Zinc deficiency in mice alters myelopoiesis and hematopoiesis

Endogenous small molecule effectors in GATA transcription factor mechanisms governing biological and pathological processes

Transcriptional mechanisms establish and maintain complex genetic and protein networks to control cell state transitions. The hematopoietic transcription factor GATA1 is a master regulator of erythropoiesis and megakaryopoiesis, and human GATA1 genetic variants cause anemia and megakaryoblastic leukemia. Multiomic analyses revealed that GATA1 controls expression of transporters and metabolic enzymes that dictate intracellular levels of endogenous small molecules, including heme, metal ions, and sphingolipids. Besides its canonical function as a hemoglobin component, heme facilitates or antagonizes GATA1 function to regulate erythropoiesis via mechanisms dependent or independent of the heme-binding transcription factor BTB domain and CNC homology 1 (BACH1). GATA1 regulates the expression of genes encoding heme biosynthetic enzymes and BACH1. GATA1 maintains homeostasis of bioactive ceramides during erythroid differentiation by regulating genes encoding sphingolipid metabolic enzymes. Disrupting ceramide homeostasis impairs critical cytokine signaling and is detrimental to erythroid cells. During erythroid maturation, GATA1 induces a zinc transporter switch that favors export versus import, thus dictating the intracellular zinc level, erythroblast survival, and differentiation. In aggregate, these studies support an emerging paradigm in which GATA factor-dependent transcriptional mechanisms control the intracellular levels of endogenous small molecules and small molecule-dependent feedback loops that serve as vital effectors of transcription factor activity, genome function, and cell state transitions.

Zinc and aging: a narrative review of the effects on hematopoiesis and its link with diseases

There has been a global increase in the older population in recent decades and, as age advances, complex metabolic and epigenetic changes occur in the organism, and these may trigger some health complications commonly found among this population. Additionally, several changes occur in older people that can reduce the dietary intake or the process of nutrient absorption. In this way, tissues with high nutrient requirements are more affected. Hematopoiesis is the process of formation, development, and maturation of blood cells and is a process with a high turnover. This high demand makes the integrity of the hematopoietic process susceptible to various factors that impair physiological function, such as aging and micronutrient bioavailability. Among these micronutrients, Zinc is considered an important micronutrient, playing diverse roles across various tissues and cell types. Some of the alterations in hematopoiesis that appear as a consequence of aging and due to insufficient micronutrient intake are well described in the literature; however, not much is known about how zinc deficiency contributes towards the development of diseases seen in aging. Considering the importance of zinc to act on several biological processes, this narrative review discusses several studies related to the physiological requirements, deficiency, or excess of zinc, including studies in experimental models and humans, and aimed to shed light on the relationship between zinc and the regulation of hematopoietic tissue, exploring possible links between this mineral with common disorders that appear during aging.

Identification of the natural chalcone glycoside hydroxysafflor yellow A as a suppressor of P53 overactivation-associated hematopoietic defects

Enhanced P53 signaling may lead to hematopoietic disorders, yet an effective therapeutic strategy is still lacking. Our study, along with previous research, suggests that P53 overactivation and hematopoietic defects are major consequences of zinc deficiency. However, the relationship between these two pathological processes remains unclear. In this study, we observed a severe reduction in the number of hematopoietic stem cells (HSCs) and multi-lineage progenitor cells in zebrafish treated with the zinc chelator N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine and showed the indispensable role of P53 signaling in the process. Next, we took advantage of HSCs-labeled transgenic zebrafish and conducted a highly efficient phenotypic screening for small molecules against P53-dependent hematopoietic disorders. Hydroxysafflor yellow A (HSYA), a natural chalcone glycoside, exhibited potent protection against hematopoietic failure in zinc-deficient zebrafish and strongly inhibited the P53 pathway. We confirmed the protective effect of HSYA in zinc-deficient mice bone marrow nucleated cells, which showed a significant suppression of P53 signaling and oxidative stress. Furthermore, the hematopoietic-protective activity of HSYA was validated using a mice model of myelotoxicity induced by 5-FU. In summary, our work provides an effective phenotypic screening strategy for identifying hematopoietic-protective agents and reveals the novel role of HSYA as a promising lead compound in rescuing hematopoietic disorders associated with P53 overactivation.

Association between Dietary Zinc Intake, Serum Zinc Level and Multiple Comorbidities in Older Adults

Zinc is one of the essential micronutrients in the geriatric population, but the importance of zinc status and dietary zinc intake has been poorly characterized. We aimed to explore the relationships among dietary zinc intake, serum zinc concentrations and multimorbidity in a cross-sectional study of 300 employees of Electric Generating Authority of Thailand aged ≥ 60 years. Comprehensive questionnaires were completed, and clinical and laboratory assessments were performed. Factors associated with low serum zinc concentrations were identified using multivariate multinomial logistic regression analyses. The mean serum zinc level was 80.5 (12.8) µg/dL. After adjustment for baseline characteristics, being female and having been in education for ≤12 years were independent risk factors for the lowest tertile (T1) of serum zinc. After additional adjustment for clinical and biochemical parameters, there was a significant association between depression (Thai Geriatric Depression Scale-15 score > 5) and low serum zinc levels (T1 vs. T3, odds ratio (OR): 2.24; 95% confidence interval (CI): 1.06−4.77). Furthermore, as serum albumin increased, serum zinc concentration substantially increased (T1 vs. T3, OR: 0.01; 95% CI: 0.002−0.070). Therefore, the early detection of risk factors and the further management of depression and low serum albumin may assist physicians in preventing low serum concentrations.

Cellular Zinc Deficiency Impairs Heme Biosynthesis in Developing Erythroid Progenitors

Anemia is the most prevalent nutrition-related disorder worldwide. Zinc is an essential trace element for various biological processes in the body, and zinc deficiency has been associated with anemia in humans. However, the molecular mechanisms by which zinc availability alters red blood cell development remain uncertain. The present study identifies the essentiality of zinc during erythroid development, particularly for normal heme biosynthesis. G1E-ER4 mouse cells were used as an in vitro model of terminal erythroid differentiation, which featured elevated cellular zinc content by development. Restriction of zinc import compromised the rate of heme and α-globin production and, thus, the hemoglobinization of the erythroid progenitors. Heme is synthesized by the incorporation of iron into protoporphyrin. The lower heme production under zinc restriction was not due to changes in iron but was attributable to less porphyrin synthesis. The requirement of adequate zinc for erythroid heme metabolism was confirmed in another erythropoietic cell model, MEL-DS19. Additionally, we found that a conventional marker of iron deficiency anemia, the ZnPP-to-heme ratio, responded to zinc restriction differently from iron deficiency. Collectively, our findings define zinc as an essential nutrient integral to erythroid heme biosynthesis and, thus, a potential therapeutic target for treating anemia and other erythrocyte-related disorders.

