A systemic granulomatous response to Schistosoma mansoni eggs alters responsiveness of bone-marrow-derived macrophages to Toll-like receptor agonists

Innate immune receptors are differentially expressed in mice during experimental Schistosoma mansoni early infection

BACKGROUND

The impact of Schistosoma mansoni infection over the immune response and the mechanisms involved in pathogenesis are not yet completely understood.

OBJECTIVES

This study aimed to evaluate the expression of innate immune receptors in three distinct mouse lineages (BALB/c, C57BL/6 and Swiss) during experimental S. mansoni infection with LE strain.

METHODS

The parasite burden, intestinal tissue oogram and presence of hepatic granulomas were evaluated at 7- and 12-weeks post infection (wpi). The mRNA expression for innate Toll-like receptors, Nod-like receptors, their adaptor molecules, and cytokines were determined at 2, 7 and 12 wpi in the hepatic tissue by real-time quantitative polymerase chain reaction (qPCR).

FINDINGS

Swiss mice showed 100% of survival, had lower parasite burden and intestinal eggs, while infected BALB/c and C57BL/6 presented 80% and 90% of survival, respectively, higher parasite burden and intestinal eggs. The three mouse lineages displayed distinct patterns in the expression of innate immune receptors, their adaptor molecules and cytokines, at 2 and 7 wpi.

MAIN CONCLUSIONS

Our results suggest that the pathogenesis of S. mansoni infection is related to a dynamic early activation of innate immunity receptors and cytokines important for the control of developing worms.

Protective effects of resolvin D1 in Pseudomonas aeruginosa keratitis

PURPOSE

Here, we explored the protective effects of resolvin D1 (RvD1) in Pseudomonas aeruginosa (PA) keratitis.

METHODS

C57BL/6 (B6) mice were used as an animal model of PA keratitis. Plate counting and clinical scores were used to assess the severity of the infection and the therapeutic effects of RvD1 in the model. Myeloperoxidase assay was used to detect neutrophil infiltration and activity. Quantitative PCR (qPCR) was used to examine the expression of proflammatory and anti-inflammatory mediators. Immunofluorescence staining and qPCR were performed to identify macrophage polarization.

RESULTS

RvD1 treatment alleviated PA keratitis severity by decreasing corneal bacterial load and inhibiting neutrophil infiltration in the mouse model. Furthermore, RvD1 treatment decreased mRNA levels of TNF-α, IFN-γ, IL-1β, CXCL1, and S100A8/9 while increasing those of IL-1RA, IL-10, and TGF-β1. RvD1 treatment also reduced the aggregation of M1 macrophages and increased that of M2 macrophages. RvD1 provided an auxiliary effect in gatifloxacin-treated mice with PA keratitis.

CONCLUSION

Based on these findings, RvD1 may improve the prognosis of PA keratitis by inhibiting neutrophil recruitment and activity, dampening the inflammatory response, and promoting M2 macrophage polarization. Thus, RvD1 may be a potential complementary therapy for PA keratitis.

Analysis of necroptosis-related prognostic genes and immune infiltration in idiopathic pulmonary fibrosis

Background

IPF is an undetermined, progressive lung disease. Necroptosis is a type of programmed apoptosis, which involved in the pathogenesis of lung diseases like COPD and ARDS. However, necroptosis in IPF have not been adequately studied. This study aimed to investigate the necroptosis in IPF and the relationship between necroptosis and immune infiltration, to construct a prognostic prediction model of IPF based on necroptosis-related genes.

Methods

GSE110147 was downloaded from the GEO database and utilized to analyze the expression of necroptosis-related differentially expressed genes (NRDEGs). Then NRDEGs were used to construct protein-protein interaction (PPI) networks in the STRING database, and Cytoscape software was used to identify and visualize hub genes. Necroptosis-related prognosticgenes were explored in GSE70866, and a prognostic prediction model was constructed. The ImmuCellAI algorithm was utilized to analyze the landscape of immune infiltration in GSE110147. The single-cell RNA sequencing dataset GSE122960 was used to explore the association between necroptosis and type II alveolar epithelial cells (AT II) in IPF. The GSE213001 and GSE93606 were used for external validation. The expression of prognostic genes was quantified using RT-qPCRin the IPF A549 cell model, and was further verified by western blotting in the bleomycin-induced pulmonary fibrosis mouse model.

Results

It was observed that necroptosis-related signaling pathways were abundantly enriched in IPF. 29 NRDEGs were screened, of which 12 showed consistent expression trends in GSE213001. Spearman correlation analysis showed that the expression of NRDEGs was positively correlated with the infiltration of proinflammatory immune cells, and negatively correlated with the infiltration of anti-inflammatory immune cells. NRDEGs, including MLKL, were highly expressed in AT II of fibrotic lung tissue. A necroptosis-related prediction model was constructed based on 4 NRDEGsby the cox stepwise regression. In the validation dataset GSE93606, the prognostic prediction model showed good applicability. The verification results of RT-qPCR and western blotting showed the reliability of most of the conclusions.

Conclusions

This study revealed that necroptosis existed in IPF and might occur in AT II. Necroptosis was associated with immune infiltration, suggesting that necroptosis of AT II might involve in IPF by activating immune infiltration and immune response.

Experimental venous thrombus resolution is driven by IL-6 mediated monocyte actions

Deep venous thrombosis and residual thrombus burden correlates with circulating IL-6 levels in humans. To investigate the cellular source and role of IL-6 in thrombus resolution, Wild type C57BL/6J (WT), and IL-6-/- mice underwent induction of VT via inferior vena cava (IVC) stenosis or stasis. Vein wall (VW) and thrombus were analyzed by western blot, immunohistochemistry, and flow cytometry. Adoptive transfer of WT bone marrow derived monocytes was performed into IL6-/- mice to assess for rescue. Cultured BMDMs from WT and IL-6-/- mice underwent quantitative real time PCR and immunoblotting for fibrinolytic factors and matrix metalloproteinase activity. No differences in baseline coagulation function or platelet function were found between WT and IL-6-/- mice. VW and thrombus IL-6 and IL-6 leukocyte-specific receptor CD126 were elevated in a time-dependent fashion in both VT models. Ly6Clo Mo/MØ were the predominant leukocyte source of IL-6. IL-6-/- mice demonstrated larger, non-resolving stasis thrombi with less neovascularization, despite a similar number of monocytes/macrophages (Mo/MØ). Adoptive transfer of WT BMDM into IL-6-/- mice undergoing stasis VT resulted in phenotype rescue. Human specimens of endophlebectomized tissue showed co-staining of Monocyte and IL-6 receptor. Thrombosis matrix analysis revealed significantly increased thrombus fibronectin and collagen in IL-6-/- mice. MMP9 activity in vitro depended on endogenous IL-6 expression in Mo/MØ, and IL-6-/- mice exhibited stunted matrix metalloproteinase activity. Lack of IL-6 signaling impairs thrombus resolution potentially via dysregulation of MMP-9 leading to impaired thrombus recanalization and resolution. Restoring or augmenting monocyte-mediated IL-6 signaling in IL-6 deficient or normal subjects, respectively, may represent a non-anticoagulant target to improve thrombus resolution.

A Dual Role for Cysteinyl Leukotriene Receptors in the Pathogenesis of Corneal Infection

Cysteinyl leukotrienes (CysLTs) have been defined as central mediators of inflammation. Despite our extensive understanding of these bioactive lipid mediators in the pathogenesis of diseases such as asthma, allergic rhinitis, and even neurological disorders, information regarding the eye is markedly lacking. As a result, this study examined the expression profiles of two major CysLT receptors, CysLT₁ and CysLT₂, in the cornea using experimental mouse models of Pseudomonas aeruginosa-induced keratitis with contrasting outcomes: susceptible C57BL/6 (B6) and resistant BALB/c. Postinfection, disparate levels of CysLT receptors were accompanied by distinct expression profiles for select proinflammatory and anti-inflammatory cell surface markers detected on macrophages and polymorphonuclear neutrophils between the two strains. Further, inhibition of either CysLT receptor converted the disease response of both strains, where corneal perforation was prevented in B6 mice, and BALB/c mice fared significantly worse. In addition, receptor antagonist studies revealed changes in inflammatory cell infiltrate phenotypes and an influence on downstream CysLT receptor signaling pathways. Although the B6 mouse model highlights the established proinflammatory activities related to CysLT receptor activation, results generated from BALB/c mice indicate a protective mechanism that may be essential to disease resolution. Further, basal expression levels of CysLT₁ and CysLT₂ were significantly higher in uninfected corneas of both mouse strains as opposed to during infection, suggestive of a novel role in homeostatic maintenance within the eye. In light of these findings, therapeutic targeting of CysLT receptors extends beyond inhibition of proinflammatory activities and may impact inflammation resolution, as well as corneal surface homeostasis.

