Epigallocatechin gallate exacerbates fluoride-induced oxidative stress mediated testicular toxicity in rats through the activation of Nrf2 signaling pathway

Activation of Nrf-2 Transcription Factor and Caspase Pathway with Royal Jelly Reduces Fluoride Induced Testicular Damage and Infertility in Rats

This study was carried out to investigate the protective properties of royal jelly on the testicular tissue of rats with testicular damage by giving fluoride. Sperm motility, epididymal sperm density and abnormal sperm ratios were examined and visualized with a light microscope. Expression levels of Caspase-3, Bcl-2, Nrf-2, NF-κB, COX-2, TNF-α and IL1-α proteins in testis tissue were determined by western blot technique. As a result of the study, MDA level, expression level of Bcl-2, NFҡB, COX-2, TNF-α and IL1-α proteins, abnormal sperm rates were found higher in Fluoride-50 and Fluoride100 groups compared to other groups. In addition GSH, Catalase enzyme levels, expression levels of Caspase-3 and Nrf-2 proteins were found to be higher in Fluoride + Royal Jelly groups compared to Fluoride-50 and Fluoride-100 groups. In addition, lower degeneration of testicular tissue was found in the histological evaluation in the Fluoride + Royal Jelly groups compared to the other groups. When the data are evaluated royal jelly provides effective protection against testicular damage. From this point of view, we hope that similar results will be obtained when royal jelly is tested on humans.

Role of oxidative stress-mediated cell death and signaling pathways in experimental fluorosis

Free radicals and other oxidants have enticed the interest of researchers in the fields of biology and medicine, owing to their role in several pathophysiological conditions, including fluorosis (Fluoride toxicity). Radical species affect cellular biomolecules such as nucleic acids, proteins, and lipids, resulting in oxidative stress. Reactive oxygen species-mediated oxidative stress is a common denominator in fluoride toxicity. Fluorosis is a global health concern caused by excessive fluoride consumption over time. Fluoride alters the cellular redox homeostasis, and its toxicity leads to the activation of cell death mechanisms like apoptosis, autophagy, and necroptosis. Even though a surfeit of signaling pathways is involved in fluorosis, their toxicity mechanisms are not fully understood. Thus, this review aims to understand the role of reactive species in fluoride toxicity with an outlook on the effects of fluoride in vitro and in vivo models. Also, we emphasized the signal transduction pathways and the mechanism of cell death implicated in fluoride-induced oxidative stress.

Antioxidant Phytochemicals for the Prevention of Fluoride-Induced Oxidative Stress and Apoptosis: a Review

Fluorosis is a major public health problem globally. The non-availability of specific treatment and the irreversible nature of dental and skeletal lesions poses a challenge in the management of fluorosis. Oxidative stress is known to be one of the most important mechanisms of fluoride toxicity. Fluoride promotes the accumulation of reactive oxygen species by inhibiting the activity of antioxidant enzymes, resulting in the excessive production of reactive oxygen species at the cellular level which further leads to activation of cell death processes such as apoptosis. Phytochemicals that act as antioxidants have the potential to protect cells from oxidative stress. Evidence confirms that clinical symptoms of fluorosis can be mitigated to some extent or prevented by long-term intake of antioxidants and plant products. The primary purpose of this review is to examine recent findings that focus on the amelioration of fluoride-induced oxidative stress and apoptosis by natural and synthetic phytochemicals and their molecular mechanisms of action.

(-)-Epigallocatechin-3-O-gallate at a high concentration may induce lipolysis via ATP consumption by activation of stress defense mechanisms

Green tea catechins have thus far been demonstrated to have antiobesity effects in a variety of experimental models. However, upstream molecular events triggering those phenomena remain to be identified. In this study, we found that (-)-epigallocatechin-3-O-gallate (EGCG) promoted lipolysis in lipid-loaded Huh7 human hepatoma cells. Notably, EGCG at a high concentration induced both oxidative stress and protein stress (proteo-stress), leading to activation of stress defense mechanisms, such as mRNA expressions of antioxidant and phase-2 detoxifying enzymes, and heat shock proteins. Furthermore, EGCG decreased the level of intracellular ATP, while glucose uptake from culture media was promoted possibly for energy homeostasis. EGCG also upregulated the expression of adipose triglyceride lipase, and activated AMP-activated protein kinase. Collectively, these results suggest that EGCG induces lipolysis to compensate for ATP reduction derived from activation of stress defense systems against its oxidative and proteo-stress properties.