Association of Zinc with Anemia

Zinc is an essential trace element, and anemia is the most common blood disorder. The association of zinc with anemia may be divided into three major forms: (1) zinc deficiency contributing to anemia, (2) excess intake of zinc leading to anemia, and (3) anemia leading to abnormal blood-zinc levels in the body. In most cases, zinc deficiency coexists with iron deficiency, especially in pregnant women and preschool-age children. To a lesser extent, zinc deficiency may cooperate with other factors to lead to anemia. It seems that zinc deficiency alone does not result in anemia and that it may need to cooperate with other factors to lead to anemia. Excess intake of zinc is rare. However, excess intake of zinc interferes with the uptake of copper and results in copper deficiency that leads to anemia. Animal model studies indicate that in anemia, zinc is redistributed from plasma and bones to the bone marrow to produce new red blood cells. Inadequate zinc status (zinc deficiency or excess) could have effects on anemia; at the same time, anemia could render abnormal zinc status in the body. In handling anemia, zinc status needs to be observed carefully, and supplementation with zinc may have preventive and curative effects.

Exploration of the relationship between anemia and iron and zinc deficiencies in children under 5 years of age living in the malaria endemic area of South Kivu/Democratic Republic of Congo

The aim of this study was to explore the relationship of iron and zinc deficiencies and anemia in children aged under 5 years living in malaria endemic area of South Kivu/DRC. We conducted a cross-sectional study in the health zone of Miti Murhesa in South Kivu/DRC. A total of 1088 children in good general health were included in this study. Almost 40% of children were anemic. The prevalence of iron deficiency (ID) was found in 34.9% and 49.1% children based on ferritin or free erythrocyte protoporphyrin (FEP), respectively. If anemia is present, we found iron deficiency anemia (IDA) according to the WHO-criteria (ferritin) in 31%, and according to FEP in 66% of children. The overall prevalence of zinc deficiency was 17.6%. If anemia is present, zinc deficiency was found in 24.4% of children. Inflammation/infection, based upon CRP, was present in 39.7% children. The independent factors associated with anemia were recent illness, middle upper arm circumference, weight-for-height, ID according to FEP, zinc deficiency, and submicroscopic Plasmodium infection. A high prevalence of ID was observed in children in South Kivu according to FEP. Ferritin as acute phase protein was less suited in this population due to a high frequency of infection/inflammation. Iron and zinc deficiencies were found to be significantly associated with anemia in this population.

Rebalancing the unbalanced aged immune system - A special focus on zinc

Nowadays, aging is understood as a dynamic and multifaceted dysregulation process that spares almost no human organ or cell. The immune system being among the most affected, it has been shown predominantly that its integrity determines the tightrope walk between the difference of escaping or suffering from age-related diseases. Next to drug-based anti-aging strategies, micronutrient intervention may represent an emerging but less radical way to slow immune aging. While a sufficient supply of a variety of micronutrients is undeniably important, adequate intake of the trace element zinc appears to tower over others in terms of reaching old age. Inconveniently, zinc deficiency prevalence among the elderly is high, which in turn contributes to increased susceptibility to infection, decreased anti-tumor immunity as well as attenuated response to vaccination. Driven by this research, this review aims to provide a comprehensive and up-to-date overview of the various rebalancing capabilities of zinc in the unbalanced immune system of the elderly. This includes an in-depth and cell type-centered discussion on the role of zinc in immunosenescence and inflammaging. We further address upcoming translational aspects e.g. how zinc deficiency promotes the flourishing of certain pathogenic taxa of the gut microbiome and how zinc supply counteracts such alterations in a manner that may contribute to longevity. In the light of the ongoing COVID-19 pandemic, we also briefly review current knowledge on the interdependency between age, zinc status, and respiratory infections. Based on two concrete examples and considering the latest findings in the field we conclude our remarks by outlining tremendous parallels between suboptimal zinc status and accelerated aging on the one hand and an optimized zinc status and successful aging on the other hand.

Zinc deficiency as a possible risk factor for increased susceptibility and severe progression of Corona Virus Disease 19

The importance of Zn for human health becomes obvious during Zn deficiency. Even mild insufficiencies of Zn cause alterations in haematopoiesis and immune functions, resulting in a proinflammatory phenotype and a disturbed redox metabolism. Although immune system malfunction has the most obvious effect, the functions of several tissue cell types are disturbed if Zn supply is limiting. Adhesion molecules and tight junction proteins decrease, while cell death increases, generating barrier dysfunction and possibly organ failure. Taken together, Zn deficiency both weakens the resistance of the human body towards pathogens and at the same time increases the danger of an overactive immune response that may cause tissue damage. The case numbers of Corona Virus Disease 19 (COVID-19) are still increasing, which is causing enormous problems for health systems and economies. There is an urgent need to reduce both the number of severe cases and the resulting deaths. While therapeutic options are still under investigation, and first vaccines have been approved, cost-effective ways to reduce the likelihood of or even prevent infection, and the transition from mild symptoms to more serious detrimental disease, are highly desirable. Nutritional supplementation might be an effective option to achieve these aims. In this review, we discuss known Zn deficiency effects in the context of an infection with Severe Acute Respiratory Syndrome-Coronavirus-2 and its currently known pathogenic mechanisms and elaborate on how severe pre-existing Zn deficiency may pre-dispose patients to a severe progression of COVID-19. First published clinical data on the association of Zn homoeostasis with COVID-19 and registered studies in progress are listed.