Switched phenotypes of macrophages during the different stages of Schistosoma japonicum infection influenced the subsequent trends of immune responses

BACKGROUND

Macrophages play crucial roles in immune responses during the course of schistosomal infections.

METHODS

We currently investigated influence of immunocompetent changes in macrophages via microarray-based analysis, mRNA expression analysis, detection of serum cytokines, and subsequent evaluation of the immune phenotypes following the differentiation of infection-induced lymphocytes in a unique T1/T2 double-transgenic mouse model.

RESULTS

The gradual upregulation of genes encoding YM1, YM2, and interleukin (IL)-4/IL-13 receptors in infected mice indicated the role of type 2 alternatively activated macrophages (M2, AAMφs) in immune responses after Schistosoma japonicum egg production. FACS analysis showed that surface markers MHC class II (IA/IE) and CD8α⁺ of the macrophages also exhibited a dramatic change at the various time points before and after egg-production. The transgenic mouse experiments further demonstrated that the shifting of macrophage phenotypes influenced the percentage of helper T (Th)-2 cells, which was observed to be higher than that of Th1 cells, which increased only at 3 and 5 weeks post-infection. The differentiation of effector B cells showed a similar but more significant trend toward type-2 immunity.

CONCLUSION

These results suggest that the infection of mice with S. japonicum resulted in a final Th2- and Be2-skewed immune response. This may be due to phenotypic changes in the macrophages. The influence of alternatively activated macrophages was also activated by S. japonicum egg production. This study elucidated the existence of variations in immune mechanisms at the schistosome infection stages.

The Role of Hypoxia-Induced Mitogenic Factor in Organ-Specific Inflammation in the Lung and Liver: Key Concepts and Gaps in Knowledge Regarding Molecular Mechanisms of Acute or Immune-Mediated Liver Injury

Hypoxia-induced mitogenic factor (HIMF), which is also known as resistin-like molecule α (RELM-α), found in inflammatory zone 1 (FIZZ1), or resistin-like alpha (retlna), is a cysteine-rich secretory protein and cytokine. HIMF has been investigated in the lung as a mediator of pulmonary fibrosis, inflammation and as a marker for alternatively activated macrophages. Although these macrophages have been found to have a role in acute liver injury and acetaminophen toxicity, few studies have investigated the role of HIMF in acute or immune-mediated liver injury. The aim of this focused review is to analyze the literature and examine the effects of HIMF and its human homolog in organ-specific inflammation in the lung and liver. We followed the guidelines set by PRISMA in constructing this review. The relevant checklist items from PRISMA were included. Items related to meta-analysis were excluded because there were no randomized controlled clinical trials. We found that HIMF was increased in most models of acute liver injury and reduced damage from acetaminophen-induced liver injury. We also found strong evidence for HIMF as a marker for alternatively activated macrophages. Our overall risk of bias assessment of all studies included revealed that 80% of manuscripts demonstrated some concerns in the randomization process. We also demonstrated some concerns (54.1%) and high risk (45.9%) of bias in the selection of the reported results. The need for randomization and reduction of bias in the reported results was similarly detected in the studies that focused on HIMF and the liver. In conclusion, we propose that HIMF could be utilized as a marker for M2 macrophages in immune-mediated liver injury. However, we also detected the need for randomized clinical trials and additional experimental and human prospective studies in order to fully comprehend the role of HIMF in acute or immune-mediated liver injury.

P21 activated kinase-1 (PAK1) in macrophages is required for promotion of Th17 cell response during helminth infection

CD4⁺T cells differentiate into distinct functional effector and inhibitory subsets are facilitated by distinct cytokine cues present at the time of antigen recognition. Maintaining a balance between T helper 17 (Th17) and regulatory T (Treg) cells are critical for the control of the immunopathogenesis of liver diseases. Here, by using the mouse model of helminth Schistosoma japonicum (Sjaponicum) infection, we show that the hepatic mRNA levels of P21‐activated kinase 1 (PAK1), a key regulator of the actin cytoskeleton, adhesion and cell motility, are significantly increased and associated with the development of liver pathology during Sjaponicum infection. In addition, PAK1‐deficient mice are prone to suppression of Th17 cell responses but increased Treg cells. Furthermore, PAK1 enhances macrophage activation through promoting IRF1 nuclear translocation in an NF‐κB‐dependent pathway, resulting in promoting Th17 cell differentiation through inducing IL‐6 production. These findings highlight the importance of PAK1 in macrophages fate determination and suggest that PAK1/IRF1 axis‐dependent immunomodulation can ameliorate certain T cell–based immune pathologies.

Intravital microscopy: Imaging host-parasite interactions in lymphoid organs

Intravital microscopy allows imaging of biological phenomena within living animals, including host-parasite interactions. This has advanced our understanding of both, the function of lymphoid organs during parasitic infections, and the effect of parasites on such organs to allow their survival. In parasitic research, recent developments in this technique have been crucial for the direct study of host-parasite interactions within organs at depths, speeds and resolution previously difficult to achieve. Lymphoid organs have gained more attention as we start to understand their function during parasitic infections and the effect of parasites on them. In this review, we summarise technical and biological findings achieved by intravital microscopy with respect to the interaction of various parasites with host lymphoid organs, namely the bone marrow, thymus, lymph nodes, spleen and the mucosa-associated lymphoid tissue, and present a view into possible future applications.

Loss of myeloid-specific protein phosphatase 2A enhances lung injury and fibrosis and results in IL-10-dependent sensitization of epithelial cell apoptosis

Protein phosphatase 2A (PP2A), a ubiquitously expressed Ser/Thr phosphatase is an important regulator of cytokine signaling and cell function. We previously showed that myeloid-specific deletion of PP2A (LysM^crePP2A^-/-) increased mortality in a murine peritoneal sepsis model. In the current study, we assessed the role of myeloid PP2A in regulation of lung injury induced by lipopolysaccharide (LPS) or bleomycin delivered intratracheally. LysM^crePP2A^-/- mice experienced increased lung injury in response to both LPS and bleomycin. LysM^crePP2A^-/- mice developed more exuberant fibrosis in response to bleomycin, elevated cytokine responses, and chronic myeloid inflammation. Bone marrow-derived macrophages (BMDMs) from LysM^crePP2A^-/- mice showed exaggerated inflammatory cytokine release under conditions of both M1 and M2 activation. Notably, secretion of IL-10 was elevated under all stimulation conditions, including activation of BMDMs by multiple Toll-like receptor ligands. Supernatants collected from LPS-stimulated LysM^crePP2A^-/- BMDMs induced epithelial cell apoptosis in vitro but this effect was mitigated when IL-10 was also depleted from the BMDMs by crossing LysM^crePP2A^-/- mice with systemic IL-10^-/- mice (LysM^crePP2A^-/- × IL-10^-/-) or when IL-10 was neutralized. Despite these findings, IL-10 did not directly induce epithelial cell apoptosis but sensitized epithelial cells to other mediators from the BMDMs. Taken together our results demonstrate that myeloid PP2A regulates production of multiple cytokines but that its effect is most pronounced on IL-10 production. Furthermore, IL-10 sensitizes epithelial cells to apoptosis in response to myeloid-derived mediators, which likely contributes to the pathogenesis of lung injury and fibrosis in this model.

Macrophages: friend or foe in idiopathic pulmonary fibrosis?

