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Jeong A Choi, Bo-Ra Seo, Young Hee Yoon, Jae-Young Koh; Protective effect of zinc against A2E-induced toxicity in ARPE19 cells: Possible involvement of lysosomal acidification. Invest. Ophthalmol. Vis. Sci. 2019;60(9):1945.
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Dry age-related macular degeneration (AMD) is characterized by accumulation of extracellular aggregates called drusen and degeneration of photoreceptor and retinal pigment epithelial (RPE) cells. It has been proposed that lysosomal dysfunction in RPE cells contributes to dry AMD pathology by hindering the degradation of shed photoreceptor membranes. We have previously shown that raising intracellular zinc levels can restore lysosomal acidity and its degradative function (Yoon et al. IOVS, 2010; Seo et al Neurobiol Aging, 2015). In the present study, we examined the effects of raising intracellular zinc on lysosomal alkalization/dysfunction and cell death induced by retinal lipofuscin, A2E.
To induce lysosomal dysfunction in a human RPE cell line (ARPE19), we used A2E. To examine the effect of raising intracellular zinc against A2E-induced changes, we used zinc ionophores (clioquinol and 1H10). A2E accumulation in ARPE19 cells was evaluated by measuring its autofluorescence. Lysosomal pH was measured by using pHrodo™ Red-AM. A2E-induced cell death was quantitatively assessed by measuring lactate dehydrogenase (LDH) activity released into the culture medium.
Twenty-four hours after A2E treatment, ARPE19 cells exhibited A2E accumulation and decreases in pHrodo™ Red fluorescence (i.e. increases in lysosomal pH), and subsequently underwent cell death. Zinc ionophores reduced A2E accumulation and restored lysosomal pH back to the acidic range. In addition, zinc ionophores substantially reduced cell death induced by A2E. All the effects of zinc ionophores on A2E-induced changes were blocked by the addition of TPEN, a membrane-permeant zinc chelator.
Our results support the possibility that adequate levels of zinc, especially in lysosomes, may help overcome A2E-induced cytotoxic changes in ARPE19 cells, which may contribute to the pathogenesis of AMD.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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