DESCRIPTION: During the current budget period, we have been able to develop two lines of transgenic mice, producing extra copies of thioredoxin (Trx1) and glutaredoxin (Grx1) genes in the heart. Since Trx1 and Grx1 are the principal redox regulated genes, this achievement has opened up a new avenue of research to study the molecular mechanisms of myocardial ischemic injury. Recent studies from several laboratories including our own have shown the importance of redox signaling in myocardial ischemia reperfusion injury. Since redox signaling originates from the oxidative stress developed during ischemia and reperfusion and preconditioning triggers a redox-regulated survival signaling involving MAP kinases-Akt, we plan to study the underlying molecular mechanisms of Trx/Grx redox signaling in ischemic injury using preconditioned heart model. We plan to accomplish our goal by addressing five Specific Aims: i) to study if peroxiredoxin (Prx), the intracellular antioxidant protein with thioredoxin peroxidase activity, is responsible for the cardioprotective ability of Trx, and if so, whether Prx is regulated by PKC/MAPK signaling; ii) to examine the regulation of apoptosis signal regulating kinase 1 (ASK1) in Trx signaling by examining its upstream and downstream targets; iii) to study if the cardioprotective ability of Trx is realized via other cardioprotective proteins including MnSOD, HO-1, iNOS, and/or growth factors such as VEGF and HIF1a, which are known to be induced by Trx1; iv) to further examine the role of Grx in cardioprotection by generating Grx2+/+ and Grx-/- mice; and v) to study Akt signaling by Grx using Grx1+/+, Grx2+/+ and Grx-/- mice, and to examine if Akt gene therapy can rescue the Grx-/- hearts from apoptotic cell death. The results of this proposed research will hopefully increase our understanding of redox regulation by Trx/Grx in the ischemic myocardium.