Adrenomedullin in Heart Failure: Molecular Mechanism and Therapeutic Implication

Many neurohumoral factors play an important role in regulation of the cardiovascular system and in the pathophysiology of heart failure. Adrenomedullin (AM) is a potent long-lasting vasodilatory peptide that was discovered in acid extracts of human pheochromocytoma tissues. Both AM and its gene expression are widely distributed in the cardiovascular system, including the heart, vessels, and kidneys. AM co-localizes with its receptor components such as calcitonin receptor-like receptor (CRLR), receptor activity modifying protein (RAMP)2 and RAMP3 in the heart, vessels and kidneys, suggesting that it plays an important role in the regulation of cardiovascular function through an autocrine and/or paracrine mechanism. AM has inotropic action in vitro and in vivo and inhibits cardiac hypertrophy in myocytes as well as proliferation and collagen production in cardiac fibroblasts. These results suggest that AM functions as an antifibrotic, antihypertrophic and positive inotropic factor in the failing heart. In addition, AM has anti-apoptotic, angiogenic, anti-inflammatory and anti-oxidant effects. Several mechanisms such as cAMP/PKA, NO/cGMP, PI-3K/Akt and/or ERK are thought to mediate cellular AM signaling, suggesting that increased AM levels play a protective role in heart failure. Indeed, acute AM administration exerts beneficial vasodilatory, diuretic, natriuretic and inotropic effects on experimental and human heart failure. A recent pilot study has shown that AM has potential as a therapeutic drug in the clinical setting of acute decompensated heart failure.