Dual acute proinflammatory and antifibrotic pulmonary effects of short palate, lung, and nasal epithelium clone-1 after exposure to carbon nanotubes

Acidic Microenvironment Determines Antibiotic Susceptibility and Biofilm Formation of Pseudomonas aeruginosa

Pseudomonas aeruginosa is the most prevalent bacterial species that contribute to cystic fibrosis (CF) respiratory failure. The impaired function of CF transmembrane conductance regulator leads to abnormal epithelial Cl^-/HCO₃ ^- transport and acidification of airway surface liquid. However, it remains unclear why the CF lung is most commonly infected by Pseudomonas aeruginosa versus other pathogens. We carried out studies to investigate if lower pH helps Pseudomonas aeruginosa adapt and thrive in the CF-like acidic lung environment. Our results revealed that Pseudomonas aeruginosa generally forms more biofilm, induces antibiotic resistance faster in acidic conditions, and can be reversed by returning the acidic environment to physiologically neutral conditions. Pseudomonas aeruginosa appears to be highly adaptive to the CF-like acidic pH environment. By studying the effects of an acidic environment on bacterial response, we may provide a new therapeutic option in preventing chronic Pseudomonas aeruginosa infection and colonization.

Lung carcinomas induced by NNK and LPS

Cigarette smoking is the major culprit of chronic lung diseases and the most dominant risk factor for the development of both lung cancer and chronic obstructive pulmonary disease (COPD). In addition, chronic inflammation has been shown to increase the risk of lung cancer and COPD in clinical and epidemiological studies. For pulmonary disease-related research, mice are the most commonly used model system. Multiple lung cancer mouse models driven by targeted genetic alterations are used to evaluate the critical roles of oncogenes and tumor suppressor genes. These models are useful in addressing lung tumorigenesis associated with specific genetic changes, but they are not able to provide a global insight into cigarette smoke-induced carcinogenesis. To fill this knowledge gap, we developed a lung cancer model by treating mice with cigarette smoke carcinogen nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) with/without repeated lipopolysaccharides (LPS) exposure in order to determine the role of chronic inflammation in lung tumorigenesis. Notably, combined LPS/NNK treatment increased tumor number, tumor incidence, and tumor area compared to NNK treatment alone. Therefore, this model offers a feasible approach to investigate lung cancer development on a more global level, determine the role of inflammation in carcinogenesis, and provide a tool for evaluating chemoprevention and immunotherapy.

Salivary BPIFA proteins are altered in patients undergoing hematopoietic cell transplantation

OBJECTIVE

The aim of this study was to evaluate the expression of BPIFA proteins in the saliva and salivary glands of hematopoietic cell transplant (HCT) patients.

MATERIAL AND METHODS

This longitudinal study included patients who had undergone autologous HCT (auto-HCT) and allogeneic HCT (allo-HCT), and unstimulated saliva was collected at three time points, with a fourth collection at oral chronic graft-versus-host disease (cGVHD) onset. BPIFA expression was analysed by Western blotting in saliva and immunostaining in the minor salivary glands of cGVHD patients.

RESULTS

Auto-HCT patients showed increased levels of BPIFA1 (p = .021) and BPIFA2 at D+7 (p = .040), whereas allo-HCT group demonstrated decreased expression of BPIFA2 at D+8 (p = .002) and at D+80 (p = .001) and a significant association between BPIFA2 low levels and hyposalivation was observed (p = .02). BPIFA2 was significantly lower in the cGVHD patients when compared to baseline (p = .04).

CONCLUSIONS

The results of this study show distinct pattern of expression of BPIF proteins in both auto-HCT and allo-HCT recipients with decreased levels of BPIFA2 during hyposalivation and cGVHD. Further studies are necessary to elucidate these proteins mechanisms and their clinical implications in these groups of patients.

