Effects of vitamin E on cortical cataractogenesis induced by elevated temperature in intact rat lenses in medium 199

Association of nuclear cataract prevalence with UV radiation and heat load in lens of older people -five city study

Epidemiological studies have reported that the frequency of nuclear cataracts (NUCs) is high among the elderly and in tropical countries. Ultraviolet (UV) irradiation and lens temperature are considered as key physical contributors, although their precise quantification is difficult. The aim of this study is to investigate the association of NUC prevalence with UV irradiation and heat load. First, we assessed the lens temperature using thermodynamic modeling considering the thermophysiological response. We then conducted a multivariate linear regression analysis for the epidemiological analysis of NUC prevalence across five cities. A strong correlation was observed between NUC prevalence and the combined effects of UV irradiation and cumulative equivalent minutes at 43 °C (CEM43°C) derived from the computed lens temperature (adjusted R2 = 0.933, p < 0.0001). Heat load significantly contributed to the prevalence at 52%, surpassing the contributions of UV irradiation (31%) and the decline in DNA repair capacity in the lens (17%). These results suggested that both UV radiation and heat load are associated with NUC, with heat load contributing more. Our findings provided important implications for future interventions, particularly in the context of global warming.

Associations of Humidity and Temperature With Cataracts Among Older Adults in China

Background

The burden of cataracts was substantial in the current aging world. However, few epidemiological studies have examined the associations between climate and weather conditions and cataract in older populations. We aimed to investigate the associations of air relative humidity and temperature with cataracts in older adults in China.

Methods

We used the cohort data from 2002, 2005, 2008, 2011, 2014, and 2018 waves of the Chinese Longitudinal Healthy Longevity Survey (CLHLS). A total of 62,595 Chinese older adults aged between 65 and 105 years were included in the analyses. City-level annual average air humidity and temperature during 2001 and 2017 (before the survey year) was used to measure population exposure. A cataract was self-reports based on the medical record or the doctor's diagnosis and 8,071 older adults had cataract. Covariates included socio-demographic, health status, lifestyles, and chronic conditions. We adopted the Generalized estimation equation (GEE) model to analyze the associations of relative humidity and temperature with cataracts.

Results

We found that the average relative humidity (OR: 0.99; 95% CI: 0.98–0.99) in the past year was inversely associated with cataract likelihoods in older adults and a positive association between temperature (OR: 1.04; 95%CI: 1.03,1.05) in the past year and cataract likelihoods in older adults. The associations were robust in stratified analyses by sex, urban/rural residence, and education level. Furthermore, we found a nonlinear J-shaped relationship between temperature and cataract prevalence.

Conclusion

Our findings provide the evidence that higher temperature and low relative humidity may be associated with cataracts in older adults.

Reported evidence of vitamin E protection against cataract and glaucoma

Cataract and glaucoma are the major causes of severe visual loss and blindness in older adults. This review article describes the currently available basic and clinical evidence regarding vitamin E protection against these eye diseases in the chronologic order of the publications. Experimental evidence has suggested both that oxidative stress due to the accumulation of free radicals plays a role in the pathogenesis of cataracts and glaucoma and that the process can be prevented or ameliorated by vitamin E. The results of observational studies have been inconsistent regarding the association between blood vitamin E levels and the risk of age-related cataract or glaucoma. Despite the encouraging effects of vitamin E from case series, case-control studies, and cross-sectional studies in humans, the effects on cataract formation and/or progression have not been consistent among prospective and randomized control studies; few randomized control studies have tested the effects of supplemental vitamin E on glaucoma development or progression. Given the high prevalence of cataract and glaucoma in the elderly population, even a modest reduction in the risk for these eye diseases would potentially have a substantial public health impact; however, the potential benefits of vitamin E on cataract or glaucoma remain inconclusive and need to be carefully considered.

