Antioxidant properties of green and black tea, and their potential ability to retard the progression of eye lens cataract

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.

Protective role of hesperetin against posttranslational oxidation of tryptophan residue of human γD-crystallin: A molecular level study

Crystallin proteins undergo various posttranslational modifications with aging of eye lens. Oxidation of tryptophan (Trp) residues of a major γ-crystallin namely human γD-crystallin (HGD) was found to be inhibited by a naturally occurring flavonoid hesperetin at relatively low concentration mostly due to its antioxidant activity. Further the molecular interactions between HGD and hesperetin were elucidated on the basis of the quenching of Trp fluorescence of the protein by the flavonoid. Ground state complexation between HGD and hesperetin caused static quenching of the Trp fluorescence of HGD. Binding and quenching constants were in the order of (10³- 10⁴ M^-1). Energy transfer from protein to hesperetin was suggested by FRET calculations. Thermodynamic parameters reveal significant hydrophobic association between the protein and hesperetin. Synchronous fluorescence and CD spectroscopic results had ruled out conformational changes in the protein due to binding of hesperetin. Docking studies suggested the proximity of hesperetin with Trp 42, which largely corroborates our experimental findings.

Inhibition of copper-induced aggregation of human γD-crystallin by rutin and studies on its role in molecular level for enhancing the chaperone activity of human αA-crystallin by using multi-spectroscopic techniques

Oxidative aggregation of γ-crystallins induced by copper in aged lens increases the lens opacity and causes cataract formation. Therefore, chelation of free Cu²⁺ by small molecules can inhibit metal-mediated aggregation of γ-crystallin. In this work, the inhibition potency of several naturally occurring flavonoid compounds was studied against aggregation of human γD-crystallin (HGD) mediated by copper ions. Among them, rutin demonstrated ~20% inhibition of HGD aggregation induced by Cu²⁺ through its metal chelation ability. Not only that, the chaperone activity of lens chaperone, human αA-crystallin (HAA) was found to be enhanced in the presence of rutin. Subsequently, the molecular interactions between HAA and rutin were investigated using fluorescence and CD spectroscopy to understand the molecular basis of the chaperone activity enhancement by rutin. Quenching of HAA fluorescence by rutin with a quenching constant in the order of ~10⁵ M^-1 depicts a complexation between them. Entropy driven process of complexation between HAA and rutin suggests significant involvement of hydrophobic interactions. Fluorescence resonance energy transfer between protein and ligand can occur at a distance of 2.73 nm. Synchronous fluorescence and circular dichroism spectroscopy revealed that protein-ligand interaction does not cause any notable conformational changes in HAA. Experimental observations have been well substantiated by docking.

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.

Risk factors of age-related cataract in a Chinese adult population: the Taizhou Eye Study

IMPORTANCE

Cataract risk factors data will provide epidemic evidence for cataract prevention.

BACKGROUND

This study aimed to study the risk factors for age-related cataract in a Chinese adult population.

DESIGN

This is a population-based, cross-sectional study.

PARTICIPANTS

A total of 10 234 eligible subjects ≥45 years old (response rate: 78.1%) were included in the study.

METHODS

We conducted detailed eye examinations including presenting visual acuity, best-corrected visual acuity, slit lamp examination of lens opacities and fundus examination. Questionnaires about lifestyle were administered. Measurements of blood pressure, heart rate and body mass index were collected. Serological metabolic indicators, including fasting blood glucose, triglycerides, cholesterol, lipoprotein, were also evaluated. We used stepwise multivariate logistic regression model to evaluate the association of these risk factors with any cataract and subtypes of cataract.

MAIN OUTCOME MEASURES

Odds ratios of risk factors for cataract were calculated.

RESULTS

For any cataract, we found age, gender (female), increased outdoor activity, no outdoor eye protection, high myopia, high low-density lipoprotein, low high-density lipoprotein, lower education level and increased pickled food intake were independent risk factors. When further examined the risk factors of different subtypes of cataract, we found that these risk factors also existed, but there were slight differences among different subtypes. In addition, for cortical cataract, lower annual family income and high diastolic pressure were additional independent risk factors.

