Direct activation of murine peritoneal macrophages for nitric oxide production and tumor cell killing by interferon-gamma

Exploring the role of CITED transcriptional regulators in the control of macrophage polarization

Macrophages are tissue resident innate phagocytic cells that take on contrasting phenotypes, or polarization states, in response to the changing combination of microbial and cytokine signals at sites of infection. During the opening stages of an infection, macrophages adopt the proinflammatory, highly antimicrobial M1 state, later shifting to an anti-inflammatory, pro-tissue repair M2 state as the infection resolves. The changes in gene expression underlying these transitions are primarily governed by nuclear factor kappaB (NF-κB), Janus kinase (JAK)/signal transducer and activation of transcription (STAT), and hypoxia-inducible factor 1 (HIF1) transcription factors, the activity of which must be carefully controlled to ensure an effective yet spatially and temporally restricted inflammatory response. While much of this control is provided by pathway-specific feedback loops, recent work has shown that the transcriptional co-regulators of the CBP/p300-interacting transactivator with glutamic acid/aspartic acid-rich carboxy-terminal domain (CITED) family serve as common controllers for these pathways. In this review, we describe how CITED proteins regulate polarization-associated gene expression changes by controlling the ability of transcription factors to form chromatin complexes with the histone acetyltransferase, CBP/p300. We will also cover how differences in the interactions between CITED1 and 2 with CBP/p300 drive their contrasting effects on pro-inflammatory gene expression.

Effects of l-arginine and l-ornithine supplementations on the treatment of chronic periodontitis: A preliminary randomized short-term clinical trial

The growing interest in the possibilities of modulating macrophages in inflammatory diseases with therapeutic purpose has prompted the development of new approaches for the treatment of periodontitis. This randomized add-on open preliminary clinical study evaluated the short-term effects of L-arginine or L-ornithine as an adjuvant to scaling and root planing (SRP) in patients with chronic periodontitis.

Materials and methods

Seventy-five periodontitis patients were recruited and monitored clinically and immunologically at baseline (before SRP) and 30 ± 5 days after SRP. All patients were assigned by stratified randomization to SRP (SRP only, n = 25), Arg (SRP + L-arginine, n = 25) or Control (SRP + L-ornithine, n = 25) Group. The medicines were used according to available instructions for 10 and 15 days, respectively. During the study, all patients were on a stable diet, without changing their rations and regiments. As immunological monitoring immunohistochemical study of CD68+ and CD163 + single positive gingival macrophages for 5 patients per group in the same time-point was conducted. The data were statistically analyzed.

Results

Reduction of periodontal pocket depth (PPD) and bleeding on probing (BoP) was observed in all groups, with significant between-group differences for BoP in the Arg Group (p < 0.0001) at 30 days. The SRP and Arg groups demonstrated nonsignificantly increased density of CD68+ and CD163 + cells. The Orn Group showed an increase in the density of CD68+ and CD163 + macrophages at intragroup (p = 0.0066 and p < 0.0001) and between-group levels (p = 0.001 and p < 0.0001), and these changes corresponded to clinical PPD and BoP reduction. In the Arg and Orn groups at 30 days, CD163 + macrophages significantly predominated over CD68+ (p = 0.013, p < 0.0001).

Conclusion

The use of L-arginine and L-ornithine as an adjunct to SRP promotes additional limited immunological benefit in the treatment of periodontitis. Metabolic stimulation with L-ornithine, but not L-arginine, is preferable for CD163+ Mφs subpopulation in periodontitis-affected gingiva.

The Role of Innate Immune Cells in Tumor Invasion and Metastasis

Simple Summary

Tumor invasion and metastasis are one of the main reasons patients succumb to cancer. In this review, we summarize recent studies which provide evidence on the involvement of cells of the innate immune system and their function in invasion and metastasis.

Abstract

Metastasis is considered one of the hallmarks of cancer and enhanced tumor invasion and metastasis is significantly associated with cancer mortality. Metastasis occurs via a series of integrated processes involving tumor cells and the tumor microenvironment. The innate immune components of the microenvironment have been shown to engage with tumor cells and not only regulate their proliferation and survival, but also modulate the surrounding environment to enable cancer progression. In the era of immune therapies, it is critical to understand how different innate immune cell populations are involved in this process. This review summarizes recent literature describing the roles of innate immune cells during the tumor metastatic cascade.

Interactions of helminths with macrophages: therapeutic potential for inflammatory intestinal disease

Macrophages represent a highly heterogeneous and plastic cell type found in most tissues of the body; the intestine is home to enormous numbers of these cells. Considerable interest surrounds the 'M2 macrophage,' as it is able to control and regulate inflammation, while promoting tissue repair. Areas covered: As potent inducers of M2 macrophages, intestinal helminths and helminth-derived products are ideal candidates for small molecule drug design to drive M2 macrophage polarization. Several gastrointestinal helminths have been found to cause M2 macrophage-inducing infections. This review covers current knowledge of helminth products and their impact on macrophage polarization, which may in the future lead to new therapeutic strategies. A literature search was performed using the following search terms in PubMed: M2 macrophage, alternative activation, helminth products, helminth ES, helminth therapy, nanoparticle, intestinal macrophages. Other studies were selected by using references from articles identified through our original literature search. Expert commentary: While the immunomodulatory potential of helminth products is well established, we have yet to fully characterize many components of the intestinal helminth product library. Current work aims to identify the protein motifs responsible for modulation of macrophages and other components of the immune system.

