A novel, NH2-terminal sequence-characterized human monokine possessing neutrophil chemotactic, skin-reactive, and granulocytosis-promoting activity

The COOH-terminal peptide of platelet factor-4 variant (CXCL4L1/PF-4var47-70) strongly inhibits angiogenesis and suppresses B16 melanoma growth in vivo

Chemokines influence tumor growth directly or indirectly via both angiogenesis and tumor-leukocyte interactions. Platelet factor-4 (CXCL4/PF-4), which is released from alpha-granules of activated platelets, is the first described angiostatic chemokine. Recently, it was found that the variant of CXCL4/PF-4 (CXCL4L1/PF-4var) could exert a more pronounced angiostatic and antitumoral effect than CXCL4/PF-4. However, the molecular mechanisms of the angiostatic activities of the PF-4 forms remain partially elusive. Here, we studied the biological properties of the chemically synthesized COOH-terminal peptides of CXCL4/PF-4 (CXCL4/PF-4(47-70)) and CXCL4L1/PF-4var (CXCL4L1/PF-4var(47-70)). Both PF-4 peptides lacked monocyte and lymphocyte chemotactic activity but equally well inhibited (25 nmol/L) endothelial cell motility and proliferation in the presence of a single stimulus (i.e., exogenous recombinant fibroblast growth factor-2). In contrast, when assayed in more complex angiogenesis test systems characterized by the presence of multiple mediators, including in vitro wound-healing (2.5 nmol/L versus 12.5 nmol/L), Matrigel (60 nmol/L versus 300 nmol/L), and chorioallantoic membrane assays, CXCL4L1/PF-4var(47-70) was found to be significantly (5-fold) more angiostatic than CXCL4/PF-4(47-70). In addition, low (7 microg total) doses of intratumoral CXCL4L1/PF-4var(47-70) inhibited B16 melanoma growth in mice more extensively than CXCL4/PF-4(47-70). This antitumoral activity was predominantly mediated through inhibition of angiogenesis (without affecting blood vessel stability) and induction of apoptosis, as evidenced by immunohistochemical and fluorescent staining of B16 tumor tissue. In conclusion, CXCL4L1/PF-4var(47-70) is a potent antitumoral and antiangiogenic peptide. These results may represent the basis for the design of CXCL4L1/PF-4var COOH-terminal-derived peptidomimetic anticancer drugs.

Expression of bovine granulocyte chemotactic protein-2 (GCP-2) in neutrophils and a mammary epithelial cell line (MAC-T) in response to various bacterial cell wall components

CXC chemokines are potential attractants for polymorphonuclear leucocytes (PMNs) and play an important role in resistance to infectious diseases, such as bovine mastitis. In this study, a bovine mammary epithelial cell line (MAC-T) and blood PMNs were stimulated with bacterial cell wall components of gram negative and gram positive bacteria, including lipopolysaccharide (LPS), lipoteichoic acid (LTA) and peptidoglycan (PGN). The expression of two CXC chemokines, interleukin (IL)-8 and granulocyte chemotactic protein (GCP)-2 was analysed by real-time PCR. High concentrations (1 or 10 μg/mL) of LPS and LTA, but not PGN, significantly increased the expression of GCP-2 and IL-8 in both MAC-T and PMNs. Biopsies from mammary glands of cattle with clinical Escherichia coli mastitis also had increased expression of GCP-2. Using an in vitro transepithelial migration assay, recombinant human GCP-2 (rhGCP-2) showed weak chemoattractant effects on bovine blood PMNs. It was concluded that PMNs and MAC-T cells can express GCP-2 in response to certain bacterial cell components during the course of mastitis.

Citrullination of CXCL8 increases this chemokine's ability to mobilize neutrophils into the blood circulation

BACKGROUND

During the first line defense of an infected host, circulating neutrophils invade the inflamed tissue, whereas mature neutrophils from the bone marrow pool migrate into the blood circulation and from there reinforce tissue infiltration. The CXC chemokine CXCL8, also know as interleukin-8, is a potent attractant of neutrophils. Recently, we discovered a new natural post-translational modification of CXCL8, i.e. the deimination of arginine into citrulline by peptidylarginine deiminases.

DESIGN AND METHODS

The ability to provoke leukocytosis was assessed by intravenous administration of citrullinated CXCL8 in rabbits. Adsorption of citrullinated CXCL8 to the Duffy antigen/receptor for chemokines on human or rabbit erythrocytes was evaluated using a competitive binding assay. Finally, surface expression of adhesion molecules was studied after stimulating neutrophils with citrullinated CXCL8.

RESULTS

Citrullination of CXCL8 significantly increased this chemokine's ability to recruit neutrophils into the blood circulation. In addition, the competitive binding properties of CXCL8 for the Duffy antigen/receptor for chemokines were impaired upon citrullination. Since the Duffy antigen/receptor for chemokines is an important scavenging receptor for CXCL8 in the blood stream, citrullination may delay CXCL8 clearance from the circulation. Furthermore, the shedding of CD62L (L-selectin) and the upregulation of CD11b (beta2-integrin) protein expression on CXCL8-induced neutrophils were improved by deimination of CXCL8, possibly contributing to the neutrophil egress from the bone marrow. Conversely, surface expression of CD15, the neutrophilic ligand of endothelial selectins, was equally well upregulated by intact and citrullinated CXCL8.

CONCLUSIONS

These data show that citrullination of CXCL8 enhances leukocytosis, possibly through impaired chemokine clearance from the blood circulation and prolonged presentation to the bone marrow.

Interferon-gamma: a historical perspective

This article reviews the main lines of thinking and exploration that have led to our current conception of the role of IFN-gamma in immune defense and autoimmunity. In 1965 the first report appeared describing production of an interferon-like virus inhibitor in cultured human leukocytes following exposure to the mitogen phytohemagglutinin. In the early 1970s the active principle became recognized as being distinct from classical virus-induced interferons, leading to its designation as immune interferon or Type II interferon, and eventually IFN-gamma. Up to that point interest in the factor had come almost exclusively from virologists, in particular those among them who were believers in interferon. Evidence first coming forward in the 1980s that IFN-gamma is indistinguishable from macrophage-activating factor (MAF), then a prototype lymphokine, was the signal for immunologists at large to become interested. Today IFN-gamma ranks among the most important endogenous regulators of immune responses.

Th17 cytokines interleukin (IL)-17 and IL-22 modulate distinct inflammatory and keratinocyte-response pathways

BACKGROUND

Psoriasis vulgaris is an inflammatory skin disease mediated by Th1 and Th17 cytokines, yet the relative contribution of interferon (IFN)-gamma, interleukin (IL)-17 and IL-22 on disease pathogenesis is still unknown.

OBJECTIVES

In this study, we sought to identify the cytokines produced by skin-resident T cells in normal skin, localize the receptors for these cytokines, and examine how these cytokines alter gene expression profiles of the cells bearing cognate receptors.

METHODS

We used intracellular cytokine staining and flow cytometry to evaluate T cell cytokine production, and immunohistochemistry and double-label immunofluorescence to localize cytokine receptors in skin. Gene array analysis of cytokine-treated keratinocytes was performed using moderated paired t-test controlling for false discovery rate using the Benjamini-Hochberg procedure.

RESULTS

We demonstrate that T-helper cells producing IL-17, IL-22 and/or IFN-gamma, as well as the cells bearing cognate cytokine receptors, are present in normal human skin. Keratinocytes stimulated with IL-17 expressed chemokines that were different from those induced by IFN-gamma, probably contributing to the influx of neutrophils, dendritic cells and memory T cells into the psoriatic lesion. In contrast, IL-22 downregulated genes associated with keratinocyte differentiation and caused epidermal alterations in an organotypic skin model.

CONCLUSIONS

Our results suggest that the Th17 cytokines IL-17 and IL-22 mediate distinct downstream pathways that contribute to the psoriatic phenotype: IL-17 is more proinflammatory, while IL-22 retards keratinocyte differentiation.

