Signalling of sphingosine-1-phosphate in Müller glial cells via the S1P/EDG-family of G-protein-coupled receptors

Signalling of sphingosine-1-phosphate (S1P) via G-protein-coupled receptors of the Endothelial Differentiation Gene family differentially regulates cellular processes such as migration, proliferation and morphogenesis in a variety of cell types. Proliferation and migration of retinal Müller glial cells are involved in pathological events such as proliferative vitreoretinopathy and proliferative diabetic retinopathy. Investigation of possible functional roles of S1P receptors might thus open new insights into Müller cell pathophysiology. Here we show that cultured Müller cells from the guinea pig retina respond to application of S1P with an increase in the intracellular calcium content in a concentration-dependent manner (EC50 11 nM). This calcium increase consists of two components; an initial fast peak and a slow plateau component. The initial transient is caused by a release of calcium from intracellular stores and is suppressed by U-73122, a selective phospholipase C inhibitor. The slow plateau component is caused by a calcium influx. These results suggest that the S1P-induced calcium response in Müller cells partially involves signalling via G-protein-coupled receptors. Moreover, S1P slightly induced Müller cell migration but no proliferation. Thus, the data indicate that Müller cells might be involved in S1P signalling in the retina.