4-Acetylantroquinonol B inhibits lipopolysaccharide-induced cytokine release and alleviates sepsis through of MAPK and NFκB suppression

Background

Antrodia cinnamomea is an indigenous medicinal mushroom in Taiwan, commonly used for the treatment of cancers and inflammatory disorders. 4-acetylantroquinonol B (4AAQB) is one of the active component isolated from the mycelium of A. cinnamomea. However, whether 4AAQB exhibits anti-inflammatory effect is not clear.

Methods

The anti-inflammatory activity of 4AAQB was examined by ELISA to measure the pro-inflammatory cytokines production in lipopolysaccharide (LPS)-simulated RAW264.7 cells, peritoneal macrophages and in mice. The effect of 4AAQB for MAPK kinase molecules phosphorylation in LPS-stimulated RAW264.7 macrophage including ERK, JNK and p38 were evaluated. The in vivo efficacy of 4AAQB was also demonstrated.

Results

In the present study, we found that 4AAQB exhibits anti-inflammatory effects inhibit tumor necrosis factor-α (TNF-α)/interleukin-6 (IL-6) releasing and LPS-stimulated phagocytes migration without affect cell growth. In addition, the MAPK kinase molecules phosphorylation in LPS-stimulated RAW264.7 macrophage including ERK, JNK and p38 was inhibited by 4AAQB. The phosphorylation of NFκB subunit p65 and IkBα were also decreased after 4AAQB treatment. Furthermore, 4AAQB attenuates the cytokine production in LPS-induced and CLP-induced septic mice.

Conclusion

These results showed that 4AAQB exhibited anti-inflammatory property both in vitro and in vivo, suggesting that 4AAQB may be a therapeutic candidate which used in inflammatory disorders treatment.

Electronic supplementary material

The online version of this article (10.1186/s12906-018-2172-2) contains supplementary material, which is available to authorized users.

Toll-Like Receptor Ligands and Interferon-γ Synergize for Induction of Antitumor M1 Macrophages

Tumor-associated macrophages may either promote or suppress tumor growth depending on their activation status. Interferon-γ (IFN-γ) has been identified as a key factor for inducing tumoricidal M1 phenotype in macrophages. However, it remains unclear whether IFN-γ is sufficient or if additional stimuli are required. Here, we tested IFN-γ and a panel of toll-like receptor (TLR) agonists for the ability to activate murine macrophages toward a tumoricidal M1 phenotype. The following TLR ligands were used: TLR1/TLR2 agonist Pam3CSK4, TLR2/TLR6 agonist lipotechoic acid, TLR3 agonist poly(I:C), TLR4 agonist lipopolysaccharide (LPS), TLR5 agonist flagellin, TLR7 agonist CL264, and TLR9 agonist CpG. We used an in vitro growth inhibition assay to measure both cytotoxic and cytostatic activity of mouse macrophages against Lewis lung carcinoma (LLC) and MOPC315 plasmacytoma tumor cells. Production of nitric oxide (NO) and cytokines by activated macrophages was quantified. We found that IFN-γ alone was not able to render macrophages tumoricidal. Similarly, macrophage activation with single TLR agonists was inefficient. In sharp contrast, IFN-γ was shown to synergize with TLR agonists for induction of macrophage tumoricidal activity and production of both NO and pro-inflammatory cytokines (TNF-α, IL-12p40, and IL-12p70). Furthermore, IFN-γ was shown to suppress macrophage IL-10 secretion induced by TLR agonists. NO production was necessary for macrophage tumoricidal activity. We conclude that two signals from the microenvironment are required for optimal induction of antitumor M1 macrophage phenotype. Combination treatment with IFN-γ and TLR agonists may offer new avenues for macrophage-based cancer immunotherapy.

Functions of arginase isoforms in macrophage inflammatory responses: impact on cardiovascular diseases and metabolic disorders

Macrophages play a paramount role in immunity and inflammation-associated diseases, including infections, cardiovascular diseases, obesity-associated metabolic imbalances, and cancer. Compelling evidence from studies of recent years demonstrates that macrophages are heterogeneous and undergo heterogeneous phenotypic changes in response to microenvironmental stimuli. The M1 killer type response and the M2 repair type response are best known, and are two extreme examples. Among other markers, inducible nitric oxide synthase and type-I arginase (Arg-I), the enzymes that are involved in l-arginine/nitric oxide (NO) metabolism, are associated with the M1 and M2 phenotype, respectively, and therefore widely used as the markers for characterization of the two macrophage phenotypes. There is also a type-II arginase (Arg-II), which is expressed in macrophages and prevalently viewed as having the same function as Arg-I in the cells. In contrast to Arg-I, little information on the role of Arg-II in macrophage inflammatory responses is available. Emerging evidence, however, suggests that differential roles of Arg-I and Arg-II in regulating macrophage functions. In this article, we will review recent developments on the functional roles of the two arginase isoforms in regulation of macrophage inflammatory responses by focusing on their impact on the pathogenesis of cardiovascular diseases and metabolic disorders.

A defective TLR4 signaling for IFN-β expression is responsible for the innately lower ability of BALB/c macrophages to produce NO in response to LPS as compared to C57BL/6

C57BL/6 mice macrophages innately produce higher levels of NO than BALB/c cells when stimulated with LPS. Here, we investigated the molecular events that account for this intrinsic differential production of NO. We found that the lower production of NO in BALB/c is not due to a subtraction of L-arginine by arginase, and correlates with a lower iNOS accumulation, which is independent of its degradation rate. Instead, the lower accumulation of iNOS is due to the lower levels of iNOS mRNA, previously shown to be also independent of its stability, suggesting that iNOS transcription is less efficient in BALB/c than in C57BL/6 macrophages. Activation of NFκB is more efficient in BALB/c, thus not correlating with iNOS expression. Conversely, activation of STAT-1 does correlate with iNOS expression, being more prominent in C57BL/6 than in BALB/c macrophages. IFN-β and IL-10 are more highly expressed in C57BL/6 than in BALB/c macrophages, and the opposite is true for TNF-α. Whereas IL-10 and TNF-α do not seem to participate in their differential production of NO, IFN-β has a determinant role since 1) anti-IFN-β neutralizing antibodies abolish STAT-1 activation reducing NO production in C57BL/6 macrophages to levels as low as in BALB/c cells and 2) exogenous rIFN-β confers to LPS-stimulated BALB/c macrophages the ability to phosphorylate STAT-1 and to produce NO as efficiently as C57BL/6 cells. We demonstrate, for the first time, that BALB/c macrophages are innately lower NO producers than C57BL/6 cells because they are defective in the TLR-4-induced IFN-β-mediated STAT-1 activation pathway.

