Tpl2 kinase regulates T cell interferon-gamma production and host resistance to Toxoplasma gondii

Tumor progression locus 2 (TPL2): A Cot-plicated progression from inflammation to chronic liver disease

The cytoplasmic protein tumor progression locus 2 (TPL2), also known as cancer Osaka thyroid (Cot), or MAP3K8, is thought to have a significant role in a variety of cancers and illnesses and it is a key component in the activation pathway for the expression of inflammatory mediators. Despite the tight connection between inflammation and TPL2, its function has not been extensively studied in chronic liver disease (CLD), a major cause of morbidity and mortality worldwide. Here, we analyze more in detail the significance of TPL2 in CLD to shed light on the pathological and molecular transduction pattern of TPL2 during the progression of CLD. This might result in important advancements and enable progress in the diagnosis and treatment of CLD.

Heterogeneity of circulating CD4+CD8+ double-positive T cells characterized by scRNA-seq analysis and trajectory inference

The frequency of CD4⁺CD8⁺ double-positive (DP) T cells is highly associated with a variety of diseases. Recently, we used high-throughput single-cell RNA sequencing to show that circulating DP T cells in cynomolgus monkeys comprise nine heterogeneous populations. To better understand the characteristics of DP T cells, we analyzed 7601 cells from a rhesus monkey and detected 14,459 genes. Rhesus monkey DP T cells comprised heterogeneous populations (naïve, Treg-, Tfh-, CCR9⁺ Th-, Th17-, Th2-, Eomes⁺ Tr1-, CTL-, PLZF⁺ innate- and Eomes⁺ innate-like cells) with multiple potential functions. We also identified two new subsets using aggregated scRNA-seq datasets from the rhesus and the cynomolgus monkey: CCR9⁺ Th-like cells expressing ICAM2 and ITGA1, and PLZF⁺ innate-like cells that display innate-associated gene signatures such as ZBTB16, TYROBP, MAP3K8, and KLRB1. Trajectory inference of cell differentiation status showed that most DP T cells in the rhesus monkey were found in the mid-to-late pseudotime, whereas DP T cells from the cynomolgus monkey were found in early pseudotime. This suggests that DP T cells in rhesus monkeys may exhibit more diverse differentiation states than those in cynomolgus monkeys. Thus, scRNA-seq and trajectory inference identified a more diverse subset of the circulating DP T cells than originally thought.

Influenza-induced Tpl2 expression within alveolar epithelial cells is dispensable for host viral control and anti-viral immunity

Tumor progression locus 2 (Tpl2) is a serine/threonine kinase that regulates the expression of inflammatory mediators in response to Toll-like receptors (TLR) and cytokine receptors. Global ablation of Tpl2 leads to severe disease in response to influenza A virus (IAV) infection, characterized by respiratory distress, and studies in bone marrow chimeric mice implicated Tpl2 in non-hematopoietic cells. Lung epithelial cells are primary targets and replicative niches of influenza viruses; however, the specific regulation of antiviral responses by Tpl2 within lung epithelial cells has not been investigated. Herein, we show that Tpl2 is basally expressed in primary airway epithelial cells and that its expression increases in both type I and type II airway epithelial cells (AECI and AECII) in response to influenza infection. We used Nkx2.1-cre to drive Tpl2 deletion within pulmonary epithelial cells to delineate epithelial cell-specific functions of Tpl2 during influenza infection in mice. Although modest increases in morbidity and mortality were attributed to cre-dependent deletion in lung epithelial cells, no alterations in host cytokine production or lung pathology were observed. In vitro, Tpl2 inhibition within the type I airway epithelial cell line, LET1, as well as genetic ablation in primary airway epithelial cells did not alter cytokine production. Overall, these findings establish that Tpl2-dependent defects in cells other than AECs are primarily responsible for the morbidity and mortality seen in influenza-infected mice with global Tpl2 ablation.

Unravelling the Impact of the Genetic Variant rs1042058 within the TPL2 Risk Gene Locus on Molecular and Clinical Disease Course Patients with Inflammatory Bowel Disease

Background: The single nucleotide polymorphism (SNP) rs1042058 within the gene locus encoding tumor progression locus 2 (TPL2) has been recently identified as a risk gene for inflammatory bowel disease (IBD). TPL2 has been shown to regulate pro-inflammatory signaling and cytokine secretion, while inhibition of TPL2 decreases intestinal inflammation in vivo. However, the clinical and molecular implications of this disease-associated TPL2 variation in IBD patients have not yet been studied. Methods: We analyzed the impact of the IBD-associated TPL2 variation using clinical data of 2145 genotyped patients from the Swiss IBD Cohort Study (SIBDCS). Furthermore, we assessed the molecular consequences of the TPL2 variation in ulcerative colitis (UC) and Crohn’s disease (CD) patients by real-time PCR and multiplex ELISA of colon biopsies or serum, respectively. Results: We found that presence of the SNP rs1042058 within the TPL2 gene locus results in significantly higher numbers of CD patients suffering from peripheral arthritis. In contrast, UC patients carrying this variant feature a lower risk for intestinal surgery. On a molecular level, the presence of the rs1042058 (GG) IBD-risk polymorphism in TPL2 was associated with decreased mRNA levels of IL-10 in CD patients and decreased levels of IL-18 in the intestine of UC patients. Conclusions: Our data suggest that the presence of the IBD-associated TPL2 variation might indicate a more severe disease course in CD patients. These results reveal a potential therapeutic target and demonstrate the relevance of the IBD-associated TPL2 SNP as a predictive biomarker in IBD.

Tpl2 Ablation Leads to Hypercytokinemia and Excessive Cellular Infiltration to the Lungs During Late Stages of Influenza Infection

Tumor progression locus 2 (Tpl2) is a serine-threonine kinase known to promote inflammation in response to various pathogen-associated molecular patterns (PAMPs), inflammatory cytokines and G-protein-coupled receptors and consequently aids in host resistance to pathogens. We have recently shown that Tpl2-/- mice succumb to infection with a low-pathogenicity strain of influenza (x31, H3N2) by an unknown mechanism. In this study, we sought to characterize the cytokine and immune cell profile of influenza-infected Tpl2-/- mice to gain insight into its host protective effects. Although Tpl2-/- mice display modestly impaired viral control, no virus was observed in the lungs of Tpl2-/- mice on the day of peak morbidity and mortality suggesting that morbidity is not due to virus cytopathic effects but rather to an overactive antiviral immune response. Indeed, increased levels of interferon-β (IFN-β), the IFN-inducible monocyte chemoattractant protein-1 (MCP-1, CCL2), Macrophage inflammatory protein 1 alpha (MIP-1α; CCL3), MIP-1β (CCL4), RANTES (CCL5), IP-10 (CXCL10) and Interferon-γ (IFN-γ) was observed in the lungs of influenza-infected Tpl2-/- mice at 7 days post infection (dpi). Elevated cytokine and chemokines were accompanied by increased infiltration of the lungs with inflammatory monocytes and neutrophils. Additionally, we noted that increased IFN-β correlated with increased CCL2, CXCL1 and nitric oxide synthase (NOS2) expression in the lungs, which has been associated with severe influenza infections. Bone marrow chimeras with Tpl2 ablation localized to radioresistant cells confirmed that Tpl2 functions, at least in part, within radioresistant cells to limit pro-inflammatory response to viral infection. Collectively, this study suggests that Tpl2 tempers inflammation during influenza infection by constraining the production of interferons and chemokines which are known to promote the recruitment of detrimental inflammatory monocytes and neutrophils.

TRAF2 regulates T cell immunity by maintaining a Tpl2-ERK survival signaling axis in effector and memory CD8 T cells

Generation and maintenance of antigen-specific effector and memory T cells are central events in immune responses against infections. We show that TNF receptor-associated factor 2 (TRAF2) maintains a survival signaling axis in effector and memory CD8 T cells required for immune responses against infections. This signaling axis involves activation of Tpl2 and its downstream kinase ERK by NF-κB-inducing kinase (NIK) and degradation of the proapoptotic factor Bim. NIK mediates Tpl2 activation by stimulating the phosphorylation and degradation of the Tpl2 inhibitor p105. Interestingly, while NIK is required for Tpl2-ERK signaling under normal conditions, uncontrolled NIK activation due to loss of its negative regulator, TRAF2, causes constitutive degradation of p105 and Tpl2, leading to severe defects in ERK activation and effector/memory CD8 T cell survival. Thus, TRAF2 controls a previously unappreciated signaling axis mediating effector/memory CD8 T cell survival and protective immunity.

Cytokine signaling pathway in cystic fibrosis: expression of SOCS and STATs genes in different clinical phenotypes of the disease

This was an observational cross-sectional study which was done to assess the expression profile of STATs and SOCS genes in cystic fibrosis. The mRNA was isolated from peripheral blood mononuclear cells of CF patients in exacerbation, colonization and post exacerbation phases of the disease. The relative gene expression level for SOCS 1, -3, -5 and STAT 1, -3,-4,-6 genes was quantified by Real-time PCR. The levels of IL-6 were also measured in the serum by ELISA. The expression of the Th1 pathway associated genes (SOCS1, SOCS5, STAT4 and STAT1) was downregulated while the expression of Th2/Th17 pathway genes (SOCS3, STAT3, STAT6) was upregulated in both exacerbation and colonization phases as compared to healthy controls. The serum levels of IL-6 were also elevated in both the disease groups. After antibiotic treatment, the expression of SOCS5 and STAT4 was increased while the expression of rest of the genes showed downregulation which shows a shift in immune response from Th2/Th17 to Th1. Our results suggest that infection alters the cytokine signaling pathway through modulation of STATs and SOCS genes which is not able to regulate the overstimulation of cytokine signaling further leading to chronic inflammation in CF.

