Quantitative characterization of changes in the cardiac mitochondrial proteome during anesthetic preconditioning and ischemia.

Changes in mitochondrial bioenergetics have been proposed to be critical for triggering and effecting anesthetic-induced preconditioning (APC) against cardiac ischemia and reperfusion injury. The objective of this study was to analyze changes in mitochondrial protein levels and link those changes to potential functional changes. A (18)O-labeling method was applied for relative comparison of cardiac mitochondrial samples from control and isoflurane exposed rats before and after ischemia and reperfusion. Wistar rats were exposed to isoflurane for 30 min (APC) or did not receive the anesthetic (control). Rats were subjected to 30 min coronary occlusion and 15 min reperfusion without (ischemia) or after APC (ischemia + APC). The following comparisons were made: control vs. APC, control vs. ischemia, and APC vs. ischemia + APC. Proteins were analyzed by liquid chromatography-mass spectrometry. A total of 98 proteins currently annotated as mitochondrial proteins in the UniProt database were positively identified from three replicate experiments. Most of the changes during APC and ischemia occur in complexes of the electron transport chain. Overall, fewer changes in ETC complexes were found when comparing APC with APC + ischemia than when comparing control and ischemia. This corresponds to the preservation of bioenergetics due to APC after ischemia and reperfusion as indicated by preserved ATP level and generation. APC itself induced changes in complex I, but those changes were not correlated with activity changes in mitochondria after APC. Thus, a proteomic mass spectral approach does not only assess quantitative changes without prior knowledge of proteins, but also allows insight into the mechanisms of ischemia and reperfusion injury and APC.