How cellular Zn2+ signaling drives physiological functions. Cell Calcium. 2018;75:53-63. [PMID: 30145429 DOI: 10.1016/j.ceca.2018.08.004]

Molecular Biomarkers of Canine Reproductive Functions

The aim of the current study is to review potential molecular biomarker substances selected so far as useful for assessing the quality of dog semen. Proteins, lipids, carbohydrates, and ions can serve as molecular biomarkers of reproductive functions (BRFs) for evaluating male reproductive health and identifying potential risk factors for infertility or reproductive disorders. Evaluation of BRF levels in semen samples or reproductive tissues may provide insights into the underlying causes of infertility, such as impaired sperm function, abnormal sperm-egg interaction, or dysfunction of the male reproductive tract. Molecular biomarker proteins may be divided into two groups: proteins that are well-studied, such as A-kinase anchoring proteins (AKAPs), albumins (ALBs), alkaline phosphatase (ALPL), clusterin (CLU), canine prostate-specific esterase (CPSE), cysteine-rich secretory protein 2 (CRISP2), lactotransferrin (LTF), metalloproteinases (MMPs), and osteopontin (OPN) and proteins that are not well-studied. Non-protein markers include lipid-based substances (fatty acids, phosphatidylcholine), carbohydrates (glycosaminoglycans), and ions (zinc, calcium). Assessing the levels of BRFs in semen samples may provide valuable information for breeding management and reproductive assessments in dogs. This review systematizes current knowledge that could serve as a starting point for developing practical tests with the use of biomarkers of canine reproductive functions and their predictive value for assisted reproductive technique outcomes and semen preservation.

Recent Advances in Organic Small-Molecule Fluorescent Probes for the Detection of Zinc Ions (Zn2+)

Zinc(II) ions (Zn2g) play crucial roles in the growth, propagation, and metabolism of animals, plants, and humans. Abnormal concentrations of Zn2+ in the environment and living organisms pose potential risks to environmental protection and human health. Therefore, it is imperative to develop rapid, reliable and in-situ detection methods for Zn2+ in both environmental and biological contexts. Furthermore, effective analytical methods are required for diagnosing diseases and understanding physiological metabolic mechanisms associated with Zn2+ concentration levels. Organic small-molecule fluorescent probes offer advantages such as fast, reliable, convenient, non-destructive detection capabilities and have significant application potential in Zn2+ detection and bioimaging; thus garnering extensive attention. Over the past two years alone, various organic small-molecule probes for Zn2+ based on different detection mechanisms and fluorophores have been rapidly developed. However, these probes still exhibit several limitations that need further resolution. In light of this context, we provide a comprehensive summary of the detection mechanisms, performance characteristics, and application scope of Zn2+ fluorescence probes since year 2022 while highlighting their advantages. We also propose solutions to address existing issues with these probes and outline future directions for their advancement. This review aims to serve as a valuable reference source offering insights into the development of advanced organic small-molecule-based fluorescence probes specifically designed for detecting Zn2+.

Advances in Organic Fluorescent Probes for Intracellular Zn2+ Detection and Bioimaging

Zinc ions (Zn2+) play a key role in maintaining and regulating protein structures and functions. To better understand the intracellular Zn2+ homeostasis and signaling role, various fluorescent sensors have been developed that allow the monitoring of Zn2+ concentrations and bioimaging in live cells in real time. This review highlights the recent development of organic fluorescent probes for the detection and imaging of intracellular Zn2+, including the design and construction of the probes, fluorescent response mechanisms, and their applications to intracellular Zn2+ detection and imaging on-site. Finally, the current challenges and prospects are discussed.

Cross-talk between zinc and calcium regulates ion transport: A role for the zinc receptor, ZnR/GPR39

Zinc is essential for many physiological functions, with a major role in digestive system, skin health, and learning and memory. On the cellular level, zinc is involved in cell proliferation and cell death. A selective zinc sensing receptor, ZnR/GPR39 is a Gq-coupled receptor that acts via the inositol trisphosphate pathway to release intracellular Ca2+. The ZnR/GPR39 serves as a mediator between extracellular changes in Zn2+ concentration and cellular Ca2+ signalling. This signalling pathway regulates ion transporters activity and thereby controls the formation of transepithelial gradients or neuronal membrane potential, which play a fundamental role in the physiological function of these tissues. This review focuses on the role of Ca2+ signalling, and specifically ZnR/GPR39, with respect to the regulation of the Na+/H+ exchanger, NHE1, and of the K+/Cl- cotransporters, KCC1-3, and also describes the physiological implications of this regulation.

The role of metal ions in the occurrence, progression, drug resistance, and biological characteristics of gastric cancer

Metal ions exert pivotal functions within the human body, encompassing essential roles in upholding cell structure, gene expression regulation, and catalytic enzyme activity. Additionally, they significantly influence various pathways implicated in divergent mechanisms of cell death. Among the prevailing malignant tumors of the digestive tract worldwide, gastric cancer stands prominent, exhibiting persistent high mortality rates. A compelling body of evidence reveals conspicuous ion irregularities in tumor tissues, encompassing gastric cancer. Notably, metal ions have been observed to elicit distinct contributions to the progression, drug resistance, and biological attributes of gastric cancer. This review consolidates pertinent literature on the involvement of metal ions in the etiology and advancement of gastric cancer. Particular attention is directed towards metal ions, namely, Na, K, Mg, Ca, Fe, Cu, Zn, and Mn, elucidating their roles in the initiation and progression of gastric cancer, cellular demise processes, drug resistance phenomena, and therapeutic approaches.

Zinc-sensing receptor activation induces endothelium-dependent hyperpolarization-mediated vasorelaxation of arterioles

BACKGROUND

The micronutrient zinc (Zn2+) is critical for cell function as intracellular signaling and endogenous ligand for Zn2+ sensing receptor (ZnR). Although cytosolic Zn2+ (cyt) signaling in the vascular system was studied previously, role of the ZnR has not been explored in vascular physiology.

METHODS

ZnR-mediated relaxation response of human submucosal arterioles and the mesenteric arterioles from wide-type (WT), ZnR-/- and TRPV4-/- mice were determined by a Mulvany-style wire myograph. The perfused vessel density (PVD) of mouse mesenteric arterioles was also measured in in vivo study. The expression of ZnR in arterioles and vascular endothelial cells (VEC) were examined by immunofluorescence staining, and its function was characterized in VEC by Ca2+ imaging and patch clamp study.

RESULTS

ZnR expression was detected on human submucosal arterioles, murine mesenteric arterioles and VEC but not in ZnR-/- mice. ZnR activation predominately induced endothelium-dependent hyperpolarization (EDH)-mediated vasorelaxation of arterioles in vitro and in vivo via Ca2+ signaling, which is totally different from endothelium-dependent vasorelaxation via Zn2+ (cyt) signaling reported previously. Furthermore, ZnR-induced vasorelaxation via EDH was significantly impaired in ZnR-/- and TRPV4-/- mice. Mechanistically, ZnR induced endothelium-dependent vasorelaxation predominately via PLC/IP3/IP3R and TRPV4/SOCE. The role of ZnR in regulating Ca2+ signaling and ion channels on VEC was verified by Ca2+ imaging and patch clamp techniques.

CONCLUSION

ZnR activation induces endothelium-dependent vasorelaxation of resistance vessels predominately via TRPV4/Ca2+/EDH pathway. We therefore not only provide new insights into physiological role of ZnR in vascular system but also may pave a potential pathway for developing Zn2+-based treatments for vascular disease.

Lithium and zinc levels along with oxidative status in myocardial infarction: A case-control study

Background

Coronary artery disease (CAD) and myocardial infarction (MI) are the most prevalent diseases globally. While several risk factors for MI are well assessed, the influence of trace elements on MI has not been thoroughly studied. This study aimed to evaluate lithium (Li) and zinc (Zn) levels in MI patients and healthy control and assess their relationship with oxidative stress (OS) parameters, such as nitric oxide (NO) and total antioxidant capacity (TAC).

Methods

This case-control study was performed on 182 patients with MI and 83 healthy subjects at Shafa Hospital in Kerman, Iran. MI patients were divided into two groups based on the angiography results: those with coronary artery block above 50 % (CAB >50 %, n = 92) and those with coronary artery block below 50 % (CAB <50 %, n = 90). A flame atomic absorption spectrometer was used to detect Li and Zn levels, and biochemical indices were measured by an autoanalyzer. Also, ferric reducing antioxidant power assay and the Griess method were used to measure the amounts of NO and TAC.

