Genetics and genomics of pseudoexfoliation syndrome/glaucoma

Prevalence and Associated Factors of Pseudoexfoliation Syndrome in an Iranian Elderly Population: The Tehran Geriatric Eye Study

PURPOSE

To investigate the prevalence and associated factors of pseudoexfoliation syndrome (PEX) in an Iranian elderly population.

METHODS

This study, a population-based cross-sectional study conducted on individuals ≥60 years in Tehran, the capital of Iran in 2019 using a multi-stage stratified random cluster sampling. All study participants underwent complete ocular examination (including measurement of uncorrected and best-corrected visual acuity, refraction, slit-lamp biomicroscopy). The PEX was diagnosed based on the presence of white fluffy dandruff-like pseudoexfoliative material on the pupillary margin, on the anterior lens capsule, and/or the trabecular meshwork.

RESULTS

Of the 3791 invitees, 3310 participated in the TGES (response rate: 87.3%). After applying exclusion criteria, the data of 3274 individuals were analyzed for this report. The overall prevalence of PEX was 3.63% (95% CI:2.67-4.58) in this study. 81.1% of PEX cases were bilateral. The prevalence of PEX increased significantly with advancing age in a linear trend from 2.38% (95%: 1.27-3.48) in the age group 60-64 years to 6.48% (95%: 2.02-10.95) in the age group ≥80 years (OR = 1.05, p = 0.008). According to the multiple logistic regression model, advancing age (OR: 1.06, p = 0.002) and the presence of cataract (OR: 5.02, p < 0.001) were significantly associated with increased odds of PEX.

CONCLUSION

The results showed a lower prevalence of PEX in the Iranian elderly compared to previous studies on the elderly population. Advancing age and cataracts were the only associated factors of PEX in the present study.

Histopathological Analysis of Pseudoexfoliation Material in Ocular Surgeries: Clinical Implications

BACKGROUND

Pseudoexfoliation syndrome (PEX) is a common age-related ocular condition characterized by the accumulation of a fibrillar, pseudoexfoliative material on the anterior segment of the eye. This study aims to investigate the histopathological characteristics of pseudoexfoliative material within different ocular structures, including the eyelid, conjunctiva, and anterior lens capsule.

METHODS

A total of 32 anterior lens capsules, 3 eyelid fragments, and 12 conjunctival specimens were obtained from patients clinically diagnosed with PEX during ocular surgeries at the Onioptic Hospital of Ophthalmology. The tissue specimens were subsequently processed using the classical histological technique of paraffin embedding. This process enabled the production of serial sections with a thickness of 4 microns, facilitating the microscopic examination of fine details. The sections were stained with the hematoxylin-eosin (HE) method for the observation of microscopic structures.

RESULTS

This study's findings reveal that PEX material, characterized by its fibrillar and amorphous components, is consistently present across multiple ocular structures, including the anterior lens capsule, eyelid, and conjunctiva. When stained with H&E, the PEX material typically appears as amorphous, eosinophilic deposits. Under higher magnification, these deposits exhibit a fibrillar structure, often appearing as irregular, granular, or filamentous aggregates.

CONCLUSIONS

The deposit of fibrillar material in the eyelid and conjunctiva, though less commonly emphasized compared to other structures, is a significant finding that sheds light on the systemic nature of the syndrome. The consistent identification of fibrillar eosinophilic deposits across these structures highlights the systemic distribution of PEX material, reinforcing the notion that PEX syndrome is not confined to the anterior segment of the eye.

Systemic Vascular Parameters in Ocular Pseudoexfoliation

Background Pseudoexfoliation syndrome (PEX) is characterized by a dandruff-like substance in the anterior chamber, composed of various glycoproteins that have an unclear origin. Its deposition is observed on the pupillary margin, lens zonules, and trabecular meshwork. Proteomic studies have identified numerous proteins in the affected individuals, suggesting associations with systemic conditions like heart disease, stroke, and Alzheimer's disease. However, the systemic associations of PEX remain inconclusive, particularly in regions like southern India. Materials and methods A cross-sectional study was conducted on 114 participants. Pseudoexfoliation was graded as mild, moderate, and severe as per standard photographic grading. Systemic examinations included blood pressure measurements, electrocardiography (ECG), and blood investigations for serum lipid profile, fasting and postprandial blood sugar levels, and serum C-reactive protein levels. Small incision cataract surgery was performed for all the patients. Intraoperative complications and postoperative status were recorded. Results Thirty-eight patients (33.3%) had mild PEX, 44 (38.6%) had moderate PEX, and 32 (28.1%) had severe PEX. Hypertension was present in 54 participants (47.4%), diabetes in 21 (18.4%), coronary artery disease in nine (7.9%), and cerebrovascular accidents in three (2.6%). The mean systolic blood pressure was 140.39 mmHg and the mean diastolic blood pressure was 90.37 mmHg. Systolic blood pressure exceeded 140 mmHg in 29 participants (90.6%) with severe PEX, while diastolic blood pressure surpassed 90 mmHg in 26 participants with severe PEX, both with a p-value of 0.001. Mean fasting and postprandial blood sugar levels were 103.80 ± 31.81 mg/dl and 131.72 ± 48.24 mg/dl, respectively. Serum lipid profiles showed mean low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), cholesterol, and triglyceride levels of 103.00 ± 34.49 mg/dl, 29.04 ± 15.51 mg/dl, 172.73 ± 43.34 mg/dl, and 129.33 ± 64.65 mg/dl respectively. Electrocardiographic results indicated that 54 participants (47.37%) had abnormal ECG including rate abnormality in 13.2%, conduction defects in 12.3%, ischemic changes in 10.5%, and structural defects in 11.4%. Eighty-seven percent of patients had non-dilating pupils and iris atrophy, 13.2% had zonular dialysis and intraoperatively, 78% had capsulorhexis extension, 49.12% had difficult nucleus prolapse, and 28.95% had posterior capsular rent. Conclusion This study highlights the significantly elevated parameters of systemic vascular diseases in PEX patients, like elevated blood pressure and more frequent cardiac anomalies, emphasizing the need for comprehensive systemic evaluation and careful preoperative assessment for ocular comorbidities.

APOE ε2-Carriers Are Associated with an Increased Risk of Primary Angle-Closure Glaucoma in Patients of Saudi Origin

This study investigated the association between apolipoprotein E (APOE) gene polymorphisms (rs429358 and rs7412) and primary angle-closure glaucoma (PACG) and pseudoexfoliation glaucoma (PXG) in a Saudi cohort. Genotyping of 437 DNA samples (251 controls, 92 PACG, 94 PXG) was conducted using PCR-based Sanger sequencing. The results showed no significant differences in the allele and genotype frequencies of rs429358 and rs7412 between the PACG/PXG cases and controls. Haplotype analysis revealed ε3 as predominant, followed by ε4 and ε2 alleles, with no significant variance in PACG/PXG. However, APOE genotype analysis indicated a significant association between ε2-carriers and PACG (odds ratio = 4.82, 95% CI 1.52-15.26, p = 0.007), whereas no notable association was observed with PXG. Logistic regression confirmed ε2-carriers as a significant predictor for PACG (p = 0.008), while age emerged as significant for PXG (p < 0.001). These findings suggest a potential role of ε2-carriers in PACG risk within the Saudi cohort. Further validation and larger-scale investigations are essential to elucidate the precise role of APOE in PACG pathogenesis and progression.

Secondary glaucoma: Toward interventions based on molecular underpinnings

Glaucoma is a heterogeneous group of progressive diseases that leads to irreversible blindness. Secondary glaucoma refers to glaucoma caused by a known underlying condition. Pseudoexfoliation and pigment dispersion syndromes are common causes of secondary glaucoma. Their respective deposits may obstruct the trabecular meshwork, leading to aqueous humor outflow resistance, ocular hypertension, and optic neuropathy. There are no disease-specific interventions available for either. Pseudoexfoliation syndrome is characterized by fibrillar deposits (pseudoexfoliative material) on anterior segment structures. Over a decade of multiomics analyses taken together with the current knowledge on pseudoexfoliative glaucoma warrant a re-think of mechanistic possibilities. We propose that the presence of nucleation centers (e.g., vitamin D binding protein), crosslinking enzymes (e.g., transglutaminase 2), aberrant extracellular matrix, flawed endocytosis, and abnormal aqueous-blood barrier contribute to the formation of proteolytically resistant pseudoexfoliative material. Pigment dispersion syndrome is characterized by abnormal iridolenticular contact that disrupts iris pigment epithelium and liberates melanin granules. Iris melanogenesis is aberrant in this condition. Cytotoxic melanogenesis intermediates leak out of melanosomes and cause iris melanocyte and pigment epithelium cell death. Targeting melanogenesis can likely decrease the risk of pigmentary glaucoma. Skin and melanoma research provides insights into potential therapeutics. We propose that specific prostanoid agonists and fenofibrates may reduce melanogenesis by inhibiting cholesterol internalization and de novo synthesis. Additionally, melatonin is a potent melanogenesis suppressor, antioxidant, and hypotensive agent, rendering it a valuable agent for pigmentary glaucoma. In pseudoexfoliative glaucoma, where environmental insults drive pseudoexfoliative material formation, melatonin's antioxidant and hypotensive properties may offer adjunct therapeutic benefits. This article is categorized under: Neurological Diseases > Molecular and Cellular Physiology.

