Abstract 1530: A Central Role For p53 and MAP Kinase Signaling in Rage-Dependent, S100B-Induced Myocyte Apoptosis
We have recently shown that the co-expression and interaction of the receptor for advanced glycation end products (RAGE) and its ligand S100B post myocardial infarction play a role in myocyte apoptosis. In other cell types, the S100B/RAGE interaction triggers signaling pathways including NF-kB activation and translocation, MAP kinases, and p53. To determine the signaling pathways modulated by the S100B/RAGE interaction contributing to myocyte apoptosis, rat neonatal cardiac myocyte cultures transfected with a full-length cDNA of the RAGE gene, a dominant-negative cytoplasmic deletion mutant of RAGE, or vector control were treated with nanomolar (1–1000) concentrations of recombinant bovine brain S100B for 48 hrs. 1 μM S100B induced vector alone-transfected myocyte apoptosis, as evidenced by increased terminal deoxynucleotidyltransferase-mediated UTP end labeling (TUNEL) [12.4±0.7% vs. 5.6±0.3% (untreated) of total cells p<0.05], DNA fragmentation, cytochrome C release from the mytochondria to the cytoplasm, and increased mRNA expression and activity of the apoptotic related gene caspase-3. Compared to vector alone, RAGE overexpression resulted in increased S100B-induced myocyte apoptosis (20.5±0.6%, p<0.05) in association with attenuated NF-κB transactivation and decreased phosphorylation of p38 and ERK1/2. By contrast p53 phosphorylation was augmented. In myocytes expressing a dominant-negative cytoplasmic deletion of RAGE, myocyte apoptosis was attenuated (7.6±0.8%, p<0.05) and phosphorylation of p38, ERK1/2, and p53 was not detected. In keeping with a central role for p53, transfection of a dominant negative p53 mutant comparably inhibited S100B-induced myocyte apoptosis (6.9±0.3%, p<0.05). In conclusion, these in vitro results provide direct evidence that the interaction of RAGE and its ligand S100B induce myocyte apoptosis by activating p53 and inhibiting MAP kinase and NF-κB signaling.