Impairment of cell-mediated immunity functions by dietary zinc deficiency in mice

Antiviral activity of zinc against hepatitis viruses: current status and future prospects

Viral hepatitis is a major public health concern globally. World health organization aims at eliminating viral hepatitis as a public health threat by 2030. Among the hepatitis causing viruses, hepatitis B and C are primarily transmitted via contaminated blood. Hepatitis A and E, which gets transmitted primarily via the feco-oral route, are the leading cause of acute viral hepatitis. Although vaccines are available against some of these viruses, new cases continue to be reported. There is an urgent need to devise a potent yet economical antiviral strategy against the hepatitis-causing viruses (denoted as hepatitis viruses) for achieving global elimination of viral hepatitis. Although zinc was known to mankind for a long time (since before Christ era), it was identified as an element in 1746 and its importance for human health was discovered in 1963 by the pioneering work of Dr. Ananda S. Prasad. A series of follow up studies involving zinc supplementation as a therapy demonstrated zinc as an essential element for humans, leading to establishment of a recommended dietary allowance (RDA) of 15 milligram zinc [United States RDA for zinc]. Being an essential component of many cellular enzymes and transcription factors, zinc is vital for growth and homeostasis of most living organisms, including human. Importantly, several studies indicate potent antiviral activity of zinc. Multiple studies have demonstrated antiviral activity of zinc against viruses that cause hepatitis. This article provides a comprehensive overview of the findings on antiviral activity of zinc against hepatitis viruses, discusses the mechanisms underlying the antiviral properties of zinc and summarizes the prospects of harnessing the therapeutic benefit of zinc supplementation therapy in reducing the disease burden due to viral hepatitis.

Impacts of organic manganese supplementation on blood mineral, biochemical, and hematology in Afshari Ewes and their newborn lambs in the transition period

OBJECTIVE

Maternal mineral status, including manganese (Mn), is critical for fetal growth as well as the health of the newborn lamb. Consequently, it is essential to supply minerals at sufficient levels for the pregnant animal to achieve the development of the embryo and fetus during gestation.

METHODS

The current research was conducted to investigate the impact of organic Mn supplementation on blood biochemical, other mineral and, hematology in Afshari ewes and their newborn lambs in the transition period. Twenty-four ewes were randomly divided into three groups with eight replications. The control group was fed with a diet without organic Mn. The other groups were fed a diet supplemented with 40 (recommended by the NRC) and 80 (twice-recommended by the NRC) mg/kg of DM organic Mn.

RESULTS

In this study, the consumption of organic Mn caused a significant increase in ewes and lambs plasma Mn concentration. Moreover, in the groups mentioned, levels of glucose, insulin, and superoxide dismutase were significantly increased in both ewes and lambs. Concentrations of total protein and albumin were higher in ewes fed whit organic Mn. In both ewes and newborn lambs, the levels of red blood cells, hemoglobin, hematocrit, mean corpuscular hemoglobin, and mean corpuscular concentration in groups fed with organic Mn raised.

CONCLUSION

In general, the nutrition of organic Mn, improved factors of blood biochemical and hematology in ewes and their newborn lambs, and since the twice-recommended NRC level did not cause poisoning, it was recommended to supplement the diet with 80 mg of organic Mn per kg of DM.

Role of thymus in health and disease

The thymus is a primary lymphoid organ, essential for the development of T-cells that will protect from invading pathogens, immune disorders, and cancer. The thymus decreases in size and cellularity with age referred to as thymus involution or atrophy. This involution causes decreased T-cell development and decreased naive T-cell emigration to the periphery, increased proportion of memory T cells, and a restricted, altered T-cell receptor (TCR) repertoire. The changes in composition and function of the circulating T cell pool as a result of thymic involution led to increased susceptibility to infectious diseases including the recent COVID and a higher risk for autoimmune disorders and cancers. Thymic involution consisting of both structural and functional loss of the thymus has a deleterious effect on T cell development, T cell selection, and tolerance. The mechanisms which act on the structural (cortex and medulla) matrix of the thymus, the gradual accumulation of genetic mutations, and altered gene expressions may lead to immunosenescence as a result of thymus involution. Understanding the molecular mechanisms behind thymic involution is critical for identifying diagnostic biomarkers and targets for treatment help to develop strategies to mitigate thymic involution-associated complications. This review is focused on the consequences of thymic involution in infections, immune disorders, and diseases, identifying potential checkpoints and potential approaches to sustain or restore the function of the thymus particularly in elderly and immune-compromised individuals.

Zinc Status Impacts the Epidermal Growth Factor Receptor and Downstream Protein Expression in A549 Cells

Zinc has been suggested to play a role in carcinogenesis and tumor progression. Serum zinc levels of lung cancer patients are for example lower than in healthy individuals. The activation and expression of the epidermal growth factor receptor (EGFR), which plays a role in tumor biology, are presumably influenced by zinc. EGFR activation influences cell adhesion and immune escape. This study provides insights into the impacts of zinc on the EGFR activation and expression of downstream proteins such as E-cadherin and PD-L1 in the alveolar carcinoma cell line A549. To model chronic changes in zinc homeostasis, A549 cells were cultured in media with different zinc contents. EGFR surface expression of unstimulated and stimulated A549 cells was determined by flow cytometry. EGFR phosphorylation as well as the protein expression of E-cadherin and PD-L1 were analyzed by Western blot. In our hands, chronic zinc deficiency led to increased EGFR surface expression, decreased E-cadherin protein expression and increased PD-L1 protein expression. Zinc supplementation decreased EGFR surface expression and PD-L1 protein expression. In summary, zinc-deficient A549 cells may display a more malignant phenotype. Thus, future clinical research should further focus on the possible benefits of restoring disturbed zinc homeostasis, especially in lung cancer patients.

Bioinorganic Chemistry of Zinc in Relation to the Immune System

Zinc is well-known to have a central role in human inflammation and immunity and is itself an anti-inflammatory and antiviral agent. Despite its massively documented role in such processes, the underlying chemistry of zinc in relation to specific proteins and pathways of the immune system has not received much focus. This short review provides an overview of this topic, with emphasis on the structures of key proteins, zinc coordination chemistry, and probable mechanisms involved in zinc-based immunity, with some focus points for future chemical and biological research.

