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

Increase in tumor necrosis factor alpha- and interleukin-6-secreting cells in peripheral blood mononuclear cells from subjects infected with Mycobacterium tuberculosis

We detected and quantified tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6) from monocytes/macrophages (M phi) in the peripheral blood of subjects from three different population groups, i.e., tuberculin-negative healthy subjects, tuberculin-positive healthy subjects, and patients with active pulmonary tuberculosis. TNF-alpha or IL-6 activity in the culture supernatant of these cells was determined by the cytotoxicity of murine L-929 cells or by enzyme-linked immunosorbent assay, respectively. Detection and enumeration of cells secreting either TNF-alpha or IL-6 were performed by an adaptation of the enzyme-linked immunospot assay. Monocytes/M phi from tuberculin-positive healthy subjects or patients with tuberculosis showed higher TNF-alpha- and IL-6-producing activities than those from tuberculin-negative healthy subjects. The number of TNF-alpha- and IL-6-secreting cells in either lipopolysaccharide- or muramyl dipeptide-stimulated mononuclear cells from tuberculin-positive healthy subjects and patients was significantly higher than that in cells from the tuberculin-negative healthy subjects.

Presence of NAP-1/IL-8 in synovial fluids indicates a possible pathogenic role in rheumatoid arthritis

The synovial fluid in affected joints of rheumatoid arthritis (RA) patients contains many cells, in numbers strongly correlated with the severity of disease. As the disease worsens and the cell count increases, the polymorphonuclear leucocyte becomes the predominant cell type. Although the inflammatory cytokines interleukin 1 (IL-1) and tumour necrosis factor (TNF) have no direct neutrophil-attractant activity, they are both potent inducers of interleukin 8 (IL-8) in a variety of cell types. Chemotactic attraction of neutrophils is a major activity of IL-8. Examination of a number of synovial fluids showed that significant levels of IL-8 are present in a high proportion of RA cases (10 out of 17), at concentrations directly related to the number of cells in the joint, and to circulating C-reactive protein (CRP) levels. The cytokine is present only at background levels in other diseases accompanied by arthritic manifestations, including systemic lupus erythematosus (SLE) and induced arthritis. The progressive joint destruction seen in all cases where high IL-8 levels were measured, coupled with the neutrophil-rich cell count and the strong correlation between concentration of IL-8 and both serum CRP and cellular influx into the joint, is strongly suggestive of a pathogenic role for IL-8 in RA.

Expression of monocyte chemotactic protein and interleukin-8 by cytokine-activated human vascular smooth muscle cells

The present study was designed to investigate the capacity of human vascular smooth muscle cells (SMCs) to produce a cytokine chemotactic for monocytes (monocyte chemotactic protein [MCP]) and by way of comparison, a related polypeptide activator of neutrophils (known as interleukin-8 [IL-8] or neutrophil activating protein-1 [NAP-1]. On exposure to IL-1, SMCs released high levels of chemotactic activity for monocytes, which could be removed by absorption with anti-MCP antibodies. MCP production by activated SMCs was comparable to that of IL-1-stimulated umbilical vein endothelial cells. Activated SMCs released appreciable levels of IL-8, as determined by a specific enzyme-linked immunosorbent assay, but little chemotactic activity for neutrophils. IL-1-treated SMCs expressed high levels of both MCP and IL-8 mRNA transcripts, as assessed by Northern blot analysis. Tumor necrosis factor and bacterial lipopolysaccharide but not IL-6 also induced MCP and IL-8 gene expression in SMCs. Nuclear runoff analysis revealed that IL-1 augmented transcription of the MCP and IL-8 genes. The capacity of SMCs to produce a cytokine (MCP) that recruits and activates circulating mononuclear phagocytes may be of considerable importance in the pathogenesis of vascular diseases (e.g., vasculitis and atherosclerosis) that are characterized by monocyte infiltration of the vessel wall.

Interleukin 8-inhibitor and inducer of histamine and leukotriene release in human basophils

We have shown previously that interleukin 8 (IL-8) induces histamine and leukotriene release in human basophils exposed to interleukin 3 (IL-3). We now found that pretreatment with low concentrations of IL-8 selectively inhibits this response. Inhibition was significant at 0.01 nM IL-8 and virtually complete at 1 nM, which is about 100-fold lower than the concentration required for induction of mediator release. IL-8 dependent responses were also inhibited, albeit to a lesser extent, by preincubation with neutrophil-activating peptide 2 (NAP-2), but not with connective tissue-activating peptide III (CTAP-III) or platelet factor 4 (PF4). Release induced by C5a, fMet-Leu-Phe, or anti-IgE antibody, by contrast, was not affected.

Tumour necrosis factor-alpha induces neutrophil-mediated injury of cultured human endothelial cells

We investigated the ability of TNF-alpha to mediate damage of endothelial cells in the presence of neutrophils, by measuring detachment of cultured human umbilical vein endothelial cells (HUVEC). Endothelial cell detachment was increased from 5% to about 75% by the presence of 1-10 ng/ml TNF-alpha during incubation with neutrophils, whereas negligible endothelial cell lysis was observed as measured by 51Cr release. TNF-alpha was compared with the cytokines IL-1 alpha and IFN-gamma and with PMA and LPS. Both TNF-alpha and PMA appeared to be strong triggers for neutrophil-induced endothelial cell detachment, whilst reduced injury was seen after addition of IL-1 alpha and LPS. IFN-gamma did not induce endothelial cell detachment, but potentiated the effect of both TNF-alpha and IL-1 alpha. TNF-alpha-induced endothelial cell detachment was neutrophil dependent, since pre-incubation of neutrophils, but not pre-incubation of endothelial cells with TNF-alpha, caused endothelial cell detachment. Thus, TNF-alpha-induced increase in neutrophil-adhesiveness of HUVEC was found not to be essential for endothelial damage. Pre-incubation of neutrophils in suspension with TNF-alpha induced rapid activation, followed by nearly complete deactivation of neutrophils, as measured by their capacity to induce detachment of endothelial cells after removal of TNF-alpha. These results indicate that local presence of TNF-alpha might be critical in tissue or organ damage during early, neutrophil-mediated inflammatory processes, independent of enhanced adhesiveness of endothelium for neutrophils.

