Blunted peripheral vasodilatory response is a hallmark of progressive deterioration in mild to moderate congestive heart failure

The Endothelium as a Target for the Treatment of Heart Failure

The functional integrity of endothelial cells is a marker and a prerequisite for vascular health. It is well established that the endothelium not only modulates, but also mediates vascular disease processes. Certain diseases such as diabetes, dyslipidaemia, obesity, and arterial hypertension advance endothelial injury. The disease process induces cellular and functional changes in endothelial cells leading to a pathophysiological phenomenon referred to as endothelial cell dysfunction, which involves abnormal vasomotion, an imbalance in reactive oxygen species and nitric oxide, the activation of inflammation, and disruption of the coagulation process of the endothelial cells. With this knowledge, it is now known that vascular function plays a central role in the development and progression of heart failure (HF). HF is the primary cause of patient hospitalization. There is a strong desire to intervene and prevent the growing HF epidemic. Over the last decade, numerous therapies have been evaluated but few have led to positive results in the later stages of clinical trials. Efforts are currently being made to understand the pathophysiology of endothelial dysfunction and use this knowledge to identify novel agents or therapeutic targets that will improve the outcome of patients with HF and restore the normal function of the endothelium. The purpose of this review is to present a brief summary of the traditional approaches that have been taken to improve endothelial dysfunction and combat HF and, more importantly, to discuss some novel therapeutic approaches that are still under investigation, including the use of gene therapy and nanocarriers as means of delivering targets to the dysfunctional endothelium as treatment for HF.

Alteration of vascular reactivity in heart failure: role of phosphodiesterases 3 and 4

BACKGROUND AND PURPOSE

This study examined the role of the main vascular cAMP-hydrolysing phosphodiesterases (cAMP-PDE) in the regulation of basal vascular tone and relaxation of rat aorta mediated by β-adrenoceptors, following heart failure (HF).

EXPERIMENTAL APPROACH

Twenty-two weeks after proximal aortic stenosis, to induce HF, or SHAM surgery in rats, we evaluated the expression, activity and function of cAMP-PDE in the descending thoracic aorta.

KEY RESULTS

HF rat aortas exhibited signs of endothelial dysfunction, with alterations of the NO pathway, and alteration of PDE3 and PDE4 subtype expression, without changing total aortic cAMP-hydrolytic activity and PDE1, PDE3 and PDE4 activities. Vascular reactivity experiments using PDE inhibitors showed that PDE3 and PDE4 controlled the level of PGF2α -stimulated contraction in SHAM aorta. PDE3 function was partially inhibited by endothelial NO, whereas PDE4 function required a functional endothelium and was under the negative control of PDE3. In HF, PDE3 function was preserved, but its regulation by endothelial NO was altered. PDE4 function was abolished and restored by PDE3 inhibition. In PGF2α -precontracted arteries, β-adrenoceptor stimulation-induced relaxation in SHAM aorta, which was abolished in the absence of functional endothelium, as well as in HF aortas, but restored after PDE3 inhibition in all unresponsive arteries.

CONCLUSIONS AND IMPLICATIONS

Our study underlines the key role of the endothelium in controlling the contribution of smooth muscle PDE to contractile function. In HF, endothelial dysfunction had a major effect on PDE3 function and PDE3 inhibition restored a functional relaxation to β-adrenoceptor stimulation.

