Ctr1 and its role in body copper homeostasis

Investigation of the concentration and isotopic composition of Cu, Fe and Zn in human biofluids in the context of Alzheimer's disease via tandem and multi-collector inductively coupled plasma-mass spectrometry

Studies on essential trace elements in the context of Alzheimer's disease (AD) concluded that Cu, Fe and Zn interact with amyloid-β, accelerating plaque formation in the brain. Additionally, Cu and Fe in the vicinity of plaques produce reactive oxygen species (ROS) resulting in oxidative stress, whereas Zn plays a role in the antioxidant defence as a co-factor for antioxidants. In this work, the Cu, Fe and Zn concentrations and isotope ratios were determined in whole blood, blood serum and cerebrospinal fluid of 10 patients diagnosed with AD and 8 control individuals, using tandem (ICP-MS/MS) and multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS), respectively. In whole blood and blood serum of AD patients, a heavier Cu isotopic composition was observed (significant for whole blood only) compared to controls. Albumin levels in cerebrospinal fluid tend to increase with age, which could indicate an increased leakiness of the blood-brain barrier. In cerebrospinal fluid, a large variability was observed for the Cu and Fe isotope ratios, potentially resulting from that leakiness at the blood-brain barrier. Therefore, potential effects of AD on the concentration and isotopic composition of essential elements in cerebrospinal fluid related to amyloid-β formation could be hidden. Finally, in blood serum, Zn, urea and creatinine concentrations showed an increase with age and showed a significant difference between sexes.

Cuproptosis, the novel type of oxidation-induced cell death in thoracic cancers: can it enhance the success of immunotherapy?

Copper is an important metal micronutrient, required for the balanced growth and normal physiological functions of human organism. Copper-related toxicity and dysbalanced metabolism were associated with the disruption of intracellular respiration and the development of various diseases, including cancer. Notably, copper-induced cell death was defined as cuproptosis which was also observed in malignant cells, representing an attractive anti-cancer instrument. Excess of intracellular copper leads to the aggregation of lipoylation proteins and toxic stress, ultimately resulting in the activation of cell death. Differential expression of cuproptosis-related genes was detected in normal and malignant tissues. Cuproptosis-related genes were also linked to the regulation of oxidative stress, immune cell responses, and composition of tumor microenvironment. Activation of cuproptosis was associated with increased expression of redox-metabolism-regulating genes, such as ferredoxin 1 (FDX1), lipoic acid synthetase (LIAS), lipoyltransferase 1 (LIPT1), dihydrolipoamide dehydrogenase (DLD), drolipoamide S-acetyltransferase (DLAT), pyruvate dehydrogenase E1 subunit alpha 1 (PDHA1), and pyruvate dehydrogenase E1 subunit beta (PDHB)). Accordingly, copper-activated network was suggested as an attractive target in cancer therapy. Mechanisms of cuproptosis and regulation of cuproptosis-related genes in different cancers and tumor microenvironment are discussed in this study. The analysis of current findings indicates that therapeutic regulation of copper signaling, and activation of cuproptosis-related targets may provide an effective tool for the improvement of immunotherapy regimens.

Regenerating Chemotherapeutics through Copper-Based Nanomedicine: Disrupting Protein Homeostasis for Enhanced Tumor Therapy

The bis-(diethyldithiocarbamate)-copper (CuET), the disulfiram (DSF)-Cu complex, has exhibited noteworthy anti-tumor property. However, its efficacy is compromised due to the inadequate oxidative conditions and the limitation of bioavailable copper. Because CuET can inactivate valosin-containing protein (VCP), a bioinformatic pan-cancer analysis of VCP is first conducted in this study to identify CuET as a promising anticancer drug for diverse cancer types. Then, based on the drug action mechanism, a nanocomposite of CuET and copper oxide (CuO) is designed and fabricated utilizing bovine serum albumin (BSA) as the template (denoted as CuET-CuO@BSA, CCB). CCB manifests peroxidase (POD)-mimicking activity to oxidize the tumor endogenous H2O2 to generate reactive oxygen species (ROS), enhancing the chemotherapy effect of CuET. Furthermore, the cupric ions released after enzymatic reaction can regenerate CuET, which markedly perturbs intracellular protein homeostasis and induces apoptosis of tumor cells. Meanwhile, CCB triggers cuproptosis by inducing the aggregation of lipoylated proteins. The multifaceted action of CCB effectively inhibits tumor progression. Therefore, this study presents an innovative CuET therapeutic strategy that creates an oxidative microenvironment in situ and simultaneously self-supply copper source for CuET regeneration through the combination of CuO nanozyme with CuET, which holds promise for application of CuET for effective tumor therapy.

Glycyl-l-histidyl-l-lysine prevents copper- and zinc-induced protein aggregation and central nervous system cell death in vitro

Common features of neurodegenerative diseases are oxidative and inflammatory imbalances as well as the misfolding of proteins. An excess of free metal ions can be pathological and contribute to cell death, but only copper and zinc strongly promote protein aggregation. Herein we demonstrate that the endogenous copper-binding tripeptide glycyl-l-histidyl-l-lysine (GHK) has the ability to bind to and reduce copper redox activity and to prevent copper- and zinc-induced cell death in vitro. In addition, GHK prevents copper- and zinc-induced bovine serum albumin aggregation and reverses aggregation through resolubilizing the protein. We further demonstrate the enhanced toxicity of copper during inflammation and the ability of GHK to attenuate this toxicity. Finally, we investigated the effects of copper on enhancing paraquat toxicity and report a protective effect of GHK. We therefore conclude that GHK has potential as a cytoprotective compound with regard to copper and zinc toxicity, with positive effects on protein solubility and aggregation that warrant further investigation in the treatment of neurodegenerative diseases.