Fluoride induced testicular toxicities in adult Wistar rats

Fluoride is essential for the development of teeth and bone but its excessive exposure causes reprotoxic effects. We have studied the graded effects of different doses of sodium fluoride (NaF) on 24 adult Wistar rats which were randomly divided into four groups (n = 6). All the rats were given normal diet prepared in our laboratory. Control (group I) rats were received vehicle only and treated rats (group II, III, and IV) were administered NaF orally at 10, 15, and 20 mg/kg/d doses, respectively, for 30 consecutive days. Gravimetric index of testis was decreased significantly in group III and IV rats but such changes were not observed in the accessory reproductive organs. Marked alterations in number, motility, viability, and plasma membrane functional integrity of caudal spermatozoa were noted in most of the treated groups. Noticeable alterations in testicular histoarchitecture were observed in group III and IV rats. Graded Changes of testicular redox homeostasis were noted by assessment of enzymatic (superoxide dismutase [SOD], catalase, glutathione s-transferase [GST], and glutathione peroxidase [GPx]) and nonenzymatic (malondialdehyde [MDA] and protein carbonyl [PC]) markers. Changes of testicular functional markers (acid phosphatase [ACP], alkaline phosphatase [ALP], and lactate dehydrogenase (LDH) activity) were noted in group III and IV rats. DNA fragmentation assay proved the possibility of DNA damage caused by oxidative stress, as evidenced by prominent trailing pattern of fragmented testicular genomic DNA from group III and IV rats. The study concludes that fluoride-mediated oxidative stress not only impedes the structural and functional facets of testis but also results in testicular DNA damage.

New insights into the role of the Nrf2 signaling pathway in green tea catechin applications

Nuclear factor-erythroid 2-related factor 2 (Nrf2) is a transcriptional signaling pathway that plays a crucial role in numerous clinical complications. Pivotal roles of Nrf2 have been proved in cancer, autoimmune diseases, neurodegeneration, cardiovascular diseases, diabetes mellitus, renal injuries, respiratory conditions, gastrointestinal disturbances, and general disorders related to oxidative stress, inflammation, apoptosis, gelatinolysis, autophagy, and fibrogenesis processes. Green tea catechins as a rich source of phenolic compounds can deal with various clinical problems and manifestations. In this review, we attempted to focus on intervention between green tea catechins and Nrf2. Green tea catechins especially epigallocatechin gallate (EGCG) elucidated the protective role of Nrf2 and its downstream molecules in various disorders through Keap-1, HO-1, NQO-1, GPx, GCLc, GCLm, NF-kB cross-link, kinases, and apoptotic proteins. Subsequently, we compiled an updated expansions of the Nrf2 role as a gate to manage and protect different disorders and feasible indications of green tea catechins through this signaling pathway. The present review highlighted recent evidence-based data in silico, in vitro, and in vivo studies on an outline for future clinical trials.

A review for physiological activities of EGCG and the role in improving fertility in humans/mammals

Epigallocatechin-3-gallate (EGCG) is a secondary metabolite in green tea, which has various physiological activities, including antioxidant, antitumor, and antiviral activities. Studies have shown that EGCG has a preventive effect on infertility by protecting germ cells and oocytes from damage. EGCG functions mainly through the regulation of ROS (reactive oxygen species) levels, which affect the expression of catalase (CAT), superoxide dismutase 1(SOD1), superoxide dismutase 2(SOD2), and glutathione peroxidase (GPx), has positive influence on other enzyme activities in germ cells and oocytes, and actively alters antioxidant activities. These enzymes above can inhibit the activation of extracellular signal-regulated proteins (Erk), induce apoptosis, and control the production of ROS in tissue cells. Here, we present a comprehensive overview of the mechanisms underlying the main physiological activities of EGCG, including antioxidant, antitumor, and antiviral activities, and their potential roles in male and female reproductive systems and fertility. This paper discusses the mechanisms by which EGCG retards the infertility of germ cells and oocytes and provides a supportive recommendation for improving fertility in humans and animals. We hope it will provide useful references for related research in mammalian reproduction.

