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Introduction Increasing bacteria resistance to antibiotics is a major problem of healthcare system. There is a need for solutions that broaden the spectrum of bactericidal agents improving the efficacy of commonly used antibiotics. One of the promising directions of search are silver nanoparticles (obtained by different methods and displaying diversified physical and chemical properties), and their combination with antibiotics. Purpose In this study, we tested the role of reactive oxygen species in the mechanism of synergistic antibacterial activity of gentamicin and Tween-stabilized silver nanoparticles against gentamicin-resistant clinical strains of Staphylococcus epidermidis. Methods Synergistic bactericidal activity of gentamicin and silver nanoparticles stabilized with non-ionic detergent (Tween 80) was tested by the checkerboard titration method on microtiter plates. Detection of reactive oxygen species was based on the chemiluminescence of luminol. Results Hydrophilic non-ionic surface functionalization of silver nanoparticles enabled the existence of non-aggregated active nanoparticles in a complex bacterial culture medium. Tween-stabilized silver nanoparticles in combination with gentamicin exhibited bactericidal activity against multidrug-resistant biofilm forming clinical strains of Staphylococcus epidermidis. A synergistic effect significantly decreased the minimal inhibitory concentration of gentamicin (the antibiotic with numerous undesirable effects). Gentamicin significantly enhanced the generation of reactive oxygen species by silver nanoparticles. Conclusion Generation of reactive oxygen species by Tween-coated metallic silver nanoparticles was significantly enhanced by gentamicin, confirming the hypothesis of oxidative-associated mechanism of the synergistic antibacterial effect of the gentamicin-silver nanoparticles complex.

Some misfolded proteins, e.g., immunoglobulin monoclonal free light chains (FLC), tend to form fibrils. Protein deposits in tissue may lead to amyloidosis and dysfunction of different organs. There is currently no technique allowing for the identification of FLC that are prone to aggregate. The development of such a method would enable the early selection of patients at high risk of developing amyloidosis. The aim of this study was to investigate whether silver nanoparticles (AgNPs) could be a useful tool to study the process of aggregation of FLC and their susceptibility to form the protein deposits. Mixtures of AgNPs and urine samples from patients with multiple myeloma were prepared. To evaluate the aggregation process of nanoparticles coated with proteins, UV-visible spectroscopy, transmission electron microscopy, and the original laser light scattering method were used. It has been shown that some clones of FLC spontaneously triggered aggregation of the nanoparticles, while in the presence of others, the nanoparticle solution became hyperstable. This is probably due to the structure of the chains themselves, unique protein-AgNPs interactions and perhaps correlates with the tendency of some FLC clones to form deposits. Nanoparticle technology has proven to be helpful in identifying clones of immunoglobulin FLC that tend to aggregate.

Background and Aims The aim of the study was to analyse the utility of retinol binding protein (RBP) in case of renal impairment in MM patients and investigate its relationship with acclaimed parameters of renal failure and markers of MM stages. Method We recruited 73 patients (35 women, 38 men, in age range of 29-90 years, mean 70 ± 10 years) with multiple myeloma (MM), including 6 (8%) with smoldering MM, 40 (55%) with International Staging System (ISS) stage I, 15 (21%) with ISS II and 12 (16%) with ISS III. The majority of patients (65, 89%) received at least one treatment scheme. Thirty patients (41%) received maintenance treatment at recruitment. Median eGFR based on serum creatinine (CKD-EPICr) equaled 67 (range 9 – 117) ml/min/1.73 m2. Results Significant correlation was observed between RBP and the ordered variable describing MM stage from smoldering myeloma to ISS III (R=0.36; p=0.002). There were no differences between patients in CR, PR, SD and PD at the time of samples’ collection. Patients who were on maintenance treatment at recruitment tended to have higher serum RBP (median 42.6 versus 37.7 mg/l), however, the difference was not statistically significant (p=0.068). The patients who received steroid treatment had significantly higher RBP concentrations. There were no such association with other medications. There was no association between RBP and the number of previous treatment lines (p=0.8). Serum RBP did not differ between men and women (p=0.7) and did not correlate with age (p=0.6). Significant correlations were found between RBP and serum creatinine, cystatin C and eGFR values calculated based on creatinine and/or cystatin C (Table 1). In multiple regression, serum creatinine or cystatin C and the treatment with steroids were associated with RBP independently of ISS stage (Table 2). Moreover, RBP correlated with β2-microglobulin, LDH, leukocyte count, α-klotho, FGF-23, GDF-15, uNGAL and uIGFBP-7, however, only the associations with β2-microglobulin and sTfR were independent of serum creatinine in multiple regression (Table 1). Baseline serum RBP concentration was significantly correlated with eGFR after a median of 19 months follow-up (range 1-24 months) (R=-0.35; p=0.003), however, the correlation was not independent of baseline serum creatinine ((beta ± SE: 0.06 ± 0.10; p=0.5). To the contrary, baseline serum cystatin C (beta ± SE: -0.36 ± 0.13; p=0.009) predicted final eGFR independently of baseline serum creatinine. Conclusion RBP may be useful marker in renal damage in patients with chronic kidney injury among patients with MM. This can lead to noninvasive biomarker-targeted diagnostic interventions and contribute to early beginning of treatment that may improve life expectancy quality of life in MM.

