Effect of MR blockade on collagen formation and cardiovascular disease with a specific emphasis on heart failure.

Collagen is the major extracellular matrix protein in the heart and represents a crucial target for anti-remodeling and cardioprotective therapy. Collagen quantity and quality have been shown to be regulated under various physiological and pathologic conditions. Excessive deposition of collagen, leading to cardiac fibrosis, is a major determinant of cardiac dysfunction and arrhythmogenecity associated with sudden death. Serological markers of collagen turnover were proven as a noninvasive reliable tool for monitoring from a distance cardiac tissue repair and fibrosis, both in experimental and clinical conditions. Some markers of collagen synthesis and degradation were shown to have a prognostic significance in myocardial infarction, cardiomyopathy and heart failure, and were reported as independent predictors of mortality. Aldosterone represents the end-product of the renin angiotensin aldosterone system and may play a role in cardiac collagen deposition independent of its effect on blood pressure. Production of aldosterone is mainly regulated by angiotensin II and is activated in the failing human ventricle in proportion to heart failure severity. Circulating or locally produced aldosterone stimulates fibrillar collagen accumulation in the heart directly via mineralocorticoid receptors or, indirectly, modifying angiotensine II receptors number and/or function. The use of mineralocorticoid receptor antagonists counters collagen deposition, even when used on top of classical RAAS inhibitors, such as ACE inhibitors and angiotensine II receptor blockers. There is now accumulating evidence from experimental and clinical studies showing antifibrotic and cardioprotective effect for aldosterone antagonists, spironolactone and eplerenone. In chronic heart failure and post myocardial infarction patients, aldosterone receptor blockade benefit was associated with decreased serum levels of collagen synthesis marker PIIINP (procollagen type III amino-terminal peptide), without affecting collagen degradation. Understanding various autocrine/paracrine mechanisms involved in extracellular matrix remodeling in heart failure represents a major challenge, essential for developing new cardioreparative and cardioprotective strategies.