Effect of natriuretic peptide family on the oxidized LDL-induced migration of human coronary artery smooth muscle cells

CNP Ameliorates Macrophage Inflammatory Response and Atherosclerosis

BACKGROUND

CNP (C-type natriuretic peptide), an endogenous short peptide in the natriuretic peptide family, has emerged as an important regulator to govern vascular homeostasis. However, its role in the development of atherosclerosis remains unclear. This study aimed to investigate the impact of CNP on the progression of atherosclerotic plaques and elucidate its underlying mechanisms.

METHODS

Plasma CNP levels were measured in patients with acute coronary syndrome. The potential atheroprotective role of CNP was evaluated in apolipoprotein E-deficient (ApoE-/-) mice through CNP supplementation via osmotic pumps, genetic overexpression, or LCZ696 administration. Various functional experiments involving CNP treatment were performed on primary macrophages derived from wild-type and CD36 (cluster of differentiation 36) knockout mice. Proteomics and multiple biochemical analyses were conducted to unravel the underlying mechanism.

RESULTS

We observed a negative correlation between plasma CNP concentration and the burden of coronary atherosclerosis in patients. In early atherosclerotic plaques, CNP predominantly accumulated in macrophages but significantly decreased in advanced plaques. Supplementing CNP via osmotic pumps or genetic overexpression ameliorated atherosclerotic plaque formation and enhanced plaque stability in ApoE-/- mice. CNP promoted an anti-inflammatory macrophage phenotype and efferocytosis and reduced foam cell formation and necroptosis. Mechanistically, we found that CNP could accelerate HIF-1α (hypoxia-inducible factor 1-alpha) degradation in macrophages by enhancing the interaction between PHD (prolyl hydroxylase domain-containing protein) 2 and HIF-1α. Furthermore, we observed that CD36 bound to CNP and mediated its endocytosis in macrophages. Moreover, we demonstrated that the administration of LCZ696, an orally bioavailable drug recently approved for treating chronic heart failure with reduced ejection fraction, could amplify the bioactivity of CNP and ameliorate atherosclerotic plaque formation.

CONCLUSIONS

Our study reveals that CNP enhanced plaque stability and alleviated macrophage inflammatory responses by promoting HIF-1α degradation, suggesting a novel atheroprotective role of CNP. Enhancing CNP bioactivity may offer a novel pharmacological strategy for treating related diseases.

The natriuretic peptide system in heart failure: Diagnostic and therapeutic implications

Natriuretic peptides, which are activated in heart failure, play an important cardioprotective role. The most notable of the cardioprotective natriuretic peptides are atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), which are abundantly expressed and secreted in the atrium and ventricles, respectively, and C-type natriuretic peptide (CNP), which is expressed mainly in the vasculature, central nervous system, and bone. ANP and BNP exhibit antagonistic effects against angiotensin II via diuretic/natriuretic actions, vasodilatory actions, and inhibition of aldosterone secretion, whereas CNP is involved in the regulation of vascular tone and blood pressure, among other roles. ANP and BNP are of particular interest with respect to heart failure, as their levels, most notably BNP and N-terminal proBNP-a cleavage product produced when proBNP is processed to mature BNP-are increased in patients with heart failure. Furthermore, the identification of natriuretic peptides as sensitive markers of cardiac load has driven significant research into their physiological roles in cardiovascular homeostasis and disease, as well as their potential use as both biomarkers and therapeutics. In this review, I discuss the physiological functions of the natriuretic peptide family, with a particular focus on the basic research that has led to our current understanding of its roles in maintaining cardiovascular homeostasis, and the pathophysiological implications for the onset and progression of heart failure. The clinical significance and potential of natriuretic peptides as diagnostic and/or therapeutic agents are also discussed.

Clinical impact of cardiovascular disease on patients with bronchiectasis

Background

Patients with bronchiectasis have a higher cardiovascular risk than their matched controls. However, the effect of cardiovascular (CV) disease on bronchiectasis remains unclear. Thus, we aimed to investigate the clinical impacts of cardiovascular disease on adult patients with bronchiectasis.

Methods

The study cohort comprised 603 consecutive inpatients diagnosed with bronchiectasis in the Affiliated Yancheng Hospital of Southeast University Medical College (Jiangsu, China) from January 2014 to December 2017. Symptoms, bacterial cultures, blood biochemical indicator levels, and chest high-resolution computed tomography scans were assessed during their initial hospitalization for bronchiectasis. Three hundred and thirty five subjects finished 1 year follow-up after their hospital discharge.

Results

Three hundred thirty five patients had at least one bronchiectasis exacerbation during the 1-year follow-up period. Patients with CV comorbidities were more likely to present with symptoms of wheezing (65.3%) and had a higher levels of brain natriuretic peptide (P < 0.001) and D-dimer (P < 0.001) than those without CV comorbidities. Independent risk factors associated with bronchiectasis exacerbations were the presence of comorbidities of cardiovascular diseases (odds ratio [OR] 2.503, 95% confidence interval [CI] 1.298–4.823; P = 0.006), the isolation of Pseudomonas aeruginosa (OR 2.076, 95% CI 1.100–3.919; P = 0.024), and extension to more than two lobes (OR 2.485, 95% CI 1.195–5.168; P = 0.015).

Conclusion

The existence of cardiovascular disease was independently associated with increased bronchiectasis exacerbation.

C-type Natriuretic Peptide: A Multifaceted Paracrine Regulator in the Heart and Vasculature

C-type natriuretic peptide (CNP) is an autocrine and paracrine mediator released by endothelial cells, cardiomyocytes and fibroblasts that regulates vital physiological functions in the cardiovascular system. These roles are conveyed via two cognate receptors, natriuretic peptide receptor B (NPR-B) and natriuretic peptide receptor C (NPR-C), which activate different signalling pathways that mediate complementary yet distinct cellular responses. Traditionally, CNP has been deemed the endothelial component of the natriuretic peptide system, while its sibling peptides, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP), are considered the endocrine guardians of cardiac function and blood volume. However, accumulating evidence indicates that CNP not only modulates vascular tone and blood pressure, but also governs a wide range of cardiovascular effects including the control of inflammation, angiogenesis, smooth muscle and endothelial cell proliferation, atherosclerosis, cardiomyocyte contractility, hypertrophy, fibrosis, and cardiac electrophysiology. This review will focus on the novel physiological functions ascribed to CNP, the receptors/signalling mechanisms involved in mediating its cardioprotective effects, and the development of therapeutics targeting CNP signalling pathways in different disease pathologies.

N-Terminal pro C-Type Natriuretic Peptide (NTproCNP) and myocardial function in ageing

Ageing-related alterations in cardiovascular structure and function are commonly associated with chronic inflammation. A potential blood-based biomarker indicative of a chronic inflammatory state is N-Terminal Pro C-Type Natriuretic Peptide (NTproCNP). We aim to investigate associations between NTproCNP and ageing-related impairments in cardiovascular function. Community-based participants underwent same-day assessment of cardiovascular function and circulating profiles of plasma NTproCNP. Associations between cardiovascular and biomarker profiles were studied in adjusted models including standard covariates. We studied 93 participants (mean age 73 ± 5.3 years, 36 women), of whom 55 (59%) had impaired myocardial relaxation (ratio of peak velocity flow in early diastole E (m/s) to peak velocity flow in late diastole by atrial contraction A (m/s) <0.84). Participants with impaired myocardial relaxation were also found to have lower peak early phase filling velocity (0.6 ± 0.1 vs 0.7 ± 0.1, p < 0.0001) and higher peak atrial phase filling velocity (0.9 ± 0.1 vs 0.7 ± 0.1, p < 0.0001). NTproCNP levelswere significantly lower among participants with impaired myocardial relaxation (16.4% vs 39.5% with NTproCNP ≥ 19, p = 0.012). After multivariable adjustments, NTproCNP was independently associated with impaired myocardial relaxation (OR 2.99, 95%CI 1.12–8.01, p = 0.029). Community elderly adults with myocardial ageing have lower NTproCNP levels compared to those with preserved myocardial function. Given that impaired myocardial relaxation probably represents early changes within the myocardium with ageing, NTproCNP may be useful as an ‘upstream’ biomarker useful for charting myocardial ageing.

