Expression and biology of neutrophil and endothelial cell-derived chemokines

Differences in Sulfotyrosine Binding amongst CXCR1 and CXCR2 Chemokine Ligands

Tyrosine sulfation, a post-translational modification found on many chemokine receptors, typically increases receptor affinity for the chemokine ligand. A previous bioinformatics analysis suggested that a sulfotyrosine (sY)-binding site on the surface of the chemokine CXCL12 may be conserved throughout the chemokine family. However, the extent to which receptor tyrosine sulfation contributes to chemokine binding has been examined in only a few instances. Computational solvent mapping correctly identified the conserved sulfotyrosine-binding sites on CXCL12 and CCL21 detected by nuclear magnetic resonance (NMR) spectroscopy, demonstrating its utility for hot spot analysis in the chemokine family. In this study, we analyzed five chemokines that bind to CXCR2, a subset of which also bind to CXCR1, to identify hot spots that could participate in receptor binding. A cleft containing the predicted sulfotyrosine-binding pocket was identified as a principal hot spot for ligand binding on the structures of CXCL1, CXCL2, CXCL7, and CXCL8, but not CXCL5. Sulfotyrosine titrations monitored via NMR spectroscopy showed specific binding to CXCL8, but not to CXCL5, which is consistent with the predictions from the computational solvent mapping. The lack of CXCL5–sulfotyrosine interaction and the presence of CXCL8–sulfotyrosine binding suggests a role for receptor post-translational modifications regulating ligand selectivity.

Alpha-1 antitrypsin and granulocyte colony-stimulating factor as serum biomarkers of disease severity in ulcerative colitis

BACKGROUND

Initial assessment of patients with ulcerative colitis (UC) is challenging and relies on apparent clinical symptoms and measurements of surrogate markers (e.g., C-reactive protein [CRP] or similar acute phase proteins). As CRP only reliably identifies patients with severe disease, novel biomarkers are currently needed for identification of patients with mild or moderate disease activity. Using a commercially available platform, we aimed at identifying serum biomarkers that are able to grade the disease severity.

METHODS

Serum samples from 65 patients with UC with varying disease activity (Mayo score) and from 40 healthy controls were analyzed by multiplex enzyme-linked immunosorbent assay for 78 potential disease biomarkers. Using the statistical software SIMCA-P+ and GraphPad Prism, multivariate statistical analyses were conducted to identify a limited number of biomarkers to assess disease severity.

RESULTS

Alpha-1 antitrypsin (AAT) differentiated between mild and moderate UC (area under the curve [AUC] = 0.79) with a sensitivity of 0.90 and a specificity of 0.70, thereby exceeding the predictive ability of CRP (AUC = 0.52). Combining alpha-1 antitrypsin and granulocyte colony-stimulating factor produced a predictive model with an AUC of 0.72 when differentiating mild and moderate UC, and an AUC of 0.96 when differentiating moderate and severe UC, the latter being as reliable as CRP.

CONCLUSIONS

Alpha-1 antitrypsin is identified as a potential serum biomarker of mild-to-moderate disease activity in UC. With the ability to differentiate between mild, moderate, and severe stages of UC using a simple serum biomarker that is already commercially available, clinicians can initiate individualized treatment regimens at an earlier stage before endoscopic examinations are available.

Cytokine-induced neutrophil chemotaxis assay

Chemotaxis is directed migration of a cell type to a distant chemoattractant. When this chemoattractant is a cytokine, the term chemokine is often used. Chemotaxis by neutrophils, specifically polymorphonuclear leukocytes (PMNs), plays a critical role in the innate immune response. On an equimolar basis, interleukin-8 (IL-8) is one of the most potent PMN chemokines known. This chapter describes an in vitro chemotaxis technique using PMNs and IL-8 which can serve the investigator as an established model from which new studies can be developed.

Dynamic Expression of Chemokines and the Infiltration of Inflammatory Cells in the HSV-Infected Cornea and its Associated Tissues

BACKGROUND

The chemotactic signals regulating cell trafficking in the herpes simplex virus type 1 (HSV-1) infected cornea are well documented, however, those in the cornea-associated tissues, such as the trigeminal ganglion (TG) and draining lymph nodes (LNs), are largely unknown.

OBJECTIVES

To examine chemokine expression and subsequent cell infiltration in the HSV-1 infected cornea and its associated tissues.

