Association of diabetes with age-related macular degeneration in the EUREYE study

Objective: To examine the association between self-reported diabetes history and early or late age-related macular degeneration (AMD) in the European population.

Retinal VEGF mRNA measured by SYBR Green I fluorescence: A versatile approach to quantitative PCR

PURPOSE: To determine whether continuous monitoring of SYBR Green I fluorescence provides a reliable and flexible method of quantitative RT-PCR. Our aims were (i) to test whether SYBR Green I analysis could quantify a wide range of known VEGF template concentrations, (ii) to apply this method in an experimental model, and (iii) to determine whether 20 existing primer pairs could be used to quantify their cognate mRNAs.

The 67-kd laminin receptor is preferentially expressed by proliferating retinal vessels in a murine model of ischemic retinopathy.

Endothelial cell association with vascular basement membranes is complex and plays a critical role in regulation of cell adhesion and proliferation. The interaction between the membrane-associated 67-kd receptor (67LR) and the basement membrane protein laminin has been studied in several cell systems where it was shown to be crucial for adhesion and attachment during angiogenesis. As angiogenesis in the pathological setting of proliferative retinopathy is a major cause of blindness in the Western world we examined the expression of 67LR in a murine model of hyperoxia-induced retinopathy that exhibits retinal neovascularization. Mice exposed to hyperoxia for 5 days starting at postnatal day 7 (P7) and returned to room air (at P12) showed closure of the central retinal vasculature. In response to the ensuing retinal ischemia, there was consistent preretinal neovascularization starting around P17, which persisted until P21, after which the new vessels regressed. Immunohistochemistry was performed on these retinas using an antibody specific for 67LR. At P12, immunoreactivity for 67LR was absent in the retina, but by P17 it was observed in preretinal proliferating vessels and also within the adjacent intraretinal vasculature. Intraretinal 67LR immunoreactivity diminished beyond P17 until by P21 immunoreactivity was almost completely absent, although it persisted in the preretinal vasculature. Control P17 mice (not exposed to hyperoxia) failed to demonstrate any 67LR immunoreactivity in their retinas. Parallel in situ hybridization studies demonstrated 67LR gene expression in the retinal ganglion cells of control and hyperoxia-exposed mice. In addition, the neovascular intra- and preretinal vessels of hyperoxia-treated P17 and P21 mice labeled strongly for 67LR mRNA. This study has characterized 67LR immunolocalization and gene expression in a murine model of ischemic retinopathy. Results suggest that, although the 67LR gene is expressed at high levels in the retinal ganglion cells, the mature receptor protein is preferentially localized to the proliferating retinal vasculature and is almost completely absent from quiescent vessels. The differential expression of 67LR between proliferating and quiescent retinal vessels suggests that this laminin receptor is an important and novel target for future chemotherapeutic intervention during proliferative vasculopathies.

Retinal pericytes control expression of nitric oxide synthase and endothelin-1 in microvascular endothelial cells

Pericytes are known to communicate with endothelial cells by direct contact and by releasing cytokines such as TGF-beta. There is also strong evidence that pericytes act as regulators of endothelial cell proliferation and differentiation. We have investigated the effect of pericyte-conditioned medium (PCM) on proliferation of human microvascular endothelial cells in vitro, together with the expression of the vasoregulatory molecules, constitutive and inducible nitric oxide synthases (ecNOS and iNOS), and endothelin-1 (ET-1). Expression was measured at the mRNA level using semiquantitative RT-PCR for all three genes and at the protein level for ecNOS and iNOS using Western blotting. Growth curves for HMECs showed that PCM inhibits proliferation, eventually leading to cell death. Exposure to PCM repressed iNOS mRNA expression fivefold after 6 h. A similar, though delayed, reduction in protein levels was observed. ecNOS mRNA was slightly induced at 6 h, though there was no significant change in ecNOS protein. By contrast, ET-1 mRNA was induced 2.3-fold after 6 h exposure to PCM. We conclude that pericytes release a soluble factor or factors that are potent inhibitors of endothelial cell growth and promote vasoconstriction by up-regulating endothelin-1 and down-regulating iNOS. (C) 2000 Academic Press.

An Ecological Correlation Study of Late Age-Related Macular Degeneration and the Complement Factor H Y402H Polymorphism

PURPOSE:
To investigate whether variation in the distribution of the risk allele frequency of the Y402H single-nucleotide polymorphism (SNP) across various ethnicities and geographic regions reflects differences in the prevalence of late age-related macular degeneration (AMD) in those ethnicities.

