Influence of Metoprolol Treatment on Sympatho-Adrenal Activation of Fibrinolysis

Impact of Acute and Chronic Stress on Thrombosis in Healthy Individuals and Cardiovascular Disease Patients

Psychological stress induces different alterations in the organism in order to maintain homeostasis, including changes in hematopoiesis and hemostasis. In particular, stress-induced hyper activation of the autonomic nervous system and hypothalamic–pituitary–adrenal axis can trigger cellular and molecular alterations in platelets, coagulation factors, endothelial function, redox balance, and sterile inflammatory response. For this reason, mental stress is reported to enhance the risk of cardiovascular disease (CVD). However, contrasting results are often found in the literature considering differences in the response to acute or chronic stress and the health condition of the population analyzed. Since thrombosis is the most common underlying pathology of CVDs, the comprehension of the mechanisms at the basis of the association between stress and this pathology is highly valuable. The aim of this work is to give a comprehensive review of the studies focused on the role of acute and chronic stress in both healthy individuals and CVD patients, focusing on the cellular and molecular mechanisms underlying the relationship between stress and thrombosis.

Potential Protective Role of Blood Pressure-Lowering Drugs on the Balance between Hemostasis and Fibrinolysis in Hypertensive Patients at Rest and During Exercise

In patients with hypertension, the triad represented by endothelial dysfunction, platelet hyperactivity, and altered fibrinolytic function disturbs the equilibrium between hemostasis and fibrinolysis and translates into a hypercoagulable state, which underlies the risk of thrombotic complications. This article reviews the scientific evidence regarding some biological effects of antihypertensive drugs, which can protect patients from the adverse consequences of hypertensive disease, improving endothelial function, enhancing antioxidant activity, and restoring equilibrium between hemostatic and fibrinolytic factors. These protective effects appear not to be mediated through blood pressure reduction and are not shared by all molecules of the same pharmacological class.

Inhalation of a Short-Acting β2-Adrenoreceptor Agonist Induces a Hypercoagulable State in Healthy Subjects

Background

Catecholamine infusion elicits an increase in clotting factors and this increase has been attributed to stimulation of β₂-adrenorecptors (β2AR). Accordingly, we tested the hypothesis that inhalation of a short-acting selective β2AR agonist can induce a procoagulant state in healthy individuals.

Methods

We recruited 23 healthy volunteers (nine females; mean age: 26±0.8 years; body mass index: 24.7±0.5 kg/m²) and randomly allocated them into two groups, the β2AR arm (seventeen subjects) and the saline arm (six subjects). Hemodynamics, plasma norepinephrine concentration, and procoagulant, anticoagulant, and fibrinolytic profiles of each participant were determined using specific assays before and after inhalation of either 2 mL nebulized normal saline or a mixture of 1 mL saline and 1 mL of salbutamol (5 mg salbutamol sulfate), a selective β2AR agonist, which were delivered by a nebulizer over ten minutes.

Results

Saline inhalation had no effect on the procoagulant, anticoagulant and fibrinolytic profiles of the six healthy volunteer in the study's saline arm. Salbutamol inhalation caused (a) a significant increase in the activity or levels of the procoagulant factors; FVIII increased by 11±3% (p = 0.04), von Willebrand factor increased by 7±1% (p = 0.03), and (b) a significant decrease in the activated partial prothrombin time from 27.4±0.4 seconds to 25.5 ±0.5 seconds (p<0.001) in the 17 volunteers in the study's β2AR arm. D-dimer and prothrombin fragments F1+2 were elevated by 200 ±90% and 505.0 ±300.0%, respectively. In addition, the activity of the anticoagulant protein C pathway (demonstrated by the protein C Global assay) decreased from 1.0±0.08 to 0.82±0.06 (p<0.001). Although plasma levels of tissue plasminogen activator decreased, all other indices of the fibrinolytic system did not change following salbutamol inhalation.

Conclusion

We found that a single inhalation of salbutamol, a short-acting β2AR agonist, activates the clotting system without affecting the fibrinolytic system. This induction of a procoagulant state in healthy subjects warrants further investigation in patients treated with these agents.

Peptidergic regulation of plasminogen activator inhibitor-1 gene expression in vivo

BACKGROUND

The mechanisms by which PAI-1 biosynthesis is altered during stress have not been fully elucidated. Studies suggest a major role for neuro-peptidergic modulation of the stress response by PACAP (pituitary adenylate cyclase-activating polypeptide), a member of the VIP/secretin/glucagon family.

OBJECTIVE

We tested the hypothesis that PACAP regulates PAI-1 biosynthesis during stress in vivo.

METHODS

PAI-1 gene expression was monitored by RT-PCR in adrenal glands harvested from C57BL/6J mice that were unstressed, or subjected to restraint stress for 2 h, or treated with PACAP.

