Clémence Martin

Heme Oxygenase-1 Prevents Airway Mucus Hypersecretion Induced by Cigarette Smoke in Rodents and Humans

We investigated the role of heme oxygenase-1 (HO-1), a powerful anti-inflammatory and anti-oxidant enzyme, in modulating cigarette smoke (CS)-induced mucus secretion. In both rats and mice, 5-day CS exposure increased HO-1 expression and activity, mucus secretion, MUCIN 5AC (MUC5AC) gene and protein expression, and local inflammation, along with up-regulation of dual oxidase 1 gene expression and both the activity and phosphorylation of the epidermal growth factor receptor, which is involved in MUC5AC induction. Pharmacological induction of HO-1 prevented these actions and inhibition of HO-1 expression by a specific siRNA potentiated them. In French participants to the European Community Respiratory Health Survey II (n = 210, 30 to 53 years of age, 50% males) exposed to CS, a significant increase in the percentage of participants with chronic sputum was observed in those harboring at least one allele with a long (GT)(n) in the HO-1 promoter gene (>33 repeats), which is associated with a low level of HO-1 protein expression, compared with those with a short number of (GT)n repeats (21.7% versus 8.6%, P = 0.047). No such results were observed in those who had never smoked (n = 297). We conclude that HO-1 has a significant protective effect against airway mucus hypersecretion in animals and humans exposed to CS.

Pseudomonas aeruginosa induces vascular endothelial growth factor synthesis in airway epithelium in vitro and in vivo

Pseudomonas aeruginosa (PA) airway infection and bronchial blood vessel proliferation are features of bronchiectasis. Because vascular endothelial growth factor (VEGF)-A regulates angiogenesis, we hypothesised that PA infection induces VEGF synthesis in epithelium and peribronchial angiogenesis. Because epidermal growth factor receptor (EGFR) activation regulates VEGF synthesis in cancer, we also evaluated the roles of EGFR. Airway epithelial cells were incubated for 24 h with PA supernatants and VEGF concentrations were measured in culture medium by ELISA. C57BL/6N mice were instilled intratracheally with sterile agarose beads or with agarose beads coated with the PA strain PAO1 (mean±sem 6×105±3×105 cfu·animal−1), with or without the EGFR inhibitor AG1478 (12.5 mg·kg−1·day−1 intraperitoneally). Epithelial immunostaining for VEGF and phosphorylated EGFR, and peribronchial vascularity, were quantified using morphometric analysis. VEGF expression was further assessed by western blot in mouse lung homogenates. PA supernatants induced dose-dependent VEGF synthesis in cultured airway epithelial cells, effects which were prevented by EGFR antagonists. In mice, persistent PAO1 infection increased immunostaining for VEGF and phosphorylated EGFR in airway epithelium, and resulted in increased peribronchial vascularity within 7 days. These effects were reduced by EGFR inhibition. Persistent PA infection induced VEGF synthesis in airway epithelium and peribronchial angiogenesis, at least in part via EGFR-dependent mechanisms.

Toll-Like Receptor 2 Deficiency Increases Resistance to Pseudomonas aeruginosa Pneumonia in the Setting of Sepsis-Induced Immune Dysfunction

BACKGROUND Sepsis is characterized by a dysregulated inflammatory response followed by immunosuppression that favors the development of secondary infections. Toll-like receptors (TLRs) are major regulators of the hosts response to infections. How variability in TLR signaling may impact the development of sepsis-induced immune dysfunction has not been established. We sought to establish the role of TLR2, TLR4, and TLR5 in postseptic mice with Pseudomonas aeruginosa pneumonia. METHODS We used an experimental model of sublethal polymicrobial sepsis induced by cecal ligation and puncture (CLP). Wild-type, tlr2(-/-), tlr4(-/-), tlr5(-/-), tlr2 4(-/-) mice that underwent CLP were secondarily subjected to P. aeruginosa pulmonary infection. RESULTS Postseptic wild-type and tlr4(-/-) and tlr5(-/-) mice displayed high susceptibility to P. aeruginosa pneumonia. In contrast, TLR2-deficient mice, either tlr2(-/-)or tlr2 4(-/-), that underwent CLP were resistant to the secondary pulmonary infection. As compared to wild-type mice, tlr2(-/-) mice displayed improvement in bacterial clearance, decreased bacteremic dissemination, and attenuated lung damage. Furthermore, tlr2(-/-) mice exhibited a pulmonary proinflammatory cytokine balance, with increased production of tumor necrosis factor α and decreased release of interleukin 10. CONCLUSIONS In a model of secondary P. aeruginosa pneumonia in postseptic mice, TLR2 deficiency improves survival by promoting efficient bacterial clearance and restoring a proinflammatory cytokine balance in the lung.

