Pathological consequences of copper deficiency and cobalt deficiency

Aspects of the pathology of copper deficiency in several species, and cobalt deficiency in sheep, are summarized. An attempt is made to interpret morphological changes in copper-deficient animals in terms of biochemical defects. The common denominator may be mitochondrial lesions, with a generalized effect on energy-dependent synthetic functions of the cell. In copper deficiency, such defects can be attributed to depletion of copper-dependent enzymes, while deficiency of cobalt in ruminants is, in effect, deficiency of vitamin B12. The pathological consequences of vitamin B12 deficiency form a syndrome, notable features of which are neurological and muscular lesions, in which the metabolic consequences of hepatic damage may play a significant role.     

Marginal copper deficiency and atherosclerosis

Copper is an essential trace element in the maintenance of the cardiovascular system. Copper-deficient diets can elicit, in animals, structural and functional changes that are comparable to those observed in coronary heart disease. In this study, the effect of dietary-induced copper deficiency on aortic lesion development was measured by quantitative image analysis in C57BL/6 mice that are susceptible to diet-induced aortic lesions. The diets administered were severely copper deficient (0.2 mg/kg diet), marginally deficient (0.6 mg/kg diet), or copper adequate (6.0 mg/kg diet). Similarly, increased aortic lesion areas and elevated serum cholesterol were demonstrated in both deficient groups, compared with the copper-adequate group. Evidence for graded differences in copper status among the dietary groups was shown by the dose-response increase in liver copper concentration, copper-zinc superoxide dismutase and cytochrome-c oxidase activities, together with serum caeruloplasmin oxidase with increasing intakes of dietary copper. Despite the difference in copper status between the copper marginal and severely deficient groups, similar lesions found in both groups of mice suggest a threshold effect of copper deficiency on lesion formation.     

Cardiovascular effects of dietary copper deficiency

Dietary copper deficiency may impair cardiovascular health by contributing to high blood pressure, enhancement of inflammation, anemia, reduced blood clotting and arteriosclerosis. The purpose of this review is to compile information on the numerous changes of the heart, blood and blood vessels that may contribute to these cardiovascular defects. These alterations include weakened structural integrity of the heart and blood vessels, impairment of the use of energy by the heart, reduced ability of the heart to contract, altered ability of blood vessels to control their diameter and to grow, and altered structure and function of circulating blood cells. The fundamental causes of these changes rest largely on reduced effectiveness of enzymes that depend on copper for their activity.     

Suspected copper deficiency in radiata pine

Summary Growth disorders in 3-year-old radiata pine associated with very low copper concentrations in the foliage are described. The low concentrations of copper appear to have been nitrogen induced. The effect of remedial measures is being investigated.     

Renal copper as an index of copper status in marginal deficiency

Marginal copper (Cu) deficiency is difficult to study, in part because its effects may be small, but also because feeding of a deficient diet may not cause a discernable change in Cu status. The key to resolution of effects may be in the choice of Cu status index. In this study, liver Cu concentration, a commonly used index of Cu status, was compared with activity of ceruloplasmin (CP), a circulating Cu-dependent enzyme, and kidney Cu concentration for their utility in resolving effects of marginal Cu deficiency. Seventy male, weanling rats were fed diets containing, nominally, 0, 1.5, 3, 4.5, or 6 mg Cu/kg diet for 5 wk. All three indices showed strong depression with severe deficiency (dietary Cu=0), but were relatively weak in their ability to distinguish between animals fed marginally deficient diets when compared by group statistics (ANOVA). Further, group statistics revealed no effect of marginal deficiency on six other variables known to change with severe Cu deficiency: heart weight/body weight, hematocrit, red cell distribution width, neutrophil count, glycated hemoglobin, and platelet count. To take into account interanimal variation, the three putative indices were plotted against these six variables and linear regression was performed on points representing marginally deficient rats. None of the variables showed significant regression with liver Cu or serum ceruloplasmin, but three showed significant regression with kidney Cu. These findings indicate that kidney Cu is preferable to liver Cu or ceruloplasmin as an index of Cu status in marginal deficiency and that linear regression is a possible way of testing for effects of marginal Cu deficiency, especially when effects are subtle.     

Development of copper deficiency in neonatal mice

Dietary copper (Cu) deficiency was produced in Swiss albino mice to determine the temporal relationship between depletion of Cu and changes in the cardiovascular and nervous system. Dams were placed on a Cu-deficient diet 4 days after parturition. Half the dams were provided with deionized water and their offspring are referred to as Cu-deficient (-Cu). Half the dams were given cupric sulfate in their drinking water (20 microg Cu/mL) and their offspring are referred to as Cu-adequate (+Cu). At 6 weeks of age a sample of the -Cu mice were repleted with CuSO(4). Mice were sampled 1 day after birth and at weekly intervals for 7 weeks. Both +Cu and -Cu mice grew at the same rate: birth weight increased 16-fold at 6 weeks of age. Liver Cu more than doubled between 1 and 7 days of age. At 2 weeks of age -Cu mice were anemic (lower hematocrit and hemoglobin) and had lower liver Cu and plasma ceruloplasmin activity compared to +Cu mice. Liver Fe was not elevated in -Cu mice until 2 weeks after anemia developed. At weaning first signs of altered catecholamine metabolism included elevation of dopamine in both heart and spleen. Norepinephrine concentrations and content, in contrast, were not both lowered in -Cu mice until 5 weeks of age. Heart weight was first elevated in -Cu mice at 6 weeks of age and relative weight (mg/g body wt) at 4 weeks of age. Liver Cu concentration was lower in 1-week repleted mice than in +Cu mice. Anemia preceded the development of cardiac hypertrophy and altered catecholamine levels in -Cu mice.     