Foot-and-Mouth Disease Virus Capsid Protein VP1 Antagonizes TPL2-Mediated Activation of the IRF3/IFN-β Signaling Pathway to Facilitate the Virus Replication

Foot-and-mouth disease (FMD) is a severe, highly contagious viral disease of cloven-hoofed animals. In order to establish an infection, the FMD virus (FMDV) needs to counteract host antiviral responses. Tumor progression locus 2 (TPL2), a mitogen-activated protein kinase, can regulate innate and adaptive immunity; however, its exact mechanisms underlying TPL2-mediated regulation of the pathogenesis of FMDV infection remain unknown. In this study, we confirmed that TPL2 could inhibit FMDV replication in vitro and in vivo. The virus replication increased in Tpl2-deficient suckling mice in association with reduced expression of interferon-stimulated genes interferon-α (IFN-α) and myxovirus resistance (MX2) and significantly reduced expression of C-X-C motif chemokine ligand 10 (CXCL10), interferon regulatory factor 3 (IRF3), and IRF7, while the phosphorylation of IRF3 was not detected. Moreover, the interactions between TPL2 and VP1 were also confirmed. The overexpression of TPL2 promoted IRF3-mediated dose-dependent activation of the IFN-β signaling pathway in association with interactions between IRF3 and TPL2. VP1 also inhibited phosphorylation of TPL2 at Thr290, while Thr290 resulted as the key functional site associated with the TPL2-mediated antiviral response. Taken together, this study indicated that FMDV capsid protein VP1 antagonizes TPL2-mediated activation of the IRF3/IFN-β signaling pathway for immune escape and facilitated virus replication.

Toll-Like Receptor 2-Tpl2-Dependent ERK Signaling Drives Inverse Interleukin 12 Regulation in Dendritic Cells and Macrophages

This study investigated responses to Toll-like receptor 2 (TLR2)-driven extracellular signal-related kinase (ERK) signaling in dendritic cells (DCs) versus macrophages. TLR2 signaling was induced with Pam₃Cys-Ser-Lys₄, and the role of ERK signaling was interrogated pharmacologically with MEK1/2 inhibitor U0126 or genetically with bone marrow-derived macrophages or DCs from Tpl2^-/- mice. We assessed cytokine production via enzyme-linked immunosorbent assay (ELISA) or V-Plex, and mRNA levels were assessed via reverse transcriptase quantitative PCR (qRT-PCR). In macrophages, blockade of ERK signaling by pharmacologic or genetic approaches inhibited interleukin 10 (IL-10) expression and increased expression of the p40 subunit shared by IL-12 and IL-23 (IL-12/23p40). In DCs, blockade of ERK signaling similarly inhibited IL-10 expression but decreased IL-12/23p40 expression, which is opposite to the effect of ERK signaling blockade on IL-12/23p40 in macrophages. This difference in IL-12/23p40 regulation correlated with the differential expression of transcription factors cFos and IRF1, which are known to regulate IL-12 family members, including IL-12 and IL-23. Thus, the impact of ERK signaling in response to TLR2 stimulation differs between macrophages and DCs, potentially regulating their distinctive functions in the immune system. ERK-mediated suppression of IL-12/23p40 in macrophages may prevent excessive inflammation and associated tissue damage following TLR2-stimulation, while ERK-mediated induction of IL-12/23p40 in DCs may promote priming of T helper 1 (Th1) responses. A greater understanding of the role that ERK signaling plays in different immune cell types may inform the development of host-directed therapy and optimal adjuvanticity for a number of infectious pathogens.

Tumor progression locus 2 (TPL2) in tumor-promoting Inflammation, Tumorigenesis and Tumor Immunity

Over the years, tumor progression locus 2 (TPL2) has been identified as an essential modulator of immune responses that conveys inflammatory signals to downstream effectors, subsequently modulating the generation and function of inflammatory cells. TPL2 is also differentially expressed and activated in several cancers, where it is associated with increased inflammation, malignant transformation, angiogenesis, metastasis, poor prognosis and therapy resistance. However, the relationship between TPL2-driven inflammation, tumorigenesis and tumor immunity has not been addressed. Here, we reconcile the function of TPL2-driven inflammation to oncogenic functions such as inflammation, proliferation, apoptosis resistance, angiogenesis, metastasis, immunosuppression and immune evasion. We also address the controversies reported on TPL2 function in tumor-promoting inflammation and tumorigenesis, and highlight the potential role of the TPL2 adaptor function in regulating the mechanisms leading to pro-tumorigenic inflammation and tumor progression. We discuss the therapeutic implications and limitations of targeting TPL2 for cancer treatment. The ideas presented here provide some new insight into cancer pathophysiology that might contribute to the development of more integrative and specific anti-inflammatory and anti-cancer therapeutics.

Activation Receptor-Dependent IFN-γ Production by NK Cells Is Controlled by Transcription, Translation, and the Proteasome

NK cells can recognize target cells such as virus-infected and tumor cells through integration of activation and inhibitory receptors. Recognition by NK cells can lead to direct lysis of the target cell and production of the signature cytokine IFN-γ. However, it is unclear whether stimulation through activation receptors alone is sufficient for IFN-γ production. In this study, we show that NK activation receptor engagement requires additional signals for optimal IFN-γ production, which could be provided by IFN-β or IL-12. Stimulation of murine NK cells with soluble Abs directed against NK1.1, Ly49H, Ly49D, or NKp46 required additional stimulation with cytokines, indicating that a range of activation receptors with distinct adaptor molecules require additional stimulation for IFN-γ production. The requirement for multiple signals extends to stimulation with primary m157-transgenic target cells, which triggers the activation receptor Ly49H, suggesting that NK cells do require multiple signals for IFN-γ production in the context of target cell recognition. Using quantitative PCR and RNA flow cytometry, we found that cytokines, not activating ligands, act on NK cells to express Ifng transcripts. Ly49H engagement is required for IFN-γ translational initiation. Results using inhibitors suggest that the proteasome-ubiquitin-IKK-TPL2-MNK1 axis was required during activation receptor engagement. Thus, this study indicates that activation receptor-dependent IFN-γ production is regulated on the transcriptional and translational levels.

Advancement in TPL2-regulated innate immune response

Tumor progression locus 2 (TPL2) is a serine/threonine kinase that belongs to the MAP3K family. The activated TPL2 regulates the innate immune-relevant signaling pathways, such as ERK, JNK, and NF-κB, and the differentiation of immune cells, for example, CD4+ T and NK cells. Therefore, TPL2 plays a critical role in regulating the innate immune response. The present review summarizes the recent advancements in the TPL2-regulated innate immune response.

Transcription factors STAT-4, STAT-6 and CREB regulate Th1/Th2 response in leprosy patients: effect of M. leprae antigens

Background

Leprosy is an ideal human disease to study T cell regulation as patients show correlation between cytokine skewed Th1-Th2 responses and clinical forms of the disease. The Role of transcription factors on the modulation of Th1 and Th2 responses by M. leprae antigens has not been adequately studied. In the present study, we studied the effect of M. leprae antigens on transcription factors STAT-4, STAT-6 and CREB and their correlation with Th1/Th2 cell mediated immune responses in leprosy.

Methods

Leprosy patients of both categories of tuberculoid leprosy (BT/TT) and lepromatous leprosy (BL/LL) were selected from the OPD of NJ1L & OMD, (ICMR), Agra and healthy individuals (H) were chosen from the staff and students working in the institute. Peripheral blood mononuclear cells (PBMCs) of the study subjects were stimulated with M. leprae antigens (WCL, MLSA, and PGL-1). Sandwich ELISA was done in the culture supernatants of healthy and leprosy patients to detect IL-4, IL-10 and IFN-γ. Further, expression of IFN-γ and IL-4 and activation of STAT4, STAT6 and CREB transcription factors in CD4⁺ T cell with or without stimulation of M. leprae antigens was investigated by flow cytometry.

Results

Lepromatous leprosy patients showed significantly lower IFN-γ and higher IL-4 levels in culture supernatant and significantly low expression of IFN-γ and higher expression of IL-4 by CD4⁺ T cells than healthy individuals with or without antigenic stimulation. Antigenic stimulation significantly increased IL-10 in BL/LL patients but not in BT/TT patients or healthy individuals. PGL-1 stimulation led to significantly higher activation of STAT-6 in BT/TT and BL/LL patients in comparison to healthy individuals. All the three antigens led to activation of CREB in healthy and BT/TT patients but not in BL/LL patients.

Conclusion

Our findings show that M. leprae antigens differentially modulate activation of T cell transcription factors STAT-4/STAT-6 and CREB. These transcription factors are well known to regulate Th1 and Th2 mediated immune response which in turn could play vital role in the clinical manifestations of leprosy. These observations may help to determine how these T cell transcription factors affect the development of immune dysfunction and whether these new pathways have a role in immunomodulation in intracellular diseases like leprosy and TB.

