Electrophoretic study of proteins associated with pseudo-exfoliation syndrome

What is the effect of pseudoexfoliation syndrome on renal function in patients without glaucoma?

PURPOSE

To evaluate renal function in patients with pseudoexfoliation syndrome.

MATERIALS AND METHODS

This prospective, cross-sectional, case-control study involved 49 patients with pseudoexfoliation syndrome (PEX) and 42 control subjects. Renal function was examined by biochemical parameters and Doppler ultrasonography. Serum creatinine, blood urea nitrogen, urea levels, urine microalbumin level and creatinine clearance were measured. Renal volume, resistive index and pulsatility index were calculated using Doppler ultrasonography.

RESULTS

The mean laboratory values for both groups were as follows: Creatinine, PEX: 0.81 ± 0.28 mg/dL - Control: 0.79 ± 0.22 mg/dL; urea, PEX: 31.6 ± 9.7 mg/dL - Control: 32.2 ± 8.4 mg/dL; blood urea nitrogen, PEX: 14.8 ± 4.6 mg/dL - Control: 15.1 ± 4.0 mg/dL; creatinine clearance, PEX: 89.1 ± 35.6 mL/min - Control: 99.0 ± 47.2 mL/min; microalbumin, PEX: 5.8 ± 22.7 mg/dL - Control: 2.7 ± 6.0 mg/dL. The differences between groups were not significant (p > 0.300). Renal volume, resistive index and pulsatility index values were similar in both groups (p > 0.200).

CONCLUSIONS

This study showed that pseudoexfoliation syndrome does not affect biochemical and ultrasonographic parameters associated with renal function.

Detecting protein aggregates on untreated human tissue samples by atomic force microscopy recognition imaging

We apply topography and recognition (TREC) imaging to the analysis of whole, untreated human tissue for what we believe to be the first time. Pseudoexfoliation syndrome (PEX), a well-known cause of irreversible blindness worldwide, is characterized by abnormal protein aggregation on the anterior lens capsule of the eye. However, the development of effective therapies has been hampered by a lack of detailed knowledge of the protein constituents in these pathological deposits and their distribution. Using both TREC and immunofluorescence, one of the proteins implicated in the PEX pathology--the apolipoprotein clusterin--was detected, and differences in its distribution pattern on the surface of untreated human lens capsule tissue in both PEX and normal control samples were investigated. Our study shows the potential of TREC imaging for the analysis of whole, untreated human tissue samples.

Detection of Alzheimer Peptides and Chemokines in the Aqueous Humor

Purpose

Alzheimer disease (AD) and age-related ocular diseases are characterized by inflammation and accumulation of insoluble proteins. We aimed to investigate the detectability and clinical relevance of a panel of AD-related markers, such as Alzheimer peptides and chemokines, in the aqueous humor (AH) samples taken from patients with cataract only, or cataract and 1 other ocular disease.

Methods

The AH samples were obtained during cataract surgery from patients with cataract only (n=162), cataract and glaucoma (n=21), cataract and exfoliation (PEX) (n=31), cataract and macular degeneration (n=36), and cataract and diabetic retinopathy (n=16). The AD peptides (Aβ1–42, Aβ1–40, Aβ1–38) and chemokines (eotaxin, eotaxin 3, interleukin [IL]-8, inducible protein-10, monocyte chemotactic protein [MCP]-1, MCP-4, macrophage-derived chemokine, macrophage inflammatory protein-1β, thymus and activation-regulated chemokine) were quantified by using multiplex immunoassays.

Results

The levels of the AH peptides (Aβ1–38, Aβ1–40, Aβ1–42) did not differ between disease groups. Independently of disease group, the Aβ1–38 levels correlated with Aβ1–40 and Aβ1–42 (p<0.001, n=277). Notably the ratio Aβ1–42 to Aβ1–38 differed between PEX and macular degeneration (mean 95% confidence interval [CI] = 8.12 [11.3–3.99] vs 2.23 [2.67–0.52], p=0.003). Among chemokines examined, only MCP-1 and IL-8 were detected in about 90% to 46% of all analyzed (n=266) samples. Higher levels of AH IL-8 were found in the glaucoma group than in cataract only (p=0.011). Independently of disease group, a correlation was observed between AH MCP-1 and IL-8 (rho=0.275, p<0.001, n=266) and between MCP-1 and Aβ1–40 (rho=0.239, p<0.001, n=266).

Conclusions

Our findings highlight pathologic similarities between AD and eye diseases, and show the potential of modern technologies to detect AD biomarkers in age-related eye diseases.

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.

