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Green tea averts age-dependent decline of hippocampal signaling systems related to antioxidant defenses and survival

We previously found that prolonged consumption of green tea (GT), a rich source of antioxidant polyphenols, protected proteins and lipids against oxidation and reduced lipofuscin deposition in the rat hippocampal formation as well as improving spatial memory during aging. In this work, we sought to investigate whether GT treatment could interfere with age-related changes in redox status and cellular signaling systems related to oxidative stress and survival in the same brain region. To address this issue, five male Wistar rats were fed with GT from 12 to 19 months of age and results were compared to those obtained from controls age 19 months (C-19 M). A third group of rats was evaluated at 12 months of age to provide baseline data. At completion of the specified time points, the glutathione levels and antioxidant enzyme activities, the activation of the transcription factors cyclic AMP response element-binding (CREB) and nuclear factor-kappaB (NF-kappaB, p50 and p65 subunits), and the levels of brain-derived neurotrophic factor (BDNF) and B-cell lymphoma-2 (Bcl-2) were measured in hippocampal formations. GT-treated rats presented higher reduced and lower oxidized glutathione levels and displayed favorable alterations in antioxidant enzyme activities compared to C-19 M animals. In addition, GT increased CREB activation and the levels of BDNF and Bcl-2, but had no effect on activation of NF-kappaB subunits, relative to age-matched controls. We conclude that long-term GT ingestion improves antioxidant systems and activates CREB in the aging rat hippocampal formation, leading to neuroprotection mediated by downstream upregulation of BDNF and Bcl-2.

Protective Effects of Chronic Green Tea Consumption on Age-related Neurodegeneration

Dietary antioxidant compounds, due to their pivotal role in the modulation of cellular redox mechanisms, are gaining attention of researchers in the field of brain aging and related degenerative diseases. In this perspective, green tea (GT) can be an excellent resource, as it contains large amounts of brain-accessible polyphenols. Many of these compounds are monomeric catechins, which have been shown to exert antioxidant effects, acting directly as radical scavengers or metal-chelators. In the current article, we review the general properties of GT, the direct antioxidant action of its polyphenols and the fine modulation of signaling systems related to survival and antioxidant defenses in the central nervous system of aging rats. The effects in the glutathione system and the activation of several transcription factors including cyclic AMP response element-binding (CREB) protein, levels of the brain-derived neurotrophic factor (BDNF) and the anti-apoptotic protein B-cell lymphoma-2 (Bcl-2) are given in detail. We discuss also the beneficial action of catechins in learning and memory with a particular focus on the hippocampal formation. We conclude that GT polyphenols can have a promising role in the reversal of age-related loss of neuronal plasticity and recovery after neuronal lesions associated with aging.

Red wine antioxidants protect hippocampal neurons against ethanol-induced damage: a biochemical, morphological and behavioral study.

Chronic ethanol consumption increases oxidative stress, which accounts for the striking neurological changes seen in this condition. Notwithstanding, there is well-documented evidence that polyphenols, present in grape skin and seeds, exhibit a strong antioxidant activity. As red wine is rich in polyphenols, the aim of the present work was to evaluate their putative protective effects on the hippocampal formation by applying biochemical, morphological and behavioral approaches. Six-month old male Wistar rats were fed with red wine (ethanol content adjusted to 20%) and the results were compared with those from ethanol-treated (20%) rats and pair-fed controls. Biochemical markers of oxidative stress (lipid peroxidation, glutathione levels and antioxidant enzyme activities) were assessed on hippocampal homogenates. Lipofuscin pigment, an end product of lipid peroxidation, was quantified in hippocampal cornu ammonis 1 and 3 (CA1 and CA3) pyramidal neurons using stereological methods. All animals were behaviorally tested on the Morris water maze in order to assess their spatial learning and memory skills. In red wine-treated rats, lipid peroxidation was the lowest while presenting the highest levels of reduced glutathione and an induction of antioxidant enzyme activities. Morphological findings revealed that, contrary to ethanol, red wine did not increase lipofuscin deposition in CA1 and CA3 pyramidal neurons. Besides, red wine-treated animals learned the water maze task at a higher rate than ethanol group and had better performance scores by the end of the training period and on a probe trial. Actually, no significant differences were found between pair-fed controls and red wine-treated rats in morphological and behavioral data. Thus, our findings demonstrate that chronic consumption of red wine, unlike the ethanol solution alone, does not lead to a decline in hippocampal-dependent spatial memory. This may be due to the ability of red wine polyphenols to improve the antioxidant status in the brain and to prevent free radical-induced neuronal damage.