STUDY DESIGN

Eight-week-old female BALB/c mice were infected with 10 mu l HSV-1 (CHR3 strain: 5 x 106 PFU/ml) by corneal scarification. Total RNAs were extracted from the corneas, TGs, and LNs at pre-inoculation, 3 days post-inoculation (P.I.) and 7 days P.I. The mRNA for 28 different chemokines in the extracts was amplified by RT-PCR. Infiltrating cells were identified by immunohistochemistry.

RESULT

After the HSV-1 infection, the corneal stroma became edematous by infiltrated cells under the eroded epithelium. The TG and LNs were markedly swollen. The cornea was infiltrated with granulocytes and CD11b+ cells at 3 days P.I., followed by CD4+ and CD8+ T cells at 12 days P.I. In the TG, CD11b+ cells, but no granulocytes, infiltrated throughout the observation period. T cells migrated into the TG earlier than into the cornea. Gene expressions of neutrophil-attracting chemokines (CXCL1, 2, 3, and 5) increased in the cornea, but they did not enhance in the TG or LNs. On the other hand, gene expressions of chemokines which attract CD11b+ cells such as CCL2, 8, 7, 12, CCL3, 4, and CCL5, increased in the cornea and TG with its peak at 3 days P.I. Gene expressions of chemokines those work on T cells and B cells, such as CCL19, CCL21, CXCL9, CXCL13, CXCL10, XCL1, and CXCL16, were up-regulated and peaked at 3 days P.I. in the cornea and in the TG. Thus, pattern of chemokine gene expression was similar in the cornea and in the TG. On the contrary, gene expressions of chemokines in the draining LNs affecting CD11b+ cells and T cells were temporarily down-regulated.

CONCLUSION

Upon HSV-1 infection, dynamic gene expression of chemokines was observed not only in the inoculated cornea but also in its associated tissues.

The biology of exhaled nitric oxide (NO) in ischemia–reperfusion-induced lung injury: A tale of dynamism of NO production and consumption

The main objective of this paper is to review the potential diagnostic roles of exhaled nitric oxide (NO) in evaluating ischemia-reperfusion-induced lung injury associated with cardiac surgery. We shall start by elaborating on current clinical practice of cardiac surgery and to arrive at the conclusion that clinically important ischemia-reperfusion injury is a common scenario of many forms of these surgical procedures. We shall conclude this part by establishing the clinical need for biomarkers of inflammation in cardiothoracic surgery and by proposing that exhaled NO could be an important new addition to our anaesthetic monitoring repertoire based on our expertise with exhaled breath monitoring. We shall then take a closer look at mechanisms of ischemia-reperfusion injury and will propose the role of reactive oxygen and nitrogen species as mediators and biomarkers of acute lung injury. This analysis will provide a good opportunity to highlight major potential mechanisms of altered NO production and bioactivity of NO. We shall conclude that multiple relevant mechanisms may either lead to increased production of NO or enhance consumption of NO, leaving us with the paradigm that NO maybe used either as a positive or negative biomarker of inflammation. In order to explore this dilemma further, we will investigate the predominant effect of oxidative stress on NO bioactivity in cell culture models of ischemia-reperfusion injury. We will then turn to animal models of ischemia-reperfusion injury to elucidate the ultimate effects of this condition on lung NO production and concentrations of NO in the lung. Finally, we shall complete this journey by highlighting the human relevance of these observations by reviewing our own experience at Harefield Hospital, UK, and that of others, regarding exhaled NO in ischemia-reperfusion injury associated with cardiac surgery and lung transplantation.

Science review: Cell membrane expression (connectivity) regulates neutrophil delivery, function and clearance

As the principal cellular component of the inflammatory host defense and contributor to host injury after severe physiologic insult, the neutrophil is inherently coupled to patient outcome in both health and disease. Extensive research has focused on the mechanisms that regulate neutrophil delivery, function, and clearance from the inflammatory microenvironment. The neutrophil cell membrane mediates the interaction of the neutrophil with the extracellular environment; it expresses a complex array of adhesion molecules and receptors for various ligands, including mediators, cytokines, immunoglobulins, and membrane molecules on other cells. This article presents a review and analysis of the evidence that the neutrophil membrane plays a central role in regulating neutrophil delivery (production, rolling, adhesion, diapedesis, and chemotaxis), function (priming and activation, microbicidal activity, and neutrophil-mediated host injury), and clearance (apoptosis and necrosis). In addition, we review how change in neutrophil membrane expression is synonymous with change in neutrophil function in vivo. Employing a complementary analysis of the neutrophil as a complex system, neutrophil membrane expression may be regarded as a measure of neutrophil connectivity, with altered patterns of connectivity representing functionally distinct neutrophil states. Thus, not only does the neutrophil membrane mediate the processes that characterize the neutrophil lifecycle, but characterization of neutrophil membrane expression represents a technology with which to evaluate neutrophil function.

