Protective effects of lycopene against methylmercury-induced neurotoxicity in cultured rat cerebellar granule neurons

Lycopene protects against ionizing radiation-induced testicular damage by inhibition of apoptosis and mitochondrial dysfunction

Ionizing radiation (IR) is one of the key contributors that cause male infertility by disturbing spermatogenesis. Lycopene, a carotenoid with strong antioxidant properties, was shown to protect against oxidative damage induced by IR in several experimental models. The present study was designed to explore the possible protective effects of lycopene against IR-induced testicular damage in C57BL/6 mice. Mice were administered lycopene (20 mg/kg) by oral gavage for seven consecutive days prior to a single dose of whole-body X-ray irradiation (4 Gy, 1 Gy/min). We observed that lycopene remarkably augmented sperm motility and reduced sperm abnormalities in mice following IR exposure. Histopathological analyses also revealed that lycopene ameliorated the structural damage of seminiferous tubules and enhanced the regeneration of seminiferous epithelium following IR stress. Moreover, lycopene attenuated IR-induced oxidative stress, as evidenced by a decreasing lipid peroxidation level and an increase in the antioxidant enzyme superoxide dismutase activity. In addition, lycopene reduced the γH2AX expression and the number of TUNEL-positive cells in the germinal epithelium, as well as restoring the imbalance of Bax/Bcl-2 expression induced by IR exposure. Furthermore, lycopene prevented mitochondrial membrane potential depolarization and ATP reduction and preserved the activities of mitochondrial complexes I-IV in the testes of mice after exposure to IR. Lycopene also improved mitochondrial biogenesis in testes of mice exposed to IR, presenting as restored expressions of PGC-1α, Nrf1, and Tfam. Taken together, our results suggest that lycopene alleviates IR-induced testicular damage, and the underlying mechanism involves at least in part the inhibition of the mitochondrial apoptotic pathway and the maintenance of mitochondrial respiration and biogenesis. The beneficial effect of lycopene highlights the therapeutic potential of this plant-derived antioxidant against impaired spermatogenesis and male infertility induced by IR.

Overview of the Potential Beneficial Effects of Carotenoids on Consumer Health and Well-Being

Well-known experimental research demonstrates that oxidative stress is the leading cause of the onset and progression of major human health disorders such as cardiovascular, neurological, metabolic, and cancer diseases. A high concentration of reactive oxygen species (ROS) and nitrogen species leads to damage of proteins, lipids, and DNA associated with susceptibility to chronic human degenerative disorders. Biological and pharmaceutical investigations have recently focused on exploring both oxidative stress and its defense mechanisms to manage health disorders. Therefore, in recent years there has been considerable interest in bioactive food plant compounds as naturally occurring antioxidant sources able to prevent, reverse, and/or reduce susceptibility to chronic disease. To contribute to this research aim, herein, we reviewed the beneficial effects of carotenoids on human health. Carotenoids are bioactive compounds widely existing in natural fruits and vegetables. Increasing research has confirmed that carotenoids have various biological activities, such as antioxidant, anti-tumor, anti-diabetic, anti-aging, and anti-inflammatory activities. This paper presents an overview of the latest research progress on the biochemistry and preventative and therapeutic benefits of carotenoids, particularly lycopene, in promoting human health. This review could be a starting point for improving the research and investigation of carotenoids as possible ingredients of functional health foods and nutraceuticals in the fields of healthy products, cosmetics, medicine, and the chemical industry.

LYC loaded ferritin nanoparticles for intracerebral delivery and the attenuation of neurodegeneration in D-gal-induced mice

Recombinant human H-ferritin nanocage (rHuHF) loaded with natural antioxidative lycopene molecules (LYC) was successfully constructed for the first time, aiming to enrich LYC in the brain and explore the regulation mechanism of this nanoparticles on neurodegeneration. Here, the mouse model was constructed via D-galactose-induced neurodegeneration based on behavioural analysis, histological observation, immunostaining analysis, Fourier transform infrared microscopy, and Western blotting analysis for the regulation of rHuHF-LYC. rHuHF-LYC improved the behaviour of mice in a dose-dependent manner. Besides, rHuHF-LYC can attenuate neuronal damage, maintain the number of Nissl body, increase the level of unsaturated fat, inhibit the activation of glial cells, and prevent excessive accumulation of neurotoxic proteins in the hippocampus of mice. More importantly, synaptic plasticity was activated in response to the regulation of rHuHF-LYC with excellent biocompatibility and biosafety. This study proved the validity of the direct use of natural antioxidant nano drugs for treating neurodegeneration, providing a promising therapeutic option against further imbalances in the degenerative brain microenvironment.

L-Ascorbic Acid 2-Phosphate Attenuates Methylmercury-Induced Apoptosis by Inhibiting Reactive Oxygen Species Accumulation and DNA Damage in Human SH-SY5Y Cells

Methylmercury (MeHg) is a toxin that causes severe neuronal oxidative damage. As vitamin C is an antioxidant well-known to protect neurons from oxidative damage, our goal was to elucidate its protective mechanism against MeHg-induced oxidative stress in human neuroblastomas (SHSY5Y). We treated cells with MeHg, L-ascorbic acid 2-phosphate (AA2P), or both, and used MTT, flow cytometry, and Western blot analyses to assess cell damage. We found that MeHg significantly decreased the survival rate of SH-SY5Y cells in a time- and dose-dependent manner, increased apoptosis, downregulated PAR and PARP1 expression, and upregulated AIF, Cyto C, and cleaved Caspase-3 expression. A time course study showed that MeHg increased reactive oxygen species (ROS) accumulation; enhanced apoptosis; increased DNA damage; upregulated expression ofγH2A.X, KU70, 67 and 57 kDa AIF, CytoC, and cleaved Caspase-3; and downregulated expression of 116 kDa PARP1, PAR, BRAC1, and Rad51. Supplementation with AA2P significantly increased cell viability and decreased intrinsic ROS accumulation. It also reduced ROS accumulation in cells treated with MeHg and decreased MeHg-induced apoptosis. Furthermore, AA2P conversely regulated gene expression compared to MeHg. Collectively, we demonstrate that AA2P attenuates MeHg-induced apoptosis by alleviating ROS-mediated DNA damage and is a potential treatment for MeHg neurotoxicity.