Recent Advances of Natural Polyphenols Activators for Keap1-Nrf2 Signaling Pathway

The Keap1-Nrf2/ARE signaling pathway is an important defense system against exogenous and endogenous oxidative stress injury. The dysregulation of the signaling pathway is associated with many diseases, such as cancer, diabetes, and respiratory diseases. Over the years, a wide range of natural products has provided sufficient resources for the discovery of potential therapeutic drugs. Among them, polyphenols possess Nrf2 activation, not only inhibit the production of ROS, inhibit Keap1-Nrf2 protein-protein interaction, but also degrade Keap1 and regulate the Nrf2 related pathway. In fact, with the continuous improvement of natural polyphenols separation and purification technology and further studies on the Keap1-Nrf2 molecular mechanism, more and more natural polyphenols monomer components of Nrf2 activators have been gradually discovered. In this view, we summarize the research status of natural polyphenols that have been found with apparent Nrf2 activation and their action modes. On the whole, this review may guide the design of novel Keap1-Nrf2 activator.

Fluoride Exposure Induces Inhibition of Sodium/Iodide Symporter (NIS) Contributing to Impaired Iodine Absorption and Iodine Deficiency: Molecular Mechanisms of Inhibition and Implications for Public Health

The sodium iodide symporter (NIS) is the plasma membrane glycoprotein that mediates active iodide transport in the thyroid and other tissues, such as the salivary, gastric mucosa, rectal mucosa, bronchial mucosa, placenta and mammary glands. In the thyroid, NIS mediates the uptake and accumulation of iodine and its activity is crucial for the development of the central nervous system and disease prevention. Since the discovery of NIS in 1996, research has further shown that NIS functionality and iodine transport is dependent on the activity of the sodium potassium activated adenosine 5'-triphosphatase pump (Na+, K+-ATPase). In this article, I review the molecular mechanisms by which F inhibits NIS expression and functionality which in turn contributes to impaired iodide absorption, diminished iodide-concentrating ability and iodine deficiency disorders. I discuss how NIS expression and activity is inhibited by thyroglobulin (Tg), tumour necrosis factor alpha (TNF-α), transforming growth factor beta 1 (TGF-β1), interleukin 6 (IL-6) and Interleukin 1 beta (IL-1β), interferon-γ (IFN-γ), insulin like growth factor 1 (IGF-1) and phosphoinositide 3-kinase (PI3K) and how fluoride upregulates expression and activity of these biomarkers. I further describe the crucial role of prolactin and megalin in regulation of NIS expression and iodine homeostasis and the effect of fluoride in down regulating prolactin and megalin expression. Among many other issues, I discuss the potential conflict between public health policies such as water fluoridation and its contribution to iodine deficiency, neurodevelopmental and pathological disorders. Further studies are warranted to examine these associations.

The Contribution of Fluoride to the Pathogenesis of Eye Diseases: Molecular Mechanisms and Implications for Public Health

This study provides diverse lines of evidence demonstrating that fluoride (F) exposure contributes to degenerative eye diseases by stimulating or inhibiting biological pathways associated with the pathogenesis of cataract, age-related macular degeneration and glaucoma. As elucidated in this study, F exerts this effect by inhibiting enolase, τ-crystallin, Hsp40, Na⁺, K⁺-ATPase, Nrf2, γ -GCS, HO-1 Bcl-2, FoxO1, SOD, PON-1 and glutathione activity, and upregulating NF-κB, IL-6, AGEs, HsP27 and Hsp70 expression. Moreover, F exposure leads to enhanced oxidative stress and impaired antioxidant activity. Based on the evidence presented in this study, it can be concluded that F exposure may be added to the list of identifiable risk factors associated with pathogenesis of degenerative eye diseases. The broader impact of these findings suggests that reducing F intake may lead to an overall reduction in the modifiable risk factors associated with degenerative eye diseases. Further studies are required to examine this association and determine differences in prevalence rates amongst fluoridated and non-fluoridated communities, taking into consideration other dietary sources of F such as tea. Finally, the findings of this study elucidate molecular pathways associated with F exposure that may suggest a possible association between F exposure and other inflammatory diseases. Further studies are also warranted to examine these associations.