Zinc homeostasis in immunity and its association with preterm births

Preterm birth is among the most common adverse pregnancy outcomes and is the leading cause of neonatal mortality and morbidity. While trace elements are essential for humans, their specific roles in the prenatal period remain unexplored. Zinc, a ubiquitous element plays a pivotal role in protein synthesis, cell division, nucleic acid metabolism, apoptosis, ageing, reproduction, immunological as well as antioxidant defense mechanism. Although zinc quantities are very small in body tissue, it is involved in every conceivable biochemical pathway which is critical for the performance of various functions necessary to sustain life. Owing to the multifactorial role of zinc, it is not possible to attribute a certain zinc dependent mechanism in pre-term births. Although the effect of zinc deficiency on immunity, its impact on maternal function and health as well as its role in the developing foetus is well documented, much less attention has been given to the understanding of micronutrient zinc homeostasis in immunity and its association with preterm births. Despite extensive research, the pathway by which zinc regulates pregnancy outcomes as well as the function of immune cells in controlling the delivery status (term/ preterm) is still obscure. The present review aims to focus on the understanding of relationship of micronutrient zinc homeostasis in immunity and its association with preterm births.

The impact of metal availability on immune function during infection

Nutrient transition metals are required cofactors for many proteins to perform functions necessary for life. As such, the concentration of nutrient metals is carefully maintained to retain critical biological processes while limiting toxicity. During infection, invading bacterial pathogens must acquire essential metals, such as zinc, manganese, iron, and copper, from the host to colonize and cause disease. To combat this, the host exploits the essentiality and toxicity of nutrient metals by producing factors that limit metal availability, thereby starving pathogens or accumulating metals in excess to intoxicate the pathogen in a process termed 'nutritional immunity'. As a result of inflammation, a heterogeneous environment containing both metal-replete and -deplete niches is created, in which nutrient metal availability may have an underappreciated role in regulating immune cell function during infection. How the host manipulates nutrient metal availability during infection, and the downstream effects that nutrient metals and metal-sequestering proteins have on immune cell function, are discussed in this review.

Effect of zinc depletion/repletion on intestinal iron absorption and iron status in rats

Iron and zinc deficiencies likely coexist in general population. We have previously demonstrated that zinc treatment induces while zinc deficiency inhibits iron absorption in intestinal cell culture models, but this needs to be tested in vivo. In the present study we assessed intestinal iron absorption, iron status (haemoglobin), red blood cell number, plasma ferritin, transferrin receptor, hepcidin) and tissue iron levels in zinc depleted, replete and pair fed control rats. Zinc depletion led to reduction in body weight, tissue zinc levels, intestinal iron absorption, protein and mRNA expression of iron transporters, the divalent metal ion transporter-1, hephaestin and ferroportin, but elevated the intestinal and liver tissue iron levels compared with the pair fed control rats. Zinc repletion led to a significant weight gain compared to zinc deficient rats and normalized the iron absorption, iron transporter expression, tissue iron levels to that of pair fed control rats. Surprisingly, haemoglobin levels and red blood cell number reduced significantly in zinc repleted rats, which could be due to rapid weight gain. Together, these results indicate that whole body zinc status has profound influence on growth, intestinal absorption and systemic utilization of iron, mediated via modulation of iron transporter expression.

Dietary and Physiological Effects of Zinc on the Immune System

Evidence for the importance of zinc for all immune cells and for mounting an efficient and balanced immune response to various environmental stressors has been accumulating in recent years. This article describes the role of zinc in fundamental biological processes and summarizes our current knowledge of zinc's effect on hematopoiesis, including differentiation into immune cell subtypes. In addition, the important role of zinc during activation and function of immune cells is detailed and associated with the specific immune responses to bacteria, parasites, and viruses. The association of zinc with autoimmune reactions and cancers as diseases with increased or decreased immune responses is also discussed. This article provides a broad overview of the manifold roles that zinc, or its deficiency, plays in physiology and during various diseases. Consequently, we discuss why zinc supplementation should be considered, especially for people at risk of deficiency. Expected final online publication date for the Annual Review of Nutrition, Volume 41 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

The adverse impact of cadmium on immune function and lung host defense

Cadmium (Cd) is a transition metal, also referred to as a heavy metal, that is naturally abundant in the earth's crust. It has no known benefit to humans. It is primarily released into our environment through mining and smelting in industrial processes and enters the food chain through uptake by plants from contaminated soil and water. In humans, Cd primarily enters the body through ingestion of foods and cigarette smoke and has an extremely long resident half-life in the body compared to other transition metals. Environmental workplace exposure is also a source through inhalation, although much less common. The principal organs adversely affected by Cd following acute and chronic exposure are the kidneys, bone, vasculature and lung. Cd adversely impacts cell function through changes in gene expression and signal transduction and is recognized as a carcinogen. Despite a substantial body of mechanistic studies in cells and animal models, the overall impact of Cd on innate immune function in humans remains poorly understood. The best evidence is perhaps alteration of reactive oxygen species balance and signaling in cells that regulate innate immunity causing alteration of the inflammatory response that is postulated to contribute to chronic diseases. Epidemiologic studies support this possibility since increased tissue levels in humans are strongly associated with leading chronic diseases including chronic obstructive pulmonary disease (COPD), which will be discussed in depth. Additional studies are required to understand how chronic exposure and accumulation of this leading environmental toxicant in vital organs negatively impact innate immune function and host defense leading to chronic disease in humans.

Update on the multi-layered levels of zinc-mediated immune regulation

The significance of zinc for an efficient immune response is well accepted. During zinc deficiency, an increase in the myeloid to lymphoid immune cells ratio was observed. This results in a disturbed balance of pro- and anti-inflammatory processes as well as defects in tolerance during infections. Consequently, instead of efficiently defending the body against invading pathogens, damage of host cells is frequently observed. This explains the increased susceptibility to infections and their severe progression observed for zinc deficient individuals as well as the association of autoimmune diseases with low serum zinc levels. Together with the advances in techniques for investigating cellular development, communication and intracellular metabolism, our understanding of the mechanisms underlying the benefits of zinc for human health and the detriments of zinc deficiency has much improved. As analyses of the zinc status and effects of zinc supplementation were more frequently included into clinical studies, our knowledge of the association of zinc deficiency to a variety of diseases was strongly improved. Still there are several areas in zinc biology that require further in-depth investigation such as the interaction with other nutritional elements, the direct association between zinc transportation, membrane-structure, receptors, and signaling as well as its role in cell degeneration. This article will describe our current understanding of the role of zinc during the immune response focusing on the most recent findings and underlying mechanisms. Research questions that need to be addressed in the future will be discussed as well.