ASH2L upregulation contributes to diabetic endothelial dysfunction in mice through STEAP4-mediated copper uptake

Endothelial dysfunction is a common complication of diabetes mellitus (DM) and contributes to the high incidence and mortality of cardiovascular and cerebrovascular diseases. Aberrant epigenetic regulation under diabetic conditions, including histone modifications, DNA methylation, and non-coding RNAs (ncRNAs) play key roles in the initiation and progression of diabetic vascular complications. ASH2L, a H3K4me3 regulator, triggers genetic transcription, which is critical for physiological and pathogenic processes. In this study we investigated the role of ASH2L in mediating diabetic endothelial dysfunction. We showed that ASH2L expression was significantly elevated in vascular tissues from diabetic db/db mice and in rat aortic endothelial cells (RAECs) treated with high glucose medium (11 and 22 mM). Knockdown of ASH2L in RAECs markedly inhibited the deteriorating effects of high glucose, characterized by reduced oxidative stress and inflammatory responses. Deletion of endothelial ASH2L in db/db mice by injection of an adeno-associated virus (AAV)-endothelial specific system carrying shRNA against Ash2l (AAV-shAsh2l) restored the impaired endothelium-dependent relaxations, and ameliorated DM-induced vascular dysfunction. We revealed that ASH2L expression activated reductase STEAP4 transcription in vitro and in vivo, which consequently elevated Cu(I) transportation into ECs by the copper transporter CTR1. Excess copper produced by STEAP4-mediated copper uptake triggered oxidative stress and inflammatory responses, resulting in endothelial dysfunction. Our results demonstrate that hyperglycemia triggered ASH2L-STEAP4 axis contributes to diabetic endothelial dysfunction by modulating copper uptake into ECs and highlight the therapeutic potential of blocking the endothelial ASH2L in the pathogenesis of diabetic vascular complications.

Hepatic depletion of nucleolar protein mDEF causes excessive mitochondrial copper accumulation associated with p53 and NRF1 activation

Copper is an essential component in the mitochondrial respiratory chain complex IV (cytochrome c oxidases). However, whether any nucleolar factor(s) is(are) involved in regulating the mitochondrial copper homeostasis remains unclear. The nucleolar localized Def-Capn3 protein degradation pathway cleaves target proteins, including p53, in both zebrafish and human nucleoli. Here, we report that hepatic depletion of mDEF in mice causes an excessive copper accumulation in the mitochondria. We find that mDEF-depleted hepatocytes show an exclusion of CAPN3 from the nucleoli and accumulate p53 and NRF1 proteins in the nucleoli. Furthermore, we find that NRF1 is a CAPN3 substrate. Elevated p53 and NRF1 enhances the expression of Sco2 and Cox genes, respectively, to allow more copper acquirement in the mDef^loxp/loxp, Alb:Cre mitochondria. Our findings reveal that the mDEF-CAPN3 pathway serves as a novel mechanism for regulating the mitochondrial copper homeostasis through targeting its substrates p53 and NRF1.

Integrating reduced amino acid composition into PSSM for improving copper ion-binding protein prediction

Copper ion-binding proteins play an essential role in metabolic processes and are critical factors in many diseases, such as breast cancer, lung cancer, and Menkes disease. Many algorithms have been developed for predicting metal ion classification and binding sites, but none have been applied to copper ion-binding proteins. In this study, we developed a copper ion-bound protein classifier, RPCIBP, which integrating the reduced amino acid composition into position-specific score matrix (PSSM). The reduced amino acid composition filters out a large number of useless evolutionary features, improving the operational efficiency and predictive ability of the model (feature dimension from 2900 to 200, ACC from 83 % to 85.1 %). Compared with the basic model using only three sequence feature extraction methods (ACC in training set between 73.8 %-86.2 %, ACC in test set between 69.3 %-87.5 %), the model integrating the evolutionary features of the reduced amino acid composition showed higher accuracy and robustness (ACC in training set between 83.1 %-90.8 %, ACC in test set between 79.1 %-91.9 %). Best copper ion-binding protein classifiers filtered by feature selection progress were deployed in a user-friendly web server (http://bioinfor.imu.edu.cn/RPCIBP). RPCIBP can accurately predict copper ion-binding proteins, which is convenient for further structural and functional studies, and conducive to mechanism exploration and target drug development.

Exploration of the Potential Role of Serum Albumin in the Delivery of Cu(I) to Ctr1

Human serum albumin (HSA) is the major copper (Cu) carrier in blood. The majority of previous studies that have investigated Cu interactions with HSA have focused primarily on the Cu(II) oxidation state. Yet, cellular Cu uptake by the human copper transport protein (Ctr1), a plasma membrane-embedded protein responsible for Cu uptake into cells, requires Cu(I). Recent in vitro work has determined that reducing agents, such as the ascorbate present in blood, are sufficient to reduce the Cu(II)HSA complex to form Cu(I)HSA and that Cu(I) is bound to HSA with pM affinity. The biological accessibility of Cu(I)HSA suggests that HSA-bound Cu(I) may be an unappreciated form of Cu cargo and a key player in extracellular Cu trafficking. To better understand Cu trafficking by HSA, we sought to investigate the exchange of Cu(I) from HSA to a model peptide of the Cu-binding ectodomain of Ctr1. In this study, we used X-ray absorption near-edge spectroscopy to show that Cu(I) becomes more highly coordinated as increasing amounts of the Ctr_1-14 model peptide are added to a solution of Cu(I)HSA. Extended X-ray absorption fine structure (EXAFS) spectroscopy was used to further characterize the interaction of Cu(I)HSA with Ctr_1-14 by determining the ligands coordinating Cu(I) and their bond lengths. The EXAFS data support that some Cu(I) likely undergoes complete transfer from HSA to Ctr_1-14. This finding of HSA interacting with and releasing Cu(I) to an ectodomain model peptide of Ctr1 suggests a mechanism by which HSA delivers Cu(I) to cells under physiological conditions.

Association of Zn and Cu Levels in Cord Blood and Maternal Milk with Pregnancy Outcomes among the Slovenian Population

Trace elements, including zinc (Zn) and copper (Cu), are known to play important roles in human health. The present study aimed to assess the levels of Zn and Cu in cord blood and maternal milk and to analyze their association with maternal and infant characteristics and pregnancy outcomes in a Slovenian study population of mothers and their neonates recruited within the PHIME prospective cohort study. The study included 324 mothers, but the data on Zn and Cu levels in both cord blood and maternal milk was available for 243 mothers. Questionnaires were used to assess the socio-demographic and health status of the mothers, their lifestyle habits (including detailed nutritional habits), and their residential and occupational histories. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to measure Zn and Cu levels in cord blood and maternal milk. Low Zn levels in cord blood were associated with lower gestational age and birth weight and were correlated with an increased probability of the birth of small for gestational age (SGA) infants. Maternal smoking influenced the Cu levels in both cord blood and maternal milk. Cord blood Cu levels were higher and Cu levels in maternal milk were lower in smoking compared to non-smoking mothers. Most importantly, a decreased Zn/Cu ratio in cord blood was associated with lower gestational age and lower birth weight. This indicates the overall positive effects of Zn and negative effects of Cu on pregnancy outcomes.