Peripheral helper lymphocytes produce interleukin 12 in cancer patients

The aim of the study was to seek evidence for the production of IL-12 by CD4(+) T lymphocytes in in vitro and ex vivo trials. We performed in vitro trials with spleen cells from mice subjected to carcinogenesis, as well as ex vivo trials with cells obtained from the peripheral blood of healthy individuals and cancer patients. We were able to verify a significantly increased expression of IL-12 in CD4(+) T lymphocytes from mice and patients with tumors, compared to controls. Follow-up studies are needed to clarify whether this difference is related to being in a chronic disease state or whether it is an attempt by the immune system to produce an anti-tumor response, since T lymphocytes from healthy donors were not able to produce IL-12 when in contact with polyclonal stimuli. We concluded that, in cancer, T helper cells are capable of synthesizing IL-12, raising the question of whether we are faced with another profile, Th12.

Reactive oxygen species and nitric oxide in cutaneous leishmaniasis

Cutaneous leishmaniasis affects millions of people around the world. Several species of Leishmania infect mouse strains, and murine models closely reproduce the cutaneous lesions caused by the parasite in humans. Mouse models have enabled studies on the pathogenesis and effector mechanisms of host resistance to infection. Here, we review the role of nitric oxide (NO), reactive oxygen species (ROS), and peroxynitrite (ONOO⁻) in the control of parasites by macrophages, which are both the host cells and the effector cells. We also discuss the role of neutrophil-derived oxygen and nitrogen reactive species during infection with Leishmania. We emphasize the role of these cells in the outcome of leishmaniasis early after infection, before the adaptive T_h-cell immune response.

CD101 expression and function in normal and rheumatoid arthritis-affected human T cells and monocytes/macrophages

OBJECTIVE

It was recently reported that CD101 surface expression discriminates potency among CD4+CD25+ FoxP3+ regulatory T cells in the mouse. We investigated whether CD101 may also have a role in the suppressor function of regulatory T cells in humans given that the latter population may affect the autoimmune response in patients with rheumatoid arthritis (RA).

METHODS

Sorted T cells and monocyte/macrophage cell populations were analyzed by flow cyto metry using conjugated antibodies specific for cell-surface markers. T cell proliferation assays were conducted by [(3)H]thymidine incorporation and CD8(high) cytotoxicity measurements by Cyto-Scan-LDH cytotoxicity assays. ELISA were used to measure cytokines in cell culture supernatants and Western blotting was performed for profiling mitogen-activated protein (MAP) kinase activation using specific antiphospholipid antibodies.

RESULTS

CD101 expression coincided with PMA-induced monocyte/leukocyte lineage differentiation. CD8(high)CD101- T cells exhibited greater cytotoxic activity than CD8(high)CD101+ T cells, while no difference was observed between CD4CD25(high)CD101+ and CD4CD25(high)CD101- Treg inhibitory activity through responder T cells. LPS-induced proinflammatory cytokine production and p38 MAP kinase activation were made possible by ligation of CD101 with an anti-CD101 antibody F(ab')(2) fragment.

CONCLUSION

These results suggested a modulatory/coregulatory function of CD101 in the human immune system, in contrast to murine models, in which CD101 surface expression discriminates potency among FoxP3+ regulatory T cells. Cytotoxic CD8(high)CD101+ T cells were markedly less cytotoxic than CD8(high) T cells negative for the CD101 antigen and were conspicuously downregulated in patients with RA, suggesting a possible role for CD101 expression and function in the control of certain manifestations of RA pathology.

Susceptibility to Yersinia pseudotuberculosis infection is linked to the pattern of macrophage activation

T helper 1 cells play a crucial role in the clearance of Yersinia pseudotuberculosis infection. By producing cytokines and presenting antigens to T cells, activated macrophages can orientate the adaptive immune response. The pathway used by macrophages to metabolize arginine has been employed as an important parameter to discriminate their activation state. In this study, the pattern of macrophage activation in Y. pseudotuberculosis-infected BALB/c (Yersinia-susceptible) and C57BL/6 (Yersinia-resistant) mice and their immunostimulatory capacity were analysed. In the early phase of infection, macrophages obtained from C57BL/6 mice produced higher levels of NO, lower arginase activity, and larger amounts of IL-12 and TNF-alpha than macrophages from BALB/c mice. On the other hand, macrophages derived from BALB/c mice produced higher levels of IL-10 and TGF-beta than C57BL/6 mice. The Y. pseudotuberculosis infection leads to a fall in the macrophage immunostimulatory capacity of both strains of mice, with T-cell proliferation significantly reduced 12 h after infection. Moreover, we observed in the supernatant of co-culture of macrophages from infected mice with T lymphocytes from heat-killed Yersinia-immunized mice lower IFN-gamma production by cells from BALB/c mice than by C57BL/6 mice, and IL-4 was produced only by BALB/c mice on the first- and third-day post-infection. These results suggest that the pattern of macrophage activation is associated with susceptibility and resistance to Y. pseudotuberculosis infection in BALB/c and C57BL/6 mice.

