Caffeine eye drops protect against UV-B cataract

A grape-supplemented diet prevented ultraviolet (UV) radiation-induced cataract by regulating Nrf2 and XIAP pathways

The purpose of this study is to investigate if grape consumption, in the form of grape powder (GP), could protect against ultraviolet (UV)-induced cataract. Mice were fed with the regular diet, sugar placebo diet, or a grape diet (regular diet supplemented with 5%, 10%, and 15% GP) for 3 months. The mice were then exposed to UV radiation to induce cataract. The results showed that the GP diet dose-dependently inhibited UV-induced cataract and preserved glutathione pools. Interestingly, UV-induced Nrf2 activation was abolished in the groups on the GP diet, suggesting GP consumption may improve redox homeostasis in the lens, making Nrf2 activation unnecessary. For molecular target prediction, a total of 471 proteins regulated by GP were identified using Agilent Literature Search (ALS) software. Among these targets, the X-linked inhibitor of apoptosis (XIAP) was correlated with all of the main active ingredients of GP, including resveratrol, catechin, quercetin, and anthocyanins. Our data confirmed that GP prevented UV-induced suppression of XIAP, indicating that XIAP might be one of the critical molecular targets of GP. In conclusion, this study demonstrated that GP protected the lens from UV-induced cataract development in mice. The protective effects of GP may be attributed to its ability to improve redox homeostasis and activate the XIAP-mediated antiapoptotic pathway.

Eye Diseases: When the Solution Comes from Plant Alkaloids

Plants are an incredible source of metabolites showing a wide range of biological activities. Among these, there are the alkaloids, which have been exploited for medical purposes since ancient times. Nowadays, many plant-derived alkaloids are the main components of drugs used as therapy for different human diseases. This review deals with providing an overview of the alkaloids used to treat eye diseases, describing the historical outline, the plants from which they are extracted, and the clinical and molecular data supporting their therapeutic activity. Among the different alkaloids that have found application in medicine so far, atropine and pilocarpine are the most characterized ones. Conversely, caffeine and berberine have been proposed for the treatment of different eye disorders, but further studies are still necessary to fully understand their clinical value. Lastly, the alkaloid used for managing hypertension, reserpine, has been recently identified as a potential drug for ameliorating retinal disorders. Other important aspects discussed in this review are different solutions for alkaloid production. Given that the industrial production of many of the plant-derived alkaloids still relies on extraction from plants, and the chemical synthesis can be highly expensive and poorly efficient, alternative methods need to be found. Biotechnologies offer a multitude of possibilities to overcome these issues, spanning from genetic engineering to synthetic biology for microorganisms and bioreactors for plant cell cultures. However, further efforts are needed to completely satisfy the pharmaceutical demand.

Microbial metabolism of caffeine and potential applications in bioremediation

With increasing global consumption of caffeine-rich products, such as coffee, tea, and energy drinks, there is also an increase in urban and processing waste full of residual caffeine with limited disposal options. This waste caffeine has been found to leach into the surrounding environment where it poses a threat to microorganisms, insects, small animals, and entire ecosystems. Growing interest in harnessing this environmental contaminant has led to the discovery of 79 bacterial strains, eight yeast strains, and 32 fungal strains capable of metabolizing caffeine by N-demethylation and/or C-8 oxidation. Recently observed promiscuity of caffeine-degrading enzymes in vivo has opened up the possibility of engineering bacterial strains capable of producing a wide variety of caffeine derivatives from a renewable resource. These engineered strains can be used to reduce the negative environmental impact of leached caffeine-rich waste through bioremediation efforts supplemented by our increasing understanding of new techniques such as cell immobilization. Here, we compile all of the known caffeine-degrading microbial strains, discuss their metabolism and related enzymology, and investigate their potential application in bioremediation.