The Molecular Mechanisms of Defective Copper Metabolism in Diabetic Cardiomyopathy

Copper is an essential trace metal element that significantly affects human physiology and pathology by regulating various important biological processes, including mitochondrial oxidative phosphorylation, connective tissue crosslinking, and antioxidant defense. Copper level has been proved to be closely related to the morbidity and mortality of cardiovascular diseases such as atherosclerosis, heart failure, and diabetic cardiomyopathy (DCM). Copper deficiency can induce cardiac hypertrophy and aggravate cardiomyopathy, while copper excess can mediate various types of cell death, such as autophagy, apoptosis, cuproptosis, pyroptosis, and cardiac hypertrophy and fibrosis. Both copper excess and copper deficiency lead to redox imbalance, activate inflammatory response, and aggravate diabetic cardiomyopathy. This defective copper metabolism suggests a specific metabolic pattern of copper in diabetes and a specific role in the pathogenesis and progression of DCM. This review is aimed at providing a timely summary of the effects of defective copper homeostasis on DCM and discussing potential underlying molecular mechanisms.

Neurometals in the Pathogenesis of Prion Diseases

Prion diseases are progressive and transmissive neurodegenerative diseases. The conformational conversion of normal cellular prion protein (PrP^C) into abnormal pathogenic prion protein (PrP^Sc) is critical for its infection and pathogenesis. PrP^C possesses the ability to bind to various neurometals, including copper, zinc, iron, and manganese. Moreover, increasing evidence suggests that PrP^C plays essential roles in the maintenance of homeostasis of these neurometals in the synapse. In addition, trace metals are critical determinants of the conformational change and toxicity of PrP^C. Here, we review our studies and other new findings that inform the current understanding of the links between trace elements and physiological functions of PrP^C and the neurotoxicity of PrP^Sc.

The influence of sex and strain on trace element dysregulation in the brain due to diet-induced obesity

BACKGROUND

The objective of this study was to identify interaction effects between diet, sex, and strain on trace element dysregulation and gene expression alterations due to diet-induced obesity (DIO) in the hippocampus, striatum, and midbrain.

METHODS

Male and female C57BL/6 J (B6 J) and DBA/2 J (D2 J) mice were fed either a low fat (10 % kcal) diet (LFD) or high fat (60 % kcal) diet (HFD) for 16 weeks, then assessed for trace element concentrations and gene expression patterns in the brain.

RESULTS

In the hippocampus, zinc was significantly increased by 48 % in D2 J males but decreased by 44 % in D2 J females, and divalent metal transporter 1 was substantially upregulated in B6 J males due to DIO. In the striatum, iron was significantly elevated in B6 J female mice, and ceruloplasmin was significantly upregulated in D2 J female mice due to DIO. In the midbrain, D2 J males fed a HFD had a 48 % reduction in Cu compared to the LFD group, and D2 J females had a 37 % reduction in Cu compared to the control group.

CONCLUSIONS

The alteration of trace element homeostasis and gene expression due to DIO was brain-region dependent and was highly influenced by sex and strain. A significant three-way interaction between diet, sex, and strain was discovered for zinc in the hippocampus (for mice fed a HFD, zinc increased in male D2 Js, decreased in female D2 Js, and had no effect in B6 J mice). A significant diet by sex interaction was observed for iron in the striatum (iron increased only in female mice fed a HFD). A main effect of decreased copper in the midbrain was found for the D2 J strain fed a HFD. These results emphasize the importance of considering sex and genetics as biological factors when investigating potential associations between DIO and neurodegenerative disease.

Promotion of cadmium uptake and cadmium-induced toxicity by the copper transporter CTR1 in HepG2 and ZFL cells

Cadmium (Cd²⁺) is considered a human carcinogen as it causes oxidative stress and alters DNA repair responses. However, how Cd²⁺ is taken up by cells remains unclear. We hypothesized that Cd²⁺ could be transported into cells via a membrane copper (Cu) transporter, CTR1. CTR1 expression was not affected by Cd²⁺ exposure at the mRNA or protein level. Stable cell lines overexpressing either hCTR1, in the human liver cell line HepG2, or zCTR1, in the zebrafish liver cell line ZFL, were created to study their responses to Cd²⁺ insult. It was found that both HepG2 and ZFL cells overexpressing CTR1 had higher Cd²⁺ uptake and thus became sensitive to Cd²⁺. In contrast, hCTR1 knockdown in HepG2 cells led to a reduced uptake of Cd²⁺, making the cells relatively resistant to Cd²⁺. Localization studies revealed that hCTR1 had a clustered pattern after Cd²⁺ exposure, possibly in an attempt to reduce both Cd²⁺ uptake and Cd²⁺-induced toxicity. These in vitro results indicate that CTR1 can transport Cd²⁺ into the cell, resulting in Cd²⁺ toxicity.

The Role of Fe, Zn, and Cu in Pregnancy

Iron (Fe), copper (Cu), and zinc (Zn) are microelements essential for the proper functioning of living organisms. These elements participatein many processes, including cellular metabolism and antioxidant and anti-inflammatory defenses, and also influence enzyme activity, regulate gene expression, and take part in protein synthesis. Fe, Cu, and Zn have a significant impact on the health of pregnant women and in the development of the fetus, as well as on the health of the newborn. A proper concentration of these elements in the body of women during pregnancy reduces the risk of complications such as anemia, induced hypertension, low birth weight, preeclampsia, and postnatal complications. The interactions between Fe, Cu, and Zn influence their availability due to their similar physicochemical properties. This most often occurs during intestinal absorption, where metal ions compete for binding sites with transport compounds. Additionally, the relationships between these ions have a great influence on the course of reactions in the tissues, as well as on their excretion, which can be stimulated or delayed. This review aims to summarize reports on the influence of Fe, Cu, and Zn on the course of single and multiple pregnancies, and to discuss the interdependencies and mechanisms occurring between Fe, Cu, and Zn.