Background and Aims Zonulin is a haptoglobin 2 precursor, that regulates the intestinal permeability. As a double-chain form it takes part in scavenging haemoglobin. Chronic inflammation is common complication of chronic kidney disease which affects iron metabolism. The most frequent manifestation of multiple myeloma is anaemia in up to 73% of patients. Serum concentrations of zonulin are associated with inflammation process, age, kidney failure and iron status and anaemia. The aim of the study was to analyse zonulin as a marker of anaemia in MM patients and investigate its relationship with acclaimed parameters of renal failure, inflammation, bone metabolism and stages of MM. Method The studied group of seventy-three patients with MM (67 symptomatic, 6 smoldering) included 35 women and 38 man, with mean age 69 ± 10 years. Median (IQR) of time from initial MM diagnosis was 36 (17; 69) months. Forty patients were in ISS stage 1, 15 in stage 2, and 12 in stage 3 at the time of blood collection. Remission of MM was diagnosed in 52 patients and stable or progressive disease in 21. Twenty-six patients had eGFR Results Median (IQR) serum zonulin in the studied group was 23.9 (19.9; 27.4) ng/ml. There were no differences in zonulin concentrations between patients with smoldering versus symptomatic MM (p=0.4), with ISS 1 to 3 (p=0.7), with remission versus stable or progressive MM (p=0.9), or with eGFR Conclusion Zonulin as a biomarker may promote diagnosis of etiology and management of MM-associated anaemia, which can contribute to biomarker-targeted therapeutic interventions. Early treatment may result in improved life expectancy in patients with MM and increase their quality of life.

Background and Aims Transgelin (SM22) is a cytoskeletal actin-binding protein involved in differentiation of smooth muscle cells, osteoblasts and adipocytes. It is present in fibroblasts, some epithelium, immune cells and acts as a tumor suppressor. It was found as a marker of interstitial fibrosis and glomerulosclerosis. Transgelin upregulation depends on the etiology of the disease in various cells (glomerular parietal or visceral, or tubular interstitial cells). Elevated SM22 expression was detected in glomerular and in tubulointerstitial injury. Among patients with multiple myeloma (MM) up to 50% suffer from renal insufficiency (RI) in early stages. Free light chains (FLCs), potential nephrotoxic substances, where lambda light chains are more commonly associated with renal damage, appear to have a prognostic value in MM and indicate the stages of MM. The aim of the study was to analyse the utility of transgelin in case of renal impairment in MM patients and investigate its relationship with acclaimed parameters of renal failure and markers of MM stages. Method The analysis included 126 patients (73 women and 53 men) in mean age 66 ± 10 years. Symptomatic MM was diagnosed in 119 patients, including 84 (67%) with ISS stage 1, 20 (16%) with stage 2 and 15 (12%) with stage 3; 7 (6%) patients had smoldering MM. Mean baseline eGFR (CKD-EPICr) was 74 ± 24 ml/min/1.73 m2 and 31 (25%) patients had eGFR Results Median serum transgelin in the whole studied group was 84.1 (IQR: 65.4; 116.4) ng/ml. Transgelin concentrations were higher in men (median 96.2 versus 78.8 ng/ml; p=0.022) and in patients with smoldering MM (median 149.2 versus 82.4 ng/ml; p=0.003). Transgelin did not differ according to ISS stage (p=0.3) or disease state (regression, stable disease or progression) (p=0.3). Significant correlations were detected between transgelin and serum creatinine (R=0.29; p=0.001), eGFR (CKD-EPICr) (R=-0.25; p=0.007), uric acid (R=0.19; p=0.036), alanine (R=0.18; p=0.048) and aspartate (R=0.26; p=0.003) aminotransferases, ferritin (R=-0.22; p=0.049), hepcidin (R=-0.25; p=0.033), and urine cystatin C (R=0.19; p=0.042). Moreover, after exclusion of patients with smoldering MM, transgelin significantly correlated with serum FLC lambda (R=0.18; p=0.047) and serum periostin (R=-0.22; p=0.013). After median follow-up of 21 (IQR: 15; 24) months, eGFR decreased in 47 (37%) of patients and increased in 71 (56%) patients (no follow-up data were available in 8, i.e. 6% of patients). Patients in whom eGFR decreased had higher transgelin (median 106.6 versus 83.9 ng/ml), although the difference was marginally significant (p=0.05). However, baseline transgelin positively correlated with serum creatinine after follow-up (R=0.37; p Conclusion Transgelin may be useful in investigating renal damage because of its proven role in regulation of fibrosis, especially in kidney. As a biomarker it may indicate diagnosis and etiology of MM-related chronic kidney disease, which can lead to beginning of early therapeutic interventions and improved overall survival and quality of life in patients with MM. Moreover, elevated transgelin at the beginning of the disease may induce future development of chronic kidney disease.