Chemotactic cytokine (IL-8 and MCP-1) gene expression by human whole blood

The salient features of systemic or local inflammation are the myriad of cellular and humoral interactions that result in elicitation of inflammatory leukocytes. In this study using specialized connective tissue, intact whole blood, we demonstrate the gene expression of two novel chemotactic factors. The buffy-coat cellular expression of neutrophil chemotactic/activating factor/interleukin 8 (IL-8) and monocyte chemotactic/activating protein (MCP-1) mRNA were time and dose-dependent in response to either lipopolysaccharide or zymosan stimulation. This system with the complexity of tissue provides a unique model for the determination of chemotactic cytokine gene expression.

Cytokine-activated human mesangial cells generate the neutrophil chemoattractant, interleukin 8

Human mesangial cells (MC) in culture, when stimulated by interleukin 1 alpha(IL-1 alpha) or tumour necrosis factor (TNF alpha), but not with lipopolysaccharide (LPS), express interleukin 8 (IL-8) mRNA, and both cell associated and extracellular IL-8. Dexamethasone treatment of mesangial cells induced partial inhibition of the release of extracellular IL-8, while cell-associated IL-8 and IL-8 mRNA were not significantly altered. We propose that the mesangial cell has a direct role in the initiation and propagation of inflammatory events within the glomerulus via the generation of the chemotactic cytokine IL-8.

Monocyte-derived neutrophil chemotactic factor/interleukin-8 is a potential mediator of crystal-induced inflammation

The physical interaction of particulates with resident mononuclear phagocytes is a consistent feature in certain forms of crystal-induced inflammation. In this study, we observed that monosodium urate crystals stimulated the rapid release of neutrophil chemotactic activity from monocytes, and that this activity steadily increased over 24 hours. Because the release of monocyte-derived neutrophil chemotactic activity was markedly diminished by pretreatment of the monocytes with cycloheximide, and was completely removed from conditioned media by adsorption to heparin-agarose, we addressed the possibility that monocyte-derived neutrophil chemotactic factor/interleukin-8 (IL-8), a heparin-binding neutrophil-activating polypeptide, might modulate these activities. Urate crystal-induced IL-8 secretion from monocytes was verified by radioimmunoassay. In addition, an IL-8-specific antibody markedly inhibited the neutrophil-activating capacity of the conditioned media from monocytes activated by urate crystals, as well as by inflammatory silica crystals. Last, IL-8 was significantly increased in gouty synovial fluids (range 3.0-16.8 ng/ml, mean 8.4 ng/ml, n = 6) relative to osteoarthritic synovial fluids (range 1.1-1.7 ng/ml, mean 1.5 ng/ml, n = 6) (P = 0.006). We conclude that microcrystal-induced secretion of IL-8 by mononuclear phagocytes may mediate a number of forms of crystal-induced inflammation.

Neutrophil-activating peptide 1/interleukin 8 mRNA expression and protein secretion by human monocytes: effect of cyclosporin A

Neutrophil-activating peptide 1/interleukin 8 (NAP-1/IL-8) is a recently described cytokine with potent chemotactic activity for human neutrophil granulocytes (PMN) and T cells. In psoriasis, a chronic hyperproliferative and inflammatory skin disorder, PMN and T cells are found as prominent cells in the inflammatory infiltrate of the lesions; however, monocytes were shown to be the first cells invading a newly formed plaque. NAP-1/IL-8 was found to be present in high amounts in the skin and in scale material of psoriatic patients. Psoriasis responds well to systemic treatment with cyclosporin A (CsA), an immunosuppressive peptide. Therefore, we addressed the question of whether the clinical improvement of psoriatic patients during CsA therapy may be due to an inhibition of NAP-1/IL-8 production and secretion from monocytes. Purified human monocytes were stimulated by lipopolysaccharide in the presence or absence of various concentrations of CsA. Production of NAP-1/IL-8 was determined as expression of specific mRNA by fluorescent in situ hybridization. Secreted peptide was measured by bioassay (PMN chemotaxis) and enzyme-linked immunosorbent assay (ELISA) using specific monoclonal antibodies. The results show that CsA neither inhibited mRNA expression for NAP-1/IL-8 nor secretion of the peptide. These findings support the hypothesis that the pharmacological effect of CsA may be restricted to the inhibition of T-cell activation and proliferation.

Assignment of the human small inducible cytokine A2 gene, SCYA2 (encoding JE or MCP-1), to 17q11.2-12: evolutionary relatedness of cytokines clustered at the same locus

The JE gene, cloned from platelet-derived growth factor (PDGF)-treated mouse 3T3 cells, was the first PDGF-inducible gene to be described. Its human homolog (gene name "small inducible cytokine A2" [SCYA2]) encodes the monocyte specific chemotactic factor MCP-1 (or MCAF) which is structurally related to a recently described family of cytokines. By a combination of in situ hybridization and study of somatic cell hybrids, we have assigned the human SCYA2 gene to 17q11.2-12, the locus to which other members of this family have been mapped. We have also reconstructed a phylogenetic tree relating the members of this family to each other and to their murine homologs which suggests that these genes arose by duplication and divergence prior to the murine/human divergence. Four of the five members of this subfamily have now been assigned to the same locus (and the fifth to chromosome 17), while several of the members of a related gene family have been assigned to 4q. We propose that the two subfamilies be designated the 17q and 4q subfamilies.

