Potent protective effect of melatonin on in vivo paraquat-induced oxidative damage in rats

Melatonin and oral diseases: possible therapeutic roles based on cellular mechanisms

Oral diseases, including periodontal disorders, oral cancer, periodontitis, and mucositis are the major challenges for both patients and healthcare providers. These conditions often involve inflammation, oxidative stress, and impaired cellular processes, leading to symptoms ranging from discomfort to severe debilitation. Conventional treatments for such oral diseases exhibit constraints, prompting the investigation of innovative therapeutic approaches. Considering the anti-inflammatory, anti-oxidant, and anti-cancer effects of melatonin, this study was carried out to investigate the potential protective effects of melatonin in mitigating the severity of oral diseases. Studies indicate that melatonin influences the differentiation of periodontal stem cells, inhibits oral cancer progression, reduces inflammation associated with periodontitis, and alleviates the severity of oral mucositis. Melatonin has demonstrated potential efficacy in both preclinical and clinical investigations; however, findings are frequently heterogeneous and contingent upon contextual factors. This review provides a comprehensiveoverview of current state of knowledge in this domain, elucidating the multifaceted role that melatonin may assume in combatingoral diseases. Further research should be directed toward determining the most effective dosing, timing, and administration methods for melatonin-based therapies for oral diseases.

Dual sources of melatonin and evidence for different primary functions

This article discusses data showing that mammals, including humans, have two sources of melatonin that exhibit different functions. The best-known source of melatonin, herein referred to as Source #1, is the pineal gland. In this organ, melatonin production is circadian with maximal synthesis and release into the blood and cerebrospinal fluid occurring during the night. Of the total amount of melatonin produced in mammals, we speculate that less than 5% is synthesized by the pineal gland. The melatonin rhythm has the primary function of influencing the circadian clock at the level of the suprachiasmatic nucleus (the CSF melatonin) and the clockwork in all peripheral organs (the blood melatonin) via receptor-mediated actions. A second source of melatonin (Source # 2) is from multiple tissues throughout the body, probably being synthesized in the mitochondria of these cells. This constitutes the bulk of the melatonin produced in mammals and is concerned with metabolic regulation. This review emphasizes the action of melatonin from peripheral sources in determining re-dox homeostasis, but it has other critical metabolic effects as well. Extrapineal melatonin synthesis does not exhibit a circadian rhythm and it is not released into the blood but acts locally in its cell of origin and possibly in a paracrine matter on adjacent cells. The factors that control/influence melatonin synthesis at extrapineal sites are unknown. We propose that the concentration of melatonin in these cells is determined by the subcellular redox state and that melatonin synthesis may be inducible under stressful conditions as in plant cells.

Impact of organophosphate pesticides exposure on human semen parameters and testosterone: a systematic review and meta-analysis

Background

Organophosphate (OP) pesticides have been associated with a decline in semen quality, although there are still considerable arguments about the magnitude of the association.

Objective

This study provides a systematic review and meta-analysis of the impacts of OP pesticides on semen quality and male reproductive hormones.

Methods

This study was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocols. Strategic search was conducted using combined text words as search terms. The eligibility criteria were developed based on Population, Exposure, Comparator, Outcome, and Study designs (PECOS) framework. Relevant data were extracted, risk of bias was evaluated by The Office of Health Assessment and Translation (OHAT) tool, and certainty of evidence was assessed by the Grading of Recommendations Assessment, Development and Evaluation (GRADE) Working Group guidelines. Quantitative meta-analysis was performed by using Review Manager.

Results

A total of 766 male subjects (349 exposed to OP pesticides and 417 unexposed controls) were included in the meta-analysis. There was no significant difference in the ejaculate volume, seminal fluid volume, sperm multiple anomaly index, sperm, and leukocytes levels of the OP-exposed subjects compared to the control. In addition, OP pesticides exposure did not significantly affect serum concentrations of FSH, LH, and testosterone in subjects who were exposed to OP pesticides compared to their unexposed counterparts. However, we found a significant reduction in the sperm count, sperm concentration, progressive sperm motility, total sperm motility, and normal sperm morphology of OP pesticides-exposed subjects compared to the unexposed subjects. However, after subtype and sensitivity analyses, exposure to OP pesticides did not reduce sperm count. Also, after sensitivity analysis, OP pesticides exposure did not alter progressive sperm motility.

Conclusion

This study demonstrates that OP pesticides exposure reduced sperm count, concentration, total and progressive motility, and normal sperm morphology, possibly via a testosterone-independent mechanism.

Melatonin modulates tumor metabolism and mitigates metastasis

INTRODUCTION

Melatonin, originally isolated from the mammalian pineal gland, was subsequently identified in many animal cell types and in plants. While melatonin was discovered to inhibit cancer more than 5 decades ago, its anti-cancer potential has not been fully exploited despite its lack of serious toxicity over a very wide dose range, high safety margin, and its efficacy.

AREAS COVERED

This review elucidates the potential mechanisms by which melatonin interferes with tumor growth and metastasis, including its ability to alter tumor cell metabolism, inhibit epithelial-mesenchymal transition, reverse cancer chemoresistance, function synergistically with conventional cancer-inhibiting drugs while limiting many of their side effects. In contrast to its function as a potent antioxidant in normal cells, it may induce oxidative stress in cancer cells, contributing to its oncostatic actions.

EXPERT OPINION

Considering the large amount of experimental data supporting melatonin's multiple and varied inhibitory effects on numerous cancer types, coupled with the virtual lack of toxicity of this molecule, it has not been thoroughly tested as an anti-cancer agent in clinical trials. There seems to be significant resistance to such investigations, possibly because melatonin is inexpensive and non-patentable, and as a result there would be limited financial gain for its use.

Melatonin as a Possible Natural Anti-Viral Compound in Plant Biocontrol

Melatonin is a multifunctional and ubiquitous molecule. In animals, melatonin is a hormone that is involved in a wide range of physiological activities and is also an excellent antioxidant. In plants, it has been considered a master regulator of multiple physiological processes as well as of hormonal homeostasis. Likewise, it is known for its role as a protective biomolecule and activator of tolerance and resistance against biotic and abiotic stress in plants. Since infections by pathogens such as bacteria, fungi and viruses in crops result in large economic losses, interest has been aroused in determining whether melatonin plays a relevant role in plant defense systems against pathogens in general, and against viruses in particular. Currently, several strategies have been applied to combat infection by pathogens, one of them is the use of eco-friendly chemical compounds that induce systemic resistance. Few studies have addressed the use of melatonin as a biocontrol agent for plant diseases caused by viruses. Exogenous melatonin treatments have been used to reduce the incidence of several virus diseases, reducing symptoms, virus titer, and even eradicating the proliferation of viruses such as Tobacco Mosaic Virus, Apple Stem Grooving Virus, Rice Stripe Virus and Alfalfa Mosaic Virus in tomato, apple, rice and eggplant, respectively. The possibilities of using melatonin as a possible natural virus biocontrol agent are discussed.

Melatonin as a Possible Natural Safener in Crops

Melatonin is a well-known animal hormone with relevant and multiple cellular and hormonal roles. Its discovery in plants in 1995 has led to a great diversity of molecular and physiological studies that have been showing its multiple actions also in plants. Its roles as a biostimulator and modulator agent of responses to abiotic and biotic stresses have been widely studied. This review raises the possible use of melatonin as a natural safener in herbicide treatments. Existing studies have shown excellent co-acting qualities between both the following agents: herbicide and melatonin. The presence of melatonin reduces the damage caused by the herbicide in the crop and enhances the stress antioxidant response of plants. In this area, a similar role is suggested in the co-action between fungicides and melatonin, where a synergistic response has been demonstrated in some cases. The possible reduction in the fungicide doses is proposed as an eco-friendly advance in the use of these pesticides in certain crops. Finally, future research and applied actions of melatonin on these pest control agents are suggested.

Potentiating the Benefits of Melatonin through Chemical Functionalization: Possible Impact on Multifactorial Neurodegenerative Disorders

Although melatonin is an astonishing molecule, it is possible that chemistry will help in the discovery of new compounds derived from it that may exceed our expectations regarding antioxidant protection and perhaps even neuroprotection. This review briefly summarizes the significant amount of data gathered to date regarding the multiple health benefits of melatonin and related compounds. This review also highlights some of the most recent directions in the discovery of multifunctional pharmaceuticals intended to act as one-molecule multiple-target drugs with potential use in multifactorial diseases, including neurodegenerative disorders. Herein, we discuss the beneficial activities of melatonin derivatives reported to date, in addition to computational strategies to rationally design new derivatives by functionalization of the melatonin molecular framework. It is hoped that this review will promote more investigations on the subject from both experimental and theoretical perspectives.

