Lung NF-kappaB activation and neutrophil recruitment require IL-1 and TNF receptor signaling during pneumococcal pneumonia

Pulmonary inflammation is an essential component of the host defense against Streptococcus pneumoniae infection of the lungs. The early response cytokines, TNF-alpha and IL-1, are rapidly induced upon microbial exposure. Mice deficient in all TNF- and IL-1-dependent signaling receptors were used to determine the roles of these cytokines during pneumococcal pneumonia. The deficiency of signaling receptors for TNF and IL-1 decreased bacterial clearance. Neutrophil recruitment to alveolar air spaces was impaired by receptor deficiency, as was pulmonary expression of the neutrophil chemokines KC and MIP-2. Because NF-kappaB mediates the expression of both chemokines, we assessed NF-kappaB activation in the lungs. During pneumococcal pneumonia, NF-kappaB proteins translocate to the nucleus and activate gene expression; these functions were largely abrogated by the deficiency of receptors for TNF-alpha and IL-1. Thus, the combined deficiency of TNF and IL-1 signaling reduces innate immune responses to S. pneumoniae in the lungs, probably due to essential roles for these receptors in activating NF-kappaB.     

Early response cytokines and innate immunity: essential roles for TNF receptor 1 and type I IL-1 receptor during Escherichia coli pneumonia in mice

The early response cytokines, TNF and IL-1, have overlapping biologic effects that may function to propagate, amplify, and coordinate host responses to microbial challenges. To determine whether signaling from these early response cytokines is essential to orchestrating innate immune responses to intrapulmonary bacteria, the early inflammatory events induced by instillation of Escherichia coli into the lungs were compared in wild-type (WT) mice and mice deficient in both TNF receptor 1 (TNFR1) and the type I IL-1 receptor (IL1R1). Neutrophil emigration and edema accumulation induced by E. coli were significantly compromised by TNFR1/IL1R1 deficiency. Neutrophil numbers in the circulation and within alveolar septae did not differ between WT and TNFR1/IL1R1 mice, suggesting that decreased neutrophil emigration did not result from decreased sequestration or delivery of intravascular neutrophils. The nuclear translocation of NF-kappa B and the expression of the chemokine macrophage inflammatory protein-2 did not differ between WT and TNFR1/IL1R1 lungs. However, the concentration of the chemokine KC was significantly decreased in the bronchoalveolar lavage fluids of TNFR1/IL1R1 mice compared with that in WT mice. Thus, while many of the molecular and cellular responses to E. coli in the lungs did not require signaling by either TNFR1 or IL1R1, early response cytokine signaling was critical to KC expression in the pulmonary air spaces and neutrophil emigration from the alveolar septae.     

Absence of host tumor necrosis factor receptor 1 attenuates manifestations of idiopathic pneumonia syndrome

The interaction of TNF-alpha with TNF receptor 1 (TNFR1) activates several signal transduction pathways that lead to apoptosis or NF-kappa B-dependent inflammation and immunity. We hypothesized that host TNFR1 expression contributes to noninfectious lung injury and inflammation commonly observed after bone marrow transplantation (BMT), termed idiopathic pneumonia syndrome (IPS). C57BL/6 TNFR1-sufficient (TNFR1(+/+)) and -deficient (TNFR1(-/-)) mice were total body irradiated with or without cyclophosphamide conditioning and were given bone marrow plus IPS-inducing donor spleen T cells from B10.BR wild-type mice. TNFR1(-/-) recipient mice exhibited improved early post-BMT survival associated with decreased permeability edema. In addition, the low lung compliance measured in anesthetized, ventilated TNFR1(+/+) mice on day 7 after BMT was restored to baseline during TNFR1 deficiency. Importantly, bronchoalveolar lavage fluid (BALF) inflammatory cells from TNFR1(-/-) vs. TNFR1(+/+) mice generated less nitric oxide (.NO) and nitrating species and exhibited suppressed programmed cell death as assessed using flow cytometry. However, cellular infiltration and levels of proinflammatory cytokines and chemokines were generally higher in BALF collected on day 7 after BMT from TNFR1(-/-) compared with TNFR1(+/+) recipient mice. Our results support a major role of host TNFR1 in regulation of .NO production and lung dysfunction after allogeneic BMT.     