Disparities in Trace Metal Levels in Hodgkin/Non-Hodgkin Lymphoma Patients in Comparison with Controls

Lymphoma arises from cells of the immune system and trace metals augment the immune system and their imbalance may promote immunological disorders including tumorigenesis. The primary aim of the present investigation was to evaluate the levels of essential/toxic trace metals in the nails of non-Hodgkin and Hodgkin lymphomas patients in comparison with controls. The samples collected from patients and controls were digested in the mixture of HNO₃-HClO₄ and selected trace metals were analysed using flame atomic absorption spectrometry. The results showed that mean concentrations of some elements (Pb, Ni, Cd, Cu and Cr) in nails of non-Hodgkin lymphoma patients were significantly elevated (p < 0.05) than that of the controls whereas mean contents of Pb, Cu, Cd and Cr were observed to be significantly higher in the nails of Hodgkin lymphoma patients compared with healthy donors. Additionally, correlation study pointed out significantly diverse mutual associations of the trace metals among the patients and controls. The present results revealed noticeable disparities in the metal concentrations based on gender, food habits, tobacco use and types/stages of the donor's groups. Overall, the pathogenesis of disease significantly affected the trace metal balance in both patients' groups.

Serum lipid profiles of young Japanese women with iron deficiency without anemia

PURPOSE

We aimed to evaluate the association between iron deficiency without anemia (IDNA) and serum lipid profiles in young women of around 20 years of age.

METHODS

This study included non-anemic (hemoglobin ≥ 12 g/dL) female volunteers aged 18 to 22 years who were not taking mineral/vitamin supplements and living in the metropolitan area of Tokyo, Japan. These volunteers were classified into two groups based on their sFer (serum ferritin) levels: normal group (sFer ≥ 20 ng/mL, n = 36) and IDNA group (sFer < 20 ng/mL, n = 29). Venous blood samples were obtained from the antecubital veins of these volunteers after 10-12-h fasting to measure the hematological and biochemical parameters, including lipid levels and iron status. The results of each group were compared using Student's t-test or the Mann-Whitney U test (for inhomogeneous variance).

RESULTS

The serum cholesterol levels varied depending on the iron status in the women. Serum high-density lipoprotein cholesterol (HDL-C) levels in the IDNA group were significantly higher (P = 0.006) than that in the normal group. However, the levels of total cholesterol (T-CHO), triglycerides (TG), and low-density lipoprotein cholesterol (LDL-C) were not significantly different between the groups. Serum LDL-C levels were positively and significantly correlated with sFer levels in the IDNA group (Kendall's rank correlation 0.264, P = 0.044), but not in the normal group. The sFer level was not correlated with serum HDL-C in both groups. The reason for the high serum HDL-C levels in young women with IDNA is not yet clear. Compared to the normal group, the frequency of eating bread containing bran was significantly higher (P = 0.031) and that for yogurt was significantly lower (P = 0.040) in the IDNA group. The proportion of the women who were susceptible to infection, which was measured using the Cornell Medical Index, was significantly higher in the IDNA group than in the normal group. Among those susceptible to infection, the serum HDL-C level of the volunteers in the IDNA group was significantly higher than that of the volunteers in the normal group (P = 0.024).

CONCLUSIONS

Our findings suggest that lipid parameters may be associated with IDNA and susceptibility to infection. Further research is needed to elucidate the mechanisms underlying the changes in the serum cholesterol levels in individuals with IDNA and the clinical significance of these findings.

Alterations in membrane fluidity are involved in inhibition of GM-CSF-induced signaling in myeloid cells by zinc

Zinc has a strong influence on the function of the immune system and is a driving factor for immune cell development. In this regard, studies revealed cell type specific effects of zinc. During zinc deficiency for example, development and activity of myeloid cells seems to be prioritized at the cost of cells from the lymphoid lineage. In T-cells, the altered proliferation was found to be due to zinc's effect on IL-2-induced signaling processes, but in contrast to lymphoid cells, effects of zinc homeostasis on growth-factor-induced signaling in myeloid cells have not been investigated yet. The granulocyte-macrophage colony-stimulating factor (GM-CSF) is one of the major factors inducing monopoiesis. Considering the structural similarities between the GM-CSF receptor and those of the IL-receptor family as well as a similar set of signaling molecules involved, an impact of zinc on the GM-CSF signaling seems to be likely. Therefore, the effect of zinc on GM-CSF-induced signaling molecules was investigated here, using U937 cells as a model myeloid cell line. GM-CSF stimulation significantly increased STAT5 phosphorylation which was prevented completely by pre-incubation with zinc and pyrithione. U937 cells showed a strong pre-activation regarding c-Raf, which was significantly decreased by zinc and pyrithione incubation, independently from GM-CSF stimulation. As current literature was not sufficient to explain the observed effects, we hypothesized an altered receptor-complex assembly. As membrane composition and plasticity, subsumed under the term of membrane fluidity, was found to affect receptor multimerization, the impact of zinc on membrane fluidity was considered as a completely novel approach. Indeed, addition of zinc also decreased GM-CSFR expression on the cell surface and most interestingly altered membrane fluidity. In conclusion, we hypothesize that the incubation with zinc causes an alteration of membrane fluidity that hinders efficient receptor assembly as well as phosphorylation of signal molecules and therefore signal transduction.

Zinc Supplementation Stimulates Red Blood Cell Formation in Rats

In rats, mice, and humans, it is known that zinc deficiency may be related to anemia, and zinc supplementation influences hemoglobin production. Our previous studies indicate that in fish, zinc supplementation stimulates red blood cell (RBC) formation (erythropoiesis). However, it is not clear whether the mechanism of zinc-induced erythropoiesis stimulation in fish also occurs in rats. We induced anemia in rats using phenylhydrazine (PHZ) and injected either saline or ZnSO₄ solution. We found that an appropriate amount of zinc stimulated erythropoiesis in the PHZ-induced anemic rats. The effects of ZnSO₄ injection were dose-dependent. When the concentration of ZnSO₄ was higher than 2.8 mg zinc/kg body weight, the RBC level of the anemic rats increased from 60 ± 7% to 88 ± 10% that of the normal rats in two days. Rat bone marrow cells with or without ZnCl₂ supplementation were cultured in suspension in vitro. In the cell culture when the zinc concentration was at 0.3 mM, a 1.6-fold proliferation of nascent immature reticulocytes (new RBCs) was observed after one day. In the rat blood, zinc was combined with serum transferrin to induce erythropoiesis. The stimulation of RBC formation by zinc appears to be common among different animals.