Comparison of Pancreatic Damage in Rats for Two Methods of Paraquat Administration

It is noted that elevated serum amylase levels suggesting pancreatic damage has an association with prognosis in PQ patients. This study aimed to determine whether PQ can cause pancreatic damage. The two conventional models (intragastric infusion (iG) and intraperitoneal injection (iP)) may exhibit different effects on the pancreas depending on whether or not they pass through the digestive tract. In this study, the rats were divided into four groups: the intragastric infusion group (PQ-iG, n = 45), intraperitoneal injection group (PQ-iP, n = 53), normal control group 1 (NC-iG, n = 6) and normal control group 2 (NC-iP, n = 6). Pancreatic damage was compared between groups using serum amylase activity assay, hematoxylin and eosin (H&E) staining, TUNEL assay, and transmission electron microscopy (TEM). Serum amylase levels in group PQ-iG were significantly higher than in group PQ-iP (p < 0.05). Examination of the H&E sections showed damage to the pancreas. Both experimental groups were displayed inflammatory infiltration within 9 h of PQ treatment. After 9 h, patchy necrosis was observed in group PQ-iP, when inflammatory infiltration was still the dominant pathology. Necrosis appeared and gradually worsened in group PQ-iG, in which necrosis was the dominant pathology. The TUNEL assay showed significantly higher numbers of apoptotic cells in the pancreas of PQ-groups than in the control NC- groups (p < 0.05). TEM showed expansive endoplasmic reticulum lumens and mitochondria swelling in the pancreas of the PQ-groups. It is concluded that both methods of modeling could cause pancreatic damage and the type and degree of damage would change over time. Note that pancreatic damage in group PQ-iG was more severe than that in group PQ-iP. Therefore, clinical practitioners should pay close attention to pancreatic damage caused by PQ, especially when the route of PQ administration was oral.

Melatonin promotes male reproductive performance and increases testosterone synthesis in mammalian Leydig cells†

Leydig cells play a critical role in male reproductive physiology, and their dysfunction is usually associated with male infertility. Melatonin has an important protective and regulatory role in these cells. However, the lack of suitable animal models impedes us from addressing the impact of endogenous melatonin on these cells. In the current study, by using arylalkylamine N-acetyltransferase (AANAT) overexpression transgenic sheep and AANAT knockout mice, we confirmed the regulatory effects of endogenously occurring melatonin on Leydig cells as well as its beneficial effects on male reproductive performance. The results showed that the endogenously elevated melatonin level was correlated with decreased Leydig cell apoptosis, increased testosterone production, and improved quality of sperm in melatonin-enriched transgenic mammals. Signal transduction analysis indicated that melatonin targeted the mitochondrial apoptotic Bax/Bcl2 pathway and thus suppressed Leydig cell apoptosis. In addition, melatonin upregulated the expression of testosterone synthesis-related genes of Steroidogenic Acute Regulatory Protein (StAR), Steroidogenic factor 1 (SF1), and Transcription factor GATA-4 (Gata4) in Leydig cells. This action was primarily mediated by the melatonin nuclear receptor RAR-related orphan receptor alpha (RORα) since blockade of this receptor suppressed the effect of melatonin on testosterone synthesis. All of these actions of melatonin cause Leydig cells to generate more testosterone, which is necessary for spermatogenesis in mammals. In contrast, AANAT knockout animals have dysfunctional Leydig cells and reduced reproductive performance.

Protective effect of melatonin against herbicides-induced hepatotoxicity in rats

Exposure to the herbicides Paraquat and Roundup® may cause cell lesions due to an increase in oxidative stress levels in different biological systems, even in the liver. The aim of this study was to analyze the effect of melatonin on liver of rats exposed to herbicides. A total of 35 rats were randomly divided into seven equal-sized groups: control, Paraquat, Roundup®, Paraquat + Roundup®, Paraquat + melatonin, Roundup® + melatonin, and Paraquat + Roundup® + melatonin. Samples of blood and hepatic tissue were collected at the end of the seventh day of exposure and treatment with melatonin. Body weight, hematological parameters, and histopathological, biochemical analyses and determination of oxidative stress levels in liver were evaluated. Body weight was compromised (P < 0.01). Alterations of hematologic parameters were significant when compared to control (P < 0.001). Biochemically, serum levels of albumin decreased (P < 0.001), but serum levels of alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase increased (P < 0.001). Histopathology revealed necrotic hepatocytes, portal and central-lobular inflammatory infiltrate, congestion of capillaries. Serum levels of thiobarbituric acid reactive substances were found to be significantly elevated (P < 0.05; P < 0.001), and serum level of reduced glutathione was significantly lower (P < 0.05; P < 0.001). The groups treated concomitantly with melatonin revealed results similar to those of the control. However, melatonin acted as a protective agent for the liver against experimentally induced hepatic toxicity, promoting prevention of body weight, oxidative stress, and normalization of hematological and biochemical parameters.

Melatonin, aging, and COVID-19: Could melatonin be beneficial for COVID-19 treatment in the elderly?

The aim of this review is to summarize current studies on the relationship between melatonin and aging. Nowadays, age-related diseases come into prominence, and identifying age-related changes and developing proper therapeutic approaches are counted as some of the major issues regarding community health. Melatonin is the main hormone of the pineal gland. Melatonin is known to influence many biological processes in the body, including circadian rhythms, the immune system, and neuroendocrine and cardiovascular functions.Melatoninrhythms also reflect the biological process of aging. Aging is an extremely complex and multifactorial process. Melatonin levels decline considerably with aging and its decline is associated with several age-related diseases. Aging is closely associated with oxidative damage and mitochondrial dysfunction. Free radical reactions initiated by the mitochondria constitute the inherent aging process. Melatonin plays a pivotal role in preventing age-related oxidative stress. Coronavirus disease 2019 (COVID-19) fatality rates increase with chronic diseases and age, where melatonin levels decrease. For this reason, melatonin supplementation in elderly could be beneficial in COVID-19 treatment. Therefore, studies on the usage of melatonin in COVID-19 treatment are needed.

The Role of Oxidative Stress in Parkinson's Disease

Parkinson’s disease (PD) is caused by progressive neurodegeneration of dopaminergic (DAergic) neurons with abnormal accumulation of α-synuclein in substantia nigra (SN). Studies have suggested the potential involvement of dopamine, iron, calcium, mitochondria and neuroinflammation in contributing to overwhelmed oxidative stress and neurodegeneration in PD. Function studies on PD-causative mutations of SNCA, PRKN, PINK1, DJ-1, LRRK2, FBXO7 and ATP13A2 further indicate the role of oxidative stress in the pathogenesis of PD. Therefore, it is reasonable that molecules involved in oxidative stress, such as DJ-1, coenzyme Q10, uric acid, 8-hydroxy-2’-deoxyguanosin, homocysteine, retinoic acid/carotenes, vitamin E, glutathione peroxidase, superoxide dismutase, xanthine oxidase and products of lipid peroxidation, could be candidate biomarkers for PD. Applications of antioxidants to modulate oxidative stress could be a strategy in treating PD. Although a number of antioxidants, such as creatine, vitamin E, coenzyme Q10, pioglitazone, melatonin and desferrioxamine, have been tested in clinical trials, none of them have demonstrated conclusive evidence to ameliorate the neurodegeneration in PD patients. Difficulties in clinical studies may be caused by the long-standing progression of neurodegeneration, lack of biomarkers for premotor stage of PD and inadequate drug delivery across blood–brain barrier. Solutions for these challenges will be warranted for future studies with novel antioxidative treatment in PD patients.

Simultaneous Suppression of Two Distinct Serotonin N-Acetyltransferase Isogenes by RNA Interference Leads to Severe Decreases in Melatonin and Accelerated Seed Deterioration in Rice

Serotonin N-acetyltransferase (SNAT) is the penultimate enzyme in the melatonin biosynthetic pathway, in which serotonin is converted into N-acetylserotonin (NAS) in plants. To date, two SNAT isogenes with low amino acid sequence homologies have been identified. Their single suppression in rice has been reported, but their double suppression in rice has not yet been attempted. Here, we generated double-suppression transgenic rice (snat1+2) using the RNA interference technique. The snat1+2 exhibited retarded seedling growths in conjunction with severe decreases in melatonin compared to wild-types and single-suppression rice plants (snat1 or snat2). The laminar angle was decreased in the snat1+2 rice compared to that of the wild-types and snat1, but was comparable to that of snat2. The reduced germination speed in the snat1+2 was comparable to that of snat2. Seed-aging testing revealed that snat1 was the most severely deteriorated, followed by snat1+2 and snat2, suggesting that melatonin is positively involved in seed longevity.