Modulation of endotoxin-induced NF-kappa B activation in lung and liver through TNF type 1 and IL-1 receptors

We investigated the requirement for tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-1 receptors in the pathogenesis of the pulmonary and hepatic responses to Escherichia coli lipopolysaccharide (LPS) by studying wild-type mice and mice deficient in TNF type 1 receptor [TNFR1 knockout (KO)] or both TNF type 1 and IL-1 receptors (TNFR1/IL-1R KO). In lung tissue, NF-kappaB activation was similar among the groups after exposure to aerosolized LPS. After intraperitoneal injection of LPS, NF-kappaB activation in liver was attenuated in TNFR1 KO mice and further diminished in TNFR1/IL-1R KO mice; however, in lung tissue, no impairment in NF-kappaB activation was found in TNFR1 KO mice and only a modest decrease was found in TNFR1/IL-1R KO mice. Lung concentrations of KC and macrophage-inflammatory peptide 2 were lower in TNFR1 KO and TNFR1/IL-1R KO mice after aerosolized and intraperitoneal LPS. We conclude that LPS-induced NF-kappaB activation in liver is mediated through TNF-alpha- and IL-1 receptor-dependent pathways, but, in the lung, LPS-induced NF-kappaB activation is largely independent of these receptors.     

Functions and regulation of NF-kappaB RelA during pneumococcal pneumonia

Eradication of bacteria in the lower respiratory tract depends on the coordinated expression of proinflammatory cytokines and consequent neutrophilic inflammation. To determine the roles of the NF-kappaB subunit RelA in facilitating these events, we infected RelA-deficient mice (generated on a TNFR1-deficient background) with Streptococcus pneumoniae. RelA deficiency decreased cytokine expression, alveolar neutrophil emigration, and lung bacterial killing. S. pneumoniae killing was also diminished in the lungs of mice expressing a dominant-negative form of IkappaBalpha in airway epithelial cells, implicating this cell type as an important locus of NF-kappaB activation during pneumonia. To study mechanisms of epithelial RelA activation, we stimulated a murine alveolar epithelial cell line (MLE-15) with bronchoalveolar lavage fluid (BALF) harvested from mice infected with S. pneumoniae. Pneumonic BALF, but not S. pneumoniae, induced degradation of IkappaBalpha and IkappaBbeta and rapid nuclear accumulation of RelA. Moreover, BALF-induced RelA activity was completely abolished following combined but not individual neutralization of TNF and IL-1 signaling, suggesting either cytokine is sufficient and necessary for alveolar epithelial RelA activation during pneumonia. Our results demonstrate that RelA is essential for the host defense response to pneumococcus in the lungs and that RelA in airway epithelial cells is primarily activated by TNF and IL-1.     

TNF receptor 1 and 2 contribute in different ways to resistance to Legionella pneumophila-induced mortality in mice

