Serotonin-Cu(II)-mediated DNA cleavage: mechanism of copper binding by serotonin

Association between serum copper, zinc, and selenium concentrations and depressive symptoms in the US adult population, NHANES (2011-2016)

BACKGROUND

Evidence suggests that alterations in serum trace element concentrations are closely associated with mental illness. However, ​studies on the relationship between serum copper, zinc, and selenium concentrations and depressive symptoms are limited and with controversial results. We aimed to investigate the association between serum concentrations of these trace elements and depressive symptoms in US adults.

METHODS

Data from the National Health and Nutrition Examination Survey (NHANES) (2011-2016) were used in this cross-sectional study. The Patient Health Questionnaire-9 Items (PHQ-9) was employed to assess depressive symptoms. Multiple logistic regression was performed to determine the relationship between the serum concentrations of copper, zinc, and selenium and depressive symptoms.

RESULTS

A total of 4552 adults were included. Subjects with depressive symptoms had higher serum copper concentrations (123.88 ± 1.87) than those without depressive symptoms (116.99 ± 0.86) (p < 0.001). In Model 2, weighted logistic regression analysis showed that the second (Q2) quartile of zinc concentrations (odds ratio [OR] = 1.534, 95% confident interval [CI]: 1.018 to 2.313) were significantly associated with an increased risk of depressive symptoms. Subgroup analysis revealed that the third (Q3) and fourth (Q4) quartiles of copper concentrations (Q3: OR = 2.699, 95% CI: 1.285 to 5.667; Q4: OR = 2.490, 95% CI: 1.026 to 6.046) were also positively associated with depressive symptoms in obese individuals after controlling for all confounders. However, no significant relationship between serum selenium concentrations and depressive symptoms was observed.

CONCLUSIONS

Obese US adults with high serum copper concentrations, as well as US adults in general with low serum zinc concentrations, were susceptible to depressive symptoms. Nevertheless, the causal mechanisms underlying these relationships need to be further explored.

Escitalopram Targets Oxidative Stress, Caspase-3, BDNF and MeCP2 in the Hippocampus and Frontal Cortex of a Rat Model of Depression Induced by Chronic Unpredictable Mild Stress

In recent years, escitalopram (ESC) has been suggested to have different mechanisms of action beyond its well known selective serotonin reuptake inhibition. The aim of this study is to investigate the effects of escitalopram on oxidative stress, apoptosis, brain-derived neurotrophic factor (BDNF), Methyl-CpG-binding protein 2 (MeCP2), and oligodendrocytes number in the brain of chronic unpredictable mild stress-induced depressed rats. The animals were randomised in four groups (8 in each group): control, stress, stress + ESC 5 and stress + ESC 5/10. ESC was administered for 42 days in a fixed dose (5 mg/kg b.w.) or in an up-titration regimen (21 days ESC 5 mg/kg b.w. then 21 days ESC 10 mg/kg b.w.). Sucrose preference test (SPT) and elevated plus maze (EPM) were also performed. ESC improved the percentage of sucrose preference, locomotion and anxiety. ESC5/10 reduced the oxidative damage in the hippocampus and improved the antioxidant defence in the hippocampus and frontal lobe. ESC5/10 lowered caspase 3 activity in the hippocampus. Escitalopram had a modulatory effect on BDNF and the number of oligodendrocytes in the hippocampus and frontal lobe and also improved the MeCP2 expressions. The results confirm the multiple pathways implicated in the pathogenesis of depression and suggest that escitalopram exerts an antidepressant effect via different intricate mechanisms.

