Abstract
Purpose :
Inflammation and inflammasome activation contribute to the development and progression of pathology in diabetic retinopathy (DR). The stress response protein REDD1 (regulated in development and DNA damage 1) has also been implicated in visual deficits in diabetic patients. Recent pre-clinical studies support a role for REDD1 as a modulator of pro-inflammatory signaling. The studies here were designed to investigate the hypothesis that REDD1 contributes to the activation of the NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) inflammasome and development of retinal inflammation in DR.
Methods :
Diabetes was induced in B6;129 REDD1+/+ and REDD1-/- mice via low-dose intraperitoneal streptozotocin administration. Retinas were examined after 16 weeks of diabetes and protein expression and mRNA abundance were estimated by western blotting and qPCR, respectively. Whole eyes were examined by immunofluorescence. In some studies, mice were treated with the GSK3 inhibitor VP3.15. Mechanistic studies were also performed in human MIO-M1 retinal Müller glia cultures wherein REDD1 and GSK3 expression were genetically manipulated.
Results :
Expression of REDD1, NLRP3, and IL-1β were all increased in the retina of diabetic REDD1+/+ mice in association with macrophage infiltration of the inner retina. However, a similar effect was not observed in the retina of diabetic REDD1-/- mice. REDD1 was required for activation of the transcription factor Nuclear factor-kappa B (NF-kB) in the retina of diabetic mice. In Müller glia cultures exposed to hyperglycemic conditions, NLRP3 and IL-1β expression were enhanced and suppression of either REDD1 or GSK3 prevented the effect. REDD1 was required for enhanced GSK3 signaling and upregulated NLRP3/IL-1β expression in both the retina of diabetic mice and in Müller glia cultures exposed to hyperglycemic conditions. When diabetic mice were treated with VP3.15, NLRP3 and IL-1β expression were reduced in coordination with attenuated retinal macrophage infiltration.
Conclusions :
The data provide new insight into the molecular events that contribute to the retinal inflammatory response to diabetes. The findings support a role for REDD1-dependent activation of GSK3 in NF-kB-mediated NLRP3 inflammasome priming, and ultimately the production of pro-inflammatory cytokines.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.