TY - JOUR
T1 - Downregulation of CuZn-superoxide dismutase contributes to β-adrenergic receptor-mediated oxidative stress in the heart
AU - Srivastava, Sanjay
AU - Chandrasekar, Bysani
AU - Gu, Yan
AU - Luo, Jianzhu
AU - Hamid, Tariq
AU - Hill, Bradford G.
AU - Prabhu, Sumanth D.
N1 - Funding Information:
This work was supported by VA Merit Awards, the Jewish Hospital Foundation, and NIH grants ES11860, HL078825, HL65618, and HL68020.
PY - 2007/6/1
Y1 - 2007/6/1
N2 - Objective: Sustained β-adrenergic receptor (β-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 μg/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 ∼ 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 β1-AR antagonist, but not by ICI118,551, a β2-AR antagonist. CuZn-SOD downregulation paralleled the increase in ROS, and were similarly blocked by β1- but not β2-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 ∼ 40-50% (analogous to the in vivo changes) induced cellular apoptosis. Conclusions: Sustained β-AR stimulation transcriptionally downregulates CuZn-SOD in myocardium via the β1-AR, thereby contributing to β-AR-mediated oxidative stress.
AB - Objective: Sustained β-adrenergic receptor (β-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 μg/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 ∼ 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 β1-AR antagonist, but not by ICI118,551, a β2-AR antagonist. CuZn-SOD downregulation paralleled the increase in ROS, and were similarly blocked by β1- but not β2-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 ∼ 40-50% (analogous to the in vivo changes) induced cellular apoptosis. Conclusions: Sustained β-AR stimulation transcriptionally downregulates CuZn-SOD in myocardium via the β1-AR, thereby contributing to β-AR-mediated oxidative stress.
KW - Copper-zinc superoxide dismutase
KW - Oxidative stress
KW - β-adrenergic receptor
UR - http://www.scopus.com/inward/record.url?scp=34247892469&partnerID=8YFLogxK
U2 - 10.1016/j.cardiores.2007.02.016
DO - 10.1016/j.cardiores.2007.02.016
M3 - Article
C2 - 17362897
AN - SCOPUS:34247892469
SN - 0008-6363
VL - 74
SP - 445
EP - 455
JO - Cardiovascular Research
JF - Cardiovascular Research
IS - 3
ER -