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D. A. Maerker, R. Foeckler, V. Milenkovic, O. Strauss, H. Helbig, T. Dietrich; Modulation of Cytokine Expression by Protein Tyrosine Phosphatase 1b Treatment in Retinal Pigment Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2010;51(13):467.
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© ARVO (1962-2015); The Authors (2016-present)
The retinal pigment epithelium (RPE) plays an important role in degenerative and neovascular diseases of the retina. Protein tyrosin phosphatases (PTP) regulate signaling pathways of essential cellular processes; their role in diseases of retina and RPE has not been determined yet. The PTP interacting protein 51 (PTPIP51) has been identified in human embryonic and adult RPE tissue. In order to analyze PTPs and their functional role in RPE, immunohistochemistry and cell culture experiments using specific PTP inhibition were performed.
Immunohistochemical analysis of human and mouse RPE in situ was performed using specific PTP1B antibodies (Abcam, Calbiochem). Human retinal pigment epithelium cells (ARPE19) were cultured and incubated for 24 hours and 48 hours with the specific protein tyrosine phosphatase inhibitor bpV(phen) (peroxovanadium 1,10-phenanthroline) to analyze the impact on cytokine expression. Cell lysates were used for quantitative real time RT-PCR. The expression of mRNA of the cytokines vascular endothelial growth factor A (VEGF-A), thrombospondin-1 (TSP-1), transforming growth factor beta 1 and 2 (TGFß-1/-2), connective tissue growth factor (CTGF), and pigment epithelium-derived factor (PEDF) was analyzed.
Immunohistochemistry of human and mouse adult tissue revealed PTP1B positive staining in retinal pigment epithelium in situ. A focal staining pattern of PTP1B was observed in human tissue. PTP inhibition by incubation for 24h/48h with bpV(phen) resulted in a 9 fold/6 fold higher expression of VEGF-A in ARPE19 cells compared to control, detected by RT-PCR. TSP-1 expression was 2 fold higher after 24h while the expression level of TSP-1 was not significantly different from control after 48h incubation. TGFß-1 expression was increased 3 fold after 24h and remained on that level after 48h. TGFß-2 and CTGF expression doubled the control after 24h, while there was no detectable difference after 48h incubation. PEDF mRNA levels remained unchanged after 24h, whereas 48h incubation resulted in a 2 fold increase.
PTP1B is expressed in human and mouse RPE. PTPs seem to be of functional importance for cellular processes as cytokine expression, because treatment with PTP inhibitor bpV(phen) resulted in modulation of cytokine expression, e.g. in increased VEGF-A, TSP-1, CTGF, TGFß-1 and -2, and PEDF levels. This finding might offer new insights and therapeutic options for neovascular degenerative retinal diseases such as age related macular degeneration.
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