Flagellin-stimulated Cl- secretion and innate immune responses in airway epithelia: role for p38.
Activation of an innate immune response in airway epithelia by the human pathogen Pseudomonas aeruginosa requires bacterial expression of flagellin. Addition of flagellin (10(-7) M) to airway epithelial cell monolayers (Calu-3, airway serous cell-like) increased Cl(-) secretion (I(Cl)) beginning after 3-10 min, reaching a plateau after 20-45 min at DeltaI(Cl) = 15-50 microA/cm(2). Similar, although 10-fold smaller, responses were observed in well-differentiated bronchial epithelial cultures. Flagellin stimulated I(Cl) in the presence of maximally stimulating doses of the purinergic agonist ATP, but had no effects following forskolin. IL-1beta (produced by both epithelia and neutrophils during infections) stimulated I(Cl) similar to flagellin. Flagellin-, IL-1beta-, ATP-, and forskolin-stimulated I(Cl) were inhibited by cystic fibrosis transmembrane conductance regulator (CFTR) blockers GlyH101, CFTRinh172, and glibenclamide. Neither flagellin nor IL-1beta altered transepithelial fluxes of membrane-impermeant dextran (10 kDa) or lucifer yellow (mol wt = 457), but both activated p38, NF-kappaB, and IL-8 secretion. Blockers of p38 (SB-202190 and SB-203580) reduced flagellin- and IL-1beta-stimulated I(Cl) by 33-50% but had smaller effects on IL-8 and NF-kappaB. It is concluded that: 1) flagellin and IL-1beta activated p38, NF-kappaB, IL-8, and CFTR-dependent anion secretion without altering tight junction permeability; 2) p38 played a role in regulating I(Cl) and IL-8 but not NF-kappaB; and 3) p38 was more important in flagellin- than IL-1beta-stimulated responses. During P. aeruginosa infections, flagellin and IL-1beta are expected to increase CFTR-dependent ion and fluid flow into and bacterial clearance from the airways. In cystic fibrosis, the secretory response would be absent, but activation of p38, NF-kappaB, and IL-8 would persist.
Illek
Beate
B
Dept. of Molecular and Cell Biology, Univ. of California-Berkeley, Berkeley, CA 94720-3200, USA.
Fu
Zhu
Z
Schwarzer
Christian
C
Banzon
Tina
T
Jalickee
Stephen
S
Miller
Sheldon S
SS
Machen
Terry E
TE
D001980:Bronchi / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000502:physiology*; D002460:Cell Line; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000235:genetics*; D005408:Flagellin / Q000494:pharmacology*; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D007113:Immunity, Innate; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D020545:Respiratory Mucosa / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
D002712:Chlorides; C083487:I kappa B beta protein; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D011994:Recombinant Proteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005408:Flagellin; D000072000:NF-KappaB Inhibitor alpha; D005576:Colforsin; D048051:p38 Mitogen-Activated Protein Kinases