Enzyme-modified non-oxidized LDL (ELDL) induces human coronary artery smooth muscle cell transformation to a migratory and osteoblast-like phenotype

Enzyme modified non-oxidative LDL (ELDL) is effectively taken up by vascular smooth muscle cells (SMC) and mediates transition into foam cells and produces phenotypic changes in SMC function. Our data show that incubation of human coronary artery SMC (HCASMC) with low concentration of ELDL (10 μg/ml) results in significantly enhanced foam cell formation compared to oxidized LDL (200 μg/ml; p < 0.01) or native LDL (200 μg/ml; p < 0.01). Bioinformatic network analysis identified activation of p38 MAPK, NFkB, ERK as top canonical pathways relevant for biological processes linked to cell migration and osteoblastic differentiation in ELDL-treated cells. Functional studies confirmed increased migration of HCASMC upon stimulation with ELDL (10 μg/ml) or Angiopoietin like protein 4, (ANGPTL4, 5 μg/ml), and gain in osteoblastic gene profile with significant increase in mRNA levels for DMP-1, ALPL, RUNX2, OPN/SPP1, osterix/SP7, BMP and reduction in mRNA for MGP and ENPP1. Enhanced calcification of HCASMC by ELDL was demonstrated by Alizarin Red staining. In summary, ELDL is highly potent in inducing foam cells in HCASMC and mediates a phenotypic switch with enhanced migration and osteoblastic gene profile. These results point to the potential of ELDL to induce migratory and osteoblastic effects in human smooth muscle cells with potential implications for migration and calcification of SMCs in human atherosclerosis.

Malondialdehyde-modified LDL-related variables are associated with diabetic kidney disease in type 2 diabetes

BACKGROUND AND AIMS

Oxidized low-density lipoprotein (oxLDL) causes the development of atherosclerosis and kidney injury. Although circulating oxLDL levels were reportedly increased in type 2 diabetic patients with macroalbuminuria, it remains unclear whether albuminuria or the reduced glomerular filtration rate (GFR) is independently associated with the circulating oxLDL level. This study aimed to elucidate the association between the stage of diabetic nephropathy and serum malondialdehyde-modified LDL (MDA-LDL) and the ratio of MDA-LDL to LDL-cholesterol (MDA-LDL/LDL).

METHODS AND RESULTS

This retroactive cross-sectional study used data from 402 patients with type 2 diabetes. Patients undergoing hemodialysis were excluded. Serum MDA-LDL levels were significantly increased with increases in severity of albuminuria (103 ± 44 U/L, 109 ± 54 U/L, and 135 ± 72 U/L for normoalbuminuria, microalbuminuria, and macroalbuminuria, respectively; P for trend = 0.020) but not according to the estimated GFR (eGFR). An increased MDA-LDL/LDL ratio was significantly associated with both increased albuminuria (35 ± 13, 37 ± 14, and 40 ± 15 for normoalbuminuria, microalbuminuria, and macroalbuminuria, respectively; P for trend = 0.003) and reduced eGFR (34 ± 13, 36 ± 13, 38 ± 12, and 51 ± 28 for grade 1, 2, 3 and 4, respectively; P for trend = 0.002). Multiple linear regression analysis showed that neither the albumin excretion rate nor eGFR but ln-transformed triglycerides and LDL-C levels were independent determinants of both serum MDA-LDL levels and MDA-LDL/LDL ratios.

CONCLUSION

Serum MDA-LDL levels and MDA-LDL/LDL ratios were increased in those with dyslipidemia associated with diabetic kidney disease.

Characterization of Atherosclerosis Formation in a Murine Model of Type IIa Human Familial Hypercholesterolemia

A murine genetic model of LDL-cholesterol- (LDL-C-) driven atherosclerosis, based on complete deficiencies of both the LDL-receptor (Ldlr^-/-) and key catalytic component of an apolipoprotein B-edisome complex (Apobec1^-/-), which converts apoB-100 to apoB-48, has been extensively characterized. These gene deficiencies allow high levels of apoB-100 to be present and inefficiently cleared, thus leading to very high levels of LDL-C in mice on a normal diet. Many key features of atherosclerotic plaques observed in human familial hypercholesterolemia are found in these mice as they are allowed to age through 72 weeks. The general characteristics include the presence of high levels of LDL-C in plasma and macrophage-related fatty streak formation in the aortic tree, which progressively worsens with age. More specifically, plaque found in the aortic sinuses contains a lipid core with relatively high numbers of macrophages and a smooth muscle cell α-actin- and collagen-containing cap, which thins with age. These critical features of plaque progression suggest that the Ldlr^-/-/Apobec1^-/- mouse line presents a superior model of LDL-C-driven atherosclerosis.

Synthesis, secretion, function, metabolism and application of natriuretic peptides in heart failure

As a family of hormones with pleiotropic effects, natriuretic peptide (NP) system includes atrial NP (ANP), B-type NP (BNP), C-type NP (CNP), dendroaspis NP and urodilatin, with NP receptor-A (guanylate cyclase-A), NP receptor-B (guanylate cyclase-B) and NP receptor-C (clearance receptor). These peptides are genetically distinct, but structurally and functionally related for regulating circulatory homeostasis in vertebrates. In humans, ANP and BNP are encoded by NP precursor A (NPPA) and NPPB genes on chromosome 1, whereas CNP is encoded by NPPC on chromosome 2. NPs are synthesized and secreted through certain mechanisms by cardiomyocytes, fibroblasts, endotheliocytes, immune cells (neutrophils, T-cells and macrophages) and immature cells (embryonic stem cells, muscle satellite cells and cardiac precursor cells). They are mainly produced by cardiovascular, brain and renal tissues in response to wall stretch and other causes. NPs provide natriuresis, diuresis, vasodilation, antiproliferation, antihypertrophy, antifibrosis and other cardiometabolic protection. NPs represent body's own antihypertensive system, and provide compensatory protection to counterbalance vasoconstrictor-mitogenic-sodium retaining hormones, released by renin-angiotensin-aldosterone system (RAAS) and sympathetic nervous system (SNS). NPs play central roles in regulation of heart failure (HF), and are inactivated through not only NP receptor-C, but also neutral endopeptidase (NEP), dipeptidyl peptidase-4 and insulin degrading enzyme. Both BNP and N-terminal proBNP are useful biomarkers to not only make the diagnosis and assess the severity of HF, but also guide the therapy and predict the prognosis in patients with HF. Current NP-augmenting strategies include the synthesis of NPs or agonists to increase NP bioactivity and inhibition of NEP to reduce NP breakdown. Nesiritide has been established as an available therapy, and angiotensin receptor blocker NEP inhibitor (ARNI, LCZ696) has obtained extremely encouraging results with decreased morbidity and mortality. Novel pharmacological approaches based on NPs may promote a therapeutic shift from suppressing the RAAS and SNS to re-balancing neuroendocrine dysregulation in patients with HF. The current review discussed the synthesis, secretion, function and metabolism of NPs, and their diagnostic, therapeutic and prognostic values in HF.

The effects of sacubitril/valsartan on coronary outcomes in PARADIGM-HF

BACKGROUND

Angiotensin converting enzyme inhibitors (ACE-I), are beneficial both in heart failure with reduced ejection fraction (HF-REF) and after myocardial infarction (MI). We examined the effects of the angiotensin-receptor neprilysin inhibitor sacubitril/valsartan, compared with the ACE-I enalapril, on coronary outcomes in PARADIGM-HF.

METHODS AND RESULTS

We examined the effect of sacubitril/valsartan compared with enalapril on the following outcomes: i) the primary composite endpoint of cardiovascular (CV) death or HF hospitalization, ii) a pre-defined broader composite including, in addition, MI, stroke, and resuscitated sudden death, and iii) a post hoc coronary composite of CV-death, non-fatal MI, angina hospitalization or coronary revascularization. At baseline, of 8399 patients, 3634 (43.3%) had a prior MI and 4796 (57.1%) had a history of any coronary artery disease. Among all patients, compared with enalapril, sacubitril/valsartan reduced the risk of the primary outcome (HR 0.80 [0.73-0.87], P<.001), the broader composite (HR 0.83 [0.76-0.90], P<.001) and the coronary composite (HR 0.83 [0.75-0.92], P<.001). Although each of the components of the coronary composite occurred less frequently in the sacubitril/valsartan group, compared with the enalapril group, only CV death was reduced significantly.

CONCLUSIONS

Compared with enalapril, sacubitril/valsartan reduced the risk of both the primary endpoint and a coronary composite outcome in PARADIGM-HF. Additional studies on the effect of sacubitril/valsartan on atherothrombotic outcomes in high-risk patients are merited.

