Antioxidants slow photoreceptor cell death in mouse models of retinitis pigmentosa

Retinitis pigmentosa (RP) is a heterogeneous group of diseases in which one of a wide variety of mutations selectively causes rod photoreceptor cell death. After rods die, cone photoreceptors gradually die resulting in blindness. Antioxidants reduce cone cell death in rdl/rdl mice indicating that cones die from oxidative damage in that model of rapidly progressive RP. In this study, we sought to determine if this observation could be generalized to models of other types of RP, rdl0/rdl0 mice, a model of more slowly progressive recessive RP, and Q344ter mice, a model of rapidly progressive dominant RP. Compared to appropriate vehicle-treated controls, rdl0/rdl0 and Q344ter mice treated between P18 and P35 with a mixture of antioxidants previously found to be effective in rdl/rdl mice showed significantly greater cone survival. Antioxidant-treated rd10/rdl0 mice showed preservation of cone function as shown by a significant increase in photopic ERG b-wave amplitudes, and surprisingly showed temporary preservation of scotopic a-wave amplitudes, prolonged rod survival, and slowed depletion of rhodopsin mRNA. These data suggest that oxidative damage contributes to cone cell death regardless of the disease causing mutation that leads to the demise of rods, and that in more slowly progressive rod degenerations, oxidative damage may also contribute to rod cell death. Protection from oxidative damage may be a broadly applicable treatment strategy in RP.