Heublein, Denise M.

The present study was undertaken to investigate the presence of C-type natriuretic peptide (CNP) immunoreactivity in cultured human vascular endothelial cells and in human plasma. CNP immunoreactivity was present in cultured human aortic endothelial cells by both immunohistochemical staining and by radioimmunoassay. With the utilization of gel permeation chromatography, this immunoreactivity proved to be consistent with the higher molecular weight CNP-53. CNP immunoreactivity was also present in human plasma (n = 22) at low picogram concentrations (6.5 +/- 0.2 pg/ml) by specific radioimmunoassay. This immunoreactivity was consistent with the lower molecular weight CNP-22 by gel permeation chromatography. These findings suggest that the vascular endothelium may be the site of CNP production. The isolation of different molecular forms of CNP in tissue and plasma may be consistent with a storage form of the peptide in endothelial cells CNP-53, while CNP-22 circulates in plasma. In summary, the present study is consistent with CNP being a peptide of endothelial cell origin.

C-type natriuretic peptide (CNP) is a newly described 22-amino acid peptide of endothelial cell origin, which has selective cardiovascular actions and is structurally related to atrial natriuretic peptide (ANP). Recent in vitro studies have demonstrated that an important regulatory pathway for the clearance of natriuretic peptides involves binding to a common clearance receptor [natriuretic peptide C receptor (NPR-C)]. Although CNP has also been identified as a ligand for NPR-C in binding assays, no studies have defined the in vivo interaction of CNP with NPR-C. CNP (10 ng.kg-1.min-1) followed by C-ANP-(4-23), a specific ligand for NPR-C blockade, was infused intravenously in two groups (both n = 7) of anesthetized dogs at two different doses (0.1 or 1.0 micrograms.kg-1.min-1) to permit calculation of total metabolic clearance rate (TMCR). C-ANP-(4-23) increased circulating CNP and reduced TMCR in both groups. Pulmonary metabolic clearance rate was negative at baseline, suggesting a net secretion of CNP across the lung, which was increased during CNP infusion and was abolished with NPR-C blockade. Renal and femoral metabolic clearance rates were positive at baseline and increased with CNP infusion. A decrease in cardiac output and cardiac filling pressures in response to CNP administration was potentiated by NPR-C blockade. We conclude that 1) circulating CNP achieved by CNP infusion is regulated by NPR-C in vivo, 2) the pulmonary circulation is a possible site of CNP secretion, 3) the renal and peripheral circulations are sites of CNP clearance, and 4) NPR-C blockade potentiates the selective cardiovascular actions of CNP.

The endothelium is the production site of several potent vasoactive substances that modulate vascular tone and growth. The present study was undertaken to investigate the presence and secretion of atrial natriuretic peptide (ANP) immunoreactivity from vascular endothelial cells. ANP immunoreactivity was present in cultured human aortic endothelial cells by both immunohistochemical staining and radioimmunoassay. ANP immunoreactivity was also detectable in culture medium from human aortic endothelial cells in low picogram concentrations. These findings suggest that vascular endothelium is a site of ANP production and secretion of ANP. There was a differential distribution of ANP and endothelin-1 (ET-1), with a higher ANP concentration in cell extracts and a higher ET-1 concentration in cell culture media. Although ANP has been conceived as a circulating endocrine hormone, these findings are consistent with ANP functioning also as an autocrine and paracrine modulator in the regulation of vascular tone and growth.