Lysophosphatidic acid-induced vascular neointimal formation in mouse carotid arteries is mediated by the matricellular protein CCN1/Cyr61

Vascular smooth muscle cell (SMC) migration is an essential step involved in neointimal formation in restenosis and atherosclerosis. Lysophosphatidic acid (LPA) is a bioactive component of oxidized low-density lipoprotein and is produced by activated platelets, implying that LPA influences vascular remodeling. Our previous study revealed that matricellular protein CCN1, a prominent extracellular matrix (ECM) protein, mediates LPA-induced SMC migration in vitro. Here we examined the role of CCN1 in LPA-induced neointimal formation. By using LPA infusion of carotid artery in a mouse model, we demonstrated that LPA highly induced CCN1 expression (approximately six- to sevenfold) in neointimal lesions. Downregulation of CCN1 expression with the specific CCN1 siRNA in carotid arteries blocked LPA-induced neointimal formation, indicating that CCN1 is essential in LPA-induced neointimal formation. We then used LPA receptor knockout (LPA₁-/-, LPA₂-/-, and LPA₃-/-) mice to examine LPA receptor function in CCN1 expression in vivo and in LPA-induced neointimal formation. Our data reveal that LPA₁ deficiency, but not LPA₂ or LPA₃ deficiency, prevents LPA-induced CCN1 expression in vivo in mouse carotid arteries. We also observed that LPA₁ deficiency blunted LPA infusion-induced neointimal formation, indicating that LPA₁ is the major mediator for LPA-induced vascular remodeling. Our in vivo model of LPA-induced neointimal formation established a key role of the ECM protein CCN1 in mediating LPA-induced neointimal formation. Our data support the notion that the LPA₁-CCN1 axis may be the central control for SMC migration and vascular remodeling. CCN1 may serve as an important vascular disease marker and potential target for vascular therapeutic intervention.

The natriuretic peptides system in the pathophysiology of heart failure: from molecular basis to treatment

After its discovery in the early 1980s, the natriuretic peptide (NP) system has been extensively characterized and its potential influence in the development and progression of heart failure (HF) has been investigated. HF is a syndrome characterized by the activation of different neurohormonal systems, predominantly the renin-angiotensin (Ang)-aldosterone system (RAAS) and the sympathetic nervous system (SNS), but also the NP system. Pharmacological interventions have been developed to counteract the neuroendocrine dysregulation, through the down modulation of RAAS with ACE (Ang-converting enzyme) inhibitors, ARBs (Ang receptor blockers) and mineralcorticoid antagonists and of SNS with β-blockers. In the last years, growing attention has been paid to the NP system. In the present review, we have summarized the current knowledge on the NP system, focusing on its role in HF and we provide an overview of the pharmacological attempts to modulate NP in HF: from the negative results of the study with neprilysin (NEP) inhibitors, alone or associated with an ACE inhibitor and vasopeptidase inhibitors, to the most recently and extremely encouraging results obtained with the new pharmacological class of Ang receptor and NEP inhibitor, currently defined ARNI (Ang receptor NEP inhibitor). Indeed, this new class of drugs to manage HF, supported by the recent results and a vast clinical development programme, may prompt a conceptual shift in the treatment of HF, moving from the inhibition of RAAS and SNS to a more integrated target to rebalance neurohormonal dysregulation in HF.

Natriuretic Peptides and Cardiometabolic Health

Natriuretic peptides are cardiac-derived hormones with a range of protective functions, including natriuresis, diuresis, vasodilation, lusitropy, lipolysis, weight loss, and improved insulin sensitivity. Their actions are mediated through membrane-bound guanylyl cyclases that lead to production of the intracellular second-messenger cyclic guanosine monophosphate. A growing body of evidence demonstrates that genetic and acquired deficiencies of the natriuretic peptide system can promote hypertension, cardiac hypertrophy, obesity, diabetes mellitus, the metabolic syndrome, and heart failure. Clinically, natriuretic peptides are robust diagnostic and prognostic markers, and augmenting natriuretic peptides is a target for therapeutic strategies in cardiometabolic disease. This review will summarize current understanding and highlight novel aspects of natriuretic peptide biology.

Circulating C-type natriuretic peptide and its relationship to cardiovascular disease in the general population

C-type natriuretic peptide (CNP) is an endothelium-derived peptide that is released as a protective mechanism in response cardiovascular injury or disease. However, no studies have investigated circulating CNP, identifying clinical factors that may influence CNP and its relationship to cardiovascular disease in the general population. We studied 1841 randomly selected subjects from Olmsted County, MN (mean age, 63±11 years; 48% men). Plasma CNP was measured by a well-established radioimmunoassay and echocardiography, clinical characterization, and detailed medical record review were performed. We report that CNP circulates at various concentrations (median, 13 pg/mL), was unaffected by sex, was weakly associated by age, and that highest quartile of CNP identified a high-risk phenotype. Subjects with CNP in the highest quartile were associated with increased risk of myocardial infarction (multivariable-adjusted hazard ratio, 1.51; 95% confidence interval, 1.09-2.09; P=0.01) but not heart failure, cerebrovascular accidents, or death during a follow-up of 12 years. Addition of the highest quartile of CNP to clinical variables led to a modest increase in the integrated discrimination improvement for risk of myocardial infarction. In a large community-based cohort, elevated circulating CNP identified a high-risk phenotype that included cardiovascular comorbidities and left ventricular dysfunction, and provided evidence that highest concentrations of CNP potentially has prognostic value in predicting future risk of myocardial infarction. Together, these data from the general population highlight the potential value of CNP and support the need for additional studies to evaluate whether mechanisms regulating CNP could improve outcomes.

Endothelial C-type natriuretic peptide maintains vascular homeostasis

The endothelium plays a fundamental role in maintaining vascular homeostasis by releasing factors that regulate local blood flow, systemic blood pressure, and the reactivity of leukocytes and platelets. Accordingly, endothelial dysfunction underpins many cardiovascular diseases, including hypertension, myocardial infarction, and stroke. Herein, we evaluated mice with endothelial-specific deletion of Nppc, which encodes C-type natriuretic peptide (CNP), and determined that this mediator is essential for multiple aspects of vascular regulation. Specifically, disruption of CNP leads to endothelial dysfunction, hypertension, atherogenesis, and aneurysm. Moreover, we identified natriuretic peptide receptor-C (NPR-C) as the cognate receptor that primarily underlies CNP-dependent vasoprotective functions and developed small-molecule NPR-C agonists to target this pathway. Administration of NPR-C agonists promotes a vasorelaxation of isolated resistance arteries and a reduction in blood pressure in wild-type animals that is diminished in mice lacking NPR-C. This work provides a mechanistic explanation for genome-wide association studies that have linked the NPR-C (Npr3) locus with hypertension by demonstrating the importance of CNP/NPR-C signaling in preserving vascular homoeostasis. Furthermore, these results suggest that the CNP/NPR-C pathway has potential as a disease-modifying therapeutic target for cardiovascular disorders.

Natriuretic peptides in cardiometabolic regulation and disease

In the 30 years since the identification of the natriuretic peptides, their involvement in regulating fluid and blood pressure has become firmly established. Data indicating a role for these hormones in lifestyle-related metabolic and cardiovascular disorders have also accumulated over the past decade. Dysregulation of the natriuretic peptide system has been associated with obesity, glucose intolerance, type 2 diabetes mellitus, and essential hypertension. Moreover, the natriuretic peptides have been implicated in the protection against atherosclerosis, thrombosis, and myocardial ischaemia. All these conditions can coexist and potentially lead to heart failure, a syndrome associated with a functional natriuretic peptide deficiency despite high circulating concentrations of immunoreactive peptides. Therefore, dysregulation of the natriuretic peptide system, a 'natriuretic handicap', might be an important factor in the initiation and progression of metabolic dysfunction and its accompanying cardiovascular complications. This Review provides a summary of the natriuretic peptide system and its involvement in these cardiometabolic conditions. We propose that these peptides might have an integrating role in lifestyle-related metabolic and cardiovascular disorders.

Brain natriuretic peptide is related to carotid plaques and predicts atherosclerosis in pre-dialysis patients with chronic kidney disease

BACKGROUND

Although brain natriuretic peptide (BNP) concentration has been associated with atherosclerosis and ischemic cardiovascular diseases (CVD) in the general population, less is known about this relationship in pre-dialysis chronic kidney disease (CKD) patients.

