Intracellular zinc during cell activation and zinc deficiency

INTRODUCTION

Zinc is an essential trace element having manifold functions within living cells. Zinc deficiency but also zinc excess impairs cell-specific functions whereas a balanced zinc level is required for an adequate cell behavior.

MATERIAL AND METHODS

This study deals with the impact of cellular priming due to stimulation with interleukin (IL)-1, IL-2, IL-4, IL-6 or the chemokine CXCL12a and its subsequent influence on the intracellular free zinc concentration. Since cellular priming and activation is essential for proper immunological reactions, and across that highly cell-type specific, we investigated T cells, B cells, and peripheral blood mononuclear cells (PBMCs). Additionally, alterations of the intracellular zinc content was investigated by inducing zinc deficiency using the zinc chelator N,N,N',N'-tetrakis(2-pyridylmethyl)ethane-1,2-diamine (TPEN) with subsequent re-supplementation of zinc, hence generating an intracellular zinc flux. Evaluation of zinc staining with FluoZin3-AM, Zinpyr-1 and Zinquin was done by flow cytometry or by fluorescence microscopy.

RESULTS

Our results indicate that cellular priming for different periods of time (10 minutes/one hour) causes decreased intracellular free zinc concentrations in the FluoZin3-AM staining and increased zinc concentrations stained with Zinpyr-1. Furthermore, zinc supplementation after induced zinc deficiency leads to a fast and excessive rise of the intracellular free zinc levels in most cellular compartments.

CONCLUSION

Our study emphasizes the importance of zinc homeostasis and zinc distribution during cellular priming and for certain signaling cascades especially in T and B cells. Moreover, we demonstrated that zinc re-supplementation of zinc deficient cells results in significantly elevated intracellular free zinc concentrations compared to untreated controls. Hence, this underlines the need of a balanced zinc homeostasis for proper immune cell function.

The Interaction of Sodium and Zinc in the Priming of T Cell Subpopulations Regarding Th17 and Treg Cells

SCOPE

Nutrition is a critical determinant of a functional immune system. The aim of this study is to investigate the molecular mechanisms by which immune cells are influenced by zinc and sodium.

METHODS AND RESULTS

Mixed lymphocyte cultures and Jurkat cells are generated and incubated with zinc, sodium, or a combination of both for further tests. Zinc induces the number of regulatory T cells (Treg) and decreases T helper 17 cells (Th17), and sodium has the opposite effect. The transforming growth factor beta receptor signaling pathway is also enhanced by zinc and reduced by sodium as indicated by contrary phosphoSmad 2/3 induction. Antagonistic effects can also be seen on zinc transporter and metallothionein-1 (MT-1) mRNA expression: zinc declines Zip10 mRNA expression while sodium induces it, whereas MT-1 mRNA expression is induced by zinc while it is reduced by sodium.

CONCLUSION

This data indicate that zinc and sodium display opposite effects regarding Treg and Th17 induction in MLC, respectively, resulting in a contrary effect on the immune system. Additionally, it reveals a direct interaction of zinc and sodium in the priming of T cell subpopulations and shows that Zip10 and MT-1 play a significant role in those differentiation pathways.

Zinc supplementation plays a crucial role in T helper 9 differentiation in allogeneic immune reactions and non-activated T cells

T helper (Th) 9 cells play a critical role in immune-mediated diseases, including allergic airway inflammation, autoimmune diseases, and cancer development. Thus, the promotion or suppression of Th9 cell differentiation, transcriptional control, and function is very important for a healthy immune system. Interestingly, T cell maturation, differentiation and function are highly dependent on the individuals' zinc status. This is especially seen in zinc deficient individuals as in the elderly population often suffering of autoimmunity and increased incidence of infections. In this regard, this study examines the impact of zinc supplementation in pharmacological doses on Th9 differentiation in two in vitro models: 1) in mixed lymphocyte cultures (MLC) displaying allogeneic activated T cells in graft versus host disease, and 2) on non-activated resting T cells in peripheral blood mononuclear cells (PBMC). On the one hand, zinc supplementation significantly diminishes IL-4-induced Th9 differentiation in MLC thereby ameliorating this pro-inflammatory allogeneic immunoreaction. On the other hand, Th9 cells are induced in resting T cells in PBMC hence triggering the immunological defense. Thus, zinc supplementation can be considered as useful additive to dampen unwanted allogeneic immunoreactions. Moreover, the pro-inflammatory immune defense in non-reactive T cells can be strengthened, which is a frequent issue in the elderly population having a weakened immune response against invading pathogens.

