Diabetic Cataract Formation Research Articles

The Association Between Trace Elements and Osmolality in Plasma and Aqueous Humor Fluid in Diabetic Rabbits.

Trace element metabolism plays an important role in the formation of diabetes and complications of diabetes. Although trace elements changes in lenses in diabetic cataract and glaucoma formation have been investigated, there were few studies evaluating trace elements levels in plasma and aqueous humor fluid in diabetic and non-diabetic conditions. Therefore, we aimed to investigate zinc (Zn), copper (Cu), and chromium (Cr) levels in plasma and aqueous humor fluids of rabbits in the diabetic rabbit model. New Zealand male rabbits were divided into two groups as control (n = 8), and diabetes (n = 8) induced by alloxane. At the end of the experimental period, the osmolality in blood, plasma, and aqueous humor fluids from rabbits were measured by osmometer and Zn, Cu, and Cr levels in plasma and aqueous humor fluid were measured by inductively coupled plasma-optical emission spectrophotometer (ICP-OES). The osmolality in blood, plasma, and aqueous humor fluid of the diabetic group was significantly increased compared to the control group (respectively p < 0.01, p < 0.001, p < 0.001). It was analyzed that plasma Zn and Cu levels of diabetic rabbits increased significantly (respectively, p < 0.01; p < 0.001), whereas Cr level significantly decreased according to the control group (p < 0.01). It was observed that Cr and Zn levels in aqueous humor fluid in diabetes group decreased (respectively p < 0.001 and p < 0.01), and a significantly increased in Cu level (p < 0.001) compared to the control group. Related with these changes that may occur in the eye due to the measured parameters, we consider that comparative studies of these types of diabetic animal models would be useful in the evaluation of diabetes and its complications.

Mapping glucose metabolites in the normal bovine lens: Evaluation and optimisation of a matrix-assisted laser desorption/ionisation imaging mass spectrometry method.

The spatial resolution of microdissection-based analytical methods to detect ocular lens glucose uptake, transport and metabolism are poor, whereas the multiplexing capability of fluorescence microscopy-based approaches to simultaneously detect multiple glucose metabolites is limited in comparison with mass spectrometry-based methods. To better understand lens glucose transport and metabolism, a more highly spatially resolved technique that maintains the fragile ocular lens tissue is required. In this study, a sample preparation method for matrix-assisted laser desorption/ionisation imaging mass spectrometry (MALDI IMS) analysis of ocular lens glucose uptake and metabolism has been evaluated and optimised. Matrix choice, tissue preparation and normalisation strategy were determined using negative ion mode MALDI-Fourier transform-ion cyclotron resonance MS of bovine lens tissue and validation performed using gas chromatography-MS. An internal standard was applied concurrently with N-(1-naphthyl)ethylenediamine dihydrochloride (NEDC) matrix to limit cracking of the fresh frozen lens tissue sections. MALDI IMS data were collected at a variety of spatial resolutions to detect both endogenous lens metabolites and stable isotopically labelled glucose introduced by ex vivo lens culture. Using this approach, initial steps in important metabolic processes that are linked to diabetic cataract formation were spatially mapped in the bovine lens. In the future, this method can be applied to study the dynamics of glucose uptake, transport and metabolic flux to aid in the study of diabetic lens cataract pathophysiology.

Identification of potential phytochemical lead against diabetic cataract: An insilico approach

Cataract is one of the leading causes for blindness among worldwide devoid of effective treatment. Glycation of γ-crystallin under hyperglycemic condition leads to diabetic cataract formation. It is important to design a drug which could inhibit lens protein glycation and prevent the diabetic cataract. The use of plant based natural compounds could have potential bioavailability and fewer toxicity. The current investigation aim is to determine the efficient phytochemicals for inhibition of γ-crystallin glycation. In this study the phytochemicals with anticataract property were virtually screened against γ-crystallin. The potent phytochemicals were filtered based on their interaction site and binding affinity. These phytochemicals were further scrutinized and evaluated with pharmacokinetics, druggability and Pharmacophore feature analysis. Among the phytochemicals, Alizarin (polyketide), Pseudobaptigenin (flavonoid) and Ellagic acid (tannin) are three phytochemicals which had preferred druglike behavior and binding affinity for the inhibition of glycation against γ-crystallin protein. The features of these three phytochemicals could be used as prototype for synthesizing new molecules against diabetic cataract.

