The MyD88-dependent, but not the MyD88-independent, pathway of TLR4 signaling is important in clearing nontypeable haemophilus influenzae from the mouse lung

Imp7 siRNA nanoparticles protect against mechanical ventilation-associated liver injury by inhibiting HMGB1 production and NETs formation

Mechanical ventilation (MV) has the potential to induce extra-pulmonary organ damage by adversely affecting the lungs and promoting the secretion of inflammatory cytokines. High-mobility group box 1 protein (HMGB1) is a pro-inflammatory mediator in ventilator-induced lung injury (VILI), but its effect on MV-associated liver injury and the mechanisms are poorly understood. In the present study, mice were subjected to high-volume MV (20 ml/kg) to induce VILI. MV-induced HMGB1 prompted neutrophil extracellular traps (NETs) formation and PANoptosis within the liver. Inhibiting NETs formation by DNase I or PAD4 inhibitor, or by HMGB1 neutralizing ameliorated the liver injury. HMGB1 activated neutrophils to form NETs through TLR4/MyD88/TRAF6 pathway. Importantly, Importin7 siRNA nanoparticles inhibited HMGB1 release and protected against MV-associated liver injury. These data provide evidence of MV-induced HMGB1 prompted NETs formation and PANoptosis in the liver via the TLR4/MyD88/TRAF6 pathway. HMGB1 is a potential therapeutic target for MV-associated liver injury.

Role of toll-like receptors and nod-like receptors in acute lung infection

The respiratory system exposed to microorganisms continuously, and the pathogenicity of these microbes not only contingent on their virulence factors, but also the host's immunity. A multifaceted innate immune mechanism exists in the respiratory tract to cope with microbial infections and to decrease tissue damage. The key cell types of the innate immune response are macrophages, neutrophils, dendritic cells, epithelial cells, and endothelial cells. Both the myeloid and structural cells of the respiratory system sense invading microorganisms through binding or activation of pathogen-associated molecular patterns (PAMPs) to pattern recognition receptors (PRRs), including Toll-like receptors (TLRs) and NOD-like receptors (NLRs). The recognition of microbes and subsequent activation of PRRs triggers a signaling cascade that leads to the activation of transcription factors, induction of cytokines/5chemokines, upregulation of cell adhesion molecules, recruitment of immune cells, and subsequent microbe clearance. Since numerous microbes resist antimicrobial agents and escape innate immune defenses, in the future, a comprehensive strategy consisting of newer vaccines and novel antimicrobials will be required to control microbial infections. This review summarizes key findings in the area of innate immune defense in response to acute microbial infections in the lung. Understanding the innate immune mechanisms is critical to design host-targeted immunotherapies to mitigate excessive inflammation while controlling microbial burden in tissues following lung infection.

Frenemies in the Microenvironment: Harnessing Mast Cells for Cancer Immunotherapy

Tumor development, progression, and resistance to therapies are influenced by the interactions between tumor cells and the surrounding microenvironment, comprising fibroblasts, immune cells, and extracellular matrix proteins. In this context, mast cells (MCs) have recently emerged as important players. Yet, their role is still controversial, as MCs can exert pro- or anti-tumor functions in different tumor types depending on their location within or around the tumor mass and their interaction with other components of the tumor microenvironment. In this review, we describe the main aspects of MC biology and the different contribution of MCs in promoting or inhibiting cancer growth. We then discuss possible therapeutic strategies aimed at targeting MCs for cancer immunotherapy, which include: (1) targeting c-Kit signaling; (2) stabilizing MC degranulation; (3) triggering activating/inhibiting receptors; (4) modulating MC recruitment; (5) harnessing MC mediators; (6) adoptive transferring of MCs. Such strategies should aim to either restrain or sustain MC activity according to specific contexts. Further investigation would allow us to better dissect the multifaceted roles of MCs in cancer and tailor novel approaches for an "MC-guided" personalized medicine to be used in combination with conventional anti-cancer therapies.

Increased expression of miR146a dysregulates TLR2-induced HBD2 in airway epithelial cells from patients with COPD

Background

Airway epithelial cells from patients with COPD show suboptimal innate immune responses to nontypeable Haemophilus influenzae (NTHi) and Toll-like receptor (TLR)2 ligands despite expressing TLR2 similar to normal airway epithelial cells, but the underlying mechanisms are poorly understood.

Methods

Normal or COPD mucociliary-differentiated airway epithelial cells were treated with TLR2 agonists or infected with NTHi and expression of β-defensin (HBD)2 was examined. Interleukin-1 receptor-associated kinase (IRAK)-1 and microRNA (miR)146a were genetically inhibited in normal and COPD airway epithelial cell cultures, respectively, and HBD2 responses to TLR2 ligands were determined. IRAK-1 expression in lung sections was determined by immunofluorescence microscopy.

Results

Compared to normal, COPD airway epithelial cell cultures showed impaired expression of HBD2 in response to TLR2 agonists or NTHi infection. Apical secretions from TLR2 agonist-treated normal, but not COPD, airway epithelial cells efficiently killed NTHi. Knockdown of HBD2 significantly reduced NTHi killing by apical secretions of normal airway epithelial cells. Compared to normal, COPD cells showed significantly reduced expression of IRAK-1 and this was associated with increased expression of miR146a. Inhibition of miR146a increased the expression of IRAK-1, improved the expression of HBD2 in response to TLR2 agonists in COPD cells and enhanced the killing of bacteria by apical secretions obtained from TLR2 agonist-treated COPD cells. Bronchial epithelium of COPD patients showed reduced expression of IRAK-1.

Conclusions

These results suggest that reduced levels of IRAK-1 due to increased expression of miR146a may contribute to impaired expression of TLR2-induced HBD2 in COPD airway epithelial cells.

Glycolipid Metabolite β-Glucosylceramide Is a Neutrophil Extracellular Trap-Inducing Ligand of Mincle Released during Bacterial Infection and Inflammation

Neutrophil extracellular traps (NETs) are implicated in host defense and inflammatory pathologies alike. A wide range of pathogen- and host-derived factors are known to induce NETs, yet the knowledge about specific receptor-ligand interactions in this response is limited. We previously reported that macrophage-inducible C-type lectin (Mincle) regulates NET formation. In this article, we identify glycosphingolipid β-glucosylceramide (β-GlcCer) as a specific NET-inducing ligand of Mincle. We found that purified β-GlcCer induced NETs in mouse primary neutrophils in vitro and in vivo, and this effect was abrogated in Mincle deficiency. Cell-free β-GlcCer accumulated in the lungs of pneumonic mice, which correlated with pulmonary NET formation in wild-type, but not in Mincle^-/-, mice infected intranasally with Klebsiella pneumoniae Although leukocyte infiltration by β-GlcCer administration in vivo did not require Mincle, NETs induced by this sphingolipid were important for bacterial clearance during Klebsiella infection. Mechanistically, β-GlcCer did not activate reactive oxygen species formation in neutrophils but required autophagy and glycolysis for NET formation, because ATG4 inhibitor NSC185058, as well as glycolysis inhibitor 2-deoxy-d-glucose, abrogated β-GlcCer-induced NETs. Forced autophagy activation by tamoxifen could overcome the inhibitory effect of glycolysis blockage on β-GlcCer-mediated NET formation, suggesting that autophagy activation is sufficient to induce NETs in response to this metabolite in the absence of glycolysis. Finally, β-GlcCer accumulated in the plasma of patients with systemic inflammatory response syndrome, and its levels correlated with the extent of systemic NET formation in these patients. Overall, our results posit β-GlcCer as a potent NET-inducing ligand of Mincle with diagnostic and therapeutic potential in inflammatory disease settings.

HMGB1-Mediated Neutrophil Extracellular Trap Formation Exacerbates Intestinal Ischemia/Reperfusion-Induced Acute Lung Injury

Influx of activated neutrophils into the lungs is the histopathologic hallmark of acute lung injury (ALI) after intestinal ischemia/reperfusion (I/R). Neutrophils can release DNA and granular proteins to form cytotoxic neutrophil extracellular traps (NETs), which promotes bystander tissue injury. However, whether NETs are responsible for the remote ALI after intestinal I/R and the mechanisms underlying the dissemination of harmful gut-derived mediators to the lungs are unknown. In the C57BL/6J mouse intestinal I/R model, DNase I-mediated degradation and protein arginine deiminase 4 (PAD4) inhibitor-mediated inhibition of NET treatments reduced NET formation, tissue inflammation, and pathological injury in the lung. High-mobility group protein B1 (HMGB1) blocking prevented NET formation and protected against tissue inflammation, as well as reduced cell apoptosis and improved survival rate. Moreover, recombinant human HMGB1 administration further drives NETs and concurrent tissue toxic injury, which in turn can be reversed by neutrophil deletion via anti-Ly6G Ab i.p. injection. Furthermore, global MyD88 deficiency regulated NET formation and alleviated the development of ALI induced by intestinal I/R. Thus, HMGB1 released from necroptotic enterocytes caused ALI after intestinal I/R by inducing NET formation. Targeting NETosis and the HMGB1 pathway might extend effective therapeutic strategies to minimize intestinal I/R-induced ALI.