Recent studies have found endothelin-1 (ET), a potent vasoconstrictor of endothelial cell origin, is increased in congestive heart failure (CHF) in plasma and correlates with increased atrial pressures. Additionally, it has been shown that, despite increased circulating ET concentrations in CHF, a decreased responsiveness to exogenous ET infusion exists in an experimental model of CHF induced by rapid pacing. The present study was designed to determine whether plasma ET would be increased in a model of low cardiac output congestive failure without elevated atrial pressures produced by thoracic inferior vena caval constriction (TIVCC). In addition, we sought to determine whether this model of low cardiac output would show a full vasoconstrictive response to exogenous ET infusion and whether atrial natriuretic factor (ANF) infused acutely to achieve pathophysiological concentrations would modulate the systemic and renal hemodynamic responses to exogenous ET. Dogs were studied in the anesthetized state at 8-9 days after the TIVCC or sham operation. Baseline ET levels were significantly increased in the TIVCC dogs (n = 14) compared with sham operated dogs (n = 6; 41.4 +/- 7.1 vs. 17.9 +/- 1.5 pg/ml, respectively; P less than 0.05). With exogenous ET infusion (5 ng.kg-1.min-1), an intact systemic and renal vasoconstrictor response in the TIVCC dogs was observed. ANF prevented the systemic vascular and arterial pressure responses to ET. However, the potent renal vasoconstricting action of ET was not prevented by ANF. These studies suggest that ET may play an important role in maintaining blood pressure in the setting of low cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)

The natriuretic peptides (NPs) B-type NP (BNP) and urodilatin (URO) exert renal protective properties via the particulate guanylyl cyclase A receptor (pGC-A). As a potential renal-enhancing strategy, we engineered a novel designer peptide that we call CRRL269. CRRL269 was investigated in human cell lines and in normal canines to define potential cardiorenal enhancing actions. The mechanism of its cardiorenal selective properties was also investigated. In vitro NP receptor activity was quantified with guanosine 3′,5′-cyclic monophosphate generation. In vivo effects were determined in normal canine acute infusion studies. We observed that CRRL269 demonstrated enhanced pGC-A activity in renal compared with nonrenal cell lines. CRRL269 exerted enhanced resistance to neprilysin compared with URO. Importantly, CRRL269 exhibited significant and greater increases in urinary sodium excretion and diuresis, with less blood pressure reduction, than BNP or URO in normal canines. CRRL269 retained potent renin-angiotensin-aldosterone system (RAAS) suppressing properties shared by URO and BNP. Also, CRRL269 exerted less arterial relaxation and higher cAMP cardiomyocytes generation than BNP. CRRL269 possessed superior renal and pGC-A activating properties compared with BNP or URO in vitro. CRRL269 exerted enhanced renal actions while suppressing RAAS in vivo and with less hypotension compared with URO or BNP. Together, our study suggests that CRRL269 is a promising innovative renal-enhancing drug, with favorable protective actions targeting cardiorenal disease states through the pGC-A receptor.

Background Cyclic guanosine monophosphate‐protein kinase G‐phosphodiesterase 5 signaling may be disturbed in heart failure ( HF ) with preserved ejection fraction, contributing to cardiac remodeling and dysfunction. The purpose of this study was to manipulate cyclic guanosine monophosphate signaling using the dipeptidyl‐peptidase 4 inhibitor saxagliptin and phosphodiesterase 5 inhibitor tadalafil. We hypothesized that preservation of cyclic guanosine monophosphate cGMP signaling would attenuate pathological cardiac remodeling and improve left ventricular ( LV ) function. Methods and Results We assessed LV hypertrophy and function at the organ and cellular level in aortic‐banded pigs. Concentric hypertrophy was equal in all groups, but LV collagen deposition was increased in only HF animals. Prevention of fibrotic remodeling by saxagliptin and tadalafil was correlated with neuropeptide Y plasma levels. Saxagliptin better preserved integrated LV systolic and diastolic function by maintaining normal LV chamber volumes and contractility (end‐systolic pressure‐volume relationship, preload recruitable SW ) while preventing changes to early/late diastolic longitudinal strain rate. Function was similar to the HF group in tadalafil‐treated animals including increased LV contractility, reduced chamber volume, and decreased longitudinal, circumferential, and radial mechanics. Saxagliptin and tadalafil prevented a negative cardiomyocyte shortening‐frequency relationship observed in HF animals. Saxagliptin increased phosphodiesterase 5 activity while tadalafil increased cyclic guanosine monophosphate levels; however, neither drug increased downstream PKG activity. Early mitochondrial dysfunction, evident as decreased calcium‐retention capacity and Complex II ‐dependent respiratory control, was present in both HF and tadalafil‐treated animals. Conclusions Both saxagliptin and tadalafil prevented increased LV collagen deposition in a manner related to the attenuation of increased plasma neuropeptide Y levels. Saxagliptin appears superior for treating heart failure with preserved ejection fraction, considering its comprehensive effects on integrated LV systolic and diastolic function.