Analysis of cataract-regulated genes using chemical DNA damage induction in a rat ex vivo model

Although cataracts affect almost all people at advanced age and carry a risk of blindness, the mechanisms of cataract development remain incompletely understood. Oxidative stress, which is a causative factor in cataract, results in DNA breakage, which suggests that DNA damage could contribute to the formation of cataracts. We developed an ex vivo experimental system to study changes in gene expression during the formation of opacities in the lens by culturing explanted rat lenses with Methylmethanesulfonate (MMS) or Bleomycin, which induce DNA damage. Lenses cultured using this experimental system developed cortical opacity, which increased in a concentration- and time-dependent manner. In addition, we compared expression profiles at the whole gene level using microarray analysis of lenses subjected to MMS or Bleomycin stress. Microarray findings in MMS-induced opacity were validated and gene expression was measured from Days 1-4 using RT-qPCR. Altered genes were classified into four groups based on the days of peak gene expression: Group 1, in which expression peaked on Day 1; Group 2, in which expression peaked on Day 2; Group 3, in which expression progressively increased from Days 1-4 or were upregulated on Day 1 and sustained through Day 4; and Group 4, in which expression level oscillated from Days 1-4. Genes involved in lipid metabolism were restricted to Group 1. DNA repair- and cell cycle-related genes were restricted to Groups 1 and 2. Genes associated with oxidative stress and drug efflux were restricted to Group 2. These findings suggest that in temporal changes of MMS-induced opacity formation, the activated pathways could occur in the following order: lipid metabolism, DNA repair and cell cycle, and oxidative stress and drug efflux.

The human lens: An antioxidant-dependent tissue revealed by the role of caffeine

Cataract is the leading cause of blindness worldwide and surgery is the only option to treat the disease. Although the surgery is considered to be relatively safe, complications may occur in a subset of patients and access to ophthalmic care may be limited. Due to a growing and ageing population, an increase in cataract prevalence is expected and its management will become a socioeconomic challenge. Hence, there is a need for an alternative to cataract surgery. It is well known that oxidative stress is one of the main pathological processes leading to the generation of the disease. Antioxidant supplementation may, therefore, be a strategy to delay or to prevent the progression of cataract. Caffeine is a widely consumed high-potency antioxidant and may be of interest for the prevention of the disease. This review aims to give an overview of the anatomy and function of the lens, its antioxidant and reactive oxygen species (ROS) composition, and the role of oxidative stress in cataractogenesis. Also, the pharmacokinetics and -dynamics of caffeine will be described and the literature will be reviewed to give an overview of its anti-cataract potential and its possible role in the prevention of the disease.

Single high-dose peroral caffeine intake inhibits ultraviolet radiation-induced apoptosis in human lens epithelial cells in vitro

PURPOSE

The aim of the present study was to determine whether caffeine concentrations in human lens epithelial cells (LECs) achieved from acute peroral caffeine intake inhibit ultraviolet radiation-induced apoptosis in vitro.

METHODS

Patients were planned for cataract surgery of both eyes with a caffeine abstinence of 2 weeks in total, starting 1 week before surgery of the first eye. The second eye was scheduled 1 week after the first eye. At the day of the second eye surgery, patients were given coffee containing 180 mg caffeine shortly before surgery. Lens capsules including LEC, harvested after capsulorhexis, were transferred to a cell culture dish and immediately exposed to close to threshold ultraviolet radiation (UVR). At 24 hr after UVR exposure, apoptotic LECs were analysed by TdT-mediated dUTP-biotin nick end labeling (TUNEL) staining.

RESULTS

TUNEL-positive cells were detected in UVR-exposed lens capsules both after caffeine intake and in controls. The mean difference in TUNEL-positive cells between caffeine intake and contralateral controls (no caffeine) resulted in a 95% CI 15.3 ± 10.4% (degrees of freedom: 16).

CONCLUSION

Peroral caffeine consumption significantly decreased UVR-induced apoptosis in LEC supporting epidemiological findings that caffeine delays the onset of cataract.

