The neutrophil: one of the cellular targets of interleukin-10

Cytokine balance in infants undergoing cardiac operation

BACKGROUND

The control of the systemic inflammatory response taking place during cardiac operations depends on adequate antiinflammatory reaction. In this prospective study we tested the hypothesis that cytokine balance during pediatric cardiac surgical procedures would be influenced by the patients' preoperative clinical condition, defined as hypoxemia or heart failure.

METHODS

Twenty infants (median age, 8 months) with hypoxemia owing to intracardiac right-to-left shunt (group 1, n = 10) or with heart failure because of intracardiac left-to-right shunt (group 2, n = 10), scheduled for elective primary corrective operation, were enrolled. Plasma levels of the proinflammatory cytokine interleukin (IL) 6, the natural antiinflammatory cytokine IL-10, and the markers of the acute-phase response, C-reactive protein and procalcitonin, were sequentially measured before, during, and after cardiac operation up to the 10th postoperative day. The ratio of IL-10 to IL-6 levels served as a marker for the individual's antiinflammatory cytokine balance.

RESULTS

Group 1 showed higher preoperative IL-6 (p < 0.001), lower IL-10 levels (p < 0.02), and lower ratio of IL-10 to IL-6 levels (p < 0.001) than group 2. Preoperative C-reactive protein and procalcitonin were not detectable. In group 1, preoperative IL-6 levels inversely correlated with preoperative oxygen saturation (Spearman correlation coefficient, -0.74, p < 0.02). During cardiopulmonary bypass, IL-6 levels were higher, whereas IL-10 and ratio of IL-10 to IL-6 levels were lower in group 1 than in group 2. In all patients, postoperative IL-6 levels were positively correlated with duration of inotropic support and serum creatinine value and inversely correlated with oxygenation index and diuresis.

CONCLUSIONS

Infants with hypoxemia show a preoperative inflammatory state with low antiinflammatory cytokine balance in contrast to those with heart failure. This in turn is associated with lower perioperative antiinflammatory cytokine balance and might contribute to postoperative morbidity.

Endogenous anti-inflammatory mediators from arachidonate in human neutrophils

Eicosanoids have been historically involved in the pathogenesis of various inflammatory diseases. Lipoxins (LXs) and epi-LXs show physiological effects relevant to inflammation regulation. In this study, we focused on LX precursors based on the hypothesis that their entrance and metabolism into the cell may facilitate their targeting at the inflammation site. Because compound chirality is of considerable importance in the efficacy of therapeutic agents, our aim was to study the anti-inflammatory effects of various epimers of LXA(4) precursors compared to LXA(4). Blood polymorphonuclear cells (PMNs) were incubated with 15(S)- or 15(R)-hydroxyeicosatetraenoic acid (HETE), 14(R)-,15(S)-, or 14(S),15(S)-diHETE, and LXA(4) and then stimulated with the calcium ionophore A23187. We found that 15(R)-HETE rather than 15(S)-HETE was preferentially metabolized and that 15-epi-LXs were produced in larger amounts than LXs. In contrast, when PMNs were incubated with the diastereoisomers of 14,15(S)-diHETE, 14-epi-LXB(4) was produced in lower amounts than LXB(4). Enantiomers of 15-HETE and diastereoisomers of 14,15-diHETE and LXA(4) were able to significantly decrease LTB(4) release by PMNs. These results suggest a potential resolution of the inflammatory process through endogenous anti-inflammatory mediators released by the way of trans-cellular metabolism.

Pro- and anti-inflammatory cytokine release in open versus endovascular repair of abdominal aortic aneurysm

BACKGROUND

Pro- and anti-inflammatory cytokine release occurs with abdominal aortic aneurysm (AAA) repair although the relative contribution of each is currently poorly understood. Ischaemia-reperfusion injury is thought to play a greater role following open (OR) than endovascular (ER) repair, with resultant greater perioperative morbidity.

METHODS

Thirty-two patients undergoing OR (n = 16) and ER (n = 16) of AAA were studied. Systemic venous (SV) blood was taken at induction (baseline), 0 h (last clamp off), 4, 24, 72 and 144 h, and femoral venous (FV) blood (indwelling catheter; lower torso venous effluent) at 0, 4 and 24 h. The cytokines interleukin (IL) 6, IL-8 and IL-10 were measured in these samples.

