Interleukin-10 contributes development of macrophage suppressor activities by macrophage colony-stimulating factor, but not by granulocyte-macrophage colony-stimulating factor

Defining GM-CSF- and macrophage-CSF-dependent macrophage responses by in vitro models

GM-CSF and M-CSF (CSF-1) induce different phenotypic changes in macrophage lineage populations. The nature, extent, and generality of these differences were assessed by comparing the responses to these CSFs, either alone or in combination, in various human and murine macrophage lineage populations. The differences between the respective global gene expression profiles of macrophages, derived from human monocytes by GM-CSF or M-CSF, were compared with the differences between the respective profiles for macrophages, derived from murine bone marrow cells by each CSF. Only 17% of genes regulated differently by these CSFs were common across the species. Whether a particular change in relative gene expression is by direct action of a CSF can be confounded by endogenous mediators, such as type I IFN, IL-10, and activin A. Time-dependent differences in cytokine gene expression were noted in human monocytes treated with the CSFs; in this system, GM-CSF induced a more dramatic expression of IFN-regulated factor 4 (IRF4) than of IRF5, whereas M-CSF induced IRF5 but not IRF4. In the presence of both CSFs, some evidence of "competition" at the level of gene expression was observed. Care needs to be exercised when drawing definitive conclusions from a particular in vitro system about the roles of GM-CSF and M-CSF in macrophage lineage biology.

Fat-1 transgenic cattle as a model to study the function of ω-3 fatty acids

ω-3 polyunsaturated fatty acids have been shown to play an important role in health. Enriched with ω-3 polyunsaturated fatty acids modulate expression of a number of genes with such broad functions as cell proliferation, growth and apoptosis and cell signaling and transduction, these effects, seem to regulate coronary artery disease, hypertension, atherosclerosis, psychiatric disorders and various cancer. In this context, fat-1 transgenic cattle was designed to convert ω-6 to ω-3 fatty acids could form an ideal model to study the effect of ω-3 fatty acids on the above functions. This study focuses on the total genomic difference of gene expression between fat-1 transgenic cattle and wild-type using cDNA microarrays, several genes were found to be overexpressed or suppressed in transgenic cattle relative to wild-type, these discrepancy genes related with lipid metabolism, immunity, inflammation nervous development and fertility.

NDRG2 is one of novel intrinsic factors for regulation of IL-10 production in human myeloid cell

N-myc downstream-regulated gene 2 (NDRG2) implicated in cellular growth and differentiation was previously reported as it is specifically expressed in primary and in vitro-differentiated dendritic cells (DCs) from monocytes and CD34(+) progenitor cells. However, its function has yet to be investigated in DCs. Here, the novel NDRG2 function about modulation of cytokines in DC was observed in this study. The secretion of IL-10 was not found in the monocyte-derived DC cells with high level of NDRG2 expression, but IL-10 was abundantly secreted up to 1ng/ml in the monocyte-derived macrophages with low level of NDRG2 expression, and further confirmed that the expression of IL-10 was dramatically increased in NDRG2-silenced DCs under presence of LPS, and significantly reduced in the NDRG2-overexpressed U937 cells under stimulation of PMA. The secretion of IL-12p70 was significantly reduced in the siNDRG2 introduced DC cells. The intracellular signaling of IL-10 secretion was markedly inhibited by SB203580, inhibitor of p38 MAPK, in the LPS-activated DCs and phosphorylation of p38 MAPK was decreased in the NDRG2 introduced U937 cells under PMA-stimulation. Taken together, NDRG2 might have a pivotal role as one of intrinsic factors for the modulation of p38 MAPK phosphorylation, and subsequently involve in controlling of IL-10 production.

Subpopulations of bovine WC1(+) gammadelta T cells rather than CD4(+)CD25(high) Foxp3(+) T cells act as immune regulatory cells ex vivo

