometrium of virgin rats with 17β-estradiol (E2), progesterone (P4), or E2+P4 was associated with further reduction in contraction and increased MMP expression and activity. MMP-2 and MMP-9 caused significant reduction of oxytocin-induced contraction of myometrium of virgin rat. Thus, normal pregnancy is associated with reduced myometrium contraction and increased MMPs expression and activity. The results are consistent with the possibility that myometrium stretch and concomitant increase in sex hormones during pregnancy are associated with increased expression/activity of specific MMPs, which in turn inhibit uterine contraction and promote uterine relaxation.

Local oestrogenic/androgenic balance in the cerebral vasculature

Reproductive effects of sex steroids are well-known; however it is increasingly apparent that these hormones have important actions on non-reproductive tissues such as the vasculature. The latter effects can be relevant throughout the lifespan, not just limited to reproductive years, and are not necessarily restricted to one gender or the other. Our work has established that cerebral blood vessels are a non-reproductive target tissue for sex steroids. We have found that oestrogen and androgens alter vascular tone, endothelial function, oxidative stress and inflammatory responses in cerebral vessels. Often the actions of oestrogen and androgens oppose each other. Moreover, it is clear that cerebral vessels are directly targeted by sex steroids, as they express specific receptors for these hormones. Interestingly, cerebral blood vessels also express enzymes that metabolize sex steroids. These findings suggest that local synthesis of 17ß-estradiol and dihydrotestosterone can occur within the vessel wall. One of the enzymes present, aromatase, converts testosterone to 17ß-estradiol, which would alter the local balance of androgenic and oestrogenic influences. Thus cerebral vessels are affected by circulating sex hormones as well as locally synthesized sex steroids. The presence of vascular endocrine effector mechanisms has important implications for male-female differences in cerebrovascular function and disease. Moreover, the cerebral circulation is a target for gonadal hormones as well as anabolic steroids and therapeutic drugs used to manipulate sex steroid actions. The long-term consequences of these influences are yet to be determined.

Mechanisms of cerebrovascular protection: oestrogen, inflammation and mitochondria

Investigation of oestrogen action reveals a multitude of diverse effects. This brief review focuses on the impact of oestrogen on the vasculature, with particular emphasis on the cerebral circulation. Three major actions of oestrogen are discussed: enhancement of vasodilator capacity, suppression of vascular inflammation and increase in mitochondrial efficiency. In both humans and animals, oestrogen increases vasodilator tone, an effect dependent on a functional endothelium. Two distinct mechanisms are involved: increase in endothelial nitric oxide synthase (eNOS) mRNA and protein and phosphorylation of eNOS via the PI-3 kinase/Akt pathway. Both effects are mediated by oestrogen receptors (ER), but through two pathways, ER-mediated nuclear gene transcription and cell membrane-associated ERs respectively. Oestrogen also increases function of other endothelium-dependent vasodilators. Oestrogen suppresses vascular inflammation through an NF-κB-dependent effect. The inflammatory response has also been shown to vary significantly during the oestrous cycle of rodents. Emerging information shows that oestrogen increases mitochondrial biogenesis and decreases superoxide production. Suppression of mitochondrial superoxide production by 17β-estradiol in cerebral blood vessels is mediated by the ER-alpha receptor and not dependent on increased Mn superoxide dismutase activity. Oestrogen treatment also increases protein levels for a number of components of the electron transfer chain, as well as levels of transcription factors that regulate mitochondrial function. All of these actions of oestrogen could be important in mediating vascular protection, especially in the cerebral circulation. Furthermore, given the potential of mitochondrial DNA damage to contribute to pathophysiology and ageing, mitochondrial protective effects of oestrogen might contribute to the longer average lifespan of women.

