Copper exposure and potential biomarkers of copper metabolism

Inflammation in Metal-Induced Neurological Disorders and Neurodegenerative Diseases

Essential metals play critical roles in maintaining human health as they participate in various physiological activities. Nonetheless, both excessive accumulation and deficiency of these metals may result in neurotoxicity secondary to neuroinflammation and the activation of microglia and astrocytes. Activation of these cells can promote the release of pro-inflammatory cytokines. It is well known that neuroinflammation plays a critical role in metal-induced neurotoxicity as well as the development of neurological disorders, such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Initially seen as a defense mechanism, persistent inflammatory responses are now considered harmful. Astrocytes and microglia are key regulators of neuroinflammation in the central nervous system, and their excessive activation may induce sustained neuroinflammation. Therefore, in this review, we aim to emphasize the important role and molecular mechanisms underlying metal-induced neurotoxicity. Our objective is to raise the awareness on metal-induced neuroinflammation in neurological disorders. However, it is not only just neuroinflammation that different metals could induce; they can also cause harm to the nervous system through oxidative stress, apoptosis, and autophagy, to name a few. The primary pathophysiological mechanism by which these metals induce neurological disorders remains to be determined. In addition, given the various pathways through which individuals are exposed to metals, it is necessary to also consider the effects of co-exposure to multiple metals on neurological disorders.

Antibacterial copper-filled TiO2 coating of cardiovascular implants to prevent infective endocarditis-A pilot study

BACKGROUND

Infective endocarditis (IE) poses a significant health risk, especially in patients with prosthetic heart valves. Despite advances in treatment, mortality rates remain high. This study aims to investigate the antibacterial properties of a copper titanium dioxide (4× Cu-TiO2) coating on cardiovascular implants against Staphylococcus aureus, a common causative agent of IE.

METHODS

Titanium oxide carriers functionalized with copper ions were employed as an antibacterial coating for heart and vascular prostheses. The coating's antibacterial efficacy was assessed using S. aureus ATCC 29213. Microscopic evaluations were conducted on both biological and artificial materials. Antibacterial activity was qualitatively assessed via a modified disc diffusion method and quantitatively measured through colony counts in NaCl suspensions.

RESULTS

The coating process was successfully applied to all tested cardiovascular prosthetic materials. Qualitative assessments of antibacterial effectiveness revealed an absence of bacterial growth in the area directly beneath the coated valve. Quantitative evaluations showed a significant reduction in bacterial colonization on coated mechanical valves, with 2.95 × 104 CFU per valve, compared to 1.91 × 105 CFU in control valves.

CONCLUSIONS

The 4× Cu-TiO2 coating demonstrated promising antibacterial properties against S. aureus, suggesting its potential as an effective strategy for reducing the risk of bacterial colonization of cardiovascular implants. Further studies are needed to assess the longevity of the coating and its efficacy against other pathogens.

FDX1 inhibits thyroid cancer malignant progression by inducing cuprotosis

Cuprotosis is a recently identified cell death form that caused by intracellular copper accumulation and regulated by FDX1. This work aimed to explore the role of cuprotosis and the pivotal regulatory gene FDX1 in thyroid cancer development. We observed that expression of FDX1 in tumor section was notably lower than that in non-tumor sections in clinical samples. Induction of cuprotosis by elesclomol (ES) significantly repressed the in vitro and in vivo growth of thyroid cancer cells, simultaneously elevated Cu level and expression of FDX1, whereas depletion of FDX1 abolished these effects. Knockdown of FDX1 decreased the lipoylation level of DLAT and DLST in thyroid cancer cells, alleviated cuprotosis-induced cell death, simultaneously upregulated the levels of PA and α-KG. These findings demonstrated that FDX1 promotes the cuprotosis of thyroid cancer cells via regulating the lipoylation of DLAT.

Analysis of the value of copper erythrocyte concentration measurement in the diagnosis of copper deficiency in bovines

BACKGROUND

A reliable and practical method for assessing Cu status in live animals is not available. Blood Cu levels may not accurately reflect the true Cu status of the herd, and can over-predict Cu status during stress and inflammation. On the other hand, assessment of liver Cu is the most reliable indicator of Cu stores, but it is an invasive procedure that requires specialized training. The aim of this study was to evaluate the usefulness of Cu levels in red blood cells to determine the Cu status, with special emphasis in their correlation with erythrocyte Cu, Zn superoxide dismutase enzyme activity (ESOD), in bovines with Cu deficiency induced by high molybdenum and sulfur levels in the diet.

METHODS

Three similar assays were performed, with a total of twenty eight calves. The Cu-deficient group (n = 15) received a basal diet supplemented with 11 mg of Mo/kg DM as sodium molybdate, and S as sodium sulfate. The control group (n = 13) received a basal diet supplemented with 9 mg of Cu/kg DM as copper sulfate. Samples of blood and liver were taken every 28-35 days. Cu levels were measured in liver (expressed as µg/g DM), plasma (expressed as µg/dl), and erythrocytes (expressed as µg/g Hb) by flame atomic absorption spectroscopy. Superoxide dismutase (SOD1) activity was determined in red blood cells and was expressed as IU/mg hemoglobin. InfoStat Statistical Software 2020 was used for the statistical analysis. Cu levels in plasma, red blood cells and liver, and ESOD activity were analyzed by ANOVA. The correlation between erythrocyte Cu levels and the rest of the parameters were analyzed by Pearson Correlation test. Unweighted Least Squares Linear Regression of SOD1 was developed. The autocorrelation between the monthly measurements was also determined by Durbin-Watson test and autocorrelation function.

