Flavonoids improve the stability and function of P23H rhodopsin slowing down the progression of retinitis pigmentosa in mice

Abstract

The balanced homeostasis of the G protein–coupled receptor (GPCR), rhodopsin (Rho), is required for vision. Misfolding mutations in Rho cause photoreceptor death, leading to retinitis pigmentosa (RP) and consequently blindness. With no cure currently available, the development of efficient therapy for RP is an urgent need. Pharmacological supplementation with molecular chaperones, including flavonoids, improves stability, folding, and membrane targeting of the RP Rho mutants in vitro. Thus, we hypothesized that flavonoids by binding to P23H Rho and enhancing its conformational stability could mitigate detrimental effects of this mutation on retinal health. In this work, we evaluated the pharmacological potential of two model flavonoids, quercetin and myricetin, by using in silico, in vitro, and in vivo models of P23H Rho. Our computational analysis showed that quercetin could interact within the orthosteric binding pocket of P23H Rho and shift the conformation of its N‐terminal loop toward the wild type (WT)‐like state. Quercetin added to the NIH‐3T3 cells stably expressing P23H Rho increased the stability of this receptor and improved its function. Systemic administration of quercetin to P23H Rho knock‐in mice substantially improved retinal morphology and function, which was associated with an increase in levels of Rho and cone opsins. In addition, treatment with quercetin resulted in downregulation of the UPR signaling and oxidative stress‐related markers. This study unravels the pharmacological potential of quercetin to slow down the progression of photoreceptor death in Rho‐related RP and highlights its prospective as a lead compound to develop a novel therapeutic remedy to counter RP pathology.

Chromenone derivatives as novel pharmacological chaperones for retinitis pigmentosa-linked rod opsin mutants

“…Moreover, CR5 prolonged the survival of photoreceptors in RP-related knock-in P23H mice, likely due to its ability to increase the conformational stability of mutated rod opsin, which assisted the correct folding and transport of the mutant receptor. As we recently demonstrated, quercetin provided similar advantageous effects slowing the progression of RP in these mice (19).…”

“…Indeed, we recently found that polyphenolic compounds such as flavonoids bind to rod opsin and enhance its stability (18). For instance, quercetin restores multiple native interactions within the chromophore-binding site of the P23H rod opsin and improves the function of this mutant in vitro (19). Moreover, treatment with quercetin prevents retinal degeneration caused by excessive accumulation of unliganded opsin upon exposure to bright light and importantly slows the progression of photoreceptor cell death in the P23H Rho knock-in mouse model of RP (19,20).…”

“…Rho P23H/+ mice (34) were used to examine the effects of the CR5 compound on the progression of retinal degeneration in RP at 21–33 days of age as described in (19). CR5 at 10 mg/kg b.w.…”

“…Alternatively, we found that compounds with natural product scaffold could accommodate within the opsin’s orthosteric site, providing an option to screen for new chemical correctors of pathogenic variants (18). These biologically active polyphenolic compounds, specifically flavonoids, could enhance the stability of unliganded rod opsin, and improve the membrane expression and function of P23H mutant in vitro (18,19). Moreover, as we discovered treatment with quercetin could prevent retinal degeneration in mouse models of acute light damage and importantly, slowed down the progression of photoreceptors death in the P23H Rho knock-in mice, a model of autosomal dominant RP (adRP) (19,20).…”

“…On the other hand, the P23H Rho knock-in mice resemble many features of human RP (34). Both mouse models were proven to be excellent models to evaluate drug-like activity of retinal and non-retinal opsin ligands against retina degeneration (16,19,20,35). The identified here chromenone-containing compound showed beneficial effects for retina health in both Abca4 -/- Rdh8 -/- and P23H Rho mice, suggesting its potential as a therapeutic lead compound with broad application for retinal diseases related to photoreceptor degeneration.…”