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

S100A9 Regulated M1/M2 Macrophage Polarization in Interleukin-10-Induced Promotion of Malignant Pleural Effusion

Interleukin-10 (IL-10) promotes the formation and development of malignant pleural effusion (MPE). Previous studies have elucidated the pathogenesis from the view of the immune-regulation function of CD4+ T-cells. However, the underlying mechanism is still not fully understood. In this study, our results showed that IL-10 deficiency reduced the percentage of macrophages in mouse MPE and regulated M1/M2 polarization in vivo and in vitro. The migration capacity of tumor cells was suppressed, and apoptosis was promoted when tumor cells were cocultured with MPE macrophages in the absence of IL-10. Messenger RNA sequencing of MPE macrophages showed that S100A9 was downregulated in IL-10-/- mice. Bone marrow-derived macrophages obtained from wild-type mice transfected with S100A9-specific small interfering RNAs (siRNAs) also showed less M2 and more M1 polarization than those from the siRNA control group. Furthermore, downregulation of S100A9 using S100A9-specific siRNA suppressed MPE development, decreased macrophages, and modulated macrophage polarization in MPE in vivo. In conclusion, S100A9 plays a vital role in the process of IL-10 deficiency-mediated MPE suppression by regulating M1/M2 polarization, thus influencing the tumor-migration capacity and apoptosis. This could result in clinically applicable strategies to inhibit the formation of MPE by regulating the polarization of MPE macrophages.

The Regulation of Neutrophil Migration in Patients with Sepsis: The Complexity of the Molecular Mechanisms and Their Modulation in Sepsis and the Heterogeneity of Sepsis Patients

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Common causes include gram-negative and gram-positive bacteria as well as fungi. Neutrophils are among the first cells to arrive at an infection site where they function as important effector cells of the innate immune system and as regulators of the host immune response. The regulation of neutrophil migration is therefore important both for the infection-directed host response and for the development of organ dysfunctions in sepsis. Downregulation of CXCR4/CXCL12 stimulates neutrophil migration from the bone marrow. This is followed by transmigration/extravasation across the endothelial cell barrier at the infection site; this process is directed by adhesion molecules and various chemotactic gradients created by chemotactic cytokines, lipid mediators, bacterial peptides, and peptides from damaged cells. These mechanisms of neutrophil migration are modulated by sepsis, leading to reduced neutrophil migration and even reversed migration that contributes to distant organ failure. The sepsis-induced modulation seems to differ between neutrophil subsets. Furthermore, sepsis patients should be regarded as heterogeneous because neutrophil migration will possibly be further modulated by the infecting microorganisms, antimicrobial treatment, patient age/frailty/sex, other diseases (e.g., hematological malignancies and stem cell transplantation), and the metabolic status. The present review describes molecular mechanisms involved in the regulation of neutrophil migration; how these mechanisms are altered during sepsis; and how bacteria/fungi, antimicrobial treatment, and aging/frailty/comorbidity influence the regulation of neutrophil migration.

Complex Exercise Improves Anti-Inflammatory and Anabolic Effects in Osteoarthritis-Induced Sarcopenia in Elderly Women

We investigated the effects of a 15-week complex exercise program on osteoarthritis and sarcopenia by analyzing anabolic effects and the impact on the activities of daily living (ADLs). Nineteen women aged ≥60 years with sarcopenia (SEG, n = 9) or diagnosed with osteoarthritis with sarcopenia (OSEG, n = 10) were enrolled and underwent an exercise program. Insulin-like growth factor 1 (IGF-1), irisin, myostatin, interleukin-10 (IL-10), and tumor necrosis factor alpha (TNF-a) levels were analyzed pre- and post-intervention. Thigh cross-sectional area (TCSA) was measured pre- and post-intervention via computed tomography. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Short Physical Performance Battery (SPBB) were assessed pre- and post-interventions to assess ADL. There was a significant interaction effect between SEG and OSEG at the IGF-1 level post-intervention. Irisin increased and myostatin decreased post-intervention in both groups. IL-10 increased and TNF-α decreased post-intervention with a significant interaction effect in the OSEG group. TCSAs increased post-intervention in both groups. There was a significant interaction between the two groups. OSEG showed a greater WOMAC decrease and SPPB increase post-intervention, and there was a significant interaction effect. Combined exercise may be effective in improving biochemical factors, anabolic effects, and ADL in elderly women with osteoarthritis and sarcopenia.

Neutrophils and COVID-19: Active Participants and Rational Therapeutic Targets

Whilst the majority of individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative pathogen of COVID-19, experience mild to moderate symptoms, approximately 20% develop severe respiratory complications that may progress to acute respiratory distress syndrome, pulmonary failure and death. To date, single cell and high-throughput systems based analyses of the peripheral and pulmonary immune responses to SARS-CoV-2 suggest that a hyperactive and dysregulated immune response underpins the development of severe disease, with a prominent role assigned to neutrophils. Characterised in part by robust generation of neutrophil extracellular traps (NETs), the presence of immature, immunosuppressive and activated neutrophil subsets in the circulation, and neutrophilic infiltrates in the lung, a granulocytic signature is emerging as a defining feature of severe COVID-19. Furthermore, an assessment of the number, maturity status and/or function of circulating neutrophils at the time of hospital admission has shown promise as a prognostic tool for the early identification of patients at risk of clinical deterioration. Here, by summarising the results of studies that have examined the peripheral and pulmonary immune response to SARS-CoV-2, we provide a comprehensive overview of the changes that occur in the composition, phenotype and function of the neutrophil pool in COVID-19 patients of differing disease severities and discuss potential mediators of SARS-CoV-2-induced neutrophil dysfunction. With few specific treatments currently approved for COVID-19, we conclude the review by discussing whether neutrophils represent a potential therapeutic target for the treatment of patients with severe COVID-19.

Leukocyte-Derived Interleukin-10 Aggravates Postoperative Ileus

Objective: Postoperative ileus (POI) is an inflammation-mediated complication of abdominal surgery, characterized by intestinal dysmotility and leukocyte infiltration into the muscularis externa (ME). Previous studies indicated that interleukin (IL)-10 is crucial for the resolution of a variety of inflammation-driven diseases. Herein, we investigated how IL-10 affects the postoperative ME inflammation and found an unforeseen role of IL-10 in POI. Design: POI was induced by a standardized intestinal manipulation (IM) in C57BL/6 and multiple transgenic mouse strain including C-C motif chemokine receptor 2^-/-, IL-10^-/-, and LysM^cre/IL-10^fl/fl mice. Leukocyte infiltration, gene and protein expression of cytokines, chemokines, and macrophage differentiation markers as well as intestinal motility were analyzed. IL-10 serum levels in surgical patients were determined by ELISA. Results: IL-10 serum levels were increased in patient after abdominal surgery. In mice, a complete or leucocyte-restricted IL-10 deficiency ameliorated POI and reduced the postoperative ME neutrophil infiltration. Infiltrating monocytes were identified as main IL-10 producers and undergo IL-10-dependent M2 polarization. Interestingly, M2 polarization is not crucial to POI development as abrogation of monocyte infiltration did not prevent POI due to a compensation of the IL-10 loss by resident macrophages and neutrophils. Organ culture studies demonstrated that IL-10 deficiency impeded neutrophil migration toward the surgically traumatized ME. This mechanism is mediated by reduction of neutrophil attracting chemokines. Conclusion: Monocyte-derived macrophages are the major IL-10 source during POI. An IL-10 deficiency decreases the postoperative expression of neutrophil-recruiting chemokines, consequently reduces the neutrophil extravasation into the postsurgical bowel wall, and finally protects mice from POI.

