Effects of acute angiotensin II type 1 receptor antagonism and angiotensin converting enzyme inhibition on plasma fibrinolytic parameters in patients with heart failure

Beta-blockers and inhibitors of the renin-angiotensin aldosterone system for chronic heart failure with preserved ejection fraction

BACKGROUND

Beta-blockers and inhibitors of the renin-angiotensin-aldosterone system improve survival and reduce morbidity in people with heart failure with reduced left ventricular ejection fraction (LVEF); a review of the evidence is required to determine whether these treatments are beneficial for people with heart failure with preserved ejection fraction (HFpEF).

OBJECTIVES

To assess the effects of beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, angiotensin receptor neprilysin inhibitors, and mineralocorticoid receptor antagonists in people with HFpEF.

SEARCH METHODS

We updated searches of CENTRAL, MEDLINE, Embase, and one clinical trial register on 14 May 2020 to identify eligible studies, with no language or date restrictions. We checked references from trial reports and review articles for additional studies.  SELECTION CRITERIA: We included randomised controlled trials with a parallel group design, enrolling adults with HFpEF, defined by LVEF greater than 40%.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included 41 randomised controlled trials (231 reports), totalling 23,492 participants across all comparisons. The risk of bias was frequently unclear and only five studies had a low risk of bias in all domains. Beta-blockers (BBs) We included 10 studies (3087 participants) investigating BBs. Five studies used a placebo comparator and in five the comparator was usual care. The mean age of participants ranged from 30 years to 81 years. A possible reduction in cardiovascular mortality was observed (risk ratio (RR) 0.78, 95% confidence interval (CI) 0.62 to 0.99; number needed to treat for an additional benefit (NNTB) 25; 1046 participants; three studies), however, the certainty of evidence was low. There may be little to no effect on all-cause mortality (RR 0.82, 95% CI 0.67 to 1.00; 1105 participants; four studies; low-certainty evidence). The effects on heart failure hospitalisation, hyperkalaemia, and quality of life remain uncertain. Mineralocorticoid receptor antagonists (MRAs) We included 13 studies (4459 participants) investigating MRA. Eight studies used a placebo comparator and in five the comparator was usual care. The mean age of participants ranged from 54.5 to 80 years. Pooled analysis indicated that MRA treatment probably reduces heart failure hospitalisation (RR 0.82, 95% CI 0.69 to 0.98; NNTB = 41; 3714 participants; three studies; moderate-certainty evidence). However, MRA treatment probably has little or no effect on all-cause mortality (RR 0.91, 95% CI 0.78 to 1.06; 4207 participants; five studies; moderate-certainty evidence) and cardiovascular mortality (RR 0.90, 95% CI 0.74 to 1.11; 4070 participants; three studies; moderate-certainty evidence). MRA treatment may have little or no effect on quality of life measures (mean difference (MD) 0.84, 95% CI -2.30 to 3.98; 511 participants; three studies; low-certainty evidence). MRA treatment was associated with a higher risk of hyperkalaemia (RR 2.11, 95% CI 1.77 to 2.51; number needed to treat for an additional harmful outcome (NNTH) = 11; 4291 participants; six studies; high-certainty evidence). Angiotensin-converting enzyme inhibitors (ACEIs) We included eight studies (2061 participants) investigating ACEIs. Three studies used a placebo comparator and in five the comparator was usual care. The mean age of participants ranged from 70 to 82 years. Pooled analyses with moderate-certainty evidence suggest that ACEI treatment likely has little or no effect on cardiovascular mortality (RR 0.93, 95% CI 0.61 to 1.42; 945 participants; two studies), all-cause mortality (RR 1.04, 95% CI 0.75 to 1.45; 1187 participants; five studies) and heart failure hospitalisation (RR 0.86, 95% CI 0.64 to 1.15; 1019 participants; three studies), and may result in little or no effect on the quality of life (MD -0.09, 95% CI -3.66 to 3.48; 154 participants; two studies; low-certainty evidence). The effects on hyperkalaemia remain uncertain. Angiotensin receptor blockers (ARBs) Eight studies (8755 participants) investigating ARBs were included. Five studies used a placebo comparator and in three the comparator was usual care. The mean age of participants ranged from 61 to 75 years. Pooled analyses with high certainty of evidence suggest that ARB treatment has little or no effect on cardiovascular mortality (RR 1.02, 95% 0.90 to 1.14; 7254 participants; three studies), all-cause mortality (RR 1.01, 95% CI 0.92 to 1.11; 7964 participants; four studies), heart failure hospitalisation (RR 0.92, 95% CI 0.83 to 1.02; 7254 participants; three studies), and quality of life (MD 0.41, 95% CI -0.86 to 1.67; 3117 participants; three studies). ARB was associated with a higher risk of hyperkalaemia (RR 1.88, 95% CI 1.07 to 3.33; 7148 participants; two studies; high-certainty evidence). Angiotensin receptor neprilysin inhibitors (ARNIs) Three studies (7702 participants) investigating ARNIs were included. Two studies used ARBs as the comparator and one used standardised medical therapy, based on participants' established treatments at enrolment. The mean age of participants ranged from 71 to 73 years. Results suggest that ARNIs may have little or no effect on cardiovascular mortality (RR 0.96, 95% CI 0.79 to 1.15; 4796 participants; one study; moderate-certainty evidence), all-cause mortality (RR 0.97, 95% CI 0.84 to 1.11; 7663 participants; three studies; high-certainty evidence), or quality of life (high-certainty evidence). However, ARNI treatment may result in a slight reduction in heart failure hospitalisation, compared to usual care (RR 0.89, 95% CI 0.80 to 1.00; 7362 participants; two studies; moderate-certainty evidence). ARNI treatment was associated with a reduced risk of hyperkalaemia compared with valsartan (RR 0.88, 95% CI 0.77 to 1.01; 5054 participants; two studies; moderate-certainty evidence).

AUTHORS' CONCLUSIONS

There is evidence that MRA and ARNI treatment in HFpEF probably reduces heart failure hospitalisation but probably has little or no effect on cardiovascular mortality and quality of life. BB treatment may reduce the risk of cardiovascular mortality, however, further trials are needed. The current evidence for BBs, ACEIs, and ARBs is limited and does not support their use in HFpEF in the absence of an alternative indication. Although MRAs and ARNIs are probably effective at reducing the risk of heart failure hospitalisation, the treatment effect sizes are modest. There is a need for improved approaches to patient stratification to identify the subgroup of patients who are most likely to benefit from MRAs and ARNIs, as well as for an improved understanding of disease biology, and for new therapeutic approaches.

Beta-blockers and inhibitors of the renin-angiotensin aldosterone system for chronic heart failure with preserved ejection fraction

BACKGROUND

Beta-blockers and inhibitors of the renin-angiotensin aldosterone system improve survival and reduce morbidity in people with heart failure with reduced left ventricular ejection fraction. There is uncertainty whether these treatments are beneficial for people with heart failure with preserved ejection fraction and a comprehensive review of the evidence is required.

OBJECTIVES

To assess the effects of beta-blockers, angiotensin converting enzyme inhibitors, angiotensin receptor blockers, angiotensin receptor neprilysin inhibitors, and mineralocorticoid receptor antagonists in people with heart failure with preserved ejection fraction.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase and two clinical trial registries on 25 July 2017 to identify eligible studies. Reference lists from primary studies and review articles were checked for additional studies. There were no language or date restrictions.

SELECTION CRITERIA

We included randomised controlled trials with a parallel group design enrolling adult participants with heart failure with preserved ejection fraction, defined by a left ventricular ejection fraction of greater than 40 percent.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies for inclusion and extracted data. The outcomes assessed included cardiovascular mortality, heart failure hospitalisation, hyperkalaemia, all-cause mortality and quality of life. Risk ratios (RR) and, where possible, hazard ratios (HR) were calculated for dichotomous outcomes. For continuous data, mean difference (MD) or standardised mean difference (SMD) were calculated. We contacted trialists where neccessary to obtain missing data.

