Ceruloplasmin: macromolecular assemblies with iron-containing acute phase proteins

Reactive Halogen Species: Role in Living Systems and Current Research Approaches

Reactive halogen species (RHS) are highly reactive compounds that are normally required for regulation of immune response, inflammatory reactions, enzyme function, etc. At the same time, hyperproduction of highly reactive compounds leads to the development of various socially significant diseases - asthma, pulmonary hypertension, oncological and neurodegenerative diseases, retinopathy, and many others. The main sources of (pseudo)hypohalous acids are enzymes from the family of heme peroxidases - myeloperoxidase, lactoperoxidase, eosinophil peroxidase, and thyroid peroxidase. Main targets of these compounds are proteins and peptides, primarily methionine and cysteine residues. Due to the short lifetime, detection of RHS can be difficult. The most common approach is detection of myeloperoxidase, which is thought to reflect the amount of RHS produced, but these methods are indirect, and the results are often contradictory. The most promising approaches seem to be those that provide direct registration of highly reactive compounds themselves or products of their interaction with components of living cells, such as fluorescent dyes. However, even such methods have a number of limitations and can often be applied mainly for in vitro studies with cell culture. Detection of reactive halogen species in living organisms in real time is a particularly acute issue. The present review is devoted to RHS, their characteristics, chemical properties, peculiarities of interaction with components of living cells, and methods of their detection in living systems. Special attention is paid to the genetically encoded tools, which have been introduced recently and allow avoiding a number of difficulties when working with living systems.

A Current State of Proteomics in Adult and Pediatric Inflammatory Bowel Diseases: A Systematic Search and Review

Inflammatory bowel diseases (IBD) are systemic immune-mediated conditions with predilection for the gastrointestinal tract and include Crohn's disease and ulcerative colitis. Despite the advances in the fields of basic and applied research, the etiopathogenesis remains largely unknown. As a result, only one third of the patients achieve endoscopic remission. A substantial portion of the patients also develop severe clinical complications or neoplasia. The need for novel biomarkers that can enhance diagnostic accuracy, more precisely reflect disease activity, and predict a complicated disease course, thus, remains high. Genomic and transcriptomic studies contributed substantially to our understanding of the immunopathological pathways involved in disease initiation and progression. However, eventual genomic alterations do not necessarily translate into the final clinical picture. Proteomics may represent a missing link between the genome, transcriptome, and phenotypical presentation of the disease. Based on the analysis of a large spectrum of proteins in tissues, it seems to be a promising method for the identification of new biomarkers. This systematic search and review summarize the current state of proteomics in human IBD. It comments on the utility of proteomics in research, describes the basic proteomic techniques, and provides an up-to-date overview of available studies in both adult and pediatric IBD.

Host-Derived Cytotoxic Agents in Chronic Inflammation and Disease Progression

At inflammatory sites, cytotoxic agents are released and generated from invading immune cells and damaged tissue cells. The further fate of the inflammation highly depends on the presence of antagonizing principles that are able to inactivate these host-derived cytotoxic agents. As long as the affected tissues are well equipped with ready-to-use protective mechanisms, no damage by cytotoxic agents occurs and resolution of inflammation is initiated. However, long-lasting and severe immune responses can be associated with the decline, exhaustion, or inactivation of selected antagonizing principles. Hence, cytotoxic agents are only partially inactivated and contribute to damage of yet-unperturbed cells. Consequently, a chronic inflammatory process results. In this vicious circle of permanent cell destruction, not only novel cytotoxic elements but also novel alarmins and antigens are liberated from affected cells. In severe cases, very low protection leads to organ failure, sepsis, and septic shock. In this review, the major classes of host-derived cytotoxic agents (reactive species, oxidized heme proteins and free heme, transition metal ions, serine proteases, matrix metalloproteases, and pro-inflammatory peptides), their corresponding protective principles, and resulting implications on the pathogenesis of diseases are highlighted.

Hepatic SEL1L-HRD1 ER-associated degradation regulates systemic iron homeostasis via ceruloplasmin

Iron homeostasis is critical for cellular and organismal function and is tightly regulated to prevent toxicity or anemia due to iron excess or deficiency, respectively. However, subcellular regulatory mechanisms of iron remain largely unexplored. Here, we report that SEL1L-HRD1 protein complex of endoplasmic reticulum (ER)-associated degradation (ERAD) in hepatocytes controls systemic iron homeostasis in a ceruloplasmin (CP)-dependent, and ER stress-independent, manner. Mice with hepatocyte-specific Sel1L deficiency exhibit altered basal iron homeostasis and are sensitized to iron deficiency while resistant to iron overload. Proteomics screening for a factor linking ERAD deficiency to altered iron homeostasis identifies CP, a key ferroxidase involved in systemic iron distribution by catalyzing iron oxidation and efflux from tissues. Indeed, CP is highly unstable and a bona fide substrate of SEL1L-HRD1 ERAD. In the absence of ERAD, CP protein accumulates in the ER and is shunted to refolding, leading to elevated secretion. Providing clinical relevance of these findings, SEL1L-HRD1 ERAD is responsible for the degradation of a subset of disease-causing CP mutants, thereby attenuating their pathogenicity. Together, this study uncovers the role of SEL1L-HRD1 ERAD in systemic iron homeostasis and provides insights into protein misfolding-associated proteotoxicity.

Methylglyoxal-Modified Human Serum Albumin Binds to Leukocyte Myeloperoxidase and Inhibits its Enzymatic Activity

Hyperglycemia in diabetes mellitus induces modification of proteins by glucose and its derivative methylglyoxal (MG). Neutrophils perform their bactericidal activity mainly via reactive halogen (RHS) and oxygen (ROS) species generation catalyzed by myeloperoxidase (MPO) stored in neutrophil azurophilic granules (AGs) and membrane NADPH oxidase, respectively. Herein, we study the binding of human serum albumin (HSA) modified with MG (HSA-MG) to MPO and its effects on MPO activity and release by neutrophils. Peroxidase activity of MPO was registered by oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, and chlorinating activity by decolorization of Celestine blue B dye. Binding of HSA-MG to MPO was studied by affinity chromatography, disc-electrophoresis, ligand Western blotting and enzyme-linked solid phase immunoassay using monoclonal antibodies (mAbs) to MPO. ROS and RHS generation were detected by lucigenin (Luc) and luminol (Lum) chemiluminescence (CL), respectively. Neutrophil degranulation was assessed by flow cytometry using fluorescent labeled antibodies to the marker proteins CD63 from AGs and CD11b from peroxidase-negative granules (PNGs). NETosis was assayed by quantifying DNA network-like structures (NET-like structures) in blood smears stained by Romanowsky. HSA-MG bound to MPO, giving a stable complex (Kd = 1.5 nM) and competing with mAbs, and non-competitively inhibited peroxidase and chlorinating MPO activity and induced degranulation of PNGs but not of AGs. HSA-MG enhanced Luc-CL per se or following PMA, unlike Lum-CL, and did not affect spontaneous or PMA-stimulated NETosis. Thus, HSA modified under hyperglycemia-like conditions stimulated NADPH oxidase of neutrophils but dampened their functions dependent on activity of MPO, with no effect on its release via degranulation or NETosis. This phenomenon could underlie the downregulation of bactericidal activity of MPO and neutrophils, and hence of innate immunity, giving rise to wound healing impairment and susceptibility to infection in patients with hyperglycemia.