Impact of sex hormone metabolism on the vascular effects of menopausal hormone therapy in cardiovascular disease

Epidemiological studies have shown that cardiovascular disease (CVD) is less common in pre-menopausal women (Pre-MW) compared to men of the same age or post-menopausal women (Post-MW), suggesting cardiovascular benefits of estrogen. Estrogen receptors (ERs) have been identified in the vasculature, and experimental studies have demonstrated vasodilator effects of estrogen/ER on the endothelium, vascular smooth muscle (VSM) and extracellular matrix. Several natural and synthetic estrogenic preparations have been developed for relief of menopausal vasomotor symptoms. However, whether menopausal hormone therapy (MHT) is beneficial in postmenopausal CVD remains controversial. Despite reports of vascular benefits of MHT from observational and experimental studies, randomized clinical trials (RCTs), such as the Heart and Estrogen/progestin Replacement Study (HERS) and the Women's Health Initiative (WHI), have suggested that, contrary to expectations, MHT may increase the risk of CVD. These discrepancies could be due to agerelated changes in sex hormone synthesis and metabolism, which would influence the effective dose of MHT and the sex hormone environment in Post-MW. Age-related changes in the vascular ER subtype, structure, expression, distribution, and post-ER signaling pathways in the endothelium and VSM, along with factors related to the design of RCTs, preexisting CVD condition, and structural changes in the blood vessels architecture have also been suggested as possible causes of MHT failure in CVD. Careful examination of these factors should help in identifying the causes of the changes in the vascular effects of estrogen with age. The sex hormone metabolic pathways, the active versus inactive estrogen metabolites, and their effects on vascular function, the mitochondria, the inflammatory process and angiogenesis should be further examined. Also, the genomic and non-genomic effects of estrogenic compounds should be viewed as integrated rather than discrete responses. The complex interactions between these factors highlight the importance of careful design of MHT RCTs, and the need of a more customized approach for each individual patient in order to enhance the vascular benefits of MHT in postmenopausal CVD.

Mechanisms of estrogens' dose-dependent neuroprotective and neurodamaging effects in experimental models of cerebral ischemia

Ever since the hypothesis was put forward that estrogens could protect against cerebral ischemia, numerous studies have investigated the mechanisms of their effects. Despite initial studies showing ameliorating effects, later trials in both humans and animals have yielded contrasting results regarding the fundamental issue of whether estrogens are neuroprotective or neurodamaging. Therefore, investigations of the possible mechanisms of estrogen actions in brain ischemia have been difficult to assess. A recently published systematic review from our laboratory indicates that the dichotomy in experimental rat studies may be caused by the use of insufficiently validated estrogen administration methods resulting in serum hormone concentrations far from those intended, and that physiological estrogen concentrations are neuroprotective while supraphysiological concentrations augment the damage from cerebral ischemia. This evidence offers a new perspective on the mechanisms of estrogens’ actions in cerebral ischemia, and also has a direct bearing on the hormone replacement therapy debate. Estrogens affect their target organs by several different pathways and receptors, and the mechanisms proposed for their effects on stroke probably prevail in different concentration ranges. In the current article, previously suggested neuroprotective and neurodamaging mechanisms are reviewed in a hormone concentration perspective in an effort to provide a mechanistic framework for the dose-dependent paradoxical effects of estrogens in stroke. It is concluded that five protective mechanisms, namely decreased apoptosis, growth factor regulation, vascular modulation, indirect antioxidant properties and decreased inflammation, and the proposed damaging mechanism of increased inflammation, are currently supported by experiments performed in optimal biological settings.

Age-dependent susceptibility to infarct growth in women

BACKGROUND AND PURPOSE

It is not known if there is a relationship between gender and tissue outcome in human ischemic stroke. We sought to identify whether the proportion of initially ischemic to eventually infarcted tissue was different between men and women with ischemic stroke.