Inflammation and tumor progression: signaling pathways and targeted intervention

Cancer development and its response to therapy are regulated by inflammation, which either promotes or suppresses tumor progression, potentially displaying opposing effects on therapeutic outcomes. Chronic inflammation facilitates tumor progression and treatment resistance, whereas induction of acute inflammatory reactions often stimulates the maturation of dendritic cells (DCs) and antigen presentation, leading to anti-tumor immune responses. In addition, multiple signaling pathways, such as nuclear factor kappa B (NF-kB), Janus kinase/signal transducers and activators of transcription (JAK-STAT), toll-like receptor (TLR) pathways, cGAS/STING, and mitogen-activated protein kinase (MAPK); inflammatory factors, including cytokines (e.g., interleukin (IL), interferon (IFN), and tumor necrosis factor (TNF)-α), chemokines (e.g., C-C motif chemokine ligands (CCLs) and C-X-C motif chemokine ligands (CXCLs)), growth factors (e.g., vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β), and inflammasome; as well as inflammatory metabolites including prostaglandins, leukotrienes, thromboxane, and specialized proresolving mediators (SPM), have been identified as pivotal regulators of the initiation and resolution of inflammation. Nowadays, local irradiation, recombinant cytokines, neutralizing antibodies, small-molecule inhibitors, DC vaccines, oncolytic viruses, TLR agonists, and SPM have been developed to specifically modulate inflammation in cancer therapy, with some of these factors already undergoing clinical trials. Herein, we discuss the initiation and resolution of inflammation, the crosstalk between tumor development and inflammatory processes. We also highlight potential targets for harnessing inflammation in the treatment of cancer.

Circ_0038467 regulates lipopolysaccharide-mediated cell proliferation, apoptosis, and inflammatory response by miR-195-5p/TLR4 axis through NF-κB pathway in MRC-5 cells

Infantile pneumonia (IP) is an acute lower respiratory infection and brings a heavy burden to children health. Circular RNAs (circRNAs) participate in the regulation of pneumonia process. In this research, the effects of circ_0038467 in regulating lipopolysaccharide (LPS)-induced cell injury and underlying mechanism were revealed. Results showed that circ_0038467 expression and TLR4 protein level were upregulated, while miR-195-5p expression was downregulated in LPS-induced MRC-5 cells. Circ_0038467 silencing restored LPS-mediated inhibition on cell proliferation and promotion on apoptosis and inflammatory response. Additionally, circ_0038467 acted as a sponge of miR-195-5p, which was further revealed to target TLR4. MiR-195-5p inhibitor reversed circ_0038467 silencing-mediated influences under LPS treatment. Furthermore, LPS-activated NF-κB pathway was partly blocked by circ_0038467 silencing, which was restrained by TLR4 overexpression. Circ_0038467 silencing protected MRC-5 cells from LPS-induced injury by miR-195-5p/TLR4 axis through NF-κB pathway, providing a theoretical basis for circRNA-directed IP therapy.

Role of microbiota-gut-brain axis dysfunctions induced by infections in the onset of anorexia nervosa

Anorexia nervosa (AN) is an eating disorder characterized by low food intake, severe body weight loss, intense fear of gaining weight, and dysmorphophobia. This chronic disease is associated with both psychiatric and somatic comorbidities. Over the years, clinical studies have accumulated evidence that viral or bacterial infections may promote the onset of eating disorders such as AN. This review aims to describe how infections and the subsequent immune responses affect food intake regulation in the short term and also how these processes may lead to long-term intestinal disorders, including gut barrier disruption and gut microbiota dysbiosis, even after the clearance of the pathogens. We discuss in particular how infection-mediated intestinal dysbiosis may promote the onset of several AN symptoms and comorbidities, including appetite dysregulation, functional gastrointestinal disorders, and mood disorders.

Microbial Phagocytic Receptors and Their Potential Involvement in Cytokine Induction in Macrophages

Phagocytosis is an essential process for the uptake of large (>0.5 µm) particulate matter including microbes and dying cells. Specialized cells in the body perform phagocytosis which is enabled by cell surface receptors that recognize and bind target cells. Professional phagocytes play a prominent role in innate immunity and include macrophages, neutrophils and dendritic cells. These cells display a repertoire of phagocytic receptors that engage the target cells directly, or indirectly via opsonins, to mediate binding and internalization of the target into a phagosome. Phagosome maturation then proceeds to cause destruction and recycling of the phagosome contents. Key subsequent events include antigen presentation and cytokine production to alert and recruit cells involved in the adaptive immune response. Bridging the innate and adaptive immunity, macrophages secrete a broad selection of inflammatory mediators to orchestrate the type and magnitude of an inflammatory response. This review will focus on cytokines produced by NF-κB signaling which is activated by extracellular ligands and serves a master regulator of the inflammatory response to microbes. Macrophages secrete pro-inflammatory cytokines including TNFα, IL1β, IL6, IL8 and IL12 which together increases vascular permeability and promotes recruitment of other immune cells. The major anti-inflammatory cytokines produced by macrophages include IL10 and TGFβ which act to suppress inflammatory gene expression in macrophages and other immune cells. Typically, macrophage cytokines are synthesized, trafficked intracellularly and released in response to activation of pattern recognition receptors (PRRs) or inflammasomes. Direct evidence linking the event of phagocytosis to cytokine production in macrophages is lacking. This review will focus on cytokine output after engagement of macrophage phagocytic receptors by particulate microbial targets. Microbial receptors include the PRRs: Toll-like receptors (TLRs), scavenger receptors (SRs), C-type lectin and the opsonic receptors. Our current understanding of how macrophage receptor stimulation impacts cytokine production is largely based on work utilizing soluble ligands that are destined for endocytosis. We will instead focus this review on research examining receptor ligation during uptake of particulate microbes and how this complex internalization process may influence inflammatory cytokine production in macrophages.

LncRNA NEAT1 activates MyD88/NF-κB pathway in bronchopneumonia through targeting miR-155-5p

BACKGROUND

Bronchopneumonia is a disease of the respiratory tract. It leads to other complications and endangers life and health. Long non-coding RNA (lncRNA) participates in the occurrence and development of bronchopneumonia. Nuclear paraspeckle assembly transcript 1 (NEAT1) plays a key role in inflammatory diseases, but the function of NEAT1 in bronchopneumonia remains unclear.

METHODS

RT-qPCR and Western blotting were performed to determine genes and proteins expressions. MTT was applied to test cell viability. Cell apoptosis was detected by flow cytometry. RIP was used to investigate the correlation between NEAT1 and miR-155-5p. The interaction between miR-155-5p and NEAT1 or MyD88 was evaluated by the dual-luciferase reporter gene.

RESULTS

NEAT1 and MyD88 were upregulated in BEAS-2B cells by LPS, while miR-155-5p was downregulated. Knockdown of NEAT1 inhibited LPS-induced BEAS-2B cells growth inhibition by inhibiting the apoptosis. In addition, NEAT1 silencing suppressed LPS-induced inflammatory responses in BEAS-2B cells via suppression of TNF-α, IL-1β, IL-6, and IL-18. Meanwhile, NEAT1 is directly bound to miR-155-5p to regulate MyD88/NF-κB axis, and overexpression of miR-155-5p increased cell proliferation and suppressed inflammatory factors expression levels and cell apoptosis. Furthermore, sh-NEAT1-induced inhibition of BEAS-2B cells injury was partially reversed by miR-155-5p inhibitor or MyD88 overexpression.

CONCLUSION

NEAT1 silencing suppressed LPS-induced BEAS-2B cells injury and inflammation by the mediation of miR-155-5p/MyD88/NF-κB axis. Thus, our study might shed new light on exploring the new strategies for the treatment of bronchopneumonia.

Phloretin, an Apple Polyphenol, Inhibits Pathogen-Induced Mucin Overproduction

SCOPE

Bacterial infection induces mucus overproduction, contributing to acute exacerbations and lung function decline in chronic respiratory diseases. A diet enriched in apples may provide protection from pulmonary disease development and progression. This study examined whether phloretin, an apple polyphenol, inhibits mucus synthesis and secretion induced by the predominant bacteria associated with chronic respiratory diseases.

METHODS AND RESULTS

The expression of mucus constituent mucin 5AC (MUC5AC) in FVB/NJ mice and NCI-H292 epithelial cells is analyzed. Nontypeable Haemophilus influenzae (NTHi)-infected mice developed increased MUC5AC mRNA, which a diet containing phloretin inhibited. In NCI-H292 cells, NTHi, Moraxella catarrhalis, Streptococcus pneumoniae, and Pseudomonas aeruginosa increased MUC5AC mRNA, which phloretin inhibited. Phloretin also diminished NTHi-induced MUC5AC protein secretion. NTHi-induced increased MUC5AC required toll-like receptor 4 (TLR4) and NADH oxidase 4 (NOX4) signaling and subsequent activation of the epidermal growth factor receptor (EGFR)/mitogen-activated protein kinase (MAPK) pathway. Phloretin inhibited NTHi-induced TLR4/NOX4 and EGFR/MAPK signaling, thereby preventing increased MUC5AC mRNA. EGFR activation can also result from increased EGFR ligand synthesis and subsequent ligand activation by matrix metalloproteinases (MMPs). In NCI-H292 cells, NTHi increased EGFR ligand and MMP1 and MMP13 mRNA, which phloretin inhibited.

