The DmsABC S-oxide reductase is an essential component of a novel, hypochlorite-inducible system of extracellular stress defense in Haemophilus influenzae

Defenses against oxidative damage to cell components are essential for survival of bacterial pathogens during infection, and here we have uncovered that the DmsABC S-/N-oxide reductase is essential for virulence and in-host survival of the human-adapted pathogen, Haemophilus influenzae. In several different infection models, H. influenzae ΔdmsA strains showed reduced immunogenicity as well as lower levels of survival in contact with host cells. Expression of DmsABC was induced in the presence of hypochlorite and paraquat, closely linking this enzyme to defense against host-produced antimicrobials. In addition to methionine sulfoxide, DmsABC converted nicotinamide- and pyrimidine-N-oxide, precursors of NAD and pyrimidine for which H. influenzae is an auxotroph, at physiologically relevant concentrations, suggesting that these compounds could be natural substrates for DmsABC. Our data show that DmsABC forms part of a novel, periplasmic system for defense against host-induced S- and N-oxide stress that also comprises the functionally related MtsZ S-oxide reductase and the MsrAB peptide methionine sulfoxide reductase. All three enzymes are induced following exposure of the bacteria to hypochlorite. MsrAB is required for physical resistance to HOCl and protein repair. In contrast, DmsABC was required for intracellular colonization of host cells and, together with MtsZ, contributed to resistance to N-Chlorotaurine. Our work expands and redefines the physiological role of DmsABC and highlights the importance of different types of S-oxide reductases for bacterial virulence.

CFTR is required for zinc-mediated antibacterial defense in human macrophages

Cystic fibrosis transmembrane conductance regulator (CFTR) is an anion transporter required for epithelial homeostasis in the lung and other organs, with CFTR mutations leading to the autosomal recessive genetic disease CF. Apart from excessive mucus accumulation and dysregulated inflammation in the airways, people with CF (pwCF) exhibit defective innate immune responses and are susceptible to bacterial respiratory pathogens such as Pseudomonas aeruginosa. Here, we investigated the role of CFTR in macrophage antimicrobial responses, including the zinc toxicity response that is used by these innate immune cells against intracellular bacteria. Using both pharmacological approaches, as well as cells derived from pwCF, we show that CFTR is required for uptake and clearance of pathogenic Escherichia coli by CSF-1-derived primary human macrophages. CFTR was also required for E. coli-induced zinc accumulation and zinc vesicle formation in these cells, and E. coli residing in macrophages exhibited reduced zinc stress in the absence of CFTR function. Accordingly, CFTR was essential for reducing the intramacrophage survival of a zinc-sensitive E. coli mutant compared to wild-type E. coli. Ectopic expression of the zinc transporter SLC30A1 or treatment with exogenous zinc was sufficient to restore antimicrobial responses against E. coli in human macrophages. Zinc supplementation also restored bacterial killing in GM-CSF-derived primary human macrophages responding to P. aeruginosa, used as an in vitro macrophage model relevant to CF. Thus, restoration of the zinc toxicity response could be pursued as a therapeutic strategy to restore innate immune function and effective host defense in pwCF.

Azithromycin Augments Bacterial Uptake and Anti-Inflammatory Macrophage Polarization in Cystic Fibrosis

BACKGROUND

Azithromycin (AZM) is widely being used for treating patients with cystic fibrosis (pwCF) following clinical trials demonstrating improved lung function and fewer incidents of pulmonary exacerba-tions. While the precise mechanisms remain elusive, immunomodulatory actions are thought to be involved. We previously reported impaired phagocytosis and defective anti-inflammatory M2 macrophage polarization in CF. This study systematically analyzed the effect of AZM on the functions of unpolarized and M1/M2 polarized macrophages in CF.

METHODS

Monocytes, isolated from the venous blood of patients with CF (pwCF) and healthy controls (HCs), were differentiated into monocyte-derived macrophages (MDMs) and subsequently infected with P. aeruginosa. P. aeruginosa uptake and killing by MDMs in the presence or absence of AZM was studied. M1 and M2 macrophage polarizations were induced and their functions and cytokine release were analyzed.

RESULTS

Following AZM treatment, both HC and CF MDMs exhibited a significant increase in P. aeruginosa uptake and killing, however, lysosomal acidification remained unchanged. AZM treatment led to higher activation of ERK1/2 in both HC and CF MDMs. Pharmacological inhibition of ERK1/2 using U0126 significantly reduced P. aeruginosa uptake in HC MDMs. M1 macrophage polarization remained unaffected; however, AZM treatment led to increased IL-6 and IL-10 release in both HC and CF M1 macrophages. AZM also significantly increased the phagocytic index for both pHrodo E. coli and S. aureus in CF M1 macrophages. In CF, AZM treatment promoted anti-inflammatory M2 macrophage polarization, with an increased percentage of CD209+ M2 macrophages, induction of the M2 gene CCL18, along with its secretion in the culture supernatant. However, AZM d'd not restore endocytosis in CF, another essential feature of M2 macrophages.

CONCLUSIONS

This study highlights the cellular functions and molecular targets of AZM which may involve an improved uptake of both Gram-positive and Gram-negative bacteria, restored anti-inflammatory macrophage polarization in CF. This may in turn shape the reduced lung inflammation observed in clinical trials. In addition, we confirmed the role of ERK1/2 activation for bacterial uptake.

