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RATIONALE: Pulmonary fibrosis is a devastating as yet untreatable disease. We previously investigated the endogenous mediators released on lung injury and showed that uric acid is a danger signal activating Nod-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome in lung inflammation and fibrosis (Gasse et al., Am J Respir Crit Care Med 2009;179:903-913). OBJECTIVES: Here we address the role of extracellular adenosine triphosphate (eATP) in pulmonary inflammation and fibrosis. METHODS: ATP was quantified in bronchoalveolar lavage fluid (BALF) of control subjects and patients with idiopathic pulmonary fibrosis. The contribution of eATP as a danger signal was assessed in a murine model of lung fibrosis induced by airway-administered bleomycin (BLM), an intercalating agent that causes DNA strand breaks. MEASUREMENTS AND MAIN RESULTS: Fibrotic patients have elevated ATP content in BALF in comparison with control individuals. In mice, we report an early increase in eATP levels in BALF on BLM administration. Modulation of eATP levels with the ATP-degrading enzyme apyrase greatly reduced BLM-induced inflammatory cell recruitment, lung IL-1[beta], and tissue inhibitor of metalloproteinase (TIMP)-1 production, while administration of ATP-[gamma]S, a stable ATP derivative, enhanced inflammation. P2X(7) receptor-deficient mice presented dramatically reduced lung inflammation, with reduced fibrosis markers such as lung collagen content and matrix-remodeling proteins TIMP-1 and matrix metalloproteinase-9. The acute inflammation depends on a functional pannexin-1 hemichannel protein. In vitro, ATP is released by pulmonary epithelial cells on BLM-induced stress and this is partly dependent on the presence of functional P2X(7) receptor and pannexin-1 hemichannel. CONCLUSIONS: ATP released from BLM-injured lung cells constitutes a major endogenous danger signal that engages the P2X(7) receptor/pannexin-1 axis, leading to IL-1[beta] maturation and lung fibrosis. [ABSTRACT FROM AUTHOR]

Rationale: Lung injury leads to pulmonary inflammation and fibrosis through myeloid differentiation primary response gene 88 (MyD88) and the IL-1 receptor 1 (IL-1R1) signaling pathway. The molecular mechanisms by which lung injury triggers IL-1beta production, inflammation, and fibrosis remain poorly understood. Objectives: To determine if lung injury depends on the NALP3 inflammasome and if bleomycin (BLM)-induced lung injury triggers local production of uric acid, thereby activating the NALP3 inflammasome in the lung. Methods: Inflammation upon BLM administration was evaluated in vivo in inflammasome-deficient mice. Pulmonary uric acid accumulation, inflammation, and fibrosis were analyzed in mice treated with the inhibitor of uric acid synthesis or with uricase, which degrades uric acid. Measurements and Main Results: Lung injury depends on the NALP3 inflammasome, which is triggered by uric acid locally produced in the lung upon BLM-induced DNA damage and degradation. Reduction of uric acid levels using the inhibitor of uric acid synthesis allopurinol or uricase leads to a decrease in BLM-induced IL-1beta production, lung inflammation, repair, and fibrosis. Local administration of exogenous uric acid crystals recapitulates lung inflammation and repair, which depend on the NALP3 inflammasome, MyD88, and IL-1R1 pathways and Toll-like receptor (TLR)2 and TLR4 for optimal inflammation but are independent of the IL-18 receptor. Conclusions: Uric acid released from injured cells constitutes a major endogenous danger signal that activates the NALP3 inflammasome, leading to IL-1beta production. Reducing uric acid tissue levels represents a novel therapeutic approach to control IL-1beta production and chronic inflammatory lung pathology. [ABSTRACT FROM AUTHOR]

Background: Tumor necrosis factor (TNF) is associated with the development of inflammatory pathologies. Antibodies and soluble TNF (solTNF) receptors that neutralize excessive TNF are effective therapies for inflammatory and autoimmune diseases. However, clinical use of TNF inhibitors is associated with an increased risk of infections. Methods: A novel dominant-negative (DN) strategy of selective TNF neutralization, consisting of blocking solTNF while sparing transmembrane TNF (tmTNF), was tested in mouse models of mycobacterial infection and acute liver inflammation. XENP1595, a DN-TNF biologic, was compared with etanercept, a TNF receptor 2 (TNFR2)-IgG1 Fc fusion protein that inhibits murine solTNF and tmTNF. Results: XENP1595 protected mice from acute liver inflammation induced by endotoxin challenge in Mycobacterium bovis bacillus Calmette-Guérin (BCG)-infected mice, but, in contrast to etanercept, it did not compromise host immunity to acute M. bovis BCG and Mycobacterium tuberculosis infections in terms of bacterial burden, granuloma formation, and innate immune responses. Conclusions: A selective inhibitor of solTNF efficiently protected mice from acute liver inflammation yet maintained immunity to mycobacterial infections. In contrast, nonselective inhibition of solTNF and tmTNF suppressed immunity to M. bovis BCG and M. tuberculosis. Therefore, selective inhibition of solTNF by DN-TNF biologics may represent a new therapeutic strategy for the treatment of inflammatory diseases without compromising host immunity. [ABSTRACT FROM AUTHOR]

Rationale: The mechanisms by which oxidants are sensed by cells and cause inflammation are not well understood.Objectives: This study aimed to determine how cells "sense" soluble oxidants and how this is translated into an inflammatory reaction.Methods: Monocytes, macrophages, or HEK293 cells (stably transfected with human Toll-like receptor [TLR]2, TLR2/1, TLR2/6, or TLR4/MD2-CD14) were used. CXC ligand-8 (CXCL8) levels were measured using ELISA. Phosphorylated IL-1 receptor-associated kinase 1 levels were measured using Western blot. TLR2(-/-) and TLR4(-/-) mice were challenged with oxidants, and inflammation was measured by monitoring cell infiltration and KC levels.Measurements and Main Results: Oxidants evoked the release of CXCL8 from monocytes/macrophages; this was abrogated by pretreatment with N-acetylcysteine or binding antibodies to TLR2 and was associated with the rapid phosphorylation of IL-1 receptor-associated kinase 1. Oxidants added to HEK293 cells transfected with TLR2, TLR1/2, or TLR2/6 but not TLR4/MD2-CD14 or control HEK nulls resulted in the release of CXCL8. Oxidant challenge delivered intraperitoneally (2-24 hours) or by inhalation to the lungs (3 days) resulted in a robust inflammation in wild-type mice. TLR2(-/-) mice did not respond to oxidant challenge in either model. TLR4(-/-) mice responded as wild-type mice to oxidants at 2 hours but as TLR2(-/-) mice at later time points.Conclusions: Oxidant-TLR2 interactions provide a signal that initiates the inflammatory response. [ABSTRACT FROM AUTHOR]

Background: Severe refractory, neutrophilic asthma remains an unsolved clinical problem. STING agonists induce a neutrophilic response in the airways, suggesting that STING activation may contribute to the triggering of neutrophilic exacerbations. We aim to determine whether STING-induced neutrophilic lung inflammation mimics severe asthma., Methods: We developed new models of neutrophilic lung inflammation induced by house dust mite (HDM) plus STING agonists diamidobenzimidazole (diABZI) or cGAMP in wild-type, and conditional-STING-deficient mice. We measured DNA damage, cell death, NETs, cGAS/STING pathway activation by immunoblots, N1/N2 balance by flow cytometry, lung function by plethysmography, and Th1/Th2 cytokines by multiplex. We evaluated diABZI effects on human airway epithelial cells from healthy or patients with asthma, and validated the results by transcriptomic analyses of rhinovirus infected healthy controls vs patients with asthma., Results: DiABZI administration during HDM challenge increased airway hyperresponsiveness, neutrophil recruitment with prominent NOS2 + ARG1 - type 1 neutrophils, protein extravasation, cell death by PANoptosis, NETs formation, extracellular dsDNA release, DNA sensors activation, IFNγ, IL-6 and CXCL10 release. Functionally, STING agonists exacerbated airway hyperresponsiveness. DiABZI caused DNA and epithelial barrier damage, STING pathway activation in human airway epithelial cells exposed to HDM, in line with DNA-sensing and PANoptosis pathways upregulation and tight-junction downregulation induced by rhinovirus challenge in patients with asthma., Conclusions: Our study identifies that triggering STING in the context of asthma induces cell death by PANoptosis, fueling the flame of inflammation through a mixed Th1/Th2 immune response recapitulating the features of severe asthma with a prognostic signature of type 1 neutrophils., (Allergy© 2024 The Author(s). Allergy published by European Academy of Allergy and Clinical Immunology and John Wiley & Sons Ltd.)

