Oxidative modification of human ceruloplasmin by peroxyl radicals

Exploring the significance of potassium homeostasis in copper ion binding to human αB-Crystallin

αB-Crystallin (αB-Cry) is a small heat shock protein known for its protective role, with an adaptable structure that responds to environmental changes through oligomeric dynamics. Cu(II) ions are crucial for cellular processes but excessive amounts are linked to diseases like cataracts and neurodegeneration. This study investigated how optimal and detrimental Cu(II) concentrations affect αB-Cry oligomers and their chaperone activity, within the potassium-regulated ionic-strength environment. Techniques including isothermal titration calorimetry, differential scanning calorimetry, fluorescence spectroscopy, inductively coupled plasma atomic emission spectroscopy, cyclic voltammetry, dynamic light scattering, circular dichroism, and MTT assay were employed and complemented by computational methods. Results showed that potassium ions affected αB-Cry's structure, promoting Cu(II) binding at multiple sites and scavenging ability, and inhibiting ion redox reactions. Low concentrations of Cu(II), through modifications of oligomeric interfaces, induce regulation of surface charge and hydrophobicity, resulting in an increase in chaperone activity. Subunit dynamics were regulated, maintaining stable interfaces, thereby inhibiting further aggregation and allowing the functional reversion to oligomers after stress. High Cu(II) disrupted charge/hydrophobicity balance, sewing sizable oligomers together through subunit-subunit interactions, suppressing oligomer dissociation, and reducing chaperone efficiency. This study offers insights into how Cu(II) and potassium ions influence αB-Cry, advancing our understanding of Cu(II)-related diseases.

A role for ceruloplasmin in the control of human glioblastoma cell responses to radiation

Background

Glioblastoma (GB) is the most common and most aggressive malignant brain tumor. In understanding its resistance to conventional treatments, iron metabolism and related pathways may represent a novel avenue. As for many cancer cells, GB cell growth is dependent on iron, which is tightly involved in red-ox reactions related to radiotherapy effectiveness. From new observations indicating an impact of RX radiations on the expression of ceruloplasmin (CP), an important regulator of iron metabolism, the aim of the present work was to study the functional effects of constitutive expression of CP within GB lines in response to beam radiation depending on the oxygen status (21% O₂ versus 3% O₂).

Methods and results

After analysis of radiation responses (Hoechst staining, LDH release, Caspase 3 activation) in U251-MG and U87-MG human GB cell lines, described as radiosensitive and radioresistant respectively, the expression of 9 iron partners (TFR1, DMT1, FTH1, FTL, MFRN1, MFRN2, FXN, FPN1, CP) were tested by RTqPCR and western blots at 3 and 8 days following 4 Gy irradiation. Among those, only CP was significantly downregulated, both at transcript and protein levels in the two lines, with however, a weaker effect in the U87-MG, observable at 3% O₂. To investigate specific role of CP in GB radioresistance, U251-MG and U87-MG cells were modified genetically to obtain CP depleted and overexpressing cells, respectively. Manipulation of CP expression in GB lines demonstrated impact both on cell survival and on activation of DNA repair/damage machinery (γH2AX); specifically high levels of CP led to increased production of reactive oxygen species, as shown by elevated levels of superoxide anion, SOD1 synthesis and cellular Fe2 + .

Conclusions

Taken together, these in vitro results indicate for the first time that CP plays a positive role in the efficiency of radiotherapy on GB cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09808-6.

Retinoids rescue ceruloplasmin secretion and alleviate oxidative stress in Wilson's disease-specific hepatocytes

Wilson’s disease (WD) is a copper metabolic disorder caused by a defective ATP7B function. Conventional therapies cause severe side effects and significant variation in efficacy, according to cohort studies. Thus, exploring new therapeutic approaches to prevent progression to liver failure is urgent. To study the physiology and pathology of WD, immortalized cell lines and rodent WD models have been used conventionally; however, a large gap remains among different species as well as in genetic backgrounds among individuals. We generated induced pluripotent stem cells (iPSCs) from four WD patients carrying compound heterozygous mutations in the ATP7B gene. ATP7B loss- and gain-of-functions were further manifested with ATP7B-deficient iPSCs and heterozygously corrected R778L WD patient-derived iPSCs using CRISPR-Cas9-based gene editing. Although the expression of ATP7B protein varied among WD-specific hepatocytes differentiated from these iPSCs, the expression and secretion of ceruloplasmin (Cp), a downstream copper carrier in plasma, were consistently decreased in WD patient-derived and ATP7B-deficient hepatocytes. A transcriptome analysis detected abnormalities in the retinoid signaling pathway and lipid metabolism in WD-specific hepatocytes. Drug screening using WD patient-derived hepatocytes identified retinoids as promising candidates for rescuing Cp secretion. All-trans retinoic acid also alleviates reactive oxygen species production induced by lipid accumulation in WD-specific hepatocytes treated with oleic acid. These patient-derived iPSC-based hepatic models function as effective platforms for the development of potential therapeutics for hepatic steatosis in WD and other fatty liver diseases.

A Comparison of Oxidative Stress Biomarkers in the Serum of Healthy Polish Dairy Goats with Those Naturally Infected with Small Ruminant Lentivirus in the Course of Lactation

The present study examines the effects of natural infection by small ruminant lentivirus (SRLV) in the two most common goat breeds in Poland, i.e., Polish white improved and polish fawn improved. It focuses on biomarkers of oxidative stress, oxidatively modified proteins and antioxidant defenses, ceruloplasmin level as an acute phase protein, and the activities of antioxidant enzymes in the goat serum. It was conducted on 24 goats divided into two equal groups: one SRLV-seropositive (SRLV-SP) and another SRLV-seronegative (SRLV-SN). Both groups were identical in terms of breed and parity. Despite infection, the SRLV-SP goats demonstrated no symptoms of caprine arthritis-encephalitis. In addition, the SRLV-SP goats did not reveal pronounced dysfunctions in oxidative stress biomarkers in the serum compared to the SRLV-SN animals. However, both groups demonstrated elevated levels of the aldehydic and ketonic derivatives of oxidatively modified proteins during the lactation period. In addition, both groups retained a high total antioxidant capacity in serum despite the decrease of enzyme antioxidant defenses throughout the 200-day lactation period.

