Neuroprotective attributes of L-theanine, a bioactive amino acid of tea, and its potential role in Parkinson's disease therapeutics

L-theanine ameliorates traumatic-brain-injury-induced hippocampal neuronal death in rats

BACKGROUND

Traumatic brain injury (TBI) is a major health concern, often resulting in significant brain damage and functional impairments. A key contributing factor to TBI-induced neuronal injury is the overactivation of AMPA glutamate receptors, leading to an increased influx of calcium and zinc ions. This study investigates the neuroprotective potential of l-theanine, known for its antioxidant potential and ability to enhance glutathione synthesis, against hippocampal damage in a TBI rat model.

METHODS

Rats subjected to TBIs were treated with two dosages of l-theanine (100 and 200 mg/kg) and an AMPA receptor inhibitor, NBQX (30 mg/kg). The neuronal damage assessment, conducted 24 h post-injury, involved a histological analysis, focusing on the factors of neuronal death, oxidative damage, and glial cell activation. The statistical analysis included the performance of an ANOVA followed by a Bonferroni post hoc test, with the data presented as mean ± SEM values and the significance determined at p < 0.05.

RESULTS

Treatment with l-theanine was observed to significantly mitigate the zinc accumulation, neuronal death, and cognitive impairments associated with TBI. These benefits are likely attributed to the inhibition of AMPA receptor activity and reduction in neuroinflammation, possibly enhanced as a result of increased glutathione production.

CONCLUSION

This study suggests that l-theanine can perform a neuroprotective role in TBI, modulating AMPA receptor activation and diminishing neuroinflammation. Its antioxidant and anti-inflammatory properties further enhance the material's potential use as a therapeutic agent for reducing hippocampal damage caused as a result of a TBI.

L-Theanine Metabolism in Tea Plants: Biological Functions and Stress Tolerance Mechanisms

L-theanine, a unique non-protein amino acid predominantly found in tea plants (Camellia sinensis), plays a pivotal role in plant responses to abiotic stress and significantly influences tea quality. In this review, the metabolism and transport mechanisms of L-theanine are comprehensively discussed, highlighting its spatial distribution in tea plants, where it is most abundant in young leaves and less so in roots, stems, and older leaves. The biosynthesis of L-theanine occurs through the enzymatic conversion of glutamate and ethylamine, catalyzed by theanine synthase, primarily in the roots, from where it is transported to aerial parts of the plant for further catabolism. Environmental factors such as temperature, light, drought, elevated CO2, nutrient unavailability, and heavy metals significantly affect theanine biosynthesis and hydrolysis, with plant hormones and transcription factors playing crucial regulatory roles. Furthermore, it has been demonstrated that applying L-theanine exogenously improves other crops' resistance to a range of abiotic stresses, suggesting its potential utility in improving crop resilience amid climate change. This review aims to elucidate the physiological mechanisms and biological functions of L-theanine metabolism under stress conditions, providing a theoretical foundation for enhancing tea quality and stress resistance in tea cultivation.

Glutaminase inhibition as potential cancer therapeutics: current status and future applications

Alterations in normal metabolic processes are defining features of cancer. Glutamine, an abundant amino acid in the human blood, plays a critical role in regulating several biosynthetic and bioenergetic pathways that support tumour growth. Glutaminolysis is a metabolic pathway that converts glutamine into various metabolites involved in the tricarboxylic acid (TCA) cycle and generates antioxidants that are vital for tumour cell survival. As glutaminase catalyses the initial step of this metabolic pathway, it is of great significance in cancer metabolism and tumour progression. Inhibition of glutaminase and targeting of glutaminolysis have emerged as promising strategies for cancer therapy. This review explores the role of glutaminases in cancer metabolism and discusses various glutaminase inhibitors developed as potential therapies for tumour regression.

Biological potential and mechanisms of Tea's bioactive compounds: An Updated review

BACKGROUND

Tea (Camellia sinensis) has a rich history and is widely consumed across many countries, and is categorized into green tea, white tea, oolong tea, yellow tea, black tea, and dark tea based on the level of fermentation. Based on a review of previous literature, the commonly recognized bioactive substances in tea include tea polyphenols, amino acids, polysaccharides, alkaloids, terpenoids, macro minerals, trace elements, and vitamins, which have been known to have various potential health benefits, such as anticancer, antioxidant, anti-inflammatory, anti-diabetes, and anti-obesity properties, cardiovascular protection, immune regulation, and control of the intestinal microbiota. Most studies have only pointed out the characteristics of tea's bioactivities, so a comprehensive summary of the pharmacological characteristics and mechanisms of tea's bioactivities and their use risks are vital.

AIM OF REVIEW

This paper aims to summarize tea's bioactive substances of tea and their pharmacological characteristics and mechanisms, providing a scientific basis for the application of bioactive substances in tea and outlining future research directions for the study of bioactive substances in tea.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This review summarizes the main biologically active substances, pharmacological effects, and mechanisms and discusses the potential risks. It may help researchers grasp more comprehensive progress in the study of tea bioactive substances to further promote the application of tea as a natural bioactive substance in the medical field.

l-theanine, the unique constituent of tea, improves neuronal survivability by curtailing inflammatory responses in MPTP model of Parkinson's disease

Discrete components of tea possess multitude of health advantages. Escalating evidence advocate a consequential association between habitual tea consumption and a subsided risk of Parkinson's disease (PD). l-theanine is a non-protein amino acid inherent in tea plants, which exhibits structural resemblance with glutamate, the copious excitatory neurotransmitter in brain. Neuromodulatory effects of l-theanine are evident from its competency in traversing the blood brain barrier, promoting a sense of calmness beyond enervation, and enhancing cognition and attention. Despite the multifarious reports on antioxidant properties of l-theanine and its potential to regulate brain neurotransmitter levels, it is obligatory to understand its exact contribution in ameliorating the pathophysiology of PD. In this study, MPTP-induced mouse model was established and PD-like symptoms were developed in test animals where an increasing dosage of l-theanine (5, 25, 50, 100 and 250 mg/kg) was intraperitoneally administered for 23 days. 50 and 100 mg/kg dosage of l-theanine alleviated motor impairment and specific non-motor symptoms in Parkinsonian mice. The dosage of 100 mg/kg of l-theanine also improved striatal dopamine and serotonin level and tyrosine-hydroxylase positive cell count in the substantia nigra. Most crucial finding of the study is the proficiency of l-theanine to diminish astroglial injury as well as nitric oxide synthesis, which suggests its possible credential to prevent neurodegeneration by virtue of its anti-inflammatory attribute.

