Synergistic and feedback signaling mechanisms in the regulation of inflammation in respiratory infections

Therapeutic effect of Yinhuapinggan granules mediated through the intestinal flora in mice infected with the H1N1 influenza virus

Objective

In this study, we examined the therapeutic effects of Yinhuapinggan granules (YHPGs) in influenza-infected mice. We also examined how YHPGs affect the composition of the intestinal flora and associated metabolites.

Methods

We used the nasal drip method to administer the influenza A virus (IAV) H1N1 to ICR mice. Following successful model construction, the mice were injected with 0.9% sterile saline and low (5.5 g/kg), medium (11 g/kg), and high (22 g/kg) doses of YHPGs. The pathological changes in the lungs and intestines were evaluated by gavage for 5 consecutive days. Detection of sIgA, IL-6, TNF-α, INF-γ, and TGF-β cytokine levels in serum by enzyme-linked immunosorbent assay. Real-time fluorescence quantitative polymerase chain reaction and Western blot were used to measure the mRNA and protein expression of the tight junction proteins claudin-1, occludin, and zonula occludens-1 (ZO-1) in the colon. To assess the influence of YHPGs on the intestinal microbiota, feces were obtained from the mice for 16s rRNA sequencing, and short-chain fatty acids (SCFAs) were measured in the feces.

Results

By reducing the production of pro-inflammatory cytokines and increasing the relative expression of claudin-1, occludin, and ZO-1 in colon tissues, YHPGs had a protective effect in tissues from the lungs and colon. When YHPGs were administered to mice with IAV infection, the relative abundance of Lactobacillus, Coprobacillus, Akkermansia, Prevotella, Oscillospira, and Ruminococcus increased, whereas the relative abundance of Desulfovibrio decreased.

Conclusion

The therapeutic mechanism of YHPGs against IAV infection in mice may be underpinned by modulation of the structural composition of colonic bacteria and regulation of SCFA production.

VISTA Stimulation of VSIG4-Positive Macrophages Strongly Suppresses T Cell Proliferation via Excessive Nitric Oxide Production in Sepsis

Organ damage and immune deficiency are important problems in sepsis caused by an excessive immune response. There is controversy about the cause of immune suppression. In this study, we investigated the roles of macrophages that exhibit excessive activity on T cell immunity. Peritoneal macrophages from mice with cecal ligation and puncture (CLP)-induced sepsis migrated to different organs. In particular, V-set immunoglobulin (Ig)-domain-containing 4 (VSIG4) positive macrophages appeared in the spleen 48 h after CLP induction. When cocultured with splenic T cells, VSIG4(+) cells inhibited the proliferation of activated T cells through the release of nitric oxide (NO) compared to VSIG4(-) cells. Stimulation of VSIG4(+) cells with V-domain Ig suppressor of T cell activation (VISTA) antibody increased the expression of several cytokine genes and the release of NO, but not phagocytosis, compared to those of hamster IgG-stimulated VSIG4(+) cells. When cocultured with splenic T cells, VISTA-stimulated VSIG4(+) cells induced excessive T cell suppression via more NO secretion compared to hamster IgG-stimulated VSIG4(+) cells. Taken together, the current study demonstrates that VSIG4(+) peritoneal macrophages play important roles in inducing immunosuppression and that VISTA acts as a costimulatory receptor in these cells. These data suggest that blocking the migration of VSIG4(+) cells might alleviate excessive immune activity and that blocking VISTA on VSIG4(+) macrophages might play a crucial role in the development of new therapies to prevent T cell suppression in sepsis.

