IL-10 inhibits prostaglandin E2 production by lipopolysaccharide-stimulated monocytes

Adeno-Associated Virus-Mediated Overexpression of Interleukin-10 Affects the Immunomodulatory Properties of Equine Bone Marrow-Derived Mesenchymal Stem Cells

Joint injury can cause posttraumatic inflammation, which if severe enough can lead to posttraumatic osteoarthritis (PTOA), a progressive and debilitating condition. Posttraumatic inflammation is characterized by an influx of T lymphocytes and upregulation of inflammatory cytokines and degradative enzymes by activated chondrocytes and synoviocytes. Intra-articular bone marrow-derived mesenchymal stem cell (BM-MSC) injection for the treatment of osteoarthritis (OA) has been of interest due to the immunomodulatory properties of these cells. Interleukin (IL)-10, a potent immunomodulatory cytokine, has also been investigated as an OA therapeutic. Therefore, the objective of this study was to evaluate the combinatorial effects of BM-MSCs and IL-10 in OA using a gene therapy approach. We hypothesized that BM-MSCs overexpressing IL-10 would have superior immunomodulatory effects leading to increased suppression of T cell proliferation and decreased production of proinflammatory cytokines, providing protection of the extracellular matrix (ECM) in a stimulated, co-culture OA model. Treatment groups included the following: untransduced BM-MSC, adeno-associated virus (AAV)-IL10-transduced BM-MSC, and AAV-null transduced BM-MSC, which were unstimulated or stimulated with IL-1β/tumor necrosis factor-α (TNF-α). T cell proliferation was significantly decreased by the presence of BM-MSCs, especially when these BM-MSCs were AAV transduced. There was no significant difference in T cell suppression when cells were cultured with AAV-IL10-transduced or AAV-null transduced BM-MSCs. AAV transduction itself was associated with decreased synthesis of IL-1β, IL-6, and TNF-α. Expression of IL-1β and MMP13 was downregulated in AAV-transduced BM-MSCs and MMP13 expression was downregulated in cartilage explants co-cultured with AAV-transduced BM-MSCs. Despite mitigation of some proinflammatory cascades, rescue of ECM loss, as determined by glycosaminoglycan quantification and histological evaluation, did not occur in either AAV-IL10-transduced or AAV-null transduced co-cultures. Although IL-10 overexpression may enhance BM-MSC-mediated T cell suppression, we did not observe significant modulation of inflammation-driven cartilage degradation in cultures containing AAV-IL10-transduced BM-MSCs. AAV transduction itself does appear to affect paracrine signaling by BM-MSCs, which warrants further investigation.

Bioinformatics Analysis of Differentially Expressed Genes and Protein-Protein Interaction Networks Associated with Functional Pathways in Ulcerative Colitis

Background

This bioinformatics study aimed to identify differentially expressed genes (DEGs) and protein–protein interaction (PPI) networks associated with functional pathways in ulcerative colitis based on 3 Gene Expression Omnibus (GEO) datasets.

Material/Methods

The GSE87466, GSE75214, and GSE48958 MINiML formatted family files were downloaded from the GEO database. DEGs were identified from the 3 datasets, and volcano maps and heat maps were drawn after R language standardization and analysis, respectively. Venn diagram software was used to identify common DEGs. PPI analysis of common DEGs was performed using the Search Tool for the Retrieval of Interacting Genes. Gene modules and hub genes were visualized in the PPI network using Cytoscape. Enrichment analysis was performed for all common DEGs, module genes, and hub genes.

Results

A total of 90 DEGs were selected, which included 3 functional modules and 1 hub gene module. CXCL8 module genes were mainly enriched in cytokine-mediated signaling pathways and interleukin (IL)-10 signaling. CCL20 module genes were mainly enriched in the IL-17 signaling pathway and cellular response to IL-1. Hub gene modules mainly involved IL-10, IL-4, and IL-13 signaling pathways. CXCL8, CXCL1, and IL-1β were the top 3 hub genes and were mainly involved in IL-10 signaling.

Conclusions

Bioinformatics analysis using 3 GEO datasets identified CXCL8, CXCL1, and IL-1β, which are involved in IL-10 signaling, as the top 3 hub genes in ulcerative colitis. The findings from this study remain to be validated, but they may contribute to the further understanding of the pathogenesis of ulcerative colitis.

Loss of IL-10 signaling in macrophages limits bacterial killing driven by prostaglandin E2

Cytokines and lipid mediators are key regulators of inflammation; but how they are mechanistically linked is poorly understood. Here, Mukhopadhyay et al. show a novel regulation between cytokine IL-10 and lipid mediator PGE2 that functionally connects them to intestinal inflammation.

Loss of IL-10 signaling in macrophages (Mφs) leads to inflammatory bowel disease (IBD). Induced pluripotent stem cells (iPSCs) were generated from an infantile-onset IBD patient lacking a functional IL10RB gene. Mφs differentiated from IL-10RB^−/− iPSCs lacked IL-10RB mRNA expression, were unable to phosphorylate STAT3, and failed to reduce LPS induced inflammatory cytokines in the presence of exogenous IL-10. IL-10RB^−/− Mφs exhibited a striking defect in their ability to kill Salmonella enterica serovar Typhimurium, which was rescuable after experimentally introducing functional copies of the IL10RB gene. Genes involved in synthesis and receptor pathways for eicosanoid prostaglandin E2 (PGE2) were more highly induced in IL-10RB^−/− Mφs, and these Mφs produced higher amounts of PGE2 after LPS stimulation compared with controls. Furthermore, pharmacological inhibition of PGE2 synthesis and PGE2 receptor blockade enhanced bacterial killing in Mφs. These results identify a regulatory interaction between IL-10 and PGE2, dysregulation of which may drive aberrant Mφ activation and impaired host defense contributing to IBD pathogenesis.

The In Vitro and In Vivo Anti-Inflammatory Effects of a Phthalimide PPAR-γ Agonist

Previously, the authors found that 4-hydroxy-2-(4-hydroxyphenethyl) isoindoline-1,3-dione (PD1) (a phthalimide analogue) bound to and activated peroxisome proliferator-activated receptor-γ (PPAR-γ). Since PPAR-γ suppresses inflammatory responses, the present study was undertaken to investigate the anti-inflammatory effects of PD1. In lipopolysaccharide (LPS)-stimulated murine RAW264.7 macrophages, PD1 suppressed the inductions of pro-inflammatory factors, including inducible nitric oxide synthase (iNOS), nitric oxide (NO), cyclooxygenase 2 (COX-2), tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6). Concomitantly, PD1 enhanced the expressions of anti-inflammatory factors, such as arginase-1 and interleukin-10 (IL-10), and suppressed LPS-evoked nuclear factor kappa B (NF-κB) p65 subunit phosphorylation in macrophages. In addition, PPAR-γ activated by PD1 was intensively translocated to the nucleus. These observations suggest that the anti-inflammatory mechanism of PD1 involves inhibition of the NF-κB pathway. In a subsequent in vivo animal experiment conducted using a carrageenan-induced acute inflammatory rat paw edema model, intraperitoneal injection of PD1 significantly reduced paw swelling. Histological analysis of rat paw tissue sections revealed less infiltration of immune cells in PD1-pretreated animals. These findings suggest that PD1 be viewed as a lead compound for the development of novel anti-inflammatory therapeutics.