Mediators, initiating the inflammatory response, released in organ culture by full-thickness human skin explants exposed to the irritant, sulfur mustard

Mediators released from injured human skin that initiate the inflammatory response have not been adequately identified. Organ culture of full-thickness skin explants enables us to do so, because injury to the skin can be made in vitro, eliminating the rapid leakage of serum and infiltration of leukocytes that occur in vivo. In our studies, the military vesicant sulfur mustard (SM) (10 microliters of a 0.01 to 1.0% dilution) was topically applied to injure the epidermis of the explant. Then, the explants were cultured in small Petri dishes, usually for 18 h at 36 degrees C, and the organ-culture fluids were assayed for various inflammatory mediators. We found that the culture fluids from SM-exposed and control explants contained similar amounts of angiotensin-converting enzyme, trypsin-like and chymotrypsin-like proteases, acid phosphatase, beta-glucuronidase, beta-galactosidase, lysozyme, deoxyribonuclease, ribonuclease, interleukin 1, and lactic dehydrogenase. However, the culture fluids from SM-exposed explants contained increased amounts of histamine and plasminogen-activating activity, and often prostaglandin E2, when compared to culture fluids from control explants. After 3 to 4 d in culture, full-thickness human skin explants, when exposed to 0.2% SM (but not when exposed to 1.0% SM), sometimes showed separation of the epidermis and increased collagenase activity (i.e., hydroxyproline release). Thus, histamine (from local mast cells), and prostaglandin E2 and plasminogen-activating activity (probably from both mast cells and epidermal cells) are apparently involved in early mediation of the inflammatory response.

Immunoregulators in the nervous system

The nervous system, through the production of neuroregulators (neurotransmitters, neuromodulators and neuropeptides) can regulate specific immune system functions, while the immune system, through the production of immunoregulators (immunomodulators and immunopeptides) can regulate specific nervous system functions. This indicates a reciprocal communication between the nervous and immune systems. The presence of immunoregulators in the brain and cerebrospinal fluid is the result of local synthesis--by intrinsic and blood-derived macrophages, activated T-lymphocytes that cross the blood-brain barrier, endothelial cells of the cerebrovasculature, microglia, astrocytes, and neuronal components--and/or uptake from the peripheral blood through the blood-brain barrier (in specific cases) and circumventricular organs. Acute and chronic pathological processes (infection, inflammation, immunological reactions, malignancy, necrosis) stimulate the synthesis and release of immunoregulators in various cell systems. These immunoregulators have pivotal roles in the coordination of the host defense mechanisms and repair, and induce a series of immunological, endocrinological, metabolical and neurological responses. This review summarizes studies concerning immunoregulators--such as interleukins, tumor necrosis factor, interferons, transforming growth factors, thymic peptides, tuftsin, platelet activating factor, neuro-immunoregulators--in the nervous system. It also describes the monitoring of immunoregulators by the central nervous system (CNS) as part of the regulatory factors that induce neurological manifestations (e.g., fever, somnolence, appetite suppression, neuroendocrine alterations) frequently accompanying acute and chronic pathological processes.

Neutrophil chemotactic factors in synovial fluids of patients with Lyme disease

We examined synovial fluid samples from 14 patients with Lyme arthritis for the presence of neutrophil chemotactic factors. Thirteen of the synovial fluids stimulated chemotaxis of normal human neutrophils. The chemotactic activity was heat-sensitive and was not inhibited by antibody to C5a or antibody to interleukin-8, or by a competitive inhibitor of the chemotactic peptide f-Met-Leu-Phe. A culture supernatant of Borrelia burgdorferi also contained neutrophil chemoattractants. Chromatography demonstrated that the chemoattractants in the synovial fluid samples were different from those in the B burgdorferi culture supernatant. One of the major chemotactic factors in Lyme disease synovial fluid had a calculated molecular weight of 13,900. We conclude that a novel, host-derived chemoattractant is present in the synovial fluid of patients with Lyme disease.

Cytokine- and LPS-induced synthesis of interleukin-8 from human mesangial cells

The cytokine neutrophil-activating peptide-1/interleukin-8 (NAP/IL-8) activates neutrophils (PMN) and elicits selective diapedesis of PMN into the extracellular space. The glomerular mesangial cell (MC) is a specialized pericyte that controls glomerular filtration and synthesizes and responds to a variety of cytokines. Because of its location within the glomerulus, the MC is in a pivotal position to orchestrate events underlying immune injury. Since immune-injured glomeruli have been shown to produce NAP/IL-8 activity in vitro, we assessed whether lipopolysaccharide (LPS)- or cytokine-activated MC might be a source of this activity. Pure human MC, devoid of monocyte/macrophage and fibroblast contamination, were grown by explant from collagenase-treated glomeruli. Human recombinant interleukin-1 alpha (IL-1 alpha, 20 ng/ml), IL-1 beta (50 ng/ml), tumor necrosis factor alpha (TNF, 100 ng/ml) and lipopolysaccharide (LPS, 10 micrograms/ml) stimulated release of a neutrophil chemotactic factor from cultured MC. Both concentrated (fivefold) and unconcentrated MC supernatants stimulated directed neutrophil migration under agarose at a level similar to that of the bacterial chemotactic factor, FMLP. In contrast, unstimulated MC-conditioned media and IL-1 alpha, IL-1 beta. TNF and LPS in medium alone did not directly induce PMN migration. Molecular sizing studies using sequential membrane ultrafiltration identified significant TNF-stimulated, MC-derived chemotactic activity in the 3000 to 10000 kD fraction. An anti-NAP/IL-8 monoclonal antibody, 46E5, significantly inhibited PMN chemotaxis stimulated by TNF-stimulated, MC-conditioned media in a dose-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Shape changes, exocytosis, and cytosolic free calcium changes in stimulated human eosinophils

