The immunobiology of zinc

Zinc induces caspase-dependent mitochondrial pathway of the programmed cell death in haemocytes of Drosophila melanogaster

Zinc is an essential trace element in cells. However, its high level in cytoplasm promotes activation of stress signaling pathways and may lead to cell death. In the present study we used Drosophila melanogaster blood cells (haemocytes), obtained from the third instar larvae, to study the effects of high concentrations of Zn(2+) on programmed cell death (PCD). We analyzed the activity of caspases, the level of caspase inhibitor protein DIAP1 and metallothioneins, as well as calcium concentrations and activity of mitochondria in haemocytes exposed to 0.35 and 1.7 mM concentrations of Zn. The obtained results showed that rapid increase of [Zn(2+)]( i ) in the cytoplasm up-regulates metallothionein MtnB but not MtnA gene expression in cells treated with Zn(2+) in both concentrations. Excess of Zn(2+) also induced activation of the initiator caspase Dronc, associated with the mitochondrial pathway of PCD, and the effector caspase DrICE. In turn, the activity of receptor-regulated Dredd caspase was not changed. The level of DIAP1 decreased significantly in haemocytes in the presence of high Zn(2+) concentration in comparison to untreated cells. Moreover, mitochondrial membrane potential was significantly decreased after exposure to Zn ions. These results indicate that high concentration of Zn(2+) in the cytoplasm of haemocytes induces PCD via a mitochondrial pathway and that caspases play a pivotal role in this process.

Zinc aspartate suppresses T cell activation in vitro and relapsing experimental autoimmune encephalomyelitis in SJL/J mice

Zinc is an essential trace element with a critical role in normal growth and development and in immune homeostasis. Zinc deficiency impairs both the innate and the adaptive immune system and can be normalized by zinc supplementation. On the other end of the spectrum, high dosages of zinc diminish immune cell functions similar to zinc deficiency. Here, we investigated the influence of zinc aspartate on proliferation and cytokine production of stimulated human T cells and mouse splenocytes in vitro. Furthermore, the effect of zinc aspartate was examined in mice with experimental autoimmune encephalomyelitis (EAE), an animal model of Multiple Sclerosis (MS) with a Th1/Th17 T cell-mediated immunopathogenesis. Zinc aspartate suppressed proliferation as well as IL-2, IL-10 and IL-17 production in stimulated human T cells and mouse splenocytes. Importantly, administration of a medium range dose of 30 μg/day zinc aspartate [1.5 mg/kg body weight (BW)] in a therapeutic manner led to a significant reduction of the clinical severity of the EAE during the first relapse of the disease. A lower zinc aspartate dose (6 μg/day, 0.3 mg/kg BW) had no significant therapeutic effect on the severity of the EAE, while administration of higher zinc aspartate amounts (120 μg/day, 6 mg/kg BW) led to more severe disease. Taken together, our data suggest that zinc aspartate can modulate activation, proliferation and cytokine production of effector T cells in vitro and in vivo and that activated autoreactive T cells may be potential therapeutic targets of tightly controlled zinc supplementation in autoimmune diseases like MS.

Systematic functional characterization of putative zinc transport genes and identification of zinc toxicosis phenotypes in Drosophila melanogaster

The heavy metal zinc is an essential component of the human diet and is incorporated as a structural component in up to 10% of all mammalian proteins. The physiological importance of zinc homeostasis at the cellular level and the molecular mechanisms involved in this process have become topics of increasing interest in recent years. We have performed a systematic functional characterization of the majority of the predicted Drosophila Zip (Zinc/iron regulated transporter-related protein) and ZnT genes, using the Gal4-UAS system to carry out both ubiquitous and targeted over expression and suppression studies for thirteen of the seventeen putative zinc transport genes identified to date. We find that six of these thirteen genes may be essential for fly viability and that three of the remaining seven demonstrate over expression phenotypes. Our findings reaffirm the previously proposed function of dZnT63C (CG17723: FBgn005432) as an important zinc efflux protein and indicate that the fly homolog of hZip1, dZip42C.1 (CG9428: FBgn0033096), is a strong zinc importer in Drosophila. By combining over expression of dZip42C.1 with suppression of dZnT63C we were able to produce easily identifiable zinc toxicosis phenotypes which can be rescued or worsened by modifying dietary zinc content. Our findings show that a genetically based zinc toxicosis situation can be therapeutically treated or exacerbated by modifications to the diet, providing a sensitized background for future, more detailed studies of Zip / ZNT function.

Coordination study of recombinant human-like collagen and zinc (II)

In the present investigation, the complex of recombinant human-like collagen (r-HLC) with zinc (II) has been synthesized in aqueous solution and was analyzed by UV-vis spectroscopy, FTIR spectroscopy, circular dichroism (CD) spectroscopy, thermo gravimetric (TG) and differential scanning calorimetry (DSC) analysis. It can be concluded from UV-vis spectra that there exists interaction between r-HLC and zinc, and the complex is a new chemical compound different from pure r-HLC. In the complex of Zn, recombinant human-like collagen acts as ligand, linking the zinc ion via both groups of C=O and N-H. Besides, the results of TG and DSC confirm that the complex was significantly different from ligand, and the former is more thermally stable in comparison with the latter. The results obtained from the current investigation are of crucial importance to understand the r-HLC-Zn complex and provide theoretical evidence for the further study.

