D-Serine Induced by Ocular Hypertension is Associated with Retinal Cell Death

Purpose: The purpose of this study is to investigate the role of free D-serine in the death of retinal cells caused by ocular hypertension.Methods: Adult Wistar rats were used as an experimental model of ocular hypertension. Immunohistochemistry was used to identify the retinal sites and expression patterns of D-serine and serine racemase in the rat retina. The concentrations of free D-serine and L-serine in the retina were measured by two-dimensional high-performance liquid chromatography. Retinal cell death was investigated by Immunohistochemistry.Results: D-serine was expressed on the retinal ganglion cell layer in the retinas of rats with ocular hypertension. A serine racemase was specifically expressed in the retinal ganglion cells. The ratio of free D-/L-serine in the retinas with ocular hypertension was higher than that in the retinas with normal tension. Annexing-V-positive cells were observed in the retinal ganglion cell layer in the retinas of the rats with ocular hypertension, and these cells were also co-localized with D-serine expression.Conclusions: We suspect that the up-regulation of serine racemase expression induced by ocular hypertensionleads to an increase in free D-serine converted from free L-serine in retinal ganglion cells and that retinal cell death is associated with D-serine expression.