Idiopathic pulmonary fibrosis (IPF) is a prototype of lethal, chronic, progressive interstitial lung disease of unknown etiology. Over the past decade, macrophage has been recognized to play a significant role in IPF pathogenesis. Depending on the local microenvironments, macrophages can be polarized to either classically activated (M1) or alternatively activated (M2) phenotypes. In general, M1 macrophages are responsible for wound healing after alveolar epithelial injury, while M2 macrophages are designated to resolve wound healing processes or terminate inflammatory responses in the lung. IPF is a pathological consequence resulted from altered wound healing in response to persistent lung injury. In this review, we intend to summarize the current state of knowledge regarding the process of macrophage polarization and its mediators in the pathogenesis of pulmonary fibrosis. Our goal is to update the understanding of the mechanisms underlying the initiation and progression of IPF, and by which, we expect to provide help for developing effective therapeutic strategies in clinical settings.

Persimmon-derived tannin has bacteriostatic and anti-inflammatory activity in a murine model of Mycobacterium avium complex (MAC) disease

Nontuberculous mycobacteria (NTM), including Mycobacterium avium complex (MAC), cause opportunistic chronic pulmonary infections. Notably, MAC susceptibility is regulated by various factors, including the host immune system. Persimmon (Ebenaceae Diospyros kaki Thunb.) tannin is a condensed tannin composed of a polymer of catechin groups. It is well known that condensed tannins have high antioxidant activity and bacteriostatic properties. However, it is hypothesized that condensed tannins might need to be digested and/or fermented into smaller molecules in vivo prior to being absorbed into the body to perform beneficial functions. In this study, we evaluated the effects of soluble persimmon-derived tannins on opportunistic MAC disease. Soluble tannins were hydrolyzed and evaluated by the oxygen radical absorbance capacity (ORAC) method. The ORAC value of soluble tannin hydrolysate was approximately five times greater than that of soluble tannin powder. In addition, soluble tannin hydrolysate exhibited high bacteriostatic activity against MAC in vitro. Furthermore, in an in vivo study, MAC infected mice fed a soluble tannin-containing diet showed significantly higher anti-bacterial activity against MAC and less pulmonary granuloma formation compared with those fed a control diet. Tumor necrosis factor α and inducible nitric oxide synthase levels were significantly lower in lungs of the soluble tannin diet group compared with the control diet group. Moreover, proinflammatory cytokines induced by MAC stimulation of bone marrow-derived macrophages were significantly decreased by addition of soluble tannin hydrolysate. These data suggest that soluble tannin from persimmons might attenuate the pathogenesis of pulmonary NTM infection.

Cu,Zn-Superoxide Dismutase-Mediated Redox Regulation of Jumonji Domain Containing 3 Modulates Macrophage Polarization and Pulmonary Fibrosis

M2 macrophages are implicated in the development of pulmonary fibrosis as they generate profibrotic signals. The polarization process, at least in part, is regulated by epigenetic modulation. Because Cu,Zn-superoxide dismutase-induced H2O2 can polarize macrophages to a profibrotic M2 phenotype, we hypothesized that modulation of the redox state of the cell is involved in the epigenetic modulation of the macrophage phenotype. In this study, we show that signal transducer and activator of transcription 6 (STAT6) regulates Jumonji domain containing (Jmjd) 3, a histone H3 lysine 27 demethylase, and mutation of a redox-sensitive cysteine in STAT6 attenuates jmjd3 expression. Moreover, Jmjd3 deficiency abrogates profibrotic M2 gene expression. Treatment with leflunomide, which reduces mitochondrial reactive oxygen species production and tyrosine phosphorylation, inhibits jmjd3 expression and M2 polarization, as well as development of a fibrotic phenotype. Taken together, these observations provide evidence that the redox regulation of Jmjd3 is a unique regulatory mechanism for Cu,Zn-superoxide dismutase-mediated profibrotic M2 polarization. Furthermore, leflunomide, which reduces reactive oxygen species production and tyrosine phosphorylation, may prove to be therapeutic in the treatment of asbestos-induced pulmonary fibrosis.

Galectin-3, histone deacetylases, and Hedgehog signaling: Possible convergent targets in schistosomiasis-induced liver fibrosis

Schistosomiasis affects approximately 240 million people in the world. Schistosoma mansoni eggs in the liver induce periportal fibrosis and hepatic failure driven by monocyte recruitment and macrophage activation, resulting in robust Th2 response. Here, we suggested a possible involvement of Galectin-3 (Gal-3), histone deacetylases (HDACs), and Hedgehog (Hh) signaling with macrophage activation during Th1/Th2 immune responses, fibrogranuloma reaction, and tissue repair during schistosomiasis. Gal-3 is highly expressed by liver macrophages (Kupffer cells) around Schistosoma eggs. HDACs and Hh regulate macrophage polarization and hepatic stellate cell activation during schistosomiasis-associated fibrogenesis. Previously, we demonstrated an abnormal extracellular matrix distribution in the liver that correlated with atypical monocyte-macrophage differentiation in S. mansoni-infected, Gal-3-deficient (Lgals3-/-) mice. New findings explored in this review focus on the chronic phase, when wild-type (Lgals3+/+) and Lgals3-/- mice were analyzed 90 days after cercariae infection. In Lgals3-/- infected mice, there was significant inflammatory infiltration with myeloid cells associated with egg destruction (hematoxylin and eosin staining), phagocytes (specifically Kupffer cells), numerically reduced and diffuse matrix extracellular deposition in fibrotic areas (Gomori trichrome staining), and severe disorganization of collagen fibers surrounding the S. mansoni eggs (reticulin staining). Granuloma-derived stromal cells (GR cells) of Lgals3-/- infected mice expressed lower levels of alpha smooth muscle actin (α-SMA) and eotaxin and higher levels of IL-4 than Lgals3+/+ mice (real-time PCR). The relevant participation of macrophages in these events led us to suggest distinct mechanisms of activation that culminate in defective fibrosis in the liver of Lgals3-/- infected mice. These aspects were discussed in this review, as well as the possible interference between Gal-3, HDACs, and Hh signaling during progressive liver fibrosis in S. mansoni-infected mice. Further studies focused on macrophage roles could elucidate these questions and clear the potential utility of these molecules as antifibrotic targets.

Gestation and breastfeeding in schistosomotic mothers differently modulate the immune response of adult offspring to postnatal Schistosoma mansoni infection

Schistosoma mansoni antigens in the early life alter homologous and heterologous immunity during postnatal infections. We evaluate the immunity to parasite antigens and ovalbumin (OA) in adult mice born/suckled by schistosomotic mothers. Newborns were divided into: born (BIM), suckled (SIM) or born/suckled (BSIM) in schistosomotic mothers, and animals from noninfected mothers (control). When adults, the mice were infected and compared the hepatic granuloma size and cellularity. Some animals were OA + adjuvant immunised. We evaluated hypersensitivity reactions (HR), antibodies levels (IgG1/IgG2a) anti-soluble egg antigen and anti-soluble worm antigen preparation, and anti-OA, cytokine production, and CD4⁺FoxP3⁺T-cells by splenocytes. Compared to control group, BIM mice showed a greater quantity of granulomas and collagen deposition, whereas SIM and BSIM presented smaller granulomas. BSIM group exhibited the lowest levels of anti-parasite antibodies. For anti-OA immunity, immediate HR was suppressed in all groups, with greater intensity in SIM mice accompanied of the remarkable level of basal CD4⁺FoxP3⁺T-cells. BIM and SIM groups produced less interleukin (IL)-4 and interferon (IFN)-g. In BSIM, there was higher production of IL-10 and IFN-g, but lower levels of IL-4 and CD4⁺FoxP3⁺T-cells. Thus, pregnancy in schistosomotic mothers intensified hepatic fibrosis, whereas breastfeeding diminished granulomas in descendants. Separately, pregnancy and breastfeeding could suppress heterologous immunity; however, when combined, the responses could be partially restored in infected descendants.

