Malondialdehyde and Antioxidant Enzyme Levels in the Aqueous Humor of Rabbits in Endotoxin-Induced Uveitis

PURPOSE

To investigate the role of oxidative stress in endotoxin-induced uveitis.

METHODS

Lipopolysaccharide was injected intravitreally into the right eyes of rabbits. Sterile saline was injected intravitreally into the left eyes as a control. Inflammation was assessed according to clinical score, aqueous humor cell count, and protein levels. Malondialdehyde, superoxide dismutase, glutathione peroxidase, catalase, and nitrite levels were measured in the aqueous humor.

RESULTS

The clinical grade (p < 0.01), inflammatory cell count (p < 0.001), and protein content (p < 0.001) were significantly higher in the aqueous humor of eyes with uveitis than in that of controls. Malondialdehyde (p < 0.01) and nitrite (p < 0.001) levels in the aqueous humor of eyes with uveitis were significantly higher than in the control group. Superoxide dismutase (p < 0.001), glutathione peroxidase (p < 0.001), and catalase (p < 0.001) levels were significantly lower in the aqueous humor of eyes with uveitis than in that of the controls.

CONCLUSIONS

Oxygen free radicals may be implicated as a mediator of inflammation in endotoxin-induced uveitis. The increase in free radicals in the aqueous humor may play a role in the pathogenesis of endotoxin-induced uveitis.

Matrix Metalloproteinase-1 and Matrix Metalloproteinase-9 in the Aqueous Humor of Diabetic Macular Edema Patients

Purpose

To assess the concentrations of matrix metalloproteinase (MMP)-1 and MMP-9 in the aqueous humor of diabetic macular edema (DME) patients.

Method

The concentrations of MMP-1 and MMP-9 in the aqueous humors of 15 cataract patients and 25 DME patients were compared. DME patients were analyzed according to the diabetic retinopathy (DR) stage, diabetes mellitus (DM) duration, pan-retinal photocoagulation (PRP) treatment, recurrence within 3 months, HbA1C (glycated hemoglobin) level, and axial length.

Results

The concentrations of MMP-1 and MMP-9 of the DME groups were higher than those of the control group (p = 0.005 and p = 0.002, respectively). There was a significant difference in MMP-1 concentration between the mild non-proliferative diabetic retinopathy (NPDR) group and the proliferative diabetic retinopathy (PDR) group (p = 0.012). MMP-1 concentrations were elevated in PRP-treated patients (p = 0.005). There was a significant difference in MMP-9 concentrations between the mild NPDR group and the PDR group (p < 0.001), and between the moderate and severe NPDR group and the PDR group (p < 0.001). The MMP-9 concentrations in PRP treated patients, DM patients with diabetes ≥ 10 years and recurrent DME within 3months were elevated (p = 0.023, p = 0.011, and p = 0.027, respectively). In correlation analyses, the MMP-1 level showed a significant correlation with age (r = -0.48, p = 0.01,), and the MMP-9 level showed significant correlations with axial length (r = -0.59, p < 0.01) and DM duration (r = 049, p = 0.01).

Conclusions

Concentrations of MMP-1 and MMP-9 were higher in the DME groups than in the control group. MMP-9 concentrations also differed depending on DR staging, DM duration, PRP treatment, and degree of axial myopia. MMP-9 may be more important than MMP-1 in the induction of DM complications in eyes.

Role of matrix metalloproteinase 9 and its tissue inhibitor 1 in development and prognosis of diabetic retinopathy

The article presents the results of investigation of violations in the proteolysis system in patients with type 2 diabetes and diabetic retinopathy (DR). We studied the levels of matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of matrix metalloproteinase-I (TIMP-1) in the blood and in the intraocularfluid ofpatients with type 2 diabetes depending upon the stage of DR. We have established that the level of MMP-9 and TIMP- in the blood and in the intraocular fluid increased in patients with type 2 diabetes without signs of DR and with any stage of DR compared to the levels of these parameters in patients without diabetes. Increasing the levels of MMP-9 and TIMP-J took place with increasing of DR severity and reached its maximum levels at the proliferative stage of DR. It was found that the levels of MMP-9 in the intraocular fluid and type 2 diabetes duration affected theprobability of developing diabetic macular edema. At the level of MMP-9 105 ng/ml and 2 diabetes duration 10 years, the probability of developing macular edema was 100%. As a result of the construction ofpredictive models it was found that the level of MMP-9 in the intraocular fluid, stage of DR at the beginning of observation and type 2 diabetes duration had influence on the probability of the development ofproliferative DR over 4 years offollow-up. If the level of MMP-9 100 ng/ml, type 2 diabetes duration 10 years and absence of DR at the beginning of observation were observed the probability of developing proliferative DR would compose 85.9%.

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.

A cross-sectional study on aqueous humour lactate dehydrogenase level in retinoblastoma

Lactate dehydrogenase enzyme is a non-specific marker found raised in different body fluids in various pathological conditions. This cross-sectional study was done in a medical college of Kolkata, India to find out lactate dehydrogenase level of aqueous humour in retinoblastoma cases. Aqueous humour lactate dehydrogenase level from 21 histology proved retinoblastoma cases and 21 controls was estimated and compared. Range of lactate dehydrogenase levels in retinoblastoma cases were 863-4819 IU/l; mean being 3396.9 IU/l; and in controls range was 48-146 IU/l; mean being 90.6 IU/l; 76.19% of retinoblastoma cases had value over 3000 IU/l. None of the controls had value above 150 IU/l. The difference between lactate dehydrogenase values of cases and controls was significant (p<0.001).

Does the aqueous humor have a role in mitogen-activated protein kinase (MAPK) intracellular signaling in Glaucoma?

Glaucoma is a common blinding disease worldwide. Glaucoma treatment today is based on reduction of aqueous humor production or increase aqueous humor drainage. By medical manipulation, the treatment goal is to reduce the main risk factor, elevated intra ocular pressure. Here we hypothesize that the aqueous humor has a role, beside oxygen and nutrient supply, in transferring signaling to the trabecular meshwork. This signaling might be delivered from the ciliary body were the aqueous humor is produced, or from the lens or the cornea. Recently in our lab we proposed that MAPKs present in the aqueous humor are a novel signal involved in glaucoma pathology. Here we show that this pathway exists at an unexpected, extracellular media. Western blot analysis of aqueous humor from congenital glaucomatic rabbits and a rat model of induced elevated intra ocular pressure (IOP) were found to express several signaling members of the MAPK family. Although these members are usually found in an intracellular environment, they can be detected at an extracellular environment, namely the aqueous humor. These signaling proteins are found also in normal eyes. Moreover the MAPK signaling proteins are found in the active phosphorylated form and in non-active form in elevated IOP animals as well as in the control, normal IOP groups. Understanding the signaling cascade, at the aqueous humor, opens a new area for treatment of glaucoma patients. By interfering with the signaling cascade, taking place at a reachable location, the anterior chamber, we will be able to manipulate these protein effects on the trabecular meshwork.

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.