Causing DNA damage and stopping DNA repair - Vitamin D supplementation with Poly(ADP-ribose) polymerase 1 (PARP1) inhibitors may cause selective cell death of cancer cells: A novel therapeutic paradigm utilizing elevated copper levels within the tumour

Inhibitors of PARP1 are currently being used to treat malignancies and as maintenance drugs post chemotherapy. Vitamin D has been shown to have an anticancer effect (mediated by multiple mechanisms) and is usually deficient in cancer patients. We had previously proposed and experimentally validated the selective cell death of cancer cells caused due to interaction of vitamin D with elevated copper within malignant cells, leading to ROS mediated DNA damage. In this communication we propose a Vitamin D supplementation strategy with PARP1 inhibitor treatment which would have multifaceted benefits for therapy. Besides exerting its anticancer effects by other mechanisms and addressing the deficiency, Vitamin D in principle would cause selective ROS mediated DNA breakage in malignant cells, while sparing healthy non malignant cells. Since Vitamin D is also a known inhibitor of PARP1, this therapeutic strategy would push the malignant cells to apoptosis due to DNA breakage via the vitamin D-copper mechanism, in addition to inhibiting DNA repair. Since the available levels copper within normal cells are several fold less as compared to malignant cells, the normal cells would be spared of the Vitamin D induced, ROS mediated DNA damage and would be less likely to die due to PARP1 inhibition.

Sertraline induces DNA damage and cellular toxicity in Drosophila that can be ameliorated by antioxidants

Sertraline hydrochloride is a commonly prescribed antidepressant medication that acts by amplifying serotonin signaling. Numerous studies have suggested that children of women  taking sertraline during pregnancy have an increased risk of developmental defects. Resolving the degree of risk for human fetuses requires comprehensive knowledge of the pathways affected by this drug. We utilized a Drosophila melanogaster model system to assess the effects of sertraline throughout development. Ingestion of sertraline by females did not affect their fecundity or embryogenesis in their progeny. However, larvae that consumed sertraline experienced delayed developmental progression and reduced survival at all stages of development. Genetic experiments showed that these effects were mostly independent of aberrant extracellular serotonin levels. Using an ex vivo imaginal disc culture system, we showed that mitotically active sertraline-treated tissues accumulate DNA double-strand breaks and undergo apoptosis at increased frequencies. Remarkably, the sertraline-induced genotoxicity was partially rescued by co-incubation with ascorbic acid, suggesting that sertraline induces oxidative DNA damage. These findings may have implications for the biomedicine of sertraline-induced birth defects.

Antioxidant and Pro-Oxidant Activities of Melatonin in the Presence of Copper and Polyphenols In Vitro and In Vivo

Melatonin is a well-documented antioxidant. Physicochemical analysis using the density functional theory suggests that melatonin is a copper chelating agent; however, experimental evidence is still in demand. The present study investigated the influence of melatonin on reactive oxygen species (ROS) generated from polyphenol autoxidation in the presence of copper. Surprisingly, we found that melatonin paradoxically enhanced ROS formation in a redox system containing low concentrations of copper and quercetin (Que) or (−)-epigallocatechin-3-gallate (EGCG), due to reduction of cupric to cuprous ion by melatonin. Addition of DNA to this system inhibited ROS production, because DNA bound to copper and inhibited copper reduction by melatonin. When melatonin was added to a system containing high concentrations of copper and Que or EGCG, it diminished hydroxyl radical formation as expected. Upon addition of DNA to high concentrations of copper and Que, this pro-oxidative system generated ROS and caused DNA damage. The DNA damage was not prevented by typical scavengers of hydroxyl radical DMSO or mannitol. Under these conditions, melatonin or bathocuproine disulfonate (a copper chelator) protected the DNA from damage by chelating copper. When melatonin was administered intraperitoneally to mice, it inhibited hepatotoxicity and DNA damage evoked by EGCG plus diethyldithiocarbamate (a copper ionophore). Overall, the present study demonstrates the pro-oxidant and antioxidant activities of melatonin in the redox system of copper and polyphenols. The pro-oxidant effect is inhibited by the presence of DNA, which prevents copper reduction by melatonin. Interestingly, in-vivo melatonin protects against copper/polyphenol-induced DNA damage probably via acting as a copper-chelating agent rather than a hydroxyl radical scavenger. Melatonin with a dual function of scavenging hydroxyl radical and chelating copper is a more reliable DNA guardian than antioxidants that only have a single function of scavenging hydroxyl radical.

