Copper induces histone hypoacetylation through directly inhibiting histone acetyltransferase activity

Harnessing nanomaterials for copper-induced cell death

Copper (Cu), an essential micronutrient with redox properties, plays a pivotal role in a wide array of pathological and physiological processes across virtually all cell types. Maintaining an optimal copper concentration is critical for cellular survival: insufficient copper levels disrupt respiration and metabolism, while excess copper compromises cell viability, potentially leading to cell death. Similarly, in the context of cancer, copper exhibits a dual role: appropriate amount of copper can promote tumor progression and be an accomplice, yet beyond befitting level, copper can bring about multiple types of cell death, including autophagy, apoptosis, ferroptosis, immunogenic cell death, pyroptosis, and cuproptosis. These forms of cell death are beneficial against cancer progression; however, achieving precise copper regulation within tumors remains a significant challenge in the pursuit of effective cancer therapies. The emergence of nanodrug delivery systems, distinguished by their precise targeting, controlled release, high payload capacity, and the ability to co-deliver multiple agents, has revitalized interest in exploiting copper's precise regulatory capabilities. Nevertheless, there remains a dearth of comprehensive review of copper's bidirectional effects on tumorigenesis and the role of copper-based nanomaterials in modulating tumor progression. This paper aims to address this gap by elucidating the complex role in cancer biology and highlighting its potential as a therapeutic target. Through an exploration of copper's dualistic nature and the application of nanotechnology, this review seeks to offer novel insights and guide future research in advancing cancer treatment.

From bioinformatics to clinical applications: a novel prognostic model of cuproptosis-related genes based on single-cell RNA sequencing data in hepatocellular carcinoma

OBJECTIVE AND METHODS

To ascertain the connection between cuproptosis-related genes (CRGs) and the prognosis of hepatocellular carcinoma (HCC) via single-cell RNA sequencing (scRNA-seq) and RNA sequencing (RNA-seq) data, relevant data were downloaded from the GEO and TCGA databases. The differentially expressed CRGs (DE-CRGs) were filtered by the overlaps in differentially expressed genes (DEGs) between HCC patients and normal controls (NCs) in the scRNA-seq database, DE-CRGs between high- and low-CRG-activity cells, and DEGs between HCC patients and NCs in the TCGA database.

RESULTS

Thirty-three DE-CRGs in HCC were identified. A prognostic model (PM) was created employing six survival-related genes (SRGs) (NDRG2, CYB5A, SOX4, MYC, TM4SF1, and IFI27) via univariate Cox regression analysis and LASSO. The predictive ability of the model was validated via a nomogram and receiver operating characteristic curves. Research has employed tumor immune dysfunction and exclusion as a means to examine the influence of PM on immunological heterogeneity. Macrophage M0 levels were significantly different between the high-risk group (HRG) and the low-risk group (LRG), and a greater macrophage level was linked to a more unfavorable prognosis. The drug sensitivity data indicated a substantial difference in the half-maximal drug-suppressive concentrations of idarubicin and rapamycin between the HRG and the LRG. The model was verified by employing public datasets and our cohort at both the protein and mRNA levels.

CONCLUSION

A PM using 6 SRGs (NDRG2, CYB5A, SOX4, MYC, TM4SF1, and IFI27) was developed via bioinformatics research. This model might provide a fresh perspective for assessing and managing HCC.

Molecular variations to the proteome of zebrafish larvae induced by environmentally relevant copper concentrations

Contaminants are increasingly accumulating in aquatic environments and biota, with potential adverse effects on individual organisms, communities and ecosystems. However, studies that explore the molecular changes in fish caused by environmentally relevant concentrations of metals, such as copper (Cu), are limited. This study uses embryos of the model organism zebrafish (Danio rerio) to investigate effect of Cu on the proteome and amino acid (AA) composition of fish. Wild-type embryos at 24 h post-fertilisation were exposed to Cu (2 µg L-1 to 120 µg L-1) for 96 h and the number of healthy larvae were determined based on larvae that had hatched and did not display loss of equilibrium (LOE). The effect concentrations where Cu caused a 10 % (EC10) or 50 % (EC50) decrease in the number of healthy larvae were calculated as 3.7 µg L-1 and 10.9 µg L-1, respectively. Proteomics analysis of embryos exposed to the EC10 and EC50 concentrations of Cu revealed the proteome to differ more strongly after 48 h than 96 h, suggesting the acclimatisation of some larvae. Exposure to excess Cu caused differentially expressed proteins (DEPs) involved in oxidative stress, mitochondrial respiration, and neural transduction as well as the modulation of the AAs (Proline, Glycine and Alanine). This is the first study to suggest that LOE displayed by Cu-stressed fish may involve the disruption to GABAergic proteins and the calcium-dependent inhibitory neurotransmitter GABA. Moreover, this study highlights that proteomics and AA analysis can be used to identify potential biomarkers for environmental monitoring.