RESULTS

PAI-1 mRNA expression was markedly increased in adrenals from stressed mice. Restraint stress resulted in much smaller increments in adrenal tPA mRNA, suggesting that local adrenal tPA/PAI-1 biosynthetic balance is markedly altered by stress. The observed increases in PAI-1mRNA during stress were substantially blunted (55 ± 4%, P < 0.001) by pretreatment with the specific PACAP receptor antagonist, PACAP6-38, compared with pretreatment with vehicle. Administration of the agonist PACAP1-38 alone resulted in a dose-dependent increase in tissue PAI-1 mRNA. PACAP1-38 administration also resulted in substantial increases in plasma PAI-1 antigen and active PAI-1 concentrations that were significantly greater in male mice than in female mice.

CONCLUSIONS

We conclude that adrenal PAI-1 mRNA expression is markedly increased by stress, and that the PACAP peptidergic signaling pathway plays a major role in mediating the stress-induced increase in PAI-1 biosynthesis.

Prevalence of myocardial infarction polymorphisms in Afyonkarahisar, Western Turkey

The aim of the study was to investigate relationship between polymorphisms in genes that are clinical and environmental features and the risk of myocardial infarction (MI) in Afyonkarahisar subjects living in Turkey. Prevalence of the several genes polymorphisms, ≤45 (42.04 ± 3.3) and ≥46 (57.19 ± 7.5) years were studied in individuals with MI and without MI (40.30 ± 9.01) individuals were studied. We tested 140 with MI individuals for factor V (FV) Leiden, FV H1299R, Prothrombin G20210A, factor XIII (FXIII) V34L, β-fibrinogen b-455G/A, plasminogen activator inhibitor-1 (PAI-1)-675 4G/5G, human platelet antigens 1 (HPA-1) a/b, apolipoprotein B (ApoB) R3500Q, apolipoprotein E (ApoE), E2, E3, and E4, angiotensin-converting enzyme (ACE) D/I, 5,10 methylenetetrahydrofolate reductase (MTHFR) 677C/T, and MTHFR 1298A/C polymorphisms using a ViennaLab CVD strip assay. This study results were compared without MI control groups. According to the our results, prothrombin, factor XIII and MTHFRC677T deletions were the most frequent genetic variants in risk groups of hyperlipidemic patients (value of odds ratio sequentially [OR] = 4.5, p = 0.05, [OR] = 2.16, p = 0.04 and [OR] = 2.8, p = 0.09). MTHFRA1298C and PAI-1 deletions were most frequent genetic variants in risk groups for MI in patients with diabetes mellitus (value of odds ratio sequentially [OR] = 3.79, p = 0.06 and [OR] = 5 × 10(8), p = 0.000). ACE deletions were positively associated with family history of cardiovascular events (OR = 3.62, p = 0.03). We found a strong relationship between genetic variants and risk factors. Significant associations between genetic variants predicting cardiovascular events and common risk factors (hyperlipidemia, smoking, diabetes mellitus and family history) patients were found.

Plasminogen activator inhibitor-1 (PAI-1): a key factor linking fibrinolysis and age-related subclinical and clinical conditions

INTRODUCTION

The close relationship existing between aging and thrombosis has growingly been studied in this last decade. The age-related development of a prothrombotic imbalance in the fibrinolysis homeostasis has been hypothesized as the basis of this increased cardiovascular and cerebrovascular risk. Fibrinolysis is the result of the interactions among multiple plasminogen activators and inhibitors constituting the enzymatic cascade, and ultimately leading to the degradation of fibrin. The plasminogen activator system plays a key role in a wide range of physiological and pathological processes.

METHODS

Narrative review.

RESULTS

Plasminogen activator inhibitor-1 (PAI-1) is a member of the superfamily of serine-protease inhibitors (or serpins), and the principal inhibitor of both the tissue-type and the urokinase-type plasminogen activator, the two plasminogen activators able to activate plasminogen. Current evidence describing the central role played by PAI-1 in a number of age-related subclinical (i.e., inflammation, atherosclerosis, insulin resistance) and clinical (i.e., obesity, comorbidities, Werner syndrome) conditions is presented.

CONCLUSIONS

Despite some controversial and unclear issues, PAI-1 represents an extremely promising marker that may become a biological parameter to be progressively considered in the prognostic evaluation, in the disease monitoring, and as treatment target of age-related conditions in the future.

Altered interaction between plasminogen activator inhibitor type 1 activity and sympathetic nerve activity with aging

BACKGROUND

It has been reported that sympathetic nerve activity (SNA) is associated with fibrinolysis, but the interaction between SNA and the fibrinolytic system with aging has not been elucidated in humans. The purpose of this study was to examine the effect of age-related SNA on the activity of plasminogen activator inhibitor type 1 (PAI-1) and tissue plasminogen activator (tPA) using muscle SNA (MSNA).

METHODS AND RESULTS

This study included 16 young subjects (mean age 26.1 years) and 10 aged subjects (mean age 56.9 years). Lower body negative pressure (LBNP) was performed at -40 mmHg for 30 min. LBNP significantly increased both tPA and PAI-1 activity (from 5.2+/-0.5 to 7.3+/-1.2 IU/ml and from 2.85+/-0.68 to 4.06+/-0.73 U/ml, p<0.01, respectively) in the aged group. In the young group, tPA activity tended to increase, whereas PAI-1 activity was unchanged. There was a correlation between MSNA and PAI-1 activity in the aged group (r=0.47, p<0.01).

