(-)-Epigallocatechin-3-gallate protects against neuronal cell death and improves cerebral function after traumatic brain injury in rats

Protective Effects of Plant-Derived Compounds Against Traumatic Brain Injury

Inflammation in the nervous system is one of the key features of many neurodegenerative diseases. It is increasingly being identified as a critical pathophysiological primitive mechanism associated with chronic neurodegenerative diseases following traumatic brain injury (TBI). Phytochemicals have a wide range of clinical properties due to their antioxidant and anti-inflammatory effects. Currently, there are few drugs available for the treatment of neurodegenerative diseases other than symptomatic relief. Numerous studies have shown that plant-derived compounds, in particular polyphenols, protect against various neurodegenerative diseases and are safe for consumption. Polyphenols exert protective effects on TBI via restoration of nuclear factor kappa B (NF-κB), toll-like receptor-4 (TLR4), and Nod-like receptor family proteins (NLRPs) pathways. In addition, these phytochemicals and their derivatives upregulate the phosphatidylinositol-3-Kinase/Protein Kinase B (PI3K/AKT) and nuclear factor erythroid 2-related factor 2 (Nrf2) pathways, which have critical functions in modulating TBI symptoms. There is supporting evidence that medicinal plants and phytochemicals are protective in different TBI models, though future clinical trials are needed to clarify the precise mechanisms and functions of different polyphenolic compounds in TBI.

Promising Roles of Phytocompounds and Nutrients in Interventions to Mitigate Chemotherapy-Induced Peripheral Neuropathy

OBJECTIVES

Provide an overview of scientific reports and literature related to the role(s) of phytocompounds and nutrients in neuroprotection. Discuss how these properties may inform nutrition- and dietary interventions to mitigate chemotherapy-induced peripheral neuropathy (CIPN), for which there are no effective treatments.

METHODS

A literature search (2010-2023) was conducted in PubMed and Google Scholar where search terms-diet, nutrition, neuroprotection, neurodegenerative diseases, and social determinants of health-were used to narrow articles. From this search, manuscripts were reviewed to provide an overview of the neuroprotective properties of various phytocompounds and nutrients and their observed effects in neurodegenerative conditions and CIPN. Social determinant of health factors (SDOH) related to economic stability and access to nutritious foods were also reviewed as potential barriers to dietary interventions.

RESULTS

Twenty-eight publications were included in this literature review. Phytocompounds found in green tea (EGCG), turmeric (curcumin), cruciferous vegetables (sulforaphane), as well as certain vitamins, are promising, targeted interventions to mitigate CIPN. SDOH factors such as economic instability and limited access to nutritious foods may act as barriers to dietary interventions and limit their generalizability.

CONCLUSION

Dietary interventions focused on the use of phytocompounds and vitamins with known antioxidant, anti-inflammatory, and neuroprotective properties, hold promise and may provide patients with natural, non-pharmacological therapeutics for the management and/or prevention of CIPN. However, rigorous clinical trial research is needed to explore these effects in humans.

IMPLICATIONS FOR NURSING PRACTICE

Nurses support cancer survivors at the point-of-care, particularly during and after neurotoxic chemotherapy treatments. If future research supports dietary interventions to mitigate CIPN, nurses will ultimately be positioned to help translate this knowledge into clinical practice through educating patients on how to infuse nutrient-rich foods into their diets. Further, nurses will need to be conscious of SDOH factors that may impede access to these foods.

Alzheimer's Disease and Green Tea: Epigallocatechin-3-Gallate as a Modulator of Inflammation and Oxidative Stress

Alzheimer's disease (AD) is the most common cause of dementia, characterised by a marked decline of both memory and cognition, along with pathophysiological hallmarks including amyloid beta peptide (Aβ) accumulation, tau protein hyperphosphorylation, neuronal loss and inflammation in the brain. Additionally, oxidative stress caused by an imbalance between free radicals and antioxidants is considered one of the main risk factors for AD, since it can result in protein, lipid and nucleic acid damage and exacerbate Aβ and tau pathology. To date, there is a lack of successful pharmacological approaches to cure or even ameliorate the terrible impact of this disease. Due to this, dietary compounds with antioxidative and anti-inflammatory properties acquire special relevance as potential therapeutic agents. In this context, green tea, and its main bioactive compound, epigallocatechin-3-gallate (EGCG), have been targeted as a plausible option for the modulation of AD. Specifically, EGCG acts as an antioxidant by regulating inflammatory processes involved in neurodegeneration such as ferroptosis and microglia-induced cytotoxicity and by inducing signalling pathways related to neuronal survival. Furthermore, it reduces tau hyperphosphorylation and aggregation and promotes the non-amyloidogenic route of APP processing, thus preventing the formation of Aβ and its subsequent accumulation. Taken together, these results suggest that EGCG may be a suitable candidate in the search for potential therapeutic compounds for neurodegenerative disorders involving inflammation and oxidative stress, including Alzheimer's disease.

