Local expression of C-type natriuretic peptide suppresses inflammation, eliminates shear stress-induced thrombosis, and prevents neointima formation through enhanced nitric oxide production in rabbit injured carotid arteries

Auto/Paracrine C-Type Natriuretic Peptide/Cyclic GMP Signaling Prevents Endothelial Dysfunction

Endothelial dysfunction is cause and consequence of cardiovascular diseases. The endothelial hormone C-type natriuretic peptide (CNP) regulates vascular tone and the vascular barrier. Its cGMP-synthesizing guanylyl cyclase-B (GC-B) receptor is expressed in endothelial cells themselves. To characterize the role of endothelial CNP/cGMP signaling, we studied mice with endothelial-selective GC-B deletion. Endothelial EC GC-B KO mice had thicker, stiffer aortae and isolated systolic hypertension. This was associated with increased proinflammatory E-selectin and VCAM-1 expression and impaired nitric oxide bioavailability. Atherosclerosis susceptibility was evaluated in such KO and control littermates on Ldlr (low-density lipoprotein receptor)-deficient background fed a Western diet for 10 weeks. Notably, the plaque areas and heights within the aortic roots were markedly increased in the double EC GC-B/Ldlr KO mice. This was accompanied by enhanced macrophage infiltration and greater necrotic cores, indicating unstable plaques. Finally, we found that EC GC-B KO mice had diminished vascular regeneration after critical hind-limb ischemia. Remarkably, all these genotype-dependent changes were only observed in female and not in male mice. Auto/paracrine endothelial CNP/GC-B/cGMP signaling protects from arterial stiffness, systolic hypertension, and atherosclerosis and improves reparative angiogenesis. Interestingly, our data indicate a sex disparity in the connection of diminished CNP/GC-B activity to endothelial dysfunction.

Association of natriuretic peptides and receptor activity with cardio-metabolic health at middle age

Natriuretic peptides (NP) have multiple actions benefitting cardiovascular and metabolic health. Although many of these are mediated by Guanylyl Cyclase (GC) receptors NPR1 and NPR2, their role and relative importance in vivo is unclear. The intracellular mediator of NPR1 and NPR2, cGMP, circulates in plasma and can be used to examine relationships between receptor activity and tissue responses targeted by NPs. Plasma cGMP was measured in 348 participants previously recruited in a multidisciplinary community study (CHALICE) at age 50 years at a single centre. Associations between bio-active NPs and bio-inactive aminoterminal products with cGMP, and of cGMP with tissue response, were analysed using linear regression. Mediation of associations by NPs was assessed by Causal Mediation Analysis (CMA). ANP's contribution to cGMP far exceed those of other NPs. Modelling across three components (demographics, NPs and cardiovascular function) shows that ANP and CNP are independent and positive predictors of cGMP. Counter intuitively, findings from CMA imply that in specific tissues, NPR1 responds more to BNP stimulation than ANP. Collectively these findings align with longer tissue half-life of BNP, and direct further therapeutic interventions towards extending tissue activity of ANP and CNP.

The Predictive Value of A, B, and C-Type Natriuretic Peptides in People at Risk of Heart Disease: Protocol for a Longitudinal Observational Study

BACKGROUND

Heart disease and stroke are major and often unheralded causes of serious morbidity and premature death in middle age. Early detection of those most at risk is an urgent unmet need for instituting preventative measures. In an earlier community study (Canterbury Health, Ageing and Life Course [CHALICE]) of healthy people aged 50 years, contrary to previous reports, low levels of the heart hormone B-type natriuretic peptide (BNP) were associated with reduced measures of heart function and higher markers of vascular risk. A specific gene variant (rs198358) was found to be an independent contributor to higher BNP levels. A closely related vascular hormone (C-type natriuretic peptide [CNP]) showed opposite associations-higher levels were correlated with higher vascular risk and reduced cardiac function. To determine whether these novel findings predict serious heart or vascular disease in later life, this proposal re-examines the same CHALICE participants 15 years later.

OBJECTIVE

The primary objective is to determine the predictive value of (1) low plasma concentrations of the circulating cardiac hormones (atrial natriuretic peptide [ANP] and BNP) and (2) high levels of the vascular hormone CNP at age 50 years in detecting impaired cardiac and vascular function 15 years later. Secondary objectives are to determine specific associations of individual analytes (ANP, BNP, CNP, cyclic guanosine monophosphate [cGMP]) with echo-derived changes in cardiac performance at ages 50 years and 65 years.

METHODS

All of the 348 participants (205/348, 58.9% female; 53/348, 15.2% Māori or Pacifica ethnicity) participating in the original CHALICE study-free of history of heart or renal disease at age 50 years and who consented to further study-will be contacted, recruited, and restudied as previously described. Data will include intervening health history, physical examination, heart function (speckle-tracking echocardiography), vascular status (carotid intimal thickness), and genetic status (genome-wide genotyping). Laboratory measures will include fasting blood sampling and routine biochemistry, ANP, BNP, CNP, their downstream effector (cGMP), and their bio-inactive products. Humoral metabolic-cardiovascular risk factors will be measured after an overnight fast. Primary outcomes will be analyzed using multiple linear regression.

RESULTS

The study will commence in 2022 and be completed in 2024.

CONCLUSIONS

Proving our hypothesis-that low BNP and high CNP at any age in healthy people predict premature aging of heart and blood vessels, respectively-opens the way to early detection and improved outcomes for those most at risk. Confirmation of our hypotheses would improve current methods of screening and, in appropriate cases, enable interventions aimed at increasing natriuretic hormones and reducing risk of serious cardiovascular complications using drugs already available. Such advances in detection, and from interventional corrections, have the potential to not only improve health in the community but also reduce the high costs inevitably associated with heart failure.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/37011.

The loading of C-type natriuretic peptides improved hemocompatibility and vascular regeneration of electrospun poly(ε-caprolactone) grafts

As a result of thrombosis or intimal hyperplasia, synthetic artificial vascular grafts had a low success rate when they were used to replace small-diameter arteries (inner diameter < 6 mm). C-type natriuretic peptides (CNP) have anti-thrombotic effects, and can promote endothelial cell (EC) proliferation and inhibit vascular smooth muscle cell (SMC) over-growth. In this study, poly(ε-caprolactone) (PCL) vascular grafts loaded with CNP (PCL-CNP) were constructed by electrospinning. The PCL-CNP grafts were able to continuously release CNP at least 25 days in vitro. The results of scanning electron microscopy (SEM) and mechanical testing showed that the loading of CNP did not change the microstructure and mechanical properties of the PCL grafts. In vitro blood compatibility analysis displayed that PCL-CNP grafts could inhibit thrombin activity and reduce platelet adhesion and activation. In vitro cell experiments demonstrated that PCL-CNP grafts activated ERK1/2 and Akt signaling in human umbilical vein endothelial cells (HUVECs), as well as increased cyclin D1 expression, enhanced proliferation and migration, and increased vascular endothelial growth factor (VEGF) secretion and nitric oxide (NO) production. The rabbit arteriovenous (AV)-shunt ex vitro indicated that CNP loading significantly improved the antithrombogenicity of PCL grafts. The assessment of vascular grafts in rat abdominal aorta implantation model displayed that PCL-CNP grafts promoted the regeneration of ECs and contractile SMCs, modulated macrophage polarization toward M2 phenotype, and enhanced extracellular matrix remodeling. These findings confirmed for the first time that loading CNP is an effective approach to improve the hemocompatibility and vascular regeneration of synthetic vascular grafts. STATEMENT OF SIGNIFICANCE: : Small-diameter (< 6 mm) vascular grafts (SDVGs) have not been made clinically available due to their prevalence of thrombosis, limited endothelial regeneration and intimal hyperplasia. The incorporation of bioactive molecules into SDVGs serves as an effective solution to improve hemocompatibility and endothelialization. In this study, for the first time, we loaded C-type natriuretic peptides (CNP) into PCL grafts by electrospunning and confirmed the effectiveness of loading CNP on improving the hemocompatibility and vascular regeneration of artificial vascular grafts. Regenerative advantages included enhancement of endothelialization, modulation of macrophage polarization toward M2 phenotypes, and improved contractile smooth muscle cell regeneration. Our investigation brings attention to CNP as a valuable bioactive molecule for modifying cardiovascular biomaterial.

