Cataract Development In Mice Research Articles

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.

Genotype, Age, Genetic Background, and Sex Influence Epha2-Related Cataract Development in Mice.

PurposeAge-related cataract is the leading cause of blindness worldwide. Variants in the EPHA2 gene increase the disease risk, and its knockout in mice causes cataract. We investigated whether age, sex, and genetic background, risk factors for age-related cataract, and Epha2 genotype influence Epha2-related cataract development in mice.MethodsCataract development was monitored in Epha2+/+, Epha2+/−, and Epha2−/− mice (Epha2Gt(KST085)Byg) on C57BL/6J and FVB:C57BL/6J (50:50) backgrounds. Cellular architecture of lenses, endoplasmic reticulum (ER) stress, and redox state were determined using histological, molecular, and analytical techniques.ResultsEpha2−/− and Epha2+/− mice on C57BL/6J background developed severe cortical cataracts by 18 and 38 weeks of age, respectively, compared to development of similar cataract significantly later in Epha2−/− mice and no cataract in Epha2+/− mice in this strain on FVB background, which was previously reported. On FVB:C57BL/6J background, Epha2−/− mice developed severe cortical cataract by 38 weeks and Epha2+/− mice exhibited mild cortical cataract up to 64 weeks of age. Progression of cataract in Epha2−/− and Epha2+/− female mice on C57BL/6J and mixed background, respectively, was slower than in matched male mice. N-cadherin and β-catenin immunolabeling showed disorganized lens fiber cells and disruption of lens architecture in Epha2−/− and Epha2+/− lenses, coinciding with development of severe cataracts. EPHA2 immunolabeling showed intracellular accumulation of the mutant EPHA2-β-galactosidase fusion protein that induced a cytoprotective ER stress response and in Epha2+/− lenses was also accompanied by glutathione redox imbalance.ConclusionsBoth, Epha2−/− and Epha2+/− mice develop age-related cortical cataract; age as a function of Epha2 genotype, sex, and genetic background influence Epha2-related cataractogenesis in mice.

Biochemical and biomechanical characteristics of dystrophin-deficient mdx3cv mouse lens

The molecular and cellular basis for cataract development in mice lacking dystrophin, a scaffolding protein that links the cytoskeleton to the extracellular matrix, is poorly understood. In this study, we characterized lenses derived from the dystrophin-deficient mdx3cv mouse model. Expression of Dp71, a predominant isoform of dystrophin in the lens, was induced during lens fiber cell differentiation. Dp71 was found to co-distribute with dystroglycan, connexin-50 and 46, aquaporin-0, and NrCAM as a large cluster at the center of long arms of the hexagonal fibers. Although mdx3cv mouse lenses exhibited dramatically reduced levels of Dp71, only older lenses revealed punctate nuclear opacities compared to littermate wild type (WT) lenses. The levels of dystroglycan, syntrophin, and dystrobrevin which comprise the dystrophin-associated protein complex (DAPC), and NrCAM, connexin-50, and aquaporin-0, were significantly lower in the lens membrane fraction of adult mdx3cv mice compared to WT mice. Additionally, decreases were observed in myosin light chain phosphorylation and lens stiffness together with a significant elevation in the levels of utrophin, a functional homolog of dystrophin in mdx3cv mouse lenses compared to WT lenses. The levels of perlecan and laminin (ligands of α-dystroglycan) remained normal in dystrophin-deficient lens fibers. Taken together, although mdx3cv mouse lenses exhibit only minor defects in lens clarity possibly due to a compensatory increase in utrophin, the noted disruptions of DAPC, stability, and organization of membrane integral proteins of fibers, and stiffness of mdx3cv lenses reveal the importance of dystrophin and DAPC in maintaining lens clarity and function.

