Disrupted calcium homeostasis is involved in elevated zinc ion-induced photoreceptor cell death

From ferroptosis to cuproptosis, and calcicoptosis, to find more novel metals-mediated distinct form of regulated cell death

Regulated cell death (RCD), also known as programmed cell death (PCD), plays a critical role in various biological processes, such as tissue injury/repair, development, and homeostasis. Dysregulation of RCD pathways can lead to the development of many human diseases, such as cancer, neurodegenerative disorders, and cardiovascular diseases. Maintaining proper metal ion homeostasis is critical for human health. However, imbalances in metal levels within cells can result in cytotoxicity and cell death, leading to a variety of diseases and health problems. In recent years, new types of metal overload-induced cell death have been identified, including ferroptosis, cuproptosis, and calcicoptosis. This has prompted us to examine the three defined metal-dependent cell death types, and discuss other metals-induced ferroptosis, cuproptosis, and disrupted Ca2+ homeostasis, as well as the roles of Zn2+ in metals' homeostasis and related RCD. We have reviewed the connection between metals-induced RCD and various diseases, as well as the underlying mechanisms. We believe that further research in this area will lead to the discovery of novel types of metal-dependent RCD, a better understanding of the underlying mechanisms, and the development of new therapeutic strategies for human diseases.

Enhancing the growth of thermophilic Bacillus licheniformis YYC4 by low-intensity fixed-frequency continuous ultrasound

The effect of low-intensity fixed-frequency continuous ultrasound (LIFFCU) on the growth of Bacillus licheniformis YYC4 was investigated. The changes in morphology and activity of the organism, contributing to the growth were also explored. Compared with the control, a significant increase (48.95%) in the biomass of B. licheniformis YYC4 (at the logarithmic metaphase) was observed following the LIFFCU (28 kHz, 1.5 h and 120 W (equivalent to power density of 40 W/L)) treatment. SEM images showed that ultrasonication caused sonoporation, resulting in increased membrane permeability, evidenced by increase in cellular membrane potential, electrical conductivity of the culture, extracellular protein and nucleic acid, and intracellular Ca2+ content. Furthermore, LIFFCU action remarkably increased the extracellular protease activity, volatile components of the culture medium, microbial metabolic activity, and spore germination of the strain. Therefore, LIFFCU could be used to efficiently promote the growth of targeted microorganisms.

Bioimaging tools reveal copper processing in fish cells by mitophagy

As an essential trace metal, copper (Cu) regulation, distribution and detoxification among different cellular organelles remain much unknown. In the current study, bioimaging tool was used in visualizing the locations of Cu among different organelles in fish fin cells isolated from rabbitfish Siganus fuscescens. Exposure concentration of Cu directly affected the Cu bioaccumulation and toxicity. When the exposure dosage of Cu reached 100 µM, it began to damage the cells and affect the cell viability after 10 min of exposure. Remarkably, while various Cu concentrations (50∼150 µM) initially reduced the cell viability, they did not lead to a further loss in viability over extended exposure period. Upon entry to the cells, Cu was mainly targeted to the mitochondria whose number, size and network responded immediately to the incoming Cu. However, Cu toxicity did not increase time-dependently, strongly indicating that these mitochondria damaged by Cu could be removed and its cytotoxicity could be relieved. Bioimaging results showed that lysosomes interacted with the mitochondria, which were subsequently digested within a few minutes. Meanwhile the lysosomal number increased, and the size and pH of lysosomes decreased. These reactions were in line with the observed mitophagy, suggesting that mitochondrial Cu could be detoxified, and the damaged mitochondria were removed by lysosome via mitophagy. By further purifying the cellular organelles, the mitochondrial and lysosomal Cu amounts were quantified and found to be in line with the imaging results. The present study suggested that excessive mitochondrial Cu could be removed via mitophagy to relieve the Cu toxicity.

How fish cells responded to zinc challenges: Insights from bioimaging

Zinc ion (Zn) is an essential nutrition element and it is important to understand its regulation and distribution among different cellular organelles. Here, subcellular trafficking of Zn in rabbitfish fin cells was investigated through bioimaging, and the results showed that the toxicity and bioaccumulation of Zn were both dose- and time-dependent. Cytotoxicity of Zn only occurred when the Zn concentration reached 200-250 μM after 3 h of exposure when the cellular quota of Zn:P reached a threshold level around 0.7. Remarkably, the cells were able to maintain homeostasis at a low Zn exposure concentration or within the first 4-h exposure. Zn homeostasis was mainly regulated by the lysosomes which stored Zn within the short exposure period, during which the number and size of lysosomes as well as the lysozyme activity increased in response to incoming Zn. However, with increasing Zn concentration beyond a threshold concentration (> 200 μM) and an exposure time > 3 h, homeostasis was disrupted, leading to an Zn spillover to cytoplasm and other cellular organelles. At the same time, cell viability decreased due to the Zn damage on mitochondria which caused morphological changes (smaller and rounder dots) and over production of reactive oxygen species, indicating the dysfunction of mitochondria. By further purifying the cellular organelles, cell viability was found to be consistent with the mitochondrial Zn amount. This study suggested that the amount of mitochondrial Zn was an excellent predictor of Zn toxicity on fish cells.

