Attenuation by metallothionein of early cardiac cell death via suppression of mitochondrial oxidative stress results in a prevention of diabetic cardiomyopathy.
OBJECTIVE
We aimed to test whether attenuation of early-phase cardiac cell death can prevent diabetic cardiomyopathy.


BACKGROUND
Our previous study showed that cardiac apoptosis as a major early cellular response to diabetes is induced by hyperglycemia-derived oxidative stress that activates a mitochondrial cytochrome c-mediated caspase-3 activation pathway. Metallothionein (MT) as a potent antioxidant prevents the development of diabetic cardiomyopathy.


METHODS
Diabetes was induced by a single dose of streptozotocin (STZ) (150 mg/kg) in cardiac-specific, metallothionein-overexpressing transgenic (MT-TG) mice and wild-type (WT) controls. On days 7, 14, and 21 after STZ treatment, cardiac apoptosis was examined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay and caspase-3 activation. Cardiomyopathy was evaluated by cardiac ultrastructure and fibrosis in the diabetic mice 6 months after STZ treatment.


RESULTS
A significant reduction in diabetes-induced increases in TUNEL-positive cells, caspase-3 activation, and cytochrome c release from mitochondria was observed in the MT-TG mice as compared to WT mice. Cardiac protein nitration (3-nitrotyrosine [3-NT]) and lipid peroxidation were significantly increased, and there was an increase in mitochondrial oxidized glutathione and a decrease in mitochondrial reduced glutathione in the WT, but not in the MT-TG, diabetic mice. Double staining for cardiomyocytes with alpha sarcomeric actin and caspase-3 or 3-NT confirmed the cardiomyocyte-specific effects. A significant prevention of diabetic cardiomyopathy and enhanced animal survival were observed in the MT-TG diabetic mice as compared to WT diabetic mice.


CONCLUSIONS
These results suggest that attenuation of early-phase cardiac cell death by MT results in a significant prevention of the development of diabetic cardiomyopathy. This process is mediated by MT suppression of mitochondrial oxidative stress.
Cai
Lu
L
Department of Medicine, the University of Louisville, Louisville, Kentucky, USA. L0cai001@louisville.edu
Wang
Yuehui
Y
Zhou
Guihua
G
Chen
Teresa
T
Song
Ye
Y
Li
Xiaokun
X
Kang
Y James
YJ
D000199:Actins / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects; D009202:Cardiomyopathies / Q000209:etiology / Q000517:prevention & control*; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death; D045304:Cytochromes c / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000150:complications* / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D004789:Enzyme Activation; D005978:Glutathione / Q000037:antagonists & inhibitors; D019803:Glutathione Disulfide / Q000378:metabolism; D015227:Lipid Peroxidation; D008668:Metallothionein / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic / Q000235:genetics; D008929:Mitochondria, Heart / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D032383:Myocytes, Cardiac; D018384:Oxidative Stress; D012518:Sarcomeres / Q000378:metabolism; D016019:Survival Analysis; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D000199:Actins; D000975:Antioxidants; C002744:3-nitrotyrosine; D014443:Tyrosine; D045304:Cytochromes c; D008668:Metallothionein; D053148:Caspase 3; D005978:Glutathione; D019803:Glutathione Disulfide