CONCLUSIONS

SNA in an aging subject leads to an increase in the activity of PAI-1, which indicates that an altered interaction between SNA and PAI-1 activity contributes to increased cardiovascular events in the elderly population.

The effects of nebivolol on fibrinolytic parameters in mild and moderate hypertensive patients

BACKGROUND

The aim of the present study was to investigate the effects of nebivolol (5 mg daily) on plasma levels of hemostatic and fibrinolytic endothelial function markers in mild or moderate hypertensive patients.

METHODS AND RESULTS

Thirty-five (22 female, 13 male; mean +/- SD 54.7 +/- 11.3 years of age) mild and moderate hypertensive patients were included the study. The mean systolic blood pressure [BP] was 160 mmHg (range 150 mmHg to 165 mmHg) and the mean diastolic BP was 100 mmHg (range 90 mmHg to 100 mmHg). Plasma tissue plasminogen activator antigen (tPA-Ag), plasminogen activator inhibitor type 1 antigen (PAI-1-Ag), PAI-1 activity, tPA-Ag/PAI-1-Ag index, fibrinogen and euglobulin lysis time were determined before and after two months of therapy. tPA-Ag and PAI-Ag levels were measured by ELISA. After this period, treatment with nebivolol (5 mg/day) in all patients was associated with a significant decrease in systolic BP and diastolic BP (P<0.001 for each), heart rate (P<0.01), fibrinogen (P<0.005) and euglobulin lysis time (P<0.01). The tPA-Ag and tPA-Ag/PAI-1-Ag index levels were increased significantly (P<0.001 for each) in all patients, but the PAI-1-Ag (P>0.05) and PAI-1 activity (P>0.05) did not show significant change. In the present study, there was no correlation between decreases in arterial BP and decreases in fibrinolytic parameters (P>0.05), but there was a positive, statistically significant correlation between fibrinogen and body mass index (P<0.001).

CONCLUSIONS

The results indicated that, compared with no treatment, a two-month treatment trial with nebivolol was associated with a more favourable modification of hemostatic and fibrinolytic status in addition to antihypertensive effects.

Is the effect of antihypertensive drugs on platelet aggregability and fibrinolysis clinically relevant?

Hypertension is associated with decreased fibrinolytic potential, mainly expressed as elevated plasma plasminogen activator inhibitor type 1 (PAI-1) levels, and increased platelet aggregability, which may account in part for the increased risk of atherosclerosis and its clinical complications in hypertensive patients. The effects of antihypertensive drugs on this prothrombotic state have been investigated and controversial findings have been reported, possibly because of differences in study designs, patients selected, and methodology used. Scarce and conflicting data exist about the effects of diuretics and beta-adrenoceptor antagonists on the fibrinolytic system, whereas ACE inhibitors have generally been reported to improve the fibrinolytic balance by decreasing plasma PAI-1 levels, calcium channel antagonists have been shown to increase tissue plasminogen activator (tPA) activity, and angiotensin II type 1 (AT(1)) receptor antagonists seem to exert neutral effects. beta-Adrenoceptor antagonists, calcium channel antagonists, and AT(1)-receptor antagonists have been reported to exert anti-aggregatory effects on platelets, while contrasting data exist about the influence of ACE inhibitors. Clinical implications of the changes induced by antihypertensive drugs on the fibrinolytic balance and platelet function are still debated. In particular, the question of whether these changes may translate into different degrees of cardiovascular protection in hypertensive patients remains unanswered. While awaiting more information from clinical trials, the choice of antihypertensive drugs, particularly in high-risk patients, should take into account effects beyond their BP-lowering efficacy. Selected agents should have a favorable, or at least neutral, impact on fibrinolytic function and platelet activity.

Overcommitment to work is associated with changes in cardiac sympathetic regulation

OBJECTIVE

Work stress is associated with an increased risk for cardiovascular disease (CVD). Exaggerated cardiovascular reactivity to work-related stressors or incomplete recovery after work is a proposed mechanism underlying this increase in risk. This study examined the effects of work stress on 24-hour profiles of the pre-ejection period (PEP), a measure of cardiac sympathetic activity, obtained from ambulatory measurement of the impedance cardiogram.

METHODS

A total of 67 male white-collar workers (age 47.1 +/- 5.2) underwent ambulatory monitoring on 2 workdays and 1 non-workday. Work stress was defined according to Siegrist's model as 1) a combination of high effort and low reward at work (high imbalance) or 2) an exhaustive work-related coping style (high overcommitment).

RESULTS

High overcommitment was associated with shorter absolute PEP levels during all periods on all 3 measurement days, reduced wake-to-sleep PEP differences and reduced PEP variability, as indexed by the SD.

CONCLUSIONS

Overcommitment to work was associated with an increase in basal sympathetic drive and a reduction in the dynamic range of cardiac sympathetic regulation. Both findings are compatible with the hypothesis that overcommitment induces beta-receptor down-regulation.

