Oxidative Stress-Related Molecular Biomarker Candidates for Glaucoma

Assessment of Causality Between Diet-Derived Antioxidants and Primary Open-Angle Glaucoma: A Mendelian Randomization Study

Purpose

This study aimed to investigate the genetic causal relationships among diet-derived circulating antioxidants, primary open-angle glaucoma (POAG), and glaucoma-related traits using two-sample Mendelian randomization (MR).

Methods

Genetic variants associated with diet-derived circulating antioxidants (retinol, ascorbate, β-carotene, lycopene, α-tocopherol, and γ-tocopherol) were assessed as absolute and metabolic instrumental variables. POAG and glaucoma-related traits data were derived from a large, recently published genome-wide association study database; these traits included intraocular pressure (IOP), macular retinal nerve fiber layer (mRNFL) thickness, macular ganglion cell-inner plexiform layer (mGCIPL) thickness, and vertical cup-to-disc ratio (vCDR). MR analyses were performed per outcome for each exposure.

Results

We found no causal association between six diet-derived antioxidants and POAG using the International Glaucoma Genetics Consortium data. For absolute antioxidants, the odds ratios (ORs) ranged from 1.011 (95% confidence interval [CI], 0.854-1.199; P = 0.895) per natural log-transformed β-carotene to 1.052 (95% CI, 0.911-1.215; P = 0.490) for 1 µmol/L of ascorbate. For antioxidant metabolites, the OR ranged from 0.998 (95% CI, 0.801-1.244; P = 0.989) for ascorbate to 1.210 (95% CI, 0.870-1.682; P = 0.257) for γ-tocopherol, using log-transformed levels. A similar result was obtained with the FinnGen Biobank. Furthermore, our results showed no significant genetic association between six diet-derived antioxidants and glaucoma-related traits.

Conclusions

Our study did not support a causal association among six diet-derived circulating antioxidants, POAG, and glaucoma-related traits. This suggests that the intake of antioxidants may not have a preventive effect on POAG and offers no protection to retinal nerve cells.

Translational Relevance

This study provides valid evidence regarding the use of diet-derived antioxidants for glaucoma patients.

Role of mitophagy in ocular neurodegeneration

Neurons in the central nervous system are among the most metabolically active cells in the body, characterized by high oxygen consumption utilizing glucose both aerobically and anaerobically. Neurons have an abundance of mitochondria which generate adequate ATP to keep up with the high metabolic demand. One consequence of the oxidative phosphorylation mechanism of ATP synthesis, is the generation of reactive oxygen species which produces cellular injury as well as damage to mitochondria. Mitochondria respond to injury by fusion which serves to ameliorate the damage through genetic complementation. Mitochondria also undergo fission to meet an increased energy demand. Loss of mitochondria is also compensated by increased biogenesis to generate new mitochondria. Damaged mitochondria are removed by mitophagy, an autophagic process, in which damaged mitochondria are surrounded by a membrane to form an autophagosome which ultimately fuses with the lysosome resulting in degradation of faulty mitochondria. Dysregulation of mitophagy has been reported in several central nervous system disorders, including, Alzheimer's disease and Parkinson's disease. Recent studies point to aberrant mitophagy in ocular neurodegenerative disorders which could be an important contributor to the disease etiology/pathology. This review article highlights some of the recent findings that point to dysregulation of mitophagy and it's underlying mechanisms in ocular neurodegenerative diseases, including, glaucoma, age-related macular degeneration and diabetic retinopathy.

Smoking, alcohol consumption and corneal biomechanical parameters among Chinese university students

BACKGROUND/OBJECTIVES

Smoking and alcohol consumption are important risk factors for several ocular disorders, but their effects on corneal biomechanics remain unclear. Our study aims to explore the association between smoking and alcohol consumption with corneal biomechanical parameters measured by Corvis-ST (CST) among university students.

SUBJECTS/METHODS

A total of 1645 healthy university students from a university-based study were included, and all participants underwent corneal biomechanical parameters measurement by CST. We selected 10 reliable parameters that can reflect the corneal deformation response. All participants had a standardised interview to determine their smoking and alcohol consumption status.

RESULTS

The mean age of the participants was 19.0 ± 0.9 years, and 1132 (68.8%) were women. Smoking was significantly associated with stiffer corneas. Smokers showed significantly slower second applanation velocity (A2v) (β = 0.007 m/s, 95% confidence interval 0.001 to 0.014, P = 0.032) and lower integrated radius (IR) (β = -0.214 mm-1, 95% confidence interval -0.420 to -0.007, P = 0.043) than non-smokers after adjusting for age, gender, eye-rubbing, myopia, and body mass index (BMI). Smokers with BMI no less than 24.0 showed slower A2v and lower IR. Alcohol consumption and passive smoking were found no significant association with corneal biomechanics.

CONCLUSION

Smokers had less deformable corneas, especially those with BMI no less than 24.0. Our findings provide new evidence for the association between smoking and ocular disorders associated with corneal biomechanics like glaucoma.

Autophagy Mediates MMP-2 Expression in Glaucomatous Trabecular Meshwork Cells

Purpose

To investigate the effect of 3-methyladenine (3-MA) and starvation on the expression of matrix metalloproteinase (MMP-2) in patients with primary open-angle glaucoma.

Methods

Primary TM cells were cultured and divided into three groups. The control group was treated with a normal medium, the 3-MA group was stimulated with 3-MA, and the starvation group received nutrient depletion by replacing the normal media with Earle's balanced salt solution. Cellular mRNA and protein were measured at different 3-MA concentrations and starvation time periods. The level of autophagy was accessed by monodansylcadaverine fluorescent staining and expression of specific autophagy-related genes, light chain 3 (LC3), and Beclin1. The effects of 3-MA and starvation on cell proliferation were determined with a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay kit. The mRNA and protein expression of LC3-II, Beclin1, and MMP-2 were measured by reverse transcription-polymerase chain reaction and western blot, respectively.

Results

Compared to the control group, starvation significantly upregulated LC3-II and Beclin1 in TM cells after 3 h of stimulation, which peaked at 6 h and 9 h, respectively. Increased MDC-labeled cells were also observed. Starvation downregulated the expression of MMP-2. On the contrary, 3-MA suppressed the activation of autophagy, as shown by the marked downregulation of LC3-II and Beclin1. The expressions of MMP-2 were higher in the 3-MA group compared to the control group, reaching a peak at a concentration of 5 mM.

Conclusion

Autophagy may be involved in the pathogenesis of POAG via regulating the expression of MMP-2 and, subsequently, the deposition of the extracellular matrix.