New roles for mononuclear phagocytes in cancer biology

The primary focus in the pathogenesis and treatment of human malignancies has been the tumor cell. However, the biologic properties of a malignancy are not all intrinsically determined. Interactions between heterogeneous cell populations influence the growth and survival of both normal and malignant cells. Studies defining the origin of endothelial cells involved in tumor angiogenesis first demonstrated the contributions of normal cellular environment. Recently, the mononuclear phagocyte lineage has been found to have biologically and clinically significant tumor enhancing and tumor suppressive effects. This article reviews the multiple roles of mononuclear phagocytes in cancer biology. A companion manuscript (J Pediatr Hematol Oncol. 2008, in press) describes the targeting of these cells for therapeutic benefit. Incorporating these strategies into future childhood cancer protocols could be an innovative approach for improving patient outcome.

Pattern of macrophage activation in yersinia-resistant and yersinia-susceptible strains of mice

Th1 cells, in cooperation with activated macrophages, are required to overcome Yersinia enterocolitica infection in mice. The pathway macrophages utilize to metabolize arginine can alter the outcome of inflammation in different ways. The objective of this study was to verify the pattern of macrophages activation in Y. enterocolitica infection of BALB/c (Yersinia-susceptible) and C57BL/6 (Yersinia-resistant) mice. Both strains of mice were infected with Y. enterocolitica O:8 WA 2707. Peritoneal macrophages and spleen cells were obtained on the 1st, 3rd and 5th day post-infection. The iNOS and the arginase activities were assayed in supernatants of macrophage cultures, by measuring their NO/citrulline and ornithine products, respectively. TGFbeta-1 production was also assayed. The Th1 and Th2 responses were evaluated in supernatants of lymphocyte cultures, by IFN-gamma and IL-4 production. Our results showed that in the early phase of Y. enterocolitica infection (1st and 3rd day), the macrophages from C57BL/6 mice produced higher levels of NO/citrulline and lower levels of ornithine than macrophages from BALB/c mice. The infection with Y. enterocolitica leads to an increase in the TGF-beta1 and IL-4 production by BALB/c mice and to an increase in the IFN-gamma levels produced by C57BL/6 mice. These results suggest that Y. enterocolitica infection leads to the modulation of M1 macrophages in C57Bl/6 mice, and M2 macrophages in BALB/c mice. The predominant macrophage population (M1 or M2) at the 1st and 3rd day of infection thus seems to be important in determining Y. enterocolitica susceptibility or resistance.

Differential sensitivity of C57BL/6 (M-1) and BALB/c (M-2) macrophages to the stimuli of IFN-gamma/LPS for the production of NO: correlation with iNOS mRNA and protein expression

C57BL/6 and BALB/c mice are prototype hosts for the study of resistance and susceptibility to several infectious diseases. In many cases, resistance of C57BL/6 is due to the microbicidal effect of nitric oxide (NO) produced by macrophages in response to interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha), mainly secreted by Th1 cells and macrophages, respectively. BALB/c, usually unable to give rise to Th1 lymphocytes, does not control certain infections. However, we and others have previously observed that regardless of the adaptive immune response, C57BL/6 (M-1) macrophages are far more sensitive to the stimulus of IFN-gamma-plus lipopolysaccharide (LPS) for the production of NO than are BALB/c (M-2) cells, a feature that might also account for resistance. Here, we report that the differential production of NO by M-1 and M-2 macrophages correlates with the accumulation of inducible nitric oxide synthase (iNOS) mRNA and protein, which shows that expression of iNOS is differentially regulated in M-1 and M-2 cells. The higher accumulation of iNOS mRNA in M-1 cells is independent of its stability, and, thus, it is possible that transcription of the iNOS gene in these cells may be more efficient than in M-2 cells. A remarkable finding is that the level of iNOS protein is much higher in M-1 macrophages than in M-2 cells, as compared with the mRNA levels, which makes us speculate that differential translational or posttranslational controls of iNOS gene are operative.

MAPK phosphatases--regulating the immune response

Mitogen-activated protein kinase (MAPK) phosphatases (MKPs) are protein phosphatases that dephosphorylate both the phosphothreonine and phosphotyrosine residues on activated MAPKs. Removal of the phosphates renders MAPKs inactive, effectively halting their cellular function. In recent years, evidence has emerged that, similar to MAPKs, MKPs are pivotal in the regulation of immune responses. By deactivating MAPKs, MKPs can modulate both innate and adaptive immunity. A number of immunomodulatory agents have been found to influence the expression of MKP1 in particular, highlighting the central role of this phosphatase in immune regulation. This Review discusses the properties, function and regulation of MKPs during immune responses.

Human conjunctival epithelial cells lack lipopolysaccharide responsiveness due to deficient expression of MD2 but respond after interferon-gamma priming or soluble MD2 supplementation