GATA/Heme Multi-omics Reveals a Trace Metal-Dependent Cellular Differentiation Mechanism

By functioning as an enzyme cofactor, hemoglobin component, and gene regulator, heme is vital for life. One mode of heme-regulated transcription involves amplifying the activity of GATA-1, a key determinant of erythrocyte differentiation. To discover biological consequences of the metal cofactor-transcription factor mechanism, we merged GATA-1/heme-regulated sectors of the proteome and transcriptome. This multi-omic analysis revealed a GATA-1/heme circuit involving hemoglobin subunits, ubiquitination components, and proteins not implicated in erythrocyte biology, including the zinc exporter Slc30a1. Though GATA-1 induced expression of Slc30a1 and the zinc importer Slc39a8, Slc39a8 dominantly increased intracellular zinc, which conferred erythroblast survival. Subsequently, a zinc transporter switch, involving decreased importer and sustained exporter expression, reduced intracellular zinc during terminal differentiation. Downregulating Slc30a1 increased intracellular zinc and, strikingly, accelerated differentiation. This analysis established a conserved paradigm in which a GATA-1/heme circuit controls trace metal transport machinery and trace metal levels as a mechanism governing cellular differentiation.

Serum Zinc Levels in Iron Deficient Women: A Case-Control Study

Since similar symptoms and findings can be seen in the deficiencies of both iron and zinc, we aimed to evaluate the serum zinc levels of women with iron deficiency anemia (IDA). This study was conducted with women with iron deficiency and a healthy control group. When serum zinc levels were compared, they were found to be lower in the IDA group, which was statistically significant. With the help of these studies, iron and zinc treatment instead of only iron replacement may be considered in cases of iron deficiency.

Serum zinc levels in patients with iron deficiency anemia and its association with symptoms of iron deficiency anemia

Iron deficiency anemia (IDA) is a major public health problem especially in underdeveloped and developing countries. Zinc is the co-factor of several enzymes and plays a role in iron metabolism, so zinc deficiency is associated with IDA. In this study, it was aimed to investigate the relationship of symptoms of IDA and zinc deficiency in adult IDA patients. The study included 43 IDA patients and 43 healthy control subjects. All patients were asked to provide a detailed history and were subjected to a physical examination. The hematological parameters evaluated included hemoglobin (Hb); hematocrit (Ht); red blood cell (erythrocyte) count (RBC); and red cell indices mean corpuscular volume (MCV), mean corpuscular hemoglobin (МСН), mean corpuscular hemoglobin concentration (МСНС), and red cell distribution width (RDW). Anemia was defined according to the criteria defined by the World Health Organization (WHO). Serum zinc levels were measured in the flame unit of atomic absorption spectrophotometer. Symptoms attributed to iron deficiency or depletion, defined as fatigue, cardiopulmonary symptoms, mental manifestations, epithelial manifestations, and neuromuscular symptoms, were also recorded and categorized. Serum zinc levels were lower in anemic patients (103.51 ± 34.64 μ/dL) than in the control subjects (256.92 ± 88.54 μ/dL; <0.001). Patients with zinc level <99 μ/dL had significantly more frequent mental manifestations (p < 0.001), cardiopulmonary symptoms (p = 0.004), restless leg syndrome (p = 0.016), and epithelial manifestations (p < 0.001) than patients with zinc level > 100 μ/dL. When the serum zinc level was compared with pica, no statistically significant correlation was found (p = 0.742). Zinc is a trace element that functions in several processes in the body, and zinc deficiency aggravates IDA symptoms. Measurement of zinc levels and supplementation if necessary should be considered for IDA patients.

Zinc as a micronutrient and its preventive role of oxidative damage in cells

Zinc deficiency leads to increased ROS production, thereby causing lipid peroxidation. Subsequently, signallingviathe NF-κB pathway is increased, resulting in the expression of pro-inflammatory cytokines which in turn cause chronic inflammatory diseases.

Enhancement of hematopoiesis and lymphopoiesis in diet-induced obese mice

A rodent model of diet-induced obesity revealed that obesity significantly altered hematopoietic and lymphopoietic functions in the bone marrow and thymus. C57BL/6 mice were fed a mixed high-fat diet (HFD) of 45% fat or 10% fat diet (lean controls) for 180 d. A sustained increase in the numbers of cells found in bone marrow and thymus of HFD mice occurred from day 90 to day 180. However, with the exception of a 10-18% increase in the proportion of lymphocytes, the composition of monocytes, granulocytes, erythrocytes, and mixed progenitor lineages remained normal in the marrow. Likewise, thymuses of HFD mice increased 30-50% in size compared with controls, with analogous increases in thymocyte numbers. The overall thymus cellular composition remained normal. Although increased blood and lymphatic volume in obese mice would play a role in increased hematopoiesis, there were large and disproportionate increases in blood leukocytes of HFD mice, indicating that homeostasis was not maintained. Leptin, which promotes lymphopoiesis and myelopoiesis, reached 100 ng/mL in sera from HFD mice. Moreover, a three- to sixfold increase in adipocytes in marrow resulted in spiked leptin mRNA expression in bones of HFD mice compared with lean controls. Other cytokines and growth factors did not show any increases in obese marrow. The substantial increase in lymphopoietic and hematopoietic processes in HFD mice indicates that the primary tissues are another facet of the immune system dysregulated by obesity, which was perhaps fostered by higher amounts of leptin in marrow and serum.

