Pulmonary Defense Research Articles

Bronchial epithelial DNA methyltransferase 3b dampens pulmonary immune responses during Pseudomonas aeruginosa infection.

DNA methyltransferase (Dnmt)3b mediates de novo DNA methylation and modulation of Dnmt3b in respiratory epithelial cells has been shown to affect the expression of multiple genes. Respiratory epithelial cells provide a first line of defense against pulmonary pathogens and play a crucial role in the immune response during pneumonia caused by Pseudomonas (P.) aeruginosa, a gram-negative bacterium that expresses flagellin as an important virulence factor. We here sought to determine the role of Dntm3b in respiratory epithelial cells in immune responses elicited by P. aeruginosa. DNMT3B expression was reduced in human bronchial epithelial (BEAS-2B) cells as well as in primary human and mouse bronchial epithelial cells grown in air liquid interface upon exposure to P. aeruginosa (PAK). Dnmt3b deficient human bronchial epithelial (BEAS-2B) cells produced more CXCL1, CXCL8 and CCL20 than control cells when stimulated with PAK, flagellin-deficient PAK (PAKflic) or flagellin. Dnmt3b deficiency reduced DNA methylation at exon 1 of CXCL1 and enhanced NF-ĸB p65 binding to the CXCL1 promoter. Mice with bronchial epithelial Dntm3b deficiency showed increased Cxcl1 mRNA expression in bronchial epithelium and CXCL1 protein release in the airways during pneumonia caused by PAK, which was associated with enhanced neutrophil recruitment and accelerated bacterial clearance; bronchial epithelial Dnmt3b deficiency did not modify responses during pneumonia caused by PAKflic or Klebsiella pneumoniae (an un-flagellated gram-negative bacterium). Dnmt3b deficiency in type II alveolar epithelial cells did not affect mouse pulmonary defense against PAK infection. These results suggest that bronchial epithelial Dnmt3b impairs host defense during Pseudomonas induced pneumonia, at least in part, by dampening mucosal responses to flagellin.

The impact of influenza pulmonary infection and inflammation on vagal bronchopulmonary sensory neurons.

Influenza A virus (IAV) is rapidly detected in the airways by the immune system, with resident parenchymal cells and leukocytes orchestrating viral sensing and the induction of antiviral inflammatory responses. The airways are innervated by heterogeneous populations of vagal sensory neurons which also play an important role in pulmonary defense. How these neurons respond to IAV respiratory infection remains unclear. Here, we use a murine model to provide the first evidence that vagal sensory neurons undergo significant transcriptional changes following a respiratory IAV infection. RNA sequencing on vagal sensory ganglia showed that IAV infection induced the expression of many genes associated with an antiviral and pro-inflammatory response and this was accompanied by a significant increase in inflammatory cell recruitment into the vagal ganglia. Assessment of gene expression in single-vagal sensory neurons confirmed that IAV infection induced a neuronal inflammatory phenotype, which was most prominent in bronchopulmonary neurons, and also evident in some neurons innervating other organs. The altered transcriptome could be mimicked by intranasal treatment with cytokines and the lung homogenates of infected mice, in the absence of infectious virus. These data argue that IAV pulmonary infection and subsequent inflammation induces vagal sensory ganglia neuroinflammation and this may have important implications for IAV-induced morbidity.

TRP channels in airway sensory nerves

Transient Receptor Potential (TRP) channels expressed in specific subsets of airway sensory nerves function as transducers and integrators of a diverse range of sensory inputs including chemical, mechanical and thermal signals. These TRP sensors can detect inhaled irritants as well as endogenously released chemical substances. They play an important role in generating the afferent activity carried by these sensory nerves and regulating the centrally mediated pulmonary defense reflexes. Increasing evidence reported in recent investigations has revealed important involvements of several TRP channels (TRPA1, TRPV1, TRPV4 and TRPM8) in the manifestation of various symptoms and pathogenesis of certain acute and chronic airway diseases. This mini-review focuses primarily on these recent findings of the responses of these TRP sensors to the biological stresses emerging under the pathophysiological conditions of the lung and airways.

