Charles J. Ferro

Systemic Endothelin Receptor Blockade Decreases Peripheral Vascular Resistance and Blood Pressure in Humans

BACKGROUND Although local inhibition of the generation or actions of endothelin-1 has been shown to cause forearm vasodilatation, the systemic effects of endothelin receptor blockade in healthy humans are unknown. We therefore investigated the cardiovascular effects of a potent peptide endothelin ETA/B receptor antagonist, TAK-044, in healthy men. METHODS AND RESULTS Two randomized, placebo-controlled, crossover studies were performed. In nine subjects, TAK-044 (10 to 1000 mg IV over a 15-minute period) caused sustained dose-dependent peripheral vasodilatation and hypotension. Four hours after infusion of the highest dose (1000 mg), there were decreases in mean arterial pressure of 18 mm Hg and total peripheral resistance of 665 AU and increases in heart rate of 8 bpm and cardiac index of 0.9 L x min(-1) x m(-2) compared with placebo. TAK-044 caused a rapid, dose-dependent increase in plasma immunoreactive endothelin (from 3.3 to 35.7 pg/mL within 30 minutes after 1000 mg). In a second study in eight subjects, intravenous administration of TAK-044 at doses of 30, 250, and 750 mg also caused peripheral vasodilatation, and all three doses abolished local forearm vasoconstriction to brachial artery infusion of endothelin-1. Brachial artery infusion of TAK-044 caused local forearm vasodilation. CONCLUSIONS The endothelin ETA/B receptor antagonist TAK-044 decreases peripheral vascular resistance and, to a lesser extent, blood pressure; increases circulating endothelin concentrations; and blocks forearm vasoconstriction to exogenous endothelin-1. These results suggest that endogenous generation of endothelin-1 plays a fundamental physiological role in maintenance of peripheral vascular tone and blood pressure. The vasodilator properties of endothelin receptor antagonists may prove valuable therapeutically.

Effect of Spironolactone on Left Ventricular Mass and Aortic Stiffness in Early-Stage Chronic Kidney Disease: A Randomized Controlled Trial

OBJECTIVES We sought to determine whether the addition of spironolactone to angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) improves left ventricular mass and arterial stiffness in early-stage chronic kidney disease (CKD). BACKGROUND Chronic kidney disease is associated with a high risk of cardiovascular disease and a high prevalence of left ventricular hypertrophy and arterial stiffness that confer an adverse prognosis. It is believed that these abnormalities are in part a result of activation of the renin-angiotensin-aldosterone system. METHODS After an active run-in phase with spironolactone 25 mg once daily, 112 patients with stage 2 and 3 CKD with good blood pressure control (mean daytime ambulatory blood pressure <130/85 mm Hg) on established treatment with ACE inhibitors or ARBs were randomized to continue spironolactone or to receive a matching placebo. Left ventricular mass (cardiac magnetic resonance) and arterial stiffness (pulse wave velocity/analysis, aortic distensibility) were measured before run in and after 40 weeks of treatment. RESULTS Compared with placebo, the use of spironolactone resulted in significant improvements in left ventricular mass (-14 +/- 13 g vs. +3 +/- 11 g, p < 0.01), pulse wave velocity (-0.8 +/- 1.0 m/s vs. -0.1 +/- 0.9 m/s, p < 0.01), augmentation index (-5.2 +/- 6.1% vs. -1.4 +/- 5.9%, p < 0.05), and aortic distensibility (0.69 +/- 0.86 x 10(-3) mm Hg vs. 0.04 +/- 1.04 x 10(-3) mm Hg, p < 0.01). CONCLUSIONS The use of spironolactone reduces left ventricular mass and improves arterial stiffness in early-stage CKD. These effects suggest that aldosterone exerts adverse cardiovascular effects in CKD and that spironolactone is worthy of further study as a treatment that could reduce adverse cardiovascular events. (Is Spironolactone Safe and Effective in the Treatment of Cardiovascular Disease in Mild Chronic Renal Failure; NCT00291720).

