Acute and chronic effects of oestrogen on endothelial tissue-type plasminogen activator release in postmenopausal women

Effect of 17β-Estradiol on Endothelial Cell Expression of Inflammation- Related MicroRNA

BACKGROUND

Estrogen plays a protective role in vascular health due, in part, to its regulation of endothelial inflammation. However, the mechanism(s) by which estrogen negatively regulates inflammatory signaling pathways is not completely understood. MicroRNAs (miRNAs) are recognized as sensitive and selective regulators of cardiovascular function, inflammation, and disease, yet the effects of 17β-estradiol on the endothelial miRNA profile are largely unknown.

OBJECTIVE

The aim of this study was to determine the effect of 17β-estradiol on the expression of inflammation-associated miRNAs in endothelial cells in vitro.

METHODS

Human Umbilical Vein Endothelial cells (HUVECs) were treated with media in the absence (control) and presence of 17β-estradiol (100 nM) for 24 hr. Thereafter, endothelial cell release of cytokines (IL-6 and IL-8), the intracellular expression of the central protein inflammatory mediator NF-κB, and the levels of inflammatory-associated miRNAs: miR-126, miR-146a, miR-181b, miR-204, and miR-Let-7a, were determined.

RESULTS

17β-estradiol-treated cells released significantly lower levels of IL-6 (47.6±1.5 pg/mL vs. 59.3±4.9 pg/mL) and IL-8 (36.3±2.3 pg/mL vs. 44.0±2.0 pg/mL). Cellular expression of total NF-κB (26.0±2.8 AU vs. 21.2±3.1 AU) was not different between groups; however, activated NF-κB (Ser536) (12.9±1.7 AU vs. 20.2±2.2 AU) was markedly reduced in 17β-estradiol-treated cells as compared to untreated cells. Furthermore, cellular expressions of miR-126 (1.8±0.3 fold), miR-146a (1.7±0.3 fold), miR-181b (2.1±0.4 fold), miR-204 (1.9±0.4 fold), and miR-Let-7a (1.8±0.3 fold) were markedly increased in response to 17β-estradiol treatment.

CONCLUSION

These data suggest that the anti-inflammatory effect of 17β-estradiol in endothelial cells may be mediated by miRNAs.

Menstrual cycle and the protective effects of remote ischemic preconditioning against endothelial ischemia/reperfusion injury: comparison with postmenopausal women

The aim of this study was to determine whether the capacity of remote ischemic preconditioning (IPC) against endothelial ischemia/reperfusion (I/R) injury changes across the menstrual cycle in premenopausal women and to compare IPC responses to postmenopausal women. Thirty-five women were studied (22 premenopausal/13 postmenopausal). Changes in endothelial function were determined during the early follicular vs. the late follicular phase (after positive urine ovulation test; Study 1), vs. the mid-luteal phase (after positive urine progesterone test; Study 2), and vs. estrogen-deficient postmenopausal women; Study 3). Endothelium-dependent vasodilation was assessed by the forearm blood flow (FBF) to reactive hyperemia with/without I/R injury with remote IPC (3 × 5 min cycles of upper arm ischemia). In the premenopausal women, peak FBF responses during the early follicular phase were blunted 20% (P < 0.0001) with I/R injury (from baseline: 23.4 ± 6.2 to 19.5 ± 4.9 mL/100 mL tissue/min) compared with the late follicular/mid-luteal phases despite IPC. In postmenopausal women, peak FBF was diminished (from: 21.1 ± 5.1 to 17.2 ± 4.4 mL/100 mL tissue/min), and total FBF (area under the curve) was decreased a third (-32%; P < 0.001) with I/R injury. Protection from I/R injury was preserved during the late follicular (from baseline: 21.7 ± 5.3 to 24.8 ± 5.9 mL/100 mL tissue/min; P = 0.109) and mid-luteal phases (from: 25.1 ± 3.9 to 27.2 ± 5.7 mL/100 mL tissue/min; P = 0.267). Reduced estrogen during the early follicular phase and the rise in estrogen associated with ovulation and the mid-luteal phase may contribute to changes in IPC-mediated protection in premenopausal women and shed light on how cardioprotection may change with ovarian hormone deficiency with the menopause transition.NEW & NOTEWORTHY The capacity of remote ischemic preconditioning to protect against vascular endothelial ischemia/reperfusion injury varies widely across the phases of the menstrual cycle in healthy premenopausal women. Robust protection was afforded during the late follicular and mid-luteal phases. In contrast, weakened protection was demonstrated during the early follicular phase, with a level of impairment similar to estrogen-deficient postmenopausal women.

