Abstract 17477: Role of NADPH Oxidase Subunit p67phox in Regulation of Pressure-Overload-Induced Cardiac Hypertrophic Oxidative Stress and Antioxidant Gene Expression
We had reported a transgenic (Tg) mouse model with cardiac-specific overexpression of a dominant-negative (DN) mutant (V204A) of NADPH oxidase (NOX) subunit p67phox that inhibits NOX activity. We showed that transverse aortic constriction (TAC)-induced cardiac hypertrophy was significantly attenuated in the Tg mice, but not in wild type (WT) mice. Since TAC had been reported to increase mouse myocardial reactive oxygen species (ROS) level, we thus tested if the myocardial ROS contributed to the above difference between WT and Tg. Age (10-12 weeks)-, body weight (BW)-matched Tg and WT C57BL/6 male mice were subjected to TAC or sham operation. Cardiac hypertrophy were confirmed 4-week post-TAC by echocardiography, heart weight/BW ratio, and fetal gene expression. Freshly isolated hearts were perfused and the left ventricle (LV) ROS level was determined using chemiluminescence method. Surprisingly, we found that the WT-TAC mouse heart showed consistently decreased ROS level (42±2% ↓, p<0.01, n=4) vs. WT-sham; whereas there is no difference among the WT-sham, Tg-sham and Tg-TAC groups (n=6). This finding was different from the previous reports showing the increased ROS in WT-TAC heart. Next, we screened the LV expression profile of various antioxidant proteins. We found that the mRNA expression of SOD3 (3.0-fold↑) and thioredoxin1 (Trx1, 3.8-fold↑) was 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 and Tg-TAC groups. The increased SOD3 and Trx1 mRNA expression was confirmed by Western blotting for protein expression (3.0-fold↑). In contrast, the expression of other antioxidants including SOD1, SOD2, catalase, Trx2, Nrf2, NQO1 and glutaredoxin were not changed in WT-TAC heart. The selectively increased expression of SOD3 and Trx1 may contribute to the decreased ROS level detected in WT-TAC heart. Unlike WT-TAC, the ROS, SOD3 and Trx1 levels in Tg heart were not increased by TAC vs. sham, suggesting the critical role of p67phox in regulation of TAC-induced myocardial ROS generation and antioxidants expression. In summary, our data show that NOX/p67phox regulates pressure-overload-induced cardiac oxidative stress and myocardial expression of antioxidants SOD3 and Trx1.
- © 2011 by American Heart Association, Inc.