Macrophage autophagy protects mice from cerium oxide nanoparticle-induced lung fibrosis

BACKGROUND

Cerium (Ce) is a rare earth element, rapidly oxidizing to form CeO2, and currently used in numerous commercial applications, especially as nanoparticles (NP). The potential health effects of Ce remain uncertain, but literature indicates the development of rare earth pneumoconiosis accompanied with granuloma formation, interstitial fibrosis and inflammation. The exact underlying mechanisms are not yet completely understood, and we propose that autophagy could be an interesting target to study, particularly in macrophages. Therefore, the objective of our study was to investigate the role of macrophagic autophagy after pulmonary exposure to CeO2 NP in mice. Mice lacking the early autophagy gene Atg5 in their myeloid lineage and their wildtype counterparts were exposed to CeO2 NP by single oropharyngeal administration and sacrificed up to 1 month after. At that time, lung remodeling was thoroughly characterized (inflammatory cells infiltration, expression of fibrotic markers such as αSMA, TGFβ1, total and type I and III collagen deposition), as well as macrophage infiltration (quantification and M1/M2 phenotype).

RESULTS

Such pulmonary exposure to CeO2 NP induces a progressive and dose-dependent lung fibrosis in the bronchiolar and alveolar walls, together with the activation of autophagy. Blockage of macrophagic autophagy protects from alveolar but not bronchiolar fibrosis, via the modulation of macrophage polarization towards M2 phenotype.

CONCLUSION

In conclusion, our findings bring novel insight on the role of macrophagic autophagy in lung fibrogenesis, and add to the current awareness of pulmonary macrophages as important players in the disease.

Immunomodulatory function of the cystic fibrosis modifier gene BPIFA1

BACKGROUND

Cystic fibrosis (CF) is characterized by a progressive decline in lung function due to airway obstruction, infection, and inflammation. CF patients are particularly susceptible to respiratory infection by a variety of pathogens, and the inflammatory response in CF is dysregulated and prolonged. BPI fold containing family A, member 1 (BPIFA1) and BPIFB1 are proteins expressed in the upper airways that may have innate immune activity. We previously identified polymorphisms in the BPIFA1/BPIFB1 region associated with CF lung disease severity.

METHODS

We evaluated whether the BPIFA1/BPIFB1 associations with lung disease severity replicated in individuals with CF participating in the International CF Gene Modifier Consortium (n = 6,365). Furthermore, we investigated mechanisms by which the BPIFA1 and BPIFB1 proteins may modify lung disease in CF.

RESULTS

The association of the G allele of rs1078761 with reduced lung function was replicated in an independent cohort of CF patients (p = 0.001, n = 2,921) and in a meta-analysis of the full consortium (p = 2.39x10-5, n = 6,365). Furthermore, we found that rs1078761G which is associated with reduced lung function was also associated with reduced BPIFA1, but not BPIFB1, protein levels in saliva from CF patients. Functional assays indicated that BPIFA1 and BPIFB1 do not have an anti-bacterial role against P. aeruginosa but may have an immunomodulatory function in CF airway epithelial cells. Gene expression profiling using RNAseq identified Rho GTPase signaling pathways to be altered in CF airway epithelial cells in response to treatment with recombinant BPIFA1 and BPIFB1 proteins.

CONCLUSIONS

BPIFA1 and BPIFB1 have immunomodulatory activity and genetic variation associated with low levels of these proteins may increase CF lung disease severity.

Antibacterial Properties and Efficacy of a Novel SPLUNC1-Derived Antimicrobial Peptide, α4-Short, in a Murine Model of Respiratory Infection

The rise of superbugs underscores the urgent need for novel antimicrobial agents. Antimicrobial peptides (AMPs) have the ability to kill superbugs regardless of resistance to traditional antibiotics. However, AMPs often display a lack of efficacy in vivo. Sequence optimization and engineering are promising but may result in increased host toxicity. We report here the optimization of a novel AMP (α4-short) derived from the multifunctional respiratory protein SPLUNC1. The AMP α4-short demonstrated broad-spectrum activity against superbugs as well as in vivo efficacy in the P. aeruginosa pneumonia model. Further exploration for clinical development is warranted.

