An Unsuspected Property of Natriuretic Peptides

Abstract

Background Although natriuretic peptides are considered cardioprotective, clinical heart failure trials with recombinant BNP (nesiritide) failed to prove it. Unsuspected proadrenergic effects might oppose the anticipated benefits of natriuretic peptides. Methods and Results We investigated whether natriuretic peptides induce catecholamine release in isolated hearts, sympathetic nerve endings (cardiac synaptosomes) and PC12 cells bearing a sympathetic neuron phenotype. Perfusion of isolated guinea pig hearts with BNP elicited a 3-fold increase in norepinephrine release which doubled in ischemia/reperfusion conditions. BNP and ANP also released norepinephrine from cardiac synaptosomes and dopamine from nerve-growth-factor-differentiated PC12 cells in a concentration-dependent manner. These catecholamine-releasing effects were associated with an increase in intracellular calcium, and abolished by blockade of calcium channels and calcium transients, demonstrating a calcium-dependent exocytotic process. Activation of the guanylyl cyclase-cGMP-protein-kinase-G system with nitroprusside or membrane-permeant cGMP analogs mimicked the proexocytotic effect of natriuretic peptides, an action associated with an increase in intracellular cAMP and protein-kinase-A activity. cAMP enhancement resulted from an inhibition of phosphodiesterase-type-3-induced cAMP hydrolysis. Collectively, these findings indicate that, by inhibiting phosphodiesterase-type-3, natriuretic peptides sequentially enhance intracellular cAMP levels, protein-kinase-A activity, intracellular calcium and catecholamine exocytosis. Conclusions Our results show that natriuretic peptides, at concentrations likely to be reached at cardiac sympathetic nerve endings in advanced congestive heart failure, promote norepinephrine release via a protein-kinase-G-induced inhibition of phosphodiesterase-type-3-mediated cAMP hydrolysis. We propose that this proadrenergic action may counteract the beneficial cardiac and hemodynamic effects of natriuretic peptides, and thus explain the ineffectiveness of nesiritide as a cardiac failure medication.

C2238 Atrial Natriuretic Peptide Molecular Variant Is Associated With Endothelial Damage and Dysfunction Through Natriuretic Peptide Receptor C Signaling

“…13 In contrast, intracellular concentrations of cAMP were significantly reduced by C2238-αANP at all tested concentrations, consistent with NPR-C activation. Accordingly, reduction of cAMP levels on exposure to C2238-αANP was abrogated by inhibition of NPR-C, as well as by the Giα inhibitor PTX.…”

“…9,15 Physiological activation of NPR-C by the endogenous ligand CNP is crucial for maintaining endothelial integrity and promoting cell proliferation. 9,15 In contrast, supraphysiological activation of NPR-C by cANF [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] has been shown to exert antigrowth properties in vascular smooth muscle cells through inhibition of cAMP and Akt. 16,17 The remarkable difference in intracellular cAMP levels achieved after exposure of HUVEC to C2238-αANP versus wild-type T2238-αANP suggests that mutant ANP activates NPR-C in a unique, dysregulated manner that is detrimental.…”

“…We speculate that the NPR-C-dependent activation of NADPH oxidase could be the consequence of lower cAMP levels, which have been previously shown to activate NADPH oxidase. 22 Of note, previous evidence indicated that NPR-C activation by cANF [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] reduces ammonium chloride-induced ROS production in astrocytes, thus suggesting that the effect of NPR-C activation on ROS accumulation is dependent on the level of receptor activation, on cell type, and on different cellular-stress conditions. 23 C2238-αANP impaired acetylcholine-induced vascular responses in rat isolated resistance arteries, which was rescued by NPR-C pharmacological blockade.…”

“…The latter stimulated cAMP levels ( Figure 2B), consistently with previous evidence. 13 This observation indicates an activation of NPR-C by C2238-αANP, because active NPR-C leads to reduction of cAMP intracellular levels through activation of Giα and inhibition of adenylate cyclase.…”

“…cGMP and cAMP measurements were performed with specific enzyme immunoassay kits (Biotrak System, Amersham), as per the manufacturer's instructions. C2238-and T2238-αANP binding affinity at NPR-C was assessed through the evaluation of their ability to displace biotinylated cANF [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] from the NPR-C by fluorescence-activated cell sorter analysis. cANF [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] is a specific ligand for NPR-C.…”