CONCLUSIONS AND RELEVANCE

Reduced outdoor activity, outdoor eye protection, prevention of high myopia, higher education level, controlled blood pressure, improved high-density lipoprotein and low-density lipoprotein levels and reduced pickled food intake may help to reduce the risk of age-related cataract development.

In vitro antioxidant and anticataractogenic potential of silver nanoparticles biosynthesized using an ethanolic extract of Tabernaemontana divaricata leaves

Silver nanoparticles (AgNPs) have been found useful in biological systems and in medicine since they possess a large surface area to volume ratio, which confers on them several unique properties. In the present study, AgNPs that had been biosynthesized using an ethanolic extract of Tabernaemontana divaricata leaf were evaluated for putative antioxidant potential and efficacy in preventing experimental in-vitro selenite-induced opacification of the ocular lens (cataractogenesis). The antioxidant potential of the AgNPs was evaluated in-vitro by looking for radical-scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide (H₂O₂) free radicals as well as by determining reducing power. The anticataractogenic potential of the AgNPs was evaluated in an in-vitro model of selenite-induced cataractogenesis in five groups of Wistar rat lenses cultured in Dulbecco's modified Eagle's medium (DMEM) for 24h: Group I lenses (negative control) were cultured in DMEM alone; Group II lenses were exposed to sodium selenite alone (100μM); Group III lenses were exposed simultaneously to sodium selenite and the T. divaricata extract (250μg/ml); Group IV lenses were exposed simultaneously to sodium selenite and the biosynthesized AgNPs (125μg/ml); and Group V lenses were exposed to the AgNPs alone. In these lenses, gross morphological changes, as well as activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-S-transferase (GST), and levels of reduced glutathione (GSH) and malondialdehyde (MDA), were determined. In-vitro, the AgNPs (which were spherical in shape with an average diameter ranging from 15 to 50nm) showed potent and concentration-dependent radical-scavenging activity on DPPH and H₂O₂ free radicals as well as reducing power. The gross morphological changes seen in the cultured rat lenses were: all eight control (Group I) lenses remained transparent; dense opacification was noted in all eight selenite-challenged untreated (Group II) lenses; in selenite-challenged, simultaneously T. divaricata extract-treated (Group III) lenses, no opacification occurred in seven of eight (87.5%) lenses and only minimal opacification in one (12.5%) lens; all the eight Group IV (selenite-challenged, simultaneously AgNPs-treated) lenses did not show any opacification; and all the eight Group V lenses (exposed to AgNPs alone) remained as transparent as control lenses. The mean activities of CAT, SOD, GPx and GST, and the mean levels of GSH, were significantly (p<0.05) lower in Group II lenses than those in Groups I, III, IV and V lenses, while the mean MDA level was significantly (p<0.05) higher in Group II lenses than those in Groups I, III, IV and V lenses; oxidative damage possibly occurred in Group II lenses, whereas this appears to have been prevented in Groups III and IV lenses. These observations suggest that the T. divaricata leaf ethanolic extract, and also the AgNPs biosynthesized using the T. divaricata extract, possess effective in-vitro antioxidant activity and the potential to prevent experimental selenite-induced opacification in cultured Wistar rat lenses.

Chemoprevention of skin cancer with 1,1-Bis (3'-indolyl)-1-(aromatic) methane analog through induction of the orphan nuclear receptor, NR4A2 (Nurr1)

Background

The objective of this study was to demonstrate the anti-skin cancer and chemopreventive potential of 1,1-bis(3′-indolyl)-1-(p-chlorophenyl methane) (DIM-D) using an in vitro model.