Citrullination of CXCL8 by peptidylarginine deiminase alters receptor usage, prevents proteolysis, and dampens tissue inflammation

Biological functions of proteins are influenced by posttranslational modifications such as on/off switching by phosphorylation and modulation by glycosylation. Proteolytic processing regulates cytokine and chemokine activities. In this study, we report that natural posttranslational citrullination or deimination alters the biological activities of the neutrophil chemoattractant and angiogenic cytokine CXCL8/interleukin-8 (IL-8). Citrullination of arginine in position 5 was discovered on 14% of natural leukocyte-derived CXCL8(1-77), generating CXCL8(1-77)Cit(5). Peptidylarginine deiminase (PAD) is known to citrullinate structural proteins, and it may initiate autoimmune diseases. PAD efficiently and site-specifically citrullinated CXCL5, CXCL8, CCL17, CCL26, but not IL-1beta. In comparison with CXCL8(1-77), CXCL8(1-77)Cit(5) had reduced affinity for glycosaminoglycans and induced less CXCR2-dependent calcium signaling and extracellular signal-regulated kinase 1/2 phosphorylation. In contrast to CXCL8(1-77), CXCL8(1-77)Cit(5) was resistant to thrombin- or plasmin-dependent potentiation into CXCL8(6-77). Upon intraperitoneal injection, CXCL8(6-77) was a more potent inducer of neutrophil extravasation compared with CXCL8(1-77). Despite its retained chemotactic activity in vitro, CXCL8(1-77)Cit(5) was unable to attract neutrophils to the peritoneum. Finally, in the rabbit cornea angiogenesis assay, the equally potent CXCL8(1-77) and CXCL8(1-77)Cit(5) were less efficient angiogenic molecules than CXCL8(6-77). This study shows that PAD citrullinates the chemokine CXCL8, and thus may dampen neutrophil extravasation during acute or chronic inflammation.

The role of CXC chemokines and their receptors in cancer

Chemokines, or chemotactic cytokines, and their receptors have been discovered as essential and selective mediators in leukocyte migration to inflammatory sites and to secondary lymphoid organs. Besides their functions in the immune system, they also play a critical role in tumor initiation, promotion and progression. There are four subgroups of chemokines: CXC, CC, CX(3)C, and C chemokine ligands. The CXC or alpha subgroup is further subdivided in the ELR(+) and ELR(-) chemokines. Members that contain the ELR motif bind to CXC chemokine receptor 2 (CXCR2) and are angiogenic. In contrast, most of the CXC chemokines without ELR motif bind to CXCR3 and are angiostatic. An exception is the angiogenic ELR(-)CXC chemokine stromal cell-derived factor-1 (CXCL12/SDF-1), which binds to CXCR4 and CXCR7 and is implicated in tumor metastasis. This review is focusing on the role of CXC chemokines and their receptors in tumorigenesis, including angiogenesis, attraction of leukocytes to tumor sites and induction of tumor cell migration and homing in metastatic sites. Finally, their therapeutic use in cancer treatment is discussed.

Novel perspectives on the pathogenesis of Lonomia obliqua caterpillar envenomation based on assessment of host response by gene expression analysis

Animal venomous secretions have been explored as source of active substances affecting mammal hemostasis. These active principles impinge on key elements of almost all physiologic pathways and have an enormous potential in the development of new therapeutic drugs. The envenomation caused by the caterpillar Lonomia obliqua (lonomism) is characterized by a hemorrhagic clinical profile. Investigations of caterpillar venom have, in general, involved the isolation and biochemical characterization of active principles related to the pathophysiology of envenomation. In the last few years, these studies focused on the caterpillar's secretions pro-coagulant, fibrin(ogen)olytic, hemolytic, edematogenic and nociceptive activities. Recently, a significant advance was achieved as a result of a transcriptome study, which generated a catalog of putative toxic proteins in the caterpillar venom, giving rise to hypotheses on the molecular basis of pathogenesis which could be experimentally explored. In this investigation, using a microarray methodology, we analyzed the effects of the caterpillar venom on the gene expression profile of cultured human fibroblasts with the aim of gaining insight into genes possibly associated with the clinical manifestations of lonomism. Our hypothesis was that both the direct action L. obliqua venomous proteins on the host as well as an indirect effect caused by alteration in the gene expression pattern in host tissues could function in concert and perhaps synergistically to give rise to the profound symptoms observed during lonomism. Interesting changes in the expression pattern of some genes, such as IL-8, prostaglandin-endoperoxide synthase 2, urokinase-type plasminogen activator receptor and tissue factor, were observed in treated fibroblasts, which could contribute to some of the observed pathological sequela in lonomism. Thus, lonomism appears to be a result of both the previously described direct effects of the venom as well as indirect effects caused by changes in host gene expression profiles. These studies have enhanced our understanding of lonomism and may contribute to insights into more effective treatments.

Interleukin-8 modulates growth and invasiveness of estrogen receptor-negative breast cancer cells

Breast cancer, especially estrogen receptor (ER)-negative breast cancer, remains hard to treat despite major advances in surgery and adjuvant therapies. The deletion of ER has been consistently associated with tumor progression, recurrence, metastasis and poor prognosis. Among other differences in biological features, ER-negative breast cancers express high levels of interleukin-8 (IL-8), whereas their ER-positive counterparts do not. IL-8 is a multi-functional cytokine with many important biological functions in tumor formation and development. We aimed to study the role(s) of IL-8 in ER-negative breast cancer progression by using RNA interference to specifically knockdown IL-8 expression in ER-negative breast cancer cell lines MDA-MB-231 and MDA-MB-468. In vitro, suppression of IL-8 led to significant reductions in cell invasion (p<0.001), but had no effects on cell proliferation or cell cycle. In vivo, suppression of IL-8 significantly reduced the microvessel density (p<0.05), and markedly reduced neutrophil infiltration into the tumors (p<0.05). In contrast to in vitro observations, suppression of IL-8 promoted tumor growth in nude mice (p<0.05). Our results imply that the complex roles of IL-8 in the regulation of ER-negative breast cancer progression may in part be related to its potent chemotactic effects on neutrophils, which in turn mediates many of the biological functions of IL-8.

Platelet factor-4 variant chemokine CXCL4L1 inhibits melanoma and lung carcinoma growth and metastasis by preventing angiogenesis

The platelet factor-4 variant, designated PF-4var/CXCL4L1, is a recently described natural non-allelic gene variant of the CXC chemokine platelet factor-4/CXCL4. PF-4var/CXCL4L1 was cloned, and the purified recombinant protein strongly inhibited angiogenesis. Recombinant PF-4var/CXCL4L1 was angiostatically more active (at nanomolar concentration) than PF-4/CXCL4 in various test systems, including wound-healing and migration assays for microvascular endothelial cells and the rat cornea micropocket assay for angiogenesis. Furthermore, PF-4var/CXCL4L1 more efficiently inhibited tumor growth in animal models of melanoma and lung carcinoma than PF-4/CXCL4 at an equimolar concentration. For B16 melanoma in nude mice, a significant reduction in tumor size and the number of small i.t. blood vessels was obtained with i.t. applied PF-4var/CXCL4L1. For A549 adenocarcinoma in severe combined immunodeficient mice, i.t. PF-4var/CXCL4L1 reduced tumor growth and microvasculature more efficiently than PF-4/CXCL4 and prevented metastasis to various organs better than the angiostatic IFN-inducible protein 10/CXCL10. Finally, in the syngeneic model of Lewis lung carcinoma, PF-4var/CXCL4L1 inhibited tumor growth equally well as monokine induced by IFN-gamma (Mig)/CXCL9, also known to attract effector T lymphocytes. Taken together, PF-4var/CXCL4L1 is a highly potent antitumoral chemokine preventing development and metastasis of various tumors by inhibition of angiogenesis. These data confirm the clinical potential of locally released chemokines in cancer therapy.