Topically instilled caffeine selectively alters emmetropizing responses in infant rhesus monkeys

Oral administration of the adenosine receptor (ADOR) antagonist, 7-methylxanthine (7-MX), reduces both form-deprivation and lens-induced myopia in mammalian animal models. We investigated whether topically instilled caffeine, another non-selective ADOR antagonist, retards vision-induced axial elongation in monkeys. Beginning at 24 days of age, a 1.4% caffeine solution was instilled in both eyes of 14 rhesus monkeys twice each day until the age of 135 days. Concurrent with the caffeine regimen, the monkeys were fitted with helmets that held either -3 D (-3D/pl caffeine, n = 8) or +3 D spectacle lenses (+3D/pl caffeine, n = 6) in front of their lens-treated eyes and zero-powered lenses in front of their fellow-control eyes. Refractive errors and ocular dimensions were measured at baseline and periodically throughout the lens-rearing period. Control data were obtained from 8 vehicle-treated animals also reared with monocular -3 D spectacles (-3D/pl vehicle). In addition, historical comparison data were available for otherwise untreated lens-reared controls (-3D/pl controls, n = 20; +3D/pl controls, n = 9) and 41 normal monkeys. The vehicle controls and the untreated lens-reared controls consistently developed compensating axial anisometropias (-3D/pl vehicle = -1.44 ± 1.04 D; -3D/pl controls = -1.85 ± 1.20 D; +3D/pl controls = +1.92 ± 0.56 D). The caffeine regime did not interfere with hyperopic compensation in response to +3 D of anisometropia (+1.93 ± 0.82 D), however, it reduced the likelihood that animals would compensate for -3 D of anisometropia (+0.58 ± 1.82 D). The caffeine regimen also promoted hyperopic shifts in both the lens-treated and fellow-control eyes; 26 of the 28 caffeine-treated eyes became more hyperopic than the median normal monkey (mean (±SD) relative hyperopia = +2.27 ± 1.65 D; range = +0.31 to +6.37 D). The effects of topical caffeine on refractive development, which were qualitatively similar to those produced by oral administration of 7-MX, indicate that ADOR antagonists have potential in treatment strategies for preventing and/or reducing myopia progression.

The potential health benefits of dietary natural plant products in age related eye diseases

In the past decade, there has been a tremendous increase in the number of cases of age-related eye diseases such as age-related macular degeneration (AMD), cataract, diabetic retinopathy and glaucoma. These diseases are the leading causes of visual impairment and blindness all over the world and are associated with many pathological risk factors such as aging, pollution, high levels of glucose (hyperglycaemia), high metabolic rates, and light exposure. These risk factors lead to the generation of uncontrollable reactive oxygen species (ROS), which causes oxidative stress. Oxidative stress plays a crucial role in the pathogenesis of age-related eye diseases through the activation of nuclear factor kappa B (NF-κB), vascular endothelial growth factor (VEGF), and lipid peroxidation, which leads to the production of inflammatory cytokines, angiogenesis, protein and DNA damages, apoptosis that causes macular degeneration (AMD), cataract, diabetic retinopathy and glaucoma. This review provides updated information on the beneficial effects of dietary natural plant products (DPNPs) against age-related eye diseases. In this review, supplementation of DPNPs demonstrated preventive and therapeutic effects on people at risk of or with age-related eye diseases due to their capacity to scavenge free radicals, ameliorate inflammatory molecules, neutralize the oxidation reaction that occurs in photoreceptor cells, decrease vascular endothelial growth factor and the blood-retinal barrier and increase the antioxidant defence system. However, further experiments and clinical trials are required to establish the daily doses of DPNPs that will safely and effectively prevent age-related eye diseases.

Caffeine Uptake into the Vitreous after Peroral Coffee Consumption

INTRODUCTION

Caffeine and its metabolites have antioxidant activity, scavenging reactive oxygen species. The aim of our study was to measure caffeine concentrations in vitreous samples after peroral caffeine intake.

METHODS

This prospective study included patients scheduled for 23-G pars plana vitrectomy with membrane peeling due to epiretinal membranes. The study was performed in two parts: in the first part, patients were recruited into three different groups: group A consisted of habitual coffee drinkers who agreed to drink coffee containing 180 mg caffeine 1 h before surgery (n = 10), group B consisted of habitual coffee drinkers who were not offered coffee before surgery (n = 5), and group C consisted of non-habitual coffee drinkers, forming the control group (n = 5). In the second part (group D) patients (habitual coffee drinkers) agreed to give additional blood serum samples for measurement of caffeine concentration. Harvested samples of vitreous (groups A-D), epiretinal membranes (groups A-C), and blood serum samples (group D) were examined for concentrations of caffeine with gas chromatography-mass spectrometry.

