EGCG ameliorates the suppression of long-term potentiation induced by ischemia at the Schaffer collateral-CA1 synapse in the rat

Effect of epigallocatechin-3-gallate (EGCG) on cognitive functioning and the expression of APP and BDNF in the hippocampus of rats with streptozotocin -induced Alzheimer-like disease

We aimed to investigate the potential therapeutic effects of the active substance of green tea, epigallocatechin-3-gallate (EGCG), on behavioral phenotypes and markers of neurogenesis in an Alzheimer disease (AD) rat model. The groups included sham, AD, and three AD groups receiving orally EGCG with different doses of 25, 50, and 100 mg/kg. The AD model was induced by intracerebroventricular (icv) injection of streptozocin (STZ) at a dose of 3 mg/kg. Spatial learning and memory were evaluated in the Morris water maze (MWM) test. Real-time PCR assay was used for evaluating the expression of beta-amyloid precursor protein (APP) and brain-derived neurotrophic factor (BDNF) in the hippocampus of animals. STZ disrupted the function of animals in MWM acquisition phase by almost 65 % and all doses of EGCG could return the learning parameters to those of control animals. STZ also impaired the memory function (P < 0.05) and a dose of 25 mg/kg EGCG could significantly return it to the control level (29 % vs 53 %, P < 0.01). Hippocampal APP gene expression was increased in the AD group and EGCG with dose 25 mg/kg decreased it significantly (P < 0.05). AD animals had decreased levels of hippocampal BDNF and treating with dose 25 mg/kg of EGCG could significantly increase it (P < 0.05). EGCG with dose 25 mg/kg can improve spatial memory deficits in AD model rats. It may be due to the impact on the expression of hippocampal factors involved in AD pathology. These findings could provide a beneficial insight for developing novel, safe, and efficient natural compounds for preventing or alleviation AD symptoms in humans.

Therapeutic potentialities of green tea (Camellia sinensis) in ischemic stroke: biochemical and molecular evidence

Ischemic stroke is a leading cause of disability and death in patients. Despite considerable recent advances in the treatment of ischemic stroke, only a limited number of effective neuroprotective agents are available for stroke. Green tea (Camellia sinensis) is a popular herbal plant, and numerous studies have indicated its health benefits for several diseases. Green tea is of interest due to its high content of catechin derivatives, including epicatechin, gallocatechin, epicatechin gallate, epigallocatechin, and epigallocatechin-3-gallate. This review tried to develop a feasible background for the potential effects of green tea and its bioactive derivatives concerning protection against ischemic stroke. Green tea's antioxidants, anti-inflammatory, anti-apoptotic, and neuroprotective effects are believed to be efficacious in stroke treatment. Evidence supports the idea that green tea can be used to assist in treating ischemic stroke.

Epigallocatechin-3-gallate Enhances Cognitive and Memory Performance and Protects Against Brain Injury in Methionine-induced Hyperhomocysteinemia Through Interdependent Molecular Pathways

Brain injury and cognitive impairment are major health issues associated with neurodegenerative diseases in young and aged persons worldwide. Epigallocatechin-3-gallate (EGCG) was studied for its ability to protect against methionine (Met)-induced brain damage and cognitive dysfunction. Male mice were given Met-supplemented in drinking water to produce hyperhomocysteinemia (HHcy)-induced animals. EGCG was administered daily concurrently with Met by gavage. EGCG attenuated the rise in homocysteine levels in the plasma and the formation of amyloid-β and tau protein in the brain. Cognitive and memory impairment in HHcy-induced mice were significantly improved by EGCG administration. These results were associated with improvement in glutamate and gamma-aminobutyric acid levels in the brain. EGCG maintained the levels of glutathione and the activity of antioxidant enzymes in the brain. As a result of the reduction of oxidative stress, EGCG protected against DNA damage in Met-treated mice. Moreover, maintaining the redox balance significantly ameliorated neuroinflammation evidenced by the normalization of IL-1β, IL-6, tumor necrosis factor α, C-reactive protein, and IL-13 in the same animals. The decreases in both oxidative stress and inflammatory cytokines were significantly associated with upregulation of the antiapoptotic Bcl-2 protein and downregulation of the proapoptotic protein Bax, caspases 3 and 9, and p53 compared with Met-treated animals, indicating a diminution of neuronal apoptosis. These effects reflect and explain the improvement in histopathological alterations in the hippocampus of Met-treated mice. In conclusion, the beneficial effects of EGCG may be due to interconnecting pathways, including modulation of redox balance, amelioration of inflammation, and regulation of antiapoptotic proteins.