Melatonin-loaded lipid-core nanocapsules protect against lipid peroxidation caused by paraquat through increased SOD expression in Caenorhabditis elegans

BACKGROUND

Melatonin has been described in the literature as a potent antioxidant. However, melatonin presents variable, low bioavailability and a short half-life. The use of polymeric nanoparticulated systems has been proposed for controlled release. Thus, the purpose of this study was to investigate the action of melatonin-loaded lipid-core nanocapsules (Mel-LNC) in the antioxidant system of Caenorhabditis elegans, and the possible protective effect of this formulation against lipid peroxidation caused by paraquat (PQ).

METHODS

The suspensions were prepared by interfacial deposition of the polymer and were physiochemically characterized. C. elegans N2 wild type and transgenic worm CF1553, muls84 [sod-3p::gfp; rol6(su1006)] were obtained from the Caenorhabditis Genetics Center (CGC). The worms were divided into 5 groups: Control, PQ 0.5 mM, PQ 0.5 mM + Mel-LNC 10 μg/mL, PQ + unloaded lipid-core nanocapsules (LNC), and PQ + free melatonin (Mel) 10 μg/mL. The lipid peroxidation was assessed through thiobarbituric acid (TBARS) levels and the fluorescence levels of the transgenic worms expressing GFP were measured.

RESULTS

The LNC and Mel-LNC presented a bluish-white liquid, with pH values of 5.56 and 5.69, respectively. The zeta potential was - 6.4 ± 0.6 and - 5.2 ± 0.2, respectively. The mean particle diameter was 205 ± 4 nm and 203 ± 3 nm, respectively. The total melatonin content was 0.967 mg/ml. The TBARS levels were significantly higher in the PQ group when compared to the control group (p < 0.001). Mel-LNC reduced TBARS levels to similar levels found in the control group. Moreover, only Mel-LNC significantly enhanced the SOD-3 expression (p < 0.05). Mel-LNC was capable of protecting C. elegans from lipid peroxidation caused by PQ and this was not observed when free melatonin was used. Moreover, Mel-LNC increased the fluorescence intensity of the transgenic strain that encodes the antioxidant enzyme SOD-3, demonstrating a possible mechanism of protection from PQ-induced damage.

CONCLUSION

These findings demonstrated that melatonin, when associated with nanocapsules, had improved antioxidant properties and the protective activity against PQ-induced lipid peroxidation could be associated with the activation of antioxidant enzymes by Mel-LNC in C. elegans.

Diplomats' Mystery Illness and Pulsed Radiofrequency/Microwave Radiation

Importance: A mystery illness striking U.S. and Canadian diplomats to Cuba (and now China) "has confounded the FBI, the State Department and US intelligence agencies" (Lederman, Weissenstein, & Lee, 2017). Sonic explanations for the so-called health attacks have long dominated media reports, propelled by peculiar sounds heard and auditory symptoms experienced. Sonic mediation was justly rejected by experts. We assessed whether pulsed radiofrequency/microwave radiation (RF/MW) exposure can accommodate reported facts in diplomats, including unusual ones. Observations: (1) Noises: Many diplomats heard chirping, ringing or grinding noises at night during episodes reportedly triggering health problems. Some reported that noises were localized with laser-like precision or said the sounds seemed to follow them (within the territory in which they were perceived). Pulsed RF/MW engenders just these apparent "sounds" via the Frey effect. Perceived "sounds" differ by head dimensions and pulse characteristics and can be perceived as located behind in or above the head. Ability to hear the "sounds" depends on high-frequency hearing and low ambient noise. (2) Signs/symptoms: Hearing loss and tinnitus are prominent in affected diplomats and in RF/MW-affected individuals. Each of the protean symptoms that diplomats report also affect persons reporting symptoms from RF/MW: sleep problems, headaches, and cognitive problems dominate in both groups. Sensations of pressure or vibration figure in each. Both encompass vision, balance, and speech problems and nosebleeds. Brain injury and brain swelling are reported in both. (3) Mechanisms: Oxidative stress provides a documented mechanism of RF/MW injury compatible with reported signs and symptoms; sequelae of endothelial dysfunction (yielding blood flow compromise), membrane damage, blood-brain barrier disruption, mitochondrial injury, apoptosis, and autoimmune triggering afford downstream mechanisms, of varying persistence, that merit investigation. (4) Of note, microwaving of the U.S. embassy in Moscow is historically documented. Conclusions and relevance: Reported facts appear consistent with pulsed RF/MW as the source of injury in affected diplomats. Nondiplomats citing symptoms from RF/MW, often with an inciting pulsed-RF/MW exposure, report compatible health conditions. Under the RF/MW hypothesis, lessons learned for diplomats and for RF/MW-affected civilians may each aid the other.

Melatonin Mitigates Mitochondrial Meltdown: Interactions with SIRT3

Melatonin exhibits extraordinary diversity in terms of its functions and distribution. When discovered, it was thought to be uniquely of pineal gland origin. Subsequently, melatonin synthesis was identified in a variety of organs and recently it was shown to be produced in the mitochondria. Since mitochondria exist in every cell, with a few exceptions, it means that every vertebrate, invertebrate, and plant cell produces melatonin. The mitochondrial synthesis of melatonin is not photoperiod-dependent, but it may be inducible under conditions of stress. Mitochondria-produced melatonin is not released into the systemic circulation, but rather is used primarily in its cell of origin. Melatonin's functions in the mitochondria are highly diverse, not unlike those of sirtuin 3 (SIRT3). SIRT3 is an NAD+-dependent deacetylase which regulates, among many functions, the redox state of the mitochondria. Recent data proves that melatonin and SIRT3 post-translationally collaborate in regulating free radical generation and removal from mitochondria. Since melatonin and SIRT3 have cohabitated in the mitochondria for many eons, we predict that these molecules interact in many other ways to control mitochondrial physiology. It is predicted that these mutual functions will be intensely investigated in the next decade and importantly, we assume that the findings will have significant applications for preventing/delaying some age-related diseases and aging itself.

Responses of Transgenic Melatonin-Enriched Goats on LPS Stimulation and the Proteogenomic Profiles of Their PBMCs

The anti-inflammatory activity of melatonin (MT) has been well documented; however, little is known regarding endogenously occurring MT in this respect, especially for large animals. In the current study, we created a MT-enriched animal model (goats) overexpressing the MT synthetase gene Aanat. The responses of these animals to lipopolysaccharide (LPS) stimulation were systematically studied. It was found that LPS treatment exacerbated the inflammatory response in wild-type (WT) goats and increased their temperature to 40 °C. In addition, their granulocyte counts were also significantly elevated. In contrast, these symptoms were not observed in transgenic goats with LPS treatment. The rescue study with MT injection into WT goats who were treated with LPS confirmed that the protective effects in transgenic goats against LPS were attributed to a high level of endogenously produced MT. The proteomic analysis in the peripheral blood mononuclear cells (PBMCs) isolated from the transgenic animals uncovered several potential mechanisms. MT suppressed the lysosome formation as well as its function by downregulation of the lysosome-associated genes Lysosome-associated membrane protein 2 (LAMP2), Insulin-like growth factor 2 receptor (IGF2R), and Arylsulfatase B (ARSB). A high level of MT enhanced the antioxidant capacity of these cells to reduce the cell apoptosis induced by the LPS. In addition, the results also uncovered previously unknown information that showed that MT may have protective effects on some human diseases, including tuberculosis, bladder cancer, and rheumatoid arthritis, by downregulation of these disease-associated genes. All these observations warranted further investigations.

Effects of AANAT overexpression on the inflammatory responses and autophagy activity in the cellular and transgenic animal levels

To explore the anti-inflammatory activity of endogenous produced melatonin, a melatonin-enriched animal model (goat) with AANAT transfer was successfully generated with somatic cell nuclear transfer (SCNT) technology. Basically, a pIRES2-EGFP-AANAT expression vector was constructed and was transferred into the female fetal fibroblast cells (FFCs) via electrotransfection and then the nuclear of the transgenic FFC was transferred to the eggs of the donor goats. The peripheral blood mononuclear cells (PBMCs) of the transgenic offspring expressed significantly higher levels of AANAT and melatonin synthetic function than those PBMCs from the wild-type (WT) animals. After challenge with lipopolysaccharide (LPS), the transgenic PBMCs had increased autophagosomes and LC3B expression while they exhibited suppressed production of the proinflammatory cytokines, IL1B and IL12 (IL12A-IL12B/p70), compared to their WT. The mechanistic analysis indicated that the anti-inflammatory activity of endogenous melatonin was mediated by MTNR1B (melatonin receptor 1B). MTNR1B stimulation activated the MAPK14 signaling pathway to promote cellular macroautophagy/autophagy, thus, suppressing the excessive inflammatory response of cellular. However, when the intact animals challenged with LPS, the serum proinflammatory cytokines were significantly higher in the transgenic goats than that in the WT. The results indicated that endogenous melatonin inhibited the MAPK1/3 signaling pathway and ROS production, subsequently downregulated gene expression of BECN1, ATG5 in PMBCs and then suppressed the autophagy activity of PBMCs and finally elevated levels of serum proinflammatory cytokines in transgenic animals, Herein we provided a novel melatonin-enriched animal model to study the potential effects of endogenously produced melatonin on inflammatory responses and autophagy activity.