DJ-1 modulates Nrf2-mediated MRP1 expression by activating Wnt3a/β-catenin signalling in A549 cells exposed to cigarette smoke extract and LPS

BackgroundChronic obstructive pulmonary disease (COPD) is an inflammatory disease characterized by airway obstruction and abnormal inflammatory responses. Multidrug resistance-related protein 1 (MRP1) can reduce lung inflammation and damage by excreting various toxic exogenous substances and certain pro-inflammatory molecules. AimsWe studied whether DJ-1 modulates nuclear factor erythroid 2-related factor 2 (Nrf2) by activating the Wnt3a/β-catenin signalling pathway to further regulate MRP1 expression and pulmonary antioxidant defences in alveolar epithelial (A549) cells treated with smoke extract (CSE) and lipopolysaccharide (LPS). Main methodsMarker expression was studied by western blot analysis, quantitative real-time PCR and immunofluorescence staining of A549 cells. Key findingsA549 cells exposed to CSE and LPS showed downregulation of DJ-1, Wnt3a, MRP1 and haem oxygenase-1 (HO-1) and upregulation of inflammatory factors. Additionally, Nrf2 protein levels were significantly decreased, while there was no change in Nrf2 mRNA levels. Overexpression of DJ-1 and Wnt3a activated Nrf2 signalling, increased MRP1 and HO-1 levels and decreased IL-6 protein expression, while knockdown of DJ-1 and Wnt3a had the opposite effects. Furthermore, DJ-1 overexpression and DJ-1 knockdown increased and decreased, respectively, the levels of Wnt3a and β-catenin. Interestingly, Nrf2 and Wnt3a deficiency reduced the protective effects of Wnt3a and DJ-1, respectively, in A549 cells. However, the levels of DJ-1 and Wnt3a were not altered by Wnt3a and Nrf2 deletion, respectively. SignificanceIn A549 cells treated with CSE and LPS, DJ-1 regulates Nrf2-mediated MRP1 expression and antioxidant defences by activating the Wnt3a/β-catenin signalling pathway. These findings may provide potential therapeutic targets for COPD intervention.

Airway Inflammation and Host Responses in the Era of CFTR Modulators.

The arrival of cystic fibrosis transmembrane conductance regulator (CFTR) modulators as a new class of treatment for cystic fibrosis (CF) in 2012 represented a pivotal advance in disease management, as these small molecules directly target the upstream underlying protein defect. Further advancements in the development and scope of these genotype-specific therapies have been transformative for an increasing number of people with CF (PWCF). Despite clear improvements in CFTR function and clinical endpoints such as lung function, body mass index (BMI), and frequency of pulmonary exacerbations, current evidence suggests that CFTR modulators do not prevent continued decline in lung function, halt disease progression, or ameliorate pathogenic organisms in those with established lung disease. Furthermore, it remains unknown whether their restorative effects extend to dysfunctional CFTR expressed in phagocytes and other immune cells, which could modulate airway inflammation. In this review, we explore the effects of CFTR modulators on airway inflammation, infection, and their influence on the impaired pulmonary host defences associated with CF lung disease. We also consider the role of inflammation-directed therapies in light of the widespread clinical use of CFTR modulators and identify key areas for future research.

COVID-19 Susceptibility in chronic obstructive pulmonary disease.

In barely nine months, the pandemic known as COVID‐19 has spread over 200 countries, affecting more than 22 million people and causing over than 786 000 deaths. Elderly people and patients with previous comorbidities such as hypertension and diabetes are at an increased risk to suffer a poor prognosis after severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection.Although the same could be expected from patients with chronic obstructive pulmonary disease (COPD), current epidemiological data are conflicting. This could lead to a reduction of precautionary measures in these patients, in the context of a particularly complex global health crisis.Most COPD patients have a long history of smoking or exposure to other harmful particles or gases, capable of impairing pulmonary defences even years after the absence of exposure. Moreover, COPD is characterized by an ongoing immune dysfunction, which affects both pulmonary and systemic cellular and molecular inflammatory mediators. Consequently, increased susceptibility to viral respiratory infections have been reported in COPD, often worsened by bacterial co‐infections and leading to serious clinical outcomes.The present paper is an up‐to‐date review that discusses the available research regarding the implications of coronavirus infection in COPD. Although validation in large studies is still needed, COPD likely increases SARS‐CoV‐2 susceptibility and increases COVID‐19 severity. Hence, specific mechanisms to monitor and assess COPD patients should be addressed in the current pandemic.