CONCLUSIONS

In summary, phloretin is a promising therapeutic candidate for preventing bacterial-induced mucus overproduction.

LncRNA UCA1 remits LPS-engendered inflammatory damage through deactivation of miR-499b-5p/TLR4 axis

Neonatal pneumonia is a high neonatal mortality disease. The current research was designed to elucidate the modulatory function and feasible molecular mechanism of UCA1 in LPS-induced injury in pneumonia. Herein, LPS was applied to induce WI-38 cell inflammatory damage. We displayed that UCA1 was elevated in LPS-injured WI-38 cells. In the functional aspect, intervention of UCA1 evidently aggrandized cell viability in LPS-triggered WI-38 cells. In the meanwhile, elimination of UCA1 distinctly assuaged cell apoptosis concomitant with declined levels of proapoptotic proteins Bax and C-caspase-3, and ascended the expression of antiapoptotic protein Bcl-2. Subsequently, disruption of UCA1 manifestly restrained inflammatory damage as characterized by declination of multiple pro-inflammatory factors IL-1β, IL-6, and TNF-α in WI-38 cells under LPS circumstance. More importantly, we predicted and verified that UCA1 functioned as a ceRNA by efficaciously binding to miR-499b-5p thereby inversely adjusting miR-499b-5p expression. Interesting, TLR4 was identified as direct target of miR-499b-5p, and positively regulated by UCA1 through sponging miR-499b-5p. Mechanistically, absence of miR-499b-5p or restoration of TLR4 impeded the beneficial effects of UCA1 ablation on LPS-stimulated apoptosis and inflammatory response. Collectively, these observations illuminated that UCA1 inhibition protected WI-38 cells against LPS-managed inflammatory injury and apoptosis process via miR-499b-5p/TLR4 crosstalk, which ultimately influencing the development of pneumonia.

CD14 release induced by P2X7 receptor restricts inflammation and increases survival during sepsis

P2X7 receptor activation induces the release of different cellular proteins, such as CD14, a glycosylphosphatidylinositol (GPI)-anchored protein to the plasma membrane important for LPS signaling via TLR4. Circulating CD14 has been found at elevated levels in sepsis, but the exact mechanism of CD14 release in sepsis has not been established. Here, we show for first time that P2X7 receptor induces the release of CD14 in extracellular vesicles, resulting in a net reduction in macrophage plasma membrane CD14 that functionally affects LPS, but not monophosphoryl lipid A, pro-inflammatory cytokine production. Also, we found that during a murine model of sepsis, P2X7 receptor activity is important for maintaining elevated levels of CD14 in biological fluids and a decrease in its activity results in higher bacterial load and exacerbated organ damage, ultimately leading to premature deaths. Our data reveal that P2X7 is a key receptor for helping to clear sepsis because it maintains elevated concentrations of circulating CD14 during infection.

When the immune system detects an infection, it often launches an inflammatory response to fight off the disease. This defense mechanism is activated by a cascade of signaling molecules that can aggravate inflammation, causing it to damage the body’s own tissues and organs. This life-threatening reaction is referred to as sepsis, and kills around 11 million people each year. New approaches are therefore needed to help alleviate the damage caused by this condition.

The inflammatory response is often triggered by proteins called receptors, which sit on the surface of immune cells. When these receptors are activated, they induce cells to secrete proteins that travel around the body and activate immune cells that can eliminate the infection. In 2016, a group of researchers showed that a receptor called P2X7 stimulates the release of a signaling molecule called CD14. Patients with sepsis often have elevated amounts of CD14 in their bloodstream. Yet, it remained unclear what causes this rise in CD14 and what role this molecule plays in the development of sepsis.

Now, Alarcón-Vila et al. – including some of the researchers involved in the 2016 study – have investigated the role of P2X7 in mice undergoing sepsis. This was done by puncturing the mice’s intestines, causing bacteria to leak out and initiate an over-active immune response. Alarcón-Vila et al. found that mice lacking the P2X7 receptor had less CD14 and struggled to eliminate the bacterial infection from their system. This increase in bacteria caused excessive damage to the mice’s organs, ultimately leading to premature death.

These findings suggest that P2X7 plays an important role in preventing the onset of sepsis by helping maintain high levels of CD14 following infection. This result could help to identify new therapies that reduce the mortality rates of septic infections.

Mannheimia haemolytica and lipopolysaccharide induce airway epithelial inflammatory responses in an extensively developed ex vivo calf model

Pulmonary infection is associated with inflammation and damage to the bronchial epithelium characterized by an increase in the release of inflammatory factors and a decrease in airway barrier function. Our objective is to optimize a method for the isolation and culture of primary bronchial epithelial cells (PBECs) and to provide an ex vivo model to study mechanisms of epithelial airway inflammation. PBECs were isolated and cultured from the airways of calves in a submerged cell culture and liquid-liquid interface system. A higher yield and cell viability were obtained after stripping the epithelium from the bronchial section compared to cutting the bronchial section in smaller pieces prior to digestion. Mannheimia haemolytica and lipopolysaccharide (LPS) as stimulants increased inflammatory responses (IL-8, IL-6 and TNF-α release), possibly, by the activation of "TLR-mediated MAPKs and NF-κB" signaling. Furthermore, M. haemolytica and LPS disrupted the bronchial epithelial layer as observed by a decreased transepithelial electrical resistance and zonula occludens-1 and E-cadherin expression. An optimized isolation and culture method for calf PBECs was developed, which cooperated with animal use Replacement, Reduction and Refinement (3R's) principle, and can also contribute to the increased knowledge and development of effective therapies for other animal and humans (childhood) respiratory diseases.

MicroRNA‑93 contributes to the suppression of lung inflammatory responses in LPS‑induced acute lung injury in mice via the TLR4/MyD88/NF‑κB signaling pathway

Acute lung injury (ALI) is a severe inflammatory lung disease with a rapid onset. The anti-inflammatory functions of microRNA-93 (miRNA/miR-93) have been described in various types of tissue injury and disease. However, the biological role of miR-93 and its molecular mechanisms underlying the initiation and progression of ALI have not yet been reported, at least to the best of our knowledge. The present study aimed to investigate the regulatory effects exerted by miR-93 in ALI. Using an in vivo murine model of ALI induced by lipopolysaccharide (LPS), miR-93 expression was found to be downregulated in the lung tissues and bronchoalveolar lavage fluid (BALF) compared with the control group. Following agomiR-93 injection, it was observed that agomiR-93 attenuated lung injury, as evidenced by decreased lung permeability, a reduced lung wet/dry weight ratio and an increased survival rate of the mice. Concomitantly, agomiR-93 significantly reduced LPS-induced the interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α levels in BALF. Of note, Toll-like receptor 4 (TLR4), an upstream regulator of the nuclear factor (NF)-κB signaling pathway, was directly suppressed by miR-93 in RAW 264.7 cells. Importantly, agomiR-93 induced a significant suppression of the TLR4/myeloid differentiation primary response 88 (MyD88)/NF-κB signaling pathway, as demonstrated by the downregulation of MyD88, and the phosphorylation of IκB-α and p65 in the lung tissues of mice with ALI. Taken together, the findings of the present study indicate that miR-93 attenutes LPS-induced lung injury by regulating the TLR4/MyD88/NF-κB signaling pathway, suggesting that miR-93 may prove to be a potential therapeutic target for ALI.

Impact of Bacterial Toxins in the Lungs

Bacterial toxins play a key role in the pathogenesis of lung disease. Based on their structural and functional properties, they employ various strategies to modulate lung barrier function and to impair host defense in order to promote infection. Although in general, these toxins target common cellular signaling pathways and host compartments, toxin- and cell-specific effects have also been reported. Toxins can affect resident pulmonary cells involved in alveolar fluid clearance (AFC) and barrier function through impairing vectorial Na⁺ transport and through cytoskeletal collapse, as such, destroying cell-cell adhesions. The resulting loss of alveolar-capillary barrier integrity and fluid clearance capacity will induce capillary leak and foster edema formation, which will in turn impair gas exchange and endanger the survival of the host. Toxins modulate or neutralize protective host cell mechanisms of both the innate and adaptive immunity response during chronic infection. In particular, toxins can either recruit or kill central players of the lung's innate immune responses to pathogenic attacks, i.e., alveolar macrophages (AMs) and neutrophils. Pulmonary disorders resulting from these toxin actions include, e.g., acute lung injury (ALI), the acute respiratory syndrome (ARDS), and severe pneumonia. When acute infection converts to persistence, i.e., colonization and chronic infection, lung diseases, such as bronchitis, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF) can arise. The aim of this review is to discuss the impact of bacterial toxins in the lungs and the resulting outcomes for pathogenesis, their roles in promoting bacterial dissemination, and bacterial survival in disease progression.

