Caeruloplasmin: a multi-functional metalloprotein of vertebrate plasma

Determination of Essential and Toxic Elements in Cattle Blood: Serum vs Plasma

Simple Summary

Knowledge of type of blood sample (serum or plasma) for determination of essential and toxic elements is essential for assessing the health and nutritional status of the animals and the herd. We demonstrate that both plasma and serum samples are suitable and interchangeable for the determination of most of the essential and toxic elements in blood in cattle. Nevertheless, we must take into account that the concentrations of Cu and Se are lower in the serum than in plasma.

Abstract

This study was designed to evaluate the influence of type of blood sample (serum or plasma) on essential and toxic element analysis in cattle. Paired plasma and serum samples (n = 20) were acid digested, and the concentrations of As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, Li, Mg, Mn. Mo, Ni, P, Pb, Sb, Se, Sr and Zn were determined by inductively coupled plasma mass spectrometry (ICP-MS). The study findings indicate that plasma and serum samples appear suitable and interchangeable for the determination of most of the essential and toxic elements in blood in cattle. The only exceptions are Cu and Se, the concentrations of which were significantly lower (40.9 and 29.9% respectively) in serum than in plasma. Some of the Cu in blood samples from bovine ruminants is known to be sequestered during clotting. However, further research on Se in ruminants and other animal species is warranted. Finally, the significantly higher Mn (9.9%) concentrations in serum than in plasma may have been caused by haemolysis of some samples. Special attention should be paid to preventing haemolysis of samples during collection and processing, in order to prevent overestimation of elements present at high concentrations inside erythrocytes (i.e., Fe, Mn and Zn).

Association of copper levels in the hair with gray matter volume, mean diffusivity, and cognitive functions

Although copper plays a critical role in normal brain functions and development, it is known that excess copper causes toxicity. Here we investigated the associations of copper levels in the hair with regional gray matter volume (rGMV), mean diffusivity (MD), and cognitive differences in a study cohort of 924 healthy young adults. Our findings showed that high copper levels were associated mostly with low cognitive abilities (low scores on the intelligence test consisting of complex speed tasks, involving reasoning task, a complex arithmetic task, and a reading comprehension task) as well as lower reverse Stroop interference, high rGMV over widespread areas of the brain [mainly including the bilateral lateral and medial parietal cortices, medial temporal structures (amygdala, hippocampus, and parahippocampal gyrus), middle cingulate cortex, orbitofrontal cortex, insula, perisylvian areas, inferior temporal lobe, temporal pole, occipital lobes, and supplementary motor area], as well as high MD of the right substantia nigra and bilateral hippocampus, which are indicative of low density in brain tissues. These results suggest that copper levels are associated with mostly aberrant cognitive functions, greater rGMV in extensive areas, greater MD (which are indicative of low density in brain tissues) in subcortical structures in the healthy young adults, possibly reflecting copper's complex roles in neural mechanisms.

The Influence of α-Tocopherol on Serum Biochemical Markers During Experimentally Induced Pleuritis in Rats Exposed to Dioxin

Toxicity of dioxins is wide ranging. Amongst the organs, the liver is the most susceptible to damage by dioxins. Damage caused to liver cells results in promoting inflammatory processes. The aim of this work was to evaluate whether high doses of tocopherol will change the inflammatory response, monitored by biochemical indicators, by improving liver function in rats exposed to tetrachlorodibenzo-p-dioxin (TCDD). The study was conducted on a population of female Buffalo rats. The animals were divided into the following groups: Control Group A—representing physiological norms for the studied diagnostic indicators; Control Group B—subjects were administered a 1% ceragenin solution to induce pleuritis; Study Group 1—where rats were administered α-tocopherol acetate for 3 weeks, after which pleuritis was induced; Study Group 2—rats were administered a single dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), while 3 weeks later, pleuritis was induced; and Study Group 3—rats were administered a single dose of TCDD and next, were administered α-tocopherol acetate for 3 weeks, followed by pleuritis induction. The results clearly show that administering tocopherol in the course of inflammation causes changes to the distribution and ratio of in the serum protein fractions, including acute phase proteins. The latter proteins are indicative to the improvement in liver function and linked to protein synthesis and stimulation of the antibody-mediated immunity. Moreover, in the course of inflammation caused by exposure of rats to TCDD, tocopherol significantly affected the acute phase protein concentration.

