Matrix metalloproteinases and their inhibitors in exfoliation syndrome

Platelet Proteome Reveals Novel Targets for Hypercoagulation in Pseudoexfoliation Syndrome

Pseudoexfoliation syndrome (PEX) is characterized by the accumulation of abnormal extracellular matrix material in ocular and non-ocular tissues, including blood vessel walls. Clot-forming dysfunction might be responsible for venous thrombosis in PEX. We investigated global coagulation, the proteome, and functions of platelets in PEX patients and aimed to determine prognostic biomarkers for thrombosis risk in PEX. Peripheral blood was collected from PEX and retinal vein occlusion (RVO) patients, and age-sex matched controls. Viscoelastic hemostasis was evaluated by rotational thromboelastometry (ROTEM). Platelet markers (CD41, CD42, CD61, and CD62p) and endothelial markers (P-selectin, E-selectin, and von Willebrand factor) were investigated by flow cytometry and ELISA, respectively. The platelet proteome was analyzed by 2D fluorescence difference gel electrophoresis followed by mass spectrometry. Clot formation time (CFT) is significantly reduced in PEX patients compared to the controls (p < 0.05). P-selectin levels were higher in PEX patients than in controls (p < 0.05); E-selectin and von Willebrand factor remained unchanged. The monitorization of CFT by ROTEM, and soluble P-selectin, may help assess thrombotic risk in PEX patients. Proteomic analysis revealed differential expression of Profilin-1 in platelets. Profilin-1 regulates the stability of actin-cytoskeleton and may contribute to impaired platelet hemostatic functions. Increased P-selectin levels together with impaired coagulation dynamics might be responsible for the thrombotic events in PEX disease.

Prolidase activity in aqueous and serum samples of cataract cases with Pseudoexfoliation syndrome

Pseudoexfoliation syndrome (PEX) represents an age-related systemic disease that is characterized by the accumulation of extracellular matrix material in ocular tissues and visceral organs. Abnormal matrix remodeling is thought to be one of the important factors in the etiopathogenesis of the disease. Prolidase represents an enzyme, which takes a significant part in collagen biosynthesis and remodeling of the extracellular matrix. The purpose of the current research was to assess the prolidase enzyme activity in the aqueous and serum samples of subjects with PEX. The study population consisted of 66 subjects, involving 33 subjects with age-related cataract among patients with PEX and 33 subjects with age-related cataract without PEX. The prolidase activity measurement was performed using the modified Chinard's method. Significantly increased aqueous prolidase activity was detected in the group with PEX (p < 0.01). Despite about a three times higher increase in the serum prolidase activity of the group with PEX in comparison with the control group, the two groups did not differ statistically significantly (p > 0.05). The high prolidase enzyme activity in the aqueous samples of subjects with PEX suggests that the collagen cycle and the remodeling of the extracellular matrix are accelerated. These results can be a guide for understanding the formation mechanisms of PEX.

Novel Data about Association of the Functionally Significant Polymorphisms of the MMP9 Gene with Exfoliation Glaucoma in the Caucasian Population of Central Russia

AIM

This study aimed to investigate the role of functionally significant polymorphisms of the MMP1, MMP3, and MMP9 genes in the development of exfoliation glaucoma (XFG) in the Caucasian population of Central Russia.

METHODS

The study sample consisted of 724 participants, including 328 patients with XFG and 396 individuals in the control group. The participants were of Russian ethnicity (self-reported) born in Central Russia. The participants were genotyped at 8 functionally significant polymorphisms of the MMP genes (rs3918242, rs3918249, rs17576, rs3787268, rs2250889, rs17577 MMP9, rs679620 MMP3, and rs1799750 MMP1). The association analysis was performed using logistic regression. Two polymorphisms, which were associated with XFG, and 12 polymorphisms linked to them (r2 ≥ 0.8) were analyzed for their functional significance in silico.