Background and Aims Urine tissue inhibitor of metalloproteinases-2 (TIMP-2) and insulin-like growth factor-binding protein 7 (IGFBP7) seem to be novel kidney injury related biomarkers, especially in tubular cells damage. Free light chains (FLCs) are associated with renal failure in multiple myeloma (MM) and appear to have a prognostic value and indicate stages in MM. The aim of the study was to investigate the correlation between new biomarkers and acclaimed parameters of renal failure and markers of MM stages and prognosis. Method The study included 124 patients with MM in the mean age of 66 +/- 10 years, with median time from MM diagnosis of 30 (lower; upper quartile 14; 63) months. There were 7(6%) patients with smoldering MM, 80(65%) with ISS stage 1, 22 (18%)with stage 2 and 15 (12%) with stage 3 MM. Mean eGFR was 71 +/- 25 ml/min/1.73 m2 and 30 (24%) patients had eGFR Results Except for urine cystatin C and urine TIMP-2, all the studied markers were higher among patients with eGFR Serum and urine IGFBP-7 and urine NGAL were also higher among patients with ISS grade 3 comparing to the rest of the group (p=0.008, p Conclusion Urine TIMP-2 and IGFBP-7 may be useful in investigating tubular renal damage in patients with chronic kidney injury among patients with MM. This can lead to noninvasive biomarker-targeted diagnostic interventions and contribute to early beginning of treatment that may improve life expectancy quality of life in MM.

Growth differentiation factor 15 (GDF-15), a member of the transforming growth factor-β superfamily, participates in processes associated with myeloma development and its end-organ complications. It plays a significant role in both physiological and abnormal erythropoiesis and regulates iron homeostasis through modulation of hepcidin. It is abnormally secreted in marrow stromal cells of patients with multiple myeloma (MM), which may reflect the tumor microenvironment. We analyzed the associations of serum GDF-15 with clinical characteristics of 73 MM patients (including asymptomatic MM) and the laboratory indices of renal function, anemia, and inflammation. Baseline serum GDF-15 was studied as the predictor of two-year survival. We defined five clinically relevant subgroups of patients (symptomatic MM only, patients with and without remission, patients on chemotherapy, and without treatment). Increased GDF-15 concentrations were associated with more advanced MM stage, anemia, renal impairment (lower glomerular filtration and higher markers of tubular injury), and inflammation. Most of the results were confirmed in the subgroup analysis. Serum cystatin C and urine neutrophil gelatinase-associated lipocalin were associated with GDF-15 independently of other variables. In the studied MM patients, GDF-15 did not significantly predict survival ( p = 0.06 ). Our results suggest that serum GDF-15 reflects myeloma burden and shares a relationship with several markers of prognostic significance, as well as major manifestations.