Multidrug resistance (MDR) by bacterial pathogens constitutes a global health crisis, and resistance to treatment displayed by biofilm-associated infections (e.g., cystic fibrosis, surgical sites, and medical implants) only exacerbates a problem that is already difficult to overcome. Antimicrobial peptides (AMPs) are a promising class of therapeutics that may be useful in the battle against antibiotic resistance, although certain limitations have hindered their clinical development. The goal of this study was to examine the therapeutic potential of novel AMPs derived from the multifunctional respiratory host defense protein SPLUNC1. Using standard growth inhibition and antibiofilm assays, we demonstrated that a novel structurally optimized AMP, α4-short, was highly effective against the most common group of MDR bacteria while showing broad-spectrum bactericidal and antibiofilm activities. With negligible hemolysis and toxicity to white blood cells, the new peptide also demonstrated in vivo efficacy when delivered directly into the airway in a murine model of Pseudomonas aeruginosa-induced respiratory infection. The data warrant further exploration of SPLUNC1-derived AMPs with optimized structures to assess the potential application to difficult-to-cure biofilm-associated infections.

Utilization of Near Infrared Fluorescence Imaging to Track and Quantify the Pulmonary Retention of Single-Walled Carbon Nanotubes in Mice

As nanomaterials are used in a wide array of applications, investigations regarding health impacts associated with inhalation are a concern. Reports show that exposure to single-walled carbon nanotubes (SWCNTs) can induce fibrosis, allergic-type reactions, and pathogen susceptibility. Airway clearance is known to play a primary role in these disease states, yet SWCNT detection in biological systems is challenging. Common techniques, such as electron microscopy, lack spatial resolution and specificity to delineate SWCNTs in carbon-based organisms. Here we validated a near-infrared fluorescence imaging (NIRFI) system to track and semi-quantify SWCNTs over 21 days in tissues of mice exposed intratracheally to 1 dose of SWCNTs. In tandem, we optimized a NIRF-based spectrometry method to quantify SWCNTs, showing that NIRFI was consistent with SWCNT burdens quantified by NIRF spectroscopy in whole lung tissue homogenates. Finally, NIRFI was utilized to localize SWCNTs on lung tissue sections used for pathological analysis. Results revealed that SWCNTs remained in the lung over 21 days and were consistent with alveolar wall restructuring and granuloma formation. This study is the first to quantify SWCNTs in mouse lungs using both semi-quantitative tracking and quantitative mass measurements using NIRF, highlighting this as a sensitive and specific technique for assessing SWCNT clearance in vivo.

BPIFA1 regulates lung neutrophil recruitment and interferon signaling during acute inflammation

Bpifa1 (BPI fold-containing group A member 1) is an airway host-protective protein with immunomodulatory properties that binds to LPS and is regulated by infectious and inflammatory signals. Differential expression of Bpifa1 has been widely reported in lung disease, yet the biological significance of this observation is unclear. We sought to understand the role of Bpifa1 fluctuations in modulating lung inflammation. We treated wild-type (WT) and Bpifa1^-/- mice with intranasal LPS and performed immunological and transcriptomic analyses of lung tissue to determine the immune effects of Bpifa1 deficiency. We show that neutrophil (polymorphonuclear cells, PMNs) lung recruitment and transmigration to the airways in response to LPS is impaired in Bpifa1^-/- mice. Transcriptomic analysis revealed a signature of 379 genes that differentiated Bpifa1^-/- from WT mice. During acute lung inflammation, the most downregulated genes in Bpifa1^-/- mice were Cxcl9 and Cxcl10. Bpifa1^-/- mice had lower bronchoalveolar lavage concentrations of C-X-C motif chemokine ligand 10 (Cxcl10) and Cxcl9, interferon-inducible PMN chemokines. This was consistent with lower expression of IFNγ, IFNλ, downstream IFN-stimulated genes, and IFN-regulatory factors, which are important for the innate immune response. Administration of Cxcl10 before LPS treatment restored the inflammatory response in Bpifa1^-/- mice. Our results identify a novel role for Bpifa1 in the regulation of Cxcl10-mediated PMN recruitment to the lungs via IFNγ and -λ signaling during acute inflammation.

