Oxidative stress and antioxidant function in relation to risk for cataract

A grape-supplemented diet prevented ultraviolet (UV) radiation-induced cataract by regulating Nrf2 and XIAP pathways

The purpose of this study is to investigate if grape consumption, in the form of grape powder (GP), could protect against ultraviolet (UV)-induced cataract. Mice were fed with the regular diet, sugar placebo diet, or a grape diet (regular diet supplemented with 5%, 10%, and 15% GP) for 3 months. The mice were then exposed to UV radiation to induce cataract. The results showed that the GP diet dose-dependently inhibited UV-induced cataract and preserved glutathione pools. Interestingly, UV-induced Nrf2 activation was abolished in the groups on the GP diet, suggesting GP consumption may improve redox homeostasis in the lens, making Nrf2 activation unnecessary. For molecular target prediction, a total of 471 proteins regulated by GP were identified using Agilent Literature Search (ALS) software. Among these targets, the X-linked inhibitor of apoptosis (XIAP) was correlated with all of the main active ingredients of GP, including resveratrol, catechin, quercetin, and anthocyanins. Our data confirmed that GP prevented UV-induced suppression of XIAP, indicating that XIAP might be one of the critical molecular targets of GP. In conclusion, this study demonstrated that GP protected the lens from UV-induced cataract development in mice. The protective effects of GP may be attributed to its ability to improve redox homeostasis and activate the XIAP-mediated antiapoptotic pathway.

Opium Use and the Risk of Cataract: a Hospital-based, Group-matched, Case-control Study in Iran

PURPOSE

Cataract is the most prevalent cause of reversible blindness worldwide. Although studies have identified risk factors for cataract, its association with opium use has not been studied. This study aimed to evaluate the association between opium use and cataract in Iran in 2020.

METHODS

In a hospital-based, group-matched case-control study in Kerman, a city in southeast Iran, 160 new cases of cataract and 320 controls without cataract underwent ophthalmological examination and were interviewed. Logistic regression models tested the association between cataract and history of opium use, adjusting for demographic characteristics and history of hypertension, coronary heart disease, renal disease, smoking, alcohol use, and unprotected sun exposure.

RESULTS

After controlling for potential confounders, opium use increased the odds of cataract, exhibiting a dose-response relationship. The adjusted odds ratio (aOR) for mild use was 1.44 (95% confidence intervals [CI] 0.80-2.58), and 2.10 (95% CI 1.04-4.25) for heavy use. Exposure to opium juice use further increased the odds of cataract (aOR 2.24, 95% CI 1.00-5.10). Other significant associations with cataract were lower education level (aOR 5.46, 95% CI 2.45-11.29), being unmarried (aOR 2.88, 95% CI 1.65-5.00), both underweight (BMI <18.5, aOR 5.27, 95% CI 2.02-13.70) and overweight (BMI >25, aOR 1.82, 95% CI 1.15-2.87), and family history of cataract (aOR 2.07, 95% CI 1.32-3.23).

CONCLUSION

Our study provides evidence that opium use could increase the odds of cataract. Results also support the association of cataract with other modifiable risk factors, such as very low and high BMI and unprotected sun exposure.

Comparison of aqueous humor ascorbic acid level in smokers and non-smokers

In this study, we studied effect of smoking on ascorbic acid level in aqueous humor. A cohort of 112 individuals undergoing cataract surgery for senile cataract (mean ± SD age-65 ± 8 years) was sub-grouped as smoker (n = 56) and non-smoker (n = 56) based on smoking habit. The aqueous humor sample was collected in beginning of the surgery and quantitative ascorbic acid estimation was done by colorimetric method (spectrophotometry at λ = 578 nm) using commercially available assay kits using the auto-analyzer assay procedure. The mean (±SD) aqueous humor ascorbic acid level was 1396 ± 629 μmol/L among non-smokers and 774 ± 436 μmol/L among smokers (p < 0.0001). The aqueous humor ascorbic acid concentration is significantly lower in smokers compared to non-smokers. The aqueous humor ascorbic acid concentration is affected by gender but not by age or morphology of cataract.