Growth of ZIF-8 Nanoparticles In Situ on Graphene Oxide Nanosheets: A Multifunctional Nanoplatform for Combined Ion-Interference and Photothermal Therapy

The regulation of intracellular ions' overload to interrupt normal bioprocesses and cause cell death has been developed as an efficient strategy (named as ion-interference therapy/IIT) to treat cancer. In this study, we design a multifunctional nanoplatform (called BSArGO@ZIF-8 NSs) by in situ growth of metal organic framework nanoparticles (ZIF-8 NPs) onto the graphene oxide (GO) surface, subsequently reduced by ascorbic acid and modified by bovine serum albumin. This nanocomplex causes the intracellular overload of Zn²⁺, an increase of reactive oxygen species (ROS), and exerts a broad-spectrum lethality to different kinds of cancer cells. BSArGO@ZIF-8 NSs can promote cell apoptosis by initiating bim (a pro-apoptotic protein)-mediated mitochondrial apoptotic events, up-regulating PUMA/NOXA expression, and down-regulating the level of Bid/p53AIP1. Meanwhile, Zn²⁺ excess triggers cellular dysfunction and mitochondria damage by activating the autophagy signaling pathways and disturbing the intracellular environmental homeostasis. Combined with the photothermal effect of reduced GO (rGO), BSArGO@ZIF-8 NSs mediated ion-interference and photothermal combined therapy leads to effective apoptosis and inhibits cell proliferation and angiogenesis, bringing a higher efficacy in tumor suppression in vivo. This designed Zn-based multifunctional nanoplatform will allow promoting further the development of IIT and the corresponding combined cancer therapy strategy.

The role of metal ions in the Golgi apparatus

The Golgi apparatus is a membrane-bound organelle that functions as a central role in the secretory pathway. Since the discovery of the Golgi apparatus, its structure and function have attracted ever-increasing attention from researchers. Recently, it has been demonstrated that metal ions are necessary for the Golgi apparatus to maintain its proper structure and functions. Given that metal ions play an important role in various biological processes, their abnormal homeostasis is related to many diseases. Therefore, in this paper, we reviewed the uptake and release mechanisms of the Golgi apparatus Ca²⁺ , Cu, and Zn²⁺ . Furthermore, we describe the diseases associated with Golgi apparatus Ca²⁺ , Cu, and Zn²⁺ imbalance.

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.

Comparing the Influence of High Doses of Different Zinc Salts on Oxidative Stress and Energy Depletion in IPEC-J2 Cells

The current study aimed to investigate the influence of four supplemental zinc salts (chelated: Zn glycine; non-chelated: Zn sulfate, Zn citrate, Zn gluconate) among different zinc concentrations (30-300 μM) on cell proliferation, oxidative stress, and energy depletion in intestinal porcine jejunum epithelial cells (IPEC-J2). Different zinc salts affected cell viability in a time- and dose-dependent manner, which was mainly dependent on the uptake of intracellular Zn²⁺. Intracellular Zn²⁺ of Zn sulfate has taken up almost twice as high as Zn glycine when cells were loaded with 100-200 μM zinc. After loading cells with 300 μM zinc, Zn glycine and Zn sulfate had a similar trend in accumulation of Zn²⁺. When the intracellular Zn²⁺ overloads, cells will gradually be damaged and subsequently die bearing biochemical features of necrosis or late apoptosis. Meanwhile, obviously, increased levels of intracellular ROS, mitochondrial ROS, MDA, and NO and decreased levels of GSH were observed. Excessive intracellular Zn²⁺ significantly decreased mitochondria membrane potential accompanied by an obvious loss of ATP and NAD⁺ levels. Overall, exposure to high doses of zinc salts caused cell damage, which was mainly dependent on the uptake of Zn²⁺. Zinc overload induced oxidative stress and energy depletion in IPEC-J2 cells, and the cell damage with non-chelated zinc addition was more serious than Zn glycine.