Zinc Source and Concentration Altered Physiological Responses of Beef Heifers during a Combined Viral-Bacterial Respiratory Challenge

Simple Summary

Bovine respiratory disease is one of the greatest health challenges cattle producers face and is most commonly treated with antibiotics. With the current push to reduce the use of antibiotics in livestock production, producers are looking at non-pharmaceutical alternatives such as nutritional supplements. This study aimed to determine if different forms of zinc supplementation could reduce some of the negative health effects associated with bovine respiratory disease. Overall, cattle supplemented with ZinMet (zinc methionine/organic zinc) responded better during the disease as evidenced by blood parameters, decreased lesion severity, and decreased fever. Conversely, cattle fed a large dose of zinc sulfate (inorganic zinc) displayed a higher fever and blood parameters that indicated a greater sickness response. Findings from this study suggest that the type and amount of zinc fed to cattle may influence their response to bovine respiratory disease.

Abstract

To determine the effects of zinc supplementation on the immune response to a combined viral-bacterial respiratory disease challenge, thirty-two beef heifers (255 ± 15 kg) were subjected to a 30-d period of Zn depletion, then randomly assigned to one of three treatment diets fed for 30 d before the challenge: (1) supplementation with 100 mg of Zn from Zn sulfate/kg of DM (Zn100), (2) supplementation with 200 mg of Zn from Zn sulfate/kg of DM (Zn200), and (3) supplementation with 80 mg of Zn/kg of DM from zinc methionine and 20 mg of Zn from Zn sulfate/kg of DM (ZinMet). After the 30-d supplementation period, all heifers were fitted with indwelling vaginal temperature (VT) devices and intra-nasally challenged with 1 × 10⁸ PFU bovine herpesvirus-1 on d -3, and then allowed to rest in outdoor pens for 3 d. On d 0, each heifer was challenged intra-tracheally with an average dose of 2.38 × 10⁷ CFU Mannheimia haemolytica (MH), fitted with an indwelling jugular catheter, and then moved into individual stalls in an environmentally-controlled enclosed barn. Whole blood samples were collected at 1-h (serum) and 2-h (complete blood counts) intervals from 0 to 8 h, and at 12, 24, 36, 48, 60, 72, 168, and 360 h relative to MH challenge. Data were analyzed using the MIXED procedure of SAS specific for repeated measures with fixed effects of treatment, time, and their interaction. There was a treatment effect (p < 0.01) for VT such that Zn200 heifers had greater VT than Zn100 and ZinMet heifers. There was a trend (p = 0.10) for a serum cortisol treatment effect with Zn100 heifers having greater cortisol than ZinMet heifers. Total leukocytes and lymphocytes were greater (p ≤ 0.01) in Zn100 heifers than Zn200 and ZinMet heifers, whereas monocytes were less (p = 0.05) in ZinMet heifers than Zn100 and Zn200 heifers. Concentrations of IL-6 were greater (p = 0.02) in ZinMet heifers than Zn100 and Zn200 heifers. Concentrations of IFN-γ were greater in Zn200 heifers than ZinMet heifers at 0 h, and Zn100 heifers from 0 to 12 h post-MH challenge (treatment x time p = 0.02). Serum haptoglobin was not affected by treatment or treatment x time (p ≥ 0.36) but increased over time (p < 0.01) in all groups. There was a trend (p = 0.11) for ZinMet heifers to have less severe nasal lesion scores than Zn100 heifers. The observed differential physiological responses in this study indicate that zinc source and concentration may alter the response to a bovine respiratory challenge in heifers.

Zinc Supplementation Modulates NETs Release and Neutrophils' Degranulation

Zinc plays an important physiological role in the entire body, especially in the immune system. It is one of the most abundant microelements in our organism and an essential component of enzymes and antibacterial proteins. Zinc levels were reported to be correlated with the intensity of innate immunity responses, especially those triggered by neutrophils. However, as the results are fragmentary, the phenomenon is still not fully understood and requires further research. In this study, we aimed to perform a comprehensive assessment and study the impact of zinc on several basic neutrophils’ functions in various experimental setups. Human and murine neutrophils were preincubated in vitro with zinc, and then phagocytosis, oxidative burst, degranulation and release of neutrophil extracellular traps (NETs) were analyzed. Moreover, a murine model of zinc deficiency and zinc supplementation was introduced in the study and the functions of isolated cells were thoroughly studied. We showed that zinc inhibits NETs release as well as degranulation in both human and murine neutrophils. Our study revealed that zinc decreases NETs release by inhibiting citrullination of histone H3. On the other hand, studies performed in zinc-deficient mice demonstrated that low zinc levels result in increased release of NETs and enhanced neutrophils degranulation. Overall, it was shown that zinc affects neutrophils’ functions in vivo and in vitro. Proper zinc level is necessary to maintain efficient functioning of the innate immune response.

Natural variation in the sequestosome-related gene, sqst-5, underlies zinc homeostasis in Caenorhabditis elegans

Zinc is an essential trace element that acts as a co-factor for many enzymes and transcription factors required for cellular growth and development. Altering intracellular zinc levels can produce dramatic effects ranging from cell proliferation to cell death. To avoid such fates, cells have evolved mechanisms to handle both an excess and a deficiency of zinc. Zinc homeostasis is largely maintained via zinc transporters, permeable channels, and other zinc-binding proteins. Variation in these proteins might affect their ability to interact with zinc, leading to either increased sensitivity or resistance to natural zinc fluctuations in the environment. We can leverage the power of the roundworm nematode Caenorhabditis elegans as a tractable metazoan model for quantitative genetics to identify genes that could underlie variation in responses to zinc. We found that the laboratory-adapted strain (N2) is resistant and a natural isolate from Hawaii (CB4856) is sensitive to micromolar amounts of exogenous zinc supplementation. Using a panel of recombinant inbred lines, we identified two large-effect quantitative trait loci (QTL) on the left arm of chromosome III and the center of chromosome V that are associated with zinc responses. We validated and refined both QTL using near-isogenic lines (NILs) and identified a naturally occurring deletion in sqst-5, a sequestosome-related gene, that is associated with resistance to high exogenous zinc. We found that this deletion is relatively common across strains within the species and that variation in sqst-5 is associated with zinc resistance. Our results offer a possible mechanism for how organisms can respond to naturally high levels of zinc in the environment and how zinc homeostasis varies among individuals.