Environmentally persistent free radicals enhance SARS-CoV-2 replication in respiratory epithelium

Epidemiological evidence links lower air quality with increased incidence and severity of COVID-19; however, mechanistic data have yet to be published. We hypothesized air pollution-induced oxidative stress in the nasal epithelium increased viral replication and inflammation. Nasal epithelial cells (NECs), collected from healthy adults, were grown into a fully differentiated epithelium. NECs were infected with the ancestral strain of SARS-CoV-2. An oxidant combustion by-product found in air pollution, the environmentally persistent free radical (EPFR) DCB230, was used to mimic pollution exposure four hours prior to infection. Some wells were pretreated with antioxidant, astaxanthin, for 24 hours prior to EPFR-DCB230 exposure and/or SARS-CoV-2 infection. Outcomes included viral replication, epithelial integrity, surface receptor expression (ACE2, TMPRSS2), cytokine mRNA expression (TNF-α, IFN-β), intracellular signaling pathways, and oxidative defense enzymes. SARS-CoV-2 infection induced a mild phenotype in NECs, with some cell death, upregulation of the antiviral cytokine IFN-β, but had little effect on intracellular pathways or oxidative defense enzymes. Prior exposure to EPFR-DCB230 increased SARS-CoV-2 replication, upregulated TMPRSS2 expression, increased secretion of the proinflammatory cytokine TNF-α, inhibited expression of the mucus producing MUC5AC gene, upregulated expression of p21 (apoptosis pathway), PINK1 (mitophagy pathway), and reduced levels of antioxidant enzymes. Pretreatment with astaxanthin reduced SARS-CoV-2 replication, downregulated ACE2 expression, and prevented most, but not all EPFR-DCB230 effects. Our data suggest that oxidant damage to the respiratory epithelium may underly the link between poor air quality and increased COVID-19. The apparent protection by antioxidants warrants further research.

Factors in childhood associated with lung function decline to adolescence in cystic fibrosis

BACKGROUND

Despite improvements in general health and life expectancy in people with cystic fibrosis (CF), lung function decline continues unabated during adolescence and early adult life.

METHODS

We examined factors present at age 5-years that predicted lung function decline from childhood to adolescence in a longitudinal study of Australasian children with CF followed from 1999 to 2017.

RESULTS

Lung function trajectories were calculated for 119 children with CF from childhood (median 5.0 [25%-75%=5.0-5.1]) years) to early adolescence (median 12.5 [25%-75%=11.4-13.8] years). Lung function fell progressively, with mean (standard deviation) annual change -0.105 (0.049) for forced vital capacity (FVC) Z-score (p<0.001), -0.135 (0.048) for forced expiratory volume in 1-second (FEV₁) Z-score (p<0.001), -1.277 (0.221) for FEV₁/FVC% (p<0.001), and -0.136 (0.052) for forced expiratory flow between 25% and 75% of FVC Z-score (p<0.001). Factors present in childhood predicting lung function decline to adolescence, in multivariable analyses, were hospitalisation for respiratory exacerbations in the first 5-years of life (FEV₁/FVC p = 0.001, FEF_25-75p = 0.01) and bronchoalveolar lavage neutrophil elastase activity (FEV₁/FVC% p = 0.001, FEV₁p = 0.05, FEF_25-75p = 0.02). No examined factor predicted a decline in the FVC Z-score.

CONCLUSIONS

Action in the first 5-years of life to prevent and/or treat respiratory exacerbations and counteract neutrophilic inflammation in the lower airways may reduce lung function decline in children with CF, and these should be targets of future research.

Neutrophil respiratory burst activity is not exaggerated in cystic fibrosis

BACKGROUND

Exaggerated neutrophil-dominated inflammation underlies progressive cystic fibrosis (CF) lung disease. Older studies reported a defective respiratory burst in CF, but more recent studies suggest neutrophil function is normal.

METHODS

We measured the amount and rate of reactive oxygen species (ROS) during PMA-stimulated respiratory burst activity in children [70 CF, 13 disease controls, 19 health controls] and adults [31 CF, 14 health controls] in neutrophils harvested from peripheral blood. Blood was collected from participants with CF when clinically stable (60 children, 9 adults) and on hospital admission (38 children, 24 adults) and discharge (18 children, 21 adults) for acute pulmonary exacerbations.

RESULTS

When clinically stable, children with CF had lower ROS production [median 318,633, 25% 136,810 - 75% 569,523 RLU] than disease controls [median 599,459, 25% 425,566 - 75% 730,527 RLU] and healthy controls [median 534,073, 25% 334,057 - 75% 738,593 RLU] (p = 0.008). The rate of ROS production was also lower (p = 0.029). In neither children nor adults with CF did ROS production increase on hospital admission for acute pulmonary exacerbation, nor fall prior to discharge. There were no associations between ROS production and high-sensitivity C-reactive protein (indicating systemic inflammation) in either children or adults with CF.

CONCLUSIONS

Our data do not support a role for exaggerated respiratory burst activity contributing to the exaggerated neutrophil-dominated inflammation seen with CF lung disease.

Access to highly specialized growth substrates and production of epithelial immunomodulatory metabolites determine survival of Haemophilus influenzae in human airway epithelial cells

Haemophilus influenzae (Hi) infections are associated with recurring acute exacerbations of chronic respiratory diseases in children and adults including otitis media, pneumonia, chronic obstructive pulmonary disease and asthma. Here, we show that persistence and recurrence of Hi infections are closely linked to Hi metabolic properties, where preferred growth substrates are aligned to the metabolome of human airway epithelial surfaces and include lactate, pentoses, and nucleosides, but not glucose that is typically used for studies of Hi growth in vitro. Enzymatic and physiological investigations revealed that utilization of lactate, the preferred Hi carbon source, required the LldD L-lactate dehydrogenase (conservation: 98.8% of strains), but not the two redox-balancing D-lactate dehydrogenases Dld and LdhA. Utilization of preferred substrates was directly linked to Hi infection and persistence. When unable to utilize L-lactate or forced to rely on salvaged guanine, Hi showed reduced extra- and intra-cellular persistence in a murine model of lung infection and in primary normal human nasal epithelia, with up to 3000-fold attenuation observed in competitive infections. In contrast, D-lactate dehydrogenase mutants only showed a very slight reduction compared to the wild-type strain. Interestingly, acetate, the major Hi metabolic end-product, had anti-inflammatory effects on cultured human tissue cells in the presence of live but not heat-killed Hi, suggesting that metabolic endproducts also influence HI-host interactions. Our work provides significant new insights into the critical role of metabolism for Hi persistence in contact with host cells and reveals for the first time the immunomodulatory potential of Hi metabolites.