MAIN RESULTS

37 randomised controlled trials (207 reports) were included across all comparisons with a total of 18,311 participants.Ten studies (3087 participants) investigating beta-blockers (BB) were included. A pooled analysis indicated a reduction in cardiovascular mortality (15% of participants in the intervention arm versus 19% in the control arm; RR 0.78; 95% confidence interval (CI) 0.62 to 0.99; number needed to treat to benefit (NNTB) 25; 1046 participants; 3 studies). However, the quality of evidence was low and no effect on cardiovascular mortality was observed when the analysis was limited to studies with a low risk of bias (RR 0.81; 95% CI 0.50 to 1.29; 643 participants; 1 study). There was no effect on all-cause mortality, heart failure hospitalisation or quality of life measures, however there is uncertainty about these effects given the limited evidence available.12 studies (4408 participants) investigating mineralocorticoid receptor antagonists (MRA) were included with the quality of evidence assessed as moderate. MRA treatment reduced heart failure hospitalisation (11% of participants in the intervention arm versus 14% in the control arm; RR 0.82; 95% CI 0.69 to 0.98; NNTB 41; 3714 participants; 3 studies; moderate-quality evidence) however, little or no effect on all-cause and cardiovascular mortality and quality of life measures was observed. MRA treatment was associated with a greater risk of hyperkalaemia (16% of participants in the intervention group versus 8% in the control group; RR 2.11; 95% CI 1.77 to 2.51; 4291 participants; 6 studies; high-quality evidence).Eight studies (2061 participants) investigating angiotensin converting enzyme inhibitors (ACEI) were included with the overall quality of evidence assessed as moderate. The evidence suggested that ACEI treatment likely has little or no effect on cardiovascular mortality, all-cause mortality, heart failure hospitalisation, or quality of life. Data for the effect of ACEI on hyperkalaemia were only available from one of the included studies.Eight studies (8755 participants) investigating angiotensin receptor blockers (ARB) were included with the overall quality of evidence assessed as high. The evidence suggested that treatment with ARB has little or no effect on cardiovascular mortality, all-cause mortality, heart failure hospitalisation, or quality of life. ARB was associated with an increased risk of hyperkalaemia (0.9% of participants in the intervention group versus 0.5% in the control group; RR 1.88; 95% CI 1.07 to 3.33; 7148 participants; 2 studies; high-quality evidence).We identified a single ongoing placebo-controlled study investigating the effect of angiotensin receptor neprilysin inhibitors (ARNI) in people with heart failure with preserved ejection fraction.

AUTHORS' CONCLUSIONS

There is evidence that MRA treatment reduces heart failure hospitalisation in heart failure with preserverd ejection fraction, however the effects on mortality related outcomes and quality of life remain unclear. The available evidence for beta-blockers, ACEI, ARB and ARNI is limited and it remains uncertain whether these treatments have a role in the treatment of HFpEF in the absence of an alternative indication for their use. This comprehensive review highlights a persistent gap in the evidence that is currently being addressed through several large ongoing clinical trials.

Antithrombotic effects of losartan in patients with hypertension complicated by atrial fibrillation: 4A (Angiotensin II Antagonist of platelet Aggregation in patients with Atrial fibrillation), a pilot study

Angiotensin receptor blockers (ARBs) are widely used for the treatment of hypertension. It has been reported that the ARB losartan has antiplatelet, anticoagulant and profibrinolytic effects experimentally. These properties could be desirable to treat hypertensive patients with high atherothrombotic and/or thromboembolic risk. To examine the antithrombotic effects of losartan in hypertension, 20 consecutive patients with hypertension complicated by atrial fibrillation (AF) were enrolled in this study. The patients were treated with losartan 50 mg for 8 weeks followed by 100 mg for 4 weeks. Blood samples were obtained from each patient at 0 (pretreatment), 8 and 12 weeks after initiating treatment. Platelet aggregability, plasma levels of tissue factor (TF) and type 1 plasminogen activator inhibitor (PAI-1) activity levels were measured. The area under the curve for small platelet aggregability decreased from 100 to 42.8% at 12 weeks (P<0.0001). TF levels (ng ml(-1)) and PAI-1 activity (IU ml(-1); mean±s.d.) also changed from 14.2±3.6 to 10.9±4.5 at 12 weeks (P=0.0299) and from 11.7±3.6 to 8.5±3.1 at 12 weeks (P=0.0122), respectively. Losartan inhibited platelet activity and coagulation factors in a dose- and time-dependent manner in patients with hypertension complicated by AF, whereas the fibrinolytic capacity was increased. The use of losartan could be advantageous in the treatment of hypertensive patients with high atherothrombotic risk.

A modern understanding of the traditional and nontraditional biological functions of angiotensin-converting enzyme

Angiotensin-converting enzyme (ACE) is a zinc-dependent peptidase responsible for converting angiotensin I into the vasoconstrictor angiotensin II. However, ACE is a relatively nonspecific peptidase that is capable of cleaving a wide range of substrates. Because of this, ACE and its peptide substrates and products affect many physiologic processes, including blood pressure control, hematopoiesis, reproduction, renal development, renal function, and the immune response. The defining feature of ACE is that it is composed of two homologous and independently catalytic domains, the result of an ancient gene duplication, and ACE-like genes are widely distributed in nature. The two ACE catalytic domains contribute to the wide substrate diversity of ACE and, by extension, the physiologic impact of the enzyme. Several studies suggest that the two catalytic domains have different biologic functions. Recently, the X-ray crystal structure of ACE has elucidated some of the structural differences between the two ACE domains. This is important now that ACE domain-specific inhibitors have been synthesized and characterized. Once widely available, these reagents will undoubtedly be powerful tools for probing the physiologic actions of each ACE domain. In turn, this knowledge should allow clinicians to envision new therapies for diseases not currently treated with ACE inhibitors.

The angiotensin-converting enzyme 2/angiotensin-(1-7)/Mas receptor axis: a potential target for treating thrombotic diseases

Despite many therapeutic advances leading to increasingly effective drug treatments, thrombotic events (such as ischaemic stroke, pulmonary embolism, deep venous thrombosis and acute myocardial infarction) still represent a major worldwide cause of morbidity and mortality. Remarkable effort has been made to identify new drug targets. There is growing evidence indicating that the recently described counter-regulator axis of the renin-angiotensin system (RAS), composed of Angiotensin-Converting Enzyme 2 (ACE2), Angiotensin-(1-7) and the Mas receptor, has protective effects against thrombosis. In addition, it could be considered as a promising target for treating or preventing this disease. In this narrative review, we focused on the recent findings of the role of the ACE2/Angiotensin-(1-7)/Mas axis on the haemostatic process and its therapeutic potential.

Physiological regulation of MMPs and tPA/PAI in the arterial wall of rats by noradrenergic tone and angiotensin II

The interactions between the sympathetic nervous system (SNS) and angiotensin II (ANG II), and their direct effects in vitro on the enzymes involved in vascular extracellular matrix (ECM) degradation, were examined.

Rats were treated with guanethidine, losartan or the combined treatments. mRNA, protein and activity of matrix metalloproteinase (MMP)-2 and MMP-9 and mRNA of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor 1 (PAI-1) were quantified in abdominal aorta (AA) and femoral artery (FA). Norepinephrine (NE) or ANG II with adrenergic (β, α1 and α2) or losartan antagonists was tested for MMP mRNA response in cultured vascular smooth muscle cells (VSMCs).

Combined treatment enhances the inhibition of MMP-2 mRNA and protein level induced by simple treatment in AA. However MMP-9 in AA and MMP mRNA in FA were reduced in the same order by treatments. MMP activities were not affected by treatments. The t-PA/PAI-1 ratio, which reflects the fibrinolytic balance, remained higher after treatments. In cultured VSMCs, NE induced stimulation of MMP mRNA via α2 and β adrenergic receptors and MMP-2 activity via β adrenergic receptors, while ANG II-induced stimulation was abrogated by losartan.

Overall, there is a synergic inhibition of both systems on the level of MMP-2 in AA.

