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

Sex differences in treatment effect in neuroprotectant trials for acute ischemic stroke: A systematic review

BACKGROUND

Pre-clinical data suggest sex differences in mechanisms of cerebral ischemic injury. This might result in differential outcomes of putative neuroprotectants by sex, though little systematic data is available to assess this.

METHODS

We performed a systematic review of multicenter randomized controlled trials published from January 1980-June 2022 enrolling >100 subjects and testing neuroprotectants in acute ischemic stroke (AIS). For each trial, reported treatment effect by sex was extracted. When published results by sex were not available, we contacted individual authors to attempt to retrieve these data.

RESULTS

We identified 59 publications reporting 64 trials that met inclusion criteria. Of these, data on treatment effect by sex were published for 14/64 trials. Unpublished data for an additional 5 trials were obtained from trial investigators (19/64, or 29.7%). Two trials (one testing uric acid and one dexborneol) reported treatment benefit in women but not men. Pooled analysis of six trials of tirilazad reported worse treatment outcomes in women and no effect in men. No clear difference was apparent in the other trials.

CONCLUSIONS

Most trials did not report treatment effect by sex. Of those that did, there was little evidence of systematic sex differences in treatment response.

The Pharmacological Effect of Hemin in Inflammatory-Related Diseases: A Systematic Review

BACKGROUND

Hemin is clinically used in acute attacks of porphyria; however, recent evidence has also highlighted its capability to stimulate the heme oxygenase enzyme, being associated with cytoprotective, antioxidant, and anti-inflammatory effects. Indeed, current preclinical evidence emphasizes the potential anti-inflammatory role of hemin through its use in animal models of disease. Nevertheless, there is no consensus about the underlying mechanism(s) and the most optimal therapeutic regimens. Therefore, this review aims to summarize, analyze, and discuss the current preclinical evidence concerning the pharmacological effect of hemin.

METHODS

Following the application of the search expression and the retrieval of the articles, only nonclinical studies in vivo written in English were considered, where the potential anti-inflammatory effect of hemin was evaluated.

RESULTS

Forty-nine articles were included according to the eligibility criteria established. The results obtained show the preference of using 30 to 50 mg/kg of hemin, administered intraperitoneally, in both acute and chronic contexts. This drug demonstrates significant anti-inflammatory and antioxidant activities considering its capacity for reducing the expression of proinflammatory and oxidative markers.

CONCLUSIONS

This review highlighted the significant anti-inflammatory and antioxidant effects of hemin, providing a clearer vision for the medical community about the use of this drug in several human diseases.

Exploring sex differences for acute ischemic stroke clinical, imaging and thrombus characteristics in the INTERRSeCT study

Women, especially following menopause, are known to have worse outcomes following acute ischemic stroke. One primary postulated biological mechanism for worse outcomes in older women is a reduction in the vasculoprotective effects of estrogen. Using the INTERRseCT cohort, a multicentre international observational cohort studying recanalization in acute ischemic stroke, we explored the effects of sex, and modifying effects of age, on neuroradiological predictors of recanalization including robustness of leptomeningeal collaterals, thrombus burden and thrombus permeability. Ordinal regression analyses were used to examine the relationship between sex and each of the neuroradiological markers. Further, we explored both multiplicative and additive interactions between age and sex. All patients (n = 575) from INTERRseCT were included. Mean age was 70.2 years (SD: 13.1) and 48.5% were women. In the unadjusted model, female sex was associated with better collaterals (OR 1.37, 95% CIs: 1.01-1.85), however this relationship was not significant after adjusting for age and relevant comorbidities. There were no significant interactions between age and sex. In a large prospective international cohort, we found no association between sex and radiological predictors of recanalization including leptomeningeal collaterals, thrombus permeability and thrombus burden.

Worsened Stroke Outcome in a Model of Preeclampsia is Associated With Poor Collateral Flow and Oxidative Stress

BACKGROUND

Preeclampsia increases the incidence of maternal stroke, a devastating condition that is on the rise. We investigated stroke outcome in a model of experimental preeclampsia with and without treatment with clinically relevant doses of magnesium sulfate (experimental preeclampsia+MgSO4) compared to normal late-pregnant and nonpregnant rats.

METHODS

Transient middle cerebral artery occlusion was used to induce focal stroke for either 1.5 or 3 hours. Infarct volume and hemorrhagic transformation were determined as measures of stroke outcome. Changes in core middle cerebral artery and collateral flow were measured by dual laser Doppler. The relationship between middle cerebral artery perfusion deficit and infarction was used as a measure of ischemic tolerance. Oxidative stress and endothelial dysfunction were measured by 3-nitrotyrosine and 8-isoprostane, in brain and serum, respectively.

RESULTS

Late-pregnant animals had robust collateral flow and greater ischemic tolerance of brain tissue, whereas experimental preeclampsia had greater infarction that was related to poor collateral flow, endothelial dysfunction, and oxidative stress. Importantly, pregnancy appeared preventative of hemorrhagic transformation as it occurred only in nonpregnant animals. MgSO4 did not provide benefit to experimental preeclampsia animals for infarction.

CONCLUSIONS

Stroke outcome was worse in a model of preeclampsia. As preeclampsia increases the risk of future stroke and cardiovascular disease, it is worth understanding the influence of preeclampsia on the material brain and factors that might potentiate injury both during the index pregnancy and years postpartum.

Sexual Dimorphism in Neurodegenerative Diseases and in Brain Ischemia

Epidemiological studies and clinical observations show evidence of sexual dimorphism in brain responses to several neurological conditions. It is suggested that sex-related differences between men and women may have profound effects on disease susceptibility, pathophysiology, and progression. Sexual differences of the brain are achieved through the complex interplay of several factors contributing to this phenomenon, such as sex hormones, as well as genetic and epigenetic differences. Despite recent advances, the precise link between these factors and brain disorders is incompletely understood. This review aims to briefly outline the most relevant aspects that differ between men and women in ischemia and neurodegenerative disorders (AD, PD, HD, ALS, and SM). Recognition of disparities between both sexes could aid the development of individual approaches to ameliorate or slow the progression of intractable disorders.

A multivariate prediction model and its application in forecasting acute ischemic stroke: Protocol for a retrospective clinical study

BACKGROUND

Acute ischemic stroke (AIS) occurs due to brain ischemia as a result of thrombosis of a cerebral blood vessel. It is a common cerebral blood circulation disorder worldwide and an important cause of death and disability.

OBJECTIVE

This study aims to establish a prediction model of multiple single category indicators and a joint model, through which to plot multiple receiver operating characteristic curves and compare area under curve of the models so as to predict the occurrence of AIS, explore the pathogenesis of AIS, and provide reference for clinical diagnosis and treatment of AIS.

METHODS

A retrospective clinical study was conducted in a Level A tertiary hospital in Sichuan Province, China. The patients participated in this study were over 18 years of age and suffered from acute ischemic stroke. They were hospitalized in department of neurology from October 1, 2019 to September 30, 2022, and underwent coronary artery computed tomographic arteriography (CTA) and blood biomarker detection. We collected demographic information, CTA data and blood biomarker detection values of all these patients.

CONCLUSION

Through analyzing the clinical data of high-risk groups, this study provides guidance for the prevention and treatment of AIS, and promote further research.

