Platelet characteristics change with aging: role of estrogen receptor beta

Integrated liver and serum proteomics uncover sexual dimorphism and alteration of several immune response proteins in an aging Werner syndrome mouse model

Werner syndrome (WS) is a progeroid disorder caused by mutations in a protein containing both a DNA exonuclease and DNA helicase domains. Previous studies indicated that males lacking the helicase domain of the Wrn protein orthologue exhibited hepatic transcriptomic and metabolic alterations. In this study, we used a label-free liquid chromatography-tandem mass spectrometry approach to uncover proteins abundance associated with specific biological processes that differed depending on the age (four or ten months) and/or the genotype (wild type or Wrn mutant) in the serum and liver of mice. Principal component analysis of the proteomic data from both serum and hepatic tissue revealed a sexual dimorphism regardless of the age and the genotype of the mice. Moreover, although all Wrn mutant mice exhibited fatty liver by the age of ten months, a significant age and genotype dependent enrichment of proteins involved in lipid and fatty acid metabolic processes were uncovered only in males. Also, a genotype dependent increase in serum oxidant detoxification processes was observed in the serum of Wrn mutant males. Despite these sexual differences, several aspects of the immune system were affected in both females and males. Finally, an increase of specific immunoglobulin molecules was common in the liver and serum of both older Wrn mutant females and males. Such results suggest that specific immunoglobulin variants maybe associated with fatty liver progression in WS.

Single-cell transcriptomics of peripheral blood in the aging mouse

Compositional and transcriptional changes in the hematopoietic system have been used as biomarkers of immunosenescence and aging. Here, we use single-cell RNA-sequencing to study the aging peripheral blood in mice and characterize the changes in cell-type composition and transcriptional profiles associated with age. We identified 17 clusters from a total of 14,588 single cells. We detected a general upregulation of antigen processing and presentation and chemokine signaling pathways and a downregulation of genes involved in ribosome pathways with age. In old peripheral blood, we also observed an increased percentage of cells expressing senescence markers (Cdkn1a, and Cdkn2a). In addition, we detected a cluster of activated T cells exclusively found in old blood, with lower expression of Cd28 and higher expression of Bcl2 and Cdkn2a, suggesting that the cells are senescent and resistant to apoptosis.

Evaluation of sex differences in the relationship between diastolic dysfunction and thromboembolism using propensity score analysis

BACKGROUND

Female sex is a risk factor for thromboembolism (TE) in atrial fibrillation (AF); however, the underlying mechanisms are unclear. We postulated that left ventricular (LV) diastolic dysfunction (LVDD) could be associated with increased thromboembolic risk in women.

METHODS

From a retrospective cohort, 158 patients (female : male = 79:79) with nonvalvular AF were propensity score-matched for age, presence of diabetes, hypertension, coronary artery disease, congestive heart failure, embolic history, AF type, and AF duration. Cardiac size and function and central aortic stiffness parameters were evaluated. Diastolic function was classified as normal, indeterminate, and LVDD according to recent guidelines. Surrogate markers for thromboembolism (dense spontaneous echo contrast and thrombus) were evaluated using transesophageal echocardiography.

RESULTS

Surrogate markers for TE showed a trend to be more frequent in women than in men (21.5% vs 11.4%, P = .086). LVDD was more prevalent in women than in men (22.8% vs 2.5%, P < .001); however, the prevalence of indeterminate diastolic function was not different between sexes (26.6% vs 20.3%, P = .453). Surrogate markers for TE were detected mostly in women with LVDD. LV diastolic parameters showed a restrictive pattern, and aortic stiffness parameters were worse in women than in men. Women with LVDD had increased aortic stiffness compared to women with indeterminate and normal function, whereas aortic stiffness did not differ among men in all groups. Significant relations between LV diastolic function and aortic stiffness parameters were observed only in women.

CONCLUSION

LVDD due to increased aortic stiffness could be related to a higher thromboembolic risk in women with AF.