Divergent effects of Tlr9 deletion in experimental late venous thrombosis resolution and vein wall injury

Deep-vein thrombosis (DVT) resolves via a sterile inflammatory response. Defining the inflammatory response of DVT may allow for new therapies that do not involve anticoagulation. Previously, we have shown that Toll-like receptor 9 (Tlr9) gene deleted mice had impaired venous thrombosis (VT) resolution. Here, we further characterise the role of Tlr9 signalling and sterile inflammation in chronic VT and vein wall responses. First, we found a human precedent exists with Tlr9+ cells present in chronic post thrombotic intraluminal tissue. Second, in a stasis VT mouse model, endogenous danger signal mediators of uric acid, HMGB-1, and neutrophil extracellular traps marker of citrullinated histone-3 (and extracellular DNA) were greater in Tlr9-/- thrombi as compared with wild-type (WT), corresponding with larger VT at 8 and 21 days. Fewer M1 type (CCR2+) monocyte/macrophages (MØ) were present in Tlr9-/- thrombi than WT controls at 8 days, suggesting an impaired inflammatory cell influx. Using bone marrow-derived monocyte (BMMØ) cell culture, we found decreased fibrinolytic gene expression with exposure to several endogenous danger signals. Next, adoptive transfer of cultured Tlr9+/+ BMMØ to Tlr9-/- mice normalised VT resolution at 8 days. Lastly, although the VT size was larger at 21 days in Tlr9-/- mice and correlated with decreased endothelial antigen markers, no difference in fibrosis was found. These data suggest that Tlr9 signalling in MØ is critical for later VT resolution, is associated with necrosis clearance, but does not affect later vein wall fibrosis. These findings provide insight into the Tlr9 MØ mechanisms of sterile inflammation in this disease process.

IL-10 function, regulation, and in bacterial keratitis

The immune system protects the host from pathogenic microbes, but tight regulation of the evoked response is requisite to limit bystander damage. The interleukin (IL)-10 family of cytokines, composed of 9 members: IL-10, IL-19, IL-20, IL-22, IL-24, IL-26, and 3 distantly related members, IL-28A, IL-28B, and IL-29, plays a central role in this regulation. IL-10 family cytokines emerged before the adaptive immune response and elicit diverse host defense mechanisms, especially from epithelial cells during an infection. IL-10 family cytokines are also essential for maintenance and integrity of tissue epithelial layers. These cytokines promote innate immune responses from tissue epithelia that limit the damage caused by both viral and bacterial infections. They also facilitate tissue healing after infection/inflammation. In this regard, IL-10 suppresses pro-inflammatory responses, limiting tissue disruption resulting from an inflammatory response. Thus, a central functional theme of IL-10 family cytokines is their role in tissue protection. This review focuses on IL-10, the founding member of this family of cytokines, and integrates recent data on the function and regulation of IL-10 during bacterial infections. Emphasis is placed on the role of IL-10 in Pseudomonas aeruginosa keratitis and the subsequent infectious/inflammatory processes evoked.

PI3K/Akt signaling pathway modulates influenza virus induced mouse alveolar macrophage polarization to M1/M2b

Macrophages polarized to M1 (pro-inflammation) or M2 (anti-inflammation) phenotypes in response to environmental signals. In this study, we examined the polarization of alveolar macrophage (AM), following induction by different influenza virus strains (ST169 (H1N1), ST602 (H3N2) and HKG9 (H9N2)). Macrophages from other tissues or cell line exert alternative responding pattern, and AM is necessary for investigating the respiratory system. AM polarized toward the M1 phenotype after 4 hours of infection by all three virus strains, and AM to presented M2b phenotype after 8 hours induction, and immunosuppressive phenotype after 24 hours of induction. Protein expression assay showed similar results as the gene expression analysis for phenotype verification. The ELISA assay showed that TNF-α secretion was up-regulated after 4 and 8 hours of infection by influenza viruses, and it returned to basal levels after 24 hours of infection. IL-10 expression was elevated after 8 and 24 hours of infection. Immunofluorescence showed that iNOS expression was up-regulated but not Arg1 expression. Influenza virus notably increased phospho-Akt but not phospho-Erk1/2 or phospho-p38, and the AM polarization pattern have been changed by LY294002 (PI3K inhibitor). In conclusion, our results demonstrate the dynamic polarization of AM induced by influenza viruses, and suggested that PI3K/Akt signaling pathway modulates AM polarization to M1/M2b.

Resistin-like molecule alpha enhances the proliferation and migration of aortic vascular smooth muscle cells

OBJECTIVE

The mitogenic and chemotactic effects of resistin-like molecule alpha (RELMα) are thought to contribute to vascular remodeling in pulmonary arterial hypertension. Here we evaluate the expression of RELMα in atherosclerotic plaque and investigate its effects on the proliferation and migration of vascular smooth muscle cells (VSMCs).

METHODS

An atherosclerotic model was established by feeding 4-week-old C57BL/6J ApoE-/- mice (n = 9) with a high-fat diet. Wild-type 4-week-old C57BL/6J (n = 9) were fed the same diet and were used as controls. RELMα expression was evaluated by immunohistochemistry and quantified using real-time PCR (RT-PCR). A (3)H-thymidine incorporation assay and the Boyden chamber assay, respectively, were used to explore the effects of different concentrations of RELMα on the proliferation and migration of VSMCs.

RESULTS

Immunohistochemistry identified positively stained granules in atherosclerotic plaques. These results were confirmed by detection of RELMα mRNA using RT-PCR. We also demonstrated that in vitro exposure to RELMα significantly promoted the proliferation and migration of VSMCs in a dose-related manner (p < 0.01).

CONCLUSIONS

RELMα expressed in atherosclerotic plaque of ApoE-/- mice appears to enhance the proliferation and migration of aortic VSMCs in a dose-related manner.

The linkage of innate and adaptive immune response during granulomatous development

Granulomas represent a spectrum of inflammatory sequestration responses that may be initiated by a variety of agents, including non-infectious environmental factors and infectious microbial pathogens. Although this reaction is designed to be protective, the associated tissue injury is often responsible for a profound degree of pathology. While many of the mechanisms that sustain the development of the granuloma are enigmatic, it is accepted that the maintenance of this inflammatory process is dependent upon dynamic interactions between an inciting agent, inflammatory mediators, various immune and inflammatory cells, and structural cells of the involved tissue. The best studied of the host-dependent processes during granuloma development is the innate and adaptive immune response. The innate immune response by antigen-presenting cells [APCs; dendritic cells (DCs) and macrophages] is initiated quickly to protect from overwhelming pathogens, but with time, can also activate the adaptive immune response. APCs, essential regulators of the innate immune response, can respond to microbial ligands through Toll-like receptors (TLRs), which function in the recognition of microbial components and play an important role to link the innate and adaptive immune responses. CD4(+) T helper (Th) cells are essential regulators of adaptive immune responses and inflammatory diseases. Recently, the Notch system has been shown to be an important bridge between APCs and T cell communication circuits. In the present review, we discuss recent findings that explore the mechanisms in the linkage of innate and adaptive immunity, including granulomatous formation though TLRs and Notch activation.

Substance P affects growth factors in Pseudomonas aeruginosa-infected mouse cornea

PURPOSE

This study analyzed the influence of substance P (SP) on growth factors related to wound healing in mice in the presence of infectious keratitis.

METHODS

Naturally resistant mice were injected intraperitoneally with SP or phosphate-buffered saline and infected with Pseudomonas aeruginosa, and corneal messenger RNA (mRNA) levels of growth factors and apoptosis genes were tested. Enzyme-linked immunosorbent assay determined the protein levels, whereas immunohistochemistry tested the distribution, macrophage phenotype, and cell quantitation. In vitro, macrophages were stimulated with lipopolysaccharide (LPS; with or without SP) and mRNA levels of proinflammatory and antiinflammatory cytokines and apoptosis genes were tested.

RESULTS

After SP, epidermal growth factor mRNA and protein levels were disparately regulated early, with no differences later in the disease. Hepatocyte growth factor and fibroblast growth factor-7 mRNA and protein levels were increased after SP treatment. Enumerating dual-labeled stromal cells revealed no difference between SP-treated versus phosphate-buffered saline-treated groups in the percentage of epidermal growth factor-labeled fibroblasts or macrophages, but there were significant increases in both hepatocyte growth factor- and fibroblast growth factor-7-labeled cells. Type 2 (M2) macrophages and caspase-3 mRNA levels were decreased, whereas B-cell lymphoma-2 mRNA expression was increased after SP treatment. In vitro, mRNA levels of several proinflammatory cytokines and B-cell lymphoma-2 were elevated, whereas transforming growth factor β was decreased after macrophage stimulation with SP (with LPS) over LPS alone. (Mice: n = 105 control; 105 experimental.)