IL-10 mediates plasmacytosis-associated immunodeficiency by inhibiting complement-mediated neutrophil migration

BACKGROUND

Plasmacytosis (ie, an expansion of plasma cell populations to much greater than the homeostatic level) occurs in the context of various immune disorders and plasma cell neoplasia. This condition is often associated with immunodeficiency that causes increased susceptibility to severe infections. Yet a causative link between plasmacytosis and immunodeficiency has not been established.

OBJECTIVE

Because recent studies have identified plasma cells as a relevant source of the immunosuppressive cytokine IL-10, we sought to investigate the role of IL-10 during conditions of polyclonal and neoplastic plasmacytosis for the regulation of immunity and its effect on inflammation and immunodeficiency.

METHODS

We used flow cytometry, IL-10 reporter (Vert-X) and B cell-specific IL-10 knockout mice, migration assays, and antibody-mediated IL-10 receptor blockade to study plasmacytosis-associated IL-10 expression and its effect on inflammation and Streptococcus pneumoniae infection in mice. ELISA was used to quantify IL-10 levels in patients with myeloma.

RESULTS

IL-10 production was a common feature of normal and neoplastic plasma cells in mice, and IL-10 levels increased with myeloma progression in patients. IL-10 directly inhibited neutrophil migration toward the anaphylatoxin C5a and suppressed neutrophil-dependent inflammation in a murine model of autoimmune disease. MOPC.315.BM murine myeloma leads to an increased incidence of bacterial infection in the airways, which was reversed after IL-10 receptor blockade.

CONCLUSION

We provide evidence that plasmacytosis-associated overexpression of IL-10 inhibits neutrophil migration and neutrophil-mediated inflammation but also promotes immunodeficiency.

Interleukin-18 increases TLR4 and mannose receptor expression and modulates cytokine production in human monocytes

Interleukin-18 is a proinflammatory cytokine belonging to the interleukin-1 family of cytokines. This cytokine exerts many unique biological and immunological effects. To explore the role of IL-18 in inflammatory innate immune responses, we investigated its impact on expression of two toll-like receptors (TLR2 and TLR4) and mannose receptor (MR) by human peripheral blood monocytes and its effect on TNF-α, IL-12, IL-15, and IL-10 production. Monocytes from healthy donors were stimulated or not with IL-18 for 18 h, and then the TLR2, TLR4, and MR expression and intracellular TNF-α, IL-12, and IL-10 production were assessed by flow cytometry and the levels of TNF-α, IL-12, IL-15, and IL-10 in culture supernatants were measured by ELISA. IL-18 treatment was able to increase TLR4 and MR expression by monocytes. The production of TNF-α and IL-10 was also increased by cytokine treatment. However, IL-18 was unable to induce neither IL-12 nor IL-15 production by these cells. Taken together, these results show an important role of IL-18 on the early phase of inflammatory response by promoting the expression of some pattern recognition receptors (PRRs) that are important during the microbe recognition phase and by inducing some important cytokines such as TNF-α and IL-10.

Multi-step pathogenesis and induction of local immune response by systemic Candida albicans infection in an intravenous challenge mouse model

Different murine species differ in their susceptibility to systemic infection with Candida albicans, giving rise to varied host immune responses, and this is compounded by variations in virulence of the different yeast strains used. Hence, this study was aimed at elucidating the pathogenesis of a clinical C. albicans isolate (HVS6360) in a murine intravenous challenge model by examining the different parameters which included the counts of red blood cells and associated components as well as the organ-specific expression profiles of cytokines and chemokines. Kidneys and brains of infected mice have higher fungal recovery rates as compared to other organs and there were extensive yeast infiltration with moderate to severe inflammation seen in kidney and brain tissues. Red blood cells (RBCs) and haemoglobin (Hb) counts were reduced throughout the infection period. Pattern recognition receptors (PRRs), chemokines and cytokine transcription profiles were varied among the different organs (kidney, spleen and brain) over 72 h post infections. Transcription of most of the PRRs, cytokines and chemokines were suppressed at 72 h post infection in spleen while continuous expression of PRRs, cytokines and chemokines genes were seen in brain and kidney. Reduction in red blood cells and haemoglobin counts might be associated with the action of extracellular haemolysin enzyme and haeme oxygenase of C. albicans in conjunction with iron scavenging for the fungal growth. Renal cells responsible for erythropoietin production may be injured by the infection and hence the combined effect of haemolysis plus lack of erythropoietin-induced RBC replenishment leads to aggravated reduction in RBC numbers. The varied local host immune profiles among target organs during systemic C. albicans infection could be of importance for future work in designing targeted immunotherapy through immunomodulatory approaches.

The therapeutic role of interleukin-10 after spinal cord injury

Spinal cord injury (SCI) is a devastating condition affecting 270,000 people in the United States. A potential treatment for decreasing the secondary inflammation, excitotoxic damage, and neuronal apoptosis associated with SCI, is the anti-inflammatory cytokine interleukin-10. The best characterized effects of IL-10 are anti-inflammatory-it downregulates pro-inflammatory species interleukin-1β (IL-1β), interleukin-2 (IL-2), interleukin-6 (IL-6), tumor necrosis factor-α, interferon-γ, matrix metalloproteinase-9, nitric oxide synthase, myeloperoxidase, and reactive oxygen species. Pro-apoptotic factors cytochrome c, caspase 3, and Bax are downregulated by IL-10, whereas anti-apoptotic factors B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X, B-cell lymphoma-extra large (Bcl-xl) are upregulated by IL-10. IL-10 also provides trophic support to neurons through the IL-10 receptor. Increased tissue sparing, functional recovery, and neuroprotection are seen with an immediate post-SCI systemic administration of IL-10. Treatment of SCI with IL-10 has been used successfully in combination with Schwann cell and olfactory glial cell grafts, as well as methylprednisolone. Minocycline, tetramethylpyrazine, and hyperbaric oxygen treatment all increase IL-10 levels in a SCI models and result in increased tissue sparing and functional recovery. A chronic systemic administration of IL-10 does not appear to be beneficial to SCI recovery and causes increased susceptibility to septicemia, pneumonia, and peripheral neuropathy. However, a localized upregulation of IL-10 has been shown to be beneficial and can be achieved by herpes simplex virus gene therapy, injection of poliovirus replicons, or surgical placement of a slow-release compound. IL-10 shows promise as a treatment for SCI, although research on local IL-10 delivery timeline and dosage needs to be expanded.

Inflammatory monocytes regulate pathologic responses to commensals during acute gastrointestinal infection

Commensal flora can promote both immunity to pathogens and mucosal inflammation. How commensal driven inflammation is regulated in the context of infection remains poorly understood. Here, we show that during acute mucosal infection, Ly6C^hi inflammatory monocytes acquire a tissue specific regulatory phenotype associated with production of the lipid mediator prostaglandin E₂ (PGE₂). Notably, in response to commensals, Ly6C^hi monocytes can directly inhibit neutrophil activation in a PGE₂-dependent manner. Further, in the absence of inflammatory monocytes, mice develop severe neutrophil-mediated pathology that can be controlled by PGE₂ analog treatment. Complementing these findings, inhibition of PGE₂ led to enhanced neutrophil activation and host mortality. These data demonstrate a previously unappreciated dual action of inflammatory monocytes in controlling pathogen expansion while limiting commensal mediated damage to the gut. Collectively, our results place inflammatory monocyte derived PGE₂ at the center of a commensal driven regulatory loop required to control host-commensal dialogue during inflammation.