Natterin is a potent pro-inflammatory fish molecule, inducing local and systemic IL-1β/IL-1R1-dependent neutrophilia mediated by non-canonical NLRP6 and NLRC4 inflammasome activation in mice, independent of NLRP3. In this work, we investigated whether Natterin activates mitochondrial damage, resulting in self-DNA leaks into the cytosol, and whether the DNA sensor cGAS and STING pathway participate in triggering the innate immune response. Employing a peritonitis mouse model, we found that the deficiency of the tlr2/tlr4, myd88 and trif results in decreased neutrophil influx to peritoneal cavities of mice, indicative that in addition to MyD88, TRIF contributes to neutrophilia triggered by TLR4 engagement by Natterin. Next, we demonstrated that gpcr91 deficiency in mice abolished the neutrophil recruitment after Natterin injection, but mice pre-treated with 2-deoxy-d-glucose that blocks glycolysis presented similar infiltration than WT Natterin-injected mice. In addition, we observed that, compared with the WT Natterin-injected mice, DPI and cyclosporin A treated mice had a lower number of neutrophils in the peritoneal exudate. The levels of dsDNA in the supernatant of the peritoneal exudate and processed IL-33 in the supernatant of the peritoneal exudate or cytoplasmic supernatant of the peritoneal cell lysate of WT Natterin-injected mice were several folds higher than those of the control mice. The recruitment of neutrophils to peritoneal cavity 2 h post-Natterin injection was intensely impaired in ifnar KO mice and partially in il-28r KO mice, but not in ifnγr KO mice. Finally, using cgas KO, sting KO, or irf3 KO mice we found that recruitment of neutrophils to peritoneal cavities was virtually abolished in response to Natterin. These findings reveal cytosolic DNA sensors as critical regulators for Natterin-induced neutrophilia.

Airborne ozone exposure causes severe lung injury and inflammation. The aryl hydrocarbon Receptor (AhR) (1), activated in pollutant-induced inflammation, is critical for cytokine production, especially IL-22 and IL-17A. The role of AhR in ozone-induced lung inflammation is unknown. We report here that chronic ozone exposure activates AhR with increased tryptophan and lipoxin A4 production in mice. AhR -/- mice show increased lung inflammation, airway hyperresponsiveness, and tissue remodeling with an increased recruitment of IL-17A and IL-22-expressing cells in comparison to control mice. IL-17A- and IL-22-neutralizing antibodies attenuate lung inflammation in AhR -/- and control mice. Enhanced lung inflammation and recruitment of ILC3, ILC2, and T cells were observed after T cell-specific AhR depletion using the AhR CD4cre -deficient mice. Together, the data demonstrate that ozone exposure activates AhR, which controls lung inflammation, airway hyperresponsiveness, and tissue remodeling via the reduction of IL-22 expression., (Copyright © 2020 Michaudel, Bataille, Maillet, Fauconnier, Colas, Sokol, Straube, Couturier-Maillard, Dumoutier, van Snick, Quesniaux, Togbe and Ryffel.)

Background: IL-33 plays a critical role in regulation of tissue homeostasis, injury, and repair. Whether IL-33 regulates neutrophil recruitment and functions independently of airways hyperresponsiveness (AHR) in the setting of ozone-induced lung injury and inflammation is unclear., Objective: We sought to examine the role of the IL-33/ST2 axis in lung inflammation on acute ozone exposure in mice., Methods: ST2- and Il33-deficient, IL-33 citrine reporter, and C57BL/6 (wild-type) mice underwent a single ozone exposure (1 ppm for 1 hour) in all studies. Cell recruitment in lung tissue and the bronchoalveolar space, inflammatory parameters, epithelial barrier damage, and airway hyperresponsiveness (AHR) were determined., Results: We report that a single ozone exposure causes rapid disruption of the epithelial barrier within 1 hour, followed by a second phase of respiratory barrier injury with increased neutrophil recruitment, reactive oxygen species production, AHR, and IL-33 expression in epithelial and myeloid cells in wild-type mice. In the absence of IL-33 or IL-33 receptor/ST2, epithelial cell injury with protein leak and myeloid cell recruitment and inflammation are further increased, whereas the tight junction proteins E-cadherin and zonula occludens 1 and reactive oxygen species expression in neutrophils and AHR are diminished. ST2 neutralization recapitulated the enhanced ozone-induced neutrophilic inflammation. However, myeloid cell depletion using GR-1 antibody reduced ozone-induced lung inflammation, epithelial cell injury, and protein leak, whereas administration of recombinant mouse IL-33 reduced neutrophil recruitment in Il33-deficient mice., Conclusion: Data demonstrate that ozone causes an immediate barrier injury that precedes myeloid cell-mediated inflammatory injury under the control of the IL-33/ST2 axis. Thus IL-33/ST2 signaling is critical for maintenance of intact epithelial barrier and inflammation., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

One of the hallmarks of acute inflammation is neutrophil infiltration of tissues. We investigated molecular mechanisms implicated in acute neutrophilic inflammation induced by the venom of a freshwater stingray (Potamotrygon cf. henlei) in mice. Ray venom induced early mobilization of neutrophil in the microvasculature of cremaster mice and infiltration of the peritoneal cavity 2 hours after injury, in a dose-response manner. IL-1β, IL-6, TNF-α, and KC were produced. The neutrophilic infiltration did not occur in mice with ST2 receptor and MyD88 adapters neutralized, or in those with PI3K and p38 MAPK signaling blocked. Drastic reduction of neutrophil infiltration to peritoneal cavities was observed in ST2 -/- , TLR2/TLR4 -/- , MyD88 -/- , TRIF -/- and IL-17A -/- mice, and a partial reduction was observed in IL-18R -/- mice. Mast cell Kit W(sh)/W(sh)-, AHR-, NLRP3-, ICE-, IL-1β-, P2RX7-, CD39-, IL-17RA-, and TBX21 KO mice retain the ability to induce neutrophilia in peritoneal cavity after ray venom injection. IL-6 and TNF-α alone were insufficient for promote neutrophilia in the absence of ST2 signaling. Finally, abundant production of IL-33 by cardiomyocytes was observed. These results refine our understanding of the importance of the IL-33/ST2 axis and IL-33-producing cardiomyocytes in the early acute neutrophilia induced by freshwater stingray venoms.

