Protective Effects of Spirulina maxima against Blue Light-Induced Retinal Damages in A2E-Laden ARPE-19 Cells and Balb/c Mice

Antioxidants and Mechanistic Insights for Managing Dry Age-Related Macular Degeneration

Age-related macular degeneration (AMD) severely affects central vision due to progressive macular degeneration and its staggering prevalence is rising globally, especially in the elderly population above 55 years. Increased oxidative stress with aging is considered an important contributor to AMD pathogenesis despite multifaceted risk factors including genetic predisposition and environmental agents. Wet AMD can be managed with routine intra-vitreal injection of angiogenesis inhibitors, but no satisfactory medicine has been approved for the successful management of the dry form. The toxic carbonyls due to photo-oxidative degradation of accumulated bisretinoids within lysosomes initiate a series of events including protein adduct formation, impaired autophagy flux, complement activation, and chronic inflammation, which is implicated in dry AMD. Therapy based on antioxidants has been extensively studied for its promising effect in reducing the impact of oxidative stress. This paper reviews the dry AMD pathogenesis, delineates the effectiveness of dietary and nutrition supplements in clinical studies, and explores pre-clinical studies of antioxidant molecules, extracts, and formulations with their mechanistic insights.

Marine Natural Products Rescuing the Eye: A Narrative Review

Different degrees of visual impairment lead to a decrease in patient wellbeing, which has an adverse effect on many facets of social and professional life. Eye disorders can affect several parts of the eye, most notably the retina and the cornea, and the impacted areas might share a common form of cellular damage or dysfunction (such as inflammation, oxidative stress and neuronal degeneration). Considering that marine organisms inhabit a broad variety of marine habitats, they display a great degree of chemical diversity. As a result, molecules with a marine origin are receiving more and more attention in the hopes of developing novel therapeutic approaches. For instance, fucoxanthin has been demonstrated to be effective in protecting the retina against photo-induced damage, while largazole, astaxanthin and spirulina have all shown antioxidant, anti-inflammatory and antiapoptotic activities that can be useful for the management of several ocular diseases, such as age-related macular degeneration and ocular surface disorders. The aim of this review is to analyze the scientific literature relating to the therapeutic effects on the eye of the main natural marine products, focusing on their mechanism of action and potential clinical uses for the management of ocular diseases.

Protective Effects of Dipterocarpus tuberculatus in Blue Light-Induced Macular Degeneration in A2E-Laden ARPE19 Cells and Retina of Balb/c Mice

Natural products with significant antioxidant activity have been receiving attention as one of the treatment strategies to prevent age-related macular degeneration (AMD). Reactive oxygen intermediates (ROI) including oxo-N-retinylidene-N-retinylethanolamine (oxo-A2E) and singlet oxygen-induced damage, are believed to be one of the major causes of the development of AMD. To investigate the therapeutic effects of methanol extracts of Dipterocarpus tuberculatus Roxb. (MED) against blue light (BL)-caused macular degeneration, alterations in the antioxidant activity, apoptosis pathway, neovascularization, inflammatory response, and retinal degeneration were analyzed in A2E-laden ARPE19 cells and Balb/c mice after exposure of BL. Seven bioactive components, including 2α-hydroxyursolic acid, ε-viniferin, asiatic acid, bergenin, ellagic acid, gallic acid and oleanolic acid, were detected in MED. MED exhibited high DPPH and ABTS free radical scavenging activity. BL-induced increases in intracellular reactive oxygen species (ROS) production and nitric oxide (NO) concentration were suppressed by MED treatment. A significant recovery of antioxidant capacity by an increase in superoxide dismutase enzyme (SOD) activity, SOD expression levels, and nuclear factor erythroid 2-related factor 2 (NRF2) expression were detected as results of MED treatment effects. The activation of the apoptosis pathway, the expression of neovascular proteins, cyclooxygenase-2 (COX-2)-induced inducible nitric oxide synthase (iNOS) mediated pathway, inflammasome activation, and expression of inflammatory cytokines was remarkably inhibited in the MED treated group compared to the Vehicle-treated group in the AMD cell model. Furthermore, MED displayed protective effects in BL-induced retinal degeneration through improvement in the thickness of the whole retina, outer nuclear layer (ONL), inner nuclear layer (INL), and photoreceptor layer (PL) in Balb/c mice. Taken together, these results indicate that MED exhibits protective effects in BL-induced retinal degeneration and has the potential in the future to be developed as a treatment option for dry AMD with atrophy of retinal pigment epithelial (RPE) cells.

