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Hepatic iron overload associated with a decreased serum ceruloplasmin level in a novel clinical type of aceruloplasminemia.

BACKGROUND & AIMS: Aceruloplasminemia is a novel hereditary iron overload disease caused by a mutation in the ceruloplasmin gene and characterized by a complete deficiency of serum ceruloplasmin and iron accumulation in the liver and brain. METHODS: We herein studied a novel clinical type of aceruloplasminemia in which a low amount of ceruloplasmin was detected in the serum of a patient. The patient presented with an asymptomatic hepatic iron overload, retinal degeneration, and diabetes mellitus. Magnetic resonance imaging of the liver and basal ganglia showed T2-hypointensity signals associated with parenchymal iron accumulation because of an absence of the ferroxidase activity in ceruloplasmin. RESULTS: A gene analysis showed a novel G969S mutation in the ceruloplasmin gene. A biochemical analysis of the patients' serum and a biogenesis study of G969S mutant ceruloplasmin using mammalian cell culture system resulted in the synthesis and secretion of only apoceruloplasmin without any ferroxidase activity. CONCLUSIONS: This novel clinical type of aceruloplasminemia should therefore be considered in the differential diagnosis of unexplained hemochromatosis, which is associated with a decrease in the serum ceruloplasmin level.

Aged↗

Acute phase reactants ceruloplasmin and haptoglobin and their relationship to plasma prostaglandins in rabbits bearing the VS2 carcinoma.

Results of previous studies have shown that the VX2 carcinoma in rabbits synthesizes large amounts of prostaglandin E2 (PGE2). PGE2 secreted by the tumor is rapidly metabolized and can be measured in plasma as the metabolite 13,14-dihydro-15-keto-PGE2 (PGE2-M). We have previously proposed that the hypercalcemia that occurs in rabbits bearing the VX2 carcinoma is due to excessive secretion of PGE2 by the tumor and its subsequent action on the skeleton as a bone resorption-stimulating factor. In the course of these studies, we noted that the plasma of rabbits bearing the VS2 carcinoma became blue about 1 wk after tumor implantation. The intensity of the color increased markedly thereafter. We therefore measured ceruloplasmin in plasma by both chemical and immunological assay methods. Plasma ceruloplasmin and PGE2-M rose in parallel (within 7-10 days) and preceded by 7-10 days the development of hypercalcemia. 2 wk after tumor implantation, plasma PGE2-M and ceruloplasmin had risen about 20- and 6-fold, respectively, while the rise in plasma calcium was just beginning. Indomethacin, an inhibitor of prostaglandin synthesis, given from the time of tumor implantation prevented completely the hypercalcemia and largely inhibited the rise in ceruloplasmin. When given after hyperprostaglandinemia had developed, indomethacin produced a fall in both PGE2-M and ceruloplasmin. A rise in plasma haptoglobin concentrations similar to that seen for ceruloplasmin was also observed. No changes in plasma albumin concentrations occurred. We conclude that the acute phase reactants ceruloplasmin and haptoglobin rise rapidly in the plasma of rabbits bearing the VX2 carcinoma, and that this increase is related to arachidonic acid metabolism in these animals. It is possible that arachidonic acid metabolites also play a role in the elevations of these two plasma proteins observed in certain patients with malignant tumors.

Animals↗

Expression of the ceruloplasmin gene in the human retina and brain: implications for a pathogenic model in aceruloplasminemia.

Aceruloplasminemia is an autosomal recessive disorder of iron metabolism characterized by progressive neurodegeneration of the retina and basal ganglia in association with inherited mutations of the ceruloplasmin gene. To begin to elucidate the pathogenesis of this disease, ceruloplasmin gene expression was examined in human brain and retinal tissue. RNA blot analysis and RNAse protection studies demonstrate ceruloplasmin-specific transcripts in multiple regions of the human brain, and biosynthetic studies reveal ceruloplasmin synthesis and secretion in these same regions. Consistent with these observations, in situ hybridization of central nervous system tissue utilizing ceruloplasmin cRNA probes reveals abundant ceruloplasmin gene expression in specific populations of glial cells associated with the brain microvasculature, surrounding dopaminergic melanized neurons in the substantia nigra and within the inner nuclear layer of the retina. Taken in the context of the clinical and pathological features observed in patients with aceruloplasminemia, these data reveal that glial cell-specific ceruloplasmin gene expression is essential for iron homeostasis and neuronal survival in the human central nervous system.