Essentially pure preparations of normal density eosinophils obtained from patients with hypereosinophilic syndrome (HES) were stimulated with complement factor 5a (C5a), platelet-activating factor (PAF), FMLP and neutrophil-activating peptide (NAP-1/IL-8). Three responses were studied, the transient rise in cytosolic free calcium concentration ([Ca2+]i) (derived from indo-1 fluorescence), shape changes (measured by laser turbidimetry), and exocytosis of eosinophil peroxidase (EPO) (assessed by H2O2/luminol-dependent chemiluminescence). Responses were obtained with all four agonists, but C5a and PAF were by far more potent than FMLP and NAP-1/IL-8, which induced only minor effects. Pretreatment of the cells with pertussis toxin attenuated [Ca2+]i changes, EPO release and, to a lesser extent, shape changes, indicating that GTP-binding proteins of Gi-type are involved in receptor-dependent signal transduction processes leading to these responses. A clear dissociation was observed in the control of the shape change response and EPO exocytosis. The shape change was not affected by Ca2+ depletion or treatment with the protein kinase inhibitor staurosporine, but exocytosis was prevented by Ca2+ depletion and markedly enhanced by staurosporine. The activation of the contractile system, leading to shape changes and motility, thus appears to be independent of the classical signal transduction pathway involving phospholipase C, a [Ca2+]i rise and protein kinase C activation. Exocytosis is, as expected, Ca2+ dependent and appears to be under a negative control involving protein phosphorylations.

Receptor-operated activation of polymorphonuclear leukocytes: different effects of NAP-1/IL-8 and fMet-Leu-Phe or C5a

We examined the production of PAF and LTB4 by PMN in response to NAP1/IL-8 alone, or after preincubation with GM-CSF, which has been shown to enhance PMN responsiveness and to prime PMN for production of those bioactive lipids. NAP-1/IL-8 does not induce the synthesis of PAF and LTB4 from endogenous phospholipid precursors, even after preincubation with GM-CSF. In addition and again in contrast to fMLP and C5a, NAP-1/IL-8 fails to induce an enhanced oxidative burst in GM-CSF primed PMN. Exogenously added PAF or LTB4 can mimic the priming effect of GM-CSF for an enhanced oxidative burst in response to all examined chemotactic peptides including NAP1/IL-8. Our data reveal a possible autocrine role of PAF and LTB4 in the enhanced responsiveness of GM-CSF primed PMN towards fMLP or C5a, but not NAP-1/IL-8.

Generation of interleukin-8 by plasmin from AVLPR-interleukin-8, the human fibroblast-derived neutrophil chemotactic factor

Plasmin mainly cleaved the Arg5-Ser6 bond of Arg-Val-Leu-Pro-Arg-interleukin-8 (AVLPR-IL-8) produced by human dermal fibroblasts, which resulted in the conversion of AVLPR-IL-8 to IL-8 and the inactive pentapeptide, though a minor cleavage of AVLPR-IL-8 by plasmin at Lys8-Glu9 bond occurred.

Inflammatory properties of neutrophil-activating protein-1/interleukin 8 (NAP-1/IL-8) in human skin: a light- and electronmicroscopic study

Neutrophil-activating protein-1/interleukin 8 (NAP-1/IL-8), purified to homogeneity from lipopolysaccharide-stimulated human peripheral blood monocytes, was injected intracutaneously into human skin. Sequential biopsy specimens were taken in order to investigate the sequence of ultrastructural changes induced by the cytokine. Whereas intracutaneous injection of 100 ng of NAP-1/IL-8 per site caused no macroscopic changes, by histology infiltration with polymorphonuclear leukocytes (PMN) and monocytes was present within 1 h and increased at 3 and 5 h. No lymphocyte infiltration was noted. The first ultrastructural changes (30 min) consisted of the presence of cytoplasmic 7-nm microfilament bundles, as well as numerous protrusions of the luminal plasma membrane of endothelial cells (EC). As a striking feature, multiple 100- to 160-nm electron lucent vesicles could be observed in the EC cytoplasm. These structures differed from plasmalemmal vesicles and suggest secretory activity. When PMN and monocytes appeared in the vascular lumen (1 h and later), the number of 100-160-nm electron-lucent vesicles had decreased significantly. In contrast to C5a-injected skin sites, mast cell degranulation was absent.

Formation of neutrophil-activating peptide 2 from platelet-derived connective-tissue-activating peptide III by different tissue proteinases

Neutrophil-activating peptide 2 (NAP-2) is generated by cleavage of two inactive precursors, connective-tissue-activating peptide III (CTAP-III) and platelet basic protein (PBP), which are stored in the alpha-granules of blood platelets. Using highly purified CTAP-III as the substrate we studied the generation of NAP-2 by several neutral tissue proteinases. CTAP-III was rapidly cleaved by chymotrypsin, cathepsin G and trypsin, yielding products with neutrophil-stimulating activity. This activity remained unchanged for 24 h in the presence of chymotrypsin, decreased only slowly in the presence of cathepsin G, but was rapidly destroyed by trypsin. CTAP-III was also degraded by human neutrophil elastase and porcine pancreatic elastase, but no active fragments were obtained. By contrast, no degradation of CTAP-III was observed with thrombin, plasmin or 'granzymes' from cytolytic T-lymphocyte granules. Two active fragments of CTAP-III, generated by chymotrypsin or cathepsin G, were purified and partially sequenced, and were found to have the same N-terminal sequence as NAP-2. These results indicate that both proteinases cleave preferentially the bond between amino acids 15 (Tyr) and 16 (Ala) of CTAP-III. We conclude that chymotrypsin-like proteolytic activity in the vicinity of activated platelets may generate NAP-2 intravascularly. Due to its presence in the primary granules of neutrophils and monocytes cathepsin G is likely to be involved in this process.

