TLR5 as an anti-inflammatory target and modifier gene in cystic fibrosis

Flagellum-deficient Pseudomonas aeruginosa is more virulent than non-motile but flagellated mutants in a cystic fibrosis mouse model

Loss of the flagellum marks the pathoadaptation of Pseudomonas aeruginosa to the cystic fibrosis (CF) airway environment during lung disease. Losing the flagellum is advantageous to the bacterium as the flagellum can be recognized by immune cells. The primary purpose of the flagellum is, however, to provide motility to the bacterium. Our goal was to determine whether the loss of flagellar motility or the loss of flagellum expression contributes to P. aeruginosa lung infection in CF. To address this, wild-type and gut-corrected FABP-human cystic fibrosis transmembrane conductance regulator (hCFTR) mice deficient in the murine Cftr gene were infected intratracheally with lethal doses of wild-type or flagellum-deficient P. aeruginosa. While there was no significant difference in the survival of wild-type mice after infection with either of the bacterial strains, a significantly higher mortality was observed in FABP-hCFTR mice infected with flagellum-deficient P. aeruginosa, compared to mice infected with their flagellated counterparts. When FABP-hCFTR mice were infected with isogenic, motility-deficient flagellated mutants, animal survival and lung bacterial titers were similar to those observed in mice infected with the wild-type bacterium. Airway levels of neutrophils and the amount neutrophil elastase were similar in mice infected with either the wild-type bacteria or the flagellum-deficient P. aeruginosa. Our results show that FABP-hCFTR mice have a different response to flagellum loss in P. aeruginosa compared to wild-type animals. The loss of flagellum expression, rather than the loss of motility, is the main driver behind the increased virulence of flagellum-deficient P. aeruginosa in CF. These observations provide new insight into P. aeruginosa virulence in CF.IMPORTANCEPseudomonas aeruginosa, a major respiratory pathogen in cystic fibrosis, is known to lose its flagellum during the course of infection in the airways. Here, we show that the loss of flagellum leads to a more enhanced virulence in Cftr-deficient cystic fibrosis mice than in control animals. Loss of flagellum expression, rather than the loss of flagellar swimming motility, represents the main driver behind this increased virulence suggesting that this appendage plays a specific role in P. aeruginosa virulence in cystic fibrosis airways.

Lung Inflammatory Genes in Cystic Fibrosis and Their Relevance to Cystic Fibrosis Transmembrane Conductance Regulator Modulator Therapies

Cystic fibrosis (CF) is a monogenic syndrome determined by over 2000 mutations in the CF Transmembrane Conductance Regulator (CFTR) gene harbored on chromosome 7. In people with CF (PWCF), lung disease is the major determinant of morbidity and mortality and is characterized by a clinical phenotype which differs in the presence of equal mutational assets, indicating that genetic and environmental modifiers play an important role in this variability. Airway inflammation determines the pathophysiology of CF lung disease (CFLD) both at its onset and progression. In this narrative review, we aim to depict the inflammatory process in CF lung, with a particular emphasis on those genetic polymorphisms that could modify the clinical outcome of the respiratory disease in PWCF. The natural history of CF has been changed since the introduction of CFTR modulator therapies in the clinical arena. However, also in this case, there is a patient-to-patient variable response. We provide an overview on inflammatory/immunity gene variants that affect CFLD severity and an appraisal of the effects of CFTR modulator therapies on the inflammatory process in lung disease and how this knowledge may advance the optimization of the management of PWCF.

Endogenous Reverse Transcriptase Inhibition Attenuates TLR5-Mediated Inflammation

Transposable elements (TEs) are mobile genomic sequences that encompass roughly 50% of the human genome. Class 1 TEs, or "retrotransposons," mobilize through the production of an RNA intermediate that is then reverse transcribed to form complementary DNA (cDNA) molecules capable of genomic reinsertion. While TEs are traditionally silenced to maintain genomic integrity, the recognition of immunostimulatory cues, such as those provided by microorganisms, drastically alters host transcription to induce the differential expression of TEs. Emerging evidence demonstrates that the inducible production of TE cDNA is not an inert phenomenon but instead has been coopted by host immunity to facilitate cross talk between host and constituents of the microbiota by agonizing intrinsic antiviral receptors. Here, we demonstrate that immunostimulation of toll-like receptor 4 (TLR4) with lipopolysaccharide (LPS) and TLR5 with bacterial flagella (FLA) alters the expression of retrotransposons, such as human endogenous retroviruses (HERVs) and long interspersed nuclear elements (LINEs). Next, we demonstrate that reverse transcriptase inhibitor (RTi) delivery ameliorates the acute production of the proinflammatory cytokine "tumor necrosis factor alpha" (TNF-α) in response to FLA in a monocytic cell line (THP-1). Collectively, our findings demonstrate that TLR5-mediated cross talk between the host and microbiota is partially dependent on the reverse transcription (RT) of retrotransposons. IMPORTANCE The microbiota is a potent reservoir of immunostimulatory and immunosuppressive motifs that fundamentally shape host immunity. Despite broad associations between microbial composition and host immunity, the mechanisms underlying host microbiota-induced immunoregulation remain poorly defined. Here, we demonstrate a novel mechanism by which motifs overabundant during dysbiotic conditions influence host immunity through the upregulation of endogenous RT to produce motifs that agonize antiviral receptors.

Genetic Modifying Factors of Cystic Fibrosis Phenotype: A Challenge for Modern Medicine

Cystic fibrosis (CF) is a monogenic autosomal recessive disease caused by cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations. CF is characterized by a high phenotypic variability present even in patients with the same genotype. This is due to the intervention of modifier genes that interact with both the CFTR gene and environmental factors. The purpose of this review is to highlight the role of non-CFTR genetic factors (modifier genes) that contribute to phenotypic variability in CF. We analyzed literature data starting with candidate gene studies and continuing with extensive studies, such as genome-wide association studies (GWAS) and whole exome sequencing (WES). The results of both types of studies revealed that the number of modifier genes in CF patients is impressive. Their identification offers a new perspective on the pathophysiological mechanisms of the disease, paving the way for the understanding of other genetic disorders. In conclusion, in the future, genetic analysis, such as GWAS and WES, should be performed routinely. A challenge for future research is to integrate their results in the process of developing new classes of drugs, with a goal to improve the prognosis, increase life expectancy, and enhance quality of life among CF patients.

Flagellin From Pseudomonas aeruginosa Modulates SARS-CoV-2 Infectivity in Cystic Fibrosis Airway Epithelial Cells by Increasing TMPRSS2 Expression

In the coronavirus disease 2019 (COVID-19) health crisis, one major challenge is to identify the susceptibility factors of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) in order to adapt the recommendations for populations, as well as to reduce the risk of COVID-19 development in the most vulnerable people, especially patients with chronic respiratory diseases such as cystic fibrosis (CF). Airway epithelial cells (AECs) play a critical role in the modulation of both immune responses and COVID-19 severity. SARS-CoV-2 infects the airway through the receptor angiotensin-converting enzyme 2, and a host protease, transmembrane serine protease 2 (TMPRSS2), plays a major role in SARS-CoV-2 infectivity. Here, we show that Pseudomonas aeruginosa increases TMPRSS2 expression, notably in primary AECs with deficiency of the ion channel CF transmembrane conductance regulator (CFTR). Further, we show that the main component of P. aeruginosa flagella, the protein flagellin, increases TMPRSS2 expression in primary AECs and Calu-3 cells, through activation of Toll-like receptor-5 and p38 MAPK. This increase is particularly seen in Calu-3 cells deficient for CFTR and is associated with an intracellular increased level of SARS-CoV-2 infection, however, with no effect on the amount of virus particles released. Considering the urgency of the COVID-19 health crisis, this result may be of clinical significance for CF patients, who are frequently infected with and colonized by P. aeruginosa during the course of CF and might develop COVID-19.