METHODS

We prospectively analyzed 227 pre-dialysis patients with CKD [median estimated glomerular filtration rate (eGFR): 28.82 (11.65-48.20) ml/min/1.73 m(2)]. At enrollment, BNP concentrations, biochemical and echocardiographic parameters were measured, and carotid artery ultrasound was performed. Patients were prospectively followed for a mean 31.8 months (range 0.5-57.0 months). Ischemic CV events and patient outcomes were recorded.

RESULTS

Median BNP concentration at enrollment was significantly higher in the CKD patients than in a control group [53.9 (16.2-181.0) pg/ml vs. 9.4 (7.0-15.3) pg/ml, P<0.01]. BNP concentration was positively related with the carotid intima-media thickness of the common carotid artery (CCA-IMT) and left ventricular mass index (LVMI) and was significantly higher in patients with than without carotid plaques (P<0.01). Logistic regression analysis confirmed that lgBNP concentration was independently correlated with carotid plaques. Thirty-two patients experienced ischemic cardiovascular (ICV) events during follow-up. Kaplan-Meier analysis showed that cumulative survival without new ICV events was better in patients with lower than with higher BNP concentrations (P<0.01). Cox regression analysis showed that BNP was an independent risk factor for ICV events (HR=3.167, 95%CI=1.398-7.171, P<0.01).

CONCLUSIONS

Similar to findings in the general population, elevated BNP level is related to atherosclerosis and an increased risk of ICV events in pre-dialytic CKD patients.

Induction of brain natriuretic peptide and monocyte chemotactic protein-1 gene expression by oxidized low-density lipoprotein: relevance to ischemic heart failure

Brain natriuretic peptide (BNP) and monocyte chemotactic protein-1 (MCP-1) are biomarkers of heart failure (HF). The aim of the present study was to determine the role of oxidized low-density lipoprotein (Ox-LDL) in the induction of these biomarkers and the signaling pathways involved in vitro. Incubation of HL-1 cardiomyocytes and human myocytes with Ox-LDL induced the expression of BNP and MCP-1 genes, while native LDL had no effect. When peroxides associated with Ox-LDL were reduced to hydroxides, the ability to induce BNP and MCP-1 gene expression was abolished. Furthermore, exposure of HL-1 cells to ischemic conditions alone had no effect on BNP gene expression, while ischemia followed by reperfusion resulted in increased expression of BNP gene. Inhibitors of ERK and JNK inhibited the induction of BNP. Signaling array results suggested that the induction of both MAPK and NF-κB pathways is involved in the induction of BNP by Ox-LDL. These results suggest that Ox-LDL or peroxidized lipids formed in oxidatively stressed myocytes during ischemia-reperfusion injury may play a role in the induction of BNP and MCP-1.

Signaling pathways involved in DNA synthesis and migration in response to lysophosphatidic acid and low-density lipoprotein in coronary artery smooth muscle cells

Low-density lipoprotein (LDL) and lysophosphatidic acid (LPA), one of the lipid components of lipoprotein, induced the DNA synthesis of coronary artery smooth muscle cells (CASMCs). The LDL- and LPA-induced DNA synthesis was markedly inhibited by the LPA receptor antagonist Ki16425, pertussis toxin, small interfering RNAs targeted for LPA1 receptors, and a potent calcineurin inhibitor cyclosporine A. It has been reported that LDL and LPA induced a migration response in a manner sensitive to Ki16425, pertussis toxin, and a LPA1 receptor-specific small interfering RNA. However, cyclosporine A was ineffective in inhibiting the migration response. Instead, an epidermal growth factor (EGF) receptor tyrosine kinase inhibitor markedly suppressed the migration response to LDL and LPA without having any significant effect on DNA synthesis. Thus, the LDL-induced stimulation of DNA synthesis and migration in CASMCs is mediated by its component LPA through LPA1 receptors and G(i/o)-proteins. Ca2+/calcineurin pathways and transactivation of EGF receptors mediate LPA1-receptor-induced DNA synthesis and migration, respectively.

Accuracy of N-terminal pro-brain natriuretic peptide in the identification of left ventricular dysfunction in high-risk asymptomatic patients

OBJECTIVE

The role of natriuretic peptides in the screening of left ventricular dysfunction is still unclear. The aim of this study was to assess the usefulness of N-terminal pro-brain natriuretic peptide (NT-proBNP) measurement in asymptomatic patients at high risk of developing left ventricular dysfunction.

METHODS

One hundred and thirty-four consecutive ambulatory patients (mean age 56.1 +/- 7 years) were studied and selected on the basis of a history of hypertension of at least 5 years. Systolic dysfunction was defined as an ejection fraction of 45% or less. Statistical analysis was performed by both parametric and nonparametric approaches. Diagnostic accuracy was evaluated by receiver operating characteristic analysis.

RESULTS

Echocardiography showed normal left ventricular function in 40 patients, diastolic dysfunction in 80 patients and systolic dysfunction in 14 patients. NT-proBNP levels were significantly higher in patients with systolic dysfunction (356.1 +/- 294.8 vs. 85.2 +/- 85.8 pg/ml; P < 0.05). Receiver operating characteristic analysis showed a high value of the area under the curve (0.89) for the detection of systolic dysfunction with a sensitivity of 83% and a specificity of 80% for a cut-off value of 114 pg/ml and with a negative predictive value of 0.98.

CONCLUSION

In asymptomatic patients at high risk for heart failure because of a history of hypertension, the measurement of NT-proBNP levels may represent a useful screening test for left ventricular systolic dysfunction. Therefore, more expensive examinations, such as echocardiography, may be restricted only to patients with higher NT-proBNP levels.

Influence of oxidized low density lipoprotein on the proliferation of human artery smooth muscle cells in vitro

The effects of oxidized low density lipoprotein (ox-LDL) on the proliferation of cultured human vascular smooth muscle cells (vSMC) were investigated in vitro. By using NaBr density gradient centrifugation, LDL was isolated and purified from human plasma. Ox-LDL was produced from LDL by being incubated with CuSO(4). ox-LDL was then added to the culture medium at different concentrations (35, 60, 85, 110, 135 and 160 microg/mL) for 7 days. The influence of ox-LDL on vSMC proliferation was observed in growth curve, mitosis index, and in situ determination of apoptosis. The data were analyzed with SPSS 10.0 software. The results showed that the ox-LDL produced in vitro had a good purity and optimal oxidative degree, which was similar to the intrinsic ox-LDL in atherosclerotic plaque. ox-LDL at a concentration of 35 microg/mL demonstrated the strongest proliferation inducement, and at a concentration of 135 microg/mL, ox-LDL could inhibit the growth of vSMC. ox-LDL at concentrations of 35 and 50 microg/mL presented powerful mitotic trigger, and with the increase of ox-LDL concentration, the mitotic index of vSMC was decreased gradually. ox-LDL at higher concentrations promoted more apoptotic vSMCs. ox-LDL at lower concentrations triggered proliferation of vSMCs, and at higher concentrations induced apoptosis in vSMCs. ox-LDL played a promotional role in the pathogenesis and development of atherosclerosis by affecting vSMC proliferation and apoptosis.

Role of lipoprotein-associated lysophospholipids in migratory activity of coronary artery smooth muscle cells

The migration of vascular smooth muscle cells (SMCs) is a hallmark of the pathogenesis of atherosclerosis and restenosis after angioplasty. Plasma low-density lipoprotein (LDL), but not high-density lipoprotein (HDL), induced the migration of human coronary artery SMCs (CASMCs). Among bioactive lipids postulated to be present in LDL, lysophosphatidic acid (LPA) appreciably mimicked the LDL action. In fact, the LDL-induced migration was markedly inhibited by pertussis toxin, an LPA receptor antagonist Ki-16425, and a small interfering RNA (siRNA) targeted for LPA(1) receptors. Moreover, LDL contains a higher amount of LPA than HDL does. HDL markedly inhibited LPA- and platelet-derived growth factor (PDGF)-induced migration, and sphingosine 1-phosphate (S1P), the content of which is about fourfold higher in HDL than in LDL, mimicked the HDL action. The inhibitory actions of HDL and S1P were suppressed by S1P(2) receptor-specific siRNA. On the other hand, the degradation of the LPA component of LDL by monoglyceride lipase or the antagonism of LPA receptors by Ki-16425 allowed LDL to inhibit the PDGF-induced migration. The inhibitory effect of LDL was again suppressed by S1P(2) receptor-specific siRNA. In conclusion, LPA/LPA(1) receptors and S1P/S1P(2) receptors mediate the stimulatory and inhibitory migration response to LDL and HDL, respectively. The balance of not only the content of LPA and S1P in lipoproteins but also the signaling activity between LPA(1) and S1P(2) receptors in the cells may be critical in determining whether the lipoprotein is a positive or negative regulator of CASMC migration.