Potentiation of indomethacin-induced anti-inflammatory response by pioglitazone in carrageenan-induced acute inflammation in rats: Role of PPARγ receptors

This study aimed to assess the interaction between anti-inflammatory effects of pioglitazone (peroxysome proliferator activated receptor-gamma (PPARγ) agonist, PGL), and indomethacin (cyclooxygenase (COX) inhibitor, IND) and to evaluate the possible underlying mechanisms. Paw edema induced by carrageenan was used to induce inflammation. Different doses of IND (0.3-10mg/kg) and PGL (1-20mg/kg) alone or in combination were administered intraperitoneally to rats. Paw tissue levels of PPARγ, COX-2, and prostaglandin E2 and serum levels of TNF-α and IL-10 were also estimated. Doses of IND and PGL showed a statistically significant anti-inflammatory effect. Combination of a non-effective dose of IND (0.3mg/kg) with increasing doses of PGL (1-10mg/kg) resulted in potentiated anti-inflammation and vise versa. IND, PGL and the combination were able to reduce the COX-2, PGE2 contents and TNF-α level. Moreover, all these treatments caused elevation in PPARγ levels and IL-10 levels. However, when the rats were pre-treated with GW-9662 (a selective PPARγ antagonist), all the anti-inflammation and alterations in the biochemical factors were antagonized. These results showed that PGL markedly enhanced the anti-inflammatory activity of IND and this effect mediated partly at least, through PPARγ. Possible mechanisms of the interaction were that PGL stimulates the PPARγ and inhibits COX-2 by those cytokines that trigger the PPARγ and also inhibit COX-2. This study suggests that combination therapy with pioglitazone and indomethacin may provide an alternative for the clinical control of inflammation especially in patients with diabetes.

N-Acetyl-l-cysteine exacerbates generation of IL-10 in cells stimulated with endotoxin in vitro and produces antipyresis via IL-10 dependent pathway in vivo

N-Acetyl-l-cysteine (NAC) is a well-known medication, primarily used as a mucolytic agent in pulmonary disease. Recently, we have found that NAC possesses antipyretic properties. The aim of the present study was to investigate the mechanism by which NAC attenuates fever. The concentration of interleukin (IL)-10 and prostaglandin (PG) E2 were measured using ELISA kit in the supernatants aspirated after stimulation of peripheral blood mononuclear cells (PBMCs) with lipopolysaccharide (LPS, 1μg/mL) and NAC (10mM). The body temperature of the Wistar rats was measured using biotelemetry system. To inhibit endotoxic fever, NAC (200mg/kg; i.p.) was injected into the rats one hour prior to the LPS administration (50μg/kg; i.p.). The pre-treatment of LPS-stimulated PBMCs with NAC resulted in a significant decrease in PGE2 concentration in comparison to the cells treated with LPS alone (PGE2 level was 386.1±61.9pg/mL vs. 2078.9±157.9pg/mL, respectively, p<0.001). Furthermore, in these cells we observed a significant increase in IL-10 level (142.1±2.62pg/mL in NAC+LPS stimulated cells vs. 54.4±0.6pg/mL in LPS stimulated cells, p<0.001). The injection of anti-IL-10 antibody into the rats abolished antipyretic properties of NAC. Body temperature in animals treated with anti-IL-10+NAC/LPS was 38.28±0.12°C vs. 37.73±0.06°C in IgG+NAC/LPS rats (p<0.001) and 38.31±0.20°C in NaCl/LPS-treated animals (n.s.). Based on these data, we conclude that NAC acts as an antipyretic via IL-10 stimulation. This finding provides a new insight into the immunopharmacology of NAC, and we believe that in a future it will contribute to the new and/or more accurate application of NAC in medicine.

Cyprinid Herpesvirus 3 Il10 Inhibits Inflammatory Activities of Carp Macrophages and Promotes Proliferation of Igm+ B Cells and Memory T Cells in a Manner Similar to Carp Il10

Cyprinid herpesvirus 3 (CyHV-3) is the causative agent of a lethal disease of carp and encodes for an Il10 homolog (ORF134). Our previous studies with a recombinant ORF134-deleted strain and the derived revertant strain suggested that cyprinid herpesvirus 3 Il10 (CyHV-3 Il10 [cyhv3Il10]) is not essential for viral replication in vitro, or virulence in vivo. In apparent contrast, cyhv3Il10 is one of the most abundant proteins of the CyHV-3 secretome and is structurally very similar to carp Il10 and also human IL10. To date, studies addressing the biological activity of cyhv3Il10 on cells of its natural host have not been performed. To address the apparent contradiction between the presence of a structurally conserved Il10 homolog in the genome of CyHV-3 and the lack of a clear phenotype in vivo using recombinant cyhv3Il10-deleted viruses, we used an in vitro approach to investigate in detail whether cyhv3Il10 exerts any biological activity on carp cells. In this study, we provide direct evidence that cyhv3Il10 is biologically active and, similarly to carp Il10, signals via a conserved Stat3 pathway modulating immune cells of its natural host, carp. In vitro, cyhv3Il10 deactivates phagocytes with a prominent effect on macrophages, while also promoting proliferation of Igm(+) B cells and memory T cells. Collectively, this study demonstrates a clear biological activity of cyhv3Il10 on cells of its natural host and indicates that cyhv3Il10 is a true viral ortholog of carp Il10. Furthermore, to our knowledge, this is the first report on biological activities of a nonmammalian viral Il10 homolog.

Peritoneal exudate cells from long-lived rats exhibit increased IL-10/IL-1β expression ratio and preserved NO/urea ratio following LPS-stimulation in vitro

In humans, usual aging, differently from successful aging, is associated with deregulation of proinflammatory/anti-inflammatory cytokine balance. The corresponding data from rat studies are limited. Therefore, we examined (i) cytokine messenger RNA (mRNA) profile of fresh peritoneal cells from 6- (adult), 24- (old), and 31-month-old (long-lived) AO rats and (ii) proinflammatory (IL-1β and IL-6) and anti-inflammatory (IL-10) cytokine, NO, and urea production in their LPS-stimulated cultures. Comparing with adult rats, cells from old ones expressed lower amount of TNF-α and IL-6 mRNAs, but greater amount of IL-1β mRNA. On the other hand, cells from long-lived rats exhibited a dramatic increase in IL-10 mRNA expression followed by diminished TNF-α and IL-6 mRNA expression, and comparable expression of IL-1β mRNA relative to adult rats. Consequently, IL-10/IL-1β mRNA ratio was greater in cells from long-lived rats than in adult and old rats. In LPS-stimulated peritoneal cell cultures (contained ≥95 % macrophages) from old rats, concentration of common proinflammatory cytokines was higher than in those from adult rats. Comparing with adult and old rats, in LPS-stimulated macrophage cultures from long-lived rats, TNF-α and IL-6 concentrations were lower; IL-1β concentration was comparable or greater (in respect to adult rats), whereas that of IL-10 was strikingly higher. Consistently, in macrophage cultures from long-lived rats, NO (iNOS activity marker)/urea (arginase activity marker) ratio was less and not different from that in old and adult rats, respectively. The study suggests that macrophages from long-lived rats, differently from those of old ones, have substantial ability to limit proinflammatory mediator production, which may contribute to their longevity.

IL-10 encoded by viruses: a remarkable example of independent acquisition of a cellular gene by viruses and its subsequent evolution in the viral genome

Many viruses have evolved strategies to deregulate the host immune system. These strategies include mechanisms to subvert or recruit the host cytokine network. IL-10 is a pleiotropic cytokine that has both immunostimulatory and immunosuppressive properties. However, its key features relate mainly to its capacity to exert potent immunosuppressive effects. Several viruses have been shown to upregulate the expression of cellular IL-10 (cIL-10) with, in some cases, enhancement of infection by suppression of immune functions. Other viruses encode functional orthologues of cIL-10, called viral IL-10s (vIL-10s). The present review is devoted to these virokines. To date, vIL-10 orthologues have been reported for 12 members of the family Herpesviridae, two members of the family Alloherpesviridae and seven members of the family Poxviridae. Study of vIL-10s demonstrated several interesting aspects on the origin and the evolution of these viral genes, e.g. the existence of multiple (potentially up to nine) independent gene acquisition events at different times during evolution, viral gene acquisition resulting from recombination with cellular genomic DNA or cDNA derived from cellular mRNA and the evolution of cellular sequence in the viral genome to restrict the biological activities of the viral orthologues to those beneficial for the virus life cycle. Here, various aspects of the vIL-10s described to date are reviewed, including their genetic organization, protein structure, origin, evolution, biological properties and potential in applied research.