RESULTS

Samples of 40 eyes of 40 patients were harvested. The concentrations of caffeine in the vitreous samples were 1,998 ± 967 ng/mL in group A and 1,108 ± 874 ng/mL in group B. In group C, caffeine concentrations were below 176 ng/mL in all vitreous samples. Both groups A and B had significantly higher concentrations of caffeine in the vitreous samples than group C (p < 0.002, p < 0.01, Mann-Whitney U test). Caffeine concentrations in epiretinal membranes were below the limits of detection. Correlation of caffeine concentrations between blood serum samples and vitreous samples in group D was high, with significantly higher caffeine concentrations in the blood serum.

CONCLUSION

Coffee consumption leads to significant caffeine levels in the vitreous compared to patients in the control group, and caffeine concentrations in the vitreous showed a high correlation to blood serum concentrations of caffeine after peroral coffee consumption.

Current Trends in the Pharmacotherapy of Cataracts

Cataracts, one of the leading causes of preventable blindness worldwide, refers to lens degradation that is characterized by clouding, with consequent blurry vision. As life expectancies improve, the number of people affected with cataracts is predicted to increase worldwide, especially in low-income nations with limited access to surgery. Although cataract surgery is considered safe, it is associated with some complications such as retinal detachment, warranting a search for cheap, pharmacological alternatives to the management of this ocular disease. The lens is richly endowed with a complex system of non-enzymatic and enzymatic antioxidants which scavenge reactive oxygen species to preserve lens proteins. Depletion and/or failure in this primary antioxidant defense system contributes to the damage observed in lenticular molecules and their repair mechanisms, ultimately causing cataracts. Several attempts have been made to counteract experimentally induced cataract using in vitro, ex vivo, and in vivo techniques. The majority of the anti-cataract compounds tested, including plant extracts and naturally-occurring compounds, lies in their antioxidant and/or free radical scavenging and/or anti-inflammatory propensity. In addition to providing an overview of the pathophysiology of cataracts, this review focuses on the role of various categories of natural and synthetic compounds on experimentally-induced cataracts.

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.

The acute effects of single cup of coffee on ocular biometric parameters in healthy subjects

Purpose

To evaluate ocular biometric changes in healthy subjects after caffeine consumption from a cup of coffee.

Methods

A total of 36 subjects were included in this prospective observational study. Axial length (AL) and anterior segment parameters including aqueous depth (AD), anterior chamber depth (ACD), lens thickness (LT), and central corneal thickness (CCT) were measured with optic biometry, Lenstar LS 900 (Haag-Streit, Inc., Koeniz, Switzerland) before and 1 and 4 h after ingesting a cup of coffee (60 mg caffeine/100 mL).

Results

Mean age of the participants was 30.05 ± 7.43 years (range, 19–45). At baseline, 1st, and 4th hour, AL values were 23.9 ± 1.04 mm, 23.91 ± 1.04 mm, and 23.89 ± 1.04 mm, respectively, and no significant difference was observed (P>0.05). At baseline, 1st, and 4th hour, AD values were 3.06 ± 0.3 mm, 3.11 ± 0.3 mm, and 3.09 ± 0.3 mm, and ACD values were 3.6 ± 0.32, 3.66 ± 0.31, and 3.64 ± 0.31, respectively. AD and ACD values were significantly greater than baseline at 1st and 4th hours following coffee ingestion. Coffee intake caused a significant reduction in LT, compared with baseline and at the 1st and 4th hours which were 3.76 ± 0.28 mm, 3.69 ± 0.32 mm, and 3.72 ± 0.27 mm, respectively. No statistically significant difference was determined in between the 3 measurements in terms of CCT (P>0.05).