Mixture of Tomato and Lemon Extracts Synergistically Prevents PC12 Cell Death from Oxidative Stress and Improves Hippocampal Neurogenesis in Aged Mice

Dietary habits have a great impact on one's health, especially in cognitive decline. Tomato and lemon contain diverse bioactive compounds and possess various effects, including the enhancement of cognitive function. We observed the protective effect of tomato, lemon extract and the mixture of them on H2O2-induced cytotoxicity of PC12 cells. To measure the in vivo effect in a murine model, each extract was orally administered to forty 1-year-old mice for 6 weeks, and a novel object recognition (NOR) test was performed to observe cognitive function, and hippocampal neurogenesis was observed through a doublecortin (DCX) stain. PC12 cell death by oxidative stress was reduced by pretreating with each extract, and a synergistic reduction was observed in the mixture. Newly generated DCX-positive neurons were synergistically increased in the hippocampus by the mixture. NOR test showed a tendency to significantly improve age-related cognitive dysfunction by consuming the mixture of tomato and lemon. In conclusion, tomato and lemon extracts can reduce cellular oxidative stress and increase NOR, likely due to enhanced neurogenesis, while the mixture of the two showed synergistic anti-oxidative effects and hippocampal neurogenesis.

Effect of methylmercury on fetal neurobehavioral development: an overview of the possible mechanisms of toxicity and the neuroprotective effect of phytochemicals

Methylmercury (MeHg) is a global environmental pollutant with neurotoxic effects. Exposure to MeHg via consumption of seafood and fish can severely impact fetal neurobehavioral development even when MeHg levels in maternal blood are as low as about 5 μg/L, which the mother tolerates well. Persistent motor dysfunctions and cognitive deficits may result from trans-placental exposure. The present review summarizes current knowledge on the mechanisms of MeHg toxicity during the period of nervous system development. Although cerebellar Purkinje cells are MeHg targets, the actions of MeHg on thiol components in the neuronal cytoskeleton as well as on mitochondrial enzymes and induction of disturbances of glutamate signaling can impair extra-cerebellar functions, also at levels well tolerated by adult individuals. Numerous herbal substances possess neuroprotective effects, predominantly represented by natural polyphenolic molecules that might be utilized to develop natural drugs to alleviate neurotoxicity symptoms caused by MeHg or other Hg compounds.

The Impact of Oxidative Stress of Environmental Origin on the Onset of Placental Diseases

Oxidative stress (OS) plays a pivotal role in placental development; however, abnormal loads in oxidative stress molecules may overwhelm the placental defense mechanisms and cause pathological situations. The environment in which the mother evolves triggers an exposure of the placental tissue to chemical, physical, and biological agents of OS, with potential pathological consequences. Here we shortly review the physiological and developmental functions of OS in the placenta, and present a series of environmental pollutants inducing placental oxidative stress, for which some insights regarding the underlying mechanisms have been proposed, leading to a recapitulation of the noxious effects of OS of environmental origin upon the human placenta.

Antioxidant and Anti-Inflammatory Potential of Thymoquinone and Lycopene Mitigate the Chlorpyrifos-Induced Toxic Neuropathy

CPF (chlorpyrifos) is an organophosphate pesticide used in agricultural and veterinary applications. Our experiment aimed to explore the effects of thymoquinone (TQ) and/or lycopene (LP) against CPF-induced neurotoxicity. Wistar rats were categorized into seven groups: first group served as a control (corn oil only); second group, TQ (10 mg/kg); third group, LP (10 mg/kg); fourth group, CPF (10 mg/kg) and deemed as CPF toxic control; fifth group, TQ + CPF; sixth group, (LP + CPF); and seventh group, (TQ + LP + CPF). CPF intoxication inhibited acetylcholinesterase (AchE), decreased glutathione (GSH) content, and increased levels of malondialdehyde (MDA), an oxidative stress biomarker. Furthermore, CPF impaired the activity of antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT) along with enhancement of the level of inflammatory mediators such as tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β. CPF evoked apoptosis in brain tissue. TQ or LP treatment of CPF-intoxicated rats greatly improved AchE activity, oxidative state, inflammatory responses, and cell death. Co-administration of TQ and LP showed better restoration than their sole treatment. In conclusion, TQ or LP supplementation may alleviate CPF-induced neuronal injury, most likely due to TQ or LPs’ antioxidant, anti-inflammatory, and anti-apoptotic effects.

