Increased cardiac endothelial nitric oxide synthase expression in patients taking angiotensin-converting enzyme inhibitor therapy

Cardiac remodelling and RAS inhibition

Risk factors such as hypertension and diabetes are known to augment the activity and tissue expression of angiotensin II (Ang II), the major effector peptide of the renin-angiotensin system (RAS). Overstimulation of the RAS has been implicated in a chain of events that contribute to the pathogenesis of cardiovascular (CV) disease, including the development of cardiac remodelling. This chain of events has been termed the CV continuum. The concept of CV disease existing as a continuum was first proposed in 1991 and it is believed that intervention at any point within the continuum can modify disease progression. Treatment with antihypertensive agents may result in regression of left ventricular hypertrophy, with different drug classes exhibiting different degrees of efficacy. The greatest decrease in left ventricular mass is observed following treatment with angiotensin converting enzyme inhibitors (ACE-Is), which inhibit Ang II formation. Although ACE-Is and angiotensin receptor blockers (ARBs) provide significant benefits in terms of CV events and stroke, mortality remains high. This is partly due to a failure to completely suppress the RAS, and, as our knowledge has increased, an escape phenomenon has been proposed whereby the human sequence of the 12 amino acid substrate angiotensin-(1-12) is converted to Ang II by the mast cell protease, chymase. Angiotensin-(1-12) is abundant in a wide range of organs and has been shown to increase blood pressure in animal models, an effect abolished by the presence of ACE-Is or ARBs. This review explores the CV continuum, in addition to examining the influence of the RAS. We also consider novel pathways within the RAS and how new therapeutic approaches that target this are required to further reduce Ang II formation, and so provide patients with additional benefits from a more complete blockade of the RAS.

Enalapril Normalizes Endothelium-Derived Hyperpolarizing Factor-Mediated Relaxation in Mesenteric Artery of Adult Hypertensive Rats Prenatally Exposed to Testosterone

Prenatal exposure to elevated testosterone levels induces adult life hypertension associated with selective impairments in endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxation in mesenteric arteries. We tested whether the angiotensin-converting enzyme inhibitor enalapril restores EDHF function through regulating the activities of small (Kcnn3) and intermediate (Kcnn4) conductance calcium-activated potassium channels in mesenteric arteries. Pregnant Sprague-Dawley rats were injected subcutaneously with vehicle or testosterone propionate (0.5 mg/kg/day from Gestation Day 15 to 19), and their 6-mo-old adult male offspring were examined. A subset of rats in these two groups was given enalapril (40 mg/kg/day) for 2 wk through drinking water. Blood pressures were assessed through carotid arterial catheter and endothelium-dependent mesenteric arterial EDHF relaxation, using wire myography. Ace and Kcnn3 and Kcnn4 channel expression levels were also examined. Renal and vascular Ace expression and plasma angiotensin II levels were increased in testosterone offspring. Blood pressure levels were significantly higher in testosterone offspring than in controls, and treatment with enalapril significantly attenuated blood pressure in testosterone offspring. EDHF relaxation in testosterone offspring was reduced compared to that in controls, and it was significantly restored by enalapril treatment. Kcnn4 channel expression and function were similar between control and testosterone rats, but it was not affected by enalapril treatment. Relaxation mediated by Kcnn3 was impaired in testosterone offspring, and it was normalized by enalapril treatment. Furthermore, enalapril treatment restored expression levels of Kcnn3 channels. These findings suggest that enalapril has a positive influence on endothelial function with improvement in EDHF relaxation through normalization of Kcnn3 expression and activity.

Hypertension in African Americans with heart failure: progression from hypertrophy to dilatation; perhaps not

AIM

Concentric hypertrophy is thought to transition to left ventricular (LV) dilatation and systolic failure in the presence of long standing hypertension (HTN). Whether or not this transition routinely occurs in humans is unknown.

METHODS

We consecutively enrolled African American patients hospitalized for acute decompensated volume overload heart failure (HF) in this retrospective study. All patients had a history of HTN and absence of obstructive coronary disease. Patients were divided into those with normal left ventricular ejection fraction (LVEF) and reduced LVEF. LV dimensions were measured according to standard ASE recommendations. LV mass was calculated using the ASE formula with Devereux correction.

RESULTS

Patients with normal LVEF HF were significantly older, female and had a longer duration of HTN with higher systolic blood pressure on admission. LV wall thickness was similarly elevated in both groups. LV mass was elevated in both groups however was significantly greater in the reduced LVEF HF group compared to the normal LVEF HF group. Furthermore, gender was an independent predictor for LV wall thickness in normal LVEF HF group.

CONCLUSION

In African American patients with HF our study questions the paradigm that concentric hypertrophy transitions to LV dilatation and systolic failure in the presence of HTN. Genetics and gender likely play a role in an individual's response to long standing hypertension.

