Association of endothelial nitric oxide synthase (NOS3) gene polymorphisms with primary open-angle glaucoma in a Saudi cohort

Aim

To investigate the association of endothelial nitric oxide synthase (NOS3) gene polymorphisms in patients with primary open-angle glaucoma (POAG) of Saudi origin.

Methods

This case-control study included 173 patients with POAG (94 men and 79 women) and 171 controls (98 men and 73 women). Genotyping of rs2070744 (T-786C) and rs1799983 (G894T) variants of the NOS3 gene was performed using TaqMan^® assay.

Results

Rs1799983 genotypes showed a significant association with POAG but did not survive Bonferroni correction (p_correction = 0.01). The minor ‘T’ allele was significantly associated with the risk of POAG among men (p = 0.025, odds ratio (OR) = 1.77, 95% confidence interval (CI) = 1.07–2.94). Likewise, the genotypes were significantly associated with POAG among men in dominant (p = 0.030, OR = 1.92, 95% CI = 1.06–3.48) and log-additive models (p = 0.022, OR = 1.82, 95% CI = 1.08–3.07), and after adjustment for age and smoking. Genotype and allele frequencies of rs2070744 were not significantly different between POAG cases and controls, and after sex stratification. CG haplotype was significantly protective (p = 0.011, OR = 0.52, 95% CI = 0.32–0.87) and CT haplotype conferred significantly increased risk of POAG (p = 0.016, OR = 2.60, 95% CI = 1.16–5.82) among men. Rs1799983 showed trend (p = 0.054) towards risk of POAG independent of age, gender, smoking, and rs2070744 polymorphism in logistic regression analysis. Both the polymorphisms showed no association with POAG phenotypes such as intraocular pressure and cup/disc ratio.

Conclusion

Our results suggest that the polymorphism rs1799983 and the haplotypes of rs20707440 and rs1799983 in the NOS3 gene may significantly modulate the risk of POAG in Saudi’s, particularly among men. Further larger studies are needed to confirm these findings.

Exfoliation Syndrome: A Disease of Autophagy and LOXL1 Proteopathy

Exfoliation syndrome (XFS) is an age-related disease involving the deposition of aggregated fibrillar material (exfoliation material) at extracellular matrices in tissues that synthesize elastic fibers. Its main morbidity is in the eye, where exfoliation material accumulations form on the surface of the ciliary body, iris, and lens. Exfoliation glaucoma (XFG) occurs in a high proportion of persons with XFS and can be a rapidly progressing disease. Worldwide, XFG accounts for about 25% of open-angle glaucoma cases. XFS and XFG show a sharp age-dependence, similarly to the many age-related diseases classified as aggregopathies. Progress in understanding the cellular bases for XFS/XFG has been slowed by a lack of experimental models. Working with primary human tenon fibroblasts (TF) derived from trabeculectomies of XFG patients and age-matched primary open-glaucoma controls, we found that TF from XFG cells display many of the functional features observed in cells from other protein aggregate diseases, such as Parkinson, Alzheimer, Huntington, and age-related macular degeneration. We have documented defects in lysosomal positioning, microtubule organization, autophagy processing rate, and mitochondrial health. In regard to failure of lysosomal and autophagosome positioning in XFG cells, we have found that XFG TF are unable to establish the transnuclear microtubule organizing center that is required for efficient centripetal vesicular locomotion along microtubules. In regard to potential sources of the autophagy malfunction, we have directed our attention to a potential role of the lysyl oxidase-like 1 protein (LOXL1), the elastic fiber catalyst that displays variant-dependent association with risk for XFG. Our experiments show that (a) in XFG cells, a substantial fraction of LOXL1 is processed for degradation by the autophagic system; (b) most of the LOXL1 N-terminus domain exists in a highly disordered state, a condition known to greatly increase the frequency of polypeptide misfolding; (c) that maximum misfolding occurs at amino acid position 153, the location of the high risk variant G153D; and (d) that replacement of glycine (G) by aspartate (D) there results in a substantial decrease in disorder within the 20 amino acid surrounding domain. Finally, we show that clusterin, a protein that can be induced by the presence of intracellular, or extracellular aggregates, is uniformly overexpressed in XFG TF. The implications of our results for a theory relating XFG to cellular aggregopathy are discussed.

Exfoliation syndrome: a disease with an environmental component

PURPOSE OF REVIEW

Exfoliation syndrome (XFS), the most common cause of secondary open angle glaucoma, is associated with significant ocular morbidity. Recent studies have pointed toward environmental components that may alter the risk of XFS development. This review focuses on the recent studies elucidating the role of environmental factors that play a role in the development of exfoliation syndrome.

RECENT FINDINGS

In XFS, aberrant microfibril formation emanating from the cell-extracellular matrix interface admixes with other macromolecules and is cross-linked by lysyl oxidase like 1 (LOXL1) activity. A common gene variant in the LOXL1 enzyme, an enzyme critical for enhancing the tensile strength of collagen and elastin in extracellular matrices, has been found in approximately 90% of XFS cases. However, approximately 80% of controls also have disease-associated LOXL1 gene variants. These findings point toward other nongenetic factors influencing the development of XFS. Increasing latitude, solar radiation, climatic variables and dietary factors such as high coffee consumption and low dietary folate intake are among the nongenetic factors associated with increased risk of XFS.

SUMMARY

A greater understanding of the environmental components associated with XFS may lead to lifestyle preventive strategies to ameliorate disease burden.

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.

Role of the APOE ε2/ε3/ε4 polymorphism in the development of primary open-angle glaucoma: evidence from a comprehensive meta-analysis

Primary open-angle glaucoma (POAG) is one of the leading causes of blindness worldwide. The association between the APOE ε2/ε3/ε4 polymorphism and the risk of POAG has been widely reported, but the results of previous studies remain controversial. To comprehensively evaluate the APOE ɛ2/ɛ3/ε4 polymorphism on the genetic risk for POAG, we performed a systematic review and meta-analysis of previously published studies. The PubMed and Web of Science databases were systematically searched to identify relevant studies. Data were extracted from these studies and odds ratios with corresponding 95% confidence intervals were computed to estimate the strength of the association. Stratified analyses according to ethnicity and sensitivity analyses were also conducted for further confirmation. A total of nine studies were eligible for the meta-analysis, and these studies included data on 1928 POAG cases and 1793 unrelated match controls. The combined results showed that there were no associations between the APOE ε2/ε3/ε4 polymorphism and POAG risk in any of the 10 comparison models. The analysis that was stratified by ethnicity subgroups also failed to reveal a significant association. The sensitivity analysis confirmed the stability and reliability of the findings. There was no risk of publication bias. Our meta-analysis provides strong evidence that the APOE ε2/ε3/ε4 polymorphism is not associated with POAG susceptibility in any populations.

Lack of association between the C677T single nucleotide polymorphism of the MTHFR gene and glaucoma in Iranian patients

Glaucoma is a major cause of blindness worldwide. A single nucleotide polymorphism of the MTHFR gene (C677T) has been associated with susceptibility to this disease, although this is controversial in the last decade. In this study, the possible association between the MTHFR C677T polymorphism and the risk of developing primary open angle (POAG) and pseudoexfoliation glaucoma (PEXG) was investigated. For this, a prospective study consisting of 73 POAG, 85 PEXG and 90 matched controls was undertaken in an Iranian population. Genomic DNA was extracted from whole blood. Genotyping of all individuals for the MTHFR C677T polymorphism was conducted using the PCR-RFLP technique. Our findings revealed no significant association between the MTHFR C677T polymorphism in POAG and PEXG compared with controls. Consistent with several other studies, our analysis suggests that the MTHFR C677T polymorphism is unlikely to be a factor contributing to the risk of developing specific forms of glaucoma.

Endothelial nitric oxide synthase gene variants and primary open-angle glaucoma: interactions with hypertension, alcohol intake, and cigarette smoking

OBJECTIVE

To evaluate whether an association between risk of any of the factors of hypertension, alcohol intake, and cigarette smoking and the risk of primary open-angle glaucoma (POAG) depended on nitric oxide synthase 3 (NOS3) gene variants.