The Effect of a Rotating Cone on Horseradish Peroxidase Aggregation on Mica Revealed by Atomic Force Microscopy

Our study reported herein aims to determine whether an electromagnetic field, induced triboelectrically by a metallic cone, rotating at a frequency of 167 Hz, has an effect on the properties of the horseradish peroxidase (HRP) enzyme. Atomic force microscopy (AFM) was employed to detect even the most subtle effects on single enzyme molecules. In parallel, a macroscopic method (spectrophotometry) was used to reveal whether the enzymatic activity of HRP in solution was affected. An aqueous solution of the enzyme was incubated at a distance of 2 cm from the rotating cone. The experiments were performed at various incubation times. The control experiments were performed with a non-rotating cone. The incubation of the HRP solution was found to cause the disaggregation of the enzyme. At longer incubation times, this disaggregation was found to be accompanied by the formation of higher-order aggregates; however, no change in the HRP enzymatic activity was observed. The results of our experiments could be of interest in the development of enzyme-based biosensors with rotating elements such as stirrers. Additionally, the results obtained herein are important for the correct interpretation of data obtained with such biosensors.

Molecular mimicry of the receptor-binding domain of the SARS-CoV-2 spike protein: from the interaction of spike-specific antibodies with transferrin and lactoferrin to the antiviral effects of human recombinant lactoferrin

The pathogenesis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection involves dysregulations of iron metabolism, and although the mechanism of this pathology is not yet fully understood, correction of iron metabolism pathways seems a promising pharmacological target. The previously observed effect of inhibiting SARS-CoV-2 infection by ferristatin II, an inducer of transferrin receptor 1 (TfR1) degradation, prompted the study of competition between Spike protein and TfR1 ligands, especially lactoferrin (Lf) and transferrin (Tf). We hypothesized molecular mimicry of Spike protein as cross-reactivity of Spike-specific antibodies with Tf and Lf. Thus, strong positive correlations (R² > 0.95) were found between the level of Spike-specific IgG antibodies present in serum samples of COVID-19-recovered and Sputnik V-vaccinated individuals and their Tf-binding activity assayed with peroxidase-labeled anti-Tf. In addition, we observed cross-reactivity of Lf-specific murine monoclonal antibody (mAb) towards the SARS-CoV-2 Spike protein. On the other hand, the interaction of mAbs produced to the receptor-binding domain (RBD) of the Spike protein with recombinant RBD protein was disrupted by Tf, Lf, soluble TfR1, anti-TfR1 aptamer, as well as by peptides RGD and GHAIYPRH. Furthermore, direct interaction of RBD protein with Lf, but not Tf, was observed, with affinity of binding estimated by K_D to be 23 nM and 16 nM for apo-Lf and holo-Lf, respectively. Treatment of Vero E6 cells with apo-Lf and holo-Lf (1–4 mg/mL) significantly inhibited SARS-CoV-2 replication of both Wuhan and Delta lineages. Protective effects of Lf on different arms of SARS-CoV-2-induced pathogenesis and possible consequences of cross-reactivity of Spike-specific antibodies are discussed.

Halogenation Activity of Mammalian Heme Peroxidases

Mammalian heme peroxidases are fascinating due to their unique peculiarity of oxidizing (pseudo)halides under physiologically relevant conditions. These proteins are able either to incorporate oxidized halides into substrates adjacent to the active site or to generate different oxidized (pseudo)halogenated species, which can take part in multiple (pseudo)halogenation and oxidation reactions with cell and tissue constituents. The present article reviews basic biochemical and redox mechanisms of (pseudo)halogenation activity as well as the physiological role of heme peroxidases. Thyroid peroxidase and peroxidasin are key enzymes for thyroid hormone synthesis and the formation of functional cross-links in collagen IV during basement membrane formation. Special attention is directed to the properties, enzymatic mechanisms, and resulting (pseudo)halogenated products of the immunologically relevant proteins such as myeloperoxidase, eosinophil peroxidase, and lactoperoxidase. The potential role of the (pseudo)halogenated products (hypochlorous acid, hypobromous acid, hypothiocyanite, and cyanate) of these three heme peroxidases is further discussed.

Regulation of zinc-dependent enzymes by metal carrier proteins

Zn²⁺ ions are essential in many physiological processes, including enzyme catalysis, protein structural stabilization, and the regulation of many proteins. The affinities of proteins for Zn²⁺ ions span several orders of magnitude, with catalytic Zn²⁺ ions generally held more tightly than structural or regulatory ones. Metal carrier proteins, most of which are not specific for Zn²⁺, bind these ions with a broad range of affinities that overlap those of catalytic, structural, and regulatory Zn²⁺ ions and are thought to be responsible for distributing the metal through most cells, tissues, and fluid compartments. While little is known about how many proteins obtain or release these ions, there is now considerable experimental evidence suggesting that metal carrier proteins may be responsible for transferring metals to and from some Zn²⁺-dependent proteins, thus serving as a major regulatory factor for them. In this review, the biological roles of Zn²⁺ and structures of Zn²⁺ binding sites are examined, and experimental evidence demonstrating the direct participation of metal carrier proteins in enzyme regulation is discussed. Mechanisms of metal ion transfer are also offered, and the potential physiological significance of this phenomenon is explored.

Molecular Functions of Ceruloplasmin in Metabolic Disease Pathology

Ceruloplasmin (CP) is a multicopper oxidase and antioxidant that is mainly produced in the liver. CP not only plays a crucial role in the metabolic balance of copper and iron through its oxidase function but also exhibits antioxidant activity. In addition, CP is an acute-phase protein. In addition to being associated with aceruloplasminemia and neurodegenerative diseases such as Wilson's disease, Alzheimer's disease, and Parkinson's disease, CP also plays an important role in metabolic diseases, which are caused by metabolic disorders and vigorous metabolism, mainly including diabetes, obesity, hyperlipidemia, etc. Based on the physiological functions of CP, we provide an overview of the association of type 2 diabetes, obesity, hyperlipidemia, coronary heart disease, CP oxidative stress, inflammation, and metabolism of copper and iron. Studies have shown that metabolic diseases are closely related to systemic inflammation, oxidative stress, and disorders of copper and iron metabolism. Therefore, we conclude that CP, which can reduce the formation of free radicals in tissues, can be induced during inflammation and infection, and can correct the metabolic disorder of copper and iron, has protective and diagnostic effects on metabolic diseases.

Caught red handed: modeling and confirmation of the myeloperoxidase ceruloplasmin alpha-thrombin complex

The work is devoted to the study of the structural characteristics of the myeloperoxidase-ceruloplasmin-thrombin complex using small-angle neutron scattering methods in combination with computer modeling, as well as surface plasmon resonance and solid-phase enzyme assay. We have previously shown that the functioning of active myeloperoxidase during inflammation, despite the presence in the blood of an excess of ceruloplasmin which inhibits its activity, is possible due to the partial proteolysis of ceruloplasmin by thrombin. In this study, the myeloperoxidase-ceruloplasmin-thrombin heterohexamer was obtained in vitro. The building of a heterohexamer full-atomic model in silico, considering the glycosylation of the constituent proteins, confirmed the absence of steric barriers for the formation of protein-protein contacts. It was shown that the partial proteolysis of ceruloplasmin does not affect its ability to bind to myeloperoxidase, and a structural model of the heterohexamer was obtained using the small-angle neutron scattering method.