Alzheimer's peptide and serine proteinase inhibitors in glaucoma and exfoliation syndrome

The occurrence of inflammation with accompanying amyloid formation in pseudoexfoliation syndrome (PEX) resembles other inflammation-associated amyloidoses such as Alzheimer's disease (AD). To test whether the same proteins can be identified in PEX as in AD, we qualitatively analysed for Alzheimer's peptide (Abeta1-42) and the proteinase inhibitors alpha1-antichymotrypsin (ACT) and alpha-antitrypsin (AAT) in the aqueous humor of patients with and without PEX material. Ninety aqueous humor samples were collected from patients in the age group between 46 and 95 during cataract surgery. Protein profiles in samples were analysed by electrophoresis followed by Western blotting. Blots were developed using specific antibodies against Abeta1-42, AAT and ACT and peroxidase-conjugated IgG as a second antibody. At least one of the analysed proteins was found in 68.8% of 90 cases studied. Abeta1-42 peptide was found in 22.2% of all cases, among them in seven cases with PEX (total n =16) and in four with glaucoma (total n = 10). ACT and AAT were detected in 17.8 and 28.9% of all cases, respectively. In addition, female patients had significantly higher frequencies of detected ACT and AAT, compared to males. Abeta1-42, ACT and AAT were also found in 17.6, 14.7 and 23.5% of the control (non-XF and non-glaucoma) samples (n = 68). Alzheimer's peptide is present in the aqueous humor of patients with PEX and glaucoma suggesting that these diseases may share common features in the biochemistry and etiologies with AD. The presence of Abeta and inflammation-associated proteins in aqueous from cataract cases without detectable PEX raises the possibility that these proteins may reflect early amyloid-related changes in the eye.

Exfoliation syndrome

Exfoliation syndrome (XFS) is an age-related disease in which abnormal fibrillar extracellular material is produced and accumulates in many ocular tissues. Its ocular manifestations involve all of the structures of the anterior segment, as well as conjunctiva and orbital structures. Glaucoma occurs more commonly in eyes with XFS than in those without it; in fact, XFS has recently been recognized as the most common identifiable cause of glaucoma. Patients with XFS are also predisposed to develop angle-closure glaucoma, and glaucoma in XFS has a more serious clinical course and worse prognosis than primary open-angle glaucoma. There is increasing evidence for an etiological association of XFS with cataract formation, and possibly with retinal vein occlusion. XFS is now suspected to be a systemic disorder and has been associated preliminarily with transient ischemic attacks, stroke, systemic hypertension, and myocardial infarction. Further ramifications await discovery. Deposits of white material on the anterior lens surface are the most consistent and important diagnostic feature of XFS. The classic pattern consists of three distinct zones that become visible when the pupil is fully dilated. Whereas the classic picture of manifest XFS has been often described, the early stages of beginning exfoliation have not been well defined. Next to the lens, exfoliation material is most prominent at the pupillary border. Pigment loss from the iris sphincter region and its deposition on anterior chamber structures is a hallmark of XFS. Despite extensive research, the exact chemical composition of exfoliation material (XFM) remains unknown. An overproduction and abnormal metabolism of glycosaminoglycans have been suggested as one of the key changes in XFS. The protein components of XFM include both noncollagenous basement membrane components and epitopes of the elastic fiber system such as fibrillium. Regardless of etiology, typical exfoliation fibers have been demonstrated electron microscopically in close association with the pre-equatorial lens epithelium, the nonpigmented ciliary epithelium, the iris pigment epithelium, the corneal endothelium, the trabecular endothelium, and with almost all cell types of the iris stroma, such as fibrocytes, melanocytes, vascular endothelial cells, pericytes, and smooth muscle cells. The presence of XFS should alert the physician to the increased risks of intraocular surgery, most commonly zonular dehiscence, capsular rupture, and vitreous loss during cataract extraction. Heightened awareness of this condition and its associated clinical signs are important in the detection and management of glaucoma, and preoperative determination of those patients at increased risk for surgical complications.

Possible role of transferrin in exfoliation syndrome

Protein concentration was measured in 30 exfoliation syndrome samples and 22 age matched controls. Exfoliation samples contained significantly more protein than controls. We also analyzed by SDS gel electrophoresis 32 aqueous samples, 12 with exfoliation syndrome and 20 age matched controls. A novel finding in all samples was a double band with 77 kDa and 78 kDa. These bands probably represent transferrin isoforms, with different carbohydrate side chains. Exfoliation samples contained a lower amount of the 77 kDa band in comparison to the amount of the 78 kDa band. The lower relative concentration of this transferrin isoform in the exfoliation syndrome samples may be indicative of its possible involvement in the disorder. A different oligosaccharide side chain in combination with a relatively high protein concentration may lead to sedimentation of this molecule. On the other hand, laminin, a glycoprotein detected previously in exfoliation material, contains similar oligosaccharide side chains with transferrin. Thus the oligosaccharide side chains of both proteins may be influenced by the same factors.