Genome-level expression profiles in pediatric septic shock indicate a role for altered zinc homeostasis in poor outcome

Human septic shock involves multiple genome-level perturbations. We have conducted microarray analyses in children with septic shock within 24 h of intensive care unit admission, using whole blood-derived RNA. Based on sequential statistical and expression filters, there were 2,482 differentially regulated gene probes (1,081 upregulated and 1,401 downregulated) between patients with septic shock ( n = 42) and controls ( n = 15). Both gene lists encompassed several biologically relevant gene ontologies and canonical pathways. Notably, many of the genes downregulated in the patients with septic shock, relative to the controls, participate in gene ontologies related to metal or zinc homeostasis. Comparison of septic shock survivors ( n = 33) and nonsurvivors ( n = 9) demonstrated differential regulation of 63 gene probes. Among the 63 gene probes differentially regulated between septic shock survivors and nonsurvivors, two isoforms of metallothionein (MT) demonstrated increased expression in the nonsurvivors. Consistent with the ability of MT to sequester zinc in the intracellular compartment, nonsurvivors had lower serum zinc levels compared with survivors. In a corroborating study of murine sepsis, MT-null mice demonstrated a survival advantage compared with wild-type mice. These data represent the largest reported cohort of pediatric patients with septic shock that has undergone genome-level expression profiling based on microarray. The data are biologically plausible and demonstrate that genome-level alterations of zinc homeostasis may be prevalent in clinical pediatric septic shock.

Download Full-text

Functional properties of human ferroportin, a cellular iron exporter reactive also with cobalt and zinc

AJP Cell Physiology ◽

10.1152/ajpcell.00348.2013 ◽

2014 ◽

Vol 306 (5) ◽

pp. C450-C459 ◽

Cited By ~ 70

Author(s):

Colin J. Mitchell ◽

Ali Shawki ◽

Tomas Ganz ◽

Elizabeta Nemeth ◽

Bryan Mackenzie

Keyword(s):

Iron Homeostasis ◽

Fluorescent Protein ◽

Serum Zinc ◽

Functional Expression ◽

Extracellular Ph ◽

Zinc Homeostasis ◽

Affinity Constant ◽

Protein Fusion ◽

Zinc Levels ◽

Green Fluorescent

Iron homeostasis is achieved by regulating the intestinal absorption of the metal and its recycling by macrophages. Iron export from enterocytes or macrophages to blood plasma is thought to be mediated by ferroportin under the control of hepcidin. Although ferroportin was identified over a decade ago, little is understood about how it works. We expressed in Xenopus oocytes a human ferroportin-enhanced green fluorescent protein fusion protein and observed using confocal microscopy its exclusive plasma-membrane localization. As a first step in its characterization, we established an assay to detect functional expression of ferroportin by microinjecting oocytes with 55Fe and measuring efflux. Ferroportin expression increased the first-order rate constants describing 55Fe efflux up to 300-fold over control. Ferroportin-mediated 55Fe efflux was saturable, temperature-dependent (activation energy, Ea ≈ 17 kcal/mol), maximal at extracellular pH ≈ 7.5, and inactivated at extracellular pH < 6.0. We estimated that ferroportin reacts with iron at its intracellular aspect with apparent affinity constant < 10−7 M. Ferroportin expression also stimulated efflux of 65Zn and 57Co but not of 64Cu, 109Cd, or 54Mn. Hepcidin treatment of oocytes inhibited efflux of 55Fe, 65Zn, and 57Co. Whereas hepcidin administration in mice resulted in a marked hypoferremia within 4 h, we observed no effect on serum zinc levels in those same animals. We conclude that ferroportin is an iron-preferring cellular metal-efflux transporter with a narrow substrate profile that includes cobalt and zinc. Whereas hepcidin strongly regulated serum iron levels in the mouse, we found no evidence that ferroportin plays an important role in zinc homeostasis.

