Interleukin 33 supports squamous cell carcinoma growth via a dual effect on tumour proliferation, migration and invasion, and T cell activation.

Interleukin (IL)-33 is an important cytokine in the tumour microenvironment; it is known to promote the growth and metastasis of solid cancers, such as gastric, colorectal, ovarian and breast cancer. Our group demonstrated that the IL-33/ST2 pathway enhances the development of squamous cell carcinoma (SCC). Conversely, other researchers have reported that IL-33 inhibits tumour progression. In addition, the crosstalk between IL-33, cancer cells and immune cells in SCC remains unknown. The aim of this study was to investigate the effect of IL-33 on the biology of head and neck SCC lines and to evaluate the impact of IL-33 neutralisation on the T cell response in a preclinical model of SCC. First, we identified epithelial and peritumoural cells as a major local source of IL-33 in human SCC samples. Next, in vitro experiments demonstrated that the addition of IL-33 significantly increased the proliferative index, motility and invasiveness of SCC-25 cells, and downregulated MYC gene expression in SCC cell lines. Finally, IL-33 blockade significantly delayed SCC growth and led to a marked decrease in the severity of skin lesions. Importantly, anti-IL-33 monoclonal antibody therapy increase the percentage of CD4+IFNγ+ T cells and decreased CD4+ and CD8+ T cells secreting IL-4 in tumour-draining lymph nodes. Together, these data suggest that the IL-33/ST2 pathway may be involved in the crosstalk between the tumour and immune cells by modulating the phenotype of head and neck SCC and T cell activity. IL-33 neutralisation may offer a novel therapeutic strategy for SCC.

The antimetastatic activity of orlistat is accompanied by an antitumoral immune response in mouse melanoma.

PURPOSE: Fatty acid synthase (FASN), the multifunctional enzyme responsible for endogenous fatty acid synthesis, is highly expressed and associated with poor prognosis in several human cancers, including melanoma. Our group has previously shown that pharmacological inhibition of FASN with orlistat decreases proliferation, promotes apoptosis, and reduces the metastatic spread of B16-F10 cells in experimental models of melanoma. While most of the orlistat antitumor properties seem to be closely related to direct effects on malignant cells, its impact on the host immune system is still unknown. METHODS: The effects of orlistat on the phenotype and activation status of infiltrating leukocytes in primary tumors and metastatic lymph nodes were assessed using a model of spontaneous melanoma metastasis (B16-F10 cells/C57BL/6 mice). Cells from the primary tumors and lymph nodes were mechanically dissociated and immune cells phenotyped by flow cytometry. The expression of IL-12p35, IL-12p40, and inducible nitric oxide synthase (iNOS) was analyzed by qRT-PCR and production of nitrite (NO2-) evaluated in serum samples with the Griess method. RESULTS: Orlistat-treated mice exhibited a 25% reduction in the number of mediastinal lymph node metastases (mean 3.96 ± 0.78, 95% CI 3.63-4.28) compared to the controls (mean 5.7 ± 1.72; 95% CI 5.01-6.43). The drug elicited an antitumor immune response against experimental melanomas by increasing maturation of intratumoral dendritic cells (DC), stimulating the expression of cytotoxicity markers in CD8 T lymphocytes and natural killer (NK) cells, as well as reducing regulatory T cells (Tregs). Moreover, the orlistat-treatment increased serum levels of nitric oxide (NO) concentrations. CONCLUSION: Taken together, these findings suggest that orlistat supports an antitumor response against experimental melanomas by increasing CD80/CD81-positive and IL-12-positive DC populations, granzyme b/NKG2D-positive NK populations, and perforin/granzyme b-positive CD8 T lymphocytes as well as reducing Tregs counts within experimental melanomas.

Circulating monocytes from prostate cancer patients promote invasion and motility of epithelial cells.