TLR5 signalling is hyper-responsive in porcine cystic fibrosis airways epithelium

Excessive lung inflammation and airway epithelium damage are hallmarks of cystic fibrosis (CF) disease. It is unclear whether lung inflammation is related to an intrinsic defect in the immune response or to chronic infection. We aimed to determine whether TLR5-mediated response is defective in the CF airway epithelium. We used a newborn CF pig model to study intrinsic alterations in CF airway epithelium innate immune response. Airway epithelial cells (AECs) were stimulated with flagellin or lipopolysaccharide to determine responses specific for TLR5 and TLR4, respectively. We observed a significant increase in cytokine secretion when CF AECs were stimulated with flagellin compared to wild type (WT) AECs. These results were recapitulated when AECs were treated with an inhibitor of CFTR channel activity. We show that TLR5-signalling is altered in CF lung epithelium at birth. Modulation of TLR5 signalling could contribute to better control the excessive inflammatory response observed in CF lungs.

Airway Administration of Flagellin Regulates the Inflammatory Response to Pseudomonas aeruginosa

Excessive lung inflammation and airway epithelial damage are hallmarks of human inflammatory lung diseases, such as cystic fibrosis (CF). Enhancement of innate immunity provides protection against pathogens while reducing lung-damaging inflammation. However, the mechanisms underlying innate immunity–mediated protection in the lung remain mysterious, in part because of the lack of appropriate animal models for these human diseases. TLR5 (Toll-like receptor 5) stimulation by its specific ligand, the bacterial protein flagellin, has been proposed to enhance protection against several respiratory infectious diseases, although other cellular events, such as calcium signaling, may also control the intensity of the innate immune response. Here, we investigated the molecular events prompted by stimulation with flagellin and its role in regulating innate immunity in the lung of the pig, which is anatomically and genetically more similar to humans than rodent models. We found that flagellin treatment modulated NF-κB signaling and intracellular calcium homeostasis in airway epithelial cells. Flagellin pretreatment reduced the NF-κB nuclear translocation and the expression of proinflammatory cytokines to a second flagellin stimulus as well as to Pseudomonas aeruginosa infection. Moreover, in vivo administration of flagellin decreased the severity of P. aeruginosa–induced pneumonia. Then we confirmed these beneficial effects of flagellin in a pathological model of CF by using ex vivo precision-cut lung slices from a CF pigz model. These results provide evidence that flagellin treatment contributes to a better regulation of the inflammatory response in inflammatory lung diseases such as CF.

Dysregulated signalling pathways in innate immune cells with cystic fibrosis mutations

Cystic fibrosis (CF) is one of the most common life-limiting recessive genetic disorders in Caucasians, caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). CF is a multi-organ disease that involves the lungs, pancreas, sweat glands, digestive and reproductive systems and several other tissues. This debilitating condition is associated with recurrent lower respiratory tract bacterial and viral infections, as well as inflammatory complications that may eventually lead to pulmonary failure. Immune cells play a crucial role in protecting the organs against opportunistic infections and also in the regulation of tissue homeostasis. Innate immune cells are generally affected by CFTR mutations in patients with CF, leading to dysregulation of several cellular signalling pathways that are in continuous use by these cells to elicit a proper immune response. There is substantial evidence to show that airway epithelial cells, neutrophils, monocytes and macrophages all contribute to the pathogenesis of CF, underlying the importance of the CFTR in innate immune responses. The goal of this review is to put into context the important role of the CFTR in different innate immune cells and how CFTR dysfunction contributes to the pathogenesis of CF, highlighting several signalling pathways that may be dysregulated in cells with CFTR mutations.

Toll-like receptor gene polymorphisms in patients with keratitis

OBJECTIVE

To investigate differences in SNPs in TLR genes between people who had keratitis and controls in an Indian population.

METHODS

145 cases of keratitis and 189 matched controls were recruited. DNA was extracted from peripheral blood. Single nucleotide polymorphisms (SNP) in TLR2 (n = 6), TLR4 (n = 15), TLR5 (n = 13) and TLR9 (n = 10) were analysed. The risk of developing keratitis was assessed based on allele, genotype and haplotype associations.

RESULTS

For all cases of keratitis, the TLR4 SNP rs4986791 TC genotype frequency was significantly higher in cases (p = 0.006, OR = 1.96, 95 % CI 1.19-3.2). Including cases of only microbial keratitis (MK) revealed that genotypes in TLR2 SNP rs5743706 TA (p = 0.0001; OR = 8.61; 95 % CI 2.59-28.56)), TLR4 SNP s4986791 TC (p = 0.002; OR = 2.65; 95 % CI 1.39-5.07) were significantly more common for MK, whereas the TLR5 SNP rs2241096 A allele (p = 0.00316, OR = 0.42, 95 % CI 0.2-0.9286) and GA genotype (p = 0.016; OR = 0.45; 95 % CI 0.23-0.86) was significantly less common in MK cases. The TLR2 SNP rs5743706 genotype TA was significantly less common in the sterile keratitis (SK) group (p = 0.004, OR = 0.43, 95 %CI 0.24-0.77). Haplotype analysis of MK compared to controls showed that TLR2 AT was more common in controls (p = 0.003); TLR4 ACAC was more common in cases (p = 0.004); TLR5 TGGCA was more common in controls (p = 0.001).

CONCLUSION

The present study revealed multiple associations between variants across TLR genes, which may have implications for understanding the underlying host factors, risk of developing keratitis and molecular pathogenesis in keratitis.

TLR5 Activation Exacerbates Airway Inflammation in Asthma

INTRODUCTION

Innate immune activation through exposure to indoor and outdoor pollutants is emerging as an important determinant of asthma severity. For example, household levels of the bacterial product lipopolysaccharide (LPS) are associated with increased asthma severity. We hypothesized that activation of the innate immune receptor TLR5 by its bacterial ligand flagellin will exacerbate airway inflammation and asthma symptoms.

METHODS

We determined the effect of flagellin co-exposure with ovalbumin in a murine model of allergic asthma. We evaluated the presence of flagellin activity in house dust of asthma patients. Finally, we analyzed the association of a dominant-negative polymorphism in TLR5 (rs5744168) with asthma symptoms in patients with asthma.

RESULTS

We showed that bacterial flagellin can be found in the house dust of patients with asthma and that this bacterial product exacerbates allergic airway inflammation in an allergen-specific mouse model of asthma. Furthermore, a dominant-negative genetic polymorphism in TLR5, the receptor for flagellin, is associated with decreased symptoms in patients with asthma.

CONCLUSION

Together, our results reveal a novel genetic protective factor (TLR5 deficiency) and a novel environmental pollutant (microbial flagellin) that influence asthma severity. (Clinical trials NCT01688986 and NCT01087307).

Flagellin-independent effects of a Toll-like receptor 5 polymorphism in the inflammatory response to Burkholderia pseudomallei

Background

Toll-like receptors (TLRs) are sentinel receptors of the innate immune system. TLR4 detects bacterial lipopolysaccharide (LPS) and TLR5 detects bacterial flagellin. A common human nonsense polymorphism, TLR5:c.1174C>T, results in a non-functional TLR5 protein. Individuals carrying this variant have decreased mortality from melioidosis, infection caused by the flagellated Gram-negative bacterium Burkholderia pseudomallei. Although impaired flagellin-dependent signaling in carriers of TLR5:c.1174C>T is well established, this study tested the hypothesis that a functional effect of TLR5:c.1174C>T is flagellin-independent and involves LPS-TLR4 pathways.