Vinpocetine Suppresses Streptococcus pneumoniae-Induced Inflammation via Inhibition of ERK1 by CYLD

Otitis media (OM) is the most common bacterial infection in children. It remains a major health problem and a substantial socioeconomic burden. Streptococcus pneumoniae (S. pneumoniae) is one of the most common bacterial pathogens causing OM. Innate inflammatory response plays a critical role in host defense against bacterial pathogens. However, if excessive, it has a detrimental impact on the middle ear, leading to middle ear inflammation, a hallmark of OM. Currently, there has been limited success in developing effective therapeutic agents to suppress inflammation without serious side effects. In this study, we show that vinpocetine, an antistroke drug, suppressed S. pneumoniae-induced inflammatory response in cultured middle ear epithelial cells as well as in the middle ear of mice. Interestingly, vinpocetine inhibited S. pneumoniae-induced inflammation via upregulating a key negative regulator cylindromatosis (CYLD). Moreover, CYLD suppressed S. pneumoniae-induced inflammation via inhibiting the activation of ERK. Importantly, the postinfection administration of vinpocetine markedly inhibited middle ear inflammation induced by S. pneumoniae in a well-established mouse OM model. These studies provide insights into the molecular mechanisms underlying the tight regulation of inflammation via inhibition of ERK by CYLD and identified vinpocetine as a potential therapeutic agent for suppressing the inflammatory response in the pathogenesis of OM via upregulating negative regulator CYLD expression.

miR‑197‑3p‑induced downregulation of lysine 63 deubiquitinase promotes cell proliferation and inhibits cell apoptosis in lung adenocarcinoma cell lines

Lung adenocarcinoma (LUAD) is a common cause of cancer-associated mortality. The dysregulation of microRNA (miR) expression has been reported to induce lung carcinogenesis. In the present study, miR-197-3p upregulation was detected within LUAD tissues compared with in adjacent noncancerous tissues. The suppression of miR-197-3p expression was confirmed to inhibit proliferative ability and induce apoptosis of LUAD cell lines; miR-197-3p overexpression within the HBE cell line exhibited opposing effects. Via in silico modeling, western blot analyses and dual-luciferase assays, it was confirmed that miR-197-3p directly targets the lysine 63 deubiquitinase (CYLD) gene. In the present study, the expression of miR-197-3p was negatively associated with CYLD mRNA expression within LUAD cell lines. In conclusion, the findings of the present study have provided novel insight into the association of miR-197-3p with LUAD proliferation and apoptotic regulation; the miR-197-3p/CYLD axis may serve as a novel potential therapeutic target for the treatment of LUAD.

Resveratrol therapeutics combines both antimicrobial and immunomodulatory properties against respiratory infection by nontypeable Haemophilus influenzae

The respiratory pathogen nontypeable Haemophilus influenzae (NTHi) is an important cause of acute exacerbation of chronic obstructive pulmonary disease (AECOPD) that requires efficient treatments. A previous screening for host genes differentially expressed upon NTHi infection identified sirtuin-1, which encodes a NAD-dependent deacetylase protective against emphysema and is activated by resveratrol. This polyphenol concomitantly reduces NTHi viability, therefore highlighting its therapeutic potential against NTHi infection at the COPD airway. In this study, resveratrol antimicrobial effect on NTHi was shown to be bacteriostatic and did not induce resistance development in vitro. Analysis of modulatory properties on the NTHi-host airway epithelial interplay showed that resveratrol modulates bacterial invasion but not subcellular location, reduces inflammation without targeting phosphodiesterase 4B gene expression, and dampens β defensin-2 gene expression in infected cells. Moreover, resveratrol therapeutics against NTHi was evaluated in vivo on mouse respiratory and zebrafish septicemia infection model systems, showing to decrease NTHi viability in a dose-dependent manner and reduce airway inflammation upon infection, and to have a significant bacterial clearing effect without signs of host toxicity, respectively. This study presents resveratrol as a therapeutic of particular translational significance due to the attractiveness of targeting both infection and overactive inflammation at the COPD airway.

In the Shadow of Fibrosis: Innate Immune Suppression Mediated by Transforming Growth Factor-β

Transforming growth factor-β (TGFB) regulates cell proliferation, differentiation, apoptosis, and matrix homeostasis and is intimately involved in fibrosis. TGFB expression is increased in fibrotic lung diseases, such as idiopathic pulmonary fibrosis, and in chronic inflammatory conditions, such as chronic obstructive pulmonary disease and asthma. In addition to exhibiting profibrotic activities, the protein exhibits profound immune-suppressive actions involving both innate and adaptive responses, but often this aspect of TGFB biology is overlooked. Recent investigations have demonstrated that TGFB causes wide-ranging immune suppression, including blunting of pivotal early innate IFN responses. These activities permit severe virus infections, often followed by secondary bacterial infections, which may last longer, with augmented inflammation, scarring, fibrosis, and loss of lung function. Strategies to oppose TGFB actions or to enhance IFN responses may help ameliorate the detrimental consequences of infection in patients with diseases characterized by TGFB overexpression, inflammation, and fibrosis.