Brain↗

Sertoli cells synthesize and secrete a ceruloplasmin-like protein.

Sertoli cells synthesize and secrete a ceruloplasmin-like protein (testicular ceruloplasmin) that is immunologically similar to serum ceruloplasmin. Rat serum ceruloplasmin was purified and an antiserum was produced to the purified protein which specifically immunoprecipitated a 130,000 dalton protein from rat serum. This ceruloplasmin antiserum was found to also immunoprecipitate a 130,000 dalton protein synthesized and secreted by Sertoli cells. The presence of a protease inhibitor, phenylmethylsulfonyl fluoride (PMSF), was required during the immunoprecipitation procedure to prevent the proteolytic degradation of testicular ceruloplasmin. Immunoprecipitation of proteins secreted by Sertoli cells with an antiserum to rat serum proteins was found to precipitate two proteins, testicular ceruloplasmin and testicular transferrin.

Animals↗

Ceruloplasmin and regulation of transferrin iron during Neisseria meningitidis infection in mice.

The role of ceruloplasmin (ferroxidase I; EC 1.16.3.1) in iron metabolism during experimental Neisseria meningitidis infection was investigated. Plasma ceruloplasmin activity was found to increase greatly in mice during the convalescence phase of iron-controlled infection and after a plasma hypoferremia had occurred. Ceruloplasmin activity-deficient animals became hypoferremic as a result of an impaired release of iron from the reticuloendothelial system as shown by impaired return of reticuloendothelial system-processed heme iron in these mice. Hypoferremia in ceruloplasmin activity-deficient mice was associated with an increased resistance to N. meningitidis infection, an effect reversed readily by ceruloplasmin supplementation or iron addition. This evidence implicated ceruloplasmin activity as an important component in the regulation of the plasma transferrin iron pool and suggested that an important role of additional ceruloplasmin as an acute-phase protein might be related to the requirement of additional transferrin iron. This study also provided further evidence of the importance of transferrin iron and host hypoferremia in bacterial infection.

Animals↗

Ceruloplasmin and transferrin levels are altered in serum and bronchoalveolar lavage fluid of patients with the adult respiratory distress syndrome.

The respiratory burst of neutrophils generates oxygen radicals that can result in lipid peroxidation and may contribute to acute lung injury in the adult respiratory distress syndrome (ARDS). Because ceruloplasmin and transferrin are inhibitors of lipid peroxidation and may play a role in regulating tissue injury, antigen levels of ceruloplasmin and transferrin and ceruloplasmin oxidase levels were measured in the serum and bronchoalveolar lavage fluid (BALF) of ARDS patients (n = 28), patients at risk for ARDS (n = 22), and normal control subjects (n = 45). Serum ceruloplasmin levels were similar in ARDS (mean +/- SEM) (3.8 +/- 0.3 microM) and at-risk (3.3 +/- 0.4 microM) patients compared with control subjects (3.2 +/- 0.2 microM). Serum transferrin levels were decreased in ARDS (14.9 +/- 1.7 microM) and at-risk (20.4 +/- 1.7 microM) patients compared with normal control subjects (32.9 +/- 1.2 microM), and serum transferrin levels correlated with serum unsaturated iron binding capacity (UIBC). Ceruloplasmin was detected in only one of 38 normal BALF samples (0.002 +/- 0.002 microM) and two of 13 at-risk BALF samples (0.15 +/- 0.1 microM), yet it was present in 17 of 23 ARDS BALF samples (0.9 +/- 0.2 microM). Transferrin was also increased in ARDS BALF (5.4 +/- 1.1 microM) compared with at-risk (0.7 +/- 0.5 microM) and normal (0.4 +/- 0.1 microM) samples. Ceruloplasmin that was present in the BALF and serum samples had functional oxidase activity, and purified human ceruloplasmin inhibited hydroxyl radical formation by phorbol myristate acetate (PMA)-stimulated neutrophils.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchoalveolar Lavage Fluid↗

Ceruloplasmin gene expression in the murine central nervous system.