Dietary (Poly)phenols in Traumatic Brain Injury

Traumatic brain injury (TBI) remains one of the leading causes of death and disability in young adults worldwide. Despite growing evidence and advances in our knowledge regarding the multifaceted pathophysiology of TBI, the underlying mechanisms, though, are still to be fully elucidated. Whereas initial brain insult involves acute and irreversible primary damage to the brain, the processes of subsequent secondary brain injury progress gradually over months to years, providing a window of opportunity for therapeutic interventions. To date, extensive research has been focused on the identification of druggable targets involved in these processes. Despite several decades of successful pre-clinical studies and very promising results, when transferred to clinics, these drugs showed, at best, modest beneficial effects, but more often, an absence of effects or even very harsh side effects in TBI patients. This reality has highlighted the need for novel approaches that will be able to respond to the complexity of the TBI and tackle TBI pathological processes on multiple levels. Recent evidence strongly indicates that nutritional interventions may provide a unique opportunity to enhance the repair processes after TBI. Dietary (poly)phenols, a big class of compounds abundantly found in fruits and vegetables, have emerged in the past few years as promising agents to be used in TBI settings due to their proven pleiotropic effects. Here, we give an overview of the pathophysiology of TBI and the underlying molecular mechanisms, followed by a state-of-the-art summary of the studies that have evaluated the efficacy of (poly)phenols administration to decrease TBI-associated damage in various animal TBI models and in a limited number of clinical trials. The current limitations on our knowledge concerning (poly)phenol effects in TBI in the pre-clinical studies are also discussed.

The second phase of brain trauma can be controlled by nutraceuticals that suppress DAMP-mediated microglial activation

INTRODUCTION

A delayed second wave of brain trauma is mediated in large part by microglia that are activated to a pro-inflammatory M1 phenotype by DAMP proteins released by dying neurons. These microglia can promote apoptosis or necrosis in neighboring neurons by producing a range of pro-inflammatory cytokines and the deadly oxidant peroxynitrite. This second wave could therefore be mitigated with agents that blunt the post-traumatic M1 activation of microglia and that preferentially promote a pro-healing M2 phenotype.

AREAS COVERED

The literature on nutraceuticals that might have clinical potential in this regard.

EXPERT OPINION

The chief signaling pathway whereby DAMPs promote M1 microglial activation involves activation of toll-like receptor 4 (TLR4), NADPH oxidase, NF-kappaB, and the stress activated kinases JNK and p38. The green tea catechin EGCG can suppress TLR4 expression. Phycocyanobilin can inhibit NOX2-dependent NADPH oxidase, ferulate and melatonin can oppose pro-inflammatory signal modulation by NADPH oxidase-derived oxidants. Long-chain omega-3 fatty acids, the soy isoflavone genistein, the AMPK activator berberine, glucosamine, and ketone bodies can down-regulate NF-kappaB activation. Vitamin D activity can oppose JNK/p38 activation. A sophisticated program of nutraceutical supplementation may have important potential for mitigating the second phase of neuronal death and aiding subsequent healing.

Nutraceutical induction and mimicry of heme oxygenase activity as a strategy for controlling excitotoxicity in brain trauma and ischemic stroke: focus on oxidative stress

Introduction: Ischemic stroke and traumatic brain injury are leading causes of acute mortality, and in the longer run, major causes of significant mental and physical impairment. Most of the brain neuronal cell death in the minutes and hours following an ischemic stroke or brain trauma is mediated by the process of excitotoxicity, in which sustained elevations of extracellular glutamate, reflecting a failure of ATP-dependent mechanism which sequester glutamate in neurons and astrocytes, drive excessive activation of NMDA receptors. Areas covered: A literature search was undertaken to clarify the molecular mechanisms whereby excessive NMDA activation leads to excitotoxic neuronal death, and to determine what safe nutraceutical agents might have practical potential for rescuing at-risk neurons by intervening in these mechanisms. Expert opinion: Activation of both NADPH oxidase and neuronal nitric oxide synthase in the microenvironment of activated NMDA receptors drives production of superoxide and highly toxic peroxynitrite. This leads to excessive activation of PARP and p38 MAP kinase, mitochondrial dysfunction, and subsequent neuronal death. Heme oxygenase-1 (HO-1) induction offers protection via inhibition of NADPH oxidase and promotion of cGMP generation. Phase 2-inductive nutraceuticals can induce HO-1, and other nutraceuticals can mimic the effects of its products biliverdin and carbon monoxide.

Pathological Findings in Male Patients With Anti-N-methyl-d-Aspartate Receptor Encephalitis

Anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis is the most common type of autoimmune encephalitis. The disease predominantly affects women (1:5-1:10), with only 3 reports of autopsy findings in women being published to date. The present study reports findings from the first autopsy performed on a man with anti-NMDAR encephalitis. The patient had some scattered lesions in the limbic system with neuronal loss, gliosis, and microglial activation. The temporal and frontal cortices showed additional patchy demyelination. T-lymphocyte infiltration was detectable in the fusiform gyrus lesion. These findings were partly similar to those reported in female patients. Although clinical differences based on the sex of the patient are reported for this disease, the observed pathological similarities potentially help to establish common therapeutic strategies for all patients. Severe testicular damage was additionally observed in the male patient in this study. Biopsy-proven severe testicular damage was also confirmed in another, previously fertile man who became azoospermic. Moreover, serum follicle-stimulating hormone levels, which often increased in response to disturbed spermatogenesis, were elevated, and testosterone/luteinizing hormone ratio reflecting Leydig cell function was low in all 5 male patients in this study. Overall, these findings suggest similar brain pathology in patients of both sexes and severe testicular damage in male patients.