Methodology/Principal findings

Whole blood from two independent cohorts of individuals genotyped at TLR5:c.1174C>T was stimulated with wild type or aflagellated B. pseudomallei or purified bacterial motifs followed by plasma cytokine measurements. Blood from individuals carrying the TLR5:c.1174C>T variant produced less IL-6 and IL-10 in response to an aflagellated B. pseudomallei mutant and less IL-8 in response to purified B. pseudomallei LPS than blood from individuals without the variant. TLR5 expression in THP1 cells was silenced using siRNA; these cells were stimulated with LPS before cytokine levels in cell supernatants were quantified by ELISA. In these cells following LPS stimulation, silencing of TLR5 with siRNA reduced both TNF-α and IL-8 levels. These effects were not explained by differences in TLR4 mRNA expression or NF-κB or IRF activation.

Conclusions/Significance

The effects of the common nonsense TLR5:c.1174C>T polymorphism on the host inflammatory response to B. pseudomallei may not be restricted to flagellin-driven pathways. Moreover, TLR5 may modulate TLR4-dependent cytokine production. While these results may have broader implications for the role of TLR5 in the innate immune response in melioidosis and other conditions, further studies of the mechanisms underlying these observations are required.

Toll-like receptors (TLRs) are important receptors of the innate immune system. TLR4 detects bacterial lipopolysaccharide (LPS) and TLR5 detects bacterial flagellin. A common human polymorphism in TLR5 encodes a shortened protein and blunts the immune response to flagellin. Individuals carrying this variant have decreased mortality from melioidosis, infection caused by the flagellated Gram-negative bacterium Burkholderia pseudomallei. The mechanism of protection is not known. We tested the hypothesis that the observed effect of the polymorphism is independent of flagellin and involves LPS-TLR4 pathways. We found that blood from individuals carrying the polymorphism produced lower levels of cytokines IL-6 and IL-10 in response to an aflagellated B. pseudomallei mutant and less IL-8 in response to purified B. pseudomallei LPS than blood from individuals without the variant. We further observed that in THP1 cells stimulated with LPS, silencing of TLR5 with siRNA reduced levels of both TNF-α and IL-8. These effects were not explained by differences in TLR4 mRNA expression. We conclude that the effects of the TLR5 polymorphism on the host inflammatory response to B. pseudomallei may not be restricted to flagellin-driven pathways. These results provide insights into the role of TLR5 in the innate immune response in melioidosis and other conditions.

Functional expression of TLR5 of different vertebrate species and diversification in intestinal pathogen recognition

Toll-like receptor 5 (TLR5) is activated by bacterial flagellins and plays a crucial role in the first-line defence against pathogenic bacteria and in immune homeostasis, and is highly conserved in vertebrate species. However, little comparative information is available on TLR5 functionality. In this study, we compared TLR5 activation using full-length and chimeric TLR5 of various vertebrate species (human, chicken, mouse, pig, cattle). Chimeric TLR5 receptors, consisting of human transmembrane and intracellular domains, linked to extracellular domains of animal origin, were generated and expressed. The comparison of chimeric TLR5s and their full-length counterparts revealed significant functional disparities. While porcine and chicken full-length TLR5s showed a strongly reduced functionality in human cells, all chimeric receptors were functional when challenged with TLR5 ligand Salmonella FliC. Using chimeric receptors as a tool allowed for the identification of ectodomain-dependent activation potential and partially host species-specific differences in response to various enteric bacterial strains and their purified flagellins. We conclude that both the extra- and intracellular determinants of TLR5 receptors are crucial for compatibility with the species expression background and hence for proper receptor functionality. TLR5 receptors with a common intracellular domain provide a useful system to investigate bacteria- and host-specific differences in receptor activation.

Extension and refinement of the recognition motif for Toll-like receptor 5 activation by flagellin

TLRs sense conserved and essential molecular components of microbes that invade multicellular organisms. The wide range of TLR agonists, differing in size and shape, is recognized either through a single or a pair of binding sites on the ectodomains of TLRs. TLR5 recognizes bacterial flagellin through two distinct binding sites on the ectodomain, the first facilitating primary binding of flagellin and the second guiding receptor dimerization necessary for signaling. The regions of flagellin recognized by TLR5 encompass key functional regions within the D1 domain of flagellin, which is also required for the assembly of functional flagella. In addition to previously identified binding sites at the N-terminal and central segment of the TLR5 ectodomain, we extended the TLR5'-D1 interaction interface on TLR5 and showed a species-specific recognition relevance of this extended region. In addition, we showed that the loop and following β-hairpin region of flagellin, previously proposed to participate in the TLR5-flagellin dimerization interface, is not accountable for these species-specific differences. We further identified residues that contribute to the interaction between two TLR5 ectodomains in an active signaling complex. Our work demonstrates that flagellin is recognized by TLR5 through a more extensive interaction surface than previously characterized.

The Epithelial Sodium Channel Is a Modifier of the Long-Term Nonprogressive Phenotype Associated with F508del CFTR Mutations

Cystic fibrosis (CF) remains the most lethal genetic disease in the Caucasian population. However, there is great variability in clinical phenotypes and survival times, even among patients harboring the same genotype. We identified five patients with CF and a homozygous F508del mutation in the CFTR gene who were in their fifth or sixth decade of life and had shown minimal changes in lung function over a longitudinal period of more than 20 years. Because of the rarity of this long-term nonprogressive phenotype, we hypothesized these individuals may carry rare genetic variants in modifier genes that ameliorate disease severity. Individuals at the extremes of survival time and lung-function trajectory underwent whole-exome sequencing, and the sequencing data were filtered to include rare missense, stopgain, indel, and splicing variants present with a mean allele frequency of <0.2% in general population databases. Epithelial sodium channel (ENaC) mutants were generated via site-directed mutagenesis and expressed for Xenopus oocyte assays. Four of the five individuals carried extremely rare or never reported variants in the SCNN1D and SCNN1B genes of the ENaC. Separately, an independently enriched rare variant in SCNN1D was identified in the Exome Variant Server database associated with a milder pulmonary disease phenotype. Functional analysis using Xenopus oocytes revealed that two of the three variants in δ-ENaC encoded by SCNN1D exhibited hypomorphic channel activity. Our data suggest a potential role for δ-ENaC in controlling sodium reabsorption in the airways, and advance the plausibility of ENaC as a therapeutic target in CF.

Syk inhibitor R406 downregulates inflammation in an in vitro model of Pseudomonas aeruginosa infection

As Pseudomonas aeruginosa infections are characterized by strong inflammation of infected tissues, anti-inflammatory therapies in combination with antibiotics have been considered for the treatment of associated diseases. Syk tyrosine kinase is an important regulator of inflammatory responses, and its specific inhibition was explored as a therapeutic option in several inflammatory conditions; however, this has not been studied in bacterial infections. We used a model of in vitro infection of human monocytic cell line THP-1 and lung epithelial cell line H292 with both wild-type and flagella-deficient mutant of P. aeruginosa strain K, as well as with clinical isolates from cystic fibrosis patients, to study the effect of a small molecule Syk inhibitor R406 on inflammatory responses induced by this pathogen. One-hour pretreatment of THP-1 cells with 10 μmol/L R406 resulted in a significant downregulation of the expression of the adhesion molecule ICAM-1, pro-inflammatory cytokines TNF-α and IL-1β, and phosphorylated signaling proteins ERK2, JNK, p-38, and IκBα, as well as significantly decreased TNF-α release by infected H292 cells. The results suggest that Syk is involved in the regulation of inflammatory responses to P. aeruginosa, and R406 may potentially be useful in dampening the damage caused by severe inflammation associated with this infection.