Results

The levels of TAC and Li were significantly higher in the control group than in the patient groups (in both CAB >50 % and CAB <50 % groups). Furthermore, in the CAB <50 % group, TAC and Li levels were significantly higher than in the CAB >50 % group. In the Zn levels evaluation, higher concentration was seen in the CAB >50 % group compared to the CAB <50 % group (P < 0.05). Moreover, Zn and NO levels were significantly higher in both CAB groups compared to controls. In continue, Li levels had a positive association with TAC and ejection fraction percentage (EF%) as well as a negative association with NO levels and Zn levels had a significant positive association with NO and a negative association with TAC. In logistic regression analysis, Li, TAC, and high-density lipoprotein-cholesterol significantly decreased the odds ratio (OR) of MI, whereas Zn, NO, total cholesterol, triglyceride, low-density lipoprotein-cholesterol, and high-sensitivity C-reactive protein (hs-CRP) significantly increased the OR of MI. Furthermore, the area under the curve (AUC) analysis indicated that Li had the highest AUC for the diagnosis of CAB >50 % (Li < 167 ng/mL), and Zn ≥ 1810 μg/mL increased disease severity.

Conclusion

Our investigation revealed that Li had a protective effect against CAD by decreasing OS and increasing EF%. However, Zn at concentrations higher than 1810 μg/mL was found to be cytotoxic and increased the risk of MI through increased OS. Taken togather, it could be concluded that Li supplementation may decrease the risk of CAD.

Dopamine Activates the D1R-Zn2+ Signaling Pathway to Trigger Inflammatory Response in Primary-Cultured Rat Embryonic Cortical Neurons

Neuroinflammation is an early event during the pathogenesis of neurodegenerative disorders. Most studies focus on how the factors derived from pathogens or tissue damage activate the inflammation-pyroptosis cell death pathway. It is unclear whether endogenous neurotransmitters could induce inflammatory responses in neurons. Our previous reports have shown that dopamine-induced elevation of intracellular Zn2+ concentration via the D1-like receptor (D1R) is a prerequisite for autophagy and cell death in primary cultured rat embryonic neurons. Here we further examined that this D1R-Zn2+ signaling initiates the transient inflammatory response leading to cell death in cultured cortical neurons. Pretreating the cultured neurons with Zn2+ chelator and inhibitors against inflammation could enhance the cell viability in neurons treated with dopamine and dihydrexidine, an agonist of D1R. Both dopamine and dihydrexidine greatly enhanced inflammasome formation; a Zn2+ chelator, N,N,N',N'-tetrakis(2-pyridinylmethyl)-1,2-ethanediamine, suppressed this increment. Dopamine and dihydrexidine increased the expression levels of NOD-like receptor pyrin domain-containing protein 3 and enhanced the maturation of caspase-1, gasdermin D, and IL-1β; these changes were all Zn2+-dependent. Dopamine treatment did not recruit the N-terminal of the gasdermin D to the plasma membrane but enhanced its localization to the autophagosomes. Pretreating the neurons with IL-1β could increase the viability of neurons challenged with dopamine. These results demonstrate a novel D1R-Zn2+ signaling cascade activating neuroinflammation and cell death. Therefore, maintaining a balance between dopamine homeostasis and inflammatory responses is an important therapeutic target for neurodegeneration. Dopamine elicits transient inflammatory responses in cultured cortical neurons via the D1R-Zn2+ signaling pathway. Dopamine elevates [Zn2+]i to induce the formation of inflammasomes, which activates caspase-1, resulting in the maturation of IL-1β and gasdermin D (GSDMD). Therefore, the homeostasis of dopamine and Zn2+ are critical therapeutic targets for inflammation-derived neurodegeneration.

Extracellularly Detectable Electrochemical Signals of Living Cells Originate from Metabolic Reactions

Direct detection of cellular redox signals has shown immense potential as a novel living cell analysis tool. However, the origin of such signals remains unknown, which hinders the widespread use of electrochemical methods for cellular research. In this study, the authors found that intracellular metabolic pathways that generate adenosine triphosphate (ATP) are the main contributors to extracellularly detectable electrochemical signals. This is achieved through the detection of living cells (4,706 cells/chip, linearity: 0.985) at a linear range of 7,466-48,866. Based on this discovery, the authors demonstrated that the cellular signals detected by differential pulse voltammetry (DPV) can be rapidly amplified with a developed medium containing metabolic activator cocktails (MACs). The DPV approach combined with MAC treatment shows a remarkable performance to detect the effects of the anticancer drug CPI-613 on cervical cancer both at a low drug concentration (2 µm) and an extremely short treatment time (1 hour). Furthermore, the senescence of mesenchymal stem cells could also be sensitively quantified using the DPV+MAC method even at a low passage number (P6). Collectively, their findings unveiled the origin of redox signals in living cells, which has important implications for the characterization of various cellular functions and behaviors using electrochemical approaches.

Nucleotide-Based Lanthanide Coordination Polymer Nano-Probe for Turn-On Fluorescence Sensing of Zn2+ in Serum

BACKGROUND

Water-dispersed lanthanide coordination polymers (LCPs) have attracted considerable attention owing to their superiority in bioanalysis. However, so far, most of the reported LCPs, due to the employment of water-insoluble and toxic organic molecules as ligands, are only competent in organic solution or the gaseous phase. Therefore, the construction of a water-dispersed, LCP-based, especially LCP nanoparticle (LCPNP)-based, sensor is still lacking and challenging.

OBJECTIVE

The aim was to obtain a novel and effective LCPNP-based sensor for Zn2+ by simple self-assembly, utilizing water-soluble guanosine monophosphate (GMP) as ligand and Eu3+ as luminescence center, .

METHODS

In aqueous solutions, Eu-GMP NPs were formed via self-assembly reaction between Eu3+ and GMP, and displayed very weak fluorescence due to low energy transfer from GMP to Eu3+ and the rate constant of nonradiactive deactivation of the excited states caused by the O-H vibration of coordinated water molecules. After the introduce of Zn2+, forming Eu-GMP/Zn, very interestingly, an 8-fold fluorescence enhancement was observed due to the removal of coordination water molecules and fluorescence sensitization of Zn2+.

RESULTS

The fluorescence intensity of Eu-GMP NPs at 614 nm showed a linear relationship with the concentration of Zn2+ from 4 to 240 μM with a detection limit of 4 μM. Due to possessing long fluorescence, Eu-GMP showed prominent achievment for application in serum Zn2+ determination.

CONCLUSION

The LCPNP probe exhibited excellent performance for the determination of Zn2+ in serum.

HIGHLIGHTS

For the first time, we developed and designed a kind of water-dispersed, LCPNP-based turn-on fluorescence assay for Zn2+ in serum. High sensitivity and good recoveries were achieved due to long fluorescence life, good water-dispersed behavior, and the turn-on fluorescence response of the LCPNP probe.

Iron, Zinc, Copper, Cadmium, Mercury, and Bone Tissue

The paper presents the current understanding on the effects of five metals on bone tissue, namely iron, zinc, copper, cadmium, and mercury. Iron, zinc, and copper contribute significantly to human and animal metabolism when present in sufficient amounts, but their excess or shortage increases the risk of developing bone disorders. In contrast, cadmium and mercury serve no physiological purpose and their long-term accumulation damages the osteoarticular system. We discuss the methods of action and interactions between the discussed elements as well as the concentrations of each element in distinct bone structures.

Continuous dynamic identification of key genes and molecular signaling pathways of periosteum in guided bone self-generation in swine model

BACKGROUND

Guided bone self-generation with periosteum-preserved has successfully regenerated mandibular, temporomandibular and interphalangeal joint. The aim of this study was to investigate the dynamic changes of gene expression of periosteum which was involved in the guided bone self-generation.

METHODS

Rib defects of critical size were created in mature swine with periosteum-preserved. The periosteum was sutured into a sealed sheath that closed the bone defect. The periosteum of trauma and control sites were harvested at postoperative 9 time points, and total RNA was extracted. Microarray analysis was conducted to identify the differences in the transcriptome of different time points between two groups.

RESULTS

The differentially expressed genes (DEGs) between control and trauma group were different at postoperative different time points. The dynamic changes of the number of DEGs fluctuated a lot. There were 3 volatility peaks, and we chose 3 time points of DEG number peak (1 week, 5 weeks and 6 months) to study the functions of DEGs. Oxidoreductase activity, oxidation-reduction process and mitochondrion are the most enriched terms of Go analysis. The major signaling pathways of DEGs enrichment include oxidative phosphorylation, PI3K-Akt signaling pathway, osteoclast differentiation pathway and Wnt signaling.

