Reduced Endoplasmic Reticulum Stress Might Alter the Course of Heart Failure Via Caspase-12 and JNK Pathways

Background: Endoplasmic reticulum (ER) stress plays an important role in mediating ischemic heart cell death. The aim of this study was to investigate whether manipulation of a key factor of the ER stress pathway, eukaryotic translation initiation factor 2 subunit alpha (eIF2 alpha), can change the natural history of heart failure (HF). Methods: HF was induced using coronary artery ligation in adult rats and a selective eIF2 alpha dephosphorylation inhibitor, salubrinal (Sal), was used. Thirty minutes after ligation, rats were randomly assigned to 3 groups: myocardial infarction (MI) plus placebo injections (dimethyl sulfoxide; n = 12), MI plus Sal injection (Sal; n = 12), and MI (HF; n = 12). Hemodynamic parameters were examined. Hearts were harvested for apoptosis assessment after 8 weeks of Sal treatment by terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labelling and flow cytometric analysis. Hearts were harvested to determine ER chaperones by Western analysis, real-time polymerase chain reaction and immunohistochemical analysis. Results: Cardiac function was significantly improved in Sal-treated rats. Apoptosis was reduced by Sal treatment. Glucose-regulated protein-78 and -94 were increased in HF but normalized by Sal treatment. HF caused a significant increase in eIF2 alpha phosphorylation, which was further increased by Sal treatment, and caspase-12 and phospho-c-JUN NH2-terminal kinase were markedly increased in rats with HF alone but significantly reduced by Sal treatment. Conclusions: Our results suggest that reduction of ER stress and myocardial apoptosis through inhibition of eIF2 alpha dephosphorylation might alter the natural history of HF, which might provide a new approach for its treatment.