Inhibition of interleukin-10 signaling in lung dendritic cells by toll-like receptor 4 ligands

Shaping of the alveolar landscape by respiratory infections and long-term consequences for lung immunity

Respiratory infections and especially viral infections, along with other extrinsic environmental factors, have been shown to profoundly affect macrophage populations in the lung. In particular, alveolar macrophages (AMs) are important sentinels during respiratory infections and their disappearance opens a niche for recruited monocytes (MOs) to differentiate into resident macrophages. Although this topic is still the focus of intense debate, the phenotype and function of AMs that recolonize the niche after an inflammatory insult, such as an infection, appear to be dictated in part by their origin, but also by local and/or systemic changes that may be imprinted at the epigenetic level. Phenotypic alterations following respiratory infections have the potential to shape lung immunity for the long-term, leading to beneficial responses such as protection against allergic airway inflammation or against other infections, but also to detrimental responses when associated with the development of immunopathologies. This review reports the persistence of virus-induced functional alterations in lung macrophages, and discusses the importance of this imprinting in explaining inter-individual and lifetime immune variation.

The Monocyte, a Maestro in the Tumor Microenvironment (TME) of Breast Cancer

Simple Summary

Breast cancer is one of the most prevalent cancers worldwide, surpassing lung cancer as the leading cause of overall cancer incidence. Available possible treatments nowadays include chemotherapy, hormonal therapy, and HER2-targeted therapy. Chemotherapy is notorious for its severe adverse effects. On the other hand, hormonal and HER2-targeted therapies only cover a narrow range of breast cancer subtypes. Accordingly, it is important to shed light on other therapy options. For this reason, immunotherapy nowadays is one of the most important research topics. It can be accomplished either by enhancing the pro-inflammatory immunity or suppressing the anti-inflammatory immunity. This review article aims to shed light on the importance of monocytes in the TME of breast cancer. The review also aims to highlight the behavior of the monocyte-derived populations, especially the anti-inflammatory populations. Thus, suppressing this anti-inflammatory activity might have a remarkable impact on future immunotherapy research.

Abstract

Breast cancer (BC) is well-known for being a leading cause of death worldwide. It is classified molecularly into luminal A, luminal B HER2−, luminal B HER2+, HER2+, and triple-negative breast cancer (TNBC). These subtypes differ in their prognosis; thus, understanding the tumor microenvironment (TME) makes new treatment strategies possible. The TME contains populations that exhibit anti-tumorigenic actions such as tumor-associated eosinophils. Moreover, it contains pro-tumorigenic populations such as tumor-associated neutrophils (TANs), or monocyte-derived populations. The monocyte-derived populations are tumor-associated macrophages (TAMs) and MDSCs. Thus, a monocyte can be considered a maestro within the TME. Moreover, the expansion of monocytes in the TME depends on many factors such as the BC stage, the presence of macrophage colony-stimulating factor (M-CSF), and the presence of some chemoattractants. After expansion, monocytes can differentiate into pro-inflammatory populations such as M1 macrophages or anti-inflammatory populations such as M2 macrophages according to the nature of cytokines present in the TME. Differentiation to TAMs depends on various factors such as the BC subtype, the presence of anti-inflammatory cytokines, and epigenetic factors. Furthermore, TAMs and MDSCs not only have a role in tumor progression but also are key players in metastasis. Thus, understanding the monocytes further can introduce new target therapies.

Granulocyte-macrophage colony-stimulating factor negatively regulates early IL-10-mediated responses

Aim:

Treatment of inflammatory disorders relies on the intervention in immune responses thereby restoring homeostasis. IL-10 is a cytokine with therapeutic potential, but until now has not been as successful as previously anticipated. A reason for this may be that IL-10 responsiveness depends on the environment of the inflamed tissue. In this study we investigated whether GM-CSF is able to influence IL-10-mediated responses.