Potential Role of Nrf2 Activators with Dual Antiviral and Anti-Inflammatory Properties in the Management of Viral Pneumonia.

The outbreak of coronavirus disease 2019 (COVID-19) pandemic has already caused a huge burden to the global healthcare system, with the death toll reached tens of thousands. Although some antiviral agents were identified and used to inhibit viral replication, the management of cytokine storm is also a critical issue. In this article, we reviewed the literature on drug candidates for severe acute respiratory syndrome (SARS-CoV-1) and provided a brief overview of a class of drugs that exert antiviral and anti-inflammatory effects. These molecules mitigated inflammatory cytokine cascades induced by viral infections via Nrf2 activating capacity and might have additional anti-fibrotic and anti-remodeling properties. Besides, their effects on the regulation of scavenger receptors expression by macrophages may offer some benefits to the pulmonary antibacterial defense system after viral infection. The potential roles of these agents assessed on the basis of the pathophysiology of viral pneumonia and acute respiratory distress syndrome were also discussed. Further research is needed to ascertain whether Nrf2 activators are useful in the management of viral pneumonia.

Impact of Key Nicotinic AChR Subunits on Post-Stroke Pneumococcal Pneumonia.

Pneumonia is the most frequent severe medical complication after stroke. An overactivation of the cholinergic signaling after stroke contributes to immunosuppression and the development of spontaneous pneumonia caused by Gram-negative pathogens. The α7 nicotinic acetylcholine receptor (α7nAChR) has already been identified as an important mediator of the anti-inflammatory pathway after stroke. However, whether the α2, α5 and α9/10 nAChR expressed in the lung also play a role in suppression of pulmonary innate immunity after stroke is unknown. In the present study, we investigate the impact of various nAChRs on aspiration-induced pneumonia after stroke. Therefore, α2, α5, α7 and α9/10 nAChR knockout (KO) mice and wild type (WT) littermates were infected with Streptococcus pneumoniae (S. pneumoniae) three days after middle cerebral artery occlusion (MCAo). One day after infection pathogen clearance, cellularity in lung and spleen, cytokine secretion in bronchoalveolar lavage (BAL) and alveolar-capillary barrier were investigated. Here, we found that deficiency of various nAChRs does not contribute to an enhanced clearance of a Gram-positive pathogen causing post-stroke pneumonia in mice. In conclusion, these findings suggest that a single nAChR is not sufficient to mediate the impaired pulmonary defense against S. pneumoniae after experimental stroke.

Immunoregulatory Property of C-Type Lectin-Like Receptors in Fibrosing Interstitial Lung Diseases.

The innate immune system identifies exogenous threats or endogenous stress through germline-encoded receptors called pattern recognition receptors (PRRs) that initiate consecutive downstream signaling pathways to control immune responses. However, the contribution of the immune system and inflammation to fibrosing interstitial lung diseases (ILD) remains poorly understood. Immunoreceptor tyrosine-based motif-bearing C-type lectin-like receptors (CTLRs) may interact with various immune cells during tissue injury and wound repair processes. Dectin-1 is a CTLR with dominant mechanisms manifested through its intracellular signaling cascades, which regulate fibrosis-promoting properties through gene transcription and cytokine activation. Additionally, immune impairment in ILD facilitates microbiome colonization; hence, Dectin-1 is the master protector in host pulmonary defense against fungal invasion. Recent progress in determining the signaling pathways that control the balance of fibrosis has implicated immunoreceptor tyrosine-based motif-bearing CTLRs as being involved, either directly or indirectly, in the pathogenesis of fibrosing ILD.

