Scavenging of cation radicals of the visual cycle retinoids by lutein, zeaxanthin, taurine, and melanin

Rozanowska, Malgorzata ORCID: https://orcid.org/0000-0003-2913-8954, Edge, Ruth, Land, Edward J., Navaratnam, Suppiah, Sarna, Tadeusz and Truscott, T. George 2024. Scavenging of cation radicals of the visual cycle retinoids by lutein, zeaxanthin, taurine, and melanin. International Journal of Molecular Sciences 25 (1) , 506. 10.3390/ijms25010506

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Abstract

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 × 107 M−1s−1 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.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Optometry and Vision Sciences
Publisher:	MDPI
ISSN:	1661-6596
Funders:	This research was funded by the Wellcome Trust Travelling Fellowship to M.R. and the European Union Vth Framework Programme (Contract ICAI-CT-2000-70012). The pulse radiolysis experiments were performed at the Christie Hospital, Manchester or at the Free Radical Research Facility at Daresbury Synchrotron Laboratory and supported by the European Commission Human Potential Programme Access to Infrastructure (Contract HPRI-CT-2002-00183).
Date of First Compliant Deposit:	5 January 2024
Date of Acceptance:	28 December 2023
Last Modified:	07 Mar 2024 12:13
URI:	https://orca.cardiff.ac.uk/id/eprint/165104

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