Copper deficiency reversibly impairs DNA synthesis in activated T lymphocytes by limiting interleukin 2 activity

Regulation of anti-tumor immunity by metal ion in the tumor microenvironment

Metal ions play an essential role in regulating the functions of immune cells by transmitting intracellular and extracellular signals in tumor microenvironment (TME). Among these immune cells, we focused on the impact of metal ions on T cells because they can recognize and kill cancer cells and play an important role in immune-based cancer treatment. Metal ions are often used in nanomedicines for tumor immunotherapy. In this review, we discuss seven metal ions related to anti-tumor immunity, elucidate their roles in immunotherapy, and provide novel insights into tumor immunotherapy and clinical applications.

The roles of essential trace elements in T cell biology

T cells are crucial for adaptive immunity to regulate proper immune response and immune homeostasis. T cell development occurs in the thymus and mainly differentiates into CD4+ and CD8+ T cell subsets. Upon stimulation, naive T cells differentiate into distinct CD4+ helper and CD8+ cytotoxic T cells, which mediate immunity homeostasis and defend against pathogens or tumours. Trace elements are minimal yet essential components of human body that cannot be overlooked, and they participate in enzyme activation, DNA synthesis, antioxidant defence, hormone production, etc. Moreover, trace elements are particularly involved in immune regulations. Here, we have summarized the roles of eight essential trace elements (iron, zinc, selenium, copper, iodine, chromium, molybdenum, cobalt) in T cell development, activation and differentiation, and immune response, which provides significant insights into developing novel approaches to modulate immunoregulation and immunotherapy.

Effect of Astaxanthin and Copper Supplementation on Growth, Immunity, Antioxidant, and Blood Biochemical Status of Growing Murrah Buffalo Heifers

This study was aimed to explore the effect of astaxanthin (ASTX) and copper (Cu) supplementation on the growth, immunity, antioxidant, and blood biochemical status of growing Murrah buffalo heifers. Twenty-eight Murrah buffalo heifers were selected and randomly divided into 4 groups (n = 7) after blocking by body weight (BW) (129.86 ± 5.37 kg) and age (9.05 ± 1.02 months). The heifers were fed basal total mixed ration diet without supplementation (CON) or with ASTX (0.20 mg/kg BW; AX), Cu (10 mg/kg DM; CU), or ASTX + Cu (0.20 mg/kg BW + 10 mg/kg DM; AX + CU) for 90 days of study period. The result showed that BW and dry matter intake (DMI) were significantly higher (P < 0.05) in AX + CU than that in other groups. The average daily gain (ADG) and feed conversion efficiency (FCE) were statistically higher (P < 0.05) in treatments than the values observed in CON. The feed conversion ratio (FCR) was reported significantly lower (P < 0.05) in the AX + CU group followed by AX, CU, and CON groups. The total leukocytes count (TLC), lymphocytes, and total immunoglobulin (TIG) were statistically higher (P < 0.05) in AX + CU groups than that found in other groups. However, neutrophil % decreased (P < 0.05) in the AX + CU group than its level in other groups. Superoxide dismutase (SOD), catalase (CAT), and total antioxidant (TAA) levels were observed higher (P < 0.05) in treatments supplemented with ASTX, Cu, or both than CON group. Thiobarbituric acid reactive substance (TBARS) concentration was lower (P < 0.05) in treatments than its level found in the CON group. Glucose level was higher (P < 0.05); however, non-esterifies fatty acid (NEFA) was lower (P < 0.05) in AX + CU than that in others groups. The level of cholesterol (CH), HDL cholesterol (HDL-CH), alkaline phosphatase (ALP), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) were reported lower (P < 0.05) in the AX + CU group followed by CU, AX, and CON groups. The copper (Cu) level was higher (P < 0.05) in CU and AX + CU than AX and CON groups. The result of the present study indicated that the supplementation of ASTX, Cu alone, or their combination improved the growth, immunity, antioxidant status, and liver function of growing heifers.

The Role of Copper Homeostasis in Brain Disease

In the human body, copper is an important trace element and is a cofactor for several important enzymes involved in energy production, iron metabolism, neuropeptide activation, connective tissue synthesis, and neurotransmitter synthesis. Copper is also necessary for cellular processes, such as the regulation of intracellular signal transduction, catecholamine balance, myelination of neurons, and efficient synaptic transmission in the central nervous system. Copper is naturally present in some foods and is available as a dietary supplement. Only small amounts of copper are typically stored in the body and a large amount of copper is excreted through bile and urine. Given the critical role of copper in a breadth of cellular processes, local concentrations of copper and the cellular distribution of copper transporter proteins in the brain are important to maintain the steady state of the internal environment. The dysfunction of copper metabolism or regulatory pathways results in an imbalance in copper homeostasis in the brain, which can lead to a myriad of acute and chronic pathological effects on neurological function. It suggests a unique mechanism linking copper homeostasis and neuronal activation within the central nervous system. This article explores the relationship between impaired copper homeostasis and neuropathophysiological progress in brain diseases.

