title: The retinal pigment epithelium (RPE) induces FasL and reduces iNOS and Cox2 in primary monocytes.
abstract: OBJECTIVE
  Retinal pigment epithelium (RPE) cells may alter the phenotype of monocytes by soluble factors that may be influenced by stimulation of the RPE. Since RPE cells carry the toll-like receptor-3 (TLR3) that detects and reacts to viral infection through binding of dsRNA we investigated the effects of RPE cells with or without TLR3 stimulation on blood-derived monocytes with respect to regulation of pro-/anti-inflammatory cytokines, anti-angiogenic factors and migratory properties.
  
  
  METHODS
  Primary RPE cells were prepared from porcine eyes; monocytes were prepared from porcine blood. TLR3 activation was induced by polyinosinic:polycytidylic acid (Poly I:C). RPE cells were stimulated with Poly I:C in different concentrations for 24 hours and a cell culture supernatant was applied to the monocytes. Expression of CD14 and Fas ligand (FasL) was determined via flow cytometry. The expression of IL-6, IL-1ß, TNFα, Cox2, iNOS and IL-10 was determined via quantitative RT-PCR. Migration was determined using Boyden chamber experiments.
  
  
  RESULTS
  The supernatant of RPE cells, irrespective of TLR3 activation, induced FasL expression in the monocytes. Expression of iNOS and Cox2 was reduced by RPE cells and the reduction of Cox2 but not if iNOS was lost under TLR3 activation. No induction of IL-6, IL-1ß, IL-10 or TNFα by the RPE was seen. TLR3-activated RPE cells induced monocyte migration.
  
  
  CONCLUSIONS
  RPE cells induce an upregulation of FasL and a downregulation of iNOS and Cox2 without upregulating inflammatory cytokines, possibly inducing an anti-angiogenic phenotype in the monocytes. This phenotype is still upheld after challenging RPE cells with dsRNA, mimicking a viral infection.
authors: Department of Ophthalmology, University of Kiel, University Medical Center, Arnold-Heller-Str. 3, 24105, Kiel, Germany.
authors: Christin
authors: C
authors: Hettich
authors: Sebastian
authors: S
authors: Wilker
authors: Rolf
authors: R
authors: Mentlein
authors: Ralph
authors: R
authors: Lucius
authors: Johann
authors: J
authors: Roider
authors: Alexa
authors: A
authors: Klettner
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002465:Cell Movement; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D053222:Fas Ligand Protein / Q000378:metabolism*; D005434:Flow Cytometry; D018950:Lipopolysaccharide Receptors / Q000378:metabolism; D009000:Monocytes / Q000201:enzymology*; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D011070:Poly I-C / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D055213:Retinal Pigment Epithelium / Q000187:drug effects / Q000502:physiology*; D013552:Swine; D051196:Toll-Like Receptor 3 / Q000378:metabolism
chemical_list: D016207:Cytokines; D053222:Fas Ligand Protein; D018950:Lipopolysaccharide Receptors; D012333:RNA, Messenger; D051196:Toll-Like Receptor 3; D052247:Nitric Oxide Synthase Type II; D051546:Cyclooxygenase 2; D011070:Poly I-C