Metabolic adaptation orchestrates tissue context-dependent behavior in regulatory T cells

The diverse distribution and functions of regulatory T cells (Tregs) ensure tissue and immune homeostasis; however, it remains unclear which factors can guide distribution, local differentiation, and tissue context-specific behavior in Tregs. Although the emerging concept that Tregs could re-adjust their transcriptome based on their habitations is supported by recent findings, the underlying mechanisms that reprogram transcriptome in Tregs are unknown. In the past decade, metabolic machineries have been revealed as a new regulatory circuit, known as immunometabolic regulation, to orchestrate activation, differentiation, and functions in a variety of immune cells, including Tregs. Given that systemic and local alterations of nutrient availability and metabolite profile associate with perturbation of Treg abundance and functions, it highlights that immunometabolic regulation may be one of the mechanisms that orchestrate tissue context-specific regulation in Tregs. The understanding on how metabolic program instructs Tregs in peripheral tissues not only represents a critical opportunity to delineate a new avenue in Treg biology but also provides a unique window to harness Treg-targeting approaches for treating cancer and autoimmunity with minimizing side effects. This review will highlight the metabolic features on guiding Treg formation and function in a disease-oriented perspective and aim to pave the foundation for future studies.

Role of Zinc in Immune System and Anti-Cancer Defense Mechanisms

The human body cannot store zinc reserves, so a deficiency can arise relatively quickly, e.g., through an improper diet. Severe zinc deficiency is rare, but mild deficiencies are common around the world. Many epidemiological studies have shown a relationship between the zinc content in the diet and the risk of cancer. The anti-cancer effect of zinc is most often associated with its antioxidant properties. However, this is just one of many possibilities, including the influence of zinc on the immune system, transcription factors, cell differentiation and proliferation, DNA and RNA synthesis and repair, enzyme activation or inhibition, the regulation of cellular signaling, and the stabilization of the cell structure and membranes. This study presents selected issues regarding the current knowledge of anti-cancer mechanisms involving this element.

Hemicellulose from Plant Biomass in Medical and Pharmaceutical Application: A Critical Review

BACKGROUND

Due to the non-toxicity, abundance and biodegradability, recently more and more attention has been focused on the exploration of hemicellulose as the potential substrate for the production of liquid fuels and other value-added chemicals and materials in different fields. This review aims to summarize the current knowledge on the promising application of nature hemicellulose and its derivative products including its degradation products, its new derivatives and hemicellulosebased medical biodegradable materials in the medical and pharmaceutical field, especially for inmmune regulation, bacteria inhibition, drug release, anti-caries, scaffold materials and anti-tumor.

METHODS

We searched the related papers about the medical and pharmaceutical application of hemicellulose and its derivative products, and summarized their preparation methods, properties and use effects.

RESULTS

Two hundred and twenty-seven papers were included in this review. Forty-seven papers introduced the extraction and application in immune regulation of nature hemicellulose, such as xylan, mannan, xyloglucan (XG) and β-glucan. Seventy-seven papers mentioned the preparation and application of degradation products of hemicellulose for adjusting intestinal function, maintaining blood glucose levels, enhancing the immunity and alleviating human fatigue fields such as xylooligosaccharides, xylitol, xylose, arabinose, etc. The preparation of hemicellulose derivatives were described in thirty-two papers such as hemicellulose esters, hemicellulose ethers and their effects on anticoagulants, adsorption of creatinine, the addition of immune cells and the inhibition of harmful bacteria. Finally, the preparations of hemicellulose-based materials such as hydrogels and membrane for the field of drug release, cell immobilization, cancer therapy and wound dressings were presented using fifty-five papers.

CONCLUSION

The structure of hemicellulose-based products has the significant impact on properties and the use effect for the immunity, and treating various diseases of human. However, some efforts should be made to explore and improve the properties of hemicellulose-based products and design the new materials to broaden hemicellulose applications.

Role of Zinc Signaling in the Regulation of Mast Cell-, Basophil-, and T Cell-Mediated Allergic Responses

Zinc is essential for maintaining normal structure and physiological function of cells. Its deficiency causes growth retardation, immunodeficiency, and neuronal degeneration. Zinc homeostasis is tightly regulated by zinc transporters and metallothioneins that control zinc concentration and its distribution in individual cells and contributes to zinc signaling. The intracellular zinc signaling regulates immune reactions. Although many molecules involved in these processes have zinc-binding motifs, the molecular mechanisms and the role of zinc in immune responses have not been elucidated. We and others have demonstrated that zinc signaling plays diverse and specific roles in vivo and in vitro in studies using knockout mice lacking zinc transporter function and metallothionein function. In this review, we discuss the impact of zinc signaling focusing particularly on mast cell-, basophil-, and T cell-mediated inflammatory and allergic responses. We also describe zinc signaling dysregulation as a leading health problem in inflammatory disease and allergy.

Zinc: A Potential Antiviral Against Hepatitis E Virus Infection?

Hepatitis E virus (HEV) is a major cause of viral hepatitis worldwide. Owing to its feco oral transmission route, sporadic as well as epidemic outbreaks recurrently occur. No specific antiviral therapy is available against the disease caused by HEV. Broad spectrum antivirals such as ribavirin and interferon alfa are prescribed in severe and chronic HEV cases. However, the side effects, cost, and limitations of usage render the available treatment unsuitable for several categories of patients. We recently reported the ability of zinc to inhibit viral replication in mammalian cell culture models of HEV infection. Zinc will be a safe and economical antiviral therapy option if it inhibits HEV replication during the natural course of infection. This essay discusses the putative mechanism(s) by which zinc inhibits HEV replication and provides an overview of the possible therapeutic potential of zinc in HEV patients.