Relationship between copper and immunity: The potential role of copper in tumor immunity

Copper is an essential trace element in an organism, and changes in copper levels in vivo often indicate a diseased state. Copper and immunity have been discussed since the last century, with copper deficiency significantly affecting the development and function of the immune system, such as increased host susceptibility to various pathogens, decreased number and impaired function of neutrophils, reduced antibacterial activity of macrophages, decreased proliferation of splenocytes, impaired B cell ability to produce antibodies and impaired function of cytotoxic T lymphocyte and helper T cells. In the past 20 years, some studies have shown that copper ions are related to the development of many tumors, including lung cancer, acute lymphoid leukaemia, multiple myeloma and other tumors, wherein copper ion levels were significantly elevated, and current studies reveal that copper ions are involved in the development, growth and metastasis of tumors through various pathways. Moreover, recent studies have shown that copper ions can regulate the expression of PD-L1, thus, attention should be paid to the important role of copper in tumor immunity. By exploring and studying copper ions and tumor immunity, new insights into tumor immunity could be generated and novel therapeutic approaches to improve the clinical prognosis of patients can be provided.

Antioxidant, Anti-inflammatory, and Immunomodulatory Roles of Nonvitamin Antioxidants in Anti-SARS-CoV-2 Therapy

Viral pathologies encompass activation of pro-oxidative pathways and inflammatory burst. Alleviating overproduction of reactive oxygen species and cytokine storm in COVID-19 is essential to counteract the immunogenic damage in endothelium and alveolar membranes. Antioxidants alleviate oxidative stress, cytokine storm, hyperinflammation, and diminish the risk of organ failure. Direct antiviral roles imply: impact on viral spike protein, interference with the ACE2 receptor, inhibition of dipeptidyl peptidase 4, transmembrane protease serine 2 or furin, and impact on of helicase, papain-like protease, 3-chyomotrypsin like protease, and RNA-dependent RNA polymerase. Prooxidative environment favors conformational changes in the receptor binding domain, promoting the affinity of the spike protein for the host receptor. Viral pathologies imply a vicious cycle, oxidative stress promoting inflammatory responses, and vice versa. The same was noticed with respect to the relationship antioxidant impairment-viral replication. Timing, dosage, pro-oxidative activities, mutual influences, and interference with other antioxidants should be carefully regarded. Deficiency is linked to illness severity.

Emerging roles of the copper-CTR1 axis in tumorigenesis

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

Immunoinflammatory effects of dietary bioactive compounds

Inflammation is a key mechanism of the immune system that can be elicited by several factors, among them several chemical, physical and biological agents. Once stimulated, the inflammatory response activates a series of signaling pathways and a number of immune cells which promote, in a very coordinated manner, the neutralization of the infectious agent. However, if uncontrolled, the inflammatory status may become chronic leading, potentially, to tissue damage and disease onset. Several risk factors are associated with the development of chronic inflammation and, among these factors, diet plays an essential role. In this chapter the effects of some dietary bioactive compounds, including micronutrients, omega-3 fatty acids, nucleotides and polyphenols, on the immunoinflammatory responses in different cellular, animal and human studies have been summarized.

Revisiting the Pathoetiology of Multiple Sclerosis: Has the Tail Been Wagging the Mouse?

Multiple Sclerosis (MS) is traditionally considered an autoimmune-mediated demyelinating disease, the pathoetiology of which is unknown. However, the key question remains whether autoimmunity is the initiator of the disease (outside-in) or the consequence of a slow and as yet uncharacterized cytodegeneration (oligodendrocytosis), which leads to a subsequent immune response (inside-out). Experimental autoimmune encephalomyelitis has been used to model the later stages of MS during which the autoimmune involvement predominates. In contrast, the cuprizone (CPZ) model is used to model early stages of the disease during which oligodendrocytosis and demyelination predominate and are hypothesized to precede subsequent immune involvement in MS. Recent studies combining a boost, or protection, to the immune system with disruption of the blood brain barrier have shown CPZ-induced oligodendrocytosis with a subsequent immune response. In this Perspective, we review these recent advances and discuss the likelihood of an inside-out vs. an outside-in pathoetiology of MS.

Is copper beneficial for COVID-19 patients?

Copper (Cu) is an essential micronutrient for both pathogens and the hosts during viral infection. Cu is involved in the functions of critical immune cells such as T helper cells, B cells, neutrophils natural killer (NK) cells, and macrophages. These blood cells are involved in the killing of infectious microbes, in cell-mediated immunity and the production of specific antibodies against the pathogens. Cu-deficient humans show an exceptional susceptibility to infections due to the decreased number and function of these blood cells. Besides, Cu can kill several infectious viruses such as bronchitis virus, poliovirus, human immunodeficiency virus type 1(HIV-1), other enveloped or nonenveloped, single- or double-stranded DNA and RNA viruses. Moreover, Cu has the potent capacity of contact killing of several viruses, including SARS-CoV-2. Since the current outbreak of the COVID-19 continues to develop, and there is no vaccine or drugs are currently available, the critical option is now to make the immune system competent to fight against the SARS-CoV-2. Based on available data, we hypothesize that enrichment of plasma copper levels will boost both the innate and adaptive immunity in people. Moreover, owing to its potent antiviral activities, Cu may also act as a preventive and therapeutic regime against COVID-19.