Serum Ceruloplasmin Is the Candidate Predictive Biomarker for Acute Aortic Dissection and Is Related to Thrombosed False Lumen: a Propensity Score-Matched Observational Case-Control Study

Acute aortic dissection (AAD), one of the fatal diseases observed at the department of vascular surgery, is associated with a great mortality rate at the early stage. Ceruloplasmin (CP) is the plasma protein that functions as a copper transporter. The current retrospective research was carried out to assess CP contents and to examine the possible part in diagnosing patients with AAD. In addition, propensity score matching (PSM) was also utilized for reducing the bias in case screening as well as the clinical confounders. Using PSM, this study included 85 pairs of AAD cases (Stanford A and B dissection) and matched controls, and their CP levels were also detected through enzyme-linked immunosorbent assay (ELISA). Additionally, the relative clinical data were extracted from participants included in this study. After PSM adjustment for clinical variables, including gender, age, body mass index (BMI), heart ratio (HR), smoking, hypertension, diabetes mellitus, coronary heart disease (CHD), and stroke, the serum CP contents among AAD cases were remarkably increased compared with those among the normal subjects. Besides, the CP contents showed independent association with the AAD risk. Typically, the CP level was significantly positively correlated with platelet (R = 0.329) or C-reactive protein (R = 0.340) level. Meanwhile, the area under the receiver operating characteristic (ROC) curve (AUC) was 0.929 when CP was used to diagnose AAD, and the best threshold value was 36.82mg/dL. Serum CP content significantly increased in cases with thrombosed false lumen (FL) relative to those in patent FL cases. Results of logistic regression analysis suggested that a greater CP content indicated an increased thrombosed FL risk (OR = 1.11; 95% CI: 1.01-1.23; P = 0.040). Findings in this study suggest that serum ceruloplasmin contents evidently increased among acute aortic dissection cases. CP shows close correlation with the inflammatory factors among AAD cases. Further, CP may serve as the candidate biomarker to diagnose AAD and to identify an increased risk of thrombosed false lumen.

Azocompounds as generators of defined radical species: Contributions and challenges for free radical research

Peroxyl radicals participate in multiple processes involved in critical changes to cells, tissues, pharmacueticals and foods. Some of these reactions explain their association with degenerative pathologies, including cardiovascular and neurological diseases, as well as cancer development. Azocompounds, and particularly AAPH (2,2'-Azobis(2-methylpropionamidine) dihydrochloride), a cationic water-soluble derivative, have been employed extensively as sources of model peroxyl radicals. A considerable number of studies have reported mechanistic data on the oxidation of biologically-relevant targets, the scavenging activity of foods and natural products, and the reactions with, and responses of, cultured cells. However, despite the (supposed) experimental simplicity of using azocompounds, the chemistry of peroxyl radical production and subsequent reactions is complicated, and not always considered in sufficient depth when analyzing experimental data. The present work discusses the chemical aspects of azocompounds as generators of peroxyl (and other) radicals, together with their contribution to our understanding of biochemistry, pharmaceutical and food chemistry research. The evidence supporting a role for the formation of alkoxyl (RO•) and other radicals during thermal and photochemical decomposition of azocompounds is assessed, together with the potential influence of such species on the reactions under study.

TRAIL and Ceruloplasmin Inverse Correlation as a Representative Crosstalk between Inflammation and Oxidative Stress

Objective

“Oxinflammation” is a recently coined term that defines the deleterious crosstalk between inflammatory and redox systemic processes, which underlie several diseases. Oxinflammation could be latently responsible for the predisposition of certain healthy individuals to disease development. The oxinflammatory pathway has been recently suggested to play a crucial role in regulating the activity of TNF-related apoptosis-inducing ligand (TRAIL), a TNF superfamily member that can mediate multiple signals in physiological and pathological processes. Therefore, we investigated the associations between TRAIL and key players of vascular redox homeostasis.

Methods

We measured circulating TRAIL levels relative to praoxonas-1, lipoprotein phospholipase-A2, and ceruloplasmin levels in a cohort of healthy subjects (n = 209).

Results

Multivariate analysis revealed that ceruloplasmin levels were significantly inversely associated with TRAIL levels (r = −0.431, p < 0.001). The observed association retained statistical significance after adjustment for additional confounding factors. After stratification for high-sensitivity C-reactive protein levels, the inverse association between TRAIL and ceruloplasmin levels remained strong and significant (r = −0.508, p < 0.001, R² = 0.260) only in the presence of inflammation, confirming the role of inflammation as emerged in in vitro experiments where recombinant TRAIL decreased ceruloplasmin expression levels in TNF-treated PBMC cultures.

Conclusion

The results indicated that in an inflammatory milieu, TRAIL downregulates ceruloplasmin expression, highlighting a signaling axis involving TRAIL and ceruloplasmin that are linked via inflammation and providing important insights with potential clinical implications.

Serum Haptoglobin Levels in Ocular Behçet Disease and Acute Phase Proteins in the Course of Behçet Disease

Purpose

Changes in concentrations of acute phase proteins in the serum of patients might be significant in the pathogenesis of Behçet disease. This report investigates the association between ocular disease activity and serum haptoglobin levels in patients with Behçet disease, and summarizes the current understanding of the correlation between acute phase proteins and Behçet disease based on both personal studies and data from the literature.

Methods

Thirty patients with Behçet disease with ocular involvement and 15 healthy subjects were included in the study. Of the 30 patients, 14 had acute uveitis and 16 had inactive ocular involvement at the time of enrollment.

Results

There was a significant difference in haptoglobin levels between the patients with active ocular disease and controls (p=0.0005). There was also a significant difference in haptoglobin levels between the patients with inactive ocular disease and control subjects (p<0.0001). However, no significant difference was observed among patients with active versus inactive uveitis with regard to serum haptoglobin levels.

Conclusions

Higher serum haptoglobin levels in patients with Behçet disease compared to control subjects were obtained. However, elevated serum haptoglobin levels do not seem to be a risk factor for uveitis activity. Behçet disease is generally diagnosed by physical examinations and no laboratory marker has been widely accepted for follow-up of disease activity.

