Haemodynamic, hormonal and renal actions of osteocrin in normal sheep.

Osteocrin (OSTN) is an endogenous protein sharing structural similarities with the natriuretic peptides [NPs; atrial (ANP), B-type (BNP) and C-type (CNP) NP], which are hormones known for their crucial role in maintaining pressure/volume homeostasis. Osteocrin competes with the NPs for binding to the receptor involved in their clearance (NPR-C). In the present study, having identified, for the first time, the major circulating form of OSTN in human and ovine plasma, we examined the integrated haemodynamic, endocrine and renal effects of vehicle-controlled incremental infusions of ovine proOSTN (83-133) and its metabolism in eight conscious normal sheep. Incremental i.v. doses of OSTN produced stepwise increases in circulating concentrations of the peptide, and its metabolic clearance rate was inversely proportional to the dose. Osteocrin increased plasma levels of ANP, BNP and CNP in a dose-dependent manner, together with concentrations of their intracellular second messenger, cGMP. Increases in plasma cGMP were associated with progressive reductions in arterial pressure and central venous pressure. Plasma cAMP, renin and aldosterone were unchanged. Despite significant increases in urinary cGMP levels, OSTN administration was not associated with natriuresis or diuresis in normal sheep. These results support OSTN as an endogenous ligand for NPR-C in regulating plasma concentrations of NPs and associated cGMP-mediated bioactivity. Collectively, our findings support a role for OSTN in maintaining cardiovascular homeostasis.

Interrogating the Role of miR-125b and Its 3'isomiRs in Protection against Hypoxia.

MiR-125b has therapeutic potential in the amelioration of myocardial ischemic injury. MicroRNA isomiRs, with either 5' or 3' addition or deletion of nucleotide(s), have been reported from next-generation sequencing data (NGS). However, due to technical challenges, validation and functional studies of isomiRs are few. In this study, we discovered using NGS, four 3'isomiRs of miR-125b, i.e., addition of A (adenosine), along with deletions of A, AG (guanosine) and AGU (uridine) from rat and sheep heart. These findings were validated using RT-qPCR. Comprehensive functional studies were carried out in the H9C2 hypoxia model. After miR-125b, isomiRs of Plus A, Trim A, AG and AGU mimic transfection, the H9C2 cells were subjected to hypoxic challenge. As assessed using cell viability, apoptosis, CCK-8 and LDH release, miR-125b and isomiRs were all protective against hypoxia. However, Plus A and Trim A were more effective than miR-125b, whilst Trim AG and Trim AGU had far weaker effects than miR-125b. Interestingly, both the gene regulation profile and apoptotic gene validation indicated a major overlap among miR-125b, Plus A and Trim A, whilst Trims AG and AGU revealed a different profile compared to miR-125b. Conclusions: miR-125b and its 3' isomiRs are expressed stably in the heart. miR-125b and isomiRs with addition or deletion of A might function concurrently and concordantly under specific physiological and pathophysiological conditions. In-depth understanding of isomiRs' metabolism and function will contribute to better miRNA therapeutic drug design.

Comparison of SPEED, S-Trap, and In-Solution-Based Sample Preparation Methods for Mass Spectrometry in Kidney Tissue and Plasma.

Mass spectrometry is a powerful technique for investigating renal pathologies and identifying biomarkers, and efficient protein extraction from kidney tissue is essential for bottom-up proteomic analyses. Detergent-based strategies aid cell lysis and protein solubilization but are poorly compatible with downstream protein digestion and liquid chromatography-coupled mass spectrometry, requiring additional purification and buffer-exchange steps. This study compares two well-established detergent-based methods for protein extraction (in-solution sodium deoxycholate (SDC); suspension trapping (S-Trap)) with the recently developed sample preparation by easy extraction and digestion (SPEED) method, which uses strong acid for denaturation. We compared the quantitative performance of each method using label-free mass spectrometry in both sheep kidney cortical tissue and plasma. In kidney tissue, SPEED quantified the most unique proteins (SPEED 1250; S-Trap 1202; SDC 1197). In plasma, S-Trap produced the most unique protein quantifications (S-Trap 150; SDC 148; SPEED 137). Protein quantifications were reproducible across biological replicates in both tissue (R2 = 0.85-0.90) and plasma (SPEED R2 = 0.84; SDC R2 = 0.76, S-Trap R2 = 0.65). Our data suggest SPEED as the optimal method for proteomic preparation in kidney tissue and S-Trap or SPEED as the optimal method for plasma, depending on whether a higher number of protein quantifications or greater reproducibility is desired.