Different gender-derived gut microbiota influence stroke outcomes by mitigating inflammation

Background and purpose

Stroke is associated with high disability and mortality rates and increases the incidence of organ-related complications. Research has revealed that the outcomes and prognosis of stroke are regulated by the state of the intestinal microbiota. However, the possibility that the manipulation of the intestinal microbiota can alter sex-related stroke outcomes remain unknown.

Methods

To verify the different effects of microbiota from different sexes on stroke outcomes, we performed mouse fecal microbiota transplantation (FMT) and established a model of ischemic stroke. Male and female mice received either male or female microbiota through FMT. Ischemic stroke was triggered by MCAO (middle cerebral artery occlusion), and sham surgery served as a control. Over the next few weeks, the mice underwent neurological evaluation and metabolite and inflammatory level detection, and we collected fecal samples for 16S ribosomal RNA analysis.

Results

We found that when the female mice were not treated with FMT, the microbiota (especially the Firmicutes-to-Bacteroidetes ratio) and the levels of three main metabolites tended to resemble those of male mice after experimental stroke, indicating that stroke can induce an ecological imbalance in the biological community. Through intragastric administration, the gut microbiota of male and female mice was altered to resemble that of the other sex. In general, in female mice after MCAO, the survival rate was increased, the infarct area was reduced, behavioral test performance was improved, the release of beneficial metabolites was promoted and the level of inflammation was mitigated. In contrast, mice that received male microbiota were much more hampered in terms of protection against brain damage and the recovery of neurological function.

Conclusion

A female-like biological community reduces the level of systemic proinflammatory cytokines after ischemic stroke. Poor stroke outcomes can be positively modulated following supplementation with female gut microbiota.

Impact of diabetes and ischemic stroke on the cerebrovasculature: A female perspective

There is a very complex interaction between the brain and the cerebral vasculature to meet the metabolic demands of the brain for proper function. Preservation of vascular networks and cerebrovascular function ultimately plays a key role in this intricate communication within the brain in health and disease. Experimental evidence showed that diabetes not only affects the architecture of cerebral blood arteries causing adverse remodeling, pathological neovascularization, and vasoregression, but also alters cerebrovascular function resulting in compromised myogenic reactivity and endothelial dysfunction. Coupled with the disruption of blood brain barrier (BBB) integrity, changes in blood flow and microbleeds into the brain can rapidly occur. When an ischemic insult is superimposed on this pathology, not only is the neurovascular injury greater, but repair mechanisms fail, resulting in greater physical and cognitive deficits. While clinically it is known that women suffer disproportionately from diabetes as well as ischemic stroke and post-stroke cognitive impairment, the cerebrovascular architecture, patho/physiology, as well as cerebrovascular contributions to stroke recovery in female and diabetic animal models are inadequately studied and highlighted in this review.

Relationship between Neuronal Damage/Death and Astrogliosis in the Cerebral Motor Cortex of Gerbil Models of Mild and Severe Ischemia and Reperfusion Injury

Neuronal loss (death) occurs selectively in vulnerable brain regions after ischemic insults. Astrogliosis is accompanied by neuronal death. It can change the molecular expression and morphology of astrocytes following ischemic insults. However, little is known about cerebral ischemia and reperfusion injury that can variously lead to damage of astrocytes according to the degree of ischemic injury, which is related to neuronal damage/death. Thus, the purpose of this study was to examine the relationship between damage to cortical neurons and astrocytes using gerbil models of mild and severe transient forebrain ischemia induced by blocking the blood supply to the forebrain for five or 15 min. Significant ischemia tFI-induced neuronal death occurred in the deep layers (layers V and VI) of the motor cortex: neuronal death occurred earlier and more severely in gerbils with severe ischemia than in gerbils with mild ischemia. Distinct astrogliosis was detected in layers V and VI. It gradually increased with time after both ischemiae. The astrogliosis was significantly higher in severe ischemia than in mild ischemia. The ischemia-induced increase of glial fibrillary acidic protein (GFAP; a maker of astrocyte) expression in severe ischemia was significantly higher than that in mild ischemia. However, GFAP-immunoreactive astrocytes were apparently damaged two days after both ischemiae. At five days after ischemiae, astrocyte endfeet around capillary endothelial cells were severely ruptured. They were more severely ruptured by severe ischemia than by mild ischemia. However, the number of astrocytes stained with S100 was significantly higher in severe ischemia than in mild ischemia. These results indicate that the degree of astrogliosis, including the disruption (loss) of astrocyte endfeet following ischemia and reperfusion in the forebrain, might depend on the severity of ischemia and that the degree of ischemia-induced neuronal damage may be associated with the degree of astrogliosis.

Glial estradiol synthesis after brain injury

Glial cells are important contributors to the hormonal milieu of the brain, particularly following damage. In birds and mammals, neural injury induces the expression of aromatase in astroglia at and around the site of damage. This review describes the progression of our understanding about the incidence, regulation, and function of estrogens synthesized in glia. Following a quick discussion of the landmark studies that first demonstrated steroidogenesis in glia, I go on to describe how the inflammatory response following perturbation of the brain results in the transcription of aromatase and the resultant rise in local estradiol. I end with several unanswered questions, the answers to which may reveal the precise manner in which neurosteroids protect the brain from injury, both prior to and immediately following injury.

Determinants of Leptomeningeal Collateral Status Variability in Ischemic Stroke Patients

BACKGROUND

Collateral status is an indicator of a favorable outcome in stroke. Leptomeningeal collaterals provide alternative routes for brain perfusion following an arterial occlusion or flow-limiting stenosis. Using a large cohort of ischemic stroke patients, we examined the relative contribution of various demographic, laboratory, and clinical variables in explaining variability in collateral status.

METHODS

Patients with acute ischemic stroke in the anterior circulation were enrolled in a multi-center hospital-based observational study. Intracranial occlusions and collateral status were identified and graded using multiphase computed tomography angiography. Based on the percentage of affected territory filled by collateral supply, collaterals were graded as either poor (0-49%), good (50-99%), or optimal (100%). Between-group differences in demographic, laboratory, and clinical factors were explored using ordinal regression models. Further, we explored the contribution of measured variables in explaining variance in collateral status.

RESULTS

386 patients with collateral status classified as poor (n = 64), good (n = 125), and optimal (n = 197) were included. Median time from symptom onset to CT was 120 (IQR: 78-246) minutes. In final multivariable model, male sex (OR 1.9, 95% CIs [1.2, 2.9], p = 0.005) and leukocytosis (OR 1.1, 95% CIs [1.1, 1.2], p = 0.001) were associated with poor collaterals. Measured variables only explained 44.8-53.0% of the observed between-patient variance in collaterals.

CONCLUSION

Male sex and leukocytosis are associated with poorer collaterals. Nearly half of the variance in collateral flow remains unexplained and could be in part due to genetic differences.

Do Outcomes between Women and Men Differ after Endovascular Thrombectomy? A Meta-analysis

BACKGROUND

Research on the presence of sex-based differences in the outcomes of patients undergoing endovascular thrombectomy for acute ischemic stroke has reached differing conclusions.

PURPOSE

This review aimed to determine whether sex influences the outcome of patients with large-vessel occlusion stroke undergoing endovascular thrombectomy.

STUDY SELECTION

We performed a systematic review and meta-analysis of endovascular thrombectomy studies with either stratified cohort outcomes according to sex (females versus males) or effect size reported for the consequence of sex versus outcomes. We included 33 articles with 7335 patients.

DATA ANALYSIS

We pooled ORs for the 90-day mRS score, 90-day mortality, symptomatic intracranial hemorrhage, and recanalization.