Methods

In vitro cell cytotoxicity and viability assays were carried out in A431 human epidermoid carcinoma cell line and normal human epidermal keratinocytes (NHEK) respectively by crystal violet staining. Apoptosis induction in A431 cells (DIM-D treated) and NHEK cells pretreated with DIM-D (2 hr) prior to UVB irradiation, were assessed. The accumulation of reactive oxygen species (ROS) in DIM-D pretreated NHEK cells (2 hr) prior to UVB exposure was also determined. Immunocytochemistry and western blot analysis was performed to determine cleaved caspase 3 and DNA damage markers in DIM-D treated A431 cells and in DIM-D pretreated NHEK cells prior to UVB irradiation.

Results

The IC50 values of DIM-D were 68.7±7.3, 48.3±10.1 and 11.5±3.1 μM whilst for Epigallocatechin gallate (EGCG) were 419.1±8.3, 186.1±5.2 and 56.7±3.1 μM for 24, 48 and 72 hr treatments respectively. DIM-D exhibited a significantly (p<0.05) greater induction of DNA fragmentation in A431 cells compared to EGCG with percent cell death of 38.9. In addition, DIM-D induced higher expression in A431 cells compared to EGCG of cleaved caspase 3 (3.0-fold vs. 2.4-fold changes), Nurr1 (2.7-fold vs. 1.7-fold changes) and NFκB (1.3-fold vs. 1.1-fold changes). DIM-D also exhibited chemopreventive activity in UVB-irradiated NHEK cells by significantly (p<0.05) reducing UVB-induced ROS formation and apoptosis compared to EGCG. Additionally, DIM-D induced expression of Nurr1 but reduced expression of 8-OHdG significantly in UVB-irradiated NHEK cells compared to EGCG and UV only.

Conclusion

Our results suggest that DIM-D exhibits Nurr1-dependent transactivation in the induction of apoptosis in A431 cells and it protects NHEK cells against UVB-induced ROS formation and DNA damage.

Comparative antimutagenic and anticancer activity of three fractions of black tea polyphenols thearubigins

Antimutagenic and anticancer effects of black tea polyphenols theaflavins (TF) and thearubigins (TR) have previously been reported. TR is a complex mixture of polyphenols. In this study, our interest was to fractionate TR and to study the antimutagenic and anticancer activities of the fractions. Three fractions of TR, namely TR-1, TR-2, and TR-3, were isolated by chromatographic processes. Antimutagenic activity of these 3 fractions was carried out on 4 Salmonella strains by Ames assay. Anticancer activity was studied on human leukemic cells U937. Our findings clearly indicated antimutagenic and anticancer activities of the TR-1, TR-2, and TR-3 fractions on Salmonella strains and on U937 cells, respectively. However, all 3 fractions, at or below 100 μg/ml dose, did not show any significant toxic effects on the normal human cells (peripheral blood mononuclear cells). TR-2 was found to be the most active fraction among the 3. Flow cytometric and confocal microscopic studies further indicate that apoptosis induction could be an important mechanism behind the anticancer effects of these fractions. To our knowledge, this study is the first attempt to describe the antimutagenic and anticancer activity of TR fractions, and it also suggests that TR-2 is the most active component of TR.

Natural flavonoids as potential multifunctional agents in prevention of diabetic cataract

Cataract is one of the earliest secondary complications of diabetes mellitus. The lens is a closed system with limited capability to repair or regenerate itself. Current evidence supports the view that cataractogenesis is a multifactorial process. Mechanisms related to glucose toxicity, namely oxidative stress, processes of non-enzymatic glycation and enhanced polyol pathway significantly contribute to the development of eye lens opacity under conditions of diabetes. There is an urgent need for inexpensive, non-surgical approaches to the treatment of cataract. Recently, considerable attention has been devoted to the search for phytochemical therapeutics. Several pharmacological actions of natural flavonoids may operate in the prevention of cataract since flavonoids are capable of affecting multiple mechanisms or etiological factors responsible for the development of diabetic cataract. In the present paper, natural flavonoids are reviewed as potential agents that could reduce the risk of cataract formation via affecting multiple pathways pertinent to eye lens opacification. In addition, the bioavailability of flavonoids for the lens is considered.