Zinc mediates the interaction between ceruloplasmin and apo-transferrin for the efficient transfer of Fe(III) ions

Fe(II) exported from cells is oxidized to Fe(III), possibly by a multi-copper ferroxidase (MCF) such as ceruloplasmin (CP), to efficiently bind with the plasma iron transport protein transferrin (TF). As unbound Fe(III) is highly insoluble and reactive, its release into the blood during the transfer from MCF to TF must be prevented. A likely mechanism for preventing the release of unbound Fe(III) is via direct interaction between MCF and TF; however, the occurrence of this phenomenon remains controversial. This study aimed to reveal the interaction between these proteins, possibly mediated by zinc. Using spectrophotometric, isothermal titration calorimetric, and surface plasmon resonance methods, we found that Zn(II)-bound CP bound to iron-free TF (apo-TF) with a Kd of 4.2 μM and a stoichiometry CP:TF of ∼2:1. Computational modeling of the complex between CP and apo-TF predicted that each of the three Zn(II) ions that bind to CP further binds to acidic amino acid residues of apo-TF to play a role as a cross-linker connecting both proteins. Domain 4 of one CP molecule and domain 6 of the other CP molecule fit tightly into the clefts in the N- and C-lobes of apo-TF, respectively. Upon the binding of two Fe(III) ions to apo-TF, the resulting diferric TF [Fe(III)2TF] dissociated from CP by conformational changes in TF. In human blood plasma, zinc deficiency reduced the production of Fe(III)2TF and concomitantly increased the production of non-TF-bound iron. Our findings suggest that zinc may be involved in the transfer of iron between CP and TF.

Heme Peroxidases at Unperturbed and Inflamed Mucous Surfaces

In our organism, mucous surfaces are important boundaries against the environmental milieu with defined fluxes of metabolites through these surfaces and specific rules for defense reactions. Major mucous surfaces are formed by epithelia of the respiratory system and the digestive tract. The heme peroxidases lactoperoxidase (LPO), myeloperoxidase (MPO), and eosinophil peroxidase (EPO) contribute to immune protection at epithelial surfaces and in secretions. Whereas LPO is secreted from epithelial cells and maintains microbes in surface linings on low level, MPO and EPO are released from recruited neutrophils and eosinophils, respectively, at inflamed mucous surfaces. Activated heme peroxidases are able to oxidize (pseudo)halides to hypohalous acids and hypothiocyanite. These products are involved in the defense against pathogens, but can also contribute to cell and tissue damage under pathological conditions. This review highlights the beneficial and harmful functions of LPO, MPO, and EPO at unperturbed and inflamed mucous surfaces. Among the disorders, special attention is directed to cystic fibrosis and allergic reactions.

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.

Hyper-truncated Asn355- and Asn391-glycans modulate the activity of neutrophil granule myeloperoxidase

Myeloperoxidase (MPO) plays essential roles in neutrophil-mediated immunity via the generation of reactive oxidation products. Complex carbohydrates decorate MPO at discrete sites, but their functional relevance remains elusive. To this end, we have characterised the structure-biosynthesis-activity relationship of neutrophil MPO (nMPO). Mass spectrometry demonstrated that nMPO carries both characteristic under-processed and hyper-truncated glycans. Occlusion of the Asn355/Asn391-glycosylation sites and the Asn323-/Asn483-glycans, located in the MPO dimerisation zone, was found to affect the local glycan processing, thereby providing a molecular basis of the site-specific nMPO glycosylation. Native mass spectrometry, mass photometry and glycopeptide profiling revealed significant molecular complexity of diprotomeric nMPO arising from heterogeneous glycosylation, oxidation, chlorination and polypeptide truncation variants and a previously unreported low-abundance monoprotomer. Longitudinal profiling of maturing, mature, granule-separated and pathogen-stimulated neutrophils demonstrated that nMPO is dynamically expressed during granulopoiesis, unevenly distributed across granules and degranulated upon activation. We also show that proMPO-to-MPO maturation occurs during early/mid-stage granulopoiesis. While similar global MPO glycosylation was observed across conditions, the conserved Asn355-/Asn391-sites displayed elevated glycan hyper-truncation, which correlated with higher enzyme activities of MPO in distinct granule populations. Enzymatic trimming of the Asn355-/Asn391-glycans recapitulated the activity gain and showed that nMPO carrying hyper-truncated glycans at these positions exhibits increased thermal stability, polypeptide accessibility and ceruloplasmin-mediated inhibition potential relative to native nMPO. Finally, molecular modelling revealed that hyper-truncated Asn355-glycans positioned in the MPO-ceruloplasmin interface are critical for uninterrupted inhibition. Here, through an innovative and comprehensive approach, we report novel functional roles of MPO glycans, providing new insight into neutrophil-mediated immunity.

Myeloperoxidase: A versatile mediator of endothelial dysfunction and therapeutic target during cardiovascular disease

Myeloperoxidase (MPO) is a prominent mammalian heme peroxidase and a fundamental component of the innate immune response against microbial pathogens. In recent times, MPO has received considerable attention as a key oxidative enzyme capable of impairing the bioactivity of nitric oxide (NO) and promoting endothelial dysfunction; a clinically relevant event that manifests throughout the development of inflammatory cardiovascular disease. Increasing evidence indicates that during cardiovascular disease, MPO is released intravascularly by activated leukocytes resulting in its transport and sequestration within the vascular endothelium. At this site, MPO catalyzes various oxidative reactions that are capable of promoting vascular inflammation and impairing NO bioactivity and endothelial function. In particular, MPO catalyzes the production of the potent oxidant hypochlorous acid (HOCl) and the catalytic consumption of NO via the enzyme's NO oxidase activity. An emerging paradigm is the ability of MPO to also influence endothelial function via non-catalytic, cytokine-like activities. In this review article we discuss the implications of our increasing knowledge of the versatility of MPO's actions as a mediator of cardiovascular disease and endothelial dysfunction for the development of new pharmacological agents capable of effectively combating MPO's pathogenic activities. More specifically, we will (i) discuss the various transport mechanisms by which MPO accumulates into the endothelium of inflamed or diseased arteries, (ii) detail the clinical and basic scientific evidence identifying MPO as a significant cause of endothelial dysfunction and cardiovascular disease, (iii) provide an up-to-date coverage on the different oxidative mechanisms by which MPO can impair endothelial function during cardiovascular disease including an evaluation of the contributions of MPO-catalyzed HOCl production and NO oxidation, and (iv) outline the novel non-enzymatic mechanisms of MPO and their potential contribution to endothelial dysfunction. Finally, we deliver a detailed appraisal of the different pharmacological strategies available for targeting the catalytic and non-catalytic modes-of-action of MPO in order to protect against endothelial dysfunction in cardiovascular disease.

