Molecular basis of the synergistic production of IL-1 receptor antagonist by human neutrophils stimulated with IL-4 and IL-10

Bronchoalveolar lavage fluid cytokine, cytology and IgE allergen in horses with equine asthma

The pathophysiology of equine asthma (EA) is still not fully described, but the involvement of an allergic reaction is strongly suspected. This theory has led to the use of allergen-specific immunoglobulin (Ig)E tests to support a diagnosis of asthma. The objective of this descriptive study was to evaluate the correlation between four subgroups of EA (mastocytic mild equine asthma [MEA], neutrophilic MEA, mixed MEA, and severe equine asthma [SEA]), allergen specific IgE (measured in both serum and BALF) and mRNA expression of selected genes in bronchoalveolar lavage fluid (BALF). Serum and BALF were collected from 64 horses with a history of lower airway problems with or without poor performance. Differential cell counts from BALF were used to assign horses to one of four groups (mastocytic MEA; neutrophilic MEA, mixed MEA, and SEA). The expression of messenger RNA (mRNA) coding for IL4, IL5, IL8, IL10, TGFB, TNFA, toll-like receptor (TLR)4, IL1RA, IL1B, matrix metalloproteinase 8 (MMP8), TLR9, chemokine ligand 5 (CCL5) and cluster of differentiation (CD)14 in BALF were measured using reverse transcriptase (RT) quantitative PCR (qPCR). Allergen-specific IgE was measured in serum and BALF using an allergen-specific IgE ELISA test with the screening panel: house mites, storage mites, mould and pollen. As expected, the BALF neutrophil differential count correlated with mRNA expression of MMP-8 (r = 0.611, p < 0.001), TLR-4 (r = 0.540, p < 0.001), IL-1RA (r = 0.490, p < 0.001), IL-1β (r = 0.463, p < 0.001) and IL-8 (r = 0.302, p = 0.015). Cytokine expression of IL-1β (p = 0.014), MMP8 (p = 0.028) and IL-1RA (p = 0.037) was significantly higher in the SEA group compared to the MEA subgroups. The BALF mast cell count was correlated with allergen-specific IgE for insects (r = 0.370, p = 0.002) and pollen (r = 0.313, p = 0.011). Eosinophils in BALF were correlated with BALF mRNA expression of IL-4 (r = 0.340, p = 0.006) together with a significant correlation between BALF eosinophils and allergen-specific IgE for mites (r = 0.930, p < 0.001) and pollen in BALF (r = 0.837, p < 0.001). No correlation was found between allergen-specific IgE in serum and BALF for any of the allergen in the screening panel. Based on these results from allergen-specific IgE in horses with EA is not found in systemic circulation, and only the mastocytic and mixed subgroups of horses with EA had allergen-specific IgE in BALF. Further studies are needed to clarify the relationships identified here.

Comprehensive biology of antipyretic pathways

Pyrogens, the fever inducing substances accidently enter into a human body through contamination from medical or pharmaceutical products may create mild to severe complications including septicaemia and shocking syndromes. To avoid such drastic situations all the pharmaceuticals and medical devices are analysed for presence of pyrogens prior to their release into market. The entry of exogenous pyrogens like bacterial endotoxins induces the release of endogenous pyrogens or inflammatory cytokines that activate immune system to defend against these pathogens. Generation of heat is considered as one of the important defence mechanism of body achieved through receptor mediated interaction of endogenous pyrogens at the thermoregulatory centre of hypothalamus. However, uncontrolled fever and febrile reaction may cause lethal effects to the subject itself. So a well sophistically functioning antipyretic mechanism is necessary to achieve thermoregulation. The coordinated interaction of antipyretic cytokines and other mediators are active in human immune system which play a crucial role in maintaining thermal homeostasis. The multiple interacting antipyretic signals and their mechanism are the major subjects of this review.