Loss of the homeostatic protein BPIFA1, leads to exacerbation of otitis media severity in the Junbo mouse model

Otitis Media (OM) is characterized by epithelial abnormalities and defects in innate immunity in the middle ear (ME). Although, BPIFA1, a member of the BPI fold containing family of putative innate defence proteins is abundantly expressed by the ME epithelium and SNPs in Bpifa1 have been associated with OM susceptibility, its role in the ME is not well characterized. We investigated the role of BPIFA1 in protection of the ME and the development of OM using murine models. Loss of Bpifa1 did not lead to OM development. However, deletion of Bpifa1 in Evi1^Jbo/+ mice, a model of chronic OM, caused significant exacerbation of OM severity, thickening of the ME mucosa and increased collagen deposition, without a significant increase in pro-inflammatory gene expression. Our data suggests that BPIFA1 is involved in maintaining homeostasis within the ME under steady state conditions and its loss in the presence of inflammation, exacerbates epithelial remodelling leading to more severe OM.

In vivo therapeutic efficacy of frog skin-derived peptides against Pseudomonas aeruginosa-induced pulmonary infection

Pseudomonas aeruginosa is an opportunistic and frequently drug-resistant pulmonary pathogen especially in cystic fibrosis sufferers. Recently, the frog skin-derived antimicrobial peptide (AMP) Esc(1-21) and its diastereomer Esc(1-21)-1c were found to possess potent in vitro antipseudomonal activity. Here, they were first shown to preserve the barrier integrity of airway epithelial cells better than the human AMP LL-37. Furthermore, Esc(1-21)-1c was more efficacious than Esc(1-21) and LL-37 in protecting host from pulmonary bacterial infection after a single intra-tracheal instillation at a very low dosage of 0.1 mg/kg. The protection was evidenced by 2-log reduction of lung bacterial burden and was accompanied by less leukocytes recruitment and attenuated inflammatory response. In addition, the diastereomer was more efficient in reducing the systemic dissemination of bacterial cells. Importantly, in contrast to what reported for other AMPs, the peptide was administered at 2 hours after bacterial challenge to better reflect the real life infectious conditions. To the best of our knowledge, this is also the first study investigating the effect of AMPs on airway-epithelia associated genes upon administration to infected lungs. Overall, our data highly support advanced preclinical studies for the development of Esc(1-21)-1c as an efficacious therapeutic alternative against pulmonary P. aeruginosa infections.

Early signs of multi-walled carbon nanotbues degradation in macrophages, via an intracellular pH-dependent biological mechanism; importance of length and functionalization

Background

Carbon nanotubes (CNT) can interact with the biological environment, which could participate in their associated toxicity. We recently demonstrated that pH is an important player of CNT fate inside macrophages. We wanted to further characterize such process, and therefore designed a study dedicated to decipher CNT biodegradation by macrophages, as a function of two major physico-chemical properties in regard with nanotoxicology; length and degree of functionalization. To achieve our aim, we synthesized, following a single initial production process, four MWCNT differing in length and/or surface chemistry: S-CNT (short), SF-CNT (short functionalized), L-CNT (long) and LF-CNT (long functionalized).

Results

Raman spectroscopy analysis performed on CNT recovered after exposure of RAW 264.7 macrophages for 6, 24, or 48 h demonstrate that CNT show early signs of biodegradation over time inside macrophages. The modulation of CNT length and functionalization, resulting in the modification of iron accessibility, both represent critical determinants of the biodegradation process; short pristine CNT were more prone to biodegradation than long CNT (pristine or functionalized), while short functionalized CNT were protected. Incubation of cells with Concanamycin completely prevents CNT from being modified, demonstrating that this biodegradation process is dependent on an intracellular pH-dependent mechanism. Interestingly, and despite evidence of degradation via Raman spectroscopy, the CNT length and diameter were not altered during the course of the study.

Conclusions

In conclusion, our results identify a new mechanism of CNT biodegradation inside macrophages. This could give new insights for the understanding of CNT-associated toxicity, and represent important tools to develop safe(r)-by-design nanomaterials.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0175-z) contains supplementary material, which is available to authorized users.