Mitochondria: Central Organelles for Melatonin's Antioxidant and Anti-Aging Actions

Melatonin, along with its metabolites, have long been known to significantly reduce the oxidative stress burden of aging cells or cells exposed to toxins. Oxidative damage is a result of free radicals produced in cells, especially in mitochondria. When measured, melatonin, a potent antioxidant, was found to be in higher concentrations in mitochondria than in other organelles or subcellular locations. Recent evidence indicates that mitochondrial membranes possess transporters that aid in the rapid uptake of melatonin by these organelles against a gradient. Moreover, we predicted several years ago that, because of their origin from melatonin-producing bacteria, mitochondria likely also synthesize melatonin. Data accumulated within the last year supports this prediction. A high content of melatonin in mitochondria would be fortuitous, since these organelles produce an abundance of free radicals. Thus, melatonin is optimally positioned to scavenge the radicals and reduce the degree of oxidative damage. In light of the "free radical theory of aging", including all of its iterations, high melatonin levels in mitochondria would be expected to protect against age-related organismal decline. Also, there are many age-associated diseases that have, as a contributing factor, free radical damage. These multiple diseases may likely be deferred in their onset or progression if mitochondrial levels of melatonin can be maintained into advanced age.

Pre-treatment with melatonin decreases abamectin induced toxicity in a nocturnal insect Spodoptera litura (Lepidoptera: Noctuidae)

AIM

Oxidative stress is an important component of the mechanism of pesticide toxicity. The aim of the present study was to investigate the time-dependent melatonin effects against abamectin-induced oxidative stress in a S.litura model. Larvae were divided into 5 different groups; (1) control group,(2) Melatonin group (4.3×10^-5M/100ml diet), (3) Abamectin group 1.5ml/L, (4) Pre-melatonin treated group (PM) (4.3×10^-5M/100ml diet) before abamectin exposure 1.5ml/L, (5) Post-melatonin treated group (TM) after abamectin exposure. Melatonin was supplemented via artificial diet in PM and TM animals during 24h.

MAIN METHODS

Midgut, fatbody, and hemolymph, were collected for the analysis of oxidative stress markers (Total ROS, GSH, nitrite, TBARS, LPO), antioxidant enzyme levels (SOD, GST, CAT, POX, APOX) in fifth instar larvae. Midgut damage was examined by using morphological analysis.

KEY FINDINGS

Our results observed that ABA group showed significant changes (p<0.001) in the ROS and carbonyl content in midgut. The increase of antioxidant enzyme levels (SOD, CAT, POX, and APOX) in midgut was led by the continuous free radical scavenger cascade of melatonin. Significant (p<0.01) increases in CAT and APOX levels were seen in the fatbody of PM and TM treated insects.

SIGNIFICANCE

In conclusion, the results of the study revealed that abamectin toxicity generates oxidative stress in the insect, while pre-melatonin treatment reduces this damage due to its antioxidant properties, especially POX levels in midgut, fatbody, and hemolymph. Therefore, indoleamine can play a vital role curtailing the abamectin toxicity in time dependent manner in S.litura.

Melatonin promotes self-renewal of nestin-positive pancreatic stem cells through activation of the MT2/ERK/SMAD/nestin axis

Although melatonin has been shown to exhibit a wide variety of biological functions, its effects on promotion of self-renewal in pancreatic stem cells remain unknown. In this study, we incubated murine pancreatic stem cells (PSCs) with various concentrations of melatonin (0.01, 0.1, 1, 10 or 100 μM) to screen for the optimum culture medium for increasing cell proliferation. We found that 10 μM melatonin can significantly increase proliferation and enhance expression of a stem cell marker, nestin, in PSCs via melatonin receptor 2 (MT2). Thus, we used 10 μM melatonin to study the melatonin-mediated molecular mechanisms of cell proliferation in PSCs. We applied extracellular signal-regulated kinase (ERK) pathway inhibitor SCH772984 and transforming growth factor beta (TGF-β) pathway inhibitor SB431542, along with interfering RNAs siERK1, siERK2, siSmad2, siSmad3, siSmad4 and siNestin, to melatonin-treated PSCs to research the roles of these genes in self-renewal. The results revealed a novel molecular mechanism by which melatonin promotes self-renewal of PSCs: a chain reaction in the MT2/ERK/SMAD/nestin axis promoted the aforementioned self-renewal as well as inhibited differentiation. In addition, upregulation of nestin created a positive feedback loop in the regulation of the transforming growth factor beta 1 (TGF-β1)/SMADs pathway by promoting expression of Smad4. Conversely, knockdown of nestin significantly suppressed the proliferative effect in melatonin-treated PSCs. These are all novel mechanisms through which the ERK pathway cooperatively crosstalks with the SMAD pathway to regulate nestin expression, thereby enhancing self-renewal in PSCs.

Protective Role of Melatonin and Coenzyme Q10 in Ochratoxin A Toxicity in Rat Liver and Kidney

Melatonin (MEL) and coenzyme Q10 (CoQ10) both display antioxidant and free radical scavenger properties. In the present study, the effect of MEL and CoQ10 on the oxidative stress and fibrosis induced by ochratoxin A (OTA) administration in rats was investigated. Rats were divided into five equal groups, each consisting of seven rats: (1) controls; (2) OTA-treated rats (289 μg/kg/day); (3) OTA+MEL–treated rats (289 μg/kg/day OTA + 10 mg/kg/day MEL); and (4) OTA+CoQ10–treated rats (289 μg/kg/day OTA +1 mg/100 g/day body weight (bw) CoQ10). After 4 weeks of treatment, the level of malondialdehyde (MDA), glutathione peroxidase (GPx), and hydroxyproline (Hyp) were measured in the homogenates of liver and kidney. In the OTA-treated group, the levels of MDA and Hyp in both liver and kidney were significantly increased when compared with the levels of control, whereas GPx activities decreased. In OTA+MEL–treated rats, the levels of MDA and Hyp in both liver and kidney were significantly decreased when compared with the levels of OTA-treated rats; however; GPX activities increased. In the OTA+CoQ10–treated group, the levels of MDA and Hyp were decreased when compared with the levels of OTA-treated rats, whereas GPx activities increased. In the OTA+CoQ 10–treated group, the levels of MDA, Hyp, and GPx were not significantly changed in kidney when compared with OTA-treated group. MEL has a protective effect against OTA toxicity through an inhibition of the oxidative damage and fibrosis both liver and kidney. Although CoQ10 has protective effect against OTA toxicity in liver tissue, it has no effect in kidney tissue.

Effects of melatonin in rats in the initial third stage of pregnancy exposed to sub-lethal doses of herbicides

Exposure to the herbicides Paraquat (PQ) and Roundup® may cause cell lesions due to an increase in oxidative stress levels in different biological systems, even in the reproductive system.

OBJECTIVE

Evaluate the possible changes in reproductive parameters and hepatic, as well as its prevention by simultaneous application of melatonin.

METHODS

Thirty-five female rats at the age of 3 months were divided into seven groups: three groups exposed to sub-lethal doses of the herbicides PQ (50mg/kg) and Roundup® (500mg/kg) (n=5, G2, G3 and G4); three groups exposed to herbicides and simultaneous treatment with 10mg/kg of Melatonin (n=5, G5, G6 and G7) and control group (n=5, G1) from the first to the seventh day of pregnancy. On the seventh day of pregnancy, the rats were anesthetized and euthanized, followed by laparotomy to remove their reproductive tissues and liver. Body and ovary weights were taken and the number of implantation sites, corpora lutea, preimplantation losses, implantation rates were counted and histopathology of the implantation sites, morphometry of the surface and glandular epithelia of endometrium and hepatic oxidative stress were undertaken.