The Dual Role of Myeloperoxidase in Immune Response

The heme protein myeloperoxidase (MPO) is a major constituent of neutrophils. As a key mediator of the innate immune system, neutrophils are rapidly recruited to inflammatory sites, where they recognize, phagocytose, and inactivate foreign microorganisms. In the newly formed phagosomes, MPO is involved in the creation and maintenance of an alkaline milieu, which is optimal in combatting microbes. Myeloperoxidase is also a key component in neutrophil extracellular traps. These helpful properties are contrasted by the release of MPO and other neutrophil constituents from necrotic cells or as a result of frustrated phagocytosis. Although MPO is inactivated by the plasma protein ceruloplasmin, it can interact with negatively charged components of serum and the extracellular matrix. In cardiovascular diseases and many other disease scenarios, active MPO and MPO-modified targets are present in atherosclerotic lesions and other disease-specific locations. This implies an involvement of neutrophils, MPO, and other neutrophil products in pathogenesis mechanisms. This review critically reflects on the beneficial and harmful functions of MPO against the background of immune response.

Investigation of the Influence of Liquid Motion in a Flow-based System on an Enzyme Aggregation State with an Atomic Force Microscopy Sensor: The Effect of Water Flow

The influence of liquid motion in flow-based systems on the aggregation state of an enzyme and on its enzymatic activity was studied, with horseradish peroxidase (HRP) as an example. Our experiments were carried out in a setup modeling the flow section of the biosensor communication with a measuring cell containing a protein solution. Studies were conducted for a biosensor measuring cell located along the axis of a spiral-moving liquid flow. The aggregation state of the protein was determined with an atomic force microscopy-based sensor (AFM sensor). It has been demonstrated that upon flowing of water through silicone biosensor communications, an increased aggregation of HRP protein was observed, but, at the same time, its enzymatic activity did not change. Our results obtained herein are useful in the development of models describing the influence of liquid flow in biosensor communications on the properties of enzymes and other proteins. This is particularly important for the development of serologic protein biosensors, which are beginning to be used for the early diagnosis of oncological diseases (such as brain cancer, prostate cancer, breast cancer etc.). The results obtained herein should also be taken into account when considering possible changes in hemodynamics due to increased protein aggregation.

The Estimation of Blood Paramagnetic Center Changes during Burns Management with Biodegradable Propolis-Nanofiber Dressing

The evolution of the paramagnetic center system in blood during the healing of skin burn wounds dressed with a biodegradable apitherapeutic nanofiber dressing was examined. The aim of this study was to determine the changes in paramagnetic centers in blood during the influence of apitherapeutic nanofiber dressings on the healing process. The blood samples were tested before burn infliction (day 0) and, respectively, on the 10^th and 21^st days of the experiment. Paramagnetic centers in the blood of the pig used as the model animal were examined with an X-band (9.3 GHz) electron paramagnetic resonance spectroscopy. The EPR spectra were measured with Bruker spectrometer at 230 K with a modulation frequency of 100 kHz. The EPR lines of the high spin Fe³⁺ in methemoglobin, high spin Fe³⁺ in transferrin, Cu²⁺ in ceruloplasmin, and free radicals were observed in the multicomponent spectra of blood. For the application of the apitherapeutic nanofiber dressing, the amplitudes of the EPR signals of Fe³⁺ in methemoglobin were similar up to 10 days. For the experiment with the apitherapeutic formulation, the heights of EPR signals of Fe³⁺ in transferrin were lower after 10 days and 21 days of therapy, compared to day 0. For the application of the apitherapeutic formulation the signals of Cu²⁺ in ceruloplasmin and free radicals, strongly decreased after 10 days of therapy, and after 21 days it increased to the initial values characteristic for day 0. The apitherapeutic formulation caused that after 21 days the EPR spectrum of Cu²⁺ in ceruloplasmin and free radicals was considerably high. The apitherapeutic formulation interaction after 10 days and after 21 days of therapy resulted in the low EPR lines of Fe³⁺ in methemoglobin. EPR spectra of blood may be useful for presentation of the changes in its paramagnetic centers during the healing process of the burn wounds.

AFM Imaging of Protein Aggregation in Studying the Impact of Knotted Electromagnetic Field on A Peroxidase

The phenomenon of knotted electromagnetic field (KEMF) is now actively studied, as such fields are characterized by a nontrivial topology. The research in this field is mainly aimed at technical applications - for instance, the development of efficient communication systems. Until present, however, the influence of KEMF on biological objects (including enzyme systems) was not considered. Herein, we have studied the influence of KEMF on the aggregation and enzymatic activity of a protein with the example of horseradish peroxidase (HRP). The test HRP solution was irradiated in KEMF (the radiation power density was 10^-12 W/cm² at 2.3 GHz frequency) for 40 min. After the irradiation, the aggregation of HRP was examined by atomic force microscopy (AFM) at the single-molecule level. The enzymatic activity was monitored by conventional spectrophotometry. It has been demonstrated that an increased aggregation of HRP, adsorbed on the AFM substrate surface, was observed after irradiation of the protein sample in KEMF with low (10^-12 W/cm²) radiation power density; at the same time, the enzymatic activity remained unchanged. The results obtained herein can be used in the development of models describing the interaction of enzymes with electromagnetic field. The obtained data can also be of importance considering possible pathological factors that can take place upon the influence of KEMF on biological objects- for instance, changes in hemodynamics due to increased protein aggregation are possible; the functionality of protein complexes can also be affected by aggregation of their protein subunits. These effects should also be taken into account in the development of novel highly sensitive systems for human serological diagnostics of breast cancer, prostate cancer, brain cancer and other oncological pathologies, and for diagnostics of diseases in animals, and crops.

Genetic and Clinical Heterogeneity in Thirteen New Cases with Aceruloplasminemia. Atypical Anemia as a Clue for an Early Diagnosis

Aceruloplasminemia is a rare autosomal recessive genetic disease characterized by mild microcytic anemia, diabetes, retinopathy, liver disease, and progressive neurological symptoms due to iron accumulation in pancreas, retina, liver, and brain. The disease is caused by mutations in the Ceruloplasmin (CP) gene that produce a strong reduction or absence of ceruloplasmin ferroxidase activity, leading to an impairment of iron metabolism. Most patients described so far are from Japan. Prompt diagnosis and therapy are crucial to prevent neurological complications since, once established, they are usually irreversible. Here, we describe the largest series of non-Japanese patients with aceruloplasminemia published so far, including 13 individuals from 11 families carrying 13 mutations in the CP gene (7 missense, 3 frameshifts, and 3 splicing mutations), 10 of which are novel. All missense mutations were studied by computational modeling. Clinical manifestations were heterogeneous, but anemia, often but not necessarily microcytic, was frequently the earliest one. This study confirms the clinical and genetic heterogeneity of aceruloplasminemia, a disease expected to be increasingly diagnosed in the Next-Generation Sequencing (NGS) era. Unexplained anemia with low transferrin saturation and high ferritin levels without inflammation should prompt the suspicion of aceruloplasminemia, which can be easily confirmed by low serum ceruloplasmin levels. Collaborative joint efforts are needed to better understand the pathophysiology of this potentially disabling disease.