Complexation of histone deacetylase inhibitor belinostat to Cu(II) prevents premature metabolic inactivation in vitro and demonstrates potent anti-cancer activity in vitro and ex vivo in colon cancer

PURPOSE

The histone deacetylase inhibitor (HDACi), belinostat, has had limited therapeutic impact in solid tumors, such as colon cancer, due to its poor metabolic stability. Here we evaluated a novel belinostat prodrug, copper-bis-belinostat (Cubisbel), in vitro and ex vivo, designed to overcome the pharmacokinetic challenges of belinostat.

METHODS

The in vitro metabolism of each HDACi was evaluated in human liver microsomes (HLMs) using mass spectrometry. Next, the effect of belinostat and Cubisbel on cell growth, HDAC activity, apoptosis and cell cycle was assessed in three colon cancer cell lines. Gene expression alterations induced by both HDACis were determined using RNA-Seq, followed by in silico analysis to identify master regulators (MRs) of differentially expressed genes (DEGs). The effect of both HDACis on the viability of colon cancer patient-derived tumor organoids (PDTOs) was also examined.

RESULTS

Belinostat and Cubisbel significantly reduced colon cancer cell growth mediated through HDAC inhibition and apoptosis induction. Interestingly, the in vitro half-life of Cubisbel was significantly longer than belinostat. Belinostat and its Cu derivative commonly dysregulated numerous signalling and metabolic pathways while genes downregulated by Cubisbel were potentially controlled by VEGFA, ERBB2 and DUSP2 MRs. Treatment of colon cancer PDTOs with the HDACis resulted in a significant reduction in cell viability and downregulation of stem cell and proliferation markers.

CONCLUSIONS

Complexation of belinostat to Cu(II) does not alter the HDAC activity of belinostat, but instead significantly enhances its metabolic stability in vitro and targets anti-cancer pathways by perturbing key MRs in colon cancer. Complexation of HDACis to a metal ion might improve the efficacy of clinically used HDACis in patients with colon cancer.

The Tao of Copper Metabolism: From Physiology to Pathology

As a transitional metal, copper plays a crucial role in maintaining the normal physiological activities of mammals. The intracellular copper concentration is meticulously regulated to maintain extremely low levels through homeostatic regulation. Excessive accumulation of free copper in cells can have deleterious effects, as observed in conditions such as Wilson's disease. Moreover, data accumulated over the past few decades have revealed a crucial role of copper imbalance in tumorigenesis, progression and metastasis. Recently, cuproptosis, also known as copper-induced cell death, has been proposed as a novel form of cell death. This discovery offers new prospects for treating copperrelated diseases and provides a promising avenue for developing copper-responsive therapies, particularly in cancer treatment. We present a comprehensive overview of the Yin- Yang equilibrium in copper metabolism, particularly emphasising its pathophysiological alterations and their relevance to copper-related diseases and malignancies.

Copper in Cancer: from transition metal to potential target

In recent years, with the continuous in-depth exploration of the molecular mechanisms of tumorigenesis, numerous potential new targets for cancer treatment have been identified, some of which have been further developed in clinical practice and have produced positive outcomes. Notably, researchers' initial motivation for studying copper metabolism in cancer stems from the fact that copper is a necessary trace element for organisms and is closely connected to body growth and metabolism. Moreover, over the past few decades, considerable progress has been made in understanding the molecular processes and correlations between copper and cancer. Certain achievements have been made in the development and use of relevant clinical medications. The concept of "cuproptosis," a novel concept that differs from previous forms of cell death, was first proposed by a group of scientists last year, offering fresh perspectives on the targeting capabilities of copper in the treatment of cancer. In this review, we introduced the fundamental physiological functions of copper, the key components of copper metabolism, and a summary of the current research contributions on the connection between copper and cancer. In addition, the development of new copper-based nanomaterials and their associated mechanisms of action are discussed. Finally, we described how the susceptibility of cancer cells to this metallic nutrition could be leveraged to further improve the existing cancer treatment paradigm in the new setting.

Cuproptosis: Harnessing Transition Metal for Cancer Therapy

Transition metal elements, such as copper, play diverse and pivotal roles in oncology. They act as constituents of metalloenzymes involved in cellular metabolism, function as signaling molecules to regulate the proliferation and metastasis of tumors, and are integral components of metal-based anticancer drugs. Notably, recent research reveals that excessive copper can also modulate the occurrence of programmed cell death (PCD), known as cuprotosis, in cancer cells. This modulation occurs through the disruption of tumor cell metabolism and the induction of proteotoxic stress. This discovery uncovers a mode of interaction between transition metals and proteins, emphasizing the intricate link between copper homeostasis and tumor metabolism. Moreover, they provide innovative therapeutic strategies for the precise diagnosis and treatment of malignant tumors. At the crossroads of chemistry and oncology, we undertake a comprehensive review of copper homeostasis in tumors, elucidating the molecular mechanisms underpinning cuproptosis. Additionally, we summarize current nanotherapeutic approaches that target cuproptosis and provide an overview of the available laboratory and clinical methods for monitoring this process. In the context of emerging concepts, challenges, and opportunities, we emphasize the significant potential of nanotechnology in the advancement of this field.