Transient elevation of temperature promotes cross-linking of α-crystallin-client proteins through formation of advanced glycation endproducts: A potential role in presbyopia and cataracts

The chaperone activity of α-crystallin is important for maintaining the transparency of the human lens. αB-crystallin (αBC) is a long-lived protein in the lens that accumulates chemical modifications during aging. The formation of advanced glycation end products (AGEs) through glycation is one such modification. αBC is a small heat shock protein that exhibits chaperone activity. We have previously shown that αBC-client protein complexes can undergo AGE-mediated interprotein cross-linking. Here, we demonstrate that short-term (1 h) exposure to elevated temperatures and methylglyoxal (MGO) during the chaperoning of client proteins by αBC promotes AGE-mediated interprotein cross-linking. Liquid chromatography/mass spectrometry (LC-MS/MS) analyses revealed the rapid formation of AGEs by MGO. Interestingly, we found that despite protein cross-linking, the chaperone activity of αBC increased during the transient elevation of temperature in the presence of MGO. Together, these results imply that transient and subtle elevation of temperature in the lens of the eye can promote protein cross-linking through AGEs, and if this phenomenon recurs over a period of many years, it could lead to early onset of presbyopia and age-related cataracts.

Effect of vitamin C and E activity on surgically removed cataractous human lens epithelium cells

Oxidative stress has been proposed as a common underlying mechanism of cataractogenesis. Experimental and observational data suggest that micronutrients like vitamin C and vitamin E with antioxidant capabilities may retard the development of age-related cataract. Effect of these factors on lens epithelium cells, center of lens metabolic activities, is not completely elucidated. The aim of present study was to examine the effect of vitamin C and E on surgically removed lens epithelium cells of patients with cataract. Capsulorhexis samples were collected from 170 patients, admitted for cataract surgery. Catalase specific activity was estimated in lens epithelium cells with and without vitamin (C or E) treatment at different concentration for different time duration. Student's t-test was employed for data analysis. We observed that in ex-vivo condition, a) both vitamin C and E bring about a decrease in catalase activity in lens epithelial cells. b) vitamin C showed toxic effect at high concentration. c) 100μM was the optimum concentration at which both vitamins showed maximum antioxidant activity. It was concluded that both vitamin C and E has direct effect on lens epithelium cells. At optimum concentration, they can reduce oxidative stress in these cells thus can support to prevent or delay cataract development.

Topical tocopherol acetate reduces post-UVB, sunburn-associated erythema, edema, and skin sensitivity in hairless mice

Exposure of the skin of the back of skh-1 hairless mice to UVB (310 nm peak) irradiation at doses of 0.115-0.23 J/cm2 results after 24-48 h in an erythema which can be quantified using an erythema meter, providing a useful model of sunburn. Application of pure d-alpha-tocopherol acetate, a thick oil, to the skin immediately following the exposure to UVB significantly reduces the increase in erythema index, by 40-55%. At the lower dose (0.115 J/cm2), skin thickness (associated with edematous swelling of the sunburned skin) was measured by a novel non-invasive technique not previously reported for this purpose--magnetic resonance imaging (MRI). In two experiments the UVB-induced increase in skin thickness was significantly reduced at 24 hr by 29 and 54%, and at 48 hr by 26 and 61%. After 8 days the untreated irradiated mouse skin still showed a significant increase in thickness (24%) compared to the untreated unirradiated control, while the treated irradiated control was not significantly thicker than the unexposed control. Skin sensitivity was tested using a modification of the technique of esthesiometry, by observing rapid avoidance responses of the mouse to a pressure of 0.96 g/cm2 exerted by applying to the skin the tip of a nylon esthesiometer fiber extended to 60 mm in length. The untreated irradiated mice were more sensitive (p less than 0.07, Wilcoxon test) than the treated irradiated mice, and also significantly different from the untreated unirradiated control mice (p less than 0.04, Wilcoxon test), but the treated irradiated mice were not significantly differently sensitive when compared to the unirradiated controls (p less than 0.32). Taken together these data indicate that the erythema, edema, and skin sensitivity commonly associated with UVB-induced sunburn are significantly reduced by topical application of tocopherol acetate even after the exposure has occurred. This observation suggests that treatment of sunburn may be possible even after the irradiation has stopped, by a derivative of d-alpha-tocopherol which is stable to autooxidation.