N-terminal pro-brain natriuretic peptide used for the prediction of coronary artery stenosis

BACKGROUND

The level of the inactive N-terminal fragment of pro-brain (B-type) natriuretic peptide (NT-proBNP) is a prognostic marker in patients with acute and chronic coronary artery disease (CAD). It might also be valuable for non-invasive diagnosis of coronary artery disease.

MATERIALS AND METHODS

The NT-proBNP was measured in 781 consecutive patients with normal left ventricular function referred for coronary angiography owing to symptoms or signs of CAD. The diagnostic value of NT-proBNP was assessed for predicting CAD at angiography.

RESULTS

Elevated NT-proBNP levels were associated with the extent of CAD and with the female sex (P < 0.001). The ability of NT-proBNP to predict significant coronary disease at angiography was assessed separately for men using a cut-off point of 85 pg mL(-1), positive likelihood ratio 2.2 (95% CI, 1.7-3.0), negative likelihood ratio 0.53 (95% CI 0.45-0.63) and area under the receiver-operating-characteristic (ROC) curve 0.72: for women, it was assessed using a cut-off point of 165 pg mL(-1), positive likelihood ratio 2.4 (95% CI, 1.7-3.4), negative likelihood ratio 0.55 (95% CI, 0.44-0.70) and area under ROC curve 0.71. In multiple logistic-regression analysis, NT-proBNP added significant independent predictive power to other clinical variables in models predicting CAD (odds ratio 2.76, 95% CI, 1.76-4.32, P < 0.001).

CONCLUSIONS

The NT-proBNP is a marker of non-obstructive CAD and of significant coronary stenosis. In conjunction with other clinical information, measurement of NT-proBNP with the use of sex-specific reference ranges may improve the non-invasive prediction of CAD.

Increase of C-type natriuretic peptide expression by serum and platelet-derived growth factor-BB in human aortic smooth muscle cells is dependent on protein kinase C activation

C-type natriuretic peptide (CNP) is produced by the vascular smooth muscle cells (SMCs) of injured and atherosclerotic arteries, in which it may exert autocrine control over SMCs by binding to its principal receptors, NPR-B and NPR-C, but few studies have examined the factors that regulate CNP expression in human SMCs. In the present report, we show that serum induces significant increases in both CNP and NPR-C transcript levels in human, but not rat SMCs in culture, and that pretreatment with either the general tyrosine kinase inhibitor genistein, the platelet-derived growth factor (PDGF) tyrosine kinase inhibitor AG 1296, or the protein kinase C (PKC) inhibitor GF109203X blocks most of the serum-induced increase in CNP. PDGF-BB also induced significant dose-dependent increases in CNP transcript that correlated temporally with the serum effect on CNP mRNA. Inhibition of several PDGF-BB signaling pathways downstream of receptor activation showed that PKC inhibition with GF109203X was almost as effective as genistein in abolishing the PDGF-BB-induced up-regulation of CNP mRNA. Furthermore, PKC activation by phorbol 12-myristate 13-acetate (PMA) produced an extremely high level of CNP mRNA that was abolished by GF109203X. Immunoreactive CNP was markedly increased in SMCs receiving 10% serum, 20 ng/ml PDGF-BB, or PMA, and was decreased in PDGF-treated and PMA-treated cells by AG 1296 and GF109203X, respectively. This report suggests that in humans, PDGF and other factors signaling through receptor tyrosine kinases and downstream activation of PKC could represent an important control for CNP expression in vascular smooth muscle.

Natriuretic peptides as therapeutic targets

Natriuretic peptides (atrial natriuretic peptide, brain natriuretic peptide and C-type natriuretic peptide) are cardiac and vascular peptides with vasodilatory, diuretic, natriuretic, anti-inflammatory, antifibrotic and antimitogenic actions. Natriuretic peptides are implicated in normal pressure and volume homeostasis and in the defence against excessive increases in overload-related factors, vasopressive and cardiotoxic factors and their impact on the heart, blood vessels and brain. Genetic manipulation studies confirmed the importance of natriuretic peptides in these functions. Natriuretic peptides are metabolised by NPR-C (clearance receptors) and by enzymatic degradation by neutral endopeptidase. Natriuretic peptide levels (mainly brain natriuretic peptide) correlate with left ventricular hypertrophy and with the severity of heart failure, and are reduced by effective treatment, thus used as diagnostic and prognostic tools. Based on the multiple protective effects of natriuretic peptides, pharmacological therapy has been approved and includes potentiating natriuretic peptide levels by intravenous infusion or by inhibition of endogenous natriuretic peptide degradation. Because each approach has its limitations, the field remains open for improvement.

Natriuretic peptides, their receptors, and cyclic guanosine monophosphate-dependent signaling functions

Natriuretic peptides are a family of structurally related but genetically distinct hormones/paracrine factors that regulate blood volume, blood pressure, ventricular hypertrophy, pulmonary hypertension, fat metabolism, and long bone growth. The mammalian members are atrial natriuretic peptide, B-type natriuretic peptide, C-type natriuretic peptide, and possibly osteocrin/musclin. Three single membrane-spanning natriuretic peptide receptors (NPRs) have been identified. Two, NPR-A/GC-A/NPR1 and NPR-B/GC-B/NPR2, are transmembrane guanylyl cyclases, enzymes that catalyze the synthesis of cGMP. One, NPR-C/NPR3, lacks intrinsic enzymatic activity and controls the local concentrations of natriuretic peptides through constitutive receptor-mediated internalization and degradation. Single allele-inactivating mutations in the promoter of human NPR-A are associated with hypertension and heart failure, whereas homozygous inactivating mutations in human NPR-B cause a form of short-limbed dwarfism known as acromesomelic dysplasia type Maroteaux. The physiological effects of natriuretic peptides are elicited through three classes of cGMP binding proteins: cGMP-dependent protein kinases, cGMP-regulated phosphodiesterases, and cyclic nucleotide-gated ion channels. In this comprehensive review, the structure, function, regulation, and biological consequences of natriuretic peptides and their associated signaling proteins are described.

Plasma N-terminal pro-brain natriuretic peptide concentration predicts coronary events in men at work: a report from the BELSTRESS study

AIMS

Increased levels of neurohormonal markers, including the N-terminal fragment of pro-brain natriuretic peptide (NT-pro-BNP), have been shown to be of prognostic significance in patients with heart failure or coronary heart disease (CHD). The aim of this study was to study the predictive value of NT-pro-BNP for coronary events in a middle-aged population of men at work.

METHODS AND RESULTS

A nested case-control study was performed in a large cohort of over 10 000 men at work (aged 35-59) after a median follow-up of 2.66 years. In total, 66 individuals who developed coronary events were matched on a 3-to-1 basis to 198 controls free of coronary events during follow-up. Besides clinical characteristics and conventional cardiac risk factors, NT-pro-BNP (electrochemiluminiscence assay, Roche diagnostics) and serum creatinine levels were determined. In univariable analysis, cases were more frequently current smokers and diabetics, had more frequently a history of CHD, and had higher levels of total cholesterol and systolic blood pressure (SBP), and lower levels of HDL cholesterol. A highly significant difference (P < 0.0001) was noted for NT-pro-BNP levels between cases (median 48.5 pg/mL, interquartile range 26.4-116.6 pg/mL) and controls (30.0 pg/mL, 19.5-47.6 pg/mL). In multivariable conditional logistic regression analysis, NT-pro-BNP remained strongly associated with risk for coronary events [third vs. first tertile, odds ratio (95% CI) 3.24 (1.18-8.85)], independent of body mass index, smoking, diabetes, SBP, total and HDL cholesterol, creatinine, and previous CHD.

CONCLUSION

NT-pro-BNP is a strong predictor of coronary events in men at work after a relatively short period, even after adjustment for conventional risk factors.