Extracellular matrix metalloproteinase-9 (MMP-9) is required in female mice for 17β-estradiol enhancement of hippocampal memory consolidation

Hippocampal plasticity and memory are modulated by the potent estrogen 17β-estradiol (E₂). Research on the molecular mechanisms of hippocampal E₂ signaling has uncovered multiple intracellular pathways that contribute to these effects, but few have questioned the role that extracellular signaling processes may play in E₂ action. Modification of the extracellular matrix (ECM) by proteases like matrix metalloproteinase-9 (MMP-9) is critical for activity-dependent remodeling of synapses, and MMP-9 activity is required for hippocampal learning and memory. Yet little is known about the extent to which E₂ regulates MMP-9 in the hippocampus, and the influence this interaction may have on hippocampal memory. Here, we examined the effects of hippocampal MMP-9 activity on E₂-induced enhancement of spatial and object recognition memory consolidation. Post-training bilateral infusion of an MMP-9 inhibitor into the dorsal hippocampus of ovariectomized female mice blocked the enhancing effects of E₂ on object placement and object recognition memory, supporting a role for MMP-9 in estrogenic regulation of memory consolidation. E₂ also rapidly increased the activity of dorsal hippocampal MMP-9 without influencing its protein expression, providing further insight into hippocampal E₂/MMP-9 interactions. Together, these results provide the first evidence that E₂ regulates MMP-9 to modulate hippocampal memory and highlight the need to further study estrogenic regulation of extracellular modification.

Sex differences in carcinoid syndrome: A gap to be closed

The incidence of neuroendocrine neoplasms and related carcinoid syndrome (CS) has markedly increased over the last decades and women seem to be more at risk than men for developing CS. Nevertheless, very few studies have investigated sex differences in clinical presentation and outcomes of CS. However, as per other tumours, sex might be relevant in influencing tumour localization, delay in diagnosis, clinical outcomes, prognosis and overall survival in CS. The present review was aimed at evaluating sex differences in CS, as they emerge from an extensive search of the recent literature. It emerged that CS occurs more frequently in female than in male patients with NENs and women seem to have a better prognosis and a slight advantage in overall survival and response to therapy. Moreover, the disease likely impacts differently the quality of life of men and women, with different psychological and social consequences. Nevertheless, sex differences, even if partially known, are deeply underestimated in clinical practice and data from clinical trials are lacking. There is urgent need to increase our understanding of the sex-related differences of CS, in order to define tailored strategies of management of the disease, improving both the quality of life and the prognosis of affected patients.

Estrogen's Effects on Excitatory Synaptic Transmission Entail Integrin and TrkB Transactivation and Depend Upon β1-integrin function

