Abstract
Purpose::
It has been shown that Interleukin-1ß (IL-1ß) is present in the inflamed diabetic retina. The aim of this study was to test the hypothesis that IL-1ß alters synaptic protein content and the intracellular calcium response to depolarization in cell culture models of retinal neurons.
Methods::
R28 and RGC-5 cells were grown to sub-confluence and treated with 10ng/ml of IL-1ß for 24 hours. The synaptic vesicle associated protein (VAMP-2) and synapsin were quantified by immunoblotting. The intracellular calcium response to 20mM KCl was measured by live-cell confocal microscopy after incubation with Fluo-4, a cell-permeable calcium indicator.
Results::
Synapsin and VAMP-2 protein contents were significantly decreased after 24 hours of IL-1ß treatment. Concentrations of IL-1ß between 0.1 and 10 ng/ml significantly decreased synapsin protein content. The intracellular Ca2+ response to depolarization was significantly increased by IL-1ß treatment.
Conclusions::
IL-1ß may down-regulate synaptic protein expression in retinal neurons. It may also increase intracellular Ca2+ signaling in response to depolarization. Ca2+signaling is an important regulator of neural function, including synaptic vesicle proteins. These data suggest that inflammatory cytokines, which are elevated in the retina by diabetes, have the potential to alter neuronal function.
Keywords: diabetic retinopathy • synapse • calcium