Neutrophil-activating peptide-1/interleukin 8, a novel cytokine that activates neutrophils

Interleukin-8 (IL-8): the major neutrophil chemotactic factor in the lung

A number of novel chemotactic cytokines are becoming increasingly recognized as important participants in the elicitation of specific inflammatory cells from the peripheral blood to sites of inflammation. Recent observations have now demonstrated that certain chemotactic cytokines possess specificity for the selected movement of individual immune/inflammatory cell populations. One of the more studied chemotactic cytokines is a neutrophil chemotactic factor identified as interleukin-8 (IL-8). This polypeptide mediator is produced in abundance by mononuclear phagocytic cells, as well as a number of non-inflammatory cells. This latter list includes both fibroblasts and epithelial cells. Moreover, the synthesis of IL-8 by fibroblasts and epithelial cells involves stimulus specificity, as the production of this mediator by non-inflammatory cells is dependent upon an initial host response. In the context of the lung, the alveolar macrophage appears to play a central role by generating factors, such as interleukin-1 and tumor-necrosis factor, which are potent stimuli for the induction of IL-8 by the lung fibroblasts and type II epithelial cells. The cascade-like interaction may lead to the rapid production of significant quantities of IL-8 by the lung and may selectively recruit neutrophils to the pulmonary interstitium and/or airspace. This sequence of events, which leads to cytokine networking in the lung, may be an important phenomenon for the generation of a major chemotaxin important to a variety of lung diseases.

Lymphocyte chemokinetic factors derived from human tonsils: modulation by 1,25-dihydroxyvitamin D3 (calcitriol)

Although interleukin (IL)-2 may in part be responsible for lymphocyte accumulation to sites of active sarcoidosis, other cytokines that control such recruitment are not well characterized. Similarly, the pathogenic rationale for the ability of sarcoid macrophages to produce 1,25-dihydroxycholecalciferol (calcitriol) is not understood. We studied the release of chemokinetic lymphokines from human nylon wool-non-adherent tonsillar lymphocytes (HNTLs) employing a standard in vitro lymphocyte migration assay. If mitogen-stimulated HNTL supernatants were fractionated by high-performance liquid chromatography, five positive and one negative chemokinetic factors could be identified. The five lymphocyte chemoattractant factors (LCFs) ranged in mol wt from 5 to 35 kD and stimulated the in vitro migration of nonsensitized human lymphocytes by 200 to 500%. The LCFs appeared distinct from IL-2, IL-1, or gamma-interferon. Co-incubation of HNTLs with mitogen and 1 nM calcitriol prevented the production or release of two of the LCFs and significantly decreased the quantity of a third LCF. Calcitriol also resulted in the appearance of a second negative chemokinetic factor, lymphocyte migration inhibitory factor (LyMIF). Combined with our previous studies demonstrating that calcitriol interferes with IL-2-induced lymphocyte migration, these results provide a rationale for an anti-inflammatory role for calcitriol in sarcoidosis and other granulomatous disorders. These experiments also demonstrate that the control of lymphocyte recruitment to inflammatory foci is multifactorial.

Chemotactic cytokine gene expression and production induced in human monocytes by membrane proteoglycans from Klebsiella pneumoniae

The present study was designed to investigate the effect of membrane proteoglycans (MPG) from Klebsiella pneumoniae on production of the chemotactic cytokine, IL-8, and monocyte chemotactic protein (MCP) by human peripheral blood monocytes. Exposure of human peripheral blood monocytes to MPG in vitro induced high levels of mRNA transcripts for IL-8 and MCP, as assessed by Northern blot analysis. Cytokine gene expression was associated with the production of chemotactic activity in the supernatants. The levels of IL-8 and MCP expression induced by MPG were comparable with those elicited by LPS. Induction of chemotactic cytokines in mononuclear phagocytes may play a role in the immunomodulatory activity of MPG.