The role of zinc in neurodegenerative inflammatory pathways in depression

According to new hypothesis, depression is characterized by decreased neurogenesis and enhanced neurodegeneration which, in part, may be caused by inflammatory processes. There is much evidence indicating that depression, age-related changes often associated with impaired brain function and cognitive performances or neurodegenerative processes could be related to dysfunctions affecting the zinc ion availability. Clinical studies revealed that depression is accompanied by serum hypozincemia, which can be normalized by successful antidepressant treatment. In patients with major depression, a low zinc serum level was correlated with an increase in the activation of markers of the immune system, suggesting that this effect may result in part from a depression-related alteration in the immune-inflammatory system. Moreover, a preliminary clinical study demonstrated the benefit of zinc supplementation in antidepressant therapy in both treatment non-resistant and resistant patients. In the preclinical study, the antidepressant activity of zinc was observed in the majority of rodent tests and models of depression and revealed a causative role for zinc deficiency in the induction of depressive-like symptoms, the reduction of neurogenesis and neuronal survival or impaired learning and memory ability. This paper provides an overview of the clinical and experimental evidence that implicates the role of zinc in the pathophysiology and therapy of depression within the context of the inflammatory and neurodegenerative hypothesis of this disease.

Zinc in innate and adaptive tumor immunity

Zinc is important. It is the second most abundant trace metal with 2-4 grams in humans. It is an essential trace element, critical for cell growth, development and differentiation, DNA synthesis, RNA transcription, cell division, and cell activation. Zinc deficiency has adverse consequences during embryogenesis and early childhood development, particularly on immune functioning. It is essential in members of all enzyme classes, including over 300 signaling molecules and transcription factors. Free zinc in immune and tumor cells is regulated by 14 distinct zinc importers (ZIP) and transporters (ZNT1-8). Zinc depletion induces cell death via apoptosis (or necrosis if apoptotic pathways are blocked) while sufficient zinc levels allows maintenance of autophagy. Cancer cells have upregulated zinc importers, and frequently increased zinc levels, which allow them to survive. Based on this novel synthesis, approaches which locally regulate zinc levels to promote survival of immune cells and/or induce tumor apoptosis are in order.

Zinc and redox signaling: perturbations associated with cardiovascular disease and diabetes mellitus

Cellular signal transduction pathways are influenced by the zinc and redox status of the cell. Numerous chronic diseases, including cardiovascular disease (CVD) and diabetes mellitus (DM), have been associated with impaired zinc utilization and increased oxidative stress. In humans, mutations in the MT-1A and ZnT8 genes, both of which are involved in the maintenance of zinc homeostasis, have been linked with DM development. Changes in levels of intracellular free zinc may exacerbate oxidative stress in CVD and DM by impacting glutathione homeostasis, nitric oxide signaling, and nuclear factor-kappa B-dependent cellular processes. Zinc ions have been shown to influence insulin and leptin signaling via the phosphoinositide 3′-kinase/Akt pathway, potentially linking an imbalance of zinc at the cellular level to insulin resistance and dyslipidemia. The oxidative modification of cysteine residues in zinc coordination sites in proteins has been implicated in cellular signaling and regulatory pathways. Despite the many interactions between zinc and cellular stress responses, studies investigating the potential therapeutic benefit of zinc supplementation in the prevention and treatment of oxidative stress-related chronic disease in humans are few and inconsistent. Further well-designed randomized controlled trials are needed to determine the effects of zinc supplementation in populations at various stages of CVD and DM progression.

Essential role of vitamin C and zinc in child immunity and health

With the progressive elimination of dietary protein-energy deficits, deficiencies of micronutrients are emerging as the limiting factors in ensuring children's optimal health. Data from several countries in Asia and Latin America indicate that deficiencies of vitamin C and zinc continue to be at alarming levels. This article reviews the roles of vitamin C and zinc in supporting children's growth and development, with a particular focus on the complementary roles they play in supporting immune functions and combating infections. The contemporary relevance of vitamin C and zinc deficiency in the Asian and Latin American regions, both undergoing a rapid nutritional transition, are also discussed. Overall, there is increasing evidence that deficiency of vitamin C and zinc adversely affects the physical and mental growth of children and can impair their immune defences. Nutrition should be the main vehicle for providing these essential nutrients; however, supplementation can represent a valid support method, especially in developing regions.

Alterations in early cytokine-mediated immune responses to Plasmodium falciparum infection in Tanzanian children with mineral element deficiencies: a cross-sectional survey

Background

Deficiencies in vitamins and mineral elements are important causes of morbidity in developing countries, possibly because they lead to defective immune responses to infection. The aim of the study was to assess the effects of mineral element deficiencies on early innate cytokine responses to Plasmodium falciparum malaria.

Methods

Peripheral blood mononuclear cells from 304 Tanzanian children aged 6-72 months were stimulated with P. falciparum-parasitized erythrocytes obtained from in vitro cultures.

Results

The results showed a significant increase by 74% in geometric mean of TNF production in malaria-infected individuals with zinc deficiency (11% to 240%; 95% CI). Iron deficiency anaemia was associated with increased TNF production in infected individuals and overall with increased IL-10 production, while magnesium deficiency induced increased production of IL-10 by 46% (13% to 144%) in uninfected donors. All donors showed a response towards IL-1β production, drawing special attention for its possible protective role in early innate immune responses to malaria.

