Antioxidants in the Retina and Retinal Pigment Epithelium
As mentioned earlier, several antioxidant mechanisms have been established in biological systems, including free radical scavenging, quenching of 1O2, and enzymatic reduction of ROOH. Antioxidants found in vertebrate retinas and RPE include the following:
See Figure 14-2, which depicts the relation between some of these antioxidants and the protective mechanisms.
Selenium, Glutathione, and Glutathione Peroxidase
The role of GSH (discussed earlier in the chapter) is depicted in Figures 14-1 and 14-2. The primary enzyme involved in GSH-mediated detoxification of peroxides is GSH-Px, which is selenium dependent. The highest concentration of selenium in the human eye is present in the RPE: 100–400 ng in the RPE cells of a single human eye, up to 10 times as many as in the retina (40 ng). The selenium level in the human retina remains constant with age; in the human RPE, however, the level increases with age.
González de Vega R, García M, Fernández-Sánchez ML, González-Iglesias H, Sanz-Medel A. Protective effect of selenium supplementation following oxidative stress mediated by glucose on retinal pigment epithelium. Metallomics. 2018;10(1):83–92.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.