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Brandon Coughlin, Derrick J Feenstra, Susanne Mohr; Diverse Actions of Interleukin-6 on Human Müller Versus Human Retinal Endothelial Cells Under Hyperglycemic Conditions. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3237.
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Chronic inflammation and cell death seem to be involved in the induction and progression of diabetic retinopathy. Interleukin-6 (IL-6), a pleiotropic cytokine, is known to participate in acute and chronic inflammatory events. Its actions depend on cellular environment, cell type, and receptor expression promoting protective as well as detrimental effects. We have discovered that IL-6 protects Müller cells from hyperglycemic insult. In contrast, effects of IL-6 on the vasculature have been associated with angiogenesis, one of the detrimental events in diabetic retinopathy. Therefore, this study aimed to better understand the effects of IL-6 on different retinal cell types and to identify potential differences in IL-6 receptor expression by these cells.
Primary human Müller cells (hMC) and retinal endothelial cells (HREC) were isolated from retinas of non-diabetic donors. hMCs (1x106 cells) and HRECs (1x106 cells) were treated with normal (7.8mM) and high (25mM) glucose for 48 hours in the presence or absence of recombinant IL-6 (1-10 ng/ml). Cell death was assessed by trypan blue exclusion. Western blot analysis and ELISA assays were used to determine expression levels of receptors such as glycoprotein 130 (GP130), soluble GP130 (sGP130), and the membrane-bound interleukin-6 receptor (mIL-6R) as well as inflammatory mediators. Statistical analysis was done using ANOVA followed by Tukey test.
Treatment of hMCs with IL-6 (2ng/ml) significantly attenuated high glucose-induced GAPDH nuclear accumulation (an early parameter for cell death) by 64% ± 7.5% (p<0.05; n=6). Consequently, IL-6 (2ng/ml) treatment significantly reduced high glucose-induced cell death from 18.6% ± 3.6% to 9.4% ± 3.2% (p<0.05; n=6). hMCs express GP130. Expression levels of GP130 did not alter under high glucose conditions (n=3). hMCs also express the membrane bound IL-6R. In contrast, HRECs expressed GP130 but lack mIL-6R expression indicating that IL-6 action on these different cell types is mediated by differences in receptor expression.
Our results suggest that IL-6 exerts diverse effects by activating different receptor combinations depending on the cell type affected. Therefore, in order to develop therapies for diabetic retinopathy targeting IL-6, a more complete understanding of IL-6 signaling in the diabetic retina is necessary.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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