Platelet function and ageing

There are clear age-related changes in platelet count and function, driven by changes in hematopoietic tissue, the composition of the blood and vascular health. Platelet count remains relatively stable during middle age (25–60 years old) but falls in older people. The effect of age on platelet function is slightly less clear. The longstanding view is that platelet reactivity increases with age in an almost linear fashion. There are, however, serious limitations to the data supporting this dogma. We can conclude that platelet function increases during middle age, but little evidence exists on the changes in platelet responsiveness in old age (>75 years old). This change in platelet function is driven by differential mRNA and microRNA expression, an increase in oxidative stress and changes in platelet receptors. These age-related changes in platelets are particularly pertinent given that thrombotic disease and use of anti-platelet drugs is much more prevalent in the elderly population, yet the majority of platelet research is carried out in young to middle-aged (20–50 years old) human volunteers and young mice (2–6 months old). We know relatively little about exactly how platelets from people over 75 years old differ from those of middle-aged subjects, and we know even less about the mechanisms that drive these changes. Addressing these gaps in our knowledge will provide substantial understanding in how cell signalling changes during ageing and will enable the development of more precise anti-platelet therapies.

Age-related changes in platelet function are more profound in women than in men

Age is a risk factor for cardiovascular disease (CVD), however the effect of age on platelet function remains unclear. Ideally, platelet function should be assayed under flow and shear conditions that occur in vivo. Our study aimed to characterise the effect of age on platelet translocation behaviour using a novel flow-based assay that measures platelet function in less than 200 μl of blood under conditions of arterial shear. Blood from males (n = 53) and females (n = 56), ranging in age from 19–82 and 21–70 respectively were perfused through custom-made parallel plate flow chambers coated with immobilised human von Willebrand Factor (VWF) under arterial shear (1,500s⁻¹). Platelet translocation behaviour on VWF was recorded by digital-image microscopy and analysed. The study showed that aging resulted in a significant decrease in the number of platelet tracks, translocating platelets and unstable platelet interactions with VWF. These age related changes in platelet function were more profound in women than in men indicating that age and gender significantly impacts on platelet interactions with VWF.

Female sex as an independent risk factor for stroke in atrial fibrillation: possible mechanisms

Atrial fibrillation (AF) is an independent risk factor for thromboembolism and stroke. Women with AF are at a higher overall risk for thromboembolic stroke when compared to men with AF. Recent evidence suggests that female sex, after adjusting for stroke risk profile and sex differences in utilisation of anticoagulation, is an independent stroke risk factor in AF. The inclusion of female sex has improved the accuracy of the CHADS2 stroke risk stratification schema (Congestive heart failure, Hypertension, Age 75 years or greater, Diabetes mellitus, and prior Stroke or TIA). The newly revised and validated schema, CHA2DS2-VASc, dichotomises age and incorporates female sex and vascular disease history. The pathophysiological mechanisms to explain this increased risk in women are not well understood. According to Virchow's triad, thrombosis that leads to stroke in AF should arise from three co-existing phenomena: structural abnormalities, blood stasis, and a hypercoagulable state. Herein, we explore the sex differences in the biological processes that lead to thrombus formation as applied to Virchow's Triad. The objective of this review is to describe the potential mechanisms behind the increased risk of stroke in AF associated with female sex.

Changes in mitochondrial energy utilization in young and old worker honeybees (Apis mellifera)

Trophocytes and fat cells in honeybees (Apis mellifera) have served as targets for cellular senescence studies, but mitochondrial energy utilization with advancing age in workers is unknown. In this study, mitochondrial energy utilization was evaluated in the trophocytes and fat cells of young and old workers reared in a field hive. The results showed that (1) mitochondrial density increased with advancing age; (2) mitochondrial membrane potential (∆Ψm), nicotinamide adenine dinucleotide oxidized form (NAD(+)) concentration, adenosine triphosphate (ATP) concentration, and NAD(+)/nicotinamide adenine dinucleotide reduced form (NADH) ratio decreased with advancing age; and (3) the expression of NADH dehydrogenase 1 (ND1), ATP synthase, and voltage-dependent anion channel 1 (VDAC1) increased with advancing age, whereas ND1 and ATP synthase did not differ with advancing age after normalization to mitochondrial density and VDAC1. These results show that the trophocytes and fat cells of young workers have higher mitochondrial energy utilization efficiency than those of old workers and that aging results in a decline in mitochondrial energy utilization in the trophocytes and fat cells of worker honeybees.

Evaluation of microparticles in whole blood by multicolour flow cytometry assay

OBJECTIVE

To develop and evaluate a multicolour flow cytometry method for analysis of microparticles (MPs) in fresh whole blood without any centrifugation steps or freezing/thawing procedure.