Severe dermatitis with loss of epidermal Langerhans cells in human and mouse zinc deficiency

Zinc deficiency can be an inherited disorder, in which case it is known as acrodermatitis enteropathica (AE), or an acquired disorder caused by low dietary intake of zinc. Even though zinc deficiency diminishes cellular and humoral immunity, patients develop immunostimulating skin inflammation. Here, we have demonstrated that despite diminished allergic contact dermatitis in mice fed a zinc-deficient (ZD) diet, irritant contact dermatitis (ICD) in these mice was more severe and prolonged than that in controls. Further, histological examination of ICD lesions in ZD mice revealed subcorneal vacuolization and epidermal pallor, histological features of AE. Consistent with the fact that ATP release from chemically injured keratinocytes serves as a causative mediator of ICD, we found that the severe ICD response in ZD mice was attenuated by local injection of soluble nucleoside triphosphate diphosphohydrolase. In addition, skin tissue from ZD mice with ICD showed increased levels of ATP, as did cultured wild-type keratinocytes treated with chemical irritants and the zinc-chelating reagent TPEN. Interestingly, numbers of epidermal Langerhans cells (LCs), which play a protective role against ATP-mediated inflammatory signals, were decreased in ZD mice as well as samples from ZD patients. These findings suggest that upon exposure to irritants, aberrant ATP release from keratinocytes and impaired LC-dependent hydrolysis of nucleotides may be important in the pathogenesis of AE.

Cellular zinc homeostasis is a regulator in monocyte differentiation of HL-60 cells by 1 alpha,25-dihydroxyvitamin D3

It was reported previously that zinc-deficient mice show impaired lymphopoiesis. At the same time, monocyte numbers in these animals are increased, indicating a negative impact of zinc on monocyte development. Here, we investigate the role of zinc homeostasis in the differentiation of myeloid precursors into monocytes. Reduced gene expression of several zinc transporters, predominantly from the Zip family, was observed during 1 alpha, 25-dihydroxyvitamin D(3) (1,25D(3))-induced differentiation of HL-60 cells. This was accompanied by a reduction of intracellular-free zinc, measured by FluoZin-3. Amplifying this reduction with the zinc chelator TPEN or zinc-depleted cell-culture medium enhanced 1,25D(3)-induced expression of monocytic surface markers CD11b and CD14 on HL-60, THP-1, and NB4 cells. In contrast, differentiation of NB4 cells to granulocytes was not zinc-sensitive, pointing toward a specific effect of zinc on monocyte differentiation. Further, monocyte functions, such as TNF-alpha secretion, phagocytosis, and oxidative burst, were also augmented by differentiation in the presence of TPEN. The second messenger cAMP promotes monocyte differentiation. We could show that zinc inhibits the cAMP-synthesizing enzyme adenylate cyclase, and chelation of zinc by TPEN increases cAMP generation after stimulation with the adenylate cyclase activator forskolin. Based on our in vitro results and the in vivo observations from the literature, we suggest a model in which the intracellular-free zinc concentration limits AC activity, and the decrease of zinc after 1,25D(3) treatment promotes differentiation by relieving AC inhibition. Thus, cellular zinc homeostasis acts as an endogenous modulator of monocyte differentiation.

The ubiquitous role of zinc in health and disease

OBJECTIVE

To review zinc physiology and pathophysiology and the importance of zinc toxicity and deficiency in veterinary patients.

DATA SOURCES

A review of human and veterinary medical literature.

HUMAN DATA SYNTHESIS

There is a significant amount of original research in humans and animals on the role of zinc in multiple organ systems. There is also significant data available on human patients with zinc abnormalities.

VETERINARY DATA SYNTHESIS

Zinc deficiency has been studied in dogs with genetic disease and dietary deficiency leading to dermatological disease and immune deficiency. Zinc toxicity has been described after ingestion of metallic foreign bodies containing zinc.

CONCLUSIONS

Historically, the role of zinc in health and disease has been studied through patients with toxicity or severe deficiency with obvious clinical signs. As the ubiquitous contribution of zinc to structure and function in biological systems was discovered, clinically significant but subtle deficiency states have been revealed. In human medicine, mild zinc deficiencies are currently thought to cause chronic metabolic derangement leading to or exacerbating immune deficiency, gastrointestinal problems, endocrine disorders, neurologic dysfunction, cancer, accelerated aging, degenerative disease, and more. Determining the causal relationships between mild zinc deficiency and concurrent disease is complicated by the lack of sensitive or specific tests for zinc deficiency. The prevalence of zinc deficiency and its contribution to disease in veterinary patients is not well known. Continued research is warranted to develop more sensitive and specific tests to assess zinc status, to determine which patients are at risk for deficiency, and to optimize supplementation in health and disease.

Natural glucocorticoids induce expansion of all developmental stages of murine bone marrow granulocytes without inhibiting function

Natural glucocorticoids (Gc) produced during stress have profound effects on the immune system. It is well known that Gc induce apoptosis in precursor T and B cells, markedly altering lymphopoiesis. However, it has been noted that marrow myeloid cells expanded both in proportion and absolute numbers in the mouse after Gc exposure. Mice were implanted with a corticosterone (CS) tablet that increased serum Gc and caused atrophied thymuses, both classic signs of activation of the stress axis. Blood neutrophil counts were elevated (4.8x), whereas lymphocyte counts declined. Flow cytometric analysis of the marrow revealed that the phenotypic distribution of the various major classes of cells was shifted by Gc exposure. As expected, marrow lymphocyte numbers declined >40% after 3 days of exposure to Gc. Conversely, in the myeloid compartment, both monocytes and granulocytes increased in number by >40%. Further, all granulocyte developmental stages showed large increases in both total number and percentage of cells. To investigate the functional capacity of mature granulocytes from Gc-treated mice, an improved granulocyte isolation method was developed. Gc exposure had little effect on the ability of granulocytes to produce superoxide or undergo chemotaxis or phagocytose bacteria. These results indicate that Gc treatment shifts bone marrow composition and provides evidence that granulocytes and their progenitors are selectively preserved under stressful conditions without losing function.

A role for leptin in sustaining lymphopoiesis and myelopoiesis

Although leptin is known for its regulation of food intake, it has many emerging roles in immune function. To better define the role of leptin in hematopoietic processes, a leptin-deficient obese mouse (ob/ob) and C57BL/6 lean wild-type controls were compared. Despite their large size and consumption of substantial amounts of nutrients, the ob/ob mice had only 60% as many nucleated cells in their marrow as controls. The greatest impact of leptin deficiency was on the B cell compartment that had 70% fewer cells, reducing the absolute number of pre-B and immature B cells to 21% and 12% of normal, respectively, and indicating a significant reduction in lymphopoiesis in ob/ob mice. Whereas the proportion of myeloids remained nearly normal in the obese mice, they also exhibited a reduction of 40% and 25%, respectively, in absolute numbers of granulocytes and monocytes. Seven days of provision of recombinant leptin promoted substantial lymphopoiesis, increasing the numbers of B cells in the marrow of the obese mice twofold, while doubling and tripling, respectively, the numbers of pre-B and immature B cells. Twelve days of supplementation brought these subpopulations to near-normal proportions. Leptin treatment also facilitated myelopoiesis such that the marrow of the obese mice contained normal numbers of monocytes and granulocytes after 7 days. Taken together, the data support an important role for leptin in sustaining lymphopoiesis and myelopoiesis.