Dynamic Analysis of Changes of Protein Levels and Selected Biochemical Indices in Rat Serum in the Course of Experimental Pleurisy

A significant role is played in inflammation by the liver, which, stimulated by inflammatory mediators, synthetizes plasma proteins with various dynamics. The purpose of these studies is to generate a detailed dynamic analysis of changes to concentrations of plasma and serum protein fractions and selected acute-phase proteins as well as nonspecific biochemical indices during the course of an induced pleurisy. The studies were conducted on female inbred Buffalo rats, which were divided into two groups: a control group (C) and an experimental group (IP) in which pleurisy was induced. In the IP group, significant changes in biochemical indices were observed between the 48th and 96th hours of pleurisy. A reduction of albumin, transferrin, urea, and creatinine concentrations was observed, while concentrations of the complement components C3 and C4, haptoglobin, and fibrinogen increased. An early increase of IL-1 was observed, while increases of IL-6 and TNF were noted in the later period. The maximum intensity of the processes described above occurred between the 72nd and 96th hours of pleurisy.

Establishment of a prediction method for premature rupture of membranes in term pregnancy using active ceruloplasmin in cervicovaginal secretion as a clinical marker

AIM

Term pregnancy complicated by premature rupture of membranes (PROM) is thought to be associated in part with subclinical infection, and places mothers and neonates at an increased risk for several complications. Therefore, perinatal care would be greatly helped if a reliable clinical measure were available for predicting the incidence of PROM.

METHODS

One hundred and ninety-six pregnant women who consented to enter this study were screened using a method developed to assess active ceruloplasmin in cervicovaginal secretion as a clinical marker for predicting the incidence of PROM. Cervicovaginal secretions were obtained from the cervical canal at about 36 weeks of pregnancy. The active ceruloplasmin level in the cervicovaginal secretion was measured using an original enzyme-linked immunoabsorbent assay.

RESULTS

Of 196 women, 27 women (13.8%) developed PROM and 169 women (86.2%) did not develop PROM. Active ceruloplasmin in the cervicovaginal secretion was significantly higher in the PROM group than in the non-PROM group (P < 0.001). Analysis using receiver-operating characteristic curves showed that the active ceruloplasmin level (1420.0 ng/mL) proved to be the proper cut-off value to best predict the incidence of PROM.

CONCLUSION

Active ceruloplasmin in the cervicovaginal secretion might be a reliable clinical marker for term PROM.

The effect of Au injection on the ceruloplasmin, metallothionein and 8-hydroxydeoxyguanosine of rat serum, kidney and liver

The present study was carried out to investigate the effect of gold (Au) injection on copper (Cu) and two types of ceruloplasmin (Cp), total Cp (ID1) and active Cp (ID2), metallothionein (MT) in the serum, kidney and liver, and 8-hydroxydeoxyguanosine (8-OHdG) in the rat kidney. The Cu contents in sera and kidneys of Au-injected rats were 1.7 and 5.5 times higher than those in sera and kidneys of control rats, respectively. The most of Cu in the sera of the control rats or Au-injected rats were observed in the Cp fractions from a Sephacryl S-200 column. The Cu concentration in the Cp fractions was increased by Au injection. Significant increases of ID1 and ID2 were found in the sera of the control rats and Au-injected rats, while there was no significant difference in those concentrations of livers or kidneys between the control rats and Au-injected rats. Our results indicated that the most of Cp existed as active ID1. The immunoreactivity of 8-OHdG was located in the cortex of the Au-injected rat. These results indicated that the oxidative DNA damage occurred in the renal cortex of the Au-injected rat and the localization of DNA damage did not coincide with that of Cu-MT. These findings suggest that the oxidative DNA damage in the kidneys of rats injected with Au is associated with Cu except Cu-MT.

Divalent cation binding to ceruloplasmin

Binding of calcium to human and sheep ceruloplasmin was investigated by metal substitution with manganese and competitive displacement of bound manganese by calcium monitored by electron paramagnetic resonance spectroscopy. The Kd for calcium was found to be 1.4 mM. Magnesium also bound to ceruloplasmin, with Kd = 0.3 and 0.7 mM for the human and sheep protein, respectively. The thermal stability of ceruloplasmin, as studied by differential scanning calorimetry, was affected by calcium but not by magnesium. A considerable increase of the Tm value, from 73.8 to 83.1 degrees C, was observed for sheep ceruloplasmin in the presence of calcium. The Tm value of the human protein was only slightly altered by calcium (from 85.1 to 87 degrees C). The interaction of ceruloplasmin with the chromatographic material used for its isolation, Sepharose 4B derivatized with chloroethylamine, was weakened by calcium. This allowed us to set up a novel purification scheme that made it possible to efficiently isolate ceruloplasmin and prothrombin from plasma with the same single-step chromatography.