Genetic background determines severity of Loxl1-mediated systemic and ocular elastosis in mice

Pseudoexfoliation syndrome (PEX) is a systemic, age-related disorder characterized by elastosis and extracellular matrix deposits. Its most significant ocular manifestation is an aggressive form of glaucoma associated with variants in the gene encoding lysyl oxidase-like 1 (LOXL1). Depending upon the population, variants in LOXL1 can impart risk or protection for PEX, suggesting the importance of genetic context. As LOXL1 protein levels are lower and the degree of elastosis is higher in people with PEX, we studied Loxl1-deficient mice on three different genetic backgrounds: C57BL/6 (BL/6), 129S×C57BL/6 (50/50) and 129S. Early onset and high prevalence of spontaneous pelvic organ prolapse in BL/6 Loxl1-/- mice necessitated the study of mice that were <2 months old. Similar to pelvic organ prolapse, most elastosis endpoints were the most severe in BL/6 Loxl1-/- mice, including skin laxity, pulmonary tropoelastin accumulation, expansion of Schlemm's canal and dilation of intrascleral veins. Interestingly, intraocular pressure was elevated in 50/50 Loxl1-/- mice, depressed in BL/6 Loxl1-/- mice and unchanged in 129S Loxl1-/- mice compared to that of control littermates. Overall, the 129S background was protective against most elastosis phenotypes studied. Thus, repair of elastin-containing tissues is impacted by the abundance of LOXL1 and genetic context in young animals.

Pseudoexfoliation Glaucoma: Clinical Presentation and Therapeutic Options

Pseudoexfoliation syndrome (PES) is one of the most common causes of open-angle glaucoma, with a higher risk of vision loss, a higher maximum and mean intraocular pressure (IOP) at diagnosis, and a wider range of IOP fluctuation compared to primary open-angle glaucoma. Patients with this syndrome have a ten-fold higher risk of developing glaucoma than the normal population. A definite diagnosis can be made by the observation of pseudoexfoliation material (PEM) on the anterior lens surface, ciliary processes, zonules, and iris. PEM deposits on the zonules may explain the clinically observed zonular weakness and lens subluxation or dislocation. An increased incidence of cataract development is also associated with PES. There is growing evidence for systemic associations of PES with peripheral, cardiovascular, and cerebrovascular system diseases, Alzheimer's disease, hearing loss, and increased plasma homocysteine levels. Indications for surgery are markedly more common in patients with pseudoexfoliation glaucoma than primary open-angle glaucoma. The goal of this article is to review the latest perspectives on the clinical features, therapy, and systemic associations of this clinically and biologically challenging disease.

Comparative Proteomic Analysis of the Aqueous Humor from Patients with Pseudoexfoliation Syndrome

Purpose

The goal of this study was to pinpoint potential molecular pathways that may have contributed to the onset of pseudoexfoliation syndrome (PEX), a systemic illness associated with aging that has no known cause and is brought on by the deposition of fibrillary white flaky debris in ocular tissues.

Materials and methods

Protein pools representing each group were created using two-dimensional gel electrophoresis (2DE) in conjunction with a matrix-assisted laser desorption ionization-time of flight/time of flight (MALDI-TOF/TOF) mass spectrometer. Aqueous humor (AH) from patients with PEX and cataracts was also collected for a comprehensive study of the data; ingenuity pathway analysis (IPA) was used for the discovered proteins.

Results

In comparison to controls, 2DE showed that 10 sites in PEX patients had differently altered gene expression. Two of these proteins, transthyretin (TTR) and apolipoprotein A4 (ApoA4) were significantly overexpressed in PEX patients, but the remaining proteins were only mildly altered. The liver X receptor (LXR) and the retinoid X receptors (RXR) may play a crucial role in the pathophysiology of PEX according to IPA employing these 10 proteins.

Conclusion

The altered proteins, particularly ApoA4 and TTR, may be important in revealing the molecular process behind PEX, as anticipated by IPA.

How to cite this article

Toprak M, Yuksel N, Akpinar G, et al. Comparative Proteomic Analysis of the Aqueous Humor from Patients with Pseudoexfoliation Syndrome. J Curr Glaucoma Pract 2023;17(3):118-125.

Analysis of genetically determined gene expression suggests role of inflammatory processes in exfoliation syndrome

BACKGROUND

Exfoliation syndrome (XFS) is an age-related systemic disorder characterized by excessive production and progressive accumulation of abnormal extracellular material, with pathognomonic ocular manifestations. It is the most common cause of secondary glaucoma, resulting in widespread global blindness. The largest global meta-analysis of XFS in 123,457 multi-ethnic individuals from 24 countries identified seven loci with the strongest association signal in chr15q22-25 region near LOXL1. Expression analysis have so far correlated coding and a few non-coding variants in the region with LOXL1 expression levels, but functional effects of these variants is unclear. We hypothesize that analysis of the contribution of the genetically determined component of gene expression to XFS risk can provide a powerful method to elucidate potential roles of additional genes and clarify biology that underlie XFS.

RESULTS

Transcriptomic Wide Association Studies (TWAS) using PrediXcan models trained in 48 GTEx tissues leveraging on results from the multi-ethnic and European ancestry GWAS were performed. To eliminate the possibility of false-positive results due to Linkage Disequilibrium (LD) contamination, we i) performed PrediXcan analysis in reduced models removing variants in LD with LOXL1 missense variants associated with XFS, and variants in LOXL1 models in both multiethnic and European ancestry individuals, ii) conducted conditional analysis of the significant signals in European ancestry individuals, and iii) filtered signals based on correlated gene expression, LD and shared eQTLs, iv) conducted expression validation analysis in human iris tissues. We observed twenty-eight genes in chr15q22-25 region that showed statistically significant associations, which were whittled down to ten genes after statistical validations. In experimental analysis, mRNA transcript levels for ARID3B, CD276, LOXL1, NEO1, SCAMP2, and UBL7 were significantly decreased in iris tissues from XFS patients compared to control samples. TWAS genes for XFS were significantly enriched for genes associated with inflammatory conditions. We also observed a higher incidence of XFS comorbidity with inflammatory and connective tissue diseases.

CONCLUSION

Our results implicate a role for connective tissues and inflammation pathways in the etiology of XFS. Targeting the inflammatory pathway may be a potential therapeutic option to reduce progression in XFS.

Small Nucleolar RNAs in Pseudoexfoliation Glaucoma

Small nucleolar RNAs (snoRNAs) are small non-coding regulatory RNAs that have been investigated extensively in recent years. However, the relationship between snoRNA and glaucoma is still unknown. This study aims to analyze the levels of snoRNA expression in the aqueous humor (AH) of patients with pseudoexfoliation glaucoma (PEXG) compared to a control group and identify hypothetical snoRNA-dependent mechanisms contributing to PEXG. The AH was obtained from eighteen Caucasian patients, comprising nine PEXG and nine age-matched control patients. RNA was isolated, and a microarray system was used to determine the snoRNA expression profiles. Functional and enrichment analyses were performed. We identified seven snoRNAs, SNORD73B, SNORD58A, SNORD56, SNORA77, SNORA72, SNORA64, and SNORA32, in the AH of the PEXG and control group patients. Five snoRNAs showed statistically significantly lower expression in the PEXG group, and two snoRNAs had statistically significantly higher expression in the PEXG group compared to the control group. In addition, we identified two factors-CACNB3 for SNORA64 and TMEM63C for SNORA32, similar to PEX-related genes (CACNA1A and TMEM136). The enrichment analysis for four genes targeted by snoRNAs revealed possible mechanisms associated with glaucoma and/or PEX, but the direct role of snoRNAs in these biological processes was not proven.

