Oleanolic Acid, a Novel Endothelin A Receptor Antagonist, Alleviated High Glucose-Induced Cardiomyocytes Injury

Abstract

Endothelin-1 (ET-1) and its receptor endothelin A receptor (ETA) have been shown to be upregulated in a high glucose environment, which increase the incidence of diabetes-related heart failure. Our previous study demonstrated that oleanolic acid (OA), a natural compound found in Chinese herbs had ET-1 antagonistic effects. We aimed to verify whether OA could ameliorate diabetes mellitus (DM)-induced injury in cardiomyocytes by reducing the antagonistic effects of the ET-1 pathway. For the induction of high glucose-related injury in cardiomyocytes, neonatal rat ventricular cardiomyocytes (NRVMs) were subjected to culture medium containing 25mM of glucose. Natriuretic peptide B (BNP), mitochondrial membrane potential (MMP) and cell surface area were measured to evaluate the severity of NRVMs injury. mRNA expression of ET-1 and ETA was determined using quantitative PCR. Moreover, a Ca2+ influx assay was used to evaluate potential ETA antagonistic effects. Molecular docking of OA and ETA was performed using the Sulflex-Dock program. Human induced pluripotent stem cell (iPS-C)-derived cardiomyocytes and real time cell analysis system (RTCA) were used to verify the effect of OA on the ET-1 pathway. High glucose levels increased the expression of BNP at both mRNA and protein levels in cardiomyocytes. Moreover, cell surface area and MMP were also elevated in a high glucose environment. High glucose-induced injury in NRVMs was not reversible by hypoglycemic therapy. In addition, ETA was upregulated by high glucose treatment and levels could not be reduced by hypoglycemic treatment. The Ca2+ influx assay on ETA/HEK293 cells showed that OA had a partial ETA antagonistic effect. Molecular docking approaches showed that OA was docked into the active site of ETA. Furthermore, functionality tests based on iPS-C and RTCA demonstrated that treatment with OA could reverse ET-1-induced alternation of beating rates and amplitude. Thus, OA could reverse high glucose-induced BNP upregulation, and increased both the cell area and MMP in NRVMs. High glucose-induced irreversible ETA upregulation is a major reason of continuous diabetes-related injury in cardiomyocytes. Treatment with OA had a protective effect on high glucose-induced injury in cardiomyocytes through a partial ETA antagonistic role.