Mitigative effects of epigallocatechin gallate in terms of diminishing apoptosis and oxidative stress generated by the combination of lead and amyloid peptides in human neuronal cells

Treatment of manganese and lead poisoning with sodium para-aminosalicylic acid: A contemporary update

Sodium para-aminosalicylic acid (PAS-Na) treatment for manganese (Mn) intoxication has shown efficacy in experimental and clinical studies, giving rise to additional studies on its efficacy for lead (Pb) neurotoxicity and its associated mechanisms of neuroprotection. The difference between PAS-Na and other metal complexing agents, such as edetate calcium sodium (CaNa2-EDTA), is firstly that PAS-Na can readily pass through the blood-brain barrier (BBB), and complex and facilitate the excretion of manganese and lead. Secondly, PAS-Na has anti-inflammatory effects. Recent studies have broadened the understanding on the mechanisms associated with efficacy of PAS-Na. The latter has been shown to modulate multifarious manganese- and lead- induced neurotoxicity, via its anti-apoptotic and anti-inflammatory effects, as well as its ability to inhibit pyroptosis, and regulate abnormal autophagic processes. These observations provide novel scientific bases and new concepts for the treatment of lead, mercury, copper, thallium, as well as other toxic encephalopathies, and implicate PAS-Na as a compound with greater prospects for clinical medical application.

The physiological levels of epigallocatechin gallate (EGCG) enhance the Cd-induced oxidative stress and apoptosis in CHO-K1 cells

Currently, the increasing pollution of the environment by heavy metals is observed, caused both by natural factors and those related to human activity. They pose a significant threat to human health and life. It is therefore important to find an effective way of protecting organisms from their adverse effects. One potential product showing a protective effect is green tea. It has been shown that EGCG, which is found in large amounts in green tea, has strong antioxidant properties and can therefore protect cells from the adverse effects of heavy metals. Therefore, the aim of the study was to investigate the effect of EGCG on cells exposed to Cd. In the study, CHO-K1 cells (Chinese hamster ovary cell line) were treated for 24 h with Cd (5 and 10 µM) and EGCG (0.5 and 1 µM) together or separately. Cell viability, ATP content, total ROS activity, mitochondrial membrane potential and apoptosis potential were determined. The results showed that, in tested concentrations, EGCG enhanced the negative effect of Cd. Further analyses are needed to determine the exact mechanism of action of EGCG due to the small number of publications on the subject and the differences in the results obtained in the research.

A Comprehensive Analytical Review of Polyphenols: Evaluating Neuroprotection in Alzheimer's Disease

Alzheimer's Disease (AD), a prevalent neurodegenerative disorder, is the primary cause of dementia. Despite significant advancements in neuroscience, a definitive cure or treatment for this debilitating disease remains elusive. A notable characteristic of AD is oxidative stress, which has been identified as a potential therapeutic target. Polyphenols, secondary metabolites of plant origin, have attracted attention due to their potent antioxidant properties. Epidemiological studies suggest a correlation between the consumption of polyphenol-rich foods and the prevention of chronic diseases, including neurodegenerative disorders, which underscores the potential of polyphenols as a therapeutic strategy in AD management. Hence, this comprehensive review focuses on the diverse roles of polyphenols in AD, with a particular emphasis on neuroprotective potential. Scopus, ScienceDirect, and Google Scholar were used as leading databases for study selection, from 2018 to late March 2024. Analytical chemistry serves as a crucial tool for characterizing polyphenols, with a nuanced exploration of their extraction methods from various sources, often employing chemometric techniques for a holistic interpretation of the advances in this field. Moreover, this review examines current in vitro and in vivo research, aiming to enhance the understanding of polyphenols' role in AD, and providing valuable insights for forthcoming approaches in this context.

Unveiling Potential Neurotoxic Mechansisms: Pb-Induced Activation of CDK5-p25 Signaling Axis in Alzheimer's Disease Development, Emphasizing CDK5 Inhibition and Formation of Toxic p25 Species