Prediagnostic Plasma Metabolomics and the Risk of Exfoliation Glaucoma

Purpose

The etiology of exfoliation glaucoma (XFG) is poorly understood. We aimed to identify a prediagnostic plasma metabolomic signature associated with XFG.

Methods

We conducted a 1:1 matched case-control study nested within the Nurses' Health Study and Health Professionals Follow-up Study. We collected blood samples in 1989-1990 (Nurses' Health Study) and 1993-1995 (Health Professionals Follow-up Study). We identified 205 incident XFG cases through 2016 (average time to diagnosis from blood draw = 11.8 years) who self-reported glaucoma and were confirmed as XFG cases with medical records. We profiled plasma metabolites using liquid chromatography-mass spectrometry. We evaluated 379 known metabolites (transformed for normality using probit scores) using multiple conditional logistic models. Metabolite set enrichment analysis was used to identify metabolite classes associated with XFG. To adjust for multiple comparisons, we used number of effective tests (NEF) and the false discovery rate (FDR).

Results

Mean age of cases (n = 205) at diagnosis was 71 years; 85% were women and more than 99% were Caucasian; controls (n = 205) reported eye examinations as of the matched cases' index date. Thirty-three metabolites were nominally significantly associated with XFG (P < 0.05), and 4 metabolite classes were FDR-significantly associated. We observed positive associations for lysophosphatidylcholines (FDR = 0.02) and phosphatidylethanolamine plasmalogens (FDR = 0.004) and inverse associations for triacylglycerols (FDR < 0.0001) and steroids (FDR = 0.03). In particular, the multivariable-adjusted odds ratio with each 1 standard deviation higher plasma cortisone levels was 0.49 (95% confidence interval, 0.32-0.74; NEF = 0.05).

Conclusions

In plasma from a decade before diagnosis, lysophosphatidylcholines and phosphatidylethanolamine plasmalogens were positively associated and triacylglycerols and steroids (e.g., cortisone) were inversely associated with XFG risk.

Red cell distribution width levels in patients with pseudoexfoliation syndrome and pseudoexfoliation glaucoma

Purpose

The purpose of this study was to assess the levels of red cell distribution width (RDW) in patients with pseudoexfoliation syndrome (PEX) and pseudoexfoliation glaucoma (PEXG), and to compare their RDW values with healthy controls.

Methods

40 patients with PEX, 40 with PEXG, and 80 control subjects were enrolled in this study. Complete ophthalmologic examination and complete blood count measurements were performed of all subjects. Complete blood counts were performed within one hour of blood collection.

Results

RDW levels were significantly higher in patients with PEX and PEXG than in controls (P = 0.027 and P < 0.001, respectively). Furthermore, a significant difference was found in RDW values between PEXG and PEX groups (P = 0.016). RDW levels were gradually increased from control group to PEXG group (P < 0.001). Multivariate logistic regression analysis revealed that RDW was independently associated with the presence of PEX/PEXG (odds ratio 1.765, 95% confidence interval (CI) 1.095-2.867, P = 0.013).

Conclusion

We conclude that RDW may be a useful marker for predicting the presence of PEX and progression to PEXG.

Emerging roles of oxidative stress in the pathogenesis of pseudoexfoliation syndrome (Review)

Pseudoexfoliation syndrome (PEXS) is a systemic disease caused by defects in the extracellular matrix (ECM) remodelling process leading to the chronic deposition of extracellular, fibrillary, white flaky pseudoexfoliation material (PEXM) throughout the body. Specifically, PEXM deposits on the lens capsule cause open-angle glaucoma, cataracts and blindness in patients with PEXS. Several gene single nucleotide polymorphisms are linked to the development of PEXS in humans, including lysyl oxidase-like 1 gene, clusterin and fibulin-5. The exact reason for the PEXM generation and its resulting pathogenesis is not well understood. However, defective ECM remodelling and oxidative stress (OS) have been hypothesized as significant events leading to the PEXM. Specifically, the link between OS and PEXS has been well studied, although the investigation is still ongoing. The present review explored recent advances in various aspects of PEXS and the involvement of OS in the eye for PEXS development.

Diet, Oxidative Stress, and Blood Serum Nutrients in Various Types of Glaucoma: A Systematic Review

Glaucoma is one of the most common causes of irreversible vision loss worldwide. It is an insidious disease with a multifactorial pathogenesis. Despite progress in treatment methods, prevention and lifestyle modifications may be useful in slowing the progression of this disease. This systematic review aimed to evaluate the influence of diet, oxidative stress, and disturbances in blood serum levels of nutrients on the incidence and severity of glaucoma based on scientific reports on the role of nutrition in the pathogenesis and course of glaucoma. This paper presents an analysis of the above issues; however, further research is required to develop this topic. Future clinical trials are needed to assess the influence of nutrition and to develop nutritional management strategies for patients with glaucoma.

Pseudoexfoliation syndrome: The critical role of the extracellular matrix in pathogenesis and treatment

Pseudoexfoliation syndrome (PEXS) is an age-related condition manifesting mainly in ocular tissues. PEXS is manifested through excess aggregation of fibrillary extracellular material at the anterior part of the eye that consists of a plethora of biomolecules, such as different proteoglycans (PGs) and glycosaminoglycans. PEXS is often linked to increased intraocular pressure, and can also lead to pseudoexfoliation glaucoma with very poor prognosis. Various stimuli are known to affect PEXS, including oxidation stress (OS), UV radiation and osmotic pressure. OS, is prominently involved on the progression of the syndrome as it promotes fibrogenesis, possibly via the induction of transforming growth factor-β (TGF-β) and other biomolecular effectors. In addition, PEXS initiation is tightly connected with the dysregulation of extracellular matrix (ECM) homeostasis since aberrant expression of ECM molecules is linked to both the accumulation and low degradation of pseudoexfoliation material. This article aims at uncovering the crucial role of various ECM effectors such as lysyl oxidase-like proteins, matrix metalloproteinases, and TGF-β1, as well as the biochemical pathways involved in the development and the progression of the PEXS.

Effect of pseudoexfoliation syndrome on lamina cribrosa morphology after uneventful phacoemulsification

AIM

To evaluate the behavior of the lamina cribrosa (LC) following successful phacoemulsification (PE) surgery in non-glaucomatous PXS cases with cataract.

METHODS

A total of 25 bilateral PXS and 56 non-PXS cataract patients were included in this prospective, interventional, and controlled study. The lamina cribrosa thickness (LCt) and anterior laminar depth (ALD) were measured horizontally and vertically from two sections using EDI-OCT. The measurements were taken preoperatively, and the LCt and ALD measurements were repeated at week one (W1), month one (M1), month two (M2), and month three (M3) postoperatively.

RESULTS

The baseline horizontal and vertical LCt values were found to be significantly thinner in the PXS group (p = 0.001, p = 0.006 respectively). The horizontal section ALD values were 463.32 ± 98.82 µm and 383.88 ± 85.8 µm (p < 0.001) for the PXS and non-PXS groups, respectively, and this significance continued during follow-up. The vertical ALD values were 469.64 ± 117.83 µm and 390.3 ± 98.1 µm (p = 0.002) in the PXS and non-PXS groups, respectively. There was no significant change in the PXS group for the depth following PE, but a statistically significant depth increase response was observed in the non-PXS group during follow-up.

CONCLUSION

It is possible to conclude that the bending capacity of the lamina cribrosa may be lower than seen in the normal population, but we do not know how this lack of flexibility will affect the eye.

