IL-4 and IL-13 exposure during mucociliary differentiation of bronchial epithelial cells increases antimicrobial activity and expression of antimicrobial peptides

The airway epithelium forms a barrier against infection but also produces antimicrobial peptides (AMPs) and other inflammatory mediators to activate the immune system. It has been shown that in allergic disorders, Th2 cytokines may hamper the antimicrobial activity of the epithelium. However, the presence of Th2 cytokines also affects the composition of the epithelial layer which may alter its function. Therefore, we investigated whether exposure of human primary bronchial epithelial cells (PBEC) to Th2 cytokines during mucociliary differentiation affects expression of the human cathelicidin antimicrobial protein (hCAP18)/LL-37 and human beta defensins (hBD), and antimicrobial activity

Asymptomatic worsening of airway inflammation during low-dose allergen exposure in asthma: protection by inhaled steroids

Asthma is a chronic inflammatory disease that persists even during adequate therapy and asymptomatic episodes. We questioned whether "silent" chronic allergen exposure can induce and maintain airway inflammation and whether this still occurs during regular treatment with inhaled steroids. Twenty-six patients with house dust mite allergy and mild asthma (dual responders) participated in a parallel, double-blind study. All patients inhaled a low-dose of allergen on 10 subsequent working days (Days 1-5, 8-12). They were treated with 400 micro g budesonide once daily (n = 13) or placebo (n = 13) from Days -3 to 19. At baseline (Day -6) and on Days 5, 12, and 19 we measured the provocative concentration of methacholine causing a 20% fall in FEV(1) (PC(20)), and percent eosinophils, interleukin (IL)-5/interferon-gamma messenger RNA ratio (in sputum cells by real-time reverse transcription-polymerase chain reaction [RT-PCR]), and eosinophilic cationic protein (ECP) in induced sputum. Symptoms, peak expiratory flow (PEF), FEV(1), and exhaled nitric oxide (NO) were recorded repeatedly during the study. In the placebo group, repeated low-dose allergen exposure resulted in a significant increase in sputum eosinophils (p = 0.043), ECP (p = 0.011), IL-5/IFN-gamma messenger RNA ratio (p = 0.04), and in exhaled NO (p = 0.001), without worsening of symptoms, PEF, or baseline FEV(1) (p > 0.07). In the budesonide group, the changes in PC(20), sputum ECP, and exhaled NO were significantly different as compared with the placebo group (p < 0.03). We conclude that repeated low-dose allergen exposure in asthma can lead to airway inflammation without worsening of symptoms, which can be prevented by inhaled steroid treatment. This suggests that antiinflammatory therapy is beneficial during allergen exposure, even during asymptomatic episode

Pro-inflammatory Cytokines Impair Vitamin D-induced Host Defense in Cultured Airway Epithelial Cells

Vitamin D is a regulator of host defense against infections and induces expression of the antimicrobial peptide hCAP18/LL-37. Vitamin D deficiency is associated with chronic inflammatory lung diseases and respiratory infections. However, it is incompletely understood if and how (chronic) airway inflammation affects vitamin D metabolism and action. We hypothesized that long-term exposure of primary bronchial epithelial cells (PBEC) to pro-inflammatory cytokines alters their vitamin D metabolism, antibacterial activity and expression of hCAP18/LL-37. To investigate this, PBEC were differentiated at the air-liquid interphase for 14 days in presence of the pro-inflammatory cytokines TNF-α and IL-1β (TNF-α/IL-1β), and subsequently exposed to vitamin D (inactive 25(OH)D3 and active 1,25(OH)2D3). Expression of hCAP18/LL-37, vitamin D receptor (VDR) and enzymes involved in vitamin D metabolism (CYP24A1 and CYP27B1) was determined using qPCR, Western blot and immunofluorescence staining. Furthermore, vitamin D-mediated antibacterial activity was assessed using non-typeable Haemophilus influenzae (NTHi). We found that TNF-α/IL-1β treatment reduced vitamin D-induced expression of hCAP18/LL-37 and killing of NTHi. In addition, CYP24A1 (a vitamin D-degrading enzyme) was increased by TNF-α/IL-1β, whereas CYP27B1 (that converts 25(OH)D3 to its active form) and VDR expression remained unaffected. Furthermore, we demonstrated that the TNF-α/IL-1β-mediated induction of CYP24A1 was at least in part mediated by the transcription factor specific protein 1 (Sp1) and the EGFR-MAPK-pathway. These findings indicate that TNF-α/IL-1β decreases vitamin D-mediated antibacterial activity and hCAP18/LL-37 expression via induction of CYP24A1, and suggests that chronic inflammation impairs protective responses induced by vitamin D

Aberrant epithelial differentiation by cigarette smoke dysregulates respiratory host defence

