Discovering the Potential of Natural Antioxidants in Age-Related Macular Degeneration: A Review

New Perspectives in Stem Cell Transplantation and Associated Therapies to Treat Retinal Diseases: From Gene Editing to 3D Bioprinting

Inherited and non-inherited retinopathies can affect distinct cell types, leading to progressive cell death and visual loss. In the last years, new approaches have indicated exciting opportunities to treat retinopathies. Cell therapy in retinitis pigmentosa, age-related macular disease, and glaucoma have yielded encouraging results in rodents and humans. The first two diseases mainly impact the photoreceptors and the retinal pigmented epithelium, while glaucoma primarily affects the ganglion cell layer. Induced pluripotent stem cells and multipotent stem cells can be differentiated in vitro to obtain specific cell types for use in transplant as well as to assess the impact of candidate molecules aimed at treating retinal degeneration. Moreover, stem cell therapy is presented in combination with newly developed methods, such as gene editing, Müller cells dedifferentiation, sheet & drug delivery, virus-like particles, optogenetics, and 3D bioprinting. This review describes the recent advances in this field, by presenting an updated panel based on cell transplants and related therapies to treat retinopathies.

Role of flavonoids in age-related macular degeneration

A common eye disorder known as age-related macular degeneration (AMD) eventually results in blindness and vision loss. AMD has a complicated and poorly understood aetiology. The main pathological processes associated with AMD include oxidative damage, inflammation, and neovascularization. Flavonoids are naturally occurring bioactive substances with extensive distribution and antioxidant, anti-inflammatory, and neovascularization inhibitory properties. Several in vitro and in vivo AMD-related models pertinent to vision and this ocular ailment have been used to assess the mechanisms of action of various flavonoids. This article will discuss the research progress of flavonoids in AMD, especially the characteristics and mechanism of flavonoids in treating AMD.

Novel Approaches in the Drug Development and Delivery Systems for Age-Related Macular Degeneration

The number of patients with ocular disorders has increased due to contributing factors such as aging populations, environmental changes, smoking, genetic abnormalities, etc. Age-related macular degeneration (AMD) is one of the common ocular disorders which may advance to loss of vision in severe cases. The advanced form of AMD is classified into two types, dry (non-exudative) and wet (exudative) AMD. Although several therapeutic approaches are explored for the management of AMD, no approved therapy can substantially slow down the progression of dry AMD into the later stages. The focus of researchers in recent times has been engaged in developing targeted therapeutic products to halt the progression and maintain or improve vision in individuals diagnosed with AMD. The delivery of anti-VEGF agents using intravitreal therapy has found some success in managing AMD, and novel formulation approaches have been introduced in various studies to potentiate the efficacy. Some of the novel approaches, such as hydrogel, microspheres, polymeric nanoparticles, liposomes, implants, etc. have been discussed. Apart from this, subretinal, suprachoroidal, and port delivery systems have also been investigated for biologics and gene therapies. The unmet potential of approved therapeutic products has contributed to several patent applications in recent years. This review outlines the current treatment options, outcomes of recent research studies, and patent details around the novel drug delivery approach for the treatment of AMD.

Effects of galectin-3 protein on UVA-induced damage in retinal pigment epithelial cells

Several inflammatory molecules have been suggested as biomarkers of age-related macular degeneration (AMD). Galectin-3 (Gal-3), which has been shown to have a protective role in corneal injury by promoting epithelial cells adhesion and migration to the extracellular matrix, is also highly expressed in the retinal pigment epithelium (RPE) of patients with AMD. This study evaluated the role of Gal-3 in an in vitro model of UVA-induced RPE damage, as a proof-of-concept. ARPE-19 cells (human RPE cell line), were incubated with Gal-3 at 0.5-2.5 µg/mL concentrations prior to UVA irradiation for 15, 30, and 45 min, which resulted in accumulated doses of 2.5, 5, and 7.5 J/cm², respectively. After 24 h incubation, MTT and LDH assays, immunofluorescence, and ELISA were performed. UVA irradiation for 15, 30, and 45 min proved to reduce viability in 83%, 46%, and 11%, respectively. Based on the latter results, we chose the intermediate dose (5-J/cm²) for further analysis. Pretreatment with Gal-3 at concentrations > 1.5 µg/mL showed to increase the viability of UVA-irradiated cells (~ 75%) compared to untreated cells (64%). Increased levels of cleaved caspase 3, a marker of cell death, were detected in the ARPE cells after UVA irradiation with or without addition of exogenous Gal-3. The inhibitory effect of Gal-3 on UVA-induced cell damage was characterized by decreased ROS levels and increased p38 activation, as detected by fluorescence analysis. In conclusion, our study suggests a photoprotective effect of Gal-3 on RPE by reducing oxidative stress and increasing p38 activation.