Klotho ameliorates the onset and progression of cataract via suppressing oxidative stress and inflammation in the lens in streptozotocin-induced diabetic rats

Increased oxidative stress and inflammation play an important role in the pathogenesis of diabetic cataract. Klotho, known as an anti-ageing protein, has antioxidative and anti-inflammatory properties. Klotho is expressed in limited tissues including the lens. Here we examined whether klotho expression is decreased in diabetic lens and, if so, whether klotho treatment can prevent diabetic cataract formation. Streptozotocin (STZ)-induced diabetic rats and age-matched control rats were treated with vehicle or klotho protein, starting at 1 week after STZ injection. Twelve weeks after treatment, cataract formation was observed in diabetic rats but not control rats. Cataract formation and scores were significantly less in klotho-treated diabetic rats than vehicle-treated diabetic rats. Levels of klotho in plasma, aqueous humor and lens were significantly decreased in vehicle-treated diabetic rats, compared with control rats, but were restored in klotho-treated diabetic rats. Additionally, vehicle-treated diabetic rats had increased oxidative stress and inflammation in the lens, which were associated with decreased antioxidant transcriptional master regulator Nrf2 activity and increased transcription factor NF-κB activity. All of these findings were ameliorated in klotho-treated diabetic rats. Notably, klotho treatment did not alter blood glucose in diabetic rats. These results indicate that klotho reduction may increase susceptibility of the lens to oxidative and inflammatory insults, promoting cataract formation under diabetic conditions. Klotho treatment can ameliorate the onset and progression of diabetic cataract via enhancing Nrf2-mediated antioxidant defense and suppressing NF-κB-mediated inflammatory responses. Klotho in the lens may be a novel therapeutic target for prevention of cataract formation in diabetes.

AKR1B1-Induced Epithelial-Mesenchymal Transition Mediated by RAGE-Oxidative Stress in Diabetic Cataract Lens.

Purpose: Cataracts are a major cause of visual acuity deterioration in diabetes mellitus (DM) in developed and developing countries. Studies have demonstrated that overproduction of AKR1B1 and receptor for advanced glycation end products (RAGE) plays a major role in the pathogenesis of diabetic cataracts, but it is unclear whether the prevalence of diabetic cataracts is related to epithelial–mesenchymal transition (EMT) in lens epithelial cells. This study aimed to analyze the role of EMT in cataract formation of DM patients. Methods: Immunofluorescence and immunohistochemistry assays were used to estimate AKR1B1, RAGE, AMPK, and EMT levels in epithelial human lens of DM or non-DM cataracts. Results: Immunohistochemical staining demonstrated that pathologic phases and N-cadherin expression levels were significantly higher in epithelial human lens of DM (+) compared to DM (−) cataracts. Immunofluorescent staining showed that AKR1B1 and RAGE were significantly higher in epithelial human lens of DM (+) compared to DM (−) cataracts. Interestingly, acetyl superoxide dismutase 2 (AcSOD2) levels were significantly higher in DM patients’ lens epithelial cells (LECs), whereas AMPKT172 phosphorylation was significantly increased in non-DM patients. This indicates that AMPKT172 might be related to superoxide reduction and diabetic cataract formation. Conclusions: Our results suggest that AKR1B1 overexpression can decrease AMPK activation, thereby increasing AcSOD2 and RAGE-induced EMT in epithelial human lens of DM cataracts. These novel findings suggest that AKR inhibitors may be candidates for the pharmacological prevention of cataracts in patients with DM.

Histone acetyltransferase and Polo-like kinase 3 inhibitors prevent rat galactose-induced cataract

Diabetic cataracts can occur at an early age, causing visual impairment or blindness. The detailed molecular mechanisms of diabetic cataract formation remain incompletely understood, and there is no well-documented prophylactic agent. Galactose-fed rats and ex vivo treatment of lenses with galactose are used as models of diabetic cataract. To assess the role of histone acetyltransferases, we conducted cataract prevention screening with known histone acetyltransferase (HAT) inhibitors. Ex vivo treatment with a HAT inhibitor strongly inhibited the formation of lens turbidity in high-galactose conditions, while addition of a histone deacetylase (HDAC) inhibitor aggravated turbidity. We conducted a microarray to identify genes differentially regulated by HATs and HDACs, leading to discovery of a novel cataract causative factor, Plk3. Plk3 mRNA levels correlated with the degree of turbidity, and Plk3 inhibition alleviated galactose-induced cataract formation. These findings indicate that epigenetically controlled Plk3 influences cataract formation. Our results demonstrate a novel approach for prevention of diabetic cataract using HAT and Plk3 inhibitors.