Background We recently reported that normal aldosterone levels are associated with cardiovascular, renal, and metabolic disease in a sample of the US general community (Visit 1). For the current analyses we used the same cohort in a new 4‐year follow‐up study (Visit 2). Methods and Results We measured aldosterone at Visit 1 and analyzed its predictive role for new diseases at Visit 2 (n=1140). We measured aldosterone at Visit 2 and investigated its associations with disease at Visit 2 (n=1368). We analyzed aldosterone continuously and we also dichotomized the variable as whether subjects were in the third tertile versus second and first tertiles. As continuous variable at Visit 1, aldosterone predicted new onset hypertension ( HTN ) ( OR =1.36, CI =1.13–1.63, P =0.001), central obesity ( OR =1.36, CI =1.07–1.73, P =0.011), and use of lipid‐lowering drugs ( OR =1.25, CI =1.05–1.48, P =0.012) at Visit 2, after adjustment for age, sex, and body mass index. When in the third tertile (8.5–88.6 ng/dL), aldosterone predicted type 2 diabetes (T2 DM , OR =1.96, CI =1.03–3.70, P =0.039). At Visit 2, aldosterone remained associated with HTN , obesity, and chronic kidney disease ( CKD ), as reported for Visit 1. However, aldosterone was not associated with heart failure ( HF ) at Visit 1 and 2, nor was aldosterone a predictor of HF between visits. Conclusions Aldosterone predicts new HTN , central obesity, T2 DM , and use of lipid‐lowering drugs in the general community and remains associated with HTN , obesity, and CKD over 4 years. Aldosterone is not associated nor predicts HF . Further studies are warranted to evaluate aldosterone as therapeutic target in the general community.

1.A family of structurally related but genetically distinct natriuretic peptides exist which include atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) of myocardial cell origin and C-type natriuretic peptide (CNP) of endothelial and renal epithelial cell origin. All three exert actions via cGMP, with ANP and BNP functioning via the natriuretic peptide A receptor and CNP via the natriuretic peptide B receptor. 2.Circulating and urinary natriuretic peptides were determined in response to acute intravascular volume overload (AVO). Additionally, their functional role in cardiorenal regulation during AVO was investigated by utilizing the natriuretic peptide receptor antagonist HS-142-1. Control (n = 5) and study dogs (HS-142-1, n = 9) underwent AVO with normal saline equal to 10% of body weight over 1 ;h. Both groups demonstrated similar significant increases in right atrial pressure, pulmonary capillary wedge pressure, pulmonary artery pressure and cardiac output. Circulating ANP paralleled increases in right atrial pressure and pulmonary capillary wedge pressure, with no changes in plasma BNP or CNP. At peak AVO, urinary CNP excretion was increased compared with baseline (7.0±4.2 versus 62±8.0 ;pg/min, P< 0.05). 3.In the HS-142-1-treated group, plasma cGMP was decreased compared with the control group (9.6±1.1 to 5.0±1.2 ;pmol/ml, P< 0.05). A significant attenuation of natriuresis (566±91 versus 1241±198 ;μEq/min, P< 0.05) and diuresis (4.8±0.7 versus 10.1±2.0 ;ml/min, P< 0.05) was also observed at peak AVO in the HS-142-1 treated group. 4.These findings support differential and selective responses of the three natriuretic peptides to AVO, in which plasma ANP and urinary CNP are markers for AVO. Secondly, these studies confirm the role of ANP and CNP but not BNP in the natriuretic and diuretic response to acute volume overload.

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.