Inhibition of Neutral Endopeptidase Causes Vasoconstriction of Human Resistance Vessels In Vivo

BACKGROUND Neutral endopeptidase (NEP) degrades vasoactive peptides, including the natriuretic peptides, angiotensin II, and endothelin-1. Systemic inhibition of NEP does not consistently lower blood pressure, even though it increases natriuretic peptide concentrations and causes natriuresis and diuresis. We therefore investigated the direct effects of local inhibition of NEP on forearm resistance vessel tone. METHODS AND RESULTS Four separate studies were performed, each with 90-minute drug infusions. In the first study, 10 healthy subjects received a brachial artery infusion of the NEP inhibitor candoxatrilat (125 nmol/min), which caused a slowly progressive forearm vasoconstriction (12+/-2%; P=0.001). In a second two-phase study, 6 healthy subjects received, 4 hours after enalapril (20 mg) or placebo, an intra-arterial infusion of the NEP inhibitor thiorphan (30 nmol/min). Thiorphan caused similar degrees of local forearm vasoconstriction (P=0.6) after pretreatment with both placebo (13+/-1%, P=0.006) and enalapril (17+/-6%, P=0.05). In a third three-phase study, 8 healthy subjects received intra-arterial thiorphan (30 nmol/min), the endothelin ETA antagonist BQ-123 (100 nmol/min), and both combined. Thiorphan caused local forearm vasoconstriction (13+/-1%, P=0.0001); BQ-123 caused local vasodilatation (33+/-3%, P=0.0001). Combined thiorphan and BQ-123 caused vasodilatation (32+/-1%, P=0.0001) similar to BQ-123 alone (P=0.98). In a fourth study, 6 hypertensive patients (blood pressure >160/100 mm Hg) received intra-arterial thiorphan (30 nmol/min). Thiorphan caused a slowly progressive forearm vasoconstriction (10+/-2%, P=0.0001). CONCLUSIONS Inhibition of local NEP causes vasoconstriction in forearm resistance vessels of both healthy volunteers and patients with hypertension. The lack of effect of ACE inhibition on the vasoconstriction produced by thiorphan and its absence during concomitant ETA receptor blockade suggest that it is mediated by endothelin-1 and not angiotensin II. These findings may help to explain the failure of systemic NEP inhibition to lower blood pressure.

Arterial stiffness in chronic kidney disease: causes and consequences

Chronic kidney disease is associated with elevated cardiovascular risk, and heart failure and arrhythmias are the biggest causes of cardiovascular death in this population. Increased arterial stiffness is a hallmark of chronic kidney disease and is associated with adverse alterations in cardiac structure and function that may predispose to an increased risk of cardiovascular death. These changes are already apparent in early kidney disease, which is highly prevalent in the developed world. The mechanisms underlying increased arterial stiffness in chronic kidney disease are undoubtedly complex, but an understanding is paramount to enable the development of novel therapeutic strategies to prevent or reverse this pathophysiology and therefore reduce the cardiovascular disease burden in this high-risk cohort.

The clinical potential of endothelin receptor antagonists in cardiovascular medicine

SummaryThe endothelin family of peptides are extremely potent endogenous vasoconstrictor and pressor agents. Of the 3 isoforms, endothelin-1 is the major isoform produced by the vascular endothelium and is, therefore, likely to be of most importance for regulation of vascular function. Two endothelin receptor subtypes have so far been cloned in mammalian species; ETA and ETB. Both receptor subtypes are found on smooth muscle cells and mediate the vasoconstrictor and pressor actions of endothelin. The ETB receptor is also found on vascular endothelial cells and mediates endothelin-dependent vasodilatation through release of nitric oxide and prostacyclin.Since their discovery in 1988, the endothelins have been the subject of intense research on their physiological function and potential pathophysiological role in cardiovascular disease. There is now good evidence that endothelin regulates vascular tone and blood pressure, and studies to support the development of endothelin receptor antagonists in conditions associated with chronic vasoconstriction, such as hypertension and heart failure, as well as in vasospastic disorders, such as subarachnoid haemorrhage and Raynaud’s disease.There are now a number of selective ETA and combined ETA/B receptor antagonists available for preclinical studies. However, it is still not clear which of these will prove to be of most therapeutic value. Some of these agents are currently being assessed in early phase clinical trials. Endothelin receptor antagonists represent a novel therapeutic approach to a fundamental and newly discovered endogenous vasoconstrictor mechanism. The results of the current clinical trials are awaited with considerable interest.