Pseudoexfoliation and Cataract Syndrome Associated with Genetic and Epidemiological Factors in a Mayan Cohort of Guatemala

The Mayan population of Guatemala is understudied within eye and vision research. Studying an observational homogenous, geographically isolated population of individuals seeking eye care may identify unique clinical, demographic, environmental and genetic risk factors for blinding eye disease that can inform targeted and effective screening strategies to achieve better and improved health care distribution. This study served to: (a) identify the ocular health needs within this population; and (b) identify any possible modifiable risk factors contributing to disease pathophysiology within this population. We conducted a cross-sectional study with 126 participants. Each participant completed a comprehensive eye examination, provided a blood sample for genetic analysis, and received a structured core baseline interview for a standardized epidemiological questionnaire at the Salama Lions Club Eye Hospital in Salama, Guatemala. Interpreters were available for translation to the patients’ native dialect, to assist participants during their visit. We performed a genome-wide association study for ocular disease association on the blood samples using Illumina’s HumanOmni2.5-8 chip to examine single nucleotide polymorphism SNPs in this population. After implementing quality control measures, we performed adjusted logistic regression analysis to determine which genetic and epidemiological factors were associated with eye disease. We found that the most prevalent eye conditions were cataracts (54.8%) followed by pseudoexfoliation syndrome (PXF) (24.6%). The population with both conditions was 22.2%. In our epidemiological analysis, we found that eye disease was significantly associated with advanced age. Cataracts were significantly more common among those living in the 10 districts with the least resources. Furthermore, having cataracts was associated with a greater likelihood of PXF after adjusting for both age and sex. In our genetic analysis, the SNP most nominally significantly associated with PXF lay within the gene KSR2 (p < 1 × 10⁻⁵). Several SNPs were associated with cataracts at genome-wide significance after adjusting for covariates (p < 5 × 10⁻⁸). About seventy five percent of the 33 cataract-associated SNPs lie within 13 genes, with the majority of genes having only one significant SNP (5 × 10⁻⁸). Using bioinformatic tools including PhenGenI, the Ensembl genome browser and literature review, these SNPs and genes have not previously been associated with PXF or cataracts, separately or in combination. This study can aid in understanding the prevalence of eye conditions in this population to better help inform public health planning and the delivery of quality, accessible, and relevant health and preventative care within Salama, Guatemala.

Aqueous humor metabolite profile of pseudoexfoliation glaucoma is distinctive

Pseudoexfoliation (PEX) is a known cause of secondary open angle glaucoma. PEX glaucoma is associated with structural and metabolic changes in the eye. Despite similarities, PEX and primary open angle glaucoma (POAG) may have differences in the composition of metabolites. We analyzed the metabolites of the aqueous humor (AH) of PEX subjects sequentially first using nuclear magnetic resonance (1H NMR: HSQC and TOCSY), and subsequently with liquid chromatography tandem mass spectrometry (LC-MS/MS) implementing isotopic ratio outlier analysis (IROA) quantification. The findings were compared with previous results for POAG and control subjects analyzed using identical sequential steps. We found significant differences in metabolites between the three conditions. Principle component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) indicated clear grouping based on the metabolomes of the three conditions. We used machine learning algorithms and a percentage set of the data to train, and utilized a different or larger dataset to test whether a trained model can correctly classify the test dataset as PEX, POAG or control. Three different algorithms: linear support vector machines (SVM), deep learning, and a neural network were used for prediction. They all accurately classified the test datasets based on the AH metabolome of the sample. We next compared the AH metabolome with known AH and TM proteomes and genomes in order to understand metabolic pathways that may contribute to alterations in the AH metabolome in PEX. We found potential protein/gene pathways associated with observed significant metabolite changes in PEX.

Pseudoexfoliation syndrome and glaucoma: from genes to disease mechanisms

PURPOSE OF REVIEW

The genetic basis of pseudoexfoliation (PEX) syndrome, the most common identifiable cause of open-angle glaucoma, is steadily being elucidated. This review summarizes the recent advances on genetic risk factors for PEX syndrome/glaucoma and their potential functional implications in PEX pathophysiology.

RECENT FINDINGS

As of today, seven loci associated with the risk of PEX surpassing genome-wide significance have been identified by well-powered genome-wide association studies and sequencing efforts. LOXL1 (lysyl oxidase-like 1) represents the major genetic effect locus, although the biological role of common risk variants and their reversed effect in different ethnicities remain an unresolved problem. Rare protein-coding variants at LOXL1 and a single noncoding variant downstream of LOXL1 showed no allele effect reversal and suggested potential roles for elastin homeostasis and vitamin A metabolism in PEX pathogenesis. Other PEX-associated genetic variants provided biological insights into additional disease processes and pathways, including ubiquitin-proteasome function, calcium signaling, and lipid biosynthesis. Gene-environment interactions, epigenetic alterations, and integration of multiomics data have further contributed to our knowledge of the complex etiology underlying PEX syndrome and glaucoma.

SUMMARY

PEX-associated genes are beginning to reveal relevant biological pathways and processes involved in disease development. To understand the functional consequences and molecular mechanisms of these loci and to translate them into novel therapeutic approaches are the major challenges for the future.

Mechanical properties of anterior lens capsule assessed with AFM and nanoindenter in relation to human aging, pseudoexfoliation syndrome, and trypan blue staining

The purpose of this study is the mechanical characterization of the mid-to- old-age human anterior lens capsules (ALCs) obtained by capsulorhexis using Atomic Force Microscopy (AFM) and a nanoindenter at different spatial scales. The dependencies on the human age, presence or absence of pseudoexfoliation syndrome (PEX), and application of trypan blue staining during the surgery were analyzed. The measurements on both the anterior (AS) and epithelial (ES) sides of the ALC were conducted and the effect of cells present on the epithelial side was carefully accounted for. The ES of the ALC had a homogenous distribution of the Young's modulus over the surface as shown by the macroscale mapping with the nanoindenter and local AFM indentations, while the AS was more heterogeneous. Age-related changes were assessed in groups ranging from the mid-age (from 48 years) to old-age (up to 93 years). We found that the ES was always stiffer than the AS, and this difference decreased with age due to a gradual decrease in the Young's modulus of the ES and an increase in the modulus of the AS. No significant changes were found in the mechanical properties of ALCs of PEX patients versus the PEX-free group, as well as in the properties of the ALC with and without trypan blue staining.

XEN Gel Stent in Pseudoexfoliative Glaucoma: 2-Year Results of a Prospective Evaluation

PRéCIS:: This study confirms the safety and efficacy of XEN gel stents in the management of pseudoexfoliative glaucoma 2 years after implantation, with success rates similar to primary open-angle glaucoma regardless of the definition of success.

PURPOSE

To compare the long-term safety and efficacy of XEN gel implant surgery (Allergan Inc., Irvine, CA) in patients with pseudoexfoliative glaucoma (PEXG) and primary open-angle glaucoma (POAG).

SETTING

Prospective, interventional study in a tertiary glaucoma center.

METHODS

A total of 110 eyes of 85 patients with POAG (57 eyes) or PEXG (53 eyes) and uncontrolled intraocular pressure (IOP) despite medical treatment underwent combined XEN+cataract surgery or standalone XEN surgery. Mean IOP, mean number of medications, needling rates, and incidence of adverse effects were compared between the 2 groups. Complete surgical success was defined as an unmedicated IOP≤12, 15, 16, or 18 mm Hg at 2 years, both with and without a 20% reduction from baseline.

RESULTS

Combined XEN+cataract surgery was performed in 72% of POAG and 76% of PEXG eyes (P=0.67), the remainder underwent standalone XEN surgery. Patient characteristics were similar between the 2 groups except for older age for the patients with PEXG (78.5±8.5 vs. 71.3±8.7 y; P<0.005). Mean medicated IOP were 19.8±5.8 mm Hg (POAG) versus 19.8±8.2 mm Hg (PEXG) at baseline (P=0.98), and 14.5±3.6 mm Hg (-26.8%) versus 14.2±3.8 mm Hg (-28.3%), respectively, at 2 years (P=0.75). Mean medications concomitantly dropped from 1.9±1.6 (POAG) versus 2.0±1.3 (PEXG) to 0.6±0.9 versus 0.4±0.7, respectively (P=0.29). Using the 16 mm Hg threshold, 51.4% (POAG) versus 57.1% (PEXG) eyes achieved complete success (P=0.70) at 2 years. The difference in success rates between the 2 groups was not statistically significant under any of the definitions of success. By 24 months, needling was performed in 42.8% (POAG) and 43.2% (PEXG) (P=0.64), with an average time to needling of 162.8 and 134.9 days, respectively (P=0.46). The rates of adverse effects were 30.6% (POAG) and 36.4% (PEXG) (P=0.66), and additional glaucoma surgeries were carried out in 14.3% (POAG) versus 15.9% (PEXG) (P=0.89).

CONCLUSIONS

The XEN gel implant as a standalone or combined procedure demonstrated similar efficacy and safety results in PEXG and POAG eyes.

