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.

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.

Ischemic stroke is major cause of disability and mortality worldwide, and aging is strong risk factor for poor post-stroke outcome. Neutrophils traffic rapidly to the brain following ischemic stroke, and recent evidence has suggested that aging may alter neutrophil function after tissue injury. In this study, we hypothesize that aging enhances the pro-inflammatory function of neutrophils, directly contributing to the poorer outcomes seen in aging patients. We utilized demographic data and biological specimens from ischemic stroke patients and an experimental mouse model to determine the correlation between age, neutrophil function and stroke outcomes. In ischemic stroke patients, age was associated with increased mortality and morbidity and higher levels of neutrophil-activating cytokines. In mice, aged animals had higher stroke mortality and morbidity, higher levels of neutrophil-activating cytokines and enhanced generation of neutrophil reactive oxygen species compared to young mice. Finally, depletion of neutrophils via a specific monoclonal antibody after ischemic stroke led to long-term benefits in functional outcome in aged male and female animals, with no benefit observed in young. These results demonstrate that aging is associated with augmented neutrophil pathogenicity in ischemic stroke, and that neutrophil-targeted therapies may confer greater benefit in aged subjects.

The prevalence of cardiovascular disease has increased among middle-aged women in the United States, yet has declined in middle-aged men. In experimental stroke, middle-aged females have larger strokes and greater inflammation than age-matched males or younger females. The mechanism underlying this shift from an “ischemia-protected” to an “ischemia-sensitive” phenotype in aging females is unknown. One potential factor is an age-related increase in systemic factors that induce inflammation. Increased abdominal fat deposition is seen in women during middle age. Adipose tissue plays a key role in obesity-induced systemic inflammation, including increased pro-inflammatory cytokines. We hypothesized that age and sex differences in adipose immune cells promote an augmented pro-inflammatory milieu in middle-aged females driven by a balance shift between pro-inflammatory and anti-inflammatory T cells. Abdominal adipose tissue immune cells from young (3–4 months) and middle-aged (15–16 months) male and female C57BL/6J mice were analyzed by flow cytometry. Plasma triglyceride (TG), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) levels were determined with colorimetric assays. Middle-aged mice had higher adipose tissue mass compared to young mice. Lipid profiling showed no sex differences in TG and LDL, but middle-aged females had lower HDL (0.84 ± 0.07 μg/μl) than middle-aged males (1.35 ± 0.06 μg/μl). Flow cytometry data demonstrated an age-associated increase in adipose tissue CD8+ T cells that was augmented by female sex, with middle-aged females having a higher percentage of CD8+ cells (34.4 ± 3.2% of CD3+ T cells) than middle-aged males (24.4 ± 2.2%). This increase in CD8+ T-cell proportion was adipose tissue-specific, as this change was not observed in blood. Middle-aged females had higher numbers of activated (CD69+) CD8+ T cells than males. In addition, female CD8+ T cells produced higher levels of IFN-γ, TNF-α, and granzyme B ex vivo, and females had higher adipose levels of IFN-γ, RANTES and MIP-1β than middle-aged males. In parallel, females had lower levels of regulatory T cells (Tregs), an anti-inflammatory T-cell subtype, compared to age-matched males. In conclusion, middle-aged females have a detrimental combination of elevated pro-inflammatory T cells and decreased anti-inflammatory Tregs in adipose tissue, which may promote a pro-inflammatory milieu and contribute to increased cardiovascular disease burden in aging females.

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Females show a varying degree of ischemic sensitivity throughout their lifespan, which is not fully explained by hormonal or genetic factors. Epidemiological data suggest that sex-specific life experiences such as pregnancy increase stroke risk. This work evaluated the role of parity on stroke outcome. Age-matched virgin (i.e., nulliparous) and multiparous mice were subjected to 60 min of reversible middle cerebral artery occlusion and evaluated for infarct volume, behavioral recovery, and inflammation. Using an established mating paradigm, fetal microchimeric cells present in maternal mice were also tracked after parturition and stroke. Parity was associated with sedentary behavior, weight gain, and higher triglyceride and cholesterol levels. The multiparous brain exhibited features of immune suppression, with dampened baseline microglial activity. After acute stroke, multiparous mice had smaller infarcts, less glial activation, and less behavioral impairment in the critical recovery window of 72 h. Behavioral recovery was significantly better in multiparous females compared with nulliparous mice 1 mo after stroke. This recovery was accompanied by an increase in poststroke angiogenesis that was correlated with improved performance on sensorimotor and cognitive tests. Multiparous mice had higher levels of VEGF, both at baseline and after stroke. GFP + fetal cells were detected in the blood and migrated to areas of tissue injury where they adopted endothelial morphology 30 d after injury. Reproductive experience has profound and complex effects on neurovascular health and disease. Inclusion of female mice with reproductive experience in preclinical studies may better reflect the life-long patterning of ischemic stroke risk in women.sex differences | multiparity | microglia | ischemic stroke | microchimerism N early 800,000 people in the United States experience a new or recurrent stroke each year, and 55,000 more women than men are affected by stroke (1). Stroke is a sexually dimorphic disease impacted by genetics, hormones, and the environment (2). According to CDC data, 85% of women in the United States have given birth by age 40, whereas the number of lifetime pregnancies per woman varies by race and socioeconomic status. Therefore, child-bearing women represent a significant proportion of the female population, including those at risk for stroke. Moreover, this suggests that a large proportion of the elderly female populationwho is at highest risk for stroke-may be differentially at risk. Epidemiological data suggest that increasing parity is associated with higher risk of cardiovascular disease (CVD) and stroke and late-life vascular comorbidities, including carotid atherosclerosis (3, 4). However, recent reports suggest that parity has a significant protective effect against CVD mortality (5). The effect of parity on outcome following ischemic stroke is yet unresolved.Pregnancy induces profound acute and long-term physiological changes in the body that influence future vascular health through hormonally med...