Copper(II)-binding equilibria in human blood

It has been reported that Cu(II) ions in human blood are bound mainly to serum albumin (HSA), ceruloplasmin (CP), alpha-2-macroglobulin (α2M) and His, however, data for α2M are very limited and the thermodynamics and kinetics of the copper distribution are not known. We have applied a new LC-ICP MS-based approach for direct determination of Cu(II)-binding affinities of HSA, CP and α2M in the presence of competing Cu(II)-binding reference ligands including His. The ligands affected both the rate of metal release from Cu•HSA complex and the value of K_D. Slow release and K_D = 0.90 pM was observed with nitrilotriacetic acid (NTA), whereas His showed fast release and substantially lower K_D = 34.7 fM (50 mM HEPES, 50 mM NaCl, pH 7.4), which was explained with formation of ternary His•Cu•HSA complex. High mM concentrations of EDTA were not able to elicit metal release from metallated CP at pH 7.4 and therefore it was impossible to determine the K_D value for CP. In contrast to earlier inconclusive evidence, we show that α2M does not bind Cu(II) ions. In the human blood serum ~75% of Cu(II) ions are in a nonexchangeable manner bound to CP and the rest exchangeable copper is in an equilibrium between HSA (~25%) and Cu(II)-His-Xaa ternary complexes (~0.2%).

Insights from molecular dynamics simulation of human ceruloplasmin (ferroxidase enzyme) binding with biogenic monoamines

Human ceruloplasmin (hCP) is a multi-copper oxidase with ferroxidase and amine oxidase activities. Molecular dynamics simulation (MDS) and docking analysis of biogenic monoamines with ceruloplasmin explain the role of Asp1025, Glu935, Glu272, Glu232 and Glu230 together with the binding site water molecules (referred as conserved water molecules) in the stabilization of neurotransmitter (Serotonin, Norepinephrine and Epinephrine) molecules within the binding cavity of hCP. Conserved water molecules are found at specific positions interacting with the protein structures that have sequence similarity. The ethylamine side chain nitrogen atom (N1) of neurotransmitter molecules interacts with water molecules in the binding cavity formed by Asp1025, Glu935 and Glu232 residues. These residues form an acidic triad mimicking a substrate binding cavity. The hydroxyl groups attached to the catechol ring of epinephrine and norepinephrine have been stabilized by Asp230 and Asp232 residues. Data suggests that the recognition of biogenic amines mediates through the N+(amine) ...Asp1025-His1026-Cu_Cis-His path. The potential recognition path of biogenic monoamines to trinuclear copper cluster supported by active site water molecules (referred as conserved water molecules) is described in this report.

Variations in ATP7B in cats with primary copper-associated hepatopathy

OBJECTIVES

Primary copper-associated hepatopathy (PCH) has been reported in young cats. Although our group recently reported a young cat with PCH harbouring single-nucleotide variations in ATP7B, limited information is available regarding its association with the pathogenesis of feline PCH. The objective of this study was to investigate the prevalence of ATP7B variations in cats with PCH.

METHODS

Rhodanine staining was performed to detect hepatic copper accumulation (HCA) in intraoperative liver tissue specimens from 54 cats. In cats with HCA, variations in ATP7B and COMMD1 and serum ceruloplasmin activity were analysed.

RESULTS

Based on age, liver histopathological findings and hepatic distribution of accumulated copper, PCH was suspected in 4/54 cats. Sequence analysis of ATP7B and COMMD1 revealed single-nucleotide variations in ATP7B in 3/4 cats with PCH. Among the cats with PCH, one showed remarkably low serum ceruloplasmin activity, while the other three did not.

CONCLUSIONS AND RELEVANCE

The results of this study suggest that some cats with PCH harbour single-nucleotide variations in ATP7B, suggesting that feline PCH is an equivalent disorder to human Wilson's disease. This study provides basic evidence facilitating further studies of the pathophysiology and treatment of feline PCH.

Relationships between meconium concentrations of acute phase proteins

Meconium concentrations of naturally accumulated ceruloplasmin (CER), lactoferrin (LF), and neutrophil gelatinase-associated lipocalin (NGAL) and their relationships considered as a panel of acute phase proteins could be used for the assessment of fetal homeostasis. CER, LF and NGAL concentrations were measured using enzyme-linked immunosorbent assay kits in meconium portions (n = 80) collected from 19 healthy neonates. The coefficients of variation (CV) of the meconium LF (1.77) and NGAL (1.26) were about two-fold higher than that of CER (0.73) with significant (P < 0.05) correlations between all three parameters. The LF to NGAL ratio (CV = 0.67) correlated strongly with the CER concentrations (r = 0.39, P < 0.01). These correlations between CER, LF and NGAL concentrations suggest their combined involvement in the metabolic processes in the developing fetus.

Putative role of conserved water molecules in the hydration and inter-domain recognition of mono nuclear copper centers in O2-bound human ceruloplasmin: A comparative study between X-ray and MD simulated structures

Human Ceruloplasmin (hCP) is an unique multicopper oxidase which involves in different biological functions e.g., iron metabolism, copper transportation, biogenic amine oxidation ,and its malfunction causes Wilson's and Menkes diseases. MD- simulation studies of O2- bound solvated structure have revealed the role of several conserved/ semi-conserved water molecules in the hydration of type-I copper centers and their involvement to recognition dynamics of these metal centers. In O2- bound structure, hydration potentiality of CuRS (Cu1106) type-I copper center is observed to be unique, where two water molecules (W1-W2) are interacting with the metal sites, which was not found in X-ray structures of hCP. Generally, in the interdomain recognition of CuCys-His to CuRS, CuRS to CuPR and CuPR to CuCys-His centers, the copper bound His-residue of one domain interacts with the Glu-residue of other complementary domain through conserved/ semi-conserved (W3 to W5) water- mediated hydrogen bonds (Cu-His...W...Glu), however direct salt-bridge (Cu-His...Glu) interaction were observed in the X- ray structures. The MD- simulated and X- ray structures have indicated some possibilities on the Cu-His...W...Glu ↔ Cu-His...Glu transition during the interdomain recognition of type-I copper centers, which may have some importance in biology and chemistry of ceruloplasmin.

Biallelic HEPHL1 variants impair ferroxidase activity and cause an abnormal hair phenotype

Maintenance of the correct redox status of iron is functionally important for critical biological processes. Multicopper ferroxidases play an important role in oxidizing ferrous iron, released from the cells, into ferric iron, which is subsequently distributed by transferrin. Two well-characterized ferroxidases, ceruloplasmin (CP) and hephaestin (HEPH) facilitate this reaction in different tissues. Recently, a novel ferroxidase, Hephaestin like 1 (HEPHL1), also known as zyklopen, was identified. Here we report a child with compound heterozygous mutations in HEPHL1 (NM_001098672) who presented with abnormal hair (pili torti and trichorrhexis nodosa) and cognitive dysfunction. The maternal missense mutation affected mRNA splicing, leading to skipping of exon 5 and causing an in-frame deletion of 85 amino acids (c.809_1063del; p.Leu271_ala355del). The paternal mutation (c.3176T>C; p.Met1059Thr) changed a highly conserved methionine that is part of a typical type I copper binding site in HEPHL1. We demonstrated that HEPHL1 has ferroxidase activity and that the patient's two mutations exhibited loss of this ferroxidase activity. Consistent with these findings, the patient's fibroblasts accumulated intracellular iron and exhibited reduced activity of the copper-dependent enzyme, lysyl oxidase. These results suggest that the patient's biallelic variants are loss-of-function mutations. Hence, we generated a Hephl1 knockout mouse model that was viable and had curly whiskers, consistent with the hair phenotype in our patient. These results enhance our understanding of the function of HEPHL1 and implicate altered ferroxidase activity in hair growth and hair disorders.

