Abstract 1497: A Novel Designer Natriuretic Peptide, CAA-NP, as Assessed in Human Aortic Endothelial Cells: Evidence for Involvement of Natriuretic Peptide Receptor-A (NPR-A) and NPR-B in Cyclic GMP Response
Recent clinical studies have reported that human atrial natriuretic peptide (hANP), a NP receptor (NPR)-A agonist, attenuated cardiac ischemia reperfusion injury and remodeling. One limitation in the use of ANP is hypotension, which may reduce renal perfusion pressure (RPP) and function. We have designed a novel NP, named CAA-NP, by replacing the 17-amino-acid ring of hANP with that of hCNP, as the latter is known to activate NPR-B which is found in greater abundance in veins than in arteries, with in a lesser effect on BP. Here, we tested CAA-NP for the first time in human aortic endothelial cells (HAEC) and further assessed its effect on BP in vivo to test our hypotheses that CAA-NP would activate cGMP, the 2nd messenger for the NPs, without inducing hypotension and that CAA-NP may stimulate cGMP via both NPR-A and NPR-B. CAA-NP was synthesized (SLRRSSCFGLKLDRIGSMSGLGCNSFRY with a disulfide bond joining the C residues) and was infused iv (14 pmol/kg/min) in 5 normal anesthetized dogs. GFR was assessed by inulin clearance. Data are reported for pre-infusion (pre-I) and 30 min I (mean±SEM, P<0.05*, <0.01†). In vitro, HAEC were incubated with ANP, BNP, CNP or CAA-NP for 10 min (10−6 M) with or without a NPR-A antagonist (antag), A71915 (10−6 M) or an antibody (ab) against the ligand-binding domain of NPR-B (1:100). CAA-NP increased plasma cGMP (8.8 ±1.8 to 22.6±3.1† pmol/mL), urinary cGMP excretion (1010±152 to 3191±467† pmol/min) and net renal cGMP generation (692±128 to 2097±365† pmol/min). MAP (120±5 to 118±5 mmHg), RPP (117.4±5.2 to 116.9±4.8 mmHg) and GFR (37±2 to 49±4 mL/min) were preserved. In HAEC, the cGMP responses (pmol/mL) elicited by ANP, BNP, CNP and CAA-NP were 0.027±.002, 0.054±.003, 0.174±.036‡ and 0.251±.029‡§*, respectively (‡P<0.001 vs control 0.001±.001; §P<0.001 vs ANP and BNP; *P<0.05 vs CNP). With the NPR-A antag, the cGMP responses were 0.025±.001, 0.036±.004, 0.137±.024 and 0.172±.027*, respectively (*P<0.05 vs no antag). With the NPR-B ab, the responses were 0.021±.002, 0.044±.004, 0.082±.007† and 0.155±.016†, respectively (†P<0.01 vs no ab). CAA-NP stimulates cGMP in vitro and in vivo, and preserves RPP without lowering BP. Its cGMP-stimulating actions in vitro may involve both NPR-A and NPR-B.