Interleukin (IL) 17A in chronic inflammation is also produced by innate immune cells as neutrophils. Mice with chronic humoral response induced by venom of Thalassophryne nattereri (VTn) proved to be a good tool for evaluating the impact of IL-17A on the development of long-lived plasma cells in the inflamed peritoneal cavity. Here, we report that VTn induces IL-17A production by neutrophils accumulating in the peritoneal cavity and triggers the extrusion of IL-17A along with neutrophil extracellular traps (NETs). Neutrophil depletion reduced the number of IL17A-producing cells in VTn-immunized mice and blocked the differentiation of long-lived plasma cells. Specific antibody production and survival of long-lived plasma cells was ablated in VTn-immunized mice deficient in CD4, while CD28 signaling had the opposite effect on differentiation of long-lived plasma cells. Further, maturation of long-lived plasma cells in inflamed peritoneal cavity was IL-1R1 and COX-2 dependent. Finally, when both the Raf-MEK-ERK pathway and the IL-17A or IL-1R1 activities were blocked, neutrophils were unable to promote the differentiation of memory B cells into long-lived plasma cells, confirming the essential role of neutrophils and IL-17A along with NETs in an IL-1/IL-1R-dependent manner as the novel helping partner for plasma cell differentiation in chronically inflamed tissues.

Tuberculosis of the central nervous system (CNS-TB) is a devastating complication of tuberculosis, and tumor necrosis factor (TNF) is crucial for innate immunity and controlling the infection. TNF is produced by many cell types upon activation, in particularly the myeloid and T cells during neuroinflammation. Here we used mice with TNF ablation targeted to myeloid and T cell (MT-TNF -/- ) to assess the contribution of myeloid and T cell-derived TNF in immune responses during CNS-TB. These mice exhibited impaired innate immunity and high susceptibility to cerebral Mycobacterium tuberculosis infection, a similar phenotype to complete TNF-deficient mice. Further, MT-TNF -/- mice were not able to control T cell responses and cytokine/chemokine production. Thus, our data suggested that collective TNF production by both myeloid and T cells are required to provide overall protective immunity against CNS-TB infection.

The pleiotropic activities of TNF are mediated by two structurally related but functionally distinct type I transmembrane receptors, p55TNFR and p75TNFR expressed in most cell types, that can be cleaved and act as TNF scavengers. Here, we investigated the effect of persistent p55TNFR cell surface expression during aerosol inhalation challenge with virulent M. tuberculosis H37Rv. We demonstrated that persistency of p55TNFR in macrophage cultures increased the synthesis of soluble TNF, p75TNFR and NO, however, had no effects on bacteria killing ability. Furthermore, it did not facilitate enhanced protection to primary acute M. tuberculosis infection in p55 ∆NS mice. Without exacerbated lung inflammation, we found a compensatory increase in p75TNFR shedding and decrease in bioactive TNF in BAL of p55 ∆NS mice after M. tuberculosis challenge. Defective expressions of CD44 and INFγ attributed to an impaired T cell response during persistent p55TNFR expression that caused marginal transient susceptibility during chronic infection. Moreover, persistent p55TNFR expression induced early reactivation during latent tuberculosis infection. These data indicate a prominent role of p55TNFR shedding in Th1 mediated protection against chronic and latent tuberculosis infection.

Antibodies targeting IL-17A or its receptor IL-17RA show unprecedented efficacy in the treatment of autoimmune diseases such as psoriasis. These therapies, by neutralizing critical mediators of immunity, may increase susceptibility to infections. Here, we compared the effect of antibodies neutralizing IL-17A, IL-17F or TNFα on murine host responses to Mycobacterium tuberculosis infection by evaluating lung transcriptomic, microbiological and histological analyses. Coinciding with a significant increase of mycobacterial burden and pathological changes following TNFα blockade, gene array analyses of infected lungs revealed major changes of inflammatory and immune gene expression signatures 4 weeks post-infection. Specifically, gene expression associated with host-pathogen interactions, macrophage recruitment, activation and polarization, host-antimycobacterial activities, immunomodulatory responses, as well as extracellular matrix metallopeptidases, were markedly modulated by TNFα blockade. IL-17A or IL-17F neutralization elicited only mild changes of few genes without impaired host resistance four weeks after M. tuberculosis infection. Further, the absence of both IL-17RA and IL-22 pathways in genetically deficient mice did not profoundly compromise host control of M. tuberculosis over a 6-months period, ruling out potential compensation between these two pathways, while TNFα-deficient mice succumbed rapidly. These data provide experimental confirmation of the low clinical risk of mycobacterial infection under anti-IL-17A therapy, in contrast to anti-TNFα treatment.

Glufosinate-ammonium (GLA), the active component of an herbicide, is known to cause neurotoxicity. GLA shares structural analogy with glutamate. It is a powerful inhibitor of glutamine synthetase (GS) and may bind to glutamate receptors. Since these potentials targets of GLA are present in lung and immune cells, we asked whether airway exposure to GLA may cause lung inflammation in mice. A single GLA exposure (1 mg/kg) induced seizures and inflammatory cell recruitment in the broncho-alveolar space, and increased myeloperoxidase (MPO), inducible NO synthase (iNOS), interstitial inflammation and disruption of alveolar septae within 6-24 h. Interleukin 1β (IL-1β) was increased and lung inflammation depended on IL-1 receptor 1 (IL-1R1). We demonstrate that glutamate receptor pathway is central, since the N-methyl-D-aspartate (NMDA) receptor inhibitor MK-801 prevented GLA-induced lung inflammation. Chronic exposure (0.2 mg/kg 3× per week for 4 weeks) caused moderate lung inflammation and enhanced airway hyperreactivity with significant increased airway resistance. In conclusion, GLA aerosol exposure causes glutamate signalling and IL-1R-dependent pulmonary inflammation with airway hyperreactivity in mice., (© 2016 The Author(s). published by Portland Press Limited on behalf of the Biochemical Society.)

Tumor necrosis factor (TNF) is crucial to control Mycobacterium tuberculosis infection, which remains a leading cause of morbidity and mortality worldwide. TNF blockade compromises host immunity and may cause reactivation of latent infection, resulting in overt pulmonary, pleural, and extrapulmonary tuberculosis. Herein, we investigate the roles of TNF and TNF receptors in the control of Mycobacterium bovis bacillus Calmette-Guerin (BCG) pleural infection in a murine model. As controls, wild-type mice and those with a defective CCR5, a receptor that is crucial for control of viral infection but not for tuberculosis, were used. BCG-induced pleural infection was uncontrolled and progressive in absence of TNF or TNF receptor 1 (TNFR1)/TNFR2 (TNFR1R2) with increased inflammatory cell recruitment and bacterial load in the pleural cavity, and heightened levels of pleural and serum proinflammatory cytokines and chemokines, compared to wild-type control mice. The visceral pleura was thickened with chronic inflammation, which was prominent in TNF(-/-) and TNFR1R2(-/-) mice. The parietal pleural of TNF(-/-) and TNFR1R2(-/-) mice exhibited abundant inflammatory nodules containing mycobacteria, and these mice developed nonresolving inflammation and succumbed from disseminated BCG infection. By contrast, CCR5(-/-) mice survived and controlled pleural BCG infection as wild-type control mice. In conclusion, BCG-induced pleurisy was uncontrolled in the absence of TNF or TNF receptors with exacerbated inflammatory response, impaired bacterial clearance, and defective mesothelium repair, suggesting a critical role of TNF to control mycobacterial pleurisy., (Copyright © 2016 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Exposure to ambient ozone causes airway hyperreactivity and lung inflammation, which represent an important health concern in humans. Recent clinical and experimental studies contributed to the understanding of the mechanisms of epithelial injury, inflammation and airway hyperreactivity, which is reviewed here. The present data suggest that ozone induced oxidative stress causes inflammasome activation with the release of IL-1, other cytokines and proteases driving lung inflammation leading to the destruction of alveolar epithelia with emphysema and respiratory failure. Insights in the pathogenic pathway may allow to identify novel biomarkers of ozone-induced lung disease and therapeutic targets.