Screening Bioactive Nanoparticles in Phagocytic Immune Cells for Inhibitors of Toll-like Receptor Signaling

Pharmacological regulation of Toll-like receptor (TLR) responses holds great promise in the treatment of many inflammatory diseases. However, there have been limited compounds available so far to attenuate TLR signaling and there have been no clinically approved TLR inhibitors (except the anti-malarial drug hydroxychloroquine) in clinical use. In light of rapid advances in nanotechnology, manipulation of immune responsiveness using nano-devices may provide a new strategy to treat these diseases. Herein, we present a high throughput screening method for quickly identifying novel bioactive nanoparticles that inhibit TLR signaling in phagocytic immune cells. This screening platform is built on THP-1 cell-based reporter cells with colorimetric and luciferase assays. The reporter cells are engineered from the human THP-1 monocytic cell line by stable integration of two inducible reporter constructs. One expresses a secreted embryonic alkaline phosphatase (SEAP) gene under the control of a promoter inducible by the transcription factors NF-κB and AP-1, and the other expresses a secreted luciferase reporter gene under the control of promoters inducible by interferon regulatory factors (IRFs).Upon TLR stimulation, the reporter cells activate transcription factors and subsequently produce SEAP and/or luciferase, which can be detected using their corresponding substrate reagents. Using a library of peptide-gold nanoparticle (GNP) hybrids established in our previous studies as an example, we identified one peptide-GNP hybrid that could effectively inhibit the two arms of TLR4 signaling cascade triggered by its prototypical ligand, lipopolysaccharide (LPS). The findings were validated by standard biochemical techniques including immunoblotting. Further analysis established that this lead hybrid had a broad inhibitory spectrum, acting on multiple TLR pathways, including TLR2, 3, 4, and 5. This experimental approach allows a rapid assessment of whether a nanoparticle (or other therapeutic compounds) can modulate specific TLR signaling in phagocytic immune cells.

Corticosteroid-resistant inflammatory signalling in Pseudomonas-infected bronchial cells

Decreasing the inflammatory response that leads to tissue damage during cystic fibrosis (CF) lung disease has been a long-standing goal of CF therapy. While corticosteroids are widely used anti-inflammatory drugs, their efficacy in CF lung disease remains debated. The complex interaction between the colonising bacteria and the host environment may impact corticosteroid responsiveness.

In this study, sputum samples from adult CF patients were collected at baseline and during pulmonary exacerbation episodes. Lung function measurements and sputum microbiological analyses were performed. In parallel, the inflammatory response and corticosteroid sensitivity of airway epithelial cells to Pseudomonas-derived exoproducts was investigated.

We report that adult CF patients colonised with mucoid Pseudomonas aeruginosa have higher levels of baseline inflammation, more frequent exacerbations and worse lung function compared with patients colonised with nonmucoid P. aeruginosa. Moreover, mucoid P. aeruginosa activates NF-κB via Toll-like receptor (TLR) 2, which acts in an additive manner to TLR5 to drive inflammation in airway epithelial cells. Furthermore, TLR2-mediated intracellular signalling is more resistant to the anti-inflammatory effects of corticosteroid when compared with other TLR signalling pathways.

Overall, these results suggest that airway inflammation triggered by mucoid P. aeruginosa is less responsive to the anti-inflammatory action of corticosteroids. Whether this translates into a diminished response of CF patients to corticosteroid therapy should be examined in future clinical studies.

TLR2 activation by mucoid Pseudomonas increases corticosteroid-resistant inflammation in airway epithelial cellshttp://ow.ly/lR3d30bsRrr

Leukocyte TLR5 deficiency inhibits atherosclerosis by reduced macrophage recruitment and defective T-cell responsiveness

Toll-like receptors (TLR) provide a critical link between innate and adaptive immunity, both important players in atherosclerosis. Since evidence for the role of TLR5 is lacking, we aimed to establish this in the immune axis of atherosclerosis. We assessed the effect of the TLR5-specific ligand Flagellin on macrophage maturation and T-cell polarisation. Next, we generated TLR5^−/−LDLr^−/− chimeras to study the effect of hematopoietic TLR5 deficiency on atherosclerosis formation. Flagellin stimulation did not influence wildtype or TLR5^−/− macrophage maturation. Only in wildtype macrophages, Flagellin exposure increased MCP-1 and IL6 expression. Flagellin alone reduced T-helper 1 proliferation, which was completely overruled in the presence of T-cell receptor activation. In vivo, hematopoietic TLR5 deficiency attenuated atherosclerotic lesion formation by ≈25% (1030*10³ ± 63*10³ vs. 792*10³ ± 61*10³ μm²; p = 0.013) and decreased macrophage area (81.3 ± 12.0 vs. 44.2 ± 6.6 μm²; p = 0.011). In TLR5^−/− chimeric mice, we observed lower IL6 plasma levels (36.4 ± 5.6 vs. 15.1 ± 2.2 pg/mL; p = 0.003), lower (activated) splenic CD4⁺ T-cell content (32.3 ± 2.1 vs. 21.0 ± 1.2%; p = 0.0018), accompanied by impaired T-cell proliferative responses. In conclusion, hematopoietic TLR5 deficiency inhibits atherosclerotic lesion formation by attenuated macrophage accumulation and defective T-cell responsiveness.

Ulinastatin downregulates TLR4 and NF-kB expression and protects mouse brains against ischemia/reperfusion injury

BACKGROUND

Inflammatory damage plays an important role in ischemic stroke and provides potential targets for therapy. Ulinastatin (UTI), a drug used to treat shock and acute pancreatitis in clinic, has attracted attention for its protective effects through immunomodulatory and anti-inflammatory properties. However, the effect of UTI in the acute phase of cerebral ischemia/reperfusion (I/R) is not clear. This study is to investigate the potential neuroprotective effect of UTI and explore its underlying mechanisms.

METHODS

Male CD-1 mice were subjected to transient middle cerebral artery occlusion (tMCAO) and randomly assigned into four groups: Sham (sham-operated) group, tMCAO (tMCAO + 0.9% saline) group, UTI-L (tMCAO + UTI 1500 U/100 g), and UTI-H (tMCAO + UTI 3000 U/100 g) group. UTI was administered immediately after reperfusion in the UTI-L and UTI-H groups. About 24 h after the reperfusion, the neurological deficit, brain water content, and infarct volume were detected. Immunohistochemistry, western blot and quantitative reverse transcription polymerase chain reaction (qRT-PCR) were used to detect the expression of TLR4 and NF-κB in the ischemic cerebral cortex.

RESULTS

Compared with tMCAO group, both UTI-L and UTI-H groups dramatically ameliorated neurological deficit (p < 0.05), lessened the brain water content (p < 0.05) and infarct volume (p < 0.05), and decreased the expression of TLR4 and NF-κB.

CONCLUSION

These results showed that UTI protected the brain against ischemic injury which may be due to the alleviation of inflammation reaction in early stage through downregulating TLR4 and NF-κB expression.