The Joint Effect of a Combination of Components From the Fruit of Crataegus pinnatifida Bge. Var. major N.E. Br. and the Root of Salvia miltiorrhiza Bge. With Exercises on Swimming in Focal Cerebral Infraction in Rat

Background: In our previous study, we found that the combination of a traditional Chinese medicine (TCM) and swimming could prevent atherosclerosis through a synergistic interaction. However, whether the combined application of active components from the fruit of Crataegus pinnatifida Bge. Var. major N.E. Br. and the root of Salvia miltiorrhiza Bge. (CPSM) and swimming has been effective in the prevention and treatment of focal cerebral infraction remained unclear. This work aimed to conduct detailed investigation on the joint effects of CPSM extract with swimming on focal cerebral infraction in rats and its underlying mechanisms. Method: A photochemical method of the combination of Rose Bengal (RB) injection and cold-light source irradiation was performed to establish the rat focal cerebral thrombosis model. The pathological changes of the brain were observed by a DCP-7030 laser multifunction machine, and the protein levels of von Willebrand factor (vWF), vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) were detected by Western blotting. Blood samples were collected to assay tissue plasminogen activator (t-PA), plasminogen activator inhibitor type-1 (PAI-1), endothelin-1 (ET-1), 6-keto-prostaglandin F1α (6-keto-PGF1α), and thromboxane B2 (TXB2). Finally, the gene expression of t-PA, PAI-1, and ICAM-1 in human umbilical vein endothelial cells (HUVECs) stimulated by tumor necrosis factor-α (TNF-α) was assayed via real-time (RT) quantitative PCR (qPCR). Results: The joint effects of CPSM extract and swimming demonstrated significant interactions, which including increased blood perfusion, increased serum t-PA and 6-keto-PGF1α, decreased serum PAI-1 and TXB2, decreased protein levels of vWF, VCAM-1 and ICAM-1, and decreased ICAM-1 gene expression. Conclusion: This research demonstrated that the combined therapy of CP and SM extracts with swimming could prevent focal cerebral infraction through interactions on the regulation of vascular endothelial functions and inflammatory factors. It stresses the promising effects of the drugs and shear stress of blood flow in prevention and treatment of thrombosis. The mechanism may be related to regulating the protein expression of vWF, VCAM-1, and ICAM-1, and downregulating the gene expression of ICAM-1.

Effect of statin therapy on plasma C-type Natriuretic Peptides and Endothelin-1 in males with and without symptomatic coronary artery disease

C-type Natriuretic Peptide (CNP) and Endothelin-1 (ET-1) have reciprocal roles in maintaining vascular homeostasis and are acutely modulated by statins in human cultured endothelial cells. Whether these actions of statins in vitro are reflected in studies in vivo is unknown. In a prospective study of 66 subjects with or without post- acute coronary syndrome (ACS), plasma concentrations of bioactive CNP and bio-inactive aminoterminal proCNP (NTproCNP), ET-1, B-type Natriuretic Peptide (BNP) and high sensitivity C Reactive Protein (hsCRP) were measured together with lipids before and at intervals of 1, 2 and 7 days after commencing atorvastatin 40 mg/day - and for a further period of 6months in those with ACS. Plasma lipids fell significantly in all subjects but plasma CNP, NTproCNP and ET-1 were unchanged by atorvastatin. In ACS, baseline hsCRP, BNP and CNP but not NTproCNP or ET-1 were significantly raised compared to values in age-matched controls. The ratio of NTproCNP to CNP was significantly lower in ACS throughout the study and was unaffected by statin therapy. We conclude that conventional doses of atorvastatin do not affect plasma CNP products or ET-1. Elevated CNP after cardiac injury likely results from regulated changes in clearance, not enhanced production.

The effect of natriuretic C-type peptide and its change over time on mortality in patients on haemodialysis or haemodiafiltration

Background

C-type natriuretic peptide (CNP) and its co-product N-terminal proCNP (NTproCNP) have been associated with beneficial effects on the cardiovascular system. In prevalent dialysis patients, however, a relation between NTproCNP and mortality has not yet been investigated. Furthermore, as a middle molecular weight substance, its concentration might be influenced by dialysis modality.

Methods

In a cohort of patients treated with haemodialysis (HD) or haemodiafiltration (HDF), levels of NTproCNP were measured at baseline and 6, 12, 24 and 36 months. The relation between serum NTproCNP and mortality and the relation between the 6-month rate of change of NTproCNP and mortality were analysed using Cox regression models. For the longitudinal analyses, linear mixed models were used.

Results

In total, 406 subjects were studied. The median baseline serum NTproCNP was 93 pmol/L and the median follow-up was 2.97 years. No relation between baseline NTproCNP or its rate of change over 6 months and mortality was found. NTproCNP levels remained stable in HD patients, whereas NTproCNP decreased significantly in HDF patients. The relative decline depended on the magnitude of the convection volume.

Conclusions

In our study, levels of NTproCNP appear strongly elevated in prevalent dialysis patients. Second, while NTproCNP remains unaltered in HD patients, its levels decline in individuals treated with HDF, with the decline dependent on the magnitude of the convection volume. Third, NTproCNP is not related to mortality in this population. Thus NTproCNP does not seem to be a useful marker for mortality risk in dialysis patients.

High-sensitive cardiac troponin T as a marker of hemorrhagic complications in elderly patients anticoagulated for non-massive pulmonary embolism

BACKGROUND

Recent data have raised concerns about the risk/benefit ratio of thrombolysis in non-high risk pulmonary embolism patients due to increased serious bleeding events. Whether cardiac biomarkers could be of help for bleeding risk stratification in this setting remains elusive.

OBJECTIVES

To determine the prognostic accuracy of hs-cTnT, NT-proBNP, RIETE and PESI score for the occurrence of clinically relevant bleeding (CRB) in elderly patients under conventional anticoagulation therapy for non-massive pulmonary embolism (NMPE).

METHODS

We evaluated 230 elderly patients with available blood sample taken within one day from diagnosis. The primary study endpoint was CRB at 1, 3 and 24 months. Prognostic accuracies and associations were determined using C-statistics and subhazard ratios (SHR), respectively.