TNF is crucial for controlling Mycobacterium tuberculosis infection and understanding how will help immunomodulating the host response. Here we assessed the contribution of TNFR1 pathway from innate myeloid versus T cells. We first established the prominent role of TNFR1 in haematopoietic cells for controlling M. tuberculosis in TNFR1 KO chimera mice. Further, absence of TNFR1 specifically on myeloid cells (M-TNFR1 KO) recapitulated the uncontrolled M. tuberculosis infection seen in fully TNFR1 deficient mice, with increased bacterial burden, exacerbated lung inflammation, and rapid death. Pulmonary IL-12p40 over-expression was attributed to a prominent CD11b(+) Gr1(high) cell population in infected M-TNFR1 KO mice. By contrast, absence of TNFR1 on T-cells did not compromise the control of M. tuberculosis infection over 6-months. Thus, the protective TNF/TNFR1 pathway essential for controlling primary M. tuberculosis infection depends on innate macrophage and neutrophil myeloid cells, while TNFR1 pathway in T cells is dispensable.

Neuropathic pain from injury to the peripheral and CNS represents a major health care issue. We have investigated the role of IL-33/IL-33 receptor (ST2) signaling in experimental models of neuropathic pain in mice. Chronic constriction injury (CCI) of the sciatic nerve induced IL-33 production in the spinal cord. IL-33/citrine reporter mice revealed that oligodendrocytes are the main cells expressing IL-33 within the spinal cord together with a minor expression by neurons, microglia. and astrocytes. CCI-induced mechanical hyperalgesia was reduced in IL-33R (ST2)(-/ -) mice compared with wild-type (WT) mice. Intrathecal treatment of WT mice with soluble IL-33 receptor (IL-33 decoy receptor) markedly reduced CCI-induced hyperalgesia. Consistent with these observations, intrathecal injection of IL-33 enhanced CCI hyperalgesia and induced hyperalgesia in naive mice. IL-33-mediated hyperalgesia during CCI was dependent on a reciprocal relationship with TNF-α and IL-1β. IL-33-induced hyperalgesia was markedly attenuated by inhibitors of PI3K, mammalian target of rapamycin, MAPKs (p38, ERK, and JNK), NF-κB, and also by the inhibitors of glial cells (microglia and astrocytes). Furthermore, targeting these signaling pathways and cells inhibited IL-33-induced TNF-α and IL-1β production in the spinal cord. Our study, therefore, reveals an important role of oligodendrocyte-derived IL-33 in neuropathic pain., (© FASEB.)

Tumor necrosis factor (TNF) is an important cytokine for host defense against pathogens but is also associated with the development of human immunopathologies. TNF blockade effectively ameliorates many chronic inflammatory conditions but compromises host immunity to tuberculosis. The search for novel, more specific human TNF blockers requires the development of a reliable animal model. We used a novel mouse model with complete replacement of the mouse TNF gene by its human ortholog (human TNF [huTNF] knock-in [KI] mice) to determine resistance to Mycobacterium bovis BCG and M. tuberculosis infections and to investigate whether TNF inhibitors in clinical use reduce host immunity. Our results show that macrophages from huTNF KI mice responded to BCG and lipopolysaccharide similarly to wild-type macrophages by NF-κB activation and cytokine production. While TNF-deficient mice rapidly succumbed to mycobacterial infection, huTNF KI mice survived, controlling the bacterial burden and activating bactericidal mechanisms. Administration of TNF-neutralizing biologics disrupted the control of mycobacterial infection in huTNF KI mice, leading to an increased bacterial burden and hyperinflammation. Thus, our findings demonstrate that human TNF can functionally replace murine TNF in vivo, providing mycobacterial resistance that could be compromised by TNF neutralization. This new animal model will be helpful for the testing of specific biologics neutralizing human TNF., (Copyright © 2015, American Society for Microbiology. All Rights Reserved.)

The cysteine protease caspase-1 (Casp-1) contributes to innate immunity through the assembly of NLRP3, NLRC4, AIM2, and NLRP6 inflammasomes. Here we ask whether caspase-1 activation plays a regulatory role in house dust mite (HDM)-induced experimental allergic airway inflammation. We report enhanced airway inflammation in caspase-1-deficient mice exposed to HDM with a marked eosinophil recruitment, increased expression of IL-4, IL-5, IL-13, as well as full-length and bioactive IL-33. Furthermore, mice deficient for NLRP3 failed to control eosinophil influx in the airways and displayed augmented Th2 cytokine and chemokine levels, suggesting that the NLPR3 inflammasome complex controls HDM-induced inflammation. IL-33 neutralization by administration of soluble ST2 receptor inhibited the enhanced allergic inflammation, while administration of recombinant IL-33 during challenge phase enhanced allergic inflammation in caspase-1-deficient mice. Therefore, we show that caspase-1, NLRP3, and ASC, but not NLRC4, contribute to the upregulation of allergic lung inflammation. Moreover, we cannot exclude an effect of caspase-11, because caspase-1-deficient mice are deficient for both caspases. Mechanistically, absence of caspase-1 is associated with increased expression of IL-33, uric acid, and spleen tyrosine kinase (Syk) production. This study highlights a critical role of caspase-1 activation and NLPR3/ASC inflammasome complex in the down-modulation of IL-33 in vivo and in vitro, thereby regulating Th2 response in HDM-induced allergic lung inflammation., (© The Author (2015). Published by Oxford University Press on behalf of Journal of Molecular Cell Biology, IBCB, SIBS, CAS. All rights reserved.)

IL-36 cytokines are members of the IL-1 family of cytokines that stimulate dendritic cells and T cells leading to enhanced T helper 1 responses in vitro and in vivo; however, their role in host defense has not been fully addressed thus far. The objective of this study was to examine the role of IL-36R signaling in the control of mycobacterial infection, using models of systemic attenuated M. bovis BCG infection and virulent aerogenic M. tuberculosis infection. IL-36γ expression was increased in the lung of M. bovis BCG infected mice. However, IL-36R deficient mice infected with M. bovis BCG showed similar survival and control of the infection as compared to wild-type mice, although their lung pathology and CXCL1 response were transiently different. While highly susceptible TNF-α deficient mice succumbed with overwhelming M. tuberculosis infection, and IL-1RI deficient mice showed intermediate susceptibility, IL-36R-deficient mice controlled the infection, with bacterial burden, lung inflammation and pathology, similar to wild-type controls. Therefore, IL-36R signaling has only limited influence in the control of mycobacterial infection.