There is a wide spectrum of malignant diseases that are connected with the clonal proliferation of plasma cells, which cause the production of complete immunoglobulins or their fragments (heavy or light immunoglobulin chains). These proteins may accumulate in tissues, leading to end organ damage. The quantitative determination of immunoglobulin free light chains (FLCs) is considered to be the gold standard in the detection and treatment of multiple myeloma (MM) and amyloid light-chain (AL) amyloidosis. In this study, a silver nanoparticle-based diagnostic tool for the quantitation of FLCs is presented. The optimal test conditions were achieved when a metal nanoparticle (MNP) was covered with 10 particles of an antibody and conjugated by 5&ndash, 50 protein antigen particles (FLCs). The formation of the second antigen protein corona was accompanied by noticeable changes in the surface plasmon resonance spectra of the silver nanoparticles (AgNPs), which coincided with an increase of the hydrodynamic diameter and increase in the zeta potential, as demonstrated by dynamic light scattering (DLS). A decrease of repulsion forces and the formation of antigen&ndash, antibody bridges resulted in the agglutination of AgNPs, as demonstrated by transmission electron microscopy and the direct formation of AgNP aggregates. Antigen-conjugated AgNPs clusters were also found by direct observation using green laser light scattering. The parameters of the specific immunochemical aggregation process consistent with the sizes of AgNPs and the protein particles that coat them were confirmed by four physical methods, yielding complementary data concerning a clinically useful AgNPs aggregation test.

Lactoperoxidase (LPO) together with its (pseudo)halogenation cycle substrates, H2O2 and thiocyanate ions oxidized to hypothiocyanite ions, form one of the main systems involved in antimicrobial defense within the oral cavity. In bacterial diseases such as dental caries, lactoperoxidase is oxidized to a form known as Compound II, which is characterized by its inability to oxidize SCN–, resulting in a decreased generation of antimicrobial products. Reynoutria sp. rizome extracts, due to their high polyphenol content, have been tested as a source of compounds able to regenerate the antimicrobial activity of lactoperoxidase through converting the Compound II to the native LPO state. In the presented study, acetone extracts of R. japonica, R. sachalinensis, and R. x bohemica, together with their five fractions and four selected polyphenols dominating in the studied in extracts, were tested toward lactoperoxidase reactivating potential. For this purpose, IC50, EC50, and activation percentage were determined by Ellman’s method. Furthermore, the rate constants for the conversion of Compound I–Compound II and Compound II–native-LPO in the presence of extracts, extracts fractions, and selected polyphenols were determined. Finally, the ability to enhance the antimicrobial properties of the lactoperoxidase system was tested against Streptococcus mutans. We proved that Reynoutria sp. rhizome is the source of lactoperoxidase peroxidation cycle substrates, which can act as activators and inhibitors of the antimicrobial properties of that system. The presented study shows that the reactivation of lactoperoxidase could become a potential therapeutic target in prevention and treatment support in some infectious oral diseases.

Within the first week of the disease, acute kidney injury (AKI) is among the most common causes of mortality in acute pancreatitis (AP). Recently, serum angiopoietin-2 (Ang-2) has been associated with hyperdynamic state of the systemic circulation. The aim of this study was to examine the associations between Ang-2 and the clinical AP severity during the first 72 hours of the disease, and organ disfunction, including AKI.Methods. Study included patients admitted to the surgery ward, diagnosed with AP. AKI was diagnosed according to KDIGO guidelines and renal failure according to modified Marshall scoring system. Ang-2 was determined in serum with ELISA.Results. AP was classified as mild (MAP) in 71% of patients, moderately severe (MSAP) in 22%, and severe (SAP) in 8%. During the first 72 hours of AP, 11 patients developed AKI and 6 developed renal failure. Ang-2 at 24, 48, and 72 hours following the onset of AP symptoms significantly predicted SAP and MSAP, as well as AKI and renal failure. Also, Ang-2 significantly correlated with acute phase proteins as well as with the indicators of renal disfunction.Conclusions. Serum Ang-2 may be a relevant predictor of AP severity, in particular of the development of AP-renal syndrome.

