Abstract
Purpose :
The P23H variant of rhodopsin represents the most common causes of autosomal dominant retinitis pigmentosa (adRP) in the United States. Our previous data have shown that the persistent activation of both Fas (CD95 death receptor) and autophagy contribute to photoreceptor death in a mouse model of P23H. We have also demonstrated the protective effect of Fas inhibition or autophagy suppression alone in the P23H mice. The purpose of this study is to examine whether combined inhibition of both autophagy and Fas pathways could further protect photoreceptor survival.
Methods :
A proof-of-concept study of the combined approach was first conducted in the Lpr/P23H mice, a Fas-deficient mouse line. Hydroxychloroquine (HCQ) was giving in the drinking water at 1.2 mg/mL starting at P21 to reduce autophagy flux. Pharmacological combination was conducted in P23H mice by combining HCQ in drinking water with intravitreal injections of a Fas inhibitor, ONL1204, at P14 and 2 months of age. The fellow eyes were injected with vehicle solution as controls. Photoreceptor death was assessed by TUNEL cell counts and caspase 8 activity assay. Retinal structure was examined by histology and OCT analysis. ERG recording and IHC staining of rhodopsin and m-opsin were performed to evaluate the retinal function. The activation of inflammatory cells was assessed by Iba1 staining on 30μm retinal sections and on retinal whole mount. Transcript levels of inflammatory cytokines were analyzed by rt-PCR.
Results :
Consistent with previous data, Fas-deficient Lpr/P23H mice exhibited decreased rate of photoreceptor degeneration and reduced inflammation compared with P23H. Treatment with autophagy inhibitor HCQ further preserved photoreceptor survival and function, lowered the activation of immune cells and the production of inflammatory cytokines in the retinas of the Lpr/P23H mice. In HCQ treated P23H mice, combining intravitreal injections of ONL1204 further reduced photoreceptor cell loss and increased visual function as compared to the control vehicle injected eyes.
Conclusions :
In the adRP model of P23H mice, inhibition of Fas pathway or autophagy alone is protective, and inhibiting both pathways showed greater protective effects. Our results suggest that the combined treatment of inhibiting autophagy by HCQ, and suppressing Fas pathway by ONL1204 represents a potential combined therapeutic approach in patients with P23H.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.