Alterations in serum and brain trace element levels after antidepressant treatment: part I. Zinc

Gender-related alterations of serum trace elements and neurometabolism in the anterior cingulate cortex of patients with major depressive disorder

BACKGROUND

It is widely known that sex differences have a significant impact on patients with major depressive disorder (MDD). This study aims to evaluate the sex-related connection between serum trace elements and changes in neurometabolism in the anterior cingulate cortex (ACC) of MDD patients.

METHODS

109 untreated MDD patients and 59 healthy controls underwent proton magnetic resonance spectroscopy (1H-MRS) under resting conditions. We measured metabolic ratios in the ACC from both sides. Additionally, venous blood samples were taken from all participants to detect calcium (Ca), phosphorus, magnesium (Mg), copper (Cu), ceruloplasmin (CER), zinc (Zn), and iron (Fe) levels. We performed association and interaction analyses to explore the connections between the disease and gender.

RESULTS

In individuals with MDD, the Cu/Zn ratio increased, while the levels of Mg, CER, Zn and Fe decreased. Male MDD patients had lower Cu levels, while female patients had an increased Cu/Zn ratio. We observed significant gender differences in Cu, CER and the Cu/Zn ratio in MDD. Male patients showed a reduced N-acetyl aspartate (NAA)/phosphocreatine + creatine (PCr + Cr) ratio in the left ACC. The NAA/PCr + Cr ratio decreased in the right ACC in patients with MDD. In the left ACC of male MDD patients, the Cu/Zn ratio was inversely related to the NAA/PCr + Cr ratio, and Fe levels were negatively associated with the GPC + PC/PCr + Cr ratio.

CONCLUSIONS

Our findings highlight gender-specific changes in Cu homeostasis among male MDD patients. The Cu/Zn ratio and Fe levels in male MDD patients were significantly linked to neurometabolic alterations in the ACC.

Zinc and Central Nervous System Disorders

Zinc (Zn²⁺) is the second most abundant necessary trace element in the human body, exerting a critical role in many physiological processes such as cellular proliferation, transcription, apoptosis, growth, immunity, and wound healing. It is an essential catalyst ion for many enzymes and transcription factors. The maintenance of Zn²⁺ homeostasis is essential for the central nervous system, in which Zn²⁺ is abundantly distributed and accumulates in presynaptic vesicles. Synaptic Zn²⁺ is necessary for neural transmission, playing a pivotal role in neurogenesis, cognition, memory, and learning. Emerging data suggest that disruption of Zn²⁺ homeostasis is associated with several central nervous system disorders including Alzheimer's disease, depression, Parkinson's disease, multiple sclerosis, schizophrenia, epilepsy, and traumatic brain injury. Here, we reviewed the correlation between Zn²⁺ and these central nervous system disorders. The potential mechanisms were also included. We hope that this review can provide new clues for the prevention and treatment of nervous system disorders.

Combined hyperforin and lanicemine treatment instead of ketamine or imipramine restores behavioral deficits induced by chronic restraint stress and dietary zinc restriction in mice

Clinical and preclinical studies show evidence that chronic stress or nutritional deficits in dietary zinc (Zn) intake may be risk factors for developing major depressive disorder (MDD). Furthermore, there may be possible links between low serum Zn levels and development of treatment-resistant depression. In the present work, we combined chronic restraint stress (CRS) and a low-zinc diet (ZnD) in mice and carried out a set of behavioral and biochemical studies. The mice were treated with four different antidepressant compounds, namely, ketamine, Ro 25–6981 (Ro), hyperforin and lanicemine (Hyp + Lan), and imipramine (IMI). We show that CRS or ZnD alone or a combination of CRS and ZnD (CRS + ZnD) induces anhedonia observed in the sucrose preference test (SPT). The behavioral effects of CRS were restored by ketamine or IMI. However, only Hyp + Lan restored the deficits in behavioral phenotype in mice subjected to CRS + ZnD. We also showed that the antidepressant-like effects observed in Hyp + Lan-treated CRS + ZnD mice were associated with changes in the morphology of the dendritic spines (restored physiological level) in the hippocampus (Hp). Finally, we studied the metabolism of ketamine and its brain absorption in CRS and CRS + ZnD mice. Our results suggest that CRS + ZnD does not alter the metabolism of ketamine to (2R,6R;2S,6S)-HNK; however, CRS + ZnD can induce altered bioavailability and distribution of ketamine in the Hp and frontal cortex (FC) in CRS + ZnD animals compared to the control and CRS groups.

Zinc Deficiency Blunts the Effectiveness of Antidepressants in the Olfactory Bulbectomy Model of Depression in Rats

Currently used antidepressants do not always provide the desired results, and many patients suffer from treatment-resistant depression. Clinical studies suggest that zinc deficiency (ZnD) may be an important risk factor for depression and might blunt the effect of antidepressants. This study aimed to examine whether ZnD might blunt the effectiveness of antidepressants in the olfactory bulbectomy model (OB) of depression in rats. For this purpose, rats were subjected to the OB model, fed a zinc-deficient diet (3 mg Zn/kg) for 3 weeks, and finally treated with escitalopram (Esc), venlafaxine (Ven) 10 mg/kg, i.p., or combined Esc/Ven (1 mg/kg, i.p.) with zinc (5 mg/kg) for another 3 weeks. Open field (OFT), forced swim (FST), and sucrose intake (SIT) tests were used to evaluate depressive-like behavioral changes. In addition, serum, intracellular, and synaptic Zn concentrations and the level of zinc transporter (ZnT) proteins were analyzed. The OB + ZnD model induced hyperactivity in rats in the OFT, increased immobility time in the FST, and anhedonia in the SIT. Chronic treatment with Esc reduced immobility time in the FST in the OB + ZnD model. Esc/Ven +Zn increased sucrose intake in rats from the OB + ZnD group. The OB + ZnD decreased serum zinc levels and intracellular and synaptic Zn concentration in the prefrontal cortex (PFC) and cerebellum. These changes were normalized by chronic administration of Esc/Ven +Zn. Moreover, OB + ZnD decreased levels of the ZnT1 protein in the PFC and Hp and ZnT3 in Hp. Chronic administration of antidepressants did not alter the levels of ZnT proteins. The OB + ZnD model induces more depressive-like effects than either model alone. Our results show that ZnD may induce drug resistance in rats. Normalizing serum or brain zinc concentration is insufficient to reverse behavioral abnormalities caused by the OB + ZnD model. However, zinc supplementation might improve the effectiveness of antidepressants in reversing particular depression symptoms.

PTPRM Is Critical for Synapse Formation Regulated by Zinc Ion

In the nervous system, the trace metal ion zinc is required for normal mammalian brain development and physiology. Zinc homeostasis is essential for the control of physiological and pathophysiological brain functions. Synapses, the junctions between neurons, are the center of the brain’s information transmission. Zinc deficiency or excess leads to neurological disorders. However, it is still unclear whether and how zinc ion regulates synapse formation. Here, we investigated the effect of zinc on synapse formation in a cultured neuron system, and found that synapse formation and synaptic transmission were regulated by zinc ions. Finally, we identified that PTPRM is the key gene involved in synapse formation regulated by zinc ions. This study provides a new perspective to understanding the regulation of brain function by zinc ion.

Increased Cerebrospinal Fluid Concentration of ZnT3 Is Associated with Cognitive Impairment in Alzheimer's Disease

BACKGROUND

Cognitive deficits arising in the course of Alzheimer's disease (AD), dementia with Lewy bodies (DLB), and Parkinson's disease with dementia (PDD) are directly linked to synaptic loss. Postmortem studies suggest that zinc transporter protein 3 (ZnT3), AMPA glutamate receptor 3 (GluA3), and Dynamin1 are associated with cognitive decline in AD and Lewy body dementia patients.