Inflammatory responses to Gram-positive and Gram-negative bacterial cell wall components are initiated by Toll-like receptor 2 (TLR2) and TLR4, respectively. Therefore, the existence of functionally active TLR2 and TLR4 in human conjunctival epithelial cells (HCEC) are critical for the effective host defense against bacterial infections in the eye. We examined the ability of HCEC to respond to TLR4 ligand, lipopolysaccharide (LPS), or TLR2 ligands, lipoteichoic acid (LTA) and peptidoglycan (PGN) using the Chang conjunctival epithelial cell line and the primary conjunctival epithelial cell line (IOBA-NHC) as in vitro models. Incubation of Chang cells with LPS (1 to 1,000 ng/ml) failed to stimulate IL-6 production where as stimulation with LTA or PGN resulted in marked increases in IL-6 production. Semi-quantitative RT-PCR and immunofluorescence analyses showed that Chang cells express TLR2 and TLR4 mRNA and proteins. However, these cells expressed little or no mRNA encoding MD2, an accessory molecule required for TLR4 signaling. Incubation of Chang epithelial cells with interferon-gamma (IFNgamma), but not TNF-alpha, stimulated MD2 mRNA expression and restored LPS responsiveness. In addition, when Chang cell cultures were supplemented with soluble MD2, LPS was able to stimulate IL-6 production. The lack of LPS response, deficient expression of MD2, and induction of MD2 expression and LPS response after IFNgamma priming, were also evident in IOBA-NHC cells. These results demonstrate that HCEC lack LPS responsiveness due to deficient expression of MD2 and that the response can be restored by IFN-gamma priming or MD2 supplementation.

Differential activation of macrophages in vitro by lectin Concanavalin A, Phytohemagglutinin and Wheat germ agglutinin: production and regulation of nitric oxide

The role of Concanavalin A (ConA), Phytohemagglutinin (PHA) and Wheat germ agglutinin (WGA) in the activation of murine peritoneal macrophages particularly with reference to production and regulation of nitric oxide (NO) has been investigated. Macrophages on treatment with ConA and PHA showed significantly enhanced production of NO, which was dose and time dependent. On the other hand macrophages treated with WGA did not produce NO. L-N-monomethyal-l-arginine (L-NMMA), an inhibitor of NOS inhibited the ConA and PHA induced NO production. ConA and PHA treatment of macrophages induced transcription of iNOS gene and the enhanced expression of iNOS protein. Pharmacological inhibitors of PI3 kinase-Wortmannin, tyrosine kinase-Genestein, protein kinase C-H-7 and p42/44-PD98059 inhibited the ConA and PHA induced production of NO and p38 MAP kinase inhibitor SB202190 inhibited NO production only in ConA treated macrophage, while Galphai protein inhibitor-PTX and JNK inhibitor-SP600125 inhibited NO production in PHA treated macrophages. Tyrophostin (AG490), an inhibitor of JAK2 and TMB-8, an intracellular calcium immobilizing agent also inhibited the ConA and PHA induced NO production, suggesting the involvement of JAK-STAT pathway and calcium. The data also provides the relative measure and importance of different key signaling molecules in the regulation of NO production by macrophages on activation.

Protein vaccination with the HER2/neu extracellular domain plus anti-HER2/neu antibody-cytokine fusion proteins induces a protective anti-HER2/neu immune response in mice

Previously protein vaccines consisting of the extracellular domain of HER2/neu (ECD(HER2)) were shown to elicit an immune response that does not provide protection against transplantable tumors expressing HER2/neu. Here, we showed that when mice were vaccinated with a mixture of human ECD(HER2) and anti-human HER2/neu IL-12, IL-2 or GM-CSF fusion proteins, significant retardation of the growth of a syngeneic carcinoma expressing rat HER2/neu, and long-term survivors were observed. Immune sera inhibited the in vitro growth of SK-BR-3, a human breast cancer overexpressing HER2/neu. Transfer of immune sera into mice challenged with TUBO also led to partial inhibition of tumor growth. Splenocytes from mice vaccinated with ECD(HER2) plus IgG3-(GM-CSF) incubated with ECD(HER2) demonstrated significant proliferation and IFN-gamma secretion. Taken together these results suggest that vaccines including ECD(HER2) and Ab-cytokine fusion proteins may be used to elicit both humoral and cell-mediated responses against HER2/neu.

A potential role of macrophage activation in the treatment of cancer

One of the functions of macrophages is to provide a defense mechanism against tumor cells. In the last decades the mechanism of tumor cell killing by macrophages have been studied extensively. The tumor cytotoxic function of macrophages requires stimulation either with bacterial cell wall products such as lipopolysaccharide (LPS) or muramyldipeptide (MDP) or with cytokines such as interferon-gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Activated macrophages secrete several substances that are directly involved in tumor cell killing i.e. tumor necrosis factor (TNF) and nitric oxide (NO). On the other hand, substances are secreted that are able to stimulate tumor cell growth, depending on the stage and the nature of the tumor. Several clinical trials have been performed aiming at the activation of macrophages or dendritic cells, a subpopulation of the macrophages. In this review we will summarize and discuss experimental studies and clinical trials based on the activation of macrophages.

Effect of Tityus serrulatus venom on cytokine production and the activity of murine macrophages

THE purpose of this study was to investigate the effects of Tityus serrulatus venom (TSV) on murine peritoneal macrophages evaluated in terms of activation. The effects of crude TSV were analysed by detection of cytokines, oxygen intermediate metabolites (H2O2) and nitric oxide (NO) in supernatants of peritoneal macrophages. Several functional bioassays were employed including an in vitro model for envenomating: cytotoxicity of TSV was assessed using the lyses percentage. Tumor necrosis factor (TNF) activity was assayed by measuring its cytotoxic activity on L-929 cells, and interleukin-6 (IL-6) and interferon-gamma (IFN-gamma) were assayed by enzyme-linked immunosorbent assay, whereas NO levels were detected by Griess colorimetric reactions in culture supernatant of macrophages incubated with TSV and subsequently exposed to either lipopolysaccharide or IFN-gamma. Incubation of macrophages with TSV increased production of IL-6 and IFN-gamma in a dose-dependent manner. TNF production was not detected in supernatants treated with TSV at any concentration. The increase in IL-6 secretion was not associated with concentration-dependent cytoxicity of TSV on these cells. These data suggest that the cytotoxicity does not appear to be the main cause of an increased cytokine production by these cells. Although NO is an important effector molecule in macrophage microbicidal activity, the inducing potential of the test compounds for its release was found to be very moderate, ranging from 125 to 800 mM. Interestingly, NO levels of peritoneal macrophages were increased after IFN-gamma. Moreover, NO production had an apparent effect on macrophage activity. The results obtained here also shown that the TSV induces an important elevation in H2O2 release. These results combined with NO production suggest that TSV possesses significant immunomodulatory activities capable of stimulating immune functions in vitro.

