Apoptosis-mediating receptor-ligand systems in human retinal pigment epithelial cells.
BACKGROUND
To establish new strategies for the treatment of proliferative vitreoretinopathy (PVR), we investigated new members of a recently discovered apoptosis-inducing receptor-ligand system in human retinal pigment epithelial (RPE) cells. TRAIL (Apo2-L) and Apo3-L are capable of inducing cell death via their receptors Trail-R1 to Trail-R4 and TRAMP. The goal of this study was to prove the existence of these new apoptosis-inducing receptors and ligands in RPE cells.


METHODS
Human RPE cells, cultured or prepared directly from the eye, were examined by RT-PCR. Immunohistochemistry of epiretinal membranes of traumatic PVR was performed for the detection of TRAIL and Trail-R1. Protein expression of Trail-R1 was examined in cultured human RPE cells by western blot. Cell death after TRAIL treatment of human RPE cells was measured by crystal violet staining.


RESULTS
For RPE cells derived directly from the eye, we detected mRNAs of Trail-R2, Trail-R3, TRAIL, and APO3-L, but not Trail-R1, Trail-R4, and TRAMP. All the examined transcripts were detected in human P0 RPE cells in vitro. Immunohistochemical studies on PVR membranes identified TRAIL and Trail-R1. Western blot confirmed the presence of Trail-R1 in cultured human RPE cells. TRAIL failed to kill RPE cells in vitro, but showed a strong synergistic killing effect when coincubated with protein (cycloheximide) or RNA (actinomycin D) synthesis inhibitor.


CONCLUSIONS
We detected a novel apoptosis-inducing receptor-ligand system in RPE cells. An induction of apoptosis as a treatment of PVR seems to be possible. Further investigations are needed including an animal model of PVR.
Department of Vitreo-Retinal Surgery, Center of Ophthalmology, University of Cologne, Joseph-Stelzmann-Strasse 9, Germany. Arno.Hueber@uni-koeln.de
Arno
A
Hueber
Sanjay
S
Aduckathil
Norbert
N
Kociok
Gerhard
G
Welsandt
Sven
S
Dinslage
Bernd
B
Kirchhof
Peter J
PJ
Esser
D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins; D015153:Blotting, Western; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004357:Drug Synergism; D019773:Epiretinal Membrane / Q000378:metabolism / Q000473:pathology; D058851:GPI-Linked Proteins; D006801:Humans; D007124:Immunoenzyme Techniques; D008024:Ligands; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor / Q000235:genetics* / Q000378:metabolism; D053320:Receptors, Tumor Necrosis Factor, Member 10c; D020133:Reverse Transcriptase Polymerase Chain Reaction; D053221:TNF-Related Apoptosis-Inducing Ligand; D053319:Tumor Necrosis Factor Decoy Receptors; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology
D051017:Apoptosis Regulatory Proteins; D058851:GPI-Linked Proteins; D008024:Ligands; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D018124:Receptors, Tumor Necrosis Factor; D053320:Receptors, Tumor Necrosis Factor, Member 10c; D053221:TNF-Related Apoptosis-Inducing Ligand; C505639:TNFRSF10B protein, human; C108661:TNFRSF10C protein, human; C505653:TNFSF10 protein, human; D053319:Tumor Necrosis Factor Decoy Receptors; D014409:Tumor Necrosis Factor-alpha; D003609:Dactinomycin; D003513:Cycloheximide