Estradiol (E2) perfusion rapidly increases the strength of fast excitatory transmission and facilitates long-term potentiation in the hippocampus, two effects likely related to its memory-enhancing properties. Past studies showed that E2's facilitation of transmission involves activation of RhoA signaling leading to actin polymerization in dendritic spines. Here we report that brief exposure of adult male hippocampal slices to 1 nM E2 increases the percentage of postsynaptic densities associated with high levels of immunoreactivity for activated forms of the BDNF receptor TrkB and β1-integrins, two synaptic receptors that engage actin regulatory RhoA signaling. The effects of E2 on baseline synaptic responses were unaffected by pretreatment with the TrkB-Fc scavenger for extracellular BDNF or TrkB antagonism, but were eliminated by neutralizing antisera for β1-integrins. E2 effects on synaptic responses were also absent in conditional β1-integrin knockouts, and with inhibition of matrix metalloproteinases, extracellular enzymes that generate integrin ligands. We propose that E2, acting through estrogen receptor-β, transactivates synaptic TrkB and β1-integrin, and via mechanisms dependent on integrin activation and signaling, reversibly reorganizes the spine cytoskeleton and thereby enhances synaptic responses in adult hippocampus.

Self-reported habitual short sleep duration is associated with endothelial fibrinolytic dysfunction in men: a preliminary report

STUDY OBJECTIVES

Habitual short sleep duration is associated with increased cardiovascular disease morbidity and mortality resulting from atherothrombotic events. The mechanisms responsible for this heightened cardiovascular risk are not fully understood. The capacity of the endothelium to release tissue-type plasminogen activator (t-PA), the primary activator of the fibrinolytic system, is a key endogenous defense mechanism against intravascular fibrin deposition and thrombosis. We tested the hypothesis that endothelial t-PA release is impaired in adults who sleep less than 7 h/night compared with adults who sleep between 7 and 9 h/night.

DESIGN

THIRTY ADULT MEN WERE STRATIFIED BASED ON AVERAGE NIGHTLY HABITUAL SLEEP DURATION: 15 with normal sleep duration (age: 55 ± 2 years; sleep duration: 7.6 h/night) and 15 with short sleep duration (56 ± 2 years; 6.1 h/night). Net endothelial release of t-PA was determined, in vivo, in response to intra-brachial infusions of bradykinin (12.5-50.0 ng/100 mL tissue/min) and sodium nitroprusside (1.0-4.0 μg/100 mL tissue/min).

MEASUREMENTS AND RESULTS

Net endothelial t-PA release to bradykinin was significantly lower (∼25%) in the short (from 0.4 ± 0.8 to 41.5 ± 4.3 ng/100 mL tissue/min) compared with the normal (0.4 ± 0.5 to 64.9 ± 6.7 ng/100 mL/tissue/min) sleep duration group. Furthermore, there was an inverse relation between average nightly sleep duration and peak t-PA release to bradykinin (r = 0.36, P < 0.05).

CONCLUSIONS

Endothelial t-PA release is impaired in adults who report short habitual sleep duration. Impaired endothelial fibrinolytic function may underlie the increased atherothrombotic risk associated with chronic short sleep.

The impaired fibrinolytic capacity in hypertension is unaffected by acute blood pressure lowering

The endogenous fibrinolytic system and the ability of the endothelium to release tissue-plasminogen activator (t-PA) play a pivotal role to protect humans from atherothrombotic events. We have recently reported that the decreased capacity for t-PA release in hypertension is restored with chronic blood pressure lowering. Thus, we explored if acute blood pressure lowering has the same effect. The capacity for acute t-PA release was investigated in the perfused-forearm model during stimulation by intra-arterial substance P 8 pmol/min in hypertensive subjects. The procedure was then repeated during acute blood pressure lowering (n = 9) induced by sodium nitroprusside (SNP) infusion or during placebo infusion (n = 3). SNP lowered mean arterial pressure from 108.6 (2.6) to 83.0 (2.6) (mean and SEM) mmHg (P < 0.001). Substance P induced significant increase in t-PA release during both high- and low-pressure conditions (P < 0.01, ANOVA). Peak t-PA release rate was 199 (77) and 167 (41) (mean and SEM) ng/min/l tissue, and accumulated t-PA release was 2,395 (750) and 2,394 (473) ng, during high- and low-pressure conditions, respectively. t-PA release and hemodynamic responses were almost identical during high- and low-pressure conditions (P = ns, for all). Acute blood pressure lowering does not restore stimulated t-PA release from the endothelium in hypertensive subjects. These findings are in contrast to previously described effects of chronic blood pressure treatment. Although data need to be confirmed in a larger study, they suggest that high blood pressure decreases the cellular t-PA pool rather than interferes with release mechanisms of the protein.