Resveratrol and Astaxanthin Protect Primary Human Nasal Epithelial Cells Cultured at an Air-liquid Interface from an Acute Oxidant Exposure

Oxidative stress (OS) in the airway epithelium is associated with cell damage, inflammation, and mitochondrial dysfunction that may initiate or worsen respiratory disease. However, it is unclear whether exogenous antioxidants can provide protection to the airway epithelium from OS. Resveratrol and astaxanthin are nutritional compounds that have shown diverse benefits including protection against OS and inflammation in various situations. The aim of this study was to examine the utility of pre-treatment with resveratrol and astaxanthin to prevent the negative effects of oxidant exposure and restore redox homeostasis in a well-differentiated epithelium grown from primary human nasal epithelial cells (NECs) at the air-liquid interface. Fully differentiated NECs were pretreated with the antioxidants for 24 hours and the cultured epithelia was subsequently exposed to hydrogen peroxide (H₂O₂) for 1 hour to induce an acute OS. Responses measured included mitochondrial reactive oxygen species (mtROS) generation, redox status (GSH/GSSG ratio), cellular ATP, and signaling pathways (SIRT1, FOXO3, p21, PINK1, PARKIN, NRF2). Following H₂O₂ exposure, mtROS production increased by 4-fold compared with control (p<0.01) and pre-treatment with resveratrol or astaxanthin reduced this by 50% (p<0.05). H₂O₂ exposure reduced GSH/GSSG ratio and this decline was prevented by antioxidants pre-treatment. H₂O₂ exposure caused 2.5-fold increase in p21 mRNA expression compared with control (p<0.05), while a slight decrease in p21 mRNA expression was observed when cells were pre-treated with resveratrol or astaxanthin. Our results demonstrate that antioxidants, resveratrol, and astaxanthin were able to protect cells from an acute OS. These agents show promise that encourages further research.

Redox Homeostasis in Well-differentiated Primary Human Nasal Epithelial Cells

Oxidative stress (OS) in the airway epithelium is associated with inflammation, cell damage, and mitochondrial dysfunction that may initiate or worsen respiratory disease. Redox regulation maintains the equilibrium of pro-oxidant/antioxidant reactions but can be disturbed by environmental exposures. The mechanism(s) underlying the induction and impact of OS on airway epithelium and how these influences on respiratory disease is poorly understood. The aim of this study was to develop a stress response model in primary human nasal epithelial cells (NECs) grown at the air-liquid interface (ALI) into a well-differentiated epithelium and to use this model to investigate the mechanisms underlying OS. Hydrogen peroxide (H₂O₂) was used to induce acute OS and the responses were measured with trans epithelial electrical resistance (TEER), membrane permeability, cell death (LDH release), mitochondrial reactive oxygen species (mtROS) generation, redox status (GSH/GSSG ratio), cellular ATP, and signaling pathways (SIRT1, FOXO3, p53, p21, PINK1, PARKIN, NRF2). Following 25 mM (sensitive) or 50mM (resistant) H₂O₂ exposure, cell integrity decreased (p<0.05), GSH/GSSG ratio reduced (p<0.05), and ATP production declined by 83% (p<0.05) in the sensitive and 55% (p<0.05) in the resistant group; mtROS production increased 3.4-fold (p<0.001). Significant inter-individual differences between healthy humans with regards to susceptibility to OS, and differential activation of various pathways (FOXO3, PARKIN) were observed. These intra-individual differences in susceptibility to OS may be attributed to resistant individuals having more mitochondria or greater mitochondrial function.

Author Correction: Increased susceptibility of airway epithelial cells from ataxia-telangiectasia to S. pneumoniae infection due to oxidative damage and impaired innate immunity

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Anti-inflammatory effects of lenabasum, a cannabinoid receptor type 2 agonist, on macrophages from cystic fibrosis

BACKGROUND

Lenabasum is an oral synthetic cannabinoid receptor type 2 agonist previously shown to reduce the production of key airway pro-inflammatory cytokines known to play a role in cystic fibrosis (CF). In a double-blinded, randomized, placebo-control phase 2 study, lenabasum lowered the rate of pulmonary exacerbation among patients with CF. The present study was undertaken to investigate anti-inflammatory mechanisms of lenabasum exhibits in CF macrophages.

METHODS

We used monocyte-derived macrophages (MDMs) from healthy donors (n = 15), MDMs with CFTR inhibited with C-172 (n = 5) and MDMs from patients with CF (n = 4). Monocytes were differentiated to macrophages and polarized into classically activated (M1) macrophages by LPS or alternatively activated (M2) macrophages by IL-13 in presence or absence of lenabasum.

RESULTS

Lenabasum had no effect on differentiation, polarization and function of macrophages from healthy individuals. However, in CF macrophages lenabasum downregulated macrophage polarization into the pro-inflammatory M1 phenotype and secretion of the pro-inflammatory cytokines IL-8 and TNF-α in a dose-dependent manner. An improvement in phagocytic activity was also observed following lenabasum treatment. Although lenabasum did not restore the impaired polarization of anti-inflammatory M2 macrophage, it reduced the levels of IL-13 and enhanced the endocytic function of CF MDMs. The effects of lenabasum on MDMs with CFTR inhibited by C-172 were not as obvious.

CONCLUSION

In CF macrophages lenabasum modulates macrophage polarization and function in vitro in a way that would reduce inflammation in vivo. Further studies are warranted to determine the link between activating the CBR2 receptor and CFTR.

Personalized Transcriptomics Reveals Heterogeneous Immunophenotypes in Children with Viral Bronchiolitis