Caeruloplasmin biosynthesis by the human uterus

The blue copper protein caeruloplasmin is synthesized mainly by hepatocytes. An alternative transcript for caeruloplasmin produced in certain extrahepatic tissues, CP-1, contains an additional 12 nucleotides encoding 4 amino acids not present in the hepatic transcript, CP-2 [Yang, Friedrichs, Cupples, Bonifacio, S Sanford, Horton & Bowman (1990) J. Biol. Chem. 265, 10780-10785]. We have demonstrated transcription of caeruloplasmin mRNA by a well-differentiated human uterine epithelial adenocarcinoma cell line, Ishikawa, and by human uterine endometrium and purified endometrial glands. Identical CP-2 nucleotide sequences were obtained for partial caeruloplasmin transcripts from human liver and Ishikawa cells, indicating that CP-2 transcripts are produced by uterine epithelial lining cells. The synthesis of caeruloplasmin protein was demonstrated for Ishikawa cells and another uterine adenocarcinoma cell line, ECC1. Peptide-mapping analysis indicated that caeruloplasmin secreted by Ishikawa cells was structurally identical with the protein synthesized by the human hepatoblastoma cell line HepG2. The secretion of a 135,000-M(r) caeruloplasmin by Ishikawa and ECC1 cells, comparable with that of the human hepatoblastoma cell line, HepG2, indicated similar processing of uterine and hepatic caeruloplasmin. Incorporation of 67Cu into caeruloplasmin was demonstrated for Ishikawa and ECC1 cells, suggesting that the human uterus produces a bioactive form of caeruloplasmin and possesses the necessary metal transporters and intracellular machinery for copper incorporation into this protein.

The valency state of absorbed iron appearing in the portal blood and ceruloplasmin substitution

(1) Attempts to determine the redox-state of the absorbed iron, which appeared in the portal blood when the free iron-binding capacity was previously saturated, indicate that about 30-90% of this iron was in the ferrous state. This effect was particularly prominent after luminal administration of ferrous iron, but was also seen when iron was given in the ferric state. (2) Total iron absorption is significantly higher in ceruloplasmin-substituted copper-deficient animals as compared to copper-deficient controls. (3) The appearance rate of absorbed iron in the portal blood of copper-deficient animals increased several times immediately after the intravenous infusion of ceruloplasmin. (5) The distribution of absorbed iron was changed due to the ceruloplasmin substitution: it was increased in the reticulocytes (+66%), plasma (+400%) and the body (+112%), whereas in the liver it was decreased by about 78%. (5) In iron-deficient rats intravenously injected ceruloplasmin did not increase iron absorption. (6) The conclusion was drawn that, as for the entrance into the mucosa from the luminal side, also for the release at the contraluminal side into the portal blood, the ferrous state of iron is favoured and that ceruloplasmin accelerates the release into the portal blood by catalyzing the oxidation of ferrous iron due to its high Fe(II): oxygen oxidoreductase (EC 1.16.3.1) activity.

Isolation and partial nucleotide sequence of the laccase gene from Neurospora crassa: amino acid sequence homology of the protein to human ceruloplasmin

The laccase (benzenediol:oxygen oxidoreductase, EC 1.10.3.2) gene from Neurospora crassa was cloned and part of its nucleotide sequence corresponding to the carboxyl-terminal region of the protein has been determined. The gene was cloned by cDNA synthesis with a laccase-specific synthetic deoxyundecanucleotide as primer and poly(A) RNA isolated from cycloheximide-treated N. crassa cultures as template. Based on the nucleotide sequence of the cDNA obtained, a unique 21-mer was synthesized and used to screen a genomic DNA library from N. crassa. Five different positive clones were isolated and shown to share an overlapping DNA region with the same pattern of restriction sites. Sequence analysis of the common 1.36-kilobase Sal I fragment revealed an open reading frame of 726 nucleotides. The amino acid sequence deduced is in complete agreement with the primary structures of several tryptic peptides isolated previously from N. crassa laccase. The analyzed carboxyl-terminal region of laccase exhibits a striking sequence homology to the carboxyl-terminal part of the third homology unit of the multicopper oxidase ceruloplasmin and to a smaller extent, to the low molecular weight blue copper proteins plastocyanin and azurin. Based on amino acid sequence comparison between these proteins, putative copper ligands of N. crassa laccase are proposed. Moreover, these data further support the hypothesis that the small blue copper proteins and the multicopper oxidases have evolved from the same ancestral gene.