Silver Ions as a Tool for Understanding Different Aspects of Copper Metabolism

In humans, copper is an important micronutrient because it is a cofactor of ubiquitous and brain-specific cuproenzymes, as well as a secondary messenger. Failure of the mechanisms supporting copper balance leads to the development of neurodegenerative, oncological, and other severe disorders, whose treatment requires a detailed understanding of copper metabolism. In the body, bioavailable copper exists in two stable oxidation states, Cu(I) and Cu(II), both of which are highly toxic. The toxicity of copper ions is usually overcome by coordinating them with a wide range of ligands. These include the active cuproenzyme centers, copper-binding protein motifs to ensure the safe delivery of copper to its physiological location, and participants in the Cu(I) ↔ Cu(II) redox cycle, in which cellular copper is stored. The use of modern experimental approaches has allowed the overall picture of copper turnover in the cells and the organism to be clarified. However, many aspects of this process remain poorly understood. Some of them can be found out using abiogenic silver ions (Ag(I)), which are isoelectronic to Cu(I). This review covers the physicochemical principles of the ability of Ag(I) to substitute for copper ions in transport proteins and cuproenzyme active sites, the effectiveness of using Ag(I) to study copper routes in the cells and the body, and the limitations associated with Ag(I) remaining stable in only one oxidation state. The use of Ag(I) to restrict copper transport to tumors and the consequences of large-scale use of silver nanoparticles for human health are also discussed.

DNA profiling and in vitro cytotoxicity studies of tetrazolo[1,5-a]pyrimidine-based copper(II) complexes

A series of N-benzoylated mononuclear copper(II) complexes of the type [Cu(L^1-6)Cl₂] (1-6), where L¹= ethyl 4-benzoyl-5-methyl-7-aryl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate, L²= ethyl 4-(4-nitrobenzoyl)-5-methyl-7-aryl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate, L³ = ethyl 4-benzoyl-5-methyl-7-(4-methoxyphenyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate, L⁴ = ethyl 4-(4-nitrobenzoyl)-5-methyl-7-(4-methoxyphenyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate, L⁵ = ethyl 4-benzoyl-5-methyl-7-(4-chlorophenyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate and L⁶ = ethyl 4-(4-nitrobenzoyl)-5-methyl-7-(4-chlorophenyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate have been synthesized and characterized by spectral methods. Electron paramagnetic resonance spectra of complexes show four lines, characteristic of square planar geometry. The binding studies of the complexes with calf thymus DNA (CT-DNA) revealed groove mode of binding, which were further supported by molecular docking studies. Gel electrophoresis experiments demonstrated the ability of the complexes to cleave plasmid DNA in the absence of activators. Further, the cytotoxicity activity of the complexes were examined on three cancerous cell lines (lung (A549), cervical (HeLa) and colon (HCT-15)), and on two normal cells (human embryonic kidney (HEK) and peripheral blood mononuclear cells (PBMC)) by MTT assay.

Life-time exposure to waterborne copper II: Patterns of tissue accumulation and gene expression of the metal-transport proteins ctr1 and atp7b in the killifish Poecilia vivipara

The involvement of transporting proteins on copper (Cu) bioaccumulation was evaluated in the killifish Poecilia vivipara chronically exposed to environmentally relevant concentrations of waterborne Cu. Fish (<24 h-old) were maintained under control condition or exposed to different waterborne Cu concentrations (5, 9 and 20 μg/L) for 28 and 345 days in saltwater. Following exposure periods, Cu accumulation and the expression of genes encoding for the high affinity Cu-transporter (ctr1) and the P-type Cu-ATPase (atp7b) were evaluated. Whole-body metal accumulation and gene expression were evaluated in fish exposed to 28 days. Similarly, in fish exposed to 345 days, liver, gills and gut were also evaluated. No fish survival was observed after exposure to 20 μg/L for 345 days. Whole-body Cu accumulation was significantly higher in fish exposed to 20 μg/L Cu for 28 days and in fish exposed to 9 μg/L for 345 days in comparison to control animals. Similarly, tissue Cu accumulation was significantly higher in fish exposed to 9 μg/L for 345 days in comparison to control animal. However, no significant accumulation was observed in fish muscle. Following exposure for 28 days, whole-body ctr1 expression was slightly induced in fish exposed to 9 μg/L. In turn, no significant change in ctr1 expression was observed following exposure to Cu for 345 days. Differently, whole-body atp7b expression was markedly up-regulated in the whole-body of fish exposed Cu for 28 days and in tissues of fish exposed to Cu for 345 days. These findings indicate the expression of atp7b is more responsive to Cu accumulation in P. vivipara than ctr1 expression and, therefore, more suitable to be used as a biomarker of exposure to this metal. Also, we argue that the expression of atp7b is sustained at elevated levels for as much time as fish are maintained in Cu contaminated water.

CRISP-R/Cas9 Mediated Deletion of Copper Transport Genes CTR1 and DMT1 in NSCLC Cell Line H1299. Biological and Pharmacological Consequences

Copper, the highly toxic micronutrient, plays two essential roles: it is a catalytic and structural cofactor for Cu-dependent enzymes, and it acts as a secondary messenger. In the cells, copper is imported by CTR1 (high-affinity copper transporter 1), a transmembrane high-affinity copper importer, and DMT1 (divalent metal transporter). In cytosol, enzyme-specific chaperones receive copper from CTR1 C-terminus and deliver it to their apoenzymes. DMT1 cannot be a donor of catalytic copper because it does not have a cytosol domain which is required for copper transfer to the Cu-chaperons that assist the formation of cuproenzymes. Here, we assume that DMT1 can mediate copper way required for a regulatory copper pool. To verify this hypothesis, we used CRISPR/Cas9 to generate H1299 cell line with CTR1 or DMT1 single knockout (KO) and CTR1/DMT1 double knockout (DKO). To confirm KOs of the genes qRT-PCR were used. Two independent clones for each gene were selected for further studies. In CTR1 KO cells, expression of the DMT1 gene was significantly increased and vice versa. In subcellular compartments of the derived cells, copper concentration dropped, however, in nuclei basal level of copper did not change dramatically. CTR1 KO cells, but not DMT1 KO, demonstrated reduced sensitivity to cisplatin and silver ions, the agents that enter the cell through CTR1. Using single CTR1 and DMT1 KO, we were able to show that both, CTR1 and DMT1, provided the formation of vital intracellular cuproenzymes (SOD1, COX), but not secretory ceruloplasmin. The loss of CTR1 resulted in a decrease in the level of COMMD1, XIAP, and NF-κB. Differently, the DMT1 deficiency induced increase of the COMMD1, HIF1α, and XIAP levels. The possibility of using CTR1 KO and DMT1 KO cells to study homeodynamics of catalytic and signaling copper selectively is discussed.