Role of angiotensin II in plasma PAI-1 changes induced by imidapril or candesartan in hypertensive patients with metabolic syndrome

To evaluate the relationship between plasma plasminogen activator inhibitor-1 (PAI-1) and angiotensin II (Ang II) changes during treatment with imidapril and candesartan in hypertensive patients with metabolic syndrome. A total of 84 hypertensive patients with metabolic syndrome were randomized to imidapril 10 mg or candesartan 16 mg for 16 weeks. At weeks 4 and 8, there was a dose titration to imidapril 20 mg and candesartan 32 mg in nonresponders (systolic blood pressure (SBP) >140 and/or diastolic blood pressure (DBP) >90 mm Hg). We evaluated, at baseline and after 2, 4, 8, 12 and 16 weeks, clinic blood pressure, Ang II and PAI-1 antigen. Both imidapril and candesartan induced a similar SBP/DBP reduction (-19.4/16.8 and -19.5/16.3 mm Hg, respectively, P<0.001 vs. baseline). Both drugs decreased PAI-1 antigen after 4 weeks of treatment, but only the PAI-1 lowering effect of imidapril was sustained throughout the 16 weeks (-9.3 ng ml(-1), P<0.01 vs. baseline), whereas candesartan increased PAI-1 (+6.5 ng ml(-1), P<0.05 vs. baseline and P<0.01 vs. imidapril). Imidapril significantly decreased Ang II levels (-14.6 pg ml(-1) at week 16, P<0.05 vs. baseline), whereas candesartan increased them (+24.2 pg ml(-1), P<0.01 vs. baseline and vs. imidapril). In both groups there was a positive correlation between Ang II and PAI-1 changes (r=0.61, P<0.001 at week 16 for imidapril, and r=0.37, P<0.005 at week 16 for candesartan). Imidapril reduced plasma PAI-1 and Ang II levels, whereas candesartan increased them. This suggests that the different effect of angiotensin-converting enzyme inhibitors and Ang II blockers on Ang II production has a role in their different influence on fibrinolysis.

Effect of renin-angiotensin-aldosterone system triple blockade on non-diabetic renal disease: addition of an aldosterone blocker, spironolactone, to combination treatment with an angiotensin-converting enzyme inhibitor and angiotensin II receptor blocker

Although dual blockade of the renin-angiotensin-aldosterone system (RAAS) with the combination of an angiotensin-converting enzyme inhibitor (ACE-I) and angiotensin II receptor blocker (ARB) is generally well-established as a treatment for nephropathy, this treatment is not fully effective in some patients. Based on the recent evidence implicating aldosterone in renal disease progression, this study was conducted to examine the efficacy of blockade with three different mechanisms by adding an aldosterone blocker in patients who do not respond adequately to the dual blockade. A 1-year randomized, open-label, multicenter, prospective controlled study was conducted, in which 32 non-diabetic nephropathy patients with proteinuria exceeding 0.5 g/day were enrolled after more than 12 weeks of ACE-I (5 mg enalapril) and ARB (50 mg losartan) combination treatment. These patients were allocated into two groups of 16 patients each: a triple blockade group in which 25 mg of spironolactone daily was added to the ACE-I and ARB combination treatment, and a control group in which 1 mg of trichlormethiazide or 20 mg of furosemide was added to the combination treatment instead of spironolactone depending upon the creatinine level. After 1 year of treatment, the urinary protein level decreased by 58% (p<0.05) with the triple blockade but was unchanged in the controls. Furthermore, urinary type IV collagen level decreased by 40% (p<0.05) with the triple blockade but was unchanged in the controls. The decreases in urinary protein and urinary type IV collagen were not accompanied by a decrease in blood pressure. Mean serum creatinine, potassium and blood pressure did not change significantly by either treatment. In conclusion, triple blockade of the RAAS was effective for the treatment of proteinuria in patients with non-diabetic nephropathy whose increased urinary protein had not responded sufficiently to a dual blockade.

Vascular benefits of angiotensin receptor blockers

There is convincing evidence that angiotensin II, through activation of the angiotensin II type 1 (AT1) receptor, is involved in the atherosclerotic process. Similarly, angiotensin receptor blockers decrease vascular inflammation, hypertrophy and thrombosis, which are the key components of the progression of atherosclerosis. In addition, in several animal models, angiotensin receptor blockade was able to inhibit atherosclerosis. However, the effects of angiotensin receptor blockers on clinical outcome in cardiovascular patients remains to be established. Contradictory results have been found on the reduction of the risk on myocardial infarctions and in-stent restenosis, although there is solid evidence for cerebroprotective effects of these receptor blockers. These differences may be related to the role of the AT2 receptor. This review discusses the role of angiotensin II and angiotensin receptor blockers in the atherosclerotic process and its translation into clinical practice.

Changes in fibrinolytic activity after angiotensin II receptor blockade in therapy-resistant hypertensive patients

BACKGROUND

In hypertensive patients, the activated renin-angiotensin system induces a prothrombotic state resulting from imbalance between coagulation and fibrinolysis. Although blood pressure cannot be regulated in therapy-resistant hypertensive patients, they may still be responsive to medication that attenuates the renin-angiotensin system.

OBJECTIVE

our objective was to study possible attenuating properties of angiotensin II type 1 receptor blockers (AT1RBs) on the prothrombotic state in therapy-resistant hypertensive patients, focusing on parameters of fibrinolysis and coagulation.

METHODS

Fourteen therapy-resistant hypertensive patients received AT1RB eprosartan infusion (45 and 150 microg kg(-1)) (study group), and 33 therapy-resistant hypertensive patients received saline (0.9%) infusion (control group) prior to renal angiography. Baseline values of parameters of coagulation and fibrinolysis were set at 1.00, and relative changes were calculated.

RESULTS

Plasminogen activator inhibitor type 1 (PAI-1) antigen showed non-significant decreases in both the study group (arterial 1.00-0.45, venous 1.00-0.42) and control group (arterial 1.00-0.84, venous 1.00-0.88). PAI-1 activity significantly decreased in the study group (arterial 1.00-0.72, venous 1.00-0.71) and control group (arterial 1.00-0.83, venous 1.00-0.94). In the study group, tissue-type plasminogen activator (t-PA) antigen decreased significantly (arterial 1.00-0.62, venous 1.00-0.67), whereas t-PA activity significantly increased (arterial 1.00-6.15, venous 1.00-2.66). In the control group, t-PA antigen remained unchanged. No changes were observed in blood pressure during and after infusion of eprosartan.

CONCLUSION

Therapy-resistant hypertensive patients show beneficial changes in fibrinolytic activity after infusion of a non-pressor dose of AT1RB.

Modulation of angiotensin II and norepinephrine-induced plasminogen activator inhibitor-1 expression by AT1a receptor deficiency

Angiotensin (Ang) II stimulates plasminogen activator inhibitor-1 (PAI-1) expression in many cell types by mechanisms that are cell-type specific. We measured effects of Ang II or norepinephrine on PAI-1 expression in wild type (WT) and Ang type-1a receptor knockout mice (AT(1a)-/-) in the presence or absence of the non-specific AT(1) antagonist losartan. Ang II and norepinephrine increased systolic blood pressure equally, whereas losartan decreased the pressor response of the former but not the latter in WT mice. In AT(1a)-/- mice, baseline systolic blood pressure was lower with no effect of Ang II, norepinephrine, or losartan. Ang II stimulated PAI-1 expression in the heart, aorta, and kidney and markedly in the liver of WT mice. In AT(1a)-/- mice, Ang II-stimulated PAI-1 was significantly attenuated compared with the WT in the heart and aorta but significantly enhanced in the kidney. Losartan decreased the induction in the aorta and liver of WT, and in the kidney and liver of AT(1a)-/- mice. Norepinephrine increased PAI-1 expression in WT heart and aorta, and in AT(1a)-/- heart, kidney, and liver with no effect of losartan. Renal PAI-1 expression correlated with AT(1b) receptor mRNA. We conclude that Ang II stimulates PAI-1 expression in part through the AT(1b) receptor in the kidney and liver. Further, norepinephrine induces PAI-1 expression in vivo with AT(1a) receptor deficiency modulating the effect.

Effects of Candesartan and Lisinopril on the Fibrinolytic System in Hypertensive Patients

The effects of the angiotensin II receptor blocker candesartan and the angiotensin-converting enzyme inhibitor lisinopril on the fibrinolytic system were investigated in a double-blinded, prospective, randomized study. Seventy-seven hypertensive patients taking candesartan (n=41) and lisinopril (n=36) with a systolic blood pressure >130 mm Hg and/or a diastolic blood pressure >80 mm Hg obtained by 24-hour ambulatory blood pressure measurement were included in the study. Blood pressure, plasminogen activator inhibitor 1 (PAI-1), tissue plasminogen activator (tPA), and the molar ratio of PAI-1/tPA were determined before treatment and 6 weeks later. Blood pressure decreased in both groups (candesartan, 155/85 mm Hg to 140/84 mm Hg; P<.05; lisinopril, 152/85 mm Hg to 138/83 mm Hg; P<.05). The fibrinolytic balance was significantly different between treatment groups (molar ratio of PAI-1/tPA: candesartan, 3.66 [2.2;] lisinopril, 5.44 [2.6;] P<.05). In contrast to lisinopril, the balance between coagulation and fibrinolytic activity shifted toward fibrinolysis during candesartan treatment.