Relation of C-reactive protein to endothelial fibrinolytic function in healthy adults

Increased plasma concentrations of C-reactive protein (CRP) independently predict future atherothrombotic events in healthy asymptomatic adults. CRP may promote atherothrombosis by altering fibrinolytic balance; however, the influence of increased plasma CRP concentrations on endothelial fibrinolysis in healthy adults is unclear. We tested the hypothesis that endothelial release of tissue-type plasminogen activator (t-PA) is impaired in adults with increased plasma CRP concentrations independent of other cardiometabolic risk factors. Fifty-four healthy adults were studied: 24 with CRP <1.0 mg/L (low CRP; 18 men and 6 women, 55 ± 2 years old), 18 with CRP 1.0 to 3.0 mg/L (moderate CRP; 8 men and 10 women, 58 ± 2 years old), and 12 with CRP >3.0 mg/L (high CRP; 7 men and 5 women, 56 ± 2 years old). Net endothelial release of t-PA was determined in vivo in response to intrabrachial infusions of bradykinin (125 to 500 ng/min) and sodium nitroprusside (2.0 to 8.0 μg/min). Capacity of the endothelium to release t-PA was significantly lower (∼30%) in the high (0.32 ± 0.5 to 38.9 ± 6.0 ng · 100 ml tissue(-1) · min(-1)) and moderate (-0.05 ± 0.4 to 39.3 ± 5.2 ng · 100 ml tissue(-1) · min(-1)) compared to the low (0.42 ± 0.9 to 61.8 ± 5.2 ng · 100 ml tissue(-1) · min(-1)) CRP group. There was no significant difference in t-PA release between the high and moderate CRP groups. Plasma CRP concentrations were inversely related to t-PA release (r = -0.38, p <0.05). In conclusion, these results indicate that the capacity of the endothelium to release t-PA is decreased in adults with plasma CRP ≥1.0 mg/L. Endothelial fibrinolytic dysfunction may underlie the increased atherothrombotic risk associated with increases in plasma CRP concentrations in otherwise healthy adults.

Angiotensin-Converting Enzyme Inhibition Augments Coronary Release of Tissue Plasminogen Activator in Women But Not in Men

The renin-angiotensin system regulates the vascular fibrinolytic balance. In the human forearm vasculature, angiotensin-converting enzyme (ACE) inhibitors (ACE-Is) increase the release of t-PA through endogenous bradykinin. We tested the hypothesis that ACE inhibition and sex modulate the endogenous coronary release of tissue plasminogen activator (t-PA) in hypertensive patients. Seventy-three patients underwent diagnostic coronary angiography and had normal coronary angiograms. Thirty-three patients (21 men and 12 women) were treated with imidapril (5 mg/day) for 4 weeks (ACE-I group), and 40 (23 men and 17 women) were not treated with ACE-I (non–ACE-I group). All of the women were postmenopausal. Coronary blood flow in the left anterior descending artery was evaluated by measuring Doppler flow velocity. Net coronary t-PA release was determined as (coronary sinus−aorta gradient of t-PA)×(coronary blood flow)×[(100−hematocrit)/100]. Age, arterial pressure, heart rate, lipid levels, coronary flow, and the plasma level of t-PA at either aorta or coronary sinus were comparable among the 4 groups. In women, net t-PA release in the ACE-I group was significantly higher than that in the other groups ( P <0.05; man non–ACE-I group: 1.4±2.6 ng/mL; woman non–ACE-I group: 1.4±3.1 ng/mL; man ACE-I group: −1.8±2.8 ng/mL; woman ACE-I group: 14.8±3.6 ng/mL). Correction for smoking status gave similar results. There was a significant negative correlation between serum ACE activity and coronary t-PA release in women ( r =−0.38; P <0.05) but not in men. ACE inhibition increases coronary release of t-PA in women but not in men.