Pellino-1 Regulates Immune Responses to Haemophilus influenzae in Models of Inflammatory Lung Disease

Non-typeable Haemophilus influenzae (NTHi) is a frequent cause of lower respiratory tract infection in people with chronic obstructive pulmonary disease (COPD). Pellino proteins are a family of E3 ubiquitin ligases that are critical regulators of TLR signaling and inflammation. The aim of this study was to identify a role for Pellino-1 in airway defense against NTHi in the context of COPD. Pellino-1 is rapidly upregulated by LPS and NTHi in monocyte-derived macrophages (MDMs) isolated from individuals with COPD and healthy control subjects, in a TLR4 dependent manner. C57BL/6 Peli1^−/− and wild-type (WT) mice were subjected to acute (single LPS challenge) or chronic (repeated LPS and elastase challenge) airway inflammation followed by NTHi infection. Both WT and Peli1^−/− mice develop airway inflammation in acute and chronic airway inflammation models. Peli1^−/− animals recruit significantly more neutrophils to the airway following NTHi infection which is associated with an increase in the neutrophil chemokine, KC, in bronchoalveolar lavage fluid as well as enhanced clearance of NTHi from the lung. These data suggest that therapeutic inhibition of Pellino-1 may augment immune responses in the airway and enhance bacterial clearance in individuals with COPD.

TLR4 antagonist ameliorates combined allergic rhinitis and asthma syndrome (CARAS) by reducing inflammatory monocytes infiltration in mice model

The present study aims to investigate the effects of toll-like receptor 4 (TLR4) antagonist in an ovalbumin (OVA)-induced mouse model of combined allergic rhinitis and asthma syndrome (CARAS). An OVA-induced mouse model of CARAS was established and TLR4 antagonist, TAK-242, was administrated intranasally or intraperitoneally. The number of sneezing and nasal rubbing was counted. The frequency of different cell types in the bronchoalveolar lavage fluid (BALF) and nasal lavage fluid (NLF) was analyzed using flow cytometry. Expressions of protein in nasal mucosa and lungs were determined using western blotting. Levels of interleukin (IL)-4, IL-5, and IL-13 were determined using Enzyme-linked Immunosorbent Assay (ELISA). Histological scores were applied for the assessment of lung injury. Treatment of TAK-242 downregulated CCL2 expression and reduced monocyte infiltration in nasal mucosa and lung tissues. Additionally, treatment of TAK-242 ameliorated upper airway symptoms including the sneezing and nasal rubbing by the regulation of cytokines including IL-4, IL-5, and IL-13. Furthermore, treatment of TAK-242 ameliorated lower airway symptoms including decreasing the frequency of CD45⁺SiglecF⁺CD11b⁺CD11c^- eosinophils in BALF and IL13⁺ Th2 cells in the lungs. In conclusion, treatment of TAK-242 ameliorated CARAS-related lung injury by inhibiting lymphocyte infiltration, reducing monocytes infiltration, as well as regulating the frequency of eosinophils and Th2 cells.

Sodium Butyrate Inhibits the Inflammation of Lipopolysaccharide-Induced Acute Lung Injury in Mice by Regulating the Toll-Like Receptor 4/Nuclear Factor κB Signaling Pathway

Bacterial pneumonia is a common disease in dairy herds worldwide, which brings great economic losses to farmers. Sodium butyrate (SB), an inhibitor of histone deacetylase, plays an important role in limiting inflammation. The purpose of this study was to investigate the protective effects of SB on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice and explore the potential mechanism of SB protection. A total of 30 ICR mice were randomly divided into three groups ( n = 10): a phosphate-buffered saline (PBS) intratracheal instillation group, a LPS intratracheal instillation group, and a SB gavage group (SB was given 1 h before the LPS stimulation). After 12 h, samples of the blood and lung tissue were collected from the mice for experimental analysis. The results showed that the concentration of inflammatory cytokines [interleukin 1β (IL1β) and tumor necrosis factor α (TNF-α)], myeloperoxidase (MPO) activity in the lung tissue and blood, protein abundance of toll-like receptor 4 (TLR4), nuclear factor κB (NF-κB, p65), phosphorylated p65 (p-p65), inhibitor κBα (IκBα), and phosphorylated IκBα (p-IκBα), and relative mRNA expression of genes associated with inflammation, such as TLR4, NF-κB, IL1β, interleukin 6 (IL6), and TNF-α, were significantly upregulated in the LPS group compared to the PBS group. However, the SB addition markedly downregulated the levels of these parameters in the LSB group compared to those in the LPS group. Furthermore, the structure of the lung tissue from the LPS group was severely disrupted in comparison to that of the PBS group. However, with SB administration, the severe structural disruption was relieved. In addition, an immunohistochemical analysis showed that positive immunoreactions to TLR4, p65, and TNF-α were significant in the LPS group; however, SB addition markedly attenuated this phenomenon. In conclusion, the ALI mouse model was successfully established with an intratracheal instillation of LPS. Furthermore, gavage with SB inhibited inflammation in LPS-induced ALI.

The Interplay Between Immune Response and Bacterial Infection in COPD: Focus Upon Non-typeable Haemophilus influenzae

Chronic obstructive pulmonary disease (COPD) is a debilitating respiratory disease and one of the leading causes of morbidity and mortality worldwide. It is characterized by persistent respiratory symptoms and airflow limitation due to abnormalities in the lower airway following consistent exposure to noxious particles or gases. Acute exacerbations of COPD (AECOPD) are characterized by increased cough, purulent sputum production, and dyspnea. The AECOPD is mostly associated with infection caused by common cold viruses or bacteria, or co-infections. Chronic and persistent infection by non-typeable Haemophilus influenzae (NTHi), a Gram-negative coccobacillus, contributes to almost half of the infective exacerbations caused by bacteria. This is supported by reports that NTHi is commonly isolated in the sputum from COPD patients during exacerbations. Persistent colonization of NTHi in the lower airway requires a plethora of phenotypic adaptation and virulent mechanisms that are developed over time to cope with changing environmental pressures in the airway such as host immuno-inflammatory response. Chronic inhalation of noxious irritants in COPD causes a changed balance in the lung microbiome, abnormal inflammatory response, and an impaired airway immune system. These conditions significantly provide an opportunistic platform for NTHi colonization and infection resulting in a "vicious circle." Episodes of large inflammation as the consequences of multiple interactions between airway immune cells and NTHi, accumulatively contribute to COPD exacerbations and may result in worsening of the clinical status. In this review, we discuss in detail the interplay and crosstalk between airway immune residents and NTHi, and their effect in AECOPD for better understanding of NTHi pathogenesis in COPD patients.

Lentiviral‑mediated inducible silencing of TLR4 attenuates neuropathic pain in a rat model of chronic constriction injury

An increasing body of evidence has indicated that spinal microglial Toll-like receptor 4 (TLR4) may serve a significant role in the development and maintenance of neuropathic pain (NP). In the present study, experiments were conducted to evaluate the contribution of a tetracycline inducible lentiviral-mediated delivery system for the expression of TLR4 small interfering (si)RNA to NP in rats with chronic constriction injury (CCI). Behavioral tests, including paw withdrawal latency and paw withdrawal threshold, and biochemical analysis of the spinal cord, including western blotting, reverse transcription-quantitative polymerase chain reaction and ELISA, were conducted following CCI to the sciatic nerve. Intrathecal administration of LvOn-si-TLR4 with doxycycline (Dox) attenuated allodynia and hyperalgesia. Biochemical analysis revealed that the mRNA and proteins levels of TLR4 were unregulated following CCI to the sciatic nerve, which was then blocked by intrathecal administration of LvOn-siTLR4 with Dox. The LvOn-siTLR4 was also demonstrated to have no effect on TLR4 or the pain response without Dox, which indicated that the expression of siRNA was Dox-inducible in the lentivirus delivery system. In conclusion, TLR4 may serve a significant role in neuropathy and the results of the present study provide an inducible lentivirus-mediated siRNA against TLR4 that may serve as a potential novel strategy to be applied in gene therapy for NP in the future.

