Successive Action of Meprin A and Neprilysin Catabolizes B-Type Natriuretic Peptide

Abstract

Abstract-Natriuretic peptides such as B-type natriuretic peptide (BNP) are important cardioprotective hormones with essential functions in sodium excretion, water balance and blood pressure regulation. Consequently, the catabolism of these peptides is in the focus of clinical research. In previous studies, we demonstrated that BNP, in contrast to the structurally related atrial and C-type natriuretic peptide, was not hydrolyzed by neprilysin (NEP). Because membrane preparations of several organs of NEP-knockout mice rapidly degrade BNP, the aim of this study was to identify BNP-catabolizing peptidases responsible for this fast clearance. Using kidney membranes of wild-type and NEPknockout mice, as well as several peptidase inhibitors, we monitored the catabolism of BNP and analyzed its degradation products. We identified meprin A, a multimeric metalloprotease expressed in the brush borders of kidney proximal tubules, to initially truncate mouse BNP in the N terminus to mBNP7-32, a BNP metabolite with conserved biological activity. Consequently, in vivo experiments with the meprin inhibitor actinonin successfully elevated plasma BNP concentration in rats. We further demonstrated that the generation of mBNP7-32 is the prerequisite to catabolize BNP and identified NEP as the peptidase degrading the truncated BNP. Thus, the cooperative, successive action of the 2 transmembranal peptidases meprin A and NEP is crucial for rapid renal BNP inactivation. Therefore, the inhibition of meprin A could be a potent tool for increasing circulating BNP levels. Key Words: B-type natriuretic peptide Ⅲ natriuretic peptides Ⅲ meprin Ⅲ neutral endopeptidase Ⅲ peptide degradation N atriuretic peptides, as essential regulators of cardiovascular function in health and disease, are emerging as a focus of circulation research. Natriuretic peptides are naturally occurring cyclic peptide hormones with relevance to cardiovascular, endocrine, and renal homeostasis. They serve as functional antagonists of the renin-angiotensin system and counteract fibrosis, cardiac hypertrophy, and remodeling in the heart. 1-3 Atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) are secreted by cardiomyocytes in response to stretch or hormonal stimuli (angiotensin II, endothelin-1). 2 C-Type natriuretic peptide (CNP) is mainly produced by endothelium and brain and acts as a local regulator of vascular tone and remodeling. 4 The propeptides of the natriuretic peptides must be activated by limited proteolysis. Essentially involved in this activating process are serine peptidases, especially corin (S1 family) for ANP and furin (S8 family) for BNP and CNP. 5-7 All 3 natriuretic peptides share a highly conserved 17-aa ring structure formed by a Cys-Cys disulfide bridge. This intact ring system is essential for biological activity. 8 ANP and BNP mediate their functions via the natriuretic peptide receptor A (NPRA) and CNP via the natriuretic peptide receptor B (NPRB); both receptors are linked to a guanylyl cyclase, which leads to the production of...

Different Susceptibility of B-Type Natriuretic Peptide (BNP) and BNP Precursor (proBNP) to Cleavage by Neprilysin: The N-Terminal Part Does Matter

“…We explain the different susceptibilities of the assays to BNP neprilysin cleavage by the observation that different sites within the BNP sequence are not cleaved by neprilysin simultaneously, but instead are cleaved consecutively. As shown by our MS studies, the site Arg 17 -Ile 18 is attacked before the other sites, i.e., Lys 14 -Met 15 , Gly 23 -Leu 24 , and Val 28 -Leu 29 .…”

“…There are data showing that, in mice, meprin A, a protease expressed in kidney, may increase the effect of neprilysin by cleaving the first 6 N-terminal residues of mouse BNP (29 ). The simultaneous action of meprin A and neprilysin together on degradation of human BNP and proBNP appears also to be important to test, although the ability of meprin A to degrade human BNP is rather questionable (28 ).…”

Characterization of NT-proBNP in Human Urine

“…Renal tubular epithelial cells possess numerous peptidases, including enzymes that are known to degrade BNP (31 ). These include the membrane-bound Scatter plots indicate relationships between urinary NTproBNP index in heart failure subjects and left ventricular ejection fraction (B) and estimated glomerular filtration rate (GFR) (C).…”

The anti-inflammatory peptide Ac-SDKP is released from thymosin-β4 by renal meprin-α and prolyl oligopeptidase

“…Since meprin-␣ and POP are also present in other cells and tissues (8,17,46), the possibility that Ac-SDKP is released elsewhere cannot be excluded. However, actinonin has been suggested to inhibit the activity of MMP(s) and other enzyme(s) (18,32). To test the specificity of meprin-␣ for T␤4 hydrolysis, we obtained kidney tissue from meprin-␣ KO mice.…”