A Reappraisal on the Potential Ability of Human Neutrophils to Express and Produce IL-17 Family Members In Vitro: Failure to Reproducibly Detect It

Neutrophils are known to perform a series of effector functions that are crucial for the innate and adaptive responses, including the synthesis and secretion of a variety of cytokines. In light of the controversial data in the literature, the main objective of this study was to more in-depth reevaluate the capacity of human neutrophils to express and produce cytokines of the IL-17 family in vitro. By reverse transcription quantitative real-time PCR, protein measurement via commercial ELISA, immunohistochemistry (IHC) and immunofluorescence (IF), flow cytometry, immunoblotting, chromatin immunoprecipitation (ChIP), and ChIP-seq experiments, we found that highly pure (>99.7%) populations of human neutrophils do not express/produce IL-17A, IL-17F, IL-17AF, or IL-17B mRNA/protein upon incubation with a variety of agonists. Similar findings were observed by analyzing neutrophils isolated from active psoriatic patients. In contrast with published studies, IL-17A and IL-17F mRNA expression/production was not even found when neutrophils were incubated with extremely high concentrations of IL-6 plus IL-23, regardless of their combination with inactivated hyphae or conidia from Aspergillus fumigatus. Consistently, no deposition of histone marks for active (H3K27Ac) and poised (H3K4me1) genomic regulatory elements was detected at the IL-17A and IL-17F locus of resting and IL-6 plus IL-23-stimulated neutrophils, indicating a closed chromatin conformation. Concurrent experiments revealed that some commercial anti-IL-17A and anti-IL-17B antibodies (Abs), although staining neutrophils either spotted on cytospin slides or present in inflamed tissue samples by IHC/IF, do not recognize intracellular protein having the molecular weight corresponding to IL-17A or IL-17B, respectively, in immunoblotting experiments of whole neutrophil lysates. By contrast, the same Abs were found to more specifically recognize other intracellular proteins of neutrophils, suggesting that their ability to positively stain neutrophils in cytospin preparations and, eventually, tissue samples derives from IL-17A- or IL-17B-independent detections. In sum, our data confirm and extend, also at epigenetic level, previous findings on the inability of highly purified populations of human neutrophils to express/produce IL-17A, IL-17B, and IL-17F mRNAs/proteins in vitro, at least under the experimental conditions herein tested. Data also provide a number of justifications explaining, in part, why it is possible to false positively detect IL-17A⁺-neutrophils.

Human Neutrophils Produce CCL23 in Response to Various TLR-Agonists and TNFα

CCL23, also known as myeloid progenitor inhibitory factor (MPIF)-1, macrophage inflammatory protein (MIP)-3, or CKβ8, is a member of the CC chemokine subfamily exerting its effects via CCR1 binding. By doing so, CCL23 selectively recruits resting T lymphocytes and monocytes, inhibits proliferation of myeloid progenitor cells and promotes angiogenesis. Previously, we and other groups have reported that human neutrophils are able to produce chemokines upon appropriate activation, including CCR1-binding CCL2, CCL3, and CCL4. Herein, we demonstrate that human neutrophils display the capacity to also express and release CCL23 when stimulated by R848 and, to a lesser extent, by other pro-inflammatory agonists, including LPS, Pam3CSK4, and TNFα. Notably, we show that, on a per cell basis, R848-activated neutrophils produce higher levels of CCL23 than autologous CD14⁺-monocytes activated under similar experimental conditions. By contrast, we found that, unlike CD14⁺-monocytes, neutrophils do not produce CCL23 in response to IL-4, thus indicating that they express CCL23 in a stimulus-specific fashion. Finally, we show that the production of CCL23 by R848-stimulated neutrophils is negatively modulated by IFNα, which instead enhances that of CCL2. Together, data extend our knowledge on the chemokines potentially produced by neutrophils. The ability of human neutrophils to produce CCL23 further supports the notion on the neutrophil capacity of orchestrating the recruitment of different cell types to the inflamed sites, in turn contributing to the control of the immune response.

Peripheral neutrophil functions and cell signalling in Crohn`s disease

The role of the innate immunity in the pathogenesis of Crohn's disease (CD), an inflammatory bowel disease, is a subject of increasing interest. Neutrophils (PMN) are key members of the innate immune system which migrate to sites of bacterial infection and initiate the defence against microbes by producing reactive oxygen species (ROS), before undergoing apoptosis. It is believed that impaired innate immune responses contribute to CD, but it is as yet unclear whether intrinsic defects in PMN signal transduction and corresponding function are present in patients with quiescent disease. We isolated peripheral blood PMN from CD patients in remission and healthy controls (HC), and characterised migration, bacterial uptake and killing, ROS production and cell death signalling. Whereas IL8-induced migration and signalling were normal in CD, trans-epithelial migration was significantly impaired. Uptake and killing of E. coli were normal. However, an increased ROS production was observed in CD PMN after stimulation with the bacterial peptide analogue fMLP, which was mirrored by an increased fMLP-triggered ERK and AKT signal activation. Interestingly, cleavage of caspase-3 and caspase-8 during GMCSF-induced rescue from cell-death was decreased in CD neutrophils, but a reduced survival signal emanating from STAT3 and AKT pathways was concomitantly observed, resulting in a similar percentage of end stage apoptotic PMN in CD patients and HC. In toto, these data show a disturbed signal transduction activation and functionality in peripheral blood PMN from patients with quiescent CD, which point toward an intrinsic defect in innate immunity in these patients.

