Serum superoxide dismutase and malondialdehyde levels in a group of Chinese patients with age-related macular degeneration

Antioxidants and Mechanistic Insights for Managing Dry Age-Related Macular Degeneration

Age-related macular degeneration (AMD) severely affects central vision due to progressive macular degeneration and its staggering prevalence is rising globally, especially in the elderly population above 55 years. Increased oxidative stress with aging is considered an important contributor to AMD pathogenesis despite multifaceted risk factors including genetic predisposition and environmental agents. Wet AMD can be managed with routine intra-vitreal injection of angiogenesis inhibitors, but no satisfactory medicine has been approved for the successful management of the dry form. The toxic carbonyls due to photo-oxidative degradation of accumulated bisretinoids within lysosomes initiate a series of events including protein adduct formation, impaired autophagy flux, complement activation, and chronic inflammation, which is implicated in dry AMD. Therapy based on antioxidants has been extensively studied for its promising effect in reducing the impact of oxidative stress. This paper reviews the dry AMD pathogenesis, delineates the effectiveness of dietary and nutrition supplements in clinical studies, and explores pre-clinical studies of antioxidant molecules, extracts, and formulations with their mechanistic insights.

Oxidative Stress and Antioxidants in Age-Related Macular Degeneration

Oxidative stress plays a crucial role in aging-related eye diseases, including age-related macular degeneration (AMD), cataracts, and glaucoma. With age, antioxidant reparative capacity decreases, and excess levels of reactive oxygen species produce oxidative damage in many ocular cell types underling age-related pathologies. In AMD, loss of central vision in the elderly is caused primarily by retinal pigment epithelium (RPE) dysfunction and degeneration and/or choroidal neovascularization that trigger malfunction and loss of photo-sensing photoreceptor cells. Along with various genetic and environmental factors that contribute to AMD, aging and age-related oxidative damage have critical involvement in AMD pathogenesis. To this end, dietary intake of antioxidants is a proven way to scavenge free radicals and to prevent or slow AMD progression. This review focuses on AMD and highlights the pathogenic role of oxidative stress in AMD from both clinical and experimental studies. The beneficial roles of antioxidants and dietary micronutrients in AMD are also summarized.

Malondialdehyde-Modified Photoreceptor Outer Segments Promote Choroidal Neovascularization in Mice

Purpose

This study aimed to establish a novel choroidal neovascularization (CNV) mouse model through subretinally injecting malondialdehyde (MDA)-modified photoreceptor outer segments (POS), which was more consistent with the pathogenesis of wet age-related macular degeneration (AMD).

Methods

MDA-modified POS were subretinally injected in C57BL/6J mice. Four weeks later, to assess the volume of CNV and the morphology of retinal pigment epithelium (RPE), isolectin B4 and zonula occludens-1 antibody were used for immunostaining. Fundus fluorescent angiography and optical coherence tomography imaging were used to describe the morphologic features of CNV. Transepithelial resistance was measured on polarized ARPE-19 cells. Vascular endothelial growth factor levels in the cell culture medium were detected by enzyme-linked immunosorbent assay. The protein and messenger RNA expression levels of autophagy markers were measured using Western blot and quantitative polymerase chain reaction.

Results

CNV and RPE atrophy were successfully induced in the mouse model. MDA-modified POS also significantly increased the expression of vascular endothelial growth factor and disrupted cell junctions in RPE cells. In addition, MDA-modified POS induced autophagy–lysosomal impairment in RPE cells.

Conclusions

Subretinal injection of MDA-modified POS may generate a feasible CNV model that simulates the AMD pathological process.

Translational Relevance

This study expands the understanding of the role of MDA in AMD pathogenesis, which provides a potential therapeutic target of AMD.