Association between cataract progression and ischemia-modified albumin in relation to oxidant-antioxidant profiles in the serum, aqueous humor, and lens

PURPOSE

To evaluate the levels of ischemia-modified albumin (IMA) in relation to oxidant-antioxidant profiles in the serum, aqueous, and lens in cataract patients.

SETTING

Department of Ophthalmology, Menoufia University, Shebin El Kom, Menoufia, Egypt.

DESIGN

Prospective case series.

METHODS

Patients were divided into 2 groups. The cataract (study) group comprised patients with senile cataract and the control group, age- and sex-matched healthy persons. Patients with systemic disease or cataract formation secondary to identifiable causes were excluded. In all cases, a complete history was taken and a clinical examination was performed. In the cataract group, the lens was examined, and the cataract type and severity were graded. Blood levels of catalase, malondialdehyde (MDA), superoxide dismutase (SOD), and IMA were measured in all participants and in the aqueous and lens lysate of cataract patients.

RESULTS

Each group comprised 30 participants. Cataract patients had significant higher levels of serum MDA and IMA than the control group but had lower levels of serum catalase and SOD. Patients with cortical cataracts had higher level of serum IMA, aqueous catalase, and SOD levels patients with nuclear cataracts but had a lower level of lens SOD. There was a significant positive correlation between serum MDA and the patient's age and serum catalase levels.

CONCLUSION

Patients with cortical cataract had increased local oxidative stress and diminished antioxidant activity compared with systemic oxidative activity, which was not the same in patients with nuclear cataract.

Phytochemical characterization and evaluation of anticataract potential of seabuckthorn leaf extract

OBJECTIVE

This study was undertaken to carry out phytochemical characterization of aqueous extract of Seabuckthorn (SBT, Hippophae rhamnoides L.) leaves and evaluation of its therapeutic role in oxidative stress-induced cataract in isolated goat lenses using Vit. E as reference compound.

ANIMAL STUDIED

A total of 42 goat eye lenses were used in the present study.

PROCEDURE

Seabuckthorn leaf extract was characterized by total phenol content estimation and HPLC analysis of quercetin and catechin. Further, cataract was induced in goat lenses using hydrogen peroxide (H2O2) and anticataract activity was evaluated using the extract in the dose range of 100, 200, 500, and 1000 μg/mL concentrations through estimation of biochemical markers such as superoxide dismutase (SOD), reduced glutathione (GSH), and malonaldehyde (MDA).

RESULTS

The results of the phytochemical characterization showed the total phenol content of the extract to be 365 mg/g in terms of gallic acid equivalents. Quercetin and catechin were estimated to be 0.01 and 0.12% w/w, respectively. In biochemical analysis, H2O2 introduction resulted in a decrease in SOD (approximately 85%) and GSH (approximately 63%) contents and an increase in MDA content (approximately 300%). The decreased levels of SOD and GSH were significantly restored in experimental groups receiving 500 and 1000 1g/mL of SBT extract. All the experimental groups showed significantly reduced MDA level in all the doses.

CONCLUSION

Aqueous extract of SBT leaves showed the potential to delay onset and/or progression of cataract, at least during in vitro conditions. Results indicate the possibilities of evaluating this extract for its use as anticataract agent during in vivo conditions.

Nutritional modulation of cataract

Lens opacification or cataract reduces vision in over 80 million people worldwide and blinds 18 million. These numbers will increase dramatically as both the size of the elderly demographic and the number of those with carbohydrate metabolism-related problems increase. Preventative measures for cataract are critical because the availability of cataract surgery in much of the world is insufficient. Epidemiologic literature suggests that the risk of cataract can be diminished by diets that are optimized for vitamin C, lutein/zeaxanthin, B vitamins, omega-3 fatty acids, multivitamins, and carbohydrates: recommended levels of micronutrients are salutary. The limited data from intervention trials provide some support for observational studies with regard to nuclear - but not other types of - cataracts. Presented here are the beneficial levels of nutrients in diets or blood and the total number of participants surveyed in epidemiologic studies since a previous review in 2007.