Mechanisms of corticosteroid insensitivity in COPD alveolar macrophages exposed to NTHi

Background

Non-typeable Haemophilus influenza (NTHi) infection is common in COPD. Corticosteroids can have limited therapeutic effects in COPD patients. NTHi causes corticosteroid insensitive cytokine production from COPD alveolar macrophages. We investigated the mechanisms by which NTHi causes corticosteroid insensitive inflammatory responses, and the effects of NTHi exposure on COPD macrophage polarisation.

Method

Alveolar macrophages from COPD patients and controls were exposed to NTHi in conjunction with the corticosteroid dexamethasone and/or the p38 MAPK inhibitor BIRB-796. Cytokine release, GR phosphorylation and modulation and macrophage phenotype were analysed.

Results

Dexamethasone significantly inhibited NTHi induced TNF-α, IL-6 and IL-10 from COPD macrophages but, CXCL8 was not suppressed.

BIRB-796 combined with dexamethasone caused significantly greater inhibition of all cytokines than either drug alone (p < 0.05 all comparisons). NTHi caused phosphorylation of GR S226 reducing GR nuclear localisation, an effect regulated by p38 MAPK. NTHi altered macrophage polarisation by increasing IL-10 and decreasing CD36, CD206, CD163 and HLA-DR.

Conclusion

NTHi exposure causes p38 MAPK dependent GR phosphorylation associated with decreased GR function in COPD alveolar macrophages. Combining a p38 MAPK inhibitor with corticosteroids can enhance anti-inflammatory effects during NTHi exposure of COPD alveolar macrophages. NTHi causes macrophage polarisation that favours bacterial persistence.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-017-0539-4) contains supplementary material, which is available to authorized users.

A recombinant TGF-β1 vaccine ameliorates diabetic nephropathy in OLETF rats

AIM

The aim of this study was to investigate the potential of a recombinant vaccine encoding TGF-β1 in OLETF rats with diabetic nephropathy (DN).

METHODS

OLETF rats were treated with vehicle or TGF-β1 vaccine. LETO rats were used as normal controls. At 42 weeks after immunization with vaccine, samples from blood, urine and kidney were collected for biochemical, histologic, immunohistochemical and molecular analyses.

RESULTS

OLETF rats treated with the vaccine reduced blood glucose levels, improved renal pathological changes, and inhibited overexpression of TGF-β1 and p-Smad3, as well as MCP-1, TNF-α and IL-1β.

CONCLUSION

TGF-β1 vaccine attenuated diabetic nephropathy in OLETF rats through reduction of inflammation, improvement of kidney fibrosis and partial correction of glucose metabolism.

Local Epidermal Growth Factor Receptor Signaling Mediates the Systemic Pathogenic Effects of Staphylococcus aureus Toxic Shock Syndrome

Secreted factors of Staphylococcus aureus can activate host signaling from the epidermal growth factor receptor (EGFR). The superantigen toxic shock syndrome toxin-1 (TSST-1) contributes to mucosal cytokine production through a disintegrin and metalloproteinase (ADAM)-mediated shedding of EGFR ligands and subsequent EGFR activation. The secreted hemolysin, α-toxin, can also induce EGFR signaling and directly interacts with ADAM10, a sheddase of EGFR ligands. The current work explores the role of EGFR signaling in menstrual toxic shock syndrome (mTSS), a disease mediated by TSST-1. The data presented show that TSST-1 and α-toxin induce ADAM- and EGFR-dependent cytokine production from human vaginal epithelial cells. TSST-1 and α-toxin also induce cytokine production from an ex vivo porcine vaginal mucosa (PVM) model. EGFR signaling is responsible for the majority of IL-8 production from PVM in response to secreted toxins and live S. aureus. Finally, data are presented demonstrating that inhibition of EGFR signaling with the EGFR-specific tyrosine kinase inhibitor AG1478 significantly increases survival in a rabbit model of mTSS. These data indicate that EGFR signaling is critical for progression of an S. aureus exotoxin-mediated disease and may represent an attractive host target for therapeutics.