Phosphodiesterase 1 regulation is a key mechanism in vascular aging

Reduced nitric oxide (NO)/cGMP signalling is observed in age-related vascular disease. We hypothesize that this disturbed signalling involves effects of genomic instability, a primary causal factor in aging, on vascular smooth muscle cells (VSMCs) and that the underlying mechanism plays a role in human age-related vascular disease. To test our hypothesis, we combined experiments in mice with genomic instability resulting from the defective nucleotide excision repair gene ERCC1 (Ercc1(d/-) mice), human VSMC cultures and population genome-wide association studies (GWAS). Aortic rings of Ercc1(d/-) mice showed 43% reduced responses to the soluble guanylate cyclase (sGC) stimulator sodium nitroprusside (SNP). Inhibition of phosphodiesterase (PDE) 1 and 5 normalized SNP-relaxing effects in Ercc1(d/-) to wild-type (WT) levels. PDE1C levels were increased in lung and aorta. cGMP hydrolysis by PDE in lungs was higher in Ercc1(d/-) mice. No differences in activity or levels of cGMP-dependent protein kinase 1 or sGC were observed in Ercc1(d/-) mice compared with WT. Senescent human VSMC showed elevated PDE1A and PDE1C and PDE5 mRNA levels (11.6-, 9- and 2.3-fold respectively), which associated with markers of cellular senescence. Conversely, PDE1 inhibition lowered expression of these markers. Human genetic studies revealed significant associations of PDE1A single nucleotide polymorphisms with diastolic blood pressure (DBP; β=0.28, P=2.47×10(-5)) and carotid intima-media thickness (cIMT; β=-0.0061, P=2.89×10(-5)). In summary, these results show that genomic instability and cellular senescence in VSMCs increase PDE1 expression. This might play a role in aging-related loss of vasodilator function, VSMC senescence, increased blood pressure and vascular hypertrophy.

Activation of inducible NOS in peripheral vessels and outcomes in heart failure patients

BACKGROUND

Activation of inducible nitric oxide synthase (iNOS) has been reported in congestive heart failure (CHF) conditions. However, it is unknown whether activation of iNOS affects prognosis of CHF patients. We prospectively studied the influence of activation of iNOS in the forearm on the outcome of CHF patients.

METHODS AND RESULTS

Forearm blood flow (FBF) responses to 3 doses of acetylcholine (ACh) and nitroglycerin (NTG), and 4 doses of a selective iNOS inhibitor (aminoguanidine: Amn) and a nonselective NOS inhibitor (L-NMMA) were examined using plethysmography in 68 patients with CHF from idiopathic dilated cardiomyopathy. Plasma brain natriuretic peptide (BNP) and tumor necrosis factor-alpha (TNF-alpha) were also measured in all patients. During the mean follow-up period of 3.8 years, 25 patients were hospitalized for worsening heart failure and 9 of these patients died. Patients with adverse events had a diminished vasodilator response to ACh (P < .001) compared to patients without adverse events. Amn significantly decreased FBF (P < .001) in patients with adverse events, but not in patients without adverse events. FBF responses to NTG and L-NMMA were not significantly different between the 2 groups. When grouped by maximum FBF responses to each drug above and below the median value, multivariate Cox proportional hazards model analyses for cardiac event showed a significance in the FBF response to Amn (adjusted hazard ratio 5.89, P < .001). FBF responses to maximum dose of Amn significantly correlated with BNP and TNF-alpha levels (both P < .001).

CONCLUSIONS

CHF patients with vascular iNOS activation, as demonstrated by a greater vasoconstrictor response to Amn, had poor outcomes. Activation of iNOS in peripheral vessels, associated with proinflammatory cytokines in accordance to the severity of heart failure, is a marker for, or contributes to, adverse events in patients with CHF.

Systemic endothelial dysfunction as an early predictor of adverse outcome in heart failure

OBJECTIVE

Endothelial dysfunction is an early event in the natural progression of heart failure. Increased oxidative stress has been linked to impaired endothelial function and both may play a prognostic role.

METHODS AND RESULTS

Endothelium-dependent and endothelium-independent vasodilatation were determined in 289 patients with mild left ventricular dysfunction by measuring forearm blood flow responses to acetylcholine and sodium nitroprusside using venous occlusion plethysmography. Vascular effects of the coadministration of the antioxidant vitamin C at pharmacological doses (24 mg/min) were assessed. Occurrence of death, heart transplantation, and readmission with worsening heart failure were recorded as clinical outcome parameters during a follow-up period of 4.8 years. Patients experiencing adverse events (n=79) had lower vasodilator responses to acetylcholine (P<0.001) and to sodium nitroprusside (P=0.03) compared with patients without events. However, beneficial effects of vitamin C did not differ between both groups. Cox proportional hazards model demonstrated that age (P=0.001), renal function (P=0.001), and blunted acetylcholine-induced vasodilatation (P=0.007) remained independent predictors of adverse outcome.