Hepatic copper concentrations in 546 dogs (1982-2015)

BACKGROUND

Copper associated hepatitis (CAH) has been increasingly recognized in dogs, and speculation exists that hereditary defects in copper metabolism have been exacerbated by increased environmental copper exposure. However, no broad epidemiological investigations have been performed to investigate quantitative hepatic copper concentrations ([Cu]H ) over time in both dogs that are (predisposed breed [PB]), and are not (non-predisposed breed [NPB]), considered at-risk for CAH.

OBJECTIVES

To investigate [Cu]H in dogs and explore temporal, demographic, and histologic associations spanning 34 years.

ANIMALS

546 archived liver specimens.

METHODS

Retrospective study. Searches of the Michigan State University Veterinary Diagnostic Laboratory database identified dogs that had undergone hepatic histopathologic assessment. Cases with archived tissue were reviewed and classified by breed, time period, and presence or absence of hepatitis. Inductively coupled plasma mass spectrometry was used to determine [Cu]H .

RESULTS

In time period 2009-2015, median [Cu]H were 101 μg/g and 313 μg/g greater than median [Cu]H in time period 1982-1988 for NPB and PB dogs, respectively (P < .001 for both comparisons). The proportion of dogs with [CU]H > 300 μg/g increased in NPB (28% to 49%) and PB dogs (48% to 71%) during these periods (P = .002 for both comparisons). Median [Cu]H in dogs with hepatitis increased 3-fold over time in both NPB (P = .004) and PB populations (P < .001).

CONCLUSIONS AND CLINICAL IMPORTANCE

The frequent recognition of CAH in recent years is likely due to the observed increases in [Cu]H over time. Importantly, effects are not limited to PB dogs.

Copper Metabolism of Newborns Is Adapted to Milk Ceruloplasmin as a Nutritive Source of Copper: Overview of the Current Data

Copper, which can potentially be a highly toxic agent, is an essential nutrient due to its role as a cofactor for cuproenzymes and its participation in signaling pathways. In mammals, the liver is a central organ that controls copper turnover throughout the body, including copper absorption, distribution, and excretion. In ontogenesis, there are two types of copper metabolism, embryonic and adult, which maintain the balance of copper in each of these periods of life, respectively. In the liver cells, these types of metabolism are characterized by the specific expression patterns and activity levels of the genes encoding ceruloplasmin, which is the main extracellular ferroxidase and copper transporter, and the proteins mediating ceruloplasmin metalation. In newborns, the molecular genetic mechanisms responsible for copper homeostasis and the ontogenetic switch from embryonic to adult copper metabolism are highly adapted to milk ceruloplasmin as a dietary source of copper. In the mammary gland cells, the level of ceruloplasmin gene expression and the alternative splicing of its pre-mRNA govern the amount of ceruloplasmin in the milk, and thus, the amount of copper absorbed by a newborn is controlled. In newborns, the absorption, distribution, and accumulation of copper are adapted to milk ceruloplasmin. If newborns are not breast-fed in the early stages of postnatal development, they do not have this natural control ensuring alimentary copper balance in the body. Although there is still much to be learned about the neonatal consequences of having an imbalance of copper in the mother/newborn system, the time to pay attention to this problem has arrived because the neonatal misbalance of copper may provoke the development of copper-related disorders.

Metal cofactors trafficking and assembly in the cell: a molecular view

Metal ions are essential cofactors required by the proteome of organisms from any kingdom of life to correctly exert their functions. Dedicated cellular import, transport and homeostasis systems assure that the needed metal ion is correctly delivered and inserted into the target proteins and avoid the presence of free metal ions in the cell, preventing oxidative damaging. Among metal ions, in eukaryotic organisms copper and iron are required by proteins involved in absolutely essential functions, such as respiration, oxidative stress protection, catalysis, gene expression regulation. Copper and iron binding proteins are localized in essentially all cellular compartments. Copper is physiologically present mainly as individual metal ion. Iron can be present both as individual metal ion or as part of cofactors, such as hemes and iron-sulfur (Fe-S) clusters. Both metal ions are characterized by the ability to cycle between different oxidation states, which enable them to catalyze redox reactions and to participate in electron transfer processes. Here we describe in detail the main processes responsible for the trafficking of copper and iron sulfur clusters, with particular interest for the structural aspects of the maturation of copper and iron-sulfur-binding proteins.

A Perspective - can copper complexes be developed as a novel class of therapeutics?

Although copper-ligand complexes appear to be promising as a new class of therapeutics, other than the family of copper(ii) coordination compounds referred to as casiopeínas these compounds have yet to reach the clinic for human use. The pharmaceutical challenges associated with developing copper-based therapeutics will be presented in this article along with a discussion of the potential for high-throughput chemistry, computer-aided drug design, and nanotechnology to address the development of this important class of drug candidates.

Pilot Study of 64CuCl₂ for PET Imaging of Inflammation

Copper(II) ion (Cu²⁺) is the essential element for numerous pathophysiological processes in vivo. Copper transporter 1 (CTR1) is mainly responsible for maintaining Cu²⁺ accumulation in cells, which has been found to be over-expressed in inflammatory tissues. Therefore, we explored the potential application of ⁶⁴CuCl₂ for PET imaging of inflammation through targeting CTR1. The animal models of H₂O₂ induced muscle inflammation and lipopolysaccaharide induced lung inflammation were successfully established, then imaged by small animal PET (PET/CT) post-injection of ⁶⁴CuCl₂, and PET images were quantitatively analyzed. H&E and immunohistochemical (IHC) staining and western blot experiments were performed for evaluating CTR1 levels in the inflammatory and control tissues. Both inflammatory muscle and lungs can be clearly imaged by PET. PET image quantitative analysis revealed that the inflammatory muscle and lungs showed significantly higher ⁶⁴Cu accumulation than the controls, respectively (p < 0.05). Furthermore, IHC staining and western blot analysis demonstrated that compared with the controls, CTR1 expression was increased in both the inflammatory muscle and lungs, which was consistent with the levels of ⁶⁴Cu²⁺ accumulation in these tissues. ⁶⁴CuCl₂ can be used as a novel, simple, and highly promising PET tracer for CTR1 targeted imaging of inflammation.