Potential role of serotonin as a biological reductant associated with copper transportation

Serotonin (5-HT) is a neurotransmitter that is derived from tryptophan. Owing to a hydroxyl group attached to the indole nucleus, 5-HT exhibits a considerably higher redox activity than tryptophan. To gain insight into the biological relevance of the redox activity of 5-HT, the effect of Cu(I)-binding ligands on the 5-HT-mediated copper reduction was investigated. The d-d transition band of Cu(II) complexed with glycine [Cu(II)-Gly₂] was not affected by addition of 5-HT alone but was diminished when a thioether-containing compound coexists with 5-HT. Concomitant with disappearance of the d-d transition band of Cu(II)-Gly₂, the π-π* transition band of 5-hydroxyindole of 5-HT exhibits a red-shift which is consistently explained by oxidation of 5-HT and subsequent formation of a dimeric species. The redox reactions between 5-HT and copper are also accelerated by a peptide composed of a methionine (Met)-rich region in the extracellular domain of an integral membrane protein, copper transporter 1 (Ctr1). Since Ctr1 transports copper across the plasma membrane with specificity for Cu(I), reduction of extracellular Cu(II) to Cu(I) is required for copper uptake by Ctr1. Metalloreductases that can donate Cu(I) for Ctr1 have been identified in yeast but not yet been found in mammals. The results of this study indicate that the Met-rich region in the N-terminal extracellular domain of Ctr1 promotes the 5-HT-mediated Cu(II) reduction in order to acquire Cu(I) via a non-enzymatic process.

Combined brain Fe, Cu, Zn and neurometabolite analysis - a new methodology for unraveling the efficacy of transcranial direct current stimulation (tDCS) in appetite control

Obesity is a chronic, multifactorial origin disease that has recently become one of the most frequent lifestyle disorders. Unfortunately, current obesity treatments seem to be ineffective. At present, transcranial direct current brain stimulation (tDCS) represents a promising novel treatment methodology that seems to be efficient, well-tolerated and safe for a patient. Unfortunately, the biochemical action of tDCS remains unknown, which prevents its widespread use in the clinical arena, although neurobiochemical changes in brain signaling and metal metabolism are frequently reported. Therefore, our research aimed at exploring the biochemical response to tDCS in situ, in the brain areas triggering feeding behavior in obese animals. The objective was to propose a novel neurochemical (serotoninergic and dopaminergic signaling) and trace metal analysis of Fe, Cu and Zn. In doing so, we used energy-dispersive X-ray fluorescence (EDXRF) and high-performance liquid chromatography (HPLC). Anodal-type stimulation (atDCS) of the right frontal cortex was utilized to down-regulate food intake and body weight gain in obese rats. EDXRF was coupled with the external standard method in order to quantify the chemical elements within appetite-triggering brain areas. Major dopamine metabolites were assessed in the brains, based on the HPLC assay utilizing the external standard assay. Our study confirms that elemental analysis by EDXRF and brain metabolite assay by HPLC can be considered as a useful tool for the in situ investigation of the interplay between neurochemical and Fe/Cu/Zn metabolism in the brain upon atDCS. With this methodology, an increase in both Cu and Zn in the satiety center of the stimulated group could be reported. In turn, the most significant neurochemical changes involved dopaminergic and serotoninergic signaling in the brain reward system.

Effects of Physical Activity on Trace Elements and Depression Related Biomarkers in Children and Adolescents

Not much is known about the role of physical activity (PA), obesity related variables, and trace elements as potential risk factors affecting neurotransmitters in schoolchildren with depression. Our objective was to investigate the effect of physical activity (PA) on depressive symptoms in children and adolescents. Also, we aimed to study the association of demographic variables, serum levels of Copper (Cu), Zinc (Zn), serotonin, and salivary cortisol with depression in this population. One hundred and fifty school children (90 boys and 60 girls) aged 7-18 years were recruited for this study. All participants were evaluated for depression using CDI-score analysis. Their physical activity levels were checked using pre-validated questionnaires. The serum levels of Copper (Cu), Zinc (Zn), cortisol, and serotonin were estimated using atomic absorption, and immunoassay techniques. About 48.7 % of the study population had depressive symptoms (CDI-score; ≥13), and were classified into mild, moderate, and severe categories. Older children, especially girls, had higher levels of depression. Participants with moderate and severe depression had significantly lower physical activity, serotonin, and zinc levels, Zn/Cu ratios, and significantly higher copper and cortisol levels. Physically active boys showed significantly lower depressive CDI-scores and improvement in cortisol, serotonin, Cu, and Zn concentrations compared to girls of sedentary life style. CDI- scores correlated positively with BMI, cortisol and Cu, and negatively with PA, serotonin and Zn concentrations. BMI, cortisol, serotonin, Cu and Zn, could explain about 59.3-79 % of the depressive symptoms among schoolchildren, according to stepwise regression analysis. This was especially true in especially older girls. PA and an adequate balance in Zn and Cu levels, plays a positive role in improving CDI-depressive score, BMI, serotonin and cortisol levels among schoolchildren.