METHODS:
Published data were obtained via a systematic search. Study samples were grouped into clusters by ethnicity and geographic location and the Spearman correlation coefficient of the prevalence of late AMD and risk allele frequencies was calculated across clusters.

RESULTS:
Across all ethnicities, AMD prevalence was seen to increase with age. Populations of European descent had both higher risk allele frequencies and prevalence of late AMD than did Japanese, Chinese, and Hispanic descendants. Results for African descendants were anomalous: although allele frequency was similar to that in European populations, the age-specific prevalence of late AMD was considerably lower. The correlation coefficient for the association between allele frequency and AMD prevalence was 0.40 (95% confidence interval [CI] = -0.36 to 0.84, P = 0.28) in all populations combined and 0.71 (95% CI = 0.02-0.94, P = 0.04) when people of African descent were excluded.

CONCLUSIONS:
Evidence was found at the population level to support a positive association between the Y204H risk allele and the prevalence of AMD after exclusion of studies undertaken on persons of African ancestry. Data in African, Middle Eastern, and South American populations are needed to provide a better understanding of the association of late AMD genetic risk across ethnicities.

Prevalence of Early and Late Age-Related Macular Degeneration in India: The INDEYE Study

PURPOSE. To estimate the prevalence of early and late age-related macular degeneration (AMD) in India.

Sunlight exposure, antioxidants, and age-related macular degeneration

Objective: To examine the association of sunlight exposure and antioxidant level with age-related macular degeneration (AMD). Methods: Four thousand seven hundred fifty-three participants aged 65 years or older in the European Eye Study underwent fundus photography, were interviewed for adult lifetime sunlight exposure, and gave blood for antioxidant analysis. Blue light exposure was estimated by combining meteorologic and questionnaire data. Results: Data on sunlight exposure and antioxidants were available in 101 individuals with neovascular AMD, 2182 with early AMD, and 2117 controls. No association was found between blue light exposure and neovascular or early AMD. Significant associations were found between blue light exposure and neovascular AMD in individuals in the quartile of lowest antioxidant level - vitamin C, zeaxanthin, vitamin E, and dietary zinc - with an odds ratio of about 1.4 for 1 standard deviation unit increase in blue light exposure. Higher odds ratios for blue light were observed with combined low antioxidant levels, especially vitamin C, zeaxanthin, and vitamin E (odds ratio, 3.7; 95% confidence interval, 1.6-8.9), which were also associated with early stages of AMD. Conclusions: Although it is not possible to establish causality between sunlight exposure and neovascular AMD, our results suggest that people in the general population should use ocular protection and follow dietary recommendations for the key antioxidant nutrients. ©2008 American Medical Association. All rights reserved.

Oily fish consumption, dietary docosahexaenoic acid and eicosapentaenoic acid intakes, and associations with neovascular age-related macular degeneration

Background: Fish intake, the major source of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), may reduce the risk of age-related macular degeneration (AMD). Objective: We investigated the association of oily fish and dietary DHA and EPA with neovascular AMD (NV-AMD). Design: Participants aged =65 y in the cross-sectional population-based EUREYE study underwent fundus photography and were interviewed by using a food-frequency questionnaire. Fundus images were graded by the International Classification System for Age Related Maculopathy. Questionnaire data were converted to nutrient intakes with the use of food-composition tables. Survey logistic regression was used to calculate odds ratios (ORs) and 95% CIs of energy-adjusted quartiles of EPA or DHA with NV-AMD, taking into account potential confounders. Results: Dietary intake data and fundus images were available for 105 cases with NV-AMD and for 2170 controls without any features of early or late AMD. Eating oily fish at least once per week compared with less than once per week was associated with a halving of the odds of NV-AMD (OR = 0.47; 95% CI: 0.33, 0.68; P = 0.002). Compared with the lowest quartile, there was a significant trend for decreased odds with increasing quartiles of either DHA or EPA. ORs in the highest quartiles were 0.32 (95% CI: 0.12, 0.87; P = 0.03) for DHA and 0.29 (95% CI: 0.11, 0.73; P = 0.02) for EPA. Conclusions: Eating oily fish at least once per week compared with less than once per week was associated with a halving of the OR for NV-AMD. © 2008 American Society for Nutrition.