Looking for a partner: ceruloplasmin in protein-protein interactions

Ceruloplasmin (CP) is a mammalian blood plasma ferroxidase. More than 95% of the copper found in plasma is carried by this protein, which is a member of the multicopper oxidase family. Proteins from this group are able to oxidize substrates through the transfer of four electrons to oxygen. The essential role of CP in iron metabolism in humans is particularly evident in the case of loss-of-function mutations in the CP gene resulting in a neurodegenerative syndrome known as aceruloplasminaemia. However, the functions of CP are not limited to the oxidation of ferrous iron to ferric iron, which allows loading of the ferric iron into transferrin and prevents the deleterious reactions of Fenton chemistry. In recent years, a number of novel CP functions have been reported, and many of these functions depend on the ability of CP to form stable complexes with a number of proteins.

Smoking-induced iron dysregulation in the lung

Iron is one of the most abundant transition elements and is indispensable for almost all organisms. While the ability of iron to participate in redox chemistry is an essential requirement for participation in a range of vital enzymatic reactions, this same feature of iron also makes it dangerous in the generation of hydroxyl radicals and superoxide anions. Given the high local oxygen tensions in the lung, the regulation of iron acquisition, utilization, and storage therefore becomes vitally important, perhaps more so than in any other biological system. Iron plays a critical role in the biology of essentially every cell type in the lung, and in particular, changes in iron levels have important ramifications on immune function and the local lung microenvironment. There is substantial evidence that cigarette smoke causes iron dysregulation, with the implication that iron may be the link between smoking and smoking-related lung diseases. A better understanding of the connection between cigarette smoke, iron, and respiratory diseases will help to elucidate pathogenic mechanisms and aid in the identification of novel therapeutic targets.

Application of Proteomics to Inflammatory Bowel Disease Research: Current Status and Future Perspectives

Inflammatory bowel disease (IBD) is a chronic relapsing/remitting inflammatory illness of the gastrointestinal tract of unknown aetiology. Despite recent advances in decoding the pathophysiology of IBD, many questions regarding disease pathogenesis remain. Genome-wide association studies (GWAS) and knockout mouse models have significantly advanced our understanding of genetic susceptibility loci and inflammatory pathways involved in IBD pathogenesis. Despite their important contribution to a better delineation of the disease process in IBD, these genetic findings have had little clinical impact to date. This is because the presence of a given gene mutation does not automatically correspond to changes in its expression or final metabolic or structural effect(s). Furthermore, the existence of these gene susceptibility loci in the normal population suggests other driving prerequisites for the disease manifestation. Proteins can be considered the main functional units as almost all intracellular physiological functions as well as intercellular interactions are dependent on them. Proteomics provides methods for the large-scale study of the proteins encoded by the genome of an organism or a cell, to directly investigate the proteins and pathways involved. Understanding the proteome composition and alterations yields insights into IBD pathogenesis as well as identifying potential biomarkers of disease activity, mucosal healing, and cancer progression. This review describes the state of the art in the field with respect to the study of IBD and the potential for translation from biomarker discovery to clinical application.

Peroxidase Activity of Human Hemoproteins: Keeping the Fire under Control

The heme in the active center of peroxidases reacts with hydrogen peroxide to form highly reactive intermediates, which then oxidize simple substances called peroxidase substrates. Human peroxidases can be divided into two groups: (1) True peroxidases are enzymes whose main function is to generate free radicals in the peroxidase cycle and (pseudo)hypohalous acids in the halogenation cycle. The major true peroxidases are myeloperoxidase, eosinophil peroxidase and lactoperoxidase. (2) Pseudo-peroxidases perform various important functions in the body, but under the influence of external conditions they can display peroxidase-like activity. As oxidative intermediates, these peroxidases produce not only active heme compounds, but also protein-based tyrosyl radicals. Hemoglobin, myoglobin, cytochrome c/cardiolipin complexes and cytoglobin are considered as pseudo-peroxidases. Рeroxidases play an important role in innate immunity and in a number of physiologically important processes like apoptosis and cell signaling. Unfavorable excessive peroxidase activity is implicated in oxidative damage of cells and tissues, thereby initiating the variety of human diseases. Hence, regulation of peroxidase activity is of considerable importance. Since peroxidases differ in structure, properties and location, the mechanisms controlling peroxidase activity and the biological effects of peroxidase products are specific for each hemoprotein. This review summarizes the knowledge about the properties, activities, regulations and biological effects of true and pseudo-peroxidases in order to better understand the mechanisms underlying beneficial and adverse effects of this class of enzymes.

Capacity of ceruloplasmin to scavenge products of the respiratory burst of neutrophils is not altered by the products of reactions catalyzed by myeloperoxidase

CP is a copper-containing ferroxidase of blood plasma, which acts as an acute phase reactant during inflammation. The effect of oxidative modification of CP induced by oxidants produced by MPO, such as HOCl, HOBr, and HOSCN, on its spectral, enzymatic, and anti-inflammatory properties was studied. We monitored the chemiluminescence of lucigenin and luminol along with fluorescence of hydroethidine and scopoletin to assay the inhibition by CP of the neutrophilic respiratory burst induced by PMA or fMLP. Superoxide dismutase activity of CP and its capacity to reduce the production of oxidants in respiratory burst of neutrophils remained virtually unchanged upon modifications caused by HOCl, HOBr, and HOSCN. Meanwhile, the absorption of type I copper ions at 610 nm became reduced, along with a drop in the ferroxidase and amino oxidase activities of CP. Likewise, its inhibitory effect on the halogenating activity of MPO was diminished. Sera of either healthy donors or patients with Wilson disease were co-incubated with neutrophils from healthy volunteers. In these experiments, we observed an inverse relationship between the content of CP in sera and the rate of H2O2 production by activated neutrophils. In conclusion, CP is likely to play a role of an anti-inflammatory factor tempering the neutrophil respiratory burst in the bloodstream despite the MPO-mediated oxidative modifications.