Neuroprotective Phytochemicals in Experimental Ischemic Stroke: Mechanisms and Potential Clinical Applications

Ischemic stroke is a challenging disease with high mortality and disability rates, causing a great economic and social burden worldwide. During ischemic stroke, ionic imbalance and excitotoxicity, oxidative stress, and inflammation are developed in a relatively certain order, which then activate the cell death pathways directly or indirectly via the promotion of organelle dysfunction. Neuroprotection, a therapy that is aimed at inhibiting this damaging cascade, is therefore an important therapeutic strategy for ischemic stroke. Notably, phytochemicals showed great neuroprotective potential in preclinical research via various strategies including modulation of calcium levels and antiexcitotoxicity, antioxidation, anti-inflammation and BBB protection, mitochondrial protection and antiapoptosis, autophagy/mitophagy regulation, and regulation of neurotrophin release. In this review, we summarize the research works that report the neuroprotective activity of phytochemicals in the past 10 years and discuss the neuroprotective mechanisms and potential clinical applications of 148 phytochemicals that belong to the categories of flavonoids, stilbenoids, other phenols, terpenoids, and alkaloids. Among them, scutellarin, pinocembrin, puerarin, hydroxysafflor yellow A, salvianolic acids, rosmarinic acid, borneol, bilobalide, ginkgolides, ginsenoside Rd, and vinpocetine show great potential in clinical ischemic stroke treatment. This review will serve as a powerful reference for the screening of phytochemicals with potential clinical applications in ischemic stroke or the synthesis of new neuroprotective agents that take phytochemicals as leading compounds.

The effect of epigallocatechin-3-gallate on morphine-induced memory impairments in rat: EGCG effects on morphine neurotoxicity

AIM OF STUDY

This investigation evaluated the capacity of epigallocatechin-3-gallate (EGCG) as the main polyphenolic compound in the green tea extract against memory impairment and neurotoxicity in morphine-treated rats.

METHODS

To measure the EGCG effect (5 and 50 mg/kg, i.p., co-treated with morphine) on spatial learning and memory of morphine-administrated male Wistar rats (45 mg/kg, s.c., 4 weeks), the Morris water maze test was used. Some apoptotic protein levels (Bax, Bcl-2, and cleaved caspase 3) were evaluated in the hippocampus tissue by the Western blot test. Also, oxidative stress status (malondialdehyde level, glutathione peroxidase, and superoxide dismutase activity) was measured in hippocampus tissue.

RESULTS

The data presented that EGCG treatment (50 mg/kg) inhibited the morphine-induced memory deficits in rats. Also, EGCG administration reduced the apoptosis and oxidative stress in the hippocampus of morphine-treated rats.

CONCLUSIONS

Our data indicate that EGCG can improve memory in morphine-treated rats. Molecular mechanisms underlying the detected effects could be related to the prevention of apoptosis and oxidative stress in the hippocampus of morphine-treated rats.