Signaling and proapoptotic functions of transformed cell-derived reactive oxygen species

Transformed fibroblasts generate extracellular superoxide anions through the recently identified membrane-associated NADPH oxidase. These cell-derived superoxide anions exhibit signaling functions such as regulation of proliferation and maintenance of the transformed state. Their dismutation product hydrogen peroxide regulates the intracellular level of catalase, whose activity has been observed to be upregulated in certain transformed cells. After glutathione depletion, transformed cell-derived reactive oxygen species (ROS) exhibit apoptosis-inducing potential through the metal-catalyzed Haber-Weiss reaction. Moreover, transformed cell-derived ROS represent key elements for selective and efficient apoptosis induction by natural antitumor systems (such as fibroblasts, granulocytes and macrophages). These effector cells release peroxidase, which utilizes target cell-derived hydrogen peroxide for HOCl synthesis. In a second step, HOCl interacts with target cell-derived superoxide anions and forms apoptosis-inducing hydroxyl radicals. In a parallel signaling pathway, effector cell-derived NO interacts with target cell-derived superoxide anions and generates the apoptosis inducer peroxynitrite. Therefore, transformed cell-derived ROS determine transformed cells as selective targets for induction of apoptosis by these effector systems. It is therefore proposed that transformed cell derived ROS interact with associated cells to exhibit directed and specific signaling functions, some of which are beneficial and some of which can become detrimental to transformed cells.

Regulation of nitric oxide production by murine peritoneal macrophages treated in vitro with chemokine monocyte chemoattractant protein 1

Monocyte chemoattractant protein 1 (MCP-1) is an important mediator of monocyte/macrophage recruitment and activation at the sites of chronic inflammation and neoplasia. In the current study, the role of nitrogen monoxide (NO) in the activation of murine peritoneal macrophages to the tumoricidal state in response to in vitro MCP-1 treatment and the regulatory mechanisms involved therein were investigated. Murine peritoneal macrophages upon activation with MCP-1 showed a dose- and time-dependent production of NO together with increased tumoricidal activity against P815 mastocytoma cells. N-monomethyl-l-arginine (L-NMMA), a specific inhibitor of the l-arginine pathway, inhibited the MCP-1-induced NO secretion and generation of macrophage-mediated tumoricidal activity against P815 (NO-sensitive, TNF-resistant) cells but not the L929 (TNF-sensitive, NO-resistant) cells. These results indicated l-arginine-dependent production of NO to be one of the effector mechanisms contributing to the tumoricidal activity of MCP-1-treated macrophages. Supporting this fact, expression of iNOS mRNA was also detected in the murine peritoneal macrophages upon treatment with MCP-1. Investigating the signal transduction pathway responsible for the NO production by the MCP-1-activated murine peritoneal macrophages, it was observed that the pharmacological inhibitors wortmannin, H-7 (1-(5-isoquinoline sulfonyl)-2-methyl piperazine dihydrochloride), and PD98059 blocked the MCP-1-induced NO production, suggesting the probable involvement of phosphoinositol-3-kinase, protein kinase C, and p42/44 MAPkinases in the above process. Various modulators of calcium and calmodulin (CaM) such as EGTA, nifedipine, TMB-8 (3,4,5-trimethoxybenzoic acid-8-(diethylamino)octyl ester), A23187, and W-7 (N-(6-aminohexyl)-5-chloro-1-napthalenesulfonamide) were also found to modulate the in vitro macrophage NO release in response to MCP-1. This observation indicated the regulatory role of calcium/CaM in the process of MCP-1-induced macrophage NO production. Similarly, the role of serine/threonine and protein tyrosine phosphatases in the above pathway was suggested using the specific inhibitors of these phosphatases, okadaic acid and sodium orthovanadate.

Tumor cytotoxicity of peritoneal macrophages induced by OK-432

In the present study we investigated the enhancement of cytotoxicity of peritoneal macrophages induced by OK-432. Rats received an i.p. injection of OK-432 at doses of 0.1, 0.5 or 1.0 KE/rat. Two days later, rats were sacrificed and peritoneal macrophages were isolated. Then the number of macrophages was counted, and the macrophages were analyzed for their lactic dehydrogenase (LDH) activity, acid phosphatase (ACP) activity, phagocytic activity, secretion of nitric oxide (NO) and cytotoxicity. The number of peritoneal macrophages, the activity of LDH and ACP, phagocytic activity, NO secretion, and cytotoxicity were increased with the increasing doses of OK-432. The results suggested that OK-432 enhanced tumor cytotoxicity of peritoneal macrophages by three steps. The first step is to attract a great number of macrophages into the peritoneal cavity. The second step is to enhance the phagocytic and eliminating function of these macrophages. The last step is to increase the non-contact cytotoxicity of macrophages.