Urocortins as biomarkers in cardiovascular disease.

The urocortins (Ucns) belong to the corticotropin-releasing factor (CRF) family of peptides and have multiple effects within the central nervous and the cardiovascular systems. With growing evidence indicating significant cardioprotective properties and cardiovascular actions of these peptides, the question arises as to whether the plasma profiles of the Ucns are altered in pathologic settings. While reports have shown conflicting results and findings have not been corroborated in multiple independent cohorts, it seems likely that plasma Ucn concentrations are elevated in multiple cardiovascular conditions. The degree of increase and accurate determination of circulating values of the Ucns requires further validation.

Identifying Candidate Protein Markers of Acute Kidney Injury in Acute Decompensated Heart Failure.

One-quarter of patients with acute decompensated heart failure (ADHF) experience acute kidney injury (AKI)-an abrupt reduction or loss of kidney function associated with increased long-term mortality. There is a critical need to identify early and real-time markers of AKI in ADHF; however, to date, no protein biomarkers have exhibited sufficient diagnostic or prognostic performance for widespread clinical uptake. We aimed to identify novel protein biomarkers of AKI associated with ADHF by quantifying changes in protein abundance in the kidneys that occur during ADHF development and recovery in an ovine model. Relative quantitative protein profiling was performed using sequential window acquisition of all theoretical fragment ion spectra-mass spectrometry (SWATH-MS) in kidney cortices from control sheep (n = 5), sheep with established rapid-pacing-induced ADHF (n = 8), and sheep after ~4 weeks recovery from ADHF (n = 7). Of the 790 proteins quantified, we identified 17 candidate kidney injury markers in ADHF, 1 potential kidney marker of ADHF recovery, and 2 potential markers of long-term renal impairment (differential abundance between groups of 1.2-2.6-fold, adjusted p < 0.05). Among these 20 candidate protein markers of kidney injury were 6 candidates supported by existing evidence and 14 novel candidates not previously implicated in AKI. Proteins of differential abundance were enriched in pro-inflammatory signalling pathways: glycoprotein VI (activated during ADHF development; adjusted p < 0.01) and acute phase response (repressed during recovery from ADHF; adjusted p < 0.01). New biomarkers for the early detection of AKI in ADHF may help us to evaluate effective treatment strategies to prevent mortality and improve outcomes for patients.

(Pro)renin Receptor Blockade Ameliorates Cardiac Injury and Remodeling and Improves Function After Myocardial Infarction.

BACKGROUND: The (pro)renin receptor [(P)RR] is implicated in the pathogenesis of cardiovascular disease. We investigated the effects of (P)RR blockade after myocardial infarction (MI) in a mouse coronary-ligation model. METHODS AND RESULTS: Mice underwent sham control surgeries (n = 8) or induction of MI followed by 28 days' treatment with a vehicle control (n = 8) or (P)RR antagonist (n = 8). Compared with sham control subjects, MI + vehicle mice demonstrated reduced left ventricular (LV) ejection fraction (LVEF: P < .001) and fractional shortening (P < .001), and increased LV end-systolic and -diastolic volumes (LVESV: P < .001; LVEDV: P < .001) 28 days after MI. In addition, MI decreased LV posterior wall and septal diameters (both P < .001), increased heart weight-body weight ratios (P < .05), LV collagen deposition, and cardiomyocyte diameter (both P < .001), and up-regulated collagen 1 (P < .01) and ß-myosin heavy chain (ß-MHC: P < .05) mRNA. Compared with MI + vehicle mice, (P)RR antagonism after MI reduced infarct size (P < .01), improved LVEF (P < .001), fractional shortening (P < .001), and stroke volume (P < .05), and decreased LVESV (P < .001) and LVEDV (P < .001). (P)RR antagonism also reversed MI-induced transmural thinning (P < .001) and reduced LV fibrosis (P < .01), cardiomyocyte size (P < .001), and ventricular collagen 1 (P < .01), ß-MHC (P = .06), transforming growth factor ß1 (P < .01), and angiotensin-converting enzyme (P < .05) expression. CONCLUSIONS: The present study found that (P)RR blockade after MI in mice ameliorates infarct size, cardiac fibrosis/hypertrophy, and cardiac dysfunction and identifies the receptor as a potential therapeutic target in this setting.