Radiation-induced bystander effects in the Atlantic salmon (salmo salar L.) following mixed exposure to copper and aluminum combined with low-dose gamma radiation

Very little is known about the combined effects of low doses of heavy metals and radiation. However, such "multiple stressor" exposure is the reality in the environment. In the work reported in this paper, fish were exposed to cobalt 60 gamma irradiation with or without copper or aluminum in the water. Doses of radiation ranged from 4 to 75 mGy delivered over 48 or 6 h. Copper doses ranged from 10 to 80 μg/L for the same time period. The aluminum dose was 250 μg/L. Gills and skin were removed from the fish after exposure and explanted in tissue culture flasks for investigation of bystander effects of the exposures using a stress signal reporter assay, which has been demonstrated to be a sensitive indicator of homeostatic perturbations in cells. The results show complex synergistic interactions of radiation and copper. Gills on the whole produce more toxic bystander signals than skin, but the additivity scores show highly variable results which depend on dose and time of exposure. The impacts of low doses of copper and low doses of radiation are greater than additive, medium levels of copper alone have a similar level of effect of bystander signal toxicity to the low dose. The addition of radiation stress, however, produces clear protective effects in the reporters treated with skin-derived medium. Gill-derived medium from the same fish did not show protective effects. Radiation exposure in the presence of 80 μg/L led to highly variable results, which due to animal variation were not significantly different from the effect of copper alone. The results are stressor type, stressor concentration and time dependent. Clearly co-exposure to radiation and heavy metals does not always lead to simple additive effects.

Alterations of intestinal serotonin following nanoparticle exposure in embryonic zebrafish

The increased use of engineered nanoparticles (NPs) in manufacturing and consumer products raises concerns about the potential environmental and health implications on the ecosystem and living organisms. Organs initially and more heavily affected by environmental NPs exposure in whole organisms are the skin and digestive system. We investigate the toxic effect of two types of NPs, nickel (Ni) and copper oxide (CuO), on the physiology of the intestine of a living aquatic system, zebrafish embryos. Embryos were exposed to a range of Ni and CuO NP concentrations at different stages of embryonic development. We use changes in the physiological serotonin (5HT) concentrations, determined electrochemically with carbon fiber microelectrodes inserted in the live embryo, to assess this organ dysfunction due to NP exposure. We find that exposure to both Ni and CuO NPs induces changes in the physiological 5HT concentration that varies with the type, exposure period and concentration of NPs, as well as with the developmental stage during which the embryo is exposed. These data suggest that exposure to NPs might alter development and physiological processes in living organisms and provide evidence of the effect of NPs on the physiology of the intestine.