Involvement of SAPK/JNK Signaling Pathway in Copper Enhanced Zinc-Induced Neuronal Cell Death

Zinc (Zn) plays an important role in many organisms in various physiological functions such as cell division, immune mechanisms and protein synthesis. However, excessive Zn release is induced in pathological situations and causes neuronal cell death. Previously, we reported that Cu ions (Cu2+) markedly exacerbates Zn2+-induced neuronal cell death by potentiating oxidative stress and the endoplasmic reticulum stress response. In contrast, the stress-activated protein kinase/c-Jun amino-terminal kinase (SAPK/JNK) signaling pathway is important in neuronal cell death. Thus, in this study, we focused on the SAPK/JNK signaling pathway and examined its involvement in Cu2+/Zn2+-induced neurotoxicity. Initially, we examined expression of factors involved in the SAPK/JNK signaling pathway. Accordingly, we found that phosphorylated (ie, active) forms of SAPK/JNK (p46 and p54) are increased by CuCl2 and ZnCl2 co-treatment in hypothalamic neuronal mouse cells (GT1-7 cells). Downstream factors of SAPK/JNK, phospho-c-Jun, and phospho-activating transcription factor 2 are also induced by CuCl2 and ZnCl2 co-treatment. Moreover, an inhibitor of the SAPK/JNK signaling pathway, SP600125, significantly suppressed neuronal cell death and activation of the SAPK/JNK signaling pathway induced by CuCl2 and ZnCl2 cotreatment. Finally, we examined involvement of oxidative stress in activation of the SAPK/JNK signaling pathway, and found that human serum albumin-thioredoxin fusion protein, an antioxidative protein, suppresses activation of the SAPK/JNK signaling pathway. On the basis of these results, our findings suggest that activation of ZnCl2-dependent SAPK/JNK signaling pathway is important in neuronal cell death, and CuCl2-induced oxidative stress triggers the activation of this pathway.

"Iron free" zinc oxide nanoparticles with ion-leaking properties disrupt intracellular ROS and iron homeostasis to induce ferroptosis

Exposure to nanomaterials (NMs) is an emerging threat to human health, and the understanding of their intracellular behavior and related toxic effects is urgently needed. Ferroptosis is a newly discovered, iron-mediated cell death that is distinctive from apoptosis or other cell-death pathways. No evidence currently exists for the effect of “iron free” engineered NMs on ferroptosis. We showed by several approaches that (1) zinc oxide nanoparticles (ZnO NPs)-induced cell death involves ferroptosis; (2) ZnO NPs-triggered ferroptosis is associated with elevation of reactive oxygen species (ROS) and lipid peroxidation, along with depletion of glutathione (GSH) and downregulation of glutathione peroxidase 4 (GPx4); (3) ZnO NPs disrupt intracellular iron homeostasis by orchestrating iron uptake, storage and export; (4) p53 largely participates in ZnO NPs-induced ferroptosis; and (5) ZnO particle remnants and dissolved zinc ion both contribute to ferroptosis. In conclusion, our data provide a new mechanistic rationale for ferroptosis as a novel cell-death phenotype induced by engineered NMs.

Research and Discussion on the Relationships between Noise-Induced Hearing Loss and ATP2B2 Gene Polymorphism

Long-term and continuous noise exposure can result in noise-induced hearing loss (NIHL), which is a worldwide problem resulting from the interaction of environmental and genetic factors. The ATP2B2 gene polymorphism can destroy cochlear hair cells and increase the risk of NIHL. A case-control study of 760 Chinese textile workers was conducted to investigate the relationship between ATP2B2 polymorphisms and NIHL susceptibility. Venous blood was collected and questionnaires were conducted by professional physicians. A case group and a control group which were typed by individuals' pure-tone audiometry test results were set. Three polymorphism sites of ATP2B2 were genotyped by using the PCR technique. Analysis results revealed that the C allele of rs3209637 (95%CI = 1.08-2.58, odds ratio (OR) = 1.67, P = 0.027) was a dangerous factor and could add to risks of NIHL in the Chinese employees. The data of stratified analysis revealed that individuals who are exposed to noise > 95 dB with the rs3209637 C genotype have a higher susceptibility to NIHL (OR = 1.34, 95%CI = 1.07-1.68). Multifactor dimensionality reduction analysis revealed that the interaction between rs14154 and rs3209637 is linked to increased NIHL risk, and for the interaction among rs14154, smoking and drinking had the same function (OR = 1.54 and 1.77, 95%CI = 1.15-2.07, 1.33-2.37, and P = 0.0037 and P < 0.0001, respectively). Our results suggest that genetic polymorphism rs3209637 C within ATP2B2 is a risk factor for NIHL among Chinese employees and rs3209637 C could be a potential biomarker for NIHL patients.