OBJECTIVE

We aimed to evaluate the diagnostic value of ZnT3, GluA3, and Dynamin 1 in the cerebrospinal fluid (CSF) of patients with dementia due to AD, DLB, and PDD compared to cognitively normal subjective cognitive decline (SCD) patients in a retrospective study. In addition, we assessed the relationship between synaptic markers and age, sex, cognitive impairment, and depressive symptoms as well as CSF amyloid, phosphorylated tau (p-tau), and total tau (T-tau).

METHODS

Commercially available ELISA immunoassay was used to measure the levels of proteins in a total of 97 CSF samples from AD (N = 24), PDD (N = 18), DLB (N = 27), and SCD (N = 28) patients. Cognitive impairment was assessed using the Mini-Mental State Examination (MMSE).

RESULTS

We found a significant increase in the concentrations of ZnT3, GluA3, and Dynamin1 in AD (p = 0.002) and of ZnT3 and Dynamin 1 in DLB (p = 0.001, p = 0.002) when compared to SCD patients. Changes in ZnT3 concentrations correlated with MMSE scores in AD (p = 0.011), and with depressive symptoms in SCD (p = 0.041).

CONCLUSION

We found alteration of CSF levels of synaptic proteins in AD, PDD, and DLB. Our results reveal distinct changes in CSF concentrations of ZnT3 that could reflect cognitive impairment in AD with implications for future prognostic and diagnostic marker development.

Interaction between zinc, the GPR39 zinc receptor and the serotonergic system in depression

Zinc signalling has a crucial impact on the proper functioning of the brain. Disturbances within the zincergic system may lead to neuropsychological disorders, including major depression. Studying this disease and designing effective treatment is hampered by its heterogeneous etiology and the diversified nature of the symptoms. Over the years, studies have shown that zinc deficiency and disturbances in the expression profile of the zinc receptor - GPR39 - might be a useful neurobiological indicator of a pathological state. Zinc levels and the zinc receptor are altered by classic antidepressant treatment, which indicates possible reciprocity between the monoaminergic system and zinc signalling. Disruptions in this specific interplay might be a cause of a pathological depressive state, and restoring balance and cooperation between those systems might be key to a successful form of pharmacotherapy. In this review, we aim to describe interactions between the serotonergic and zincergic systems and to highlight their significance in the pathophysiology and treatment of depression.

Lowered zinc and copper levels in drug-naïve patients with major depression: Effects of antidepressants, ketoprofen and immune activation

Objectives: The aim of the present work is to examine the effects of treatment with sertraline with and without ketoprofen on serum levels of zinc and copper in association with immune-inflammatory biomarkers in drug-naïve major depressed patients.Methods: We measured serum zinc and copper, interleukin (IL)-1β, IL-4, IL-6, IL-18, interferon-γ, and transforming growth factor-β1 in 40 controls and 133 depressed patients. The clinical efficacy of the treatment was measured using the Beck Depression Inventory-II (BDI-II) at baseline and 8 weeks later.Results: We found significantly reduced serum zinc and copper in association with upregulation of all cytokines, indicating activation of the immune-inflammatory responses system (IRS) and the compensatory immune regulatory system (CIRS). Treatment with sertraline significantly increased zinc and decreased copper. During treatment, there was a significant inverse association between serum zinc and immune activation. The improvement in the BDI-II during treatment was significantly associated with increments in serum zinc coupled with attenuation of the IRS/CIRS.Conclusions: Lower zinc is a hallmark of depression, while increments in serum zinc and attenuation of the immune-inflammatory response during treatment appear to play a role in the clinical efficacy of sertraline.

Antidepressant-like activity of hyperforin and changes in BDNF and zinc levels in mice exposed to chronic unpredictable mild stress

Chronic unpredictable mild stress (CUMS) - a rodent model of depression mimics a variety of neurochemical and behavioral alterations similar to those seen in human depression. This study evaluated the antidepressant activity of hyperforin in the CUMS model using fluoxetine (FLX) as a reference drug. The antidepressant-like effects of hyperforin and FLX were evaluated in the tail suspension test (TST), forced swim test (FST), and splash test (SPT). CUMS induced an increase in immobility time in mice (pro-depressive effects) in the FST and TST. CUMS-induced changes were reversed by chronic treatment with hyperforin (2.5 and 5 mg/kg), as well as FLX (10 mg/kg). SPT results revealed a decrease in the frequency and duration of grooming in stressed mice. These effects were normalized by hyperforin (5 mg/kg) and FLX treatment. Hyperforin (2.5 mg/kg) only reversed the CUMS-induced deficits related to the frequency of grooming. CUMS also caused a decrease in zinc concentration in the frontal cortex (FC) and hippocampus (Hp) of mice; hyperforin (2.5 mg/kg) increased zinc concentration in the Hp of control rats. CUMS also induced a decrease in BDNF protein levels in the FC and Hp, while decreasing the pCREB/CREB ratio only in the Hp. Hyperforin (2.5 and 5 mg/kg) reversed the CUMS-induced reduction of BDNF only in the Hp. Our results demonstrate the antidepressant-like activity of hyperforin in the CUMS model in mice and the possible involvement of hippocampal BDNF/zinc alterations in this activity.

Alterations of serum macro-minerals and trace elements are associated with major depressive disorder: a case-control study

BACKGROUND

Major depressive disorder (MDD) is a mixed disorder with the highly irregular course, inconsistent response to treatment and has no well-known mechanism for the pathophysiology. Major causes of depression are genetic, neurobiological, and environmental. However, over the past few years, altered serum levels of macro-minerals (MM) and trace elements (TE) have been recognized as major causative factors to the pathogenesis of many mental disorders. The purpose of this study was to determine the serum levels of MM (calcium and magnesium) and TE (copper, iron, manganese, selenium, and zinc) in MDD patients and find out their associations with depression risk.

METHODS

This prospective case-control study recruited 247 patients and 248 healthy volunteers matched by age and sex. The serum levels of MM and TE were analyzed by atomic absorption spectroscopy (AAS). Statistical analysis was performed with independent sample t-tests and Pearson's correlation test.

RESULTS

We found significantly decreased concentrations of calcium and magnesium, iron, manganese, selenium, and zinc in MDD patients compared with control subjects (p < 0.05). But the concentration of copper was significantly increased in the patients than control subjects (p < 0.05). Data obtained from different inter-element relations in MDD patients and control subjects strongly suggest that there is a disturbance in the element homeostasis.

CONCLUSION

Our study suggests that altered serum concentrations of MM and TE are major contributing factors for the pathogenesis of MDD. Alterations of these elements in serum levels of MDD patients arise independently and they may provide a prognostic tool for the assessment of depression risk.