RESULTS

In OR, SV and FV IL-6 increased from baseline to a peak at 24 h (SV 589 pg/ml (P = 0.001 versus baseline) and FV 848 pg/ml (P = 0.05)) before declining at 144 h. In ER, there was a similar pattern but the increase was smaller (24 h: SV 260 pg/ml (P = 0.003 versus baseline) and FV 319 pg/ml (P = 0.06)) at all equivalent timepoints compared with OR. IL-8 peaked earlier (4 h) from baseline in both groups before declining by 144 h, and significant differences between SV and FV were seen only in the OR group. IL-10 levels peaked in both groups at 24 h before declining at 144 h, and there were no significant locosystemic differences between the groups.

CONCLUSION

Venous pro-inflammatory cytokine changes (IL-6) are consistent with significantly greater lower-torso reperfusion injury in patients undergoing OR. Smaller responses were seen after ER (IL-6 and IL-8), although both groups showed a similar anti-inflammatory response (IL-10); this pro- and anti-inflammatory imbalance may account for the increased morbidity associated with OR.

Up-regulation of IL-10R1 expression is required to render human neutrophils fully responsive to IL-10

We have recently shown that IL-10 fails to trigger Stat3 and Stat1 tyrosine phosphorylation in freshly isolated human neutrophils. In this study, we report that IL-10 can nonetheless induce Stat3 tyrosine phosphorylation and the binding of Stat1 and Stat3 to the IFN-gamma response region or the high-affinity synthetic derivative of the c-sis-inducible element in neutrophils that have been cultured for at least 3 h with LPS. Similarly, the ability of IL-10 to up-regulate suppressor of cytokine signaling (SOCS)-3 mRNA was dramatically enhanced in cultured neutrophils and, as a result, translated into the SOCS-3 protein. Since neutrophils' acquisition of responsiveness to IL-10 required de novo protein synthesis, we assessed whether expression of IL-10R1 or IL-10R2 was modulated in cultured neutrophils. We detected constitutive IL-10R1 mRNA and protein expression in circulating neutrophils, at levels which were much lower than those observed in autologous monocytes or lymphocytes. In contrast, IL-10R2 expression was comparable in both cell types. However, IL-10R1 (but not IL-10R2) mRNA and protein expression was substantially increased in neutrophils stimulated by LPS. The ability of IL-10 to activate Stat3 tyrosine phosphorylation and SOCS-3 synthesis and to regulate IL-1 receptor antagonist and macrophage-inflammatory protein 1beta release in LPS-treated neutrophils correlated with this increased IL-10R1 expression, and was abolished by neutralizing anti-IL-10R1 and anti-IL-10R2 Abs. Our results demonstrate that the capacity of neutrophils to respond to IL-10, as assessed by Stat3 tyrosine phosphorylation, SOCS-3 expression, and modulation of cytokine production, is very dependent on the level of expression of IL-10R1.

Interleukin-10 and the interleukin-10 receptor

Interleukin-10 (IL-10), first recognized for its ability to inhibit activation and effector function of T cells, monocytes, and macrophages, is a multifunctional cytokine with diverse effects on most hemopoietic cell types. The principal routine function of IL-10 appears to be to limit and ultimately terminate inflammatory responses. In addition to these activities, IL-10 regulates growth and/or differentiation of B cells, NK cells, cytotoxic and helper T cells, mast cells, granulocytes, dendritic cells, keratinocytes, and endothelial cells. IL-10 plays a key role in differentiation and function of a newly appreciated type of T cell, the T regulatory cell, which may figure prominently in control of immune responses and tolerance in vivo. Uniquely among hemopoietic cytokines, IL-10 has closely related homologs in several virus genomes, which testify to its crucial role in regulating immune and inflammatory responses. This review highlights findings that have advanced our understanding of IL-10 and its receptor, as well as its in vivo function in health and disease.