Combining protein and metabolic engineering strategies for high-level production of L-theanine in Corynebacterium glutamicum

L-theanine is a natural non-protein amino acid with wide applications. Thus, a high yield of L-theanine production is required on an industrial scale. Herein, an efficient L-theanine-producing strain of Corynebacterium glutamicum was constructed by combining protein and metabolic engineering. Firstly, a γ-glutamylmethylamide synthetase from Paracoccus aminovorans (PaGMAS) was isolated and engineered by computer-aided design, the resulting mutant E179K/N105R improved L-theanine yield by 36.61 %. Subsequently, to increase carbon flux towards L-theanine production, the gene ggt which degrades L-theanine, the gene alaT which participated in L-alanine synthesis, and the gene NCgl1221 which encodes glutamate-exporting protein were deleted. Finally, ppk gene was overexpressed to enhance intracellular ATP production. The reprogramed strain produced 44.12 g/L L-theanine with a yield of 57.11 % and productivity of 1.16 g/L/h, which is the highest L-theanine titer reported by Corynebacterium glutamicum. This study provides an efficient and economical biosynthetic pathway for the industrial production of L-theanine.

Regulatory Effects and Mechanisms of L-Theanine on Neurotransmitters via Liver-Brain Axis Under a High Protein Diet

Excessive protein intake causes liver and brain damage and neurotransmitter disorders, thereby inducing cognitive dysfunction. L-theanine can regulate the neurotransmitter content and show great potential in liver and brain protection. However, it remains unclear whether l-theanine effectively regulates neurotransmitter content under high-protein diet. A 40-day feeding experiment was performed in Sprague Dawley rats to investigate the regulatory effects and mechanisms of l-theanine on neurotransmitters via liver-brain axis in high-protein diets. The results showed that a 30% protein diet increased the liver and brain neurotransmitter content while maintaining the normal structure of liver and the hippocampal CA1 of brain and improving the autonomous behavior of rats. In contrast, 40% and 50% protein diets decreased the content of neurotransmitters, affected autonomous behavior, destroyed the hippocampal CA1 of brain structure, increased hepatic inflammatory infiltration, lipid degeneration, and hepatocyte eosinophilic change in liver, increased liver AST, ALT, MDA, CRP, and blood ammonia level, and decreased liver SOD and CAT level. However, l-theanine improved liver and brain neurotransmitter content, autonomous behavior, liver and hippocampal brain structure, and liver biochemical indicators in 40% and 50% protein diets. To explore how LTA can eliminate the adverse effects of a high-protein diet, we analyzed different metabolites and proteomes and using western blotting for validate quantitatively. We found that l-theanine regulates the activity of PF4 and G protein subunit alpha i2, increases the content of brain-derived neurotrophic factor and dopamine under a 20% protein diet. In addition, l-theanine can activate the adenylate cyclase-protein kinase A pathway through the protein alpha/beta-hydrolase domain protein 12 to regulate the content of neurotransmitters under a 40% protein diet, thereby exerting a neuroprotective effect.

L-Theanine adjunct to risperidone in the treatment of chronic schizophrenia inpatients: a randomized, double-blind, placebo-controlled clinical trial

RATIONALE

Inadequate responses to current schizophrenia treatments have accelerated research into novel therapeutic approaches.

OBJECTIVES

This study investigated the efficacy and tolerability of adjunctive L-theanine, an ingredient with neuroimmunomodulatory and neuroprotective properties, for chronic schizophrenia.

METHODS

Eighty chronic schizophrenia inpatients were equally assigned to receive risperidone (6 mg/day) plus either L-theanine (400 mg/day) or matched placebo in this 8-week, randomized, parallel-group, double-blind, placebo-controlled trial. The participants were assessed using the Positive and Negative Syndrome Scale (PANSS) by recording the results of subscales at baseline and weeks 4 and 8 to measure treatment efficacy. Additionally, the participants were assessed for the Hamilton Depression Rating Scale (HDRS) and adverse events, including the Extrapyramidal Symptom Rating Scale (ESRS).

RESULTS

Sixty patients, 30 in each group, were included in the analyses. All baseline demographic and clinical characteristics were comparable between the groups (p-values > 0.05). The reduction rates from baseline to endpoint in negative, general psychopathology, and total scores of PANSS were greater in the L-theanine group (p-values = 0.03, 0.01, and 0.04, respectively). Regarding general psychopathology scores, the reduction in the L-theanine group was also greater until week 4 (p-value < 0.01). The time × treatment interaction effect was significant on negative (p-value = 0.03), general psychopathology (p-value < 0.01), and total (p-value = 0.04) scores of PANSS, indicating additional improvements in the L-theanine group. The HDRS and side effects were comparable between the groups (p-values > 0.05).

CONCLUSIONS

L-Theanine adjunct to risperidone safely and tolerably outperformed adjunctive placebo for schizophrenia, and promising evidence indicated its effects on primary negative symptoms, which need to be scrutinized in further studies.

TRIAL REGISTRATION

The study protocol was registered and published prospectively in the Iranian Registry of Clinical Trials ( http://www.irct.ir ; registration number: IRCT20090117001556N133) on 2020-12-12.

External application of brassinolide enhances cold resistance of tea plants (Camellia sinensis L.) by integrating calcium signals

MAIN CONCLUSION

Exogenous brassinolide can activate the expression of key genes in the calcium signalling pathway to enhance cold resistance of tea plants. Brassinolide is an endogenous sterol phytohormone containing multiple hydroxyl groups that has the important function of improving plant cold resistance and alleviating freeze damage. To explore the molecular mechanism of how brassinolide improves the cold resistance of tea plants, "Qiancha 1" was used as the material, and the method of spraying brassinolide on the leaves was adopted to explore its effects on the tea plants under 4 °C low-temperature treatment. The results showed that brassinolide can significantly increase the protective enzyme activity of tea plants under cold stress and reduce cold damage. At the transcriptome level, brassinolide significantly enhanced the expression of key genes involved in calcium signal transduction, Calmodulin (CaM), Calcium-dependent protein kinase (CDPK), calcineurin B-like protein (CBL) and calmodulin-binding transcriptional activators (CAMTA), which then activated the downstream key genes transcriptional regulator CBF1 (CBF1) and transcription factor ICE1 (ICE1) during cold induction. Quantitative real-time PCR (qRT‒PCR) results showed that the expression of these genes was significantly induced after treatment with brassinolide, especially CaM and CBF1. When calcium signalling was inhibited, the upregulated expression of CBF1 and ICE1 disappeared, and when CAMTA was knocked down, the expression of other genes under cold stress was also significantly reduced. The above results indicate that brassinolide combined with the calcium signalling pathway can improve the cold resistance of tea plants. This study provides a new theoretical basis for the study of the cold resistance mechanism of brassinolide.

