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Comparison of Antioxidant Properties of Dehydrolutein with Lutein and Zeaxanthin, and Their Effects on Cultured Retinal Pigment Epithelial Cells

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Comparison of Antioxidant Properties of Dehydrolutein with Lutein and Zeaxanthin, and Their Effects on Cultured Retinal Pigment Epithelial Cells antioxidants Article Comparison of Antioxidant Properties of Dehydrolutein with Lutein and Zeaxanthin, and their Effects on Cultured Retinal Pigment Epithelial Cells Małgorzata B. Rózanowska˙ 1,2,* , Barbara Czuba-Pelech 3, John T. Landrum 4 and Bartosz Rózanowski˙ 5 1 School of Optometry and Vision Sciences, Cardiff University, Cardiff CF24 4HQ, Wales, UK 2 Cardiff Institute for Tissue Engineering and Repair (CITER), Cardiff University, Cardiff CF24 4HQ, Wales, UK 3 Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland; [email protected] 4 Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA; LandrumJ@fiu.edu 5 Institute of Biology, Pedagogical University, 30-084 Kraków, Poland; [email protected] * Correspondence: [email protected]; Tel.: +44-292-087-5057 Abstract: Dehydrolutein accumulates in substantial concentrations in the retina. The aim of this study was to compare antioxidant properties of dehydrolutein with other retinal carotenoids, lutein, and zeaxanthin, and their effects on ARPE-19 cells. The time-resolved detection of characteristic singlet oxygen phosphorescence was used to compare the singlet oxygen quenching rate constants of dehydrolutein, lutein, and zeaxanthin. The effects of these carotenoids on photosensitized oxidation were tested in liposomes, where photo-oxidation was induced by light in the presence of photosensi- Citation: Rózanowska,˙ M.B.; tizers, and monitored by oximetry. To compare the uptake of dehydrolutein, lutein, and zeaxanthin, Czuba-Pelech, B.; Landrum, J.T.; ARPE-19 cells were incubated with carotenoids for up to 19 days, and carotenoid contents were Rózanowski,˙ B. Comparison of determined by spectrophotometry in cell extracts. To investigate the effects of carotenoids on photo- Antioxidant Properties of cytotoxicity, cells were exposed to light in the presence of rose bengal or all-trans-retinal. The results Dehydrolutein with Lutein and × 10 × 10 Zeaxanthin, and their Effects on demonstrate that the rate constants for singlet oxygen quenching are 0.77 10 , 0.55 10 , and 10 −1 −1 Cultured Retinal Pigment Epithelial 1.23 × 10 M s for dehydrolutein, lutein, and zeaxanthin, respectively. Overall, dehydrolutein is Cells. Antioxidants 2021, 10, 753. similar to lutein or zeaxanthin in the protection of lipids against photosensitized oxidation. ARPE-19 https://doi.org/10.3390/ cells accumulate substantial amounts of both zeaxanthin and lutein, but no detectable amounts antiox10050753 of dehydrolutein. Cells pre-incubated with carotenoids are equally susceptible to photosensitized damage as cells without carotenoids. Carotenoids provided to cells together with the extracellular Academic Editor: Marialaura Amadio photosensitizers offer partial protection against photodamage. In conclusion, the antioxidant proper- ties of dehydrolutein are similar to lutein and zeaxanthin. The mechanism responsible for its lack of Received: 1 April 2021 accumulation in ARPE-19 cells deserves further investigation. Accepted: 7 May 2021 Published: 10 May 2021 Keywords: carotenoid; lutein; zexanthin; dehydrolutein; retina; retinal pigment epithelium; singlet oxygen; photosensitized oxidation; age-related macular degeneration Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. 1. Introduction 30-Dehydrolutein, ((3R,60R)-3-hydroxy- β,"-caroten-30-one also sometimes referred to as 30-oxolutein or 30-ketolutein; Figure1 ) has been identified in substantial concentrations in human and monkey liver, blood serum, and ocular tissues [1–10]. It has been suggested Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. that dehydrolutein is a product of oxidative transformation of dietary carotenoids, lutein β " 0 β β 0 This article is an open access article ( , -carotene-3,3 -diol; Figure1 ), and zeaxanthin ( , -carotene-3,3 -diol; Figure1 ). Out distributed under the terms and of the approximately 40 carotenoids present in a typical human diet, lutein and zeax- conditions of the Creative Commons anthin are the only carotenoids of dietary origin that accumulate in the retina [11–15]. Attribution (CC BY) license (https:// Antioxidant properties of lutein and zeaxanthin have been widely investigated, and it has creativecommons.org/licenses/by/ been well documented that they are very efficient quenchers of excited electronic states of 4.0/). photosensitizers and singlet oxygen, and can act as scavengers of free radicals [15–17]. Antioxidants 2021, 10, 753. https://doi.org/10.3390/antiox10050753 https://www.mdpi.com/journal/antioxidants