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Shida Chen, Defen Shen, Nicholas Popp, Jingsheng Tuo, Mones S Abu-Asab, Ting Xie, Chi-Chao Chan; The involvement of IL-17RC pathway in the inflammatory stimuli of the multipotent retinal stem cells. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3984.
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© ARVO (1962-2015); The Authors (2016-present)
Multipotent retinal stem cells (RSCs) from the adult mouse retina are capable of producing functional photoreceptor cells to replace degenerative and atrophic photoreceptor cells in animal models. Inflammasome activation has been implicated in the pathogenesis of age-related macular degeneration (AMD). The downstream effectors of inflammasome activation are maturation of IL-1β and IL-18, which can induce the expression of IL-17A in Th17 cells. IL-17A mediates signal transduction and pro-inflammatory activities through its receptor, IL-17RC, which may contribute to AMD pathogenesis. Additionally, IL-1β and IL-18 signals may lead to apoptosis. This study aimed to determine whether IL-1β and IL-18 could induce expression of IL-17A and IL-17RC and to characterize their effect on apoptosis in RSCs.
RSCs were cultured in culture medium for retinal stem cells supplemented with 5% Knockout Serum Replacement, EGF and FGF, and the cells doubled every 24 hours. The protein levels of IL-17RC, cleaved caspase-3, and cleaved-caspase-9 were detected by confocal immunofluorescent microscopy. Cells were treated with IL-1β (1ng/ml, 10ng/ml, and 100ng/ml) or IL-18 (1ng/ml, 10ng/ml, and 100ng/ml) for 24 hours. Expression of IL-6, IL-17A, and IL-17RC transcript was evaluated by quantitative RT-PCR.
Naive RSCs expressed IL-17RC on the cell membrane and in the cytoplasm. Expression of IL-17RC mRNA increased by 2-fold when the cells were treated with the high dose of IL-1β (100ng/ml) but was enhanced in a dose-dependent manner when treated with IL-18. Treatment with IL-1β at 100ng/ml concentration induced a 3-fold increase in IL-6 mRNA expression. IL-18 treatment led to increased expression of IL-6 in a dose-dependent manner. IL-17A was not induced by either IL-1β or IL-18 treatment. IL-1β (100ng/ml) or IL-18 (10ng/ml) treatment induced expression of cleaved caspase-3 and cleaved-caspase-9 in the RSCs.
RSCs express IL-17 receptor, which is upregulated by IL-1β and IL-18. Neither IL-1β nor IL-18 treatment led to measurable IL-17A expression in this cell line. However, both IL-1β and IL-18, which are activated by inflammasome, can have pro-apoptotic effects on RSCs and may induce other pro-inflammatory cytokine produced by these cells.
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