RESULTS

hs-cTnT displayed the highest discriminatory power at 1 month (C-statistics: 0.77, 95% CI: 0.68-0.88) which remained stable over time. Although C-statistics comparison indicated that hs-cTnT was not statistically superior to RIETE score (0.77 vs 0.67, p = 0.11), adding hs-cTnT to RIETE score significantly improved the C-statistics from 0.67 to 0.78 (p = 0.02). SHRs indicated that for each hs-cTnT log-unit increase, there was a 58% increase in the risk of CRB independently of the RIETE score (adjusted SHR: 1.58, 95% CI: 1.31-1.92). At the pre-specified cut-off of 14 ng/l, the negative predictive value of hs-cTnT was 96.9% (95% CI: 91.4-99.0) and 94.9 (95%CI: 88.6-97.8) at 1 and 3 months, respectively.

CONCLUSION

In elderly, hs-cTnT provides incremental prognostic information over the RIETE score and could represent a valuable tool to identify NMPE patients at low risk of bleeding.

Contrasting signals of cardiovascular health among natriuretic peptides in subjects without heart disease

Natriuretic Peptides (NP) are important in maintaining normal cardiac and metabolic status and have been used to predict cardiovascular events. Whether plasma concentrations of NP products within the normal range reflect cardio-metabolic health is unknown. Plasma NTproANP, NTproBNP and NTproCNP and their bioactive counterparts were measured in a random sample of 348 community dwellers aged 49-51 yr without heart disease and associations sought with established vascular risk factors, echocardiographic indices and a genetic variant previously linked with BNP. Stratified by sex, each of ten vascular risk factors were positively associated with NTproCNP whereas associations with NTproBNP and NTproANP were all negative. In both sexes, higher plasma NTproCNP was associated with higher arterial elastance, lower LV stroke volume and lower LV end diastolic volume. Exactly opposite associations were found with plasma NTproBNP or NTproANP. Sex specific differences were identified: positive association of NTproBNP with LV end systolic volume and the negative association with LV elastance were found only in males. The genetic variant rs198358 was independently associated with NTproBNP but not with NTproANP. In conclusion, higher NTproCNP is likely to be an adaptive response to impaired LV relaxation whereas genetic factors likely contribute to higher NTproBNP and improved cardio-metabolic health at midlife.

Cardiovascular Pleiotropic Effects of Natriuretic Peptides

Atrial natriuretic peptide (ANP) is a cardiac hormone belonging to the family of natriuretic peptides (NPs). ANP exerts diuretic, natriuretic, and vasodilatory effects that contribute to maintain water–salt balance and regulate blood pressure. Besides these systemic properties, ANP displays important pleiotropic effects in the heart and in the vascular system that are independent of blood pressure regulation. These functions occur through autocrine and paracrine mechanisms. Previous works examining the cardiac phenotype of loss-of-function mouse models of ANP signaling showed that both mice with gene deletion of ANP or its receptor natriuretic peptide receptor A (NPR-A) developed cardiac hypertrophy and dysfunction in response to pressure overload and chronic ischemic remodeling. Conversely, ANP administration has been shown to improve cardiac function in response to remodeling and reduces ischemia-reperfusion (I/R) injury. ANP also acts as a pro-angiogenetic, anti-inflammatory, and anti-atherosclerotic factor in the vascular system. Pleiotropic effects regarding brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) were also reported. In this review, we discuss the current evidence underlying the pleiotropic effects of NPs, underlying their importance in cardiovascular homeostasis.

Natriuretic peptides in human heart: Novel insight into their molecular forms, functions, and diagnostic use

Among the three natriuretic peptides, atrial/A-type natriuretic peptide (ANP) and brain/B-type natriuretic peptide (BNP) are primarily produced by, and secreted from, heart tissue. They maintain cardiovascular homeostasis by binding to natriuretic peptide receptor-A. Since plasma ANP and BNP concentrations, as well as expression, are elevated in response to increased body fluid volume and pressure load on the heart wall, these peptides are widely utilized as diagnostic biomarkers for evaluating heart failure. Regardless of their high utility, differences in their molecular forms between healthy and diseased subjects and how these relate to pathophysiology have not well been examined. Recent studies have shown that the circulating molecular forms of ANP and BNP are not uniform; bioactive α-ANP is the major ANP form, whereas the weakly active proBNP is the major BNP form. The relative ratios of the different molecular forms are altered under different pathophysiological conditions. These facts indicate that detailed measurements of each form may provide useful information on the pathophysiological state of heart tissue. Here, we revisit the relationship between the molecular forms of, and pathophysiological alterations in, human ANP and BNP and discuss the possible utility of the measurement of each of the molecular forms. The third peptide, C-type natriuretic peptide, activates natriuretic peptide receptor-B, but little is known about its production and function in the heart because of its extremely low levels. However, through recent studies, its role in the heart is gradually becoming clear. Here, we summarize its molecular forms, assay systems, and functions in the heart.

C-Type Natriuretic Peptide (CNP) Inhibition of Interferon-γ-Mediated Gene Expression in Human Endothelial Cells In Vitro

Cardiovascular diseases, including atherosclerosis, now account for more deaths in the Western world than from any other cause. Atherosclerosis has a chronic inflammatory component involving Th1 pro-inflammatory cytokines such as IFN-γ, which is known to induce endothelial cell inflammatory responses. On the other hand CNP, which acts via its receptors to elevate intracellular cGMP, is produced by endothelium and endocardium and is upregulated in atherosclerosis. It is believed to be protective, however its role in vascular inflammation is not well understood. The aim of this study was to investigate the effects of CNP on human endothelial cell inflammatory responses following IFN-γ stimulation. Human umbilical vein endothelial cells were treated with either IFN-γ (10 ng/mL) or CNP (100 nm), or both in combination, followed by analysis by flow cytometry for expression of MHC class I and ICAM-1. IFN-γ significantly increased expression of both molecules, which was significantly inhibited by CNP or the cGMP donor 8-Bromoguanosine 3',5'-cyclic monophosphate (1 µm). CNP also reduced IFN-γ mediated kynurenine generation by the IFN-γ regulated enzyme indoleamine-2,3-deoxygenase (IDO). We conclude that CNP downmodulates IFN-γ induced pro-inflammatory gene expression in human endothelial cells via a cGMP-mediated pathway. Thus, CNP may have a protective role in vascular inflammation and novel therapeutic strategies for CVD based on upregulation of endothelial CNP expression could reduce chronic EC inflammation.

New Insights into Cardiac and Vascular Natriuretic Peptides: Findings from Young Adults Born with Very Low Birth Weight

BACKGROUND

In community studies, plasma B-type natriuretic peptide (BNP) is positively associated with cardiovascular disorders. Those born with very low birth weight (VLBW) have increased risk of metabolic and vascular disorders in later life, but plasma concentrations of natriuretic peptides have not been studied. The objectives here were to evaluate BNP and C-type natriuretic peptide (CNP)—a putative marker of vascular risk—in young adults born with VLBW.

METHODS

In all, 220 VLBW cases and 97 matched controls were studied 28 years after birth during a 2-day period at 1 research center. Aminoterminal (NT) products (NTproBNP, NTproCNP) and a range of conventional vascular risk factors including echocardiographic indices were measured along with genetic polymorphisms known to increase plasma NTproBNP.