Secreted leukocyte protease inhibitor is present in aqueous humours from cataracts and other eye pathologies

Previous studies identified serine, cysteine and metalloproteases in normal aqueous humours (AH) and suggested that a balance between proteases and their inhibitors may play a role in the modulation of the AH outflow. We aimed to determine whether secretory leukocyte protease inhibitor (SLPI), a serine protease inhibitor, is present in AH of patients with cataract and other eye pathologies. AH was collected from 117 cataract patients of which 55 were diagnosed with more when one eye disease: cataract only (n=62), pseudoexfoliation (PEX) (n=26), glaucoma (n=6), diabetes retinopathy (n=4), iritis-uveitis (n=4) and macular degeneration (n=28). The total protein in AH was determined by a Bradford assay and SLPI was analyzed by Western blot and ELISA methods. The average concentration of total protein and SLPI in AH samples was 160+/-15 microg/ml (n=117, +/-SEM) and 500+/-94 pg/ml (n=105), respectively. The cataract patients with additional eye disease(s) showed higher protein levels (201+/-35 microg/ml) than cataract (controls) (128+/-31 microg/ml), P<0.01. It is noteworthy that no correlation was found between SLPI and the total protein concentrations in AH, but SLPI was positively correlated with age (r=0.2, P<0.05). No statistical difference in SLPI levels was found between controls (cataract) and other pathologies, while patients with iritis/uveitis had higher SLPI levels compared to those with diabetes (P<0.05). We show here for the first time that SLPI is present in AH and may play a role as well as serve as a marker in pathological states.

Latanoprost therapy reduces the levels of TGF beta 1 and gelatinases in the aqueous humour of patients with exfoliative glaucoma

The aim of the present study was to evaluate the effect of latanoprost monotherapy on the aqueous humour concentrations of TGF-beta1, MMP-2, TIMP-2, MMP-9 and gelatinolytic activity in patients treated for exfoliative glaucoma (XFG). Aqueous samples from 50 XFG patients treated with latanoprost and 50 age-matched XFG patients treated with timolol were collected during phacoemulsification cataract surgery. The concentrations of TGF-beta1, MMP-2, TIMP-2, MMP-9 and gelatinase activity were determined by commercial immunoassays. The mean active TGF-beta1 concentration in the aqueous was significantly lower in XFG patients treated with latanoprost compared with those treated with timolol (3.1 +/- 0.65 vs 13.4 +/- 1.5 pg ml(-1)); (P = 0.0014). The mean total MMP-2 concentration was lower in latanoprost treated patients (31.75 +/- 3.8 vs 81.5 +/- 7.2 ng ml(-1)); (P < 0.0001). The TIMP-2 concentration was also lower in XFG-latanoprost treated patients (73.8 +/- 6.81 vs 101.28 +/- 7.29 ng ml(-1)); (P = 0.0096). Latanoprost monotherapy has a marked effect on the aqueous concentration of TGF-beta1, MMP-2 and TIMP-2 in XFG patients. A better understanding of its effect on the pathobiology of the disease may lead to its earlier use in the disease process to prevent progression from XFS to XFG.

Matrix metalloproteinase gelatinase B (MMP-9) is associated with leaking glaucoma filtering blebs

The goal of glaucoma filtering surgery is to create a low resistance pathway for aqueous outflow. The result is a blister or 'bleb' on the conjunctiva, from which fluid drains into the vasculature. Filtering surgery results may be compromised if blebs develop leaks, a problem that surfaces more frequently when antimetabolites are used to control the wound healing response. We investigated the role of tissue remodelling enzymes of the Matrix metalloproteinase (MMP) family in the development of bleb leaks. Our design was a case series. We enrolled glaucoma patients with leaking blebs, glaucoma patients with overhanging blebs and normal eyes. Leaking bleb tissues (n=11) and bleb leak fluid were collected from patients undergoing bleb revision surgery. Overhanging bleb tissues (from non-leaking blebs, n=3), normal conjunctiva (n=8), and aqueous humour (n=4) were collected for comparison. Samples were analysed for MMP content and proteinase activity by the methods of zymography, western blotting, immunohistochemistry, and in situ zymography. Our main outcome measures were presence and activity of MMP in sample. Zymography revealed the presence of a high molecular weight caseinase and a 92-kDa gelatinase of a size appropriate for the proenzyme form of gelatinase B (gelB; MMP-9), in extracts from leaking bleb tissue, but not in bleb leak fluid or aqueous humour samples. In contrast, a 65-kDa gelatinase of a size appropriate for gelatinase A (MMP-2) proenzyme was observed in all samples. All proteinases disappeared when 10mm EDTA was added to the development buffer, consistent with their identity as MMPs. Western blotting and immunohistochemical analyses confirmed the identity of the 92kDa proteinase as gelB, and further revealed its absence from extracts of overhanging bleb tissue and normal conjunctiva. In situ zymography demonstrated strong gelatinolytic activity in leaking bleb tissue, but not overhanging bleb tissue or normal conjunctiva. MMP-g may be involved in the mechanism of formation of bleb leaks. Precise description of the cascade of events leading to bleb leakage may allow the design of therapeutic interventions to prevent, stabilize or reverse bleb leakage.

Pathogenesis ofStaphylococcusin the Rabbit Anterior Chamber

PURPOSE

To investigate the host defense against Staphylococcus in the rabbit anterior chamber.

METHODS

The bactericidal activity of rabbit aqueous humor was investigated in vitro. Rabbit anterior chambers were injected with viable Staphylococcus aureus or Staphylococcus epidermidis (1,000 or 500,000 colony-forming units [CFU]), killed bacteria, culture supernatants of either organism, or purified S. aureus alpha-toxin. CFU as well as phospholipase (PLA(2)) and myeloperoxidase (MPO) activities of aqueous humor were determined up to 25 hours postinfection (PI).

RESULTS

The number of viable S. aureus or S. epidermidis was significantly reduced when incubated with aqueous humor for 30 minutes (P </= 0.0001). Rabbits challenged with either S. aureus or S. epidermidis demonstrated a significant reduction in CFU in aqueous humor by 1 hour PI (P </= 0.0044). Eyes infected with either S. aureus or S. epidermidis demonstrated a significant increase in MPO activity beginning at 1 hour PI (P </= 0.0455), but only S. aureus caused an increase in PLA(2) activity at 20 and 25 hours PI (P </= 0.0002). No significant increases in PLA(2) activity were observed after injection of killed bacteria into the aqueous humor at any time point; however, injection of S. aureus supernatant or alpha-toxin into the anterior chamber significantly increased PLA(2) activity (P </= 0.0210). Injection of alpha-toxin also resulted in significant increases in MPO activity beginning at 10 hours after injection (P </= 0.001).

CONCLUSIONS

This study demonstrates that aqueous humor has a potent host defense capability and that S. aureus, but not S. epidermidis, triggers a PLA(2) response in the rabbit anterior chamber that appears to be due to alpha-toxin.

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.

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.

Levels of iron, zinc, and copper in aqueous humor, lens, and serum in nondiabetic and diabetic patients: their relation to cataract

The purpose of this study was to investigate iron (Fe), zinc (Zn), and copper (Cu) levels of aqueous humor, lens, and serum in nondiabetics and diabetics and to determine the effects of diabetes on Fe, Zn, and Cu contents in the lens. Fe, Zn, and Cu contents of aqueous humor, lens, and serum samples of 19 patients (9 nondiabetic patients with a mean age of 62.3 +/- 5.4 yr, and 10 diabetic patients with a mean age of 59.5 +/- 5.9 yr) were analyzed by atomic absorption spectrometry using a prospective study design. The lens levels of Cu in diabetic patients were significantly higher compared with nondiabetic patients (p = 0.02); however; there was no difference in the other elements (Zn, Fe; p = 0.28, p = 0.74, respectively). The levels of Fe, Zn, and Cu in the aqueous humor and serum of diabetic patients were not found to be statistically significant when compared to nondiabetics (p = 0.46, p = 0.11, p = 0.18, and p = 0.22, p = 0.43, p = 0.72, respectively). These results demonstrate that increased Cu content of the lens presumably has a greater association with the development of lens opacification in diabetics than Zn and Fe content.

