Lee, Candace Y.W.

Background: C-type natriuretic peptide (CNP), a 22-amino-acid peptide and a ligand of the natriuretic peptide receptor-B (NPR-B), exhibits venodilating, anti-fibrotic, and vascular-regenerating properties but limited renal actions. A Mayo-designed chimeric peptide, CD-NP, which consists of CNP and the C-terminus of Dendroaspis NP, was synthesized to test the hypothesis that CD-NP would possess CNP-like properties with an improved pharmacodynamic profile. Methods: Normal anesthetized dogs were given CD-NP 50 ng/kg/min (n = 10) or an equimolar dose of CNP 29.3 ng/kg/min (n = 9) i.v. for 75 min. Hemodynamic, renal, and hormonal data were obtained pre-infusion (pre-I), at 30 and 60 min I, and post-I, and were compared both within group vs pre-I (mean ± SE, P< 0.05*, < 0.01 † ) and between groups ( P < 0.05 ‡ , < 0.01 § , < 0.001 ¶ ). Plasma BNP was measured by radioimmunoassay. Results: CD-NP resulted in greater increases in plasma cGMP (7±.4 to 25±3 †¶ to 36±3 †¶ to 23±3 †¶ pmol/ml), urinary cGMP excretion (978±145, 3170±205 †¶ , 5919±616 †¶ , 3077±298 †¶ pmol/min) vs CNP (8±.8, 10±.6 † , 11±.7 † , 8±.5 pmol/ml; 976±110, 1104±115, 1317±103, 998±101 pmol/min, respectively). CD-NP also increased urine Na + excretion (19±4, 168±24 †§ , 237±26 †¶ , 96±12 † μEq/min), urine flow (0.2±.1, 1.3±.2 † , 1.8±.3 † , 0.8±.2 † ml/min), and GFR (37±2 ‡ , 48±3 † , 51±3 † , 53±4 † ml/min) vs CNP (36±12, 68±10, 85±26, 81±25 μEq/min; 0.4±.1, 0.9±.2, 1.2±.3*, 0.9±.3 ml/min; 52±5, 53±7, 50±4, 49±6 ml/min, respectively). CD-NP reduced PCWP (5.7±.7, 4.1±1*, 3.2±.7 † , 4.3±.8 mmHg), RAP (1.8±.4, 1.1±.4 † , 0.9±.5 †§ , 1.3±.5 § mmHg), PAP (12±.6, 10±.4*, 10±.6, 11±.7 mmHg) vs CNP (6±.6, 5±.8, 6±.8, 7±.9 † mmHg; 2.6±.3, 2.5±.3 to 2.9±.3 to 3.5±.5 † mmHg; 13±1, 12±1, 12±1, 13±1 mmHg, respectively). Mean blood pressure was unchanged in either group. CD-NP increased circulating BNP during infusion vs CNP (40±4 vs 18±2 pg/ml, P<0.001). Conclusion: This study demonstrates the successful transformation of CNP to a CNP-like peptide with enhanced natriuretic, diuretic, GFR-enhancing, and cardiac-unloading actions. CD-NP may also promote increases in plasma BNP which via the NPR-A receptor may contribute to its biological actions. The therapeutic potential of CD-NP in heart failure warrants further studies.

BACKGROUND: C-type natriuretic peptide (CNP) is a 22-amino-acid peptide produced mainly in the endothelium with potent cardiac unloading and modest blood pressure lowering actions, but minimal renal actions. Based on our previous knowledge, we recently fused a 6 aa sequence from BNP to the C-terminus and a 5 aa sequence from ANP to the N-terminus of CNP. This novel hybrid peptide, CBA-NP, has cardiac unloading actions and mild hypotensive effects similar to CNP. Importantly however, the N and C terminus alterations resulted in potent renal excretory actions. here we test the hypothesis that the 3 aa GSM 15–17 in the disulfide-ring mediate the vascular and hypotensive actions. We therefore mutated GSM 15–17 to REA 15–17 , which we named ABC-NP and compared its in vivo and in vitro actions to CBA-NP. METHODS: We determined the cardiorenal and humoral actions of intravenous bolus administration of CBA-NP (n=5) and ABC-NP (n=5) at 25 microgram/Kg in 2 separate group of normal anesthetized dogs. We also assessed the cGMP response of both peptides in human aortic endothelial cells (HAEC), human cardiac fibroblast (HCF) and isolated canine glomeruli. * p<0.05 RESULTS: IV bolus administration of CBA-NP and ABC-NP resulted in diuresis* and natriuresis*. There was a significant decrease in mean arterial blood (MAP) pressure with CBA-NP (126±6 to113±7 mmHg*) but no change with ABC-NP(126±8 to126±8 mmHg) . In addition, the reduction in pulmonary capillary wedge pressure (PCWP) and right atrial pressure (RAP) was significantly greater with CBA-NP as compared to ABC-NP. cGMP generation in HAEC and HCF was minimal with ABC-NP and was significantly higher with CBA-NP*. In contrast, cGMP generation was similar in isolated glomeruli between the two peptides. CONCLUSION: Our studies demonstrates that mutation of three amino acid (aa) residues within the CNP ring of CBA-NP from GSM 15–17 to REA alters the vascular but not the renal excretory properties. Hence by this strategic mutation within the ring of CBA-NP, we have designed a renal specific peptide ABC-NP resulting in new sequence specific functional information which can be used to design organ specific therapeutic peptides with unique properties tailored for a specific disease state.

