提高视网膜中玉米黄质含量以降低光信号转导细胞死亡危险
Elevated Retinal Zeaxanthin and Prevention of
Light-Induced Photoreceptor Cell Death in Quail
Lauren R. Thomson,1,2,3,4 Yoko Toyoda,1,2,4,5 Andrea Langner,1,2,6
Francois C. Delori,1,2 Kevin M. Garnett,7,8 Neal Craft,9 Cathleen R. Nichols,10
Kimberly M. Cheng,10 and C. Kathleen Dorey1,2
目的：已有一些理论和证据指出黄斑色素（叶黄素和玉米黄质）能够保护感光器和阻止AMD的发展。本实验验证黄斑色素与否可降低感光细胞的死亡率。
方法：以6个月的类萝卜素不足（用C_表示）饮食评定视网膜损害。由16人（8男8女）组成的一组，给予C_饮食，在第1、3、7天时，补充35mg3R,3_R的玉米黄质。其中一组持续给予C_饮食，另一组的一般被暴露在间断的3200－lux白光中（间隔时间为2小时）。14小时后，对每个组员的一个视网膜进行HPLC分析，对侧的视网膜则植入石蜡以计算调亡的细胞核。
结果：7天的补充，玉米黄质集中在血清、肝脏和脂肪的浓度分别为50.8、43.2和6.5（P<0.001）。相反，视网膜的玉米黄质在第3天时有显著的提高，而在第7天不能看到这个变化。在光损害视网膜中调亡杆细胞和锥细胞的数量有相关显著性，对侧的视网膜则相反（r_0.61; P _ 0.0001 and r_0.54; P_0.002），血清中玉米黄质没有此类情况。视网膜叶黄素也出现与玉米黄质显著的相关性（r_0.95; P_0.0001）。
结论：视网膜中玉米黄质剂量提高光信号转导细胞调亡的减少，而血清中浓度的提高无效。这些数据为叶黄素在体内保护感光器的理论提供了第一个实验证据。
PURPOSE. Inferential evidence indicates that macular pigments (lutein and zeaxanthin) protect photoreceptors and/or retard age-related macular degeneration. These experiments tested the hypothesis that retinal zeaxanthin prevents light-induced photoreceptor cell death.
METHODS. Retinal damage was assessed in quail fed a carotenoid-deficient (C_) diet for 6 months. Groups of 16 birds (8 male, 8 female) were fed a C_ diet supplemented with 35 mg 3R,3_R-zeaxanthin for 1, 3, or 7 days; one group was continued on C_ diets. Half of each group was exposed to intermittent 3200-lux white light (10 1-hour intervals separated by 2 hours in dark). After 14 additional hours in the dark, one retina of each quail was collected for HPLC analysis, and the contralateral retina was embedded in paraffin for counts of apoptotic nuclei.
RESULTS. After 7 days’ supplementation, concentrations of zeaxanthin in serum, liver, and fat had increased by factors of 50.8, 43.2, and 6.5, respectively (all P _ 0.001). In contrast, retinal zeaxanthin fluctuated significantly upward on day 3, but there was no net change on day 7. The number of apoptotic rods and cones in light-damaged eyes correlated significantly and inversely with zeaxanthin concentration in the contralateral retina (r__0.61; P _ 0.0001 and r__0.54; P _ 0.002), but not with serum zeaxanthin. Similar correlations were observed with retinal lutein, which correlated strongly with retinal zeaxanthin (r _ 0.95; P _ 0.0001).
CONCLUSIONS. Retinal zeaxanthin dose dependently reduced light-induced photoreceptor apoptosis; elevated serum levels did not. These data provide the first experimental evidence that xanthophyll carotenoids protect photoreceptors in vivo. (Invest Ophthalmol Vis Sci. 2002;43:3538–3549)