Impact of rs11024102 PLEKHA7, rs3753841 COL11A1 single nucleotide polymorphisms, and serum levels of oxidative stress markers on the risk of primary angle-closure glaucoma in Egyptians

Background

Primary angle-closure glaucoma (PACG) is one of the major causes of blindness in the Middle East with genetic loci and systemic oxidative stress as potential risk factors. The current case-control study aimed to investigate the associations of rs11024102 in Pleckstrin homology domain-containing family A member 7 (PLEKHA7), rs3753841 in collagen 11 A1 (COL11A1), and the systemic oxidative stress markers with PACG in Egyptian patients. Thirty-five control subjects and 64 PACG patients were enrolled in this study. The polymorphisms in PLEKHA7 and COL11A1 were analyzed using quantitative PCR, and their associations were statistically tested with PACG at homozygous, heterozygous, dominant, and recessive genetic models. The levels of malondialdehyde (MDA), advanced glycation-end product (AOPP), protein carbonyl (PC), and ischemia modified albumin (IMA) were quantitated colorimetrically, and their associations with PACG were analyzed statistically. The associations of MDA, AOPP, PC, and IMA with elevated intraocular pressure (IOP) were statistically tested.

Results

Neither significant difference in the genotype distribution nor allele frequency of PLEKHA7 11024102 T>C (p = 0.425 and 0.517, respectively) and COL11A1 rs3753841 G>A (p = 0.600 and 0.473, respectively) were recorded under any of the tested genetic models. Either rs11024102 PLEKHA7 or rs3753841 COL11A1 was not significantly (p > 0.025 after Bonferroni correction) associated with an increased risk of PACG in Egyptians. Egyptian patients with PACG showed significant elevations in the serum levels of MDA, AOPP, and PC either in patients with or without cases with diabetes mellites, hypertension, coronary vascular diseases, and smoking. Serum levels of MDA, AOPP, and PC were significantly associated with PACG in Egyptians (p < 0.013 after Bonferroni correction). However, MDA and PC only showed significant associations with the elevation in the IOP (p = 0.007 and 0.045, respectively) in PACG patients.

Conclusion

Both rs11024102 and rs3753841 could not be considered as potential gene-dependent risk factors for PACG pathogenesis in Egyptians. On the other hand, serum levels of MDA, AOPP, and PC might be considered risk factors for PACG. Moreover, MDA and PC could serve as good predictors for the elevation of the IOP in PACG disease.

Comparative study of oxidative stress and antioxidative markers in patients infected with Toxoplasma gondii

Recently, oxidative stress and antioxidative compounds have been described as potential biomarkers. However, there is no consensus on the most appropriate oxidative and antioxidative biomarkers for patients with Toxoplasma gondii. In the present study, we evaluated the levels of lipid, protein, DNA oxidative damage and antioxidants in samples from patients infected with T. gondii with and without ocular toxoplasmosis. The levels of MDA, TBARS, micronuclei, carbonyl, GSH, vitamin C and vitamin E were measured on samples from 8 patients positive for T. gondii antibodies with ocular toxoplasmosis (OT), 20 patients positive for T. gondii antibodies without ocular toxoplasmosis (non OT), and 12 healthy individuals negative for T. gondii antibodies. The levels of MDA, TBARS, carbonyl and micronuclei were significantly higher in non OT patients, while MDA and TBARS levels were lower in OT patients. In contrast, the antioxidative factors, GSH and vitamin E levels were significantly lower in non OT patients, while vitamin C was lower in non OT and OT patients. Additionally, non OT patients were indicated to be high producers of oxidative markers (TBARS, MDA, micronuclei and carbonyl), while control group was indicated to be high producer of antioxidative markers (GSH, vitamins C and E). However, OT patients were not found as high producers of oxidative nor antioxidative markers. Our results provide a starting point of possible markers to better understand the disease pathogenesis in patients infected with T. gondii. Additional studies are needed to clarify the potential contribution of oxidative and antioxidative markers in these patients population.

NUTRARET: Effect of 2-Year Nutraceutical Supplementation on Redox Status and Visual Function of Patients With Retinitis Pigmentosa: A Randomized, Double-Blind, Placebo-Controlled Trial

Oxidative stress plays a major role in the pathogenesis of retinitis pigmentosa (RP). The main goal of this study was to evaluate the effect of 2-year nutritional intervention with antioxidant nutraceuticals on the visual function of RP patients. Secondly, we assessed how nutritional intervention affected ocular and systemic redox status. We carried out a randomized, double-blind, placebo-controlled study. Thirty-one patients with RP participated in the study. RP patients randomly received either a mixture of nutraceuticals (NUT) containing folic acid, vitamin B6, vitamin A, zinc, copper, selenium, lutein, and zeaxanthin or placebo daily for 2 years. At baseline and after 2-year of the nutritional supplementation, visual function, dietetic-nutritional evaluations, serum concentration of nutraceuticals, plasma and aqueous humor concentration of several markers of redox status and inflammation were assessed. Retinal function and structure were assessed by multifocal electroretinogram (mfERG), spectral domain-optical coherence tomography (SD-OCT) and automated visual field (VF) tests. Nutritional status was estimated with validated questionnaires. Total antioxidant capacity, extracellular superoxide dismutase (SOD3), catalase (CAT), and glutathione peroxidase (GPx) activities, protein carbonyl adducts (CAR) content, thiobarbituric acid reactive substances (TBARS) formation (as indicator of lipid peroxidation), metabolites of the nitric oxide (NOX) and cytokine (interleukin 6 and tumor necrosis factor alpha) concentrations were assessed by biochemical and immunological techniques in aqueous humor or/and blood. Bayesian approach was performed to determine the probability of an effect. Region of practical equivalence (ROPE) was used. At baseline, Bayesian analysis revealed a high probability of an altered ocular redox status and to a lesser extent systemic redox status in RP patients compared to controls. Twenty-five patients (10 in the treated arm and 15 in the placebo arm) completed the nutritional intervention. After 2 years of supplementation, patients who received NUT presented better retinal responses (mfERG responses) compared to patients who received placebo. Besides, patients who received NUT showed better ocular antioxidant response (SOD3 activity) and lower oxidative damage (CAR) than those who received placebo. This study suggested that long-term NUT supplementation could slow down visual impairment and ameliorate ocular oxidative stress.

Restoring the oxidative balance in age-related diseases - An approach in glaucoma

As human life expectancy increases, age-related health issues including neurodegenerative diseases continue to rise. Regardless of genetic or environmental factors, many neurodegenerative conditions share common pathological mechanisms, such as oxidative stress, a hallmark of many age-related health burdens. In this review, we describe oxidative damage and mitochondrial dysfunction in glaucoma, an age-related neurodegenerative eye disease affecting 80 million people worldwide. We consider therapeutic approaches used to counteract oxidative stress in glaucoma, including untapped treatment options such as novel plant-derived antioxidant compounds that can reduce oxidative stress and prevent neuronal loss. We summarize the current pre-clinical models and clinical work exploring the therapeutic potential of a range of candidate plant-derived antioxidant compounds. Finally, we explore advances in drug delivery systems, particular those employing nanotechnology-based carriers which hold significant promise as a carrier for antioxidants to treat age-related disease, thus reviewing the key current state of all of the aspects required towards translation.

