gms | German Medical Science

Background: Degenerative ocular disorders like age-related macular degeneration (AMD) may induce long-term pro-inflammatory signals on retinal pigment epithelial (RPE) cells. In this study, we investigated the effect of long term treatment of RPE cells with agonists of toll-like receptor (TLR)3 (Poly I:C), TLR4 (LPS) and the pro-inflammatory cytokine TNFα.

Methods: All tests were conducted with primary porcine RPE. Cells were stimulated with Poly I:C (1, 10, 100 µg/ml), LPS (0.1, 1, 10 µg/ml) or TNFα (12.5, 25 or 50 ng/ml) for 1 day, 7 days or 4 weeks. Cytokine secretion (IL-6, IL-1ß, IL-8, TNFα, TGFß) was tested in ELISA, phagocytosis in an assay, and expression of RPE65 in Western blot. Barrier function was tested in transwell-cultured cells by measuring transepithelial resistance for up to 3 days.

Results: LPS and TNFα significantly reduce cell viability after 1 day and 7 days, Poly I:C after 7 days and 4 weeks. LPS, Poly I:C and TNFα significantly induce the secretion of IL-6 and IL-8 at all tested time points. IL-1ß is increased by LPS after 1 day, but not by Poly I:C or TNFα. TNFα secretion is increased by Poly I:C and LPS after 1 day but not at later time points. TGFß secretion is not influenced by any stimulus. Concerning RPE function, LPS decreased phagocytosis after 7 days, and Poly I:C and TNFα after 1 day. Poly I:C reduced RPE65 expression after 1 day and 7 days, while incubation for 4 weeks with LPS or TNFα significantly reduced RPE65 expression. Barrier function was not affected by Poly I:C, while LPS and TNFα reduced barrier function after 1 h, 4 h and 3 days.

Conclusion: Long term pro-inflammatory stimuli reduce RPE viability, barrier properties and cellular function and therefore may contribute directly to atrophic changes in AMD.