Urinary 8-isoprostane as a biomarker for oxidative stress. A systematic review and meta-analysis

Oxidative stress is defined as an imbalance between the production and elimination of reactive oxygen species (ROS) are associated with various inflammation-related human disease. ROS can oxidize lipids, which subsequently undergo fragmentation to produce F2-isoprostanes (F2-IsoPs). Eight-isoprostane is one of the most extensively studied F2-IsoPs and the most commonly used biomarker for the assessment of oxidative stress in human studies. This urinary biomarker is quantified using either chemical or immunological techniques. A "physiological" range for 8-isoprostanes is needed to use this biomarker as a measure of excess oxidative stress originating from occupational exposures. However, ranges reported in the literature are inconsistent. We designed a standardized protocol of a systematic review and meta-analysis to assess baseline values for 8-isoprostane concentrations in urine of healthy adults and identify determinants of their inter- and intra-individual variability. We searched PubMed from journal inception and up to April 2019, and screened articles for studies containing F2-IsoPs concentrations in urine for healthy adult participants. We grouped studies in three biomarker groups: "8-isoprostane", "Isoprostanes" "15- F2t-Isoprostane". We computed geometric mean (GM) and geometric standard deviation (GSD) as the basis for the meta-analysis. Of the initial 1849 articles retrieved, 63 studies were included and 107 subgroups within these study populations were identified. We stratified the subgroups analyzed with the chemical methods by body mass index (BMI) reported. We provide pooled GM values for urinary 8-isoprostane concentrations in healthy adults, separately for chemical and immunological analysis in this review. The interquartile range (IQR) in subgroups with a mean BMI below 25 measured using chemical methods was 0.18 to 0.40 μg/g creatinine. We show that there is a significant positive association between BMI and urinary 8-isoprostane concentrations. We recommend adjusting urinary 8-isoprostane concentrations in spot urine with creatinine, quantifying 8-isoprostane with chemical analytical methods, and reporting results as median and quartiles. This will help in comparing results across studies.

Reference ranges of oxidative stress biomarkers selected for non-invasive biological surveillance of nanotechnology workers: Study protocol and meta-analysis results for 8-OHdG in exhaled breath condensate

In the field of engineered nanomaterials (ENMs) and other airborne particulate exposure biomonitoring, circulating oxidative stress biomarkers appear promising. These biomarkers could be monitored in different biological matrices. Exhaled breath condensate (EBC) enables their measurements in the respiratory tract, without affecting airway function or creating inflammation. The 8-hydroxy-2-deoxyguanosine (8-OHdG) was found increased in the EBC of ENM-exposed workers. Our objectives were to assess the reference range of 8-OHdG in the EBC and to identify determinants of its inter- and intra-individual variability. The meta-analysis was stratified by analytical method (chemical versus immunochemical analysis) and resulted in a between-study variability over 99 % of the total variability. The between-study variability completely dominated the within-studies variability. By using a mixed model with study ID as a random effect rather than a meta-regression, only smoking was evidenced as a potential determinant of 8-OHdG inter-individual variability, and only when immunochemical analysis was used. To our knowledge, this is the first meta-analysis aimed at estimating reference values for 8-OHdG in the EBC. The estimated values should be considered preliminary, as they are based on a limited number of studies, mostly of moderate to low quality of evidence. Further research is necessary to standardize EBC sampling, storage and analytical methods. Such a standardization would enable a more accurate estimation of the reference ranges of the 8-OHdG and potentially other biomarkers measurable in the EBC, which are essential for a meaningful interpretation of the biomonitoring results.

Fatal Parastrongylus dujardini Infection in Captive Callitrichids

Intravascular nematodes were considered the cause of death of 14 captive callitrichids. All animals were captive born at zoos in France and died with little or no premonitory signs of disease. No consistent gross lesions were observed at necropsy, although in certain cases intracardiac adult parasites were noted. The most significant histologic findings were verminous pneumonia and pulmonary endarteritis. In all cases except one, intravascular adult nematodes were observed with eggs and larvae in the lungs. Adult nematodes were obtained from 8 animals and in all cases were identified as Parastrongylus dujardini. To the authors’ knowledge, this is the first report of intravascular angiostrongylosis with primary cardiopulmonary location in callitrichids in France.

Strategies for the structural analysis of multi-protein complexes: lessons from the 3D-Repertoire project

Structural studies of multi-protein complexes, whether by X-ray diffraction, scattering, NMR spectroscopy or electron microscopy, require stringent quality control of the component samples. The inability to produce 'keystone' subunits in a soluble and correctly folded form is a serious impediment to the reconstitution of the complexes. Co-expression of the components offers a valuable alternative to the expression of single proteins as a route to obtain sufficient amounts of the sample of interest. Even in cases where milligram-scale quantities of purified complex of interest become available, there is still no guarantee that good quality crystals can be obtained. At this step, protein engineering of one or more components of the complex is frequently required to improve solubility, yield or the ability to crystallize the sample. Subsequent characterization of these constructs may be performed by solution techniques such as Small Angle X-ray Scattering and Nuclear Magnetic Resonance to identify 'well behaved' complexes. Herein, we recount our experiences gained at protein production and complex assembly during the European 3D Repertoire project (3DR). The goal of this consortium was to obtain structural information on multi-protein complexes from yeast by combining crystallography, electron microscopy, NMR and in silico modeling methods. We present here representative set case studies of complexes that were produced and analyzed within the 3DR project. Our experience provides useful insight into strategies that are more generally applicable for structural analysis of protein complexes.