Association between plasma free fatty acid levels and primary angle-closure glaucoma based on a mass spectrometry metabolomics analysis

PURPOSE

To determine the association between plasma free fatty acid (FFA) levels and primary angle-closure glaucoma (PACG).

METHODS

Free fatty acid (FFA) levels in patients with PACG (n = 181) and people without glaucoma (n = 340) were compared. Twenty-two FFAs and six lipid classes were measured using metabolomics analysis. Odds ratio (OR) of these metabolites and their 95% confidence intervals (95%CI) for PACG were obtained by logistic regression. Stepwise forward selection was performed to identify FFAs that influenced PACG risk. Areas under the curve (AUC) were applied to assess the predictive performance. Spearman's rank correlation was used to assess the relationship between ocular parameters and FFAs.

RESULTS

Most FFAs in the PACG group were lower than those in the non-glaucoma group. Docosahexaenoic acid (DHA; OR for fourth quartile (Q4) vs. first quartile (Q1): 0.32 (0.16-0.66); per standard deviation (SD) increase: 0.64 (0.49-0.83); p for trend: 0.0007) and total saturated fatty acids (SFAs; OR for Q4 versus Q1: 0.27 (0.13-0.56); per SD increase: 0.65 (0.50-0.87); p for trend: 0.0004) were associated with decreased PACG risk. The AUC of the model that included DHA, total SFAs, demographic and ophthalmic factors increased from 0.8230 (0.7811-0.8649) to 0.8512 (0.8133-0.8891) (increased AUC: 0.0282 (0.0112-0.0453); p for increased AUC: 0.0012). Additionally, the cup-disc ratio had a weak negative correlation with DHA and total SFAs (DHA: r = -0.12085, p = 0.0065; total SFAs: r = -0.13318, p = 0.0024).

CONCLUSIONS

Decrease in FFA levels may be related to lipid peroxidation. Docosahexaenoic acid (DHA) and total SFAs may be screening indices for PACG patients.

Treatment of Glaucoma with Natural Products and Their Mechanism of Action: An Update

Glaucoma is one of the leading causes of irreversible blindness. It is generally caused by increased intraocular pressure, which results in damage of the optic nerve and retinal ganglion cells, ultimately leading to visual field dysfunction. However, even with the use of intraocular pressure-lowering eye drops, the disease still progresses in some patients. In addition to mechanical and vascular dysfunctions of the eye, oxidative stress, neuroinflammation and excitotoxicity have also been implicated in the pathogenesis of glaucoma. Hence, the use of natural products with antioxidant and anti-inflammatory properties may represent an alternative approach for glaucoma treatment. The present review highlights recent preclinical and clinical studies on various natural products shown to possess neuroprotective properties for retinal ganglion cells, which thereby may be effective in the treatment of glaucoma. Intraocular pressure can be reduced by baicalein, forskolin, marijuana, ginsenoside, resveratrol and hesperidin. Alternatively, Ginkgo biloba, Lycium barbarum, Diospyros kaki, Tripterygium wilfordii, saffron, curcumin, caffeine, anthocyanin, coenzyme Q10 and vitamins B3 and D have shown neuroprotective effects on retinal ganglion cells via various mechanisms, especially antioxidant, anti-inflammatory and anti-apoptosis mechanisms. Extensive studies are still required in the future to ensure natural products' efficacy and safety to serve as an alternative therapy for glaucoma.

Role of Oxidative Stress in Retinal Disease and the Early Intervention Strategies: A Review

The retina, owing to its cellular anatomy and physical location, is susceptible to generating reactive oxygen species (ROS), which are associated with several major retinal diseases. When ROS exceeds the body's natural antioxidants, the retina is in a state of oxidative stress, which is recognized as the pathogenesis of retinal diseases. The early stage of the pathogenic process is an adaptive change in which oxidative stress and endogenous defense mechanisms occur. If no treatment is applied, the retinal diseases will progress to the pathological stage with neuronal and vascular dysfunction or damage and even blindness. This review summarizes the role of oxidative stress in several common retinal diseases, including retinitis pigmentosa, age-related macular degeneration, diabetic retinopathy, glaucoma, and retinopathy of prematurity. In addition, we discuss the early intervention strategies for these diseases. An outline is provided to identify potential intervention targets for further research. Early intervention for retinal diseases is necessary and urgent and may offer hope to improve patients' quality of life through functional vision.

Protein Biomarkers in Glaucoma: A Review

Glaucoma is a multifactorial disease. Early diagnosis of this disease can support treatment and reduce the effects of pathophysiological processes. A significant problem in the diagnosis of glaucoma is limited access to the tested material. Therefore, intensive research is underway to develop biomarkers for fast, noninvasive, and reliable testing. Biomarkers indicated in the formation of glaucoma include chemical compounds from different chemical groups, such as proteins, sugars, and lipids. This review summarizes our knowledge about protein and/or their protein-like derived biomarkers used for glaucoma diagnosis since 2000. The described possibilities resulting from a biomarker search may contribute to identifying a group of compounds strongly correlated with glaucoma development. Such a find would be of great importance in the diagnosis and treatment of this disorder, as current screening techniques have low sensitivity and are unable to diagnose early primary open-angle glaucoma.

Multiplex protein analysis for the study of glaucoma

INTRODUCTION

Glaucoma, a leading cause of irreversible blindness in the world, is a chronic neurodegenerative disease of multifactorial origin. Extensive research is ongoing to better understand, prevent, and treat progressive degeneration of retinal ganglion cells in glaucoma. While experimental models of glaucoma and postmortem tissues of human donors are analyzed for pathophysiological comprehension and improved treatment of this blinding disease, clinical samples of intraocular biofluids and blood collected from glaucoma patients are analyzed to identify predictive, diagnostic, and prognostic biomarkers. Multiplexing techniques for protein analysis offer a valuable approach for translational glaucoma research.

AREAS COVERED

This review provides an overview of the increasing applications of multiplex protein analysis for glaucoma research and also highlights current research challenges in the field and expected solutions from emerging technological advances.

EXPERT OPINION

Analytical techniques for multiplex analysis of proteins can help uncover neurodegenerative processes for enhanced treatment of glaucoma and can help identify molecular biomarkers for improved clinical testing and monitoring of this complex disease. This evolving field and continuously growing availability of new technologies are expected to broaden the comprehension of this complex neurodegenerative disease and speed up the progress toward new therapeutics and personalized patient care to prevent blindness from glaucoma.

Association Between Diabetes, Diabetic Retinopathy, and Glaucoma

PURPOSE OF REVIEW

The strength of the relationship between diabetes, diabetic retinopathy (DR), and glaucoma remains controversial. We review evidence supporting and refuting this association and explore mechanistic pathological and treatment relationships linking these diseases.