Relevance of neutrophils in the murine model of haemolytic uraemic syndrome: mechanisms involved in Shiga toxin type 2-induced neutrophilia

It has been demonstrated that infections due to Shiga toxins (Stx) producing Escherichia coli are the main cause of the haemolytic uraemic syndrome (HUS). However, the contribution of the inflammatory response in the pathogenesis of the disease has also been well established. Neutrophils (PMN) represent a central component of inflammation during infections, and patients with high peripheral PMN counts at presentation have a poor prognosis. The mouse model of HUS, by intravenous injection of pure Stx type 2 (Stx2), reproduces human neutrophilia and allows the study of early events in the course of Stx2-induced pathophysiological mechanisms. The aim of this study was to address the contribution of PMN on Stx2 toxicity in a murine model of HUS, by evaluating the survival and renal damage in mice in which the granulocytic population was depleted. We found that the absence of PMN reduced Stx2-induced lethal effects and renal damage. We also investigated the mechanisms underlying Stx2-induced neutrophilia, studying the influence of Stx2 on myelopoyesis, on the emergence of cells from the bone marrow and on the in vivo migration into tissues. Stx2 administration led to an accelerated release of bone marrow cells, which egress at an earlier stage of maturation, together with an increase in the proliferation of myeloid progenitors. Moreover, Stx2-treated mice exhibited a lower migratory capacity to a local inflammatory site. In conclusion, PMN are essential in the pathogenesis of HUS and neutrophilia is not merely an epiphenomenon, but contributes to Stx2-damaging mechanism by potentiating Stx2 toxicity.

Synergy in cytokine and chemokine networks amplifies the inflammatory response

The inflammatory response is a highly co-ordinated process involving multiple factors acting in a complex network as stimulators or inhibitors. Upon infection, the sequential release of exogenous agents (e.g. bacterial and viral products) and induction of endogenous mediators (e.g. cytokines and chemokines) contribute to the recruitment of circulating leukocytes to the inflamed tissue. Microbial products trigger multiple cell types to release cytokines, which in turn are potent inducers of chemokines. Primary cytokines act as endogenous activators of the immune response, whereas inducible chemokines act as secondary mediators to attract leukocytes. Interaction between exogenous and endogenous mediators thus enhances the inflammatory response. In this review, the synergistic interaction between cytokines to induce chemokine production and the molecular mechanisms of the cooperation amongst co-induced chemokines to further increase leukocyte recruitment to the site of inflammation are discussed.

Gelatinase B/matrix metalloproteinase-9 provokes cataract by cleaving lens betaB1 crystallin

Cataract is a common cause of blindness and results from destruction of the microarchitecture of the lens. It is observed in many genetic syndromes, infections, inflammatory diseases and during aging. Fluctuations in lens density and light scattering by altered refraction index form the physical basis for this process, but the pathogenesis is poorly understood. Increased levels of gelatinase B/matrix metalloproteinase-9 have been reported for cataract-associated disorders such as eye inflammation and diabetes. We demonstrate that incubation of lenses with gelatinase B leads immediately to cataract. In complete eye extracts, betaB1 crystallin was identified as the major gelatinase B substrate by combination of proteomics, mass spectrometry, and Edman degradation analysis. The cleavage of betaB1 crystallin was also observed in vivo after endogenous gelatinase B-induction by the chemokine granulocyte chemotactic protein-2 in wild-type mice but not in gelatinase B-/- mice.

Early hemoperfusion with an immobilized polymyxin B fiber column eliminates humoral mediators and improves pulmonary oxygenation

Introduction

The objective of this study was to clarify the efficacy and mechanism of action of direct hemoperfusion with an immobilized polymyxin B fiber column (DHP-PMX) in patients with acute lung injury or acute respiratory distress syndrome caused by sepsis.

Method

Thirty-six patients with sepsis were included. In each patient a thermodilution catheter was inserted, and the oxygen delivery index and oxygen consumption index were measured. DHP-PMX was performed in patients with a normal oxygen delivery index and oxygen consumption index (> 500 ml/minute per m² and >120 ml/minute per m², respectively). The Acute Physiology and Chronic Health Evaluation II score was used as an index of the severity of sepsis, and survival was assessed after 1 month. The humoral mediators measured were the chemokine IL-8, plasminogen activator inhibitor-1, and neutrophil elastase (NE). These mediators were measured before DHP-PMX treatment, and at 24, 48, and 78 hours after the start of treatment. The arterial oxygen tension (PaO₂)/fractional inspired oxygen (FiO₂) ratio was measured before DHP-PMX treatment and at 24, 48, 72, 92, and 120 hours after the start of treatment.

Results

All patients remained alive after 1 month. Before DHP-PMX treatment, the Acute Physiology and Chronic Health Evaluation II score was 24 ± 2.0, the IL-8 level was 54 ± 15.8 pg/ml, plasminogen activator inhibitor-1 was 133 ± 28.1 ng/ml, and NE was 418 ± 72.1 μg/l. These three humoral mediators began to decrease from 24 hours after DHP-PMX treatment, and the decline became significant from 48 hours onward. The PaO₂/FiO₂ ratio was 244 ± 26.3 before DHP-PMX treatment but improved significantly from 96 hours onward. There were significant negative correlations between the PaO₂/FiO₂ ratio and blood levels of NE and IL-8.

Conclusion

The mechanism of action of DHP-PMX is still not fully understood, but we report the following findings. The mean blood levels of plasminogen activator inhibitor-1, NE, and IL-8 were significantly decreased from 48 hours after DHP-PMX treatment. The mean PaO₂/FiO₂ ratio was significantly improved from 96 hours after DHP-PMX treatment. Improvement in the PaO₂/FiO₂ ratio appeared to be related to the decreases in blood NE and IL-8 levels.

Chemokines synergize in the recruitment of circulating neutrophils into inflamed tissue

The innate immune response against micro-organisms is mediated by phagocytes, attracted by chemokines and other G protein-coupled receptor (GPCR) ligands. Originally, we observed increased neutrophil migration by the interaction of inflammatory CXC chemokines such as IL-8/CXCL8 and granulocyte chemotactic protein (GCP)-2/CXCL6 with regakine-1, a CC chemokine constitutively present in plasma. We here demonstrate statistically significant synergy between regakine-1 and the neutrophil attractants C5a or IL-8/CXCL8 in inducing neutrophil shape change and migration under agarose. In addition, regakine-1 attracted human bone marrow granulocytes and enhanced their chemotactic response to IL-8/CXCL8 in a dose-dependent manner. Thus, plasma chemokines may regulate the number of circulating leukocytes under homeostatic conditions and may facilitate extra recruitment of bone marrow neutrophils during inflammation. Indeed, in vivo, regakine-1 provoked a mild neutrophilia in rabbits upon intravenous injection. We also observed that the CC chemokines regakine-1 and monocyte chemotactic protein-3/CCL7 as well as the CXC chemokine stromal cell-derived factor-1alpha/CXCL12 co-operated with murine GCP-2 after intraperitoneal co-administration to increase neutrophil influx in mice. These data demonstrate that inducible and constitutive GPCR ligands synergize to enhance inflammation and facilitate a more effective immune response.

GCP-2/CXCL6 synergizes with other endothelial cell-derived chemokines in neutrophil mobilization and is associated with angiogenesis in gastrointestinal tumors

The precise role of chemokines in neovascularization during inflammation or tumor growth is not yet fully understood. We show here that the chemokines granulocyte chemotactic protein-2 (GCP-2/CXCL6), interleukin-8 (IL-8/CXCL8), and monocyte chemotactic protein-1 (MCP-1/CCL2) are co-induced in microvascular endothelial cells after stimulation with pro-inflammatory stimuli. In contrast with its weak proliferative effect on endothelial cells, GCP-2 synergized with MCP-1 in neutrophil chemotaxis. This synergy may represent a mechanism for tumor development and metastasis by providing efficient leukocyte infiltration in the absence of exogenous immune modulators. To mimic endothelial cell-derived GCP-2 in vivo, GCP-2 was intravenously injected and shown to provoke a dose-dependent systemic response, composed of an immediate granulopenia, followed by a profound granulocytosis. By immunohistochemistry, GCP-2 was further shown to be expressed by endothelial cells from human patients with gastrointestinal (GI) malignancies. GCP-2 staining correlated with leukocyte infiltration into the tumor and with the expression of the matrix metalloproteinase-9 (MMP-9/gelatinase B). Together with previous findings, these data suggest that the production of GCP-2 by endothelial cells within the tumor can contribute to tumor development through neovascularization due to endothelial cell chemotaxis and to tumor cell invasion and metastasis by attracting and activating neutrophils loaded with proteases that promote matrix degradation.