C-type natriuretic peptide in vascular physiology and disease

Natriuretic peptides play a critical role in coordination of fluid/electrolyte balance and vascular tone. The renal effects of circulating atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are distinct from the paracrine effects of vascular C-type natriuretic peptide (CNP). CNP is widely expressed throughout the vasculature and is found in particularly high concentrations in the endothelium. Recent studies demonstrate that CNP is a novel endothelium-derived hyperpolarising factor (EDHF) that complements the actions of other endothelial vasorelaxant mediators such as nitric oxide (NO) and prostacyclin. Since several cardiovascular disorders are associated with dysfunction of natriuretic peptide activity, selective modulation of the natriuretic peptide pathways represents an important therapeutic target; whilst this has been exploited to some degree in terms of ANP/BNP, the therapeutic potential of CNP has yet to be tapped. This review focuses on recent findings on the actions and mechanism of locally produced endothelial-derived CNP in the cardiovascular system and highlights many potential avenues for therapeutic intervention, via modulation of CNP-signalling, in cardiovascular disease.

Risk factors for heart failure

Despite remarkable therapeutic advances in the management of patients with heart failure (HF), the mortality due to this syndrome remains high. Identifying free-living individuals who are at high risk for developing HF may allow implementing strategies that can prevent HF. Prospective epidemiologic studies have identified several risk factors and risk markers for HF. This article reviews current knowledge regarding conventional and newer risk markers for HF, outlines possible underlying mechanisms for the increased HF risk, and provides a framework for clinical multivariate risk prediction using HF risk factors.

Embryonic expression and multifunctional actions of the natriuretic peptides and receptors in the developing nervous system

Atrial natriuretic peptide (ANP) binding sites have been detected in the embryonic brain, but the specific receptor subtypes and biological functions for ANP family ligands therein remain undefined. We now characterize the patterns of gene expression for the natriuretic peptides [ANP, brain natriuretic peptide (BNP), type-C natriuretic peptide (CNP)] and their receptors (NPR-A, NPR-B, NPR-C) at several early stages in the embryonic mouse nervous system by in situ hybridization, and begin to define the potential developmental actions using cell culture models of peripheral (PNS) and central nervous systems (CNS). In the CNS, gene transcripts for CNP were present at the onset of neurogenesis, embryonic day 10.5 (E10.5), primarily in the dorsal part of the ventricular zone (VZ) throughout the hindbrain and spinal cord. On E14.5, new CNP signals were observed in the ventrolateral spinal cord where motor neurons reside, and in bands of cells surrounding the spinal cord and hindbrain, localized to dura and/or cartilage primordia. ANP and BNP gene transcripts were not detected in embryonic brain, but were highly abundant in the heart. The CNP-specific receptor (NPR-B) gene was expressed in cells just outside the VZ, in regions where post-mitotic neurons are differentiating. Gene expression for NPR-C, which recognizes all natriuretic peptides, was present in the roof plate of the hindbrain and spinal cord and in bilateral stripes just dorsolateral to the floor plate at E12.5. In the PNS, NPR-B and NPR-C transcripts were highly expressed in dorsal root sensory (DRG) and cranial ganglia beginning at E10.5, with NPR-C signal also prominent in adjoining nerves, consistent with Schwann cell localization. In contrast, NPR-A gene expression was undetectable in neural tissues. To define ontogenetic functions, we employed embryonic DRG and hindbrain cell cultures. The natriuretic peptides potently stimulated DNA synthesis in neuron-depleted as well as neuron-containing Schwann cell cultures and differentially inhibited neurite outgrowth in DRG sensory neuron cultures. CNP also exhibited modest survival-promoting effects for sensory neurons. In marked contrast to PNS effects, the peptides inhibited proliferation of neural precursor cells of the E10.5 hindbrain. Moreover, CNP, alone and in combination with sonic hedgehog (Shh), induced the expression of the Shh target gene gli-1 in hindbrain cultures, suggesting that natriuretic peptides may also modify patterning events in the embryonic brain. These studies reveal widespread, but discrete patterns of natriuretic peptide and receptor gene expression in the early embryonic nervous system, and suggest that the peptides play region- and stage-specific roles during the development of the peripheral and central nervous systems.

Local overexpression of C-type natriuretic peptide ameliorates vascular adaptation of porcine hemodialysis grafts

BACKGROUND

Outflow obstruction at the outflow tract of arteriovenous grafts contributes significantly to the poor patency rates of dialysis grafts in vivo. We addressed the potential of local periadventitial gene therapy at the outflow tract for improving access patency in a validated porcine model of arteriovenous grafts using an adenoviral vector encoding murine C-type natriuretic peptide (Ad.CNP).

METHODS

Gene transfer efficiency and optimal virus concentration were determined using Ad.LacZ on porcine jugular veins in vivo (N= 2). Next, in 14 pigs, arteriovenous grafts were implanted bilaterally between the carotid artery and the jugular vein, followed local venous transduction with Ad.CNP (right) and Ad.mock (left). Transduction efficiency of Ad.CNP was evaluated by reverse transcription-polymerase chain reaction (RT-PCR) and cyclic guanosine monophosphate (cGMP) measurements (N= 2). Fourteen days after gene transfer, arteriovenous grafts were excised for histologic analysis (N= 12).

RESULTS

Ad.LacZ transduction (1 x 10E10 IU) of porcine veins resulted in evident expression of beta-galactosidase, mainly in the adventitia. At termination, intima/media ratio was decreased by 37% in CNP-treated veins, predominantly due to medial thickening (Ad.CNP 3.1 +/- 0.6 mm(2) vs. Ad.mock 1.70 +/- 0.3 mm(2); P < 0.01) rather than decreased intimal hyperplasia (NS). Adventitial delivery of CNP resulted in increased external elastic lamina (EEL) (Ad.CNP 11.8 +/- 1.4 mm vs. Ad.mock 9.4 +/- 1.0 mm; P= 0.04) and luminal area (Ad.CNP 10.7 +/- 1.4 mm(2) vs. Ad.mock 8.8 +/- 1.7 mm(2); P= 0.05) at the venous anastomosis.

CONCLUSION

Overexpression of CNP enhances venous medial thickening and increases outward remodeling in the outflow tract of porcine arteriovenous grafts. These findings underscore the potential of local gene-therapeutic interventions in preventing luminal narrowing at the outflow tract of hemodialysis grafts.

Cyclic adenosine monophosphate (cAMP) increases natriuretic peptide receptor C (NPR-C) expression in human aortic smooth muscle cells

Activation of the intracellular cAMP-signaling pathway by either forskolin or the cAMP-mimetic dibutyryl cAMP significantly increased transcript levels of NPR-C in primary cultures of human aortic smooth muscle cells. The time course of the increase was rapid, with significant differences from control occurring within 3 h of treatment and reaching approximately 6 times control value after 24 h of exposure to 10 microM forskolin. Expression levels of the natriuretic peptide receptor B (NPR-B), but not the natriruetic peptide receptor A (NPR-A) were also increased by forskolin, rising to a level of approximately 2 times control at 96 h. NPR-B transcript levels in the presence of dibutyryl cAMP were unaltered by the protein kinase A (PKA) inhibitor KT-5720, suggesting a PKA-independent pathway to NPR-B up-regulation. In contrast, KT-5720 reduced NPR-C transcript to a lower level that was not significantly different from control. Partial re-differentiation of AOSMC by culture in growth factor-reduced matrix (Matrigel) did not significantly change NPR-C transcript levels compared with cells grown on plastic, and the dibutyryl cAMP-induced increase in NPR-C (approximately eight-nine-fold control value) was retained. The dibutyryl cAMP/forskolin effect on NPR-C transcript was not reproduced by the beta2-selective adrenergic agonist isoproterenol (10 microM), but was replicated by incubation with the phosphodiesterase inhibitor isobutylmethylxanthine (0.5 mM). Up-regulated NPR-B and NPR-C transcript levels were reflected, respectively, in a two-fold increase in CNP-stimulated cGMP and an increase in 125I-ANF binding competed by the NPR-C-specific natriuretic peptide, C-ANF(4-23) following a 4-day treatment with 0.125 mM dbcAMP. The present data suggest that elevation of cAMP in human vascular smooth muscle may potentiate the vasoactive effects of natriuretic peptides acting through the NPR-B and NPR-C receptors.