Habitual exercise and arterial aging

Aging affects the function and structure of arteries and increases the risk of cardiovascular diseases (CVD). In healthy sedentary adults, aging is associated with increased stiffness (reduced compliance) of large elastic arteries; impaired vascular endothelial function, including reductions in endothelium-dependent dilation (EDD), release of tissue-type plasminogen activator (fibrinolytic capacity) and endothelial progenitor cell number and function; increased intima-media wall thickness (IMT); and peripheral vasoconstriction (decreased basal leg blood flow). Habitual physical activity/increased aerobic exercise capacity is associated with reduced risk of CVD. Compared with their sedentary peers, adults who regularly perform aerobic exercise demonstrate smaller or no age-associated increases in large elastic artery stiffness, reductions in vascular endothelial function, and increases in femoral artery IMT. A short-term, moderate-intensity aerobic exercise intervention (brisk daily walking for 12 wk) improves carotid artery compliance and can restore vascular endothelial function in previously sedentary middle-aged and older adults. Reduced oxidative stress may be an important mechanism contributing to these effects. Habitual resistance exercise increases (high-intensity) or does not affect (moderate-intensity) large elastic artery stiffness, and prevents/restores the age-associated reduction in basal leg blood flow independent of changes in leg fat-free mass. Habitual exercise favorably modulates several expressions of arterial aging, thus preserving vascular function and possibly reducing the risk of CVD.

Hemostatic markers in healthy postmenopausal women during intranasal and oral hormone therapy

OBJECTIVE

To study changes in the hemostatic balance during intranasal compared with oral administration of 17beta-estradiol (E2) and norethisterone (NET) or NET acetate in postmenopausal women. A wide range of markers of coagulation and fibrinolysis associated with coronary artery disease was tested.

DESIGN

In a two-center, randomized, double-blind, comparative trial, 90 healthy postmenopausal women (aged 56.6 +/- 4.7 y) received daily continuous combined hormone therapy, either E2/NET 175 microg/275 mug intranasally as a spray (n = 47) or E2/NET acetate 1 mg/0.5 mg orally as a capsule (n = 43) for 1 year. Hemostatic markers were measured in blood samples taken at baseline and after 12, 24, and 52 weeks of treatment.

RESULTS

After 52 weeks of treatment, changes in the intranasal group in markers of coagulation-fibrinogen (-1.3%), factor VII activity (-14.0%), and prothrombin fragment 1 + 2 (+5.8%)-were significantly less (P < 0.05) than the changes in the oral group for these parameters (-6.5%, -20.3%, and +19.0%, respectively). Changes in activated factor VII did not differ between the groups. Neither group showed significant changes in thrombin-antithrombin complex. In the intranasal group, decreases in markers of fibrinolysis-tissue-type plasminogen activator (-10.4%) and plasminogen activator inhibitor-1 antigen (-13.8%)-were significantly less (P < 0.05) than the decreases in the oral group (-17.8% and -38.0%, respectively). A decrease in plasminogen activator inhibitor-1 activity and increases in D-dimer and plasmin-alpha2-antiplasmin complex did not differ between the groups. No differences were found between the groups in homocysteine, which overall was unaltered in both groups.

CONCLUSIONS

During intranasal E2/NET therapy, changes in the coagulatory and fibrinolytic markers were to some extent less than those observed during oral therapy.