Legionella pneumophila is one of the most important pathogens which cause community-acquired pneumonia. Although TNF-alpha is considered to play an important role in response to bacteria, the role of the TNF-alpha receptor on L. pneumophila infection remains to be elucidated. To investigate this, we infected TNF receptor deficient mice with L. pneumophila. L. pneumophila was inoculated intranasally into TNF receptor (TNFR)-1-knock-out mice or TNFR2-knock-out mice. The mortality rate, histology of the lung, bacterial growth in the lung, and bronchoalveolar lavage (BAL) fluids were investigated. The bacterial growth of L. pneumophila in the macrophages was also studied. Almost all the mice survived after an intranasal inoculation of 1x10(6)CFU/head of L. pneumophila, but more than 90% mice were killed after inoculation of 1x10(8)CFU/head of L. pneumophila. In the case of TNFR1-knock-out mice and TNFR2-knock-out mice, a high mortality rate was observed after inoculation of 1x10(7)CFU/head of L. pneumophila in comparison to wild-type mice. The lung histology from both the TNFR1-knock-out mice documented severe lung injury at day 3 after inoculation. The clearance of L. pneumophila in the lung of the TNFR1-knock-out mice was slower than those from both the TNFR2-knock-out mice and the wild-type mice. Moreover, L. pneumophila growth in the peritoneal macrophages from the TNFR1-knock-out mice was observed. Interestingly, a lack of neutrophils accumulation in the BAL fluids and a dysregulation of cytokines (IFN-gamma, interleukin-12, and TNF-alpha) were observed in the TNFR1-knock-out mice. On the contrary, large accumulation of neutrophils in BAL fluids was observed in TNFR2-knock-out mice. These data suggested that a TNFR1 deficiency led to a compromise of the innate immunity against L. pneumophila, while a TNFR2 deficiency induced an excessive inflammatory response and resulted in death. The present study confirmed that TNFR1 and TNFR2 play a crucial, but different role in the control of L. pneumophila-induced mortality.     

Modulation of allergic inflammation in mice deficient in TNF receptors

Tumor necrosis factor-alpha (TNF) is implicated as an important proinflammatory cytokine in asthma. We evaluated mice deficient in TNF receptor 1 (TNFR1) and TNFR2 [TNFR(-/-) mice] in a murine model of allergic inflammation and found that TNFR(-/-) mice had comparable or accentuated responses compared with wild-type [TNFR(+/+)] mice. The responses were consistent among multiple end points. Airway responsiveness after methacholine challenge and bronchoalveolar lavage (BAL) fluid leukocyte and eosinophil numbers in TNFR(-/-) mice were equivalent or greater than those observed in TNFR(+/+) mice. Likewise, serum and BAL fluid IgE; lung interleukin (IL)-2, IL-4, and IL-5 levels; and lung histological lesion scores were comparable or greater in TNFR(-/-) mice compared with those in TNFR(+/+) mice. TNFR(+/+) mice chronically treated with anti-murine TNF antibody had BAL fluid leukocyte numbers and lung lesion scores comparable to control antibody-treated mice. These results suggest that, by itself, TNF does not have a critical proinflammatory role in the development of allergic inflammation in this mouse model and that the production of other cytokines associated with allergic disease may compensate for the loss of TNF bioactivity in the TNFR(-/-) mouse.     

Ozone-induced lung inflammation and hyperreactivity are mediated via tumor necrosis factor-alpha receptors

This study was designed to investigate the mechanisms through which tumor necrosis factor (Tnf) modulates ozone (O(3))-induced pulmonary injury in susceptible C57BL/6J (B6) mice. B6 [wild-type (wt)] mice and B6 mice with targeted disruption (knockout) of the genes for the p55 TNF receptor [TNFR1(-/-)], the p75 TNF receptor [TNFR2(-/-)], or both receptors [TNFR1/TNFR2(-/-)] were exposed to 0.3 parts/million O(3) for 48 h (subacute), and lung responses were determined by bronchoalveolar lavage. All TNFR(-/-) mice had significantly less O(3)-induced inflammation and epithelial damage but not lung hyperpermeability than wt mice. Compared with air-exposed control mice, O(3) elicited upregulation of lung TNFR1 and TNFR2 mRNAs in wt mice and downregulated TNFR1 and TNFR2 mRNAs in TNFR2(-/-) and TNFR1(-/-) mice, respectively. Airway hyperreactivity induced by acute O(3) exposure (2 parts/million for 3 h) was diminished in knockout mice compared with that in wt mice, although lung inflammation and permeability remained elevated. Results suggested a critical role for TNFR signaling in subacute O(3)-induced pulmonary epithelial injury and inflammation and in acute O(3)-induced airway hyperreactivity.     