Swimming Motility Mediates the Formation of Neutrophil Extracellular Traps Induced by Flagellated Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen causing severe infections often characterized by robust neutrophilic infiltration. Neutrophils provide the first line of defense against P. aeruginosa. Aside from their defense conferred by phagocytic activity, neutrophils also release neutrophil extracellular traps (NETs) to immobilize bacteria. Although NET formation is an important antimicrobial process, the details of its mechanism are largely unknown. The identity of the main components of P. aeruginosa responsible for triggering NET formation is unclear. In this study, our focus was to identify the main bacterial factors mediating NET formation and to gain insight into the underlying mechanism. We found that P. aeruginosa in its exponential growth phase promoted strong NET formation in human neutrophils while its NET-inducing ability dramatically decreased at later stages of bacterial growth. We identified the flagellum as the primary component of P. aeruginosa responsible for inducing NET extrusion as flagellum-deficient bacteria remained seriously impaired in triggering NET formation. Purified P. aeruginosa flagellin, the monomeric component of the flagellum, does not stimulate NET formation in human neutrophils. P. aeruginosa-induced NET formation is independent of the flagellum-sensing receptors TLR5 and NLRC4 in both human and mouse neutrophils. Interestingly, we found that flagellar motility, not flagellum binding to neutrophils per se, mediates NET release induced by flagellated bacteria. Immotile, flagellar motor-deficient bacterial strains producing paralyzed flagella did not induce NET formation. Forced contact between immotile P. aeruginosa and neutrophils restored their NET-inducing ability. Both the motAB and motCD genetic loci encoding flagellar motor genes contribute to maximal NET release; however the motCD genes play a more important role. Phagocytosis of P. aeruginosa and superoxide production by neutrophils were also largely dependent upon a functional flagellum. Taken together, the flagellum is herein presented for the first time as the main organelle of planktonic bacteria responsible for mediating NET release. Furthermore, flagellar motility, rather than binding of the flagellum to flagellum-sensing receptors on host cells, is required for P. aeruginosa to induce NET release.

Current Concepts and Controversies in Innate Immunity of Cystic Fibrosis Lung Disease

Cystic fibrosis (CF) lung disease is characterized by chronic infection and inflammation. The inflammatory response in CF is dominated by the activation of the innate immune system. Bacteria and fungi represent the key pathogens chronically colonizing the CF airways. In response, innate immune pattern recognition receptors, expressed by airway epithelial and myeloid cells, sense the microbial threat and release chemoattractants to recruit large numbers of neutrophils into CF airways. However, neutrophils fail to efficiently clear the invading pathogens, but instead release harmful proteases and oxidants and finally cause tissue injury. Here, we summarize and discuss current concepts and controversies in the field of innate immunity in CF lung disease, facing the ongoing questions of whether inflammation is good or bad in CF and how innate immune mechanisms could be harnessed therapeutically.

Toll-Like Receptors in Cystic Fibrosis: Impact of Dysfunctional microRNA on Innate Immune Responses in the Cystic Fibrosis Lung

Toll-like receptors (TLRs) are a class of pattern recognition receptors that are particularly expressed in the sentinel and epithelial cells in the body, including the lung. They are central players in the innate immune system in response to microbial infection, and are the triggers of a complex pathway network that both promotes the inflammatory response and influences the adaptive immune response. These pathways are transiently and finely tuned by cellular factors, including a cell's microRNA response program. MicroRNAs are small, non-coding RNAs that specifically regulate gene expression. In this article, we review the disease-specific microRNA regulatory network of cystic fibrosis, a debilitating and ultimately fatal disease and, specifically, its effect on TLR signalling.

MicroRNA-induced negative regulation of TLR-5 in grass carp, Ctenopharyngodon idella

MicroRNAs (miRNAs) are endogenous small non-coding RNAs that play crucial roles in numerous biological processes. However, the role of miRNAs in antibacterial defence in fish has not been fully determined. Here, we identified that nine miRNAs are differentially expressed in kidney between susceptible and resistant grass carp strains. Analysis of spatial and temporal miRNA expression patterns suggests that cid-miRn-115 and miR-142a-3p are potential regulators of anti-bacterial activity. Overexpressing of cid-miRn-115 and miR-142a-3p results in a visible change in Ctenopharyngodon idella kidney (CIK) cells immune effector activity. Bioinformatics analysis and overexpressing assay shows that cid-miRn-115 and miR-142a-3p directly regulate tlr5 expression. cid-miRn-115 and miR-142a-3p overexpressing leads to a significant decrease in tlr5 expression in CIK, thereby repressing its downstream genes, such as il-1β, il-8 and tnf-α. These findings provide a novel insight into the determination of anti-bacterial compounds in grass carp.

Acetylbritannilactone Modulates MicroRNA-155-Mediated Inflammatory Response in Ischemic Cerebral Tissues

Inflammatory responses play a critical role in ischemic brain injury. MicroRNA-155 (miR-155) induces the expression of inflammatory cytokines, and acetylbritannilactone (ABL) exerts potent antiinflammatory actions by inhibiting expression of inflammation-related genes. However, the functions of miR-155 and the actual relationship between ABL and miR-155 in ischemia-induced cerebral inflammation remain unclear. In this study, cerebral ischemia of wild-type (WT) and miR-155(-/-) mice was induced by permanent middle cerebral artery occlusion (MCAO). pAd-miR-155 was injected into the lateral cerebral ventricle 24 h before MCAO to induce miR-155 overexpression. MCAO mice and oxygen-glucose deprivation (OGD)-treated BV2 cells were used to examine the effects of ABL and miR-155 overexpression or deletion on the expression of proinflammatory cytokines. We demonstrated that ABL treatment significantly reduced neurological deficits and cerebral infarct volume by inhibiting tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) expression in ischemic cerebral tissue and OGD-treated BV2 cells. Mechanistic studies suggested that the observed decrease in TNF-α and IL-1β expression was attributable to the ABL-induced suppression of the expression of nuclear factor-kappa B (NF-κB) and Toll-like receptor 4 (TLR4). We further found that miR-155 promoted TNF-α and IL-1β expression by upregulating TLR4 and downregulating the expression of suppressor of cytokine signaling 1 (SOCS1) and myeloid differentiation primary response gene 88 (MyD88), while ABL exerted an inhibitory effect on miR-155-mediated gene expression. In conclusion, miR-155 mediates inflammatory responses in ischemic cerebral tissue by modulating TLR4/MyD88 and SOCS1 expression, and ABL exerts its antiinflammatory action by suppressing miR-155 expression, suggesting a novel miR-155-based therapy for ischemic stroke.

Secreted phosphoprotein 1 is a determinant of lung function development in mice

Secreted phosphoprotein 1 (Spp1) is located within quantitative trait loci associated with lung function that was previously identified by contrasting C3H/HeJ and JF1/Msf mouse strains that have extremely divergent lung function. JF1/Msf mice with diminished lung function had reduced lung SPP1 transcript and protein during the peak stage of alveologenesis (postnatal day [P]14-P28) as compared with C3H/HeJ mice. In addition to a previously identified genetic variant that altered runt-related transcription factor 2 (RUNX2) binding in the Spp1 promoter, we identified another promoter variant in a putative RUNX2 binding site that increased the DNA protein binding. SPP1 induced dose-dependent mouse lung epithelial-15 cell proliferation. Spp1((-/-)) mice have decreased specific total lung capacity/body weight, higher specific compliance, and increased mean airspace chord length (Lm) compared with Spp1((+/+)) mice. Microarray analysis revealed enriched gene ontogeny categories, with numerous genes associated with lung development and/or respiratory disease. Insulin-like growth factor 1, Hedgehog-interacting protein, wingless-related mouse mammary tumor virus integration site 5A, and NOTCH1 transcripts decreased in the lung of P14 Spp1((-/-)) mice as determined by quantitative RT-PCR analysis. SPP1 promotes pneumocyte growth, and mice lacking SPP1 have smaller, more compliant lungs with enlarged airspace (i.e., increased Lm). Microarray analysis suggests a dysregulation of key lung developmental transcripts in gene-targeted Spp1((-/-)) mice, particularly during the peak phase of alveologenesis. In addition to its known roles in lung disease, this study supports SPP1 as a determinant of lung development in mice.