Glucose-dependent insulinotropic polypeptide induces cytokine expression, lipolysis, and insulin resistance in human adipocytes

Obesity-related insulin resistance is linked to a chronic state of systemic and adipose tissue-derived inflammation. Glucose-dependent insulinotropic polypeptide (GIP) is an incretin hormone also acting on adipocytes. We investigated whether GIP affects inflammation, lipolysis, and insulin resistance in human adipocytes. Human subcutaneous preadipocyte-derived adipocytes, differentiated in vitro, were treated with human GIP to analyze mRNA expression and protein secretion of cytokines, glycerol, and free fatty acid release and insulin-induced glucose uptake. GIP induced mRNA expression of IL-6, IL-1β, and the IL-1 receptor antagonist IL-1Ra, whereas TNFα, IL-8, and monocyte chemotactic protein (MCP)-1 remained unchanged. Cytokine induction involved PKA and the NF-κB pathway as well as an autocrine IL-1 effect. Furthermore, GIP potentiated IL-6 and IL-1Ra secretion in the presence of LPS, IL-1β, and TNFα. GIP induced lipolysis via activation of hormone-sensitive lipase and was linked to NF-κB activation. Finally, chronic GIP treatment impaired insulin-induced glucose uptake possibly due to the observed impaired translocation of glucose transporter GLUT4. In conclusion, GIP induces an inflammatory and prolipolytic response via the PKA -NF-κB-IL-1 pathway and impairs insulin sensitivity of glucose uptake in human adipocytes.

IL-4 alone and in combination with IL-10 protects against blood-induced cartilage damage

OBJECTIVE

It has been reported that interleukin (IL)-10 limits blood-induced cartilage damage. Our aim was to study the effect of IL-4 alone and in combination with IL-10 on blood-induced cartilage damage.

DESIGN

Healthy human full thickness cartilage explants were cultured for 4 days in the presence of 50% v/v blood. IL-4, IL-10, or a combination of both cytokines was added during blood exposure. Cartilage matrix turnover was determined after a recovery period; additionally cytokine production, chondrocyte apoptosis, and expression of the IL-4 and IL-10 receptors were analyzed directly after exposure.

RESULTS

Blood-induced damage to the cartilage matrix was limited by IL-4 in a dose-dependent way (P<0.05). Also IL-10 limited this damage, although to a lesser extent (P<0.03). The effect of IL-4 plus IL-10 was more pronounced and protective than IL-10 alone (P<0.05). Production of IL-1β and tumor necrosis factor (TNF)-α was limited by both IL-4 and IL-10 (P<0.05), but more strongly by IL-4. Blood-induced apoptosis of chondrocytes was limited by IL-4 and the combination, and not by IL-10 alone. No direct beneficial effect of IL-4 or IL-10 on cartilage was found, however, the chondrocyte receptor expression of both cytokine receptors was upregulated by exposure to blood.

CONCLUSIONS

This study demonstrates that IL-4 alone and in combination with IL-10 prevents blood-induced cartilage damage. Expectedly, anti-inflammatory effects on monocytes in the blood fraction and protective effects on chondrocytes are both involved. IL-4 in combination with IL-10 might be used to prevent blood-induced joint damage as a result of trauma or surgery.

Understanding the molecular mechanisms of the multifaceted IL-10-mediated anti-inflammatory response: lessons from neutrophils

Analysis of the molecular mechanisms governing the ability of IL-10 to keep inflammation under control has highlighted the existence of a great degree of plasticity and specificity with regard to innate immune cells. In this respect, neutrophils represent a perfect example of innate immune cells conditioned by external signals (for instance, by LPS), as well as by intracellular regulatory pathways, that render them optimally responsive to IL-10 only when required. The focus of this review are the recent experimental findings that have uncovered the sophisticated and complex molecular mechanisms responsible for the modulation of pro- and anti-inflammatory cytokine production by IL-10 in neutrophils and other innate immune cells. Understanding how IL-10 exerts its anti-inflammatory response, particularly in the case of neutrophils, will provide novel clues leading, hopefully, to the therapeutic control of neutrophil-driven inflammatory reactions, such as septic infections, rheumatoid arthritis, osteoarthritis and chronic obstructive pulmonary disease.