Pharmacokinetics and pharmacodynamics in copper deficiency I

The effect of nutritional copper (Cu) deficiency on the antiinflammatory activity and pharmacokinetics of aspirin (ASA) was investigated in rats. Male, weanling Sprague-Dawley rats were fed either a Cu-deficient (CuD) or Cu-sufficient (CuS) diet for 49–50 d. The antiinflammatory activity of ASA was studied using the carrageenan-induced paw edema (CPE) test. ANOVA analyses of edema volumes at 2, 3, 4, 5, and 21 h postcarrageenan indicated significant differences between groups. The percent inhibition of edema due to ASA treatment in CuS was lower than that in CuD rats at 5 h, AUC_5h, and AUC_21h. ASA was found to be significantly more effective in inhibiting the CPE in CuD rats when compared to the CuS rats. Thus, we hypothesized that the increase in ASA's antiinflammatory activity in CuD rats was a result of a decrement in its elimination during nutritional Cu deficiency. The elimination of ASA in CuD and CuS rats was studied using an iv dose of 200 mg/kg. Concentrations of ASA and salicylic acid (SA) were determined in blood; whereas the concentrations of SA, salicylic phenol-glucuronide (SPG), and salicyluric acid (SUA) were determined in urine by HPLC. The results of the pharmacokinetic analyses from blood and urinary data indicated no significant differences in the disposition of ASA between CuD and CuS rats. For instance, the total body clearance for ASA (mean±SD, mL/min/kg) was 37.9±9.4 and 38.5±13.9 (p>0.05); and the volume of distribution (Vd) for ASA (mean±SD, mL/kg) was 385.5±110.3 and 397.1.1±137.9 (p>0.05) for CuD and CuS groups, respectively. Thus, contrary to our hypothesis, the enhanced antiinflammatory activity of ASA in CuD rats does not appear to be mediated via a decrement in the elimination of the drug. In addition, plasma ASA-esterase activity was found to be independent of Cu nutritional status.     

Iron overload can induce mild copper deficiency

Dietary copper in the U.S. often is lower than that proved insufficient for men and women under controlled conditions. Iron overload can have adverse effects on copper nutriture and can produce cardiac disease in people. The hypothesis that iron can interfere with copper utilization to produce adverse effects related to cardiovascular function was tested.

Rats were fed a diet high in iron and marginal, but not deficient in copper for comparison with similar diets containing iron at the recommended amount. Copper and iron were measured by atomic absorption spectroscopy; cholesterol was measured by fluorescence, ceruloplasmin was measured by oxidase activity and hematology was done by an automated cell counter. When dietary copper was 2.0 mg/kg of diet, high iron decreased (p<0.008) cardiac and hepatic copper, plasma copper and ceruloplasmin, and increased (p<0.02) cardiac weight, hepatic iron and plasma cholesterol. When dietary copper was increased to 2.5 mg/kg, copper in heart and plasma decreased (p<0.04) and hepatic iron increased (p=0.001) with high iron but other effects disappeared. No harmful changes in hematology, such as hematocrit, mean corpuscular volume, etc. were found. High iron increased the dietary copper requirement of the animals. People with iron overload may benefit from copper supplementation, particularly if they habitually consume a diet low in copper.     

Clastogenic effect of copper deficiency in cattle

Copper plays an essential role as a micronutrient. Deficiency of this element (hypocuprosis) in experimental and domestic animals has a severe impact on growth as well as on reproduction. The occurrence of lesions during hypocuprosis is correlated with the depletion of an enzymatic group in which copper takes part. The aim of this work was to analyse chromosomal aberrations in Aberdeen Angus cows of the province of Buenos Aires in relation with the Cu plasma levels. Short term lymphocyte cultures were made from samples obtained from four groups of animals: two groups with normal levels of copper in plasma and two groups with severe hypocupremia. This analysis showed a significant increase of the frequency of chromosomal aberrations (p<0.001) in the hypocupremic groups in relation with control groups. Finally, the Spearman correlation analysis showed a significant negative association (p<0.05) between copper levels and the yield of chromosomal aberrations. The increase of the frequencies of chromosomal aberrations found in the hypocupremic groups could be explained by the higher oxidative stress suffered by these animals. A lower catalytic activity of enzymes such as Cu/Zn superoxide dismutase (Cu/Zn-SOD) and cytochrome-c oxidase could increase the intracellular production of active oxygen species (O(2)(-), H(2)O(2) and OH(o)) with the consequent clastogenic effects.     