Chronic urocortin 2 administration improves cardiac function and ameliorates cardiac remodeling after experimental myocardial infarction.

The impact of chronic urocortin 2 (Ucn2) treatment after myocardial infarction (MI) has not previously been investigated. In this study, we examined the effects of 30-day Ucn2 administration (415 µg·kg·d SC per day) in mice post-MI. Compared with surgical sham + vehicle controls (n = 10), MI + vehicle animals (n = 10) after 30 days demonstrated decreased ejection fraction (75.6 ± 1.2 vs. 43.6% ± 0.8%, P < 0.001) and fractional shortening (38.20 ± 0.83 vs. 18.4% ± 0.54%, P < 0.001) in association with increased heart weight-to-body weight ratio (4.57 ± 0.25 vs. 5.29 ± 0.18, P < 0.01), left ventricular (LV) mass (91 ± 7 vs. 126 ± 8 mg, P < 0.01), LV internal diameters at both systole (1.91 ± 0.14 vs. 3.45 ± 0.09 mm, P < 0.001) and diastole (3.14 ± 0.15 vs. 4.25 ± 0.10 mm, P < 0.001), LV end systolic volumes (0.02 ± 0.01 vs. 0.11 ± 0.01 mL, P < 0.001), and ventricular collagen 1 and ß-myosin heavy chain gene expression. Compared with MI + vehicle mice, MI + Ucn2 animals (n = 10) exhibited significantly reduced infarct size (4.00 ± 0.39 vs. 1.83 ± 0.44 mm, P < 0.01), heart weight-to-body weight ratio (4.75 ± 0.19, P = 0.06), LV mass (101 ± 6 mg, P < 0.01), LV internal diameters (systole 2.61 ± 0.09 mm, P < 0.001; diastole 3.78 ± 0.09 mm, P < 0.001), and end systolic volumes (0.14 ± 0.02 mL, P < 0.01) in conjunction with improved ejection fraction (65.2% ± 0.9%, P < 0.001) and fractional shortening (18.4 ± 0.5 vs. 30.5% ± 0.5%, P < 0.001). Ucn2 treatment also decreased collagen 1 and ß-myosin heavy chain expression. In conclusion, chronic Ucn2 treatment significantly improves cardiovascular function and attenuates cardiac injury and remodeling in experimental MI.

Thoracic impedance measures tissue characteristics in the vicinity of the electrodes, not intervening lung water: implications for heart failure monitoring.

The rationale for intrathoracic impedance (Z) detection of worsening heart failure (HF) presupposes that changes in Z reflect changes in pulmonary congestion, but is confounded by poor specificity in clinical trials. We therefore tested the hypothesis that Z is primarily affected by tissue/water content in proximity to electrodes rather than by lung water distribution between electrodes through the use of a new computational model for deriving the near-field impedance contributions from the various electrodes. Six sheep were implanted with a left atrial pressure (LAP) monitor and a cardiac resynchronization therapy device which measured Z from six vectors comprising of five electrodes. The vector-based Z was modelled as the summation of the near-field impedances of the two electrodes forming the vector. During volume expansion an acute increase in LAP resulted in simultaneous reductions in the near-field impedances of the intra-cardiac electrodes, while the subcutaneous electrode showed several hours of lag (all p<0.001). In contrast, during the simulated formation of device-pocket edema (induced by fluid injection) the near-field impedance of the subcutaneous electrode had an instantaneous response, while the intra-cardiac electrodes had a minimal inconsistent response. This study suggests that the primary contribution to the vector based Z is from the tissue/water in proximity to the individual electrodes. This novel finding may help explain the limited utility of Z for detecting worsening HF.

Low-dose B-type natriuretic peptide raises cardiac sympathetic nerve activity in sheep.