CONCLUSIONS

The oxidoreductase reaction was activated during this bone regeneration process. The oxidative phosphorylation, PI3K-Akt signaling pathway, osteoclast differentiation pathway and Wnt signaling may play important roles in the guided bone self-generation with periosteum-preserved. This study can provide a reference for how to improve the application of this concept of bone regeneration.

The interplay of intracellular calcium and zinc ions in response to electric field stimulation in primary rat cortical neurons in vitro

Recent pharmacological studies demonstrate a role for zinc (Zn²⁺) in shaping intracellular calcium (Ca²⁺) dynamics and vice versa in excitable cells including neurons and cardiomyocytes. Herein, we sought to examine the dynamic of intracellular release of Ca²⁺ and Zn²⁺ upon modifying excitability of primary rat cortical neurons using electric field stimulation (EFS) in vitro. We show that exposure to EFS with an intensity of 7.69 V/cm induces transient membrane hyperpolarization together with transient elevations in the cytosolic levels of Ca²⁺ and Zn²⁺ ions. The EFS-induced hyperpolarization was inhibited by prior treatment of cells with the K⁺ channel opener diazoxide. Chemical hyperpolarization had no apparent effect on either Ca²⁺ or Zn²⁺. The source of EFS-induced rise in Ca²⁺ and Zn²⁺ seemed to be intracellular, and that the dynamic inferred of an interplay between Ca²⁺ and Zn²⁺ ions, whereby the removal of extracellular Ca²⁺ augmented the release of intracellular Ca²⁺ and Zn²⁺ and caused a stronger and more sustained hyperpolarization. We demonstrate that Zn²⁺ is released from intracellular vesicles located in the soma, with major co-localizations in the lysosomes and endoplasmic reticulum. These studies further support the use of EFS as a tool to interrogate the kinetics of intracellular ions in response to changing membrane potential in vitro.

Immunomodulatory biomaterials for implant-associated infections: from conventional to advanced therapeutic strategies

Implant-associated infection (IAI) is increasingly emerging as a serious threat with the massive application of biomaterials. Bacteria attached to the surface of implants are often difficult to remove and exhibit high resistance to bactericides. In the quest for novel antimicrobial strategies, conventional antimicrobial materials often fail to exert their function because they tend to focus on direct bactericidal activity while neglecting the modulation of immune systems. The inflammatory response induced by host immune cells was thought to be a detrimental force impeding wound healing. However, the immune system has recently received increasing attention as a vital player in the host's defense against infection. Anti-infective strategies based on the modulation of host immune defenses are emerging as a field of interest. This review explains the importance of the immune system in combating infections and describes current advanced immune-enhanced anti-infection strategies. First, the characteristics of traditional/conventional implant biomaterials and the reasons for the difficulty of bacterial clearance in IAI were reviewed. Second, the importance of immune cells in the battle against bacteria is elucidated. Then, we discuss how to design biomaterials that activate the defense function of immune cells to enhance the antimicrobial potential. Based on the key premise of restoring proper host-protective immunity, varying advanced immune-enhanced antimicrobial strategies were discussed. Finally, current issues and perspectives in this field were offered. This review will provide scientific guidance to enhance the development of advanced anti-infective biomaterials.

Zn2+ protect cardiac H9c2 cells from endoplasmic reticulum stress by preventing mPTP opening through MCU

Zn2+ regulates endoplasmic reticulum stress (ERS) and is essential for myocardial protection through gating the mitochondrial permeability transition pore (mPTP). However, the underlining mechanism of the mPTP opening remains uncertain. Cells under sustained ERS induce unfolded protein responses (UPR) and cell apoptosis. Glucose regulatory protein 78 (GRP 78) and glucose regulatory protein 94 (GRP 94) are marker proteins of ERS and regulate the onset of apoptosis through the endoplasmic reticulum signaling pathway. We found tunicamycin (TM) treatment activates ERS and significantly increases intracellular Ca2+ and mitochondrial reactive oxygen species (ROS) levels in H9c2 cardiomyocyte cells. Zn2+ markedly decreased protein level of GRP 78/94 and suppressed intracellular Ca2+ and ROS elevation. Mitochondrial calcium uniporter (MCU) is an important Ca2+ transporter protein, through which Zn2+ enter mitochondria. MCU inhibitor ruthenium red (RR) or siRNA significantly reversed the Zinc effect on GRP 78, mitochondrial Ca2+ and ROS. Additionally, Zn2+ prevented TM-induced mPTP opening and decreased mitochondrial Ca2+ concentration, which were blocked through inhibiting or knockdown MCU with siRNA. In summary, our study suggests that Zn2+ protected cardiac ERS by elevating Ca2+ and closing mPTP through MCU.

A549 Cell-Covered Electrodes as a Sensing Element for Detection of Effects of Zn2+ Ions in a Solution

Electrochemical-based biosensors have the potential to be a fast, label-free, simple approach to detecting the effects of cytotoxic substances in liquid media. In the work presented here, a cell-based electrochemical biosensor was developed and evaluated to detect the cytotoxic effects of Zn²⁺ ions in a solution as a reference test chemical. A549 cells were attached to the surface of stainless-steel electrodes. After treatment with ZnCl₂, the morphological changes of the cells and, ultimately, their death and detachment from the electrode surface as cytotoxic effects were detected through changes in the electrical signal. Electrochemical cell-based impedance spectroscopy (ECIS) measurements were conducted with cytotoxicity tests and microscopic observation to investigate the behavior of the A549 cells. As expected, the Zn²⁺ ions caused changes in cell confluency and spreading, which were checked by light microscopy, while the cell morphology and attachment pattern were explored by scanning electron microscopy (SEM). The ECIS measurements confirmed the ability of the biosensor to detect the effects of Zn²⁺ ions on A549 cells attached to the low-cost stainless-steel surfaces and its potential for use as an inexpensive detector for a broad range of chemicals and nanomaterials in their cytotoxic concentrations.

Construction of Mussel-Inspired Dopamine-Zn2+ Coating on Titanium Oxide Nanotubes to Improve Hemocompatibility, Cytocompatibility, and Antibacterial Activity

Zinc ions (Zn2+) are a highly potent bioactive factor with a broad spectrum of physiological functions. In situ continuous and controllable release of Zn2+ from the biomaterials can effectively improve the biocompatibility and antibacterial activity. In the present study, inspired by the adhesion and protein cross-linking in the mussel byssus, with the aim of improving the biocompatibility of titanium, a cost-effective one-step metal-catecholamine assembly strategy was developed to prepare a biomimetic dopamine-Zn2+ (DA-Zn2+) coating by immersing the titanium oxide nanotube (TNT) arrays on the titanium surface prepared by anodic oxidation into an aqueous solution containing dopamine (DA) and zinc ions (Zn2+). The DA-Zn2+ coatings with the different zinc contents exhibited excellent hydrophilicity. Due to the continuous release of zinc ions from the DA-Zn2+ coating, the coated titanium oxide nanotubes displayed excellent hemocompatibility characterized by platelet adhesion and activation and hemolysis assay. Moreover, the DA-Zn2+-coated samples exhibited an excellent ability to enhance endothelial cell (EC) adhesion and proliferation. In addition, the DA-Zn2+ coating can also enhance the antibacterial activity of the nanotubes. Therefore, long-term in situ Zn2+-releasing coating of the present study could serve as the bio-surfaces for long-term prevention of thrombosis, improvement of cytocompatibility to endothelial cells, and antibacterial activity. Due to the easy operation and strong binding ability of the polydopamine on various complicated shapes, the method of the present study can be further applied to other blood contact biomaterials or implantable medical devices to improve the biocompatibility.

The Role of Zinc in Bone Mesenchymal Stem Cell Differentiation

Zinc is an essential trace element for bone growth and bone homeostasis in the human body. Bone mesenchymal stem cells (BMSCs) are multipotent progenitors existing in the bone marrow stroma with the capability of differentiating along multiple lineage pathways. Zinc plays a paramount role in BMSCs, which can be spurred differentiating into osteoblasts, chondrocytes, or adipocytes, and modulates the formation and activity of osteoclasts. The expression of related genes also changed during the differentiation of various cell phenotypes. Based on the important role of zinc in BMSC differentiation, using zinc as a therapeutic approach for bone remodeling will be a promising method. This review explores the role of zinc ion in the differentiation of BMSCs into various cell phenotypes and outlines the existing research on their molecular mechanism.