Development and validation of a ready to use cryo-EROD assay for the standardized screening of dioxins and dioxin-like compounds in foodstuffs

Recent European regulations have indicated the need for new bioanalytical screening methods capable of monitoring dioxin and dioxin-like compounds in foodstuffs and environmental samples, cost-effectively and with a quicker turnaround. Cryo-cells of the hepatic H4IIE line preserved in 96-well plates were exposed to sample extracts prepared from various foodstuffs and analysed for their content of dioxins and dioxin-like compounds by means of the 7-Ethoxyresorufin-O-Deethylase (EROD)-assay in two laboratories. Assay data were compared between both laboratories and results from instrumental analysis used as a confirmatory method. Additionally, cut-off values for the different studied matrices were derived. The current European regulation regarding methods of analysis for the control of foodstuffs was applied with the aim of determining the feasibility of the cryo-methodology. Results obtained in both laboratories were in congruence with the required validation parameters of the Commission Regulation (EU) No 2017/644. Cut-off values should be established matrix-dependent to reduce the rate of false compliant results and to keep the rate of false non-compliant results under control. In summary, the ready-to-use cryo-assay method for the bioanalytical screening of foodstuffs in control laboratories without cell-culture facilities has successfully proven to be accurate, far quicker and more cost effective than current methods.

Zinc deficiency drives Th17 polarization and promotes loss of Treg cell function

A high number of illnesses and disorders are connected to zinc deficiency. Equally, T cell polarization and a balance between different T helper (Th) cell subsets are essential. Therefore, in this study, the influence of zinc deficiency on T cell polarization and on respective signaling pathways was investigated. We uncovered a significantly increased number of regulatory T cells (Treg) and Th17 cells in expanded T cells during zinc deficiency after 3 days of combined treatment with IL-2 and TGF-β1 (Treg) or IL-6 and TGF-β1 (Th17). No difference in Th1 and Th2 cell polarization between zinc-deficient and zinc-adequate status was prominent. On the molecular level, Smad signaling was significantly enhanced by stimulation with TGF-β1/IL-6 during zinc deficiency compared to adequate zinc condition. This represents an explanation for the elevated Th17 cell numbers associated with autoimmune disease especially during zinc deficiency. Moreover, Treg cell numbers are increased during zinc deficiency as well. However, those cells might be nonfunctional since a lower expression of miR-146a was uncovered compared to normal zinc concentrations. In summary, an adequate zinc homeostasis is fundamental to slow down or probably stop the progression of autoimmune diseases and infections. Therefore, supplementing zinc might be a therapeutic approach to dampen autoimmune diseases connected to Th17 cells.

Proton-pump inhibitors elevate infection rate in cardiothoracic surgery patients by influencing PMN function in vitro and in vivo

Proton-pump inhibitors (PPI) as pantoprazole are highly effective acid suppressive agents that belong to the world's most sold medication. However, they are pronounced to have immunosuppressive aspects. In our study, a negative influence of PPI on functions of polymorphonuclear cells in vitro like phagocytosis, oxidative burst, chemotaxis, and killing activity was shown, whereas formation of neutrophil extracellular traps (NET)osis remained unaffected. Pantoprazole stimulation additionally reduced the production of the proinflammatory cytokine IL-1β in whole blood assay as well as the production of IL-2 and IFN-γ after whole blood stimulation with phytohaemagglutinin. Moreover, IFN-γ feedback mechanisms and signaling by STAT-1 was impaired by PPI. Cardiac surgery is accompanied by developing systemic inflammatory response syndrome with immunosuppressive aspects. We exhibited reduced oxidative burst analyzing cardiac surgery patients' samples receiving or not receiving PPI. Furthermore, a higher rate of infections in patients receiving permanent PPI medication in retrospective analysis was uncovered. Patients undergoing cardiac surgery with cardiopulmonary bypass and regular PPI medication developed significant more infections retrospectively indicating a clinical impact of the immunosuppressive influence of PPI.

Zinc as a Gatekeeper of Immune Function

After the discovery of zinc deficiency in the 1960s, it soon became clear that zinc is essential for the function of the immune system. Zinc ions are involved in regulating intracellular signaling pathways in innate and adaptive immune cells. Zinc homeostasis is largely controlled via the expression and action of zinc "importers" (ZIP 1-14), zinc "exporters" (ZnT 1-10), and zinc-binding proteins. Anti-inflammatory and anti-oxidant properties of zinc have long been documented, however, underlying mechanisms are still not entirely clear. Here, we report molecular mechanisms underlying the development of a pro-inflammatory phenotype during zinc deficiency. Furthermore, we describe links between altered zinc homeostasis and disease development. Consequently, the benefits of zinc supplementation for a malfunctioning immune system become clear. This article will focus on underlying mechanisms responsible for the regulation of cellular signaling by alterations in zinc homeostasis. Effects of fast zinc flux, intermediate "zinc waves", and late homeostatic zinc signals will be discriminated. Description of zinc homeostasis-related effects on the activation of key signaling molecules, as well as on epigenetic modifications, are included to emphasize the role of zinc as a gatekeeper of immune function.