Association of sputum microbiota profiles with severity of community-acquired pneumonia in children

BACKGROUND

Competitive interactions among bacteria in the respiratory tract microbiota influence which species can colonize and potentially contribute to pathogenesis of community-acquired pneumonia (CAP). However, understanding of the role of respiratory tract microbiota in the clinical course of pediatric CAP is limited.

METHODS

We sought to compare microbiota profiles in induced sputum and nasopharyngeal/oropharyngeal (NP/OP) samples from children and to identify microbiota profiles associated with CAP severity. We used 16S ribosomal RNA sequencing and several measures of microbiota profiles, including principal component analysis (PCA), to describe the respiratory microbiota in 383 children, 6 months to <18 years, hospitalized with CAP. We examined associations between induced sputum and NP/OP microbiota profiles and CAP severity (hospital length of stay and intensive care unit admission) using logistic regression.

RESULTS

Relative abundance of bacterial taxa differed in induced sputum and NP/OP samples. In children 6 months to < 5 years, the sputum PCA factor with high relative abundance of Actinomyces, Veillonella, Rothia, and Lactobacillales was associated with decreased odds of length of stay ≥ 4 days [adjusted odds ratio (aOR) 0.69; 95 % confidence interval (CI) 0.48-0.99]. The sputum factor with high relative abundance of Haemophilus and Pasteurellaceae was associated with increased odds of intensive care unit admission [aOR 1.52; 95 % CI 1.02-2.26]. In children 5 to < 18 years, the sputum factor with high relative abundance of Porphyromonadaceae, Bacteriodales, Lactobacillales, and Prevotella was associated with increased odds of length of stay ≥ 4 days [aOR 1.52; 95 % CI 1.02-2.26]. Taxa in NP/OP samples were not associated with CAP severity.

CONCLUSION

Certain taxa in the respiratory microbiota, which were detected in induced sputum samples, are associated with the clinical course of CAP.

Serum Cytokine Responses over the Entire Clinical-Immunological Spectrum of Human Leishmania (L.) infantum chagasi Infection

The clinical-immunological spectrum of human Leishmania (L.) infantum chagasi infection in Amazonian Brazil was recently reviewed based on clinical, DTH, and IFAT (IgG) evaluations that identified five profiles: three asymptomatic (asymptomatic infection, AI; subclinical resistant infection, SRI; and indeterminate initial infection, III) and two symptomatic (symptomatic infection, SI; American visceral leishmaniasis, AVL; and subclinical oligosymptomatic infection, SOI). TNF-α, IL-4, IL-6, and IL-10 serum cytokines were analyzed using multiplexed Cytometric Bead Array in 161 samples from endemic areas in the Brazilian Amazon: SI [AVL] (21 cases), III (49), SRI (19), SOI (12), AI (36), and a control group [CG] (24). The highest IL-6 serum levels were observed in the SI profile (AVL); higher IL-10 serum levels were observed in SI than in SOI or CG and in AI and III than in SOI; higher TNF-α serum levels were seen in SI than in CG. Positive correlations were found between IL-6 and IL-10 serum levels in the SI and III profiles and between IL-6 and TNF-α and between IL-4 and TNF-α in the III profile. These results provide strong evidence for associating IL-6 and IL-10 with the immunopathogenesis of AVL and help clarify the role of these cytokines in the infection spectrum.