Lisinopril alters contribution of nitric oxide and K(Ca) channels to vasodilatation in small mesenteric arteries of spontaneously hypertensive rats

To investigate lisinopril effect on the contribution of nitric oxide (NO) and K(Ca) channels to acetylcholine (ACh)-induced relaxation in isolated mesenteric arteries of spontaneously hypertensive rats (SHRs). Third branch mesenteric arteries isolated from lisinopril treated SHR rats (20 mg/kg/day for ten weeks, SHR-T) or untreated (SHR-UT) or normotensive WKY rats were mounted on tension myograph and ACh concentration-response curves were obtained. Westernblotting of eNOS and K(Ca) channels was performed. ACh-induced relaxations were similar in all groups while L-NMMA and indomethacin caused significant rightward shift only in SHR-T group. Apamin and TRAM-34 (SK(Ca) and IK(Ca) channels blockers, respectively) significantly attenuated ACh-induced maximal relaxation by similar magnitude in vessels from all three groups. In the presence of L-NMMA, indomethacin, apamin and TRAM-34 further attenuated ACh-induced relaxation only in SHR-T. Furthermore, lisinopril treatment increased expression of eNOS, SK(Ca) and BK(Ca) proteins. Lisinopril treatment increased expression of eNOS, SK(Ca), BK(Ca) channel proteins and increased the contribution of NO to ACh-mediated relaxation. This increased role of NO was apparent only when EDHF component was blocked by inhibiting SK(Ca) and IK(Ca) channels. Such may suggest that in mesenteric arteries, non-EDHF component functions act as a reserve system to provide compensatory vasodilatation if (and when) hyperpolarization that is mediated by SK(Ca) and IK(Ca) channels is reduced.

Lipoprotein apheresis of hypercholesterolemic patients mediates vasoprotective gene expression in human endothelial cells

OBJECTIVE

Hypercholesterolemia is an important risk factor of cardiovascular diseases. Lipoprotein apheresis is an efficient strategy to reduce the serum low-density lipoprotein (LDL)-cholesterol and lipoprotein(a) levels and cardiovascular complications in patients with severe hypercholesterolemia. The underlying molecular mechanisms are not well-understood. In this study, we analyzed the impact of lipoprotein apheresis on gene expression in human endothelial cells.

METHODS

Human endothelial cells were stimulated with serum of hypercholesterolemic patients before and after lipoprotein apheresis. The expression of endothelial lipoprotein receptors, nitric oxide (NO) synthase and adhesion molecules was quantified by real-time PCR and Western blot.

RESULTS

Lipoprotein apheresis reduced the expression of the lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) in endothelial cells. Low-density lipoprotein (LDL) receptor expression remained unchanged. The mRNA expression of the endothelial nitric oxide synthase (eNOS) was increased with serum of hypercholesterolemic patients after lipoprotein apheresis. In contrast, endothelial expression of vascular cell adhesion molecule 1 (VCAM-1) was reduced in response to serum after lipoprotein apheresis.

CONCLUSION

Lipoprotein apheresis reduced the expression of the proatherosclerotic oxLDL receptor LOX-1 and adhesion molecule VCAM-1 and increased the expression of vasoprotective and NO generating eNOS in human endothelial cells in response to serum of hypercholesterolemic patients. These novel molecular mechanisms may account for the antiatherosclerotic and vasoprotective potential of lipoprotein apheresis in patients with hypercholesterolemia.

An Angiotensin receptor blocker prevents arrhythmogenic left atrial remodeling in a rat post myocardial infarction induced heart failure model

This study investigated the role of angiotensin II receptor blocker in atrial remodeling in rats with atrial fibrillation (AF) induced by a myocardial infarction (MI). MIs were induced by a ligation of the left anterior descending coronary artery. Two days after, the rats in the losartan group were given losartan (10 mg/kg/day for 10 weeks). Ten weeks later, echocardiography and AF induction studies were conducted. Ejection fraction was significantly lower in the MI rats. Fibrosis analysis revealed much increased left atrial fibrosis in the MI group than sham (2.22 ± 0.66% vs 0.25 ± 0.08%, P = 0.001) and suppression in the losartan group (0.90 ± 0.27%, P 0.001) compared with the MI group. AF inducibility was higher in the MI group than sham (39.4 ± 43.0% vs 2.0 ± 6.3%, P = 0.005) and significantly lower in losartan group (12.0 ± 31.6%, P = 0.029) compared with the MI. The left atrial endothelial nitric oxide synthase (NOS) and sarco/endoplasmic reticulum Ca(2+)-ATPase levels were lower in the MI group and higher in the losartan group significantly. The atrial inducible NOS and sodium-calcium exchanger levels were higher in the MI and lower in the losartan group significantly. Losartan disrupts collagen fiber formation and prevents the alteration of the tissue eNOS and iNOS levels, which prevent subsequent AF induction.