Effects of Zinc Acetate Hydrate Treatment on Serum Oxidative Stress Markers in Patients with Macular Drusen

Purpose: To measure the serum levels of the oxidative stress markers superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione peroxidase (GPx) and compare them before and after zinc supplementation in patients with early age-related macular degeneration (AMD). Methods: We measured serum zinc levels in 65 patients with early AMD. Of these, 29 patients with macular drusen and a serum zinc level <80 μg/dL received oral zinc acetate dihydrate (50 mg/day). Serum trace metal levels (zinc and copper) and oxidative stress marker levels (SOD, MDA, and GPx) were measured at baseline and 12 weeks after the treatment. The macular drusen areas and best-corrected visual acuity were evaluated in 24 participants who attended the 3-month follow-up. Results: MDA level was significantly decreased from baseline to 12 weeks after zinc administration (170.5 ± 100.9 vs. 148.3 ± 57.9 pmol/mL, P = 0.03), while SOD was significantly increased from baseline to 12 weeks after zinc intake (4.2 ± 0.9 vs. 4.6 ± 0.9 U/mL, P = 0.03). The serum zinc level was significantly correlated with the MDA level (P = 0.03, ρ = -0.26). The area of soft drusen was significantly decreased after zinc treatment (1,936,654.9 ± 1,348,267.6 vs. 966,883.9 ± 719,938.1 μmm², P = 0.04). Conclusions: The levels of oxidative stress markers MDA and SOD decreased and increased, respectively, after oral zinc administration to 24 patients with AMD. The therapeutic effect of zinc treatment on drusen area might differ depending on the drusen phenotype in early AMD.

From Oxidative Stress to Inflammation in the Posterior Ocular Diseases: Diagnosis and Treatment

Most irreversible blindness observed with glaucoma and retina-related ocular diseases, including age-related macular degeneration and diabetic retinopathy, have their origin in the posterior segment of the eye, making their physiopathology both complex and interconnected. In addition to the age factor, these diseases share the same mechanism disorder based essentially on oxidative stress. In this context, the imbalance between the production of reactive oxygen species (ROS) mainly by mitochondria and their elimination by protective mechanisms leads to chronic inflammation. Oxidative stress and inflammation share a close pathophysiological process, appearing simultaneously and suggesting a relationship between both mechanisms. The biochemical end point of these two biological alarming systems is the release of different biomarkers that can be used in the diagnosis. Furthermore, oxidative stress, initiating in the vulnerable tissue of the posterior segment, is closely related to mitochondrial dysfunction, apoptosis, autophagy dysfunction, and inflammation, which are involved in each disease progression. In this review, we have analyzed (1) the oxidative stress and inflammatory processes in the back of the eye, (2) the importance of biomarkers, detected in systemic or ocular fluids, for the diagnosis of eye diseases based on recent studies, and (3) the treatment of posterior ocular diseases, based on long-term clinical studies.

The Contribution of Fluoride to the Pathogenesis of Eye Diseases: Molecular Mechanisms and Implications for Public Health

This study provides diverse lines of evidence demonstrating that fluoride (F) exposure contributes to degenerative eye diseases by stimulating or inhibiting biological pathways associated with the pathogenesis of cataract, age-related macular degeneration and glaucoma. As elucidated in this study, F exerts this effect by inhibiting enolase, τ-crystallin, Hsp40, Na⁺, K⁺-ATPase, Nrf2, γ -GCS, HO-1 Bcl-2, FoxO1, SOD, PON-1 and glutathione activity, and upregulating NF-κB, IL-6, AGEs, HsP27 and Hsp70 expression. Moreover, F exposure leads to enhanced oxidative stress and impaired antioxidant activity. Based on the evidence presented in this study, it can be concluded that F exposure may be added to the list of identifiable risk factors associated with pathogenesis of degenerative eye diseases. The broader impact of these findings suggests that reducing F intake may lead to an overall reduction in the modifiable risk factors associated with degenerative eye diseases. Further studies are required to examine this association and determine differences in prevalence rates amongst fluoridated and non-fluoridated communities, taking into consideration other dietary sources of F such as tea. Finally, the findings of this study elucidate molecular pathways associated with F exposure that may suggest a possible association between F exposure and other inflammatory diseases. Further studies are also warranted to examine these associations.

Analysis of antioxidative factors related to AMD risk development in the polish patients

PURPOSE

Age-related macular degeneration (AMD) is a major cause of blindness in developed countries. Oxidative mechanisms may play a key role in the aetiology of AMD. The main aim of this study was to investigate antioxidative markers in the pathogenesis of AMD.

