Oxidative stress of crystalline lens in rat menopausal model / O estresse oxidativo do cristalino em modelo de rata na menopausa

ABSTRACT Purpose: To evaluate lenticular oxidative stress in rat menopausal models. Methods: Forty Wistar female albino rats were included in this study. A total of thirty rats underwent oophorectomy to generate a menopausal model. Ten rats that did not undergo oophorectomy formed the control group (Group 1). From the rats that underwent oophorectomy, 10 formed the menopause control group (Group 2), 10 were administered a daily injection of methylprednisolone until the end of the study (Group 3), and the remaining 10 rats were administered intraperitoneal streptozocin to induce diabetes mellitus (Group 4). Total oxidant status (TOS), total antioxidant capacity (TAC), and oxidative stress index (OSI) measurements of the crystalline lenses were analyzed. Results: The mean OSI was the lowest in group 1 and highest in group 4. Nevertheless, the difference between the groups was not statistically significant in terms of OSI (p >0.05). The mean TOS values were similar between the groups (p >0.05), whereas the mean TAC of group 1 was significantly higher than that of the other groups (p <0.001). Conclusions: Our results indicate that menopause may not promote cataract formation.

RESUMO Objetivo: Avaliar o estresse oxidativo lenticular em modelos de ratas na menopausa. Métodos: Quarenta ratos albinos femininos tipo Wistar foram incluídos neste estudo. Trinta ratas foram submetidas à ooforectomia para gerar o modelo de menopausa e 10 ratas formaram o grupo controle (Grupo 1). Dentre as ratas ooforectomizadas, 10 formaram o grupo controle menopausa (Grupo 2), 10 ratas receberam injeção diária de metilprednisolona até ao final do estudo (Grupo 3) e 10 ratas receberam estreptozotocina por via intraperitoneal para induzir diabetes mellitus (Grupo 4). O estado oxidante total (TOS), a capacidade total antioxidante (TAC) e as medições do índice de estresse oxidativo (OSI) dos cristalinos foram analisados. Resultados: A média de OSI foi menor no grupo 1 e maior no grupo 4. Todavia, a diferença entre os grupos não foi estatisticamente significativa (p>0,05). Os valores médios TOS foram semelhantes entre os grupos (p>0,05), enquanto a média de TAC grupo 1 foi mais elevada do que nos outros grupos ( p<0,001). Conclusões: Nossos resultados indicam que a menopausa podem não promover a formação de catarata.

Catarata em árvore de Natal / Christmas tree cataract

A catarata em árvore de Natal é um tipo raro de opacificação do cristalino caracterizado por depósitos policromáticos em forma de agulhas no córtex profundo e no núcleo do mesmo, que podem ser isolados ou associados a outras opacidades. Neste estudo relatamos e registramos, por meio de fotografias, dois casos deste tipo de opacidade cristaliniana.

The Christmas tree cataract is a rare type of lens opacification characterized by deposits of needle-shaped polychromatic cortex deep in the core, that can be isolated or associated with other opacities. We report and record, through photographs, two cases of this type of lens opacity.

Benefits of early glycemic control by insulin on sensory neuropathy and cataract in diabetic rats.

While there is an emphasis on the early glycemic control for its long-term benefits in preventing microvascular complications of diabetes, the biochemical mechanisms responsible for the long-lasting effects are not clearly understood. Therefore the impact of early insulin (EI) versus late insulin (LI) treatment on diabetic sensory neuropathy and cataract in streptozotocin-induced diabetic Wistar male rats were evaluated. EI group received insulin (2.5 IU/animal, once daily) treatment from day 1 to 90 while LI group received insulin from day 60 to 90. Early insulin treatment significantly reduced the biochemical markers like glucose, triglyceride, glycated hemoglobin, thiobarbituric acid reactive substances, advanced glycation end products and ratio of reduced glutathione and oxidized glutathione in diabetic rats. The late insulin treatment failed to resist the biochemical changes in diabetic rats. Diabetic rats developed sensory neuropathy as evidenced by mechanical and thermal hyperalgesia and showed a higher incidence and severity of cataract as revealed by slit lamp examination. Early insulin treatment protected the rats from the development of neuropathy and cataract, but late insulin administration failed to do so. The results demonstrate the benefits of early glycemic control in preventing neuropathy and cataract development in diabetic rats.

Plasticity and reprogramming of differentiated ocular tissue of tadpoles of the frog, Euphlyctis cyanophlyctis under the influence of vitamin A.