Conclusions

In view of these results, the findings show plasticity in cytokine profiles of mononuclear cells reacting to malaria infection under conditions of different micronutrient deficiencies. These findings lay the foundations for future inclusion of a combination of precisely selected set of micronutrients rather than single nutrients as part of malaria vaccine intervention programmes in endemic countries.

Effects of zinc on programmed cell death of Musca domestica and Drosophila melanogaster blood cells

Programmed cell death (PCD) and phagocytotic activity of immune cells play a pivotal role in insect development. We examined the influence of Zn(2+), an important element to fundamental biological processes, on phagocytosis and apoptosis of hemocytes in two fly species: Musca domestica and Drosophila melanogaster. Hemocytes were isolated from the third instar larvae of both species and treated for 3h with zinc chloride solutions, containing 0.35 mM or 1.7 mM of Zn(2+), and untreated as control. Phagocytotic activity of hemocytes was examined by flow cytometry after adding latex fluorescent beads to the medium, while apoptosis was evaluated by application of annexinV-FITC and pan-caspase-FITC inhibitor. Mitochondrial viability was determined by measuring resazurin absorbancy in the cell medium. The obtained results showed that Zn(2+) increases phagocytosis and affects PCD of both species hemocytes but each in a different way. Zinc decreases fraction of annexin-positive hemocytes in M. domestica but increases it in D. melanogaster. The pan-caspase analysis revealed low and high activity of caspases in hemocytes of M. domestica and D. melanogaster, respectively. Zn(2+) also decreased the viability of hemocyte mitochondria but only in D. melanogaster. It suggests that flies use different pathways of PCD, or that Zn plays a different role in this process in M. domestica than in D. melanogaster.

Zinc suppresses Th17 development via inhibition of STAT3 activation

Zinc (Zn) is an essential trace metal required by many enzymes and transcription factors for their activity or the maintenance of their structure. Zn has a variety of effects in the immune responses and inflammation, although it has not been well known how Zn affects these reactions on the molecular basis. We here showed that Zn suppresses T(h)17-mediated autoimmune diseases at lest in part by inhibiting the development of T(h)17 cells via attenuating STAT3 activation. In mice injected with type II collagen to induce arthritis, Zn treatment inhibited T(h)17 cell development. IL-6-mediated activation of STAT3 and in vitro T(h)17 cell development were all suppressed by Zn. Importantly, Zn binding changed the alpha-helical secondary structure of STAT3, disrupting the association of STAT3 with JAK2 kinase and with a phospho-peptide that included a STAT3-binding motif from the IL-6 signal transducer gp130. Thus, we conclude that Zn suppresses STAT3 activation, which is a critical step for T(h)17 development.

Study on the trace elements in Swertia chirayita (Roxb.) H. Karsten

An attempt has been made to analyze some trace elements and electrolytes like Zn, Cu, Mn, Fe, Co, Na, K, Ca, and Li present in the Swertia chirayita roots and leaves. The concentration of Ca in all the samples was more than 1,346.0 mg/kg and the concentration of other elements was found in the order K > Ca > Fe > Na > Mn > Zn > Co > Cu > Li in different samples of S. chirayita.

Effects of zinc glycine chelate on growth, hematological, and immunological characteristics in broilers

Three hundred sixty healthy Ross x Ross 1-day-old broilers were used to study the effects of zinc glycine chelate (Zn-Gly) on growth performance, hematological, and immunological characteristics. All broilers were randomly assigned into six treatments. Diets were as follows: (1) control (containing 29.3 mg Zn kg(-1) basic diet [0-3 weeks] and 27.8 mg Zn kg(-1) [4-6 weeks]); (2) basic diet plus 30 mg Zn kg(-1) from Zn-Gly; (3) basic diet plus 60 mg Zn kg(-1) from Zn-Gly; (4) basic diet plus 90 mg Zn kg(-1) from Zn-Gly; (5) basic diet plus 120 mg Zn kg(-1) from Zn-Gly; (6) positive control, basic diet plus 120 mg Zn kg(-1) from zinc sulfate (ZnSO(4)). After the 21- and 42-day feeding trials, the results showed that both of Zn-Gly and ZnSO(4) could improve the growth performance of broilers, with the greatest average daily feed intake observed in the broilers fed 90 mg Zn kg(-1) from Zn-Gly, but the greatest average daily gain observed with 120 mg Zn kg(-1) from Zn-Gly (0-3 weeks) and 90 mg Zn kg(-1) from Zn-Gly (4-6 weeks). Adding additional Zn-Gly improved the levels of immunoglobulins (IgA, IgM, and IgG) and the contents of total protein and Ca in serum and increased the immune organs index especially with 90 mg Zn kg(-1) as Zn-Gly. However, there were no significant differences in responses to complements (C3 and C4) and albumin in serum among the treatments.

Zinc and diabetes--clinical links and molecular mechanisms

Zinc is an essential trace element crucial for the function of more than 300 enzymes and it is important for cellular processes like cell division and apoptosis. Hence, the concentration of zinc in the human body is tightly regulated and disturbances of zinc homeostasis have been associated with several diseases including diabetes mellitus, a disease characterized by high blood glucose concentrations as a consequence of decreased secretion or action of insulin. Zinc supplementation of animals and humans has been shown to ameliorate glycemic control in type 1 and 2 diabetes, the two major forms of diabetes mellitus, but the underlying molecular mechanisms have only slowly been elucidated. Zinc seems to exert insulin-like effects by supporting the signal transduction of insulin and by reducing the production of cytokines, which lead to beta-cell death during the inflammatory process in the pancreas in the course of the disease. Furthermore, zinc might play a role in the development of diabetes, since genetic polymorphisms in the gene of zinc transporter 8 and in metallothionein (MT)-encoding genes could be demonstrated to be associated with type 2 diabetes mellitus. The fact that antibodies against this zinc transporter have been detected in type 1 diabetic patients offers new diagnostic possibilities. This article reviews the influence of zinc on the diabetic state including the molecular mechanisms, the role of the zinc transporter 8 and MT for diabetes development and the resulting diagnostic and therapeutic options.