Pulmonary immune cells and inflammatory cytokine dysregulation are associated with mortality of IL-1R1-/-mice infected with influenza virus (H1 N1)

Respirovirus infection can cause viral pneumonia and acute lung injury (ALI).The interleukin-1 (IL-1) family consists of proinflammatory cytokines that play essential roles in regulating immune and inflammatory responses in vivo.IL-1 signaling is associated with protection against respiratory influenza virus infection by mediation of the pulmonary anti-viral immune response and inflammation.We analyzed the infiltration lung immune leukocytes and cytokines that contribute to inflammatory lung pathology and mortality of fatal H1N1 virus-infected IL-1 receptor 1 (IL-1R1) deficient mice.Results showed that early innate immune cells and cytokine/chemokine dysregulation were observed with significantly decreased neutrophil infiltration and IL-6,TNF-α,G-CSF,KC,and MIP-2 cytokine levels in the bronchoalveolar lavage fluid of infected IL-1R1-/-mice in comparison with that of wild type infected mice.The adaptive immune response against the H1N1 virus in IL-1R1-/-mice was impaired with downregulated anti-viral Th1 cell,CD8+ cell,and antibody functions,which contributes to attenuated viral clearance.Histological analysis revealed reduced lung inflammation during early infection but severe lung pathology in late infection in IL-1R1-/-mice compared with that in WT infected mice.Moreover,the infected IL-1R1-/-mice showed markedly reduced neutrophil generation in bone marrow and neutrophil recruitment to the inflamed lung.Together,these results suggest that IL-1 signaling is associated with pulmonary anti-influenza immune response and inflammatory lung injury,particularly via the influence on neutrophil mobilization and inflammatory cytokine/chemokine production.     

CD47 deficiency protects mice from lipopolysaccharide-induced acute lung injury and Escherichia coli pneumonia

CD47 modulates neutrophil transmigration toward the sites of infection or injury. Mice lacking CD47 are susceptible to Escherichia coli (E. coli) peritonitis. However, less is known concerning the role of CD47 in the development of acute lung inflammation and injury. In this study, we show that mice lacking CD47 are protected from LPS-induced acute lung injury and E. coli pneumonia with a significant reduction in pulmonary edema, lung vascular permeability, and bacteremia. Reconstitution of CD47(+/-) mice with CD47(-/-) neutrophils significantly reduced lung edema and neutrophil infiltration, thus demonstrating that CD47(+) neutrophils are required for the development of lung injury from E. coli pneumonia. Importantly, CD47-deficient mice with E. coli pneumonia had an improved survival rate. Taken together, deficiency of CD47 protects mice from LPS-induced acute lung injury and E. coli pneumonia. Targeting CD47 may be a novel pathway for treatment of acute lung injury.     

Death receptors mediate the adverse effects of febrile-range hyperthermia on the outcome of lipopolysaccharide-induced lung injury

We have shown that febrile-range hyperthermia enhances lung injury and mortality in mice exposed to inhaled LPS and is associated with increased TNF-α receptor activity, suppression of NF-κB activity in vitro, and increased apoptosis of alveolar epithelial cells in vivo. We hypothesized that hyperthermia enhances lung injury and mortality in vivo by a mechanism dependent on TNF receptor signaling. To test this, we exposed mice lacking the TNF-receptor family members TNFR1/R2 or Fas (TNFR1/R2(-/-) and lpr) to inhaled LPS with or without febrile-range hyperthermia. For comparison, we studied mice lacking IL-1 receptor activity (IL-1R(-/-)) to determine the role of inflammation on the effect of hyperthermia in vivo. TNFR1/R2(-/-) and lpr mice were protected from augmented alveolar permeability and mortality associated with hyperthermia, whereas IL-1R(-/-) mice were susceptible to augmented alveolar permeability but protected from mortality associated with hyperthermia. Hyperthermia decreased pulmonary concentrations of TNF-α and keratinocyte-derived chemokine after LPS in C57BL/6 mice and did not affect pulmonary inflammation but enhanced circulating markers of oxidative injury and nitric oxide metabolites. The data suggest that hyperthermia enhances lung injury by a mechanism that requires death receptor activity and is not directly associated with changes in inflammation mediated by hyperthermia. In addition, hyperthermia appears to enhance mortality by generating a systemic inflammatory response and not by a mechanism directly associated with respiratory failure. Finally, we observed that exposure to febrile-range hyperthermia converts a modest, survivable model of lung injury into a fatal syndrome associated with oxidative and nitrosative stress, similar to the systemic inflammatory response syndrome.     