Differential Effects of Low- and High-dose Zinc Supplementation on Synaptic Plasticity and Neurogenesis in the Hippocampus of Control and High-fat Diet-fed Mice

In the present study, we investigated the concentration-dependent effect of zinc (Zn) supplementation on the adult hippocampus in a high-fat diet (HFD)-fed obese mouse model. Four-weeks after HFD- and control diet (CD)-feeding, mice were provided with low (15 ppm) or high (60 ppm) doses of Zn in their drinking water for additional 4 more weeks along with their respective diets. Compared to the CD-fed mice, HFD-feeding elicited the reduction of neurogenic markers such as nestin, Ki67, doublecortin (DCX), and 5-bromo-2'-deoxyuridine (BrdU) in the dentate gyrus. Additionally, HFD-feeding reduced the levels of synaptic markers (synaptophysin and N-methyl-D-aspartate receptor) and brain-derived neurotrophic factor (BDNF), while lipid peroxidation was significantly increased in the hippocampus of HFD-fed mice. Against detrimental effects of high-dose Zn, low-dose Zn supplementation in CD-fed mice did not yield any remarkable changes in these parameters. Interestingly, administration of low doses of Zn to HFD-induced obese mice prominently ameliorated HFD-induced changes in neurogenic, synaptic plasticity markers and BDNF levels as well as lipid peroxidation in the hippocampus. In contrast, high-dose Zn supplementation in HFD-fed mice exacerbated the reduction of markers for neurogenesis and synaptic plasticity as well as BDNF levels, but not 4-HNE levels, in the hippocampus. These results suggest that low-dose Zn supplementation in obese mice could reverse the HFD-induced reduction in neurogenic and synaptic marker proteins in the hippocampus by reducing lipid peroxidation and improving BDNF expression, while high-dose Zn supplementation exacerbates the reduction of neurogenesis by affecting synaptic markers and BDNF levels in the hippocampus.

The Emerging Role for Zinc in Depression and Psychosis

Zinc participation is essential for all physiological systems, including neural functioning, where it participates in a myriad of cellular processes. Converging clinical, molecular, and genetic discoveries illuminate key roles for zinc homeostasis in association with clinical depression and psychosis which are not yet well appreciated at the clinical interface. Intracellular deficiency may arise from low circulating zinc levels due to dietary insufficiency, or impaired absorption from aging or medical conditions, including alcoholism. A host of medications commonly administered to psychiatric patients, including anticonvulsants, oral medications for diabetes, hormones, antacids, anti-inflammatories and others also impact zinc absorption. Furthermore, inefficient genetic variants in zinc transporter molecules that transport the ion across cellular membranes impede its action even when circulating zinc concentrations is in the normal range. Well powered clinical studies have shown beneficial effects of supplemental zinc in depression and it important to pursue research using zinc as a potential therapeutic option for psychosis as well. Meta-analyses support the adjunctive use of zinc in major depression and a single study now supports zinc for psychotic symptoms. This manuscript reviews the biochemistry and bench top evidence on putative molecular mechanisms of zinc as a psychiatric treatment.

Analysis of Relations Between the Level of Mg, Zn, Ca, Cu, and Fe and Depressiveness in Postmenopausal Women

Numerous observations suggest a possible connection between the levels of Mg, Zn, Fe, and Zn and the incidence of depressive symptoms. Depression is two to three times more common in women than in men. The menopausal period is extremely conducive to depressive disorders. The aim of this study was to assess the severity of depressive symptoms in postmenopausal women depending on the levels of Mg, Zn, Ca, Cu, and Fe. The study included 198 healthy postmenopausal women at the average age of 56.26 ± 5.55 years. In the first part of the study, standardized research tools were used, namely the Primary Care Evaluation of Mental Disorders (PRIME-MD) and the Beck Depression Inventory (BDI). The second part involved biochemical analysis of Mg, Zn, Ca, Cu, and Fe levels in blood serum. The lowest Cu levels were observed in women without depressive symptoms (1.07 ± 0.22 mg/l) and the highest in those with severe depressive symptoms (1.19 ± 0.17 mg/l), (p ≤ 0.05). The lowest Mg levels were observed in women with depressive symptoms (14.28 ± 2.13 mg/l), and the highest in women without depressive symptoms (16.30 ± 3.51 mg/l), (p ≤ 0.05). The average serum Mg levels (15.75 ± 3.23 mg/l) decreased compared to the reference values (18.77-24 mg/l). What is striking is a potential relation between the levels of Mg and Cu and depressiveness. Our results indicate to a higher vulnerability to depression in a group of women with lower levels of Mg and higher levels of Cu.

Zinc in the Monoaminergic Theory of Depression: Its Relationship to Neural Plasticity

Preclinical and clinical studies have demonstrated that zinc possesses antidepressant properties and that it may augment the therapy with conventional, that is, monoamine-based, antidepressants. In this review we aim to discuss the role of zinc in the pathophysiology and treatment of depression with regard to the monoamine hypothesis of the disease. Particular attention will be paid to the recently described zinc-sensing GPR39 receptor as well as aspects of zinc deficiency. Furthermore, an attempt will be made to give a possible explanation of the mechanisms by which zinc interacts with the monoamine system in the context of depression and neural plasticity.

The level of the zinc homeostasis regulating proteins in the brain of rats subjected to olfactory bulbectomy model of depression

BACKGROUND

Zinc transporters (ZnTs) and metallothioneins (MT) are important in maintaining Zn homeostasis in the brain. The present study was designed to find out whether alterations in ZnTs and MTs are associated with the pathophysiology of depression and the mechanism of antidepressant action.

METHODS

Messenger RNA and proteins of ZnT1, ZnT3, ZnT4, ZnT5, ZnT6 and MT1/2 were measured in the prefrontal cortex (PFC) and hippocampus (Hp) of rats subjected to olfactory bulbectomy (OB) (a model of depression) and chronic amitriptyline (AMI) treatment by Real Time PCR and Western Blot/Immunohistochemistry (IHP).

RESULTS

Results in the OB rats showed: increases in the protein levels of ZnT1 in the PFC and Hp and MT1/2 in the PFC; a decrease in ZnT3 protein level in the PFC; no changes in ZnT4, ZnT5 and ZnT6 in the PFC and Hp. IHP labeling revealed increases in the optical densities of ZnT1-IR in the PFC and Hp and decreases in ZnT3 and ZnT4-IR in the PFC of OB rats. Although OB had no effects on gene expression of ZnTs, mRNAs for MT1/2 were increased. Chronic AMI treatment did not influence protein levels of ZnTs and MT1/2 in Sham and OB rats; however decreased mRNA levels of ZnT4 and ZnT5 in PFC and ZnT1, ZnT3, ZnT4 and ZnT6 in Hp of Sham rats and normalized OB induced increase in MT1/2 gene expression.

CONCLUSIONS

Changes in ZnTs and MT1/2 suggest altered cortical distribution of Zn in the OB model which further supports the hypothesis that Zn dyshomeostasis may be involved in the pathophysiology of depression.

Zinc transporters protein level in postmortem brain of depressed subjects and suicide victims

BACKGROUND

Major depressive disorder (MDD) is a serious psychiatric illness, associated with an increasing rate of suicide. The pathogenesis of depression may be associated with the disruption of zinc (Zn) homeostasis. In the brain, several proteins that regulate Zn homeostasis are present, including Zn transporters (ZnTs) which remove Zn from the cytosol. The present study was designed to investigate whether depression and suicide are associated with alterations in the expression of the ZnTs protein.

METHODS

Protein levels of ZnT1, ZnT3, ZnT4, ZnT5 and ZnT6 were measured in postmortem brain tissue from two different cohorts. Cohort A contained 10 subjects diagnosed with MDD (7 were suicide victims) and 10 psychiatrically-normal control subjects and cohort B contained 11 non-diagnosed suicide victims and 8 sudden-death control subjects. Moreover, in cohort A we measured protein level of NMDA (GluN2A subunit), AMPA (GluA1 subunit) and 5-HT1A receptors and PSD-95. Proteins were measured in the prefrontal cortex (PFC) using Western blotting. In addition, Zn concentration was measured using a voltammetric method.

RESULTS

There was a significant increase in protein levels of ZnT1, ZnT4, ZnT5 in the PFC in MDD, relative to control subjects, while ZnT3 protein level was decreased in MDD. There was no significant difference in the Zn concentration in the PFC between control and MDD subjects. Similarly, in the PFC of suicide victims (non-diagnosed), an increase in protein levels of ZnT1, ZnT4, ZnT5 and ZnT6 was observed. Conversely, protein levels of ZnT3 were decreased in both suicide victims and subjects with MDD, in comparison with control subjects. There was also a significant decrease in the protein level of GluA1, GluN2A, PSD-95 and 5-HT1A in MDD.