Aceruloplasminemia is an autosomal recessive disorder resulting in neurodegeneration of the retina and basal ganglia in association with iron accumulation in these tissues. To begin to define the mechanisms of central nervous system iron accumulation and neuronal loss in this disease, cDNA clones encoding murine ceruloplasmin were isolated and characterized. RNA blot analysis using these clones detected a 3.7-kb ceruloplasmin-specific transcript in multiple murine tissues including the eye and several regions of the brain. In situ hybridization of systemic tissues revealed cell-specific ceruloplasmin gene expression in hepatocytes, the splenic reticuloendothelial system and the bronchiolar epithelium of the lung. In the central nervous system, abundant ceruloplasmin gene expression was detected in specific populations of astrocytes within the retina and the brain as well as the epithelium of the choroid plexus. Analysis of primary cell cultures confirmed that astrocytes expressed ceruloplasmin mRNA and biosynthetic studies revealed synthesis and secretion of ceruloplasmin by these cells. Taken together these results demonstrate abundant cell-specific ceruloplasmin expression within the central nervous system which may account for the unique clinical and pathologic findings observed in patients with aceruloplasminemia.

Amino Acid Sequence↗

Interrelations between ceruloplasmin and Fe status during human pregnancy.

It is well established that Fe and ceruloplasmin interact in animals and in in vitro models. However, Fe-mediated regulation of ceruloplasmin has never been investigated in humans. In an observational study, 53 pregnant women aged 19-39 yr (29.8 +/- 0.7 yr, mean +/- SEM) were recruited at the Aberdeen Antenatal Clinic, Aberdeen Maternity Hospital, UK. All requirements for local ethical committees were followed. Venous blood samples were taken from each woman at 34 wk gestation for measurement of Fe status and ceruloplasmin. Various parameters were used to test for Fe status. The most sensitive one appeared to be soluble transferrin receptor, which increased with parity. In the population studied, there was no relationship between hemoglobin or ferritin and serum ceruloplasmin. However, using soluble transferrin receptor (sTfR) levels, we were able to demonstrate an inverse linear relationship (r = 0.37, p = 0.021, n = 41) between Fe status and ceruloplasmin. Fe supplementation, number of previous pregnancies, and smoking habits did not affect this relationship. Our data support in vitro results showing regulation of ceruloplasmin by Fe and also suggest that the interactions between Fe and ceruloplasmin should be considered when Fe supplementation is given.

Adult↗

Biochemical features of ceruloplasmin gene mutations linked to aceruloplasminemia.

Aceruloplasminemia is a neurodegenerative disease characterized by parenchymal iron accumulation owing to mutations in the ceruloplasmin gene. Ceruloplasmin is expressed in the central nervous system in which most of the ceruloplasmin is located on the surface of astrocytes in a glycosylphosphatidylinositol (GPI)-anchored form. We herein describe the biochemical features of wild-type and mutant GPI-anchored ceruloplasmin. An overexpression of wild-type GPI-anchored ceruloplasmin in Chinese hamster ovary cells led to the formation of aggresome-like inclusions, especially in the presence of proteasome inhibitors. As expected from the properties of aggresomes, the inclusions were colocalized with gamma-tubulin and a disruption of microtubules using nocodazole blocked the formation of such inclusions. Aceruloplasminemia-linked mutant proteins failed to form such inclusions even after treatment with proteasomal inhibitors. An immunofluorescent analysis indicated that the mutant proteins were thus retained in the endoplasmic reticulum (ER), whereas the transfected cells showed a decreased viability. The expression of glucose-regulated protein 78 that is one of the ER stress sensor proteins, and the activity of glucose-regulated protein 78 promoter was upregulated in the cells transfected with the mutants. These findings indicated that when the overexpressed cytoplasmic wild-type ceruloplasmin was not subjected to degradation by the proteasome-ubiquitin system, then the wild-type protein was transported along the microtubules, thus forming inclusions at the microtubule organizing center, whereas the mutant ceruloplasmin failed to form any such inclusions, because the mutant protein might not have been translocated across the ER into the cytoplasm. Therefore, the mutant protein was considered to have accumulated in the ER thus leading to the ER stress, which resulted in cell death.