The induction of antitumor immune responses in tumor-bearing hosts depends on efficient uptake and processing of native or modified tumors/self-antigens by dendritic cells (DCs) to activate immune effector cells, as well as the extent of the immunosuppressive network in the tumor microenvironment (TME). Because the C-X-C motif chemokine receptor 4 (CXCR4) for the C-X-C motif chemokine 12 (CXCL12) is involved in signaling interactions between tumor cells and their TME, we used oncolytic virotherapy with a CXCR4 antagonist to investigate whether targeting of the CXCL12/CXCR4 signaling axis in murine neuroblastoma cells (NXS2)-bearing syngeneic mice affects the efficacy of bone marrow (BM)-derived DCs loaded with autologous tumor cells treated with doxorubicin for induction of immunogenic cell death. Here, we show that CXCR4 antagonist expression from an oncolytic vaccinia virus delivered intravenously to mice with neuroblastoma tumors augmented efficacy of the DC vaccines compared to treatments mediated by a soluble CXCR4 antagonist or oncolysis alone. This study is the first demonstration that modulating the tumor microenvironment by an armed oncolytic virus could have a significant impact on the efficacy of DC vaccines, leading to the generation of effective protection against neuroblastoma challenge.

Acute pancreatitis (AP) is an inflammatory disease with varied severity, ranging from mild local inflammation to severe systemic involvement resulting in substantial mortality. Early pathologic events in AP, both local and systemic, are associated with vascular derangements, including endothelial activation and injury, dysregulation of vasomotor tone, increased vascular permeability, increased leukocyte migration to tissues, and activation of coagulation. The purpose of the review was to summarize current evidence regarding the interplay between inflammation, coagulation and endothelial dysfunction in the early phase of AP. Practical aspects were emphasized: (1) we summarized available data on diagnostic usefulness of the markers of endothelial dysfunction and activated coagulation in early prediction of severe AP; (2) we reviewed in detail the results of experimental studies and clinical trials targeting coagulation-inflammation interactions in severe AP. Among laboratory tests, d-dimer and angiopoietin-2 measurements seem the most useful in early prediction of severe AP. Although most clinical trials evaluating anticoagulants in treatment of severe AP did not show benefits, they also did not show significantly increased bleeding risk. Promising results of human trials were published for low molecular weight heparin treatment. Several anticoagulants that proved beneficial in animal experiments are thus worth testing in patients.

Urinalysis is a routine and cheap laboratory test that provides clinically useful information in patients with acute abdominal conditions, including acute pancreatitis. The aim of the study was to assess the relationships between the results of urinalysis and the course of the disease among 65 patients with acute pancreatitis (34 men and 31 women, mean age 61 ± 19 years) at the early phase of the disease, i.e. during the first 72 hours from the onset of symptoms. Mild acute pancreatitis was diagnosed in 47 patients, moderately severe in 13 and severe in 5. The most prevalent abnormalities were proteinuria (43% of patients), high urinary bilirubin (20%), erythrocytes (18%), glucose (18%) and leukocytes (17%). High urinary protein and low specific gravity were associated with more severe acute disease and with acute kidney injury. The severity of bilirubinuria and proteinuria were positively correlated with urine concentrations of neutrophil gelatinase associated lipocalin (NGAL). Urinalysis should be routinely performed in patients with acute pancreatitis.

In twenty first century, the incidence of type 2 diabetes mellitus (DMt2) dramatically increases, followed by the number of patients suffering from its complications. Currently, diabetic kidney disease (DKD) is the leading cause of renal replacement therapy. Often, DMt2 is diagnosed after several years of duration, and irreversible organ damage can develop during that period. On the other hand, the early diag- nosis of DKD in the preclinical phase, when glomerular filtration rate (GFR) is still maintained and there are no evident changes in urinalysis, gives the possibility of implementing the nephroprotective treatment that can significantly delay the progression of the disease. However, the diagnostic tests available in clinical practice, i.e. serum creatinine, estimated glomerular filtration rate (eGFR) and albuminuria have important limitations. There is a need for new, early and non-invasive biomarkers specific for kidney injury, allowing for differentiation between glomerular and tubular injury, and changing dynamically in response to the degree of kidney damage. Hereby, we review the current knowledge about the novel and emerging biomarkers of kidney injury and their used for the diagnosis of DKD.

The aim was to model the influence of LASIK surgery on the optical parameters of the human eye and to ascertain which factors besides the central corneal radius of curvature and central thickness play the major role in postsurgical refractive change. Ten patients were included in the study. Pre- and postsurgical measurements included standard refraction, anterior corneal curvature and pachymetry. The optical model used in the analysis was based on the Le Grand and El Hage schematic eye, modified by the measured individual parameters of corneal geometry. A substantial difference between eye refractive error measured after LASIK and estimated from the eye model was observed. In three patients, full correction of the refractive error was achieved. However, analysis of the visual quality in terms of spot diagrams and optical transfer functions of the eye optical system revealed some differences in these measurements. This suggests that other factors besides corneal geometry may play a major role in postsurgic...