Arterial disease in chronic kidney disease

End stage renal disease is associated with a very high risk of premature cardiovascular death and morbidity. Early stage chronic kidney disease (CKD) is also associated with an increased frequency of cardiovascular events and is a common but poorly recognised and undertreated risk factor. Cardiovascular disease in CKD can be attributed to two distinct but overlapping pathological processes, namely atherosclerosis and arteriosclerosis. While the risk of athero-thrombotic events such as myocardial infarction is elevated, arteriosclerosis is the predominant pathophysiological process involving fibrosis and thickening of the medial arterial layer. This results in increased arterial stiffness causing left ventricular hypertrophy and fibrosis and the exposure of vulnerable vascular beds such as the brain and kidney to high pressure fluctuations causing small vessel disease. These pathophysiological features are manifest by a high risk of lethal arrhythmia, congestive heart failure, myocardial infarction and stroke. Recent work has highlighted the importance of aldosterone and disordered bone mineral metabolism.

Endothelial Dysfunction and Hypertension

SummaryVascular endothelial cells play a key role in cardiovascular regulation by producing a number of potent vasoactive agents, including the vasodilator molecule nitric oxide (NO) and the vasoconstrictor peptide endothelin (ET)-l. A dysfunction of the vascular endothelium has been implicated in the pathophysiology of a number of cardiovascular diseases, important among which is essential hypertension. Impairment of NO synthesis, or increased inactivation of NO by superoxide radicals, may account for the increased peripheral vascular tone associated with hypertension, as well as contribute to the clinical consequences of this condition, which include vascular hypertrophy, increased platelet and monocyte adhesion to the endothelium, atherosclerosis, myocardial infarction and stroke. Similarly, increased ET-1 synthesis, or increased smooth muscle sensitivity to ET-1, could account for many of the features of hypertension, including increased peripheral vascular tone and vascular hypertrophy. Modulation of endothelial function is, therefore, an attractive therapeutic option in the treatment of hypertension.Calcium antagonists have been shown to enhance the effects of NO, and inhibit those of ET-1, on vascular smooth muscle cells. In addition, calcium antagonists have antiatherogenic and antioxidant properties and could, therefore, prove to be useful therapeutic agents in preventing some of the important complications of hypertension. The long term effects on cardiovascular morbidity and mortality of the long-acting nifedipine gastrointestinal therapeutic system (nifedipine GITS) used in the treatment of essential hypertension are currently being investigated in the first multinational outcome study (INSIGHT) of an antihypertensive agent since the major studies of β-adrenoceptor blockers or thiazide diuretics. The results of this study are awaited with considerable interest.

Aortic distensibility and arterial–ventricular coupling in early chronic kidney disease: a pattern resembling heart failure with preserved ejection fraction

Objectives: To examine arterial and left ventricular function and their interaction in patients with early-stage chronic kidney disease (CKD). Design and setting: Cross-sectional observational study in a university teaching hospital. Patients: 117 patients with stage 2 (60–89 ml/min/1.73 m2) or stage 3 (30–59 ml/min/1.73 m2) non-diabetic CKD, without overt cardiovascular disease were compared with 40 controls. Interventions: Aortic distensibility and left ventricular mass were assessed using cardiac magnetic resonance imaging. Systolic and diastolic ventricular function and arterial–ventricular elastance (stiffness) were assessed by transthoracic echocardiography. Main outcome measures: Arterial stiffness as measured by aortic distensibility and arterial elastance. Left ventricular mass, left ventricular systolic and diastolic function, including end-diastolic and end-systolic elastance and their relationship with arterial elastance. Results: Compared with controls, patients with CKD 2 and CKD 3 had reduced aortic distensibility (4.12 (1.3) vs 2.94 (1.8) vs 2.18 (1.8)×10–3 mm Hg, p<0.01), increased arterial elastance (1.4 (1.3) vs 1.65 (0.40) vs 1.74 0.48) mm Hg, p<0.05) and increased end-systolic (1.88 (0.48) vs 2.43 (0.83) vs 2.42(0.78) mm Hg/ml, p<0.05) and end diastolic elastances (0.07 (0.04) vs 0.11 (0.04) vs 0.12 (0.04, p<0.01). Aortic distensibility was positively correlated with estimated glomerular filtration rate (r = 0.349, p<0.01) and indices of elastance were inversely correlated (r =  0.284, p<0.05). Systolic function was not impaired in patients with early CKD compared with controls but diastolic filling velocities (Em) were reduced (8.1 (0.9) vs 7.9 (0.6) vs 7.5 (0.7) cm/s, p<0.01) while mean left atrial pressure (E/Em) was increased (5.6 (1.1), vs 7.4 (1.8) vs 8.0 (2.4), p<0.01) and end-diastolic elastance was increased. Conclusions: Early-stage CKD is characterised by reduced aortic distensibility and increases in arterial, ventricular systolic and diastolic stiffness; arterial–ventricular coupling is preserved. This pattern of pathophysiological abnormalities resembles that seen in heart failure with preserved ejection fraction and may account for the high levels of cardiovascular morbidity and mortality in patients at all stages of CKD. Trial Registration Number: NCT00291720