Vitamin K1 prevents diabetic cataract by inhibiting lens aldose reductase 2 (ALR2) activity

This study investigated the potential of vitamin K1 as a novel lens aldose reductase inhibitor in a streptozotocin-induced diabetic cataract model. A single, intraperitoneal injection of streptozotocin (STZ) (35 mg/kg) resulted in hyperglycemia, activation of lens aldose reductase 2 (ALR2) and accumulation of sorbitol in eye lens which could have contributed to diabetic cataract formation. However, when diabetic rats were treated with vitamin K1 (5 mg/kg, sc, twice a week) it resulted in lowering of blood glucose and inhibition of lens aldose reductase activity because of which there was a corresponding decrease in lens sorbitol accumulation. These results suggest that vitamin K1 is a potent inhibitor of lens aldose reductase enzyme and we made an attempt to understand the nature of this inhibition using crude lens homogenate as well as recombinant human aldose reductase enzyme. Our results from protein docking and spectrofluorimetric analyses clearly show that vitamin K1 is a potent inhibitor of ALR2 and this inhibition is primarily mediated by the blockage of DL-glyceraldehyde binding to ALR2. At the same time docking also suggests that vitamin K1 overlaps at the NADPH binding site of ALR2, which probably shows that vitamin K1 could possibly bind both these sites in the enzyme. Another deduction that we can derive from the experiments performed with pure protein is that ALR2 has three levels of affinity, first for NADPH, second for vitamin K1 and third for the substrate DL-glyceraldehyde. This was evident based on the dose-dependency experiments performed with both NADPH and DL-glyceraldehyde. Overall, our study shows the potential of vitamin K1 as an ALR2 inhibitor which primarily blocks enzyme activity by inhibiting substrate interaction of the enzyme. Further structural studies are needed to fully comprehend the exact nature of binding and inhibition of ALR2 by vitamin K1 that could open up possibilities of its therapeutic application.

The expression change of autophagy-related factors in lens epithelial cells of diabetic mice

Objective To investigate the role of autophagy in the development of diabetic cataract by detecting the expression of autophagy-related factors (BECN1, LC3B, P62) in diabetic mouse lens epithelial cells. Methods Eighty C57BL/6 male mice were selected.Fifty C57 mice were consecutively dosed with streptozotocin (STZ) 50 mg/(kg·d) by intraperitoneal injection to induce type 1 diabetes mellitus model, and served as the model group; the remaining 30 mice were injected with appropriate dose of citrate buffer, and served as the control group.The fasting plasma glucose was tested by collecting the caudal vein blood in the model group.The morphological changes of autophagy of lens epithelial cells were observed by transmission electron microscopy.The expression and localization of LC3B and P62 protein were detected by immunohistochemistry.PCR was used to detect the expression of BECN1, LC3B and P62 mRNA in the anterior capsule.The relative expression of autophagy-related proteins in the anterior capsule was detected by Western blot.The use of animals complied with Regulations on the Management of Experimental Ainimals from Shandong Eye Institute. Results Compared with the control group, transmission electron microscopy revealed that the autophagosomes of lens epithelial cells in model group was large and contained more mitochondria.Immunohistochemical method showed that the expression of LC3B and P62 proteins in the anterior capsule tissue of experiment group was stronger than that of the control group.The relative expression level of BECN1, LC3B and P62 mRNA in the experiment group was 1.48±0.10, 2.62±0.15 and 1.89±0.20, respectively, which was higher than 1.10±0.02, 1.10±0.05 and 1.01±0.01 in the control group, with significant differences between the two groups (t=6.64, 14.25, 6.14; all at P<0.05). The relative expression of BECN1, LC3B and P62 protein in the experiment group was 1.50±0.10, 1.24±0.09 and 3.19±1.04, respectively, which was higher than 1.00±0.00, 1.00±0.00 and 1.00±0.00 in the control group, with significant differences between the two groups (t=8.75, 6.10, 3.65; all at P<0.05). Conclusions The phenomenon of autophagy in lens epithelial cells of diabetic mice is abnormal, and autophagy dysfunction may play an important role in the formation of diabetic cataract. Key words: Diabetic cataract; Autophagy; Lens epithelial cells; BECN1; LC3B; P62

