Unknown,Transcriptomics,Genomics,Proteomics

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Reduced Airway Surface pH Impairs Bacterial Killing in the Porcine Cystic Fibrosis Lung

ABSTRACT: Cystic fibrosis (CF) is a life-shortening disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Although bacterial lung infection and the resulting inflammation cause most of the morbidity and mortality, how loss of CFTR first disrupts airway host defense has remained uncertain. We asked what abnormality impairs elimination when a bacterium lands on the pristine surface of a newborn CF airway? To investigate this defect, we interrogated the viability of individual bacteria immobilized on solid grids and placed on the airway surface. As a model we studied CF pigs, which spontaneously develop hallmark features of CF lung disease. At birth, their lungs lack infection and inflammation, but have a reduced ability to eradicate bacteria. Here we show that in newborn wild-type pigs, the thin layer of airway surface liquid (ASL) rapidly killed bacteria in vivo, when removed from the lung, and in primary epithelial cultures. Lack of CFTR reduced bacterial killing. We found that ASL pH was more acidic in CF, and reducing pH inhibited the antimicrobial activity of ASL. Reducing ASL pH diminished bacterial killing in wild-type pigs, and increasing ASL pH rescued killing in CF pigs. These results directly link the initial host defense defect to loss of CFTR, an anion channel that facilitates HCO3- transport. Without CFTR, airway epithelial HCO3- secretion is defective, ASL pH falls and inhibits antimicrobial function, and thereby impairs killing of bacteria that enter the newborn lung. These findings suggest that increasing ASL pH might prevent the initial infection in patients with CF and that assaying ASL pH or bacterial killing could report on the benefit of therapeutic interventions. 11 samples of trachea primary airway epithelial cultures representing CFTR+/+ and CFTR-/- pigs. Pig samples representing 14 bronchus and 12 trachea tissue samples submitted in GSE21071.

ORGANISM(S): Sus scrofa

SUBMITTER: Shyam Ramachandran

PROVIDER: E-GEOD-36906 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Reduced airway surface pH impairs bacterial killing in the porcine cystic fibrosis lung.

Pezzulo Alejandro A AA Tang Xiao Xiao XX Hoegger Mark J MJ Abou Alaiwa Mahmoud H MH Ramachandran Shyam S Moninger Thomas O TO Karp Phillip H PH Wohlford-Lenane Christine L CL Haagsman Henk P HP van Eijk Martin M Bánfi Botond B Horswill Alexander R AR Stoltz David A DA McCray Paul B PB Welsh Michael J MJ Zabner Joseph J

Nature 20120704 7405

Cystic fibrosis (CF) is a life-shortening disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Although bacterial lung infection and the resulting inflammation cause most of the morbidity and mortality, how the loss of CFTR function first disrupts airway host defence has remained uncertain. To investigate the abnormalities that impair elimination when a bacterium lands on the pristine surface of a newborn CF airway, we interrogated the viability of ...[more]

PMID: 22763554

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Project description:Background: CFTR modulators will decrease some etiologies of inflammation in the CF airway; however, current data indicate that non-resolving airway infection and inflammation will persist in individuals with CF and chronic bacterial infections. Thus, identification of therapies that diminish CF airway inflammation without allowing unrestrained bacterial growth remains a critical research goal. Novel strategies for combatting deleterious airway inflammation require a better understanding of the cellular contributions to chronic CF airway disease, and how cells change after initiation of CFTR modulator therapy. Peripheral blood monocytes, which traffic to the CF airway, can develop both pro-inflammatory and inflammation-resolving phenotypes, and represent intriguing targets for focused therapies to dampen CF airway inflammation. Material and Methods: In order to characterize the inflammatory phenotype of CF blood monocytes, and how these cells change after initiation of CFTR modulator therapy, we studied adults (n=10) with CF, chronic airway infections, and the CFTR-R117H mutations before and 7 days after initiation of ivacaftor. Transcriptomes of freshly isolated blood monocytes were interrogated by RNA-sequencing (RNA-seq). Plasma concentrations of cytokines and chemokines were evaluated by multiplex ELISA. Results: RNAseq identified approximately 50 monocyte genes for which basal expression was significantly changed in all 10 subjects after 7 days of ivacaftor. Of these, the majority were increased in expression post ivacaftor, including many genes traditionally associated with enhanced inflammation and immune responses. Pathway analyses confirmed that transcriptional pathways were overwhelmingly up-regulated in monocytes after 7 days of ivacaftor, including transcriptional modules associated with immunity, cell cycle, oxidative phosphorylation, and the unfolded protein response. Ivacaftor increased plasma concentrations of CXCL2, a neutrophil chemokine secreted by monocytes and macrophages, and CCL2, a monocyte chemokine. These results demonstrate that ivacaftor causes acute changes in blood monocytes and plasma chemokines, and suggest that increased monocyte inflammatory signals and potentially improved trafficking to the lung contribute to changes in airway inflammation in people taking CFTR modulators. To our knowledge, this is the first report investigating the transcriptomic response of isolated blood monocytes in CF subjects.

Dataset Information

Reduced Airway Surface pH Impairs Bacterial Killing in the Porcine Cystic Fibrosis Lung

Publications

Reduced airway surface pH impairs bacterial killing in the porcine cystic fibrosis lung.

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