Elevation of PMN cytosolic free calcium and locomotion stimulated by novel peptides from IL-1-treated human synovial cell cultures

The forgotten key players in rheumatoid arthritis: IL-8 and IL-17 - Unmet needs and therapeutic perspectives

Despite the relevant advances in our understanding of the pathogenetic mechanisms regulating inflammation in rheumatoid arthritis (RA) and the development of effective therapeutics, to date, there is still a proportion of patients with RA who do not respond to treatment and end up progressing toward the development of joint damage, extra-articular complications, and disability. This is mainly due to the inter-individual heterogeneity of the molecular and cellular taxonomy of the synovial membrane, which represents the target tissue of RA inflammation. Tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6) are crucial key players in RA pathogenesis fueling the inflammatory cascade, as supported by experimental evidence derived from in vivo animal models and the effectiveness of biologic-Disease Modifying Anti-Rheumatic Drugs (b-DMARDs) in patients with RA. However, additional inflammatory soluble mediators such as IL-8 and IL-17 exert their pathogenetic actions promoting the detrimental activation of immune and stromal cells in RA synovial membrane, tendons, and extra-articular sites, as well as blood vessels and lungs, causing extra-articular complications, which might be excluded by the action of anti-TNFα and anti-IL6R targeted therapies. In this narrative review, we will discuss the role of IL-8 and IL-17 in promoting inflammation in multiple biological compartments (i.e., synovial membrane, blood vessels, and lung, respectively) in animal models of arthritis and patients with RA and how their selective targeting could improve the management of treatment resistance in patients.

Induction of biologically active interleukin-8 from lung epithelial cells by Burkholderia (Pseudomonas) cepacia products

The frequency of isolation of Burkholderia cepacia from the sputum of cystic fibrosis (CF) patients is increasing. Using the human A549 lung epithelial cell line, we have investigated the ability of B. cepacia exoproducts to stimulate interleukin-8 (IL-8) release. Cell-free supernatants from a panel of CF clinical, non-CF clinical, and nonclinical B. cepacia isolates were found to stimulate IL-8 release, with levels ranging from 11.8 +/- 2.8 to 80.0 +/- 3.5 ng/ml. A similar pattern was seen at the level of the IL-8 mRNA. The bioactivity of the IL-8 was confirmed by examining its effect on the intracellular free calcium in neutrophils and inhibition by a neutralizing anti-IL-8 antibody. B. cepacia lipopolysaccharide, which was able to stimulate IL-8 release from monocytes, did not release IL-8 from the A549 cells. Furthermore, the stimulating ability of the bacterial cell-free supernatant was not diminished by polymyxin B, was markedly reduced by boiling, and appeared unrelated to N-acylhomoserine lactones. The ability of B. cepacia to elicit IL-8 release from epithelial cells may be important in the pathology of CF.

Differential effects of protein kinase C inhibitors on chemokine production in human synovial fibroblasts

1. Rheumatoid arthritis is associated with the accumulation and activation of selected populations of inflammatory cells within the arthritic joint. One putative signal for this process is the production, by resident cells, of a group of inflammatory mediators known as the chemokines. 2. The chemokines interleukin-8 (IL-8), monocyte chemotactic protein-1 (MCP-1) and RANTES (regulated on activation normal T-cell expressed and presumably secreted) are target-cell specific chemoattractants produced by synovial fibroblasts in response to stimulation with interleukin-1 alpha (IL-1 alpha) or tumour necrosis factor alpha (TNF alpha). The signalling pathways involved in their production are not well defined. We therefore used four different protein kinase C inhibitors to investigate the role of this kinase in the regulation of chemokine mRNA and protein expression in human cultured synovial fibroblasts. 3. The non-selective PKC inhibitor, staurosporine (1-300 nM) significantly increased the production of IL-1 alpha-induced IL-8 mRNA and protein. A specific PKC inhibitor, chelerythrine chloride (0.1-3 microM), also caused a small concentration-dependent increase in IL-8 mRNA and protein production. In contrast, 3-[1-[3-(amidinothio)propyl]-3-indoly]-4-(1-methyl-3-indolyl )- 1H-pyrrole-2,5-dione methanesulphonate (Ro 31-8220) and 2[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3- yl)-maleimide (GF 109203X), two selective PKC inhibitors of the substituted bisindolylmaleimide family had a concentration-dependent biphasic effect on IL-1 alpha or TNF alpha-induced chemokine expression. At low concentrations they caused a stimulation in chemokine production, which was especially evident at the mRNA level. At higher concentrations both inhibited IL-1 alpha or TNF alpha-induced chemokine mRNA and protein production. Ro 31-8220 was 10 fold more potent than GF 109203X, with an IC50 of 1.6 +/- 0.08 microM (mean +/- s.e.mean, n = 4) for IL-1 alpha induced IL-8 production. Ro 31-8220 also inhibited the expression of IL-1 alpha or TNF alpha-induced MCP-1 and RANTES mRNA with a similar potency. 4. The stimulatory effect of staurosporine is discussed in relation to the known poor selectivity of this inhibitor for PKC. It is proposed that activation of an isoform of PKC, possibly PKC epsilon or zeta, which is inhibited by higher concentrations of the bisinodolylmaleimides, plays a role in the regulation of chemokine expression induced by IL-1 alpha or TNF alpha in synovial cells. 5. The inhibition of chemokine production by bisindolylmaleimide compounds heralds a novel approach for future anti-inflammatory therapies.