The reported effects of atrial natriuretic peptide (ANP) on sympathetic nerve activity (SNA) are variable, dependent on concomitant hemodynamic actions, and likely to be regionally differentiated. There are few reports of the effect of B-type natriuretic peptide (BNP) on SNA and none have measured cardiac SNA (CSNA) by direct microneurography. We measured the effects of low-dose ANP and BNP (2.4 pmol·kg(-1)·min(-1) infused for 120 min) on CSNA and hemodynamics in conscious sheep (n = 8). While there was a trend for mean arterial pressure and cardiac output to fall with both ANP and BNP, changes were not significant compared with vehicle control. However, BNP did significantly reduce systolic arterial (97 ± 4.2 vs. 107 ± 6.8 mmHg during control; P = 0.043) and pulse pressures (0.047) and increase heart rate (110 ± 6.7 vs. 96 ± 7.3 beats/min; P = 0.044). Trends for these hemodynamic parameters to change with ANP did not achieve statistical significance. ANP also had no significant effect on any CSNA parameters measured. In contrast, BNP induced a rise in both CSNA burst frequency (∼20 bursts/min higher than control, P = 0.011) and burst area (∼40% higher than control, P = 0.013). BNP-induced rises in burst incidence (bursts/100 beats), and burst area per 100 beats, however, were not significant. In conclusion, BNP infused at low doses that only had subtle effects on hemodynamics increased CSNA burst frequency and burst are per minute. This increase in CSNA may in large part be secondary to an increase in heart rate as CSNA burst incidence and burst area per 100 beats were not significantly increased. This study provides no evidence for inhibition of CSNA by natriuretic peptides.

Combined Inhibition of Phosphodiesterase-5 and -9 in Experimental Heart Failure.

BACKGROUND: Intracellular second messenger cyclic guanosine monophosphate (cGMP) mediates bioactivity of the natriuretic peptides and nitric oxide, and is key to circulatory homeostasis and protection against cardiovascular disease. Inhibition of cGMP-degrading phosphodiesterases (PDEs) PDE5 and PDE9 are emerging as pharmacological targets in heart failure (HF). OBJECTIVES: The present study investigated dual enhancement of cGMP in experimental HF by combining inhibition of PDE-5 (P5-I) and PDE-9 (P9-I). METHODS: Eight sheep with pacing-induced HF received on separate days intravenous P5-I (sildenafil), P9-I (PF-04749982), P5-I+P9-I, and vehicle control, in counterbalanced order. RESULTS: Compared with control, separate P5-I and P9-I significantly increased circulating cGMP concentrations in association with reductions in mean arterial pressure (MAP), left atrial pressure (LAP), and pulmonary arterial pressure (PAP), with effects of P5-I on cGMP, MAP, and PAP greater than those of P9-I. Only P5-I decreased pulmonary vascular resistance. Combination P5-I+P9-I further reduced MAP, LAP, and PAP relative to inhibition of either phosphodiesterase alone. P9-I and, especially, P5-I elevated urinary cGMP levels relative to control. However, whereas inhibition of either enzyme increased urine creatinine excretion and clearance, only P9-I induced a significant diuresis and natriuresis. Combined P5-I+P9-I further elevated urine cGMP with concomitant increases in urine volume, sodium and creatinine excretion, and clearance similar to P9-I alone, despite the greater MAP reductions induced by combination treatment. CONCLUSIONS: Combined P5-I+P9-I amalgamated the superior renal effects of P9-I and pulmonary effects of P5-1, while concurrently further reducing cardiac preload and afterload. These findings support combination P5-I+P9-I as a therapeutic strategy in HF.

Augmentation of Natriuretic Peptide Bioactivity via Combined Inhibition of Neprilysin and Phosphodiesterase-9 in Heart Failure.