Invasive candidiasis stimulates hepatocyte and monocyte production of active transforming growth factor beta

Candida albicans is an opportunistic fungal pathogen and a major cause of morbidity and mortality in patients with compromised immune function. The cytokine response to tissue invasion by C. albicans can influence the differentiation and function of lymphocytes and other mononuclear cells that are critical components of the host response. While the production of transforming growth factor beta (TGF-beta) has been documented in mice infected with C. albicans and is known to suppress phagocyte function, the cellular source and role of this cytokine in the pathogenesis of systemic candidiasis are not well understood. We have investigated the source of production of TGF-beta by immunohistochemical studies in tissue samples from patients with an uncommon complication of lymphoreticular malignancy, chronic disseminated candidiasis (CDC), and from a neutropenic-rabbit model of CDC. Liver biopsy specimens from patients with documented CDC demonstrated intense staining for extracellular matrix-associated TGF-beta1 within inflammatory granulomas, as well as staining for TGF-beta1 and TGF-beta3 within adjacent hepatocytes. These results correlate with the immunolocalization of TGF-beta observed in livers of infected neutropenic rabbits, using a neutralizing antibody that recognizes the mature TGF-beta protein. Human peripheral blood monocytes incubated with C. albicans in vitro release large amounts of biologically active TGF-beta1. The data demonstrate that local production of active TGF-betas by hepatocytes and by infected mononuclear cells is a component of the response to C. albicans infection that most probably contributes to disease progression in the immunocompromised host.

Intracellular pool of IL-10 receptors in specific granules of human neutrophils: differential mobilization by proinflammatory mediators

IL-10 has a wide range of effects tending to control inflammatory responses. We used flow cytometry to study IL-10 binding at the polymorphonuclear neutrophil (PMN) surface and its modulation by various proinflammatory agents. Little IL-10 bound to the surface of resting PMN. However, binding was strongly increased after stimulation with LPS and proinflammatory cytokines such as TNF and GM-CSF. IL-1 and IL-8 did not significantly modify IL-10 binding. Cycloheximide had no effect on TNF-induced IL-10 binding, strongly suggesting the release of a pre-existing pool of IL-10R rather than de novo receptor synthesis by PMN. This was confirmed by the inhibitory effect of pentoxifylline, an inhibitor of degranulation. The existence of an intracellular pool of IL-10R was shown by flow cytometry, immunocytochemical staining, and Western blotting with several anti-human IL-10R Abs. In subcellular fractions of resting PMN, IL-10R was mainly located in the specific granule fraction, and was absent from azurophil granules and cytosol. We also tested the mobilization of specific granules by measuring the release of lactoferrin, their reference marker. The differential effects of the proinflammatory agents on IL-10 binding matched their effects on lactoferrin release and may therefore be related to differential mobilization of specific granules by these agents. Furthermore, the kinetics of TNF-induced up-regulation of IL-10 binding to PMN ran parallel to the kinetics of the inhibitory effect of IL-10 on the oxidative burst, suggesting a key role of IL-10R mobilization from specific granules to the membranes in optimal regulation of inflammatory responses.

Interleukin-10 and the Interleukin-10 Receptor

Interleukin-10 (IL-10), first recognized for its ability to inhibit activation and effector function of T cells, monocytes, and macrophages, is a multifunctional cytokine with diverse effects on most hemopoietic cell types. The principal routine function of IL-10 appears to be to limit and ultimately terminate inflammatory responses. In addition to these activities, IL-10 regulates growth and/or differentiation of B cells, NK cells, cytotoxic and helper T cells, mast cells, granulocytes, dendritic cells, keratinocytes, and endothelial cells. IL-10 plays a key role in differentiation and function of a newly appreciated type of T cell, the T regulatory cell, which may figure prominently in control of immune responses and tolerance in vivo. Uniquely among hemopoietic cytokines, IL-10 has closely related homologs in several virus genomes, which testify to its crucial role in regulating immune and inflammatory responses. This review highlights findings that have advanced our understanding of IL-10 and its receptor, as well as its in vivo function in health and disease.

Beneficial intervention of experimental colitis by passive cigarette smoking through the modulation of cytokines in rats

BACKGROUND

Epidemiologic observations have indicated that cigarette smoking decreases the risk of ulcerative colitis, but the modes of action remain anonymous. The present study aimed to investigate the beneficial effects of passive cigarette smoking using an animal colitis model. We hypothesized that the underlying mechanisms may involve immunoregulation of cytokines.