Over the Counter Supplements for Memory: A Review of Available Evidence

In 2021, the Global Brain Health Supplement Industry Market size was valued at US$7.6 billion. It is predicted to increase to US$15.59 billion by 2030. Memory and its enhancement are a segment of the market that comprised the highest global revenue share in 2021. In the USA alone, dietary supplement sales reached US$18 billion in 2018. The US Food and Drug Administration (FDA) does not have the authority to approve dietary supplements' safety, effectiveness, or labeling before products go on the market. The FDA often does not even review supplements before they go to market. Supplement manufacturers are thus responsible for ensuring their products are safe and that their claims are truthful. An extensive review of current supplements on the market was performed by surveying memory products for sale at local and national pharmacies and grocery stores. A list of 103 supplements was compiled and the ingredients in these memory supplements were reviewed. The 18 most common ingredients in these supplements were identified. Each of the supplements included at least one of the 18 most common ingredients. Scientific data relative to these ingredients and their effect on memory was searched using PubMed and Cochrane library databases. Currently, there is no compelling evidence for use of apoaequorin, coenzyme Q10, coffee extracts, L-theanine, omega-3 fatty acids, vitamin B6, vitamin B9, or vitamin B12 supplementation for memory. On the other hand, there is some current evidence for memory benefit from supplementation with ashwagandha, choline, curcumin, ginger, Lion's Mane, polyphenols, phosphatidylserine, and turmeric. There are current studies with mixed results regarding the benefit of carnitine, gingko biloba, Huperzine A, vitamin D, and vitamin E supplementation for memory. Dietary supplements geared toward improving cognition are a billion-dollar industry that continues to grow despite lacking a solid scientific foundation for their marketing claims. More rigorous studies are needed relative to the long-term use of these supplements in homogenous populations with standardized measurements of cognition. Health care providers need to be aware of any and all supplements their older adult patients may be consuming and be educated about their side effects and interactions with prescription medications. Lastly, the FDA needs to take an active position relative to monitoring marketed supplements regarding safety, purity and claims of efficacy.

Isolation and antioxidant characterization of theaflavin for neuroprotective effect in mice model

The mandate of the current investigation was to elucidate the therapeutic and antioxidant perspective of black tea. Purposely, black tea compositional analysis followed by polyphenol extraction and antioxidant characterization was done. Moreover, the theaflavin from black tea extract was also isolated through the solvent partition method. Lastly, the neuroprotective effect of isolated theaflavin was assessed through a bio-efficacy trial. The outcomes delineated that black tea showed promising nutritional composition with special reference to protein and fiber. Among the extraction solvent, ethanol performed better as compared to methanol and water likewise, higher extraction was noticed at 60 min followed by 90 and 30 min. All the extracts indicated antioxidant activity reflected through significant DPPH, TPC, FRAP, and beta carotene as-69.13 ± 3.00, 1148.92 ± 14.01, 752.44 ± 10.30, and 65.74 ± 3.28, respectively. However, isolated theaflavin exhibited higher antioxidant capacity as-737.74 ± 12.55, 82.60 ± 2.33, and 853.77 ± 9.55, for TPC, DPPH, and FRAP, respectively, as compared to extracts. In 15 days' efficacy was physically induced with sciatic nerve injury h sciatic nerve injury physically and treated with isolated theaflavin. A total of 12 healthy albino mice were randomly assigned to either the control (n = 6) or theaflavin (5.0 mg/kg (n = 6)) groups. In these groups, behavioral tests were used to assess and compare enhanced functional recovery as well as skeletal muscle mass measurement. Serum samples included oxidative stress markers. In theaflavin leaves, behavioral tests revealed a statistically significant (p < .001) improvement in sensorimotor function restoration, muscle mass restoration, a substantial decrease in TOS, a significant increase in TAC, and enhanced antioxidative enzyme activity. Considering the above-mentioned therapeutic perspectives of theaflavin, the current research was planned to optimize the isolation of theaflavin from black tea and probed for their neuroprotective effect in mice models.

Biochemical Characterization of γ-Glutamyl Transpeptidase from Bacillus altitudinis IHB B1644 and Its Application in the Synthesis of l-Theanine

An extracellular γ-glutamyl transpeptidase (GGT) produced from Bacillus altitudinis IHB B1644 was purified to homogeneity employing ion-exchange chromatography. GGT comprised two subunits of 40 and 22 kDa determined by SDS-PAGE. The maximum enzyme activity was optimal at pH 9 and 37 °C. The purified enzyme was stable from pH 5-10 and <50 °C. Steady-state kinetic studies revealed a K_m value of 0.538 mM against γ-GpNA. For substrate specificity, GGT showed highest affinity for l-methionine. The inhibitors' effect demonstrated that serine or threonine and tryptophan residues are essential for enzyme activity. l-Theanine production was optimized by employing a one-variable-at-a-time approach with 60-65% conversion rate. The final reaction consisted of 20 mM l-glutamine, 200 mM ethylamine hydrochloride, and 10 U mL^-1 enzyme concentration at 37 °C in Tris-Cl (50 mM, pH 9) for 5 h. l-Theanine was purified using a Dowex 50W X 8 hydrogen form resin and confirmed by HPLC and ¹H NMR spectroscopies.

Through Its Powerful Antioxidative Properties, L-Theanine Ameliorates Vincristine-Induced Neuropathy in Rats

L-theanine (LT), which is a major amino acid found in green tea, was shown to alleviate Vincristine (VCR)-induced peripheral neuropathy and associated neuronal functional changes in rats. To induce peripheral neuropathy, rats were administered VCR at a dose of 100 mg/kg/day intraperitoneally on days 1–5 and 8–12, while control rats received LT at doses of 30, 100, and 300 mg/kg/day intraperitoneally for 21 days or saline solution. Electrophysiological measurements were taken to evaluate the nerve functional loss and recovery through motor and sensory nerve conduction velocities. The sciatic nerve was examined for several biomarkers, including nitric oxide (NO), malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), total calcium, IL-6, IL-10, MPO, and caspase-3. The results showed that VCR caused significant hyperalgesia and allodynia in rats; decreased nerve conduction velocity; increased NO and MDA levels; and decreased GSH, SOD, CAT, and IL-10 levels. LT was found to significantly reduce VCR-induced nociceptive pain thresholds, decrease oxidative stress levels (NO, MDA), increase antioxidative strength (GSH, SOD, CAT), and reduce neuroinflammatory activity and apoptosis markers (caspase-3). LT’s antioxidant, calcium homeostasis, anti-inflammatory, anti-apoptotic, and neuroprotective properties make it a potential adjuvant to conventional treatment in VCR-induced neuropathy in rats.