Zinc and Skin Disorders

The skin is the third most zinc (Zn)-abundant tissue in the body. The skin consists of the epidermis, dermis, and subcutaneous tissue, and each fraction is composed of various types of cells. Firstly, we review the physiological functions of Zn and Zn transporters in these cells. Several human disorders accompanied with skin manifestations are caused by mutations or dysregulation in Zn transporters; acrodermatitis enteropathica (Zrt-, Irt-like protein (ZIP)4 in the intestinal epithelium and possibly epidermal basal keratinocytes), the spondylocheiro dysplastic form of Ehlers-Danlos syndrome (ZIP13 in the dermal fibroblasts), transient neonatal Zn deficiency (Zn transporter (ZnT)2 in the secretory vesicles of mammary glands), and epidermodysplasia verruciformis (ZnT1 in the epidermal keratinocytes). Additionally, acquired Zn deficiency is deeply involved in the development of some diseases related to nutritional deficiencies (acquired acrodermatitis enteropathica, necrolytic migratory erythema, pellagra, and biotin deficiency), alopecia, and delayed wound healing. Therefore, it is important to associate the existence of mutations or dysregulation in Zn transporters and Zn deficiency with skin manifestations.

Untersuchungen zur Zinkkonzentration in unterschiedlichen Probenmedien von Milchkühen und Ableitung von Referenzwerten

Gegenstand und Ziel: Zink spielt bei vielen Körperfunktionen eine Schlüsselrolle und ist für die Gesundheit und Fruchtbarkeit von enormer Bedeutung. Die Beurteilung der Zinkversorgung kann durch Analyse von Blut-, Harn- oder Haarproben erfolgen. Ziel der Studie war, Referenzwerte für die unterschiedlichen Probenmedien und Laktationszeitpunkte für die Herdenuntersuchung deutscher Milchviehherden zu bestimmen. Material und Methoden: Daten von 1515 Herden, die im Rahmen der Bestandsbetreuung der Klauentierklinik der Freien Universität Berlin zwischen 1995 und 2012 beprobt wurden, gingen in die Analyse ein. Die Zinkkonzentration wurden in Serum, Plasma, Vollblut, Haar und Harn der Poolproben von 7–10 Tieren pro Gruppe bestimmt. In Herden mit mehr als 200 Tieren wurden Kühe aus fünf Gruppen beprobt (8–3 Wochen ante partum [a. p.], 3–0 Wochen a. p., 0–1 Wochen post partum [p. p.], 3–5 Wochen p. p. und 15–18 Wochen p. p.). In Herden mit weniger als 200 Tieren beschränkte sich die Beprobung auf vier Gruppen (8–3 Wochen a. p., 3–0 Wochen a. p., 0–5 Wochen p. p. und 6–20 Wochen p. p.). Ergebnisse: Die Korrelationen zwischen den Zinkkonzentrationen in den Probenmedien variierten zwischen r = 0,001 (Vollblut und Harn) und r = 0,75 (Serum und Plasma). Die Zinkkonzentrationen in Serum und Plasma änderten sich schnell und folgten einer Laktationsdynamik mit den niedrigsten Werten um die Kalbung. In Vollblut und Haar änderten sich die Zinkkonzentrationen langsam und folgten der Laktationsdynamik zeitverzögert mit niedrigsten Werten einige Wochen nach der Kalbung. Referenzwerte für Poolproben für die unterschiedlichen Probenmedien und Laktationsstadien werden vorgeschlagen. Schlussfolgerungen und klinische Relevanz: Für die Diagnostik in unterschiedlichen Probenmedien und zu verschiedenen Laktationszeitpunkten müssen verschiedene Referenzwerte angewendet werden. Um mittels wiederholter Untersuchungen Veränderungen der Zinkversorgung beurteilen zu können, sollten dasselbe Probenmedium und derselbe Laktationszeitpunkt herangezogen werden.

Zinc is a critical regulator of placental morphogenesis and maternal hemodynamics during pregnancy in mice

Zinc is an essential micronutrient in pregnancy and zinc deficiency impairs fetal growth. We used a mouse model of moderate zinc deficiency to investigate the physiological mechanisms by which zinc is important to placental morphogenesis and the maternal blood pressure changes during pregnancy. A 26% reduction in circulating zinc (P = 0.005) was exhibited in mice fed a moderately zinc-deficient diet. Zinc deficiency in pregnancy resulted in an 8% reduction in both near term fetal and placental weights (both P < 0.0001) indicative of disrupted placental development and function. Detailed morphological analysis confirmed changes to the placental labyrinth microstructure. Continuous monitoring of maternal mean arterial pressure (MAP) revealed a late gestation decrease in the zinc-deficient dams. Differential expression of a number of regulatory genes within maternal kidneys supported observations on MAP changes in gestation. Increased MAP late in gestation is required to maintain perfusion of multiple placentas within rodent pregnancies. Decreased MAP within the zinc-deficient dams implies reduced blood flow and nutrient delivery to the placenta. These findings show that adequate zinc status is required for correct placental morphogenesis and appropriate maternal blood pressure adaptations to pregnancy. We conclude that insufficient maternal zinc intake from before and during pregnancy is likely to impact in utero programming of offspring growth and development largely through effects to the placenta and maternal cardiovascular system.

Metallothioneins: Emerging Modulators in Immunity and Infection

Metallothioneins (MTs) are a family of metal-binding proteins virtually expressed in all organisms including prokaryotes, lower eukaryotes, invertebrates and mammals. These proteins regulate homeostasis of zinc (Zn) and copper (Cu), mitigate heavy metal poisoning, and alleviate superoxide stress. In recent years, MTs have emerged as an important, yet largely underappreciated, component of the immune system. Innate and adaptive immune cells regulate MTs in response to stress stimuli, cytokine signals and microbial challenge. Modulation of MTs in these cells in turn regulates metal ion release, transport and distribution, cellular redox status, enzyme function and cell signaling. While it is well established that the host strictly regulates availability of metal ions during microbial pathogenesis, we are only recently beginning to unravel the interplay between metal-regulatory pathways and immunological defenses. In this perspective, investigation of mechanisms that leverage the potential of MTs to orchestrate inflammatory responses and antimicrobial defenses has gained momentum. The purpose of this review, therefore, is to illumine the role of MTs in immune regulation. We discuss the mechanisms of MT induction and signaling in immune cells and explore the therapeutic potential of the MT-Zn axis in bolstering immune defenses against pathogens.

