The HIF1α-PFKFB3 Pathway: A Key Player in Diabetic Retinopathy

IL1R2 promotes retinal angiogenesis to participate in retinopathy of prematurity by activating the HIF1α/PFKFB3 pathway

Retinopathy of prematurity (ROP) is the leading cause of blindness in children, but there is no safe and effective treatment available. Interleukin-1 receptor type 2 (IL1R2) acts as a decoy receptor for IL-1 may affect ROP progression. This study aimed to investigate the role of IL1R2 in ROP. A microglial cell model was established under hypoxia conditions and co-cultured with choroidal endothelial cells, while an oxygen-induced retinopathy (OIR) model was also established. Microglial activation and IL1R2 levels in retinal tissues were analyzed using immunofluorescence assay. Endothelial cell migration was evaluated by Transwell assay and scratch test, angiogenesis was assessed using ELISA and tube formation assay, and proliferation was evaluated by EdU assay. The HIF1α/PFKFB3 pathway was analyzed by western blot. We observed that IL1R2 expression was predicted to be upregulated in ROP and was increased in hypoxia-treated BV2 cells. Additionally, IL1R2 levels were upregulated in the retinal tissues of OIR mice and correlated with microglial activation. In vitro experiments, we found that hypoxia promoted endothelial cell migration, angiogenesis, proliferation, and activated the HIF1α/PFKFB3 pathway, which were rescued by IL1R2 knockdown. Moreover, NHWD-870 (a HIF1α/PFKFB3 pathway inhibitor) suppressed endothelial cell migration, angiogenesis, and proliferation induced by IL1R2 overexpression. In conclusion, IL1R2 facilitates the migration, angiogenesis, and proliferation of choroidal endothelial cells by activating the HIF1α/PFKFB3 pathway to regulate ROP progression.

Reduced methylation correlates with diabetic nephropathy risk in type 1 diabetes

Diabetic nephropathy (DN) is a polygenic disorder with few risk variants showing robust replication in large-scale genome-wide association studies. To understand the role of DNA methylation, it is important to have the prevailing genomic view to distinguish key sequence elements that influence gene expression. This is particularly challenging for DN because genome-wide methylation patterns are poorly defined. While methylation is known to alter gene expression, the importance of this causal relationship is obscured by array-based technologies since coverage outside promoter regions is low. To overcome these challenges, we performed methylation sequencing using leukocytes derived from participants of the Finnish Diabetic Nephropathy (FinnDiane) type 1 diabetes (T1D) study (n = 39) that was subsequently replicated in a larger validation cohort (n = 296). Gene body-related regions made up more than 60% of the methylation differences and emphasized the importance of methylation sequencing. We observed differentially methylated genes associated with DN in 3 independent T1D registries originating from Denmark (n = 445), Hong Kong (n = 107), and Thailand (n = 130). Reduced DNA methylation at CTCF and Pol2B sites was tightly connected with DN pathways that include insulin signaling, lipid metabolism, and fibrosis. To define the pathophysiological significance of these population findings, methylation indices were assessed in human renal cells such as podocytes and proximal convoluted tubule cells. The expression of core genes was associated with reduced methylation, elevated CTCF and Pol2B binding, and the activation of insulin-signaling phosphoproteins in hyperglycemic cells. These experimental observations also closely parallel methylation-mediated regulation in human macrophages and vascular endothelial cells.