Human neutrophils exhibit disparate chemotactic factor gene expression

The evolution of acute inflammation from initiation through resolution is associated with the changing character of the infiltrating leukocytes. Recruitment of these leukocytes is dependent upon the generation of chemotactic factors that have either global or specific activity for a particular leukocyte. In this manuscript we present data demonstrating that human neutrophils can express mRNA for neutrophil chemotactic factor/interleukin 8 (IL-8), but fail to express mRNA for monocyte chemotactic protein (MCP-1). The expression of IL-8 was observed upon adherence or in response to stimulation with lipopolysaccharide. Maximal IL-8 antigenic production was noted at 24 hrs. These studies demonstrate a disparate expression of chemotactic cytokines by neutrophils.

Immune responses in the lung: basic principles

The basic elements which regulate immunomodulation at the lung level and the constituents of in situ pulmonary host defense mechanisms that recognize, destroy, and remove potentially harmful inhaled antigenic materials are discussed. The relevance of these processes in term of pathogenesis of some lung disorders is briefly exemplified.

Effect of exogenous prostaglandin E2 and actinomycin D on plasma leakage induced by neutrophil-activating peptide-1/interleukin-8

Neutrophil accumulation and plasma leakage were measured in rabbit skin at sites stimulated with recombinant human neutrophil activating peptide-1/interleukin-8 (NAP-1/IL-8). Neutrophil accumulation occurred at doses equal to or greater than 10(-11) moles NAP-1/IL-8 per site. Co-injection of prostaglandin E2 (PGE2) extended the threshold of inflammatory activity of NAP-1/IL-8 to less than 10(-13) moles/site and caused approximately three-fold increases in neutrophil accumulation and ten-fold increases in plasma leakage at the higher doses of NAP-1/IL-8 examined. Plasma leakage declined more rapidly than did neutrophil accumulation as lesions aged. It was postulated that an endothelial response may be initiated to limit plasma leakage during ongoing neutrophil emigration at sites stimulated with NAP-1/IL-8. The induction of vasodilatation by injection of PGE2 masked the decline of plasma leakage with time in lesions up to 120 min old. Co-injection of the RNA synthesis inhibitor, actinomycin D, failed to abrogate the decline of plasma leakage with time, suggesting that de novo protein synthetic events such as production of the vasoconstrictor peptide, endothelin, are unlikely to contribute to the mechanism that restricts plasma leakage in older lesions. Although plasma leakage induced by NAP-1/IL-8 is dependent on the emigration of neutrophils, the results indicate that a mechanism, independent of de novo protein synthesis, restricts the rate of plasma leakage per neutrophil as lesions age.

Interleukin-8 gene expression by a pulmonary epithelial cell line. A model for cytokine networks in the lung

Cellular constituents of the alveolar-capillary wall may be key participants in the recruitment of polymorphonuclear leukocytes to the lung through the generation of the novel neutrophil chemotactic peptide interleukin-8 (IL-8). This interaction appears to occur via the ability of human alveolar macrophage (AM)-derived monokines, tumor necrosis factor (TNF), and interleukin-1 (IL-1) to induce gene expression of IL-8 from pulmonary type II-like epithelial cells (A549). Northern blot analysis demonstrated that steady-state IL-8 mRNA expression, by either TNF- or IL-1 beta-treated A549 cells, occurred in both a dose- and time-dependent fashion. Similarly, extracellular antigenic IL-8, as assessed by specific ELISA, was expressed from TNF- or IL-1 beta-stimulated epithelial cells in a time-dependent fashion with maximal IL-8 antigen detected at 24 h poststimulation. Immunohistochemical staining utilizing rabbit anti-human IL-8 antibody identified immunoreactive, cell-associated IL-8 antigen as early as 8 h post-TNF or IL-1 beta stimulation. A549-generated neutrophil chemotactic bioactivity paralleled IL-8 steady-state mRNA levels. Signal specificity was demonstrated in this system as IL-8 mRNA or protein expression by lipopolysaccharide (LPS)-treated A549 cells was not different from unstimulated cells. Although LPS did not serve as a direct stimulus for the production of IL-8 by type II-like epithelial cells, the condition media from LPS-challenged AM induced a significant expression of IL-8 mRNA by the A549 cells. 24-h conditioned media from LPS-treated cells was as potent as either IL-1 beta or TNF in generating steady-state IL-8 mRNA by A549 cells. Preincubation of LPS-treated AM-conditioned media with anti-human TNF or IL-1 beta neutralizing antibodies resulted in significant abrogation of IL-8 gene expression by A549 pulmonary epithelial cells. These findings demonstrate potential cell-to-cell communication circuits that may be important between AMs and pulmonary epithelial cells during the recruitment phase of acute lung inflammation.