Conclusion

Caffeine causes a significant increase in AD and ACD and a significant decrease in LT following oral intake, for at least 4 h.

Cataract Preventive Role of Isolated Phytoconstituents: Findings from a Decade of Research

Cataract is an eye disease with clouding of the eye lens leading to disrupted vision, which often develops slowly and causes blurriness of the eyesight. Although the restoration of the vision in people with cataract is conducted through surgery, the costs and risks remain an issue. Botanical drugs have been evaluated for their potential efficacies in reducing cataract formation decades ago and major active phytoconstituents were isolated from the plant extracts. The aim of this review is to find effective phytoconstituents in cataract treatments in vitro, ex vivo, and in vivo. A literature search was synthesized from the databases of Pubmed, Science Direct, Google Scholar, Web of Science, and Scopus using different combinations of keywords. Selection of all manuscripts were based on inclusion and exclusion criteria together with analysis of publication year, plant species, isolated phytoconstituents, and evaluated cataract activities. Scientists have focused their attention not only for anti-cataract activity in vitro, but also in ex vivo and in vivo from the review of active phytoconstituents in medicinal plants. In our present review, we identified 58 active phytoconstituents with strong anti-cataract effects at in vitro and ex vivo with lack of in vivo studies. Considering the benefits of anti-cataract activities require critical evaluation, more in vivo and clinical trials need to be conducted to increase our understanding on the possible mechanisms of action and the therapeutic effects.

Caffeine and the eye

Caffeine, a popular psychostimulant that acts as an adenosine receptor antagonist, is the most widely used drug in history, consumed daily by people worldwide. Knowledge of the physiological and pathological effects of caffeine is crucial in improving public health because of its widespread use. We provide a summary of the current evidence on the effect of caffeine on the eye. Most of the research conducted to date is in relation to cataract and glaucoma, two of the most common eye diseases among the elderly.

Adenosine receptor distribution in Rhesus monkey ocular tissue

Adenosine receptor (ADOR) antagonists, such as 7-methylxanthine (7-MX), have been shown to slow myopia progression in humans and animal models. Adenosine receptors are found throughout the body, and regulate the release of neurotransmitters such as dopamine and glutamate. However, the role of adenosine in eye growth is unclear. Evidence suggests that 7-MX increases scleral collagen fibril diameter, hence preventing axial elongation. This study used immunohistochemistry (IHC) and reverse-transcription quantitative polymerase chain reaction (RT-qPCR) to examine the distribution of the four ADORs in the normal monkey eye to help elucidate potential mechanisms of action. Eyes were enucleated from six Rhesus monkeys. Anterior segments and eyecups were separated into components and flash-frozen for RNA extraction or fixed in 4% paraformaldehyde and processed for immunohistochemistry against ADORA1, ADORA2a, ADORA2b, and ADORA3. RNA was reverse-transcribed, and qPCR was performed using custom primers. Relative gene expression was calculated using the ΔΔCt method normalizing to liver expression, and statistical analysis was performed using Relative Expression Software Tool. ADORA1 immunostaining was highest in the iris sphincter muscle, trabecular meshwork, ciliary epithelium, and retinal nerve fiber layer. ADORA2a immunostaining was highest in the corneal epithelium, trabecular meshwork, ciliary epithelium, retinal nerve fiber layer, and scleral fibroblasts. ADORA2b immunostaining was highest in corneal basal epithelium, limbal stem cells, iris sphincter, ciliary muscle, ciliary epithelium, choroid, isolated retinal ganglion cells and scattered scleral fibroblasts. ADORA3 immunostaining was highest in the iris sphincter, ciliary muscle, ciliary epithelium, choroid, isolated retinal ganglion cells, and scleral fibroblasts. Compared to liver mRNA, ADORA1 mRNA was significantly higher in the brain, retina and choroid, and significantly lower in the iris/ciliary body. ADORA2a expression was higher in brain and retina, ADORA2b expression was higher in retina, and ADORA3 was higher in the choroid. In conclusion, immunohistochemistry and RT-qPCR indicated differential patterns of expression of the four adenosine receptors in the ocular tissues of the normal non-human primate. The presence of ADORs in scleral fibroblasts and the choroid may support mechanisms by which ADOR antagonists prevent myopia. The potential effects of ADOR inhibition on both anterior and posterior ocular structures warrant investigation.