Cope with copper: From copper linked mechanisms to copper-based clinical cancer therapies

Recent studies have established a strong link between copper and cancer biology, as copper is necessary for cancer growth and metastasis. Beyond the conventional concept of copper serving as a catalytic cofactor of metalloenzymes, emerging evidence demonstrates copper as a regulator for signaling transduction and gene expression, which are vital for tumorigenesis and cancer progression. Interestingly, strong redox-active properties make copper both beneficial and detrimental to cancer cells. Cuproplasia is copper-dependent cell growth and proliferation, whereas cuproptosis is copper-dependent cell death. Both mechanisms act in cancer cells, suggesting that copper depletion and copper supplementation may be viable approaches for developing novel anticancer therapies. In this review, we summarized the current understanding of copper's biological role and related molecular mechanisms in cancer proliferation, angiogenesis, metastasis, autophagy, immunosuppressive microenvironment development, and copper-mediated cancer cell death. We also highlighted copper-based strategies for cancer treatment. The current challenges of copper in cancer biology and therapy and their potential solutions were also discussed. Further investigation in this field will yield a more comprehensive molecular explanation for the causal relationship between copper and cancers. It will reveal a series of key regulators governing copper-dependent signaling pathways, thereby providing potential targets for developing copper-related anticancer drugs.

Emerging roles of the copper-CTR1 axis in tumorigenesis

Physiological roles of copper in metabolic homeostasis have been well established, however, whether and how copper is dysregulated in tumors and contributes to tumorigenesis are not recapitulated. Here, we comprehensively summarize the potential origins of copper accumulation in diseases especially in cancers by dysregulating copper transporter 1 (CTR1) or ATPase copper transporting alpha/beta (ATP7A/B) and further demonstrate the underlying mechanism of copper contributing to tumorigenesis. Specifically, in addition to modulating reactive oxygen species (ROS), angiogenesis, immune response, and metabolic homeostasis, copper recently has drawn more attention by directly binding to oncoproteins such as MEK, ULK, Memo, and PDK1 to activate distinct oncogenic signals and account for tumorigenesis. In the end, we disclose the emerging applications of copper in cancer diagnosis and highlight the promising strategies to target the copper-CTR1 axis for cancer therapies.

Connecting copper and cancer: from transition metal signalling to metalloplasia

Copper is an essential nutrient whose redox properties make it both beneficial and toxic to the cell. Recent progress in studying transition metal signalling has forged new links between researchers of different disciplines that can help translate basic research in the chemistry and biology of copper into clinical therapies and diagnostics to exploit copper-dependent disease vulnerabilities. This concept is particularly relevant in cancer, as tumour growth and metastasis have a heightened requirement for this metal nutrient. Indeed, the traditional view of copper as solely an active site metabolic cofactor has been challenged by emerging evidence that copper is also a dynamic signalling metal and metalloallosteric regulator, such as for copper-dependent phosphodiesterase 3B (PDE3B) in lipolysis, mitogen-activated protein kinase kinase 1 (MEK1) and MEK2 in cell growth and proliferation and the kinases ULK1 and ULK2 in autophagy. In this Perspective, we summarize our current understanding of the connection between copper and cancer and explore how challenges in the field could be addressed by using the framework of cuproplasia, which is defined as regulated copper-dependent cell proliferation and is a representative example of a broad range of metalloplasias. Cuproplasia is linked to a diverse array of cellular processes, including mitochondrial respiration, antioxidant defence, redox signalling, kinase signalling, autophagy and protein quality control. Identifying and characterizing new modes of copper-dependent signalling offers translational opportunities that leverage disease vulnerabilities to this metal nutrient.

Effect of Environmental Stressors, Xenobiotics, and Oxidative Stress on Male Reproductive and Sexual Health

This article examines the environmental factor-induced oxidative stress (OS) and their effects on male reproductive and sexual health. There are several factors that induce OS, i.e. radition, metal contamination, xenobiotic compounds, and cigarette smoke and lead to cause toxicity in the cells through metabolic or bioenergetic processes. These environmental factors may produce free radicals and enhance the reactive oxygen species (ROS). Free radicals are molecules that include oxygen and disbalance the amount of electrons that can create major chemical chains in the body and cause oxidation. Oxidative damage to cells may impair male fertility and lead to abnormal embryonic development. Moreover, it does not only cause a vast number of health issues such as ageing, cancer, atherosclerosis, insulin resistance, diabetes mellitus, cardiovascular diseases, ischemia-reperfusion injury, and neurodegenerative disorders but also decreases the motility of spermatozoa while increasing sperm DNA damage, impairing sperm mitochondrial membrane lipids and protein kinases. This chapter mainly focuses on the environmental stressors with further discussion on the mechanisms causing congenital impairments due to poor sexual health and transmitting altered signal transduction pathways in male gonadal tissues.