Importance of Dietary Changes During the Coronavirus Pandemic: How to Upgrade Your Immune Response

The new coronavirus pandemic continues to spread causing further public health, social, and economic issues. The disparities in the rates of death between countries poses questions about the importance of lifestyle habits and the immune status of populations. An exploration of dietary habits and COVID-19-related death might unravel associations between these two variables. Indeed, while both nutritional excess and deficiency are associated with immunodeficiency, adequate nutrition leading to an optimally functioning immune system may be associated with better outcomes with regards to preventing infection and complications of COVID-19, as well as developing a better immune response to other pathogenic viruses and microorganisms. This article outlines the key functions of the immune system and how macronutrients, micronutrients, and metabolites from the gut microbiome can be essential in the development of an efficient immune system. In addition, the effects of intermittent fasting on the inflammatory state as well as metabolic parameters will be discussed.

Suppression of the Peripheral Immune System Limits the Central Immune Response Following Cuprizone-Feeding: Relevance to Modelling Multiple Sclerosis

Cuprizone (CPZ) preferentially affects oligodendrocytes (OLG), resulting in demyelination. To investigate whether central oligodendrocytosis and gliosis triggered an adaptive immune response, the impact of combining a standard (0.2%) or low (0.1%) dose of ingested CPZ with disruption of the blood brain barrier (BBB), using pertussis toxin (PT), was assessed in mice. 0.2% CPZ(±PT) for 5 weeks produced oligodendrocytosis, demyelination and gliosis plus marked splenic atrophy (37%) and reduced levels of CD4 (44%) and CD8 (61%). Conversely, 0.1% CPZ(±PT) produced a similar oligodendrocytosis, demyelination and gliosis but a smaller reduction in splenic CD4 (11%) and CD8 (14%) levels and no splenic atrophy. Long-term feeding of 0.1% CPZ(±PT) for 12 weeks produced similar reductions in CD4 (27%) and CD8 (43%), as well as splenic atrophy (33%), as seen with 0.2% CPZ(±PT) for 5 weeks. Collectively, these results suggest that 0.1% CPZ for 5 weeks may be a more promising model to study the ‘inside-out’ theory of Multiple Sclerosis (MS). However, neither CD4 nor CD8 were detected in the brain in CPZ±PT groups, indicating that CPZ-mediated suppression of peripheral immune organs is a major impediment to studying the ‘inside-out’ role of the adaptive immune system in this model over long time periods. Notably, CPZ(±PT)-feeding induced changes in the brain proteome related to the suppression of immune function, cellular metabolism, synaptic function and cellular structure/organization, indicating that demyelinating conditions, such as MS, can be initiated in the absence of adaptive immune system involvement.

Micronutrient-gene interactions related to inflammatory/immune response and antioxidant activity in ageing and inflammation. A systematic review

Recent longitudinal studies in dietary daily intake in human centenarians have shown that a satisfactory content of some micronutrients within the cells maintain several immune functions, a low grade of inflammation and preserve antioxidant activity. Micronutrients (zinc, copper, selenium) play a pivotal role in maintaining and reinforcing the performances of the immune and antioxidant systems as well as in affecting the complex network of the genes (nutrigenomic) with anti- and pro-inflammatory tasks. Genes of pro- and anti-inflammatory cytokines and some key regulators of trace elements homeostasis, such as Metallothioneins (MT), are involved in the susceptibility to major geriatric disease/disorders. Moreover, the genetic inter-individual variability may affect the nutrients' absorption (nutrigenetic) with altered effects on inflammatory/immune response and antioxidant activity. The interaction between genetic factors and micronutrients (nutrigenomic and nutrigenetic approaches) may influence ageing and longevity because the micronutrients may become also toxic. This review reports the micronutrient-gene interactions in ageing and their impact on the healthy state with a focus on the method of protein-metal speciation analysis. The association between micronutrient-gene interactions and the protein-metal speciation analysis can give a complete picture for a personalized nutrient supplementation or chelation in order to reach healthy ageing and longevity.

Bactericidal activity of lachrymal secretion and complement system in copper deficient bovines

Copper deficiency in humans and animals has been related to increased susceptibility to infections. Neutrophils are one of the most studied components of the immune response; however, to the best of our knowledge, other defenses of the innate immune system have not been analyzed in copper-deficient animals. Our previous studies in copper-deficient bovines have shown increased susceptibility to infectious keratoconjunctivitis, an ocular disease caused by Moraxella bovis. The objective of this work was to evaluate the bactericidal activity of lachrymal secretion and complement system, two main mechanisms of the innate immune response against M. bovis, in copper-deficient cattle. Our results indicate that copper deficiency has no effect on bactericidal activity of complement system and lachrymal secretion against M. bovis in calves. Other components of local and systemic ocular defense mechanisms that could explain the increased susceptibility to infectious keratoconjunctivitis observed in copper-deficient bovines should be investigated.