The Role of Epidermal Cytokines in Inflammatory Skin Diseases

Cytokines (hormone-like polypeptide mediators) play a major role in inflammatory and immunoregulatory responses. Skin, and particularly keratinocytes in the skin, represent a potent source for many cytokines, including interleukins 1, 6, 8, and the hemopoietic colony stimulating factors. Cytokines initiate their biologic action by interacting with target cells bearing cytokine receptors and then initiating a cascade of cellular interactions. Certain inflammatory skin diseases have been associated with overproduction of cytokines, alteration in cytokine receptors, or dysregulation of cytokines. While data is still quite preliminary, it is likely that cytokines contribute to the pathogenesis of many inflammatory skin diseases.

A novel neutrophil chemoattractant generated during an inflammatory reaction in the rabbit peritoneal cavity in vivo. Purification, partial amino acid sequence and structural relationship to interleukin 8

An inflammatory reaction was induced in vivo by injection of zymosan into the peritoneal cavity of the rabbit. The inflammatory exudate was found to contain oedema-inducing and neutrophil chemoattractant activity when assayed in rabbit skin in vivo, using 125I-albumin and 111In-neutrophils. This activity was additional to that of complement fragment C5a, which was removed by an affinity gel. Two chemoattractants were isolated by cation-exchange, gel-filtration and reversed-phase h.p.l.c. One of these, which ran as a single band of 6-8 kDa on SDS/PAGE, was subjected to N-terminal sequence analysis without reduction and alkylation of cysteine residues. Positive identification of 28 of the first 31 amino acids revealed a rabbit homologue of interleukin-8 (75% sequence identity with human interleukin-8). The demonstration of interleukin-8 as a major neutrophil chemoattractant in an inflammatory reaction in vivo provides the basis for further investigations into the role of this cytokine in the inflammatory process.

Identification of a novel platelet-derived neutrophil-chemotactic polypeptide with structural homology to platelet-factor 4

A novel protein, NAP-4, could be isolated from human platelet lysates. NAP-4 preparations induced chemotaxis of human neutrophils with an ED50 near 400 ng/ml. Purification by anti NAP-1/IL-8 affinity chromatography and reversed phase HPLC revealed a single peak showing a single line upon SDS-PAGE corresponding to a Mr of 8000. NH2-terminal sequence analysis indicated an unique sequence showing strong homology to human platelet factor 4 and weak homology to tumor necrosis factor alpha as well. The most interesting finding is the absence of the first two cysteins, known to be strongly conserved in members of the family of platelet-factor 4-like host defense cytokines.

