title: Differential effects of the estrogen receptor agonist estradiol on toxicity induced by enzymatically-derived or autoxidation-derived oxysterols in human ARPE-19 cells.
abstract: OBJECTIVE
  Disturbances in cholesterol metabolism and increased levels of cholesterol oxidation products (oxysterols) in retina may contribute to age-related macular degeneration (AMD). The role of oxysterols or of their target receptors liver X receptors (LXRs) and estrogen receptors (ERs) in the pathogenesis of MD is ill-known. The purpose of this study is to determine the extent to which the oxysterols 27-hydroxycholesterol (27-OHC), 25-hydroxycholesterol (25-OHC) and 7-ketocholesterol (7-KC) affect the transcriptional activity of LXR and ER.
  
  
  METHODS
  ARPE-19 cells, untreated or incubated with 27-OHC, 25-OHC or 7-KC for 24 h were harvested. We used Western blot analyses for detecting ERs and LXRs expression, dual luciferase assays for measuring LXRs and ERs transcriptional activity, cytotox-ONE homogeneous membrane integrity assay for measuring cytotoxicity, JC-1 method for measuring mitochondrial membrane potential changes and ELISA for measuring cytokine levels.
  
  
  RESULTS
  Both LXRs and ERs are expressed and are transcriptionally active in ARPE-19 cells. 27-OHC, 25-OHC and 7-KC inhibited ER-mediated transcriptional activity, whereas 27-OHC and 25-OHC increased LXR-mediated transcription. E2 reduced 25-OHC and 27-OHC-induced cytotoxicity, mitochondrial permeability potential decline, and cytokine secretion. The LXR agonist GW3965 or the LXR antagonist 5α-6α-epoxycholesterol-3-sulfate (ECHS) did not offer protection against either 27-OHC and 25-OHC or 7-KC.
  
  
  CONCLUSIONS
  Increased levels of oxysterols can decrease ER and increase LXR signaling. ER agonists can offer protection against cytotoxic effects of 27-OHC and 25-OHC, two oxysterols derived by enzymatic reactions. Although they exert similar toxicity, the cellular mechanisms involved in the toxic effects of oxysterols whether derived by enzymatic or autoxidation reactions appear to be different.
authors.affiliation: Department of Pharmacology, Physiology and Therapeutics and.
authors.forename: Bhanu
authors.initials: B
authors.lastname: Dasari
authors.forename: Jaya R P
authors.initials: JR
authors.lastname: Prasanthi
authors.forename: Craig
authors.initials: C
authors.lastname: Meiers
authors.forename: Brij B
authors.initials: BB
authors.lastname: Singh
authors.forename: Othman
authors.initials: O
authors.lastname: Ghribi
mesh_terms: D002460:Cell Line; D018932:Chemokine CCL2 / Q000378:metabolism; D004347:Drug Interactions; D004958:Estradiol / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D047629:Estrogen Receptor beta / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D006801:Humans; D006888:Hydroxycholesterols / Q000378:metabolism / Q000633:toxicity*; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D007653:Ketocholesterols / Q000378:metabolism / Q000633:toxicity*; D000071518:Liver X Receptors; D008268:Macular Degeneration / Q000235:genetics / Q000378:metabolism; D057093:Orphan Nuclear Receptors / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000187:drug effects*; D014158:Transcription, Genetic / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: C111835:CCL2 protein, human; C508606:CXCL8 protein, human; D018932:Chemokine CCL2; C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D006888:Hydroxycholesterols; C508600:IL6 protein, human; D015850:Interleukin-6; D016209:Interleukin-8; D007653:Ketocholesterols; D000071518:Liver X Receptors; D057093:Orphan Nuclear Receptors; D010982:Platelet-Derived Growth Factor; D014409:Tumor Necrosis Factor-alpha; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D004958:Estradiol; C076996:27-hydroxycholesterol; C007997:25-hydroxycholesterol; C003001:7-ketocholesterol