Effects and Mechanisms of Tea for the Prevention and Management of Diabetes Mellitus and Diabetic Complications: An Updated Review

Diabetes mellitus has become a serious and growing public health concern. It has high morbidity and mortality because of its complications, such as diabetic nephropathy, diabetic cardiovascular complication, diabetic neuropathy, diabetic retinopathy, and diabetic hepatopathy. Epidemiological studies revealed that the consumption of tea was inversely associated with the risk of diabetes mellitus and its complications. Experimental studies demonstrated that tea had protective effects against diabetes mellitus and its complications via several possible mechanisms, including enhancing insulin action, ameliorating insulin resistance, activating insulin signaling pathway, protecting islet β-cells, scavenging free radicals, and decreasing inflammation. Moreover, clinical trials also confirmed that tea intervention is effective in patients with diabetes mellitus and its complications. Therefore, in order to highlight the importance of tea in the prevention and management of diabetes mellitus and its complications, this article summarizes and discusses the effects of tea against diabetes mellitus and its complications based on the findings from epidemiological, experimental, and clinical studies, with the special attention paid to the mechanisms of action.

Role of green tea catechins in prevention of age-related cognitive decline: Pharmacological targets and clinical perspective

Over the past decade, a wide range of scientific investigations have been performed to reveal neuropathological aspects of cognitive disorders; however, only limited therapeutic approaches currently exist. The failures of conventional therapeutic options as well as the predicted dramatic rise in the prevalence of cognitive decline in the coming future show the necessity for novel therapeutic agents. Recently, a wide range of research has focused on pharmacological activities of green tea catechins worldwide. Current investigations have clarified mechanistic effects of the catechins in inflammatory cascades, oxidative damages, different cellular transcription as well as transduction pathway in various body systems. It has been demonstrated that green tea polyphenols prevent age-related neurodegeneration through improvement of endogenous antioxidant defense mechanisms, modulation of neural growth factors, attenuation of neuroinflammatory pathway, and regulation of apoptosis. The catechins exhibited beneficial effects in cellular and animal models of neurodegenerative diseases including Alzheimer's disease, MS, and Parkinson's disease. The present review discusses the current pharmacological targets, which can be involved in the treatment of cognitive decline and addresses the action of catechin derivatives elicited from green tea on the multiple neural targets.

Possible role of antioxidative capacity of (-)-epigallocatechin-3-gallate treatment in morphological and neurobehavioral recovery after sciatic nerve crush injury

OBJECTIVE This study examined the capacity of the major polyphenolic green tea extract (-)-epigallocatechin-3-gallate (EGCG) to suppress oxidative stress and stimulate the recovery and prompt the regeneration of sciatic nerve after crush injury. METHODS Adult male Wistar rats were randomly assigned to one of 4 groups: 1) Naïve, 2) Sham (sham injury, surgical control group), 3) Crush (sciatic nerve crush injury treated with saline), and 4) Crush+EGCG (sciatic nerve crush injury treated with intraperitoneally administered EGCG, 50 mg/kg). All animals were tested for motor and sensory neurobehavioral parameters throughout the study. Sciatic nerve and spinal cord tissues were harvested and processed for morphometric and stereological analysis. For the biochemical assays, the time points were Day 1, Day 7, Day 14, and Day 28 after nerve injury. RESULTS After sciatic nerve crush injury, the EGCG-treated animals (Crush+EGCG group) showed significantly better recovery of foot position and toe spread and 50% greater improvement in motor recovery than the saline-treated animals (Crush group). The Crush+EGCG group displayed an early hopping response at the beginning of the 3rd week postinjury. Animals in the Crush+EGCG group also showed a significant reduction in mechanical allodynia and hyperalgesia latencies and significant improvement in recovery from nociception deficits in both heat withdrawal and tail flick withdrawal latencies compared with the Crush group. In both the Crush+EGCG and Crush groups, quantitative evaluation revealed significant morphological evidence of neuroregeneration according to the following parameters: mean cross-sectional area of axons, myelin thickness in the sciatic nerve (from Week 4 to Week 8), increase of myelin basic protein concentration and gene expression in both the injured sciatic nerve and spinal cord, and fiber diameter to axon diameter ratio and myelin thickness to axon diameter ratio at Week 2 after sciatic nerve injury. However, the axon area remained much smaller in both the Crush+EGCG and Crush groups compared with the Sham and Naïve groups. The number of axons per unit area was significantly decreased in the Crush+EGCG and Crush groups compared with controls. Sciatic nerve injury produced generalized oxidative stress manifested as a significant increase of isoprostanes in the urine and decrease of the total antioxidant capacity (TAC) of the blood from Day 7 until Day 14. EGCG-treated rats showed significantly less increase of isoprostanes than saline-treated animals and also showed full recovery of TAC levels by Day 14 after nerve injury. In spinal cord tissue analysis, EGCG-treated animals showed induced glutathione reductase and suppressed induction of heme oxygenase 1 gene expression compared with nontreated animals. CONCLUSIONS EGCG treatment suppressed the crush-induced production of isoprostanes and stimulated the recovery of the TAC and was associated with remarkable alleviation of motor and sensory impairment and significant histomorphological evidence of neuronal regeneration following sciatic nerve crush injury in rats. The findings of this study suggest that EGCG can be used as an adjunctive therapeutic remedy for nerve injury. However, further investigations are needed to establish the antioxidative mechanism involved in the regenerative process after nerve injury. Only upregulation of glutathione reductase supports the idea that EGCG is acting indirectly via induction of enzymes or transcription factors.