Interleukin-10 controls human peripheral PMN activation triggered by lipopolysaccharide

Large amounts of anti-inflammatory mediators, such as interleukin (IL)-10, are produced and found early in the course of sepsis. We explore the role of IL-10 on neutrophil (PMN) activation/function using an in vitro model. Isolated human PMN were pre-incubated with lipopolysaccharide (LPS) and/or IL-10 for 18h. Subsequently, a second LPS exposure was performed and CD11b and CD66b up-regulation, and the reactive oxygen species (ROS) generation were measured 2h later. We found that IL-10 prevented PMN activation and the secretion of TNF-α and IL-8 induced by the first LPS contact. In the absence of IL-10, a second LPS exposure induced additive effects that were prevented by IL-10. Only ROS generation was highly affected by the blockade of PMN-secreted TNF-α or IL-8. Additionally, IL-10 prevented other possible mechanisms of LPS priming. Therefore, IL-10 modulates PMN activation preventing autocrine activating loops and priming mechanisms, rendering PMN less responsive to a second LPS exposure.

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.

Excess neutrophil infiltration during cytomegalovirus brain infection of interleukin-10-deficient mice

Wild-type mice control murine cytomegalovirus (MCMV) brain infection, but identical infection is lethal to animals deficient in interleukin (IL)-10. Here, we report that MCMV-infected IL-10 knockout (KO) mice displayed a marked increase in neutrophil infiltration into the infected, IL-10-deficient brain when compared to wild-type animals. Enhanced microglial cell activation, determined by MHC class II up-regulation, overexpression of CXCL2, and elevated P-selectin mRNA levels were observed. In vivo blocking of CXCL2 attenuated neutrophil infiltration and significantly improved the outcome of infection. Collectively, these data indicate that the absence of IL-10 results in pathologic neutrophil infiltration into MCMV-infected brains.

Interleukin-10 but not Transforming Growth Factor beta inhibits murine activated macrophages Paracoccidioides brasiliensis killing: effect on H2O2 and NO production

Paracoccidioidomycosis is caused by the thermally dimorphic fungus Paracoccidioides brasiliensis (P. brasiliensis). Most often, this mycosis runs as a chronic progressive course affecting preferentially the lungs. In vitro fungicidal activity against a high virulent strain of P. brasiliensis by murine peritoneal macrophages preactivated with IFN-gamma or TNF-alpha is high and correlates with increased NO and H2O2 production. Within this context, the purpose of this work was to study the role of suppressor cytokines, such as IL-10 and TGF-beta, in this process. Incubation of either IFN-gamma or TNF-alpha with IL-10 inhibits fungicidal activity of these cells. However, TGF-beta had no effect on fungicidal activity of IFN-gamma or TNF-alpha-activated macrophages. The suppression of fungicidal activity by IL-10 correlated with the inhibition of NO and H2O2 production supporting the involvement of these metabolites in P. brasiliensis killing. These results suggest that IL-10 production in vivo could represent an evasion mechanism of the fungus to avoid host immune response.

T(H)2 cytokines modulate the IL-9R expression on human neutrophils

Interleukin (IL)-9 is associated with key pathological features of asthma such as airway hyperresponsiveness, bronchoconstriction and mucus production. Inflammatory responses mediated by IL-9 rely on the expression of the IL-9R which has been reported on lung epithelial cells, T lymphocytes and recently on airway granulocyte infiltrates. In this study, we assessed the regulatory and constitutive cell surface expression of the IL-9Ralpha in unfractionated and purified human neutrophils from atopic asthmatics, atopic non-asthmatics and healthy normal controls. We demonstrate that T(H)2 cytokines (IL-4 or IL-13) and granulocyte macrophage-colony stimulating factor (GM-CSF) up-regulated mRNA and cell surface expression levels of the IL-9Ralpha in primary human and HL-60 differentiated neutrophils. Pharmacological inhibition of NF-kappaB did not affect T(H)2-mediated IL-9Ralpha expression in human neutrophils although IFN-gamma and IL-10 down-regulated IL-9Ralpha expression when co-incubated with IL-4, IL-13 or GM-CSF. Collectively, our results reveal a regulatory function for IFN-gamma and IL-10 on modulating the inducible IL-9Ralpha expression levels on peripheral blood neutrophils by T(H)2 cytokines.

Bone marrow stromal cells attenuate sepsis via prostaglandin E(2)-dependent reprogramming of host macrophages to increase their interleukin-10 production

Sepsis causes over 200,000 deaths yearly in the US; better treatments are urgently needed. Administering bone marrow stromal cells (BMSCs -- also known as mesenchymal stem cells) to mice before or shortly after inducing sepsis by cecal ligation and puncture reduced mortality and improved organ function. The beneficial effect of BMSCs was eliminated by macrophage depletion or pretreatment with antibodies specific for interleukin-10 (IL-10) or IL-10 receptor. Monocytes and/or macrophages from septic lungs made more IL-10 when prepared from mice treated with BMSCs versus untreated mice. Lipopolysaccharide (LPS)-stimulated macrophages produced more IL-10 when cultured with BMSCs, but this effect was eliminated if the BMSCs lacked the genes encoding Toll-like receptor 4, myeloid differentiation primary response gene-88, tumor necrosis factor (TNF) receptor-1a or cyclooxygenase-2. Our results suggest that BMSCs (activated by LPS or TNF-alpha) reprogram macrophages by releasing prostaglandin E(2) that acts on the macrophages through the prostaglandin EP2 and EP4 receptors. Because BMSCs have been successfully given to humans and can easily be cultured and might be used without human leukocyte antigen matching, we suggest that cultured, banked human BMSCs may be effective in treating sepsis in high-risk patient groups.

Role of the chemokine receptor CXCR2 in bleomycin-induced pulmonary inflammation and fibrosis

Pulmonary fibrosis is characterized by chronic inflammation and excessive collagen deposition. Neutrophils are thought to be involved in the pathogenesis of lung fibrosis. We hypothesized that CXCR2-mediated neutrophil recruitment is essential for the cascade of events leading to bleomycin-induced pulmonary fibrosis. CXCL1/KC was detected as early as 6 hours after bleomycin instillation and returned to basal levels after Day 8. Neutrophils were detected in bronchoalveolar lavage and interstitium from 12 hours and peaked at Day 8 after instillation. Treatment with the CXCR2 receptor antagonist, DF2162, reduced airway neutrophil transmigration but led to an increase of neutrophils in lung parenchyma. There was a significant reduction in IL-13, IL-10, CCL5/RANTES, and active transforming growth factor (TGF)-beta(1) levels, but not on IFN-gamma and total TGF-beta(1,) and enhanced granulocyte macrophage-colony-stimulating factor production in DF2162-treated animals. Notably, treatment with the CXCR2 antagonist led to an improvement of the lung pathology and reduced collagen deposition. Using a therapeutic schedule, DF2162 administered from Days 8 to 16 after bleomycin reduced pulmonary fibrosis and levels of active TGF-beta(1) and IL-13. DF2162 treatment reduced bleomycin-induced expression of von Willebrand Factor, a marker of angiogenesis, in the lung. In vitro, DF2162 reduced the angiogenic activity of IL-8 on human umbilical vein endothelial cells. In conclusion, we show that CXCR2 plays an important role in mediating fibrosis after bleomycin instillation. The compound blocks angiogenesis and the production of pro-angiogenic cytokines, and decreases IL-8-induced endothelial cell activation. An effect on neutrophils does not appear to account for the major effects of the blockade of CXCR2 in the system.

