Pseudomonas aeruginosainduces changes in fluid transport across airway surface epithelia

Abstract

Fluid transport across cultures of bovine tracheal epithelium was measured with a capacitance probe technique. Baseline fluid absorption ( Jv) across bovine cells of 3.2 μl ⋅ cm−2⋅ h−1was inhibited by ∼78% after 1 h of exposure to suspensions of Pseudomonas aeruginosa, with a concomitant decrease in transepithelial potential (TEP) and increase in transepithelial resistance ( Rt). Effects of P. aeruginosa were blocked by amiloride, which decreased Jvby 112% from baseline of 2.35 ± 1.25 μl ⋅ cm−2⋅ h−1, increased Rtby 101% from baseline of 610 ± 257 Ω ⋅ cm2, and decreased TEP by 91% from baseline of −55 ± 18.5 mV. Microelectrode studies suggested that effects of P. aeruginosa on amiloride-sensitive Na absorption were due in part to a block of basolateral membrane K channels. In the presence of Cl transport inhibitors [5-nitro-2-(3-phenylpropylamino)-benzoic acid, H2-DIDS, and bumetanide], P. aeruginosa induced a fluid secretion of ∼2.5 ± 0.4 μl ⋅ cm−2⋅ h−1and decreased Rtwithout changing TEP. However, these changes were abolished when the transport inhibitors were used in a medium in which Cl was replaced by an impermeant organic anion. Filtrates of P. aeruginosa suspensions had no effect on Jv, TEP, or Rt. Mutants lacking exotoxin A or rhamnolipids or with defective lipopolysaccharide still inhibited fluid absorption and altered bioelectrical properties. By contrast, mutations in the rpoN gene encoding a ς factor of RNA polymerase abolished actions of P. aeruginosa. In vivo, changes in transepithelial salt and water transport induced by P. aeruginosa may alter viscosity and ionic composition of airway secretions so as to foster further bacterial colonization.