Antioxidants 2021, 10, x FOR PEER REVIEW 2 of 25 Antioxidants 2021, 10, 753 2 of 25 well documented that they are very efficient quenchers of excited electronic states of pho- tosensitizers and singlet oxygen, and can act as scavengers of free radicals [15–17]. Figure 1. Structure of dietaryFigure carotenoids, 1. Structure zeaxanthin of dietary, and carotenoids, lutein, and zeaxanthin, their metabolite, and lutein, dehydro- and their metabolite, dehydrolutein. lutein. The ability of lutein, zeaxanthin, and their derivatives to quench electronically excited The ability of lutein,states zeaxanthin, is of physiological and their derivatives importance to because quench these electronically carotenoids ex- accumulate in the areas cited states is of physiologicalof thehuman importance body, because such as these the skin carotenoids and eye, accumulate where, due in to the exposure to ultraviolet or areas of the human body,visible such lightas the in skin the presenceand eye, where, of photosensitisers, due to exposure generation to ultraviolet of excited electronic states of or visible light in the presencephotosensitizers of photosensiti and singletsers, generation oxygen can of occurexcited [18 electronic–22]. Moreover, states in the macular part of of photosensitizers and thesinglet retina, oxygen where can lutein occur and [18–22]. zeaxanthin Moreover, accumulate in the macular in particularly part high concentrations, of the retina, where luteinthey and can zeaxanthin act as optical accumulate filters absorbing in particularly incoming high blue concentrations, light, thereby preventing blue light they can act as optical filtersfrom absorbing reaching theincomi partsng of blue photoreceptive light, thereby neurons preventing and retinalblue light pigment epithelium (RPE), from reaching the parts whereof photoreceptive visual pigments neurons are presentand retinal and pigment potent photosensitizers epithelium (RPE), can accumulate [14,23–31]. where visual pigments areTherefore, present and the potent macular photosensitizers carotenoids are can credited accumulate with [14,23–31]. improving visual functions and Therefore, the macular carotenoidsprotecting photosensitiveare credited with parts improving of the retina visual from functions blue-light-induced and pro- oxidative damage. tecting photosensitive partsAltogether, of the retina the antioxidant from blue-light-induced and blue-light filtering oxidative properties damage. of Al- lutein and zeaxanthin are together, the antioxidantbelieved and blue-light to play filtering an important properties role in of protecting lutein and the zeaxanthin retina against are oxidative stress, and, believed to play an importanttherefore, role in in protecting protecting from the retina the development against oxidative and progression stress, and, of age-related macular therefore, in protecting fromdegeneration the developmen [15,16,32t ,and33]. progression Macular degeneration of age-related is the macular primary de- cause of blindness in the generation [15,16,32,33].elderly Macular in developeddegeneration countries. is the primary cause of blindness in the elderly in developed countries.It has been determined that about 15% to 25% of retinal carotenoids are present in It has been determinedthe photoreceptor that about 15% outer to 25% segments, of retinal and, carotenoids in smaller concentrations, are present in in the RPE [34,35]. The the photoreceptor outerphotoreceptor segments, and, outer in sma segmentsller concentrations, are the parts in of the photoreceptive RPE [34,35]. The neurons where visual pig- photoreceptor outer segmentsments areare present,the parts and of where,photoreceptive following neurons absorption where of light, visual all- pig-trans-retinal can be released ments are present, and fromwhere, photoactivated following absorption visual pigments of light, andall-trans accumulate-retinal can in high be re- concentrations [21,34–36]. leased from photoactivatedAll-trans visual-retinal pigments is a potent and photosensitizer accumulate in with high an concentrations absorption spectrum that extends into [21,34–36]. All-trans-retinalthe visibleis a potent range. photosensitizer In the presence with of oxygen,an absorption 30% of spectrum photons absorbedthat by all-trans-retinal extends into the visible range.can be In used the forpresence photosensitized of oxygen, generation 30% of photons of a singlet absorbed oxygen by all- [20]. Therefore, the ability of lutein, zeaxanthin, and their derivatives to quench singlet oxygen deserves particular trans-retinal can be used for photosensitized generation of a singlet oxygen [20]. Therefore, attention. Lutein and zeaxanthin each have the ability to deactivate singlet oxygen with the the ability of lutein, zeaxanthin, and their derivatives to quench
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