RESULTS

Allele C of rs3918249 MMP9 was associated with XFG according to the additive model (OR = 0.75, 95% CI: 0.56-0.93, pperm = 0.015), and allele G of the rs2250889 MMP9 locus was associated with XFG according to the additive (OR = 1.59, 95% CI: 1.10-2.29, pperm = 0.013) and dominant (OR = 1.68, 95% CI: 1.11-2.56, pperm = 0.016) models. Two XFG-associated loci of the MMP9 gene and 12 SNPs linked to them had a significant regulatory potential (they are located in the evolutionarily conserved regions, promoter and enhancer histone marks, the DNAase-hypersensitivity regions, a region binding to regulatory protein, and a region of regulatory motifs) and may influence the expression of 13 genes and alternative splicing of 4 genes in various tissues and organs related to the pathogenesis of XFG.

CONCLUSION

Allele C rs3918249 MMP9 decreased risk for XFG (OR = 0.75), and allele G of the rs2250889 MMP9 locus increased risk for XFG (OR = 1.59-1.68) in the Caucasian population of Central Russia.

Bone Mineral Density and 25-Hydroxyvitamin D Levels in Patients With Ocular Pseudoexfoliation Syndrome: A Case-Control Study

The objective of this study was to evaluate bone mineral density (BMD) and 25-hydroxyvitamin D (25(OH)D) levels in patients with ocular pseudoexfoliation (PEX) syndrome. Subjects with ocular PEX syndrome were included in the PEX group and subjects without PEX syndrome were defined as the control group. 25(OH)D levels were measured by chemiluminescence microparticle immunoassay method. BMD measurements were obtained from the femoral neck and lumbar spine by using dual-energy X-ray absorptiometry. The results were expressed as gram per square centimeter, T-scores (standard deviation compared to a healthy 30-yr-old male), and Z-scores (standard deviation compared to the subject's age). Independent t-test was used to compare the mean and medians of the groups. The PEX group consisted of 23 subjects with a mean age of 71.09 ± 2.02 yr and the control group consisted 46 subjects with a mean age of 67.04 ± 1.34 yr. There was no significant difference between the groups as regards the BMD measurements (gram per square meter), T-scores, and Z-scores. Both groups have low 25(OH)D, yet vitamin 25(OH)D levels were similar in the groups (p > 0.05). In the light of our results, although patients with ocular PEX have low BMD and 25(OH)D, BMD and 25(OH)D do not appear to be linked to ocular PEX syndrome in our study population.

Correlation of Aqueous Humor Lysyl Oxidase Activity with TGF-ß Levels and LOXL1 Genotype in Pseudoexfoliation

PURPOSE

Pseudoexfoliation (PXF) is a microfibrillopathy involving disordered elastogenesis. Abnormal extracellular matrix (ECM) production underlies the pathophysiology of PXF. The enzyme Lysyl oxidase (LOX) and its isoforms are known to cross-link the elastin and collagen. Though the etiopathogensis of PXF is not well understood, studies report on the genetic risk involving LOXL1 gene. This study aims to screen LOXL1 coding variants rs1048661 and rs3825942 in the South Indian population and the implication of the single nucleotide polymorphism (SNP) with LOX activity. The levels of transforming growth factor β (TGF-β) in aqueous humor and its correlation with the LOX activity were also examined.

METHODS

Blood, plasma, and aqueous aspirates were prospectively collected from PXF cases with and without glaucoma and cataract cases as controls. DNA was extracted from 48 PXF cases without glaucoma, 12 PXF cases with glaucoma, and 40 age-matched cataract-alone controls without PXF/glaucoma for analyzing LOX SNPs. LOX activity was measured in aqueous humor and plasma of 30 PXF cases without glaucoma, 24 age-matched cataract-alone controls without PXF/glaucoma, and 14 PXF cases with glaucoma. Protein levels of LOX, LOXL1, LOXL2, and total TGF-β were estimated in plasma and aqueous humor by ELISA.