METHODS

Two functional single-nucleotide polymorphisms (SNPs) (T-786C [rs2070744] and Glu298Asp [rs1799983]) and 2 tagging SNPs (rs7830 and rs3918188) were evaluated in nested case-control studies from the Nurses' Health Study (1980-2002) and the Health Professionals' Follow-up Study (1986-2002). Participants were 40 years of age or older and white, and were followed up biennially. We included 527 incident case patients with POAG and 1539 control participants, matched by cohort, age, and eye examination at the matched case patients' diagnosis dates. Cohort-specific relative risks were estimated using multivariable conditional logistic regression and were pooled using meta-analytic methods.

RESULTS

The association between hypertension and POAG depended on T-786C SNP variants. Compared with TT homozygotes without hypertension, the TT homozygotes with hypertension were at significantly higher risk of POAG (relative risk,1.45 [95% confidence interval, 1.01-2.08]); however, among carriers of the variant (C) allele, hypertension was not associated with POAG (P interaction = .007). Similarly, compared with CC homozygotes with the rs7830 tagging SNP who never smoked, CC homozygotes who were past or current smokers were at significantly higher risk of POAG (relative risk, 1.63 [95% confidence interval, 1.15-2.31]); however, among carriers of the variant allele (A), smoking was not associated with POAG (P interaction = .004). Interactions were not observed with alcohol intake.

CONCLUSIONS

The associations between hypertension and cigarette smoking in relation to POAG depended on NOS3 SNPs.

Mapping of the disease locus and identification of ADAMTS10 as a candidate gene in a canine model of primary open angle glaucoma

Primary open angle glaucoma (POAG) is a leading cause of blindness worldwide, with elevated intraocular pressure as an important risk factor. Increased resistance to outflow of aqueous humor through the trabecular meshwork causes elevated intraocular pressure, but the specific mechanisms are unknown. In this study, we used genome-wide SNP arrays to map the disease gene in a colony of Beagle dogs with inherited POAG to within a single 4 Mb locus on canine chromosome 20. The Beagle POAG locus is syntenic to a previously mapped human quantitative trait locus for intraocular pressure on human chromosome 19. Sequence capture and next-generation sequencing of the entire canine POAG locus revealed a total of 2,692 SNPs segregating with disease. Of the disease-segregating SNPs, 54 were within exons, 8 of which result in amino acid substitutions. The strongest candidate variant causes a glycine to arginine substitution in a highly conserved region of the metalloproteinase ADAMTS10. Western blotting revealed ADAMTS10 protein is preferentially expressed in the trabecular meshwork, supporting an effect of the variant specific to aqueous humor outflow. The Gly661Arg variant in ADAMTS10 found in the POAG Beagles suggests that altered processing of extracellular matrix and/or defects in microfibril structure or function may be involved in raising intraocular pressure, offering specific biochemical targets for future research and treatment strategies.

Primary open angle glaucoma (POAG) is a leading cause of vision loss and blindness affecting tens of millions of people. Ocular hypertension is a strong risk factor for the disease and the only effective target of treatment. Ocular hypertension results from increased resistance to outflow of aqueous humor through the trabecular meshwork, a specialized filtration tissue consisting of alternating layers of cells and connective tissue, but the specific reasons for the increased resistance are not known. The animal model for human POAG used in this study was a colony of Beagle dogs that carry an inherited form of the disease in which ocular hypertension is the primary manifestation. We have found a variant in ADAMTS10 that belongs to a family of genes that contribute to formation of extracellular matrix and may itself be involved in formation of elastic microfiber structures. We found that the ADAMTS10 protein is expressed at particularly high levels in the trabecular meshwork. The candidate variant in ADAMTS10 found in the POAG–affected Beagles suggests that altered processing of connective tissue and/or elastic microfiber defects may be involved in raising eye pressure, offering specific biochemical targets for future research and treatment strategies.

Lactate dehydrogenase and oxidative stress activity in primary open-angle glaucoma aqueous humour

Lactate dehydrogenase (LDH) and lactate are some of the hypoxy biochemical parameters. Extracellular activity of this enzyme increases under the condition of oxidative stress, since the cell integrity can be disrupted during the lipid peroxidation process. Subsequently that leads to the increase level of the lactic acid and lactic acid salts. The objective of this investigation is establishing the level of LDH, LDH1 (HBDH) and the lactate concentration in aqueous humour in patients with primary open-angle glaucoma. Biochemical analysis have been made by enzymatic-colometric method (lactate) and UV-kinetic method (LDH and HBDH) in aqueous humour of 30 patients (42 eyes) with primary open-angle glaucoma (POAG) and 30 patients (40 eyes) with cataract (the control group). The increased values of lactate and the activity of LDH and HBDH enzyme in aqueous humour of POAG patients in correlation with the control group are the results not only of oxidative stress but also of hypoxy and the mitochondry oxidative function (p<0,001). The increased activity of the examined biochemical parameters in the aqueous humour of the POAG patients points to the fact that other mechanisms, besides IOP, have a role in glaucoma pathogenesis.

[Study of kini-kallikrein and renin--angiotensin systems in patients with primary open angle glaucoma]

PURPOSE

To evaluate the activity of Renin-Angiotensin (SRA) and Kinin-Kalikrein (SKK) systems in patients with primary open-angle glaucoma (POAG) in tears, blood and aqueous flow.

METHODS

Components of SRA and SKK were analysed in the blood, tears and aqueous flow of 38 patients found in different stages of POAG. The samples of aqueous flow were harvested during glaucoma surgery The results were compared to those from a healthy group of patients (for tears and blood) and to a group of normal patiens that had ocular surgery for cataract and high ametropias (for samples af aqueous flow).

RESULTS

In patients with high pressure primary open-angle glaucoma, when comparing them to those from the control group, the measurements showed: a high level of angiotensin converting enzyme (ACE) activity (in tears up to 108-125%, p < 0.001 and in aqueous flow up to 40-47% p < 0.001), a high level of kalikrein (in tears up to 21-29%, p < 0.001 and in aqueous flow up to 35-44% p < 0.001) and a high level of the summed activity of prekalikrein +kalikrein (up to 11-14, p < 0.001). A decrease in the prekalikrein/kalikrein ratio was found (up to 21-25% p < 0.01 in tears and aqueous flow) and this decrease was proved to be in direct correlation to the glaucoma stages of evolution. A decrease in prekalikrein activity was also found; up to 7% in the tears for each developing glaucoma stage. After the glaucoma surgery, the levels of ACE activity and kalikrein measured in tears decreased (up to 17% p < 0.001 and 17% p < 0.001 respectively) without reaching the levels in the normal group while the levels of prekalikrein and the prekalikrein/kalikrein ratio grew (up to 7% p < 0.01 and 16% < 0.001 respectively).

CONCLUSIONS

The results show a high level of kalikrein and angiotensin converting enzyme (ACE) activity (measured in aqueous flow and tears) when comparing the group with POAG to the normal group. A decrease in prekalikrein activity was found, and the prekalikrein/kalikrein ratio was also low in the aqueous flow and tears. After the glaucoma surgery the levels of ACE activity and kalikrein decreased without reaching the levels in the normal group while the levels of prekalikrein and the prekalikrei/kalikrein ratio grew.

[Matrix metalloproteinases (MMPs): modern molecular markers of open-angle glaucoma diagnosis and therapy]

Glaucoma is one of the most important civilization diseases and leads to irreversible blindness. Inspite of many years of research, the causes of this disorder remain unclear. This disease is extremely difficult to diagnose because its primary phase is asymptomatic. After laborious research it has been discovered that metalloproteinases, i.e. proteolytic enzymes involved in the pathogenesis of many kinds of glaucoma, are crucial in glaucoma diagnosis. The overexpression of matrixins leads to degradation of extracellular matrix components, which results in eye tissue injury and changes of tissue properties. Structural disorders occurring in this way are one of the many key reasons for progressive glaucomatous optic neuropathy. The presence of altered expressions of MMP-1, -2, -3, -7, -9, and -12 and their tissue inhibitors TIMP-1 and -2 in the glaucomatous eye paves new ways for the diagnosis and treatment of open-angle glaucoma. The detection of polymorphisms and mutations in genes encoding these enzymes will allow qualifying a patient to a risk group and people who are already ill may be treated by regulation of metalloproteinases activity. This review focuses on the presence and function of metalloproteinases in open-angle glaucoma and on treatment possibilities through MMP regulation.