Rationale: A subset of infants are hypersusceptible to severe/acute viral bronchiolitis (AVB), for reasons incompletely understood. Objectives: To characterize the cellular/molecular mechanisms underlying infant AVB in circulating cells/local airway tissues. Methods: Peripheral blood mononuclear cells and nasal scrapings were obtained from infants (<18 mo) and children (≥18 mo to 5 yr) during AVB and after convalescence. Immune response patterns were profiled by multiplex analysis of plasma cytokines, flow cytometry, and transcriptomics (RNA-Seq). Molecular profiling of group-level data used a combination of upstream regulator and coexpression network analysis, followed by individual subject-level data analysis using personalized N-of-1-pathways methodology. Measurements and Main Results: Group-level analyses demonstrated that infant peripheral blood mononuclear cell responses were dominated by monocyte-associated hyperupregulated type 1 IFN signaling/proinflammatory pathways (drivers: TNF [tumor necrosis factor], IL-6, TREM1 [triggering receptor expressed on myeloid cells 1], and IL-1B), versus a combination of inflammation (PTGER2 [prostaglandin E receptor 2] and IL-6) plus growth/repair/remodeling pathways (ERBB2 [erbb-b2 receptor tyrosine kinase 2], TGFB1 [transforming growth factor-β1], AREG [amphiregulin], and HGF [hepatocyte growth factor]) coupled with T-helper cell type 2 and natural killer cell signaling in children. Age-related differences were not attributable to differential steroid usage or variations in underlying viral pathogens. Nasal mucosal responses were comparable qualitatively in infants/children, dominated by IFN types 1-3, but the magnitude of upregulation was higher in infants (range, 6- to 48-fold) than children (5- to 17-fold). N-of-1-pathways analysis confirmed differential upregulation of innate immunity in infants and natural killer cell networks in children, and additionally demonstrated covert AVB response subphenotypes that were independent of chronologic age. Conclusions: Dysregulated expression of IFN-dependent pathways after respiratory viral infections is a defining immunophenotypic feature of AVB-susceptible infants and a subset of children. Susceptible subjects seem to represent a discrete subgroup who cluster based on (slow) kinetics of postnatal maturation of innate immune competence.

Characterizing well-differentiated culture of primary human nasal epithelial cells for use in wound healing assays

The nasal epithelium is the initial contact between the external environment and the respiratory tract and how it responds to noxious stimuli and repairs epithelial damage is important. Growing airway epithelial cells in culture at air-liquid interface allows for a physiologically relevant model of the human upper airways. The aim of the present study was to characterize human primary nasal epithelial cells grown at the air-liquid interface and establish a model for use in wound healing assays. This study determined the time required for full differentiation of nasal epithelial cells in an air-liquid interface culture to be at least 7 weeks using the standardized B-ALI media. Also, a model was established that studied the response to wounding and the effect of EGFR inhibition on this process. Nasal epithelial cultures from healthy subjects were differentiated at air-liquid interface and manually wounded. Wounds were monitored over time to complete closure using a time lapse imaging microscope with cultures identified to have a rate of wound healing above 2.5%/h independent of initial wound size. EGFR inhibition caused the rate of wound healing to drop a significant 4.6%/h with there being no closure of the wound after 48 h. The robust model established in this study will be essential for studying factors influencing wound healing, including host disease status and environmental exposures in the future.

Differential expression of genes and receptors in monocytes from patients with cystic fibrosis

INTRODUCTION

We previously reported defective alternative polarization (M2) of macrophages and early expression of classically polarized (M1) macrophage markers in unpolarized monocyte-derived macrophages (MDMs) in patients with cystic fibrosis (CF). The present study assessed whether the mechanism(s) underlying defective macrophage polarization resided in circulating monocytes.

METHODS

Monocyte subsets (classical, intermediate and non-classical), markers for monocyte activation (CD163) and recruitment (CD195), receptors/genes associated with macrophage differentiation and polarization were analyzed in CF and compared with healthy individuals.

RESULTS

No differences were observed in the monocyte subsets or in the expression of CD163 or CD195. Expression of the M-CSF receptor, TLR4, γC, IL-4Rα, IL-13Rα1, TIMP-1 and Cox-2 were higher in CF monocytes, albeit at low levels, whereas, LRP1, MMP9, MMP28 were downregulated compared to mooncytes from healthy individuals.

CONCLUSIONS

Our data suggest that differences in CF monocytes may contribute to the reported CFTR-dependent defect in macrophage differentiation, polarization and function.

The Impact of Early-Life Exposure to Air-borne Environmental Insults on the Function of the Airway Epithelium in Asthma

The airway epithelium is both a physical barrier protecting the airways from environmental insults and a significant component of the innate immune response. There is growing evidence that exposure of the airway epithelium to environmental insults in early life may lead to permanent changes in structure and function that underlie the development of asthma. Here we review the current published evidence concerning the link between asthma and epithelial damage within the airways and identify gaps in knowledge for future studies.

Streptococcus pneumoniae colonization of the nasopharynx is associated with increased severity during respiratory syncytial virus infection in young children

Background and Objective

Respiratory syncytial virus (RSV) is the most significant cause of acute respiratory infection (ARI) in early life. RSV and other respiratory viruses are known to stimulate substantial outgrowth of potentially pathogenic bacteria in the upper airways of young children. However, the clinical significance of interactions between viruses and bacteria is currently unclear. The present study aimed to clarify the effect of viral and bacterial co‐detections on disease severity during paediatric ARI.

Methods

Nasopharyngeal aspirates from children under 2 years of age presenting with ARI to the emergency department were screened by quantitative PCR for 17 respiratory viruses and the bacterial pathogens Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis. Associations between pathogen detection and clinical measures of disease severity were investigated.

Results

RSV was the most common virus detected, present in 29 of 58 samples from children with ARI (50%). Detection of S. pneumoniae was significantly more frequent during RSV infections compared to other respiratory viruses (adjusted effect size: 1.8, P: 0.03), and co‐detection of both pathogens was associated with higher clinical disease severity scores (adjusted effect size: 1.2, P: 0.03).

Conclusion

Co‐detection of RSV and S. pneumoniae in the nasopharynx was associated with more severe ARI, suggesting that S. pneumoniae colonization plays a pathogenic role in young children.

http://onlinelibrary.wiley.com/doi/10.1111/resp.13209/abstract

High loads of bacteria colonizing the upper respiratory tract are often observed during paediatric respiratory syncytial virus (RSV) infections. The present study identified an association between co‐detection of RSV and Streptococcus pneumoniae and more severe disease, suggesting the bacteria has a pathogenic role in these young children.