Molecular cloning, characterization and mRNA expression of copper-binding protein hemocyanin subunit in Chinese mitten crab, Eriocheir sinensis

Hemocyanin is a copper-binding protein and plays a crucial role in the physiological processes in crustacean. In this study, the cDNA encoding hemocyanin subunit from Chinese mitten crab Eriocheir sinensis (EsHc) was cloned by using EST analysis and rapid amplification of cDNA ends (RACE) approach. The full-length cDNA of EsHc was 2573 bp, consisting of a 5' untranslated region of 51 bp, a 3' untranslated region of 458 bp, and an open reading frame of 2064 bp. The deduced protein had 688 amino acid residues with molecular mass of 77,997.31 Da. Quantitative real-time RT-PCR analysis showed that the EsHc gene was expressed in haemocytes, hepatopancreas, muscles, gills, and intestines with the highest level of expression in the hepatopancreas and the lowest in the muscles. After Aeromonas hydrophila challenge, the relative expression level of EsHc in hemolymph was up-regulated at 3 h post-injection of bacteria followed by a gradual recovery from 12 to 24 h. In the second set of transcriptional studies, the mRNA expression patterns of EsHc in haemocytes and hepatopancreas were measured by quantitative real-time RT-PCR after the Chinese mitten crab were fed six diets containing different levels of copper (0, 10, 20, 40, 80 and 400 mg kg(-1)) for 8 weeks, respectively. The feeding trial showed that the expression levels of EsHc mRNA significantly increased at the copper levels of 20-40 mg kg(-1). This study implies that the expression levels of EsHc could be affected by dietary copper in the hepatopancreas and haemocytes, and hemocyanin may be potentially involved in the immune responses of the Chinese mitten crab.

Serum levels of copper, selenium and manganese in forestry workers testing IgG positive for Brucella, Borrelia, and Rickettsia

The aim of this study is to measure the alterations in the trace levels of serum copper (Cu), selenium (Se), and manganese (Mn) in forestry workers testing immunoglobulin G (IgG)-positive for Brucella, Borrelia, and Rickettsia. The study was conducted on a sample of 758 subjects (560 male and 198 female). All the subjects underwent medical examinations, which investigated particularly the presence of clinical signs compatible with zoonoses, and routine blood tests from venous blood sample, which tested previous immunisation versus cited microorganisms and serum concentration of Cu, Se, and Mn. The subjects were divided according to IgG positivity versus the cited microorganisms. The group of subjects with IgG positive versus Brucella showed statistically significant higher Cu levels than controls, while the Mn levels were not; the group of subjects with IgG positive versus Rickettsia showed higher levels of all three tested metals. The concentration of the examined metals did not show statistically significant difference between IgG-positive subjects versus subjects with Borrelia compared to controls. These data could confirm the role of both Cu and Se  in the regulation of immune response.

Micronutrient (Zn, Cu, Fe)-gene interactions in ageing and inflammatory age-related diseases: implications for treatments

In ageing, alterations in inflammatory/immune response and antioxidant capacity lead to increased susceptibility to diseases and loss of mobility and agility. Various essential micronutrients in the diet are involved in age-altered biological functions. Micronutrients (zinc, copper, iron) play a pivotal role either in maintaining and reinforcing the immune and antioxidant performances or in affecting the complex network of genes (nutrigenomic approach) involved in encoding proteins for a correct inflammatory/immune response. By the other side, the genetic inter-individual variability may affect the absorption and uptake of the micronutrients (nutrigenetic approach) with subsequent altered effects on inflammatory/immune response and antioxidant activity. Therefore, the individual micronutrient-gene interactions are fundamental to achieve healthy ageing. In this review, we report and discuss the role of micronutrients (Zn, Cu, Fe)-gene interactions in relation to the inflammatory status and the possibility of a supplement in the event of a micronutrient deficiency or chelation in presence of micronutrient overload in relation to specific polymorphisms of inflammatory proteins or proteins related of the delivery of the micronutriemts to various organs and tissues. In this last context, we report the protein-metal speciation analysis in order to have, coupled with micronutrient-gene interactions, a more complete picture of the individual need in micronutrient supplementation or chelation to achieve healthy ageing and longevity.