Zinc supplementation augments TGF-β1-dependent regulatory T cell induction

SCOPE

Regulatory T cells (Treg) play a pivotal role in immune regulation. For proper immune function, also trace elements such as zinc, and anti-inflammatory cytokines, including transforming growth factor beta 1 (TGF-β1) and interleukin (IL)-10 are indispensable. Hence, in this study the influence of TGF-β1, IL-10, and zinc supplementation on Treg cells differentiation was investigated.

METHODS AND RESULTS

A synergistic effect of a combined zinc and TGF-β1 treatment on Foxp3 expression in peripheral blood mononuclear cells and mixed lymphocyte cultures (MLC) was found by performing Western blot analysis. Additionally, combined treatment causes elevated Smad 2/3 phosphorylation, which plays an important role in Foxp3 expression. This is due to a TGF-β1-mediated increase of intracellular-free zinc measured by zinc probes Fluozin3-AM and ZinPyr-1. Moreover, zinc as well as TGF-β1 treatment caused significantly reduced interferon (IFN)-γ secretion in MLC.

CONCLUSION

Combined zinc and TGF-β1 treatment provoked an increased Treg cell induction due to a triggered intracellular zinc signal, which in association with an increased Smad 2/3 activation leads to a boosted Foxp3 expression and resulting in an ameliorated allogeneic reaction in MLC. Thus, zinc can be used as a favorable additive to elevate the induction of Treg cells in adverse immune reactions.

Zinc supplementation induces regulatory T cells by inhibition of Sirt-1 deacetylase in mixed lymphocyte cultures

SCOPE

Zinc is an essential trace element, regulating immune function. Its deficiency results in immune dysfunction and transplant rejection. In here, a benefit of zinc supplementation for the induction of tolerance was investigated, focusing on the TH 1-dominated allogeneic immune reaction.

METHODS AND RESULTS

Allogeneic immune reaction was modeled by mixed lymphocyte culture (MLC). The effect of zinc supplementation was monitored via expression of cytokines and surface lineage markers using ELISA and flow cytometry. Epigenetic analyses were performed to investigate mechanisms underlying zinc-induced changes in regulatory T cell (Treg) activation. Results reveal that Tregs are induced when MLCs are treated with 50 μM zinc causing a decrease in IFNγ production. IL-2 and IL-10 expression were not affected. The teleology of this effect includes the inhibition of histone deacetylase Sirt-1-mediated Foxp3 deacetylation, resulting in its decreased degradation.

CONCLUSION

In conclusion, zinc should be considered to prevent graft-versus-host disease (GVHD) as it is capable of stabilizing iTregs, resulting in increased numbers of this cell type while not suppressing the immune system.

Induction of regulatory T cells in Th1-/Th17-driven experimental autoimmune encephalomyelitis by zinc administration

The essential trace element zinc is indispensable for proper immune function as zinc deficiency accompanies immune defects and dysregulations like allergies, autoimmunity and an increased presence of transplant rejection. This point to the importance of the physiological and dietary control of zinc levels for a functioning immune system. This study investigates the capacity of zinc to induce immune tolerance. The beneficial impact of physiological zinc supplementation of 6 μg/day (0.3mg/kg body weight) or 30 μg/day (1.5mg/kg body weight) on murine experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis with a Th1/Th17 (Th, T helper) cell-dominated immunopathogenesis, was analyzed. Zinc administration diminished EAE scores in C57BL/6 mice in vivo (P<.05), reduced Th17 RORγT(+) cells (P<.05) and significantly increased inducible iTreg cells (P<.05). While Th17 cells decreased systemically, iTreg cells accumulated in the central nervous system. Cumulatively, zinc supplementation seems to be capable to induce tolerance in unwanted immune reactions by increasing iTreg cells. This makes zinc a promising future tool for treating autoimmune diseases without suppressing the immune system.

Zinc homeostasis and immunosenescence

For more than 50 years, zinc is known to be an essential trace element, having a regulatory role in the immune system. Deficiency in zinc thus compromises proper immune function, like it is observed in the elderly population. Here mild zinc deficiency is a common condition, documented by a decline of serum or plasma zinc levels with age. This leads to a dysregulation mainly in the adaptive immunity that can result in an increased production of pro-inflammatory cytokines, known as a status called inflamm-aging. T cell activation as well as polarization of T helper (Th) cells into their different subpopulations (Th1, Th2, Th17, regulatory T cells (Treg)) is highly influenced by zinc homeostasis. In the elderly a shift of the Th cell balance towards Th2 response is observed, a non-specific pre-activation of T cells is displayed, as well as a decreased response to vaccination is seen. Moreover, an impaired function of innate immune cells indicate a predominance of zinc deficiency in the elderly that may contribute to immunosenescence. This review summarizes current findings about zinc deficiency and supplementation in elderly individuals.