BACKGROUND: The natriuretic peptides (NPs) are potent natriuretic/diuretic and vasodilatory factors, and augmentation of their levels or signaling via inhibition of the enzymes neprilysin (NEP) and phosphodiesterase 9 (PDE9), respectively, has beneficial actions in heart failure (HF). OBJECTIVES: The authors investigated dual enhancement of NP bioactivity by combining PDE9 inhibition and NEP inhibition in HF using an ovine model. METHODS: Eight sheep with pacing-induced HF received on 4 separate days intravenous PDE9 inhibition (PF-04749982), NEP inhibition (SCH-32615), PDE9 inhibition + NEP inhibition (PI+NI), and vehicle control treatment. RESULTS: Compared with the control treatment, NEP inhibition significantly increased plasma NP concentrations with a corresponding rise in second messenger cyclic guanosine monophosphate (cGMP), whereas PDE9 inhibition increased circulating cGMP with a negligible effect on NP levels. Combined PI+NI elevated plasma NPs to an extent comparable to that seen with NEP inhibition alone but further increased cGMP, resulting in a rise in the cGMP-to-NP ratio. All active treatments reduced mean arterial pressure, left atrial pressure, pulmonary arterial pressure, and peripheral resistance, with combined PI+NI further reducing mean arterial pressure and left atrial pressure relative to either inhibitor separately. Active treatments increased urine volume and sodium, potassium and creatinine excretion, and creatinine clearance, in association with rises in urine cGMP levels. PI+NI induced a significantly greater natriuresis and increase in urinary cGMP relative to either inhibitor singly. CONCLUSIONS: The present study demonstrates for the first time that combined PI+NI has additional beneficial hemodynamic and renal effects when compared with either PDE9 inhibition or NEP inhibition alone. The superior efficacy of this 2-pronged augmentation of NP bioactivity supports PI+NI as a potential therapeutic strategy for HF.

Haemodynamic, endocrine and renal actions of adrenomedullin 5 in an ovine model of heart failure.

AM5 (adrenomedullin 5), a newly described member of the CGRP (calcitonin gene-related peptide) family, is reported to play a role in normal cardiovascular physiology. The effects of AM5 in HF (heart failure), however, have not been investigated. In the present study, we intravenously infused two incremental doses of AM5 (10 and 100 ng/min per kg of body weight each for 90 min) into eight sheep with pacing-induced HF. Compared with time-matched vehicle control infusions, AM5 produced progressive and dose-dependent increases in left ventricular dP/dt(max) [LD (low dose), +56 mmHg/s and HD (high dose), +152 mmHg/s] and cardiac output (+0.83 l/min and +1.81 l/min), together with decrements in calculated total peripheral resistance (-9.4 mmHg/min per litre and -14.7 mmHg/min per litre), mean arterial pressure (-2.8 mmHg and -8.4 mmHg) and LAP (left atrial pressure; -2.6 mmHg and -5.6 mmHg) (all P<0.001). HD AM5 significantly raised PRA (plasma renin activity) (3.5-fold increment, P<0.001), whereas plasma aldosterone levels were unchanged over the intra-infusion period and actually fell in the post-infusion period (70% decrement, P<0.01), resulting in a marked decrease in the aldosterone/PRA ratio (P<0.01). Despite falls in LAP, plasma atrial natriuretic peptide and B-type natriuretic peptide concentrations were maintained relative to controls. AM5 infusion also induced significant increases in urine volume (HD 2-fold increment, P<0.05) and urine sodium (2.7-fold increment, P<0.01), potassium (1.7-fold increment, P<0.05) and creatinine (1.4-fold increment, P<0.05) excretion and creatinine clearance (60% increment, P<0.05). In conclusion, AM5 has significant haemodynamic, endocrine and renal actions in experimental HF likely to be protective and compensatory in this setting. These results suggest that AM5 may have potential as a therapeutic agent in human HF.

Monitoring of heart failure: comparison of left atrial pressure with intrathoracic impedance and natriuretic peptide measurements in an experimental model of ovine heart failure.