Cardiac sympathetic nerve stimulation triggers coronary t-PA release

OBJECTIVE

This study was undertaken to determine whether stimulation of sympathetic cardiac nerves induces release of the thrombolytic enzyme tissue-type plasminogen activator (t-PA) in the coronary vascular bed.

METHODS AND RESULTS

Anesthetized pigs were studied in an open chest model. Bilateral vagotomy was performed, and sympathetic cardiac nerves were activated by electrical stimulation (1 and 8 Hz). To evaluate possible mediating effects of increased heart rate and enhanced local blood flow, tachycardia was induced by pacing and hyperemia by local infusion of sodium nitroprusside and clevedipine. Furthermore, to study the effects of alpha- and beta-adrenergic receptor stimulation, phenylephrine and isoprenaline were infused locally. In response to low- and high-frequency sympathetic stimulation, mean coronary net release of total t-PA increased approximately 6- and 25-fold, respectively. Active t-PA showed a similar response pattern. Neither tachycardia nor coronary hyperemia stimulated t-PA release. In contrast, beta-adrenergic stimulation by isoprenaline induced an approximately 6-fold increase in coronary t-PA release, whereas no significant change in release rates occurred in response to alpha-adrenergic stimulation by phenylephrine.

CONCLUSIONS

Stimulation of cardiac sympathetic nerves induces a marked coronary release of t-PA, and part of this response may be mediated through stimulation of beta-adrenergic receptors.

Effect of beta2-adrenergic receptor functioning and increased norepinephrine on the hypercoagulable state with mental stress

BACKGROUND

Procoagulant stress responses may contribute to atherosclerosis development and acute coronary thrombosis. In the present study, we examined the role of beta2-adrenergic receptor function and plasma catecholamines in the stress-induced increase in the 2 hypercoagulability markers thrombin-antithrombin III (TAT) complex and fibrin D-dimer (DD).

METHODS

Lymphocyte beta2-adrenoreceptor sensitivity and density were assessed at rest, and plasma levels of TAT, DD, epinephrine, and norepinephrine were measured at rest and in response to a standardized mental stress task in 19 normotensive and mildly hypertensive nonmedicated subjects (mean age 38 years, age range 29 to 48 years).

RESULTS

The stressor elicited a significant increase in TAT (P =.024), DD (P =.026), and norepinephrine (P =.005). Resting beta2-adrenoreceptor sensitivity (isoproterenol-stimulated cyclic adenosine monophosphate production) plus the norepinephrine change scores (stress minus rest) accounted for 59% of the variance in the absolute TAT increase in response to stress (P =.001). Hypertension status and demographic variables such as sex did not influence the results.

CONCLUSIONS

Acute mental stress may trigger a hypercoagulable state evidenced by increased thrombin activity and increased fibrin turnover. Beta2-adrenergic receptor sensitivity and plasma catecholamine activity may mediate the procoagulant response to acute stressors. These mechanisms may help explain the adverse impact of mental stress on the cardiovascular system.

Retained fibrinolytic response and no coagulation activation after acute physical exercise in middle-aged women with previous myocardial infarction

Sudden physical exertion is associated with an increased risk of acute myocardial infarction (MI) and sudden cardiac death. In addition, activation of the coagulation cascade and/or reduced fibrinolytic capacity after physical exercise has been reported in patients with cardiovascular disease. We investigated the haemostatic responses to an acute submaximal physical exercise in middle-aged women with a history of MI compared with healthy, age-matched controls. Resting plasma von Willebrand factor antigen (vWF Ag) and tissue plasminogen activator (tPA) antigen concentrations and plasminogen activator inhibitor-1 (PAI-1) activity were higher in the patients compared with control subjects. After 30 min of submaximal exercise on a bicycle ergometer, small, but still significant, increases in fibrinogen and vWF Ag concentrations were found in both groups. However, exercise did not induce thrombin generation and fibrin formation, as assessed by thrombin-antithrombin complex and fibrin D-dimer, in either group. Both tPA antigen concentration and activity increased and PAI-1 activity decreased significantly with exercise in both groups. Interestingly, the magnitude of changes in these latter variables did not differ between the groups (P=.99, P=.88 and P=.24, respectively). The present study demonstrates that some middle-aged women with previous MI have no signs of coagulation activation and retained fibrinolytic response after submaximal exercise. The clinical implication of these results might be that women with stable coronary heart disease can participate in rehabilitative exercise training without exhibiting a procoagulative state.

