OBJECTIVE: Sustained beta-adrenergic receptor (beta-AR) activation augments oxidative stress in the heart; whether alterations in antioxidant enzymes contribute to this effect is unknown. METHODS AND RESULTS: Adult male Wistar rats were implanted with osmotic minipumps to infuse either l-isoproterenol (ISO, 25 microg/kg/h) or saline (SAL). After 7-days, ISO-treated hearts exhibited significant (p<0.005): 1) concentric hypertrophy and augmentation of systolic function, 2) reductions of end-systolic wall stress, and 3) augmentation of oxidative stress, with a approximately 3-fold increase in 4-hydroxy-2-nonenal-and malondialdehyde-protein adducts. ISO-treated hearts also exhibited significant (p<0.01) reductions of CuZn-superoxide dismutase (SOD) enzyme activity (30%), protein (40%), and mRNA (60%), without changes in Mn-SOD, catalase, or glutathione peroxidase. Elk-1 and YinYang1 (YY1) are transcription factors that positively and negatively regulate CuZn-SOD expression, respectively. ISO-treated hearts exhibited a 3-fold increase in YY1 and a 2-fold reduction in Elk-1 DNA binding activity, strongly favoring CuZn-SOD gene repression. In isolated cardiomyocytes, sustained (24 h) ISO stimulation significantly (p<0.01) increased reactive oxygen species (ROS), an effect blocked by CGP20712A, a beta1-AR antagonist, but not by ICI118,551, a beta2-AR antagonist. CuZn-SOD downregulation paralleled the increase in ROS, and were similarly blocked by beta1- but not beta2-AR blockade. There were no changes in CuZn-SOD mRNA stability or myocyte size with ISO treatment. However, nuclear run-on revealed a 40% reduction in CuZn-SOD mRNA expression (p<0.01), consistent with transcriptional repression. ISO also depressed total cellular antioxidant capacity, reduced glutathione (GSH) levels, and the GSH:GSSG ratio. Moreover, CuZn-SOD siRNA transfection of H9c2 cardiomyocytes to suppress CuZn-SOD protein by approximately 40-50% (analogous to the in vivo changes) induced cellular apoptosis. CONCLUSIONS: Sustained beta-AR stimulation transcriptionally downregulates CuZn-SOD in myocardium via the beta1-AR, thereby contributing to beta-AR-mediated oxidative stress.
OBJECTIVE: Sustained beta-adrenergic receptor (beta-AR) activation augments oxidative stress in the heart; whether alterations in antioxidant enzymes contribute to this effect is unknown. METHODS AND RESULTS: Adult male Wistar rats were implanted with osmotic minipumps to infuse either l-isoproterenol (ISO, 25 microg/kg/h) or saline (SAL). After 7-days, ISO-treated hearts exhibited significant (p<0.005): 1) concentric hypertrophy and augmentation of systolic function, 2) reductions of end-systolic wall stress, and 3) augmentation of oxidative stress, with a approximately 3-fold increase in 4-hydroxy-2-nonenal-and malondialdehyde-protein adducts. ISO-treated hearts also exhibited significant (p<0.01) reductions of CuZn-superoxide dismutase (SOD) enzyme activity (30%), protein (40%), and mRNA (60%), without changes in Mn-SOD, catalase, or glutathione peroxidase. Elk-1 and YinYang1 (YY1) are transcription factors that positively and negatively regulate CuZn-SOD expression, respectively. ISO-treated hearts exhibited a 3-fold increase in YY1 and a 2-fold reduction in Elk-1 DNA binding activity, strongly favoring CuZn-SOD gene repression. In isolated cardiomyocytes, sustained (24 h) ISO stimulation significantly (p<0.01) increased reactive oxygen species (ROS), an effect blocked by CGP20712A, a beta1-AR antagonist, but not by ICI118,551, a beta2-AR antagonist. CuZn-SOD downregulation paralleled the increase in ROS, and were similarly blocked by beta1- but not beta2-AR blockade. There were no changes in CuZn-SOD mRNA stability or myocyte size with ISO treatment. However, nuclear run-on revealed a 40% reduction in CuZn-SOD mRNA expression (p<0.01), consistent with transcriptional repression. ISO also depressed total cellular antioxidant capacity, reduced glutathione (GSH) levels, and the GSH:GSSG ratio. Moreover, CuZn-SOD siRNA transfection of H9c2 cardiomyocytes to suppress CuZn-SOD protein by approximately 40-50% (analogous to the in vivo changes) induced cellular apoptosis. CONCLUSIONS: Sustained beta-AR stimulation transcriptionally downregulates CuZn-SOD in myocardium via the beta1-AR, thereby contributing to beta-AR-mediated oxidative stress.
Authors: Brian E Sansbury; Daniel W Riggs; Robert E Brainard; Joshua K Salabei; Steven P Jones; Bradford G Hill Journal: Biochem J Date: 2011-04-15 Impact factor: 3.857
Authors: Shahid P Baba; Deqing Zhang; Mahavir Singh; Sujith Dassanayaka; Zhengzhi Xie; Ganapathy Jagatheesan; Jingjing Zhao; Virginia K Schmidtke; Kenneth R Brittian; Michael L Merchant; Daniel J Conklin; Steven P Jones; Aruni Bhatnagar Journal: J Mol Cell Cardiol Date: 2018-04-05 Impact factor: 5.000
Authors: E Bernadette Cabigas; Guoliang Ding; Tao Chen; Talib B Saafir; Karl D Pendergrass; Mary B Wagner; Michael E Davis Journal: Pediatr Cardiol Date: 2011-11-06 Impact factor: 1.655
Authors: Lo Lai; Lin Yan; Shumin Gao; Che-Lin Hu; Hui Ge; Amy Davidow; Misun Park; Claudio Bravo; Kousaku Iwatsubo; Yoshihiro Ishikawa; Johan Auwerx; David A Sinclair; Stephen F Vatner; Dorothy E Vatner Journal: Circulation Date: 2013-03-27 Impact factor: 29.690
Authors: Jingjing Zhao; Dheeraj Kumar Posa; Vijay Kumar; David Hoetker; Amit Kumar; Smirthy Ganesan; Daniel W Riggs; Aruni Bhatnagar; Michael F Wempe; Shahid P Baba Journal: Amino Acids Date: 2018-11-17 Impact factor: 3.520