Interleukin-10 From Transplanted Bone Marrow Mononuclear Cells Contributes to Cardiac Protection After Myocardial Infarction

Bone marrow mononuclear cells (BM-MNCs) have successfully been used as a therapy for the improvement of left ventricular (LV) function after myocardial infarction (MI). It has been suggested that paracrine factors from BM-MNCs may be a key mechanism mediating cardiac protection. We previously performed microarray analysis and found that the pleiotropic cytokine interleukin (IL)-10 was highly upregulated in human progenitor cells in comparison with adult endothelial cells and CD14 + cells. Moreover, BM-MNCs secrete significant amounts of IL-10, and IL-10 could be detected from progenitor cells transplanted in infarcted mouse hearts. Specifically, intramyocardial injection of wild-type BM-MNCs led to a significant decrease in LV end-diastolic pressure (LVEDP) and LV end-systolic volume (LVESV) compared to hearts injected with either diluent or IL-10 knock-out BM-MNCs. Furthermore, intramyocardial injection of wild-type BM-MNCs led to a significant increase in stroke volume (SV) and rate of the development of pressure over time (+dP/dt) compared to hearts injected with either diluent or IL-10 knock-out BM-MNCs. The IL-10–dependent improvement provided by transplanted cells was not caused by reduced infarct size, neutrophil infiltration, or capillary density, but rather was associated with decreased T lymphocyte accumulation, reactive hypertrophy, and myocardial collagen deposition. These results suggest that BM-MNCs mediate cardiac protection after myocardial infarction and this is, at least in part, dependent on IL-10.

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.

[Clinical usefulness of plasma interleukin-6 and interleukin-10 in disseminated intravascular coagulation]

BACKGROUND

Disseminated intravascular coagulation (DIC) is a syndrome characterized by a systemic activation of coagulation leading to the intravascular deposition of fibrin and the simultaneous consumption of coagulation factors and platelets. Inflammatory cytokines can activate the coagulation system. This study investigated the diagnostic and prognostic usefulness of the plasma level of interleukin-6 (IL-6) and interleukin-10 (IL-10) for predicting DIC.

METHODS

The study populations were 15 healthy controls and 81 patients who were clinically suspected of having DIC and were requested to perform DIC battery tests. The presence of overt DIC was defined by the International Society on Thrombosis and Haemostasis Subcommittee cumulative score of 5 or above. The 28 day mortality was used to assess the prognostic outcome. The plasma levels of the cytokines were measured by ELISA.

RESULTS

The plasma levels of IL-6 and IL-10 in patients (N=81) were higher than those of control (N=15). IL-6 and IL-10 levels of overt DIC group (N=31) were 3 times and 1.5 times higher than those, respectively, of non-overt DIC group (N=50). In infection group (N=48), IL-6 and IL-10 levels of overt DIC group (N=18) were 5 times and 3 times higher than those, respectively, of non-overt DIC group (N=30). The diagnostic efficiency of IL-6 (optimal cut off >40.4 pg/mL) and IL-10 (>9.7 pg/mL) for the diagnosis of overt DIC were 67% and 69%, respectively, which were similar to that of D-dimer. Plasma levels of IL-6 and IL-10 were also higher in non-survivors than in survivors. The patients with higher levels of IL-6 and IL-10 showed a poorer prognosis.

CONCLUSIONS

The proinflammatory cytokine, IL-6 and anti-inflammatory cytokine, IL-10 were useful for the diagnosis of overt DIC and the prediction of its prognosis. These results also showed the evidence of a close interaction between coagulation and inflammation.

Effect of interleukin-10 on the Paracoccidioides brasiliensis killing by gamma-interferon activated human neutrophils

Paracoccidioidomycosis, a deep mycosis endemic in Latin America, is a chronic granulomatous disease caused by the fungus Paracoccidioides brasiliensis. Phagocytic cells play a critical role against this fungus, and several studies have shown the effects of activator and suppressive cytokines on macrophage and monocyte functions. However, studies on polymorphonuclear neutrophils (PMNs), that are the first cells recruited to the infection sites, are scarcer. Thus, the objective of this paper was to assess whether interleukin-10 (IL-10), a potent anti-inflammatory cytokine, is able to block the activity of IFN-gamma-activated human PMNs upon P. brasiliensis intracellular killing, in vitro. The results showed that IFN-gamma-activated PMNs have an effective fungicidal activity against the fungus. This activity was associated with the release of high levels of H(2)O(2), the metabolite involved in phagocytic cells antifungal activities. However, the concomitant incubation of these cells with IFN-gamma and IL-10 significantly blocked IFN-gamma activation. As a consequence, PMNs killing activity and H(2)O(2) release were inhibited. Together, our results show the importance of PMNs exposure to activator or suppressor cytokines in the early stages of paracoccidioidomycosis infection.

The neutrophil/Th1 lymphocyte balance and the therapeutic effect of granulocyte colony-stimulating factor in TNBS-induced colitis of rat strains

Intramucosal neutrophil infiltration is related to the activity of ulcerative colitis, and Th1 immunity is responsible for the onset of Crohn's disease. We examined the therapeutic effects of recombinant human granulocyte colony-stimulating factor (rHuG-CSF) in the two types of 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis of five rat strains. SD and DA rats showed much lower mRNA expression levels of endogenous G-CSF in lipopolysaccharide (LPS)-stimulated splenocytes than did Lewis, F344, and BN rats. On day 7 after anal instillation of TNBS, SD and DA rats demonstrated massive lymphocyte infiltration with an interferon-gamma (IFN-gamma) mRNA upregulation, whereas Lewis, F344, and BN rats showed an intense submucosal neutrophil accumulation with high tumor necrosis factor-alpha (TNF-alpha) mRNA levels. A 5-day course of rHuG-CSF pretreatment (250 microg/kg/day, s.c.) reduced the elevated levels of both cytokines. The treatment improved the survival rate of DA and reduced the degree of body weight loss of SD, while not significantly influencing the wasting disease of other strains. Interleukin-10 (IL-10) mRNA levels were highly upregulated by rHuG-CSF treatment on day 1 in the neutrophil-dominant lesions of F344 but not in the Th1-type lesions of SD, and IL-12p35 mRNA levels were downregulated in both. A supply of G-CSF prevents the onset of Th1-type TNBS colitis and does not deteriorate neutrophil-dominant chronic colitis in hosts showing higher expression of endogenous G-CSF.

Interleukin-10 Gene Transfer: Prevention of Multiple Organ Injury in a Murine Cecal Ligation and Puncture Model of Sepsis

INTRODUCTION

The aim of this study was to determine the effect of immunoregulatory cytokine interleukin-10 (IL-10) gene therapy on multiple organ injury (MOI) induced by a cecal ligation and puncture (CLP) model of sepsis in mice.

METHODS

Male Balb/c mice subjected to CLP were treated with either an hIL-10-carrying vector or an empty control vector. We assessed the degree of lung, liver, and kidney tissue destruction biochemically by measuring myeloperoxidase (MPO) and malondialdehyde (MDA) activity. Histologic assessments were based on neutrophil infiltration in lung and liver tissue. IL-10 protein expression was examined immunohistochemically, and ultrastructural changes in the liver were studied by transmission electron microscopy. We analyzed the expression of tumor necrosis factor-alpha (TNFalpha) mRNA by reverse transcription polymerase chain reaction 3, 8, and 24 hours after CLP in all organs.

RESULTS

Organ damage was significantly reduced by hIL-10 gene transfer, which was associated at the tissue level with reduced MPO activity in the liver, lung, and kidney and decreased leukocyte sequestration and MDA formation in the lung. The liver MDA was not significantly higher in the hIL-10 gene therapy group than in the controls and seemed not to be affected by hIL-10 gene transfer. The reduced portal tract neutrophilic infiltration and preserved ultrastructure of the hepatocytes also showed that tissue function was not impaired. The lung and kidney TNFalpha mRNA expression was suppressed markedly in the hIL-10 gene therapy group, but liver TNFalpha mRNA expression varied over time.

CONCLUSIONS

These findings showed that IL-10 gene therapy significantly attenuated sepsis-induced MOI.