A review of recent developments and applications of morphometry/stereology in lung research

Design-based stereology is the gold standard of morphometry in lung research. Here, we analyze the current use of morphometric and stereological methods in lung research and provide an overview on recent methodological developments and biological observations made by the use of stereology. Based on this analysis we hope to provide useful recommendations for a good stereological practice to further the use of advanced and unbiased stereological methods.

Bactericidal/Permeability-increasing protein fold-containing family member A1 in airway host protection and respiratory disease

Bactericidal/permeability-increasing protein fold-containing family member A1 (BPIFA1), formerly known as SPLUNC1, is one of the most abundant proteins in respiratory secretions and has been identified with increasing frequency in studies of pulmonary disease. Its expression is largely restricted to the respiratory tract, being highly concentrated in the upper airways and proximal trachea. BPIFA1 is highly responsive to airborne pathogens, allergens, and irritants. BPIFA1 actively participates in host protection through antimicrobial, surfactant, airway surface liquid regulation, and immunomodulatory properties. Its expression is modulated in multiple lung diseases, including cystic fibrosis, chronic obstructive pulmonary disease, respiratory malignancies, and idiopathic pulmonary fibrosis. However, the role of BPIFA1 in pulmonary pathogenesis remains to be elucidated. This review highlights the versatile properties of BPIFA1 in antimicrobial protection and its roles as a sensor of environmental exposure and regulator of immune cell function. A greater understanding of the contribution of BPIFA1 to disease pathogenesis and activity may clarify if BPIFA1 is a biomarker and potential drug target in pulmonary disease.

SPLUNC1 reduces the inflammatory response of nasopharyngeal carcinoma cells infected with the EB virus by inhibiting the TLR9/NF-κB pathway

Studies indicate that the natural immune-related protein short palate, lung, and nasal epithelium clone 1 (SPLUNC1) plays an antitumor role in nasopharyngeal epithelial tissue. However, the detailed mechanism of the tumor-suppressor effect of SPLUNC1 in the inflammatory microenvironment of Epstein-Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC) remains elusive. The aim of the present study was to explore how SPLUNC1 reduces the inflammatory response of NPC cells infected with EBV by regulating the Toll-like receptor (TLR)9/NF-κB signaling pathway. As detected by immunohistochemistry and western blotting, SPLUNC1 protein expression exhibited low or negative expression in the NPC epithelial samples/cells, while it demonstrated positive expression in normal nasopharyngeal epithelial tissues/cells; this pattern of expression was the contrary to that of TLR9. The poorly differentiated HNE2 cell line had the highest efficiency of transfer of infection with EBV by 'cell-to-cell' contact method. The group of EBV-infected HNE2 cells showed significantly higher activation of the expression of TLR9/NF-κB signaling pathway-associated factors (TLR9, CD14, MyD88, IKK, P-IKβα, P-NF-κB and NF-κB). The levels of inflammatory cytokines IL-6, IL-8, IL-1β and TNF-α in the HNE2 cell group after EBV infection were higher than these levels in the uninfected cell group (P<0.05); Meanwhile, after EBV infection, the expression levels of TLR9/NF-κB pathway associated-protein and inflammatory cytokines IL-6, IL-8, IL-1β and TNF-α in the HNE2/SPLUNC1 cell group were lower than these levels in the HNE2/Vector cell group (P<0.05). After EBV-DNA direct transfection, cytokine mRNA expression levels of TLR9, IL-6, IL-8, IL-1β and TNF-α in the HNE2 cell group were significantly higher than these levels in the NP69 cell group (P<0.05). The expression levels of these cytokines in the HNE2/SPLUNC1 cell group were obviously lower than these levels in the HNE2/Vector cell group (P<0.05). These results suggest that EBV infection of NPC cells can activate the TLR9/NF-κB signaling pathway, promote the release of inflammatory cytokines and consequently enhance the inflammatory response, while SPLUNC1 can weaken the inflammatory response induced by EBV infection in NPC cells through the regulation of the TLR9/NF-κB signaling pathway and control of the tumor inflammatory microenvironment.

