Large-scale phenotypic drug screen identifies neuroprotectants in zebrafish and mouse models of retinitis pigmentosa.

Liyun Zhang,Hyejin Park,Cynthia Berlinicke,Hongkai Ji,Justin Hanes,Jie Fu,Guohua Wang,Joong Sup Shim,Daniel Shou,Ying Ye,Kevin Emmerich,Tao Wang,Carlene Brandon,Jiang Qian,Conan Chen,Kelsi R Hall,Ding Ding,Ted M Dawson ,Jun O Liu ,Baranda S Hansen ,Valina L Dawson ,Donald J Zack ,Abigail V Sharrock ,Brendan N Lilley ,Mohit Saxena ,Timothy S Mulligan ,Tae-In Kam ,David F Ackerley ,Bäerbel Rohrer ,Jeff S Mumm

doi:10.7554/elife.57245

Abstract

Retinitis pigmentosa (RP) and associated inherited retinal diseases (IRDs) are caused by rod photoreceptor degeneration, necessitating therapeutics promoting rod photoreceptor survival. To address this, we tested compounds for neuroprotective effects in multiple zebrafish and mouse RP models, reasoning drugs effective across species and/or independent of disease mutation may translate better clinically. We first performed a large-scale phenotypic drug screen for compounds promoting rod cell survival in a larval zebrafish model of inducible RP. We tested 2934 compounds, mostly human-approved drugs, across six concentrations, resulting in 113 compounds being identified as hits. Secondary tests of 42 high-priority hits confirmed eleven lead candidates. Leads were then evaluated in a series of mouse RP models in an effort to identify compounds effective across species and RP models, that is, potential pan-disease therapeutics. Nine of 11 leads exhibited neuroprotective effects in mouse primary photoreceptor cultures, and three promoted photoreceptor survival in mouse rd1 retinal explants. Both shared and complementary mechanisms of action were implicated across leads. Shared target tests implicated parp1-dependent cell death in our zebrafish RP model. Complementation tests revealed enhanced and additive/synergistic neuroprotective effects of paired drug combinations in mouse photoreceptor cultures and zebrafish, respectively. These results highlight the value of cross-species/multi-model phenotypic drug discovery and suggest combinatorial drug therapies may provide enhanced therapeutic benefits for RP patients.

Highlights

Inherited retinal diseases (IRDs) encompass a group of genetically-linked retinopathies characterized by progressive photoreceptor death (Duncan et al, 2018)
An immunohistological analysis of rod and cone photoreceptor markers was performed on 7 days post-fertilization zebrafish retinal sections to test if Mtz-induced ablation was specific to rod cells
Concluding the experiment by 7 dpf avoids challenges associated with feeding, as zebrafish can subsist on their yolk sac up to that time point (Hernandez et al, 2018; Jardine and Litvak, 2003)

Summary

Introduction

Inherited retinal diseases (IRDs) encompass a group of genetically-linked retinopathies characterized by progressive photoreceptor death (Duncan et al, 2018). Retinitis pigmentosa (RP), the most common IRD with approximately 1.5 to 2.5 million RP patients a worldwide (Dias et al, 2017; Hartong et al, 2006a; Verbakel et al, 2018), is characterized by early onset night blindness, gradual loss of visual field, and eventual loss of central vision (Ferrari et al, 2011; Hamel, 2006). Mutations in more than 70 genes have been linked to RP (Dias et al, 2017; https://sph.uth.edu/retnet/). How these mutations affect gene function or initiate aberrant photoreceptor cell loss is largely unknown. The purpose of our study was to identify 77 compounds capable of promoting rod cell survival in multiple RP models and across species

Objectives

Results

Conclusion