NF-kappa B regulation in human neutrophils by nuclear I kappa B alpha: correlation to apoptosis

Neutrophils are among the first circulating leukocytes involved in acute inflammatory processes. Transcription factor NF-kappaB plays a key role in the inflammatory response, regulating the expression of proinflammatory and anti-apoptotic genes. Recently we have shown that human neutrophils contain a significant amount of NF-kappaB inhibitor, IkappaBalpha, in the nucleus of unstimulated cells. The present objective was to examine the mechanisms controlling the nuclear content of IkappaBalpha in human neutrophils and to determine whether increased accumulation of IkappaBalpha in the nucleus is associated with increased neutrophil apoptosis. We show for the first time that neutrophil stimulation with pro-inflammatory signals results in degradation of IkappaBalpha that occurs in both cytoplasm and nucleus. Prolonged (2-h) stimulation with TNF and LPS induces resynthesis of IkappaBalpha that is again translocated to the nucleus in human neutrophils, but not in monocytic cells. Leptomycin B, a specific inhibitor of nuclear export, increases nuclear accumulation of IkappaBalpha in stimulated neutrophils by blocking the IkappaBalpha nuclear export, and this is associated with inhibition of NF-kappaB activity, induction of caspase-3 activation, and apoptosis. Based on our data we present a new model of NF-kappaB regulation in human neutrophils by nuclear IkappaBalpha. Our results demonstrate that the NF-kappaB activity in human neutrophils is regulated by mechanisms clearly different from those in monocytes and other human cells and suggest that the increased nuclear content of IkappaBalpha in human neutrophils might represent one of the underlying mechanisms for the increased apoptosis in these cells.

Effect of theophylline on induced sputum inflammatory indices and neutrophil chemotaxis in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterized by a neutrophilic airway inflammation that can be demonstrated by examination of induced sputum. Theophylline has antiinflammatory effects in asthma, and in the present study we investigated whether a similar effect occurs in COPD patients treated with low doses of theophylline. Twenty-five patients with COPD were treated with theophylline (plasma level of 9-11 mg/L) for 4 weeks in a placebo-controlled, randomized, double-blind crossover study. Theophylline was well tolerated. Induced sputum inflammatory cells, neutrophils, interleukin-8, myeloperoxidase, and lactoferrin were all significantly reduced by about 22% by theophylline. Neutrophils from subjects treated with theophylline showed reduced chemotaxis to N-formyl-met-leu-phe (approximately 28%) and interleukin-8 (approximately 60%). Neutrophils from a healthy donor showed reduced chemotaxis (approximately 30%) to induced sputum samples obtained during theophylline treatment. These results suggest that theophylline has antiinflammatory properties that may be useful in the long-term treatment of COPD.

Novel mode of action of iloprost: in vitro down-regulation of endothelial cell adhesion molecules

Iloprost is a stable prostacyclin analog commonly employed in the treatment of peripheral vascular disease and also indicated in the treatment of patients affected by systemic sclerosis (SSc) in the presence of severe Raynaud's phenomenon (RP). Several mechanisms of action of the drug other than vasodilation and antiplatelet effect have been demonstrated that may be involved in the exertion of its clinical efficacy. Aim of the present study was to investigate whether iloprost down-regulated lymphocyte adhesion to endothelium through a modulation of adhesion molecule expression on the surface of endothelial cells. In the presence of iloprost, both lymphocyte adhesion and IL-1 stimulated expression of ICAM-1 and ELAM-1 exhibited a significant reduction, while unstimulated adhesion molecule expression was not significantly affected. Our results confirm that iloprost is able to down-regulate lymphocyte adhesion to endothelial cells and indicate that endothelium itself could be target of iloprost administration. Attenuation of the inflammatory response through modulation of cellular interactions could be suggested as a potential mechanism of action of iloprost, when used in the treatment of pathological conditions characterized by endothelial activation.

