Abstract 11989: Cardiac 12-Lipoxygenase-Induced Oxidative Stress Promotes the Development of Diabetic Cardiomyopathy

Abstract

Diabetes mellitus affects cardiac structure and function, and it has been suggested that diabetes leads to cardiomyopathy. Arachidonic acid (AA) metabolism was thought to be a potential mediator of cardiac fibrosis and heart failure associated with oxidative stress. 12-lipoxygenase (12-LOX) is a key lipid peroxidizing enzyme of the AA cascade that plays an important role in the development of atherogenesis and neurodegenerative disease. However, the role of 12-LOX in diabetic cardiomyopathy has not been examined. To determine whether 12-LOX is a key molecule in the development of diabetic cardiomyopathy, we created streptozotocin (STZ)-induced diabetic mice (WT-STZ) and compared to control mice. Cardiac expression of 12-LOX pathway was up-regulated after induction of diabetes. Histological analysis revealed that expression of 12-LOX was specifically up-regulated in cardiomyocytes but not vascular cells and fibroblast cells. Cardiac fibrosis was increased after induction of diabetes. We next created STZ-induced diabetic mice using 12-LOX KO mice (KO-STZ) and compared them to WT-STZ. Cardiac dysfunction and fibrosis in WT-STZ were significantly inhibited in KO-STZ. We next examined the relationship between 12-LOX and cardiac oxidative stress in the diabetic heart. Cardiac expression of 4-hydroxy-2-nonenal (4-HNE) and nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4) were up-regulated in the diabetic heart. This increase was inhibited by disruption of 12-LOX. To further investigate the subcellular mechanism of the increase reactive oxygen species (ROS) in the diabetic heart, intracellular ROS levels in cardiomyocytes were estimated under high glucose condition (HG) and normal glucose condition (LG) by fluorimetry and using MitoTracker® Red in vitro. Cardiomyocytes under HG showed the enhancement of fluorescence intensity of DCF-DA and loss of mitochondrial membrane potential. Treatment with 12-LOX inhibitor (CDC) improved the enhancement of DCF-DA and mitochondrial membrane potential under HG condition. These in vivo and in vitro results suggest that 12-LOX pathway is important in the process of production of ROS and oxidative stress in diabetic heart and promotes the development of diabetic cardiomyopathy.