L-Theanine alleviates MPTP-induced Parkinson's disease by targeting Wnt/β-catenin signaling mediated by the MAPK signaling pathway

We evaluated the neuroprotective effect of L-theanine in Parkinson's disease and the underlying mechanism focusing on WNT/β-catenin signaling mediated by the MAPK pathway. We treated MPTP-induced SH-SY5Y cells with various concentrations of L-theanine (50, 100, 200, and 500 μg/mL), and we also treated Parkinson's model mice with L-theanine. L-theanine treatment effectively reduced the immunohistochemical hallmarks of Parkinson's disease, particularly Lewy bodies and α-synuclein, and increased the number of tyrosine hydroxylase-positive cells. L-theanine also improved the motor dysfunction in MPTP-induced Parkinson's disease model mice as measured by the rotarod test. The levels of several pro-inflammatory mediators that are overexpressed in Parkinson's disease, namely TNF-α, IL-6, COX-2, and MAC-1, were reduced following L-theanine treatment, and the levels of the pro-apoptotic proteins Bcl-2, caspase-3, p53, and PARP-1 were significantly reduced. L-theanine regulated the oxidative stress-related factors SOD-1, GST, and NOX-4 by targeting several proteins related to WNT/β-catenin signaling, i.e., β-catenin, WNT-3a, WNT-5a, TCF1/TCF7, and LEF1, via the MAPK pathway (p-JNK, p-ERK, and p-p38). Our results indicate that L-theanine is neuroprotective and has anti-inflammatory effects that could be beneficial for treating Parkinson's disease.

New Perspectives on Sleep Regulation by Tea: Harmonizing Pathological Sleep and Energy Balance under Stress

Sleep, a conservative evolutionary behavior of organisms to adapt to changes in the external environment, is divided into natural sleep, in a healthy state, and sickness sleep, which occurs in stressful environments or during illness. Sickness sleep plays an important role in maintaining energy homeostasis under an injury and promoting physical recovery. Tea, a popular phytochemical-rich beverage, has multiple health benefits, including lowering stress and regulating energy metabolism and natural sleep. However, the role of tea in regulating sickness sleep has received little attention. The mechanism underlying tea regulation of sickness sleep and its association with the maintenance of energy homeostasis in injured organisms remains to be elucidated. This review examines the current research on the effect of tea on sleep regulation, focusing on the function of tea in modulating energy homeostasis through sickness sleep, energy metabolism, and damage repair in model organisms. The potential mechanisms underlying tea in regulating sickness sleep are further suggested. Based on the biohomology of sleep regulation, this review provides novel insights into the role of tea in sleep regulation and a new perspective on the potential role of tea in restoring homeostasis from diseases.

Role of Nrf2 in aging, Alzheimer's and other neurodegenerative diseases

Nuclear Factor-Erythroid Factor 2 (Nrf2) is an important transcription factor that regulates the expression of large number of genes in healthy and disease states. Nrf2 is made up of 605 amino acids and contains 7 conserved regions known as Nrf2-ECH homology domains. Nrf2 regulates the expression of several key components of oxidative stress, mitochondrial biogenesis, mitophagy, autophagy and mitochondrial function in all organs of the human body, in the peripheral and central nervous systems. Mounting evidence also suggests that altered expression of Nrf2 is largely involved in aging, neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's diseases, Amyotrophic lateral sclerosis, Stroke, Multiple sclerosis and others. The purpose of this article is to detail the essential role of Nrf2 in oxidative stress, antioxidative defense, detoxification, inflammatory responses, transcription factors, proteasomal and autophagic/mitophagic degradation, and metabolism in aging and neurodegenerative diseases. This article also highlights the Nrf2 structural and functional activities in healthy and disease states, and also discusses the current status of Nrf2 research and therapeutic strategies to treat aging and neurodegenerative diseases.

The therapeutic potential of matcha tea: A critical review on human and animal studies

Matcha is a powdered form of Japanese green tea that has been gaining global popularity recently. Matcha tea has various health benefits, including an enhancing effect on cognitive function, cardio-metabolic health, and anti-tumorogenesis. To date, randomized clinical trials (RCT) showed that matcha decreases stress, slightly enhances attention and memory, and has no effect on mood. Results regarding the effect of matcha on cognitive function are contradictory and more RCTs are warranted. The cardio-metabolic effects of matcha have only been studied in animals, but findings were more homogenous. Consuming matcha with a high-fat diet resulted in decreased weight gain velocity, food intake, improved serum glucose and lipid profile, reduced inflammatory cytokines and ameliorated oxidative stress. Evidence regarding the anti-tumor function of matcha is very limited. Findings showed that matcha can affect proliferation, viability, antioxidant response, and cell cycle regulation of breast cancer cells. Nonetheless, more studies are needed to examine this effect on different types of cancer cells, and there is also a need to verify it using animal models. Overall, the evidence regarding the effect of matcha tea on cognitive function, cardio-metabolic function, and anti-tumor role is still limited, and conclusions cannot be drawn.

Green Tea (Camellia sinensis): A Review of Its Phytochemistry, Pharmacology, and Toxicology

Objectives Green tea (Camellia sinensis) is a kind of unfermented tea that retains the natural substance in fresh leaves to a great extent. It is regarded as the second most popular drink in the world besides water. In this paper, the phytochemistry, pharmacology, and toxicology of green tea are reviewed systematically and comprehensively. Key findings Green tea has been demonstrated to be good for human health. Nowadays, multiple pharmacologically active components have been isolated and identified from green tea, including tea polyphenols, alkaloids, amino acids, polysaccharides, and volatile components. Recent studies have demonstrated that green tea shows versatile pharmacological activities, such as antioxidant, anticancer, hypoglycemic, antibacterial, antiviral, and neuroprotective. Studies on the toxic effects of green tea extract and its main ingredients have also raised concerns including hepatotoxicity and DNA damage. Summary Green tea can be used to assist the treatment of diabetes, Alzheimer’s disease, oral cancer, and dermatitis. Consequently, green tea has shown promising practical prospects in health care and disease prevention.

