title: Effects of the vegetable polyphenols epigallocatechin-3-gallate, luteolin, apigenin, myricetin, quercetin, and cyanidin in primary cultures of human retinal pigment epithelial cells.
abstract: OBJECTIVE
  Vegetable polyphenols (bioflavonoids) have been suggested to represent promising drugs for treating cancer and retinal diseases. We compared the effects of various bioflavonoids (epigallocatechin-3-gallate [EGCG], luteolin, apigenin, myricetin, quercetin, and cyanidin) on the physiological properties and viability of cultured human retinal pigment epithelial (RPE) cells.
  
  
  METHODS
  Human RPE cells were obtained from several donors within 48 h of death. Secretion of vascular endothelial growth factor (VEGF) was determined with enzyme-linked immunosorbent assay. Messenger ribonucleic acid levels were determined with real-time reverse transcription polymerase chain reaction. Cellular proliferation was investigated with a bromodeoxyuridine immunoassay, and chemotaxis was examined with a Boyden chamber assay. The number of viable cells was determined by Trypan Blue exclusion. Apoptosis and necrosis rates were determined with a DNA fragmentation enzyme-linked immunosorbent assay. The phosphorylation level of signaling proteins was revealed by western blotting.
  
  
  RESULTS
  With the exception of EGCG, all flavonoids tested decreased dose-dependently the RPE cell proliferation, migration, and secretion of VEGF. EGCG inhibited the secretion of VEGF evoked by CoCl2-induced hypoxia. The gene expression of VEGF was reduced by myricetin at low concentrations and elevated at higher concentrations. Luteolin, apigenin, myricetin, and quercetin induced significant decreases in the cell viability at higher concentration, by triggering cellular necrosis. Cyanidin reduced the rate of RPE cell necrosis. Myricetin caused caspase-3 independent RPE cell necrosis mediated by free radical generation and activation of calpain and phospholipase A2. The myricetin- and quercetin-induced RPE cell necrosis was partially inhibited by necrostatin-1, a blocker of programmed necrosis. Most flavonoids tested diminished the phosphorylation levels of extracellular signal-regulated kinases 1/2 and Akt proteins.
  
  
  CONCLUSIONS
  The intake of luteolin, apigenin, myricetin, and quercetin as supplemental cancer therapy or in treating retinal diseases should be accompanied by careful monitoring of the retinal function. The possible beneficial effects of EGCG and cyanidin, which had little effect on RPE cell viability, in treating retinal diseases should be examined in further investigations.
authors.affiliation: Department of Ophthalmology and Eye Hospital, University of Leipzig, Leipzig, Germany.
authors.forename: Rui
authors.initials: R
authors.lastname: Chen
authors.affiliation: Department of Ophthalmology and Eye Hospital, University of Leipzig, Leipzig, Germany.
authors.forename: Margrit
authors.initials: M
authors.lastname: Hollborn
authors.affiliation: Institute of Human Genetics, University of Regensburg, Regensburg, Germany.
authors.forename: Antje
authors.initials: A
authors.lastname: Grosche
authors.affiliation: Paul Flechsig Institute of Brain Research, University of Leipzig, Leipzig, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Reichenbach
authors.affiliation: Department of Ophthalmology and Eye Hospital, University of Leipzig, Leipzig, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Wiedemann
authors.affiliation: Department of Ophthalmology and Eye Hospital, University of Leipzig, Leipzig, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Bringmann
authors.affiliation: Department of Ophthalmology and Eye Hospital, University of Leipzig, Leipzig, Germany ; Helios Klinikum Aue, Aue, Germany.
authors.forename: Leon
authors.initials: L
authors.lastname: Kohen
mesh_terms: D000872:Anthocyanins / Q000494:pharmacology; D047310:Apigenin / Q000494:pharmacology; D002392:Catechin / Q000031:analogs & derivatives / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002633:Chemotaxis / Q000187:drug effects; D053938:DNA Fragmentation / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D047311:Luteolin / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D059808:Polyphenols / Q000494:pharmacology*; D011794:Quercetin / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D055213:Retinal Pigment Epithelium / Q000166:cytology*; D015398:Signal Transduction / Q000187:drug effects; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis / Q000235:genetics; D014675:Vegetables / Q000737:chemistry*
chemical_list: D000872:Anthocyanins; D005419:Flavonoids; D007093:Imidazoles; D007211:Indoles; D059808:Polyphenols; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; C507699:necrostatin-1; C040015:myricetin; C017154:cyanidin; D047310:Apigenin; D002392:Catechin; D011794:Quercetin; C045651:epigallocatechin gallate; D047311:Luteolin