Rac1 is required for cardiomyocyte apoptosis during hyperglycemia.
OBJECTIVE
Hyperglycemia induces reactive oxygen species (ROS) and apoptosis in cardiomyocytes, which contributes to diabetic cardiomyopathy. The present study was to investigate the role of Rac1 in ROS production and cardiomyocyte apoptosis during hyperglycemia.


METHODS
Mice with cardiomyocyte-specific Rac1 knockout (Rac1-ko) were generated. Hyperglycemia was induced in Rac1-ko mice and their wild-type littermates by injection of streptozotocin (STZ). In cultured adult rat cardiomyocytes, apoptosis was induced by high glucose.


RESULTS
The results showed a mouse model of STZ-induced diabetes, 7 days of hyperglycemia-upregulated Rac1 and NADPH oxidase activation, elevated ROS production, and induced apoptosis in the heart. These effects of hyperglycemia were significantly decreased in Rac1-ko mice or wild-type mice treated with apocynin. Interestingly, deficiency of Rac1 or apocynin treatment significantly reduced hyperglycemia-induced mitochondrial ROS production in the heart. Deficiency of Rac1 also attenuated myocardial dysfunction after 2 months of STZ injection. In cultured cardiomyocytes, high glucose upregulated Rac1 and NADPH oxidase activity and induced apoptotic cell death, which were blocked by overexpression of a dominant negative mutant of Rac1, knockdown of gp91(phox) or p47(phox), or NADPH oxidase inhibitor. In type 2 diabetic db/db mice, administration of Rac1 inhibitor, NSC23766, significantly inhibited NADPH oxidase activity and apoptosis and slightly improved myocardial function.


CONCLUSIONS
Rac1 is pivotal in hyperglycemia-induced apoptosis in cardiomyocytes. The role of Rac1 is mediated through NADPH oxidase activation and associated with mitochondrial ROS generation. Our study suggests that Rac1 may serve as a potential therapeutic target for cardiac complications of diabetes.
Shen
E
E
Critical Illness Research, Lawson Health Research Institute, University of Western Ontario, Ontario, Canada.
Li
Yanwen
Y
Li
Ying
Y
Shan
Limei
L
Zhu
Huaqing
H
Feng
Qingping
Q
Arnold
J Malcolm O
JM
Peng
Tianqing
T
D000818:Animals; D017209:Apoptosis; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism; D006321:Heart / Q000503:physiopathology; D006943:Hyperglycemia / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000172:deficiency / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D008929:Mitochondria, Heart / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000473:pathology; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015854:Up-Regulation; D020830:rac1 GTP-Binding Protein / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
D008562:Membrane Glycoproteins; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C500593:Cybb protein, rat; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1; D020830:rac1 GTP-Binding Protein