Human Metapneumovirus Impairs Apoptosis of Nasal Epithelial Cells in Asthma via HSP70

Asthmatics are highly susceptible to respiratory viral infections, possibly due to impaired innate immunity. However, the exact mechanisms of susceptibility are likely to differ amongst viruses. Therefore, we infected primary nasal epithelial cells (NECs) from adults with mild-to-moderate asthma, with respiratory syncytial virus (RSV) or human metapneumovirus (hMPV) in vitro and investigated the antiviral response. NECs from these asthmatics supported elevated hMPV but not RSV infection, compared to non-asthmatic controls. This correlated with reduced apoptosis and reduced activation of caspase-9 and caspase-3/7 in response to hMPV, but not RSV. The expression of heat shock protein 70 (HSP70), a known inhibitor of caspase activation and subsequent apoptosis, was amplified in response to hMPV infection. Chemical inhibition of HSP70 function restored caspase activation and reduced hMPV infection in NECs from asthmatic subjects. There was no impairment in the production of IFN by NECs from asthmatics in response to either hMPV or RSV, demonstrating that increased infection of asthmatic airway cells by hMPV is IFN-independent. This study demonstrates, for the first time, a mechanism for elevated hMPV infection in airway epithelial cells from adult asthmatics and identifies HSP70 as a potential target for antiviral and asthma therapies.

Brief exposure to cigarette smoke impairs airway epithelial cell innate anti-viral defence

BACKGROUND

Human rhinovirus (hRV) infections commonly cause acute upper respiratory infections and asthma exacerbations. Environmental cigarette smoke exposure is associated with a significant increase in the risk for these infections in children.

OBJECTIVE

To determine the impact of short-term exposure to cigarette smoke on innate immune responses of airway epithelial cells infected with hRV.

METHODS

A human bronchial epithelial cell line (HBEC-3KT) was exposed to cigarette smoke extract (CSE) for 30 min and subsequently infected with hRV serotype 1B. Viral-induced cytokine release was measured with AlphaLISA and viral replication quantified by shed viral titer and intracellular viral copy number 24h post-infection.

RESULTS

CSE induced a concentration-dependent decrease in CXCL10 (p<0.001) and IFN-β (p<0.001), with a 79% reduction at the highest dose with an associated 3-fold increase in shed virus. These effects were maintained when infection was delayed up to 24h post CSE exposure. Exogenous IFN-β treatment at t=0 after infection blunts the effects of CSE on viral replication (p<0.05).

CONCLUSION

A single exposure of 30 min to cigarette smoke has a lasting impact on epithelial innate defence providing a plausible mechanism for the increase in respiratory infections seen in children exposed to second-hand tobacco smoke.

Viral and host factors determine innate immune responses in airway epithelial cells from children with wheeze and atopy

BACKGROUND

Airway epithelial cells (AEC) from patients with asthma, appear to have an impaired interferon (IFN)-β and -λ response to infection with rhinovirus.

OBJECTIVES

To determine if impaired IFN responses can be identified in young children at risk of developing asthma due to atopy and/or early life wheeze, and if the site of infection or the infecting virus influence the antiviral response.

METHODS

Nasal (N) and tracheal (T) epithelial cells (EC) were collected from children categorised with atopy and/or wheeze based on specific IgE to locally common aeroallergens and a questionnaire concerning respiratory health. Submerged primary cultures were infected with respiratory syncytial virus (RSV) or human metapneumovirus (hMPV), and IFN production, inflammatory cytokine expression and viral replication quantified.

RESULTS

Nasal epithelial cells (NEC), but not tracheal epithelial cells (TEC), from children with wheeze and/or atopy produced less IFN-β, but not IFN-λ, in response to RSV infection; this was associated with higher viral shedding. However, IFN-regulated factors IRF-7, Mx-1 and CXCL-10, and inflammatory cytokines were not differentially regulated. NECs and TECs from children with wheeze and/or atopy demonstrated no impairment of the IFN response (β or λ) to hMPV infection. Despite this, more hMPV was shed from these cells.

CONCLUSIONS

AECs from children with wheeze and/or atopy do not have an intrinsic defect in the production of IFN-β or -λ, however, this response is influenced by the infecting virus. Higher viral load is associated with atopy and wheeze suggesting an impaired antiviral response to RSV and hMPV that is not influenced by production of IFNs.

Airway, but not serum or urinary, levels of YKL-40 reflect inflammation in early cystic fibrosis lung disease

BACKGROUND

Cystic fibrosis (CF) lung disease begins in early life and is progressive with the major risk factor being an exaggerated inflammatory response. Currently, assessment of neutrophilic inflammation in early cystic fibrosis (CF) lung disease relies on bronchoalveolar lavage (BAL). The chitinase-like protein YKL-40 is raised in sputum and serum of adults with CF. We investigated YKL-40 in BAL, serum and urine to determine whether this reflected inflammation and infection in young children with CF.

METHODS

YKL-40 was measured in matched samples of BAL, serum and urine obtained from 36 infants and young children with CF participating in an early surveillance program. Levels were compared to clinical data and markers of inflammation detected in the lung.

RESULTS

YKL-40 in BAL correlated with pulmonary infection [β=1.30 (SE 0.34), p < 0.001] and BAL markers of inflammation [macrophage number: r2 = 0.34, p < 0.001; neutrophil number: r2 = 0.74, p < 0.001; neutrophil elastase: r2 = 0.47, p < 0.001; CXCL8: r2 = 0.45, p < 0.001; IL-β: r2 = 0.62, p < 0.001]. YKL-40 was detectable in serum but levels did not correlate with BAL levels in the same individuals (r2 = 0.04, p = 0.14) or with inflammatory markers. YKL-40 was below the limit of detection in urine (30 pg/ml).

CONCLUSIONS

This study demonstrates that levels of the chitinase-like protein YKL-40 reflect airway inflammation and infection in early CF lung disease. The lack of increased YKL-40 in serum in the absence of systemic inflammation limits the benefit of this potential biomarker in early disease.

Hanging drop: an in vitro air toxic exposure model using human lung cells in 2D and 3D structures

Using benzene as a candidate air toxicant and A549 cells as an in vitro cell model, we have developed and validated a hanging drop (HD) air exposure system that mimics an air liquid interface exposure to the lung for periods of 1h to over 20 days. Dose response curves were highly reproducible for 2D cultures but more variable for 3D cultures. By comparing the HD exposure method with other classically used air exposure systems, we found that the HD exposure method is more sensitive, more reliable and cheaper to run than medium diffusion methods and the CULTEX(®) system. The concentration causing 50% of reduction of cell viability (EC50) for benzene, toluene, p-xylene, m-xylene and o-xylene to A549 cells for 1h exposure in the HD system were similar to previous in vitro static air exposure. Not only cell viability could be assessed but also sub lethal biological endpoints such as DNA damage and interleukin expressions. An advantage of the HD exposure system is that bioavailability and cell concentrations can be derived from published physicochemical properties using a four compartment mass balance model. The modelled cellular effect concentrations EC50cell for 1h exposure were very similar for benzene, toluene and three xylenes and ranged from 5 to 15 mmol/kgdry weight, which corresponds to the intracellular concentration of narcotic chemicals in many aquatic species, confirming the high sensitivity of this exposure method.