Influence of the Bioactive Diet Components on the Gene Expression Regulation

Diet bioactive components, in the concept of nutrigenetics and nutrigenomics, consist of food constituents, which can transfer information from the external environment and influence gene expression in the cell and thus the function of the whole organism. It is crucial to regard food not only as the source of energy and basic nutriments, crucial for living and organism development, but also as the factor influencing health/disease, biochemical mechanisms, and activation of biochemical pathways. Bioactive components of the diet regulate gene expression through changes in the chromatin structure (including DNA methylation and histone modification), non-coding RNA, activation of transcription factors by signalling cascades, or direct ligand binding to the nuclear receptors. Analysis of interactions between diet components and human genome structure and gene activity is a modern approach that will help to better understand these relations and will allow designing dietary guidances, which can help maintain good health.

Copper: An Intracellular Achilles' Heel Allowing the Targeting of Epigenetics, Kinase Pathways, and Cell Metabolism in Cancer Therapeutics

Copper is an essential transition metal frequently increased in cancer known to strongly influence essential cellular processes. Targeted therapy protocols utilizing both novel and repurposed drug agents initially demonstrate strong efficacy, before failing in advanced cancers as drug resistance develops and relapse occurs. Overcoming this limitation involves the development of strategies and protocols aimed at a wider targeting of the underlying molecular changes. Receptor Tyrosine Kinase signaling pathways, epigenetic mechanisms and cell metabolism are among the most common therapeutic targets, with molecular investigations increasingly demonstrating the strong influence each mechanism exerts on the others. Interestingly, all these mechanisms can be influenced by intracellular copper. We propose that copper chelating agents, already in clinical trial for multiple cancers, may simultaneously target these mechanisms across a wide variety of cancers, serving as an excellent candidate for targeted combination therapy. This review summarizes the known links between these mechanisms, copper, and copper chelation therapy.

Proteomic characterization of the hepatopancreas in the Pacific white shrimp Litopenaeus vannamei under cold stress: Revealing the organism homeostasis mechanism

To understand the homeostasis mechanism of crustacean hepatopancreas to cold stress, iTRAQ proteomics based on the genome database of Litopenaeus vannamei (L. vannamei) was applied to investigate proteins changes and variety of the hepatopancreas during cold stress stage in this study. A total of 4062 distinct proteins were identified, 137 differentially expressed proteins (DEPs) including 62 differentially up-regulated proteins (DUPs) and 75 differentially down-regulated proteins (DDPs) were identified in G1 (18 °C) compared with CK (28 °C), 359 DEPs including 131 DUPs and 228 DDPs were identified in G2 (13 °C for 24 h) compared with CK. Based on bioinformatics analysis, the cold tolerance of L. vannamei might be related to energy metabolism such as amino acid, carbohydrate, lipid, and oxidative phosphorylation. Moreover, shrimp immunity was declined during cold stress stage. However, L. vannamei could cope with cold stress by enhancing the production of ATP and UFA. Notably, arginine kinase, heat shock proteins, and histones may act as positive regulators in L. vannamei under cold stress. Ten randomly selected proteins were used for validation using qRT-PCR and the expressions on the transcription level for most of the genes were similar to the results of iTRAQ. These results indicated that L. vannamei can maintain the organism homeostasis by a series of orderly regulatory process during cold stress. Furthermore, the results can provide guidance for shrimp farming.

Manganese chloride induces histone acetylation changes in neuronal cells: Its role in manganese-induced damage

Manganese neurotoxicity presents with Parkinson-like symptoms, with degeneration of dopaminergic neurons in the basal ganglia as the principal pathological feature. Manganese neurotoxicity studies may contribute to a better understanding of the mechanism of Parkinson's disease. Here, we examined the effects of manganese on histone acetylation, a major epigenetic change in chromatin that can regulate gene expression, chromatin remodelling, cell cycle progression, DNA repair and apoptosis. In this study, we found that manganese chloride (MnCl₂) may significantly suppress the acetylation of histone H3 and H4 in PC12 cells and SHSY5Y cells in a time-dependent manner. Then we tested the role of manganese chloride on histone acetyltransferase (HAT) and histone deacetylase (HDAC). The results showed that MnCl₂ increased the activity of HDAC but decreased that of HAT in PC12 cells. Further experiments showed that MnCl₂ selectively increased the expression levels of HDAC3 and HDAC4 rather than HDAC1 and HDAC2, but decreased that of HAT in PC12 cells and SHSY5Y cells. Pretreatment with the HAT inhibitor anacardic acid (AA) enhanced manganese-induced decrease in cell viability and apoptosis, but HDAC inhibition by TSA drug had an opposite effect in PC12 cells. Collectively, MnCl₂ inhibited the acetylation of core histones in cell culture models of PD, and that inhibition of HDAC activity by TSA protects against manganese-induced cell death, indicating that histone acetylation may represent key epigenetic changes in manganese-induced dopaminergic neurotoxicity.