Disease-modifying genes and monogenic disorders: experience in cystic fibrosis

The mechanisms responsible for the determination of phenotypes are still not well understood; however, it has become apparent that modifier genes must play a considerable role in the phenotypic heterogeneity of Mendelian disorders. Significant advances in genetic technologies and molecular medicine allow huge amounts of information to be generated from individual samples within a reasonable time frame. This review focuses on the role of modifier genes using the example of cystic fibrosis, the most common lethal autosomal recessive disorder in the white population, and discusses the advantages and limitations of candidate gene approaches versus genome-wide association studies. Moreover, the implications of modifier gene research for other monogenic disorders, as well as its significance for diagnostic, prognostic, and therapeutic approaches are summarized. Increasing insight into modifying mechanisms opens up new perspectives, dispelling the idea of genetic disorders being caused by one single gene.

Flagellin concentrations in expectorations from cystic fibrosis patients

Background

The aim was to measure flagellin concentrations in the expectorations of CF patients and to examine whether there are correlations with the level of respiratory insufficiency and inflammation.

Methods

Sputum samples from 31 adult patients chronically colonized with P. aeruginosa were collected and analysed for their content of flagellin and IL-8. Clinical data were extracted from patient files.

Results

Regardless of whether patients are colonized with mucoid strains or not, they carry clones of P. aeruginosa that express flagellin. While flagellin was present in airways of all of our CF patients, it is difficult to ascertain its contribution to inflammation (IL-8) and lung function deterioration.

Conclusions

This is the first demonstration that flagellin is present in the sputum of patients. Thus, attempts to down regulate inflammation by the use of TLR5 (flagellin receptor) antagonists remain a possibility. However, this result needs to be extended to a larger number of patients to validate it for future research on this subject.

Toxoplasma gondii- derived profilin triggers human toll-like receptor 5-dependent cytokine production

Up to a third of the world's population is infected with Toxoplasma gondii. Natural infection in humans can be life threatening during pregnancy and in immunocompromised individuals. Toll-like receptor (TLR) 11 is the mouse innate sensor that recognizes T. gondii profilin; however, in humans the TLR11 gene leads to transcription of no functional protein. Herein, by using a multiple sequence alignment phylogenetic analysis program between human and mouse species, we found that human TLR5 seems to be the evolutionarily closest member of the TLR gene family to mouse tlr11. We therefore asked whether human TLR5 could mediate IL-6, IL-8 and IL-12p70 production in response to the T. gondii profilin. We found that this was the case both in human cell lines as well as peripheral blood monocytes. Moreover, TLR5 neutralization and gene silencing mediated specific ablation of cytokine production after profilin exposure. Finally, peripheral blood monocytes carrying the TLR5 R392X mutation failed to produce cytokines in response to stimulation with profilin. Taken together, the results presented herein reveal a previously unappreciated cross-recognition of a relevant human pathogen-derived pathogen-associated molecular pattern.

Lung disease modifier genes in cystic fibrosis

Cystic fibrosis (CF) is recognized as a single gene disorder. However, a considerable diversity in its clinical phenotype has been documented since the description of the disease. Identification of additional gene alleles, so called "modifier genes" that directly influence the phenotype of CF disease became a challenge in the late '90ies, not only for the insight it provides into the CF pathophysiology, but also for the development of new potential therapeutic targets. One of the most studied phenotype has been the lung disease severity as lung dysfunction is the major cause of morbidity and mortality in CF. This review details the results of two main genetic approaches that have mainly been explored so far: (1) an "a priori" approach, i.e. the candidate gene approach; (2) a "without a priori" approach, analyzing the whole genome by linkage and genome-wide association studies (GWAS), or the whole exome by exome sequencing.

Phagocytic and signaling innate immune receptors: are they dysregulated in cystic fibrosis in the fight against Pseudomonas aeruginosa?

Cystic fibrosis (CF) is a genetic disease that affects mainly the lung and the digestive system, causing progressive disability and organ failure. The most prevalent CFTR mutation dF508 (which constitutes 70% of all mutations) results in an incorrect targeting of the CFTR molecule to the membrane. It is now a well-accepted concept that mucosal innate immune responses are dysregulated in cystic fibrosis through a cycle of infectious and inflammatory episodes. However, although much work has focused on the late consequences of chronic lung inflammation in CF, very little is known on the early events leading to infection and colonization, such as that of Pseudomonas aeruginosa (P.a). We review here the involvement of a range of innate phagocytic/signaling receptors in the control of this pathogen (mannose receptor, complement receptor-3, Toll-like receptors, etc.) and evaluate the possibility that the activity of some of these receptors may be dysregulated in cystic fibrosis, potentially explaining the florid infections encountered in this disease.

Current concepts of immune dysregulation in cystic fibrosis

Cystic fibrosis (CF) lung disease is caused by mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene and is characterized by a perpetuated feedback loop of bacterial infection and inflammation. Both intrinsic (CFTR-dependent) and extrinsic (CFTR-independent) mechanisms contribute to the inflammatory phenotype of CF lung disease. Innate immune cells, initially recruited to combat bacterial pathogens, are acting in a dysregulated and non-resolving fashion in CF airways and cause harm to the host by releasing proteases and oxidants. Targeting harmful immune pathways, while preserving protective ones, remains the challenge for the future. This review highlights current concepts of innate immune dysregulation in CF lung disease.

Unbiased screening of marine sponge extracts for anti-inflammatory agents combined with chemical genomics identifies girolline as an inhibitor of protein synthesis

Toll-like receptors (TLRs) play a critical role in innate immunity, but activation of TLR signaling pathways is also associated with many harmful inflammatory diseases. Identification of novel anti-inflammatory molecules targeting TLR signaling pathways is central to the development of new treatment approaches for acute and chronic inflammation. We performed high-throughput screening from crude marine sponge extracts on TLR5 signaling and identified girolline. We demonstrated that girolline inhibits signaling through both MyD88-dependent and -independent TLRs (i.e., TLR2, 3, 4, 5, and 7) and reduces cytokine (IL-6 and IL-8) production in human peripheral blood mononuclear cells and macrophages. Using a chemical genomics approach, we identified Elongation Factor 2 as the molecular target of girolline, which inhibits protein synthesis at the elongation step. Together these data identify the sponge natural product girolline as a potential anti-inflammatory agent acting through inhibition of protein synthesis.

Functional characterisation of bovine TLR5 indicates species-specific recognition of flagellin

Mammalian toll-like receptor 5 (TLR5) senses flagellin of several bacterial species and has been described to activate the innate immune system. To assess the role of bovine TLR5 (boTLR5) in the cattle system, we cloned and successfully expressed boTLR5 in human embryonic kidney (HEK) 293 cells, as indicated by quantitative PCR and confocal microscopy. However, in contrast to huTLR5-transfected cells, exposure of boTLR5-transfected cells to flagellin neither activated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) nor CXCL8 production. Subsequent comparison of the flagellin response induced in human and bovine primary macrophages revealed that flagellin did not lead to phosphorylation of major signalling molecules. Furthermore, the CXCL8 and TNFα response of primary bovine macrophages stimulated with flagellin was very low compared to that observed in human primary macrophages. Our results indicate that cattle express a functional TLR5 albeit with different flagellin sensing qualities compared to human TLR5. However, boTLR5 seemed to play a different role in the bovine system compared to the human system in recognizing flagellin, and other potentially intracellular expressed receptors may play a more important role in the bovine system to detect flagellin.