Causes of death in French cystic fibrosis patients: The need for improvement in transplantation referral strategies!

BACKGROUND Little data exist on causes of death in cystic fibrosis (CF) patients in the era of lung transplantation. METHODS Deaths in CF patients in France (2007-2010) were identified using the French CF Registry and causes of deaths were determined based on medical files by a mortality adjudication committee. RESULTS Of 256 deaths, half occurred after lung transplantation and were related to early or late complications of transplantation, whereas half occurred in patients who did not receive lung transplantation and were primarily related to respiratory failure or massive hemoptysis. Among patients who did not receive lung transplantation, only 19% died while waiting on a lung transplantation list. Lack of listing for lung transplantation was primarily related to late, or to lack of transplantation referral, rather than to contraindication to transplantation. CONCLUSIONS These data suggest that improvement in transplantation referral strategies may result in transplantation-related survival benefits.

Dysfunctional lung anatomy and small airways degeneration in COPD

Chronic obstructive pulmonary disease (COPD) is characterized by incompletely reversible airflow obstruction. Direct measurement of airways resistance using invasive techniques has revealed that the site of obstruction is located in the small conducting airways, ie, bronchioles with a diameter < 2 mm. Anatomical changes in these airways include structural abnormalities of the conducting airways (eg, peribronchiolar fibrosis, mucus plugging) and loss of alveolar attachments due to emphysema, which result in destabilization of these airways related to reduced elastic recoil. The relative contribution of structural abnormalities in small conducting airways and emphysema has been a matter of much debate. The present article reviews anatomical changes and inflammatory mechanisms in small conducting airways and in the adjacent lung parenchyma, with a special focus on recent anatomical and imaging data suggesting that the initial event takes place in the small conducting airways and results in a dramatic reduction in the number of airways, together with a reduction in the cross-sectional area of remaining airways. Implications of these findings for the development of novel therapies are briefly discussed.

Reduced risk of nontuberculous mycobacteria in cystic fibrosis adults receiving long-term azithromycin

BACKGROUND Azithromycin reduces exacerbations in cystic fibrosis (CF) patients. Our aim was to investigate its association with nontuberculous mycobacteria isolation and macrolide susceptibility. METHODS From 2006 to 2010, all adult CF subjects at Cochin Hospital (Paris, France) harboring at least one positive NTM isolate were identified (Cases). In a nested case-control study, each Case was individually matched for age and gender with up to 4 CF adults with no NTM isolate (Controls). Clinical data at the time of first NTM isolate (index date) in Cases were compared with those of Controls using multivariate conditional regression analysis. RESULTS CF subjects with positive NTM isolates (Cases, n=41) were matched to 155 Controls. Among Cases, 48.7% had isolates from Mycobacterium avium complex and 58.5% from Mycobacterium abscessus complex, and 31 Cases fulfilled the 2007 American Thoracic Society criteria for NTM infection (ATS+ Cases). Cases and ATS+ Cases were more likely to have low body mass index and colonization with Aspergillus fumigatus. Azithromycin was associated with a two-fold reduction in NTM isolates. Only one M. avium complex isolate had acquired macrolide resistance. CONCLUSION These data suggest that azithromycin is a primary prophylaxis for NTM infection in CF adults.

Targeting Mucus Hypersecretion: New Therapeutic Opportunities for COPD?

Airway mucus has a key role in protective innate immune responses, but excessive mucus production and secretion in proximal and in distal airways are associated with disabling symptoms (cough and sputum), lung function decline, exacerbations and mortality in patients with chronic obstructive pulmonary disease (COPD). Cellular and molecular mechanisms leading to mucin production and secretion have largely been identified using cultured epithelial cells and animal models. Cigarette smoke and microbial products are potent triggers of mucin production, which involves recognition of specific molecular patterns by cognate receptors and activation of metalloproteases at the epithelial cell surface, leading to epidermal growth factor receptor activation and mucin mRNA and protein synthesis. After mucin synthesis has occurred, mucins are tightly packed into intracytoplasmic granules. Many stimuli induce secretion of mucin granules from epithelial cells, but neutrophil serine proteases are the most potent inducers of mucin secretion. Neutrophils recruited to the airway epithelium also promote mucin production via neutrophil proteases and oxidative stress. Several drugs currently available for the treatment of COPD patients reduced mucus hypersecretion in preclinical models relevant to COPD, but their effects on mucus hypersecretion in humans have not been assessed. Testing the effects of these drugs and of novel molecules designed for reducing mucus production and/or secretion will require performing specifically designed clinical trials. These trials will be necessary to explore the hypothesis that reducing mucus hypersecretion is beneficial in COPD patients.