In the presence of molecular oxygen and iron or copper ions, a number of antioxidants paradoxically generate reactive oxygen species (ROS) leading to free radical damage of nucleic acids and oxidative modification of lipids and proteins. The present work demonstrates that the combination of three components, which are often considered as part of an antioxidant protection system, can generate ROS. Purified human gamma-glutamyltransferase (GGT) in the presence of 2 mM glutathione (GSH) and 80 microM transferrin, as an iron source, at pH 7.4 generates ROS, as measured by chemiluminescence of luminol. Initiated by the addition of purified GGT, generation of ROS reached a maximal rate in the first 6 min. Intensity of the chemiluminescence was only slightly enhanced by addition of 200 microM hydrogen peroxide. Generation of ROS was also investigated in transfected V79 cells expressing human GGT. In comparison with GGT negative V79 cells, only recombinant cells expressing a high level of GGT on the cell membrane were able to generate ROS. Generation of ROS in these cells reached a maximum within 2 min and was enhanced by 200 microM hydrogen peroxide. We further confirmed the hypothesis that cysteinylglycine (CysGly), a product of GGT/GSH reaction, identified by high-performance liquid chromatography, but not GSH, was responsible for ROS formation initiated by the reductive release of iron from transferrin. These data clearly indicate that under physiological conditions, GGT is directly involved in ROS generation.

IgA, IgG and IgM were cleaved by hypochlorous acid treatment. The apparent calculated molecular masses of three polypeptides obtained from IgA were 81.1. 25.8 and 13.9 kDa. The amounts of released IgA fragments were proportional to the amount of HOCl employed. At a HOCl:IgA molar ratio above 320:1, a profound degradation of IgA polypeptide chains occurred, resulting in a yellow-coloured product. The HOCl treatment of IgG resulted in similar effects, the liberation of three fragments, one of them being of a size slightly larger than that of the light chain (30.4 kDa). The treatment of IgM with HOCl also produced three fragments: one corresponding to the monomeric IgM molecule, the second to the light chain (26.4 kDa) and the third of a size smaller than the heavy chain. The optimal protein/HOCl ratios for the degradation of IgG and IgM were 375:1 and 808:1, respectively.

A potentiometric procedure for cysteine thiol group concentration monitoring in media generating free radicals was developed using a thiol specific silver-mercury electrode. Electrolytic deposition of mercury on a silver wire and treatment with 20 mM cysteine in 0.5 M NaOH were used to produce the electrode. A silver-chloride electrode in saturated KCl was the reference. A glass capillary with 1 M KNO3 in 1% agarose gel was the liquid junction. The electrode responded to cysteine concentration in the range from 0.01 to 20 mM yielding a perfect linear relationship for the dependence of log [cysteine] versus electrode potential [mV], with b0 (constant) = -373.43 [mV], b1 (slope) = -53.82 and correlation coefficient r2 = 0.97. The electrode potential change per decade of cysteine concentration was 57 mV. The minimal measurable signal response was at a cysteine concentration of 0.01 mM. The signal CV amounted to 4-6% for cysteine concentrations of 0.01 to 0.05 mM and to less than 1% for cysteine concentrations of 0.5 to 20 mM. The response time ranged from about 100 s for cysteine concentrations of 0.01 to 0.1 mM to 30 s at higher cysteine concentrations. The standard curve reproducibility was the best at cysteine concentrations from 0.1 to 20 mM. In a reaction medium containing cysteine and copper(II)-histidine complex ([His-Cu]2+) solution in 55 mM phosphate buffer pH 7.4 the electrode adequately responded to changes in cysteine concentration. Beside cysteine, the silver-mercury electrode responded also to thiol groups of homocysteine and glutathione, however, the Nernst equation slope was about half of that for cysteine.