Regulatory T cells (Treg) are regarded essential components for maintenance of immune homeostasis. Especially CD4(+)CD25(high) T cells are considered to be important regulators of immune reactivity. In humans and rodents these natural Treg are characterized by their anergic nature, defined as a non-proliferative state, suppressive function and expression of Foxp3. In this study the potential functional role of flowcytometry-sorted bovine white blood cell populations, including CD4(+)CD25(high) T cells and gammadelta T cell subpopulations, as distinct ex vivo regulatory cells was assessed in co-culture suppression assays. Our findings revealed that despite the existence of a distinct bovine CD4(+)CD25(high) T cell population, which showed Foxp3 transcription/expression, natural regulatory activity did not reside in this cell population. In bovine co-culture suppression assays these cells were neither anergic nor suppressive. Subsequently, the following cell populations were tested functionally for regulatory activity: CD4(+)CD25(low) T cells, WC1(+), WC1.1(+) and WC1.2(+) gammadelta T cells, NK cells, CD8(+) T cells and CD14(+) monocytes. Only the WC1.1(+) and WC1.2(+) gammadelta T cells and CD14(+) monocytes proved to act as regulatory cells in cattle, which was supported by the fact that these regulatory cells showed IL-10 transcription/expression. In conclusion, our data provide first evidence that cattle CD4(+)CD25(high)Foxp3(+) and CD4(+)CD25(low) T cells do not function as Treg ex vivo. The bovine Treg function appears to reside in the gammadelta T cell population, more precisely in the WC1.1(+) and the WC1.2(+) subpopulation, major populations present in blood of cattle in contrast to non-ruminant species.

GM-CSF-mediated T-cell activation by macrophages infected with recombinant BCG that secretes major membrane protein-II of Mycobacterium leprae

The potential of Mycobacterium bovis Bacillus Calmette-Guerin (BCG) needs to be augmented to efficiently activate CD4(+) T cells through macrophages. Mycobacterium leprae-derived recombinant major membrane protein (MMP)-II induced GM-CSF production from macrophages. A recombinant BCG-SM that secretes MMP-II more efficiently produced GM-CSF and activated interferon (IFN)-gamma-producing CD4(+) T cells than did vector control BCG when infected with macrophages. The T-cell activation by BCG-SM was dependent on the GM-CSF production by macrophages. Interleukin (IL)-10 production by macrophages stimulated with M. leprae was inhibited in a GM-CSF-dependent manner when the precursor monocytes were infected with BCG-SM. BCG inducing GM-CSF production was effective in macrophage-mediated T-cell activation partially through IL-10 inhibition.

Role of M-CSF-dependent macrophages in colitis is driven by the nature of the inflammatory stimulus

Although macrophages are considered a critical factor in determining the severity of acute inflammatory responses in the gut, recent evidence has indicated that macrophages may also play a counterinflammatory role. In this study, we examined the role of a macrophage subset in two models of colitis. Macrophage colony-stimulating factor (M-CSF)-deficient osteopetrotic mice (op/op) and M-CSF-expressing heterozygote (+/?) mice were studied following the induction of colitis by either dinitrobenzene sulfonic acid (DNBS) or dextran sulfate sodium (DSS). DNBS induced a severe colitis in M-CSF-deficient op/op mice compared with +/? mice. This was associated with increased mortality and more severe macroscopic and microscopic injury. Colonic tissue myeloperoxidase (MPO) activity as well as concentrations of TNF-alpha, IL-1beta, and IL-6 were higher and IL-10 lower in op/op mice with DNBS colitis. The severity of inflammation and mortality was attenuated in op/op mice that had received human recombinant M-CSF prior to the induction of colitis. In contrast, op/op mice appeared less vulnerable to colitis induced by DSS. Macroscopic damage, microscopic injury, MPO activity, and tissue concentrations of TNF-alpha, IL-1beta, and IL-6 were all lower in op/op mice compared with +/? mice with DSS colitis, and no changes were seen in IL-10. Macrophage inflammatory protein-1alpha concentrations were increased in op/op but not +/? mice following colitis induced by DNBS but not DSS. These results indicate that M-CSF-dependent macrophages may play either a pro- or counterinflammatory role in acute experimental colitis, depending on the stimulus used to induce colitis.