Download Full-text

Zinc dyshomeostasis in azoxymethane induced colonic precancerous and cancerous lesions in Fisher rats

Metallomics ◽

10.1093/mtomcs/mfaa009 ◽

2020 ◽

Author(s):

Kavitha Velagapudi ◽

J Naveena Lavanya Latha ◽

Vijaya Lakshmi Bodiga

Keyword(s):

Bystander Effect ◽

Zinc Concentration ◽

Precancerous Lesions ◽

Serum Zinc ◽

Zinc Homeostasis ◽

Dna Integrity ◽

Normal Colonic Mucosa ◽

Altered Expression ◽

Zinc Concentrations ◽

Zinc Levels

Abstract Zinc is an essential micronutrient involved in various biological processes, including growth, maintenance, proliferation and immune functions. It is also argued that tumors need zinc for maintenance and proliferation, although excess zinc may induce tumor cell apoptosis. Thus, the role of zinc merits attention in the carcinogenic process. Scanty literature is available on the mechanisms underlying the alterations in tissue zinc in colon cancer and how the altered zinc levels contribute to the preneoplastic lesions and progression to cancer. Zinc homeostasis is regulated by the gastrointestinal tract and involves interplay of host, dietary, environmental and social factors such as alcohol consumption. The DNA alkylation agent azoxymethane (AOM), which is primarily activated in the liver, induces a high incidence of initiation and promotion steps of precancerous lesions in the colon of rats. The altered expression of hepatic zinc transporters by AOM may lead to zinc dyshomeostasis in liver. Earlier reports showed that ZIP14 was located on the inner lane of plasma membrane of hepatocytes, and increased level of ZIP14 could sequester zinc from plasma into liver under infection or in response to cancer. Decreased serum zinc concentration, despite increased liver zinc also indicates altered liver zinc mobilization and failure to regulate zinc homeostasis. During the transformation from normal colonic mucosa to colonic epithelial hyperplasia and aberrant crypt formation, a reduction in zinc concentration is observed. It will be interesting to study further if the same trend continues throughout tumor progression towards adenocarcinomas. Lowered local zinc concentrations in the colon epithelium may not just reflect a bystander effect, but may induce cell proliferation and compromise DNA integrity due to impairment of zinc-containing proteins. In congruence with the tissue zinc concentrations, metallothionein levels were found to be less induced in AOM—administered colon compared to normal healthy colon, indicating less accumulation and sequestration of zinc. Lowered tissue zinc levels in small and large intestine were also associated with increased expression of mRNA and protein ZnT1, known to transport cytosolic zinc to extracellular space. In this regard, the mode of zinc responsiveness to ZnT1 mimics that of metallothionein, albeit at a lower level for ZnT1.

Download Full-text

Role of serum zinc levels in simple febrile convulsions in children

MedPulse International Journal of Pediatrics ◽

10.26611/10149111 ◽

2019 ◽

Vol 9 (1) ◽

pp. 36-38

Author(s):

S W Srikanth ◽

◽

Sharanagouda Patil ◽

Rachapudi Venkata Anusha ◽

◽

...

Keyword(s):

Serum Zinc ◽

Febrile Convulsions ◽

Zinc Levels ◽

Serum Zinc Levels

Download Full-text

Alterations in ZnT1 expression and function lead to impaired intracellular zinc homeostasis in cancer

Cell Death Discovery ◽

10.1038/s41420-019-0224-0 ◽

2019 ◽

Vol 5 (1) ◽

Cited By ~ 2

Author(s):

Adrian Israel Lehvy ◽

Guy Horev ◽

Yarden Golan ◽

Fabian Glaser ◽

Yael Shammai ◽

...

