The Role of Short-Chain Fatty Acids, Produced by Anaerobic Bacteria, in the Cystic Fibrosis Airway.
BACKGROUND
Anaerobic bacteria are present in large numbers in the airways of people with cystic fibrosis (PWCF). In the gut, anaerobes produce short-chain fatty acids (SCFAs) that modulate immune and inflammatory processes.


OBJECTIVE
To investigate the capacity of anaerobes to contribute to cystic fibrosis (CF) airway pathogenesis via SCFAs.


METHODS
Samples of 109 PWCF were processed using anaerobic microbiological culture with bacteria present identified by 16S RNA sequencing. SCFA levels in anaerobic supernatants and bronchoalveolar lavage (BAL) were determined by gas chromatography. The mRNA and/or protein expression of two SCFA receptors, GPR41 and GPR43, in CF and non-CF bronchial brushings and 16HBE14o(-) and CFBE41o(-) cells were evaluated using reverse transcription polymerase chain reaction, Western blot analysis, laser scanning cytometry, and confocal microscopy. SCFA-induced IL-8 secretion was monitored by ELISA.


RESULTS
Fifty-seven (52.3%) of 109 PWCF were anaerobe positive. Prevalence increased with age, from 33.3% to 57.7% in PWCF younger (n = 24) and older (n = 85) than 6 years of age. All evaluated anaerobes produced millimolar concentrations of SCFAs, including acetic, propionic, and butyric acids. SCFA levels were higher in BAL samples of adults than in those of children. GPR41 levels were elevated in CFBE41o(-) versus 16HBE14o(-) cells; CF versus non-CF bronchial brushings; and 16HBE14o(-) cells after treatment with cystic fibrosis transmembrane conductance regulator inhibitor CFTR(inh)-172, CF BAL, or inducers of endoplasmic reticulum stress. SCFAs induced a dose-dependent and pertussis toxin-sensitive IL-8 response in bronchial epithelial cells, with a higher production of IL-8 in CFBE41o(-) than in 16HBE14o(-) cells.


CONCLUSIONS
This study illustrates that SCFAs contribute to excessive production of IL-8 in CF airways colonized with anaerobes via up-regulated GPR41.
1 Respiratory Research Division, Department of Medicine, Royal College of Surgeons in Ireland, Education and Research Centre, Beaumont Hospital, Dublin, Ireland.
Bojana
B
Mirković
1 Respiratory Research Division, Department of Medicine, Royal College of Surgeons in Ireland, Education and Research Centre, Beaumont Hospital, Dublin, Ireland.
Michelle A
MA
Murray
1 Respiratory Research Division, Department of Medicine, Royal College of Surgeons in Ireland, Education and Research Centre, Beaumont Hospital, Dublin, Ireland.
Gillian M
GM
Lavelle
1 Respiratory Research Division, Department of Medicine, Royal College of Surgeons in Ireland, Education and Research Centre, Beaumont Hospital, Dublin, Ireland.
Kevin
K
Molloy
1 Respiratory Research Division, Department of Medicine, Royal College of Surgeons in Ireland, Education and Research Centre, Beaumont Hospital, Dublin, Ireland.
Ahmed Abdul
AA
Azim
1 Respiratory Research Division, Department of Medicine, Royal College of Surgeons in Ireland, Education and Research Centre, Beaumont Hospital, Dublin, Ireland.
Cedric
C
Gunaratnam
2 Temple Street Children's University Hospital, Dublin, Ireland.
Fiona
F
Healy
2 Temple Street Children's University Hospital, Dublin, Ireland.
Dubhfeasa
D
Slattery
3 Our Lady's Children's Hospital, Crumlin, Dublin, Ireland.
Paul
P
McNally
4 Cystic Fibrosis/Pulmonary Research and Treatment Center.|5 Department of Microbiology and Immunology, and.
Joe
J
Hatch
4 Cystic Fibrosis/Pulmonary Research and Treatment Center.|5 Department of Microbiology and Immunology, and.
Matthew
M
Wolfgang
6 CF & Airways Microbiology Group and.|7 School of Pharmacy, Queen's University Belfast, Belfast, United Kingdom; and.
Michael M
MM
Tunney
8 Department of Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
Marianne S
MS
Muhlebach
9 School of Biotechnology, Dublin City University, Dublin, Ireland.
Rosaleen
R
Devery
1 Respiratory Research Division, Department of Medicine, Royal College of Surgeons in Ireland, Education and Research Centre, Beaumont Hospital, Dublin, Ireland.
Catherine M
CM
Greene
1 Respiratory Research Division, Department of Medicine, Royal College of Surgeons in Ireland, Education and Research Centre, Beaumont Hospital, Dublin, Ireland.
Noel G
NG
McElvaney
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001421:Bacteria, Anaerobic; D015153:Blotting, Western; D001992:Bronchoalveolar Lavage Fluid / Q000382:microbiology; D002648:Child; D002675:Child, Preschool; D002849:Chromatography, Gas; D003550:Cystic Fibrosis / Q000382:microbiology*; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000032:analysis; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000382:microbiology; D005227:Fatty Acids / Q000096:biosynthesis*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D020545:Respiratory Mucosa / Q000382:microbiology; D015854:Up-Regulation; D055815:Young Adult
D005227:Fatty Acids; D019005:Cystic Fibrosis Transmembrane Conductance Regulator
anaerobic bacteria; cystic fibrosis; inflammation; short-chain fatty acids