BACKGROUND: Recruited myeloid cells are known to promote cancer initiation, malignant progression, metastasis, and resistance to therapy in the tumor niche. We tested the hypothesis that circulating blood monocytes from advanced prostate cancer (PCa) patients exhibit a protumor phenotype and directly influence the tumor microenvironment in response to tumor-derived signals. METHODS: Blood monocytes from advanced and stable PCa patients were cultured, and the conditioned media (CM) were collected and analyzed using standard invasion and wound closure assays to measure effects on invasion and motility of PCa tumor cells. We then identified the proteome profile of these monocytes using proteome array and ELISA. RESULTS: Conditioned media from circulating monocytes in patients with metastatic prostate cancer (PCa-M) increased invasion of epithelial PCa cells in vitro. Proteome Profiler Analysis revealed that monocyte-derived CM from metastatic castration-resistant (mCRPC) patients presented high levels of chitinase-3-like 1 (CHI3L1, YKL-40) when compared to patients with stable disease (PCa-N) and healthy control individuals (HC). The only described receptor for CHI3L1, interleukin-13 receptor α2 (IL-13Rα2), was significantly up-regulated in the human metastatic PCa cell line, ARCaPM . Accordingly, we observed that the activation of IL-13Rα2 from PCa-M CM increased the invasiveness of ARCaPM cells while siRNA directed against this receptor significantly reduced invasiveness of these cells in the presence of CM from PCa-M patients. CONCLUSIONS: Thus, we show that circulating monocytes from metastatic PCa patients exert a tumor-promoting role via the secretion of CHI3L1, and CHI3L1 demands further exploration as a possible therapeutic target in advanced PCa.

ST2/IL-33 signaling promotes malignant development of experimental squamous cell carcinoma by decreasing NK cells cytotoxicity and modulating the intratumoral cell infiltrate.

Squamous cell carcinoma (SCC) is the second most common form of skin cancer and the mechanism(s) involved in the progression of this tumor are unknown. Increases in the expression of IL-33/ST2 axis components have been demonstrated to contribute to neoplastic transformation in several tumor models and interleukin-33 is correlated with poor prognosis of patients with squamous cell carcinoma of the tongue. Based on these observations, we sought to determine the role of the IL-33/ST2 pathway during the development of SCC. Our findings show that ST2-deficiency led to a marked decrease in the severity of skin lesions, suggesting that ST2 signaling contributed to tumor development. An analysis of tumor lesions in wild-type and ST2KO mice revealed that a lack of ST2 was associated with specific and significant reductions in the numbers of CD4+ T cells, CD8+ T cells, dendritic cells, and macrophages. In addition, NK cells that were isolated from ST2KO mice exhibited higher cytotoxic activity than cells isolated from wild-type mice. Notably, ST2 deficiency resulted in lower IFN-γ, TNF-α, IL-10, and IL-17 production in tumor samples. Our findings indicate that the IL-33/ST2 pathway contributes to the development of SCC by affecting leukocyte migration to tumor microenvironment and impairing NK cytotoxic activity.

TRAIL-Dependent Resolution of Pulmonary Fibrosis.

Idiopathic pulmonary fibrosis (IPF) is the most common form of interstitial lung disease characterized by the persistence of activated myofibroblasts resulting in excessive deposition of extracellular matrix proteins and profound tissue remodeling. In the present study, the expression of tumor necrosis factor- (TNF-) related apoptosis-inducing ligand (TRAIL) was key to the resolution of bleomycin-induced pulmonary fibrosis. Both in vivo and in vitro studies demonstrated that Gr-1+TRAIL+ bone marrow-derived myeloid cells blocked the activation of lung myofibroblasts. Although soluble TRAIL was increased in plasma from IPF patients, the presence of TRAIL+ myeloid cells was markedly reduced in IPF lung biopsies, and primary lung fibroblasts from this patient group expressed little of the TRAIL receptor-2 (DR5) when compared with appropriate normal samples. IL-13 was a potent inhibitor of DR5 expression in normal fibroblasts. Together, these results identified TRAIL+ myeloid cells as a critical mechanism in the resolution of pulmonary fibrosis, and strategies directed at promoting its function might have therapeutic potential in IPF.

Modulation of cabozantinib efficacy by the prostate tumor microenvironment.