Erythropoietin and Nrf2: key factors in the neuroprotection provided by apo-lactoferrin

Among the properties of lactoferrin (LF) are bactericidal, antianemic, immunomodulatory, antitumour, antiphlogistic effects. Previously we demonstrated its capacity to stabilize in vivo HIF-1-alpha and HIF-2-alpha, which are redox-sensitive multiaimed transcription factors. Various tissues of animals receiving recombinant human LF (rhLF) responded by expressing the HIF-1-alpha target genes, hence such proteins as erythropoietin (EPO), ceruloplasmin, etc. were synthesized in noticeable amounts. Among organs in which EPO synthesis occurred were brain, heart, spleen, liver, kidneys and lungs. Other researchers showed that EPO can act as a protectant against severe brain injury and status epilepticus in rats. Therefore, we tried rhLF as a protector against the severe neurologic disorders developed in rats, such as the rotenone-induced model of Parkinson's disease and experimental autoimmune encephalomyelitis as a model of multiple sclerosis, and observed its capacity to mitigate the grave symptoms. Moreover, an intraperitoneal injection of rhLF into mice 1 h after occlusion of the medial cerebral artery significantly diminished the necrosis area measured on the third day in the ischaemic brain. During this period EPO was synthesized in various murine tissues. It was known that EPO induces nuclear translocation of Nrf2, which, like HIF-1-alpha, is a transcription factor. In view that under conditions of hypoxia both factors demonstrate a synergistic protective effect, we suggested that LF activates the Keap1/Nrf2 signaling pathway, an important link in proliferation and differentiation of normal and malignant cells. J774 macrophages were cultured for 3 days without or in the presence of ferric and ferrous ions (RPMI-1640 and DMEM/F12, respectively). Then cells were incubated with rhLF or Deferiprone. Confocal microscopy revealed nuclear translocation of Nrf2 (the key event in Keap1/Nrf2 signaling) induced by apo-rhLF (iron-free, RPMI-1640). The reference compound Deferiprone (iron chelator) had the similar effect. Upon iron binding (in DMEM/F12) rhLF did not activate the Keap1/Nrf2 pathway. Added to J774, apo-rhLF enhanced transcription of Nrf2-dependent genes coding for glutathione S-transferase P and heme oxygenase-1. Western blotting revealed presence of Nrf2 in mice brain after 6 days of oral administration of apo-rhLF, but not Fe-rhLF or equivalent amount of PBS. Hence, apo-LF, but not holo-LF, induces the translocation of Nrf2 from cytoplasm to the nucleus, probably due to its capacity to induce EPO synthesis.

Variations in serum concentrations of C-reactive protein, ceruloplasmin, lactoferrin and myeloperoxidase and their interactions during normal human pregnancy and postpartum period

BACKGROUND

Serum proteins may provide information about homeostasis of redox status and inflammatory processes also during pregnancy. The aim of the study was to assess the dynamics of changes in serum concentrations of C-reactive protein (CRP), ceruloplasmin (CP), lactoferrin (LF) and myeloperoxidase (MPO) and their interactions during normal pregnancy and the postpartum period.

METHODS

The concentrations of proteins were measured in serum (n=113) from pregnant in consecutive trimesters and in postpartum period (n=28) and in non-pregnant women (n=17), using immunoturbidimetric assays (CRP, CP) and ELISA Kits (LF, MPO).

RESULTS

The concentrations [mg/dl] CP and CRP (mean±SD respectively): second trimester (43.1±6.2; 0.49±0.57), third trimester (44.5±5.8; 0.41±0.37), postpartum (42.39±6.4; 4.15±3.6) were higher than in the first trimester (33.0.5±8.7; 0.31±0.36) or non-pregnant women (24.12±7.4; 0.12±0.13). The increases in concentrations of CP and CRP between the first and the second trimesters were by approximately 35% and 50% respectively and the correlation coefficients in the first trimester and in non-pregnant women were twice higher than in the second trimester and the postpartum period. The concentrations [μg/ml] LF and MPO were no significant differences (mean±SD respectively): first (6.19±4.54; 0.17±0.12), second (5.68±4.4; 0.14±0.08), third (6.34±6.98; 0.17±0.14), the postpartum (4.86±3.64; 0.25±0.4), and non-pregnant (3.9±2.56; 3.2; 0.14±0.05). However, significant correlations were established (p<0.05) between MPO and LF in all groups and between the following ratios CRP/LF vs CP/MPO and CRP/MPO vs CP/LF.

CONCLUSIONS

The concentrations of proteins synthesized by the liver (CP, CRP) dynamically increase during consecutive trimesters of pregnancy unlike neutrophil-derived proteins (LF, MPO). Statistically significant correlations between the proportions of the serum proteins may suggest their combined role for the maintenance of homeostasis during pregnancy.

The ferroportin-ceruloplasmin system and the mammalian iron homeostasis machine: regulatory pathways and the role of lactoferrin

In the last 20 years, several new genes and proteins involved in iron metabolism in eukaryotes, particularly related to pathological states both in animal models and in humans have been identified, and we are now starting to unveil at the molecular level the mechanisms of iron absorption, the regulation of iron transport and the homeostatic balancing processes. In this review, we will briefly outline the general scheme of iron metabolism in humans and then focus our attention on the cellular iron export system formed by the permease ferroportin and the ferroxidase ceruloplasmin. We will finally summarize data on the role of the iron binding protein lactoferrin on the regulation of the ferroportin/ceruloplasmin couple and of other proteins involved in iron homeostasis in inflamed human macrophages.

Fine Regulation of Neutrophil Oxidative Status and Apoptosis by Ceruloplasmin and Its Derivatives

Timely neutrophil apoptosis is an essential part of the resolution phase of acute inflammation. Ceruloplasmin, an acute-phase protein, which is the predominant copper-carrying protein in the blood, has been suggested to have a marked effect on neutrophil life span. The present work is a comparative study on the effects of intact holo-ceruloplasmin, its copper-free (apo-) and partially proteolyzed forms, and synthetic free peptides RPYLKVFNPR (883-892) and RRPYLKVFNPRR (882-893) on polymorphonuclear leukocyte (PMNL, neutrophil) oxidant status and apoptosis. The most pronounced effect on both investigated parameters was found with copper-containing samples, namely, intact and proteolyzed proteins. Both effectively reduced spontaneous and tumor necrosis factor-α (TNF-α)-induced extracellular and intracellular accumulation of superoxide radicals, but induced a sharp increase in the oxidation of intracellular 2',7'-dichlorofluorescein upon short exposure. Therefore, intact and proteolyzed ceruloplasmin have both anti- and pro-oxidant effects on PMNLs wherein the latter effect is diminished by TNF-α and lactoferrin. Additionally, all compounds investigated were determined to be inhibitors of delayed spontaneous apoptosis. Intact enzyme retained its pro-survival activity, whereas proteolytic degradation converts ceruloplasmin from a mild inhibitor to a potent activator of TNF-α-induced neutrophil apoptosis.

Rat ceruloplasmin: a new labile copper binding site and zinc/copper mosaic

Ceruloplasmin (Cp) is a copper-containing multifunctional oxidase of plasma, an antioxidant, an acute-phase protein and a free radical scavenger. The structural organization of Cp causes its sensitivity to proteolysis and ROS (reactive oxygen species), which can alter some of the important Cp functions. Elucidation of the orthorhombic crystal structure of rat Cp at 2.3 Å resolution revealed the basis for stronger resistance of rat Cp to proteolysis and a new labile copper binding site. The presence of this site appears as a very rare and distinctive feature of rat Cp as was shown by sequence alignment of ceruloplasmin, hephaestin and zyklopen in the Deuterostomia taxonomic group. The trigonal crystal form of rat Cp at 3.2 Å demonstrates unexpected partial substitution of copper by zinc.