17Beta-estradiol increases basal but not bradykinin-stimulated release of active t-PA in young postmenopausal women

Angiotensin-converting enzyme inhibition potentiates basal and bradykinin-stimulated tissue-type plasminogen activator (t-PA) release to a greater extent in women than in men. This study tested the hypothesis that 17beta-estradiol enhances the effect of angiotensin-converting enzyme inhibition on t-PA release in young postmenopausal women. We conducted a double-blind, prospective, crossover study in 14 young postmenopausal women (mean age 48.2+/-2.3 years) who were randomized to receive 17beta-estradiol (1 mg/d) or matching placebo for 4 weeks. At the end of each treatment period, we measured the effect of intraarterial infusion of bradykinin, methacholine, and nitroprusside on forearm blood flow and net t-PA release, before and during intraarterial enalaprilat (0.33 microg/min/100 mL forearm volume). 17Beta-estradiol significantly reduced baseline venous plasminogen activator inhibitor-1 antigen (4.4+/-1.4 versus 10.4+/-2.5 ng/mL, P=0.001) and t-PA antigen (5.5+/-0.6 versus 7.5+/-1.3 ng/mL, P=0.022) compared with placebo. 17Beta-estradiol increased basal forearm vascular release of active t-PA compared with placebo (1.2+/-0.3 IU/mL/min versus 0.4+/-0.1 IU/mL/min respectively, P=0.032), without increasing t-PA antigen release (P=0.761). Enalaprilat significantly increased basal net t-PA antigen release (from -0.8+/-1.0 to 3.2+/-1.2 ng/min/100 mL, P=0.012), but not the release of active t-PA, during either placebo or 17beta-estradiol. Enalaprilat potentiated bradykinin-stimulated vasodilation and t-PA antigen and activity release similarly during placebo and 17beta-estradiol treatment. 17Beta-estradiol treatment does not alter the effect of angiotensin-converting enzyme inhibition on basal t-PA antigen or on bradykinin-stimulated t-PA antigen or activity release. 17Beta-estradiol increases basal release of active t-PA in young postmenopausal women, consistent with enhanced vascular fibrinolytic function.

Bradykinin type 2 receptor BE1 genotype influences bradykinin-dependent vasodilation during angiotensin-converting enzyme inhibition

To test the hypothesis that the bradykinin receptor 2 (BDKRB2) BE1+9/-9 polymorphism affects vascular responses to bradykinin, we measured the effect of intra-arterial bradykinin on forearm blood flow and tissue-type plasminogen activator (t-PA) release in 89 normotensive, nonsmoking, white American subjects in whom degradation of bradykinin was blocked by enalaprilat. BE1 genotype frequencies were +9/+9:+9/-9:-9/-9=19:42:28. BE1 genotype was associated with systolic blood pressure (121.4+/-2.8, 113.8+/-1.8, and 110.6+/-1.8 mm Hg in +9/+9, +9/-9, and -9/-9 groups, respectively; P=0.007). In the absence of enalaprilat, bradykinin-stimulated forearm blood flow, forearm vascular resistance, and net t-PA release were similar among genotype groups. Enalaprilat increased basal forearm blood flow (P=0.002) and decreased basal forearm vascular resistance (P=0.01) without affecting blood pressure. Enalaprilat enhanced the effect of bradykinin on forearm blood flow, forearm vascular resistance, and t-PA release (all P<0.001). During enalaprilat, forearm blood flow was significantly lower and forearm vascular resistance was higher in response to bradykinin in the +9/+9 compared with +9/-9 and -9/-9 genotype groups (P=0.04 for both). t-PA release tended to be decreased in response to bradykinin in the +9/+9 group (P=0.08). When analyzed separately by gender, BE1 genotype was associated with bradykinin-stimulated t-PA release in angiotensin-converting enzyme inhibitor-treated men but not women (P=0.02 and P=0.77, respectively), after controlling for body mass index. There was no effect of BE1 genotype on responses to the bradykinin type 2 receptor-independent vasodilator methacholine during enalaprilat. In conclusion, the BDKRB2 BE1 polymorphism influences bradykinin type 2 receptor-mediated vasodilation during angiotensin-converting enzyme inhibition.