Blood and aqueous humour antioxidants in cataractous poodles

BACKGROUND

Cataract is an important cause of blindness in dogs and frequently develops in young animals of certain breeds, such as the English cocker spaniel and the poodle. Protein oxidation is one of the mechanisms involved in lens opacification and may be causally related to depleted or diminished endogenous antioxidant defences. We evaluated the levels of enzymatic and nonenzymatic antioxidants in blood and aqueous humour of cataractous poodles in comparison to noncataractous poodles.

METHODS

We studied 35 cataractous poodles aged 2 to 11 years, 14 noncataractous poodles and 15 noncataractous mixed-breed dogs. The activity of erythrocyte antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase and glucose-6-phosphate dehydrogenase [G6PD]) was evaluated in 18 cataractous poodles and 14 noncataractous poodles. We evaluated ascorbic acid levels in plasma of all animals and in aqueous humour of cataractous poodles and mixed-breed dogs. The dogs were deprived of food for 12 hours before sampling. Blood samples were obtained from the jugular vein before and during anesthesia. Aqueous humour samples were obtained just before the anterior chamber was opened.

RESULTS

The activity of superoxide dismutase, G6PD and catalase was significantly higher in noncataractous poodles than in cataractous poodles (p < or = 0.05). The activity of glutathione peroxidase was lower in noncataractous poodles than in cataractous poodles, but not significantly so. There was no difference in mean plasma ascorbic acid concentration between cataractous poodles (21.3 microM [standard deviation (SD) 7.4 microM]), noncataractous poodles (21.6 microM [SD 7.4 microM]) and non-cataractous mixed-breed dogs (25.8 microM [SD 7.5 microM]). Similarly, there was no difference in mean aqueous humour ascorbic acid concentration between cataractous poodles (191.7 microM [SD 62.0 microM] and noncataractous mixed-breed dogs (215.7 microM [SD 91.8 microM]).

INTERPRETATION

The results indicate that, at least in the population studied here, no correlation exists between the onset of cataract and ascorbic acid concentration in blood and aqueous humour. The decreased activity of antioxidant enzymes may explain in part the onset of cataract in poodles.

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.

Inhibition of 11beta-hydroxysteroid dehydrogenase type 1 lowers intraocular pressure in patients with ocular hypertension

BACKGROUND

Intraocular pressure (IOP) is maintained by a balance between aqueous humour (AH) production (dependent on sodium transport across a ciliary epithelial bi-layer) and drainage (predominantly through the trabecular meshwork). In peripheral epithelial tissues, sodium and water transport is regulated by corticosteroids and the 11beta-hydroxysteroid dehydrogenase (11beta-HSD) isozymes (11beta-HSD1 activating cortisol from cortisone, 11beta-HSD2 inactivating cortisol to cortisone).

AIM

To analyse expression of 11beta-HSD in the human eye and investigate its putative role in AH formation.

DESIGN

Multipart prospective study, including a randomized controlled clinical trial.

METHODS

The expression of 11beta-HSD1 in normal human anterior segments was evaluated by in situ hybridization (ISH). RT-PCR for 11beta-HSDs, glucocorticoid and mineralocorticoid receptors (GR, MR) was performed on human ciliary body tissue. AH cortisol and cortisone concentrations were measured by radioimmunoassay on specimens taken from patients with primary open-angle glaucoma (POAG) and age-matched controls. Randomized, placebo-controlled studies of healthy volunteers and patients with ocular hypertension (OHT, raised IOP but no optic neuropathy) assessed the effect of oral carbenoxolone (CBX, an inhibitor of 11beta-HSD) on IOP.

RESULTS

ISH defined expression of 11beta-HSD1 in the ciliary epithelium, while RT-PCR analysis of ciliary body tissue confirmed expression of 11beta-HSD1, with additional GR and MR, but not 11beta-HSD2 expression. In both POAG patients and controls, AH concentrations of cortisol exceeded those of cortisone. The CBX-treated healthy volunteers who demonstrated the largest change in urinary cortisol metabolites, indicative of 11beta-HSD1 inhibition, had the greatest fall in IOP. Patients with OHT showed an overall reduction of IOP by 10% following CBX administration, compared to baseline (p<0.0001).

DISCUSSION

CBX lowers IOP in patients with ocular hypertension. Our data suggest that this is mediated through inhibition of 11beta-HSD1 in the ciliary epithelium. Selective and topical inhibitors of 11beta-HSD1 could provide a novel treatment for patients with glaucoma.

Phospholipase A2 activity in normal and Staphylococcus aureus-infected rabbit eyes

PURPOSE

To quantify phospholipase A(2) (PLA(2)) activity in normal rabbit eyes and in eyes with Staphylococcus aureus keratitis.

METHODS

PLA(2) was assayed by the killing of S. aureus at 33 degrees C or by the release of arachidonic acid from S. aureus labeled with radioactive oleic acid. Rabbit corneas were intrastromally injected with 100 log phase colony-forming units (CFU) of S. aureus 8325-4. The activity of myeloperoxidase (MPO) and PLA(2) were quantified in ocular tissues.

RESULTS

The PLA(2)-mediated killing of S. aureus by normal rabbit tears decreased by more than 70% as the rabbits aged from 10 to 28 weeks and by nearly 50% from early morning to afternoon. In rabbits with S. aureus keratitis, the activity of PLA(2) and MPO increased proportionally with time from 5 to 25 hours postinfection (PI), as measured in ocular tissues. PLA(2) activity increased fivefold in tears from infected eyes collected at 25 hours PI compared with normal tears (P < or = 0.0001), whereas a ninefold increase was found in aqueous humor of infected eyes at 25 hours PI (P < or = 0.0001). Infected eyes demonstrated a significant increase in MPO activity compared with uninfected eyes beginning at 10 hours PI for the aqueous humor (P = 0.03), at 16 hours PI for the tear film (P = 0.0024) and at 22 hours PI for the corneal homogenate (P = 0.0007).

CONCLUSIONS

The decrease in PLA(2) activity in the rabbit eye with age or after sleep and its increase during sleep or with the progression of infection are consistent with its role as an innate host defense factor.

Neutrophil accumulation correlates with type IV collagenase/gelatinase activity in endotoxin induced uveitis

BACKGROUND/AIM

Anterior uveitis is a common inflammatory ocular disease characterised by protein accumulation and leucocyte infiltration in the anterior chamber. The aim of this study was to determine the expression of gelatinases in the aqueous humour (AH) and uvea in an animal model of endotoxin induced uveitis (EIU).

METHODS

EIU was established in Lewis rats following an intraperitoneal injection of lipopolysaccharide (LPS). AH and ocular tissue were obtained from control animals and those with EIU over a 1 week time course and the samples analysed immunohistochemically and by gelatin zymography.

RESULTS

Matrix metalloproteinase (MMP) 2 and 9 levels were elevated in rat AH over a 1 week time course. MMP-2 and MMP-9 levels peaked at the time of maximum uveal inflammation, before returning to baseline levels as the inflammation subsided. MMP-9 was detected in the latent and functionally active form. Total protein extracted from inflamed rat uveal tissue displayed no significant gelatinolytic modulation throughout the time course of EIU. Anterior chamber neutrophils and ciliary body epithelial cells were the most abundant source of the gelatinases.

CONCLUSION

This study has revealed a correlation between infiltrating neutrophils and the presence of elevated gelatinases in EIU. The results suggest that these proteolytically active enzymes may be important mediators of the inflammatory response and contribute to matrix remodelling observed in uveitis. Furthermore, the excess production of MMPs may be a mechanism by which leucocytes, such as neutrophils, gain access to uveal tissue and AH. Therapeutic strategies aimed at reducing MMP activity may be of some benefit in the treatment of uveitis.

