Abstract
Pseudomonas aeruginosa causes severe life-threatening airway infections that are a frequent cause for hospitalization of cystic fibrosis (CF) patients. These Gram-negative pathogens possess flagella that contain the protein flagellin as a major structural component. Flagellin binds to the host cell glycolipid asialoGM1 (ASGM1), which appears enriched in luminal membranes of respiratory epithelial cells. We demonstrate that in mouse airways, luminal exposure to flagellin leads to inhibition of Na+ absorption by the epithelial Na+ channel ENaC, but does not directly induce a secretory response. Inhibition of ENaC was observed in tracheas of wild-type mice and was attenuated in mice homozygous for the frequent cystic fibrosis conductance regulator (CFTR) mutation G551D. Similar to flagellin, anti-ASGM1 antibody also inhibited ENaC. The inhibitory effects of flagellin on ENaC were attenuated by blockers of the purinergic signaling pathway, although an increase in the intracellular Ca2+ concentration by recombinant or purified flagellin or whole flagella was not observed. Because an inhibitor of the mitogen-activated protein kinase (MAPK) pathway also attenuated the effects of flagellin on Na+ absorption, we conclude that flagellin exclusively inhibits ENaC, probably due to release of ATP and activation of purinergic receptors of the P2Y subtype. Stimulation of these receptors activates the MAPK pathway, thereby leading to inhibition of ENaC. Thus, P. aeruginosa reduces Na+ absorption, which could enhance local mucociliary clearance, a mechanism that seem to be attenuated in CF.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adenosine Triphosphate / metabolism
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Amiloride / metabolism
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Animals
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Bronchi / cytology
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Bronchi / metabolism
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Butadienes / pharmacology
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Calcium Signaling / drug effects
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Cells, Cultured
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Cystic Fibrosis / complications
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Cystic Fibrosis / physiopathology
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Egtazic Acid / analogs & derivatives
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Egtazic Acid / pharmacology
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Epithelial Cells / metabolism
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Epithelial Cells / microbiology
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Epithelial Sodium Channels
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Estrenes / pharmacology
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Flagellin / genetics
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Flagellin / metabolism
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Flagellin / pharmacology*
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G(M1) Ganglioside / metabolism
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Humans
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Ion Transport / drug effects*
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MAP Kinase Signaling System / drug effects
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Membrane Proteins / physiology
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Mice
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Mice, Inbred C57BL
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Mice, Inbred CFTR
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Nitriles / pharmacology
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Patch-Clamp Techniques
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Phosphatidylinositol 4,5-Diphosphate / metabolism
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Pseudomonas Infections / complications
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Pseudomonas Infections / physiopathology*
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Pseudomonas aeruginosa / physiology*
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Pyrrolidinones / pharmacology
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Receptors, Purinergic P2 / physiology
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Receptors, Purinergic P2Y12
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Respiratory Tract Infections / complications
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Respiratory Tract Infections / microbiology
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Respiratory Tract Infections / physiopathology
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Sodium / metabolism*
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Sodium Channels / drug effects*
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Sodium Channels / physiology
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Trachea / metabolism
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Trachea / microbiology
Substances
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Butadienes
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Epithelial Sodium Channels
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Estrenes
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Membrane Proteins
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Nitriles
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P2RY12 protein, human
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P2ry12 protein, mouse
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Phosphatidylinositol 4,5-Diphosphate
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Pyrrolidinones
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Receptors, Purinergic P2
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Receptors, Purinergic P2Y12
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Sodium Channels
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U 0126
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1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione
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Flagellin
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1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester
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G(M1) Ganglioside
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Egtazic Acid
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asialo GM1 ganglioside
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Amiloride
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Adenosine Triphosphate
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Sodium