PET and SPECT imaging of melanoma: the state of the art

Melanoma represents the most aggressive form of skin cancer, and its incidence continues to rise worldwide. 18F-FDG PET imaging has transformed diagnostic nuclear medicine and has become an essential component in the management of melanoma, but still has its drawbacks. With the rapid growth in the field of nuclear medicine and molecular imaging, a variety of promising probes that enable early diagnosis and detection of melanoma have been developed. The substantial preclinical success of melanin- and peptide-based probes has recently resulted in the translation of several radiotracers to clinical settings for noninvasive imaging and treatment of melanoma in humans. In this review, we focus on the latest developments in radiolabeled molecular imaging probes for melanoma in preclinical and clinical settings, and discuss the challenges and opportunities for future development.

Pilot Study of 64Cu(I) for PET Imaging of Melanoma

At present, ⁶⁴Cu(II) labeled tracers including ⁶⁴CuCl₂ have been widely applied in the research of molecular imaging and therapy. Human copper transporter 1 (hCTR1) is the major high affinity copper influx transporter in mammalian cells, and specially responsible for the transportation of Cu(I) not Cu(II). Thus, we investigated the feasible application of ⁶⁴Cu(I) for PET imaging. ⁶⁴Cu(II) was reduced to ⁶⁴Cu(I) with the existence of sodium L-ascorbate, DL-Dithiothreitol or cysteine. Cell uptake and efflux assay was investigated using B16F10 and A375 cell lines, respectively. Small animal PET and biodistribution studies were performed in both B16F10 and A375 tumor-bearing mice. Compared with ⁶⁴Cu(II), ⁶⁴Cu(I) exhibited higher cellular uptake by melanoma, which testified CTR1 specially influx of Cu(I). However, due to oxidation reaction in vivo, no significant difference between ⁶⁴Cu(I) and ⁶⁴Cu(II) was observed through PET images and biodistribution. Additionally, radiation absorbed doses for major tissues of human were calculated based on the mouse biodistribution. Radiodosimetry calculations for ^64/67Cu(I) and ^64/67Cu(II) were similar, which suggested that although melanoma were with high radiation absorbed doses, high radioactivity accumulation by liver and kidney should be noticed for the further application. Thus, ⁶⁴Cu(I) should be further studied to evaluate it as a PET imaging radiotracer.

The effect of administration of copper nanoparticles to chickens in drinking water on estimated intestinal absorption of iron, zinc, and calcium

Copper nanoparticles used as a dietary supplement for poultry could affect the absorption of mineral elements. Hence the aim of the study was to determine the effect of administration of copper nanoparticles to chickens in drinking water on intestinal absorption of iron, zinc, and calcium. The experiment was carried out on 126 chicks assigned to seven experimental groups of 18 birds each (3 replications of 6 individuals each). The control group (G-C) did not receive copper nanoparticles. Groups: Cu-5(7), Cu-10(7), and Cu-15(7) received gold nanoparticles in their drinking water in the amounts of 5 mg/L for group Cu-5(7), 10 mg/L for group Cu-10(7), and 15 mg/L for group Cu-15(7) during 8 to 14, 22 to 28, and 36 of 42 days of the life of the chicks. The birds in groups Cu-5(3), Cu-10(3), and Cu-15(3) received copper nanoparticles in the same amounts, but only during 8 to 10, 22 to 24, and 36 to 38 days of life. Blood for analysis was collected from the wing vein of all chicks at the age of 42 days. After the rearing period (day 42), six birds from each experimental group with body weight similar to the group average were slaughtered. The carcasses were dissected and samples of the jejunum were collected for analysis of absorption of selected minerals. Mineral absorption was tested using the in vitro gastrointestinal sac technique. Oral administration of copper nanoparticles to chickens in the amount of 5, 10, and 15 mg/L led to accumulation of this element in the intestinal walls. The highest level of copper nanoparticles applied increased Cu content in the blood plasma of the birds. The in vitro study suggests that copper accumulated in the intestines reduces absorption of calcium and zinc, but does not affect iron absorption.

Membrane-Associated Transporter Protein (MATP) Regulates Melanosomal pH and Influences Tyrosinase Activity

The SLC45A2 gene encodes a Membrane-Associated Transporter Protein (MATP). Mutations of this gene cause oculocutaneous albinism type 4 (OCA4). However, the molecular mechanism of its action in melanogenesis has not been elucidated. Here, we discuss the role of MATP in melanin production. The SLC45A2 gene is highly enriched in human melanocytes and melanoma cell lines, and its protein, MATP, is located in melanosomes. The knockdown of MATP using siRNAs reduced melanin content and tyrosinase activity without any morphological change in melanosomes or the expression of melanogenesis-related proteins. Interestingly, the knockdown of MATP significantly lowered the melanosomal pH, as verified through DAMP analysis, suggesting that MATP regulates melanosomal pH and therefore affects tyrosinase activity. Finally, we found that the reduction of tyrosinase activity associated with the knockdown of MATP was readily recovered by copper treatment in the in vitro L-DOPA oxidase activity assay of tyrosinase. Considering that copper is an important element for tyrosinase activity and that its binding to tyrosinase depends on melanosomal pH, MATP may play an important role in regulating tyrosinase activity via controlling melanosomal pH.

Membrane-Associated Transporter Protein (MATP) Regulates Melanosomal pH and Influences Tyrosinase Activity

The SLC45A2 gene encodes a Membrane-Associated Transporter Protein (MATP). Mutations of this gene cause oculocutaneous albinism type 4 (OCA4). However, the molecular mechanism of its action in melanogenesis has not been elucidated. Here, we discuss the role of MATP in melanin production. The SLC45A2 gene is highly enriched in human melanocytes and melanoma cell lines, and its protein, MATP, is located in melanosomes. The knockdown of MATP using siRNAs reduced melanin content and tyrosinase activity without any morphological change in melanosomes or the expression of melanogenesis-related proteins. Interestingly, the knockdown of MATP significantly lowered the melanosomal pH, as verified through DAMP analysis, suggesting that MATP regulates melanosomal pH and therefore affects tyrosinase activity. Finally, we found that the reduction of tyrosinase activity associated with the knockdown of MATP was readily recovered by copper treatment in the in vitro L-DOPA oxidase activity assay of tyrosinase. Considering that copper is an important element for tyrosinase activity and that its binding to tyrosinase depends on melanosomal pH, MATP may play an important role in regulating tyrosinase activity via controlling melanosomal pH.