Neuron specific enolase in retinal detachment

PURPOSE

Neuron Specific Enolase (NSE) is released following central nervous system (CNS) distress. As retina is part of the CNS, NSE levels were measured in the subretinal fluid (SRF), aqueous, and serum of patients with primary rhegmatogenous retinal detachment (RD).

METHODS

Radioimmunoassay was used to determine NSE levels in the SRF, aqueous, and serum of 13 patients (28-92 years old, mean = 71 years) with RD. As controls, NSE was measured in the aqueous of 6 patients undergoing cataract surgery and in serum of 18 patients without ophthalmological or neurological diseases.

RESULTS

SRF levels of NSE ranged from 50-200 microg/l (mean +/- s.d. = 150 +/- 57). NSE levels in aqueous from patients with RD were 2-140 microg/l (mean +/- s.d. = 39 +/- 42), significantly higher than in controls (0-6 microg/l; mean +/- s.d. = 1.58 +/- 2.24; p = 0.04). Serum NSE levels in RD patients ranged from 6.5-80 microg/l (mean +/- s.d. = 26 +/- 21) and was significantly higher than in controls (5.3 +/- 1.66 microg/l; p = 0.005).

CONCLUSIONS

Retinal neuron injury in retinal detachment (RD) releases sufficient Neuron Specific Enolase (NSE) to be detected in subretinal fluid, aqueous, and even in serum. Thus, NSE could index disease severity in RD and provide a means by which to assess the response to neuroprotection in RD.

Metabolism of angiotensin I by guinea pig aqueous humor

We investigated the degradation of angiotensin I (Ang I) by guinea pig aqueous humor at physiological pH (pH 7.4) and assessed the activity of responsible enzymes using various enzyme inhibitors. The aqueous humor was incubated with Ang I in the presence or absence of an enzyme inhibitor at 37 degrees C for the appropriate time period. The resulting peptides were analyzed by a Beckman HPLC system with a Waters microBondapak C18 analytical column using a 30-min increasing linear gradient of 10 to 40% acetonitrile containing 0.05% trifluoroacetic acid (TFA) and H2O containing 0.05% TFA at a flow rate of 1 mL/min. Detection was done by absorbance at 214 nm. Angiotensin II (Ang II) was a major product (39.3+/-4.10 nmol x h(-1) mL(-1), n = 5) of Ang I hydrolysis. Traces of angiotensin 1-9, angiotensin IV, and angiotensin 1-7 were also produced. Chymostatin (0.05 mmol/L), EDTA (1 mmol/L), enalaprilat (0.1 mmol/L), and ebelacton B (0.01 mmol/L) inhibited generation of Ang II from Ang I by guinea pig aqueous humor by 89+/-4.6, 56+/-7.6, 33+/-5.1, 20+/-6.5%, respectively. Our findings indicate that guinea pig aqueous humor contains several enzymes that can form Ang II. The chymostatin-sensitive type of enzyme was the most active one found in guinea pig aqueous humor. Angiotensin I converting enzyme, carboxypeptidase A, and deamidase may also contribute to angiotensin II formation in guinea pig ocular fluid.

Update on topical carbonic anhydrase inhibitors

Topical carbonic anhydrase inhibitors are a novel addition to the armamentarium of medical glaucoma treatment; dorzolamide has been available since 1995 and brinzolamide since 1998. They lower intraocular pressure by inhibiting carbonic anhydrase, a key enzyme for aqueous humor formation. Intraocular pressure-lowering activity of the substances appears to be the same and is similar to that of most other agents, but it does not reach the activity of the unselective beta-blocker timolol or the prostaglandin latanoprost. On concomitant treatment, additivity is reached with all other topical agents. A possible improvement of blood flow may offer an additional benefit, but its significance for the long-term outcome for human glaucoma remains to be shown. Side effects are mostly local. A more physiologic pH of brinzolamide appears to be advantageous.

Oculohypotensive effect of angiotensin-converting enzyme inhibitors in acute and chronic models of glaucoma

We have studied the effects of various angiotensin-converting enzyme (ACE) inhibitors on intraocular pressure (IOP) of rabbits with experimentally induced ocular hypertension and their mechanism of action. Acute ocular hypertension was induced by infusion of 5% glucose (15 ml/kg) through marginal ear vein, whereas chronic glaucoma was induced by injection of alpha-chymotrypsin into the posterior chamber of the eye. IOP was measured by tonometer. All ACE inhibitors were instilled topically in the eye in a sterile solution. The effect of ACE inhibitors also was studied on serum cholinesterase (true and pseudo) and the enzyme ACE in vitro. Enalaprilat, ramiprilat, and fosinopril produced a time-dependent decrease of IOP in both acute and chronic models of ocular hypertension in rabbits. The decrease in IOP was observed for >4 h, and the extent of decrease was comparable to that with both pilocarpine and betaxolol. Prodrugs enalapril and ramipril failed to produced any change in IOP. Losartan also produced a significant decrease in IOP in the chronic model of ocular hypertension in rabbits. All the three ACE inhibitors were found to inhibit ACE activity in aqueous humor. The enzyme cholinesterase was found to be inhibited by enalaprilat, ramiprilat, and fosinopril. However, atropine did not alter the IOP-lowering effect of enalaprilat in rabbits. Indomethacin pretreatment produced slight but significant inhibition of the IOP-lowering effect of enalaprilat in rabbits. Our data suggest that ACE inhibitors enalaprilat, ramiprilat, and fosinopril produce a significant ocular hypotensive effect in acute and chronic models of ocular hypertension in rabbits. Inhibition of ACE in aqueous humor, and in ocular tissues, resulting in reduced angiotensin II formation, could be one of the major mechanisms responsible for the IOP reduction by ACE inhibitors in rabbits.

Effect of IOP elevation on matrix metalloproteinase-2 in rabbit anterior chamber

To investigate changes in the level of matrix metalloproteinase-2 (MMP-2) in the anterior chamber of rabbit with intraocular pressure (IOP) elevation. The IOP was elevated with scleral encircling in 12 rabbits. In the control group (4 rabbits), IOP was not changed after scleral encircling, and in group 1 (4 rabbits) and 2 (4 rabbits), IOP was elevated about 10 and 20 mmHg respectively after scleral encircling. At 2 days after scleral encircling, aqueous sampling was performed and levels of MMP-2 were checked by Western blots and gelatin zymograms. The greater the IOP elevation, the more MMP-2 expression in the anterior chamber by Western blots and gelatin zymograms. The increase in MMP-2 expression in response to IOP elevation may have important implications for the IOP feedback control mechanism.

Transscleral delivery of bioactive protein to the choroid and retina

PURPOSE

To investigate the feasibility of transscleral drug delivery to the choroid and retina.

METHODS

An osmotic pump was used to deliver IgG across the sclera of pigmented rabbits, and levels were measured in the choroid, retina, vitreous humor, aqueous humor, orbit, and plasma over 28 days. This method was then used to deliver an anti-intercellular adhesion molecule-1 (ICAM-1) monoclonal antibody (mAb), and its effect on inhibiting vascular endothelial growth factor (VEGF)-induced leukostasis in the choroid and retina was determined by measuring tissue myeloperoxidase (MPO) activity.

RESULTS

Levels of retinal and choroidal IgG were significantly higher than baseline at all points up to 28 days (P < or = 0.01). IgG levels in the orbit, vitreous humor, aqueous humor, and plasma were negligible (P > 0.05). MPO activity in the choroid of eyes treated with anti-ICAM-1 mAb was 80% less (P = 0.01) than in eyes receiving an equal rate of delivery of an isotype control antibody. Inhibition of MPO activity in the retina was 70% (P = 0.01). The plasma concentration of anti-ICAM-1 mAb was 31,000-fold less than the concentration in the osmotic pump.