Astrocyte Reaction to Catechol-Induced Cytotoxicity Relies on the Contact with Microglia Before Isolation

Astrocytes preserve the brain microenvironment homeostasis in order to protect other brain cells, mainly neurons, against damages. Glial cells have specific functions that are important in the context of neuronal survival in different models of central nervous system (CNS) diseases. Microglia are among these cells, secreting several molecules that can modulate astrocyte functions. Although 1,2-dihydroxybenzene (catechol) is a neurotoxic monoaromatic compound of exogenous origin, several endogenous molecules also present the catechol group. This study compared two methods to obtain astrocyte-enriched cultures from newborn Wistar rats of both sexes. In the first technique (P1), microglial cells began to be removed early 48 h after primary mixed glial cultures were plated. In the second one (P2), microglial cells were late removed 7 to 10 days after plating. Both cultures were exposed to catechol for 72 h. Catechol was more cytotoxic to P1 cultures than to P2, decreasing cellularity and changing the cell morphology. Microglial-conditioned medium (MCM) protected P1 cultures and inhibited the catechol autoxidation. P2 cultures, as well as P1 in the presence of 20% MCM, presented long, dense, and fibrillary processes positive for glial fibrillary acidic protein, which retracted the cytoplasm when exposed to catechol. The Ngf and Il1beta transcription increased in P1, meanwhile astrocytes expressed more Il10 in P2. Catechol decreased Bdnf and Il10 in P2 cultures, and it decreased the expression of Il1beta in both conditions. A prolonged contact with microglia before isolation of astrocyte-enriched cultures modifies astrocyte functions and morphology, protecting these cells against catechol-induced cytotoxicity.

Tea and its components reduce the production of uric acid by inhibiting xanthine oxidase

Background

The health benefits of tea are as diverse including the reduction of uric acid levels. Xanthine oxidase is the most directly mediated enzyme in the production of uric acid.

Objective

To explore the inhibitory effects of different teas and its main bioactive components on the production of uric acid.

Design

Experimental study. The experiments were conducted in vitro using human immortalized normal liver cell line HL-7702 (L-02).

Results

The inhibition of the xanthine oxidase activities and the expression level of xanthine dehydrogenase mRNA stimulated in the hyperuric hepatocyte cell model showed that the unfermented green tea and th1e lightly fermented yellow tea, white tea, and oolong tea significantly stronger than the highly fermented black tea and dark tea. The main bioactive compound, gallic acid, showed the strongest inhibitory effect on uric acid production, followed by tea polyphenols and theaflavins.

Discussion

All teas exhibited significant inhibition of xanthine oxidase activities, and the degree of fermentation of tea may be inversely proportional to its ability to inhibit the production of uric acid. Compared with tea polyphenols rich in tea, gallic acid may be a more potential uric acid-lowering component.

Conclusion

In this article, we first compared the effects of six traditional Chinese tea made from a single variety in stabilizing the synthesis of uric acid and found that the lighter the fermentation, the greater the potential for inhibiting the production of uric acid. Furthermore, we analyzed the inhibitory effects of its main biochemical active ingredients and found that the inhibitory effects of polyphenols rich in lightly fermented tea were significantly stronger than caffeine rich in highly fermented tea. Our findings will be helpful for people to choose a proper tea for alleviating hyperuricemia and provide a scientific basis for uric acid-lowering tea processing.

Regulation of biosynthesis of the main flavor-contributing metabolites in tea plant (Camellia sinensis): A review

In the process of adapting to the environment, tea plants (Camellia sinensis) endow tea with unique flavor and health functions, which should be attributed to secondary metabolites, including catechins, L-theanine, caffeine and terpene volatiles. Since the content of these flavor-contributing metabolites are mainly determined by the growth of tea plant, it is very important to understand their alteration and regulation mechanisms. In the present work, we first summarize the distribution, change characteristics of the main flavor-contributing metabolites in different cultivars, organs and under environmental stresses of tea plant. Subsequently, we discuss the regulating mechanisms involved in the biosynthesis of these metabolites based on the existing evidence. Finally, we propose the remarks and perspectives on the future study relating flavor-contributing metabolites. This review would contribute to the acceleration of research on the characteristic secondary metabolites and the breeding programs in tea plants.

A Novel Theanine Complex, Mg-L-Theanine Improves Sleep Quality via Regulating Brain Electrochemical Activity

L-Theanine is commonly used to improve sleep quality through inhibitory neurotransmitters. On the other hand, Mg²⁺, a natural NMDA antagonist and GABA agonist, has a critical role in sleep regulation. Using the caffeine-induced brain electrical activity model, here we investigated the potency of L-theanine and two novel Mg-L-theanine compounds with different magnesium concentrations on electrocorticography (ECoG) patterns, GABAergic and serotonergic receptor expressions, dopamine, serotonin, and melatonin levels. Furthermore, we evaluated the sleep latency and duration in the pentobarbital induced sleep model. We herein showed that L-theanine, particularly its various complexes with magnesium increases the expression of GABAergic, serotonergic, and glutamatergic receptors, which were associated with decreased ECoG frequency, increased amplitude, and enhanced delta wave powers. Besides increased dopamine, serotonin, and melatonin; decreased MDA and increased antioxidant enzyme levels were also observed particularly with Mg-complexes. Protein expression analyses also showed that Mg-L-theanine complexes decrease inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) levels significantly. In accordance with these results, Mg complexes improved the sleep latency and duration even after caffeine administration. As a result, our data indicate that Mg-L-theanine compounds potentiate the effect of L-theanine on sleep by boosting slow-brain waves, regulating brain electrical activity, and increasing neurotransmitter and GABA receptor levels.

A focus on natural products for preventing and cure of mitochondrial dysfunction in Parkinson's disease

Mitochondria are considered the only source of energy production within cells. This organelle is vital for neural function and survival by producing energy (adenosine triphosphate (ATP)) and regulating intracellular calcium. Mitochondrial dysfunction, which significantly contributes to both idiopathic and familial types of Parkinson's disease (PD), depletes cellular energy, disrupts homeostasis, and induces oxidative stress, leading to cell death. In recent years several natural products have been discovered to be protective against mitochondrial dysfunction. This review discusses the role of mitochondria in the progression of PD to define the path for using natural products to prevent and/or cure PD.