Roles of Zinc Signaling in the Immune System

Zinc (Zn) is an essential micronutrient for basic cell activities such as cell growth, differentiation, and survival. Zn deficiency depresses both innate and adaptive immune responses. However, the precise physiological mechanisms of the Zn-mediated regulation of the immune system have been largely unclear. Zn homeostasis is tightly controlled by the coordinated activity of Zn transporters and metallothioneins, which regulate the transport, distribution, and storage of Zn. There is growing evidence that Zn behaves like a signaling molecule, facilitating the transduction of a variety of signaling cascades in response to extracellular stimuli. In this review, we highlight the emerging functional roles of Zn and Zn transporters in immunity, focusing on how crosstalk between Zn and immune-related signaling guides the normal development and function of immune cells.

ATSDR evaluation of the health effects of zinc and relevance to public health

As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals found at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) sites, which have the greatest public health impact. These profiles comprehensively summarise toxicological and environmental information. This article constitutes the release of portions of the Toxicological Profile for Zinc. The primary purpose of this article is to provide public health officials, physicians, toxicologists, and other interested individuals and groups with an overall perspective on the toxicology of zinc. It contains descriptions and evaluations of toxicological studies and epidemiological investigations, and provides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health. Toxicology and Industrial Health 2006; 22: 423-493.

Zinc in gut-brain interaction in autism and neurological disorders

A growing amount of research indicates that abnormalities in the gastrointestinal (GI) system during development might be a common factor in multiple neurological disorders and might be responsible for some of the shared comorbidities seen among these diseases. For example, many patients with Autism Spectrum Disorder (ASD) have symptoms associated with GI disorders. Maternal zinc status may be an important factor given the multifaceted effect of zinc on gut development and morphology in the offspring. Zinc status influences and is influenced by multiple factors and an interdependence of prenatal and early life stress, immune system abnormalities, impaired GI functions, and zinc deficiency can be hypothesized. In line with this, systemic inflammatory events and prenatal stress have been reported to increase the risk for ASD. Thus, here, we will review the current literature on the role of zinc in gut formation, a possible link between gut and brain development in ASD and other neurological disorders with shared comorbidities, and tie in possible effects on the immune system. Based on these data, we present a novel model outlining how alterations in the maternal zinc status might pathologically impact the offspring leading to impairments in brain functions later in life.

The importance of having zinc during in vitro maturation of cattle cumulus-oocyte complex: role of cumulus cells

The aim of this study was to investigate the influence of zinc (Zn) on the health of cumulus-oocyte complex (COC) during in vitro maturation (IVM). Experiments were designed to evaluate the effect of Zn added to IVM medium on: DNA integrity, apoptosis, cumulus expansion and superoxide dismutase (SOD) activity of cumulus cells (CC). Also, role of CC on Zn transport during IVM was evaluated on oocyte developmental capacity. DNA damage and early apoptosis were higher in CC matured with 0 μg/ml Zn compared with 0.7, 1.1 and 1.5 μg/ml Zn (p < 0.05). Cumulus expansion did not show differences in COC matured with or without Zn supplementation (p > 0.05). Superoxide dismutase activity was higher in COC matured with 1.5 μg/ml Zn than with 0 μg/ml Zn (p < 0.05). Cleavage and blastocyst rates were recorded after IVM in three maturation systems: intact COCs, denuded oocytes with cumulus cells monolayer (DO + CC) and denuded oocytes (DO). Cleavage rates were similar when COC, DO + CC or DO were matured with 1.5 μg/ml Zn compared with control group (p > 0.05). Blastocyst rates were significantly higher in COC than in DO + CC and DO with the addition of 1.5 μg/ml Zn during IVM (p < 0.01). Blastocyst quality was enhanced in COC and DO + CC compared with DO when Zn was added to IVM medium (p < 0.001). The results of this study indicate that Zn supplementation to IVM medium (i) decreased DNA damage and apoptosis in CC; (ii) increased SOD activity in CC; (iii) did not modify cumulus expansion and cleavage rates after in vitro fertilization; (iv) improved subsequent embryo development up to blastocyst stage; and (v) enhanced blastocyst quality when CC were present either in intact COC or in coculture during IVM.

Zinc, its biological role and use in dermatology

This literature review detines the biological role ot zinc in the human body, immune homeostasis and skin physiology as well as pathophysiology ot skin diseases. It describes the current range ot systemic and topical zinc preparations and their pharmacological characteristics. The review also describes skin diseases that may be treated with the use ot zinc preparations on a grounded basis, and discloses the clinical experience ot the use ot these drugs described in the world literature. It sets out certain recommendations tor using zinc preparations in clinical practice.

Nutraceuticals of anti-inflammatory activity as complementary therapy for rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by elevated oxidative stress and inflammatory biomarkers. The severe side effects of drug used during such disease necessitate the search for new and safe approaches. Food is a rich source of antioxidants and anti-inflammatory bioactive constituents including phenolic compounds, polyunsaturated fatty acids, phytosterols, toccopherols, and carotenoids. We have a series of publications dealing with the anti-inflammatory activity of different food extracts (as nutraceuticals) in experimental animals (acute and chronic inflammation model) and in clinical study (RA patients). Fish oil, primrose oil, extracts of black cumin, fenugreek, liquorice, coriander, tomato, carrot, sweet potato, broccoli, green tea, rosemary, hazelnut, walnut, wheat germ, and date in addition to the probiotic Bifidobacterium bifidum were the nutraceuticals studied. During these studies, changes in inflammatory biomarkers (erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), seromucoids, fibrinogen, tumor necrosis factor-α (TNF-α), prostaglandin E2), oxidative stress (malondialdehyde), antioxidant status (total antioxidant capacity, vitamin C, vitamin E, retinol, β-carotene), the level of copper (Cu) and zinc (Zn) and colonic microflora in response to the administration of nutraceuticals have been assessed. Results of these studies showed that the majority of nutraceuticals studied possess beneficial effect toward chronic inflammatory diseases, which might be due to the presence of one or more of the above-mentioned phytochemicals. Conclusion: Anti-inflammatory and antioxidant nutraceuticals may serve as complementary medicine for the management of RA.