Diverse cellular actions of tert-butylhydroquinone, a food additive, on rat thymocytes

Tertiary butylhydroquinone (TBHQ) is a food additive that possesses antioxidant activity. Its alternative applications have been explored in recent studies. However, there is controversy regarding safety. In this study using rat thymocytes, the cellular actions of TBHQ at sublethal concentrations were examined. TBHQ at concentrations of 3 μM or more elevated intracellular Zn²⁺ concentration ([Zn²⁺]_i) in a dose-dependent manner, by increasing membrane Zn²⁺ permeability and releasing Zn²⁺ from cellular stores. TBHQ at 30 μM significantly increased side scatter (cell density) and the exposure of phosphatidylserine (PS) on cell membrane surfaces. It also decreased cellular glutathione (GSH) content without affecting cell lethality. Forward scatter was attenuated by 100 μM TBHQ. Thus, it is considered that TBHQ at sublethal concentrations (30 μM or less) exerts some adverse actions on cells. TBHQ at 10-30 μM attenuated the increase in cell lethality induced by hydrogen peroxide (H₂O₂), while potentiation of H₂O₂ cytotoxicity by 100 μM TBHQ was observed. The range of concentrations of TBHQ from benefit to toxicity under in vitro conditions may be 10-30 μM. Although TBHQ exhibits antioxidative actions at concentrations that are lower than those which elicit adverse cellular effects, sublethal levels of TBHQ cause some adverse actions that may be clinically concerned.

Ultrasonic irradiation of low intensity with a mode of sweeping frequency enhances the membrane permeability and cell growth rate of Candida tropicalis

Here we report the enhancement of both cellular permeability and cell growth rate of Candida tropicalis after treatment with the ultrasonic irradiation of low intensity using a mode of sweeping frequency (UILS) generated by a self-developed ultrasonic device in our lab. After the ultrasonic treatment, remarkable biomass enhancement of the yeast was observed; the hyphae became significantly longer; the seeped cellular protein and nucleic acid from the yeast increased and the cellular Ca²⁺ content became lower. Illumina transcriptome sequencing showed that the ultrasonic treatment affected the expression of genes involved in diverse cellular components, biological processes and molecular functions. RT-PCR and Western blotting further confirmed the up-/down-regulation of genes in the ultrasound-treated yeasts. The optimal conditions of the ultrasonic treatment for the maximum biomass addition were determined as follows: the yeast was treated for 1h at the mid logarithmic phase, the frequency was 28±2kHz and the power density was 120W/L. Under these conditions, the Candida tropicalis biomass increased by 142.5% compared with the untreated yeast.

Metal ions influx is a double edged sword for the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a common form of dementia in aged people, which is defined by two pathological characteristics: β-amyloid protein (Aβ) deposition and tau hyperphosphorylation. Although the mechanisms of AD development are still being debated, a series of evidence supports the idea that metals, such as copper, iron, zinc, magnesium and aluminium, are involved in the pathogenesis of the disease. In particular, the processes of Aβ deposition in senile plaques (SP) and the inclusion of phosphorylated tau in neurofibrillary tangles (NFTs) are markedly influenced by alterations in the homeostasis of the aforementioned metal ions. Moreover, the mechanisms of oxidative stress, synaptic plasticity, neurotoxicity, autophagy and apoptosis mediate the effects of metal ions-induced the aggregation state of Aβ and phosphorylated tau on AD development. More importantly, imbalance of these mechanisms finally caused cognitive decline in different experiment models. Collectively, reconstructing the signaling network that regulates AD progression by metal ions may provide novel insights for developing chelators specific for metal ions to combat AD.

Alzheimer's disease due to loss of function: A new synthesis of the available data

