Abstract
Abstract: :
Purpose: We have recently demonstrated that the Müller cell line, rMC–1, undergoes high glucose–induced apoptosis in vitro by a mechanism involving glyceraldehyde–3–phosphate dehydrogenase (GAPDH) nuclear translocation. In this study, we investigated hyperglycemia induced nuclear translocation of GAPDH and apoptosis in cultured human Müller cells. In addition, we studied GAPDH nuclear accumulation in Müller cells in the retina of diabetic rats. Methods: Isolated human Müller cells were cultured in normal glucose (7.8mM), high glucose (25mM), and high glucose plus R–(–)–deprenyl for up to 5 days. Retinas from diabetic rats (12 weeks) and age–matched controls were used for in vivo analysis. Subcellular distribution of GAPDH was determined in vitro and in vivo by immunocytochemistry. Apoptosis in tissue cultures was determined by annexin–V staining and caspase–3 activity. Results: Hyperglycemia significantly increased the amount of GAPDH protein in the nucleus above normal within the first 48 hours in human Müller cells. The addition of R–(–)–deprenyl to these cells incubated in high glucose reduced the amount of GAPDH protein in the nucleus and decreased hyperglycemia–induced apoptosis. In vivo studies confirmed the accumulation of GAPDH in nuclei of Müller cells in diabetes. Conclusions: Our study provides evidence that hyperglycemia leads to Müller cell loss in vitro and in vivo. The presence of the nuclear accumulation of GAPDH in Müller cells from the retina of diabetic rats demonstrates an initial step towards cell death of these cells. However, future studies need to determine the extent of Müller cell loss in vivo during the development of diabetic retinopathy.
Keywords: diabetic retinopathy • Muller cells • apoptosis/cell death