Serum antioxidative enzymes levels and oxidative stress products in age-related cataract patients

PURPOSE

To investigate the activity of antioxidative enzymes and the products of oxidative stress in patients with age-related cataracts and compare the findings with those in healthy control subjects.

METHOD

Sixty patients with age-related cataract and sixty healthy controls of matched age and gender were included in this study. Serum samples were obtained to detect the antioxidative enzymes of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px), and oxidation degradation products of malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), conjugated diene (CD), advanced oxidation protein products (AOPP), protein carbonyl (PC), and 8-hydroxydeoxyguanosine (8-OHdG).

RESULTS

Serum SOD, GSH-Px, and CAT activities in cataract group were significantly decreased as compared to the control subjects (P < 0.05). The levels of MDA, 4-HNE, and CD in cataract patients were significantly higher than those in the control subjects (P < 0.05, P < 0.01). Cataract patients had higher levels of 8-OHdG, AOPP, and PC with respect to the comparative group of normal subjects (P < 0.01). And there was no statistical significance in concentration of antioxidative enzymes and oxidative stress products in patients with different subtype cataract.

CONCLUSIONS

Oxidative stress is an important risk factor in the development of age-related cataract, and augmentation of the antioxidant defence systems may be of benefit to prevent or delay cataractogenesis.

Pseudoexfoliation syndrome, a systemic disorder with ocular manifestations

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

In vivo inhibition of l-buthionine-(S,R)-sulfoximine-induced cataracts by a novel antioxidant, N-acetylcysteine amide

The effects of N-acetylcysteine amide (NACA), a free radical scavenger, on cataract development were evaluated in Wistar rat pups. Cataract formation was induced in these animals with an intraperitoneal injection of a glutathione (GSH) synthesis inhibitor, l-buthionine-(S,R)-sulfoximine (BSO). To assess whether NACA has a significant impact on BSO-induced cataracts, the rats were divided into four groups: (1) control, (2) BSO only, (3) NACA only, and (4) NACA+BSO. The control group received only saline ip injections on postpartum day 3, the BSO-only group was given ip injections of BSO (4mmol/kg body wt), the NACA-only group received ip injections of only NACA (250mg/kg body wt), and the NACA+BSO group was given a dose of NACA 30min before administration of the BSO injection. The pups were sacrificed on postpartum day 15, after examination under a slit-lamp microscope. Their lenses were analyzed for selective oxidative stress parameters, including glutathione (reduced and oxidized), protein carbonyls, catalase, glutathione peroxidase, glutathione reductase, and malondialdehyde. The lenses of pups in both the control and the NACA-only groups were clear, whereas all pups within the BSO-only group developed well-defined cataracts. It was found that supplemental NACA injections during BSO treatment prevented cataract formation in most of the rat pups in the NACA+BSO group. Only 20% of these pups developed cataracts, and the rest retained clear lenses. Further, GSH levels were significantly decreased in the BSO-only treated group, but rats that received NACA injections during BSO treatment had these levels of GSH replenished. Our findings indicate that NACA inhibits cataract formation by limiting protein carbonylation, lipid peroxidation, and redox system components, as well as replenishing antioxidant enzymes.

Different experimental approaches in modelling cataractogenesis: An overview of selenite-induced nuclear cataract in rats

Cataract, the opacification of eye lens, is the leading cause of blindness worldwide. At present, the only remedy is surgical removal of the cataractous lens and substitution with a lens made of synthetic polymers. However, besides significant costs of operation and possible complications, an artificial lens just does not have the overall optical qualities of a normal one. Hence it remains a significant public health problem, and biochemical solutions or pharmacological interventions that will maintain the transparency of the lens are highly required. Naturally, there is a persistent demand for suitable biological models. The ocular lens would appear to be an ideal organ for maintaining culture conditions because of lacking blood vessels and nerves. The lens in vivo obtains its nutrients and eliminates waste products via diffusion with the surrounding fluids. Lens opacification observed in vivo can be mimicked in vitro by addition of the cataractogenic agent sodium selenite (Na₂SeO₃) to the culture medium. Moreover, since an overdose of sodium selenite induces also cataract in young rats, it became an extremely rapid and convenient model of nuclear cataract in vivo. The main focus of this review will be on selenium (Se) and its salt sodium selenite, their toxicological characteristics and safety data in relevance of modelling cataractogenesis, either under in vivo or in vitro conditions. The studies revealing the mechanisms of lens opacification induced by selenite are highlighted, the representatives from screening for potential anti-cataract agents are listed.