RECENT FINDINGS

While studies have shown diabetes/DR may increase the risk for glaucoma, this remains inconsistently demonstrated. Diabetes/DR may contribute toward glaucomatous optic neuropathy indirectly (either by increasing intraocular pressure or vasculopathy) or through direct damage to the optic nerve. However, certain elements of diabetes may slow glaucoma progression, and diabetic treatment may concurrently be beneficial in glaucoma management. Diabetes plays a significant role in poor outcomes after glaucoma surgery. While the relationship between diabetes/DR and glaucoma remains controversial, multiple mechanistic links connecting pathophysiology and management of diabetes, DR, and glaucoma have been made. However, a deeper understanding of the causes of disease association is needed.

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.

Candidate Glaucoma Biomarkers: From Proteins to Metabolites, and the Pitfalls to Clinical Applications

Glaucoma is an insidious group of eye diseases causing degeneration of the optic nerve, progressive loss of vision, and irreversible blindness. The number of people affected by glaucoma is estimated at 80 million in 2021, with 3.5% prevalence in people aged 40-80. The main biomarker and risk factor for the onset and progression of glaucoma is the elevation of intraocular pressure. However, when glaucoma is diagnosed, the level of retinal ganglion cell death usually amounts to 30-40%; hence, the urgent need for its early diagnosis. Molecular biomarkers of glaucoma, from proteins to metabolites, may be helpful as indicators of pathogenic processes observed during the disease's onset. The discovery of human glaucoma biomarkers is hampered by major limitations, including whether medications are influencing the expression of molecules in bodily fluids, or whether tests to validate glaucoma biomarker candidates should include human subjects with different types and stages of the disease, as well as patients with other ocular and neurodegenerative diseases. Moreover, the proper selection of the biofluid or tissue, as well as the analytical platform, should be mandatory. In this review, we have summarized current knowledge concerning proteomics- and metabolomics-based glaucoma biomarkers, with specificity to human eye tissue and fluid, as well the analytical approach and the main results obtained. The complex data published to date, which include at least 458 different molecules altered in human glaucoma, merit a new, integrative approach allowing for future diagnostic tests based on the absolute quantification of local and/or systemic biomarkers of glaucoma.

A Blood Biomarker for Duchenne Muscular Dystrophy Shows That Oxidation State of Albumin Correlates with Protein Oxidation and Damage in Mdx Muscle

Duchenne muscular dystrophy (DMD) is a severe X-linked muscle wasting disease with no cure. While the precise mechanisms of progressive dystropathology remain unclear, oxidative stress caused by excessive generation of oxidants is strongly implicated. Blood biomarkers that could track oxidant levels in tissues would be valuable to measure the effectiveness of clinical treatments for DMD; our research has focused on developing such biomarkers. One target of oxidants that has the potential to be harnessed as a clinical biomarker is the thiol side chain of cysteine 34 (Cys34) of the blood protein albumin. This study using the mdx mouse model of DMD shows that in plasma, albumin Cys34 undergoes thiol oxidation and these changes correlate with levels of protein thiol oxidation and damage of the dystrophic muscles. A comparison with the commonly used biomarker protein carbonylation, confirmed that albumin thiol oxidation is the more sensitive plasma biomarker of oxidative stress occurring in muscle tissue. We show that plasma albumin oxidation reflects muscle dystropathology, as increased after exercise and decreased after taurine treatment of mdx mice. These data support the use of albumin thiol oxidation as a blood biomarker of dystropathology to assist with advancing clinical development of therapies for DMD.

The Role of MicroRNAs in Mitochondria-Mediated Eye Diseases

The retina is among the most metabolically active tissues with high-energy demands. The peculiar distribution of mitochondria in cells of retinal layers is necessary to assure the appropriate energy supply for the transmission of the light signal. Photoreceptor cells (PRs), retinal pigment epithelium (RPE), and retinal ganglion cells (RGCs) present a great concentration of mitochondria, which makes them particularly sensitive to mitochondrial dysfunction. To date, visual loss has been extensively correlated to defective mitochondrial functions. Many mitochondrial diseases (MDs) show indeed neuro-ophthalmic manifestations, including retinal and optic nerve phenotypes. Moreover, abnormal mitochondrial functions are frequently found in the most common retinal pathologies, i.e., glaucoma, age-related macular degeneration (AMD), and diabetic retinopathy (DR), that share clinical similarities with the hereditary primary MDs. MicroRNAs (miRNAs) are established as key regulators of several developmental, physiological, and pathological processes. Dysregulated miRNA expression profiles in retinal degeneration models and in patients underline the potentiality of miRNA modulation as a possible gene/mutation-independent strategy in retinal diseases and highlight their promising role as disease predictive or prognostic biomarkers. In this review, we will summarize the current knowledge about the participation of miRNAs in both rare and common mitochondria-mediated eye diseases. Definitely, given the involvement of miRNAs in retina pathologies and therapy as well as their use as molecular biomarkers, they represent a determining target for clinical applications.

Protein oxidation - Formation mechanisms, detection and relevance as biomarkers in human diseases

Generation of reactive oxygen species and related oxidants is an inevitable consequence of life. Proteins are major targets for oxidation reactions, because of their rapid reaction rates with oxidants and their high abundance in cells, extracellular tissues, and body fluids. Additionally, oxidative stress is able to degrade lipids and carbohydrates to highly reactive intermediates, which eventually attack proteins at various functional sites. Consequently, a wide variety of distinct posttranslational protein modifications is formed by protein oxidation, glycoxidation, and lipoxidation. Reversible modifications are relevant in physiological processes and constitute signaling mechanisms ("redox signaling"), while non-reversible modifications may contribute to pathological situations and several diseases. A rising number of publications provide evidence for their involvement in the onset and progression of diseases as well as aging processes. Certain protein oxidation products are chemically stable and formed in large quantity, which makes them promising candidates to become biomarkers of oxidative damage. Moreover, progress in the development of detection and quantification methods facilitates analysis time and effort and contributes to their future applicability in clinical routine. The present review outlines the most important classes and selected examples of oxidative protein modifications, elucidates the chemistry beyond their formation and discusses available methods for detection and analysis. Furthermore, the relevance and potential of protein modifications as biomarkers in the context of disease and aging is summarized.

miRNAs and Genes Involved in the Interplay between Ocular Hypertension and Primary Open-Angle Glaucoma. Oxidative Stress, Inflammation, and Apoptosis Networks