IL-4 activates equine neutrophils and induces a mixed inflammatory cytokine expression profile with enhanced neutrophil chemotactic mediator release ex vivo

Neutrophils are potent contributors to the lung pathophysiological changes occurring in allergic airway inflammation, which typically involve T helper type 2 (Th2) cytokine overexpression. We have previously reported that equine pulmonary endothelial cells are activated by the Th2 cytokine IL-4 and express chemotactic factors for neutrophils after stimulation. We have further explored the possible mechanisms linking Th2-driven inflammation and neutrophilia by studying the effects of recombinant equine IL-4, a prototypical Th2 cytokine, on peripheral blood neutrophils (PBN) isolated from normal animals and from horses with asthmatic airway inflammation (equine heaves). We found that IL-4 induced morphological changes in PBN, dose- and time-dependent expression of IL-8 mRNA, as well as the release of chemotactic factors for neutrophils in culture supernatants. Also, IL-4 induced a mixed inflammatory response in PBN from control and asthmatic-animals with increased expression of proinflammatory IL-8 and TNF-α but a marked inhibition of IL-1β. IL-4 type I receptor (IL-4Rα) and CD23 (FcεRII) expression were also upregulated by IL-4. Importantly, disease as well as chronic antigenic exposure modified gene expression by PBN. Finally, we found that activation of equine neutrophils with IL-4 involved STAT6 phosphorylation and p38 MAPK and phosphatidylinositol 3-kinase (PI3K); the pharmacological inhibitors, SB-203580 and LY-294002, respectively, significantly reversed IL-4-induced gene modulation in PBN. Overall, results from this study add to the link between Th2-driven inflammation and neutrophilia in the equine model and further extend the characterization of IL-4 effects on neutrophils.

Interleukin (IL)-4 induces leukocyte infiltration in vivo by an indirect mechanism

Interleukin (IL)-4 is a cytokine known mainly for its anti-inflammatory activity. Using the in vivo murine air pouch model, we found that IL-4 significantly increased the number of leukocytes after 9 hours of treatment, consisting mainly of neutrophil (60%) and monocytic (40%) cell populations. Using an antibody array, we found that the expression of several analytes (predominantly CCL2) was increased by IL-4 before the arrival of leukocytes. The IL-4-induced expression of CCL-2 was confirmed by ELISA. Air pouch resident lining cells were harvested and were found to express IL-4Rα. CCL2 mRNA expression was monitored in lining cells, cells isolated from the air pouch skin, in RAW264.7 macrophage and in epithelial Mode-K cells and its expression was increased in response to IL-4 in all conditions. We conclude that IL-4 can attract leukocytes in vivo by an indirect mechanism involving the production of several analytes by, at least, resident cells.

Immunogenetics of drug-induced skin blistering disorders. Part II: Synthesis

The overall immunopathogenesis relevant to a large series of disorders caused by a drug or its associated hyperimmune condition is discussed based upon examining the genetics of severe drug-induced bullous skin problems (sporadic idiosyncratic adverse events including Stevens–Johnson syndrome and Toxic epidermal necrolysis). New results from an exemplar study on shared precipitating and perpetuating inner causes with other related disease phenotypes including aphtous stomatitis, Behçets, erythema multiforme, Hashimoto’s thyroiditis, pemphigus, periodic fevers, Sweet’s syndrome and drug-induced multisystem hypersensitivity are presented. A call for a collaborative, wider demographic profiling and deeper immunotyping in suggested future work is made.