Lycopene prevents oxygen-glucose deprivation-induced autophagic death in SH-SY5Y cells via inhibition of the oxidative stress-activated AMPK/mTOR pathway

Lycopene has been reported to exert a protective effect on the brain against transient ischemia‑induced damage; however, whether it could regulate autophagic neuronal death remains elusive. The present study aimed to investigate the role of autophagy in the protective effects of lycopene against neuronal damage and its underlying mechanism. Oxygen‑glucose deprivation (OGD) was used to simulate neuronal ischemic injury in human SH‑SY5Y cells. Lactate dehydrogenase (LDH) release assay revealed that OGD induced SH‑SY5Y cell death. Western blotting demonstrated that OGD upregulated the expression levels of the autophagy marker proteins autophagy protein 5 (ATG5) and LC3II, but downregulated the autophagy substrate p62 in a time‑dependent manner. By contrast, OGD‑induced cell death was significantly inhibited by the autophagy inhibitors 3‑methyladenine or bafilomycin A1 or by knockdown of ATG5, indicating that OGD may induce autophagic death in SH‑SY5Y cells. Notably, lycopene was shown not only to prevent OGD‑induced SH‑SY5Y cell death, but was also able to effectively inhibit OGD‑induced upregulation of ATG5 and LC3II, and downregulation of p62 in a dose‑dependent manner. Mechanistically, it was suggested that lycopene inhibited OGD‑induced activation of the AMPK/mTOR pathway via attenuation of oxidative stress by maintaining the intracellular antioxidant glutathione (GSH). Furthermore, the inhibitory role of lycopene in GSH depletion was found to be associated with the prevention of OGD‑induced depletion of intracellular cysteine and downregulation of xCT. Collectively, the present study demonstrated that lycopene protected SH‑SY5Y cells against OGD‑induced autophagic death by inhibiting oxidative stress‑dependent activation of the AMPK/mTOR pathway.

The Developing Cerebellum as a Target for Toxic Substances: Protective Role of Antioxidants

Cerebellar development begins during the late embryological period and continues to undergo organizational changes long after birth. The cerebellum is particularly susceptible to developmental abnormalities on exposure to oxidants and free radicals, thus leading to oxidative stress. Oxidative stress occurs when there is an imbalance between reactive oxygen species generation and antioxidant defences which may disrupt signalling pathways, leading to cerebellar anomalies and dysfunction. In this regard, this review assesses current research underlining the importance of the cerebellum, provides an update on substances affecting cerebellar development and highlights some promising antioxidants that may play a role in attenuating toxicity in the developing cerebellum. To accomplish this, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) system was employed and key scientific databases such as Science Direct, PubMed, Scopus, Web of Science and Google Scholar were searched to explore and collect information on the cerebellum and the role of antioxidants during its development. Originally, 109 articles were obtained but 22 articles which met the inclusion criteria were selected for the review. These findings provide an updated compilation of antioxidants capable of attenuating oxidative damage in the developing cerebellum, thus allowing future interdisciplinary studies in the form of clinical applications for screening and possible development of novel therapeutic agents from the identified products.

Astrocytes in heavy metal neurotoxicity and neurodegeneration

With the industrial development and progressive increase in environmental pollution, the mankind overexposure to heavy metals emerges as a pressing public health issue. Excessive intake of heavy metals, such as arsenic (As), manganese (Mn), mercury (Hg), aluminium (Al), lead (Pb), nickel (Ni), bismuth (Bi), cadmium (Cd), copper (Cu), zinc (Zn), and iron (Fe), is neurotoxic and it promotes neurodegeneration. Astrocytes are primary homeostatic cells in the central nervous system. They protect neurons against all types of insults, in particular by accumulating heavy metals. However, this makes astrocytes the main target for heavy metals neurotoxicity. Intake of heavy metals affects astroglial homeostatic and neuroprotective cascades including glutamate/GABA-glutamine shuttle, antioxidative machinery and energy metabolism. Deficits in these astroglial pathways facilitate or even instigate neurodegeneration. In this review, we provide a concise outlook on heavy metal-induced astrogliopathies and their association with major neurodegenerative disorders. In particular, we focus on astroglial mechanisms of iron-induced neurotoxicity. Iron deposits in the brain are detected in main neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. Accumulation of iron in the brain is associated with motor and cognitive impairments and iron-induced histopathological manifestations may be considered as the potential diagnostic biomarker of neurodegenerative diseases. Effective management of heavy metal neurotoxicity can be regarded as a potential strategy to prevent or retard neurodegenerative pathologies.

Differential susceptibility of PC12 and BRL cells and the regulatory role of HIF-1α signaling pathway in response to acute methylmercury exposure under normoxia

Hypoxia-inducible factor 1 (HIF-1) is a critical nuclear transcription factor for adaptation to hypoxia; its regulatable subunit, HIF-1α, is a cytoprotective regulatory factor. We examined the effects of methylmercury (MeHg) in rat adrenal pheochromocytoma (PC12) cells and the rat hepatocyte cell line BRL. MeHg treatment led to time- and concentration-dependent toxicity in both lines with statistically significant cytotoxic effects at 5 μM and 10 μM in PC12 and BRL, respectively, at 0.5 h. HIF-1α protein levels were significantly decreased at 2.5 (PC12) and 5 (BRL) μM MeHg. Furthermore, MeHg reduced the protein levels of HIF-1α and its target genes (glucose transporter-1, vascular endothelial growth factor-A and erythropoietin). Overexpression of HIF-1α significantly attenuated MeHg-induced toxicity in both cell types. Notably, cobalt chloride, a pharmacological inducer of HIF-1α, significantly attenuated MeHg-induced toxicity in BRL but not PC12. In both cell lines, an inhibitor of prolyl hydroxylase, 3, 4-dihydroxybenzoic acid, and the proteasome inhibitor carbobenzoxy-L-leucyl-L-leucyl-L-leucinal(MG132), antagonized MeHg toxicity, while 2-methoxyestradiol, a HIF-1α inhibitor, significantly increased it. These data establish that: (a) neuron-like PC12 cells are more sensitive to MeHg than non-neuronal BRL cells; (b) HIF-1α plays a similar role in MeHg-induced toxicity in both cell lines; and (c) upregulation of HIF-1α offers general cytoprotection against MeHg toxicity in PC12 and BRL cell lines.