Protective effects of Lycium barbarum L. berry extracts against oxidative stress-induced damage of the retina of aging mouse and ARPE-19 cells

In this study, we investigated the preventive effect of Lycium barbarum L. berry extract on age-related macular degeneration (AMD) and the main components responsible for its antioxidant activity. An AMD mouse model was developed by feeding 18-month-old mice with a 1% hydroquinone diet. Meanwhile, the model mice were treated with water extract (LBW) and alcohol extract (LBE) of L. barbarum berries respectively for 3 months. It was found that the retinal structural abnormalities were improved and the oxidation stress and inflammatory imbalance were both attenuated in model mice treated with the extracts of L. barbarum berries. According to the metabolomics analysis of the serum of model mice, LBW regulated the metabolism of unsaturated fatty acids and sphingolipids, while LBE extracts tended to regulate taurine metabolism. On sodium iodate induced oxidative injury of ARPE-19 cells, water extracts of L. barbarum berries eluted with 95% ethanol (LBW-95E) on AB-8 macroporous resin significantly improved the cell viability and attenuated oxidative stress by increasing the superoxide dismutase (SOD) activity and glutathione (GSH) content, decreasing the reactive oxygen species (ROS) content, promoting the entry of nuclear factor erythroid-derived 2-like 2 (Nrf2) into the nucleus and up-regulating the heme oxygenase-1 (HO-1) expression. Scopoletin, N-trans-feruloyltyramine and perlolyrine were identified as the main components of LBW-95E. These results demonstrated that L. barbarum berry extracts protected the retina of aging AMD model mice from degeneration and LBW-95E was the vital antioxidant activity fraction of LBW. These findings suggest that L. barbarum berry extracts might be an excellent natural source for the development of retinal protection-related drugs or dietary supplements.

Blue light pollution causes retinal damage and degeneration by inducing ferroptosis

With the development of technology and electronic products, the problem of light pollution is becoming more and more serious. Blue light, the most energetic light in visible light, is the main culprit of teenage vision problems in the modern environment. As the tissue with the highest oxygen consumption, the retina is vulnerable to oxidative stress. However, the exact way in which blue light-triggered reactive oxygen species (ROS) cause retinal cell death remains unclear. Ferroptosis is a newly defined cell death pathway, whose core molecular mechanism is cell death caused by excessive lipid peroxidation. In this study, the results indicated that blue light-triggered ROS burst in retinal cells, in the meantime, intracellular Fe²⁺ levels were also significantly up-regulated. Further, deferoxamine (DFO) significantly improved blue light-triggered lipid peroxidation and cell death in ARPE-19 cells, and ferrostatin-1 (Fer-1) alleviated retinal oxidative stress and degeneration in rats. Furthermore, the GSH-GPX4 and FSP1-CoQ₁₀-NADH systems served as key systems for cellular defense against ferroptosis, and interestingly, our results demonstrated that blue light triggered imbalance of the GSH-GPX4 and FSP1-CoQ₁₀-NADH systems in retinal cells. Taken together, these pieces of evidence suggest that ferroptosis may be a crucial pathway for blue light-induced retinal damage and degeneration, which helps us to understand exactly why blue light pollution causes visual impairment in adolescents.

Wide Range Applications of Spirulina: From Earth to Space Missions

Spirulina is the most studied cyanobacterium species for both pharmacological applications and the food industry. The aim of the present review is to summarize the potential benefits of the use of Spirulina for improving healthcare both in space and on Earth. Regarding the first field of application, Spirulina could represent a new technology for the sustainment of long-duration manned missions to planets beyond the Lower Earth Orbit (e.g., Mars); furthermore, it could help astronauts stay healthy while exposed to a variety of stress factors that can have negative consequences even after years. As far as the second field of application, Spirulina could have an active role in various aspects of medicine, such as metabolism, oncology, ophthalmology, central and peripheral nervous systems, and nephrology. The recent findings of the capacity of Spirulina to improve stem cells mobility and to increase immune response have opened new intriguing scenarios in oncological and infectious diseases, respectively.

Protective Effect of Ribes nigrum Extract against Blue Light-Induced Retinal Degeneration In Vitro and In Vivo

Although blackcurrant has several health benefits, such as antioxidant and anti-inflammatory properties, its effects on the retina remain unclear. In this study, we investigated the efficacy of black currant extract (BCE) in an in vitro and in vivo model of dry age-related macular degeneration (AMD) induced by blue light. Dry macular degeneration is characterized by the abnormal accumulation of lipofuscin (e.g., N-retinylidene-N-retinylethanolamine, A2E) in the retina. Blue light (BL) significantly decreased the viability of A2E-laden human retinal pigment epithelial cells (ARPE-19). However, BCE treatment protected ARPE-19 cells from A2E and BL. A2E, which is oxidized by blue light, generates reactive oxygen species in RPE cells. Treatment with BCE significantly decreased (80.8%) reactive oxygen species levels induced by A2E and BL in a concentration-dependent manner. BCE inhibited A2E accumulation in ARPE-19 cells and significantly downregulated the expression of genes increased by A2E and BL in ARPE-19 cells. In vivo, oral administration of BCE (25–100 mg/kg) ameliorated ocular lesions of BL-induced retinal damage in a mouse model and rescued the thickness of the whole retina, photoreceptor segment layer, outer nuclear layer, and inner nuclear layer. The decrease in the number of nuclei in the outer nuclear layer induced by BL was also rescued by BCE. Additionally, BCE administration rescued (40.0%) the BL-induced reduction in the expression level of superoxide dismutase 1. Taken together, our results suggest that BCE may have preventive and therapeutic effects on dry AMD through its antioxidant activity and inhibition of lipofuscin accumulation in the retina.