Acute-phase protein alpha-1-acid glycoprotein mediates neutrophil migration failure in sepsis by a nitric oxide-dependent mechanism

Circulating Cytokines and Nitric Oxide are Involved in the Inhibition of Neutrophil Migration in Patients with Uterine Cervical Neoplasia

Aim

To verify if patients with cervical neoplasia produce mediators that reduce leukocyte function.

Methods

Control neutrophils incubated with normal serum or serum from pre-invasive or invasive neoplasia patients were assayed for chemotaxis. Mediators were assayed in serum and in leukocyte supernatants. Experiments were also performed in random patients after surgery.

Results

Neutrophils incubated with patient sera, but not normal sera, failed to migrate towards the chemoattractants. In invasive neoplasia compared to controls, IL-6 and IL-8, and IL-10 and TNF-α were elevated in serum and in neutrophil supernatants, respectively. Nitrite levels were elevated in mononuclear cell supernatants from patients than controls. After surgery, serum cytokine levels were reduced, mainly in pre-invasive patients. Neutrophils treated with serum from pre-invasive patients undergone surgery had restored migration.

Conclusion

Patients with cervical neoplasia produce mediators, predominantly induced by tumor cells, able to impair the inflammatory response at very early stages of disease.

Comparison of methods for the purification of alpha-1 acid glycoprotein from human plasma

Alpha-1 acid glycoprotein (AGP) is a highly glycosylated, negatively charged plasma protein suggested to have anti-inflammatory and/or immunomodulatory activities. Purification of AGP could be simplified if methods that exploit its high solubility under chemically harsh conditions could be demonstrated to leave the protein in its native conformation. Procedures involving exposure of AGP to hot phenol or sulphosalicylic acid (SSA) were compared to solely chromatographic methods. Hot phenol-purified AGP was more rapidly cleared from mice in vivo following intravenous injection than chromatographically purified AGP. In contrast, SSA-purified AGP demonstrated an identical in vivo clearance profile and circular dichroism spectrum to chromatographically purified AGP. Similarly, no differences in susceptibility to enzymatic deglycosylation or reactivity with Sambucus nigra lectin were detected between AGP purified via the two methods. Incorporation of the SSA step in the purification scheme for AGP eliminated the need for a large (4 mL resin/mL of plasma) initial chromatographic step and simplified its purification without causing any detectable distortion in the conformation of the protein. Confirmation that this procedure is nondenaturing will simplify AGP purification and investigation of its possible biological roles in laboratory animals.

Inhibition of neutrophil migration by hemopexin leads to increased mortality due to sepsis in mice

RATIONALE

The reduction of neutrophil migration to the bacterial focus is associated with poor outcome in sepsis.

OBJECTIVES

The objective of this study was to identify soluble substances in the blood of septic mice that inhibit neutrophil migration.

METHODS

A pool of serum obtained from mice 2 hours after the induction of severe sepsis by cecal ligation and puncture inhibited the neutrophil migration. The proteins with inhibitory activity on neutrophil migration were isolated by Blue-Sepharose chromatography, high-performance liquid chromatography, and electrophoresis, and identified by mass spectrometry.

MEASUREMENTS AND MAIN RESULTS

Hemopexin was identified as the serum component responsible for the inhibition of neutrophil migration. In sepsis, the pretreatment of wild-type mice with hemopexin inhibited neutrophil migration to the focus of infection and decreased the survival rate from 87.5 to 50.0%. Hemopexin-null mice subjected to severe sepsis presented normal neutrophil migration, low bacteremia, and an improvement of 40% in survival rate. Moreover, hemopexin inhibited the neutrophil chemotaxis response evoked by C5a or macrophage inflammatory protein-2 and induced a reduction of CXCR2 and L-selectin as well as the up-regulation of CD11b expression in neutrophil membranes. The inhibitory effect of hemopexin on neutrophil chemotaxis was prevented by serine protease inhibitors or ATP. In addition, serum levels of ATP were decreased 2 hours after severe sepsis.

CONCLUSIONS

These data demonstrate for the first time the inhibitory role of hemopexin in neutrophil migration during sepsis and suggest that the therapeutic inhibition of hemopexin or its protease activity could improve neutrophil migration to the focus of infection and survival in sepsis.

Effects of sepsis on neutrophil chemotaxis

PURPOSE OF REVIEW

Neutrophil recruitment to sites of infection is a critical element of the innate immune response. In patients with sepsis, this response is dysregulated, with exuberant inflammation being followed by a state of profound immune suppression, including inhibition of neutrophil recruitment. This review examines mechanisms underlying suppression of neutrophil migration during sepsis.