Disturbance of redox homeostasis in Down Syndrome: Role of iron dysmetabolism

Down Syndrome (DS) is the most common genetic form of intellectual disability that leads in the majority of cases to development of early-onset Alzheimer-like dementia (AD). The neuropathology of DS has several common features with AD including alteration of redox homeostasis, mitochondrial deficits, and inflammation among others. Interestingly, some of the genes encoded by chromosome 21 are responsible of increased oxidative stress (OS) conditions that are further exacerbated by decreased antioxidant defense. Previous studies from our groups showed that accumulation of oxidative damage is an early event in DS neurodegeneration and that oxidative modifications of selected proteins affects the integrity of the protein degradative systems, antioxidant response, neuronal integrity and energy metabolism. In particular, the current review elaborates recent findings demonstrating the accumulation of oxidative damage in DS and we focus attention on specific deregulation of iron metabolism, which affects both the central nervous system and the periphery. Iron dysmetabolism is a well-recognized factor that contributes to neurodegeneration; thus we opine that better understanding how and to what extent the concerted loss of iron dyshomeostasis and increased OS occur in DS could provide novel insights for the development of therapeutic strategies for the treatment of Alzheimer-like dementia.

Sensitive Detection of Immunoglobulin G Stability Using in Real-Time Isothermal Differential Scanning Fluorimetry: Determinants of Protein Stability for Antibody-Based Therapeutics

Protein instability is a major obstacle in the production and delivery of monoclonal antibody-based therapies for cancer. This study presents real-time isothermal differential scanning fluorimetry as an emerging method to evaluate the stability of human immunoglobulin G protein with high sensitivity. The stability of polyclonal human immunoglobulin G against urea-induced denaturation was assessed following: (1) oxidation by the free-radical generator 2,2-Azobis[2-amidinopropane]dihydrochloride and (2) in selected storage buffers. Significant differences in immunoglobulin G stability were detected by real-time isothermal differential scanning fluorimetry when the immunoglobulin G was stored in 1,4-Piperazinediethanesulfonic acid buffer compared to phosphate-buffered saline, with half-maximal rate of denaturation occurring at a higher urea concentration in 1,4-Piperazinediethanesulfonic acid than phosphate-buffered saline (K_nd;PIPES = 3.56 ± 0.09 M, K_nd;PBS = 2.94 ± 0.08 M; P < .01), but differential scanning fluorimetry did not detect differences in unfolding temperature (T_m;PIPES = 70.5 ± 0.3°C, T_m;PBS = 69.7 ± 0.2°C). The effects of 2,2-Azobis[2-amidinopropane]dihydrochloride-induced oxidation on immunoglobulin G stability were analyzed by real-time isothermal differential scanning fluorimetry; the oxidized protein showed greater sensitivity to urea (K_nd;CNTRL = 3.96 ± 0.19 M, K_nd;AAPH = 3.49 ± 0.07 M; P < .05). Similarly, differential scanning fluorimetry indicated greater thermal sensitivity of oxidized immunoglobulin G (T_m;CNTRL = 70.5 ± 0.3°C, T_m;AAPH = 62.9 ± 0.1°C; P < .001). However, a third method for assessing protein stability, pulse proteolysis, proved to be substantially less sensitive and did not detect significant effects of 2,2-Azobis[2-amidinopropane]dihydrochloride on the half-maximal concentration of urea needed to denature immunoglobulin G (C_m;CNTRL= 6.8 ± 0.1 M; C_m;AAPH = 6.4 ± 0.7 M). Overall these results demonstrate the merit of using real-time isothermal differential scanning fluorimetry as a rapid and sensitive technique for the evaluation of protein stability in solution using a quantitative real-time thermocycler.

Oxidative modification of human ceruloplasmin induced by a catechol neurotoxin, salsolinol

Salsolinol (SAL), a compound derived from dopamine metabolism, is the most probable neurotoxin involved in the pathogenesis of Parkinson's disease (PD). In this study, we investigated the modification and inactivation of human ceruloplasmin (hCP) induced by SAL. Incubation of hCP with SAL increased the protein aggregation and enzyme inactivation in a dose-dependent manner. Reactive oxygen species scavengers and copper chelators inhibited the SAL-mediated hCP modification and inactivation. The formation of dityrosine was detected in SAL-mediated hCP aggregates. Amino acid analysis post the exposure of hCP to SAL revealed that aspartate, histidine, lysine, threonine and tyrosine residues were particularly sensitive. Since hCP is a major copper transport protein, oxidative damage of hCP by SAL may induce perturbation of the copper transport system, which subsequently leads to deleterious conditions in cells. This study of the mechanism by which ceruloplasmin is modified by salsolinol may provide an explanation for the deterioration of organs under neurodegenerative disorders such as PD.

Proteomic Investigations into Hemodialysis Therapy

The retention of a number of solutes that may cause adverse biochemical/biological effects, called uremic toxins, characterizes uremic syndrome. Uremia therapy is based on renal replacement therapy, hemodialysis being the most commonly used modality. The membrane contained in the hemodialyzer represents the ultimate determinant of the success and quality of hemodialysis therapy. Membrane's performance can be evaluated in terms of removal efficiency for unwanted solutes and excess fluid, and minimization of negative interactions between the membrane material and blood components that define the membrane's bio(in)compatibility. Given the high concentration of plasma proteins and the complexity of structural functional relationships of this class of molecules, the performance of a membrane is highly influenced by its interaction with the plasma protein repertoire. Proteomic investigations have been increasingly applied to describe the protein uremic milieu, to compare the blood purification efficiency of different dialyzer membranes or different extracorporeal techniques, and to evaluate the adsorption of plasma proteins onto hemodialysis membranes. In this article, we aim to highlight investigations in the hemodialysis setting making use of recent developments in proteomic technologies. Examples are presented of why proteomics may be helpful to nephrology and may possibly affect future directions in renal research.

Ceruloplasmin potentiates nitric oxide synthase activity and cytokine secretion in activated microglia

BACKGROUND

Ceruloplasmin is a ferroxidase expressed in the central nervous system both as soluble form in the cerebrospinal fluid (CSF) and as membrane-bound GPI-anchored isoform on astrocytes, where it plays a role in iron homeostasis and antioxidant defense. It has been proposed that ceruloplasmin is also able to activate microglial cells with ensuing nitric oxide (NO) production, thereby contributing to neuroinflammatory conditions. In light of the possible role of ceruloplasmin in neurodegenerative diseases, we were prompted to investigate how this protein could contribute to microglial activation in either its native form, as well as in its oxidized form, recently found generated in the CSF of patients with Parkinson's and Alzheimer's diseases.