Contribution of GM-CSF on the enhancement of the T cell-stimulating activity of macrophages

Mycobacterium leprae is an intracellular parasitic organism that multiplies in macrophages (MØ). It inhibits the fusion of mycobacterial phagosome with lysosome and induces interleukin (IL)-10 production from macrophages. However, macrophages are heterogenous in various aspects. We examined macrophages that differentiated from monocytes using either recombinant (r) granulocyte-MØ colony-stimulating factor (GM-CSF) (these MØ are named as GM-MØ) or rMØ colony-stimulating factor (M-CSF) (cells named as M-MØ) in terms of the T cell-stimulating activity. Although both macrophages phagocytosed the mycobacteria equally, GM-MØ infected with M. leprae and subsequently treated with IFN-gamma- and CD40 ligand (L) stimulated T cells to produce interferon-gamma (IFN-gamma), but M-MØ lacked the ability to stimulate T cells. While M-MØ mounted a massive IL-10 production, GM-MØ did not produce the cytokine on infection with M. leprae. M. leprae-infected, IFN-gamma- and CD40L-treated GM-MØ expressed a higher level of HLA-DR and CD86 Ags than those of M-MØ, and expressed one of the dominant antigenic molecules of M. leprae, Major Membrane Protein-II on their surface. These results indicate that GM-CSF, but not M-CSF, contributes to the up-regulation of the T cell-stimulating activity of M. leprae-infected macrophages.

Functional heterogeneity of colony-stimulating factor-induced human monocyte-derived macrophages

OBJECTIVES

Macrophages (Mphis) have various functions and play a critical role in host defense and the maintenance of homeostasis. Mphis exist in every tissue in the body, but Mphis from different tissues exhibit a wide range of phenotypes with regard to their morphology, cell surface antigen expression and function, and are called by different names. However, the precise mechanism of the generation of macrophage heterogeneity is not known. In the present study, the authors examined the functional heterogeneity of Mphis generated from human monocytes under the influence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage-CSF (M-CSF).

METHODOLOGY

CD14 positive human monocytes (Mos) were incubated with M-CSF and GM-CSF for 6-7 days to stimulate the generation of M-CSF-induced monocyte-derived Mphis (M-Mphis) and GM-CSF-induced monocyte-derived Mphis (GM-Mphis), respectively. The expression of cell surface antigens and several functions such as antigen presenting cell activity, susceptibility to oxidant stress, and the susceptibility to HIV-1 and mycobacterium tuberculosis infection were examined.

RESULTS

GM-Mphis and M-Mphis are distinct in their morphology, cell surface antigen expression, and functions examined. The phenotype of GM-Mphis closely resembles that of human Alveolar-Mphis (A-Mphis), indicating that CSF-induced human monocyte-derived Mphis are useful to clarify the molecular mechanism of heterogeneity of human Mphis, and GM-Mphis will become a model of human A-Mphis.

Lethal and severe coronary arteritis in DBA/2 mice induced by fungal pathogen, CAWS, Candida albicans water-soluble fraction

CAWS is a microbial pathogen-associated molecular patterns (PAMPs) produced by Candida albicans. CAWS is a mannoprotein-beta-glucan complex and secreted into the culture supernatant. CAWS has various biological effects, causing acute shock and disrupting vascular permeability. Intraperitoneal administration of CAWS induces coronary arteritis in various strains of inbred mice. The CAWS-induced coronary arteritis is strain-dependent and most severe in DBA/2 mice with a significant number of these animals expiring with cardiomegaly during the observation period. In vivo and in vitro, splenocytes of DBA/2 mice produced various cytokines, such as IL-6, TNF-alpha, and IFN-gamma in response to CAWS. GM-CSF was also produced in response to CAWS. The production of cytokines was significantly enhanced in the presence of recombinant GM-CSF. In contrast, anti-GM-CSF significantly reduced the production of TNF-alpha and IFN-gamma. Augmented production of cytokines in response to CAWS would be a key to the severity of coronary arteritis.

Abnormally differentiated subsets of intestinal macrophage play a key role in Th1-dominant chronic colitis through excess production of IL-12 and IL-23 in response to bacteria