RESULTS

VLBW individuals were smaller, had smaller hearts, reduced stroke volume and endothelial function, and higher systolic blood pressure and arterial elastance. Of the many humoral vascular and metabolic risk factors measured, including NTproBNP, only plasma NTproCNP (higher in VLBW individuals) differed significantly. Across all individuals, associations of NTproCNP with each of 7 conventional risk factors, as well as with arterial elastance, were positive, whereas associations of NTproBNP with risk were all inverse. In multivariate analysis, the genetic variant rs198358 was independently associated with NTproBNP.

CONCLUSIONS

In young adults at increased risk of cardiovascular disease, higher NTproCNP likely reflects a compensatory vascular response to vascular stress, whereas the negative link with NTproBNP likely reflects beneficial genetic mutations. The ratio of NTproBNP to NTproCNP may provide a novel index of ideal cardiovascular health.

Nutrient restriction in early ovine pregnancy stimulates C-type natriuretic peptide production

C-type natriuretic peptide (CNP), a paracrine growth factor promoting vasodilation and angiogenesis, is upregulated in human and ovine pregnancy in response to vascular stress or nutrient restriction (NR) in late gestation. Postulating that maternal plasma CNP products are increased by modest NR (50% of metabolisable energy requirement) early in pregnancy, and further enhanced by litter size, we studied serial changes of maternal plasma CNP in pregnant ewes receiving a normal (NC, n=12) or restricted (NR, n=13) diet from Day 30 to Day 93 or 94 of gestation. Liveweight of NR ewes was 10kg less than that of NC ewes at slaughter. Plasma CNP products increased progressively after Day 40 and were higher in NR (P<0.05) ewes after Day 60; they were also enhanced by litter size (P<0.01) and were positively associated with increased placental efficiency. In contrast, whereas fetal and placental weight were reduced by NR, fetal plasma CNP products (Day 93/94) were not affected. We conclude that increases in CNP during rapid placental growth are further enhanced by both increasing nutrient demands and by reduced supply, presumably as part of an adaptive response benefitting placental-fetal exchange.

Targeting vasoactive peptides for managing calcific aortic valve disease

Calcific aortic valve disease (CAVD) represents a spectrum of disease spanning from milder degrees of calcification of valve leaflets, i.e., aortic sclerosis, to severe calcification i.e., aortic stenosis (AS) with hemodynamic instability. The prevalence of CAVD is increasing rapidly due to the aging of the population, being up to 2.8% among patients over 75 years of age. Even without significant aortic valve stenosis, aortic sclerosis is associated with a 50% increased risk of myocardial infarction and death from cardiovascular causes. To date, there is no pharmacological treatment available to reverse or hinder the progression of CAVD. So far, the cholesterol-lowering therapies (statins) and renin-angiotensin system (RAS) blocking drugs have been the major pharmacological agents investigated for treatment of CAVD. Especially angiotensin receptor blockers (ARB)s and angiotensin convertase enzyme inhibitors (ACEI)s, have been under active investigation in clinical trials, but have proven to be unsuccessful in slowing the progression of CAVD. Several studies have suggested that other vasoactive hormones, including endothelin and apelin systems are also associated with development of AS. In the present review, we discuss the role of vasoactive factors in the pathogenesis of CAVD as novel pharmacological targets for the treatment of aortic valve calcification. Key messages Vasoactive factors are involved in the progression of calcific aortic valve disease. Endothelin and renin-angiotensin systems seem to be most prominent targets for therapeutic interventions in the view of valvular pathogenesis. Circulating vasoactive factors may provide targets for diagnostic tools of calcified aortic valve disease.

C-Type Natriuretic Peptides in Coronary Disease

AIMS

C-type natriuretic peptide (CNP) is a paracrine growth factor expressed in the vascular endothelium. Although upregulated in atheromatous arteries, the predictive value of plasma CNP products for outcome in coronary disease is unknown. This study aimed to compare the prognostic value of plasma CNP products with those of other natriuretic peptides in individuals with coronary artery disease, and investigate their associations with cardiac and renal function.

METHODS AND RESULTS

Plasma concentrations of CNP and amino-terminal proCNP (NT-proCNP) were measured at baseline in 2129 individuals after an index acute coronary syndrome admission and related to cardiac and renal function, other natriuretic peptides [atrial NP (ANP) and B-type NP (BNP)] and prognosis (primary end point, mortality; secondary end point, cardiac readmission). Median follow-up was 4 years. At baseline, and in contrast to CNP, ANP, and BNP, plasma NT-proCNP was higher in males and weakly related to cardiac function but strongly correlated to plasma creatinine. All NPs were univariately associated with mortality. Resampling at 4 and 12 months in survivors showed stable concentrations of NT-proCNP whereas all other peptides declined. When studied by diagnosis (myocardial infarction, unstable angina) at index admission using a multivariate model, NT-proBNP predicted mortality and readmission in myocardial infarction. In unstable angina, only NT-proCNP predicted both mortality and cardiac readmission.

CONCLUSIONS

In contrast to the close association of NT-proBNP with cardiac function, and predictive value for outcome after myocardial infarction, plasma NT-proCNP is highly correlated with renal function and is an independent predictor of mortality and cardiac readmission in individuals with unstable angina.

Role of C-type natriuretic peptide signalling in maintaining cartilage and bone function

C-type natriuretic peptide (CNP) has been demonstrated in human and mouse models to play critical roles in cartilage homeostasis and endochondral bone formation. Indeed, targeted inactivation of the genes encoding CNP results in severe dwarfism and skeletal defects with a reduction in growth plate chondrocytes. Conversely, cartilage-specific overexpression of CNP was observed to rescue the phenotype of CNP deficient mice and significantly enhanced bone growth caused by growth plate expansion. In vitro studies reported that exogenous CNP influenced chondrocyte differentiation, proliferation and matrix synthesis with the response dependent on CNP concentration. The chondroprotective effects were shown to be mediated by natriuretic peptide receptor (Npr)2 and enhanced synthesis of cyclic guanosine-3',5'-monophosphate (cGMP) production. Recent studies also showed certain homeostatic effects of CNP are mediated by the clearance inactivation receptor, Npr3, highlighting several mechanisms in maintaining tissue homeostasis. However, the CNP signalling systems are complex and influenced by multiple factors that will lead to altered signalling and tissue dysfunction. This review will discuss the differential role of CNP signalling in regulating cartilage and bone homeostasis and how the pathways are influenced by age, inflammation or sex. Evidence indicates that enhanced CNP signalling may prevent growth retardation and protect cartilage in patients with inflammatory joint disease.

Diagnostic value of plasma C-type natriuretic peptide levels in determination of the duration of mesenteric ischaemia

Objective

Mesenteric arteries release C-type natriuretic peptide (CNP), which hyperpolarises vascular smooth muscle. We measured the levels of this peptide after inducing mesenteric ischaemia over a series of time intervals, so as to determine its predictive value in demonstrating the severity of ischaemia in a rat model.

Methods

A total of 32 rats were allocated to four groups containing eight rats each. Basal CNP reference levels were measured in the control group, which was not exposed to any intervention. In groups I, II and III, mesenteric ischaemia was induced over three, six and nine hours, respectively, and plasma CNP levels were measured afterwards. Mesenteric ischaemia was induced by clamping the superior mesenteric artery.