Animals↗

The value of serum zinc, copper, ceruloplasmin levels in patients with gastrointestinal tract cancers.

BACKGROUND/AIMS: Gastrointestinal cancers are frequent diseases of particular importance for surgeons with regard to their management and follow-up. Neoplastic diseases activate antioxidant defense systems. As a result, concentrations of redoxal enzymes and their co-factor elements appear to change. The levels of zinc (Zn), copper (Cu) and ceruloplasmin have been found to be critical parameters. In addition, it seems to be important to consider the Cu/Zn ratio in such cases. In this study, changes in the levels of Cu, Zn and ceruloplasmin in patients with gastrointestinal system cancers was evaluated, and the proportion of Cu to Zn (Cu/Zn) is discussed. METHODS: In this clinical trial, levels of Cu and Zn were defined with calorimetric methods and ceruloplasmin levels were measured with immunohistochemical methods in a control group of 20 healthy individuals and in 25 patients who underwent surgery for gastrointestinal system cancer. The blood samples were taken preoperatively in gastrointestinal system cancer patients. RESULTS: This study has shown that while the decrease in Zn levels and the increase in ceruloplasmin levels in patients with gastrointestinal system cancers were found to be significant (p<0. 001, p=0. 014) when compared to the control group, the increase in the level of Cu was also found to be significant (p=0. 019). In the patient group, the correlations between serum Cu and serum ceruloplasmin proved to be significant (r=991, p<0. 001). The Cu/Zn ratio, when compared with Zn, ceruloplasmin and Cu, showed significant results (r= 0. 562, r= 0. 500, r=0. 506, p<0. 001). CONCLUSIONS: This study shows that serum Cu, Zn and ceruloplasmin levels show changes in gastrointestinal system cancers, but further research is needed to demonstrate the importance and significance of these parameters and their relation with other contributing neoplastic factors.

Adult↗

Haptoglobin and ceruloplasmin as determinants of inflammation in dogs.

Assay procedures for determining serum haptoglobin concentration and ceruloplasmin oxidase activity in dogs were validated, and reference values were established. Serum haptoglobin concentration is reported as milligrams per deciliter of cyanmethemoglobin binding capacity, whereas serum ceruloplasmin oxidase activity was determined by use of p-phenylenediamine as substrate. Both assays were used to analyze serum samples from 288 dogs. In each dog's case record, clinical history and final diagnosis were evaluated to determine whether the dog had an inflammatory condition. Complete blood cell counts were performed in 265 dogs, using simultaneously collected blood samples. Plasma fibrinogen concentration was determined for 161 dogs. A positive correlation (P less than 0.01) for serum haptoglobin concentration and for ceruloplasmin oxidase activity, compared with WBC counts, segmented neutrophil and band neutrophil counts, and plasma fibrinogen concentration. Ceruloplasmin oxidase activity and haptoglobin concentration were up to 6 times more sensitive than fibrinogen concentration or leukocyte counts in detecting inflammation. Specificity of ceruloplasmin oxidase activity was comparable to fibrinogen concentration and leukocyte counts, whereas haptoglobin concentration was found to be slightly less specific. Specificity of haptoglobin concentration improved slightly (from 0.82 to 0.88) when dogs with a history of glucocorticoid administration were excluded from analysis. Predictive value of a negative test result (haptoglobin concentration less than 125 mg/dl; ceruloplasmin oxidase activity less than 20 IU/L) and predictive value of a positive test result for haptoglobin concentration and ceruloplasmin activity were comparable to or better than fibrinogen concentration or various oxidase leukocyte counts in detection of inflammation in a variety of disease conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Mechanisms of copper incorporation during the biosynthesis of human ceruloplasmin.