Effects of copper and zinc on proteoglycan metabolism in articular cartilage

Co-Cultures of porcine articular cartilage and synovium or synovial conditioned medium were used as an in vitro model to mimic inflammatory events at the cartilage/synovial junction in degenerative joint disease. This model provides a useful tool to assess the anti-inflammatory and antiarthritic properties of pharmacological agents. In this study the effects of copper and zinc on (i) PG synthesis by cartilage and (ii) synovial-induced PG depletion have been investigated. Copper sulphate at a concentration of 0.01 mM did not stimulate PG synthesis significantly in cultured cartilage explants but completely abrogated the inhibitory effects of synovial tissue in co-culture experiments. This finding was supported by the histological demonstration of copper-dependent reversal of the PG depletion in cartilage exposed to synovial conditioned medium. Zinc sulphate at 0.01 mM had no effect on PG synthesis and was unable to protect cartilage against synovialinduced PG depletion. These results reveal possible mechanisms by which copper exerts its anti-inflammatory and anti-arthritic actions.

Trace elements in foods of children from Cameroon: a focus on zinc and phytate content

In developing countries, complementary foods are based on local cereal porridges. These foods are poor in trace elements, with a high risk of inducing micronutrient deficiencies-the primary cause of mortality in children under the age of five. Inappropriate feeding of complementary foods is the major factor creating malnutrition and micronutrients deficiencies in Cameroon children, as well as in other developing countries. This study determined the zinc and phytate content of 30 complementary foods that were based on maize or Irish potatoes. The foods were blended or treated by dehusking, fermentation and germination. Zinc was measured by flame atomic absorption spectrophotometry and phytates by high pressure-liquid chromatography; then phytates/zinc molar ratios were calculated. Concentrations (mg/100g dry matter) ranged, respectively, from 0.20 to 2.58 (0.12 ± 0.67) for zinc and from 0.00 to 6.04 (1.87 ± 1.7) for phytates. The phytate/zinc ratio varied from 0.00 to 51.62 (11.12 ± 11.53). It appears that germination and fermentation reduced the level of phytates: however, zinc levels in the samples did not change significantly. The traditional, local complementary foods were not only poor in zinc, but contained very high levels of phytates. These phytates have the potential to considerately reduce the acid extraction of zinc, and could impair its bioavailability.

The efficacy of zinc supplementation on outcome of children with severe pneumonia. A randomized double-blind placebo-controlled clinical trial

OBJECTIVE

To compare the clinical outcome of children having severe pneumonia, with and without zinc supplementation by a randomized double-blind placebo controlled trial.

METHODS

In this study, 128 children (3-60 months old) admitted to the hospital with severe pneumonia were randomly divided into 2 groups (64 in each) that received either zinc sulfate (2 mg/kg/d, maximum 20 mg in 2 divided doses, for 5 days) or a placebo, along with the standard antimicrobial therapy. Primary outcome measurements included the time taken for clinical symptoms of severe pneumonia such as fever and respiratory distress symptoms to resolve, and the secondary outcome included the duration of hospital stay.

RESULTS

The time taken for all the symptoms to resolve in the zinc-supplemented group was significantly lesser then that in the placebo group (42.26 [6.66] vs. 47.52 [7.15] h respectively, p < 0.001). The zinc-treated group had a significantly shorter duration of fever (23.29 [6.67] vs. 26.6 [6.26] h, p = 0.024), respiratory distress (32.87 [7.85] vs. 37.37 [4.43] h, p = 0.001), required a shorter hospital stay (126.74 [12.8] vs. 137.74 [11.52] h, p < 0.001) than did the controls. The zinc supplement was well tolerated by the children.

CONCLUSIONS

The results suggest that adjuvant treatment with zinc accelerates recovery from severe pneumonia in young children and significantly reduces the duration of hospital stay. Further studies are required to develop appropriate recommendations for the use of zinc in the treatment of severe pneumonia in other populations.

Zinc inactivates melastatin transient receptor potential 2 channels via the outer pore

Zinc ion (Zn(2+)) is an endogenous allosteric modulator that regulates the activity of a wide variety of ion channels in a reversible and concentration-dependent fashion. Here we used patch clamp recording to study the effects of Zn(2+) on the melastatin transient receptor potential 2 (TRPM2) channel. Zn(2+) inhibited the human (h) TRPM2 channel currents, and the steady-state inhibition was largely not reversed upon washout and concentration-independent in the range of 30-1000 μM, suggesting that Zn(2+) induces channel inactivation. Zn(2+) inactivated the channels fully when they conducted inward currents, but only by half when they passed outward currents, indicating profound influence of the permeant ion on Zn(2+) inactivation. Alanine substitution scanning mutagenesis of 20 Zn(2+)-interacting candidate residues in the outer pore region of the hTRPM2 channel showed that mutation of Lys(952) in the extracellular end of the fifth transmembrane segment and Asp(1002) in the large turret strongly attenuated or abolished Zn(2+) inactivation, and mutation of several other residues dramatically changed the inactivation kinetics. The mouse (m) TRPM2 channels were also inactivated by Zn(2+), but the kinetics were remarkably slower. Reciprocal mutation of His(995) in the hTRPM2 channel and the equivalent Gln(992) in the mTRPM2 channel completely swapped the kinetics, but no such opposing effects resulted from exchanging another pair of species-specific residues, Arg(961)/Ser(958). We conclude from these results that Zn(2+) inactivates the TRPM2 channels and that residues in the outer pore are critical determinants of the inactivation.

Zinc homeostasis and signaling in health and diseases: Zinc signaling

The essential trace element zinc (Zn) is widely required in cellular functions, and abnormal Zn homeostasis causes a variety of health problems that include growth retardation, immunodeficiency, hypogonadism, and neuronal and sensory dysfunctions. Zn homeostasis is regulated through Zn transporters, permeable channels, and metallothioneins. Recent studies highlight Zn's dynamic activity and its role as a signaling mediator. Zn acts as an intracellular signaling molecule, capable of communicating between cells, converting extracellular stimuli to intracellular signals, and controlling intracellular events. We have proposed that intracellular Zn signaling falls into two classes, early and late Zn signaling. This review addresses recent findings regarding Zn signaling and its role in physiological processes and pathogenesis.