Secretome of transmissible Pseudomonas aeruginosa AES-1R grown in a cystic fibrosis lung-like environment

Pseudomonas aeruginosa is the predominant cause of mortality in patients with cystic fibrosis (CF). We examined the secretome of an acute, transmissible CF P. aeruginosa (Australian epidemic strain 1-R; AES-1R) compared with laboratory-adapted PAO1. Culture supernatant proteins from rich (LB) and minimal (M9) media were compared using 2-DE and 2DLC-MS/MS, which revealed elevated abundance of PasP protease and absence of AprA protease in AES-1R. CF lung-like artificial sputum medium (ASMDM) contains serum and mucin that generally preclude proteomics of secreted proteins. ASMDM culture supernatants were subjected to 2DLC-MS/MS, which allowed the identification of 57 P. aeruginosa proteins, and qualitative spectral counting was used to estimate relative abundance. AES-1R-specific AES_7139 and PasP were more abundant in AES-1R ASMDM culture supernatants, while AprA could only be identified in PAO1. Relative quantitation was performed using selected reaction monitoring. Significantly elevated levels of PasP, LasB, chitin-binding protein (CbpD), and PA4495 were identified in AES-1R ASMDM supernatants. Quantitative PCR showed elevated pasP in AES-1R during early (18 h) ASMDM growth, while no evidence of aprA expression could be observed. Genomic screening of CF isolates revealed aes_7139 was present in all AES-1 and one pair of sequential nonepidemic isolates. Secreted proteins may be crucial in aiding CF-associated P. aeruginosa to establish infection and for adaptation to the CF lung.

Genetic variations in toll-like receptor pathway and lung function decline in Cystic fibrosis patients

The toll-like receptor (TLR) family maintains pulmonary homeostasis by pathogen recognition, clearance and regulation of inflammation. Genes affecting inflammation response play a key role in modifying Cystic fibrosis (CF) lung disease severity. We assessed the impact of single nucleotide polymorphisms (SNPs) of TLR genes (TLR1 to TLR10, CD14, lipopolyssacharide-binding protein (LBP)) on lung function in CF patients. Each SNP was tested for time-dependent effect on FEV1, using six genetic models. In addition, we investigated associations between SNP genotypes and extreme subject specific slopes of FEV1 decline. Variant alleles of polymorphisms of TLR2 rs1898830, rs5743708, and rs3804100 demonstrated a consistent association with lung disease severity (p = 0.008, p = 0.006 and p = 0.029 respectively). Patients homozygous for variant C allele of TLR5 polymorphism rs5744174 are more frequently associated with extreme fast FEV1 decline (OR: 20 (95% Confidence Interval:1.85-216.18)). Patients homozygous AA for TLR1 polymorphism rs5743551 are more frequently associated with faster decline of FEV1 compared to heterozygous genotype (OR:7.33 (95% CI:1.63-33.11). Our findings indicate that variations in TLR1, TLR2 and TLR5 genes may influence CF lung function decline. Further functional analysis is required to provide new insights into the pathogenesis of TLRs in CF lung disease severity.

Genetic influences on cystic fibrosis lung disease severity

Understanding the causes of variation in clinical manifestations of disease should allow for design of new or improved therapeutic strategies to treat the disease. If variation is caused by genetic differences between individuals, identifying the genes involved should present therapeutic targets, either in the proteins encoded by those genes or the pathways in which they function. The technology to identify and genotype the millions of variants present in the human genome has evolved rapidly over the past two decades. Originally only a small number of polymorphisms in a small number of subjects could be studied realistically, but speed and scope have increased nearly as dramatically as cost has decreased, making it feasible to determine genotypes of hundreds of thousands of polymorphisms in thousands of subjects. The use of such genetic technology has been applied to cystic fibrosis (CF) to identify genetic variation that alters the outcome of this single gene disorder. Candidate gene strategies to identify these variants, referred to as “modifier genes,” has yielded several genes that act in pathways known to be important in CF and for these the clinical implications are relatively clear. More recently, whole-genome surveys that probe hundreds of thousands of variants have been carried out and have identified genes and chromosomal regions for which a role in CF is not at all clear. Identification of these genes is exciting, as it provides the possibility for new areas of therapeutic development.

Impaired TLR5 functionality is associated with survival in melioidosis

Melioidosis is infection caused by the flagellated saprophyte Burkholderia pseudomallei. TLR5 is a pathogen recognition receptor activated by bacterial flagellin. We studied a genetic variant that encodes a defective TLR5 protein, TLR5(1174C)>T, to elucidate the role of TLR5 in melioidosis. We measured NF-κB activation induced by B. pseudomallei in human embryonic kidney-293 cells transfected with TLR5 and found that B. pseudomallei induced TLR5(1174C)- but not TLR5(1174T)-dependent activation of NF-κB. We tested the association of TLR5(1174C)>T with outcome in 600 Thai subjects with melioidosis. In a dominant model, TLR5(1174C)>T was associated with protection against in-hospital death (adjusted odds ratio: 0.20; 95% confidence interval: 0.08-0.50; p = 0.001) and organ failure (adjusted odds ratio: 0.37; 95% confidence interval: 0.19-0.71; p = 0.003). We analyzed blood cytokine production induced by flagellin or heat-killed B. pseudomallei by TLR5(1174C)>T genotype in healthy subjects. Flagellin induced lower monocyte-normalized levels of IL-6, IL-8, TNF-α, IL-10, MCP-1, IL-1ra, G-CSF, and IL-1β in carriers of TLR5(1174T) compared with carriers of TLR5(1174C). B. pseudomallei induced lower monocyte-normalized levels of IL-10 in carriers of TLR5(1174T). We conclude that the hypofunctional genetic variant TLR5(1174C)>T is associated with reduced organ failure and improved survival in melioidosis. This conclusion suggests a deleterious immunoregulatory effect of TLR5 that may be mediated by IL-10 and identifies this receptor as a potential therapeutic target in melioidosis.

How the airway smooth muscle in cystic fibrosis reacts in proinflammatory conditions: implications for airway hyper-responsiveness and asthma in cystic fibrosis

Among patients with cystic fibrosis there is a high prevalence (40-70%) of asthma signs and symptoms such as cough and wheezing and airway hyper-responsiveness to inhaled histamine or methacholine. Whether these abnormal airway responses are due to a primary deficiency in the cystic fibrosis transmembrane conductance regulator (CFTR) or are secondary to the inflammatory environment in the cystic fibrosis lungs is not clear. A role for the CFTR in smooth muscle function is emerging, and alterations in contractile signalling have been reported in CFTR-deficient airway smooth muscle. Persistent bacterial infection, especially with Pseudomonas aeruginosa, stimulates interleukin-8 release from the airway epithelium, resulting in neutrophilic inflammation. Increased neutrophilia and skewing of CFTR-deficient T-helper cells to type 2 helper T cells creates an inflammatory environment characterised by high concentrations of tumour necrosis factor α, interleukin-8, and interleukin-13, which might all contribute to increased contractility of airway smooth muscle in cystic fibrosis. An emerging role of interleukin-17, which is raised in patients with cystic fibrosis, in airway smooth muscle proliferation and hyper-responsiveness is apparent. Increased understanding of the molecular mechanisms responsible for the altered smooth muscle physiology in patients with cystic fibrosis might provide insight into airway dysfunction in this disease.