MATERIALS AND METHODS

Flow cytometry was performed using a FC500 MPL cytometer. The compensation in the protocol was performed based on the platelet population. Polystyrene microspheres 0.50-1.27 μm were used for size position, and the MP gate was set as particles 0.5-1.0 μm. Whole blood was incubated with annexin V and antibodies to tissue factor (TF), platelets (CD41 and CD62P), monocyte (CD14) and endothelial cells (CD144). For comparison, MPs from platelet free supernatant was used. The TF activity was evaluated by Calibrated Automated Thrombogram.

RESULTS

Annexin V was used to distinguish true events from background noise. For standardization, each analysis included 10,000 events in the gate of platelets. There were 622(462-1001) MP(annV+)/10,000 platelets and of these, 66 (49-82)/10,000 platelets expressed TF. After correction for the individual platelet counts, the amount of circulating MP(annV+) was 17.1 (12.1-24.9) × 10(9)/L in whole blood, and of these, 10% (6-12%) expressed TF. The majority of the MPs expressed CD41, and 5.6% (2.2-6.9%) of these co-expressed TF. The amount of CD41 + MP(annV+) tended to correlate to the TF activity in whole blood. There was no correlation between the MP(annV+) in whole blood and MPs derived from platelet free supernatant. Patients with pulmonary arterial hypertension and stable coronary artery disease had increased concentrations of CD41 + MP(annV+) in whole blood.

CONCLUSION

This multicolour flow cytometry assay in whole blood mimics the in vivo situation by avoiding several procedure steps interfering with the MP count. By standardized quantification of MPs a reference interval of MPs can be created.

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.

Circulating and vein wall P-selectin promote venous thrombogenesis during aging in a rodent model

INTRODUCTION

The objective of this study was to identify the direct relationship between aging and selectin activation during acute venous thrombosis in mice of varying ages. We hypothesized that older animals would have increased venous thrombus formation as a result of age associated-increases of pro-inflammatory molecules within the vein wall when compared to younger animals.

MATERIALS AND METHODS

Deep venous thrombosis (DVT) was induced in 4 and 18month old C57BL/6 mice using the electrolytic inferior vena cava model (EIM) of DVT. Blood and tissue samples were collected at baseline (TC), 6hours, and 2days post-thrombosis induction.

RESULTS

Older mice had significantly larger thrombi versus younger mice at 6H (18.4±6.21 vs. 13.0±4.29×10(-3) grams, p=0.0033) and 2D (18.4±4.27 vs. 13.0±5.01×10(-3) grams, p=0.0005), higher soluble P-selectin levels at 6H (13±2.5 vs. 8.4±2.7ng/mg p=0.0010) and 2D (12.7±5.0 vs. 5.9±1.3ng/mg p=0.0020), and higher vein wall P-selectin levels at 6H (1.94×10(5)±3.56×10(4) vs. 4.81±2.29×10(4) pg/mg p=0.0001) and 2D (1.38×10(5)±5.65×10(4) vs. 3.73±1.66×10(4) pg/mg p=0.0177). Older animals also had significantly higher platelet numbers at 6H (841±203.8 vs. 564±164.8K/μL p=0.0001), and 2D (1002±342.9 vs. 690±186.1K/μL p=0.0003), with corresponding increases in mean platelet volume versus younger mice post thrombosis (p≤0.01).

CONCLUSIONS

Older animals had significantly larger venous thrombi versus younger animals post-thombosis, as a result of high levels of P-selectin both in the circulation and locally at the level of the vein wall. Expression of local and soluble P-selectin increased with age, resulting in a pro-thrombotic environment not represented in younger mice.

Preclinical characterization of a novel diphenyl benzamide selective ERα agonist for hormone therapy in prostate cancer

Androgen deprivation therapy (ADT) is the mainstay of treatment for advanced prostate cancer. ADT improves overall and disease-free survival rates, but long-term therapy is associated with severe side effects of androgen and estrogen depletion including hot flashes, weight gain, depression, and osteoporosis. Effective hormone reduction can be achieved without estrogen deficiency-related side effects by using therapy with estrogenic compounds. However, cardiovascular complications induced by estrogens coupled with the availability of LHRH agonists led to discontinuation of estrogen use for primary androgen deprivation therapy in the 1980s. New treatments for prostate cancer that improve patient outcomes without the serious estrogen deficiency-related toxicities associated with ADT using LHRH analogs are needed. Herein we describe a novel nonsteroidal selective estrogen receptor-α agonist designed for first-line therapy of advanced prostate cancer that in animal models induces medical castration and minimizes many of the estrogen deficiency-related side effects of ADT. The present studies show that orally administered GTx-758 reversibly suppressed testosterone to castrate levels and subsequently reduced prostate volume and circulating prostate-specific antigen in relevant preclinical models without inducing hot flashes, bone loss, thrombophilia, hypercoagulation, or increasing fat mass.

