Abstract 3922: O-GlcNAc Signaling Attenuates Post-Hypoxic Calcium Overload and Oxidative Stress in Cardiac Myocytes
Background: We recently discovered that the unique post-translational sugar modification of proteins, O-linked beta-N-acetylglucosamine (O-GlcNAc), confers cytoprotection in the heart. Moreover, we showed that attenuating the formation of mitochondrial permeability transition pore (mPTP) and subsequent loss of mitochondrial membrane potential were potential mechanisms through which O-GlcNAc confers cardioprotection.
Methods and Results: Because Ca2+ accumulation in the mitochondrial matrix and reactive oxygen species (ROS) generation are prominent features of post-hypoxic injury and favor mPTP formation, we hypothesized that O-GlcNAc blocks mPTP formation by preventing post-hypoxic Ca2+ overload and ROS production. We adenovirally overexpressed O-GlcNAc transferase (adds O-GlcNAc to proteins, AdOGT) in isolated cardiac myocytes (n>/=4/groups) and subjected them to hypoxia (3 hours) and reoxygenation (1 hour). During reoxygenation, we assessed changes in Ca2+ levels (via Rhod-2AM) and ROS (via DCF) using time-lapse fluorescent microscopy. OGT overexpression did not significantly (p>0.05) alter baseline Ca2+ or ROS levels. However, AdOGT significantly (p<0.05) attenuated hypoxia-induced Ca2+ overload (146+/−45 A.U. vs. 459+/−106 A.U. for AdNull, Figure 1A⇓) and ROS production (56+/−22% vs. 121+/−24% for AdNull, Figure 1B⇓).
Conclusion: We conclude that the mitochondrial mediated protective mechanism of O-GlcNAc may be through mitigation of mitochondrial Ca2+ overload, ROS production, and subsequently, attenuation of mPTP formation and preservation of mitochondrial membrane potential.
This research has received full or partial funding support from the American Heart Association, National Center.