Hibernation confers resistance to intestinal ischemia-reperfusion injury

The damaging effects of intestinal ischemia-reperfusion (I/R) on the gut and remote organs can be attenuated by subjecting the intestine to a prior, less severe I/R insult, a process known as preconditioning. Because intestines of hibernating ground squirrels experience repeated cycles of hypoperfusion and reperfusion, we examined whether hibernation serves as a model for natural preconditioning against I/R-induced injury. We induced intestinal I/R in either the entire gut or in isolated intestinal loops using rats, summer ground squirrels, and hibernating squirrels during natural interbout arousals (IBA; body temperature 37-39 degrees C). In both models, I/R induced less mucosal damage in IBA squirrels than in summer squirrels or rats. Superior mesenteric artery I/R increased MPO activity in the gut mucosa and lung of rats and summer squirrels and the liver of rats but had no effect in IBA squirrels. I/R in isolated loops increased luminal albumin levels, suggesting increased gut permeability in rats and summer squirrels but not IBA squirrels. The results suggest that the hibernation phenotype is associated with natural protection against intestinal I/R injury.

Interleukin-1 as a therapeutic target in acute brain injury

Interest in the interactions between the immune and central nervous systems has furthered our understanding of brain function in health and disease. Experimental and clinical studies increasingly reveal an inflammatory component in the pathophysiology of many forms of brain injury. Members of the interleukin (IL)-1 cytokine family are produced by diverse cell types within the brain and may determine the outcome of neuronal injury. This review discusses the neuroprotective potential of IL-1 inhibition in various acute neurological and neurosurgical diseases. The ILs comprise an expanding family of cytokines with diverse physiological and pathological actions, of which IL-1 is a key inflammatory mediator implicated in brain injury. IL-1 expression in the normal CNS is low, but is upregulated rapidly in response to brain injury. In experimental studies, IL-1 and its endogenous, competitive, selective antagonist, IL-1 receptor antagonist (IL-1RA), mediate neurotoxic and neuroprotective outcomes, respectively. Clinical studies support the relationship between inflammation, disease severity and poor prognosis in various neurological and neurosurgical disorders. Recombinant human (rh)IL-1RA shows modest blood–brain barrier penetrance and is safe for clinical use when administered parenterally. Evidence supporting the use of rhIL-1RA and other approaches to targeting IL-1 are discussed in relation to cerebral ischemia, seizures, subarachnoid hemorrhage and traumatic brain injury.

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.

Lipoteichoic acid (LTA) from Staphylococcus aureus stimulates human neutrophil cytokine release by a CD14-dependent, Toll-like-receptor-independent mechanism: Autocrine role of tumor necrosis factor-α in mediating LTA-induced interleukin-8 generation

OBJECTIVE

In sepsis, Gram-positive and Gram-negative bacteria provoke similar inflammatory processes. Whereas lipopolysaccharides (LPSs) are acknowledged as the principal immunostimulatory components of Gram-negative bacteria, the effect of the Gram-positive cell wall component lipoteichoic acid (LTA) is less well characterized. In the present study, we investigated the effect of highly purified LTA from Staphylococcus aureus on cytokine generation by isolated human neutrophils.

SUBJECTS

Isolated human neutrophils from healthy volunteers.

INTERVENTIONS

Incubation of neutrophils with purified LTA from S. aureus in the absence or presence of interleukin (IL)-10, anti-CD14, or anti-Toll-like-receptor antibodies.

MEASUREMENTS

Measurement of tumor necrosis factor (TNF)-alpha, IL-1beta, and IL-8 by enzyme-linked immunosorbent assay. Analysis of IL-8 mRNA by reverse transcriptase polymerase chain reaction.

CONCLUSIONS

The LTA challenge provoked a dramatic release of cytokines, with an early appearance of TNF-alpha and IL-1beta and a delayed liberation of IL-8. The first phase of IL-8 production was induced directly by LTA, whereas the second phase was endogenously mediated by TNF-alpha, as it was largely abrogated by neutralizing anti-TNF-alpha antibodies. In contrast, IL1-beta was not involved in LTA-induced IL-8 generation. Interestingly, the late phase of IL-8 generation could also be attenuated by exogenous IL-10, probably as a consequence of its downregulatory effects on TNF-alpha generation. When investigating the mechanism of LTA-induced cellular activation, activity-neutralizing antibodies demonstrated that CD14 was involved in LTA-mediated neutrophil cytokine generation. Using antibodies that neutralize the activity of Toll-like receptor 2 (TLR2) or 4 (TLR4), we also show that CD14-dependent, LTA-induced neutrophil activation did not proceed via TLR2- or TLR4-mediated pathways. In conclusion, LTA is a potent activator of human neutrophil cytokine generation, with the synthesis of the chemokine IL-8 being largely dependent on TNF-alpha generation in an autocrine fashion. This LTA-induced effect was inhibited by IL-10, dependent on CD14, and independent of TLR 2 or 4.

Role of alveolar macrophage and migrating neutrophils in hemorrhage-induced priming for ALI subsequent to septic challenge

Acute lung injury (ALI) is identified with the targeting/sequestration of polymorphonuclear leukocytes (PMN) to the lung. Instrumental to PMN targeting are chemokines [e.g., macrophage inflammatory protein-2 (MIP-2), keratinocyte-derived chemokine (KC), etc.] produced by macrophage, PMN, and other resident pulmonary cells. However, the relative contribution of resident pulmonary macrophages as opposed to PMN in inducing ALI is poorly understood. We therefore hypothesize that depletion of peripheral blood PMN and/or the oblation of a macrophage-mediated PMN chemokine signal (via macrophage deficiency) will reduce the inflammation and ALI observed in mice following hemorrhage (Hem) and subsequent sepsis (CLP) in our murine model of ALI. To examine this we pretreated mice with either 500 μg anti-mouse Gr1 antibody/animal (to deplete PMN) or subjected mice deficient in mature macrophage (B6C3Fe-a/a-CsF1op) to Hem (90 min at 35 ± 5 mmHg) followed by resuscitation. Twenty-four hours post-Hem, mice were subjected to CLP and killed 24 h later, and lung tissue samples were collected. Our data showed that in the absence of either peripheral blood PMN or mature tissue macrophages there was a suppression of IL-6, KC, and MIP-2 levels in lung tissue from Hem/CLP mice as well as a reduction in PMN influx to the lung and lung injury (bronchoalveolar lavage fluid protein). In contrast, lung tissue IL-10 and TNF-α levels were suppressed in the macrophage-deficient Hem/CLP mice compared with PMN-depleted Hem/CLP mice. Together, these data suggest that both the PMN and the macrophage are required to induce inflammation seen here, however, macrophage not PMN regulate the release of IL-10, independent of local changes in TNF.

Interleukin-10 gene therapy attenuates pulmonary tissue injury caused by mesenteric ischemia-reperfusion in a mouse model

To investigate the role of interleukin (IL)-10 gene therapy on the reperfusion-induced lung injury, we utilised the technique of liposomal gene delivery before the induction of intestinal ischemia. Plasmid DNA encoding human IL10 (hIL-10) or empy vector was injected intraperitoneally 24 h before the study. Male Balb/c mice randomized into three groups: Sham operated control (n = 12), empty plasmid vector (n = 12), and hIL-10 gene therapy group (n = 12). The ischemia was generated by selective occlusion of superior mesenteric artery for 60 min and followed by reperfusion for 30 min. Lung tissue neutrophil infiltration was determined by myeloperoxidase assay and neutrophil counts. For the determination of lung tissue microvascular permeability, Evans blue dye injection was made and the lung edema was assessed by wet/dry ratio. hIL-10 protein expression was studied by immunostaining and ELISA. We found that pre-ischemic hIL-10 overexpression attenuated dye extravasation, leukocyte sequestration and reduced pulmonary tissue injury compared to the empty vector-injected control. Our study indicates that pre-ischemic hIL-10 overexpression attenuates lung injury caused by intestinal ischemia-reperfusion.