Methodology:

Dendritic cells and macrophages were differentiated from mouse bone marrow and treated or depleted from GM-CSF prior to analyze their response to IL-10. Activity was assessed by measuring cytokine expression upon lipopolysaccharide stimulation, IL-10-induced signaling and down-stream gene expression.

Conclusion:

This study describes that GM-CSF negatively regulates IL-10-mediated responses.

Over the last couple of decades inflammatory disorders, like autoimmune disease and allergies, are becoming more prevalent in the western world. These inflammatory disorders are characterized by uncontrolled immune responses against harmless antigens or commensal bacteria. Treatment of these diseases relies on the intervention in inflammatory responses and thereby restoring the balance of the immune system. One approach used in the clinic to balance the immune system is by treating patients with molecules used by our own immune system to suppress inflammation, such as IL-10. However, treatment with IL-10 has not been as successful as previously anticipated. In this study we show that a particular signaling molecule of the immune system that contributes to inflammation negatively affects the response of immune cells toward IL-10 and thereby could contribute to the low efficacy of IL-10 treatment.

Transcellular delivery of vesicular SOCS proteins from macrophages to epithelial cells blunts inflammatory signaling

SOCS1 and -3 proteins are released by alveolar macrophages into exosomes and microparticles, respectively, which are then taken up by alveolar epithelial cells, resulting in inhibition of STAT signaling. This process was dampened by exposure to cigarette smoke and may thus be important in suppressing airway inflammation.

JAK-STAT signaling mediates the actions of numerous cytokines and growth factors, and its endogenous brake is the family of SOCS proteins. Consistent with their intracellular roles, SOCS proteins have never been identified in the extracellular space. Here we report that alveolar macrophages can secrete SOCS1 and -3 in exosomes and microparticles, respectively, for uptake by alveolar epithelial cells and subsequent inhibition of STAT activation. Secretion is tunable and occurs both in vitro and in vivo. SOCS secretion into lung lining fluid was diminished by cigarette smoking in humans and mice. Secretion and transcellular delivery of vesicular SOCS proteins thus represent a new model for the control of inflammatory signaling, which is subject to dysregulation during states of inflammation.

Interleukin-10 receptor-1 expression in monocyte-derived antigen-presenting cell populations: dendritic cells partially escape from IL-10's inhibitory mechanisms

Interleukin (IL)-10 is an important immunoregulatory cytokine that mediates its effects via a transmembrane receptor complex consisting of two different chains, IL-10R1 and IL-10R2. While IL-10R2 is ubiquitously expressed and does not bind IL-10 primarily, the expression of IL-10R1 determines cellular responsiveness. However, the current knowledge about the expression and regulation of IL-10R1 is still limited. Here we analyzed the expression of IL-10R1 on monocytic cells and demonstrated that human blood monocytes carried about 720 IL-10-binding sites on their surface. Compared with lymphocytes and various tissue cells and tissues, blood monocytes expressed the highest IL-10R1 levels. The in vitro differentiation of these cells into macrophages provoked a further increase of IL-10R1 surface expression. In contrast, their differentiation into myeloid dendritic cells (mDCs) resulted in reduced surface IL-10R1 levels. The different IL-10R1 levels expressed by monocyte-derived antigen-presenting cell populations were reflected in their different responsiveness toward IL-10. Importantly, also in vivo developed immature macrophages and mDCs showed different IL-10 sensitivity. These data suggest that, compared with monocytes and macrophages, mDCs partially escape from IL-10's inhibitory mechanisms by downregulating IL-10R1.