DATA SYNTHESIS

Pooled 90-day good outcomes (mRS ≤ 2) were better for men than women (OR = 1.29; 95% CI, 1.09-1.53; P = <.001, I² = 56.95%). The odds of the other outcomes, recanalization (OR = 0.94; 95% CI, 0.77-1.15; P = .38, I² = 0%), 90-day mortality (OR = 1.11; 95% CI, 0.89-1.38; P = .093, I² = 0%), and symptomatic intracranial hemorrhage (OR = 1.40; 95% CI, 0.99-1.99; P = .069, I² = 0%) were comparable between men and women.

LIMITATIONS

Moderate heterogeneity was found. Most studies included were retrospective in nature. In addition, the randomized trials included were not specifically designed to compare outcomes between sexes.

CONCLUSIONS

Women undergoing endovascular thrombectomy for large-vessel occlusion have inferior 90-day clinical outcomes. Sex-specific outcomes should be investigated further in future trials as well as pathophysiologic studies.

Potential anti-inflammatory effect of erythropoietin in non-clinical studies in vivo: A systematic review

Erythropoietin (EPO) is a hypoxia-induced hormone produced in adult kidneys with erythropoietic and non-erythropoietic effects. In vivo studies represent an important role to comprehend the efficacy and safety in the early phase of repurposing drugs. The aim is to evaluate the potential anti-inflammatory effect of EPO observed in animal models of disease. Following PRISMA statements, electronic database Medline via PubMed platform was used to search articles with the research expression ((erythropoietin [MeSH Terms]) AND (inflammation [MeSH Terms]) AND (disease models, animal [MeSH Terms])). The inclusion criteria were original articles, studies where EPO was administered, studies where inflammation was studied and/or evaluated, non-clinical studies in vivo with rodents, and articles published in English. Thirty-six articles met the criteria for qualitative analysis. Exogenous EPO was used in models of sepsis, traumatic brain injury, and autoimmune neuritis, with an average of 3000 IU/Kg for single and multiple doses, using mice and rats. Biomarkers such as immune-related effectors, cytokines, reactive oxygen species, prostaglandins, and other biomarkers were assessed. EPO has been recognized as a multifunctional cytokine with anti-inflammatory properties, showing its significant effect both in acute and chronic models of inflammation. Further non-clinical studies are suggested for the enlightenment of anti-inflammatory mechanisms of EPO in lower doses, allowing us to understand the translational data for humans.

The Impact of Sex on Arterial Ischemic Stroke in Young Patients: From Stroke Occurrence to Poststroke Consequences

The male sex has been suggested to predominate in paediatric patients with arterial ischemic stroke (AIS), especially in newborns. The explanation for this phenomenon remains unsatisfactory since it focuses on the analysis of the potential relationship with trauma and arterial dissection. In turn, in some populations of young adults, men suffer from AIS more frequently than women, which may be related to the protective role of oestrogen. On the other hand, certain data indicate that women dominate over men. Some of the disparities in the frequencies of particular symptoms of AIS and poststroke consequences in both children and young adults have been suggested; however, data are scarce. Unfortunately, the low number of studies on the subject does not allow certain conclusions to be drawn. For adults, more data are available for patients aged over 60 years, the results of which are more obvious. The present literature review aimed to discuss available data on the prevalence of AIS, its clinical presentations, and poststroke consequences in regard to the sex of young patients. We considered young patients to be children from birth up to the age of 19 years of life and young adults to be individuals up to the age of 55 years. The role of sex hormones in AIS and possible gender differences in genetic risk factors for AIS were also discussed briefly.

X chromosome escapee genes are involved in ischemic sexual dimorphism through epigenetic modification of inflammatory signals

BACKGROUND

Stroke is a sexually dimorphic disease. Previous studies have found that young females are protected against ischemia compared to males, partially due to the protective effect of ovarian hormones, particularly estrogen (E2). However, there are also genetic and epigenetic effects of X chromosome dosage that contribute to stroke sensitivity and neuroinflammation after injury, especially in the aged. Genes that escape from X chromosome inactivation (XCI) contribute to sex-specific phenotypes in many disorders. Kdm5c and kdm6a are X escapee genes that demethylate H3K4me3 and H3K27me3, respectively. We hypothesized that the two demethylases play critical roles in mediating the stroke sensitivity.

METHODS

To identify the X escapee genes involved in stroke, we performed RNA-seq in flow-sorted microglia from aged male and female wild type (WT) mice subjected to middle cerebral artery occlusion (MCAO). The expression of these genes (kdm5c/kdm6a) were confirmed in four core genotypes (FCG) mice and in post-mortem human stroke brains by immunohistochemistry (IHC), Western blot, and RT-PCR. Chromatin immunoprecipitation (ChIP) assays were conducted to detect DNA levels of inflammatory interferon regulatory factor (IRF) 4/5 precipitated by histone H3K4 and H3K27 antibodies. Manipulation of kdm5c/kdm6a expression with siRNA or lentivirus was performed in microglial culture, to determine downstream pathways and examine the regulatory roles in inflammatory cytokine production.

RESULTS

Kdm5c and kdm6a mRNA levels were significantly higher in aged WT female vs. male microglia, and the sex difference also existed in ischemic brains from FCG mice and human stroke patients. The ChIP assay showed the IRF 4/5 had higher binding levels to demethylated H3K4 or H3K27, respectively, in female vs. male ischemic microglia. Knockdown or over expression of kdm5c/kdm6a with siRNA or lentivirus altered the methylation of H3K4 or H3K27 at the IRF4/5 genes, which in turn, impacted the production of inflammatory cytokines.

CONCLUSIONS

The KDM-Histone-IRF pathways are suggested to mediate sex differences in cerebral ischemia. Epigenetic modification of stroke-related genes constitutes an important mechanism underlying the ischemic sexual dimorphism.

FTY720 administration following hypoxia-induced neonatal seizure reverse cognitive impairments and severity of seizures in male and female adult rats: The role of inflammation

Hypoxia-induced neonatal seizure mainly leads to deleterious effects on brain function, especially cognitive impairments and increased susceptibility to epilepsy later in life. Early inflammation plays an important role in the pathology of these consequences. Therefore, we explored the long-term outcomes of Fingolimod treatment as an anti-inflammatory and neuroprotective agent in a rat model of HINS. Seizures were induced in rats (postnatal day 10) by 5% O2 exposure for 15 min. Sixty minutes after the onset of hypoxia, pups received FTY720 (0.3 mg.kg-1) or normal saline for 12 consecutive days (lactation period), and they were used at P60-P63 for behavioral tests, ELISA and Pentylenetetrazole kindling model. The results of open field, novel object recognition and elevated plus maze tasks showed that Fingolimod prevents hippocampal memory dysfunction and anxiety-like behavior in both male and female hypoxic groups, which was accompanied with decreased TNF-α level in hippocampus. In addition, FTY720 postponed epileptogenesis just in female hypoxic + FTY group and decreased severity of seizures in both genders. Our results suggest that, FTY720 treatment in immature rats, which were previously subjected to HINS, prevented the long-lasting deficits, like cognitive impairments, decreased the severity of seizures and related inflammation. In addition, FTY720 did not show significant interaction with gender in most of the experiments, except the average day to reach fully kindled state. Taken together, FTY720 has therapeutic potential for long lasting effects of HINS in both male and female animals at puberty.