Dietary zinc deficiency lowers the proportions of splenic CD90+ (Thy-1+) B-cells and late thymic emigrant T-cells in growing rats

Zn-deficient (ZD) rats have a lower proportion of splenic CD90+T-cells which could be due to fewer new T-cells exiting the thymus, defective post-thymic maturation or increased cell death. Post-thymic maturation of splenic lymphocytes and their viability were determined by flow cytometry in weanling rats assigned to ZD ( < 1 mg Zn/kg; ad libitum), diet-restricted (DR; 30 mg Zn/kg; limited to the amount of feed as consumed by ZD rats), marginally Zn-deficient (MZD; 10 mg Zn/kg; ad libitum) or control (30 mg Zn/kg; ad libitum) groups for 3 weeks. ZD rats had a 29 % lower percentage of splenic CD90+T-cells and both ZD and DR rats had a 30 % lower proportion of splenic CD90+B-cells compared with control rats. When the splenic CD90+T-cells were characterised further, there was no difference among the groups in the first two stages of post-thymic development; however, ZD, DR and MZD rats had a 42 % lower proportion of late thymic emigrants (TCRαβ+CD90+CD45RC+RT6.1+) compared with control rats. There was no difference among groups in the proportion of splenic CD90+T-cells in the non-viable region; however, ZD rats had a higher proportion of CD90+B-cells in the non-viable region compared with MZD and control animals, suggesting that this phenotype was more susceptible to cell death during deficiency. The lower proportion of splenic CD90+T-cells in ZD rats does not appear to be due to a defect in thymic production or increased cell death in the spleen. Future studies should determine if late thymic emigrants have homed to other peripheral organs.

Targeting of the mouse Slc39a2 (Zip2) gene reveals highly cell-specific patterns of expression, and unique functions in zinc, iron, and calcium homeostasis

Fourteen members of the Slc39a superfamily of metal ion uptake transporters have been identified in mice and humans, but the physiological functions of most remain obscure. Herein, we created mice with Zip2 (Slc39a2) genes in which the open reading frame was replaced with that of the enhanced green fluorescent protein (EGFP), to study temporal and spatial patterns of Zip2 gene expression and examine the physiological roles of this transporter. Expression of this gene was remarkably cell-type specific and developmentally regulated in pericentral hepatocytes, developing keratinocytes, and a subset of immature dendritic cells in the immune system. In addition, the Zip2 gene was transiently expressed in giant trophoblast cells in the placenta. Although the Zip2 gene was not essential under conditions of normal dietary zinc, it played an important role in adapting to dietary zinc deficiency during pregnancy, and in the homeostasis of iron in the liver as well as iron and calcium in developing embryos. These studies suggest that active expression of the Zip2 gene in these few specific cell types, aforementioned, plays a particularly important role during zinc deficiency. These studies further reveal novel interactions between zinc transporter function and the homeostasis of other essential metals.

Hormonal adjuvants for the treatment of renal anaemia

Hormonal adjuvants, besides being erythropoietic agents, broaden the spectrum of therapeutic options for the treatment of the anaemia of chronic kidney disease (CKD). Lowering elevated parathyroid hormone levels by oral calcium supplementation and phosphate restriction, by varying dialysate calcium concentrations, by administration of vitamin D3 derivatives and, in the near future, by treatment with calcimimetics may prove efficient in some patients to fight extensive requirements of erythropoietic agents. Clinical evidence for a principal role of secondary hyperparathyroidism in resistance to erythropoietin, however, is lacking. Active vitamin D3 derivatives, in addition to their beneficial effects on secondary hyperparathyroidism, appear to exert a direct, stimulatory action on erythroid precursor cells and possibly also an inhibitory action on collagen synthesis by bone marrow stromal cells. Growth hormone (GH) induces insulin-like growth factor (IGF)-1, which in turn counteracts apoptosis similarly to erythropoietin, and fosters proliferation of burst- and colony-forming units-erythroid (BFU-E, CFU-E). If erythropoietic agents improve survival of CKD patients, a similar benefit should apply for strategies that increase synthesis and bioavailabilty of IGF-1. The latter appears to be reduced in CKD patients, and zinc supplementation potentially enhances it via an increase in free IGF-1. Finally, androgens also exert anti-anaemic effects. Nandrolone decanoate constitutes the only androgen currently applicable for selected male dialysis patients over the age of 50 years. It should not be given to women, however, because of serious side effects. Collectively, hormonal interventions offer the potential to reduce requirements of erythropoietic agents, and some may also improve physical performance.

Chronic Zinc Deficiency in Mice Disrupted T Cell Lymphopoiesis and Erythropoiesis While B Cell Lymphopoiesis and Myelopoiesis Were Maintained

OBJECTIVE

The purpose of this study was to determine the impact of chronic zinc deficiency (ChrZD) on T and B cell lymphopoiesis, myelopoiesis and erythropoiesis in mice.

METHODS

Young adult mice were fed a zinc adequate (ZA) or ChrZD synthetic diet for 34, 45, and 50 days. The cellular composition of the thymus and marrow were determined to assess the impact of ChrZD on lymphopoietic and hematopoietic processes using flow cytometry. Body weights, serum zinc and corticosterone (Cs) were monitored.

RESULTS

For ChrZD mice growth was reduced 10% and serum zinc declined 15% by d 34 compared to ZA mice. By d 50 a 25% decrease in growth and 70% depression in serum zinc was noted though there was never any significant reduction in diet intake. Corticosterone rose 2.5 fold by d 34 and remained elevated in ChrZD mice indicating induction of the stress axis. At d 34 the thymus of ChrZD mice was normal but by d 50 there was a 50% cell loss and a 10% reduction in the proportion of Pre-T cells. Most importantly there was a 60% increase in Pre-T cells undergoing apoptosis in ChrZD mice. Pro-T, T helper, and T cytolytic populations were more resistant to ChrZD. Bone marrow cellularity and granulocyte, monocyte, and lymphocyte compartments remained unchanged in ChrZD mice. However, the erythroid compartment was reduced by 35% at d 50.