RESULTS

The present study shows the decrease in body and ovary weight, decrease in the number of implantation sites, implantation rate, in the total number of corpora lutea and increase of preimplantation percentages were observed when compared to the G1: Fig. 1 and Table 1, (p>0.001 ANOVA/Tukey). The histopathological analysis of the implantation sites showed a disorder of the cytotrophoblast and cell degeneration within the blastocyst cavity in Fig. 4. Morphometry revealed a reduction in surface and glandular epithelia and in the diameter of the endometrial glands (Table 2; p>0.05 ANOVA/Tukey), whereas in liver, serum levels of thiobarbituric acid reactive substances (TBARS) were found to be significantly elevated (Fig. 2; p>0.001; p>0.05 ANOVA/Tukey), and serum level of reduced glutathione (GSH) was significantly lower (Fig. 3; p>0.001 ANOVA/Tukey). However, treatments with melatonin exhibited improvements in reproductive parameters, as well as reduced lesions in the implantation sites (Fig. 4.) and in serum levels TBARS (Fig. 2; p>0.001 ANOVA/Tukey), serum levels GSH (Fig. 3; p>0.001; p>0.05 ANOVA/Tukey).

CONCLUSIONS

These results reveal that melatonin is a protective agent against experimentally induced maternal/embryo toxicity with herbicides and favoring normalization of reproductive parameters and hepatic.

Anti-Oxidants in Parkinson's Disease Therapy: A Critical Point of View

Parkinson’s disease (PD) is a degenerative neurological syndrome, which is characterized by the preferential death of dopaminergic (DAergic) neurons in the Substantia Nigra. The pathogenesis of this disorder remains poorly understood and PD is still incurable. Current drug treatments are aimed primarily for the treatment of symptoms to improve the quality of life. Therefore, there is a need to find out new therapeutic strategies that not only provide symptomatic relief but also halt or reverse the neuronal damage hampering PD progression. Oxidative stress has been identified as one of the major contributors for the nigral loss in both sporadic and genetic forms of PD. In this review we first evaluate the current literature that links oxidative stress and mitochondrial dysfunction to PD. We then consider the results obtained through the treatment of animal models or PD patients with molecules that prevent oxidative stress or reduce mitochondrial dysfunction.

Phenolic Melatonin-Related Compounds: Their Role as Chemical Protectors against Oxidative Stress

There is currently no doubt about the serious threat that oxidative stress (OS) poses to human health. Therefore, a crucial strategy to maintain a good health status is to identify molecules capable of offering protection against OS through chemical routes. Based on the known efficiency of the phenolic and melatonin (MLT) families of compounds as antioxidants, it is logical to assume that phenolic MLT-related compounds should be (at least) equally efficient. Unfortunately, they have been less investigated than phenols, MLT and its non-phenolic metabolites in this context. The evidence reviewed here strongly suggests that MLT phenolic derivatives can act as both primary and secondary antioxidants, exerting their protection through diverse chemical routes. They all seem to be better free radical scavengers than MLT and Trolox, while some of them also surpass ascorbic acid and resveratrol. However, there are still many aspects that deserve further investigations for this kind of compounds.

Melatonin as an antioxidant: under promises but over delivers

Melatonin is uncommonly effective in reducing oxidative stress under a remarkably large number of circumstances. It achieves this action via a variety of means: direct detoxification of reactive oxygen and reactive nitrogen species and indirectly by stimulating antioxidant enzymes while suppressing the activity of pro-oxidant enzymes. In addition to these well-described actions, melatonin also reportedly chelates transition metals, which are involved in the Fenton/Haber-Weiss reactions; in doing so, melatonin reduces the formation of the devastatingly toxic hydroxyl radical resulting in the reduction of oxidative stress. Melatonin's ubiquitous but unequal intracellular distribution, including its high concentrations in mitochondria, likely aid in its capacity to resist oxidative stress and cellular apoptosis. There is credible evidence to suggest that melatonin should be classified as a mitochondria-targeted antioxidant. Melatonin's capacity to prevent oxidative damage and the associated physiological debilitation is well documented in numerous experimental ischemia/reperfusion (hypoxia/reoxygenation) studies especially in the brain (stroke) and in the heart (heart attack). Melatonin, via its antiradical mechanisms, also reduces the toxicity of noxious prescription drugs and of methamphetamine, a drug of abuse. Experimental findings also indicate that melatonin renders treatment-resistant cancers sensitive to various therapeutic agents and may be useful, due to its multiple antioxidant actions, in especially delaying and perhaps treating a variety of age-related diseases and dehumanizing conditions. Melatonin has been effectively used to combat oxidative stress, inflammation and cellular apoptosis and to restore tissue function in a number of human trials; its efficacy supports its more extensive use in a wider variety of human studies. The uncommonly high-safety profile of melatonin also bolsters this conclusion. It is the current feeling of the authors that, in view of the widely diverse beneficial functions that have been reported for melatonin, these may be merely epiphenomena of the more fundamental, yet-to-be identified basic action(s) of this ancient molecule.

Melatonin improves reprogramming efficiency and proliferation of bovine-induced pluripotent stem cells

Melatonin can modulate neural stem cell (NSC) functions such as proliferation and differentiation into NSC-derived pluripotent stem cells (N-iPS) in brain tissue, but the effect and mechanism underlying this are unclear. Thus, we studied how primary cultured bovine NSCs isolated from the retinal neural layer could transform into N-iPS cell. NSCs were exposed to 0.01, 0.1, 1, 10, or 100 μm melatonin, and cell viability studies indicated that 10 μm melatonin can significantly increase cell viability and promote cell proliferation in NSCs in vitro. Thus, 10 μm melatonin was used to study miR-302/367-mediated cell reprogramming of NSCs. We noted that this concentration of melatonin increased reprogramming efficiency of N-iPS cell generation from primary cultured bovine NSCs and that this was mediated by downregulation of apoptosis-related genes p53 and p21. Then, N-iPS cells were treated with 1, 10, 100, or 500 μm melatonin, and N-iPS (M-N-iPS) cell proliferation was measured. We noted that 100 μm melatonin increased proliferation of N-iPS cells via increased phosphorylation of intracellular ERK1/2 via activation of its pathway in M-N-iPS via melatonin receptors 1 (MT1). Finally, we verified that N-iPS cells and M-N-iPS cells are similar to typical embryonic stem cells including the expression of pluripotency markers (Oct4 and Nanog), the ability to form teratomas in vivo, and the capacity to differentiate into all three embryonic germ layers.

Effects of Melatonin on Oxidative Stress in Streptozotocin-Induced Diabetic Rats

Oxidative stress plays an important role in diabetes and other oxygen-related diseases. Melatonin, a pineal hormone thought to be a scavenger of oxygen radicals and a potentially advantageous therapeutic agent in diseases having oxidative stress, was administered (10 mg/kg ip, in gum tragacanth to prolong its absorption, once a day for 4 successive days) to normal and 30-day streptozotocin-induced diabetic Sprague-Dawley rats, after which markers of oxidative stress were assessed in the liver, kidney, intestine, and spleen. Alanine and aspartate aminotransferase activities in serum, which were increased after diabetes, were not increased further by melatonin administration, indicating that there was no melatonin-related liver toxicity. Most melatonin-induced effects were seen in the liver, and very few in extrahepatic tissues. In livers of diabetic rats, reduced concentration of nitrite and increased lipid peroxidation were both restored to normal levels following treatment with melatonin. Hepatic glutathione peroxidase activity was not changed in diabetics, but was decreased after melatonin administration in both normal and diabetic animals. Total glutathione concentrations were significantly decreased in livers of all diabetics and were not normalized by melatonin treatment. Hepatic superoxide dis-mutase activity was elevated following melatonin dosing in normal rats, but dropped below normal levels in diabetic rats and was not restored by melatonin treatment. Glutathione 5-transferase activity was higher than normal in melatonin-dosed normal rat livers. These results suggest that after 4 days of administration, melatonin may enable various enzymes of the hepatic antioxidative defense system to better detoxify harmful oxygen radicals without producing overt toxicity in a disease such as diabetes.

Neurobehavioural Changes and Brain Oxidative Stress Induced by Acute Exposure to GSM900 Mobile Phone Radiations in Zebrafish (Danio rerio)

The impact of mobile phone (MP) radiation on the brain is of specific interest to the scientific community and warrants investigations, as MP is held close to the head. Studies on humans and rodents revealed hazards MP radiation associated such as brain tumors, impairment in cognition, hearing etc. Melatonin (MT) is an important modulator of CNS functioning and is a neural antioxidant hormone. Zebrafish has emerged as a popular model organism for CNS studies. Herein, we evaluated the impact of GSM900MP (GSM900MP) radiation exposure daily for 1 hr for 14 days with the SAR of 1.34W/Kg on neurobehavioral and oxidative stress parameters in zebrafish. Our study revealed that, GSM900MP radiation exposure, significantly decreased time spent near social stimulus zone and increased total distance travelled, in social interaction test. In the novel tank dive test, the GSM900MP radiation exposure elicited anxiety as revealed by significantly increased time spent in bottom half; freezing bouts and duration and decreased distance travelled, average velocity, and number of entries to upper half of the tank. Exposed zebrafish spent less time in the novel arm of the Y-Maze, corroborating significant impairment in learning as compared to the control group. Exposure decreased superoxide dismutase (SOD), catalase (CAT) activities whereas, increased levels of reduced glutathione (GSH) and lipid peroxidation (LPO) was encountered showing compromised antioxidant defense. Treatment with MT significantly reversed the above neurobehavioral and oxidative derangements induced by GSM900MP radiation exposure. This study traced GSM900MP radiation exposure induced neurobehavioral aberrations and alterations in brain oxidative status. Furthermore, MT proved to be a promising therapeutic candidate in ameliorating such outcomes in zebrafish.