3D-Printed PCL/Zn scaffolds for bone regeneration with a dose-dependent effect on osteogenesis and osteoclastogenesis

Polycaprolactone (PCL) is a polymer material suitable for being prepared into porous scaffolds used in bone tissue engineering, however, insufficient osteogenic ability and mechanical strength limit its application. Zinc (Zn) alloy with proper mechanical strength and osteogenesis is a promising biodegradable metal that have attracted much attention. Herein, we combined the advantages of PCL and Zn by fabricating PCL/Zn composite scaffolds with different Zn powder contents (1 ​wt%, 2 ​wt%, 3 ​wt%) through fused deposition modelling. The ​mechanical property, cytocompatibility and Zn ​ions release ​behavior of PCL/Zn scaffolds were analyzed ​in vitro. The osteogenesis and osteoclastogenesis properties of the scaffolds were evaluated by being implanted into Sprague-Dawley rats calvaria defect. Results showed that the PCL/Zn scaffolds exhibited improved mechanical properties and cytocompatibility compared with the pure PCL scaffolds. At 8 weeks after in vivo implantaion, the addition of Zn powder promoted new bone formation, in a dose-dependent manner. The scaffolds with 2 ​wt% Zn displayed the best osteogenic effect, while the osteogenic effect was slightly reduced in the scaffolds with 3 ​wt% Zn. In the studied Zn contents, the PCL/Zn scaffolds gradually promoted osteoclastogenesis with increasd Zn content. In the 3 ​wt% Zn group, TRAP-positive cells were observed on the newly formed bone edges around the scaffolds. These dose-dependent effects were verified in vitro using MC3T3-E1 and RAW264.7 ​cells. Finally, we revealed that Zn2+ regulated osteogenesis and osteoclastogenesis by activation of the Wnt/β-catenin and NF-κB signalling pathways, respectively.

ZnT1 is a neuronal Zn2+/Ca2+ exchanger

Zinc transporter 1 (ZnT1; SLC30A1) is present in the neuronal plasma membrane, critically modulating NMDA receptor function and Zn²⁺ neurotoxicity. The mechanism mediating Zn²⁺ transport by ZnT1, however, has remained elusive. Here, we investigated ZnT1-dependent Zn²⁺ transport by measuring intracellular changes of this ion using the fluorescent indicator FluoZin-3. In primary mouse cortical neurons, which express ZnT1, transient addition of extracellular Zn²⁺ triggered a rise in cytosolic Zn²⁺, followed by its removal. Knockdown of ZnT1 by adeno associated viral (AAV)-short hairpin RNA (shZnT1) markedly increased rates of Zn²⁺ rise, and decreased rates of its removal, suggesting that ZnT1 is a primary route for Zn²⁺ efflux in neurons. Although Zn²⁺ transport by other members of the SLC30A family is dependent on pH gradients across cellular membranes, altered H⁺ gradients were not coupled to ZnT1-dependent transport. Removal of cytoplasmic Zn²⁺, against a large inward gradient during the initial loading phase, suggests that Zn²⁺ efflux requires a large driving force. We therefore asked if Ca²⁺ gradients across the membrane can facilitate Zn²⁺ efflux. Elimination of extracellular Ca²⁺ abolished Zn²⁺ efflux, while increased extracellular Ca²⁺ levels enhanced Zn²⁺ efflux. Intracellular Ca²⁺ rises, measured in GCaMP6 expressing neurons, closely paralleled cytoplasmic Zn²⁺ removal. Taken together, these results strongly suggest that ZnT1 functions as a Zn²⁺/Ca²⁺ exchanger, thereby regulating the transport of two ions of fundamental importance in neuronal signaling.

The expression and clinical significance of GPR39 in colon cancer

BACKGROUND

Colorectal cancer is the third most common cancer and requires more prognostic biomarkers for precise treatment. GPR39 is a GPCR which can interact with Zn and modulate the colonocytes' survival. The clinical significance of GPR39 in colon cancer has never been reported.

MATERIALS

In our study, we compared GPR39 expression between colon cancers and tumor-adjacent tissues by retrieving TCGA data and detected the expression of GPR39 in colon cancers with qPCR and immunohistochemistry. The clinical significance of GPR39 was evaluated by analyzing the correlations with clinicopathological factors with the chi-square test. The prognostic significance of GPR39 was estimated with univariate and multivariate analyses. The expression of several other biomarkers including PPARG, EPCAM, and PD-L1 was investigated by re-analyzing TCGA data, qPCR, and IHC. The prognostic value of PPARG, EPCAM, and PD-L1 was also estimated with univariate analysis.

RESULTS

In both TCGA database and our 15 colon cancer pairs, GPR39 expression was significantly upregulated in colon cancer tissues. GPR39 was an independent prognostic biomarker in colon cancer for poor prognosis. With TCGA data re-analysis, qPCR, and IHC, we showed that GPR39 expression was significantly correlated with the expression of EPCAM and PD-L1, but not PPARG. EPCAM and PD-L1 were also unfavorable prognostic biomarkers of colon cancer.

CONCLUSIONS

GPR39 was upregulated in colon cancer tissues compared with tumor-adjacent tissues. GPR39 was an independent prognostic biomarker in colon cancer for poor prognosis. EPCAM and PD-L1 were substantially associated with GPR39 expression, and they were also identified as prognostic biomarkers in colon cancers.

Cancer therapeutic strategies based on metal ions

As a necessary substance to maintain the body's normal life activities, metal ions are ubiquitous in organisms and play a major role in various complex physiological and biochemical processes, such as material transportation, energy conversion, information transmission, metabolic regulation, etc. Their abnormal distribution/accumulation in cells can interfere with these processes, causing irreversible physical damage to cells or activating biochemical reactions to induce cell death. Therefore, metal ions can be exploited against a wide spectrum of cancers with high efficiency and without drug resistance, which can effectively inhibit the growth of cancer cells by triggering biocatalysis, breaking the osmotic balance, affecting metabolism, interfering with signal transduction, damaging DNA, etc. This perspective systematically summarizes the latest research progress of metal ion-based anti-tumor therapy, and emphasizes the challenges and development directions of this type of therapeutic strategy, hoping to provide a general implication for future research.

The Influence of Zinc and Heavy Metals in Feed and Water on the Quality of Cryopreserved Bull Semen

This study aimed to assess the influence of different concentrations of zinc (Zn), lead (Pb), mercury (Hg) and cadmium (Cd) found in the feed and water provided to bulls on the concentrations of these metals in cryopreserved bull semen, and to determine their influence onto semen quality parameters. Correlations between heavy metal concentrations in the semen and the quality parameters of semen as estimated by computer-assisted sperm analysis (CASA) and flow cytometry (FC) methods were determined.

A total of 40 cryopreserved semen samples originating from bulls housed in 4 different centers for artificial insemination (A, B, C and D) were examined, making a total of 160 samples. The concentrations of metals and semen quality parameters were determined in cryopreserved semen of 10 bulls from each center, namely 4 samples from each bull. Concentrations of Zn, Pb, Hg and Cd in hay and concentrated feed were within the allowed limits as proposed by the National Research Council (NRC, 2000). A strong negative correlation was detected between curvilinear velocity (VCL) and Zn concentrations in the semen (P < 0.01; r = -0.772) in group D, and a positive correlation of VCL with Pb concentrations (P < 0.05 and r = 0.718) in group B. Mercury concentrations in cryopreserved semen correlated negatively to the percent of live sperm cells with intact acrosomes (V/IA: P < 0.05; r = -0.640) and positively with the percent of dead sperm cells with damaged acrosomes (D/DA: P < 0.01; r = 0.766) in group D. This finding confirms the hypothesis that Hg, even at low concentrations, may cause acrosome damage.

Effects of Extracellular Osteoanabolic Agents on the Endogenous Response of Osteoblastic Cells

The complex multidimensional skeletal organization can adapt its structure in accordance with external contexts, demonstrating excellent self-renewal capacity. Thus, optimal extracellular environmental properties are critical for bone regeneration and inextricably linked to the mechanical and biological states of bone. It is interesting to note that the microstructure of bone depends not only on genetic determinants (which control the bone remodeling loop through autocrine and paracrine signals) but also, more importantly, on the continuous response of cells to external mechanical cues. In particular, bone cells sense mechanical signals such as shear, tensile, loading and vibration, and once activated, they react by regulating bone anabolism. Although several specific surrounding conditions needed for osteoblast cells to specifically augment bone formation have been empirically discovered, most of the underlying biomechanical cellular processes underneath remain largely unknown. Nevertheless, exogenous stimuli of endogenous osteogenesis can be applied to promote the mineral apposition rate, bone formation, bone mass and bone strength, as well as expediting fracture repair and bone regeneration. The following review summarizes the latest studies related to the proliferation and differentiation of osteoblastic cells, enhanced by mechanical forces or supplemental signaling factors (such as trace metals, nutraceuticals, vitamins and exosomes), providing a thorough overview of the exogenous osteogenic agents which can be exploited to modulate and influence the mechanically induced anabolism of bone. Furthermore, this review aims to discuss the emerging role of extracellular stimuli in skeletal metabolism as well as their potential roles and provide new perspectives for the treatment of bone disorders.