Expression of SIRT1 and P53 in Rat Lens Epithelial cells in Experimentally Induced DM

ABSTRACTPurpose: To determine the etiopathogenesis of diabetic cataract by studying changes in relative expressions of silent information regulator protein-1 (SIRT1) and P53 in rat lens epithelial cells (LECs) in experimentally induced diabetes mellitus (DM).Methods: Six-week-old male SD rats (n = 120) were randomly divided into experimental (n = 80 rats) and control (n = 40 rats) groups. DM was induced in the experimental group (diabetic model) by intraperitoneal (i.p.) injection of 60 mg/kg streptozotocin (STZ). Control group rats were injected similarly with phosphate-buffered saline (PBS). Four and eight weeks after successful induction of DM, relative expressions of SIRT1 and P53 in LECs were analyzed using quantitative real-time (qRT) fluorescence polymerase chain reaction (qRT-PCR) and Western blot analysis.Results: Expression of both SIRT1 and P53 was observed in LECs of control and experimental group rats at 4 and 8 weeks but was significantly greater in experimental compared with control group rats (p < 0.05).Conclusions: Expression of both SIRT1 and P53 increases in the early stages of diabetic cataract formation, indicating that they play potentially important roles in the pathogenesis of diabetic cataract.

Does oxidative stress play any role in diabetic cataract formation? ----Re-evaluation using a thioltransferase gene knockout mouse model

Oxidative stress is a known risk factor in senile cataract formation. In recent years, it has been suggested that oxidation may also be associated with cataract induced by hyperglycemia, but this concept has not been well examined or validated. Since thioltransferase (TTase) is one of the key enzymes that regulates redox homeostasis and protects against oxidative stress in the lens, we have used TTase gene knockout (KO) mice as a model to examine this new concept. Lenses from 4 months old TTase KO and wild-type (WT) mice were incubated in TC199 culture medium containing 30 mM glucose for 48 h. Each lens was assessed for opacity, graded by LOCSII system, and the wet weight was recorded after which it was homogenized in lysis buffer and analyzed for water-soluble protein and free glutathione (GSH). In vivo studies were carried out using 4 months old TTase KO and WT mouse groups. Each mouse received two consecutive days of intraperitoneal streptozotozin (STZ) injections to induce diabetes. The lenses were examined weekly for 4 weeks using a slit-lamp biomicroscope, and then extracted and analyzed for levels of GSH, water-soluble protein, ATP and protein-GSH mixed disulfide (PSSG). TTase KO lenses cultured in high glucose developed a mild cortical opacity but slightly more than that of the WT lenses. Both groups had similar contents of soluble proteins and GSH. Exposure to high glucose did not change the soluble protein level but did suppress GSH by 20% in lenses with or without TTase. STZ-induced diabetic KO mice also developed a higher degree of mild cortical lens opacity compared to that of the diabetic WT controls. Similar 15–20% losses in lens GSH and ATP were found after one-month induced diabetes in WT and KO mice. There was a 20% greater amount of PSSG in the lenses of TTase KO than the WT control. Under diabetic condition, both groups displayed more glutathionylated proteins in the beta-actin (42 kDa) and lens crystallin proteins (18–22 kDa) regions, and some additional modified proteins at 15–17 kDa and 60–70 kDa, with a total 20–30% PSSG increment in both groups. In conclusion, we have found that hyperglycemia induced some oxidative stress-associated biochemical changes with mild lens opacity in both WT and KO mice. However, these changes were only marginally higher in the TTase KO mouse than that of the WT control, suggesting that TTase deletion may only play a minor role in the early stage of hyperglycemia-induced cataract formation in the mice.