The cuprizone model: regional heterogeneity of pathology

The cuprizone model is a model of de- and remyelination secondary to oligodendrocyte death, likely to be mediated by an inhibition of mitochondrial function. The aim of this study was to characterize histopathological changes associated with de/remyelination in grey and white matter at different disease stages in C57Bl/6 mice after per oral administration of cuprizone. Oligodendrocyte loss, astrocytosis and complement activation was detected in areas of demyelination. Demyelination, astrocytosis and complement activation occurred earlier in the cerebral cortex than in the corpus callosum. There was no perivascular lymphocyte infiltration. Microglia- and macrophage activation was observed in the corpus callosum, but not in the cerebral cortex. After cuprizone exposure was stopped, remyelination was extensive in the corpus callosum, but scarce in the cortex. In conclusion, cortical demyelination and oligodendrocyte loss in the cuprizone model may be due to a direct effect on oligodendrocyte mitochondrial function, as it occurs in the absence of microglial activation. The histopathology of de/remyelination in the cuprizone treated mice show regional heterogeneities which suggest differences in the underlying pathophysiology. Cuprizone-induced demyelination is a relevant model for the study of regional heterogeneity of demyelination and lesion pathology in multiple sclerosis.

Copper deficiency increases the virulence of amyocarditic and myocarditic strains of coxsackievirus B3 in mice

Deficiency in several trace elements, including copper and selenium, is associated with increased levels of oxidative stress. Copper deficiency also has been shown to impair immune function. Previous work by others demonstrated that passage of an amyocarditic or myocarditic strain of coxsackievirus B3 (CVB3) through selenium- or vitamin E-deficient mice led to increased cardiac pathology. To determine whether a copper deficiency would similarly alter the pathogenesis of CVB3 infections, Swiss outbred dams and their litters were fed copper-deficient diets from birth and received either deionized water or water with 0.315 mmol/L copper as copper sulfate. At 4 wk of age, copper-adequate or -deficient male and female offspring were infected with an amyocarditic or myocarditic strain of CVB3. Heart titers were elevated at d 3 and 7 postinfection in copper-deficient mice infected with the myocarditic CVB3 strain (CVB3/20) but only at d 7 in deficient mice infected with the amyocarditic CVB3 strain (CVB3/0) compared with copper-adequate controls. Copper-deficient mice infected with either strain of CVB3 had increased cardiac pathology compared with copper-adequate controls. Genomic sequences of viruses isolated from copper-adequate and -deficient mice were identical. Heart cytokine expression was elevated in copper-deficient CVB3-infected mice compared with infected controls. Circulating CVB3-specific IgG2a but not IgM levels were decreased in copper-deficient mice. Thus, copper deficiency is associated with an increased inflammatory response but decreased acquired immune response to CVB3 infection that results in increased cardiac pathology, presumably due to increased viral load.

Clioquinol promotes cancer cell toxicity through tumor necrosis factor alpha release from macrophages

Copper has an important role in cancer growth, angiogenesis, and metastasis. Previous studies have shown that cell-permeable metal ligands, including clioquinol (CQ) and pyrrolidine dithiocarbamate, inhibit cancer cell growth in cell culture and in vivo. The mechanism of action has not been fully determined but may involve metal-mediated inhibition of cancer cell proteasome activity. However, these studies do not fully account for the ability of cell-permeable metal ligands to inhibit cancer cell growth without affecting normal cells. In this study, we examined the effect of CQ on macrophage-mediated inhibition of HeLa cancer cell growth in vitro. When CQ was added to RAW 264.7 macrophage-HeLa cell cocultures, a substantial increase in HeLa cell toxicity was observed compared with CQ treatment of HeLa cells cultured alone. Transfer of conditioned medium from CQ-treated macrophages to HeLa cells also induced HeLa cell toxicity, demonstrating the role of secreted factors in the macrophage-mediated effect. Further investigation revealed that CQ induced copper-dependent activation of macrophages and release of tumor necrosis factor (TNF) alpha. In studies with recombinant TNFalpha, we showed that the level of TNFalpha released by CQ-treated macrophages was sufficient to induce HeLa cell toxicity. Moreover, the toxic effect of conditioned medium from CQ-treated macrophages could be prevented by addition of neutralizing antibodies to TNFalpha. These studies demonstrate that CQ can induce cancer cell toxicity through metal-dependent release of TNFalpha from macrophages. Our results may help to explain the targeted inhibition of tumor growth in vivo by CQ.

The immune system as a physiological indicator of marginal copper status?

Cu appears to have many important functional roles in the body that apparently relate, among others, to the maintenance of immune function, bone health and haemostasis. Some have suggested a role for long-term marginal Cu deficiency in the aetiology of a number of degenerative diseases. Accurate diagnosis of marginal Cu deficiency, however, has remained elusive despite an increased understanding of the biochemistry of Cu and its physiological roles in the body. Traditional markers of Cu status, such as serum Cu and caeruloplasmin protein concentrations are insensitive to subtle changes in Cu status. Cu-containing enzymes, such as Cu–Zn-superoxide dismutase, cytochromecoxidase and diamine oxidase, may be more reliable but evidence to date is not conclusive. Development of markers sensitive to marginal Cu status is essential before conclusions can be drawn concerning the risks of long-term intake of suboptimal dietary Cu. As Cu appears to be essential for maintenance of immune function, activities of specific immunological markers, altered in Cu deficiency, offer alternatives. This review evaluates a selection of immunological markers that could be considered potentially sensitive markers of marginal Cu status. The indices of immune function reviewed are neutrophil function, interleukin 2 production, blastogenic response to mitogens and lymphocyte subset phenotyping.