Adenosine and blood platelets

Adenosine is an important regulatory metabolite and an inhibitor of platelet activation. Adenosine released from different cells or generated through the activity of cell-surface ectoenzymes exerts its effects through the binding of four different G-protein-coupled adenosine receptors. In platelets, binding of A(2) subtypes (A(2A) or A(2B)) leads to consequent elevation of intracellular cyclic adenosine monophosphate, an inhibitor of platelet activation. The significance of this ligand and its receptors for platelet activation is addressed in this review, including how adenosine metabolism and its A(2) subtype receptors impact the expression and activity of adenosine diphosphate receptors. The expression of A(2) adenosine receptors is induced by conditions such as oxidative stress, a hallmark of aging. The effect of adenosine receptors on platelet activation during aging is also discussed, as well as potential therapeutic applications.

Sex-based differences in vascular function

Cardiovascular disease is the leading cause of morbidity and mortality for both men and women in the USA. However, there are differences between the sexes in age-dependent onset, severity, symptoms and outcomes. Basic research into the causes of sex-dependent differences in cardiovascular disease is ongoing and includes investigation into genetic variation in expression and distribution of receptors for the sex steroids; specificity of natural and synthetic ligands that activate the sex steroid receptors; and intracellular mechanisms that are activated by the receptors in all components of the vessel wall and blood elements, which integrate to regulate vascular tone, vascular repair and remodeling in health and disease. In this era of personalized medicine, basic research into mechanisms of sex differences in vascular function will result in improved prevention, detection and treatment of cardiovascular disease in both men and women.

The platelet as a model system for the acute actions of nuclear receptors

Platelets are circulating cell fragments which play a critical role in thrombosis, and whose activity is associated with the progress of cardiovascular diseases, diabetes, inflammation, and cancer cell metastasis. Recently, a number of nuclear receptors have been found present in human platelets, including the receptors for sex steroids, and glucocorticoids, along with peroxisome proliferator-activated receptors (PPAR)s and retinoid X receptors (RXR)s. Although the platelet contains no nucleus, selective ligands for these receptors activate their respective platelet nuclear receptors and regulate platelet aggregation and activation. The human platelet, because of its abundance and accessibility therefore represents an excellent model system to study the rapid non-genomic mechanism of nuclear receptors. Moreover, since targeting platelets is a major clinical therapeutic area, analysis of platelet nuclear receptors may provide clues for new drug targets as well as provide important information regarding the physiological roles of nuclear receptors in the circulation.

Loss of estrogen receptor beta decreases mitochondrial energetic potential and increases thrombogenicity of platelets in aged female mice

Platelets derived from aged (reproductively senescent) female mice with genetic deletion of estrogen receptor beta (betaER) are more thrombogenic than those from age-matched wild-type (WT) mice. Intracellular processes contributing to this increased thrombogenicity are not known. Experiments were designed to identify subcellular localization of estrogen receptors and evaluate both glycolytic and mitochondrial energetic processes which might affect platelet activation. Platelets and blood from aged (22-24 months) WT and estrogen receptor beta knockout (betaERKO) female mice were used in this study. Body, spleen weight, and serum concentrations of follicle-stimulating hormone and 17beta-estradiol were comparable between WT and betaERKO mice. Number of spontaneous deaths was greater in the betaERKO colony (50% compared to 30% in WT) over the course of 24 months. In resting (nonactivated) platelets, estrogen receptors did not appear to colocalize with mitochondria by immunostaining. Lactate production and mitochondrial membrane potential of intact platelets were similar in both groups of mice. However, activities of NADH dehydrogenase, cytochrome bc ( 1 ) complex, and cytochrome c oxidase of the electron transport chain were reduced in mitochondria isolated from platelets from betaERKO compared to WT mice. There were a significantly higher number of phosphatidylserine-expressing platelet-derived microvesicles in the plasma and a greater thrombin-generating capacity in betaERKO compared to WT mice. These results suggest that deficiencies in betaER affect energy metabolism of platelets resulting in greater production of circulating thrombogenic microvesicles and could potentially explain increased predisposition to thromboembolism in some elderly females.