Glaucoma has no cure and is a sight-threatening neurodegenerative disease affecting more than 100 million people worldwide, with primary open angle glaucoma (POAG) being the most globally prevalent glaucoma clinical type. Regulation of gene expression and gene networks, and its multifactorial pathways involved in glaucoma disease are landmarks for ophthalmic research. MicroRNAs (miRNAs/miRs) are small endogenous non-coding, single-stranded RNA molecules (18–22 nucleotides) that regulate gene expression. An analytical, observational, case-control study was performed in 42 patients of both sexes, aged 50 to 80 years, which were classified according to: (1) suffering from ocular hypertension (OHT) but no glaucomatous neurodegeneration (ND) such as the OHT group, or (2) have been diagnosed of POAG such as the POAG group. Participants were interviewed for obtaining sociodemographic and personal/familial records, clinically examined, and their tear samples were collected and frozen at 80 °C until processing for molecular-genetic assays. Tear RNA extraction, libraries construction, and next generation sequencing were performed. Here, we demonstrated, for the first time, the differential expression profiling of eight miRNAs when comparing tears from the OHT versus the POAG groups: the miR-26b-5p, miR-152-3p, miR-30e-5p, miR-125b-2-5p, miR-224-5p, miR-151a-3p, miR-1307-3p, and the miR-27a-3p. Gene information was set up from the DIANA-TarBase v7, DIANA-microT-CDS, and TargetScan v7.1 databases. To build a network of metabolic pathways, only genes appearing in at least four of the following databases: DisGeNet, GeneDistiller, MalaCards, OMIM PCAN, UniProt, and GO were considered. We propose miRNAs and their target genes/signaling pathways as candidates for a better understanding of the molecular-genetic bases of glaucoma and, in this way, to gain knowledge to achieve optimal diagnosis strategies for properly identifying HTO at higher risk of glaucoma ND. Further research is needed to validate these miRNAs to discern the potential role as biomarkers involved in oxidative stress, immune response, and apoptosis for the diagnosis and/or prognosis of OHT and the prevention of glaucoma ND.

Looking into the future: Gene and cell therapies for glaucoma

Glaucoma is a complex group of optic neuropathies that affects both humans and animals. Intraocular pressure (IOP) elevation is a major risk factor that results in the loss of retinal ganglion cells (RGCs) and their axons. Currently, lowering IOP by medical and surgical methods is the only approved treatment for primary glaucoma, but there is no cure, and vision loss often progresses despite therapy. Recent technologic advances provide us with a better understanding of disease mechanisms and risk factors; this will permit earlier diagnosis of glaucoma and initiation of therapy sooner and more effectively. Gene and cell therapies are well suited to target these mechanisms specifically with the potential to achieve a lasting therapeutic effect. Much progress has been made in laboratory settings to develop these novel therapies for the eye. Gene and cell therapies have already been translated into clinical application for some inherited retinal dystrophies and age-related macular degeneration (AMD). Except for the intravitreal application of ciliary neurotrophic factor (CNTF) by encapsulated cell technology for RGC neuroprotection, there has been no other clinical translation of gene and cell therapies for glaucoma so far. Possible application of gene and cell therapies consists of long-term IOP control via increased aqueous humor drainage, including inhibition of fibrosis following filtration surgery, RGC neuroprotection and neuroregeneration, modification of ocular biomechanics for improved IOP tolerance, and inhibition of inflammation and neovascularization to prevent the development of some forms of secondary glaucoma.

Increased Antioxidant Capacity and Pro-Homeostatic Lipid Mediators in Ocular Hypertension-A Human Experimental Model

The main risk factor for primary open-angle glaucoma (POAG) is increased intraocular pressure (IOP). It is of interest that about half of the patients have an IOP within the normal range (normal-tension glaucoma, NTG). Additionally, there is a group of patients with a high IOP but no glaucomatous neurodegeneration (ocular hypertension, OHT). Therefore, risk factors other than IOP are involved in the pathogenesis of glaucoma. Since the retina has a very high oxygen-demand, decreased autoregulation and a fluctuating oxygen supply to the retina have been linked to glaucomatous neurodegeneration. To assess the significance of these mechanisms, we have utilized a human experimental model, in which we stress participants with a fluctuating oxygen supply. Levels of oxidative stress molecules, antioxidants, and lipid mediators were measured in the plasma. Patients with NTG, OHT, and control subjects were found to have similar levels of oxidative stress markers. In contrast, patients with OHT had a higher level of total antioxidant capacity (TAC) and pro-homeostatic lipid mediators. Thus, we suggest that OHT patients manage fluctuating oxygen levels more efficiently and, thus, are less susceptible to glaucomatous neurodegenerations, due to enhanced systemic antioxidant protection.

Evaluating the Correlation between Alzheimer's Amyloid-β Peptides and Glaucoma in Human Aqueous Humor

Purpose

Recent studies suggest that glaucoma may share common pathogenic mechanisms with Alzheimer's disease. To test this hypothesis, we investigated the correlation between glaucoma and amyloid-β₄₂ (Aβ₄₂) concentration in human samples of aqueous humor (AH).

Methods

Eighty-one candidates for cataract or glaucoma surgery were consecutively enrolled, with a median age of 77 years; of these, 32 subjects were affected by glaucoma and 49 were controls. Before surgery, each patient received an ophthalmological examination including biometry, intraocular pressure (IOP) measurement, fundus photography, and determination of the mean thickness of the ganglion cell complex (GCC) and/or retinal nerve fiber layer. During the surgical procedure, an AH sample was collected and immediately processed for total protein (TP) and Aβ₄₂ evaluation.

Results

Aβ₄₂ levels were not statistically different between the glaucomatous and control samples, but a significant increase in TP concentration was found in the AH of glaucoma patients compared with controls (P = 0.02). In addition, positive correlations were observed between TP and Aβ₄₂ (r = 0.51; P < 0.0001), between TP and IOP (r = 0.44; P < 0.0001), and between Aβ₄₂ and IOP (r = 0.22; P = 0.033).

Conclusions

Our results indicate that an increased protein concentration in the AH could play a role in the pathogenesis of glaucomatous disease.

Translational Relevance

This study strongly supports the hypothesis that increased TP in the AH may have a pathogenic role in glaucoma. Further investigations are needed to clarify whether the protein enhancement represents a causative factor and whether it can be used as a marker of disease or as a novel therapeutic target.

Advanced Glycation End Product Accumulation in Subjects with Open-Angle Glaucoma with and without Exfoliation

Advanced glycation end products (AGEs), which are the products of a non-enzymatic reaction between reducing sugars and other macromolecules, are critical in aging, as well as metabolic and degenerative diseases. To assess the involvement of AGEs in glaucoma, skin autofluorescence (sAF) level, which is a measurement of AGEs' accumulation, was compared among Japanese patients with glaucoma (316 with primary open-angle glaucoma (PG) and 127 exfoliation syndrome and glaucoma (EG)) and controls (133 nonglaucomatous controls) (mean age 71.6 ± 12.8 years, 254 men and 322 women). The sAF values were estimated from the middle fingertip using a 365 nm light-emitting diode for excitation and detection at 440 nm emission light. The estimated AGE values (arbitrary unit) were 0.56 ± 0.15, 0.56 ± 0.11, and 0.61 ± 0.11 in the control, PG, and EG groups, respectively (p < 0.0001, analysis of variance); and were significantly higher in the EG group than the control (p = 0.0007) and PG (p < 0.0001) groups. After adjustment for various demographic parameters by multivariate analyses, male sex (standard β = 0.23), EG (0.19), and diabetes (0.09) were associated with higher AGE levels; PG (-0.18) and smoking (-0.19) were associated with lower AGE levels. Age, visual acuity, intraocular pressure, glaucoma medications, lens status, and systemic hypertension were not associated with AGEs. The high AGE level in EG suggested that specific oxidation and glycation mechanisms underlie the glaucoma pathogenesis associated with pseudoexfoliation syndrome.