Structural model of human ceruloplasmin based on internal triplication, hydrophilic/hydrophobic character, and secondary structure of domains

A molecular model for the structure of human ceruloplasmin is proposed that is based on the determination of the complete amino acid sequence, studies of the products of limited proteolytic cleavage, calculations of the hydrophilic/hydrophobic character (hydropathy profile), and predictions of the local secondary structure. This multicopper oxidase (Mr approximately 132,000) consists of a single polypeptide chain (1046 amino acid residues) with four attached glucosamine oligosaccharides. Computer-assisted statistical analysis of the internal repetition in the amino acid sequence confirms that the entire polypeptide chain is divided into three contiguous homology units, each containing about 350 amino acid residues. Each homology unit is subdivided into three domains, designated A1, A2, and B, that differ in structure and probably in function. Calculations of the hydropathy profile and predictions of the secondary structure support a molecular model based on internal repetition of three homology units and help to identify characteristic features of the interdomain junctions. The alignment scores for internal duplication of pairings of the three homology units of ceruloplasmin exceed the scores yet reported for contiguous internal duplication of any other protein. This highly significant evidence for intragenic repetition suggests that the ceruloplasmin molecule evolved by tandem triplication of ancestral genes coding for a primordial copper oxidase.

Immunosuppression by D-penicillamine in vitro. Inhibition of human T lymphocyte proliferation by copper- or ceruloplasmin-dependent generation of hydrogen peroxide and protection by monocytes

It has been suggested that D-penicillamine is active in rheumatoid arthritis because of its capacity to function as a selective inhibitor of T lymphocyte function. The basis for the immunosuppressive action of this drug as well as mechanisms whereby the effect of D-penicillamine could be modified by elements of rheumatoid synovial tissue were examined. As previously reported, D-penicillamine, in the presence of copper ions markedly inhibited mitogen-induced human T lymphocyte DNA synthesis. Since the vast majority of copper in the body exists as an integral part of the ceruloplasmin molecule, the capacity of this cuproprotein to augment D-penicillamine-mediated inhibition of T cell function was examined. The requirement for copper ions could be entirely replaced by purified ceruloplasmin, which had been depleted of nonspecifically bound copper by passage over Chelex-100 columns. The mechanism by which D-penicillamine in the presence of either copper ions or ceruloplasmin caused inhibition of T lymphocyte responsiveness was examined. Partial protection from this inhibitory effect was accomplished by sodium borohydride. While superoxide dismutase had no protective effect, catalase was found to protect lymphocyte responsiveness totally from the inhibitory action of D-penicillamine and either copper ions or ceruloplasmin. Similarly, horseradish peroxidase and myeloperoxidase also protected responsiveness from these inhibitors while boiled catalase was without effect. These results indicate that inhibition of T lymphocyte responsiveness resulted from the generation of hydrogen peroxide. Since a number of cells likely to be present at chronic inflammatory sites, such as mononuclear phagocytes, contain enzymatic mechanisms to degrade hydrogen peroxide, the modulatory influence of these cells on the inhibition of T cell function caused by D-penicillamine and copper was examined. Monocytes, whose function was not suppressed by D-penicillamine and copper, were found to protect T lymphocyte responsiveness from the inhibitory effects of either the mixture of D-penicillamine and CuSO4 or of hydrogen peroxide. By contrast, endothelial cells, fibroblasts, or cells obtained from enzyme-digested noninflamed synovium could not protect T cells from the inhibitory effects of D-penicillamine and copper. Protection of T cells was afforded by means of a heat labile, azide-sensitive soluble factor present in lysates of human monocytes. These results indicate that the mechanism whereby D-penicillamine in the presence of copper or ceruloplasmin inhibits T lymphocyte responsiveness involves the generation of hydrogen peroxide and that other neighboring cells likely to be found w

A possible role for copper-mediated oxidation of thiols in the regulation of the release of luteinizing hormone releasing hormone from isolated hypothalamic granules