Protein expression profiling of lens epithelial cells from Prdx6-depleted mice and their vulnerability to UV radiation exposure

Oxidative stress is one of the causative factors in progression and etiology of age-related cataract. Peroxiredoxin 6 (Prdx6), a savior for cells from internal or external environmental stresses, plays a role in cellular signaling by detoxifying reactive oxygen species (ROS) and thereby controlling gene regulation. Using targeted inactivation of the Prdx6 gene, we show that Prdx6-deficient lens epithelial cells (LECs) are more vulnerable to UV-triggered cell death, a major cause of skin disorders including cataractogenesis, and these cells display abnormal protein profiles. PRDX6-depleted LECs showed phenotypic changes and formed lentoid body, a characteristic of terminal cell differentiation and epithelial-mesenchymal transition. Prdx6(-/-) LECs exposed to UV-B showed higher ROS expression and were prone to apoptosis compared with wild-type LECs, underscoring a protective role for Prdx6. Comparative proteomic analysis using fluorescence-based difference gel electrophoresis along with mass spectrometry and database searching revealed a total of 13 proteins that were differentially expressed in Prdx6(-/-) cells. Six proteins were upregulated, whereas expression of seven proteins was decreased compared with Prdx6(+/+) LECs. Among the cytoskeleton-associated proteins that were highly expressed in Prdx6-deficient LECs was tropomyosin (Tm)2beta. Protein blot and real-time PCR validated dramatic increase of Tm2beta and Tm1alpha expression in these cells. Importantly, Prdx6(+/+) LECs showed a similar pattern of Tm2beta protein expression after transforming growth factor (TGF)-beta or H(2)O(2) treatment. An extrinsic supply of PRDX6 could restore Tm2beta expression, demonstrating that PRDX6 may attenuate adverse signaling in cells and thereby maintain cellular homeostasis. Exploring redox-proteomics (Prdx6(-/-)) and characterization and identification of abnormally expressed proteins and their attenuation by PRDX6 delivery should provide a basis for development of novel therapeutic interventions to postpone ROS-mediated abnormal signaling deleterious to cells or tissues.

Glutathione-S-transferase M1 and T1 Genetic Polymorphisms and the Risk of Cataract Development: A Study in the Turkish Population

In this study, we aimed to determine the effects of genetic polymorphisms of glutathione-S-transferase M1 (GSTM1) and glutathione-S-transferase T1 (GSTT1) on risk of developing different subtypes of age-related cataract in the Turkish population. Using a multiplex polymerase chain reaction (PCR), GSTM1 and GSTT1 gene polymorphisms were analyzed in 195 patients with age-related cataract (75 patients with cortical, 53 with nuclear, 37 with posterior subcapsular, and 30 with mixed type) and in 136 patients of an otherwise healthy control group of similar age. GSTM1 null genotype had a significant association with the development of cataract in female subjects (p < 0.0029; OR, 2.98; 95% CI, 1.41-6.34). This relationship in female subjects was only in nuclear and mixed types cataract cases (p < 0.002; OR, 4.58; 95% CI, 1.67-12.78 and p < 0.03, respectively). There was also a statistically significant association between the combination of GSTM1-null and GSTT1-positive genotypes and the risk of cataract development in female subjects (p = 0.01; OR = 2.87; 95% CI = 1.25-6.69). Stratification by the subtypes revealed that this association was only in nuclear type cataract (p = 0.001; OR, 3.92; 95% CI, 1.34-11.71). GSTM1-null genotype or combination of the GSTM1-null and GSTT1-positive genotypes in females may be associated with increased risk of cataract development in the Turkish population.