Anticataractogenic effect of an extract of the oyster mushroom, Pleurotus ostreatus, in an experimental animal model

PURPOSE

To evaluate the efficacy of Pleurotus ostreatus extract in preventing selenite-induced cataractogenesis.

METHODS

In vitro, enucleated rat lenses, divided into one control and three experimental groups (selenite only, simultaneous selenite and extract, initial extract and subsequent selenite), underwent morphological and biochemical evaluation. The anti-cataractogenic effect was also evaluated in vivo.

RESULTS

In vitro, simultaneous incubation of extract with selenite-challenged lenses caused a decrease in lens opacification by maintaining antioxidant components at near normal levels. In vivo, P.ostreatus (300 mg/kg body weight) prevented cataract in 75% of rats.

CONCLUSION

Extract of P. ostreatus prevents experimental selenite-induced cataractogenesis.

Advances in pharmacological strategies for the prevention of cataract development

Cataractous-opacification of the lens is one of the leading causes of blindness in India. The situation can be managed by surgical removal of the cataractous lens. Various pharmacological strategies have been proposed for the prevention and treatment of cataract. Information on possible benefits of putative anticataract agents comes from a variety of approaches, ranging from laboratory experiments, both in vitro and in vivo, to epidemiological studies in patients. This review deals with the various mechanisms, and possible pharmacological interventions for the prevention of cataract. The article also reviews research on potential anticataractous agents, including aldose reductase inhibitors, glutathione boosters, antiglycating agents, vitamins and various drugs from indigenous sources.

A thought on the biological activities of black tea

Tea is the most widely used ancient beverage in the world and black tea possesses many biological effects on the organisms. It acts as an effective antioxidant because of its free radical-scavenging and metal-chelating ability. Due to this, it is active against inflammation, clastogenesis, and several types of cancer. Tea reduces DNA damage and mutagenesis due to oxidative stress or the presence of pro-mutagens through antioxidant function, blocking activation pathways of mutagens, suppressing transcription of enzymes involved etc. Inhibition of low-density lipoprotein (LDL) peroxidation, suppression of fatty acid synthase etc., suggest that tea may have a role in preventing cardiovascular diseases. Some epidemiological studies support the protective role of black tea against cardiovascular diseases but some do not. Besides, black tea has beneficial effects on the gastrointestinal tract; it affects motility, absorption, microflora etc., by influencing the hormonal balance and antioxidant function black tea improves bone mineral density. It is also antiviral due to its enzyme-inhibiting and receptor-blocking properties. Although its role in cancers of the gastrointestinal tract, liver, and prostate is confirmed, its effect against urinary tract cancer is uncertain and further studies are required. Apart from these, excess consumption may lead to the formation of a stained pellicle layer on teeth, which is difficult to eliminate, inhibits trypsin, influences mineral absorption, causes convulsions etc. Excess caffeine intake may have adverse effects on selected organs as reported in studies on some organisms. These reports indicate that there is a wide scope of further research for the efficient use of black tea active conserves/isolates to reap health benefits.

Green tea modulates reserpine toxicity in animal models

Reserpine, a natural product extracted from Rauwolfia serpintina or Rauwolfia vomitoria, is a known dopamine depleter that inhibits several neurotransmitters. Reserpine has been used clinically to control hypertension, schizophrenia, insomnia and insanity. The use of this drug, however, has been limited because of its side effects which include oxidative damage to organs, including the liver. Green tea catechins are potent antioxidants that have the potential to counteract reserpine induced oxidative stress. This study investigated the merits of administering green tea concurrently with reserpine to prevent oxidative hepatic damage in Sprague-Dawely (SD) rats. Reserpine was found to cause hepatic damage, with elevated levels of oxidative stress markers, such as Thiobarbituric Acid Reactive Substances (TBARS), transaminases and cholesterol. Reserpine also induced hepatic ultra-structural damage in the cytoplasmic membrane, nuclear envelope, endoplasmic reticulum (rER), ribosomal stripping and mitochondria. Electron microscopy examination showed revival of liver cells as a result of green tea extract administration to experimental rats.

