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The death receptors TRAMP and Trail-R1, R2, R3, R4 and their corresponding ligands Apo3-L and TRAIL are present in retinal pigment epithelial cellsS. Aduckathil, P. Esser, N. Kociok, A. Hueber, G. Thumann
Introduction: Apoptosis, or programmed cell death, is a natural, process that causes cells to die withoutinducing an inflammatory response and has been shown to play an important role in retinal degeneration and other retinal pathologies like proliferative vitreoretinopathy (PVR). Recently, several death-receptors with a predominant function in induction of apoptotic cell death have been identified. Here, we sought to investigate the presence of newly discovered death-receptors from the TNF-receptor superfamily, i.e. TNF-receptor-related apoptosis-mediated protein (TRAMP) and its ligand Apo3-L and TNF-related apoptosis-inducing ligand (TRAIL) and its four receptors Trail-R1,R2,R3,R4 in human retinal pigment epithelial cells, which are thought to play a major role in the development of PVR.
Methods: Total RNA was isolated from freshly harvested and cultured human RPE cells of passage P0. The presence of Apo3-L, TRAMP, TRAIL-ligand and TRAIL-R1-4 mRNA was investigated by RT-PCR using specific PCR primers. Using commercially available antibodies, we analysed the expression of TRAIL and TRAIL-receptor-1 on the protein level by Western Blot in cell lysates. Results: Specific bands for the chosen primer combinations could be detected by RT-PCR in freshly harvested and P0 cells and verified by DNA-sequencing. Western Blot revealed the specific bands for TRAIL-ligand and TRAIL-receptor-1 at the expected molecular weight range. Immunohistochemical studies of surgically removed membranes (n=10) from patients, suffering from proliferative vitreoretinopathy also confirmed the presence of these proteins in the specimens.
Conclusions: The presence of death receptors in human retinal pigment epithelial cells has implications for future studies of retinal degenerations. Moreover, antiproliferative and proapoptotic therapeutic strategies in the treatment of PVR may need to comprise the presence of multiple death receptors in RPE-cells.
Ophthalmology, University Eye Clinic Cologne, Cologne, Germany