Epithelins 1 and 2: isolation and characterization of two cysteine-rich growth-modulating proteins

Two proteins, termed epithelin 1 and epithelin 2, that inhibit the growth of A431 cells, derived from a human epidermal carcinoma of the vulva, have been purified from rat kidney. Epithelin 1 stimulates the proliferation of murine keratinocytes, whereas epithelin 2 inhibits the epithelin 1-elicited growth of these cells. Thus epithelin 1 and 2 behave as agonist and antagonist, respectively, for normal epithelial cells. Epithelins are low molecular mass (approximately 6 kDa), acid- and heat-stable, single-chain proteins containing approximately 20% cysteine. Some of these cysteines form disulfide linkage(s) that are essential for biological activity. The amino-terminal amino acid sequences of epithelin 1 and epithelin 2 have been determined. The two proteins showed no substantial sequence homology with other proteins. However, a significant homology was seen between the amino-terminal sequences of epithelin 1 and epithelin 2. Epithelins 1 and 2, therefore, appear to represent members of a distinct family of growth regulators.

Disparate regulation of interleukin 8 gene expression from blood monocytes, endothelial cells, and fibroblasts by interleukin 4

The role(s) of novel chemotactic cytokines as mediators in the pathogenesis of many acute and chronic disease states is becoming increasingly apparent. One of these cytokines, interleukin 8, is a product of both immune and non-immune cells. In this manuscript, we describe the suppression of IL-8 gene expression from stimulated monocytes by IL-4, while IL-4 had no suppressive effects on IL-8 gene expression from stimulated fibroblasts and endothelial cells. Our data suggest that IL-4 may function as an endogenous regulator of monocyte cytokine expression, including the chemotactic cytokine IL-8.

Interleukin 1 (IL-1) gene expression, synthesis, and effect of specific IL-1 receptor blockade in rabbit immune complex colitis

Interleukin 1 (IL-1) may be a key mediator of inflammation and tissue damage in inflammatory bowel disease (IBD). In rabbits with immune complex-induced colitis, IL-1 alpha and beta mRNA levels were detectable at 4 h, peaked at 12 but were absent at 96 h after the induction of colitis. Colonic IL-1 tissue levels were measured by specific radioimmunoassays. IL-1 alpha was significantly elevated at 4 h (9.4 +/- 1.5 ng/g colon), progressively increased at 48 h (31 +/- 5.8 ng/g) and then decreased by 96 h (11.5 +/- 3.4 ng/g). IL-1 beta levels were 2.0 +/- 0.5 ng/g colon at 4 h, 5.0 +/- 1.6 ng/g at 48 h and undetectable by 96 h. By comparison, colonic levels of PGE2 and LTB4 were unchanged during the first 12 h and did not become elevated until 24 h. IL-1 alpha levels were highly correlated with inflammation (r = 0.885, P less than 0.0001), edema (r = 0.789, P less than 0.0001) and necrosis (r = 0.752, P less than 0.0005). Treatment with a specific IL-1 receptor antagonist (IL-1 ra) before and during the first 33 h after the administration of immune complexes markedly reduced inflammatory cell infiltration index (from 3.2 +/- 0.4 to 1.4 +/- 0.3, P less than 0.02), edema (from 2.2 +/- 0.4 to 0.6 +/- 0.3, P less than 0.01) and necrosis (from 43 +/- 10% to 6.6 +/- 3.2%, P less than 0.03) compared to vehicle-matched colitis animals. These studies demonstrate that (a) IL-1 gene expression and synthesis occur early in the course of immune complex-induced colitis; (b) are significantly elevated for 12 h before the appearance of PGE2 and LTB4; (c) tissue levels of IL-1 correlate with the degree of tissue inflammation and; (d) specific blockade of IL-1 receptors reduces the inflammatory responses associated with experimental colitis.

Crystallization and preliminary X-ray crystallographic study of interleukin-8

Interleukin-8 (neutrophil-activating factor; NAP-1) has been crystallized by the vapour diffusion technique to give single crystals suitable for three-dimensional structural study at a resolution higher than 2.4 A. The crystals belong to the space group P3(1)21 or P3(2)21 and have unit cell dimensions a = b = 40.9 A, c = 90.3 A.

