Abstract
Purpose :
Diabetic retinopathy (DR) continues to lack effective therapies for early stages of disease. Inflammation was noted to be associated with DR as early as 1960’s. Only recently, however, has the extent of inflammation in driving DR disease pathogenesis been investigated more closely. Type 1 and type 2 cytokines are responsible, in large part, for directing a predominant pro-inflammatory vs anti-inflammatory response, respectively. As such, in an effort to identify therapeutic points of intervention, the current study examines pathways regulated by type 1 vs type 2 cytokines in REC cultured in high glucose.
Methods :
Primary HREC were exposed to either normal glucose (5 mM, NG) or high glucose (25 mM, HG) with growth supplements for three days. Cells were quiesced for 24 h (no growth supplements), then treated with IL-1β (type 1 cytokine) or IL-4 (type 2 cytokine) in both HG and NG for an additional 24 h. Total protein was collected for Western blot and ELISA analyses of selected inflammatory mediators, pro-resolving molecules (including enzymes/receptors) and apoptotic markers known to be altered during diabetes.
Results :
Protein analyses indicated increased ratio of phosphorylated to total NF-κB in REC exposed to HG. While IL-4 significantly suppressed this change, IL-1β amplified the NF-κB response under HG conditions. Among changes in the pro-resolving pathway, resolvin D1 (RvD1) receptor GPR32 was upregulated with IL-4 treatment under both HG and NG conditions; IL-1β had no effect. Regarding cell death, preliminarily it appears that IL-1β promotes apoptosis though elevated Bax levels, while IL-4 appears to have no significant effect under HG conditions.
Conclusions :
These data suggest that exposure to a type 2-dominant cytokine could suppress inflammation in HREC exposed to HG by decreasing levels of inflammatory mediators, promoting pro-resolving pathways and inhibiting apoptosis. In contrast, IL-1β, a type 1 cytokine, appears to promote chronic inflammation through increased levels of inflammatory mediators and enhanced apoptosis. Most notably, the potential therapeutic effects of a type 2 environment could be mediated partially through pro-resolving lipid mediators. This study suggests pathogenesis of diabetic retinopathy could be manipulated by promoting Th1 vs Th2 dominant immune response.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.