Expression and cellular localization of melatonin-synthesizing enzymes in the rat lens

Melatonin (N-acetyl-5-methoxytryptamine) prevents oxidative stress-induced cataract development, and previous studies have suggested that the ocular lens synthesizes melatonin. In the present study, we examined whether two key enzymes in melatonin biosynthesis, arylalkylamine N-acetyltransferase (AANAT) and hydroxyindole-O-methyltransferase (HIOMT), are expressed in the lens of adult male rats. Reverse transcriptase-polymerase chain reaction analyses demonstrated that both AANAT and HIOMT mRNAs are expressed in the lens. Western blotting for AANAT protein showed that the lens, like the pineal gland, contains this enzyme protein with a molecular mass of 24 kDa. Immunohistochemistry revealed that AANAT protein is localized to the lens cortical fiber cells. Serotonin, which is a substrate for AANAT and a melatonin precursor, was also found in this region. These findings demonstrate that the lens expresses AANAT and HIOMT, and suggest that the cortical fiber cells are the main melatonin-synthesizing sites in the lens. Locally synthesized melatonin in the lens cortical fiber cells may protect the lens itself from cataract development.

The maillard reaction in eye diseases

Diabetes and age-related eye disorders remain leading causes of blindness worldwide. While defined pathogenic mechanisms for many of these diseases remain elusive, there is increasing evidence that products of the Maillard reaction may play an important role in their etiology. Advanced glycation end products (AGEs) form though a range of pathways within Maillard chemistry, and there is evidence to suggest that these adducts accumulate in the intracellular and/or extracellular environment of ocular structures. This review evaluates the ever-growing literature on AGEs in biological systems and draws relevant links to diseases such as diabetic retinopathy, age-related macular degeneration, and cataract formation. It also outlines recent pharmaceutical strategies to inhibit Maillard reaction products and provides links to how these may serve to limit ocular cell dysfunction.

Cataract formation in a strain of rats selected for high oxidative stress

The primary purpose of this study was to define the clinical and morphological features of cataractogenesis in the OXYS strain of rats that generate excess reactive oxygen species. Rats were sequentially examined from birth to the development of mature cataracts with slit lamp biomicroscopy. Morphology of selected stages of cataract development was studied using light and transmission electron microscopy (TEM), immunohistochemical localization of the lipid peroxidation product 4-hydroxynonenal (HNE) and fluorescent antibody labeling for DNA oxidation products. Lenses from age-matched normal rats were used as controls. OXYS rats developed cataracts as young as two weeks of age with progression to maturity by 1 year. Clinically, cataracts appeared initially either as nuclear or sub-capsular cortical changes and progressed to pronounced nuclear cataracts within months. TEM confirmed the light microscopic impression of region-specific alterations in both fiber cell cytoplasmic protein matrix and membrane structure. The outer adult nuclear region showed extensive cellular damage similar to osmotic cataracts, which is consistent with the postulated high uptake of glucose in the OXYS strain. The adult and outer fetal nuclear cells displayed several types of focal damage. The inner fetal and embryonic nuclear cells demonstrated textured cytoplasm, suggesting protein degradation or redistribution. Staining for HNE was increased in epithelium, cortex and nucleus compared to control lenses. Fluorescent antibody probes demonstrated increased levels of DNA oxidation products in OXYS rat lenses compared to age-matched controls. Fourier analysis of nuclear cytoplasm revealed significant components with corresponding sizes greater than 100 nm and, using a new theoretical approach, the texturing of the cytoplasm was shown to be sufficient to cause opacification of the nucleus. The OXYS rat appears to be an ideal model for oxidative stress cataractogenesis. The potential oxidative damage observed is extensive and characteristic of the developmental region. The source of oxidative damage may in part be a response to elevated levels of glucose. Because oxidative stress is thought to be a major factor in cataract formation in both diabetic and non-diabetic aging humans, this animal model may be a useful tool in assessing efficacy of antioxidant treatments that may slow or prevent cataract formation.