Targeted mutation of TNF receptor I rescues the RelA-deficient mouse and reveals a critical role for NF-kappa B in leukocyte recruitment

NF-kappaB binding sites are present in the promoter regions of many acute phase and inflammatory response genes, suggesting that NF-kappaB plays an important role in the initiation of innate immune responses. However, targeted mutations of the various NF-kappaB family members have yet to identify members responsible for this critical role. RelA-deficient mice die on embryonic day 15 from TNF-alpha-induced liver degeneration. To investigate the importance of RelA in innate immunity, we genetically suppressed this embryonic lethality by breeding the RelA deficiency onto a TNFR type 1 (TNFR1)-deficient background. TNFR1/RelA-deficient mice were born healthy, but were susceptible to bacterial infections and bacteremia and died within a few weeks after birth. Hemopoiesis was intact in TNFR1/RelA-deficient newborns, but neutrophil emigration to alveoli during LPS-induced pneumonia was severely reduced relative to that in wild-type or TNFR1-deficient mice. In contrast, radiation chimeras reconstituted with RelA or TNFR1/RelA-deficient hemopoietic cells were healthy and demonstrated no defect in neutrophil emigration during LPS-induced pneumonia. Analysis of RNA harvested from the lungs of mice 4 h after LPS insufflation revealed that the induction of several genes important for neutrophil recruitment to the lung was significantly reduced in TNFR1/RelA-deficient mice relative to that in wild-type or TNFR1-deficient mice. These results suggest that TNFR1-independent activation of RelA is essential in cells of nonhemopoietic origin during the initiation of an innate immune response.     

Differential requirement for c-Jun N-terminal kinase 1 in lung inflammation and host defense

The c-Jun N-terminal kinase (JNK) - 1 pathway has been implicated in the cellular response to stress in many tissues and models. JNK1 is known to play a role in a variety of signaling cascades, including those involved in lung disease pathogenesis. Recently, a role for JNK1 signaling in immune cell function has emerged. The goal of the present study was to determine the role of JNK1 in host defense against both bacterial and viral pneumonia, as well as the impact of JNK1 signaling on IL-17 mediated immunity. Wild type (WT) and JNK1 -/- mice were challenged with Escherichia coli, Staphylococcus aureus, or Influenza A. In addition, WT and JNK1 -/- mice and epithelial cells were stimulated with IL-17A. The impact of JNK1 deletion on pathogen clearance, inflammation, and histopathology was assessed. JNK1 was required for clearance of E. coli, inflammatory cell recruitment, and cytokine production. Interestingly, JNK1 deletion had only a small impact on the host response to S. aureus. JNK1 -/- mice had decreased Influenza A burden in viral pneumonia, yet displayed worsened morbidity. Finally, JNK1 was required for IL-17A mediated induction of inflammatory cytokines and antimicrobial peptides both in epithelial cells and the lung. These data identify JNK1 as an important signaling molecule in host defense and demonstrate a pathogen specific role in disease. Manipulation of the JNK1 pathway may represent a novel therapeutic target in pneumonia.     

