Differential effects of imidapril and candesartan cilexetil on plasminogen activator inhibitor-1 expression induced by prolonged inhibition of nitric oxide synthesis in rat hearts

Renoprotective effects of soy protein hydrolysates in N(omega)-nitro-L-arginine methyl ester hydrochloride-induced hypertensive rats

Pepsin-digested soy protein hydrolysate (SPH) has been reported to be responsible for many of the physiological benefits associated with soy protein consumption. In the present study, we investigated the effects of SPH with angiotensin-converting enzyme (ACE) inhibitory potential on blood pressure and renal injuries in rats with N(omega)-nitro-L-arginine methyl ester hydrochloride (L-NAME)-induced hypertension. Rats were fed a diet containing L-NAME (50 mg/kg body weight) with or without SPH (at 1%, 3%, or 5%) for 6 weeks. We found that ingestion of SPH ameliorated the development of hypertension during the 6-week experimental period. SPH was also found to ameliorate renal function by decreasing urinary protein excretion and elevating the creatinine clearance rate. The levels of kidney ACE activity, malonaldehyde, tumor necrosis factor-a and plasminogen activator inhibitor-1, and the expression of CYP4A decreased in the 5% SPH group. Consumption of 5% SPH also ameliorated renal damage according to the histopathological analysis. These findings suggest that SPH might ameliorate the elevation of blood pressure and show renoprotective effects in nitric oxide (NO)-deficient rats, and one possible mechanism might be mediation via its ACE inhibitory activity.

PAI-1 plays an important role in liver failure after excessive hepatectomy in the rat

BACKGROUND/AIMS

Well-organized turnover of the extracellular matrix is important in liver regeneration, which is regulated by the plasminogen activating system. The aim of this study was to investigate the role of plasminogen activator inhibitor-1 (PAI-1) after excessive hepatectomy and to ascertain whether angiotensin-converting enzyme (ACE) inhibitors, which are PAI-1 inhibitors as well, successfully improve the survival rate of rats that have undergone 95% partial hepatectomy (PHx).

METHODS

Using liver tissues sampled after 90% or 95% PHx, the expression of PAI-1 mRNA was evaluated using reverse transcription polymerase chain reaction. Hepatic PAI-1 protein and urokinase-type plasminogen activator (uPA) levels were determined by enzyme-linked immunosorbent assay. Survival study and cytodynamic analysis by 5-bromo-2'-deoxyuridine staining were performed to evaluate the effects of ACE inhibition.

RESULTS

The levels of PAI-1 mRNA and hepatic PAI-1 protein in the 95% PHx group peaked and were then maintained. By contrast, the uPA level fell relative to the 90% PHx group. Additionally, the hepatic PAI-1 protein level decreased and the survival rate improved in the 95% PHx rats that had undergone ACE inhibition.

CONCLUSIONS

Our experimental results suggest that PAI-1 plays a role in the occurrence of liver failure after excessive hepatectomy via accelerated maturation of pro-uPA and fibrinolytic factors. These are potential molecular therapeutic targets for liver failure after excessive hepatectomy.

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.

Effects of angiotensin receptor blockade on haemodynamics and gene expression after myocardial infarction

INTRODUCTION

Despite the fact that congestive heart failure (CHF) remains the most common disease in the developed world and has been extensively studied, there is little known about the molecular and cellular mechanisms of cardiac dysfunction. Angiotensin has been implicated as a mediator of cardiac injury; however, the mechanisms of its action have not been delineated. The objective of this study was to examine the relationship between the haemodynamic and molecular events during cardiac dysfunction and the role of the angiotensin system.

STUDY DESIGN

We examined the effects of the angiotensin receptor blocker, valsartan, on changes in the haemodynamic and gene expression patterns in a postmyocardial infarction model in the rat.

METHODS

Myocardial infarction (MI) was induced in rats by coronary artery ligation. Cardiac haemodynamics were monitored using echocardiography. Gene expression profiles after myocardial infarction were identified using Affymetrix Genechip oligonucleotide arrays.

