Leo T. Chylack

Cytosolic β-amyloid deposition and supranuclear cataracts in lenses from people with Alzheimer's disease

Summary Background Pathological hallmarks of Alzheimers disease include cerebral β-amyloid (Aβ) deposition, amyloid accumulation, and neuritic plaque formation. We aimed to investigate the hypothesis that molecular pathological findings associated with Alzheimers disease overlap in the lens and brain. Methods We obtained postmortem specimens of eyes and brain from nine individuals with Alzheimers disease and eight controls without the disorder, and samples of primary aqueous humour from three people without the disorder who were undergoing cataract surgery. Dissected lenses were analysed by slit-lamp stereophotomicroscopy, western blot, tryptic-digest/mass spectrometry electrospray ionisation, and anti-Aβ surface-enhanced laser desorption ionisation (SELDI) mass spectrometry, immunohistochem-istry, and immunogold electron microscopy. Aqueous humour was analysed by anti-Aβ SELDI mass spectrometry. We did binding and aggregation studies to investigate Aβ-lens protein interactions. Findings We identified Aβ1–40 and Aβ1–42 in lenses from people with and without Alzheimers disease at concentrations comparable with brain, and Aβ1–40 in primary aqueous humour at concentrations comparable with cerebrospinal fluid. Aβ accumulated in lenses from individuals with Alzheimers disease as electron-dense deposits located exclusively in the cytoplasm of supranuclear/deep cortical lens fibre cells (n=4). We consistently saw equatorial supranuclear cataracts in lenses from people with Alzheimers disease (n=9) but not in controls (n=8). These supranuclear cataracts colocalised with enhanced Aβ immunoreactivity and birefringent Congo Red staining. Synthetic Aβ bound βB-crystallin, an abundant cytosolic lens protein. Aβ promoted lens protein aggregation that showed protofibrils, birefringent Congo Red staining, and Aβ/αB-crystallin coimmunoreactivity. Interpretation Aβ is present in the cytosol of lens fibre cells of people with Alzheimers disease. Lens Aβ might promote regionally-specific lens protein aggregation, extracerebral amyloid formation, and supranuclear cataracts.

Epidemiologic evidence of a role for the antioxidant vitamins and carotenoids in cataract prevention.

The relationship between antioxidant nutrient status and senile cataract was examined in 77 subjects with cataracts and 35 control subjects with clear lenses. Subjects with low (below the 20th percentile) and moderate (20th-80th percentiles) plasma nutrient and nutrient intake levels of vitamin C, vitamin E, and carotenoids were compared with subjects with high levels (above the 80th percentile). The odds ratio (OR) of cortical (CX) cataract among subjects with low plasma carotenoid levels was 7.2 (P less than 0.05) and the OR of posterior subcapsular (PSC) cataract for persons with low plasma vitamin C was 11.3 (P less than 0.10). Low vitamin C intake was associated with an increased risk of CX (OR = 3.7, P less than 0.10) and PSC (OR = 11.0, P less than 0.05) cataract. Subjects who consumed fewer than 3.5 servings of fruit or vegetables per day had an increased risk of both CX (OR = 5.0, P less than 0.05) and PSC cataract (OR = 12.9, P less than 0.01).

The Roche European American Cataract Trial (REACT): A randomized clinical trial to investigate the efficacy of an oral antioxidant micronutrient mixture to slow progression of age-related cataract

context Funding surgery worldwide for age-related cataract (ARC), a leading cause of blindness, is a huge economic burden. Non-surgical means of slowing ARC progression could benefit patients and reduce this burden. objective To determine if a mixture of oral antioxidant micronutrients [mg/day] (ß-carotene [18], vitamin C [750], and vitamin E [600]) would modify progression of ARC. design REACT was a multi-centered, prospective, double-masked, randomized, placebo-controlled, 3-year trial. setting Consecutive adult American and English outpatients with early ARC were recruited. patients Four-hundred-and-forty-five patients were eligible; 297 were randomized; 231 (78%) were followed for two years; 158 (53%) were followed for three years; 36 (12%) were followed for four years. Twelve patients died during the trial (9 on vitamins; 3 on placebo (p = 0.07)). There were no serious safety issues. intervention After a three-month placebo run-in, patients were randomized by clinical center to the vitamin or placebo groups and followed every four months. main outcome measure Cataract severity was documented with serial digital retroillumination imagery of the lens; progression was quantified by image analysis assessing increased area of opacity. This measure of area, ‘increase % pixels opaque’ (IPO), was the main outcome measure. results There were no statistically significant differences between the treatment groups at baseline. The characteristics of dropouts and the mean follow-up times by treatment group were the same. After two years of treatment, there was a small positive treatment effect in U.S. patients (p = 0.0001); after three years a positive effect was apparent (p = 0.048) in both the U.S. and the U.K. groups. The positive effect in the U.S. group was even greater after three years: (IPO = 0.389 (vitamin) vs. IPO = 2.517 (placebo); p = 0.0001). There was no statistically significant benefit of treatment in the U.K. group. In spite of nearly perfect randomization into treatment groups, the U.S. and U.K. cohorts differed significantly. conclusion Daily use of the afore-mentioned micronutrients for three years produced a small deceleration in progression of ARC.