Judgment and decision making: Behavioral approaches

The area of judgment and decision making has given rise to the study of many interesting phenomena, including reasoning fallacies, which are also of interest to behavior analysts. Indeed, techniques and principles of behavior analysis may be applied to study these fallacies. This article reviews research from a behavioral perspective that suggests that humans are not the information-seekers we sometimes suppose ourselves to be. Nor do we utilize information effectively when it is presented. This is shown from the results of research utilizing matching to sample and other behavioral tools (monetary reward, feedback, instructional control) to study phenomena such as the conjunction fallacy, base-rate neglect, and probability matching. Research from a behavioral perspective can complement research from other perspectives in furthering our understanding of judgment and decision making.

Behavior analysis and behavioral ecology: A synergistic coupling

Recent trends in behavioral ecology and behavior analysis suggest that the two disciplines complement one another, underscoring the desirability of an integrated approach to behavior. Three examples from the foraging literature illustrate the potential value of an interdisciplinary approach. For example, a model of natural selection for foraging efficiency-optimal foraging theory-makes several predictions consistent with an hypothesis of a more proximate phenomenon, the reduction in delay to primary reinforcement. Not only are the ecological and behavior analytic approaches to behavior complementary, but each may provide insights into the operation of controlling variables in situations usually thought of as being the other's domain.

The microtubule depolymerizing agent CYT997 causes extensive ablation of tumor vasculature in vivo

The orally active microtubule-disrupting agent (S)-1-ethyl-3-(2-methoxy-4-(5-methyl-4-((1-(pyridin-3-yl)butyl)amino)pyrimidin-2-yl)phenyl)urea (CYT997), reported previously by us (Bioorg Med Chem Lett 19:4639-4642, 2009; Mol Cancer Ther 8:3036-3045, 2009), is potently cytotoxic to a variety of cancer cell lines in vitro and shows antitumor activity in vivo. In addition to its cytotoxic activity, CYT997 possesses antivascular effects on tumor vasculature. To further characterize the vascular disrupting activity of CYT997 in terms of dose and temporal effects, we studied the activity of the compound on endothelial cells in vitro and on tumor blood flow in vivo by using a variety of techniques. In vitro, CYT997 is shown to potently inhibit the proliferation of vascular endothelial growth factor-stimulated human umbilical vein endothelial cells (IC(50) 3.7 ± 1.8 nM) and cause significant morphological changes at 100 nM, including membrane blebbing. Using the method of corrosion casting visualized with scanning electron microscopy, a single dose of CYT997 (7.5 mg/kg i.p.) in a metastatic cancer model was shown to cause destruction of tumor microvasculature in metastatic lesions. Furthermore, repeat dosing of CYT997 at 10 mg/kg and above (intraperitoneally, b.i.d.) was shown to effectively inhibit development of liver metastases. The time and dose dependence of the antivascular effects were studied in a DLD-1 colon adenocarcinoma xenograft model using the fluorescent dye Hoechst 33342. CYT997 demonstrated rapid and dose-dependent vascular shutdown, which persists for more than 24 h after a single oral dose. Together, the data demonstrate that CYT997 possesses potent antivascular activity and support continuing development of this promising compound.

"Automaintenance": the role of reinforcement

A key was illuminated on the average of every 30 sec for a duration of 6 sec and this was followed by food presentations. When key pecks in the presence of the light produced immediate access to grain (autoshaping procedure) pigeons were likely to peck. When pecks terminated the keylight but prevented access to grain (automaintenance procedure) pigeons were much less likely to peck. Seven of 12 pigeons failed to develop responding during the automaintenance procedure. Four of the five pigeons that responded during the automaintenance procedure were exposed to a procedure in which responses could not immediately terminate the light. Three of the four ceased to respond during optimal automaintenance conditions, suggesting that the response-dependent offset of the keylight had been reinforcing their pecking. Responding during the automaintenance procedure was eliminated for a fifth pigeon by eliminating the contiguity of light-offset and food-onset on those trials in which the pigeon did not peck. These results suggest that: (1) automaintenance (unlike autoshaping) is not an effective procedure for reliably generating responding; (2) responding that does occur during the automaintenance procedure is reinforced by the response-dependent offset of the keylight.

Percentage reinforcement and choice

Pigeons responded on identical concurrent variable-interval schedules (choice phase), producing outcomes of either periodic reinforcement schedules always terminating in reinforcement (reliable schedule) or otherwise identical schedules providing reinforcement on only a percentage of instances (percentage reinforcement schedule). Comparisons of this type constituted two assessments of the generality of preference for percentage reinforcement reported by Kendall (1974). In a third set of conditions, a reliable schedule was pitted against a percentage reinforcement schedule in which the more negative outcome was a leaner schedule of reinforcement (rather than nonreinforcement, as in the other two conditions). In all three types of conditions, the schedule providing the higher rate of reinforcement was preferred. Results from a subsequent manipulation suggest that Kendall's contrasting results may have depended on the fact that the stimuli in his choice phase (unlit keys) were physically identical to the stimulus correlated with the nonchosen outcome in his outcome phase.