The tumor microenvironment (TME) is increasingly recognized as the arbiter of metastatic progression and drug resistance in advanced prostate cancer (PCa). Cabozantinib is a potent tyrosine kinase inhibitor (TKI) with reported biological activity in the PCa epithelia, but failed to provide an overall survival benefit in phase 3 clinical trials. However, the promising biologic efficacy of the drug in early trials warranted a better understanding of the mechanism of action, with the goal of improving patient selection for TKI-based therapy such as cabozantinib. We found a 100-fold lower cabozantinib IC50 in macrophages, PCa associated fibroblasts, and bone marrow fibroblasts compared to PCa epithelia. In PCa mouse models, pre-treatment with cabozantinib potentiated osseous and visceral tumor engraftment, suggesting a pro-tumorigenic host response to the drug. We further found that the host effects of cabozantinib impacted bone turnover, but not necessarily tumor expansion. Cabozantinib affected M1 macrophage polarization in mice. Analogously, circulating monocytes from PCa patients treated with cabozantinib, demonstrated a striking correlation of monocyte reprograming with therapeutic bone responsivity, to support patient selection at early stages of treatment. Thus, a re-evaluation of TKI-based therapeutic strategies in PCa can be considered for suitable patient populations based on TME responses.

The STAT4/MLL1 Epigenetic Axis Regulates the Antimicrobial Functions of Murine Macrophages.

Macrophages are critical immune cells for the clearance of microbial pathogens and cellular debris from peripheral tissues. Macrophage inflammatory responses are governed by gene expression patterns, and these patterns are often subject to epigenetic control. Chromatin modifications, such as histone methylation, regulate gene accessibility in macrophages, and macrophage polarization is governed in part by the expression and function of chromatin-modifying enzymes. The histone methyltransferase mixed-lineage leukemia 1 (MLL1) preferentially modifies lysine residue 4 on the unstructured protein tail of histone H3. MLL1 expression and function have been shown to be governed by signal transduction pathways that are activated by inflammatory stimuli, such as NF-κB. Therefore, we sought to investigate the role of MLL1 in mediating macrophage inflammatory responses. Bone marrow-derived macrophages from mice with a targeted MLL1 gene knockout (Lys2-Cre+/- MLL1fx/fx) exhibited decreased proinflammatory gene expression with concurrent decreases in activating histone methylation. However, MLL1-deficient macrophages also exhibited increased phagocytic and bacterial killing activity in vitro. RNA profiling of MLL1-knockout macrophages identified numerous genes involved with inflammatory responses whose expression was altered in response to TLR ligands or proinflammatory cytokines, including STAT4. STAT4-dependent cytokines, such as type I IFNs were able to drive MLL1 expression in macrophages, and MLL1-knockout macrophages exhibited decreased activating histone methylation in the STAT4 promoter. These results implicate an important role for MLL1-dependent epigenetic regulation of macrophage antimicrobial functions.

SRC family kinase FYN promotes the neuroendocrine phenotype and visceral metastasis in advanced prostate cancer.

FYN is a SRC family kinase (SFK) that has been shown to be up-regulated in human prostate cancer (PCa) tissues and cell lines. In this study, we observed that FYN is strongly up-regulated in human neuroendocrine PCa (NEPC) tissues and xenografts, as well as cells derived from a NEPC transgenic mouse model. In silico analysis of FYN expression in prostate cancer cell line databases revealed an association with the expression of neuroendocrine (NE) markers such as CHGA, CD44, CD56, and SYP. The loss of FYN abrogated the invasion of PC3 and ARCaPM cells in response to MET receptor ligand HGF. FYN also contributed to the metastatic potential of NEPC cells in two mouse models of visceral metastasis with two different cell lines (PC3 and TRAMPC2-RANKL). The activation of MET appeared to regulate neuroendocrine (NE) features as evidenced by increased expression of NE markers in PC3 cells with HGF. Importantly, the overexpression of FYN protein in DU145 cells was directly correlated with the increase of CHGA. Thus, our data demonstrated that the neuroendocrine differentiation that occurs in PCa cells is, at least in part, regulated by FYN kinase. Understanding the role of FYN in the regulation of NE markers will provide further support for ongoing clinical trials of SFK and MET inhibitors in castration-resistant PCa patients.

