RESUMEN
The purpose of these studies was to evaluate the effects of light damage on Japanese quail whose retinal carotenoids had been experimentally manipulated through altered diets. The birds were raised 6 months on a commercial turkey diet (T), on a custom carotenoid-deficient diet (C-) containing 90% less carotenoid than the T diet, or on Z+ diet [the C- diet supplemented with natural zeaxanthin (35mgkg(-1) food)]. Equal numbers of males and females on each diet were exposed to nine intervals (1hr on, 2hr off) of 3200lux cool white light, then placed in the dark for 14hr before tissue collection. One retina was immediately frozen for HPLC analysis; the other eye was immediately fixed and processed for microscopy. There were no significant differences in the retinal carotenoid concentrations in hatch-mates that were and were not exposed to light. Supplementation resulted in three- to four-fold increases in retinal zeaxanthin and no change in retinal lutein or alpha-tocopherol, but the C- diet did not reduce the retinal carotenoid concentration in C- birds below that in T birds. The light-exposed retinas had significant numbers of apoptotic photoreceptors and photoreceptor ghosts. The number of ghosts was negatively correlated with the number of dying photoreceptors (P<0.05), and with retinal concentrations of zeaxanthin, alpha-tocopherol or gamma-tocopherol (P<0.04, 0.02, 0.04, respectively), but not with lutein. The number of dying photoreceptors was positively correlated with alpha-tocopherol and the sum alpha-tocopherol plus zeaxanthin (P<0.1; P0.04). Photoreceptor death was semi-quantitatively scored, assuming that ghosts were formed by removal of apoptotic photoreceptors with nuclear condensation. Stepwise regression produced a good model (r(2)=0.67;P <0.0001) for predicting death scores from retinal concentrations of zeaxanthin (Standard Coefficient=-0.76) and lutein (Standard Coefficients=+0.43). Absence of lutein in gender-specific analyses suggests lutein served as surrogate marker for gender. Combined analysis of the C- and T birds also demonstrated that dying photoreceptors were negatively correlated with retinal zeaxanthin. These data confirm our previous report that retinal carotenoids prevent photoreceptor cell death, and provide the first direct evidence that retinal zeaxanthin protects photoreceptors from light-induced death.
Asunto(s)
Coturnix/fisiología , Suplementos Dietéticos , Luz , Células Fotorreceptoras de Vertebrados/efectos de los fármacos , Enfermedades de la Retina/dietoterapia , beta Caroteno/análogos & derivados , beta Caroteno/farmacología , Factores de Edad , Animales , Apoptosis/efectos de los fármacos , Carotenoides/análisis , Femenino , Luteína/análisis , Mácula Lútea/patología , Masculino , Enfermedades de la Retina/patología , Factores de Tiempo , Tocoferoles/análisis , Xantófilas , Zeaxantinas , beta Caroteno/administración & dosificación , beta Caroteno/análisisRESUMEN
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.
Asunto(s)
Apoptosis/efectos de la radiación , Células Fotorreceptoras de Vertebrados/efectos de la radiación , Traumatismos Experimentales por Radiación/prevención & control , Degeneración Retiniana/prevención & control , beta Caroteno/análogos & derivados , beta Caroteno/administración & dosificación , Tejido Adiposo/metabolismo , Animales , Recuento de Células , Cromatografía Líquida de Alta Presión , Coturnix , Citoprotección , Dieta , Femenino , Luz , Hígado/metabolismo , Luteína/administración & dosificación , Masculino , Células Fotorreceptoras de Vertebrados/metabolismo , Células Fotorreceptoras de Vertebrados/patología , Traumatismos Experimentales por Radiación/metabolismo , Traumatismos Experimentales por Radiación/patología , Retina/metabolismo , Degeneración Retiniana/metabolismo , Degeneración Retiniana/patología , Xantófilas , ZeaxantinasRESUMEN
PURPOSE: The xanthophyll carotenoids (lutein and zeaxanthin) are hypothesized to delay progression of age-related macular degeneration. The quail has a cone-dominant retina that accumulates carotenoids. The purpose of these experiments was to characterize the carotenoid composition of retina, serum, liver, and fat in quail and to determine whether dietary enrichment with zeaxanthin alters zeaxanthin or lutein concentrations in these tissues. METHODS: Quail were fed for 6 months with a commercial turkey diet (T group; n = 8), carotenoid-deficient diet (C- group; n = 8), or a carotenoid-deficient diet supplemented with 35 mg 3R,3'R-zeaxanthin per kilogram of food, (Z+ group; n = 8). Zeaxanthin was derived from Sphingobacterium multivorum (basonym Flavobacterium). Carotenoids in serum, retina, liver, and fat were analyzed by HPLC. RESULTS: As in the primate fovea, the retina accumulated zeaxanthin, lutein, and cryptoxanthin, and preferentially absorbed zeaxanthin (P < 0.005). In contrast, lutein was preferentially absorbed by liver (P < 0.01) and fat (P < 0.0001). In supplemented females, zeaxanthin increased approximately 4-fold in retina, and 74-, 63- and 22-fold in serum, liver, and fat, respectively. In males, zeaxanthin was elevated approximately 3-fold in retina, and 42-, 17-, and 12-fold in serum, liver, and fat, respectively. Birds fed the Z+ diet absorbed a higher fraction of dietary lutein into serum, but lutein was reduced in the retina (P < 0.05). CONCLUSIONS: Xanthophyll profiles in quail mimic those in primates. Dietary supplements of zeaxanthin effectively increased zeaxanthin concentrations in serum, retina, liver, and fat. The robust response to zeaxanthin supplementation identifies the quail as an animal model for exploration of factors regulating delivery of dietary carotenoids to the retina.