Combination of melatonin and Wnt-4 promotes neural cell differentiation in bovine amniotic epithelial cells and recovery from spinal cord injury

Although melatonin has been shown to exhibit a wide variety of biological functions, its effects on promoting differentiation of neural cells remain unknown. Wnt signaling mediates major developmental processes during embryogenesis and regulates maintenance, self-renewal, and differentiation of adult mammalian stem cells. However, the role of the noncanonical Wnt pathway during neurogenesis remains poorly understood. In this study, the amniotic epithelial cells ( AECs) were isolated from bovine amnion and incubated with various melatonin concentrations (0.01, 0.1, 1, 10, or 100 μm) and 5 × 10(-5) m all-trans retinoic acid (RA) for screening optimum culture medium of neural differentiation, compared with each groups, 1 μm melatonin and 5 × 10(-5) m RA were selected to induce neural differentiation of AECs, and then siMT1, siMT2, oWnt-4, and siWnt-4 were expressed in AECs to research role of these genes in neural differentiation. Efficiency of neural differentiation was evaluated after expressed above genes using flow cytometry. Cell function of neural cells was demonstrated in vivo using spinal cord injury model after cell transplantation, and damage repair of spinal cord was assessed using cell tracking and Basso, Beattie, Bresnahan Locomotor Rating Scale scores. Results demonstrated that melatonin stimulated melatonin receptor 1, which subsequently increased bovine amniotic epithelial cell vitality and promoted differentiation into neural cells. This took place through cooperation with Wnt-4. Additionally, following cotreatment with melatonin and Wnt-4, neurogenesis gene expression was significantly altered. Furthermore, single inhibition of melatonin receptor 1 or Wnt-4 expression decreased expression of neurogenesis-related genes, and bovine amniotic epithelial cell-derived neural cells were successfully colonized into injured spinal cord, which suggested participation in tissue repair.

Melatonin inhibits paraquat-induced cell death in bovine preimplantation embryos

Preimplantation embryos are sensitive to oxidative stress-induced damage that can be caused by reactive oxygen species (ROS) originating from normal embryonic metabolism and/or the external surroundings. Paraquat (PQ), a commonly used pesticide and potent ROS generator, can induce embryotoxicity. The present study aimed to investigate the effects of melatonin on PQ-induced damage during embryonic development in bovine preimplantation embryos. PQ treatment significantly reduced the ability of bovine embryos to develop to the blastocyst stage, and the addition of melatonin markedly reversed the developmental failure caused by PQ (20.9% versus 14.3%). Apoptotic assay showed that melatonin pretreatment did not change the total cell number in blastocysts, but the incidence of apoptotic nuclei and the release of cytochrome c were significantly decreased. Using real-time quantitative polymerase chain reaction analysis, we found that melatonin pre-incubation significantly altered the expression levels of genes associated with redox signaling, particularly by attenuating the transcript level of Txnip and reinforcing the expression of Trx. Furthermore, melatonin pretreatment significantly reduced the expression of the pro-apoptotic caspase-3 and Bax, while the expression of the anti-apoptotic Bcl-2 and XIAP was unaffected. Western blot analysis showed that melatonin protected bovine embryos from PQ-induced damage in a p38-dependent manner, but extracellular signal-regulated kinase (ERK) and c-JUN N-terminal kinase (JNK) did not appear to be involved. Together, these results identify an underlying mechanism by which melatonin enhances the developmental potential of bovine preimplantation embryos under oxidative stress conditions.

Heavy Metals and Human Health: Mechanistic Insight into Toxicity and Counter Defense System of Antioxidants

Heavy metals, which have widespread environmental distribution and originate from natural and anthropogenic sources, are common environmental pollutants. In recent decades, their contamination has increased dramatically because of continuous discharge in sewage and untreated industrial effluents. Because they are non-degradable, they persist in the environment; accordingly, they have received a great deal of attention owing to their potential health and environmental risks. Although the toxic effects of metals depend on the forms and routes of exposure, interruptions of intracellular homeostasis include damage to lipids, proteins, enzymes and DNA via the production of free radicals. Following exposure to heavy metals, their metabolism and subsequent excretion from the body depends on the presence of antioxidants (glutathione, α-tocopherol, ascorbate, etc.) associated with the quenching of free radicals by suspending the activity of enzymes (catalase, peroxidase, and superoxide dismutase). Therefore, this review was written to provide a deep understanding of the mechanisms involved in eliciting their toxicity in order to highlight the necessity for development of strategies to decrease exposure to these metals, as well as to identify substances that contribute significantly to overcome their hazardous effects within the body of living organisms.

Caenorhabditis elegans as an alternative in vivo model to determine oral uptake, nanotoxicity, and efficacy of melatonin-loaded lipid-core nanocapsules on paraquat damage

Caenorhabditis elegans is an alternative in vivo model that is being successfully used to assess the pharmacological and toxic effects of drugs. The exponential growth of nanotechnology requires the use of alternative in vivo models to assess the toxic effects of theses nanomaterials. The use of polymeric nanocapsules has shown promising results for drug delivery. Moreover, these formulations have not been used in cases of intoxication, such as in treatment of paraquat (PQ) poisoning. Thus, the use of drugs with properties improved by nanotechnology is a promising approach to overcome the toxic effects of PQ. This research aimed to evaluate the absorption of rhodamine B-labeled melatonin (Mel)-loaded lipid-core nanocapsules (LNC) by C. elegans, the application of this model in nanotoxicology, and the protection of Mel-LNC against PQ damage. The formulations were prepared by self-assembly and characterized by particle sizing, zeta potential, drug content, and encapsulation efficiency. The results demonstrated that the formulations had narrow size distributions. Rhodamine B-labeled Mel-LNC were orally absorbed and distributed in the worms. The toxicity assessment of LNC showed a lethal dose 50% near the highest dose tested, indicating low toxicity of the nanocapsules. Moreover, pretreatment with Mel-LNC significantly increased the survival rate, reduced the reactive oxygen species, and maintained the development in C. elegans exposed to PQ compared to those worms that were either untreated or pretreated with free Mel. These results demonstrated for the first time the uptake and distribution of Mel-LNC by a nematode, and indicate that while LNC is not toxic, Mel-LNC prevents the effects of PQ poisoning. Thus, C. elegans may be an interesting alternative model to test the nanocapsules toxicity and efficacy.

Biomedical implications of heavy metals induced imbalances in redox systems

Several workers have extensively worked out the metal induced toxicity and have reported the toxic and carcinogenic effects of metals in human and animals. It is well known that these metals play a crucial role in facilitating normal biological functions of cells as well. One of the major mechanisms associated with heavy metal toxicity has been attributed to generation of reactive oxygen and nitrogen species, which develops imbalance between the prooxidant elements and the antioxidants (reducing elements) in the body. In this process, a shift to the former is termed as oxidative stress. The oxidative stress mediated toxicity of heavy metals involves damage primarily to liver (hepatotoxicity), central nervous system (neurotoxicity), DNA (genotoxicity), and kidney (nephrotoxicity) in animals and humans. Heavy metals are reported to impact signaling cascade and associated factors leading to apoptosis. The present review illustrates an account of the current knowledge about the effects of heavy metals (mainly arsenic, lead, mercury, and cadmium) induced oxidative stress as well as the possible remedies of metal(s) toxicity through natural/synthetic antioxidants, which may render their effects by reducing the concentration of toxic metal(s). This paper primarily concerns the clinicopathological and biomedical implications of heavy metals induced oxidative stress and their toxicity management in mammals.