Metallothioneins and Megalin Expression Profiling in Premalignant and Malignant Oral Squamous Epithelial Lesions

This study aimed to assess the relationship and possible interactions between metallothioneins (MTs) and megalin (LRP-2) in different grades of oral squamous cell carcinoma (OSCC) and premalignant lesions of the oral mucosa (oral leukoplakia and oral lichen planus). The study included archived samples of 114 patients and control subjects. Protein expression was examined by immunohistochemistry and immunofluorescence, and staining quantification was performed by ImageJ software. Protein interaction in cancer tissue was tested and visualized by proximity ligation assay. Mann-Whitney and Kruskal-Wallis tests were used to determine the significance of differences between each group, whereas Pearson correlation coefficient was performed to test correlation. Expression of both proteins differed significantly between each group showing the same pattern of gradual increasing from oral lichen planus to poorly differentiated OSCC. Moreover, MTs and megalin were found to co-express and interact in cancer tissue, and their expression positively correlated within the overall study group. Findings of prominent nuclear and chromosomal megalin expression suggest that it undergoes regulated intramembrane proteolysis upon MTs binding, indicating its ability to directly affect gene expression and cellular division in cancer tissue. The data obtained point to the onco-driving potential of MTs-megalin interaction.

Role of GPR39 in Neurovascular Homeostasis and Disease

GPR39, a member of the ghrelin family of G protein-coupled receptors, is zinc-responsive and contributes to the regulation of diverse neurovascular and neurologic functions. Accumulating evidence suggests a role as a homeostatic regulator of neuronal excitability, vascular tone, and the immune response. We review GPR39 structure, function, and signaling, including constitutive activity and biased signaling, and summarize its expression pattern in the central nervous system. We further discuss its recognized role in neurovascular, neurological, and neuropsychiatric disorders.

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.

ZIF-Based Nanoparticles Combine X-Ray-Induced Nitrosative Stress with Autophagy Management for Hypoxic Prostate Cancer Therapy

Although reactive oxygen species (ROS)-mediated tumor treatments are predominant in clinical applications, ROS-induced protective autophagy promotes cell survival, especially in hypoxic tumors. Herein, X-ray triggered nitrite (NO₂ ^- ) is used for hypoxic prostate cancer therapy by inhibiting autophagy and inducing nitrosative stress based on an electrophilic zeolitic imidazole framework (ZIF-82-PVP). After internalization of pH-responsive ZIF-82-PVP nanoparticles, electrophilic ligands and Zn²⁺ are delivered into cancer cells. Electrophilic ligands can not only consume GSH under hypoxia but also capture low-energy electrons derived from X-rays to generate NO₂ ^- , which inhibits autophagy and further elevates lethal nitrosative stress levels. In addition, dissociated Zn²⁺ specifically limits the migration and invasion of prostate cancer cells through ion interference. In vitro and in vivo results indicate that ZIF-82-PVP nanoparticles under X-ray irradiation can effectively promote the apoptosis of hypoxic prostate cancer cells. Overall, this nitrosative stress-mediated tumor therapy strategy provides a novel approach targeting hypoxic tumors.

The Zinc-Sensing Receptor GPR39 in Physiology and as a Pharmacological Target

The G-protein coupled receptor GPR39 is abundantly expressed in various tissues and can be activated by changes in extracellular Zn²⁺ in physiological concentrations. Previously, genetically modified rodent models have been able to shed some light on the physiological functions of GPR39, and more recently the utilization of novel synthetic agonists has led to the unraveling of several new functions in the variety of tissues GPR39 is expressed. Indeed, GPR39 seems to be involved in many important metabolic and endocrine functions, but also to play a part in inflammation, cardiovascular diseases, saliva secretion, bone formation, male fertility, addictive and depression disorders and cancer. These new discoveries offer opportunities for the development of novel therapeutic approaches against many diseases where efficient therapeutics are still lacking. This review focuses on Zn²⁺ as an endogenous ligand as well as on the novel synthetic agonists of GPR39, placing special emphasis on the recently discovered physiological functions and discusses their pharmacological potential.

Copper Toxicity Is Not Just Oxidative Damage: Zinc Systems and Insight from Wilson Disease

Essential metals such as copper (Cu) and zinc (Zn) are important cofactors in diverse cellular processes, while metal imbalance may impact or be altered by disease state. Cu is essential for aerobic life with significant functions in oxidation-reduction catalysis. This redox reactivity requires precise intracellular handling and molecular-to-organismal levels of homeostatic control. As the central organ of Cu homeostasis in vertebrates, the liver has long been associated with Cu storage disorders including Wilson Disease (WD) (heritable human Cu toxicosis), Idiopathic Copper Toxicosis and Endemic Tyrolean Infantile Cirrhosis. Cu imbalance is also associated with chronic liver diseases that arise from hepatitis viral infection or other liver injury. The labile redox characteristic of Cu is often discussed as a primary mechanism of Cu toxicity. However, work emerging largely from the study of WD models suggests that Cu toxicity may have specific biochemical consequences that are not directly attributable to redox activity. This work reviews Cu toxicity with a focus on the liver and proposes that Cu accumulation specifically impacts Zn-dependent processes. The prospect that Cu toxicity has specific biochemical impacts that are not entirely attributable to redox may promote further inquiry into Cu toxicity in WD and other Cu-associated disorders.

ZnR/GPR39 controls cell migration by orchestrating recruitment of KCC3 into protrusions, re-organization of actin and activation of MMP

Actin re-organization and degradation of extracellular matrix by metalloproteases (MMPs) facilitate formation of cellular protrusions that are required for cell proliferation and migration. We find that Zn²⁺ activation of the Gq-coupled receptor ZnR/GPR39 controls these processes by regulating K⁺/Cl^- co-transporter KCC3, which modulates cell volume. Silencing of KCC3 expression or activity reverses ZnR/GPR39 enhancement of cell proliferation, migration and invasion through Matrigel. Activation of ZnR/GPR39 recruits KCC3 into F-actin rich membrane protrusions, suggesting that it can locally control volume changes. Immunofluorescence analysis indicates that Zn²⁺ activation of ZnR/GPR39 and KCC3 are required to enhance formation of F-actin stress fibers and cellular protrusions. In addition, ZnR/GPR39 upregulation of KCC3-dependent transport increases the activity of matrix metalloproteases MMP2 and MMP9. Our study establishes a mechanism in which ZnR/GPR39 orchestrates localization and activation of KCC3, formation of F-actin rich cell protrusions and activation of MMPs, and thereby controls cell proliferation and migration.

Zn2+ and mPTP mediate resveratrol-induced myocardial protection from endoplasmic reticulum stress

Resveratrol displays cardioprotective activity; however, its mechanism of action remains unclear. In the current study, resveratrol-induced myocardial protection from endoplasmic reticulum stress (ERS) was investigated, focusing on the roles of Zn2+ and the mitochondrial permeability transition pore (mPTP). We found, using the MTT/LDH kit, that 2-DG-induced ERS significantly decreased H9c2 cell viability. Resveratrol markedly inhibited the expression of endoplasmic reticulum chaperone GRP 78/94 and ERS-related apoptosis proteins CHOP, Caspase12, and JNK induced by 2-DG. The zinc ion chelator TPEN, and ERK/GSK-3β inhibitors PD98059 and SB216763 and their siRNAs blocked resveratrol function. The AKT inhibitor LY294002 and siRNA did not alter the action of resveratrol. In addition, resveratrol significantly increased the phosphorylation of ERK and GSK-3β. Resveratrol prevented 2-DG-induced mPTP opening and increased intracellular Zn2+ concentration indicated by TMRE and Newport Green DCF fluorescence intensity, which were further abrogated by ERK/GSK-3β inhibitors and siRNAs. Our data suggested that resveratrol protected cardiac cells from ERS by mobilizing intracellular Zn2+ and preventing mPTP opening through the ERK/GSK-3β but not PI3K/AKT signaling pathway.

