Eye-Light on Age-Related Macular Degeneration: Targeting Nrf2-Pathway as a Novel Therapeutic Strategy for Retinal Pigment Epithelium.

Michele Catanzaro,Filippo Basagni,Marialaura Amadio,Michela Rosini,Cristina Lanni,Stefano Govoni

doi:10.3389/fphar.2020.00844

Michele Catanzaro, Filippo Basagni + Show 4 more

Open Access

https://doi.org/10.3389/fphar.2020.00844

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Abstract

Age-related macular degeneration (AMD) is a common disease with a multifactorial aetiology, still lacking effective and curative therapies. Among the early events triggering AMD is the deterioration of the retinal pigment epithelium (RPE), whose fundamental functions assure good health of the retina. RPE is physiologically exposed to high levels of oxidative stress during its lifespan; thus, the integrity and well-functioning of its antioxidant systems are crucial to maintain RPE homeostasis. Among these defensive systems, the Nrf2-pathway plays a primary role. Literature evidence suggests that, in aged and especially in AMD RPE, there is an imbalance between the increased pro-oxidant stress, and the impaired endogenous detoxifying systems, finally reverberating on RPE functions and survival. In this in vitro study on wild type (WT) and Nrf2-silenced (siNrf2) ARPE-19 cells exposed to various AMD-related noxae (H2O2, 4-HNE, MG132 + Bafilomycin), we show that the Nrf2-pathway activation is a physiological protective stress response, leading downstream to an up-regulation of the Nrf2-targets HO1 and p62, and that a Nrf2 impairment predisposes the cells to a higher vulnerability to stress. In search of new pharmacologically active compounds potentially useful for AMD, four nature-inspired hybrids (NIH) were individually characterized as Nrf2 activators, and their pharmacological activity was investigated in ARPE-19 cells. The Nrf2 activator dimethyl-fumarate (DMF; 10 μM) was used as a positive control. Three out of the four tested NIH (5 μM) display both direct and indirect antioxidant properties, in addition to cytoprotective effects in ARPE-19 cells under pro-oxidant stimuli. The observed pro-survival effects require the presence of Nrf2, with the exception of the lead compound NIH1, able to exert a still significant, albeit lower, protection even in siNrf2 cells, supporting the concept of the existence of both Nrf2-dependent and independent pathways mediating pro-survival effects. In conclusion, by using some pharmacological tools as well as a reference compound, we dissected the role of the Nrf2-pathway in ARPE-19 stress response, suggesting that the Nrf2 induction represents an efficient defensive strategy to prevent the stress-induced damage.

Highlights

Age-related macular degeneration (AMD) is one of the most common neurodegenerative diseases and leading causes of irreversible blindness in the elderly worldwide (Lim et al, 2012)
Since oxidative stress is one of the main factors contributing to the AMD pathogenesis, and literature evidence suggests that nuclear factor E2-related factor 2 (Nrf2)-signalling pathway is compromised in AMD-like animal models (Sachdeva et al, 2014; Batliwala et al, 2017), we evaluated the relevance of Nrf2 in retinal pigment epithelium (RPE) under adverse conditions
To determine whether the Nrf2 impairment affects the susceptibility of ARPE-19 to stress in term of cell viability, according to both our previous experience and new explorative experiments, we preliminary selected the best conditions for each stress inducing a significant mortality in wild type (WT) ARPE-19 cells

Summary

Introduction

Age-related macular degeneration (AMD) is one of the most common neurodegenerative diseases and leading causes of irreversible blindness in the elderly worldwide (Lim et al, 2012). The most comprehensive transcription system used by RPE to neutralize oxidative stress and maintain cellular homeostasis is the Keap1-Nrf2-ARE pathway (Sachdeva et al, 2014; Lambros and Plafker, 2016). Keap undergoes a conformational change and dissociates from Nrf, that is free to translocate to the nucleus, where it binds to the antioxidant response element (ARE) in the promoter of target genes, initiating their transcription (Motohashi and Yamamoto, 2004). Since oxidative stress is one of the main factors contributing to the AMD pathogenesis, and literature evidence suggests that Nrf2-signalling pathway is compromised in AMD-like animal models (Sachdeva et al, 2014; Batliwala et al, 2017), we evaluated the relevance of Nrf in RPE under adverse conditions

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