Differential Regulation of High Glucose-Induced Glyceraldehyde-3-Phosphate Dehydrogenase Nuclear Accumulation in Muller Cells by IL-1 beta and IL-6

PURPOSE. This study determined the role of the proinflammatory cytokines known to be elevated in the diabetic retina, namely IL-1 beta, TNF alpha, and IL-6, in a high glucose-induced nuclear accumulation of GAPDH in retinal Muller cells, an event considered crucial for the induction of cell death. METHODS. With use of the transformed rat Muller cell line (rMC-1) and isolated human Muller cells (HMCs), the authors examined the effect of high glucose (25 mM), IL-1 beta, TNF alpha, IL-6, and high glucose (25 mM) plus inhibitors of the caspase1/IL-1 beta signaling pathway on GAPDH nuclear accumulation, which was evaluated by immunofluorescence analysis. RESULTS. High glucose induced IL-1 beta, weak IL-6, and no TNF alpha production by rMC-1 and HMCs. IL-1 beta (1-10 ng/mL) significantly increased GAPDH nuclear accumulation in Muller cells in a concentration-dependent manner within 24 hours. Further, high glucose-induced GAPDH nuclear accumulation in Muller cells was mediated by IL-1 beta. Inhibition of the IL-1 receptor using an IL-1 receptor antagonist (IL-1ra; 50 ng/mL) or inhibition of IL-1 beta production using a specific caspase-1 inhibitor (YVAD-fmk; 100 mu M) significantly decreased high glucose-induced GAPDH nuclear accumulation. In contrast, IL-6 (2 ng/mL) had a strong protective effect attenuating high glucose and IL-1 beta-induced GAPDH nuclear accumulation in Muller cells. TNF alpha (1-10 ng/mL) did not have any effect on GAPDH nuclear accumulation. CONCLUSIONS. These results revealed a novel mechanism for high glucose-induced GAPDH nuclear accumulation in Muller cells through production and autocrine stimulation by IL-1 beta. The protective role of IL-6 in high glucose- and IL-1 beta-induced toxicity indicates that changes in the balance of these cytokines might contribute to cellular damage mediated by elevated glucose levels. (Invest Ophthalmol Vis Sci. 2009; 50: 1920-1928) DOI: 10.1167/iovs.08-2082