The dietary antioxidant quercetin reduces hallmarks of bleomycin-induced lung fibrogenesis in mice

BackgroundIdiopathic pulmonary fibrosis (IPF) is a chronic, lethal disease of which the etiology is still not fully understood. Current treatment comprises two FDA-approved drugs that can slow down yet not stop or reverse the disease. As IPF pathology is associated with an altered redox balance, adding a redox modulating component to current therapy might exert beneficial effects. Quercetin is a dietary antioxidant with strong redox modulating capacities that is suggested to exert part of its antioxidative effects via activation of the redox-sensitive transcription factor Nrf2 that regulates endogenous antioxidant levels. Therefore, the aim of the present study was to investigate if the dietary antioxidant quercetin can exert anti-fibrotic effects in a mouse model of bleomycin-induced pulmonary fibrogenesis through Nrf2-dependent restoration of redox imbalance.MethodsHomozygous Nrf2 deficient mice and their wildtype littermates were fed a control diet without or with 800 mg quercetin per kg diet from 7 days prior to a single 1 μg/2 μl per g BW bleomycin challenge until they were sacrificed 14 days afterwards. Lung tissue and plasma were collected to determine markers of fibrosis (expression of extracellular matrix genes and histopathology), inflammation (pulmonary gene expression and plasma levels of tumor necrosis factor-α (TNFα) and keratinocyte chemoattrachtant (KC)), and redox balance (pulmonary gene expression of antioxidants and malondialdehyde-dG (MDA)- DNA adducts).ResultsMice fed the enriched diet for 7 days prior to the bleomycin challenge had significantly enhanced plasma and pulmonary quercetin levels (11.08 ± 0.73 μM versus 7.05 ± 0.2 μM) combined with increased expression of Nrf2 and Nrf2-responsive genes compared to mice fed the control diet in lung tissue. Upon bleomycin treatment, quercetin-fed mice displayed reduced expression of collagen (COL1A2) and fibronectin (FN1) and a tendency of reduced inflammatory lesions (2.8 ± 0.7 versus 1.9 ± 0.8). These beneficial effects were accompanied by reduced pulmonary gene expression of TNFα and KC, but not their plasma levels, and enhanced Nrf2-induced pulmonary antioxidant defences. In Nrf2 deficient mice, no effect of the dietary antioxidant on either histology or inflammatory lesions was observed.ConclusionQuercetin exerts anti-fibrogenic and anti-inflammatory effects on bleomycin-induced pulmonary damage in mice possibly through modulation of the redox balance by inducing Nrf2. However, quercetin could not rescue the bleomycin-induced pulmonary damage indicating that quercetin alone cannot ameliorate the progression of IPF.

Diagnosis of Chronic Obstructive Air Way Disease-Made Easy

Chronic obstructive pulmonary disease is an inflammatory disease. Together with oxidant stimuli, which directly affect lung structures, macrophages, neutrophils and CD8+ lymphocytes actively participate in the pathogenesis of the disease and promote biochemical reactions that result in progressive alteration of the upper airways and irreversible lung remodeling. The release of substances promoted by inflammatory cell recruitment and by oxidative stress lead to a temporary imbalance in the pulmonary defense mechanisms. Understanding the long-term maintenance of this imbalance is key to understanding the current physiopathology of the disease. The present study explores the cellular and molecular alterations seen in chronic obstructive pulmonary disease.

Respiratory complications in Cerebral Palsy: physiopathological consequences and clinical manifestations

Cerebral palsy (CP) is a condition that can occur at any time during brain development. Although its etiology is multifactorial, CP is usually linked to brain injury or infections during prenatal, perinatal, neonatal or early childhood period. The disability associated with CP varies from mild to severe, and may include involuntary movements, poor coordination, maintaining balance problems and the difficulty of performing voluntary movements. Although this condition (brain impairment) does not directly cause pulmonary complications, neuromuscular dysfunctions do so. In fact, aspiration and ineffective coughing could interfere with normal airway clearance, impair respiratory function, and worsen lung damage, resulting in increased mucus production and reduced secretions elimination. This consequent alteration of the pulmonary defense system increases the susceptibility to serious, progressive lung diseases. Physiotherapy is an essential component in the management of respiratory complications associated with severe CP. For optimal results, however, it is important customized treatment for every patient. This mini non-ystematic review would highlight the possible complications and the possible interventions for reduce them.