METHODS

We studied 141 consecutive patients with acute ischemic stroke who had a baseline MRI obtained within 12 hours of symptom onset, a follow-up imaging on Day 4 or later, and diffusion-weighted imaging/mean transmit time mismatch on initial MRI. Lesion growth was calculated as percentage of mismatch tissue that underwent infarction on follow-up (percentage mismatch lost). Multivariable analyses explored the effect of gender and other predictors of tissue outcome on percentage mismatch lost.

RESULTS

There was no difference in median percentage mismatch lost between men (19%) and women (11%; P=0.720). There was, however, an interaction between gender and age; median percentage mismatch lost was 7% (0% to 12%) in women and 18% (1% to 35%) in men younger than the population median (71 years, P=0.061). The percentage mismatch lost was not different between men and women ≥71 years old (25% in both groups). The linear regression model revealed gender (P=0.027) and the interaction between age and gender (P=0.023) as independent predictors of percentage mismatch lost.

CONCLUSIONS

There is an age-by-gender interaction in tissue outcome after ischemic stroke; brain infarcts in women <70 years grow approximately 50% less than infarcts in their male counterparts. These findings extend the well-known concept that there is a differential age-by-gender effect on stroke incidence, mortality, and functional outcome to the tissue level.

Emerging role of epigenetics in stroke: part 1: DNA methylation and chromatin modifications

Epigenetic mechanisms refer to the complex and interrelated molecular processes that dynamically modulate gene expression and function within every cell in the body. These regulatory systems represent the long-sought-after molecular interfaces that mediate gene × environment interactions. Changes in the epigenome throughout life are responsible not only for controlling normal development, adult homeostasis, and aging but also for mediating responses to injury. Emerging evidence implicates a spectrum of epigenetic processes in the pathophysiology of stroke. In this review, we describe conventional epigenetic mechanisms (including DNA methylation, histone code modifications, nucleosome remodeling, and higher-order chromatin formation) and highlight the emerging roles each of these processes play in the pathobiology of stroke. We suggest that understanding these mechanisms may be important for discovering more sensitive and specific biomarkers for risk, onset, and progression of stroke. In addition, we highlight epigenetic approaches for stroke therapy, including the inhibition of DNA methyltransferase and histone deacetylase enzyme activities. These therapeutic approaches are still in their infancy, but preliminary results suggest that contemporary agents targeting these pathways can regulate the deployment of stress responses that modulate neural cell viability and promote brain repair and functional reorganization. Indeed, these agents even appear to orchestrate sophisticated cognitive functions, including learning and memory.

Endothelial damage due to impaired nitric oxide bioavailability triggers cerebral aneurysm formation in female rats

OBJECTIVE

Epidemiological data indicate a high incidence of cerebral aneurysms in postmenopausal women. To elucidate the pathogenesis of cerebral aneurysms, we focused on the contribution of endothelial damage in rats.

METHODS

We induced estradiol deficiency by oophorectomy (OVX), hypertension, or both, and hemodynamic stress in 7-week-old female Sprague-Dawley rats. They were then given hormone-replacement therapy with 17beta-estradiol or an angiotensin II type 1 receptor blocker (ARB). The effects of estradiol, angiotensin II type 1 receptor blocker, or both on cultured endothelial cells were also examined.

RESULTS

The number of anomalously shaped endothelial cells was higher in OVX than hypertensive rats (P < 0.05). Rats subjected to hypertension and OVX exhibited a marked increase in the incidence of saccular cerebral aneurysms. Estradiol or angiotensin II type 1 receptor blocker treatment reduced this incidence (P < 0.05). The endothelial nitric oxide synthase (eNOS) mRNA level in the intracranial artery of OVX and hypertensive and OVX rats was low (P < 0.05). Immunohistochemically, the expression of eNOS and estrogen receptor alpha (ERalpha) in the vascular wall of hypertensive and OVX rats was decreased; angiotensin II and the nicotinamide adenine dinucleotide phosphate oxidase subunits nicotinamide adenine dinucleotide phosphate oxidase 4 and p22phox were strongly expressed in cerebral aneurysms. In the absence of estradiol, eNOS was downregulated and nicotinamide adenine dinucleotide phosphate oxidase expression was increased in endothelial cells; angiotensin II augmented these phenomena. The regulation of eNOS was mediated by ERalpha. These results suggest that estrogen deficiency induces endothelial dysfunction and reactive oxygen species generation, triggering endothelial damage that leads to cerebral aneurysms and that hypertension is an additional risk factor.

