Dark rearing does not prevent prodromal rod oxidative stress in vivo in male Pde6b^rd10 mice

Abstract

Purpose : In cyclic light reared Pde6b^rd10 mice, rod cell oxidative stress contributes to the degenerative phenotype. Dark rearing Pde6b^rd10 mice slows but does not prevent atrophy. This suggests that outer retinal oxidative stress occurs in Pde6b^rd10 mice independent of light exposure, a hypothesis that has not yet been tested.

Methods : Pde6b^rd10 and C57Bl/6 [wild type (wt)] mice were dark reared (DR) until postnatal day 23. In subgroups of DR mice, we measured: i) layer-specific excessive free radical production in vivo via QUEnch-assiSTed MRI [QUEST MRI] in which a positive response was defined as 1/T1 values that are both greater-than-normal with a saline injection and significantly reduced with a methylene blue (MB) injection, ii) superoxide production in whole retina ex vivo (lucigenin), and iii) retinal layer spacing and thickness in vivo (optical coherence tomography, MRI).

Results : Male Pde6b^rd10 mice had a positive QUEST MRI response localized to the inner segment layer in vivo. Female Pde6b^rd10 mice did not have a positive response at any retinal depth. Male, but not female, Pde6b^rd10 mice retina exhibited a supernormal production of superoxide. Male and female Pde6b^rd10 mice had normal retinal thicknesses.

Conclusions : QUEST MRI is a novel and powerful in vivo approach to measure a relevant oxidative stress biomarker within rod subcompartments co-localized with retinal thickness in experimental RP. The present results raise the possibility that mutant PDE6b protein in DR Pde6b^rd10 mice is a sufficient condition for generating pre-degenerative inner segment oxidative stress. The unexpected sex difference in this process is discussed.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.