title: Oxidized LDL induces apoptosis of human retinal pigment epithelium through activation of ERK-Bax/Bcl-2 signaling pathways.
abstract: OBJECTIVE
  Retinal pigment epithelium (RPE) cell dysfunction and death play a vital role in the pathogenesis of age-related macular degeneration (AMD). We previously reported that oxidized low-density lipoprotein (OX-LDL) induces retinal degeneration in vivo. In this study, we investigated the role of the ERK-Bax/Bcl-2 signaling pathways in OX-LDL-induced apoptosis in human RPE.
  
  
  METHODS
  ARPE-19 cells were incubated with 10-100 mg/mL n-LDL or OX-LDL for 24 h. Cell viability was assessed using the Cell Titer 96 Aqueous One Solution cell proliferation assay. RPE apoptosis was measured with a flow cytometer. Reverse transcription polymerase chain reaction was used to detect Bcl-2 and Bax mRNA levels in RPE cells. Bcl-2 and Bax protein expression was measured by western blotting. Activation of extracellular signal-regulated kinase (ERK) protein was evaluated by western blot analysis. One-way analysis of variance was used to compare differences.
  
  
  RESULTS
  OX-LDL treatment decreased ARPE-19 cell viability in a dose-dependent manner, whereas n-LDL had no effect. Compared with the control group, OX-LDL significantly increased the apoptosis of RPE, 10 mg/mL, 50 mg/mL, 100 mg/mL apoptosis rate was 6.43 ± 0.19%, 5.12 ± 0.27%, 5.53 ± 0.35%, respectively. OX-LDL also increased Bcl-2 expression and decreased Bax expression significantly. The Bcl-2 to Bax ratio was elevated after OX-LDL treatment. Inhibition of ERK downregulated Bax and was associated with RPE apoptosis.
  
  
  CONCLUSIONS
  Our data suggest that apoptosis induced by OX-LDL in RPE partly depends on Erk-Bax/Bcl-2 signaling pathway activation. These results may provide further information regarding the effects of OX-LDL in human RPE and their potential role in AMD pathogenesis.
authors: Department of Ophthalmology, Affiliated First People's Hospital, Shanghai Jiaotong University , Shanghai , China.
authors: Qiu
authors: Q
authors: Yating
authors: Yao
authors: Y
authors: Yuan
authors: Zhang
authors: Z
authors: Wei
authors: Gu
authors: G
authors: Qing
authors: Wu
authors: W
authors: Xingwei
authors: Qinhua
authors: Q
authors: Qiu
authors: Yin
authors: Y
authors: Lili
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics* / Q000378:metabolism; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D055213:Retinal Pigment Epithelium / Q000378:metabolism / Q000473:pathology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D051028:bcl-2-Associated X Protein / Q000235:genetics* / Q000378:metabolism
chemical_list: C494826:BAX protein, human; D008077:Lipoproteins, LDL; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein; C099252:oxidized low density lipoprotein; D048049:Extracellular Signal-Regulated MAP Kinases
keywords: Age related macular degeneration; Oxidized LDL; apoptosis; retinal pigment epithelium