RESULTS

Myocardial contractility, as assessed by cardiac output and left ventricle (LV) fraction of shortening, was reduced in untreated animals by week 3 after MI (p < 0.05 versus baseline), and preserved with valsartan treatment as observed by the nonsignificant changes versus baseline. LV dilatation, as demonstrated by increases in LV systolic and diastolic diameters, developed by week 3 in untreated animals (p < 0.05 versus baseline) while valsartan-treated animals were protected and showed no significant increases in diameter size compared with baseline. LV hypertrophy, as shown by LV posterior wall thickness, was more profound in untreated animals (p < 0.05 versus baseline) than in those treated with valsartan at weeks 3 and 4. Changes in gene expression at 4 weeks after MI included those encoding muscle-specific genes, fibrous tissue proliferation, immune response and various others. Treatment with valsartan reversed these changes in 67% of overexpressed genes and 83% of underexpressed genes.

CONCLUSION

Angiotensin receptor blockade with valsartan was found to protect cardiac function, and this beneficial effect was accompanied by a reversal of changes in gene expression induced by MI.

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.

ACE inhibition versus angiotensin type 1 receptor antagonism: differential effects on PAI-1 over time

ACE inhibition reduces plasminogen activator inhibitor-1 (PAI-1), a risk factor for myocardial infarction, whereas the effect of angiotensin receptor antagonism on PAI-1 is uncertain. The present study compares the time course of effects of ACE inhibition and angiotensin type 1 (AT1) receptor antagonism on morning plasma PAI-1 antigen. Blood pressure and endocrine, metabolic, and fibrinolytic variables were measured in 20 insulin-resistant (defined by fasting glucose >8.3 mmol/L, body mass index >28 kg/m2, or fasting serum triglyceride > or =2.8 mmol/L) hypertensive subjects (mean age, 47.9+/-2.1 years) (1) before and after 1 week of hydrochlorothiazide 12.5 mg/d, and (2) before and 1, 3, 4, and 6 weeks after addition of ramipril (escalated to 10 mg/d) or losartan (escalated to 100 mg/d). Hydrochlorothiazide decreased systolic (P=0.011) and diastolic (P=0.019) pressure. Ramipril (from 133.6+/-5.1/94.5+/-2.4 to 127.0+/-3.1/91.4+/-3.3 mm Hg) or losartan (from 137.0+/-3.9/93.1+/-2.9 to 123.7+/-2.6/86.4+/-2.1 mm Hg) further reduced systolic (P=0.009) and diastolic (P=0.037) pressure. The pressure effects of the 2 drugs were similar. Hydrochlorothiazide increased plasma PAI-1 (P=0.013) but not tissue-type plasminogen activator (tPA) (P=0.431) antigen. Addition of either ramipril or losartan significantly decreased plasma PAI-1 antigen (P=0.046). However, the effect of losartan on PAI-1 antigen was not sustained throughout the 6-week treatment period, such that there was a significant drugxtime interaction (P=0.043). tPA antigen decreased during either ramipril or losartan (P=0.032), but tPA activity decreased only during losartan (P=0.018). Short-term interruption of the renin-angiotensin-aldosterone system by either ACE inhibition or AT1 receptor antagonism decreases PAI-1 antigen, but the duration of this effect is greater for ACE inhibition than for AT1 receptor antagonism.

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.

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.

The renin-angiotensin-aldosterone system and fibrinolysis

Activation of the RAAS has been linked with an increased risk of myocardial infarction and stroke,(1,2,37,38) and recently these beneficial effects have, in part, been attributed to the effects of the RAAS on the fibrinolytic system. Indeed, ACE seems to occupy a central position in modulating the fibrinolytic balance, where an angiotensin II-mediated increase of PAI-1 plays a major role. By contrast, the effect on bradykinin stimulated t-PA release may be of lesser importance, although the data are conflicting. Importantly, the impact of the RAAS on the fibrinolytic balance may also contribute to the favourable effects of ACE inhibition and AT1-receptor antagonists on cardiovascular events, particularly when considering the activation of the RAAS in hypertension and heart failure. More work is clearly required in this area to elucidate potential therapeutic targets.