RESULTS

The assays lasted 314-341 days, approximately. Levels indicative of Cu deficiency for bovines were detected at 224 days (23 ± 11.6 µg/g DM) for liver Cu concentration; and at 198 days (55 ± 10.4 µg/dl) for plasma Cu concentration, in Cu-deficient animals. Liver and plasma Cu values indicative of Cu deficiency were not observed in the control group. Pearson Correlation test indicated that all indices of Cu status used in this study were significantly correlated. The highest value was obtained between ESOD and red blood Cu (0.74). There was a significant correlation between red blood Cu and plasma Cu (0.65), and with hepatic Cu (0.57). ESOD activity showed a similar significant positive correlation with liver Cu concentrations and with plasma Cu (0.59 and 0.58, respectively).

CONCLUSION

The extremely low levels of liver and plasma Cu, the ESOD activity, erythrocyte Cu levels, and the periocular achromotrichia observed in the Cu-deficient animals showed that the clinic phase of Cu deficiency was reached in this group. The ESOD activity and erythrocyte Cu levels showed a strong association, indicating that the values of erythrocyte Cu may serve as an effective tool in assessing Cu status and diagnose a long-term Cu deficiency in cattle.

Copper in grape and wine industry: Source, presence, impacts on production and human health, and removal methods

Heavy metals are of particular concern in grape and wine processing, especially copper. The sources of copper are diverse, including vineyard soil, copper-containing pesticides on the fruit surface, copper wine-making equipment, and exogenous addition in winemaking. Copper has potential risks to human nerves, metabolism, and others. It can inhibit yeast growth, delay fermentation, and also mediate oxidation reactions, which has a huge impact on the nutritional quality and sensory quality of fresh wine and aged wine. It is therefore crucial to detect, quantify, and remove copper from grapes and wine. However, the copper situations in the wine industries of various countries are complicated and diverse, and the existing forms of copper are quite different, which makes the research challenging. This review summarizes and analyzes the existence and influence of copper in the wine industry by analyzing the sources of, the current situation regarding, and the detection and removal methods for copper in wine. With the study, a better understanding of copper's impact on wine production will be gained, facilitating further control of copper in wine and helping the wine industry grow.

Interactive Effects of Copper and Functional Substances in Wine on Alcoholic Hepatic Injury in Mice

This study analyzed the interaction between copper and functional substances in wine under different drinking amounts on alcoholic liver injury in mice. When the daily drinking amount reached 500 mL/60 kg/day (14% abv) with just ethyl alcohol, the liver aspartate aminotransferase, alanine aminotransferase, and total triglyceride levels of mice were significantly increased to 130.71 U/L, 37.45 U/L, 2.55 U/L, the total antioxidant capacity, catalase, and glutathione level decreased significantly to 1.01 U/mL, 30.20 U/mgprot, and 2.10 U/mgprot, and the liver became gradually damaged. Wine could alleviate and reduce the damage caused by ethyl alcohol well. Low concentrations of copper (0.33, 0.66 mg/L) in wine hardly caused hepatic injury in mice and only significantly improved the aspartate aminotransferase values (109.21 U/L, 127.29 U/L) of serum. Combined with the staining evidence, in the case of medium and high intragastric doses (≥500 mL/60 kg/day), 0.99 mg/L copper (the maximum allowed by China’s national standards) in wine began to damage the liver, indicating that under this concentration, the damage of copper to the liver had begun to exceed the protective effect of wine’s functional substances on alcoholic hepatic injury. At all experimental doses, high concentrations (1.33 mg/L, 2.00 mg/L) of copper significantly aggravated alcoholic hepatic injury in mice, indicating that high concentrations of copper have a great toxicological risk. In the future, it is necessary to further strengthen the control of copper content in wine and the inspection of market wines in order to protect the health of consumers.

Bone Health in Aging Men: Does Zinc and Cuprum Level Matter?

The aim of this study was to assess the associations of serum and bone zinc (Zn) and cuprum (Cu) with bone mineral density (BMD) and content (BMC), markers of bone turnover, and sex hormones. The study group comprised 144 men treated with total hip replacement due to hip osteoarthritis. We measured total, free, and bioavailable testosterone, estradiol, and sex-hormone-binding globulin (sex hormones), as well as parathyroid hormone, osteocalcin, carboxy terminal collagen crosslinks, and N-terminal propeptide of type I procollagen (markers of bone turnover). Total body BMD, BMC, total and visceral fat, and appendicular skeletal mass (ASM) were measured using dual-energy X-ray absorptiometry. ASM index, and total and visceral fat were positively correlated with BMD. Bone Zn correlated neither with sex hormones nor with bone turnover markers; however, it was positively associated both with BMD and with BMC, while bone Cu (as opposed to serum Cu) was not. In multiple regression, the ASM index, Zn/Cu ratio (in both the serum and the bone), and serum Cu concentration were significantly associated with BMD and BMC after adjustment for age and body mass index (BMI). Our results suggest that the Zn/Cu ratio in both the serum and the bone may exert a significant positive effect on total BMD and BMC.

Urinary copper, systemic inflammation, and blood lipid profiles: Wuhan-Zhuhai cohort study

Copper have been reported to be associated with metabolic diseases. However, results on copper exposure with blood lipid profiles are inconsistent, and the underlying mechanisms of this association remain unclear. This study focused on investigating associations between urinary copper and blood lipid profiles; and exploring the potential role of systemic inflammation in such relationships. Concentrations of urinary copper, plasma C-reactive protein (CRP), and four blood lipid parameters (e.g., Total cholesterol [TC], triglycerides [TG], low-density lipoprotein cholesterol [LDL-C], and high-density lipoprotein cholesterol [HDL-C]) were measured in the adult participants from Wuhan-Zhuhai cohort. The associations between copper, CRP, and four blood lipids were assessed by the multivariable linear regression models, and the 3D mesh graphs was used to examine the joint effects of copper exposure and CRP on four blood lipid parameters. In addition, we used mediation analysis to investigate the mediated effects of CRP in the relationships between copper exposure and blood lipid profiles. Each 1% increase in urinary copper was statistically significantly associated with a 5.32% (95% CI: 2.48%, 8.24%) increase in TG after adjusting for the confounders (P < 0.05). No significant associations were observed between urinary copper and the other three blood lipid parameters (all P > 0.05). In addition, urinary copper increased monotonically with plasma CRP elevation, which in turn, was positively associated with TC, TG, and LDL-C and negatively related to HDL-C (all P < 0.05). Results from 3D mesh graphs demonstrated that increased levels of plasma CRP with higher urinary copper corresponded to higher TC, TG, LDL-C, and lower HDL-C concentrations. Mediation analysis observed that CRP mediated 6.27% in the relationships of urinary copper and TG. These findings suggest that systemic inflammation partly mediated the association between copper exposure and abnormal blood lipid, and may contribute to the development of dyslipidemias.

