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: Yanan Liu, Jiqin Jin, Shigang Qiao, Shaoqing Lei, Songyan Liao, Zhi-Dong Ge, Haobo Li, Gordon Tin-Chun Wong, Michael G Irwin, Zhengyuan Xia
• Journal: Clinical science (London, England : 1979) (Clin Sci (Lond)) Vol. 129 Issue 4 Pg. 331-44 (Aug 2015) ISSN: 1470-8736 [Electronic] England
• PMID: 25849791 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Cav3 protein, rat
• Caveolin 3
• Indoles
• Isoprostanes
• Maleimides
• Phthalimides
• Protein Kinase Inhibitors
• 8-epi-prostaglandin F2alpha
• ruboxistaurin
• Dinoprost
• Proto-Oncogene Proteins c-akt
• Protein Kinase C beta
• 4,5-dianilinophthalimide

Topics

• Animals
• Apoptosis (drug effects)
• Caveolin 3 (genetics, metabolism)
• Cell Line
• Diabetes Mellitus, Experimental (blood, drug therapy, enzymology, genetics)
• Dinoprost (analogs & derivatives)
• Enzyme Activation
• Indoles (pharmacology)
• Isoprostanes (blood)
• Male
• Maleimides (pharmacology)
• Membrane Potential, Mitochondrial (drug effects)
• Mitochondria, Heart (drug effects, enzymology)
• Myocardial Infarction (blood, enzymology, genetics, physiopathology, prevention & control)
• Myocardial Reperfusion Injury (blood, enzymology, genetics, physiopathology, prevention & control)
• Myocytes, Cardiac (drug effects, enzymology, pathology)
• Phosphorylation
• Phthalimides (pharmacology)
• Protein Kinase C beta (antagonists & inhibitors, genetics, metabolism)
• Protein Kinase Inhibitors (pharmacology)
• Proto-Oncogene Proteins c-akt (genetics, metabolism)
• RNA Interference
• Rats, Sprague-Dawley
• Signal Transduction (drug effects)
• Time Factors
• Transfection
• Ventricular Function, Left (drug effects)