Natural Compounds as a Therapeutic Intervention following Traumatic Brain Injury: The Role of Phytochemicals

There has been a tremendous focus on the discovery and development of neuroprotective agents that might have clinical relevance following traumatic brain injury (TBI). This type of brain injury is very complex and is divided into two major components. The first component, a primary injury, occurs at the time of impact and is the result of the mechanical insult itself. This primary injury is thought to be irreversible and resistant to most treatments. A second component or secondary brain injury, is defined as cellular damage that is not immediately obvious after trauma, but that develops after a delay of minutes, hours, or even days. This injury appears to be amenable to treatment. Because of the complexity of the secondary injury, any type of therapeutic intervention needs to be multi-faceted and have the ability to simultaneously modulate different cellular changes. Because of diverse pharmaceutical interactions, combinations of different drugs do not work well in concert and result in adverse physiological conditions. Research has begun to investigate the possibility of using natural compounds as a therapeutic intervention following TBI. These compounds normally have very low toxicity and have reduced interactions with other pharmaceuticals. In addition, many natural compounds have the potential to target numerous different components of the secondary injury. Here, we review 33 different plant-derived natural compounds, phytochemicals, which have been investigated in experimental animal models of TBI. Some of these phytochemicals appear to have potential as possible therapeutic interventions to offset key components of the secondary injury cascade. However, not all studies have used the same scientific rigor, and one should be cautious in the interpretation of studies using naturally occurring phytochemical in TBI research.

Therapies targeting lipid peroxidation in traumatic brain injury

Lipid peroxidation can be broadly defined as the process of inserting a hydroperoxy group into a lipid. Polyunsaturated fatty acids present in the phospholipids are often the targets for peroxidation. Phospholipids are indispensable for normal structure of membranes. The other important function of phospholipids stems from their role as a source of lipid mediators - oxygenated free fatty acids that are derived from lipid peroxidation. In the CNS, excessive accumulation of either oxidized phospholipids or oxygenated free fatty acids may be associated with damage occurring during acute brain injury and subsequent inflammatory responses. There is a growing body of evidence that lipid peroxidation occurs after severe traumatic brain injury in humans and correlates with the injury severity and mortality. Identification of the products and sources of lipid peroxidation and its enzymatic or non-enzymatic nature is essential for the design of mechanism-based therapies. Recent progress in mass spectrometry-based lipidomics/oxidative lipidomics offers remarkable opportunities for quantitative characterization of lipid peroxidation products, providing guidance for targeted development of specific therapeutic modalities. In this review, we critically evaluate previous attempts to use non-specific antioxidants as neuroprotectors and emphasize new approaches based on recent breakthroughs in understanding of enzymatic mechanisms of lipid peroxidation associated with specific death pathways, particularly apoptosis. We also emphasize the role of different phospholipases (calcium-dependent and -independent) in hydrolysis of peroxidized phospholipids and generation of pro- and anti-inflammatory lipid mediators. This article is part of a Special Issue entitled SI:Brain injury and recovery.

Effects of epigallocatechin-3-gallate on proliferation and differentiation of mouse cochlear neural stem cells: Involvement of PI3K/Akt signaling pathway

Since the majority of hearing impaired patients suffer from the significant loss of sensory hair cells and associated neurons, stem cell-based approaches hold great promise by replacing the damaged tissues in the ears. For instance, stem cells from the spiral ganglion could be isolated and expanded to regenerate neural structures of the inner ear. It is thus necessary to explore the potential procedures that may promote the proliferation and differentiation of such cochlear neural stem cells. In the present study, we study the effects of epigallocatechin-3-gallate (EGCG), a known antioxidant, for potential therapeutic use in NSC regeneration. At a non-toxic concentration, EGCG stimulated both proliferation and neurosphere formation in isolated mouse cochlear neural stem cell (NSC) in vitro. Specifically, the neural differentiation of NSC was promoted by EGCG treatment. The up-regulated neural function by EGCG was also supported by the increased calcium spike frequencies and enhanced neurite complexity in NSC-differentiated neurons. Finally, the induced neuron differentiation and Akt activation of cochlear NSC by EGCG were blocked by PI3 kinase inhibition. These data suggested that EGCG acts through phosphoinositide 3-kinase (PI3K)/Akt signaling in cochlea NSC to promote cell growth and neuron differentiation, which may be exploited for the treatment of hearing loss.

