Mechanisms of TNF-alpha stimulation of amiloride-sensitive sodium transport across alveolar epithelium.

Academic Article

Abstract

  • Because tumor necrosis factor (TNF)-alpha can upregulate alveolar fluid clearance (AFC) in pneumonia or septic peritonitis, the mechanisms responsible for the TNF-alpha-mediated increase in epithelial fluid transport were studied. In rats, 5 microg of TNF-alpha in the alveolar instillate increased AFC by 67%. This increase was inhibited by amiloride but not by propranolol. We also tested a triple-mutant TNF-alpha that is deficient in the lectinlike tip portion of the molecule responsible for its membrane conductance effect; the mutant also has decreased binding affinity to both TNF-alpha receptors. The triple-mutant TNF-alpha did not increase AFC. Perfusion of human A549 cells, patched in the whole cell mode, with TNF-alpha (120 ng/ml) resulted in a sustained increase in Na(+) currents from 82 +/- 9 to 549 +/- 146 pA (P < 0.005; n = 6). The TNF-alpha-elicited Na(+) current was inhibited by amiloride, and there was no change when A549 cells were perfused with the triple-mutant TNF-alpha or after preincubation with blocking antibodies to the two TNF-alpha receptors before perfusion with TNF-alpha. In conclusion, although TNF- alpha can initiate acute inflammation and edema formation in the lung, TNF-alpha can also increase AFC by an amiloride-sensitive, cAMP-independent mechanism that enhances the resolution of alveolar edema in pathological conditions by either binding to its receptors or activating Na(+) channels by means of its lectinlike domain.
  • Keywords

  • Adrenergic beta-Agonists, Adrenergic beta-Antagonists, Amiloride, Amino Acid Substitution, Animals, Antibodies, Blocking, Antigens, CD, Biological Transport, Cell Line, Humans, Instillation, Drug, Male, Membrane Potentials, Mutation, Patch-Clamp Techniques, Propranolol, Pulmonary Alveoli, Rats, Rats, Sprague-Dawley, Receptors, Tumor Necrosis Factor, Receptors, Tumor Necrosis Factor, Type I, Receptors, Tumor Necrosis Factor, Type II, Respiratory Mucosa, Sodium, Sodium Channels, Tumor Necrosis Factor-alpha
  • Digital Object Identifier (doi)

    Author List

  • Fukuda N; Jayr C; Lazrak A; Wang Y; Lucas R; Matalon S; Matthay MA
  • Start Page

  • L1258
  • End Page

  • L1265
  • Volume

  • 280
  • Issue

  • 6