Phenylalanine ammonia-lyase (PAL) and cinnamate 4-hydroxylase (C4H) and catechins (flavan-3-ols) accumulation in tea

Phenylalanine ammonia-lyase and cinnamate 4-hydroxylase are important enzymes in allocating significant amounts of carbon from phenylalanine into the biosynthesis of several important secondary metabolites. Tea is an important crop of commerce known for its beverage and medicinally important flavonoid compounds, mainly catechins. As metabolic flux for the operation of the flavonoid pathway is maintained through the activities of PAL and C4H, thus, catechins biosynthesis in tea is critically dependent on the products of these enzymes. We examined the expression of PAL and C4H. Sequence encoding CsPAL was isolated from tea by polymerase chain reaction using sequence information available at the NCBI GenBank. Sequence encoding C4H was isolated from tea by using differential display of mRNA and rapid amplification of cDNA ends technology. CsC4H (AY641731) comprised of 1,352 bp full-length cDNA with open reading frame of 1,173 bp encoding 390 amino acids. Catechin contents decreased in response to drought stress (DS), abscisic acid (ABA), and gibberellic acid (GA(3)) treatments but increased in response to wounding. The expression of CsPAL and CsC4H showed the same behavior under the above treatments and was also in accordance with the catechin contents. A positive correlation between catechin contents and gene expression suggested a critical role of the enzymes in catechins biosynthesis and a crosstalk between phenylpropanoid and flavonoid pathways.

Cloning and differential expression of QM like protein homologue from tea [Camellia sinensis (L.) O. Kuntze]

The QM like protein gene encodes for ribosomal protein L10, which is implicated in tumor suppression, transcription factor regulation, and ribosome stability in yeast and mammals. Present study describes cloning of a full-length QM cDNA (CsQM) from tea leaves using differential display of mRNA followed by rapid amplification of cDNA ends. Expression of CsQM was studied in leaves of different stages of development and under various external cues. CsQM contained an open reading frame of 651 bases, encoding 216 amino acids. CsQM shared 71-87% and 85-91% identity at nucleotide and amino acid sequences, respectively with QM genes isolated from other plant species. During active-growth period of tea, higher expression was observed in apical buds that decreased gradually with increasing age of the leaf. During dormancy season, the expression of CsQM gene was severely down-regulated in all the leaves studied. CsQM transcript was found to be down regulated in response to drought stress and abscisic acid treatment but up-regulated by gibberellic acid treatment. A positive association of CsQM transcript abundance with active cellular growth suggested its role in plant growth and development.

Corneal tattoo with tea infusion

Except in animal models of cataractogenesis, the literature on the effects of tea infusion on ocular tissue is scant. In our patient, prolonged exposure to tea infusion may have led to a hypesthetic cornea with secondary limbal stem cell loss. In turn, the eye developed keratinization and corneal neovascularization.

Orally administered epigallocatechin gallate attenuates light-induced photoreceptor damage