It is currently unknown how cigarette smoke-induced airway remodelling affects highly expressed respiratory epithelial defence proteins and thereby mucosal host defence.Localisation of a selected set of highly expressed respiratory epithelial host defence proteins was assessed in well-differentiated primary bronchial epithelial cell (PBEC) cultures. Next, PBEC were cultured at the air-liquid interface, and during differentiation for 2-3 weeks exposed daily to whole cigarette smoke. Gene expression, protein levels and epithelial cell markers were subsequently assessed. In addition, functional activities and persistence of the cigarette smoke-induced effects upon cessation were determined.Expression of the polymeric immunoglobulin receptor, secretory leukocyte protease inhibitor and long and short PLUNC (palate, lung and nasal epithelium clone protein) was restricted to luminal cells and exposure of differentiating PBECs to cigarette smoke resulted in a selective reduction of the expression of these luminal cell-restricted respiratory host defence proteins compared to controls. This reduced expression was a consequence of cigarette smoke-impaired end-stage differentiation of epithelial cells, and accompanied by a significant decreased transepithelial transport of IgA and bacterial killing.These findings shed new light on the importance of airway epithelial cell differentiation in respiratory host defence and could provide an additional explanation for the increased susceptibility of smokers and patients with chronic obstructive pulmonary disease to respiratory infection

Original Paper Airway proteoglycans are differentially altered in fatal asthma

Abstract It has been suggested that airway remodelling is responsible for the persistent airway obstruction and decline in lung function observed in some asthmatic patients. The small airways are thought to contribute significantly to this functional impairment. Proteoglycans (PGs) are important components of the extracellular matrix (ECM) in the lungs. Besides controlling biophysical properties of the ECM, they play important roles in the regulation of some cytokines. Increased subepithelial PG deposition in the airways of mild asthmatics has been reported. However, there are no data on the PG content in small airways in asthma. This study has compared the content and distribution of PGs in large and small airways of patients who died of asthma with those in control lungs. Immunohistochemistry and image analysis were used to determine the content of lumican, decorin, biglycan, and versican in large (internal perimeter &gt;6 mm) and small (internal perimeter ≤6 mm) airways of 18 patients who had died of asthma (A) and ten controls (C). The results were expressed as PG area (µm 2 )/epithelial basement membrane length (µm). The main differences between asthmatics and controls were observed in the small airways. There was a significant decrease in decorin and lumican contents in the external area of small airways in asthmatics (decorin: A = 1.05 ± 0.27 µm, C = 3.97 ± 1.17 µm, p = 0.042; lumican: A = 1.97 ± 0.37 µm, C = 5.66 ± 0.99 µm, p = 0.002). A significant increase in versican content in the internal area of small and large airways in asthmatics was also observed (small: A = 7.48 ± 0.84 µm, C = 5.16 ± 0.61 µm, p = 0.045; large: A = 18.38 ± 1.94 µm, C = 11.90 ± 2.86 µm, p = 0.028). The results show that PGs are differentially expressed in the airways of fatal asthma and may contribute to airway remodelling. These data reinforce the importance of the small airways in airway remodelling in asthma

Are rhinovirus-induced airway responses in asthma aggravated by chronic allergen exposure?

Airway inflammation in asthma may represent a favorable environment for respiratory viral infections, augmenting virus-induced exacerbations in asthma. We postulated that repeated low-dose allergen exposure preceding experimental rhinovirus 16 (RV16) infection increases the severity of RV-induced airway obstruction and inflammation. Thirty-six house dust mite-allergic patients with mild to moderate asthma participated in a three-arm, parallel, placebo-controlled, double-blind study. Patients inhaled a low dose of house dust mite allergen for 10 subsequent working days (Days 1-5 and 8-12) and/or were subsequently infected with RV16 (Days 15 and 16). Allergen exposure resulted in a significant fall in FEV1 (p < 0.001) and provocative concentration of histamine causing a 20% fall in FEV1 (p < 0.001) and an increase in exhaled nitric oxide (p < 0.001) and percentage of sputum eosinophils (p < 0.001). RV16 infection led to a fall in FEV1 (p = 0.02) and increases in the percentage of sputum neutrophils (p = 0.01), sputum interleukin-8 (p = 0.04), and neutrophil elastase (p = 0.04). Successive allergen exposure and RV16 infection had no synergistic or additive effect on any of the clinical or inflammatory outcomes. In conclusion, repeated low-dose allergen exposure and RV16 infection induce distinct inflammatory profiles within the airways in asthma without apparent interaction between these two environmental triggers. This suggests that preceding allergen exposure, at the used dose and duration, is not a determinant of the severity of RV-induced exacerbations in patients with mild to moderate asthm