Cerebrovascular disease in women

Cerebrovascular disease is a major cause of morbidity, mortality, and disability in women. The spectrum of disease differs between men and women, with women being particularly vulnerable to certain conditions, especially during specific periods of life such as pregnancy. There are several unique risk factors for cerebrovascular disease in women, and the influence of some traditional risk factors for stroke is stronger in women. Moreover, disparities persist in representation of women in clinical trials, acute intervention, and stroke outcomes. In this review, we aimed to explore the epidemiology, etiologies, and management of cerebrovascular disease in women, highlighting some of these differences and the growing need for sex-specific management guidelines and health policies.

Impact of aging and comorbidities on ischemic stroke outcomes in preclinical animal models: A translational perspective

Ischemic stroke is a highly complex and devastating neurological disease. The sudden loss of blood flow to a brain region due to an ischemic insult leads to severe damage to that area resulting in the formation of an infarcted tissue, also known as the ischemic core. This is surrounded by the peri-infarct region or penumbra that denotes the functionally impaired but potentially salvageable tissue. Thus, the penumbral tissue is the main target for the development of neuroprotective strategies to minimize the extent of ischemic brain damage by timely therapeutic intervention. Given the limitations of reperfusion therapies with recombinant tissue plasminogen activator or mechanical thrombectomy, there is high enthusiasm to combine reperfusion therapy with neuroprotective strategies to further reduce the progression of ischemic brain injury. Till date, a large number of candidate neuroprotective drugs have been identified as potential therapies based on highly promising results from studies in rodent ischemic stroke models. However, none of these interventions have shown therapeutic benefits in stroke patients in clinical trials. In this review article, we discussed the urgent need to utilize preclinical models of ischemic stroke that more accurately mimic the clinical conditions in stroke patients by incorporating aged animals and animal stroke models with comorbidities. We also outlined the recent findings that highlight the significant differences in stroke outcome between young and aged animals, and how major comorbid conditions such as hypertension, diabetes, obesity and hyperlipidemia dramatically increase the vulnerability of the brain to ischemic damage that eventually results in worse functional outcomes. It is evident from these earlier studies that including animal models of aging and comorbidities during the early stages of drug development could facilitate the identification of neuroprotective strategies with high likelihood of success in stroke clinical trials.

Does the Occurrence of Particular Symptoms and Outcomes of Arterial Ischemic Stroke Depend on Sex in Pediatric Patients?-A Pilot Study

Arterial ischemic stroke (AIS) in childhood is reported to occur more frequently in boys, which may lead to the assumption that the prevalence of post-stroke deficits is sex related. The present study aimed to evaluate sex-related differences in functional outcomes (hemiparesis, seizures, aphasia, and motor disturbances other than hemiparesis) in pediatric patients with AIS. A total of 89 children (52 boys and 37 girls; mean age at stroke onset: 8.4 ± 5.6 years) were evaluated retrospectively based on data from medical records. The patients were divided into subgroups according to age (i.e., infants and toddlers, children, and adolescents), stroke subtype (i.e., lacunar anterior circulation infarct (LACI), total anterior circulation infarct (TACI), partial anterior circulation infarct (PACI), posterior circulation infarct (POCI)) and stroke location (i.e., anterior stroke, posterior stroke). Significant differences in the prevalence of stroke subtypes between girls and boys were observed (p = 0.034). POCI stroke were found to be more frequent in boys than in girls (OR = 8.57 95%CI 1.05–70.23, p = 0.023). Males predominated in the total group and in all analyzed age subgroups. The proportions of boys within the subgroups according to stroke subtype were extremely high for the POCI and TACI stroke subgroups. On the other hand, girls predominated in the LACI stroke subgroup. Frequency of central type facial nerve palsy and other symptoms of AIS were found to significantly differ between male subgroups according to stroke subtype (p = 0.050 and p < 0.001, respectively), as well as between children with anterior stroke and those with posterior stroke (p = 0.059 and p < 0.001, respectively). Post-stroke seizures appeared significantly more commonly in girls with TACI and POCI stroke than in girls with LACI and PACI stroke (p = 0.022). In turn, the prevalence of post-stroke hemiparesis differed between stroke subtypes in boys (p = 0.026). In conclusion, sex may have an impact in predisposing to a certain type of AIS in the patient. Post-stroke seizure may be related to stroke subtype in girls and hemiparesis in boys. However, further studies are needed to confirm the results.

Androgens' effects on cerebrovascular function in health and disease

Androgens affect the cerebral vasculature and may contribute to sex differences in cerebrovascular diseases. Men are at a greater risk for stroke and vascular contributions to cognitive impairment and dementia (VCID) compared to women throughout much of the lifespan. The cerebral vasculature is a target for direct androgen actions, as it expresses several sex steroid receptors and metabolizing enzymes. Androgens’ actions on the cerebral vasculature are complex, as they have been shown to have both protective and detrimental effects, depending on factors such as age, dose, and disease state. When administered chronically, androgens are shown to be pro-angiogenic, promote vasoconstriction, and influence blood-brain barrier permeability. In addition to these direct effects of androgens on the cerebral vasculature, androgens also influence other vascular risk factors that may contribute to sex differences in cerebrovascular diseases. In men, low androgen levels have been linked to metabolic and cardiovascular diseases including hypertension, diabetes, hyperlipidemia, and obesity, which greatly increase the risk of stroke and VCID. Thus, a better understanding of androgens’ interactions with the cerebral vasculature under physiological and pathological conditions is of key importance.

Estrogen as a Neuroprotectant in Both Sexes: Stories From the Bird Brain

Estrogens such as estradiol (E2) are potent effectors of neural structure and function via peripheral and central synthesis. In the zebra finch (Taeniopygia guttata), neural E2 synthesis is among the highest reported in homeotherms due to the abundant constitutive expression of aromatase (E-synthase) in discrete neuronal pools across the forebrain. Following penetrating or concussive trauma, E2 synthesis increases even further via the induced expression of aromatase in reactive astrocytes around the site of damage. Injury-associated astrocytic aromatization occurs in the brains of both sexes regardless of the site of injury and can remain elevated for weeks following trauma. Interestingly, penetrating injury induces astrocytic aromatase more rapidly in females compared to males, but this sex difference is not detectable 24 h posttrauma. Indeed, unilateral penetrating injury can increase E2 content 4-fold relative to the contralateral uninjured hemisphere, suggesting that glial aromatization may be a powerful source of neural E2 available to circuits. Glial aromatization is neuroprotective as inhibition of injury-induced aromatase increases neuroinflammation, gliosis, necrosis, apoptosis, and infarct size. These effects are ameliorated upon replacement with E2, suggesting that the songbird may have evolved a rapidly responsive neurosteroidogenic system to protect vulnerable brain circuits. The precise signals that induce aromatase expression in astrocytes include elements of the inflammatory cascade and underscore the sentinel role of the innate immune system as a crucial effector of trauma-associated E2 provision in the vertebrate brain. This review will describe the inductive signals of astroglial aromatase and the neuroprotective role for glial E2 synthesis in the adult songbird brains of both sexes.