Inhibition of archaeal growth and DNA topoisomerase VI activities by the Hsp90 inhibitor radicicol

Type II DNA topoisomerases have been classified into two families, Topo IIA and Topo IIB, based on structural and mechanistic dissimilarities. Topo IIA is the target of many important antibiotics and antitumoural drugs, most of them being inactive on Topo IIB. The effects and mode of action of Topo IIA inhibitors in vitro and in vivo have been extensively studied for the last twenty-five years. In contrast, studies of Topo IIB inhibitors were lacking. To document this field, we have studied two Hsp90 inhibitors (radicicol and geldanamycin), known to interact with the ATP-binding site of Hsp90 (the Bergerat fold), which is also present in Topo IIB. Here, we report that radicicol inhibits the decatenation and relaxation activities of Sulfolobus shibatae DNA topoisomerase VI (a Topo IIB) while geldanamycin does not. In addition, radicicol has no effect on the Topo IIA Escherichia coli DNA gyrase. In agreement with their different effects on DNA topoisomerase VI, we found that radicicol can theoretically fit in the ATP-binding pocket of the DNA topoisomerase VI ‘Bergerat fold’, whereas geldanamycin cannot. Radicicol inhibited growths of Sulfolobus acidocaldarius (a crenarchaeon) and of Haloferax volcanii (a euryarchaeon) at the same doses that inhibited DNA topoisomerase VI in vitro. In contrast, the bacteria E.coli was resistant to this drug. Radicicol thus appears to be a very promising compound to study the mechanism of Topo IIB in vitro, as well as the biological roles of these enzymes in vivo.

Crystal structure of the S. cerevisiae D-ribose-5-phosphate isomerase: comparison with the archaeal and bacterial enzymes

Ribose-5-phosphate isomerase A has an important role in sugar metabolism by interconverting ribose-5-phosphate and ribulose-5-phosphate. This enzyme is ubiquitous and highly conserved among the three kingdoms of life. We have solved the 2.1 A resolution crystal structure of the Saccharomyces cerevisiae enzyme by molecular replacement. This protein adopts the same fold as its archaeal and bacterial orthologs with two alpha/beta domains tightly packed together. Mapping of conserved residues at the surface of the protein reveals strong invariability of the active site pocket, suggesting a common ligand binding mode and a similar catalytic mechanism. The yeast enzyme associates as a homotetramer similarly to the archaeal protein. The effect of an inactivating mutation (Arg189 to Lys) is discussed in view of the information brought by this structure.

Immunoglobulin-binding domains: Protein L from Peptostreptococcus magnus

Protein L is a multidomain cell-wall protein isolated from Peptostreptococcus magnus. It belongs to a group of proteins that contain repeated domains that are able to bind to Igs without stimulating an immune response, the most characterized of this group being Protein A ( Staphylococcus aureus ) and Protein G ( Streptococcus ). Both of these proteins bind predominantly to the interface of C(H)2-C(H)3 heavy chains, while Protein L binds exclusively to the V(L) domain of the kappa -chain. The function of these proteins in vivo is not clear but it is thought that they enable the bacteria to evade the host's immune system. Two binding sites for kappa -chain on a single Ig-binding domain from Protein L have recently been reported and we give evidence that one site has a 25-55-fold higher affinity for kappa -chain than the second site.

Antithrombotic therapy is associated with better survival in patients with severe heart failure and left ventricular systolic dysfunction (EPICAL study)

BACKGROUND

In patients with congestive heart failure (CHF), clinical trials have demonstrated the benefit of a number of drugs on morbidity and mortality. Nevertheless so far, there is no published controlled study of long-term antithrombotic therapy in patients with CHF. The aim of this work was to identify the relationship between cardiovascular drug use, especially antithrombotic therapy, and survival of CHF patients in current clinical practice, using an observational, population-based database.

METHODS

The EPICAL study (Epidémiologie de l'Insuffisance Cardiaque Avancée en Lorraine) has identified prospectively all patients with severe CHF in the community of Lorraine. Inclusion criteria were age 20-80 years in 1994, at least one hospitalisation for cardiac decompensation, NYHA III/IV HF, ventricular ejection fraction < or =30% or cardiothoracic index > or =60% and arterial hypotension or peripheral and/or pulmonary oedema. A total of 417 consecutive patients surviving at hospital discharge were included in the database. The average follow-up period was 5 years. Univariate Cox models were used to test the relationship of baseline biological and clinical factors to survival. Cardiovascular drug prescriptions were tested in a multivariate Cox model adjusted by other known predictive factors.