CD4+ T-cell responses to an oral inactivated cholera vaccine in young children in a cholera endemic country and the enhancing effect of zinc supplementation

Immunization of young children with the oral inactivated whole cell cholera vaccine Dukoral((R)) containing recombinant cholera toxin B subunit (CTB) induces antibody responses which can be further enhanced by zinc supplementation. We have investigated if immunization with the cholera vaccine induces specific T-cell responses in young children and also whether zinc supplementation influences these responses. Bangladeshi children (10-18 months old) received vaccine alone, vaccine together with zinc supplementation or only zinc. T-cell blast formation indicating a proliferative response was analyzed by the flow cytometric assay of cell-mediated immune response in activated whole blood (FASCIA) and cytokines were measured by ELISA. Stronger T-cell responses were detected if a modified CTB molecule (mCTB) with reduced binding to GM1 ganglioside was used for cell stimulation compared to normal CTB. After vaccination, CD4+ T cells responded to mCTB with significantly increased blast formation (P<0.01) and IFN-gamma production (P<0.05) compared to before vaccination. No responses to mCTB were detected in children receiving zinc alone (P>0.05). The IFN-gamma production was significantly higher (P<0.01) but the blast formation comparable (P>0.05) in children receiving zinc plus vaccine compared to in children receiving vaccine alone. The vibriocidal antibody responses induced by the vaccine were also significantly higher in children receiving zinc supplementation (P<0.001). Our results thus show that oral cholera vaccination induces a Th1 T-cell response in young children, and that the IFN-gamma as well as the vibriocidal antibody responses can be enhanced by zinc supplementation.

Use of zinc chloride as alternative stimulant for in vitro study of nitric oxide production pathway in avian splenocyte culture

Nitric Oxide (NO) plays an important role for regulation of cellular and vascular response of inflammation and initiates killing mechanism in the host-defense reactions. NO production is regulated through inducible nitric oxide synthase (iNOS) pathway in response to infections and injurious agents besides pro-inflammatory cytokines secreted by the host. Evaluation of NO pathway is one of the major targets which can evaluate various immunomodulators for their therapeutic interaction on innate immune system. Lipopolysaccharide (LPS) and concavalin A (ConA) are used as standard mitogen for peripheral blood mononuclear cells and splenocyte of mammalian and avian cell culture. During the present investigation ZnCl(2) has been explored as standard mitogen and result was comparable with standard mitogen. The result has been evaluated on the basis of relative mRNA expression of iNOS and interferon gamma and nitrite assay. Observation indicated significantly higher expression of both biomolecules in comparison to control, LPS, ConA treated group. This study indicated that, ZnCl(2) can also be used as standard stimulant for molecular mining of innate immunity.

The EVER proteins as a natural barrier against papillomaviruses: a new insight into the pathogenesis of human papillomavirus infections

Infections by human papillomaviruses (HPVs) are the most frequently occurring sexually transmitted diseases. The crucial role of genital oncogenic HPV in cervical carcinoma development is now well established. In contrast, the role of cutaneous HPV in skin cancer development remains a matter of debate. Cutaneous beta-HPV strains show an amazing ubiquity. The fact that a few oncogenic genotypes cause cancers in patients suffering from epidermodysplasia verruciformis is in sharp contrast to the unapparent course of infection in the general population. Our recent investigations revealed that a natural barrier exists in humans, which protects them against infection with these papillomaviruses. A central role in the function of this HPV-specific barrier is played by a complex of the zinc-transporting proteins EVER1, EVER2, and ZnT-1, which maintain cellular zinc homeostasis. Apparently, the deregulation of the cellular zinc balance emerges as an important step in the life cycles not only of cutaneous but also of genital HPVs, although the latter viruses have developed a mechanism by which they can break the barrier and impose a zinc imbalance. Herein, we present a previously unpublished list of the cellular partners of EVER proteins, which points to future directions concerning investigations of the mechanisms of action of the EVER/ZnT-1 complex. We also present a general overview of the pathogenesis of HPV infections, taking into account the latest discoveries regarding the role of cellular zinc homeostasis in the HPV life cycle. We propose a potential model for the mechanism of function of the anti-HPV barrier.

The immune system and the impact of zinc during aging

The trace element zinc is essential for the immune system, and zinc deficiency affects multiple aspects of innate and adaptive immunity. There are remarkable parallels in the immunological changes during aging and zinc deficiency, including a reduction in the activity of the thymus and thymic hormones, a shift of the T helper cell balance toward T helper type 2 cells, decreased response to vaccination, and impaired functions of innate immune cells. Many studies confirm a decline of zinc levels with age. Most of these studies do not classify the majority of elderly as zinc deficient, but even marginal zinc deprivation can affect immune function. Consequently, oral zinc supplementation demonstrates the potential to improve immunity and efficiently downregulates chronic inflammatory responses in the elderly. These data indicate that a wide prevalence of marginal zinc deficiency in elderly people may contribute to immunosenescence.