Results

In comparison with the controls (2.38 ± 0.18 pg/ml), CNP levels were relatively lower in group I (2.54 ± 0.42 pg/ml). However, significant increases in plasma CNP levels were observed over longer periods of ischaemia in group II, at 5.23 ± 0.22 pg/ml, and in group III, at 6.19 ± 0.67 pg/ml (p < 0.05). A significant direct relationship was determined between plasma CNP levels and prolonged intervals of mesenteric ischaemia (R = 0.56, p < 0.001).

Conclusion

Measuring plasma CNP levels in patients with acute mesenteric ischaemia may be beneficial in estimating the time period over which the ischaemic injury has occurred.

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.

C-type natriuretic peptide in complicated pregnancy: increased secretion precedes adverse events

CONTEXT

C-type natriuretic peptide (CNP), a vasoactive product of the endothelium, is markedly increased during placentation in ovine pregnancy and is further stimulated by nutrient restriction. Whether CNP products change in human pregnancy is unknown.

OBJECTIVES

The objective of the study was to compare serial changes in maternal plasma CNP peptides during normal pregnancy with changes in pregnancy complicated by adverse events and relate these to fetal growth and placental CNP content.

DESIGN

This was a prospective observational study undertaken in a tertiary care center.

METHODS

We studied changes in maternal plasma aminoterminal proCNP (NTproCNP) and CNP at monthly intervals, fetal growth, and placental and umbilical plasma CNP peptides in 51 women, 28 of whom experienced an adverse event and 23 were uneventful. Age matched healthy nonpregnant women served as a reference range for NTproCNP.

RESULTS

Compared with nonpregnant women, maternal plasma NTproCNP in an uneventful pregnancy was significantly reduced from first sampling (16 wk gestation) until 36 weeks. In contrast, in complicated pregnancy, levels did not decline and were significantly higher (P < .001 by ANOVA) than in normal pregnancy from 20 weeks. Highest values occurred in women later developing hypertension and fetal growth disorders. Placental concentration of NTproCNP was unrelated to maternal NTproCNP but strongly correlated with cord plasma levels.

CONCLUSIONS

Maternal NTproCNP is significantly raised in women who later exhibit a range of obstetric adverse events. Lack of association with placental concentrations suggests that these changes represent an adaptive response within the maternal circulation to a threatened nutrient supply to the fetus.

C-type natriuretic peptide transcriptomic profiling increases in human leukocytes of patients with chronic heart failure as a function of clinical severity

The aim of this study was to evaluate the transcriptomic profiling of C-type natriuretic peptide (CNP) and of its specific receptor, NPR-B in human leukocytes of heart failure (HF) patients as a function of clinical severity, assessing the possible changes with respect to healthy subjects (C). mRNA expression was evaluated by Real-Time PCR and total RNA was extracted from leukocytes of C (n=8) and of HF patients (NYHA I-II, n=7; NYHA III-IV, n=13) with PAXgene Blood RNA Kit. Significantly higher levels of CNP mRNA expression were found in HF patients as a function of clinical severity (C=0.23±0.058, NYHA I-II=0.47±0.18, NYHA III-IV=2.58±0.71, p=0.005 C vs NYHA III-IV, p=0.017 NYHA I-II vs NYHA III-IV) and NPR-B transcript levels resulted down-regulated in HF patients with higher NYHA class (C=2.2±0.61, NYHA I-II=2.76±0.46, NYHA III-IV=0.29±0.13, p=0.001 C vs NYHA III-IV, p<0.0001 NYHA I-II vs NYHA III-IV). A significant negative correlation between CNP and NPR-B mRNA expression (r=0.5, p=0.03) was also observed. These results suggest a co-regulation of NPR-B and CNP expression supporting the relevance of this receptor in human disease characterized by a marked inflammatory/immune component and suggesting the possibility of manipulating inflammation via pharmacological agents selective for this receptor.

Novel vasodilators in heart failure

Heart failure is an important public health problem that is increasing in prevalence throughout the world. Not only is this condition common, but it is associated with significant morbidity and mortality as well as high costs to medical care systems. Vasodilator drugs help unload the heart and may have other effects that could benefit heart failure patients. Consequently, they have emerged as an important therapeutic approach for patients with this condition. Novel vasodilator therapies that are currently in development target new pathways, potentially giving clinicians alternate options for improving outcomes in this vulnerable population. This review focuses on investigational drugs that have the ability to dilate blood vessels amongst their therapeutic properties. These drugs include the natriuretic peptides that activate particulate guanylate cyclase, the novel agent cinaciguat that activates the soluble guanylate cyclase system, and finally a recombinant form of the naturally occurring vasodilating agent relaxin, a hormone that mediates many of the changes that allows the cardiovascular system to successfully adapt to pregnancy.

Role and interactions of annexin A1 and oestrogens in the manifestation of sexual dimorphisms in cerebral and systemic inflammation

BACKGROUND AND PURPOSE

Gender differences in inflammation are well described, with females often showing more robust, oestrogen-associated responses. Here, we investigated the influence of gender, oestrogen and the anti-inflammatory protein annexin A1 (AnxA1) on lipopolysaccharide (LPS)-induced leukocyte-endothelial cell interactions in murine cerebral and mesenteric microvascular beds.

EXPERIMENTAL APPROACH

Intravital microscopy was used to visualize and quantify the effects of LPS (10 μg·per mouse i.p.) on leukocyte-endothelial interactions in male and female wild-type (WT) mice. The effects of ovariectomy ± oestrogen replacement were examined in WT and AnxA1-null (AnxA1(-/-) ) female mice.

KEY RESULTS

LPS increased leukocyte adherence in the cerebral and mesenteric beds of both male and female WT mice; females showed exacerbated responses in the brain versus males, but not the mesentery. Ovariectomy further enhanced LPS-induced adhesion in the brain but not the mesentery; its effects were reversed by oestrogen treatment. OVX AnxA1(-/-) mice also showed exaggerated adhesive responses to LPS in the brain. However, these were unresponsive to ovariectomy and, paradoxically, responded to oestrogen with a pronounced increase in basal and LPS-induced leukocyte adhesion in the cerebrovasculature.

CONCLUSIONS AND IMPLICATIONS

Our data confirm the fundamental role of AnxA1 in limiting the inflammatory response in the central and peripheral microvasculature. They also (i) show that oestrogen acts via an AnxA1-dependent mechanism to protect the cerebral, but not the mesenteric, vasculature from the damaging effects of LPS and (ii) reveal a paradoxical and potentially toxic effect of the steroid in potentiating the central response to LPS in the absence of AnxA1.

Systems biology and biomechanical model of heart failure

Heart failure is seen as a complex disease caused by a combination of a mechanical disorder, cardiac remodeling and neurohormonal activation. To define heart failure the systems biology approach integrates genes and molecules, interprets the relationship of the molecular networks with modular functional units, and explains the interaction between mechanical dysfunction and cardiac remodeling. The biomechanical model of heart failure explains satisfactorily the progression of myocardial dysfunction and the development of clinical phenotypes. The earliest mechanical changes and stresses applied in myocardial cells and/or myocardial loss or dysfunction activate left ventricular cavity remodeling and other neurohormonal regulatory mechanisms such as early release of natriuretic peptides followed by SAS and RAAS mobilization. Eventually the neurohormonal activation and the left ventricular remodeling process are leading to clinical deterioration of heart failure towards a multi-organic damage. It is hypothesized that approaching heart failure with the methodology of systems biology we promote the elucidation of its complex pathophysiology and most probably we can invent new therapeutic strategies.

