Gene silencing of the mitochondrial adaptor p66(Shc) suppresses vascular hyperglycemic memory in diabetes.
BACKGROUND
Hyperglycemic memory may explain why intensive glucose control has failed to improve cardiovascular outcomes in patients with diabetes. Indeed, hyperglycemia promotes vascular dysfunction even after glucose normalization. However, the molecular mechanisms of this phenomenon remain to be elucidated.


OBJECTIVE
The present study investigated the role of mitochondrial adaptor p66(Shc) in this setting.


RESULTS
In human aortic endothelial cells (HAECs) exposed to high glucose and aortas of diabetic mice, activation of p66(Shc) by protein kinase C βII (PKCβII) persisted after returning to normoglycemia. Persistent p66(Shc) upregulation and mitochondrial translocation were associated with continued reactive oxygen species (ROS) production, reduced nitric oxide bioavailability, and apoptosis. We show that p66(Shc) gene overexpression was epigenetically regulated by promoter CpG hypomethylation and general control nonderepressible 5-induced histone 3 acetylation. Furthermore, p66(Shc)-derived ROS production maintained PKCβII upregulation and PKCβII-dependent inhibitory phosphorylation of endothelial nitric oxide synthase at Thr-495, leading to a detrimental vicious cycle despite restoration of normoglycemia. Moreover, p66(Shc) activation accounted for the persistent elevation of the advanced glycated end product precursor methylglyoxal. In vitro and in vivo gene silencing of p66(Shc), performed at the time of glucose normalization, blunted ROS production, restored endothelium-dependent vasorelaxation, and attenuated apoptosis by limiting cytochrome c release, caspase 3 activity, and cleavage of poly (ADP-ribose) polymerase.


CONCLUSIONS
p66(Shc) is the key effector driving vascular hyperglycemic memory in diabetes. Our study provides molecular insights for the progression of diabetic vascular complications despite glycemic control and may help to define novel therapeutic targets.
Cardiovascular Research, Institute of Physiology, University of Zürich, Switzerland.
Francesco
F
Paneni
Pavani
P
Mocharla
Alexander
A
Akhmedov
Sarah
S
Costantino
Elena
E
Osto
Massimo
M
Volpe
Thomas Felix
TF
Lüscher
Francesco
F
Cosentino
D000818:Animals; D002478:Cells, Cultured; D003921:Diabetes Mellitus, Experimental / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D055785:Gene Knockdown Techniques / Q000379:methods; D020868:Gene Silencing / Q000502:physiology; D005947:Glucose / Q000494:pharmacology; D006801:Humans; D006943:Hyperglycemia / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008928:Mitochondria / Q000187:drug effects / Q000473:pathology*; D009924:Organ Culture Techniques; D055765:Shc Signaling Adaptor Proteins / Q000172:deficiency* / Q000235:genetics* / Q000502:physiology; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1
D055765:Shc Signaling Adaptor Proteins; C528034:Shc1 protein, mouse; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D005947:Glucose