The Associated Regulatory Mechanisms of Zinc Lactate in Redox Balance and Mitochondrial Function of Intestinal Porcine Epithelial Cells

Zinc lactate (ZnLA) is a new organic zinc salt which has antioxidant properties in mammals and can improve intestinal function. This study explored the effects of ZnLA and ZnSO₄ on cell proliferation, Zn transport, antioxidant capacity, mitochondrial function, and their underlying molecular mechanisms in intestinal porcine epithelial cells (IPEC-J2). The results showed that addition of ZnLA promoted cell proliferation, inhibited cell apoptosis and IL-6 secretion, and upregulated the mRNA expression and concentration of MT-2B, ZNT-1, and CRIP, as well as affected the gene expression and activity of oxidation or antioxidant enzymes (e.g., CuZnSOD, CAT, and Gpx1, GSH-PX, LDH, and MDA), compared to ZnSO₄ or control. Compared with the control, ZnLA treatment had no significant effect on mitochondrial membrane potential, whereas it markedly increased the mitochondrial basal OCR, nonmitochondrial respiratory capacity, and mitochondrial proton leakage and reduced spare respiratory capacity and mitochondrial reactive oxygen (ROS) production in IPEC-J2 cells. Furthermore, ZnLA treatment increased the protein expression of Nrf2 and phosphorylated AMPK, but reduced Keap1 and p62 protein expression and autophagy-related genes LC3B-1 and Beclin mRNA abundance. Under H₂O₂-induced oxidative stress conditions, ZnLA supplementation markedly reduced cell apoptosis and mitochondrial ROS levels in IPEC-J2 cells. Moreover, ZnLA administration increased the protein expression of Nrf2 and decreased the protein expression of caspase-3, Keap1, and p62 in H₂O₂-induced IPEC-J2 cells. In addition, when the activity of AMPK was inhibited by Compound C, ZnLA supplementation did not increase the protein expression of nuclear Nrf2, but when Compound C was removed, the activities of AMPK and Nfr2 were both increased by ZnLA treatment. Our results indicated that ZnLA could improve the antioxidant capacity and mitochondrial function in IPEC-J2 cells by activating the AMPK-Nrf2-p62 pathway under normal or oxidative stress conditions. Our novel finding also suggested that ZnLA, as a new feed additive for piglets, has the potential to be an alternative for ZnSO₄.

Co-implantation of magnesium and zinc ions into titanium regulates the behaviors of human gingival fibroblasts

Soft tissue sealing around implants acts as a barrier between the alveolar bone and oral environment, protecting implants from the invasion of bacteria or external stimuli. In this work, magnesium (Mg) and zinc (Zn) are introduced into titanium by plasma immersed ion implantation technology, and their effects on the behaviors of human gingival fibroblasts (HGFs) as well as the underlying mechanisms are investigated. Surface characterization confirms Mg and Zn exist on the surface in metallic and oxidized states. Contact angle test suggests that surface wettability of titanium changes after ion implantation and thus influences protein adsorption of surfaces. In vitro studies disclose that HGFs on Mg ion-implanted samples exhibit better adhesion and migration while cells on Zn ion-implanted samples have higher proliferation rate and amounts. The results of immunofluorescence staining and real-time reverse-transcriptase polymerase chain reaction (RT-PCR) suggest that Mg mainly regulates the motility and adhesion of HGFs through activating the MAPK signal pathway whereas Zn influences HGFs proliferation by triggering the TGF-β signal pathway. The synergistic effect of Mg and Zn ions ensure that HGFs cultured on co-implanted samples possessed both high proliferation rate and motility, which are critical to soft tissue sealing of implants.

Zinc: Roles in pancreatic physiology and disease

Zinc is an essential trace element. Deficiencies are frequently seen with gastrointestinal diseases, including chronic pancreatitis, nutritional deficiency, and reduced intestinal absorption. Additionally, reduced zinc levels have been linked to cellular changes associated with acute pancreatitis such as enhanced inflammation with increased macrophage activation and production of inflammatory cytokines such as IL-1β, impaired autophagy, and modulation of calcium homeostasis. Preliminary data suggest that zinc deficiency may lead to pancreatic injury in animal models. The purpose of this review is to explore the biologic effects of zinc deficiency that could impact pancreatic disease. MESH KEYWORDS: Malnutrition, inflammation, trace element.

Reduced hepatic metallothionein expression in first trimester fetuses in response to intrauterine smoking exposure: a consequence of low maternal zinc levels?

STUDY QUESTION

Does maternal smoking in early pregnancy affect metallothionein 1 and 2 (MT1 and MT2) mRNA and protein expression in first trimester placenta or embryonic/fetal liver?

SUMMARY ANSWER

In the first trimester, MT protein expression is seen only in liver, where smoking is associated with a significantly reduced expression.

WHAT IS KNOWN ALREADY

Zinc homeostasis is altered by smoking. Smoking induces MT in the blood of smokers properly as a result of the cadmium binding capacities of MT. In term placenta MT is present and smoking induces gene and protein expression (MT2 in particular), but the MT presence and response to smoking have never been examined in first trimester placenta or embryonic/fetal tissues.

STUDY DESIGN, SIZE, DURATION

Cross sectional study where the presence of MT mRNA and protein was examined at the time of the abortion. The material was collected with informed consent after surgical intervention and frozen immediately. For protein expression analysis, liver tissue originating from smoking exposed n = 10 and unexposed n = 12 pregnancies was used. For mRNA expression analyses, placental tissue originating from smokers n = 19 and non-smokers n = 23 and fetal liver tissue from smoking exposed n = 16 and smoking unexposed pregnancies n = 13, respectively, were used.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Tissues were obtained from women who voluntarily and legally chose to terminate their pregnancy between gestational week 6 and 12. Western blot was used to determine the protein expression of MT, and real-time PCR was used to quantify the mRNA expression of MT2A and eight MT1 genes alongside the expression of key placental zinc transporters: zinc transporter protein-1 (ZNT1), Zrt-, Irt-related protein-8 and -14 (ZIP8 and ZIP14).

MAIN RESULTS AND THE ROLE OF CHANCE

A significant reduction in the protein expression of MT1/2 in liver tissue (P = 0.023) was found by western blot using antibodies detecting both MT forms. Overall, a similar tendency was observed on the mRNA level although not statistically significant. Protein expression was not present in placenta, but the mRNA regulation suggested a down regulation of MT as well. A suggested mechanism based on the known role of MT in zinc homeostasis could be that the findings reflect reduced levels of easily accessible zinc in the blood of pregnant smokers and hence a reduced MT response in smoking exposed fetal/embryonic tissues.

LIMITATIONS AND REASONS FOR CAUTION

Smoking was based on self-reports; however, our previous studies have shown high consistency regarding cotinine residues and smoking status. Passive smoking could interfere but was found mainly among smokers. The number of fetuses was limited, and other factors such as medication and alcohol might affect the findings. Information on alcohol was not consistently obtained, and we cannot exclude that it was more readily obtained from non-users. In the study, alcohol consumption was reported by a limited number (less than 1 out of 5) of women but with more smokers consuming alcohol. However, the alcohol consumption reported was typically limited to one or few times low doses. The interaction between alcohol and smoking is discussed in the paper. Notably we would have liked to measure zinc status to test our hypothesis, but maternal blood samples were not available.

WIDER IMPLICATIONS OF THE FINDINGS

Zinc deficiency-in particular severe zinc deficiency-can affect pregnancy outcome and growth. Our findings indicate that zinc homeostasis is also affected in early pregnancy of smokers, and we know from pilot studies that even among women who want to keep their babies, the zinc status is low. Our findings support that zinc supplements should be considered in particular to women who smoke.

STUDY FUNDING/COMPETING INTEREST(S)

We thank the Department of Biomedicine for providing laboratory facilities and laboratory technicians and the Lundbeck Foundation and Læge Sofus Carl Emil Friis og Hustru Olga Doris Friis Legat for financial support. The authors have no competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

How Dysregulated Ion Channels and Transporters Take a Hand in Esophageal, Liver, and Colorectal Cancer

Over the last two decades, the understanding of how dysregulated ion channels and transporters are involved in carcinogenesis and tumor growth and progression, including invasiveness and metastasis, has been increasing exponentially. The present review specifies virtually all ion channels and transporters whose faulty expression or regulation contributes to esophageal, hepatocellular, and colorectal cancer. The variety reaches from Ca²⁺, K⁺, Na⁺, and Cl^- channels over divalent metal transporters, Na⁺ or Cl^- coupled Ca²⁺, HCO₃^- and H⁺ exchangers to monocarboxylate carriers and organic anion and cation transporters. In several cases, the underlying mechanisms by which these ion channels/transporters are interwoven with malignancies have been fully or at least partially unveiled. Ca²⁺, Akt/NF-κB, and Ca²⁺- or pH-dependent Wnt/β-catenin signaling emerge as cross points through which ion channels/transporters interfere with gene expression, modulate cell proliferation, trigger epithelial-to-mesenchymal transition, and promote cell motility and metastasis. Also miRs, lncRNAs, and DNA methylation represent potential links between the misexpression of genes encoding for ion channels/transporters, their malfunctioning, and cancer. The knowledge of all these molecular interactions has provided the basis for therapeutic strategies and approaches, some of which will be broached in this review.