Anti-inflammatory effects of carvacrol: evidence for a key role of interleukin-10

Carvacrol, a phenolic monoterpene, has been reported to possess anti-inflammatory properties. However, the mechanisms involved in its pharmacological properties are currently not well understood. In the present study, the contribution of cytokine modulation to the anti-inflammatory effects of carvacrol was investigated in a classical inflammation model: the complete Freund's adjuvant (CFA)-induced paw inflammation in mice. The paw edema was measured using a plesthismometer. Paw tissue was removed 2h after the inflammatory stimulus to determine the levels of prostaglandin E(2) (PGE(2)) by enzyme immunoassay, the levels of interleukin-1 β (IL-1β), tumor necrosis factor-α (TNF-α), and interleukin-10 (IL-10) by ELISA or the mRNA expression of cyclooxygenase-2 (COX-2), IL-1β, TNF-α, and IL-10 by real-time PCR. Administration of carvacrol produced anti-inflammatory effects against CFA-induced inflammation in mice. Treatment of mice with carvacrol at 50 and 100mg/kg attenuated the paw edema and reduced the IL-1β and PGE(2), but not TNF-α, local levels. Similarly, carvacrol (100mg/kg) reduced the COX-2 and IL-1β mRNA expression. The levels of IL-10, an anti-inflammatory cytokine, and the IL-10 mRNA expression in the inflamed paw were enhanced by carvacrol. In addition, the treatment with carvacrol did not reduce the CFA-induced paw edema in IL-10 knockout mice. The present results suggest that carvacrol causes anti-inflammatory effects by reducing the production of inflammatory mediators, such as IL-1β and prostanoids, possibly through the induction of IL-10 release.

Different potency of bacterial antigens TLR2 and TLR4 ligands in stimulating mature mast cells to cysteinyl leukotriene synthesis

The aim of study was to compare the potency of different bacterial antigens to induce rat mature mast cell to cysteinyl leukotriene (cysLT) generation. We examined Toll-like receptor (TLR)2 agonists, i.e. lipoteichoic acid (LTA) Staphylococcus faecalis, Streptococcus pyogenes, Bacillus subtilis and Staphylococcus aureus, lipoarabinomannan (LAM) Mycobacterium smegmatis, peptydoglican (PGN) Staphylococcus aureus, as well as TLR4 agonists, i.e. lipopolysaccharide (LPS) Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella enteritidis, Pophyromonas gingivalis and Escherichia coli. We also estimated the effect of tumor necrosis factor (TNF)-, interleukin (IL)-6-, CCL5-, and IL-10-priming on mast cell cysLT synthesis following bacterial antigen activation. We found that all bacterial antigens activated mast cells to cysLT generation; however, the extent of cysLT release in response to stimulation varied. Out of the examined antigens LPS P. gingivalis exhibited the highest potency, as it induced cysLT generation acting at a very low concentration (10(-4) ng/mL). Other LPSs affected mast cells at higher (up to 10(5) -fold) concentrations. LTAs were the most effective at concentrations of 5 × 10(2) ng/mL, while LAM and PGN stimulated mast cells to maximal cysLT generation at concentrations as high as 10(5) ng/mL. Anti-TLR2 and anti-TLR4 antibodies, as well as nuclear factor κB (NF-κB) inhibitor significantly diminished cysLT generation in response to bacterial antigen stimulation. Priming with TNF, IL-6 and CCL5 did not affect bacterial antigen-induced cysLT generation, while IL-10-pretreatment caused significant decrease in cysLT synthesis by mast cells. These observations might have a great pathophysiological importance; inasmuch cysLTs strongly influence the development and intensity of inflammation during bacterial infection.

IL-10 administration reduces PGE-2 levels and promotes CR3-mediated clearance of Escherichia coli K1 by phagocytes in meningitis

Ineffectiveness of antibiotics in treating neonatal Escherichia coli K1 meningitis and the emergence of antibiotic-resistant strains evidently warrants new prevention strategies. We observed that administration of interleukin (IL)-10 during high-grade bacteremia clears antibiotic-sensitive and -resistant E. coli from blood of infected mice. Micro-CT studies of brains from infected animals displayed gross morphological changes similar to those observed in infected human neonates. In mice, IL-10, but not antibiotic or anti-TNF antibody treatment prevented brain damage caused by E. coli. IL-10 administration elevated CR3 expression in neutrophils and macrophages of infected mice, whereas infected and untreated mice displayed increased expression of FcγRI and TLR2. Neutrophils or macrophages pretreated with IL-10 ex vivo exhibited a significantly greater microbicidal activity against E. coli compared with cells isolated from wild-type or IL-10^−/− mice. The protective effect of IL-10 was abrogated when CR3 was knocked-down in vivo by siRNA. The increased expression of CR3 in phagocytes was caused by inhibition of prostaglandin E-2 (PGE-2) levels, which were significantly increased in neutrophils and macrophages upon E. coli infection. These findings describe a novel modality of IL-10–mediated E. coli clearance by diverting the entry of bacteria via CR3 and preventing PGE-2 formation in neonatal meningitis.

Modulation of dendritic cell differentiation and cytokine secretion by the hydatid cyst fluid of Echinococcus granulosus

Chronic infection by Echinococcus granulosus results in establishment of fluid-filled cysts (hydatid cysts) in liver or lungs of infected hosts, which can escape destruction by the host immune system for long periods. This study explores the modulation by hydatid cyst fluid of the in vitro human monocyte to dendritic cell (DC) transition induced by granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). Addition of the fluid to adherent peripheral blood monocytes cultured in GM-CSF/IL-4 stimulates release of prostaglandin E2 (PGE2) and IL-6. Exposure of differentiating DC to the fluid during the 7-day culture in GM-CSF/IL-4 impairs their subsequent ability to secrete IL-12, IL-6 or PGE2 in response to lipopolysaccharide (LPS) stimulation. This inhibition is not dependent on the initial release of PGE2. The presence of hydatid cyst fluid also modulates the phenotype of the cells generated during culture, resulting in increased CD14 expression and decreased expression of CD1a. Finally, hydatid fluid can stimulate predifferentiated DC to mature, as evidenced by release of IL-12 and IL-6, and by up-regulation of class II major histocompatibility complex and CD86. The possible role of dendritic cell modulation in regulating the host immune response to hydatid cysts is discussed.

Inhibition of inflammatory responses by FC-77, a perfluorochemical, in lipopolysaccharide-treated RAW 264.7 macrophages

OBJECTIVE

This study tested whether FC-77, a perfluorochemical, inhibits inflammatory responses in lipopolysaccharide (LPS) stimulated RAW 264.7 macrophages. The possible anti-inflammatory mechanisms involved were also investigated.

METHODS

RAW 264.7 macrophages were simultaneously incubated with pure FC-77 at final volume of 10% or 30% (v/v) and LPS (1 microg/ml) for 12 or 24 h on a mechanical shaker. In some tests FC-77 was added after cells stimulated by LPS for 12 h. Then the levels of prostaglandin E2(PGE2), tumor necrosis factor alpha (TNF-alpha), and interleukins (IL)-1beta, -6), and -10 were measured in medium. Alterations in cyclooxygenase (COX) 2 expression and nuclear transcription factor (NF) kappaB activation in cells were also evaluated.

RESULTS

Pre- or posttreatment with FC-77 dose-dependently reduced the LPS-induced TNF-alpha, IL-1beta, and IL-6 formation and enhanced IL-10 production compared to LPS-stimulated alone cells. FC-77 also attenuated the LPS-induced PGE2 formation accompanied by suppressing COX-2 expression, the degradation of cytosolic inhibitor of kappaB-alpha and NF-kappaB activation.

CONCLUSIONS

FC-77 inhibits inflammatory responses in LPS-stimulated macrophages by a mechanism that involves the attenuation of NF-kappaB dependent induction of COX-2/PGE2 pathway and the pro- /anti-inflammatory cytokine ratio.