Copper Supplementation, A Challenge in Cattle

Ensuring adequate copper supplementation in ruminants is a challenging task due to the complexity of copper metabolism in these animals. The three-way interaction between copper, molybdenum and sulphur (Cu-Mo-S) in the rumen makes ruminants, particularly cattle, very susceptible to suffering from secondary copper deficiency. Paradoxically, excessive copper storage in the liver to prevent deficiency becomes a hazard when ruminants are fed copper-supplemented diets even slightly above requirements. While cattle were traditionally thought to be relatively tolerant of copper accumulation, and reports of copper poisoning were until recently somewhat rare, in recent years an increased number of episodes/outbreaks of copper toxicity in cattle, particularly in dairy cattle, have been reported worldwide. The growing number of lethal cases reported seems to indicate that copper intoxication is spreading silently in dairy herds, urging the development of strategies to monitor herd copper status and improve farmers' awareness of copper toxicity. In fact, monitoring studies carried out on numerous samples collected from culled animals in slaughterhouses and/or diagnostic laboratories have demonstrated that large numbers of animals have hepatic copper concentrations well above adequate levels in many different countries. These trends are undoubtedly due to copper supplementation aimed at preventing copper deficiency, as dietary copper intake from pasture alone is unlikely to cause such high levels of accumulation in liver tissue. The reasons behind the copper overfeeding in cattle are related both to a poor understanding of copper metabolism and the theory of "if adding a little produces a response, then adding a lot will produce a better response". Contrary to most trace elements, copper in ruminants has narrow margins of safety, which must also be formulated considering the concentrations of copper antagonists in the diet. This review paper aims to provide nutritionists/veterinary practitioners with the key points about copper metabolism in cattle to guarantee an adequate copper supply while preventing excessive hepatic copper loading, which requires à la carte copper supplementation for each herd.

Mycorrhizal Inoculation Differentially Affects Grapevine's Performance in Copper Contaminated and Non-contaminated Soils

Plant inoculation with arbuscular mycorrhizal fungi (AMF) is increasingly employed to enhance productivity and sustainability in agricultural ecosystems. In the present study, the potential benefits of AMF inoculation on young grapevines replanted in pots containing vineyard soil with high Cu concentration were evaluated. For this purpose, one-year-old cv. Touriga Nacional grapevines grafted onto 1103P rootstocks were further inoculated with Rhizoglomus irregulare or Funneliformis mosseae, or left non-inoculated, and maintained in a sterilized substrate under greenhouse conditions for three months. After this time, half of the plants were transplanted to containers filled with an Arenosol from a vineyard which had been artificially contaminated or not with 300 mg kg-1 of Cu. At the end of the growing season, soil nutrient concentration, soil dehydrogenase activity and mycorrhizal colonization rate were analyzed. Grapevine performance was assessed by measuring several vegetative growth and physiological parameters as well as nutrient concentrations in leaves and roots. In the non-contaminated soil, R. irregulare- and F. mosseae-inoculated plants had significantly greater root biomass than the non-inoculated ones. However, the opposite effect was observed in the Cu-contaminated soil, where non-inoculated plants performed better regarding shoot and root development. Concerning nutrient levels, an increase in Cu, Mg and Mn concentrations was observed in the roots of plants growing in the contaminated soil, although only Mn was translocated to leaves. This led to a large increase in leaf Mn concentrations, which was significantly higher in non-inoculated and F. mosseae- inoculated plants than in the R. irregulare- inoculated ones. Copper contamination induced a general decrease in leaf N, P and Fe concentrations as well as chlorosis symptoms. The largest decrease in N and P was observed in F. mosseae- inoculated plants, with 73 and 31.2%, respectively. However, these plants were the ones with the least decrease in Fe concentration (10% vs. almost 30% in the other two inoculation treatments). In conclusion, this study indicates that soil Cu levels can modify the outcome of AMF inoculations in young grapevines, disclosing new AMF-plant associations potentially relevant in vineyards with a tradition of Cu-based fungicide application.

Release of Cu2+ from a copper-filled TiO2 coating in a rabbit model for total knee arthroplasty

The aim of this study was the investigation of a copper-filled TiO2 coating, that in vitro showed good antibacterial properties combined with good tissue tolerance in an animal model. To better understand the antibacterial mechanism of the bioactive coating the release of copper (Cu) ions over time was monitored to be able to detect possible threats as well as possible fields of application. 30 New Zealand White rabbits were divided into two groups with 15 animals per group. In group 1 (control group) Ti6Al4 V bolts were implanted into the distal femur, in group 2 the Ti6Al4 V bolts were coated with four TiO2-coatings with integrated Cu(2+)-ions (4 × Cu-TiO2). Blood tests were performed weekly until the animals were sacrificed 4 weeks postoperative. The maximum peak of Cu and ceruloplasmin concentration could be seen in both groups one week postoperative, whereas the Cu values in group II were significantly higher. The Cu concentration in both groups approximated the initial basic values 4 weeks postoperative. The 4 × Cu-TiO2 coating tested in our rabbit model for total knee arthroplasty is an active coating that releases potentially antibacterial Cu(2+) for 4 weeks with a peak 1 week postoperative. The bioactive coating could be a promising approach for a use in the field of implant related infection, orthopaedic revision and tumor surgery in the future.