Lycopene protects neuroblastoma cells against oxidative damage via depression of ER stress

Lycopene is a pigment derived from tomatoes and other red fruits, and has potent antioxidant and antitumor effects. However, its potential role in alleviating oxidative damage in neuronal cells is not well defined. In this study, we investigated the effects of lycopene on H₂ O₂ -induced damage in neuroblastoma cells, as well as the underlying mechanisms. Exposure to H₂ O₂ markedly decreased the viability of SH-SY5Y cells and increased LDH release, both of which were reversed by lycopene pretreatment. Lycopene also ameliorated H₂ O₂ -induced damage and reduced the expression of apoptotic markers, such as Bcl-2, Bax, and cleaved caspase 3. In addition, the H₂ O₂ -induced oxidative markers, including MDA, 8-OHdG, and protein carbonyls, were also downregulated by lycopene. Exogenous H₂ O₂ activated the GRP78/PERK/eIF2α signaling pathway, which was inhibited by pretreatment with lycopene. Finally, lycopene significantly ameliorated ER stress-induced activation and nuclear translocation of CHOP. Overexpression of CHOP markedly reversed the antiapoptotic effects of lycopene, indicating that it is essential for the latter's protective effects. Taken together, lycopene protects neuroblastoma cells from oxidative stress and ER stress-induced damage by inhibiting the PERK-CHOP signaling pathway, which is a potential therapeutic target in neurodegenerative diseases. PRACTICAL APPLICATION: Lycopene demonstrated antioxidative damage properties in protecting the neural system in vitro. The present study provides a novel preventive strategy against neurodegenerative diseases. Increased consumption of lycopene-based products and lycopene-rich fruits and vegetables may result in a lower risk for neurodegenerative diseases.

Lycopene antagonizes lead toxicity by reducing mitochondrial oxidative damage and mitochondria-mediated apoptosis in cultured hippocampal neurons

Lead (Pb) exhibits serious adverse effects on the central nervous system, and the major pathogenic mechanism of Pb toxicity is oxidative stress. As one of the carotenoid family members with potent antioxidant properties, lycopene has shown its protections by inhibiting oxidative stress damage in numerous models of neurotoxicity. The current study was designed to explore the possible protective property in primary cultured rat hippocampal neurons challenged with Pb. We observed that 5 μM lycopene pretreatment for 4 h efficiently ameliorated Pb‐caused damage in cell viability, accumulation of reactive oxygen species (ROS), and apoptosis in a dose‐dependent manner. Moreover, lycopene (5 μM) attenuated the 50 μM Pb‐induced mitochondrial ROS production, improved the activities of mitochondrial respiratory chain enzymes and ATP production, and ameliorated the 50 μM Pb‐induced depolarization of mitochondrial membrane potential as well as opening of mitochondrial permeability transition pores. In addition, 5 μM lycopene restored the imbalance of Bax/Bcl‐2, inhibited translocation of cytochrome c, and reduced caspase‐3 activation. Taken together, these findings indicate that lycopene antagonizes against Pb‐induced neurotoxicity and the underlying mechanism probably involves reduction of mitochondrial oxidative damage and mitochondria‐mediated apoptosis.

Lycopene as a Natural Antioxidant Used to Prevent Human Health Disorders

Lycopene, belonging to the carotenoids, is a tetraterpene compound abundantly found in tomato and tomato-based products. It is fundamentally recognized as a potent antioxidant and a non-pro-vitamin A carotenoid. Lycopene has been found to be efficient in ameliorating cancer insurgences, diabetes mellitus, cardiac complications, oxidative stress-mediated malfunctions, inflammatory events, skin and bone diseases, hepatic, neural and reproductive disorders. This review summarizes information regarding its sources and uses amongst different societies, its biochemistry aspects, and the potential utilization of lycopene and possible mechanisms involved in alleviating the abovementioned disorders. Furthermore, future directions with the possible use of this nutraceutical against lifestyle-related disorders are emphasized. Its protective effects against recommended doses of toxic agents and toxicity and safety are also discussed.

Lycopene protects against central and peripheral neuropathy by inhibiting oxaliplatin-induced ATF-6 pathway, apoptosis, inflammation and oxidative stress in brains and sciatic tissues of rats

The fact that oxaliplatin (OXL), a platinum-based chemotherapeutic drug, causes severe neuropathy greatly limits its clinical use. This study investigated the effects of lycopene, a potent antioxidant, on OXL-induced central and peripheral neuropathy. In this study, 30 min after oral administration of LY at a dose of 2 mg/kg b.w./day and 4 mg/kg b.w./day on 1 st, 2nd, 4th and 5th days, rats were given 4 mg/kg b.w./day of OXL intraperitoneally. It was detected that LY decreased OXL-induced lipid peroxidation and increased the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) and the levels of glutathione (GSH) in brain tissue. LY showed anti-inflammatory effects by decreasing levels of mitogen-activated protein kinase-14 (MAPK14), nuclear factor kappa-B (NF-κB) and tumor necrosis factor-α (TNF-α) in brain and sciatic tissue. It was determined that OXL-induced endoplasmic reticulum stress (ERS) decreased because LY administration reduced the expressions of activating transcription factor-6 (ATF6), glucose-regulated protein-78 (GRP78), RNA-activated protein kinase (PKR)-like ER kinase and inositol-requiring enzyme-1 (IRE1). LY administration also reduced the damage of OXL-induced brain and sciatic tissue by increasing NCAM levels and decreasing GFAP levels. It was determined that caspase-3 immunopositivity markedly decreased by OXL and LY in combination. It was also observed that LY provided neuronal protection by increasing brain-derived neurotrophic factor (BDNF) levels, which decreased with OXL administration in sciatic tissue. The results demonstrate that LY can be beneficial in ameliorating OXL-induced central and peripheral nerve injuries by showing antioxidant, anti-inflammatory and anti-apoptotic properties in the brain and sciatic tissue.