Downregulation of miR-362-5p inhibits proliferation, migration and invasion of human breast cancer MCF7 cells

An increasing number of studies have indicated that the deregulation of microRNAs (miRNAs) contributes to tumorigenesis and metastasis. In the present study, significant upregulation of miR-362-5p was identified in the breast cancer MDA-MB-231 and MCF7 cell lines compared with the control CCD-1095Sk cell line. The inhibition of miR-362-5p was demonstrated to significantly inhibit the cell proliferation, migration and invasion of human breast cancer MCF7 cells. In addition, the knockdown of miR-362-5p induced G1 arrest and promoted apoptosis in the breast cancer cells. Mechanistic investigations confirmed that the tumor suppressor gene CYLD is a direct target of miR-362-5p. The ectopic expression of miR-362-5p represses CYLD expression, whereas miR-362-5p inhibitor treatment induces CYLD protein expression and decreases NF-κB expression in the downstream signaling pathway. Thus, these findings may provide novel insights into the molecular mechanisms through which miR-362-5p regulates breast cancer cell proliferation, migration and invasion. This study also suggests that miR-362-5p may act as a novel potential therapeutic target for the treatment of breast cancer.

Genome Expression Profiling-Based Identification and Administration Efficacy of Host-Directed Antimicrobial Drugs against Respiratory Infection by Nontypeable Haemophilus influenzae

Therapies that are safe, effective, and not vulnerable to developing resistance are highly desirable to counteract bacterial infections. Host-directed therapeutics is an antimicrobial approach alternative to conventional antibiotics based on perturbing host pathways subverted by pathogens during their life cycle by using host-directed drugs. In this study, we identified and evaluated the efficacy of a panel of host-directed drugs against respiratory infection by nontypeable Haemophilus influenzae (NTHi). NTHi is an opportunistic pathogen that is an important cause of exacerbation of chronic obstructive pulmonary disease (COPD). We screened for host genes differentially expressed upon infection by the clinical isolate NTHi375 by analyzing cell whole-genome expression profiling and identified a repertoire of host target candidates that were pharmacologically modulated. Based on the proposed relationship between NTHi intracellular location and persistence, we hypothesized that drugs perturbing host pathways used by NTHi to enter epithelial cells could have antimicrobial potential against NTHi infection. Interfering drugs were tested for their effects on bacterial and cellular viability, on NTHi-epithelial cell interplay, and on mouse pulmonary infection. Glucocorticoids and statins lacked in vitro and/or in vivo efficacy. Conversely, the sirtuin-1 activator resveratrol showed a bactericidal effect against NTHi, and the PDE4 inhibitor rolipram showed therapeutic efficacy by lowering NTHi375 counts intracellularly and in the lungs of infected mice. PDE4 inhibition is currently prescribed in COPD, and resveratrol is an attractive geroprotector for COPD treatment. Together, these results expand our knowledge of NTHi-triggered host subversion and frame the antimicrobial potential of rolipram and resveratrol against NTHi respiratory infection.

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.

Modular Transcriptional Networks of the Host Pulmonary Response during Early and Late Pneumococcal Pneumonia

Streptococcus pneumoniae (Spneu) remains the most lethal bacterial pathogen and the dominant agent of community-acquired pneumonia. Treatment has perennially focused on the use of antibiotics, albeit scrutinized due to the occurrence of antibiotic-resistant Spneu strains. Immunomodulatory strategies have emerged as potential treatment options. Although promising, immunomodulation can lead to improper tissue functions either at steady state or upon infectious challenge. This argues for the availability of tools to enable a detailed assessment of whole pulmonary functions during the course of infection, not only those functions biased to the defense response. Thus, through the use of an unbiased tissue microarray and bioinformatics approach, we aimed to construct a comprehensive map of whole-lung transcriptional activity and cellular pathways during the course of pneumococcal pneumonia. We performed genome-wide transcriptional analysis of whole lungs before and 6 and 48 h after Spneu infection in mice. The 4,000 most variable transcripts across all samples were used to assemble a gene coexpression network comprising 13 intercorrelating modules (clusters of genes). Fifty-four percent of this whole-lung transcriptional network was altered 6 and 48 h after Spneu infection. Canonical signaling pathway analysis uncovered known pathways imparting protection, including IL17A/IL17F signaling and previously undetected mechanisms that included lipid metabolism. Through in silico prediction of cell types, pathways were observed to enrich for distinct cell types such as a novel stromal cell lipid metabolism pathway. These cellular mechanisms were furthermore anchored at functional hub genes of cellular fate, differentiation, growth and transcription. Collectively, we provide a benchmark unsupervised map of whole-lung transcriptional relationships and cellular activity during early and late pneumococcal pneumonia.