Associations between serum C-reactive protein and serum zinc, ferritin, and copper in Guatemalan school children

Inflammation affects trace nutrient concentrations, but research on copper and particularly in children is limited. We assessed associations between serum C-reactive protein (CRP) and zinc, iron, copper, and other biomarkers (alkaline phosphatase, hemoglobin, and albumin), in 634 healthy 6- to 11-year-old Guatemalan schoolchildren. CRP was measured by a standardized, high-sensitive method. For significant associations with CRP, we stratified nutrient concentrations across categories of CRP and compared concentrations above and below several CRP cutoff points (0.5, 1, 3, 5, and 10 mg/L), and then adjusted values using correction factors (ratios of geometric means of the nutrients in the low and high groups). Prevalence of serum zinc (<65 μg/dL0, ferritin (<15 μg/L), and copper (<90 μg/dL) deficiency were 21%, 2.1%, and 23.8%, respectively. Median (25th and 75th percentiles) CRP was 0.56 (0.26 and 1.54) mg/L. CRP concentration was positively associated with ferritin and copper concentrations (r = 0.23 and 0.29, respectively; P < 0.0001) but not with zinc and other biomarkers (P > 0.05). Regardless of CRP cutoffs, high (> cutoff) vs. low (≤ cutoff) CRP levels had higher ferritin and copper concentrations and lower prevalence of copper deficiency of <90 μg/dL (P < 0.05). Adjustment for inflammation had the greatest influence on recalculated prevalence for the CRP 0.5 mg/L cutoff. The low ferritin prevalence hardly changed (from 2.1% to 2.5%) while the low copper prevalence changed appreciably (from 23.8% to 31.2%). In conclusion, CRP was positively associated with ferritin and copper but not with zinc concentrations. Adjustment for inflammation had little effect on low ferritin prevalence, low to begin with, and a large impact on low copper prevalence. High-sensitive CRP methods and the use of very low CRP cutoffs may be more accurate than traditional CRP methods in the adjustment of serum copper concentrations for inflammation in healthy school children.

Administration of high doses of copper to capuchin monkeys does not cause liver damage but induces transcriptional activation of hepatic proliferative responses

Liver cells respond to copper loading upregulating protective mechanisms. However, to date, except for liver content, there are no good indicators that identify individuals with excess liver copper. We hypothesized that administering high doses of copper to young (5.5 mg Cu · kg⁻¹ . d⁻¹) and adult (7.5 mg Cu · kg⁻¹ . d⁻¹) capuchin monkeys would induce detectable liver damage. Study groups included adult monkeys (2 females, 2 males) 3-3.5 y old at enrollment treated with copper for 36 mo (ACu); age-matched controls (1 female, 3 males) that did not receive additional copper (AC); young monkeys (2 female, 2 males) treated from birth with copper for 36 mo (YCu); and young age-matched controls (2 female, 2 males) that did not receive additional copper (YC). We periodically assessed clinical, blood biochemical, and liver histological indicators and at 36 mo the hepatic mRNA abundance of MT2a, APP, DMT1, CTR1, HGF, TGFβ, and NFκΒ only in adult monkeys. After 36 mo, the liver copper concentration was 4-5 times greater in treated monkeys relative to controls. All monkeys remained healthy with normal routine serum biochemical indices and there was no evidence of liver tissue damage. Relative mRNA abundance of HGF, TGFβ and NFκB was significantly greater in ACu than in AC monkeys. In conclusion, capuchin monkeys exposed to copper at doses up to 50 times the current upper level enhanced expression of genes related to inflammation and injury without clinical, blood biochemical, or histological evidence of liver damage.

Risks and benefits of copper in light of new insights of copper homeostasis

Copper is an essential micronutrient involved in a variety of biological processes indispensable to sustain life. At the same time, it can be toxic when present in excess, the most noticeable chronic effect being liver damage. Potent, efficient regulatory mechanisms control copper absorption in the digestive tract and copper biliary excretion; absorption ranges between 12 and 60% in humans, depending on Cu intake, presence of other factors in the diet that may promote or inhibit its absorption and on the copper status of the individual. Current evidence suggests that copper deficiency may be more prevalent than previously thought, while copper toxicity is uncommon under customary daily life conditions. Menkes syndrome and Wilson disease are genetic conditions associated with severe copper deficiency and severe copper toxicity, respectively. Effects of milder degrees of copper deficiency and excess copper exposure are not well described, mainly due to lack of sensitive and specific indicators; serum copper concentration and ceruloplasmin are the most frequently used indicators, but they only detect rather intense changes of copper status. Of the many proteins assessed as potential markers of copper status the chaperone of Zn-Cu superoxide dismutase (CCS1) has yielded promising results; data on its performance under different conditions are needed to confirm its use as an indicator of early copper deficiency. Defining copper requirements and upper safe limits of consumption (UL) is a complex process since there are adverse health consequences from both copper deficiency and copper excess (U shape curve). The regulatory framework for risk assessment of essential trace elements introduced by the International Programme on Chemical Safety (IPCS) has proposed a homeostatic model to determine the Adequate Range of Oral Intake (AROI) of essential trace elements; the nadir of the resulting U shape curve serves to define the AROI. At this range of intake physiological mechanisms allow for normal homeostasis and basically, there are no detectable adverse effects. At present, Recommended Dietary Intakes (DRIs) and Adequate Intakes (AIs) are used to recommend copper intakes at different ages and life situations. Evidence obtained in humans and non-human primates presented here suggest that current copper UL should be re evaluated. Developing the scientific basis for a copper UL and evaluating the relevance of copper deficiency globally are future key challenges for copper researchers.