Recent advances in the utilization of tea active ingredients to regulate sleep through neuroendocrine pathway, immune system and intestinal microbiota

Sleep disorders have received widespread attention nowadays, which have been promoted by the accelerated pace of life, unhealthy diets and lack of exercise in modern society. The chemical medications to improve sleep has shown serious side effects and risks with high costs. Therefore, it is urgent to develop efficient nutraceuticals from natural sources to ensure sleep quality as a sustainable strategy. As the second most consumed beverage worldwide, the health-promoting effects of tea have long been widely recognized. However, the modulatory effect of teas on sleep disorders has received much less attention. Tea contains various natural sleep-modulating active ingredients such as L-theanine (LTA), caffeine, tea polyphenols (TPP), tea pigments, tea polysaccharides (TPS) and γ-aminobutyric acid (GABA). This review focuses on the potential influence and main regulating mechanisms of different tea active ingredients on sleep, including being absorbed by the small intestine and then cross the blood-brain barrier to act on neurons in the brain as neurotransmitters, manipulating the immune system and further affect sleep-wake cycle by regulating the levels of cytokines, and controlling the gut microbes to maintain the homeostasis of circadian rhythm. Current research progress and limitations are summarized and several future development directions are also proposed. This review hopes to provide new insights into the future elucidation of the sleep-regulating mechanisms of different teas and their natural active ingredients and the development of tea-based functional foods for alleviating sleep disorders. HighlightsNatural sleep-modulating active ingredients in tea have been summarized.Influences of drinking tea or tea active ingredients on sleep are reviewed.Three main regulating mechanisms of tea active ingredients on sleep are explained.The associations among nervous system, immune system and intestinal microbiota are investigated.The potential of developing delivery carriers for tea active ingredients is proposed.

Parkinson's Disease: Is there a Role for Dietary and Herbal Supplements?

Parkinson's Disease (PD) is characterised by degeneration of the neurons of the nigrostriatal dopaminergic pathway of the brain. The pharmacological cornerstone of PD management is mainly the use of dopamine precursors, dopamine receptor agonists, and agents that inhibit the biochemical degradation of dopamine. While these drugs initially provide relief to the symptoms and improve the quality of life of the patients, progression of the underlying pathological processes, such as oxidative stress and neuroinflammation (which have been strongly associated with PD and other neurodegenerative disorders), eventually reduce their benefits, making further benefits achievable, only at high doses due to which the magnitude and frequency of side-effects are amplified. Also, while it is becoming obvious that mainstream pharmacological agents may not always provide the much-needed answer, the question remains what succour can nature provide through dietary supplements, nutraceuticals and herbal remedies? This narrative review examines current literature for evidence of the possible roles (if any) of nutraceuticals, dietary supplements and herbal remedies in the prevention or management of PD by examining how these compounds could modulate key factors and pathways that are crucial to the pathogenesis and/or progression of PD. The likely limitations of this approach and its possible future roles in PD prevention and management are also considered.

Tremor and Rigidity in Patients with Parkinson's Disease: Emphasis on Epidemiology, Pathophysiology and Contributing Factors

Parkinson's disease (PD) is the second most prominent neurodegenerative movement disorder after Alzheimer's disease, involving 2-3% of the population aged above 65 years. This is mainly triggered by the depletion of dopaminergic neurons located in substantia nigra pars compacta (SNpc) in the region of basal ganglia. At present, diagnosis for symptoms of PD is clinical, contextual, unspecified and therapeutically incomprehensive. Analysis of various causes of PD is essential for an accurate examination of the disease. Among the different causes, such as tremors and rigidity, unresponsiveness to the current treatment approach contributes to mortality. In the present review article, we describe various key factors of pathogenesis and physiology associated with tremors and rigidity necessary for the treatment of PI (postural instability) in patients with PD. Additionally, several reports showing early tremor and rigidity causes, particularly age, cortex lesions, basal ganglia lesions, genetic abnormalities, weakened reflexes, nutrition, fear of fall, and altered biomechanics, have been explored. By summarizing the factors that contribute to the disease, histopathological studies can assess rigidity and tremor in PD. With a clear understanding of the contributing factors, various prospective studies can be done to assess the incidence of rigidity and tremors.

Recent insights on tea metabolites, their biosynthesis and chemo-preventing effects: A review

Tea manufactured from the cultivated shoots of Camellia sinensis (L.) O. Kuntze is the most commonly consumed nonalcoholic drink around the world. Tea is an agro-based, environmentally sustainable, labor-intensive, job-generating, and export-oriented industry in many countries. Tea includes phenolic compounds, flavonoids, alkaloids, vitamins, enzymes, crude fibers, protein, lipids, and carbohydrates, among other biochemical constituents. This review described the nature of tea metabolites, their biosynthesis and accumulation with response to various factors. The therapeutic application of various metabolites of tea against microbial diseases, cancer, neurological, and other metabolic disorders was also discussed in detail. The seasonal variation, cultivation practices and genetic variability influence tea metabolite synthesis. Tea biochemical constituents, especially polyphenols and its integral part catechin metabolites, are broadly focused on potential applicability for their action against various diseases. In addition to this, tea also contains bioactive flavonoids that possess health-beneficial effects. The catechin fractions, epigallocatechin 3-gallate and epicatechin 3-gallate, are the main components of tea that has strong antioxidant and medicinal properties. The synergistic function of natural tea metabolites with synthetic drugs provides effective protection against various diseases. Furthermore, the application of nanotechnologies enhanced bioavailability, enhancing the therapeutic potential of natural metabolites against numerous diseases and pathogens.

Nutraceuticals as Potential Targets for the Development of a Functional Beverage for Improving Sleep Quality

Functional beverages can be a valuable component of the human diet with the ability to not only provide essential hydration but to deliver important bioactive compounds that can contribute to chronic disease treatment and prevention. One area of the functional beverage market that has seen an increase in demand in recent years are beverages that promote relaxation and sleep. Sleep is an essential biological process, with optimal sleep being defined as one of adequate duration, quality and timing. It is regulated by a number of neurotransmitters which are, in turn, regulated by dietary intake of essential bioactive compounds. This narrative review aimed to evaluate the latest evidence of the sleep promoting properties of a selection of bioactive compounds (such as L-theanine and L-tryptophan) for the development of a functional beverage to improve sleep quality; and the effectiveness of traditional sleep promoting beverages (such as milk and chamomile). Overall, the bioactive compounds identified in this review, play essential roles in the synthesis and regulation of important neurotransmitters involved in the sleep-wake cycle. There is also significant potential for their inclusion in a number of functional beverages as the main ingredient on their own or in combination. Future studies should consider dosage; interactions with the beverage matrix, medications and other nutraceuticals; bioavailability during storage and following ingestion; as well as the sensory profile of the developed beverages, among others, when determining their effectiveness in a functional beverage to improve sleep quality.