Vitamin E intake and risk of cataracts in humans

Experimental evidence suggests that oxidative stress due to the accumulation of free radicals plays a role in the pathogenesis of cataracts and that the process can be prevented or ameliorated by antioxidants. In addition, a recent study found that cataract patients tended to have lower serum levels of vitamins C, E, or carotenoids than did control subjects. This investigation, which compared the self-reported consumption of supplementary vitamins by 175 cataract patients with that of 175 individually matched, cataract-free subjects, revealed that the latter group used significantly more supplementary vitamins C and E (p = 0.01 and 0.004, respectively). Inasmuch as the observed reduction in risk of cataracts was at least 50%, a randomized, controlled trial of vitamin supplementation in cataract prevention seems justified.

Modeling cortical cataractogenesis: IX. Activity of vitamin E and esters in preventing cataracts and gamma-crystallin leakage from lenses in diabetic rats

Normal and streptozotocin diabetic female Wistar rats were given vitamin E in the diet as the tocopherol, acetate, or succinate form (2,850 IU/kg food). At the end of 6 weeks, the rats were examined for weight gain or loss, general body condition, and cataracts. At sacrifice, blood was collected for measurement of serum glucose, and gamma-crystallin levels were measured in aqueous and vitreous humors using a radioimmunoassay. One lens was homogenized in 8 M guanidinium chloride for ATP analysis. In normal rats, gamma-crystallin was detected in both aqueous and vitreous humors, with the higher concentration in the vitreous humor. Diabetes caused a sixfold increase in gamma-crystallin in both the aqueous and vitreous humors. Diabetes also led to a significant worsening in general body condition, loss of body weight, formation of cataracts, and decrease in lens ATP levels. Addition of vitamin E and vitamin E succinate, but not vitamin E acetate, to the diet resulted in reduction of gamma-crystallin leakage into the vitreous humors and an increase in body weight. There was no improvement noted for the lens ATP levels, the general body condition, or visual cataract score. Neither streptozotocin-induced diabetes nor vitamin E in the diet appeared to affect the weight of the lenses.

Antioxidant vitamins in cataract prevention

The ocular lens, which is continually exposed to light and ambient oxygen, is at high risk of photooxidative damage resulting in cataract. Oxygen free radicals appear to impair not only lens crystallins which will aggregate and precipitate forming opacities but also proteolytic enzymes whose function it would be to eliminate the damaged proteins. Apart from an enzymatic defense system consisting of superoxide dismutase, catalase and glutathione peroxidase against excited oxygen species the lens contains the antioxidant vitamins C, E and presumably beta-carotene as another line of defense. In vitro and in vivo studies in different animal species have demonstrated a significant protective effect of vitamins C and E against light-induced cataract. Sugar and steroid cataracts were prevented as well. Epidemiological evidence in humans suggests that persons with comparatively higher intakes or blood concentrations of antioxidant vitamins are at a reduced risk of cataract development. These positive findings established by several research groups justify extensive intervention trials with antioxidant vitamins in humans using presenile cataract development as a model.

Inhibition of phase separation by reagents that prevent X-irradiation cataract in vivo

Galactose, and the phosphorothioates, WR-77913 and WR-2721, which inhibit cataract produced by X-irradiation, were evaluated for their effects on the phase separation temperature, Tc, of calf lens homogenate. The reagents were added to nuclear homogenate and the change in Tc per mol, dTc/dC, was measured. Galactose decreased Tc, -65 degrees C mol-1, WR-77913 decreased Tc, -28 degrees C mol-1 and WR-2721 decreased Tc, -76 degrees C mol-1. These are the first phase separation inhibitors that can be used in vivo to study the inhibition of lens opacification.