Cytokine induced phenotypic and epigenetic signatures are key to establishing specific macrophage phenotypes.

Macrophages (MΦ) play an essential role in innate immune responses and can either display a pro-inflammatory, classically activated phenotype (M1) or undergo an alternative activation program (M2) promoting immune regulation. M-CSF is used to differentiate monocytes into MΦ and IFN-γ or IL-4+IL-13 to further polarize these cells towards M1 or M2, respectively. Recently, differentiation using only GM-CSF or M-CSF has been described to induce a M1- or M2-like phenotype, respectively. In this study, we combined both approaches by differentiating human MΦ in GM-CSF or M-CSF followed by polarization with either IFN-γ or IL-4+IL-13. We describe the phenotypic differences between CD14(hi) CD163(hi) CD206(int) FOLR2-expressing M-CSF MΦ and CD14(lo) CD163(lo) CD206(hi) GM-CSF MΦ but show that both macrophage populations reacted similarly to further polarization with IFN-γ or IL-4+IL-13 with up- and down-regulation of common M1 and M2 marker genes. We also show that high expression of the mannose receptor (CD206), a marker of alternative activation, is a distinct feature of GM-CSF MΦ. Changes of the chromatin structure carried out by chromatin modification enzymes (CME) have been shown to regulate myeloid differentiation. We analyzed the expression patterns of CME during MΦ polarization and show that M1 up-regulate the histone methyltransferase MLL and demethylase KDM6B, while resting and M2 MΦ were characterized by DNA methyltransferases and histone deacetylases. We demonstrate that MLL regulates CXCL10 expression and that this effect could be abrogated using a MLL-Menin inhibitor. Taken together we describe the distinct phenotypic differences of GM-CSF or M-CSF MΦ and demonstrate that MΦ polarization is regulated by specific epigenetic mechanisms. In addition, we describe a novel role for MLL as marker for classical activation. Our findings provide new insights into MΦ polarization that could be helpful to distinguish MΦ activation states.

Toll like receptor 3 plays a critical role in the progression and severity of acetaminophen-induced hepatotoxicity.

Toll-like receptor (TLR) activation has been implicated in acetaminophen (APAP)-induced hepatotoxicity. Herein, we hypothesize that TLR3 activation significantly contributed to APAP-induced liver injury. In fasted wildtype (WT) mice, APAP caused significant cellular necrosis, edema, and inflammation in the liver, and the de novo expression and activation of TLR3 was found to be necessary for APAP-induced liver failure. Specifically, liver tissues from similarly fasted TLR3-deficient (tlr3(-/-) ) mice exhibited significantly less histological and biochemical evidence of injury after APAP challenge. Similar protective effects were observed in WT mice in which TLR3 was targeted through immunoneutralization at 3 h post-APAP challenge. Among three important death ligands (i.e. TNFα, TRAIL, and FASL) known to promote hepatocyte death after APAP challenge, TNFα was the only ligand that was significantly reduced in APAP-challenged tlr3(-/-) mice compared with APAP-challenged WT controls. In vivo studies demonstrated that TLR3 activation contributed to TNFα production in the liver presumably via F4/80(+) and CD11c(+) immune cells. In vitro studies indicated that there was cooperation between TNFα and TLR3 in the activation of JNK signaling in isolated and cultured liver epithelial cells (i.e. nMuLi). Moreover, TLR3 activation enhanced the expression of phosphorylated JNK in APAP injured livers. Thus, the current study demonstrates that TLR3 activation contributes to APAP-induced hepatotoxicity.

The critical role of Notch ligand Delta-like 1 in the pathogenesis of influenza A virus (H1N1) infection.