Influence of a muramyl dipeptide on human blood leukocyte functions and their membrane antigens

Murabutide, which belongs to the immunomodulator family of muramyl peptides, was applied directly to fresh human blood to evaluate changes in leukocyte properties. After blood incubation with murabutide, lymphocytes presented a higher responsiveness to T-mitogens, and monocytes and polymorphonuclear cells exhibited an increase in their capacity to produce hydrogen peroxide. In addition, murabutide treatment enhanced phagocytic activity of neutrophils, whereas monocytes presented a decrease in this activity. Some surface markers were also investigated in the distinct leukocyte populations. After incubation with murabutide, a larger number of lymphocytes expressed Ta1 antigen (CD W26) and transferrin receptor (CD 71). In contrast, expression of interleukin-2 receptor (CD 25) was slightly decreased. Monocytes from treated blood displayed a larger number of receptors for C3bi (CD 11b), whereas the surface marker CD 14 and the class I receptor for the Fc portion of IgG were down-regulated. Activation of polymorphonuclear cells by murabutide was confirmed by the up-regulation of the C3bi receptor, Fc receptor, and CD 14 surface antigen. The effects of murabutide on leukocytes described in this paper may contribute to understanding mechanisms of the modulating activity of muramyl peptides on specific and nonspecific immunity.

Detection of interleukin 8 and tumor necrosis factor in normal humans after intravenous endotoxin: the effect of antiinflammatory agents

Interleukin 8 (IL-8), a potent activator of neutrophils, may be important in the early host response to serious Gram-negative infections. IL-8 was measured with other acute phase cytokines (tumor necrosis factor alpha [TNF-alpha], IL-6 and IL-1 beta) in 25 normal humans randomized to receive either intravenous endotoxin alone or endotoxin after oral administration of ibuprofen or pentoxifylline, agents that alter some of the inflammatory responses induced by endotoxin in vitro. TNF immunoreactivity was maximum at 1.5 h, and total TNF (area under the curve) was 4.2- and 4.5-fold greater in subjects given endotoxin/ibuprofen compared to subjects given endotoxin alone (p = 0.026) or endotoxin/pentoxifylline (p = 0.004), respectively. IL-6 levels were maximum at 2-3 h and did not differ among the three groups. No IL-1 beta was detected in any subject. IL-8 levels peaked at 2 h in subjects given either endotoxin alone or endotoxin/pentoxifylline, falling towards baseline by 5 h. Subjects given endotoxin/ibuprofen had a more sustained rise in IL-8 with peak levels 2.8- and 2.5-fold higher at 3 h compared to endotoxin alone (p = 0.048) or endotoxin/pentoxifylline (p = 0.023), respectively. Differences in total IL-8 release among groups approached statistical significance (ANOVA, p = 0.07). This trend reflected the increased release of IL-8 by the subjects receiving ibuprofen compared to pentoxifylline (1.9-fold higher; p = 0.024). This suggests that cyclooxygenase products may provide important negative feedback loops for cytokine production in vivo. Increases in circulating IL-8 are part of the acute inflammatory response of humans to endotoxin. Altered cytokine responses caused by antiinflammatory therapy may have important implications for both host defense and injury during septicemia.

Interleukin-1 beta and tumor necrosis factor-alpha induce gene expression and production of leukocyte chemotactic factors, colony-stimulating factors, and interleukin-6 in human mesangial cells

The capacity of human cultured mesangial cells to produce soluble factors potentially relevant for mechanisms of inflammation and immunity at the glomerular site was analyzed. The nature of the secreted factors initially was investigated by Northern blot analysis using total cellular RNAs isolated from resting and activated mesangial cells. On exposure of mesangial cells to human recombinant interleukin-1 beta (IL-1 beta), high levels of interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) mRNAs were detected. Similar transcripts were found after stimulation with human recombinant tumor necrosis factor-alpha (TNF-alpha). Active secretion of IL-8 was documented by radioimmunoassay in supernatants of mesangial cells activated by either IL-1 beta or TNF-alpha. Using an in vitro migration assay, supernatants from resting mesangial cells were found to be devoid of any chemotactic activity for granulocytes or monocytes. On stimulation with IL-1 beta, however, mesangial cell supernatants expressed MCP-1 biologic activity detected as induction of a strong migratory response for human monocytes but not for granulocytes. In addition, IL-1 beta and TNF-alpha induced high levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage colony-stimulating factor (M-CSF) mRNAs. Similarly IL-1 beta and TNF-alpha induced the interleukin-6 (IL-6) gene and active secretion of its mature protein. These data strongly support an effector role for mesangial cells in modulating immune-inflammatory responses in glomeruli. Release of cytokines may activate not only infiltrating inflammatory cells through short paracrine pathways, but also mesangial cells themselves through an autocrine pathway.