CYLD negatively regulates nontypeable Haemophilus influenzae-induced IL-8 expression via phosphatase MKP-1-dependent inhibition of ERK

Nontypeable Haemophilus influenzae (NTHi), a Gram-negative bacterium, is the primary cause of otitis media in children and the exacerbation of chronic obstructive pulmonary disease in adults. A hallmark of both diseases is an overactive inflammatory response, including the upregulation of chemokines, such as interleukin-8 (IL-8). An appropriate inflammatory response is essential for eradicating pathogens. However, excessive inflammation can cause host tissue damage. Therefore, expression of IL-8 must be tightly regulated. We previously reported that NTHi induces IL-8 expression in an ERK-dependent manner. We also have shown that the deubiquitinase cylindromatosis (CYLD) suppresses NTHi-induced inflammation. However, the underlying molecular mechanism of how CYLD negatively regulates ERK-mediated IL-8 production is largely unknown. Here, we examine both human lung epithelial A549 cells and lung of Cyld^−/− mice to show that CYLD specifically targets the activation of ERK. Interestingly, CYLD enhances NTHi-induced upregulation of another negative regulator, MAP Kinase Phosphatase-1 (MKP-1), which, in turn, leads to reduced ERK activation and subsequent suppression of IL-8. Taken together, the CYLD suppression of ERK-dependent IL-8 via MKP-1 may bring novel insights into the tight regulation of inflammatory responses and also lead to innovative therapeutic strategies for controlling these responses by targeting key negative regulators of inflammation.

MicroRNA-362-5p promotes tumor growth and metastasis by targeting CYLD in hepatocellular carcinoma

MicroRNAs are increasingly recognized as playing important roles in hepatocellular carcinoma (HCC) tumorigenesis. Here we identified an essential role for miR-362-5p in the regulation of HCC development. We found that miR-362-5p was significantly up-regulated in HCCs and associated with HCC progression. Inhibition of miR-362-5p in HCC cells dramatically decreased cell proliferation, clonogenicity, migration and invasion in vitro as well as tumor growth and metastasis in vivo. We subsequently identified that CYLD was a target gene of miR-362-5p. Furthermore, knockdown of CYLD expression partially counteracted the tumor suppressive effects of miR-362-5p inhibitors. Finally, we have shown that miR-362-5p acts through CYLD to activate the NF-κB signaling pathway, which contributes to HCC progression. Taken together, our findings indicate that miR-362-5p belongs to a new class of oncomiR that regulates HCC cell aggressiveness, thus providing new insight into the molecular mechanisms underlying HCC development. This study also suggests that miR-362-5p may serve as a novel therapeutic target for miRNA based HCC therapy.

MFG-E8, a novel homeostatic regulator of osteoclastogenesis

Although the glycoprotein MFG-E8 (milk fat globule-epidermal growth factor-factor 8) has been investigated extensively as an anti-inflammatory and homeostatic molecule, a possible role in bone homeostasis and disease was not addressed until recently. Our group has now shown that MFG-E8 is expressed by human and mouse osteoclasts and regulates their differentiation and function (Abe et al., J Immunol 2014;193:1383-1391). Whereas genetic deficiency or antibody-mediated neutralization of MFG-E8 enhances osteoclastogenesis and promotes inflammation-induced bone loss in mice, local administration of recombinant MFG-E8 blocks bone loss. These findings establish MFG-E8 as a novel homeostatic regulator of osteoclastogenesis and suggest that MFG-E8 could be exploited therapeutically to treat disorders associated with inflammatory bone loss, such as periodontitis and rheumatoid arthritis.