Increased levels of lead in the blood and frequencies of lymphocytic micronucleated binucleated cells among workers from an electronic-waste recycling site

In recent years, adverse health effects of chemicals from electronic waste (e-waste) have been reported. However, little is known about the genotoxic effects of chemicals in e-waste. In the present study, air concentrations of the toxic metals at e-waste and control sites were analyzed using inductively-coupled plasma mass spectrometry. Levels of toxic metals (lead, copper and cadmium) in blood and urine were detected using atomic absorption spectrophotometry in 48 exposed individuals and 56 age- and sex-matched controls. The frequencies of lymphocytic micronucleated binucleated cells (MNBNCs) were determined using a cytokinesis-block micronucleus assay. Results indicated that blood lead levels were significantly higher in the exposed group (median: 11.449 μg/dL, 1st/3rd quartiles: 9.351-14.410 μg/dL) than in the control group (median: 9.104 μg/dL, 1st/3rd quartiles: 7.275-11.389 μg/dL). The exposed group had higher MNBNCs frequencies (median: 4.0 per thousand, 1st/3rd quartiles: 2.0-7.0 per thousand) compared with the controls (median: 1.0 per thousand, 1st/3rd quartiles: 0.0-2.0 per thousand). Additionally, MNBNCs frequencies and blood lead levels were positively correlated (r = 0.254, p<0.01). Further analysis suggested that a history of working with e-waste was a predictor for increased blood lead levels and MNBNCs frequencies in the subjects. The results suggest that both the living and occupational environments at the e-waste site may be risk factors for increased MNBNCs frequencies among those who are exposed.

Influence of estrogens on copper indicators: in vivo and in vitro studies

Classic copper indicators are not sensitive and specific for detecting excess copper exposure when this is higher than customary but not markedly elevated. Serum copper and ceruloplasmin (Cp) are the most commonly used indicators to assess nutritional status of copper. The objective of this paper was to study the influence of estrogens on these indicators and others used to assess early effects of excess copper exposure in humans and the expression of a set of copper related proteins in a hepatic cellular model. For the studies in humans, 107 healthy participants (18-50 years) were allocated as follows: group 1 (n = 39), women assessed on day 7 of their hormonal cycle; group 2 (n = 34), women assessed on day 21 of their hormonal cycle, and group 3 (n = 34, comparison group), healthy men. Participants received 8 mg Cu/day (as copper sulfate) during 6 months. Serum Cp and Cu, Cu-Zn-superoxide dismutase activity, liver function indicators [aspartate aminotransferase (AST), alanine aminotransferase (ALT), and gamma glutamyltransferase (GGT)], and serum Fe and Zn concentrations were measured monthly. In addition, the influence of estradiol on intracellular total copper content, hctr1, dmt1 and shbg mRNA abundance and hCTR1, and DMT1 expression was measured in HepG2 cells. Serum Cu, Fe, and Zn and liver aminotransferases but not Cu-Zn-superoxide dismutase varied depending on sex. Fe nutrition indicators, GGT, and ALT activities showed significant differences between the hormonal phases. Cellular experiments showed that estradiol increased cellular Cu concentration and hCTR1 and DMT1 mRNA expression and changed these proteins expression patterns. Estradiols significantly influence the responses to copper at the whole body and the cellular levels, suggesting that they help maintaining copper availability for metabolic needs.

Relevance of animal models for understanding mammalian copper homeostasis

As a trace element, copper has a crucial role in mammalian metabolism, but it can be toxic in excess. The importance of a balanced copper homeostasis is illustrated by several copper-associated disorders in man, such as Menkes and Wilson disease, and in a wide variety of animal models (eg, mice, dogs, and sheep). Proteins involved in controlling copper metabolism have been well studied in yeast and in vitro. Recently, naturally occurring mutants and transgenic mouse models have been used to study the physiologic role of copper transporters in copper homeostasis. We discuss the most common mammalian animal models used to study copper-related diseases, evaluate what these model systems have recently shown about copper metabolism, and discuss the importance of these models for identifying specific and sensitive biomarkers associated with copper status in the near future.

Ceruloplasmin as a marker of occupational copper exposure

Estimation of serum copper to indicate copper status in the human system in the context of moderate chronic occupational copper exposure requires a sophisticated and expensive method. Hence, a search for a suitable marker has been made and few studies have found potential in serum ceruloplasmin. In this context, the present study was initiated to explore whether ceruloplasmin could serve as a predictor of occupational copper exposure. An interviewer-administered questionnaire survey (personal, occupational and health-related information) was undertaken involving 185 employees of a copper handling industry. Serum alkaline phosphatase, serum glutamic pyruvic transaminase (SGPT), serum ceruloplasmin and serum copper were estimated in all the subjects. Multivariate analysis was undertaken using a linear regression model to understand the contribution of serum copper on serum ceruloplasmin values adjusting for the role of other confounders. Serum copper and serum ceruloplasmin values were found to have a statistically significant positive correlation (R=0.169, adjusted R(2)=0.024) after adjustment for other predictors like age, nature of job (department), job duration, smoking, serum alkaline phosphatase and SGPT. This study concludes that the serum ceruloplasmin level can act as a reliable indicator of copper status in the human body following copper exposure in cases of chronic moderate occupational exposure to copper.

Ceruloplasmin, an indicator of copper status

For clinical purposes, the non-ceruloplasmin copper fraction is routinely derived on the basis that ceruloplasmin binds six Cu atoms. However, this approach is limited because the actual ceruloplasmin copper binding is unclear. We performed direct measurement of the total serum copper and ceruloplasmin in 790 healthy individuals. We used an immunoprecipitation technique to separate ceruloplasmin and determined Cu content. With these values, we calculated the Cu/ceruloplasmin (Cp) ratio and thus generated data to support or discard the theoretical calculation of the non-ceruloplasmin fraction. Average of serum Cu and Cp levels were 18.4 +/- 4.4 micromol/l and 390 +/- 100 mg/l, respectively. The immunoprecipitation procedure allowed us to calculate a Cu/Cp ratio of 5.8, respectively, which supports the methodology of calculation that assigns a mean of six copper atoms to each ceruloplasmin molecule. With these values, we calculated that, in apparently normal adults, the non-ceruloplasmin copper (NCPC) fraction is lower than 1.3 micromol/l of Cu. In this report, we examine the Cp/Cu ratio by using Cp immunoprecipitation procedure. Our in vitro and in vivo studies indicate that, as a mean, there are 5.8 atoms of Cu per Cp molecule and that <1.3 micromol/l of Cu would correspond to the NCPC.