Chemokine-protease interactions in cancer

Solid tumour and leukemic cells expressing chemokine receptors, metastasize to chemokine-secreting organs. Chemokines indirectly affect tumour development by attracting immunocompetent cells with pro- or anti-tumoral activities. Various membrane-associated and soluble proteases selectively cleave specific chemokines. Precursor plasma chemokines (CXCL7, CCL14) need to be proteolytically processed to obtain receptor affinity. Angiogenic CXC chemokines (CXCL1, CXCL8) have increased CXCR1/CXCR2 affinity after limited NH2-terminal processing, whereas truncated angiostatic chemokines (CXCL10) show lower CXCR3 affinity without loss of angiostatic potential. NH2-terminally cleaved monocyte chemotactic proteins (CCL2, CCL7, CCL8) have impaired capacity to attract tumour-associated macrophages and function as receptor antagonists for intact CC chemokines. Migration of Th1/CCR5+ and Th2/CCR4+ effector lymphocytes toward CCR5 (CCL5, CCL3L1) and CCR4 (CCL22) ligands is affected by cleavage. Although proteolytical processing of chemokines is well studied in vitro, the direct or indirect effects on tumour invasion and metastasis are only poorly evaluated.

Rabbit neutrophil chemotactic protein (NCP) activates both CXCR1 and CXCR2 and is the functional homologue for human CXCL6

Neutrophil chemotactic protein (NCP) is a rabbit CXC chemokine with activating and chemotactic properties on neutrophilic granulocytes. Although its selective activity on neutrophils is demonstrated, its interactions with specific chemokine receptors are not defined. For further functional characterization, NCP was chemically synthesized and was found to be equipotent as natural NCP in neutrophil chemotaxis. To identify its human homologue, we separately expressed two potential rabbit NCP receptors (CXCR1 and CXCR2) in Jurkat cells. Pure synthetic NCP was equally efficient to promote chemotaxis through either rabbit CXCR1 or CXCR2. Moreover, chemotaxis assays on rabbit CXCR1 and CXCR2 transfectants showed that NCP uses the same receptors as interleukin-8 (IL-8), a major rabbit CXC chemokine, but not rabbit GROalpha, which only recognized CXCR2. In addition, specific inhibitors for CXCR1 or CXCR2 reduced rabbit neutrophil chemotaxis induced by NCP and rabbit IL-8. Furthermore, NCP and the structurally related human CXCR1/CXCR2 agonist CXCL6/GCP-2 (granulocyte chemotactic protein-2) cross-desensitized each other in intracellular calcium release assays on human neutrophils, further indicating that both chemokines share the same receptors. The inflammatory role of NCP was also evidenced by its potent granulocytosis inducing capacity in rabbits upon systemic administration. This study provides in vitro and in vivo evidences that NCP is the functional rabbit homologue for human CXCL6/GCP-2 rather than the most related CXCR2 agonist CXCL5/ENA-78 (epithelial cell-derived neutrophil activating peptide-78). It is concluded that the rabbit is a better model to study human neutrophil activation compared to mice, which lack CXCL8/IL-8.

Increased CXCL8 (IL-8) expression in Multiple Sclerosis

Multiple Sclerosis (MS) is a chronic inflammatory disease of the CNS which is characterized by large mononuclear cell infiltration and significant demyelination. CXCL8 is a chemo-attractant for both neutrophils and monocytes and triggers their firm adhesion to endothelium. In this study, we demonstrate that serum CXCL8 and CXCL8 secretion from PBMCs are significantly higher in untreated MS patients compared to controls and are significantly reduced in MS patients receiving interferon-beta1a therapy. We suggest that CXCL8 may serve as a marker of monocyte activity in MS and may play a role in monocyte recruitment to the CNS.

Clinical significance of gelatinases in septic arthritis of native and replaced knees

We hypothesized that more gelatinases appear in effusions of septic arthritis than aseptic arthritis. This study examined the laboratory variables of inflammation and the levels of gelatinase A and B (matrix metalloproteinases-2 and -9) in 75 effusions from the knees of 37 patients with inflammatory arthritis and compared them with effusions of septic and aseptic arthritis. Gelatin zymography revealed that the levels of the latent matrix metalloproteinase-9 were higher in 24 effusions of septic arthritis than in 51 effusions of aseptic arthritis. The latent matrix metalloproteinase-9 levels of septic arthritis also correlated with the neutrophil counts in effusions. Significantly more activated matrix metalloproteinases-2 and -9 appeared in effusions of septic arthritis in native and replaced knees than in effusions of aseptic arthritis. A high matrix metalloproteinase-9 level and the appearance of activated matrix metalloproteinases-2 and -9 may distinguish septic from aseptic arthritis, even in cases with a low neutrophil count in the replaced knee. Joint aspiration may not only reduce the bacteria counts, endotoxins, and proinflammatory cytokines, but also decrease the amount of matrix metalloproteinases in effusions that attack the extracellular matrix of native and artificial joints.

Cloning and characterization of guinea pig interleukin-8 receptor

CXC-chemokine receptors 1 and 2 and their ligands (CXCL1, 2, 3, 5, 6, 7, and 8) induce the selective recruitment of neutrophils during inflammation. Such receptors have not been characterized yet in guinea pig, an animal inflammation model of interest. We report the identification, cloning, and characterization of a CXCL8 receptor in guinea pig. Human CXCL8 produced in vivo neutrophilia, chemotaxis and intracellular calcium release of guinea pig neutrophils. The expression of this receptor at their neutrophil surface was investigated. The cDNA encoding a functional CXCL8 receptor was cloned from guinea pig neutrophils and sequenced. It was synthesized using RT-PCR, with oligonucleotide primers derived from well conserved regions of published CXCL8 receptors. This sequence presented an open reading frame coding for 352 amino acids and shares, at the amino acid level, 70 and 69% identity with human and rabbit CXCR2, respectively. The receptor was mainly expressed in neutrophils but it was also present in kidney, lung, spleen and, to a less extent, in heart. Cloned receptor transfected cells showed that this receptor displayed high affinity for human CXCL8, slightly lower than the affinity observed with guinea pig neutrophils. CXC chemokines from both rabbit and human were shown to induce inositol phosphate accumulation in these transfected cells. Receptor binding and activation characteristics together with sequence homology suggested that we identified a guinea pig equivalent of the human CXCR2 receptor.

Gelatinase B/MMP-9 and neutrophil collagenase/MMP-8 process the chemokines human GCP-2/CXCL6, ENA-78/CXCL5 and mouse GCP-2/LIX and modulate their physiological activities

On chemokine stimulation, leucocytes produce and secrete proteolytic enzymes for innate immune defence mechanisms. Some of these proteases modify the biological activity of the chemokines. For instance, neutrophils secrete gelatinase B (matrix metalloproteinase-9, MMP-9) and neutrophil collagenase (MMP-8) after stimulation with interleukin-8/CXCL8 (IL-8). Gelatinase B cleaves and potentiates IL-8, generating a positive feedback. Here, we extend these findings and compare the processing of the CXC chemokines human and mouse granulocyte chemotactic protein-2/CXCL6 (GCP-2) and the closely related human epithelial-cell derived neutrophil activating peptide-78/CXCL5 (ENA-78) with that of human IL-8. Human GCP-2 and ENA-78 are cleaved by gelatinase B at similar rates to IL-8. In addition, GCP-2 is cleaved by neutrophil collagenase, but at a lower rate. The cleavage of GCP-2 is exclusively N-terminal and does not result in any change in biological activity. In contrast, ENA-78 is cleaved by gelatinase B at eight positions at various rates, finally generating inactive fragments. Physiologically, sequential cleavage of ENA-78 may result in early potentiation and later in inactivation of the chemokine. Remarkably, in the mouse, which lacks IL-8 which is replaced by GCP-2/LIX as the most potent neutrophil activating chemokine, N-terminal clipping and twofold potentiation by gelatinase B was also observed. In addition to the similarities in the potentiation of IL-8 in humans and GCP-2 in mice, the conversion of mouse GCP-2/LIX by mouse gelatinase B is the fastest for any combination of chemokines and MMPs so far reported. This rapid conversion was also performed by crude neutrophil granule secretion under physiological conditions, extending the relevance of this proteolytic cleavage to the in vivo situation.

