a Department of Biophysics, Faculty of Biochemistry , Biophysics and Biotechnology, Jagiellonian University , Krakow , Poland.
Free Radic Res. 2017 Oct;51(9-10):799-811. doi: 10.1080/10715762.2017.1380307. Epub 2017 Oct 3.
The risk of chronic oxidative stress in the retinal pigment epithelium (RPE) increases with age due to accumulation of the photoreactive age pigment lipofuscin (LFG). Here, we asked whether sublethal and weakly lethal photic stress, induced by irradiation of ARPE-19 cells containing phagocytised LFG, affected the cell specific phagocytic activity, which is critically important for proper functioning and survival of the retina, and if natural antioxidants could modify the observed outcomes. ARPE-19 cells preloaded with LFG isolated from human donors of different age or containing LFG enriched with zeaxanthin and α-tocopherol (LFG-A), were irradiated with blue light. Phagocytosis of fluorescein-5-isothiocyanate (FITC)-labelled photoreceptor outer segments was determined by flow cytometry. Photoreactivity of LFG and LFG-A was analysed by measuring photoconsumption of oxygen and photogeneration of singlet oxygen mediated by the granules. LFG-mediated photic stress in ARPE-19 cells induced significant inhibition of their specific phagocytosis. The inhibitory effect increased with age of LFG donors and was reduced by enrichment of the granules with antioxidants. Oxygen consumption and generation of singlet oxygen induced by the photoexcited LFG increased with donor's age and was partially quenched by antioxidants. Although the phototoxic potential of lipofuscin increased with age, natural antioxidants reduced photoreactivity of LFG and their efficiency to induce oxidative stress. This study has demonstrated, for the first time, that mild oxidative stress, mediated by the age pigment lipofuscin, impairs specific phagocytic activity of RPE, and that natural antioxidants can protect this important cellular function by reducing lipofuscin photoreactivity.
视网膜色素上皮 (RPE) 中的慢性氧化应激风险随着年龄的增长而增加,这是由于感光性年龄色素脂褐素 (LFG) 的积累所致。在这里,我们询问了亚致死和弱致死光应激是否会影响细胞特异性吞噬活性,这对于视网膜的正常功能和存活至关重要,以及天然抗氧化剂是否可以改变观察到的结果。用含有吞噬 LFG 的 ARPE-19 细胞或富含玉米黄质和α-生育酚的 LFG(LFG-A)照射 ARPE-19 细胞,诱导亚致死和弱致死光应激。通过流式细胞术测定异硫氰酸荧光素(FITC)标记的光感受器外段的吞噬作用。通过测量颗粒介导的氧光消耗和单线态氧的光生成来分析 LFG 和 LFG-A 的光反应性。LFG 在 ARPE-19 细胞中引起的光应激导致其特异性吞噬作用明显抑制。抑制作用随 LFG 供体年龄的增加而增加,并通过抗氧化剂富集颗粒而降低。光激发的 LFG 诱导的氧消耗和单线态氧的生成随供体年龄的增加而增加,并且部分被抗氧化剂猝灭。尽管脂褐素的光毒性潜力随年龄增长而增加,但天然抗氧化剂降低了 LFG 的光反应性及其诱导氧化应激的效率。这项研究首次表明,由年龄色素脂褐素介导的轻度氧化应激会损害 RPE 的特异性吞噬活性,并且天然抗氧化剂可以通过降低脂褐素的光反应性来保护这种重要的细胞功能。