Differential effects of antipsychotic drugs on contrast response functions of retinal ganglion cells in wild-type Sprague-Dawley rats and P23H retinitis pigmentosa rats

Preservation of retinal structure and function in two mouse models of inherited retinal degeneration by ONL1204, an inhibitor of the Fas receptor

Due to the large number of genes and mutations that result in inherited retinal degenerations (IRD), there has been a paucity of therapeutic options for these patients. There is a large unmet need for therapeutic approaches targeting shared pathophysiologic pathways in a mutation-independent manner. The Fas receptor is a major activator and regulator of retinal cell death and inflammation in a variety of ocular diseases. We previously reported the activation of Fas-mediated photoreceptor (PR) cell death in two different IRD mouse models, rd10 and P23H, and demonstrated the protective effect of genetic Fas inhibition. The purpose of this study was to examine the effects of pharmacologic inhibition of Fas in these two models by intravitreal injection with a small peptide inhibitor of the Fas receptor, ONL1204. A single intravitreal injection of ONL1204 was given to one eye of rd10 mice at P14. Two intravitreal injections of ONL1204 were given to the P23H mice, once at P14 and again at 2-months of age. The fellow eyes were injected with vehicle alone. Fas activation, rate of PR cell death, retinal function, and the activation of immune cells in the retina were evaluated. In both rd10 and P23H mice, ONL1204 treatment resulted in decreased number of TUNEL (+) PRs, decreased caspase 8 activity, enhanced photoreceptor cell counts, and improved visual function compared with vehicle treated fellow eyes. Treatment with ONL1204 also reduced immune cell activation in the retinas of both rd10 and P23H mice. The protective effect of pharmacologic inhibition of Fas by ONL1204 in two distinct mouse models of retinal degeneration suggests that targeting this common pathophysiologic mechanism of cell death and inflammation represents a potential therapeutic approach to preserve the retina in patients with IRD, regardless of the genetic underpinning.

Loss of Fas Receptor Function Preserves Photoreceptor Structure and Function in Two Mouse Models of Inherited Retinal Degeneration

Purpose

The genetic heterogeneity of inherited retinal degeneration (IRD) has limited the development of mutation-specific therapies, necessitating the development of therapeutic approaches targeting broadly shared pathophysiologic pathways. The Fas receptor has been reported as a contributor to retinal cell death and inflammation in a wide variety of ocular diseases. The purpose of this study was to assess targeting the Fas pathway as a novel mutation-independent approach to improve photoreceptor survival in IRD.

Methods

We examined the effects of genetic inactivation of the Fas receptor on retinal degeneration in two distinct IRD mouse models, P23H and rd10. The Fas-lpr mouse, which contains a functionally inactive Fas receptor, was crossed with the P23H and rd10 mice to generate P23H/Fas-lpr and rd10/Fas-lpr mice. Fas activation, photoreceptor survival and retinal function were assessed.

Results

We detected elevated levels of Fas receptor and microglial activation in the retinas of both P23H and rd10 mice. Inactivation of Fas in these two IRD models (P23H/Fas-lpr and rd10/Fas-lpr mice) resulted in reduced cell death, increased photoreceptor survival, improved retinal function, and reduced microglial activation and inflammatory cytokine production.

Conclusions

The protective effect of a nonfunctional Fas receptor in two different mouse models of retinal degeneration suggests that whereas the individual IRD mutation may be specific, the retina's response to the different stressors appears to be shared and driven by Fas. Reducing Fas activity might represent a potential mutation-independent therapeutic approach to preserve retinal structure and function in patients with IRD.

Loss of αA or αB-Crystallin Accelerates Photoreceptor Cell Death in a Mouse Model of P23H Autosomal Dominant Retinitis Pigmentosa

Inherited retinal degenerations (IRD) are a leading cause of visual impairment and can result from mutations in any one of a multitude of genes. Mutations in the light-sensing protein rhodopsin (RHO) is a leading cause of IRD with the most common of those being a missense mutation that results in substitution of proline-23 with histidine. This variant, also known as P23H-RHO, results in rhodopsin misfolding, initiation of endoplasmic reticulum stress, the unfolded protein response, and activation of cell death pathways. In this study, we investigate the effect of α-crystallins on photoreceptor survival in a mouse model of IRD secondary to P23H-RHO. We find that knockout of either αA- or αB-crystallin results in increased intraretinal inflammation, activation of apoptosis and necroptosis, and photoreceptor death. Our data suggest an important role for the ⍺-crystallins in regulating photoreceptor survival in the P23H-RHO mouse model of IRD.