Abstract 230: Advanced Glycation Endproducts (AGEs) Directly Damage the Myocardium by Reducing Calcium Transients via NADPH Oxidase
Cardiomyopathy is one of the commonest causes of morbidity and mortality in patients with diabetes, but it is unknown what the mechanisms of direct injury to the myocardium are that occur in addition to macro- and microvascular disease. Advanced glycation end products (AGEs) have been shown to play a central role in endothelial dysfunction and other vascular damage, but little is known regarding their direct effects on the myocardium. We therefore investigated the effect of AGEs on cardiomyocytes. Western blot analysis demonstrated that AGE receptors (RAGE) were strongly expressed in adult rat and mouse cardiac myocytes as well as neonatal rat cardiomyocytes (NRCM). Incubation of NRCM with glycated albumin (AGE) over 24 hrs was associated with a dose dependant reduction in calcium transient amplitude. At 1g/L AGE (a typical concentration in diabetics), a 52 ± 12% reduction in cytosolic Ca2+ transient amplitude (n=12, P<0.01) was observed. After Thapsigargin (Inhibitor of Sarcoplasmic Reticulum Ca2+ ATPase, SERCA), the transient was similar with or without AGE demonstrating that SERCA is the target. The NAPDH oxidase inhibitor apocyanin (100μM), an inhibitor of reactive oxygen species (ROS) formation completely abated the effect of AGE on calcium. This data demonstrate the presence and functionality of AGE receptors in rat and mouse myocardium. RAGE activation severely perturbs cytosolic Ca2+ transients through NADPH-dependent ROS formation with SERCA as the principal target in this context. This data provide insight into the mechanisms of myocardial damage in diabetes that occur independent of vascular disease.