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Daniel Ardeljan, Yujuan Wang, De Fen Shen, Jingsheng Tuo, Chi-Chao Chan; Treatment With Recombinant Interleukin-17A Reduces ARPE-19 Cell Viability. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1227.
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Age-related macular degeneration (AMD) is a degenerative disease that impairs primarily photoreceptors and the retinal pigment epithelium (RPE) in the macula. Recently, expression of significantly higher IL-17A transcripts was found in human AMD maculae and elevated serum IL-17A levels were measured in AMD patients. IL-17A is known to induce a robust immune response, but its exact effect on the RPE remains elusive. This study explores the role of IL-17A in human RPE cells.
Cultured ARPE-19 cells were serum-starved for 24h and then treated for 48h with recombinant IL-17A (100 ng/ml). A Taqman gene expression array of 92 human signal transduction genes revealed IL-8 to be differentially expressed after the treatment, which was further examined by quantitative RT-PCR. An experiment to characterize the role of NF-kB, the upstream regulator of IL-8, was conducted by co-incubating IL-17A and an NF-kB inhibitor (SN50, 18μM) with ARPE-19 cells. Apoptosis was evaluated by immunohistochemical detection of Caspase-3 and Caspase-9 activation and by flow cytometry using Annexin V/7AAD. An MTT assay was performed to evaluate ARPE-19 cell viability with respect to changes in IL-17A doses.
IL-17A-treated ARPE-19 cells had substantially increased IL-8 mRNA along with elevated Caspase-9 activity and diminished Caspase-3 activity as detected by immunohistochemistry. Inhibition of NF-kB with SN50 resulted in increased apoptotic activity as measured by flow cytometry and this effect was marginally strengthened with the addition of IL-17A. The MTT assay revealed that IL-17A doses ranging from 1 pg/ml to 10 ug/ml decreased cell viability from approximately 20-35%.
IL-17A might play a role in the apoptosis of RPE cells and IL-8 might be one of its major mediators. IL-17A-treated ARPE-19 cells exhibit altered caspase activity in a process largely but not completely mediated by the NF-kB pathway. IL-17A was shown to have a negative effect on cell viability in culture. It seems that IL-17A is not only a mediator of inflammation, but also a regulator of apoptosis.
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