BLOOD NEUTROPHIL BACTERICIDAL ACTIVITY AGAINST METHICILLIN-RESISTANT AND METHICILLIN-SENSITIVE STAPHYLOCOCCUS AUREUS DURING CARDIAC SURGERY

Whether methicillin-resistant Staphylococcus aureus (MRSA) constitutes per se an independent risk factor for morbidity and mortality after surgery as compared with methicillin-sensitive Staphylococcus aureus (MSSA) remains a subject of debate. The aim of this study was to assess whether innate defenses against MRSA and MSSA strains are similarly impaired after cardiac surgery. Both intracellular (isolated neutrophil functions) and extracellular (plasma) defenses of 12 patients undergoing scheduled cardiac surgery were evaluated preoperatively (day 0) and postoperatively (day 3) against two MSSA strains with a low level of catalase secretion and two MRSA strains with a high level of catalase secretion, inasmuch as SA killing by neutrophils relies on oxygen-dependent mechanisms. After surgery, an increase in plasma concentration of IL-10, an anti-inflammatory cytokine able to inhibit reactive oxygen species secretion and bactericidal activity of neutrophils, was evidenced. Despite the fact that univariate analysis suggested a specific impairment of neutrophil functions against MRSA strains, two-way repeated-measures ANOVA failed to demonstrate that the effect of S. aureus phenotype was significant. On the other hand, an increase in type-II secretory phospholipase A2 activity, a circulating enzyme involved in SA lysis, was evidenced and was associated with an enhancement of extracellular defenses (bactericidal activity of plasma) against MRSA. Overall, cardiac surgery and S. aureus phenotype had a significant effect on plasma bactericidal activity. Cardiac surgery was characterized by enhanced antibacterial defenses of plasma, whereas neutrophil killing properties were reduced. The overall effect of S. aureus phenotype on neutrophil functions did not seem significant.

Inflammatory profile in nasal secretions of infants hospitalized with acute lower airway tract infections

OBJECTIVE

The aim of this study was to determine whether the regulatory immune response (interleukin (IL)-10 response) differed between children hospitalized with acute respiratory infections and wheezing.

METHODOLOGY

Infants with signs and symptoms of acute viral respiratory infection, admitted during winter 2000 to Princess Margaret Hospital for Children, Perth, WA, Australia, were enrolled in this study. Nasopharyngeal aspirates were collected in the first 48 h of admission. Total cell count and differential cell counts were assessed. Samples were tested for the presence of respiratory viruses. The concentrations of the anti-inflammatory cytokine IL-10, and pro-inflammatory cytokines IL-8, interferon-gamma, and IL-11 were determined by ELISA.

RESULTS

Children with acute bronchiolitis (AB; n = 36), recurrent wheeze (RW; n = 17) and upper respiratory infection (URI; n = 18) were enrolled. Respitory syncytial virus was the most commonly detected virus in all groups. IL-10 concentrations were significantly increased in AB (median, 0.019 ng/mL) when compared to URI (median, 0.006 ng/mL) or to RW (median, 0.007 ng/mL; P < 0.05). Neutrophils were the predominant cells in the cytological analysis in all subjects.

CONCLUSION

These data argue that host-response factors are important in determining the clinical phenotype, independent of the causative virus.

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).

Expression of mRNA encoding interleukin (IL)-10, IL-12p35 and IL-12p40 in lungs from pigs experimentally infected with Actinobacillus pleuropneumoniae

The expression of mRNA encoding interleukin (IL)-10, IL-12p35 and IL-12p40 was studied, by reverse transcription-polymerase chain reaction and by in situ hybridization with a non-radioactive digoxigenin-labelled cDNA probe, in formalin-fixed, paraffin-wax-embedded lung tissue from pigs experimentally infected with Actinobacillus pleuropneumoniae. Forty-eight 7-week-old colostrum-deprived pigs were randomly allocated to infected (n = 24) or control (n = 24) groups. Three pigs from each group were euthanized at 3, 6, 9, 12, 24, 36, 48 and 60 h post inoculation (hpi). IL-10 mRNA was detected in the lung at 3 hpi, numbers of cells positive for IL-10 increasing at 36 hpi. IL-12p35 mRNA was detected in the lung at 3 hpi, numbers of cells positive for IL-12p35 increasing at 36 and 48 hpi and rapidly decreasing thereafter whereas IL-12p40 mRNA was constitutively expressed at low levels during the experiment. Hybridization signals for IL-10, IL-12p35 and IL-12p40 were always associated with inflammation, in particular with macrophages and neutrophils within alveolar spaces. Expression of these cytokines was minimal in non-lesional lung of A. pleuropneumoniae-infected pigs and in normal lung from control pigs. In situ hybridization of A. pleuropneumoniae and these cytokines in serial sections of lung tissues indicated close co-localization of A. pleuropneumoniae and these cytokines in pleuropneumonia. The results suggest that the expression of IL-10 and IL-12 play a role in pathogenesis of A. pleuropneumoniae infection.

Influence of PMN leukocyte-mediated pancreatic damage on the systemic immune response in severe acute pancreatitis in rats

The outcome of severe acute pancreatitis is determined by the development of the systemic inflammatory response and subsequent multiorgan dysfunction. Using the taurocholate-induced model of acute pancreatitis in rats, we investigated the relationship between early polymorphonuclear (PMN)-mediated pancreatic tissue damage and the systemic inflammatory response. The respiratory burst of PMN leukocytes was increased in animals with acute pancreatitis and was reduced by anti-ICAM-1 antibody and oxygen radical scavenger treatment after 24 hr. In acute pancreatitis a reduced number of peripheral helper T cells was evident, most likely due to L-selectin-mediated increased lymphocyte homing. After 24 hr the CD45RC(high)/CD45RC(low) ratio of helper T cells, a critical factor in T cell-mediated disease was increased due to a reduction of regulatory CD45RC(low) cells. Only the treatment with anti-ICAM-1 mAb affected these changes, indicating that immunological changes in necrotizing pancreatitis are only in part affected by early PMN leukocyte-mediated pancreatic damage.

CXCR2 inhibition suppresses hemorrhage-induced priming for acute lung injury in mice

Polymorphonuclear neutrophil (PMN) extravasation/sequestration in the lung and a dysregulated inflammatory response characterize the pathogenesis of acute lung injury (ALI). Previously, we have shown that hemorrhage (Hem) serves to prime PMN such that subsequent septic challenge [cecal ligation and puncture (CLP)] produces a pathological, inflammatory response and consequent lung injury in mice. Keratinocyte-derived chemokine (KC) and macrophage inflammatory protein-2 (MIP-2) are murine CXC chemokines found elevated in the lungs and plasma following Hem/CLP and have been reported by others to share a common receptor (CXCR2). Based on these data, we hypothesize that blockade of CXCR2 immediately following Hem would suppress KC and MIP-2 priming of PMN, thereby reducing the inflammatory injury observed following CLP. To assess this, Hem mice (90 min at 35+/-5 mmHg) were randomized to receive 0, 0.4, or 1 mg antileukinate (a hexapeptide inhibitor of CXCRs) in 100 microl phosphate-bufferd saline (PBS)/mouse subcutaneously, immediately following resuscitation (Ringer's lactate-4x drawn blood volume). Twenty-four hours post-Hem, mice were subjected to CLP and killed 24 h later. The results show that blockade of CXCR2 significantly (P<0.05, Tukey's test) reduced PMN influx, lung protein leak, and lung-tissue content of interleukin (IL)-6, KC, and MIP-2 and increased tissue IL-10 levels. Plasma IL-6 was significantly decreased, and IL-10 levels increased in a dose-dependent manner compared with PBS-treated mice. A differential effect was observed in plasma levels of KC and MIP-2. KC showed a significant reduction at the 0.4 mg antileukinate dose. In contrast, plasma MIP-2 was significantly elevated at both doses compared with the PBS-treated controls. Together, these data demonstrate that blockade of CXCR2 signaling attenuates shock-induced priming and ALI observed following Hem and subsequent septic challenge in mice.