Corneal Stiffness and Collagen Cross-Linking Proteins in Glaucoma: Potential for Novel Therapeutic Strategy

Biomechanical properties of the cornea have recently emerged as clinically useful in risk assessment of diagnosing glaucoma and predicting disease progression. Corneal hysteresis (CH) is a dynamic tool, which measures viscoelasticity of the cornea. It represents the overall deformability of the cornea, and reduces significantly with age. Low CH has also been associated with optic nerve damage and progression of visual field loss in glaucoma. The extracellular matrix (ECM) constituents of the cornea, trabecular meshwork (TM), sclera, and lamina cribrosa (LC) are similar, as they are predominantly made of fibrillar collagen. This suggests that biomechanical changes in the cornea may also reflect optic nerve compliance in glaucomatous optic neuropathy, and in the known increase of TM tissue stiffness in glaucoma. Increased collagen cross-linking contributes to tissue stiffening throughout the body, which is observed in normal aging and occurs at an accelerated rate in systemic conditions such as fibrotic and cardiovascular diseases, cancer, and glaucoma. We reviewed 3 ECM cross-linking proteins that may have a potential role in the disease process of increased tissue stiffness in glaucoma, including lysyl oxidase (LOX)/lysyl oxidase-like 1 (LOXL1), tissue transglutaminase (TG2), and advanced glycation end products. We also report elevated messenger RNA (mRNA) levels of LOX and TG2 in glaucoma LC cells to support our proposed theory that increased levels of cross-linking proteins in glaucoma play a role in LC tissue stiffness. We highlight areas of research that are needed to better understand the role of cross-linking in glaucoma pathogenesis, leading potentially to a novel therapeutic strategy.

The mito-QC Reporter for Quantitative Mitophagy Assessment in Primary Retinal Ganglion Cells and Experimental Glaucoma Models

Mitochondrial damage plays a prominent role in glaucoma. The only way cells can degrade whole mitochondria is via autophagy, in a process called mitophagy. Thus, studying mitophagy in the context of glaucoma is essential to understand the disease. Up to date limited tools are available for analyzing mitophagy in vivo. We have taken advantage of the mito-QC reporter, a recently generated mouse model that allows an accurate mitophagy assessment to fill this gap. We used primary RGCs and retinal explants derived from mito-QC mice to quantify mitophagy activation in vitro and ex vivo. We also analyzed mitophagy in retinal ganglion cells (RGCs), in vivo, using different mitophagy inducers, as well as after optic nerve crush (ONC) in mice, a commonly used surgical procedure to model glaucoma. Using mito-QC reporter we quantified mitophagy induced by several known inducers in primary RGCs in vitro, ex vivo and in vivo. We also found that RGCs were rescued from some glaucoma relevant stress factors by incubation with the iron chelator deferiprone (DFP). Thus, the mito-QC reporter-based model is a valuable tool for accurately analyzing mitophagy in the context of glaucoma.

Transient receptor potential channels TRPC1/TRPC6 regulate lamina cribrosa cell extracellular matrix gene transcription and proliferation

The lamina cribrosa (LC) in glaucoma is with augmented production of extracellular matrix proteins (ECM) and connective tissue fibrosis. Fundamental pathological mechanisms for this fibrosis comprise fibrotic growth factors and oxidative stress. Transient receptor potential canonical channels (TRPC) channels play a key role in ECM fibrosis. Here, we study TRPC expression in glaucomatous LC cells, and investigate the role of TRPC in oxidative stress induced-profibrotic ECM gene transcription and cell proliferation in normal LC cells. Age-matched human LC cells (normal, n = 3 donors; glaucoma, n = 3 donors) were used. Hydrogen peroxide (H₂O₂, 100 μM), was used to induce oxidative stress in LC cells in the presence or absence of the pan TRPC inhibitor SKF96365 (10 μM) or knockdown of TRPC1/6 with siRNA. After treatments, ECM gene transcription, LC cell viability and proliferation and the phosphorylation of the transcription factor NFATc3, were measured using real time RT-PCR, colorimetric cell counting with the methyl-thiazolyl tetrazolium salt (MTS) assay, and Western immunoblotting, respectively. Results showed that TRPC1/C6 transcript and protein expression levels were significantly (p < 0.05) enhanced in glaucoma LC cells. Both SKF96365 and siRNA-TRPC1/C6 treatments significantly reduced the oxidative stress induced-ECM gene expression (transforming growth factor-β1 (TGFβ1), alpha smooth muscle actin (α-SMA), and collagen type 1A1 (Col1A1)), and cell proliferation in normal and glaucoma LC cells. Also, SKF96365 treatment inhibited the H₂O₂-induced NFATc3 protein dephosphorylation in LC cells. In conclusion, TRPC1/C6 expression is enhanced in glaucoma LC cells. These channels may contribute to oxidative stress-induced ECM gene transcription and cell proliferation in normal and glaucoma LC cells through Ca²⁺-NFATc3 signaling pathway mechanism. TRPC1 and TRPC6 channels could be important therapeutic targets to prevent ECM remodeling and fibrosis development in glaucoma optic neuropathy.

Biomarkers of inflammation and oxidative stress in ophthalmic disorders

The review article focuses on free radicals and oxidative stress involved in ophthalmological diseases such as retinopathy, cataract, glaucoma, etc. Oxidative stress is considered as a key factor involved in the pathology of many chronic diseases including ophthalmic complication and inflammatory process. Oxidative stress and inflammation are closely related pathophysiological processes and are simultaneously found in many pathological conditions. The free radicals produced oxidize cellular components such as lipids and phospholipids leading to lipid peroxidation and trigger the onset of retinopathy. Cataract is a significant cause of visual disability and it is proposed that the high incidence is related to oxidative stress induced by continued intraocular penetration of light and consequent photochemical generation of free radical oxidants. Glaucoma is the leading cause of irreversible blindness and comprises a group of diseases characterized by progressive optic nerve degeneration. Oxidative injury and altered antioxidant defense mechanisms in glaucoma appear to play a role in the pathophysiology of glaucomatous neurodegeneration that is characterized by death of retinal ganglion cells. The UVB radiations through this way may cause a number of diseases like photo-keratitis, pterygium, damage to epithelium, edema, and corneal cell apoptosis.Abbreviations: ROS: reactive oxygen species; RNS: reactive nitrogen species; O_2.: superoxide anion; H₂O₂: hydrogen peroxide;. OH: hydroxyl radicals; ONOO^-, ONO₂^-: peroxynitrite; NO: nitric oxide; IOP: intraocular pressure; RGC: retinal ganglion cells. WHO: World Health Organization; IAPB: International Agency for the Prevention of Blindness.