RESULTS

The specific activity of LOX in aqueous humor was found to be significantly lowered in PXF cases compared with cataract-alone controls (p = 0.014). This decrease in LOX activity in PXF cases was associated with high-risk GG haplotype. However, this was not statistically significant and a larger sample size is warranted. TGF-β1 and TGF-β2 negatively correlated with LOX activity in aqueous humor (p = 0.028; p = 0.046, respectively).

CONCLUSIONS

The LOXL1 SNPs, rs1048661 and rs3825942, are associated with PXF in the South Indian population correlating with lowered LOX activity in the aqueous humor. The increased level of total TGF-β in the aqueous humor of PXF cases is possibly associated with LOX regulation which needs further investigation.

Pseudoexfoliation syndrome and cardiovascular diseases

Pseudoexfoliation (PEX) syndrome is a well-recognized late-onset disease caused by a generalized fibrillopathy. It is linked to a broad spectrum of ocular complications including glaucoma and perioperative problems during cataract surgery. Apart from the long-known intraocular manifestations, PEX deposits have been found in a variety of extraocular locations and they appear to represent a systemic process associated with increased cardiovascular and cerebrovascular morbidity. However, as published results are inconsistent, the clinical significance of the extraocular PEX deposits remains controversial. Identification of PEX deposits in the heart and the vessel wall, epidemiologic studies, as well as, similarities in pathogenetic mechanisms have led to the hypothesis of a possible relation between fibrillar material and cardiovascular disease. Recent studies suggest that PEX syndrome is frequently linked to impaired heart and blood vessels function. Systemic and ocular blood flow changes, altered parasympathetic vascular control and baroreflex sensitivity, increased vascular resistance and decreased blood flow velocity, arterial endothelial dysfunction, high levels of plasma homocysteine and arterial hypertension have all been demonstrated in PEX subjects. Common features in the pathogenesis of both atherosclerosis and PEX, like oxidative stress and inflammation and a possible higher frequency of abdominal aorta aneurysm in PEX patients, could imply that these grey-white deposits and cardiovascular disorders are related or reflect different manifestations of the same process.

Matrix metalloproteinase-2, tissue inhibitor of matrix metalloproteinase-2, and transforming growth factor beta 1 in the aqueous humor and serum of patients with pseudoexfoliation syndrome

Purpose

The aim of the study reported in this article was to determine the presence and quantitative differences of matrix metalloproteinase-2 (MMP-2), its tissue inhibitor (TIMP-2) and transforming growth factor beta 1 (TGF-β1) in the aqueous humor and serum samples of patients with pseudoexfoliation (PEX) syndrome.

Methods

Aqueous humor and serum samples were collected from 32 patients with PEX syndrome (with and without glaucoma) and a control group, who underwent routine cataract surgery. Levels of MMP-2, TIMP-2, and TGF-β1 were determined by specific immunoassays (enzyme-linked immunosorbent assay).

Results

MMP-2, TIMP-2, and TGF-β1 were identified in aqueous humor and serum samples from all groups of patients. The aqueous and serum samples of MMP-2, TIMP-2, and TGF-β1 showed no significant differences between PEX syndrome and control groups. Serum levels of MMP-2, TIMP-2, and TGF-β1 were statistically greater than their aqueous levels (P<0.05), except for TIMP-2 levels in the control group.

Conclusion

No statistically significant difference among mean MMP-2, TIMP-2, and TGF-β1 levels in both aqueous humor and serum samples was found between patients with PEX syndrome and the control group. It is important to simultaneously evaluate serum and aqueous samples from patients with PEX syndrome, which is related to an impaired blood–aqueous barrier.