MicroRNA-30a Regulation of Epithelial-Mesenchymal Transition in Diabetic Cataracts Through Targeting SNAI1

Epithelial-mesenchymal transition (EMT) is a highly conserved and fundamental process in development, fibrosis, and metastasis. During the process, epithelial cells lose their morphology and transcriptional program, and transdifferentiate to mesenchymal cells. It has been reported that lens epithelial cells undergo EMT during cataract formation, and regulation of microRNAs on genes is associated with lens development. However, the molecular mechanisms of this regulation in diabetic cataract still need to be investigated. In the present study, the expression of E-cadherin was downregulated, while the expression of alpha-SMA and vimentin was upregulated in diabetic cataract tissues and the in vitro model, suggesting the involvement of EMT in diabetic cataract formation. Results of miRNA profiling demonstrated that miR-30a was markedly downregulated in diabetic cataract tissues. Overexpression of miR-30a-5p decreased SNAI1, a known modulator of EMT, and the expression of vimentin and alpha-SMA in our diabetic cataract model in vitro. It is concluded that EMT is involved in human diabetic cataract, and upregulation of miR-30a can repress EMT through its targeting of SNAI1 in lens epithelial cells, which make miR-30a a novel target of therapeutic intervention for human diabetic cataract.

Expression and regulation of microRNA-29a and microRNA-29c in early diabetic rat cataract formation.

To determine the role of microRNA (miRNA)-29a and miRNA-29c in the regulation of apoptosis in early rat diabetic cataract formation. Streptozotocin (STZ)-induced diabetic Sprague-Dawley (SD) rats were used in the study. The expression level of miRNA-29a, miRNA-29c, and BCL2-modifying factor (BMF) in lens epithelial cells (LECs) samples were measured using quantitative real-time polymerase chain reaction. Prediction algorithms of miRanda, TargetScan 6.2, and mirRDB to perform a miRNA gene network analysis were used for the potential miRNA-29a and miRNA-29c targets. The miRNA-29a and miRNA-29c expression levels were all significantly lower in the control group compared to the 2 and 4wk diabetic samples (P<0.01). The network analysis indicated that one miRNA-29a and miRNA-29c targets was BMF. There was significantly higher expression of BMF mRNA compared to the normal controls (P<0.01). Apoptosis occurs in rat LECs following high blood glucose exposure. It is likely that apoptosis during diabetic cataract formation involves the decreased expression of miRNA-29a and miRNA-29c and the increased expression of BMF.

Investigation of synergistic mechanism and identification of interaction site of aldose reductase with the combination of gigantol and syringic acid for prevention of diabetic cataract.

BackgroundGigantol and syringic acid (SA) have been shown to synergistically prevent formation of diabetic cataract (DC). However, the exact mechanism of this effect is unknown. Here, we investigate the effect of these compounds on the activity of aldose reductase (AR) and cataract formation.MethodsWe examined the synergistic anti-cataract efficacy of gigantol and SA in the high glucose- and streptozotocin -induced DC rat model; synergism was evaluated using Jin’s formula. We investigated possible mechanisms of action by measuring AR expression and activity and levels of sorbitol using enzyme kinetics, Western blot, and RT-PCR. Finally, we examined binding interaction between AR and both compounds using a combination of site-directed mutagenesis, recombinant expression of wild-type and mutant proteins, and enzyme kinetics.ResultsCombination treatment of gigantol and SA synergistically protected both HLECs(human lens epithelial cells) grown in vitro and DC formation in STZ-induced rats in vivo. Synergism was attributed to inhibition of AR activity, downregulation of AR expression via impaired transcription, and decreased sorbitol levels. Enzyme kinetics studies showed that the activity of an AR Asn160Ala mutant protein was significantly decreased compared to wild-type AR, confirming that Asn160 is a key residue for interaction between AR and both compounds.ConclusionCombined administration of gigantol and SA synergize to enhance anti-cataract efficacy. The synergistic effect is mainly attributed to disruption of the polyol pathway and inhibition of AR activity.