The serum protein profile of early parity which induces protection against breast cancer

Early parity reduces the risk of breast cancer in women while nulliparity and late parity increase the risk of breast cancer. In order to translate this protection to women where early pregnancy is not feasible, much work has focused on understanding how parity confers protection against breast cancer, the molecular mechanisms by which this occurs is still not well understood. Healthy parous and nulliparous women were recruited for this study. We assessed serum protein profiles of early parous, late parous, and nulliparous women using the Phospho Explorer antibody array. Significantly altered proteins identified were validated by Western blot analysis. In silico analysis was performed with the data obtained. Our findings indicate increased phosphorylation levels of CDK1, AKT1 and Epo-R increased cell cycle and cell proliferation in late/nulliparous women. Increased levels of LIMK1, paxillin, caveolin-1, and tyrosine hydroxylase in late/nulliparous women demonstrate enhanced cell stress while decreased activity of p-p53 and pRAD51 in late/nulliparous women indicates decreased apoptosis and increased genomic instability. Further, increased levels of pFAK, pCD3zeta, pSTAT5B, MAP3K8 in early parous women favor enhanced innate/adaptive immunity. Overall, we have identified a unique protein signature that is responsible for the decreased risk of breast cancer and these proteins can also serve as biomarkers to predict the risk of breast cancer.

TPL2 kinase action and control of inflammation

Tumor progression locus 2 (TPL2, also known as COT or MAP3K8) is a mitogen-activated protein kinase kinase (MAP3K) activated downstream of TNFαR, IL1R, TLR, CD40, IL17R, and some GPCRs. TPL2 regulates the MEK1/2 and ERK1/2 pathways to regulate a cascade of inflammatory responses. In parallel to this, TPL2 also activates p38α and p38δ to drive the production of various inflammatory mediators in neutrophils. We discuss the implications of this finding in the context of various inflammatory diseases.

Tpl2 Promotes Innate Cell Recruitment and Effector T Cell Differentiation To Limit Citrobacter rodentium Burden and Dissemination

Tumor progression locus 2 (Tpl2) is a serine-threonine kinase that regulates Th1 differentiation, secretion of the inflammatory cytokine gamma interferon (IFN-γ), and host defense against the intracellular pathogens Toxoplasma gondii, Listeria monocytogenes, and Mycobacterium tuberculosis However, relatively little is known about the contribution of Tpl2 to Th17 differentiation and immune cell function during infection with an extracellular pathogen. The goal of this study was to determine whether Tpl2 influences the immune response generated to the extracellular bacterium Citrobacter rodentium, which induces a mixed Th1 and Th17 response. During peak infection with C. rodentium, Tpl2-/- mice experienced greater bacterial burdens with evidence of dissemination to the liver and spleen but ultimately cleared the bacteria within 3 weeks postinfection, similar to the findings for wild-type mice. Tpl2-/- mice also recruited fewer neutrophils and monocytes to the colon during peak infection, which correlated with increased bacterial burdens. In mixed bone marrow chimeras, Tpl2 was shown to play a T cell-intrinsic role in promoting both IFN-γ and interleukin-17A production during infection with C. rodentium However, upon CD4 T cell transfer into Rag-/- mice, Tpl2-/- CD4 T cells were as protective as wild-type CD4 T cells against the dissemination of bacteria and mortality. These data indicate that the enhanced bacterial burdens in Tpl2-/- mice are not caused primarily by impairments in CD4 T cell function but result from defects in innate immune cell recruitment and function.

Severe Dermatitis Associated with Spontaneous Staphylococcus xylosus Infection in Rag-/-Tpl2-/- Mice

Staphylococcus xylosus is a commensal bacterium found on the skin and mucosal surfaces of SPF mice. S. xylosus is rarely pathogenic, most often causing skin lesions and dermatitis in immunocompromised mice, particularly those with impaired NADPH oxidase function. Here we report spontaneous infection with S. xylosus in Rag1-/-Tpl2-/- mice. Infection was characterized by the presence of alopecia, crusts, and scaly skin. S. xylosus was detected in the feces, skin, lymph nodes, and lungs of Rag1-/-Tpl2-/- mice and led to mortality or euthanasia due to humane endpoints. C57BL/6 mice were culture-positive for S. xylosus on the skin, and Rag1-/- and Tpl2-/- mice were culture-positive on the skin and occasionally in the feces. However, S. xylosus did not cause clinical symptoms in C57BL/6, Rag1-/-, or Tpl2-/- mice. Compared with those in Rag1-/- mice, relative concentrations of circulating monocytes, but not neutrophils or lymphocytes, were increased in Rag1-/-Tpl2-/- mice, consistent with their increased incidence of clinical symptoms. Overall, this case study suggests a novel role for Tpl2 in T-cell-independent host resistance to the otherwise commensal organism S. xylosus.

TPL-2 restricts Ccl24-dependent immunity to Heligmosomoides polygyrus

TPL-2 (COT, MAP3K8) kinase activates the MEK1/2-ERK1/2 MAPK signaling pathway in innate immune responses following TLR, TNFR1 and IL-1R stimulation. TPL-2 contributes to type-1/Th17-mediated autoimmunity and control of intracellular pathogens. We recently demonstrated TPL-2 reduces severe airway allergy to house dust mite by negatively regulating type-2 responses. In the present study, we found that TPL-2 deficiency resulted in resistance to Heligmosomoides polygyrus infection, with accelerated worm expulsion, reduced fecal egg burden and reduced worm fitness. Using co-housing experiments, we found resistance to infection in TPL-2 deficient mice (Map3k8-/-) was independent of microbiota alterations in H. polygyrus infected WT and Map3k8-/-mice. Additionally, our data demonstrated immunity to H. polygyrus infection in TPL-2 deficient mice was not due to dysregulated type-2 immune responses. Genome-wide analysis of intestinal tissue from infected TPL-2-deficient mice identified elevated expression of genes involved in chemotaxis and homing of leukocytes and cells, including Ccl24 and alternatively activated genes. Indeed, Map3k8-/-mice had a significant influx of eosinophils, neutrophils, monocytes and Il4GFP+ T cells. Conditional knockout experiments demonstrated that specific deletion of TPL-2 in CD11c+ cells, but not Villin+ epithelial cells, LysM+ myeloid cells or CD4+ T cells, led to accelerated resistance to H. polygyrus. In line with a central role of CD11c+ cells, CD11c+ CD11b+ cells isolated from TPL-2-deficient mice had elevated Ccl24. Finally, Ccl24 neutralization in TPL-2 deficient mice significantly decreased the expression of Arg1, Retnla, Chil3 and Ear11 correlating with a loss of resistance to H. polygyrus. These observations suggest that TPL-2-regulated Ccl24 in CD11c+CD11b+ cells prevents accelerated type-2 mediated immunity to H. polygyrus. Collectively, this study identifies a previously unappreciated role for TPL-2 controlling immune responses to H. polygyrus infection by restricting Ccl24 production.

Map3k8 controls granulocyte colony-stimulating factor production and neutrophil precursor proliferation in lipopolysaccharide-induced emergency granulopoiesis

Map3k8 has been proposed as a useful target for the treatment of inflammatory diseases. We show here that during lipopolysaccharide-induced emergency granulopoiesis, Map3k8 deficiency strongly impairs the increase in circulating mature (Ly6G^highCD11b⁺) and immature (Ly6G^lowCD11b⁺) neutrophils. After chimaeric bone marrow (BM) transplantation into recipient Map3k8^−/− mice, lipopolysaccharide treatment did not increase circulating Ly6G^highCD11b⁺ cells and strongly decreased circulating Ly6G^lowCD11b⁺ cells. Lipopolysaccharide-treated Map3k8^−/− mice showed decreased production of granulocyte colony-stimulating factor (G-CSF), a key factor in neutrophil expansion, and a Map3k8 inhibitor blocked lipopolysaccharide-mediated G-CSF expression in endothelial cell lines. Ly6G^lowCD11b⁺ BM cells from lipopolysaccharide-treated Map3k8^−/− mice displayed impaired expression of CCAAT-enhancer-binding protein β, which depends on G-CSF for expression and is crucial for cell cycle acceleration in this life-threatening condition. Accordingly, lipopolysaccharide-treated Map3k8^−/− mice showed decreased Ly6G^lowCD11b⁺ BM cell proliferation, as evidenced by a decrease in the percentage of the most immature precursors, which have the highest proliferation capacity among this cell population. Thus, Map3k8 expression by non-haematopoietic tissue is required for lipopolysaccharide-induced emergency granulopoiesis. The novel observation that inhibition of Map3k8 activity decreases neutrophilia during life-threatening systemic infection suggests a possible risk in the proposed use of Map3k8 blockade as an anti-inflammatory therapy.