METHODS

A total of 510 subjects including 240 patients with AMD (mean age 77.9 ± 8.5 year) and 270 controls (mean age 74.0 ± 10.4 year) were allowed in this study. We measured activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) and examined their association with the SNPs of respective genes (SOD1 + 35A/C, CAT C-262T and GPx Pro197Leu). Restriction fragment length polymorphism (RFLP) technique was used to determine the selected gene polymorphisms. Sixty subjects including 30 patients with AMD (mean age 69.4 ± 9.3) and 30 controls (mean age 64.6 ± 8.2) were enrolled to determine the activity of antioxidant enzymes by spectrometry method.

RESULTS

A significant decrease in enzymes, SOD (p = 0.011), CAT (p = 0.002) and GPx (p ≤ 0.001) in AMD patients compared to controls, was indicated. The risk of susceptibility to AMD was significantly higher in patients with AMD who had Pro197Leu C/T genotype of GPx (OR = 2.78; 95% CI = 1.78-4.35). The A/C genotype and the C allele frequencies of A/C polymorphism of SOD1 gene significantly reduce the risk of AMD (OR=0.48; 95% CI 0.27; 0.85).

CONCLUSION

In conclusion, our data showed that insufficient antioxidant capacity may have an important role in age-related macular degeneration. The polymorphism of GPx Pro197Leu may reduce the ability to scavenge free radicals in retina and contribute to the development of AMD.

Systemic and ocular fluid compounds as potential biomarkers in age-related macular degeneration

Biomarkers can help unravel mechanisms of disease and identify new targets for therapy. They can also be useful in clinical practice for monitoring disease progression, evaluation of treatment efficacy, and risk assessment in multifactorial diseases, such as age-related macular degeneration (AMD). AMD is a highly prevalent progressive retinal disorder for which multiple genetic and environmental risk factors have been described, but the exact etiology is not yet fully understood. Many compounds have been evaluated for their association with AMD. We performed an extensive literature review of all compounds measured in serum, plasma, vitreous, aqueous humor, and urine of AMD patients. Over 3600 articles were screened, resulting in more than 100 different compounds analyzed in AMD studies, involved in neovascularization, immunity, lipid metabolism, extracellular matrix, oxidative stress, diet, hormones, and comorbidities (such as kidney disease). For each compound, we provide a short description of its function and discuss the results of the studies in relation to its usefulness as AMD biomarker. In addition, biomarkers identified by hypothesis-free techniques, including metabolomics, proteomics, and epigenomics, are covered. In summary, compounds belonging to the oxidative stress pathway, the complement system, and lipid metabolism are the most promising biomarker candidates for AMD. We hope that this comprehensive survey of the literature on systemic and ocular fluid compounds as potential biomarkers in AMD will provide a stepping stone for future research and possible implementation in clinical practice.

Smoking and age-related macular degeneration: review and update

Age-related macular degeneration (AMD) is one of the main socioeconomical health issues worldwide. AMD has a multifactorial etiology with a variety of risk factors. Smoking is the most important modifiable risk factor for AMD development and progression. The present review summarizes the epidemiological studies evaluating the association between smoking and AMD, the mechanisms through which smoking induces damage to the chorioretinal tissues, and the relevance of advising patients to quit smoking for their visual health.

Superoxide dismutase1 levels in North Indian population with age-related macular degeneration

Aim. The aim of the study was to estimate the levels of superoxide dismutase1 (SOD1) in patients of age-related macular degeneration (AMD) and examine the role of oxidative stress, smoking, hypertension, and other factors involved in the pathogenesis of AMD. Methods. 115 AMD patients and 61 healthy controls were recruited for this study. Serum SOD1 levels were determined by ELISA and were correlated to various risk factors. Logistic regression model of authenticity, by considering SOD1 as independent variable, has been developed along with ROC curve. Results. The SOD1 levels were significantly higher in AMD patients as compared to those of the controls. The difference was not significant for wet and dry AMD. However, the difference was significant between wet AMD subtypes. Nonsignificance of the Hosmer-Lemeshow goodness of fit statistic (χ² = 10.516, df = 8, P = 0.231) indicates the appropriateness of logistic regression model to predict AMD. Conclusion. Oxidative stress in AMD patients may mount compensatory response resulting in increased levels of SOD1 in AMD patients. To predict the risk of AMD on the basis of SOD1, a logistic regression model shows authenticity of 78%, and area under the ROC curve (0.827, P = .0001) with less standard error of 0.033 coupled with 95% confidence interval of 0.762–0.891 further validates the model.