Platelet activation is caused not by aging but by atherosclerosis

Platelet activation increases with age, although it is still controversial whether it derives from aging per se or from atherosclerosis concomitant with aging. The purpose of this study is to clarify the association between platelet activation and aging or atherosclerosis. We studied the ultrastructure of platelets in the elderly subjects with or without atherosclerosis and healthy young subjects. The platelet shape changes were evaluated by transmission electron microscopy and the contents of peroxidase and fibrinogen were assessed using a scoring system based on cytochemical staining and immunogold marking methods. No significant differences in platelet shape changes and the contents of peroxidase and fibrinogen in platelet were observed between healthy young and nonatherosclerotic elderly subjects, although the frequency of pseudopods increased and the content of peroxidase decreased in atherosclerotic elderly patients. It is suggested that platelet activation is not derived from aging but from atherosclerosis, although it is difficult to separate aging from coexisting atherosclerosis.

Longitudinal platelet reactivity to acute psychological stress among older men and women

Platelet reactivity to acute stress is associated with increased cardiovascular disease risk; however, little research exists to provide systematic methodological foundations needed to generate strong longitudinal research designs. Study objectives were: 1) to evaluate whether markers of platelet function increase in response to an acute psychological stress test among older adults, 2) to establish whether reactivity remains robust upon repeated administration (i.e. three occasions approximately 1 year apart), and 3) to evaluate whether two different acute speech stress tasks elicit similar platelet responses. The 149 subjects (mean age 71 years) gave a brief impromptu speech on one of two randomly assigned topics involving interpersonal conflict. Blood samples drawn at baseline and post-speech were assayed using flow cytometry for platelet responses on three outcomes (% aggregates, % P-selectin expression, and % fibrinogen receptor expression). Three-level hierarchical linear modeling analyses revealed significant stress-induced increases in platelet activation on all outcomes (p < 0.001). No significant habituation on any measure was found. Additional reactivity differences were associated with male gender, history of myocardial infarction, and use of aspirin, statins, and antidepressants. The results demonstrate that laboratory acute stress tests continued to produce robust platelet reactivity on three activation markers among older adults over 3 years.

Increased cardiovascular mortality after early bilateral oophorectomy

OBJECTIVE

To investigate the mortality associated with cardiovascular diseases and the effect of estrogen treatment in women who underwent unilateral or bilateral oophorectomy before menopause.

DESIGN

We conducted a cohort study with long-term follow-up of women in Olmsted County, MN, who underwent either unilateral or bilateral oophorectomy before the onset of menopause from 1950 through 1987. Each member of the oophorectomy cohort was matched by age to a referent woman from the same population who had not undergone any oophorectomy. We studied the mortality associated with cardiovascular disease in a total of 1,274 women with unilateral oophorectomy, 1,091 women with bilateral oophorectomy, and 2,383 referent women.

RESULTS

Women who underwent unilateral oophorectomy experienced a reduced mortality associated with cardiovascular disease compared with referent women (hazard ratio [HR], 0.82; 95% CI, 0.67-0.99; P = 0.04). In contrast, women who underwent bilateral oophorectomy before age 45 years experienced an increased mortality associated with cardiovascular disease compared with referent women (HR, 1.44; 95% CI, 1.01-2.05; P = 0.04). Within this age stratum, the HR for mortality was significantly increased in women who were not treated with estrogen through age 45 years or longer (HR, 1.84; 95% CI, 1.27-2.68; P = 0.001) but not in women treated with estrogen (HR, 0.65; 95% CI, 0.30-1.41; P = 0.28; test of interaction, P = 0.01). Mortality was further increased after deaths associated with cerebrovascular causes were excluded.

CONCLUSIONS

Bilateral oophorectomy performed before age 45 years is associated with increased cardiovascular mortality, especially with cardiac mortality. However, estrogen treatment may reduce this risk.

Need for research on estrogen receptor function: importance for postmenopausal hormone therapy and atherosclerosis

BACKGROUND

Cardiovascular disease is the leading cause of morbidity and mortality in men and women worldwide. Although rare in premenopausal women, its incidence rises sharply after menopause, indicating atheroprotective effects of endogenous estrogens.

OBJECTIVE

This review discusses the differential effects of estrogen receptor function on atherosclerosis progression in pre- and postmenopausal women, including aspects of gender differences in vascular physiology of estrogens and androgens.

METHODS

Recent advances in the understanding of the pathogenesis of atherosclerosis, estrogen receptor function, and hormone therapy are reviewed, with particular emphasis on clinical and molecular issues.

