The role of glycogen synthase kinase-3β phosphorylation in the protective effects of preconditioning with endoplasmic reticulum stress induced by low dose tunicamycin in myocardial ischemia-reperfusion injury

Abstract

Objective To evaluate the role of glycogen synthase kinase-3beta phosphorylation (p-GKS-3β) in the protective effects of preconditioning with endoplasmic reticulum stress (ERS) induced by tunicamycin (TM) against myocardial ischemia reperfusion (I/R) injury. Methods Forty Sprague-Dawley rats were randomly divided into four groups: Sham, TM [Rats were treated by TM (0.6 mg/kg) at 30 min before model established], I/R, and TM+ LY [Rats were treated by TM (0.6 mg/kg) and protein kinase B (Akt) inhibitor LY294002 (10 mg/kg) before model established]. The models of I/R were established by occlusion of the left anterior descending coronary artery for 0.5 h followed by reperfusion for 2 h. Blood samples were withdrawn from carotid artery after thoracotomy and 2 h after reperfusion. The levels of creatine kinase isozyme (CK-MB) and lactic dehydrogenase (LDH) were detected. The expression of phosphorylated Akt (p-Akt) and p-GSK-3β in the heart at the end of the I/R was examined by Western blotting in all groups. The myocardial apoptosis index (AI) was measured using terminal deoxynucleotidyl nick-end labeling in all groups. Results The levels of CK-MB, LDH and AI in TM+ LY group were higher than TM group[(987±103) U/L vs. (746±99) U/L, t=2.945, P=0.006; (4 761±636) U/L vs. (3 681±518) U/L, t=2.789, P=0.008; (18.7±2.9)% vs. (14.4±2.8)%, t=2.864, P=0.007; respectively] at 2 h after reperfusion. The expressions of p-Akt, p-GSK-3β protein in TM group (0.613±0.068, 0.717±0.086 respectively) and TM+ I/R group (0.364±0.046, 0.452±0.053) were higher than I/R group (0.251±0.032, 0.232±0.031), but expressions in TM group were higher than TM+ LY group at 2 h after reperfusion (t=2.925, P=0.006; t=2.858, P=0.007; respectively). Conclusion Preconditioning with ERS induced by low dose TM attenuates I/R injury, which may be associated with GSK-3β phosphorylation level by Akt-GSK-3β pathway in rats. Key words: Myocardial ischemia reperfusion injury; Endoplasmic reticulum stress; Preconditioning; Glycogen synthase kinase-3β