Circulating levels of cyclooxygenase metabolites in experimental Trypanosoma cruzi infections

Trypanosoma cruzi induces inflammatory reactions in several tissues. The production of prostaglandin F2alpha, 6-keto-prostaglandin F1alpha and thromboxane B2, known to regulate the immune response and to participate in inflammatory reactions, was studied in mice experimentally infected with T. cruzi. The generation of nitric oxide (NO), which could be regulated by cyclooxygenase metabolites, was also evaluated. In the acute infection the extension of inflammatory infiltrates in skeletal muscle as well as the circulating levels of cyclooxygenase metabolites and NO were higher in resistant C3H mice than in susceptible BALB/c mice. In addition, the spontaneous release of NO by spleen cells increased earlier in the C3H mouse strain. In the chronic infections, the tissue inflammatory reaction was still prominent in both groups of mice, but a moderate increase of thromboxane B2 concentration and in NO released by spleen cells was observed only in C3H mice. This comparative study shows that these mediators could be mainly related to protective mechanisms in the acute phase, but seem not to be involved in its maintenance in the chronic T. cruzi infections.

Novel regulatory mechanisms of CD40-induced prostanoid synthesis by IL-4 and IL-10 in human monocytes

Interleukins IL-4 and IL-10 are considered to be central regulators for the limitation and eventual termination of inflammatory responses in vivo, based on their potent anti-inflammatory effects toward LPS-stimulated monocytes/macrophages and neutrophils. However, their role in T cell-dependent inflammatory responses has not been fully elucidated. In this study, we investigated the effects of both cytokines on the production of PGE(2), a key molecule of various inflammatory conditions, in CD40-stimulated human peripheral blood monocytes. CD40 ligation of monocytes induced the synthesis of a significant amount of PGE(2) via inducible expression of the cyclooxygenase (COX)-2 gene. Both IL-10 and IL-4 significantly inhibited PGE(2) production and COX-2 expression in CD40-stimulated monocytes. Using specific inhibitors for extracellular signal-related kinase (ERK) and p38 mitogen-activated protein kinase (MAPK), we found that both kinase pathways are involved in CD40-induced COX-2 expression. CD40 ligation also resulted in the activation of NF-kappaB. Additional experiments exhibited that CD40 clearly induced the activation of the upstream kinases MAPK/ERK kinase 1/2, MAPK kinase 3/6, and I-kappaB in monocytes. IL-10 significantly inhibited CD40-induced activation of the ERK, p38 MAPK, and NF-kappaB pathways; however, inhibition by IL-4 was limited to the ERK pathway in monocytes. Neither IL-10 nor IL-4 affected the recruitment of TNFR-associated factors 2 and 3 to CD40 in monocytes. Collectively, IL-10 and IL-4 use novel regulatory mechanisms for CD40-induced prostanoid synthesis in monocytes, thus suggesting a potential role for these cytokines in regulating T cell-induced inflammatory responses, including autoimmune diseases.

Characterisation, expression and promoter analysis of an interleukin 10 homologue in the puffer fish, Fugu rubripes

Using computer-based tools, an interleukin (IL) 10 homologue has been identified from the puffer fish ( Fugu rubripes) genome database. This is the first report on the existence of an IL-10 homologue in a non-mammalian vertebrate species. The Fugu IL-10 gene is located within a 2790-bp fragment including 549 bp of coding sequence which translates into an 183-amino-acid protein. It is predicted to contain five exons and four introns, sharing the same organization with the mammalian IL-10 genes. The size of the introns in the Fugu IL-10 gene is much smaller compared to mammalian IL-10 genes, whilst the size of the exons is similar. The deduced protein sequence shares 44-50% homology with the mammalian IL-10 sequences, 39-42% with the viral IL-10 sequences and 37-42% with other members of the IL-10 family, IL-20 and IL-22. Southern blot analysis indicates that a single copy of the IL-10 gene is present in the Fugu genome. A very low level of constitutive expression was detected in tissues of healthy fish including liver, kidney, gut and spinal cord, whilst no expression was detectable in spleen, gill, brain, gonad and eye. Analysis of the transcription regulation elements in the promoter region revealed that trans elements are located in the region between 1 bp and 721 bp, cis elements between 934 bp and 1114 bp and a tumour necrosis factor alpha responsive transcription element was located 92 bp upstream of the TATA box.

Interleukin-10 expression after intramuscular DNA electrotransfer: kinetic studies

Transfected muscle can be used as a secreting tissue for therapeutic proteins. Skeletal muscle transfection is increased by suitable electric pulse application (electrotransfer). We and others had shown that electrotransfer of interleukin-10 encoding plasmid is an effective strategy in animal models of chronic diseases such as myocarditis, atherosclerosis, or rheumatoid arthritis. In the present work, we have studied murine interleukin-10 production and secretion after i.m. electrotransfer. In immunocompetent mice, serum and muscle mIL-10 levels were enhanced by electrotransfer. Serum mIL-10 concentration reached rapidly a peak level 2 days after electrotransfer. It then decreased to background at day 14. Muscle mIL-10 mRNA and protein remained more stable, being detectable up to 84 days after electrotransfer. A boost reinjection led to similar high level of circulating mIL-10. The fast decrease of serum mIL-10 was not observed in SCID mice.

The modulatory effects of prostaglandin-E on cytokine production by human peripheral blood mononuclear cells are independent of the prostaglandin subtype

The production of inflammatory mediators, relevant to (auto)immune diseases and chronic inflammatory conditions, can be modulated by dietary intake of n-3 and n-6 long chain polyunsaturated fatty acids (PUFAs). It was suggested that these effects are related to the formation of different series of eicosanoids, in particular prostaglandin-E (PGE). In this study we investigated whether prostaglandin subtypes metabolized from arachidonic acid (PGE2), dihomo-gamma-linolenic acid (PGE1) or eicosapentaenoic acid (PGE3) have different effects on T-cell proliferation and cytokine production in vitro. Freshly isolated human peripheral blood mononuclear cells (PBMC) were stimulated with concanavalin A (ConA) or lipopolysaccharide (LPS) in the presence or absence of exogenous PGE1, PGE2 or PGE3. We found that tumour necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma) and to a lesser extent interleukin (IL)-10 production was inhibited by all PGE-subtypes in ConA-stimulated PBMC concomitant with unaffected IL-2 levels. The modulated cytokine production of ConA stimulated cells was independent of T-cell proliferation. PGE2 and PGE1 moderately stimulated proliferation, while PGE3 inhibited the proliferative response to some extent. In LPS-stimulated PBMC, TNF-alpha production was inhibited by all PGE-subtypes, whereas IL-6 remained unaffected and IL-10 production was increased. Time course experiments on the effects of PGE-subtypes on cytokine production after ConA or LPS stimulation showed these effects to be time dependent, but indifferent of the prostaglandin subtype added. Overall, the modulatory effects of PGE on cytokine production were irrespective of the subtype. This may implicate that the immunomodulatory effects of PUFAs, with respect to cytokine production, are not caused by a shift in the subtype of PGE.

Type I interferons inhibit interleukin-10 production in activated human monocytes and stimulate IL-10 in T cells: implications for Th1-mediated diseases

Type I interferons (IFNs) directly induce development of Th1 cells. However, IFN-alpha and IFN-beta should generate Th2 cells because these IFNs induce interleukin-10 (IL-10) and block secretion of IFN-gamma. We hypothesized that paradoxical effects of IFNs on Th1-mediated immunity could be from monocyte-specific and T cell-specific IL-10 regulation. We demonstrate that IFN-alpha and IFN-beta inhibit IL-10 mRNA and protein production by activated monocytes but stimulate IL-10 production by activated T cells from the same healthy donors. Without IFN-beta, Staphylococcus aureus, Cowan strain I (SAC)-activated monocytes secreted 15-fold more IL-10 than phorbol myristate acetate (PMA) anti-CD3-activated T cells. With IFN-beta, the two subsets had nearly equivalent secretion. Prostaglandin (PGE) and other cAMP agonists had subset-specific effects on IL-10 production opposite to IFN-beta. The differential IFN-beta effect on transcriptional regulation of IL-10 in monocytes and T cells was from lineage-specific modification of RNA stability. IFN-beta decreased the half-life of IL-10 mRNA in activated monocytes but prolonged the half-life in activated T cells. Subset-specific IL-10 regulation has important implications for Th1-mediated disease. When activated macrophages and microglia are in excess, as in rheumatoid joints or possibly in chronic multiple sclerosis brain lesions, IFNs may inhibit overall IL-10 production and worsen disease. When T cells outnumber monocytes, IFN-beta will induce IL-10 and ameliorate Th1-mediated disease.