The protein phosphatase inhibitor calyculin A stimulates chemokine production by human synovial cells

Cultured human synovial fibroblasts express mRNA for the chemotactic cytokines (chemokines) interleukin-8 (IL-8), monocyte chemotactic protein 1 (MCP-1) and regulated upon activation normal T-cell expressed and presumably secreted (RANTES), when stimulated with IL-1 or tumour necrosis factor alpha (TNF alpha). Calyculin A, a potent type 1/2A protein serine/threonine phosphatase inhibitor, was used to examine the role of protein phosphatases in the regulation of chemokine gene expression. Calyculin A (1 nM) mimicked IL-1 by inducing IL-8 and MCP-1 mRNA expression in synovial cells. IL-8 mRNA was induced over a similar time period (1-6 h) in response to IL-1 or calyculin A, whereas MCP-1 mRNA was induced more rapidly (1-2 h) by calyculin A than by IL-1 (4-6 h). Expression of RANTES mRNA occurred in response to TNF alpha, but could not be induced by stimulation with calyculin A alone. These results suggest that inhibition of protein phosphatase type 1/2A may have a differential role in the regulation of the expression of each of the chemokine genes. Synovial fibroblasts also secreted IL-8 and IL-6 peptide when stimulated with either IL-1/TNF alpha or calyculin A. The amount of IL-8 and IL-6 peptide produced in response to calyculin A was significantly increased above that produced by untreated synovial cells, though it was much less than the amount induced by IL-1 or TNF alpha. Calyculin A also acted synergistically with IL-1 or TNF alpha to cause a 2-fold potentiation of IL-1- or TNF alpha-induced IL-8 mRNA and peptide and RANTES mRNA expression. These results suggest that although inhibition of a protein phosphatase may be able to regulate the magnitude of IL-1-induced chemokine gene expression, the IL-1 signal transduction pathway involves components in addition to phosphatase inhibition, possibly including the activation of a protein kinase, the action of which may be opposed by a protein phosphatase inhibited by calyculin A.

Interleukin-8 gene expression in chronic sinusitis

PURPOSE

Interleukin-8 (IL-8), a monocyte-derived and macrophage-derived cytokine, displays potent chemotactic activating properties toward neutrophils and thus may contribute to the pathogenesis of chronic sinusitis. The object of this investigation was to show the expression of the IL-8 gene in chronic sinusitis by Northern blot analysis and a reverse transcription-polymerase chain reaction (RT-PCR).

MATERIALS AND METHODS

For Northern blot analysis, RNAs were extracted from maxillary mucosa and nasal polyps from two patients with chronic sinusitis, respectively, and from the inferior turbinate of a nasal allergy patient. For RT-PCR, RNAs were extracted from 11 patients with chronic sinusitis, 8 patients with allergic rhinitis, and 4 patients with hypertrophic rhinitis.

RESULTS

Whereas IL-8 mRNA was expressed in the maxillary mucosa, IL-8 transcript was not detected in the inferior turbinate by Northern blot analysis. IL-8 transcripts were detected in 45% of chronic sinusitis RNAs (5/11) and in 50% of allergic rhinitis RNAs (5/10) by RT-PCR.

CONCLUSION

These data suggest IL-8 may contribute to neutrophil involvement in chronic sinusitis.