The Challenge of Dimethyl Fumarate Repurposing in Eye Pathologies

Dimethyl fumarate (DMF) is a small molecule currently approved and used in the treatment of psoriasis and multiple sclerosis due to its immuno-modulatory, anti-inflammatory, and antioxidant properties. As an Nrf2 activator through Keap1 protein inhibition, DMF unveils a potential therapeutical use that is much broader than expected so far. In this comprehensive review we discuss the state-of-art and future perspectives regarding the potential repositioning of this molecule in the panorama of eye pathologies, including Age-related Macular Degeneration (AMD). The DMF's mechanism of action, an extensive analysis of the in vitro and in vivo evidence of its beneficial effects, together with a search of the current clinical trials, are here reported. Altogether, this evidence gives an overview of the new potential applications of this molecule in the context of ophthalmological diseases characterized by inflammation and oxidative stress, with a special focus on AMD, for which our gene-disease (KEAP1-AMD) database search, followed by a protein-protein interaction analysis, further supports the rationale of DMF use. The necessity to find a topical route of DMF administration to the eye is also discussed. In conclusion, the challenge of DMF repurposing in eye pathologies is feasible and worth scientific attention and well-focused research efforts.

Nanoscale Delivery Systems of Lutein: An Updated Review from a Pharmaceutical Perspective

Carotenoids are natural lipid-soluble pigments that produce yellow to red colors in plants as well as providing bright coloration in vegetables and fruits. Lutein belongs to the xanthophyll subgroup of the carotenoid family, which plays an essential role in photosynthesis and photoprotection in nature. In the human body, lutein, together with its isomer zeaxanthin and its metabolite meso-zeaxanthin, accumulates in the macula of the eye retina, which is responsible for central, high-resolution, and color vision. As a bioactive phytochemical, lutein has essential physiological functions, providing photoprotection against damaging blue light, along with the neutralization of oxidants and the preservation of the structural and functional integrity of cellular membranes. As a potent antioxidant and anti-inflammatory agent, lutein unfortunately has a low bioavailability because of its lipophilicity and a low stability as a result of its conjugated double bonds. In order to enhance lutein stability and bioavailability and achieve its controlled delivery to a target, nanoscale delivery systems, which have great potential for the delivery of bioactive compounds, are starting to be employed. The current review highlights the advantages and innovations associated with incorporating lutein within promising nanoscale delivery systems, such as liposomes, nanoemulsions, polymer nanoparticles, and polymer–lipid hybrid nanoparticles, as well as their unique physiochemical properties.

Microbiota mitochondria disorders as hubs for early age-related macular degeneration

Age-related macular degeneration (AMD) is a progressive neurodegenerative disease affecting the central area (macula lutea) of the retina. Research on the pathogenic mechanism of AMD showed complex cellular contribution governed by such risk factors as aging, genetic predisposition, diet, and lifestyle. Recent studies suggested that microbiota is a transducer and a modifier of risk factors for neurodegenerative diseases, and mitochondria may be one of the intracellular targets of microbial signaling molecules. This review explores studies supporting a new concept on the contribution of microbiota-mitochondria disorders to AMD. We discuss metabolic, vascular, immune, and neuronal mechanism in AMD as well as key alterations of photoreceptor cells, retinal pigment epithelium (RPE), Bruch's membrane, choriocapillaris endothelial, immune, and neuronal cells. Special attention was paid to alterations of mitochondria contact sites (MCSs), an organelle network of mitochondria, endoplasmic reticulum, lipid droplets (LDs), and peroxisomes being documented based on our own electron microscopic findings from surgically removed human eyes. Morphometry of Bruch's membrane lipids and proteoglycans has also been performed in early AMD and aged controls. Microbial metabolites (short-chain fatty acids, polyphenols, and secondary bile acids) and microbial compounds (lipopolysaccharide, peptidoglycan, and bacterial DNA)-now called postbiotics-in addition to local effects on resident microbiota and mucous membrane, regulate systemic metabolic, vascular, immune, and neuronal mechanisms in normal conditions and in various common diseases. We also discuss their antioxidant, anti-inflammatory, and metabolic effects as well as experimental and clinical observations on regulating the main processes of photoreceptor renewal, mitophagy, and autophagy in early AMD. These findings support an emerging concept that microbiota-mitochondria disorders may be a crucial pathogenic mechanism of early AMD; and similarly, to other age-related neurodegenerative diseases, new treatment approaches should be targeted at these disorders.