Role of CCR5 in the pathogenesis of IL-13-induced inflammation and remodeling

IL-13 is a major effector at sites of Th2 inflammation and tissue remodeling. In these locations, it frequently coexists with the CCR5 chemokine receptor and its ligands MIP-1alpha/CCL3 and MIP-1beta/CCL4. We hypothesized that CCR5 induction and activation play important roles in the pathogenesis of IL-13-induced tissue responses. To test this hypothesis, we evaluated the effects of IL-13 on the expression of CCR5 in the murine lung. We also compared the effects of lung-targeted transgenic IL-13 in mice treated with anti-CCR5 or an Ab control and mice with wild-type or null CCR5 loci. These studies demonstrate that IL-13 is a potent stimulator of epithelial cell CCR5 expression. They also demonstrate that CCR5 neutralization or a deficiency of CCR5 significantly decreases IL-13-induced inflammation, alveolar remodeling, structural and inflammatory cell apoptosis, and respiratory failure and death. Lastly, these studies provide mechanistic insights by demonstrating that CCR5 is required for optimal IL-13 stimulation of select chemokines (MIP-1alpha/CCL3, MIP-1beta/CCL4, MCP-1/CCL-2), matrix metalloproteinase-9 and cell death regulators (Fas, TNF, TNFR1, TNFR2, Bid), optimal IL-13 inhibition of alpha1-antitrypsin, and IL-13-induction of and activation of caspases-3, -8, and-9. Collectively, these studies demonstrate that CCR5 plays a critical role in the pathogenesis of IL-13-induced inflammation and tissue remodeling.     

Disruption of tumor necrosis factor alpha receptor 1 signaling accelerates NAFLD progression in mice upon a high-fat diet

Obesity is accompanied by a low-grade inflammation state, characterized by increased proinflammatory cytokines levels such as tumor necrosis factor alpha (TNFα) and interleukin-1 beta (IL-1β). In this regard, there exists a lack of studies in hepatic tissue about the role of TNFα receptor 1 (TNFR1) in the context of obesity and insulin resistance during the progression of nonalcoholic fatty liver disease (NAFLD). The aim of this work was to evaluate the effects of high-caloric feeding (HFD) (40% fat, for 16 weeks) on liver inflammation-induced apoptosis, insulin resistance, hepatic lipid accumulation and its progression toward nonalcoholic steatohepatitis (NASH) in TNFR1 knock-out and wild-type mice. Mechanisms involved in HFD-derived IL-1β release and impairment of insulin signaling are still unknown, so we determined whether IL-1β affects liver insulin sensitivity and apoptosis through TNFα receptor 1 (TNFR1)-dependent pathways. We showed that knocking out TNFR1 induces an enhanced IL-1β plasmatic release upon HFD feed. This was correlated with higher hepatic and epididymal white adipose tissue mRNA levels. In vivo and in vitro assays confirmed an impairment in hepatic insulin signaling, in part due to IL-1β-induced decrease of AKT activation and diminution of IRS1 levels, followed by an increase in inflammation, macrophage (resident and recruited) accumulation, hepatocyte apoptotic process and finally hepatic damage. In addition, TNFR1 KO mice displayed higher levels of pro-fibrogenic markers. TNFR1 signaling disruption upon an HFD leads to an accelerated progression from simple steatosis to a more severe phenotype with many NASH features, pointing out a key role of TNFR1 in NAFLD progression.     

CD36, but not G2A,modulates efferocytosis,inflammation, and fibrosis following bleomycin-induced lung injury

Macrophage G2A and CD36 lipid receptors are thought to mediate efferocytosis following tissue injury and thereby prevent excessive inflammation that could compromise tissue repair. To test this, we subjected mice lacking G2A or CD36 receptor to bleomycin-induced lung injury and measured efferocytosis, inflammation, and fibrosis. Loss of CD36 (but not G2A) delayed clearance of apoptotic alveolar cells (mean 78% increase in apoptotic cells 7 days postinjury), potentiated inflammation (mean 56% increase in lung neutrophils and 75% increase in lung KC levels 7 days postinjury, 51% increase in lung macrophages 14 days postinjury), and reduced lung fibrosis (mean 41% and 29% reduction 14 and 21 days postinjury, respectively). Reduced fibrosis in CD36^−/− mice was associated with lower levels of profibrotic TH2 cytokines (IL-9, IL-13, IL-4), decreased expression of the M2 macrophage marker Arginase-1, and reduced interstitial myofibroblasts. G2A, on the other hand, was required for optimal clearance of apoptotic neutrophils during zymosan-induced peritoneal inflammation (50.3% increase in apoptotic neutrophils and 30.6% increase in total neutrophils 24 h following zymosan administration in G2A^−/− mice). Thus, CD36 is required for timely removal of apoptotic cells in the context of lung injury and modulates subsequent inflammatory and fibrotic processes relevant to fibrotic lung disease.     