Attachment of the ubiquitin-related protein Urm1p to the antioxidant protein Ahp1p

Urm1p is a ubiquitin-related protein that serves as a posttranslational modification of other proteins. Urm1p conjugation has been implicated in the budding process and in nutrient sensing. Here, we have identified the first in vivo target for the urmylation pathway as the antioxidant protein Ahp1p. The attachment of Urm1p to Ahp1p requires the E1 for the urmylation pathway, Uba4p. Loss of the urmylation pathway components results in sensitivity to a thiol-specific oxidant, as does loss of Ahp1p, implying that urmylation has a role in an oxidative-stress response. Moreover, treatment of cells with thiol-specific oxidants affects the abundance of Ahp1p-Urm1p conjugates. These results suggest that the conjugation of Urm1p to Ahp1p could regulate the function of Ahp1p in antioxidant stress response in Saccharomyces cerevisiae.

Pharmacological prevention of diabetic cataract

Cataract--opacification of the lens--is closely related to diabetes as one of its major late complications. This review deals with three molecular mechanisms that may be involved in the development of diabetic cataract: nonenzymatic glycation of eye lens proteins, oxidative stress, and activated polyol pathway in glucose disposition. Implications resulting from these mechanisms for possible pharmacological interventions to prevent diabetic cataract are discussed. The article reviews research on potential anticataract agents, including glycation inhibitors, antioxidants, and aldose reductase inhibitors. Information on possible benefits of putative anticataract agents comes from a variety of approaches, ranging from laboratory experiments, both in vitro and in vivo, to epidemiological studies in patients.

Vitamin E supplementation and cataract: randomized controlled trial

OBJECTIVE

To determine whether treatment with vitamin E (500 IU daily) reduces either the incidence or rate of progression of age-related cataracts.

DESIGN

A prospective, randomized, double-masked, placebo-controlled clinical trial entitled the Vitamin E, Cataract and Age-Related Maculopathy Trial.

PARTICIPANTS

Of 1906 screened volunteers, 1193 eligible subjects with early or no cataract, aged 55 to 80 years, were enrolled and followed up for 4 years.

INTERVENTION

Subjects were assigned randomly to receive either 500 IU of natural vitamin E in soybean oil encapsulated in gelatin or a placebo with an identical appearance.

MAIN OUTCOME MEASURES

The incidence and progression rates of age-related cataract were assessed annually with both clinical lens opacity gradings and computerized analysis of Scheimpflug and retroillumination digital lens images obtained with a Nidek EAS-1000 lens camera. The analysis was undertaken using data from the eye with the more advanced opacity for each type of cataract separately and for any cataract changes in each individual.

RESULTS

Overall, 87% of the study population completed the 4 years of follow-up, with 74% of the vitamin E group and 76% of the placebo group continuing on their randomized treatment allocation throughout this time. For cortical cataract, the 4-year cumulative incidence rate was 4.5% among those randomized to vitamin E and 4.8% among those randomized to placebo (P = 0.87). For nuclear cataract, the corresponding rates were 12.9% and 12.1% (P = 0.77). For posterior subcapsular cataract, the rates were 1.7% and 3.5% (P = 0.08), whereas for any of these forms of cataract, they were 17.1% and 16.7%, respectively. Progression of cortical cataract was seen in 16.7% of the vitamin E group and 18.4% of the placebo group (P = 0.76). Corresponding rates for nuclear cataract were 11.4% and 11.9% (P = 0.84), whereas those of any cataract were 16.5% and 16.7%, respectively. There was no difference in the rate of cataract extraction between the 2 groups (P = 0.87). Lens characteristics of the participants withdrawn from the randomized medications were not different from those who continued.

CONCLUSIONS

Vitamin E given for 4 years at a dose of 500 IU daily did not reduce the incidence of or progression of nuclear, cortical, or posterior subcapsular cataracts. These findings do not support the use of vitamin E to prevent the development or to slow the progression of age-related cataracts.

