Advanced glycation endproduct induces ROS accumulation, apoptosis, MAT kinase activation and nuclear O-GlcNAcylation in human cardiac myocytes

Accumulation of advanced glycation endproduct (AGE) has been implicated in the pathogenesis of diabetic complications. However, the precise tole and mechanism behind AGE-associated diabetic heart injury are not fully clear. This study was designed to evaluate the effect of AGE on accumulation of reactive oxygen species (ROS), apoptosis, mitogen-activated protein kinase (MAPK) activation and nuclear O-GlcNAcylation in fetal human cardiac myocytes. Myocytes were maintained for 24-72 h in a defined culture medium containing high glucose, the AGE carbon precursor methylglyoxal (MG), and MG-AGE derived from MG and bovine serum albumin (BSA). Generation of ROS was detected by 5-(6)chloromethyl-2', 7'-dichlorodihydro fluorescein diacetate. Apoptosis was evaluated by caspase-3activity and quantitative DNA fragmentation. Both high glucose (25.5 mM) and MG (200 mu M) significantly enhanced ROS and AGE formation with greater effects elicited by MG. Both high glucose MG-AGE significantly facilitated apoptosis with a more predominant effect from MG-AGE. In addition, phosphorylation of MAPK cascade and MG [extracellular signal-regulated kinase-1/2 (ERK1/2) and p38] and nuclear O-GlcNAcylation were enhanced in MG-AGE-treated myocytes, similar to those elicited by high glucose. MG-AGE-induced phosphorylation of ERK1/2 and p38 was nullified by neutralizing AGE with specific anti-AGE antibody but not nonspecific antiserum. Collectively, these results indicated that AGE or its precursor MG may trigger ROS generation, apoptosis, MAPK activation and nuclear O-GlcNAcylation in human cardiac myocytes, in a manner reminiscent of high extracellular glucose. (c) 2006 Elsevier Inc. All rights reserved.