Circulating neutrophils of septic patients constitutively express IL-10R1 and are promptly responsive to IL-10

Previous studies have demonstrated that neutrophils isolated from the blood of healthy donors do not respond to IL-10 in terms of either activation of signal transducer and activator of transcription-3 (STAT3) tyrosine phosphorylation or induction of suppressor of cytokine signalling (SOCS)-3 protein, unlike autologous mononuclear cells. This was explained by the fact that circulating neutrophils of healthy donors express only IL-10R2, but not IL-10R1, the latter IL-10R chain being essential for mediating IL-10 responsiveness. In this study, we report that peripheral blood neutrophils of septic patients constitutively display, besides IL-10R2, also abundant levels of surface IL-10R1. Consequently, septic neutrophils are promptly responsive to IL-10 in vitro, as revealed by a direct IL-10-mediated induction of STAT3 tyrosine phosphorylation and SOCS-3 gene transcription, mRNA and protein expression. Consistent with the presence of a fully functional IL-10R, modulation of LPS-induced CXCL8, CCL4, tumour necrosis factor-alpha and IL-1ra gene expression was also rapidly induced by IL-10 in septic, but not normal, neutrophils. Collectively, these data uncover that neutrophils of septic patients are predisposed to be promptly responsive to IL-10, presumably to help limiting their pro-inflammatory state. They also fully validate our previous observations, herein in the context of a human disease, that responsiveness of human neutrophils to IL-10 is strictly dependent upon the modulation of IL-10R1 expression.

Plasma Cytokine and Soluble Receptor Signature Predicts Outcome of Patients With Classical Hodgkin's Lymphoma: A Study From the Groupe d'Etude des Lymphomes de l'Adulte

Purpose

Approximately 15% of patients with localized and 30% with disseminated classical Hodgkin's lymphoma fail to respond or relapse after first-line treatment. Usual prognosis scoring systems are actually unable to identify this small subset of patients with good confidence, pointing out the need for additional prognostic biomarkers.

Patients and Methods

We prospectively analyzed the prognosis value of plasma levels of tumor necrosis factor (TNF), its soluble receptors TNF-R1 and TNF-R2, IL-10, IL1-RA, IL-6, and soluble CD30 (sCD30) when taken before any treatment in 519 consecutive patients with a first diagnosis of classical Hodgkin's lymphoma.

Results

Levels of TNFα higher than 46 pg/mL, TNF-R1 higher than 3 ng/mL, TNF-R2 higher than 5 ng/mL, IL-10 higher than 30 pg/mL, IL1-RA higher than 668 pg/mL, IL-6 higher than 30 pg/mL, and sCD30 higher than 80 U/mL were associated with poor event-free and overall survival. In multivariate analysis, high levels of IL1-RA, IL-6, and sCD30 were independent poor prognosis factors, and the cytokine signature based on their combination allowed the stratification of patients in four prognosis classes, reaching a 5-year event-free survival probability of 92%, 85%, 76%, and 15%, respectively. This index was more potent than other scoring systems to predict patient event-free survival, and remained independent from the international prognostic score (P < .001), adding significant prognostic information to its predictive power.

Conclusion

Plasma cytokine signature is sufficient to predict disease-related outcome in classical Hodgkin's lymphoma, and allows the identification of patients with very high risk of treatment failure.

Molecular mechanisms involved in interleukin-4-induced human neutrophils: expression and regulation of suppressor of cytokine signaling

Interleukin-4 (IL-4) is a CD132-dependent cytokine known to activate the Jak-STAT pathway in different cells and cell lines. Although IL-4 has been demonstrated previously to be an agonist in human neutrophils, its capacity to activate different cell signaling pathways in these cells has never been investigated. Two types of IL-4 receptor (IL-4R) exist: the Type I (CD132/IL-4Ralpha heterodimer) and the Type II (IL-4Ralpha/IL-13Ralpha1 heterodimer). In a previous study, we demonstrated that neutrophils express the Type I receptor. Herein, using flow cytometry, we demonstrated that neutrophils, unlike U-937 cells, do not express IL-13Ralpha1 and IL-13Ralpha2 and confirmed the expression of CD132 and IL-4Ralpha on their surface. We also demonstrated that IL-4 induced phosphorylation of Syk, p38, Erk-1/2, JNK, Jak-1, Jak-2, STAT6, and STAT1 and that treatment of cells with the inhibitors piceatannol, SB203580, PD98059, or AG490 reversed the ability of IL-4 to delay neutrophil apoptosis. Using RT-PCR, we demonstrated for the first time that neutrophils express mRNA for all suppressor of cytokine signaling (SOCS) members, namely SOCS1-7 and cytokine-inducible Src homology 2 protein. It is interesting that IL-4 increased expression of SOCS3 at the mRNA and protein levels. The effect of IL-4 on SOCS3 protein expression was increased markedly when the proteasome inhibitor MG132 was added to the cultures, but this was inhibited by cycloheximide, suggesting that SOCS3 is de novo-synthesized in response to IL-4. We conclude that neutrophils express only the Type I IL-4R on their surface and that IL-4 signals via different cell signaling pathways, including the Jak/STAT/SOCS pathway.