Introduction: Sex differences in ischemic stroke are seen in clinical and experimental studies. Men have a higher risk of stroke throughout most of the life-span. Women have greater stroke mortality than men, however a recent multi-continental meta-analysis showed lower mortality in women when adjusted for age, pre-morbid function, stroke severity and other confounding factors. In experimental models, middle-aged female mice have larger strokes, likely due to the loss of estrogen. Less is known about outcomes in very aged animals. Hypothesis: Inflammatory responses are key determinants of stroke outcome and there are important sex differences in the immune response in aged mice. Methods: Male and female C57BL/6 mice (21-22 months) were subjected to 60 min middle cerebral artery occlusion (n=28-32), or sham surgery (n=16). Neutrophils and T cells were quantified in brain and blood at 24 h and 15 days post-stroke by flow cytometry. Functional outcomes were assessed at day 3, 7 and 14. Results: Male mortality was significantly higher than in females (41% vs 16%, P<0.05). Hemorrhagic transformation was seen in 55% of the males that died (6/11) and in none of the females (0/4). Aged males had greater stroke-induced loss of body temperature, splenic contraction and gut permeability (FITC-dextran assay, n=6-7, P<0.05). Acutely after stroke (24 h), aged males had significantly higher brain infiltration of neutrophils and plasma levels of MCP-1 and G-CSF compared to females. Aged males had elevated levels of CD8 + T cells in the blood compared to females at day 15 (73±5% of CD3 + T cells vs 52±3%, P<0.001). Brain T regulatory cells were increased after stroke in males (P<0.01), but not in females. Open-field test showed decreased center visits after stroke at day 3, however males spent more time immobile (P<0.01), indicating decreased locomotor activity/anxiety. This difference equalized at 7 and 14 days post-stroke. Conclusion: Higher mortality and hemorrhagic transformation rates were seen in aged males compared to females after ischemic stroke. This was associated with higher levels of neutrophils/Tregs in the brain and CD8 + T cells in the blood suggesting a greater stroke-induced immune response in aged males.

Background and Purpose: Age and sex have important effects on stroke-induced inflammation. We conducted CBC analysis and RNA-sequencing of ischemic stroke patient blood, with follow-up studies in an experimental mouse model, to test the hypothesis that there are sex differences in neutrophil function and neutrophil-mediated damage after ischemic stroke. Methods: Blood from male and female stroke patients was collected 24 hours after stroke, with transient ischemic attack patients serving as controls. Absolute neutrophil count was quantified and RNA-sequencing was performed on an age and severity matched subset of patients. Results were analyzed by multivariate regression and differential expression analysis, respectively. For animal experiments, aged (18-20 month) and young (8-10 week) male and female mice were subjected to 60 minute middle cerebral artery occlusion and sacrificed at 24 hours. Neutrophils from blood, bone marrow, lung, brain and spleen were quantified and phenotyped by flow cytometry. Results were analyzed by student T-test and two way ANOVA. Results: Absolute neutrophil counts increased significantly after stroke in both sexes (p=.01). Interestingly, females had more differentially expressed genes after stroke than males, including matrix metalloproteinase 9 and TNFa. In animal experiments, aged animals were found to have higher percentages of neutrophils in the blood, spleen, lungs and bone marrow than young animals. In addition, aged female animals were found to have more activated neutrophils 24 hours after stroke than aged males (p=<.05). Conclusion: These results suggest that the immune response to ischemic stroke differs in aged males and females. Female neutrophils appear to exhibit enhanced activation, which may contribute to the poorer stroke outcomes seen in aged female patients. Understanding sex and age differences in the acute immune response is crucial to developing future immunomodulatory drugs for the safe and effective treatment of ischemic stroke in both sexes.