Anthocyanin can arrest the cone photoreceptor degeneration and act as a novel treatment for retinitis pigmentosa

Abstract

Retinitis pigmentosa (RP) is a group of heterogeneous inherited retinal diseases that is characterized by primary death rod photoreceptors and the secondary loss of cones. The degeneration of cones causes gradual constriction of visual fields, leaving the central islands that are eventually snuffed out. Studies indicate that the hyperoxia causes oxidative damage in the retina and contributes to the cone death of RP. Moreover, abundant reactive oxidative species (ROS) which are generated in cones may result in mitochondria membrane depolarization, which has been ascribed a central role in the apoptotic process and has been proposed to act as a forward feeding loop for the activation of downstream cascades. Anthocyanin is a potent antioxidant which has been evidenced to be able to counteract oxidative damages, scavenge surplus ROS, and rectify abnormities in the apoptotic cascade. Taken together with its ability to attenuate inflammation which also contributes to the etiology of RP, it is reasonable to hypothesize that the anthocyanin could act as a novel therapeutic strategy to retard or prevent cone degeneration in RP retinas, particularly if the treatment is timed appropriately and delivered efficiently. Future pharmacological investigations will identify the anthocyanin as an effective candidate for PR therapy and refinements of that knowledge would ignite the hope of restoring the visual function in RP patients.

A Re-Appraisal of Pathogenic Mechanisms Bridging Wet and Dry Age-Related Macular Degeneration Leads to Reconsider a Role for Phytochemicals

“…The beneficial effects of resveratrol and lutein are reproduced by Vaccinium myrtillus since it contains high amounts of antioxidant and anti-inflammatory polyphenols (anthocyanins and resveratrol) [ 49 , 217 , 218 , 219 ]. This is documented in various experimental models of retinal degeneration [ 217 , 218 , 219 ].…”

“…Nonetheless, a deep knowledge of AMD pathogenic mechanisms is still lacking so far, which complicates the establishment or approval of effective treatment strategies. While the overactive angiogenesis and visual deficits occurring in wet AMD can be mitigated by anti-VEGF drugs, this is not the case for dry AMD [ 45 ] Recent evidence-based studies show that dietary phytochemicals such as lutein/zeaxanthin, resveratrol, and Vaccinium myrtillus may be beneficial in retinal diseases including AMD [ 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ]. In general, these compounds have been claimed to interfere with the biology of disease by mitigating oxidative stress and inflammation, which play a critical role in the initiation and progression of AMD [ 47 , 53 , 54 , 55 , 56 ].…”

The synthetic progestin norgestrel modulates Nrf2 signaling and acts as an antioxidant in a model of retinal degeneration

“…Although the disease-causing mutation resides within rod genes, it is the secondary loss of cones that leads to total blindness. The mechanism behind this is not fully understood, but it is known that oxidative stress is a key factor [6] , [7] , [8] , [41] , [60] . Gene therapy is a promising therapeutic approach for RP, however targeting the multitude of RP-related genes is complex and so ROS pathways provide viable indiscriminate therapeutic targets, where the aim is to retard retinal degeneration and preserve vision.…”

Anthocyanins from Purple Tomatoes as Novel Antioxidants to Promote Human Health

“…Anthocyanins can exert different effects on vision health, as attested by many recent studies (reviewed in [ 74 ]): (i) they showed relaxing activities on ciliary smooth muscle, which is involved in the control of lens focus, in the production of aqueous humour and in the maintenance of ocular pressure, thus demonstrating possible therapeutic uses in the treatment of visual fatigue and important ocular disorders such as myopia and glaucoma; (ii) they stimulated the regeneration of rhodopsin, after being photo-bleached by light, a mechanism that is necessary to make this photoreceptor active to carry out again its function in the visual photo transduction process; (iii) being able to inhibit the elongation of axial and ocular lengths caused by wearing a negative lens in animal models, they could be useful in the prevention of myopia, a very common cause of impaired vision in young and adult people, due to a refractive error induced by the elongation or curvature of the eye shape; (iv) they improved dark adaptation and night vision by the enhanced generation of retinal pigments; and (v) they increased retinal blood circulation and could therefore be useful in preventing the early stages of diabetic retinopathy or glaucoma. The antioxidant and scavenging activities of anthocyanins could also affect the production of ROS inducing the apoptotic degeneration of the photoreceptor cells, which is responsible for the gradual constriction of the central visual field, leading to blindness in retinitis pigmentosa [ 75 , 76 ]. In this context, the extract of the Japan blue tomato was tested in vitro on murine photoreceptor cells and found to significantly reduce cone cell death by scavenging hydrogen peroxide [ 62 ].…”