Cerebral malaria, a severe complication of Plasmodium falciparum infection, can be modeled in murine Plasmodium berghei ANKA (PbA) infection. PbA-induced experimental cerebral malaria (ECM) is CD8(+) T-cell mediated, and influenced by TH 1/TH 2 balance. Here, we show that IL-33 expression is increased in brain undergoing ECM and we address the role of the IL-33/ST2 pathway in ECM development. ST2-deficient mice were resistant to PbA-induced neuropathology. They survived >20 days with no ECM neurological sign and a preserved cerebral microcirculation, while WT mice succumbed within 10 days with ECM, brain vascular leakage, distinct microvascular pathology obstruction, and hemorrhages. Parasitemia and brain parasite load were similar in ST2-deficient and WT mice. Protection was accompanied by reduced brain sequestration of activated CD4(+) T cells and perforin(+) CD8(+) T cells. While IFN-γ and T-cell-attracting chemokines CXCL9 and CXCL10 were not affected in the absence of functional ST2 pathway, the local expression of ICAM-1, CXCR3, and LT-α, crucial for ECM development, was strongly reduced, and this may explain the diminished pathogenic T-cell recruitment and resistance to ECM. Therefore, IL-33 is induced in PbA sporozoite infection, and the pathogenic T-cell responses with local microvascular pathology are dependent on IL-33/ST2 signaling, identifying IL-33 as a new actor in ECM development., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Cystic fibrosis is associated with increased inflammatory responses to pathogen challenge. Here we revisited the role of IL-1β in lung pathology using the experimental F508del-CFTR murine model on C57BL/6 genetic background (Cftr(tm1eur) or d/d), on double deficient for d/d and type 1 interleukin-1 receptor (d/d X IL-1R1-/-), and antibody neutralization. At steady state, young adult d/d mice did not show any signs of spontaneous lung inflammation. However, IL-1R1 deficiency conferred partial protection to repeated P. aeruginosa endotoxins/LPS lung instillation in d/d mice, as 50% of d/d mice succumbed to inflammation, whereas all d/d x IL-1R1-/- double mutants survived with lower initial weight loss and less pulmonary collagen and mucus production, suggesting that the absence of IL-1R1 signaling is protective in d/d mice in LPS-induced lung damage. Using P. aeruginosa acute lung infection we found heightened neutrophil recruitment in d/d mice with higher epithelial damage, increased bacterial load in BALF, and augmented IL-1β and TNF-α in parenchyma as compared to WT mice. Thus, F508del-CFTR mice show enhanced IL-1β signaling in response to P. aeruginosa. IL-1β antibody neutralization had no effect on lung homeostasis in either d/d or WT mice, however P. aeruginosa induced lung inflammation and bacterial load were diminished by IL-1β antibody neutralization. In conclusion, enhanced susceptibility to P. aeruginosa in d/d mice correlates with an excessive inflammation and with increased IL-1β production and reduced bacterial clearance. Further, we show that neutralization of IL-1β in d/d mice through the double mutation d/d x IL-1R1-/- and in WT via antibody neutralization attenuates inflammation. This supports the notion that intervention in the IL-1R1/IL-1β pathway may be detrimental in CF patients.

Development of host protective immunity against Mycobacterium tuberculosis infection is critically dependent on the inflammatory cytokine TNF. TNF signals through 2 receptors, TNFRp55 and TNFRp75; however, the role of TNFRp75-dependent signaling in immune regulation is poorly defined. Here we found that mice lacking TNFRp75 exhibit greater control of M. tuberculosis infection compared with WT mice. TNFRp75-/- mice developed effective bactericidal granulomas and demonstrated increased pulmonary recruitment of activated DCs. Moreover, IL-12p40-dependent migration of DCs to lung draining LNs of infected TNFRp75-/- mice was substantially higher than that observed in WT M. tuberculosis-infected animals and was associated with enhanced frequencies of activated M. tuberculosis-specific IFN-γ-expressing CD4+ T cells. In WT mice, TNFRp75 shedding correlated with markedly reduced bioactive TNF levels and IL-12p40 expression. Neutralization of TNFRp75 in M. tuberculosis-infected WT BM-derived DCs (BMDCs) increased production of bioactive TNF and IL-12p40 to a level equivalent to that produced by TNFRp75-/- BMDCs. Addition of exogenous TNFRp75 to TNFRp75-/- BMDCs infected with M. tuberculosis decreased IL-12p40 synthesis, demonstrating that TNFRp75 shedding regulates DC activation. These data indicate that TNFRp75 shedding downmodulates protective immune function and reduces host resistance and survival; therefore, targeting TNFRp75 may be beneficial for improving disease outcome.

The nuclear receptor PPARγ acts as a key modulator of lipid metabolism, inflammation and pathogenesis in BCG-infected macrophages. However, the molecular mechanisms involved in PPARγ expression and functions during infection are not completely understood. Here, we investigate signaling pathways triggered by TLR2, the involvement of co-receptors and lipid rafts in the mechanism of PPARγ expression, lipid body formation and cytokine synthesis in macrophages during BCG infection. BCG induces NF-κB activation and increased PPARγ expression in a TLR2-dependent manner. Furthermore, BCG-triggered increase of lipid body biogenesis was inhibited by the PPARγ antagonist GW9662, but not by the NF-κB inhibitor JSH-23. In contrast, KC/CXCL1 production was largely dependent on NF-κB but not on PPARγ. BCG infection induced increased expression of CD36 in macrophages in vitro. Moreover, CD36 co-immunoprecipitates with TLR2 in BCG-infected macrophages, suggesting its interaction with TLR2 in BCG signaling. Pretreatment with CD36 neutralizing antibodies significantly inhibited PPARγ expression, lipid body formation and PGE2 production induced by BCG. Involvement of CD36 in lipid body formation was further confirmed by decreased BCG-induced lipid body formation in CD36 deficient macrophages. Similarly, CD14 and CD11b/CD18 blockage also inhibited BCG-induced lipid body formation, whereas TNF-α synthesis was not affected. Disruption of rafts recapitulates the latter result, inhibiting lipid body formation, but not TNF-α synthesis in BCG-infected macrophages. In conclusion, our results suggest that CD36-TLR2 cooperation and signaling compartmentalization within rafts, divert host response signaling through PPARγ-dependent and NF-κB-independent pathways, leading to increased macrophage lipid accumulation and down-modulation of macrophage response., (© 2013.)

TNF and IL-1 are major mediators involved in severe inflammatory diseases against which therapeutic neutralizing antibodies are developed. However, both TNF and IL-1 receptor pathways are essential for the control of Mycobacterium tuberculosis infection, and it is critical to assess the respective role of IL-1α, IL-1β, and TNF. Using gene-targeted mice we show that absence of both IL-1α and IL-1β recapitulates the uncontrolled M. tuberculosis infection with increased bacterial burden, exacerbated lung inflammation, high IFNγ, reduced IL-23 p19 and rapid death seen in IL-1R1-deficient mice. However, presence of either IL-1α or IL-1β in single-deficient mice is sufficient to control acute M. tuberculosis infection, with restrained bacterial burden and lung pathology, in conditions where TNF deficient mice succumbed within 4 weeks with overwhelming infection. Systemic infection by attenuated M. bovis BCG was controlled in the absence of functional IL-1 pathway, but not in the absence of TNF. Therefore, although both IL-1α and IL-1β are required for a full host response to virulent M. tuberculosis, the presence of either IL-1α or IL-1β allows some control of acute M. tuberculosis infection, and IL-1 pathway is dispensable for controlling M. bovis BCG acute infection. This is in sharp contrast with TNF, which is essential for host response to both attenuated and virulent mycobacteria and may have implications for anti-inflammatory therapy with IL-1β neutralizing antibodies.