CONCLUSIONS

The thymus was the most sensitive primary tissue to ChrZD. By d 50 it had atrophied by 36% with significant loss of Pre-T cells via apoptosis such that T-cell lymphopoiesis was disrupted. Significant reductions were also noted in the erythropoietic population by d 50. Conversely the marrow maintained myelopoiesis and B cell lymphopoiesis for the 50 d period indicating greater ability to survive a chronic zinc deficiency and exposure to Cs. The anemia and T cell lymphopenia associated with ChrZD in both rodents and humans may result from a greater sensitivity of their precursor cells to zinc deficiency and elevated Cs.

Generation and characterization of mice lacking the zinc uptake transporter ZIP3

The mouse ZIP3 (SLC39A3) gene encodes an eight-transmembrane-domain protein that has been conserved in mammals and can function to transport zinc. To analyze the expression of ZIP3 in the early embryo and neonate and to determine its in vivo function, we generated ZIP3 null mice in which the ZIP3 open reading frame was replaced with that of the enhanced green fluorescent protein (EGFP) reporter. EGFP fluorescence revealed that ZIP3 was expressed in the inner cell mass of the blastocyst and later during embryonic development in many tissues. Elevated expression was apparent in the embryonic brain and neurotube and neonatal gonads. Homozygous knockout mice were viable and fertile and under normal growth conditions exhibited no obvious phenotypic abnormalities. Deletion of ZIP3 did not alter zinc homeostasis at the molecular level as assessed by essential metal levels and the expression of zinc-responsive genes. In knockout mice stressed with a zinc-deficient diet during pregnancy or at weaning, a subtle increase in the sensitivity to abnormal morphogenesis of the embryo and to depletion of thymic pre-T cells, respectively, was noted. These results suggest that this protein plays an ancillary role in zinc homeostasis in mice.

Zinc deficiency, DNA damage and cancer risk

A large body of evidence suggests that a significant percentage of deaths resulting from cancer in the United States could be avoided through greater attention to proper and adequate nutrition. Although many dietary compounds have been suggested to contribute to the prevention of cancer, there is strong evidence to support the fact that zinc, a key constituent or cofactor of over 300 mammalian proteins, may be of particular importance in host defense against the initiation and progression of cancer. Remarkably, 10% of the U.S. population consumes less than half the recommended dietary allowance for zinc and are at increased risk for zinc deficiency. Zinc is known to be an essential component of DNA-binding proteins with zinc fingers, as well as copper/zinc superoxide dismutase and several proteins involved in DNA repair. Thus, zinc plays an important role in transcription factor function, antioxidant defense and DNA repair. Dietary deficiencies in zinc can contribute to single- and double-strand DNA breaks and oxidative modifications to DNA that increase risk for cancer development. This review will focus on potential mechanisms by which zinc deficiency impairs host protective mechanisms designed to protect against DNA damage, enhances susceptibility to DNA-damaging agents and ultimately increases risk for cancer.

Roles for cell death in zinc deficiency

Studies of zinc deficiency (ZD) have become important for demonstrating that nutritional imbalances can readily induce programmed cell death (PCD) or apoptosis in a variety of kinds of cells. In mice, ZD caused a 300% increase in the amount of apoptosis among pre T-cells, which was a major cause of thymic atrophy that alters host defense. Embryogenesis was significantly altered in ZD mice due to increased apoptosis in the neural crest, optic, and head regions. Insufficient zinc initiated PCD in hepatocytes, glioma, kidney, monocytes, fibroblasts, and testicular cells, demonstrating the scope of this phenomenon. New forms of cell death continue to emerge. For example, autophagy is initiated by starvation and various nutritional and metabolic imbalances. Autophagy is a form of PCD whereby the cell digests some of its own organelles to provide needed nutrients. Understanding the interplay between these different forms of cell death and nutritional imbalances is very important because of their profound impact on development, growth, immune function, and health.

Reprogramming of the immune system during zinc deficiency

Thymic atrophy, lymphopenia, and compromised cell- and antibody-mediated responses that cause increased rates of infections of longer duration are the immunological hallmarks of zinc deficiency (ZD) in humans and higher animals. As the deficiency advances, a reprogramming of the immune system occurs, beginning with the activation of the stress axis and chronic production of glucocorticoids that accelerate apoptosis among pre-B and -T cells. This reduces lymphopoiesis and causes atrophy of the thymus. In contrast, myelopoiesis is preserved, thereby providing protection for the first line of immune defense or innate immunity. Changes in gene expression for cytokines, DNA repair enzymes, zinc transporters, signaling molecules, etc., suggest that cells of the immune system are attempting to adapt to the stress of suboptimal zinc. Better understanding of the molecular and cellular changes made in response to inadequate zinc should lead to the development of immunotherapeutic interventions.

Chronic consumption of a moderately low protein diet does not alter hematopoietic processes in young adult mice

The current studies examined whether hematopoiesis in the bone marrow and T-cell development in the thymus were attenuated in young adult A/J mice fed a moderately low protein diet (MPD, 50 g protein/kg) for 15 wk compared with mice fed a control protein diet (CPD, 180 g protein/kg). Flow cytometric analyses using antibodies against CD31 and Ly-6C as well as CD4 and CD8 were performed to identify stem, mixed progenitor, erythroid, lymphoid, granuloid and monocytic compartments in the bone marrow and four thymocyte subsets, respectively. Chronic restriction of young adult mice to MPD neither decreased the cellularity nor altered the distribution of subpopulations in either primary tissue. Subsequently, a new set of mice were provided with CPD and a low protein diet (LPD, 25 g protein/kg). After 5 wk, body and thymus weights in LPD group were reduced 26 and 30%, respectively, which was accompanied by a 505% increase in serum corticosterone. Surprisingly, LPD did not alter the number or distribution of cells in the bone marrow and the percentages of thymocyte subsets, supporting the findings from the MPD group. We conclude that chronic consumption of a marginal protein diet by young adult mice does not disrupt hematopoietic processes.