Pseudoexfoliation syndrome, a systemic disorder with ocular manifestations

Pseudoexfoliation syndrome (PXS) is a systemic condition with eye manifestations. In the eye, pseudoexfoliation material deposits on various structures of the anterior segment. The nature of this material is mostly fibrillar with fibers made up of microfibrils and coated with amorphous material. The composition of these fibrils is diverse and includes basement membrane components as well as enzymes involved in extracellular matrix maintenance. Pseudoexfoliation is the most common cause of secondary open-angle glaucoma (pseudoexfoliation glaucoma, PXG) worldwide. The goal of this review is to summarize our knowledge on the genetics of this systemic disorder and its resultant ocular manifestations. PXS familial aggregation suggests genetic inheritance. PXS has been strongly associated with single nucleotide polymorphisms (SNPs) of the lysyl oxidase-like 1 (LOXL1) gene on chromosome 15q24.1. Two of these SNPs confer a higher than 99% population attributable risk for PXS and PXG in the Nordic population; however, they carry different risks in different populations. The high risk haplotypes also vary among different populations. LOXL1 is one of group of the enzymes involved in the cross-linking of collagen and elastin in the extracellular matrix. Its function in connective tissue maintenance has been confirmed in mice; however, its actual role in PXS remains unclear. Contactin-associated protein-like 2 also has a strong genetic association with PXS in a German cohort and is an attractive candidate molecule. It encodes for a protein involved in potassium channel trafficking. Other candidate genes linked to PXS include lysosomal trafficking regulator, clusterin, adenosine receptors, matrix metalloproteinase-1 (MMP1), and glutathione transferase. These genes may be modifying genes for development of PXS and PXG.

Aqueous humor and plasma levels of vascular endothelial growth factor and nitric oxide in patients with pseudoexfoliation syndrome and pseudoexfoliation glaucoma

PURPOSE

To investigate levels of vascular endothelial growth factor (VEGF) and nitric oxide (NO) in the aqueous humor and plasma of patients with pseudoexfoliation syndrome (PXS) and pseudoexfoliation glaucoma (PXG), compared with controls.

METHODS

This prospective study involved 37 patients with PXS, 15 with PXG, and 32 control subjects in whom cataract surgery was indicated. Aqueous humor and plasma VEGF and NO levels were measured with enzyme-linked immunosorbent assay and chemiluminescence methods, respectively.

RESULTS

Aqueous humor and plasma VEGF concentrations were higher in patients with PXS and PXG than in controls (P<0.001). Aqueous humor NO concentrations were higher in patients with PXS and PXG than in controls (P<0.05 and P=0.001, respectively). Plasma NO concentrations did not differ between the 3 groups. Aqueous humor and plasma VEGF and NO levels were not significantly different in patients with PXS versus PXG. VEGF and NO levels showed no significant correlation among the 3 groups (P>0.05).

CONCLUSIONS

Elevated aqueous humor VEGF and NO levels and plasma VEGF concentrations in eyes with PXS and PXG can be explained by the ischemic nature of these disorders. The lack of correlation between VEGF and NO levels may indicate impaired downregulation, which may have a role in the progression to PXG.

Pseudoexfoliation as a risk factor for peripheral vascular disease: a case-control study

AIM

To determine the association between pseudoexfoliation (PEX) and peripheral vascular disease (PVD) among age-related cataract.

SETTING

Iladevi Cataract and IOL Research Center, Ahmedabad, India.

MATERIAL AND METHODS

An observational age-matched case-control study of 160 patients over 60 years of age with age-related cataract. A total of 40 subjects with PEX (cases) were compared with 120 subjects with cataract but without PEX (controls). A detailed medical history, including hypertension, diabetes mellitus, cerebrovascular stroke and ischaemic heart disease, was recorded. Ankle brachial index (ABI) was used to determine the risk of PVD among age-related cataract patients. Color Doppler imaging was performed on the brachial and dorsalis pedis artery to measure ABI and detect PVD. Least mean ABI was the main outcome measure, as low ABI indicates higher risk for PVD. The lowest mean ABI was measured for each subject. An ABI ratio of <0.90 was considered abnormal. The Mann-Whitney U-test and logistic regression were used for analysis.