Cerebral malaria is a severe complication of Plasmodium falciparum infection. Although T-cell activation and type II IFN-γ are required for Plasmodium berghei ANKA (PbA)-induced murine experimental cerebral malaria (ECM), the role of type I IFN-α/β in ECM development remains unclear. Here, we address the role of the IFN-α/β pathway in ECM devel-opment in response to hepatic or blood-stage PbA infection, using mice deficient for types I or II IFN receptors. While IFN-γR1⁻/⁻ mice were fully resistant, IFNAR1⁻/⁻ mice showed delayed and partial protection to ECM after PbA infection. ECM resistance in IFN-γR1⁻/⁻ mice correlated with unaltered cerebral microcirculation and absence of ischemia, while WT and IFNAR1⁻/⁻ mice developed distinct microvascular pathologies. ECM resistance appeared to be independent of parasitemia. Instead, key mediators of ECM were attenuated in the absence of IFNAR1, including PbA-induced brain sequestration of CXCR3⁺-activated CD8⁺ T cells. This was associated with reduced expression of Granzyme B, IFN-γ, IL-12Rβ2, and T-cell-attracting chemokines CXCL9 and CXCL10 in IFNAR1⁻/⁻ mice, more so in the absence of IFN-γR1. Therefore, the type I IFN-α/β receptor pathway contributes to brain T-cell responses and microvascular pathology, although it is not as essential as IFN-γ for the development of cerebral malaria upon hepatic or blood-stage PbA infection., (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Interleukin 1 is a critical inflammatory mediator and involved in host defense to several pathogens. Oral T. gondii infection causes lethal ileitis in C57BL/6 (BL6) mice and serves to investigate the mechanisms of acute intestinal inflammation. Here we show that IL-1 is expressed upon oral T. gondii (76K strain) infection in the small intestine and mediates ileitis as IL-1R1 deficient mice have reduced neutrophil recruitment in the lamina propria, parasite invasion, inflammatory lesions and enhanced survival as compared to BL6 infected control mice. Protection in the absence of IL-1R1 signaling was associated with reduced IFN-γ expression and preserved Paneth cells, while these cells were eliminated in infected BL6 mice. Furthermore, blockade of IL-1 by IL-1β antibody attenuated inflammation in BL6 mice. In conclusion, IL-1 signaling contributes to the inflammatory response with increase IFN-γ expression and Paneth cell depletion upon oral T. gondii infection.

Tuberculosis (TB) is a major health problem requiring sustained immunity to inhibit Mycobacterium tuberculosis growth and appropriate antimicrobial therapy to prevent dissemination and drug resistance. Cell-mediated immune responses to M. tuberculosis involve the activation of cytokines such as Tumor Necrosis Factor (TNF) which is critical for granuloma formation and host resistance against TB. TNF inhibition, used as therapy for the treatment of inflammatory diseases, disrupts granuloma allowing replication of mycobacteria which may increase the efficacy of TB chemotherapy. To test this hypothesis mice infected with M. tuberculosis were treated with isoniazid (INH) and rifampicin (RMP) in the presence or absence of Enbrel, a soluble TNF receptor antagonist during three phases of M. tuberculosis infection. Inhibition of TNF with Enbrel augmented the efficacy of TB chemotherapy as shown by enhanced mycobacterial clearance from the lung of acute and established infection as well as in chronically infected mice. Furthermore, TNF inhibition significantly reduced lung pathology as compared to TB chemotherapy alone. Therefore, the experimental data suggest that TB chemotherapy may be more effective in the presence of a TNF inhibitor, which may be relevant to eradicate mycobacteria during chronic M. tuberculosis infection or reactivation.

Phosphatidyl inositol mannosides (PIMs) are constituents of the mycobacterial cell wall; these glycolipids are known to exhibit potent inhibitory activity toward the LPS-induced production of cytokines by macrophages, and therefore have potential as anti-inflammatory agents. Recently, heterocyclic analogues of PIMs in which the inositol is replaced by a piperidine (aza-PIM mimics) or a tetrahydropyran moiety (oxa-PIM mimics) have been prepared by short synthetic sequences and shown to retain the biological activity of the parent PIM structures. In this investigation, the aza-PIM analogue was used as a convenient scaffold to link biotin or a fluorescent label (tetramethyl-rhodamine) by way of an aminocaproyl spacer, with the goal of using these conjugates for intracellular localization and for the study of the mechanism of their antiinflammatory action. The synthesis of these compounds is reported, as well as the evaluation of their activities as inhibitors of LPS-induced cytokine production by macrophages (TNFα, IL12p40); preliminary investigations by FACS and confocal microscopy indicated that PIM-biotin conjugate binds to macrophage membranes with rapid kinetics.

Tumour Necrosis Factor (TNF) is critical for host control of M. tuberculosis, but the relative contribution of TNF from innate and adaptive immune responses during tuberculosis infection is unclear. Myeloid versus T-cell-derived TNF function in tuberculosis was investigated using cell type-specific TNF deletion. Mice deficient for TNF expression in macrophages/neutrophils displayed early, transient susceptibility to M. tuberculosis but recruited activated, TNF-producing CD4(+) and CD8(+) T-cells and controlled chronic infection. Strikingly, deficient TNF expression in T-cells resulted in early control but susceptibility and eventual mortality during chronic infection with increased pulmonary pathology. TNF inactivation in both myeloid and T-cells rendered mice critically susceptible to infection with a phenotype resembling complete TNF deficient mice, indicating that myeloid and T-cells are the primary TNF sources collaborating for host control of tuberculosis. Thus, while TNF from myeloid cells mediates early immune function, T-cell derived TNF is essential to sustain protection during chronic tuberculosis infection.

A Th1 response is required for the development of Plasmodium berghei ANKA (PbA)-induced experimental cerebral malaria (ECM). The role of pro-Th1 IL-12 in malaria is complex and controversial. In this study, we addressed the role of IL-12Rβ2 in ECM development. C57BL/6 mice deficient for IL-12Rβ2, IL-12p40, or IL-12p35 were analyzed for ECM development after blood-stage PbA infection in terms of ischemia and blood flow by noninvasive magnetic resonance imaging and angiography, T cell recruitment, and gene expression. Without IL-12Rβ2, no neurologic sign of ECM developed upon PbA infection. Although wild-type mice developed distinct brain microvascular pathology, ECM-resistant, IL-12Rβ2-deficient mice showed unaltered cerebral microcirculation and the absence of ischemia after PbA infection. In contrast, mice deficient for IL-12p40 or IL-12p35 were sensitive to ECM development. The resistance of IL-12Rβ2-deficient mice to ECM correlated with reduced recruitment of activated T cells and impaired overexpression of lymphotoxin-α, TNF-α, and IFN-γ in the brain after PbA infection. Therefore, IL-12Rβ2 signaling is essential for ECM development but independent from IL-12p40 and IL-12p35. We document a novel link between IL-12Rβ2 and lymphotoxin-α, TNF-α, and IFN-γ expression, key cytokines for ECM pathogenesis.