Antioxidant vitamins and nuclear opacities: the longitudinal study of cataract.

OBJECTIVE The association of antioxidant nutrients and risk of nuclear opacification was evaluated in the Longitudinal Study of Cataract. DESIGN Nutritional data were collected at baseline on the 764 participants, which included assessment of dietary intake, use of vitamin supplements, and plasma levels of vitamin E. Ophthalmologic and other data were collected at baseline and at yearly follow-up visits, including lens photographs, which were graded using the Lens Opacities Classification System III protocol. MAIN OUTCOME MEASURES Analyses examined whether the nutritional factors at baseline were related to increases in nuclear opacification at follow-up. The MULCOX2 approach, an extension of the Cox regression model, was used. Results are presented as relative risks (RRs) and 95% confidence intervals. INTERVENTION Intervention was not applicable. RESULTS The risk of nuclear opacification at follow-up was decreased in regular users of multivitamin supplements (RR = 0.69; 0.48-0.99), vitamin E supplements (RR = 0.43; 0.19-0.99), and in persons with higher plasma levels of vitamin E (RR = 0.58; 0.36-0.94). CONCLUSIONS In regular users of multivitamin supplements, the risk of nuclear opacification was reduced by one third; in regular users of vitamin E supplements and persons with higher plasma levels of vitamin E, the risk was reduced by approximately half. These results are similar to those obtained in our earlier case-control study. Because these data are based on observational studies only, the results are suggestive but inconclusive. The possible effect of nutritional supplements on the lens requires confirmation by ongoing clinical trials.

Direct Measurement of Polyol Pathway Activity in the Ocular Lens

A method to measure the polyol pathway metabolic flux in the intact rabbit lens by 13C nuclear magnetic resonance spectroscopy is described. In the lens exposed to 35.5 mM glucose, the polyol pathway accounts for ⅓ of the total glucose turnover. The high metabolic activity of the pathway suggests a significant alteration in the reduced to oxidized pyridine nucleotide ratio in the lens exposed to high glucose.

A simplified cataract grading system The WHO Cataract Grading Group

A simplified method for grading the presence and severity of different cataract types is needed for field use in assessment of the magnitude of the cataract problem. A cataract grading system was developed by a panel of experts with the objective of making available a simple system for use with a slit lamp to allow for the reliable grading of the most common forms of cataract by relatively inexperienced observers. Three levels, reflecting progressive severity, for grading of nuclear, cortical and posterior subcapsular (PSC) cataract were included in the classification; three standard photos were used for grading nuclear cataract. Field evaluation from four different sites indicated very good to fair interobserver agreement with the use of this system following minimal training of residents in ophthalmology at each site. Further testing of this system is warranted. The WHO simplified cataract grading system should allow for the obtaining of comparable data across countries based on field assessment of the most common forms of cataract.

Early-Onset Pauciarticular Juvenile Rheumatoid Arthritis Associated with Human Leukocyte Antigen-DRw5, Iritis, and Antinuclear Antibody

Evidence has been sought for a genetically determined predisposition among children with juvenile rheumatoid arthritis (JRA) who are also at particular risk for the development of inflammatory eye disease.45 unrelated Caucasian patients (41 female) with early-onset pauciarticular JRA were human leukocyte antigen (HLA) types. 28 of the study group were found to be HLA-DRw5 compared with 16 of 84 controls (X(2), 24.3, P = <0.001). 9 patients were HLA-DRw8 compared with 4 of 84 controls (X(2), 7.51, P = <0.01). Iritis developed in 24 of the 45 children studied, 17 of whom were typed as HLA-DRw5 when compared to controls (X(2), 26.76, P = <0.001) and 6 with iritis typed as HLA-DRw8 (X(2), 9.10, P = <0.01). Antinuclear antibody was found in the serum of 17 of the 28 patients typing as HLA-DRw5 compared with 4 of the 17 who did not have this antigen (X(2), 5.88, P = <0.02). No such association was seen in patients with HLA-DRw8. In a study of linked genes, a delta value of 0.090 was found for HLA-DRw5 with HLA-B12, of 0.070 for DRw5 with HLA-Cw4, and a value of 0.050 for DRw5 and HLA-Bw35. This suggests a linkage disequilibrium between HLA-DRw5 and these two B series alleles, a conclusion which was supported by haplotype analysis in families of 11 of the disease probands. HLA-DRw5 has not previously been reported to be increased in any rheumatic disease group. It is proposed that HLA-DRw5 is a genetic marker defining those at risk for early-onset pauciarticular JRA with iritis.