Is there a role for neurotrophic factors and their receptors in augmenting the neuroprotective effect of (-)-epigallocatechin-3-gallate treatment of sciatic nerve crush injury?

This study analyzed and compared the effects of EGCG treatment on the expression of NTFs and NTF receptors expression in the sciatic nerve and the L3-L6 spinal cord segments at the early phase of regeneration following sciatic nerve crush injury. Analysis of BDNF, GDNF and NT3 neurotropic factors and Trk-B, Trk-C and NGFR-p75 receptors in neurons in the spinal cord of CRUSH and CRUSH + EGGC rats showed significant (p < 0.0001) decrease compared to NAÏVE and SHAM at day 1, 3, 7 and 14 after nerve injury. EGCG treatment significantly (p < 0.0001) increased the BDNF, GDN, NT3, Trk-B, Trk-C and NGFR-p75 immunostaining in the L3-L6 spinal cord compared to CRUSH animals. Also, EGCG treatment significantly increased the Trk-B protein concentration and Trk-B, NT3 and Trk-C gene expression in the spinal cords compared to CRUSH group. However, at day 1 and 3 post nerve injury, EGCG treatment significantly decreased the NGFR-p75 expression compared to CRUSH rats. In the sciatic nerve, EGCG treatment significantly (p < 0.01) increased the Trk-B and NGFR-p75 protein concentration in the controls. EGCG treatment significantly (p < 0.0001) increased the Trk-B, Trk-C and NGFR-p75 mRNA gene expressions in the sciatic nerves compared to CRUSH group. Only at day 1, CRUSH + EGCG animals displayed significant rise in the sciatic nerves NT3 gene expression compared to CRUSH group. Our data suggest that the EGCG neuroprotective effect on the spinal cord neurons may be mediated through the modulation of NTFs and NTF receptors following nerve crush injury in a rat model.

Can Tea Consumption be a Safe and Effective Therapy Against Diabetes Mellitus-Induced Neurodegeneration?

Diabetes mellitus (DM) is a metabolic disease that is rapidly increasing and has become a major public health problem. Type 2 DM (T2DM) is the most common type, accounting for up to 90-95% of the new diagnosed DM cases. The brain is very susceptible to glucose fluctuations and hyperglycemia-induced oxidative stress (OS). It is well known that DM and the risk of developing neurodegenerative diseases are associated. Tea, Camellia sinensis L., is one of the most consumed beverages. It contains several phytochemicals, such as polyphenols, methylxanthines (mainly caffeine) and L-theanine that are often reported to be responsible for tea's health benefits, including in brain. Tea phytochemicals have been reported to be responsible for tea's significant antidiabetic and neuroprotective properties and antioxidant potential. Epidemiological studies have shown that regular consumption of tea has positive effects on DM-caused complications and protects the brain against oxidative damage, contributing to an improvement of the cognitive function. Among the several reported benefits of tea consumption, those related with neurodegenerative diseases are of great interest. Herein, we discuss the potential beneficial effects of tea consumption and tea phytochemicals on DM and how their action can counteract the severe brain damage induced by this disease.

(-)-Epigallocatechin-3-gallate modulates spinal cord neuronal degeneration by enhancing growth-associated protein 43, B-cell lymphoma 2, and decreasing B-cell lymphoma 2-associated x protein expression after sciatic nerve crush injury

Our previous studies have established that (-)-epigallocatechin-3-gallate (EGCG) has both neuroprotective and -regenerative capacity after sciatic nerve injury. Moreover, this improvement was evident on the behavioral level. The aim of this study was to investigate the central effects of ECGC on spinal cord motor neurons after sciatic nerve injury. Our study showed that administering 50 mg/kg intraperitoneally i.p. of EGCG to sciatic nerve-injured rats improved their performance on different motor functions and mechanical hyperesthesia neurobehavioral tests. Histological analysis of spinal cords of EGCG-treated sciatic nerve-injured (CRUSH+ECGC) animals showed an increase in the number of neurons in the anterior horn, when compared to the naïve, sham, and saline-treated sciatic nerve-injured (CRUSH) control groups. Additionally, immunohistochemical study of spinal cord sections revealed that EGCG reduced the expression of glial fibrillary acidic protein and increased the expression of growth-associated protein 43, a marker of regenerating axons. Finally, EGCG reduced the ratio of B-cell lymphoma 2 (Bcl-2)-associated X protein/Bcl-2 and increased the expression of survivin gene. This study may shed some light on the future clinical use of EGCG and its constituents in the treatment of peripheral nerve injury.