Phospholipase A2 in chamber angle of normal eyes and patients with primary open angle glaucoma and exfoliation glaucoma

PURPOSE

Phospholipase A2 (PLA2) is a growing family of lipolytic enzymes that play a key role in various biological processes including general lipid metabolism, membrane homeostasis, and in diseases such as atherosclerosis, arthritis, and acute pancreatitis. Oxidative stress as well as inflammation may be associated with glaucoma pathogenesis. Therefore, our aim was to examine the expression of group IIA secretory PLA2 (sPLA2-IIA), group V secretory PLA2 (sPLA2-V), calcium-independent PLA2 (iPLA2), and cytosolic PLA2 (cPLA2) type in the trabecular meshwork (TM) and the canal of Schlemm in normal eyes and in juxtacanalicular tissue samples from patients with primary open angle glaucoma (POAG) or exfoliation glaucoma (ExG).

METHODS

TM tissues were isolated from healthy donor eyes for corneal transplantation. Specimens of inner wall of the Schlemm's canal and the juxtacanalicular tissue were collected during deep sclerectomy from the eyes of patients who had POAG or ExG. Antibodies against PLA2s (sPLA2-IIA, sPLA2-V, iPLA2, and cPLA2) and a standard immunohistochemical procedure were used for the analysis. Quantification of immunoreactions was provided using a Photoshop-based image analysis. Double-staining immunofluorescence of macrophages and sPLA2-IIA was performed by using confocal microscopy.

RESULTS

sPLA2-IIA was not present in normal TM. In contrast, sPLA2-IIA levels were significantly higher in glaucoma patients than in controls. Furthermore, sPLA2-IIA expression was much higher in POAG when compared to ExG. iPLA2 was found to predominate in normal human TM, and it demonstrated strong labeling in the uveal and corneoscleral meshwork. The staining of juxtacanalicular meshwork was only moderate in density. In contrast, expression of the enzyme was significantly decreased in glaucoma patients, especially in ExG, when compared to normal controls or to POAG. In addition, strong regional differences were detected in sPLA2-IIA and iPLA2 levels in POAG, whereas immunostaining of these enzymes was much lower and rather uniform throughout ExG sample. In POAG, sPLA2-IIA staining was restricted to certain parts of the trabecular samples where sPLA2-IIA positive macrophages were also present. Immunostaining of sPLA2-V or cPLA2 was low, and no significant changes were found in levels of these enzymes between normal and glaucomatous samples.

CONCLUSIONS

sPLA2-IIA, an oxidative stress marker in atherosclerosis, is overexpressed especially in POAG. This result supports the hypothesis that oxidative stress may play a significant role in the pathogenesis of POAG. In ExG, a dramatic decrease in the expression level of iPLA2, a housekeeping enzyme in phospholipid remodeling, may indicate imbalance in phospholipid turnover and also inhibition of normal physiological functions in the TM. These findings may contribute to understanding the pathogenesis of POAG and ExG and may be important for the development of novel therapeutic strategies to different glaucomas.

[The future started: nitric oxide in glaucoma]

Nitric oxide (NO) is an important messenger intra and extra molecular implicated in vasodilatation, contractility, neurotransmission, neurotoxicity and inflammation. NO is formed from L-arginine by nitric oxide synthase (NOS). Nitric oxide synthase has three isoforms: NOS- 1 neuronal, NOS-2 inducible and NOS-3 endothelial (role in vasodilatation). Nitric oxide has a demonstrate role in many neurodegenerative diseases like: glaucoma, Alzheimer disease, multiple sclerosis and cerebral-cardio-vascular diseases.

PURPOSE

To investigate the activity of the NOS by immunohistochemistry in patients with primary open angle glaucoma (POAG).

METHODS

Observational, prospective, clinical study, during 9 months on one group of 9 patients with POAG that have underwent filtering surgery - trabeculectomy. The fragments of trabecular meshwork harvested during surgery were studied by immunohistochemistry for NOS. The exclusion criteria at the beginning of the study were any ocular or general pathology associated.

RESULTS AND CONCLUSIONS

After laboratory analyses in patients with primary open angle glaucoma we observed the presence of the activity of NOS in trabecular meshwork. The trabecular distribution of NOS suggests an important role of nitric oxide in the future therapies for the glaucoma. The increase of nitric oxide makes vasodilatation and improves contractility in the trabecular meshwork; the final effect being the decrease of intraocular pressure and on the other hand the contra-apoptotic effect giving neuroprotection.

Matrix metalloproteinases and their inhibitors in the chamber angle of normal eyes and patients with primary open-angle glaucoma and exfoliation glaucoma

BACKGROUND

In glaucoma, extensive pathological changes occur in the trabecular meshwork (TM) and juxtacanalicular tissue of the chamber angle. Aqueous humor drainage is disturbed due to the accumulation of extracellular matrix (ECM) material in the outflow system. Matrix metalloproteinases (MMPs) remodel ECM material and, thus, they may have a role in regulating outflow facility and intraocular pressure (IOP). This study examined the expression of MMPs and tissue inhibitors of MMPs (TIMPs) in the chamber angle of normal eyes and in primary open-angle glaucoma (POAG) and in exfoliation glaucoma (ExG).

METHODS

TM tissues were isolated from healthy donor eyes for corneal transplantation. Specimens of the inner wall of Schlemm's canal and the juxtacanalicular tissue were collected from patients with POAG or ExG during deep sclerectomy operation. Monoclonal antibodies against MMPs (MMP-1, -2, -3, and -9) and antibodies against TIMPs (TIMP-1, -2, and -3) were used for immunohistochemical staining.

RESULTS

Immunoreactivity for MMP-2, TIMP-2, or TIMP-3 was observed in human normal TM and in the inner wall of Schlemm's canal. In general, immunoreactions for all of the tested MMPs were more intense in POAG samples than in ExG samples or in the control group. The only exception was the MMP-2 level, which was the highest in the control group. The staining intensity of MMP-1 or MMP-3 was significantly higher in POAG when compared to ExG. TIMP-1 was significantly increased in POAG compared with ExG and there were no marked differences in the levels of TIMP-2 or TIMP-3 between POAG and ExG. The ratios of MMP-1/TIMP-1 and MMP(1+2+3+9) and TIMP(1+2+3) were significantly higher in samples from POAG compared to those of ExG.

CONCLUSIONS

Our results reveal an expression imbalance between MMPs and their endogenous tissue inhibitors in tissue samples from patients with POAG and ExG. Differences in immunohistochemical reactions reflect discrete local pathogenic mechanisms involved in POAG and ExG. With respect to the proposed role of MMPs in the remodeling of ECM material, this may point to a weaker reactivity to the accumulation of ECM material in TM in ExG than POAG eyes.

Potential Role of Tissue Transglutaminase in Glaucoma Filtering Surgery

PURPOSE

Scarring of the filtering bleb site is the main cause of failure in glaucoma filtration surgery. In the present study, the role of tissue transglutaminase (tTgase) in the accumulation of extracellular matrix (ECM) proteins in these scars was investigated. Transglutaminases are enzymes capable of cross-linking ECM proteins to proteolysis-resistant complexes.

METHODS

Expression of tTgase, its reaction product epsilon-(gamma-glutamyl)-lysine, and fibronectin and their colocalization were investigated immunohistochemically in failed blebs and in an in vitro trabeculectomy model. Failed blebs were analyzed by RT-PCR for the presence of tTgase mRNA. Human Tenon fibroblasts (HTFs) were treated with transforming growth factor-beta2 (TGF-beta2). The effect was studied with immunohistochemistry, Northern blot analysis, and Western blot analysis. tTgase activity was assayed by incorporation of biotinylated cadaverine into fibronectin.