Comparison of neuronal death and expression of TNF‑α and MCT4 in the gerbil hippocampal CA1 region induced by ischemia/reperfusion under hyperthermia to those under normothermia

Monocarboxylate transporter 4 (MCT4) is a high-capacity lactate transporter in cells and the alteration in MCT4 expression harms cellular survival. The present study investigated whether hypothermia affects tumor necrosis factor-α (TNF-α) and MCT4 immunoreactivity in the subfield cornu ammonis 1 (CA1) following cerebral ischemia/reperfusion (IR) in gerbils. Hypothermia was induced for 30 min before and during ischemia. It was found that IR-induced death of pyramidal neurons was markedly augmented and occurred faster under hyperthermia than under normothermia. TNF-α immunoreactivity in the pyramidal cells started to increase at 3 h after IR and peaked at 1 day after IR under normothermia. However, in hyperthermic control and sham operated gerbils, TNF-α immunoreactivity was significantly increased compared with the normothermic gerbils, and IR under hyperthermia caused a more rapid and significant increase in TNF-α immunoreactivity in pyramidal neurons than under normothermia. In addition, in the normothermic gerbils, MCT4 immunoreactivity began to decrease in pyramidal neurons from 3 h after IR and markedly increased at 1 and 2 days after IR. On the other hand, MCT4 immunoreactivity in pyramidal neurons of the hyperthermic gerbils was significantly increased from 3 h after IR, maintained until 1 day after IR and markedly decreased at 2 days after IR. These results indicate that acceleration of IR-induced neuronal death under hyperthermia might be closely associated with early alteration of TNF-α and MCT4 protein expression in the gerbil hippocampus after IR.

Molecular Mechanisms of Intermittent Fasting-induced Ischemic Tolerance

Diet is a significant factor in determining human well-being. Excessive eating and/or diets with higher than needed amounts of carbohydrates, salt, and fat are known to cause metabolic disorders and functional changes in the body. To compensate the ill effects, many designer diets including the Mediterranean diet, the Okinawa diet, vegetarian/vegan diets, keto diet, anti-inflammatory diet, and the anti-oxidant diet have been introduced in the past 2 decades. While these diets are either enriched or devoid of one or more specific components, a better way to control diet is to limit the amount of food consumed. Caloric restriction (CR), which involves limiting the amount of food consumed rather than eliminating any specific type of food, as well as intermittent fasting (IF), which entails limiting the time during which food can be consumed on a given day, have gained popularity because of their positive effects on human health. While the molecular mechanisms of these 2 dietary regimens have not been fully deciphered, they are known to prolong the life span, control blood pressure, and blood glucose levels. Furthermore, CR and IF were both shown to decrease the incidence of heart attack and stroke, as well as their ill effects. In particular, IF is thought to promote metabolic switching by altering gene expression profiles leading to reduced inflammation and oxidative stress, while increasing plasticity and regeneration.

Genetic Variations of CYP19A1 Gene and Stroke Susceptibility: A Case-Control Study in the Chinese Han Population

OBJECTIVE

This study aimed to explore the association between genetic variations of CYP19A1 and stroke susceptibility in the Chinese Han population.

METHODS

A total of 477 stroke patients and 480 healthy controls were recruited in this study. The genotyping of CYP19A1 polymorphisms (rs4646, rs6493487, rs1062033, rs17601876, and rs3751599) was performed by the Agena MassARRAY platform. Under logistic regression models, we evaluated the associations of CYP19A1 polymorphisms and stroke susceptibility by odds ratio and 95% confidence interval.

RESULTS

Our study showed that rs4646 (codominant: P = 0.020; recessive: P = 0.016) and rs17601876 (allele: P = 0.044; codominant: P = 0.011; dominant: P = 0.009; recessive: P = 0.046) significantly decreased the risk of stroke. In the stratification analysis, rs4646 is associated with decreased stroke risk among the individuals older than 64 years (codominant: P = 0.028; recessive: P = 0.010) and women (codominant: P = 0.029; recessive: P = 0.029), whereas rs1062033 increased stroke risk in the subgroup of age 64 years and younger (recessive: P = 0.042). The rs17601876 polymorphism has a strong relationship with stroke susceptibility, which is age and gender dependent. In haplotype analysis, we found a block (rs17601876 and rs3751599), and Ars17601876Grs3751599 haplotype is related to an increased stroke risk (P < 0.05). In addition, CYP19A1 variations had effects on clinical characteristics.

CONCLUSION

CYP19A1 polymorphisms were significantly associated with stroke susceptibility in the Chinese Han population.

Exploratory, cognitive, and depressive-like behaviors in adult and pediatric mice exposed to controlled cortical impact

Objective

Sequelae of behavioral impairments associated with human traumatic brain injury (TBI) include neurobehavioral problems. We compared exploratory, cognitive, and depressive-like behaviors in pediatric and adult male mice exposed to controlled cortical impact (CCI).

Methods

Pediatric (21 to 25 days old) and adult (8 to 12 weeks old) male C57Bl/6 mice underwent CCI at a 2-mm depth of deflection. Hematoxylin and eosin staining was performed 3 to 7 days after recovery from CCI, and injury volume was analyzed using ImageJ. Neurobehavioral characterization after CCI was performed using the Barnes maze test (BMT), passive avoidance test, open-field test, light/dark test, tail suspension test, and rotarod test. Acutely and subacutely (3 and 7 days after CCI, respectively), CCI mice showed graded injury compared to sham mice for all analyzed deflection depths.

Results

Time-dependent differences in injury volume were noted between 3 and 7 days following 2-mm TBI in adult mice. In the BMT, 2-mm TBI adults showed spatial memory deficits compared to sham adults (P<0.05). However, no difference in spatial learning and memory was found between sham and 2-mm CCI groups among pediatric mice. The open-field test, light/dark test, and tail suspension test did not reveal differences in anxiety-like behaviors in both age groups.

Conclusion

Our findings revealed a graded injury response in both age groups. The BMT was an efficient cognitive test for assessing spatial/non-spatial learning following CCI in adult mice; however, spatial learning impairments in pediatric mice could not be assessed.

Hydrogen sulfide: Therapeutic or injurious in ischemic stroke?

Hydrogen sulfide (H2S) has been identified as a vasodilatory, neuromodulatory, and anti-inflammatory gasotransmitter with antioxidant properties. Studies focused in cardiac tissue suggest H2S functions as a protective agent; however in the central nervous system (CNS) the effects of H2S during states of stress or injury, such as stroke, remain controversial. Currently, the application of H2S donors and modulators in stroke depends on the type of H2S donor and the timing of the therapy.

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.

Experimental models of focal and multifocal cerebral ischemia: a review

Rodent and rabbit stroke models have been instrumental in our current understanding of stroke pathophysiology; however, translational failure is a significant problem in preclinical ischemic stroke research today. There are a number of different focal cerebral ischemia models that vary in their utility, pathophysiology of causing disease, and their response to treatments. Unfortunately, despite active preclinical research using these models, treatment options for ischemic stroke have not significantly advanced since the food and drug administration approval of tissue plasminogen activator in 1996. This review aims to summarize current stroke therapies, the preclinical experimental models used to help develop stroke therapies, as well as their advantages and limitations. In addition, this review discusses the potential for naturally occurring canine ischemic stroke models to compliment current preclinical models and to help bridge the translational gap between small mammal models and human clinical trials.