Interleukin-10 inhibits interleukin-12 p40 gene transcription by targeting a late event in the activation pathway

Interleukin-10 (IL-10) is a potent anti-inflammatory cytokine that suppresses the induction of proinflammatory cytokine genes, including the IL-12 p40 gene. Despite considerable effort examining the effect of IL-10 on specific transcription factors and signaling molecules, the mechanism by which IL-10 inhibits gene transcription has remained elusive. To provide a different perspective to this problem, we examined the effect of IL-10 on molecular events occurring at the endogenous IL-12 p40 locus in lipopolysaccharide-stimulated peritoneal macrophages. IL-10 abolished recruitment of RNA polymerase II to the p40 promoter. However, it only modestly reduced binding of C/EBPbeta, as monitored by genomic footprinting and chromatin immunoprecipitation. It also had little effect on NF-kappaB complexes that are critical for p40 induction. A substantial reduction in nucleosome remodeling at the p40 promoter was observed, but the magnitude of this reduction appeared insufficient to account for the strong inhibition of transcription. Finally, a lipopolysaccharide-inducible DNase I hypersensitive site identified 10 kb upstream of the start site was unaffected by IL-10. Thus, despite a dramatic reduction in p40 transcription, several events required for activation of the endogenous p40 gene occurred relatively normally. These findings suggest that IL-10 blocks one or more events that occur after p40 locus decondensation and nucleosome remodeling and after, or in parallel with, the binding of a subset of p40 transcriptional activators.

Lipopolysaccharide from the periodontal pathogen Porphyromonas gingivalis prevents apoptosis of HL60-derived neutrophils in vitro

Lipopolysaccharide (LPS) from Porphyromonas gingivalis prevented apoptosis of HL60-derived neutrophils, which could not be restored upon the addition of interleukin-10. Signaling of P. gingivalis LPS through Toll-like receptor 2 (TLR2), not TLR4, may account for the inhibiting effect of P. gingivalis LPS on apoptosis and provide a mechanism for the development of destructive periodontal inflammation.

The effects of endogenous interleukin-10 on gray matter damage and the development of pain behaviors following excitotoxic spinal cord injury in the mouse

Interleukin-10 (IL-10) has been utilized as a neuroprotective agent in experimental models of spinal cord injury because of its potent anti-inflammatory properties. Previous studies have delivered a single dose (5 microg) of IL-10 following experimental spinal cord injury in the rat, and demonstrated various degrees of neuroprotection. However, the role of endogenous production of IL-10 has not been considered. Therefore, the purpose of the current study was to establish the role of endogenous IL-10 and demonstrate the true potential of exogenous IL-10 administration through the use of IL-10((-/-)) mice. Using the quisqualic acid model of spinal cord injury, we examined the extent of gray matter damage and onset of injury-induced pain behaviors at various time points following injury in wild-type vs. IL-10((-/-)) mice. Additionally, IL-10 was reconstituted in IL-10 deficient mice by the intraperitoneal administration of 50 ng recombinant murine (rm) IL-10 30 min following quisqualic acid injection. Animals were observed daily following injury for the onset of pain-behaviors. At days 1, 7, and 14 following injection, lesion analysis revealed a greater extent of damage at early time points (1 day, 7 days) following injury in the IL-10((-/-)) animals as compared with wild-type animals. However, by 14 days post-experimental spinal cord injury, the extent of damage between the two groups was not significant. IL-10((-/-)) animals that received the single (50 ng) rmIL-10 injection following injury displayed gray matter damage patterns similar to wild-type animals. The pronounced early damage noted in the IL-10((-/-)) animals was associated with an approximately two-fold increase in peripheral neutrophils, an index of an innate immune response to injury, compared with wild-type mice. In addition, wild type and IL-10((-/-)) animals receiving rmIL-10 demonstrated a delay in the onset of injury-induced pain behaviors. However, by 14 days post-experimental spinal cord injury the overall incidence of pain behaviors was similar between all treatment groups. Therefore, the absence of IL-10 expression accelerates the kinetics of lesion expansion, the onset of pain behaviors, and the peripheral immune response to spinal cord injury. Endogenous IL-10 and low doses of exogenous IL-10 are neuroprotective at 1 and 7 days following injury. Therefore, the results of the current study suggest that low dose IL-10 administration acutely following spinal cord injury has potential as a therapeutic agent for limiting tissue loss following injury.

Interleukin-10 inhibits proinflammatory chemokine release by neutrophils of the newborn without suppression of nuclear factor-kappa B

An increase in polymorphonuclear leukocytes (PMNs) and proinflammatory chemokines, such as IL-8 and macrophage inflammatory protein-1 alpha (MIP), are found in the airways during early stages of bronchopulmonary dysplasia. We determined whether IL-10 produces a dose-related inhibition of proinflammatory chemokine release from stimulated neutrophils of the newborn and whether the mechanism involves the pivotal transcription factor, nuclear factor-kappa B. PMNs isolated from the cord blood of healthy newborns were stimulated submaximally with either lipopolysaccharide (n = 5) or tumor necrosis factor (n = 4), with and without IL-10 (0.01-1000 ng/mL). IL-8 and MIP release were measured in cell culture supernatants at 18 h. The presence or absence of nuclear factor-kappa B activity and inhibitor-kappa B alpha degradation was measured at 30 min and 3 h after PMN stimulation began. During lipopolysaccharide stimulation, IL-10 significantly reduced IL-8 levels from 50 +/- 16 ng/mL to 7 +/- 3 ng/mL, and MIP levels from 14 +/- 5 to 0.7 +/- 0.1 ng/mL (mean +/- SEM, p < 0.01). IL-10 produced an insignificant reduction in IL-8 and MIP levels after stimulation of PMNs with tumor necrosis factor. IL-10 did not inhibit nuclear factor-kappa B activation and inhibitor-kappa B alpha degradation in PMNs stimulated with tumor necrosis factor or lipopolysaccharide for 30 min. After PMN stimulation for 3 h, inhibitor-kappa B alpha cytoplasmic levels were restored; however, they were unaffected by IL-10. We conclude that IL-10 is a potent inhibitor of lipopolysaccharide-stimulated release of IL-8 and MIP from neutrophils of the newborn via a mechanism not involving nuclear factor-kappa B activity. Further work is needed to determine whether exogenous IL-10 may be useful for suppressing inflammation in bronchopulmonary dysplasia.

Bactericidal activity response of blood neutrophils from critically ill patients to in vitro granulocyte colony-stimulating factor stimulation

OBJECTIVE

Neutrophil function impairment is common in nonneutropenic critically ill patients. Whether granulocyte colony-stimulating factor (G-CSF) may be useful for preventing nosocomial infection in these patients is debated. The response of blood neutrophils from critically ill patients to G-CSF was investigated in vitro.

DESIGN AND SETTING

Prospective study, laboratory investigation in two intensive care units.

PATIENTS

52 critically ill patients without immunosuppression.

MEASUREMENTS

Neutrophils obtained from 52 patients on the 5th day of their intensive care unit stay were incubated with and without G-CSF (1, 10, 100 ng/ml). Reactive oxygen species (ROS) release and bactericidal activity against Staphylococcus aureus and Pseudomonas aeruginosa were evaluated. Plasma cytokines (interleukin 10, tumor necrosis factor alpha, and G-CSF) were measured.

RESULTS

Median values (25th-75th percentiles) indicated no stimulatory effect of G-CSF on neutrophil bactericidal activity against either organism: S. aureus, 100% (95-109) of the unstimulated condition with 1 ng/ml G-CSF, and P. aeruginosa, 102% (98-109) with 1 ng/ml G-CSF. However, wide interindividual variability was found, ranging from marked inhibition to marked stimulation. Similar variability was found for ROS release. No correlations were found between ROS release and bactericidal activities against either bacterial strain. Inhibition of neutrophil bactericidal activity by G-CSF was associated with significantly higher plasma interleukin 10 concentrations. Plasma G-CSF levels were significantly higher in patients whose neutrophil bactericidal activity was unresponsive to G-CSF, suggesting G-CSF receptor downregulation.