Increased susceptibility to otitis media in a Splunc1-deficient mouse model

Otitis media (inflammation of the middle ear) is one of the most common diseases of early childhood. Susceptibility to otitis is influenced by a number of factors, including the actions of innate immune molecules secreted by the epithelia lining the nasopharynx, middle ear and Eustachian tube. The SPLUNC1 (short palate, lung, nasal epithelial clone 1) protein is a highly abundant secretory product of the mammalian nasal, oral and respiratory mucosa that is thought to play a multifunctional role in host defense. In this study we investigated Splunc1 expression in the ear of the mouse, and examined whether this protein contributes to overall host defense in the middle ear and/or Eustachian tube. We found that Splunc1 is highly expressed in both the surface epithelium and in submucosal glands in these regions in wild-type mice. In mice lacking Splunc1, we noted histologically an increased frequency of otitis media, characterized by the accumulation of leukocytes (neutrophils with scattered macrophages), proteinaceous fluid and mucus in the middle ear lumens. Furthermore, many of these mice had extensive remodeling of the middle ear wall, suggesting a chronic course of disease. From these observations, we conclude that loss of Splunc1 predisposes mice to the development of otitis media. The Splunc1^−/− mouse model should help investigators to better understand both the biological role of Splunc1 as well as host defense mechanisms in the middle ear.

Summary: We document expression of the innate immune factor Splunc1 in the murine middle ear and Eustachian tube, and describe spontaneous development of otitis media in mice lacking functional Splunc1.

Autophagy as a Possible Underlying Mechanism of Nanomaterial Toxicity

The rapid development of nanotechnologies is raising safety concerns because of the potential effects of engineered nanomaterials on human health, particularly at the respiratory level. Since the last decades, many in vivo studies have been interested in the pulmonary effects of different classes of nanomaterials. It has been shown that some of them can induce toxic effects, essentially depending on their physico-chemical characteristics, but other studies did not identify such effects. Inflammation and oxidative stress are currently the two main mechanisms described to explain the observed toxicity. However, the exact underlying mechanism(s) still remain(s) unknown and autophagy could represent an interesting candidate. Autophagy is a physiological process in which cytoplasmic components are digested via a lysosomal pathway. It has been shown that autophagy is involved in the pathogenesis and the progression of human diseases, and is able to modulate the oxidative stress and pro-inflammatory responses. A growing amount of literature suggests that a link between nanomaterial toxicity and autophagy impairment could exist. In this review, we will first summarize what is known about the respiratory effects of nanomaterials and we will then discuss the possible involvement of autophagy in this toxicity. This review should help understand why autophagy impairment could be taken as a promising candidate to fully understand nanomaterials toxicity.

The effects of physical exercise and smoking habits on the expression of SPLUNC1 in nasal lavage fluids from allergic rhinitis subjects

OBJECTIVE

Palate lung nasal epithelial clone (PLUNC) is a family of proteins, which are proposed to participate in the innate immune defense against infections in the upper aero-digestive tract. The aim of this study was to investigate the expression of SPLUNC1 in allergic rhinitis subjects with considerations taken to the mucosal function and smoking habits.

METHODS

The participants, recruited from a cohort followed from infancy, were re-examined at the age of 18 years regarding allergy development. Based on medical histories and skin prick tests the participants were classified into groups with persistent allergic rhinitis (n=18), intermittent allergic rhinitis (n = 8) and healthy controls (n = 13). Seven subjects (3, 2 and 2 in each group, respectively) reported smoking habits. The SPLUNC1 levels in nasal lavage fluids were analyzed by Western blot. Changes in the volume of the proper nasal cavity before and after physical exercise (Vol2(increase)) were analyzed by acoustic rhinometry.

RESULTS

Compared to the control group the SPLUNC1 level was significantly lower in the persistent allergy group (3.8 ± 3.4 OD vs. 1.3 ± 1.5 OD; p = 0.02), but not in the intermittent allergy group without current exposure to allergens (3.6 ± 4.7 OD). No differences were found in Vol2(increase) between any of the allergy groups and controls. In smokers Vol2(increase) was significantly reduced (p < 0.01) and the SPLUNC1 levels were lower compared to non-smokers. A significant correlation was found between SPLUNC1 and Vol2(increase) (p < 0.01; r = 0.53) in non-smokers.

