Altered Cardiac Annexin mRNA and Protein Levels in the Left Ventricle of Patients with End-stage Heart Failure

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±0.16v2.79±0.20 A.U.C. unit, determined by laser densitometry, mean± ). In contrast, we found a 67% increase (2.32±0.27v3.88±0.29) in annexin II mRNA levels and a two-fold increase (1.00±0.24v2.21±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±0.22v4.88±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±0.67v3.61±0.32). Annexin V protein levels were also significantly increased (45%) in heart failure patients compared with normal (2.14±0.19v1.48±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.