Coronary Vascular Resilience by Modulation of Mitochondrial ROS in Endothelium - The main objective of this study is to elucidate molecular mechanisms by which coronary endothelial cells (EC) can survive and proliferate in ischemic (low oxygen, low glucose) conditions and help improve cardiac This proposal is based on our recent report that reduction in mitochondrial (mito)-ROS, using EC-specific transgenic overexpression of mito-antioxidant MnSOD (SOD-OE) or using mito-specific antioxidant nanoparticle JP4-039, improves survival and proliferation of coronary EC, and help recover cardiac function in a post-myocardial infarct (MI) animal model. Coronary ECs from SOD-OE demonstrated 50% reduction in mito-ROS (by mito-roGFP), significant increase in mitochondrial complexes I and IV biogenesis (proteomic data), super-complex formation, and oxidative phosphorylation (Ox-Phos). The shift from less-efficient energy production system glycolysis (2 ATP/glucose molecule), to a more efficient Ox-Phos (32 ATP/glucose) may provide critical energy support to EC needed during ischemia (low glucose, oxygen). However, two major concerns about these counterintuitive findings of increased OxPhos in ischemic EC should be addressed: (1) OxPhos requires oxygen but ischemic EC has low oxygen and high ROS, and (2) in ischemia, glucose is catalyzed to lactate but not pyruvate that is required for OxPhos. Indeed, studies reported lactate accumulation during ischemia induced endothelial-to-mesenchymal transition (EMT) and cardiac remodeling. Here, we hypothesize that reduction of excess mito-ROS by MnSOD during ischemia results in recycling of endothelial mito-superoxide to molecular oxygen (O2- to H2O2 by MnSOD, and O2 by Gpx4) to be utilized by mito-complexes (e.g. complex IV) for efficient electron transport chain (ETC) in EC super-complexes. In addition, glycolytic product lactate is catalyzed to pyruvate for the TCA cycle in EC mitochondria. We propose 3 Aims: function by rendering coronary vessels resilient in ischemia. Specific Aim 1: Elucidate the molecular mechanisms by which mitochondrial MnSOD protect coronary EC by inducing mitochondrial oxidative phosphorylation and coronary angiogenesis in ischemic myocardium. We hypothesize that reduction in EC-mito-ROS by MnSOD resulting in increased OxPhos depends on Gpx4-mediated conversion of mitochondrial H2O2 to oxygen as electron acceptor at ETC. Specific Aim 2: Elucidate the mechanisms by which coronary endothelial TCA cycle of OxPhos receive pyruvate/Ac-CoA during ischemia that favors lactate accumulation. Specific Aim 3: Determine whether mitochondria-specific antioxidant nanoparticles JP4-039 and XJB-5-131 induce post-MI recovery of cardiac function in large animals (swine) in vivo and increase OxPhos and angiogenic sprouting in human atrial tissue ex vivo.