Susceptibility of the cerebral cortex to spreading depolarization in neurological disease states: The impact of aging

Secondary injury following acute brain insults significantly contributes to poorer neurological outcome. The spontaneous, recurrent occurrence of spreading depolarization events (SD) has been recognized as a potent secondary injury mechanism in subarachnoid hemorrhage, malignant ischemic stroke and traumatic brain injury. In addition, SD is the underlying mechanism of the aura symptoms of migraineurs. The susceptibility of the nervous tissue to SD is subject to the metabolic status of the tissue, the ionic composition of the extracellular space, and the functional status of ion pumps, voltage-gated and other cation channels, glutamate receptors and excitatory amino acid transporters. All these mechanisms tune the excitability of the nervous tissue. Aging has also been found to alter SD susceptibility, which appears to be highest at young adulthood, and decline over the aging process. The lower susceptibility of the cerebral gray matter to SD in the old brain may be caused by the age-related impairment of mechanisms implicated in ion translocations between the intra- and extracellular compartments, glutamate signaling and surplus potassium and glutamate clearance. Even though the aging nervous tissue is thus less able to sustain SD, the consequences of SD recurrence in the old brain have proven to be graver, possibly leading to accelerated lesion maturation. Taken that recurrent SDs may pose an increased burden in the aging injured brain, the benefit of therapeutic approaches to restrict SD generation and propagation may be particularly relevant for elderly patients.

Sex-Dependent Effects of Bmal1-Deficiency on Mouse Cerebral Cortex Infarction in Response to Photothrombotic Stroke

Stroke is a leading cause of disability and death worldwide. There is increasing evidence that occurrence of ischemic stroke is affected by circadian system and sex. However, little is known about the effect of these factors on structural recovery after ischemic stroke. Therefore, we studied infarction in cerebral neocortex of male and female mice with deletion of the clock gene Bmal1 (Bmal1-/-) after focal ischemia induced by photothrombosis (PT). The infarct core size was significantly smaller 14 days (d) as compared to seven days after PT, consistent with structural recovery during the sub-acute phase. However, when sexes were analyzed separately 14 days after PT, infarct core was significantly larger in wild-type (Bmal1+/+) female as compared to male Bmal1+/+ mice, and in female Bmal1+/+, as compared to female Bmal1-/- mice. Volumes of reactive astrogliosis and densely packed microglia closely mirrored the size of infarct core in respective groups. Estradiol levels were significantly higher in female Bmal1-/- as compared to Bmal1+/+ mice. Our data suggests a sex-dependent effect and an interaction between sex and genotype on infarct size, the recruitment of astrocytes and microglia, and a relationship of these cells with structural recovery probably due to positive effects of estradiol during the subacute phase.

Elucidating sex differences in response to cerebral ischemia: immunoregulatory mechanisms and the role of microRNAs

Cerebral ischemia remains a major cause of death and disability worldwide, yet therapeutic options remain limited. Differences in sex and age play an important role in the final outcome in response to cerebral ischemia in both experimental and clinical studies: males have a higher risk and worse outcome than females at younger ages and this trend reverses in older ages. Although the molecular mechanisms underlying sex dimorphism are complex and are still not well understood, studies suggest steroid hormones, sex chromosomes, differential cell death and immune pathways, and sex-specific microRNAs may contribute to the outcome following cerebral ischemia. This review focuses on differential effects between males and females on cell death and immunological pathways in response to cerebral ischemia, the central role of innate sex differences in steroid hormone signaling, and upstreamregulation of sexually dimorphic gene expression by microRNAs.

Age and Sex Are Critical Factors in Ischemic Stroke Pathology

Ischemic stroke is a devastating brain injury resulting in high mortality and substantial loss of function. Understanding the pathophysiology of ischemic stroke risk, mortality, and functional loss is critical to the development of new therapies. Age and sex have a complex and interactive effect on ischemic stroke risk and pathophysiology. Aging is the strongest nonmodifiable risk factor for ischemic stroke, and aged stroke patients have higher mortality and morbidity and poorer functional recovery than their young counterparts. Importantly, patient age modifies the influence of patient sex in ischemic stroke. Early in life, the burden of ischemic stroke is higher in men, but stroke becomes more common and debilitating for women in elderly populations. The profound effects of sex and age on clinical ischemic stroke are mirrored in the results of experimental in vivo and in vitro studies. Here, we review current knowledge on the influence of age and sex in the incidence, mortality, and functional outcome of ischemic stroke in clinical populations. We also discuss the experimental evidence for sex and age differences in stroke pathophysiology and how a better understanding of these biological variables can improve clinical care and enhance development of novel therapies.

Age-related changes in the gut microbiota influence systemic inflammation and stroke outcome

Objective

Chronic systemic inflammation contributes to the pathogenesis of many age‐related diseases. Although not well understood, alterations in the gut microbiota, or dysbiosis, may be responsible for age‐related inflammation.

Methods

Using stroke as a disease model, we tested the hypothesis that a youthful microbiota, when established in aged mice, produces positive outcomes following ischemic stroke. Conversely, an aged microbiota, when established in young mice, produces negative outcomes after stroke. Young and aged male mice had either a young or an aged microbiota established by fecal transplant gavage (FTG). Mice were subjected to ischemic stroke (middle cerebral artery occlusion; MCAO) or sham surgery. During the subsequent weeks, mice underwent behavioral testing and fecal samples were collected for 16S ribosomal RNA analysis of bacterial content.

Results

We found that the microbiota is altered after experimental stroke in young mice and resembles the biome of uninjured aged mice. In aged mice, the ratio of Firmicutes to Bacteroidetes (F:B), two main bacterial phyla in gut microbiota, increased ∼9‐fold (p < 0.001) compared to young. This increased F:B ratio in aged mice is indicative of dysbiosis. Altering the microbiota in young by fecal gavage to resemble that of aged mice (∼6‐fold increase in F:B ratio, p < 0.001) increased mortality following MCAO, decreased performance in behavioral testing, and increased cytokine levels. Conversely, altering the microbiota in aged to resemble that of young (∼9‐fold decrease in F:B ratio, p < 0.001) increased survival and improved recovery following MCAO.

Interpretation

Aged biome increased the levels of systemic proinflammatory cytokines. We conclude that the gut microbiota can be modified to positively impact outcomes from age‐related diseases. Ann Neurol 2018;83:23–36

Ischemic stroke across sexes: What is the status quo?

Stroke prevalence is expected to increase in the next decades due to the aging of the Western population. Ischemic stroke (IS) shows an age- and sex-dependent distribution in which men represent the most affected population within 65 years of age, being passed by post-menopausal women in older age groups. Furthermore, a sexual dimorphism concerning risk factors, presentation and treatment of IS has been widely recognized. In order to address these phenomena, a number of issue have been raised involving both socio-economical and biological factors. The latter can be either dependent on sex hormones or due to intrinsic factors. Although women have poorer outcomes and are more likely to die after a cerebrovascular event, they are still underrepresented in clinical trials and this is mirrored by the lack of sex-tailored therapies. A greater effort is needed in the future to ensure improved treatment and quality of life to both sexes.

Ischemic stroke and select adipose-derived and sex hormones: a review

Ischemic stroke is the fifth leading cause of death in the USA and is the leading cause of serious, long-term disability worldwide. The principle sex hormones (estrogen, progesterone, and testosterone), both endogenous and exogenous, have profound effects on various stroke outcomes and have become the focus of a number of studies evaluating risk factors and treatment options for ischemic stroke. In addition, the expression of other hormones that may influence stroke outcome, including select adipose-derived hormones (adiponectin, leptin, and ghrelin), can be regulated by sex hormones and are also the focus of several ischemic stroke studies. This review aims to summarize some of the preclinical and clinical studies investigating the principle sex hormones, as well as select adipose-derived hormones, as risk factors or potential treatments for ischemic stroke. In addition, the potential for relaxin, a lesser studied sex hormone, as a novel treatment option for ischemic stroke is explored.