Alzheimer's disease (AD) is a complex neurodegenerative disorder with an etiology influenced by various genetic and environmental factors. Heavy metals, such as lead (Pb), have been implicated in AD pathogenesis, but the underlying mechanisms remain poorly understood. This study investigates the potential neurodegenerative role of Pb and amyloid β peptides (1-40 and 25-35) via their interaction with cyclin-dependent kinase 5 (CDK5) and its activator, p25, in an attempt to unravel the molecular basis of Pb-induced neurotoxicity in neuronal cells. To this end, a CDK5 inhibitor was utilized to selectively inhibit CDK5 activity and investigate its impact on neurodegeneration. The results revealed that Pb exposure led to elevated Pb uptake (56.7% at 15 μM Pb) and disturbances in intracellular calcium (19.6% increase upon Pb treatment). The results revealed a significant decrease in total antioxidant capacity (by 88.6% upon Pb treatment) and also elevation in protein carbonylation (by 26.2% upon Pb and Aβp's combination treatment), indicative of oxidative damage, suggesting an impaired cellular defence against oxidative stress and elevated DNA oxidative damage (178 pg/ml and 182 pg/ml of 8-OH-dG upon Pb and All treatment). Additionally, dysregulations in levels of calpain, p25-35 and CDK5 are observed and markers associated with antioxidant metabolism (phospho-Peroxiredoxin 1), DNA damage responses (phospho-ATM and phospho-p53), and nuclear membrane disruption (phospho-lamin A/C) were observed, supporting the role of Pb-induced CDK5-p25 signaling in AD pathogenesis. These findings shed light on the intricate molecular events underlying Pb-induced neurotoxicity and provide valuable insights into the mechanisms that contribute to AD development.

Heavy Metal Mediated Progressive Degeneration and Its Noxious Effects on Brain Microenvironment

Heavy metals, including lead (Pb), cadmium (Cd), arsenic (As), cobalt (Co), copper (Cu), manganese (Mn), zinc (Zn), and others, have a significant impact on the development and progression of neurodegenerative diseases in the human brain. This comprehensive review aims to consolidate the recent research on the harmful effects of different metals on specific brain cells such as neurons, microglia, astrocytes, and oligodendrocytes. Understanding the potential influence of these metals in neurodegeneration is crucial for effectively combating the ongoing advancement of these diseases. Metal-induced neurodegeneration involves molecular mechanisms such as apoptosis induction, dysregulation of metabolic and signaling pathways, metal imbalance, oxidative stress, loss of synaptic transmission, pathogenic peptide aggregation, and neuroinflammation. This review provides valuable insights by compiling the supportive evidence from recent research findings. Additionally, we briefly discuss the modes of action of natural neuroprotective compounds. While this comprehensive review aims to consolidate the recent research on the harmful effects of various metals on specific brain cells, it may not cover all studies and findings related to metal-induced neurodegeneration. Studies that are done using bioinformatics tools, microRNAs, long non-coding RNAs, emerging disease models, and studies based on the modes of exposure to toxic metals are a future prospect to be explored.

Mitochondria-Mediated Moderation of Apoptosis by EGCG in Cytotoxic Neuronal Cells Induced by Lead (Pb) and Amyloid Peptides

The developmental, epigenetic, and epidemiological studies on lead (Pb) toxicity have reported a strong connection between lead exposure and the progression of Alzheimer's disease (AD). The amyloid peptides were the main triggering elements, in the generation of extracellular plaques through which multiple cellular signaling events such as apoptosis and primarily oxidant-antioxidant balancing system will be affected, which leads to neuronal cell death. Our previous studies indicated that epigallocatechin gallate (EGCG), abundantly present in green tea, was found to be effective in alleviating the metal-induced neurotoxicity at the cellular level in terms of cell viability and apoptosis The aim of this study was to explore the protective mechanism of EGCG on the markers of oxidant-antioxidant system and mitochondria, which are involved in metal-induced neuronal cell death. Initially, the IC₅₀ values for lead(Pb-5 µM), amyloid peptides (AP(1-40)-60 µM; AP(1-40)-8 µM), and EC₅₀ value for EGCG(50 µM) were determined by both time- (12 h, 24 h, 48 h) and concentration-dependent manner and analyzed by MTT assay. The experimental groups were designed initially by treating with Pb and APs individually and in different combinations along with the presence of EGCG and are compared to the Pb and AP treated group without EGCG exposure. The cell lysates were used for analyzing oxidative stress markers by standardized laboratory protocol and the expression of mitochondrial markers such as VDAC and cytochrome C which were analyzed by both western blot and real-time PCR. Our results indicate that the EGCG-treated group has shown a significant increase in antioxidant marker expression levels (GSH, SOD, catalase, vitamin C) and a decrease in oxidative stress marker (NOS, MDA) levels when compared to the group without EGCG treatment (p < 0.05). Similarly, a significant decrease in expression levels of VDAC and cytochrome c were observed in the EGCG-treated group when compared to the group without EGCG treatment (p < 0.05). Our approach revealed that EGCG protects SH-SY5Y cells from Pb- and AP-induced cytotoxicity by regulating voltage-dependent anion channel (VDAC) expression and oxidant-antioxidant system and inhibits neuronal cell death.