Plasminogen activator inhibitor-1 is a major stress-regulated gene: implications for stress-induced thrombosis in aged individuals

Plasminogen activator inhibitor-1 (PAI-1) is one of the primary inhibitors of the fibrinolytic system and has been implicated in a variety of thrombotic disorders. In this report, stress-induced changes in murine PAI-1 gene expression were investigated to study the role of this inhibitor in the development of stress-induced hypercoagulability. Restraint stress led to a dramatic induction of plasma PAI-1 antigen and of tissue PAI-1 mRNA with maximum induction in adipose tissues. In situ hybridization analysis of the stressed mice revealed that strong signals for PAI-1 mRNA were localized to hepatocytes, renal tubular epithelial cells, adrenomedullar chromaffin cells, neural cells in the paraaortic sympathetic ganglion, vascular smooth muscle cells, and adipocytes, but not to endothelial cells. These observations indicate that the stress induces the PAI-1 gene expression in a tissue-specific and cell type-specific manner. The induction of PAI-1 mRNA by restraint stress was greater than that observed for heat shock protein, a typical stress protein, suggesting that PAI-1 is one of the most highly induced stress proteins. Importantly, the magnitude of induction of PAI-1 mRNA by stress increased markedly with age, and this increase in PAI-1 correlated with tissue thrombosis in the older stressed mice. Moreover, much less tissue thrombosis was induced by restraint stress in young and aged PAI-1-deficient mice compared with age-matched wild-type mice. These results suggest that the large induction of PAI-1 by stress increases the risk for thrombosis in the older populations, and that the adipose tissue may be involved.

Cilnidipine more highly attenuates cold pressor stress-induced platelet activation in hypertension than does amlodipine

The clinical significance of N-type calcium channel blockade has not been fully examined. We here compared the effects of the N-type calcium channel blockers cilnidipine and amlodipine on the sympathetic nervous system and platelet function in hypertension under resting and stressed conditions. Thirty-two patients with hypertension (58+/-9 years) received cilnidipine or amlodipine for 4 weeks in this crossover study. On day 28 of each treatment, plasma levels of epinephrine (EP), norepinephrine (NEP), and beta-thromboglobulin (BTG), and EC50 of ADP-induced platelet aggregation (ADPE50) were determined at rest and after a cold pressor test. On day 29, the group receiving cilnidipine was switched to amlodipine treatment, and vice versa. At rest, the blood pressure, heart rates, EP, NEP, ADPEC50, and BTG, were similar in both treatments. After the cold pressor test, increases in EP (35+/-17 to 44+/-25 pg/ml; p<0.05) and BTG (40+/-13 to 49+/-22 ng/ml; p<0.01) and a decrease in ADPEC50 (32+/-26 to 27+/-24 micromol; p<0.05) were observed in the amlodipine treatment, but not in the cilnidipine treatment. In addition, the increase in NEP was significantly greater (p<0.05) in the amlodipine (276+/-78 to 318+/-87 pg/ml; p<0.01) than in the cilnidipine treatment (273+/-88 to 291+/-100 pg/ml; p<0.05). Cilnidipine more highly attenuates the activation of platelet function in response to cold pressor stress than does amlodipine. Attenuated activation of the sympathetic nervous system via N-type calcium channel blockade may contribute to this phenomenon.

Effects of psychological stress and psychiatric disorders on blood coagulation and fibrinolysis: a biobehavioral pathway to coronary artery disease?

OBJECTIVE

A hypercoagulable state before overt thrombosis resulting from an imbalance between the coagulation and fibrinolysis systems is related to cardiovascular disease progression and acute coronary syndromes. Psychological stressors and depressive and anxiety disorders also are associated with coronary artery disease. This review explores whether changes in blood coagulation, anticoagulant, and fibrinolytic activity may constitute psychobiological pathways that link psychological factors with coronary syndromes.

METHODS

Literature on coagulation, anticoagulation, and fibrinolysis measures in conjunction with psychological factors (mental stress, psychosocial strain, and psychiatric disorders) was identified by MEDLINE search back to 1966 and through checking the bibliographies of these sources. Sixty-eight articles were critically reviewed.

RESULTS

In healthy subjects, acute mental stress simultaneously activates coagulation (ie, fibrinogen or von Willebrand factor) and fibrinolysis (ie, tissue-type plasminogen activator) within a physiological range. In patients with atherosclerosis and impaired endothelial anticoagulant function, however, procoagulant responses to acute stressors may outweigh anticoagulant mechanisms and thereby promote a hypercoagulable state. Chronic psychosocial stressors (job strain or low socioeconomic status) are related to a hypercoagulable state reflected by increased procoagulant molecules (ie, fibrinogen or coagulation factor VII) and by reduced fibrinolytic capacity. There is also some evidence that points to hypercoagulability in depression.

CONCLUSIONS

Different categories of psychological measures to varying extent are associated with characteristic patterns of coagulation and fibrinolysis activity. Associations between psychological factors and several coagulation and fibrinolysis variables related to atherosclerosis provide a plausible biobehavioral link to coronary artery disease.

Both atenolol and propranolol blunt the fibrinolytic response to exercise but not resting fibrinolytic potential

This randomized, double-blind trial found that tissue plasminogen activator activity increased and plasminogen activator inhibitor-1 activity decreased significantly more with exercise during placebo treatment than during treatment with beta blockade. These results suggest that beta blockade blunts the fibrinolytic response to maximal exercise.

