Regulation of IgE-dependent zinc release from human mast cells

Loss of zinc transporters ZIP1 and ZIP3 augments platelet reactivity in response to thrombin and accelerates thrombus formation in vivo

Zinc (Zn2+) is considered as important mediator of immune cell function, thrombosis and haemostasis. However, our understanding of the transport mechanisms that regulate Zn2+ homeostasis in platelets is limited. Zn2+ transporters, ZIPs and ZnTs, are widely expressed in eukaryotic cells. Using mice globally lacking ZIP1 and ZIP3 (ZIP1/3 DKO), our aim was to explore the potential role of these Zn2+ transporters in maintaining platelet Zn2+ homeostasis and in the regulation of platelet function. While ICP-MS measurements indicated unaltered overall Zn2+ concentrations in platelets of ZIP1/3 DKO mice, we observed a significantly increased content of FluoZin3-stainable free Zn2+, which, however, appears to be released less efficiently upon thrombin-stimulated platelet activation. On the functional level, ZIP1/3 DKO platelets exhibited a hyperactive response towards threshold concentrations of G protein-coupled receptor (GPCR) agonists, while immunoreceptor tyrosine-based activation motif (ITAM)-coupled receptor agonist signalling was unaffected. This resulted in enhanced platelet aggregation towards thrombin, bigger thrombus volume under flow ex vivo and faster in vivo thrombus formation in ZIP1/3 DKO mice. Molecularly, augmented GPCR responses were accompanied by enhanced Ca2+ and PKC, CamKII and ERK1/2 signalling. The current study thereby identifies ZIP1 and ZIP3 as important regulators for the maintenance of platelet Zn2+ homeostasis and function.

The Role of Transient Receptor Potential A1 and G Protein-Coupled Receptor 39 in Zinc-Mediated Acute and Chronic Itch in Mice

Itching is a common symptom of many skin or systemic diseases and has a negative impact on the quality of life. Zinc, one of the most important trace elements in an organism, plays an important role in the regulation of pain. Whether and how zinc regulates itching is largely unclear. Herein, we explored the role of Zn²⁺ in the regulation of acute and chronic itch in mice. It is found that intradermal injection (i.d.) of Zn²⁺ dose-dependently induced acute itch and transient receptor potential A1 (TRPA1) participated in Zn²⁺-induced acute itch in mice. Moreover, the pharmacological analysis showed the involvement of histamine, mast cells, opioid receptors, and capsaicin-sensitive C-fibers in Zn²⁺-induced acute itch in mice. Systemic administration of Zn²⁺ chelators, such as N,N,N′,N′-Tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), pyrithione, and clioquinol were able to attenuate both acute itch and dry skin-induced chronic itch in mice. Quantitative polymerase chain reaction (Q-PCR) analysis showed that the messenger RNA (mRNA) expression levels of zinc transporters (ZIPs and ZnTs) significantly changed in the dorsal root ganglia (DRG) under dry skin-induced chronic itch condition in mice. Activation of extracellular signal-regulated kinase (ERK) pathway was induced in the DRG and skin by the administration of zinc or under dry skin condition, which was inhibited by systemic administration of Zn²⁺ chelators. Finally, we found that the expression of GPR39 (a zinc-sensing GPCR) was significantly upregulated in the dry skin mice model and involved in the pathogenesis of chronic itch. Together, these results indicated that the TRPA1/GPR39/ERK axis mediated the zinc-induced itch and, thus, targeting zinc signaling may be a promising strategy for anti-itch therapy.

Zinc Signaling in the Mammary Gland: For Better and for Worse

Zinc (Zn²⁺) plays an essential role in epithelial physiology. Among its many effects, most prominent is its action to accelerate cell proliferation, thereby modulating wound healing. It also mediates affects in the gastrointestinal system, in the testes, and in secretory organs, including the pancreas, salivary, and prostate glands. On the cellular level, Zn²⁺ is involved in protein folding, DNA, and RNA synthesis, and in the function of numerous enzymes. In the mammary gland, Zn²⁺ accumulation in maternal milk is essential for supporting infant growth during the neonatal period. Importantly, Zn²⁺ signaling also has direct roles in controlling mammary gland development or, alternatively, involution. During breast cancer progression, accumulation or redistribution of Zn²⁺ occurs in the mammary gland, with aberrant Zn²⁺ signaling observed in the malignant cells. Here, we review the current understanding of the role of in Zn²⁺ the mammary gland, and the proteins controlling cellular Zn²⁺ homeostasis and signaling, including Zn²⁺ transporters and the Gq-coupled Zn²⁺ sensing receptor, ZnR/GPR39. Significant advances in our understanding of Zn²⁺ signaling in the normal mammary gland as well as in the context of breast cancer provides new avenues for identification of specific targets for breast cancer therapy.

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.