METHODS

Primary rat microglial-enriched cultures were treated with either ceruloplasmin or oxidized-ceruloplasmin, alone or in combination with lipopolysaccharide (LPS). Production of NO and expression of inducible nitric oxide synthase (iNOS) were evaluated by Griess assay and Western blot analysis, respectively. The productions of the pro-inflammatory cytokine IL-6 and the chemokine MIP-1α were assessed by quantitative RT-PCR and ELISA.

RESULTS

Regardless of its oxidative status, ceruloplasmin by itself was not able to activate primary rat microglia. However, ceruloplasmin reinforced the LPS-induced microglial activation, promoting an increase of NO production, as well as the induction of IL-6 and MIP-1α. Interestingly, the ceruloplasmin-mediated effects were observed in the absence of an additional induction of iNOS expression. The evaluation of iNOS activity in primary glial cultures and in vitro suggested that the increased NO production induced by the combined LPS and ceruloplasmin treatment is mediated by a potentiation of the enzymatic activity.

CONCLUSIONS

Ceruloplasmin potentiates iNOS activity in microglial cells activated by a pro-inflammatory stimulus, without affecting iNOS expression levels. This action might be mediated by the activation of a yet unknown Cp receptor that triggers intracellular signaling that cross-talks with the response elicited by LPS or other pro-inflammatory stimuli. Therefore, ceruloplasmin might contribute to pathological conditions in the central nervous system by exacerbating neuroinflammation.

Identifying early urinary metabolic changes with long-term environmental exposure to cadmium by mass-spectrometry-based metabolomics

Cadmium (Cd) is a common environmental pollutant, and urinary Cd (UCd) is generally used as a marker of exposure; however, our understanding on the related urinary metabolic changes caused by Cd exposure is still not clear. In this study, we applied a mass-spectrometry-based metabolomic approach to assess the urinary metabolic changes in human with long-term environmental Cd exposure, aimed to identify early biomarkers to assess Cd nephrotoxicity. Urine samples from 94 female never smokers aged 44-70 with UCd in the range of 0.20-68.67 μg/L were analyzed by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-ToF-MS) and gas chromatography-mass spectrometry (GC-MS). It was found that metabolites related to amino acid metabolism (L-glutamine, L-cystine, L-tyrosine, N-methyl-L-histidine, L-histidinol, taurine, phenylacetylglutamine, hippurate, and pyroglutamic acid), galactose metabolism (D-galactose and myo-inositol), purine metabolism (xanthine, urea, and deoxyadenosine monophosphate), creatine pathway (creatine and creatinine), and steroid hormone biosynthesis (17-α-hydroxyprogesterone, tetrahydrocortisone, estrone, and corticosterone) were significantly higher among those with a UCd level higher than 5 μg/L. Moreover, we noticed that the level of N-methyl-L-histidine had already started to elevate among individuals with a UCd concentration of ≥2 μg/L. The overall findings illustrate that metabolomics offer a useful approach for revealing metabolic changes as a result of Cd exposure.

Oxidation-induced structural changes of ceruloplasmin foster NGR motif deamidation that promotes integrin binding and signaling

Asparagine deamidation occurs spontaneously in proteins during aging; deamidation of Asn-Gly-Arg (NGR) sites can lead to the formation of isoAsp-Gly-Arg (isoDGR), a motif that can recognize the RGD-binding site of integrins. Ceruloplasmin (Cp), a ferroxidase present in the cerebrospinal fluid (CSF), contains two NGR sites in its sequence: one exposed on the protein surface ((568)NGR) and the other buried in the tertiary structure ((962)NGR). Considering that Cp can undergo oxidative modifications in the CSF of neurodegenerative diseases, we investigated the effect of oxidation on the deamidation of both NGR motifs and, consequently, on the acquisition of integrin binding properties. We observed that the exposed (568)NGR site can deamidate under conditions mimicking accelerated Asn aging. In contrast, the hidden (962)NGR site can deamidate exclusively when aging occurs under oxidative conditions, suggesting that oxidation-induced structural changes foster deamidation at this site. NGR deamidation in Cp was associated with gain of integrin-binding function, intracellular signaling, and cell pro-adhesive activity. Finally, Cp aging in the CSF from Alzheimer disease patients, but not in control CSF, causes Cp deamidation with gain of integrin-binding function, suggesting that this transition might also occur in pathological conditions. In conclusion, both Cp NGR sites can deamidate during aging under oxidative conditions, likely as a consequence of oxidative-induced structural changes, thereby promoting a gain of function in integrin binding, signaling, and cell adhesion.

Association between serum ceruloplasmin levels and arterial stiffness in Korean men with type 2 diabetes mellitus

BACKGROUND

Increased oxidative stress contributes to the development of arterial stiffness. Arterial stiffness, as measured by brachial-ankle pulse wave velocity (baPWV), has been known to be correlated with oxidative stress. Serum ceruloplasmin (CP), a copper-carrying protein, may indicate the overall level of oxidative stress in the body. The present study investigated whether serum CP levels are associated with baPWV in Korean men with type 2 diabetes mellitus (DM).

SUBJECTS AND METHODS

Serum CP levels and conventional risk factors were measured in 760 Korean men with type 2 DM. Arterial stiffness was assessed by baPWV obtained with an automatic device (model VP-1000; Colin, Komaki, Japan).

RESULTS

Correlation analysis indicated a significant positive association between serum CP and baPWV (r = 0.109, P = 0.003). Age-adjusted baPWV increased gradually according to serum CP quartiles (Q1, 1,500.3 ± 18.4 cm/s; Q2, 1,511.6 ± 17.8 cm/s; Q3, 1,551.8 ± 17.9 cm/s; Q4, 1,622.1 ± 17.8 cm/s; P for trend < 0.001). Multivariate linear regression analysis showed that serum CP was independently associated with baPWV in various models.

CONCLUSIONS

A positive relationship was identified between CP and baPWV in adult male subjects with type 2 DM, which was independent of conventional cardiovascular risk factors. Further studies are needed to confirm whether CP contributes to the pathogenesis of increased arterial stiffness in subjects with type 2 DM.