Drug delivery to the lens for the management of cataracts

Cataracts are one of the most prevalent diseases of the lens, affecting its transparency and are the leading cause of reversible blindness in the world. The clarity of the lens is essential for its normal physiological function of refracting light onto the retina. Currently there is no pharmaceutical treatment for prevention or cure of cataracts and surgery to replace the affected lens remains the gold standard in the management of cataracts. Pharmacological treatment for prevention of cataracts is hindered by many physiological barriers that must be overcome by a therapeutic agent to reach the avascular lens. Various therapeutic agents and formulation strategies are currently being investigated to prevent cataract formation as access to surgery is limited. This review provides a summary of recent research in the field of drug delivery to the lens for the management of cataracts including models used to study cataract treatments and discusses the future perspectives in the field.

Effect of coffee (caffeine) against human cataract blindness

Previous biochemical and morphological studies with animal experiments have demonstrated that caffeine given topically or orally to certain experimental animal models has significant inhibitory effect on cataract formation. The present studies were undertaken to examine if there is a correlation between coffee drinking and incidence of cataract blindness in human beings. That has been found to be the case. Incidence of cataract blindness was found to be significantly lower in groups consuming higher amounts of coffee in comparison to the groups with lower coffee intake. Mechanistically, the caffeine effect could be multifactorial, involving its antioxidant as well as its bioenergetic effects on the lens.

DL-3-n-butylphthalide delays the onset and progression of diabetic cataract by inhibiting oxidative stress in rat diabetic model

DL-3-n-butylphthalide (NBP) is a therapeutic drug used for ischemic stroke treatment. Here, we investigated the impact of NBP on the development of rat diabetic cataract induced by intraperitoneal injection of streptozotocin (STZ). NBP was then administrated by oral gavage for nine weeks. Cataract development was monitored through ophthalmoscope inspections. The levels of blood glucose and serum reactive oxygen species (ROS), malondialdehyde (MDA) and 8-Hydroxydeovexyguanosine (8-OHdG) were measured. Total and soluble protein and oxidative stress parameters, such as 2, 4- dinitrophenylhydrazone (DNP), 4-hydroxynonenal (4-HNE) and MDA in the lenses were determined by Western blot and thiobarbituric acid analyses. The expressions of NF-E2-related factor 2 (Nrf2) and its downstream antioxidant enzymes, thioredoxin (TRX), Catalase and nuclear accumulation of Nrf2 were determined by Western blot and immunohistochemistry analyses. We showed that NBP treatment significantly improved the cataract scores, the levels of DNP, 4-HNE, and MDA in the lens compared to the non-treated groups. NBP also enhanced the expressions of Nrf2, TRX and catalase in the lens of diabetic rats. In addition, NBP treatment also decreased levels of blood glucose, serum MDA and 8-OHdG. These results suggested that NBP treatment significantly delayed the onset and progression of diabetic cataract by inhibiting the oxidative stresses.

Expression of the microRNAs hsa-miR-15a and hsa-miR-16-1 in lens epithelial cells of patients with age-related cataract