Evolving roles of lysyl oxidase family in tumorigenesis and cancer therapy

The lysyl oxidase (LOX) family is comprised of LOX and four LOX-like proteins (LOXL1, LOXL2, LOXL3, and LOXL4), and mainly functions in the remodeling of extracellular matrix (ECM) and the cross-linking of collagen and elastic fibers. Recently, a growing body of research has demonstrated that LOX family is critically involved in the regulation of cancer cell proliferation, migration, invasion and metastasis. In this review, we discuss the roles of LOX family members in the development and progression of different types of human cancers. Furthermore, we also describe the potential inhibitors of LOX family proteins and highlight that LOX family might be an important therapeutic target for cancer therapy.

Link of ocular pseudoexfoliation syndrome and vascular system changes: results from 10-year follow-up study

PURPOSE

To examine the 10-year incidence of the pseudoexfoliation syndrome (PEX) in adults in a population-based follow-up study, to determine its link with vascular diseases, and to identify possible risk factors of the PEX.

METHODS

The baseline examination was performed in 2006 on a random sample of 1033 participants from Kaunas city (Lithuania) population. In 2016, a follow-up study of 686 participants who returned for the examination was conducted. The respondents filled out a questionnaire, an ophthalmological examination was performed, and the presence of vascular diseases was determined by the anamnesis and electrocardiogram evaluation data. Binary univariate and multivariate logistic regression analyses were conducted with the PEX and vascular diseases as predictors, controlling for age. Odds ratios (OR) and 95% confidence intervals of OR were calculated for the risk of new PEX cases.

RESULTS

During 10 years, the prevalence of the PEX in the study population increased from 10.3 to 34.2%. The rates of ischemic heart disease (IHD) and IHD combined with stroke were significantly higher in the PEX subjects than in the non-PEX subjects. The risk of the PEX among persons with IHD was, on the average, by 1.5-fold higher, and among those with IHD and stroke, on the average, by 1.6-fold higher as compared to persons without the aforementioned pathologies (accordingly, p = 0.014 and p = 0.010).

CONCLUSION

The prevalence of the PEX increased significantly with age. The risk of the PEX was significantly higher among persons with IHD and even higher among persons with IHD and stroke. In the future, a greater understanding of the cardiovascular, metabolic, and environmental components associated with the PEX may lead to more specific lifestyle-related preventive strategies to decrease the disease burden.

De novo variants in an extracellular matrix protein coding gene, fibulin-5 (FBLN5) are associated with pseudoexfoliation

Fibulin-5 (FBLN5), an extracellular scaffold protein, plays a crucial role in the activation of Lysyl oxidase like-1 (LOXL1), a tropoelastin crosslinking enzyme, and subsequent deposition of elastin in the extracellular matrix. Following study identifies polymorphisms within FBLN5 gene as risk factors and its aberrant expression in the pathogenesis of an ocular disorder, pseudoexfoliation (PEX). Exons and exon-intron boundaries within FBLN5 gene were scanned through fluorescence-based capillary electrophoresis for polymorphisms as risk factors for PEX pathogenesis in recruited study subjects with Indian ethnicity. mRNA and protein expression of FBLN5 was checked in lens capsule of study subjects through qRT-PCR and western blotting, respectively. In vitro functional analysis of risk variants was done through luciferase reporter assays. Thirty study subjects from control and PEX affected groups were scanned for potential risk variants. Putative polymorphisms identified by scanning were further evaluated for genetic association in a larger sample size comprising of 338 control and 375 PEX affected subjects. Two noncoding polymorphisms, hg38 chr14:g.91947643G>A (rs7149187:G>A) and hg38 chr14:g.91870431T>C (rs929608:T>C) within FBLN5 gene are found to be significantly associated with PEX as risk factors with a p-value of 0.005 and 0.004, respectively. Molecular assays showed a decreased expression of FBLN5 at both mRNA and protein level in lens capsule of pseudoexfoliation syndrome (PEXS) affected subjects than control. This study unravels two novel risk variants within FBLN5 gene in the pathogenesis of PEX. Further, a decreased expression of FBLN5 in PEXS affected lens capsules implicates a pathogenic link between extracellular matrix maintenance and onset of PEX.

CLU Polymorphisms in Patients with Pseudoexfoliation Syndrome in Polish Population

Purpose

To evaluate CLU polymorphisms in patients with pseudoexfoliation syndrome.

Materials and Methods

We studied 81 patients (23 males and 58 females, the median age 76 years) and 91 control subjects (27 males and 64 females, the median age 75 years). Genotypes of the CLU polymorphisms (SNPs), rs3087554 and rs2279590, were determined using a commercially available validated genotyping assays. The χ ² test was performed to compare patient and control groups for possible associations between SNP genotype/allele frequency and disease state.

Results

There were no significant differences for both allele and genotype frequencies between PEX patients and controls for rs3087554 and rs2279590 polymorphisms. The haplotypes distribution shows statistically significant difference between groups (p=0.03). The haplotype (CT) more often was found in controls than in PEX patients, conferring an 18-fold decreased risk to the disease.

Conclusion

Our results indicate that CLU variants may contribute to the risk of PEX in the Polish population.

Role of Oxidative Stress in Pseudoexfoliation Syndrome and Pseudoexfoliation Glaucoma

Objectives

To investigate the role of oxidative stress on pseudoexfoliation formation and progression from pseudoexfoliation syndrome (XFS) to pseudoexfoliation glaucoma (XFG).

Materials and Methods

This study investigated oxidative stress biomarkers in blood samples from 58 patients with XFG, 47 patients with XFS, and 134 healthy age- and sex-matched controls.

Results

The highest serum malondialdehyde (MDA) levels were measured in XFG patients (p<0.001), and MDA level was higher in XFS patients than controls (p<0.001). Superoxide dismutase (SOD) and catalase (CAT) enzyme activities were significantly lower in XFS and XFG patients than in the control group, whereas a significant increase was observed in glutathione (GSH) levels (p<0.001 for all). However, levels of these three biomarkers did not differ significantly between XFS and XFG patients (p=0.188, p=0.185, and p=0.733, respectively). Nitric oxide (NO) concentration was significantly lower in XFG patients compared to XFS patients and controls (p<0.001) but did not differ between XFS patients and controls (p=0.476).

Conclusion

Elevated MDA levels suggest that lipid peroxidation is important in XFS and XFG development and progression from XFS to XFG. In addition, reduction in SOD and CAT enzyme activities is considered a deficiency in the enzymatic antioxidant protection system. Furthermore, GSH values may be evaluated as a compensatory response to oxidative stress in XFS and XFG. Alterations in NO indicate the role of a vascular regulatory factor in the progression from XFS to glaucoma.

Three Single Nucleotide Polymorphisms of LOXL1' in a Turkish Population with Pseudoexfoliation Syndrome and Pseudoexfoliation Glaucoma

Objectives:

To investigate the three single nucleotide polymorphisms (SNPs) (rs3825942, rs1048661, and rs2165241) of the LOXL1 gene in pseudoexfoliation syndrome (XFS) and pseudoexfoliation glucoma (XFG) in the Turkish population.

Materials and Methods:

DNA was obtained from blood samples of 48 XFS, 58 XFG, and 171 control subjects. Three LOXL1 SNPs (rs3825942, rs1048661, rs2165241) were investigated with real time PCR, a probe-based genotyping method, and melting curve analysis.

Results:

All three SNPs of LOXL1 were significantly associated with XFS (rs3825942 p=3.54x10^-6, odds ratio [OR]=∞; rs1048661 p=0.008, OR=2.18; rs2165241 p=8.69x10^-9, OR=4.30) and XFG (rs3825942 p=3.41x10^-7, OR=∞; rs1048661 p=1.75x10^-5, OR=3.78; rs2165241 p=3.85x10^-11 OR=4.90). No significant differences were observed between the XFS and XFG groups for any of the SNPs. The GG genotype of rs3825942 was more valuable for distinguishing pseudoexfoliative cases from healthy individuals. The homozygous TT genotype of rs2165241 was associated with 6-fold increased XFS risk (p=8.15x10^-8, OR=6.32) and 7-fold increased XFG risk (p=1.45x10^-10 OR=7.95). The GGT haplotype consisting of all three risk alleles was associated with a 7.45-fold higher risk of XFS/XFG (p=8.65x10^-14, OR=7.45). Presence of T allele of rs2165241 conferred 3 times higher risk for men than women (p=6.78x10^-5, OR=3.202).

Conclusion:

LOXL1 SNPs are associated with increased risk for pseudoexfoliation in the Turkish population. T allele of rs2165241 was found to be the most important characterized risk factor for our cohort. All SNP distributions were similar to other European and American populations.