Chronic green tea consumption prevents age-related changes in rat hippocampal formation

The hippocampal formation undergoes considerable structural and functional modifications during aging and oxidative stress emerges as a key player in the process. In the present study, we investigated whether prolonged consumption of green tea (GT), which contains large amounts of polyphenols, could interfere with age-related changes in this brain region using biochemical, morphological and behavioral approaches. Ten male Wistar rats aged 19 months were fed with GT since 12 months of age and results compared to those obtained from controls aged 19 months (C-19M). At 12 months of age, another group of rats was evaluated to provide baseline data. Oxidative stress markers (protein carbonyls and malondialdehyde) were quantified in hippocampal homogenates and stereological methods were applied to estimate the deposition of lipofuscin in hippocampal CA3 pyramidal neurons. Morris water maze was used to assess spatial learning and memory. Aging increased oxidative markers and lipofuscin accumulation and was associated with impaired memory acquisition. However, GT treatment protected proteins and lipids against oxidation and prevented the increase of lipofuscin deposition compared to age-matched controls. Furthermore, the spatial learning abilities of GT-treated rats were significantly improved when compared to those from C-19M group. Taken together, these findings confirm the neuroprotective ability of GT in the hippocampal formation probably due to the reduction of oxidative stress-related damage observed during aging.

Loss of synapses in the entorhinal-dentate gyrus pathway following repeated induction of electroshock seizures in the rat.

The goal of this study was to answer the question of whether repeated administration of electroconvulsive shock (ECS) seizures causes structural changes in the entorhinal‐dentate projection system, whose neurons are known to be particularly vulnerable to seizure activity. Adult rats were administered six ECS seizures, the first five of which were spaced by 24‐hr intervals, whereas the last two were only 2 hr apart. Stereological approaches were employed to compare the total neuronal and synaptic numbers in sham‐ and ECS‐treated rats. Golgi‐stained material was used to analyze dendritic arborizations of the dentate gyrus granule cells. Treatment with ECS produced loss of neurons in the entorhinal layer III and in the hilus of the dentate gyrus. The number of neurons in the entorhinal layer II, which provides the major source of dentate afferents, and in the granular layer of the dentate gyrus, known to receive entorhinal projections, remained unchanged. Despite this, the number of synapses established between the entorhinal layer II neurons and their targets, dentate granule cells, was reduced in ECS‐treated rats. In addition, administration of ECS seizures produced atrophic changes in the dendritic arbors of dentate granule cells. The total volumes of entorhinal layers II, III, and V–VI were also found to be reduced in ECS‐treated rats. By showing that treatment with ECS leads to partial disconnection of the entorhinal cortex and dentate gyrus, these findings shed new light on cellular processes that may underlie structural and functional brain changes induced by brief, generalized seizures.

Protective effects of a catechin-rich extract on the hippocampal formation and spatial memory in aging rats

Green tea (GT) displays strong anti-oxidant and anti-inflammatory properties mostly attributed to (-)-epigallocatechin-3-gallate (EGCG), while experiments focusing on other catechins are scarce. With the present work we intended to analyze the neuroprotective effects of prolonged consumption of a GT extract (GTE) rich in catechins but poor in EGCG and other GT bioactive components that could also afford benefit. The endpoints evaluated were aging-induced biochemical and morphological changes in the rat hippocampal formation (HF) and behavioral alterations. Male Wistar rats aged 12 months were treated with GTE until 19 months of age. This group of animals was compared with control groups aged 19 (C-19M) or 12 months (C-12M). We found that aging increased oxidative markers but GTE consumption protected proteins and lipids against oxidation. The age-associated increase in lipofuscin content and lysosomal volume was also prevented by treatment with GTE. The dendritic arborizations of dentate granule cells of GTE-treated animals presented plastic changes accompanied by an improved spatial learning evaluated with the Morris water maze. Altogether our results demonstrate that the consumption of an extract rich in catechins other than EGCG protected the HF from aging-related declines contributing to improve the redox status and preventing the structural damage observed in old animals, with repercussions on behavioral performance.

Grape seed flavanols, but not Port wine, prevent ethanol-induced neuronal lipofuscin formation

Lipofuscin is an end-product of lipid peroxidation which dramatically increases following ethanol consumption, as we have shown in hippocampal and cerebellar neurons. In this work, we corroborated observations indicating that supplementation of ethanol with 200 mg/l of grape seed flavanols prevents increased lipofuscin formation, an action that has been ascribed to the antioxidant properties of the flavanols. Because wine is an alcoholic beverage naturally rich in flavanols, we decided to study the effect of chronic ingestion of Port wine (PW), which also contains 20% ethanol and approximately 200 mg/l of flavanol oligomers, upon lipofuscin accumulation in the hippocampal CA1 and CA3 pyramidal neurons and in the cerebellar Purkinje cells. Six months old rats were fed with PW and results were compared with those obtained in ethanol-treated groups and pair-fed controls. After 6 months of treatment, the volume of lipofuscin per neuron was estimated using unbiased stereological methods. Treatment with PW resulted in an increase of lipofuscin in all neuronal populations studied when compared to controls and to rats treated with ethanol supplemented with flavanols. No differences were observed when comparisons were made with ethanol drinking rats. We conclude that PW, despite containing 20% ethanol and flavanols, does not prevent ethanol-induced lipofuscin formation as previously found in animals drinking ethanol plus flavanols. The reduced antioxidant capacity of PW might depend on the type and amount of flavanols present and on its content in sugars.

