Role Of Autophagy In Human Umbilical Vein Endothelial Cells Exposed To Advanced Glycation Endproduct-BSA

Objective:To investigate the role of autophagy in the injury of human umbilical vein endothelial cells ( HUVECs ) induced by advanced glycation endproduct-BSA(AGE-BSA)Methods:1. The instable atherosclerosis (AS) plaques from patients with diabetes mellitus (DM) were used for this study. HE and Immunofluorescence staining methods were used to examine the vascular endothelial cell (VEC) marker, vWF, and the autophagic protein microtubule-associated protein light chain 3(MAP1-LC3). The formations of autophagic vacuole (AV) in VEC were examined by transmission electron microscopy (TEM).2. After AGE-BSA exposure to HUVECs, the formation of autophagosomes was observed by TEM. Monodansylcadaverine (MDC) staining, MAP1-LC3 protein immunofluorescence staining, and western-blot were used for the detection of the ratio of LC3-II/β-actin and lysosome associated membrane protein 1(Lamp1) protein levels.3. To investigate the role of autophagy in AGE-BSA-induced injury in HUVECs, cultured HUVECs were randomly divided into four groups: the control, AGE-BSA, AGE-BSA +rapamycin, and AGE-BSA +3-MA. The cells were used to detect the ratio of LC3-II/β-actin by western blot, while the proliferation of cells was measured by MTT , lactate dehydrogenase ( LDH ) content in culture medium was detected with enzyme linked immunosorbent assay. In addition, the role of autophagy in AGE-BSA-induced injury of HUVECs was assessed.4. The content of ROS in culture medium was assessed by flow cytometry. The roles of oxidative stress in the activation of autophagy induced by AGE were investigated by usingα-tocopherol.Results:HE and Immunofluorescence staining showed increased new endothelial cells in instable plaques of the carotid artery. The increased AV and high expression of MAP1-LC3 were observed in these endothelial cells, especially in the cells near the shoulder and lipid-rich core of atherosclerotic plaques.Autophagy was induced in HUVECs detected by MDC staining, immunofluorescence staining and TEM. The upregulation of the ratio of LC3-II/β-actin protein level induced by AGE-BSA reached the peak at 6 h after exposure. AGE-BSA also increased the Lamp1protein level at the 6 h time point. While the upregulation of HUVECs autophagy induced by AGE-BSA was decreased by autophagic inhibitor 3-MA, but increased by the autophagic inducer rapamycin.Aggregated AGE-BSA in HUVECs brought about a decrease of cell proliferation, which was decreased by autophagic inhibitor 3-MA, but increased by the autophagic inducer rapamycin. The upregulation of autophagic level induced by AGE-BSA increased the content of LDH and the AGE-BSA-induced inhibition of cell proliferation. Conversely, the autophagic inhibitor 3-MA decreased the increases of LC3-II/β-actin induced by AGE-BSA. In addition, HUVECs treated with AGE-BSA showed a much greater degree of overlap of MAP1-LC3 than that of control. After 6 hours exposure to AGE-BSA, the level of ROS was increased in HUVECs, but this was inhibited byα-tocopherol while the increase of the ratio of LC3-II/β-actin was reversed byα-tocopherol pretreatment,Conclusion:Autophagy was observed in the instable plaques in the patients with DM. AGE-BSA increased the autophagic level of HUVECs. The upregulation of autophagy reduce the AGE-BSA-induced cell damage and LDH release; thus, autophagy palys a protective role in the injury of HUVECs induced by AGE-BSA. ROS decreased the level of autophagy in HUVECs exposed to AGE-BSA...