Effects of chromium and copper depletion on lymphocyte reactivity to mitogens in diabetes-prone BHE/cdb rats

OBJECTIVE

The purpose of this study was to measure effects of chromium (Cr) and copper (Cu) depletion on lymphocyte reactivity to mitogens in diabetes-prone BHE/cdb rats.

METHODS

A 2 x 2 factorial research design was used, and 40 BHE/cdb rats were fed with Cr- and/or Cu-depleted diets or adequate Cr and/or Cu diets for 21 wk. Cr and Cu concentrations in diets and mineral concentrations of tissues of BHE/cdb rats were measured by using flame and graphite furnace atomic absorption spectrometry. Three glucose tolerance tests were performed to monitor the development of diabetes or glucose intolerance at weeks 12, 18, and 21. Splenocytes (2 x 10(6)) were incubated with phytohemagglutinin-l (PHA-L), concanavalin A (ConA), and lipopolysaccharides (LPSs), respectively, for 72 h. Four hours before the end of the incubation, splenocytes were pulsed with 3H-thymidine. The 3H-thymidine uptake by lymphocytes was used to calculate a stimulation index.

RESULTS

According to glucose tolerance tests, these rats did not develop diabetes or impaired glucose tolerance throughout the study. Average Cr concentrations were 0.98 to 1.03 mg Cr/kg of diet in adequate Cr diets and 8.2 to 14 micrograms Cr/kg of diet in Cr-depletion diets. Average Cu concentrations were 3.6 to 6.4 mg Cu/kg of diet in adequate Cu diets and 1.1 to 1.3 mg Cu/kg of diet in Cu-depletion diets. Organ weights did not differ significantly among treatment groups at the end of the study. Cr or Cu depletion significantly affected iron, zinc, and magnesium concentrations in the liver. A significant interactive effect of Cr and Cu was observed on lymphocyte proliferation with PHA-L stimulation at 25 micrograms/mL (P < 0.006). However, there were no significant effects of dietary treatment on lymphocyte proliferation with 10 micrograms/mL of PHA-L, ConA, or LPS stimulations.

CONCLUSIONS

When Cr and Cu were adequate in the diets, there was an enhanced effect of Cu or Cr on lymphocyte proliferation. However, when Cr was depleted in the diet, there was a suppressive effect of Cu on lymphocyte proliferation. This result indicates that adequate amounts of Cr and Cu in the diet support the immune system.

Impact of high flaxseed diet on mitogen-induced proliferation, IL-2 production, cell subsets and fatty acid composition of spleen cells from pregnant and F1 generation Sprague-Dawley rats

Flaxseed (FS) being rich in alpha-linolenic acid may alter the immune parameters. Therefore, we assessed the impact of FS and defatted flaxseed meal (FLM) on fatty acid composition, cell subsets, proliferation and IL-2 production by splenic lymphocytes. Pregnant female Sprague-Dawley rats were fed diets containing 0% FS and FLM, 20 or 40% FS, 13 or 26% FLM during gestation or gestation, lactation and 8 week post-weaning period. FS and FLM resulted in up to 8.3 fold and 4.6 fold increase in splenic ALA among pregnant rats, 4.5 fold and 1.2 fold increase in splenic ALA among F(1) generation rats. Splenic linoleic acid (LA) and arachidonic acid (AA) were 18 and 40% lower in 40% FS fed pregnant rats, and AA was 15% lower in all the other groups. Among F(1) rats, splenic LA and AA were 16 and 48% lower in 40% FS group, and AA was 18% lower in 20% FS and 26% FLM groups. Concanavalin A and phytohemagglutinin mediated proliferation of spleen cells were 60 and 52% lower in 40% FS fed pregnant and F(1) generation rats, respectively. No significant changes were observed in the cell subsets or IL-2 production by splenic cells from different groups.

Tetrathiomolybdate anticopper therapy for Wilson's disease inhibits angiogenesis, fibrosis and inflammation

The need for agents to lower body copper in Wilson's disease, a disease which results from copper toxicity has been the driving force for the development of the effective anticopper drugs penicillamine, trientine, zinc, and now tetrathiomolybdate (TM). Because of its rapid action, potency, and safety, TM is proving to be a very effective drug for initial treatment of acutely ill Wilson's disease patients. Beyond this, TM has antiangiogenic effects, because many proangiogenic cytokines require normal levels of copper. This has led to use of TM in cancer, where it is generally effective in animal tumor models, and has shown efficacy in preliminary clinical studies. Most recently, it has been found that TM has antifibrotic and antiinflammatory effects through inhibition of profibrotic and proinflammatory cytokines.