CONCLUSIONS

These data show that treatment with SP in infectious keratitis elevates growth factors but also adversely affects the disease by enhancing the inflammatory response and its sequelae.

Stem cell conditioned medium improves acute lung injury in mice: in vivo evidence for stem cell paracrine action

Mortality and morbidity of acute lung injury and acute respiratory distress syndrome remain high because of the lack of pharmacological therapies to prevent injury or promote repair. Mesenchymal stem cells (MSCs) prevent lung injury in various experimental models, despite a low proportion of donor-derived cell engraftment, suggesting that MSCs exert their beneficial effects via paracrine mechanisms. We hypothesized that soluble factors secreted by MSCs promote the resolution of lung injury in part by modulating alveolar macrophage (AM) function. We tested the therapeutic effect of MSC-derived conditioned medium (CdM) compared with whole MSCs, lung fibroblasts, and fibroblast-CdM. Intratracheal MSCs and MSC-CdM significantly attenuated lipopolysaccharide (LPS)-induced lung neutrophil influx, lung edema, and lung injury as assessed by an established lung injury score. MSC-CdM increased arginase-1 activity and Ym1 expression in LPS-exposed AMs. In vivo, AMs from LPS-MSC and LPS-MSC CdM lungs had enhanced expression of Ym1 and decreased expression of inducible nitric oxide synthase compared with untreated LPS mice. This suggests that MSC-CdM promotes alternative macrophage activation to an M2 "healer" phenotype. Comparative multiplex analysis of MSC- and fibroblast-CdM demonstrated that MSC-CdM contained several factors that may confer therapeutic benefit, including insulin-like growth factor I (IGF-I). Recombinant IGF-I partially reproduced the lung protective effect of MSC-CdM. In summary, MSCs act through a paracrine activity. MSC-CdM promotes the resolution of LPS-induced lung injury by attenuating lung inflammation and promoting a wound healing/anti-inflammatory M2 macrophage phenotype in part via IGF-I.

Antigen-specific B memory cell responses to Plasmodium falciparum malaria antigens and Schistosoma haematobium antigens in co-infected Malian children

Polyparasitism is common in the developing world. We have previously demonstrated that schistosomiasis-positive (SP) Malian children have age-dependent protection from malaria compared to matched schistosomiasis-negative (SN) children. Evidence of durable immunologic memory to malaria antigens is conflicting, particularly in young children and the effect of concomitant schistomiasis upon acquisition of memory is unknown. We examined antigen-specific B memory cell (MBC) frequencies (expressed as percentage of total number of IgG-secreting cells) in 84 Malian children aged 4–14 to malaria blood-stage antigens, apical membrane antigen 1 (AMA-1) and merozoite surface protein 1 (MSP-1) and to schistosomal antigens, Soluble Worm Antigenic Preparation (SWAP) and Schistosoma Egg Antigen (SEA), at a time point during the malaria transmission season and a follow-up dry season visit. We demonstrate, for the first time, MBC responses to S. haematobium antigens in Malian children with urinary egg excretion and provide evidence of seasonal acquisition of immunologic memory, age-associated differences in MBC acquisition, and correlation with circulating S. haematobium antibody. Moreover, the presence of a parasitic co-infection resulted in older children, aged 9–14 years, with underlying S. haematobium infection having significantly more MBC response to malaria antigens (AMA1 and MSP1) than their age-matched SN counterparts. We conclude that detectable MBC response can be measured against both malaria and schistosomal antigens and that the presence of S. haematobium may be associated with enhanced MBC induction in an age-specific manner.

Natural killer T cells suppress zymosan A-mediated granuloma formation in the liver by modulating interferon-γ and interleukin-10

Wild-type (WT) and CD1d(-/-) [without natural killer (NK) T cells] mice were treated with zymosan A to induce granuloma formation in the liver. Increased granuloma formation was seen in NKT-less mice on days 7 and 14 after administration. WT mice showed limited granuloma formation, and zymosan A eventually induced NKT cell accumulation as identified by their surface marker (e.g. CD1d-tetramer). Zymosan A augmented the expression of Toll-like receptor 2 on the cell surface of both macrophages and NKT cells. One possible reason for accelerated granuloma formation in NKT-less mice was increased production of interferon- γ (IFN-γ); a theory that was confirmed using IFN-γ(-/-) mice. Also, zymosan A increased interleukin-10 production in WT mice, which suppresses IFN-γ production. Taken together, these results suggest that NKT cells in the liver have the potential to suppress zymosan A-mediated granuloma formation.

Protection from bacterial-toxin-induced apoptosis in macrophages requires the lipogenic transcription factor sterol regulatory element binding protein 1a

Sterol regulatory element binding protein (SREBP) transcription factors activate genes of lipid metabolism, but recent studies indicate they also activate genes involved in other physiologic processes, suggesting that SREPBs have evolved to connect lipid metabolism with diverse physiologic responses. There are three major mammalian SREBPs, and the 1a isoform is specifically expressed at very high levels in macrophages, where a recent study showed that it couples lipid synthesis to the proinflammatory phase of the innate immune response. In the present study, we show that loss of SREBP-1a also results in an increase in apoptosis after exposure to bacterial pore-forming toxins and we show this is a result of a selective reduction in the expression of the gene coding for the antiapoptotic factor apoptosis inhibitor 6 (Api6). Additional studies demonstrate that SREBP-1a specifically activates the Api6 gene through a binding site in its proximal promoter, thus establishing the Api6 gene as a newly identified SREBP-1a target gene.

Effects of a recombinant schistosomal-derived anti-inflammatory molecular (rSj16) on the lipopolysaccharide (LPS)-induced activated RAW264.7

Macrophages as a principal component of immune system play an important role in the initiation, modulation, and final activation of immune response against pathogens including schistosomes. Classical (M1) or alternative (M2) activation states of macrophage have different functions during infections. Previously, we report that the schistosomal-derived anti-inflammatory molecule coding gene (named Sj16) was isolated and the recombinant Sj16 (rSj16) was expressed in Escherichia coli. rSj16 has been demonstrated to have definite anti-inflammatory effect in vivo and in vitro on rodent model. To study the molecular basis on anti-inflammatory of rSj16, in the present paper, we investigate the effects of rSj16 on the lipopolysaccharide (LPS)-induced activated RAW264.7, a murine macrophage cell line. We found that rSj16 inhibited LPS-induced activation of RAW264.7, as evidenced by impacting the proliferation, phagocytosis, and migration of the RAW264.7. After pretreated with rSj16, it showed the most potent inhibitory effects of rSj16 on the nitric oxide production in RAW264.7 cells. Furthermore, rSj16 also significantly decreased the levels of proinflammatory cytokines such as PGE2, IL-1β, IL-6, IL-12, IL-23, and TNF-α, whereas it increased the levels of immunosuppressive cytokine IL-10. rSj16 can also inhibit the LPS-induced activation of NF-κβ. These results further imply that Sj16 contributes to the immune evasion of Schistosoma japonicum through alternatively activated macrophage (M2), and rSj16 is expected to serve as a potential drug source for the medication of inflammatory disorders.

Enhanced pro-inflammatory cytokine responses following Toll-like-receptor ligation in Schistosoma haematobium-infected schoolchildren from rural Gabon

Background

Schistosoma infection is thought to lead to down-regulation of the host's immune response. This has been shown for adaptive immune responses, but the effect on innate immunity, that initiates and shapes the adaptive response, has not been extensively studied. In a first study to characterize these responses, we investigated the effect of Schistosoma haematobium infection on cytokine responses of Gabonese schoolchildren to a number of Toll-like receptor (TLR) ligands.

Methodology

Peripheral blood mononuclear cells (PBMCs) were collected from S. haematobium-infected and uninfected schoolchildren from the rural area of Zilé in Gabon. PBMCs were incubated for 24 h and 72 h with various TLR ligands, as well as schistosomal egg antigen (SEA) and adult worm antigen (AWA). Pro-inflammatory TNF-α and anti-inflammatory/regulatory IL-10 cytokine concentrations were determined in culture supernatants.