Joint Toxicity of a Multi-Heavy Metal Mixture and Chemoprevention in Sprague Dawley Rats

To explore the joint toxicity and bio-accumulation of multi-heavy metals and potential chemoprevention strategies, Male Sprague Dawley (SD) rats (n = 30) were treated orally once a week for six months with 500mg/kg•bw of eight heavy metals which were commonly identified in aquatic products in the Ningbo area including chromium, manganese, nickel, copper, zinc, cadmium, mercury, and lead. At the same time, 200mg/kg•bw of epigallocatechin-3-gallate (EGCG), trisodium citrate dihydrate (TCD) or glutathione (GSH) were administered to evaluate their antagonistic effects against adverse effects of multi-heavy metal mixture. The Morris water maze test was used to evaluate spatial learning and memory in the treated rats. Then the rats were anesthetized by pentobarbital sodium (40 mg/kg•bw) to obtain blood samples for biochemical analysis and organs (heart, liver, spleen, lungs, kidneys, brain, testis) to be conducted for biopsy and organ coefficients. Inductively coupled plasma mass spectrometer (ICP-MS) was used to analyze the concentrations of heavy metals. Results indicated that six months of exposure to a multi-heavy metal mixture under this experimental dosage resulted in accumulation in organs and adverse effects on the blood, reproductive system, and liver function. EGCG, TCD or GSH all showed certain chemoprevention effects against the joint toxicity induced by the multi-heavy metal mixture and indicated alleviation and the potential mechanism that also included the promotion of excretion of metals to which animals were exposed.

Pure mechanistic analysis of additive neuroprotective effects between baicalin and jasminoidin in ischemic stroke mice

Both baicalin (BA) and jasminoidin (JA) are active ingredients in Chinese herb medicine Scutellaria baicalensis and Fructus gardeniae, respectively. They have been shown to exert additive neuroprotective action in ischemic stroke models. In this study we used transcriptome analysis to explore the pure therapeutic mechanisms of BA, JA and their combination (BJ) contributing to phenotype variation and reversal of pathological processes. Mice with middle cerebral artery obstruction were treated with BA, JA, their combination (BJ), or concha margaritifera (CM). Cerebral infarct volume was examined to determine the effect of these compounds on phenotype. Using the hippocampus microarray and ingenuity pathway analysis (IPA) software, we exacted the differentially expressed genes, networks, pathways, and functions in positive-phenotype groups (BA, JA and BJ) by comparing with the negative-phenotype group (CM). In the BA, JA, and BJ groups, a total of 7, 4, and 11 specific target molecules, 1, 1, and 4 networks, 51, 59, and 18 canonical pathways and 70, 53, and 64 biological functions, respectively, were identified. Pure therapeutic mechanisms of BA and JA were mainly overlapped in specific target molecules, functions and pathways, which were related to the nervous system, inflammation and immune response. The specific mechanisms of BA and JA were associated with apoptosis and cancer-related signaling and endocrine and hormone regulation, respectively. In the BJ group, novel target profiles distinct from mono-therapies were revealed, including 11 specific target molecules, 10 functions, and 10 pathways, the majority of which were related to a virus-mediated immune response. The pure additive effects between BA and JA were based on enhanced action in virus-mediated immune response. This pure mechanistic analysis may provide a clearer outline of the target profiles of multi-target compounds and combination therapies.

Lifestyle Modulators of Neuroplasticity: How Physical Activity, Mental Engagement, and Diet Promote Cognitive Health during Aging

The number of the elderly across the globe will approximate 2.1 billion by 2050. Juxtaposed against this burgeoning segment of the population is evidence that nonpathological aging is associated with an increased risk for cognitive decline in a variety of domains, changes that can cause mild disability even before the onset of dementia. Given that pharmacological treatments that mitigate dementia are still outstanding, alternative therapeutic options are being investigated increasingly. The results from translational studies have shown that modifiable lifestyle factors-including physical activity, cognitive engagement, and diet-are a key strategy for maintaining brain health during aging. Indeed, a multiplicity of studies has demonstrated relationships between lifestyle factors, brain structure and function, and cognitive function in aging adults. For example, physical activity and diet modulate common neuroplasticity substrates (neurotrophic signaling, neurogenesis, inflammation, stress response, and antioxidant defense) in the brain whereas cognitive engagement enhances brain and cognitive reserve. The aims of this review are to evaluate the relationship between modifiable lifestyle factors, neuroplasticity, and optimal brain health during aging; to identify putative mechanisms that contribute positive brain aging; and to highlight future directions for scientists and clinicians. Undoubtedly, the translation of cutting-edge knowledge derived from the field of cognitive neuroscience will advance our understanding and enhance clinical treatment interventions as we endeavor to promote brain health during aging.