Epithelial neutrophil activating peptide-78: a novel chemotactic cytokine for neutrophils in arthritis

We and others have shown that cells obtained from inflamed joints of rheumatoid arthritis (RA) patients produce interleukin-8, a potent chemotactic cytokine for neutrophils (PMNs). However, IL-8 accounted for only 40% of the chemotactic activity for PMNs found in these synovial fluids. Currently, we have examined the production of the novel PMN chemotactic cytokine, epithelial neutrophil activating peptide-78 (ENA-78), using peripheral blood, synovial fluid, and synovial tissue from 70 arthritic patients. RA ENA-78 levels were greater in RA synovial fluid (239 +/- 63 ng/ml) compared with synovial fluid from other forms of arthritis (130 +/- 118 ng/ml) or osteoarthritis (2.6 +/- 1.8 ng/ml) (P < 0.05). RA peripheral blood ENA-78 levels (70 +/- 26 ng/ml) were greater than normal peripheral blood levels (0.12 +/- 0.04 ng/ml) (P < 0.05). Anti-ENA-78 antibodies neutralized 42 +/- 9% (mean +/- SE) of the chemotactic activity for PMNs found in RA synovial fluids. Isolated RA synovial tissue fibroblasts in vitro constitutively produced significant levels of ENA-78, and this production was further augmented when stimulated with tumor necrosis factor-alpha (TNF-alpha). In addition RA and osteoarthritis synovial tissue fibroblasts as well as RA synovial tissue macrophages were found to constitutively produce ENA-78. RA synovial fluid mononuclear cells spontaneously produced ENA-78, which was augmented in the presence of lipopolysaccharide. Immunohistochemical localization of ENA-78 from the synovial tissue of patients with arthritis or normal subjects showed that the predominant cellular source of this chemokine was synovial lining cells, followed by macrophages, endothelial cells, and fibroblasts. Synovial tissue macrophages and fibroblasts were more ENA-78 immunopositive in RA than in normal synovial tissue (P < 0.05). These results, which are the first demonstration of ENA-78 in a human disease state, suggest that ENA-78 may play an important role in the recruitment of PMNs in the milieu of the inflamed joint of RA patients.

Interleukin-8 gene expression in middle ear effusions

Interleukin-8 (IL-8), a monocyte- and macrophage-derived cytokine, displays potent chemotactic-activating properties toward neutrophils, and thus may contribute to the pathogenesis of otitis media with effusion (OME). The objective of this investigation was to demonstrate the expression of the IL-8 gene in middle ear effusion (MEEs) of children and adults with OME. Ribonucleic acids (RNAs) were extracted from MEEs from 16 ears of 13 pediatric patients and 12 ears of 12 adult patients with OME. The RNAs were reverse-transcribed and amplified by the polymerase chain reaction. Interleukin-8 transcripts were detected in 75% of both pediatric (12/16) and adult MEEs (9/12). The levels of expression of IL-8 and beta-actin messenger RNAs were quantitated. No significant difference was observed in IL-8/beta-actin ratios between pediatric MEEs and adult MEEs. These data suggest that IL-8 may contribute to neutrophil involvement in both pediatric and adult OME.

Monocyte chemoattractant protein 1 and interleukin 8 production by rheumatoid synoviocytes. Effects of anti-rheumatic drugs

Activated synoviocytes are major effector cells in the pathogenesis of rheumatoid arthritis (RA) because of their capacity to secrete a variety of inflammatory mediators. Among these mediators, the chemotactic proteins monocyte chemoattractant protein 1 (MCP-1) and interleukin 8 (IL-8) are likely to contribute to the recruitment of inflammatory cells into the arthritic joint. We examined the effects of anti-rheumatic drugs on the MCP-1 and IL-8 production by cultured RA synoviocytes exposed to pro-inflammatory agonists. Both chemotactic cytokines were quantified by specific enzyme-linked immunosorbent assays (ELISA), and found to accumulate in the culture supernatants. Although the time course of formation was similar, the yield of IL-8 was three to 10-fold higher than that of MCP-1. Non-steroidal anti-inflammatory drugs inhibited the synthesis of prostaglandins, but did not influence the production and release of both chemotactic cytokines. Of three disease-modifying drugs tested, dexamethasone and gold sodium thiomalate (GST) inhibited the production of IL-8 and MCP-1, while methotrexate (MTX) was inactive. Dexamethasone reduced the production of MCP-1 and IL-8 by 20-65% and 60-80%, respectively, whilst GST inhibited MCP-1 and IL-8 synthesis in suboptimally, but not in optimally stimulated synoviocytes. Taken together, these results show that the production of MCP-1 and IL-8 is similarly affected by anti-rheumatic drugs and that dexamethasone is the most potent inhibitor suggesting that part of the anti-rheumatic action of glucocorticoids is due to prevention of accumulation of chemotactic cytokines acting on neutrophils and monocytes.