Supplementation of Mango (Mangifera indicaL.) Peel in Diet Ameliorates Cataract in Streptozotocin-Induced Diabetic Rats

Cataract is a secondary complication of diabetes and consumption of diet rich in antioxidants and dietary fiber exerts beneficial effects. The effect of mango peel on delay in progression of cataract was evaluated in streptozotocin-induced diabetic rats. Diets supplemented with mango peel at 5 and 10% levels ameliorated cataract formation. On treatment of diabetic rats with peel for 16 weeks, lens soluble protein content, glutathione levels and antioxidant enzyme activities were increased by 1.5–2.5 fold while lipid peroxidation and protein carbonyl levels as well as advanced glycation end products formation in lens proteins of diabetic rats were significantly decreased. Mango peel supplementation also inhibited polyol pathway enzyme activities in diabetic rats. Thus, mango peel was effective against development of diabetic cataract mainly through augmentation of antioxidant levels, inhibition of polyol pathway enzymes and AGEs formation in lens of diabetic rats. PRACTICAL APPLICATIONS Oxidative damage to the constituents of eye lens is considered to be the major mechanism for development of various types of cataract and intake of food rich in antioxidants has been reported to delay progression of cataract. Mango peel is a by-product of mango pulp processing industry and is rich in antioxidants and exhibits antidiabetic properties. This study found that mango peel supplemented diet delayed the progression of diabetic cataract formation. Thus, mango peel can be supplemented in foods for management of diabetes and its complications.

Differential proteomic analyses of cataracts from rat models of type 1 and 2 diabetes.

To identify differential changes in proteins and metabolites underlying "fast" type 1 (T1DC) and "slow" type 2 (T2DC) diabetic cataract (DC) formation in rat. Rat models of types 1 and 2 diabetes consisted of streptozotocin injection without and with high-fat diet, respectively. Cataract progression was examined weekly. At week 6, total protein changes were comparatively and quantitatively assessed by two-dimensional differential in-gel electrophoresis (2-D DIGE) coupled with mass spectrometry, and relevant metabolic changes were examined. Differences in high molecular weight (HMW) crystallin species between diabetic and control lenses were similarly identified. Cataracts were morphologically different and progressed more slowly in T2DC versus T1DC. αA-crystallin, βB2-crystallin, and βA4-crystallin were significantly decreased in both DC types versus control. αB-crystallin was increased while βB1-crystallin was markedly decreased in T2DC. In T1DC, γB-crystallin and γS-crystallin fragmentation were increased. High-fat diet by itself had little impact, except for lowering γS-crystallin fragmentation. Despite significantly decreased opacity, a greater decrease in intermediate filaments (IFs) and more HMW crystallin species were observed in T2DC versus T1DC. However, aldose reductase expression and activity and sorbitol levels were increased to a greater extent in T1DC, while reduced glutathione (GSH) and reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) levels were decreased to a greater extent and adenosine triphosphate (ATP) level was much lower in T1DC versus T2DC. The results suggest that osmotic damage, GSH loss, and decreased ATP production might be important pathological mechanisms in T1DC formation, whereas crystallin modification and cross-linking/aggregation as well as IF degradation may play more crucial roles in T2DC formation.

Retraction. Activation of aldose reductase by interaction with tubulin and involvement of this mechanism in diabetic cataract formation. Diabetes. 10 April 2014 [Epub ahead of print]. DOI: 10.2337/db13-1265.

Our previous studies have shown that high levels of glucose induce inhibition of Na + ,K + -ATPase (NKA) via stimulation of aldose reductase (AR), polymerisation of microtubules, and formation of an acetylated tubulin/NKA complex. Inhibition of AR eliminated the effect of high glucose on NKA activity. In this study, we investigated the mechanism of regulation of AR activity by tubulin. Purified tubulin and AR were used. The results indicate that: (i) tubulin and AR interact with each other directly; (ii) tubulin/AR interaction results in a 6-fold increase of AR activity under microtubule growing conditions; (iii) AR interacts preferentially with tubulin that contains 3-nitro-L-tyrosine (3-NTyr); (iv) free tyrosine and 3-nitro-tyrsine are able to block tubulin/AR interaction and thereby prevent AR activation; (v) exposure of cultured COS cells to high glucose concentrations promotes microtubule polymerisation and NKA inhibition, and both these promoting effects are inhibited by addition of free Tyr or 3-NTyr; (vi) treatment of experimental (STZ-induced) diabetic rats with 3-NTyr prevented cataract formation, suggesting that this complication of diabetes involves tubulin/AR interaction and AR activity. Taken together, these findings indicate that AR activity is controlled by association/dissociation of the tubulin/AR complex, that Tyr and 3-NTyr block such effect by preventing tubulin/AR complex formation, and that AR activity can be reduced by 3-NTyr or other compounds that inhibit tubulin/AR interaction.