Chronic blockade of the angiotensin II receptor has a differential effect on adipose and vascular PAI-1 in OLETF rats

Angiotensinogen (AGT) and plasminogen activator inhibitor-1 (PAI-1) are expressed in both vascular and adipose tissues. Angiotensin II (AG II) has an adipogenic effect and increases PAI-1 expression. To evaluate the chronic effects of AG II type 1 receptor (AT(1)R) antagonism on adipose mass and PAI-1 expression in vascular and adipose tissues, losartan (30mg/kg/day) was administered to Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of type 2 diabetes, for 20 weeks. Adipose mass and regional fat distribution in the abdomen did not change after chronic AT(1)R antagonism in OLETF rats. AGT and PAI-1 mRNA expressions in adipose tissue of OLETF rats were significantly increased compared with Long-Evans Tokushima Otsuka (LETO) rats, the normal control. Chronic losartan therapy further increased the level of adipose AGT in OLETF rats, but did not affect the level of adipose PAI-1 mRNA. In contrast, aortic PAI-1 expression in OLETF rats was attenuated by chronic losartan therapy. Our results have two implications. First, adipose tissue may be an important source of AG II in metabolic syndrome even after chronic losartan therapy. Second, chronic AT(1)R antagonism with losartan causes differential effects on vascular and adipose PAI-1 expression.

Vascular and metabolic effects of candesartan: insights from therapeutic interventions

BACKGROUND

Effects of angiotensin II type 1 receptor blockers (ARBs) to improve endothelial dysfunction may be due to mechanisms in addition to the reduction of high blood pressure per se. Endothelial dysfunction is characterized by vascular inflammation that contributes to clinically significant atherosclerosis and by an increased tendency for thrombus formation. Hypertensive patients have impaired endothelial functions that have positive predictive power with respect to future cardiovascular events.

OBJECTIVES

The present review will focus on multiple mechanisms underlying vascular and metabolic effects of ARBs that may synergize to prevent or regress atherosclerosis, onset of diabetes, and coronary heart disease.

CONCLUSIONS

Angiotensin II accelerates the development of atherosclerosis by activating angiotensin II type 1 receptors that then promote superoxide anion generation and oxidative stress, leading to activation of nuclear transcription factor and endothelial dysfunction. Activation of angiotensin II type 1 receptors also stimulates increased expression of plasminogen activator inhibitor type 1 and tissue factor. Endothelial dysfunction associated with the metabolic syndrome and other insulin-resistant states is characterized by impaired insulin-stimulated production of nitric oxide from the endothelium and decreased blood flow to skeletal muscle. Increasing insulin sensitivity therefore improves endothelial function, and this may be an additional mechanism whereby ARBs decrease the incidence of coronary heart disease and the onset of diabetes. Adiponectin serves to link obesity with insulin resistance. In addition, adiponectin has anti-atherogenic properties.

Targeting the renin-angiotensin-aldosterone-system in atrial fibrillation: a shift from electrical to structural therapy?

Despite its increasing incidence and prevalence, treatment options in atrial fibrillation (AF) are far from ideal and often limited. After decades of focus on the electrical aspects of AF with unsatisfactory results, recent research is focusing increasingly on the atrial structural remodelling that underlies the development of AF in different pathological conditions, such as hypertension, heart failure, diabetes mellitus and coronary artery disease. The aim of this review is to provide a comprehensive overview of the role of the renin-angiotensin-aldosterone-system in AF and to highlight the clinical evidence on renin-angiotensin-aldosterone-system blockade as a therapeutic option in AF.

Salutary effects of attenuation of angiotensin II on coronary perivascular fibrosis associated with insulin resistance and obesity

Obesity and insulin resistance confer increased risk for accelerated coronary disease and cardiomyopathic phenomena. We have previously shown that inhibition of angiotensin-converting enzyme (ACE) prevents coronary perimicrovascular fibrosis in genetically obese mice that develop insulin resistance. This study was performed to elucidate mechanism(s) implicated and to determine the effects of attenuation of angiotensin II (Ang) II. Genetically obese ob/ob mice were given ACE inhibitor (temocapril) or Ang II type 1 (AT(1)) receptor blocker (olmesartan) from 10 to 20 weeks. Cardiac expressions of plasminogen activator inhibitor (PAI)-1, the major physiologic inhibitor of fibrinolysis, and transforming growth factor (TGF)-beta(1), a prototypic profibrotic molecule, were determined and extent of perivascular coronary fibrosis was measured. Twenty-week-old obese mice exhibited increased plasma levels of PAI-1 and TGF-beta(1) compared with the values in lean counterpart. Perivascular coronary fibrosis in arterioles and small arteries was evident in obese mice that also showed increased left ventricular collagen as measured by hydroxyproline assay. Immunohistochemistry confirmed the deposition of perivascular type 1 collagen. Markedly increased PAI-1 and TGF-beta were seen immunohistochemically in coronary vascular wall and confirmed by western blotting. When obese mice were treated with temocapril or olmesartan from 10 to 20 weeks, both were equally effective and prevented increases in perivascular fibrosis, plasma PAI-1 and TGF-beta(1), left ventricular collagen and mural immunoreactivity for PAI-1, TGF-beta and collagen type 1. The c-Jun NH(2)-terminal kinase (JNK) activity was elevated in the left ventricle of obese mice (western) and blocked by temocapril and olmesartan. Ang II-mediated upregulation of PAI-1 and TGF-beta(1) with collagen deposition may explain the mechanism of perivascular fibrosis in obese mice. ACE inhibition and blockade of AT(1) receptor may prevent coronary perivascular fibrosis and collagen deposition even before development of overt diabetes. JNK activation may be a mediator of obesity-related cardiac dysfunction and a potential therapeutic target.

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.

Angiotensin II type 1 receptor blockers reduce tissue factor activity and plasminogen activator inhibitor type-1 antigen in hypertensive patients: a randomized, double-blind, placebo-controlled study

Angiotensin II stimulates the expression of tissue factor (TF) and plasminogen activator inhibitor type-1 (PAI-1), and AT1 receptor blockade (ARB) reduces PAI-1 and TF activities in experimental studies. We investigated the effects of ARBs on TF activity, tissue plasminogen activator (tPA), PAI-1 antigen levels, plasma renin activity (PRA) and aldosterone levels in hypertensive patients. Placebo, losartan 100mg, irbesartan 300 mg, and candesartan 16 mg daily were administered to 122 patients for 2 months. Compared with placebo, ARBs significantly reduced TF activity (P <0.001 by ANOVA), and candesartan was the most potent. Compared with placebo or losartan, irbesartan and candesartan significantly lowered plasma levels of PAI-1 antigen (P <0.001 by ANOVA) with no differences between the two. Compared with placebo, all ARBs lowered plasma levels of aldosterone (P=0.012 by ANOVA) and increased PRA (P=0.005 by ANOVA). There were significant correlations between the degree of change in TF activity and PAI-1 antigen levels (r=0.458, P <0.0001) and between the change in TF activity and PRA (r=-0.296, P=0.006), but not with the magnitude of reduction in blood pressure following ARB therapy. ARBs significantly reduced TF activity, PAI-1 antigen levels, and aldosterone levels in hypertensive patients. The clinical significance of the varying potency of some ARBs needs to be further investigated.

Questioning a class effect: does ACE inhibitor tissue penetration influence the degree of fibrinolytic balance alteration following an acute myocardial infarction?