Immune mechanisms in atherosclerosis

Atherosclerosis is an inflammatory disease. Its lesions are filled with immune cells that can orchestrate and effect inflammatory responses. In fact, the first lesions of atherosclerosis consist of macrophages and T cells. Unstable plaques are particularly rich in activated immune cells, suggesting that they may initiate plaque activation. We have seen a rapid increase in the understanding of the mechanisms that govern the recruitment, differentiation, and activation of immune cells in atherosclerosis. Experimental research has identified several candidate antigens, and there are encouraging data suggesting that immune modulation as well as immunization can reduce the progression of the disease. This review provides an overview of our current understanding of the role of immune mechanisms in atherosclerosis.

Interleukin-10 and the interleukin-10 receptor

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

Transforming growth factor-beta suppresses macrophage-induced mesangial cell fibronectin expression

BACKGROUND

We have previously shown that macrophages are able to promote prosclerotic responses in rat mesangial cells. Th2-type cytokines, including interleukin-10 (IL-10), IL-13, and IL-4 as well as transforming growth factor-beta (TGF-beta), are known to have suppressive effects on various aspects of macrophage function. In the current study, we investigated the effect of TGF-beta pretreatment on the ability of macrophages to induce fibronectin expression.

RESULTS

Conditioned medium from TGF-beta pretreated macrophages (MPCM(TGF)) induced lower fibronectin levels in mesangial cells in both the secreted and cell-associated forms, compared with conditioned medium from standard macrophages (MPCM) (5.5 +/- 0.2 vs. 3.4 +/- 0.3 and 4.05 +/- 0.45 vs. 2.3 +/- 0.2-fold increase over medium alone for MPCM versus MPCM(TGF) in supernatants and cell lysates, respectively). Northern blot analysis demonstrated that fibronectin message was marginally reduced to 0.88 +/- 0.04 (P < 0.03 vs. MPCM, N = 3) of MPCM-induced levels. However, mesangial cell transin mRNA levels induced in response to MPCM(TGF) were 2.29 +/- 0.47-fold greater than those induced by standard MPCM (P = 0.03 vs. MPCM, N = 4). TIMP-1 mRNA levels were also increased in response to MPCM(TGF), but only by 1.43 +/- 0.1-fold (P = 0.02 vs. MPCM, N = 5). Casein-FITC digestion studies confirmed that MPCM(TGF) stimulated more mesangial cell caseinolytic activity than did MPCM. In addition, MPCM-mediated up-regulation of mesangial cell TGF-beta mRNA and protein expression was significantly reduced in response to conditioned medium from macrophages pretreated with TGF-beta.

CONCLUSION

This study suggests that TGF-beta is able to regulate negatively the profibrotic effects of macrophages on mesangial cells by both enhancing matrix degradation and reducing synthesis.

Differential Effects of Apoptotic Versus Lysed Cells on Macrophage Production of Cytokines: Role of Proteases

Granulocytes undergoing apoptosis are recognized and removed by phagocytes before their lysis. The release of their formidable arsenal of proteases and other toxic intracellular contents into tissues can create significant damage, prolonging the inflammatory response. Binding and/or uptake of apoptotic cells by macrophages inhibits release of proinflammatory cytokines by mechanisms that involve anti-inflammatory mediators, including TGF-beta. To model the direct effects of necrotic cells on macrophage cytokine production, we added lysed or apoptotic neutrophils and lymphocytes to mouse and human macrophages in the absence of serum to avoid complement activation. The results confirmed the ability of lysed neutrophils, but not lymphocytes, to significantly stimulate production of macrophage-inflammatory protein 2 or IL-8, TNF-alpha, and IL-10. Concomitantly, induction of TGF-beta1 by lysed neutrophils was significantly lower than that observed for apoptotic cells. The addition of selected serine protease inhibitors and anti-human elastase Ab markedly reduced the proinflammatory effects, the lysed neutrophils then behaving as an anti-inflammatory stimulus similar to intact apoptotic cells. Separation of lysed neutrophils into membrane and soluble fractions showed that the neutrophil membranes behaved like apoptotic cells. Thus, the cytokine response seen when macrophages were exposed to lysed neutrophils was largely due to liberated proteases. Therefore, we suggest that anti-inflammatory signals can be given by PtdSer-containing cell membranes, whether from early apoptotic, late apoptotic, or lysed cells, but can be overcome by proteases liberated during lysis. Therefore, the outcome of an inflammatory reaction and the potential immunogenicity of Ags within the damaged cell will be determined by which signals predominate.

Interleukin-10 and the Interleukin-10 Receptor

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

Plasma levels of interleukin-6 and interleukin-10 are affected by ketorolac as an adjunct to patient-controlled morphine after abdominal hysterectomy

OBJECTIVE

Because morphine affects various immune functions, patient-controlled analgesia with morphine may further deteriorate the immune mechanisms after surgery. Therefore, the purpose of this study was to determine differences between morphine patient-controlled analgesia and a combination of morphine and ketorolac in interleukin-6 and interleukin-10 responses, and in analgesia and morphine-related side effects.

DESIGN

Prospective study.

PATIENTS

Twenty-two patients who underwent abdominal hysterectomy were classified randomly into two groups: (1) patient-controlled analgesia with morphine; and (2) patient-controlled analgesia with a combination of morphine and ketorolac. Blood samples to measure cytokines were collected at preoperatively, immediately postoperatively, and 2 hours, 4 hours, and 24 hours postoperatively.

OUTCOME MEASURES

Plasma was separated and frozen until the analysis of cytokines using enzyme-linked immunosorbent assays. Postoperative pain was assessed using a visual analog score. Sedation was checked based on a protocol developed at the Samsung Medical Center.

RESULTS

In the two groups, interleukin-6 increased immediately postoperatively, and it remained consistent for 24 hours. Interleukin-10 concentrations peaked at 2 hours postoperatively and progressively decreased. Cytokine concentrations between the two groups were significantly different for interleukin-6 24 hours postoperatively (p = 0.026) and for interleukin-10 4 hours postoperatively (p = 0.045). Total analgesic use was not different, but morphine consumption was significantly different (p = 0.037 at 4 hours postoperatively, p = 0.015 at 24 hours postoperatively). Pain scores, sedation, and side effects were unaffected by the patient-controlled analgesia regimen.

CONCLUSIONS

The authors conclude that supplementation using ketorolac plus administration of morphine modifies cytokine responses and may contribute to immune augmentations during postoperative periods.

The expression of cyclooxygenase and the production of prostaglandin E2 in neutrophils after burn injury and infection

Recent studies have demonstrated that neutrophils have the capacity to produce a variety of cytokines after stimulation. The synthesis and release of prostaglandin E2 (PGE2) via the cyclooxygenase (COX) pathway has been reported to occur in activated neutrophils. In the present study, we sought to determine the status of COX protein synthesis and PGE2 production in murine neutrophils after burn injury. The effect of burn injury on neutrophil COX and PGE2 response to infection or lipopolysaccharide (LPS) was also examined. Peritoneal neutrophils were obtained from BDF1 mice at 4, 18, 24, and 36 hours after a 15% TBSA full-thickness scald burn or sham burn. We found that neutrophils from healthy mice express a low level of COX-2 protein. Neutrophil COX-2 protein expression in burn animals was significantly increased at 4 hours and dramatically decreased at 36 hours after burn injury. Animals 36 hours after burn and topically infected with Pseudomonas Aeruginosa had neutrophil COX-2 expression almost identical to burn injury only. Neutrophils harvested from healthy mice cocultured with LPS (1 microg/ml) had a marked induction of COX-2 protein. Neutrophils 24 hours after burn were unresponsive to LPS-stimulated COX-2 enhancement. COX-1 protein was strongly expressed constitutively and not affected further by burn injury or LPS. The production of PGE2 corresponded with the changes in COX-2 expression for all groups of mice. Our data suggested that neutrophils express both COX-1 and COX-2 and produce PGE2. The effects of burn injury on neutrophil COX-2 protein synthesis and PGE2 production suggest that after burn there is a time-dependent response. Insights into not only the global cellular response to injury and infection but also temporal nature of the response are important in the development of the therapeutic treatment strategies for burn patients.