To examine the mechanisms of copper incorporation during ceruloplasmin biosynthesis, we developed methods to resolve and identify apo and holoceruloplasmin. The identity of holoceruloplasmin was confirmed by oxidase activity staining, immunoblotting, 67Cu-ligand exchange, and 67Cu-ligand blotting. Following metabolic labeling of human liver and lung cell lines with 67Cu, newly synthesized holoceruloplasmin was detected in the culture media as two species with apparent molecular masses of 84 and 79 kDa. Pulse-chase studies demonstrate that exogenous copper is readily available for incorporation into newly synthesized ceruloplasmin and that the kinetics of apo and holoceruloplasmin synthesis and secretion are identical. Inhibition of N-linked glycosylation did not affect the rate or amount of copper incorporated into newly synthesized ceruloplasmin but did result in the secretion of a single 68-kDa holoceruloplasmin moiety. Despite differences in the kinetics of copper uptake between cell lines a linear rate of copper incorporation into newly synthesized ceruloplasmin was observed with no evidence of copper exchange following biosynthesis. Under the conditions studied, holoceruloplasmin accounted for less than 5% of the total ceruloplasmin synthesized and secreted by each cell line. The data indicate that copper is incorporated into newly synthesized ceruloplasmin early in the course of biosynthesis by a process independent of N-linked carbohydrate addition. This process of copper incorporation results in an apparent conformational change in the ceruloplasmin molecule which does not affect the secretory rate of the protein.

Apoproteins↗

Decreased ceruloplasmin ferroxidase activity in cigarette smokers.

Ceruloplasmin is one of the most important antioxidant proteins in serum. Ceruloplasmin functions as a ferroxidase that oxidizes iron to the Fe3+ state, thereby preventing Fe2+-catalyzed lipid peroxidation and cellular damage. Despite increased antigenic amounts of ceruloplasmin, cigarette smoker serum has previously been shown to exhibit significantly less antioxidant activity than non-smoker serum. We demonstrate that the decreased antioxidant activity of cigarette smoker serum may be explained by a decrease in ceruloplasmin ferroxidase activity. Smokers had a 14% decrease in serum ceruloplasmin ferroxidase activity (units per milliliter) compared with nonsmokers. There was a 24% decrease in ferroxidase activity per milligram of ceruloplasmin in smokers compared with nonsmokers (0.32 +/- 0.009 U/mg vs 0.42 +/- 0.020 U/mg, p less than 0.005). Smoker serum also contained significantly less ceruloplasmin-specific antioxidant activity than nonsmoker serum. These observations may explain the decrement in smoker serum antioxidant activity that could predispose cigarette smokers to increased oxidant injury.

Adult↗

Rat ceruloplasmin. Molecular cloning and gene expression in liver, choroid plexus, yolk sac, placenta, and testis.

A rat ceruloplasmin cDNA clone was isolated from a rat liver cDNA library and identified by partial nucleotide sequence analysis. Rat liver ceruloplasmin mRNA levels were measured during the acute phase response to inflammation by cytoplasmic dot hybridization to ceruloplasmin cDNA. Regulation of ceruloplasmin synthesis appeared to be at the mRNA level, with the concentration of ceruloplasmin mRNA increasing significantly 12 h after induction of inflammation, reaching a maximum of 350% of normal at 36 h and returning to normal levels within 60 h. Using Northern blot analysis, extrahepatic ceruloplasmin gene expression was observed in choroid plexus, yolk sac, placenta, and testis. All these tissues are at the interface between, and possibly involved in maintaining homeostasis in, adjacent extracellular compartments. No ceruloplasmin mRNA was detected in RNA from stomach and small intestine.

Amino Acid Sequence↗

Ceruloplasmin as an indicator of copper status in cattle and sheep.

The relationship between ceruloplasmin, a metalloenzyme with oxidase activity, and copper was investigated in cattle and sheep. The oxidase activity of ceruloplasmin correlated closely with the serum or plasma copper concentrations in cattle. The respective correlation coefficients were 0.83 and 0.60. In sheep serum, a correlation coefficient of 0.92 was obtained. In each instance, the relationship remained linear from the deficient to the high normal ranges of copper. Comparison of the linear regression relationships indicated the ceruloplasmin activity in bovine serum was statistically lower than the activity in bovine plasma (P less than 0.0001), through the intercepts from the regression lines of the two relationships were similar (P = 0.412). Comparisons of ovine and bovine serum-ceruloplasmin relationships indicated that a significant species difference was present. Ovine ceruloplasmin activity increased more rapidly as compared to the corresponding bovine activity over the range of copper concentrations investigated (P less than 0.0001). The intercept from the ovine regression relationship was also lower (P less than 0.0001). A correlation coefficient of 0.35 was observed between the serum ceruloplasmin activity and hepatic copper concentrations in cattle indicating that the mathematical relationship was not as well defined. Ceruloplasmin activity appears to correlate more closely with serum or plasma copper concentrations as compared to corresponding liver copper concentrations.