Gene expression of C-type natriuretic peptide and of its specific receptor NPR-B in human leukocytes of healthy and heart failure subjects

C-type natriuretic peptide (CNP), a member of the family of natriuretic peptides, is synthesized and secreted from monocytes and macrophages that resulted to be a source of CNP at inflammatory sites. This suggests that special attention should be focused on the possible role of CNP in the immune system, in addition to its effects on the cardiovascular system. The aim of this study was to evaluate the possibility of measuring the mRNA expression of CNP and NPR-B, its specific receptor, in human whole blood samples of healthy (N; n=7) and heart failure (HF; n=7) subjects by Real-Time PCR (RT-PCR). Total RNA was extracted from leukocytes with QIAamp RNA Blood Kit and/or with PAXgene Blood RNA Kit. RT-PCR was performed and optimized for each primer. The experimental results were normalized with the three most stably expressed genes. CNP and NPR-B expression trend was similar in both fresh and frozen human whole blood. Significant higher levels of CNP and NPR-B mRNA expression were found in HF patients with respect to controls (CNP: N=1.23±0.33 vs. HF=6.54±2.09 p=0.027; NPR-B: N=0.85±0.23 vs. HF=5.31±1.98 p=0.04). A significant correlation between CNP and NPR-B (r=0.86, p<0.0001) was observed. Further studies are needed to clarify the pathophysiological properties of this peptide but the possibility to measure CNP and NPR-B mRNA expression in human leukocytes with a fast and easy procedure is a useful starting point for future investigation devoted to better understand the biomolecular processes associated to different diseases.

Natriuretic peptide receptor-3 underpins the disparate regulation of endothelial and vascular smooth muscle cell proliferation by C-type natriuretic peptide

BACKGROUND AND PURPOSE

C-type natriuretic peptide (CNP) is an endothelium-derived vasorelaxant, exerting anti-atherogenic actions in the vasculature and salvaging the myocardium from ischaemic injury. The cytoprotective effects of CNP are mediated in part via the G_i-coupled natriuretic peptide receptor (NPR)3. As GPCRs are well-known to control cell proliferation, we investigated if NPR3 activation underlies effects of CNP on endothelial and vascular smooth muscle cell mitogenesis.

EXPERIMENTAL APPROACH

Proliferation of human umbilical vein endothelial cells (HUVEC), rat aortic smooth muscle cells (RAoSMC) and endothelial and vascular smooth muscle cells from NPR3 knockout (KO) mice was investigated in vitro.

KEY RESULTS

CNP (1 pM–1 µM) facilitated HUVEC proliferation and inhibited RAoSMC growth concentration-dependently. The pro- and anti-mitogenic effects of CNP were blocked by the NPR3 antagonist M372049 (10 µM) and the extracellular signal-regulated kinase (ERK) 1/2 inhibitor PD98059 (30 µM) and were absent in cells from NPR3 KO mice. Activation of ERK 1/2 by CNP was inhibited by Pertussis toxin (100 ng·mL⁻¹) and M372049 (10 µM). In HUVEC, ERK 1/2 activation enhanced expression of the cell cycle promoter, cyclin D1, whereas in RAoSMC, ERK 1/2 activation increased expression of the cell cycle inhibitors p21^waf1/cip1 and p27^kip1.

CONCLUSIONS AND IMPLICATIONS

A facet of the vasoprotective profile of CNP is mediated via NPR3-dependent ERK 1/2 phosphorylation, resulting in augmented endothelial cell proliferation and inhibition of vascular smooth muscle growth. This pathway may offer an innovative approach to reversing the endothelial damage and vascular smooth muscle hyperplasia that characterize many vascular disorders.

Circulating forms of the b-type natriuretic peptide prohormone: pathophysiologic and clinical considerations

Recent studies reported that many different biochemical forms of B-type-related peptides circulate in human blood. In particular, a significant amount of the prohormone peptide (i.e., proBNP108) can be detected in plasma of patients with heart failure. These data indicate that the posttranslational maturation processing of the B-type natriuretic peptide (BNP) precursor may not be efficient in heart failure. The aim of this chapter is to describe the biochemical pathways of proBNP108 maturation and to discuss the pathophysiological relevance of alteration of the posttranslational maturation mechanisms in heart failure. An impaired cardiac endocrine function was proposed to explain the altered electrolyte and fluid homeostasis occurring in chronic heart failure. Recent studies demonstrated that a great part of BNPs assayed by immunoassay methods in healthy subjects and in patients with cardiovascular disease is devoid of biological activity. These findings suggest that an alteration in posttranslational maturation of BNP precursor may promote the resistance to biological action of BNP in patients with heart failure at a prereceptor level. These studies also open a new and more complex scenario regarding the circulating BNPs. The active hormone (i.e., BNP1-32) may be produced even in vivo from the circulating precursor proBNP108 by plasma enzyme degradation, such as the soluble form of corin, possibly able to process the circulating intact precursor of natriuretic hormones. As a future perspective, the simultaneous measurement of the proBNP1-108 and the active peptide BNP1-32 with more specific methods could allow a more accurate estimation of both production/secretion of B-type-related peptides from cardiomyocytes and the true activity of the cardiac endocrine function.

Endogenous vascular synthesis of B-type and C-type natriuretic peptides in the rainbow trout

In mammals, natriuretic peptides (NPs) lower blood pressure, reduce blood volume and broadly inhibit cardiovascular remodeling. NPs are often referred to as cardiac hormones, though they also have integral roles in regulating vascular tone, endothelial remodeling and inhibiting vascular smooth muscle cell hypertrophy. Two NPs [atrial (ANP) and C-type (CNP)] have been identified as endogenous constituents in the vasculature of mammals, though such a phenomenon has not previously been described in fishes. Here we describe the endogenous production of B-type NP (BNP) and CNP in multiple blood vessels of the rainbow trout. Western blot analysis showed pro-BNP and pro-CNP production in the efferent branchial artery, celiacomesenteric artery, ventral aorta and anterior cardinal vein. The detection of pro-BNP and pro-CNP was also supported by MALDI-TOF mass spectrometry analysis of NP-enriched tissue extracts. Although vascular pro-peptide levels of BNP and CNP were quantitatively quite comparable to those found in reference tissues (the atrium for BNP and brain for CNP), mRNA levels of these NPs in the vasculature were greatly reduced as determined by quantitative PCR. When the evolutionarily conserved vascular NP (CNP) was infused into un-anesthetized trout, it reduced central venous pressure and mean circulatory filling pressure. CNP also decreased cardiac output via a reduction in preload. The presence of endogenous NP production in the trout vasculature and potent in vivo hypotensive effects further support the numerous functional similarities between teleost and mammalian NP systems.