IL-10, but not IL-4, suppresses infection-stimulated bone resorption in vivo

Periapical bone resorption occurs following infection of the dental pulp and is mediated mainly by IL-1alpha in the murine model. The production and activity of IL-1alpha is modulated by a network of regulatory cytokines, including those produced by Th1 (pro-inflammatory) and Th2 (anti-inflammatory) subset T cells. This study was designed to assess the functional role of the Th2-type cytokines IL-4 and IL-10 in infection-stimulated bone resorption in vivo. The dental pulps of the first molars were exposed and infected with a mixture of four common endodontic pathogens, and bone destruction was determined by micro-computed tomography at sacrifice on day 21. The results demonstrate that IL-10(-/-) mice had significantly greater infection-stimulated bone resorption in vivo compared with wild-type mice (p < 0.001), whereas IL-4(-/-) exhibited no increased resorption. IL-10(-/-) had markedly elevated IL-1alpha production within periapical inflammatory tissues (>10-fold) compared with wild type (p < 0.01), whereas IL-4(-/-) exhibited decreased IL-1alpha production (p < 0.05). IL-10 also suppressed IL-1alpha production by macrophages in a dose-dependent fashion in vitro, whereas IL-4 had weak and variable effects. We conclude that IL-10, but not IL-4, is an important endogenous suppressor of infection-stimulated bone resorption in vivo, likely acting via inhibition of IL-1alpha expression.

Exaggerated human monocyte IL-10 concomitant to minimal TNF-alpha induction by heat-shock protein 27 (Hsp27) suggests Hsp27 is primarily an antiinflammatory stimulus

Unlike more well-studied large heat shock proteins (hsp) that induce both T cell antiinflammatory (IL-10, IL-4) and macrophage proinflammatory (TNF-alpha, IL-15, IL-12) cytokines, hsp27, a small hsp, has been primarily identified as a substrate of mitogen-activated protein kinase-activated protein kinase-2 involved in the p38 signaling pathway and activated during monocyte IL-10 production. Hsp27 can also act as an endogenous protein circulating in the serum of breast cancer patients and a protein whose induction correlates to protection from LPS shock. However, the cytokine-stimulating properties of hsp27 have been unexplored. In this study, exogenous hsp27 is demonstrated for the first time as a potent activator of human monocyte IL-10 production, but only a modest inducer of TNF-alpha. Although exogenous hsp27 stimulation activated all three monocyte mitogen-activated protein kinase pathways (extracellular signal-related kinase (ERK) 1/2, c-Jun N-terminal kinase, and p38), only p38 activation was sustained and required for hsp27 induction of monocyte IL-10, while both ERK 1/2 and p38 activation were required for induction of TNF-alpha when using the p38 inhibitor SB203580 or the ERK inhibitor PD98059. Hsp27's transient activation of the c-Jun N-terminal kinase pathway, which can down-regulate IL-10, may contribute to its potent IL-10 induction. Hsp27's ERK 1/2 activation was also less sustained than activation by stimuli like LPS, possibly contributing to its modest TNF-alpha induction. The failure of either PD98059 or anti-TNF-alpha Ab to substantially inhibit IL-10 induction implied that hsp27 induces IL-10 via activation of p38 signaling independently of TNF-alpha activation and may be predominantly an antiinflammatory monokine stimulus.

IL-10 inhibits Porphyromonas gingivalis LPS-stimulated human gingival fibroblasts production of IL-6

Lipopolysaccharides (LPS) of Porphyromonas gingivalis have been implicated in the initiation and development of periodontal diseases. In a previous study, we investigated the signal transduction pathway of P. gingivalis and demonstrated that LPS stimulates the production of interleukin (IL)-6 in human gingival fibroblasts (HGFs), which in turn activates osteoclasts in vitro. The cytokine, IL-10, was initially described as cytokine synthesis inhibitory factor. In this study, we examined that effect of IL-10 on P. gingivalis LPS-induced human gingival fibroblast production of IL-6. LPS-induced IL-6 production was inhibited by IL-10 in a dose-dependent manner. Flow cytometric analysis showed that HGFs bind to fluorescein-isothiocyanate (FITC) labeled IL-10. Western blotting analysis demonstrated the expression of IL-10 receptor on the cell surface of these cells. Engagement of LPS initiated the protein tyrosine phosphorylation of several intracellular proteins including extracellular signal-regulated kinase 2 (ERK2), and these events were suppressed by IL-10. These results suggest that IL-10 inhibits the inflammatory response via the IL-10 receptor in P. gingivalis LPS-initiated periodontal diseases.

Antagonistic effects of an alternative splice variant of human IL-4, IL-4delta2, on IL-4 activities in human monocytes and B cells

IL-4 is a pleiotropic cytokine which exerts its actions on various lineages of hematopoietic and nonhematopoietic cells. This cytokine is one of the central regulators of immunity in health and disease states. An alternative splice variant, in which the second of four exons is omitted, has been recently described and designated as IL-4delta2. The variant has been previously described as a potential naturally occurring antagonist of human IL-4 (hIL-4)-stimulated T cell proliferation. In this study, we investigated the effects of recombinant human (rh) IL-4delta2 on monocytes and B cells. In monocytes, rhIL-4delta2 blocked inhibitory action of hIL-4 on LPS-induced cyclooxygenase-2 expression and subsequent prostaglandin E2 secretion. In B cells, rhIL-4delta2 was an antagonist of the hIL-4-induced synthesis of IgE and expression of CD23. Our results broaden the spectrum of hIL-4-antagonistic activities of rhIL-4delta2, thus creating the background for the potential use of rhIL-4delta2 as a therapeutic anti-hIL-4 agent.

Interleukin-10 expression and function in experimental murine liver inflammation and fibrosis

Kupffer cells (KC) play a central role in the initiation and perpetuation of hepatic inflammation, which, if uncontrolled, can result in tissue damage, fibrosis, and cirrhosis. Interleukin-10 (IL-10) can inhibit a range of macrophage functions. We hypothesized that the transcription, synthesis, and release of IL-10 may influence the development of liver injury. Rat KC were activated in vitro with lipopolysaccharide (LPS), and expression of IL-10 mRNA compared with IL-13 and IL-1beta by reverse-transcription polymerase chain reaction (RT-PCR). The effects of pretreatment with recombinant IL-10 (rIL-10) on KC phagocytosis, production of superoxide (SO), and tumor necrosis factor (TNF-) were examined by fluorescent activated cell sorter (FACS), reduction of ferricytochrome C, and bioassay, respectively. Rats were administered intraperitoneal carbon tetrachloride (CCl4), and expression of IL-10 mRNA and protein in vivo compared with IL-13 and IL-1beta by RT-PCR and immunoblotting. Results were correlated with histological inflammatory changes. Finally, IL-10 gene-deleted (IL-10-/-) mice and wild-type (WT) controls were administered intraperitoneal CCl4 biweekly for up to 70 days, and the development of inflammation and fibrosis compared by scoring histological changes. IL-10 mRNA was up-regulated early, both in KC in vitro and in whole liver in vivo, concurrent with that of IL-1beta. IL-10 was able to inhibit KC production of both SO and TNF- in vitro, and this was achieved more effectively than IL-4 or IL-13; no such effects were seen on KC phagocytosis. After 70 days of treatment with CCl4, IL-10-/- mice showed significantly more severe fibrosis and exhibited higher hepatic TNF- levels than WT controls. These results suggest that IL-10 synthesized during the course of liver inflammation and fibrosis may modulate KC actions, and influence subsequent progression of fibrosis.