Protective effect of melatonin on propoxur-induced impairment of memory and oxidative stress in rats

Propoxur (a carbamate pesticide) has been shown to adversely affect memory and induce oxidative stress on both acute and chronic exposure. This study was designed to explore the modulation of the effects of propoxur over cognitive function by melatonin (MEL). Cognitive function was assessed using step-down latency (SDL) on a passive avoidance apparatus, and transfer latency (TL) on an elevated plus maze. Oxidative stress was assessed by examining brain malondialdehyde (MDA) and reduced glutathione (GSH) levels and catalase (CAT) activity. A significant reduction in SDL and prolongation of TL was observed for the propoxur (10 mg/kg/d; p.o.) treated group at weeks 6 and 7 when compared with control. One week treatment with MEL (50 mg/kg/d; i.p.) antagonized the effect of propoxur on SDL, as well as TL. Propoxur produced a statistically significant increase in the brain MDA levels and decrease in the brain GSH levels and CAT activity. Treatment with MEL attenuated the effect of propoxur on oxidative stress. The results of the present study thus show that MEL has the potential to attenuate cognitive dysfunction and oxidative stress induced by toxicants like propoxur in the brain.

Arabidopsis transcriptome analysis reveals key roles of melatonin in plant defense systems

Melatonin is a ubiquitous molecule and exists across kingdoms including plant species. Studies on melatonin in plants have mainly focused on its physiological influence on growth and development, and on its biosynthesis. Much less attention has been drawn to its affect on genome-wide gene expression. To comprehensively investigate the role(s) of melatonin at the genomics level, we utilized mRNA-seq technology to analyze Arabidopsis plants subjected to a 16-hour 100 pM (low) and 1 mM (high) melatonin treatment. The expression profiles were analyzed to identify differentially expressed genes. 100 pM melatonin treatment significantly affected the expression of only 81 genes with 51 down-regulated and 30 up-regulated. However, 1 mM melatonin significantly altered 1308 genes with 566 up-regulated and 742 down-regulated. Not all genes altered by low melatonin were affected by high melatonin, indicating different roles of melatonin in regulation of plant growth and development under low and high concentrations. Furthermore, a large number of genes altered by melatonin were involved in plant stress defense. Transcript levels for many stress receptors, kinases, and stress-associated calcium signals were up-regulated. The majority of transcription factors identified were also involved in plant stress defense. Additionally, most identified genes in ABA, ET, SA and JA pathways were up-regulated, while genes pertaining to auxin responses and signaling, peroxidases, and those associated with cell wall synthesis and modifications were mostly down-regulated. Our results indicate critical roles of melatonin in plant defense against various environmental stresses, and provide a framework for functional analysis of genes in melatonin-mediated signaling pathways.

The antidote effect of quinone oxidoreductase 2 inhibitor against paraquat-induced toxicity in vitro and in vivo

BACKGROUND AND PURPOSE The mechanisms of paraquat (PQ)-induced toxicity are poorly understood and PQ poisoning is often fatal due to a lack of effective antidotes. In this study we report the effects of N-[2-(2-methoxy-6H-dipyrido{2,3-a:3,2-e}pyrrolizin-11-yl)ethyl]-2-furamide (NMDPEF), a melatonin-related inhibitor of quinone oxidoreductase2 (QR2) on the toxicity of PQ in vitro & in vivo. EXPERIMENTAL APPROACH Prevention of PQ-induced toxicity was tested in different cells, including primary pneumocytes and astroglial U373 cells. Cell death and reactive oxygen species (ROS) were analysed by flow cytometry and fluorescent probes. QR2 silencing was achieved by lentiviral shRNAs. PQ (30 mg·kg(-1)) and NMDPEF were administered i.p. to Wistar rats and animals were monitored for 28 days. PQ toxicity in the substantia nigra (SN) was tested by a localized microinfusion and electrocorticography. QR2 activity was measured by fluorimetry of N-benzyldihydronicotinamide oxidation. KEY RESULTS NMDPEF potently antagonized non-apoptotic PQ-induced cell death, ROS generation and inhibited cellular QR2 activity. In contrast, the cytoprotective effect of melatonin and apocynin was limited and transient compared with NMDPEF. Silencing of QR2 attenuated PQ-induced cell death and reduced the efficacy of NMDPEF. Significantly, NMDPEF (4.5 mg·kg(-1)) potently antagonized PQ-induced systemic toxicity and animal mortality. Microinfusion of NMDPEF into SN prevented severe behavioural and electrocortical effects of PQ which correlated with inhibition of malondialdehyde accumulation in cells and tissues. CONCLUSIONS AND IMPLICATIONS NMDPEF protected against PQ-induced toxicity in vitro and in vivo, suggesting a key role for QR2 in the regulation of oxidative stress.

Melatonin ameliorates oxidative stress and reproductive toxicity induced by cyclophosphamide in male mice

The present study evaluated the efficacy of melatonin in cyclophosphamide (CP)-induced testicular injury, lipid peroxidative damage, and antioxidant enzymes status of the mice testis on the basis of biochemical and histological studies. Mice were pretreated with four different doses of melatonin (2.5, 5, 10, and, 20 mg/kg by body weight (b.w.)) via intraperitoneal injection for five consecutive days followed by injection with CP (200 mg/kg b.w.) 1 h after the last injection of melatonin on the 5th day. After 24 h, mice were euthanized, testes were immediately removed, and biochemical and histological studies were conducted. Treatment with melatonin significantly mitigates lipid peroxidation, superoxide dismutase, and catalase activity and the level of reduced glutathione content abnormality induced by CP in mice testis. Histological examination clearly demonstrates that pretreatment of melatonin prevented CP-induced spermatogenesis toxicity and spermatogenic cells reduction in mice testis. The protective effect of melatonin is likely due to the antioxidative properties of the indolamine existed in the chemical structure. Because melatonin is a safe, natural compound, it could be used concomitantly as a supplement to protect people undergoing chemotherapy against reproductive toxicity.

Melatonin induces autophagy via an mTOR-dependent pathway and enhances clearance of mutant-TGFBIp

The hallmark of granular corneal dystrophy type 2 (GCD2) is the deposit of mutant transforming growth factor-β (TGF-β)-induced protein (TGFBIp) in the cornea. We have recently shown that there is a delay in autophagic degradation of mutant-TGFBIp via impaired autophagic flux in GCD2 corneal fibroblasts. We hypothesized that melatonin can specifically induce autophagy and consequently eliminate mutant-TGFBIp in GCD corneal fibroblasts. Our results show that melatonin activates autophagy in both wild-type (WT) and GCD2-homozygous (HO) corneal fibroblast cell lines via the mammalian target of rapamycin (mTOR)-dependent pathway. Melatonin treatment also led to increased levels of beclin 1, which is involved in autophagosome formation and maturation. Furthermore, melatonin significantly reduced the amounts of mutant- and WT-TGFBIp. Treatment with melatonin counteracted the autophagy-inhibitory effects of bafilomycin A1, a potent inhibitor of autophagic flux, demonstrating that melatonin enhances activation of autophagy and increases degradation of TGFBIp. Cotreatment with melatonin and rapamycin, an autophagy inducer, had an additive effect on mutant-TGFBIp clearance compared to treatment with either drug alone. Treatment with the selective melatonin receptor antagonist luzindole did not block melatonin-induced autophagy. Given its ability to activate autophagy, melatonin is a potential therapeutic agent for GCD2.

Melatonin protects against oxidative stress in granular corneal dystrophy type 2 corneal fibroblasts by mechanisms that involve membrane melatonin receptors

Considering that oxidative stress plays a role in corneal fibroblast degeneration during granular corneal dystrophy type 2 (GCD2) and melatonin is an effective antioxidant, we examined the ability of melatonin to protect against oxidative stress-induced cell death of primary cultured normal and GCD2-homozygous corneal fibroblasts. Melatonin treatment protected primary cultured normal and GCD2 corneal fibroblasts from paraquat (PQ)-induced oxidative stress and caused increased expression levels of Cu/Zn-superoxide dismutase (SOD1) and glutathione reductase (GR) in both types of cells. Interestingly, catalase expression increased in normal corneal fibroblasts, but decreased in GCD2 corneal fibroblasts after melatonin treatment. Melatonin also reduced the levels of intracellular reactive oxygen species and H(2)O(2) in both cell types. In addition, the selective melatonin receptor antagonist luzindole blocked melatonin-induced expression of SOD1 and GR. The expression levels of melatonin receptors 1A (MT1) and 1B (MT2) were significantly higher in GCD2 corneal fibroblasts than in normal cells. These results suggest that increased expression of melatonin receptors may be involved in the defense mechanisms against oxidative stress in GCD2 corneal fibroblasts, and melatonin may have potential therapeutic implications for GCD2 treatment.