A role for copper in the release of luteinizing hormone releasing hormone (LHRH) from hypothalamic neurons has been previously proposed. To elucidate further the mechanism of action of copper, we addressed two questions: (a) what is the active form of copper that interacts with the LHRH granule (ionic or chelated)? and (b) is copper-stimulated LHRH release a result of an interaction of copper with thiol groups and, if so, does it require oxygen? Granules were isolated from hypothalami of adult male rats and were then incubated at 37 degrees C for 3-5 min in a buffered medium. When granules were incubated with various copper complexes, CuATP stimulated LHRH release by 45 +/- 4% (mean +/- SE), copper tartrate by 44 +/- 4%, CuBSA by 27 +/- 7%, and copper histidine by 16 +/- 6%. Neither CuEDTA nor CuCl2 stimulated LHRH release. CuATP-stimulated LHRH release from granules incubated under N2 was 50% of that incubated under air. Furthermore, the CuATP-stimulated release of LHRH was completely inhibited by dithiothreitol or glutathione (10(-3) M each), partially (40-50%) by iodoacetate or 5,5-dithiobis-(2-nitrobenzoic acid), and not at all by oxidized dithiothreitol. Thus, chelated copper, rather than ionic copper, is the active form of the metal, and the action of copper involves an oxidation reaction and granule thiol groups. The precise mechanism of action of copper, however, has yet to be elucidated. We propose that copper may affect LHRH release as follows: copper, bound to an intracellular chelator (protein, peptide, or amino acid), oxidizes thiols of the LHRH granule, leading to a change in granule-membrane permeability and hence to LHRH release.

Hormonally produced changes in caeruloplasmin synthesis and secretion in primary cultured rat hepatocytes. Relationship to hepatic copper metabolism

Hormonally produced changes in the synthesis and secretion of the serum copper-containing protein caeruloplasmin were studied in primary cultures of rat liver parenchymal cells isolated by the collagenase-perfusion technique. A rabbit antibody directed against rat caeruloplasmin was used to immunoprecipitate labelled caeruloplasmin. Isolated liver cells synthesized and secreted caeruloplasmin over a period of 3 days. Synthesis and secretion of this protein was enhanced when cells were treated with dexamethasone. The accumulation of copper was also moderately enhanced with glucocorticoid treatment. Inclusion of adrenaline in the culture medium resulted in elevated incorporation of copper into newly synthesized caeruloplasmin as well as an increase in 64Cu-labelled caeruloplasmin in the culture medium. However, adrenaline did not seem to increase the secretion of 3H-labelled protein, despite the elevation in secreted 64Cu-caeruloplasmin. This may be due to a large increase in the intracellular pool of 64Cu caused by enhanced accumulation of this metal when adrenaline is included in the incubation medium. Enhanced copper accumulation was also seen when cells were treated with glucagon. Adrenaline-stimulated accumulation of 64Cu could be inhibited by including phenoxybenzamine, an alpha-adrenergic blocker, in the culture medium. Elevation of extracellular copper caused enhancement in the detection of labelled caeruloplasmin in the medium of cultured cells, probably owing to the ability of this metal to stabilize the protein.

Internal duplication and evolution of human ceruloplasmin

With the completion of the primary structure of the 50,000- and 19,000-dalton fragments of human ceruloplasmin [ferroxidase; iron(II):oxygen oxidoreductase, EC 1.16.3.1], over half of the covalent structure of the single polypeptide chain of this protein is known. Visual and computer analysis of the sequence of the 564 amino acid residues in the two fragments gives clear evidence of statistically significant internal homology suggestive of evolutionary replication of two smaller units. Two homology regions, each composed of 224 residues, were defined by an intrasequence alignment that required only three gaps in each 224-residue segment. The two homology regions exhibited 43% identity in sequence, and 13% of the remaining positions had similar residues. The sequence of a 160-residue segment in ceruloplasmin exhibits significant homology to the active (copper-binding) sites of blue electron-transfer proteins such as azurins and plastocyanins and multicopper oxidases such as cytochrome oxidase and superoxide dismutase. It is proposed that a primitive ceruloplasmin gene was formed by the fusion of two genes coding, respectively, for protein abut 160 and 190 amino acid residues in length and that this precursor gene coding for about 350 amino acids was later triplicated to form the gene for the present-day ceruloplasmin molecule of about 1050 amino acids.