Phenotypic and functional characterization of blood gammadelta T cells in sleep apnea

Hypoxia-induced lymphocyte dysfunction may be implicated in endothelial cell damage in obstructive sleep apnea (OSA) syndrome. gammadelta T cells' unique migration, cytotoxic features, and accumulation in atherosclerotic plaques are considered critical in cardiovascular disorders. We characterized the phenotype, cytokine profile, adhesion properties, and cytotoxicity of gammadelta T cells in patients with OSA and control subjects. The following is a summary of our major findings regarding OSA gammadelta T cells: (1) a significant increase in the expression of the inhibitory natural killer B1 receptors was found; (2) the intracellular content of proinflammatory cytokines tumor necrosis factor (TNF)-alpha and interleukin-8 was increased, and the content of the antiinflammatory cytokine interleukin-10 was decreased; (3) gammadelta T cells of patients with OSA adhered significantly more avidly to nonactivated endothelial cells in culture than those of control subjects; (4) L-selectin expression was higher; (5) anti-E/P-selectin antibodies and anti-TNF-alpha antibodies decreased the adhesion index of OSA gammadelta T lymphocytes/endothelial cells but not of control subjects; and (6) cytotoxicity of OSA gammadelta T lymphocytes against endothelial cells in culture was 2.5-fold higher than that of control subjects and could be prevented by pretreatment with anti-TNF-alpha. Collectively these data implicate gammadelta T lymphocyte function in atherogenic sequelae in OSA.

Identification of interleukin-8 converting enzyme as cathepsin L

IL-8 is produced by various cells, and the NH(2)-terminal amino acid sequence of IL-8 displays heterogeneity among cell types. The mature form of IL-8 has 72 amino acids (72IL-8), while a precursor form (77IL-8) of IL-8 has five additional amino acids to the 72IL-8 NH(2)-terminal. However, it has been unclear how IL-8 is processed to yield the mature form. In this study, converting enzyme was purified as a single 31-kDa band on silver-stained polyacrylamide gel from 160 l of cultured fibroblast supernatant by sequential chromatography. NH(2)-terminal amino acid sequence analysis revealed a sequence, EAPRSVDWRE, which was identified as a partial sequence of cathepsin L. Polyclonal antibodies raised against cathepsin L recognized the purified converting enzyme on Western blot. Moreover, human hepatic cathepsin L cleaved 77IL-8 between Arg(5) and Ser(6), which is the same cleavage site as the putative converting enzyme, resulting in 72IL-8 formation. These data indicate that the converting enzyme of the partially purified fraction of the human fibroblast culture supernatant was cathepsin L. Furthermore, 72IL-8 was sevenfold more potent than 77IL-8 in a neutrophil chemotaxis assay. These results show that cathepsin L is secreted from human fibroblasts in response to external stimuli and plays an important role in IL-8 processing in inflammatory sites.

Modulation of growth factor/cytokine synthesis and signaling by 1alpha,25-dihydroxyvitamin D(3): implications in cell growth and differentiation

Distinct from its classic functions in the regulation of calcium and phosphorus metabolism as a systemic hormone, 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)] is involved in the local control and regulation of cellular growth and differentiation in various tissues, including epidermis (keratinocytes) and bone (osteoblasts and osteoclasts). In this review, the impact of 1alpha,25(OH)(2)D(3) on growth factor/cytokine synthesis and signaling is discussed, particularly as it pertains to bone cells and keratinocytes. 1alpha,25(OH)(2)D(3) not only regulates growth factor/cytokine synthesis but may also alter growth factor signaling. Recently discovered examples for such interactions are the interactions between the vitamin D receptor and the mothers against decapentaplegic-related proteins that function downstream of TGFbeta receptors. Inhibitory effects of 1alpha,25(OH)(2)D(3) on keratinocytes through TGFbeta activation and IL-1alpha, IL-6, and IL-8 suppression may provide a rationale for its beneficial effects in the treatment of hyperproliferative skin disorders, whereas stimulatory effects through the epidermal growth factor-related family members and platelet-derived growth factor may be operative in its beneficial effects in skin atrophy and wound healing. Modulation of cytokines and growth factors by 1alpha,25(OH)(2)D(3) during bone remodeling plays an important role in the coupling of osteoblastic bone formation with osteoclastic resorption to maintain bone mass.

A monoclonal antibody and an enzyme immunoassay for human Ala-IL-8(77)

Interleukin-8 (IL-8) plays a central role in neutrophil chemotaxis and exerts a wide range of effects on various cells, ranging from tumor angiogenesis to impairment of neuronal signaling. Two main forms of IL-8 exist, one containing 77 amino acids (Ala-IL-8(77)) and a second containing 72 amino acids (Ser-IL-8(72)), which comprise more than 90% of IL-8 protein in cell cultures. IL-8(77) was reported to be produced predominantly by endothelial cells and is known as "endothelial" IL-8. IL-8(72) predominates in monocyte cultures and is known as "leukocyte" IL-8. While both forms have equal chemotactic activity in vivo, recent data suggest that their biological activities might be different. Here we describe the generation of a mouse monoclonal antibody (mAb) specific for IL-8(77) and the development of a corresponding immunoassay. Various immunization protocols were investigated. Immunization with conjugates of a peptide from the N-terminus of IL-8(77) (NTP(77)) resulted in the production of an IgG1 mAb (N11) that recognizes human IL-8(77) and neutralizes its chemotactic activity. A sensitive ELISA specific for IL-8(77) was developed using N11 for capture and a biotinylated mAb to IL-8(72) for detection. Using this immunoassay it was shown that the only form of IL-8 secreted in cell culture was IL-8(77) and that the IL-8(72) present was the result of proteolysis of IL-8(77). IL-8(77) was detected in plasma and cerebrospinal fluid (CSF) from patients with sepsis and meningitis.

Recombinant mouse granulocyte chemotactic protein-2: production in bacteria, characterization, and systemic effects on leukocytes

Granulocyte chemotactic protein-2 (GCP-2) is an important neutrophil chemotactic factor in the mouse that belongs to the CXC chemokine family. Although the local tissular effects of chemokines are well known, only recently has the systemic regulation of leukocytes become accepted. To study the pharmacokinetics of mouse GCP-2 and the systemic effects on leukocytes, we expressed a potent natural isoform of mouse GCP-2, GCP-2(9-78), in Escherichia coli and produced electrophoretically pure material. GCP-2(9-78) was 10-fold more potent to chemoattract neutrophils than recombinant GCP-2(5-78). After intravenous (i.v.) injection in mice, GCP-2(9-78) persisted in the circulation with an average half-life of 42 min. When a bolus of 1 mg/kg recombinant mouse GCP-2(9-78) was injected systemically, a significant effect on circulating leukocytes was observed. After a neutropenic phase, at its height at 1 h after injection, neutrophil numbers increased to a maximum at 4 h postinjection, and a concomitant decrease in lymphocyte numbers was observed. In control mice injected with isotonic saline, changes in leukocyte numbers were less pronounced and followed a different kinetic. Whereas tissular neutrophil chemotaxis to GCP-2 is influenced by gelatinase B, the systemic effects on neutrophilia and lymphopenia were not different in gelatinase B-deficient and wild-type mice. These data reinforce the idea that chemokines, including GCP-2, influence the homeostasis of circulating leukocyte numbers.