Citrate zinc hydroxyapatite nanorods with enhanced cytocompatibility and osteogenesis for bone regeneration

The development of biomaterials that mimicking the hydroxyapatite nanoparticles existent in the immature bone tissue is crucial, especially to accelerate the bone remodeling and regeneration. In this work, it was developed for the first time, hydroxyapatite nanoparticles (NPs) incorporating citrate and zinc (cit-Zn-Hap) in their composition towards a one-step hydrothermal procedure. For comparison purposes, hydroxyapatite NPs incorporating only zinc (Zn-Hap) or citrate (cit-Hap), as well as hydroxyapatite without any of these elements (Hap) were synthesised. The physicochemical characterization was carried out reveling that, the presence of zinc on hydroxyapatite (cit-Zn-Hap), reduced the size of nanoparticles, changed the phosphate environment and decreased the surface charge when compared with cit-Hap nanoparticles. The osteogenic potential of cit-Zn-Hap NPs was analysed in human bone marrow-derived stromal cells (BMSCs), in the absence of osteoinductive factors. NPs were internalized by endocytosis appearing trapped in endosomes and lysosomes scattered through the cytoplasm. Exposure to these NPs resulted in a significant induction of ALP activity, extracellular matrix mineralization, and gene expression of early and later osteogenic transcription factors, as well as of osteoblastic markers. The osteoinductive effect might be regulated, at least in part, by the increased signalling through the canonical WNT pathway. Evaluation of the cell behaviour following exposure to Zn-Hap and cit-Hap strongly suggested a synergistic effect of citrate and Zn in cit-Zn-Hap NPs towards the induction of the osteogenic commitment and functionality of BMSCs. These findings will allow the design of new biomimetic hydroxyapatite nanoparticles with great potential for bone regeneration.

ROS induced bactericidal activity of amorphous Zn-doped titanium oxide coatings and enhanced osseointegration in bacteria-infected rat tibias

Titanium-based endosseous implants with high antibacterial and osseointegration activities are extremely required in clinics. To achieve this line, herein the doped coatings with three kinds of Zn doses were micro-arc oxidized (MAOed) on Ti. They were examined to reveal a bilayered structure, in which the outer layer consisted completely of the amorphism comprising elements of Ti, O and Zn with Zn doped in the form of weaken Zn-O bonds, and the underlying layer was partially crystallized with nanocrystalline TiO₂ and Zn₂TiO₄ to embed an amorphous matrix. While the Zn doped doses of the surface amorphous layers increased with elevating the MAOed voltages, the weaken Zn-O bonds in the amorphism were identified to act as both the contributor of Zn²⁺ controllable release and the generator of reactive oxide species (ROS) on the coatings. The enhanced HO• and O₂^-• formation on the elevated voltage MAOed coatings caused serious break of the cell walls and plasma membranes of S. aureus. In parallel, the enhanced Zn²⁺ release and extracellular H₂O₂ formation led to the enhanced intracellular ROS level of S. aureus, further aggravating the damage of plasma membrane, resulting in bacteria death. On contrary to the overdose of Zn doped coating, the moderate doses of Zn doped coatings did not induce additional intracellular ROS and attenuate viability and proliferation of osteoblasts in vitro, and promoted osseointegration in both S. aureus-uninfected and infected rat tibias, which ascribed to the strong antibacterial activity and un-attenuated cell function of the coatings in the infected case. STATEMENT OF SIGNIFICANCE: (1) The Zn-doped coatings revealed a bilayered structure of the surface layer comprising the Ti, O and Zn constructed amorphism with Zn in the form of weaken Zn-O bonds, and the underlying layer comprising nanocrystalline TiO₂ and Zn₂TiO₄ to embed amorphous matrix. (2) The weaken Zn-O bonds in the amorphism were identified to act as both the contributor of Zn²⁺ controllable release and the generator of ROS on the coatings. (3) The enhanced Zn²⁺ release and ROS formation on the coatings killed S. aureus by inducing serious break of their cell walls and plasma membranes. This effect in combination of un-attenuated osteoblast proliferation endowed the moderate Zn doped coatings with enhanced osseointegration in S. aureus-infected rat tibias.

Improved Blood Compatibility and Endothelialization of Titanium Oxide Nanotube Arrays on Titanium Surface by Zinc Doping

Titanium dioxide nanotube arrays are widely used in biomaterials due to their unique tubular structure and tunable biocompatibility. In the present study, titanium oxide nanotube arrays with different diameters were prepared on the titanium surface by anodization, followed by zinc doping using hydrothermal treatment to enhance the biocompatibility. Both the nanotube dimensions and zinc doping had obvious influences on the hydrophilicity, protein adsorption, blood compatibility, and endothelial cell behaviors of the titanium surface. The increase of the diameter and zinc doping can improve the hydrophilicity of the titanium surface. The increase of nanotube diameter could reduce the albumin adsorption while increasing the fibrinogen adsorption. However, zinc doping can simultaneously promote the adsorption of albumin and fibrinogen, and the effect was more obvious for albumin. Zinc doping can significantly improve the blood compatibility of the titanium oxide nanotubes because it cannot only increase the activity of cyclophosphate guanylate (cGMP) but also significantly reduce the platelets adhesion and hemolysis rate. Moreover, it was also found that both the smaller diameter and zinc doping nanotubes can enhance the endothelial cell adhesion and proliferation as well as up-regulate the expression of NO and VEGF. Therefore, the zinc doped titanium dioxide nanotube array can be used to simultaneously improve the blood compatibility and promote endothelialization of the titanium-based biomaterials and implants, such as intravascular stents.

A novel dual-function probe for recognition of Zn2+ and Al3+ and its application in real samples

A dual-function probe NAHH based on naphthalene was synthesized and characterized. Based on the combination effects derived from the inhabitation of photo-induced electron transfer (PET) and CN isomerization, probe NAHH achieved in the recognition of Zn2+ and Al3+ both through obvious fluorescence enhancement and color changes detected by naked eye, respectively. Probe NAHH showed high sensitivity with the limit of detection as low as 3.02 × 10-7 M for Zn2+ and 7.55 × 10-8 M for Al3+, indicated the capability of probe NAHH in trace detection for Zn2+ and Al3+. The binding ratio of NAHH with Zn2+ and Al3+ were all 1:1 determined by Job plot, and the corresponding association constant was calculated as 8.48 × 104 M-1 and 4.45 × 105 M-1, respectively. The mechanism was further confirmed by FT-IR, 1H NMR titration and ESI-MS analysis. Furthermore, probe NAHH was successfully applied in logic gate construction and the detection of Zn2+ and Al3+ in Songhua River and test stripe. Fluorescence imaging experiments confirmed that NAHH could be used to monitor Zn2+ in plant root.

Dissociated Hippocampal Neurons Exhibit Distinct Zn2+ Dynamics in a Stimulation-Method-Dependent Manner

Ionic Zn2+ has increasingly been recognized as an important neurotransmitter and signaling ion in glutamatergic neuron pathways. Intracellular Zn2+ transiently increases as a result of neuronal excitation, and this Zn2+ signal is essential for neuron plasticity, but the source and regulation of the signal is still unclear. In this study, we rigorously quantified Zn2+, Ca2+, and pH dynamics in dissociated mouse hippocampal neurons stimulated with bath application of high KCl or glutamate. While both stimulation methods yielded Zn2+ signals, Ca2+ influx, and acidification, glutamate stimulation induced more sustained high intracellular Ca2+ and a larger increase in intracellular Zn2+. However, the stimulation-induced pH change was similar between conditions, indicating that a different cellular change is responsible for the stimulation-dependent difference in Zn2+ signal. This work provides the first robust quantification of Zn2+ dynamics in neurons using different methods of stimulation.