L-theanine inhibits foam cell formation via promoting the scavenger receptor A degradation

Atherosclerosis is one of the most common cardiovascular diseases with highly mortality worldwide. The formation of foam cell plays an important role in the early stage of atherosclerosis pathogenesis. L-theanine is the most abundant free amino acid in tea, which possesses anti-inflammatory, anti-tumor and anti-atherosclerosis effects. However, little is known about the effects of L-theanine on the foam cell formation. In our study, RAW264.7 cells and primary mouse peritoneal macrophages were exposed to oxidized low density lipoprotein (ox-LDL) for inducing foam cell formation. We found that L-theanine significantly impeded cholesterol accumulation in macrophages, while inhibiting the formation of foam cell. Our further experiments showed that L-theanine attenuated the cholesterol uptake of RAW264.7 cells and primary mouse peritoneal macrophages by reducing the protein level of macrophage scavenger receptor A (SR-A), but not the level of mRNA suggesting that L-theanine regulates scavenger receptor A at the translational rather than transcriptional level. The present results demonstrated that L-theanine obviously promoted the degradation of scavenger receptor A protein and scavenger receptor A was degraded by ubiquitination dependent manner. Collectively, our research indicates that L-theanine suppresses the formation of macrophage foam cell by promoting the ubiquitination dependent degradation of scavenger receptor A.

Shading Promoted Theanine Biosynthesis in the Roots and Allocation in the Shoots of the Tea Plant (Camellia sinensis L.) Cultivar Shuchazao

Shading was thought as an effective approach to increase theanine in harvested tea shoots. Previous studies offered conflicting findings, perhaps since the integration of theanine metabolism and transport in different tissues was not considered. Theanine is synthesized primarily in the roots and is then transported, via the vascular system, to new vegetative tissues. Here, we found that theanine increased in the stem, was reduced in the leaf, and remained stable in the roots, under shading conditions. Notably, in tea roots, shading significantly increased ethylamine and activated the theanine biosynthesis pathway and theanine transporter genes. Furthermore, shading significantly increased the expression of theanine transporter genes, CsAAP2/4/5/8, in the stem, while decreasing the expression of CsAAP1/2/4/5/6 in the leaf, in accordance with shading effects on theanine levels in these tissues. These findings reveal that shading of tea plants promotes theanine biosynthesis and allocation in different tissues, processes which appear to involve the theanine biosynthesis pathway enzymes and AAP family of theanine transporters.

Semi-quantitative activity assays for high-throughput screening of higher activity gamma glutamyl transferase and enzyme immobilization to efficiently synthesize L-theanine

The bio-production of theanine is currently of significant interest due to its wide applications in food and healthcare products. Gamma glutamyl transferase (GGT) has been widely applied in L-theanine synthesis, but L-theanine yields remain prohibitively low for commercial production. In this study, a robust high-throughput screening process for isolating GGT mutants was developed through a combination of error-prone PCR techniques and a colorimetric reaction. The co-expression of PrsA lipoprotein enhances the secretion of GGT, thus GGT could be obtained quickly and easily without crushing cells. Random mutations on ggt genes were introduced by using error-prone PCR kits to build a large mutant library. A colorless compound generated by the reaction between NH⁴⁺ (released from L-theanine synthesis) and OPA was measured quantitatively by UV/visible spectroscopy when mixed with TCA and DMSO. Approximately 30 positive clones with improved color formation on the 96-well plates were identified, and mutants T413P and T463S with more than by 30 % higher transpeptidation activity versus the original GGT were isolated. To improve the operational stability and economical use, mutant GGT was immobilized on a prepared oxidized cellulose nanofiber membrane. The remaining activity of immobilized GGT was 88 % versus 72 % of free enzyme over 15 h. A fed-batch conversion was performed with the immobilized GGT, and over 70 g/L L-theanine could be accumulated within 18 h after feeding twice. Versus other studies, this is one of the best L-theanine synthesis systems using immobilized GGT.

Gene Coexpression Network Reveals Insights into the Origin and Evolution of a Theanine-Associated Regulatory Module in Non-Camellia and Camellia Species

Theanine (thea) is one of the most important plant-derived characteristic secondary metabolites and a major healthcare product because of its beneficial biological activities, such as being an antianxiety agent, promoting memory, and lowering blood pressure. Thea mostly accumulates in Camellia plants and is especially rich in Camellia sinensis (tea plant). Although some functional genes (e.g., TS, GOGAT, and GS) attributed to thea accumulation have been separately well explored in tea plants, the evolution of a regulatory module (highly interacting gene group) related to thea metabolism remains to be elaborated. Herein, a thea-associated regulatory module (TARM) was mined by using a comprehensive analysis of a weighted gene coexpression network in Camellia and non-Camellia species. Comparative genomic analysis of 84 green plant species revealed that TARM originated from the ancestor of green plants (algae) and that TARM genes were recruited from different evolutionary nodes with the most gene duplication events at the early stage. Among the TARM genes, two core transcription factors of NAC080 and LBD38 were deduced, which may play a crucial role in regulating the biosynthesis of thea. Our findings provide the first insights into the origin and evolution of TARM and indicate a promising paradigm for identifying vital regulatory genes involved in thea metabolism.

Theanine Improves Salt Stress Tolerance via Modulating Redox Homeostasis in Tea Plants (Camellia sinensis L.)

Theanine, a unique non-proteinogenic amino acid, is one of the most abundant secondary metabolites in tea. Its content largely determines green tea quality and price. However, its physiological roles in tea plants remain largely unknown. Here, we showed that salt stress significantly increased the accumulation of glutamate, glutamine, alanine, proline, and γ-aminobutyric acid, as well as theanine, in the new shoots of tea plants. We further found that salt stress induced the expression of theanine biosynthetic genes, including CsGOGATs, CsAlaDC, and CsTSI, suggested that salt stress induced theanine biosynthesis. Importantly, applying theanine to the new shoots significantly enhanced the salt stress tolerance. Similar effects were also found in a model plant Arabidopsis. Notably, exogenous theanine application increased the antioxidant activity of the shoots under salt stress, suggested by reduced the reactive oxygen species accumulation and lipid peroxidation, as well as by the increased SOD, CAT, and APX activities and expression of the corresponding genes. Finally, genetic evidence supported that catalase-mediated antioxidant scavenging pathway is required for theanine-induced salt stress tolerance. Taken together, this study suggested that salt stress induces theanine biosynthesize in tea plants to enhance the salt stress tolerance through a CAT-dependent redox homeostasis pathway.

