Abstract 045: Highly-reactive Lipid Aldehydes Are Downstream Mediators Of Oxidant-induced Spontaneous Ca Waves
Background: Reactive oxygen species (ROS) can activate ryanodine receptor (RyR2) Ca release channel and generate arrhythmogenic Ca waves (SCWs) in myocytes. ROS also cause lipid peroxidation in cell membranes that produce highly-reactive g-ketoaldehydes (IsoK), which can react immediately with proteins (RyR2) and accumulate in ischemic human heart. We previously found that specific IsoK scavengers reduce infarct size and prevent ventricular arrhythmia in an MI mouse model, suggesting a biological role of IsoK in oxidant heart injury. We hypothesize that IsoK mediate in part the ROS-induced SCW in myocytes.
Methods: We compared the effect of H2O2, synthetic IsoK, the specific IsoK scavenger (SA, salicylamine), its inactive homolog (4-SA, 4-OH-salicylamine), and the ROS scavenger (MPG, 2-mercaptopropionyl glycine) in field-stimulated mouse ventricular myocytes loaded with Fura-2AM.
Results: Thirty min exposure to H2O2 (10μM) or IsoK (1μM) both generated SCWs (H2O2 37%, IsoK 37%, p<0.05 vs.vehicle, VEH). MPG, (100μM, 60 min) prevented H2O2-induced SCWs, but had no effect on IsoK-induced SCWs (Fig.A). Pre-treatment with SA (8 μM, 60 min) significantly reduced H2O2-induced SCWs, whereas 4-SA had no effect on H2O2-induced SCWs (%SCWs, H2O2; 53%, SA+H2O2; 27%*, 4-SA+H2O2; 56%. *p<0.05 vs. VEH, Fig. B). In the absence of H2O2, MPG, SA, or 4-SA had no significant effect on Ca handling in myocytes.
Conclusion: IsoK directly activate SCWs independent of ROS production in myocytes. Specific IsoK scavengers inhibit 50% of ROS-induced SCWs. Hence, our data suggested that IsoK are biologically-relevant downstream mediators of oxidant-induced RyR2 dysfunction.
- © 2013 by American Heart Association, Inc.