MAP kinase pathways as a route for regulatory mechanisms of IL-10 and IL-4 which inhibit COX-2 expression in human monocytes

Mitogen-activated protein kinases (MAPKs) are activated by various extracellular stimuli and play an important role in regulating the expression of proinflammatory molecules in monocytes/macrophages. We first questioned whether MAPK activation in involved in cyclooxygenase (COX)-2 expression in lipopolysaccharide (LPS)-stimulated human monocytes. LPS induced the expression of COX-2 protein and COX-2 mRNA as well as the phosphorylation and activation of extracellular signal-regulated protein kinase (ERK)2 and p38 MAPK in monocytes. The induction of COX-2 mRNA, COX-2 protein, and prostaglandin (PG)E2 by LPS was inhibited by the specific inhibitors of ERK and p38 MAPK, suggesting that the activation of ERK2 and p38 MAPK is involved in COX-2 expression in LPS-stimulated monocytes. Since we previously showed that interleukin (IL)-10 and IL-4 similarly inhibited COX-2 expression in LPS-stimulated monocytes, we next questioned whether these cytokines regulate the phosphorylation and activation of ERK2 and p38 MAPK in LPS-stimulated monocytes. Interestingly, LPS-induced phosphorylation and activation of ERK2 was significantly inhibited by IL-4 and IL-10, while that of p38 MAPK was inhibited by IL-10, but not IL-4. These results suggest that the mechanisms of inhibition by IL-10 and IL-4 of the LPS-induced expression of proinflammatory molecules could be ascribed to the regulatory effects of both cytokines on MAPK activation.

IL-10 as a therapeutic strategy in the treatment of rheumatoid arthritis

IL-10 has anti-inflammatory and immunoregulatory properties that suggest a potential therapeutic role in RA. IL-10 inhibits proinflammatory cytokine and chemokine production in addition to blocking T-cell responses to specific antigens. It acts primarily through inhibition of costimulatory properties of macrophages. IL-10 stimulates proliferation and differentiation of antibody-forming B-cells. Preclinical studies in a variety of animal models, including collagen-induced arthritis, have shown that IL-10 is effective in preventing or inhibiting inflammation and autoreactivity. Although in RA, circulating and synovial levels of IL-10 are increased, accumulated evidence suggests that there may be a relative deficit of available IL-10. Moreover, exogenous addition of IL-10 in vitro has been shown to affect the immunopathological processes involved in RA. Preliminary studies of human recombinant IL-10 in patients with RA have demonstrated a trend towards efficacy with a good safety profile. Taken together, the data support a therapeutic role for IL-10 in the treatment of RA.

Interleukin-10 as a regulatory cytokine induced by cellular stress: molecular aspects

Interleukin-10 is an ubiquitous cytokine which plays a major regulatory role in the course of inflammatory responses by downregulating the synthesis of cytokines. In this paper, we summarize the major biological properties of IL-10 and the current knowledge of the molecular mechanisms by which IL-10 inhibits the expression of genes encoding proinflammatory cytokines. We then review the factors upregulating IL-10 synthesis and we present the concept that IL-10 is a stress cytokine produced not only in response to microbial pathogens but also to cellular injuries of diverse origins.

Different pattern of cytokine production and mRNA expression by lymphoid and non-lymphoid cells isolated from human palatine tonsil

To investigate the cytokines involved in the interaction between circulating (B and T lymphocytes) and non-circulating (stromal cells) elements present in lymphoid tissue, highly purified populations were isolated from human tonsils and the cytokine production and mRNA expression (interleukin-1 alpha, -2, -4, -5, -6, -8, -10, leukocyte inhibitory factor, granulocyte-macrophage colony-stimulating factor, and interferon-gamma) were assessed both by immunoassay and reverse transcriptase polymerase chain reaction under resting conditions and after activation with tumor necrosis factor-alpha. Under basal conditions most cytokines were not detected, except for interleukin-8 which was produced by T lymphocytes and lymphoid cells. Activation by tumor necrosis factor-alpha induced interleukin-8 production by B lymphocytes. Tonsillar T lymphocytes expressed mRNA for interleukin-1 alpha, -8, -10, -4, leukocyte inhibitory factor, and interferon-gamma, only interleukin-4 was expressed by resting peripheral blood T lymphocytes. Tonsillar B lymphocytes were mRNA positive for interleukin-1 alpha, -8, -10, leukocyte inhibitory factor, and interferon-gamma, these were not expressed by peripheral blood B lymphocytes. Stromal cells constitutively produce interleukin-6 whose levels increased 5 times upon tumor necrosis factor-alpha activation Granulocyte-macrophage colony-stimulating factor and interleukin-8 were detected only after tumor necrosis factor-alpha activation. Only stromal cells constitutively express interleukin-6 and granulocyte-macrophage colony-stimulating factor and show a cytokine pattern different from that described for other non-lymphoid cells, such as follicular dendritic cells. These data indicate that in the human tonsil population, lymphoid and non-lymphoid cells can be distinguished by different patterns of cytokine expression.

Macrophages that have ingested apoptotic cells in vitro inhibit proinflammatory cytokine production through autocrine/paracrine mechanisms involving TGF-beta, PGE2, and PAF

Apoptosis in vivo is followed almost inevitably by rapid uptake into adjacent phagocytic cells, a critical process in tissue remodeling, regulation of the immune response, or resolution of inflammation. Phagocytosis of apoptotic cells by macrophages has been suggested to be a quiet process that does not lead to production of inflammatory mediators. Here we show that phagocytosis of apoptotic neutrophils (in contrast to immunoglobulin G-opsonized apoptotic cells) actively inhibited the production of interleukin (IL)-1beta, IL-8, IL-10, granulocyte macrophage colony-stimulating factor, and tumor necrosis factor-alpha, as well as leukotriene C4 and thromboxane B2, by human monocyte-derived macrophages. In contrast, production of transforming growth factor (TGF)-beta1, prostaglandin E2, and platelet-activating factor (PAF) was increased. The latter appeared to be involved in the inhibition of proinflammatory cytokine production because addition of exogenous TGF-beta1, prostaglandin E2, or PAF resulted in inhibition of lipopolysaccharide-stimulated cytokine production. Furthermore, anti-TGF-beta antibody, indomethacin, or PAF receptor antagonists restored cytokine production in lipopolysaccharide-stimulated macrophages that had phagocytosed apoptotic cells. These results suggest that binding and/or phagocytosis of apoptotic cells induces active antiinflammatory or suppressive properties in human macrophages. Therefore, it is likely that resolution of inflammation depends not only on the removal of apoptotic cells but on active suppression of inflammatory mediator production. Disorders in either could result in chronic inflammatory diseases.

Action of immunoregulatory agents on 5-HETE production by cultured human amnion cells

Labor in women is associated with increased amniotic fluid prostaglandin (PG) concentrations. AF of women with term and preterm labor also contains elevated concentrations of arachidonic acid metabolites from the lipoxygenase pathway including 5-hydroxyeicosatetraenoic acid (5-HETE). We and others have shown that 5-HETE production within the uterus is increased by inflammatory cytokines. The purpose of this study was to determine whether 5-HETE production is regulated by immunotherapeutic agents that inhibit prostaglandin E2 (PGE2) production, such as interleukin-10 (IL-10) and cyclosporin A (CsA). Cultured confluent amnion cells were incubated for 16 hr with IL-10 (1 100 ng/ml), CsA (1 1000 ng/ml), or controls. Additional incubation of IL-10 and CsA (both at 10 and 100 ng/ml) were conducted on amnion cells in the presence and absence of interleukin-1 beta at 1 ng/ml. 5-HETE was measured by radioimmunoassay and cellular protein determined. IL-1 beta stimulated amnion cell 5-HETE production as expected. However, 5-HETE production by amnion cells was significantly inhibited by incubation with IL-10 and CsA, and both significantly attenuated 5-HETE production in response to IL-1 beta. We speculate that the inhibitory effect of IL-10 and CsA on amnion cell 5-HETE production is at the level of substrate release or inhibition of 5-lipoxygenase and that the use of these agents during pregnancy may not adversely affect pregnancy outcomes.