CONCLUSIONS

Minimally invasive transscleral delivery can be used to deliver therapeutic levels of bioactive drugs to the choroid and retina with negligible systemic absorption. This method of ocular drug delivery may be used in the treatment of a variety of chorioretinal disorders.

Correlation of metalloproteinase-2 and -9 with proinflammatory cytokines interleukin-1b, interleukin-12 and the interleukin-1 receptor antagonist in patients with chronic uveitis

PURPOSE

Matrix metalloproteinases have been shown to play a role in active uveitis. Transcription of MMPs is induced by a number of growth factors and cytokines. This study investigates the role of MMPs in chronic uveitis and correlates the amounts of MMP-2 and -9 in intraocular samples to the intraocular levels of proinflammatory cytokines (Interleukin-1 [IL-1], Interleukin-12 [IL-12] and Interleukin-1 receptor antagonist [IL-1ra]).

METHODS

Aqueous humor of 16 patients was collected during surgical or diagnostic procedures (control group: cataract patients). MMP-2 and -9 were measured using zymography. IL-1beta, IL-12 and IL-1ra were evaluated by ELISA.

RESULTS

We found MMP-2 and -9 in all of our uveitis patients. In the control group only MMP-2 was seen. Higher levels of MMP-2 and -9 were found in patients with higher activity of uveitis (p < 0.014 for MMP-2, p < 0.0054 for MMP-9). The amounts of IL-1beta, IL-12 and IL-1ra detected in our uveitis patients correlated with levels of MMP-2 (p < 0.07, p < 0.0004, p < 0.03) and MMP-9 (p < 0. 003, p < 0.0001, p < 0.002), and IL-12 (p < 0.004, p < 0.0001). Patients with moderately active uveitis presented with twice the level of MMP-2 as the control group; MMP-9 levels reached up to 92% of the amounts found in patients with active uveitis. Two patients in remission for almost one year still had detectable intraocular MMP-9 levels.

CONCLUSION

Our data suggests that the high levels of MMPs found in patients with chronic uveitis might contribute to the damage often seen in these eyes. Since MMPs are capable of releasing proinflammatory cytokines bound to components of the extracellular matrix, and facilitate the secretion of active TNF-alpha by cleavage of the membrane bound form, it is conceivable that MMPs contribute to the chronicity of some uveitis cases.

[Role of lactate dehydrogenase (LDH) level in the aqueous humor in the diagnosis of retinoblastoma (RB)]

In spite of the progress of the imagery in ophthalmology, the retinoblastoma remains in some particular cases, difficult to make. Moreover, the therapy sanction is often heavy. The lactate dehydrogenase (LDH) dosage in aqueous humor is an invasive technique conceivable when there are diagnosis problems particularly in retino-blastoma of old children and in affections simulating retino-blastoma. The purpose of this work is to lay out three observations where the LDH dosage enabled to keep the retinoblastoma diagnosis in one 8-year old child and eliminate it in two children having pseudoglioma with spontaneous evolution allowing to confirm the non-tumoral nature of the affection. Thus, the technique of LDH dosage has been reliable for the 3 cases which we have introduced. The authors compare the reliability of the different cytochemical techniques during the retinoblastoma diagnosis.

[The effects of single mitomycin C application on the expression of matrix metalloproteinase in the sclera and aqueous of albino rabbits]

BACKGROUND

Topically applied mitomycin C, which is used to prevent scar formation after filtering surgery for glaucoma, is known to cause reduction in scleral cells and abnormal remodelling of scleral extracellular matrices. I examined in this study the effects of mitomycin C on the expression of matrix metalloproteinase in the sclera and aqueous humor.

METHOD

Mytomycin C was applied for 5 minutes to the bared sclera of 14 albino rabbit eyes. The sclera was organ cultured after 1 week, 2 weeks, and 1 month. The culture medium was subjected to zymography to quantitate the gelatinase activity. In situ zymography was performed on the sclera obtained 1 month after mitomycin C application. The aqueous was also subjected to zymography.

FINDINGS

The scleral tissue and its cultured media showed enhanced gelatinase activity. The aqueous showed no changes in gelatinase activity.

CONCLUSION

Increased activity in matrix metalloproteinase may be involved in the abnormal remodelling of scleral extracellular matrices after application of mitomycin C.

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.

How an increase in the carbon chain length of the ester moiety affects the stability of a homologous series of oxprenolol esters in the presence of biological enzymes

beta-Blockers including timolol and propranolol are administered in eye-drops for the treatment of glaucoma. Due to high incidence of cardiovascular and respiratory side-effects, their therapeutic value is limited. As a result of poor ocular bioavailability, many ocular drugs are applied in high concentrations, which give rise to both ocular and systemic side-effects. Therefore, some methods have been employed to increase ocular bioavailability such as (a) the development of drug delivery devices designed to release drugs at controlled rates, (b) the use of various vehicles that retard precorneal drug loss, and (c) the conversion of drugs to biologically reversible derivatives (prodrugs) with increased corneal penetration properties, from which the active drugs are released by enzymatic hydrolysis. A series of structurally related oxprenolol esters were synthesized and investigated as potential prodrugs for improved ocular use. The stability of each ester was studied in phosphate buffer (pH 7.4), also in the presence of (a) 30% human plasma, (b) aqueous humor, and (c) corneal extract at pH 7. 4 and at 37 degreesC. An account is given of how the stability of a homologous series of oxprenolol esters in the presence of biological enzymes is affected by an increase in the carbon chain length of the ester moiety.

Localization of lipocalin-type prostaglandin D synthase (beta-trace) in iris, ciliary body, and eye fluids

PURPOSE

Prostaglandin (PG) D synthase is present in neural tissues and cerebrospinal fluid (beta-trace). This enzyme belongs to the lipocalin family which consists of transporter proteins for lipophilic substances in the extracellular space. PGD synthase is found in retinal pigment epithelium, from where it is secreted into the interphotoreceptor matrix. The authors have undertaken the localization of this unique enzyme within the tissues and spaces of the anterior segment of the eye.

METHODS

Iris, ciliary body, lens, and aqueous and vitreous humors were collected from adult rats and mice. PGD synthase activity was determined, and the protein was quantified by Western blot analysis and localized immunohistochemically. Finally, in situ hybridization was performed to localize PGD synthase mRNA.

RESULTS

PGD synthase was most abundant in the aqueous and vitreous humors. It was less abundant in tissue cytosolic fractions; these fractions had almost 10-fold as much as their corresponding membrane-bound fractions. Lens tissue had the lowest amount observed. PGD synthase was localized to the epithelial cells of the iris and the ciliary body and to the adjacent extracellular chambers, but PGD synthase mRNA was found only within the epithelial cells. Several glycosylated forms of PGD synthase were also detected.

CONCLUSIONS

PGD synthase was synthesized within the epithelial cells of the iris and the ciliary body and was then secreted into the aqueous and vitreous humors, where it accumulated as an active enzyme.

Electrophoretic determination of aqueous and serum neuron-specific enolase in the diagnosis of retinoblastoma

PURPOSE

Neuron-specific enolase (NSE) of containing gamma-enolase is considered valuable in the diagnosis of tumours of neuroectodermal origin.

METHOD

We used rapid electrophoretic method on cellulose acetate plate to determine the pattern of enolase isoenzymes in 21 aqueous humor and 23 serum specimens from retinoblastoma (Rb) and 21 aqueous and 25 serum specimens from 25 control cases to evaluate NSE in the diagnosis of Rb. The assay allowed assessment of all three major isoenzymes (alpha alpha, alpha gamma and gamma gamma), and NSE relative activity and its percentage in the total relative activity of the three enolase isoenzymes were assessed by means of fluorometer.