The kinase TPL2 activates ERK and p38 signaling to promote neutrophilic inflammation

Tumor progression locus 2 (TPL2; also known as MAP3K8) is a mitogen-activated protein kinase (MAPK) kinase kinase (MAP3K) that phosphorylates the MAPK kinases MEK1 and MEK2 (MEK1/2), which, in turn, activate the MAPKs extracellular signal-regulated kinase 1 (ERK1) and ERK2 (ERK1/2) in macrophages stimulated through the interleukin-1 receptor (IL-1R), Toll-like receptors (TLRs), or the tumor necrosis factor receptor (TNFR). We describe a conserved and critical role for TPL2 in mediating the effector functions of neutrophils through the activation of the p38 MAPK signaling pathway. Gene expression profiling and functional studies of neutrophils and monocytes revealed a MEK1/2-independent branch point downstream of TPL2 in neutrophils. Biochemical analyses identified the MAPK kinases MEK3 and MEK6 and the MAPKs p38α and p38δ as downstream effectors of TPL2 in these cells. Genetic ablation of the catalytic activity of TPL2 or therapeutic intervention with a TPL2-specific inhibitor reduced the production of inflammatory mediators by neutrophils in response to stimulation with the TLR4 agonist lipopolysaccharide (LPS) in vitro, as well as in rodent models of inflammatory disease. Together, these data suggest that TPL2 is a drug target that activates not only MEK1/2-dependent but also MEK3/6-dependent signaling to promote inflammatory responses.

Tpl2 promotes neutrophil trafficking, oxidative burst, and bacterial killing

Tumor progression locus 2 (Tpl2) is a serine/threonine kinase that promotes inflammatory cytokine production by activating the MEK/ERK pathway. Tpl2 has been shown to be important for eliciting the inflammatory properties of macrophages; however, there is relatively little known about the contribution of Tpl2 to neutrophil effector functions. This is an important consideration, as neutrophils provide the first line of defense against infection in the innate immune system. We found that Tpl2 is expressed in both human and murine neutrophils, suggesting a potential function for Tpl2 in this lineage. Despite significantly higher proportions of bone marrow (BM) neutrophils in Tpl2-deficient (Tpl2^-/- ) mice compared with wild-type (WT) mice, Tpl2^-/- mice have significantly reduced proportions of circulating neutrophils. Tpl2^-/- neutrophils show impaired recruitment to thioglycollate, which was primarily a result of neutrophil-extrinsic factors in the host. In response to infection, neutrophils secrete inflammatory cytokines and produce reactive oxygen species (ROS), which promote bacterial killing. Tpl2 ablation impaired neutrophil TNF secretion in response to LPS stimulation, superoxide generation in response to the chemotactic peptide fMLP, and killing of the extracellular bacterium, Citrobacter rodentium, despite normal bacterial phagocytosis. These results implicate Tpl2 in the regulation of multiple neutrophil antimicrobial pathways, including inflammatory cytokine secretion and oxidative burst. Furthermore, they indicate that Tpl2 functions early during infection to bolster neutrophil-mediated innate immunity against extracellular bacteria.

A TPL2 (MAP3K8) disease-risk polymorphism increases TPL2 expression thereby leading to increased pattern recognition receptor-initiated caspase-1 and caspase-8 activation, signalling and cytokine secretion

OBJECTIVE

IBD is characterised by dysregulated intestinal immune homeostasis and cytokine secretion. In the intestine, properly regulating pattern recognition receptor (PRR)-mediated signalling and cytokines is crucial given the ongoing host-microbial interactions. TPL2 (MAP3K8, COT) contributes to PRR-initiated pathways, yet the mechanisms for TPL2 signalling contributions in primary human myeloid cells are incompletely understood and its role in intestinal myeloid cells is poorly defined. Furthermore, functional consequences for the IBD-risk locus rs1042058 in TPL2 are unknown.

METHODS

We analysed protein, cytokine and RNA expression, and signalling in human monocyte-derived macrophages (MDMs) through western blot, ELISA, real-time PCR and flow cytometry.

RESULTS

PRR-induced cytokine secretion was increased in MDMs from rs1042058 TPL2 GG risk individuals. TPL2 activation by the Crohn's disease-associated PRR nucleotide-oligomerisation domain (NOD)2 required PKC, and IKKβ, IKKα and IKKγ signalling. TPL2, in turn, significantly enhanced NOD2-induced ERK, JNK and NFκB signalling. We found that another major mechanism for the TPL2 contribution to NOD2 signalling was through ERK-dependent and JNK-dependent caspase-1 and caspase-8 activation, which in turn, led to early autocrine interleukin (IL)-1β and IL-18 secretion and amplification of long-term cytokines. Importantly, Salmonella typhimurium-induced cytokines from human intestinal myeloid-derived cells required TPL2 as well as autocrine IL-1β and IL-18. Finally, rs1042058 GG risk carrier MDMs from healthy individuals and patients with Crohn's disease had increased TPL2 expression and NOD2-initiated TPL2 phosphorylation, ERK, JNK and NFκB activation, and early autocrine IL-1β and IL-18 secretion.

CONCLUSIONS

Taken together, the rs1042058 GG IBD-risk polymorphism in TPL2 results in a gain-of-function by increasing TPL2 expression and signalling, thereby amplifying PRR-initiated outcomes.

de Carvalho L, Ley SC, Wilson MS. TPL-2 Regulates Macrophage Lipid Metabolism and M2 Differentiation to Control TH2-Mediated Immunopathology

Persistent T_H2 cytokine responses following chronic helminth infections can often lead to the development of tissue pathology and fibrotic scarring. Despite a good understanding of the cellular mechanisms involved in fibrogenesis, there are very few therapeutic options available, highlighting a significant medical need and gap in our understanding of the molecular mechanisms of T_H2-mediated immunopathology. In this study, we found that the Map3 kinase, TPL-2 (Map3k8; Cot) regulated T_H2-mediated intestinal, hepatic and pulmonary immunopathology following Schistosoma mansoni infection or S. mansoni egg injection. Elevated inflammation, T_H2 cell responses and exacerbated fibrosis in Map3k8^–/–mice was observed in mice with myeloid cell-specific (LysM) deletion of Map3k8, but not CD4 cell-specific deletion of Map3k8, indicating that TPL-2 regulated myeloid cell function to limit T_H2-mediated immunopathology. Transcriptional and metabolic assays of Map3k8^–/–M2 macrophages identified that TPL-2 was required for lipolysis, M2 macrophage activation and the expression of a variety of genes involved in immuno-regulatory and pro-fibrotic pathways. Taken together this study identified that TPL-2 regulated T_H2-mediated inflammation by supporting lipolysis and M2 macrophage activation, preventing T_H2 cell expansion and downstream immunopathology and fibrosis.

Chronic helminth infections can cause significant morbidity and organ damage in their definitive mammalian hosts. Managing this collateral damage can reduce morbidity and preserve vital tissues for normal organ function. One particular consequence of some chronic helminth infections is the deposition of fibrotic scar tissue, following immune responses directed towards helminth material. In this study we tested the role of a particular signalling kinase, TPL-2, and identified that it critically regulated the magnitude of fibrotic scarring following infection. Using several murine models with genetic deletions of TPL-2 in either all cells or specific deletion in subsets of immune cells (Map3k8^–/–Map3k8^fl/fl) we identified that expression of TPL-2 in myeloid cells was essential to prevent severe immune-mediated pathology. Using genome-wide analyses and metabolic assays, we discovered that TPL-2 was required for normal lipid metabolism and appropriate activation of myeloid cells / macrophages to limit fibrosis. These results revealed a previously unappreciated role for TPL-2 in preventing severe pathology following infection. Thus, activating this pathway may limit immune mediated pathology following chronic helminth infection. More broadly, this pathway is being targeted to treat inflammatory diseases and cancer [1, 2]. This study would suggest that caution should be taken to prevent untoward co-morbidities and fibrosis-related pathologies in patients when targeting TPL-2.

Tumor progression locus 2 reduces severe allergic airway inflammation by inhibiting Ccl24 production in dendritic cells

Background

The molecular and cellular pathways driving the pathogenesis of severe asthma are poorly defined. Tumor progression locus 2 (TPL-2) (COT, MAP3K8) kinase activates the MEK1/2-extracellular-signal regulated kinase 1/2 MAP kinase signaling pathway following Toll-like receptor, TNFR1, and IL-1R stimulation.

Objective

TPL-2 has been widely described as a critical regulator of inflammation, and we sought to investigate the role of TPL-2 in house dust mite (HDM)-mediated allergic airway inflammation.

Methods

A comparative analysis of wild-type and Map3k8^−/− mice was conducted. Mixed bone marrow chimeras, conditional knockout mice, and adoptive transfer models were also used. Differential cell counts were performed on the bronchoalveolar lavage fluid, followed by histological analysis of lung sections. Flow cytometry and quantitative PCR was used to measure type 2 cytokines. ELISA was used to assess the production of IgE, type 2 cytokines, and Ccl24. RNA sequencing was used to characterize dendritic cell (DC) transcripts.

Results

TPL-2 deficiency led to exacerbated HDM-induced airway allergy, with increased airway and tissue eosinophilia, lung inflammation, and IL-4, IL-5, IL-13, and IgE production. Increased airway allergic responses in Map3k8^−/− mice were not due to a cell-intrinsic role for TPL-2 in T cells, B cells, or LysM⁺ cells but due to a regulatory role for TPL-2 in DCs. TPL-2 inhibited Ccl24 expression in lung DCs, and blockade of Ccl24 prevented the exaggerated airway eosinophilia and lung inflammation in mice given HDM-pulsed Map3k8^−/− DCs.