Potential Antithrombotic and Fibrinolytic Properties of the Angiotensin Converting Enzyme Inhibitors

As a class of therapeutic agents, the ACE inhibitors have proven to have long-term mortality benefit when used after myocardial infarction and among patients with symptomatic congestive heart failure. Clinical trial data also indicate that the use of ACE inhibitors is associated with reduced rates of recurrent coronary thrombosis, an observation that raises the possibility that the renin-angiotensin system may be directly involved in the thrombotic process and that the ACE inhibitors may have valuable fibrinolytic and/or antithrombotic effects. Recent in vitro and in vivo studies of angiotensin II and its interactions with the fibrinolytic system, particularly with the primary inhibitor of intravascular fibrinolysis, plasminogen activator inhibitor type 1 (PAI-1), provide substantial support for this hypothesis. In addition, a series of cross-sectional studies have described a genetic linkage between a common ACE gene polymorphism (DD) and the prevalence of clinical cardiovascular events, an intriguing finding as this polymorphism may account for much of the population variability in plasma ACE levels. Taken together, the totality of available clinical and experimental findings support the possibility of a direct linkage between the ACE system and vascular thrombosis that merits further prospective evaluation.

Work stress and metabolic and hemostatic risk factors

OBJECTIVE

A high level of work stress has been associated with cardiovascular disease. However, the pathophysiological mechanisms underlying this association remain unclear. This study examined the effect of work stress on a cluster of metabolic and hemostatic risk factors.

METHODS

Blood was collected three times, on the first, third, and fifth day of a work week, from 124 middle-aged, white-collar workers. Metabolic measures were insulin, glucose, triglycerides, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and total cholesterol. Hemostatic measures were fibrinogen, tissue-type plasminogen activator activity, tissue-type plasminogen activator antigen, and type 1 plasminogen activator inhibitor antigen. Chronic work stress was defined according to Siegrist's model as 1) a combination of high effort and low reward at work (effort-reward imbalance) or 2) high overcommitment (an exhaustive work-related coping style).

RESULTS

Overcommitment, but not imbalance or the imbalance-overcommitment interaction, was associated with an impaired fibrinolytic system, as reflected in decreased tissue-type plasminogen activator activity levels and increased type 1 plasminogen activator inhibitor antigen levels on all three measurement occasions. After controlling for body mass index, total cholesterol, triglycerides, high-density lipoprotein/low-density lipoprotein cholesterol ratio, glucose, and insulin, the relation between overcom-mitment and the fibrinolytic factors was attenuated but remained significant.

CONCLUSIONS

The results suggest that individuals with an exhaustive coping style at work have an impaired fibrinolytic capacity that is possibly due to the effects of chronic stress on insulin resistance.

Activation of coagulation and fibrinolysis after rehabilitative exercise in patients with coronary artery disease

It has been suggested that blood coagulation be activated and fibrinolytic activity be impaired in patients with coronary artery disease (CAD). With regard to the activation of coagulation and fibrinolysis occurring during exercise in healthy individuals, we examined the hypothesis that rehabilitative exercise in patients with CAD might give rise to an exaggerated activation of coagulation. In 12 patients with angiographically documented CAD without myocardial infarction within the preceding 6 months (male, age 55+/-9 years [SD]) and in 12 healthy controls (male, 52+/-7 years), molecular markers of thrombin, fibrin, and plasmin formation were determined before and after a rehabilitative group exercise session lasting 1 hour. Resting levels of prothrombin fragment 1+2 were lower in patients with CAD (0.67+/-0.2 [SE] vs 1.04+/-0.2 nmol/L, p <0.001) and remained unchanged after exercise, whereas a significant increase was noted in controls (p <0.01). After exercise, plasma levels of thrombin-antithrombin III complexes and of fibrinopeptide A increased significantly in both groups, although there were more pronounced changes in controls. Exercise resulted in a marked generation of plasmin as indicated by plasmin-alpha2-antiplasmin complexes increasing 2.5-fold in patients (p <0.001) and threefold in controls (p <0.001). Repeated experiments in control subjects after administration of aspirin (day 1: 500 mg; days 2 to 5: 100 mg) documented that differences between groups could not be attributed to aspirin medication (100 mg/day) in patients with CAD. We concluded that rehabilitative exercise in patients with CAD beyond the immediate postinfarction period has no detrimental effects on thrombin, fibrin, and plasmin formation.

Fibrinolytic variables and cardiovascular prognosis in patients with stable angina pectoris treated with verapamil or metoprolol. Results from the Angina Prognosis study in Stockholm

BACKGROUND

Disturbed fibrinolytic function may influence the progression of coronary atherosclerosis and contribute to thrombotic cardiovascular (CV) events.

METHODS AND RESULTS

In the Angina Prognosis Study in Stockholm (APSIS), patients with stable angina pectoris were studied prospectively during double-blind treatment with metoprolol or verapamil. Various measures of fibrinolytic function were studied in 631 (of 809) patients. During a median follow-up time of 3.2 years (2132 patient-years), 32 patients suffered a CV death, 21 had a nonfatal myocardial infarction (MI), and 77 underwent revascularization. Plasma levels of tissue plasminogen activator (TPA) activity and antigen (ag), plasminogen activator inhibitor (PAI-1) activity at test, and TPA responses to exercise were determined at baseline and after 1 month's treatment and were related to subsequent fatal and nonfatal CV events. Univariate Cox regression analysis revealed that elevated levels of TPA-ag at rest (P < .05), high PAI-1 activity (P < .05), and low TPA-ag responses to exercise (P < .05) were associated with increased risk of subsequent CV death. After adjustment for baseline risk factors, TPA-ag independently predicted CV death or MI. In addition, PAI-1 activity independently predicted CV death or MI in male patients. Verapamil treatment was associated with a 10% decrease of TPA-ag levels and metoprolol treatment with a 2% increase (P < .001 for treatment difference).