Endogenous concentrations of biologically relevant metals in rat brain and cochlea determined by inductively coupled plasma mass spectrometry

Manganese (Mn), iron (Fe), copper (Cu), and zinc (Zn) are essential nutrients which aid in the proper functioning of cells, but high concentrations of these metals can be toxic to various organs. Little is known about the endogenous concentrations of these metals in the cochlea, the auditory portion of the inner ear which is extremely small and difficult to access. To fill this gap, a trace quantitative digestion and inductively coupled plasma mass spectrometry method was developed to determine the concentrations of these metals in the stria vascularis, organ of Corti, and spiral ganglion, three critically important parts of the cochlea (≤ 1.5 mg); these values were compared to those in specific brain regions (≤ 20 mg) of rats. Rats were sacrificed and the cochlea and brain regions were carefully isolated, digested, and analyzed to determine baseline concentrations of Mn, Fe, Cu, and Zn. In the cochlea, Mn, Fe, Cu, and Zn concentrations ranged from 3.2-6, 73-300, non-detect, and 13-200 µg/g respectively. In the brain, Mn, Fe, Cu, and Zn concentrations ranged from 1.3-2.72, 21-120, 5.0-10.6, and 33-47 µg/g respectively. Significant differences (p < 0.05) were observed between the tissue types within the cochlea, and between the cochlea and brain. This validated method provides the first quantitative assessment of these metals in the three key subdivisions of the cochlea compared to the levels in the brain; Mn, Fe, and Zn levels were considerably higher in the cochlea than brain.

BS, Vuyyuru H, Muthuvel B, Konerirajapuram Natrajan S. CTR1 silencing inhibits angiogenesis by limiting copper entry into endothelial cells

Increased levels of intracellular copper stimulate angiogenesis in human umbilical vein endothelial cells (HUVECs). Copper transporter 1 (CTR1) is a copper importer present in the cell membrane and plays a major role in copper transport. In this study, three siRNAs targeting CTR1 mRNA were designed and screened for gene silencing. HUVECs when exposed to 100 µM copper showed 3 fold increased proliferation, migration by 1.8-fold and tube formation by 1.8-fold. One of the designed CTR1 siRNA (si 1) at 10 nM concentration decreased proliferation by 2.5-fold, migration by 4-fold and tube formation by 2.8-fold. Rabbit corneal packet assay also showed considerable decrease in matrigel induced blood vessel formation by si 1 when compared to untreated control. The designed si 1 when topically applied inhibited angiogenesis. This can be further developed for therapeutic application.

Laser microdissection coupled with RNA-seq analysis of porcine enterocytes infected with an obligate intracellular pathogen (Lawsonia intracellularis)

BACKGROUND

Lawsonia intracellularis is an obligate intracellular bacterium and the etiologic agent of proliferative enteropathy. The disease is endemic in pigs, emerging in horses and has been described in various other species including nonhuman primates. Cell proliferation is associated with bacterial replication in enterocyte cytoplasm, but the molecular basis of the host-pathogen interaction is unknown. We used laser capture microdissection coupled with RNA-seq technology to characterize the transcriptional responses of infected enterocytes and the host-pathogen interaction.

RESULTS

Proliferative enterocytes was associated with activation of transcription, protein biosynthesis and genes acting on the G1 phase of the host cell cycle (Rho family). The lack of differentiation in infected enterocytes was demonstrated by the repression of membrane transporters related to nutrient acquisition. The activation of the copper uptake transporter by infected enterocytes was associated with high expression of the Zn/Cu superoxide dismutase by L. intracellularis. This suggests that the intracellular bacteria incorporate intracytoplasmic copper and express a sophisticated mechanism to cope with oxidative stress.

CONCLUSIONS

The feasibility of coupling microdissection and RNA-seq was demonstrated by characterizing the host-bacterial interactions from a specific cell type in a heterogeneous tissue. High expression of L. intracellularis genes encoding hypothetical proteins and activation of host Rho genes infers the role of unrecognized bacterial cyclomodulins in the pathogenesis of proliferative enteropathy.

The role of metal regulatory proteins in brain oxidative stress: a tutorial

The proteins that regulate the metabolism of a metal must also play a role in regulating the redox activity of the metal. Metals are intrinsic to a substantial number of biological processes and the proteins that regulate those activities are also considerable in number. The role these proteins play in a wide range of physiological processes involves them directly and indirectly in a variety of disease processes. Similarly, it may be therapeutically advantageous to pharmacologically alter the activity of these metal containing proteins to influence disease processes. This paper will introduce the reader to a number of important proteins in both metal metabolism and oxidative stress, with an emphasis on the brain. Potential pharmacological targets will be considered.

Serum depletion of holo-ceruloplasmin induced by silver ions in vivo reduces uptake of cisplatin

There is an emerging link between extracellular copper concentration and the uptake of cisplatin mediated by copper transporter CTR1 in cell cultures and unicellular eukaryotes. To test the link between extracellular copper level and cisplatin uptake by organs in vivo we used mice with low copper status parameters induced by AgCl-containing diet (Ag-mice). In Ag-mice, serum copper status and liver copper metabolism were characterized. It was shown that the expression level of copper transporter genes and activity of ubiquitous intracellular cuproenzymes were not affected but the level of serum holo-ceruloplasmin was not detectable. Silver was selectively absorbed by liver and accumulated in the mitochondrial matrix. Silver was present in an exchangeable form and was excreted through bile. Ag-mice model is characterized by high reproducibility, reversibility, synchronicity, and definiteness of ceruloplasmin-associated copper deficiency. After cisplatin treatment Ag-mice, as compared to control mice, demonstrated the delay in platinum uptake by organs during first 30 min. This effect was not observed at later time points probably due to cisplatin induced copper release to blood, which resulted in the recovery of copper status. These data allowed us to conclude that cisplatin uptake was coupled to copper transport in vivo.

Cisplatin-induced nephrotoxicity and targets of nephroprotection: an update

Cisplatin is a highly effective antitumor agent whose clinical application is limited by the inherent nephrotoxicity. The current measures of nephroprotection used in patients receiving cisplatin are not satisfactory, and studies have focused on the investigation of new possible protective strategies. Many pathways involved in cisplatin nephrotoxicity have been delineated and proposed as targets for nephroprotection, and many new potentially protective agents have been reported. The multiple pathways which lead to renal damage and renal cell death have points of convergence and share some common modulators. The most frequent event among all the described pathways is the oxidative stress that acts as both a trigger and a result. The most exploited pathways, the proposed protective strategies, the achievements obtained so far as well as conflicting data are summarized and discussed in this review, providing a general view of the knowledge accumulated with past and recent research on this subject.