Conclusions

TPL-2 regulates DC-derived Ccl24 production to prevent severe type 2 airway allergy in mice.

Tumor Progression Locus 2 (Tpl2) Activates the Mammalian Target of Rapamycin (mTOR) Pathway, Inhibits Forkhead Box P3 (FoxP3) Expression, and Limits Regulatory T Cell (Treg) Immunosuppressive Functions

The serine/threonine kinase tumor progression locus 2 (Tpl2, also known as Map3k8/Cot) is a potent inflammatory mediator that drives the production of TNFα, IL-1β, and IFNγ. We previously demonstrated that Tpl2 regulates T cell receptor (TCR) signaling and modulates T helper cell differentiation. However, very little is known about how Tpl2 modulates the development of regulatory T cells (Tregs). Tregs are a specialized subset of T cells that express FoxP3 and possess immunosuppressive properties to limit excess inflammation. Because of the documented role of Tpl2 in promoting inflammation, we hypothesized that Tpl2 antagonizes Treg development and immunosuppressive function. Here we demonstrate that Tpl2 constrains the development of inducible Tregs. Tpl2(-/-) naïve CD4(+) T cells preferentially develop into FoxP3(+) inducible Tregs in vitro as well as in vivo in a murine model of ovalbumin (OVA)-induced systemic tolerance. Treg biasing of Tpl2(-/-) T cells depended on TCR signal strength and corresponded with reduced activation of the mammalian target of rapamycin (mTOR) pathway. Importantly, Tpl2(-/-) Tregs have basally increased expression of FoxP3 and immunosuppressive molecules, IL-10 and cytotoxic T lymphocyte-associated protein 4 (CTLA-4). Furthermore, they were more immunosuppressive in vivo in a T cell transfer model of colitis, as evidenced by reduced effector T cell accumulation, systemic production of inflammatory cytokines, and colonic inflammation. These results demonstrate that Tpl2 promotes inflammation in part by constraining FoxP3 expression and Treg immunosuppressive functions. Overall, these findings suggest that Tpl2 inhibition could be used to preferentially drive Treg induction and thereby limit inflammation in a variety of autoimmune diseases.

Tumor Progression Locus 2 Promotes Induction of IFNλ, Interferon Stimulated Genes and Antigen-Specific CD8+ T Cell Responses and Protects against Influenza Virus

Mitogen-activated protein kinase (MAP) cascades are important in antiviral immunity through their regulation of interferon (IFN) production as well as virus replication. Although the serine-threonine MAP kinase tumor progression locus 2 (Tpl2/MAP3K8) has been implicated as a key regulator of Type I (IFNα/β) and Type II (IFNγ) IFNs, remarkably little is known about how Tpl2 might contribute to host defense against viruses. Herein, we investigated the role of Tpl2 in antiviral immune responses against influenza virus. We demonstrate that Tpl2 is an integral component of multiple virus sensing pathways, differentially regulating the induction of IFNα/β and IFNλ in a cell-type specific manner. Although Tpl2 is important in the regulation of both IFNα/β and IFNλ, only IFNλ required Tpl2 for its induction during influenza virus infection both in vitro and in vivo. Further studies revealed an unanticipated function for Tpl2 in transducing Type I IFN signals and promoting expression of interferon-stimulated genes (ISGs). Importantly, Tpl2 signaling in nonhematopoietic cells is necessary to limit early virus replication. In addition to early innate alterations, impaired expansion of virus-specific CD8+ T cells accompanied delayed viral clearance in Tpl2-/- mice at late time points. Consistent with its critical role in facilitating both innate and adaptive antiviral responses, Tpl2 is required for restricting morbidity and mortality associated with influenza virus infection. Collectively, these findings establish an essential role for Tpl2 in antiviral host defense mechanisms.

Inhibition of G-Protein βγ Signaling Decreases Levels of Messenger RNAs Encoding Proinflammatory Cytokines in T Cell Receptor-Stimulated CD4(+) T Helper Cells

Background: Inhibition of G-protein βγ (Gβγ) signaling was found previously to enhance T cell receptor (TCR)-stimulated increases in interleukin 2 (IL-2) mRNA in CD4⁺ T helper cells, suggesting that Gβγ might be a useful drug target for treating autoimmune diseases, as low dose IL-2 therapy can suppress autoimmune responses. Because IL-2 may counteract autoimmunity in part by shifting CD4⁺ T helper cells away from the Type 1 T helper cell (TH1) and TH17 subtypes towards the TH2 subtype, the purpose of this study was to determine if blocking Gβγ signaling affected the balance of TH1, TH17, and TH2 cytokine mRNAs produced by CD4⁺ T helper cells.

Methods: Gallein, a small molecule inhibitor of Gβγ, and siRNA-mediated silencing of the G-protein β₁ subunit (Gβ₁) were used to test the effect of blocking Gβγ on mRNA levels of cytokines in primary human TCR-stimulated CD4⁺ T helper cells.

Results: Gallein and Gβ₁ siRNA decreased interferon-γ (IFN-γ) and IL-17A mRNA levels in TCR-stimulated CD4⁺ T cells grown under TH1-promoting conditions. Inhibiting Gβγ also decreased mRNA levels of STAT4, which plays a positive role in TH1 differentiation and IL-17A production. Moreover, mRNA levels of the STAT4-regulated TH1-associated proteins, IL-18 receptor β chain (IL-18Rβ), mitogen-activated protein kinase kinase kinase 8 (MAP3K8), lymphocyte activation gene 3 (LAG-3), natural killer cell group 7 sequence (NKG7), and oncostatin M (OSM) were also decreased upon Gβγ inhibition. Gallein also increased IL-4, IL-5, IL-9, and IL-13 mRNA levels in TCR-stimulated memory CD4⁺ T cells grown in TH2-promoting conditions.

Conclusions: Inhibiting Gβγ to produce these shifts in cytokine mRNA production might be beneficial for patients with autoimmune diseases such as rheumatoid arthritis (RA), Crohn’s disease (CD), psoriasis, multiple sclerosis (MS), and Hashimoto’s thyroiditis (HT), in which both IFN-γ and IL-17A are elevated.

Tumor progression locus 2 differentially regulates IFNγ and IL-17 production by effector CD4+ T cells in a T cell transfer model of colitis

Autoimmune diseases are approaching epidemic levels, estimated to affect 5–8% of the population. A number of autoimmune diseases are believed to be driven by autoreactive T cells, specifically by T helper 1 (Th1) cells and T helper 17 (Th17) cells. One molecule gaining interest as a therapeutic target is the serine-threonine kinase, Tpl2, which promotes expression of proinflammatory mediators. We previously demonstrated that Tpl2 regulates Th1 differentiation, secretion of the inflammatory cytokine IFNγ, and host defense against the intracellular parasite Toxoplasma gondii. The goal of this study was to determine whether Tpl2 also regulates Th1 or Th17 differentiation in vivo in a model of colitis associated with mixed Th1/Th17 pathology. In vitro, Tpl2^−/− naïve CD4 T cells were significantly impaired in IL-17A secretion under traditional Th17 inducing conditions. Reduced IL-17A secretion correlated with increased expression of FoxP3, a transcription factor known to antagonize RORγt function. In a murine T cell transfer model of colitis, transfer of Tpl2^−/− T cells resulted in reduced proportions of CD4 T cells expressing IFNγ, but not IL-17A, compared to that induced by wild type T cells. Further studies revealed that IL-17A differentiation induced by IL-6 and IL-23, cytokines implicated in driving Th17 differentiation in vivo, was unaffected by Tpl2 deficiency. Collectively, these results implicate Tpl2 in TGF-β-induced FoxP3 expression. Additionally, they underscore the contribution of Tpl2 to Th1 immunopathology specifically, which suggests that Tpl2 inhibitors may selectively target Th1-based inflammation.

Toll-like receptor 2-dependent extracellular signal-regulated kinase signaling in Mycobacterium tuberculosis-infected macrophages drives anti-inflammatory responses and inhibits Th1 polarization of responding T cells

Mycobacterium tuberculosis survives within macrophages and employs immune evasion mechanisms to persist in the host. Protective T helper type 1 (Th1) responses are induced, and the immune response in most individuals is sufficient to restrict M. tuberculosis to latent infection, but most infections are not completely resolved. As T cells and macrophages respond, a balance is established between protective Th1-associated and other proinflammatory cytokines, such as interleukin-12 (IL-12), interferon gamma (IFN-γ), and tumor necrosis factor alpha, and anti-inflammatory cytokines, such as IL-10. The mechanisms by which M. tuberculosis modulates host responses to promote its survival remain unclear. In these studies, we demonstrate that M. tuberculosis induction of IL-10, suppression of IL-12, and inhibition of class II major histocompatibility complex (MHC-II) molecules in infected macrophages are all driven by Toll-like receptor 2 (TLR2)-dependent activation of the extracellular signal-regulated kinases (ERK). Elimination of ERK signaling downstream of TLR2 by pharmacologic inhibition with U0126 or genetic deletion of Tpl2 blocks IL-10 secretion and enhances IL-12 p70 secretion. We demonstrate that M. tuberculosis regulation of these pathways in macrophages affects T cell responses to infected macrophages. Thus, genetic blockade of the ERK pathway in Tpl2(-/-) macrophages enhances Th1 polarization and IFN-γ production by antigen-specific CD4(+) T cells responding to M. tuberculosis infection. These data indicate that M. tuberculosis and its potent TLR2 ligands activate ERK signaling in macrophages to promote anti-inflammatory macrophage responses and blunt Th1 responses against the pathogen.