Host–microbe interactions in distal airways: relevance to chronic airway diseases

This article is the summary of a workshop, which took place in November 2013, on the roles of microorganisms in chronic respiratory diseases. Until recently, it was assumed that lower airways were sterile in healthy individuals. However, it has long been acknowledged that microorganisms could be identified in distal airway secretions from patients with various respiratory diseases, including cystic fibrosis (CF) and non-CF bronchiectasis, chronic obstructive pulmonary disease, asthma and other chronic airway diseases (e.g. post-transplantation bronchiolitis obliterans). These microorganisms were sometimes considered as infectious agents that triggered host immune responses and contributed to disease onset and/or progression; alternatively, microorganisms were often considered as colonisers, which were considered unlikely to play roles in disease pathophysiology. These concepts were developed at a time when the identification of microorganisms relied on culture-based methods. Importantly, the majority of microorganisms cannot be cultured using conventional methods, and the use of novel culture-independent methods that rely on the identification of microorganism genomes has revealed that healthy distal airways display a complex flora called the airway microbiota. The present article reviews some aspects of current literature on host–microbe (mostly bacteria and viruses) interactions in healthy and diseased airways, with a special focus on distal airways. Understanding host–microbe interactions in distal airways may lead to novel therapies for chronic airway diseases http://ow.ly/HfENz

Prognostic value of six minute walk test in cystic fibrosis adults

BACKGROUND The 6 min walk test (6MWT) provides prognostic information in various respiratory diseases, but limited data exist in cystic fibrosis (CF) adults. METHODS Consecutive CF adults who performed 6MWT at Cochin Hospital (Paris, France) over 12 years were analyzed. The cut-off 6 min walking distance (6MWD) value that best predicted a combined endpoint (death without transplant or lung transplant) was established using a receiver operating curve. Determinants of low 6MWD or of desaturation (SpO2 ≤ 90%) during 6MWT were examined using multivariate logistic regressions. Prognostic value of these variables was assessed using Kaplan-Meier and Cox analyses. RESULTS 6MWT was performed in 286 CF adults (median: age, 28 yr; FEV1, 45% predicted) of whom 14% (n = 40) had lung transplant and 6% (n = 18) died without transplant. 6MWD correlated with FEV1% predicted (r = 0.43; P < 0.001), but markedly differed in subjects within the same range of FEV1. A 6MWD ≤ 475 m predicted death or transplant and was mostly found in patients with FEV1 ≤ 60% predicted. Desaturation during the 6MWT occurred in 29% of patients, exclusively in subjects with FEV1 ≤ 60% predicted. Both 6MWD ≤ 475 m and desaturation during the 6MWT were independent predictors of death or transplant. CONCLUSION The 6MWT provides prognostic information in CF adults, especially in subjects with FEV1 ≤ 60% predicted.

Aspergillus fumigatus in the cystic fibrosis lung: pros and cons of azole therapy

Aspergillus fumigatus is the main fungus cultured in the airways of patients with cystic fibrosis (CF). Allergic bronchopulmonary aspergillosis occurs in ~10% of CF patients and is clearly associated with airway damage and lung function decline. The effects of A. fumigatus colonization in the absence of allergic bronchopulmonary aspergillosis are less well established. Retrospective clinical studies found associations of A. fumigatus-positive cultures with computed tomography scan abnormalities, greater risk of CF exacerbations and hospitalizations, and/or lung function decline. These findings were somewhat variable among studies and provided only circumstantial evidence for a role of A. fumigatus colonization in CF lung disease progression. The availability of a growing number of oral antifungal triazole drugs, together with the results of nonrandomized case series suggesting positive effects of azole therapies, makes it tempting to treat CF patients with these antifungal drugs. However, the only randomized controlled trial that has used itraconazole in CF patients showed no significant benefit. Because triazoles may have significant adverse effects and drug interactions, and because their prolonged use has been associated with the emergence of azole-resistant A. fumigatus isolates, it remains unclear whether or not CF patients benefit from azole therapy.