This study aimed to examine and analyze the expression levels of hsa-miR-15a and hsa-miR-16-1 in lens epithelial cells from patients with age-related cataract to understand better the roles of these microRNAs in the pathogenesis of this disease. Lens epithelial cells of 60 age-related cataract patients (including 20 with cortical cataracts, 20 with nuclear cataracts, and 20 with posterior subcapsular cataracts) and 20 normal patients were included in the study. Real-time PCR was used to detect the expression of hsa-miR-15a-5p, hsa-miR-15a-3p, hsa-miR-16-1-5p, and hsa-miR-16-1-3p. Expression of the target genes of these microRNAs, namely bcl-2 and mcl-1, was also evaluated. hsa-miR-15a-5p, hsa-miR-15a-3p, and hsa-miR-16-1-5p were expressed at low levels in normal lens epithelial cells but at significantly higher levels in corresponding cells of patients with cortical, nuclear, or posterior subcapsular cataracts (P < 0.01). hsa-miR-16-1-3p was expressed at relatively high levels in normal lens epithelial cells but significantly decreased expression, or none at all, was detected in cells of patients from each cataract group (P < 0.01). Concerning their target genes bcl-2 and mcl-1, expression was detectable in normal lens epithelial cells, but their levels were significantly decreased in cataract patients, irrespective of type (P < 0.01). Expression of hsa-miR-15a-5p, hsa-miR-15a-3p, and hsa-miR-16-1-5p rose in lens epithelial cells in the three types of age-related cataract, which may suppress the expression of the anti-apoptotic genes bcl-2 and mcl-1, thereby contributing to the pathogenesis of age-related cataract through apoptosis.

Age-related cataract and drug therapy: opportunities and challenges for topical antioxidant delivery to the lens

Objectives

The search for anticataract drugs has been continuing for decades; some treatments no longer exist but antioxidants are still of much interest.

Key findings

The primary function of the human lens, along with the cornea, is to refract light so that it is correctly focused onto the retina for optimum image quality. With age, the human lens undergoes morphological, biochemical and physical changes leading to opacification. Age-related or senile cataract is one of the main causes of visual impairment in the elderly; given the lack of access to surgical treatment in many parts of the world, cataract remains a major cause of sight loss. Surgical treatment is the only means of treating cataract; this approach, however, has limitations and complications.

Summary

This review discusses the anatomy and physiology of the lens and the changes that are understood to occur with ageing and cataract formation to identify potential areas for effective therapeutic intervention. Experimental techniques and agents used to induce cataract in animal models, the advantages and disadvantages of potential pharmacological treatments specific barriers to delivery of exogenous antioxidants to the lens and the prospects for future research are discussed.

Sulforaphane-induced transcription of thioredoxin reductase in lens: possible significance against cataract formation

PURPOSE

Sulforaphane is a phytochemically derived organic isothiocyanate 1-isothiocyanato-4-methylsulfinyl-butane present naturally in crucifers, including broccoli and cauliflower. Biochemically, it has been reported to induce the transcription of several antioxidant enzymes. Since such enzymes have been implicated in preventing cataract formation triggered by the intraocular generation of oxy-radical species, the purpose of this investigation was to examine whether it could induce the formation of antioxidant enzymes in the eye lens. Thioredoxin reductase (TrxR) was used as the target of such induction.

METHODS

Mice lenses were cultured for an overnight period of 17 hours in medium 199 fortified with 10% fetal calf serum. Incubation was conducted in the absence and presence of sulforaphane (5 μM). Subsequently, the lenses were homogenized in phosphate-buffered saline (PBS), followed by centrifugation. TrxR activity was determined in the supernatant by measuring the nicotinamide adenine dinucleotide phosphate (reduced) (NADPH)-dependent reduction of 5,5'-dithiobis-2-nitrobenzoic acid (DTNB). Non-specific reduction of DTNB was corrected for by conducting parallel determinations in the presence of aurothiomalate. The reduction of DTNB was followed spectrophotometrically at 410 nm.

RESULTS

The activity of TrxR in the lenses incubated with sulforaphane was found to be elevated to 18 times of that observed in lenses incubated without sulforaphane. It was also noticeably higher in the lenses incubated without sulforaphane than in the un-incubated fresh lenses. However, this increase was much lower than that observed for lenses incubated with sulforaphane.

CONCLUSION

Sulforaphane has been found to enhance TrxR activity in the mouse lens in culture. In view of the protective effect of the antioxidant enzymes and certain nutrients against cataract formation, the findings suggest that it would, by virtue of its ability to enhance the activity of such enzymes, prevent the tissue against oxidative stress that leads to cataract formation. Additional studies with the activities of other antioxidant enzymes such as quinone oxidoreductase and the levels of Nrf2 are in progress.