RESULTS

The lowest mean ABI in the controls was 0.98 ± 0.03 (SD; a range of 0.86-1.08) as compared with 0.88 ± 0.02 (SD) among the cases (a range of 0.79-0.92; P < 0.001). When compared with controls, cases had a lower ABI (P < 0.001) irrespective of the presence or absence of systemic illness. On multiple regression analysis adjusting for systemic illness, the presence of PEX increased the odds of a low ABI group 150 times (P < 0.001).

CONCLUSION

Subjects with cataract and PEX had a significantly lower ABI as compared with controls (cataracts without PEX). PEX is associated with and may be a risk factor for PVD.

Application of anodic stripping voltammetry for zinc, copper, and cadmium quantification in the aqueous humor: implications of pseudoexfoliation syndrome

Anodic stripping voltammetric (ASV) procedure, using mercury film electrode, was optimized and applied to determine the concentrations of zinc, cadmium, and copper in the aqueous humor. Concentration levels as low as 1 ppb of the test metals was possible to be detected using short electrolysis times (120 s) and microquantities of aqueous humor (up to 35 μL). As a first application of the voltammetric analysis of trace metals in the aqueous humor, the role of the three selected trace elements in the pseudoexfoliation (PEX) syndrome was examined. Samples from aqueous humor were collected during cataract extraction from patients with and without PEX. The zinc and copper concentration levels in the aqueous humor did not show statistically significant difference in the study and control group. Cadmium was detected in a small number of samples, without however statistical differences between the two groups. ASV proved to be a highly precise and sensitive tool for the quantification of heavy metal ions in aqueous humor. Further studies may lead to useful conclusions for the role of zinc, copper, or cadmium in PEX syndrome.

Glutathione and Lipid Peroxide Changes in Pseudoexfoliation Syndrome

PURPOSE

To investigate the oxidative status of the aqueous humor of patients with pseudoexfoliation (PEX) syndrome.

METHODS

Aqueous humor samples obtained during cataract surgery of patients with PEX syndrome and normal age-matched control subjects were examined for changes in the levels of glutathione (GSH), glutathione disulfide (GSSG), and TBA reactive species (TBARS), products of lipid peroxidation. GSH, GSSG, and TBARS were determined by specific fluorescent assays.

RESULTS

Compared to normal controls, PEX syndrome aqueous humor samples showed a decrease of up to 28% of GSH concentration, and GSSG was increased up to 23%. The ratio of GSH/GSSG was 1.7-fold decreased in PEX syndrome samples. TBARS levels were increased by 100% in the PEX aqueous humor samples as compared to the controls.

CONCLUSIONS

High levels of GSSG and TBARS indicate high oxidative stress, as well as the decrease in the ratio of GSH/GSSG. Our findings suggest a role for oxidation stress in the pathogenesis and the progression of PEX syndrome.

Pseudoexfoliation syndrome prevalence in Greek patients with cataract and its association to glaucoma and coronary artery disease

PURPOSE

To investigate the prevalence of glaucoma and coronary artery disease (CAD) in patients with cataract and pseudoexfoliation (PEX) syndrome.

METHODS

Cross-sectional study of 2140 consecutive patients with cataract admitted at the University Hospital of Patras, Greece, for cataract surgery. Only patients with senile cataract were included in this study. All patients underwent a complete ophthalmological examination that included slit-lamp evaluation with dilated pupil for PEX material in the anterior segment, intraocular pressure (IOP) measurements, and optic disc cup examination. They also underwent an evaluation for CAD by a cardiologist. CAD was considered present if a patient had a history of myocardial infarction, or ischaemia, or abnormal coronary angiography. The patients were classified into two groups: the PEX and the non-PEX group.