Ceruloplasmin oxidation, a feature of Parkinson's disease CSF, inhibits ferroxidase activity and promotes cellular iron retention

Parkinson's disease is a neurodegenerative disorder characterized by oxidative stress and CNS iron deposition. Ceruloplasmin is an extracellular ferroxidase that regulates cellular iron loading and export, and hence protects tissues from oxidative damage. Using two-dimensional electrophoresis, we investigated ceruloplasmin patterns in the CSF of human Parkinson's disease patients. Parkinson's disease ceruloplasmin profiles proved more acidic than those found in healthy controls and in other human neurological diseases (peripheral neuropathies, amyotrophic lateral sclerosis, and Alzheimer's disease); degrees of acidity correlated with patients' pathological grading. Applying an unsupervised pattern recognition procedure to the two-dimensional electrophoresis images, we identified representative pathological clusters. In vitro oxidation of CSF in two-dimensional electrophoresis generated a ceruloplasmin shift resembling that observed in Parkinson's disease and co-occurred with an increase in protein carbonylation. Likewise, increased protein carbonylation was observed in Parkinson's disease CSF, and the same modification was directly identified in these samples on ceruloplasmin. These results indicate that ceruloplasmin oxidation contributes to pattern modification in Parkinson's disease. From the functional point of view, ceruloplasmin oxidation caused a decrease in ferroxidase activity, which in turn promotes intracellular iron retention in neuronal cell lines as well as in primary neurons, which are more sensitive to iron accumulation. Accordingly, the presence of oxidized ceruloplasmin in Parkinson's disease CSF might be used as a marker for oxidative damage and might provide new insights into the underlying pathological mechanisms.

Serum ceruloplasmin and copper are early biomarkers for traumatic brain injury-associated elevated intracranial pressure

High intracranial pressure (ICP) is a prominent secondary pathology after traumatic brain injury (TBI) and is a major contributor to morbidity and mortality. Currently, there are no clinically proven methods for predicting which TBI patients will develop high ICP. In the present study, we examined whether the serum levels of the copper-binding protein ceruloplasmin are differentially altered in patients with elevated ICP (> or =25 mmHg) vs. those whose ICP remained below 20 mmHg throughout the study period. Consistent with its role as an acute-phase reactant, we found that ceruloplasmin levels were significantly increased by 3 days post-TBI compared with healthy volunteers. However, prior to this delayed increase, ceruloplasmin levels during the first 24 hr following injury were found to be significantly reduced in patients who subsequently developed high ICP. This decrease was found to have prognostic accuracy in delineating TBI patients based on their ICP status (cutoff of 140 microg/ml; sensitivity: 87%, specificity: 73%), Likewise, low total serum copper (below 1.32 microg/ml) was also found to be predictive of high ICP (sensitivity 86%, specificity 73%). These results suggest that initial serum ceruloplasmin/copper levels may have diagnostic value in predicting patients at risk for developing high intracranial pressure.

Oxidative Aggregation of Ceruloplasmin Induced by Hydrogen Peroxide is Prevented by Pyruvate

Ceruloplasmin (CP) is a blue copper glycoprotein with multiple physiological functions including ferroxidase and oxidase activities. CP is also an important serum oxygen free radical (OFR) scavenger and antioxidant, exerting cardioprotective and antifibrillatory actions. Although it has been reported that CP activities can be inhibited by OFR, the intimate mechanism of this inactivation is still not clear. Exposure of bovine CP to H2O2 induced inactivation of the protein as well as structural alterations as indicated by loss of protein bands by SDS-PAGE. Both phenomena were H2O2 concentration and time dependent. HPLC gel filtration and capillary electrophoresis analysis of CP treated with H2O2 revealed an aggregation of the protein. Quantification of dityrosine formation by fluorescence indicated the involvement of dityrosine bridging, which could be responsible for aggregation of CP under oxidative attack. Oxidative damage to CP under H2O2 treatment was completely prevented by pyruvate, suggesting that the association of CP with antioxidants could extend the range of the protective action of this protein.

Aminoacetone Induces Loss of Ferritin Ferroxidase and Iron Uptake Activities

Aminoacetone (AA) is a threonine and glycine metabolite overproduced and recently implicated as a contributing source of methylglyoxal (MG) in conditions of ketosis. Oxidation of AA to MG, NH4+, and H2O2 has been reported to be catalyzed by a copper-dependent semicarbazide sensitive amine oxidase (SSAO) as well as by copper- and iron ion-catalyzed reactions with oxygen. We previously demonstrated that AA-generated O2*-. and enoyl radical (AA*) induce dose-dependent Fe(II) release from horse spleen ferritin (HoSF); no reaction occurs under nitrogen. In the present study we further explored the mechanism of iron release and the effect of AA on the ferritin apoprotein. Iron chelators such as EDTA, ATP and citrate, and phosphate accelerated AA-promoted iron release from HoSF, which was faster in horse spleen isoferritins containing larger amounts of phosphate in the core. Incubation of apoferritin with AA (2.5-50 mM, after 6 h) changes the apoprotein electrophoretic behavior, suggesting a structural modification of the apoprotein by AA-generated ROS. Superoxide dismutase (SOD) was able to partially protect apoferritin from structural modification whereas catalase, ethanol, and mannitol were ineffective in protection. Incubation of apoferritin with AA (1-10 mM) produced a dose-dependent decrease in tryptophan fluorescence (13-30%, after 5 h), and a partial depletion of protein thiols (29% after 24 h). The AA promoted damage to apoferritin produced a 40% decrease in apoprotein ferroxidase activity and an 80% decrease in its iron uptake ability. The current findings of changes in ferritin and apoferritin may contribute to intracellular iron-induced oxidative stress during AA formation in ketosis and diabetes mellitus.

Ceruloplasmin/Transferrin system is related to clinical status in acute stroke

BACKGROUND AND PURPOSE

In acute stroke, Iron (Fe) may amplify reperfusion injury by catalyzing the conversion of superoxide and hydrogen peroxide into highly reactive radicals. Transferrin (Tf) is the main protein regulating Fe homeostasis, whereas Ceruplasmin (CP) is a circulating ferroxidase enzyme able to oxidize ferrous ions to less toxic ferric forms. This study aims at investigating whether CP, Copper (Cu), Tf, and Fe play a role in the pathophysiology of acute stroke.