Interleukin-4 regulates proteoglycan-induced arthritis by specifically suppressing the innate immune response

OBJECTIVE

Interleukin-4 (IL-4) is an antiinflammatory cytokine that inhibits the onset and severity of proteoglycan-induced arthritis (PGIA). To distinguish the role of IL-4 in the innate immune response versus the adaptive immune response, we generated mice with a specific deletion of the IL-4 receptor alpha-chain (IL-4Ralpha) in macrophages and neutrophils.

METHODS

To obtain mice in which IL-4Ralpha is deleted in macrophages and neutrophils, we intercrossed mice carrying a loxP-flanked (floxed) IL-4Ralpha allele and Cre recombinase expressed under control of the regulatory region for the lysozyme M gene (LysM(cre) mice) with conditional IL-4Ralpha(flox/flox) mice and then mated them to complete IL-4Ralpha(-/-) mice to obtain hemizygous LysM(cre)IL-4Ralpha(flox/-) mice. LysM(cre)-negative IL-4Ralpha(flox/-) mice (IL-4Ralpha(flox/-) mice) were used as control mice. PGIA was induced by immunization with human PG in adjuvant. The onset, incidence, and severity of arthritis were monitored over time. Levels of proinflammatory cytokines were measured in the sera of PG-immunized mice, and cytokine and chemokine transcripts were measured in joints.

RESULTS

The severity of PGIA was exacerbated in IL-4Ralpha(-/-) and LysM(cre)IL-4Ralpha(flox/-) mice in comparison with control (IL-4Ralpha(flox/-)) mice. The increase in arthritis susceptibility in IL-4Ralpha(-/-) and LysM(cre)IL-4Ralpha(flox/-) mice correlated with elevated serum levels of the proinflammatory cytokines IL-1beta and IL-6 and with elevated cytokine (IL-1beta and IL-6) and chemokine (macrophage inflammatory protein 1alpha [MIP-1alpha] and MIP-2) transcripts from joints. However, arthritis susceptibility did not correlate with IL-2 or interferon-gamma (IFNgamma) concentrations or with PG-specific antibody IgG2a isotype, since levels of IL-2, IFNgamma, or PG-specific antibody IgG2a isotype in control (IL-4Ralpha(flox/-)) and LysM(cre)IL-4Ralpha(flox/-) mice were reduced in comparison with those in IL-4Ralpha(-/-) mice.

CONCLUSION

These findings indicate that IL-4 functions as a major antiinflammatory cytokine in PGIA by governing the activity of macrophages/neutrophils and less so by controlling T cell activity and autoantibody isotype expression.

Anti-inflammatory effect of interleukin-10 on human neutrophil respiratory burst involves inhibition of GM-CSF-induced p47PHOX phosphorylation through a decrease in ERK1/2 activity

Interleukin-10 (IL-10) exerts its anti-inflammatory properties by down-regulating polymorphonuclear neutrophil (PMN) functions such as reactive oxygen species (ROS) production via NADPH oxidase. The molecular mechanisms underlying this process are unclear. Partial phosphorylation of the NADPH oxidase cytosolic component p47(PHOX) induced by proinflammatory cytokines, such as granulocyte-macrophage colony stimulating factor (GM-CSF) and tumor necrosis factor (TNF)-alpha, is essential for priming ROS production by PMN. The aim of this study was to determine whether IL-10 inhibits GM-CSF- and TNFalpha-induced p47(PHOX) phosphorylation and to investigate the molecular mechanisms involved in this effect. We found that IL-10 selectively inhibited GM-CSF- but not TNFalpha-induced p47PHOX phosphorylation in a concentration-dependent manner. As GM-CSF-induced p47PHOX phosphorylation is mediated by extracellular signal-regulated kinase 1/2 (ERK1/2), we tested the effect of IL-10 on this pathway. We found that IL-10 inhibited GM-CSF-induced ERK1/2 activity in an immunocomplex kinase assay. This inhibitory effect was confirmed by analyzing the phosphorylation status of the endogenous substrate of ERK1/2, p90RSK, in intact PMN. Furthermore, IL-10 decreased ROS production by adherent GM-CSF-treated PMN in keeping with the higher ROS production observed in whole blood from IL-10 knockout mice compared to their wild-type counterparts. Together, these results suggest that IL-10 inhibits GM-CSF-induced priming of ROS production by inhibiting p47PHOX phosphorylation through a decrease in ERK1/2 activity. This IL-10 effect could contribute to the tight regulation of NADPH oxidase activity at the inflammatory site.