Identification and analysis of an interleukin 8-like molecule in rainbow trout Oncorhynchus mykiss

An interleukin 8 (IL-8) homologue has been identified in the rainbow trout Oncorhynchus mykiss. The transcript contains an open reading frame of 294 nucleotides that translates into a 97 amino acid putative peptide, with 5' and 3' untranslated regions (UTR) of 171 and 453 nucleotides, respectively. As with previously sequenced lamprey and flounder genes, the trout amino acid sequence lacks the typical ELR motif upstream of the first pair of cysteines, where DLR is present. The trout IL-8 gene contains four exons divided by three short introns of 341, 247 and 292bp, and occupies 1824bp of genomic DNA. RT-PCR reveals a low level constitutive expression of the IL-8 homologue in many tissues, including spleen, heart, liver, head kidney and gill. Expression was not detectable in the brain. Whilst no apparent affect of lipopolysaccharide (LPS) on IL-8 expression was observed in vivo, stimulation of a trout macrophage cell line (RTS-11) with either LPS or poly I:C did result in clear up-regulation of IL-8 expression, detectable by RT-PCR and Northern blot analysis.

Neutrophil gelatinase B and chemokines in leukocytosis and stem cell mobilization

Leukocytosis is a physiopathological mechanism primarily to combat infections, whereas stem cell mobilization is induced for therapeutical purposes. Both processes are dependent on the balance between leukocyte and stem cell retention and mobilization. The retention is mediated by the specific architecture of the bone marrow, adhesion molecules and the production of chemokines in the bone marrow, which attract escaped immature cells to the marrow. Mobilization is the effect of the action of "peripheral" chemokines, such as interleukin-8 (IL-8 or CXCL8) and the remodeling of the matrix and basement membranes by matrix enzymes, such as gelatinase B (MMP-9). Recent studies lead to the conclusion that neutrophils, IL-8/CXCL8 and gelatinase B/MMP-9 play control roles in leukocytosis and stem cell mobilization. Neutrophils are the predominant circulating leukocyte type and IL-8/CXCL8 is the major neutrophil chemoattractant in humans. Gelatinase B and no gelatinase A is rapidly released from prestored granules after activation of neutrophils by IL-8/CXCL8. Moreover, neutrophils do not produce TIMP-1 and can chemically activate latent progelatinase B. Activated gelatinase B catalyses the aminoterminal truncation of IL-8/CXCL8 into a tenfold more potent chemokine. This implies that, when IL-8/CXCL8 appears in the circulation, the bone marrow is instructed to release neutrophils and concomitantly stem cells. These studies suggest that IL-8/CXCL8 and gelatinase B/MMP-9 are targets for the modulation of stem cell mobilization.

Gene cloning of a new plasma CC chemokine, activating and attracting myeloid cells in synergy with other chemoattractants

Chemokines are important mediators of cell migration during inflammation and normal leukocyte trafficking. Inflammatory chemokines are induced in multiple cell types at sites of infection. Here, we describe a novel bovine CC chemokine, designated regakine-1, that is constitutively present at high concentrations in plasma. Cloning of its gene revealed an expected two intron/three exon organization, with a rather long first intron. In addition to a 21-residue signal peptide, the coding sequence corresponded to a 71-residue secreted protein. However, the natural regakine-1 protein missed the COOH-terminal lysine residue. Regakine-1 has only weak sequence similarity (<50% identical residues) with other animal or human chemokines. Northern blot analysis demonstrated regakine-1 RNA expression in spleen and lung. At physiological concentrations (30-100 ng/mL), natural 7.5 kDa regakine-1 stimulated gelatinase B release from neutrophils and chemoattracted immature myeloid HL-60 cells, as well as mature granulocytes. Regakine-1 was more potent on human myeloid cells than the human plasma CC chemokine hemofiltrate CC chemokine-1 (HCC-1). Moreover, regakine-1 synergized with the bacterial peptide N-formylmethionylleucylphenylalanine (fMLP), yielding a 10-fold increase in neutrophil chemotactic response above their additive effect. Regakine-1 did not compete with interleukin-8 (IL-8) for binding to neutrophils, nor did it affect fMLP-induced calcium signaling, suggesting that regakine-1 recognizes a different receptor. In view of its high constitutive plasma concentration, regakine-1 is believed to recruit myeloid cells into the circulation, whereas its synergy with other neutrophil chemoattractants suggests that it also enhances the inflammatory response to infection.

Tumor angiogenesis induced by granulocyte chemotactic protein-2 as a countercurrent principle

Chemokine production by tumors is a well-known phenomenon, but its role in tumor biology remains debatable. Although intratumoral injection of granulocyte chemotactic protein-2 (GCP-2) had no effect on tumor parameters, needle-free stable expression of the chemokine resulted in enhanced tumor growth. It is shown here that tumors that express a potent form of GCP-2 induce a strong influx and activation of tumor-associated neutrophils. The production of GCP-2 leads to intratumoral expression of gelatinase B and advantage for tumor growth by increased angiogenesis. These results are in line with the countercurrent principle of chemokine action and support the notion that paraneoplastic expression of ELR-positive CXC chemokines has to be blocked rather than stimulated in cancer therapy.

CXC chemokine redundancy ensures local neutrophil recruitment during acute inflammation

Previous publications demonstrated that elevated systemic levels of interleukin (IL)-8 decrease local neutrophil recruitment. We tested whether sustained, high plasma levels of IL-8 would prevent local inflammation after inflammatory insults. Mice carrying the transgene for human IL-8 were separated on the basis of their plasma levels of IL-8 into IL-8-positive (plasma levels >90 ng/ml) and IL-8-negative (IL-8 below detection). Presence of the IL-8 transgene did not improve survival or morbidity nor did it alter peritoneal neutrophil recruitment induced by the cecal ligation and puncture model of sepsis. In an acute lung injury model created by intratracheal injection of acid, IL-8-positive mice showed no reduction in alveolar neutrophil recruitment. There was no difference in the local recruitment of neutrophils when either thioglycollate or glycogen was injected intraperitoneally. We examined the chemotactic response to murine chemokines to test how neutrophil recruitment occurs in the setting of elevated plasma IL-8 and found that neutrophils from both IL-8-positive and -negative mice respond equally well to recombinant KC or macrophage inflammatory protein (MIP)-2. We measured KC and MIP-2 in the peritoneum after thioglycollate injection and demonstrated that IL-8-positive mice have significantly higher levels of the chemokines compared to the IL-8-negative mice. Antibody inhibition of KC and MIP-2 in the IL-8-positive mice significantly decreased peritoneal neutrophil recruitment in response to thioglycollate, clarifying their important role in the local neutrophil recruitment. Our data demonstrate that despite the presence of high plasma levels of IL-8, neutrophils may still be recruited to sites of local inflammation because of chemokine redundancy.

Diverging binding capacities of natural LD78beta isoforms of macrophage inflammatory protein-1alpha to the CC chemokine receptors 1, 3 and 5 affect their anti-HIV-1 activity and chemotactic potencies for neutrophils and eosinophils

Recently, the LD78beta isoform of the CC chemokine macrophage inflammatory protein (MIP)-1alpha was shown to efficiently chemoattract lymphocytes and monocytes and to inhibit infection of mononuclear cells by R5 HIV-1 strains. We have now demonstrated that after cleavage of the NH2-terminal Ala-Pro dipeptide by CD26, LD78beta(3 - 70) became the most potent chemokine blocking HIV-1. LD78beta(3 - 70) competed tenfold more efficiently than LD78beta(1 - 70) with [125I] RANTES for binding to the CC chemokine receptors CCR5 and CCR1. Contrary to LD78alpha, LD78beta(1 - 70) at 30 ng/ml efficiently competed with [125I] RANTES for binding to CCR3 and mobilized calcium in CCR3 transfectants, whereas LD78beta(3 - 70) showed a 30-fold decrease in CCR3 affinity compared to LD78beta(1 - 70). This demonstrates the importance of the penultimate proline in LD78beta(1 - 70) for CCR3 recognition. Both LD78beta isoforms efficiently chemoattracted eosinophils from responsive donors. In contrast, only the CCR3 agonist LD78beta(1 - 70) and not LD78beta(3 - 70), induced calcium increases in eosinophils with low levels of CCR1. In responder neutrophils, LD78beta(3 - 70) elicited calcium fluxes at a 30-fold lower dose (10 ng/ml) compared to intact LD78beta and LD78alpha, whereas the three MIP-1alpha isoforms were equipotent neutrophil chemoattractants. Taken together, both LD78beta isoforms are potent HIV-1 inhibitors (CCR5) and activators for neutrophils (CCR1) and eosinophils (CCR1, CCR3), affecting infection and inflammation.

