Induction of Autophagy Promotes Clearance of RHOP23H Aggregates and Protects From Retinal Degeneration

Abstract

Autophagy is a critical metabolic process that acts as a major self-digestion and recycling pathway contributing to maintain cellular homeostasis. An emerging field of research supports the therapeutic modulation of autophagy for treating human neurodegenerative disorders, in which toxic aggregates are accumulated in neurons. Our previous study identified Ezrin protein as an inhibitor of autophagy and lysosomal functions in the retina; thus, in turn, identifying it as a potential pharmacological target for increasing retinal cell clearance to treat inherited retinal dystrophies in which misfolded proteins have accumulated. This study aimed to verify the therapeutic inhibition of Ezrin to induce clearance of toxic aggregates in a mouse model for a dominant form of retinitis pigmentosa (i.e., RHOP23H/+). We found that daily inhibition of Ezrin significantly decreased the accumulation of misfolded RHOP23H aggregates. Remarkably, induction of autophagy, by a drug-mediated pulsatile inhibition of Ezrin, promoted the lysosomal clearance of disease-linked RHOP23H aggregates. This was accompanied with a reduction of endoplasmic reticulum (ER)-stress, robust decrease of photoreceptors' cell death, amelioration in both retinal morphology and function culminating in a better preservation of vision. Our study opens new perspectives for a pulsatile pharmacological induction of autophagy as a mutation-independent therapy paving the way toward a more effective therapeutic strategy to treat these devastating retinal disorders due to an accumulation of intracellular toxic aggregates.

miR ‐181a/b downregulation: a mutation‐independent therapeutic approach for inherited retinal diseases

“…Count of nuclei in ONL was performed on three eyes/genotype (at least two sections per eye) at p30. Only sections in which the optic nerve was contained were used, and two images from each section were photographed under a Leica DM‐5500 microscope, with the objective Leica ∞/0.17/D, HCX PL FLUOTAR, 40×/0.75 that acquires an area of 0.31 mm 2 , in comparable regions equidistant from the optic nerve head (Barbato et al , 2017; Karali et al , 2020; Ciampi et al , 2022; Intartaglia et al , 2022). The acquired images were used for nuclei counts.…”

The Essential Role of Light-Induced Autophagy in the Inner Choroid/Outer Retinal Neurovascular Unit in Baseline Conditions and Degeneration

“…Light-induced autophagy activity may be the key in triggering such a coordination. This may explain why autophagy machinery in the retina is finely tuned at the level of gene and protein expression to allow visual acuity [55,115]. In fact, more autophagy structures are generated within the "inner choroid/outer retina" neurovascular unit during periods of light.…”

“…This is confirmed by the fact that, when measuring autophagy in the retina, this is induced during the process of phototransduction. In fact, autophagy stimulation in the outer retina generates a protein named RPEDF, which is key in regulating the process of vision [115].…”

“…In this scenario, an ON retinal field should undergo downstream autophagy activation when impacted by light, whereas an OFF retinal field should feature autophagy suppression following the same light exposure. As shown by Intartaglia et al [115], timing and spacing in retinal regulation of autophagy is under the influence of a specific molecule known as "ezrin". Intartaglia et al [115] consider the alternation of the autophagy status and light exposure as an appropriate stimulus to maintain retinal integrity.…”

“…As shown by Intartaglia et al [115], timing and spacing in retinal regulation of autophagy is under the influence of a specific molecule known as "ezrin". Intartaglia et al [115] consider the alternation of the autophagy status and light exposure as an appropriate stimulus to maintain retinal integrity. It is likely that pulses of light, owing to the right wavelength, may produce ezrin inhibition and autophagy activation to sustain a burst of trophic retinal activity.…”