Lipopolysaccharide primes neutrophils for a rapid response to IL-10

Responsiveness of human neutrophils to IL-10 was recently shown to be strictly dependent on the levels of IL-10R1 expression. Activation of signal transducer and activator of transcription 3 (STAT3) phosphorylation and induction of suppressor of cytokine signaling (SOCS)-3 protein by IL-10 are in fact negligible in circulating or freshly isolated ("time 0") neutrophils, but become readily measurable in neutrophils cultured for 4 h in the presence or absence of LPS. In this study, we show that modulation by IL-10 of LPS-induced TNF-alpha, CXCL8/IL-8 and IL-1 receptor antagonist (IL-1ra) mRNA accumulation in neutrophils already expressing a functional IL-10R and antigenic SOCS-3 (i.e. in "4-h-cultured" neutrophils) occurs with kinetics that are similar to those observed in "time 0" neutrophils, depends on de novo protein synthesis, but does not require SOCS-1, SOCS-3, heme oxygenase and Bcl-3 induction. By contrast, we show that IL-10 alone rapidly modulates the expression of TNF-alpha, CXCL8/IL-8 and IL-1ra mRNA, without any new protein synthesis requirement, if neutrophils have been previously exposed to LPS for at least 4 h. These findings suggest that LPS prepares neutrophils to optimally respond to IL-10 in terms of rapid gene modulation via mechanisms that, presumably, depend on specific LPS-induced protein(s).

Role of Interleukin-4 in Regulation of Age-related Inflammatory Changes in the Hippocampus

It is well documented that long term potentiation (LTP) is impaired in the hippocampus of the aged animal. Among the changes that contribute to this impairment is an increase in hippocampal concentration of the pro-inflammatory cytokine interleukin-1beta (IL-1beta), and increased IL-1beta-induced signaling. In this study we investigated the possibility that these changes were a consequence of decreased concentration of the anti-inflammatory cytokine, IL-4, and decreased IL-4-stimulated signaling. We report that functional IL-4 receptors are expressed on granule cells of the dentate gyrus and that receptor activation results in phosphorylation of JAK1 and STAT6. Hippocampal IL-4 concentration was decreased with age, and this was accompanied by a decrease in phosphorylation of JAK1 and STAT6. The evidence indicates that IL-4 modulates expression of IL-1beta mRNA and protein and that it attenuates IL-1beta-induced impairment of LTP and phosphorylation of JNK and c-Jun. We argued that, if a decrease in hippocampal IL-4 concentration significantly contributed to the age-related impairment in LTP, then restoration of IL-4 should restore LTP. To test this, we treated rats with VP015 (phospholipid microparticles-incorporating phosphatidylserine), which increases IL-4 concentration in hippocampus. The data indicate that the VP015-induced increase in IL-4 concentration in hippocampus of aged rats and lipopolysaccharide (LPS)-treated rats was accompanied by a reversal of the age-related and LPS-induced impairment in LTP in perforant path granule cell synapses. We propose that interplay between pro-inflammatory and anti-inflammatory responses impact significantly on synaptic function in the hippocampus of the aged rat.

Interleukin-22: a potential immunomodulatory molecule in the lung

Interleukin (IL)-22 is a member of the human type I interferon family, which includes IL-10. IL-22 has the potential to interact with IL-10 because it binds to the IL-10R2c chain with IL-22R1 in its receptor complex. Binding can be blocked by the soluble receptor, IL-22 binding protein (IL-22BP). We hypothesize that IL-22 and IL-22BP are involved in inflammatory regulation and its subsequent role in the pathogenesis of inflammatory lung disease. We have demonstrated IL-22 mRNA expression in alveolar macrophages (AM), monocytes, and alveolar epithelial (AE) cells. IL-22BP mRNA is expressed in AM, AE cells, and neutrophils. In contrast, IL-22R1 is expressed in AE only. Immunohistochemistry on normal and interstitial lung disease lung sections has confirmed IL-22 protein expression. Western blotting for IL-22 in bronchoalveolar lavage fluid demonstrated that lower levels of IL-22 were present in patients with acute respiratory distress syndrome and sarcoidosis relative to control subjects (P = 0.0152 and P = 0.0213). Levels of IL-22 in idiopathic pulmonary fibrosis were not different than those of the control subjects (P = 0.5838). IL-22 did not affect IL-10 inhibition of tumor necrosis factor-alpha in monocytes, which do not express IL-22R1. By contrast, we demonstrated synergy between IL-10 and IL-22 in terms of IL-8 inhibition in IL-22R1-expressing A549 cells. These data suggest a role for IL-22 in the regulation of pulmonary inflammation.

