Regulation of Alveolar Epithelial Na+ Channels by ERK1/2 in Chlorine-Breathing Mice

A Lazrak, L Chen, A Jurkuvenaite… - American journal of …, 2012 - atsjournals.org
A Lazrak, L Chen, A Jurkuvenaite, SF Doran, G Liu, Q Li, JR Lancaster Jr, S Matalon
American journal of respiratory cell and molecular biology, 2012atsjournals.org
The mechanisms by which the exposure of mice to Cl2 decreases vectorial Na+ transport
and fluid clearance across their distal lung spaces have not been elucidated. We examined
the biophysical, biochemical, and physiological changes of rodent lung epithelial Na+
channels (ENaCs) after exposure to Cl2, and identified the mechanisms involved. We
measured amiloride-sensitive short-circuit currents (Iamil) across isolated alveolar Type II
(ATII) cell monolayers and ENaC single-channel properties by patching ATII and ATI cells in …
The mechanisms by which the exposure of mice to Cl2 decreases vectorial Na+ transport and fluid clearance across their distal lung spaces have not been elucidated. We examined the biophysical, biochemical, and physiological changes of rodent lung epithelial Na+ channels (ENaCs) after exposure to Cl2, and identified the mechanisms involved. We measured amiloride-sensitive short-circuit currents (Iamil) across isolated alveolar Type II (ATII) cell monolayers and ENaC single-channel properties by patching ATII and ATI cells in situ. α-ENaC, γ-ENaC, total and phosphorylated extracellular signal-related kinase (ERK)1/2, and advanced products of lipid peroxidation in ATII cells were measured by Western blot analysis. Concentrations of reactive intermediates were assessed by electron spin resonance (ESR). Amiloride-sensitive Na+ channels with conductances of 4.5 and 18 pS were evident in ATI and ATII cells in situ of air-breathing mice. At 1 hour and 24 hours after exposure to Cl2, the open probabilities of these two channels decreased. This effect was prevented by incubating lung slices with inhibitors of ERK1/2 or of proteasomes and lysosomes. The exposure of ATII cell monolayers to Cl2 increased concentrations of reactive intermediates, leading to ERK1/2 phosphorylation and decreased Iamil and α-ENaC concentrations at 1 hour and 24 hours after exposure. The administration of antioxidants to ATII cells before and after exposure to Cl2 decreased concentrations of reactive intermediates and ERK1/2 activation, which mitigated the decrease in Iamil and ENaC concentrations. The reactive intermediates formed during and after exposure to Cl2 activated ERK1/2 in ATII cells in vitro and in vivo, leading to decreased ENaC concentrations and activity.
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