RESULT

Aqueous from all patients with Rb contained alpha alpha, alpha gamma and gamma gamma isoenzymes and presented strong positive, the positive rate of NSE being 100% and its relative activity accounting for 45 +/- 9% of the total relative activity of the 3 enolase isoenzymes; No enolase was detectable in control aqueous with cataract, glaucoma and Coats's diseases (4 cases), but in two patients with traumatic hyphema alpha alpha and faint alpha gamma and gamma gamma were presented in aqueous. The control serum contained only an alpha alpha band, while the sera form patients with Rb contained alpha alpha, alpha gamma and gamma gamma bands in 18 of 23 specimens, the positive rate being 78.2%, and only alpha alpha bands in the rest 5 specimens (21.8%). In patients with Rb, the NSE relative activity and its percentage in the total relative activity of the 3 isoenzymes in serum (36 +/- 9%) were significantly lower lever than those in aqueous.

CONCLUSION

The amounts of NSE increase significantly in both serum and aqueous from patients with Rb, and the immunoelectrophoretic assay for determination of enolase patterns is valuable in the diagnosis of Rb and differential diagnosis of Rb. In addition, the method is rapid, simple and requires only a little amount (< 5 microL) of samples.

Increased matrix metalloproteinases in the aqueous humor of patients and experimental animals with uveitis

PURPOSE

Matrix metalloproteinases (MMPs) play a major role in connective tissue remodelling, wound healing and embryogenesis. They have also been implicated in pathological tissue degradation in diseases such as rheumatoid arthritis (RA), osteoarthritis (OA), and tumor invasion. The aim of this study was to define the potential role of MMPs in the inflammatory process of uveitis by identifying these proteases in the aqueous humor (AH) of patients with uveitis and in rabbits with endotoxin-induced uveitis (EIU).

METHODS

Aqueous humor samples from 6 patients with uveitis and 5 control patients who had undergone elective cataract surgery were examined. The profile of MMPs in the AH of experimentally-induced acute anterior uveitis in rabbits was also assessed. Western blot analysis and SDS-PAGE substrate zymography were used to detect metalloenzymes and their natural inhibitor, tissue inhibitor of metalloproteinase (TIMP-1) in aqueous samples.

RESULTS

Aqueous humor from all patients contained interstitial collagenase (MMP-1), stromelysin (MMP-3), gelatinase B (MMP-9) and TIMP-1. Although the amount of MMPs varied considerably, TIMP-1 levels remained unchanged in the aqueous of uveitis patients. Using substrate gel zymography, we were able to reveal several gelatinolytic bands, including one major band at approximately 92-kDa whose activity differed between uveitis and cataract AH. The gelatinase activity found in human AH samples was shown to be inhibited by 10 mM EDTA and activated in vitro by APMA, indicating that these enzymes were indeed of the metalloproteinase class. Aqueous humor samples from the rabbit EIU model revealed a 100-kDa molecular weight species likely to correspond to gelatinase B. This gelatinolytic activity was maximal at 6 hours after the lipopolysaccharide (LPS) injection, declined at 12 and 24 hours post LPS, and was absent at later time points. The induction of gelatinase activity in rabbit AH preceded the increase in cell number during the inflammatory process in the anterior chamber.

CONCLUSIONS

Metalloproteinases found in normal human AH may participate in physiological turnover of extracellular matrix in the eye. Elevated levels of MMPs were found in the AH of patients with uveal inflammation and animals with LPS-induced uveitis, where they are likely to be critical to tissue destructive and repair processes. It is likely that pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 alpha (IL-1 alpha), which are known modulators of MMPs, induce their secretion in acute anterior uveitis.

[Electrophoretic determination of aqueous and serum neuron-specific enolase (NSE) in the diagnosis of retinoblastoma]

OBJECTIVE

Neuron-specific enolase (NSE) or isoenzymes containing gamma-enolase are considered valuable in the diagnosis of tumors of neuroectodermal origin.

METHOD

We used rapid electrophoretic method on cellulose acetate plate to determine the patterns of enolase isoenzymes in the 21 aqueous humor and 23 serum specimens from 23 patients with retinoblastoma (Rb) and 21 aqueous and 25 serum specimens from 25 control cases to evaluate NSE in the diagnosis of RB. The assay allowed assessment of all three major isoenzymes (alpha alpha, alpha gamma, and gamma gamma), and NSE relative activity and its percentage in the total relative activity of the three enolase isoenzymes were assessed by means of a fluorometer.

RESULTS

Aqueous from all patients with Rb contained alpha alpha, alpha gamma, and gamma gamma isoenzymes and presented strong positive, the positive rate of NSE being 100% and its relative activity accounting for 45 +/- 9% of the total relative activity of the 3 enolase isoenzymes; no enolase was detectable in the control aqueous with cataract, glaucoma and Coats's diseases (4 cases), but in two patients with traumatic hyphema alpha alpha band, while the sera faint alpha gamma and gamma gamma presented in the aqueous. The control serum contained only an alpha alpha band, while the sera from patients with RB contained alpha alpha, alpha gamma and gamma gamma bands in 18 of 23 specimens, the positive rate being 78.2%, and only alpha alpha bands in the rest 5 specimens (21.8%). In the patients with Rb, the NSE relative activity and its percentage in the total relative activity of the 3 isoenzymes in serum (36 +/- 9%) were significantly lower than that in aqueous.

CONCLUSION

The amounts of NSE significantly in both serum and aqueous from patients with Rb, and the immunoelectrophoretic assay for determination of enolase patterns is valuable in the diagnosis and differential diagnosis of Rb. In addition, the method is rapid, simple and requires only a little among (< 5 microliters) of sample.

Matrix metalloproteinases and their inhibitors in aqueous humor

Matrix metalloproteinase activity is the rate-limiting step in extracellular matrix degradation. One mechanism by which metalloproteinases are regulated is through the activity of their endogenous inhibitors, the tissue inhibitors of metalloproteinases. Since metalloproteinase activity is a key component of the angiogenic process and many anterior segment structures are largely avascular, we became interested in examining aqueous humor for the presence of metalloproteinases and their endogenous inhibitors. Using zymography, we have identified the presence of several metalloproteinases in normal aqueous humor. Treatment with 4-aminophenylmercuric acetate, an organomercurial which activates latent metalloproteinases, revealed that all metalloproteinases were in their active state. By Western blot analysis, normal aqueous humor was also found to contain at least two tissue inhibitors of metalloproteinases. Subsequent partial purification by two successive chromatographic steps revealed the presence of inhibitory activity against collagenase, endothelial cell DNA synthesis, and angiogenesis on the chick chorioallantoic membrane. The presence of metalloproteinases and their inhibitors in normal aqueous humor, a fluid which bathes avascular ocular structures, suggests that future studies should examine whether an imbalance in this protease/inhibitor family may contribute to the anterior chamber extracellular matrix alterations associated with diseases such as ocular neovascularization and glaucoma.

Role of nitric oxide synthase isozymes in endotoxin-induced uveitis

PURPOSE

The authors previously reported that in vitro treatment with N(G)-nitro L-arginine (L-NNA), an inhibitor of nitric oxide synthase (NOS), reduces aqueous humor (AH) protein and cellular infiltration in endotoxin-induced uveitis in the rat eye. The objective of the current study was to determine the role(s) of respective major forms (constitutive and inducible) of NOS by comparing the effects of relatively selective inhibitors of these NOS isozymes.

METHODS

N(G)-nitro L-arginine (L-NNA), a relatively selective inhibitor for constitutive NOS (c-NOS), and N-iminoethyl L-ornithine (L-NIO), a more selective inhibitor for inducible NOS (i-NOS), were administered in vivo. Male Lewis rats were footpad injected with bacterial lipopolysaccharide (LPS, 200 microgram) and were injected intraperitoneally at 0 hours, 6 hours, or both, after LPS injection with 10 mg of NIO, NNA, or saline as a control. Nitric oxide synthase activity in the ocular tissue and AH protein and cell content were determined at various times after treatment with LPS.