Monitoring of HF (heart failure) with intracardiac pressure, intrathoracic impedance and/or natriuretic peptide levels has been advocated. We aimed to investigate possible differences in the response patterns of each of these monitoring modalities during HF decompensation that may have an impact on the potential for early therapeutic intervention. Six sheep were implanted with a LAP (left atrial pressure) sensor and a CRT-D (cardiac resynchronization therapy defibrillator) capable of monitoring impedance along six lead configuration vectors. An estimate of ALAP (LAP from admittance) was determined by linear regression. HF was induced by rapid ventricular pacing at 180 and 220 bpm (beats/min) for a week each, followed by a third week with daily pacing suspensions for increasing durations (1-5 h). Incremental pacing induced progressively severe HF reflected in increases in LAP (5.9 ± 0.4 to 24.5 ± 1.6 mmHg) and plasma atrial (20 ± 3 to 197 ± 36 pmol/l) and B-type natriuretic peptide (3.7 ± 0.7 to 32.7 ± 5.4 pmol/l) (all P<0.001) levels. All impedance vectors decreased in proportion to HF severity (all P<0.001), with the LVring (left ventricular)-case vector correlating best with LAP (r2=0.63, P<0.001). Natriuretic peptides closely paralleled rapid acute changes in LAP during alterations in pacing (P<0.001), whereas impedance changes were delayed relative to LAP. ALAP exhibited good agreement with LAP. In summary, impedance measured with an LV lead correlates significantly with changes in LAP, but exhibits a delayed response to acute alterations. Natriuretic peptides respond rapidly to acute LAP changes. Direct LAP, impedance and natriuretic peptide measurements all show promise as early indicators of worsening HF. ALAP provides an estimate of LAP that may be clinically useful.

Hemodynamic, hormonal, and renal actions of adrenomedullin-5 in normal conscious sheep.

Although blood pressure effects have been reported for adrenomedullin 5 (AM-5), a newly identified member of the calcitonin gene-related peptide superfamily, little is known about other biological actions. We report the integrated hemodynamic, hormonal, and renal actions of AM-5 (10 and 100 ng·kg·min each for 90 minutes) in normal conscious sheep. AM-5 reduced the mean arterial pressure by 12 mm Hg at the end of the high dose (P < 0.001) in association with dose-dependent increments in the heart rate (40 beats/min--high dose, P < 0.001) and cardiac output (50%-high dose, P < 0.001) and dose-dependent falls in calculated total peripheral resistance (P < 0.001). Plasma renin activity (4-fold increment, P < 0.001), aldosterone (2-fold increment, P = 0.014), and cyclic adenosine monophosphate (50% increment, P < 0.001) all rose in response to high dose AM-5. Urine volume and sodium excretion were unchanged. In conclusion, it is observed that intravenous infusions of AM-5 administered to normal conscious sheep induced significant hemodynamic actions including reduced mean arterial pressure and calculated total peripheral resistance and increased heart rate and cardiac output. Concurrently, AM-5 activated plasma cyclic adenosine monophosphate, plasma renin activity, and aldosterone. These actions are similar to those previously reported for AM and AM-2. Thus, AM-5 may be an another important regulator of volume and pressure homeostasis and may play a role in the pathophysiology of heart disease.

Urocortin 3 inhibits cardiac sympathetic nerve activity in conscious sheep.

There is an increasing body of evidence suggesting a role for the urocortin (Ucn) peptides in blood pressure regulation and in the pathophysiology of cardiovascular disease. Both Ucn1 and Ucn2 have recently been shown to inhibit cardiac sympathetic nerve activity (CSNA) in sheep. However, there are few studies reporting the effects of Ucn3 on the sympathetic nervous system. Hence, this study performed in normal conscious sheep examines the effects of Ucn3 on CSNA. Intravenous Ucn3 (administered at doses of 25 and 100 µg) caused transient falls in arterial pressure (P = 0.025), more prolonged rises in heart rate (P < 0.001), and falls in stroke volume (P < 0.001) and peripheral resistance (P = 0.018). CSNA, measured as burst area and burst incidence, fell in a dose-dependent manner after Ucn3 bolus (all P < 0.001). CSNA burst frequency tended to be reduced after high-dose Ucn3. Ucn3 had no significant effect on plasma catecholamine levels. In conclusion, this study reports for the first time that Ucn3 induces potent inhibition of sympathetic traffic directed toward the heart. This provides further support for a role for Ucn3 in pressure and volume homeostasis and suggests that further investigation of potential therapeutic applications for Ucn3 in cardiovascular disease is warranted.

Natriuretic peptide analogues with distinct vasodilatory or renal activity: integrated effects in health and experimental heart failure.