Contrasting roles for tumor necrosis factor in the pathogeneses of IgA and IgG immune complex lung injury

Recent studies suggest that development of acute gamma G immunoglobulin (IgG) immune complex lung injury is partially dependent on a tumor necrosis factor (TNF)-dependent mechanisms of neutrophil (PMN) recruitment. The authors have sought to further define the role of intrapulmonary TNF in IgG alveolitis and to examine its role in IgA immune complex alveolitis, a neutrophil-independent model of acute lung injury. IgG immune complex lung injury resulted in a marked rise in intrapulmonary TNF activity accompanied by progressive pulmonary PMN accumulation. Intratracheal instillation of neutralizing concentrations of anti-TNF markedly reduced PMN influx measured at 4 hours but had no effect on PMN recruitment quantitated at 2 hours. IgA immune complex deposition resulted in acute lung injury accompanied by increased numbers of intrapulmonary mononuclear phagocytes but few neutrophils. Lung lavage fluids obtained from IgA immune complex-injured rats contained both neutrophil and monocyte chemotactic activities, albeit at twofold to fourfold lower concentrations than observed in IgG-mediated alveolitis. In contrast to IgG complex-mediated alveolitis, lung lavage fluids from IgA-injured rats contained no TNF activity. Intratracheal administration of anti-TNF antibodies had no effect on the development of IgA lung injury as assessed by morphology and measurements of vascular permeability. In vitro exposure of isolated alveolar macrophages to performed IgG immune complexes resulted in dose-dependent TNF secretion, while exposure to IgA complexes resulted in very low levels of TNF secretion. These data suggest that TNF-mediated pulmonary neutrophil recruitment (in IgG lung injury) is manifest chiefly in the late phase (approximately 4 hours) of developing alveolitis. The virtual absence of intrapulmonary TNF activity in evolving IgA immune complex alveolitis may in part account for the limited PMN recruitment observed in this model.

Induction of neutrophil-mediated cartilage degradation by interleukin-8

Neutrophil influx into the inflamed joint is a characteristic feature of disease flares in patients with rheumatoid arthritis. Recently, a protein produced by monocytes and fibroblasts that has chemoattractive/activating properties for neutrophils has been identified and characterized. This protein has been called interleukin-8 (IL-8). In this study, we cocultured neutrophils with 35S-sulfate-labeled cartilage and found that the addition of recombinant human IL-8 (rHuIL-8) caused rapid, neutrophil-mediated cartilage degradation that was the result of induction of neutrophil degranulation by the cytokine. With 10(-7)M rHuIL-8, 23% of the radiolabel was released into the culture medium in 4 hours, compared with a 9% release without the factor. At concentrations of up to 10(-6)M, rHuIL-8 had no direct effect upon cartilage breakdown. These findings indicate that IL-8 may participate in the pathogenesis of rheumatoid arthritis through the induction of neutrophil-mediated cartilage damage.

Paradoxical regulation by PGE-2 on release of neutrophil chemoattractants by rat bone marrow macrophages

Prostaglandin E2 (PGE2) was shown to cause up to a 110% increase in the release into media of soluble chemoattractants for neutrophils by cultured rat bone marrow macrophages (RBMM) during a 16 hour incubation period. Coincubating with concentrations of PGE2 of 10 nM and below did not stimulate release of chemoattractants while concentrations between 10(2) and 10(4) nM increased the chemotactic activity of conditioned medium by 40% to 110% (p less than 0.05). In contrast to the effect of coincubating, pre-treatment with PGE2 for 2 and 4 hours was ineffective in stimulating the release of chemoattractants by RBMM. We also assessed whether PGE-2 modulated the release of chemoattractants by RBMM stimulated with endotoxin (LPS). LPS caused a four fold increase in the production of chemoattractants with a peak effect found at an LPS concentration of 1 microgram/ml. Coincubating with PGE2 in concentrations between 10(2) and 10(4) nM paradoxically decreased LPS-stimulated production of chemoattractants by up to 40% (p less than 0.05). Pre-treatment with PGE2 for 4 hours partially blocked LPS-stimulated release of chemotactic activity. These data indicate that PGE-2 has paradoxical effects on the production of chemoattractants by RBMM: being independently stimulatory but down regulating the effects of LPS. These findings suggest the possibility that the activation state of the RBMM may determine the effect of PGE2: quiescent RBMM can be stimulated by PGE2 but LPS-activated RBMM may be suppressed.

Phagocytosing neutrophils produce and release high amounts of the neutrophil-activating peptide 1/interleukin 8

After phagocytosis of yeast opsonized with IgG, neutrophil leukocytes (polymorphonuclear leukocytes [PMN]) expressed high levels of neutrophil-activating peptide 1/interleukin 8 (NAP-1/IL-8) mRNA, which peaked after 3-5 h and were still elevated after 18 h. A similar but quantitatively less prominent effect was obtained with lipopolysaccharide (LPS). After phagocytosis, but not after exposure to LPS, the PMN progressively released considerable amounts of NAP-1/IL-8 into the culture medium (18.6-50 ng/ml in 18 h). The peptide released was biologically active, as indicated by the transient elevation of cytosolic-free calcium in PMN exposed to aliquots of the culture supernatants, and desensitization by prestimulation of the cells with recombinant NAP-1/IL-8. By producing NAP-1/IL-8 at sites where they phagocytose invading microorganisms, PMN could enhance the recruitment of new defense cells.

The hematopoietic microenvironment

Hematopoietic microenvironment is comprised of an admixture of several adherent cell types including fibroblasts, reticular adventitial cells, and marcophages. The biologic interaction of these cells with the most primitive hematopoietic progenitor cells capable of reconstituting all hematopoietic lineages within an irradiated host, as well as differentiated progenitor cells and cells of each committed lineage, has been the subject of intense investigation. Transplantation of the hematopoietic microenvironment has recently been demonstrated and this technique has been used to partially correct the microenvironmental defect in the Sl/Sld mouse. The molecular mechanism of cell surface interaction between stromal and hematopoietic stem cells is being elucidated by molecular transfection techniques in which genes for specific receptors are introduced into hematopoietic stem cell lines and then demonstrated to adhere and proliferate in contact with stromal cells expressing transfected recombinant ligands. This model has been demonstrated with the EGF receptor bearing 32D cl 3 stem cells bound to TGF alpha-producing stromal cells. Extracellular matrix components of the adherent cell layer, the binding of hematopoietic growth factor interaction with matrix components, as well as the positive and negative feedback regulatory role of hematopoietic stem cells bound to the microenvironment, represents the focus of current investigation.