Background CD‐NP is a novel chimeric natriuretic peptide (NP) consisting of the full‐length human C‐type natriuretic peptide (CNP), a NP receptor (NPR)‐B agonist, and the C‐terminus of Dendroaspis NP (DNP), a NPR‐A agonist. In the first‐in‐human clinical trial, CD‐NP activated plasma and urinary cGMP, the second messenger for the NPs, and increased Na + excretion in normal subjects. Here we report for the first time plasma aldosterone (ALDO) and angiotensin II (ANG II) levels. Methods In the double‐blind, PLB‐controlled phase of this trial, adults received CD‐NP 17.5 ng/kg/min (n = 6) or PLB (n = 4) i.v. for 4 hours. Plasma ALDO and ANG II were quantified by RIA. Data were analyzed by 2‐tailed paired t‐test and signed‐rank (S‐R) test (SAS v9). Results In subjects who received CD‐NP, plasma ALDO (mean±SD) decreased from a baseline of 21.9±2.7 to 9.5±3.2 ng/dL (P<0.001 t‐test, P<0.05 S‐R test) at the end of infusion. Plasma ANG II tended to decrease (29.2±5.2 to 23.0±3.5 ng/L, P=0.086 t‐test, P=0.69 S‐R test). In the PLB group, ALDO (20.3±4.2 to 13.6±4.5 ng/dL) and ANG II (23.3±2.2 to 19.8±8.2 ng/L) did not change. Conclusion CD‐NP suppressed plasma ALDO in normal subjects, consistent with NPR‐A activation by a novel NP with dual NPR‐A and NPR‐B activating properties. CD‐NP may be of therapeutic potential in disease states that are characterized by ALDO activation, such as in heart failure warranting further studies. Sources of funding: Mayo Foundation and Nile Therapeutics, Inc.

Background CBB‐NP is a novel fully humanized designer natriuretic peptide (NP) integrating the 17‐amino‐acid ring of human C‐type NP (CNP) with the N‐ and the C‐termini of human B‐type NP (BNP). CBB‐NP exerted natriuretic, diuretic, renal‐preserving and cardiac‐unloading actions in anesthetized dogs. In this investigation, we compared for the first time the cGMP stimulating actions of CBB‐NP vs human atrial NP (ANP), BNP and CNP in human aortic endothelial cells (HAEC). Methods CBB‐NP was synthesized (SPKMVQGSGCFGLKLDRIGSMSGLGCKVLRRH with a disulfide bond joining the C residues). HAEC were incubated with ANP, BNP, CNP or CBB‐NP for 10 min (10 −6 M). Cyclic GMP was quantified by RIA. Results CBB‐NP and CNP increased cGMP (pmol/mL) vs control (0.108±0.020 and 0.174±0.036 vs 0.001±0.001, P<0.01 and <0.001, respectively). CBB‐NP elicited a greater cGMP response vs ANP (0.027±0.002, P<0.05), whereas comparable responses were observed vs BNP and CNP. When the native NPs were compared, a greater cGMP stimulating response was detected with CNP vs ANP and BNP (P<0.001 and <0.01, respectively). Conclusions The novel designer NP, CBB‐NP, stimulates cGMP in human aortic endothelial cells to a comparable extent as compared to the native BNP and CNP. Moreover, its cGMP stimulating action is greater than that of ANP. The therapeutic potential of CBB‐NP in models of cardiovascular diseases warrants further investigation. Supported by NIH, HFSA and ASCPT

