Abstract 416: Mnsod Cardiomyocyte-specific Knockout Live Up to Four Months: Role in Heart Failure Development and Progression

Abstract

In our earlier investigation, we have shown that the manganese superoxide dismutase (MnSOD) mimetic, MnTnBuOE-2-PyP 5+ distributes 3-fold more in mitochondria than in cytosol. The exceptional ability of MnTnBuOE-2-PyP5+ to quench O2 •- parallels its ability to reduce ONOO – and CO3 – . The absence of SOD2 (a gene that encodes MnSOD) knocked out globally is found to be embryonic lethal. We have generated mice that specifically lack MnSOD in cardiomyocytes (Mhy6-SOD2 Δ ). Amazingly, we could prolong the lethality for up to four months in these conditional specific knockout mice (Mhy6-SOD2 Δ ) as compared to global knockout mice. FACS analyses using Mito-Tracker Green indicated that the mass of mitochondria per cell was slightly decreased in the Mhy6-SOD2 Δ to the wild type. We then examined Oxidative phosphorylation (OXPHOS) levels in Mhy6-SOD2 Δ v.s. Wild-Type using a Seahorse XF analyzer. The rate of oxygen consumption per cells was significantly lower in Mhy6-SOD2 Δ cardiomyocytes than that in wild-type. The most noticeable difference in the O 2 consumption was found in the presence of FCCP (H + ionophore/uncoupler). Remarkably, while the FCCP treatment increased O 2 consumption in wild-type, the treatment showed no effect on the O 2 consumption in the Mhy6-SOD2 Δ cardiomyocytes. The result indicated that the low basal OXPHOS activity in Mhy6-SOD2 Δ was due to unusually low OXPHOS potential. We examined glycolysis in these cells by measuring extracellular acidification (ECAR), and the pattern precisely opposite to that of oxygen consumption rate (OCR) was observed for glycolysis rates between Mhy6-SOD2 Δ and wild-type. Herein we present the first study ever done to show the existence of cardiac-specific MnSOD knockout mice and the importance of antioxidant enzyme MnSOD that is guarding/protecting the myocardium from cardiac failures.