Keyword(s):

Malignant Tumors ◽

Zinc Homeostasis ◽

Healthy Population ◽

Missense Mutations ◽

Protein Alignment ◽

Loss Of Function ◽

Intracellular Zinc ◽

Dismal Prognosis ◽

Zinc Levels ◽

And Function

Abstract Zinc is vital for the structure and function of ~3000 human proteins and hence plays key physiological roles. Consequently, impaired zinc homeostasis is associated with various human diseases including cancer. Intracellular zinc levels are tightly regulated by two families of zinc transporters: ZIPs and ZnTs; ZIPs import zinc into the cytosol from the extracellular milieu, or from the lumen of organelles into the cytoplasm. In contrast, the vast majority of ZnTs compartmentalize zinc within organelles, whereas the ubiquitously expressed ZnT1 is the sole zinc exporter. Herein, we explored the hypothesis that qualitative and quantitative alterations in ZnT1 activity impair cellular zinc homeostasis in cancer. Towards this end, we first used bioinformatics to analyze inactivating mutations in ZIPs and ZNTs, catalogued in the COSMIC and gnomAD databases, representing tumor specimens and healthy population controls, respectively. ZnT1, ZnT10, ZIP8, and ZIP10 showed extremely high rates of loss of function mutations in cancer as compared to healthy controls. Analysis of the putative functional impact of missense mutations in ZnT1-ZnT10 and ZIP1-ZIP14, using homologous protein alignment and structural predictions, revealed that ZnT1 displays a markedly increased frequency of predicted functionally deleterious mutations in malignant tumors, as compared to a healthy population. Furthermore, examination of ZnT1 expression in 30 cancer types in the TCGA database revealed five tumor types with significant ZnT1 overexpression, which predicted dismal prognosis for cancer patient survival. Novel functional zinc transport assays, which allowed for the indirect measurement of cytosolic zinc levels, established that wild type ZnT1 overexpression results in low intracellular zinc levels. In contrast, overexpression of predicted deleterious ZnT1 missense mutations did not reduce intracellular zinc levels, validating eight missense mutations as loss of function (LoF) mutations. Thus, alterations in ZnT1 expression and LoF mutations in ZnT1 provide a molecular mechanism for impaired zinc homeostasis in cancer formation and/or progression.

Download Full-text

Expression Analysis of Zinc Transporters in Nervous Tissue Cells Reveals Neuronal and Synaptic Localization of ZIP4

International Journal of Molecular Sciences ◽

10.3390/ijms22094511 ◽

2021 ◽

Vol 22 (9) ◽

pp. 4511

Author(s):

Chiara A. De Benedictis ◽

Claudia Haffke ◽

Simone Hagmeyer ◽

Ann Katrin Sauer ◽

Andreas M. Grabrucker

Keyword(s):

Brain Function ◽

Zinc Homeostasis ◽

Zinc Transporters ◽

Excitatory Synapses ◽

Short Term ◽

Synaptic Localization ◽

Zinc Levels ◽

Rat Astrocyte ◽

Cellular Zinc ◽

The Brain

In the last years, research has shown that zinc ions play an essential role in the physiology of brain function. Zinc acts as a potent neuromodulatory agent and signaling ions, regulating healthy brain development and the function of both neurons and glial cells. Therefore, the concentration of zinc within the brain and its cells is tightly controlled. Zinc transporters are key regulators of (extra-) cellular zinc levels, and deregulation of zinc homeostasis and zinc transporters has been associated with neurodegenerative and neuropsychiatric disorders. However, to date, the presence of specific family members and their subcellular localization within brain cells have not been investigated in detail. Here, we analyzed the expression of all zinc transporters (ZnTs) and Irt-like proteins (ZIPs) in the rat brain. We further used primary rat neurons and rat astrocyte cell lines to differentiate between the expression found in neurons or astrocytes or both. We identified ZIP4 expressed in astrocytes but significantly more so in neurons, a finding that has not been reported previously. In neurons, ZIP4 is localized to synapses and found in a complex with major postsynaptic scaffold proteins of excitatory synapses. Synaptic ZIP4 reacts to short-term fluctuations in local zinc levels. We conclude that ZIP4 may have a so-far undescribed functional role at excitatory postsynapses.