RESULTS

Expression of tTgase and epsilon-(gamma-glutamyl)-lysine was present in all failed blebs. Staining was most prominent at the rim of the Tenon cyst. In the in vitro trabeculectomy model, tTgase and epsilon-(gamma-glutamyl)-lysine were barely present at the incision side of the flap but were perspicuously increased by TGF-beta2 treatment. Enzyme and its reaction product were colocalized with fibronectin. Cultured HTFs contained a basal level of tTgase mRNA. After treatment with TGF-beta2, expression and activity of tTgase significantly increased.

CONCLUSIONS

The findings demonstrated that tTgase is present and functionally active in failed blebs. Expression and activity of tTgase appeared to be stimulated by TGF-beta2, a growth factor known to be increased in primary open angle glaucoma. Intervention at this pathway might open a new approach to prevent scarring after glaucoma filtration surgery.

Levels and Activation of Matrix Metalloproteinases in Aqueous Humor Are Elevated in Uveitis-Related Secondary Glaucoma

PURPOSE

To measure the levels of matrix metalloproteinase (MMP)-2 and tissue inhibitors of metalloproteinases (TIMP)-2 and to study the expression pattern and molecular forms of MMP-2, 8, 9, 13, and 14 and TIMP-1 and 2 in aqueous humor samples in cases of uveitis-related secondary glaucoma (USG) with a history of up to 20 years by comparison with primary open-angle glaucoma (POAG) and cataracts.

METHODS

33 aqueous humor samples were collected during intraocular surgery. MMP-2 and TIMP-2 levels were analyzed by enzyme-linked immunosorbent assay. Molecular forms and activation degrees of MMPs and TIMPs were analyzed by Western immunoblotting and zymography. The results were related to the clinical data.

RESULTS

Enzyme-linked immunosorbent assay measurements of both MMP-2 and TIMP-2 were statistically significantly increased in the USG samples relative to POAG and cataracts (P=0.002). In Western blotting all the MMPs showed increased expression and conversion to their active forms in USG, whereas in the POAG and cataract samples MMPs were found mainly in their latent forms. MMP-8, 9, 13, and 14 showed statistically significantly elevated expression in USG relative to POAG and cataracts on densitometric scanning of Western blots. On zymography, MMP-2 and 9 activation was significantly enhanced in USG compared with POAG and cataracts.

CONCLUSIONS

Increased expression of MMPs and their conversion to active forms is characteristics of the aqueous humor in USG, even with a very long history. This emphasizes the fact that increased MMP expression reflects inflammatory disease activity and is probably associated with the development of USG and its complications. Although intraocular pressure is elevated in both glaucoma types, MMP expression in POAG more closely resembles that in cataracts, and therefore the role of MMPs in USG differs very markedly from that in POAG.

Proteomics Implicates Peptidyl Arginine Deiminase 2 and Optic Nerve Citrullination in Glaucoma Pathogenesis

PURPOSE

Proteomic analyses of normal and glaucomatous human optic nerve were pursued for insights into the molecular pathology of primary open-angle glaucoma (POAG). Peptidyl arginine deiminase 2 (PAD2), an enzyme that converts protein arginine to citrulline, was found only in POAG optic nerve and was probed further for a mechanistic role in glaucoma.

METHODS

Protein identification used liquid chromatography-tandem mass spectrometry. Northern, Western, and immunohistochemical analyses measured PAD2 expression and/or protein citrullination and arginyl methylation in human and mouse optic nerve and in astrocyte cultures before and after pressure treatment. Proteins were identified after anticitrulline immunoprecipitation. In vitro translation of PAD2 was monitored in polyA RNA depleted optic nerve extracts. PAD2 shRNA transfections were evaluated in pressure-treated astrocytes.

RESULTS

Western and immunohistochemical analyses confirmed elevated PAD2 and citrullination in POAG optic nerve and decreased arginyl methylation. PAD2 was also detected in optic nerve from older, glaucomatous DBA/2J mice, but not in younger DBA/2J or control C57BL6J mice. Myelin basic protein was identified as a major citrullinated protein in POAG optic nerve. Pressure-treated astrocytes exhibited elevated PAD2 and citrullination without apparent change in PAD2 mRNA. Addition of exogenous polyA RNA to depleted optic nerve extracts yielded increased PAD2 expression in POAG but not in control extracts. Transfection with shRNA restored PAD2 and citrullination to control levels in pressure-treated astrocytes.

CONCLUSIONS

Current results support translational modulation of PAD2 expression and a possible role for the enzyme in POAG optic nerve damage through citrullination and structural disruption of myelination.

Cellular senescence in the glaucomatous outflow pathway

The mechanisms responsible for the progressive malfunction of the trabecular meshwork (TM)-Schlemm's canal (SC) conventional outflow pathway tissue in primary open angle glaucoma (POAG) are still not fully understood. To determine whether POAG is characterized by an accumulation of senescent cells, similar to what has been described in other diseases, we have compared the levels of the senescence marker senescence-associated-beta-galactosidase (SA-beta-gal) in the outflow pathway cells of POAG and age-matched control donors. POAG donors demonstrated a statistically significant fourfold increase in the percentage of SA-beta-gal positive cells. These results suggest a potential role for cellular senescence in the pathophysiology of the outflow pathway.

Paraoxonase 1 gene polymorphisms influence clinical features of open-angle glaucoma

BACKGROUND

The purpose of this study was to determine whether genetic polymorphisms affecting high-density lipoprotein (HDL)-associated antioxidant enzymes were associated with open-angle glaucoma (OAG). The rationale for this study was that the modification of low-density lipoprotein (LDL) by HDL prevents oxidative modification which can then cause dysfunction of endothelial cells.

METHODS

We studied 284 normal Japanese controls and 555 Japanese patients with OAG, including primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG). The possible associations of polymorphisms of PON1/L55M, PON1/Q192R, PON2/S311C, and PAF-AH/V279F with OAG were investigated. We compared the genotype distributions and allele frequency in controls and patient groups. The age at diagnosis, intraocular pressure (IOP) at diagnosis, and visual field score at diagnosis were examined for association with polymorphisms.

RESULTS

The distributions of genotypes and allele frequency for the four polymorphisms were not significantly different between any patient group and controls. In NTG patients, 55M carriers of the PON1 gene were significantly older at diagnosis than 55M non-carriers (P=0.001). The IOP at diagnosis was significantly higher in glaucoma patients carrying 192R in the PON1 gene than in patients not carrying 192R (P=0.006). No significant differences were seen in clinical characteristics of OAG patients in relation to other polymorphisms.

CONCLUSION

PON1 gene polymorphisms may influence the features of Japanese patients with OAG.

[Matrix-metalloproteinases and glaucoma]

PURPOSE

To analyze the matrix-metalloproteinases' activity (MMP-2 and MMP-9) in primary open angle glaucoma patients with indication for filtrating surgery.

METHODS

A prospective study, 8 months, in the Ophthalmology Department of the Central Military Hospital, with the collaboration of "Victor Babes" Institute. The study was conducted on 27 eyes with primary open glaucoma and that have underwent filtrating surgery. Patients with other ocular or systemic associated conditions were excluded. Patients were distributed in 3 groups, according to their topical treatment with prostaglandin analogs: Group A: 11 eyes with travoprost 0,004%. Group B: 9 eyes with latanoprost 0,005%. Group C: 7 eyes without prostaglandin analogs. The fragments collected during surgery were processed for imunohistochimical analysis for MMPs. It has used the indirect tristadial method: streptavidine-biotin-peroxidase.

Red blood cell (RBC) surface acetylcholinesterase showing a hemorheological pattern during glaucoma treatment

BACKGROUND

Glaucoma is currently attributed to two different possible pathogenetic mechanisms: mechanical (the ocular damage is induced by physical injury), and vascular (the ocular damage is sustained by ischemia of the optic nerve head).

AIM

We considered the possibility that several anti-glaucoma drugs (beta-blockers, carbonic anhydrase inhibitors and prostaglandins) could have an influence on optic nerve head hemorheology and oxygen supply.