Modulation of Synaptic Plasticity by Exercise Training as a Basis for Ischemic Stroke Rehabilitation

In recent years, rehabilitation of ischemic stroke draws more and more attention in the world, and has been linked to changes of synaptic plasticity. Exercise training improves motor function of ischemia as well as cognition which is associated with formation of learning and memory. The molecular basis of learning and memory might be synaptic plasticity. Research has therefore been conducted in an attempt to relate effects of exercise training to neuroprotection and neurogenesis adjacent to the ischemic injury brain. The present paper reviews the current literature addressing this question and discusses the possible mechanisms involved in modulation of synaptic plasticity by exercise training. This review shows the pathological process of synaptic dysfunction in ischemic roughly and then discusses the effects of exercise training on scaffold proteins and regulatory protein expression. The expression of scaffold proteins generally increased after training, but the effects on regulatory proteins were mixed. Moreover, the compositions of postsynaptic receptors were changed and the strength of synaptic transmission was enhanced after training. Finally, the recovery of cognition is critically associated with synaptic remodeling in an injured brain, and the remodeling occurs through a number of local regulations including mRNA translation, remodeling of cytoskeleton, and receptor trafficking into and out of the synapse. We do provide a comprehensive knowledge of synaptic plasticity enhancement obtained by exercise training in this review.

Advances in Herbal Medicine for Treatment of Ischemic Brain Injury

Ischemic brain injury is one of the leading causes of death worldwide and has attracted a lot of attention in the field of drug discovery. Cerebral ischemia is a complex pathological process involving a series of mechanisms, including generation of free radicals, oxidative stress, disruption of the membrane function, release of neurotransmitters and apoptosis. Thrombolytic therapy is the most effective therapeutic strategy, but the benefits are far from being absolute. Increased attention in the field of drug discovery has been focused on using natural compounds from traditional medicinal herbs for neuroprotection, which appears to be a promising therapeutic option for cerebral ischemia with minimal systemic adverse effects that could limit their long term use. The scenario calls for extensive investigations which can result in the development of lead molecules for neuroprotection in the future. In this context, the present review focuses on possible mechanisms underlying the beneficial effects of herbal drugs in patients with cerebral ischemic injury. Natural compounds have been demonstrated to have neurofunctional regulatory actions with antioxidative, anti-inflammatory, calcium antagonizing and anti-apoptotic activities. Among the several leads obtained from plant sources as potential neuroprotective agents, resveratrol, EGb761, curcumin and epigallocatechin-3-gallate have shown significant therapeutic benefits in cerebral ischemic conditions. However, ligustilide, tanshinone, scutellarin and shikonin are the few lead molecules which are under investigation for treatment of cerebral ischemia.

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.

Epigallocatechin-3-gallate: a useful, effective and safe clinical approach for targeted prevention and individualised treatment of neurological diseases?

Neurodegenerative disorders show an increasing prevalence in a number of highly developed countries. Often, these diseases require life-long treatment mostly with drugs which are costly and mostly accompanied by more or less serious side-effects. Their heterogeneous manifestation, severity and outcome pose the need for individualised treatment options. There is an intensive search for new strategies not only for treating but also for preventing these diseases. Green tea and green tea extracts seem to be such a promising and safe alternative. However, data regarding the beneficial effects and possible underlying mechanism, specifically in clinical trials, are rare and rather controversial or non-conclusive. This review outlines the existing evidence from preclinical studies (cell and tissue cultures and animal models) and clinical trials regarding preventive and therapeutic effects of epigallcatechin-3-gallate in neurodegenerative diseases and considers antioxidative vs. pro-oxidative properties of the tea catechin important for dosage recommendations.