Elastin modulation and modification by homocysteine: a key factor in the pathogenesis of Pseudoexfoliation syndrome?

BACKGROUND

Pseudoexfoliation syndrome (PXF) is an idiopathic, elastogenesis-associated systemic disease characterised by amyloid-like material aggregates in the eye. Elevated plasma and aqueous humour (aqH) homocysteine (Hcy) is reportedly associated with PXF. This study is aimed to probe Hcy-mediated alterations in elastin expression.

METHODOLOGY

Lens level of Hcy (total Hcy (tHcy)), mRNA expression of Eln, CBS and MTR in lens capsule, protein expression of elastin in aqH were estimated by enzyme immunoassay, quantitative PCR and western blot, respectively in PXF, PXF with glaucoma (PXF-G) cases, in comparison with cataract-alone disease controls. Human lens epithelial cells (hLECs) were exposed to Hcy and homocysteine thiolactone (HCTL) to evaluate elastin expression in vitro. Furthermore, elastin recombinant protein was incubated with Hcy and HCTL to assess secondary and tertiary structural modifications based on circular dichroism spectroscopy, spectrophotometric and SEM studies.

RESULTS

The lens tHcy was significantly high in PXF (p=0.02) and PXF-G (p=0.009). Eln expression was elevated in PXF and PXF-G (p=0.0007). Elastin level in aqH was elevated in PXF (p=0.01) and PXF-G (p=0.002). Hcy (200 µM) and HCTL (1 µM) promoted elastin expression at mRNA level by 36-fold (p=0.02) and 10-fold (p=0.05), respectively, and at protein level by nearly two-fold in cultured hLECs. Secondary structure changes in elastin protein caused by Hcy were evident from 34.11% drop in α-helix and 6.17% gain in β-sheet. Fluorescence, spectral assays and SEM analyses showed aggregation and amyloid formation of elastin with homocysteinylation.

CONCLUSION

The study reveals that lens accumulation of Hcy associated with hyperhomocysteinaemia is characteristic of PXF that augments elastin expression. Hcy causes structural changes promoting elastin aggregation, thereby contributing to defective elastin in PXF and PXF-G.

Lack of association between lysyl oxidase-like 1 polymorphism in pseudoexfoliation syndrome and pseudoexfoliation glaucoma in North Indian population

INTRODUCTION

Pseudoexfoliation syndrome is commonly associated with pseudoexfoliation glaucoma. The two nonsynonymous single-nucleotide polymorphisms rs1048661 (R141L) and rs3825942 (G153D) within exon 1 of LOXL1 gene have been found to confer risk of pseudoexfoliation syndrome and pseudoexfoliation glaucoma in different geographical populations. This study aims to find association between two nonsynonymous single-nucleotide polymorphisms with pseudoexfoliation syndrome and pseudoexfoliation glaucoma in North Indian population.

METHODS

North Indian subjects clinically diagnosed with pseudoexfoliation syndrome/pseudoexfoliation glaucoma and normal age-matched control were enrolled in the study. Genomic DNA was extracted and the two single-nucleotide polymorphisms of LOXL1 gene were genotyped by polymerase chain reaction and sequencing. The association between single-nucleotide polymorphisms with pseudoexfoliation syndrome/pseudoexfoliation glaucoma was evaluated by chi-square test.

RESULTS

A total of 30 pseudoexfoliation glaucoma, 27 pseudoexfoliation syndrome and 61 control subjects were enrolled in the study. Patients with pseudoexfoliation syndrome and pseudoexfoliation glaucoma did not show any genetic association with either single-nucleotide polymorphism rs1048661 or rs3825942.

CONCLUSION

The study shows lack of association between LOXL1 single-nucleotide polymorphisms and pseudoexfoliation in North Indian population.

Aging and ocular tissue stiffness in glaucoma

Glaucoma is a progressive and chronic neurodegenerative disorder characterized by damage to the inner layers of the retina and deformation of the optic nerve head. The degeneration of retinal ganglion cells and their axons results in an irreversible loss of vision and is correlated with increasing age. Extracellular matrix changes related to natural aging generate a stiffer extracellular environment throughout the body. Altered age-associated ocular tissue stiffening plays a major role in a significant number of ophthalmic pathologies. In glaucoma, both the trabecular meshwork and the optic nerve head undergo extensive extracellular matrix remodeling, characterized by fibrotic changes associated with cellular and molecular events (including myofibroblast activation) that drive further tissue fibrosis and stiffening. Here, we review the literature concerning the role of age-related ocular stiffening in the trabecular meshwork, lamina cribrosa, sclera, cornea, retina, and Bruch membrane/choroid and discuss their potential role in glaucoma progression. Because both trabecular meshwork and lamina cribrosa cells are mechanosensitive, we then describe molecular mechanisms underlying tissue stiffening and cell mechanotransduction and how these cellular activities can drive further fibrotic changes within ocular tissues. An improved understanding of the interplay between age-related tissue stiffening and biological responses in the trabecular meshwork and optic nerve head could potentially lead to novel therapeutic strategies for glaucoma treatment.

Immunohistochemical analysis of microsomal glutathione S-transferase 1 and clusterin expression in lens epithelial cells of patients with pseudoexfoliation syndrome

Pseudoexfoliation syndrome (PEX) is an age-associated, sight disorder affecting elastic fibers in the eye and visceral organs but its exact etiology remains unknown. The purpose of the current study was to determine the morphology and ultrastructure of lens epithelial cells (LECs), and to use immunohistochemistry to examine localization of microsomal glutathione S-transferase 1 (MGST1) and clusterin. Anterior lens capsules were obtained from 24 patients (13 PEX and 11 controls) who underwent phacoemulsification. Immunohistochemistry was performed, using antibodies against MGST1 and clusterin, to determine their expression. The morphology and ultrastructure of LECs were evaluated by light and transmission electron microscopy, respectively. The PEX LECs were characterized by significantly lower MGST1 (P=0.0001) and clusterin expression (P=0.0005) compared with the control group patients. PEX LECs were also observed to have significantly increased thickness compared with the control group patients (P=0.0002). The current findings suggest that low MGST1 and clusterin expression levels may be an early clinical indicator of PEX, and that oxidative stress may serve an important role, but that the specific etiology of this disease has yet to be revealed.

Immunohistochemical Profiles of LOXL-1, FBN1, TGF-β1, and COX-2 in Pseudoexfoliation Syndrome

PURPOSES

To (i) determine expression patterns of lysyl oxidase-like 1 (LOXL1), fibrillin-1 (FBN1), transforming growth factor beta-1 (TGF-β1), and cyclooxygenase-2 (COX-2) in lens epithelium and anterior lens capsule in pseudoexfoliation (PEX) syndrome and (ii) delineate the roles of these proteins in the etiopathogenesis of PEX.

MATERIALS AND METHODS

Study participants, all of whom had undergone cataract surgery, comprised 47 patients with and 27 patients without (controls) PEX syndrome. Immunohistochemistry on paraffin sections of lens capsule and lens epithelium was performed.

RESULTS

Immunoexpression of LOXL1 and FBN1 on the outer surface of the lens capsule was significantly higher (p < 0.001), and nuclear immunopositivity for LOXL1 was more frequently observed (p = 0.017), in PEX patients compared with control patients. Cytoplasmic expression of LOXL1 and COX-2 was significantly lower (p = 0.015 and p = 0.042, respectively) in PEX patients compared with controls. TGF-β1 exhibited diffuse immunostaining detected in all cell layers in PEX patients (p <0.001). Significant direct correlations of cytoplasmic LOXL1 with FBN1 and TGF-β1, and of COX-2 with FBN1, TGF-β1, and LOXL-1, were observed only in PEX patients.

CONCLUSIONS

Results of our study provide valuable information vis-à-vis expression and localization of TGF-β1, LOXL1, and FBN1, as well as their associations in the lens epithelium and lens capsule. These data not only advance our knowledge of the etiopathogenesis of PEX syndrome, but also include novel findings, for example, immunostaining patterns of TGF-β1 in PEX syndrome. We suggest that COX-2 plays a role in the pathobiology of PEX syndrome and should be the subject of future investigations.

Nitric oxide and tumour necrosis factor alpha in the process of pseudoexfoliation glaucoma

AIM

To establish the role of nitric oxide (NO), ascorbic acid and tumour necrosis factor-α (TNF-α) in the pathogenesis of pseudoexfoliation glaucoma (XFG).