MATERIALS AND METHOD

We studied 4 groups of 10 subjects each: a control group, and 3 primary open angle glaucoma (POAG) groups, treated with topical beta-blockers, (10 patients), carbonic anhydrase inhibitors (CAI), and prostaglandin analogs (PG), respectively. In these 4 groups we investigated the RBC surface AchE and cytosolic calcium levels in order to assess their possible influence on the hemorheology and microcirculation in optic nerve head blood perfusion.

RESULTS

A significant correlation (p < 0.048) was found between the RBC surface acetylcholinesterase and RBC intracytosolic calcium values in patients with POAG treated with beta-blockers. We found no significant correlation (p = n.s.) between the same patterns in the other Groups or in Controls.

CONCLUSION

These data indicate that CAI and PG drugs do not interfere with AchE in POAG patients, whereas beta-blockers negatively affect the RBC deformability.

Is GST gene polymorphism a risk factor in developing exfoliation syndrome?

PURPOSE

To evaluate the distribution of GSTM1, GSTP1, and GSTT1 gene polymorphisms in exfoliation syndrome (XFS) and the possible associations between the presence of exfoliation syndrome and glutathione S-transferase (GST) gene polymorphisms.

METHODS

Using a real-time polymerase chain reaction, GSTM1, GSTP1, and GSTT1 gene polymorphisms were detected in 60 patients with exfoliation syndrome, among which 71.7% had exfoliative glaucoma (43 patients), 16.7% had XFS with elevated intraocular pressure (IOP) (10 patients), and 11.7% had XFS only (7 cases), and in 65 otherwise healthy control group of similar age.

RESULTS

Although the exfoliation syndrome group presented a higher prevalence of the GSTM1 null and GSTP1 Ile/Val genotypes than the control group, this increase was not statistically significant. GSTT1 null and GSTP1 Val/Val polymorphisms were also not different among groups. The risk of exfoliation syndrome was not increased as the number of putative high-risk genotypes increase (p = 0.73).

CONCLUSIONS

GSTM1, GSTP1, and GSTT1 gene polymorphisms were not different among exfoliation syndrome patients, with or without glaucoma, and the controls therefore GSTM1, GSTP1, and GSTT1 gene polymorphisms did not seem to be associated with the risk of development of exfoliation syndrome.

Distribution of oxidation enzyme eNOS and myeloperoxidase in primary open angle glaucoma

Genetic factors and the influence of superoxide are known to play roles in the etiology of glaucoma. We evaluated the association between primary open angle glaucoma (POAG) and two polymorphisms in the epithelial nitric oxide synthase (eNOS) gene, and one polymorphism in the myeloperoxidase (MPO) gene. We enrolled 66 patients with POAG and 100 healthy volunteers in this study. The polymorphisms in the eNOS and the polymorphism MPO -463 G-to-A in the MPO gene were resolved by polymorphism polymerase chain reaction (PCR). There were no significant differences in the distribution of the eNOS intron -4 (P=0.481), eNOS promotor -786 (P=0.555), and MPO -463 (P=0.292) gene polymorphisms between the POAG patients and the volunteers (P-values=0.481, 0.555, and 0.292, respectively). None of the alleles from either gene differed between the groups (P-values=0.483, 0.554, and 0.183, respectively). Superoxide is closely related to glaucoma, and eNOS and MPO are two important enzymes in the free radical pathway. However, polymorphisms of the eNOS intron-4, eNOS promotor -786, and MPO -463 gene polymorphisms did not reveal significant differences between POAG patients and controls in our study. The use of these agents and other superoxide-related genes for clinical applications requires further investigation.

Evaluation of inducible nitric oxide synthase in glaucomatous optic neuropathy and pressure-induced optic nerve damage

PURPOSE

To determine whether inducible nitric oxide synthase (NOS-2) is involved in glaucomatous optic neuropathy.

METHODS

Chronic elevation of rat intraocular pressure (IOP) leading to optic nerve damage was induced by episcleral injection of hypertonic saline, which caused sclerosis and blockade of aqueous humor outflow pathways. Expression of NOS-2 in the retina and optic nerve head (ONH) was evaluated by immunohistochemistry, gene array analysis, and quantitative PCR (Q-PCR). Immunohistochemistry was also used to assess the NOS-2 level in the ONH from primary open-angle glaucoma (POAG) and nonglaucomatous human eyes. Finally, an NOS-2 inhibitor, aminoguanidine, administered orally in the drinking water, was tested for its effect on optic nerve injury in rats with ocular hypertension.

RESULTS

Chronically elevated IOP in the rat produced optic nerve damage that correlated with pressure change (r(2) = 0.77), but did not increase NOS-2 immunoreactivity in the optic nerve, ONH, or ganglion cell layer. Retinal and ONH NOS-2 mRNA levels did not correlate with either IOP level or severity of optic nerve injury. Similarly, there was no difference in NOS-2 immunoreactivity in the optic nerve or ONH between POAG and nonglaucomatous eyes. Furthermore, aminoguanidine treatment did not affect the development of pressure-induced optic neuropathy in the rat.

CONCLUSIONS

As demonstrated by several independent methods, glaucomatous optic neuropathy was not associated with a significant change in the expression of NOS-2 in the retina, ONH, or optic nerve.

C677T variant in the methylentetrahydrofolate reductase gene is a genetic risk factor for primary open-angle glaucoma

PURPOSE

To estimate the prevalence of C677T single nucleotide polymorphism in the 5,10-methylentetrahydrofolate reductase (MTHFR) gene in primary open-angle glaucoma (POAG) and pseudoexfoliation open-angle glaucoma (PEXG).

DESIGN

Case-control study

METHODS

MTHFR was assessed in 147 patients (76 POAG, 71 PEXG) and 71 control subjects with cataract. Associations of genotypes were assessed by Armitage's trend test and the corresponding odds ratio (OR) for allele positivity with 95% confidence interval (CI).

RESULTS

We observed significant evidence of a higher prevalence of C677T in POAG (9% homozygote, 49% heterozygote, 42% wildtype, P = .01, OR = 2.38, 95% CI 1.23-4.62), but not in PEXG (9% homozygote, 41% heterozygote, 50% wildtype, P = .09, OR = 1.78, 95% CI 0.91-3.50) compared with the controls (3% homozygote, 34% heterozygote, 63% wildtype).

CONCLUSIONS

The MTHFR C677T variant leading to moderate hyperhomocysteinemia may play a role in the pathogenesis of POAG acting as a genetic risk factor.

Matrix metalloproteinases and their tissue inhibitors in aqueous humor of patients with primary open-angle glaucoma, exfoliation syndrome, and exfoliation glaucoma

PURPOSE

To study extracellular matrix (ECM) metabolism by matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in aqueous humor (AH) samples collected from primary open-angle glaucoma (POAG), exfoliation syndrome (EXS), and exfoliation glaucoma (EXG) in relation to samples derived from cataract control patients.

MATERIALS AND METHODS

Seventy-one AH samples were collected during cataract extraction and trabeculectomy. The expression and molecular forms of MMP-2, -8, -9, -13, and -14 and tissue inhibitor of metalloproteinases-1 and -2 (TIMPs) were analyzed by Western immunoblotting. Gelatinase and collagenase activities were studied by zymography and type I collagen degradation assays, respectively. MMP-2 and TIMP-2 concentrations were measured by ELISA assays.

RESULTS

By Western immunoblotting all the studied MMPs were mainly in their latent form in all diagnostic groups. Zymography demonstrated that MMP-2 represents the major gelatinase in AH. Similarly, type I collagenolytic activity was low and similar in cataract and glaucoma samples. In ELISA measurements the TIMP-2 levels were significantly elevated in glaucoma and EXS samples in comparison to cataract controls (P < 0.05).

CONCLUSION

TIMP-2 is elevated in glaucomatous process over MMP-2, which support and further extend the conjuncture that the ECM accumulation rather than degradation predominates in the pathogenesis of POAG and EXG.

Altered transcripts expression of matrix metalloproteinases and their tissue inhibitors in tenon capsule of patients with glaucoma

PURPOSE

To determine the transcripts expression of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in Tenon capsule of patients with primary glaucoma and non-glaucomatous patients who serve as the control.

