Oxidative stress disrupts glucocorticoid hormone-dependent transcription of the amiloride-sensitive epithelial sodium channel α-subunit in lung epithelial cells through ERK-dependent and thioredoxin-sensitive pathways

Hao Chien Wang, Mark D. Zentner, Hong Tao Deng, Kwang Jin Kim, Reen Wu, Pan Chyr Yang, David K. Ann

Research output: Contribution to journalArticle

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Abstract

The amiloride-sensitive epithelial Na+ channel (ENaC) plays a critical role in the maintenance of alveolar fluid balance. It is generally accepted that reactive oxygen and nitrogen species can inhibit ENaC activity and aggravate acute lung injury; however, the molecular mechanism for free radical-mediated ENaC inhibition is unclear. Previously, we showed that the expression of the α-subunit of ENaC, α-ENaC, which is indispensable for ENaC activity, is repressed by Ras activation in salivary epithelial cells. Here, we investigated whether exogenous H2O2 modulates α-ENaC gene expression in lung epithelial cells through a similar molecular mechanism. Utilizing transient transfection reporter assays and site-directed mutagenesis analyses, we found that the glucocorticoid response element (GRE), located at -1334 to -1306 base pairs of the α-ENaC 5'-flanking region, is the major enhancer for the stimulated α-ENaC expression in A549 lung epithelial cells. We further demonstrate that the presence of an intact GRE is necessary and sufficient for oxidants to repress α-ENaC expression. Consistent with our hypothesis, exogenous H2O2-mediated repression of α- ENaC GRE activity is partially blocked by either a specific inhibitor for extracellular signal-regulated kinase (ERK) pathway activation, U0126, or dominant negative ERK, suggesting that, in part, activated ERK may mediate the repressive effects of H2O2 on α-ENaC expression. In addition, overexpression of thioredoxin restored glucocorticoid receptor action on the α-ENaC GRE in the presence of exogenous H2O2. Taken together, we hypothesize that oxidative stress impairs Na+ transport activity by inhibiting dexamethasone-dependent α-ENaC GRE activation via both ERK- dependent and thioredoxin-sensitive pathways. These results suggest a putative mechanism whereby cellular redox potentials modulate the glucocorticoid receptor/dexamethasone effect on α-ENaC expression in lung and other tight epithelia.

Original languageEnglish (US)
Pages (from-to)8600-8609
Number of pages10
JournalJournal of Biological Chemistry
Volume275
Issue number12
DOIs
StatePublished - Mar 24 2000

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Epithelial Sodium Channels
Thioredoxins
Oxidative stress
Extracellular Signal-Regulated MAP Kinases
Transcription
Glucocorticoids
Oxidative Stress
Epithelial Cells
Hormones
Lung
Response Elements
Chemical activation
Glucocorticoid Receptors
Dexamethasone
Reactive Nitrogen Species
Mutagenesis
Water-Electrolyte Balance
Acute Lung Injury
Amiloride
5' Flanking Region

ASJC Scopus subject areas

  • Biochemistry

Cite this

Oxidative stress disrupts glucocorticoid hormone-dependent transcription of the amiloride-sensitive epithelial sodium channel α-subunit in lung epithelial cells through ERK-dependent and thioredoxin-sensitive pathways. / Wang, Hao Chien; Zentner, Mark D.; Deng, Hong Tao; Kim, Kwang Jin; Wu, Reen; Yang, Pan Chyr; Ann, David K.

In: Journal of Biological Chemistry, Vol. 275, No. 12, 24.03.2000, p. 8600-8609.

Research output: Contribution to journalArticle

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abstract = "The amiloride-sensitive epithelial Na+ channel (ENaC) plays a critical role in the maintenance of alveolar fluid balance. It is generally accepted that reactive oxygen and nitrogen species can inhibit ENaC activity and aggravate acute lung injury; however, the molecular mechanism for free radical-mediated ENaC inhibition is unclear. Previously, we showed that the expression of the α-subunit of ENaC, α-ENaC, which is indispensable for ENaC activity, is repressed by Ras activation in salivary epithelial cells. Here, we investigated whether exogenous H2O2 modulates α-ENaC gene expression in lung epithelial cells through a similar molecular mechanism. Utilizing transient transfection reporter assays and site-directed mutagenesis analyses, we found that the glucocorticoid response element (GRE), located at -1334 to -1306 base pairs of the α-ENaC 5'-flanking region, is the major enhancer for the stimulated α-ENaC expression in A549 lung epithelial cells. We further demonstrate that the presence of an intact GRE is necessary and sufficient for oxidants to repress α-ENaC expression. Consistent with our hypothesis, exogenous H2O2-mediated repression of α- ENaC GRE activity is partially blocked by either a specific inhibitor for extracellular signal-regulated kinase (ERK) pathway activation, U0126, or dominant negative ERK, suggesting that, in part, activated ERK may mediate the repressive effects of H2O2 on α-ENaC expression. In addition, overexpression of thioredoxin restored glucocorticoid receptor action on the α-ENaC GRE in the presence of exogenous H2O2. Taken together, we hypothesize that oxidative stress impairs Na+ transport activity by inhibiting dexamethasone-dependent α-ENaC GRE activation via both ERK- dependent and thioredoxin-sensitive pathways. These results suggest a putative mechanism whereby cellular redox potentials modulate the glucocorticoid receptor/dexamethasone effect on α-ENaC expression in lung and other tight epithelia.",
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AU - Wang, Hao Chien

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AU - Deng, Hong Tao

AU - Kim, Kwang Jin

AU - Wu, Reen

AU - Yang, Pan Chyr

AU - Ann, David K.

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