Sepsis Upregulates CD14 Expression in a MyD88-Dependent and Trif-Independent Pathway

An overwhelming immune response, particularly from macrophages, plays a critical role in survival and organ damage in sepsis patients. Toll-like receptors (TLRs) are important receptors to recognize the conserved motifs expressed by invading bacteria. The TLRs except TLR3 signal via a MyD88-dependent pathway. TLR3 uses a TRIF-dependent pathway, while TLR4 uses both MyD88 and TRIF-dependent pathways. Previous studies indicated that CD14 was necessary for TLRs-dependent production of pro-inflammatory cytokines. Blocking CD14 protected against the deleterious systemic inflammatory response associated with sepsis. The aim of this study was to determine the signaling pathway of TLR activation-induced CD14 expression in models of polymicrobial sepsis and in peritoneal macrophages. We found that CD14 expression was upregulated in the lung, liver, and kidney of septic mice induced by cecal ligation puncture. In cultured peritoneal macrophages, specific agonists for all TLRs, except for TLR3, increased CD14 expression. Lipopolysaccharide-induced upregulation of CD14 was abolished in peritoneal macrophages from MyD88 KO mice but increased in TRIF inhibitor, resveratrol pretreated wild-type macrophages. Moreover, MyD88 KO, but not TRIF KO mice, showed a decreased CD14 expression in the tissue of septic mice, which was associated with a strongly attenuated inflammatory response and increased survival rate. These data suggest that a MyD88-dependent and TRIF-independent pathway of TLR is activated in upregulating CD14 expression under septic conditions. This study deciphers a critical cross-talk between TLRs and CD14.

MyD88 as a therapeutic target for inflammatory lung diseases

INTRODUCTION

Myeloid differentiation primary response protein 88 (MyD88) is a critical adaptor protein involved in Toll-like and IL-1 receptor family signaling controlling innate immune responses and inflammation. Genetic deletion of MyD88 function results in profound suppression of inflammation and reduced resistance of the host to pathogens indicating non-redundant roles of MyD88. The TIR domain is critical for MyD88 dimerization and signaling for TLR and IL-1R family receptor. Areas covered: Emerging evidence suggests that chemical disruption of the TIR domain attenuates cell activation and inhibits in vivo MyD88-dependent inflammation. We review the development of MyD88 dimerization disruptors as a novel therapeutic approach of respiratory diseases with a focus on COPD. Expert opinion: There is a proof of concept that therapeutic targeting of MyD88 is feasible and first preclinical data are highly promising. This opens a great opportunity to treat exacerbations of COPD and other chronic respiratory diseases. However, extensive preclinical investigations and risk analyses are required with carefully evaluation of reduced host resistance and opportunistic infections.

Evidence of functional cell-mediated immune responses to nontypeable Haemophilus influenzae in otitis-prone children

Otitis media (OM) remains a common paediatric disease, despite advances in vaccinology. Susceptibility to recurrent acute OM (rAOM) has been postulated to involve defective cell-mediated immune responses to common otopathogenic bacteria. We compared the composition of peripheral blood mononuclear cells (PBMC) from 20 children with a history of rAOM (otitis-prone) and 20 healthy non-otitis-prone controls, and assessed innate and cell-mediated immune responses to the major otopathogen nontypeable Haemophilus influenzae (NTHi). NTHi was a potent stimulator of inflammatory cytokine secretion from PBMC within 4 hours, with no difference in cytokine levels produced between PBMC from cases or controls. In the absence of antigen stimulation, otitis-prone children had more circulating Natural Killer (NK) cells (p<0.01), particularly NKdim (CD56lo) cells (p<0.01), but fewer CD4+ T cells (p<0.01) than healthy controls. NTHi challenge significantly increased the proportion of activated (CD107a+) NK cells in otitis-prone and non-otitis-prone children (p<0.01), suggesting that NK cells from otitis-prone children are functional and respond to NTHi. CD8+ T cells and NK cells from both cases and controls produced IFNγ in response to polyclonal stimulus (Staphylococcal enterotoxin B; SEB), with more IFNγ+ CD8+ T cells present in cases than controls (p<0.05) but similar proportions of IFNγ+ NK cells. Otitis-prone children had more circulating IFNγ-producing NK cells (p<0.05) and more IFNγ-producing CD4+ (p<0.01) or CD8+ T-cells (p<0.05) than healthy controls. In response to SEB, more CD107a-expressing CD8+ T cells were present in cases than controls (p<0.01). Despite differences in PBMC composition, PBMC from otitis-prone children mounted innate and T cell-mediated responses to NTHi challenge that were comparable to healthy children. These data provide evidence that otitis-prone children do not have impaired functional cell mediated immunity.

LRP1: A chameleon receptor of lung inflammation and repair

The lung displays a remarkable capability to regenerate following injury. Considerable effort has been made thus far to understand the cardinal processes underpinning inflammation and reconstruction of lung tissue. However, the factors determining the resolution or persistence of inflammation and efficient wound healing or aberrant remodeling remain largely unknown. Low density lipoprotein receptor-related protein 1 (LRP1) is an endocytic/signaling cell surface receptor which controls cellular and molecular mechanisms driving the physiological and pathological inflammatory reactions and tissue remodeling in several organs. In this review, we will discuss the impact of LRP1 on the consecutive steps of the inflammatory response and its role in the balanced tissue repair and aberrant remodeling in the lung.

Expression of Toll-like Receptor 2 and 4 in Peripheral Blood Neutrophil Cells from Patients with Chronic Obstructive Pulmonary Disease

Objectives

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of morbidity and mortality around the world. Preliminary studies have evaluated the association between innate immunity including Toll-like receptors (TLRs) and airway samples of patients with COPD. The role of TLRs in peripheral blood neutrophils is poorly understood. Hence, this study aimed to investigate the role of TLR2 and TLR4 in peripheral blood neutrophils of COPD patients.

Methods

A total of 101 COPD cases and an equal number of healthy controls participated in this case-control study. Peripheral blood neutrophils were isolated from all participants and cultured for 24 hours through lipopolysaccharide (LPS) stimulation. The gene expressions of TLR2 and TLR4 were assessed by real-time polymerase chain reaction. The protein levels of interleukin (IL)-8 and matrix metalloproteinase (MMP)-9 were measured in neutrophils cell culture supernatants using enzyme-linked immunosorbent assay (ELISA).

Results

The levels of IL-8 and MMP-9 were significantly higher in patients with COPD compared to healthy controls. Similarly, the gene expression of TLR2 and TLR4 were increased in LPS stimulated peripheral blood neutrophils of patients with COPD. Smoke pack years was positively correlated with IL-8 levels and negatively correlated with forced expiratory volume in the first second % (r = -0.33; p = 0.023) and FEV1/forced vital capacity (FVC) (r = -0.27; p = 0.011).

Conclusions

The increased expression of TLR2 and TLR4 suggests its role in disease pathogenesis of COPD. Smoke pack years was negatively associated with spirometric parameters in COPD patients. This may help to predict the smokers without COPD who risk developing the condition in the future.

Bronchial inflammation and bacterial load in stable COPD is associated with TLR4 overexpression

Toll-like receptors (TLRs) and nucleotide-binding oligomerisation domain (NOD)-like receptors (NLRs) are two major forms of innate immune sensors but their role in the immunopathology of stable chronic obstructive pulmonary disease (COPD) is incompletely studied. Our objective here was to investigate TLR and NLR signalling pathways in the bronchial mucosa in stable COPD.

Using immunohistochemistry, the expression levels of TLR2, TLR4, TLR9, NOD1, NOD2, CD14, myeloid differentiation primary response gene 88 (MyD88), Toll-interleukin-1 receptor domain-containing adaptor protein (TIRAP), and the interleukin-1 receptor-associated kinases phospho-IRAK1 and IRAK4 were measured in the bronchial mucosa of subjects with stable COPD of different severity (n=34), control smokers (n=12) and nonsmokers (n=12). The bronchial bacterial load of Pseudomonas aeruginosa, Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae was measured by quantitative real-time PCR.

TLR4 and NOD1 expression was increased in the bronchial mucosa of patients with severe/very severe stable COPD compared with control subjects. TLR4 bronchial epithelial expression correlated positively with CD4+ and CD8+ cells and airflow obstruction. NOD1 expression correlated with CD8+ cells. The bronchial load of P. aeruginosa was directly correlated, but H. influenzae inversely correlated, with the degree of airflow obstruction. Bacterial load did not correlate with inflammatory cells.

Bronchial epithelial overexpression of TLR4 and NOD1 in severe/very severe stable COPD, associated with increased bronchial inflammation and P. aeruginosa bacterial load, may play a role in the pathogenesis of COPD.

Role of Neutrophil Extracellular Traps in Asthma and Chronic Obstructive Pulmonary Disease

Objective:

Asthma and chronic obstructive pulmonary disease (COPD) are representative chronic inflammatory airway diseases responsible for a considerable burden of disease. In this article, we reviewed the relationship between neutrophil extracellular traps (NETs) and chronic inflammatory airway diseases.

Data Sources:

Articles published up to January 1, 2017, were selected from the PubMed, Ovid Medline, Embase databases, with the keywords of “asthma” or “pulmonary disease, chronic obstructive”, “neutrophils” and “extracellular traps.”

Study Selection:

Articles were obtained and reviewed to analyze the role of NETs in asthma and COPD.

