title: Autophagy and Apoptosis in the Response of Human Vascular Endothelial Cells to Oxidized Low-Density Lipoprotein.
abstract: OBJECTIVE
  Oxidized low-density lipoprotein (ox-LDL) may induce autophagy, apoptosis, necrosis or proliferation of cultured endothelial cells depending on the concentration and exposure time. Our previous studies found that ox-LDL exposure for 6 h increases the autophagic level of human umbilical vein endothelial cells (HUVECs) in a concentration-dependent manner. The present study investigates the relationship between autophagy and apoptosis in HUVECs exposed to ox-LDL.
  
  
  METHODS
  Flow cytometry and Western blot were used to study the apoptotic and autophagic phenomena. The contribution of autophagic and apoptotic mechanisms to ox-LDL-induced upregulation of MAP1-LC3, beclin1 and p53 protein levels were assessed by pretreatment with the autophagic inhibitors 3-MA and Atg5 small interfering (si)RNA, as well as z-vad-fmk, an apoptosis inhibitor.
  
  
  RESULTS
  ox-LDL induced the apoptosis of HUVECs in a concentration-dependent way. The increased expression of the autophagic proteins, LC3-II and beclin1, can be reversed by 3-MA and z-vad-fmk pretreatment. 3-MA and Atg5 siRNA increased the ox-LDL-induced increases of the p53 protein level and the annexin V-positive staining, which was decreased by z-vad-fmk.
  
  
  CONCLUSIONS
  These results suggest that overstimulation of ox-LDL can induce autophagy and apoptosis in HUVECs. Inhibition of apoptosis leads to an inhibition of autophagy induced by ox-LDL. However, inhibition of autophagy leads to an increase in the ox-LDL-induced apoptosis.
authors.affiliation: Department of Neurology, The Second Affiliated Hospital of Soochow University, Suzhou, PR China.
authors.forename: Yanlin
authors.initials: Y
authors.lastname: Zhang
authors.forename: Ying
authors.initials: Y
authors.lastname: Xie
authors.forename: Shoujiang
authors.initials: S
authors.lastname: You
authors.forename: Qiao
authors.initials: Q
authors.lastname: Han
authors.forename: Yongjun
authors.initials: Y
authors.lastname: Cao
authors.forename: Xia
authors.initials: X
authors.lastname: Zhang
authors.forename: Guodong
authors.initials: G
authors.lastname: Xiao
authors.forename: Rui
authors.initials: R
authors.lastname: Chen
authors.forename: Chunfeng
authors.initials: C
authors.lastname: Liu
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D001343:Autophagy / Q000502:physiology*; D002478:Cells, Cultured; D061307:Human Umbilical Vein Endothelial Cells / Q000378:metabolism*; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D008077:Lipoproteins, LDL; C099252:oxidized low density lipoprotein