The Effect of Oxidation on Sorbitol Pathway Kinetics

The rapid conversion of glucose to sorbitol by aldose reductase and the consequent hyperosmolarity of the cytoplasm has been shown to be the primary cause of the so-called “sugar” or “osmotic” cataract in many animal lenses. It is not as clear, however, that hyperosmolarity is the principal factor in the etiology of cataracts in human diabetic subjects. In fact, the comparatively low activity of aldose reductase in the human lens as compared with several animal lenses, and the osmotically insignificant levels of sorbitol pathway products (sorbitol and fructose), suggest that hyperosmolarity, per se, may not be as important a factor in human cataract formation as it is in animals. We present evidence that the flux of glucose and sorbitol through the rat lens is markedly reduced by oxidative stress (0.1 mM H2O2). Sorbitol accumulation is reduced by 114%, sorbitol turnover is reduced by 78%, sorbitol production is reduced by 90%, fructose accumulation is reduced by 60%, and fructose turnover is reduced by 76% in the presence of 36 mM glucose. H2O2 does not affect glucose turnover, the glucose rate constant, or the ATP level significantly at 36 mM glucose, but at 5.5 mM glucose, 0.2 mM H2O2 leads to a rapid loss of ATP that can be prevented by 0.04 mM sorbinil, an aldose reductase inhibitor. These results suggest that inhibition of aldose reductase by sorbinil renders rat lenses better able to cope with oxidative stress. In the absence of an aldose reductase inhibitor, elevating ambient glucose may render a lens less able to scavenge oxidants by diverting NADPH into sorbitol production. The importance of the rate of flux of glucose through the sorbitol pathway, rather than the absolute concentration of sorbitol or fructose, is stressed in considering the mechanisms underlying complications of diabetes mellitus.

Choroidal Detachment: Clinical Manifestation, Therapy and Mechanism of Formation

One hundred and twelve eyes of 103 patients were analyzed during a 9 1/2-year period after surgical drainage of a choroidal (ciliochoroidal) detachment (CD). Choroidal detachment in five groups of postoperative patients was studied. CD after surgery for cataract, for cataract and glaucoma, and for glaucoma alone had different time courses, but in all of these, there were similar amounts of protein (67% of plasma protein concentration) in the suprachoroidal fluid (SCF). In marked contrast was a group of patients with intraoperative choroidal effusions and very little protein (18% of plasma concentration) in the SCF. Identified also was a chronic recurrent form of CD that usually persisted for more than three months. Three distinct mechanisms by which choroidal effusion is formed were recognized, (1) one with evidence for the effusion occurring through an intact isoporous membrane (groups 1-3); (2) a second in which hemorrhagic SCF appeared acutely or subacutely (groups 1 and 2) through a disrupted isoporous membrane; and (3) a third form, an intraoperative choroidal effusion in patients with elevated episcleral venous pressure. Increased filtration rate of serum through an intact choriocapillary membrane caused molecular sieving of serum proteins. Inflammation, infection, cataract formation, and corneal edema were uncommonly encountered. Indications for surgery and recommended surgical technique are outlined in detail.

Nonenzymatic glycation of human lens crystallin. Effect of aging and diabetes mellitus.

We have examined the nonenzymatic glycation of human lens crystallin, an extremely long-lived protein, from 16 normal human ocular lenses 0.2-99 yr of age, and from 11 diabetic lenses 52-82-yr-old. The glucitol-lysine (Glc-Lys) content of soluble and insoluble crystallin was determined after reduction with H-borohydride followed by acid hydrolysis, boronic acid affinity chromatography, and high pressure cation exchange chromatography. Normal lens crystallin, soluble and insoluble, had 0.028 +/- 0.011 nanomoles Glc-Lys per nanomole crystallin monomer. Soluble and insoluble crystallins had equivalent levels of glycation. The content of Glc-Lys in normal lens crystallin increased with age in a linear fashion. Thus, the nonenzymatic glycation of nondiabetic lens crystallin may be regarded as a biological clock. The diabetic lens crystallin samples (n = 11) had a higher content of Glc-Lys (0.070 +/- 0.034 nmol/nmol monomer). Over an age range comparable to that of the control samples, the diabetic crystallin samples contained about twice as much Glc-Lys. The Glc-Lys content of the diabetic lens crystallin samples did not increase with lens age.