Results:

NETs are composed of extracellular DNA, histones, and granular proteins, which are released from activated neutrophils. Multiple studies have indicated that there are a large amount of NETs in the airways of asthmatics and COPD patients. NETs can engulf and kill invading pathogens in the host. However, disordered regulation of NET formation has shown to be involved in the development of asthma and COPD. An overabundance of NETs in the airways or lung tissue could cause varying degrees of damage to lung tissues by inducing the death of human epithelial and endothelial cells, and thus resulting in impairing pulmonary function and accelerating the progress of the disease.

Conclusions:

Excessive NETs accumulate in the airways of asthmatics and COPD patients. Although NETs play an essential role in the innate immune system against infection, excessive components of NETs can cause lung tissue damage and accelerate disease progression in asthmatics and COPD patients. These findings suggest that administration of NETs could be a novel approach to treat asthma and COPD. Mechanism studies, clinical practice, and strategies to regulate neutrophil activation or directly interrupt NET function in asthmatics and COPD patients are desperately needed.

Crude Ecklonia cava Flake Extracts Attenuate Inflammation through the Regulation of TLR4 Signaling Pathway in LPS-Induced RAW264.7 Cells

We investigated the beneficial effects of the crude Ecklonia cava flake (CEF), which is a residual product after polyphenol extraction from Ecklonia cava, on inflammation in LPS-stimulated RAW264.7 cells. A group of five different CEF extracts was obtained by a preparation process using water, hydrochloric acid or temperature. We observed that large-size (>19 kDa) CEF extract, which was extracted with water at 95 °C (CEF-W, 95 °C), suppressed the production of inflammatory cytokines by inhibiting its mRNA expression in LPS-induced RAW264.7 cells. TLR4 signaling involvements were negatively regulated by CEF-W, 95 °C. CEF-W, 95 °C repressed the translocation of NF-κB from cytoplasm into nucleus in LPS-induced RAW264.7 cells. CEF-W, 95 °C attenuated the phosphorylation of TBK1 and IRF3 by inhibiting the phosphorylation of ERK. Taken together, we demonstrated that large-size CEF-W, 95 °C may act as a negative regulator of inflammation through the suppression of TLR4 signaling constituents in LPS-induced RAW264.7 cells.

Characterization of TLR-induced inflammatory responses in COPD and control lung tissue explants

PURPOSE

Viruses are a common cause of exacerbations in chronic obstructive pulmonary disease (COPD). They activate toll-like receptors (TLRs) 3, 7, and 8, leading to a pro-inflammatory response. We have characterized the responses of TLR3 and TLR7/8 in lung tissue explants from COPD patients and control smokers.

METHODS

We prepared lung whole tissue explants (WTEs) from patients undergoing surgery for confirmed or suspected lung cancer. In order to mimic the conditions of viral infection, we used poly(I:C) for TLR3 stimulation and R848 for TLR7/8 stimulation. These TLR ligands were used alone and in combination. The effects of tumor necrosis factor α (TNFα) neutralization and dexamethasone on TLR responses were examined. Inflammatory cytokine release was measured by enzyme-linked immunosorbent assay and gene expression by quantitative real-time polymerase chain reaction.

RESULTS

WTEs from COPD patients released higher levels of pro-inflammatory cytokines compared with WTEs from smokers. Activation of multiple TLRs led to a greater than additive release of TNFα and CCL5. TNFα neutralization and dexamethasone treatment decreased cytokine release.

CONCLUSION

This WTE model shows an enhanced response of COPD compared with controls, suggesting an increased response to viral infection. There was amplification of innate immune responses with multiple TLR stimulation.

Altered Expression of TLR2 and TLR4 on Peripheral CD14+ Blood Monocytes in Children with Urinary Tract Infection

Urinary tract infection (UTI) is the second most common bacterial infection, after otitis media, in infants and children. The mechanisms of disease susceptibility and the role of immunity in the pathogenesis of UTI in children have been evaluated. In recent years, Toll-Like Receptors (TLRs) have been recognized as specific components of the innate immune system constituting important mediators in host immune recognition. The aim of the present study was to determine ΤLR2 and TLR4 expression during the acute phase of UTI in infants and children by measuring the CD14/TLR2 and CD14/TLR4 expression on monocytes. We also attempted to compare the TLRs expression with the immunological status of the patients to healthy children. The study group consisted of 60 children (36 females and 24 males) and the control group included 60 age-matched pediatric subjects (27 females and 33 males). In our study, no antibody deficiency was found either in the children with UTI or in healthy subjects. There might be a connection between low IgA, IgG, and IgG subclasses serum levels and UTI as there was a statistically significant difference between patients and healthy children. A higher expression of CD14/TLR2 was revealed in patients (90,07%) compared to controls (85,48%) as well as CD14/TLR4 in patients (90,53%) compared to controls (87,25%) (statistically significant difference, p < 0,05). The results of this study could provide new understanding of UTIs' pathogenesis in children.

Roles of Toll-Like Receptor 2 (TLR2), TLR4, and MyD88 during Pulmonary Coxiella burnetii Infection

Coxiella burnetii, the causative agent of Q fever, is an obligate intracellular, primarily pulmonary, bacterial pathogen. Although much is known about adaptive immune responses against this bacterium, our understanding of innate immune responses against C. burnetii is not well defined, particularly within the target tissue for infection, the lung. Previous studies examined the roles of the innate immune system receptors Toll-like receptor 2 (TLR2) and TLR4 in peripheral infection models and described minimal phenotypes in specific gene deletion animals compared to those of their wild-type controls (S. Meghari et al., Ann N Y Acad Sci 1063:161-166, 2005,http://dx.doi.org/10.1196/annals.1355.025; A. Honstettre et al., J Immunol 172:3695-3703, 2004,http://dx.doi.org/10.4049/jimmunol.172.6.3695) . Here, we assessed the roles for TLR2, TLR4, and MyD88 in pulmonary C. burnetii infection and compared responses to those that occurred in TLR2- and TLR4-deficient animals following peripheral infection. As observed previously, neither TLR2 nor TLR4 was needed for limiting bacterial growth after peripheral infection. In contrast, TLR2 and, to a lesser extent, TLR4 limited growth (or dissemination) of the bacterium in the lung and spleen after pulmonary infection. TLR2, TLR4, and MyD88 were not required for the general inflammatory response in the lungs after pulmonary infection. However, MyD88 signaling was important for infection-induced morbidity. Finally, TLR2 expression on hematopoietic cells was most important for limiting bacterial growth in the lung. These results expand on our knowledge of the roles for TLR2 and TLR4 in C. burnetii infection and suggest various roles for these receptors that are dictated by the site of infection.

Protective effects of polydatin on lipopolysaccharide-induced acute lung injury through TLR4-MyD88-NF-κB pathway

The purpose of this study was to investigate the protective effect of PD against lipopolysaccharide (LPS)-induced acute lung injury (ALI) and explore its potential mechanism. In vivo, PD and dexamethasone were intraperitoneally administered 1h before LPS stimulation. Then, mice were sacrificed at 6h post-LPS stimulation. Neutrophil number, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) in bronchoalveolar lavage fluid (BALF) were determined, as well as lung wet to dry ratio (W/D) and polymorphonuclear (MPO) activity. The protein expressions of Toll like receptor 4 (TLR4), myeloid differentiating factor 88 (MyD88), IL-1R-associated kinases 1 (IRAK1), IRAK4, inhibitor of nuclear factor kappa-B kinase (IKK)α, p-IKKα, IKKβ, p-IKKβ, inhibitor of NF-κB (IκBα), p-IκBα and NF-κB in lung tissues were assessed. Besides, we detected the IL-6, IL-1β, IL-8, TNF-α levels and TLR4, MyD88, NF-κB protein expressions in LPS-induced BEAS-2B cells. Consequently, PD significantly inhibited the levels of W/D, MPO, neutrophils number, TNF-α, IL-6, IL-1β and reversed TLR4-MyD88-NF-κB signaling pathway in lung tissues. In vitro assays, PD effectively negatively mediated the inflammatory cytokines and ameliorated the high expressions of TLR4, MyD88, NF-κB caused by LPS simulation in Human bronchial epithelial BEAS-2B cells. This study indicated that PD played a protective role in LPS-induced ALI and BEAS-2B cells. The results supported further study of PD as potential candidate for acute lung injury.

Trypanosoma cruzi and Its Soluble Antigens Induce NET Release by Stimulating Toll-Like Receptors

Neutrophils release fibrous traps of DNA, histones, and granule proteins known as neutrophil extracellular traps (NETs), which contribute to microbicidal killing and have been implicated in autoimmunity. The role of NET formation in the host response to nonbacterial pathogens is not well-understood. In this study, we investigated the release of NETs by human neutrophils upon their interaction with Trypanosoma cruzi (Y strain) parasites. Our results showed that human neutrophils stimulated by T. cruzi generate NETs composed of DNA, histones, and elastase. The release occurred in a dose-, time-, and reactive oxygen species-dependent manner to decrease trypomastigote and increase amastigote numbers of the parasites without affecting their viability. NET release was decreased upon blocking with antibodies against Toll-like receptors 2 and 4. In addition, living parasites were not mandatory in the release of NETs induced by T. cruzi, as the same results were obtained when molecules from its soluble extract were tested. Our results increase the understanding of the stimulation of NETs by parasites, particularly T. cruzi. We suggest that contact of T. cruzi with NETs during Chagas's disease can limit infection by affecting the infectivity/pathogenicity of the parasite.