Tumor progression locus 2 (Tpl2) kinase as a novel therapeutic target for cancer: double-sided effects of Tpl2 on cancer

Tumor progression locus 2 (Tpl2) is a mitogen-activated protein kinase (MAPK) kinase kinase (MAP3K) that conveys various intra- and extra-cellular stimuli to effector proteins of cells provoking adequate adoptive responses. Recent studies have elucidated that Tpl2 is an indispensable signal transducer as an MAP3K family member in diverse signaling pathways that regulate cell proliferation, survival, and death. Since tumorigenesis results from dysregulation of cellular proliferation, differentiation, and apoptosis, Tpl2 participates in many decisive molecular processes of tumor development and progression. Moreover, Tpl2 is closely associated with cytokine release of inflammatory cells, which has crucial effects on not only tumor cells but also tumor microenvironments. These critical roles of Tpl2 in human cancers make it an attractive anti-cancer therapeutic target. However, Tpl2 contradictorily works as a tumor suppressor in some cancers. The double-sided effects of Tpl2 originate from the specific upstream and downstream signaling environment of each tumor, since Tpl2 interacts with various signaling components. This review summarizes recent studies concerning the possible roles of Tpl2 in human cancers and considers its possibility as a therapeutic target, against which novel anti-cancer agents could be developed.

Proprotein convertase FURIN constrains Th2 differentiation and is critical for host resistance against Toxoplasma gondii

The proprotein convertase subtilisin/kexin enzymes proteolytically convert immature proproteins into bioactive molecules, and thereby they serve as key regulators of cellular homeostasis. The archetype proprotein convertase subtilisin/kexin, FURIN, is a direct target gene of the IL-12/STAT4 pathway and it is upregulated in Th1 cells. We have previously demonstrated that FURIN expression in T cells critically regulates the maintenance of peripheral immune tolerance and the functional maturation of pro-TGF-β1 in vivo, but FURIN's role in cell-mediated immunity and Th polarization has remained elusive. In this article, we show that T cell-expressed FURIN is essential for host resistance against a prototypic Th1 pathogen, Toxoplasma gondii, and for the generation of pathogen-specific Th1 lymphocytes, including Th1-IL-10 cells. FURIN-deficient Th cells instead show elevated expression of IL-4R subunit α on cell surface, sensitized IL-4/STAT6 signaling, and a propensity to polarize toward the Th2 phenotype. By exploring FURIN-interacting proteins in Jurkat T cells with Strep-Tag purification and mass spectrometry, we further identify an association with a cytoskeleton modifying Ras-related C3 botulinum toxin substrate/dedicator of cytokinesis 2 protein complex and unravel that FURIN promotes F-actin polymerization, which has previously been shown to downregulate IL-4R subunit α cell surface expression and promote Th1 responses. In conclusion, our results demonstrate that in addition to peripheral immune tolerance, T cell-expressed FURIN is also a central regulator of cell-mediated immunity and Th1/2 cell balance.

CD8 T cells in innate immune responses: using STAT4-dependent but antigen-independent pathways to gamma interferon during viral infection

The cytokine gamma interferon (IFN-γ), with antimicrobial and immunoregulatory functions, can be produced by T cells following stimulation through their T cell receptors (TCRs) for antigen. The innate cytokines type 1 IFNs and interleukin-12 (IL-12) can also stimulate IFN-γ production by natural killer (NK) but not naive T cells. High basal expression of signal transducer and activator of transcription 4 (STAT4), used by type 1 IFN and IL-12 to induce IFN-γ as well as CD25, contributes to the NK cell responses. During acute viral infections, antigen-specific CD8 T cells are stimulated to express elevated STAT4 and respond to the innate factors with IFN-γ production. Little is known about the requirements for cytokine compared to TCR stimulation. Primary infections of mice with lymphocytic choriomeningitis virus (LCMV) demonstrated that although the elicited antigen-specific CD8 T cells acquired STAT4-dependent innate cytokine responsiveness for IFN-γ and CD25 induction ex vivo, TCR stimulation induced these through STAT4-independent pathways. During secondary infections, LCMV-immune CD8 T cells had STAT4-dependent IFN-γ expression at times of innate cytokine induction but subsequently expanded through STAT4-independent pathways. At times of innate cytokine responses during infection with the antigen-distinct murine cytomegalovirus virus (MCMV), NK and LCMV-immune CD8 T cells both had activation of pSTAT4 and IFN-γ. The T cell IFN-γ response was STAT4 and IL-12 dependent, but antigen-dependent expansion was absent. By dissecting requirements for STAT4 and antigen, this work provides novel insights into the endogenous regulation of cytokine and proliferative responses and demonstrates conditioning of innate immunity by experience.

Understanding the regulation and function of adaptive immunity is key to the development of new and improved vaccines. Its CD8 T cells are activated through antigen-specific receptors to contribute to long-lasting immunity after natural infections or purposeful immunization. The antigen-receptor pathway of stimulation can lead to production of gamma interferon (IFN-γ), a cytokine having both direct antimicrobial and immunoregulatory functions. Natural killer cells can also produce IFN-γ in response to the innate cytokines type 1 IFNs and/or interleukin-12. This work demonstrates that CD8 T cells acquire parallel responsiveness to innate cytokine signaling for IFN-γ expression during their selection and development and maintain this capability to participate in innate immune responses as long-lived memory cells. Thus, CD8 T cells are conditioned to play a role in innate immunity, and their presence under immune conditions has the potential to regulate resistance to either secondary challenges or primary infections with unrelated agents.

Intestinal myofibroblast-specific Tpl2-Cox-2-PGE2 pathway links innate sensing to epithelial homeostasis

Tumor progression locus-2 (Tpl2) kinase is a major inflammatory mediator in immune cell types recently found to be genetically associated with inflammatory bowel diseases (IBDs). Here we show that Tpl2 may exert a dominant homeostatic rather than inflammatory function in the intestine mediated specifically by subepithelial intestinal myofibroblasts (IMFs). Mice with complete or IMF-specific Tpl2 ablation are highly susceptible to epithelial injury-induced colitis showing impaired compensatory proliferation in crypts and extensive ulcerations without significant changes in inflammatory responses. Following epithelial injury, IMFs sense innate or inflammatory signals and activate, via Tpl2, the cyclooxygenase-2 (Cox-2)-prostaglandin E2 (PGE2) pathway, which we show here to be essential for the epithelial homeostatic response. Exogenous PGE2 administration rescues mice with complete or IMF-specific Tpl2 ablation from defects in crypt function and susceptibility to colitis. We also show that Tpl2 expression is decreased in IMFs isolated from the inflamed ileum of IBD patients indicating that Tpl2 function in IMFs may be highly relevant to human disease. The IMF-mediated mechanism we propose also involves the IBD-associated genes IL1R1, MAPK1, and the PGE2 receptor-encoding PTGER4. Our results establish a previously unidentified myofibroblast-specific innate pathway that regulates intestinal homeostasis and may underlie IBD susceptibility in humans.

The quality of methods reporting in parasitology experiments

There is a growing concern both inside and outside the scientific community over the lack of reproducibility of experiments. The depth and detail of reported methods are critical to the reproducibility of findings, but also for making it possible to compare and integrate data from different studies. In this study, we evaluated in detail the methods reporting in a comprehensive set of trypanosomiasis experiments that should enable valid reproduction, integration and comparison of research findings. We evaluated a subset of other parasitic (Leishmania, Toxoplasma, Plasmodium, Trichuris and Schistosoma) and non-parasitic (Mycobacterium) experimental infections in order to compare the quality of method reporting more generally. A systematic review using PubMed (2000-2012) of all publications describing gene expression in cells and animals infected with Trypanosoma spp was undertaken based on PRISMA guidelines; 23 papers were identified and included. We defined a checklist of essential parameters that should be reported and have scored the number of those parameters that are reported for each publication. Bibliometric parameters (impact factor, citations and h-index) were used to look for association between Journal and Author status and the quality of method reporting. Trichuriasis experiments achieved the highest scores and included the only paper to score 100% in all criteria. The mean of scores achieved by Trypanosoma articles through the checklist was 65.5% (range 32-90%). Bibliometric parameters were not correlated with the quality of method reporting (Spearman's rank correlation coefficient <-0.5; p>0.05). Our results indicate that the quality of methods reporting in experimental parasitology is a cause for concern and it has not improved over time, despite there being evidence that most of the assessed parameters do influence the results. We propose that our set of parameters be used as guidelines to improve the quality of the reporting of experimental infection models as a pre-requisite for integrating and comparing sets of data.

TPL2 mediates autoimmune inflammation through activation of the TAK1 axis of IL-17 signaling

TPL2 is required for Th17-mediated neuroinflammation during EAE by regulating the TAK1 signaling axis downstream of the IL-17R in astrocytes.