PATIENTS AND METHODS

Specimens of Tenon capsule were obtained intraoperatively and evaluated with the reverse transcriptase-polymerase chain reaction method. The transcripts levels of MMP-1, MMP-2, MMP-9, TIMP-1, and TIMP-2 relative to that of glyceraldehyde phosphate dehydrogenase were determined.

RESULTS

The transcripts levels of MMP-1, MMP-2, MMP-9, TIMP-1, and TIMP-2 were not correlated with age in the control group. There were differences in the transcripts expression of MMP-2 (P < 0.001), MMP-9 (P = 0.017), TIMP-1 (P < 0.001), and TIMP-2 (P = 0.001) among the control, primary open angle glaucoma, and primary angle-closure glaucoma groups (Kruscal-Wallis H test). Comparing with the controls, open angle glaucoma had decreased transcripts levels of MMP-2 (P = 0.001) and TIMP-1 (P = 0.006) while angle-closure glaucoma had decreased transcripts levels of MMP-2 (P < 0.001), MMP-9 (P = 0.004), TIMP-1 (P < 0.001), and TIMP-2 (P < 0.001) (Mann-Whitney U tests).

CONCLUSION

The transcripts expression of certain MMPs and TIMPs is altered in Tenon capsule of glaucoma patients, which might result from long-term application of topical glaucoma medications.

Angiotensin-Converting Enzyme Insertion-Deletion Polymorphism in Primary Open-Angle Glaucoma

PURPOSE

To investigate the hypothesis that primary open-angle glaucoma (POAG) is associated with a common insertion-deletion (I/D) polymorphism in the angiotensin-converting enzyme (ACE) gene.

METHODS

ACE I/D polymorphism was investigated in a control group of healthy subjects (n = 101) and in a group of patients diagnosed with POAG (n = 104). Polymerase chain reaction detection of I/D polymorphism was used to determine the presence of the two ACE alleles in the groups.

RESULTS

Neither the I/D genotype distributions nor the allele frequencies differed significantly between POAG and control subjects (DD genotype 34.6 vs. 39.6%; ID genotype 53.9 vs. 40.6%; II genotype 11.5 vs. 19.8%, p = 0.1; D allele 61.5 vs. 60%; I allele 38.5 vs. 40%, p = 0.8).

CONCLUSION

We could not identify a possible association of the I/D polymorphism in the ACE gene with POAG, however further studies with larger patient numbers in different populations are required to clarify the role of ACE gene in susceptibility to POAG.

May glutathione S-transferase M1 positive genotype afford protection against primary open-angle glaucoma?

PURPOSE

To find out whether the polymorphism at GSTM1, GSTT1 and GSTP1 loci is associated with increased susceptibility to glaucoma.

METHODS

We genotyped 153 primary open angle patients and 159 healthy controls. Genomic DNA from peripheral blood was examined using polymerase chain reaction and defined for the genetic polymorphisms of glutathione S-transferase.

RESULTS

The frequency of the GSTM1 null genotype individuals among the glaucoma patients was significanlty higher than in controls (54.9 vs 40.9%) with odds ratio of 1.64 (95% CI: 1.10-2.59). The frequency of the GSTT1 and GSTP1 in both groups were not statistically different.

CONCLUSION

The present study suggests that the GSTM1 null genotype may be a genetic risk factor for development of primary open angle glaucoma. Further associations studies in other polymorphic genes for xenobiotic-metabolizing enzymes are needed to elucidate the environmental-genetic interaction in the underlying cause of primary open angle glaucoma.

Role of oxidative stress enzymes in open-angle glaucoma

PURPOSE

To investigate the role of oxidative stress and lipid peroxidation in the pathogenesis of primary open-angle glaucoma (POAG).

MATERIALS AND METHODS

The activities of myeloperoxidase (MPO), catalase (CAT), and the levels of plasma malondialdehyde (MDA) were measured in 40 (15 men and 25 women) patients with POAG and 60 (30 men and 30 women) healthy controls.

RESULTS

There was no significant difference in the activities of CAT and MPO between the POAG patients and the controls. However, the plasma MDA level was significantly higher in patients than the controls.

CONCLUSION

The results of this preliminary study suggest that the possible alterations of plasma MDA levels may be associated with the pathogenesis of POAG, but further research is needed to understand the role of oxidative damage in this important disorder of aging.

Oxidative stress markers in aqueous humor of glaucoma patients

PURPOSE

Oxidative stress and antioxidant status in eye tissues may be associated with glaucomatous damage. The aim of this study was to establish the antioxidant status of aqueous humor of patients with primary open-angle glaucoma. For this purpose the authors measured the total reactive antioxidant potential (TRAP) and the activities of the antioxidant enzymes superoxide dismutase (SOD), catalase, and glutathione peroxidase.

DESIGN

Case control study.

METHODS

Aqueous humor was obtained at the time of surgery from 24 patients with glaucoma and 24 cataract patients; TRAP was measured by chemiluminescence. Activities of the antioxidant enzymes were measured spectrophotometrically. Superoxide dismutase activity was determined by inhibition of the rate of adrenochrome formation at 480 nm. Catalase activity was evaluated by decrease of H(2)O(2) absorbance at 240 nm. Glutathione peroxidase (GPx) activity was determined following nicotinamide adenine dinucleotide phosphate oxidation at 340 nm.

RESULTS

Total reactive antioxidant potential value of the cataract group was 124 +/- 5 micromol/l Trolox. This value was significantly decreased, by 64%, in glaucoma patients. An increase of 57% in SOD activity was observed in glaucoma patients when compared with cataract patients (41.7 +/- 2.7 U SOD/ml). Glutathione activity was threefold higher in glaucoma patients than in the cataract group (6.1 +/- 0.6 U/ml). No significant changes were found in catalase levels.

CONCLUSIONS

Oxidative stress may lead to an induction of antioxidant enzymes and contribute to TRAP decrease. Superoxide dismutase, GPx activities, and TRAP may be useful oxidative stress markers in aqueous humor of glaucoma patients.

Immunohistochemical assessment of the glial mitogen-activated protein kinase activation in glaucoma

PURPOSE

To determine whether retinal glial cells exhibit an activated phenotype in glaucomatous human eyes and whether the mitogen-activated protein kinases (MAPKs) are associated with glial activation in glaucoma.

METHODS

Activated phenotypes of retinal macroglia (astrocytes and Müller cells) and microglia were identified by morphologic assessment and immunostaining for the cell markers glial fibrillary acidic protein (GFAP) and HLA-DR, respectively, in 30 eyes obtained from glaucomatous donor eyes in comparison with normal control eyes from 20 age-matched donors. Cellular localization of the activated forms of MAPKs, including extracellular signal-regulated kinases (ERK), c-Jun amino(N)-terminal kinase (JNK), and p38, were studied in the retina of these eyes by immunoperoxidase staining and double immunofluorescence labeling with phosphorylation site-specific antibodies.

RESULTS

Retinal astrocytes and Müller cells exhibited a hypertrophic morphology and increased immunostaining for GFAP in the glaucomatous retina. Although an increase was detectable in the number and size of cells positive for HLA-DR immunostaining in the glaucomatous retina compared with the control retina, microglial activation was not as prominent or widespread as the macroglial activation detected in the same eyes. The intensity of immunostaining and the number of immunostained cells for the activated MAPKs were greater in retina sections from glaucomatous eyes than in control eyes, being most prominent for phospho-ERK. Double immunofluorescence labeling demonstrated that the increased retinal immunostaining for phospho-ERK was predominantly, but not exclusively, localized to glial cells, whereas, the immunostaining for phospho-JNK or phospho-p38 was mainly associated with nonglial cells.

CONCLUSIONS

These findings provide evidence that retinal glial cells undergo activation in the glaucomatous human retina. A prominent and persistent activation of ERK in activated glial cells suggests that this signaling pathway is probably associated with the induction and/or maintenance of the activated glial phenotype in glaucoma. Because MAPKs are involved in determination of ultimate cell fate, their differential activity in neuronal and activated glial cells in the glaucomatous retina may be associated, in part, with the differential susceptibility of these cell types to glaucomatous injury.