Perspectives on molecular biomarkers of oxidative stress and antioxidant strategies in traumatic brain injury

Traumatic brain injury (TBI) is frequently associated with abnormal blood-brain barrier function, resulting in the release of factors that can be used as molecular biomarkers of TBI, among them GFAP, UCH-L1, S100B, and NSE. Although many experimental studies have been conducted, clinical consolidation of these biomarkers is still needed to increase the predictive power and reduce the poor outcome of TBI. Interestingly, several of these TBI biomarkers are oxidatively modified to carbonyl groups, indicating that markers of oxidative stress could be of predictive value for the selection of therapeutic strategies. Some drugs such as corticosteroids and progesterone have already been investigated in TBI neuroprotection but failed to demonstrate clinical applicability in advanced phases of the studies. Dietary antioxidants, such as curcumin, resveratrol, and sulforaphane, have been shown to attenuate TBI-induced damage in preclinical studies. These dietary antioxidants can increase antioxidant defenses via transcriptional activation of NRF2 and are also known as carbonyl scavengers, two potential mechanisms for neuroprotection. This paper reviews the relevance of redox biology in TBI, highlighting perspectives for future studies.

Molecular Advances Leading to Treatment Implications for Fragile X Premutation Carriers

Fragile X syndrome (FXS) is the most common single gene cause of intellectual disability and it is characterized by a CGG expansion of more than 200 repeats in the FMR1 gene, leading to methylation of the promoter and gene silencing. The fragile X premutation, characterized by a 55 to 200 CGG repeat expansion, causes health problems and developmental difficulties in some, but not all, carriers. The premutation causes primary ovarian insufficiency in approximately 20% of females, psychiatric problems (including depression and/or anxiety) in approximately 50% of carriers and a neurodegenerative disorder, the fragile X-associated tremor ataxia syndrome (FXTAS), in approximately 40% of males and 16% of females later in life. Recent clinical studies in premutation carriers have expanded the health problems that may be seen. Advances in the molecular pathogenesis of the premutation have shown significant mitochondrial dysfunction and oxidative stress in neurons which may be amenable to treatment. Here we review the clinical problems of carriers and treatment recommendations.

Epigallocatechin-3-gallate suppresses transforming growth factor-beta signaling by interacting with the transforming growth factor-beta type II receptor

AIM: To investigate the (-)-epigallocatechin-3-gallate (EGCG) binding to transforming growth factor-β (TGF-β) type II receptor (TGFRII).

METHODS: The expression of α-smooth muscle actin (α-SMA) was used as a marker for fibrotic change in human lung fibroblast MRC-5 cells. The α-SMA expression level was determined by western blotting and immunohistological analysis. We examined whether the anti-fibrotic effects of EGCG on MRC-5 cells was dependent on antioxidant mechanism by using edaravone and N-acetylcysteine (NAC). The suppression effects of EGCG on Smad2/3 activation were studied by confocal fluorescence microscopy. The binding of EGCG to recombinant TGFRII protein was analyzed by immunoprecipitation and affinity chromatography.

RESULTS: When MRC-5 cells were treated with TGF-β, EGCG decreased the expression of α-SMA in a dose dependent manner, whereas catechin did not influence the α-SMA expression in the cells. Except for EGCG, antioxidant compounds (e.g., edaravone and NAC) had no effects on the TGF-β-induced α-SMA expression. Nuclear localization of phosphorylated Smad2/3 was observed after TGF-β treatment; however, EGCG treatment attenuated the nuclear transportation of Smad2/3 in the presence or absence of TGF-β. After a TGFRII expression vector was introduced into COS-7 cells, cell lysates were untreated or treated with EGCG or catechin. The immunoprecipitation experiments using the lysates showed that EGCG dose-dependently bound to TGFRIIand that catechin did not at all. Affinity chromatography study indicated that EGCG would bind to TGFRII.

CONCLUSION: Our results demonstrate that EGCG interacts with TGFRII and inhibits the expression of α-SMA via the TGF-β-Smad2/3 pathway in human lung fibroblast MRC-5 cells.

Dose- and time-dependent neuroprotective effects of Pycnogenol following traumatic brain injury

After traumatic brain injury (TBI), both primary and secondary injury cascades are initiated, leading to neuronal death and cognitive dysfunction. We have previously shown that the combinational bioflavonoid, Pycnogenol (PYC), alters some secondary injury cascades and protects synaptic proteins when administered immediately following trauma. The purpose of the present study was to explore further the beneficial effects of PYC and to test whether it can be used in a more clinically relevant fashion. Young adult male Sprague-Dawley rats were subjected to a unilateral moderate/severe cortical contusion. Subjects received a single intravenous (i.v.) injection of PYC (1, 5, or 10 mg/kg) or vehicle, with treatment initiated at 15 min, 2 h, or 4 h post injury. All rats were killed at 96 h post TBI. Both the cortex and hippocampus ipsilateral and contralateral to the injury were evaluated for possible changes in oxidative stress (thiobarbituric acid reactive species; TBARS) and both pre- and post-synaptic proteins (synapsin-I, synaptophysin, drebrin, post synaptic density protein-95, and synapse associated protein-97). Following TBI, TBARS were significantly increased in both the injured cortex and ipsilateral hippocampus. Regardless of the dose and delay in treatment, PYC treatment significantly lowered TBARS. PYC treatment significantly protected both the cortex and hippocampus from injury-related declines in pre- and post-synaptic proteins. These results demonstrate that a single i.v. treatment of PYC is neuroprotective after TBI with a therapeutic window of at least 4 h post trauma. The natural bioflavonoid PYC may provide a possible therapeutic intervention in neurotrauma.