Zinc deficiency adversely influences interleukin-4 and interleukin-6 signaling

Zinc deficiency is accompanied by a severe impairment of the immune system, causing a high risk for infections and autoimmune diseases due to altered functionality of B- and T- cells. The influence of zinc deficiency on T- and B- cells via alteration of cytokine expression is well established. The aim of this study was to examine potential direct effects of zinc deficiency on the reactivity of B- and T- cells. Zinc deficient B- and T- cells revealed divergent reaction patterns compared to zinc sufficienT-cells. This was manifested by a stronger proliferative response following IL-6 and IL-2 stimulation on the one hand, but less proliferation following IL-4 stimulation on the other hand. Moreover, these results were supported by the finding that the B- and T-cell signaling cascades activated by IL-4 or IL-6, respectively, were affected directly by zinc deficiency, resulting in reduced Stat6 phosphorylation and increased Stat3 phosphorylation. Whereas the transcription factor Stat6 is involved in IL-4 signaling, Stat3 is activated by IL-6 signaling. Consequently, these results show opposing effects of zinc deficiency on IL-4 and IL-6/IL-2 signaling pathways, thus underlying the importance of zinc for proper immune function.

In vitro studies of ferritin iron release and neurotoxicity

The increase in brain iron associated with several neurodegenerative diseases may lead to an increased production of free radicals via the Fenton reaction. Intracellular iron is usually tightly regulated, being bound by ferritin in an insoluble ferrihydrite core. The neurotoxin 6-hydroxydopamine (6-OHDA) releases iron from the ferritin core by reducing it to the ferrous form. Iron release induced by 6-OHDA and structurally related compounds and two other dopaminergic neurotoxins, 1-methyl-4-phenylpyridinium iodide (MPP+) and 1-trichloromethyl-1,2,3,4-tetrahydro-beta-carboline (TaClo), were compared, to identify the structural characteristics important for such release. 1,2,4-Trihydroxybenzene (THB) was most effective in releasing ferritin-bound iron, followed by 6-OHDA, dopamine, catechol, and hydroquinone. Resorcinol, MPP , and TaClo were ineffective. The ability to release iron was associated with a low oxidation potential. It is proposed that a low oxidation potential and an ortho-dihydroxyphenyl structure are important in the mechanism by which ferritin iron is mobilized. In the presence of ferritin, both 6-OHDA and THB strongly stimulated lipid peroxidation, an effect abolished by the addition of the iron chelator deferoxamine. These results suggest that ferritin iron release contributes to free radical-induced cell damage in vivo.

[Ocular involvement in ectodermal dysplasia]

The authors describe the ophthalmological findings and clinical course in two patients with EEC syndrome and one patient with anhydrotic ectodermal dysplasia. A retinal complication was seen in a 43-year-old patient which seems to be associated with the EEC syndrome and has not yet been described. A review of the literature indicates the frequency of ocular findings. So far, primary ocular changes in anhydrotic ectodermal dysplasia have never been observed. The older the patient, the more severe the secondary complications affecting the lids and cornea can be; the eye may even be lost.

[Etiology of corneal ulcers with special reference to bacterial genesis]

The authors report on 134 patients (141 eyes) seen between May 1982 and December 1985 with corneal ulcers with or without hypopyon. Eight patients (11 eyes) had a facial palsy, 7 (7 eyes) a varicella zoster infection, 1 (2 eyes) a marginal ulcer ("furrow keratitis") associated with collagenosis, 29 (29 eyes) an ulcerative keratitis with endophthalmitis, 1 (2 eyes) a pemphigoid-associated ulcer and 90 (92 eyes) a herpetic infection. Pathogenic bacterial strains were isolated from 20 patients: 10 coagulase-positive Staphylococcus aureus (4 coinfections), 3 Pseudomonas aeruginosa (1 coinfection), 2 Proteus mirabilis (1 coinfection), 2 Escherichia coli and Enterobacter cloacae, Citrobacter freundii and beta-hemolyzing streptococci as well as enterococci in one case each, and non-hemolyzing streptococci and alpha-hemolyzing streptococci in two cases each as coinfections. A comparison of the range of bacterial strains of postoperative endophthalmitis and kerato-/conjunctivitis with bacterial corneal ulcers revealed a high percentage of gram-negative organisms in the latter. Laboratory work-up should include microscopy, agar plating and differentiation as well as antibiotic sensitivity testing and modern immunofluorescent direct techniques. Management includes bactericidal topical and systemic antibiotic regimens as well as surgical procedures if necessary, e.g., perforating tectonic and mini-keratoplasty, and conjunctival flapping followed by lamellar keratoplasty.