EGCG, a major component of green tea, has a number of properties which includes it being a powerful antioxidant. The purpose of this investigation was to deduce whether inclusion of EGCG in the drinking water of albino rats attenuates the effect of a light insult (2200lx, for 24h) to the retina. TUNEL-positive cells were detected in the outer nuclear layer of the retina, indicating the efficacy of the light insult in inducing photoreceptor degeneration. Moreover, Ret-P1 and the mRNA for rhodopsin located at photoreceptors were also significantly reduced as well as the amplitude of both the a- and b-waves of the electroretinogram was also reduced showing that photoreceptors in particular are affected by light. An increase in protein/mRNA of GFAP located primarily to Müller cells caused by light shows that other retinal components are also influenced by the light insult. However, antigens associated with bipolar (alpha-PKC), ganglion (Thy-1) and amacrine (GABA) cells, in contrast, appeared unaffected. The light insult also caused a change in the content of various proteins (caspase-3, caspase-8, PARP, Bad, and Bcl-2) involved in apoptosis. A number of the changes to the retina caused by a light insult were significantly attenuated when EGCG was in the drinking water. The reduction of the a- and b-waves and photoreceptor specific mRNAs/protein caused by light were significantly less. In addition, EGCG attenuated the changes caused by light to certain apoptotic proteins (especially at after 2 days) but did not appear to significantly influence the light-induced up-regulation of GFAP protein/mRNA. It is concluded that orally administered EGCG blunts the detrimental effect of light to the retina of albino rats where the photoreceptors are primarily affected.

Differential expression of Histone H3 gene in tea (Camellia sinensis (L.) O. Kuntze) suggests its role in growing tissue

Histone proteins are integral part of chromatin and their expression is typically linked to DNA replication in the S phase of cell cycle. Histone H3 is one of the four histones, along with H2A, H2B and H4, which forms the eukaryotic nucleosome octomer core. Using differential display of mRNA and rapid amplification of cDNA ends (RACE), a full-length Histone H3.1 cDNA (CsH3) was isolated from tea leaves. The open reading frame consisted of 411 nucleotides and deduced amino acid sequence comprised of 136 amino acid residues. CsH3 shared 79-82% and 98% identity at nucleotide and amino acid sequences, respectively with Histone H3 isolated from other plant species. During active-growth period of tea, higher expression was observed in apical buds that decreased gradually with increasing age of the leaf. During dormancy season, the expression of CsH3 was severely down-regulated in all the leaves studied. CsH3 was found to be down regulated in response to drought stress and ABA treatment and up-regulated by GA(3) treatment. A positive association of CsH3 abundance with active cellular growth suggested its role in plant growth and development.

Acetyl-L-carnitine prevents selenite-induced cataractogenesis in an experimental animal model

PURPOSE

To investigate whether acetyl-L-carnitine (ALCAR) retards selenite-induced cataractogenesis in vivo.

METHODS

On postpartum day 10, group I pups received intraperitoneal saline and group II and group III pups received subcutaneous sodium selenite; Group III pups also received intraperitoneal ALCAR once daily on postpartum days 9-14. Both eyes of each pup were examined up to postpartum day 30. After sacrifice, extricated pup lenses were analyzed for antioxidant and redox system components.

RESULTS

There was dense lenticular opacification in all group II pups, minimal opacification in 33% of group III pups, and no opacification in 67% of group III and in all group I pups. Group II lenses exhibited significantly lower values of antioxidant and redox system components and higher malondialdehyde concentrations than group I or group III lenses.

CONCLUSION

ALCAR prevents selenite-induced cataractogenesis in Wistar rat pups, possibly by inhibiting depletion of antioxidant enzyme and redox system components and inhibiting lipid peroxidation.

Therapeutic potential of green tea: a new horizon in drug discovery

Worldwide, tea is one of the most widely consumed beverages. Green tea consumption is especially popular in China, Japan and other Asian countries. It has been found to be rich in polyphenolic compounds, of which catechins are the major constituents. A large number of clinical and preclinical studies have explored its pharmacologic activities. It holds promise as an antioxidant, anti-inflammatory, antibacterial, antiarteriosclerotic, cardioprotective, neuroprotective and anticarcinogenic agent, to name a few. This review summarizes the pharmacodynamics and pharmacokinetics of green tea polyphenols and explores their future as novel drugs for both health and disease conditions.