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.

Intrathecal epigallocatechin gallate treatment improves functional recovery after spinal cord injury by upregulating the expression of BDNF and GDNF

This study aimed to investigate the therapeutic effects of epigallocatechin-3-gallate (EGCG) administered by subarachnoid injection following spinal cord injury (SCI) in rats and to explore the underlying mechanism. Sprague-Dawley rats were randomly divided into four groups of 12 as follows: a sham group (laminectomy only); a control group; a 10 mg/kg EGCG-treated group; and a 20 mg/kg EGCG-treated group. SCI was induced in the rats using the modified weight-drop method (10 g × 4 cm) at the T10 (10th thoracic vertebral) level. EGCG (10 or 20 mg/kg) or vehicle as control was administered by subarachnoid injection at lumbar level 4 immediately after SCI. Locomotor functional recovery was assessed during the four weeks post-operation using open-field locomotor tests and inclined-plane tests. At the end of the study, the segments of spinal cord encompassing the injury site were removed for histopathological analysis. Immunohistochemical and Western blot analyses were performed to observe the expression of: the B cell CLL/lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax), brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF). The results showed that the EGCG-treated animals had significantly better recovery of locomotor function, less myelin loss, greater Bcl-2 expression and attenuated Bax expression. In addition, the EGCG treatment significantly increased the expression of BDNF and GDNF after SCI. These findings suggest that EGCG treatment can significantly improve locomotor recovery, and this neuroprotective effect may be related to the up-regulation of BDNF and GDNF, and the inhibition of apoptosis-related proteins. Therefore, EGCG may be a promising therapeutic agent for SCI.

Neuroprotective effect of (-)-epigallocatechin-3-gallate in rats when administered pre- or post-traumatic brain injury

Our previous study indicated that consuming (-)-epigallocatechin gallate (EGCG) before or after traumatic brain injury (TBI) eliminated free radical generation in rats, resulting in inhibition of neuronal degeneration and apoptotic death, and improvement of cognitive impairment. Here we investigated the effects of administering EGCG at various times pre- and post-TBI on cerebral function and morphology. Wistar rats were divided into five groups and were allowed access to (1) normal drinking water, (2) EGCG pre-TBI, (3) EGCG pre- and post-TBI, (4) EGCG post-TBI, and (5) sham-operated group with access to normal drinking water. TBI was induced with a pneumatic controlled injury device at 10 weeks of age. Immunohistochemistry and lipid peroxidation studies revealed that at 1, 3, and 7 days post-TBI, the number of 8-Hydroxy-2'-deoxyguanosine-, 4-Hydroxy-2-nonenal- and single-stranded DNA (ssDNA)-positive cells, and levels of malondialdehyde around the damaged area were significantly decreased in all EGCG treatment groups compared with the water group (P < 0.05). Although there was a significant increase in the number of surviving neurons after TBI in each EGCG treatment group compared with the water group (P < 0.05), significant improvement of cognitive impairment after TBI was only observed in the groups with continuous and post-TBI access to EGCG (P < 0.05). These results indicate that EGCG inhibits free radical-induced neuronal degeneration and apoptotic death around the area damaged by TBI. Importantly, continuous and post-TBI access to EGCG improved cerebral function following TBI. In summary, consumption of green tea may be an effective therapy for TBI patients.

Neuroprotective effect of Pycnogenol® following traumatic brain injury

Traumatic brain injury (TBI) involves primary and secondary injury cascades that underlie delayed neuronal dysfunction and death. Oxidative stress is one of the most celebrated secondary injury mechanisms. A close relationship exists between levels of oxidative stress and the pathogenesis of TBI. However, other cascades, such as an increase in proinflammatory cytokines, also play important roles in the overall response to the trauma. Pharmacologic intervention, in order to be successful, requires a multifaceted approach. Naturally occurring flavonoids are unique in possessing not only tremendous free radical scavenging properties but also the ability to modulate cellular homeostasis leading to a reduction in inflammation and cell toxicity. This study evaluated the therapeutic role of Pycnogenol (PYC), a patented combinational bioflavonoid. Young adult Sprague-Dawley rats were subjected to a unilateral moderate cortical contusion and treated post injury with PYC or vehicle. At either 48 or 96 h post trauma, the animals were killed and the cortex and hippocampus analyzed for changes in enzymatic and non-enzymatic oxidative stress markers. In addition, possible changes in both pre- and post-synaptic proteins (synapsin-1, PSD-95, drebrin, synapse associated protein-97) were analyzed. Finally, a separate cohort of animals was used to evaluate two proinflammatory cytokines (IL-6, TNF-α). Following the trauma there was a significant increase in oxidative stress in both the injured cortex and the ipsilateral hippocampus. Animals treated with PYC significantly ameliorated levels of protein carbonyls, lipid peroxidation, and protein nitration. The PYC treatment also significantly reduced the loss of key pre- and post-synaptic proteins with some levels in the hippocampus of PYC treated animals not significantly different from sham operated controls. Although levels of the proinflammatory cytokines were significantly elevated in both injury groups, the cohort treated with PYC showed a significant reduction compared to vehicle treated controls. These results are the first to show a neuroprotective effect of PYC following TBI. They also suggest that the diverse effects of bioflavonoids may provide a unique avenue for possible therapeutic intervention following head trauma.