CONCLUSIONS

Impaired peripheral endothelial function independently predicts long-term adverse outcome in patients with early-stage heart failure. The findings suggest that assessment of peripheral endothelial function may represent an additional mean for risk stratification and therapy management in these patients.

MESENTERIC VASCULAR DYSFUNCTION AFTER CARDIOPULMONARY BYPASS WITH CARDIAC ARREST IS AGGRAVATED BY COEXISTENT HEART FAILURE

Although patients suffering from heart failure (HF) have an increased incidence of nonocclusive mesenteric ischemia after opened heart surgery, the impact of cardiopulmonary bypass with cardiac arrest (CPB) on mesenteric vascular circulation in such situation remains unexplored. Therefore, the present study investigates the effects of CPB on mesenteric vascular reactivity, regional metabolism, and oxidative stress in an experimental model of HF. Volume-overload HF was induced in six dogs by bilateral femoral arteriovenous fistula. Six sham-operated dogs were used as controls. Eight weeks later, the short-term effects of 90 min of CPB were assessed in vivo during acute experiments. The significant increase in left ventricular end-diastolic volume in HF animals did not influence the vasodilator response of the superior mesenteric artery to acetylcholine (ACH) and nitroprusside (SNP) under baseline conditions. However, reduced mesenteric oxygen delivery, increased oxygen extraction, and lactate release were found during CPB in the HF group. In addition, an increased free radical production was assessed in the HF group during (89 +/- 23 x 10 relative light units [RLU]) and after CPB (93 +/- 15 x 10 RLU) compared with controls (45 +/- 15 and 49 +/- 7 x 10 RLU, respectively). Finally, 90 min of CPB led to a more pronounced decrease of ACH- (-22% +/- 5% vs. -42% +/- 9%, P < 0.05) and SNP- (-14% +/- 4% vs. -50% +/- 7%, P < 0.002) induced mesenteric vasodilations in the HF group compared with controls. We conclude that coexistent HF significantly enhances the pathological effects of CPB on the mesenteric vascular circulation by additionally altering endothelial and smooth muscle vascular function consequent to augmented oxidative stress.

Vascular reactivity in heart failure: role of myosin light chain phosphatase

Congestive heart failure (CHF) is a clinical syndrome, which is the result of systolic or diastolic ventricular dysfunction. During CHF, vascular tone is regulated by the interplay of neurohormonal mechanisms and endothelial-dependent factors and is characterized by both central and peripheral vasoconstriction as well as a resistance to nitric oxide (NO)-mediated vasodilatation. At the molecular level, vascular tone depends on the level of regulatory myosin light chain phosphorylation, which is determined by the relative activities of myosin light chain kinase and myosin light chain phosphatase (MLCP). The MLCP is a trimeric enzyme with a catalytic, a 20-kDa and a myosin targeting (MYPT1) subunit. Alternative splicing of a 3' exon produces leucine zipper positive and negative (LZ+/-) MYPT1 isoforms. Expression of a LZ+ MYPT1 has been suggested to be required for NO-mediated smooth muscle relaxation. Thus, we hypothesized that the resistance to NO-mediated vasodilatation in CHF could be attributable to a change in the relative expression of LZ+/- MYPT1 isoforms. To test this hypothesis, left coronary artery ligation was used to induce CHF in rats, and both the dose response relationship of relaxation to 8-Br-cGMP in skinned smooth muscle and the relative expression of LZ+/- MYPT1 isoforms were determined. In control animals, the expression of the LZ+ MYPT1 isoform predominated in both the aorta and iliac artery. In CHF rats, LVEF was reduced to 30+/-5% and there was a significant decrease in both the sensitivity to 8-Br-cGMP and expression of the LZ+ MYPT1 isoform. These results indicate that CHF is associated with a decrease in the relative expression of the LZ+ MYPT1 isoform and the sensitivity to 8-Br-cGMP-mediated smooth muscle relaxation. The data suggest that the resistance to NO-mediated relaxation observed during CHF lies at least in part at the level of the smooth muscle and is a consequence of the decrease in the expression of the LZ+ MYPT1 isoform.