Some histologic and biochemical evidence for mitigation of cyanide-induced tissue lesions by antioxidant vitamin administration in rabbits

The effect of antioxidant vitamins on cyanide-induced tissue damage was investigated in New Zealand White rabbits using a combination of colorimetric, spectrophotometric, enzymatic, gravimetric and histological methods. Three groups of rabbits (six per group) were used in a 4-week feeding experiment. One group received pure grower's mash, while a second group was fed mash containing 400 ppm inorganic cyanide. The third group received daily oral doses of vitamins A, C and E, in addition to mash and 400 ppm cyanide. There were significant decreases (P < 0.05) in activities of superoxide dismutase (SOD), catalase and alkaline phosphatase (AP) in the liver, lung and kidney of the two groups given cyanide, but the decreases were significantly lower (P < 0.05) in the group fed antioxidant vitamins. In addition, the antioxidant vitamin supplementation led to marked reductions in the severity of histopathological degeneration in these tissues. These results strongly suggest that cyanide-induced tissue lesions may be relieved by adequate intake of antioxidant vitamin supplements.

H(2)O(2)-mediated oxidative stress activates NF-kappa B in lens epithelial cells

In the mammalian lens, intracellular oxidants produced by photo-oxidative processes and exposure to toxic chemicals constitute stresses that produce cellular oxidative damage, result in changes in gene expression, and are causally related to cataract formation. Currently, it is believed that H(2)O(2) is the major oxidant to which the lens is exposed. In this report, we examine the activation and regulation of the oxidant-sensitive transcription factor, NF-kappa B, by H(2)O(2)-mediated oxidative stress in lens epithelial cells. Lens epithelial cells treated with H(2)O(2) demonstrated at 1 h a strong activation of NF-kappa B which returned to basal levels by 2 h. Under proteasome inhibition using both MG132 and lactacystin, H(2)O(2)-mediated activation of NF-kappa B was prevented, implicating the involvement of proteasome degradation of I kappa B proteins as being necessary for this activation. However, Western blot analysis demonstrated no degradation of I kappa B-alpha, -beta, or -epsilon associated with H(2)O(2)-mediated NF-kappa B activation. In comparison, when cells were treated with the cytokine TNF-alpha, NF-kappa B was strongly activated and degradation of both I kappa B-alpha and -beta was observed. These results clearly demonstrate that H(2)O(2)-mediated oxidative stress activates NF-kappa B in lens epithelial cells, which may subsequently lead to changes in gene expression. The results also reveal that different signaling pathways in the activation of NF-kappa B in lens epithelial cells are utilized by H(2)O(2) and TNF-alpha. These different pathways of NF-kappa B activation may be required to effect specific NF-kappa B-dependent gene expression in response to these different stimuli.

Antioxidant profile of cataractous English Cocker Spaniels

Cataracts have been attributed to oxidative injury in proteins and lipids. Primary defenses that directly protect the lens against oxidative damage include small molecule antioxidants (vitamin C, vitamin E, glutathione and carotenoids) and antioxidant enzymes (superoxide dismutase, catalase, and the glutathione enzyme systems - glutathione peroxidase, glutathione reductase and glucose-6-phosphate dehydrogenase). In humans, low plasmatic levels of vitamin C, vitamin E and carotenoids have been associated with a high risk of senile cataracts. Dogs are more prone to develop cataracts. A decrease in antioxidant defenses could be responsible for increased lens oxidation and cataract development. In this study we report the levels of erythrocytic enzymatic antioxidants (superoxide dismutase, catalase, glutathione peroxidase and glucose-6-phosphate dehydrogenase) and plasma vitamin C as well as malondialdehyde, in normal and cataractous English Cocker Spaniel dogs. Plasma vitamin C levels were consistently lower in cataractous dogs (20.17 &mgr;M +/- 8.2 &mgr;M) when compared with normal dogs (24.1 &mgr;M +/- 9.4 &mgr;M). These results indicate a possibly decreased synthesis in vitamin C, leading to lower aqueous humor levels of this vitamin. Considering that vitamin C levels in the aqueous humor may be responsible for lens antioxidant maintenance, and that these levels are obtained from plasma secretion through the ciliary epithelium, decreased plasma levels may indicate a decrease in the antioxidant capacity of the aqueous humor.