Fibrinolytic markers and vasodilatory capacity following acute exercise among men of differing training status

We evaluated the effect of differing physical activity patterns on fibrinolysis and vasodilatory capacity using a cross-sectional design with 16 endurance-trained (ET) (mean+/-SE) (28+/-6 years), 14 resistance-trained (RT) (28+/-7 years), and 10 untrained (UT) (26+/-7 years) men. t-PA and PAI-1 activity and t-PA antigen were measured before and after a maximal treadmill test (VO2peak). Vasodilatory capacity was assessed using strain-gauge plethysmography on the forearm following reactive hyperemia (RH) before and after the treadmill test. The ET group had a smaller body mass index (BMI) (22.8+/-0.5 ET, 26.4+/-0.4 RT, 25.1+/-0.8 UT kg m(-2)) (P<0.05) and a greater VO2peak (57+/-1 ET, 42+/-2 RT, 45+/-2 UT mL min(-1) kg(-1)) (P<0.05). Peak vasodilatory capacity (29.7+/-2 ET, 32.0+/-2 RT, 27.4+/-2 UT mL min(-1) 100 mL of tissue) was similar between groups before and after exercise. Area under the curve for forearm blood flow was greater following acute exercise (212 vs. 122, P<0.05), again with no differences between groups. t-PA activity and antigen increased following maximal exercise in all groups (P<0.0001), with no group differences. PAI-1 activity decreased the least in RT after exercise (70% decrease vs. 86% ET and 82% UT; P<0.05). The change in t-PA activity with exercise was not related to exercise-induced change in overall vasodilatory capacity. These findings demonstrate that in healthy young men different physical activity patterns do not appear to impact the exercise-induced changes in fibrinolysis or vasodilatory capacity.

Gender-specific correlations of plasminogen activator inhibitor-1 and tissue plasminogen activator levels with cardiovascular disease-related traits

BACKGROUND

The purpose of this study was to examine the correlations between plasma levels of plasminogen activator inhibitor-1 (PAI-1) and tissue plasminogen activator (t-PA) and cardiovascular disease-related traits in a general population and whether these correlations differed between females and males.

METHODS

Plasma PAI-1 and t-PA antigen levels and C-reactive protein (CRP), HDL-cholesterol, triglycerides, total cholesterol, systolic blood pressure, diastolic blood pressure, urinary albumin excretion, and glucose were measured in the population-based PREVEND study in Groningen, the Netherlands (n = 2527).

RESULTS

Except for CRP and total cholesterol levels, all traits were significantly different between gender (P < 0.001). PAI-1 levels were correlated with all measured cardiovascular disease-related traits (P < 0.01) in both females and males. Except for urinary albumin excretion, similar results, albeit less significant, were found for t-PA levels. Age-adjusted correlations between PAI-1 and CRP, triglycerides, total cholesterol, systolic blood pressure, and diastolic blood pressure differed significantly between females and males (P < 0.01). Many of the gender differences were predominantly present between premenopausal females and males.

CONCLUSION

PAI-1 and t-PA levels were correlated with cardiovascular disease-related traits in subjects obtained from the general population and several of these correlations differed across gender. The correlations found in the present study suggest the presence of coordinated patterns of cardiovascular risk factors and indicate which traits might influence PAI-1 and t-PA levels and thereby provide a framework and potential tool for therapeutic intervention to reduce thromboembolic events in the general population.

Stimulated Tissue Plasminogen Activator Release as a Marker of Endothelial Function in Humans

The initiation, modulation, and resolution of thrombus associated with eroded or unstable coronary plaques are critically dependent on the efficacy of endogenous fibrinolysis. This is dependent on the cellular function of the surrounding endothelium and vascular wall. In particular, the acute release of tissue plasminogen activator from the endothelium makes an important contribution to the defense against intravascular thrombosis. Here, we describe the rationale and methodology for, and clinical relevance of, assessing acute endothelial tissue plasminogen activator release in humans. The investigation of endothelial fibrinolytic function has the potential to provide major new insights into the pathophysiology of cardiovascular disease, and to shape future therapeutic interventions.