Principal Findings

Infected children produced higher adaptive IL-10 responses than uninfected children against schistosomal antigens (72 h incubation). On the other hand, infected children had higher TNF-α responses than uninfected children and significantly higher TNF-α to IL-10 ratios in response to FSL-1 and Pam3, ligands of TLR2/6 and TLR2/1 respectively. A similar trend was observed for the TLR4 ligand LPS while Poly(I:C) (Mda5/TLR3 ligand) did not induce substantial cytokine responses (24 h incubation).

Conclusions

This pilot study shows that Schistosoma-infected children develop a more pro-inflammatory TLR2-mediated response in the face of a more anti-inflammatory adaptive immune response. This suggests that S. haematobium infection does not suppress the host's innate immune system in the context of single TLR ligation.

Inflammatory cytokine and chemokine expression in sympathetic ophthalmia: a pilot study

Sympathetic ophthalmia is a bilateral uveitis that develops after penetrating injury to one eye. This study aimed to identify the inflammatory cellular sub-phenotypes and expression of pertinent inflammatory cytokines/chemokines in sympathetic ophthalmia (SO). Dalen-Fuchs nodules (DFN), granulomas, and non-granulomatous foci of inflammation were micro-dissected from 15 cases. RNA was extracted, and quantitative PCR was performed to measure IL-17, IL-18, IL-23, IFN-γ, CCL19, CXCL11, CCL17, and CCL22 transcripts. Immunohistochemical methods were used to characterize CD3, CD4, CD8, CD20, CD68, and CD163 expression. Non-granulomatous lymphocytes were predominantly CD3-positive and expressed more IFN-γ than cells within granulomas, consistent with Th1 cells. In contrast, granulomas and DFN contained mainly CD68+, CD163+/- and expressed more IL-17, IL-18, IL-23, CCL19, and CXCL11 than non-granulomatous cells. Our data indicate for the first time that M1 macrophages are the predominant inflammatory cells within granulomas and DFN of SO. We further observed high levels of IL-17 within granulomas and the presence of Th1 and M1 cells.

Triggering receptor expressed on myeloid cells-1 (TREM-1) modulates immune responses to Aspergillus fumigatus during fungal asthma in mice

Triggering receptor expressed on myeloid cells-1 (TREM-1) expression is increased during pulmonary fungal infection suggesting that this receptor might be involved in anti-fungal immune responses. To address the role of TREM-1 in a murine model of fungal allergic airway disease, A. fumigatus-sensitized CBA/J mice received by intratracheal injection a mixture of live A. fumigatus conidia and one of a control adenovirus vector (Ad70), an adenovirus containing a gene encoding for the extracellular domain of mouse TREM-1 and the F(c) portion of human IgG (AdTREM-1Ig; a soluble inhibitor of TREM-1 function), or an adenovirus containing mouse DAP12 (AdDAP12; DAP12 is an intracellular adaptor protein required for TREM-1 signaling), and examined at various days after challenge. Whole lung TREM-1 levels peaked at day 3 whereas circulating TREM-1 levels peaked at day 30 in this fungal asthma model. AdTREM-1Ig-treated mice exhibited significantly higher airway hyperresponsiveness following methacholine challenge compared with Ad70- and AdDAP12-treated mice. Whole lung analysis of AdTREM-1Ig treated mice revealed markedly higher amounts of fungal material compared with the other groups. ELISA analysis of whole lung and bronchoalveolar lavage samples indicated that several pro-allergic cytokine and chemokines including CCL17 and CCL22 were significantly increased in the AdTREM-1Ig group compared with the other groups. Finally, Pam3Cys and soluble Aspergillus antigens induced TREM-1 transcript expression in macrophages in a TLR2 dependent manner. In conclusion, TREM-1 modulates the immune response directed against A. fumigatus during experimental fungal asthma.

Therapeutic DNA vaccine reduces schistosoma mansoni-induced tissue damage through cytokine balance and decreased migration of myofibroblasts

Helminths are known to elicit a wide range of immunomodulation characterized by dominant Th2-type immune responses. Our group previously showed that a DNA vaccine encoding the mycobacterial 65-kDa heat shock protein (DNA-hsp65) showed immunomodulatory properties. We also showed, using a helminth-tuberculosis (TB) co-infection model, that the DNA-hsp65 vaccine protected mice against TB. We next investigated the mechanistic role of the vaccine during helminth-TB co-infection. Clinically, helminth infection causes type 2 granulomas in the lung. Mice were immunized with DNA-hsp65 while they were submitted to the type 2 granuloma induction protocol by Schistosoma mansoni eggs infusion. In this work we investigated the effects of DNA-hsp65 on the pathology and immune response during the development of type 2 granuloma induced by S. mansoni eggs. Histologic analyses of lung parenchyma showed that the DNA-hsp65 vaccine protected mice against exacerbated fibrosis induced by Schistosoma eggs, and decreased the size of the granulomas. These changes were correlated with a reduction in the number of T cells specific for the egg antigens in the lung and also with modulation of Th2 cytokine expression. Taken together, our results showed that the adjuvant properties of the DNA-hsp65 vaccine regulated the immune response in this Th2 model, and resulted in a preserved lung parenchyma.

Linking lipid metabolism to the innate immune response in macrophages through sterol regulatory element binding protein-1a

We show that mice with a targeted deficiency in the gene encoding the lipogenic transcription factor SREBP-1a are resistant to endotoxic shock and systemic inflammatory response syndrome induced by cecal ligation and puncture (CLP). When macrophages from the mutant mice were challenged with bacterial lipopolysaccharide, they failed to activate lipogenesis as well as two hallmark inflammasome functions, activation of caspase-1 and secretion of IL-1β. We show that SREBP-1a activates not only genes required for lipogenesis in macrophages but also the gene encoding Nlrp1a, which is a core inflammasome component. Thus, SREBP-1a links lipid metabolism to the innate immune response, which supports our hypothesis that SREBPs evolved to regulate cellular reactions to external challenges that range from nutrient limitation and hypoxia to toxins and pathogens.

New concepts of IL-10-induced lung fibrosis: fibrocyte recruitment and M2 activation in a CCL2/CCR2 axis

IL-10 is most commonly recognized as an anti-inflammatory cytokine possessing immunosuppressive effects necessary for regulated resolution of proinflammation. However, its role in the development of fibrosis during inflammatory resolution has not been clear. Few prior studies have linked IL-10 with the inhibition of fibrosis principally on the basis of regulating inflammation thought to be driving fibroproliferation. In contrast, in a model of long-term overexpression of IL-10, we observed marked induction of lung fibrosis in mice. The total cell number retrieved by bronchoalveolar lavage (BAL) increased 10-fold in the IL-10 overexpression (IL-10 OE) mice, with significant infiltration of T and B lymphocytes and collagen-producing cells. The presence of increased fibrocytes, isolated from collagenase-digested lungs, was identified by flow cytometry using dual staining of CD45 and collagen 1. Quantitative PCR analysis on an array of chemokine/chemokine receptor genes showed that receptor CCR2 and its ligand, CCL2, were highly upregulated in IL-10 OE mice, suggesting that IL-10-induced fibrocyte recruitment was CCL2/CCR2 specific. Given the prior association of alternatively activated (M(2)) macrophages with development of fibrosis in other disease states, we also examined the effect of IL-10 OE on the M(2) macrophage axis. We observed significantly increased numbers of M(2) macrophages in both BAL and whole lung tissue from the IL-10 OE mice. Administration of rabbit anti-CCL2 antiserum to IL-10 OE mice for three consecutive weeks significantly decreased fibrosis as evidenced by lung hydroxyproline content, compared with mice that received preimmune rabbit serum. These results indicate that overexpression of IL-10 induces fibrosis, in part, by fibrocyte recruitment and M(2) macrophage activation, and likely in a CCL2/CCR2 axis.