Present study has shown that differentiated cell types may loose their definitive characteristics and acquire features of another specialized cell type. Young (3 toe stage) and mature (5 toe stage) tadpoles of the frog, Euphylictis cyanophlyctis were employed as experimental animals. Experiments were completed in two phases: in the first part of experiment, lenses were extracted from right eye balls of tadpoles and treated with vitamin A; in the second part of the experiment, meshed lentectomized eye ball tissues were implanted into the pit made on mid lateral position of the tail of young and mature tadpoles and were treated with vitamin A. The results obtained gave clear evidence of plasticity and reprogramming of terminally differentiated ocular tissue into lens, retina and even complete eye. Vitamin A was found to be good model for accelerating the reprogramming of differentiated ocular tissue in anuran frog tadpoles.

Influence of galactose cataract on erythrocytic and lenticular glutathione metabolism in albino rats.

Context: Glutathione depletion has been postulated to be the prime reason for galactose cataract. The current research seeks the prospect of targeting erythrocytes to pursue the lens metabolism by studying the glutathione system. Aims: To study the activity of the glutathione-linked scavenger enzyme system in the erythrocyte and lens of rats with cataract. Materials and Methods: Experiments were conducted in 36 male albino rats weighing 80 ± 20 g of 28 days of age. The rats were divided into two major groups, viz. experimental and control. Six rats in each group were sacrificed every 10 days, for 30 days. Cataract was induced in the experimental group by feeding the rats 30% galactose (w/w). The involvement of reduced glutathione (GSH) and the linked enzymes was studied in the erythrocytes and lens of cataractous as well as control rats. Statistical Analysis: Parametric tests like one-way ANOVA and Student's ‘t’ test were used for comparison. Correlation linear plot was used to compare the erythrocyte and lens metabolism. Results: Theconcentration of GSH and the activity of linked enzymes were found decreased with the progression of cataract, and also in comparison to the control. The same linear fashion was also observed in the erythrocytes. Conclusion: Depletion of GSH was the prime factor for initiating galactose cataract in the rat model. This depletion may in turn result in enzyme inactivation leading to cross-linking of protein and glycation. The correlation analysis specifies that the biochemical mechanism in the erythrocytes and lens is similar in the rat model.

Targeting CYP450 modulation to decrease the risk of induced cataract in the experimental model.

Background: Diabetes is one of the major causes of cataract. Some drugs prescribed for the treatment of diabetes are the modulators of CYP450, which may alter the risk of cataract. Objective: To study the effect of CYP450 modulation in galactosemic cataract. Materials and Methods: Male Sprague-Dawley suckling rats were allotted to four groups (n = 6), as follows: Group 1: Normal control, Group 2: Galactose control, Group 3: CYP450 inhibitor pretreated and Group 4: CYP450 inducer pretreated. Cataract was induced in animals of all groups except group 1 by feeding them galactose (50%), 21 days after parturition. From the eighteenth day of life, CYP450 inhibitor (nifedipine; 8.1 mg/kg) and CYP450 inducer (pioglitazone; 3.8 mg/kg) were given orally to groups 3 and 4, respectively. The maturation pattern of the cataract was observed by an operating microscope, every third day. Biochemical changes in the lenses of all groups, for example, CYP450 activity expressed as µM NADPH oxidized / unit time, alterations in the levels of total proteins, soluble proteins, and reduced glutathione (GSH) following the induction of cataract, were estimated. Results: The microscopic examination of the lenses indicated that CYP450 inhibitor pre-treatment delayed (fourteenth day) the occurrence of cataract, while CYP450 inducer pretreatment demonstrated an early (ninth day) cataract as compared to galactose control rats (twelfth day). A significant decrease and increase in CYP450 activity was observed with the CYP450 inhibitor and inducer pre-treatment, respectively. There was no alteration in the GSH level, but a significant increase in total and soluble protein was found in groups 3 and 4 as compared to group 2. Conclusion: CYP450 may have a role in the initiation of cataract without any effect on the maturation pattern, as revealed by the delayed occurrence of cataract with the CYP450 inhibitor and an early onset of cataract with the CYP450 inducer.

Preventive effect of onion juice on selenite-induced experimental cataract.