Sandwich ELISA for detection of picogram quantities of interleukin-8

A sensitive sandwich enzyme-linked immunosorbent assay (ELISA) was developed for interleukin-8 (IL-8), a neutrophil chemoattractant and activator. A polyclonal antibody to recombinant human IL-8 was raised in rabbits, and the IgG was isolated from the antisera using a protein A column. Native and biotinylated forms of this antibody served as the capture antibody and developing antibody for the ELISA, respectively, and avidin-conjugated horse radish peroxidase provided the means for enzymatic color development. The lower limit of sensitivity for the assay was found to be 84 +/- 20 pg/ml IL-8 (mean +/- SD for 10 determinations). An inter-assay variability of 15-29% and an intra-assay variability of 12% were observed. The assay was able to detect IL-8 when the samples were prepared in either normal saline, RPMI, or human plasma. The development of this rapid, sensitive assay should provide a means to more fully evaluate the role of this cytokine in diverse disease states.

The priming effects of the products of stimulated mononuclear cells on the response of neutrophils to C5a des arg

Certain recombinant human cytokines have been shown to enhance polymorphonuclear leucocyte (PMN) responses to subsequent stimulation. Mononuclear cells (MNC) from normal healthy individuals were stimulated for 5 h with 1 micrograms/ml bacterial lipopolysaccharide (LPS) in order to induce production and secretion of inflammatory cytokines into the surrounding medium. These mononuclear cell conditioned media (MNCM) were then used to prime PMN isolated from healthy volunteers. Preincubating the PMN with MNCM for 15 min at 4 degrees C followed by washing and warming to 37 degrees C caused a 344% increase (n = 26) in the rate of superoxide anion production in response to zymosan-activated serum (ZAS), a source of C5a des arg. This effect could not be reproduced with recombinant human forms of interleukin 1 beta (Il-1 beta) or granulocyte-macrophage-colony stimulating factor (GM-CSF), although, with the latter, there was some effect when the preincubation stage was carried out for 60 min at 37 degrees C. Only recombinant human tumour necrosis factor-alpha (rh-TNF-alpha) gave a similar PMN priming effect to that seen with MNCM. This effect could not be reversed by washing away either the MNCM or rh-TNF-alpha. The priming effect could be markedly reduced (74.8%, n = 6) by employing the use of polyclonal antibody to TNF-alpha in the preincubation step; assaying for TNF-alpha in these MNCMs showed that the degree of priming corresponded to the amount of TNF-alpha present. Rh-TNF-alpha alone appeared to have very little direct stimulatory effect on respiratory burst activity. The results show that TNF-alpha produced by LPS stimulated MNC after 5 h binds to a PMN surface receptor in the cold and warming of the cells to 37 degrees C allows for an immediate and dramatic response to ZAS stimulation. This suggests that TNF-alpha is the important cytokine upregulating PMN responses to other physiological mediators, including C5a des arg during the early phases of an inflammatory reaction.

Inhibition of leukotriene biosynthesis and polymorphonuclear leukocyte functions by orally active quinolylmethoxyphenylamines

The N-substituted quinolylmethoxyphenylamines, ETH603, ETH615 and ETH647, inhibited the formation of LTB4 in rat peritoneal leukocytes, human peripheral polymorphonuclear leukocytes and canine whole blood. In rat and human cells, the compounds also inhibited the formation of 5-HETE and stimulated the synthesis of 15-HETE. In rat leukocytes, the compounds were 15-30 times more potent inhibitors of LTB4 synthesis than nordihydroguaiaretic acid, but in canine whole blood they were significantly less potent, possibly due to protein binding. However, after oral administration of the compounds to dogs a long-lasting inhibition of LTB4 production in peripheral blood was observed at serum concentrations much lower than those required in vitro. Furthermore, the compounds inhibited the LTB4-directed chemotaxis and the phagocytosis of C. albicans blastospores by canine polymorphonuclear leukocytes both in vitro and following oral administration. The calcium ionophore A23187-induced release of LTB4 in the peritoneal cavity of rats was also inhibited by systemic administration of the compounds. We therefore conclude that these novel quinolines are orally active 5-lipoxygenase inhibitors which may accumulate in inflammatory cells in vivo, leading to potent inhibition of leukotriene biosynthesis and cell function.

Enhanced production of neutrophil-activating peptide-1/interleukin-8 in rheumatoid arthritis

Production of the neutrophil-activating peptide (NAP)-1/IL-8 by mononuclear phagocytes from patients with RA and from control subjects was studied under various conditions. Mononuclear cells from bone marrow (BMMC), PBMC, and synovial fluid (SFMC) were cultured for up to 48 h in the absence or presence of Escherichia coli LPS, different interleukins, interferon-gamma, zymosan, or immune complexes, and the neutrophil-stimulating activity released into the culture medium was determined. As shown by neutralization with an antiserum raised against human recombinant NAP-1/IL-8, over 90% of this activity could be attributed to NAP-1/IL-8. In unstimulated mononuclear cells from control individuals and BMMC from RA patients, the production of NAP-1/IL-8 was very low and was enhanced moderately by stimulation with LPS. By contrast, the spontaneous production of NAP-1/IL-8 was 3- to 10-fold higher in PBMC and even much higher in SFMC from RA patients. In all instances, the yield of NAP-1/IL-8 could be enhanced by stimulation in culture. In addition to LPS, rheumatoid factor-containing immune complexes, zymosan, and IL-1 were highly effective in inducing NAP-1/IL-8 production, while IL-3, GM-CSF, tumor necrosis factor (TNF), and IL-2 were somewhat less potent. An inhibitory effect was obtained with IFN-gamma, which significantly decreased the spontaneous NAP-1/IL-8 release from SFMC and the IL-1- and LPS-induced NAP-1/IL-8 from RA and control PBMC. Inhibition was also observed with glucocorticoids. The production of NAP-1/IL-8 was markedly reduced by dexamethasone in phagocytosis-stimulated PBMC, and almost totally inhibited in SFMC obtained from joints after intraarticular administration of betamethasone. By contrast, the cyclooxygenase inhibitor, indomethacin, tended to increase the NAP-1/IL-8 yield from PBMC in culture.