Metal-mediated Epigenetic Regulation of Gene Expression

Epigenetics is the study of heritable changes in gene expression that occur without alterations in the DNA sequence. Several studies have shown that environmental chemicals can alter epigenetic modifications, including histone modifications and DNA methylation. Environmental chemicals may show toxic effects via epigenetic mechanism-regulated changes in gene expression. Previously, we reported that zinc treatment rapidly decreased Lys(4)-trimethylated and Lys(9)-acetylated histone H3 in the metallothionein (MT) promoter, and also decreased total histone H3. The chromatin structure in the MT promoter may be locally disrupted by zinc-induced nucleosome removal. We also showed that chromium (VI) inhibited MT gene transcription by modifying the transcription potential of the co-activator p300. MT is a small cysteine-rich protein that is active in zinc homeostasis, cadmium detoxification, and protection against reactive oxygen species. Epigenetic changes might influence the cytoprotective function of the MT gene. In this review, I briefly summarize the results of previous studies and discuss the mechanisms and toxicological significance of metal-mediated epigenetic modifications.

Chronic MeHg exposure modifies the histone H3K4me3 epigenetic landscape in Caenorhabditis elegans

Methylmercury (MeHg) is a persistent environmental pollutant that occurs in the food chain, at occupational sites, and via medical procedures. Exposure in humans and animal models results in renal, neuro, and reproductive toxicities. In this study, we demonstrate that chronic exposure to MeHg (10μM) causes epigenetic landscape modifications of histone H3K4 trimethylation (H3K4me3) marks in Caenorhabditis elegans using chromatin immuno-precipitation sequencing (ChIP-seq). The modifications correspond to the locations of 1467 genes with enhanced and 508 genes with reduced signals. Among enhanced genes are those encoding glutathione-S-transferases, lipocalin-related protein and a cuticular collagen. ChIP-seq enhancement of these genes was confirmed with increased mRNA expression levels revealed by qRT-PCR. Furthermore, we observed enhancement of H3K4me3 marks in these genes in animals exposed to MeHg in utero and assayed at L4 stage. In utero exposure enhanced marks without alterations in mRNA expression except for the lpr-5 gene. Finally, knockdown of lipocalin-related protein gene lpr-5, which is involved in intercellular signaling, and cuticular collagen gene dpy-7, structural component of the cuticle, by RNA interference (RNAi) resulted in increased lethality of animals after MeHg exposure. Our results provide new data on the epigenetic landscape changes elicited by MeHg exposure, as well as describe a unique model for studying in utero effects of heavy metals. Together, these findings may help to understand the toxicological effects of MeHg at the molecular level.

Influence of toxicologically relevant metals on human epigenetic regulation

Environmental toxicants such as toxic metals can alter epigenetic regulatory features such as DNA methylation, histone modification, and non-coding RNA expression. Heavy metals influence gene expression by epigenetic mechanisms and by directly binding to various metal response elements in the target gene promoters. Given the role of epigenetic alterations in regulating genes, there is potential for the integration of toxic metal-induced epigenetic alterations as informative factors in the risk assessment process. Here, we focus on recent advances in understanding epigenetic changes, gene expression, and biological effects induced by toxic metals.

Alterations in the endometrium of rats, rabbits, and Macaca mulatta that received an implantation of copper/low-density polyethylene nanocomposite

A copper/low-density polyethylene nanocomposite (nano-Cu/LDPE), a potential intrauterine device component material, has been developed from our research. A logical extension of our previous work, this study was conducted to investigate the expression of plasminogen activator inhibitor 1 (PAI-1), substance P (SP), and substance P receptor (SP-R) in the endometrium of Sprague Dawley rats, New Zealand White rabbits, and Macaca mulatta implanted with nano-Cu/LDPE composite. The influence of the nano-Cu/LDPE composite on the morphology of the endometrium was also investigated. Animals were randomly divided into five groups: the sham-operated control group (SO group), bulk copper group (Cu group), LDPE group, and nano-Cu/LDPE groups I and II. An expression of PAI-1, SP, and SP-R in the endometrial tissues was examined by immunohistochemistry at day 30, 60, 90, and 180 postimplantation. The significant difference for PAI-1, SP, and SP-R between the nano-Cu/LDPE groups and the SO group (P<0.05) was identified when the observation period was terminated, and the changes of nano-Cu/LDPE on these parameters were less remarkable than those of the Cu group (P<0.05). The damage to the endometrial morphology caused by the nano-Cu/LDPE composite was much less than that caused by bulk copper. The nano-Cu/LDPE composite might be a potential substitute for conventional materials for intrauterine devices in the future because of its decreased adverse effects on the endometrial microenvironment.