RESULTS

Whether hormone therapy can improve cardiovascular health in postmenopausal women remains controversial. Current evidence suggests that the vascular effects of estrogen are affected by the stage of reproductive life, the time since menopause, and the extent of subclinical atherosclerosis. The mechanisms of vascular responsiveness to sex steroids during different stages of atherosclerosis development remain poorly understood in women and men.

CONCLUSION

In view of the expected increase in the prevalence of atherosclerotic vascular disease worldwide due to population aging, research is needed to determine the vascular mechanism of endogenous and exogenous sex steroids in patients with atherosclerosis. Such research may help to define new strategies to improve cardiovascular health in women and possibly also in men.

Estrogen, inflammation, and platelet phenotype

BACKGROUND

Although exogenous estrogenic therapies increase the risk of thrombosis, the effects of estrogen on formed elements of blood are uncertain.

OBJECTIVE

This article examines the genomic and nongenomic actions of estrogen on platelet phenotype that may contribute to increased thrombotic risk.

METHODS

To determine aggregation, secretion, protein expression, and thrombin generation, platelets were collected from experimental animals of varying hormonal status and from women enrolled in the Kronos Early Estrogen Prevention Study.

RESULTS

Estrogen receptor beta predominates in circulating platelets. Estrogenic treatment in ovariectomized animals decreased platelet aggregation and adenosine triphosphate (ATP) secretion. However, acute exposure to 17beta-estradiol did not reverse decreases in platelet ATP secretion invoked by lipopolysaccharide. Thrombin generation was positively correlated to the number of circulating microvesicles expressing phosphatidylserine.

CONCLUSION

Assessing the effect of estrogen treatments on blood platelets may lead to new ways of identifying women at risk for adverse thrombotic events with such therapies.

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.

The impact of an aging population on the diagnosis of pulmonary embolism: comparison of young and elderly patients

The influence of age on predisposing factors, diagnostic tests, and clinical presentation of pulmonary embolism was evaluated in 582 subjects with suspected pulmonary embolism (180 aged <65 years; 402 aged > or =65 years) consecutively enrolled at the Emergency Department. Pulmonary embolism was confirmed in 40% of patients, 75% of those were aged >65 years. Age was directly related to the diagnosis, and the observed probability was higher than the expected probability in the 70 to 79 year subgroup. Score at the Cumulative Illness Rating Scale significantly increased as a function of both age and pulmonary embolism. Dyspnea, syncope, jugular distension, and history of previous venous thromboembolism were more frequently observed in elderly patients. In-hospital mortality rate among the elderly and younger patients was 2% and 0.2%, respectively. The authors conclude that age > or =65 years and high comorbidity are risk factors for pulmonary embolism.

Ageing, oestrogen, platelets and thrombotic risk

1. Adverse thrombotic cardiovascular events increase in women coincident with the onset of menopause. 2. Age past menopause may be an important variable in defining the benefit/risk of hormone treatments. 3. Few studies have examined hormonal status as a variable of ageing using a polygenomic approach of both humoral and cellular components of the coagulation system. 4. Longitudinal studies of a global set of platelet functions that define procoagulant activity (i.e. adhesion, aggregation, secretion and thrombin production) in individuals with documented hormonal status are needed to better understand how hormonal changes associated with ageing impact thrombotic risk.

In vivo effects of lipopolysaccharide and TLR4 on platelet production and activity: implications for thrombotic risk

Gram-negative bacteria release LPS, which activates Toll-like-receptor-4 (TLR4) in the host, initiating an inflammatory response to infection. Infection increases risk for thrombosis. Platelets contribute to defense from infection and to thrombosis. Experiments were designed to determine whether LPS, through TLR4 signaling, affects platelet phenotype. Platelet responses in wild-type (WT) mice and mice that lack the TLR4 gene (dTLR4) were compared following a single nonlethal injection of LPS (0.2 mg/kg iv). Compared with WT mice, mice without TLR4 had fewer circulating platelets with lower RNA content and were less responsive to thrombin-activated expression of P-selectin but were equally sensitive to aggregation or ATP secretion. One week following the LPS injection, the time it takes for the circulating platelet pool to turnover, the number of circulating platelets, thrombin-induced expression of P-selectin, and collagen-activated aggregation were increased comparably in both groups of mice. Therefore, the change of the platelet pool to an activated phenotype 1 wk after a single exposure to LPS appears to arise from a process that is independent of TLR4. The persistence of the effect 1 wk after the injection suggests that the changes reflect an action of LPS on megakaryocytes and their platelet progeny rather than on circulating platelets, which would have been cleared.