Pankow Kristin, Wang Yong, Gembardt Florian, Krause Eberhard, Sun Xiaoou, Krause Gerd, Schultheiss Heinz-Peter, Siems Wolf-Eberhard, Walther Thomas
Fachbereich Biologie, Chemie, Pharmazie, Freie Universität Berlin, Germany.
Circ Res. 2007 Oct 26;101(9):875-82. doi: 10.1161/CIRCRESAHA.107.153585. Epub 2007 Sep 6.
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 NEP-knockout 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.
利钠肽，如B型利钠肽（BNP），是重要的心脏保护激素，在钠排泄、水平衡和血压调节中发挥着重要作用。因此，这些肽的分解代谢成为临床研究的重点。在先前的研究中，我们发现与结构相关的心房利钠肽和C型利钠肽不同，BNP不会被中性内肽酶（NEP）水解。由于NEP基因敲除小鼠多个器官的膜制剂能快速降解BNP，本研究旨在鉴定负责这种快速清除的BNP分解肽酶。我们使用野生型和NEP基因敲除小鼠的肾膜以及几种肽酶抑制剂，监测了BNP的分解代谢并分析了其降解产物。我们鉴定出meprin A，一种在肾近端小管刷状缘表达的多聚体金属蛋白酶，它最初将小鼠BNP的N末端截短为mBNP7-32，这是一种具有保守生物活性的BNP代谢产物。因此，使用meprin抑制剂放线菌素进行的体内实验成功提高了大鼠血浆BNP浓度。我们进一步证明，mBNP7-32的产生是分解BNP的前提条件，并鉴定出NEP是降解截短型BNP的肽酶。因此，两种跨膜肽酶meprin A和NEP的协同、相继作用对于肾脏中BNP的快速失活至关重要。因此，抑制meprin A可能是提高循环BNP水平的有效手段。