RESULTS

One thousand and eighty-eight (50.8%) patients were men and 1052 (49.2%) were women. The overall prevalence of PEX syndrome was found to be 27.9% and it was found to increase with progressing age. Bilateral PEX was more frequent than unilateral PEX, with the percentage of bilateral PEX raising with progressing age. A total of 132 patients (22.1%) in the PEX group exhibited glaucoma, while in the non-PEX group only 2.5% suffered glaucoma. PEX was also found to be positively associated with the risk for CAD among subjects 50 years or older. No association between CAD and glaucoma was found.

CONCLUSIONS

PEX syndrome constitutes a major glaucoma risk factor and a CAD risk factor. Patients with PEX should be informed and examined frequently as the risk is present throughout.

Ocular and systemic pseudoexfoliation syndrome

PURPOSE

To provide an update on most recent developments regarding ocular and systemic manifestations and complications, clinical diagnosis and management, and molecular pathophysiology of pseudoexfoliation (PEX) syndrome, and to discuss future tasks and challenges in this field.

DESIGN

Perspective.

METHODS

Review of recent literature and authors' own clinical and laboratory studies.

RESULTS

PEX syndrome is a common age-related generalized fibrotic matrix process of worldwide significance, which may not only cause severe chronic open-angle glaucoma and cataract, but also a spectrum of other serious spontaneous and surgical intraocular complications. Recent progress and advances have led to (1) improvements in clinical management by understanding the effects of the PEX process on ocular tissues, by refining diagnostic criteria, by applying new treatment regimes, and by developing preventive strategies to reduce surgical complications; (2) increasing evidence for systemic associations of PEX with cardiovascular and cerebrovascular morbidity; and (3) new insights into the molecular pathophysiology by analyzing the composition of PEX material, the differential gene expression of affected tissues, and key factors involved in pathogenesis. The current pathogenetic concept describes PEX syndrome as an elastic microfibrillopathy involving transforming growth factor-beta1, oxidative stress, and impaired cellular protection mechanisms as key pathogenetic factors.

CONCLUSIONS

Future tasks and challenges comprise epidemiologic prevalence and genetic studies of PEX syndrome, prospective randomized clinical and histopathological screening studies on its systemic manifestations and associations, and intensified basic research on differential protein and gene expression, animal and in vitro models, as well as potential biomarkers for PEX syndrome and its associated glaucoma.

Collagen type IX and HNK-1 epitope in tears of patients with pseudoexfoliation syndrome

Pseudoexfoliation syndrome (PEX) is an age-related condition, which may cause open-angle glaucoma and has increasing interest since it seems to affect additional human tissues, i.e., cardiovascular tissue, skin, and still lacks elucidated pathogenesis. Collagen type IX and HNK-1 epitope have been considered characteristic constituents of the aqueous humour of PEX patients, since their amounts were increased in PEX aqueous humour compared to normal eyes. Since it has been proposed that the initial manifestations of PEX syndrome occur in conjunctiva, the present study was undertaken to investigate the presence of the same antigens in tears of PEX patients and their possible use as the biochemical markers for early diagnosis. Tears of PEX patients and healthy individuals were subjected to western blotting analysis for various basement membrane components identified in aqueous humour. It was found that collagen type IX and HNK-1 epitope were present in tears, the amount of the former being increased 2.7 times compared to normal (P<0.05), surprisingly high as compared with total protein or lysozyme activity in tears, which were found to be increased in PEX patients about 25% with no statistical differences (P approximately 0.4). The results suggest the possible use of tears' collagen type IX for the diagnosis of PEX syndrome.

Elevated aqueous humour tissue inhibitor of matrix metalloproteinase-1 and connective tissue growth factor in pseudoexfoliation syndrome

BACKGROUND/AIMS

Pseudoexfoliation syndrome (PXF) was recently found to be associated with increased expression of transforming growth factor beta(1) (TGFbeta(1)) in the aqueous humour. As concern has been raised regarding anti-TGFbeta therapy, which can potentially disrupt the maintenance of anterior chamber associated immune deviation, the authors explored the levels of tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), matrix metalloproteinase-9 (MMP-9), and connective tissue growth factor (CTGF) in aqueous humour to determine if these may represent alternative therapeutic targets.