CONCLUSIONS

Our studies suggest that alterations in Zn transport proteins are associated with the pathophysiology of MDD and suicide.

Effects of Aqueous Extracts of Chicory and Milk Thistle on Serum Concentrations of Copper, Zinc, and Manganese in Tamoxifen-Treated Rats

Some medications may change trace element levels in the body. Extracts of various plants, due to having the several elements, can have beneficial effects. Consumption of herbal extracts with chemical drugs may reduce adverse effects of medication. The goal of this study was to evaluate copper (Cu), zinc (Zn), and manganese (Mn) concentrations in serum of rats treated with tamoxifen, chicory, and/or milk thistle extracts. Therefore, 36 adult female Wistar rats were divided into six groups: normal control, chicory control, milk thistle control, tamoxifen, tamoxifen-chicory, and tamoxifen-milk thistle. At the end of the study, the blood samples were collected and sera isolated by centrifugation and analyzed by the atomic absorption spectrophotometry for Cu, Zn, and Mn levels. The Zn concentration increased in milk thistle-supplemented groups. The Cu level increased in the chicory control group only. Tamoxifen had no affect on Cu, Zn, and Mn levels, but seed extract of milk thistle increased Zn concentration, and chicory root extract increased Cu concentration. Although elevated levels of Cu in rats receiving tamoxifen-chicory were milder than rats treated only with chicory, it seems that the extract and tamoxifen impact on the Cu are in conflict with each other.

Zinc and imipramine reverse the depression-like behavior in mice induced by chronic restraint stress

Depression is a common psychopathological disorders. Studies of depression have indicated that zinc play a role in the depression pathophysiology and treatment. In present study, we examined the effects of zinc and imipramine supplement alone or combination of zinc and imipramine in mice induced by chronic restraint stress (CRS). Moreover, the possible roles of zinc receptor (G protein-coupled receptor 39, GPR39)-related pathway was investigated. Decreased weight and increased corticosterone (CORT) were observed after 3 weeks CRS exposure. It was shown that CRS induced lower serum zinc, higher hippocampal zinc, increased immobility time in tail suspension test and decreased movement distance in spontaneous activity test, which could be normalized by zinc (30 mg/kg) and imipramine (20 mg/kg) supplement alone and combination of zinc (15 mg/kg) and imipramine (5 mg/kg) for 3 weeks after CRS exposure. Moreover, the changes in mRNA expressions of GPR39, cAMP-response element binding protein (CREB), brain-derived neurotropic factor (BDNF) and n-methytl-d-aspartate receptors (NMDAR) could be reversed by the same treatment mentioned above. These results suggested that zinc dyshomeostasis in serum and hippocampus and depression-like behavior in CRS exposure animals observed in present study could be normalized by zinc and imipramine. The combination of zinc and imipramine in low dose has synergetic effects. The possible mechanism might be correlated to GPR39 receptor-related pathway.

Decreased serum zinc concentration during depressive episode in patients with bipolar disorder

OBJECTIVES

Zinc may be involved in the pathophysiology and treatment of depressive disorder. However, data on this issue in bipolar disorder (BD) are limited. The aim of the study was to assess zinc concentrations in the blood serum of patients at various phases and stages of bipolar disorder.

METHODS

The study included 129 patients with a diagnosis of bipolar disorder type I (n=69) or type II (n=60). Fifty-eight were in a depressive episode, 23 in a manic episode and 48 in remission. Fifty healthy volunteers made a control group. Zinc concentration was measured using flame atomic absorption spectrometry.

RESULTS

Serum zinc level in patients diagnosed with BD type I in the depressive phase was significantly reduced as compared with mania, remission and healthy subjects. In the BD type II, serum zinc level in hypomania, depression or remission phase was not significantly different from the control group. In the whole group, lower level of zinc in depression compared to remission and control subjects was found during late stage of the illness but not in the early stage. Zinc concentration was not dependent on the severity of manic or depressive symptoms and subtype of depression but correlated positively with the number of manic/hypomanic relapses in the past year.

LIMITATIONS

Lack of prospective model, heterogeneity of pharmacological treatment, small number of subgroups presenting specified clinical features.

CONCLUSIONS

Decreased serum zinc concentration occurs in depression in BD type I and probably in depression in the late stage of BD.

Zinc Improves Cognitive and Neuronal Dysfunction During Aluminium-Induced Neurodegeneration

Metals are considered as important components of a physiologically active cell, and imbalance in their levels can lead to various diseased conditions. Aluminium (Al) is an environmental neurotoxicant, which is etiologically related to several neurodegenerative disorders like Alzheimer's, whereas zinc (Zn) is an essential trace element that regulates a large number of metabolic processes in the brain. The objective of the present study was to understand whether Zn provides any physiological protection during Al-induced neurodegeneration. Male Sprague Dawley rats weighing 140-160 g received either aluminium chloride (AlCl₃) orally (100 mg/kg b.wt./day), zinc sulphate (ZnSO₄) in drinking water (227 mg/L) or combined treatment of aluminium and zinc for 8 weeks. Al treatment resulted in a significant decline in the cognitive behaviour of rats, whereas zinc supplementation caused an improvement in various neurobehavior parameters. Further, Al exposure decreased (p ≤ 0.001) the levels of neurotransmitters, acetylcholinesterase activity, but increased (p ≤ 0.001) the levels of L-citrulline as well as activities of nitric oxide and monoamine oxidase in the brain. However, zinc administration to Al-treated animals increased the levels of neurotransmitters and regulated the altered activities of brain markers. Western blot of tau, amyloid precursor protein (APP), glial fibrillary acidic protein (GFAP), ubiquitin, α-synuclein and Hsp 70 were also found to be elevated after Al exposure, which however were reversed following Zn treatment. Al treatment also revealed alterations in neurohistoarchitecture in the form of loss of pyramidal and Purkinje cells, which were improved upon zinc co-administration. Therefore, the present study demonstrates that zinc improves cognitive functions by regulating α-synuclein and APP-mediated molecular pathways during aluminium-induced neurodegeneration.

GPR39 Zn(2+)-sensing receptor: a new target in antidepressant development?

Zinc is a trace element released from glutamatergic terminals, and modulates the pre- and postsynaptic areas, giving a diverse biological response. Zinc is a natural ligand that inhibits the N-methyl-d-aspartate (NMDA) receptor and regulates the excessive release of glutamate. Moreover, zinc exhibits an antidepressant-like profile, as demonstrated in both preclinical and clinical studies. Recent reports indicate that the GPR39 Zn(2+)-sensing receptor is an important target for zinc "transmission" (its activation modulates/induces diverse biochemical pathways involved in neuroprotection). Preclinical studies provide evidence that zinc deficiency leads to depressive-like behavior related to down-regulation of the GPR39 Zn(2+)-sensing receptor. Zinc binds to the GPR39 and triggers signals, leading to CRE-dependent gene transcription, resulting in increases in proteins such as brain-derived neurotrophic factor (BDNF), that plays a pivotal role in antidepressant action. Chronic administration of many antidepressants induces GPR39 up-regulation, which suggests that the Zn(2+)-sensing receptor may be considered as a new target for drug development in the field of depression.