Cuprizone and piperonyl butoxide, proposed inhibitors of T-cell function, attenuate experimental allergic encephalomyelitis in SJL mice

Multiple sclerosis (MS) and its animal model, experimental allergic encephalomyelitis (EAE), are autoimmune demyelinating diseases with autoreactive T-cells acting as important mediators of pathogenesis. Cuprizone, a copper chelator, and piperonyl butoxide (PBO), a pesticide synergist, are implicated to inhibit T-cell activation and function. The purpose of this study was to assess whether either of these agents would suppress PLP-peptide-induced EAE in the SJL mouse. Indeed, treatment with cuprizone beginning 1 week prior to disease induction, and PBO administration from days 1 to 9 of EAE, significantly attenuated EAE clinical severity. Furthermore, both agents decreased blood CD4+/CD8+ ratios, and reduced signs of chronic graft vs. host disease (GVHD) indicating attenuation of an immune T-cell response. These results suggest that cuprizone and PBO suppress EAE and use of these agents will provide insights into the mechanisms of T-cell mediated diseases.

Copper deficiency suppresses effector activities of differentiated U937 cells

Dietary copper (Cu) deficiency impairs both innate and acquired branches of immunity. Specific roles of Cu in the activation and effector activities of host-defense cells remain largely unknown. The effects of Cu status on effector activities of a monocytic cell line were investigated as an initial step in the elucidation of specific functions of Cu in phagocytic cells. Exposure of differentiating U937 human promonocytic cells to 5 micromol/L 2,3, 2-tetraamine (tet), a high affinity Cu chelator, for 4 d decreased cellular Cu by 62% without altering cellular Cu,Zn-superoxide dismutase (SOD) activity, Zn content, mitochondrial activity and protein synthesis. In contrast, Cu deficiency suppressed the respiratory burst activity and markedly compromised the ability of U937 cells to kill Salmonella. Similarly, treatment of RAW264.7 murine macrophages with 5 micromol/L tet decreased cell Cu by 78% and Cu,Zn-SOD activity by 15% and increased bacterial survival by 180%. The tet-induced impairment of respiratory burst and bactericidal activities was blocked in cultures supplemented with Cu, but not Zn or Fe. In addition, lipopolysaccharide (LPS)-induced secretion of the inflammatory mediators, tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6 and prostaglandin E(2) (PGE(2)), was decreased by 30-60% in tet-treated U937 cells. Flow cytometric analysis of the surface antigens CD11b and CD71 showed that the suppressed activities of Cu-deficient cells were not due to an attenuation in the degree of differentiation or secondary iron deficiency. These data demonstrate that U937 cells provide a useful model for examining the biochemical roles of Cu in monocyte activity.

Considerations for determining 'optimal nutrition' for copper, zinc, manganese and molybdenum

Defining optimal dietary intakes of Cu and Zn throughout the life cycle continues to present a considerable challenge for nutrition scientists. Although the daily intake of these micronutrients is below that currently recommended for many groups, traditional biochemical indicators of nutritional status for these trace metals largely remain within the normal range. Thus, it is unclear whether the recommended daily intakes may be unnecessarily high, or if the commonly-used markers simply lack the necessary sensitivity and specificity that are required for accurately assessing Cu and Zn status. The increasing number of reports that daily supplements with these trace metals enhance the activities of selective metalloenzymes and specific cellular and organ processes further points out the need to differentiate between meeting the requirement and providing optimal nutriture. Results from recent studies suggesting that alternative molecular and functional markers possess sufficient sensitivity to better assess Cu and Zn status are discussed. Likewise, recent studies evaluating the impact of very low and excessive levels of dietary Mn and Mo on selective biochemical and metabolic indicators are reviewed.

Transcriptional regulation of interleukin-2 gene expression is impaired by copper deficiency in Jurkat human T lymphocytes

Copper deficiency reduces secretion of the cytokine interleukin-2 (IL-2) by activated rodent splenocytes, human peripheral blood mononuclear cells and Jurkat cells, a human T lymphocyte cell line. Previous studies showed that low Cu status also decreased the level of IL-2 mRNA in activated Jurkat cells by 50%. Synthesis of this cytokine is regulated by alterations in transcription of the IL-2 gene and the stability of IL-2 mRNA. To determine if Cu status influenced promoter activity of the IL-2 gene, Jurkat cells were transfected with a luciferase reporter gene construct containing the entire 300 bp human IL-2 promoter/enhancer sequence. Cu deficiency was induced by incubating stably transfected cells with the Cu chelator 2,3,2-tetraamine for 35 h prior to activating cells with phytohemagglutinin-P and phorbol myristate acetate. Luciferase activity in lysates of Cu-deficient cells was approximately 50% lower in several multiclonal and clonal cell lines of stably transfected cells than in replicate cultures that were not exposed to chelator. The relative levels of endogenous IL-2 bioactivity and luciferase activity were highly correlated in the transfected cell lines. The chelator-mediated reduction in reporter gene activity was dose-dependent at levels of 5-40 micromol 2,3,2-tetraamine/L. The addition of a slight molar excess of Cu, but not Zn or Fe, to medium containing 2,3,2-tetraamine prevented the decline in luciferase activity. IL-2 mRNA stability in parental Jurkat cells was independent of Cu status. These data indicate that decreased cellular Cu attenuates IL-2 synthesis in T lymphocytes by inhibiting transcription of the IL-2 gene.