Histone deacetylases enzyme, copper, and IL-8 levels in patients with Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive loss of cognitive abilities. Epigenetic modification, oxidative stress, and inflammation play an important role in the pathogenesis of the disease. We aimed to detect noninvasive peripheral biomarkers with a high degree of sensitivity and specificity in diagnosis and progression of AD.

METHODS

A total of 25 elderly patients with AD and 25 healthy control participants were selected and subjected to cognitive assessment and laboratory measures including histone deacetylases (HDACs), copper, and interleukin 8 (IL-8) levels.

RESULTS

The levels of HDACs, copper, and IL-8 were significantly higher in patients with AD (P < .001) and had a significant negative effect on all cognitive assessment tests. Receiver-operating curve (ROC) analysis revealed that HDACs and copper levels had higher sensitivity and specificity.

CONCLUSIONS

Plasma levels of HDACs and copper may be used as peripheral biomarkers in diagnosis of AD, while IL-8 level could be a useful biomarker in following AD progression.

Zinc therapy improves deleterious effects of chronic copper administration on mice testes: histopathological evaluation

This study was set to investigate whether the adverse effects of long-term copper (Cu) consumption on testicular tissue could be prevented by zinc (Zn) administration. Forty-five mature male mice were randomly divided into one control and two treatment groups. The first treatment group received copper sulphate (Cu experimental group). The second treatment group was given combined treatment of copper sulphate and zinc sulphate (ZC experimental group). Control animals received normal saline using the same volume. Five mice from each group were sacrificed on day 14, 28 and 56 from the beginning of treatments. Left testes were removed for histopathological and histomorphometrical evaluations. Morphometrically, the diameter of seminiferous tubules and Sertoli cell nuclei, epithelial height, meiotic index and the percentage of spermatogenesis in Cu groups showed significant decrease compared to those of the control groups (P < 0.05). A partial improvement was seen in the percentage of spermatogenesis and meiotic index (P < 0.05) in ZC groups, whereas a complete recovery was observed in the rest of parameters in ZC group after 56 days compared to the control group (P > 0.05). Results showed that long-term administration of Cu leads to histological impairments of testis and zinc supplementation might offset these damaging effects.

Ultrastructural and morphometrical changes of mice ovaries following experimentally induced copper poisoning

BACKGROUND

Copper (Cu) is an essential trace element involved in normal reproduction but its overexposure may produce some detrimental effects. The aim of this study was to investigate the effects of copper sulfate poisoning on morphometery of mice ovarian structures and probable intracellular changes.

METHODS

Thirty mature female mice were randomly allocated to control and two treatment groups. In treatment groups, two different doses of copper sulfate including 100 mg/kg and 200 mg/kg in 0.2 cc were applied once a day for 35 consecutive days by gavage. Control animals received normal saline using the same volume and similar method. Animals from each experimental group were sacrificed 14 and 35 days after the beginning of drug administration and the left ovaries were removed for stereological evaluations by light microscopy and right ovaries were obtained for preparing electron microscopic sections.

RESULTS

The morphometrical results showed that only the number of antral follicles was decreased by 100 mg/kg copper sulfate on day 14 compared to the control group (P=0.043). Hence, higher copper dose or longer consumption period significantly reduced different classes of follicles and corpora lutea. With 100 mg/kg copper sulfate some mild ultrastructural cell damages such as decrease of zona pellucida thickness, limited vacuolated areas and nuclear envelop dilation were seen on day 14. Higher or longer Cu administration produced more detrimental effects including more vacuolated areas, presence of secondary lysosomes, irregularity in cell shape and segmented nuclei with condensed and marginated chromatin and more enlarged and damaged mitochondria.

CONCLUSION

New evidences of early as well as late intracellular damages of copper has been presented by accurate stereological and ultrastructural methods. Antral follicles was the most susceptible cells with the lower and shorter copper consumption and long term or higher dose of copper affected the whole of ovarian structures.