The delay-reduction hypothesis of conditioned reinforcement and punishment: Observing behavior

Pigeons responded in an observing-response procedure in which three fixed-interval components alternated. Pecking one response key produced food reinforcement according to a mixed schedule. Pecking the second (observing) key occasionally replaced the mixed-schedule stimulus with the stimulus correlated with the fixed-interval component then in effect. In Experiment 1, observing was best maintained by stimuli correlated with a reduction in mean time to reinforcement. That finding was consistent with the conditioned-reinforcement hypothesis of observing behavior. However, low rates of observing were also maintained by stimuli not representing delay reduction. Experiment 2 assessed the role of sensory reinforcement. It showed that response rate was higher when maintained by stimuli uncorrelated with reinforcement delay than when the stimuli were correlated with a delay increase. This latter result supports a symmetrical version of the conditioned-reinforcement hypothesis that requires suppression by stimuli correlated with an increase in time to reinforcement. The results were inconsistent with hypotheses stressing the reinforcing potency of uncertainty reduction.

Choice for periodic schedules of reinforcement

Pigeons' responses in the presence of two concurrently available (initial-link) stimuli produced one of two different (terminal-link) stimuli according to identical but independent variable-interval schedules. Responding in the mutually exclusive terminal links was reinforced with food according to fixed-ratio schedules for six pigeons and according to fixed-interval schedules for two pigeons. None of the pigeons matched the proportion of (choice) responses in the initial links to the proportion of the rates of reinforcement obtained during the terminal links. Instead, as the values of each of the terminal-link schedules were increased by a constant amount, the choice proportions for the stimulus associated with the smaller of the two values increased, even though the relative rates of reinforcement during the terminal links decreased. These results are incompatible with those from previous studies with aperiodic (variable-interval or variable-ratio) schedules. The present results do suggest, however, that in transforming aperiodic schedules into their periodic equivalents, it may be necessary to consider the size of the smallest interreinforcement interval comprising the terminal-link schedules.

Choice behavior and the accessibility of the reinforcer

In Experiment 1, matching of relative response rates to relative rates of reinforcement was obtained in concurrent variable-interval schedules when the absolute values of the two concurrent variable-interval schedules varied from 6 sec and 12 sec to 600 sec and 1200 sec. Increases in the duration of the changeover delay, however, produced decreases in the relative response rates and, consequently, some deviation from matching. In Experiment 2, matching of relative response rates to the relative duration of the reinforcer failed to occur when the equal variable-interval schedules arranging access to the two different reinforcer durations (1.5 and 6 sec) were varied in size from concurrent variable-interval 10-sec schedules to concurrent variable-interval 600-sec schedules.

Relative delay of reinforcement and choice

Pigeons' responses on either of two concurrently available keys each associated with variable-interval 60-sec schedules occasionally changed the schedule on that key to a terminal-link interval schedule providing access to gain while the other key became inoperative. Experiment I compared simple fixed- and mixed-interval schedules in the terminal links, and showed that for all subjects and schedules the distribution of responses during the concurrent initial links was accurately described by the relative inverse delay of reinforcement squared. Experiment II extended the generality of this formulation to a situation in which rate of reinforcement was constant and delay alone was varied.

Effects on choice of reinforcement delay and conditioned reinforcement

Pigeons chose between fixed-interval schedules of different durations presented in the terminal links of concurrent-chains schedules. The pair of schedules was always in the ratio of 2:1, but the absolute duration of the fixed intervals varied. In one set of conditions, the different terminal-link schedules were associated with different keylight stimuli (cued conditions). In a second set of conditions, the different terminal-link schedules were associated with the same stimulus (uncued conditions). Results from the cued conditions replicated previous findings that preference for the shorter fixed-interval schedule increased with fixed-interval duration. Preferences in the uncued conditions were lower than in the corresponding cued conditions but also increased with fixed-interval length. In addition, the degree of control under the uncued conditions was correlated with the extent to which the schedule during the terminal link was discriminated immediately upon entry into the terminal link. The pattern of results in both conditions was inconsistent with the notion that choice behavior matches relative immediacy of reinforcement. Reanalysis of previous evidence for matching (Chung and Herrnstein, 1967) showed that matching in fact did not occur, as the preferences of their subjects for the shorter of two delays also increased with the absolute size of the delays.

Key-peck durations under behavioral contrast and differential reinforcement

Pigeons were maintained on a multiple schedule in which both components were variable-interval one-minute schedules. When they were switched to a condition in which one component was extinction, behavioral contrast was observed. The median durations of the key pecks in the unchanged component did not decrease in size. The results are incompatible with a theory of behavioral contrast which considers the added pecks to be short-duration responses. In a second experiment, pigeons were required to emit short-duration key pecks in one component of a multiple schedule, and long-duration pecks in the other. Two of three pigeons learned to emit responses appropriate to the requirements of the component in effect, suggesting that the duration of the key-peck response is sensitive to differential reinforcement.

Effects of reinforcer duration on responding in two-link chained interval schedules

Each of five pigeons was exposed to two or more durations of access to mixed grains on two-link, chained, interval schedules in which both links were identical fixed-interval or variable-interval schedules. Response rates were an increasing function of reinforcer duration for both initial and terminal links. For both types of interval schedules, initial-link response rates were more sensitive to reinforcer duration than were terminal-link response rates. The present results, together with prior ones, suggest that chaining and choice procedures are each sufficient for demonstrating substantial sensitivity of responding to changes in reinforcer duration.

The dissociation of discriminative and conditioned reinforcing functions of stimuli with changes in deprivation

Pigeons were studied in two experiments designed to explore the effects of deprivation level upon responding in each link of a two-link chained schedule. The stimulus associated with the terminal link of the chain can be both a discriminative stimulus (S(D)) for responding in the presence of the stimulus and a conditioned reinforcer (S(r)) for responding in the preceding link. Previous findings have indicated that the S(r) function was more readily weakened by satiation than was the S(D) function, i.e., the rate of responding decreased more rapidly in the initial link of the chain than in the terminal link. The first of the present experiments, in which tests were conducted after a series of sessions, produced different results: rates of responding in the two links declined simultaneously. The second experiment supported the hypothesis that the effects of satiation interact with the duration of maintenance on the satiation procedure: in early sessions the S(r) function was more readily disrupted, but in later sessions the rates of responding in the two links declined simultaneously. Subsequent to this extensive series of identical sessions, the pigeons' deprivation level was altered before a session by pre-feeding the pigeons up to their normal post-session weights. The rates of responding failed to reflect fully this change in deprivation in the first such session, suggesting that the pigeons' behavior had become partially independent of deprivation level.