The Lung Immune Response to Nontypeable Haemophilus influenzae (Lung Immunity to NTHi)

Haemophilus influenzae is divided into typeable or nontypeable strains based on the presence or absence of a polysaccharide capsule. The typeable strains (such as type b) are an important cause of systemic infection, whilst the nontypeable strains (designated as NTHi) are predominantly respiratory mucosal pathogens. NTHi is present as part of the normal microbiome in the nasopharynx, from where it may spread down to the lower respiratory tract. In this context it is no longer a commensal and becomes an important respiratory pathogen associated with a range of common conditions including bronchitis, bronchiectasis, pneumonia, and particularly chronic obstructive pulmonary disease. NTHi induces a strong inflammatory response in the respiratory tract with activation of immune responses, which often fail to clear the bacteria from the lung. This results in recurrent/persistent infection and chronic inflammation with consequent lung pathology. This review will summarise the current literature about the lung immune response to nontypeable Haemophilus influenzae, a topic that has important implications for patient management.

Glucocorticoids suppress inflammation via the upregulation of negative regulator IRAK-M

Glucocorticoids are among the most commonly used anti-inflammatory agents. Despite the enormous efforts in elucidating the glucocorticoid-mediated anti-inflammatory actions, how glucocorticoids tightly control overactive inflammatory response is not fully understood. Here we show that glucocorticoids suppress bacteria-induced inflammation by enhancing IRAK-M, a central negative regulator of Toll-like receptor signalling. The ability of glucocorticoids to suppress pulmonary inflammation induced by non-typeable Haemophilus influenzae is significantly attenuated in IRAK-M-deficient mice. Glucocorticoids improve the survival rate after a lethal non-typeable Haemophilus influenzae infection in wild-type mice, but not in IRAK-M-deficient mice. Moreover, we show that glucocorticoids and non-typeable Haemophilus influenzae synergistically upregulate IRAK-M expression via mutually and synergistically enhancing p65 and glucocorticoid receptor binding to the IRAK-M promoter. Together, our studies unveil a mechanism by which glucocorticoids tightly control the inflammatory response and host defense via the induction of IRAK-M and may lead to further development of anti-inflammatory therapeutic strategies.

Lower airway colonization and inflammatory response in COPD: a focus on Haemophilus influenzae

Bacterial infection of the lower respiratory tract in chronic obstructive pulmonary disease (COPD) patients is common both in stable patients and during acute exacerbations. The most frequent bacteria detected in COPD patients is Haemophilus influenzae, and it appears this organism is uniquely adapted to exploit immune deficiencies associated with COPD and to establish persistent infection in the lower respiratory tract. The presence of bacteria in the lower respiratory tract in stable COPD is termed colonization; however, there is increasing evidence that this is not an innocuous phenomenon but is associated with airway inflammation, increased symptoms, and increased risk for exacerbations. In this review, we discuss host immunity that offers protection against H. influenzae and how disturbance of these mechanisms, combined with pathogen mechanisms of immune evasion, promote persistence of H. influenzae in the lower airways in COPD. In addition, we examine the role of H. influenzae in COPD exacerbations, as well as interactions between H. influenzae and respiratory virus infections, and review the role of treatments and their effect on COPD outcomes. This review focuses predominantly on data derived from human studies but will refer to animal studies where they contribute to understanding the disease in humans.

Hematopoietic but not endothelial cell MyD88 contributes to host defense during gram-negative pneumonia derived sepsis

Klebsiella pneumoniae is an important cause of sepsis. The common Toll-like receptor adapter myeloid differentiation primary response gene (MyD)88 is crucial for host defense against Klebsiella. Here we investigated the role of MyD88 in myeloid and endothelial cells during Klebsiella pneumosepsis. Mice deficient for MyD88 in myeloid (LysM-Myd88(-/-)) and myeloid plus endothelial (Tie2-Myd88(-/-)) cells showed enhanced lethality and bacterial growth. Tie2-Myd88(-/-) mice reconstituted with control bone marrow, representing mice with a selective MyD88 deficiency in endothelial cells, showed an unremarkable antibacterial defense. Myeloid or endothelial cell MyD88 deficiency did not impact on lung pathology or distant organ injury during late stage sepsis, while LysM-Myd88(-/-) mice demonstrated a strongly attenuated inflammatory response in the airways early after infection. These data suggest that myeloid but not endothelial MyD88 is important for host defense during gram-negative pneumonia derived sepsis.

HS-23, Lonicera japonica extract, attenuates septic injury by suppressing toll-like receptor 4 signaling

ETHNOPHARMACOLOGICAL RELEVANCE

Lonicera japonica Thunberg is a traditional herbal medicine widely used in East Asia as an anti-bacterial, anti-inflammatory, and antiviral agent. This study was designed to investigate the effects of HS-23, ethanol extract of the dried flower buds of Lonicera japonica, in experimental models of sepsis and elucidate the mechanisms of action of HS-23.

MATERIALS AND METHODS

Male ICR mice were intravenously administered HS-23 (20 and 40 mg/kg) for 0 (immediately) and 24 h after cecal ligation and puncture (CLP) for survival tests, and HS-23 (40 mg/kg) immediately after CLP for biochemical assays.

RESULTS

HS-23 improved sepsis-induced mortality, enhanced bacterial clearance, and attenuated multiple organ failure. The mechanisms of action of HS-23 included attenuation of increased toll-like receptor (TLR)4 protein and mRNA expression. HS-23 suppressed sepsis-induced increases in protein expression of myeloid differentiation primary response protein 88, p38 and c-Jun N-terminal kinase in both liver and lung, as well as TIR-domain-containing adapter-inducing interferon-β and interferon regulatory transcription factor 3 protein expression in liver.

CONCLUSION

The results of this study revealed that HS-23 attenuated sepsis through suppression of TLR signaling pathways. Therefore, our findings suggest that HS-23 might be useful as a potential therapeutic agent for treatment of sepsis.

Effects of cigarette smoke on Toll-like receptor (TLR) activation of chronic obstructive pulmonary disease (COPD) macrophages

Chronic obstructive pulmonary disease (COPD) is characterized by an abnormal innate immune response. We have investigated the changes in the innate immune response of COPD alveolar macrophages exposed to both cigarette smoke and Toll-like receptor (TLR) stimulation. COPD and control alveolar macrophages were exposed to cigarette smoke extract (CSE) followed by TLR-2, -4 and -5 ligands [Pam3CSK4, lipopolysaccharide (LPS) and phase I flagellin (FliC), respectively] or non-typeable Haemophilus influenzae (NTHi). CSE exposure suppressed TLR-induced tumour necrosis factor (TNF)-α, interleukin (IL)-6, IL-10 and regulated on activation, normal T cell expressed and secreted (RANTES) production in both COPD and control alveolar macrophages, but had no effect on interleukin 8 (CXCL8) production. Similarly, CSE suppressed NTHi-induced TNF-α but not NTHi-induced CXCL8 production in COPD alveolar macrophages. Gene expression analysis showed that CSE suppressed LPS-induced TNF-α transcription but not CXCL8 transcription in COPD alveolar macrophages. The dampening effect of CSE on LPS-induced cytokine production was associated with a reduction in p38, extracellular signal regulated kinase (ERK) and p65 activation. In conclusion, CSE caused a reduced innate immune response in COPD alveolar macrophages, with the exception of persistent CXCL8 production. This could be a mechanism by which alveolar macrophages promote neutrophil chemotaxis under conditions of oxidative stress and bacterial exposure.

Systemic injection of low-dose lipopolysaccharide fails to break down the blood-brain barrier or activate the TLR4-MyD88 pathway in neonatal rat brain

We aimed to investigate whether peripheral low-dose lipopolysaccharide (LPS) induces the breakdown of the blood–brain barrier (BBB) and/or the activation of toll-like receptor 4 (TLR4) in the neonatal rat brain. Neonatal rats received intraperitoneal injections of low-dose LPS (0.3 mg/kg∙bw), and the BBB compromise was detected by Evans Blue extravasation and electron microscopy. Meanwhile, TLR4, adaptin myeloid differentiation factor 88 (MyD88), nuclear transcription factor kappa-B (NF-κB) p50 and tumor necrosis factor alpha (TNFα) in the neonatal rat brain were determined by quantitative real-time polymerase chain reaction (PCR) and Western Blot. Immunohistochemistry was used to determine the distribution and activation of microglia in the brain after LPS administration. It was demonstrated that Evans Blue extravasation was not observed in the brain parenchyma, and that tight junctions of cerebral endothelial cells remained intact after systemic injections of LPS in neonatal rats. Although intracerebroventricular injections of LPS activated microglia and up-regulated the expression of TLR4, MyD88, NF-κB p50 and TNFα in the neonatal rat brain, systemic LPS did not induce these responses. These findings indicate that while the neonatal rat brain responds to the direct intra-cerebral administration of LPS through robust TLR4 activation, systemic low-dose LPS does not induce the innate immune reaction or compromise the BBB in neonatal rats.