Prevention of selenite-induced cataractogenesis by acetyl-l-carnitine: An experimental study

Several studies have suggested that antioxidants retard the process of cataractogenesis by scavenging free oxygen radicals. The present study sought to assess the efficacy of the antioxidant acetyl-L-carnitine (ALCAR) in preventing selenite-induced cataractogenesis in an experimental setting. The first, in vitro phase of the study was performed on lenses from Wistar rats incubated for 24 h at 37 degrees C in Dulbecco's Modified Eagle Medium (DMEM) alone (control, Group I), or in DMEM containing 100 microM of selenite (Group II) or in DMEM containing 100 microM of selenite and 200 microM/ml ALCAR added at the same time as selenite (Group IIIa) or 30 min, 1 h or 2 h later (Groups IIIb, IIIc and IIId, respectively). Gross morphological examination of these lenses revealed dense opacification (cataract formation) in Group II, minimal opacification in some Group IIIa lenses and no opacification in Group I. The mean activities of the antioxidant enzymes catalase and glutathione peroxidase were significantly lower in Group II than in Group I or Group IIIa lenses, while malondialdehyde concentration (an indicator of lipid peroxidation) was significantly higher in Group II lenses than that in Group I or Group IIIa lenses. The second, in vivo phase of the study revealed dense opacification (cataract formation) in 100% of Wistar rat pups receiving subcutaneous sodium selenite alone (19 microM/kg body weight) but in only 37.5% of those receiving subcutaneous selenite and intraperitoneal ALCAR. These data suggest that ALCAR is able to significantly retard experimental selenite-induced cataractogenesis.

Uptake and distribution of catechins in fetal organs following in utero exposure in rats

BACKGROUND

Although catechins are known to be powerful antioxidants, no reports have shown their transport to fetal organs. We investigated the distribution of catechins in fetal rat organs after maternal exposure to green tea extract (GTE).

METHODS

GTE (550 mg/kg) or water was fed orally to pregnant dams at 15.5 days of gestation, the dams were sacrificed and fetal organs were dissected 0, 0.5, 1, 2, 3, 5, and 8 h later. Catechins and catechin gallates were determined by high-performance liquid chromatography (HPLC) after solid-phase extraction.

RESULTS

In the GTE-treated group, catechins were detected in most of the fetal organs studied, including the brain, eyes, heart, lungs, kidneys and liver but not in the control group. The first peak times (T(max)) were about 0.5-1 h. The maximum concentrations (C(max)) of catechins in the fetal eye were about 2-10 times higher than in the other organs, ranging from 249 pmol/g for epicatechin (EC) to 831 pmol/g for epigallocatechin gallate (EGCG). Catechin gallates were generally more readily taken up by fetal organs than catechins. EGCG had the highest level of uptake according to area under the curve (AUC) plots and the highest C(max) in all organs.

CONCLUSIONS

Various fetal organs had low but significant levels of catechins after GTE intake by the dams, and organ levels were found to be related to catechin structure. EGCG could be a potential candidate for antioxidant supplementation of the fetus in utero.

Beneficial effects of green tea--a review

Tea is the most consumed drink in the world after water. Green tea is a 'non-fermented' tea, and contains more catechins, than black tea or oolong tea. Catechins are in vitro and in vivo strong antioxidants. In addition, its content of certain minerals and vitamins increases the antioxidant potential of this type of tea. Since ancient times, green tea has been considered by the traditional Chinese medicine as a healthful beverage. Recent human studies suggest that green tea may contribute to a reduction in the risk of cardiovascular disease and some forms of cancer, as well as to the promotion of oral health and other physiological functions such as anti-hypertensive effect, body weight control, antibacterial and antivirasic activity, solar ultraviolet protection, bone mineral density increase, anti-fibrotic properties, and neuroprotective power. Increasing interest in its health benefits has led to the inclusion of green tea in the group of beverages with functional properties. However, although all the evidence from research on green tea is very promising, future studies are necessary to fully understand its contributions to human health, and advise its regular consumption in Western diets, in which green tea consumption is nowadays limited and sporadic.

