Effect of interleukin-1 beta on glutamine synthetase in rat retinal Müller cell under high glucose conditions

Abstract

To investigate the effect of cytokine interleukin-1 beta (IL-1 beta) on the glutamine synthetase (GS) in retinal Müller cell under high glucose conditions and its possible mechanism. Cultured Müller cells were divided into the control group (5 mmol/L glucose) and experimental group (25 mmol/L glucose) randomly. After being treated with different doses of IL-1 beta for 24 hours, the effect of IL-1 beta on the expressions of GS and c-Jun in retinal Müller cells in the control and experimental groups was measured by western blot analysis and indirect immunofluorescence. Apoptosis of retinal Müller cells induced by IL-1 beta in the control and experimental groups was analyzed by flow cytometry after Annexin V-fluorescein isothiocyanate/Propidium idoium (Annexin V-FITC/PI) staining. Under high glucose condition, increase in the expression of c-Jun and IL-1 beta and decrease in the expression of GS could be found by western blot analysis and immunocytochemistry (P < 0.05). After being treated by IL-1 beta, the expression of GS was down-regulated significantly and the expression of c-Jun was up-regulated significantly in a dose-dependent manner in these two groups, especially under high glucose condition. IL-1 beta caused a dose-dependent increase of apoptosis of retinal Müller cells in these two groups. Apoptosis of Müller cells under high glucose condition increased more significantly than that in cells cultured with 5 mmol/L glucose. In mimicked diabetic condition, IL-1 beta decreases the expression of GS in retinal Müller cells, which may elevate the level of glutamate and cause the damage of the ganglion cells. The possible mechanism of this effect is the activation of c-Jun by IL-1.