Melatonin attenuates cognitive dysfunction and reduces neural oxidative stress induced by phosphamidon

Melatonin is an important modulator of nervous system functioning and important neural antioxidant. Organophosphate pesticides like phosphamidon (PHOS) have been shown to adversely affect memory and induce oxidative stress on both acute and chronic exposure. This study was designed to explore the modulation of the effects of PHOS on cognitive function by melatonin (MEL). Cognitive function was assessed using step-down latency (SDL) on a passive avoidance apparatus and transfer latency (TL) on an elevated plus maze. Oxidative stress was assessed by examining the levels of malondialdehyde (MDA) and nonprotein thiols (NP-SH) in isolated homogenized whole brain samples. The results showed a significant reduction in SDL and prolongation of TL in the PHOS (1.74 mg/kg/day; p.o.)-treated group at weeks 6 and 8 as compared to the control group. Two-week treatment with MEL (5 mg/kg/day; i.p.) antagonized the effect of PHOS on SDL as well as TL. PHOS alone produced a significant increase in the brain MDA levels and decrease in the brain NP-SH levels. Treatment with MEL attenuated the effect of PHOS on oxidative stress. Together the results showed that MEL attenuated the cognitive dysfunction and decreased oxidative stress induced by PHOS in the brain.

Ameliorative action of melatonin on oxidative damage induced by atrazine toxicity in rat erythrocytes

Excessive generation of reactive oxygen species (ROS) can induce oxidative damage to vital cellular molecules and structures including DNA, lipids, proteins, and membranes. Recently, melatonin has attracted attention because of their free radical scavenging and antioxidant properties. The aim of this study was to evaluate the possible protective role of melatonin against atrazine-induced oxidative stress in rat erythrocytes in vivo. Adult male albino rats of Wistar strain were randomly divided into four groups. Control group received isotonic saline; melatonin (10 mg/kg bw/day) group; atrazine (300 mg/kg of bw/day) group; atrazine + melatonin group. Oral administration of atrazine and melatonin was given daily for 21 days. Oxidative stress was assessed by determining the glutathione (GSH) and malondialdehyde (MDA) level, and alteration in antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), glutathione-S-transferase (GST), and glucose-6-phosphate dehydrogenase (G-6-PD) in the erythrocytes of normal and experimental animals. A significant increase in the MDA levels and decrease in the GSH was observed in the atrazine treated animals (P < 0.05). Also, significant increase in the activities of SOD, CAT, GPx, and GST were observed in atrazine treated group compared to controls (P < 0.05). Moreover, significant decrease in protein, total lipids, cholesterol, and phospholipid content in erythrocyte membrane were demonstrated in atrazine treated rats. Administration of atrazine significantly inhibits the activities of G-6-PD and membrane ATPases such as Na(+)/K(+)-ATPase, Mg(2+)-ATPase, and Ca(2+)-ATPase (P < 0.05). Scanning electron microscopic (SEM) examination of erythrocytes revealed morphological alterations in the erythrocytes of atrazine treated rats. Furthermore, supplementation of melatonin significantly modulates the atrazine-induced changes in LPO level, total lipids, total ATPases, GSH, and antioxidant enzymes in erythrocytes. In conclusion, the increase in oxidative stress markers and the concomitant alterations in antioxidant defense system indicate the role of oxidative stress in erythrocytes of atrazine-induced damage. Moreover, melatonin shows a protective role against atrazine-induced oxidative damage in rat erythrocytes.

Hepatoprotective actions of melatonin: Possible mediation by melatonin receptors

Melatonin, the hormone of darkness and messenger of the photoperiod, is also well known to exhibit strong direct and indirect antioxidant properties. Melatonin has previously been demonstrated to be a powerful organ protective substance in numerous models of injury; these beneficial effects have been attributed to the hormone’s intense radical scavenging capacity. The present report reviews the hepatoprotective potential of the pineal hormone in various models of oxidative stress in vivo, and summarizes the extensive literature showing that melatonin may be a suitable experimental substance to reduce liver damage after sepsis, hemorrhagic shock, ischemia/reperfusion, and in numerous models of toxic liver injury. Melatonin’s influence on hepatic antioxidant enzymes and other potentially relevant pathways, such as nitric oxide signaling, hepatic cytokine and heat shock protein expression, are evaluated. Based on recent literature demonstrating the functional relevance of melatonin receptor activation for hepatic organ protection, this article finally suggests that melatonin receptors could mediate the hepatoprotective actions of melatonin therapy.

Effect of melatonin in the antioxidant defense system in the locomotor muscles of the estuarine crab Neohelice granulata (Decapoda, Brachyura)

In vertebrates, many studies verified different effects of melatonin in the antioxidant defense system (ADS). In crustaceans, few studies have been conducted to verify this possibility. We verified the melatonin effects in the crab Neohelice granulata using low (0.002 and 0.02 pmol/crab) and high (2.0 and 20.0 pmol/crab) melatonin dosages in short-term (0.5h) and long-term (9.5h) experiments. We analyzed the antioxidant capacity against peroxyl radicals (ACAP), reactive oxygen species (ROS) concentration, levels of by products of lipid peroxidation (LPO), oxygen consumption (VO(2)), the activity of glutamate cysteine ligase (gamma-GCL) and catalase (CAT) and glutathione content (GSH). Finally, the effects of exogenous melatonin were verified in terms of melatonin and N(1)-acetyl-N(2)-formyl-5-methoxykynuramine (AFMK) content in the muscles of N. granulata. In short-term experiment and low dosages, melatonin increased the VO(2), gamma-GCL activity and GSH content (p<0.05) and decreased melatonin content (p<0.05) without effects in ROS, ACAP and LPO (p>0.05). Possibly, melatonin is acting in the ADS increasing its efficiency and/or acting in mitochondrial activity and/or through signaling muscles to increase its consumption. AFMK was only detected in the eyestalk and cerebroid ganglia. In high dosages melatonin effects decreased, possibly by the desensitization of their receptors. In long-term experiment, melatonin decreased ACAP (p<0.05), and CAT activity (p<0.05) in low dosages. In high dosages melatonin reduced VO(2) (p<0.05) and increased ACAP (p<0.05), possibly stimulating others components of the ADS. In conclusion, melatonin in the locomotor muscles of N. granulata affects the antioxidant/pro-oxidant balance in a time and dosage dependent manner.

Melatonin Inhibits Benzene-Induced Lipid Peroxidation in Rat Liver

We studied the antioxidative role of melatonin against benzene toxicity in rat liver. The inhibition of mitochondrial and microsomal lipid peroxidation differed between 24-hour (single-dose), 15-day, and 30-day treatments. Inhibition of mitochondrial lipid peroxidation was the highest after the single dose of melatonin, whereas highest microsomal inhibition was recorded after 30 days of melatonin treatment. No significant difference was recorded between 15-day and 30-day treatments. Cytochrome P 4502E1 (CYP 4502E1) activity declined after the single-dose and 15-day melatonin treatment in the benzene-treated group, but it rose again, though not significantly after 30 days of treatment. Liver histopathology generally supported these findings. Phenol concentration in the urine samples declined in melatonin and benzene-treated rats. Our results show that melatonin affects CYP 4502E1, which is responsible for benzene metabolism. Inhibition of its metabolism correlated with lower lipid peroxidation. In conclusion, melatonin was found to be protective against lipid peroxidation induced by benzene.

Melatonin reverses urinary system and aorta damage in the rat due to chronic nicotine administration

We have evaluated the changes in contractile activity and oxidant damage of corpus cavernosum, urinary bladder, kidney and aorta after chronic nicotine administration in rats. The effects of melatonin on these parameters were investigated also. Male Wistar albino rats were injected intraperitoneally with nicotine hydrogen bitartrate (0.6 mg kg−1 daily for 21 days) or saline. Melatonin (10 mg kg−1, i.p.) was administered either alone or with nicotine injections. Corpus cavernosum, bladder and aorta were used for contractility studies, or stored with kidneys for the measurement of malondialdehyde and glutathione levels. Corpus cavernosum, bladder, and aorta samples were examined histologically and the extent of microscopic tissue damage was scored. In the nicotine-treated group, the contraction of corpus cavernosum, bladder and aorta samples and the relaxation of corporeal and aorta tissues decreased significantly compared with controls. However, melatonin treatment restored these responses. In the nicotine-treated group, there was a significant increase in the malondialdehyde levels of the corporeal tissue, bladder, kidney and aorta, with marked reductions in glutathione levels compared with controls. Melatonin treatment reversed these effects also. Melatonin administration to nicotine-treated animals caused a marked reduction in the microscopic damage of the tissues compared with those of the untreated group. In this study, nicotine-induced dysfunction of the corpus cavernosum, bladder and aorta of rats was reversed by melatonin treatment. Moreover, melatonin, as an antioxidant, abolished elevation in lipid peroxidation products, and reduction in the endogenous antioxidant glutathione, and protected the tissues from severe damage due to nicotine exposure.