Identification of a blood-derived chemoattractant for neutrophils and lymphocytes as a novel CC chemokine, Regakine-1

Chemokines constitute a large family of chemotactic cytokines that selectively attract different blood cell types. Although most inflammatory chemoattractants are only induced and released in the circulation during acute infection, a restricted number of CXC and CC chemokines are constitutively present in normal plasma at high concentrations. Here, such a chemotactic protein was purified to homogeneity from serum and fully identified as a novel CC chemokine by mass spectrometry and amino acid sequence analysis. The protein, tentatively designated Regakine-1, shows less than 50% sequence identity with any known chemokine. This novel CC chemokine chemoattracts both neutrophils and lymphocytes but not monocytes or eosinophils. Its modest chemotactic potency but high blood concentration is similar to that of other chemokines present in the circulation, such as hemofiltrate CC chemokine-1, platelet factor-4, and beta-thromboglobulin. Regakine-1 did not induce neutrophil chemokinesis. However, it synergized with the CXC chemokines interleukin-8 and granulocyte chemotactic protein-2, and the CC chemokine monocyte chemotactic protein-3, resulting in an at least a 2-fold increase of the neutrophil and lymphocyte chemotactic response, respectively. The biologic effects of homogeneous natural Regakine-1 were confirmed with chemically synthesized chemokine. Like other plasma chemokines, it is expected that Regakine-1 plays a unique role in the circulation during normal or pathologic conditions.

Identification of a possible association between carbon tetrachloride-induced hepatotoxicity and interleukin-8 expression

Hepatotoxicants can elicit liver damage by various mechanisms that can result in cell necrosis and death. The changes induced by these compounds can vary from gross alterations in DNA repair mechanisms, protein synthesis, and apoptosis, to more discrete changes in oxidative damage and lipid peroxidation. However, little is known of the changes in gene expression that are fundamental to the mechanisms of hepatotoxicity. We have used DNA microarray technology to identify gene transcription associated with the toxicity caused by the hepatotoxicant carbon tetrachloride. Labeled poly A+ RNA from cultured human hepatoma cells (HepG2) exposed to carbon tetrachloride for 8 hours was hybridized to a human microarray filter. We found that 47 different genes were either upregulated or downregulated more than 2-fold by the hepatotoxicant compared with dimethyl formamide, a chemical that does not cause liver cell damage. The proinflammatory cytokine interleukin-8 (IL-8) was upregulated over 7-fold compared with control on the array, and this was subsequently confirmed at 1 hour and 8 hours by Northern blot analyses. We also found that carbon tetrachloride caused a time-dependent increase in interleukin-8 protein release in HepG2 cells, which was paralleled by a decrease in cell viability. These data demonstrate that carbon tetrachloride causes a rapid increase in IL-8 mRNA expression in HepG2 cells and that this increase correlates with a later and significant increase in the levels of interleukin-8 protein. These results illustrate the potential of microarray technology in the identification of novel gene changes associated with toxic processes.

Neutrophil gelatinase B potentiates interleukin-8 tenfold by aminoterminal processing, whereas it degrades CTAP-III, PF-4, and GRO-α and leaves RANTES and MCP-2 intact

Chemokines are mediators in inflammatory and autoimmune disorders. Aminoterminal truncation of chemokines results in altered specific activities and receptor recognition patterns. Truncated forms of the CXC chemokine interleukin (IL)-8 are more active than full-length IL-8 (1-77), provided the Glu-Leu-Arg (ELR) motif remains intact. Here, a positive feedback loop is demonstrated between gelatinase B, a major secreted matrix metalloproteinase (MMP-9) from neutrophils, and IL-8, the prototype chemokine active on neutrophils. Natural human neutrophil progelatinase B was purified to homogeneity and activated by stromelysin-1. Gelatinase B truncated IL-8(1-77) into IL-8(7-77), resulting in a 10- to 27-fold higher potency in neutrophil activation, as measured by the increase in intracellular Ca++concentration, secretion of gelatinase B, and neutrophil chemotaxis. This potentiation correlated with enhanced binding to neutrophils and increased signaling through CXC chemokine receptor-1 (CXCR1), but it was significantly less pronounced on a CXCR2-expressing cell line. Three other CXC chemokines—connective tissue-activating peptide-III (CTAP-III), platelet factor-4 (PF-4), and GRO-α—were degraded by gelatinase B. In contrast, the CC chemokines RANTES and monocyte chemotactic protein-2 (MCP-2) were not digested by this enzyme. The observation of differing effects of neutrophil gelatinase B on the proteolysis of IL-8 versus other CXC chemokines and on CXC receptor usage by processed IL-8 yielded insights into the relative activities of chemokines. This led to a better understanding of regulator (IL-8) and effector molecules (gelatinase B) of neutrophils and of mechanisms underlying leukocytosis, shock syndromes, and stem cell mobilization by IL-8.

Neutrophil gelatinase B potentiates interleukin-8 tenfold by aminoterminal processing, whereas it degrades CTAP-III, PF-4, and GRO-α and leaves RANTES and MCP-2 intact

Chemokines are mediators in inflammatory and autoimmune disorders. Aminoterminal truncation of chemokines results in altered specific activities and receptor recognition patterns. Truncated forms of the CXC chemokine interleukin (IL)-8 are more active than full-length IL-8 (1-77), provided the Glu-Leu-Arg (ELR) motif remains intact. Here, a positive feedback loop is demonstrated between gelatinase B, a major secreted matrix metalloproteinase (MMP-9) from neutrophils, and IL-8, the prototype chemokine active on neutrophils. Natural human neutrophil progelatinase B was purified to homogeneity and activated by stromelysin-1. Gelatinase B truncated IL-8(1-77) into IL-8(7-77), resulting in a 10- to 27-fold higher potency in neutrophil activation, as measured by the increase in intracellular Ca++concentration, secretion of gelatinase B, and neutrophil chemotaxis. This potentiation correlated with enhanced binding to neutrophils and increased signaling through CXC chemokine receptor-1 (CXCR1), but it was significantly less pronounced on a CXCR2-expressing cell line. Three other CXC chemokines—connective tissue-activating peptide-III (CTAP-III), platelet factor-4 (PF-4), and GRO-α—were degraded by gelatinase B. In contrast, the CC chemokines RANTES and monocyte chemotactic protein-2 (MCP-2) were not digested by this enzyme. The observation of differing effects of neutrophil gelatinase B on the proteolysis of IL-8 versus other CXC chemokines and on CXC receptor usage by processed IL-8 yielded insights into the relative activities of chemokines. This led to a better understanding of regulator (IL-8) and effector molecules (gelatinase B) of neutrophils and of mechanisms underlying leukocytosis, shock syndromes, and stem cell mobilization by IL-8.