Long-term dietary strawberry, spinach, or vitamin E supplementation retards the onset of age-related neuronal signal-transduction and cognitive behavioral deficits

Recent research has indicated that increased vulnerability to oxidative stress may be the major factor involved in CNS functional declines in aging and age-related neurodegenerative diseases, and that antioxidants, e.g., vitamin E, may ameliorate or prevent these declines. Present studies examined whether long-term feeding of Fischer 344 rats, beginning when the rats were 6 months of age and continuing for 8 months, with diets supplemented with a fruit or vegetable extract identified as being high in antioxidant activity, could prevent the age-related induction of receptor-mediated signal transduction deficits that might have a behavioral component. Thus, the following parameters were examined: (1) oxotremorine-enhanced striatal dopamine release (OX-K+-ERDA), (2) cerebellar beta receptor augmentation of GABA responding, (3) striatal synaptosomal 45Ca2+ clearance, (4) carbachol-stimulated GTPase activity, and (5) Morris water maze performance. The rats were given control diets or those supplemented with strawberry extracts (SE), 9.5 gm/kg dried aqueous extract (DAE), spinach (SPN 6.4 gm/kg DAE), or vitamin E (500 IU/kg). Results indicated that SPN-fed rats demonstrated the greatest retardation of age-effects on all parameters except GTPase activity, on which SE had the greatest effect, whereas SE and vitamin E showed significant but equal protection against these age-induced deficits on the other parameters. For example, OX-K+-ERDA enhancement was four times greater in the SPN group than in controls. Thus, phytochemicals present in antioxidant-rich foods such as spinach may be beneficial in retarding functional age-related CNS and cognitive behavioral deficits and, perhaps, may have some benefit in neurodegenerative disease.

Regulation of ubiquitin-conjugating enzymes by glutathione following oxidative stress

Upon oxidative stress cells show an increase in the oxidized glutathione (GSSG) to reduced glutathione (GSH) ratio with a concomitant decrease in activity of the ubiquitinylation pathway. Because most of the enzymes involved in the attachment of ubiquitin to substrate proteins contain active site sulfhydryls that might be covalently modified (thiolated) upon enhancement of GSSG levels (glutathiolation), it appeared plausible that glutathiolation might alter ubiquitinylation rates upon cellular oxidative stress. This hypothesis was explored using intact retina and retinal pigment epithelial (RPE) cell models. Exposure of intact bovine retina and RPE cells to H2O2 (0.1-1.7 micromol/mg) resulted in a dose-dependent increase in the GSSG:GSH ratio and coincident dose-dependent reductions in the levels of endogenous ubiquitin-activating enzyme (E1)-ubiquitin thiol esters and endogenous protein-ubiquitin conjugates and in the ability to form de novo retinal protein-125I-labeled ubiquitin conjugates. Oxidant-induced decrements in ubiquitin conjugates were associated with 60-80% reductions in E1 and ubiquitin-conjugating enzyme (E2) activities as measured by formation of ubiquitin thiol esters. When GSH levels in RPE cells recovered to preoxidation levels following H2O2 removal, endogenous E1 activity and protein-ubiquitin conjugates were restored. Evidence that S thiolation of E1 and E2 enzymes is the biochemical link between cellular redox state and E1/E2 activities includes: (i) 5-fold increases in levels of immunoprecipitable, dithiothreitol-labile 35S-E1 adducts in metabolically labeled, H2O2-treated, RPE cells; (ii) diminished formation of E1- and E2-125I-labeled ubiquitin thiol esters, oligomerization of E225K, and coincident reductions in protein-125I-labeled ubiquitin conjugates in supernatants from nonstressed retinas upon addition of levels of GSSG equivalent to levels measured in oxidatively stressed retinas; and (iii) partial restoration of E1 and E2 activities and levels of protein-125I-labeled ubiquitin conjugates in supernatants from H2O2-treated retinas when GSSG:GSH ratios were restored to preoxidation levels by the addition of physiological levels of GSH. These data suggest that the cellular redox status modulates protein ubiquitinylation via reversible S thiolation of E1 and E2 enzymes, presumably by glutathione.