CONCLUSIONS

The effect of G-CSF on in vitro neutrophil bactericidal activity varied widely, depending on endogenous levels of G-CSF and was not predictable based on severity scores.

Distinct pathways of lipopolysaccharide priming of human neutrophil respiratory burst: role of lipid mediator synthesis and sensitivity to interleukin-10

OBJECTIVE

Exposure of neutrophils to low doses of bacterial lipopolysaccharides enhances their readiness to respond with inflammatory mediator generation including oxygen radical formation to a subsequently applied inflammatory stimulus ("priming"). In the present study, we investigated the role of lipid mediator synthesis and the impact of the anti-inflammatory cytokine interleukin-10 on the lipopolysaccharide-dependent priming of human neutrophils in response to N-formyl-methionyl-leucyl-phenylalanine.

DESIGN

Prospective, experimental study.

SETTING

Research laboratory at a university hospital.

SUBJECTS

Isolated neutrophils from healthy volunteers.

INTERVENTIONS

Incubation of isolated neutrophils with endotoxin.

MEASUREMENTS AND MAIN RESULTS

Evidence for two distinct priming mechanisms was obtained. The first was strictly serum component dependent, proceeded via CD14, and was not inhibited by even high concentrations of interleukin-10. The second priming mechanism was serum component independent but nevertheless proceeded via CD14. It was linked with neutrophil synthesis of the platelet activating factor and resulted in the appearance of leukotrienes, in particular leukotriene B4, as far as exogenous arachidonic acid was provided. The employment of a platelet-activating factor receptor antagonist (WEB 2086) blocked leukotriene synthesis, and both WEB 2086 and a 5-lipoxygenase inhibitor (MK-886) suppressed the respiratory burst linked with this second priming pathway. This sequence of priming events was inhibited by interleukin-10, when this cytokine was coadministered with the priming agent lipopolysaccharide, whereas late interleukin-10 admixture was ineffective.

CONCLUSIONS

We conclude that two mechanisms of lipopolysaccharide priming of human neutrophil respiratory burst can be differentiated. One displays serum component dependence, is independent of neutrophil lipid mediator generation, and is not affected by interleukin-10. The other is serum independent although being operated via CD14, employs autocrine loops of platelet-activating factor and leukotriene B4 synthesis, and is sensitive to the inhibitory capacity of interleukin-10. These features may be relevant when the goal is to pharmacologically modify neutrophil functions in septic events.

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

In this study, we report that the release of IL-1 receptor antagonist (IL-1ra) from IL-4-stimulated neutrophils is markedly enhanced in the presence of IL-10. We also show that up-regulation of IL-1ra release by IL-10 in IL-4-stimulated neutrophils takes place through IL-1ra mRNA stabilization and enhancement of IL-1ra de novo synthesis. Furthermore, we report that the ability of IL-10 to up-regulate IL-1ra mRNA expression in IL-4-treated neutrophils requires 5-6 h and it is preceded by the acquisition of the capacity to activate Stat3 tyrosine phosphorylation. This latter response to IL-10 was strictly dependent on the levels of expression of IL-10R1, which were in fact significantly increased by IL-4 in cultured neutrophils via a signaling pathway sensitive to the serine/threonine kinase inhibitor H-7. Collectively, our data emphasize the central role of IL-10R1 expression in regulating cell responsiveness to IL-10. In addition, the fact that IL-10 strongly up-regulates IL-1ra production in IL-4-activated neutrophils uncovers a novel mechanism whereby IL-10 and IL-4 cooperate to negatively modulate the inflammatory responses.

Involvement of suppressor of cytokine signaling-3 as a mediator of the inhibitory effects of IL-10 on lipopolysaccharide-induced macrophage activation

Previous studies have shown that IL-10 can induce the expression of the suppressor of cytokine signaling 3 (SOCS-3) mRNA in human monocytes and neutrophils, suggesting that the capacity of IL-10 to inhibit the expression of LPS-inducible proinflammatory genes may depend on SOCS-3 induction. However, no direct experimental evidence has been provided to support such hypothesis. Herein, we show that stable transfection of SOCS-3 into the mouse macrophage cell line J774 resulted in an inhibition of NO, TNF-alpha, IL-6, and GM-CSF secretion in response to LPS at levels similar to those exerted by IL-10 in LPS-stimulated wild-type J774. Constitutive SOCS-3 expression also down-regulated the mRNA expression of inducible NO synthase and IL-6 and impaired the production of TNF-alpha, mainly at a post-transcriptional level. In addition, SOCS-3-transfected cells displayed a constitutive expression of the IL-1R antagonist gene, consistent with the observation that IL-10 enhances IL-1R antagonist mRNA in LPS-stimulated wild-type cells. Furthermore, in peritoneal macrophages harvested from mice carrying heterozygous disruption of the SOCS-3 gene, IL-10 was less effective in repressing LPS-stimulated TNF-alpha and NO production. Taken together, our data show that SOCS-3 inhibits LPS-induced macrophage activation, strongly supporting the idea that it plays a role in the molecular mechanism by which IL-10 down-modulates the effector functions of LPS-activated macrophages. Finally, we show that forced expression of SOCS-3 significantly suppresses the ability of IL-10 to trigger tyrosine phosphorylation of STAT3. Therefore, SOCS-3 functions both as an LPS signal inhibitor and as a negative feedback regulator of IL-10/STAT3 signaling.

Regulatory role of interleukin-10 in experimental group B streptococcal arthritis

Intravenous inoculation of CD-1 mice with 10(7) CFU of type IV group B Streptococcus (GBS) results in a high incidence of diffuse septic arthritis, associated with high levels of systemic and local production of interleukin-1beta (IL-1beta) and IL-6. In this study, the role of the anti-inflammatory cytokine IL-10 in the evolution of GBS systemic infection and arthritis was evaluated. IL-10 production was evident in sera and joints of GBS-infected mice. Neutralization of endogenous IL-10 by administration of anti-IL-10 antibodies (1 mg/mouse) at the time of infection resulted in worsening of articular lesions and 60% mortality associated with early sustained production of IL-6, IL-1beta, and tumor necrosis factor alpha (TNF-alpha). The effect of IL-10 supplementation was assessed by administering IL-10 (100, 200, or 400 ng/mouse) once a day for 5 days, starting 1 h after infection. Treatment with IL-10 had a beneficial effect on GBS arthritis, and there was a clear-cut dose dependence. The decrease in pathology was associated with a significant reduction in IL-6, IL-1beta, and TNF-alpha production. Histological findings showed limited periarticular inflammation and a few-cell influx in the articular cavity of IL-10-treated mice, confirming clinical observations. In conclusion, this study provides further information concerning the role of IL-10 in regulating the immune response and inflammation and calls attention to the potential therapeutic use of IL-10 in GBS arthritis.

Activated host neutrophils in the larval midgut lumen of the human bot fly Dermatobia hominis

Light microscopy (LM) and transmission electron microscopy (TEM) were used to observe activated polymorphonuclear neutrophils from mammalian hosts as well as invading bacteria in the midgut lumen of larvae of the human bot fly Dermatobia hominis. Other resident or recruited cells associated with dermal myiasis were fed on by larvae and digested more rapidly than neutrophils. The latter were observed moving towards bacteria and particles of food, extending the filopodia and engulfing material to be digested within phagosomes. The larval midgut lumen, thus, appears to be a suitable environment to produce neutrophil activation at least for short periods, as seen in mammalian hosts. Although interactions between phagocytes and bacteria in the midgut lumen may be important in bot fly larval development, further studies are required to confirm this.