Recognition dynamics of trinuclear copper cluster and associated histidine residues through conserved or semi-conserved water molecules in human Ceruloplasmin: The involvement of aspartic and glutamic acid gates

Human Ceruloplasmin belongs to the family of multi-copper oxidases and it is involved in different physiological processes, copper ion transport, iron metabolism, iron homeostasis, and biogenic amine metabolism. MD-simulation studies have indicated the higher hydrophilic susceptibility of the trinuclear copper cluster in native CP compared to its oxygen bound form. The copper (T2/T3) atom Cu3047 of the cluster, which is close to T1 copper center Cu3052 (~13 Å) has a higher affinity for water molecules compared to other copper centers. The water molecules of W3, W4, W5, W9, and W12 conserved water sites are coordinated to Cu3047, where W3, W9, and W12 centers are found to play some crucial role in the stabilization of native trinuclear copper cluster. The hydrogen bonding interaction of Asp169, Glu112, Asp995, and Glu1032 residues with the copper-bound conserved water molecules (W3, W4, W5, W10, and W11) in native CP is observed to be unique. The conformational flexibility of Asp169 and Glu112 and their association with the copper-bound water molecules, but the absence of such interaction in O₂-bound simulated structure of the enzyme is indicating some plausible rational on the role of these acidic residues in the gating of O₂ molecule in the native trinuclear Cu cluster of CP. The simulation results may shade some new light on the biochemistry/chemistry of CP, specially on the hydration dynamics of the trinuclear copper cluster.

Immune evasion by a staphylococcal inhibitor of myeloperoxidase

Staphylococcus aureus is highly adapted to its host and has evolved many strategies to resist opsonization and phagocytosis. Even after uptake by neutrophils, S. aureus shows resistance to killing, which suggests the presence of phagosomal immune evasion molecules. With the aid of secretome phage display, we identified a highly conserved protein that specifically binds and inhibits human myeloperoxidase (MPO), a major player in the oxidative defense of neutrophils. We have named this protein "staphylococcal peroxidase inhibitor" (SPIN). To gain insight into inhibition of MPO by SPIN, we solved the cocrystal structure of SPIN bound to a recombinant form of human MPO at 2.4-Å resolution. This structure reveals that SPIN acts as a molecular plug that prevents H2O2 substrate access to the MPO active site. In subsequent experiments, we observed that SPIN expression increases inside the neutrophil phagosome, where MPO is located, compared with outside the neutrophil. Moreover, bacteria with a deleted gene encoding SPIN showed decreased survival compared with WT bacteria after phagocytosis by neutrophils. Taken together, our results demonstrate that S. aureus secretes a unique proteinaceous MPO inhibitor to enhance survival by interfering with MPO-mediated killing.

Ceruloplasmin-derived peptide is the strongest regulator of oxidative stress and leukotriene synthesis in neutrophils

Ceruloplasmin, an acute-phase protein, can affect the activity of leukocytes through its various enzymatic activities and protein–protein interactions (with lactoferrin, myeloperoxidase, eosinophil peroxidase, serprocidins, and 5-lipoxygenase (5-LOX), among others). However, the molecular mechanisms of ceruloplasmin activity are not clearly understood. In this study, we tested the ability of two synthetic peptides, RPYLKVFNPR (883–892) (P1) and RRPYLKVFNPRR (882–893) (P2), corresponding to the indicated fragments of the ceruloplasmin sequence, to affect neutrophil activation. Leukotriene (LT) B4 is the primary eicosanoid product of polymorphonuclear leukocytes (PMNLs, neutrophils). We studied leukotriene synthesis in PMNLs upon interaction with Salmonella enterica serovar Typhimurium. Priming of neutrophils with phorbol 12-myristate 13-acetate (PMA) elicited the strong regulatory function of P2 peptide as a superoxide formation inducer and leukotriene synthesis inhibitor. Ceruloplasmin-derived P2 peptide appeared to be a strong inhibitor of 5-LOX product synthesis under conditions of oxidative stress.

Spectrophotometric Quantification of Peroxidase with p-Phenylene-diamine for Analyzing Peroxidase-Encapsulating Lipid Vesicles

A spectrophotometric assay for the determination of horseradish peroxidase (HRP) in aqueous solution with p-phenylenediamine (PPD, benzene-1,4-diamine) as electron donor substrate and hydrogen peroxide (H2O2) as oxidant was developed. The oxidation of PPD by HRP/H2O2 leads to the formation of Bandrowski's base ((3E,6E)-3,6-bis[(4-aminophenyl)imino]cyclohexa-1,4-diene-1,4-diamine), which can be quantified by following the increase in absorbance at 500 nm. The assay was applied for monitoring the activity of HRP inside ≈180 nm-sized lipid vesicles (liposomes), prepared from POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) and purified by size exclusion chromatography. Because of the high POPC bilayer permeability of PPD and H2O2, the HRP-catalyzed oxidation of PPD occurs inside the vesicles once PPD and H2O2 are added to the vesicle suspension. In contrast, if instead of PPD the bilayer-impermeable substrate ABTS2- (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate)) is used, the oxidation of ABTS2- inside the vesicles does not occur. Therefore, using PPD and ABTS2- in separate assays allows distinguishing between vesicle-trapped HRP and HRP in the external bulk solution. In this way, the storage stability of HRP-containing POPC vesicles was investigated in terms of HRP leakage and activity of entrapped HRP. It was found that pH 7.0 suspensions of POPC vesicles (2.2 mM POPC) containing on average about 12 HRP molecules per vesicle are stable for at least 1 month without any significant HRP leakage, if stored at 4 °C. Such high stability is beneficial not only for bioanalytical applications but also for exploring the kinetic properties of vesicle-entrapped HRP through simple spectrophotometric absorption measurements with PPD as a sensitive and cheap substrate.

Copper chelation and interleukin-6 proinflammatory cytokine effects on expression of different proteins involved in iron metabolism in HepG2 cell line

Background

In vertebrates, there is an intimate relationship between copper and iron homeostasis. Copper deficiency, which leads to a defect in ceruloplasmin enzymatic activity, has a strong effect on iron homeostasis resulting in cellular iron retention. Much is known about the mechanisms underlying cellular iron retention under “normal” conditions, however, less is known about the effect of copper deficiency during inflammation.

Results

We show that copper deficiency and the inflammatory cytokine interleukin-6 have different effects on the expression of proteins involved in iron and copper metabolism such as the soluble and glycosylphosphtidylinositol anchored forms of ceruloplasmin, hepcidin, ferroportin1, transferrin receptor1, divalent metal transporter1 and H-ferritin subunit. We demonstrate, using the human HepG2 cell line, that in addition to ceruloplasmin isoforms, copper deficiency affects other proteins, some posttranslationally and some at the transcriptional level. The addition of interleukin-6, moreover, has different effects on expression of ferroportin1 and ceruloplasmin, in which ferroportin1 is decreased while ceruloplasmin is increased. These effects are stronger when a copper chelating agent and IL-6 are used simultaneously.

Conclusions

These results suggest that copper chelation has effects not only on ceruloplasmin but also on other proteins involved in iron metabolism, sometimes at the mRNA level and, in inflammatory conditions, the functions of ferroportin and ceruloplasmin may be independent.