Postischemic forearm skin reactive hyperemia is related to cardovascular risk factors in a healthy female population

OBJECTIVE

To examine whether forearm postischemic skin reactive hyperemia (SRH) measured by laser Doppler flowmetry (LDF) can be used to explore microvascular function and whether LDF response is related to cardiovascular (CV) risk in a population study.

METHODS

SRH of the forearm defined as the percentage increase in cutaneous blood flow from resting conditions to peak dilation following a 2 min upper arm occlusion and CV risk factors were measured prospectively in 862 healthy females screened for cardiovascular risk factors in the context of a campaign designed to promote the 'control' of CV risk factors in women.

RESULTS

The Framingham risk score was constructed from age, sex, systolic and diastolic blood pressure, diabetes, total and high-density lipoprotein-cholesterol and left ventricular hypertrophy (Cornell product. The Cornell product for women was calculated as the QRS duration (ms) (R aVL + S V3 + 6 mV)). Although the score was low in this female population (CV event risk at 10 years 7.89) (95% confidence interval, 7.49-8.30) aged 40 to 75 years, we observed an inverse correlation between SRH of the forearm and the CV risk score ( P<0.001). Hormonal replacement therapy (39.4% of the study population was on hormone replacement therapy) had no significant influence on forearm postischemic SRH in this particular population.

CONCLUSIONS

This study shows that in a very low CV risk female population, a significant correlation can be observed between the weight of CV risks and the impairment of postischemic forearm SRH. Thus, skin laser Doppler flowmetry may represent a valuable, simple and non-invasive tool to assess and monitor microvascular function in future prospective observational and interventional studies.

Myocardial gene expression in dilated cardiomyopathy treated with beta-blocking agents

BACKGROUND

Beta-blocker therapy may improve cardiac function in patients with idiopathic dilated cardiomyopathy. We tested the hypothesis that beta-blocker therapy produces favorable functional effects in dilated cardiomyopathy by altering the expression of myocardial genes that regulate contractility and pathologic hypertrophy.

METHODS

We randomly assigned 53 patients with idiopathic dilated cardiomyopathy to treatment with a beta-adrenergic-receptor blocking agent (metoprolol or carvedilol) or placebo. The amount of messenger RNA (mRNA) for contractility-regulating genes (those encoding beta1- and beta2-adrenergic receptors, calcium ATPase in the sarcoplasmic reticulum, and alpha- and beta-myosin heavy-chain isoforms) and of genes associated with pathologic hypertrophy (beta-myosin heavy chain and atrial natriuretic peptide) was measured with a quantitative reverse-transcription polymerase chain reaction in total RNA extracted from biopsy specimens of the right ventricular septal endomyocardium. Myocardial levels of beta-adrenergic receptors were also measured. Measurements were conducted at base line and after six months of treatment, and changes in gene expression were compared with changes in the left ventricular ejection fraction as measured by radionuclide ventriculography.

RESULTS

Twenty-six of 32 beta-blocker-treated patients (those with complete mRNA measurements) had an improvement in left ventricular ejection fraction of at least 5 ejection-fraction (EF) units (mean [+/-SE] increase, 18.8+/-1.8). As compared with the six beta-blocker-treated patients who did not have a response (mean change, a decrease of 2.5+/-1.8 EF units), those who did have a response had an increase in sarcoplasmic-reticulum calcium ATPase mRNA and alpha-myosin heavy chain mRNA and a decrease in beta-myosin heavy chain mRNA. The change in sarcoplasmic-reticulum calcium ATPase was not present in the patients in the placebo group who had a spontaneous response. There were no differences between those who had a response and those who did not in terms of the change in mRNA or protein expression of beta-adrenergic receptors.

CONCLUSIONS

In idiopathic dilated cardiomyopathy, functional improvement related to treatment with beta-blockers is associated with changes in myocardial gene expression.