In vitro studies of microwave-induced cataract. II. Comparison of damage observed for continuous wave and pulsed microwaves

Depth of damage caused by pulsed (PU) and continuous wave (CW) microwaves was estimated by scanning electron microscopy in rat lenses fixed immediately, after irradiation in vitro in circulating thermostatically controlled buffered saline. Pulses of 10 microseconds width and 24 kW peak power were delivered to the lens at different repetition rates in order to permit the same total energy to be delivered during 6, 20 or 60 min of irradiation at specific absorption rate (SAR) values of 0, 5.75, 11.5, 23, 69, 231 and 750 mW g-1; total energy [power (pow) x time] deposited in the lens was 0, 0.23, 0.46, 1.38, 4.6, and 15 W min g-1. Damage (granular degeneration of cells at the lens equator) was measured at the apex of penetration of the degeneration. The depth of degeneration (dep) of Pu or CW was compared either: (1) by a one-way analysis of variance (ANOVA) for the CW data alone and the 11 combinations of (pow x time); or (2) by using two alternative models to fit the data, to permit experimental distinguishment between: (a) reciprocal effects of pow x time; and (b) separate effects. Using the ANOVA analysis, the Pu mode of irradiation resulted in more damage at the same average power for every combination tested except one (23 mW g-1, 6 min). Although the separate-effects models explained more of the variation in depth of damage, the reciprocal effects model may provide an adequate fit for practical purposes and has the advantage of greater simplicity. For both models, the pulsed irradiation mode produced 4.7 times the depth of damage caused by CW irradiation. These results are discussed in relation to previous Pu-CW comparisons. It is proposed that this additional damage at the same average power is caused by thermoelastic expansion (TEE).

Effect of vitamin E on glutathione content in red blood cells, aqueous humor and lens of humans and other species

High doses of orally administered vitamin E have been given to humans, rabbits and rats. Placebo has been given to control groups. At the end of the treatment period, enhanced levels of reduced glutathione (GSH) were found in the red blood cells (humans and rabbits), aqueous humor (humans and rabbits) and lens (rabbits and rats) of treated subjects and animals. The percentage of GSH converted to oxidized glutathione (GSSG) was the same in both vitamin E-supplied and control groups. The GSSG--GSH ratio remained unchanged. The plasma levels of vitamin E were significantly higher in treated than in control subjects and animals. At the end of the study, the levels of vitamin E in aqueous humor and lens of rabbit were the same in animals which received vitamin E and in animals which received placebo. Lastly, vitamin E administration did not influence ascorbic-acid levels in plasma (humans and rabbits), aqueous humor, lens and vitreous body (rabbits).

Heat shock response of the rat lens

The sequence relationship between the small heat shock proteins and the eye lens protein alpha-crystallin (Ingolia, T. D., and E. E. Craig, 1982, Proc. Natl. Acad. Sci. USA, 79: 2360-2364) prompted us to subject rat lenses in organ culture to heat shock and other forms of stress. The effects on protein synthesis were followed by labeling with [35S]methionine and analysis by one- and two-dimensional gel electrophoresis and fluorography. Heat shock gave a pronounced induction of a protein that could be characterized as the stress protein SP71. This protein probably corresponds to the major mammalian heat shock protein hsp70. Also two minor proteins of 16 and 85 kD were induced, while the synthesis of a constitutive heat shock-related protein, P73, was considerably increased. The synthesis of SP71 started between 30 and 60 min after heat shock, reached its highest level after 3 h, and had stopped again after 8 h. In rat lenses that were preconditioned by an initial mild heat shock, a subsequent shock did not cause renewed synthesis of SP71. This effect resembles the thermotolerance phenomenon observed in cultured cells. The proline analogue azetidine-2-carboxylic acid, zinc chloride, ethanol, and calcium chloride did not, under the conditions used, induce stress proteins in the rat lens. Sodium arsenite, however, had very much the same effects as heat shock. Calcium ionophore A23187 specifically and effectively induced the synthesis of the glucose-regulated protein GRP78. No special response to stress on crystallin synthesis was noticed.