Transcriptomic profiling identifies a critical role of Nrf2 in regulating the inflammatory response to fly ash particles in mouse lung.

Exposure to combustion-derived nanoparticles is recognized as a major health hazard, but the molecular responses are still insufficiently described. The transcription factor erythroid 2-related factor 2 (Nrf2, also known as NFE2L2) is a master regulator of the pulmonary defense system against insults by particulate matter. However, its downstream molecular processes are not fully characterized. In the current study, BALB/c wild-type (WT) and Nrf2-/- mice were exposed by intranasal administration to fly ash particles (F3-S; 20mg/kg BW), which were collected from a municipal waste incinerator in China, for three consecutive days. Using a comparative transcriptomics approach, the pulmonary global gene expression profiles to F3-S exposure were characterized for both genotypes. The preponderance of the differentially-expressed genes (DEGs) in WT mice induced by the fly ash particles, was related to inflammation. Functional enrichment and molecular pathway mapping of the DEGs specific to Nrf2-/- mice exposed to the particles revealed that all of the top 10 perturbed molecular pathways were associated with the inflammatory response. Our study identified a transcriptional signature related to the initial pulmonary injury in mouse upon fly ash exposure, and suggests an anti-inflammatory role of Nrf2 in protecting the lung against such exposure.

Porcine Alveolar Macrophages' Nitric Oxide Synthase-Mediated Generation of Nitric Oxide Exerts Important Defensive Effects against Glaesserella parasuis Infection.

Glaesserella parasuis is a habitual bacterium of pigs’ upper respiratory tracts. Its infection initiates with the invasion and colonization of the lower respiratory tracts of pigs, and develops as the bacteria survive host pulmonary defenses and clearance by alveolar macrophages. Alveolar macrophage-derived nitric oxide (NO) is recognized as an important mediator that exerts antimicrobial activity as well as immunomodulatory effects. In this study, we investigated the effects and the signaling pathway of NO generation in porcine alveolar macrophages 3D4/21 during G. parasuis infection. We demonstrated a time and dose-dependent generation of NO in 3D4/21 cells by G. parasuis, and showed that NO production required bacterial viability and nitric oxide synthase 2 upregulation, which was largely contributed by G. parasuis-induced nuclear factor-κB signaling’s activation. Moreover, the porcine alveolar macrophage-derived NO exhibited prominent bacteriostatic effects against G. parasuis and positive host immunomodulation effects by inducing the production of cytokines and chemokines during infection. G. parasuis in turn, selectively upregulated several nitrate reductase genes to better survive this NO stress, revealing a battle of wits during the bacteria–host interactions. To our knowledge, this is the first direct demonstration of NO production and its anti-infection effects in alveolar macrophages with G. parasuis infection.

Understanding Gene Therapy in Acute Respiratory Distress Syndrome.

Acute Respiratory Distress Syndrome (ARDS) and its complications remain lifethreatening conditions for critically ill patients. The present therapeutic strategies such as prone positioning ventilation strategies, nitric oxide inhalation, restrictive intravenous fluid management, and extracorporeal membrane oxygenation (ECMO) do not contribute much to improving the mortality of ARDS. The advanced understanding of the pathophysiology of acute respiratory distress syndrome suggests that gene-based therapy may be an innovative method for this disease. Many scientists have made beneficial attempts to regulate the immune response genes of ARDS, maintain the normal functions of alveolar epithelial cells and endothelial cells, and inhibit the fibrosis and proliferation of ARDS. Limitations to effective pulmonary gene therapy still exist, including the security of viral vectors and the pulmonary defense mechanisms against inhaled particles. Here, we summarize and review the mechanism of gene therapy for acute respiratory distress syndrome and its application.