CCS and SOD1 mRNA are reduced after copper supplementation in peripheral mononuclear cells of individuals with high serum ceruloplasmin concentration

The limits of copper homeostatic regulation in humans are not known, making it difficult to define the milder effects of early copper excess. Furthermore, a robust assay to facilitate the detection of early stages of copper excess is needed. To address these issues, we assessed changes in relative mRNA abundance of methallothionein 2A (MT2A), prion (PrP), amyloid precursor-like protein 2 (APLP2), Cu/Zn superoxide dismutase (SOD1) and its copper chaperone (CCS) in peripheral mononuclear cells (PMNCs) from healthy adults representing the 5% highest and lowest extremes in the distribution curve of serum ceruloplasmin (Cp) concentrations of 800 individuals. The intracellular Cu content was also determined. PMNCs were isolated from individuals before and after exposure to a single daily dose of 10 mg Cu (as CuSO(4)) for 2 months. Results showed that although there were fluctuations in serum Cp values of the samples assessed before copper exposure, no significant differences were observed in cell copper content or in the relative abundance of MT2A, PrP and APLP2 transcripts in PMNCs. Also, these values were not modified after copper supplementation. However, CCS and SOD1 mRNA levels were reduced in PMNCs after copper supplementation in the individuals with the high Cp values, suggesting that they should be further explored as biomarkers of moderate copper overload in humans.

How reliable and robust are current biomarkers for copper status?

Cu is an essential nutrient for man, but can be toxic if intakes are too high. In sensitive populations, marginal over- or under-exposure can have detrimental effects. Malnourished children, the elderly, and pregnant or lactating females may be susceptible for Cu deficiency. Cu status and exposure in the population can currently not be easily measured, as neither plasma Cu nor plasma cuproenzymes reflect Cu status precisely. Some blood markers (such as ceruloplasmin) indicate severe Cu depletion, but do not inversely respond to Cu excess, and are not suitable to indicate marginal states. A biomarker of Cu is needed that is sensitive to small changes in Cu status, and that responds to Cu excess as well as deficiency. Such a marker will aid in monitoring Cu status in large populations, and will help to avoid chronic health effects (for example, liver damage in chronic toxicity, osteoporosis, loss of collagen stability, or increased susceptibility to infections in deficiency). The advent of high-throughput technologies has enabled us to screen for potential biomarkers in the whole proteome of a cell, not excluding markers that have no direct link to Cu. Further, this screening allows us to search for a whole group of proteins that, in combination, reflect Cu status. The present review emphasises the need to find sensitive biomarkers for Cu, examines potential markers of Cu status already available, and discusses methods to identify a novel suite of biomarkers.

Assessment of some blood parameters as potential markers of hepatic copper accumulation in cattle

The increasing frequency of copper (Cu) toxicosis episodes in cattle in recent years, mainly associated with excess Cu supplementation, underscores the need to identify animals in the clinically silent phase of hepatic Cu accumulation. The aim of the study reported here was to evaluate the suitability of various blood parameters as potential early markers of hepatic Cu accumulation in cattle. Paired liver and blood samples from 70 calves aged 6 to 10 months were obtained at slaughter in a region in northwestern Spain where animals usually have hepatic Cu concentration higher than safe values. Neither serum Cu concentration nor ceruloplasmin (CP) concentration, the 2 parameters most commonly used for diagnosis of Cu deficiency, were significantly associated with hepatic Cu concentration. However, whole-blood Cu concentration had a slight but significant correlation with hepatic Cu concentration (r = 0.269, P = 0.026). The use of calculated blood parameters, such as the serum or whole-blood non-CP Cu fraction, or the CP-to-serum Cu ratio, increased the correlation with the hepatic Cu concentration (r = 0.393, P = 0.001, in the case of whole-blood, non-CP Cu concentration), but the strength of the association remained insufficient for accurate prediction of hepatic Cu values. Likewise, hepatic enzyme (aspartate transaminase and gamma-glutamyltransferase) activities were significantly or nearly correlated significantly with hepatic Cu concentration, but the strength of the association remained too low for accurate prediction. It is concluded that direct analysis of Cu concentration in liver biopsy specimens--preferably postmortem liver samples obtained at slaughter--is the best technique currently available for detecting chronic subclinical Cu accumulation in cattle at risk for supraoptimal Cu exposure.

Changes in tubular dysfunction marker levels in parallel with the levels of copper, rather than cadmium, in urine of middle-aged women in non-polluted areas

OBJECTIVE

This study was initiated to investigate if and to what extent the elevations in urinary alpha(1)- and beta(2)-microglobulins (alpha(1)-MG and beta(2)-MG, respectively) are specific to Cd nephro-toxicity.

METHODS

Stored urine samples, collected from 1,000 adult women in 11 prefectures all over Japan, were analysed for eight elements (Ca, Cd, Co, Cu, Mg, Mn, Ni and Zn), alpha(1)-MG, beta(2)-MG, creatinine (CR) and specific gravity (SG); the data were cited from previous publications. The levels of eight elements and two MGs were expressed as observed and after correction for CR or SG (1.016). Age, CR and SG distributed normally, whereas two MGs and eight elements distributed log-normally. The 1,000 cases were classified into quartiles (i.e., 250 cases/group) of the lowest to the highest values (Groups A to D) for each element.