Influenza A viral infections have been identified as the etiologic agents for historic pandemics, and contribute to the annual mortality associated with acute viral pneumonia. While both innate and acquired immunity are important in combating influenza virus infection, the mechanism connecting these arms of the immune system remains unknown. Recent data have indicated that the Notch system is an important bridge between antigen-presenting cells (APCs) and T cell communication circuits and plays a central role in driving the immune system to overcome disease. In the present study, we examine the role of Notch signaling during influenza H1N1 virus infection, focusing on APCs. We demonstrate here that macrophages, but not dendritic cells (DCs), increased Notch ligand Delta-like 1 (Dll1) expression following influenza virus challenge. Dll1 expression on macrophages was dependent on retinoic acid-inducible gene-I (RIG-I) induced type-I IFN pathway, and not on the TLR3-TRIF pathway. We also found that IFNα-Receptor knockout mice failed to induce Dll1 expression on lung macrophages and had enhanced mortality during influenza virus infection. Our results further showed that specific neutralization of Dll1 during influenza virus challenge induced higher mortality, impaired viral clearance, and decreased levels of IFN-γ. In addition, we blocked Notch signaling by using γ-secretase inhibitor (GSI), a Notch signaling inhibitor. Intranasal administration of GSI during influenza infection also led to higher mortality, and higher virus load with excessive inflammation and an impaired production of IFN-γ in lungs. Moreover, Dll1 expression on macrophages specifically regulates IFN-γ levels from CD4(+)and CD8(+)T cells, which are important for anti-viral immunity. Together, the results of this study show that Dll1 positively influences the development of anti-viral immunity, and may provide mechanistic approaches for modifying and controlling the immune response against influenza H1N1 virus infection.

Cell-free antigens from Paracoccidioides brasiliensis drive IL-4 production and increase the severity of paracoccidioidomycosis.

The thermally dimorphic fungus Paracoccidioides brasiliensis (Pb) is the causative agent of paracoccidioidomycosis (PCM), one of the most frequent systemic mycosis that affects the rural population in Latin America. PCM is characterized by a chronic inflammatory granulomatous reaction, which is consequence of a Th1-mediated adaptive immune response. In the present study we investigated the mechanisms involved in the immunoregulation triggered after a prior contact with cell-free antigens (CFA) during a murine model of PCM. The results showed that the inoculation of CFA prior to the infection resulted in disorganized granulomatous lesions and increased fungal replication in the lungs, liver and spleen, that paralleled with the higher levels of IL-4 when compared with the control group. The role of IL-4 in facilitating the fungal growth was demonstrated in IL-4-deficient- and neutralizing anti-IL-4 mAb-treated mice. The injection of CFA did not affect the fungal growth in these mice, which, in fact, exhibited a significant diminished amount of fungus in the tissues and smaller granulomas. Considering that in vivo anti-IL-4-application started one week after the CFA-inoculum, it implicates that IL-4-CFA-induced is responsible by the mediation of the observed unresponsiveness. Further, the characterization of CFA indicated that a proteic fraction is required for triggering the immunosuppressive mechanisms, while glycosylation or glycosphingolipids moieties are not. Taken together, our data suggest that the prior contact with soluble Pb antigens leads to severe PCM in an IL-4 dependent manner.

Dysregulated cytokine expression by CD4+ T cells from post-septic mice modulates both Th1 and Th2-mediated granulomatous lung inflammation.

Previous epidemiological studies in humans and experimental studies in animals indicate that survivors of severe sepsis exhibit deficiencies in the activation and effector function of immune cells. In particular, CD4+ T lymphocytes can exhibit reduced proliferative capacity and improper cytokine responses following sepsis. To further investigate the cell-intrinsic defects of CD4+ T cells following sepsis, splenic CD4+ T cells from sham surgery and post-septic mice were transferred into lymphopenic mice. These recipient mice were then subjected to both TH1-(purified protein derivative) and TH2-(Schistosoma mansoni egg antigen) driven models of granulomatous lung inflammation. Post-septic CD4+ T cells mediated smaller TH1 and larger TH2 lung granulomas as compared to mice receiving CD4+ T cells from sham surgery donors. However, cytokine production by lymph node cells in antigen restimulation assays indicated increased pan-specific cytokine expression by post-septic CD4+ T cell recipient mice in both TH1 and TH2 granuloma models. These include increased production of T(H)2 cytokines in TH1 inflammation, and increased production of T(H)1 cytokines in TH2 inflammation. These results suggest that cell-intrinsic defects in CD4+ T cell effector function can have deleterious effects on inflammatory processes post-sepsis, due to a defect in the proper regulation of TH-specific cytokine expression.