Neutrophil attractant/activation protein-1 (NAP-1 [interleukin-8])

Neutrophil attractant/activation protein-1 (NAP-1 [interleukin-8]) is an 8,400 D protein that is a chemoattractant and granule release stimulus for neutrophils. NAP-1 was first purified from culture fluids of lipopolysaccharide-stimulated human blood mononuclear leukocytes. It was subsequently isolated from lipopolysaccharide-stimulated lung macrophages, mitogen-stimulated lymphocytes, and virus-infected fibroblasts. Interleukin-1 or tumor necrosis factor induces NAP-1 mRNA in many cells, including monocytes, fibroblasts, and endothelial cells. NAP-1 belongs in a family of host defense small proteins, which have a degree of sequence and structural similarity. Noteworthy are the four half-cystine residues in each protein, which are in register when the protein sequences are suitably aligned. Based on cloning data and N-terminal sequence analyses, NAP-1 is secreted as a 79 residue protein after cleavage of a 20 residue signal peptide. The commonly isolated 77 and 72 residue forms are probably extracellular cleavage products. NAP-1 has considerable charge heterogeneity. Charge and length variants all have chemotactic activity. In contrast to many chemoattractants, NAP-1 does not attract monocytes. Intradermal injection of NAP-1 causes neutrophil infiltration. The wide spectrum of cell sources and production stimuli suggests that NAP-1 mediates neutrophil recruitment in host defense and disease.

Neutrophil-activating properties of the melanoma growth-stimulatory activity

Melanoma growth-stimulatory activity (MGSA), a peptide reported to be mitogenic for Hs294T human melanoma cells, has extensive sequence similarity to the neutrophil-activating peptide NAP-1/IL-8, suggesting functional similarities. To test this hypothesis, MGSA was chemically synthesized and tested for its effects on human neutrophils. It was found to induce chemotaxis, exocytosis of elastase, and changes in cytosolic-free calcium to an extent and at concentrations similar to NAP-1/IL-8. However, MGSA was considerably less potent than NAP-1/IL-8 in inducing the respiratory burst. Intradermal injections in rats of MGSA resulted in a massive accumulation of neutrophils. Our data demonstrate that, apart from its growth-stimulatory activity, MGSA is a potent inflammatory agonist with neutrophil-stimulating properties.

Human alveolar macrophage gene expression of interleukin-8 by tumor necrosis factor-alpha, lipopolysaccharide, and interleukin-1 beta

The alveolar macrophage (AMO) in its pivotal position for pulmonary host defense may play a prominent role in the orchestration of polymorphonuclear leukocyte (PMN) diapedesis. We demonstrate that the human AMO may participate in these inflammatory events through the production of a novel neutrophil chemotactic factor, interleukin-8 (IL-8). The induction of AMO-derived IL-8 by tumor necrosis factor (TNF), lipopolysaccharide (LPS), and interleukin-1 (IL-1 beta) was shown to be both dose and time dependent. Maximal IL-8 gene expression, as assessed by Northern blot analyses, was achieved with 20 ng/ml and 1 microgram/ml, respectively, for each of the cytokines and LPS. A kinetic study of TNF-, IL-1 beta-, and LPS-treated AMOs showed significant steady-state IL-8 mRNA accumulation post-stimulation at 1 h, peaking by 8 h, with a decline over the next 16 h. Immunohistochemical staining using rabbit anti-human IL-8 antibody demonstrated significant immunolocalization of cell-associated IL-8 antigen at 4 h, with persistence over the next 20 h. Chemotactic bioactivity peaked by 8 h, with continued production over the next 16 h. Chemotactic bioactivity from AMO-conditioned media was inhibited by IL-8 antiserum by 2, 31, 44, and 47%, respectively, for unstimulated control, LPS-, IL-1 beta-, and TNF-treated cells. Preimmune serum had no effect on chemotactic activity. These data support the central role of the AMO in the elicitation of PMNs into the lung via the production of IL-8.