Green Tea Polyphenol Epigallocatechin-Gallate in Amyloid Aggregation and Neurodegenerative Diseases

The accumulation of protein aggregates in human tissues is a hallmark of more than 40 diseases called amyloidoses. In seven of these disorders, the aggregation is associated with neurodegenerative processes in the central nervous system such as Alzheimer’s disease (AD), Parkinson’s disease (PD), and Huntington’s disease (HD). The aggregation occurs when certain soluble proteins lose their physiological function and become toxic amyloid species. The amyloid assembly consists of protein filament interactions, which can form fibrillar structures rich in β-sheets. Despite the frequent incidence of these diseases among the elderly, the available treatments are limited and at best palliative, and new therapeutic approaches are needed. Among the many natural compounds that have been evaluated for their ability to prevent or delay the amyloidogenic process is epigallocatechin-3-gallate (EGCG), an abundant and potent polyphenolic molecule present in green tea that has extensive biological activity. There is evidence for EGCG’s ability to inhibit the aggregation of α-synuclein, amyloid-β, and huntingtin proteins, respectively associated with PD, AD, and HD. It prevents fibrillogenesis (in vitro and in vivo), reduces amyloid cytotoxicity, and remodels fibrils to form non-toxic amorphous species that lack seed propagation. Although it is an antioxidant, EGCG in an oxidized state can promote fibrils’ remodeling through formation of Schiff bases and crosslinking the fibrils. Moreover, microparticles to drug delivery were synthesized from oxidized EGCG and loaded with a second anti-amyloidogenic molecule, obtaining a synergistic therapeutic effect. Here, we describe several pre-clinical and clinical studies involving EGCG and neurodegenerative diseases and their related mechanisms.

Plant Polyphenols: Potential Antidotes for Lead Exposure

Lead is one of the most common heavy metal elements and has high biological toxicity. Long-term lead exposure will induce the contamination of animal feed, water, and food, which can cause chronic lead poisoning including nephrotoxicity, hepatotoxicity, neurotoxicity, and reproductive toxicity in humans and animals. In the past few decades, lead has caused widespread concern because of its significant threat to health. A large number of in vitro and animal experiments have shown that oxidative stress plays a key role in lead toxicity, and endoplasmic reticulum (ER) stress and the mitochondrial apoptosis pathway can also be induced by lead toxicity. Therefore, plant polyphenols have attracted attention, with their advantages of being natural antioxidants and having low toxicity. Plant polyphenols can resist lead toxicity by chelating lead with their special chemical molecular structure. In addition, scavenging active oxygen and improving the level of antioxidant enzymes, anti-inflammatory, and anti-apoptosis are also the key to relieving lead poisoning by plant polyphenols. Various plant polyphenols have been suggested to be useful in alleviating lead toxicity in animals and humans and are believed to have good application prospects.

Lead exposure and its association with neurological damage: systematic review and meta-analysis

Lead (Pb) is one of the most toxic and abundant elements in the earth's crust, which is pointed out that the intoxication caused by it may damage biological systems. This systematic review with meta-analysis aimed to evaluate the association between Pb exposure and neurological damage. This work was executed according to PRISMA guidelines, and seven online databases were consulted. Based on the PECO strategy, studies presenting humans as participants (populations) exposed to Pb (exposure) compared to non-exposed to Pb (control) evaluating the neurological impairment (outcome) were included. The quality and risk of bias were verified by Fowkes and Fulton checklist. Two meta-analyses were conducted considering Digit Symbol and Profile Mood tests. The certainty of the evidence was evaluated with the GRADE tool. This review identified 2019 studies, of which 12 were eligible according to the inclusion criteria. Eight were considered with a low risk of bias. All the studies elected showed that exposure to Pb is associated with neurological damage, but the meta-analysis did not show any difference for the evaluated tests, and the certainty of the evidence was considered very low. Nevertheless, the included studies showed that Pb occupational exposure is associated with neurological damage, and the main parameters evaluated for possible neurological damage were related to mnemonic aspects, reaction time, intelligence, attention disorders, and mood changes. Thus, our results revealed that a definitive demonstration of an association of Pb and neurological changes in humans is still a pending issue. Future studies should take into consideration more confident methods to answer this question.

Epigallocatechin Gallate for Management of Heavy Metal-Induced Oxidative Stress: Mechanisms of Action, Efficacy, and Concerns

In this review, we highlight the effects of epigallocatechin gallate (EGCG) against toxicities induced by heavy metals (HMs). This most active green tea polyphenol was demonstrated to reduce HM toxicity in such cells and tissues as testis, liver, kidney, and neural cells. Several protective mechanisms that seem to play a pivotal role in EGCG-induced effects, including reactive oxygen species scavenging, HM chelation, activation of nuclear factor erythroid 2-related factor 2 (Nrf2), anti-inflammatory effects, and protection of mitochondria, are described. However, some studies, especially in vitro experiments, reported potentiation of harmful HM actions in the presence of EGCG. The adverse impact of EGCG on HM toxicity may be explained by such events as autooxidation of EGCG, EGCG-mediated iron (Fe3+) reduction, depletion of intracellular glutathione (GSH) levels, and disruption of mitochondrial functions. Furthermore, challenges hampering the potential EGCG application related to its low bioavailability and proper dosing are also discussed. Overall, in this review, we point out insights into mechanisms that might account for both the beneficial and adverse effects of EGCG in HM poisoning, which may have a bearing on the design of new therapeutics for HM intoxication therapy.