RECENT FINDINGS

Mechanisms governing neutrophil chemotactic function in sepsis are complex. Bacterial products, cytokines, and chemokines can modulate neutrophil migratory responses during sepsis via induction of cytoskeletal changes, inhibition of polymorphonuclear leukocyte (PMN)-endothelial cell interactions, and alterations in G protein-coupled receptor expression or signaling. Impaired chemotactic responses can occur as a result of dysregulated PMN Toll-like receptor signaling. Other recently identified inhibitory mechanisms include exposure to elevated temperatures, activation of the anti-inflammatory nuclear transcription factor peroxisome proliferator-activated receptor-gamma, and suppression of PMN-endothelial interactions due to nitric oxide and its metabolites. Finally, circulating microparticles released in sepsis exert important immunomodulatory effects on PMN adherence and transmigration.

SUMMARY

Neutrophil recruitment is a coordinated process that is altered at multiple stages during sepsis, culminating in defective innate immunity and increased risk of infection in these patients. Defining mechanisms involved and strategies to interrupt these deleterious responses requires further investigation.

Two-dimensional difference gel electrophoresis (DiGE) analysis of plasmas from dengue fever patients

Dengue fever is the world's most important arthropod-born viral disease affecting humans. To contribute to a better understanding of its pathogenesis, this study aims to identify proteins differentially expressed in plasmas from severe dengue fever patients relative to healthy donors. The use of 2-D Fluorescence Difference Gel Electrophoresis to analyze plasmas depleted of six high-abundance proteins (albumin, IgG, antitrypsin, IgA, transferrin and haptoglobin) allowed for the detection of 73 differentially expressed protein spots (n = 13, p < 0.01), of which 37 could be identified by mass spectrometry. These 37 spots comprised a total of 14 proteins, as follows: 7 had increased expression in plasmas from dengue fever patients (C1 inhibitor, alpha1-antichymotrypsin, vitamin D-binding protein, fibrinogen gamma-chain, alpha1-acid glycoprotein, apolipoprotein J and complement component C3c), while 7 others had decreased expression in the same samples (alpha-2 macroglobulin, prothrombin, histidine-rich glycoprotein, apolipoproteins A-IV and A-I, transthyretin and complement component C3b). The possible involvement of these proteins in the inflammatory process triggered by dengue virus infection and in the repair mechanisms of vascular damage occurring in this pathology is discussed in this study.

Traits associated with innate and adaptive immunity in pigs: heritability and associations with performance under different health status conditions

There is a need for genetic markers or biomarkers that can predict resistance towards a wide range of infectious diseases, especially within a health environment typical of commercial farms. Such markers also need to be heritable under these conditions and ideally correlate with commercial performance traits. In this study, we estimated the heritabilities of a wide range of immune traits, as potential biomarkers, and measured their relationship with performance within both specific pathogen-free (SPF) and non-SPF environments. Immune traits were measured in 674 SPF pigs and 606 non-SPF pigs, which were subsets of the populations for which we had performance measurements (average daily gain), viz. 1549 SPF pigs and 1093 non-SPF pigs. Immune traits measured included total and differential white blood cell counts, peripheral blood mononuclear leucocyte (PBML) subsets (CD4⁺ cells, total CD8α⁺ cells, classical CD8αβ⁺ cells, CD11R1⁺ cells (CD8α⁺ and CD8α^-), B cells, monocytes and CD16⁺ cells) and acute phase proteins (alpha-₁ acid glycoprotein (AGP), haptoglobin, C-reactive protein (CRP) and transthyretin). Nearly all traits tested were heritable regardless of health status, although the heritability estimate for average daily gain was lower under non-SPF conditions. There were also negative genetic correlations between performance and the following immune traits: CD11R1⁺ cells, monocytes and the acute phase protein AGP. The strength of the association between performance and AGP was not affected by health status. However, negative genetic correlations were only apparent between performance and monocytes under SPF conditions and between performance and CD11R1⁺ cells under non-SPF conditions. Although we cannot infer causality in these relationships, these results suggest a role for using some immune traits, particularly CD11R1⁺ cells or AGP concentrations, as predictors of pig performance under the lower health status conditions associated with commercial farms.

Differential proteomics of the plasma of individuals with sepsis caused by Acinetobacter baumannii

This study examines alterations in the plasma proteome in ten adults affected by sepsis caused by Acinetobacter baumannii as compared to paired healthy controls. 2-DE profiles of plasma from patients and paired healthy donors, depleted of the six most abundant proteins, were analysed by the DIGE technique. Protein spot detection and quantification were performed with the Differential In-gel Analysis and Biological Variation Analysis modules of the DeCyder() software. Differentially expressed proteins were identified by mass spectrometry (MALDI-TOF/TOF) after colloidal Coomassie blue staining. Almost 900 spots were detected on a unique 2-D gel by the DIGE technique. A total of 269 protein spots of differential abundance were shown to be statistically significant (2.5-fold) with p values of p< or =0.01 (135 spots) and p< or =0.05 (134 spots) as determined by the t test. Seventy-one spots were submitted to mass spectrometry and about 30% could be successfully identified. This multiplex approach significantly reduced experimental variability, allowing for the confident detection of small differences in protein levels. Results include differentially expressed lipoproteins as well as proteins belonging to inflammatory/coagulation pathways and the kallikrein-kinin system. These data improves the knowledge for future developments in sepsis diagnosis, staging and therapy.