STAT6⁻/⁻ mice exhibit decreased cells with alternatively activated macrophage phenotypes and enhanced disease severity in murine neurocysticercosis

In this study, using a murine model for neurocysticercosis, macrophage phenotypes and their functions were examined. Mesocestoides corti infection in the central nervous system (CNS) induced expression of markers associated with alternatively activated macrophages (AAMs) and a scarcity of iNOS, a classically activated macrophage marker. The infection in STAT6(-/-) mice resulted in significantly reduced accumulation of AAMs as well as enhanced susceptibility to infection coinciding with increased parasite burden and greater neuropathology. These results demonstrate that macrophages in the helminth infected CNS are largely of AAM phenotypes, particularly as the infection progresses, and that STAT6 dependent responses, possibly involving AAMs, are essential for controlling neurocysticercosis.

Interleukin-33 contributes to both M1 and M2 chemokine marker expression in human macrophages

Background

Interleukin-33 is a member of the IL-1 cytokine family whose functions are mediated and modulated by the ST2 receptor. IL-33-ST2 expression and interactions have been explored in mouse macrophages but little is known about the effect of IL-33 on human macrophages. The expression of ST2 transcript and protein levels, and IL-33-mediated effects on M1 (i.e. classical activation) and M2 (i.e. alternative activation) chemokine marker expression in human bone marrow-derived macrophages were examined.

Results

Human macrophages constitutively expressed the membrane-associated (i.e. ST2L) and the soluble (i.e. sST2) ST2 receptors. M2 (IL-4 + IL-13) skewing stimuli markedly increased the expression of ST2L, but neither polarizing cytokine treatment promoted the release of sST2 from these cells. When added to naïve macrophages alone, IL-33 directly enhanced the expression of CCL3. In combination with LPS, IL-33 blocked the expression of the M2 chemokine marker CCL18, but did not alter CCL3 expression in these naive cells. The addition of IL-33 to M1 macrophages markedly increased the expression of CCL18 above that detected in untreated M1 macrophages. Similarly, alternatively activated human macrophages treated with IL-33 exhibited enhanced expression of CCL18 and the M2 marker mannose receptor above that detected in M2 macrophages alone.

Conclusions

Together, these data suggest that primary responses to IL-33 in bone marrow derived human macrophages favors M1 chemokine generation while its addition to polarized human macrophages promotes or amplifies M2 chemokine expression.

Identification of the resistance of a novel molecule heat shock protein 90alpha (HSP90alpha) in Microtus fortis to Schistosoma japonicum infection

Microtus fortis is a naturally resistant vertebrate host of Schistosoma japonicum by preventing completion of parasite's life cycle. Sera of M. fortis were found to have anti-schistosome effect in vitro and in vivo. In order to identify genes associated with the anti-schistosome effect of M. fortis, we screened a M. fortis marrow cDNA expression library by expression cloning and identified a 331-bp clone gC14.75. It was the homologue of heat shock protein 90alpha (HSP90alpha). Full-length of M. fortis HSP90alpha gene, Mf-HSP90alpha, was amplified according to gC14.75 and Cricetulus griseus HSP90alpha. To test the potential anti-schistosome function of Mf-HSP90alpha, we prepared conditioned medium of Mf-HSP90alpha and added it to schistosomula cultured in vitro. It caused 27.0% schistosomula death rate in 96h, which was considerably higher than that of negative control. We transferred Mf-HSP90alpha by retroviral expression vector pLXSN into mice to investigate its anti-schistosome effect in vivo. Compared with those of DMEM injection control, mice injected with Mf-HSP90alpha recombinant retrovirus had 40.8% worm burden reduction and 57.9% reduction in liver eggs per gram (LEPG) indicating its anti-schistosome effect in vivo. Taken together, our results suggested Mf-HSP90alpha as a novel anti-schistosome molecule in vitro and in vivo.

Differential polarization of alveolar macrophages and bone marrow-derived monocytes following chemically and pathogen-induced chronic lung inflammation

Alveolar macrophages and BDMCs undergo sequential biochemical changes during the chronic inflammatory response to chemically induced lung carcinogenesis in mice. Herein, we examine two chronic lung inflammation models-repeated exposure to BHT and infection with Mycobacterium tuberculosis-to establish whether similar macrophage phenotype changes occur in non-neoplastic pulmonary disease. Exposure to BHT or M. tuberculosis results in pulmonary inflammation characterized by an influx of macrophages, followed by systemic effects on the BM and other organs. In both models, pulmonary IFN-gamma and IL-4 production coincided with altered polarization of alveolar macrophages. Soon after BHT administration or M. tuberculosis infection, IFN-gamma content in BALF increased, and BAL macrophages became classically (M1) polarized, as characterized by increased expression of iNOS. As inflammation progressed in both models, the amount of BALF IFN-gamma content and BAL macrophage iNOS expression decreased, and BALF IL-4 content and macrophage arginase I expression rose, indicating alternative/M2 polarization. Macrophages present in M. tuberculosis-induced granulomas remained M1-polarized, implying that these two pulmonary macrophage populations, alveolar and granuloma-associated, are exposed to different activating cytokines. BDMCs from BHT-treated mice displayed polarization profiles similar to alveolar macrophages, but BDMCs in M. tuberculosis-infected mice did not become polarized. Thus, only alveolar macrophages in these two models of chronic lung disease exhibit a similar progression of polarization changes; polarization of BDMCs was specific to BHT-induced pulmonary inflammation, and polarization of granuloma macrophages was specific to the M. tuberculosis infection.

IL-33 shifts macrophage polarization, promoting resistance against Pseudomonas aeruginosa keratitis

PURPOSE

To determine the role of IL-33 in resistance to Pseudomonas aeruginosa keratitis.

METHODS

Corneal IL-33 mRNA and protein levels were tested in susceptible C57BL/6 (B6) and resistant BALB/c mice. B6 mice were injected with recombinant mouse IL-33 (rmIL-33) and disease severity, bacterial load, polymorphonuclear neutrophils (PMN) infiltrate, gene expression of inflammatory, and T-helper (Th)1/Th2 cytokines were tested by RT-PCR. IL-33 signaling and macrophage (Mvarphi) polarization also were examined.

RESULTS

IL-33 mRNA and protein were expressed constitutively in the normal corneas of both groups and were significantly elevated at 1 to 5 days after infection in BALB/c over B6 mice. rmIL-33-treated B6 mice showed less severe disease than did PBS controls and exhibited decreased bacterial load, PMN infiltrate, and corneal mRNA levels for IL-1beta, MIP-2, and TNF-alpha. Th2-type cytokines (IL-4, -5, -10) also were significantly upregulated, and protein levels for TNF-alpha and IL-10 confirmed the mRNA data. To further investigate IL-33 in corneal inflammation, it was overexpressed in Mvarphi (RAW264.7 cells). This significantly increased IL-5 and IL-10, while it decreased IFN-gamma and other pro-inflammatory cytokines. The role of the Mvarphi was further tested in infected rmIL-33 compared with PBS-injected mice. Immunostaining showed that rmIL-33 injection shifted Mvarphi polarization from NO synthase 2 to arginase production. Furthermore, peritoneally elicited cells (B6 mice) treated with lipopolysaccharide and rmIL-33 exhibited elevated ST2 levels and a shift from IL-12 to IL-10 mRNA production.

CONCLUSIONS

These data provide evidence that IL-33 promotes a Th2-type immune response and reduces inflammation by polarizing the Mvarphi production of anti-inflammatory mediators in the cornea.

Epigenetic regulation of the alternatively activated macrophage phenotype

Alternatively activated (M2) macrophages play critical roles in diverse chronic diseases, including parasite infections, cancer, and allergic responses. However, little is known about the acquisition and maintenance of their phenotype. We report that M2-macrophage marker genes are epigenetically regulated by reciprocal changes in histone H3 lysine-4 (H3K4) and histone H3 lysine-27 (H3K27) methylation; and the latter methylation marks are removed by the H3K27 demethylase Jumonji domain containing 3 (Jmjd3). We found that continuous interleukin-4 (IL-4) treatment leads to decreased H3K27 methylation, at the promoter of M2 marker genes, and a concomitant increase in Jmjd3 expression. Furthermore, we demonstrate that IL-4-dependent Jmjd3 expression is mediated by STAT6, a major transcription factor of IL-4-mediated signaling. After IL-4 stimulation, activated STAT6 is increased and binds to consensus sites at the Jmjd3 promoter. Increased Jmjd3 contributes to the decrease of H3K27 dimethylation and trimethylation (H3K27me2/3) marks as well as the transcriptional activation of specific M2 marker genes. The decrease in H3K27me2/3 and increase in Jmjd3 recruitment were confirmed by in vivo studies using a Schistosoma mansoni egg-challenged mouse model, a well-studied system known to support an M2 phenotype. Collectively, these data indicate that chromatin remodeling is mechanistically important in the acquisition of the M2-macrophage phenotype.

