LAUSR

Background and objective: Nitric oxide (NO) is known to exert cardioprotective effects against heart ischemic damage and may be involved in ischemic pre- and postconditioning. NO-triggered cardioprotective mechanisms are not well understood but may involve regulation of mitochondrial permeability transition pore (mPTP). In this study, we aimed to identify differentially phosphorylated mitochondrial proteins possibly involved in the NO/protein kinase G (PKG)/mPTP signaling pathway that can increase the resistance of cardiomyocytes to ischemic damage. Materials and methods: Isolated hearts from Wistar rats were perfused with NO donor NOC-18 prior to induction of stop–flow ischemia. To quantify and characterize the phosphoproteins, mitochondrial proteins were resolved and analyzed by two-dimensional gel electrophoresis followed by Pro-Q Diamond phosphoprotein gel staining, excision, trypsin digestions, and mass spectrometry. Quantitative proteomic analysis coupled with liquid chromatography–tandem mass spectrometry was also performed. Results: Mitochondrial protein phosphorylation patterns in NOC-18-pretreated ischemic hearts versus ischemic hearts were compared. Pretreatment of hearts with NOC-18 caused changes in mitochondrial phosphoproteome after ischemia which involved modifications of 10 mitochondrial membrane-bound and 10 matrix proteins. Among them, α-subunit of ATP synthase and adenine nucleotide (ADP/ATP) translocase 1, both of which are considered as potential structural components of mPTP, were identified. We also found that treatment of isolated non-ischemic mitochondria with recombinant PKG did not cause the same protein phosphorylation as pretreatment of hearts with NOC-18. Conclusions: Our study suggests that pretreatment of hearts with NOC-18 causes changes in mitochondrial phosphoproteome after ischemia which involves modifications of certain proteins thought to be involved in the regulation of mPTP opening and intracellular redox state. These proteins may be potential targets for pharmacological preconditioning of the heart.