Dragana Celojevic

Association of Nrf2-encoding NFE2L2 haplotypes with Parkinson's disease

BackgroundOxidative stress is heavily implicated in the pathogenic process of Parkinsons disease. Varying capacity to detoxify radical oxygen species through induction of phase II antioxidant enzymes in substantia nigra may influence disease risk. Here, we hypothesize that variation in NFE2L2 and KEAP1, the genes encoding the two major regulators of the phase II response, may affect the risk of Parkinsons disease.MethodsThe study included a Swedish discovery case-control material (165 cases and 190 controls) and a Polish replication case-control material (192 cases and 192 controls). Eight tag single nucleotide polymorphisms representing the variation in NFE2L2 and three representing the variation in KEAP1 were chosen using HapMap data and were genotyped using TaqMan Allelic Discrimination.ResultsWe identified a protective NFE2L2 haplotype in both of our European case-control materials. Each haplotype allele was associated with five years later age at onset of the disease (p = 0.001) in the Swedish material, and decreased risk of PD (p = 2 × 10-6), with an odds ratio of 0.4 (95% CI 0.3-0.6) for heterozygous and 0.2 (95% CI 0.1-0.4) for homozygous carriers, in the Polish material. The identified haplotype includes a functional promoter haplotype previously associated with high transcriptional activity. Genetic variation in KEAP1 did not show any associations.ConclusionThese data suggest that variation in NFE2L2 modifies the Parkinsons disease process and provide another link between oxidative stress and neurodegeneration.

Nrf2-encoding NFE2L2 haplotypes influence disease progression but not risk in Alzheimer's disease and age-related cataract.

Alzheimers disease (AD) and age-related cataract, disorders characterized by protein aggregation causing late-onset disease, both involve oxidative stress. We hypothesize that common variants of NFE2L2 and KEAP1, the genes encoding the main regulators of the Nrf2 system, an important defence system against oxidative stress, may influence risk of AD and/or age-related cataract. This case-control study combines an AD material (725 cases and 845 controls), and a cataract material (489 cases and 182 controls). Genetic variation in NFE2L2 and KEAP1 was tagged by eight and three tag single nucleotide polymorphisms (SNPs), respectively. Single SNPs and haplotypes were analyzed for associations with disease risk, age parameters, MMSE and AD cerebrospinal fluid biomarkers. NFE2L2 and KEAP1 were not associated with risk of AD or cataract. However, one haplotype allele of NFE2L2 was associated with 2 years earlier age at AD onset (p(c)=0.013) and 4 years earlier age at surgery for posterior subcapsular cataract (p(c)=0.019). Another haplotype of NFE2L2 was associated with 4 years later age at surgery for cortical cataract (p(c)=0.009). Our findings do not support NFE2L2 or KEAP1 as susceptibility genes for AD or cataract. However, common variants of the NFE2L2 gene may affect disease progression, potentially altering clinically recognized disease onset.

Gender and Cataract – The Role of Estrogen

Abstract There is evidence from epidemiologic data that cataract is more common in women than men. This is not solely due to a higher rate of cataract extraction in women, as is the case in the western world, but several population-based studies show that females have a higher prevalence of lens opacities, especially cortical. There is no firm evidence that lifestyle-related factors are the cause of this gender discrepancy. Focus has therefore been directed towards the role of estrogen in cataract formation. Although data on endogenous and exogenous estrogen involvement in cataractogenesis are conflicting, some studies have indicated that hormone therapy may decrease the risk of cataract and thus be protective. It has been hypothesized that the decrease in estrogen at menopause cause increased risk of cataract in women, i.e. not strictly the concentration of estrogen, but more the withdrawal effect. Estrogens are known to exert several anti-aging effects that may explain the longer lifespan in women, including metabolically beneficial effects, neuroprotection, preservation of telomeres and anti-oxidative properties. Since oxidative stress is considered important in cataractogenesis, studies have investigated the effects of estrogens on lens epithelial cells in culture or in animal models. Several investigators have found protection by physiological concentrations of 17β-estradiol against oxidative stress induced by H2O2 in cultured lens epithelial cells. Although both main types of estrogen receptors, ERα and ERβ, have been demonstrated in lens epithelium, most studies so far indicate that the estrogen-mediated protection in the lens is exerted through non-genomic, i.e. receptor-independent mechanisms, possibly through phosphorylation of extracellular signal-regulated kinase (ERK1/ERK2), a member of the mitogen-activated protein kinase (MAPK)-signaling pathway. Further studies are needed, both epidemiologic as to the role of hormone therapies, and laboratory studies regarding molecular estrogen-mediated mechanisms, in order to comprehend the role of estrogens on cataract formation.