Calcium-Involved Action of Phytochemicals: Carotenoids and Monoterpenes in the Brain

Background: Neurodegenerative and mood disorders represent growing medical and social problems, many of which are provoked by oxidative stress, disruption in the metabolism of various neurotransmitters, and disturbances in calcium homeostasis. Biologically active plant compounds have been shown to exert a positive impact on the function of calcium in the central nervous system. Methods: The present paper reviews studies of naturally occurring terpenes and derivatives and the calcium-based aspects of their mechanisms of action, as these are known to act upon a number of targets linked to neurological prophylaxis and therapy. Results: Most of the studied phytochemicals possess anticancer, antioxidative, anti-inflammatory, and neuroprotective properties, and these have been used to reduce the risk of or treat neurological diseases. Conclusion: The neuroprotective actions of some phytochemicals may employ mechanisms based on regulation of calcium homeostasis and should be considered as therapeutic agents.

Lycopene protects against t-BHP-induced neuronal oxidative damage and apoptosis via activation of the PI3K/Akt pathway

Oxidative stress is a key factor of and closely implicated in the pathogenesis of Alzheimer's disease (AD). We herein used tert-butyl hydroperoxide (t-BHP) to induce oxidative stress and mimic oxidative neurotoxicity in vitro. Lycopene is a natural antioxidant that has a strong ability to eliminate free radicals and shows effective protection in some neurodegenerative disease models. However, the effect of lycopene on t-BHP-induced neuronal damage in primary mouse neurons is unknown. This study aimed to investigate the effects of lycopene on t-BHP-induced neuronal damage and the related mechanisms. We found that lycopene pretreatment effectively enhanced the cell viability, improved the neuron morphology, increased the GSH/GSSG level, restored the mitochondrial membrane potential (ΔΨm) and decreased reactive oxygen species generation. Furthermore, lycopene reduced the ratios of Bax:Bcl-2 and cleaved caspase-3:caspase-3 and the level of cytochrome C, increased the levels of synaptophysin (SYP) and postsynaptic density 95 (PSD95) and activated the PI3K/Akt pathway. In conclusion, lycopene attenuated oxidative stress and reduced t-BHP-induced cell apoptosis, and the mechanism is likely related to activation of the PI3K/Akt pathway. Therefore, lycopene is a potential agent for preventing oxidative stress-mediated AD.

Protective effect of lycopene against chemical and natural toxins: A review

People are exposed to a number of environmental, occupational, and therapeutic toxic agents which may be natural or man made. These hazardous substances may manifest as direct side effects on the function of organs or indirectly induced alteration of gene expression, cancer-associated metabolic pathways, and/or alter homeostasis. Lycopene, as a one of the most potent antioxidant, is found in fruits and vegetables. High-intake of lycopene has been shown to be effective in decreasing the risk of both natural toxins including mycotoxins, bacterial toxins, and chemical toxins including heavy metals, pesticides as well as herbicides. Recently, there is growing attention in understanding the mechanisms of the phytochemicals and carotenoids as antioxidative, antiapoptotic, radical scavenging, and chelating agents and their roles in the modulation of inflammatory pathways. This review summarizes available data from several recent studies about lycopene and its role against chemical and natural toxicants. © 2018 BioFactors, 45(1):5-23, 2019.

Post-translational modifications in MeHg-induced neurotoxicity

Mercury (Hg) exposure remains a major public health concern due to its widespread distribution in the environment. Organic mercurials, such as MeHg, have been extensively investigated especially because of their congenital effects. In this context, studies on the molecular mechanism of MeHg-induced neurotoxicity are pivotal to the understanding of its toxic effects and the development of preventive measures. Post-translational modifications (PTMs) of proteins, such as phosphorylation, ubiquitination, and acetylation are essential for the proper function of proteins and play important roles in the regulation of cellular homeostasis. The rapid and transient nature of many PTMs allows efficient signal transduction in response to stress. This review summarizes the current knowledge of PTMs in MeHg-induced neurotoxicity, including the most commonly PTMs, as well as PTMs induced by oxidative stress and PTMs of antioxidant proteins. Though PTMs represent an important molecular mechanism for maintaining cellular homeostasis and are involved in the neurotoxic effects of MeHg, we are far from understanding the complete picture on their role, and further research is warranted to increase our knowledge of PTMs in MeHg-induced neurotoxicity.