Activation and regulation of toll-like receptors (TLRs) by helminth parasites

Helminth (worm) infections are major public health problems that have important socioeconomic consequences for the more than 2 billion infected individuals. Chronicity (their hallmark) can lead to anemia (in hookworm infection), river blindness (onchcerciasis), cirrhosis (schistosomiasis), and elephantiasis (lymphatic filariasis). Although there have been many studies examining innate immune responses (including TLR expression and function) in response to intracellular pathogens, fewer have examined the interaction of the multicellular helminth parasites and the innate immune system. This review will focus on two "systemic" helminth parasitic infections (lymphatic filariasis and schistosomiasis) and the regulation of TLRs that may contribute to infection outcome.

TLR3 modulates immunopathology during a Schistosoma mansoni egg-driven Th2 response in the lung

We examined the role of TLR3 in Th2-driven pulmonary granulomatous disease, using wildtype (TLR3(+/+)) and TLR3 gene-deficient (TLR3(-/-)) mice in a well-established model of Schistosoma mansoni egg-induced pulmonary granuloma. The intravenous bolus injection of S. mansoni eggs into S. mansoni-sensitized TLR3(+/+) mice was associated with an increase in TLR3 transcript expression in alveolar macrophages and ex vivo spleen and lung cultures at day 8 after egg injection. Lungs from TLR3(-/-) mice showed an increase in granuloma size, greater collagen deposition around the granuloma, and increased Th2 cytokine and chemokine levels compared with similarly sensitized and challenged TLR3(+/+) mice. Macrophages from TLR3(-/-) mice exhibited an M2 phenotype characterized by increased arginase and CCL2 expression. Significantly greater numbers of CD4(+)CD25(+) T cells were present in the lungs of TLR3(-/-) mice compared with TLR3(+/+) mice at day 8 after egg embolization. Cells derived from granulomatous lung and lung draining lymph nodes of TLR3(-/-) mice released significantly higher levels of IL-17 levels relative to TLR3(+/+) cells. Thus, our data suggest that TLR3 has a major regulatory role during a Th2-driven granulomatous response as its absence enhanced immunopathology.

Inflammatory and alternatively activated human macrophages attract vessel-associated stem cells, relying on separate HMGB1- and MMP-9-dependent pathways

Inflammatory macrophages recruited at the site of damaged muscles progressively acquire an alternative activation profile. Inflammatory (M1) and alternatively activated (M2) macrophages exert various and even opposite functions. M1 cells amplify tissue damage, and M2 cells dispose of necrotic fibers and deliver survival signals to myogenic precursors, finally supporting healing. A critical step in muscle healing is the recruitment of myogenic stem cells, including vessel-associated stem cells (mesoangioblasts), which have been demonstrated to home to damaged skeletal muscle selectively and preferentially. Little information is available about the signals involved and the role played by infiltrating macrophages. Here, we report that the polarization of macrophages dramatically skews the secretion of high mobility group box 1 (HMGB1), TNF-alpha, vascular endothelial growth factor, and metalloproteinase 9 (MMP-9), molecules involved in the regulation of cell diapedesis and migration. All polarized macrophage populations were strikingly effective at inducing mesoangioblast migration. By means of specific inhibitors, we verified that the recruitment of mesoangioblasts requires the secretion of HMGB1 and TNF-alpha by M1 cells and of MMP-9 by M2 cells. Together, these data demonstrate a feature, unrecognized previously, of macrophages: their ability to attract stem cells, which is conserved throughout their polarization. Moreover, they open the possibility of novel strategies, aimed at interfering selectively with signals that recruit blood-derived stem cells toward pro- or anti-inflammatory macrophages.

Parasitic helminths: a pharmacopeia of anti-inflammatory molecules

Infection with parasitic helminths takes a heavy toll on the health and well-being of humans and their domestic livestock, concomitantly resulting in major economic losses. Analyses have consistently revealed bioactive molecules in extracts of helminths or in their excretory/secretory products that modulate the immune response of the host. It is our view that parasitic helminths are an untapped source of immunomodulatory substances that, in pure form, could become new drugs (or models for drug design) to treat disease. Here, we illustrate the range of immunomodulatory molecules in selected parasitic trematodes, cestodes and nematodes, their impact on the immune cells in the host and how the host may recognize these molecules. There are many examples of the partial characterization of helminth-derived immunomodulatory molecules, but these have not yet translated into new drugs, reflecting the difficulty of isolating and fully characterizing proteins, glycoproteins and lipid-based molecules from small amounts of parasite material. However, this should not deter the investigator, since analytical techniques are now being used to accrue considerable structural information on parasite-derived molecules, even when only minute quantities of tissue are available. With the introduction of methodologies to purify and structurally-characterize molecules from small amounts of tissue and the application of high throughput immunological assays, one would predict that an assessment of parasitic helminths will yield a variety of novel drug candidates in the coming years.

TLR9 regulates the mycobacteria-elicited pulmonary granulomatous immune response in mice through DC-derived Notch ligand delta-like 4

TLR9 activation is important for the maintenance of mycobacteria-elicited pulmonary granulomatous responses, hallmarks of protective immune responses following mycobacterial infection. However, the mechanism or mechanisms underlying this effect of TLR9 are not clear. Here, we show that Tlr9-deficient mice challenged with a Mycobacterium antigen display an altered Th17 cytokine profile, decreased accumulation of granuloma-associated myeloid DCs, and profoundly impaired delta-like 4 (dll4) Notch ligand expression. Mechanistic analysis revealed that WT bone marrow-derived DCs but not macrophages promoted the differentiation of Th17 cells from bacillus Calmette-Guérin-challenged (BCG-challenged) lung CD4+ T cells. Both lung and bone marrow DCs isolated from Tlr9-deficient mice inoculated with Mycobacterium antigen expressed lower levels of dll4 Notch ligand than the same cells isolated from WT mice. Passively immunizing WT mice with neutralizing antibodies specific for dll4 during granuloma formation resulted in larger granulomas and lower levels of Th17-related cytokines. In addition, dll4 specifically regulated Th17 activation in vitro. Together, these results suggest dll4 plays an important role in promoting Th17 effector activity during a mycobacterial challenge. Furthermore, TLR9 seems to be required for optimal dll4 expression and the regulation of Mycobacterium antigen-elicited granuloma formation in mice.

A novel mechanism for CCR4 in the regulation of macrophage activation in bleomycin-induced pulmonary fibrosis

Macrophage polarization into M1 or M2 phenotypes dictates the nature, duration, and severity of an inflammatory response. The objective of this study was to examine the role of CC chemokine receptor 4 (CCR4) in macrophage polarization during pulmonary oxidative injury in wild-type [WT (CCR4(+/+))] and CCR4-deficient (CCR4(-/-)) mice. Intrapulmonary administration of bleomycin sulfate provoked lethal inflammatory and fibrotic responses in WT (CCR4(+/+)) mice, but such responses were absent in CCR4(-/-) mice. Transcript and protein analyses of alveolar and bone marrow-derived macrophages showed that cells isolated from CCR4(-/-) mice did not exhibit CCL17-dependent M1 activation in response to bleomycin. Instead, CCR4(-/-) macrophages showed an M2 phenotype characterized by significantly elevated expression of arginase 1 and FIZZ1 (found in inflammatory zone 1), particularly during the peak of pulmonary inflammation. Compared with WT (CCR4(+/+)) mice, CCR4(-/-) mice exhibited a significant increase in the expression of the nonsignaling CC chemokine scavenging receptor D6 in whole lung samples and isolated macrophages. Thus, these results demonstrate that CCL17-dependent activation of CCR4 in macrophages plays a central role in free radical-induced pulmonary injury and repair.