METHODS

Our study included 120 patients who were referred for cataract surgery. All patients were divided into four groups according to clinical findings: XFG, early and late pseudoexfoliation syndrome (XFS), and cataract (without pseudoexfoliation). Serum and aqueous humour levels of the ascorbic acid, NO and TNF-α were measured. The concentrations of the ascorbic acid and NO were measured by an appropriate spectrophotometric method. Enzyme-linked immunosorbent assay (ELISA) was used to determine TNF-α level.

RESULTS

Aqueous humour concentration of ascorbic acid was significantly lower in patients with late XFS (0.61±0.11 mmol/L) and XFG (0.48±0.15 mmol/L) compared to patients with early XFS (0.9±0.15 mmol/L) and cataract (1.16±0.22 mmol/L), while there was no difference in serum concentration in all examined groups. Aqueous humour concentration of NO was significantly higher in patients with XFG (77.7±11.4 µmol/L) compared to patients with early XFS (50.27±9.34 µmol/L) and cataract (49.77±7.1 µmol/L), while serum concentration was increased in the early stage of XFS (73.26±8.29 µmol/L). Aqueous humour level of proinflammatory cytokine TNF-α was increased in patients with XFS (early 460.04±18.32 pg/mL; late 502.42±53.23 pg/mL) and XFG (510.34±43.07 pg/mL), while there was no difference in serum level in all examined groups of patients.

CONCLUSION

Reduced ascorbic acid and elevated NO and inflammation related cytokine TNF-α level in aqueous humour of the patients with developed XFG suggest that oxidative stress induces local inflammation.

Discovery of Molecular Therapeutics for Glaucoma: Challenges, Successes, and Promising Directions

Glaucoma, a heterogeneous ocular disorder affecting ∼60 million people worldwide, is characterized by painless neurodegeneration of retinal ganglion cells (RGCs), resulting in irreversible vision loss. Available therapies, which decrease the common causal risk factor of elevated intraocular pressure, delay, but cannot prevent, RGC death and blindness. Notably, it is changes in the anterior segment of the eye, particularly in the drainage of aqueous humor fluid, which are believed to bring about changes in pressure. Thus, it is primarily this region whose properties are manipulated in current and emerging therapies for glaucoma. Here, we focus on the challenges associated with developing treatments, review the available experimental methods to evaluate the therapeutic potential of new drugs, describe the development and evaluation of emerging Rho-kinase inhibitors and adenosine receptor ligands that offer the potential to improve aqueous humor outflow and protect RGCs simultaneously, and present new targets and approaches on the horizon.

Update on pseudoexfoliation syndrome pathogenesis and associations with intraocular pressure, glaucoma and systemic diseases

PURPOSE OF REVIEW

Pseudoexfoliation (PEX) syndrome is a common age-related disorder affecting intraocular and extraocular tissues. This review focuses on recent publications related with the pathogenesis and associations of PEX syndrome with intraocular pressure (IOP), glaucoma and systemic diseases.

RECENT FINDINGS

In PEX tissues, expression of lysyl oxidase-like 1 (LOXL1) was found to be markedly dysregulated. This may adversely affect elastin metabolism and lead to elastotic alteration in tissues such as lamina cribrosa. There is increasing evidence that cellular stress conditions and low-grade chronic inflammatory processes are involved in the pathogenesis of PEX. Although there is an increased risk for glaucoma development in patients with PEX and ocular hypertension as compared with non-PEX patients with ocular hypertension, LOXL1 single nucleotide polymorphisms were not associated with intraocular pressure (IOP) differences. Lack of association of PEX with all-cause mortality or dementia has been reported recently. The association with vascular diseases is not consistent among different studies.

SUMMARY

Despite the high prevalence of the LOXL1 variants in the general population, a much lower proportion of the population develops PEX, suggesting that in addition to LOXL1, other genetic, epigenetic and environmental factors may contribute to the development of PEX. Also, LOXL1 cannot help to identify those with PEX at increased risk for glaucoma development. Increased risk for glaucoma development in PEX patients who present with increased IOP may be related to other factors beyond IOP, contributing to increased vulnerability of the optic nerve to glaucoma development in the presence of PEX.

LOXL1-associated candidate epithelial pathomechanisms in exfoliation glaucoma

Results of the present study support ocular epithelia-specific LOXL1 functions in exfoliation glaucoma that may include both dysregulated extracellular matrix cross-linking activity and cellular mechanisms involving a role for LOXL1, in direct interaction with Snail1, in promoting epithelial to mesenchymal transition and a potential shift towards fibrogenic epithelial cell phenotypes.

Animal models of exfoliation syndrome, now and future

At present, no animal models fully embody exfoliation syndrome or exfoliation glaucoma. Both genetic and environmental factors appear critical for disease manifestation, and both must be considered when generating animal models. Because mice provide a powerful mammalian platform for modeling complex disease, this paper focuses on mouse models of exfoliation syndrome and exfoliation glaucoma.

Conjunctival matrix metalloproteinases and their inhibitors in glaucoma patients

PURPOSE

Chronic conjunctival inflammation, caused by various reasons, for example long-term use of topical drugs and/or their preservatives, affects the outcome of glaucoma surgery by interfering with wound healing. Matrix metalloproteinases (MMPs) remodel extracellular matrix (ECM) and are involved in the wound healing process. This study was designed to evaluate the conjunctival expression of MMPs and their tissue inhibitors (TIMPs) in the normal eye, primary open-angle glaucoma (POAG) and exfoliation glaucoma (ExG) and whether there is an association between staining intensities and deep sclerectomy outcome.

METHODS

Immunohistochemical procedures were performed on conjunctival samples which were obtained from POAG (n=11) and ExG (n=14) patients as well as normal (n=7) subjects. Antibodies against MMPs (MMP-1, -2, -3 and -9) and TIMPs (TIMP-1, -2 and -3) were used.

RESULTS

In conjunctival stroma, expression levels of MMP-2 (p=0.047), MMP-3 (p=0.009), MMP-9 (p<0.001), TIMP-1 (p=0.003), TIMP-2 (p<0.001) and TIMP-3 (p<0.001) in ExG and MMP-9 (p=0.008), TIMP-2 (p=0.02) and TIMP-3 (p=0.002) in POAG were significantly increased compared to control. We further found correlations between expression of MMP-1 and MMP-3 and the length of pilocarpine treatment.

CONCLUSION

The expression of MMPs and TIMPs is increased in the conjunctiva of POAG and ExG patients having a long history of topical antiglaucoma drops. Antiglaucoma agents and/or their preservatives alter the remodelling balance of ECM in conjunctiva of POAG and ExG eyes. The balance between MMPs and TIMPs may play a crucial role in the conjunctival wound healing process and the outcome of glaucoma surgery.

Identification of genome-wide SNP-SNP and SNP-clinical Boolean interactions in age-related macular degeneration

We propose here a methodology to uncover modularities in the network of SNP-SNP interactions most associated with disease. We start by computing all possible Boolean binary SNP interactions across the whole genome. By constructing a weighted graph of the most relevant interactions and via a combinatorial optimization approach, we find the most highly interconnected SNPs. We show that the method can be easily extended to find SNP/environment interactions. Using a modestly sized GWAS dataset of age-related macular degeneration (AMD), we identify a group of only 19 SNPs, which include those in previously reported regions associated to AMD. We also uncover a larger set of loci pointing to a matrix of key processes and functions that are affected. The proposed integrative methodology extends and overlaps traditional statistical analysis in a natural way. Combinatorial optimization techniques allow us to find the kernel of the most central interactions, complementing current methods of GWAS analysis and also enhancing the search for gene-environment interaction.

Oxidative stress in dry age-related macular degeneration and exfoliation syndrome

Oxidative stress refers to cellular or molecular damage caused by reactive oxygen species, which especially occurs in age-related conditions as a result of an imbalance between the production of reactive oxygen species and the antioxidant defense response. Dry age-related macular degeneration (AMD) and exfoliation syndrome (XFS) are two common and complex age-related conditions that can cause irreversible vision loss. Two subtypes of AMD, which is the leading cause of blindness in the Western world, exist: the most prevalent dry type and the most severe wet type. Early dry AMD is characterized by formation of drusen, which are sub-retinal deposits, in the macular area and may progress to geographic atrophy with more dramatic manifestation. XFS is a systemic disorder of the extracellular matrix characterized by the accumulation of elastic fibrils that leads, in most cases, to glaucoma development with progressive and irreversible vision loss. Due to the aging population, the prevalence of these already-widespread conditions is increasing and is resulting in significant economic and psychological costs for individuals and for society. The exact composition of the abnormal drusen and XFS material as well as the mechanisms responsible for their production and accumulation still remain elusive, and consequently treatment for both diseases is lacking. However, recent epidemiologic, genetic and molecular studies support a major role for oxidative stress in both dry AMD and XFS development. Understanding the early molecular events in their pathogenesis and the exact role of oxidative stress may provide novel opportunities for therapeutic intervention for the prevention of progression to advanced disease.