Oxidation of proteins occurs both as a side-effect of aerobic energy metabolism and as an effect of specific metabolism of phagocytic polymorphonuclear granulocytes producing O 2 -. and H 2 O 2 . In contrast to other cells, which control their H 2 O 2 level by degrading it to O 2 and H 2 O, polymorphonuclear neutrophilic leukocytes (PMN) use H 2 O 2 as a substrate for oxidizing chloride ions to HOCI which rapidly react with all neighboring thiol, disulfide and amino residues. Chloramines, which are the most abundant HOCI reaction products, react with proteins, modifying only certain exposed methionine and cysteine residues. This may account for selective inactivation of a number of enzymes, carrier proteins and peptide mediators, including the α 1 -proteinase inhibitor, α 2 -macroglobulin and plasminogen activator inhibitor. Inactivaton of plasma proteinase inhibitors protects PMN elastase, collagenase, cathepsin G and other serine proteases in the inflammatory foci. This promotes proteolytic degradation of damaged tissue, removal of bacterial debris and wound healing, as well as tissue remodeling related to the inflammatory processes. Oxidative control of protease-anti-protease balance affects the development of the inflammatory processes. Moreover, inactivation of plasma proteinase inhibitors facilitates primary antigen processing, upregulates lymphocyte proliferative response and activates the local immune response. Oxidation produces a specific protein tagging which attracts and stimulates immune active cells. Therefore, humoral response against oxidatively modified proteins occurs more effectively than that of the native proteins. The effect is dose-dependent with respect to the amount of oxidant employed. Glycol aldehyde, which is the serine chloramine spontaneous decay product, in mice immunized with glycol aldehyde-modified egg-white albumin, yields specific IgG production manifold higher than that in mice immunized with native albumin. Immunopotentiation is produced by proliferation expansion of the same immunocompetent clones. Oxidative tagging of proteins may also affect the autoimmune-type reaction. Thus, a growing body of data suggest that the specific role of protein oxidation by activated PMN is oxidative protein tagging facilitating further development of the immune reaction.

Apolipoprotein E, the most common apolipoprotein found in the brain, is linked to several pathologies like Alzheimer's disease. Apolipoprotein E directly binds to beta-amyloid with a strong affinity. Myeloperoxidase, a protein secreted by neutrophils and involved in the inflammatory process, is also present in the brain. In vitro myeloperoxidase oxidation of recombinant human apolipoprotein E leads to fragmentation of the protein with low concentrations of hydrogen peroxide and polymerization with higher concentrations. Comparison with bovine serum albumin shows a higher susceptibility of apolipoprotein E to myeloperoxidase oxidation, which may have importance in the Alzheimer's disease process.

Egg white lysozyme treated with hypochlorous acid links together producing di-, tri-, tetra-, and pentameric derivatives with molecular masses ranging from 14,300 to 90,500. Similar oligomeric products may be obtained by treating lysozyme color derivatives produced by labeling lysozyme with fluorescein, trinitrobenzenesulfonic acid and 2,4-dinitrofluorobenzene, with hypochlorous acid. The oligomeric lysozyme derivatives thus obtained consist of a mixture of proteins with molecular masses equal to multiples of 14,300 (lysozyme molecular mass). This mixture can be applied as a set of molecular mass standards suitable for determination of protein molecular masses on sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Histidine-copper(II) complex (Cu-His2) is a form of bound copper necessary for cellular copper uptake. Due to the high affinity of histidine to copper(II) ions, the binding of copper(II) by histidine is considered a substantial part of plasma antioxidative defense. Also cysteine plays a role in the antioxidative system. However, we show here that in the presence of oxygen the histidine-copper(II) complex plus cysteine produces reactive oxygen species (ROS). Cysteine concentration was assayed using a thiol specific silver-mercury electrode. Hydrogen peroxide was assayed amperometrically using platinum electrode. ROS formation was followed by chemiluminescence of luminol-fluoresceine-enhanced system. Addition of cysteine to Cu-His2 solution at pH 7.4 in the presence of atmospheric oxygen initiates the synthesis of H2O2 and generation of ROS, which manifests as a burst of chemiluminescence. The reaction has two stages; in the first stage, cysteine is utilized for the synthesis of an unstable intermediary product which becomes a substrate for ROS formation. Anaerobic conditions inhibit ROS formation. Increased cysteine concentration enhances the lag phase of the oxidative burst without influencing the amount of ROS. The synthesis of ROS (measured by chemiluminescence) is proportional to the concentration of Cu-His2 employed. ROS production can be repetitively initiated by further additions of cysteine to the reaction medium. The study suggests that Cu-His2 catalyzes cysteine-dependent reduction of oxygen to superoxide employing an intermediary cysteine-copper(I) complex and enabling Fenton reaction with copper and hydrogen peroxide produced as a secondary product. In effect, Cu-His2 with cysteine may be a source of ROS in biological media.