CONCLUSIONS

Current allergen exposure has an impact on SPLUNC1 expression in nasal lavage fluid, why allergy ought to be considered in study populations where analyses of SPLUNC1 levels are included in the reports. The normal nasal decongestion after exercise was not affected by allergy in contrast to smoking habits. The correlation between SPLUNC1 levels and Vol2(increase) in non-smokers may indicate involvement of SPLUNC1in the regulation of the normal function of the nasal mucosa. Complementary studies are needed to confirm the smoke-related reduction of SPLUNC1 expression and to analyze the possible participation of SPLUNC1 in the nasal mucosa regulation.

Airway symptoms and biological markers in nasal lavage fluid in subjects exposed to metalworking fluids

BACKGROUNDS

Occurrence of airway irritation among industrial metal workers was investigated. The aims were to study the association between exposures from water-based metal working fluids (MWF) and the health outcome among the personnel, to assess potential effects on the proteome in nasal mucous membranes, and evaluate preventive actions.

METHODS

The prevalence of airway symptoms related to work were examined among 271 metalworkers exposed to MWF and 24 metal workers not exposed to MWF at the same factory. At the same time, air levels of potentially harmful substances (oil mist, morpholine, monoethanolamine, formaldehyde) generated from MWF was measured. Nasal lavage fluid was collected from 13 workers and 15 controls and protein profiles were determined by a proteomic approach.

RESULTS

Airway symptoms were reported in 39% of the workers exposed to MWF although the measured levels of MWF substances in the work place air were low. Highest prevalence was found among workers handling the MWF machines but also those working in the same hall were affected. Improvement of the ventilation to reduce MWF exposure lowered the prevalence of airway problems. Protein profiling showed significantly higher levels of S100-A9 and lower levels of SPLUNC1, cystatin SN, Ig J and β2-microglobulin among workers with airway symptoms.

CONCLUSIONS

This study confirms that upper airway symptoms among metal workers are a common problem and despite low levels of MWF-generated substances, effects on airway immune proteins are found. Further studies to clarify the role of specific MWF components in connection to airway inflammation and the identified biological markers are warranted.

Increased susceptibility to pulmonary Pseudomonas infection in Splunc1 knockout mice

The airway epithelium is the first line of host defense against pathogens. The short palate, lung, and nasal epithelium clone (SPLUNC)1 protein is secreted in respiratory tracts and is a member of the bacterial/permeability increasing (BPI) fold-containing protein family, which shares structural similarities with BPI-like proteins. On the basis of its homology with BPIs and restricted expression of SPLUNC1 in serous cells of submucosal glands and surface epithelial cells of the upper respiratory tract, SPLUNC1 is thought to possess antimicrobial activity in host defense. SPLUNC1 is also reported to have surfactant properties, which may contribute to anti-biofilm defenses. The objective of this study was to determine the in vivo functions of SPLUNC1 following Pseudomonas aeruginosa infection and to elucidate the underlying mechanism by using a knockout (KO) mouse model with a genetic ablation of Splunc1. Splunc1 KO mice showed accelerated mortality and increased susceptibility to P. aeruginosa infection with significantly decreased survival rates, increased bacterial burdens, exaggerated tissue injuries, and elevated proinflammatory cytokine levels as compared with those of their wild-type littermates. Increased neutrophil infiltration in Splunc1 KO mice was accompanied by elevated chemokine levels, including Cxcl1, Cxcl2, and Ccl20. Furthermore, the expression of several epithelial secretory proteins and antimicrobial molecules was considerably suppressed in the lungs of Splunc1 KO mice. The deficiency of Splunc1 in mouse airway epithelium also results in increased biofilm formation of P. aeruginosa. Taken together, our results support that the ablation of Splunc1 in mouse airways affects the mucociliary clearance, resulting in decreased innate immune response during Pseudomonas-induced respiratory infection.