Development of autoimmune diseases, such as multiple sclerosis and experimental autoimmune encephalomyelitis (EAE), involves the inflammatory action of Th1 and Th17 cells, but the underlying signaling mechanism is incompletely understood. We show that the kinase TPL2 is a crucial mediator of EAE and is required for the pathological action of Th17 cells. TPL2 serves as a master kinase mediating the activation of multiple downstream pathways stimulated by the Th17 signature cytokine IL-17. TPL2 acts by linking the IL-17 receptor signal to the activation of TAK1, which involves a dynamic mechanism of TPL2–TAK1 interaction and TPL2-mediated phosphorylation and catalytic activation of TAK1. These results suggest that TPL2 mediates TAK1 axis of IL-17 signaling, thereby promoting autoimmune neuroinflammation.

Changing partners at the dance: Variations in STAT concentrations for shaping cytokine function and immune responses to viral infections

Differential use of cellular and molecular components shapes immune responses, but understanding of how these are regulated to promote defense and health during infections is still incomplete. Examples include signaling from members of the Janus activated kinase-signal transducer and activator of transcription (JAK-STAT) cytokine family. Following receptor stimulation, individual JAK-STAT cytokines have preferences for particular key STAT molecules to lead to specific cellular responses. Certain of these cytokines, however, can conditionally activate alternative STATs as well as elicit pleiotropic and paradoxical effects. Studies examining basal and infection conditions are revealing intrinsic and induced cellular differences in various intracellular STAT concentrations to control the biological consequences of cytokine exposure. The system can be likened to changing partners at a dance based on competition and relative availability, and sets a framework for understanding the particular conditions promoting subset biological functions of cytokines as needed during evolving immune responses to infections.

Genetic and pharmacologic inhibition of Tpl2 kinase is protective in a mouse model of ventilator-induced lung injury

Background

Mechanical stress induced by injurious ventilation leads to pro-inflammatory cytokine production and lung injury. The extracellular-signal-regulated-kinase, ERK1/2, participates in the signaling pathways activated upon mechanical stress in the lungs to promote the inflammatory response. Tumor progression locus 2 (Tpl2) is a MAP3kinase that activates ERK1/2 upon cytokine or TLR signaling, to induce pro-inflammatory cytokine production. The role of Tpl2 in lung inflammation, and specifically in the one caused by mechanical stress has not been investigated. The aim of the study was to examine if genetic or pharmacologic inhibition of Tpl2 could ameliorate ventilator-induced lung injury.

Methods

Adult male wild-type and Tpl2-deficient mice were ventilated with normal or high tidal volume for 4 h. Additional wild-type mice were treated with a Tpl2 inhibitor either before or 30 min after initiation of high tidal ventilation. Non-ventilated mice of both genotypes served as controls. The development of lung injury was evaluated by measuring lung mechanics, arterial blood gases, concentrations of proteins, IL-6, and MIP-2 in bronchoalveolar lavage fluid (BALF) and by lung histology. Data were compared by Kruskal-Wallis non-parametric test and significance was defined as p < 0.05.

Results

Mechanical ventilation with normal tidal volume induced a mild increase of IL-6 in BALF in both strains. High tidal volume ventilation induced lung injury in wild-type mice, characterized by decreased lung compliance, increased concentrations of proteins, IL-6 and MIP-2 in BALF, and inflammatory cell infiltration on histology. All indices of lung injury were ameliorated in Tpl2-deficient mice. Wild-type mice treated with the Tpl2 inhibitor, either prior of after the initiation of high tidal volume ventilation were protected from the development of lung injury, as indicated by preserved lung compliance and lower BALF concentrations of proteins and IL-6, than similarly ventilated, untreated wild-type mice.

Conclusions

Genetic and pharmacologic inhibition of Tpl2 is protective in a mouse model of ventilator-induced lung injury, ameliorating both high-permeability pulmonary edema and lung inflammation.

Regulation of experimental autoimmune encephalomyelitis by TPL-2 kinase

Tumor progression locus 2 (TPL-2) expression is required for efficient polarization of naive T cells to Th1 effector cells in vitro, as well as for Th1-mediated immune responses. In the present study, we investigated the potential role of TPL-2 in Th17 cells. TPL-2 was found to be dispensable for Th17 cell differentiation in vitro, and for the initial priming of Th17 cells in experimental autoimmune encephalomyelitis (EAE), a Th17 cell-mediated disease model for multiple sclerosis. Nevertheless, TPL-2-deficient mice were protected from EAE, which correlated with reduced immune cell infiltration, demyelination, and axonal damage in the CNS. Adoptive transfer experiments demonstrated that there was no T cell-intrinsic function for TPL-2 in EAE, and that TPL-2 signaling was not required in radiation-sensitive hematopoietic cells. Rather, TPL-2 signaling in radiation-resistant stromal cells promoted the effector phase of the disease. Importantly, using a newly generated mouse strain expressing a kinase-inactive form of TPL-2, we demonstrated that stimulation of EAE was dependent on the catalytic activity of TPL-2 and not its adaptor function to stabilize the associated ubiquitin-binding protein ABIN-2. Our data therefore raise the possibility that small molecule inhibitors of TPL-2 may be beneficial in multiple sclerosis therapy.

Tpl2 inhibitors thwart endothelial cell function in angiogenesis and peritoneal dissemination

Angiogenesis is critical in the development of cancer, which involves several angiogenic factors in its peritoneal dissemination. The role of protein tumor progression locus 2 (Tpl2) in angiogenic factor-related endothelial cell angiogenesis is still unclear. To understand the precise mechanism(s) of Tpl2 inhibition in endothelial cells, this study investigated the role of Tpl2 in mediating angiogenic signals using in vitro, in vivo, and ex vivo models. Results showed that inhibition of Tpl2 inhibitor significantly reduced peritoneal dissemination in a mouse model by positron emission tomography/computed tomography imaging. Simultaneously, inhibiting Tpl2 blocked angiogenesis in tumor nodules and prevented angiogenic factor-induced proliferating cell nuclear antigen (PCNA) in endothelial cells. Vascular endothelial growth factor (VEGF) or chemokine (C-X-C motif) ligand 1 (CXCL1) increased Tpl2 kinase activity and phosphorylation in a dose- and time-dependent manner. Furthermore, Tpl2 inhibition or ablation by siRNA prevented the angiogenic signal-induced tube formation in Matrigel plug assay or aortic ring assay. Inhibiting Tpl2 also prevented the angiogenic factor-induced chemotactic motility and migration of endothelial cells. Tpl2 inhibition by CXCL1 or epidermal growth factor in endothelial cells was associated with inactivation of CCAAT/enhancer binding protein β, nuclear factor κ light-chain enhancer of activated B cells, and activating protein 1 and suppression of VEGF expression. Thus, Tpl2 inhibitors thwart Tpl2-regulated VEGF by inactivating transcription factors involved in angiogenic factor-triggered endothelial cell angiogenesis. These results suggest that the therapeutic inhibition of Tpl2 may extend beyond cancer and include the treatment of other diseases involving pathologic angiogenesis.

Pharmacological inhibition of TPL2/MAP3K8 blocks human cytotoxic T lymphocyte effector functions

CD8⁺ cytotoxic T lymphocytes (CTLs) play a major role in defense against intracellular pathogens. During development, antigen-presenting cells secrete innate cytokines such as IL-12 and IFN-α, which drive CTL differentiation into diverse populations of effector and long-lived memory cells. Using whole transcriptome analyses, the serine/threonine protein kinase Tpl2/MAP3K8 was found to be induced by IL-12 and selectively expressed by effector memory (T_EM) CTLs. Tpl2 regulates various inflammatory pathways by activating the ERK mediated MAP kinase pathway in innate immune cells such as macrophages and dendritic cells. In this study, we found that a specific small molecule Tpl2 inhibitor blocked IFN-γ and TNF-α secretion as well as cytolytic activity of human CTLs. This pathway was specific for human effector CTLs, as the Tpl2 inhibitor did not block IFN-γ and TNF-α secretion from murine effector CTLs. Further, IL-12 failed to induce expression of Tpl2 in murine CTLs, and Tpl2 deficient murine CTLs did not exhibit any functional deficiency either in vitro or in vivo in response to L. monocytogenes infection. In summary, we identified a species-specific role for Tpl2 in effector function of human CTLs, which plays a major role in adaptive immune responses to intracellular pathogens and tumors.

TPL2 signalling: from Toll-like receptors-mediated ERK1/ERK2 activation to Cystic Fibrosis lung disease

Cystic Fibrosis (CF) is the most common lethal genetic recessive disorder, with a carrier frequency of 1 in 27 among North American Caucasians. Mitogen-activated protein kinases (MAPKs) and pro-inflammatory cytokines have crucial functions in the innate immune response of epithelial cells. They determine the inflammation status and the host response to pathogenic infections. However, in CF, bacterial-driven inflammation leads to tissue destruction, reduction in lung function and mortality. Recognition of invading pathogens is mediated in part by Toll-like receptors (TLR) activation of intracellular signalling cascade leading to cytokines' synthesis. The protein kinase Tumour Progression Locus 2 (TPL2) is a key molecule in relaying inflammatory stimuli to ERK1/ERK2 MAPKs. In this review, we summarized the recent findings on TPL2 signalling and how TPL2 can contribute to the excessive inflammation found in CF. Pharmacologically targeting this kinase could have a significant benefit for CF patients dealing with chronic bacterial infections such as Pseudomonas aeruginosa. This article is part of a Directed Issue entitled: Cystic Fibrosis: From o-mics to cell biology, physiology, and therapeutic advances.