Increased plasma levels of 20S proteasome alpha-subunit in glaucoma patients: an observational pilot study

PURPOSE

Several reports have shown that proteasome levels may change during pathological processes. Here we investigated whether altered gene expression of the alpha-subunit of 20S proteasomes in leukocytes of glaucoma patients at the level of mRNA, shown by us earlier, is reflected by the level of protein synthesis.

METHODS

Western blot analysis was performed to determine the protein levels of the 20S proteasome alpha-subunit in leukocytes of 12 glaucoma patients (6 HTG and 6 NTG) and 6 healthy controls.

RESULTS

Plasma levels of the 20S proteasome alpha-subunit showed a 3.4+/-0.47 (mean+/-SD; p<0.0001) fold increase in glaucoma patients when compared to healthy controls. In addition, normal tension glaucoma patients revealed a more pronounced alpha-subunit expression (p<0.05) when compared to patients with high tension glaucoma.

CONCLUSIONS

During the pathological process of glaucoma, proteasome protein levels increase. This indicates that proteasome protein levels may be a diagnostic or eventually a prognostic marker for glaucomatous damage.

Identification of novel mutations causing familial primary congenital glaucoma in Indian pedigrees

PURPOSE

To determine the possible molecular genetic defect underlying primary congenital glaucoma (PCG) in India and to identify the pathogenic mutations causing this childhood blindness.

METHODS

Twenty-two members of five clinically well-characterized consanguineous families were studied. The primary candidate gene CYP1B1 was amplified from genomic DNA, sequenced, and analyzed in control subjects and patients to identify the disease-causing mutations.

RESULTS

Five distinct mutations were identified in the coding region of CYP1B1 in eight patients of five PCG-affected families, of which three mutations are novel. These include a novel homozygous frameshift, compound heterozygous missense, and other known mutations. One family showed pseudodominance, whereas others were autosomal recessive with full penetrance. In contrast to all known CYP1B1 mutations, the newly identified frameshift is of special significance, because all functional motifs are missing. This, therefore, represents a rare example of a natural functional CYP1B1 knockout, resulting in a null allele (both patients are blind).

CONCLUSIONS

The molecular mechanism leading to the development of PCG is unknown. Because CYP1B1 knockout mice did not show a glaucoma phenotype, the functional knockout identified in this study has important implications in elucidating the pathogenesis of PCG. Further understanding of how this molecular defect leads to PCG could influence the development of specific therapies. This is the first study to describe the molecular basis of PCG from the Indian subcontinent and has profound and multiple clinical implications in diagnosis, genetic counseling, genotype-phenotype correlations and prognosis. Hence, it is a step forward in preventing this devastating childhood blindness.

Group II phospholipase A2 content of tears in patients with senile cataract and primary open-angle glaucoma

PURPOSE

To determine the group II phospholipase A2 (PLA2) content of tears in patients with senile cataract or primary open-angle glaucoma (POAG) and to compare it with the PLA2 content of tears in age-matched healthy controls.

METHODS

The PLA2 concentration of tears was measured with time-resolved fluoroimmunoassay in 21 patients with senile cataract, 23 patients with POAG and in 40 healthy controls.

RESULTS

The PLA2 content of tears was 38.3+/-30.1 microg/ml in patients with senile cataract, 32.1+/-22.3 microg/ml in patients with POAG, and 36.6+/-31.1 microg/ml in healthy controls. There were no significant differences between the patient and the control groups.

CONCLUSIONS

We conclude that neither senile cataract nor POAG has any effect on the PLA2 content of tears.

Expression of cyclooxygenase-1 and -2 in normal and glaucomatous human eyes

PURPOSE

Primary open-angle glaucoma (POAG) is the predominant form of chronic glaucoma, but the underlying pathologic mechanisms are largely unknown. Because prostaglandins (PGs) have been introduced into POAG treatment with remarkable success, this study was undertaken to investigate whether a change in the expression of the PG-synthesizing enzymes cyclooxygenase (COX)-1 and -2 might be involved in the pathogenesis of POAG.

METHODS

Expression of COX-1 and -2 was assessed by confocal laser microscopy, immunohistochemistry, Western blot analysis, and real-time RT-PCR in human eyes with different forms of glaucoma (primary open-angle, angle-closure, congenital juvenile, and steroid-induced), as well as in age-matched control eyes. Additionally, PGE2 was measured in aqueous humor by means of an enzyme-linked immunoassay as a product of COX activity.

RESULTS

In normal eyes, ocular COX-1 and -2 expression were largely confined to the nonpigmented secretory epithelium of the ciliary body. By immunohistochemistry and real-time RT-PCR, COX-2 expression was completely lost in the nonpigmented secretory epithelium of the ciliary body of eyes with end-stage POAG, whereas COX-1 expression was unchanged. By immunohistochemistry, in the ciliary bodies of eyes in five patients with diagnosis of early POAG, eyes in two had complete loss of COX-2 expression and in three showed only a few remaining scattered COX-2-expressing cells. COX-2 expression in the ciliary body was also lost in patients with steroid-induced glaucoma and was reduced in patients receiving topical steroid treatment. Eyes of patients with either congenital juvenile or angle-closure glaucoma showed COX-2 expression indistinguishable from control eyes. Aqueous humor of eyes with POAG contained significantly less PGE2 than control eyes.

CONCLUSIONS

Both cyclooxygenase isoforms are constitutively expressed in the normal human eye. Specific loss of COX-2 expression in the nonpigmented secretory epithelium of the ciliary body appears to be linked to the occurrence of POAG and steroid-induced glaucoma.

The relationship between gelatinase A activity in aqueous humor and glaucoma

PURPOSE

To investigate whether abnormal expression of gelatinase A in aqueous humor may be related to the development of glaucoma, the activity of gelatinase A in aqueous humor of patients with glaucoma and patients with cataract was measured and compared.

METHODS

Six primary patients with open-angle glaucoma (POAG), four patients with chronic angle closure glaucoma (CACG), four patients with normal tension glaucoma (NTG), and 14 patients with cataract were enrolled. The aqueous humor of each patient was collected during surgery, and total protein concentration and gelatinase activity in the aqueous humor were measured by protein assay kit and zymography, respectively.

RESULTS

In patients with POAG, total protein concentration doubled and gelatinase A activity increased by 3.9 times compared with patients with cataract. However, there were no statistically significant differences in total protein concentration and gelatinase A activity in patients with CACG or NTG compared with patients with cataract.

CONCLUSION

The development of POAG may be associated with the abnormal expression of gelatinase A in aqueous humor.

Association study of the 5' flanking regions of endothelial-nitric oxide synthase and endothelin-1 genes in familial primary open-angle glaucoma

1. Endothelium-derived substances are important regulators of the microcirculation. Endothelium-derived nitric oxide (NO), which is catalysed by nitric oxide synthase (NOS), is a potent modulator of vascular tone in the human ophthalmic artery, which is normally in a state of constant vasodilation due to the actions of NO. Endothelin-1 (ET-1) produces vasoconstriction of the anterior optic nerve vasculature and may be associated with glaucomatous optic neuropathy. The aetiology of primary open-angle glaucoma (POAG) remains largely unknown. Thus, alterations in the regulatory sequences of the genes coding for endothelium-derived NOS (eNOS) and ET-1 may have important effects in the development of POAG and were looked for in the present study. 2. In 56 patients with familial POAG and in 100 control subjects with no family history of hypertension or POAG, we examined the 5' flanking sequences of the eNOS and ET-1 genes, which contain many positive and negative regulatory regions affecting gene transcription, using polymerase chain reaction-based single strand conformation polymorphism analysis, to search for alterations. No variant in the promoter region of the ET-1 gene was observed in familial POAG or controls. Using three primer sets spanning 706 b.p. of the eNOS gene, we observed alterations in 11 of 56 (20%) familial POAG members and in seven of 100 (7%) controls. Sequence analysis demonstrated a C/T substitution at the 5' sequence position nucleotide (nt) -690 from the transcription start site, which lies between the cAMP regulatory element (nt -726 to -732) and an activator protein-1 binding domain (nt -655 to -661). 3. In summary, genotypic and allelic frequency analysis found no association between alterations in the promoter region of the ET-1 gene and familial POAG. A variant in the promoter region of the eNOS gene was seen in a significant percentage of familial POAG patients. Future expression studies will determine whether this polymorphism results in altered eNOS gene expression.