Fluoride induced tissue hypercalcemia, IL-17 mediated inflammation and apoptosis lead to cardiomyopathy: Ultrastructural and biochemical findings

An increased prevalence of cardiac complications has been observed in residents of fluorosis endemic areas chronically exposed to fluoride. Fluoride induces soft tissue injury due to oxidative stress, lipid peroxidation (LPO) and mitochondriopathy. It was hypothesized that chronic fluoride exposure induces apoptosis in cardiomyocytes due to inflammation, lysis of extra cellular matrix and altered calcium metabolism. This study was planned to evaluate the effects of chronic fluoride exposure and the mechanism of action in the cardiac muscle. Fifteen week old male Wistar rats were administered a human equivalent dose of fluoride (50 and 100 ppm ad-libitum, HED = 5 & 10 ppm in human) for 75-days. After 75-days of fluoride exposure, the animals were euthanized and fluoride, oxidative stress (SOD, GPX, Catalase activities) and LPO were measured. Histopathological and ultrastructural pathological examinations were conducted on the cardiac tissues using light, atomic force and electron microscopies. The cardiac tissues were also assessed for apoptosis (TUNEL/Caspase assays), and tissue calcium levels (Alizarin-assay and SEM-EDX). Tissue inflammation and expression of IL-17, MMP-9, Caspase-3 and Bcl-2 were evaluated. In the fluoride exposed groups, a significant (≤0.05) increase in levels of oxidative stress, LPO and apoptosis were observed. The IL-17, MMP-9 and Caspase-3 were significantly (≤0.05) higher in the cardiac muscle after chronic fluoride exposure. The fluoride seems to have induced inflammation in the cardiac tissues, as well as an increase in tissue calcium (≤0.05). There was significant damage to cardiac muscle fibres including, thinning, distortion and neo-vasculogenesis following chronic fluoride exposure. Mitochondriopathy, lysis of ground substance, oedema, and hyper-vacuolation was seen in fluoride treated groups. Remarkable levels of distortion and bending in Z band were observed under the AFM. Many of these observed changes mimic those occurring in cardiomegaly, cardiac hypertrophy and cardiomyopathies.

Black Tea Source, Production, and Consumption: Assessment of Health Risks of Fluoride Intake in New Zealand

In countries with fluoridation of public water, it is imperative to determine other dietary sources of fluoride intake to reduce the public health risk of chronic exposure. New Zealand has one of the highest per capita consumption rates of black tea internationally and is one of the few countries to artificially fluoridate public water; yet no information is available to consumers on the fluoride levels in tea products. In this study, we determined the contribution of black tea as a source of dietary fluoride intake by measuring the fluoride content in 18 brands of commercially available products in New Zealand. Fluoride concentrations were measured by potentiometric method with a fluoride ion-selective electrode and the contribution of black tea to Adequate Intake (AI) and Tolerable Upper Intake Level (UL) was calculated for a range of consumption scenarios. We examined factors that influence the fluoride content in manufactured tea and tea infusions, as well as temporal changes in fluoride exposure from black tea. We review the international evidence regarding chronic fluoride intake and its association with chronic pain, arthritic disease, and musculoskeletal disorders and provide insights into possible association between fluoride intake and the high prevalence of these disorders in New Zealand.

Attenuation of perfluorooctanoic acid-induced testicular oxidative stress and apoptosis by quercetin in mice

Quercetin treatment attenuated PFOA-induced oxidative stress and apoptosis in the testes of mice.