Modulation of epithelial sodium channel activity by lipopolysaccharide in alveolar type II cells: involvement of purinergic signaling

Département de Médecine, Centre de Recherche, Centre Hospitalier de l'Université de Montréal-Hôtel-Dieu, 3840 St. Urbain, Montréal, PQ, Canada.
AJP Lung Cellular and Molecular Physiology (Impact Factor: 4.08). 12/2009; 298(3):L417-26. DOI: 10.1152/ajplung.00170.2009
Source: PubMed

ABSTRACT Pseudomonas aeruginosa is a gram-negative bacterium that causes chronic infection in cystic fibrosis patients. We reported recently that P. aeruginosa modulates epithelial Na(+) channel (ENaC) expression in experimental chronic pneumonia models. For this reason, we tested whether LPS from P. aeruginosa alters ENaC expression and activity in alveolar epithelial cells. We found that LPS induces a approximately 60% decrease of ENaC apical current without significant changes in intracellular ENaC or surface protein expression. Because a growing body of evidence reports a key role for extracellular nucleotides in regulation of ion channels, we evaluated the possibility that modulation of ENaC activity by LPS involves extracellular ATP signaling. We found that alveolar epithelial cells release ATP upon LPS stimulation and that pretreatment with suramin, a P2Y(2) purinergic receptor antagonist, inhibited the effect of LPS on ENaC. Furthermore, ET-18-OCH3, a PLC inhibitor, and Go-6976, a PKC inhibitor, were able to partially prevent ENaC inhibition by LPS, suggesting that the actions of LPS on ENaC current were mediated, in part, by the PKC and PLC pathways. Together, these findings demonstrate an important role of extracellular ATP signaling in the response of epithelial cells to LPS.

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Available from: Emilie Boncoeur, Jul 16, 2015
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    • "Several factors have been shown to modulate ENaC expression and activity in the lungs, including purinergic signaling [9–11], glucocorticoid [12–16], protease activation [10,17,18] and membrane recycling or lysosomal degradation of the channel [19]. Since transepithelial Na+ transport involves activity of the Na/K-ATPase expression at the basolateral side, factors that regulate the sodium pump or its membrane insertion have an impact on the Na+ transport system [14,20]. "
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    ABSTRACT: Alveolar epithelial cells are involved in Na(+) absorption via the epithelial Na(+) channel (ENaC), an important process for maintaining an appropriate volume of liquid lining the respiratory epithelium and for lung oedema clearance. Here, we investigated how a 20% hypotonic shock modulates the ionic current in these cells. Polarized alveolar epithelial cells isolated from rat lungs were cultured on permeant filters and their electrophysiological properties recorded. A 20% bilateral hypotonic shock induced an immediate, but transient 52% rise in total transepithelial current and a 67% increase in the amiloride-sensitive current mediated by ENaC. Amiloride pre-treatment decreased the current rise after hypotonic shock, showing that ENaC current is involved in this response. Since Cl(-) transport is modulated by hypotonic shock, its contribution to the basal and hypotonic-induced transepithelial current was also assessed. Apical NPPB, a broad Cl(-) channel inhibitor and basolateral DIOA a potassium chloride co-transporter (KCC) inhibitor reduced the total and ENaC currents, showing that transcellular Cl(-) transport plays a major role in that process. During hypotonic shock, a basolateral Cl(-) influx, partly inhibited by NPPB is essential for the hypotonic-induced current rise. Hypotonic shock promoted apical ATP secretion and increased intracellular Ca(2+). While apyrase, an ATP scavenger, did not inhibit the hypotonic shock current response, W7 a calmodulin antagonist completely prevented the hypotonic current rise. These results indicate that a basolateral Cl(-) influx as well as Ca(2+)/calmodulin, but not ATP, are involved in the acute transepithelial current rise elicited by hypotonic shock.
    PLoS ONE 09/2013; 8(9):e74565. DOI:10.1371/journal.pone.0074565 · 3.23 Impact Factor
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    • "LPS has also been reported to regulate airway epithelial ion transport. LPS from P. aeruginosa inhibits sodium absorption via ENaC in mammalian alveolar epithelial cells [4]. In contrast, LPS from Salmonella enterica stimulated sodium absorption by increasing Na/K ATPase expression in guinea-pig tracheal epithelium [5]. "
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    ABSTRACT: Background: Pseudomonas aeruginosa airway infection is associated with a high mortality rate in cystic fibrosis. Lipopolysaccharide (LPS), a main constituent of the outer membrane of P. aeruginosa, is responsible for activation of innate immune response but its role on airway epithelium ion transport, is not well known. The aim of this study was to determine the role for P. aeruginosa LPS in modulating chloride secretion and intracellular calcium in the human bronchial epithelial cell line, 16HBE14o-. Methods: We used intracellular calcium imaging and short-circuit current measurement upon exposure of cells to P. aeruginosa LPS. Results: Apical LPS stimulated intracellular calcium release and calcium entry and enhanced chloride secretion. This latter effect was significantly inhibited by CFTR(inh)-172 and BAPTA-AM (intracellular Ca(2+) chelator). Conclusions: Our data provides evidence for a new role of P. aeruginosa LPS in stimulating calcium entry and release and a subsequent chloride secretion via CFTR in human bronchial epithelium.
    Journal of cystic fibrosis: official journal of the European Cystic Fibrosis Society 07/2012; 12(1). DOI:10.1016/j.jcf.2012.06.007 · 3.48 Impact Factor
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    ABSTRACT: The Philips RTO7 chip consists of a complete receive chain from RF up to and including digital demodulation for Bluetooth-like radio communication. This paper describes both the implementation and verification of the test and debugs hardware for the digital core of the RTO7. The core-based DfT and DfD flow of the RTO7 is presented. The experimental results show that the RTO7 is both a fully testable and debuggable chip. State dump analysis results are also presented, showing that the state dumps obtained in the application are 100% stable, and match the state dumps made in simulation, and on the digital test system.
    Test Conference, 2005. Proceedings. ITC 2005. IEEE International; 12/2005
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