There is a common belief in a class effect among angiotensin-converting enzyme (ACE) inhibitors. This is unsubstantiated for acute myocardial infarction (AMI). Because vascular tissue is a source of the endogenous fibrinolytic markers, and ACE inhibition in vascular tissue favorably influences the fibrinolytic system, the authors hypothesized that a high-tissue-penetrating ACE inhibitor would provide a more favorable reduction in plasminogen activator inhibitor-1 (PAI-1) and an increase in tissue plasminogen activator (t-PA) after AMI compared to a low-tissue-penetrating ACE inhibitor. In a randomized open-label trial, patients received the high-tissue-penetrating quinapril (n = 15) or low-tissue-penetrating enalapril (n = 15) immediately following an AMI. PAI-1 and t-PA antigen (ng/mL) were measured at baseline and through 14 days of treatment. There was no difference in baseline PAI-1 or t-PA antigen between treatments. PAI-1 antigen trended toward being lower with quinapril versus enalapril on day 1 (24.44 +/- 14.96 vs. 36.94 +/- 19.49, respectively, p = 0.059) and was significantly lower on day 3 (17.32 +/- 9.57 vs. 27.49 +/- 9.61, respectively, p = 0.009). Analysis of PAI-1 antigen over time by two-factor ANOVA with replication found significantly lower concentrations of PAI-1 antigen over the entire treatment period with quinapril versus enalapril (p < 0.003). This investigation of ACE inhibitor tissue-penetrating influence on markers of reinfarction risk suggests there may be a greater early reduction in PAI-1 with a more highly tissue-penetrating ACE inhibitor.

Effect of ramipril on postrevascularization prevalence of angina and quality of life

BACKGROUND

The prevalence of angina after invasive revascularization is not negligible and impacts on quality of life. It has not been clarified whether potential anti-ischemic actions of angiotensin-converting enzyme inhibitors (1) may apply to non high-risk patients and (2) may reduce the prevalence of angina. We sought to test the hypothesis that ramipril, an angiotensin-converting enzyme inhibitor, may reduce the postrevascularization prevalence of angina pectoris and improve quality of life.

METHODS

In the Angiotensin-converting enzyme Post-Revascularization Study (APRES), 159 patients who underwent invasive revascularization for chronic angina and who had not had heart failure, acute myocardial infarction (AMI), or severe left ventricular dysfunction were randomized to receive 10 mg of ramipril or placebo. During the 12- to 46-month follow-up, the Specific Activity Scale class, exercise tests, and SF-36 quality of life scores were serially assessed.

RESULTS

The average prevalence of angina of Specific Activity Scale class II or worse was 26.6% in the ramipril group and 19.9% in the placebo group (p=0.16). The average prevalence of exercise-inducible ischemia was 30.8% in the ramipril group and 25.2% in the placebo group (p=0.39). There were no significant differences between the two treatment groups in the SF-36 quality of life scores or in the Duke treadmill score. Post-hoc power calculations revealed that the power to rule out a clinical significant benefit of ramipril on the prevalence of angina, quality of life, and Duke treadmill score was >90%.

CONCLUSIONS

These data do not suggest that ramipril reduces the prevalence of angina pectoris or improves quality of life after invasive revascularization in such patients

Role of thrombotic and fibrinolytic factors in acute coronary syndromes

There is a growing body of literature concerning the contribution of hemostatic factors to the development of cardiovascular disease. The mechanisms of the coagulation/fibrinolytic system are complicated and one factor is intimately interrelated with another; thus the contribution of each factor cannot be clearly understood, unless hemostatic factors are considered in accordance with endothelial function and vessel morphology. Although there are many clinical studies about the correlation between hemostatic factors and cardiovascular risk, the results are inconsistent and conflicting at times. Fibrinogen and D-dimer are associated with atherosclerosis or coronary events across multiple studies, even after multivariate adjustment. But the hemostatic factors are intimately correlated, so it can be said that focusing on one to the exclusion of others is inappropriate. The clinical trials with statins or angiotensin converting enzyme inhibitors have shown favorable effects on the prognosis of cardiovascular disease. The study of hemostatic factors in relation to these drugs has provided insights into understanding how these drugs produce beneficial effects.

Effect of the angiotensin II receptor blocker candesartan on fibrinolysis in patients with mild hypertension

AIM

Impaired fibrinolysis is frequently observed in patients with the metabolic syndrome. Aim of the study was to examine the short-term effect of angiotensin II receptor blockade on the fibrinolytic system.

METHODS

Seventy-four patients with mild hypertension were randomly assigned to a 7-day treatment period with either 16 mg candesartan cilexetil or placebo. Several variables of the fibrinolytic system such as plasminogen activator inhibitor-1 (PAI-1) antigen and activity, tissue plasminogen activator (t-PA) antigen and activity as well as circulating t-PA/PAI-1 complexes were determined.

RESULTS

At baseline, the body mass index but not blood pressure was positively associated with PAI-1 antigen (r=0.314, p<0.01) and PAI-1 activity (r=0.425, p<0.01) but negatively with t-PA activity (r=-0.187, p < 0.05). A 7-day treatment with 16 mg candesartan cilexetil resulted in a significant greater reduction of diastolic blood pressure (-10.3 +/- 10.8 mmHg vs.-5.8 +/- 8.5 mmHg, p=0.03). However, there was no significant effect of candesartan on all parameters of the fibrinolytic system under investigation, i.e. circulating PAI-1 antigen, PAI-1 activity, t-PA antigen, t-PA activity and t-PA/PAI-1 complexes. Furthermore, candesartan did not affect the characteristic circadian pattern of the variables of the fibrinolytic system.

CONCLUSION

We conclude that short-term blockade of the angiotensin II receptor subtype 1 with candesartan does not have an impact on fibrinolysis in patients with mild hypertension.

Angiotensin II in the lesional skin of systemic sclerosis patients contributes to tissue fibrosis via angiotensin II type 1 receptors

OBJECTIVE

Tissue fibrosis in systemic sclerosis (SSc) is attributed to excessive deposition of extracellular matrix components produced by fibroblasts in skin lesions. Angiotensin II (Ang II), a vasoconstrictive peptide, is reported to have profibrotic activity as a result of induction of the extracellular matrix. The aim of the present study was to examine the expression of Ang II and its type 1 (AT(1)) and type 2 (AT(2)) receptors in affected skin and dermal fibroblasts from patients with SSc and to study the role of Ang II in collagen production by SSc dermal fibroblasts.

METHODS

Levels of Ang II in sera from SSc patients and normal subjects were measured by a solid-phase immobilized-epitope immunoassay. Expression of angiotensinogen (Angt) in the skin was evaluated by immunohistochemistry. Expression of Angt, AT(1), and AT(2) in cultured dermal fibroblasts was analyzed by reverse transcription-polymerase chain reaction and immunohistochemistry. Levels of type I procollagen produced by cultured dermal fibroblasts were measured by enzyme-linked immunosorbent assay.

RESULTS

Serum Ang II levels in patients with diffuse cutaneous SSc were significantly higher than those in patients with limited cutaneous SSc and in healthy donors. Immunohistochemical and immunoblotting analyses showed that Angt was present in skin from SSc patients, but not in normal skin. Angt messenger RNA (mRNA) was expressed in fibroblasts from patients with diffuse cutaneous SSc who had high levels of serum Ang II, but not in normal fibroblasts. AT(1) mRNA expression was found in both SSc and normal fibroblasts, whereas AT(2) mRNA was found only in SSc fibroblasts. Exogenous Ang II augmented the production of type I procollagen and transforming growth factor beta1 by cultured fibroblasts via activation of AT(1).

CONCLUSION

Aberrant Ang II production may be involved in tissue fibrosis through excessive production of the extracellular matrix components in SSc dermal fibroblasts. This suggests that the use of AT(1) receptor antagonists may be a novel strategy for the treatment of tissue fibrosis in SSc patients.

Angiotensin antagonism in patients with heart failure: ACE inhibitors, angiotensin receptor antagonists or both?

