Higher Prevalence of Bacteroides fragilis in Crohn’s Disease Exacerbations and Strain-Dependent Increase of Epithelial Resistance

Bacteroides fragilis has previously been linked to Crohn’s disease (CD) exacerbations, but results are inconsistent and underlying mechanisms unknown. This study investigates the epidemiology of B. fragilis and its virulence factors bft (enterotoxin) and ubiquitin among 181 CD patients and the impact on the intestinal epithelial barrier in vitro. The prevalence of B. fragilis was significantly higher in active (n = 69/88, 78.4%) as compared to remissive (n = 58/93, 62.4%, p = 0.018) CD patients. Moreover, B. fragilis was associated with intestinal strictures. Interestingly, the intestinal barrier function, as examined by transepithelial electrical resistance (TEER) measurements of Caco-2 monolayers, increased when exposed to secretomes of bft-positive (bft-1 and bft-2 isotype; increased TEER ∼160%, p < 0.001) but not when exposed to bft-negative strains. Whole metagenome sequencing and metabolomics, respectively, identified nine coding sequences and two metabolites that discriminated TEER-increasing from non-TEER-increasing strains. This study revealed a higher B. fragilis prevalence during exacerbation. Surprisingly, bft-positive secretomes increased epithelial resistance, but we excluded Bft as the likely causative factor.

A Protective Role of FAM13A in Human Airway Epithelial Cells Upon Exposure to Cigarette Smoke Extract

BackgroundChronic Obstructive Pulmonary Disease (COPD) is a progressive lung disease characterized by chronic inflammation upon inhalation of noxious particles, e.g., cigarette smoke. FAM13A is one of the genes often found to be associated with COPD, however its function in the pathophysiology of COPD is incompletely understood. We studied its role in airway epithelial barrier integrity and cigarette smoke-induced epithelial responses.Materials and MethodsProtein level and localization of FAM13A was assessed with immunohistochemistry in lung tissue from COPD patients and non-COPD controls. In vitro, FAM13A expression was determined in the absence or presence of cigarette smoke extract (CSE) in primary airway epithelial cells (AECs) from COPD patients and controls by western blotting. FAM13A was overexpressed in cell line 16HBE14o- and its effect on barrier function was monitored real-time by electrical resistance. Expression of junctional protein E-cadherin and β-catenin was assessed by western blotting. The secretion of neutrophil attractant CXCL8 upon CSE exposure was measured by ELISA.ResultsFAM13A was strongly expressed in airway epithelium, but significantly weaker in airways of COPD patients compared to non-COPD controls. In COPD-derived AECs, but not those of controls, FAM13A was significantly downregulated by CSE. 16HBE14o- cells overexpressing FAM13A built up epithelial resistance significantly more rapidly, which was accompanied by higher E-cadherin expression and reduced CSE-induced CXCL8 levels.ConclusionOur data indicate that the expression of FAM13A is lower in airway epithelium of COPD patients compared to non-COPD controls. In addition, cigarette smoking selectively downregulates airway epithelial expression of FAM13A in COPD patients. This may have important consequences for the pathophysiology of COPD, as the more rapid build-up of epithelial resistance upon FAM13A overexpression suggests improved (re)constitution of barrier function. The reduced epithelial secretion of CXCL8 upon CSE-induced damage suggests that lower FAM13A expression upon cigarette smoking may facilitate epithelial-driven neutrophilia.

A mammalian commensal of the oropharyngeal cavity produces antibiotic and antiviral valinomycin in vivo

Around weaning, piglets are susceptible to infection by bacterial pathobionts, leading to increased morbidity and mortality. We identified isolates of Rothia nasisuis in the upper respiratory tract of weaned healthy piglets that produce valinomycin in vitro and in vivo via its vlm-encoded non-ribosomal peptide synthase (NRPS) enzyme complex. Valinomycin is an antiviral and antibiotic ionophore that shuttles potassium ions across membranes and is capable of inflammasome activation and apoptosis in LPS-primed macrophages at concentrations of 1 uM. Polarized monolayers of epithelial cells were much less sensitive to valinomycin but concentrations ≥ 10 µM decreased trans-epithelial resistance. R. nasisuis inhibited growth of closely related species of Rothia. Deliberate inoculation of valinomycin-producing R. nasisuis into newborn piglets suggested this species can shape the microbiota post weaning. Our findings support the idea that valinomycin is a competitive niche factor potentially also compromising epithelial integrity to gain access to (micro)nutrients.

