Annexins are a unique family of membrane-associated, Ca2+ and phospholipid-binding proteins found in various tissues. Among the 12 isoforms, Annexin II, V and VI exist in heart tissue in the highest amounts. Annexin VI has been shown to affect intracellular Ca2+ cycling and contractility in isolated cardiomyocytes. Annexin V is present in both cardiomyocytes and non-myocyte cell types in the heart and may play a role in the regulation of cellular ion fluxes, organization and secretion, while the cardiac effects of annexin II are unclear. To identify changes in annexin II, V and VI isoforms that might occur in human heart failure, we measured mRNA and protein levels of these three annexins in transplanted left ventricular tissue of 12 patients with end-stage congestive heart failure due to coronary artery disease (CAD, n=6) or idiopathic dilated cardiomyopathy (DCM, n=6) who underwent cardiac transplantation. Normal heart tissue (C, n=6) was used as a control. Northern blot analyses showed a significant decrease (61%) in annexin VI mRNA levels in heart failure patients compared with controls (1.08+/-0.16 v 2.79+/-0.20 A.U.C. unit, determined by laser densitometry, mean+/-s.e.). In contrast, we found a 67% increase (2. 32+/-0.27 v 3.88+/-0.29) in annexin II mRNA levels and a two-fold increase (1.00+/-0.24 v 2.21+/-0.29) in annexin V mRNA levels in cardiomyopathic hearts as compared to normal hearts. Western blot analyses demonstrated a corresponding decrease (46.1%) in annexin VI protein levels in the heart failure group as compared to controls (2. 63+/-0.22 v 4.88+/-0.52), while annexin II protein levels showed a significant 40.7% increase in patients with heart failure compared to those in normal hearts (5.08+/-0.67 v 3.61+/-0.32). Annexin V protein levels were also significantly increased (45%) in heart failure patients compared with normal (2.14+/-0.19 v 1.48+/-0.11). No difference in either annexins II, V or VI mRNA and protein levels were found between CAD and DCM patients. We conclude that human end-stage heart failure is associated with a down regulation of annexin VI and up regulation of annexin II and V proteins. Coordinate changes were observed in steady-state mRNA levels. These results suggest that these annexin isoforms may contribute to the regulation of intracellular Ca2+ homeostasis in the cardiomyopathic heart.
Copyright 1998 Academic Press Limited