Abstract
Dietary polyphenols are a group of natural compounds that have been proposed to have beneficial effects on human health. They were first known for their antioxidant properties, but several studies over the years have shown that these compounds can exert protective effects against chronic diseases. Nonetheless, the mechanisms underlying these potential benefits are still uncertain and contradictory effects have been reported. In this review, we analyze the potential effects of polyphenol compounds on some visual diseases, with a special focus on retinal degenerative diseases. Current effective therapies for the treatment of such retinal diseases are lacking and new strategies need to be developed. For this reason, there is currently a renewed interest in finding novel ligands (or known ligands with previously unexpected features) that could bind to retinal photoreceptors and modulate their molecular properties. Some polyphenols, especially flavonoids (e.g., quercetin and tannic acid), could attenuate light-induced receptor damage and promote visual health benefits. Recent evidence suggests that certain flavonoids could help stabilize the correctly folded conformation of the visual photoreceptor protein rhodopsin and offset the deleterious effect of retinitis pigmentosa mutations. In this regard, certain polyphenols, like the flavonoids mentioned before, have been shown to improve the stability, expression, regeneration and folding of rhodopsin mutants in experimental in vitro studies. Moreover, these compounds appear to improve the integration of the receptor into the cell membrane while acting against oxidative stress at the same time. We anticipate that polyphenol compounds can be used to target visual photoreceptor proteins, such as rhodopsin, in a way that has only been recently proposed and that these can be used in novel approaches for the treatment of retinal degenerative diseases like retinitis pigmentosa; however, studies in this field are limited and further research is needed in order to properly characterize the effects of these compounds on retinal degenerative diseases through the proposed mechanisms.
Highlights
Different studies have reported that dietary polyphenols exert protective and beneficial effects against chronic diseases such as neurodegenerative and cardiovascular diseases, cancer, and diabetes [1]; the mechanisms underlying these benefits are far from being completely understood and more research is needed in order to define them
Given the new properties that have been given to polyphenols over the years, the main purpose of our research is to show that these compounds may have positive effects on human visual health and encourage researchers to inquire into this field
The neuroprotective effect on the retina observed in flavonoids may be associated with its modulating effects on specific cellular pathways related to antioxidant mechanisms, apart from the stabilizing effect of Rho [127]
Summary
Different studies have reported that dietary polyphenols exert protective and beneficial effects against chronic diseases such as neurodegenerative and cardiovascular diseases, cancer, and diabetes [1]; the mechanisms underlying these benefits are far from being completely understood and more research is needed in order to define them. Despite all the benefits polyphenols can provide, there are some important aspects that have to be taken into account when discussing their physiological effects. Associating polyphenols with specific diseases is challenging [7], some promising results have been obtained in different observational studies regarding polyphenols and certain NCDs [8,9], including some visual diseases. For this reason, the implication of polyphenols in health and disease states needs to be studied and better defined because of the expected positive impact on human health
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