The regulation of IL-10 expression

Interleukin (IL)-10 is an important immunoregulatory cytokine and an understanding of how IL-10 expression is controlled is critical in the design of immune intervention strategies. IL-10 is produced by almost all cell types within the innate (including macrophages, monocytes, dendritic cells (DCs), mast cells, neutrophils, eosinophils and natural killer cells) and adaptive (including CD4(+) T cells, CD8(+) T cells and B cells) immune systems. The mechanisms of IL-10 regulation operate at several stages including chromatin remodelling at the Il10 locus, transcriptional regulation of Il10 expression and post-transcriptional regulation of Il10 mRNA. In addition, whereas some aspects of Il10 gene regulation are conserved between different immune cell types, several are cell type- or stimulus-specific. Here, we outline the complexity of IL-10 production by discussing what is known about its regulation in macrophages, monocytes, DCs and CD4(+) T helper cells.

Mitogen-activated protein kinase-mediated licensing of interferon regulatory factor 3/7 reinforces the cell response to virus

The induction of the intrinsic antiviral defense in mammals relies on the accumulation of foreign genetic material. As such, complete engagement of this response is limited to replication-competent viruses. Interferon regulatory factors (IRFs) are mediators of this defense with shared enhancer elements but display a spectrum of transcriptional potential. Here we describe a mechanism designed to enhance this response should a pathogen not be successfully inhibited. We find that activation of IRF7 results in the induction of MAP3K8 and restructuring of the antiviral transcriptome. MAP3K8 mediates the phosphorylation and repression of IRF3 homodimers to promote greater transcriptional activity through utilization of IRF3:IRF7 heterodimers. Among the genes influenced by the MAP3K8/IRF7 signaling axis are members of the SP100 gene family that serve as general transcriptional enhancers of the antiviral defense. We propose that this feed forward loop serves to reinforce the cellular response and is reserved for imminent threats to the host.

Tpl2 kinase regulates FcγR signaling and immune thrombocytopenia in mice

The MAPK3 Tpl2 controls innate and adaptive immunity by regulating TLR, TNF-α, and GPCR signaling in a variety of cell types. Its ablation gives rise to an anti-inflammatory phenotype characterized by resistance to LPS-induced endotoxin shock, DSS-induced colitis, and TNF-α-induced IBD. Here, we address the role of Tpl2 in autoimmunity. Our data show that the ablation and the pharmacological inhibition of Tpl2 protect mice from antiplatelet antibody-induced thrombocytopenia, a model of ITP. Thrombocytopenia in this model and in ITP is caused by phagocytosis of platelets opsonized with antiplatelet antibodies and depends on FcγR activation in splenic and hepatic myeloid cells. Further studies explained how Tpl2 inhibition protects from antibody-induced thrombocytopenia, by showing that Tpl2 is activated by FcγR signals in macrophages and that its activation by these signals is required for ERK activation, cytoplasmic Ca(2+) influx, the induction of cytokine and coreceptor gene expression, and phagocytosis.

TPL-2-ERK1/2 signaling promotes host resistance against intracellular bacterial infection by negative regulation of type I IFN production

Tuberculosis, caused by Mycobacterium tuberculosis, remains a leading cause of mortality and morbidity worldwide, causing ≈ 1.4 million deaths per year. Key immune components for host protection during tuberculosis include the cytokines IL-12, IL-1, and TNF-α, as well as IFN-γ and CD4(+) Th1 cells. However, immune factors determining whether individuals control infection or progress to active tuberculosis are incompletely understood. Excess amounts of type I IFN have been linked to exacerbated disease during tuberculosis in mouse models and to active disease in patients, suggesting tight regulation of this family of cytokines is critical to host resistance. In addition, the immunosuppressive cytokine IL-10 is known to inhibit the immune response to M. tuberculosis in murine models through the negative regulation of key proinflammatory cytokines and the subsequent Th1 response. We show in this study, using a combination of transcriptomic analysis, genetics, and pharmacological inhibitors, that the TPL-2-ERK1/2 signaling pathway is important in mediating host resistance to tuberculosis through negative regulation of type I IFN production. The TPL-2-ERK1/2 signaling pathway regulated production by macrophages of several cytokines important in the immune response to M. tuberculosis as well as regulating induction of a large number of additional genes, many in a type I IFN-dependent manner. In the absence of TPL-2 in vivo, excess type I IFN promoted IL-10 production and exacerbated disease. These findings describe an important regulatory mechanism for controlling tuberculosis and reveal mechanisms by which type I IFN may promote susceptibility to this important disease.

BACH2 represses effector programs to stabilize T(reg)-mediated immune homeostasis

Through their functional diversification, distinct lineages of CD4⁺ T cells play key roles in either driving or constraining immune-mediated pathology. Transcription factors are critical in the generation of cellular diversity, and negative regulators antagonistic to alternate fates often act in conjunction with positive regulators to stabilize lineage commitment¹. Genetic polymorphisms within a single locus encoding the transcription factor BACH2 are associated with numerous autoimmune and allergic diseases including asthma², Crohn’s disease^3–4, coeliac disease⁵, vitiligo⁶, multiple sclerosis⁷ and type 1 diabetes⁸. While these associations point to a shared mechanism underlying susceptibility to diverse immune-mediated diseases, a function for Bach2 in the maintenance of immune homeostasis has not been established. Here, we define Bach2 as a broad regulator of immune activation that stabilizes immunoregulatory capacity while repressing the differentiation programmes of multiple effector lineages in CD4⁺ T cells. Bach2 was required for efficient formation of regulatory (T_reg) cells and consequently for suppression of lethal inflammation in a manner that was T_reg cell dependent. Assessment of the genome-wide function of Bach2, however, revealed that it represses genes associated with effector cell differentiation. Consequently, its absence during T_reg polarization resulted in inappropriate diversion to effector lineages. In addition, Bach2 constrained full effector differentiation within Th1, Th2 and Th17 cell lineages. These findings identify Bach2 as a key regulator of CD4⁺ T-cell differentiation that prevents inflammatory disease by controlling the balance between tolerance and immunity.

TPL2 kinase is a suppressor of lung carcinogenesis

Lung cancer is a heterogeneous disease at both clinical and molecular levels, posing conceptual and practical bottlenecks in defining key pathways affecting its initiation and progression. Molecules with a central role in lung carcinogenesis are likely to be targeted by multiple deregulated pathways and may have prognostic, predictive, and/or therapeutic value. Here, we report that Tumor Progression Locus 2 (TPL2), a kinase implicated in the regulation of innate and adaptive immune responses, fulfils a role as a suppressor of lung carcinogenesis and is subject to diverse genetic and epigenetic aberrations in lung cancer patients. We show that allelic imbalance at the TPL2 locus, up-regulation of microRNA-370, which targets TPL2 transcripts, and activated RAS (rat sarcoma) signaling may result in down-regulation of TPL2 expression. Low TPL2 levels correlate with reduced lung cancer patient survival and accelerated onset and multiplicity of urethane-induced lung tumors in mice. Mechanistically, TPL2 was found to antagonize oncogene-induced cell transformation and survival through a pathway involving p53 downstream of cJun N-terminal kinase (JNK) and be required for optimal p53 response to genotoxic stress. These results identify multiple oncogenic pathways leading to TPL2 deregulation and highlight its major tumor-suppressing function in the lung.

An integrative computational systems biology approach identifies differentially regulated dynamic transcriptome signatures which drive the initiation of human T helper cell differentiation

Background

A proper balance between different T helper (Th) cell subsets is necessary for normal functioning of the adaptive immune system. Revealing key genes and pathways driving the differentiation to distinct Th cell lineages provides important insight into underlying molecular mechanisms and new opportunities for modulating the immune response. Previous computational methods to quantify and visualize kinetic differential expression data of three or more lineages to identify reciprocally regulated genes have relied on clustering approaches and regression methods which have time as a factor, but have lacked methods which explicitly model temporal behavior.

Results

We studied transcriptional dynamics of human umbilical cord blood T helper cells cultured in absence and presence of cytokines promoting Th1 or Th2 differentiation. To identify genes that exhibit distinct lineage commitment dynamics and are specific for initiating differentiation to different Th cell subsets, we developed a novel computational methodology (LIGAP) allowing integrative analysis and visualization of multiple lineages over whole time-course profiles. Applying LIGAP to time-course data from multiple Th cell lineages, we identified and experimentally validated several differentially regulated Th cell subset specific genes as well as reciprocally regulated genes. Combining differentially regulated transcriptional profiles with transcription factor binding site and pathway information, we identified previously known and new putative transcriptional mechanisms involved in Th cell subset differentiation. All differentially regulated genes among the lineages together with an implementation of LIGAP are provided as an open-source resource.

Conclusions

The LIGAP method is widely applicable to quantify differential time-course dynamics of many types of datasets and generalizes to any number of conditions. It summarizes all the time-course measurements together with the associated uncertainty for visualization and manual assessment purposes. Here we identified novel human Th subset specific transcripts as well as regulatory mechanisms important for the initiation of the Th cell subset differentiation.