Amelioratory effects of zinc supplementation on Salmonella-induced hepatic damage in the murine model

Zinc (Zn) has been reported to influence the susceptibility of the host to a diverse range of infectious pathogens, including viruses, bacteria, fungi and protozoa. We report here an evaluation of the effects of Zn supplementation on Salmonella enterica serovar Typhimurium (S. typhimurium)-induced hepatic injury in the murine model. Zinc levels in the plasma and liver tissues were measured by atomic absorption spectroscopy. The effect of Zn supplementation was evaluated by assessing the bacterial load and levels of lipid peroxidation (LPO), antioxidants and monokines present in the hepatic tissue as well as by histopathological studies. Zinc supplementation reduced the bacterial load in the liver and reversed hepatic microscopic abnormalities. It also decreased the levels of LPO but increased the levels of reduced glutathione (GSH) as well as the activities of superoxide-dismutase (SOD) and catalase in the livers of infected mice supplemented with Zn compared to the livers of infected mice not supplemented with Zn. Zinc supplementation was also able to modulate the levels of monokines such as tumour necrosis factor alpha (TNF-alpha), interleukin-1 (IL-1) and interleukin-6 (IL-6). Our results indicate a role for Zn in downregulating oxidative stress and upregulating antioxidant defense enzymes through the action of monokines, suggesting that supplementation with Zn has a protective function in Salmonella-induced liver injury.

HIV-1-transgene expression in rats decreases alveolar macrophage zinc levels and phagocytosis

HIV-1 infection impairs alveolar macrophage immune function and renders patients susceptible to pneumonia by poorly understood mechanisms. Alveolar macrophage maturation and function depends on granulocyte-macrophage colony-stimulating factor (GM-CSF), which is produced and secreted by the alveolar epithelium. Macrophages respond to GM-CSF through the GM-CSF receptor (GM-CSFR), which has a binding subunit (GM-CSFRalpha) and a signaling subunit (GM-CSFRbeta). In this study, we measured GM-CSFR expression and alveolar macrophage function in a transgene HIV-1 rat model (NL4-3Delta gag/pol); this construct bears a pro-virus with gag and pol deleted, but other HIV-1-related proteins, such as gp120 and Tat, are expressed, and the rats develop an AIDS-like phenotype as they age. We first determined that HIV-1-transgenic expression selectively decreased alveolar macrophage expression of GM-CSFRbeta and impaired bacterial phagocytosis in vitro. Next, we examined the role of zinc (Zn) deficiency as a potential mechanism underlying these effects, and determined that HIV-1-transgenic rats have significantly lower levels of Zn in the alveolar space and macrophages. To test the direct effect of Zn deficiency on macrophage dysfunction, we treated rat alveolar macrophage cell line with a Zn chelator, N,N,N',N'-tetrakis-(2-pyridyl-methyl) ethylenediamine, and this decreased GM-CSFRbeta expression and phagocytosis. In parallel, treatment with Zn acetate in vitro for 48 hours restored intracellular Zn levels and phagocytic function in alveolar macrophages from HIV-1-transgenic rats. Taken together, these data suggest that pulmonary Zn deficiency could be one of the mechanisms by which chronic HIV-1 infection impairs alveolar macrophage immune function and renders these individuals susceptible to serious lung infections.

Roles of zinc and zinc signaling in immunity: zinc as an intracellular signaling molecule

Zinc (Zn) is an essential nutrient required for cell growth, differentiation, and survival, and its deficiency causes growth retardation, immunodeficiency, and other health problems. Therefore, Zn homeostasis must be tightly controlled in individual cells. Zn is known to be important in the immune system, although its precise roles and mechanisms have not yet been resolved. Zn has been suggested to act as a kind of neurotransmitter. In addition, Zn has been shown to bind and affect the activity of several signaling molecules, such as protein tyrosine phosphatases (PTPs). However, it has not been known whether Zn itself might act as an intracellular signaling molecule, that is, a molecule whose intracellular status is altered in response to an extracellular stimulus, and that is capable of transducing the extracellular stimulus into an intracellular signaling event. Here we propose that Zn acts as a signaling molecule and that there are at least two kinds of Zn signaling: "late Zn signaling," which is dependent on a change in the expression profile of Zn transporters, and "early Zn signaling," which involves a "Zn wave" and is directly induced by an extracellular stimulus. We also review recent progress in uncovering the roles of Zn in the immune system.

Effects of long-term zinc supplementation and deprivation on gene expression in human THP-1 mononuclear cells

Zinc is an essential trace element that is critical for cellular function and structural integrity. It has an important regulatory role in the immune system, in particular in monocytes. To identify the diverse cellular targets and mechanisms of action of zinc in this cell type, we used microarray technology to assess the effects of zinc supplementation and depletion on global gene expression. mRNA expression in the human monocytic cell line THP-1 was analyzed and compared in response to 40h supplementation with 50micromol/L zinc, or zinc deprivation by 2.5micromol/L of the membrane-permeant zinc chelator TPEN [N,N,N',N'-tetrakis-(2-pyridyl-methyl)ethylenediamine]. Analysis of microarrays consisting of approximately 19,000 unique oligonucleotides identified over 1400 genes, or approximately 7%, as zinc-sensitive. Notably, this yielded several sets of structurally or functionally related genes. Among those groups, which were mainly affected by zinc deprivation, were histones, S100 calcium and zinc binding proteins, and chemokines and their receptors. These groups of genes may mediate zinc-effects on chromatin regulation, zinc homeostasis, and chemotaxis, respectively. In addition, functional networks were analyzed, showing that the well known effect of zinc on pro-inflammatory cytokines is not limited to these genes; it acts on a number of functionally connected genes, as well. These results provide novel molecular targets and pathways that may aid in explaining the role of zinc in monocyte function.