RESULTS

alpha(1)-MG and beta(2)-MG increased as a function of Ca, Cd and Cu when corrected for CR, and the two MGs increased in parallel only with Cd and Cu after SG correction. Prevalence of alpha(1)-MG-uria (cut-off values; 5.3 and 6.5 mg/g cr or l) and beta(2)-MG-uria (cut-off values; 300 and 400 microg/g cr or l) was elevated with increasing Ca, Cd and Cu when corrected for CR, but only with Cd and Cu when corrected for SG. Multiple regression analysis of 353 cases of 50-59 year-old women with the eight element levels as independent variables and one of the two MGs as a dependent variable showed that Cu was the most influential element, and both Cd and Zn were less influential.

CONCLUSIONS

Urinary levels of alpha(1)-MG and beta(2)-MG among women with no environmental Cd exposure correlated more closely with Cu levels than Cd levels in urine. The observation suggests that sub-clinical elevation in alpha(1)-MG and beta(2)-MG is not always attributable to nephro-toxicity of Cd, and that consideration on possible effects of other elements such as Cu is necessary.

Copper content of grape and wine from Italian farms

The copper content of grape and wine from 16 wine-farms in Italy was studied during the harvest of 2003. The influence of the number of copper applications, the period between the last application and harvest, and the total amount of copper applied was examined. Of the total number of samples analysed, 13% of grape samples and 18% of wine samples exceeded the maximum residue level (MRL). The total amount of copper applied and the number of days between the last application and harvest explained 44% of the concentration of copper in grape. This low correlation may be due to other influencing factors, such as meteorology and the application method. In 2003, conditions were unusually dry and the recommended safety interval for copper application (20 days) was not sufficient to guarantee a residue level in grape below the MRL (20 mg kg(-1)). In order to reduce the probability of copper residues being close to the MRL, a period of 40-50 days between the last application and harvest is suggested. Furthermore, the copper content of grape and wine was not dependent on the pest management strategy of the farm (conventional, integrated or organic). A more important factor influencing copper residue levels may be that copper applications are made in response to the prediction of a disease outbreak rather than being dependent on the pest management strategy in place. No difference in copper content was observed between red and white grape or wine.

Effects of 12 metal ions on iron regulatory protein 1 (IRP-1) and hypoxia-inducible factor-1 alpha (HIF-1alpha) and HIF-regulated genes

Several metal ions that are carcinogenic affect cellular iron homeostasis by competing with iron transporters or iron-regulated enzymes. Some metal ions can mimic a hypoxia response in cells under normal oxygen tension, and induce expression of HIF-1alpha-regulated genes. This study investigated whether 12 metal ions altered iron homeostasis in human lung carcinoma A549 cells as measured by an activation of IRP-1 and ferritin level. We also studied hypoxia signaling by measuring HIF-1alpha protein levels, hypoxia response element (HRE)-driven luciferase reporter activity, and Cap43 protein level (an HIF-1alpha responsive gene). Our results show the following: (i) Ni(II), Co(II), V(V), Mn(II), and to a lesser extent As(III) and Cu(II) activated the binding of IRP-1 to IRE after 24 h, while the other metal ions had no effect; (ii) 10 of 12 metal ions induced HIF-1alpha protein but to strikingly different degrees. Two of these metal ions, Al(III) and Cd(II), did not induce HIF-1alpha protein; however, as indicated below, only Ni(II), Co (II), and to lesser extent Mn(II) and V(V) activated HIF-1alpha-dependent transcription. The combined effects of both [Ni(II) + As(III)] and [Ni(II) + Cr(VI)] on HIF-1alpha protein were synergistic; (iii) Addition of Fe(II) with Ni(II), Co(II), and Cr(VI) attenuated the induction of HIF-1alpha after 4 h treatment; (iv) Ni(II), Co(II), and Mn(II) significantly decrease ferritin level after 24 h exposure; (v) Ni(II), Co(II), V(V), and Mn(II) activated HRE reporter gene after 20 h treatment; (vi) Ni(II), Co(II), V(V), and Mn(II) increased the HIF-1-dependent Cap43 protein level after 24 h treatment. In conclusion, only Ni (II), Co (II), and to a lesser extent Mn(II) and V(V) significantly stabilized HIF-1alpha protein, activated IRP, decreased the levels of ferritin, induced the transcription of HIF-dependent reporter, and increased the expression of Cap43 protein levels (HIF-dependent gene). The mechanism for the significant stabilization and elevation of HIF-1alpha protein which drives these other parameters was previously shown by us and others to involve a loss of cellular Fe as well as inhibition of HIF-1alpha-dependent prolyl hydroxylases which target the binding of VHL ubiquitin ligase and degrade HIF-1alpha. Even though there were small effects of some of the other metals on IRP and HIF-1alpha, downstream effects of HIF-1alpha activation and therefore robust hypoxia signaling were only observed with Ni(II), Co(II), and to much lesser extents with Mn(II) and V(V) in human A549 lung cells. It is of interest that the metal ions that were most effective in activating hypoxia signaling were the ones that were poor inducers of metallothionein protein and also decreased Ferritin levels, since both of these proteins can bind metal ions and protect the cell against toxicity in human lung cells. It is important to study effects of these metals in human lung cells since this represents a major route of human environmental and occupational exposure to these metal ions.

Effects of chronic copper exposure during early life in rhesus monkeys

BACKGROUND

Whether infants regulate copper absorption and the potential effects of excess copper in early life remain poorly defined.

OBJECTIVE

The objective of the study was to assess copper retention, liver copper content, and liver function in infant rhesus monkeys fed infant formula containing 6.6 mg Cu/L.