Deficiency of circadian protein CLOCK reduces lifespan and increases age-related cataract development in mice

Circadian clock is implicated in the regulation of aging. The transcription factor CLOCK, a core component of the circadian system, operates in complex with another circadian clock protein BMAL1. Recently it was demonstrated that BMAL1 deficiency results in premature aging in mice. Here we investigate the aging of mice deficient for CLOCK protein. Deficiency of the CLOCK protein significantly affects longevity: the average lifespan of Clock-/- mice is reduced by 15% compared with wild type mice, while maximum lifespan is reduced by more than 20%. CLOCK deficiency also results in the development of two age-specific pathologies in these mice, cataracts and dermatitis, at a much higher rate than in wild type mice. In contrast to BMAL1 deficient animals, Clock-/- mice do not develop a premature aging phenotype and do not develop the multiple age-associated pathologies characteristic of BMAL1 deficiency. Thus, although CLOCK and BMAL1 form a transcriptional complex, the physiological result of their deficiency is different. Our results suggest that CLOCK plays an important role in aging, specifically; CLOCK activity is critical for the regulation of normal physiology and aging of the lens and skin.

Hydrophobic Core Mutations Associated with Cataract Development in Mice Destabilize Human γD-Crystallin

The human eye lens is composed of fiber cells packed with crystallins up to 450 mg/ml. Human γD-crystallin (HγD-Crys) is a monomeric, two-domain protein of the lens central nucleus. Both domains of this long lived protein have double Greek key β-sheet folds with well packed hydrophobic cores. Three mutations resulting in amino acid substitutions in the γ-crystallin buried cores (two in the N-terminal domain (N-td) and one in the C-terminal domain (C-td)) cause early onset cataract in mice, presumably an aggregated state of the mutant crystallins. It has not been possible to identify the aggregating precursor within lens tissues. To compare in vivo cataract-forming phenotypes with in vitro unfolding and aggregation of γ-crystallins, mouse mutant substitutions were introduced into HγD-Crys. The mutant proteins L5S, V75D, and I90F were expressed and purified from Escherichia coli. WT HγD-Crys unfolds in vitro through a three-state pathway, exhibiting an intermediate with the N-td unfolded and the C-td native-like. L5S and V75D in the N-td also displayed three-state unfolding transitions, with the first transition, unfolding of the N-td, shifted to significantly lower denaturant concentrations. I90F destabilized the C-td, shifting the overall unfolding transition to lower denaturant concentrations. During thermal denaturation, the mutant proteins exhibited lowered thermal stability compared with WT. Kinetic unfolding experiments showed that the N-tds of L5S and V75D unfolded faster than WT. I90F was globally destabilized and unfolded more rapidly. These results support models of cataract formation in which generation of partially unfolded species are precursors to the aggregated cataractous states responsible for light scattering.

Removal of Hsf4 leads to cataract development in mice through down-regulation of γS-crystallin and Bfsp expression

BackgroundHeat-shock transcription factor 4 (HSF4) mutations are associated with autosomal dominant lamellar cataract and Marner cataract. Disruptions of the Hsf4 gene cause lens defects in mice, indicating a requirement for HSF4 in fiber cell differentiation during lens development. However, neither the relationship between HSF4 and crystallins nor the detailed mechanism of maintenance of lens transparency by HSF4 is fully understood.ResultsIn an attempt to determine how the underlying biomedical and physiological mechanisms resulting from loss of HSF4 contribute to cataract formation, we generated an Hsf4 knockout mouse model. We showed that the Hsf4 knockout mouse (Hsf4-/-) partially mimics the human cataract caused by HSF4 mutations. Q-PCR analysis revealed down-regulation of several cataract-relevant genes, including γS-crystallin (Crygs) and lens-specific beaded filament proteins 1 and 2 (Bfsp1 and Bfsp2), in the lens of the Hsf4-/- mouse. Transcription activity analysis using the dual-luciferase system suggested that these cataract-relevant genes are the direct downstream targets of HSF4. The effect of HSF4 on γS-crystallin is exemplified by the cataractogenesis seen in the Hsf4-/-,rncat intercross. The 2D electrophoretic analysis of whole-lens lysates revealed a different expression pattern in 8-week-old Hsf4-/- mice compared with their wild-type counterparts, including the loss of some αA-crystallin modifications and reduced expression of γ-crystallin proteins.ConclusionOur results indicate that HSF4 is sufficiently important to lens development and disruption of the Hsf4 gene leads to cataracts via at least three pathways: 1) down-regulation of γ-crystallin, particularly γS-crystallin; 2) decreased lens beaded filament expression; and 3) loss of post-translational modification of αA-crystallin.

Mutations associated with early cataract development in mice destabilize human gammaD‐crystallin

Mutations associated with early cataract development in mice destabilize human gammaD‐crystallin

Cataract Development in γ-Glutamyl Transpeptidase-deficient Mice

The present study was undertaken to analyse the relationship of lens glutathione (GSH) and light to cataract development in mice deficient in γ-glutamyl transpeptidase (GGT). These mice have reduced levels of cysteine and GSH in the eye and develop cataracts. GGT-deficient mice raised under normal vivarium conditions, showed no cataractous changes at birth, but by 1 week they had developed nuclear opacities. By 3 weeks more severe cataracts develop, and lens GSH levels are approximately 6–7% of wild type levels. By 6–11 weeks cataracts show nuclear and cortical involvement, liquefaction and calcification. Single cell DNA electrophoresis (comet assay) demonstrated mild DNA damage in the lens epithelium. GGT-deficient mice raised in the dark beginning the day after conception all developed cataracts, but these were less severe than those in GGT-deficient mice raised with normal vivarium lighting. Administration of N -acetyl cysteine (NAC) raises lens GSH and almost completely prevents cataract development. Our data indicate that cataract development in GGT-deficient mice is multifactorial and results from exogenous damage (exposure to light), reduced lens GSH levels, and nutritional effects secondary to low cysteine levels.

Scanning electron microscopy of X-ray-induced cataract in mice on normal and galactose diet.

The possible multiple effect of galactose diet and X-irradiation on cataract development in mice was investigated by scanning electron microscopy. X-ray cataracts were induced by maintaining animals either on a normal or 50% galactose diet. No detectable changes in lens morphology were seen in animals fed galactose alone compared with normal controls. 2 months after X-ray, less damage had occurred to the lenses of the galactose-fed animals compared to those on a normal diet. At 4 months after X-ray, animals on a normal diet developed mature cataracts, while in the galactose-fed animals they were delayed by 0.5-1.5 months. Suppression of the development of X-ray cataract by galactose feeding may be related to the ability of this sugar, which accumulates in mouse lens due to the low levels of aldose reductase, to act as a free radical scavenger.

Types and Rate of Cataract Development in Mice Irradiated at Different Ages

The effect of age on the development of radiation cataract has been investigated in an inbred A strain of mice and, as a result, the patterns of age dependence and senile mice cataract development were obtained. In general, the lenses of mice 1-3 days old were the most sensitive to radiation; the maximum resistance was noted in 5-day-old mice, and from this age up to 3-7 weeks of life there was a period of increasing sensitivity. In older animals the lens sensitivity tends to level off. The early stages of cataract occurred in all irradiated groups at a younger age than in the control group, but the late stages occurred in irradiated groups at the same age as the senile cataract occurred in the control group. Two types of cataract were observed. One was typical for young irradiated mice 1 to 5 days of age and the other was typical for all remaining irradiated groups and for a control group. Also, an attempt was made to correlate the obtained results with the cell kinetics in normal lens epithelium.

Soluble lens proteins of mutant stock mice in cataract development

Changes in soluble proteins of the maturing cataract were studied in mice of the mutant stocks: ocular retardation (gene symbol or ); white ( Mi wh ); fidget ( fi ); and dominant cataract-Fraser ( Cat Fr ). Crystallin fractions of the normal lens were first identified by polyacrylamide gel electrophoresis. In the course of cataract development in mice of the studied mutant stocks, a diminution or loss of some crystallin fractions was observed. The maturation of secondary cataracts in or/or, Mi wh / Mi wh , and fi/fi mice was accompanied by a significant increase in serum albumin, which preceded visible lens opacity. In agar electrophoresis, albumin and α-crystallin were found to migrate together, simulating quantitative maintenance of α-crystallin in the maturing cataract. Another serum protein, electrophoretically similar to transferrin, also penetrated into the lens during cataract development. Maturation of primary nuclear cataract in Cat Fr / Cat Fr mice was not accompanied by increased penetration of serum proteins into the lens. Apparently, penetration of serum proteins into the lens participates in the pathogenesis of secondary subcapsular cataracts, while primary nuclear cataracts have a different etiology.