Chronic heart failure (CHF) is a major cause of morbidity and mortality in western society. It is now widely accepted that the renin-angiotensin-aldosterone system (RAAS) and, in particular, angiotensin II (A-II) play a key role in the pathophysiology of CHF. Large-scale clinical trials have demonstrated that inhibitors of angiotensin-converting enzyme (ACE), the principal enzyme responsible for A-II production, improve symptoms and survival in patients with CHF. This enzyme is also responsible for the breakdown of the vasodilator hormone bradykinin. Administration of ACE inhibitors is associated with increased plasma bradykinin levels and this is thought to contribute to the vascular changes associated with ACE inhibitor therapy. However, RAAS inhibition with ACE inhibitors remains incomplete because ACE inhibitors do not block the non-ACE-mediated conversion of angiotensin I to A-II. Angiotensin receptor antagonists (angiotensin receptor blockers; ARBs) antagonize the action of A-II at the A-II type 1 (AT(1)) receptor, whilst allowing the potentially beneficial actions of A-II mediated via the A-II type 2 (AT(2)) receptor. Evidence that the clinical benefit demonstrated with ACE inhibitors in patients with CHF may extend to ARBs has only emerged recently. Combination therapy with both an ACE inhibitor and an ARB has a number of potential advantages and has been investigated in several large-scale clinical trials recently. In patients with CHF, first-line therapy should include an ACE inhibitor and a beta-adrenoceptor antagonist. The addition of an ARB provides symptomatic relief but has not been shown to improve survival. Where an ACE inhibitor is not tolerated, treatment with an ARB would seem an appropriate alternative. There is insufficient data to support the routine use of ARBs as first-line therapy in the management of CHF.

A Double Blind Randomized Trial to Compare the Effects of Eprosartan and Enalapril on Blood Pressure, Platelets, and Endothelium Function in Patients With Essential Hypertension

The renin-angiotensin system is the major contributor to development of hypertension, atherosclerosis, and many other cardiovascular diseases. Angiotensin II, one of the main effectors of this system, contributes to the pathogenesis of hypertension and plays an important role in monocyte, platelet, and endothelium interactions. The effects on platelet and endothelial function, either by angiotensin converting enzyme inhibitors or angiotensin receptor antagonists, are still not well understood. A double-blind, randomized, prospective trial of either enalapril (10-20 mg daily) or eprosartan (400-800 mg daily) over a 10-week period was conducted in 42 patients (27 males, 15 females). Platelet activation was evaluated by measuring platelet factor 4 (PF-4), beta-thromboglobulin (beta-TG), the ratio of platelet factor 4 to beta-thromboglobulin, and endothelial function by measuring total plasma nitrate levels, von Willebrand factor (vWF) levels, and blood flow using venous occlusive plethysmography. After a 10-week treatment with enalapril or eprosartan, the sitting blood pressure in both the enalapril group (from 152.2 +/- 18.7 mmHg to 141.9 +/- 23.5 mmHg, P < 0.05) and eprosartan group (from 151 +/- 10.0 mmHg to 142.3 +/- 12.9 mmHg, P < 0.05) was significantly reduced. Significant diastolic blood pressure (DPB) reduction (from 94 +/- 8.7 to 84.5 +/- 9.6 mmHg, P < 0.05) and a greater DBP reduction response were found in the eprosartan group (63% in eprosartan versus 25% in enalapril). Additionally, dose-dependent reductions in the indices of platelet activation and endothelial dysfunction were observed in patients administered high dose treatments of eprosartan and enalapril, and the beneficial effects of these agents were not correlated with the reduction of blood pressure using both agents. Eprosartan is effective and well-tolerated in the treatment of mid-to-moderate hypertension, and the DBP response reduction to eprosartin was better than that to enalapril. A high dose of either eprosartan or enalapril significantly decreased the indices of platelet activation and endothelial dysfunction in hypertensive patients. The benefits of both agents cannot be explained solely by their antihypertensive effects and possibly may be mediated through their unique effect on angiotensin blockade.

MEK1,2 response element mediates angiotensin II-stimulated plasminogen activator inhibitor-1 promoter activation

The MEK1,2 (MAPK/ERK kinase 1 and 2) pathway mediates the up-regulation of plasminogen activator inhibitor-1 (PAI-1) expression in vascular smooth muscle cells by a variety of hormones, including angiotensin II. Transfection of constitutively active MEKK-1, an upstream activator of the mitogen-activated protein (MAP) kinase pathways, was used to isolate an enhancer element located between -89 and -50 bp in PAI-1 promoter that was activated by MEKK-1 and selectively blocked by the MEK1,2 inhibitor PD98059. Mutational analysis revealed that the MEKK-1 response element (MRE) contained 2 cis-acting Sp1- and AP-1-like sequences, located between -75 to -70 and -63 to -52 bp, respectively. Overexpression of Sp1 enhanced MEKK-1-induced MRE promoter activity and a dominant-negative c-Fos blocked this Sp1 response. The combination of Sp1 and c-Jun or c-Fos was required to activate this MRE. Angiotensin II (Ang II) stimulation increased c-Fos, c-Jun, and Sp1 binding to the MRE by 100-, 4.9-, and 1.9-fold, respectively, and these responses were inhibited by PD98059 and AT1 receptor antagonist candesartan. Intravenous Ang II infusion in rats increased aortic c-Fos binding to the MRE. This MRE sequence mediated a 4-fold increase of MEK1,2-dependent PAI-1/luciferase mRNA expression by angiotensin II stimulation. This report identifies the MEK1,2 response element that mediates angiotensin II-stimulated PAI-1 promoter activation and shows that activation of this element requires Sp1 and AP-1 co-activation.

Pleiotropic effects of angiotensin II receptor blocker in hypertensive patients

OBJECTIVES

We investigated the vascular effects of candesartan in hypertensive patients.

BACKGROUND

The renin-angiotensin system may contribute to atherogenesis through the promotion of endothelial dysfunction. The plausible mechanisms are that angiotensin II promotes superoxide anion generation, endothelial dysfunction, inflammation, and impaired fibrinolysis. The effects of candesartan on these conditions have not been clearly observed.

METHODS

We administered placebo or candesartan 16 mg daily during two months to 45 patients with mild-to-moderate hypertension. This was a randomized, double-blind, placebo-controlled, crossover study in design.

RESULTS

Candesartan did not significantly change lipoprotein levels. However, compared with placebo, candesartan significantly reduced plasma levels of malondialdehyde from 1.50 +/- 0.07 to 1.29 +/- 0.09 microM (p = 0.009); improved the percent flow-mediated dilator response to hyperemia from 5.17 +/- 0.24 to 6.22 +/- 0.26% (p < 0.001); and, furthermore, reduced plasma levels of monocyte chemoattractant protein (MCP-1) from 213 +/- 8 to 190 +/- 7 pg/ml (p = 0.003), tumor necrosis factor-alpha from 2.93 to 2.22 pg/ml (p = 0.026), and plasminogen activator inhibitor type 1 from 74 +/- 4 to 53 +/- 4 ng/ml (p < 0.001) but not C-reactive protein (CRP), matrix metalloproteinase protein, and fibrinogen. There were no significant correlations between these changes and reduction of systolic blood pressure (BP) (-0.247 < or = r < or = 0.195) and between these changes and reduction of diastolic BP (-0.262 < or = r < or = 0.197). There were no significant correlations between markers of inflammation and flow-mediated dilation percent or reduction of oxidant stress (-0.119 < or = r < or = 0.127). Furthermore, we observed no significant correlations between CRP and MCP-1 levels (r = -0.162).

CONCLUSIONS

Inhibition of the angiotensin II type 1 (AT1) receptor in hypertensive patients reverses endothelial dysfunction, measured as an improvement in flow-mediated dilation and fibrinolysis and reduction of oxidant stress and inflammatory cytokines, suggesting that AT1 receptor blocker therapy has antiatherogenic effects.

Use of nonantiarrhythmic drugs for prevention of sudden cardiac death

It is of interest that the drugs having the most significant impact on total and sudden death mortality are those without direct electrophysiologic actions on myocardial excitable tissue. This observation may provide insight into mechanisms responsible for ventricular tachyarrhythmias causing cardiac arrest. One way to think about ventricular fibrillation is that it is the final common pathway of an electrically unstable heart. After all, the heart can "die" in only three major ways: electromechanical dissociation, asystole and heart block, and ventricular fibrillation, with the latter most common. It is the "upstream" events provoking the electrical instability that these drugs probably act upon (i.e., ischemia, fibrosis). Although we unquestionably need to pursue investigations into the electrophysiology of these ventricular tachyarrhythmias, more studies need to investigate the drugs affecting upstream events, because these agents appear to yield the greatest dividends, at least for the present. This article reviews these drugs and how they may be effective.