In vivo neutrophil recruitment by granulocyte chemotactic protein-2 is assisted by gelatinase B/MMP-9 in the mouse

Granulocyte chemotactic protein-2 (GCP-2) of the mouse is a potent neutrophil chemotactic and activating factor in vitro and in vivo. Gelatinase B/matrix metalloproteinase-9 is released from neutrophils within 1 h after stimulation with GCP-2. In vitro neutrophil chemotaxis by GCP-2 was not impaired by specific inhibitory monoclonal antibodies (mAb) against gelatinase B, indicating that gelatinase B is not involved in chemotaxis of neutrophils through polycarbonate filters. To investigate if gelatinase B degranulation is involved in in vivo cell migration toward GCP-2, experiments were performed with gelatinase B knockout mice. When mouse GCP-2 was injected intradermally in mice, a dose-dependent neutrophil chemotactic response was observed, and this cell migration was significantly impaired in young mice by genetic gelatinase B knockout. In adult vs. young gelatinase B-deficient mice, such compensatory mechanisms as higher basal neutrophil counts and less impairment of chemotaxis toward local GCP-2 injection were observed. These experiments prove the concept that gelatinase B release under pressure of GCP-2 is a relevant, but not exclusive, effector mechanism of neutrophil chemotaxis in vivo and that known mechanisms, other than the release of gelatinase B, allow for a full-blown chemotactic response and compensate for gelatinase B deficiency in adult life in the mouse.

Critical role of neutrophils for the generation of psoriasiform skin lesions in flaky skin mice

Although T cell dysregulation is thought to underlie the pathogenesis of psoriasis, prominent infiltration and microabscess formation by neutrophils is a distinctive hallmark feature of this common disorder. The exact role of neutrophils in the pathogenesis of psoriasiform alterations in vivo, however, is unknown. Similar to human psoriasis, flaky skin mice (fsn/fsn) revealed a prominent infiltrate of neutrophils, and microabscesses within the hyperproliferative epidermis were associated with de novo expression of intercellular adhesion molecule-1. Intraperitoneal injection with the neutrophil-depleting RB6-8C5 monoclonal antibody (anti-Ly-6G) resulted in a dramatic reduction of the epidermal thickness by 58% compared with isotype-treated animals (p < 0.001). In addition, epidermal microabscesses were conspicuously absent (p < 0.001), and cutaneous neutrophils and T cells, but not mast cells or dendritic cells, were markedly reduced in anti-Ly-6G-treated mice. Proinflammatory cytokines, including tumor necrosis factor alpha and interleukin-1, were also downregulated. Therapeutic effects occurred as early as 4 d after beginning of treatment. Wildtype skin was not affected. When the integrin alphaMbeta2 (CD11b/CD18), which mediates neutrophil localization through binding to intercellular adhesion molecule-1, was blocked in vivo with the M1/70 monoclonal antibody, the epidermal thickness was reduced by 31% (p < 0.002), and neutrophil and T cell accumulation was diminished compared with control animals. Likewise, treatment of fsn/fsn mice with the MP1-22E9 monoclonal antibody neutralizing granulocyte macrophage-colony stimulating factor, a cytokine stimulating neutrophils by upregulating alphaMbeta2, resulted in significant reduction of inflammation and acanthosis by 30% (p < 0.003). These results demonstrate a critical pathogenic role of neutrophils for hyperproliferative inflammatory lesions in fsn/fsn mice, suggesting that blocking neutrophil function may have therapeutic benefit in some human skin disorders.

Interleukin 8 (IL-8) and the release of leukocytes from the bone marrow

Interleukin 8 (IL-8) is produced by various cells upon stimulation and influences a variety of functions of leukocytes in particular neutrophils. Systemic administration of IL-8 induces a rapid neutropenia associated by sequestration of neutrophils in the lung that is followed by a neutrophilia characterized by the rapid release of neutrophils from the bone marrow. These cells are released predominantly from the bone marrow venous sinusoids. In addition, several studies have shown the potential role of IL-8 in hematopoiesis and trafficking of hematopoietic stem cells. Systemic administration of IL-8 induces a rapid mobilization of progenitors from the bone marrow with long-term myelo-lymphoid repopulation capacity. It has been employed clinically to mobilize hematopoietic progenitor cells into the peripheral blood and used for autologous or allogeneic bone marrow transplantation. The mechanism for these effects of IL-8 is largely speculative. This report summarizes current ideas on the possible mechanisms how IL-8 influences cell trafficking in and from the bone marrow.

Induction of functional IL-8 receptors by IL-4 and IL-13 in human monocytes

IL-8 and related Glu-Leu-Arg (ELR+) CXC chemokines are potent chemoattractants for neutrophils but not for monocytes. IL-13 and IL-4 strongly increased CXCR1 and CXCR2 chemokine receptor expression in human monocytes, macrophages, and dendritic cells. The effect was receptor- and cell type-selective, in that CCRs were not increased and no augmentation was seen in neutrophils. The effect was rapid, starting at 4 h, and concentration dependent (EC50 = 6.2 and 8.3 ng/ml for CXCR1 and CXCR2, respectively) and caused by new transcriptional activity. IL-13/IL-4-treated monocytes showed increased CXCR1 and CXCR2 membrane expression. IL-8 and related ELR+ chemokines were potent and effective chemotactic agents for IL-13/IL-4-treated monocytes, but not for untreated mononuclear phagocytes, with activity comparable to that of reference monocyte attractants, such as MCP-1. In the same cells, IL-8 also caused superoxide release. Macrophages and dendritic cells present in biopsies from Omenn's syndrome and atopic dermatitis patients, two Th2 skewed pathologies, expressed IL-8 receptors by immunohistochemistry. These results show that IL-13 and IL-4 convert IL-8 and related ELR+ chemokines, prototypic neutrophil attractants, into monocyte chemotactic agonists, by up-regulating receptor expression. Therefore, IL-8 and related chemokines may contribute to the accumulation and positioning of mononuclear phagocytes in Th2-dominated responses.

Inflammatory mediators in dengue virus infection in children: interleukin-8 and its relationship to neutrophil degranulation

The chemokine interleukin-8 (IL-8) has chemoattractant activity for neutrophils and is able to activate and degranulate these cells. We investigated whether IL-8 may exert these effects in children with dengue virus infection. Circulating levels of IL-8, neutrophilic elastase (a constituent of the azurophilic granula of neutrophils), and lactoferrin, released from specific granula, were measured in 186 children with dengue virus infection, 33 healthy children as negative controls and 11 children with bacterial infections as positive controls. Levels of IL-8 on admission were elevated in 71% of the dengue patients, while the elastase and lactoferrin levels were increased in 68 and 17% of patients, respectively. These levels were significantly higher than in healthy children (P < 0.05) for IL-8 and elastase but not for lactoferrin (by the Wilcoxon-Mann-Whitney [WMW] U test). Similar levels of IL-8 were found in patients with bacterial infections. Levels of IL-8 and elastase in patients with shock were significantly higher than in patients without shock (P = 0.02; WMW), but those of lactoferrin were not. IL-8 correlated with elastase and lactoferrin (r = 0.19 and P = 0.009 versus r = 0.24 and P = 0.001, respectively; two-tailed Spearman rank correlation). Thus, IL-8 levels are increased in most patients with dengue virus infection and correlate with degranulation of neutrophils as well as with some clinical and hemodynamic variables. These findings suggest a role for IL-8 in the pathogenesis of dengue virus infection.

The role of metalloproteinases and adhesion molecules in interleukin-8-induced stem-cell mobilization

The chemokine interleukin-8 (IL-8) is a potent chemoattractant and activator of neutrophils. Upon systemic injection, IL-8 induces an immediate neutropenia followed by a rebound granulocytosis. In this report, we discuss the effects of IL-8 on the mobilization of hematopoietic stem cells. Within 20 minutes following a single intraperitoneal injection in mice, IL-8 induces the mobilization of hematopoietic progenitor cells (HPC) with colony-forming, radioprotective, and long-term lymphomyeloid resubpopulating ability. Mobilization can be specifically prevented by pretreatment with antibodies against the beta2 integrin LFA-1 (CD11a). In monkeys, IL-8 Induces the rapid release of the metalloproteinase gelatinase-B concurrent with the mobilization of HPC. The latter effect can be prevented by blocking gelatinase-B activity using specific monoclonal antibodies, suggesting the involvement of gelatinase-B as a mediator of HPC mobilization. These results are consistent with the hypothesis that neutrophils are major regulators of stem-cell mobilization through the release of metalloproteinases (MMPs) that cleave extracellular matrix molecules to which HPC are attached.