CCAAT/enhancer binding protein homologous protein knockdown alleviates hypoxia-induced myocardial injury in rat cardiomyocytes exposed to high glucose

Abstract

Diabetic patients are more sensitive to ischemic injury than non-diabetics. Endoplasmic reticulum (ER) stress has been reported to be closely associated with the pathophysiology of ischemic injury in diabetes. The aim of the present study was to investigate the mechanisms involved in the progression of diabetes complicated by myocardial infarction (MI) and further verify the role of CCAAT/enhancer binding protein (C/EBP)-homologous protein (CHOP) using an in vitro model of diabetes/MI. The rats were exposed to 65 mg/kg streptozotocin (STZ) and left anterior descending (LAD) coronary artery ligation. ST-segment elevation, heart rate, left ventricular systolic pressure (LVSP) and LV end-diastolic pressure (LVEDP) were measured. Serum creatinine kinase-MB (CK-MB) and cardiac troponin T (cTnT) levels were examined by ELISA. Infarct size and apoptosis were measured by triphenyltetrazolium chloride staining and terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling assay. Pathological changes were evaluated by hematoxylin and eosin staining. H9c2 cells were used to establish an in vitro model of diabetes complicated by MI. Following CHOP knockdown, cell viability, cell cycle distribution and apoptosis were examined by Cell Counting Kit-8 assay, flow cytometry and Hoechst staining. Glucose-regulated protein 78 (GRP78), CHOP, B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), endoplasmic reticulum oxidoreductase 1 (Ero1)-α, Ero1β and protein disulfide isomerase (PDI) levels in both myocardial tissues and H9c2 cells were determined by western blotting. In the present study, diabetes complicated by MI promoted ST-segment elevation and myocardial apoptosis, increased infarct size, induced pathological changes and elevated LVEDP, CK-MB, cTnT, GRP78, CHOP, Bax, Ero1α, Ero1β and PDI; however, it decreased heart rate, LVSP and Bcl-2. Additionally, high glucose combined with hypoxic treatment reduced cell viability, induced cell cycle arrest at G1 phase, promoted cell apoptosis, and activated the GRP78/CHOP and Ero1/PDI signaling pathways, which were reversed by CHOP knockdown. Thus, CHOP may be an effective therapeutic target for the treatment of diabetes complicated by MI.

Diabetes Upregulates Oxidative Stress and Downregulates Cardiac Protection to Exacerbate Myocardial Ischemia/Reperfusion Injury in Rats

“…In diabetic hearts, cardiac IR injury exacerbated cardiac PTEN expression and this overexpression of PTEN impaired the PI3K/Akt and JAK2/STAT3 protective signaling pathways in the IR heart [ 39 ]. Our data and previous finding [ 40 ] consistently demonstrated that diabetic hearts depressed BAG3 and Bcl-2 expression, which promoted myocardial apoptosis, increased infarct size, induced irregular arrangement of cardiomyocytes and pathological changes and elevated LVEDP after myocardial IR injury. Our data also found a decrease in Nrf-2/HO-1 signaling in the diabetic hearts and a further depression of Nrf-2/HO-1 signaling in response to IR injury.…”

Astragaloside IV Alleviates Infarction Induced Cardiomyocyte Injury by Improving Mitochondrial Morphology and Function

“…Bax can promote apoptosis, inhibit the effect of its homolog Bcl2, reduce the level of cytochrome C, and accelerate apoptosis ( 46 , 47 ). Bcl2 inhibits apoptosis induced by many factors and affects the apoptosis rate of myocardial cells in MI ( 48 ). Cell viability was estimated by CCK-8 assay.…”

Dexmedetomidine Attenuates Myocardial Ischemia-Reperfusion Injury in Diabetes Mellitus by Inhibiting Endoplasmic Reticulum Stress

“…CHOP can activate Ero1 α , catalyze the reoxidation of protein disulfide isomerase (PDI), and ultimately regulate apoptosis. CHOP also upregulates the proapoptotic gene Bax and downregulates the antiapoptotic gene Bcl-2, resulting in the conformation change of Bax/Bak on the endoplasmic reticulum, causing the destruction of the endoplasmic reticulum membrane and Ca 2+ efflux, which further mediates apoptosis [32, 51, 52].…”