Total Intravenous Anesthesia for Immobile Cilia Syndrome. About a Case

Immotile cilia syndrome is an autosomal recessive disorder which is characterized by ciliary dysfunction and decreased mucociliary clearance. This ciliary function is a mechanism whose primary pulmonary defense alteration can be a problem during inhalational anesthesia, as these cause decreased ciliary movement. However during total intravenous anesthesia this normal ciliary movement can be preserved using remifentanil and propofol. A case of immotile cilia syndrome was handled with complete intravenous anesthesia for surgery protocol type ovarian handling post-operative pain epidural catheter is presented.

Swallowing with Noninvasive Positive-Pressure Ventilation (NPPV) in Individuals with Muscular Dystrophy: A Qualitative Analysis.

The purpose of the study is to describe experiences of swallowing with two forms of noninvasive positive-pressure ventilation (NPPV): mouthpiece NPPV (M-NPPV) and nasal bilevel positive airway pressure (BPAP) in people with muscular dystrophy. Ten men (ages 22-42years; M = 29.3; SD = 7.1) with muscular dystrophy (9 with Duchenne's; 1 with Becker's) completed the Eating Assessment Tool (EAT-10; Ann Otol Rhinol Laryngol 117(12):919-924 [33]) and took part in semi-structured interviews. The interviews were audio recorded, transcribed, and verified. Phenomenological qualitative research methods were used to code (Dedoose.com) and develop themes. All participants affirmed dysphagia symptoms via responses on the EAT-10 (M = 11.3; SD = 6.38; Range = 3-22) and reported eating and drinking with M-NPPV and, to a lesser extent, nasal BPAP. Analysis of interview data revealed three primary themes: (1) M-NPPV improves the eating/drinking experience: Most indicated that using M-NPPV reduced swallowing-related dyspnea. (2) NPPV affects breathing-swallowing coordination: Participants described challenges and compensations in coordinating swallowing with ventilator-delivered inspirations, and that the time needed to chew solid foods between ventilator breaths may lead to dyspnea and fatigue. (3) M-NPPV aids cough effectiveness: Participants described improved cough strength following large M-NPPV delivered inspirations (with or without breath stacking). Although breathing-swallowing coordination is challenging with NPPV, participants reported that eating and drinking is more comfortable than when not using it. Overall, eating and drinking with NPPV delivered via a mouthpiece is preferred and is likely safer for swallowing than with nasal BPAP. M-NPPV (but not nasal BPAP) is reported to improve cough effectiveness, an important pulmonary defense in this population.

Diallyl disulfide inhibits ethanol-induced pulmonary cell vitamin D and antimicrobial peptide cathelicidin depletion.

Ethanol has been found to affect pulmonary cells by interfering with vitamin D metabolism and pulmonary defense mechanisms. The objective of this study was to understand the mechanisms of ethanol's disruptive influence on the vitamin D pathway and inhibition of anti-microbial peptide cathelicidin (LL-37). Bronchial epithelial cells (BEAS-2Bs), primary human bronchial epithelial cells (HBECs), primary human alveolar epithelial cells (HPAEpiCs), and human monocyte cells (THP-1s) were used in this study. These cells were cultured and exposed to different treatment groups: medium-only control, ethanol (70mM) only, diallyl disulfide (DADS) (10μM) -only, and a co-exposure of ethanol (70mM) and DADS (10μM) for 10 or 24h. Calcidiol (50ng/mL) and calcitriol (0.05ng/mL) dose-response studies were conducted for 48h. After incubation, cells were trypsinized, lysed, and centrifuged, and the cellular lysate was prepared for assay. Protein was quantified, and levels of inactive vitamin D [25(OH)D3], active vitamin D [1, 25(OH)2 D3], and anti-microbial peptides (cathelicidin/LL-37) in the samples were assayed using commercially available ELISA kits. In the ethanol-exposed group, cellular lysate concentrations of 25(OH)D3 and LL-37 were significantly reduced by 30%, and 40% in BEAS-2B cells, and 35% and 80% in HPAEpi cells respectively. Overall 1, 25(OH)2D3 cellular lysate levels were lower but followed a similar trend as the 25(OH)D3 response. LL-37 levels in primary bronchial, alveolar cells, and ThP-1cells were statistically reduced in ethanol-exposed groups (60%, 80%, and 65%, respectively) when compared with control. Following the addition of DADS, levels of LL-37 were recovered to within control levels for all three cell types. This study establishes two clinically relevant observations: that the exposure of pulmonary epithelial and monocyte cells to physiologically relevant levels of excessive ethanol selectively disrupts the activation of pulmonary vitamin D and inhibits the presence of anti-microbial peptide (LL-37) invitro, and the co-exposure of DADS significantly attenuates ethanol-induced intracellular LL-37 depletion.