Observation on the ultrastructure of cataract lens epithelial cells

Objective To study the relationship of cataract with lens epithelial cell apoptosis and autophagy by observing the ultrastructure of age-related and diabetic cataract lens epithelial cells.Methods Transmission electron microscope was used to observe the apoptotic and autophagic morphology of the lens epithelial cells in 5 cases with age-related and diabetic cataract respectively,and in 2 cases with normal lens.Results The apoptosis and autophagy of lens epithelial cells was found in cases with age-related and diabetic cataract,while no expression was observed in control lens epithelial cells.Conclusion The apoptosis and autophagy of lens epithelial cells are closely related to age-related and diabetic cataract formation. Key words: Cataract; Lens epithelial cells; Apoptosis; Autophagy

Галлат (-)-эпигаллокатехина регулирует экспрессию апоптотических генов и защищает культуру клеток эпителия хрусталика глаза человека от гипергликемии

(-)-Epigallocatechin gallate (EGCG), the most abundant component in green tea, has a potent anti-apoptotic activity. The purpose of this study was to investigate the protective effects of EGCG and their molecular mechanisms on high glucose-induced apoptosis of human lens epithelial cells (HLEB-3). HLEB-3 cells were exposed to various concentrations of glucose and EGCG. Cell death was assessed by MTT assay and flow cytometry using annexin V and propidium iodide. The expression of the Bcl-2 family, c-fos, c-myc and p53 was measured by real-time PCR. EGCG decreased the Bcl-2/Bax expression stimulated by a high glucose. Moreover, EGCG suppressed the high glucose-induced expression of c-fos, c-myc and p53. These findings suggest that EGCG protects HLEB-3 cells from high glucose-induced apoptosis by regulating the gene expression of the Bcl-2 family, c-fos, c-myc and p53. Thus, EGCG may have a potential protective effect against diabetic cataract formation.

Protective effects of taurine against alloxan-induced diabetic cataracts and refraction changes in New Zealand White rabbits

The present study examined the protective effects of taurine on alloxan-induced diabetic cataracts and lens damage in male New Zealand White rabbits. The animals were randomly divided into three treatment groups: (1) normal control (vehicle administration); (2) diabetes (100 mg/kg alloxan administration); and (3) diabetes + taurine (1% [w/v] taurine dissolved in drinking water and alloxan administration). The results showed that alloxan-induced diabetes caused significant (p < 0.05) hyperglycemia, hyperopic refraction shifts, cataract formation and lens damage compared with the normal control group. In contrast, the administration of taurine for 24 weeks significantly ameliorated the alloxan-induced elevated levels of blood glucose, level of hyperopic refraction error shifts in the eyes and progression of diabetic cataract formation in the lens in rabbits. Moreover, histopathology showed that the taurine supplement reduced the incidence of lens lesions induced by hyperglycemia. Overall, the studies demonstrate that taurine exhibits potent protective effects against alloxan-induced diabetic cataracts and refraction changes in rabbits.

Osmotic stress induced oxidative damage: Possible mechanism of cataract formation in diabetes

Chronic hyperglycemia causes increased level of reactive oxygen species which is thought to be involved in the pathogenesis of diabetes associated complications including cataract. In diabetic cataractous lens, over production of free radicals and decreased capacity of antioxidant defense system are the major contributors to oxidative damage by polyol pathway and advanced glycation end products. The current study focused on analysis of factors associated with osmotic imbalance and oxidative stress in aging and diabetic human cataractous lenses. We examined activities of polyol pathway enzymes, G6PD and glutathione system in lenses from subjects suffering from cataract due to aging and diabetes. We observed elevated activities of aldose reductase and sorbitol dehydrogenase while G6PD and glutathione system enzyme activities were found to be lower in cataractous subjects suffering from diabetes. The findings from the current study support the premise that osmotic imbalance, AGEs formation and oxidative stress contribute synergistically to the development of lens opacity in hyperglycemia.