Neuroinflammation facilitates LIF entry into brain: role of TNF

Leukemia inhibitory factor (LIF) is a proinflammatory cytokine mediating a variety of central nervous system (CNS) responses to inflammatory stimuli. During lipopolysaccharide (LPS)-induced inflammation, blood concentrations of LIF increase, correlating with lethality of sepsis. Circulating LIF crosses the blood-brain barrier (BBB) by a saturable transport system. Here we determine how this transport system is regulated in neuroinflammation. Using transport assays that quantify the influx rate and volume of distribution of LIF in mice, we show that LPS facilitated the permeation of LIF from the blood to the brain without compromising the paracellular permeability of the BBB as determined by coadministration of fluorescein. Concurrently, gp130 (shared by the interleukin-6 family of cytokines), but not gp190 (the specific receptor for LIF) or cilliary neutrophic factor (CNTF-Ralpha, a unique receptor for cilliary neurotrophic factor that also uses gp130 and gp190), showed increased levels of mRNA and protein expression in cerebral microvessels from the LPS-treated mice. The upregulation of gp130 by LPS was at least partially mediated by vascular tumor necrosis factor receptor (TNFR)1 and TNFR2. This was shown by elevated TNFR1 and TNFR2 mRNA and protein in cerebral microvessels after LPS and by the absence of the LPS effect on gp130 in knockout mice lacking these receptors. The results show that neuroinflammation by LPS induces endothelial signaling and enhances cytokine transport across the BBB.     

Toll-IL-1 receptor domain-containing adaptor protein is critical for early lung immune responses against Escherichia coli lipopolysaccharide and viable Escherichia coli

Pulmonary bacterial diseases are a leading cause of mortality in the U.S. Innate immune response is vital for bacterial clearance from the lung, and TLRs play a critical role in this process. Toll-IL-1R domain-containing adaptor protein (TIRAP) is a key molecule in the TLR4 and 2 signaling. Despite its potential importance, the role of TIRAP-mediated signaling in lung responses has not been examined. Our goals were to determine the role of TIRAP-dependent signaling in the induction of lung innate immune responses against Escherichia coli LPS and viable E. coli, and in lung defense against E. coli in mice. LPS-induced neutrophil sequestration; NF-kappaB translocation; keratinocyte cell-derived chemokine, MIP-2, TNF-alpha, and IL-6 expression; histopathology; and VCAM-1 and ICAM-1 expression were abolished in the lungs of TIRAP-/- mice. A cell-permeable TIRAP blocking peptide attenuated LPS-induced lung responses. Furthermore, immune responses in the lungs of TIRAP-/- mice were attenuated against E. coli compared with TIRAP+/+ mice. TIRAP-/- mice also had early mortality, higher bacterial burden in the lungs, and more bacterial dissemination following E. coli inoculation. Moreover, we used human alveolar macrophages to examine the role of TIRAP signaling in the human system. The TIRAP blocking peptide abolished LPS-induced TNF-alpha, IL-6, and IL-8 expression in alveolar macrophages, whereas it attenuated E. coli-induced expression of these cytokines and chemokines. Taken together, this is the first study illustrating the crucial role of TIRAP in the generation of an effective early immune response against E. coli LPS and viable E. coli, and in lung defense against a bacterial pathogen.     

