Hyperglycaemia-induced pro-inflammatory responses by retinal Muller glia are regulated by the receptor for advanced glycation end-products (RAGE)

Aims/hypothesis Up-regulation of the receptor for AGEs (RAGE) and its ligands in diabetes has been observed in various tissues. Here, we sought to determine levels of RAGE and one of its most important ligands, S100B, in diabetic retina, and to investigate the regulatory role of S100B and RAGE in Muller glia. Methods Streptozotocin-diabetes was induced in Sprague Dawley rats. RAGE, S100B and glial fibrillary acidic protein (GFAP) were detected in retinal cryosections. In parallel, the human retinal Muller cell line, MIO-M1, was maintained in normal glucose (5.5 mmol/l) or high glucose (25 mmol/l). RAGE knockdown was achieved using small interfering RNA (siRNA), while soluble RAGE was used as a competitive inhibitor of RAGE ligand binding. RAGE, S100B and cytokines were detected using quantitative RTPCR, western blotting, cytokine protein arrays or EL1SA. Activation of mitogen-activated protein kinase (MAPK) by RAGE was determined by western blotting. Results Compared with non-diabetic controls, RAGE and S100B were significantly elevated in the diabetic retina with apparent localisation in the Muller glia, occurring concomitantly with upregulation of GFAP. Exposure of MIO-M1 cells to high glucose induced increased production of RAGE and S100B. RAGE signalling via MAPK pathway was linked to cytokine production. Blockade of RAGE prevented cytokine responses induced by high glucose and S100B in Muller glia. Conclusions/interpretation Hyperglycaemia in vivo and in vitro exposure to high glucose induce upregulation of RAGE and its ligands, leading to RAGE signalling, which links to pro-inflammatory responses by retinal Muller glia. These data shed light on the potential clinical application of RAGE blockade to inhibit the progression of diabetic retinopathy.