title: Cannabinoid receptor 1 blockade protects human retinal pigment epithelial cells from oxidative injury.
abstract: BACKGROUND
  Because oxidative stress is assumed to be a key mechanism in the pathological process of age-related macular degeneration (AMD), increasing numbers of studies have focused on discovering new pathways and treatments for reducing oxidative damage. Our work investigates the potential role of the cannabinoid receptor 1 (CB1) in oxidative stress of primary human retinal pigment epithelial (RPE) cells, a cellular model of AMD.
  
  
  METHODS
  Primary human RPE cells were cultured and exposed to hydrogen peroxide for 24 h to induce oxidative damage. The expression of and changes in the CB1 receptor were determined with western blot assay and confocal imaging. The CB1 receptor in the RPE cells was inhibited with small interfering RNA (siRNA) or rimonabant (SR141716). Cell viability, apoptosis, and reactive oxygen species production were measured by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and sulforhodamine B assay, annexin V and propidium iodide staining, and the dichlorofluorescein fluorescence assay, respectively. Intracellular superoxide dismutase activity was assayed with a commercially available assay kit. Phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) protein expression and activation of signaling molecules were assessed with western blot analysis.
  
  
  RESULTS
  We showed that human RPE cells express the CB1 receptor. In addition, oxidative stress upregulates the expression of the CB1 receptor. Deleting the CB1 receptor or treating with the CB1 receptor antagonist rimonabant (SR141716) rescued RPE cells from hydrogen peroxide-induced oxidative damage. Rimonabant pretreatment effectively reduced the apoptosis of RPE cells, inhibited the generation of intracellular reactive oxygen species and elevated the activity of superoxide dismutase. In addition, rimonabant significantly strengthened the oxidative stress-induced activation of the PI3K/Akt signaling pathway.
  
  
  CONCLUSIONS
  The results demonstrate the expression and regulation of CB1 receptors in human RPE cells. Inhibiting the CB1 receptor may be an effective therapeutic strategy for AMD by downregulating oxidative stress signaling and facilitating PI3K/Akt activation.
authors: Department of Ophthalmology, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People's Republic of China.
authors: Yan
authors: Y
authors: Wei
authors: Xu
authors: X
authors: Wang
authors: Feng
authors: F
authors: Zhao
authors: Pei-Quan
authors: PQ
authors: Zhao
authors: Xiao-Li
authors: XL
authors: Kang
mesh_terms: D063387:Cannabinoid Receptor Antagonists / Q000494:pharmacology; D002478:Cells, Cultured; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity; D008268:Macular Degeneration / Q000209:etiology / Q000378:metabolism / Q000628:therapy; D018384:Oxidative Stress / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010880:Piperidines / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D043884:Receptor, Cannabinoid, CB1 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000502:physiology*; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D000077285:Rimonabant; D015398:Signal Transduction / Q000187:drug effects; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: C571130:CNR1 protein, human; D063387:Cannabinoid Receptor Antagonists; D010880:Piperidines; D011720:Pyrazoles; D017382:Reactive Oxygen Species; D043884:Receptor, Cannabinoid, CB1; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D000077285:Rimonabant