Role of antioxidant enzymes and small molecular weight antioxidants in the pathogenesis of age-related macular degeneration (AMD)

Cells in aerobic condition are constantly exposed to reactive oxygen species (ROS), which may induce damage to biomolecules, including proteins, nucleic acids and lipids. In normal circumstances, the amount of ROS is counterbalanced by cellular antioxidant defence, with its main components—antioxidant enzymes, DNA repair and small molecular weight antioxidants. An imbalance between the production and neutralization of ROS by antioxidant defence is associated with oxidative stress, which plays an important role in the pathogenesis of many age-related and degenerative diseases, including age-related macular degeneration (AMD), affecting the macula—the central part of the retina. The retina is especially prone to oxidative stress due to high oxygen pressure and exposure to UV and blue light promoting ROS generation. Because oxidative stress has an established role in AMD pathogenesis, proper functioning of antioxidant defence may be crucial for the occurrence and progression of this disease. Antioxidant enzymes play a major role in ROS scavenging and changes of their expression or/and activity are reported to be associated with AMD. Therefore, the enzymes in the retina along with their genes may constitute a perspective target in AMD prevention and therapy.

Predictive model for earlier diagnosis of suspected age-related macular degeneration patients

The primary goal of tailored medicine is to presymptomatically identify individuals at high risk for disease using information of each individual's genetic profile and collection of environmental risk factors. Recently, algorithms were given the strong recognition of several replicated risk factors for age-related macular degeneration (AMD), this distant goal is beginning to seem less mysterious. The purpose of the study was to develop a statistical model for AMD. This study includes total 106 subjects. To identify the risk of earlier diagnosis of suspected AMD patients, 22 independent variables were included in the study. Forward stepwise (likelihood ratio) binary logistic regression has been used to find significant variables associated with the risk of AMD. Prediction equation, based on significant risk factors, and model authenticity have been developed. Hosmer-Lemeshow goodness of fit statistic (χ(2)=0.143, df=8, p=1.0), which is nonsignificant, indicates the appropriateness of the logistic regression model to predict AMD. After going through stepwise logistic regression, only 6 variables out of the 22 independent variables, namely, serum complement factor H (CFH), serum chemokine (C-C motif) ligand 2 (CCL2), serum superoxide dismutase 1 (SOD1), polymorphism in CCL2 (rs4586), stress, and comorbidity were found to be significant (p<0.05). The binary logistic regression model is an appropriate tool to predict AMD in the presence of serum CFH, serum CCL2, serum SOD1, polymorphism in CCL2 (rs4586), stress, and comorbidity with high specificity and sensitivity. The area under the receiver operating characteristic curve (0.909, p=0.001) with less standard error of 0.034 and close 95% confidence intervals (0.842-0.976) further validates the model.

Biomarkers of oxidative stress in patients with wet age related macular degeneration

OBJECTIVE

The aim of this study was to analyze biomarkers of oxidative stress in patients with wet age related macular degeneration (AMD).

PARTICIPANTS AND MEASUREMENTS

Case-control study that includes 163 patients with wet AMD (age group of 55-82 years with the mean age of 71 years and 170 age-matched healthy controls in the age group of 55-78 years with the mean age of 71 years. The following parameters were determined: reduced and oxidized Glutathione (GSH/GSSH), protein carbonyl groups, total antioxidant activity in plasma and the activity of endogenous antioxidant enzymes, such as, gluthatione peroxidase, gluthatione reductase and superoxide dismutase.

RESULTS

We observed total antioxidant activity higher in control group (CG) compared with patients with wet AMD (7.1 ± 1.2 μM Trolox vs 5.8 ± 1.1 μM Trolox). Values of superoxide dismutase activity (SOD), gluthatione reductase (GR) and gluthatione peroxidase (GPx) are higher in control group than in patients with wet AMD. According to the GSH/GSSH results, average values were higher in the CG than in patients with wet AMD and data were not significantly different.. Values of protein carbonyl groups were higher in patients with wet AMD than in CG and significant differences were found.

CONCLUSIONS

The finding of the present study suggests that the patients with wet AMD are an altered metabolic state of oxidation-reduction and that it is convenient to give therapeutic interventions with antioxidants. We have demonstrated that systematic oxidative stress, measured by different biomarkers is closely associated with the wet AMD.