Scavenging of Cation Radicals of the Visual Cycle Retinoids by Lutein, Zeaxanthin, Taurine, and Melanin
In the retina, retinoids involved in vision are under constant threat of oxidation, and their oxidation products exhibit deleterious properties. Using pulse radiolysis, this study determined that the bimolecular rate constants of scavenging cation radicals of retinoids by taurine are smaller than 2...
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MDPI AG
2023-12-01
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| Series: | International Journal of Molecular Sciences |
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| Online Access: | https://www.mdpi.com/1422-0067/25/1/506 |
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| author | Malgorzata Rozanowska Ruth Edge Edward J. Land Suppiah Navaratnam Tadeusz Sarna T. George Truscott |
| author_facet | Malgorzata Rozanowska Ruth Edge Edward J. Land Suppiah Navaratnam Tadeusz Sarna T. George Truscott |
| author_sort | Malgorzata Rozanowska |
| collection | DOAJ |
| description | In the retina, retinoids involved in vision are under constant threat of oxidation, and their oxidation products exhibit deleterious properties. Using pulse radiolysis, this study determined that the bimolecular rate constants of scavenging cation radicals of retinoids by taurine are smaller than 2 × 10<sup>7</sup> M<sup>−1</sup>s<sup>−1</sup> whereas lutein scavenges cation radicals of all three retinoids with the bimolecular rate constants approach the diffusion-controlled limits, while zeaxanthin is only 1.4–1.6-fold less effective. Despite that lutein exhibits greater scavenging rate constants of retinoid cation radicals than other antioxidants, the greater concentrations of ascorbate in the retina suggest that ascorbate may be the main protectant of all visual cycle retinoids from oxidative degradation, while α-tocopherol may play a substantial role in the protection of retinaldehyde but is relatively inefficient in the protection of retinol or retinyl palmitate. While the protection of retinoids by lutein and zeaxanthin appears inefficient in the retinal periphery, it can be quite substantial in the macula. Although the determined rate constants of scavenging the cation radicals of retinol and retinaldehyde by dopa-melanin are relatively small, the high concentration of melanin in the RPE melanosomes suggests they can be scavenged if they are in proximity to melanin-containing pigment granules. |
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| institution | Directory Open Access Journal |
| issn | 1661-6596 1422-0067 |
| language | English |
| last_indexed | 2024-03-08T15:05:36Z |
| publishDate | 2023-12-01 |
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| record_format | Article |
| series | International Journal of Molecular Sciences |
| spelling | doaj.art-b2b57f0630174ee999711c82ffc1ada62024-01-10T14:59:46ZengMDPI AGInternational Journal of Molecular Sciences1661-65961422-00672023-12-0125150610.3390/ijms25010506Scavenging of Cation Radicals of the Visual Cycle Retinoids by Lutein, Zeaxanthin, Taurine, and MelaninMalgorzata Rozanowska0Ruth Edge1Edward J. Land2Suppiah Navaratnam3Tadeusz Sarna4T. George Truscott5Cardiff Institute of Tissue Engineering and Repair, Cardiff University, Cardiff CF10 3AX, UKDalton Cumbrian Facility, The University of Manchester, Westlakes Science Park, Moor Row, Cumbria CA24 3HA, UKThe Paterson Institute, The University of Manchester, Wilmslow Road, Manchester M20 4BX, UKBiomedical Sciences Research Institute, University of Salford, Manchester M5 4WT, UKDepartment of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Krakow, PolandSchool of Chemical and Physical Sciences, Lennard-Jones Building, Keele University, Staffordshire ST5 5BG, UKIn the retina, retinoids involved in vision are under constant threat of oxidation, and their oxidation products exhibit deleterious properties. Using pulse radiolysis, this study determined that the bimolecular rate constants of scavenging cation radicals of retinoids by taurine are smaller than 2 × 10<sup>7</sup> M<sup>−1</sup>s<sup>−1</sup> whereas lutein scavenges cation radicals of all three retinoids with the bimolecular rate constants approach the diffusion-controlled limits, while zeaxanthin is only 1.4–1.6-fold less effective. Despite that lutein exhibits greater scavenging rate constants of retinoid cation radicals than other antioxidants, the greater concentrations of ascorbate in the retina suggest that ascorbate may be the main protectant of all visual cycle retinoids from oxidative degradation, while α-tocopherol may play a substantial role in the protection of retinaldehyde but is relatively inefficient in the protection of retinol or retinyl palmitate. While the protection of retinoids by lutein and zeaxanthin appears inefficient in the retinal periphery, it can be quite substantial in the macula. Although the determined rate constants of scavenging the cation radicals of retinol and retinaldehyde by dopa-melanin are relatively small, the high concentration of melanin in the RPE melanosomes suggests they can be scavenged if they are in proximity to melanin-containing pigment granules.https://www.mdpi.com/1422-0067/25/1/506retinalvitamin Afree radicalsxanthophyllscarotenoidsvitamin E |
| spellingShingle | Malgorzata Rozanowska Ruth Edge Edward J. Land Suppiah Navaratnam Tadeusz Sarna T. George Truscott Scavenging of Cation Radicals of the Visual Cycle Retinoids by Lutein, Zeaxanthin, Taurine, and Melanin International Journal of Molecular Sciences retinal vitamin A free radicals xanthophylls carotenoids vitamin E |
| title | Scavenging of Cation Radicals of the Visual Cycle Retinoids by Lutein, Zeaxanthin, Taurine, and Melanin |
| title_full | Scavenging of Cation Radicals of the Visual Cycle Retinoids by Lutein, Zeaxanthin, Taurine, and Melanin |
| title_fullStr | Scavenging of Cation Radicals of the Visual Cycle Retinoids by Lutein, Zeaxanthin, Taurine, and Melanin |
| title_full_unstemmed | Scavenging of Cation Radicals of the Visual Cycle Retinoids by Lutein, Zeaxanthin, Taurine, and Melanin |
| title_short | Scavenging of Cation Radicals of the Visual Cycle Retinoids by Lutein, Zeaxanthin, Taurine, and Melanin |
| title_sort | scavenging of cation radicals of the visual cycle retinoids by lutein zeaxanthin taurine and melanin |
| topic | retinal vitamin A free radicals xanthophylls carotenoids vitamin E |
| url | https://www.mdpi.com/1422-0067/25/1/506 |
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