The possible role of copper ions in atherogenesis: the Blue Janus

It has been proposed that the oxidative modification of low density lipoprotein (LDL) is a key event in human atherogenesis. Copper ions can catalyse the oxidative modification of LDL in vitro and there is some evidence that they may also participate in the oxidation of LDL within the arterial wall. However, copper ions also form an intrinsic constituent of superoxide dismutase and caeruloplasmin, enzymes that may be involved in preventing oxidative injury. Atherosclerotic lesions frequently contain considerable quantities of extracellular matrix molecules. These may contribute to the expansion of the arterial neointima, causing luminal narrowing. They may also play a beneficial role by stabilising the plaque. Copper is an essential component of lysyl oxidase, an enzyme involved in the biosynthesis of collagen, which is a major constituent of the extracellular matrix. The impact of alterations in body copper status on atherogenesis is therefore difficult to predict. Experimental and epidemiological data are conflicting and therefore do not provide a clear resolution of this issue. We have reviewed the biochemical and cellular effects of copper ions that may play a role in atherogenesis.

Copper deficiency reduces interleukin-2 (IL-2) production and IL-2 mRNA in human T-lymphocytes

Although dietary copper (Cu) deficiency has been associated with decreased production of interleukin-2 (IL-2) by activated splenic mononuclear cells in rodent models, the basis for this relationship and its relevance for humans remain unknown. To address these matters, we have developed an in vitro model of cellular copper deficiency by treating Jurkat, a human T-lymphocyte cell line, with low concentrations of 2,3,2-tetraamine (2,3,2-tet), a high affinity copper chelator. Exposure to 5-20 micromol/L 2,3,2-tet for 35 h decreased cell copper and the activity of Cu,Zn-superoxide dismutase (Cu,Zn-SOD) by 30-40% and IL-2 production by 60-70% in cultures activated with phytohemagglutinin and phorbol myristate acetate. Similarly, IL-2 mRNA levels were 40-70% lower in chelator-treated cells than in untreated cells at 3-12 h after activation. In contrast, chelator treatment had no significant effect on cell viability, growth, protein synthesis or mitochondrial activity. The presence of a slight molar excess of copper, but not zinc or iron, during exposure to 2,3,2-tet prevented the chelator-induced decrease in Cu,Zn-SOD activity and the reductions in IL-2 mRNA and bioactivity. Moreover, binding of diferric transferrin (Tf) and cellular uptake of Tf-59Fe by Jurkat cells were not increased by 2,3,2-tet, indicating that chelator-treated cells were not iron deficient. Finally, incubation of human peripheral blood mononuclear cells (PBMC) with 2,3,2-tet decreased mitogen-induced IL-2 production by 50% compared with untreated controls. These data indicate that a decline in copper status decreases IL-2 production by activated human T-cells due to reduced synthesis and/or stability of IL-2 mRNA.

Nutrition and immunity with emphasis on infection and autoimmune disease

Nutrition and nutritional status can have profound effects on immune functions, resistance to infection and autoimmunity in man and other animals. Nutrients enhance or depress immune function depending on the nutrient and level of its intake. Protein-energy malnutrition and vitamin A deficiency are strongly associated with impaired immunity and infectious disease. The essential role vitamin A plays in infection and maintenance of mucosal surfaces has long been known. Recent evidence shows that T-cell subpopulations, cytokines and antibody subclasses are all affected by vitamin A. In animal studies supplementation with vitamin E protects against infection and is linked to stimulatory effects on the immune system. In man vitamin E and other anti-oxidants increase the number of CD4+ cells. Dietary lipids and zinc have a substantial impact on autoimmunity from protective to potentiation of immuno-pathological processes in animals. There is considerable potential to modify human autoimmune disease by manipulation of lipid nutrition. Deficiency of pyridoxine induces atrophy of lymphoid organs, marked reduction in lymphocyte numbers, impairs antibody responses and IL-2 production. Dietary copper is important in the prevention of infection in some animal species and T-cell function is defective under deficiency states due to an inability to produce IL-2. Selenium has been linked to viral infection, enhanced T-cell functions and TNF beta induced increase in natural killer cell activity. Understanding the molecular and cellular immunological mechanisms involved in nutrient-immune interactions will increase our applications for nutrition of the immune system in health and in disease

Interleukin-2 production is altered by copper deficiency

Copper is an essential nutrient for optimal function of the immune system; deficiency results in impairment of both humoral and cell-mediated components. Copper deficiency in rodents results in decreased numbers of CD4+ (helper) and total T cells. This defect has been traced to impaired production of interleukin-2, a cytokine essential for T-cell division and differentiation. Impairment of quiescent cell proliferation is reversed by both in vivo and in vitro copper supplementation.