AIMS: Management of acute decompensated heart failure (ADHF) requires disparate treatments depending on the state of systemic/peripheral perfusion and the presence/absence of expanded body-fluid volumes. There is an unmet need for therapeutics that differentially treat each aspect. Atrial natriuretic peptide (ANP) plays an important role in blood pressure and volume regulation. We investigate for the first time the integrated haemodynamic, endocrine and renal effects of human ANP analogues, modified for exclusive vasodilatory (ANP-DRD) or diuretic (ANP-DGD) activities, in normal health and experimental ADHF. METHODS AND RESULTS: We compared the effects of incremental infusions of ANP analogues ANP-DRD and ANP-DGD with native ANP, in normal (n = 8) and ADHF (n = 8) sheep. ANP-DRD administration increased plasma cyclic guanosine monophosphate (cGMP) in association with dose-dependent reductions in arterial pressure in normal and heart failure (HF) sheep similarly to ANP responses. In contrast to ANP, which in HF produced a diuresis/natriuresis, this analogue was without significant renal effect. Conversely, ANP-DGD induced marked stepwise increases in urinary cGMP, urine volume, and sodium excretion in HF comparable to ANP, but without accompanying vasodilatory effects. All peptides increased packed cell volume relative to control in both states, and in HF, decreased left atrial pressure. In response to ANP-DRD-induced blood pressure reductions, plasma renin activity rose compared to control only during the high dose in normals, and not at all in HF-suggesting relative renin inhibition, with no increase in aldosterone in either state, whereas renin and aldosterone were both significantly reduced by ANP-DGD in HF. CONCLUSION: These ANP analogues exhibit distinct vasodilatory (ANP-DRD) and diuretic/natriuretic (ANP-DGD) activities, and therefore have the potential to provide precision therapy for ADHF patients with differing pathophysiological derangement of pressure-volume homeostasis.

Acute Decompensated Heart Failure and the Kidney: Physiological, Histological and Transcriptomic Responses to Development and Recovery.

BACKGROUND Acute decompensated heart failure (ADHF) is associated with deterioration in renal function-an important risk factor for poor outcomes. Whether ADHF results in permanent kidney damage/dysfunction is unknown. METHODS AND RESULTS We investigated for the first time the renal responses to the development of, and recovery from, ADHF using an ovine model. ADHF development induced pronounced hemodynamic changes, neurohormonal activation, and decline in renal function, including decreased urine, sodium and urea excretion, and creatinine clearance. Following ADHF recovery (25 days), creatinine clearance reductions persisted. Kidney biopsies taken during ADHF and following recovery showed widespread mesangial cell prominence, early mild acute tubular injury, and medullary/interstitial fibrosis. Renal transcriptomes identified altered expression of 270 genes following ADHF development and 631 genes following recovery. A total of 47 genes remained altered post-recovery. Pathway analysis suggested gene expression changes, driven by a network of inflammatory cytokines centered on IL-1ß (interleukin 1ß), lead to repression of reno-protective eNOS (endothelial nitric oxide synthase) signaling during ADHF development, and following recovery, activation of glomerulosclerosis and reno-protective pathways and repression of proinflammatory/fibrotic pathways. A total of 31 dysregulated genes encoding proteins detectable in urine, serum, and plasma identified potential candidate markers for kidney repair (including CNGA3 [cyclic nucleotide gated channel subunit alpha 3] and OIT3 [oncoprotein induced transcript 3]) or long-term renal impairment in ADHF (including ACTG2 [actin gamma 2, smooth muscle] and ANGPTL4 [angiopoietin like 4]). CONCLUSIONS In an ovine model, we provide the first direct evidence that an episode of ADHF leads to an immediate decline in kidney function that failed to fully resolve after ≈4 weeks and is associated with persistent functional/structural kidney injury. We identified molecular pathways underlying kidney injury and repair in ADHF and highlighted 31 novel candidate biomarkers for acute kidney injury in this setting.

Cardiovascular effects of DWORF (dwarf open reading frame) peptide in normal and ischaemia/reperfused isolated rat hearts.