Pharmacologic Blockade of the Renin-Angiotensin System: Vascular Benefits Beyond Commonly Understood Pharmacologic Actions

Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) are recognized primarily for their use in hypertension, in heart failure, and after myocardial infarction. New evidence, particularly with ACE inhibitors, has shown their ability to reduce acute coronary events associated with atherosclerosis in patients without a history of the aforementioned cardiac conditions. This is likely due to inhibitory effects on the renin-angiotensin system--a system that adversely influences fibrinolytic balance, vascular endothelial function, and vascular inflammation, all key components of atherosclerotic progression and adverse coronary outcomes. Results of various studies suggest favorable effects of ACE inhibitors and ARBs on markers of these components, including effects on plasminogen activator inhibitor-1, endothelin-1, and nitric oxide by ACE inhibitors, and effects on vascular cell adhesion molecule-1 and C-reactive protein by ARBs. Although early evidence suggests that ACE inhibitors may provide a greater beneficial effect on some of these markers compared with ARBs, and that certain ACE inhibitors may provide greater vascular benefits than others, further investigation is required to verify such findings. Overall, understanding the distinct coronary vascular benefits of these agents will emphasize the importance of using them, particularly ACE inhibitors, to improve outcomes in patients with coronary atherosclerotic disease.

The renin-angiotensin-aldosterone system: cardiorenal effects and implications for renal and cardiovascular disease states

The renin-angiotensin-aldosterone system (RAAS) plays an integral role in maintaining vascular tone, optimal salt and water homeostasis, and cardiac function in humans. However, it has been recognized in recent years that pathologic consequences may also result from overactivity of the RAAS. Clinical disease states such as renal artery stenosis, hypertension, diabetic and nondiabetic nephropathies, left ventricular hypertrophy, coronary atherosclerosis, myocardial infarction, and congestive heart failure (CHF) are examples. Part of the adverse cardiorenal effects of the RAAS may be related to the prominent role that this system plays in the activation of the sympathetic nervous system, the dysregulation of endothelial function and progression of atherosclerosis, as well as inhibition of the fibrinolytic system. Also, direct profibrotic actions of angiotensin II and aldosterone in the kidney and heart promote end organ injury. Current basic science and clinical research supports the use of inhibitors of the RAAS, including angiotensin converting enzyme inhibitors, angiotensin receptor blockers, and aldosterone antagonists in treating hypertension, improving diabetic nephropathy and other forms of chronic kidney disease, preventing or ameliorating CHF, and optimizing prognosis after myocardial infarction.

Can angiotensin-converting enzyme inhibitors reverse atherosclerosis?

Angiotensin II, a potent vasoconstrictor, is mainly present in the vascular endothelium. Multiple studies have confirmed that angiotensin-converting enzyme (ACE) inhibitors, which block the formation of angiotensin II, lower blood pressure and also improve heart failure. These agents not only have beneficial hemodynamic effects but also bestow additional benefits on vascular function and prevent clinical cardiovascular events in patients at risk for coronary artery disease. These latter benefits may represent effects of ACE inhibitors on local endocrine pathways, inflammatory processes, and atherosclerosis taking place within the arterial wall. Current evidence suggests that, although ACE inhibitors may not substantially reverse atherosclerotic plaque already present, they may slow the progression of such atherosclerotic lesions. In addition, by modulating inflammatory pathways within and adjacent to the atherosclerotic lesion, they may stabilize an unstable plaque and therefore decrease the risk of plaque rupture and its complications.

Angiotensin-converting enzyme inhibition but not angiotensin II type 1 receptor antagonism augments coronary release of tissue plasminogen activator in hypertensive patients

OBJECTIVES

We compared the effects of perindopril and losartan on endothelium-dependent coronary vasomotor and fibrinolytic function.

BACKGROUND

The renin-angiotensin system regulates the vascular fibrinolytic balance. However, the effects of angiotensin-converting enzyme inhibitors and angiotensin II type 1 receptor antagonists on coronary fibrinolytic function have not been compared in hypertensive patients.

METHODS

Forty-five patients with hypertension were randomly assigned to three groups: 16 patients were treated with perindopril (4 mg/day) for four weeks; 15 were treated with losartan (50 mg/day) for four weeks; and 14 were not treated with either perindopril or losartan (control group). Graded doses of bradykinin (BK) (0.2, 0.6, and 2.0 microg/min) were administered into the left coronary artery. Coronary blood flow (CBF) was evaluated by Doppler flow velocity measurement.

RESULTS

Bradykinin induced dose-dependent increases in CBF in all groups. The increases in CBF induced by BK in the perindopril and losartan groups were significantly greater than those in the control group. Net coronary tissue-type plasminogen activator (t-PA) release was enhanced by BK in all groups, and the increase in the perindopril group was greater than that in the losartan and control groups. Bradykinin did not alter plasminogen activator inhibitor type 1 levels in any of the groups.

CONCLUSIONS

Perindopril and losartan similarly augment BK-induced coronary vasodilation. Perindopril may have a greater potential to enhance the BK-induced coronary release of t-PA than losartan.

Effects of Losartan and Delapril on the Fibrinolytic System in Patients with Mild to Moderate Hypertension

BACKGROUND AND OBJECTIVES

Angiotensin-converting enzyme (ACE) probably influences the fibrinolytic system at a central point by converting angiotensin I to angiotensin II, which increases plasminogen activator inhibitor-1 (PAI-1) activity. This effect appears to be mediated in humans via the angiotensin II type 1 (AT(1)) receptor. The objective of this study was to evaluate, in patients with mild to moderate hypertension, the change in tissue plasminogen activator (t-PA) and PAI-1 plasma levels after treatment with an AT(1)-receptor blocker (losartan 50 mg/day) or an ACE inhibitor (delapril 60 mg/day).

PATIENTS AND METHODS

30 hypertensive patients and 15 controls were enrolled. Essential hypertension was established by a medical history, physical examination and the absence of clinical findings suggestive of a secondary form of hypertension. Preliminary investigations, routine biochemical tests (including clearance of creatinine and oral glucose tolerance test), chest x-ray, standard and 24-hour ECG monitoring, M- and B-mode echocardiography and fundus oculi examinations were performed. No patients had previously received ACE inhibitors or AT(1)-receptor blockers. After a 14-day run-in period with placebo, patients were randomised in a double-blind fashion into two groups: 15 patients were randomised to losartan 50 mg/day (group 1), 15 patients were randomised to delapril 60 mg/day (group 2), and 15 healthy subjects were used as controls (group 3). Plasma PAI-1 and t-PA antigen were determined by enzyme-linked immunosorbent assay and a photometric method at the end of the run-in period and after 6 months of treatment.

RESULTS

There were no significant differences among the three groups regarding age, sex, body mass index and smoking. After 6 months, both groups of patients showed a reduction in blood pressure values. The losartan group did not demonstrate significant changes in PAI-1 levels (96.52 +/- 23.73 and 99.89 +/- 22.18 mug/L, pre- and post-treatment, respectively) or in t-PA antigen levels (26.17 +/- 6.18 and 27.32 +/- 5.91 mug/L, pre- and post-treatment, respectively). The delapril group showed no significant changes in PAI-1 levels (97.73 +/- 25.75 and 86.12 +/- 13.12 mug/L, pre- and post-treatment, respectively), but did show a statistically significant difference (p < 0.005) in t-PA antigen levels (25.71 +/- 6.40 and 32.24 +/- 5.31 mug/L, pre- and post-treatment, respectively). The losartan group demonstrated significantly higher post-treatment PAI-1 values than the delapril group (p = 0.048).

CONCLUSION

The study showed that losartan does not affect fibrinolytic parameters, while delapril resulted in an insignificant reduction in PAI-1 and a significant increase in t-PA levels. Further studies are clearly required in order to establish whether these different effects on the fibrinolytic system between ACE inhibitors and AT(1)-receptor blockers may have clinical relevance.

Plasminogen activator inhibitor-1: physiologic role, regulation, and the influence of common pharmacologic agents

Plasminogen activator inhibitor-1 (PAI-1) is the major inhibitor of endogenous thrombolysis, thereby promoting thrombosis. PAI-1 is also a primary contributor to the development and recurrence of acute myocardial infarction. The renin angiotensin system, hypertriglyceridemia, hyperglycemia and hyperinsulinemia, and estrogen all influence the fibrinolytic system and PAI-1 in particular. Available data strongly suggest that angiotensin-converting enzyme (ACE) inhibitors and hormone replacement therapy with estrogen beneficially reduce PAI-1 production. Metformin, an agent commonly used for non-insulin-dependent diabetes mellitus (NIDDM), appears to favorably decrease PAI-1 production in NIDDM patients but not nondiabetic patients. Among the cholesterol-lowering statins, clinical literature evaluating pravastatin provides the most compelling data to support this agent's favorable effect on PAI-1. Other available statins either have not displayed an effect on PAI-1 or do not have clear data to conclusively define their effects on the fibrinolytic system.