In vitro cytotoxicity, DNA cleavage and SOD-mimic activity of copper(II) mixed-ligand quinolinonato complexes

Six mixed-ligand copper(II) complexes with the composition [Cu(qui)(L)]BF(4)·xH(2)O (1-6), where Hqui=2-phenyl-3-hydroxy-4(1H)-quinolinone, L=2,2'-bipyridine (bpy) (1), 1,10-phenanthroline (phen) (2), bis(2-pyridyl)amine (ambpy) (3), 5-methyl-1,10-phenanthroline (mphen) (4), 5-nitro-1,10-phenanthroline (nphen) (5) and bathophenanthroline (bphen) (6), were prepared, fully characterized and studied for their in vitro cytotoxicity on human osteosarcoma (HOS) and human breast adenocarcinoma (MCF7) cancer cell lines. The overall promising results of the cytotoxicity were found for all the complexes, while the best results were achieved for complex 6, with IC(50)=2.6 ± 0.8 μM (HOS), and 1.3 ± 0.5 μM (MCF7). The interactions of the Cu(II) complexes 1-6 with calf thymus DNA were investigated by the UV-visible spectral titration. An agarose-gel electrophoretic method of oxidative damage determination to circular plasmid pUC19 was used to assess the ability of the complexes to act as chemical nucleases. A high effectiveness of DNA cleavage was observed for 2, 4 and 5. In vitro antioxidative activity of the complexes was studied by the superoxide dismutase-mimic (SOD-mimic) method. The best result was afforded by complex 1 with IC(50)=4.7 ± 1.0 μM, which corresponds to 10.2% of the native Cu,Zn-SOD enzyme activity. The ability of the tested complexes to interact with sulfur-containing biomolecules (cysteine and reduced glutathione) at physiological levels was proved by electrospray-ionization mass spectrometry (ESI-MS).

Physiological and toxicological transcriptome changes in HepG2 cells exposed to copper

Copper is an essential trace element; however, at supraphysiological levels, it can be extremely toxic. Microarray data from HepG2 cells exposed to 100, 200, 400, and 600 microM copper for 4, 8, 12 and 24 h were generated and analyzed. Principal components, K-means, and hierarchical clustering, interactome, and pathway mapping analyses indicated that these exposure conditions induce physiological and toxicological changes in the HepG2 transcriptome. As a general trend, when the level of toxicity increases, the number and diversity of affected genes, Gene Ontology categories, regulatory pathways, and complexity of interactomes increase. Physiological responses to copper include transition metal ion binding and responses to stress/stimulus, whereas toxicological responses include apoptosis, morphogenesis, and negative regulation of biomolecule metabolism. The global gene expression profile was overlaid onto biomolecular interaction networks and signal transduction cascades using pathway mapping and interactome identification. This analysis indicated that copper modulates signal transduction pathways associated with MAPK, NF-kappaB, death receptor, IGF-I, hypoxia, IL-10, IL-2, IL-6, EGF, Toll-like receptor, protein ubiquitination, xenobiotic metabolism, leukocyte extravasation, complement and coagulation, and sonic hedgehog signaling. These results provide insights into the global and molecular mechanisms regulating the physiological and toxicological responses to metal exposure.

Copper modulates the differentiation of mouse hematopoietic progenitor cells in culture

Copper chelation has been shown to favor the expansion of human hematopoietic stem/progenitor cells in vitro. To further understand the effects of copper modulation on defined subsets of stem cells versus progenitor cells, we extended the studies in a mouse system. We isolated mouse hematopoietic stem cells (HSCs) or hematopoietic progenitor cells (HPCs) and cultured them with or without the copper chelator tetraethylenepentamine (TEPA) or CuCl(2). Cytokine-stimulated HPC cultures treated with TEPA for 7 days generated about two to three times more total and erythroid colony-forming cells (CFCs) compared to control cultures. In contrast, CuCl(2) treatment decreased the CFC numbers. Similar results were seen with HSC after 14, but not 7, days of culture. Transplant studies showed that HPCs cultured for 7 days in TEPA had about twofold higher short-term erythroid repopulation potential compared to control cultures, while CuCl(2) decreased the erythroid potential of cultured HPCs compared to control cultures. HSCs cultured with TEPA for 7 days did not exhibit significantly higher repopulation potential in either leukocyte or erythrocyte lineages compared to control cultures in short-term or long-term assays. Based on JC-1 staining, the mitochondrial membrane potential of HPCs cultured with TEPA was lower relative to control cultures. Our data suggest that decreasing the cellular copper content with TEPA results in preferential expansion or maintenance of HPC that are biased for erythroid differentiation in vivo, but does not enhance the maintenance of HSC activity in culture.

Dietary manipulation of histone structure and function

Post-translational modifications of histones are the subject of intensive investigations with the aim of decoding how they regulate, alone or in combination, chromatin structure, genomic stability, and gene expression. Major epigenetic programming events take place during gametogenesis and fetal development and are thought to have long-lasting consequences on adult health. Epidemiological and experimental studies have pointed toward maternal nutrition as a major player during prenatal development in influencing disease susceptibility later in life. Although the mechanisms underlying such observations are not well elucidated, epigenetic alterations of histones by particular maternal diets might be of central importance. Moreover, as much as dietary sources can influence epigenetic programming during pregnancy, they have started to be implicated in cancer chemoprevention, via the targeting of reversible epigenetic deregulations at the level of the histones.