Download Full-text

Association between Reduced Serum Zinc and Diastolic Dysfunction in Maintenance Hemodialysis Patients

Nutrients ◽

10.3390/nu13062077 ◽

2021 ◽

Vol 13 (6) ◽

pp. 2077

Author(s):

Jiun-Chi Huang ◽

Ya-Chin Huang ◽

Pei-Yu Wu ◽

Wen-Hsien Lee ◽

Yi-Chun Tsai ◽

...

Keyword(s):

Diastolic Dysfunction ◽

Left Atrial Volume ◽

Serum Zinc ◽

Zinc Level ◽

Volume Index ◽

Serum Zinc Level ◽

Lower Serum ◽

Echocardiographic Parameters ◽

Zinc Levels ◽

Serum Zinc Levels

Diastolic dysfunction is an emerging challenge among hemodialysis (HD) patients, and the associations between serum zinc with echocardiographic parameters and diastolic function remain uncertain. A total of 185 maintenance HD patients were stratified by the tertiles of serum zinc level to compare their clinical characteristics and echocardiography. Correlations of serum zinc levels with echocardiographic parameters were examined using Pearson’s analysis. Univariate and multivariate logistic regression analyses were performed to investigate the determinants of E/e’ ratio >15 and left atrial volume index (LAVI) > 34 mL/m2, both indicators of diastolic dysfunction. Patients belonging to the first tertile of serum zinc level had a significantly higher E/e’ ratio and LAVI. Serum zinc levels were negatively correlated with E (r = −0.204, p = 0.005), E/e’ ratio (r = −0.217, p = 0.003), and LAVI (r = −0.197, p = 0.007). In a multivariate analysis, older age, diabetes, coronary artery disease, and lower serum zinc levels (OR = 0.974, 95% CI = 0.950–0.999, p = 0.039) were significantly associated with E/e’ ratio >15. Furthermore, diabetes and lower serum zinc levels (OR = 0.978, 95% CI = 0.958–0.999, p = 0.041) were significantly associated with LAVI >34 mL/m2. Reduced serum zinc level was significantly associated with diastolic dysfunction among HD patients. Further prospective studies are warranted to investigate whether zinc supplementation can attenuate cardiac dysfunction in maintenance HD patients.

Download Full-text

Association between Serum Zinc Levels and Clinical Index or the Body Composition in Incident Hemodialysis Patients

Nutrients ◽

10.3390/nu12103187 ◽

2020 ◽

Vol 12 (10) ◽

pp. 3187

Author(s):

Tatsunori Toida ◽

Reiko Toida ◽

Shou Ebihara ◽

Risa Takahashi ◽

Hiroyuki Komatsu ◽

...

Keyword(s):

Body Composition ◽

Regression Analysis ◽

Cardiovascular Events ◽

Serum Zinc ◽

Fluid Volume ◽

The Body ◽

All Cause Mortality ◽

Cox's Regression ◽

Zinc Levels ◽

Serum Zinc Levels

Background: The relationships between serum zinc levels and body composition or clinical outcomes of incident hemodialysis (HD) patients remain unclear. Methods: This prospective observational study examined the relationships between serum zinc levels and clinical indexes, including body composition, in 142 incident HD patients using a bioelectrical impedance analysis. Patients were divided into three groups according to baseline serum zinc levels: tertile, <45, 45–59, and ≥60 µg/dL. The reference group was set as ≥60 µg/dL. Cox’s regression analysis was performed to investigate the relationships between serum zinc categories and cardiovascular events and all-cause mortality after adjustments for potential confounders. Results: Serum zinc levels positively correlated with the nutritional index and negatively correlated with fluid volume markers. In a mean follow-up of 2.5 years, there were 20 cases of cardiovascular events and 15 of all-cause mortality. In the Cox’s regression analysis for cardiovascular events and all-cause mortality, the hazard ratio increased with a decrease in serum zinc levels, but was not significant. Conclusion: Serum zinc levels were associated with nutritional and fluid volume markers in incident HD patients. To clarify the relationship between serum zinc levels and cardiovascular events or mortality, further studies with a larger number of cases will be necessary.

Download Full-text