Lung cell-specific modulation of LPS-induced TLR4 receptor and adaptor localization

Lung infection by Gram-negative bacteria is a major cause of morbidity and mortality in humans. Lipopolysaccharide (LPS), located in the outer membrane of the Gram-negative bacterial cell wall, is a highly potent stimulus of immune and structural cells via the TLR4/MD2 complex whose function is sequentially regulated by defined subsets of adaptor proteins. Regulatory mechanisms of lung-specific defense pathways point at the crucial role of resident alveolar macrophages, alveolar epithelial cells, the TLR4 receptor pathway, and lung surfactant in shaping the innate immune response to Gram-negative bacteria and LPS. During the past decade intracellular spatiotemporal localization of TLR4 emerged as a key feature of TLR4 function. Here, we briefly review lung cell type- and compartment-specific mechanisms of LPS-induced TLR4 regulation with a focus on primary resident hematopoietic and structural cells as well as modifying microenvironmental factors involved.

Impaired innate immune alveolar macrophage response and the predilection for COPD exacerbations

BACKGROUND

Alveolar macrophages (AM) in COPD have fundamentally impaired responsiveness to Toll-like receptor 2 (TLR2) and TLR4 ligands of non-typeable Haemophilus influenzae (NTHI). However, the contribution of innate immune dysfunction to exacerbations of COPD is unexplored. We hypothesised that impaired innate AM responses in COPD extend beyond NTHI to other pathogens and are linked with COPD exacerbations and severity.

METHODS

AMs, obtained by bronchoalveolar lavage from 88 volunteers with stable-to-moderate COPD, were incubated with respiratory pathogens (NTHI, Moraxella catarrhalis (MC), Streptococcus pneumoniae (SP) and TLR ligands lipopolysaccharide, Pam3Cys) and elicited IL-8 and TNF-α were measured by microsphere flow cytometry. NF-κB nuclear translocation was measured by colorimetric assay. AM TLR2 and TLR4 expression was determined by immunolabeling and quantitation of mean fluorescent indices. Participants were monitored prospectively for occurrence of COPD exacerbations for 1 year following bronchoscopy. Non-parametric analyses were used to compare exacerbation-prone and non-exacerbation-prone individuals.

RESULTS

29 subjects had at least one exacerbation in the follow-up period (exacerbation-prone) and 59 remained exacerbation-free (non-exacerbation-prone). AMs of exacerbation-prone COPD donors were more refractory to cytokine induction by NTHI (p=0.02), MC (p=0.045) and SP (p=0.046), and to TLR2 (p=0.07) and TLR4 (p=0.028) ligands, and had diminished NF-κB nuclear activation, compared with non-exacerbation-prone counterparts. AMs of exacerbation-prone subjects were more refractory to TLR2 upregulation by MC and SP (p=0.04 each).

CONCLUSIONS

Our results support a paradigm of impaired innate responses of COPD AMs to respiratory pathogens, mediated by impaired TLR responses, underlying a propensity for exacerbations in COPD.

Comparison of the innate immune responses of porcine monocyte-derived dendritic cells and splenic dendritic cells stimulated with LPS

Dendritic cell (DC) subsets form a remarkable cellular network that regulate innate and adaptive immune responses. Although pigs are the most approximate model to humans, little is known about the regulation of monocyte-derived DCs (moDCs) and splenic DCs (SDCs) in the initiation of immune responses under inflammatory conditions. We investigated the activation and maturation of porcine moDC and SDC subpopulations following LPS stimulation. Porcine monocytes that would differentiate into moDCs were isolated. SDCs were isolated directly from the porcine spleen. Following LPS stimulation, phagocytosis activity, TLR4/MyD88-dependent gene expression, co-stimulatory molecule, and pro-inflammatory cytokine (TNF-α, IL-1β) and chemokine (IL-8) expressions were increased in both cell subsets. Furthermore, moDCs showed higher levels of gene and protein expression compared with SDCs. Interestingly, moDCs were found to be more responsive via the TLR4/TRAF-dependent signalling pathway of activation. Only SDCs expressed higher level of IL-12p40 gene and protein, whereas, IFN-γ gene and protein expression were likely to be unchanged after LPS stimulation in both cell subtypes. These data demonstrate that porcine moDCs display a greater ability to initiate innate immune responses, and could be used as a model to investigate immune responses against Ags.

The effects of airway microbiome on corticosteroid responsiveness in asthma

RATIONALE

The role of airway microbiome in corticosteroid response in asthma is unknown.

OBJECTIVES

To examine airway microbiome composition in patients with corticosteroid-resistant (CR) asthma and compare it with patients with corticosteroid-sensitive (CS) asthma and normal control subjects and explore whether bacteria in the airways of subjects with asthma may direct alterations in cellular responses to corticosteroids.

METHODS

16S rRNA gene sequencing was performed on bronchoalveolar lavage (BAL) samples of 39 subjects with asthma and 12 healthy control subjects. In subjects with asthma, corticosteroid responsiveness was characterized, BAL macrophages were stimulated with pathogenic versus commensal microorganisms, and analyzed by real-time polymerase chain reaction for the expression of corticosteroid-regulated genes and cellular p38 mitogen-activated protein kinase (MAPK) activation.

MEASUREMENTS AND MAIN RESULTS

Of the 39 subjects with asthma, 29 were CR and 10 were CS. BAL microbiome from subjects with CR and CS asthma did not differ in richness, evenness, diversity, and community composition at the phylum level, but did differ at the genus level, with distinct genus expansions in 14 subjects with CR asthma. Preincubation of asthmatic airway macrophages with Haemophilus parainfluenzae, a uniquely expanded potential pathogen found only in CR asthma airways, resulted in p38 MAPK activation, increased IL-8 (P < 0.01), mitogen-activated kinase phosphatase 1 mRNA (P < 0.01) expression, and inhibition of corticosteroid responses (P < 0.05). This was not observed after exposure to commensal bacterium Prevotella melaninogenica. Inhibition of transforming growth factor-β-associated kinase-1 (TAK1), upstream activator of MAPK, but not p38 MAPK restored cellular sensitivity to corticosteroids.

CONCLUSIONS

A subset of subjects with CR asthma demonstrates airway expansion of specific gram-negative bacteria, which trigger TAK1/MAPK activation and induce corticosteroid resistance. TAK1 inhibition restored cellular sensitivity to corticosteroids.

Bacterial ligand stimulates TLR2-dependent chemokines of colon cell

Shigella spp. are known to penetrate the colonic epithelial cells causing shigellosis, which results in production of convalescent antibodies against porin, the surface exposed major outer membrane protein. Porin has been categorized as primarily TLR2-ligand and here we validated its signaling procedure in colonic INT-407 cells simulating the host scenario. Porin up-regulated TLR2 and -6 followed by TLR2·MYD88 complex formation suggesting direct involvement of MYD88 for downstream signaling. Translocation of NF-κB p65 and p50 subunits on to the nucleus indicates involvement of the transcription factor in signaling. Porin-induced TLR signaling specifically stimulated the pro-inflammatory chemokine panel comprising of MIP-1α, MCP-1 and IL-8. Inhibition studies of TLR2 and NF-κB led to abrogation of the pro-inflammatory chemokine response, showing TLR-dependent signaling through NF-κB regulate gut activity. This work elucidates TLR2 not only scans pathogen-associated molecule but also has a direct role in maneuvering colon cell response.

Role of CD14 in host protection against infections and in metabolism regulation

CD14 is a glycosylphosphatidylinositol (GPI)-anchored receptor known to serve as a co-receptor for several Toll-like Receptors (TLRs) both at the cell surface and in the endosomal compartment. CD14 can be expressed by cells of both hematopoietic and non-hematopoietic origin as a cell membrane or secreted protein. Although CD14 was discovered more than 20 years ago, its activities remain largely to be defined. Most of the information available concerns CD14's role as a co-receptor working with TLR4 and facilitating cellular responses to low doses of lipopolysaccharide (LPS). Recent studies have highlighted and molecularly defined many other functions of this pattern recognition receptor (PRR). These functions include the mechanisms through which CD14 allows the activation of the TLR4-TRAM-TRIF pathway upon LPS stimulation; the capacity of CD14 to transduce a TLR4-independent signaling pathway leading to the activation of NFAT transcription factor family members with important consequences in myeloid cells; the CD14 influence on cell metabolism in conditions predisposing to obesity. In this review, we summarize recent progresses toward the molecular definition of the multiple roles exerted by CD14 in innate immune cells in response to LPS and the consequences of CD14 activation in physiologic and pathologic conditions.