Neurotransmitter amines and antioxidant agents in neuronal protection against methylmercury-induced cytotoxicity in primary cultures of mice cortical neurons

Methylmercury (MeHg) is an environmental toxicant with detrimental effects on the developing brain and adult nervous system. The main mechanisms identified include oxidative stress, changes in intracellular calcium, mitochondrial changes, inhibition of glutamate uptake, of protein synthesis and disruption of microtubules. However, little is known about mechanisms of protection against MeHg neurotoxicity. We found that resveratrol (10 μM) and ascorbic acid (200 μM) protected MeHg-induced cell death in primary cultures of cortical neurons. In this work, we aimed at finding additional targets that may be related to MeHg mode of action in cell toxicity with special emphasis in cell protection. We wonder whether neurotransmitters may affect the MeHg effects on neuronal death. Our findings show that neurons exposed to low MeHg concentrations exhibit less mortality if co-exposed to 10 μM dopamine (DA). However, DA metabolites, HVA (homovanillic acid) and DOPAC (3,4-dihydroxyphenylacetic acid) are not responsible for such protection. Furthermore, both DA D1 and D2 receptors agonists showed a protective effect against MeHg toxicity. It is striking though that DA receptor antagonists SKF83566 (10 μM) and haloperidol (10 μM) did not inhibit DA protection against MeHg. In addition, the protective effect of 10 μM DA against MeHg-induced toxicity was not affected by additional organochlorine pollutants exposure. Our results also demonstrate that cells exposed to MeHg in presence of 100 μM acetylcholine (ACh), show an increase in cell mortality at the "threshold value" of 100 nM MeHg. Finally, norepinephrine (10 μM) and serotonin (20 μM) also had an effect on cell protection. Altogether, we propose to further investigate the additional mechanisms that may be playing an important role in MeHg-induced cytotoxicity.

Thymoquinone alleviates arsenic induced hippocampal toxicity and mitochondrial dysfunction by modulating mPTP in Wistar rats

Arsenic is a pervasive environmental pollutant that is found in ground waters globally and is related to numerous morbidities in the high-risk population areas in countries including Bangladesh, India, and the USA. Arsenic exposure has been ubiquitously reported for exacerbating free radical generation, mitochondrial dysfunction, and apoptosis by interfering with the mPTP functioning. Over the past decades, nutraceuticals with antioxidant properties have shown promising efficacy in arsenic poisoning. In the present study, we have examined, the protective efficacy of thymoquinone (TQ), an active component of seed oil of Nigella sativa with antioxidant and anti-inflammatory activity on arsenic-induced toxicity in hippocampi of Wistar rats. In our results, arsenic conditioning (10 mg/kg b.wt.; p.o.) for 8 days has caused a significant increase in intracellular ROS generation, mitochondrial dysfunction and apoptotic events. On the contrary pretreatment with TQ (2.5 and 5 mg/kg b.wt.; p.o.) inhibited arsenic-induced mitochondrial dysfunction such as lowering of mitochondrial membrane potential (Δψm). Our results indicated that the neuroprotective efficacy of TQ in arsenic-induced stress is mediated through or in part by inhibition of mPTP opening. Demonstration of neuroprotective action of TQ provides insight into the pathogenesis of arsenic-related neuropathological morbidities.

Oxidative stress, caspase-3 activation and cleavage of ROCK-1 play an essential role in MeHg-induced cell death in primary astroglial cells

Methylmercury is a toxic environmental contaminant that elicits significant toxicity in humans. The central nervous system is the primary target of toxicity, and is particularly vulnerable during development. Rho-associated protein kinase 1 (ROCK-1) is a major downstream effector of the small GTPase RhoA and a direct substrate of caspase-3. The activation of ROCK-1 is necessary for membrane blebbing during apoptosis. In this work, we examined whether MeHg could affect the RhoA/ROCK-1 signaling pathway in primary cultures of mouse astrocytes. Exposure of cells with 10 μM MeHg decreased cellular viability after 24 h of incubation. This reduction in viability was preceded by a significant increase in intracellular and mitochondrial reactive oxygen species levels, as well as a reduced NAD⁺/NADH ratio. MeHg also induced an increase in mitochondrial-dependent caspase-9 and caspase-3, while the levels of RhoA protein expression were reduced or unchanged. We further found that MeHg induced ROCK-1 cleavage/activation and promoted LIMK1 and MYPT1 phosphorylation, both of which are the best characterized ROCK-1 downstream targets. Inhibiting ROCK-1 and caspases activation attenuated the MeHg-induced cell death. Collectively, these findings are the first to show that astrocytes exposed to MeHg showed increased cleavage/activation of ROCK-1, which was independent of the small GTPase RhoA.

Methylmercury exposure causes a persistent inhibition of myogenin expression and C2C12 myoblast differentiation

Methylmercury (MeHg) is a ubiquitous environmental toxicant, best known for its selective targeting of the developing nervous system. MeHg exposure has been shown to cause motor deficits such as impaired gait and coordination, muscle weakness, and muscle atrophy, which have been associated with disruption of motor neurons. However, recent studies have suggested that muscle may also be a target of MeHg toxicity, both in the context of developmental myogenic events and of low-level chronic exposures affecting muscle wasting in aging. We therefore investigated the effects of MeHg on myotube formation, using the C2C12 mouse myoblast model. We found that MeHg inhibits both differentiation and fusion, in a concentration-dependent manner. Furthermore, MeHg specifically and persistently inhibits myogenin (MyoG), a transcription factor involved in myocyte differentiation, within the first six hours of exposure. MeHg-induced reduction in MyoG expression is contemporaneous with a reduction of a number of factors involved in mitochondrial biogenesis and mtDNA transcription and translation, which may implicate a role for mitochondria in mediating MeHg-induced change in the differentiation program. Unexpectedly, inhibition of myoblast differentiation with MeHg parallels inhibition of Notch receptor signaling. Our research establishes muscle cell differentiation as a target for MeHg toxicity, which may contribute to the underlying etiology of motor deficits with MeHg toxicity.