Bendazac and benzydamine for treatment of cataract: individualized therapy by the "BLOA test"

It was found that two chemically very close Non-Steroid Antiinflammatory Drugs (NSAID), bendazac and benzydamine, were able to reduce the Biological Liquid Oxidant Activity (BLOA) in vitro (bendezac) and in vivo (bendazac and benzydamine). Four hundred and seven patients were treated with bendazac and 599 with benzydamine. After a single dose oral administration they effected a BLOA Reducing Activity (BRA) ranging from 5% to over 20% in about 40% of cataractous patients. When these drugs were able to reduce the BLOA, they showed anticataract activity in about 50% and about 90% of patients according to the extent of BRA, i.e., less than 20% and greater than or equal to 20% of the basal value. This fact suggests that the anticataract agent is not the original NSAID (prodrug) but a NSAID metabolite or an elicited endogenous compound which produced the BLOA reduction. Individual BLOA could be reduced in vivo by benzydamine or bendazac, by both or by neither of them. This finding may be accounted for by selective biotransformation of each patient's original NSAID into the antioxidant anticataract compound. However, other possible mechanisms of the anticataract activity beside antioxidant activity might take place, such as protein and membrane stabilization, together with a not yet defined activation of enzymes within the lens effecting the reversal of cataractous opacity. Several side effects were apparent in short and long term treatments. The final conclusion of our study is that bendazac at a dosage ten-fold lower than that used in the clinics is anticataract drug when orally administered to "BLOA test selected" patients, at least for short term treatment of young, otherwise healthy humans with cortical cataract.

In vitro effect of alpha-tocopherol on lysophosphatidylcholine-induced lens damage

Lysophosphatidylcholine (LPC) has been shown to be toxic to the lens in organ culture. An investigation into whether vitamin E counteracts the in vitro damaging effect of LPC on rat lenses was undertaken. A concentration higher than 10 micrograms ml-1 LPC in the culture medium is necessary to damage rat lenses, as assessed by protein content of the medium and Na+ and K+ content of the lens. Vitamin E affords its protection when present at a concentration of 10(-3) M: both the protein efflux from the lens and the lenticular cation imbalance are prevented, also if LPC concentration is 100 micrograms ml-1. This effect may be due more to the physicochemical properties of vitamin E in the stabilization of biological membranes, than to its chemical behaviour as an antioxidant.

In vitro studies of microwave-induced cataract: reciprocity between exposure duration and dose rate for pulsed microwaves

Rat ocular lenses exposed to pulsed microwave irradiation were maintained at constant temperature by circulating phosphate buffered saline in a thermostatically-controlled chamber. Irradiations with pulsed radiation (10 musec, 24 kW pulses) of 918 MHz were done at several different specific absorption rates (SAR) for durations up to 1 hr in order to explore a possible reciprocal relationship. The extent of damage was measured by the maximum depth of granular degeneration in the equatorial region of lenses fixed immediately after irradiation. The parameters of the pulses were increased to 20 musec and 48 kW to explore the variation in the biological effects and threshold with respect to average power, as well as pulse parameters (pulse width, peak power and energy per pulse). A total of 47 lenses were used in 3 X 4 factorial experimental design to explore effects observed at different average powers and durations (6, 20 and 60 min). The results were statistically analyzed by ANOVA and multiple regression analysis with logarithmic transformation. The results are summarized as follows. This data showed clear trends towards increasing depth of granular degeneration with increasing duration of exposure and dose rate. There was considerable evidence to confirm such reciprocity suggesting that total dose is an important parameter. A model postulating reciprocity was shown to explain observed variation in depth of damage as well as one allowing for separate effects of duration and dose rate. Lens fibre cell effects were detected by scanning electron microscopy after 6 min irradiation at the SAR values of 40 and 20 mW g-1. Light microscopic evidence of lens fiber cell damage can be detected at an SAR of 10 mW g-1 after a 1 hr exposure.