RESULTS

Duration of disease >1 year, renal failure, serum sodium > or =138 mmol/l, old age, serious comorbidity, previous decompensation, high doses of furosemide and vasodilators use were independently associated with poor prognosis at 1 and 5 years. Oral anticoagulants, aspirin, lipid lowering drugs and beta-blockers use were associated with better survival. There was no interaction between aspirin and angiotensin converting enzyme inhibitor use on survival.

CONCLUSION

Antithrombotic therapy was associated with a better long-term survival in our study population of severe CHF. These results together with other previously published circumstantial evidence urge for a prospective, controlled and randomised trial specifically designed to evaluate optimal oral anticoagulants and aspirin in patients with congestive heart failure.

Complex between Peptostreptococcus magnus protein L and a human antibody reveals structural convergence in the interaction modes of Fab binding proteins

BACKGROUND

Peptostreptococcus magnus protein L (PpL) is a multidomain, bacterial surface protein whose presence correlates with virulence. It consists of up to five homologous immunoglobulin binding domains that interact with the variable (VL) regions of kappa light chains found on two thirds of mammalian antibodies.

RESULTS

We refined the crystal structure of the complex between a human antibody Fab fragment (2A2) and a single PpL domain (61 residues) to 2.7 A. The asymmetric unit contains two Fab molecules sandwiching a single PpL domain, which contacts similar VL framework regions of two light chains via independent interfaces. The residues contacted on VL are remote from the hypervariable loops. One PpL-Vkappa interface agrees with previous biochemical data, while the second is novel. Site-directed mutagenesis and analytical-centrifugation studies suggest that the two PpL binding sites have markedly different affinities for VL. The PpL residues in both interactions are well conserved among different Peptostreptococcus magnus strains. The Fab contact positions identified in the complex explain the high specificity of PpL for antibodies with kappa rather than lambda chains.

CONCLUSIONS

The PpL-Fab complex shows the first interaction of a bacterial virulence factor with a Fab light chain outside the conventional combining site. Structural comparison with two other bacterial proteins interacting with the Fab heavy chain shows that PpL, structurally homologous to streptococcal SpG domains, shares with the latter a similar binding mode. These two bacterial surface proteins interact with their respective immunoglobulin regions through a similar beta zipper interaction.

Crystal structure of a Staphylococcus aureus protein A domain complexed with the Fab fragment of a human IgM antibody: structural basis for recognition of B-cell receptors and superantigen activity

Staphylococcus aureus produces a virulence factor, protein A (SpA), that contains five homologous Ig-binding domains. The interactions of SpA with the Fab region of membrane-anchored Igs can stimulate a large fraction of B cells, contributing to lymphocyte clonal selection. To understand the molecular basis for this activity, we have solved the crystal structure of the complex between domain D of SpA and the Fab fragment of a human IgM antibody to 2.7-A resolution. In the complex, helices II and III of domain D interact with the variable region of the Fab heavy chain (V(H)) through framework residues, without the involvement of the hypervariable regions implicated in antigen recognition. The contact residues are highly conserved in human V(H)3 antibodies but not in other families. The contact residues from domain D also are conserved among all SpA Ig-binding domains, suggesting that each could bind in a similar manner. Features of this interaction parallel those reported for staphylococcal enterotoxins that are superantigens for many T cells. The structural homology between Ig V(H) regions and the T-cell receptor V(beta) regions facilitates their comparison, and both types of interactions involve lymphocyte receptor surface remote from the antigen binding site. However, T-cell superantigens reportedly interact through hydrogen bonds with T-cell receptor V(beta) backbone atoms in a primary sequence-independent manner, whereas SpA relies on a sequence-restricted conformational binding with residue side chains, suggesting that this common bacterial pathogen has adopted distinct molecular recognition strategies for affecting large sets of B and T lymphocytes.

Immunization with heat-killed Toxoplasma gondii stimulates an early IFN-gamma response and induces protection against virulent murine malaria

In this study, we describe protection of BALB/c mice by immunization with heat-killed T. gondii tachyzoites against infection with Plasmodium yoelii 17XL which causes cerebral malaria and death in mice by day 7-8 post infection. Immunization resulted significant reduction in parasitemia at the peak period of infection. Protection induced by heat-killed T. gondii was associated with marked increase in NK cell number and IFN-gamma mRNA expression early in the infection. The level of IFN-gamma or TNF-alpha was found to diminish in T. gondii-treated mice as the infection progressed to the late stage. This declined response of IFN-gamma or TNF-alpha was associated with marked increase in the expression of IL-10, a counterregulatory cytokine. Pretreatment of mice with live T. gondii induced poor level of protection as compared with that of heat-killed parasites. Mice that received P. yoelii infection alone, had an elevated IFN-gamma response in the late stage of infection. Development of cerebral malaria in untreated mice was accompanied by an augmented production of TNF-alpha and nitric oxide (NO), the proinflammatory mediators. These findings suggest that nonspecific immunization with T. gondii leads to restoration of an early IFN-gamma response in P. yoelii-infected mice and in the establishment of an immunoregulatory mechanism that effectively antagonizes the disease-promoting effects of proinflammatory cytokines in the late phase of infection.