Abstract
Purpose :
Diabetic retinopathy (DR) is a low-grade chronic inflammatory disease. Recent studies have that Ndr2 (Stk38L) kinase plays a role in innate immunity by regulating the IL-17-dependent inflammation in macrophages, immune cells that share similarities with microglial cells. However, the role of Ndr2 kinases on microglial inflammatory response in the pathophysiology of DR awaits to be uncovered. We hypothesize that Ndr2 kinase negatively regulate inflammation mediated by microglial cells in the context of DR.
Methods :
NDR2 expression was quantified from the retina of streptozotocin (STZ)-induced diabetic mice (type 1 diabetes) and from WT BV-2 microglia cells exposed to (i) high glucose (HG) conditions (30.5 mM for 7h) and to (ii) glucose variations (2 times 4h HG separated by 4h in normal glucose - CT - 5.5 mM; 12h assay). Ndr2 KO BV-2 were generated by introducing frame shift mutations into exon 6, utilizing CRISPR-Cas9 method. The response of the Ndr2 KO BV-2 to HG conditions was assess by measuring the expression of cytokines, their phagocytic efficiency, and their proliferative capabilities (resazurin and EdU).
Results :
NDR2 is downregulated in the OPL of STZ-induced diabetic retinas. NDR2 is downregulated in WT BV-2 exposed to glucose variation (77 ± 23 %). Ndr2 deletion prevents the proliferative/metabolic increases observed in HG (WT HG: 160 ± 20 % of CT; KO HG: 107 ± 26 % of CT). Ndr2 deletion decreases the phagocytic efficiency of BV-2 exposed to HG (WT CT: 79 ± 15 %; WT HG: 110 ± 12%; KO HG: 48 ± 3%). Finally, the Ndr2 deletion promotes the secretion of IL-17, IL-6, MCP1 and TNF while inhibits the secretion of sTNFRI, MCP5 and VEGF by BV-2 in CT and HG.
Conclusions :
NDR2 expression is affected in type 1 diabetic retinas. NDR2 expression is downregulated in microglial cells exposed to HG. Ndr2 prevents the adaptability of the microglial cells to HG by limiting their proliferation/metabolism and their phagocytosis efficiency. Ndr2 deletion is sufficient to modulate the inflammatory response mediated by microglial cells in non stimulated (CT) and stimulated (HG) conditions. Altogether, these results suggest that NDR2 could be a major player in the inflammation regulation in diabetic retinopathy.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.