Cerebral malaria is a severe form of the disease that may result, in part, from an overt inflammatory response during infection by Plasmodium falciparum. The understanding of the pathogenesis of cerebral malaria may aid in the development of better therapeutic strategies for patients. The immune response in cerebral malaria involves elevation of circulating levels of cytokines and chemokines associated with leukocyte accumulation and breakdown of the blood-brain barrier in the central nervous system. Platelet-activating factor (PAF) is a mediator of inflammation shown to orchestrate inflammatory processes, including recruitment of leukocytes and increase of vascular permeability. Using mice lacking the PAF receptor (PAFR(-/-)), we investigated the relevance of this molecule for the outcome and the neuroinflammatory process triggered by P. berghei ANKA, an experimental model of cerebral malaria. In PAFR(-/-) mice, lethality was markedly delayed and brain inflammation was significantly reduced, as demonstrated by histology, accumulation, and activation of CD8(+) T cells, changes in vascular permeability and activation of caspase-3 on endothelial cells and leukocytes. Similarly, treatment with the PAFR antagonist UK-74,505 delayed lethality. Taken together, the results suggest that PAFR signaling is crucial for the development of experimental cerebral malaria. Mechanistically, PAFR activation is crucial for the cascade of events leading to changes in vascular permeability, accumulation, and activation of CD8(+) T cells and apoptosis of leukocytes and endothelial cells., (Copyright © 2012 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Phosphatidyl myo-inositol mannosides (PIMs) are constituents of the mycobacterial cell wall and possess immunomodulatory activities. Certain PIM derivatives have immunoprotective activity and are of interest as anti-inflammatory agents. In order to identify simplified analogues of PIMs that retain this interesting activity, we have prepared a series of new analogues based either on an acyclic or on a heterocyclic scaffold that replaces the inositol moiety, and evaluated these compounds for their inhibition of LPS-induced release of NO and pro-inflammatory cytokines by macrophages. It was found that the inositol moiety can be favourably replaced by an aza-cyclitol (trihydroxy-piperidine) or an oxa-cyclitol (trihydroxy-tetrahydropyran) unit, and that the configuration of the OH-carrying carbons does not play a significant role. The biological activity is reduced if the nitrogen atom is free in the aza-cyclitol unit., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Tumor Necrosis Factor (TNF) is a pleiotropic cytokine consisting of soluble and transmembrane forms, with distinct roles in inflammation and immunity. TNF is an important factor in allergic airway inflammation. However, the disparate functions of soluble (sol) and transmembrane (tm) TNF in lung pathology are not well understood. Our aim was to assess the activities of solTNF and tmTNF in murine models of allergic airway disease, and to evaluate the efficacy of solTNF-selective inhibition. We used ovalbumin sensitization and challenge of TNF knockout, tmTNF knockin, and wild-type C57BL/6 mice to distinguish differences in airway inflammation and hyperreactivity mediated by solTNF and tmTNF. Functions of solTNF and tmTNF in hyperresponsive, wild-type Balb/c mice were assessed by comparing dominant-negative anti-TNF biologics, which antagonize solTNF yet spare tmTNF, to etanercept, a nonselective inhibitor of both TNF forms. Responses in transgenic C57BL/6 mice demonstrated that solTNF, and not tmTNF, is necessary to drive airway inflammation. In Balb/c mice, dominant-negative TNF biologics administered during immunization decreased the recruitment of eosinophils and lymphocytes into the bronchoalveolar space and lung parenchyma, reduced specific serum IgE, goblet-cell hyperplasia, and eosinophilic inflammation, and suppressed methacholine-induced airway hyperreactivity. Concentrations of IL-5, CCL5/RANTES, CCL11/eotaxin, and CCL17/TARC were also reduced in bronchoalveolar lavage. Dominant-negative TNFs reduced lung eosinophilia, even when given only during antigen challenge. The selective inhibition of soluble TNF suppresses inflammation, hyperreactivity, and remodeling in transgenic and wild-type murine models of allergic airway disease, and may offer safety advantages in therapies that preserve the immunoprotective functions of transmembrane TNF.

Mycobacteria develop strategies to evade the host immune system. Among them, mycobacterial LAM or PIMs inhibit the expression of pro-inflammatory cytokines by activated macrophages. Here, using synthetic PIM analogues, we analyzed the mode of action of PIM anti-inflammatory effects. Synthetic PIM(1) isomer and PIM(2) mimetic potently inhibit TNF and IL-12 p40 expression induced by TLR2 or TLR4 pathways, but not by TLR9, in murine macrophages. We show inhibition of LPS binding to TLR4/MD2/CD14 expressing HEK cells by PIM(1) and PIM(2) analogues. More specifically, the binding of LPS to CD14 was inhibited by PIM(1) and PIM(2) analogues. CD14 was dispensable for PIM(1) and PIM(2) analogues functional inhibition of TLR2 agonists induced TNF, as shown in CD14-deficient macrophages. The use of rough-LPS, that stimulates TLR4 pathway independently of CD14, allowed to discriminate between CD14-dependent and CD14-independent anti-inflammatory effects of PIMs on LPS-induced macrophage responses. PIM(1) and PIM(2) analogues inhibited LPS-induced TNF release by a CD14-dependent pathway, while IL-12 p40 inhibition was CD14-independent, suggesting that PIMs have multifold inhibitory effects on the TLR4 signalling pathway.

Background: Idiopathic pulmonary fibrosis is a devastating as yet untreatable disease. We demonstrated recently the predominant role of the NLRP3 inflammasome activation and IL-1β expression in the establishment of pulmonary inflammation and fibrosis in mice., Methods: The contribution of IL-23 or IL-17 in pulmonary inflammation and fibrosis was assessed using the bleomycin model in deficient mice., Results: We show that bleomycin or IL-1β-induced lung injury leads to increased expression of early IL-23p19, and IL-17A or IL-17F expression. Early IL-23p19 and IL-17A, but not IL-17F, and IL-17RA signaling are required for inflammatory response to BLM as shown with gene deficient mice or mice treated with neutralizing antibodies. Using FACS analysis, we show a very early IL-17A and IL-17F expression by RORγt(+) γδ T cells and to a lesser extent by CD4αβ(+) T cells, but not by iNKT cells, 24 hrs after BLM administration. Moreover, IL-23p19 and IL-17A expressions or IL-17RA signaling are necessary to pulmonary TGF-β1 production, collagen deposition and evolution to fibrosis., Conclusions: Our findings demonstrate the existence of an early IL-1β-IL-23-IL-17A axis leading to pulmonary inflammation and fibrosis and identify innate IL-23 and IL-17A as interesting drug targets for IL-1β driven lung pathology.

Cerebral malaria is the most severe neurologic complication in children and young adults infected with Plasmodium falciparum. T-cell activation is required for development of Plasmodium berghei ANKA (PbA)-induced experimental cerebral malaria (CM). To characterize the T-cell activation pathway involved, the role of protein kinase C-theta (PKC-θ) in experimental CM development was examined. PKC-θ-deficient mice are resistant to CM development. In the absence of PKC-θ, no neurologic sign of CM developed after blood stage PbA infection. Resistance of PKC-θ-deficient mice correlated with unaltered cerebral microcirculation and absence of ischemia, as documented by magnetic resonance imaging and magnetic resonance angiography, whereas wild-type mice developed distinct microvascular pathology. Recruitment and activation of CD8(+) T cells, and ICAM-1 and CD69 expression were reduced in the brain of resistant mice; however, the pulmonary inflammation and edema associated with PbA infection were still present in the absence of functional PKC-θ. Resistant PKC-θ-deficient mice developed high parasitemia, and died at 3 weeks with severe anemia. Therefore, PKC-θ signaling is crucial for recruitment of CD8(+) T cells and development of brain microvascular pathology resulting in fatal experimental CM, and may represent a novel therapeutic target of CM., (Copyright © 2011 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

The contribution of lymphotoxin (LT)α in the host immune response to virulent Mycobacterium tuberculosis and Mycobacterium bovis bacillus Calmette-Guérin infections was investigated. Despite their ability to induce Th1 cytokine, IFN-γ, and IL-12 pulmonary response, "conventional" LTα(-/-) mice succumb rapidly to virulent M. tuberculosis aerosol infection, with uncontrolled bacilli growth, defective granuloma formation, necrosis, and reduced pulmonary inducible NO synthase expression, similar to TNF(-/-) mice. Contributions from developmental lymphoid abnormalities in LTα(-/-) mice were excluded because hematopoietic reconstitution with conventional LTα(-/-) bone marrow conferred enhanced susceptibility to wild-type mice, comparable to conventional LTα(-/-) control mice. However, conventional LTα(-/-) mice produced reduced levels of TNF after M. bovis bacillus Calmette-Guérin infection, and their lack of control of mycobacterial infection could be due to a defective contribution of either LTα or TNF, or both, to the host immune response. To address this point, the response of "neo-free" LTα(-/-) mice with unperturbed intrinsic TNF expression to M. tuberculosis infection was investigated in a direct comparative study with conventional LTα(-/-) mice. Strikingly, although conventional LTα(-/-) mice were highly sensitive, similar to TNF(-/-) mice, neo-free LTα(-/-) mice controlled acute M. tuberculosis infection essentially as wild-type mice. Pulmonary bacterial burden and inflammation was, however, slightly increased in neo-free LTα(-/-) mice 4-5 mo postinfection, but importantly, they did not succumb to infection. Our findings revise the notion that LTα might have a critical role in host defense to acute mycobacterial infection, independent of TNF, but suggest a contribution of LTα in the control of chronic M. tuberculosis infection.