METHODS

We enrolled 35 acute stroke patients and 44 controls. All patients underwent: neurological examination assessed by National Institutes of Health Stroke Scale (NIHSS), ultrasound evaluation of carotid atherosclerosis, brain MRI to quantify ischemic lesion volume and measurement of serum levels of CP, Cu, Tf, Fe, hydro-peroxides, and Total plasmatic antioxidant capacity.

RESULTS

In patients, NIHSS scores were associated with Tf (r=-0.48, P=0.004), hydro-peroxides (r=0.34, P=0.046), CP (r=0.43, P=0.012), and lesion volume (r=0.50, P=0.004). Lesion volume was inversely associated with Tf (r=-0.44, P=0.012). CP and hydro-peroxides were also largely related (r=0.81, P<0.001). The model multiple R was 0.57, resulting in a 32.5% of explained NIHSS variance with Tf accounting for 23.4% and CP for 9.1%.

CONCLUSIONS

CP and Tf levels are representative of clinical status in acute stroke patients. Our findings suggest a protective role of Tf in acute stroke and a possible ambivalent role of CP.

Neutrophil activation, protein oxidation and ceruloplasmin levels in children with Henoch-Schönlein purpura

The aim of this study was to investigate the role of neutrophil activation, protein oxidation and ceruloplasmin (CLP) in the pathogenesis of Henoch-Schönlein purpura (HSP), which has not been investigated previously. Serum activities of myeloperoxidase (MPO) and arylesterase (ARYL) and levels of free thiol groups, CLP and total oxidant status (TOS) were measured in 29 children with HSP at the onset of the disease and during remission in comparison with 30 healthy subjects. Patients at active stage had significantly higher MPO activity (391+/-277 vs. 155+/-154 U/l, P<0.001), higher CLP (832+/-120 vs. 682+/-114 mg/dl, P<0.001) and TOS values (20.7+/-11.8 vs. 7.5+/-2.8 micromol H2O2/l, P<0.001) than the controls, respectively. Patients had significantly lower ARYL activity (158x10(3)+/-39x10(3) vs. 187x10(3)+/-46x10(3) U/l, P<0.001) and lower free thiol levels (234+/-48 vs. 279+/-26 micromol/l, P<0.001) than the controls, respectively. Significantly positive correlations were found between TOS and MPO (r=0.437, P=0.018) and TOS and CLP (r=0.409, P=0.028) at disease onset, whereas a negative correlation was found between MPO and thiol (r=-0.597, P=0.001) during remission. In conclusion, protein oxidation and neutrophil activation may play important roles in the pathogenesis of HSP. Further research is required to understand the potential linkage between oxidant stress and complications and to develop therapeutic strategies in HSP.

Ceruloplasmin and what it might do

The blue coloured plasma protein ceruloplasmin binds up to 95% of circulating copper, and has several possible functions. It has been proposed to function in copper transport, oxidation of organic amines, iron(II) oxidation and the regulation of cellular iron levels, and catechols, radical scavenging and other antioxidant processes. This account will consider the relative importance of these multiple functions in terms of the physiological roles of ceruloplasmin.

Orally administered penicillamine is a potent inhibitor of neointimal and medial thickening in porcine saphenous vein–carotid artery interposition grafts

OBJECTIVE

In patients who have undergone coronary artery bypass grafting, blood copper levels are elevated for 6 weeks after surgery. Copper is an established risk factor for cardiovascular disease and atherogenesis and promotes oxidative stress, lipid oxidation, cell proliferation, and matrix formation, all components of vein graft disease. This project therefore examined the effect of the copper chelator penicillamine on saphenous vein graft thickening in a pig model.

METHODS

Saphenous vein-carotid artery interposition grafts were carried out in Landrace pigs. Penicillamine (10 mg/kg once daily, n = 8) was administered orally incorporated into small amounts of mashed potato for 1 month (n = 8 controls). Vein grafts were then excised and fixed at 100 mm Hg, histologic sections were prepared, and morphometry and measurement of proliferating cell nuclear antigen count were carried out. In vitro studies on the effect of copper or penicillamine on human vascular smooth muscle cell replication was carried out with bromodeoxyuridine incorporation.

RESULTS

Administration of penicillamine had a potent inhibitory effect on both neointimal and medial thickness and proliferating cell nuclear antigen count but elicited a marked increase in luminal area and reduced serum copper concentrations. In vitro, copper augmented vascular smooth muscle cell proliferation, an effect blocked by penicillamine. Penicillamine alone also inhibited in vitro vascular smooth muscle cell replication.

CONCLUSION

The administration of penicillamine reduces vein graft thickening and promotes positive remodeling through negation of copper-induced cell proliferation. Copper chelators may therefore be therapeutically useful in preventing late vein graft failure in patients undergoing reconstructive arterial surgery.

Penicillamine administration reverses the inhibitory effect of hyperhomocysteinaemia on endothelium-dependent relaxation in the corpus cavernosum in the rabbit

OBJECTIVE

To elucidate the role of copper in mediating the impact of homocysteine on vasculogenic erectile dysfunction (VED), by investigating the effect of dietary supplementation with the copper-chelator penicillamine to rabbits rendered hyperhomocysteinaemic (HHC) with a methionine-rich diet, as a raised plasma level of homocysteine might be a risk factor for VED.

MATERIALS AND METHODS

Homocysteine inhibits the nitric oxide (NO)-dependent relaxation of the corpus cavernosum (CC), an effect which appears to be mediated via the generation of superoxide (O2*-), and H2O2. Copper is a catalyst for the generation of H2O2 in the presence of homocysteine and in the presence of copper, H2O2 undergoes reactions resulting in the generation of O2*-, which reacts with NO to produce peroxynitrite (ONOO-), thereby reducing the bioavailability of NO and impairing NO-mediated relaxation of CC. Smooth muscle strips from CC were obtained from two groups of adult New Zealand White rabbits, one rendered HHC with a diet supplemented with methionine (group 1) and another HHC group that had additional dietary supplementation with penicillamine (group 2). Tissue O2*- levels were measured in each group. After pre-contraction with phenylephrine, relaxation responses of CC strips to carbachol were also assessed in both groups.

RESULTS

Methionine supplementation led to profound HHC in all rabbits. Penicillamine in group 2 reduced the total plasma Cu2+ compared to group 1. There was a markedly lower carbachol-stimulated relaxation of CC from HHC rabbits in group 1, with a mean (sem) maximum relaxation of 37 (4)% (six samples), than in group 2, at 58 (6)%.