Pharmacokinetic studies of green tea catechins in maternal plasma and fetuses in rats

We carried out a pharmacokinetic study to determine the levels and profiles of catechins in pregnant rats and their fetuses after ingestion of green tea extract (GTE). We measured total catechin levels after enzyme digestions. Dams, at 15.5 days of gestation, were fed with GTE and catechins were measured in the maternal plasma, placenta, and fetus 0, 0.5, 1, 2, 3, 5, 8, 10, 12, 16, and 20 h after maternal GTE intake. The pharmacokinetic changes were analyzed by non compartmental models. We found that maternal plasma concentrations of catechins were about 10 times higher than in placenta and 50-100 times higher than in the fetus. AUC and Cmax levels of (-)-epicatechin (EC) were the highest in plasma while the levels of (-)-epigallocatechin gallate (EGCG) were the highest in the placenta and the fetus. The exposure level of catechin derivatives was higher than the gallate derivatives in maternal plasma after normalization but reversed in the placenta and fetus. The absorption of epi-isomers in plasma was found to be more favorable than their non epi-isomer counterparts. EGCG had the highest level of exposure (AUC) and the highest Cmax in the fetus, implying it may have potential for in utero antioxidant protection.

The effect of smoking on DNA effects in the comet assay: a meta-analysis

The comet assay (alkaline single-cell gel electrophoresis, SCG or SCGE) is frequently used in biomonitoring to detect genotoxic effects in humans exposed at the workplace or in their environment. Because of its ready accessibility, blood is most frequently used in such studies. Many studies investigated cigarette smoking either as a genotoxic exposure itself or as a potential confounding factor in occupational studies. However, although smoking is considered to be a relevant exposure towards various genotoxins, conflicting results have been reported in the comet assay studies. The actual reasons for this discrepancy are not known. To further evaluate evidence for smoking-related DNA effects in the comet assay, we now used a meta-analysis approach based on a literature search. We identified 38 studies from 37 publications which were suited for a formal meta-analysis based on the standardized mean difference (SMD) between the study groups. The evaluation of these 38 studies indicated higher levels of DNA damage in smokers than in non-smokers [under a random effects model, SMD = 0.55, 95% confidence interval = (0.16-0.93)]. Subdividing these studies into studies investigating the effect of smoking as a genotoxic exposure (Type A studies, n = 12) and studies investigating smoking as a potential confounder in occupational studies (Type B, n = 26) indicated a significant difference only in Type A studies but not in Type B studies. Furthermore, studies using image analysis or image length measurements (n = 23) only indicated a tendency for a genotoxic effect of smoking, whereas studies using an arbitrary score (n = 15) found a significantly higher level of DNA damage in smokers.

Antioxidant properties of black tea in alcohol intoxication

Food ingredients such as alcohol may modify cellular redox state. Ethanol metabolism is accompanied by generation of free radicals that can damage cell components especially when antioxidant mechanisms are no able to neutralize them. However black tea is a source of polyphenol antioxidants that may enhance cellular antioxidant abilities. The aim of this study was to investigate the effect of black tea on antioxidant abilities of the liver, blood serum and brain of 12-months old rats sub-chronically (for 28 days) intoxicated with ethanol. Administration of black tea alone caused increase in the activity and concentration of antioxidant parameters more extensively in the liver and serum than in the brain. Alcohol caused decrease in the liver glutathione peroxidase and reductase and catalase activity but increase in activity of superoxide dismutase. Moreover, decrease in the level of non-enzymatic antioxidants, such as reduced glutathione, vitamin C, A and E and beta-carotene was observed. The activity of serum glutathione peroxidase and reductase decreased while superoxide dismutase activity was not changed. The level of non-enzymatic antioxidants in serum was also decreased. However brain activity/level of all examined antioxidants enzymatic as well as non-enzymatic was decreased after ethanol intoxication. Black tea considerably prevented antioxidant parameters against changes caused by ethanol. These results indicate beneficial antioxidant effect of black tea regarding all examined tissues, but especially the liver.