High dose everolimus promotes a pro-inflammatory phenotype and facilitates the epithelial to mesenchymal transition of primary bronchial epithelial cells isolated from cystic fibrosis patients.

Background: Lung transplantation is still the best therapeutic option for cystic fibrosis (CF) patients, but, unfortunately, immunosuppressive therapies, often employed at high dosages to avoid acute rejection, may induce severe complications. In particular, patients treated with high dose of mammalian target of rapamycin inhibitors (mTOR-Is) may experience lung fibrosis (including bronchiolitis obliterans-organizing pneumonia). Although epithelial to mesenchymal transition (EMT) of airway cells has a central role in this process, the complete biological machinery is not completely clarified.Methods: In order to improve our knowledge on this process, primary bronchial epithelial cells carrying F508del mutation were treated with 5 and 100 nM everolimus (EVE) for 24 hours. Subsequently, RNA was hybridized to the Human HT-12 v3 Expression BeadChip (Illumina). Real-Time PCR was, then, used to validate microarray results and to measure major EMT biomarkers. Trans-epithelial resistance was measured by Millicell-ERS ohmmeter.Results: High dosage EVE induced a significant up-regulation of 42 genes and a down-regulation of 12 genes. After pathway analysis by Gene Set Enrichment Analysis and Ingenuity Pathway Analysis, we found that most of them were implicated in the pro-inflammatory pathway. Real-Time PCR validated these results and revealed that, in addition to pro-inflammatory genes (IL-1α, IL-8, Pim-1 Oncogene), EVE at high dosage was able to up-regulate major EMT biomarkers (such as: alpha-smooth muscle actin, connective tissue growth factor and metalloproteinase 12). In lung, EMT is the convergence point between inflammation and the progression of fibrotic damage. Additionally, EVE at this dosage reduced the trans-epithelial resistance (altering tight junction strength). In contrast, lower EVE did not trigger similar effects.Conclusions: We demonstrated that high dose EVE may trigger a pro-inflammatory/fibrotic biological machinery in bronchial epithelial cells from CF patients. Our results, although obtained in vitro, suggest that solid organ transplant recipients affected by CF should be treated with the lowest possible dose of mTOR inhibitors to minimize/avoid the onset and development of lung complications. In vivo studies might be useful to confirm our hypothesis.

Higher prevalence of Bacteroides fragilis in Crohn’s disease exacerbations and strain-dependent increase of epithelial resistance

Bacteroides fragilis has previously been linked to Crohn’s disease (CD) exacerbations, but results are inconsistent and underlying mechanisms unknown. This study investigates the epidemiology of B. fragilis and its virulence factors bft (enterotoxin) and ubiquitin among 181 CD patients and the impact on the intestinal epithelial barrier in vitro.The prevalence of B. fragilis was significantly higher in active (n=69/88, 78.4%) as compared to remissive (n=58/93, 62.4%, p=0.018) CD patients. Moreover, B. fragilis was associated with intestinal strictures. Interestingly, the intestinal barrier function, as examined by transepithelial electrical resistance (TEER) measurements of Caco-2 monolayers, improved when exposed to secretomes of bft-positive (increased TEER ∼160%, p<0.001) but not when exposed to bft- negative strains. Whole metagenome sequencing and metabolomics, respectively, identified 19 coding sequences and two metabolites that discriminated TEER-increasing from non-TEER-increasing strains.This study revealed a higher B. fragilis prevalence during exacerbation. Surprisingly, bft-positive secretomes improved epithelial resistance.