Proteomic analysis of total cellular proteins of human neutrophils

Background

Neutrophils are the most abundant leukocytes in peripheral blood and represent one of the most important elements of innate immunity. Recent subcellular proteomic studies have focused on the identification of human neutrophil proteins in various subcellular membrane and granular fractions. Although there are relatively few studies dealing with the analysis of the total extract of human neutrophils, many biological problems such as the role of chemokines, adhesion molecules, and other activating inputs involved in neutrophil responses and signaling can be approached on the basis of the identification of the total cellular proteins.

Results

Using gel-LC-MS/MS, 251 total cellular proteins were identified from resting human neutrophils. This is more than ten times the number of proteins identified by an initial proteome analysis of human neutrophils and almost five times the number of proteins identified by the first 2-DE map of extracts of rat polymorphonuclear leukocytes. Most of the proteins identified in the present study are well-known, but some of them, such as neutrophil-secreted proteins and centaurin beta-1, a cytoplasmic protein involved in the regulation of NF-κB activity, are described here for the first-time.

Conclusion

The present report provides new information about the protein content of human neutrophils. Importantly, our study resulted in the discovery of a series of proteins not previously reported to be associated with human neutrophils. These data are relevant to the investigation of comparative pathological states and models for novel classes of pharmaceutical drugs that could be useful in the treatment of inflammatory disorders in which neutrophils participate.

Reduced skin inflammatory response in mice lacking inducible nitric oxide synthase

The skin is the largest organ in the body and one of its main functions is to protect the body from environmental and endogenous noxious conditions, such as injury, infection and inflammation. The inducible nitric oxide synthase (iNOS) has been implicated as a key component in the inflammatory response. In the present study, we assessed the role of iNOS in the skin inflammation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). Mice deficient in iNOS had reduced edema and cellular infiltration in the skin following topical TPA application. Moreover, the genetic blockage of iNOS signaling inhibited the TPA-induced ERK and p38 activation resulting in reduced COX-2 upregulation. Finally, immunohistochemical studies revealed that iNOS knockout mice exhibited marked inhibition of AP-1, CREB and NF-kappaB transcriptional factors activation. Together, these results indicate that TPA induces the activation of several iNOS-dependent intracellular signaling pathways that have a key role in the control of inflammatory response in the skin. Therefore, selective iNOS inhibitors may be potentially relevant tools for cutaneous skin disease drug development.

The role of neutrophils in severe sepsis

Neutrophils are key effectors of the innate immune response. Reduction of neutrophil migration to infection sites is associated with a poor outcome in sepsis. We have demonstrated a failure of neutrophil migration in lethal sepsis. Together with this failure, we observed more bacteria in both peritoneal exudates and blood, followed by a reduction in survival rate. Furthermore, neutrophils obtained from severe septic patients displayed a marked reduction in chemotactic response compared with neutrophils from healthy subjects. The mechanisms of neutrophil migration failure are not completely understood. However, it is known that they involve systemic Toll-like receptor activation by bacteria and/or their products and result in excessive levels of circulating cytokines/chemokines. These mediators acting together with LPS stimulate expression of iNOS that produces high amounts of NO, which in turn mediates the failure of neutrophil migration. NO reduced expression of CXCR2 on neutrophils and the levels of adhesion molecules on both endothelial cells and neutrophils. These events culminate in decreased endothelium-leukocyte interactions, diminished neutrophil chemotactic response, and neutrophil migration failure. Additionally, the NO effect, at least in part, is mediated by peroxynitrite. In this review, we summarize what is known regarding the mechanisms of neutrophil migration impairment in severe sepsis.

Biliverdin is the endogenous ligand of human serum alpha1-acid glycoprotein

alpha(1)-Acid glycoprotein (AAG), an acute phase component of the human serum, is a prominent member of the lipocalin family of proteins showing inflammatory/immunomodulatory activities and promiscuous drug binding properties. Both three-dimensional structure of AAG and its precise biological function are still unknown and only a few endogenous AAG ligands have been described to date. CD spectroscopic studies performed with commercial AAG and the separated genetic variants revealed high-affinity binding of biliverdin (BV) and biliverdin dimethyl ester to the 'F1/S' fraction of the protein. The preferential accommodation of the right-handed, P-helicity conformers of the pigments by the protein matrix resulted in strong induced CD activity, which was utilized for estimation of the binding parameters and to locate the binding site. It was concluded that both pigments are bound in the central beta-barrel cavity of AAG, held principally by hydrophobic interactions. Possible biological implications of the BV binding ability of AAG with special emphasis on the heme oxygenase-1 pathway are discussed.