ABSTRACT
AIM:To investigate the inhibitory effect of ethanol extract of propolis (EEP) on oxidized low-density lipoprotein (ox-LDL)-induced vascular endothelial cell apoptosis and the underlying molecular mechanisms.METHODS:Human umbilical vein endothelial cells (HUVECs) were pretreated with EEP (7.5,15 and 30 mg/L) or 4-phenylbutyric acid (PBA,4 mmol/L) for 1 h and then treated with ox-LDL (100 mg/L) or tunicamycin (TM,4 mg/L) for 24 h.The cell viability and apoptosis were determined by MTT assay and Annexin V-FITC/PI double staining,respectively.The activities of lactic dehydrogenase (LDH) in the medium and caspase-3 in the HUVECs were measured.The protein and mRNA levels of C/EBP homologous protein (CHOP),a proapoptotic molecule under endoplasmic reticulum stress (ERS),and its downstream Bcl-2 were examined by Western blot and real-time PCR,respectively.RESULTS:Like PBA (an ERS inhibitor),EEP protected HUVECs from ox-LDL-induced injury in a dose-dependent manner,as assessed by the increased cell viability and the decreased LDH release,apoptotic rate and caspase-3 activation.The decrease in cell viability and the increases in LDH release,apoptotic rate and caspase-3 activation induced by TM,an ERS inducer,were also attenuated by EEP.Moreover,EEP suppressed ox-LDL-induced CHOP upregulation and Bcl-2 downregulation,and this effect was similar to that of PBA.Similarly,EEP significantly suppressed TM-induced CHOP upregulation both at the protein and mRNA levels.CONCLUSION:EEP may protect HUVECs from ox-LDL-induced apoptosis,and the mechanism is at least partially involved in suppressing CHOP-mediated ERS-associated apoptotic pathway.
ABSTRACT
AIM:To investigate the inhibitory effect of ethanol extract of propolis (EEP) on oxidized low-density lipoprotein (ox-LDL)-induced vascular endothelial cell apoptosis and the underlying molecular mechanisms.METHODS:Human umbilical vein endothelial cells (HUVECs) were pretreated with EEP (7.5,15 and 30 mg/L) or 4-phenylbutyric acid (PBA,4 mmol/L) for 1 h and then treated with ox-LDL (100 mg/L) or tunicamycin (TM,4 mg/L) for 24 h.The cell viability and apoptosis were determined by MTT assay and Annexin V-FITC/PI double staining,respectively.The activities of lactic dehydrogenase (LDH) in the medium and caspase-3 in the HUVECs were measured.The protein and mRNA levels of C/EBP homologous protein (CHOP),a proapoptotic molecule under endoplasmic reticulum stress (ERS),and its downstream Bcl-2 were examined by Western blot and real-time PCR,respectively.RESULTS:Like PBA (an ERS inhibitor),EEP protected HUVECs from ox-LDL-induced injury in a dose-dependent manner,as assessed by the increased cell viability and the decreased LDH release,apoptotic rate and caspase-3 activation.The decrease in cell viability and the increases in LDH release,apoptotic rate and caspase-3 activation induced by TM,an ERS inducer,were also attenuated by EEP.Moreover,EEP suppressed ox-LDL-induced CHOP upregulation and Bcl-2 downregulation,and this effect was similar to that of PBA.Similarly,EEP significantly suppressed TM-induced CHOP upregulation both at the protein and mRNA levels.CONCLUSION:EEP may protect HUVECs from ox-LDL-induced apoptosis,and the mechanism is at least partially involved in suppressing CHOP-mediated ERS-associated apoptotic pathway.