Ischemic stroke across sexes: what is the status quo?

Stroke prevalence is expected to increase in the next decades due to the aging of the Western population. Ischemic stroke (IS) shows an age- and sex-dependent distribution in which men represent the most affected population within 65 years of age, being passed by post-menopausal women in older age groups. Furthermore, a sexual dimorphism concerning risk factors, presentation and treatment of IS has been widely recognized. In order to address these phenomena, a number of issue have been raised involving both socio-economical and biological factors. The latter can be either dependent on sex hormones or due to intrinsic factors. Although women have poorer outcomes and are more likely to die after a cerebrovascular event, they are still underrepresented in clinical trials and this is mirrored by the lack of sex-tailored therapies. A greater effort is needed in the future to ensure improved treatment and quality of life to both sexes.

Pannexin1 knockout and blockade reduces ischemic stroke injury in female, but not in male mice

The membrane channel Pannexin 1 (Panx1) mediates apoptotic and inflammatory signaling cascades in injured neurons, responses previously shown to be sexually dimorphic under ischemic conditions. We tested the hypothesis that Panx1 plays an underlying role in mediating sex differences in stroke outcome responses. Middle-aged, 8-9 month old male and female wild type and Panx1 KO mice were subjected to permanent middle cerebral artery (MCA) occlusion, and infarct size and astrocyte and microglia activation were assessed 4 days later. The sexually dimorphic nature of Panx1 deletion was also explored by testing the effect of probenecid a known Panx1 blocker to alter stroke volume. Panx1 KO females displayed significantly smaller infarct volumes (~ 50 % reduction) compared to their wild-type counterparts, whereas no such KO effect occurred in males. This sex-specific effect of Panx1 KO was recapitulated by significant reductions in peri-infarct inflammation and astrocyte reactivity, as well as smaller infarct volumes in probenecid treated females, but not males. Finally, females showed overall, higher Panx1 protein levels than males under ischemic conditions. These findings unmask a deleterious role for Panx1 in response to permanent MCA occlusion, that is unique to females, and provide several new frameworks for understanding sex differences in stroke outcome.

Stroke sensitivity in the aged: sex chromosome complement vs. gonadal hormones

Stroke is a sexually dimorphic disease. Elderly women not only have higher stroke incidence than age-matched men, but also have poorer recovery and higher morbidity and mortality after stroke. In older, post-menopausal women, gonadal hormone levels are similar to that of men. This suggests that tissue damage and functional outcomes are influenced by biologic sex (XX vs. XY) rather than the hormonal milieu at older ages. We employed the Four Core Genotype (FCG) mouse model to study the contribution of sex chromosome complement and gonadal hormones to stroke sensitivity in aged mice in which the testis determining gene (Sry) is removed from the Y chromosome, allowing for the generation of XX males and XY females. XXF, XXM, XYF, XYM and XYwt aged mice were subjected to middle cerebral artery occlusion (MCAO). XXF and XXM mice had significantly larger infarct volumes than XYF and XYM cohorts respectively. There was no significant difference in hormone levels among aged FCG mice. XXF/XXM mice also had more robust microglial activation and higher serum levels of pro-inflammatory cytokines than XYF/XYM cohort respectively. We concluded that the sex chromosome complement contributes to ischemic sensitivity in aged animals and leads to sex differences in innate immune responses.

Sex differences in neuroinflammation and neuroprotection in ischemic stroke

Stroke is not only a leading cause of mortality and morbidity worldwide it also disproportionally affects women. There are currently over 500,000 more women stroke survivors in the US than men, and elderly women bear the brunt of stroke-related disability. Stroke has dropped to the fifth leading cause of death in men, but remains the third in women. This review discusses sex differences in common stroke risk factors, the efficacy of stroke prevention therapies, acute treatment responses, and post-stroke recovery in clinical populations. Women have an increased lifetime risk of stroke compared to men, largely due to a steep increase in stroke incidence in older postmenopausal women, yet most basic science studies continue to only evaluate young male animals. Women also have an increased lifetime prevalence of many common stroke risk factors, including hypertension and atrial fibrillation, as well as abdominal obesity and metabolic syndrome. None of these age-related risk factors have been well modeled in the laboratory. Evidence from the bench has implicated genetic and epigenetic factors, differential activation of cell-death programs, cell-cell signaling pathways, and systemic immune responses as contributors to sex differences in ischemic stroke. The most recent basic scientific findings have been summarized in this review, with an emphasis on factors that differ between males and females that are pertinent to stroke outcomes. Identification and understanding of the underlying biological factors that contribute to sex differences will be critical to the development of translational targets to improve the treatment of women after stroke. © 2016 Wiley Periodicals, Inc.

Sex differences in ischaemic stroke: potential cellular mechanisms

Stroke remains a leading cause of mortality and disability worldwide. More women than men have strokes each year, in part because women live longer. Women have poorer functional outcomes, are more likely to need nursing home care and have higher rates of recurrent stroke compared with men. Despite continued advancements in primary prevention, innovative acute therapies and ongoing developments in neurorehabilitation, stroke incidence and mortality continue to increase due to the aging of the U.S.

POPULATION

Sex chromosomes (XX compared with XY), sex hormones (oestrogen and androgen), epigenetic regulation and environmental factors all contribute to sex differences. Ischaemic sensitivity varies over the lifespan, with females having an "ischaemia resistant" phenotype that wanes after menopause, which has recently been modelled in the laboratory. Pharmacological therapies for acute ischaemic stroke are limited. The only pharmacological treatment for stroke approved by the Food and Drug Administration (FDA) is tissue plasminogen activator (tPA), which must be used within hours of stroke onset and has a number of contraindications. Pre-clinical studies have identified a number of potentially efficacious neuroprotective agents; however, nothing has been effectively translated into therapy in clinical practice. This may be due, in part, to the overwhelming use of young male rodents in pre-clinical research, as well as lack of sex-specific design and analysis in clinical trials. The review will summarize the current clinical evidence for sex differences in ischaemic stroke, and will discuss sex differences in the cellular mechanisms of acute ischaemic injury, highlighting cell death and immune/inflammatory pathways that may contribute to these clinical differences.

Sex differences in stroke across the lifespan: The role of T lymphocytes

Stroke is a sexually dimorphic disease. Ischemic sensitivity changes throughout the lifespan and outcomes depend largely on variables like age, sex, hormonal status, inflammation, and other existing risk factors. Immune responses after stroke play a central role in how these factors interact. Although the post-stroke immune response has been extensively studied, the contribution of lymphocytes to stroke is still not well understood. T cells participate in both innate and adaptive immune responses at both acute and chronic stages of stroke. T cell responses also change at different ages and are modulated by hormones and sex chromosome complement. T cells have also been implicated in the development of hypertension, one of the most important risk factors for vascular disease. In this review, we highlight recent literature on the lymphocytic responses to stroke in the context of age and sex, with a focus on T cell response and the interaction with important stroke risk factors.

