Inhibition of lung fluid clearance and epithelial Na+ channels by chlorine, hypochlorous acid, and chloramines.
We investigated the mechanisms by which chlorine (Cl(2)) and its reactive byproducts inhibit Na(+)-dependent alveolar fluid clearance (AFC) in vivo and the activity of amiloride-sensitive epithelial Na(+) channels (ENaC) by measuring AFC in mice exposed to Cl(2) (0-500 ppm for 30 min) and Na(+) and amiloride-sensitive currents (I(Na) and I(amil), respectively) across Xenopus oocytes expressing human alpha-, beta-, and gamma-ENaC incubated with HOCl (1-2000 microm). Both Cl(2) and HOCl-derived products decreased AFC in mice and whole cell and single channel I(Na) in a dose-dependent manner; these effects were counteracted by serine proteases. Mass spectrometry analysis of the oocyte recording medium identified organic chloramines formed by the interaction of HOCl with HEPES (used as an extracellular buffer). In addition, chloramines formed by the interaction of HOCl with taurine or glycine decreased I(Na) in a similar fashion. Preincubation of oocytes with serine proteases prevented the decrease of I(Na) by HOCl, whereas perfusion of oocytes with a synthetic 51-mer peptide corresponding to the putative furin and plasmin cleaving segment in the gamma-ENaC subunit restored the ability of HOCl to inhibit I(Na). Finally, I(Na) of oocytes expressing wild type alpha- and gamma-ENaC and a mutant form of beta ENaC (S520K), known to result in ENaC channels locked in the open position, were not altered by HOCl. We concluded that HOCl and its reactive intermediates (such as organic chloramines) inhibit ENaC by affecting channel gating, which could be relieved by proteases cleavage.
Song
Weifeng
W
Departments of Anesthesiology, Birmingham, Alabama 35205; Centers for Pulmonary Injury and Repair, Birmingham, Alabama 35205.
Wei
Shipeng
S
Departments of Anesthesiology, Birmingham, Alabama 35205; Centers for Pulmonary Injury and Repair, Birmingham, Alabama 35205.
Zhou
Yongjian
Y
Departments of Anesthesiology, Birmingham, Alabama 35205.
Lazrak
Ahmed
A
Departments of Anesthesiology, Birmingham, Alabama 35205; Centers for Pulmonary Injury and Repair, Birmingham, Alabama 35205.
Liu
Gang
G
Centers for Pulmonary Injury and Repair, Birmingham, Alabama 35205; Medicine, Birmingham, Alabama 35205.
Londino
James D
JD
Departments of Anesthesiology, Birmingham, Alabama 35205; Centers for Pulmonary Injury and Repair, Birmingham, Alabama 35205.
Squadrito
Giuseppe L
GL
Centers for Pulmonary Injury and Repair, Birmingham, Alabama 35205; Environmental Health Sciences, Schools of Medicine and Public Health, Birmingham, Alabama 35205; Free Radical Biology, University of Alabama at Birmingham, Birmingham, Alabama 35205.
Matalon
Sadis
S
Departments of Anesthesiology, Birmingham, Alabama 35205; Centers for Pulmonary Injury and Repair, Birmingham, Alabama 35205; Medicine, Birmingham, Alabama 35205; Free Radical Biology, University of Alabama at Birmingham, Birmingham, Alabama 35205. Electronic address: sadis@uab.edu.
D000818:Animals; D002700:Chloramines / Q000378:metabolism*; D053503:Epithelial Sodium Channels / Q000378:metabolism*; D006801:Humans; D006997:Hypochlorous Acid / Q000378:metabolism*; D008168:Lung / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009865:Oocytes / Q000378:metabolism; D015222:Sodium Channels / Q000378:metabolism*; D014981:Xenopus
D002700:Chloramines; D053503:Epithelial Sodium Channels; D015222:Sodium Channels; D006997:Hypochlorous Acid