Hypoxia/Reoxygenation And High Glucose Induced Endoplasmic Reticulum Stress In Cardiomyocytes

The ER is mainly recognized as a protein-folding factory.responsible for the biosynthesis, folding, assembly and modification of numerous soluble proteins and membrane proteins. Physiological states that increase the demand for protein folding, or stimuli that disrupt the reactions by which proteins fold, create an imbalance between the protein-folding load and the capacity of the ER, causing unfolded or misfolded proteins and Ca2+ to accumulate in the ER lumen—a condition referred to as ER stress(ERS).ERS has involved in a lot of diseases.such as diabets. adiposity and tumors.Meanwhile ERS has played an important role in cardic injury induced by ischemic/reperfusion(I/R). Glucose regulated protein 78 kD(GRP78) is commonly used as an indicator for ERS,and can protect DNA from damage.We undertook our research to explore whether hypoxia/reoxygenation injury and high glucose can induced ERS.Objective To investigate the effect of hypoxia/reoxygenation injury and high glucose on the ERS in cultured neonatal rat cardiomyocytes and the mechanism there of.Methods Neonatal rat cardiac myocytes in primary culture were exposed to hypoxia for 6 hours and subsequently reoxygenation for 12 hours.Western blot were applied to monitor the expression change of GRP78(glucose regulated protein 78). High glucose DMEM with the concentration of 25 mmol/L was used to culture cardiomyocytes for 24 hours.Tunicamycin was the postive control of this study.Then Western blot was used to examine the expression of GRP78. Use inverted phase contrast microscope to observe cardiac activity,and hematoxylin-eosin(HE) staining was appiled to observe the configuration. The cell viability of primary cardiomyocytes was explored using CCK-8 reduction assay.Results Cell viability was decreased obviously after hypoxia/reoxygenation,and cardiac activity had an reduction.Compared with untreated cells,the GRP78 content of the cells had increased significantly in the hypoxia/reoxygenation cells.The level of GRP78 protein elevated from the point of 6 hours after hypoxia,and increased most obviously at the point of 12 hours after reoxygenation(hypoxia:protein level 144% of control;reoxygenation:protein level 297% of control.) High glucose induced the increasing expression of GRP78 (HG:protein level 195% of control).Compared to untreated cells,cell viability and cardiac beats increased in HG..Conclusion Hypoxia/reoxygenation and high glucose can induce endopalsmic reticulum stress in cardiomyocytes.