Serial alterations of beta-adrenergic signaling in dilated cardiomyopathic hamsters: possible role of myocardial oxidative stress.
BACKGROUND
The relationship between enhanced myocardial oxidative stress and impaired beta-adrenergic signaling remains to be characterized during the development of dilated cardiomyopathy.


RESULTS
Alterations in myocardial oxidative stress and beta-adrenergic signaling, as well as left ventricular (LV) functional and structural changes, were evaluated during the development of cardiomyopathy in TO-2 hamsters; F1B hamsters served as controls. LV dysfunction was first apparent at 8 weeks of age and deteriorated thereafter in the TO-2 hamsters. At 32 weeks, the animals exhibited heart failure with an increased plasma norepinephrine concentration. Cardiac myolysis, as demonstrated by elevated plasma concentration of cardiac troponin T, peaked at 8 weeks. The glutathione redox ratio revealed increased oxidative stress in the LV myocardium in TO-2 hamsters even at 4 weeks and became manifest after 8 weeks. The hearts of TO-2 hamsters had significantly reduced superoxide dismutase activity from 8 weeks onward compared with control hamsters. However, glutathione peroxidase activity was unchanged at any time point. The LV functional response to isoproterenol was markedly reduced at 8 weeks, without any apparent changes in the amount of beta-adrenergic signaling molecules, and it deteriorated thereafter. Adenylyl cyclase activity was significantly decreased, despite increased amounts of both G(s) alpha mRNA and protein, in the LV myocardium at 18 weeks.


CONCLUSIONS
Myocardial oxidative stress is actually enhanced in the initial development of LV dysfunction. Both activation of myocardial oxidative stress and impairment of beta-adrenergic signaling become prominent at the stage of severe LV dysfunction. Myocardial oxidative stress may be involved in the development of beta-adrenergic desensitization.
Nishizawa
Takao
T
Department of Cardiovascular Genetics, Nagoya University Graduate School of Medicine, Nagoya, Japan
Iwase
Mitsunori
M
Kanazawa
Hiroaki
H
Ichihara
Sahoko
S
Ichihara
Gaku
G
Nagata
Kohzo
K
Obata
Koji
K
Kitaichi
Kiyoyuki
K
Yokoi
Toyoharu
T
Watanabe
Masato
M
Tsunematsu
Takashi
T
Ishikawa
Yoshihiro
Y
Murohara
Toyoaki
T
Yokota
Mitsuhiro
M
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002311:Cardiomyopathy, Dilated / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D006224:Cricetinae; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics; D019204:GTP-Binding Proteins / Q000378:metabolism; D008297:Male; D008647:Mesocricetus; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D018384:Oxidative Stress; D020033:Protein Isoforms / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D015398:Signal Transduction; D016277:Ventricular Function, Left; D051552:beta-Adrenergic Receptor Kinases
D020033:Protein Isoforms; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D017868:Cyclic AMP-Dependent Protein Kinases; D051552:beta-Adrenergic Receptor Kinases; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases