Oxidative Stress In Lens Research Articles

Blocking of SGLT2 to Eliminate NADPH-Induced Oxidative Stress in Lenses of Animals with Fructose-Induced Diabetes Mellitus.

Chronic hyperglycemia triggers an abnormal rise in reactive oxygen species (ROS) that leads to blindness in patients with diabetes mellitus (DM) and cataracts. In this study, the effects of dapagliflozin, metformin and resveratrol on ROS production were investigated in lens epithelial cells (LECs) of animals with fructose-induced DM. LECs were isolated from patients without DM, or with DM devoid of diabetic retinopathy. Animals were treated with 10% fructose for 8 weeks to induce DM, which was verified by monitoring blood pressure and serum parameters. For drug treatments, 1.2 mg/day of dapagliflozin was given for 2 weeks, 500 mg/kg/day of metformin was given, and 10 mg/kg/day of resveratrol was given. Dihydroethidium was used to stain endogenous O2˙− production in vivo of the LECs. Superoxide production was expressed in the cataract of DM, or patients without DM. Sodium–glucose cotransporter 2 (SGLT2), glucose transporter 1 (GLUT1), GLUT5, the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit p47/p67-phox, NOX4 and RAGE were significantly increased in LECs with DM. In addition, the dapagliflozin treatment reduced GLUT5, p47/p67-phox, NADPH oxidase 4 (NOX4) and receptor for advanced glycation end products (RAGE) expressions. On the contrary, metformin or resveratrol inhibited p47-phox, GLUT5, and SGLT2 expressions, but not nuclear factor erythroid 2–related factor 2 (NRF2). In summary, dapagliflozin, metformin or resveratrol down-regulated p47-phox expression through SGLT2 inactivation and ROS reduction. These important findings imply that SGLT2 can be blocked to ameliorate oxidative stress in the cataracts of DM patients.

Anti-cataract effects of coconut water in vivo and in vitro

ObjectiveTo determine the anti-cataract effects of coconut water (CW) in vivo and in vitro, and to explore the potential pathogenic mechanism. MethodsIn this study, 48 male Sprague-Dawley rats were randomly divided into 4 groups: control (CO), diabetic (DM), diabetic treated with CW (DM + CW), and diabetic treated with Glibenclamide (DM + Gli). Except for the CO group, in the other three groups, intraperitoneal injection of STZ (60 mg/kg) was conducted to establish diabetic models. The experiment was conducted for 20 weeks. The slit-lamp examination was undertaken during the period of experiment (20 weeks), and then, all rats were sacrificed. The levels of superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione peroxidase (GSH-Px) in the left lens were measured by using biochemical assays. The right lens was used for pathological analysis. The rat lens epithelial cells (LECs) were cultured in vitro and the subcultured cell were divided into four groups, namely the normal glucose group (5 mmol /L glucose, Group I), the high glucose group (40 mmol/L glucose, Group II), high glucose +5% CW group (Group III), and high glucose +10% CW group (Group IV). LECs were cultured under the conditions as described above for 48 h. Cell proliferation and the morphological changes were observed with interted phase contrast microscope.The level of cell apoptosis was determined by flow cytometry. the level of SOD, MDA and GSH-Px were also detected. ResultsThe lens opacity index decreased in diabetic rats, and LECs apoptosis ratio also decreased in high glucose environments that received CW. Under treatment with CW, reduced MDA level and elevated activities of SOD and GSH-Px were detected, both in vivo and in vitro experiments. The increased severity of cataract and LECs apoptosis were noted in diabetic rats that received normal water, while CW markedly mitigated the enhanced cataract severity and the reduction of LECs induced by diabetes mellitus. ConclusionCW is a functional food that can protect the lens from diabetic cataract. The possible underlying mechanism may be partly explained via the decreased oxidative stress in lens. However, further research needs to be conducted to indicate the pathogenic mechanism of anti-diabetic effects of CW.

Simultaneous amelioration of diabetic ocular complications in lens and retinal tissues using a non-invasive drug delivery system

Topically administered delivery systems for ophthalmic applications have been studied for the treatment of anterior or posterior eye diseases. However, simultaneous treatment of both anterior and posterior eye diseases has not been explored. In this study, we fabricated a topically administrable polymeric nanoparticle (NP)- based delivery system consisting of pluronic®F-68 shell and polycaprolactone core for the simultaneous treatment of both anterior and posterior eye diseases. These NPs were loaded with pyrrolidine dithiocarbamate (PDTC) or triamcinolone acetonide (TA) separately. The drug loading in NPs was optimized to initially achieve a moderate burst release of PDTC followed by slow and sustained release of both PDTC and TA. The resultant delivery system was studied for its in vivo efficacy in a diabetic retinopathy (DR) and cataract rat model. The results demonstrated that administration of PDTC NPs + TA NPs minimized oxidative stress in lens as evidenced by reduced levels of protein carbonyls and malondialdehyde, and, ameliorated DR complications in retina as evidenced by reduced expression of hypoxia inducible factor-1α along with a reduction in number of neovascular tufts and acellular capillaries. Therefore, delivery of PDTC and TA using PCL-PF68 NPs could be a useful approach for simultaneous treatment of diabetic cataract and DR.

Effect of caffeine on biomarkers of oxidative stress in lenses of rats with streptozotocin-induced diabetes.

IntroductionOne of the major causes of cataract in diabetes is oxidative stress induced by reactive oxygen species (ROS). Nowadays, new substances with antioxidative properties that may prevent cataract development are needed. One such substance is caffeine – an alkaloid with well-documented antioxidative activity.Material and methodsThe study was conducted on lenses obtained from female rats, divided into 3 groups: control rats; diabetic rats; diabetic rats treated with caffeine at a dose of 20 mg/kg p.o. Type 1 diabetes was induced by streptozotocin (60 mg/kg i.p.). After 4 weeks of caffeine administration, the rats were sacrificed, and the lenses were collected, weighed and homogenized in PBS. The homogenate was used for analysis of protein content, glutathione (GSH) concentration, advanced oxidation protein product (AOPP) concentration, malondialdehyde (MDA) concentration and the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx).ResultsThe SOD, CAT and GPx activities were found to be higher in the lenses of diabetic rats. There were also increased MDA and AOPP concentrations as well as decreased GSH concentration. The administration of caffeine resulted in decreased activity of SOD, CAT and GPx. The treatment with caffeine also caused an increase of GSH concentration and a decrease of MDA and AOPP concentrations.ConclusionsThe results of the present study may be of relevance in determining the effect of caffeine on the processes induced by ROS in vivo. Further, they can be an indication for clinical observations aiming at the assessment of both preventive and therapeutic effects of caffeine in cataract.

Effect of Resveratrol, a Dietary-Derived Polyphenol, on the Oxidative Stress and Polyol Pathway in the Lens of Rats with Streptozotocin-Induced Diabetes.

Resveratrol is found in grapes, apples, blueberries, mulberries, peanuts, pistachios, plums and red wine. Resveratrol has been shown to possess antioxidative activity and a variety of preventive effects in models of many diseases. The aim of the study was to investigate if this substance may counteract the oxidative stress and polyol pathway in the lens of diabetic rats. The study was conducted on the rats with streptozotocin-induced type 1 diabetes. After the administration of resveratrol (10 and 20 mg/kg po for 4 weeks), the oxidative stress markers in the lens were evaluated: activity of superoxide dismutase, catalase and glutathione peroxidase, as well as levels of total and soluble protein, level of glutathione, vitamin C, calcium, sulfhydryl group, advanced oxidation protein products, malonyldialdehyde, Total Oxidant Status and Total Antioxidant Reactivity. The obtained results indicate that the administration of resveratrol to the diabetic rats shows antioxidative properties. It is not a result of antiglycaemic activity but resveratrol probably directly affects the antioxidative system. Resveratrol did not affect the polyol pathway in the lens of diabetic rats. Our results may indirectly indicate benefits of consumption of foods as well as dietary supplements containing resveratrol in diminishing oxidative stress in lenses of individuals suffering from diabetes mellitus.

Fatty acids modulate the efficacy of lutein in cataract prevention: Assessment of oxidative and inflammatory parameters in rats

BackgroundEffects of lutein (L) and fatty acids [linoleic acid (LA), eicosapentaenoic acid (EPA)+docosahexaenoic acid (DHA) and oleic acid (OA)] on oxidative stress and inflammation in cataract were assessed. MethodsCataract was induced in male Wistar rat pups (11 days old) by giving a single dose of sodium selenite (25 μM/kg body weight) by IP. Lutein (1.3 μmol/kg body weight) was given one day before and five days after selenite injection as a micelle with 7.5 mM LA, or 7.5 mM EPA + DHA or 7.5 mM OA. Serum and lens oxidative stress and inflammatory parameters having a bearing cataract were assessed. ResultsSerum and lens nitric oxide, MDA and protein carbonyls were significantly (p < 0.05) increased in cataract compared to control and experimental groups. Catalase, SOD, glutathione peroxidase and glutathione transferase activity and glutathione level in serum and lens of cataract group were significantly (p < 0.05) decreased. Serum eicosanoids (PGE2, LTB4, and LTC4) and cytokines (CRP, TNF-α, IL1-β, and MCP-1) were significantly (p < 0.05) increased in cataract. The activity of cPLA2 and Cox-2 in cataract lens was higher (p < 0.05) compared to other groups. EP-1, NOS-2 and NF-kB expression were higher (p < 0.05) in cataract. The ratio of water insoluble to water soluble protein was increased in cataract lens. Group administered with L + EPA + DHA exhibited highest cataract prevention compared to L + LA and L + OA. Pups given lutein with EPA + DHA had the highest amount of lutein in the lens. ConclusionsThe anti-cataract activity of lutein was influenced by fatty acids and found to be highest with EPA + DHA compared to LA or OA.

Diosmin ameliorates the effects of oxidative stress in lenses of streptozotocin-induced type 1 diabetic rats.

Diabetic cataractogenesis is a complex process connected with hyperglycemia and oxidative stress. Free radicals induce many unfavorable changes in the activity of the antioxidative enzymes and may also lead to oxidative damage. Since diosmin, a plant-derived flavonoid, reveals antioxidative activity, the aim of the study was to investigate if this substance may counteract the oxidative stress in the lenses of diabetic rats. The study was conducted on the male Wistar rats with streptozotocin-induced type 1 diabetes. After the administration of diosmin at the doses of 50 and 100mg/kg for 4 weeks the oxidative stress markers in the lenses of these rats were evaluated. Tested markers included: activity of superoxide dismutase, catalase and glutathione peroxidase, as well as levels of total and soluble protein, level of glutathione, vitamin C, advanced oxidation protein products and malonyldialdehyde. The obtained results indicate that the administration of diosmin to the diabetic rats counteracted the unfavorable changes induced by diabetes in the lenses. It can be assumed that diosmin may be a promising compound in prevention or delaying the cataract formation during diabetes.

Reduction of oxidative-nitrosative stress underlies anticataract effect of topically applied tocotrienol in streptozotocin-induced diabetic rats.

Cataract, a leading cause of blindness, is of special concern in diabetics as it occurs at earlier onset. Polyol accumulation and increased oxidative-nitrosative stress in cataractogenesis are associated with NFκB activation, iNOS expression, ATP depletion, loss of ATPase functions, calpain activation and proteolysis of soluble to insoluble proteins. Tocotrienol was previously shown to reduce lens oxidative stress and inhibit cataractogenesis in galactose-fed rats. In current study, we investigated anticataract effects of topical tocotrienol and possible mechanisms involved in streptozotocin-induced diabetic rats. Diabetes was induced in Sprague Dawley rats by intraperitoneal injection of streptozotocin. Diabetic rats were treated with vehicle (DV) or tocotrienol (DT). A third group consists of normal, non-diabetic rats were treated with vehicle (NV). All treatments were given topically, bilaterally, twice daily for 8 weeks with weekly slit lamp monitoring. Subsequently, rats were euthanized and lenses were subjected to estimation of polyol accumulation, oxidative-nitrosative stress, NFκB activation, iNOS expression, ATP levels, ATPase activities, calpain activity and total protein levels. Cataract progression was delayed from the fifth week onwards in DT with lower mean of cataract stages compared to DV group (p<0.01) despite persistent hyperglycemia. Reduced cataractogenesis in DT group was accompanied with lower aldose reductase activity and sorbitol level compared to DV group (p<0.01). DT group also showed reduced NFκB activation, lower iNOS expression and reduced oxidative-nitrosative stress compared to DV group. Lenticular ATP and ATPase and calpain 2 activities in DT group were restored to normal. Consequently, soluble to insoluble protein ratio in DT group was higher compared to DV (p<0.05). In conclusion, preventive effect of topical tocotrienol on development of cataract in STZ-induced diabetic rats could be attributed to reduced lens aldose reductase activity, polyol levels and oxidative-nitrosative stress. These effects of tocotrienol invlove reduced NFκB activation, lower iNOS expression, restoration of ATP level, ATPase activities, calpain activity and lens protein levels.

Melatonin reduces lens oxidative stress level in STZ-induced diabetic rats through supporting glutathione peroxidase and reduced glutathione values

Hyperglycemia plays a critical role in the development and progression of diabetic cataract oxidative injuries via the increased reactive oxygen species (ROS) production. Melatonin has been considered a potent strong antioxidant that detoxifies a variety of ROS in many metabolic diseases. The present study was conducted to explore whether melatonin administration protects against diabetic lens oxidative injuries through modulation of reduced glutathione (GSH) and glutathione peroxidase (GPx) systems in streptozotocin (STZ)-induced diabetic rats. Thirty two rats were equally divided into four groups as control, STZ, melatonin and STZ and melatonin. The third and fourth groups received intraperitoneal 10 mg/kg melatonin for 2 weeks. For induction of diabetes in the second and fourth groups, intraperitoneal STZ (45 mg/kg) was given. Lipid peroxidation (MDA), total oxidant status and intracellular ROS levels in the lens were increased in STZ group although they were decreased by melatonin treatment. GPx activity, GSH concentration and total antioxidant status (TAS) were lower in STZ group than in control. However, the GSH concentration, GPx activity and TAS levels were recovered by melatonin. TAS was also higher in melatonin group than in the STZ and melatonin groups. In conclusion, the present study shows that melatonin induced protective effects against diabetes-induced lens oxidative injury through up-regulation of the GSH and GPx values but down-regulation of oxidative stress.

Inhibition of diabetic-cataract by vitamin K1 involves modulation of hyperglycemia-induced alterations to lens calcium homeostasis

This study investigated the potential of vitamin K1 against streptozotocin-induced diabetic cataract in Wistar rats. A single, intraperitoneal injection of streptozotocin (STZ) (35 mg/kg) resulted in hyperglycemia, accumulation of sorbitol and formation of advanced glycation end product (AGE) in eye lens. Hyperglycemia in lens also resulted in superoxide anion and hydroxyl radical generation and less reduced glutathione suggesting oxidative stress in lens. Hyperglycemia also resulted in increase in lens Ca2+ and significant inhibition of lens Ca2+ ATPase activity. These changes were associated with cataract formation in diabetic animals. By contrast treatment of diabetic rats with vitamin K1 (5 mg/kg, sc, twice a week) resulted in animals with partially elevated blood glucose and with transparent lenses having normal levels of sorbitol, AGE, Ca2+ ATPase, Ca2+, and oxidative stress. Vitamin K 1 may function to protect against cataract formation in the STZ induced diabetic rat by affecting the homeostasis of blood glucose and minimizing subsequent oxidative and osmotic stress. Thus, these results show that Vitamin K1 inhibits diabetic-cataract by modulating lens Ca2+ homeostasis and its hypoglycemic effect through its direct action on the pancreas.

Grape seed extract and zinc containing nutritional food supplement prevents onset and progression of age-related cataract in wistar rats.

To study possible inhibition of oxidative stress and cataract formation by single combined formulation of grape seed extract and Zincovit tablets against sodium selenite-induced age-related cataract in Wistar rat pups. Oxidative stress and consequent cataract formation was induced by subcutaneous administration of a single dose of sodium selenite (10 µmoles/kg) to Wistar rat pups on day 7 post-natally. In experiments designed to inhibit such cataract formation, the pups were pretreated subcutaneously with combined formulation of grape seed extract and Zincovit tablets (40, 80 and 160 mg/kg), one day prior to the administration of selenite and continuing such treatment till day 20, when the experiments were terminated. The extent of tissue damage caused by the selenite was assessed biochemically by measurements of the levels of reduced glutathione, glutathione peroxidase, glucose-6-phosphate dehydrogenase, protein thiol, catalase, superoxide dismutase, malondialdehyde, aldose reductase, sorbitol dehydrogenase and adenosine triphosphate in the isolated lenses. Cataract formation and its prevention were monitored by examining the eye with pen light illumination and subsequent photography of the isolated lenses. Injection of selenite led to a significant loss of lens clarity due to cataract formation. In the group treated with combined formulation of grape seed extract and Zincovit tablets, the formation of cataract was significantly prevented. In the normal and selenite induced senile cataract control group, the levels of lens oxidative stress markers, G6PD and ATP were substantially lower than in the grape seed extract with Zincovit tablets treated group (p < 0.05). Over all, the results suggest that single combined formulation of grape seed extract and Zincovit tablets may offer a prophylactic measure against onset and progression of age- related cataract of human subjects as nutritional food supplement.

Effects of melatonin on Wi-Fi-induced oxidative stress in lens of rats

Introduction:Melatonin has been considered a potent antioxidant that detoxifies a variety of reactive oxygen species in many pathophysiological states of eye. The present study was designed to determine the effects of Wi-Fi exposure on the lens oxidant, antioxidant redox systems, as well as the possible protective effects of melatonin on the lens injury induced by electromagnetic radiation (EMR).Materials and Methods:Thirty-two rats were used in the current study and they were randomly divided into four equal groups as follows: First and second groups were cage-control and sham-control rats. Rats in third group were exposed to Wi-Fi (2.45 GHz) for duration of 60 min/day for 30 days. As in the third group, the fourth group was treated with melatonin. The one-hour exposure to irradiation in second, third and fourth took place at noon each day.Results:Lipid peroxidation levels in the lens were slightly higher in third (Wi-Fi) group than in cage and sham control groups although their concentrations were significantly (P < 0.05) decreased by melatonin supplementation. Glutathione peroxidase (GSH-Px) activity was significantly (P < 0.05) lower in Wi-Fi group than in cage and sham control groups although GSH-Px (P < 0.01) and reduced glutathione (P < 0.05) values were significantly higher in Wi-Fi + melatonin group than in Wi-Fi group.Conclusions:There are poor oxidative toxic effects of one hour of Wi-Fi exposure on the lens in the animals. However, melatonin supplementation in the lens seems to have protective effects on the oxidant system by modulation of GSH-Px activity.

Xanthine oxidase and lens oxidative stress markers in diabetic and senile cataract patients

Xanthine oxidase (XOD) is a prooxidant enzyme possibly implicated in diabetic lens injury and genesis of senile cataract (SC). We evaluated the impact of diabetes on XOD activity and its relationships with lens oxidative stress markers in patients operated on for SC. Serum and lens XOD activities, lens malondialdehyde (MDA), conjugated dienes, superoxide dismutase (SOD), glutathione peroxidase (GPx) and reduced glutathione (GSH) levels were measured in 62 non-diabetic and 29 diabetic patients operated on for SC. Lens XOD, SOD, GPx and GSH levels were gradually declining, while MDA and serum XOD were increasing with patient's age. Lens XOD activity was positively correlated with conjugated dienes concentration (rho=0.316; p=0.003) while being inversely correlated with age (rho=−0.371; p<0.001), indicating that low ocular expression of XOD could be related to lower intensity of oxidative stress and delayed occurrence of SC. When samples were adjusted for confounding factors, serum XOD (p<0.001), lens XOD (p=0.003) and conjugated dienes (p=0.002) were significantly higher in diabetic than in non-diabetic group. Lens SOD and GPx were moderately increased while MDA and GSH were unchanged in diabetic, compared with non-diabetic SC group. Blood HbA1C concentration was positively correlated with lens XOD (rho=0.346; p<0.001) as well as serum XOD activity (rho=0.485; p<0.001). These results suggest that poor glycemic control may upregulate systemic and ocular XOD activities contributing to lens oxidative stress and possibly to earlier onset of cataract.

αB-crystallin/sHSP protects cytochrome c and mitochondrial function against oxidative stress in lens and retinal cells

BackgroundαB-crystallin/sHSP protects cells against oxidative stress damage. Here, we mechanistically examined its ability to preserve mitochondrial function in lens and retinal cells and protect cytochrome c under oxidative stress conditions. MethodsαB-crystallin/sHSP was localized in human lens (HLE-B3) and retinal (ARPE-19) cells. αB-crystallin/sHSP was stably over-expressed and its ability to preserve mitochondrial membrane potential under oxidative stress conditions was monitored. Interactions between αB-crystallin/sHSP and cytochrome c were examined by fluorescent resonance energy transfer (FRET) and by co-immune precipitation. The ability of αB-crystallin/sHSP to protect cytochrome c against methionine-80 oxidation was monitored. ResultsαB-crystallin/sHSP is present in the mitochondria of lens and retinal cells and is translocated to the mitochondria under oxidative conditions. αB-crystallin/sHSP specifically interacts with cytochrome c in vitro and in vivo and its overexpression preserves mitochondrial membrane potential under oxidative stress conditions. αB-crystallin/sHSP directly protects cytochrome c against oxidation. General significanceThese data demonstrate that αB-crystallin/sHSP maintains lens and retinal cells under oxidative stress conditions at least in part by preserving mitochondrial function and by protecting cytochrome c against oxidation. Since oxidative stress and loss of mitochondrial function are associated with eye lens cataract and age-related macular degeneration, loss of these αB-crystallin/sHSP functions likely plays a key role in the development of these diseases.αB-crystallin/sHSP is expressed throughout the body and its ability to maintain mitochondrial function is likely important for the prevention of multiple degenerative diseases.

Oxidative stress in the eye in diabetes

AbstractPurpose The characterize manifestations of oxidative stress in lens and retina in diabetes, and to evaluate the roles for aldose reductase (AR), Na+‐H+‐exchanger‐1 (NHE‐1), and poly(ADP‐ribose) polymerase‐1 (PARP‐1) in oxidative stress in both tissues, cataract formation, and retinal apoptosis.Methods The experiments were performed in streptozotocin‐diabetic rats and high glucose‐exposed cultured human lens epithelial cells (HLEC) and bovine retinal pericytes and endothelial cells (BRP and BREC). Cataract formation was evaluated by indirect ophthalmoscopy and slit lamp examination, oxidative stress by combination of biochemical and immunohistochemical methods, and retinal apoptosis by TUNEL assay in flat‐mounted retinae.Results Diabetes‐induced oxidative‐nitrosative stress manifested by accumulation of free lipid peroxidation products, malondialdehyde and 4‐hydroxyalkenals, as well as 4‐hydroxynonenal protein adducts, and nitrated and poly(ADP‐ribosyl)ated proteins, is present in both diabetic lens and retina as well as in high glucose‐exposed HLEC and BRP and BREC. Depletion of GSH and ascorbate and changes in the glutathione and ascorbate redox states are present in thre lens only. Activation of AR, NHE‐1 and PARP‐1 promotes oxidative damage. Inhibition of AR, NHE‐1, and PARP‐1 prevents diabetes‐induced oxidative stress, and prevents or delays cataractogenesis and retinal apoptosis.Conclusion Ozidative stress is present in lens and retina in diabetes and plays an important role in diabetic ocular comp‐lications. Commercial interest

Amelioration of selenite toxicity and cataractogenesis in cultured rat lenses by Vitex negundo

Recent evidence suggests that oxidative stress plays a significant role in the development of cataract. The present study sought to evaluate the efficacy of flavonoid fraction of Vitex negundo (FVN) in preventing the toxicity induced by sodium selenite in vitro culture condition. Enucleated rat lenses were maintained in organ culture containing DMEM medium alone (G I), supplemented with 0.1mM sodium selenite (G II), sodium selenite + 20 μg/ml quercetin (G III) and sodium selenite + 50 μg/ml FVN (G IV). Treatment was from the second to fifth day, while selenite administration was done on the third day. After the experimental period, lenses were taken out and the activities of superoxide dismutase (SOD), catalase, Ca(2+) ATPase, levels of reduced glutathione (GSH), calcium, reactive oxygen species (ROS), thiobarbituric acid reactive substances (TBARS), and sulfhydryl content were studied. Morphological examination revealed dense vacuolization and loss of cortical transparency in G II compared to control and treated group. The mean activities of the enzymes SOD, catalase and Ca(2+) ATPase, levels of GSH and sulfhydryl content were significantly reduced in lenses of G II compared to control. In addition, the mean levels of ROS, calcium and TBARS were elevated in G II compared to control. However, these changes were modulated by FVN treatment to further strengthen its protective role over selenite cataract. These results suggest that FVN treatment prevented selenite toxicity and cataractogenesis by maintaining antioxidant status, calcium homeostasis, protecting sulfhydryl group, and decreasing oxidative stress in lens, which may be due to its protective effects.

Loss of thioredoxin activity as an important contributor to oxidative stress in lens of diabetic rats

Abstract Purpose Thioredoxin (Trx) is a redox regulator whose bioavailability in mammalian tissues is regulated by its intrinsic binding protein, thioredoxin‐binding protein‐2 (TBP‐2). The purpose of this study is to investigate whether diabetic condition can alter the ratio of Trx and TBP‐2 expressions in the lens that may contribute to cataract formation. Methods Streptozotocin (STZ at 75 mg/kg) induced diabetic rats were divided into aldose reductase inhibitor (0.0125% AL1576) treated and untreated groups. Rats without STZ injection were used as controls. Lenses from 3 and 8 wks post STZ injection were used to determine GSH level, Trx activity, and Western blot analysis for Trx and TBP‐2 protein levels. Results The lenses in the diabetic untreated group showed slight haziness in 3 wks, and moderate to severe opacity in 8 wks while all lenses in the ARI‐treated or control groups remained clear in both ages. The untreated diabetic group showed severe loss in GSH (&lt; 20% of control in both 3 and 8 wks) and Trx activity (&lt; 35% of the control in both 3 and 8 wks). TBP‐2 expression although was unchanged at 3 wks but elevated ~4‐fold over the control in 8 wks while Trx expression remained constant at both time points. ARI treatment protected the GSH level, Trx activity, and TBP‐2 expression in these lenses. Conclusion Diabetic condition induced TBP‐2 expression in the lens with concurrent suppression of Trx activity. The results suggest that the loss of the bioavailability of TRx, in conjunction with a severe GSH depletion, is likely to contribute to the oxidative stress observed in diabetic conditions. Furthermore the observation that ARI can normalize these changes suggests a role of osmotic stress in Trx/TBP‐2 imbalance.

Synergistic effect of osmotic and oxidative stress in slow-developing cataract formation

Diabetes is a major contributing factor in cataract development. In animal models where cataracts develop within days or weeks of diabetes it is well established that osmotic stress from the accumulation of sorbitol leads to cataract development. This mechanism might explain the rare cases of acute cataract sometimes found in patients with uncontrolled sustained hyperglycemia but cannot account for the vast majority of cataracts that developed after years of diabetes. Thus, a model that can simulate diabetic slow-developing cataract is needed. The contribution of osmotic and oxidative stress in cataract development in sorbitol dehydrogenase (SDH) deficient mice, a model for slow-developing cataract in diabetic patients was determined. Contribution of osmotic stress was assessed by HPLC measurement of sorbitol and by observing the effect of blocking sorbitol accumulation by aldose reductase (AR) null mutation in the SDH deficient mice. Contribution of oxidative stress was assessed by observing the effect of vitamin E treatment and the effect of null mutation of glutathione peroxidase-1 (Gpx-1) on cataract development in these mice. Lenticular sorbitol level was significantly increased in the SDH deficient mice, and blocking sorbitol accumulation by the AR null mutation prevented cataract development, demonstrating the contribution of osmotic stress in cataract development. SDH deficiency did not affect lens oxidative stress status. However, treatment with vitamin E significantly reduced the incidence of cataract, and Gpx-1 deficiency exacerbated cataract development in these mice. Our findings suggest that chronic oxidative stress impaired the osmoregulatory mechanism of the lens. This was not evident until modest increases in lens sorbitol increased the demand of its osmoregulatory function. This osmoregulatory dysfunction model is supported by the fact that the activity of Na +/K +-ATPase, the key regulator of cellular ions and water balance, was dramatically reduced in the precataractous lenses of the SDH deficient mice, and that treatment with vitamin E prevented the loss of Na +/K +-ATPase activity. This osmoregulatory dysfunction model might explain why diabetic patients who control their blood glucose moderately well are still susceptible to develop cataract.

Dietary and nutritional biomarkers of lens degeneration, oxidative stress and micronutrient inadequacies in Indian cataract patients

Habitual food and nutrient intakes of 140 Indian cataract patients and 100 age- and sex-matched controls (50-75 years), from high income group and low income groups, were assessed. Food intake was recorded by food frequency questionnaire and data were examined for linkages with blood/lens parameters of oxidative stress through a case-control study. Intake of animal foods and fried snacks was significantly higher while vegetables, green leafy vegetables, fruit, tea and micronutrient intakes were lower in patients than in controls (p<0.001). Lens oxidative stress and opacity showed a significant negative association with fruit intake (p<0.05). Multiple regression analysis indicated association of intakes of iron, beta-carotene, ascorbic acid, tannic acid and inositol pentaphosphate with plasma oxidative stress (p<0.01) and association of intakes of iron, ascorbic acid and inositol triphosphate with lens oxidative stress (p<0.01). Weighted least square regression for lens opacity revealed that intakes of ascorbic acid, folic acid and inositol pentaphosphate explained 59.7% of the total variation (p<0.01). Dietary deficiency of antioxidant micronutrients was greater for patients than controls. Deficiency of beta-carotene, ascorbic acid, folic acid, iron, phytate and polyphenols increased oxidative stress in blood and lens.

PKCγ knockout mouse lenses are more susceptible to oxidative stress damage

Cataracts, or lens opacities, are the leading cause of blindness worldwide. Cataracts increase with age and environmental insults, e.g. oxidative stress. Lens homeostasis depends on functional gap junctions. Knockout or missense mutations of lens gap junction proteins, Cx46 or Cx50, result in cataractogenesis in mice. We have previously demonstrated that protein kinase Cgamma (PKCgamma) regulates gap junctions in the lens epithelium and cortex. In the current study, we further determined whether PKCgamma control of gap junctions protects the lens from cataractogenesis induced by oxidative stress in vitro, using PKCgamma knockout and control mice as our models. The results demonstrate that PKCgamma knockout lenses are normal at 2 days post-natal when compared to control. However, cell damage, but not obvious cataract, was observed in the lenses of 6-week-old PKCgamma knockout mice, suggesting that the deletion of PKCgamma causes lenses to be more susceptible to damage. Furthermore, in vitro incubation or lens oxidative stress treatment by H(2)O(2) significantly induced lens opacification (cataract) in the PKCgamma knockout mice when compared to controls. Biochemical and structural results also demonstrated that H(2)O(2) activation of endogenous PKCgamma resulted in phosphorylation of Cx50 and subsequent inhibition of gap junctions in the lenses of control mice, but not in the knockout. Deletion of PKCgamma altered the arrangement of gap junctions on the cortical fiber cell surface, and completely abolished the inhibitory effect of H(2)O(2) on lens gap junctions. Data suggest that activation of PKCgamma is an important mechanism regulating the closure of the communicating pathway mediated by gap junction channels in lens fiber cells. The absence of this regulatory mechanism in the PKCgamma knockout mice may cause those lenses to have increased susceptibility to oxidative damage.