Chelatable cellular copper modulates differentiation and self-renewal of cord blood-derived hematopoietic progenitor cells

OBJECTIVES

We have demonstrated epigenetic modulation of CD34(+) cell differentiation by the high-affinity copper (Cu) chelator tetraethylenepentamine (TEPA). TEPA slowed down the rate of CD34(+) cell differentiation and increased their engraftability in SCID mice. TEPA biological activity was attributed to its effect on cellular Cu levels as (a) treatment with TEPA resulted in reduction of cellular Cu, and (b) excess of Cu reversed TEPA's activity and accelerated differentiation. In the present study we further evaluated the role of cellular Cu in TEPA's biological activity.

METHODS

The effects of Cu-chloride, TEPA, TEPA/Cu mixtures at various ratios, and a synthesized, stable, TEPA-Cu complex on short- and long-term cord blood-derived CD34(+) cell cultures as well as on the overall and chelatable cellular Cu were investigated.

RESULTS

Addition of TEPA, TEPA/Cu mixtures at up to equimolar concentrations, and the TEPA-Cu complex to CD34(+) cell cultures resulted in inhibition of differentiation and enhancement of long-term self-renewal. Measurement of the overall cellular Cu by atomic absorption spectrophotometry showed 20 to 40% decrease by TEPA while the TEPA-Cu mixture and the TEPA-Cu complex increased cellular Cu by 10- to 20-fold, as did CuCl(2). However, measurement of the cellular pool of labile Cu showed similar reduction (50% from the control) by all the TEPA forms, while CuCl(2) increased it. Thus, inhibition of differentiation and enhancement of self-renewal of CD34(+) cells was correlated with reduction in the cellular chelatable Cu content.

CONCLUSION

The results suggest that decreasing of the chelatable Cu pool, rather than overall Cu, is the mechanism that stands behind TEPA's biological activity.

Oxidative stress is involved in inhibition of copper on histone acetylation in cells

Our previous study demonstrates that copper induces histone hypoacetylation by inhibiting histone acetyltransferase (HAT) activity. However, it lacks direct evidences whether copper-inhibited histone acetylation right contributes to the toxicity of copper. Exposure of human leukemia cells (HL-60) to Cu2+ resulted in cell proliferation arrest and a concentration- and time-dependent decrease of histone acetylation. At the same time, Cu2+-induced significant increase of H2O2 and O2.- generation via a concentration- and time-dependent manner too. The histone acetylation was efficiently suppressed by exogenous H2O2, and enhanced by superoxide dismutase (the scavenger of O2.-), catalase (the scavenger of H2O2) or the combination of both, indicating that Cu2+ at least partially inhibited histone acetylation through triggering oxidative stress. Further studies found that sodium butyrate, the inhibitor of histone deacetylase (HDAC), which had no obvious effect on oxidative stress but increased histone acetylation at the concentration of 50 microM, attenuated Cu2+-inhibited cell proliferation, indicating that histone acetylation inhibition is simultaneously involved in the cytotoxicity of Cu2+. Considering the important role of histone acetylation in gene transcription and regulation of cell fate, the present study may open a new door to further understand the mechanism of Cu2+-induced toxicity.

Histone hypoacetylation is involved in 1,10-phenanthroline?Cu2+-induced human hepatoma cell apoptosis

The 1,10-orthophenanthroline (OP)-Cu(2+) combination, one generally used reactive oxygen species (ROS) generation system, is known to induce cell apoptosis, but the mechanism of ROS generation in this process remains unclear. Here we found that in the presence of 5 microM Cu(2+), OP inhibited histone acetyltransferase (HAT) activity, resulting in decreased acetylation in both histone H3 and H4. This inhibition of histone acetylation and HAT activity was significantly attenuated by preventing or scavenging ROS generation with the Cu(2+) chelator of bathocuproine disulfonate, or the antioxidants of N-acetyl-cysteine and mannitol, respectively, indicating the involvement of ROS generation in OP-Cu(2+) -induced histone hypoacetylation. At the same time, this ROS generation is found to be involved in OP-Cu(2+) -induced apoptosis in human hepatoma Hep3B cells. The important role of histone hypoacetylation in the induction of apoptosis was also proven by the marked diminution of apoptosis by 100 nM trichostatin A, a specific inhibitor of histone deacetylase, or the overexpression of p300, an HAT protein. Collectively, these observations suggest that histone hypoacetylation represents one unrevealed mechanism involved in the in vivo function of OP-Cu(2+) -generated ROS, at least in their induction of cell apoptosis.