Effects of Matcha Green Tea Powder on Cognitive Functions of Community-Dwelling Elderly Individuals

Matcha Green Tea Powder contains a variety of active ingredients beneficial to health, such as tea catechins, lutein and vitamin K. It is also known that these ingredients confer benefits upon cognitive functions of elderly people. Therefore, we aimed to investigate the relationship between a daily supplementation of Matcha and the change in cognitive functions of community-dwelling elderly people. A randomized, double-blind, placebo-controlled 12-week trial was performed. Sixty-one participants were recruited and randomly assigned to receive test drink containing 3 g powder from fresh Matcha or placebo powder per day. Changes in cognitive function were assessed utilizing a psychometric test battery. Daily food intake was assessed by a Brief-type Self-administered Diet History Questionnaire (BDHQ). In the gender-specific analysis, a significant cognitive enhancement was observed in the Montreal Cognitive Assessment (MoCA) score in the active group of women. In dietary analysis, we found a significant inverse correlation between consumption of vitamin K in daily diet, excluding test drinks, and change in MoCA. The present study suggests that daily supplementation of Matcha Green Tea Powder has protective effects against cognitive decline in community-dwelling elderly women.

Efficient synthesis of γ-glutamyl compounds by co-expression of γ-glutamylmethylamide synthetase and polyphosphate kinase in engineered Escherichia coli

γ-Glutamyl compounds have unveiled their importance as active substances or precursors of pharmaceuticals. In this research, an approach for enzymatic synthesis of γ-glutamyl compounds was developed using γ-glutamylmethylamide synthetase (GMAS) from Methylovorus mays and polyphosphate kinase (PPK) from Corynebacterium glutamicum. GMAS and PPK were co-recombined in pETDuet-1 plasmid and co-expressed in E. coli BL21 (DE3), and the enzymatic properties of GMAS and PPK were investigated, respectively. Under the catalysis of the co-expression system, L-theanine was synthesized with 89.8% conversion when the substrate molar ratio of sodium glutamate and ethylamine (1:1.4) and only 2 mM ATP were used. A total of 14 γ-glutamyl compounds were synthesized by this one-pot method and purified by cation exchange resin and isoelectric point crystallization with a yield range from 22.3 to 72.7%. This study provided an efficient approach for the synthesis of γ-glutamyl compounds by GMAS and PPK co-expression system.

L-theanine: an astounding sui generis amino acid in poultry nutrition

L-theanine (γ-Glutamylethylamide) is a nonprotein water soluble amino acid (AA) mostly found in leaves of Camellia sinensis (green tea). This is a key component of green tea and is considered as the most abundant form of total AAs in green tea (i.e., about 50%). L-theanine is an exclusive taste ingredient of tea producing an attractive flavor and aroma in tea. It has biological effects such as antioxidant, growth promoter, immune booster, anti-stresser, hepatoprotective, antitumor, antiaging, antimicrobial, anti-inflammatory, and antianxiety activities that are worth noticing. It could reduce the oxidative impairment by reducing the synthesis of reactive oxygen species, oxidative parameters, and lipid damage as well as increasing the activity of antioxidant enzymes. The oral ingestion of L-theanine enhanced γδ T-cell proliferation. Therefore, it is being considered an essential compound of green tea that has the ability to improve immune function. The L-theanine can be used as a potential treatment for hepatic injury and immune-related liver diseases via the downregulation of the inflammatory response through the initiation of nitric oxide synthesis and glutathione production which are likely to be critical for the control of hepatic diseases as well as for the improvement of immune function. In addition, it could be used as a best natural feed additive with a potent antistressor by decreasing the levels of corticosterone, dopamine, and noradrenaline. After systematically reviewing the literature, it is noticed that most studies were carried out on mice, pig, human, and butterfly; while dietary supplementation studies of L-theanine in animal and poultry especially among broilers are very limited because of less awareness of this AA. So, the aim of this review is to encourage the veterinarian and poultry researchers to conduct more research at the molecular level about this AA to expose its more beneficial effects and its mechanism of absorption for potential use of this unique green tea AA in poultry nutrition.

Nitroxide Radical-Containing Redox Nanoparticles Protect Neuroblastoma SH-SY5Y Cells against 6-Hydroxydopamine Toxicity

Parkinson's disease (PD) patients can benefit from antioxidant supplementation, and new efficient antioxidants are needed. The aim of this study was to evaluate the protective effect of selected nitroxide-containing redox nanoparticles (NRNPs) in a cellular model of PD. Antioxidant properties of NRNPs were studied in cell-free systems by protection of dihydrorhodamine 123 against oxidation by 3-morpholino-sydnonimine and protection of fluorescein against bleaching by 2,2-azobis(2-amidinopropane) hydrochloride and sodium hypochlorite. Model blood-brain barrier penetration was studied using hCMEC/D3 cells. Human neuroblastoma SH-SY5Y cells, exposed to 6-hydroxydopamine (6-OHDA), were used as an in vitro model of PD. Cells were preexposed to NRNPs or free nitroxides (TEMPO or 4-amino-TEMPO) for 2 h and treated with 6-OHDA for 1 h and 24 h. The reactive oxygen species (ROS) level was estimated with dihydroethidine 123 and Fluorimetric Mitochondrial Superoxide Activity Assay Kit. Glutathione level (GSH) was measured with ortho-phtalaldehyde, ATP by luminometry, changes in mitochondrial membrane potential with JC-1, and mitochondrial mass with 10-Nonyl-Acridine Orange. NRNP1, TEMPO, and 4-amino-TEMPO (25-150 μM) protected SH-SY5Y cells from 6-OHDA-induced viability loss; the protection was much higher for NRNP1 than for free nitroxides. NRNP1 were better antioxidants in vitro and permeated better the model BBB than free nitroxides. Exposure to 6-OHDA decreased the GSH level after 1 h and increased it considerably after 24 h (apparently a compensatory overresponse); NRNPs and free nitroxides prevented this increase. NRNP1 and free nitroxides prevented the decrease in ATP level after 1 h and increased it after 24 h. 6-OHDA increased the intracellular ROS level and mitochondrial superoxide level. Studied antioxidants mostly decreased ROS and superoxide levels. 6-OHDA decreased the mitochondrial potential and mitochondrial mass; both effects were prevented by NRNP1 and nitroxides. These results suggest that the mitochondria are the main site of 6-OHDA-induced cellular damage and demonstrate a protective effect of NRNP1 in a cellular model of PD.