Regulation of osteoclast homeostasis and inflammatory bone loss by MFG-E8

The glycoprotein milk fat globule-epidermal growth factor factor 8 (MFG-E8) is expressed in several tissues and mediates diverse homeostatic functions. However, whether it plays a role in bone homeostasis has not been established. In this study, we show for the first time, to our knowledge, that osteoclasts express and are regulated by MFG-E8. Bone marrow-derived osteoclast precursors from MFG-E8-deficient (Mfge8(-/-)) mice underwent increased receptor activator of NF-κB ligand-induced osteoclastogenesis, leading to enhanced resorption pit formation compared with wild-type controls. Consistently, exogenously added MFG-E8 inhibited receptor activator of NF-κB ligand-induced osteoclastogenesis from mouse or human osteoclast precursors. Upon induction of experimental periodontitis, an oral inflammatory disease characterized by loss of bone support of the dentition, Mfge8(-/-) mice exhibited higher numbers of osteoclasts and more bone loss than did wild-type controls. Accordingly, local microinjection of anti-MFG-E8 mAb exacerbated periodontal bone loss in wild-type mice. Conversely, microinjection of MFG-E8 inhibited bone loss in experimental mouse periodontitis. In comparison with wild-type controls, Mfge8(-/-) mice also experienced >60% more naturally occurring chronic periodontal bone loss. In conclusion, MFG-E8 is a novel homeostatic regulator of osteoclasts that could be exploited therapeutically to treat periodontitis and perhaps other immunological disorders associated with inflammatory bone loss.

Bacterial colonization dampens influenza-mediated acute lung injury via induction of M2 alveolar macrophages

While the presence of airway bacteria is known to be associated with improved immunity against influenza virus, the mechanism by which endogenous microbiota influence antiviral immunity remains unclear. Here we show that specific pathogen-free mice are more sensitive to influenza-mediated death than mice living in a natural environment. Priming with Toll-like receptor 2-ligand⁺Staphylococcus aureus, which commonly colonizes the upper respiratory mucosa, significantly attenuates influenza-mediated lung immune injury. Toll-like receptor 2 deficiency or alveolar macrophage depletion abolishes this protection. S. aureus priming recruits peripheral CCR2⁺CD11b⁺ monocytes into the alveoli that polarize to M2 alveolar macrophages in an environment created by Toll-like receptor 2 signalling. M2 alveolar macrophages inhibit influenza-mediated lethal inflammation via anti-inflammatory cytokines and inhibitory ligands. Our results suggest a previously undescribed mechanism by which the airway microbiota may protect against influenza-mediated lethal inflammation.

Bacterial infections can influence disease outcome in influenza infection; however, the mechanisms mediating these complex interactions remain unclear. Wang et al. reveal how infection with a component of the airway microbiota enhances survival during influenza infection via induction of anti-inflammatory macrophages.

Inhibition of PDE4B suppresses inflammation by increasing expression of the deubiquitinase CYLD

The deubiquitinase CYLD acts as a key negative regulator to tightly control overactive inflammation. Most anti-inflammatory strategies have focused on directly targeting the positive regulator, which often results in significant side effects such as suppression of the host defence response. Here, we show that inhibition of phosphodiesterase 4B (PDE4B) markedly enhances upregulation of CYLD expression in response to bacteria, thereby suggesting that PDE4B acts as a negative regulator for CYLD. Interestingly, in Cyld-deficient mice, inhibition of PDE4B no longer suppresses inflammation. Moreover, PDE4B negatively regulates CYLD via specific activation of JNK2 but not JNK1. Importantly, ototopical post-inoculation administration of a PDE4 inhibitor suppresses inflammation in this animal model, thus demonstrating the therapeutic potential of targeting PDE4. These studies provide insights into how inflammation is tightly regulated via the inhibition of its negative regulator and may also lead to the development of new anti-inflammatory therapeutics that upregulate CYLD expression.

Phosphodiesterase 4 inhibitors are under development as anti-inflammatory drugs, however, their mechanisms of action remain poorly understood. Komatsu et al. show that Rolipram, a specific inhibitor of PDE4, reduces inflammation in a model of middle ear infection by upregulating the deubiquitinase CYLD.

