Functional Implications of Dystrophin-Dp71 in Potassium and Water Homeostasis in a Mouse Model of Retinal Detachment

Abstract

Purpose: : Retinal detachment, which consists on a separation of the neural retina from the pigment epithelium, causes complex alterations and remodelling of the retinal tissue. In addition to the apoptotic death of photoreceptor cells, there are morphologic and biochemical alterations of the inner retinal neurons, as well as a fast activation of pigment epithelial cells and Müller Glial Cells (MGC). In rhegmatogenous retinal detachment, MGC downregulate the K⁺ conductance of their plasma membranes; and an impaired retinal K⁺ homeostasis may favor neuronal hyperexcitation and glutamate excitotoxicity. In MGC, the major potassium (Kir4.1) and water (Aquaporin-4) channels are linked to Dp71, the major Duchenne Muscular Dystrophy (DMD) gene product in retina. Dp71/DAPs (Dystrophin Associated Proteins) complex is responsible for the localization and clustering of Kir4.1 and AQP4 in MGC.The purpose of this study was to analyze, the role of Dp71 in potassium and water homeostasis in a mouse model of retinal detachment.

Methods: : Local retinal detachment was performed in the right eye of adult mice by subretinal injection of hyaluronate while the left eye remained untreated and served as control. Retinal slices were immunostained against Glial intermediate filaments, Dp71, Kir4.1 and AQP4 chanels. Relative expression of these proteins was determined by Western blot and Real Time-PCR.

Results: : At 24 h and 7 days after retinal detachment, MGC from wt mice showed reactive gliosis, revealed by an over expression of GFAP. In detached retina, Kir4.1 and AQP4 were delocalized along the MGC. We found that the delocalization of these channels is associated with a decrease of gene and protein expression of Dp71 in detached retina. An increase of histochemical expression of utrophin (homologue of dystrophin) was also observed around vessels and in MGC after retinal detachment.

Conclusions: : These results suggest that Dp71 is implicated in the maintenance of potassium and water homeostasis by clustering Kir4.1 and AQP4 in MGC. Our results also drive the possibility that Dp71 might prevent the impairment of potassium homeostasis which leads to retinal damage.

Keywords: retinal detachment • Muller cells • proliferative vitreoretinopathy