DESIGN

From birth to 5 mo of age, infant rhesus monkeys were fed formula that was supplemented with copper (0.6 mg Cu/L; n = 5) or not supplemented (n = 4). In all animals, weight and crown-rump length (by anthropometry), hemoglobin, hematocrit, plasma ceruloplasmin activity, and zinc and copper concentrations were measured monthly (birth to 6 mo) and at 8 and 12 mo. When the animals were 1, 5, and 8 mo old, liver copper and metallothionein concentrations, liver histology (by light and electron microscopy), and the number of Kupffer cells were assessed, and 67Cu retention was measured. Liver function was assessed by measurement of plasma alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transferase, and alkaline phosphatase activities and protein, albumin, bilirubin, and blood urea nitrogen concentrations.

RESULTS

67Cu retention was 19.2% and 10.9% after 1 and 5 mo of copper treatment, respectively, compared with approximately 75% in controls at age 2 mo. At age 8 mo, 67Cu retention was 22.9% in copper-treated animals and 31.5% in controls. Liver histology remained normal by light microscopy, with mild ultrastructural signs of cell damage at 5 mo. Liver copper concentration was 4711, 1139, and 498 microg/g dry tissue at 1, 5, and 8 mo, respectively, in copper-treated animals and 250 microg/g at 2 mo in controls. Measurements could not be completed in all animals.

CONCLUSIONS

No clinical evidence of copper toxicity was observed. Copper absorption was down-regulated; increases in liver copper content at ages 1 and 5 mo did not result in histologic damage. Ultrastructural changes at age 5 mo could signal early cellular damage.

Sex and ceruloplasmin modulate the response to copper exposure in healthy individuals

Previous studies indicated that sex might influence the response to copper exposure. Ceruloplasmin (Cp) is an indicator of Cu status, but it is not clear whether and how it reflects changes of Cu status among healthy individuals. In this study, 82 apparently healthy women and men were chosen from 800 individuals because their Cp values belonged to the higher and lower 10% of the group Cp distribution curve. Before and after receiving a supplement of 10mg Cu/day (upper limit of daily intake) for 2 months, we performed blood and urinary biochemical measurement of potential Cu markers. We used principal component analysis and linear discriminant analysis to identify blood and/or urinary Cu indicators that showed a differential response to copper. Results showed that Cp values in serum represent a reliable indicator to differentiate subgroups within the normal population in their response to Cu exposure. The response depends on Cp values and on sex, such that women with higher and men with lower Cp values exhibit the greatest response.

Iron, zinc, and copper: contents in common Chilean foods and daily intakes in Santiago, Chile

OBJECTIVES

We determined the iron (Fe), zinc (Zn), and copper (Cu) contents of common Chilean foods and assessed the intakes of these elements in a population living in Santiago, Chile.

METHODS

We selected foods most consumed by a Chilean population (n = 108). We performed wet digestion of the sample by using nitric, perchloric, and sulfuric acids. Fe, Zn, and Cu were determined by atomic absorption spectrophotometry. Fe, Zn, and Cu intakes were evaluated by a dietary survey (24-h recall questionnaire for 4 non-consecutive days) in a representative sample of the population of Santiago, Chile (n = 252 subjects).

RESULTS

Fe intakes (mg/d) were 7.8 +/- 9.6 (in infants), 8.1 +/- 5.3 (in 1- to 10-y-olds), 15.1 +/- 7.3 (11- to 19-y-old males), 9.5 +/- 4.3 (11- to 19-y-old females), 13.5 +/- 6.5 (20- to 64-y-old males), 9.1 +/- 3.9 (20- to 64-y-old females), 11.4 +/- 4.9 (> or =65-y-old males), and 11.3 +/- 5.0 (> or =65-y-old females). Zn intakes (mg/d) were 3.8 +/- 1.8 (infants), 6.2 +/- 3.1 (1- to 10-y-old subjects), 8.9 +/- 4.1 (11- to 19-y-old males), 5.7 +/- 2.0 (11- to 19-y-old females), 7.6 +/- 3.4 (20- to 64-y-old males), 6.4 +/- 3.5 (20- to 64-y-old females), 6.6 +/- 2.9 (> or =65-y-old males), and 6.9 +/- 2.4 (> or =65-y-old females). Cu intakes (mg/d) were 0.5 +/- 0.3 (infants), 0.8 +/- 0.5 (1- to 10-y-old subjects), 1.4 +/- 0.7 (11- to 19-y-old males), 1.2 +/- 0.3 (11- to 19-y-old females), 0.9 +/- 0.4 (20- to 64-y-old males), 1.0 +/- 0.4 (20- to 64-y-old females), 1.1 +/- 0.3 (> or =65-y-old males), and 0.9 +/- 0.4 (> or =65-y-old females).

CONCLUSIONS

Fe deficiency was greater in infants and women of fertile age. All age and sex groups had a high risk of Zn deficiency, whereas adults of both sexes had a moderate increased risk of Cu deficiency.

Trace amounts of copper in water induce beta-amyloid plaques and learning deficits in a rabbit model of Alzheimer's disease

Despite the crucial role played by cholesterol and copper in nutrition and normal brain function, recent evidence indicates that they may both be important factors in the etiology of Alzheimer's disease (AD). Here we provide critical evidence for the role of cholesterol and copper in AD by showing that the addition of trace amounts of copper (0.12 ppm) to water given to cholesterol-fed rabbits can induce beta-amyloid (Abeta) accumulation, including senile plaque-like structures in the hippocampus and temporal lobe, and can significantly retard the ability of rabbits to learn a difficult trace conditioning task. The Abeta deposits do not affect the ability of rabbits to detect or respond to the training stimuli nor to learn a simpler delay conditioning task. Trace amounts of copper in drinking water may influence clearance of Abeta from the brain at the level of the interface between the blood and cerebrovasculature and combined with high cholesterol may be a key component to the accumulation of Abeta in the brain, having a significant impact on learning and memory. Cholesterol-fed rabbits have at least 12 pathological markers seen in AD, suggesting that the cholesterol-fed rabbit is a good animal model for studying AD.