METHODS

Experimental colitis was induced in rats by enema administration of 2,4-dinitrobenzene sulfonic acid (DNBS). Passive cigarette smoking by rats was performed for 1 hour once daily, from 3 days before DNBS enema until they were sacrificed on day 8. Other groups of DNBS-treated rats received therapeutic treatment of cyclosporin A or pentoxifylline, a tumor necrosis factor (TNF)-alpha inhibitor. Macroscopic and histologic damage were graded, and the colonic levels of different cytokines and the levels/activities of parameters related to neutrophil activation were also measured.

RESULTS

DNBS-induced colonic damage was improved in passive-cigarette-smoking rats. This was accompanied by attenuation of the elevated colonic myeloperoxidase and inducible nitric oxide synthase activities and leukotriene B4 level. Likewise, the augmentation in colonic levels of TNF-alpha, interleukin (IL)-1 beta, and IL-6 in colitis rats was also alleviated by passive cigarette smoking. In contrast, the deprivation of colonic IL-10 during colitis was preserved in cigarette-smoking rats. These effects were similarly accomplished by pentoxifylline and, to some degree, by cyclosporin A.

CONCLUSIONS

The results support the idea that the beneficial effects of passive cigarette smoking in experimental colitis involved immunoregulation of cytokines in colonic tissues.

Gene expression and production of tumor necrosis factor alpha, interleukin-1beta (IL-1beta), IL-8, macrophage inflammatory protein 1alpha (MIP-1alpha), MIP-1beta, and gamma interferon-inducible protein 10 by human neutrophils stimulated with group B meningococcal outer membrane vesicles

Accumulation of polymorphonuclear neutrophils (PMN) into the subarachnoidal space is one of the hallmarks of Neisseria meningitidis infection. In this study, we evaluated the ability of outer membrane vesicles (OMV) from N. meningitidis B to stimulate cytokine production by neutrophils. We found that PMN stimulated in vitro by OMV produce proinflammatory cytokines and chemokines including tumor necrosis factor alpha (TNF-alpha), interleukin-1beta (IL-1beta), IL-8, macrophage inflammatory protein 1alpha (MIP-1alpha), and MIP-1beta. A considerable induction of gamma interferon (IFN-gamma)-inducible protein 10 (IP-10) mRNA transcripts, as well as extracellular IP-10 release, was also observed when neutrophils were stimulated by OMV in combination with IFN-gamma. Furthermore, PMN stimulated by OMV in the presence of IFN-gamma demonstrated an enhanced capacity to release TNF-alpha, IL-1beta, IL-8, and MIP-1beta compared to stimulation with OMV alone. In line with its downregulatory effects on neutrophil-derived proinflammatory cytokines, IL-10 potently inhibited TNF-alpha, IL-1beta, IL-8, and MIP-1beta production triggered by OMV. Finally, a neutralizing anti-TNF-alpha monoclonal antibody (MAb) did not influence the release of IL-8 and MIP-1beta induced by OMV, therefore excluding a role for endogenous TNF-alpha in mediating the induction of chemokine release by OMV. In contrast, the ability of lipopolysaccharide from N. meningitidis B to induce the production of IL-8 and MIP-1beta was significantly inhibited by anti-TNF-alpha MAb. Our results establish that, in response to OMV, neutrophils produce a proinflammatory profile of cytokines and chemokines which may not only play a role in the pathogenesis of meningitis but may also contribute to the development of protective immunity to serogroup B meningococci.

IL-10 is induced in the reperfused myocardium and may modulate the reaction to injury