Sex differences in vascular physiology and pathophysiology: estrogen and androgen signaling in health and disease

Sex differences between women and men are often overlooked and underappreciated when studying the cardiovascular system. It has been long assumed that men and women are physiologically similar, and this notion has resulted in women being clinically evaluated and treated for cardiovascular pathophysiological complications as men. Currently, there is increased recognition of fundamental sex differences in cardiovascular function, anatomy, cell signaling, and pathophysiology. The National Institutes of Health have enacted guidelines expressly to gain knowledge about ways the sexes differ in both normal function and diseases at the various research levels (molecular, cellular, tissue, and organ system). Greater understanding of these sex differences will be used to steer future directions in the biomedical sciences and translational and clinical research. This review describes sex-based differences in the physiology and pathophysiology of the vasculature, with a special emphasis on sex steroid receptor (estrogen and androgen receptor) signaling and their potential impact on vascular function in health and diseases (e.g., atherosclerosis, hypertension, peripheral artery disease, abdominal aortic aneurysms, cerebral aneurysms, and stroke).

[Sex differences in acute disturbances of cerebral blood circulation]

It is shown that in the development of stroke observed sex differences, which manifest themselves both clinically and by laboratory parameters. While men have a higher incidence of stroke for most of his life, a woman in a more advanced age have a higher risk for stroke. Sex differences in the development of stroke depend on several factors, including genetic and hormonal changes throughout life. Studies sex differences in the risk of stroke is only in the initial stage, but the first results show that there are differences in neuronal cell death in males and females after experimental ischemic stroke. A better understanding of the mechanisms underlying the development of stroke in men and women will lead to more appropriate treatment strategies for patients of both sexes.

An rs13293512 polymorphism in the promoter of let-7 is associated with a reduced risk of ischemic stroke

The expression of let-7 family members was differentiated in ischemic stroke (IS), functioning as an important regulating molecular in the pathophysiology of stroke. We hypothesized that genetic polymorphism in the promoters of let-7 family may be associated with the risk of IS. To test this hypothesis, we investigated the association of the rs10877887 and rs13293512 in the promoters of let-7 family with the susceptibility to IS. A hospital-based case-control study was performed. The rs10877887 genotype was determined by using a polymerase chain reaction-restriction fragment length polymorphism assay, and the rs13293512 genotype was determined by using a TaqMan assay. We found that the rs13293512CC genotype was associated with a reduced risk of IS (CC vs. TT: adjusted OR = 0.43, 95 % CI 0.26-0.71; dominant model: adjusted OR = 0.70, 95 % CI 0.49-0.98; recessive model: adjusted OR = 0.45, 95 % CI, 0.28-0.73). Stratification analysis showed that the rs10877887TT carriers had a higher level of total cholesterol compared to rs10877887TC/CC carriers (P = 0.03). Combined analysis showed that the rs10877887TC/CC and rs13293512TC/CC genotypes had a reduced risk of IS risk (adjusted OR = 0.58, 95 % CI 0.36-0.95). Our findings suggest that the rs13293512 polymorphism may be a protective factor for the development of IS.

Sex Differences in the Cerebral Collateral Circulation

Premenopausal women and intact female rodents sustain smaller cerebral infarctions than males. Several sex-dependent differences have been identified as potential contributors, but many questions remain unanswered. Mice exhibit wide variation in native collateral number and diameter (collateral extent) that is dependent on differences in genetic background, aging, and other comorbidities and that contributes to their also-wide differences in infarct volume. Likewise, variation in infarct volume correlates with differences in collateral-dependent blood flow in patients with acute ischemic stroke. We examined whether extent of pial collateral arterioles and posterior communicating collateral arteries (PComAs) differ depending on sex in young, aged, obese, hypertensive, and genetically different mice. We combined new data with meta-analysis of our previously published data. Females of C57BL/6J (B6) and BALB/cByJ (BC) strains sustained smaller infarctions than males after permanent MCA occlusion. This protection was unchanged in BC mice after introgression of the B6 allele of Dce1, the major genetic determinant of variation in pial collaterals among mouse strains. Consistent with this, collateral extent in these and other strains did not differ with sex. Extent of PComAs and primary cerebral arteries also did not vary with sex. No dimorphism was evident for loss of pial collateral number and/or diameter (collateral rarefaction) caused by aging, obesity, and hypertension, nor for collateral remodeling after pMCAO. However, rarefaction was greater in females with long-standing hypertension. We conclude that smaller infarct volume in female mice is not due to greater collateral extent, greater remodeling, or less rarefaction caused by aging, obesity, or hypertension.

Spatiotemporal Progression of Microcalcification in the Hippocampal CA1 Region following Transient Forebrain Ischemia in Rats: An Ultrastructural Study

Calcification in areas of neuronal degeneration is a common finding in several neuropathological disorders including ischemic insults. Here, we performed a detailed examination of the onset and spatiotemporal profile of calcification in the CA1 region of the hippocampus, where neuronal death has been observed after transient forebrain ischemia. Histopathological examinations showed very little alizarin red staining in the CA1 pyramidal cell layer until day 28 after reperfusion, while prominent alizarin red staining was detected in CA1 dendritic subfields, particularly in the stratum radiatum, by 14 days after reperfusion. Electron microscopy using the osmium/potassium dichromate method and electron probe microanalysis revealed selective calcium deposits within the mitochondria of degenerating dendrites at as early as 7 days after reperfusion, with subsequent complete mineralization occurring throughout the dendrites, which then coalesced to form larger mineral conglomerates with the adjacent calcifying neurites by 14 days after reperfusion. Large calcifying deposits were frequently observed at 28 days after reperfusion, when they were closely associated with or completely engulfed by astrocytes. In contrast, no prominent calcification was observed in the somata of CA1 pyramidal neurons showing the characteristic features of necrotic cell death after ischemia, although what appeared to be calcified mitochondria were noted in some degenerated neurons that became dark and condensed. Thus, our data indicate that intrahippocampal calcification after ischemic insults initially occurs within the mitochondria of degenerating dendrites, which leads to the extensive calcification that is associated with ischemic injuries. These findings suggest that in degenerating neurons, the calcified mitochondria in the dendrites, rather than in the somata, may serve as the nidus for further calcium precipitation in the ischemic hippocampus.

Relationship Between Dynamic Changes in Expression of IL-17/IL-23 in Lacrimal Gland and Ocular Surface Lesions in Ovariectomized Mice

PURPOSE

An ovariectomized mouse model was constructed to observe the dynamic effects of hormone changes on the expression of interleukin (IL)-17A and IL-23 in the lacrimal glands.

METHODS

The ovariectomized mouse model was constructed by bilateral ovary removal. The concentrations of serum estradiol and testosterone in mouse cardiac blood were detected by radioimmunoassay. Mice in both groups underwent the phenol red cotton thread test and corneal fluorescein staining to assess the ocular surface, whereas Th17 cells in blood and spleen were detected by flow cytometry. IL-17A and IL-23 expression in the lacrimal glands was detected by immunohistochemistry, enzyme-linked immunosorbent assay, and real-time fluorescence quantitative polymerase chain reaction.

RESULTS

Serum estradiol and testosterone levels were significantly lower in the ovariectomized group compared with those in the control group. There was lymphocytic infiltration in the lacrimal gland of the ovariectomized group mice. At 6 months after the surgery, aqueous tear production was significantly lower, and statistically significant corneal fluorescein staining was found in the ovariectomized group, compared with that in the control group. In the ovariectomized group, IL-17A and the IL-23 expression in the lacrimal glands and the Th17 expression in the blood and spleen were significantly higher than in the control group.

CONCLUSION

The hormone levels are significantly reduced and lymphocytic infiltration in the lacrimal gland in ovariectomized mice, whereas the frequency of Th17 cells in the blood and spleen and IL-17A and IL-23 expression in the lacrimal glands are increased, leading to reduced tear production and positive fluorescein staining in the cornea.