Ephedrine hydrochloride inhibits PGN-induced inflammatory responses by promoting IL-10 production and decreasing proinflammatory cytokine secretion via the PI3K/Akt/GSK3β pathway

Approaches for controlling inflammatory responses and reducing the mortality rate of septic patients remain clinically ineffective; new drugs need to be identified that can induce anti-inflammatory responses. Ephedrine hydrochloride (EH) is a compound that is widely used in cardiovascular diseases, especially to treat hypotension caused by either anesthesia or overdose of antihypertensive drugs. In this study, we reported that EH also plays an important role in the control of the inflammatory response. EH increased IL-10 and decreased proinflammatory cytokine (IL-6, tumor-necrosis factor (TNF)-α, IL-12 and IL-1β) expression in primary peritoneal macrophages and Raw264.7 cells treated with peptidoglycan (PGN), a Gram-positive cell wall component. The anti-inflammatory role of EH was also demonstrated in an experimental mouse model of peritonitis induced by intraperitoneal PGN injection. The phosphatidylinositol 3-kinase (PI3K)/Akt pathway was found to be responsible for the EH-mediated increase in IL-10 production and decrease in IL-6 expression. Therefore, our results illustrated that EH can help maintain immune equilibrium and diminish host damage by balancing the production of pro- and anti-inflammatory cytokines after PGN challenge. EH may be a new potential anti-inflammatory drug that can be useful for treating severe invasive Gram-positive bacterial infection.

Lower nasopharyngeal epithelial cell repair and diminished innate inflammation responses contribute to the onset of acute otitis media in otitis-prone children

About 30 % of young children experience excessive, frequent episodes of middle ear infection and are classified as acute otitis media prone (OP). Streptococcus pneumoniae (Spn) is a predominant otopathogen in OP and non-OP (NOP) children. The pathogenesis of middle ear infection involves otopathogen nasopharyngeal (NP) colonization followed by an upper respiratory viral infection that modifies the NP environment to allow a sufficient inoculum of bacteria to reflux via the Eustachian tube into the middle ear space. Here, we analyzed the NP mucosal repair response between age-matched stringently defined OP (sOP) and NOP children who progressed to middle ear infection caused by Spn. We found lower epidermal growth factor, epidermal growth factor receptor, and angiogenin cytokine concentrations in nasal washes of sOP compared with NOP children. Despite higher expression of TLR2/4 transcript expression in nasal epithelium and in polymorphonuclear cells present in nasal secretions in sOP children, sOP children had lower expression of proinflammatory cytokines such as IL-6 and IL-8 in the NP. Chemotaxis-associated cytokine expression at onset of AOM in sOP children was also lower compared with NOP children, possibly indicating a lower capacity to signal the innate immune system. We conclude that lower epithelial cell repair responses during viral infection in the NP combined with diminished innate inflammatory responses potentiate Spn pathogenesis in the sOP child.

Relationships between rhinitis symptoms, respiratory viral infections and nasopharyngeal colonization with Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus in children attending daycare

BACKGROUND

Nasal bacterial colonization is often dubbed "asymptomatic." We hypothesized that rhinitis, common in preschool children, is associated with bacterial colonization and that respiratory viruses, which cause rhinitis, interact with bacteria in ways which promote transmission.

METHODS

Five hundred eighty-five children (4.2-73.6 months) attending daycare had clinical information, a rhinitis score and nasal swabs collected in February 2009. Swabs in soya tryptone glucose glycerine broth were cultured for Streptococcus pneumoniae (Sp), Haemophilus influenzae (Hi) and Staphylococcus aureus and analyzed by real-time polymerase chain reaction for respiratory viruses, both semiquantitatively.

RESULTS

Rhinitis symptoms, carriage of Sp and Hi and viral detection fell, whereas S. aureus carriage rates rose with age. Significant, age-independent associations between rhinitis symptoms and detection of Hi (P < 0.033) and Hi colonization density (P < 0.027) were observed. Of the 42% with detected viruses, most (78%) had picornavirus detection. There was a significant age-independent association between viral detection (and viral load, picornavirus detection and picorn aviral load) and detection of Sp (P = 0.020, 0.035, 0.005, 0.014) and between viral detection and viral load and Sp colonization density (P = 0.024, 0.028) [corrected].

CONCLUSIONS

Hi may promote its own transmission by inducing or ampli¬fying rhinitis in children. There isa close quantitative relationship between respiratory viral detection, including picornavirus detection and Spcoloni¬zation. These findings have implications for understanding disease patho¬genesis and formulating prevention strategies using vaccines [corrected].