Nutritional imbalances and infections affect the thymus: consequences on T-cell-mediated immune responses

The thymus gland, where T lymphocyte development occurs, is targeted in malnutrition secondary to protein energy deficiency. There is a severe thymic atrophy, resulting from massive thymocyte apoptosis (particularly affecting the immature CD4+CD8+ cell subset) and decrease in cell proliferation. The thymic microenvironment (the non-lymphoid compartment that drives intrathymic T-cell development) is also affected in malnutrition: morphological changes in thymic epithelial cells were found, together with a decrease of thymic hormone production, as well as an increase of intrathymic contents of extracellular proteins. Profound changes in the thymus can also be seen in deficiencies of vitamins and trace elements. Taking Zn deficiency as an example, there is a substantial thymic atrophy. Importantly, marginal Zn deficiency in AIDS subjects, children with diarrhoea and elderly persons, significantly impairs the host's immunity, resulting in an increased risk of opportunistic infections and mortality; effects that are reversed by Zn supplementation. Thymic changes also occur in acute infectious diseases, including a severe thymic atrophy, mainly due to the depletion of CD4+CD8+ thymocytes, decrease in thymocyte proliferation, in parallel to densification of the epithelial network and increase in the extracellular matrix contents, with consequent disturbances in thymocyte migration and export. In conclusion, the thymus is targeted in several conditions of malnutrition as well as in acute infections. These changes are related to the impaired peripheral immune response seen in malnourished and infected individuals. Thus, strategies inducing thymus replenishment should be considered as adjuvant therapeutics to improve immunity in malnutrition and/or acute infectious diseases.

Micronutrients and HIV infection

The immune system requires several essential micronutrients to maintain an effective immune response. HIV infection destroys the immune system and promotes nutritional deficiencies, which further impair immunity. This article reviews the role of several micronutrients (vitamins A, C, E and D, the B vitamins, and minerals, selenium, iron and zinc) that are relevant for maintaining immune function. In addition, the deficiencies of these micronutrients have been associated with faster progression of HIV-1 disease. This review examines the evidence from observational studies of an association between micronutrient status and HIV disease, as well as the effectiveness of micronutrient supplementation on HIV-disease progression, pregnancy outcomes and nutritional status, among others, utilizing randomized clinical trials. Each micronutrient is introduced with a summary of its functions in human physiology, followed by the presentation of studies conducted in HIV-infected patients in relation to this specific micronutrient. Overall findings and recommendations are then summarized.

Functional significance of zinc-related signaling pathways in immune cells

Recent years have brought a paradigm shift for the role of the essential trace element zinc in immunity. Although its function as a structural component of many enzymes has been known for decades, current experimental evidence points to an additional function of the concentration of free or loosely bound zinc ions as an intracellular signal. The activity of virtually all immune cells is modulated by zinc in vitro and in vivo. In this review, we discuss the interactions of zinc with major signaling pathways that regulate immune cell activity, and the implications of zinc deficiency or supplementation on zinc signaling as the molecular basis for an effect of zinc on immune cell function.

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.

Zinc transporter Znt5/Slc30a5 is required for the mast cell-mediated delayed-type allergic reaction but not the immediate-type reaction

Zinc (Zn) is an essential nutrient and its deficiency causes immunodeficiency. However, it remains unknown how Zn homeostasis is regulated in mast cells and if Zn transporters are involved in allergic reactions. We show that Znt5/Slc30a5 is required for contact hypersensitivity and mast cell-mediated delayed-type allergic response but not for immediate passive cutaneous anaphylaxis. In mast cells from Znt5(-/-) mice, Fc epsilon receptor I (Fc epsilonRI)-induced cytokine production was diminished, but degranulation was intact. Znt5 was involved in Fc epsilonRI-induced translocation of protein kinase C (PKC) to the plasma membrane and the nuclear translocation of nuclear factor kappaB. In addition, the Zn finger-like motif of PKC was required for its plasma membrane translocation and binding to diacylglycerol. Thus, Znt5 is selectively required for the mast cell-mediated delayed-type allergic response, and it is a novel player in mast cell activation.

Micronutrient deficiencies in maternity and child health: a review of environmental and social context and implications for Malawi

It is well documented that micronutrient malnutrition is of increasing concern in the developing world, resulting in poor health and high rates of mortality and morbidity. During pregnancy, deficiency of iron and zinc can produce cognitive and growth impairment of the foetus, which may continue into infancy. Iron and zinc are essential micronutrients for both plant growth and human nutrition. Despite significant work in the areas of soil fertility, crop biofortification and dietary interventions, the problems of micronutrient deficiencies persist in Africa. There is a need to examine why communities have not embraced intervention strategies which may offer health benefits. Bottom-up, interdisciplinary approaches are required to effectively study the relationships between local communities and their environment, and to assess the impact their behaviour has on the cycling of micronutrients within the soil-plant-human system. From a detailed consideration of diverse influencing factors, a methodological model is suggested for studying the barriers to improving micronutrient uptake within rural communities. It combines environmental understanding with health and social factors, emphasising the need for and potential benefits of understanding and coherence in true interdisciplinary working.

Vitamin B6 deficiency alters tissue iron concentrations in the Wistar rat

PURPOSE

We investigated the effect of a vitamin B6 deficiency and pair-feeding on tissue trace element status.

METHOD

Tissue zinc, copper and iron concentrations were measured in 3 groups of young, male Wistar rats receiving a diet of 3.5mg/kg (control group), 0mg/kg (deficient group) and a pair-fed group over 8 weeks. The pair-fed group received the same diet consumed by the control. Tissue trace element analysis was performed using atomic absorption spectrophotometry and plasma vitamin B6 status was determined using HPLC.

RESULTS

Deficiency resulted in elevation in liver iron concentration and reduction in muscle iron concentration. Muscle copper concentrations were reduced in the pair-fed and deficient groups vs. the control group. Tissue zinc concentrations remained unaffected by the deficiency. Kidney iron and heart copper levels were elevated in the pair-fed group.

CONCLUSIONS

The liver and muscle iron changes were due to the deficiency and not to reduced calorie intake and the latter may be due to impaired heme synthesis. The differences in copper between the groups were due to reduced food intake. Zinc seems to form a fixed pool in these animals. A dietary deficiency of vitamin B6 impacts on the trace element status of certain tissues in key metabolic tissues and hence needs to be factored into the amelioration of the condition.