Antifungal activities of surfactant protein D in an environment closely mimicking the lung lining

At the lung lining innate defenses protect our lungs against inhaled fungal cells that could pose a threat to our health. These defenses are comprised of mucociliary clearance, soluble effector molecules and roaming phagocytic cells, such as macrophages and neutrophils. How important each of these defenses is during fungal clearance depends on the specific fungal pathogen in question and on the stage of infection. In this study the localization and antifungal activity of the lung surfactant protein D (SP-D) was studied in an environment mimicking the lung lining. To this end Calu-3 cells were grown on an air-liquid interface allowing them to polarize and to produce mucus at their apical surface. Additionally, neutrophils were added to study their role in fungal clearance. Two fungal pathogens were used for these experiments: Candida albicans and Aspergillus fumigatus, both of clinical relevance. During fungal infection SP-D localized strongly to both fungal surfaces and stayed bound through the different stages of infection. Furthermore, SP-D decreased fungal adhesion to the epithelium and increased fungal clearance by neutrophils from the epithelial surface. These findings suggest that SP-D plays an important role at the different stages of pulmonary defense against fungal intruders.

Lactobacillus salivarius reverse antibiotic-induced lung defense impairment in a ventilator model

BackgroundWidespread use of antibiotics in the intensive care unit is a potential cause of the emergence of hospital-acquired pneumonia. This study determined whether Lactobacillus salivarius feeding could reverse antibiotic-induced lung defense impairment in a ventilator model.MethodsC57BL/6 wild-type (WT) mice received mechanical ventilation for 3 h after intramuscular antibiotic treatment for 6 days. Treatment with dead Lactobacillus salivarius and fructo-oligosaccharides (FOS) feeding were used to stimulate antibacterial protein expression in the intestine. Reactive oxygen species (ROS) in the intestinal mucosa was detected using 2ʹ7ʹ-dichlorofluorescein diacetate. The peroxynitrite production of alveolar macrophages (AMs) was measured using dihydrorhodamine 123 oxidation assay. N-acetylcysteine (NAC), an ROS scavenger, was orally administered to mice receiving antibiotics with FOS feeding.ResultsAntibiotic treatment decreased Pseudomonas aeruginosa (PA) phagocytic activity and activity of AMs and protein expression of regenerating islet-derived protein 3β (Reg3β) as well as Toll-like receptor 4 (TLR4) in the intestinal mucosa in the ventilator model. Antibiotic treatment also decreased ROS production in the intestinal mucosa, peroxynitrite production of AMs, and RELMβ expression as well as NF-κB DNA binding activity of the intestinal mucosa in WT mice but not in MyD88−/− mice. Treatment with dead L. salivarius or FOS feeding increased ROS production, bacterial killing activity, and protein expression of Reg3β as well as TLR4 in the intestinal mucosa and reversed the inhibitory effects of antibiotics on PA phagocytic activity of AMs.ConclusionTaken together with the finding that ablation of FOS-induced intestinal ROS using NAC decreased peroxynitrite production as well as PA phagocytic activity of AMs and protein expression of CRP-ductin, IL-17, Reg3β, and RELMβ in the intestinal mucosa, we conclude that commensal microflora plays a key role in stimulating lung immunity. Intestinal ROS plays a role as a predictive indicator and modulator of pulmonary defense mechanisms. Antibiotic treatment reduces lung defense against PA infection through the decrease in intestinal Reg3β and TLR4 expression. Treatment with dead L. salivarius or FOS feeding reverses the antibiotic-induced lung defense impairment through the intestinal ROS/MyD88 pathways.