CONCLUSIONS

Plasma TPA-ag levels at rest, and among male patients PAI-1 activity as well, independently predict subsequent CV death or MI in patients with stable angina pectoris.

Effect of angiotensin II receptor blockade on fibrinolysis during acute hyperinsulinemia in patients with essential hypertension

We performed the present study to investigate indirectly the in vivo effects of angiotensin II on fibrinolysis and catecholamines by treatment with losartan, a selective angiotensin II type 1 receptor antagonist. The effects were evaluated in basal conditions as well as in two different models of acute hyperinsulinemia physiologically induced by oral glucose ingestion and by a euglycemic glucose clamp technique. Twenty subjects with moderate hypertension were included in a randomized, double-blind, placebo-controlled crossover study of 4-week treatment periods. Plasma levels of catecholamines, tissue plasminogen activator activity and antigen, and plasminogen activator inhibitor type 1 activity and antigen were unchanged in the basal state after 4 weeks of treatment. During both models of hyperinsulinemia, plasminogen activator inhibitor activity and antigen decreased significantly (both P<.001), and tissue plasminogen activator activity increased significantly (P<.Ol). Norepinephrine did not change during any of the procedures, whereas epinephrine increased significantly after 3 hours of the oral glucose tolerance test. Changes from baseline did not differ between the treatment and placebo regimens during the hyperinsulinemic procedures with regard to either of the fibrinolytic variables or the catecholamines. In conclusion, we could not demonstrate any effects of 4 weeks of treatment with losartan on plasma levels of fibrinolytic variables or catecholamines either in basal conditions or during acute hyperinsulinemia. However, the present findings do not preclude more direct effects of angiotensin II or involvement of other receptor subtypes on fibrinolysis.

Association of chronic stress with plasminogen activator inhibitor-1 in healthy middle-aged men

The effect of chronic stress on tissue-type plasminogen activator (TPA) and plasminogen activator inhibitor-1 (PAI-1) antigens was studied in 69 healthy middle-aged men. Chronic stress, defined as feelings of fatigue, lack of energy, increased irritability, and demoralization, was positively associated with plasma concentrations of PAI-1 antigen but was unrelated to TPA. The association remained unaltered after controlling for age, smoking, alcohol consumption, and physical activity but became nonsignificant after further controlling for abdominal obesity, BMI, and serum insulin and triglyceride levels. This attenuated association implies that the relationship between vital exhaustion and PAI-1 may be secondary to the effects of the metabolic variables. Thus, the present study shows that long-term stress affects the fibrinolytic system and suggests that obesity and insulin and triglyceride concentrations, which are closely correlated with the fibrinolytic parameters, may mediate the association. These findings are consistent with the hypothesis that chronic stress causes increased synthesis of PAI-1, thus promoting the risk for atherothrombotic disease by decreasing the likelihood of spontaneous fibrinolysis and increasing the likelihood of fibrin deposition.

Can psychological traits predict the outcome of lumbar disc surgery when anamnestic and physiological risk factors are controlled for? Results of a prospective cohort study

In a prospective study 122 patients with herniated lumbar disc pre-operatively completed psychological questionnaires. Surgical outcome was evaluated 12 months post-operatively mainly by a composite clinical overall score (COS), and by its separate elements. Anxiety (HAD-A scale) and psychosomatic symptoms (MSPQ) had predictive value: fewer symptoms favoured a satisfactory overall outcome, and vice versa. The HAD-A Scale had a predictive power of poor (ppp) and satisfactory (pps) outcome of 28 and 81%, respectively. Correspondingly, for the MSPQ, the ppp and pps were 42 and 85%. Anamnestic and biological variables (including fibrinolytic variables: ECLT and PAI-1) predicted 20% of the outcome. By adding all psychological variables the prediction increased only to 24%, but the HAD-A Scale and the MSPQ were still significant. The results suggest that in order to further improve prediction of outcome, future studies should combine biological variables sensitive to the mental state of the patient, with psychometric assessments.

Stimulation of plasminogen activator inhibitor in vivo by infusion of angiotensin II. Evidence of a potential interaction between the renin-angiotensin system and fibrinolytic function

BACKGROUND

Recent clinical trial data indicate that the use of angiotensin converting enzyme (ACE) inhibitors among patients with left ventricular dysfunction results in reduced rates of coronary thrombosis, a provocative finding that suggests a potential interaction between the renin-angiotensin system and fibrinolytic function.