Depression and synaptic zinc regulation in Alzheimer disease, dementia with lewy bodies, and Parkinson disease dementia

OBJECTIVE

Depression is a common symptom in dementia with Lewy bodies (DLB), Parkinson disease dementia (PDD), and Alzheimer disease (AD), yet its molecular basis remains unclear and current antidepressants do not appear to be effective. Cerebral zinc has been implicated in depression and synaptic dysfunction. We investigated the relationship between synaptic zinc regulation (for which zinc transporter 3 [ZnT3] is responsible) and depression in a large clinicopathologic study.

METHODS

We examined brains from people with PDD (N = 29), DLB (N = 27), and AD (N = 15) and comparison subjects without depression or dementia (N = 24). Individuals were categorized according to the presence and severity of depression (on a scale of 0-3) based on standardized assessments during life (principally Neuropsychiatric Inventory). Western blotting was used to determine ZnT3 levels in Brodmann area 9 (BA9), and regression analysis was used to determine the relationship between ZnT3 and depression.

RESULTS

Reductions in ZnT3 in BA9 were significantly associated with elevated depression scores in the study cohort (β = -0.351, df = 93, t = -3.318 p = 0.0004). This association remained when only individuals with DLB, PDD, and no dementia or depression were examined (β = -0.347, df = 78, t = -3.271, p = 0.002) or only individuals with AD and no dementia or depression were examined (β = -0.433, df = 37, t = -2.924, p = 0.006).

CONCLUSION

Although decreased zinc levels have been implicated in the genesis of depression in animal models and in major depressive disorder in humans, this study provides the first evidence of a role for zinc in depression in people with dementia and highlights zinc metabolism as a therapeutic target.

Trace elemental distribution in the scalp hair of bipolars using PIXE technique

Trace metals play a significant role in neurological disorders. There is very limited information available on the role of macro and trace elements in bipolar disorders. The objective of this investigation was to identification, quantification of essential trace elements in the scalp hair samples of the patients and compare with those of normal subjects. We made a hypothesis about the role played by essential trace metals whose concentrations are significantly different to those of normals in the disease process. The analysis was carried out in the scalp hair samples of 26 male and 26 female patients suffering from bipolar disorder (BD) by Particle Induced X-ray Emission Technique (PIXE). The concentration of Cu (p < 0.002) was found to be higher in the hair samples of male bipolar disorder patients while the concentrations of Mn (p < 0.001), Fe (p < 0.005), Zn (p < 0.0001) and Se (p < 0.005) were found to be lower than those in normal subjects. The concentration of Cu (p < 0.0001) was higher in the hair samples of female bipolar patients but depressed levels of Fe (p < 0.005), Ni (p < 0.05), Zn (p < 0.00001) and Se (p < 0.05) were observed compared to controls. Cu/Zn ratio was found to be higher in the hair samples of male and female patients compared with normals. While the imbalance of certain trace elements leads to generation of more free radicals, the imbalance of some other trace elements causes changes in dopamine (neurotransmitter) activity. It is essential to monitor before and periodically during treatment the levels of essential trace elements for effective treatment of bipolar disorder.

Pivotal role of tissue plasminogen activator in the mechanism of action of electroconvulsive therapy

Electroconvulsive therapy is an important treatment option for major depressive disorders, acute mania, mood disorders with psychotic features, and catatonia. Several hypotheses have been proposed as electroconvulsive therapy's mechanism of action. Our hypothesis involves many converging pathways facilitated by increased synthesis and release of tissue-plasminogen activator. Human and animal experiments have shown that tissue-plasminogen activator participates in many mechanisms of action of electroconvulsive therapy or its animal variant, electroconvulsive stimulus, including improved N-methyl-D-aspartate receptor-mediated signaling, activation of both brain-derived neurotrophic factor and vascular endothelial growth factor, increased bioavailability of zinc, purinergic release, and increased mobility of dendritic spines. As a result, tissue-plasminogen activator helps promote neurogenesis in limbic structures, modulates synaptic transmission and plasticity, improves cognitive function, and mediates antidepressant effects. Notably, electroconvulsive therapy seems to influence tissue-plasminogen activator metabolism. For example, electroconvulsive stimulus increases the expression of glutamate decarboxylase 65 isoform in γ-aminobutyric acid-releasing neurons, which enhances the release of tissue-plasminogen activator, and the expression of p11, a protein involved in plasminogen and tissue-plasminogen activator assembling. This paper reviews how electroconvulsive therapy correlates with tissue-plasminogen activator. We suggest that interventions aiming at increasing tissue-plasminogen activator levels or its bioavailability - such as daily aerobic exercises together with a carbohydrate-restricted diet, or normalization of homocysteine levels - be evaluated in controlled studies assessing response and remission duration in patients who undergo electroconvulsive therapy.

Zinc in depression: a meta-analysis

BACKGROUND

Zinc is an essential micronutrient with diverse biological roles in cell growth, apoptosis and metabolism, and in the regulation of endocrine, immune, and neuronal functions implicated in the pathophysiology of depression. This study sought to quantitatively summarize the clinical data comparing peripheral blood zinc concentrations between depressed and nondepressed subjects.

METHODS

PubMed, Cumulated Index to Nursing and Allied Health Literature, and PsycINFO were searched for original peer-reviewed studies (to June 2012) measuring zinc concentrations in serum or plasma from depressed subjects (identified by either screening or clinical criteria) and nondepressed control subjects. Mean (±SD) zinc concentrations were extracted, combined quantitatively in random-effects meta-analysis, and summarized as a weighted mean difference (WMD).

RESULTS

Seventeen studies, measuring peripheral blood zinc concentrations in 1643 depressed and 804 control subjects, were included. Zinc concentrations were approximately -1.85 µmol/L lower in depressed subjects than control subjects (95% confidence interval: [CI]: -2.51 to -1.19 µmol/L, Z17 = 5.45, p < .00001). Heterogeneity was detected (χ(2)17 = 142.81, p < .00001, I(2) = 88%) and explored; in studies that quantified depressive symptoms, greater depression severity was associated with greater relative zinc deficiency (B = -1.503, t9 = -2.82, p = .026). Effect sizes were numerically larger in studies of inpatients (WMD -2.543, 95% CI: -3.522 to -1.564, Z9 = 5.09, p < .0001) versus community samples (WMD -.943, 95% CI: -1.563 to -.323, Z7 = 2.98, p = .003) and in studies of higher methodological quality (WMD -2.354, 95% CI: -2.901 to -1.807, Z7 = 8.43, p < .0001).

CONCLUSIONS

Depression is associated with a lower concentration of zinc in peripheral blood. The pathophysiological relationships between zinc status and depression, and the potential benefits of zinc supplementation in depressed patients, warrant further investigation.

Effects of zinc supplementation on efficacy of antidepressant therapy, inflammatory cytokines, and brain-derived neurotrophic factor in patients with major depression

OBJECTIVE

Zinc is found in abundance in the human brain. Patients with depression may have decreased consumption of food sources rich in zinc, and zinc supplementation may have a potential influence on depressive symptoms. However, clinical trials on the effect of zinc supplementation in depression are limited. The objective of the present study was to determine the effect of zinc supplementation on efficacy of antidepressant therapy. Furthermore, the effect of zinc on plasma levels of interleukin-6 (IL-6), tumor necrosis factor (TNF-α), and brain-derived neurotrophic factor-a (BDNF-a) were assessed.

DESIGN

A single-center, randomized, double-blind, placebo-controlled trial of zinc supplementation was conducted in patients with DSM-IV major depression. Forty-four patients of both sexes aged 18-55 years were recruited for this study from a university hospital. The zinc-supplemented group received zinc sulfate (25 mg elemental Zn/day) orally in addition to their selective serotonin reuptake inhibitor antidepressants for 12 weeks. Symptoms were evaluated using the Hamilton Depression Rating Scale (HDRS) on arrival, weeks 6 and 12. Plasma levels of IL-6, TNF-α and BDNF-a were measured at baseline and at the end of study.