Possible roles of excess tryptophan metabolites in cancer

Tryptophan is metabolized through serotonin, indole, and kynurenine (KN) pathways. Uptake of an excess amount of tryptophan accompanied with vitamin B6 deficiency may result in the accumulation of higher concentrations of metabolites mainly from the KN pathways in the bladder. These metabolites could interact with nitrite to become mutagenic nitrosamines. They could be a promoter in the initiator-promoter model of carcinogenesis. They produced bladder cancer when implanted in the bladder. They also interact with transition metals copper or iron to form reactive radicals or reactive oxygen species (ROS). Some metabolites, 3-hydroxy-anthranilic acid, were autooxidized to mutagenic cinnabarinic and anthranilyl radical intermediates. These radical intermediates could also be ligands that interact with aryl hydrocarbon receptor (AhR) and induce xenobiotic metabolizing enzymes (XMEs) to metabolize contaminated carcinogens. When tryptophan is exposed to either visible or UV light, a photoproduct of 6-formylindolo[3,2b]-carbazole is formed, which has a very high affinity for the AhR that plays a role in carcinogenesis. This review gives an insight into various mechanisms through which tryptophan metabolites cause carcinogenesis. It could be concluded that tryptophan metabolites play a complementary role in promoting carcinogenesis along with carcinogens like aflatoxin, CCl(4) , 2-acetylaminofluorene, 4-aminobiphenyl, 2-naphthylamine, or N-[4-(5-nitro-2-furyl)-2-thiazolyl] formamide. The underlying mechanisms could be their autoxidation, exposure to either visible or UV light, interaction with nitrite or transition metals to form reactive intermediates, serving as ligands to interact with an AhR that is known to play a role in carcinogenesis through induction of XMEs. Further research is warranted.Environ.

N-[(Dihydroxyphenyl)acyl]serotonins as potent inhibitors of tyrosinase from mouse and human melanoma cells

A series of N-acyl derivatives of tyramine, tryptamine, and serotonin were synthesized and tested on anti-melanogenic activity. The serotonin derivatives such as N-caffeoylserotonin (3) and N-protocatechuoylserotonin (9) were inhibitory to tyrosinase from mouse B16 and human HMV-II melanoma cells, while the corresponding derivatives of tryptamine and 5-methoxytryptamine were almost inactive or less active than the serotonin derivatives. The inhibitory activity of the serotonin derivatives increased with increasing number of phenolic hydroxyl groups in the acyl moiety. Melanin formation in the culture of B16 cells was suppressed by 3 and 9 with no cytotoxicity in the concentration range tested (IC(50)=15, 3 and 111muM for 3, 9, and kojic acid, respectively). Thus the N-acylserotonin derivatives having a dihydroxyphenyl group are potential anti-melanogenic agents. Their inhibition of tyrosinase is primarily performed through the 5-hydroxyindole moiety and further strengthened by the phenolic hydroxyl groups in the acyl moiety.

Selective Oxidative Stress in Brain Areas of Neonate Rats Exposed to 2,4-Dichlorophenoxyacetic Acid Through Mother's Milk

2,4-Dichlorophenoxyacetic acid (2,4-D) induced disparate alterations on enzymatic activities of the defensive mechanism and/or modifications of the reactive oxygen species levels in specific neonate rat brain regions. The midbrain, striatum, and prefrontal cortex were the areas where the alterations were more remarkable and with similar tendency. The hippocampus did not suffer many alterations, and the hypothalamus was the area where no changes were observed. The current results suggest that the developing brain areas have different susceptibilities to the adverse effect of the herbicide, especially those areas related to the dopaminergic system, and that oxidative stress is one 2,4-D mechanism of toxicity.

Copper induced oxidation of serotonin: analysis of products and toxicity

Serotonin is a major neurotransmitter that controls many functions, ranging from mood and behaviour through to sleep and motor functions. The non-enzymatic oxidation of serotonin is of significant importance as some oxidation products are considered to be neurotoxic. An interaction between copper and serotonin has been suggested by symptoms observed in a number of neurodegenerative diseases such as Wilson's and Prion diseases. Using PC12 cells as a model of neuronal cells, we show that the interaction between copper and serotonin is toxic to undifferentiated cells. The toxicity is largely due to reactive oxygen species as cell death is significantly reduced in the presence of the antioxidant mannitol. Differentiation of the PC12 cells also confers resistance to the oxidative process. In vitro oxidation of serotonin by copper results in the eventual formation of a coloured pigment, thought to be a melanin-like polymeric species. Using spectroscopic methods we provide evidence for the formation of a single intermediate product. This dimeric intermediate was identified and characterized as 5,5'-dihydroxy-4,4'-bitryptamine. These results indicate that copper structurally alters serotonin and this process may play a role in copper related neurodegenerative diseases.