Zinc supplementation for the treatment or prevention of disease: current status and future perspectives

Zinc is a nutritionally essential trace element, and thus zinc deficiency may severely affect human health. Many studies were published in which the effect of nutritional zinc supplementation on the incidence or severity of a certain disease was investigated. This review summarizes the main observations and aims to evaluate the use of nutritional zinc supplementation for prevention and treatment of human disease.

An overview of interactions between micronutrients and of micronutrients with drugs, genes and immune mechanisms

The objective of the present review is to examine critically the consequences of interactions that micronutrients undergo with nutrients and non-nutrients (mainly prescribed medicines) in diets and lifestyle factors (smoking, tea and alcohol consumption). In addition, the review describes recent work on interactions between nutrients and genes, the influence of gene polymorphisms on micronutrients, the impact of immune responses on micronutrients and specific interactions of antioxidant micronutrients in disease processes to minimise potential pro-oxidant damage.

Differential gene expression after zinc supplementation and deprivation in human leukocyte subsets

An individual's zinc status has a significant impact on the immune system, and zinc deficiency, as well as supplementation, modulates immune function. To investigate the effects of zinc on different leukocyte subsets, we used microarray technology to analyze and compare the changes in mRNA expression in cell culture models of monocytes (THP-1), T cells (Jurkat), and B cells (Raji), in response to supplementation for 40 h with 50 microM zinc or 2.5 microM of the membrane-permeant zinc chelator TPEN [N,N,N',N'-tetrakis-(2-pyridyl-methyl)ethylenediamine], respectively. In each cell type, several hundred genes were identified to be zinc sensitive, but only a total of seven genes were commonly regulated in all three cell lines. The majority of those genes were involved in zinc homeostasis, and none in immune function. Nevertheless, further analysis revealed that zinc affects entire functional networks of genes that are related to proinflammatory cytokines and cellular survival. Although the zinc-regulated activities are similar throughout the gene networks, the specific genes that are affected vary significantly between different cell types, a situation that helps to elucidate the disparity of the effects that zinc has on different leukocyte populations.

Inflammation, genes and zinc in ageing and age-related diseases

Lifelong antigenic burden determines a condition of chronic inflammation, with increased lymphocyte activation and pro-inflammatory cytokine production. A large number of studies have documented changes in Zn metabolism in experimental animal models of acute and chronic inflammation and in human chronic inflammatory diseases. In particular, modification of zinc plasma concentration as well as intracellular disturbance of antioxidant intracellular pathways have been found associated to age-related inflammatory diseases, like atherosclerosis. Zinc deficiency is extremely diffused in aged people that are educated to avoid meat and other high Zn-content foods due to fear of cholesterol. Rather, they increase consumption of refined wheat products that lack of Zn, magnesium and other critical nutrients in consequence of refining process. On the other hand, plasma concentration of metallic ions like Zn is influenced by pro-inflammatory cytokines production. A major target of Zn may be NF-kB, a transcription factor critical for the expression of many pro-inflammatory cytokines whose production is finely regulated by extra- and intracellular activating and inhibiting factors interacting with regulatory elements on cytokine genes. Moreover, this factor is regulated by the expression of specific cellular genes involved in inflammation. So it is not surprising that Zn deficiency is constantly observed in aged patients affected by infectious diseases. On the other hand, cytokine genes are highly polymorphic and some of these polymorphisms have been found associated to age-related diseases as atherosclerosis. Therefore, Zn deficiency in individuals genetically predisposed to a dis-regulation of inflammation response, may play a crucial role, in causing adverse events and in reducing the probability of a successful aging.

Immunological biomarkers of ageing in man: changes in both innate and adaptive immunity are associated with health and longevity

Scientific and clinical advances in the last century have led to increased numbers of individuals living to older ages. Thus a major concern is how to live these years with a high quality of life. The ageing immune system is less well able to cope with infectious diseases than the youthful immune system probably as a consequence of altered immune response to pathogens. Thus, both innate and adaptive immune responses show age-related changes that could be decisive for healthy ageing and survival. Longitudinal studies in healthy elderly have allowed the definition of the ''immune risk phenotype" (IRP) a predictor of mortality in elderly individuals that is based on several parameters of the adaptive immune response. Here, we hypothesize that failures in innate immunity observed in frail elderly are related to those alterations described in adaptive immunity defined as the IRP. It will be important to include assays of NK cell markers and functions in future longitudinal studies in order to investigate this point in detail as well as to consider the trace element zinc as an essential co-factor for optimal NK cell activity.

Infectious etiology modifies the treatment effect of zinc in severe pneumonia

BACKGROUND

Zinc is undergoing evaluation as an inexpensive therapeutic adjuvant for severe pediatric pneumonia.

OBJECTIVE

We explored the effect of etiology on the treatment effect of zinc in young children hospitalized for severe pneumonia.

