Abstract 13018: Mitochondrial Cx43 Modulates Changes in Oxidative Phosphorylation Proteins Associated With Preconditioning Cardioprotection
Cx43 deficiency blunts ischemic preconditioning (IP) protection, but the role of mitochondrial Cx43 in preconditioning protection and its mechanism are unknown. We analyzed the changes in mitochondrial proteome induced by preconditioning and their dependence on the presence of Cx43.
Methods and results: Subsarcolemmal (SSM) and interfibrilar mitochondria (IFM) were obtained from perfused rat hearts submitted to IP (2 cycles of 5 min global ischemia and 5 min reperfusion) followed or not by 20 min of ischemia and 5 min of reperfusion (I/R). Complex I and complex II-mediated ADP-stimulated respiration (Clark electrode) was reduced after I/R (30 and 25%, respectively, p<0.05) and this reduction was significantly prevented by IP in SSM (12% reduction, p<0.05), but not in IFM. High-throughput proteomics analysis by 16O/18O labeling and mass spectrometry allowed differential quantitation of more than 400 proteins (from which more than 95% were mitochondrial), and systems biology analysis revealed a statistically significant IP-induced increase in the group of oxidative phosphorylation (OxPhos) proteins in SSM. I/R caused a reduction in OxPhos proteins in SSM, and this effect was inhibited by a previous IP cycles. Since Cx43 is present only at SSM, we investigated its role in IP in heart mitochondria from mice in which Cx43 had been replaced by Cx32 (Cx43KI32), a genetic modification previously shown to induce basal protection against I/R and loss of IP protection. I/R induced a reduction in ADP-induced respiration that was attenuated by IP in wild type animals but not in Cx43KI32 mutants. IP induced an increase in OxPhos proteins in wild type mice, similar to that observed in rat SSM, but not in Cx43KI32. Differential analysis of Cx43KI32 mitochondrial proteome versus that from wild type animals revealed that Cx43 elimination produce the same effect on OxPhos proteins than IP.
Conclusion: The increase in OxPhos proteins at the onset of I/R limits the reduction in respiration secondary to I/R. In mitochondria lacking Cx43, OxPhos proteins are basally increased and IP fails to induce changes in OxPhos proteins. These results indicate that the effect of Cx43 on IP protection is mediated by changes in OxPhos proteins.
- © 2011 by American Heart Association, Inc.