Synergistic effect of interleukin-1 beta and tumor necrosis factor alpha on interleukin-8 gene expression in synovial fibroblasts. Evidence that interleukin-8 is the major neutrophil-activating chemokine released in response to monokine activation

OBJECTIVE

To investigate both the involvement of chemokines in general and the relative importance of specific chemokines in rheumatoid arthritis (RA), we characterized the effect of the monokines tumor necrosis factor alpha (TNF alpha) and interleukin-1 beta (IL-1 beta) on the synthesis of neutrophil-activating factors by synovial fibroblasts isolated from the joints of patients with RA.

METHODS

Neutrophil-stimulating activity was assessed by determining intracellular calcium mobilization. IL-8 synthesis and secretion was assessed by specific enzyme-linked immunosorbent assay, and IL-8 messenger RNA (mRNA) levels were determined by Northern blot.

RESULTS

Treatment of synovial fibroblasts with IL-1 beta and TNF alpha resulted in the production of an activity which induced intracellular calcium mobilization in peripheral blood neutrophils. The 2 monokines combined had a synergistic effect on the release of the neutrophil-stimulating activity. The effect of the 2 monokines required gene transcription and translation, and closely mimicked the pattern of IL-8 secretion induced in these cells by the monokines. We confirmed that the majority of the neutrophil-stimulating activity was IL-8 by 3 different approaches: cross-desensitization experiments with IL-8, melanoma growth-stimulatory activity, and neutrophil-activating peptide 2, stimulation of calcium mobilization in cells transfected with the IL-8 receptor complementary DNA, and inhibition of the activity following pretreatment of the supernatants with an anti-IL-8 antibody. TNF alpha and IL-1 beta induced a time- and dose-dependent release of immunoreactive IL-8. A synergistic effect of TNF alpha and IL-1 beta was also observed for both IL-8 production and accumulation of IL-8 mRNA.

CONCLUSION

These results indicate that the monokines TNF alpha and IL-1 beta synergistically activate IL-8 expression and protein secretion by synovial fibroblasts, and that under these conditions, IL-8 appears to be the major neutrophil-activating factor released.

Neutrophil mucosal involvement is accompanied by enhanced local production of interleukin-8 in ulcerative colitis

The concentration of myeloperoxidase, a neutrophil granule constituent, was measured in the perfusion fluid from sigmoid and rectal segments in patients with ulcerative colitis. The concentrations of myeloperoxidase were increased severalfold in the patients with ulcerative colitis compared with healthy controls pointing to an enhanced neutrophil activity. The release of myeloperoxidase correlated to an enhanced local release of the neutrophil activating peptide interleukin-8 (IL-8). Increased values of tumour necrosis factor (TNF-alpha) were also found during intestinal perfusion of the patients and correlated with those of IL-8. The results obtained are compatible with the hypothesis that local mucosal recruitment/activation of neutrophils in ulcerative colitis is mediated by an enhanced IL-8 synthesis. TNF-alpha may be one relevant factor as a stimulus to IL-8 synthesis.

Interleukin-8 in inflammatory rheumatic diseases: synovial fluid levels, relation to rheumatoid factors, production by mononuclear cells, and effects of gold sodium thiomalate and methotrexate

The content of interleukin-8 (IL-8) in the synovial fluid and its production by blood and synovial fluid mononuclear cells (PBMC and SFMC) was compared in rheumatoid arthritis (RA) and various other inflammatory rheumatic disorders. The study included 125 patients and 20 healthy individuals. The highest concentrations of IL-8 were found in the synovial fluids and culture supernatants of PBMC and SFMC from patients with seropositive RA. Only PBMC from seropositive patients, and not from other rheumatic diseases, exhibited significant spontaneous release of IL-8 that correlated with serum IgM rheumatoid factor titers. Gold sodium thiomalate (GST) and methotrexate (MTX) inhibited the spontaneous and stimulated IL-8 production by PBMC by 55-86% at 50 and 10 micrograms/ml, respectively. Two main conclusions were drawn: (1) rheumatoid factors appeared to be a major cause of enhanced IL-8 production in seropositive RA, and (2) inhibition of IL-8-mediated neutrophil migration and activation could be part of the mechanism of action of GST and MTX.