Discovery and Validation of Circulating Hsa-miR-210-3p as a Potential Biomarker for Primary Open-Angle Glaucoma

Purpose

Blood-based examination tools for glaucoma diagnosis in clinical practice, which can be useful for screening patients when traditional ophthalmic examinations cannot be utilized, are not available thus far. This study aimed to identify circulating microRNAs (miRNAs) associated with primary open-angle glaucoma (POAG) and explore their utility as diagnostic markers.

Methods

A total of 136 POAG patients and controls were enrolled. Next-generation RNA sequencing was used to explore the expression profile of circulating miRNAs in the sequencing set, and potential miRNAs from independent samples in both the screening and validation sets were validated by quantitative real-time polymerase chain reaction (qRT-PCR). Receiver operating characteristic (ROC) analysis was used to evaluate the ability of certain miRNAs to distinguish POAG patients from control subjects.

Results

Using sequencing and qRT-PCR, hsa-miR-210-3p was found to be elevated in POAG patients in all sets. ROC analysis of the screening and validation sets revealed that hsa-miR-210-3p differentiated between POAG patients and matched controls with an area under the curve (AUC) of 0.846 (sensitivity: 84.6%; specificity: 80.8%) and 0.813 (sensitivity: 84.8%; specificity: 69.7%), respectively. In case of all nonsequencing participants, analysis revealed that hsa-miR-210-3p differentiated between severe POAG patients and controls with an AUC of 0.880 (sensitivity: 85.4%; specificity: 85.7%). In addition, the expression of hsa-miR-210-3p was associated with visual field defects of |mean deviation| (β = 0.237; P = 0.022) and average retinal nerve fiber layer thickness (β = -5.792; P = 0.014).

Conclusions

Circulating hsa-miR-210-3p may serve as a potential diagnostic marker for POAG (especially for severe POAG patients).

Association of Long-term Ambient Black Carbon Exposure and Oxidative Stress Allelic Variants With Intraocular Pressure in Older Men

Importance

Elevated intraocular pressure is a major risk factor for glaucoma, a leading cause of irreversible blindness worldwide. Environmental air pollution has been suggested as a potential contributor to elevated intraocular pressure; however, no studies have demonstrated such an association to date.

Objective

To investigate the association of long-term ambient black carbon exposure with intraocular pressure in community-dwelling older adults.

Design, Setting, and Participants

This population-based analysis, conducted from October 18, 2017, through March 22, 2018, used data from the all-male, New England-based Normative Aging Study of the US Department of Veterans Affairs. The analysis included 419 older men with a total of 911 follow-up study visits between January 1, 2000, and December 30, 2011. Intraocular pressure was measured by Goldmann applanation tonometry during the study visits. Validated spatiotemporal models were used to generate 1-year black carbon exposure levels at the addresses of the participants.

Main Outcomes and Measures

An independently developed genetic score approach was used to calculate allelic risk scores for 3 pathways associated with black carbon toxicity: endothelial function, oxidative stress, and metal processing. The associations among black carbon exposure, allelic risk scores, and intraocular pressure were explored using linear mixed-effects models.

Results

All 419 participants were men with a mean (SD) age of 75.3 (6.9) years. The mean (SD) 1-year black carbon exposure was 0.51 (0.18) μg/m3, and the mean (SD) intraocular pressure for the left eye was 14.1 (2.8) mm Hg and for the right eye was 14.1 (3.0) mm Hg. Of the 911 visits, 520 (57.1%) had a high endothelial function allelic risk score, 644 (70.7%) had a high metal-processing allelic risk score, and 623 (68.4%) had a high oxidative stress allelic risk score. In fully adjusted linear mixed-effects models, the association of black carbon with intraocular pressure was greater in individuals with a high oxidative stress allelic score (β = 0.36; 95% CI, 0.003-0.73) compared with individuals with a low score (β = -0.35; 95% CI, -0.86 to 0.15).

Conclusions and Relevance

Ambient black carbon exposure may be a risk factor for increased intraocular pressure in individuals susceptible to other biological oxidative stressors. If additional studies confirm these results, monitoring ambient black carbon exposure and physiological oxidative stress may prevent the development and progression of intraocular pressure-related disease.

T-Lymphocyte Subset Distribution and Activity in Patients With Glaucoma

Purpose

Besides glia-driven neuroinflammation, growing evidence from analysis of human blood samples, isolated autoantibodies, and postmortem tissues also support systemic immune responses during neurodegeneration in glaucoma patients. To explore the T-cell–mediated component of systemic immunity, this study analyzed T lymphocytes in patients' blood.

Methods

Blood samples were collected from 32 patients with glaucoma and 21 nonglaucomatous controls, and mononuclear cells were isolated by Histopaque density gradient centrifugation. T-cell subset distribution was analyzed by multicolor flow cytometry after helper (Th) and cytotoxic fractions, and Th subpopulations, were stained with antibodies to CD4, CD8, or distinctive markers, such as IFN-γ (for Th1), IL-4 (for Th2), IL-17A (for Th17), and CD25/FoxP3 (for T regulatory cells [Tregs]). In addition, proliferative activity and cytokine secretion of T cells were analyzed after in vitro stimulation.

Results

Analysis of T-cell subset distribution detected a glaucoma-related shift. Despite similar frequencies of CD4+ or CD8+ T cells, or Th1, Th2, or Th17 subsets in glaucoma and control groups, glaucomatous samples exhibited a trend toward decreased frequency of CD4+ (or CD8+)/CD25+/FoxP3+ Tregs within the entire CD4+ (or CD8+) population (P < 0.001). Furthermore, CD4+ T cells in glaucomatous samples presented a greater stimulation response (∼3-fold) as characterized by increased proliferation and proinflammatory cytokine secretion (P < 0.05).

Conclusions

These findings suggest that the immunity activated in glaucoma may not be counterbalanced by an efficient immune suppression. More work is encouraged to determine whether shifted T-cell homeostasis may contribute to neurodegeneration in glaucoma, and/or whether T-cell subset imbalance may serve as a biomarker of autoimmune susceptibility.