CONCLUSION

These data show that elevated levels in vivo of homocysteine in the rabbit markedly impair NO-dependent relaxation of the CC. Furthermore, this effect appears to be augmented by copper. Further clinical studies on homocysteine and copper status in patients with VED are warranted.

Penicillamine administration reverses the inhibitory effect of hyperhomocysteinaemia on endothelium-dependent relaxation and superoxide formation in the aorta of the rabbit

Although hyperhomocysteinaemia is a risk factor for cardiovascular disease, the mechanisms underlying this association have not been elucidated. It has been demonstrated, however, that copper augments the inhibitory effect of homocysteine on nitric oxide (NO)-mediated relaxation of the rat aorta through increased superoxide formation, which reacts with NO thereby reducing the bioavailability of NO. Since it follows that the administration of a copper chelator may blunt the pathogenic impact of hyperhomocysteinaemia, in vivo, the effect of penicillamine administration on NO-dependent relaxation and superoxide formation in the aortae of hyperhomocysteinaemic rabbits was studied. New Zealand White rabbits were fed a methionine-rich (20 g/kg chow) diet for 1 month+/-penicillamine administered orally (10 mg/kg/day) and aortic relaxation elicited with acetylcholine and superoxide measured. The role of NADPH oxidase was also studied using a range of inhibitors and western analysis of gp47(phox) (a catalytic subunit of NADPH oxidase). The methionine-rich diet markedly increased plasma total homocysteine levels. In hyperhomocysteinaemic rabbits there was a marked reduction of acetylcholine-stimulated relaxation and an increase in superoxide formation that were both inhibited with superoxide dismutase and apocynin, an NADPH oxidase inhibitor. Gp47(phox) expression was also increased in aortae from methionine fed rabbits. Penicillamine administration significantly reduced plasma total copper in methionine-fed rabbits compared to controls. Impaired acetylcholine-stimulated relaxation, increased superoxide formation and increased gp47(phox) expression in aortae from methionine-fed rabbits was reversed by penicillamine administration. These data indicate that hyperhomocysteinaemia augments the formation of arterial superoxide through an increase in NADPH oxidase expression/activity which in turn reduces NO bioavailability. Since these effects were reversed by penicillamine, these data consolidate the hypothesis that copper plays a role in mediating homocysteine-induced vasculopathy.

Does oxidative stress change ceruloplasmin from a protective to a vasculopathic factor?

Although ceruloplasmin (CP), a copper containing metalloenzyme, possesses antioxidant properties (e.g. ferroxidase activity), elevated circulating CP is associated with cardiovascular disease (CVD). This ambivalence is possibly due to the capacity of CP, via its coppers, to promote vasculopathic effects that include lipid oxidation, negation of nitric oxide bioactivity and endothelial cell apoptosis. In turn, these effects that are mediated by increased formation of reactive oxygen species (ROS), such as superoxide and hydrogen peroxide. There is also evidence that risk factors for CVD (in particular, diabetes mellitus and hyperhomocysteinaemia) may augment the vasculopathic impact of CP. In turn, it appears that ROS disrupt copper binding to CP, thereby impairing its normal protective function while liberating copper which in turn may promote oxidative pathology. The objective of this review, therefore, is to consider the epidemiology and pathophysiology of CP in relation to CVD, with particular emphasis on the relationship between CP and oxidative stress.

Carbonylated proteins in bronchoalveolar lavage of patients with sarcoidosis, pulmonary fibrosis associated with systemic sclerosis and idiopathic pulmonary fibrosis

Oxygen-derived free radicals produced by phagocytes have been postulated to contribute to lung tissue damage occurring during diffuse lung diseases (DLD). The two-dimensional electrophoretic (2-DE) analysis of bronchoalveolar lavage (BAL) protein composition revealed different protein profiles in sarcoidosis (S), idiopathic pulmonary fibrosis (IPF) and systemic sclerosis (SSc) with a significant increase of low molecular weight proteins in IPF. Some of these proteins are involved in antioxidant processes. The aims of this report were to analyse the oxidative stress occurring in patients with DLD through determination of BAL protein carbonyl content and to identify target proteins of oxidation by a proteomic approach (2-DE combined with immunoblotting with specific antibodies for carbonyl groups). Carbonylated proteins detected by enzyme-linked immunosorbent assay (ELISA) were increased in BAL of patients with S, IPF and SSc compared to healthy controls with a significant difference for S and IPF. The proteomic approach to the analysis of BAL revealed that protein carbonylation was a process involving specific carbonylation-sensitive proteins and that in IPF a greater number of proteins target of oxidation were present. In conclusion, to our knowledge, this is the first report providing a database of proteins target of oxidation in BAL of patients with sarcoidosis, idiopathic pulmonary fibrosis and systemic sclerosis.

Metal binding by citrus dehydrin with histidine-rich domains

Dehydrins are hydrophilic proteins that are responsive to osmotic stress, such as drought, cold, and salinity in plants. Although they have been hypothesized to stabilize macromolecules in stressed cells, their functions are not fully understood. Citrus dehydrin, which accumulates mainly in response to cold stress, enhances cold tolerance in transgenic tobacco by reducing lipid peroxidation. It has been demonstrated that citrus dehydrin scavenges hydroxyl radicals. In this study, the metal binding of citrus dehydrin is reported and the specific domain responsible is identified. The metal binding property of citrus dehydrin was tested using immobilized metal ion affinity chromatography (IMAC). Fe3+, Co2+, Ni2+, Cu2+, and Zn2+ bound to citrus dehydrin, but Mg2+, Ca2+, and Mn2+ did not. Among the bound metals, the highest affinity was detected for Cu(2+)-dehydrin binding, which showed a dissociation constant of 1.6 microM. Citrus dehydrin was able to bind up to 16 Cu2+ ions. IMAC indicated that His residues contributed to Cu(2+)-dehydrin binding. The amino acid sequence of CuCOR15 was divided into five domains, of which domain 1 bound Cu2+ most strongly. One portion of domain 1, HKGEHHSGDHH, was the core sequence for the binding. These results suggest that citrus dehydrin binds metals using a specific sequence containing His. Since citrus dehydrin is a radical-scavenging protein, it may reduce metal toxicity in plant cells under water-stressed conditions.