Thirty years of the heart as an endocrine organ: physiological role and clinical utility of cardiac natriuretic hormones

Thirty years ago, De Bold et al. ( 20 ) reported that atrial extracts contain some biologically active peptides, which promote a rapid and massive diuresis and natriuresis when injected in rats. It is now clear that the heart also exerts an endocrine function and in this way plays a key role in the regulation of cardiovascular and renal systems. The aim of this review is to discuss some recent insights and still-debated findings regarding the cardiac natriuretic hormones (CNHs) produced and secreted by cardiomyocytes (i.e., atrial natriuretic peptide and B-type natriuretic peptide). The functional status of the CNH system depends not only on the production/secretion of CNHs by cardiomyocytes but also on both the peripheral activation of circulating inactive precursor of natriuretic hormones and the transduction of the hormone signal by specific receptors. In this review, we will discuss the data supporting the hypothesis that the production and secretion of CNHs is the result of a complex integration among mechanical, chemical, hemodynamic, humoral, ischemic, and inflammatory inputs. The cross talk among endocrine function, adipose tissue, and sex steroid hormones will be discussed more in detail, considering the clinically relevant relationships linking together cardiovascular risk, sex, and body fat development and distribution. Finally, we will review the pathophysiological role and the clinical relevance of both peripheral maturation of the precursor of B-type natriuretic peptides and hormone signal transduction .

Measurement of the pro-hormone of brain type natriuretic peptide (proBNP): methodological considerations and pathophysiological relevance

Recent studies demonstrated that large amounts of the pro-hormone peptide of brain natriuretic peptide (proBNP) can be detected in plasma of healthy subjects and in particular of patients with heart failure. As a result, a great part of B-type natriuretic peptides measured in patients with cardio-vascular disease may be devoid of biological activity. These findings stimulated the set up of specific immunoassay methods for the measurement of the intact proBNP peptide. The aim of this review article is to discuss the methodological characteristics and the possible clinical relevance of specific immunoassay methods for the measurement of the proBNP peptide. From an analytical point of view, a fully automated immunoassay of proBNP has some theoretical advantages (e.g., a more stable molecule with higher molecular weight than the derived peptides) compared to the active hormone BNP. Recent studies supported the concept that the precursor proBNP might be actually considered a circulating prohormone, which can be cleaved by specific plasma proteases in BNP, the active hormone, and NT-proBNP, an inactive peptide. The peripheral processing of circulating proBNP could likely be submitted to regulatory rules, which might be impaired in patients with heart failure, opening new perspectives in the treatment of heart failure (e.g., by studying drugs inducing the cleavage of the prohormone into active BNP). Furthermore, as a future perspective, the specific assay in the same plasma sample of the intact precursor proBNP and of the biologically active peptide BNP, could allow a more accurate estimation of the production/secretion of B-type related peptides from cardiomyocytes and of the global cardiac endocrine function.

Transforming growth factor-β1 regulation of C-type natriuretic peptide expression in human vascular smooth muscle cells: dependence on TSC22D1

C-type natriuretic peptide (CNP) possesses nitric oxide-like signaling mechanisms and actions in the vasculature, including the inhibition of fibrosis and vascular remodeling through counterregulation of transforming growth factor-β (TGF-β) signaling. The leucine zipper protein transforming growth factor stimulated clone 22 domain 1 (TSC22D1), cloned via its presumed binding to a GC-rich element in the CNP promoter, was the first protein to be described as a CNP transcription factor, but the lack of supporting evidence since its discovery and its lack of a classical DNA-binding site have left in question its role in the regulation of CNP by TGF-β and other factors. To define a specific role for TSC22D1 in CNP transcription, we have examined the effects of the profibrotic growth factors TGF-β1 and PDGF-BB on CNP mRNA expression in cultured human vascular smooth muscle cells (SMC) in which TSC22D1 expression was suppressed with small interfering RNA. Results showed that TGF-β and PDGF-BB significantly increased CNP expression in all three SMC types. Twenty-four-hour TGF-β-induced elevations in CNP were strongly correlated with changes in TSC22D1 mRNA levels, and both genes exhibited their greatest response to TGF-β1 in coronary artery SMC. Furthermore, siRNA suppression of TSC22D1 expression in coronary artery and aortic SMC by ∼90% resulted in 45–65% reductions of both PDGF- and TGF-β-stimulated CNP expression, respectively. These results support a postulated role of TSC22D1 as an enhancer of CNP transcription and suggest that TGF-β-induced upregulation of CNP expression in SMC may be mediated in part by increased transcription of TSC22D1.

C-type natriuretic-derived peptides as biomarkers in human disease

The natriuretic peptide system comprises three structurally related peptides: atrial natriuretic peptide, B-type natriuretic peptide and C-type natriuretic peptide. In circulation, they play an important endocrine role in the regulation of cardiovascular homeostasis by maintaining blood pressure and extracellular fluid volume. Atrial natriuretic peptide and B-type natriuretic peptide have gained considerable diagnostic interest as biomarkers in cardiovascular disease. By contrast, C-type natriuretic peptide has not yet been ascribed a role in human diagnostics. This perspective aims at recapitulating the present biochemical and clinical issues concerning C-type natriuretic peptide measurement in plasma as a potential biomarker.

Blood serum levels of amino-terminal pro-C-type natriuretic peptide in patients with systemic sclerosis

The aim of this pilot study was to examine the association of serum levels of amino-terminal fragment of pro-C-type natriuretic peptide (NT-proCNP), as a substitute measure of serum C-type natriuretic peptide (CNP), with clinical and laboratory findings in patients with systemic sclerosis (SSc). Serum NT-proCNP, soluble (s)E-and sP-selectin levels were examined using specific enzyme-linked immunosorbent assay in 30 patients with SSc and 30 healthy controls. We found no statistically significant difference in serum levels of NT-proCNP neither between patients with SSc and healthy controls nor between those treated with immunosuppressive agents and untreated patients. Nevertheless, in the investigated SSc group, serum NT-proCNP levels correlated with the concentrations of C-reactive protein (CRP) and the duration of the disease. Both sP- and sE-selectin levels were elevated in SSc patients when compared to healthy subjects. Also they did not correlate with the concentrations of NT-proCNP. The results of the study indicate that serum NT-proCNP level is likely secondary to existing inflammation. However, the magnitude of CNP action in SSc and its possible role in the pathogenesis of the disease remains to be elucidated.

Differential effects of natriuretic peptides on arterial and venous coronary artery bypass conduits

BACKGROUND

Arterial grafts have patency rates superior to venous grafts in patients undergoing coronary bypass grafting surgery. Natriuretic peptides play a major role in vascular homeostasis. We hypothesized that natriuretic peptides might have different effects on arterial and venous conduits.

METHODS

The relaxation responses and tissue levels of cyclic guanosine monophosphate (cGMP) after exposure to atrial natriuretic peptide, brain natriuretic peptide, and C-type natriuretic peptide were assessed in segments of internal mammary artery, radial artery, and saphenous vein obtained from the same patients at the time of bypass surgery (n = 12). Natriuretic peptide receptor (NPR) expression was assessed using immunohistochemistry and Western blotting.

RESULTS

Relaxation of the internal mammary artery and radial artery to all the natriuretic peptides were similar, and greater than that of saphenous vein, correlating with increased tissue levels of cGMP in both arterial conduits. Relaxation responses to all three natriuretic peptides were nearly abolished in the presence of LY83583, an inhibitor of guanylyl cyclase. Exposure of the conduits to N(G)-Nitro-L-arginine methyl ester (nitric oxide synthase inhibitor) resulted in a modest but significant blunting of the relaxation responses. Expression of NPR(A), NPR(B) and NPR(C)was strong in the endothelium and vascular smooth muscle layer of the internal mammary artery and radial artery, and was significantly less in saphenous vein.