RESULTS

Twenty patients in zinc group and 17 patients in placebo groups completed the study. At baseline, there were no significant differences in any variable between the patients allocated to receive placebo and those taking zinc supplement. Zinc supplementation significantly reduced HDRS compared to placebo (P < 0.01 at 12th week). No significant differences were observed in plasma levels of IL-6, TNF-α, and BDNF-a between zinc-supplemented and placebo-supplemented group.

CONCLUSION

Zinc supplementation in conjunction with antidepressant drugs might be beneficial for reducing depressive symptoms. However, its effect does not appear to be mediated through impact of zinc on inflammatory processes.

Antioxidants as potential therapeutics for neuropsychiatric disorders

Oxidative stress has been implicated in the pathophysiology of many neuropsychiatric disorders such as schizophrenia, bipolar disorder, major depression etc. Both genetic and non-genetic factors have been found to cause increased cellular levels of reactive oxygen species beyond the capacity of antioxidant defense mechanism in patients of psychiatric disorders. These factors trigger oxidative cellular damage to lipids, proteins and DNA, leading to abnormal neural growth and differentiation. Therefore, novel therapeutic strategies such as supplementation with antioxidants can be effective for long-term treatment management of neuropsychiatric disorders. The use of antioxidants and PUFAs as supplements in the treatment of neuropsychiatric disorders has provided some promising results. At the same time, one should be cautious with the use of antioxidants since excessive antioxidants could dangerously interfere with some of the protective functions of reactive oxygen species. The present article will give an overview of the potential strategies and outcomes of using antioxidants as therapeutics in psychiatric disorders.

Potential roles of zinc in the pathophysiology and treatment of major depressive disorder

Incomplete response to monoaminergic antidepressants in major depressive disorder (MDD), and the phenomenon of neuroprogression, suggests a need for additional pathophysiological markers and pharmacological targets. Neuronal zinc is concentrated exclusively within glutamatergic neurons, acting as an allosteric modulator of the N-methyl D-aspartate and other receptors that regulate excitatory neurotransmission and neuroplasticity. Zinc-containing neurons form extensive associational circuitry throughout the cortex, amygdala and hippocampus, which subserve mood regulation and cognitive functions. In animal models of depression, zinc is reduced in these circuits, zinc treatment has antidepressant-like effects and dietary zinc insufficiency induces depressive behaviors. Clinically, serum zinc is lower in MDD, which may constitute a state-marker of illness and a risk factor for treatment-resistance. Marginal zinc deficiency in MDD may relate to multiple putative mechanisms underlying core symptomatology and neuroprogression (e.g. immune dysfunction, monoamine metabolism, stress response dysregulation, oxidative/nitrosative stress, neurotrophic deficits, transcriptional/epigenetic regulation of neural networks). Initial randomized trials suggest a benefit of zinc supplementation. In summary, molecular and animal behavioral data support the clinical significance of zinc in the setting of MDD.

Zinc signaling through glucocorticoid and glutamate signaling in stressful circumstances

Humans and animals are constantly exposed to environmental stress. The hypothalamic-pituitary-adrenal (HPA) axis responds to stress, followed by glucocorticoid secretion from the adrenal glands. This response serves to maintain homeostasis in the living body through energy mobilization or to restore it. The brain is an important target for glucocorticoids. The hippocampus participates in the regulation of the HPA axis. Stress activates glutamatergic neurons in the hippocampus, and serious stress induces dyshomeostasis of extracellular glutamate. This dyshomeostasis, which is potentiated by glucocorticoids, modifies cognitive and emotional behavior. On the other hand, zinc is necessary for glucocorticoid signaling and is released from glutamatergic (zincergic) neurons to modulate synaptic glutamate signaling. Stress also induces dyshomeostasis of extracellular zinc, which may be linked to dyshomeostasis of extracellular glutamate. Thus, glucocorticoid signaling might also contribute to dyshomeostasis of extracellular zinc. It is likely that zinc signaling participates in cognitive and emotional behavior through glucocorticoid and glutamate signaling under stressful circumstances. This Mini-Review analyzes the relationship among signals of glucocorticoid, glutamate, and zinc under stressful circumstances to elucidate the significance of the zinc signaling in response to stress.

Convergent animal and human evidence suggests a role of PPM1A gene in response to antidepressants

BACKGROUND

Antidepressant drugs are used as first-line treatment in depression, but response has been shown to be highly heterogeneous, with drugs often failing to have the desired therapeutic effect. We report on an integrative analysis from the Genome-Based Therapeutic Drugs for Depression (GENDEP) study using gene expression from mice to inform prioritization in a human pharmacogenetic study.

METHODS

The same two antidepressants were used in mice and humans: escitalopram (a serotonin reuptake inhibitor) and nortriptyline (a norepinephrine reuptake inhibitor). The animal study used four inbred strains of mice (129S1/SvlmJ, C57LB/6J, DBA/2J, and FVB/NJ). Hippocampus mRNA levels were measured in 144 animals using the Affymetrix MOE 430 v2 chip.

RESULTS

Based on gene-expression analysis of strain-by-drug interactions, 17 genes differentially expressed with nortriptyline or escitalopram versus saline were prioritized in the human pharmacogenetic analysis. Single nucleotide polymorphisms tagging common sequence variation in human orthologs of these genes were tested for association with response to antidepressants in 706 participants of the GENDEP human pharmacogenetic study, treated with escitalopram or nortriptyline for 12 weeks, with available high-quality Illumina 610 quad array genotyping. Several polymorphisms in the protein phosphatase 1A gene (PPM1A) remained significantly associated with response to nortriptyline in humans after correction for multiple comparisons within the gene. PPM1A encodes a phosphatase involved in mitogen-activated protein kinase signaling and cell stress response.

CONCLUSIONS

Convergent evidence from mice and humans suggests a role of the PPM1A in response to noradrenergic but not serotonergic antidepressants.

Chronic treatment with zinc and antidepressants induces enhancement of presynaptic/extracellular zinc concentration in the rat prefrontal cortex

Zinc exhibits antidepressant-like activity in preclinical tests/models. Moreover, zinc homeostasis is implicated in the pathophysiology of affective disorders. The aim of the present study was to examine the effect of chronic zinc, citalopram and imipramine intraperitoneal administration on the presynaptic and extracellular zinc concentration in the rat prefrontal cortex and hippocampus. We used two methods: zinc-selenium histochemistry (which images the pool of presynaptic-vesicle zinc) and anodic stripping voltammetry (ASV) for zinc determination in microdialysate (which assays the extracellular zinc concentration). We report that chronic (14 ×) zinc (hydroaspartate, 10 and 65 mg/kg) and citalopram (20 mg/kg) administration increased the pool of presynaptic zinc (by 34, 50 and 37%, respectively) in the rat prefrontal cortex. The 21% increase induced by imipramine (20 mg/kg) was marginally significant. Likewise, zinc (hydroaspartate, 65 mg/kg), citalopram and imipramine increased the extracellular zinc (although with a different pattern: time point, area under the curve and/or basal level) in this brain region. Furthermore, zinc induced an increase in presynaptic (by 65%) and extracellular zinc (by 90%) in the hippocampus, while both citalopram and imipramine did not. These results indicate that all of the treatments increase presynaptic/extracellular zinc concentrations in the rat prefrontal cortex, which may then contribute to their antidepressant mechanisms. Alterations induced by zinc (but not antidepressants) administration in the hippocampus may be related to specific zinc mechanisms. All the data (previous and present) on the effect of antidepressant treatments on the presynaptic/extracellular zinc concentrations suggest the involvement of this biometal presynaptic/synaptic homeostasis in the antidepressant mechanism(s).