M-1/M-2 macrophages and the Th1/Th2 paradigm

Evidence is provided that macrophages can make M-1 or M-2 responses. The concept of M-1/M-2 fomented from observations that macrophages from prototypical Th1 strains (C57BL/6, B10D2) are more easily activated to produce NO with either IFN-gamma or LPS than macrophages from Th2 strains (BALB/c, DBA/2). In marked contrast, LPS stimulates Th2, but not Th1, macrophages to increase arginine metabolism to ornithine. Thus, M-1/M-2 does not simply describe activated or unactivated macrophages, but cells expressing distinct metabolic programs. Because NO inhibits cell division, while ornithine can stimulate cell division (via polyamines), these results also indicate that M-1 and M-2 responses can influence inflammatory reactions in opposite ways. Macrophage TGF-beta1, which inhibits inducible NO synthase and stimulates arginase, appears to play an important role in regulating the balance between M-1 and M-2. M-1/M-2 phenotypes are independent of T or B lymphocytes because C57BL/6 and BALB/c NUDE or SCID macrophages also exhibit M-1/M-2. Indeed, M-1/M-2 proclivities are magnified in NUDE and SCID mice. Finally, C57BL/6 SCID macrophages cause CB6F1 lymphocytes to increase IFN-gamma production, while BALB/c SCID macrophages increase TGF-beta production. Together, the results indicate that M-1- or M-2-dominant macrophage responses can influence whether Th1/Th2 or other types of inflammatory responses occur.

Transcriptional basis for the differences in inducible nitric oxide synthase (iNOS) expression between nonmetastatic and metastatic murine melanoma cell lines

An inverse correlation exists between expression of the inducible nitric oxide synthase (iNOS) gene and the ability of cloned K1735 murine melanoma cell lines to metastasize. We have analyzed the basis for the difference in iNOS induction by interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS) in metastatic and non-metastatic K1735 cells. Nuclear run-on (NRO) assays revealed an upregulation of iNOS transcription on treatment with IFN-gamma plus LPS in nonmetastatic cells but not in a metastatic line. Transcription factors IFN regulatory factor 1 (IRF-1) and NF-kappaB were induced and functional in both metastatic and nonmetastatic K1735 lines treated with IFN-gamma plus LPS. Furthermore, a reporter construct driven by the wild-type iNOS promoter was transcriptionally activated in both nonmetastatic and metastatic cells. The iNOS-inducible phenotype was dominant in somatic cell hybrids generated by the fusion of nonmetastatic and metastatic cells, suggesting that no inhibitors of iNOS expression are present in metastatic cells. We conclude that the selective block in iNOS transcription in metastatic K1735 cells is likely due to an alteration in iNOS gene regulatory sequences. However, no such alteration was detected within the 1.7 kb iNOS promoter region in metastatic cells.

Gamma interferon augments macrophage activation by lipopolysaccharide by two distinct mechanisms, at the signal transduction level and via an autocrine mechanism involving tumor necrosis factor alpha and interleukin-1

When given in the presence of gamma interferon (IFN-gamma), otherwise nontoxic doses of lipopolysaccharide (LPS or endotoxin) become highly lethal for mice. The mechanisms of this synergistic toxicity are not known. We considered the possibility that an interaction between the LPS-induced NF-kappaB and IFN-gamma-induced JAK-STAT pathways at the pretranscriptional level may enhance the LPS-induced signals. To test this hypothesis, we incubated murine macrophage RAW 264.7 cells with IFN-gamma for 2 h before addition of different doses of LPS. Consistent with the synergistic induction of inducible nitric oxide synthase mRNA and nitric oxide production by a combination of LPS and IFN-gamma, IFN-gamma strongly augmented LPS-induced NF-kappaB activation and accelerated the binding of NF-kappaB to DNA to as early as 5 min. In agreement with this, IFN-gamma pretreatment promoted rapid degradation of IkappaB-alpha but not that of IkappaB-beta. Inhibition of protein synthesis during IFN-gamma treatment suppressed LPS-initiated NF-kappaB binding. A rapidly induced protein appeared to be involved in IFN-gamma priming. Preincubation of cells with antibodies to tumor necrosis factor alpha or the interleukin-1 receptor partially reduced the priming effect of IFN-gamma. In a complementary manner, LPS enhanced the activation of signal-transducing activator of transcription 1 by IFN-gamma. These data suggest novel mechanisms for the synergy between IFN-gamma and LPS by which they cross-regulate the signal-transducing molecules. Through this mechanism, IFN-gamma may transform a given dose of LPS into a lethal stimulus capable of causing sepsis. It may also serve a beneficial purpose by enabling the host to respond quickly to relatively low doses of LPS and thereby activating antibacterial defenses.

Effect of intraperitoneally administered recombinant murine granulocyte-macrophage colony-stimulating factor (rmGM-CSF) on the cytotoxic potential of murine peritoneal cells

We studied the effect of recombinant murine granulocyte-macrophage colony-stimulating factor (rmGM-CSF) on the cytotoxic potential of murine peritoneal cells. Mice received rmGM-CSF intraperitoneally using different dosages and injection schemes. At different time points after the last injection, mice were sacrificed, peritoneal cells isolated and their tumour cytotoxicity was determined by a cytotoxicity assay using syngeneic [methyl-3H]thymidine-labelled colon carcinoma cells. Also, the cytotoxic response to a subsequent in vitro stimulation with lipopolysaccharide was determined. Upon daily injection of 6000-54,000 U rmGM-CSF over a 6-day period, the number of peritoneal cells increased over ten fold with the highest rmGM-CSF dose. Increases in cell numbers was mainly due to increases in macrophage numbers. Upon injection of three doses of 3000 U rmGM-CSF per day for 3 consecutive days, the number of macrophages remained elevated for minimally 6 days. Although the peritoneal cells from rmGM-CSF-treated mice were not activated to a tumoricidal state, they could be activated to high levels of cytotoxicity with an additional in vitro stimulation of lipopolysaccharide. Resident cells isolated from control mice could be activated only to low levels of tumour cytotoxicity with lipopolysaccharide. Tumour cytotoxicity strongly correlated with nitric oxide secretion. When inhibiting nitric oxide synthase, tumour cell lysis decreased. Thus, the expanded peritoneal cell population induced by multiple injections of rmGM-CSF has a strong tumour cytotoxic potential and might provide a favourable condition for immunotherapeutic treatment of peritoneal neoplasms.