Production of interleukin 8 by cultured synovial cells in response to interleukin 1 and tumor necrosis factor

Both interleukin 1 alpha (IL-1 alpha) and tumor necrosis factor alpha (TNF alpha) stimulated the production of interleukin 8 (IL-8) by synovial cells in time and dose dependent manners. Enhanced chemotactic activity of polymorphonuclear cells (PMN) in culture supernatants of synovial cells was neutralized with anti-IL-8 antibody, thus showing synovial cells to be capable of secreting IL-8 which may contribute to PMN accumulation in rheumatoid inflamed joints.

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.

Interleukin-1 induced gene expression of neutrophil activating protein (interleukin-8) and monocyte chemotactic peptide in human synovial cells

We report here that human synovial cells stimulated by interleukin-1 alpha and interleukin-1 beta express mRNA for both IL-8 (neutrophil chemotactic peptide) and monocyte chemotactic protein. IL-1 stimulated synovial cells from both osteoarthritis and rheumatoid arthritis patients exhibited similar mRNA expression of interleukin-8 and monocyte chemotactic protein. A capacity to produce factors selectively chemotactic for neutrophils, lymphocytes and monocytes provides a mechanism whereby synovial cells can facilitate inflammatory arthritis.

The chemotactic activity for granulocytes produced by virally infected fibroblasts is identical to monocyte-derived interleukin 8

So far, the role of fibroblasts in inflammatory processes has been underestimated. We have previously shown that stimulation of fibroblasts with viruses or bacteria results in a simultaneous production of several cytokines, including interferon-beta, interleukin (IL) 6 and colony-stimulating factors. We here report that virally infected fibroblasts produce also a chemotactic factor for granulocytes. The activity is inducible not only by measles virus but also by IL 1 beta and the double-stranded RNA poly(rI).poly(rC). This factor, when purified to homogeneity, occurs as a 6-7-kDa protein doublet upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The pure protein is serologically related to a fully characterized granulocyte chemotactic peptide (GCP) from monocytes, designated IL8. Furthermore, the chemotactic factor from fibroblasts has an NH2-terminal sequence identical to that of GCP/IL8, small differences in NH2-terminal processing being observed. Finally, in addition to diploid fibroblasts, the osteosarcoma MG-63 cell line is also a producer of GCP/IL8. It can thus be concluded that GCP/IL8 can be produced by several cell types in response to infection and that fibroblasts can contribute to chemotaxis in inflammation.

PMN stimulation by factors from IL-1-treated human synovial cell cultures

Following exposure of cultured human synovial cells to human recombinant interleukin 1 alpha (IL-1 alpha), we demonstrate the appearance of factors in the supernatant which stimulate human polymorphonuclear leukocyte (PMN) locomotion and elevate intracellular free calcium ([Ca++]i). The production of these factors can be abolished by actinomycin D or dexamethasone but not by cyclo-oxygenase or lipoxygenase inhibitors. In vivo, the supernatant induces a rapid accumulation of PMNs in rabbit skin following intradermal injection. These activities were not due to IL-1 itself, tumour necrosis factor (TNF alpha) or granulocyte-macrophage colony-stimulating factor (GM-CSF). Such factors may play an important role in inflammatory responses involving IL-1.

Inflammatory cytokines induce synthesis and secretion of gro protein and a neutrophil chemotactic factor but not beta 2-microglobulin in human synovial cells and fibroblasts

Exposure of human synovial cells and fibroblasts in monolayer culture to interleukin 1 results in prominent secretion of proteins with Mr values of 6000 and 7000. By N-terminal sequence analysis, the Mr-6000 protein is identified as the protein encoded by a recently described gro mRNA. The Mr-7000 protein is identical to a neutrophil chemotactic factor released from monocytes. Stimulation of normal human fibroblasts with tumour necrosis factor alpha also results in expression and secretion of these two proteins. In addition to these cytokine-induced proteins, we have identified beta 2-microglobulin as an Mr-8000 protein constitutively secreted by synovial cells.

Lack of effect of pertussis toxin on TNF-alpha-induced formation of reactive oxygen intermediates by human neutrophils

When human PMN were plated on fetal calf serum-coated polystyrene surfaces, addition of TNF-alpha, FMLP or PMA elicited adhesion and H2O2 formation. These effects of TNF-alpha and FMLP, but not of PMA, were impaired by removal of extracellular Ca2+. In addition, H2O2 formation induced by FMLP but not by TNF-alpha or PMA was inhibited by prior treatment with pertussis toxin (250-500 ng/ml). Thus, although the sequelae of TNF-alpha-receptor interaction on human PMN remain to be characterized in detail, they do not involve a pertussis toxin-sensitive GTP-binding protein.