title: Inhibition of PKCβ2 overexpression ameliorates myocardial ischaemia/reperfusion injury in diabetic rats via restoring caveolin-3/Akt signaling.
abstract: Activation of PKCβ (protein kinase Cβ) plays a critical role in myocardial I/R (ischaemia/reperfusion) injury in non-diabetic rodents. In the myocardium of diabetes, PKCβ2 overexpression is associated with increased vulnerability to post-ischaemic I/R injury with concomitantly impaired cardiomyocyte Cav (caveolin)-3 and Akt signalling compared with non-diabetic rats. We hypothesized that myocardial PKCβ overexpression in diabetes exacerbates myocardial I/R injury through impairing Cav-3/Akt signalling. Streptozotocin-induced diabetic rats were treated with the selective PKCβ inhibitor ruboxistaurin (RBX, 1 mg/kg per day) for 4 weeks, starting from 1 week after diabetes induction, before inducing myocardial I/R achieved by occluding the left descending coronary artery followed by reperfusion. Cardiac function was measured using a pressure-volume conductance system. In an in vitro study, cardiac H9C2 cells were exposed to high glucose (30 mmol/l) and subjected to hypoxia followed by reoxygenation (H/R) in the presence or absence of the selective PKCβ2 inhibitor CGP53353 (1 μmol/l), siRNAs of PKCβ2 or Cav-3 or Akt. Cell apoptosis and mitochondrial membrane potential were assessed by TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP nick-end labelling) and JC-1 staining respectively. RBX significantly decreased post-ischaemic myocardial infarct size (35±5% compared with 49±3% in control, P<0.05) and attenuated cardiac dysfunction, and prevented the reduction in cardiac Cav-3 and enhanced phosphorylated/activated Akt (p-Akt) in diabetic rats (P<0.05). H/R increased cardiomyocyte injury under high glucose conditions as was evident by increased TUNEL-positive and increased JC-1 monomeric cells (P<0.05 compared with control), accompanied with increased PKCβ2 phosphorylation/activation and decreased Cav-3 expression. Either CGP53353 or PKCβ2 siRNA significantly attenuated all of these changes and enhanced p-Akt. Cav-3 gene knockdown significantly reduced p-Akt and increased post-hypoxic cellular and mitochondrial injury despite a concomitant reduction in PKCβ2 phosphorylation. PKCβ2 inhibition with RBX protects diabetic hearts from myocardial I/R injury through Cav-3-dependent activation of Akt.
authors: *Department of Anesthesiology, Li Ka Shing Faculty of Medicine, University of Hong Kong, 21 Sassoon Road, Hong Kong SAR, China.
authors: Yanan
authors: Y
authors: Liu
authors: *Department of Anesthesiology, Li Ka Shing Faculty of Medicine, University of Hong Kong, 21 Sassoon Road, Hong Kong SAR, China.
authors: Jiqin
authors: J
authors: Jin
authors: *Department of Anesthesiology, Li Ka Shing Faculty of Medicine, University of Hong Kong, 21 Sassoon Road, Hong Kong SAR, China.
authors: Shigang
authors: S
authors: Qiao
authors: *Department of Anesthesiology, Li Ka Shing Faculty of Medicine, University of Hong Kong, 21 Sassoon Road, Hong Kong SAR, China.
authors: Shaoqing
authors: S
authors: Lei
authors: ‡Department of Cardiology, Li Ka Shing Faculty of Medicine, University of Hong Kong, 21 Sassoon Road, Hong Kong SAR, China.
authors: Songyan
authors: S
authors: Liao
authors: §Department of Anesthesiology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, U.S.A.
authors: Zhi-Dong
authors: ZD
authors: Ge
authors: *Department of Anesthesiology, Li Ka Shing Faculty of Medicine, University of Hong Kong, 21 Sassoon Road, Hong Kong SAR, China.
authors: Haobo
authors: H
authors: Li
authors: *Department of Anesthesiology, Li Ka Shing Faculty of Medicine, University of Hong Kong, 21 Sassoon Road, Hong Kong SAR, China.
authors: Gordon Tin-Chun
authors: GT
authors: Wong
authors: *Department of Anesthesiology, Li Ka Shing Faculty of Medicine, University of Hong Kong, 21 Sassoon Road, Hong Kong SAR, China.
authors: Michael G
authors: MG
authors: Irwin
authors: *Department of Anesthesiology, Li Ka Shing Faculty of Medicine, University of Hong Kong, 21 Sassoon Road, Hong Kong SAR, China.
authors: Zhengyuan
authors: Z
authors: Xia
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D051244:Caveolin 3 / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D003921:Diabetes Mellitus, Experimental / Q000097:blood / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics; D015237:Dinoprost / Q000031:analogs & derivatives; D004789:Enzyme Activation; D007211:Indoles / Q000494:pharmacology*; D028421:Isoprostanes / Q000097:blood; D008297:Male; D008301:Maleimides / Q000494:pharmacology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008929:Mitochondria, Heart / Q000187:drug effects / Q000201:enzymology; D009203:Myocardial Infarction / Q000097:blood / Q000201:enzymology / Q000235:genetics / Q000503:physiopathology / Q000517:prevention & control*; D015428:Myocardial Reperfusion Injury / Q000097:blood / Q000201:enzymology / Q000235:genetics / Q000503:physiopathology / Q000517:prevention & control*; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D010766:Phosphorylation; D010797:Phthalimides / Q000494:pharmacology*; D064546:Protein Kinase C beta / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors; D014162:Transfection; D016277:Ventricular Function, Left / Q000187:drug effects
chemical_list: C495549:Cav3 protein, rat; D051244:Caveolin 3; D007211:Indoles; D028421:Isoprostanes; D008301:Maleimides; D010797:Phthalimides; D047428:Protein Kinase Inhibitors; C075750:8-epi-prostaglandin F2alpha; C099154:ruboxistaurin; D015237:Dinoprost; D051057:Proto-Oncogene Proteins c-akt; D064546:Protein Kinase C beta; C098874:4,5-dianilinophthalimide