Zinc Homeostasis in Bone: Zinc Transporters and Bone Diseases

Zinc is an essential micronutrient that plays critical roles in numerous physiological processes, including bone homeostasis. The majority of zinc in the human body is stored in bone. Zinc is not only a component of bone but also an essential cofactor of many proteins involved in microstructural stability and bone remodeling. There are two types of membrane zinc transporter proteins identified in mammals: the Zrt- and Irt-like protein (ZIP) family and the zinc transporter (ZnT) family. They regulate the influx and efflux of zinc, accounting for the transport of zinc through cellular and intracellular membranes to maintain zinc homeostasis in the cytoplasm and in intracellular compartments, respectively. Abnormal function of certain zinc transporters is associated with an imbalance of bone homeostasis, which may contribute to human bone diseases. Here, we summarize the regulatory roles of zinc transporters in different cell types and the mechanisms underlying related pathological changes involved in bone diseases. We also present perspectives for further studies on bone homeostasis-regulating zinc transporters.

Triphenyltin disrupts intracellular Zn2+ homeostasis in rat thymic lymphocytes

Triphenyltin (TPT), previously used as an agricultural fungicide and industrial antifoulant, is now considered an environmental pollutant. The effect of TPT on human health is concerning due to its presence as a contaminant in seafood. In this study, the changes in intracellular Zn²⁺ concentration ([Zn²⁺]i) and cellular content of nonprotein thiols ([NPT]i) induced by triphenyltin chloride (TPTCH), were measured in rat thymic lymphocytes. This was studied by flow-cytometry using the fluorescent probes FluoZin-3-AM and 5-chloromethylfluorescein diacetate (5-CMF-DA). Incubation with TPTCH, at 0.1 μM or more (up to 3 μM), increased [Zn²⁺]i in a concentration-dependent manner. The TPTCH-induced elevation in [Zn²⁺]i was due to the increase in membrane Zn²⁺ permeability and intracellular Zn²⁺ release. Incubation with TPTCH at 0.3 μM significantly increased [NPT]i levels, whereas the addition of an intracellular Zn²⁺ chelator had no effect on the same. TPT at higher concentrations (1 or 3 μM) reduced [NPT]i. TPT may disturb intracellular Zn²⁺ signaling in lymphocytes that disturbs cellular functions.

Role of ion channels in gastrointestinal cancer

In their seminal papers Hanahan and Weinberg described oncogenic processes a normal cell undergoes to be transformed into a cancer cell. The functions of ion channels in the gastrointestinal (GI) tract influence a variety of cellular processes, many of which overlap with these hallmarks of cancer. In this review we focus on the roles of the calcium (Ca2+), sodium (Na+), potassium (K+), chloride (Cl-) and zinc (Zn2+) transporters in GI cancer, with a special emphasis on the roles of the KCNQ1 K+ channel and CFTR Cl- channel in colorectal cancer (CRC). Ca2+ is a ubiquitous second messenger, serving as a signaling molecule for a variety of cellular processes such as control of the cell cycle, apoptosis, and migration. Various members of the TRP superfamily, including TRPM8, TRPM7, TRPM6 and TRPM2, have been implicated in GI cancers, especially through overexpression in pancreatic adenocarcinomas and down-regulation in colon cancer. Voltage-gated sodium channels (VGSCs) are classically associated with the initiation and conduction of action potentials in electrically excitable cells such as neurons and muscle cells. The VGSC NaV1.5 is abundantly expressed in human colorectal CRC cell lines as well as being highly expressed in primary CRC samples. Studies have demonstrated that conductance through NaV1.5 contributes significantly to CRC cell invasiveness and cancer progression. Zn2+ transporters of the ZIP/SLC39A and ZnT/SLC30A families are dysregulated in all major GI organ cancers, in particular, ZIP4 up-regulation in pancreatic cancer (PC). More than 70 K+ channel genes, clustered in four families, are found expressed in the GI tract, where they regulate a range of cellular processes, including gastrin secretion in the stomach and anion secretion and fluid balance in the intestinal tract. Several distinct types of K+ channels are found dysregulated in the GI tract. Notable are hERG1 upregulation in PC, gastric cancer (GC) and CRC, leading to enhanced cancer angiogenesis and invasion, and KCNQ1 down-regulation in CRC, where KCNQ1 expression is associated with enhanced disease-free survival in stage II, III, and IV disease. Cl- channels are critical for a range of cellular and tissue processes in the GI tract, especially fluid balance in the colon. Most notable is CFTR, whose deficiency leads to mucus blockage, microbial dysbiosis and inflammation in the intestinal tract. CFTR is a tumor suppressor in several GI cancers. Cystic fibrosis patients are at a significant risk for CRC and low levels of CFTR expression are associated with poor overall disease-free survival in sporadic CRC. Two other classes of chloride channels that are dysregulated in GI cancers are the chloride intracellular channels (CLIC1, 3 & 4) and the chloride channel accessory proteins (CLCA1,2,4). CLIC1 & 4 are upregulated in PC, GC, gallbladder cancer, and CRC, while the CLCA proteins have been reported to be down-regulated in CRC. In summary, it is clear, from the diverse influences of ion channels, that their aberrant expression and/or activity can contribute to malignant transformation and tumor progression. Further, because ion channels are often localized to the plasma membrane and subject to multiple layers of regulation, they represent promising clinical targets for therapeutic intervention including the repurposing of current drugs.

Zn metabolism of monogastric species and consequences for the definition of feeding requirements and the estimation of feed Zn bioavailability

A major goal of mineral nutrition research is to provide information of feed zinc (Zn) utilization efficiency and gross Zn requirements as affected by changing rearing conditions. This can be achieved only by applying precise experimental models that acknowledge the basic principles of Zn metabolism. This review article summarizes the most important aspects of Zn homeostasis in monogastric species, including molecular aspects of Zn acquisition and excretion. Special emphasis is given to the role of the skeleton as well as the exocrine pancreas for animal Zn metabolism. Finally, we discuss consequences arising from these physiological principles for the experimental design of trials which aim to address questions of Zn requirements and bioavailability.

ZnR/GPR39 upregulation of K+/Cl--cotransporter 3 in tamoxifen resistant breast cancer cells

Expression of the zinc receptor, ZnR/GPR39, is increased in higher grade breast cancer tumors and cells. Zinc, its ligand, is accumulated at larger concentrations in the tumor tissue and can therefore activate ZnR/GPR39-dependent Ca²⁺ signaling leading to tumor progression. The K⁺/Cl^- co-transporters (KCC), activated by intracellular signaling, enhance breast cancer cell migration and invasion. We asked if ZnR/GPR39 enhances breast cancer cell malignancy by activating KCC. Activation of ZnR/GPR39 by Zn²⁺ upregulated K⁺/Cl^- co-transport activity, measured using NH₄⁺ as a surrogate to K⁺ while monitoring intracellular pH. Upregulation of NH₄⁺ transport was monitored in tamoxifen resistant cells with functional ZnR/GPR39-dependent Ca²⁺ signaling but not in MCF-7 cells lacking this response. The NH₄⁺ transport was Na⁺-independent, and we therefore focused on KCC family members. Silencing of KCC3, but not KCC4, expression abolished Zn²⁺-dependent K⁺/Cl^- co-transport, suggesting that KCC3 is mediating upregulated NH₄⁺ transport. The ZnR/GPR39-dependent KCC3 activation accelerated scratch closure rate, which was abolished by inhibiting KCC transport with [(DihydroIndenyl) Oxy] Alkanoic acid (DIOA). Importantly, silencing of either ZnR/GPR39 or KCC3 attenuated Zn²⁺-dependent scratch closure. Thus, a novel link between KCC3 and Zn²⁺, via ZnR/GPR39, promotes breast cancer cell migration and proliferation.

Zinc homeostasis and zinc signaling in white matter development and injury

Zinc is an essential dietary micronutrient that is abundant in the brain with diverse roles in development, injury, and neurological diseases. With new imaging tools and chelators selectively targeting zinc, the field of zinc biology is rapidly expanding. The importance of zinc homeostasis is now well recognized in neurodegeneration, but there is emerging data that zinc may be equally important in white matter disorders. This review provides an overview of zinc biology, including a discussion of clinical disorders of zinc deficiency, different zinc pools, zinc biomarkers, and methods for measuring zinc. It emphasizes our limited understanding of how zinc is regulated in oligodendrocytes and white matter. Gaps in knowledge about zinc transporters and zinc signaling are discussed. Zinc-induced oligodendrocyte injury pathways relevant to white matter stroke, multiple sclerosis, and white matter injury of prematurity are reviewed and examples of zinc-dependent proteins relevant to myelination highlighted. Finally, a novel ratiometric zinc sensor is reviewed, revealing new information about mobile zinc during oligodendrocyte differentiation. With a better understanding of zinc biology in oligodendrocytes, new therapeutic targets for white matter disorders may be possible and the necessary tools to appropriately study zinc are finally available.