Transitivity as a property of choice

Pigeons' pecks in the presence of two concurrently available initial-link stimuli occasionally produced one of two stimuli associated with mutually exclusive terminal links. Pecks during either terminal link produced food according to aperiodic (variable-interval and variable-ratio) or periodic (fixed-interval and fixed-ratio) schedules of reinforcement. Aperiodic and periodic schedules to which the pigeons were indifferent, in the sense that these schedules maintained equal responding in the initial links, often yielded different preferences in separate choice tests with a third schedule. Conversely, aperiodic and periodic schedules that were equally preferred to a third schedule often failed to generate indifference. These intransitivities imply that (1) aperiodic and periodic schedules are not functionally equivalent in their effects upon choice, and (2) efforts to find a simple method for transforming aperiodic schedules into their periodic equivalents will fail.

Choice and response contingencies

Two experiments investigated the extent to which response contingencies influence the choice between two schedules of reinforcement by exposing pigeons to a concurrent-chains procedure in which reinforcers in one terminal link were response-independent, and in the other terminal link, response-dependent. In Experiment 1, the pigeons were indifferent between an aperiodic, response-independent schedule and an aperiodic, response-dependent schedule that required a minimum rate of responding. This finding limits the generality of a required-rate contingency as a determinant of choice, which contingency had been previously demonstrated in a context of periodic reinforcement to evoke preference for an alternate schedule. In Experiment 2, the pigeons preferred a periodic, response-independent schedule to a periodic, response-dependent schedule that shared a feature with a required-rate schedule: there was a requirement to respond early in the interreinforcement interval, when responding produced reinforcement only later. The results of the two experiments suggest the following general interpretation: pigeons prefer a second schedule to the extent that the response contingencies of the first schedule must be satisfied during discriminable periods of nonreinforcement.

A model for choice in simple concurrent and concurrent-chains schedules

Pigeons' responses in the presence of two concurrently available (initial-link) stimuli produced one of two different (terminal-link) stimuli. Entrance into the mutually exclusive terminal links was arranged by different and independent variable-interval schedules for each key, while responses during the mutually exclusive terminal-link stimuli produced a single food reinforcement according to indentical and independent variable-interval schedules. The pigeons emitted more initial-link responses on the key with the shorter average interreinforcement interval in the initial link. This difference in initial-link response rates varied directly with the difference between the average inter-reinforcement intervals of the initial-link schedules and decreased when the initial-link schedule with the longer average interreinforcement interval was followed by several consecutive food reinforcements on the variable-interval schedule in the terminal link on that key. These results are incompatible with previous formulations of choice behavior with the concurrent-chains procedure. A modified formulation with a multiplier for the overall rate of primary reinforcement obtained on each key provides a better description of choice. In addition, the new formulation applies to behavior in simple (concurrent) choice situations, an advantage not achieved by previous formulations.

Some effects of interreinforcement time upon choice

Pigeons' responses were reinforced on two identical and concurrently available chain variable-interval-schedules. Unlike the typical concurrent chains procedure, both links were operative throughout, thus producing three types of concurrency: (1) concurrent initial links; (2) concurrent initial and terminal links; (3) concurrent terminal links. Choice proportions in each of these three states suggested that the pigeons were sensitive to momentary likelihoods of reinforcement: choice proportions for a schedule were higher when the schedule had been operative for some time, resulting in a higher probability of reinforcement. The study also showed that the relative rates of responding did not match the relative rates of reinforcement in any of the three states of concurrency. Instead, the choice proportions in both the concurrent initial and in the concurrent terminal links were intermediate between the scheduled and the obtained relative rates of reinforcement, while the choice proportions for a terminal link concurrent with an initial link consistently overmatched the relative interreinforcement times (and were typically 1.00). These data indicate that an accurate characterization of choice may not be obtained by considering only the relative interreinforcement interval where one interreinforcement interval is segmented into a chain. Instead, the organism's choice for a schedule will be substantially lowered by the chaining operation.

Uncertainty reduction, conditioned reinforcement, and observing

In a concurrent-chains procedure, pigeons chose between equivalent mixed and multiple fixed-interval schedules of reinforcement. In the first experiment, preference for the multiple schedule was higher when the probability of the shorter fixed interval was less than .50 than for complementary points, an outcome consistent with the delay-reduction hypothesis of conditioned reinforcement and observing, but inconsistent with the uncertainty-reduction hypothesis which requires symmetrical preferences with a maximum when the two intervals are equiprobable. A second experiment assessed preference for equivalent mixed and multiple schedules when each choice outcome resulted in two reinforcements, one on the longer and one on the shorter fixed interval. The order of the two fixed intervals was determined probabilistically. Pigeons again preferred multiple to mixed schedules, although multiple-schedule preference did not vary systematically with the likelihood of the shorter fixed interval occurring first. The results from these choice procedures are consistent with those from the observing-response literature in suggesting that the strength of a stimulus cannot be well described as a function of the degree of uncertainty reduction the stimulus provides about reinforcement.

Choice and foraging

In Experiment 1, six naive pigeons were trained on a foraging schedule characterized by different states beginning with a search state in which completion of a fixed-interval on a white key led to a choice state. In the choice state the subject could, by appropriate responding on a fixed ratio of three, either accept or reject the schedule of reinforcement that was offered (either a variable-interval five-second or a variable-interval 20-second). If the subject accepted the schedule, it entered a "handling state" in which the appropriate variable-interval schedule was presented. Completion of the variable-interval schedule produced food. The independent variable was the fixed-interval value in the search state, and the dependent variable was the rate of acceptance of the long variable-interval in the choice state. Experiment 2 was identical except that the search state required completion of a variable-interval, instead of a fixed-interval, schedule. The rate of acceptance of the long variable-interval schedule in both experiments was a direct function of the length of the search state, in accordance with both optimality theory and the delay-reduction hypothesis.

Choice and the relative immediacy of reinforcement

The relative immediacy of reinforcement in concurrent-chain schedules was varied while the relative reduction in the overall average time to reinforcement associated with terminal-link entry was held constant. For each of four pigeons, choice did not vary with relative immediacy of reinforcement. Subsequently, choice by the same subjects was shown to be sensitive to relative reduction in average time to reinforcement.