Atypical activation of the unfolded protein response in cystic fibrosis airway cells contributes to p38 MAPK-mediated innate immune responses

Inflammatory lung disease is the major cause of morbidity and mortality in cystic fibrosis (CF); understanding what produces dysregulated innate immune responses in CF cells will be pivotal in guiding the development of novel anti-inflammatory therapies. To elucidate the molecular mechanisms that mediate exaggerated inflammation in CF following TLR signaling, we profiled global gene expression in immortalized human CF and non-CF airway cells at baseline and after microbial stimulation. Using complementary analysis methods, we observed a signature of increased stress levels in CF cells, specifically characterized by endoplasmic reticulum (ER) stress, the unfolded protein response (UPR), and MAPK signaling. Analysis of ER stress responses revealed an atypical induction of the UPR, characterized by the lack of induction of the PERK-eIF2α pathway in three complementary model systems: immortalized CF airway cells, fresh CF blood cells, and CF lung tissue. This atypical pattern of UPR activation was associated with the hyperinflammatory phenotype in CF cells, as deliberate induction of the PERK-eIF2α pathway with salubrinal attenuated the inflammatory response to both flagellin and Pseudomonas aeruginosa. IL-6 production triggered by ER stress and microbial stimulation were both dependent on p38 MAPK activity, suggesting a molecular link between both signaling events. These data indicate that atypical UPR activation fails to resolve the ER stress in CF and sensitizes the innate immune system to respond more vigorously to microbial challenge. Strategies to restore ER homeostasis and normalize the UPR activation profile may represent a novel therapeutic approach to minimize lung-damaging inflammation in CF.

Innate immunity in cystic fibrosis lung disease

Chronic lung disease determines the morbidity and mortality of cystic fibrosis (CF) patients. The pulmonary immune response in CF is characterized by an early and non-resolving activation of the innate immune system, which is dysregulated at several levels. Here we provide a comprehensive overview of innate immunity in CF lung disease, involving (i) epithelial dysfunction, (ii) pathogen sensing, (iii) leukocyte recruitment, (iv) phagocyte impairment, (v) mechanisms linking innate and adaptive immunity and (iv) the potential clinical relevance. Dissecting the complex network of innate immune regulation and associated pro-inflammatory cascades in CF lung disease may pave the way for novel immune-targeted therapies in CF and other chronic infective lung diseases.

In vitro and in vivo properties of a fully human IgG1 monoclonal antibody that combats multidrug resistant Pseudomonas aeruginosa

The development of an anti-bacterial drug in the form of a monoclonal antibody (mAb) targeting an exposed virulence factor, represents an innovative therapeutic strategy. Consequently, a fully human IgG1 mAb (LST-007) targeting Pseudomonas aeruginosa (PA) flagellin type b was recombinantly expressed and characterized in vitro and in an infection model driven by a multidrug resistant (MDR) PA strain. LST-007 demonstrated a highly specific binding towards whole PA bacteria harboring flagellin type b and its recombinant counterpart, with a K(D) of 7.4x10(-10) M. In bioactivity assays, LST-007 or titers of Cmax sera derived from pharmacokinetic studies, markedly attenuated PA motility in an equipotent manner. In vivo, parenteral LST-007 (20 mg/kg) given as a single or double-dosing paradigm post-infection, afforded survival (up to 75% at Day 7) in a lethal model of pneumonia driven by the intratracheal (i.t.) instillation of an LD(80) of the MDR PA isolate. This protective effect was markedly superior to that of imipenem (30% survival at Day 7) and totally devoid with an irrelevant, human isotype mAb. These data lay credence that LST-007 may be a valuable adjunct to the limited list of anti-bacterials that can tackle MDR PA strains, thereby warranting its continued development for eventual clinical evaluation.

Inflammasome-mediated IL-1β production in humans with cystic fibrosis

BACKGROUND

Inflammation and infection are major determinants of disease severity and consequently, the quality of life and outcome for patients with cystic fibrosis (CF). Interleukin-1 beta (IL-1β) is a key inflammatory mediator. Secretion of biologically active IL-1β involves inflammasome-mediated processing. Little is known about the contribution of IL-1β and the inflammasomes in CF inflammatory disease. This study examines inflammasome-mediated IL-1β production in CF bronchial epithelial cell lines and human patients with CF.

RESULTS

Bronchial epithelial cell lines were found to produce negligible amounts of basal or stimulated IL-1β compared to hematopoeitic cells and they did not significantly upregulate caspase-1 activity upon inflammasome stimulation. In contrast, peripheral blood mononuclear cells (PBMCs) from both CF and healthy control subjects produced large amounts of IL-1β and strongly upregulated caspase-1 activity upon inflammasome stimulation. PBMCs from CF patients and controls displayed similar levels of caspase-1 activation and IL-1β production when stimulated with inflammasome activators. This IL-1β production was dependent on NF-κB activity and could be enhanced by priming with LPS. Finally, chemical inhibition of CFTR activity in control PBMCs and THP-1 cells did not significantly alter IL-1β or IL-8 production in response to P. aeruginosa.

CONCLUSION

Hematopoeitic cells appear to be the predominant source of inflammasome-induced pro-inflammatory IL-1β in CF. PBMCs derived from CF subjects display preserved inflammasome activation and IL-1β secretion in response to the major CF pathogen Pseudomonas aeruginosa. However, our data do not support the hypothesis that increased IL-1β production in CF subjects is due to an intrinsic increase in NF-κB activity through loss of CFTR function.

Recent advances in cystic fibrosis

Cystic fibrosis (CF) is an inherited chronic disease that remains a common cause of morbidity and mortality in affected patients, mostly in the young. A wealth of knowledge has been gained into the genetics, pathophysiology, and clinical manifestation of the disease. In parallel with these new insights into the disease, novel treatments have been developed or are under development that have had a major impact on quality of life and survival. Improvement in the delivery of care to patients in CF centers, using a team-based approach, and constant review of process, and by quality improvement projects, have also had an impact on outcomes in CF.

Luteolin downregulates TLR4, TLR5, NF-κB and p-p38MAPK expression, upregulates the p-ERK expression, and protects rat brains against focal ischemia

BACKGROUND

Inflammatory damage is known to be involved in ischemic stroke. Luteolin has been proved to elicit a series of biologic effects through its anti-inflammatory property in multiple sclerosis and rheumatoid arthritis. Whether this protective effect applies to ischemic injury in brain is still unknown, we therefore investigate the potential neuroprotective role of luteolin in ischemic stroke and the underlying mechanisms.

METHODS

Male Sprague-Dawley rats were subjected to pMCAO and luteolin was administered intraperitoneally immediately after surgery, then once daily thereafter. Neurological deficit, infarct volume, and brain water content were measured at 24 h and 72 h after stroke. The expression of TLR4, TLR5, and NF-κB were measured by real-time PCR, immunohistochemical staining (IHC), and Western blot. P38MAPK and extracellular signal-regulated kinase (ERK) were detected by IHC, and Western blot.

RESULTS

Compared with pMCAO group, luteolin significantly alleviated neurological deficit, decreased infarct volume and suppressed edema after ischemic stroke, which were accompanied with decreased expression of TLR4, TLR5, NF-κB and p-p38MAPK. Meanwhile, luteolin activated the expression of p-ERK1/2 (P<0.05).

CONCLUSIONS

Luteolin protected the brain from the damage caused by pMCAO, and this effect may be through downregulation of TLR4, TLR5, NF-κB, p38MAPK and upregulation of ERK expression.