RESULTS

After in vivo treatment, L-NIO was found to be a more potent inhibitor than L-NNA for ocular i-NOS (87% versus 43% inhibition), and L-NNA was more potent than L-NIO for ocular c-NOS (81% versus 39%). Two injections of L-NNA, one at time 0 and one 6 hours after LPS injection, inhibited the AH protein increase by 71%, but L-NIO did so by only 30%. L-NNA inhibited cellular infiltration by 86%, whereas L-NIO had no significant effect on cellular infiltration. A significant inhibition of cellular infiltration and AH protein increase also was observed with a single injection of 10 mg of L-NNA but not of L-NIO when the inhibitors were given simultaneously with LPS. Thus, reduction of uveitis symptoms correlates with the inhibition of c-NOS.

CONCLUSIONS

The constitutive form of NOS in ocular tissue, presumably in vascular endothelial cells, appears to play a critical role at the onset of the development of endotoxin-induced uveitis.

Cathepsin A activity of normal bovine ocular tissues and pathological human intraocular fluids

Cathepsin A activity assayed with N-Cbz-Phe-Ala, N-Cbz-Glu-Tyr and N-Cbz-Glu-Phe as substrates, was measured in fresh corneas, lenses, aqueous humor, vitreous humor and choroid plus retinal pigment epithelium taken from normal bovine eye balls and in human intraocular fluids from the eye balls in various ocular diseases (cataract, glaucoma, diabetes, intraocular tumors). Cathepsin A exhibited a pH optimum at 5.0 and showed the highest specificity towards N-Cbz-Phe-Ala as a substrate. In bovine ocular tissues high cathepsin A activity was found in the choroid plus retinal pigment epithelium and in cornea. The lens and the vitreous humor showed low enzyme activity and the aqueous humor none at all. In the human aqueous humor of the eye with cataract cathepsin A activity was more than three times higher then in the eye with choroid tumor. In human vitreous humor in absolute glaucoma the activity was twice as high as in melanoma and almost three times higher than in the case of lung metastatic tumor. Diabetes in glaucoma increased seven fold cathepsin A activity in the vitreous humor.

Vitreous and aqueous humors contain a latent proteinase activity that abolishes IGF binding to specific IGF binding proteins

Several distinct insulin-like growth factor binding proteins (IGFBPs) are present in tissues and fluids of the developing and adult eye. However, the mechanism(s) involved in the regulation of ocular IGFBP levels is unknown. We have now identified an endogenous factor in vitreous and aqueous humors that, when activated by sodium dodecyl sulfate (SDS), abolishes the capacity of specific low molecular weight IGFBPs (i.e. 24-30 kDa) to bind IGF as assessed by western ligand blotting. In contrast, IGF binding to the 46 and 32 kDa IGFBPs (IGFBP-3 and IGFBP-2 respectively) is not affected by the SDS-activated inhibitory factor (IF). Maximal activation of the IF occurs at an SDS concentration of approximately 0.015%. Incubations in the presence of the serine-proteinase inhibitor aprotinin result in marked inhibition of IF activity. Preliminary characterization by ultrafiltration suggests that the IF is large (< 100 kDa) and/or that it is present in a complex. The finding of a factor, most likely a serine proteinase, that specifically abolishes IGF binding to low molecular weight IGFBPs suggests a mechanism for regulating the levels of these IGFBPs and thus the functional activities of IGFs in ocular fluids under normal and/or pathological conditions.

The appearance of active plasminogen activator of urokinase type (u-PA) in the rabbit anterior eye segment irradiated by UVB rays. A histochemical and biochemical study

Repeated irradiation of the rabbit eye with UV rays of 312 nm wavelength (UVB) evoked the appearance of active plasminogen activator of urokinase type (u-PA) in the anterior eye segment. Using histochemistry, active u-PA appeared first in the corneal epithelium followed by the corneal endothelium, inflammatory cells in the corneal stroma and the lens epithelium. With a semiquantitative fluorescent method active u-PA was also found in the tear fluid and aqueous humour. UV rays of 365 nm wavelength (UVA) under the same conditions did not cause the appearance of active u-PA in the anterior eye segment.

The damaging effect of UV rays below 320 nm on the rabbit anterior eye segment. II. Enzyme histochemical changes and plasmin activity after prolonged irradiation

Prolonged irradiation of the rabbit eyes with UVB rays (312 nm) caused serious enzymatic disturbances in the cornea and lens and the development of an inflammatory reaction in the whole anterior eye segment, particularly in the cornea. In the corneal stroma many inflammatory cells with high activities of acid glycosidases and lysosomal proteases were present. This was accompanied with significantly elevated plasmin activity in the tear fluid (1.6 IU/ml). Plasmin appeared also in the aqueous humour (0.8 IU/ml). For the treatment of these changes catalase (1 mg/1 ml saline), aprotinin (100 micrograms/1 ml saline) and catalase-aprotinin mixture (1:1) were applied on the eye surface during irradiation. The catalase-aprotinin mixture was most efficient and decreased plasmin activity in the tear fluid and diminished disturbances of the anterior eye segment. Obviously both, active oxygen species and elevated plasmin activity in the tear fluid contribute to the damage of the anterior eye segment and development of intracorneal inflammation after irradiation of the eye with UVB rays.

Phospholipase A2 content of aqueous humour in cataract patients

In order to determine the content of group II phospholipase A2 in the aqueous humour we studied 41 cataract patients including 8 men and 33 women with age ranging between 65 and 92 (mean +/- SD being 77.0 +/- 6.7) years. In all patients preoperative biomicroscopy showed neither aqueous flare nor cells. Eleven patients (26.8%) had pseudoexfoliation syndrome. Aqueous humour tap was done at the beginning of cataract surgery before perforating the corneoscleral wound. We used time-resolved fluoroimmunoassay for the detection of group II phospholipase A2 in the aqueous humour. The group II phospholipase A2 content in the aqueous humor varied between less than measurable (in 23 patients) and 3.3 ng/ml, with an interquartile range from less than measurable to 1.4 ng/ml. There was no significant difference in the group II phospholipase A2 content of the aqueous humour whether or not the patient had pseudoexfoliation syndrome. The results show that the aqueous humour of cataract patients contains only minute amounts of group II phospholipase A2.

Identification and partial characterization of a proteinase specific for insulin-like growth factor binding protein-3 in aqueous and vitreous humors

The IGFs (-I and -II) are normally found in serum and other extracellular fluids complexed to specific binding proteins (IGFBPs). While several IGFBPs have been identified in vitreous and aqueous humors, the major serum carrier of IGF, IGFBP-3, is notably absent from these fluids. To determine if this paucity could be due to an IGFBP-3 proteinase (IGFBP-3ase), samples of bovine vitreous or aqueous humor were mixed with serum and incubated at 37 degrees C for 4 h followed by western ligand blotting. In these experiments, a distinct loss of the 46 kDa band representing IGFBP-3 was observed while other bands present at 35, 28 and 25 kDa were unaltered. The IGFBP-3ase activity is temperature sensitive, has a pH optimum of about 8.0 and is inhibited by EDTA. Acid treatment of serum to remove endogenously bound IGF does not affect the specificity or activity of the IGFBP-3 proteinase. Size exclusion chromatography of bovine aqueous indicates an approximate molecular weight of 260 kDa. Incubation of recombinant IGFBP-3 or serum with partially-purified IGFBP-3ase results in the appearance of low molecular weight fragments of approximately 30 kDa. These fragments are undetectable by western ligand blotting but are readily visualized using an IGFBP-3 specific antibody. Comparison of normal and diabetic vitreous humor reveals the presence of an increased amount of IGFBP-3 proteolytic fragments in the diabetic as compared to control. These findings indicate the presence of a IGFBP-3 proteinase in aqueous and vitreous humors that may be important in regulating ocular homeostasis.