Elevated zinc transporter ZnT3 in the dentate gyrus of mast cell-deficient mice

Zinc is important in neurogenesis, but excessive levels can cause apoptosis and other pathologies leading to cognitive impairments. Mast cells are present in many brain regions including the hippocampus, an area rich in vesicular zinc. Mast cells contain zinc-rich granules and a well-developed mechanism for uptake of zinc ions; both features point to the potential for a role in zinc homeostasis. Prior work using the Timm stain supported this hypothesis, as increased labile zinc was detected in the hippocampus of mast cell-deficient mice compared to wild-type mice while no differences in total zinc were found between the two genotypes in the whole brain or other tissues. The current report further examines differences in zinc homeostasis between wild-type and mast cell-deficient mice by exploring the zinc transporter ZnT3, which transports labile zinc into synaptic vesicles. The first study used immunocytochemistry to localize ZnT3 within the mossy fibre layer of the hippocampus to determine whether there was differential expression of ZnT3 in wild-type versus mast cell-deficient mice. The second study used inductively coupled plasma mass spectrometry (ICP-MS) to determine total zinc content in the whole dentate gyrus of the two genotypes. The immunocytochemical results indicate that there are higher levels of ZnT3 localized to the mossy fibre layer of the dentate gyrus of mast cell-deficient mice than in wild-type mice. The ICP-MS data reveal no differences in total zinc in dentate gyrus as a whole. The results are consistent with the hypothesis that mast cells participate in zinc homeostasis at the level of synaptic vesicles.

The Emerging Picture of Mast Cell Activation: The Complex Regulatory Network of High-Affinity Receptor for Immunoglobulin E Signaling

It is now well known that immunoglobulin E (IgE) and mast cells (MCs) are important participants in allergic diseases. MCs contain electron-dense secretory granules which are filled with inflammatory mediators. The interaction of an allergen (antigen) with an antigen-specific IgE-bound high-affinity receptor for IgE (FcεRI) is an essential step in MC activation as well as subsequent downstream signaling events. What we know is that IgE and FcεRI activate a complex regulatory network (i.e., signaling molecules and messengers) that governs both the type of MC activation and the symptoms of allergic disease. This review focuses on recent discoveries that shed new light on FcεRI signaling networks, holding promise for the development of new therapeutic solutions in the treatment of allergic diseases.

Serum Zinc Status and Its Association with Allergic Sensitization: The Fifth Korea National Health and Nutrition Examination Survey

Zinc (Zn) is an essential trace element that plays important roles in the immune system. There is little known about the role of trace elements in allergic diseases, and previous reports have shown conflicting results. The aim of this study was to investigate the relationship between serum Zn levels and total or allergen-specific immunoglobulin E (IgE) levels. The initial candidates for this study were those who participated in the 5^th Korean National Health and Nutrition Examination Survey 2010 (n = 8,958), and 1,867 adults who had serum total and allergen specific-IgE levels measured were included. Upon adjusting for covariates, mean total IgE, Dermatophagoides farinae and dog-specific IgE levels increased significantly as the Zn levels decrease from the highest to the lowest quartile (p = 0.009, 0.004, and < 0.001, respectively). The multiple logistic regression analyses showed significant negative linear correlations between serum Zn levels and total, D. farinae-, cockroach-, and dog-specific IgE levels (p-value for linear trend = 0.004, 0.006, 0.027, and < 0.001, respectively). This study demonstrated that total/allergen specific IgE and Zn levels are significantly inversely related.

Evidence for mast cell-mediated zinc homeostasis: Increased labile zinc in the hippocampus of mast-cell deficient mice

The dentate gyrus of the hippocampus is a site of adult neurogenesis, and is also known to contain one of the highest concentrations of labile brain zinc (Zn), thought to aid in learning and memory by supporting neurogenesis. At the same time, it is known that unbound Zn, when present at excessive levels, decreases the formation of new neurons. Since mast cells contain Zn transporters capable of moving this essential element across their plasma membrane, as well as Zn-rich granules that are dispelled upon secretion, we reasoned that mast cells contribute to Zn homeostasis in this area of the brain, as they are found in greatest numbers in and around the dentate gyrus. This line of evidence was tested by comparing Timm-stained hippocampal sections of mast cell-deficient C57BL/6-Kit^W-sh/W-sh (Sash^-/-) mice to those of mast cell-containing wild type (Sash^+/+) animals. Mast cell deficient mice were found to have significantly increased Timm-positive staining as compared to controls, reflecting an increase in labile or bioactive Zn in this region. As we observed no change in total brain Zn (protein-bound plus unbound Zn), these increases indicate that mast cells may serve to bind what would otherwise be excessive or deleterious levels of labile Zn, or that they are able to recruit metallothionein proteins. Because elevated levels of labile Zn are observed in the brains of patients with neurodegenerative diseases such as Alzheimer's, the potential contribution of mast cells to these diseases remains a compelling one. Overall, these data support a role for mast cells in either establishing or maintaining Zn homeostasis in the brain in the service of health, while Zn dysregulation has the potential to reduce learning, memory, and ultimately organismal survival.