Glycyrrhizic acid ameliorates myocardial ischemia-reperfusion injury in rats through inhibiting endoplasmic reticulum stress

The purpose of this study was to investigate the role of glycyrrhizic acid (GA) in regulating myocardial ischemia-reperfusion injury (MIRI) in rats as well as the underlying mechanism. H9c2 cells were subjected to hypoxia/re-oxygenation (H/R) to mimic the MIRI in vitro, while a rat model of ischemia-reperfusion (I/R) was constructed by occlusion of the left anterior descending coronary artery for 0.5 h followed by 2 h of reperfusion. While flow cytometry and TUNEL assay were performed to analyze apoptosis in cells and myocardial tissue, echocardiography, hematoxylin and eosin staining, and Masson's trichrome staining were conducted to evaluate cardiac function and pathological changes, respectively. The levels of serum CK, CK-MB, LDH, AST, TNF-α, and IL-6 as well as the contents of MDA and SOD in tissues were measured by ELISA, while Western blot analysis was performed to detect the expression of endoplasmic reticulum stress (ERS)-related proteins. GA treatment significantly reduced apoptosis in H9c2 cells, while it alleviated left ventricular dysfunction, fibrosis and myocardial apoptosis, down-regulated the levels of CK, CK-MB, LDH, AST, TNF-α, IL-6, and MDA, and up-regulated SOD levels in I/R rats. Moreover, GA treatment led to a decrease in the expression of CHOP, GRP78, and p-PERK in both H/R cells and I/R rats. This study demonstrates that cardioprotective role of GA in MIRI may involve the attenuation of ERS-induced apoptosis and inflammation, potentially providing an alternative strategy for intervention of MIRI.