Background The 17‐amino‐acid (AA) ring of C‐type natriuretic peptide (CNP) is essential for activation of NP receptor (NPR)‐B and the 2 nd messenger cGMP. CNP induces minimal hypotension as NPR‐B is more abundantly found in veins vs arteries, but possesses limited renal properties. We designed a novel peptide fusing the CNP ring with AAs from ANP and BNP to test our hypothesis that this unique peptide, CAB‐NP, would exert enhanced renal actions without inducing excessive hypotension. Methods CAB‐NP was synthesized (SLRRSSCFGLKLDRIGSMSGLGCKVLRRH) and infused (21 pmol/kg/min iv) in 5 anesthetized dogs. GFR was assessed by inulin clearance. Mean±SE, P<.05*, <.01 † , BL vs 30 min infusion. Results CAB‐NP increased plasma cGMP (3.5±0.6 to 10.9±1 † pmol/mL), urinary cGMP excretion (980±96 to 4587±825* pmol/min), net renal cGMP generation (823±88 to 4091±824* pmol/min), urine flow (0.2±.03 to 1.2±.4* mL/min) and Na + excretion (19±7 to 191±55* †Eq/min). Proximal (85±3 to 68±1 † %) and distal (98±1 to 91±2 † %) FRNa were reduced; GFR was preserved (46±4 to 45±3 mL/min). MAP mildly decreased (121±4 to 111±5* mmHg). PCWP (6±1 to 4±1 † mmHg) and RAP (3±1 to 2±1* mmHg) were reduced. Plasma renin activity (11±1 to 2±0.3 † ng/mL/hr) and aldosterone (15±4 to 7±2* ng/dL) were suppressed. Conclusions CAB‐NP exerts favorable in vivo actions without excessively lowering BP. The therapeutic potential of CAB‐NP warrants further studies. Supported by the NIH, HFSA, and ASCPT.

Cenderitide is a novel designer natriuretic peptide (NP) composed of C‐type natriuretic peptide (CNP) fused to the C‐terminus of Dendroaspis natriuretic peptide (DNP). Cenderitide was engineered to coactivate the two NP receptors, particulate guanylyl cyclase (pGC)‐A and ‐B. The rationale for its design was to achieve the renal‐enhancing and antifibrotic properties of dual receptor activation, but without clinically significant hypotension. Here we report the first clinical trial on the safety, tolerability, and cyclic guanosine monophosphate (cGMP) activating properties of Cenderitide in subjects with stable heart failure (HF). Four‐hour infusion of Cenderitide was safe, well‐tolerated, and significantly increased plasma cGMP levels and urinary cGMP excretion without adverse effects with no change in blood pressure. Thus, Cenderitide has a favorable safety profile and expected pharmacological effects in stable human HF. Our results support further investigations of Cenderitide in HF as a potential future cGMP‐enhancing therapeutic strategy.

Designer natriuretic peptides (NPs) are novel hybrid peptides that are engineered from the native NPs through addition, deletion, or substitution of amino acid(s) with a goal toward optimization of pharmacological actions while minimizing undesirable effects. In this article, selected peptides that were designed in our laboratory are reviewed, and future directions for research and development of designer NPs are discussed.

Alternative RNA splicing may provide unique opportunities to identify drug targets and therapeutics. We identified an alternative spliced transcript for B-type natriuretic peptide (BNP) resulting from intronic retention. This transcript is present in failing human hearts and is reduced following mechanical unloading. The intron-retained transcript would generate a unique 34 amino acid (aa) carboxyl terminus while maintaining the remaining structure of native BNP. We generated antisera to this carboxyl terminus and identified immunoreactivity in failing human heart tissue. The alternatively spliced peptide (ASBNP) was synthesized and unlike BNP, failed to stimulate cGMP in vascular cells or vasorelax preconstricted arterial rings. This suggests that ASBNP may lack the dose-limiting effects of recombinant BNP. Given structural considerations, a carboxyl-terminal truncated form of ASBNP was generated (ASBNP.1) and was determined to retain the ability of BNP to stimulate cGMP in canine glomerular isolates and cultured human mesangial cells but lacked similar effects in vascular cells. In a canine-pacing model of heart failure, systemic infusion of ASBNP.1 did not alter mean arterial pressure but increased the glomerular filtration rate (GFR), suppressed plasma renin and angiotensin, while inducing natriuresis and diuresis. Consistent with its distinct in vivo effects, the activity of ASBNP.1 may not be explained through binding and activation of NPR-A or NPR-B. Thus, the biodesigner peptide ASBNP.1 enhances GFR associated with heart failure while lacking the vasoactive properties of BNP. These findings demonstrate that peptides with unique properties may be designed based on products of alternatively splicing.