CONCLUSION

A therapy targeted at the endothelium and management of hypertension may help to prevent cerebral aneurysms.

Potential role of estrogen in the pathobiology and prevention of Alzheimer's disease

Over a decade of converging findings from clinical, observational and basic science research indicate that estrogen administration during the menopausal transition exerts beneficial effects on cognition and decreases a woman's risk of developing Alzheimer's disease (AD) later in life. This review article stresses the research focus of AD prevention, and introduces hormone therapy (HT) as a probable catalyst that may achieve this goal. Furthermore, this article outlines 3 mechanisms proposed to mediate estrogen's beneficial effects, discusses the controversy surrounding HT administration, and presents the most promising estrogen related research in AD prevention and treatment. Although controversial, cumulative evidence suggests that the potential of estrogen initiated during perimenopause to prevent AD needs to be systematically evaluated.

White blood cell count and abdominal fat distribution in female obese adolescents

The association between abdominal fat distribution and inflammatory markers is currently a subject of debate. Here, we delineate the relationship between white blood cell (WBC) counts and abdominal fat distribution in female obese adolescents. A total of 102 female obese adolescent subjects were analyzed. Anthropometry, WBC count, blood pressure, fasting plasma glucose, lipid profiles, and fasting insulin concentrations were measured. Subcutaneous adipose tissue (SAT) and visceral adipose tissue areas were calculated using computed tomography. Mean values of waist circumference (P < .05), total adipose tissue (TAT) (P < .01), and SAT (P < .01) were significantly higher in the group with the higher WBC count. The WBC count was positively related to body mass index, waist circumference, and TAT and SAT areas after adjustment for age and metabolic risk factors (P < .01). Among the WBC components, neutrophils were positively associated with body mass index (P < .01), waist circumference (P < .01), and TAT (P < .05). The WBC count escalated with a graded increase in TAT or SAT (P for trend < .01). Our findings collectively indicate that the WBC count is positively related to abdominal adiposity in female obese adolescents. Moreover, this relationship is more distinguishable with subcutaneous than visceral adiposity.

Vascular actions of estrogens: functional implications

The impact of estrogen exposure in preventing or treating cardiovascular disease is controversial. But it is clear that estrogen has important effects on vascular physiology and pathophysiology, with potential therapeutic implications. Therefore, the goal of this review is to summarize, using an integrated approach, current knowledge of the vascular effects of estrogen, both in humans and in experimental animals. Aspects of estrogen synthesis and receptors, as well as general mechanisms of estrogenic action are reviewed with an emphasis on issues particularly relevant to the vascular system. Recent understanding of the impact of estrogen on mitochondrial function suggests that the longer lifespan of women compared with men may depend in part on the ability of estrogen to decrease production of reactive oxygen species in mitochondria. Mechanisms by which estrogen increases endothelial vasodilator function, promotes angiogenesis, and modulates autonomic function are summarized. Key aspects of the relevant pathophysiology of inflammation, atherosclerosis, stroke, migraine, and thrombosis are reviewed concerning current knowledge of estrogenic effects. A number of emerging concepts are addressed throughout. These include the importance of estrogenic formulation and route of administration and the impact of genetic polymorphisms, either in estrogen receptors or in enzymes responsible for estrogen metabolism, on responsiveness to hormone treatment. The importance of local metabolism of estrogenic precursors and the impact of timing for initiation of treatment and its duration are also considered. Although consensus opinions are emphasized, controversial views are presented to stimulate future research.