Increased incidence of cardiovascular events in patients with antineutrophil cytoplasmic antibody–associated vasculitides: A matched-pair cohort study

OBJECTIVE To explore the risk of cardiovascular disease in patients with antineutrophil cytoplasmic antibody-associated vasculitides (AAVs) and to assess contributing risk factors. METHODS In a retrospective matched-pair cohort study, 113 of 131 patients with AAVs from a vasculitis clinic registry were matched 1:1 for renal function, age at diagnosis, sex, smoking status, and previous history of a cardiovascular disease to patients with noninflammatory chronic kidney disease (CKD). Cardiovascular events were defined as acute coronary syndrome, new-onset angina, symptomatic peripheral vascular disease, stroke, and transient ischemic attack. RESULTS Median followup times were 3.4 years for the AAV patients and 4.2 years for the CKD patients. More cardiovascular events occurred in the AAV group (23 of 113) than in the CKD group (16 of 113). Cox regression survival analysis showed a significantly increased risk of a cardiovascular event for AAV patients, with a hazard ratio (HR) of 2.23 (95% confidence interval [95% CI] 1.1-4.4) (P = 0.017). Within the cohort of AAV patients, the most strongly predictive factors were previous history of cardiovascular disease (HR 4 [95% CI 1.7-9.8]), history of dialysis dependency (HR 4.3 [95% CI 1.5-12.1]), ever having smoked (HR 3.9 [95% CI 1.5-10]), age at diagnosis (HR 1.038 [95% CI 1.006-1.072]), estimated glomerular filtration rate at remission (HR 0.977 [95% CI 0.957-0.998]), and serum cholesterol concentration at presentation (HR 0.637 [95% CI 0.441-0.92]). CONCLUSION In this retrospective study, patients with AAVs appear at greater risk of cardiovascular disease, with increased risk in those with a previous history of cardiovascular disease, dialysis dependency, poor renal function at remission, or a history of smoking. Measures to reduce the risk of cardiovascular disease should be integral to the management of systemic vasculitis.

Cardiovascular Effects of Sevelamer in Stage 3 CKD

Serum phosphate independently predicts cardiovascular mortality in the general population and CKD, even when levels are in the normal range. Associations between serum phosphate, arterial stiffness, and left ventricular (LV) mass suggest a possible pathophysiological mechanism, potentially mediated by the phosphaturic hormone fibroblast growth factor-23 (FGF-23). To what extent the phosphate binder sevelamer modulates these effects is not well understood. In this single-center, randomized, double-blind, placebo-controlled trial, we enrolled 120 patients with stage 3 nondiabetic CKD. After a 4-week open-label run-in period, during which time all patients received sevelamer carbonate, we randomly assigned 109 patients to sevelamer (n=55) or placebo (n=54) for an additional 36 weeks. We assessed LV mass and systolic and diastolic function with cardiovascular magnetic resonance imaging and echocardiography, and we assessed arterial stiffness by carotid-femoral pulse wave velocity. The mean age was 55 years, and the mean eGFR was 50 ml/min per 1.73 m(2). After 40 weeks, we found no statistically significant differences between sevelamer and placebo with regard to LV mass, systolic and diastolic function, or pulse wave velocity. Only 56% of subjects took ≥ 80% of prescribed therapy; in this compliant subgroup, treatment with sevelamer associated with lower urinary phosphate excretion and serum FGF-23 but not serum phosphate, klotho, vitamin D, or cardiovascular-related outcomes of interest. In conclusion, this study does not provide evidence that sevelamer carbonate improves LV mass, LV function, or arterial stiffness in stage 3 nondiabetic CKD.