Reperfusion of the ischemic myocardium is associated with a dramatic inflammatory response leading to TNF-alpha release, IL-6 induction, and subsequent neutrophil-mediated cytotoxic injury. Because inflammation is also an important factor in cardiac repair, we hypothesized the presence of components of the inflammatory reaction with a possible role in suppressing acute injury. Thus, we investigated the role of IL-10, an anti-inflammatory cytokine capable of modulating extracellular matrix biosynthesis, following an experimental canine myocardial infarction. Using our canine model of myocardial ischemia and reperfusion, we demonstrated significant up-regulation of IL-10 mRNA and protein in the ischemic and reperfused myocardium. IL-10 expression was first detected at 5 h and peaked following 96-120 h of reperfusion. In contrast, IL-4 and IL-13, also associated with suppression of acute inflammation and macrophage deactivation, were not expressed. In the ischemic canine heart, CD5-positive lymphocytes were the predominant source of IL-10 in the myocardial infarct. In the absence of reperfusion, no significant induction of IL-10 mRNA was noted. In addition, IL-12, a Th1-related cytokine associated with macrophage activation, was not detected in the ischemic myocardium. In vitro experiments demonstrated late postischemic cardiac-lymph-induced tissue inhibitor of metalloproteinases (TIMP)-1 mRNA expression in isolated canine mononuclear cells. This effect was inhibited when the incubation contained a neutralizing Ab to IL-10. Our findings suggest that lymphocytes infiltrating the ischemic and reperfused myocardium express IL-10 and may have a significant role in healing by modulating mononuclear cell phenotype and inducing TIMP-1 expression.

On the detection of neutrophil-derived vascular endothelial growth factor (VEGF)

In recent years, several investigators have addressed the question of whether mature polymorphonuclear neutrophils (PMN) are able to secrete cytokines. Their studies have brought forward new and exciting discoveries, by establishing that the release of inflammatory cytokines constitutes a novel and important aspect of the neutrophil biology, thereby emphasizing that PMN should no longer be regarded as cells that only release preformed mediators. Although it is still premature to assess the true biological significance of cytokine production by neutrophils, this new aspect of neutrophil biology opens novel perspectives as to the potential role of these cells in the inflammatory and immune responses. In this context, a correct methodological analysis and a detailed molecular investigation of the mechanisms regulating cytokine production by neutrophils in vitro is a critical and fundamental step to better understand how the release of cytokines by PMN may influence pathophysiological processes in vivo. We now describe and discuss the approach that we typically used throughout most of the last decade to characterize cytokine production by human neutrophils, as illustrated herein for a protein that is expressed and released by PMN, namely, vascular endothelial growth factor (VEGF).

Interleukin-10 (IL-10) Selectively Enhances CIS3/SOCS3 mRNA Expression in Human Neutrophils: Evidence for an IL-10–Induced Pathway That Is Independent of STAT Protein Activation

We have recently shown that, in human neutrophils, interleukin-10 (IL-10) fails to induce specific DNA-binding activities to the gamma-interferon response region (GRR), a regulatory element located in the FcγRI gene promoter, which is required for transcriptional activation by IL-10 and interferon γ (IFNγ) in monocytic cells. In this study, we report that IL-10 is also unable to induce the binding of STAT1 or STAT3 to the serum-inducible element (hSIE/m67), despite the fact that both proteins are expressed in neutrophils. Whereas IFNγ and granulocyte colony-stimulating factor (G-CSF) are efficient inducers of STAT1 and STAT3 tyrosine phosphorylation in polymorphonuclear neutrophils (PMN), IL-10 fails to trigger STAT1 and STAT3 tyrosine and serine phosphorylation, therefore explaining its inability to induce the FcγRI expression in these cells. By contrast, we demonstrate that IL-10 alone represents an efficient stimulus of CIS3/SOCS3 mRNA expression in neutrophils. CIS3/SOCS3 belongs to the recently cloned cytokine-inducible SH2-containing protein (CIS) gene family (which also includes CIS1, CIS2, CIS4, CIS5, and JAB) that is believed to be, at least in part, under the control of STAT transcription factors and whose products are potential modulators of cytokine signaling. Moreover, IL-10 synergizes with lipopolysaccharide (LPS) in upregulating CIS3/SOCS3 mRNA expression in PMN through a mechanism that involves mRNA stabilization. In contrast to CIS3/SOCS3, mRNA transcripts encoding other family members are unaffected by IL-10 in neutrophils. Finally, transfection of CIS3/SOCS3 in murine M1 myeloid cells suppresses LPS-induced growth arrest, macrophage-like differentiation, and nitric oxide synthesis, but not IL-6 mRNA expression. Collectively, our data suggest that, in neutrophils, the activation of STAT1 and STAT3 phosphorylation is neither required for CIS3/SOCS3 induction by IL-10 nor involved in the regulatory effects of IL-10 on cytokine production.