CXCR4 on human endothelial cells can serve as both a mediator of biological responses and as a receptor for HIV-2

It has been shown that deletion of the chemokine receptor, CXCR4, causes disordered angiogenesis in mouse models. In the present studies, we examined the distribution and trafficking of CXCR4 in human endothelial cells, tested their responses to the CXCR4 ligand, SDF-1, and asked whether endothelial cell CXCR4 can serve as a cell surface receptor for the binding of viruses. The results show that CXCR4 is present on endothelial cells from coronary arteries, iliac arteries and umbilical veins (HUVEC), but expression was heterogeneous, with some cells expressing CXCR4 on their surface, while others did not. Addition of SDF-1 caused a rapid decrease in CXCR4 surface expression. It also caused CXCR4-mediated activation of MAPK, release of PGI(2), endothelial migration, and the formation of capillary-like structures by endothelial cells in culture. Co-culture of HUVEC with lymphoid cells that were chronically infected with a CD4-independent/CXCR4-tropic variant of HIV-2 resulted in the formation of multinucleated syncytia. Formation of the syncytia was inhibited by each of several different CXCR4 antibodies. Thus, our findings indicate: (1) that CXCR4 is widely expressed on human endothelial cells; (2) the CXCR4 ligand, SDF-1, can evoke a wide variety of responses from human endothelial cells; and (3) CXCR4 on endothelial cells can serve as a receptor for isolates of HIV that can utilize chemokine receptors in the absence of CD4.

Acute inflammatory responses to mechanical lesions in the CNS: differences between brain and spinal cord

Lesion-induced inflammatory responses in both brain and spinal cord have recently become a topic of active investigation. Using C57BL/6J mice, we compared the tissue reaction in these two central nervous system (CNS) compartments with mechanical lesions of similar size involving both grey and white matter. This evaluation included the quantitative assessment of neutrophils, lymphocytes and activated macrophages/microglia, as well as astrocyte activation, upregulation of vascular cell adhesion molecules (ICAM-1, VCAM-1, PECAM) and the extent of blood-brain barrier (BBB) breakdown. Time points analysed post-lesioning included 1, 2, 4 and 7 days (as well as 10 and 14 days for the BBB). We found clear evidence that the acute inflammatory response to traumatic injury is significantly greater in the spinal cord than in the cerebral cortex. The numbers of both neutrophils and macrophages recruited to the lesion site were significantly higher in the spinal cord than in the brain, and the recruitment of these cells into the surrounding parenchyma was also more widespread in the cord. The area of BBB breakdown was substantially larger in the spinal cord and vascular damage persisted for a longer period. In the brain, as in spinal cord, the area to which neutrophils were recruited correlated well with the area of BBB breakdown. It will be of interest to determine the extent to which the infiltration of inflammatory cells contributes, either directly or indirectly, to the vascular permeability and secondary tissue damage or, conversely, to local tissue repair in the brain and the spinal cord.

Interleukin-8 mRNA expression in circulating leucocytes during cardiopulmonary bypass

Interleukin-8 (IL-8) is found in patients following cardiopulmonary bypass (CPB). It may contribute to microvascular injury by activating neutrophils. We examined IL-8 mRNA expression in leucocytes in bypass. IL-8 mRNA levels were measured by Northern analysis and densitometry of isolated mononuclear leucocytes and neutrophils from blood samples taken before, during, and 2 and 48 h after CPB. Plasma IL-8 was measured at each time-point by immunoassay. A strong signal for IL-8 mRNA was detected in neutrophils in five of five and, more weakly, in mononuclear leucocytes of three of five patients studied. The signal peaked consistently during, and fell following bypass, usually to undetectable levels by 48 h. There was always a detectable signal in neutrophils preoperatively. Plasma IL-8 increased from undetectable prebypass levels and peaked later (2 h postbypass) in four of five patients. In the other patient, the cytokine remained detectable throughout. These data demonstrate that IL-8 transcription occurs in leucocytes before and during CPB, but suggest that much of the IL-8 detectable in plasma following bypass may derive, not from these leucocytes, but from other cell types. The release of some IL-8 by neutrophils could lead to local positive feedback in neutrophil recruitment and associated endothelial injury.

A primer on cytokines: sources, receptors, effects, and inducers

Protection against pathogens is a prerequisite for survival of most organisms. To cope with this continuous challenge, complex defense mechanisms have evolved. The construction, adaptation, and maintenance of these mechanisms are under control of an extensive network of regulatory proteins called cytokines. A great number of cytokines have been described over the last 2 decades. This review consists of an overview of cytokines that are involved in immune responses and describes some historical and general aspects as well as prospective clinical applications. Major biological effects together with information on cytokine receptors, producers, inducers, and biochemical and molecular characteristics are listed in tables. In addition, some basic information is given on cytokine receptor signal transduction. Finally, the recent discoveries of cytokine receptors functioning as coreceptors in the pathogenesis of human immunodeficiency virus are summarized.