Nitric oxide synthesis is reduced in subjects with type 2 diabetes and nephropathy

OBJECTIVE

Nitric oxide (NO) is a key metabolic and vascular regulator. Its production is stimulated by insulin. A reduced urinary excretion of NO products (NOx) is frequently found in type 2 diabetes, particularly in association with nephropathy. However, whether the decreased NOx excretion in type 2 diabetes is caused by a defective NOx production from arginine in response to hyperinsulinemia has never been studied.

RESEARCH DESIGN AND METHODS

We measured NOx fractional (FSR) and absolute (ASR) synthesis rates in type 2 diabetic patients with diabetic nephropathy and in control subjects, after l-[(15)N(2)-guanidino]-arginine infusion, and use of precursor-product relationships. The study was conducted both before and after an euglycemic hyperinsulinemic ( approximately 1,000-1,200 pmol/l) clamp.

RESULTS

In type 2 diabetes, NOx FSR was reduced both under basal (19.3 +/- 3.9% per day, vs. 22.9 +/- 4.5% per day in control subjects) and hyperinsulinemic states (24.0 +/- 5.6% per day, vs. 37.9 +/- 6.4% per day in control subjects; P < 0.03 by ANOVA). Similarly, in type 2 diabetes, NOx ASR was lower than in control subjects under both conditions (basal, 0.32 +/- 0.06 vs. 0.89 +/- 0.34 mol per day; hyperinsulinemia, 0.35 +/- 0.07 vs. 1.15 +/- 0.38 mol per day; P = 0.01 by ANOVA). In type 2 diabetes, the ability of insulin to stimulate both the FSR (4.7 +/- 3.2% per day) and the ASR (0.03 +/- 0.04 mol per day) of NOx was several-fold lower than that in control subjects (15.0 +/- 2.9% per day and 0.25 +/- 0.07 mol per day, P < 0.03 and P < 0.02, respectively). Also the fraction of arginine flux converted to NOx (basal, 0.22 +/- 0.05% vs. 0.65 +/- 0.25%; hyperinsulinemia, 0.32 +/- 0.06% vs. 1.03 +/- 0.33%) was sharply reduced in the patients (P < 0.01 by ANOVA).

CONCLUSIONS

In type 2 diabetic patients with nephropathy, intravascular NOx synthesis from arginine is decreased under both basal and hyperinsulinemic states. This defect extends the concept of insulin resistance to NO metabolism.

Endothelial dysfunction, measured by reactive hyperaemia using strain-gauge plethysmography, is an independent predictor of adverse outcome in heart failure

AIMS

In congestive heart failure (CHF), arterial response is regulated by endothelial molecules. The aim of this study was to evaluate whether endothelial dysfunction (ED) was a predictor of outcome in a cohort of patients with heart failure.

METHODS AND RESULTS

Endothelial function was assessed in 242 patients with CHF by forearm reactive hyperaemia measured with intermittent venous occlusion plethysmography using a mercury strain gauge. The main endpoints were: 'total events' (death, heart attack, angina, stroke, NYHA class IV, or hospitalization due to heart failure) analysed using Cox regression for repeated events and 'death'. Patients were followed-up for 5 years. Post-hyperaemia forearm blood flow (PHFABF) was an independent predictor of total events [P = 0.01; hazard ratio [Exp(B)] 0.665, standard error (SE) 0.182]. Risk stratification by basal forearm blood flow (BFABF) showed that patients with basal blood flow above the median (3.03 mL min(-1) 100 mL(-1)) benefited from an increase in PHFABF, whereas in patients with a BFABF below the median, the increase in PHFABF did not diminish the risk of events. There was no relation between variations in PHFABF and death.

CONCLUSION

Post-hyperaemia forearm blood flow, as a measure of ED, is an independent predictor of major events in patients with CHF. A BFABF below the median is more predictive of an increased risk of complications.

Relevance of nitric oxide for myocardial remodeling

Endogenous myocardial nitric oxide (NO) may modulate the transition from adaptive to maladaptive remodeling leading to heart failure. In rodent models of pressure overload or myocardial infarction, the three NO synthase (NOS) isoforms were shown to play a neutral, protective, or even adverse role in myocardial remodeling, depending on the quantity of NO produced, the location of each NOS and their regulators, the prevailing oxidant stress and resultant NO/oxidant balance, as well as NOS coupling/dimerization. Beside neuronal NOS and--in specific conditions--inducible NOS isoforms, endothelial NOS (eNOS) exerts cardioprotective effects on pressure-overload, ischemia/reperfusion, and myocardial infarction-induced myocardial remodeling, provided the enzyme remains in a coupled state. Besides its effects on excitation-contraction coupling in response to stretch, eNOS acts as an "endogenous beta-blocker" by restoring the sympathovagal balance, opposing excessive hypertrophy as well as promoting vasodilatation and neoangiogenesis, thereby contributing to tissue repair. As eNOS was also shown to mediate the beneficial effects of cardiovascular drugs commonly used in patients with heart failure, strategies to increase its expression and/or coupled catalytic activity in the myocardium offer new therapeutic avenues for the treatment of this disease.