Regulation of the mucosal phenotype in dendritic cells by PPARγ: role of tissue microenvironment

Mucosal DCs play a critical role in tissue homeostasis. Several stimuli can induce a mucosal phenotype; however, molecular pathways that regulate development of mucosal DC function are relatively unknown. This study sought to determine whether PPARγ contributes to the development of the "mucosal" phenotype in mouse DCs. Experiments demonstrated that PPARγ activation in BMDCs induced an immunosuppressive phenotype in which BMDCs had reduced expression of MHC class II and costimulatory molecules, increased IL-10 secretion, and reduced the ability to induce CD4 T cell proliferation. Activation of PPARγ enhanced the ability of BMDC to polarize CD4 T cells toward iTregs and to induce T cell expression of the mucosal homing receptor, CCR9. Activation of PPARγ increased the ability of BMDCs to induce T cell-independent IgA production in B cells. BMDCs from PPARγ(ΔDC) mice displayed enhanced expression of costimulatory molecules, enhanced proinflammatory cytokine production, and decreased IL-10 synthesis. Contrary to the inflammatory BMDC phenotype in vitro, PPARγ(ΔDC) mice showed no change in the frequency or phenotype of mDC in the colon. In contrast, mDCs in the lungs were increased significantly in PPARγ(ΔDC) mice. A modest increase in colitis severity was observed in DSS-treated PPARγ(ΔDC) mice compared with control. These results indicate that PPARγ activation induces a mucosal phenotype in mDCs and that loss of PPARγ promotes an inflammatory phenotype. However, the intestinal microenvironment in vivo can maintain the mucosal DC phenotype of via PPARγ-independent mechanisms.

NK cells exacerbate the pathology of influenza virus infection in mice

NK cells offer a first line of defense against viruses and are considered beneficial to the host during infection. Nevertheless, little is understood regarding the phenotype and function of NK cells in the lung during influenza virus infection. We found that the frequency of NK cells in mouse lung increased during influenza infection, with the majority of a mature phenotype. Cell surface CD107a and intracellular IFN-γ were detected in cells expressing multiple NK-cell receptors in infected lung, suggesting that NK cells were activated during infection. The activating receptor NKp46 was predominantly negative on such cells, possibly as a result of encountering influenza HA. Depletion of NK cells in vivo with anti-asialo GM1 or anti-NK1.1 reduced mortality from influenza infection and surviving mice recovered their body weight. Pathology induced by NK cells was only observed with high, not medium or low-dose influenza infection, indicating that the severity of infection influences NK-cell-mediated pathology. Furthermore, adoptive transfer of NK cells from influenza-infected lung, but not uninfected lung, resulted in more rapid weight loss and increased mortality of influenza-infected mice. Our results indicate that during severe influenza infection of the lung, NK cells have a deleterious impact on the host, promoting mortality.

Delineation of regions of the Yersinia YopM protein required for interaction with the RSK1 and PRK2 host kinases and their requirement for interleukin-10 production and virulence

The YopM protein of Yersinia sp. is a type III secreted effector that is required for virulence in murine models of infection. YopM has previously been shown to contain leucine-rich repeats (LRRs) and to interact with two host kinases, RSK1 and PRK2, although the consequence of these interactions is unknown. A series of YopM proteins missing different numbers of LRRs or a C-terminal domain were produced and used for in vitro binding reactions to map domains required for interaction with RSK1 and PRK2. A C-terminal domain of YopM (from LRR12 to the C terminus) was shown to be required for interaction with RSK1, while an internal portion encompassing LRR6 to LRR15 was shown to be required for interaction with PRK2. The virulence of a Yersinia pseudotuberculosis Delta yopM mutant in mice via an intravenous route of infection was significantly attenuated. At day 4 postinfection, there were significantly increased levels of gamma interferon and reduced levels of interleukin-18 (IL-18) and IL-10 in the serum of the Delta yopM-infected mice compared to that of mice infected with the wild type, suggesting that YopM action alters the balance of these key cytokines to promote virulence. The PRK2 and RSK1 interaction domains of YopM were both required for IL-10 induction in vivo, irrespective of splenic colonization levels. In an orogastric model of Y. pseudotuberculosis infection, a Delta yopM mutant was defective in dissemination from the intestine to the spleen and significantly reduced in virulence. In addition, Y. pseudotuberculosis mutants expressing YopM proteins unable to interact with either RSK1 (YopM Delta 12-C) or PRK2 (YopM Delta 6-15) were defective for virulence in this assay, indicating that both interaction domains are important for YopM to promote pathogenesis.