Amelioration of sepsis by inhibiting sialidase-mediated disruption of the CD24-SiglecG interaction.

Suppression of inflammation is critical for effective therapy of many infectious diseases. However, the high rates of mortality caused by sepsis attest to the need to better understand the basis of the inflammatory sequelae of sepsis and to develop new options for its treatment. In mice, inflammatory responses to host danger-associated molecular patterns (DAMPs), but not to microbial pathogen-associated molecular patterns (PAMPs), are repressed by the interaction [corrected] of CD24 and SiglecG (SIGLEC10 in human). Here we use an intestinal perforation model of sepsis to show that microbial sialidases target the sialic acid-based recognition of CD24 by SiglecG/10 to exacerbate inflammation. Sialidase inhibitors protect mice against sepsis by a mechanism involving both CD24 and Siglecg, whereas mutation of either gene exacerbates sepsis. Analysis of sialidase-deficient bacterial mutants confirms the key contribution of disrupting sialic acid-based pattern recognition to microbial virulence and supports the clinical potential of sialidase inhibition for dampening inflammation caused by infection.

Delta-like 4 differentially regulates murine CD4 T cell expansion via BMI1.

BACKGROUND: Studies have shown that Notch is essential for the maintenance of a T cell Th2 phenotype in vivo. It has also been shown that Notch ligands have diverse functions during T cell activation. We chose to investigate the role of Notch ligands during the Th2 response. PRINCIPAL FINDINGS: We studied the relationship of two Notch ligands, delta-like 4 and jagged-1, to T cell proliferation in C57 Bl/6 mice. Our findings indicate that jagged-1 does not affect the rate of T cell proliferation in any subset examined. However, delta-like 4 causes an increase in the expansion of Th2 memory cells and a decrease in effector cell proliferation. Our in vivo studies indicate that the Notch system is dynamically regulated, and that blocking one Notch ligand increases the effective concentration of other Notch ligands, thus altering the response. Examination of genes related to the Notch pathway revealed that the Notch receptors were increased in memory T cells. Expression of BMI1, a gene involved in T cell proliferation, was also higher in memory T cells. Further experiments demonstrated that Notch directly regulates the expression of the BMI1 gene in T cells and may govern T cell proliferation through this pathway. CONCLUSIONS: From these experiments we can make several novel conclusions about the role of Notch ligands in T cell biology. The first is that delta-like 4 suppresses effector cell proliferation and enhances Th2 memory cell proliferation. The second is that blocking one Notch ligand in vivo effectively increases the concentration of other Notch ligands, which can then alter the response.

Serum amyloid P attenuates M2 macrophage activation and protects against fungal spore-induced allergic airway disease.

BACKGROUND: Aspergillus fumigatus conidia aggravate asthmatic responses. Lung macrophages normally kill fungal conidia, but the presence of type 2 cytokines during asthma contributes to the alternative (or M2) activation of these cells, which secrete proallergic factors and exhibit impaired innate immunity. OBJECTIVE: Considering that pentraxins modulate macrophage function, we examined the effect of C-reactive protein (CRP) and serum amyloid P (SAP) in an experimental model of A fumigatus-induced allergic airway disease. METHODS: The effects of SAP and CRP on M2 macrophage differentiation were examined in vitro, and the in vivo effects of these pentraxins were analyzed in the asthma model. RESULTS: SAP inhibited the generation of M2 markers, such as arginase and the chitinase Ym-1, through an FcγR-dependent mechanism in cultured macrophages. This effect correlated with a decrease in signal transducer and activator of transcription 6 (STAT6) phosphorylation in SAP-treated M2 macrophages. In vivo treatment with SAP significantly decreased methacholine-induced bronchial resistance, mucus cell metaplasia, the number of "found in inflammatory zone 1" (FIZZ1)-positive cells in the lungs, and collagen deposition compared with the control group. CRP had a modest effect on M2 differentiation, and in vivo treatment with CRP had a minor effect or exacerbated A fumigatus-induced lung disease. Finally, the adoptive transfer of SAP-pretreated M2 macrophages into allergic mice significantly attenuated disease when compared with nontransferred or M2-transferred control groups. CONCLUSIONS: These findings demonstrate that SAP is a potent inhibitor of M2 macrophage differentiation and represents a novel therapy in A fumigatus-induced allergic disease.