EPHA2 polymorphisms in Estonian patients with age-related cataract

Abstract Background: Ephrin receptors (Ephs) are tyrosine kinases that together with their ligands, ephrins, are considered important in cell–cell communication, especially during embryogenesis but also for epithelium homeostasis. Studies have demonstrated the involvement of mutations or common variants of the gene encoding Eph receptor A2 (EPHA2), in congenital cataract and in age-related cataract. This study investigated a number of disease-associated single nucleotide polymorphisms (SNPs) in EPHA2 in patients with age-related cataract. Materials and methods: The study included 491 Estonian patients who had surgery for age-related cataract, classified as nuclear, cortical, posterior subcapsular and mixed lens opacities, and 185 controls of the same ethnical origin. Seven SNPs in EPHA2 (rs7543472, rs11260867, rs7548209, rs3768293, rs6603867, rs6678616, rs477558) were genotyped using TaqMan Allelic Discrimination. Statistical analyses for single factor associations used χ2-test and logistic regression was performed including relevant covariates (age, sex and smoking). Results: In single-SNP allele analysis, only the rs7543472 showed a borderline significant association with risk of cataract (p = 0.048). Regression analysis with known risk factors for cataract showed no significant associations of the studied SNPs with cataract. Stratification by cataract subtype did not alter the results. Adjusted odds ratios were between 0.82 and 1.16 (95% confidence interval 0.61–1.60). Conclusions: The present study does not support a major role of EphA2 in cataractogenesis in an Estonian population.

Superoxide dismutase gene polymorphisms in patients with age-related cataract

ABSTRACT Background: Functional polymorphisms in genes encoding antioxidant enzymes may result in reduced enzyme activity and increased levels of reactive oxygen species, such as superoxide radicals, which in turn may contribute to increased risk of age-related disorders. Copper–zinc superoxide dismutases, SOD-1 and SOD-3, and manganese superoxide dismutase, SOD-2, are enzymes involved in the protection against oxidative stress and detoxification of superoxide. In this study, we investigated a number of disease-associated single nucleotide polymorphisms (SNPs) of SOD1, SOD2 and SOD3, in patients with age-related cataract. Materials and methods: The study included an Estonian sample of 492 patients with age-related cataract, subgrouped into nuclear, cortical, posterior subcapsular and mixed cataract, and 185 controls. Twelve SNPs in SOD1, SOD2 and SOD3 were genotyped using TaqMan Allelic Discrimination. Haplotype analysis was performed on the SNPs in SOD2. Results: None of the studied SNPs showed an association with risk of cataract. These results were consistent after adding known risk factors (age, sex and smoking) as covariates in the multivariate analyses and after stratification by cataract subtype. Analysis of SOD2 haplotypes did not show any associations with risk of cataract. Conclusions: If genetic variation in genes encoding SOD-1, SOD-2 and SOD-3 contributes to cataract formation, there is no major contribution of the SNPs analyzed in the present study.

Genetic Variation of Superoxide Dismutases in Patients with Primary Open-angle Glaucoma

Abstract Purpose: Oxidative stress has been described as an underlying pathogenetic mechanism in retinal ganglion cell apoptosis, which is a hallmark of primary open-angle glaucoma (POAG). Superoxide dismutases (SODs) are enzymes involved in the protection against oxidative stress by detoxification of superoxide. In this study, we investigated a number of disease-associated single nucleotide polymorphisms (SNPs) in the copper-zinc-containing SOD1 and SOD3, and in the manganese superoxide dismutase SOD2, in POAG patients. Methods: The study included 239 patients with POAG and 185 controls, all of Estonian origin, recruited at two ophthalmic clinics in Tartu, Estonia. Eleven SNPs, either functional, disease-associated or tag SNPs in SOD1, SOD2 and SOD3 were genotyped using TaqMan Allelic Discrimination. Haplotype analysis was performed on the SNPs in SOD2. Results: Using binary logistic regression in an additive model, the rs2842980 SNP in SOD2 was significantly associated with POAG diagnosis (p = 0.03) at a univariate level. None of the studied SNPs showed an association with risk of POAG in a multivariate analysis, including age and current smoking as covariates. Analysis of SOD2 haplotypes did not show any association with risk of POAG. Conclusions: If oxidative stress is an important mechanism in POAG-related retinal ganglion cell death, genetic variations in SOD1, SOD2 and SOD3 are not major contributors in the pathogenesis.

Cell adhesion molecule expression in human lens epithelial cells after corticosteroid exposure.

Aim: The aim of the study was to investigate changes in cell adhesion molecule expression in human lens epithelial cells (HLEC) subjected to glucocorticoids. Methods: Human lens epithelial cells were exposed to different concentrations of dexamethasone for 24 hours. Cell adhesion molecule expression was studied by western blot and immunohistochemistry of vimentin, N-cadherin, E-cadherin, α-catenin, β-catenin and γ-catenin. Expression of the glucocorticoid receptor (GR) was also studied. Cell morphology was examined by transmission electron microscopy (TEM). Result: Expression of N-cadherin, α-catenin, β-catenin and GR was significantly decreased in dexamethasone exposed cells as compared to unexposed cells. No significant change in γ-catenin was present. Visualization of adhesion molecules, N-cadherin and α-catenin, by immunohistochemistry showed decreased antigen reactivity in dexamethasone exposed as compared to the unexposed cells. However, no change was seen for β-catenin and γ-catenin. E-cadherin was not detectable using western blot or immunohistochemistry. TEM showed multilayering of cells, vacuole formation and appearance of electron-dense multivesicular bodies in HLEC exposed to 0, 0.1, 1, 10 and 100 αM dexamethasone. Conclusion: Glucocorticoids affect several adhesion molecules in lens epithelial cells, something that may contribute to the pathogenesis of posterior subcapsular opacification.