Trace elements in bipolar disorder

INTRODUCTION

Trace elements may play an important role in bipolar disorders. The objective of this study is to determine serum copper and zinc, blood lead and cadmium and urine lead, cadmium and thallium concentrations in patients diagnosed with bipolar disorders and to compare these levels with those of a healthy control group.

MATERIALS AND METHODS

A total of 25 patients diagnosed with bipolar disorder and 29 healthy subjects participated in this study. Serum copper and zinc concentrations were measured using flame atomic absorption spectrometry; the blood lead and cadmium concentrations were measured by electrothermal atomization atomic absorption spectrometry with Zeeman background correction; urine lead, cadmium and thallium concentrations were measured by inductively coupled plasma mass spectrometry.

RESULTS

Median blood and urine lead and cadmium levels were significantly higher among the bipolar patients than among the control group: Blood lead (μg/dL): patient median: 3.00 (IQR: 1.40-4.20); control median (μg/dL): 2.20 (IQR: 0.90-3.00) p=0.040. Blood cadmium (μg/L): patient median: 0.39 (IQR: 0.10-1.15); control median: 0.10 (IQR: 0.10-0.17) p<0.001. The median of cadmium (μg/L) in patients who smoked (1.20 IQR: 0.44-2.30) was higher than that in non-smokers (0.12 IQR: 0.10-0.34) p<0.001. There was a statistically significant increase (p=0.001) in zinc levels among patients in the manic phase (mean 111.28, SD: 33.36 μg/dL) with respect to the control group (mean 86.07, SD: 12.39 μg/dL).

CONCLUSIONS

The results suggest that there could be higher levels of some toxic trace elements in the group of patients with bipolar disorder than in the healthy control group.

Correlation between dietary zinc intakes and its serum levels with depression scales in young female students

It has been suggested that mood disorders and depressive status may be accompanied by lowered zinc status in the body, and adequate consumption of zinc increases a general perceived well-being. The main objective of this study was to assess the correlation between serum zinc concentrations and dietary zinc intakes with depression scores in university female students. In the first phase, Beck's depression questionnaire was applied in a random sampling of 308 selected 20-25-year-old female students (one third of total students in Ahvaz Jondi-Shapour University of Medical Sciences Golestan dormitories) to assess the major depressive disorder (MDD) scales. Then, in the second phase, 23 students who identified as having moderate and severe depression were selected as the case group, and 23 healthy age matched were chosen as the controls. Each of them completed a 12-item semiquantitative food frequency questionnaire containing the main food sources of zinc in the usual dietary patterns and also a 24-h food recall questionnaire to assure the daily zinc intakes. Daily zinc intakes were obtained by multiplying each portion size by its zinc content using food tables. A 5-ml blood sample was taken for further serum zinc status using flame atomic absorption spectrophotometry technique. Pearson's r was used to show the correlation between quantitative variables. Both daily zinc intake and serum zinc concentrations of MDD group were about two thirds of healthy index (p < 0.01). Depressed individuals used to eat lower servings of red meats and chicken as the main food sources of zinc in students' usual diets (p < 0.001). Consumption of other foods as the sources of zinc was not significantly different in two groups. A linear significant correlation between dietary zinc intakes and its serum levels was seen in samples (r = 0.62; p < 0.001) and MDD students (r = 0.55; p < 0.001). There was a linear inverse correlation between Beck questionnaire scores and serum zinc concentrations in all of the investigated students(r = -0.65; p < 0.001) and MDD girls (r = -0.71; p < 0.001). Beck questionnaire scores and diatary zinc intakes were also inversly correlated (r = -0.58; p < 0.001). However, no statistical correlation was seen between these two variables in MDD cases. In depressed female students, dietary zinc intake is correlated to its serum concentrations; however, the serum zinc levels are inversely correlated to depression scales. Consumption of the main dietary sources of zinc such as red meats and chicken should be encouraged in young depressed girls.

Role of zinc in the development and treatment of mood disorders

PURPOSE OF REVIEW

The present review is a critical examination of the most recent published work on the role of zinc in the development and treatment of mood disorders.

RECENT FINDINGS

Clinical studies and experimental work using animal models have both revealed a link between zinc status and neuropsychological disorders such as depression and anxiety. Not only has zinc deficiency been shown to induce depression-like and anxiety-like behaviors, supplementation has been used as a treatment for major depression. Zinc administration improves the efficacy of antidepressant drugs in depressed patients and may have a particular role to play in treatment-resistant patients. Recent investigations into the molecular mechanisms responsible for these observations suggest a role for zinc in the regulation of neurotransmitter systems, antioxidant mechanisms, neurotrophic factors, and neuronal precursor cells.

SUMMARY

The data reviewed here not only indicate a role for zinc deficiency in the development of mood disorders, but also show that zinc may also be important in their treatment. Given the prevalence of zinc deficiency in human populations, this work has the potential to influence strategies to prevent and treat these disorders.

Chronic administration of harmine elicits antidepressant-like effects and increases BDNF levels in rat hippocampus

A growing body of evidence has pointed to the β-carboline harmine as a potential therapeutic target for the treatment of major depression. The present study was aimed to evaluate behavioural and molecular effects of the chronic treatment with harmine and imipramine in rats. To this aim, rats were treated for 14 days once a day with harmine (5, 10 and 15 mg/kg) and imipramine (10, 20 and 30 mg/kg) and then subjected to the forced swimming and open-field tests. Harmine and imipramine, at all doses tested, reduced immobility time of rats compared with the saline group. Imipramine increased the swimming time at 20 and 30 mg/kg and harmine increased swimming time at all doses. The climbing time increased in rats treated with imipramine (10 and 30 mg/kg) and harmine (5 and 10 mg/kg), without affecting spontaneous locomotor activity. Brain-derived neurotrophic factor (BDNF) hippocampal levels were assessed in imipramine and harmine-treated rats by ELISA sandwich assay. Interestingly, chronic administration of harmine at the higher doses (10 and 15 mg/kg), but not imipramine, increased BDNF protein levels in rat hippocampus. Finally, these findings further support the hypothesis that harmine could bring about behavior and molecular effects, similar to antidepressants drugs.

Zinc: the brain's dark horse

Zinc is a life-sustaining trace element, serving structural, catalytic, and regulatory roles in cellular biology. It is required for normal mammalian brain development and physiology, such that deficiency or excess of zinc has been shown to contribute to alterations in behavior, abnormal central nervous system development, and neurological disease. In this light, it is not surprising that zinc ions have now been shown to play a role in the neuromodulation of synaptic transmission as well as in cortical plasticity. Zinc is stored in specific synaptic vesicles by a class of glutamatergic or "gluzinergic" neurons and is released in an activity-dependent manner. Because gluzinergic neurons are found almost exclusively in the cerebral cortex and limbic structures, zinc may be critical for normal cognitive and emotional functioning. Conversely, direct evidence shows that zinc might be a relatively potent neurotoxin. Neuronal injury secondary to in vivo zinc mobilization and release occurs in several neurological disorders such as Alzheimer's disease and amyotrophic lateral sclerosis, in addition to epilepsy and ischemia. Thus, zinc homeostasis is integral to normal central nervous system functioning, and in fact its role may be underappreciated. This article provides an overview of zinc neurobiology and reviews the experimental evidence that implicates zinc signals in the pathophysiology of neuropsychiatric diseases. A greater understanding of zinc's role in the central nervous system may therefore allow for the development of therapeutic approaches where aberrant metal homeostasis is implicated in disease pathogenesis.