Plasma natriuretic peptide levels and the risk of cardiovascular events and death

BACKGROUND

The natriuretic peptides are counterregulatory hormones involved in volume homeostasis and cardiovascular remodeling. The prognostic significance of plasma natriuretic peptide levels in apparently asymptomatic persons has not been established.

METHODS

We prospectively studied 3346 persons without heart failure. Using proportional-hazards regression, we examined the relations of plasma B-type natriuretic peptide and N-terminal pro-atrial natriuretic peptide to the risk of death from any cause, a first major cardiovascular event, heart failure, atrial fibrillation, stroke or transient ischemic attack, and coronary heart disease.

RESULTS

During a mean follow-up of 5.2 years, 119 participants died and 79 had a first cardiovascular event. After adjustment for cardiovascular risk factors, each increment of 1 SD in log B-type natriuretic peptide levels was associated with a 27 percent increase in the risk of death (P=0.009), a 28 percent increase in the risk of a first cardiovascular event (P=0.03), a 77 percent increase in the risk of heart failure (P<0.001), a 66 percent increase in the risk of atrial fibrillation (P<0.001), and a 53 percent increase in the risk of stroke or transient ischemic attack (P=0.002). Peptide levels were not significantly associated with the risk of coronary heart disease events. B-type natriuretic peptide values above the 80th percentile (20.0 pg per milliliter for men and 23.3 pg per milliliter for women) were associated with multivariable-adjusted hazard ratios of 1.62 for death (P=0.02), 1.76 for a first major cardiovascular event (P=0.03), 1.91 for atrial fibrillation (P=0.02), 1.99 for stroke or transient ischemic attack (P=0.02), and 3.07 for heart failure (P=0.002). Similar results were obtained for N-terminal pro-atrial natriuretic peptide.

CONCLUSIONS

In this community-based sample, plasma natriuretic peptide levels predicted the risk of death and cardiovascular events after adjustment for traditional risk factors. Excess risk was apparent at natriuretic peptide levels well below current thresholds used to diagnose heart failure.

Physiological concentration of atrial natriuretic peptide induces endothelial regeneration in vitro

Both nitric oxide (NO) and natriuretic peptides produce apoptosis of vascular smooth muscle cells. However, there is evidence that NO induces endothelial cell proliferation, which suggests that there is a difference in the response of endothelial cells to natriuretic peptides. The purpose of this study was to investigate the effect of atrial natriuretic peptide (ANP) on human endothelial cell survival. ANP within the physiological concentration (10(-11) mol/l) induced a 52% increase in the number of human coronary arterial endothelial cells and a 63% increase in human umbilical vein endothelial cells at a low concentration of serum. The increase in cell numbers was blocked by pretreatment with RP8-CPT-cGMP (RP8), a cGMP-dependent protein kinase inhibitor, with wortmannin, an Akt/PKB inhibitor, and with PD-98059, an ERK1/2 inhibitor. In a Transwell migration test, ANP also increased the cell migration, and RP8, wortmannin, and PD-98059 blocked this increase. A wound healing assay was performed to examine the effects of ANP on regeneration in vitro. ANP increased both cell numbers and migration, but the effects were blocked by the above three kinase inhibitors. ANP increased the expression of phospho-Akt and of phospho-ERK1/2 within 1.5 h. These results suggest that ANP can potentiate endothelial regeneration by cGMP-dependent protein kinase stimulation and subsequent Akt and ERK1/2 activations.

Lysophosphatidic acid inhibits C-type natriuretic peptide activation of guanylyl cyclase-B

C-type natriuretic peptide (CNP), found in endothelial cells, chondrocytes, and neurons, binds its cognate transmembrane receptor, natriuretic peptide receptor-B (NPR-B/GC-B), and stimulates the synthesis of the intracellular signaling molecule, cGMP. The known physiologic consequences of this binding event are vasorelaxation, inhibition of cell proliferation, and the stimulation of long bone growth. Here we report that 10% fetal bovine serum markedly reduced CNP-dependent cGMP elevations in NIH3T3 fibroblast. The purified serum components platelet-derived growth factor and lysophosphatidic acid (LPA) mimicked the effect of serum on CNP-dependent cGMP elevations, but the latter factor resulted in the most dramatic reductions. The LPA-dependent inhibition was rapid and dose dependent, having t(1/2) and IC(50) values of approximately 5 min and 3.0 micro M LPA, respectively. The decreased cGMP concentrations resulted from reduced CNP-dependent NPR-B guanylyl cyclase activity that did not require losses in receptor protein or activation of protein kinase C, indicating a previously undescribed desensitization pathway. These data suggest that NPR-B is repressed by LPA and that one mechanism by which LPA exerts its effects is through the heterologous desensitization of the CNP/NPR-B/cGMP pathway. We hypothesize that cross-talk between the LPA and CNP signaling pathway maximizes the response of fibroblasts in the wound-healing process.

Brain natriuretic peptide: role in cardiovascular and volume homeostasis

The identification of natriuretic peptides as key regulators of natriuresis and vasodilatation, and the appreciation that their secretion is under the control of cardiac hemodynamic and neurohumoral factors, has caused wide interest. The natriuretic peptides are structurally similar, but genetically distinct peptides that have diverse actions on cardiovascular, renal, and endocrine homeostasis. Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are of myocardial cell origin, while cardiac natriuretic peptide (CNP) is of endothelial origin. ANP and BNP bind to the natriuretic peptide receptor (NPR-A) which, via 3' 5'-cyclic guanosine monophosphate (cGMP), mediates natriuresis, vasodialation, renin inhibition, and antimitogenic properties. CNP lacks natriuretic action but possesses vasodilating and growth inhibiting effects via the guanyl cyclase linked natriuretic peptide-B (NPR-B) receptor. All three peptides are cleared by natriuretic peptide-C receptor (NPR-C) and degraded by neutral endopeptidase, both of which are widely expressed in kidney, lung, and vascular wall. Recently, a fourth member of the natriuretic peptide, dendroaspsis natriuretic peptide (DNP) has been reported to be present in human plasma and atrial myocardium.

Cardiac natriuretic peptides--hope or hype?

In recent years, biomedical science has witnessed the emergence of peptide biochemicals as significant topics of research. Some of these peptides are of little potential clinical use, while others, of which cardiac natriuretic peptides are an example, appear to be promising. This particular group of peptides (i.e. ANP, BNP and CNP) shows promising diagnostic as well as therapeutic potential for various pathological conditions. In the case of acute myocardial infarction, these peptides have significant diagnostic and predictive properties, more so than other biochemicals such as adrenaline, renin and aldosterone. In addition, ANP is found to have significant benefits over the classical anti-anginal drug glyceryl trinitrate. However, as is the case with other peptides, applying these benefits clinically may not be easy because of the structure of the compounds, but various strategies are now being applied to solve this problem. These include the use of non-peptide receptor ligands, inhibitors of ANP metabolism, gene therapy and so on. The development of drugs in clinical practice, which exploits the natriuretic peptides system therefore seems to be promising, and this article reviews advances in our understanding of these compounds.

Suppression by eicosapentaenoic acid of oxidized low-density lipoprotein and lysophosphatidylcholine-induced migration in cultured rat vascular smooth muscle cells

The migration of medial smooth muscle cells into the intima is proposed to be an initial process of intimal thickening in atherosclerotic lesions. The present study was designed to determine whether pretreatment with the antiatherogenic agent eicosapentaenoic acid (EPA) inhibits the migration induced by oxidized low-density lipoprotein (LDL) and its major phospholipid component, lysophosphatidylcholine (lyso-PC), in cultured rat vascular smooth muscle cells (VSMCs) using Boyden's chamber method. The effects of EPA pretreatment on angiotensin II (Ang II)- and platelet-derived growth factor BB (PDGF BB)-induced migration were also examined in these cells. Oxidized LDL and lyso-PC induced migration in a concentration-dependent manner. EPA pretreatment clearly suppressed oxidized LDL (200 microg/mL)- and lyso-PC (10(-5) mol/L)-induced migration between 40 and 160 micromol/L. EPA pretreatment also suppressed Ang 11 (10(-7) mol/L)- and PDGF BB (5 ng/mL)-induced migration at a concentration of 80 and 160 micromol/L. However, in a trypan blue exclusion test, dead cells stained with trypan blue were not found 24 hours after treatment with EPA. These results suggest that EPA suppresses VSMC migration induced by oxidized LDL and lyso-PC, as well as Ang II and PDGF BB. These preliminary data concerning the effects of EPA may partly explain the antiatherosclerotic effects of this agent.

