The aim of this study was to characterize the role of nucleotide-binding oligomerization domain- (NOD-) like receptor (NLR) protein 3 (NLRP3) inflammasome activation in the onset of diabetic retinopathy (DR) using retina and vitreous from donors without diabetes mellitus (CTL), with diabetes mellitus alone (DM), and with DR. Retinal expression of glial fibrillary acidic protein (GFAP) and ionized calcium-binding adapter molecule 1 (Iba-1), the key markers of retinal inflammation, connexin43 (Cx43) which is involved in upstream inflammasome regulation, as well as NLRP3 and cleaved caspase-1, the main markers of inflammasome activation, were evaluated using immunohistochemistry and Western blotting. Vitreous interleukin (IL)-1β and IL-18, biomarkers of the activated inflammasome, were measured using a Luminex multiplex assay. Results showed a significant increase in the number and size of Iba-1⁺ cells and NLRP3 expression in DM, while a significant increase in GFAP, Cx43, cleaved caspase-1 and vitreous IL-18, as well as a further increase in Iba-1 and NLRP3 was found in DR. This suggests that the inflammasome is already primed in DM before its activation in DR. Furthermore, IL-18 may act as the major effector of inflammasome activation in DR while nuclear translocation of cleaved caspase-1 may play a role in gene transcription contributing to DR onset.

The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) protein 3 (NLRP3) inflammasome pathway is believed to mediate chronic inflammation in diabetic retinopathy (DR); however, its impact on the progression of DR remains to be elucidated. Therefore, the primary aim of this pilot study was to determine whether systemic inflammasome biomarkers interleukin (IL)-1β and IL-18 can be used to predict DR progression. DR screening results were analyzed against weight, level of glycated hemoglobin (HbA1c), and plasma levels of inflammasome biomarkers (IL-1β and IL-18), as well as general inflammation markers (C-reactive protein (CRP), IL-6, IL-8, tumor necrosis factor-alpha (TNF-α), and vascular endothelial growth factor (VEGF)) in patients with type 2 diabetes at baseline and 1 year post-bariatric surgery. Cross-sectional analysis demonstrated that weight, HbA1c, CRP, and IL-18 did not correlate with DR severity. The progressed group showed a higher relative change in IL-18 and CRP levels compared to the stable and regressed groups. Furthermore, relative changes in plasma CRP levels correlated with those of IL-18. Although further validation with larger cohorts is necessary, this pilot study supports the hypothesis that systemic inflammasome activation is associated with DR progression.

While existing local therapies partially restore vision loss from diabetic retinopathy (DR), there is currently no reliable treatment to prevent the onset or stop the progression of the disease. This review seeks to explore the inflammatory molecular mechanisms underpinning DR pathogenesis, which have not been targeted by current interventions. Specifically, this review explores the role of the nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) protein 3 (NLRP3) inflammasome in DR onset and progression. Evidence through clinical trials has begun to note that specific drugs (fenofibrate, metformin) appear effective in slowing DR progression independent of lipid or glucose-lowering, respectively, suggesting that other mechanisms are at play. Novel therapeutics that inhibit the activation of the NLRP3 inflammasome pathway may provide a novel treatment for halting DR progression.