Cyclooxygenase-1 and cyclooxygenase-2 in the human optic nerve head

To investigate the hypothesis that eicosanoids act as cellular mediators in the optic nerve head of normals and of patients with glaucoma, we have determined the presence of the two cyclooxygenase (COX) isoforms in human tissue. Histological sections of optic nerve heads were studied by immunohistochemistry. Age matched normal donors were compared with eyes from glaucoma patients with moderate to severe nerve damage. Polyclonal antibodies to human COX-1 and COX-2 were localized with immunoperoxidase staining. Specific antibodies for vascular endothelia and microglia were also colocalized. In normal and glaucomatous eyes. COX-1 was localized exclusively to the prelaminar and lamina cribrosa regions of the optic nerve head. No staining for COX-1 was observed in the nerve fiber layer or the myelinated optic nerve. COX-1 was associated with the astrocytes of the glial columns and the cribriform plates, but not with the endothelia lining the capillaries. In glaucoma, more astrocytes appeared to be stained with antibody to COX-1 than in normals and staining was intensely perinuclear. There was no staining for COX-2 in normal tissue. A few COX-2 positive cells were found in the prelaminar, lamina cribrosa and postlaminar regions of the glaucomatous optic nerves. Positive staining for COX-2 was not associated with microglia. COX-1 is constitutively present in astrocytes that are localized exclusively to the prelaminar and lamina cribrosa regions of the human optic nerve head. Eicosanoids, synthesized by COX-1 in this tissue, may have a homeostatic and a neuroprotective role related to the axons of the retinal ganglion cells. The sparse presence of COX-2 in glaucomatous tissue probably reflects the lack of inflammation associated with glaucomatous optic neuropathy.

Decreased 3 alpha-hydroxysteroid dehydrogenase activity in peripheral blood lymphocytes from patients with primary open angle glaucoma

The purpose of the present study was to determine whether peripheral blood lymphocytes (PBL) from primary open angle glaucoma (POAG) patients have reduced 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD) activity as was previously found in POAG-derived cultured trabecular meshwork cells. The availability of PBL from both POAG and control patients makes this a useful system for studying the association of decreased 3 alpha-HSD activity with POAG. PBL were isolated from the venous blood of 17 POAG patients and 22 non-glaucoma controls and assayed for 3 alpha-HSD activity with tritiated 5 beta-dihydrocortisol as a substrate. The mean 3 alpha-HSD activity +/- S.E.M., expressed in comparable units of specific activity, of the POAG derived PBL was 13.8 +/- 1.3 U as compared to 32.8 +/- 2.0 U for control cells. This reduction (> 50%) was statistically significant (P < 0.001). Quantitative immunoblot analysis of PBL indicated that the POAG and control cells, despite their difference in 3 alpha-HSD activity, had nearly identical amounts of 3 alpha-HSD protein. The molecular weight of PBL 3 alpha-HSD from both groups of patients was 38,000, the same as previously reported for human liver. The results of this study show an association of decreased PBL 3 alpha-HSD activity and POAG which was not related to antiglaucoma therapy. The reduced levels of 3 alpha-HSD activity in the readily obtainable PBL may serve as a marker for POAG or those at risk for developing the disease.

Alterations of ocular nitric oxide synthase in human glaucoma

PURPOSE

The authors recently reported that sites of outflow resistance and regulation in the human eye are highly enriched in the endothelial isoform of nitric oxide (NO) synthase (ecNOS). In vasculature, ecNOS activation is associated with altered vascular resistance and, in the stomach, defects in NO are associated with pathologic gastric hypertension. Because human glaucoma sometimes is associated with an increase in intraocular pressure and resistance changes in the aqueous outflow pathway (OP), the authors have investigated the possibility that alterations in NO or defects in NO-synthesizing tissues might exist in glaucomatous eyes.

METHODS

Occurrence, distribution, and extent of sites of ocular NO production in the anterior segments of 16 normal eyes (10 patients) and 17 eyes (12 patients) with a history of primary open-angle glaucoma (POAG) were determined using the NO-indicator marker, NADPH-diaphorase (NADPH-d), which is known to colocalize with ecNOS immunoreactivity. Analysis of NADPH-d reactivity in tissues was combined with examination of overall cell distribution and use of neuron-specific markers.

RESULTS

The ciliary muscle (CM) and OP of glaucomatous eyes showed marked differences in the amount and distribution of NADPH-d and alterations in gross structure. NADPH-d reactivity was decreased in trabecular meshwork (TM) and Schlemm's canal, and there was a marked reduction of anterior longitudinal CM fibers that insert near (and may normally regulate resistance in) the TM.

CONCLUSION

Abnormalities in NO or NO-containing cells occur in POAG. These abnormalities may be causally related to glaucoma or may be a manifestation of the disease or its treatment. In either case, such alterations, together with recent pharmacologic studies showing that NO-mimicking nitrovasodilators alter IOP, indicate that NO has relevance to the course, treatment, or both, or some forms of this disease.

Increased hydrolase activities in the human trabecular meshwork of glaucomatous eyes

Alterations in the metabolic functions of trabecular meshwork (TM) cells are thought to be involved in the pathogenesis of primary open-angle glaucoma (POAG). In an investigation of this possibility, 30 trabeculectomy specimens from patients with POAG were examined histochemically for 11 lysosomal and membrane-bound enzymes. The patients ranged from 48 to 87 years in age. The degree of enzyme staining was compared with that of 15 age-matched controls obtained from an eye bank at less than 24 h after death. There was no history of eye disease in the controls. The enzymes examined were: dipeptidylpeptidases II and IV (DPPII and IV); beta-glucuronidase (beta-GLUC); acid-beta-galactosidase (s beta-GAL); N-acetyl-beta-D-glucosaminidase (NAG); nonspecific esterase (UE); acid phosphatase (SP); alkaline phosphatase (ALP); gamma-glutamyltransferase (GGT); and aminopeptidase A and M (APA and APM). Evaluation of the specimens was performed by two observers and by computer-aided optic densitometry. Results showed increased staining of SP, UE, GGT and APM in the pathological specimens as compared with the controls. SP and UE indicate phagocytic activity, APM is involved in collagen turnover and GGT participates in both drug detoxification and the breakdown of glutathione in the gamma-glutamyl cycle. Our observations show different hydrolase activities in the TM cells of human glaucomatous eyes as compared with normal values, suggesting that such metabolic differences may be related to the pathogenesis of POAG.

[Chemiluminescence and activity of acid phosphatase in the drainage zone of the eye in glaucoma patients]

Ocular drainage zone tissue, obtained during surgery from patients with glaucoma, was examined. Chemiluminescence has revealed changed amplitude of the flash and the value of its total light volume. Increased intensity of peroxide chemiluminescence evidences enhanced processes of lipid peroxidation in the tissue and a reduced antioxidant level. Histochemical study of acid phosphatase has discovered destabilization of lysosomal membranes, more marked during an acute attack of glaucoma.

Defects in cortisol-metabolizing enzymes in primary open-angle glaucoma

Assays of cortisol-metabolizing enzymes in homogenates of human trabecular meshwork cells under optimal conditions revealed two defects in primary open-angle glaucoma (POAG): one is a marked increase in delta 4-reductase and the other is a decrease in 3-oxidoreductase. Experiments indicated that the differences in enzyme activities seen between POAG and nonPOAG trabecular meshwork derived cell homogenates were due to altered amounts of enzymes rather than to alterations in cofactor availability, pH, or endogenous activators or inhibitors. This clearly demonstrates an enzymatic defect(s) in POAG which may be the basis for the ocular hypertension and sensitivity to exogenous glucocorticoids seen in this disorder.