DESIGN

We analyzed data from a randomized, double-blind, placebo-controlled clinical trial conducted at the Christian Medical College Hospital, a teaching hospital in Tamilnadu, India. Children aged 2-23 mo (n = 299) were randomly assigned to receive a 10-mg tablet of zinc sulfate or placebo twice a day during hospitalization. The primary outcomes were length of hospitalization and time to resolution of severe pneumonia stratified by etiologic classification on the basis of serum C-reactive protein (CRP) concentrations at admission.

RESULTS

CRP concentrations were available for 295 (98.7%) of the enrolled cases. Of these 295 cases, 223 (75.6%) were classified as suspected nonbacterial pneumonias (CRP concentrations <or=40 mg/L). Etiology modified the treatment effect of zinc on the length of the hospital stay [hazard ratio (HR) for interaction term: 0.52; 95% CI: 0.31, 0.91; P = 0.022]. In the 72 suspected bacterial cases (CRP concentrations >40 mg/L), the median length of hospitalization was approximately 20 h longer in the zinc-supplemented group than in the placebo group (87.3 and 68.3 h, respectively; HR: 0.56; 95% CI: 0.34, 0.93; P = 0.025). The treatment effect was not modified in the suspected nonbacterial cases of pneumonia.

CONCLUSIONS

Our results suggest that the treatment effect of zinc for severe pediatric pneumonia may be modified by bacterial infection. Further studies are required to develop appropriate recommendations for the use of zinc in the treatment of severe pneumonia. This trial was registered at clinicaltrials.gov as NCT00198666.

Can zinc be an adjuvant therapy for juvenile onset recurrent respiratory papillomatosis?

OBJECTIVES

To report a severe case of juvenile onset recurrent respiratory papillomatosis (JORRP) controlled by zinc replacement therapy. To review the contemporary adjuvant therapies used in JORRP.

METHODS

The trial of zinc was described in terms of its effect on the inter-surgical interval, site score and clinical symptoms. Long-term follow-up with dose adjustment was detailed. Articles reporting trials of adjuvant therapies over the past 20 years were reviewed in terms of regimen used, mode of assessment, side effects and final outcome.

RESULTS

Zinc was effective in decreasing the severity of the disease, the rate of relapse and the need for surgery. There was an obvious relation between the dose used and the degree of improvement. Prolonged treatment seems to be needed to sustain the positive effect. No side effects were noticed over a 45-month follow-up period. The literature does support the role of zinc in modulating the immune system. Eight adjuvant therapies were reviewed as published in 40 reports. Interferon was the most used substance. It is definitely effective but often associated with relapse upon discontinuation. The effect of cidofovir was favorable yet not dramatic as initially expected. Other less commonly used therapies showed humble effects. The HspE7 vaccine seems to be promising awaiting further trials.

CONCLUSIONS

Zinc replacement therapy may benefit JORRP patients with zinc deficiency and should be investigated in more cases. Several adjuvant therapies are available for use in JORRP. They are generally beneficial though mostly not curative.

Immunomodulative effect of glucan and/or glucan supplemented with zinc in albendazole therapy for murine alveolar echinococcosis

The effect of glucan immunomodulator (GI) and glucan supplemented with zinc (GIZn) administered separately or with albendazole (ABZ) on cellular immunity of mice with alveolar echinococcosis was observed. The stimulative effect of GI and GI + ABZ therapy on proliferative response of T lymphocytes was prolonged by GIZn or GIZn + ABZ from week 6 to 14 postinfection (p.i.). The increased proliferation of B lymphocytes was observed during combined therapies GI + ABZ and GIZn + ABZ from week 6 to 12 p.i. Number of splenic CD4 T cells in mice with GI or GI + ABZ therapy was increased only on weeks 6 and 8 p.i. GIZn and GIZn + ABZ therapy prolonged this stimulation from week 6 to 14 p.i. Serum concentration of interferon-gamma (IFN-gamma) was increased after GIZn therapy and reduced after GI therapy from week 8 to 12 p.i. GIZn + ABZ therapy had the highest effect on the IFN-gamma rise from week 8 to 22 p.i. Both GI and GIZn inhibited the serum concentration of interleukin-5 (IL-5) from week 6 p.i. The production of superoxide anion was increased after GI therapy from week 6 to 14 p.i. and after GI + ABZ or GIZn + ABZ therapies from week 12 to 18 p.i. The most effective antiparasitic therapy for alveolar echinococcosis was reached by GIZn + ABZ therapy.

Signal transduction in monocytes: the role of zinc ions

The availability of zinc has a regulatory role in the immune system. It can have either pro- or anti-inflammatory effects, which both seem to be a consequence of a direct interaction of zinc with the cytokine secretion by monocytes. In this review, the molecular basis for this effect, the interaction of zinc with the signal transduction of monocytes, is discussed. In particular, zinc seems to activate or inhibit several signaling pathways that interact with the signal transduction of pathogen sensing receptors, the so-called Toll-like receptors (TLR), which sense pathogen-derived molecular structures and, upon activation, lead to secretion of pro-inflammatory cytokines. The interaction of zinc with protein tyrosine phosphatases and protein kinase C, and a direct modulation of lipopolysaccharide binding to its receptor (TLR-4) all result in enhanced cytokine production. On the other hand, a complex interaction between zinc, NO and cyclic nucleotide signaling, and inhibition of interleukin-1 receptor associated kinase-1, and inhibitor of kappa B kinase all counteract the production of pro-inflammatory cytokines. A role for the zinc binding protein metallothionein as a regulator for intracellular zinc signaling is discussed. By acting on all these signaling molecules, the zinc status of monocytes can have a direct effect on inflammation.

