Cell surface metallopeptidases involved in blood pressure regulation: structure, inhibition and clinical perspectives.

Arterial tone and water-electrolyte homeostasis are regulated by several peptides, including angiotensin II (AII), bradykinin (BK), atrial natriuretic peptide (ANP) and endothelins (ETs). Changing the concentrations of these peptides in the plasma, tissue, or urine by decreasing the levels of angiotensin II and endothelins and increasing BK and ANP concentrations, is one way of modulating the hemodynamic load. The metabolism of these peptides in essentially controlled by three enzymes, angiotensin-converting enzyme (ACE), neutral endopeptidase (NEP), and endothelin converting enzyme (ECE), which all belong to the group of zinc metallopeptidases. Inhibition of these peptidases by a single compound (a dual inhibitor) that inhibits at once angiotensin II formation and BK and ANP inactivation, causes vasodilatation with reduction in blood pressure with reduction in blood pressure and increases natriuresis. The design of these inhibitors has often be relied on structure-activity studies, based on active-site models derived from structural data on thermolysin (TLN). The results of a large number of pharmacological experiments and those issued from some clinical studies using selective or mixed inhibitors show that in spontaneously hypertensive rats, dual ACE/NEP inhibitors such as S21,402 produce dose-related decreases (-15 to -40 mmHg) in mean arterial pressure and reductions in left ventricular hypertrophy and cardiac size. These compounds produce also an increase in urinary levels of BK, ANP and cGMP associated with enhanced urine output and sodium excretion. Moreover inhibition of NEP appears to improve the cardio- and reno-protective effects resulting from ACE inhibition and could also reduce hypertrophy of vascular walls. Inhibition of ECE seems to result in a weak reduction in blood pressure, an effect which could be emphasized by using dual ECE/ACE or ECE/NEP inhibitors. According to these results mixed dual inhibitors could be of great interest for the treatment of severe hypertension and chronic heart failure. Potent triple inhibitors blocking ACE, NEP and ECE could also be developed.