The novel peptide dwarf open reading frame (DWORF), highly conserved across species and expressed almost exclusively in cardiac ventricular muscle, may play a role in cardiac physiology and pathophysiology. The effect of direct administration of DWORF in the intact heart has not previously been examined. Accordingly, we investigated the cardiac effects of DWORF (1-30 nM) in normal isolated perfused rat hearts and hearts undergoing ischaemia/reperfusion (I/R) injury, and evaluated potential mechanisms of action. Exogenous DWORF at the top dose (30 nM) increased perfusion pressure (PP) in normal hearts, which indicates coronary vasoconstriction; and during post-ischaemic reperfusion, DWORF increased PP in a dose-dependent manner. In I/R hearts, DWORF at the top dose also increased left ventricular end-diastolic pressure and maximum and minimum derivatives of left ventricular pressure noted dP/dt(max) and dP/dt(min), respectively, without affecting developed pressure (DP). Co-infusion of DWORF with Diltiazem, an l-type Ca2+ channel blocker (1µM), in I/R hearts attenuated the falls in DP, dP/dt(max) and dP/dt(min) observed with Diltiazem alone. DWORF co-infusion with both Diltiazem and Y27632 (1µM) (a Rho-Kinase inhibitor) reversed the coronary vasodilator effect of the inhibitors administered alone. In conclusion, we provide the first evidence that DWORF has coronary vasoconstrictor actions in normal hearts and when administered during reperfusion in an ex-vivo model of cardiac I/R injury, and also exhibits positive cardiac inotropic activity in the latter setting. DWORF's effect on ventricular contractile function appears to be dependent on the l-type Ca2+ channel, whereas Rho-Kinase activity may be related to the coronary vasoconstrictor effects of DWORF.

Large Animal Models of Heart Failure: Reduced vs. Preserved Ejection Fraction.

Heart failure (HF) is the final common end point of multiple metabolic and cardiovascular diseases and imposes a significant health care burden worldwide. Despite significant improvements in clinical management and outcomes, morbidity and mortality remain high and there remains an indisputable need for improved treatment options. The pathophysiology of HF is complex and covers a spectrum of clinical presentations from HF with reduced ejection fraction (HFrEF) (≤40% EF) through to HF with preserved EF (HFpEF), with HFpEF patients demonstrating a reduced ability of the heart to relax despite an EF maintained above 50%. Prior to the last decade, the majority of clinical trials and animal models addressed HFrEF. Despite growing efforts recently to understand underlying mechanisms of HFpEF and find effective therapies for its treatment, clinical trials in patients with HFpEF have failed to demonstrate improvements in mortality. A significant obstacle to therapeutic innovation in HFpEF is the absence of preclinical models including large animal models which, unlike rodents, permit detailed instrumentation and extensive imaging and sampling protocols. Although several large animal models of HFpEF have been reported, none fulfil all the features present in human disease and few demonstrate progression to frank decompensated HF. This review summarizes well-established models of HFrEF in pigs, dogs and sheep and discusses attempts to date to model HFpEF in these species.

Adrenomedullin 2 increases cardiac sympathetic nerve activity in parallel to heart rate in normal conscious sheep.

Both adrenomedullin 2 (AM2) and sympathetic nerve activity (SNA) have been shown to be involved in regulating cardiovascular activity, but whether any interaction between these two systems exists remains to be determined. In this study, we examine the effects of intravenous AM2 infusions on SNA directed toward the heart (cardiac SNA (CSNA)) in healthy sheep studied in the conscious state. In response to AM2, arterial pressure was reduced (P = 0.005) with both heart rate (P < 0.001) and cardiac output (P < 0.001) increased compared with vehicle control response. CSNA burst frequency (bursts/min) and burst area/min both increased during infusion of AM2 (both P < 0.001). However, correcting CSNA indices for concurrent heart rate changes resulted in CSNA burst incidence (bursts/100 beats) and burst area incidence (area/100 beats) being not significantly different between AM2 and control treatments. There were no significant differences demonstrated in plasma epinephrine or norepinephrine levels between the two study days. In conclusion, AM2 administered systemically to normal conscious sheep increases both CSNA and heart rate. However, correction for heart rate responses abrogates the rise in CSNA. It remains unclear whether AM2's primary effect is to act via the central nervous system to directly stimulate CSNA with resultant increase in heart rate, or to induce a rise in heart rate by other mechanisms.