T helper 2 cytokines induce preproenkephalin mRNA expression and proenkephalin A in human peripheral blood mononuclear cells

We investigated the regulatory influence of several cytokines on the expression of preproenkephalin (PPE) mRNA in human peripheral blood mononuclear cells (PBMC). By use of a quantitative reverse-transcriptase-polymerase chain reaction (RT-PCR), we demonstrate that the T helper 2 cytokines IL-4 and IL-10 are more potent in upregulating PPE mRNA expression in human PBMC than the T helper 1 cytokines IL-2 and gamma-IFN. In addition, TGF-beta is also an effective inducer of PPE mRNA. TGF-beta, IL-4 and IL-10 increase the cytoplasmatic concentration of met-enkephalin in PBMC. Secretion of met-enkephalin in the culture supernatant of IL-4- or IL-10-stimulated PBMC could not be observed, but proenkephalin A-derived met-enkephalin containing peptides could be demonstrated. IL-4 and IL-10 do not induce PPE mRNA via the same pathways. We could observe that PKA is involved in IL-4 mediated PPE mRNA induction, whereas IL-10 apparently uses another route.

Selective IL-10 inhibition of HLA-DR expression in IFN-gamma-stimulated human retinal pigment epithelial cells

PURPOSE

Human RPE cells express HLA-DR antigens, bind leukocytes via ICAM-1, and secrete IL-8 and MCP-1, which attract and activate leukocytes. Since little is known concerning endogenous cytokines that may alter ocular immunologic and inflammatory mechanisms, we investigated whether IL-10, an immunosuppressive cytokine, modulates these HRPE features.

METHODS

IL-10 effects on HLA-DR and ICAM-1 were examined by HRPE exposures to: (1) IFN-gamma (10-1000 U/ml) + IL-10 (1-100 U/ml) and (2) IL-10 pre-incubation followed by IFN-gamma + IL-10. Immunohistochemistry for HLA-DR and ICAM-1 was graded by masked observers. Flow cytometric analysis quantitated HRPE HLA-DR and ICAM-1. Effects of IL-10 on IL-1 beta (0.2 or 2 ng/ml)-, or TNF-alpha (0.2 or 2 ng/ml)-induced IL-8 and MCP-1 secretion and gene expression were assessed using enzyme-linked immunosorbent assay (ELISA) and Northern blot analysis.

RESULTS

HLA-DR expression, detected by immunohistochemistry and flow cytometric analysis, showed dose-dependent increases to IFN-gamma. IL-10 pre-/co-incubation, but not co-incubation alone, markedly reduced HLA-DR expression, but did not modulate constitutive or IFN-gamma-induced ICAM-1. IL-10 alone did not induce MCP-1 or IL-8 secretion or steady-state mRNA expression, nor modulate IL-1 beta-, TNF-alpha- or IFN-gamma-induced IL-8 or MCP-1.

CONCLUSIONS

This study suggests that HRPE HLA-DR antigens are selectively inhibited by IL-10, but the timing of IL-10 exposure may be crucial.

Regulation of Interleukin-10 Gene Expression: Possible Mechanisms Accounting for Its Upregulation and for Maturational Differences in Its Expression by Blood Mononuclear Cells

Interleukin-10 (IL-10) downmodulates phagocytic immune responses and accentuates humoral responses. Human neonates exhibit broad immune deficits that parallel actions of IL-10. We postulated that IL-10 production would be diminished in neonatal blood cells. We found that IL-10 production by lipopolysaccharide-stimulated peripheral blood mononuclear cells (PBMNCs) in vitro was greater by adult cells than by term cells and preterm cells. Additional studies were undertaken to identify mechanisms responsible for the developmental differences in IL-10 gene expression. IL-10 transcription was present in freshly isolated adult and neonatal cells in the absence of detectable levels of transcript. Transcription rates were not different between adult and neonatal cells. IL-10 transcripts were approximately 40% more abundant in adult cells than in term cells and were consistent with differences in secreted protein; however, no differences were noted in mRNA stability. IL-10 half-life was 60 minutes for both adult and term PBMNCs. We conclude that up-regulation of IL-10 gene expression in PBMNCs is modulated at the post-transcriptional level, that IL-10 protein production and mRNA content are greater in activated cells from adults compared with those from neonates, and that maturational differences in IL-10 expression are not due to differences in transcription rate or mRNA stability. Maturational differences in IL-10 expression might be due to differences in subpopulations of cytokine-producing cells or differences in nucleo-cytoplasmic transport.

Regulation by Interleukin-10 and Interleukin-4 of Cyclooxygenase-2 Expression in Human Neutrophils

Neutrophils are important effector cells of acute inflammation because of their potential capacity to synthesize various proinflammatory mediators, and inhibition of their production is expected to result in anti-inflammatory effects. In this study, we investigate the effects of the anti-inflammatory cytokines, interleukin-10 (IL-10) and IL-4, on prostanoid synthesis in human neutrophils. Neutrophils isolated from healthy donors constitutively produced a small amount of prostaglandin E2 (PGE2 ) without any stimulations, whereas they produced a large amount of PGE2 after lipopolysaccharide (LPS) stimulation. IL-10 and IL-4 selectively inhibited their LPS-induced PGE2 production. Inhibition by both cytokines occurred at an early stage of LPS stimulation. Anti–IL-10 treatment of LPS-stimulated neutrophils resulted in enhanced PGE2 production. LPS-induced PGE2 and thromboxane B2 (TXB2 ) production in aspirin-treated neutrophils was significantly inhibited by IL-10, IL-4, and NS-398. Moreover, IL-10 and IL-4 inhibited LPS-induced cyclooxygenase (COX) activity in neutrophils. Western blot and immunocytochemical analysis showed that COX-2 protein was clearly induced in LPS-stimulated neutrophils and that its induction was inhibited by both IL-10 and IL-4. Moreover, both of these cytokines inhibited COX-2 mRNA expression in LPS-stimulated neutrophils. These results raise the possibility that these two cytokines may both offer potent clinical utility as anti-inflammatory agents in the future.

Regulation by Interleukin-10 and Interleukin-4 of Cyclooxygenase-2 Expression in Human Neutrophils

Neutrophils are important effector cells of acute inflammation because of their potential capacity to synthesize various proinflammatory mediators, and inhibition of their production is expected to result in anti-inflammatory effects. In this study, we investigate the effects of the anti-inflammatory cytokines, interleukin-10 (IL-10) and IL-4, on prostanoid synthesis in human neutrophils. Neutrophils isolated from healthy donors constitutively produced a small amount of prostaglandin E2 (PGE2 ) without any stimulations, whereas they produced a large amount of PGE2 after lipopolysaccharide (LPS) stimulation. IL-10 and IL-4 selectively inhibited their LPS-induced PGE2 production. Inhibition by both cytokines occurred at an early stage of LPS stimulation. Anti–IL-10 treatment of LPS-stimulated neutrophils resulted in enhanced PGE2 production. LPS-induced PGE2 and thromboxane B2 (TXB2 ) production in aspirin-treated neutrophils was significantly inhibited by IL-10, IL-4, and NS-398. Moreover, IL-10 and IL-4 inhibited LPS-induced cyclooxygenase (COX) activity in neutrophils. Western blot and immunocytochemical analysis showed that COX-2 protein was clearly induced in LPS-stimulated neutrophils and that its induction was inhibited by both IL-10 and IL-4. Moreover, both of these cytokines inhibited COX-2 mRNA expression in LPS-stimulated neutrophils. These results raise the possibility that these two cytokines may both offer potent clinical utility as anti-inflammatory agents in the future.