Copper complexes as therapeutic agents

The importance of transition metals in biological processes has been well established. Copper (Cu) is a transition metal that can exist in oxidised and reduced states. This allows it to participate in redox and catalytic chemistry, making it a suitable cofactor for a diverse range of enzymes and molecules. Cu deficiency or toxicity is implicated in a variety of pathological conditions; therefore inorganic complexes of Cu have been investigated for their therapeutic and diagnostic potential. These Cu complexes have been shown to be effective in cancer treatment due to their cytotoxic action on tumour cells. Alternatively, Cu complexes can also modulate Cu homeostasis in the brain, resulting in protective effects in several models of neurodegeneration. In other diseases such as coronary heart disease and skin disease, the success of Cu complexes as potential therapeutics will most likely be due to their ability to increase SOD activity, leading to relief of oxidative stress. This review seeks to provide a broad insight into some of the diverse actions of Cu complexes and demonstrate the strong future for these compounds as potential therapeutic agents.

Acquisition of dietary copper: a role for anion transporters in intestinal apical copper uptake

Copper is an essential micronutrient in humans and is required for a wide range of physiological processes, including neurotransmitter biosynthesis, oxidative metabolism, protection against reactive oxygen species, and angiogenesis. The first step in the acquisition of dietary copper is absorption from the intestinal lumen. The major human high-affinity copper uptake protein, human copper transporter hCTR1, was recently shown to be at the basolateral or blood side of both intestinal and renal epithelial cell lines and thus does not play a direct role in this initial step. We sought to functionally identify the major transport pathways available for the absorption of dietary copper across the apical intestinal membrane using Caco2 cells, a well-established model for human enterocytes. The initial rate of apical copper uptake into confluent monolayers of Caco2 cells is greatly elevated if amino acids and serum proteins are removed from the growth media. Uptake from buffered saline solutions at neutral pH (but not at lower pH) is inhibited by either d- or l-histidine, unaltered by the removal of sodium ions, and inhibited by ∼90% when chloride ions are replaced by gluconate or sulfate. Chloride-dependent copper uptake occurs with Cu(II) or Cu(I), although Cu(I) uptake is not inhibited by histidine, nor by silver ions. A well-characterized inhibitor of anion exchange systems, DIDS, inhibited apical copper uptake by 60-70%, while the addition of Mn(II) or Fe(II), competitive substrates for the divalent metal transporter DMT1, had no effect on copper uptake. We propose that anion exchangers play an unexpected role in copper absorption, utilizing copper-chloride complexes as pseudo-substrates. This pathway is also observed in mouse embryonic fibroblasts, human embryonic kidney cells, and Cos-7 cells. The special environment of low pH, low concentration of protein, and protonation of amino acids in the early intestinal lumen make this pathway especially important in dietary copper acquisition.

Dietary iron alters waterborne copper-induced gene expression in soft water acclimated zebrafish (Danio rerio)

Metals like iron (Fe) and copper (Cu) function as integral components in many biological reactions, and, in excess, these essential metals are toxic, and organisms must control metal acquisition and excretion. We examined the effects of chronic waterborne Cu exposure and the interactive effects of elevated dietary Fe on gene expression and tissue metal accumulation in zebrafish. Softwater acclimated zebrafish exposed to 8 microg/l Cu, with and without supplementation of a diet high in Fe (560 vs. 140 mg Fe/kg food) for 21 days demonstrated a significant reduction in liver and gut Cu load relative to waterborne Cu exposure alone. Gene expression levels for divalent metal transport (DMT)-1, copper transporter (CTR)-1, and the basolateral metal transporter ATP7A in the gills and gut increased when compared with controls, but the various combinations of Cu and high-Fe diet revealed altered levels of expression. Further examination of the basolateral Fe transporter, ferroportin, showed responses to waterborne Cu exposure in the gut and a significant increase with Fe treatment alone in the liver. Additionally, we examined metallothionein 1 and 2 (MT1 and MT2), which indicated that MT2 is more responsive to Cu. To explore the relationship between transcription and protein function, we examined both CTR-1 protein levels and gill apical uptake of radiolabeled Cu64, which demonstrated decreased Cu uptake and protein abundance in the elevated Cu treatments. This study shows that high dietary Fe can significantly alter the genetic expression pattern of Cu transporters at the level of the gill, liver, and gastrointestinal tract.

Radiolabeling rhesus monkey CD34+ hematopoietic and mesenchymal stem cells with 64Cu-pyruvaldehyde-bis(N4-methylthiosemicarbazone) for microPET imaging

Noninvasive positron emission tomography (PET) provides a potential method for in vivo tracking of radiolabeled cells. The goal of this study was to assess the potential toxicity of 64Cu-pyruvaldehyde-bis(N4-methylthiosemicarbazone) (PTSM) on rhesus monkey CD34+ hematopoietic and mesenchymal stem cells in vitro in preparation for developing imaging protocols posttransplantation. CD34+ hematopoietic cells were radiolabeled with 0 to 40 microCi/mL 64Cu-PTSM and viability and colony formation were assessed. Rhesus monkey mesenchymal stem cells (rhMSCs) were placed in culture postradiolabeling for assessments of growth and differentiation toward adipogenic, osteogenic, and chondrogenic lineages. The results indicated that CD34+ cells radiolabeled with 20 microCi/mL and rhMSCs radiolabeled with 10 microCi/mL 64Cu-PTSM did not result in adverse effects on growth or differentiation. Nonradioactive copper was also evaluated and showed that the presence of copper was not harmful to the cells. CD34+ cells and rhMSCs radiolabeled with the optimized concentrations of 20 and 10 microCi/mL, respectively, were also assessed using the microPET scanner. Studies showed that a minimum of 2.50x10(4) CD34+ cells (1.1 pCi/cell) and 6.25x10(3) rhMSCs (4.4 pCi/cell) could be detected. These studies indicate that CD34+ hematopoietic cells and rhMSCs can be safely radiolabeled with 64Cu-PTSM without adverse cellular effects.