Cardiovascular repercussions of the pseudoexfoliation syndrome

Pseudoexfoliation syndrome is a primarily ophthalmological disorder caused by deposition of whitish-gray protein on the lens, iris, and multiple other eye tissues. There is increasing evidence over the previous years that pseudoexfoliation syndrome is a systemic disorder with various extraocular manifestations and has recently been linked to several cardiovascular disorders. The present article aims to summarize the current knowledge on cardiovascular implications of this well-described clinical entity.

Association between polymorphisms in lysyl oxidase-like 1 and susceptibility to pseudoexfoliation syndrome and pseudoexfoliation glaucoma

The present knowledge on the association of single nucleotide polymorphisms (SNPs) of lysyl oxidase-like 1 (LOXL1) with pseudoexfoliation syndrome (PEXS) and pseudoexfoliation glaucoma (PEXG) is controversial and inconclusive. This meta-analysis sought to derive a more precise estimation of the effects of LOXL1 SNP loci (rs1048661, rs3825942, and rs2165241) on PEXS/PEXG. Literature searches were conducted on the PubMed, EMBASE, ISI Web of Science, and Cochrane Library databases through October 2013. Twelve studies describing 1810 cases and 1790 controls met the inclusion criteria. The strengths of the associations found through the meta-analysis were assessed with pooled odds ratios and their 95% confidence intervals (CI). A meta-regression analysis was also used to examine the influence of the study and population characteristics. The results indicated that rs1048661 TT carriers had 92.1% and 40.4% less risk of developing PEXS/PEXG than did the controls in the Caucasian and Asian populations, respectively. Carriers of rs3825942 AA or rs2165241 CC also had significantly less PEXS/PEXG susceptibility than did the non-carriers. Meta-regression showed that in Caucasians, the male proportion (slope: 0.272; 95% CI: 0.167–0.376; P = 0.0001) and mean age (slope: 0.796; 95% CI: 0.375–1.217; P = 0.0002) of the PEXS/PEXG subjects correlated positively with the effect of rs3825942 on PEXS/PEXG susceptibility. The meta-analysis suggested that LOXL1 rs1048661 TT, rs3825942 AA, and rs2165241 CC were associated with a reduced risk of developing PEXS/PEXG.

[New pathogenetic insights into pseudoexfoliation syndrome/glaucoma. Therapeutically relevant?]

Pseudoexfoliation (PEX) syndrome is a genetically determined, generalized disease of the extracellular matrix leading to the progressive deposition of an abnormal fibrillar material in various intraocular and extraocular tissues including the trabecular meshwork. It thus represents the most common identifiable cause of open-angle glaucoma and a leading cause of blindness worldwide. The PEX-specific fibrotic matrix process, a stress-induced elastosis, is characterized by an excessive production and abnormal cross-linking of elastic microfibrils into fibrillar PEX aggregates. Co-modulating factors triggering this fibrotic process include elevated concentrations of fibrogenic growth factors, such as TGF-β1, reduced activity of proteolytic enzymes, subtle inflammatory processes and various external stress factors, such as oxidative stress. Genetic studies identified a highly significant association between several polymorphisms in the LOXL1 (lysyl oxidase-like 1) gene with both PEX syndrome and PEX glaucoma. As these LOXL1 risk variants were found to occur in almost 100% of PEX patients throughout all geographical populations worldwide, LOXL1 appears to represent a principal risk factor for manifestation of the PEX phenotype. LOXL1 is a pivotal cross-linking enzyme in extracellular matrix metabolism and seems to be specifically required for elastic fiber formation and stabilization. The available data suggest that LOXL1 enzyme function and expression are dysregulated in PEX tissues and thereby play a central role in glaucoma development. On the one hand, increased expression of LOXL1 and elastic fiber components contributes to the formation of abnormally cross-linked PEX aggregates in the outflow pathways leading to increased outflow resistance and intraocular pressure. On the other hand, reduced expression and inadequate tissue levels of LOXL1 may lead to degenerative tissue alterations, particularly in the lamina cribrosa adversely affecting the biomechanical properties of this critical tissue. This PEX-specific elastinopathy of the lamina cribrosa rendering PEX eyes more vulnerable to pressure-induced optic nerve damage may constitute an independent risk factor for glaucoma development. The findings may have direct consequences for the clinical management of PEX patients underlining the need for an exact diagnosis, a strict IOP-reducing therapy and a close and regular follow-up.

Association of lysyl oxidase-like 1 gene common sequence variants in Greek patients with pseudoexfoliation syndrome and pseudoexfoliation glaucoma

PURPOSE

Three common sequence variants in the lysyl oxidase-like 1 (LOXL1) gene were recently associated with pseudoexfoliation (PEX) and pseudoexfoliation glaucoma (PEXG) in populations from various parts of the world. In this study, the genetic association of these variants was investigated in Greek patients with PEX and PEXG.

METHODS

The three LOXL1 single nucleotide polymorphisms (SNPs), one intronic (rs2165241) and two nonsynonymous coding SNPs (rs1048661: R141L and rs3825942: G153D), were genotyped in a total of 48 unrelated patients with PEX, 35 patients with PEXG, and 52 healthy subjects who had normal findings in repeated ophthalmic examinations. A genetic association study was performed.

RESULTS

Between the two coding SNPs, R141L did not show an association with PEX (p=0.297 for allele G, p=0.339 for genotype GG), whereas allele G of G153D showed a significant association (odds ratio [OR]=3.52, 95% confidence interval [CI]=1.735-7.166, p=3.24×10(-4) for allele G, p=0.004 for genotype GG). Likewise, for the intronic SNP of rs2165241, genotype TT (p=0.005) and its corresponding allele T (OR=2.99, 95% CI=1.625-5.527, p=3.53×10(-4)) showed a significant association with PEX. The allele G of G153D showed a significant association with PEXG (OR=3.74, 95% CI=1.670-8.387, p=0.001). The combined haplotype GGT, consisting of all three risk alleles, was associated with PEX (p=0.037), conferring a 1.8-fold of increased risk to the disease (OR=1.799, 95% CI=1.04-3.13). Furthermore, the haplotype GGT presented in 39.8% of the patients with PEX and 26.9% of the controls.

CONCLUSIONS

Certain genetic variants in LOXL1 confer risk for PEX in Greek populations, confirming in part findings in patients from Northern Europe.

Quantitative analysis of SOD2, ALDH1A1 and MGST1 messenger ribonucleic acid in anterior lens epithelium of patients with pseudoexfoliation syndrome

PURPOSE

The aim of the study was to investigate the expression of selected genes encoding enzymes involved in the antioxidant defense system (superoxide dismutase 2, SOD2; aldehyde dehydrogenase 1, ALDH1A1; microsomal glutathione S-transferase 1, MGST1) in fragments of anterior lens capsules of patients with pseudoexfoliation syndrome (PEX). The specificity and sensitivity of these molecular markers for PEX development were also assessed.

METHODS

The study group consisted of 20 patients (9 women and 11 men) with diagnosed PEX and cataract. The control group included 23 patients (8 women and 15 men) who needed cataract surgery but did not have PEX. Quantification of SOD2, ALDH1A1, and MGST1 messenger ribonucleic acid (mRNA) was performed with quantitative real-time PCR.

RESULTS

SOD2, ALDH1A1, and MGST1 mRNAs were detected in all studied samples. The examined genes had statistically significant higher expression in the group of patients with PEX than in the control group (SOD2, p=0.0015; ALDH1A1, p=0.0001; MGST1, p=0.0001, Mann-Whitney U test). The areas under the curve (AUC) of SOD2, MGST1, and ALDH1A1 were 0.766, 0.818, and 0.957, respectively.

CONCLUSIONS

Differential expression of SOD2, ALDH1A1, and MGST1 genes in the anterior lens capsules of patients with PEX suggest that diseased tissue appears to respond to the previously reported oxidative stress. A possible role of ALDH1A1 mRNA level as a risk factor or marker for PEX needs further confirmation.