Vascular actions of brain natriuretic peptide: modulation by atherosclerosis and neutral endopeptidase inhibition

OBJECTIVES

We sought to define the vascular actions of the cardiac hormone brain natriuretic peptide (BNP) on cellular proliferation and cyclic guanosine monophosphate (cGMP) in human aortic vascular smooth muscle cells (HAVSMCs). Secondly, we investigated BNP and acetylcholine (ACh) vasorelaxations in aortic rings from normal and atherosclerotic rabbits in the presence and absence of long-term oral inhibition of neutral endopeptidase (NEP).

BACKGROUND

The vascular actions of BNP are not well defined, despite the presence of its receptor in vascular smooth muscle and the upregulation of NEP, the ectoenzyme that degrades BNP, in the vascular wall in atherosclerosis.

METHODS

HAVSMCs stimulated with fetal calf serum (FCS) were pulsed with bromodeoxyuridine (BrdU) with and without BNP. The HAVSMCs were incubated in the presence and absence of BNP to assess cGMP. Vasorelaxations to BNP and ACh were assessed in rings in normal and atherosclerotic rabbits in the presence and absence of long-term oral inhibition of NEP, together with assessment of atheroma formation.

RESULTS

FCS-stimulated BrdU uptake in HAVSMCs was suppressed with BNP. BNP potentiated cGMP in HAVSMCs. BNP resulted in potent vasorelaxation in normal isolated aortic rings, which were impaired in atherosclerotic versus normal rabbits and preserved with NEP inhibition, which also decreased atheroma formation. Relaxations to ACh, which were also impaired in atherosclerosis, were preserved with inhibition of NEP.

CONCLUSIONS

We conclude that BNP potently inhibits vascular smooth muscle cell proliferation and potentiates the generation of cGMP. BNP potently relaxes the normal rabbit aorta, and this response is impaired in atherosclerosis but preserved with inhibition of NEP, together with a reduction in atheroma formation and preservation of relaxations to ACh.

Regulation of rat mesangial cell migration by platelet-derived growth factor, angiotensin II, and adrenomedullin

This study sought to determine whether platelet-derived growth factor (PDGF) and angiotensin II (AngII) stimulate migration of cultured rat glomerular mesangial cells. After finding that this was so, the effects of adrenomedullin (ADM) and cAMP-elevating agents on basal and stimulated mesangial cell migration were examined. Two isoforms of PDGF, AB and BB, stimulated migration in a concentration-dependent manner between 1 and 50 ng/ml, while the AA isoform lacked significant effect. AngII modestly but significantly stimulated migration in a concentration-dependent manner between 10(-7) and 10(-6) mol/L. Rat ADM significantly inhibited the PDGF BB- and AngII-stimulated migration in a concentration-dependent manner between 10(-8) and 10(-7) mol/L. Inhibition by rat ADM was accompanied by an increase in cellular cAMP. cAMP agonists or inducers such as 8-bromo cAMP, forskolin, and prostaglandin I2 also significantly reduced the stimulated migration. H 89, a protein kinase A (PKA) inhibitor, attenuated the inhibitory effect of ADM, and a calcitonin gene-related peptide (CGRP) receptor antagonist, human CGRP (8-37), abolished the inhibitory effects of rat ADM. These results suggest that PDGF AB and BB as well as AngII stimulate rat mesangial cell migration and that ADM can inhibit PDGF BB- and AngII-stimulated migration, at least in part through cAMP-dependent mechanisms likely to involve specific ADM receptors with which CGRP interacts. The adenylate cyclase/cAMP/PKA system may be involved in the migration-inhibitory effect of ADM in these cells.

Reciprocal antagonism coordinates C-type natriuretic peptide and mitogen-signaling pathways in fibroblasts

The fibroblast, a cell central to effective wound remodeling, not only contains various growth factor receptors but also high activities of a guanylyl cyclase receptor (GC-B). Here we demonstrate that marked elevations of cyclic GMP induced by C-type natriuretic peptide (CNP), the ligand of GC-B, blocks activation of the mitogen-activated protein kinase cascade in fibroblasts. We also show that platelet-derived growth factor, fibroblast growth factor, serum, or Na3VO4 rapidly (within 5 min) and extensively (up to 85% inhibition) disrupt CNP-dependent elevations of cyclic GMP. In addition, the mitogens also lower cyclic GMP concentrations (50% decrease) in cells not treated with CNP. Cytoplasmic forms of guanylyl cyclase, in contrast to the CNP-stimulated pathway, are not antagonized by the various mitogens. The effects of the mitogens on cellular cyclic GMP are fully explained by a direct and stable inactivation of GC-B. Homogenates obtained from fibroblasts treated with or without the various mitogens contain equivalent amounts of GC-B protein, but both ligand-dependent and ligand-independent activity are markedly (up to 90% inhibition of CNP-dependent activity) decreased after mitogen addition. The stable inactivation is correlated with the dephosphorylation of phosphoserine and phosphothreonine residues of the cyclase receptor. These results not only establish a specific and reciprocal antagonistic relationship between mitogen-activated and GC-B-regulated signaling pathways in the fibroblast but also suggest that one of the earliest events following mitogen activation of a fibroblast is an interruption of cyclic GMP production from this receptor.

Heparin inhibits human coronary artery smooth muscle cell migration

Heparin, an anticoagulant, has been shown to reduce neointimal proliferation and restenosis following vascular injury in experimental studies, but the clinical trials of heparin in coronary balloon angioplasty have been negative. The current study, therefore, examined the effect of heparin on basal or stimulated migration by serum and platelet-derived growth factor (PDGF)-BB in cultured human coronary artery smooth muscle cells (SMCs) by Boyden's chamber method. In addition, the reversibility of the heparin effect on human coronary artery SMC migration was examined. Fetal calf serum (FCS) and PDGF-BB stimulated SMC migration in a concentration-dependent manner. Heparin in moderate to high concentration (10 to 100 U/mL) exhibited concentration-related inhibition of FCS- and PDGF-BB-stimulated SMC migration; however, a low concentration (1 U/mL) of heparin had no inhibitory effects. Heparin also had weak inhibitory effects on nonstimulated SMC migration. The SMCs that were exposed to a high concentration (100 U/mL) of heparin for 6 hours were capable of migrating after a short lag period of removal of heparin from the culture medium. These SMCs also showed recovery of responses to FCS and PDGF-BB by migrating significantly greater than the nonstimulated level. Furthermore, heparin-containing medium did not contain detached cells. These results indicate that heparin inhibits human coronary artery SMC migration, especially when stimulated by FCS or PDGF-BB, and that this inhibitory effect of heparin is reversible and not simply a function of killing cells.

Effect of the endothelin family of peptides on human coronary artery smooth-muscle cell migration

The migration of coronary artery medial smooth-muscle cells (SMCs) is one of the key events in the process of intimal thickening in coronary atherosclerotic lesions. The objectives of the present study were to determine whether any of the three isoforms of endothelin (ET), ET-1, ET-2, and ET-3, or an intermediate form of ET, big ET-1, induces migration of human coronary artery SMCs, and to investigate the possible interaction of ET peptides and well-known migration-stimulatory factors, platelet-derived growth factor (PDGF)-BB and angiotensin II (Ang II), on SMC migration by the Boyden's chamber method. None of the ET peptides alone induced SMC migration between 10(-9) and 10(-7) mol/L. In contrast, ET-1 and ET-2 significantly induced SMC migration in the presence of low concentrations of PDGF-BB (0.5 ng/mL) or Ang II (10(-9) mol/L), although ET-3 was less active (ET-1 = ET-2 > ET-3). In contrast, big ET-1 was without significant activity on PDGF-BB-or Ang II-induced SMC migration. The potentiation of SMC migration by ET peptides was clearly inhibited by the ETA receptor antagonist BG-123 in a concentration-dependent manner. These results suggest that the ET family of peptides, especially ET-1 and ET-2, can induce human coronary artery SMC migration in combination with PDGF-BB or Ang II, probably via ETA receptors. Taken together with the finding that the concentrations of ET, PDGF-BB and Ang II are locally increased at sites of endothelial injury, this indicates that ET may be an initial stimulus for human coronary artery medial SMC recruitment during coronary atherosclerosis, possibly in combination with PDGF-BB or Ang II.