Protective Effect of Muller Cells on pH and Survival in a Retinal Cell Line

Abstract

Abstract: : Purpose: To look for protective effects of Muller cells on the survival and on pH changes of retinal cells after glyoxal (G) and methyglyoxal (MG) treatment. The latter are reactive intermediates of the advanced glycation endproducts (AGEs) resulting from the Maillard reaction. AGEs play a very important role in the pathogenesis of diabetic retinopathy and possibly in some forms of glaucoma. Methods: Retinal cell line R28 (rat) and primary Muller cells (rat) were cocultivated for 4 days and incubated 6 hours with MG or 15 hours with G. Necrotic and apoptotic cells were assessed by flowcytometric assays. Intracellular pH (pHi) was determined by BCECF with in vivo microscopy. Mitochondrial membrane potential was analyzed by JC1 fluorescence. Results:We have found a substantial reduction in the number of apoptotic (30%–50%) and necrotic (30%–50%) cells in cocultures compared to R28 cells alone. Furthermore, in the presence of Muller cells the retinal cells got less acidic after AGE intermediates. The Muller cells themselves had a more reduced pH, especially in the periphery of the cells and in vesicular compartments. Concommitantely to the reduced pH decrease we found in cocultures a stabilization of the mitochondrial membrane potential compared to R28 alone. Conclusions: Our results show a protective role of the Muller cells during AGE induced cell damages. In further study we try to isolate protective factors in the supernatant of Muller cell cultures.

Keywords: Muller cells • PH regulation/protons • retinal culture