Zinc supplementation of pregnant rats with adequate zinc nutriture suppresses immune functions in their offspring

The knowledge about consequences of marginal zinc (Zn) deficiency and Zn supplementation during pregnancy on immune function in the offspring is limited. The aim of this study was to examine whether effects of mild Zn deficiency and subsequent Zn supplementation during pregnancy persist after weaning and affect immune function of the offspring. Adult female rats were fed a Zn-adequate diet (ZC, n = 8) or a Zn-deficient diet (ZD, n = 8) from preconception through lactation. Pregnant rats were supplemented with either Zn (1.5 mg Zn in water) or placebo (water) 3 times/wk throughout pregnancy. Pups were orally immunized with cholera toxin and bovine serum albumin-dinitrophenol (DNP) 3 times at weekly intervals and killed 1 wk after the last dose. Proliferation and cytokine responses in lymphocytes from Payer's patches and spleen, and antigen specific antibodies in serum were studied. Zn supplementation of ZD dams led to enhanced lymphocyte proliferation and IFN-gamma responses in pups ZDZ+. In contrast, Zn supplementation of ZC dams suppressed these responses in pups ZCZ+. Total and DNP-specific IgA responses were lower in pups of the Zn-deficient group compared with the Zn-adequate group. Relative thymus weight was greater in the pups (ZDZ-) of ZD placebo-supplemented dams compared with the other groups at 31 d of age. Prepregnancy and early in utero Zn deficiency affected IgA responses in pups that could not be restored with Zn supplementation during pregnancy. Zn supplementation of ZC dams induced immunosuppressive effects in utero that may also be mediated through milk and persist in the offspring after weaning.

T-helper type 1 cytokine release is enhanced by in vitro zinc supplementation due to increased natural killer cells

OBJECTIVE

We examined the influence of zinc on T-helper type 1 (Th1)/T-helper type 2 (Th2) balance in human lymphocytes.

METHODS

Human peripheral blood mononuclear cells or diluted whole blood were cultured for 8 d in the presence of zinc (30 or 60 microM) or 1 microM of N, N, N', N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) (a zinc-specific chelator). Phytohemagglutinin-induced cytokine release was measured by enzyme-linked immunosorbent assay, and expression of CD56/CD69, CCR4/CD3, and CCR5/CD3 and intracellular labile zinc were detected by flow cytometry.

RESULTS

We found that our in vitro supplementation resulted in an increase of intracellular labile zinc comparable to that of a 7-wk administration of 10 mg of zinc per day in vivo. Zinc triggered interferon-gamma release and impaired interleukin-10 release. Phenotypically, a Th2/Th1 shift could not be confirmed after detecting the Th1-specific chemokine receptor CCR5 or CCR4 for Th2 cells. Surprisingly, we detected a larger amount of CD56+ cells after zinc stimulation, leading us to the conclusion that the amount of interferon-gamma release after zinc supplementation might be attributed to the upregulation of natural killer cells after in vitro zinc supplementation rather than to a Th2/Th1 shift.

CONCLUSION

We suggest that a nutritional intake of 10 mg of zinc increases the quantity of interferon-gamma-producing natural killer cells and strengthens the immune system against neoplasms and viral infections.

Phytic acid modulates in vitro IL-8 and IL-6 release from colonic epithelial cells stimulated with LPS and IL-1beta

Phytic acid (PA), a major fiber-associated component of wheat bran and legumes, is physiologically present in the human large gut. The aim of this study was to examine the role of PA in immunologic function of intestinal epithelial cells by analyzing its effect on interleukin (IL)-8 and IL-6 secretion by colonocytes and its role in the response of these cells to bacterial lipopolysaccharides (LPS) and IL-1beta. The human colon cell line Caco-2 was exposed to LPS isolated from two strains of Desulfovibrio desulfuricans, wild intestinal and type soil strains, as well as to LPS from E. coli. Cells were also treated with IL-1beta and with a combination of LPS and IL-1beta. PA had a suppressive effect on IL-8 basal release and it dose dependently reduced IL-8 secretion by colonocytes stimulated with LPS and IL-1beta. On the contrary, PA increased constitutive IL-6 secretion and exhibited differentiated effects on LPS responsiveness of cells depending on its concentration and LPS origin. PA was also an efficient down-regulator of IL-6 secretion stimulated by binary actions of LPS and IL-1beta. The ability of PA to modulate IL-8 and IL-6 release suggests that PA present in the intestinal milieu may exert immunoregulatory effects on colonic epithelium under physiological conditions or during microbe-induced infection/inflammation in order to maintain the colonic mucosa in a noninflammatory state or to counteract infection.

Zinc homeostasis and immunity

Zinc is an essential trace element for the immune system, and zinc deficiency compromises the function of primarily T cells but also of several other immune cells. Recently, zinc homeostasis has been demonstrated to affect dendritic cells, in particular the involvement of zinc transport proteins during lipopolysaccharide-induced upregulation of major histocompatibility complex proteins and co-stimulatory molecules. This adds to our understanding of the immunomodulatory potential of zinc and highlights its significance for immune function.