Abstract 20677: Critical Protective Role of Myocardial Extracellular Superoxide Dismutase (SOD3) in Pressure Overload-Induced Cardiac Oxidative Stress and Hypertrophy
We recently reported that a transgenic (TG) mouse model with cardiac-specific overexpression of a dominant-negative (DN) mutant (V204A) of NADPH oxidase (NOX) subunit p67phox attenuated transverse aortic constriction (TAC)-induced increase of reactive oxygen species (ROS) and cardiac hypertrophy vs that in the wild type (WT). In this study, we attempted to explore the mechanisms of these findings & hypothesized that myocardial SOD3 play a critical protective role. Using 4-hydroxynonenal staining, we found TAC-induced membrane lipid peroxidation is reduced in DN-p67 TG mouse left ventricle (54%↓ vs WT, p<0.05). The expression profile of antioxidants was determined, the mRNA expression of SOD3 (3-fold↑) and thioredoxin1 (Trx1, 3.8-fold↑) is significantly increased (p<0.05) in WT-TAC mice vs WT-sham by qRT-PCR; whereas there is no difference among the WT-sham, TG-sham & TG-TAC. In contrast, the expression of other antioxidants including SOD1, SOD2, catalase, Trx2, Nrf2, NQO1, and glutaredoxin was not changed. Interestingly, the SOD3 protein expression in isolated TG cardiomyocytes is higher (4.6 fold↑) vs WT, suggesting a unique link between cardiac SOD3 and ROS/NOX. Antioxidant-1 (Atox1), a copper chaperone required for SOD3 activity, also increases in WT-TAC (2-fold↑ vs WT-sham, p<0.05), consistent with the increase of SOD3 mRNA; whereas Atox1 level is not different between TG-TAC & TG-sham. Since SOD3 is a secreted extracellular (EC) antioxidant bound to the EC matrix (ECM) and cell surface via heparin sulfate proteoglycan, we next tested the effect of increase SOD3 byproduct H2O2 on SOD3 ECM localization. Using heparin-binding proteins chromatography assay, we found that mouse SOD3 binding capability to heparin is concentration-dependently depleted by H2O2 treatment (0.1-0.5 mM). Taken together, our data show that TAC increased oxidative stress and expression of SOD3 and Atox1 in WT heart to limit ROS level. The ROS-SOD3 byproduct H2O2 reduces SOD3 protein localization in cardiac ECM via inhibition of SOD3-heparin interaction, thus increases the heart susceptibility to oxidative injury and hypertrophy. In contrast, DN-p67 TG mice show reduced cardiac oxidative stress, preserved SOD3 ECM localization, and attenuated cardiac hypertrophy.
Author Disclosures: C. Zhang: None. M. Zheng: None. S. Varadarajan: None. Y. Cho: None. X. Zhao: None. M. Ushio-Fukai: None. R. Wu: None. T. Fukai: None. L. Xiao: None. Q. Zhao: None.
- © 2016 by American Heart Association, Inc.