Deficiency of TNFR1 protects myocardium through SOCS3 and IL-6 but not p38 MAPK or IL-1beta

Tumor necrosis factor-alpha (TNF-alpha) plays an important role in the development of heart failure. There is a direct correlation between myocardial function and myocardial TNF levels in humans. TNF may induce local inflammation to exert tissue injury. On the other hand, suppressors of cytokine signaling (SOCS) proteins have been shown to inhibit proinflammatory signaling. However, it is unknown whether TNF mediates myocardial inflammation via STAT3/SOCS3 signaling in the heart and, if so, whether this effect is through the type 1 55-kDa TNF receptor (TNFR1). We hypothesized that TNFR1 deficiency protects myocardial function and decreases myocardial IL-6 production via the STAT3/SOCS3 pathway in response to TNF. Isolated male mouse hearts (n = 4/group) from wild-type (WT) and TNFR1 knockout (TNFR1KO) were subjected to direct TNF infusion (500 pg.ml(-1).min(-1) x 30 min) while left ventricular developed pressure and maximal positive and negative values of the first derivative of pressure were continuously recorded. Heart tissue was analyzed for active forms of STAT3, p38, SOCS3 and SOCS1 (Western blot analysis), as well as IL-1beta and IL-6 (ELISA). Coronary effluent was analyzed for lactate dehydrogenase (LDH) activity. As a result, TNFR1KO had significantly better myocardial function, less myocardial LDH release, and greater expression of SOCS3 (percentage of SOCS3/GAPDH: 45 +/- 4.5% vs. WT 22 +/- 6.5%) after TNF infusion. TNFR1 deficiency decreased STAT3 activation (percentage of phospho-STAT3/STAT3: 29 +/- 6.4% vs. WT 45 +/- 8.8%). IL-6 was decreased in TNFR1KO (150.2 +/- 3.65 pg/mg protein) versus WT (211.4 +/- 26.08) mice. TNFR1 deficiency did not change expression of p38 and IL-1beta following TNF infusion. These results suggest that deficiency of TNFR1 protects myocardium through SOCS3 and IL-6 but not p38 MAPK or IL-1beta.     

The Interleukin-17 Receptor B Subunit Is Essential for the Th2 Response to Helicobacter pylori,but Not for Control of Bacterial Burden

Helicobacter pylori infection leads to an inflammatory response in 100% of infected individuals. The inflammatory cells which are recruited to the gastric mucosa during infection produce several pro- and anti-inflammatory cytokines including several cytokines in the interleukin-17 family. The anti-inflammatory cytokine, interleukin 25 (IL-25, also known as IL-17E), signals through a receptor, which is a heterotrimeric receptor comprised of two IL-17 receptor A subunits and an IL-17 receptor B subunit. Previous studies in our laboratory demonstrated that IL-17RA is required to control infection with Helicobacter pylori in the mouse model. Moreover, the absence of IL-17 receptor A leads to a significant B cell infiltrate and a remarkable increase in lymphoid follicle formation in response to infection compared to infection in wild-type mice. We hypothesized that IL-25, which requires both IL-17 receptor A and IL-17 receptor B for signaling, may play a role in control of inflammation in the mouse model of Helicobacter pylori infection. IL-17 receptor B deficient mice, IL-17 receptor A deficient mice and wild-type mice were infected with Helicobacter pylori (strains SS1 and PMSS1). At several time points H. pylori- infected mice were sacrificed to investigate their ability to control infection and inflammation. Moreover, the effects of IL-17 receptor B deficiency on T helper cytokine expression and H. pylori- specific serum antibody responses were measured. IL-17 receptor B−/− mice (unlike IL-17 receptor A−/− mice) exhibited similar or modest changes in gastric colonization, inflammation, and Th1 and Th17 helper cytokine responses to wild-type mice infected with Helicobacter pylori. However, H. pylori-infected IL-17 receptor B−/− mice have reduced expression of IL-4 and lower serum IgG1 and IgG2a levels compared to infected IL-17 receptor A−/− and wild-type mice. These data indicate that signaling through the IL-17 receptor B subunit is not necessary for control of Helicobacter pylori in our model.