Triggering of Peritoneal Macrophages with IFN-α/β Attenuates the Expression of Inducible Nitric Oxide Synthase Through a Decrease in NF-κB Activation

Triggering peritoneal macrophages with IFN-γ and a low concentration of LPS induced the expression of the inducible form of nitric oxide synthase (iNOS). This process was significantly inhibited when IFN-α/β was added during the initial 2 h after the start of IFN-γ/LPS activation. Evaluation of the transcriptional activity using run-on assays indicated that IFN-α/β inhibited the transcription of iNOS. Transfection experiments using a 1.7-kb promoter sequence corresponding to the 5′ flanking region of the murine iNOS gene showed decreased promoter activity in the presence of type I IFNs. Analysis of the transcription factors that participate in iNOS expression revealed a marked decrease of NF-κB activation, a nuclear factor required for the transcription of this gene. The degradation of IκBα and IκBβ, which is required for the translocation of NF-κB to the nucleus, was inhibited in the presence of IFN-α/β. However, the activity of other transcription factors such as IFN regulatory factor 1, which is involved in the expression of iNOS in response to IFN-γ, was not affected by IFN-α/β stimulation. These results suggest that in the presence of IFN-α/β, the activity of the iNOS promoter is impaired, and this attenuated nitric oxide synthase expression could be important in pathophysiologic situations in which secretion of type I IFNs occurs.

Pretreatment with IFN-gamma decreases infectious complications after partial hepatectomy in the rat

Infectious postoperative complications occur commonly after hepatectomy and may lead to a long hospital stay or death. The potential beneficial effects of interferon-gamma (IFN-gamma) in this setting were evaluated in a model of hepatectomy and sepsis in rodents. Incidence of bacterial translocation was measured in animals on days 1, 2, and 5 after partial hepatectomy. Macrophage function was quantified by in vitro tumoricidal activity and superoxide anion (O2-) production. Survival after partial hepatectomy and cecal ligation and puncture (CLP) was recorded. After partial hepatectomy, bacterial translocation was decreased on days 1 and 2 in animals pretreated with IFN-gamma (p < 0.05). Macrophages from animals treated with IFN-gamma had higher in vitro tumoricidal activity and production of O2- (p < 0.05). Hepatectomized animals pretreated with IFN-gamma had an increased survival after CLP (p < 0.05). IFN-gamma may be useful in decreasing the incidence of infectious complications after partial hepatectomy.

Enhanced in vivo sensitivity of in vitro interferon-treated B16 melanoma cells to CD8 cells and activated macrophages

Mouse B16 melanoma cells maintained in vitro in the presence of interferon (IFN)-alpha become resistant to the in vitro antiproliferative effects of IFN-alpha. However, IFN-alpha-treated mice inoculated with these in vitro IFN-treated cells (B16 alpha res cells) have significantly increased life spans (ILS) and significantly higher cure rates than IFN-alpha-treated mice inoculated with B16 cells. This unexpectedly greater sensitivity of B16 alpha res cells to the in vivo antitumor effects of IFN-alpha was evaluated by in vivo cell depletion experiments. Depletion of either activated peritoneal macrophages or cytotoxic T lymphocytes (CTL) reduced the ILS of IFN-treated B16 alpha res-inoculated mice to a level comparable to that of IFN-treated B16-inoculated mice. Depletion of natural killer (NK) cells did not affect the ILS for IFN-treated B16 alpha res-inoculated mice. These studies indicate that activated macrophage and CD8 cell function, but not NK cell function, is important for the enhanced antitumor effects induced by IFN-alpha against B16 alpha res cells. Macrophage killing was unlikely to be mediated by TNF-alpha or IL-1 as B16 and B16 alpha res cells were equally sensitive to TNF-alpha and insensitive to IL-1 in vitro. Further, H-2K antigen expression is significantly more readily inducible on B16 alpha res cells than on B16 cells, consistent with enhanced CD8-mediated killing due to increased MHC class I antigen expression.

Dexamethasone inhibits nitric oxide-mediated cytotoxicity via effects on both macrophages and target cells

In order to evaluate the mode of action of dexamethasone (DEX) on macrophage-mediated cytotoxicity and to understand its association with nitric oxide (NO) production, the effect of DEX on macrophage- and spermine NONOate-mediated cytotoxicity was studied. DEX caused 100% inhibition of cytotoxicity by LPS- and IFN gamma-activated macrophages whereas it caused only partial inhibition of NO production. Inhibition of macrophage-mediated cytotoxicity by DEX was not reversed by supplementation of rTNF alpha. The partial inhibition of NO production by DEX was due to partial inhibition of iNOS mRNA expression. Incubation of macrophages with DEX for up to 24 h prior to activation did not cause further inhibition of NO production. DEX failed to inhibit NO production if added 6 h after addition of LPS and IFN gamma. Addition of P815 cells after the onset of NO production resulted in partial restoration of cytotoxicity in DEX-treated macrophages. Incubation of P815 cells with spermine NONOate, a synthetic NO donor, resulted in P815 cell lysis, which was dose-dependent, had a lag phase of 3 h and was blocked by hemoglobin. DEX also inhibited spermine NONOate-mediated tumor cell lysis, indicating that DEX may have a protective effect on tumor targets. These results indicate that DEX inhibits macrophage-mediated cytotoxicity by decreasing NO production and by inhibiting the cytotoxic effects of NO on the target cells.