Effects of Chronic Red Wine Consumption on the Expression of Vascular Endothelial Growth Factor, Angiopoietin 1, Angiopoietin 2, and Its Receptors in Rat Erectile Tissue

Long-term consumption of red wine (RW) apparently confers some protection against cardiovascular diseases due to antiatherosclerotic properties of polyphenols and ethanol (EtOH). There is some evidence indicating that they do so by regulating angiogenesis, but the mechanism and the modulator factors involved are largely unknown. The aim of this study was to evaluate the effects of chronic ingestion of RW in vascular structure and in the pattern of expression of vascular growth factors in the rat corpus cavernosum. Male Wistar rats aged 6 mo were treated with RW or an equivalent EtOH solution, as the only liquid source for 6 mo. Expression of vascular endothelial growth factor (VEGF), angiopoietin 1 and angiopoietin 2, and their receptors (VEGFR1, VEGFR2, and Tie2) in cavernous tissue was assayed by immunofluorescence and Western blotting. A reduction of VEGF and VEGFR2 expression, respectively, in smooth muscle and endothelial cells was observed in RW-treated animals, which was balanced by an increase in angiopoietins/Tie2 expression. In EtOH rats, only a decrease in expression of the receptors VEGFR2 and Tie2 was observed. These results, taken together, suggest that antioxidants present in RW activate selected mechanisms for the maintenance of cavernous tissue vascularization. However, functional studies will be necessary to elucidate if RW is of benefit in the prevention of deleterious vascular events associated with ED.

Effects of food restriction on synthesis and expression of brain-derived neurotrophic factor and tyrosine kinase B in dentate gyrus granule cells of adult rats

We have previously found that the dendritic trees of dentate gyrus granule cells are selectively vulnerable to food restriction but there are reorganizational morphological events that minimize functional impairments. As the neurotrophin brain-derived neurotrophic factor (BDNF) and the cognate receptor tyrosine kinase B (TrkB) are involved in the maintenance of the structure of dendritic trees, we thought of interest to verify if there are alterations in its synthesis and expression in granule cells. To investigate this issue, 2-month-old rats were submitted to 40% caloric restriction for 6 months and compared to controls fed ad libitum. The numbers of granule cells containing BDNF and TrkB proteins were estimated from immunostained sections and the respective mRNA levels of individual neurons evaluated using nonradioactive in situ hybridization. After dietary treatment there was a 15% reduction of BDNF-immunoreactive granule cells with no changes of the number of TrkB-immunostained neurons. No alterations were found in the levels of BDNF and TrkB mRNAs of individual granule cells. As caloric restriction extends the lifespan of animals, the restrictive dietary regimens are generally regarded as beneficial to the organisms, but the present results suggest that caution is needed when extrapolating to some neuronal populations.

Red Wine, but not Port Wine, Protects Rat Hippocampal Dentate Gyrus Against Ethanol-Induced Neuronal Damage—Relevance of the Sugar Content

AIMS Chronic ethanol consumption leads to oxidative damage in the central nervous system inducing neuronal degeneration and impairment of brain functions. Nevertheless, it has been reported that grape polyphenols might prevent the alluded ethanol effects. We have reported that prolonged red wine intake improves hippocampal formation oxidative status, a finding not replicated using Port wine. Thus, we thought of interest to compare the effects of chronic ingestion of these wines in the morphology of dentate gyrus (DG) neurons that are particularly vulnerable to alcohol effects. METHODS Six-month-old Wistar rats were fed either with red wine or Port wine (both with 20% ethanol content, v/v), and the results were compared with 20% (v/v) ethanol-treated, ethanol/glucose and pair-fed control groups. After 6 months of treatment, the layer volumes of the DG and the total number of granule and hilar neurons were estimated. The dendritic trees of granule cells were also studied in Golgi-impregnated material. RESULTS The number of granule cells and the DG layer volumes were similar among all groups. However, the number of hilar neurons was reduced in Port wine, ethanol-treated and ethanol/glucose animals. Furthermore, the granule cells from these groups showed a decrease in the total dendritic length. CONCLUSIONS Although the Port wine and red wine have similar amounts of flavanols with identical ability to protect against oxidative stress, the differences observed are probably related to the very dissimilar processes of wine production, leading in Port wine to a high content of sugars, which are known to have potent pro-oxidant effects.