Disorders in enteric bacteria recognition by intestinal macrophages (Mphi) are strongly correlated with the pathogenesis of chronic colitis; however the precise mechanisms remain unclear. The aim of the current study was to elucidate the roles of Mphi in intestinal inflammation by using an IL-10-deficient (IL-10-/-) mouse colitis model. GM-CSF-induced bone marrow-derived Mphi (GM-Mphi) and M-CSF-induced bone marrow-derived Mphi (M-Mphi) were generated from bone marrow CD11b+ cells. M-Mphi from IL-10-/- mice produced abnormally large amounts of IL-12 and IL-23 upon stimulation with heat-killed whole bacteria Ags, whereas M-Mphi from wild-type (WT) mice produced large amounts of IL-10 but not IL-12 or IL-23. In contrast, IL-12 production by GM-Mphi was not significantly different between WT and IL-10-/- mice. In ex vivo experiments, cytokine production ability of colonic lamina propria Mphi (CLPMphi) but not splenic Mphi from WT mice was similar to that of M-Mphi, and CLPMphi but not splenic Mphi from IL-10-/- mice also showed abnormal IL-12p70 hyperproduction upon stimulation with bacteria. Surprisingly, the abnormal IL-12p70 hyperproduction from M-Mphi from IL-10-/- mice was improved by IL-10 supplementation during the differentiation process. These results suggest that CLPMphi and M-Mphi act as anti-inflammatory Mphi and suppress excess inflammation induced by bacteria in WT mice. In IL-10-/- mice, however, such Mphi subsets differentiated into an abnormal phenotype under an IL-10-deficient environment, and bacteria recognition by abnormally differentiated subsets of intestinal Mphi may lead to Th1-dominant colitis via IL-12 and IL-23 hyperproduction. Our data provide new insights into the intestinal Mphi to gut flora relationship in the development of colitis in IL-10-/- mice.

Monocytes stimulated by 110-kDa fibronectin fragments suppress proliferation of anti-CD3-activated T cells

One hundred ten to 120-kDa fragments of fibronectin (FNf), generated by proteases released in the course of tissue injury and inflammation, stimulate monocytes to produce proinflammatory cytokines, promote mononuclear leukocytes (MNL) transendothelial migration, up-regulate monocyte CD11b and CD86 expression, and induce monocyte-derived dendritic cell differentiation. To investigate whether the proinflammatory consequences of FNf are offset by responses that can suppress proliferation of activated T lymphocytes, we investigated the effect of FNf-treated MNL on autologous T lymphocytes induced to proliferate by substrate-immobilized anti-CD3. FNf-stimulated MNL suppressed anti-CD3-induced T cell proliferation through both contact-dependent and contact-independent mechanisms. Contact-independent suppression was mediated, at least in part, by IL-10 and TGF-beta released by the FNf-stimulated MNL. After 24-48 h exposure to FNf, activated T cells and monocytes formed clusters displaying CD25, CD14, CD3, and CD4 that were not dissociable by chelation of divalent cations. Killing monocytes with l-leucine methyl ester abolished these T cell-monocyte clusters and the ability of the FNf-stimulated MNL to suppress anti-CD3 induced T cell proliferation. Thus, in addition to activating MNL and causing them to migrate to sites of injury, FNf appears to induce suppressor monocytes.

IL-12 family members: differential kinetics of their TLR4-mediated induction by Salmonella enteritidis and the impact of IL-10 in bone marrow-derived macrophages

The members of the IL-12 family of heterodimeric cytokines play a pivotal role in initiation and regulation of cell-mediated immunity. Best known is IL-12p70, which promotes an immune response towards T(h)1 bias. Other members of this family (IL-23, IL-27) are less well characterized in terms of induction and function. Using either heat-killed or viable Salmonella Enteritidis or LPS as a stimulus, the kinetics of mRNA production of each member of the IL-12 family (p19, p28, p35, p40, Ebstein-Barr-Virus-induced gene 3 (EBI-3)) were determined in BMDMPhi originating from wild-type, Toll-like receptor (TLR)2- and/or TLR4-deficient mice. It was found that following either type of stimulation, a characteristic mRNA expression pattern was observed for each cytokine subunit. Whereas p19 was induced early and transiently, p40 and p35 were up-regulated later and then continuously, but the secretion of IL-23 and IL-12p70 was significantly reduced by IL-10. The up-regulation of p28 mRNA occurred also delayed and declined afterwards, whereas the initial high-level expression of EBI-3 remained almost unchanged in BMDMPhi. Furthermore, a splice variant of the EBI-3 mRNA was discovered. In this context, the cytokine mRNA up-regulation by whole Salmonella Enteritidis is mediated chiefly by TLR4, but depends on additional pattern recognition receptors other than TLR2 expressed by macrophages.