Zinc supplementation augments efficacy of imipramine in treatment resistant patients: a double blind, placebo-controlled study

BACKGROUND

One of the main problems in the therapy of depression is the limited efficacy of antidepressants and the limited utility of augmentation strategies. Zinc, a non competitive NMDA receptor antagonist exhibits preclinical antidepressant efficacy. Moreover, a preliminary clinical report suggests augmentation of antidepressant therapy by zinc in depression.

METHODS

A placebo-controlled, double blind study of zinc supplementation in imipramine therapy was conducted in sixty, 18-55-year old, unipolar depressed patients fulfilling the DSM-IV criteria for major depression without psychotic symptoms. After a one week washout period, patients were randomized into two groups treated with imipramine (approximately 140 mg/day) and receiving once daily either placebo (n=30) or zinc supplementation (n=30, 25 mgZn/day) for 12 weeks.

RESULTS

No significant differences in CGI, BDI, HADRS and MADRS scores were demonstrated between zinc-supplemented and placebo-supplemented antidepressant treatment non-resistant patients. However, zinc supplementation significantly reduced depression scores and facilitated the treatment outcome in antidepressant treatment resistant patients.

CONCLUSION

Zinc supplementation augments the efficacy and speed of onset of therapeutic response to imipramine treatment, particularly in patients previously nonresponsive to antidepressant pharmacotherapies. These data suggest the participation of disturbed zinc/glutamatergic transmission in the pathophysiology of drug resistance.

Involvement of the adenosine A1 and A2A receptors in the antidepressant-like effect of zinc in the forced swimming test

It was previously shown that the acute administration of zinc chloride elicits an antidepressant-like effect in the mouse forced swimming test (FST). We have also shown that the activation of adenosine A(1) and A(2A) receptors produces an antidepressant-like effect in FST. Thus, this study investigated the involvement of adenosine receptors in the antidepressant-like effect of zinc in the FST. The antidepressant-like effect of ZnCl(2) (30 mg/kg, i.p.) in the FST was prevented by the pretreatment of animals with caffeine (3 mg/kg, i.p., a non-selective adenosine receptor antagonist), DPCPX (2 mg/kg, i.p., a selective adenosine A(1) receptor antagonist) or ZM241385 (1 mg/kg, i.p., a selective adenosine A(2A) receptor antagonist), administered at doses that per se produced no anti-immobility effect. Moreover, the treatment of mice with CHA (0.05 mg/kg, i.p., a selective adenosine A(1) receptor agonist), DPMA (0.1 mg/kg, i.p., a selective adenosine A(2A) receptor agonist) or dipyridamole (0.1 microg/site, i.c.v., an adenosine transporter inhibitor) was able to potentiate the action of sub-effective doses of ZnCl(2). Taken together, the results suggest that the antidepressant-like effect of zinc in the mouse FST might involve a direct or indirect activation of adenosine A(1) and A(2A) receptors.

Zinc: the new antidepressant?

Low serum zinc levels have been linked to major depression. Furthermore, zinc treatment has been shown to have an antidepressant effect. With the hope of understanding the role of zinc in mood disorders, recent work has begun to explore possible mechanisms of zinc action on serotonin uptake in the brain.

Combined actions of zinc and fluoxetine on nicotinic acetylcholine receptors

Zinc and nicotinic acetylcholine receptors (nAChRs) seem to be associated with major depression, and some antidepressants, including fluoxetine (Prozac), antagonize nAChRs. Therefore, a study was made of the modulation of neuronal alpha4beta4 and muscle alpha1beta1gammadelta nAChRs, expressing in oocytes, by the combined action of zinc and fluoxetine. At a holding potential of -60 mV, 200 microM zinc increased by 361% the currents elicited by acetylcholine (ACh currents) for alpha4beta4 and by 182% for alpha1beta1gammadelta nAChRs. In contrast, 5 microM fluoxetine reduced the ACh currents to 31% for alpha4beta4 and to 45% for alpha1beta1gammadelta nAChRs. Additionally, fluoxetine reduced more the ACh currents in the presence of zinc: to 17% for alpha4beta4 and to 19% for alpha1beta1gammadelta nAChRs, and after washing out the fluoxetine the ACh current did not recover its zinc-potentiated value. Moreover, when ACh-activated nAChRs were exposed first to fluoxetine and then zinc was added, the potentiating effect of zinc was very small for muscle nAChRs and was nil for neuronal receptors. Thus, the inhibiting effect of fluoxetine prevails over the potentiating action of zinc. Finally, the effects of both zinc and fluoxetine were voltage independent, indicating that these substances interact outside the ion channel. As fluoxetine nullifies the effects of zinc, it appears that both substances interact in the same site. These results should help understand better the roles played by zinc, antidepressants, nAChRs and their combination in brain functions and in the treatment of depression.

Zinc modulation of serotonin uptake in the adult rat corpus callosum

Antidepressants partially inhibit the uptake of 5-hydroxytryptamine (5-HT; serotonin) in the rat corpus callosum (CC), a white matter commissure involved in interhemispheric brain communication. It is also known that zinc modulates many proteins, including neurotransmitter transporters. We examined the effects of zinc on the uptake of 5-HT into slices of the adult rat CC, in the absence or presence of some antidepressants. Zinc increased 5-HT uptake in a concentration-dependent manner when the CC slices were incubated in a solution buffered with sodium bicarbonate; however, zinc exerted no effect on 5-HT transport when HEPES was the buffer. Potentiation of 5-HT uptake by zinc was maximal with 1 microM (45% over the control uptake). Moreover, 1 microM zinc potentiated 5-HT uptake in the cingulate cortex by 58% and in the Raphe nucleus by 65%. The antidepressants fluoxetine and imipramine inhibited 5-HT uptake in the CC by approximately 50%, whereas 6-nitroquipazine, a potent 5-HT uptake blocker, inhibited uptake by only 23%. Interestingly, inhibition of 5-HT uptake by all three substances, fluoxetine, imipramine, and 6-nitroquipazine, was counteracted by the presence of 1 microM zinc. Free zinc may thus contribute to modulation of extracellular levels of 5-HT and its removal. These actions should be considered in the treatment of mental depression with antidepressants.

Emerging experimental therapeutics for bipolar disorder: clues from the molecular pathophysiology

Bipolar affective disorder (manic-depressive illness) is a common, severe, chronic, and often life-threatening illness, associated with significant comorbidity. The recognition of the significant morbidity and mortality of patients with bipolar disorder, as well as the growing appreciation that a high percentage of patients respond poorly to existing treatments, has made the task of discovering new therapeutic agents, that are both efficacious and have few side effects increasingly more important. Most recent agents introduced into the pharmacopeia for the treatment of bipolar disorder have been anticonvulsants and atypical antipsychotics. We propose that novel treatments developed specifically for bipolar disorder will arise from (1) understanding more precisely the molecular mechanisms of treatments that are clearly efficacious or (2) developing medications based on the knowledge obtained of the underlying pathophysiology of bipolar disorder. Knowledge with regard to the underlying pathophysiology of bipolar disorder is increasing at a rapid pace, including alterations in intracellular signaling cascades as well as impairments of cellular plasticity and resilience in critical neuronal circuits. We propose that therapeutics designed to enhance cellular plasticity and resilience and that counter maladaptive stress-responsive systems may have considerable utility for the treatment of bipolar disorder. Therapeutic strategies designed to address cellular resilience and plasticity include the regulation of neurotrophic pathways, glucocorticoid signaling, phosphodiesterase activity, and glutamatergic throughput and mitochondrial function. While the task of developing novel medications for bipolar disorder is truly daunting, these and similar approaches will ultimately lead to better medications for the millions who suffer from this devastating illness.