Effects of methyl mercury exposure on pancreatic beta cell development and function

Methyl mercury is an environmental contaminant of worldwide concern. Since the discovery of methyl mercury exposure due to eating contaminated fish as the underlying cause of the Minamata disaster, the scientific community has known about the sensitivity of the developing central nervous system to mercury toxicity. Warnings are given to pregnant women and young children to limit consumption of foods containing methyl mercury to protect the embryonic, fetal and postnatally developing central nervous system. However, evidence also suggests that exposure to methyl mercury or various forms of inorganic mercury may also affect development and function of other organs. Numerous reports indicate a worldwide increase in diabetes, particularly type 2 diabetes. Quite recently, methyl mercury has been shown to have adverse effects on pancreatic beta (β) cell development and function, resulting in insulin resistance and hyperglycemia and may even lead to the development of diabetes. This review discusses possible mechanisms by which methyl mercury exposure may adversely affect pancreatic β cell development and function, and the role that methyl mercury exposure may have in the reported worldwide increase in diabetes, particularly type 2 diabetes. While additional information is needed regarding associations between mercury exposure and specific mechanisms of the pathogenesis of diabetes in the human population, methyl mercury's adverse effects on the body's natural sources of antioxidants suggest that one possible therapeutic strategy could involve supplementation with antioxidants. Thus, it is important that additional investigation be undertaken into the role of methyl mercury exposure and reduced pancreatic β cell function. Copyright © 2016 John Wiley & Sons, Ltd.

Resveratrol protects PC12 cells against OGD/ R-induced apoptosis via the mitochondrial-mediated signaling pathway

In this study, we investigated the neuroprotective potential of resveratrol against oxygen glucose deprivation/reoxygenation (OGD/R)-induced apoptotic damages in well-differentiated PC12 cells and the underlying mechanisms. Cells were incubated under normal condition or OGD/R in the presence or absence of 10 μM resveratrol. Cell viability was determined with methyl-thiazolyl-tetrazolium (MTT) assay. Apoptotic ratio was determined with Hoechst 33342 staining and Annexin V-FITC/PI double staining. Oxidative stress was evaluated by measuring the intracellular reactive oxygen species (ROS), the mitochondrial superoxide, the malondialdehyde (MDA) content, and the activities of superoxide dismutase (SOD) and catalase (CAT). The intracellular calcium ([Ca2+]i) was estimated by Fluo-3/AM. The mitochondrial membrane potential (MMP) was evaluated by 5,5′,6,6′-tetrachloro-1,1,3,3′-tetraethyl-benzimidazolyl-carbocyanine iodide (JC-1) and rhodamine 123 (Rh123). The opening of mitochondrial permeability transition pore (MPTP) was determined by the Calcein/Co2+-quenching technique. The protein levels of cytochrome c, Bcl-2, Bax, cleaved caspase-9, and cleaved caspase-3 were detected by western blot analysis. The results showed that 10 μM resveratrol attenuated OGD/R-induced cell viability loss and cell apoptosis, which was associated with the decreases in the MDA content and the increases in the SOD and CAT activities. Furthermore, the accumulation of intracellular ROS and mitochondrial superoxide, disturbance of [Ca2+]i homeostasis, reduction of MMP, opening of MPTP, and release of mitochondrial cytochrome c observed in OGD/R-injured cells, which indicated a switch on the mitochondrial-mediated apoptotic pathway, were all reversed by resveratrol. These results suggest that resveratrol administration may play a neuroprotective role via modulating the mitochondrial-mediated signaling pathway in OGD/R-induced PC12 cell injury.

Lycopene protects human SH‑SY5Y neuroblastoma cells against hydrogen peroxide‑induced death via inhibition of oxidative stress and mitochondria‑associated apoptotic pathways

Oxidative stress, which is characterized by excessive production of reactive oxygen species (ROS), is a common pathway that results in neuronal injury or death due to various types of pathological stress. Although lycopene has been identified as a potent antioxidant, its effect on hydrogen peroxide (H₂O₂)-induced neuronal damage remains unclear. In the present study, pretreatment with lycopene was observed to protect SH-SY5Y neuroblastoma cells against H₂O₂-induced death via inhibition of apoptosis resulting from activation of caspase-3 and translocation of apoptosis inducing factor (AIF) to the nucleus. Furthermore, the over-produced ROS, as well as the reduced activities of anti-oxidative enzymes, superoxide dismutase and catalase, were demonstrated to be alleviated by lycopene. Additionally, lycopene counteracted H₂O₂-induced mitochondrial dysfunction, which was evidenced by suppression of mitochondrial permeability transition pore opening, attenuation of the decline of the mitochondrial membrane potential, and inhibition of the increase of Bax and decrease of Bcl-2 levels within the mitochondria. The release of cytochrome c and AIF from the mitochondria was also reduced. These results indicate that lycopene is a potent neuroprotectant against apoptosis, oxidative stress and mitochondrial dysfunction, and could be administered to prevent neuronal injury or death.