Bovine monocyte-derived macrophage function in induced copper deficiency

The effect of molybdenum-induced copper deficiency on monocyte-derived macrophage function was examined. Five female calves were given molybdenum (30 ppm) and sulphate (225 ppm) to induce experimental secondary copper deficiency. Oxidant production by bovine macrophages was measured after stimulation with phorbol myristate acetate (PMA) and opsonized zymosan (OpZ). Lipoperoxidative effects inside of macrophage, superoxide dismutase activity, superoxide anion and hydrogen peroxide formation were determined. Copper deficiency was confirmed from decreased serum copper levels, and animals with values less than 5.9 micromol/l were considered deficient. The content of intracellular copper decreased about 40% in deficient cells compared with the controls. The respiratory burst activity determined by nitroblue tetrazolium reduction was significantly impaired with both stimulants used. Superoxide anion formation was less affected than hydrogen peroxide generation. In addition, increased lipid peroxidation was observed. It could be concluded that the effect of these changes may impair the monocyte-derived macrophage function in the immune system.     

A study of copper treatment and tissue copper levels in the murine congenital copper deficiency, mottled.

The injection of copper chloride overcomes the lethality and pigment deficiency in the brindled ($\text{Mo}$^br) mouse mutant but copper levels remain depressed in the liver and brain, and a further accumulation occurs in the kidney. The copper-dependent synthesis of brain noradrenaline returns to normal but the activity of brain cytochrome c oxidase, although increased, remains depressed. Significant changes in tissue copper content of female brindled heterozygotes are reported and in each case, the changes exceed those expected on the basis of X-inactivation. The significance of these results to the development of a satisfactory treatment regime for this disease is discussed.     

Decreased brain copper due to copper deficiency has no effect on bovine prion proteins

Copper (Cu) is believed to be integral in prion biology and the lack of Cu or replacement by other metal ions on prions may be involved in prion diseases. This theory has not been evaluated in the bovine. Thus, mature cows were used to determine the effects of Cu deficiency on brain Cu concentrations and prion functional characteristics. Two Cu states were induced, Cu-adequate (n=4) and Cu-deficient (n=4). Copper deficiency resulted in decreased (44%) brain Cu concentrations but had no effect on prion concentrations. Based on Western blot analysis, the molecular weights, glycoform distributions, and elution profiles of brain prions were not affected by Cu status. Importantly, Cu status did not affect prion proteinase degradability as all prions were completely degraded by proteinase K. In conclusion, Cu status affected bovine brain Cu concentrations but had no detectable effects on brain prion protein characteristics.     

Intracellular copper deficiency increases amyloid-beta secretion by diverse mechanisms

In Alzheimer's disease there is abnormal brain copper distribution, with accumulation of copper in amyloid plaques and a deficiency of copper in neighbouring cells. Excess copper inhibits Abeta (amyloid beta-peptide) production, but the effects of deficiency have not yet been determined. We therefore studied the effects of modulating intracellular copper levels on the processing of APP (amyloid precursor protein) and the production of Abeta. Human fibroblasts genetically disposed to copper accumulation secreted higher levels of sAPP (soluble APP ectodomain)alpha into their medium, whereas fibroblasts genetically manipulated to be profoundly copper deficient secreted predominantly sAPPbeta and produced more amyloidogenic beta-cleaved APP C-termini (C99). The level of Abeta secreted from copper-deficient fibroblasts was however regulated and limited by alpha-secretase cleavage. APP can be processed by both alpha- and beta-secretase, as copper-deficient fibroblasts secreted sAPPbeta exclusively, but produced primarily alpha-cleaved APP C-terminal fragments (C83). Copper deficiency also markedly reduced the steady-state level of APP mRNA whereas the APP protein level remained constant, indicating that copper deficiency may accelerate APP translation. Copper deficiency in human neuroblastoma cells significantly increased the level of Abeta secretion, but did not affect the cleavage of APP. Therefore copper deficiency markedly alters APP metabolism and can elevate Abeta secretion by either influencing APP cleavage or by inhibiting its degradation, with the mechanism dependent on cell type. Overall our results suggest that correcting brain copper imbalance represents a relevant therapeutic target for Alzheimer's disease.     

Maintaining copper homeostasis: regulation of copper-trafficking proteins in response to copper deficiency or overload

Copper is an essential micronutrient that plays a vital role as a catalytic co-factor for a variety of metalloenzymes. The redox chemistry of copper also makes it a potentially toxic metal if not properly used. Therefore, elaborate mechanisms have evolved for controlling its cellular uptake, elimination, and distribution. In the last decade, our understanding of the systems involved in maintaining copper homeostasis has improved considerably with the characterization of copper transporters that mediate cellular copper uptake or efflux and with the identification of copper chaperones, a family of proteins required for delivering copper to specific targets in the cell. Despite the distinct roles of these proteins in copper trafficking, all seem able to respond to changes in copper status. Here, we describe recent advances in our knowledge of how copper-trafficking proteins respond to copper deficiency or overload in mammalian cells in order to maintain copper balance.