Neutrophil-activating protein 1/interleukin 8 stimulates the binding activity of the leukocyte adhesion receptor CD11b/CD18 on human neutrophils

The cytokine NAP-1/IL-8 is produced by a variety of different cells in response to inflammatory stimuli and elicits several biological responses from PMN. Experiments presented here demonstrate that PMN exposed to NAP-1/IL-8 expressed increased amounts of CD11b/CD18, as well as CD11c/CD18 and CR1, on their cell surface, while expression of Fc gamma RIII and HLA-A,B,C remained essentially unchanged. Increased CD11b/CD18 and CD11c/CD18 appears to correspond with the release of specific granules by NAP-1/IL-8. NAP-1/IL-8 was also a potent stimulator of several of the binding activities of CD11b/CD18. Ligation of EC3bi by CD11b/CD18 was rapidly enhanced by NAP-1/IL-8, but phagocytosis of the ligated particles was not induced by the agonist. In addition, enhanced binding of EC3bi was observed in the absence of an increase in receptor expression as shown with PMN cytoplasts. NAP-1/IL-8 promoted additional adhesive interactions between CD11b/CD18 and the biosynthetic precursor of LPS, lipid IVa, fibrinogen, and endothelial cells, suggesting that NAP-1/IL-8 may promote leukocyte adhesion in vivo that could lead to recruitment of PMN to sites of tissue inflammation.

Generation of the neutrophil-activating peptide NAP-2 from platelet basic protein or connective tissue-activating peptide III through monocyte proteases

We studied the origin of the neutrophil-activating peptide NAP-2, a presumed 70 amino acid cleavage product of platelet basic protein (PBP) and connective tissue-activating peptide III (CTAP-III). Purified human blood monocytes or lymphocytes were cultured with or without stimuli (LPS or PHA) in the presence or absence of platelet-release supernatant, and the formation of NAP-2 and other neutrophil-activating peptides was monitored. NAP-2 was generated whenever monocytes and platelet release supernatant were present. When a monocyte stimulus was added, NAF/NAP-1 was also formed, and in the presence of LPS a third, less potent neutrophil-stimulating fraction, consisting of NAP-2 variants with 73, 74, and 75 residues, also appeared. Monocytes alone did not yield NAP-2 and no neutrophil-activating peptide was generated by lymphocytes. The monocyte-conditioned medium was found to cleave purified CTAP-III into NAP-2 through proteinases that were highly sensitive to PMSF, moderately sensitive to leupeptin and insensitive to EDTA.

Turning on the respiratory burst

The respiratory burst is a distinguishing property of phagocytes. It is induced by chemotactic stimulation or phagocytosis and reflects the activation of a membrane-bound enzyme system that transfers electrons from cytosolic NADPH to extracellular oxygen, producing superoxide. The products of the burst are essential for the killing of microorganisms, but are also a cause of tissue damage and inflammation. Studies aimed at a better understanding of the regulation of the respiratory burst should help in the search for new ways to treat infections and inflammation.

NAP-1/IL-8 induces up-regulation of CR1 receptors in human neutrophil leukocytes

The effect of the neutrophil-activating peptide NAP-1/IL-8 on the expression of complement receptor type 1 (CR1) in human neutrophils was studied. NAP-1/IL-8 enhanced CR1 expression at concentrations between 10(-10) and 10(-8) M. The maximum increase with respect to unstimulated control cells was on average 2.3 fold. The effect was rapid: Half-maximum enhancement was obtained in 4 min and the plateau was reached in 15 min. The chemotactic peptide fMLP, tested for comparison, was effective between 10(-9) and 10(-7) M, showed a similar time course and a somewhat higher maximum effect (2.8 fold increase). The effect of NAP-1/IL-8 was prevented by pretreatment of the cells with B.pertussis toxin and desensitization was observed following restimulation. Stimulus combination experiments suggested that NAP-1/IL-8 mobilizes the same or a similar intracellular pool of CR1 receptors as fMLP or C5a.