NAD+ Supplementation Attenuates Methylmercury Dopaminergic and Mitochondrial Toxicity in Caenorhabditis Elegans

Methylmercury (MeHg) is a neurotoxic contaminant of our fish supply that has been linked to dopaminergic (DAergic) dysfunction that characterizes Parkinson's disease. We have previously shown that MeHg causes both morphological and behavioral changes in the Caenorhabditis elegans DAergic neurons that are associated with oxidative stress. We were therefore interested in whether the redox sensitive cofactor nicotinamide adenine dinucleotide (NAD(+)) may be affected by MeHg and whether supplementation of NAD( + )may prevent MeHg-induced toxicities. Worms treated with MeHg showed depletion in cellular NAD( + )levels, which was prevented by NAD( + )supplementation prior to MeHg treatment. NAD( + )supplementation also prevented DAergic neurodegeneration and deficits in DAergic-dependent behavior upon MeHg exposure. In a mutant worm line that cannot synthesize NAD( + )from nicotinamide, MeHg lethality and DAergic behavioral deficits were more sensitive to MeHg than wildtype worms, demonstrating the importance of NAD( + )in MeHg toxicity. In wildtype worms, NAD( + )supplementation provided protection from MeHg-induced oxidative stress and mitochondrial dysfunction. These data show the importance of NAD( + )levels in the response to MeHg exposure. NAD( + )supplementation may be beneficial for MeHg-induced toxicities and preventing cellular damage involved in Parkinson's disease.

Lycopene Prevents Amyloid [Beta]-Induced Mitochondrial Oxidative Stress and Dysfunctions in Cultured Rat Cortical Neurons

Brains affected by Alzheimer's disease (AD) show a large spectrum of mitochondrial alterations at both morphological and genetic level. The causal link between β-amyloid (Aβ) and mitochondrial dysfunction has been established in cellular models of AD. We observed previously that lycopene, a member of the carotenoid family of phytochemicals, could counteract neuronal apoptosis and cell damage induced by Aβ and other neurotoxic substances, and that this neuroprotective action somehow involved the mitochondria. The present study aims to investigate the effects of lycopene on mitochondria in cultured rat cortical neurons exposed to Aβ. It was found that lycopene attenuated Aβ-induced oxidative stress, as evidenced by the decreased intracellular reactive oxygen species generation and mitochondria-derived superoxide production. Additionally, lycopene ameliorated Aβ-induced mitochondrial morphological alteration, opening of the mitochondrial permeability transition pores and the consequent cytochrome c release. Lycopene also improved mitochondrial complex activities and restored ATP levels in Aβ-treated neuron. Furthermore, lycopene prevented mitochondrial DNA damages and improved the protein level of mitochondrial transcription factor A in mitochondria. Those results indicate that lycopene protects mitochondria against Aβ-induced damages, at least in part by inhibiting mitochondrial oxidative stress and improving mitochondrial function. These beneficial effects of lycopene may account for its protection against Aβ-induced neurotoxicity.

Fractionate analysis of the phytochemical composition and antioxidant activities in advanced breeding lines of high-lycopene tomatoes

The results of the first study characterizing new high-lycopene tomato advanced breeding lines, to determine the phytochemical content as well asin vitroantioxidant activities of peel, pulp and seed fractions are presented.

Mitochondrial Redox Dysfunction and Environmental Exposures

SIGNIFICANCE

Mitochondria are structurally and biochemically diverse, even within a single type of cell. Protein complexes localized to the inner mitochondrial membrane synthesize ATP by coupling electron transport and oxidative phosphorylation. The organelles produce reactive oxygen species (ROS) from mitochondrial oxygen and ROS can, in turn, alter the function and expression of proteins used for aerobic respiration by post-translational and transcriptional regulation.

RECENT ADVANCES

New interest is emerging not only into the roles of mitochondria in disease development and progression but also as a target for environmental toxicants.

CRITICAL ISSUES

Dysregulation of respiration has been linked to cell death and is a major contributor to acute neuronal trauma, peripheral diseases, as well as chronic neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease.

FUTURE DIRECTIONS

Here, we discuss the mechanisms underlying the sensitivity of the mitochondrial respiratory complexes to redox modulation, as well as examine the effects of environmental contaminants that have well-characterized mitochondrial toxicity. The contaminants discussed in this review are some of the most prevalent and potent environmental contaminants that have been linked to neurological dysfunction, altered cellular respiration, and oxidation.

Mitochondrial DNA oxidative damage contributes to cardiomyocyte ischemia/reperfusion-injury in rats: cardioprotective role of lycopene

Mitochondrial (mt) dysfunction and oxidative stress are involved in the pathogenesis of ischemia/reperfusion (I/R)-injury. Lycopene, a lipophilic antioxidant found mainly in tomatoes and in other vegetables and fruits, can protect mtDNA against oxidative damage. However, the role of mtDNA in myocardial I/R-injury is unclear. In the present study, we aimed to determine if and how lycopene protects cardiomyocytes from I/R-injury. In both in vitro and in vivo studies, I/R-injury increased mt 8-hydroxyguanine (8-OHdG) content, decreased mtDNA content and mtDNA transcription levels, and caused mitochondrial dysfunction in cardiomyocytes. These effects of I/R injury on cardiomycoytes were blocked by pre-treatment with lycopene. MtDNA depletion alone was sufficient to induce cardiomyocyte death. I/R-injury decreased the protein level of a key activator of mt transcription, mitochondrial transcription factor A (Tfam), which was blocked by lycopene. The protective effect of lycopene on mtDNA was associated with a reduction in mitochondrial ROS production and stabilization of Tfam. In conclusion, lycopene protects cardiomyocytes from the oxidative damage of mtDNA induced by I/R-injury.

In vitro models for neurotoxicology research

The nervous system has a highly complex organization, including many cell types with multiple functions, with an intricate anatomy and unique structural and functional characteristics; the study of its (dys)functionality following exposure to xenobiotics, neurotoxicology, constitutes an important issue in neurosciences.