Appearance of neural stem cells around the damaged area following traumatic brain injury in aged rats

We have previously reported free radical production after traumatic brain injury (TBI), which induces neural stem cell (NSC) degeneration and death. However, the effects of aging on NSC proliferation around the damaged area following TBI have not been investigated. Therefore, in this study, we used 10-week (young group) and 24-month-old (aged group) rat TBI models to investigate the effects of aging on NSC proliferation around damaged tissue using immunohistochemical and ex vivo techniques. Young and aged rats received TBI. At 1, 3 and 7 days after TBI, immunohistochemical and lipid peroxidation studies were performed. Immunohistochemistry revealed that the number of nestin-positive cells around the damaged area after TBI in the aged group decreased significantly when compared with those in the young group (P < 0.01). However, the number of 8-hydroxy-2'-deoxyguanosine-, 4-hydroxy-2-nonenal- and single-stranded DNA (ssDNA)-positive cells and the level of peroxidation around the damaged area after TBI significantly increased in the aged group, compared with those in the young group (P < 0.01). Furthermore, almost all ssDNA-positive cells in young and aged groups co-localized with NeuN and nestin staining. Ex vivo studies revealed that neurospheres, which differentiated into neurons and glia in culture, could only be isolated from injured brain tissue in young and aged groups at 3 days after TBI. These results indicate that, although there were fewer NSCs that have the potential to differentiate into neurons and glia, these NSCs escaped free radical-induced degeneration around the damaged area after TBI in the aged rat brain.

The immunology of traumatic brain injury: a prime target for Alzheimer's disease prevention

A global health problem, traumatic brain injury (TBI) is especially prevalent in the current era of ongoing world military conflicts. Its pathological hallmark is one or more primary injury foci, followed by a spread to initially normal brain areas via cascades of inflammatory cytokines and chemokines resulting in an amplification of the original tissue injury by microglia and other central nervous system immune cells. In some cases this may predispose individuals to later development of Alzheimer’s disease (AD). The inflammatory-based progression of TBI has been shown to be active in humans for up to 17 years post TBI. Unfortunately, all neuroprotective drug trials have failed, and specific treatments remain less than efficacious. These poor results might be explained by too much of a scientific focus on neurons without addressing the functions of microglia in the brain, which are at the center of proinflammatory cytokine generation. To address this issue, we provide a survey of the TBI-related brain immunological mechanisms that may promote progression to AD. We discuss these immune and microglia-based inflammatory mechanisms involved in the progression of post-trauma brain damage to AD. Flavonoid-based strategies to oppose the antigen-presenting cell-like inflammatory phenotype of microglia will also be reviewed. The goal is to provide a rationale for investigations of inflammatory response following TBI which may represent a pathological link to AD. In the end, a better understanding of neuroinflammation could open therapeutic avenues for abrogation of secondary cell death and behavioral symptoms that may mediate the progression of TBI to later AD.

(-)-Epigallocatechin-3-gallate increases the number of neural stem cells around the damaged area after rat traumatic brain injury

A major component of green tea is (-)-epigallocatechin gallate (EGCG), which has strong antioxidant properties. Here, we investigated the effect of EGCG on neural stem cell (NSC) proliferation around the damaged area following traumatic brain injury (TBI). In this study, male Wistar rats that had access to normal drinking water, or water containing 0.1% (w/v) EGCG, ad libitum received TBI at 10 weeks of age. Immunohistochemistry revealed that the number of nestin-positive cells around the damaged area after TBI in the EGCG treatment group increased significantly compared with the normal water group (P < 0.05). However, the number of 8-hydroxy-2'-deoxyguanosine-, 4-hydroxy-2-nonenal-, single-stranded DNA (ssDNA)-positive cells and the level of peroxidation around the damaged area after TBI significantly decreased in the EGCG treatment group when compared with the water group (P < 0.05). Furthermore, in contrast to the EGCG group, almost all ssDNA-positive cells in the water group co-localized with NeuN and nestin-staining. Ex vivo studies revealed that spheres could only be isolated from injured brain tissue in the water group at 3 days following TBI. However, in the EGCG group, spheres could be isolated at both 3 and 7 days following TBI. A greater number of spheres could be isolated from the EGCG group, which differentiated into neurons and glia in culture without basic fibroblast growth factor. These results indicate that consumption of water containing EGCG pre- and post-TBI inhibits free radical-induced degradation of NSCs, which have the potential to differentiate into neurons and glia around the area of damage following TBI.