Alzheimer's Disease (AD) is a highly complex disease involving a broad range of clinical, cellular, and biochemical manifestations that are currently not understood in combination. This has led to many views of AD, e.g. the amyloid, tau, presenilin, oxidative stress, and metal hypotheses. The amyloid hypothesis has dominated the field with its assumption that buildup of pathogenic β-amyloid (Aβ) peptide causes disease. This paradigm has been criticized, yet most data suggest that Aβ plays a key role in the disease. Here, a new loss-of-function hypothesis is synthesized that accounts for the anomalies of the amyloid hypothesis, e.g. the curious pathogenicity of the Aβ42/Aβ40 ratio, the loss of Aβ caused by presenilin mutation, the mixed phenotypes of APP mutations, the poor clinical-biochemical correlations for genetic variant carriers, and the failure of Aβ reducing drugs. The amyloid-loss view accounts for recent findings on the structure and chemical features of Aβ variants and their coupling to human patient data. The lost normal function of APP/Aβ is argued to be metal transport across neuronal membranes, a view with no apparent anomalies and substantially more explanatory power than the gain-of-function amyloid hypothesis. In the loss-of-function scenario, the central event of Aβ aggregation is interpreted as a loss of soluble, functional monomer Aβ rather than toxic overload of oligomers. Accordingly, new research models and treatment strategies should focus on remediation of the functional amyloid balance, rather than strict containment of Aβ, which, for reasons rationalized in this review, has failed clinically.

The involvement of the mitochondrial pathway in manganese-induced apoptosis of chicken splenic lymphocytes

The purpose of this study was to investigate the effect of excess manganese (Mn)-induced cytotoxicity on apoptosis in chicken splenic lymphocytes. Chicken splenic lymphocytes were cultured in medium in the absence and presence of manganese (II) chloride (MnCl2) (2 × 10(-4), 4 × 10(-4), 6 × 10(-4), 8 × 10(-4), 10 × 10(-4), and 12 × 10(-4) mM), in N-acetyl-l-cysteine (NAC) (1 mM), and the combination of MnCl2 and NAC for 12, 24, 36, and 48 h. Tests were performed on morphologic observation, reactive oxygen species (ROS) and malondialdehyde (MDA) content, manganese superoxide dismutase (Mn-SOD) and glutathione peroxidase (GSH-Px) activities, B-cell lymphoma-2 (Bcl-2), Bcl-2 associated X protein (Bax), p53, and calmodulin (CaM) messenger RNA (mRNA) expression, Caspase-3 mRNA and protein expression, intracellular free Ca(2+) ([Ca(2+)]i), and mitochondrial transmembrane potential (ΔΨm). Our research indicated that excess Mn induced ROS and MDA content, inhibited Mn-SOD and GSH-Px activities, induced Bax and p53 mRNA expression, inhibited Bcl-2 and CaM mRNA expression, induced Caspase-3 mRNA and protein expression, upregulated [Ca(2+)]i, inhibited ΔΨm, and induced apoptosis in a dose effect. NAC relieved excess Mn-caused the changes of all above factors. Mn-induced oxidative injuries were alleviated by treatment with NAC, an ROS scavenger. The above results demonstrated that excess Mn caused oxidative stress and apoptosis via mitochondrial pathway in chicken splenic lymphocytes.

Mechanistic studies of the toxicity of zinc gluconate in the olfactory neuronal cell line Odora

Zinc is both an essential and potentially toxic metal. It is widely believed that oral zinc supplementation can reduce the effects of the common cold; however, there is strong clinical evidence that intranasal (IN) zinc gluconate (ZG) gel treatment for this purpose causes anosmia, or the loss of the sense of smell, in humans. Using the rat olfactory neuron cell line, Odora, we investigated the molecular mechanism by which zinc exposure exerts its toxic effects on olfactory neurons. Following treatment of Odora cells with 100 and 200μM ZG for 0-24h, RNA-seq and in silico analyses revealed up-regulation of pathways associated with zinc metal response, oxidative stress, and ATP production. We observed that Odora cells recovered from zinc-induced oxidative stress, but ATP depletion persisted with longer exposure to ZG. ZG exposure increased levels of NLRP3 and IL-1β protein levels in a time-dependent manner, suggesting that zinc exposure may cause an inflammasome-mediated cell death, pyroptosis, in olfactory neurons.

A prochelator peptide designed to use heterometallic cooperativity to enhance metal ion affinity

A peptide has been designed so that its chelating affinity for one type of metal ion regulates its affinity for a second, different type of metal ion. The prochelator peptide (PCP), which is a fusion of motifs evocative of calcium loops and zinc fingers, forms a 1 : 2 Zn : peptide complex at pH 7.4 that increases its affinity for Zn²⁺ ∼3-fold in the presence of Tb³⁺ (log β₂ from 13.8 to 14.3), while the 1 : 1 luminescent complex with Tb³⁺ is brighter, longer lived, and 20-fold tighter in the presence of Zn²⁺ (log K from 6.2 to 7.5). This unique example of cooperative, heterometallic allostery in a biologically compatible construct suggests the possibility of designing conditionally active metal-binding agents that could respond to dynamic changes in cellular metal status.