Humoral Proinflammatory Cytokine and SAA Generation Profiles and Spatio-Temporal Relationship Between SAA and Lysosomal Cathepsin B and D in Murine Splenic Monocytoid Cells During AA Amyloidosis

Evidence shows that tissue macrophages (MPhis), in mice undergoing AA amyloidosis, endocytose acute-phase humoral serum amyloid A (SAA) and traffic it to lysosomes where it is degraded. Incomplete degradation of SAA leads to intracellular nascent AA fibril formation. In vitro, cathepsin (Cat) B is known to generate amyloidogenic SAA derivatives, whereas Cat D generates non-amyloidogenic SAA derivatives, and interferon (IFN-gamma)-treated MPhis show selective increase in Cat B concentration, a factor conducive to AA amyloidogenesis. To understand the cumulative effect of these factors in AA amyloidosis, humoral levels of SAA, IFN-gamma, tumour necrosis factor (TNF-alpha) and granulocyte-macrophage colony-stimulating factor were determined in azocasein (AZC)-treated CD-1 mice. We correlated these responses with the spatio-temporal distribution of SAA, Cat B- and Cat D-immunoreactive splenic reticuloendothelial (RE) cells. AZC-treated CD-1 mice similar to that of A/J mice showed partial amyloid resistance; their peak humoral IFN-gamma and SAA responses overlapped during the pre-amyloid phase. Unexpectedly, Cat D immunoreactivity (IR), instead of Cat B IR, was predominant in the splenic RE cells, indicating an apparent lack of causal relationship between IFN-gamma-mediated increase in Cat B expression. Partial amyloid resistance in CD-1 mice, probably a genetic trait, may be linked to high levels of Cat D expression, causing a delay in nascent AA fibril formation.

Functional heterogeneity of colony-stimulating factor-induced human monocyte-derived macrophages

Macrophages have various functions and play a critical role in host defense and the maintenance of homeostasis. However, macrophages are heterogeneous and exhibit a wide range of phenotypes with regard to their morphology, cell surface antigen expression, and function. When blood monocytes are cultured in medium alone in vitro, monocytes die, and colony-stimulating factors (CSFs) such as macrophage (M)-CSF or granulocyte-macrophage (GM)-CSF are necessary for their survival and differentiation into macrophages. However, M-CSF-induced monocyte-derived macrophages (M-Mphi) and GM-CSF-induced monocyte-derived macrophages (GM-Mphi) are distinct in their morphology, cell surface antigen expression, and functions, including Fcgamma receptor mediated-phagocytosis, H2O2 production, H2O2 sensitivity, catalase activity, susceptibility to human immunodeficiency virus type 1 and Mycobacterium tuberculosis, and suppressor activity. The characteristics of GM-Mphi resemble those of human alveolar macrophages.

IL-10 inhibits granulocyte-macrophage colony-stimulating factor-dependent human monocyte survival at the early stage of the culture and inhibits the generation of macrophages

We previously demonstrated that IL-10 alone does not stimulate growth and differentiation of human monocytes, but enhances those of monocytes stimulated with M-CSF. We studied here the effect of IL-10 on human monocytes stimulated with GM-CSF. Monocytes stimulated with GM-CSF alone survived and developed into macrophages. Monocytes cultured with GM-CSF plus IL-10, however, died through apoptosis. IL-10 decreased expression of bcl-2, bcl-x(L), and mcl-1- but not bax mRNA in monocytes stimulated with GM-CSF. IL-10 did not change the expression of mRNA of both GM-CSFR alpha-chain and beta-chain, but inhibited tyrosine phosphorylation of STAT5 and extracellular signal-regulated kinases 1 and 2 in the monocytes. The inhibitory effect of IL-10 was restricted to treatment 48 h after stimulation with GM-CSF. Addition of IL-10 after that time induced neither apoptosis nor a decrease in expression of bcl-2, bcl-x(L), and mcl-1 mRNA. IL-10, however, inhibited LPS-induced TNF-alpha production even in these cells, indicating that the cells still possessed responsiveness to IL-10. Monocytes pretreated for >48 h with GM-CSF became resistant to GM-CSF withdrawal, and the cells could survive without GM-CSF. These results indicate that IL-10 selectively inhibits GM-CSF-dependent monocyte survival by inhibiting the signaling events induced by GM-CSF, but the timing of addition of IL-10 is critical, and IL-10 had to be added within 48 h after stimulation with GM-CSF to achieve the inhibitory effect. These results taken together with our previous results indicate that IL-10 plays a pivotal role in monocyte survival and development into macrophages in concert with M-CSF and GM-CSF.