Associations between the red blood cell distribution width and primary angle-closure glaucoma: a potential for disease prediction

The red blood cell distribution width (RDW) is a simple and inexpensive laboratory parameter that can be linked to oxidative stress, inflammation and microvascular flow resistance. For this research, we performed a large-sample case-control study to describe the relationships between the RDW and primary angle-closure glaucoma (PACG). A total of 1191 PACG patients (422 males and 769 females), who were divided into mild, moderate and severe PACG groups, and 982 healthy controls (344 males and 638 females) were recruited between January 2008 and June 2018. Detailed eye and physical examinations were performed for each subject. Based on the laboratory results, the mean RDW was significantly higher (p < 0.001) in the PACG group (13.01 ± 0.82%) than in the control group (12.65 ± 0.53%). Moreover, the mean RDW level was lower (p < 0.05) in the mild PACG group than in the moderate and severe PACG groups. The Pearson correlation analyses showed significant positive correlations between the mean deviation and the RDW (r = 0.141, p < 0.001) and the intraocular pressure and the RDW (r = 0.085, p = 0.004). After adjusting for the confounding factors, the logistic regression analyses indicated that the odds ratio for the PACG group was 2.318 (p < 0.001, 95% confidence interval 1.997, 2.690) when compared to the control group. Additionally, an increased RDW was associated with the PACG severity, and this trend was also observed in the gender and age subgroups. In summary, the results of our study showed that an elevated RDW was associated with PACG and its severity. If future studies confirm this relationship, the use of an RDW assessment may help to predict the PACG severity in each patient in order to better customise effective prevention treatments.

Reducing oxidative toxicity of L-dopa in combination with two different antioxidants: an essential oil isolated from Rosa Damascena Mill., and vitamin C

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To avoid L-dopa side effects it’s administration is delayed.

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Natural antioxidants have wide range of medicinal properties.

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The natural antioxidants might inhibit oxidation and toxin formation.

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The L-dopa use with antioxidants, may be a necessary approach in modern PD therapy.

Parkinson disease (PD) is a multifactorial disease that takes a leading place among contemporary frequent diseases of the central nervous system (CNS) with not well-established mechanism. One of the most popular and effective therapy for patients with PD is Levodopa (L-dopa), but clinical effect of the drug diminished by motor complications resulting from prolonged treatment. Due to the L-dopa neurotoxic effect in the disease treatment, the L-dopa administration is delayed as long as possible in order to avoid side effects. In addition, combining L-dopa therapy with antioxidants, may decrease side-effects and provide symptomatic relief. The aim of the current research was to explore the possibility to reduce the oxidative stress (OS) induced by the L-dopa after its combining with two different antioxidants an essential oil isolated from Rosa damascena Mill., and vitamin C through experimental model of healthy mice. For this purpose, some oxidative stress indicators were evaluated - the lipid and protein oxidation end products – such as lipid peroxidation products measured as malondialdehyde (MDA) levels, protein carbonyl content (PCC), and advanced glycation end products (AGEs) in blood plasma of the experimental mice. For this purpose, was studied blood isolated from healthy mice after i.p. treatment with L-dopa (100 mg/kg). The groups with combining therapy were pre-treated first with Ascorbic acid (400 mg/kg), Rose oil (400 mg/kg). Statistically significant increased MDA levels, PCC and AGEs were found in the blood L-dopa treated mice compared to the controls, while the same parameters were significantly decreased in group pre-treated with antioxidants compared to the same controls. As a conclusion, the studied antioxidants can protect organisms from induced L-dopa oxidative toxicity and may play a key role in end products protection.

Association between Pretreatment Serum Uric Acid Levels and Progression of Newly Diagnosed Primary Angle-Closure Glaucoma: A Prospective Cohort Study

Purpose

Increased evidence reveals that uric acid (UA) may have an important neuroprotective effect through its antioxidant properties. The aim of the present study was to investigate the relationship between pretreatment serum UA levels and the progression of newly diagnosed primary angle-closure glaucoma (PACG).

Methods

This prospective observational cohort study included 64 patients with newly diagnosed PACG who were followed up for a mean period of 12.77 months (range: 3–28 months). All subjects underwent a complete ophthalmological examination during the baseline and final follow-up visits, together with the acquisition of blood samples for UA measurements. During the follow-up period, the progression of PACG was defined as a clinical diagnosis of medically uncontrolled intraocular pressure and a loss of visual field with a mean deviation of >1 dB/year. Univariable and multivariable Cox regression models were used to investigate the association between baseline serum UA levels and the progression of PACG. The cumulative probability of progression of glaucoma was analyzed using the Kaplan-Meier method.

Results

During follow-up, 32 subjects were defined as progressive PACG, among whom baseline UA values were significantly higher in nonprogressing subjects than in progressing subjects (0.314 ± 0.069 mmol/l versus [vs.] 0.258 ± 0.069 mmol/l, respectively; P = 0.002). Similar results were also observed in male and female subgroups (P < 0.05). In a multivariable model, a decreased baseline serum UA level was associated with an increased risk for progressing PACG: both in male (hazard ratio [HR] 6.088 [95% confidence interval (CI) 1.163–31.8638]; P = 0.032) and female subjects (HR 3.565 [95% CI 1.131–11.236]; P = 0.030). Subjects with high UA levels demonstrated higher cumulative probabilities of nonprogressing PACG than those with low UA levels (male [16.67% vs. 80.00%; P = 0.0084] and female [29.41% vs. 68.00%; P = 0.0182]).

Conclusion

An association between high baseline serum UA levels and a decreased risk for progressing PACG was found. This primary finding suggests that high serum UA levels may have a protective role against PACG and could slow disease progression.

Effect of Myricetin on Primary Open-angle Glaucoma

Background

Primary open angle glaucoma (POAG) is the most common form of glaucoma, with a multifactorial etiology that results in retinal ganglion cell death and loss of vision. In this study, we assessed the effects of myricetin on the trabecular meshwork cells in POAG.

Methods

In the in-vivo model, glaucoma was induced in Sprague-Dawley rats by injecting hyaluronic acid into the anterior chamber of the eye (every week for six-weeks). Treatment group rats were administered myricetin (25, 50 or 100 mg/ kg body weight via oral gavage) each day for of six weeks.

Results

POAG TM cells exposed to myricetin (25, 50 or 100 μM) exhibited significantly lowered reactive oxidative species (ROS) levels and lipid peroxidation products. The expressions of transforming growth factors (TGFβ1/β2), vascular endothelial growth factor, and senescence markers (senescence associated-β-galactosidase, cyclin-dependent kinase inhibitors-p16 and p21) were substantially down-regulated in POAG TM cells exposed to myricetin. Myricetin effectively prevented IOP elevation in glaucoma-induced rats and decreased inflammatory cytokines (IL-1α, IL-1β, IL-6, Il-8, TNF-α) in the aqueous humor and POAG TM cells of glaucoma-induced rats.

Conclusion

The observations of the study illustrate the protective effects of myricetin in glaucomatous TM cells.