Oxidative DNA damage induced by a melatonin metabolite, 6-hydroxymelatonin, via a unique non-o-quinone type of redox cycle

Melatonin, an indolic pineal hormone, is produced primarily at night in mammals and is important in controlling biological rhythms. Although melatonin is known to be effective as a free radical scavenger and has an anti-cancer effect, carcinogenic properties have also been reported. In relation to its carcinogenic potential, we have examined whether 6-hydroxymelatonin, a major melatonin metabolite, can induce DNA damage in the presence of metal ion using [32P]-5'-end-labeled DNA fragments obtained from genes relevant to human cancer. 6-Hydroxymelatonin induced site-specific DNA damage in the presence of Cu(II). Formamidopyrimidine-DNA glycosylase treatment induced cleavage sites mainly at G residues of the 5'-TG-3' sequence, whereas piperidine treatment induced cleavage sites at T mainly of 5'-TG-3'. Interestingly, 6-hydroxymelatonin strongly damaged G and C of the 5'-ACG-3' sequence complementary to codon 273 of the p53 gene. These results suggest that 6-hydroxymelatonin can cause double-base lesions. DNA damage was inhibited by both catalase and bathocuproine, Cu(I)-specific stabilizer, suggesting that reactive species derived from the reaction of H2O2 with Cu(I) participate in DNA damage. Cytochrome P450 reductase efficiently enhanced 6-hydroxymelatonin-induced oxidative DNA damage and oxygen consumption, suggesting the formation of redox cycle. It is noteworthy that 6-hydroxymelatonin can efficiently induce DNA damage via non-o-quinone type of redox cycle. Formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), a characteristic oxidative DNA lesion, in calf thymus DNA was significantly increased by 6-hydroxymelatonin in the presence of Cu(II). Furthermore, 6-hydroxymelatonin significantly increased the formation of 8-oxodG in human leukemia cell line HL-60 but not in HP100, a hydrogen peroxide (H2O2)-resistant cell line derived from HL-60. The 6-hydroxymelatonin-induced 8-oxodG formation in HL-60 cells significantly decreased by the addition of bathocuproine or o-phenanthroline. Therefore, it is concluded that melatonin may exhibit carcinogenic potential through oxidative DNA damage by its metabolite.

Electrochemical Determination of Serotonin and the Competitive Adsorption with Dopamine at 5,5-Ditetradecyl-2-(2-trimethylammonioethyl)-1,3-dioxane Bromide Lipid Film Modified by Glassy Carbon Electrode

A novel and effective approach to sensitively determine serotonin, known as 5-hydroxytryptamine (5-HT), has been proposed based on a 5,5-ditetradecyl-2-(2-trimethylammonioethyl)-1,3-dioxane bromide (DTDB) self-assembled lipid bilayer membrane modified glassy carbon electrode (DTDB/GCE). A DTDB/GCE shows the strong electrocatalysis for the oxidation of 5-HT, with the peak potential shifted to less positive value of 0.376 V vs. SCE, and effectively eliminates the interference from ascorbic acid (AA), even in the presence of 100-fold concentration of AA. Differential pulse voltammetry (DPV) gave a linear current for 5-HT from 2.0 x 10(-7) to 1.0 x 10(-5) M. At the DTDB/GCE, the oxidation of 5-HT was controlled by the adsorption process; for 5-HT coexisting with DA, the competitive adsorption was observed.

Spectroscopic and electrochemical studies of DNA breakage induced by dopamine and copper ion

Dopamine may show some biological activities in antitumor and cell apoptosis. Herein, we attempted to employ UV-Vis, CD, and electrochemical methods to investigate the interaction between DNA and dopamine. Both the spectroscopic and electrochemical evidence indicated that dopamine, which was a cation, could interact with polyanion DNA. However, this kind of interaction, mainly by a static electronic force, did not result in any damage of the DNA structure. This situation was quite different when Cu ion was added to the dopamine-DNA system; an obvious change in the color of the solution and in the spectra of UV-Vis and CD showed that some chemical changes occurred in this system, and that the DNA native structure was destroyed. The results of gel electrophores further revealed that DNA might be broken into small segments by dopamine in the presence of Cu ion. The possible reaction mechanisms are discussed.