Vascular and cardiac benefits of angiotensin receptor blockers

Angiotensin II not only is a vasoconstrictor, but it also affects cell growth and apoptosis, inflammation, fibrosis, and coagulation. Blockade of the renin-angiotensin system, either with inhibitors of the generation of angiotensin (angiotensin-converting enzyme [ACE] inhibitors) or with blockers of angiotensin receptors, reduces blood pressure and inhibits other pathophysiological actions. These other effects provide benefits in coronary heart disease, heart failure, diabetic nephropathy, and stroke beyond blood pressure reduction. These benefits were first demonstrated with ACE inhibitors. However, the mechanism of action of angiotensin receptor blockers, which block angiotensin II stimulation at the angiotensin type 1 receptor but not at the type 2 receptor, may have advantages, particularly for endothelial dysfunction and vascular remodeling, as well as cardiac and renal protection. Recent multicenter trials suggest that ACE inhibitors and angiotensin receptor blockers may reduce morbidity and mortality associated with cardiovascular and renal disease beyond blood pressure reduction. Several studies with different angiotensin receptor blockers, including comparisons with ACE inhibitors, are under way, and should provide further guidance for their clinical use.

The renin-angiotensin-aldosterone system and fibrinolysis in progressive renal disease

Renal glomerular and interstitial fibrosis is widely viewed as the final common pathway to renal failure, regardless of the initiating injury. Similarly, the renin-angiotensin-aldosterone system (RAAS) plays an important role in the progression of renal disease. This review explores the hypothesis that the RAAS causes injury and fibrosis, in part, through effects on plasminogen activator inhibitor-1 (PAI-1), the major physiologic inhibitor of plasminogen activators in vivo. PAI-1, by inhibiting the production of plasmin from plasminogen, tips the balance in favor of extracellular matrix accumulation and promotes fibrosis. Interruption of the RAAS decreases both PAI-1 expression and fibrosis in animal models. These findings have implications for the clinical management of renal disease.

Angiotensin II and IV stimulate expression and release of plasminogen activator inhibitor-1 in cultured human coronary artery endothelial cells

There is increasing evidence that angiotensin II influences thrombogenesis by regulating the expression of plasminogen activator inhibitor-1 (PAI-1). In this study, the effects of angiotensin II and its receptors on the expression and release of PAI-1 and tissue-type plasminogen activator (t-PA) were examined in human coronary artery endothelial cells (HCAECs). As control, cells were treated with angiotensin IV. HCAECs incubated with angiotensin II increased the expression of PAI-1 mRNA in a concentration (10-9-10-5 M)- and time (6-24 h)-dependent manner. PAI-1 protein release was also increased in the culture medium of HCAECs treated with angiotensin II. The effects of angiotensin II (10-6 M) were blocked completely by the AT1 receptor blocker losartan (10-6 M) but not by the AT2 receptor blocker PD123319 (10-6 M). Angiotensin II pretreatment also slightly, but significantly, increased t-PA mRNA expression. This effect of angiotensin II on t-PA mRNA was blocked by losartan but not by PD123319. HCAECS treated with angiotensin II revealed large amounts of the lipid peroxidation product, malonaldehyde (MDA). The effects of angiotensin II on PAI-1 expression and MDA release were blocked by pretreatment of cells with alpha-tocopherol (10-5 M). In control experiments, treatment of HCAECs with angiotensin IV markedly increased PAI-1 mRNA expression and protein release. This effect of angiotensin IV was blocked by the AT4 receptor blocker divalinal (10-6 M). These observations indicate that AT1 receptor activation plays an important role in the stimulation of PAI-1 expression and release in response to angiotensin II. Upregulation of t-PA gene may reflect autoregulation in response to PAI-1 release. Angiotensin II-mediated activation of oxidation pathways may relate to uupregulation of PAI-1. This study also confirms that angiotensin IV upregulates PAI-1 expression in HCAECs.

The impact of angiotensin II receptor blockade and the DASH diet on markers of endogenous fibrinolysis

Hypertension is associated with impaired fibrinolysis. Both angiotensin receptor blockers (ARB) and the DASH (Dietary Approaches to Stop Hypertension) diet effectively lower blood pressure in hypertensive patients. Some evidence suggests that treatment with ARBs could increase fibrinolysis, however, data is conflicting. The impact of the DASH diet on fibrinolytic parameters is not known. Fifty-five hypertensive participants (35 African-American, 20 white) were randomly assigned to receive 8 weeks of either a control diet or the DASH diet. The diets did not differ in sodium content (approximately 3 g/day). Within each diet, individuals were randomly assigned to receive losartan or placebo for 4 weeks in double-blind, cross-over fashion. Tissue plasminogen activator (t-PA) antigen, t-PA activity, plasminogen activator inhibitor-1 (PAI-1) activity and plasma renin activity (PRA) were measured at the end of a 2-week run-in period on the control diet and after each treatment period. The DASH diet did not affect markers of fibrinolysis. Losartan significantly lowered t-PA antigen levels (-1.8 ng/mL, P = 0.045), but had no effect on t-PA or PAI-1 activities. This effect was more pronounced in whites (-4.1 ng/mL (P = 0.003)) compared with African-Americans (-0.3 ng/mL (P = 0.7), P-interaction = 0.03). Results were not materially affected by adjustment for basline values or changes in blood pressure. This study demonstrates that losartan reduces t-PA antigen levels in white, but not African-American hypertensive individuals. In contrast, the DASH diet had no significant effect on markers of fibrinolysis in whites or African-Americans.

Biological properties of the angiotensin peptides other than angiotensin II: implications for hypertension and cardiovascular diseases

Several peptides of the RAS other than angiotensin (1-8) have been identified. They are generally referred as 'angiotensin fragments': Ang (2-8), Ang (3-8) and Ang (1-7) and have been detected in human tissues. There is evidence that they may play a functional role in humans by acting in concert with angiotensin (1-8) and aldosterone. Available knowledge on the pathways leading to synthesis and degradation of angiotensin fragments, as well as on their interactions with receptors and on their possible role in cardiovascular homeostasis and disease are reviewed.

Losartan and perindopril effects on plasma plasminogen activator inhibitor-1 and fibrinogen in hypertensive type 2 diabetic patients

BACKGROUND

This study compared the effects of losartan and perindopril on plasma plasminogen activator inhibitor-1 (PAI-1) and fibrinogen in hypertensive type 2 diabetic patients.

METHODS

We studied 85 nonsmoking outpatients, aged 46 to 64 years, with mild to moderate essential hypertension (diastolic blood pressure [BP] > 90 and < 110 mm Hg) and well controlled type 2 diabetes mellitus. After a 4-week washout placebo period, patients were randomized to received perindopril 4 mg once daily (n = 42) or losartan 50 mg once daily (n = 43) for 12 weeks according to a double-blind, parallel-group design. At the end of the placebo and active treatment periods, BP was measured and plasma PAI-1 and fibrinogen were evaluated.

RESULTS

Both perindopril and losartan reduced systolic and diastolic BP values (-16/15 mm Hg and -15/14, respectively; P < .001 v placebo), with no difference between the two treatments. Plasma PAI-1 was reduced by perindopril (-10 ng/dL, P = .028 v placebo) but not by losartan (+4 ng/dL, NS), the difference between the two treatments being statistically significant (P < .01). Plasma fibrinogen showed no significant change with both drugs, although a decreasing trend was noted with perindopril.

CONCLUSIONS

These findings indicate that perindopril but not losartan decreases PAI-1 in hypertensive type 2 diabetic patients, which suggests that the PAI-1 lowering effect is unrelated with AT, receptor blockade and could rather be due to the fact that the endothelial receptors that mediate PAI-1 expression in response to angiotensin II are not type 1 receptor subtypes. Different effects of the two drugs on the bradykinin system might also be implicated.