METHODS

Aqueous humour samples were collected from patients who underwent routine cataract surgery. All patients were categorised into three main groups-PXF, uveitis, and control. The PXF group was further subcategorised into three grades based on the density of the exfoliative material observed on biomicroscopy, as well as the presence or absence of glaucoma. TIMP-1, MMP-9, and CTGF levels were measured using specific enzyme immunoassays (ELISA).

RESULTS

Eyes with PXF had significantly higher aqueous humour TIMP-1 concentration (n = 56, mean (SE), 9.76 (1.10) ng/ml) compared with controls (n = 112, 5.73 (0.43) ng/ml, p<0.01). Similarly, the CTGF level in PXF eyes (n = 36, 4.38 (0.65) ng/ml) was higher than controls (n = 29, 2.35 (0.46) ng/ml, p<0.05). Further, the CTGF concentration in the PXF glaucoma group is significantly higher compared with PXF eyes without glaucoma (6.03 (1.09) ng/ml v 2.73 (0.45) ng/ml, p<0.01). The MMP-9 levels were low and below detection limit in all PXF and control samples with no statistical difference between groups.

CONCLUSION

A raised TIMP-1 level and a low MMP-9 level in aqueous humour of PXF eyes may imply a downregulation in proteolytic activity. The increased CTGF concentration supports the proposed fibrotic pathology of PXF. Regulation of MMP/TIMP expression and anti-CTGF therapy may offer potential therapeutic avenues for controlling PXF associated ocular morbidity.

Endothelin-1 concentration is increased in the aqueous humour of patients with exfoliation syndrome

BACKGROUND

/aim: Endothelin 1 (ET-1) is considered the most potent vasoconstrictor in the body and the eye. This molecule may play a significant role in the pathobiology of exfoliation syndrome (XFS), a disorder characterised by a progressive iris vasculopathy. The purpose of this study was to investigate the concentration of ET-1 in the aqueous humour of cataract patients with and without XFS.

METHODS

Aqueous humour samples were obtained from 25 consecutive eyes of 25 cataract patients with XFS and an equal number of age matched controls during phacoemulsification cataract surgery. None of the subjects had elevated intraocular pressure or glaucoma. ET-1 concentration in the aqueous was measured using a specific immunoassay with 100% immunoreactivity for ET-1. Total aqueous humour protein concentration was measured with a microplate Coomassie blue based method and was correlated with ET-1 concentration.

RESULTS

Mean ET-1 concentration in the XFS aqueous samples (4.6 (SD 2.3) pg/ml) was significantly higher than that measured in the age matched control samples (2.8 (SD 1.71) pg/ml); (p = 0.006). Although total protein concentration was significantly elevated in the XFS samples (0.380 (SD 0.159) v 0.279 (SD 0.144) mg/ml in the controls); (p = 0.023), no correlation was found between aqueous ET-1 and total protein concentration (p = 0.730).

CONCLUSION

The increased concentration of ET-1 in the aqueous humour of XFS patients suggests that ET-1 may play a role in the pathobiology of XFS.

Solid phase assays in glycoconjugate research: applications to the analysis of proteoglycans, glycosaminoglycans and metalloproteinases

Glycoconjugates are a class of macromolecules consisting of different constituents, one of which is sugar moieties. Glycoconjugates comprise the majority of tissue constituents, both intracellular and extracellular. Extracellular glycoconjugates (glycoproteins and proteoglycans) participate in a wide variety of interactions, through which they maintain tissue integrity. Therefore, their analysis or the study of their possible interactions would give evidence for the state of tissues. Since the amounts of some of the extracellular glycoconjugates are usually low or the amounts of tissue to be examined come from biopsies, specific analytical systems are developed for their study, the most familiar being solid phase assays, which have the advantages of analysis of multiple samples on the same time, cheap instrumentation and high specificity.