Fundus Camera-Delivered Light-Induced Retinal Degeneration in Mice With the RPE65 Leu450Met Variant is Associated With Oxidative Stress and Apoptosis

Abstract

PurposeOxidative stress, partly due to light, has an important role in many retinal diseases, including macular degeneration and retinal dystrophies. The Leu450Met variant of RPE65 is expressed in C57BL/6 and in many genetically modified mice. It confers significant resistance to light induced retinal degeneration (LIRD). Our goal was to develop an effective and efficient method to induce LIRD in resistant mice that would recapitulate mechanisms seen in known models of LIRD.MethodsThe retinas of C57BL/6J mice were exposed to light using a murine fundus camera. Two protocols (with and without intraperitoneal fluorescein) were used. Optical coherence tomography (OCT) helped determine the location and extent of retinal damage. Histology, TUNEL assay, quantitative (q) PCR, and immunohistochemistry were performed.ResultsBoth protocols consistently generated LIRD in C57BL/6J mice. Optical coherence tomography and histology demonstrated that retinal damage starts at the level of the photoreceptor/outer retina and is more prominent in the superior retina. Fundus camera-delivered light-induced retinal degeneration (FCD-LIRD) is associated with apoptosis, subretinal microglia/macrophages, increased expression of oxidative stress response genes, and C3d deposition.ConclusionsWe characterize two new models of light-induced retinal degeneration that are effective in C57BL/6J mice, and can be modulated in terms of severity. We expect FCD-LIRD to be useful in exploring mechanisms of LIRD in resistant mice, which will be important in increasing our understanding of the retinal response to light damage and oxidative stress.

Central Role of Oxidative Stress in Age-Related Macular Degeneration: Evidence from a Review of the Molecular Mechanisms and Animal Models

“…Most studies of retinal damage by light have used the BALB/c mice or SD rats, known for their genetic susceptibility to light. Recently, a novel protocol by which retinal degeneration could be induced in the commonly available C57BL/6 J mice was described [63]. The wide use of the light-induced retinal degeneration model for studying AMD is because it offers advantages such as synchronized photoreceptor death occurring with light exposure and is easy to induce within a short time [64].…”

A Mouse Model of Retinal Recovery From Photo-Oxidative/Photo-Inflammatory Injury: Nrf2, SOD1, DJ-1, and Parkin Are Not Essential to Recovery

“…These observations parallel similar findings described in primates. Furthermore, while we and others have shown that the oxidative stress response is very important in the acute injury phase, [1][2][3][4][5][6][7][8][9][27][28][29][30] we have also demonstrated that mice lacking oxidative stress response enzymes (SOD1, DJ-1, and Parkin) or the oxidative stress response master regulator Nrf2-despite suffering increased acute injury-still show significant recovery after the initial injury. This suggests that classic oxidative stress response pathways are not essential for retinal recovery after injury.…”

“…We have recently developed a new mouse model of light-induced retinal degeneration that is mediated by oxidative stress/inflammation and easily modulated in terms of severity. 27,28 This fundus camera-delivered light-induced retinal degeneration (FCD-LIRD) model is a photo-oxidative/photoinflammatory injury model, effective in mice carrying the RPE65 450-Met variant and thus can be used in C57BL/6J (B6J) mice and genetically manipulated mice on that background. We will refer to this model as ''photo-oxidative/photoinflammatory'' because oxidative stress and inflammatory process may be interrelated in this model, as they are in multiple human diseases.…”

“…We show that there are aspects of the model that are consistent with a photo-inflammatory mechanism, including the accumulation of subretinal microglia and the accumulation of C3d in the subretinal space. 27 On the other hand, some aspects that point toward a photo-oxidative mechanism include: (1) the fact that the injury is more severe in animals deficient in oxidative stress response enzymes 28 or oxidative stress master regulator Nrf2, and (2) that we have shown that, after FCD-LIRD, there is increased subretinal accumulation of hemoxygenase-1, 27 a molecule commonly used as a marker of oxidative stress. Finally, we have documented an increase in multiple genes related both to inflammation and oxidative stress, including HO-1, Srxn1, Txnrd1, Cebpd, Gadd45b, Ppard, and Socs3.…”

“…Finally, we have documented an increase in multiple genes related both to inflammation and oxidative stress, including HO-1, Srxn1, Txnrd1, Cebpd, Gadd45b, Ppard, and Socs3. 27,28 We believe that this combination of oxidative stress and inflammatory components makes this model more relevant to human disease.…”