Lens lipids

Lens cells can synthesize, degrade, and remodel lipids. Endogenous lipid synthesis, in conjunction with uptake of exogenous cholesterol and certain fatty acids, leads to the formation of a plasma membrane that is especially rich in sphingomyelin, cholesterol, and long-chain saturated fatty acids. As a result of this unusual lipid composition, lens membranes have very low fluidity, which is restricted even further by lipid-protein interactions. The composition and metabolism of membrane lipids may affect the formation of various types of cataracts. Diets rich in vegetable oils offer some protection against the formation of osmotic cataracts and the hereditary cataract of the RCS rat, although the mechanism of this effect is not clear. Vitamin E also protects against the formation of several types of cataract in vivo and in vitro, suggesting that lipid peroxidation may play a role in cataractogenesis. Certain drugs which inhibit lipid synthesis or degradation are cataractogenic, and a deficiency in cataractogenic, and a deficiency in phosphatidylserine is associated with a loss of Na+/K+ ATPase activity in several types of cataract. Human senile cataracts show a marked loss of protein-lipid interactions, although the overall lipid composition is normal. This loss of protein-lipid interactions may be related to oxidative damage to membrane-associated proteins. Interestingly, the decrease in the fluidity of lens membranes with age would counteract the formation of aqueous pores in the membrane, which can result from the oxidative cross-linking of membrane-associated proteins. Certain pathways of lipid metabolism seem to have regulatory functions. Among these are phosphatidylinositol turnover, phosphatidylethanolamine methylation, and arachidonic acid metabolism. All of these pathways function in the lens. Phosphatidylinositol turnover is correlated with the rate of lens epithelial cell division, while phosphatidylethanolamine methylation seems to be related to the initiation of lens fiber cell formation. Both pathways are associated with the release and metabolism of arachidonic acid in other cell types. While it is not known whether phosphatidylinositol turnover or phosphatidylethanolamine methylation result in the release of arachidonic acid in the lens, recent work has shown that lens cells from a variety of species can metabolize arachidonic acid by both the cyclooxygenase and lipoxygenase pathways. The possible physiological significance of these metabolites to the lens is yet to be determined.

Radiation cataract formation diminished by vitamin E in rat lenses in vitro

Eye lens cataract is a late effect of exposure to ionizing radiation. Depending on the dose and quality of radiation impinging on the lens, the development of a clinically discernible cataract usually takes several months in animal models, when the lens is irradiated in situ. However, we have developed a rapid in vitro assay with the isolated intact rat lens to study the effect of radiation and influence of antioxidants as protective agents. After only 24 hr of post-irradiation incubation at 35.5 degrees C in complete medium 199 + 10% foetal calf serum, damage in the form of globular degeneration subcapsularly and 'holes' in the cortical fibre cells is detectable. Doses as low as 0.10 Gy seem to be capable of causing some damage, and vitamin E (2.4 microns) in the medium confers some protection to the irradiated lens.

Overview of the current attempts toward the medical treatment of cataract

A variety of agents are currently available that claim to either prevent, delay, or reverse cataracts associated with aging (senile cataracts), radiation, or diabetes and galactosemia (sugar cataracts). Senile cataract therapy includes formulation containing inorganic salts, nutritional supplements, natural product extracts, sulfhydryl, and sulfonic acid containing compounds and miscellaneous redox and nonsteroidal anti-inflammatory compounds. Agents associated with the treatment of radiation cataracts include anti oxidants and free radial scavengers. Aldose reductase inhibitors have been effective in the prevention of sugar cataracts. A summary of these agents and their potential ocular effects are presented.