Oxidative modification of rat eye lens proteins by peroxyl radicals in vitro: protection by the chain-breaking antioxidants stobadine and Trolox

In an attempt to model the processes of free radical-mediated cataractogenesis, we investigated the oxidative modification of rat eye lens proteins by peroxyl radicals generated by thermal decomposition of 2,2'-azobis(2-amidinopropane)hydrochloride (AAPH) under aerobic conditions. When incubated with AAPH, the soluble eye lens proteins precipitated in a time-dependent manner. The insolubilisation was accompanied by the accumulation of protein free carbonyls and the diminution of sulfhydryls, yet the processes were shifted in time. The SDS-PAGE analysis of the AAPH-treated proteins revealed the presence of high molecular weight cross-links and, to a lesser extent, fragments. The aggregation and cross-linking of proteins along with the generation of free carbonyls was significantly inhibited by the chain-breaking antioxidants stobadine and Trolox. On the other hand, the AAPH-initiated sulfhydryl consumption was much less sensitive to the antioxidants studied. The results point to a complex mechanism of peroxyl-radical-mediated modification of eye lens proteins with implications for cataract development and they indicate a potentially protective role of antioxidants.

Copper, zinc superoxide dismutase plus hydrogen peroxide: a catalytic system for human lipoprotein oxidation

We report for the first time that bovine or human CuZnSOD plus H2O2 can catalyze human lipoprotein oxidation, inducing like free copper ions a typical oxidative kinetics with lag and propagation phases. Free copper released from CuZnSOD by H2O2, but not enzyme peroxidase activity and carbonate radical anion, is responsible for lipoprotein oxidation, which is indeed totally inhibited by copper chelators and BHT but unaffected by bicarbonate. Moreover, lipoprotein oxidation is significantly counteracted by the OH* scavengers formate and azide, which can enter the active site of CuZnSOD and decrease copper release through scavenging of copper-bound OH*; benzoate and ethanol, which cannot enter, are instead ineffective, indicating no oxidative involvement of free OH* escaped from the enzyme active site. The possibility of CuZnSOD/H2O2-catalyzed lipoprotein oxidation in vivo is discussed.

Radical scavenging activity and oxidative modification of citrus dehydrin

Dehydrins are ubiquitous proteins produced by plants in response to water stress. Their functions, however, are not fully understood. The overexpression of Citrus unshiu Marcov. dehydrin (CuCOR19) enhanced cold tolerance in transgenic plants by reducing lipid peroxidation promoted by cold stress, suggesting that the CuCOR19 protein directly scavenges radicals. In this paper, we report the radical scavenging activity and oxidative modification of CuCOR19. The hydroxyl radical generated by the Fe2+/H2O2 system and peroxyl radical generated from 2, 2'-azobis (2-amidinopropane) (AAPH) were scavenged by CuCOR19, but hydrogen peroxide and superoxide were not. The scavenging activity for the hydroxyl radical and peroxyl radical of CuCOR19 was more potent than that of mannitol, and approximately equal to that of serum albumin, which is known as an antioxidative protein in mammals. CuCOR19 was degraded by the hydroxyl radical and peroxyl radical in a time- and dose-dependent manner. Mannitol and thiourea inhibited the degradation. Analysis of the amino acid composition of CuCOR19 indicated that glycine, histidine, and lysine, which are major residues in many dehydrins, were targeted by the hydroxyl radical. These results suggest that CuCOR19 is a radical scavenging protein, and may reduce oxidative damage induced by water stress in plants.

Influences of different stress models on the antioxidant status and lipid peroxidation in rat erythrocytes

The aim of this study was to investigate the influences of different stress models on the antioxidant status and lipid peroxidation (LPO) in erythrocytes of rats. Swiss-Albino female rats (3 months old) were used in this study. Rats were randomly divided into the following four groups; control group (C), cold stress group (CS), immobilization stress group (IS) and cold + immobilization stress group (CS + IS). Control group was kept in an animal laboratory (22 +/- 2 degrees C). Rats in CS group were placed in cold room (5 degrees C) for 15min/day for 15 days. Rats in IS group were immobilized for 180 min/day for 15 days. Rats in CS + IS group were exposed to both cold and immobilization stresses for 15 days. At the end of experimental periods, the activities of glucose-6-phosphate dehydrogenase (G-6-PD), Cu,Zn-superoxide dismutase (Cu,Zn-SOD), catalase (CAT) and glutathione peroxidase (GSH-Px), and concentration of reduced glutathione (GSH) were measured. LPO was determined by measuring the contents of thiobarbituric acid-reactive substances (TBARS). Cu,Zn-SOD activity and TBARS concentration were increased after cold and immobilization stresses, but CAT and GSH-Px activities and GSH levels were decreased. Immobilization stress decreased the activity of G-6-PD. The activities of G-6-PD, CAT and GSH-Px, and the level of GSH were lower in CS + IS group than in the control group. Cu,Zn-SOD activity and TBARS levels were increased in CS + IS group when compared with the control group. From these findings, three stress models are thought to cause oxidative stress.

The role of cysteine residues in the oxidation of ferritin

We have shown that ferritin is oxidized during iron loading using its own ferroxidase activity and that this oxidation results in its aggregation (Welch et al., Free Radic. Biol. Med. 31:999-1006; 2001). In this study we determined the role of cysteine residues in the oxidation of ferritin. Loading iron into recombinant human ferritin by its own ferroxidase activity decreased its conjugation by a cysteine specific spin label, indicating that cysteine residues were altered during iron loading. Using LC/MS, we demonstrated that tryptic peptides of ferritin that contained cysteine residues were susceptible to modification as a result of iron loading. To assess the role of cysteine residues in the oxidation of ferritin, we used site-directed mutagenesis to engineer variants of human ferritin H chain homomers where the cysteines were substituted with other amino acids. The cysteine at position 90, which is located at the end of the BC-loop, appeared to be critical for the formation of ferritin aggregates during iron loading. We also provide evidence that dityrosine moieties are formed during iron loading into ferritin by its own ferroxidase activity and that the dityrosine formation is dependent upon the oxidation of cysteine residues, especially cysteine 90. In conclusion, cysteine residues play an integral role in the oxidation of ferritin and are essential for the formation of ferritin aggregates.