O2-induced ENaC expression is associated with NF-kappaB activation and blocked by superoxide scavenger.
Cultured rat fetal distal lung epithelial cells (FDLEs), when switched from fetal (3%) to postnatal (21%) O2 concentrations, have increased epithelial Na+ channel (ENaC) mRNA levels and amiloride-sensitive Na+ transport [O. Pitkänen, A. K. Tanswell, G. Downey, and H. O'Brodovich. Am. J. Physiol. 270 (Lung Cell. Mol. Physiol. 14): L1060-L1066, 1996]. The mechanisms by which O2 mediates these effects are unknown. After isolation, FDLEs were kept at 3% O2 overnight, then switched to 21% O2 (3-21% O2 group) or maintained at 3% O2 (3-3% O2 group) for 48 h. The amiloride-sensitive short-circuit current (Isc) in the 3-21% O2 group was double that in the 3-3% O2 group. Amiloride-sensitive Isc could not be induced by medium conditioned by 21% O2-exposed FDLEs but was reversed by returning the cells to 3% O2. Neither the cyclooxygenase inhibitor ibuprofen, liposome-encapsulated catalase, nor hydroperoxide scavengers (U-74389G or Trolox) blocked the O2-induced amiloride-sensitive Isc. In contrast, the cell-permeable superoxide scavenger tetramethylpiperidine-N-oxyl (TEMPO) eliminated the O2-induced increases in amiloride-sensitive Isc and ENaC mRNA levels. The switch from 3 to 21% O2 induced the transcription factor nuclear factor-kappaB, which could also be blocked by TEMPO. We conclude that 1) the O2-induced increase in amiloride-sensitive Isc is reversible and 2) the O2-induced increase in amiloride-sensitive Isc and ENaC mRNA levels is associated with activation of nuclear factor-kappaB and may be mediated, at least in part, by superoxide.
Medical Research Council Group in Lung Development, Hospital for Sick Children Research Institute and Department of Paediatrics, University of Toronto, Toronto, Ontario, Canada M5G 1X8.
B
B
Rafii
A K
AK
Tanswell
G
G
Otulakowski
O
O
Pitkänen
R
R
Belcastro-Taylor
H
H
O'Brodovich
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002478:Cells, Cultured; D016384:Consensus Sequence; D004622:Embryo, Mammalian; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D016166:Free Radical Scavengers / Q000494:pharmacology; D005786:Gene Expression Regulation; D018496:Hyperoxia; D008168:Lung / Q000166:cytology / Q000502:physiology*; D016328:NF-kappa B / Q000378:metabolism*; D009838:Oligodeoxyribonucleotides; D010100:Oxygen / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D015222:Sodium Channels / Q000096:biosynthesis / Q000235:genetics*; D013481:Superoxides / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism
D016166:Free Radical Scavengers; D016328:NF-kappa B; D009838:Oligodeoxyribonucleotides; D015222:Sodium Channels; D018808:Transcription Factor AP-1; D013481:Superoxides; D000584:Amiloride; D010100:Oxygen