Role of endogenous IL-10 in LPS-induced STAT3 activation and IL-1 receptor antagonist gene expression

The regulation of secretory interleukin (IL)-1 receptor antagonist (sIL-1Ra) in response to IL-10 is unique. In contrast to most cytokines, the lipopolysaccharide (LPS)-induced expression of the sIL-1Ra gene is enhanced by concomitant treatment with IL-10. Cotreatment of RAW 264.7 cells with IL-10 + LPS resulted in at least a twofold increase in sIL-1Ra promoter activity and mRNA expression compared with LPS alone; IL-10 alone had no effect on promoter activity or mRNA expression. Examination of sIL-1Ra mRNA expression in bone marrow-derived macrophages (BMDM) resulted in identical results. Transfection of RAW 264.7 cells with the sIL-1Ra/luc reporter and a dominant-negative signal transducer and activator of transcription (STAT)3 (Y705A) expression plasmid inhibited the enhanced response induced by exogenous IL-10 in the presence of LPS. The presence of a functional STAT3-binding site within the proximal sIL-1Ra promoter was demonstrated. As IL-10 is produced by LPS-stimulated macrophages, a role for endogenously produced IL-10 in the response of the sIL-1Ra gene to LPS was suggested. This was confirmed in IL-10-deficient BMDM, which when compared with normal BMDM, had significantly decreased LPS-induced sIL-1Ra mRNA levels that could be restored by exogenously provided IL-10, which induced a fivefold increase of LPS-induced IL-1Ra mRNA in cells from IL-10-/- BMDM. Western blot analysis of phosphorylated STAT3 from wild-type and IL-10-/- BMDM and IL-10 neutralization experiments demonstrated a role for endogenously produced IL-10 in the LPS-induced STAT3 activity. Together, these results demonstrate that endogenously produced IL-10 plays a significant role in LPS-induced sIL-1Ra gene expression via the activation of STAT3.

Interleukin-15 delays human neutrophil apoptosis by intracellular events and not via extracellular factors: role of Mcl-1 and decreased activity of caspase-3 and caspase-8

Interleukin-15 (IL-15) induces the de novo protein synthesis of intracellular polypeptides and delays neutrophil apoptosis by a mechanism that is still unclear. Herein, we investigated the potential antiapoptotic role of newly synthesized proteins released into the external milieu in IL-15-induced neutrophils. We found that IL-15 induces the de novo synthesis of an approximately 23-kDa protein, representing the predominant protein detected in the milieu, and identified it as IL-1 receptor antagonist (IL-1Ra) by Western blot and immunoprecipitation. We quantified IL-1Ra, IL-1alpha, and IL-1beta concentrations by enzyme-linked immunosorbent assay in intracellular and extracellular fractions from IL-15-induced neutrophils and found that IL-15 does not increase IL-1alpha or IL-1beta production but induces IL-1Ra release. Also, we demonstrated that IL-1Ra does not modulate apoptosis, even at a concentration 250 times greater than that measured in the external milieu. In contrast to granulocyte macrophage-colony stimulating factor, the supernatant harvested from IL-15-induced neutrophils was devoid of antiapoptotic activity. Addition of cycloheximide demonstrates that IL-15 delays apoptosis via de novo synthesis of intracellular proteins and that it increases myeloid cell differentiation factor-1 stability. We demonstrated also that IL-15 decreases the activity of caspase-3 and caspase-8, resulting in an inhibition of vimentin cleavage. Our results indicate that IL-15 can activate an anti-inflammatory loop, based on its ability to induce the synthesis of IL-1Ra by neutrophils. We conclude that IL-15 delays human neutrophil apoptosis by intracellular events and not via extracellular factors.