METHODS AND RESULTS

In four normotensive subjects and six hypertensive patients, we investigated whether infusion of angiotensin II (Ang II) affected circulating levels of plasminogen activator inhibitor-1 (PAI-1), the most important physiological inhibitor of tissue-type plasminogen activator (t-PA). Overall, mean levels of PAI-1 antigen increased significantly from 20.1 ng/mL before Ang II infusion to 36.0 ng/mL at the end of Ang II infusion (p = 0.008), whereas no change in PAI-1 was observed for control subjects infused with 5% dextrose (p = 0.46). Among the normotensive subjects for whom graded doses of Ang II were infused at 0, 1, 3, and 10 ng.kg-1.min-1, mean PAI-1 levels increased sequentially from 14.7 ng/mL to 23.0, 26.8, and 33.5 ng/mL, a dose-response relation that, compared with controls, was highly significant (p < 0.001). Among the hypertensive patients for whom a single 45-minute infusion of Ang II was given at a dose of 3 ng.kg-1.min-1, PAI-1 levels increased from 23.7 to 37.7 ng/mL, whereas PAI-1 levels among control subjects infused with 5% dextrose decreased from 16.9 to 10.8 ng/mL (p = 0.04). Finally, when compared with infusion of 5% dextrose solution, infusion of Ang II appeared to have little effect on circulating levels of t-PA antigen.

CONCLUSIONS

These in vivo data suggest that infusion of Ang II results in a rapid increase in circulating levels of PAI-1, a finding that may help to explain clinical observations linking the renin-angiotensin system and thrombotic risk.

Effects of an oral dose of isosorbide dinitrate on platelet function and fibrinolysis in healthy volunteers

1. A randomised double-blind placebo-controlled study was performed to investigate the effects of isosorbide dinitrate (ISDN; 20 mg orally) on various aspects of platelet function and fibrinolysis in vivo in 12 healthy volunteers. 2. Measurements were performed at rest (before and after tablet ingestion) and during platelet activation by adrenaline (0.4 nmol kg-1 min-1; 30 min infusion). 3. At rest, ISDN did not alter plasma concentrations of beta-thromboglobulin (beta TG). EC50 values for ADP induced aggregation in vitro (Born aggregometry) or ex vivo filtragometry readings. Adrenaline markedly increased platelet aggregability in vivo as measured by filtragometry and elevated levels of beta TG in plasma. ISDN treatment did not affect these responses in the group as a whole. 4. Individuals responding to ISDN with more pronounced vasodilatation at rest showed a lesser increase in aggregability during the ensuing adrenaline infusion (r = -0.66, P = 0.02) despite higher adrenaline levels during ISDN. In individuals showing a significant decrease in systolic blood pressure (n = 8) ISDN tended to attenuate the adrenaline induced increase in platelet aggregability (filtragometry; P = 0.08), despite higher plasma adrenaline and noradrenaline levels after ISDN ingestion. 5. Plasma concentrations of ISDN and its active metabolites isosorbide-5-mononitrate and isosorbide-2-mononitrate were not correlated to haemodynamic or platelet variables. 6. Fibrinolytic activity (t-PA antigen and activity, PAI-1 antigen and activity) increased similarly during the adrenaline infusion following ISDN and placebo. 7. It is concluded that ISDN may affect platelet aggregation responses to adrenaline in vivo, but only in individuals showing significant haemodynamic responses to ISDN.(ABSTRACT TRUNCATED AT 250 WORDS)

Fibrinolytic response during exercise and epinephrine infusion in the same subjects

To determine whether exercise-induced increases in tissue plasminogen activator (t-PA) were related to plasma epinephrine concentration during exercise, 14 healthy men (aged 24 to 62 years) were studied during epinephrine infusions (10, 25 and 50 ng/kg per min) and graded supine bicycle exercise, beginning at 33 W and increasing in 33-W increments until exhaustion. Plasma epinephrine, active and total t-PA, active plasminogen activator inhibitor type 1 (PAI-1) and t-PA/PAI-1 complex concentrations were measured at each exercise and infusion level. During epinephrine infusion, active and total t-PA levels increased linearly with the plasma epinephrine concentration (respective slopes [+/- SEM] of 0.062 +/- 0.003 and 0.076 +/- 0.003 pmol/ng epinephrine). During exercise, t-PA levels did not increase until plasma epinephrine levels increased, after which both active and total t-PA levels again increased linearly with the plasma epinephrine concentration, but at twice the rate observed with epinephrine infusion (0.131 +/- 0.005 and 0.147 +/- 0.005 pmol/ng, respectively). The t-PA level in blood was directly proportional to the plasma epinephrine concentration during both exercise and epinephrine infusion, suggesting that epinephrine release during exercise stimulates t-PA secretion. In these healthy subjects, active plasminogen activator inhibitor type 1 and t-PA/PAI-1 complex levels were low (41 +/- 11 and 21 +/- 5 pmol/liter, respectively) and did not change significantly during exercise or epinephrine infusion. It is concluded that approximately 50% of the increase in t-PA during exercise is due to stimulated release of t-PA by epinephrine.(ABSTRACT TRUNCATED AT 250 WORDS)