Purpose: To evaluate the effects of onion juice on sodium-selenite induced cataract formation. Materials and Methods: Thirty-two 10-day-old Wistar-albino rat pups were divided into four equal groups. Group 1 received only subcutaneous saline injection. In Group 2, sodium-selenite (30 nmol / g body weight) was injected subcutaneously. In Group 3, subcutaneous sodium-selenite was injected and one drop 50% diluted fresh juice of crude onion was instilled every 8 h into the right eye for 14 days; the left eye received no treatment. Group 4 rats were similar to those of Group 3, the only difference being that of undiluted fresh juice of crude onion. The development of cataract was assessed. Rat lenses were analyzed for total antioxidant (TA) level, and for activities of glutathione peroxidase (GPX) and superoxide dismutase (SOD). Results: Both eyes of all rats in Group 1 did not exhibit cataract formation . In Group 2, all rats developed Grade 3 cataract in the lenses of both eyes. The difference in exhibited cataract in the lens of the right eyes in all rats between Group 2 and any eyes of groups 3 or 4 were significant ( P = 0.001). The mean TA level and mean activities of SOD and GPX in Group 2 rat lenses were significantly lower than the values in lenses of all rats in Group 1 ( P = 0.001, 0.003, 0.001), and in the lenses of the right eyes of rats in Groups 3 and 4 ( P = 0.001, 0.020, 0.001). Conclusion: Instillation of onion juice into the rat eyes can effectively prevent selenite-induced cataract formation. This effect was associated with increased TA level, SOD and GPX activities in the lens.

Expression of transforming growth factor-beta in cultured normal human lens epithelia cells / 华中科技大学学报（医学）（英德文版）

In order to investigate whether cultured normal human lens epithelial cells (LEC) express transforming growth factor beta (TGF-beta), reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemical methods were used for detection of TGF-beta mRNA and protein in cultured normal human LEC. The results showed that a single RT-PCR amplified product about 310bp was obtained, and the sequence was homologous to the known sequence. TGF-beta immunostain was positive in the plasma of LEC. It was suggested that normal human LEC could produce TGF-beta, and LEC could be affected by TGF-beta through autocrine action.

Accumulation and Aberrant Modifications of alpha-Crystallins in Anterior Polar Cataracts

Crystallins are the major proteins found in the lens, and the localization of specific crystallins is well known. Overexpression and accumulation of alphaB-crystallin has been observed in response to stress conditions or in certain diseases, such as brain tumors and neurodegenerative diseases. The purpose of this study was to examine whether alpha-crystallins are modified during pathological myofibroblastic changes in lens epithelial cells. Lens epithelial cells attached to the anterior capsules of patients with nuclear or anterior polar cataracts were analyzed quantitatively for alpha-crystallin proteins and mRNAs using Western blot and RT-PCR analysis., respectively. The degree of modification of alpha-crystallins was determined by 2-dimensional gel electrophoresis followed by Western blotting. Higher molecular weight protein bands that were immunoreactive to anti-alphaA- and anti-alphaB-crystallin antibodies around 45 kDa accumulated more in the anterior polar cataract samples than in those with the nuclear type of cataracts. Also monomeric alphaB-crystallins accumulated more in lens epithelial cells of patients with anterior polar cataracts. By comparison, no significant changes were found in the levels of the mRNAs encoding alphaA- and alphaB-crystallins in the different types of cataracts. Both alphaA- and alphaB-crystallin proteins seemed to undergo more extensive modification in anterior polar cataracts. Conclusion. In addition to fibrotic changes, which accompany increased levels of extracellular matrix molecules, accumulation and abnormal modification of alpha-crystallins might be implicated in the pathogenic mechanism of this type of cataract.

Selenite cataract and its attenuation by vitamin E in Wistar rats.

PURPOSE: To study the role of vitamin E in preventing cataract formation in experimental animals. METHODS: An experimental model (selenite cataract) was selected for this study. Selenite cataract was produced in rats by subcutaneous administration of sodium selenite. Biochemical and histological changes following induction of selenite cataract in weanling Wistar rats were studied vis-a-vis the role of vitamin E in attenuating or preventing cataractogenesis. RESULTS: Vitamin E was capable of preventing selenite cataractogenesis. Selenite cataract did not develop in 91.6% (11 of 12) and 76.7% (8 of 12) vitamin E treated rats, when administered on the 12th and 10th post partum day respectively. CONCLUSION: The study confirmed that selenite induced cataract in Wistar rats is attenuated by vitamin E.

Molecular genetics of cataract.