Mycobacterium tuberculosis is recognized by multiple pattern recognition receptors involved in innate immune defense, but their direct role in tuberculosis pathogenesis remains unknown. Beyond TLRs, scavenger receptors (SRs) and C-type lectins may play a crucial role in the sensing and signaling of pathogen motifs, as well as contribute to M. tuberculosis immune evasion. In this study, we addressed the relative role and potential redundancy of these receptors in the host response and resistance to M. tuberculosis infection using mice deficient for representative SR, C-type lectin receptor, or seven transmembrane receptor families. We show that a single deficiency in the class A SR, macrophage receptor with collagenous structure, CD36, mannose receptor, specific ICAM-3 grabbing nonintegrin-related, or F4/80 did not impair the host resistance to acute or chronic M. tuberculosis infection in terms of survival, control of bacterial clearance, lung inflammation, granuloma formation, and cytokine and chemokine expression. Double deficiency for the SRs class A SR types I and II plus CD36 or for the C-type lectins mannose receptor plus specific ICAM-3 grabbing nonintegrin-related had a limited effect on macrophage uptake of mycobacteria and TNF response and on the long-term control of M. tuberculosis infection. By contrast, mice deficient in the TNF, IL-1, or IFN-gamma pathway were unable to control acute M. tuberculosis infection. In conclusion, we document a functional redundancy in the pattern recognition receptors, which might cooperate in a coordinated response to sustain the full immune control of M. tuberculosis infection, in sharp contrast with the nonredundant, essential role of the TNF, IL-1, or IFN-gamma pathway for host resistance to M. tuberculosis.

TNF is essential to control Mycobacterium tuberculosis infection and cannot be replaced by other proinflammatory cytokines. Overproduction of TNF may cause immunopathology, while defective TNF production results in uncontrolled infection. The critical role of TNF in the control of tuberculosis has been illustrated recently by primary and reactivation of latent infection in some patients under pharmacological anti-TNF therapy for rheumatoid arthritis or Crohn's disease. In this review, we discuss results of recent studies aimed at better understanding of molecular, cellular and kinetic aspects of TNF-mediated regulation of host-mycobacteria interactions. In particular, recent data using either mutant mice expressing solely membrane TNF or specific inhibitor sparing membrane TNF demonstrated that membrane TNF is sufficient to control acute M. tuberculosis infection. This is opening the way to selective TNF neutralization that might retain the desired anti-inflammatory effect but reduce the infectious risk., (Copyright (c) 2010 S. Karger AG, Basel.)

Mycobacterium tuberculosis modulates host immune responses through proteins and complex glycolipids. Here, we report that the glycosylphosphatidylinositol anchor phosphatidyl-myo-inositol hexamannosides PIM(6) or PIM(2) exert potent anti-inflammatory activities. PIM strongly inhibited the Toll-like receptor (TLR4) and myeloid differentiation protein 88 (MyD88)-mediated release of NO, cytokines, and chemokines, including tumor necrosis factor (TNF), interleukin 12 (IL-12) p40, IL-6, keratinocyte-derived chemokine, and also IL-10 by lipopolysaccharide (LPS)-activated macrophages. This effect was independent of the presence of TLR2. PIM also reduced the LPS-induced MyD88-independent, TIR domain-containing adaptor protein inducing interferon beta (TRIF)-mediated expression of co-stimulatory receptors. PIM inhibited LPS/TLR4-induced NFkappaB translocation. Synthetic PIM(1) and a PIM(2) mimetic recapitulated these in vitro activities and inhibited endotoxin-induced airway inflammation, TNF and keratinocyte-derived chemokine secretion, and neutrophil recruitment in vivo. Mannosyl, two acyl chains, and phosphatidyl residues are essential for PIM anti-inflammatory activity, whereas the inosityl moiety is dispensable. Therefore, PIM exert potent antiinflammatory effects both in vitro and in vivo that may contribute to the strategy developed by mycobacteria for repressing the host innate immunity, and synthetic PIM analogs represent powerful anti-inflammatory leads.

Mast Cells (MCs) express toll-like receptor 2 (TLR2), a receptor known to be triggered by several major mycobacterial ligands and involved in resistance against Mycobacterium tuberculosis (MTB) infection. This study investigated whether adoptive transfer of TLR2 positive MCs (TLR2(+/+)) corrects the increased susceptibility of TLR2(-/-) mice to MTB infection. TLR2(-/-) mice displayed increased mycobacterial burden, diminished myeloid cell recruitment and proinflammatory cytokine production accompanied by defective granuloma formation. The reconstitution of these mice with TLR2(+/+) MCs, but not TLR2(-/-), confers better control of the infection, promotes the normalization of myeloid cell recruitment associated with reestablishment of the granuloma formation. In addition, adoptive transfer of TLR2(+/+) MC to TLR2(-/-) mice resulted in regulation of the pulmonary levels of IL-beta, IL-6, TNF-alpha, enhanced Th1 response and activated CD8(+) T cell homing to the lungs. Our results suggest that activation of MCs via TLR2 is required to compensate the defect in protective immunity and inability of TLR2(-/-) mice to control MTB infection.

Background: TNF-related lymphotoxin alpha (LTalpha) is essential for the development of Plasmodium berghei ANKA (PbA)-induced experimental cerebral malaria (ECM). The pathway involved has been attributed to TNFR2. Here we show a second arm of LTalpha-signaling essential for ECM development through LTbeta-R, receptor of LTalpha1beta2 heterotrimer., Methodology/principal Findings: LTbetaR deficient mice did not develop the neurological signs seen in PbA induced ECM but died at three weeks with high parasitaemia and severe anemia like LTalphabeta deficient mice. Resistance of LTalphabeta or LTbetaR deficient mice correlated with unaltered cerebral microcirculation and absence of ischemia, as documented by magnetic resonance imaging and angiography, associated with lack of microvascular obstruction, while wild-type mice developed distinct microvascular pathology. Recruitment and activation of perforin(+) CD8(+) T cells, and their ICAM-1 expression were clearly attenuated in the brain of resistant mice. An essential contribution of LIGHT, another LTbetaR ligand, could be excluded, as LIGHT deficient mice rapidly succumbed to ECM., Conclusions/significance: LTbetaR expressed on radioresistant resident stromal, probably endothelial cells, rather than hematopoietic cells, are essential for the development of ECM, as assessed by hematopoietic reconstitution experiment. Therefore, the data suggest that both functional LTbetaR and TNFR2 signaling are required and non-redundant for the development of microvascular pathology resulting in fatal ECM.