CONCLUSIONS

Natriuretic peptides are potent vasodilators of the internal mammary artery and radial artery but not the saphenous vein. The relaxation response is mediated through guanylyl cyclase and nitric oxide synthase. These observations may provide additional insight into the mechanisms that account for superior patency of arterial conduits.

Natriuretic peptides: an update on bioactivity, potential therapeutic use, and implication in cardiovascular diseases

The natriuretic peptide system includes three known peptides: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). They contribute to the regulation of cardiovascular homeostasis through diuretic, natriuretic, and vasodilatory properties. Among them, ANP has received particular attention because of its effects on blood pressure regulation and cardiac function. Although the potential for its therapeutic application in the treatment of hypertension and heart failure has been evaluated in several experimental and clinical investigations, no pharmacological approach directly targeted at modulation of ANP levels has ever reached the stage of being incorporated into clinical practice. Recently, ANP has also received attention as being a possible cardiovascular risk factor, particularly in the context of hypertension, stroke, obesity, and metabolic syndrome. Abnormalities in either peptide levels or peptide structure are thought to underlie its implied role in mediating cardiovascular diseases. Meanwhile, BNP has emerged as a relevant marker of left ventricular (LV) dysfunction and as a useful predictor of future outcome in patients with heart failure. This review deals with the major relevant findings related to the cardiovascular and metabolic effects of natriuretic peptides, to their potential therapeutic use, and to their role in mediating cardiovascular diseases.

Distinct downregulation of C-type natriuretic peptide system in human aortic valve stenosis

BACKGROUND

Aortic valve calcification is an actively regulated process that displays hallmarks of atherosclerosis. Natriuretic peptides (A-, B-, and C-type natriuretic peptides [ANP, BNP, and CNP]) have been reported to have a role in the pathogenesis of vascular atherosclerosis, but their expression in aortic valves is not known. Here, we characterized and compared expression of natriuretic peptide system in aortic valves of patients with normal valves (n=4), aortic regurgitation (n=11), regurgitation and fibrosis (n=6), and aortic valve stenosis (n=21).

METHODS AND RESULTS

By reverse-transcription polymerase chain reaction, all 3 natriuretic peptides were found to be expressed in aortic valves. CNP mRNA levels were 92% lower (P<0.001) in stenotic valves, whereas no significant changes in the expression of ANP and BNP genes were found compared with valves obtained from patients with aortic regurgitation. CNP was localized by immunohistochemistry with specific CNP (32-53) antibody to valvular endothelial cells and myofibroblasts. Gene expression of furin, which proteolytically cleaves proCNP into active CNP, was 54% lower in aortic valve stenosis (P=0.04). Moreover, natriuretic peptide receptor-A and natriuretic peptide receptor-B mRNA levels were 78% and 76% lower, respectively, in stenotic valves. In contrast, gene expression of corin, a proANP- and proBNP-converting enzyme, and natriuretic peptide receptor-C did not differ between groups.

CONCLUSIONS

We show that natriuretic peptides, their processing enzymes, and their receptors are expressed in human aortic valves. Aortic valve stenosis is characterized by distinct downregulation of gene expression of CNP, its processing enzyme furin, and the target receptors natriuretic peptide receptor-B and natriuretic peptide receptor-A, which suggests that CNP acts as a paracrine regulator of the aortic valve calcification process.

Natriuretic peptide receptor B signaling in the cardiovascular system: protection from cardiac hypertrophy

Natriuretic peptides (NP) represent a family of structurally homologous but genetically distinct peptide hormones involved in regulation of fluid and electrolyte balance, blood pressure, fat metabolism, cell proliferation, and long bone growth. Recent work suggests a role for natriuretic peptide receptor B (NPR-B) signaling in regulation of cardiac growth by either a direct effect on cardiomyocytes or by modulation of other signaling pathways including the autonomic nervous system. The research links NPR-B for the first time to a cardiac phenotype in vivo and underlines the importance of the NP in the cardiovascular system. This manuscript will focus on the role of NPR-B and its ligand C-type natriuretic peptide in cardiovascular physiology and disease and will evaluate these new findings in the context of the known function of this receptor, with a perspective on how future research might further elucidate NPR-B function.

Effects of G-CSF on cardiac remodeling and arterial hyperplasia in rats

Although granulocyte colony-stimulating factor (G-CSF) has been shown to prevent cardiac remodeling after acute myocardial infarction, the mechanism and safety of G-CSF treatment acute myocardial infarction remain controversial. The purpose of the present study was to investigate in a rat model the mechanisms underlying the beneficial effect of G-CSF in acute myocardial infarction and to determine whether G-CSF treatment aggravates vascular remodeling of injured artery after acute myocardial infarction. Sprague-Dawley rats received transplanted bone marrow cells from green fluorescent protein (GFP) transgenic rats. Acute myocardial infarction was induced by ligation of the left coronary artery. After 24 h, the right carotid artery was injured with a balloon catheter. G-CSF (100 microg/kg/day) or saline was injected subcutaneously for 5 consecutive days after induction of acute myocardial infarction. G-CSF treatment significantly improved left ventricle function and reduced infarct size in rats with acute myocardial infarction. Expression of mRNA for the angiogenic cytokines was significantly higher in the infarction border area in the G-CSF group than in the control group. The surviving cardiomyocytes in infarction area were more in the G-CSF group. GFP-positive cells were gathered in the infarction border area in both groups; G-CSF did not increase cardiac homing of GFP-positive bone marrow cells in contrast to control group. Most GFP-positive cells were CD68-positive (macrophages). It was difficult to find bone marrow-derived cardiomyocytes in the infarcted area. G-CSF treatment inhibited neointima formation and increased reendothelialization of the injured artery. GFP-positive cells were identified most in the adventitia of the injured artery. A few cells in the neointima and reendothelialization were GFP positive. In conclusion, administration of G-CSF appears to be effective for treatment of left ventricular remodeling after acute myocardial infarction and does not aggravate vascular remodeling. The effect of G-CSF on cardiac and vascular remodeling may occur mainly through a direct action on the heart and arteries.

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.

C-type natriuretic peptide and heart failure

C-type natriuretic peptide (CNP) is a peptide produced by the vascular endothelium with vasodilative properties. It shares structural and physiological properties with the atrial and brain natriuretic peptides (ANP and BNP), whose central role in the pathophysiology of heart failure (CHF) is firmly established. The role of CNP, first isolated from porcine brain, has not been yet completely determined. The transcription of the gene, that in man is located on chromosome 2, is regulated by factors such as tumor necrosis factor and interleukin-1. Two mature forms of the peptide exist: CNP-53, that predominates in tissues and CNP-22, found mainly in plasma. As recently found, CNP is produced directly in the myocardium and an increase in plasma levels of this peptide and of its precursor was observed in CHF. The aim of this review was to examine the current literature relating to cardiovascular functions of CNP and in particular to its role in CHF. In fact, CNP may represent an important new local autocrine and endocrine mediator in CHF although further evaluations are required to define its full pathophysiological role in this disease.