The post sepsis-induced expansion and enhanced function of regulatory T cells create an environment to potentiate tumor growth.

One of the more insidious outcomes of patients who survive severe sepsis is profound immunosuppression. In this study, we addressed the hypothesis that post septic immune defects were due, in part, to the presence and/or expansion of regulatory T cells (Tregs). After recovery from severe sepsis, mice exhibited significantly higher numbers of Tregs, which exerted greater in vitro suppressive activity compared with controls. The expansion of Tregs was not limited to CD25(+) cells, because Foxp3 expression was also detected in CD25(-) cells from post septic mice. This latter group exhibited a significant increase of chromatin remodeling at the Foxp3 promoter, because a marked increase in acetylation at H3K9 was associated with an increase in Foxp3 transcription. Post septic splenic dendritic cells promoted Treg conversion in vitro. Using a solid tumor model to explore the function of Tregs in an in vivo setting, we found post septic mice showed an increase in tumor growth compared with sham-treated mice with a syngeneic tumor model. This observation could mechanistically be related to the ability of post septic Tregs to impair the antitumor response mediated by CD8(+) T cells. Together, these data show that the post septic immune system obstructs tumor immunosurveillance, in part, by augmented Treg expansion and function.

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.

TLR3 is an endogenous sensor of tissue necrosis during acute inflammatory events.

Ligands from dying cells are a source of Toll-like receptor (TLR) activating agents. Although TLR3 is known to respond to RNA from necrotic cells, the relative importance of this response in vivo during acute inflammatory processes has not been fully explored. We observed the involvement of TLR3 activation during experimental polymicrobial septic peritonitis and ischemic gut injury in the absence of an exogenous viral stimulus. In TLR3-deficient mice, increased chemokine/cytokine levels and neutrophil recruitment characterized the initial inflammatory responses in both injury models. However, the levels of inflammatory chemokines and tumor necrosis factor alpha quickly returned to baseline in tlr3(-/-) mice, and these mice were protected from the lethal effects of sustained inflammation. Macrophages from tlr3(-/-) mice responded normally to other TLR ligands but did not respond to RNA from necrotic neutrophils. Importantly, an immunoneutralizing antibody directed against TLR3 attenuated the generation of inflammatory chemokines evoked by byproducts from necrotic neutrophils cultured with wild-type macrophages. In vivo, anti-TLR3 antibody attenuated the tissue injury associated with gut ischemia and significantly decreased sepsis-induced mortality. Collectively, these data show that TLR3 is a regulator of the amplification of immune response and serves an endogenous sensor of necrosis, independent of viral activation.

Role of interleukin (IL)-18 in experimental paracoccidioidomycosis.

Interleukin (IL)-18 has been regarded as a Th1 type cytokine involved in many fungal and parasitic infections. Since there have been no studies, as of yet, evaluating the role of this cytokine in paracoccidioidomycosis (PCM), we assessed the function of IL-18 by using an experimental PCM model. Our results showed that IL-18 knockout (IL-18 -/-) BALB/c were more resistant to Paracoccidioides brasiliensis than their littermate controls (WT). In fact, mortality rate was higher in WT mice and in the first month of infection, the number of colony forming units of the etiologic agent recovered from the lungs was greater in WT mice. In histopathological analyses, well-formed granulomas were seen in both WT and IL-18(-/-) mice. However, substantial differences were observed at the second month of infection when epithelioid cells predominated in the lesions of IL-18(-/-) mice, which could infer that IL-18 postpones pulmonary healing. The levels of IL-10 were significantly higher in IL-18 sufficient mice at early stages of infection and therefore account for the delayed fungal clearance observed in WT mice. TNF-alpha augmented later in the infection of WT mice, seemingly to compensate high levels of IL-10. Our results demonstrated that IL-18 has a critical role in protecting BALB/c mice against disseminated PCM.