Epigallocatechin-3-Gallate Plus Omega-3 Restores the Mitochondrial Complex I and F0F1-ATP Synthase Activities in PBMCs of Young Children with Down Syndrome: A Pilot Study of Safety and Efficacy

Down syndrome (DS) is a major genetic cause of intellectual disability. DS pathogenesis has not been fully elucidated, and no specific pharmacological therapy is available. DYRK1A overexpression, oxidative stress and mitochondrial dysfunction were described in trisomy 21. Epigallocatechin-3-gallate (EGCG) is a multimodal nutraceutical with antioxidant properties. EGCG inhibits DYRK1A overexpression and corrects DS mitochondrial dysfunction in vitro. The present study explores safety profiles in DS children aged 1–8 years treated with EGCG (10 mg/kg/die, suspended in omega-3, per os, in fasting conditions, for 6 months) and EGCG efficacy in restoring mitochondrial complex I and F₀F₁-ATP synthase (complex V) deficiency, assessed on PBMCs. The Griffiths Mental Developmental Scales—Extended Revised (GMDS-ER) was used for developmental profiling. Results show that decaffeinated EGCG (>90%) plus omega-3 is safe in DS children and effective in reverting the deficit of mitochondrial complex I and V activities. Decline of plasma folates was observed in 21% of EGCG-treated patients and should be carefully monitored. GMDS-ER scores did not show differences between the treated group compared to the DS control group. In conclusion, EGCG plus omega-3 can be safely administered under medical supervision in DS children aged 1–8 years to normalize mitochondria respiratory chain complex activities, while results on the improvement of developmental performance are still inconclusive.

EGCG Upregulates UCP3 Levels to Protect MIN6 Pancreatic Islet Cells from Interleukin-1β-Induced Apoptosis

Objective

The protective effects of epigallocatechin gallate (EGCG) on interleukin-1β (IL-1β)-induced apoptosis were investigated in murine MIN₆ pancreatic β-cells. The role of uncoupling protein-3 (UCP₃) signaling in this process was also explored.

Methods

After treatment with IL-1β and EGCG, cells were collected and analyzed. Cell viability was measured using the CCK₈ assay and the function of β-cells was evaluated by analyzing insulin secretion. Detection of mitochondrial function in cells was performed by measuring mitochondrial membrane potential, the concentration of ATP and activity of ROS. Apoptosis was analyzed by Hochest33258 staining and flow cytometry. Expression levels of UCP₃ were interrogated using immunohistochemistry, RT-PCR and Western blotting.

Results

Compared with the control group, IL-1β treatment (20nM) for 24 h significantly decreased cell viability and insulin secretion, damaged mitochondrial function and increased ROS activity. Results also showed increased apoptosis and a decrease in UCP₃ expression levels (p<0.01). However, treatment with low (1mM) or high (5mM) concentrations of EGCG significantly decreased IL-1β-induced apoptosis (p<0.01), restored mitochondrial function and subsequently increased UCP₃ levels in IL-1β-induced β-cells (p<0.01).

Conclusion

These results suggest that EGCG protects against IL-1β-induced mitochondrial injury and apoptosis in β-cells through the up-regulation of UCP₃.

Molecular and Cellular Substrates for the Friedreich Ataxia. Significance of Contactin Expression and of Antioxidant Administration

In this study, the neural phenotype is explored in rodent models of the spinocerebellar disorder known as the Friedreich Ataxia (FA), which results from mutations within the gene encoding the Frataxin mitochondrial protein. For this, the M12 line, bearing a targeted mutation, which disrupts the Frataxin gene exon 4 was used, together with the M02 line, which, in addition, is hemizygous for the human Frataxin gene mutation (Pook transgene), implying the occurrence of 82-190 GAA repeats within its first intron. The mutant mice phenotype was compared to the one of wild type littermates in regions undergoing differential profiles of neurogenesis, including the cerebellar cortex and the spinal cord by using neuronal (β-tubulin) and glial (Glial Fibrillary Acidic Protein) markers as well as the Contactin 1 axonal glycoprotein, involved in neurite growth control. Morphological/morphometric analyses revealed that while in Frataxin mutant mice the neuronal phenotype was significantly counteracted, a glial upregulation occurred at the same time. Furthermore, Contactin 1 downregulation suggested that changes in the underlying gene contributed to the disorder pathogenesis. Therefore, the FA phenotype implies an alteration of the developmental profile of neuronal and glial precursors. Finally, epigallocatechin gallate polyphenol administration counteracted the disorder, indicating protective effects of antioxidant administration.