Taurine deficiency damages retinal neurones: cone photoreceptors and retinal ganglion cells

Abstract

In 1970s, taurine deficiency was reported to induce photoreceptor degeneration in cats and rats. Recently, we found that taurine deficiency contributes to the retinal toxicity of vigabatrin, an antiepileptic drug. However, in this toxicity, retinal ganglion cells were degenerating in parallel to cone photoreceptors. The aim of this study was to re-assess a classic mouse model of taurine deficiency following a treatment with guanidoethane sulfonate (GES), a taurine transporter inhibitor to determine whether retinal ganglion cells are also affected. GES treatment induced a significant reduction in the taurine plasma levels and a lower weight increase. At the functional level, photopic electroretinograms were reduced indicating a dysfunction in the cone pathway. A change in the autofluorescence appearance of the eye fundus was explained on histological sections by an increased autofluorescence of the retinal pigment epithelium. Although the general morphology of the retina was not affected, cell damages were indicated by the general increase in glial fibrillary acidic protein expression. When cell quantification was achieved on retinal sections, the number of outer/inner segments of cone photoreceptors was reduced (20 %) as the number of retinal ganglion cells (19 %). An abnormal synaptic plasticity of rod bipolar cell dendrites was also observed in GES-treated mice. These results indicate that taurine deficiency can not only lead to photoreceptor degeneration but also to retinal ganglion cell loss. Cone photoreceptors and retinal ganglion cells appear as the most sensitive cells to taurine deficiency. These results may explain the recent therapeutic interest of taurine in retinal degenerative pathologies.

Taurine Depletion Causes ipRGC Loss and Increases Light-Induced Photoreceptor Degeneration

“…This may also explain why in the nonlight-exposed taurine-depleted animals, we were not able to see rings of cone degeneration even when there is cone loss, because taurine deficiency causes cone loss before rod alteration. 5,9 However, it is still unclear why the cone mosaic is reorganized into rings after photoreceptor loss. It has been suggested that cone rings could be the result of cone migration through processes of Müller cells 81 ; whereas other authors have proposed that it is due to cone death, 68 these studies indicated that rods die in the ''center of the rings'' and photoreceptor (cones and rods) loss expands outward, 27,68 suggesting an interdependence between neighboring photoreceptors.…”

“…The endogenous synthesis of taurine can be insufficient, because in cats 2 and in monkeys 3 nutritional taurine depletion has been shown to cause photoreceptor degeneration. Recently it has been documented that taurine depletion also causes retinal ganglion cell (RGC) loss, [4][5][6] and therefore retinal health is dependent on taurine, at least in some species.…”

Effects of taurine and housing density on renal function in laying hens

“…Although taurine can be synthesized from endogenous production, the yield is usually inadequate, and thus dietary consumption of taurine is necessary (Kadam and Prabhasankar, 2010). It has been demonstrated that taurine deficiency can lead to renal dysfunction, cardiomyopathy, developmental abnormalities, and severe damage to retinal neurons (Chesney et al, 2010;Gaucher et al, 2012). The influence of taurine on renal physiology includes renal blood flow, glomerular filtration and its rate, osmoregulation, ion reabsorption and secretion, and composition of urine, among others (Chesney et al, 2010).…”

Quantitative and Topographical Analysis of the Losses of Cone Photoreceptors and Retinal Ganglion Cells Under Taurine Depletion

“…18 The parallel degeneration of cone photoreceptors and RGCs was also observed under taurine depletion generated in mice fed with guanidoethane sulfonate (GES), a taurine transporter blocker. 19 The direct effect of taurine on RGCs was then demonstrated using pure RGC cultures and different models of RGC degeneration. 6 Taurine depletion acts synergistically with light to trigger the photoreceptor lesion 9,[20][21][22] and photoreceptor loss appears to be more severe in the dorsal area, as it does for light damage.…”