Animals↗

[Structural organization of rat ceruloplasmin gene].

Distribution of ceruloplasmin-coding sequences among fragments of rat nuclear DNA obtained after complete cleavage with seven restriction endonucleases was studied using highly specific complementary DNA probes. Three different procedures were used for the synthesis of cDNAs, whose relative advantages and disadvantages are discussed in this work. The number of restriction fragments carrying ceruloplasmin gene sequences varied from two to five depending on the enzyme used. The total molecular weight of these fragments was several times higher than the minimal length of ceruloplasmin structural gene deduced from the molecular size of mRNA. The restriction endonuclease cleavage of the partial double-stranded transcript of ceruloplasmin mRNA coding for about 60% of its length from the 3'-end has shown that distribution of restriction endonuclease cleavage sites on the dsDNA differs in the position of cleavage sites on the ceruloplasmin gene in cellular DNA. Hybridization of cDNA with total cellular DNA allows to determine 1.3-1.4 copies of ceruloplasmin gene in the rat haploid genome. Proceeding from the data obtained it may be stated that the rat ceruloplasmin gene is constructed of several structural gene segments cut by introns.

Animals↗

Differences between serum and plasma ceruloplasmin activities and copper concentrations: investigation of possible contributing factors.

Values for ceruloplasmin activities and copper concentrations were found to be lower in serum than in paired samples of plasma in both sheep and cattle. Ceruloplasmin activities in serum were 13-40% lower relative to plasma for nine different groups of animals, and 10-65% lower for individual animals (n = 112). As the values are not directly interchangeable, plasma rather than serum should be used when estimating copper nutrition in these animals. Maximum effects in serum were apparent 3-4 h after collection, the earliest time at which serum could be obtained. Lower ceruloplasmin and copper values in serum could not be attributed to the type of blood collection vessel used, subsequent storage of samples, the methods used for measuring ceruloplasmin activities and copper concentrations, the formation of fibrin in blood, or to the effects of dietary molybdenum. In contrast, the addition of neuraminidase to whole blood before clotting decreased the differences between serum and plasma ceruloplasmin activity and copper concentration in a dose-dependent manner. Of the two major copper-containing enzymes present in blood, effects of clotting were only evident with ceruloplasmin. Cu-Zn-containing superoxide dismutase activity in erythrocytes was unaffected by clot formation. The results indicate that ceruloplasmin and the copper associated with this protein are sequestered into the clot during clot formation by attachment of the enzyme to the blood cellular fraction. The minimizing of this effect by the addition of neuraminidase suggests that this attachment may be through sialic acid residues.

Animals↗

[Molecular defect of ceruloplasmin synthesis and maturation in Wilson-Konovalov disease].

The radioimmunochemical study of ceruloplasmin-synthesizing polyribosomes was carried out using bioptic liver specimens obtained from fourteen homozygous patients with hepatolenticular degeneration (Wilson--Konovalov disease) and from eight control patients with various non-hereditary diseases. The measurement of binding of 125I-antibodies to the nascent polysome-bound ceruloplasmin chains demonstrated that in control patients this protein is only synthesized on membrane-bound polysomes, while free polysomes do not contribute to the synthesis of ceruloplasmin. The majority of homozygous carriers of Wilson--Konovalov mutation (eleven of fourteen) are characterized by the involvement of free, rather than membrane-bound polysomes, in the synthesis of ceruloplasmin. This shift of ceruloplasmin synthesis from membrane-bound to free polysomes seems to be accompanied by disturbances in the cotranslational proteolytic maturation of ceruloplasmin from its biosynthetic precursors. As a result of this defect, a putative of ceruloplasmin (preproceruloplasmin) was detected in the content of Golgi complex as well as in the serum of homozygous patients. This precursor of a molecular weight 84,000 was found neither in Golgi complex, nor in the serum of control subjects.

Adult↗