Aims Inflammation is considered to play a critical role in the pathogenesis of diabetic retinopathy, and high mobility group box protein 1 (HMGB1) could promote inflammation as an alarmin. We investigated the expression of HMGB1 signalling pathway components in type 2 diabetic rat retinas and in high glucose cultured ARPE-19 cells.

Methods Retinal expression of HMGB1 and its receptors in type 2 diabetic rats were detected by western blot and immunohistochemistry. ARPE-19 cells were cultured with low glucose, high glucose (with or without anti-HMGB1 antibody) or mannitol (control) for different lengths of time (12, 24, 48, 72 h). Then expression of HMGB1 and its receptors was measured by immunocytochemistry, ELISA or western blot. Nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) activity and tumour necrosis factor α (TNFα)/vascular endothelial growth factor (VEGF) production in retinas as well as in ARPE-19 cells were detected by ELISA. Furthermore, blood–retinal barrier permeability and ARPE-19 cell viability were measured by Evans-Blue and Cell Counting Kit-8 assay, respectively.

Results HMGB1 signalling pathway components including receptors for HMGB1 as well as NF-κB and TNFα/VEGF were significantly upregulated in type 2 diabetic retinas and in high glucose treated ARPE-19 cells, compared to their respective counterparts. HMGB1 blockage significantly alleviated NF-κB activity and VEGF secretion in ARPE-19 cells cultured with high glucose. In addition, blood–retinal barrier permeability of the diabetic retinas increased, while cell viability of high glucose treated ARPE-19 cells decreased.

Conclusions Expression of HMGB1 signalling pathway components were increased in diabetic rat retinas and in ARPE-19 cells exposed to high glucose.