MMPs and proteinase inhibitors in the human aqueous humor

PURPOSE

This study was performed to examine the gelatinolytic and caseinolytic activities and the levels of two proteinase inhibitors, alpha 1-proteinase inhibitor (alpha 1-antitrypsin) and alpha 2-macroglobulin, in the human aqueous humor.

METHODS

Aqueous humor samples were collected during elective surgery in patients with cataracts. Zymography with gelatin- and casein-containing gels was performed. The inhibitors were examined by Western blot analyses, enzyme-linked immunosorbent assay, and dot blot assays.

RESULTS

The aqueous humor contained a major band of gelatinolytic activity at a molecular weight of 66 kD and minor bands at 125, 95, and 62 kD. These gelatinases were inhibited by 10 mM ethylenediaminetetraacetic acid (EDTA) or 1,10-phenanthroline. After extended incubation (48 hours), zymography on casein-containing gels showed proteinase bands with molecular weights in the 80- to 84-kD range. Additional bands at 68 and 48 kD also were observed. All the caseinase activities were inhibited by 10 mM phenylmethylsulfonyl fluoride and 1 microgram/ml aprotinin. No inhibition was observed with 5 mM EDTA, 5 microM E-64, or 1 microM pepstatin. These results indicated that the caseinases are serine proteinases. Western blot analysis showed a 53-kD alpha 1-proteinase inhibitor band in the aqueous humor. The concentration was 32.2 +/- 9.9 micrograms/ml, constituting approximately 15% of the total protein. A 360-kD protein band immunoreactive to anti-alpha 2-macroglobulin also was detected. Its level in the aqueous humor was 3.2 +/- 1.3 micrograms/ml.

CONCLUSIONS

The gelatinases, serine-like proteinases, and proteinase inhibitors found in the aqueous humor may participate in the remodeling of extracellular matrices in the trabecular meshwork and other tissues bordering the anterior chamber.

Indoleamine 2,3-dioxygenase activity in the aqueous humor, iris/ciliary body, and retina of the bovine eye

The enzyme indoleamine 2,3-dioxygenase (IDO), which uses free oxygen radicals to cleave the pyrrole ring of indoleamines and give kynurenamines, has previously been found in most tissues, but not in the eye. In this study, IDO activity was measured in post-mortem bovine eyes using Yamazaki's method with L-tryptophan as substrate. Because of the physiological importance of IDO in the protection against free oxygen radical damage, a search was conducted to find this enzyme in the eye. Products of tryptophan degradation by IDO, the kynurenine and 3-hydroxyanthranilic acid were detected and measured in the aqueous humor, iris/ciliary body, and the retina by high-performance liquid chromatography (HPLC) coupled with electrochemical detection. IDO activity was 3.2, 9.0 and 10 nmol/mg protein per h for the aqueous humor, iris/ciliary body, and retina, respectively. These findings suggest that, because of its scavenger properties, IDO is involved in the protection of the eye where, because of its transparency, free radicals are formed not only in the normal oxidation process, but also photochemically.

NADPH diaphorase localization and nitric oxide synthetase activity in the retina and anterior uvea of the rabbit eye

The distribution of the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase was examined histochemically in the retina, iris, ciliary processes, cornea and conjunctiva of the rabbit eye. The epithelial cells of the ciliary process, iris, conjunctiva and, to a lesser extent, the cornea all showed intense staining. In the retina, staining for NADPH diaphorase was intense in the inner segments of the photoreceptors and a sparsely distributed population of amacrine cells. In addition, another population of amacrine cells, some presumed ganglion cells as well as a number of horizontal cells, stained less intensely for the enzyme. The retina, ciliary processes and, as a comparison, the cerebellum of the rabbit all contain nitric oxide synthetase (NOS) activity, as each tissue can metabolize citrulline from arginine. This process is Ca2+ dependent and is reduced by the NOS inhibitor, NG-monomethyl-L-arginine. The presence of NOS activity in the ciliary processes and the localization of NADPH diaphorase in the ciliary epithelial cells are of significance as they suggest that the ciliary epithelial cells may contain NOS which would imply a role for nitric oxide in aqueous humour production.

[Activity of selected enzymes of the anti-oxidase system in the vitreous body, aqueous humor and lens after subconjunctival ozone in experiments]

The influence of ozone on the activity of enzymes of the antioxydation system in selected structures of the eye were checked. Ozone given topically in weak concentrations acts stimulating, increasing the activity of the enzymes of the antioxydation system, instead in high concentrations causes a significant reduction of activity of the enzymes of the mentioned system.

Superoxide dismutase in the anterior chamber and the vitreous of diabetic patients

Total superoxide dismutase (SOD) activity was examined in the anterior humor of 32 diabetic patients and 34 nondiabetic controls during cataract extraction. Median age (95% confidence interval) was 77.5 yr (73.3-81.0) and 79.3 yr (76.0-83.2), respectively. The SOD activity also was examined in posterior vitreous sampled peroperatively in 10 diabetics with proliferative retinopathy and post-mortem in seven diabetic patients and 35 nondiabetic controls. Ages were 57.2 yr (35.0-73.9), 74.4 yr (40.7-83.6), and 73.8 yr (65.0-80.2), respectively. In nondiabetic patients, the total SOD activity was much lower in the anterior chamber, 9.9 U/ml (8.1-12.6), than in the posterior vitreous, 106.3 U/ml (range 65.6-119.0), P < 0.001. We found no difference between the SOD levels in the anterior chamber of nondiabetic controls and diabetic patients, who had 9.6 U/ml (7.6-13.7). The SOD activity in posterior vitreous in diabetic patients sampled peroperatively, 23.9 U/ml (8.9-39.2), P < 0.0001, and post-mortem, 39.5 U/ml (6.5-214.2), P < 0.04, was significantly lower than in the controls sampled post-mortem, 106.3 U/ml (65.6-119.0). Low levels of SOD in the anterior chamber may be involved in cataract development, in diabetic patients and nondiabetic controls. That diabetics had decreased SOD activity in the posterior vitreous points to a possible role of SOD in the complex process of diabetic retinopathy development.

Urokinase-type plasminogen activator in human aqueous humor

In the anterior segment of the eye, fibrin clots must be rapidly resorbed to prevent further fibrosis and scarring. The aqueous humor of patients undergoing cataract surgery was analyzed for the presence of components of the fibrinolytic cascade. In 30 patients, aqueous humor and plasma were compared for their content of urokinase-type plasminogen activator (uPA), tissue-type plasminogen activator (tPA), plasminogen activators inhibitors (PAIs), plasminogen, and total proteins. With gel electrophoresis and zymographic assays of serial dilutions of plasma and aqueous humor, all these components were found to be present at lower concentrations in aqueous humor than in plasma. For total proteins, the aqueous/plasma ratio was approximately 0.003, and for plasminogen it was 0.001. Interestingly, the aqueous/plasma ratio for uPA was not as low and varied from 0.01 to 0.03. A significant proportion of the uPA in aqueous humor was present in the two-chain active form. In addition to uPA, aqueous humor contained lower levels of tPA, but no detectable levels of reactive plasminogen activators inhibitors (PAIs). The presence of a relatively high concentration of active uPA shows that the proteolytic balance of the aqueous humor in the anterior chamber of the eye is shifted toward fibrinolysis.