Intracellular zinc homeostasis and zinc signaling

Zinc (Zn) is an essential heavy metal that is incorporated into a number of human Zn metalloproteins. Zn plays important roles in nucleic acid metabolism, cell replication, and tissue repair and growth. Zn deficiency is associated with a range of pathological conditions, including impaired immunity, retarded growth, brain development disorders and delayed wound healing. Moreover, many reports have suggested that Zn is involved in cancer development and levels of Zn in serum and malignant tissues of patients with various types of cancer are abnormal. Zn may directly affect tumor cells by regulating gene expression profiles and/or cell viability, both of which are mediated in part by tumor-induced changes in Zn transporter expression. On the other hand, Zn may indirectly influence tumor cells by affecting processes within the cancer microenvironment, including immune responses; the functions and/or activity levels of immune cells that attack tumor cells are influenced by the intracellular Zn concentrations within those cells. In both cases, Zn contributes to intracellular metal homeostasis and/or signal transduction in tumor and immune cells. In this review article, we will summarize the current understanding of the roles of Zn homeostasis and signaling primarily in immune cells, with a discussion of the contributions of these processes to oncogenesis.

The genesis of amniotic fluid infections

Amniotic fluid infections manifested by an inflammatory response in the extraplacental membranes and subchorionic plate of the placenta are a common phenomenon thought to be due in most cases to ascending bacterial infections via intact membranes. Fatal spread to the fetus is much less common and more likely to occur in underprivileged communities. The probable reasons are nutritional deprivation in the mother or both, leading to production of a liquor with diminished ability to suppress bacterial growth. Zinc is one component of the antibacterial system but liquor levels of zinc vary widely and inconsistently with antibacterial activity. Dietary supplementation with zinc did not improve antibacterial activity of liquors in a population with diminished liquor antibacterial activity and large number of fatal infections. Other factors in the genesis of amniotic fluid infections may be interference with normal defence mechanisms as a result of coitus in late pregnancy and vaginal infections with Trichomonas vaginalis. Socioeconomic factors may play a role apart from their association with maternal nutrition, through diminished hygiene associated with insufficient use of water and insufficient availability and use of medical facilities.

Zinc regulates the stability of repetitive minisatellite DNA tracts during stationary phase

Repetitive minisatellite DNA tracts are stable in mitotic cells but unstable in meiosis, altering in repeat number and repeat composition. As relatively little is known about the factors that influence minisatellite stability, we isolated mutations that destabilize a minisatellite repeat tract in the ADE2 gene of Saccharomyces cerevisiae. One mutant class exhibited a novel color segregation phenotype, "blebbing," characterized by minisatellite instability during stationary phase. Minisatellite tract alterations in blebbing strains consist exclusively of the loss of one 20-bp repeat. Timing experiments suggest that these tract alterations occur only after cells have entered stationary phase. Two complementation groups identified in this screen have mutations in either the high-affinity zinc transporter ZRT1 or its zinc-dependent transcriptional regulator ZAP1. The Deltazrt1 mutant specifically affects the stability of minisatellite tracts; microsatellites or simple insertions in the ADE2 reading frame are not destabilized by loss of ZRT1. The Deltazrt1 blebbing phenotype is partially dependent on a functional RAD50. Zinc is known for its role as an essential cofactor in many DNA-binding proteins. We describe possible models by which zinc can influence minisatellite stability. Our findings directly implicate zinc homeostasis in the maintenance of genomic stability during stationary phase.

The thymus is a common target in malnutrition and infection

Malnutrition, secondary to deficiency in intake of proteins, minerals or vitamins, consistently results in changes in the thymus. This organ undergoes a severe atrophy due to apoptosis-induced thymocyte depletion, particularly affecting the immature CD4+CD8+ cells, as well as a decrease in cell proliferation. This feature is apparently linked to a hormonal imbalance, involving a decrease in leptin and consequent increase in glucocorticoid hormone levels in the serum. The thymic microenvironment is also affected in malnutrition: morphological changes in thymic epithelial cells have been found, together with a decrease of thymic hormone production by these cells. Additionally, intrathymic contents of extracellular proteins, such as fibronectin, laminin and collagens, are increased in thymuses from malnourished children. Taken together, these data clearly point to the notion that the thymus is significantly affected in malnutrition. Similar patterns of thymic changes occur in acute infectious diseases, including a severe atrophy of the organ, mainly due to the apoptosis-related depletion of immature CD4+CD8+ thymocytes. Additionally, thymocyte proliferation is compromised in acutely-infected subjects. The microenvironmental compartment of the thymus is also affected in acute infections, with an increased density of the epithelial network and an increase in the deposition of extracellular matrix. In conclusion, it seems clear that the thymus is targeted in malnutrition as well as in acute infections. These changes are related to the impaired peripheral immune response seen in malnourished and infected individuals. Thus, strategies inducing thymus replenishment should be considered in therapeutic approaches, in both malnutrition and acute infectious diseases.

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.

Clinical, immunological, anti-inflammatory and antioxidant roles of zinc

The essentiality of zinc for humans was recognized only 40 years ago. Zinc deficiency was suspected to occur in Iranian patients with growth retardation, hypogonadism in males, hepato-splenomegaly, rough and dry skin, geophagia and severe iron deficiency anemia. Later we documented zinc deficiency in similar patients in Egypt. The diet of these patients consisted of mainly cereal proteins which contained high phytate and this led to decreased availability of iron and zinc. These patients had severe immune dysfunctions, inasmuch as they died of intercurrent infections by the time they were 25 years of age. In our studies in experimental human model of zinc deficiency, we documented decreased serum testosterone level, oligospermia, severe immune dysfunctions mainly affecting T helper cells, decreased serum thymulin activity hyperammonemia, neuro-sensory disorders and decreased lean body mass. The basic mechanisms of zinc action on immune cells have been reviewed in this paper. Our studies showed that the activation of many zinc dependent enzymes and transcription factors were affected adversely due to zinc deficiency. The gene expression and production of Th1 cytokines were affected adversely due to zinc deficiency. Zinc is also an antioxidant and has anti-inflammatory actions. We have reported decreased plasma zinc, increased plasma oxidative stress markers and increased generation of inflammatory cytokines in the elderly subjects which were corrected by zinc supplementation. In cell culture studies, we have observed that zinc induces A20 which inhibits NF-kappaB activation resulting in decreased generation of inflammatory cytokines.