Studies on hereditary congenital cataracts have led to the identification of genes involved in formation of these cataracts. Knowledge of the structure and function of a particular gene and the effect of disease-associated mutations on its function are providing insights into the mechanisms of cataract. Identification of the disease gene requires both the relevant clinical data as well as genetic data on the entire pedigree in which the disease is found to occur. Genes for hereditary cataract have been mapped by genetic linkage analysis, in which one examines the inheritance pattern of DNA markers throughout the genome in all individuals of the pedigree, and compares those with the inheritance of the disease. Cosegregation of a set of markers with disease implies that the disease gene is present at the same chromosomal location as those markers. The genes so far identified for hereditary cataracts in both humans and animal models encode structural lens proteins, gap junction proteins, membrane proteins and regulatory proteins involved in lens development. Understanding of the mechanisms of hereditary cataract may also help us understand the manner in which environmental and nutritional factors act on the lens to promote opacification.

Oxidative damage to the eye lens caused by cigarette smoke and fuel smoke condensates.

Cigarette smoking is reported to increase the risk of cataract. Likewise, the use of smoky cooking fuel is implicated in the etiology of cataract. In an effort to understand the cellular and molecular basis, the in vitro and in vivo cataractogenetic effects of these smoke condensates have been studied using isolated rat lenses and pigmented rats. Isolated capsulated rat lenses are incubated with cigarette smoke condensate (CSC) and firewood smoke condensate (FSC) for varying periods, with and without antioxidants, in the presence and absence of light. CSC and FSC permeate the lens capsule, impart colour and opacify the lens in a light- and dose-dependent manner. Antioxidants offer partial inhibition against the above damage. The condensates contain polycyclic aromatics which generate reactive oxygen species such as O2 photodynamically, and ppb levels of Fenton metal ions which induce oxidative reactions through .OH. Smoke induced damage possibly occurs through systemic absorption and transport of toxic components to several tissues, and specially into the lens, wherein the turnover is slow, leading to chronic accumulation causing oxidative damage to the constituent molecules and to consequent lenticular opacity.

Increased glycosylation of human lens epithelial basement membrane in diabetes mellitus

We studied the nonenzymatic glycosylation of lens epithelial basement membranes (LEBM) of senile cataractous lenses of both diabetic and nondiabetic patients. The human LEBMs were isolated from surgically removed senile cataracts and purified by osmotic lysis and detergent treatments. Glycosylation assay of LEBMs was done using the colorimetric method of Fluckiger and Winterhalter. The glycosylation value ranged from 16.39 to 92.56 n mol/mg protein overall, with a mean of 63.54 +/- 24.56 n mol/mg protein for the diabetic specimens and a mean of 29.97 +/- 14.48 n mol/mg protein for the nondiabetic controls (P = 0.009). The study confirms our previous observation of in vivo glycosylation of the LEBM and further establishes that diabetic patients have a twofold increase in the amount of LEBM glycosylation when compared to their nondiabetic counterparts.

Increased glycosylation of human lens epithelial basement membrane in diabetes mellitus

We studied the nonenzymatic glycosylation of lens epithelial basement membranes (LEBM) of senile cataractous lenses of both diabetic and nondiabetic patients. The human LEBMs were isolated from surgically removed senile cataracts and purified by osmotic lysis and detergent treatments. Glycosylation assay of LEBMs was done using the colorimetric method of Fluckiger and Winterhalter. The glycosylation value ranged from 16.39 to 92.56 n mol/mg protein overall, with a mean of 63.54 +/- 24.56 n mol/mg protein for the diabetic specimens and a mean of 29.97 +/- 14.48 n mol/mg protein for the nondiabetic controls (P = 0.009). The study confirms our previous observation of in vivo glycosylation of the LEBM and further establishes that diabetic patients have a twofold increase in the amount of LEBM glycosylation when compared to their nondiabetic counterparts.

Acid phosphatase and lipid peroxidation in human cataractous lens epithelium.

The anterior lens epithelial cells undergo a variety of degenerative and proliferative changes during cataract formation. Acid phosphatase is primarily responsible for tissue regeneration and tissue repair. The lipid hydroperoxides that are obtained by lipid peroxidation of polysaturated or unsaturated fatty acids bring about deterioration of biological membranes at cellular and tissue levels. Acid phosphatase and lipid peroxidation activities were studied on the lens epithelial cells of nuclear cataract, posterior subcapsular cataract, mature cataract, and mixed cataract. Of these, mature cataractous lens epithelium showed maximum activity for acid phosphatase (516.83 moles of p-nitrophenol released/g lens epithelium) and maximum levels of lipid peroxidation (86.29 O.D./min/g lens epithelium). In contrast, mixed cataractous lens epithelium showed minimum activity of acid phosphatase (222.61 moles of p-nitrophenol released/g lens epithelium) and minimum levels of lipid peroxidation (54.23 O.D./min/g lens epithelium). From our study, we correlated the maximum activity of acid phosphatase in mature cataractous lens epithelium with the increased areas of superimposed cells associated with the formation of mature cataract. Likewise, the maximum levels of lipid peroxidation in mature cataractous lens epithelium was correlated with increased permeability of the plasma membrane. Conversely, the minimum levels of lipid peroxidation in mixed cataractous lens epithelium makes us presume that factors other than lipid peroxidation may also account for the formation of mixed type of cataract.