Small cytokine superfamily

Proteins comprising a newly described superfamily of small inducible cytokines (tentatively designated 'scy') exhibit considerable similarity with respect to activity, regulation and genomic structure. Recent observations, however, have identified specific biological activities and contexts in which these cytokines differ and which may allow fine tuning of immune and inflammatory responses.

Kinetics of TNF, IL-6, and IL-8 gene expression in LPS-stimulated human whole blood

While the production of tumor necrosis factor (TNF) and interleukin-6 (IL-6) in septic shock and other inflammatory states is well established, the role of interleukin-8 (IL-8), a recently described neutrophil chemoattractant and activator, has yet to be fully elucidated. Using lipopolysaccharide (LPS)-stimulated human whole blood as an ex vivo model of sepsis, the kinetics of messenger RNA (mRNA) up-regulation and protein release of these cytokines were examined. Two waves of cytokine gene activation were documented. TNF and IL-6 were induced in the first wave with mRNA levels peaking between 2-4 hours and then rapidly declining. TNF and IL-6 protein peaked at 4-6 hours and then stabilized. IL-8 mRNA and protein were induced in the first wave, reached a plateau between 6-12 hours, and rose again in a second wave which continued to escalate until the end of the 24 hour study. These data demonstrate the complex patterns of cytokine gene expression and suggest that production of early mediators may augment continued expression of IL-8 to recruit and retain neutrophils at a site of inflammation.

Interleukin-8 induces neutrophil transendothelial migration

Interleukin-8 (IL-8) is a potent neutrophil chemotactic stimulant. We have used chemically synthesized IL-8 to investigate its role in human neutrophil adhesion and transendothelial migration. IL-8 enhanced the adhesiveness of human neutrophils to plastic, and to both unstimulated and tumour necrosis factor (TNF)-stimulated endothelial monolayers in vitro. Using a two-compartment model separated by a confluent endothelial monolayer, we have shown that IL-8 chemotactic stimulation induced transmigration across the monolayer of up to 87.4 +/- 2.1% of added neutrophils (compared to random unstimulated transmigration of 2.2 +/- 0.7%), while chemokinetic stimulation led to transmigration of 21 +/- 3.8% of neutrophils. Preincubation of endothelium with TNF also induced transmigration in this model, and was additive when combined with an IL-8 chemotactic stimulus. Endothelial permeability was increased at maximal rates of chemotactic transmigration, which may correlate with increased permeability of vessels at inflammatory sites in vivo. The property of IL-8 to stimulate movement of neutrophils across endothelial monolayers in vitro supports the concept of a central role for this molecule in the accumulation of neutrophils at inflammatory lesions in vivo.

Induction and regulation of interleukin-8 gene expression

Recent advances in understanding granulocyte elicitation have been made with the discovery and isolation of chemotactic cytokines. There is little doubt that these polypeptides will prove to be important mediators of disease process. Therefore, studies directed at understanding the production and regulation of interleukin-8 will continue to be a fertile area to explore mechanisms of disease processes and therapeutic targets.

Cellular and molecular mechanisms of cytokine networking

A number of scientific investigations support the theory that the coordinate expression of cytokines are paramount to the successful initiation and maintenance of inflammation. Interleukin-1 and TNF appear particularly important in that these cytokines are important as both proximal and distal mediators of disease. The importance of IL-1 and TNF during early inflammatory events are exemplified via their ability to upregulate the expression of adherence proteins on the endothelium and allow inflammatory cells to bind to a localized area. In addition, these same cytokines can induce the expression of specific chemotactic cytokines from non-immune cells by a cascade effect known as cytokine networking. This interaction essentially transforms a bystander or target cell of the inflammatory response into an effector cell. Once the appropriate inflammatory cell has arrived at an inflammatory site, cytokines continue to be expressed and exert their influence by organizing the local immune response. Finally, the appropriate endogenous suppressive factors are expressed that initiate the resolution process. Thus, cytokines are effective transmitters of intracellular information that is crucial to each phase of an inflammatory reaction.

Chemotactic potency of recombinant human neutrophil attractant/activation protein-1 (interleukin-8) for polymorphonuclear leukocytes of different species

In order to establish the species cross-reactivity of the human neutrophil attractant/activation protein-1 (interleukin-8, NAP-1/IL-8) and find which experimental species are responsive to the human cytokine, blood polymorphonuclear leukocytes (PNMLs) were isolated from chicken, dog, goat, guinea-pig, monkey, mouse, pig, rabbit, and rat and their in vitro migration in response to this cytokine was investigated. PMNLs from all of the tested species migrated in response to recombinant human NAP-1/IL-8 (rhNAP-1/IL-8). The potency of rhNAP-1/IL-8 for the PMNLs of different species varied and was considerably lower than its potency for human cells. The morphological study combined with the leukocyte enumeration in the intradermal rhNAP-1/IL-8 injection sites established an in vivo proinflammatory potency of rhNAP-1/IL-8 for rabbit and rat that was comparable to the observed in vitro chemotactic potency of rhNAP-1/IL-8 for neutrophils of these species.