Endothelial t-PA release is impaired in overweight and obese adults but can be improved with regular aerobic exercise

Endothelial release of tissue-type plasminogen activator (t-PA) regulates fibrinolysis and is considered to be a primary endogenous defense mechanism against thrombosis. Adiposity is associated with an increased risk of atherothrombotic events. We determined the influence of overweight and obesity on the capacity of the vascular endothelium to release t-PA and the effects of regular aerobic exercise on endothelial t-PA release in previously sedentary overweight and obese adults. First, we studied 66 sedentary adults: 28 normal-weight (BMI < 25 kg/m2); 22 overweight (BMI > or = 25 and < 30 kg/m2); and 16 obese (BMI > or = 30 kg/m2). Net endothelial t-PA release was determined in vivo in response to intrabrachial infusions of bradykinin (BK) and sodium nitroprusside. Second, we studied 17 overweight and obese adults who completed a 3-mo aerobic exercise intervention. Net release of t-PA in response to BK was approximately 45% lower (P < 0.01) in overweight (from 0.1 +/- 0.4 to 41.7 +/- 4.9 ng x 100 ml tissue(-1) x min(-1)) and obese (-0.1 +/- 0.6 to 47.7 +/- 5.2 ng x 100 ml tissue(-1) x min(-1)) compared with normal-weight (0.1 +/- 0.8 to 77.5 +/- 6.7 ng x 100 ml tissue(-1) x min(-1)) adults. There was no difference in t-PA release between the overweight and obese groups. Exercise training significantly increased t-PA release capacity in overweight and obese adults (from -0.3 +/- 0.5 to 37.1 +/- 4.9 ng x 100 ml tissue(-1) x min(-1) before training vs. 1.0 +/- 0.9 to 65.4 +/- 6.3 ng x 100 ml tissue(-1) x min(-1) after training) to levels comparable with those of their normal-weight peers. These results indicate that overweight and obesity are associated with profound endothelial fibrinolytic dysfunction. Importantly, however, regular aerobic exercise can increase the capacity of the endothelium to release t-PA in this at-risk population.

Angiotensin-converting enzyme inhibition increases basal vascular tissue plasminogen activator release in women but not in men

OBJECTIVE

Angiotensin-converting enzyme inhibition (ACEI) increases vascular tissue plasminogen activator (t-PA) release through endogenous bradykinin (BK). We tested the hypothesis that gender influences the effect of ACEI on t-PA release.

METHODS AND RESULTS

We measured the effect of intra-arterial enalaprilat (0.33 microg/min per 100 mL forearm volume) on forearm blood flow (FBF) and net t-PA release before and during BK (25 to 400 ng/min) and methacholine (3.2 to 12.8 microg/min) in premenopausal women, postmenopausal women not using hormone replacement, young men, and older men. Baseline net t-PA release was similar among groups. Enalaprilat increased basal t-PA release in premenopausal (from 0.9+/-1.0 to 5.1+/-1.7 ng/min per 100 mL, P=0.023) and postmenopausal women (from -3.9+/-2.2 to 3.9+/-1.1 ng/min per 100 mL, P=0.010) but not in young or older men (P=0.028 men versus women). Enalaprilat potentiated the effect of exogenous BK on FBF similarly in all groups. However, during enalaprilat, BK-stimulated t-PA release was greatest in premenopausal women (339.9+/-86.4 ng/min per 100 mL at the 100 ng/min dose, P<0.05 versus any other group), intermediate in postmenopausal women (243.8+/-51.1 ng/min per 100 mL, P<0.05 versus either male group), and least in young (111.9+/-19.2 ng/min/100 mL) and older men (103.4+/-27.6 ng/min/100 mL).

CONCLUSIONS

ACEI enhances basal t-PA release in women, independent of menopausal status, but not in men. During ACEI, both gender and menopausal status affect BK stimulated t-PA release.