Cations, oxidants, light as causative agents in senile cataracts

Lens transparency is a function of regular cell shape, regular cell volume, minimal extracellular space, and minimal scatter elements. The cellular structure and molecular structure of the lens is reviewed. The importance of the cytoarchitecture especially the sutures, is discussed. The high cholesterol: phospholipid ratio of the lens fiber cell membranes is related to the functions of low permeability, low fluidity, and mechanical stability. Also reviewed are the contributions of the lens crystallins to lens clarity and to lens refractive index. The importance of intracellular and extracellular cation and water concentrations are reviewed. Finally the effects of systemic diseases, oxidation, and light on lens clarity are discussed relative to changes in lens fiber cell cation concentrations

Melanins and lens pigments: a comparative study

Based on previous findings that lens pigments and melanins share many physicochemical properties, human lens pigments and natural (hair) and synthetic melanins were submitted to oxidation with permanganate under strong acidic conditions. This procedure has been utilized for the characterization of melanins and results in the well defined products, thiazole-4,5-dicarboxylic acid (TDCA) and pyrrole-2,3,5-tricarboxylic acid (PTCA), which can be quantitated by high performance liquid chromatography (HPLC). PTCA is regarded as a marker of black eumelanins and was therefore a main component of synthetic DOPA-eumelanin and dark hair. Its identity was established by synthesis from 5-hydroxyindole-2-carboxylic acid. TDCA derives from pheomelanins and was therefore an important component of red hair and synthetic GSH-pheomelanin. TDCA was identified by its retention time relative to PTCA. The analysis of a series of cataract digests of increasing pigmentation (type I < type IV < type V) and a purified fraction of lens pigments (DE52 pigment) revealed the presence in these preparations of both PTCA and TDCA. The concentration of TDCA significantly increased with the degree of pigmentation of the digests and reached a maximum in the DE52 pigment. The TDCA/PTCA ratio was high in the lens preparations and comparable to that given by hair pheomelanin. These findings support that pheomelanin is an integral part of lens pigments. By comparing the yields of TDCA in GSH-pheomelanin and in the purified lens pigment, a 9 per cent contribution of pheomelanin to the lens pigment was estimated

Cholesterol and lipid peroxidation in 3 beta-(2-diethylaminoethoxy)- androst-5-en-17-oneHCl (U18666A) induced cataractogenesis in rats.

Decrease in cholesterol was observed in precataractous, cataractous, advance nuclear cataractous and non-cataractous lenses when 3 beta-(2-diethylaminoethoxy)-androst-5-en-17- oneHCl (U18666A) was injected, sc, to rats. Significant increase in lipid peroxidation was observed before the onset of any apparent lenticular opacity in U18666A treated rats. The results suggest that decrease in cholesterol is capable of altering the structural integrity of lens fibers. However, 12.5% decrease in cholesterol and 5% increase in lipid peroxidation observed in non-cataractous lenses indicated that these changes are not sufficient for any apparent opacification.

Clinico-biochemical study of experimental complicated cataracts.

Clinically observed complicated cataracts, generally do not have a definite causal factor. We studied the effects of E. coli toxin injected suprachoroidally, to simulate the effect of toxins released by extraocular organisms on the lens. 79.2% of eyes had a definable cataract at the end of the 6th week of observation. The biochemical changes portrayed an increased oxidative activity in the lens, evidenced by a fall in glutathione concentration, and the consequent tertiary reorientation of proteins to increase insoluble proteins, forming a cataract.

Role of proteins and cholesterol in human senile cataractogenesis.

Cataracts are a major cause of blindness in man with far reaching personal, social and economic consequences. The clarity of the lens is dependent upon the maintenance of the integrity of the fiber cell plasma membrane whose important component is cholesterol. In the present study, we have demonstrated that cataract formation influences the cholesterol and protein distribution within the lens.